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Sample records for 13-stage dekati low-pressure

  1. Low-pressure, chemical vapor deposition polysilicon

    NASA Technical Reports Server (NTRS)

    Gallagher, B. D.; Crotty, G. C.

    1986-01-01

    The low-pressure chemical vapor deposition (LPCVD) of polycrystalline silicon was investigted. The physical system was described, as was the controlling process parameters and requirements for producing films for use as an integral portion of the solar cell contact system.

  2. New developments in low pressure SMC

    SciTech Connect

    Atkins, K.E.; Seats, R.L.; Reid, C.G.; Behar, G.

    1996-11-01

    The composites industry has expressed a keen desire for a molding material with the properties of Sheet Molding Compound (SMC) and the ability to mold at low pressures. Opportunities exist in Class A, zero shrink, low shrink pigmentable, and structural applications. Clearly, the ability to achieve SMC properties and production rates in shorter run applications in relatively inexpensive tooling is intuitively attractive. The historical problem with SMC under low pressure situations has been the difficulty in consistently controlling the chemical thickening process at low levels and achieving a dry, tack free, easily handled compound with no resin separation. In recent years developments have been made for low pressure SMC which does not contain an earth oxide thickening agent but relies on a crystalline polyester physical thickening. However, this approach requires modification of standard SMC and in-plant environmental protection equipment. The resulting compound is also tacky and difficult to handle. Developmental efforts have produced an approach to low pressure SMC that will produce molding compounds on standard SMC equipment with a wide process latitude for thickener control. The resultant compound is dry and easily handled and has a stable viscosity for several weeks. Formulations for Class A surface, inner reinforcement and pigmentable materials will be presented. Also approaches to low temperature cure with these materials will be outlined.

  3. Low Pressure Nuclear Thermal Rocket (LPNTR) concept

    NASA Technical Reports Server (NTRS)

    Ramsthaler, J. H.

    1991-01-01

    A background and a description of the low pressure nuclear thermal system are presented. Performance, mission analysis, development, critical issues, and some conclusions are discussed. The following subject areas are covered: LPNTR's inherent advantages in critical NTR requirement; reactor trade studies; reference LPNTR; internal configuration and flow of preliminary LPNTR; particle bed fuel assembly; preliminary LPNTR neutronic study results; multiple LPNTR engine concept; tank and engine configuration for mission analysis; LPNTR reliability potential; LPNTR development program; and LPNTR program costs.

  4. The low-pressure sodium lamp

    SciTech Connect

    Hooker, J.D.

    1997-12-31

    For many years before the introduction of the sodium vapor lamp, scientists had been aware of the remarkably high luminous efficacy of the sodium discharge. However, many technical problems had to be overcome before these lamps could be marketed. The first commercial low pressure sodium lamps were introduced in the early 1930s and to this day they remain the most efficient light sources available. The high efficacy is due partly to the fact that these lamps emit nearly monochromatic yellow light, which is very close to the peak sensitivity of the human eye. Sodium lamps have come a long way since their introduction, and efficacies are now approaching 200 lumens per watt. Despite increasing competition from other types of discharge lamp, low pressure sodium lamps of the SOX type find widespread use in road and security lighting, particularly in Great Britain and many other parts of Europe. This paper reviews the operation and development of the low pressure sodium lamp, and shows what makes it different from the many other types of discharge lamp available.

  5. Nanoparticle synthesis in low pressure flames

    NASA Astrophysics Data System (ADS)

    Colibaba-Evulet, Andrei

    The results of an experimental and computational study of nanoparticle synthesis in low pressure flames are presented. In a stagnation point flow configuration, hydrogen/oxygen low pressure flat flames were supplied with metalorganic vapor precursors and the flame conditions were identified for nanoparticle formation and growth, followed by deposition on a cooled substrate. The effects of pressure, burner to substrate distance, stoichiometry and flowrate on the particle size, morphology and phase were examined. Titania, alumina and zirconia non-agglomerated nanopowders were synthesized and analyzed using X-ray diffraction, BET gas absorption and TEM. A flame model with complex chemistry is used for the prediction of the temperature and flow fields. Thermophoretic effects upon the particle dynamics are estimated and the time/temperature profiles for several flames are predicted. A collision/coalescence mechanism growth model based on the predicted time/temperature is employed for computation of the deposited particle size. Laser induced fluorescence is used for determination of temperature and monoxide concentration profiles in the flame. Temperature measurements using two line fluorescence thermometry in an nitric oxide seeded flame indicate that the flame model predicts temperatures to within 200 K for simple flames. The temperatures of the precursor fed flames exceed the simple flame temperatures by as much as 600 K, showing that precursor decomposition/pyrolysls highly affects the thermochemistry of the flame. Radical concentration measurements in flames synthesizing titania, alumina and zirconia indicate that try monitoring the respective metal monoxides, the location of precursor decomposition and monomer formation in the flame can be inferred. A parametric study of the zirconia synthesis flame showed a certain degree of control on the particle size, agglomeration and crystallinity. Flames hotter than 1700 K and with high quenching rates produced a mixture of

  6. Flow fields of low pressure vent exhausts

    NASA Technical Reports Server (NTRS)

    Scialdone, John J.

    1989-01-01

    The flow field produced by low pressure gas vents are described based on experimental data obtained from tests in a large vacuum chamber. The gas density, pressure, and flux at any location in the flow field are calculated based on the vent plume description and the knowledge of the flow rate and velocity of the venting gas. The same parameters and the column densities along a specified line of sight traversing the plume are also obtained and shown by a computer-generated graphical representation. The fields obtained with a radially scanning Pitot probe within the exhausting gas are described by a power of the cosine function, the mass rate and the distance from the exit port. The field measurements were made for gas at pressures ranging from 2 to 50 torr venting from pipe fittings with diameters of 3/16 inch to 1-1/2 inches I.D. (4.76 mm to 38.1 mm). The N(2) mass flow rates ranged from 2E-4 to 3.7E-1 g/s.

  7. Flow fields of low pressure vent exhausts

    NASA Technical Reports Server (NTRS)

    Scialdone, John J.

    1990-01-01

    The flow field produced by low pressure gas vents are described based on experimental data obtained from tests in a large vacuum chamber. The gas density, pressure, and flux at any location in the flow field are calculated based on the vent plume description and the knowledge of the flow rate and velocity of the venting gas. The same parameters and the column densities along a specified line of sight traversing the plume are also obtained and shown by a computer generated graphical representation. The fields obtained with a radically scanning Pitot probe within the exhausting gas are described by a power of the cosine function, the mass rate, and the distance from the exit port. The field measurements were made for gas at pressures ranging from 2 to 50 torr venting from pipe fittings with diameters to 3/16 to 1-1/2 inches I.D. (4.76 to 38.1 mm). The N2 mass flow rates ranged from 2E-4 to 3.7E-1 g/s.

  8. Condensation of liquid metals under low pressures

    SciTech Connect

    Elafify, M.M.

    1988-01-01

    The Direct Simulation Monte Carlo (DSMC) method is used to study one-dimensional condensation phenomena for a pure vapor or vapor/gas mixture. The results are fitted to an interpolation formula describing the condensation mass flux to provide a usable engineering correlation. For pure vapor, the DSMC results are compared with the available experimental data for condensation of mercury under low pressure. Results are compared also with some of the theoretical models. The comparison shows that the DSMC method is able to detect the qualitative behavior of the condensation mass flux, although it overestimates the mass flux by 20-30%. Compared with other introduced theoretical models, the DSMC method has the most-consistent representation of the qualitative behavior of the condensation mass flux. The method was also used to represent condensation in the presence of a noncondensable gas. A formal proof for choosing collision partners was introduced and applied in the case of condensation in the presence of a noncondensable gas. The method is applied to condensation of mercury in the presence of different monatomic noncondensable gases at different partial pressures.

  9. General view of low pressure compressor (unit #3) with compressor ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    General view of low pressure compressor (unit #3) with compressor in foreground and engines in background. High pressure stage is on left, low pressure stage is on right. - Burnsville Natural Gas Pumping Station, Saratoga Avenue between Little Kanawha River & C&O Railroad line, Burnsville, Braxton County, WV

  10. 22. Fire Protection Water Pump (low pressure), view to the ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    22. Fire Protection Water Pump (low pressure), view to the southwest. - Washington Water Power Clark Fork River Cabinet Gorge Hydroelectric Development, Powerhouse, North Bank of Clark Fork River at Cabinet Gorge, Cabinet, Bonner County, ID

  11. 14. Generator Fire Protection for Unit 5 (low pressure), view ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    14. Generator Fire Protection for Unit 5 (low pressure), view to the southeast. - Washington Water Power Clark Fork River Noxon Rapids Hydroelectric Development, Powerhouse, South bank of Clark Fork River at Noxon Rapids, Noxon, Sanders County, MT

  12. Detail view of steam chest for low pressure stage engine ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Detail view of steam chest for low pressure stage engine of unit 43. - Burnsville Natural Gas Pumping Station, Saratoga Avenue between Little Kanawha River & C&O Railroad line, Burnsville, Braxton County, WV

  13. DETAIL VIEW OF STEAM CHEST FOR LOW PRESSURE STAGE ENGINE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DETAIL VIEW OF STEAM CHEST FOR LOW PRESSURE STAGE ENGINE OF UNIT #3. - Burnsville Natural Gas Pumping Station, Saratoga Avenue between Little Kanawha River & C&O Railroad line, Burnsville, Braxton County, WV

  14. Detail view of steam chest for low pressure stage of ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Detail view of steam chest for low pressure stage of unit 40. - Burnsville Natural Gas Pumping Station, Saratoga Avenue between Little Kanawha River & C&O Railroad line, Burnsville, Braxton County, WV

  15. Low pressure cooling seal system for a gas turbine engine

    DOEpatents

    Marra, John J

    2014-04-01

    A low pressure cooling system for a turbine engine for directing cooling fluids at low pressure, such as at ambient pressure, through at least one cooling fluid supply channel and into a cooling fluid mixing chamber positioned immediately downstream from a row of turbine blades extending radially outward from a rotor assembly to prevent ingestion of hot gases into internal aspects of the rotor assembly. The low pressure cooling system may also include at least one bleed channel that may extend through the rotor assembly and exhaust cooling fluids into the cooling fluid mixing chamber to seal a gap between rotational turbine blades and a downstream, stationary turbine component. Use of ambient pressure cooling fluids by the low pressure cooling system results in tremendous efficiencies by eliminating the need for pressurized cooling fluids for sealing this gap.

  16. Features of plasma glow in low pressure terahertz gas discharge

    SciTech Connect

    Bratman, V. L.; Golubev, S. V.; Izotov, I. V.; Kalynov, Yu. K.; Koldanov, V. A.; Razin, S. V.; Litvak, A. G.; Sidorov, A. V.; Skalyga, V. A.; Zorin, V. G.

    2013-12-15

    Investigations of the low pressure (1–100 Torr) gas discharge in the powerful (1 kW) quasi-optical terahertz (0.55 THz) wave beams were made. An intense afterglow was observed after the end of gyrotron terahertz radiation pulse. Afterglow duration significantly exceeded radiation pulse length (8 μs). This phenomenon could be explained by the strong dependence of the collisional-radiative recombination rate (that is supposed to be the most likely mechanism of electron losses from the low pressure terahertz gas discharge) on electron temperature.

  17. Features of plasma glow in low pressure terahertz gas discharge

    NASA Astrophysics Data System (ADS)

    Bratman, V. L.; Golubev, S. V.; Izotov, I. V.; Kalynov, Yu. K.; Koldanov, V. A.; Litvak, A. G.; Razin, S. V.; Sidorov, A. V.; Skalyga, V. A.; Zorin, V. G.

    2013-12-01

    Investigations of the low pressure (1-100 Torr) gas discharge in the powerful (1 kW) quasi-optical terahertz (0.55 THz) wave beams were made. An intense afterglow was observed after the end of gyrotron terahertz radiation pulse. Afterglow duration significantly exceeded radiation pulse length (8 μs). This phenomenon could be explained by the strong dependence of the collisional-radiative recombination rate (that is supposed to be the most likely mechanism of electron losses from the low pressure terahertz gas discharge) on electron temperature.

  18. A low pressure filter system for new containment concepts

    SciTech Connect

    Dillmann, H.G.; Pasler, H.

    1995-02-01

    It is demonstrated that after severe accidents the decay heat can be removed in a passive mode in a convective flow, i.e. without needing a fan. The filter components with sufficiently low pressure drop values which are required for this purpose will be described and the results indicated.

  19. 20. VIEW OF LOW PRESSURE PUMPING EQUIPMENT ON THE SECOND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    20. VIEW OF LOW PRESSURE PUMPING EQUIPMENT ON THE SECOND FLOOR OF BUILDING 707. THE EQUIPMENT MAINTAINS PROPER COOLANT PRESSURE IN MACHINES. (5/70) - Rocky Flats Plant, Plutonium Manufacturing Facility, North-central section of Plant, just south of Building 776/777, Golden, Jefferson County, CO

  20. Spontaneous low-pressure headache complicating bag-piping.

    PubMed

    Patrick, Alasdair; McAuley, David; Roxburgh, Richard

    2007-04-01

    We describe an interesting case of a 40-year-old lady who developed a spontaneous low-pressure headache whilst playing the bag-pipes. Playing wind instruments requires the generation of significant intra-thoracic pressure, which may have contributed to this musician's condition. PMID:17445112

  1. North-South Migration of West Coast Low Pressure Centers

    ERIC Educational Resources Information Center

    McIntosh, C. Barron

    1974-01-01

    Monthly maps of low pressure centers are presented here to attempt a concrete representation that may help students to understand the seasonal change from dry months to wet months along the mid-latitude west coast as a seasonal north-south migration of factors controlling rain and drought. (Author/JH)

  2. Performance of low-pressure thermionic converters is evaluated

    NASA Technical Reports Server (NTRS)

    Richards, H. K.

    1969-01-01

    Experiments, evaluating the performance of low-pressure thermionic converters, were conducted with cesium, potassium, and sodium-metal vapors. The results of the investigation are useful in the selection of favorable conditions for the design of thermionic reactor fuel elements, including RF output for special applications.

  3. Properties of microwave plasma torch operating at a low pressure

    SciTech Connect

    Cho, Soon C.; Uhm, Han S.; Hong, Yong C.; Kim, Jae H.

    2008-10-15

    A microwave plasma torch system is attached to a low-pressure chamber in this study. The electric field induced in a quartz discharge tube by microwave radiation breaks down the gas at a sufficiently low pressure, igniting the plasma, which is continuously sustained by the microwave radiation. The plasma profile at a very low pressure is shown to be asymmetric with higher density on the incoming side of the microwaves. The gas temperature at the bright spot of the torch plasma measured via the optical emission from hydroxide radicals is shown to increase drastically upon high-pressure operation as the microwave power increases. The electron density at the torch flame is measured by recording the Stark broadening of the hydrogen Balmer beta line. The plasma density increases as the microwave power increases. The typical argon plasma density of a plasma torch powered at 500 W under a pressure of 150 Torr is on the order of 10{sup 14}/cm{sup 3}. The electron temperature in the argon torch plasma was estimated to be 1.5 eV, thereby effectively exciting the molecules in the torch gas. Disintegration of nitrogen fluoride (NF{sub 3}) indicates that a microwave plasma torch operating at a low pressure can efficiently generate an abundant amount of chemical radicals.

  4. General interior view of pumphouse looking north. Low pressure compressor ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    General interior view of pumphouse looking north. Low pressure compressor (unit 45) is partially visible in left foreground. As shown from far end, 40, 41 and 42. - Burnsville Natural Gas Pumping Station, Saratoga Avenue between Little Kanawha River & C&O Railroad line, Burnsville, Braxton County, WV

  5. Flow Analysis of a Gas Turbine Low- Pressure Subsystem

    NASA Technical Reports Server (NTRS)

    Veres, Joseph P.

    1997-01-01

    The NASA Lewis Research Center is coordinating a project to numerically simulate aerodynamic flow in the complete low-pressure subsystem (LPS) of a gas turbine engine. The numerical model solves the three-dimensional Navier-Stokes flow equations through all components within the low-pressure subsystem as well as the external flow around the engine nacelle. The Advanced Ducted Propfan Analysis Code (ADPAC), which is being developed jointly by Allison Engine Company and NASA, is the Navier-Stokes flow code being used for LPS simulation. The majority of the LPS project is being done under a NASA Lewis contract with Allison. Other contributors to the project are NYMA and the University of Toledo. For this project, the Energy Efficient Engine designed by GE Aircraft Engines is being modeled. This engine includes a low-pressure system and a high-pressure system. An inlet, a fan, a booster stage, a bypass duct, a lobed mixer, a low-pressure turbine, and a jet nozzle comprise the low-pressure subsystem within this engine. The tightly coupled flow analysis evaluates aerodynamic interactions between all components of the LPS. The high-pressure core engine of this engine is simulated with a one-dimensional thermodynamic cycle code in order to provide boundary conditions to the detailed LPS model. This core engine consists of a high-pressure compressor, a combustor, and a high-pressure turbine. The three-dimensional LPS flow model is coupled to the one-dimensional core engine model to provide a "hybrid" flow model of the complete gas turbine Energy Efficient Engine. The resulting hybrid engine model evaluates the detailed interaction between the LPS components at design and off-design engine operating conditions while considering the lumped-parameter performance of the core engine.

  6. Energy Efficient Engine Low Pressure Subsystem Aerodynamic Analysis

    NASA Technical Reports Server (NTRS)

    Hall, Edward J.; Delaney, Robert A.; Lynn, Sean R.; Veres, Joseph P.

    1998-01-01

    The objective of this study was to demonstrate the capability to analyze the aerodynamic performance of the complete low pressure subsystem (LPS) of the Energy Efficient Engine (EEE). Detailed analyses were performed using three- dimensional Navier-Stokes numerical models employing advanced clustered processor computing platforms. The analysis evaluates the impact of steady aerodynamic interaction effects between the components of the LPS at design and off- design operating conditions. Mechanical coupling is provided by adjusting the rotational speed of common shaft-mounted components until a power balance is achieved. The Navier-Stokes modeling of the complete low pressure subsystem provides critical knowledge of component acro/mechanical interactions that previously were unknown to the designer until after hardware testing.

  7. Ion optical effects in a low pressure rf plasma

    SciTech Connect

    Oechsner, Hans; Paulus, Hubert

    2013-11-15

    Ion optical effects in low pressure gas discharges are introduced as a novel input into low pressure plasma technology. They are based on appropriate geometrical plasma confinements which enable a control of the shape of internal density and potential distributions and, hence, the ion motion in the plasma bulk. Such effects are exemplified for an electron cyclotron wave resonance plasma in Ar at 1–5 × 10{sup −3} millibars. The geometry of the plasma chamber is modified by a conical and a cylindrical insert. Computer simulations display spherical plasma density contours to be formed around the conical confinement. This effects an increase of the ratio of the ion currents into the conical and the cylindrical inserts which depends on the fourth power of the plasma electron temperature. A quantitative understanding of this behavior is presented. As another essential result, the shape of the internal plasma contours is found to be independent of the pressure controlled plasma parameters.

  8. Energy Efficient Engine Low Pressure Subsystem Flow Analysis

    NASA Technical Reports Server (NTRS)

    Hall, Edward J.; Lynn, Sean R.; Heidegger, Nathan J.; Delaney, Robert A.

    1998-01-01

    The objective of this project is to provide the capability to analyze the aerodynamic performance of the complete low pressure subsystem (LPS) of the Energy Efficient Engine (EEE). The analyses were performed using three-dimensional Navier-Stokes numerical models employing advanced clustered processor computing platforms. The analysis evaluates the impact of steady aerodynamic interaction effects between the components of the LPS at design and off-design operating conditions. Mechanical coupling is provided by adjusting the rotational speed of common shaft-mounted components until a power balance is achieved. The Navier-Stokes modeling of the complete low pressure subsystem provides critical knowledge of component aero/mechanical interactions that previously were unknown to the designer until after hardware testing.

  9. LOW-PRESSURE MEMBRANE CONTACTORS FOR CARBON DIOXIDE CAPTURE

    SciTech Connect

    Baker, Richard; Kniep, Jay; Hao, Pingjiao; Chan, Chi Cheng; Nguyen, Vincent; Huang, Ivy; Amo, Karl; Freeman, Brice; Fulton, Don; Ly, Jennifer; Lipscomb, Glenn; Lou, Yuecun; Gogar, Ravikumar

    2014-09-30

    This final technical progress report describes work conducted by Membrane Technology and Research, Inc. (MTR) for the Department of Energy (DOE NETL) on development of low-pressure membrane contactors for carbon dioxide (CO2) capture from power plant flue gas (award number DE-FE0007553). The work was conducted from October 1, 2011 through September 30, 2014. The overall goal of this three-year project was to build and operate a prototype 500 m2 low-pressure sweep membrane module specifically designed to separate CO2 from coal-fired power plant flue gas. MTR was assisted in this project by a research group at the University of Toledo, which contributed to the computational fluid dynamics (CFD) analysis of module design and process simulation. This report details the work conducted to develop a new type of membrane contactor specifically designed for the high-gas-flow, low-pressure, countercurrent sweep operation required for affordable membrane-based CO2 capture at coal power plants. Work for this project included module development and testing, design and assembly of a large membrane module test unit at MTR, CFD comparative analysis of cross-flow, countercurrent, and novel partial-countercurrent sweep membrane module designs, CFD analysis of membrane spacers, design and fabrication of a 500 m2 membrane module skid for field tests, a detailed performance and cost analysis of the MTR CO2 capture process with low-pressure sweep modules, and a process design analysis of a membrane-hybrid separation process for CO2 removal from coal-fired flue gas. Key results for each major task are discussed in the report.

  10. Method of gettering hydrogen under conditions of low pressure

    DOEpatents

    Mendelsohn, M.H.; Gruen, D.M.

    1983-08-09

    A ternary intermetallic compound having the formula Zr(V[sub 1[minus]x]Cr[sub x])[sub 2] where x is in the range of 0.01 to 0.90 is capable of reversibly sorbing hydrogen at temperatures ranging from room temperature to 200 C, at pressures down to 10[sup [minus]6] Torr. The compound is suitable for use as a hydrogen getter in low pressure, high temperature applications such as magnetic confinement fusion devices. 3 figs.

  11. Method of gettering hydrogen under conditions of low pressure

    DOEpatents

    Mendelsohn, Marshall H.; Gruen, Dieter M.

    1983-01-01

    A ternary intermetallic compound having the formula Zr(V.sub.1-x Cr.sub.x).sub.2 where x is in the range of 0.01 to 0.90 is capable of reversibly sorbing hydrogen at temperatures ranging from room temperature to 200.degree. C., at pressures down to 10.sup.-6 Torr. The compound is suitable for use as a hydrogen getter in low pressure, high temperature applications such as magnetic confinement fusion devices.

  12. A low pressure bipolar nickel-hydrogen battery

    SciTech Connect

    Golben, M.; Nechev, K.; DaCosta, D.H.; Rosso, M.J.

    1997-12-01

    Ergenics is developing a low pressure high power rechargeable battery for electric vehicles and other large battery applications. The Hy-Stor{trademark} battery couples a bipolar nickel-hydrogen electrochemical system with the high energy storage density of metal hydride technology. In addition to its long cycle life, high specific power, and energy density, this battery offers safety and economic advantages over other rechargeable batteries. Results from preliminary testing of the first Hy-Stor battery are presented.

  13. Development of the Low-Pressure Hydride/Dehydride Process

    SciTech Connect

    Rueben L. Gutierrez

    2001-04-01

    The low-pressure hydride/dehydride process was developed from the need to recover thin-film coatings of plutonium metal from the inner walls of an isotope separation chamber located at Los Alamos and to improve the safety operation of a hydride recovery process using hydrogen at a pressure of 0.7 atm at Rocky Flats. This process is now the heart of the Advanced Recovery and Integrated Extraction System (ARIES) project.

  14. Low-pressure overdriven experiments in PBX-9502

    SciTech Connect

    Jensen, Brian J; Byers, Mark E

    2009-01-01

    Symmetric impact experiments were performed on PBX 9502 to obtain Hugoniot data in the low-pressure, overdriven regime. An explosive plane wave lens (P300 with comp-B booster) was used to launch an aluminum flyer plate (4 to 4.5 km/s) into an aluminum target backed by the PBX 9502 samples and a LiF window. Photonic Doppler velocimetry (PDV) was used to obtain the shock transit time through the PBX 9502 samples and wave profile data at the PBX 9502/LiF interface. Past experimental result in the overdriven regime, utilizing a rotating mirror streak camera, revealed a well-defined high-pressure Hugoniot. In contrast, the low-pressure (overdriven) data exhibited significant scatter likely due to non-steady wave effects associated with the thin PBX 9502 samples (3-5 mm) used in the experiments. The objective of the current work was to obtain Hugoniot data in the low-pressure, overdriven regime for PBX 9502 using recently developed diagnostics along with thicker samples (5-10mm) to decrease the uncertainty and scatter in the Hugoniot data.

  15. Low pressure growth of cubic boron nitride films

    NASA Technical Reports Server (NTRS)

    Ong, Tiong P. (Inventor); Shing, Yuh-Han (Inventor)

    1997-01-01

    A method for forming thin films of cubic boron nitride on substrates at low pressures and temperatures. A substrate is first coated with polycrystalline diamond to provide a uniform surface upon which cubic boron nitride can be deposited by chemical vapor deposition. The cubic boron nitride film is useful as a substitute for diamond coatings for a variety of applications in which diamond is not suitable. any tetragonal or hexagonal boron nitride. The cubic boron nitride produced in accordance with the preceding example is particularly well-suited for use as a coating for ultra hard tool bits and abrasives, especially those intended to use in cutting or otherwise fabricating iron.

  16. Low pressure stagnation flow reactor with a flow barrier

    DOEpatents

    Vosen, Steven R.

    2001-01-01

    A flow barrier disposed at the periphery of a workpiece for achieving uniform reaction across the surface of the workpiece, such as a semiconductor wafer, in a stagnation flow reactor operating under the conditions of a low pressure or low flow rate. The flow barrier is preferably in the shape of annulus and can include within the annular structure passages or flow channels for directing a secondary flow of gas substantially at the surface of a semiconductor workpiece. The flow barrier can be constructed of any material which is chemically inert to reactive gases flowing over the surface of the semiconductor workpiece.

  17. Low pressure storage of natural gas on activated carbon

    NASA Astrophysics Data System (ADS)

    Wegrzyn, J.; Wiesmann, H.; Lee, T.

    The introduction of natural gas to the transportation energy sector offers the possibility of displacing imported oil with an indigenous fuel. The barrier to the acceptance of natural gas vehicles (NGV) is the limited driving range due to the technical difficulties of on-board storage of a gaseous fuel. In spite of this barrier, compressed natural gas (CNG) vehicles are today being successfully introduced into the market place. The purpose of this work is to demonstrate an adsorbent natural gas (ANG) storage system as a viable alternative to CNG storage. It can be argued that low pressure ANG has reached near parity with CNG, since the storage capacity of CNG (2400 psi) is rated at 190 V/V, while low pressure ANG (500 psi) has reached storage capacities of 180 V/V in the laboratory. A program, which extends laboratory results to a full-scale vehicle test, is necessary before ANG technology will receive widespread acceptance. The objective of this program is to field test a 150 V/V ANG vehicle in FY 1994. As a start towards this goal, carbon adsorbents have been screened by Brookhaven for their potential use in a natural gas storage system. This paper reports on one such carbon, trade name Maxsorb, manufactured by Kansai Coke under an Amoco license.

  18. Lattuce growth and water use in closed, low pressure environment

    NASA Astrophysics Data System (ADS)

    Fowler, P.; Rygalov, V.; Wheeler, R.; Bucklin, R.; Schumacher, N.

    Lettuce (Lactuca sativa L.) cv. Waldmann's Green plants were grown in a clear, hemispherical enclosure at a reduced atmospheric pressure to study the potential for using low pressure greenhouses on planetary missions. The atmosphere was maintained at 25 kPa total pressure, with ˜20 kPa of N_2, ˜5 kPa of O_2, and between 0.1 and 0.2 kPa of CO_2, supplied by CO_2 injection and a feed-back control system. A closed water cycle was maintained inside the low pressure greenhouse by recycling condensed humidity back to the plants, and only adding external water to offset water vapor leakage and uptake in the plant tissue. All plants were grown in a granular, arcillite medium (calcined clay chips), with nutrients supplied by adding time-release fertilizer (Osmocote 20-20-20). Plants were harvested after 45 days, averaging 237 g fresh mass, and 23.7 g dry mass. No obvious adverse effects were noted on the plants, with the exception of some minor "tip-burn" injury to some leaves. Additional studies are planned to compare growth and water flux (evapotranspiration) rates at higher pressures. Preliminary results suggest that water fluxes should be lower at the higher pressures provided equal vapor pressure deficits can be maintained. The results suggest that vegetative crops such as lettuce should grow well at reduced pressures if adequate water, nutrients, and CO_2 are provided.

  19. Performance assessment of low pressure nuclear thermal propulsion

    NASA Technical Reports Server (NTRS)

    Gerrish, Harrold P., Jr.; Doughty, Glen E.

    1993-01-01

    An increase in Isp for nuclear thermal propulsion systems is desirable for reducing the propellant requirements and cost of future applications, such as the Mars Transfer Vehicle. Several previous design studies have suggested that the Isp could be increased substantially with hydrogen dissociation/recombination. Hydrogen molecules (H2), at high temperatures and low pressures, will dissociate to monatomic hydrogen (H). The reverse process (i.e., formation of H2 from H) is exothermic. The exothermic energy in a nozzle increases the kinetic energy and therefore, increases the Isp. The low pressure nuclear thermal propulsion system (LPNTP) system is expected to maximize the hydrogen dissociation/recombination and Isp by operating at high chamber temperatures and low chamber pressures. The process involves hydrogen flow through a high temperature, low pressure fission reactor, and out a nozzle. The high temperature (approximately 3000 K) of the hydrogen in the reactor is limited by the temperature limits of the reactor material. The minimum chamber pressure is about 1 atm because lower pressures decrease the engines thrust to weight ratio below acceptable limits. This study assumes that hydrogen leaves the reactor and enters the nozzle at the 3000 K equilibrium dissociation level. Hydrogen dissociation in the reactor does not affect LPNTP performance like dissociation in traditional chemical propulsion systems, because energy from the reactor resupplies energy lost due to hydrogen dissociation. Recombination takes place in the nozzle due primarily to a drop in temperature as the Mach number increases. However, as the Mach number increases beyond the nozzle throat, the static pressure and density of the flow decreases and minimizes the recombination. The ideal LPNTP Isp at 3000 K and 10 psia is 1160 seconds due to the added energy from fast recombination rates. The actual Isp depends on the finite kinetic reaction rates which affect the amount of monatomic hydrogen

  20. 49 CFR 192.623 - Maximum and minimum allowable operating pressure; Low-pressure distribution systems.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... distribution systems. (a) No person may operate a low-pressure distribution system at a pressure high enough to...) No person may operate a low pressure distribution system at a pressure lower than the...

  1. Relatively high plasma density in low pressure inductive discharges

    SciTech Connect

    Kang, Hyun-Ju; Kim, Yu-Sin; Chung, Chin-Wook

    2015-09-15

    Electron energy probability functions (EEPFs) were measured in a low pressure argon inductive discharge. As radio frequency (RF) power increases, discharge mode is changed from E-mode (capacitively coupled) to H-mode (inductively coupled) and the EEPFs evolve from a bi-Maxwellian distribution to a Maxwellian distribution. It is found that the plasma densities at low RF powers (<30 W) are much higher than the density predicted from the slope of the densities at high powers. Because high portion of high energy electrons of the bi-Maxwellian distribution lowers the collisional energy loss and low electron temperature of low energy electrons reduces particle loss rate at low powers. Therefore, the energy loss of plasma decreases and electron densities become higher at low powers.

  2. SMALL OIL BURNER CONCEPTS BASED ON LOW PRESSURE AIR ATOMIZATION

    SciTech Connect

    BUTCHER,T.; CELEBI,Y.; WEI,G.; KAMATH,B.

    2000-03-16

    The development of several novel oil burner applications based on low pressure air atomization is described. The atomizer used is a prefilming, airblast nozzle of the type commonly used in gas turbine combustion. The air pressure used can be as low as 1,300 Pa and such pressure can be easily achieved with a fan. Advantages over conventional, pressure-atomized nozzles include ability to operate at low input rates without very small passages and much lower fuel pressure requirements. The development of three specific applications is presented. The first two are domestic heating burners covering a capacity range 10 to 26 kW. The third application presented involves the use of this burner in an oil-fired thermophotovoltaic power generator system. Here the design firing rate is 2.9 kW and the system produces 500 watts of electric power.

  3. Electron heating in low pressure capacitive discharges revisited

    SciTech Connect

    Kawamura, E.; Lieberman, M. A.; Lichtenberg, A. J.

    2014-12-15

    The electrons in capacitively coupled plasmas (CCPs) absorb energy via ohmic heating due to electron-neutral collisions and stochastic heating due to momentum transfer from high voltage moving sheaths. We use Particle-in-Cell (PIC) simulations to explore these heating mechanisms and to compare the PIC results with available theories on ohmic and stochastic heating. The PIC results for ohmic heating show good agreement with the ohmic heating calculation of Lafleur et al. [Phys. Plasmas 20, 124503 (2013)]. The PIC results for stochastic heating in low pressure CCPs with collisionless sheaths show good agreement with the stochastic heating model of Kaganovich et al. [IEEE Trans. Plasma Sci. 34, 696 (2006)], which revises the hard wall asymptotic model of Lieberman [IEEE Trans. Plasma Sci. 16, 638 (1988)] by taking current continuity and bulk oscillation into account.

  4. Very low pressure high power impulse triggered magnetron sputtering

    SciTech Connect

    Anders, Andre; Andersson, Joakim

    2013-10-29

    A method and apparatus are described for very low pressure high powered magnetron sputtering of a coating onto a substrate. By the method of this invention, both substrate and coating target material are placed into an evacuable chamber, and the chamber pumped to vacuum. Thereafter a series of high impulse voltage pulses are applied to the target. Nearly simultaneously with each pulse, in one embodiment, a small cathodic arc source of the same material as the target is pulsed, triggering a plasma plume proximate to the surface of the target to thereby initiate the magnetron sputtering process. In another embodiment the plasma plume is generated using a pulsed laser aimed to strike an ablation target material positioned near the magnetron target surface.

  5. A Wireless and Passive Low-Pressure Sensor

    PubMed Central

    Nicolay, Pascal; Lenzhofer, Martin

    2014-01-01

    This paper will discuss the results obtained with a first prototype of a completely passive and wireless low pressure sensor. The device is a heat conductivity gauge, based on a wireless and passive SAW temperature sensor. The required heating energy is applied to the sensor using inductive coupling. The prototype was successfully tested in a vacuum chamber. Its equilibrium temperature changed drastically and in a reproducible way when pressure steps were applied. However, the response time was very long. A model is provided to account for the sensor's behavior. It is then used to show that the response time could be strongly improved using basic design improvements. Further possible improvements are discussed. PMID:24549249

  6. Spatio-temporal characteristics of Trichel pulse at low pressure

    SciTech Connect

    He, Shoujie; Jing, Ha

    2014-01-15

    Trichel pulses are investigated using a needle-to-plane electrode geometry at low pressure. The evolution of current and voltage, the spatio-temporal discharge images of Trichel pulse are measured. The rising time and duration time in a pulse are about 10 μs and several tens of microseconds, respectively. One period of pulse can be divided into three stages: the stage preceding cathode breakdown, cathode glow formation, and discharge decaying process. Besides a cathode glow and a dark space, an anode glow is also observed. The emission spectra mainly originate from the C{sup 3}Π{sub u} → B{sup 3}Π{sub g} transition for nitrogen. In addition, the capacitances in parallel connected with the discharge cell have important influence on the pulsing frequency.

  7. Atomic Processes and Diagnostics of Low Pressure Krypton Plasma

    NASA Astrophysics Data System (ADS)

    Srivastava, Rajesh; Goyal, Dipti; Gangwar, Reetesh; Stafford, Luc

    2015-03-01

    Optical emission spectroscopy along with suitable collisional-radiative (CR) model is used in plasma diagnostics. Importance of reliable cross-sections for various atomic processes is shown for low pressure argon plasma. In the present work, radially-averaged Kr emission lines from the 2pi --> 1sj were recorded as a function of pressure from 1 to 50mTorr. We have developed a CR model using our fine-structure relativistic-distorted wave cross sections. The various processes considered are electron-impact excitation, ionization and their reverse processes. The required rate coefficients have been calculated from these cross-sections assuming Maxwellian energy distribution. Electron temperature obtained from the CR model is found to be in good agreement with the probe measurements. Work is supported by IAEA Vienna, DAE-BRNS Mumbai and CSIR, New Delhi.

  8. Low-Pressure Turbine Separation Control: Comparison With Experimental Data

    NASA Technical Reports Server (NTRS)

    Garg, Vijay K.

    2002-01-01

    The present work details a computational study, using the Glenn HT code, that analyzes the use of vortex generator jets (VGJs) to control separation on a low-pressure turbine (LPT) blade at low Reynolds numbers. The computational results are also compared with the experimental data for steady VGJs. It is found that the code determines the proper location of the separation point on the suction surface of the baseline blade (without any VGJ) for Reynolds numbers of 50,000 or less. Also, the code finds that the separated region on the suction surface of the blade vanishes with the use of VGJs. However, the separated region and the wake characteristics are not well predicted. The wake width is generally over-predicted while the wake depth is under-predicted.

  9. Spatio-temporal characteristics of Trichel pulse at low pressure

    NASA Astrophysics Data System (ADS)

    He, Shoujie; Jing, Ha

    2014-01-01

    Trichel pulses are investigated using a needle-to-plane electrode geometry at low pressure. The evolution of current and voltage, the spatio-temporal discharge images of Trichel pulse are measured. The rising time and duration time in a pulse are about 10 μs and several tens of microseconds, respectively. One period of pulse can be divided into three stages: the stage preceding cathode breakdown, cathode glow formation, and discharge decaying process. Besides a cathode glow and a dark space, an anode glow is also observed. The emission spectra mainly originate from the C3Пu → B3Пg transition for nitrogen. In addition, the capacitances in parallel connected with the discharge cell have important influence on the pulsing frequency.

  10. Experimental measurements in a highly loaded low pressure turbine stage

    NASA Astrophysics Data System (ADS)

    Schmitz, John Thomas

    The performance and detailed flow physics of a transonic, low-pressure turbine (LPT) stage with design Zw=1.35, DeltahT/ U2 = 2.8, φ = 0.78, and eta = 90.5% has been investigated experimentally. Recent developments in boundary layer transition modeling were utilized in the aerodynamic design of the stage. Measurements were acquired in a recently developed, high-speed turbine facility constructed to investigate the effects that Reynolds number, nozzle exit flow, freestream turbulence, vane-blade spacing, and rim seal flows have on the loss generating mechanisms of a highly loaded LPT stage. Flow control techniques were applied at the stage inlet with the intent of reducing a source of stage losses. A research dissertation designed to provide understanding of the loss mechanisms that reduce the effectiveness of the Notre Dame Highly Loaded Turbine Stage 01 (ND-HiLT01) is described.

  11. Low-pressure hydrogen plasmas explored using a global model

    NASA Astrophysics Data System (ADS)

    Samuell, Cameron M.; Corr, Cormac S.

    2016-02-01

    Low-pressure hydrogen plasmas have found applications in a variety of technology areas including fusion, neutral beam injection and material processing applications. To better understand these discharges, a global model is developed to predict the behaviour of electrons, ground-state atomic and molecular hydrogen, three positive ion species (H+, \\text{H}2+ , and \\text{H}3+ ), a single negative ion species (H-), and fourteen vibrationally excited states of molecular hydrogen ({{\\text{H}}2}≤ft(\\upsilon =1\\right. -14)). The model is validated by comparison with experimental results from a planar inductively coupled GEC reference cell and subsequently applied to the MAGPIE linear helicon reactor. The MAGPIE reactor is investigated for a range of pressures from 1 to 100 mTorr and powers up to 5 kW. With increasing power between 50 W and 5 kW at 10 mTorr the density of all charged species increases as well as the dissociative fraction while the electron temperature remains almost constant at around 3 eV. For gas pressures from 1-100 mTorr at an input power of 1 kW, the electron density remains almost constant, the electron temperature and dissociative fraction decreases, while \\text{H}3+ density increases in density and also dominates amongst ion species. Across these power and pressure scans, electronegativity remains approximately constant at around 2.5%. The power and pressure determines the dominant ion species in the plasma with \\text{H}3+ observed to dominate at high pressures and low powers whereas H+ tends to be dominant at low pressures and high powers. A sensitivity analysis is used to demonstrate how experimental parameters (power, pressure, reactor wall material, geometry etc) influence individual species’ density as well as the electron temperature. Physical reactor changes including the length, radius and wall recombination coefficient are found to have the largest influence on outputs obtained from the model.

  12. Wall thinning criteria for low temperature-low pressure piping

    SciTech Connect

    Mertz, G.E.

    1993-01-01

    This acceptance criteria is intended to prevent gross rupture or rapidly propagating failure during normal and abnormal operating conditions. Pitting may be present in the carbon steel piping. While the acceptance criteria have provisions to preclude gross rupture through a pitted region, they do not protect against throughwall pit growth and subsequent leakage. Potential leakage through a pit in low pressure piping is less than the post-DBE design basis leakage. Both the uniform thinning and LTA criteria protect against leakage, since their potential for leakage is larger. The acceptance criteria protects against gross rupture due to general wall thinning, local wall thinning (LTA's), pitting, and fracture through weld defects. General wall thinning calculations are based on the restart criteria, SEP-24. LTA criteria for hoop stresses are based on ASME Code Case N-480 [open quotes]Examination Requirements for Pipe Wall Thinning Due to Single Phase Erosion and Corrosion[close quotes]. The LTA criteria for axial stress is based on an effective average thickness concept, which prevents plastic collapse of a locally thinned pipe. Limits on pit density, based on an effective cross section concept, are used to prevent gross rupture through a group of pits. The CEGB R-6 failure assessment diagram is used in the fracture evaluation, along with postulated weld defects. This criteria is intended for low temperature, low pressure piping systems. Corrosion and/or weld defects increase the peak stresses during normal operation and may lead to a reduction in fatigue life. Piping systems subject to significant thermal or mechanical fatigue will require additional analysis which is beyond the scope of this document.

  13. Kinetic Effects in Low Pressure Capacitively Coupled Plasmas

    NASA Astrophysics Data System (ADS)

    Likhanskii, Alexandre; Roark, Christine; Stoltz, Peter

    2011-10-01

    We present results of particle-in-cell/Monte Carlo collision simulations of kinetic effects in low pressure capacitively coupled plasma discharge. In particular, we examine discharges of various gases (including Ar, Xe, and others) in the pressure range of 10s of mT and the frequency range of 10s of MHz. We track the formation of high energy electrons (e.g., at the ionization threshold or greater) as a marker for enhanced ionization, and look at the effects of elastic and inelastic collisions on the formation of these high energy electron bunches. We show results for 2D and 3D simulations where we include density gradient effects, and results for plasma chemistry effects on the bulk electron energy distribution function and the ion energy distribution function at a plasma surface interface. We discuss the role of the bunches on electron heating in the plasma bulk and on their presence on how electron heating is treated in fluid simulations of plasma sources.

  14. Low pressure plasma diagnostics by cars and other techniques

    SciTech Connect

    Hata, N. )

    1989-01-01

    Within the past several years, intensive research activities relating amorphous-silicon technology have stimulated plasma-chemical-vapor-deposition (plasma-CVD) diagnostics by laser-spectroscopic techniques. Among them, coherent anti-Stokes Raman spectroscopy (CARS) has attracted much attention because of its great success in combustion diagnostics, and has been employed for low-pressure-plasma studies. Gas-phase species such as SiH{sub 4}, H{sub 2}, Si{sub 2}H{sub 6}, SiH{sub 2}, and GeH{sub 4} have been detected, time dependences of their concentration and spatial profiles of their concentration and rotational temperature have been determined, and the gas-phase mechanisms have been discussed. This talk will employ those results as examples, and discuss (1) the potential of CARS for gas-phase analysis in CVD (including (i) what species are monitored, (ii) what information is obtained, and (iii) what are the advantages and limitations), and (2) some other diagnostic techniques that provide additional information for better understandings of CVD mechanisms.

  15. Space-time resolved kinetics of low-pressure breakdown

    NASA Astrophysics Data System (ADS)

    Marić, D.; Malović, G.; Radmilović-Radenović, M.; Petrović, Z. L.

    2008-05-01

    A review of diagnostics of low-current low-pressure discharges is given with an aim to illustrate how such discharges are used to determine swarm parameters and also how such data may be applied to model and understand the discharges. We have revised how comprehensive modelling of breakdown has led to agreement between binary collision data and the data that may be inferred from the breakdown (Paschen) curves by including processes such as space charge (current) effect on the local field in front of the cathode, photoemission, heavy particle gas phase ionization and backdiffusion. It is also discussed how modelling of Volt-Ampere characteristics in addition to Paschen curves is necessary to establish models of secondary electron emission and how these models may be applied in high current discharges. Finally we show how space time resolved anatomy of the breakdown can lead to understanding of the physics of the initial stages of gas breakdown and formation of Townsend regime, glow and abnormal glow discharges.

  16. Analytical parametric investigation of low pressure ratio fan noise

    NASA Technical Reports Server (NTRS)

    Metzger, F. B.; Hanson, D. B.; Menthe, R. W.; Towle, G. B.

    1973-01-01

    The results of an analytical study are reported which shows the effect of various physical and operating parameters on noise produced by low pressure ratio propulsive fans operating at subsonic top speeds. Acoustical duct lining effects are included in the study. The concepts used to develop the noise theory used in the study, as well as the correlation between the theory and model test results are also presented. It is shown that good correlation has been established between theory and experiment. Using the theory, it is shown that good aerodynamic design, maximum acceptable fan solidity, low tip speed operation and use of few blades and vanes leads to the lowest noise levels. Typical results of the study indicate that a fan operating at 1.2 fan pressure ratio and 700 ft/second tip speed with 12 blades and 7 vanes and including modest acoustic treatment on the duct wall would produce levels allowing a 100,000 lb. STOL aircraft to meet a noise level objective of 95 PNdB at 500 ft at takeoff.

  17. Thermodynamic analysis of cascade microcryocoolers with low pressure ratios

    SciTech Connect

    Radebaugh, Ray

    2014-01-29

    The vapor-compression cycle for refrigeration near ambient temperature achieves high efficiency because the isenthalpic expansion of the condensed liquid is a rather efficient process. However, temperatures are limited to about 200 K with a single-stage system. Temperatures down to 77 K are possible with many stages. In the case of microcryocoolers using microcompressors, pressure ratios are usually limited to about 6 or less. As a result, even more stages are required to reach 77 K. If the microcompressors can be fabricated with low-cost wafer-level techniques, then the use of many stages with separate compressors may become a viable option for achieving temperatures of 77 K with high efficiency. We analyze the ideal thermodynamic efficiency of a cascade Joule-Thomson system for various temperatures down to 77 K and with low pressure ratios. About nine stages are required for 77 K, but fewer stages are also analyzed for operation at higher temperatures. For 77 K, an ideal second-law efficiency of 83 % of Carnot is possible with perfect recuperative heat exchangers and 65 % of Carnot is possible with no recuperative heat exchangers. The results are compared with calculated efficiencies in mixed-refrigerant cryocoolers over the range of 77 K to 200 K. Refrigeration at intermediate temperatures is also available. The use of single-component fluids in each of the stages is expected to eliminate the problem of pulsating flow and temperature oscillations experienced in microcryocoolers using mixed refrigerants.

  18. Nonlinear dynamical behavior of thermionic low pressure discharges. I. Simulation

    NASA Astrophysics Data System (ADS)

    Greiner, F.; Klinger, T.; Piel, A.

    1995-06-01

    The discharge modes of a thermionic low pressure discharge (p<1Pa) are investigated with the one-dimensional particle-in-cell simulation codes PDP1 and XPDP1 [C. K. Birdsall, IEEE Trans. Plasma Sci. 19, 65 (1991)]. The simulation results provide a model approach for stable discharge modes, hysteresis, and for nonlinear relaxation-oscillations. During this potential-relaxation instability, nonlinear structures, e.g. electron holes and double layers, are observed. A Pierce-Buneman-mode is suggested as a trigger mechanism for the onset of the instability. The detailed oscillation process can be subdivided into three distinct phases: expansion phase, double layer phase, and relaxation phase. This allows one to explain the parameter dependencies of the oscillation frequency. For a periodically driven discharge, mode-locking in a period-2 state is found and explained by the model. The mode-locking phenomenon is studied systematically. The results of the simulations are well confirmed by experimental observations presented in Part II of this paper [T. Klinger et al., Phys. Plasmas 2, 1822 (1995)].

  19. Nonlinear dynamical behavior of thermionic low pressure discharges. I. Simulation

    SciTech Connect

    Greiner, F.; Klinger, T.; Piel, A.

    1995-06-01

    The discharge modes of a thermionic low pressure discharge ({ital p}{lt}1Pa) are investigated with the one-dimensional particle-in-cell simulation codes PDP1 and XPDP1 [C. K. Birdsall, IEEE Trans. Plasma Sci. {bold 19}, 65 (1991)]. The simulation results provide a model approach for stable discharge modes, hysteresis, and for nonlinear relaxation-oscillations. During this potential-relaxation instability, nonlinear structures, e.g. electron holes and double layers, are observed. A Pierce--Buneman-mode is suggested as a trigger mechanism for the onset of the instability. The detailed oscillation process can be subdivided into three distinct phases: expansion phase, double layer phase, and relaxation phase. This allows one to explain the parameter dependencies of the oscillation frequency. For a periodically driven discharge, mode-locking in a period-2 state is found and explained by the model. The mode-locking phenomenon is studied systematically. The results of the simulations are well confirmed by experimental observations presented in Part II of this paper [T. Klinger {ital et} {ital al}., Phys. Plasmas {bold 2}, 1822 (1995)]. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  20. Downhole steam generator using low pressure fuel and air supply

    DOEpatents

    Fox, Ronald L.

    1983-01-01

    An apparatus for generation of steam in a borehole for penetration into an earth formation wherein a spiral, tubular heat exchanger is used in the combustion chamber to isolate the combustion process from the water being superheated for conversion into steam. The isolation allows combustion of a relatively low pressure oxidant and fuel mixture for generating high enthalpy steam. The fuel is preheated by feedback of combustion gases from the top of the combustion chamber through a fuel preheater chamber. The hot exhaust gases of combustion at the bottom of the combustion chamber, after flowing over the heat exchanger enter an exhaust passage and pipe. The exhaust pipe is mounted inside the water supply line heating the water flowing into the heat exchanger. After being superheated in the heat exchanger, the water is ejected through an expansion nozzle and converts into steam prior to penetration into the earth formation. Pressure responsive doors are provided at a steam outlet downstream of the nozzle and close when the steam pressure is lost due to flameout.

  1. Low pressure characteristics of the multipole resonance probe

    NASA Astrophysics Data System (ADS)

    Brinkmann, Ralf Peter; Oberrath, Jens

    2014-10-01

    The term ``Active plasma resonance spectroscopy'' (APRS) denotes a class of related techniques which utilize, for diagnostic purposes, the natural ability of plasmas to resonate on or near the electron plasma frequency ωpe. The basic idea dates back to the early days of discharge physics but has recently found renewed interest as an approach to industry-compatible plasma diagnostics: A radio frequent signal (in the GHz range) is coupled into the plasma via an antenna or probe, the spectral response is recorded (with the same or another antenna or probe), and a mathematical model is used to determine plasma parameters like the electron density or the electron temperature. When the method is applied to low pressure plasmas (of a few Pa and lower), kinetic effects must be accounted for in the mathematical model. This contribution studies a particular realization of the APRS scheme, the geometrically and electrically symmetric Multipole Resonance Probe (MRP). It is shown that the resonances of the MRP exhibit a residual damping in the limit p --> 0 which cannot be explained by Ohmic dissipation but only by kinetic effects. Supported by the German Federal Ministry of Education and Research (BMBF) in the framework of the PluTO project.

  2. Low pressure high speed Stirling air engine. Final technical report

    SciTech Connect

    Ross, M.A.

    1980-06-16

    The purpose of this project was to design, construct and test a simple, appropriate technology low pressure, high speed, wood-fired Stirling air engine of 100 W output. The final design was a concentric piston/displacer engine of 454 in. bore and 1 in. stroke with a rhombic drive mechanism. The project engine was ultimately completed and tested, using a propane burner for all tests as a matter of convenience. The 100 W aim was exceeded, at atmospheric pressure, over a wide range of engine speed with the maximum power being 112 W at 1150 rpm. A pressure can was constructed to permit pressurization; however the grant funds were running out, and the only pressurized power test attempted was unsuccessful due to seal difficulties. This was a disappointment because numerous tests on the 4 cubic inch engine suggested power would be more than doubled with pressurization at 25 psig. A manifold was designed and constructed to permit operation of the engine over a standard No. 40 pot bellied stove. The engine was run successfully, but at reduced speed and power, over this stove. The project engine started out being rather noisy in operation, but modifications ultimately resulted in a very quiet engine. Various other difficulties and their solutions also are discussed. (LCL)

  3. Downhole steam generator using low pressure fuel and air supply

    SciTech Connect

    Fox, R.L.

    1983-06-28

    An apparatus is claimed for generation of steam in a borehole for penetration into an earth formation wherein a spiral, tubular heat exchanger is used in the combustion chamber to isolate the combustion process from the water being superheated for conversion into steam. The isolation allows combustion of a relatively low pressure oxidant and fuel mixture for generating high enthalpy steam. The fuel is preheated by feedback of combustion gases from the top of the combustion chamber through a fuel preheater chamber. The hot exhaust gases of combustion at the bottom of the combustion chamber, after flowing over the heat exchanger enter an exhaust passage and pipe. The exhaust pipe is mounted inside the water supply line heating the water flowing into the heat exchanger. After being superheated in the heat exchanger, the water is ejected through an expansion nozzle and converts into steam prior to penetration into the earth formation. Pressure responsive doors are provided at a steam outlet downstream of the nozzle and close when the steam pressure is lost due to flameout.

  4. A DSMC Study of Low Pressure Argon Discharge

    NASA Technical Reports Server (NTRS)

    Hash, David B.; Meyyappan, Meyya; Arnold, James O. (Technical Monitor)

    1997-01-01

    Work toward a self-consistent plasma simulation using the DSMC (Direct Simulation Monte Carlo) method for examination of the flowfields of low-pressure high density plasma reactors is presented. Presently, DSMC simulations for these applications involve either treating the electrons as a fluid or imposing experimentally determined values for the electron number density profile. In either approach, the electrons themselves are not physically simulated. Self-consistent plasma DSMC simulations have been conducted for aerospace applications but at a severe computational cost due in part to the scalar architectures on which the codes were employed. The present work attempts to conduct such simulations at a more reasonable cost using a plasma version of the object-oriented parallel Cornell DSMC code, MONACO, on an IBM SP-2. Due to availability of experimental data, the GEC reference cell is chosen to conduct preliminary investigations. An argon discharge is chosen to conduct preliminary investigations. An argon discharge is examined thus affording a simple chemistry set with eight gas-phase reactions and five species: Ar, Ar(+), Ar(*), Ar(sub 2), and e where Ar(*) is a metastable.

  5. Performance assessment of low pressure nuclear thermal propulsion

    NASA Technical Reports Server (NTRS)

    Gerrish, H. P., Jr.; Doughty, G. E.

    1993-01-01

    A low pressure nuclear thermal propulsion (LPNTP) system, which takes advantage of hydrogen dissociation/recombination, was proposed as a means of increasing engine specific impulse (Isp). The effect of hydrogen dissociation/recombination on LPNTP Isp is examined. A two-dimensional computer model was used to show that the optimum chamber pressure is approximately 100 psia (at a chamber temperature of 3,000 K), with an Isp approximately 15 s higher than at 1,000 psia. At high chamber temperatures and low chamber pressures, the increase in Isp is due to both lower average molecular weights caused by dissociation and added kinetic energy from monatomic hydrogen recombination. Monatomic hydrogen recombination increases the Isp more then hydrogen dissociation. Variations in the mole fraction of monatomic hydrogen are similar to variations in static pressure along the axial nozzle position. Most recombination occurs close to the nozzle throat. Practical variations in nozzle geometry have minimal impact on recombination. Other models which can simulate a wider range of nozzle designs should be used in the future. The uncertainty of the hydrogen kinetic reaction rates at high temperatures (approximately 3,000 K) affects the accuracy of the analysis and should be verified with simple bench tests.

  6. Employing a microbolometer as a low pressure sensor

    NASA Astrophysics Data System (ADS)

    Schoeman, J.

    2014-06-01

    Uncooled microbolometers have become extremely popular as low cost thermal detectors used in FPAs for thermal imaging cameras. Most of the emphasis of researchers have gone towards the design and optimisation of device structures, materials, processes and readout electronics with this application in mind. However, microbolometers have the potential to be utilised towards the development of alternate applications. It is well known that the thermal conduction of microbolometers depend on the pressure surrounding the device, as this governs the dominating conduction method. This work investigates the possibility of employing a Ti thinfilm microbolometer as a low pressure sensor. A well known multi-physics simulation environment is utilised to simulate the microbolometer thermoelectric response over varied atmospheric pressure conditions. These simulation results are compared with a much simpler air pressure model than previous works using microbolometers, as well as experimental data, where the fabricated prototype showed a measured device TCR of about 0.085% K-1 and a sensitivity of about 0:701 - 10-9 W K-1 Pa-1.

  7. Observing and Studying Extreme Low Pressure Events with Altimetry

    PubMed Central

    Carrère, Loren; Mertz, Françoise; Dorandeu, Joel; Quilfen, Yves; Patoux, Jerome

    2009-01-01

    The ability of altimetry to detect extreme low pressure events and the relationship between sea level pressure and sea level anomalies during extra-tropical depressions have been investigated. Specific altimeter treatments have been developed for tropical cyclones and applied to obtain a relevant along-track sea surface height (SSH) signal: the case of tropical cyclone Isabel is presented here. The S- and C-band measurements are used because they are less impacted by rain than the Ku-band, and new sea state bias (SSB) and wet troposphere corrections are proposed. More accurate strong altimeter wind speeds are computed thanks to the Young algorithm. Ocean signals not related to atmospheric pressure can be removed with accuracy, even within a Near Real Time context, by removing the maps of sea level anomaly (SLA) provided by SSALTO/Duacs. In the case of Extra-Tropical Depressions, the classical altimeter processing can be used. Ocean signal not related to atmospheric pressure is along-track filtered. The sea level pressure (SLP)-SLA relationship is investigated for the North Atlantic, North Pacific and Indian oceans; three regression models are proposed allowing restoring an altimeter SLP with a mean error of 5 hPa if compared to ECMWF or buoys SLP. The analysis of barotropic simulation outputs points out the regional variability of the SLP/Model Sea Level relationship and the wind effects. PMID:22573955

  8. "Politically-Incorrect" Electron Behavior in Low Pressure RF Discharges

    NASA Astrophysics Data System (ADS)

    Godyak, Valery; Kolobov, Vladimir

    1996-10-01

    The main interaction of plasma electrons with electromagnetic fields for bounded plasma of an rf discharge occurs in the vicinity of its boundaries (in the rf sheath of a capacitive rf discharge and in the skin layer of an inductive one). On the other hand, due to plasma inhomogeneity, a dc ambipolar field is always present in the bounded plasma. in low pressure discharges the ambipolar potential well captures low energy electrons within the discharge center while high energy electrons freely overcome the ambipolar potential and reach the plasma boundaries where heating takes place. Being segregated in space, low energy electrons are discriminated from participation in the heating process. When Coulomb interaction between low and high energy electron groups is weak, their temperatures appear to be essentially different ( a low energy peak on the EEDF). In this presentation we present theoretical and experimental evidence of such an apartheid in the low and high energy electron populations of the EEDF in rf discharge and we outline discharge conditions where such abnormal EEDF behavior is possible.

  9. Observing and studying extreme low pressure events with altimetry.

    PubMed

    Carrère, Loren; Mertz, Françoise; Dorandeu, Joel; Quilfen, Yves; Patoux, Jerome

    2009-01-01

    The ability of altimetry to detect extreme low pressure events and the relationship between sea level pressure and sea level anomalies during extra-tropical depressions have been investigated. Specific altimeter treatments have been developed for tropical cyclones and applied to obtain a relevant along-track sea surface height (SSH) signal: the case of tropical cyclone Isabel is presented here. The S- and C-band measurements are used because they are less impacted by rain than the Ku-band, and new sea state bias (SSB) and wet troposphere corrections are proposed. More accurate strong altimeter wind speeds are computed thanks to the Young algorithm. Ocean signals not related to atmospheric pressure can be removed with accuracy, even within a Near Real Time context, by removing the maps of sea level anomaly (SLA) provided by SSALTO/Duacs. In the case of Extra-Tropical Depressions, the classical altimeter processing can be used. Ocean signal not related to atmospheric pressure is along-track filtered. The sea level pressure (SLP)-SLA relationship is investigated for the North Atlantic, North Pacific and Indian oceans; three regression models are proposed allowing restoring an altimeter SLP with a mean error of 5 hPa if compared to ECMWF or buoys SLP. The analysis of barotropic simulation outputs points out the regional variability of the SLP/Model Sea Level relationship and the wind effects. PMID:22573955

  10. Longitudinal discharge pumped low-pressure XeCl laser

    SciTech Connect

    Fedorov, A I

    2013-10-31

    We have studied output parameters of a XeCl and a N{sub 2} laser pumped by a longitudinal discharge with automatic spark UV preionisation. The output parameters of a low-pressure (30 Torr) XeCl laser operating with Ar, Ne and He as buffer gases or with no buffer gas have been optimised for the first time. The laser generated 5-ns FWHM pulses with an average power of 0.5 mW and output energy of 0.15 mJ. Under longitudinal discharge pumping, an output energy per unit volume of 1.8 J L{sup -1} atm{sup -1} was reached using helium as a buffer gas. With argon-containing and buffer-free mixtures, it was 1.5 J L{sup -1} atm{sup -1}. The N{sub 2} laser generated 2.5-ns FWHM pulses with an average power of 0.35 mW and output energy of 0.05 mJ. (lasers)

  11. Low-pressure pseudospark switches for ICF pulsed power

    NASA Astrophysics Data System (ADS)

    Frank, K.; Bickes, Ch; Ernst, U.; Iberler, M.; Meier, J.; Prucker, U.; Schlaug, M.; Schwab, J.; Urban, J.; Hoffmann, D. H. H.

    Hollow-electrode pseudospark switches are gas-filled, low-pressure, high-current plasma switches which are based on cold cathode emission. They have the capability to satisfy at least a part of switching requirements for different applications in ICF drivers. The main purpose of the submitted paper is therefore to discuss the following realistic ways for the use of pseudospark switches. There are intense international activities aimed at investigating different approaches for the ignition of an ICF capsule. Most of these efforts utilize lasers of varying wavelengths to deliver the energy to initiate the ablation of the target, the compression and ignition of the fuel, and the propagation of the fusion burn. One alternative to this scheme is to provide the drive energy in form of a light ion beam produced by an efficient pulse power accelerator. A related method uses beams of heavy ion beams from high intensity versions of traditional high-energy accelerators. Dependent on the ICF driver for the power conditioning unit (PCU) arise totally different demands. These extremely different requirements mainly rely on the very specific character of the load. Flashlamps, pumping high power lasers represent a non-linear, low-impedance load. Relatively low switching voltage is necessary, but a high charge-transfer capability. Induction cells or magnetic compression units have a high impedance. Consequently high voltage (up to several 100 kV) is required to feed the energy in Marx modules and the following voltage adders produce megavolt voltages, which determines likewise the specific data of the used switch.

  12. Fuel Cells Utilizing Oxygen From Air at Low Pressures

    NASA Technical Reports Server (NTRS)

    Cisar, Alan; Boyer, Chris; Greenwald, Charles

    2006-01-01

    A fuel cell stack has been developed to supply power for a high-altitude aircraft with a minimum of air handling. The fuel cell is capable of utilizing oxygen from ambient air at low pressure with no need for compression. For such an application, it is advantageous to take oxygen from the air (in contradistinction to carrying a supply of oxygen onboard), but it is a challenging problem to design a fuel-cell stack of reasonable weight that can generate sufficient power while operating at reduced pressures. The present fuel-cell design is a response to this challenge. The design features a novel bipolar plate structure in combination with a gas-diffusion structure based on a conductive metal core and a carbon gas-diffusion matrix. This combination makes it possible for the flow fields in the stack to have a large open fraction (ratio between open volume and total volume) to permit large volumes of air to flow through with exceptionally low backpressure. Operations at reduced pressure require a corresponding increase in the volume of air that must be handled to deliver the same number of moles of oxygen to the anodes. Moreover, the increase in the open fraction, relative to that of a comparable prior fuel-cell design, reduces the mass of the stack. The fuel cell has been demonstrated to operate at a power density as high as 105 W/cm2 at an air pressure as low as 2 psia (absolute pressure 14 kPa), which is the atmospheric pressure at an altitude of about 50,000 ft ( 15.2 km). The improvements in the design of this fuel cell could be incorporated into designs of other fuel cells to make them lighter in weight and effective at altitudes higher than those of prior designs. Potential commercial applications for these improvements include most applications now under consideration for fuel cells.

  13. Low pressure granulites from the Bohemian Massif, Upper Austria

    NASA Astrophysics Data System (ADS)

    Sorger, Dominik; Daghighi, Donia; Simic, Katica; Pichler, Ruth; Schwaiger, Christian; Hauzenberger, Christoph; Linner, Manfred; Iglseder, Christoph

    2014-05-01

    Low pressure granulite facies rocks are commonly found in the Bohemian Massif in Upper Austria. They belong to the Moldanubian Unit and were metamorphosed during the last stage of the Variscan orogeny. The investigated granulites from the Donau valley (west of Linz), Lichtenberg (northwest of Linz), Sauwald (south of the river Danube) and Bad Leonfelden zone comprise mainly migmatic paragneisses. Most of these rocks underwent high degrees of melting forming meta- and diatexites (''Perlgneise)''. Al-rich metapelites with partly cm-sized garnet porphyroblasts, which are suitable for precise PT and PT-path determinations, can be found in some localities of this unit. In this study samples taken along the Danube valley between Linz and Wilhering, from Lichtenberg and from Bad Leonfelden (north of Linz) were sampled and investigated petrographically in detail. Since garnets are rare and usually consumed by cordierite, a sample with large garnets was investigated in detail. A chemical zoning profile across the c. 1cm large garnet displayed elevated Ca contents (Xgrs=0.06) in the central part which decreased discontinuously towards the rim to Xgrs=0.02. Almandine, pyrope and spessartine components do not show any pronounced zoning pattern. Most of the smaller garnet grains in other samples are also homogeneous in composition with a slight Xalm increase and Xprp decrease at the rims, typical for retrograde diffusional zoning. The cordierite-garnet-sillimanite-granulites as well as some mafic granulites were used for geothermobarometry. Metamorphic conditions of around 770°C to 850°C and 0.5-0.6 GPa could be obtained, which are similar to the values obtained by Tropper et al. (2006). P. Tropper I. Deibl F. Finger R. Kaindl (2006). P-T-t evolution of spinel-cordierite-garnet gneisses from the Sauwald Zone (Southern Bohemian Massif, Upper Austria): is there evidence for two independent late-Variscan low-P / high-T events in the Moldanubian Unit? Int J Earth Sci (Geol

  14. The NASA Low-Pressure Turbine Flow Physics Program

    NASA Technical Reports Server (NTRS)

    Ashpis, David E.

    1998-01-01

    An overview of the NASA Lewis Low-Pressure Turbine (LPT) Flow Physics Program will be presented. The program was established in response to the aero-engine industry's need for improved LPT efficiency and designs. Modern jet engines have four to seven LPT stages, significantly contributing to engine weight. In addition, there is a significant efficiency degradation between takeoff and cruise conditions, of up to 2 points. Reducing the weight and part count of the LPT and minimizing the efficiency degradation will translate into fuel savings. Accurate prediction methods of LPT flows and losses are needed to accomplish those improvements. The flow in LPT passages is at low Reynolds number, and is dominated by interplay of three basic mechanisms: transition, separation and wake interaction. The affecting parameters traditionally considered are Reynolds number, freestream turbulence intensity, wake frequency parameter, and the pressure distribution (loading). Three-dimensional effects and additional parameters, particularly turbulence characteristics like length scales, spectra and other statistics, as well as wake turbulence intensity and properties also play a role. The flow of most interest is on the suction surface, where large losses are generated as the flow tends to separate at the low Reynolds numbers. Ignoring wakes, a common flow scenario, there is laminar separation, followed by transition on the separation bubble and turbulent reattachment. If transition starts earlier the separation will be eliminated and the boundary layer will be attached leading to the well known bypass transition issues. In contrast, transition over a separation bubble is closer to free shear layer transition and was not investigated as well, particularly in the turbine environment. Unsteadiness created by wakes complicates the picture. Wakes induce earlier transition, and the calmed regions trailing the induced turbulent spots can delay or eliminate separation via shear stress

  15. Electrical breakdown caused by dust motion in low-pressure atmospheres: considerations for Mars.

    PubMed

    Eden, H F; Vonnegut, B

    1973-06-01

    Electrification of agitated dust can cause visible breakdown in a carbon dioxide atmosphere at low pressure in a laboratory experiment. Dust storms on earth become electrified, with accompanying breakdown phenomena. Martian dust storms may reduce the atmospheric conductivity by capturing fast ions on particles, and, by electrifying, may cause discharges in the relatively low pressure atmosphere. PMID:17735929

  16. Seed disinfection effect of atmospheric pressure plasma and low pressure plasma on Rhizoctonia solani.

    PubMed

    Nishioka, Terumi; Takai, Yuichiro; Kawaradani, Mitsuo; Okada, Kiyotsugu; Tanimoto, Hideo; Misawa, Tatsuya; Kusakari, Shinichi

    2014-01-01

    Gas plasma generated and applied under two different systems, atmospheric pressure plasma and low pressure plasma, was used to investigate the inactivation efficacy on the seedborne pathogenic fungus, Rhizoctonia solani, which had been artificially introduced to brassicaceous seeds. Treatment with atmospheric plasma for 10 min markedly reduced the R. solani survival rate from 100% to 3% but delayed seed germination. The low pressure plasma treatment reduced the fungal survival rate from 83% to 1.7% after 10 min and the inactivation effect was dependent on the treatment time. The seed germination rate after treatment with the low pressure plasma was not significantly different from that of untreated seeds. The air temperature around the seeds in the low pressure system was lower than that of the atmospheric system. These results suggested that gas plasma treatment under low pressure could be effective in disinfecting the seeds without damaging them. PMID:24975415

  17. Energy efficient engine low-pressure compressor component test hardware detailed design report

    NASA Technical Reports Server (NTRS)

    Michael, C. J.; Halle, J. E.

    1981-01-01

    The aerodynamic and mechanical design description of the low pressure compressor component of the Energy Efficient Engine were used. The component was designed to meet the requirements of the Flight Propulsion System while maintaining a low cost approach in providing a low pressure compressor design for the Integrated Core/Low Spool test required in the Energy Efficient Engine Program. The resulting low pressure compressor component design meets or exceeds all design goals with the exception of surge margin. In addition, the expense of hardware fabrication for the Integrated Core/Low Spool test has been minimized through the use of existing minor part hardware.

  18. A fast low-pressure transport route to large black phosphorus single crystals

    SciTech Connect

    Nilges, Tom Kersting, Marcel; Pfeifer, Thorben

    2008-08-15

    Black phosphorus, a promising candidate for lithium battery electrodes, can be prepared by a low-pressure transport reaction route representing the first effective and scalable access to this element modification. Crystal sizes larger than 1 cm were obtained at low-pressure conditions in silica ampoules. X-ray phase analyses, EDX, ICP-MS and optical microscopy were applied to characterize the resulting black phosphorus. The present method drastically improves the traditional preparation ways like mercury catalysis, bismuth-flux or high-pressure techniques and represents an easy, non-toxic, fast and highly efficient method to achieve black phosphorus. In contrast to a previously reported low-pressure route the present transport reaction allows an up-scaling to higher masses of starting materials, a larger black phosphorus yield and faster reaction time under retention of the high product crystallinity. - Graphical abstract: A low-pressure transport reaction route representing the first effective and scalable access to black phosphorus.

  19. IMPROVING DESIGN AND OPERATION OF HEAT TREATMENT/LOW PRESSURE OXIDATION SYSTEMS

    EPA Science Inventory

    The purpose of the investigation is to document possible improvements to design, operation, and maintenance of heat treatment and low pressure oxidation systems for conditioning sludge prior to dewatering in municipal wastewater treatment plants. The information in the report is ...

  20. Use of thermodynamic properties of metal-gas systems as low-pressure standards

    NASA Technical Reports Server (NTRS)

    Lundin, C. E.

    1970-01-01

    Modified version of Sievert's apparatus accurately calibrates low pressure measuring instruments. Metal-gas system is composed of hydrogen in two-phase equilibrium with erbium to obtain reproducible hydrogen pressures.

  1. Growth and mitochondrial respiration of mungbeans (Phaseolus aureus Roxb.) germinated at low pressure

    NASA Technical Reports Server (NTRS)

    Musgrave, M. E.; Gerth, W. A.; Scheld, H. W.; Strain, B. R.

    1988-01-01

    Mungbean (Phaseolus aureus Roxb.) seedlings were grown hypobarically to assess the effects of low pressure (21-24 kilopascals) on growth and mitochondrial respiration. Control seedlings grown at ambient pressure (101 kilopascals) were provided amounts of O2 equivalent to those provided experimental seedlings at reduced pressure to factor out responses to O2 concentration and to total pressure. Respiration was assayed using washed mitochondria, and was found to respond only to O2 concentration. Regardless of total pressure, seedlings grown at 2 millimoles O2 per liter had higher state 3 respiration rates and decreased percentages of alternative respiration compared to ambient (8.4 millimoles O2 per liter) controls. In contrast, seedling growth responded to total pressure but not to O2 concentration. Seedlings were significantly larger when grown under low pressure. While low O2 (2 millimoles O2 per liter) diminished growth at ambient pressure, growth at low pressure in the same oxygen concentration was enhanced. Respiratory development and growth of mungbean seedlings under low pressure is unimpaired whether oxygen or air is used as the chamber gas, and further, low pressure can improve growth under conditions of poor aeration.

  2. Low pressure drop airborne molecular contaminant filtration using open-channel networks

    NASA Astrophysics Data System (ADS)

    Dallas, Andrew J.; Ding, Lefei; Joriman, Jon; Zastera, Dustin; Seguin, Kevin; Empson, James

    2006-03-01

    Airborne molecular contamination (AMC) continues to play a very decisive role in the performance of many microelectronic devices and manufacturing processes. Currently, the state of the filtration industry is such that optimum filter life and removal efficiency for AMC is offered by granular filter beds. However, the attributes that make packed beds of adsorbents extremely efficient also impart issues related to elevated filter weight and pressure drop. Most of the low pressure drop AMC filters currently offered tend to be quiet costly and contaminant nonspecific. Many of these low pressure drop filters are simply pleated combinations of various adsorptive and reactive media. On the other hand, low pressure drop filters, such as those designed as open-channel networks (OCNs), can still offer good filter life and removal efficiency, with the additional benefits of significant reductions in overall filter weight and pressure drop. Equally important for many applications, the OCN filters can reconstruct the airflow so as to enhance the operation of a tool or process. For tool mount assemblies and full fan unit filters this can result in reduced fan and blower speeds, which subsequently can provide reduced vibration and energy costs. Additionally, these low pressure drop designs can provide a cost effective way of effectively removing AMC in full fab (or HVAC) filtration applications without significantly affecting air-handling requirements. Herein, we will present a new generation of low pressure drop OCN filters designed for AMC removal in a wide range of applications.

  3. Sensitive Measurement of Trace Mercury Using Low Pressure Laser-Induced Plasma

    NASA Astrophysics Data System (ADS)

    Wang, Zhenzhen; Deguchi, Yoshihiro; Kuwahara, Masakazu; Zhang, Xiaobo; Yan, Junjie; Liu, Jiping

    2013-11-01

    The emission of trace heavy metals, such as mercury (Hg), from power plants and other industries is a severe environmental problem concerning the public health. The laser-induced plasma technique was employed to measure Hg under various conditions, which reveals several merits of this method at low pressure. The main interferences of laser-induced breakdown spectroscopy (LIBS), which include the black-body-like emission from plasma itself and coexisting molecular and atomic emissions, decreased significantly using low pressure laser-induced plasma. Under low pressure conditions, Hg signal was rather clear without serious influence even if there is no delay time from the laser irradiation, which means the gated detection device is not necessary. This method featured the detection limit of 0.3 ppm at pressure 700 Pa. Additionally, the feasible of this method in real applications was demonstrated by measuring Hg in combustion gas which performed preferable results.

  4. Experimental and Numerical Investigation of Losses in Low-Pressure Turbine Blade Rows

    NASA Technical Reports Server (NTRS)

    Dorney, Daniel J.; Lake, James P.; King, Paul I.; Ashpis, David E.

    2000-01-01

    Experimental data and numerical simulations of low-pressure turbines have shown that unsteady blade row interactions and separation can have a significant impact on the turbine efficiency. Measured turbine efficiencies at takeoff can be as much as two points higher than those at cruise conditions. Several recent studies have revealed that the performance of low-pressure turbine blades is a strong function of the Reynolds number. In the current investigation, experiments and simulations have been performed to study the behavior of a low-pressure turbine blade at several Reynolds numbers. Both the predicted and experimental results indicate increased cascade losses as the Reynolds number is reduced to the values associated with aircraft cruise conditions. In addition, both sets of data show that tripping the boundary layer helps reduce the losses at lower Reynolds numbers. Overall, the predicted aerodynamic and performance results exhibit fair agreement with experimental data.

  5. Low-pressure airlift fermenter for single cell protein production: II. Continuous culture of Pichia yeast

    SciTech Connect

    Chen, N.Y.; Srinivasan, S.; Leavitt, R.I.; Coty, V.F.; Kondis, E.F.

    1987-03-01

    Experiments using Pichia yeast grown on n-paraffins have been conducted in laboratory 10-l airlift fermenters and in a 640-l module of commercial scale. Results confirmed the design concept with low-pressure air. However, in the absence of mass transport constraints, the build up of toxic factors in the fermenter appeared to a major variable limiting cell productivity. Foaming in the large fermenter also presented a serious problem, which must be solved before low-pressure airlift fermenters become practical. 14 references.

  6. Synthesis of lithium cobalt oxide using low-pressure spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Hidayat, Darmawan; Joni, I. Made; Setianto, Panatarani, Camellia; Okuyama, Kikuo

    2013-09-01

    A low pressure spray pyrolysis (LPSP) process was applied to synthesize crystalline lithium cobalt oxide as a battery cathode material via a liquid route. The effects of temperature and pressure of reactor on the synthesized particles characteristics were systematically investigated. Reactor temperatures of 800, 1000 and 1200 °C with pressures of 760 and 300 Torr were applied as operating conditions. The characterizations results show that the synthesized particles were highly crystalline and nearly spherical in shape. The results concluded that the low-pressure spray pyrolysis method has ability in control of particles morphology, crystallinity and atomic lithium-to-cobalt ratio.

  7. Generalization of low pressure, gas-liquid, metastable sound speed to high pressures

    NASA Technical Reports Server (NTRS)

    Bursik, J. W.; Hall, R. M.

    1981-01-01

    A theory is developed for isentropic metastable sound propagation in high pressure gas-liquid mixtures. Without simplification, it also correctly predicts the minimum speed for low pressure air-water measurements where other authors are forced to postulate isothermal propagation. This is accomplished by a mixture heat capacity ratio which automatically adjusts from its single phase values to approximately the isothermal value of unity needed for the minimum speed. Computations are made for the pure components parahydrogen and nitrogen, with emphasis on the latter. With simplifying assumptions, the theory reduces to a well known approximate formula limited to low pressure.

  8. Two-Dimensional Plasma Density Distributions in Low-Pressure Gas Discharges

    SciTech Connect

    Berlin, E.V.; Dvinin, S.A.; Mikheev, V.V.; Omarov, M.O.; Sviridkina, V. S.

    2004-12-15

    The plasma density distribution in a two-dimensional nonuniform positive column of a low-pressure gas discharge is studied in the hydrodynamic approximation with allowance for ion inertia. Exact solutions are derived for discharges in a rectangular and a cylindrical chamber. Asymptotic solutions near the coordinate origin and near the critical surface are considered. It is shown that, for potential plasma flows, the flow velocity component normal to the plasma boundary is equal to the ion acoustic velocity. The results obtained can be used to analyze the processes occurring in low-pressure plasmochemical reactors.

  9. Study of Low Reynolds Number Effects on the Losses in Low-Pressure Turbine Blade Rows

    NASA Technical Reports Server (NTRS)

    Dorney, Daniel J.; Ashpis, David E.

    1998-01-01

    Experimental data from jet-engine tests have indicated that unsteady blade row interactions and separation can have a significant impact on the efficiency of low-pressure turbine stages. Measured turbine efficiencies at takeoff can be as much as two points higher than those at cruise conditions. Several recent studies have revealed that Reynolds number effects may contribute to the lower efficiencies at cruise conditions. In the current study numerical experiments have been performed to study the models available for low Reynolds number flows, and to quantify the Reynolds number dependence of low-pressure turbine cascades and stages. The predicted aerodynamic results exhibit good agreement with design data.

  10. Low-pressure indium-halide discharges for fluorescent illumination applications

    NASA Astrophysics Data System (ADS)

    Hayashi, Daiyu; Hilbig, Rainer; Körber, Achim; Schwan, Stefan; Scholl, Robert; Boerger, Martin; Huppertz, Maria

    2010-02-01

    Low-pressure gas discharges of molecular radiators were studied for fluorescent lighting applications with a goal of reducing the energy loss due to the large Stokes shift in phosphors of conventional mercury-based fluorescent lamp technology. Indium halides (InCl, InBr, and InI) were chosen as the molecular radiators that generate ultraviolet to blue light emissions. The electrical characteristics and optical emission intensities were measured in discharges containing gaseous indium halides (InCl, InBr, and InI) as molecular radiators. The low-pressure discharges in indium halide vapor showed potential as a highly efficient gas discharge system for fluorescent lighting application.

  11. FINAL REPORT FOR LOW PRESSURE TESTS OF THE CPU-400 PILOT PLANT

    EPA Science Inventory

    This report presents the progress made during the component design phase of a program to develop an economical and environmentally safe waste-energy system known as the CPU-400. It discusses the hardware development and low pressure testing performed to evaluate CPU-400 operation...

  12. Low pressure glow discharge in a system with hollow electrode at floating potential

    NASA Astrophysics Data System (ADS)

    Babinov, N. A.

    2016-01-01

    This article describes the research of the low pressure gas discharge in a system with hollow electrode at the floating potential. The main characteristic features of the discharge distinguishing it from the glow discharge with hollow cathode are described. The studied type of discharge has good perspective to use in the plasma emission systems allowing to reach high current efficiency of the ion sources.

  13. 49 CFR 192.623 - Maximum and minimum allowable operating pressure; Low-pressure distribution systems.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 false Maximum and minimum allowable operating pressure; Low-pressure distribution systems. 192.623 Section 192.623 Transportation Other Regulations Relating... SAFETY STANDARDS Operations § 192.623 Maximum and minimum allowable operating pressure;...

  14. SEPARATION OF HAZARDOUS ORGANICS BY LOW PRESSURE REVERSE OSMOSIS MEMBRANES - PHASE II FINAL REPORT

    EPA Science Inventory

    Extensive experimental studies showed that thin-film, composite membranes can be used effectively for the separation of selected hazardous organic compounds. This waste treatment technique offers definite advantages in terms of high solute separations at low pressures (<2MPa) and...

  15. Effect of Relative Humidity and Product Moisture on Efficacy of Low Pressure Treatments Against Indianmeal Moth

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Low pressure treatment in flexible PVC containers is a potential alternative to chemical fumigants for California tree nuts. Laboratory studies investigated the effect of relative humidity and product moisture on weight loss and mortality of diapausing and non-diapausing larvae of the Indianmeal mo...

  16. Tolerance of codling moth and apple quality associated with low-pressure/low-temperature treatments

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Development of effective low-pressure/low-temperature (LPLT) disinfestation treatments for fresh fruits requires knowledge on the tolerance of target insects to the LPLT treatment environment. In this study, different life stages of codling moth (eggs, 2nd-3rd instar larvae, 5th instar larvae and pu...

  17. An improved process for high nutrition of germinated brown rice production: Low-pressure plasma.

    PubMed

    Chen, Hua Han; Chang, Hung Chia; Chen, Yu Kuo; Hung, Chien Lun; Lin, Su Yi; Chen, Yi Sheng

    2016-01-15

    Brown rice was exposed to low-pressure plasma ranging from 1 to 3kV for 10min. Treatment of brown rice in low-pressure plasma increases the germination percentage, seedling length, and water uptake in laboratory germination tests. Of the various treatments, 3-kV plasma exposure for 10min yielded the best results. In germinating brown rice, α-amylase activity was significantly higher in treated groups than in controls. The higher enzyme activity in plasma-treated brown rice likely triggers the rapid germination and earlier vigor of the seedlings. Low-pressure plasma also increased gamma-aminobutyric acid (GABA) levels from ∼19 to ∼28mg/100g. In addition, a marked increase in the antioxidant activity of brown rice was observed with plasma treatments compared to controls. The main finding of this study indicates that low-pressure plasma is effective at enhancing the growth and GABA accumulation of germinated brown rice, which can supply high nutrition to consumer. PMID:26258710

  18. ASSESSING THE EFFECTIVENESS OF LOW PRESSURE ULTRAVIOLET LIGHT FOR INACTIVATING HELICOBACTER PYLORI

    EPA Science Inventory

    Three strains of Helicobacter pylori were exposed to ultraviolet (UV) light from a low-pressure source to determine log inactivation versus applied fluence. Results indicate that H. pylori is readily inactivated at UV fluences typically used in water treatment r...

  19. SEPARATION OF HAZARDOUS ORGANICS BY LOW PRESSURE REVERSE OSMOSIS MEMBRANES - PHASE II FINAL REPORT

    EPA Science Inventory

    Extensive experimental studies shoved that thin-film, composite membranes can be used effectively for the separation of selected hazardous organic compounds. his waste treatment technique offers definite advantages in terms of high solute separations at low pressures (<2MPa) and ...

  20. Shrinkage behavior of low profile unsaturated polyester resins at low temperature and low pressure

    SciTech Connect

    Wen Li; Lee, L.J.

    1996-12-31

    In order to achieve excellent surface quality and dimension control of molded polymer composites, low profile additives (LPA) are widely used in low shrinkage unsaturated polyester (UPE) molding compound. Although the detailed LPA mechanism is still a subject of controversy, it is now generally agreed that the most important factor for the low profile behavior is the strong phase separation between LPA and UPE resin during curing. Among the extensive studies of LPA mechanism, most of the work focused on the reaction at high temperatures, since LPAs found most of their applications in high temperature and high pressure processes like sheet molding compound (SMC) and bulk molding compound (BMC). Recently, because of the growing interests of new processes such as low pressure SMC and vacuum infusion resin transfer molding, low shrinkage molding compound with the ability to be processed at low temperature and low pressure have attracted considerable attention from the composite industry. Therefore, further understanding of the low profile mechanism at low temperature and low pressure cure is necessary. Moreover, the relatively long reaction time at low temperature cure provides an opportunity to decouple the factors such as phase separation and microvoid formation, which occur almost at the same time in high temperature cure. The objective of this study is to determine LPA performance as well as to provide a better understanding of low profile mechanism at low temperature and low pressure.

  1. The beauty of frost: nano-sulfur assembly via low pressure vapour deposition.

    PubMed

    Wang, Yu; Chen, Lu; Scudiero, Louis; Zhong, Wei-Hong

    2015-11-14

    A low pressure vapour deposition (LPVD) technique is proposed as an environmentally friendly, cost-effective and versatile strategy for fabrication of sulfur nanomaterials. By controlling the characteristics of the deposit substrate for the LPVD, various sulfur-based nanomaterials have been obtained through a substrate-induced self-assembly process. PMID:26383233

  2. High- and low-pressure pneumotachometers measure respiration rates accurately in adverse environments

    NASA Technical Reports Server (NTRS)

    Fagot, R. J.; Mc Donald, R. T.; Roman, J. A.

    1968-01-01

    Respiration-rate transducers in the form of pneumotachometers measure respiration rates of pilots operating high performance research aircraft. In each low pressure or high pressure oxygen system a sensor is placed in series with the pilots oxygen supply line to detect gas flow accompanying respiration.

  3. An Engine Research Program Focused on Low Pressure Turbine Aerodynamic Performance

    NASA Technical Reports Server (NTRS)

    Castner, Raymond; Wyzykowski, John; Chiapetta, Santo; Adamczyk, John

    2002-01-01

    A comprehensive test program was performed in the Propulsion Systems Laboratory at the NASA Glenn Research Center, Cleveland Ohio using a highly instrumented Pratt and Whitney Canada PW 545 turbofan engine. A key objective of this program was the development of a high-altitude database on small, high-bypass ratio engine performance and operability. In particular, the program documents the impact of altitude (Reynolds Number) on the aero-performance of the low-pressure turbine (fan turbine). A second objective was to assess the ability of a state-of-the-art CFD code to predict the effect of Reynolds number on the efficiency of the low-pressure turbine. CFD simulation performed prior and after the engine tests will be presented and discussed. Key findings are the ability of a state-of-the art CFD code to accurately predict the impact of Reynolds Number on the efficiency and flow capacity of the low-pressure turbine. In addition the CFD simulations showed the turbulent intensity exiting the low-pressure turbine to be high (9%). The level is consistent with measurements taken within an engine.

  4. Review of recent developments and applications in low-pressure (vacuum outlet) gas chromatography

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The concept of low pressure (LP) vacuum outlet gas chromatography (GC) was introduced more than 50 years ago, but it was not until the 2000s that its theoretical applicability to fast analysis of GC-amenable chemicals was realized. In practice, LPGC is implemented by placing the outlet of a short, ...

  5. SEPARATION OF HAZARDOUS ORGANICS BY LOW PRESSURE MEMBRANES: TREATMENT OF SOIL-WASH RINSE WATER LEACHATES

    EPA Science Inventory

    Soil washing is a promising technology for treating contaminated soils. n the present work, low-pressure, thin-film composite membranes were evaluated to treat he soil-wash leachates so that the treated water could be recycled back to the soil washing step. Experiments were done ...

  6. Engine having a high pressure hydraulic system and low pressure lubricating system

    DOEpatents

    Bartley, Bradley E.; Blass, James R.; Gibson, Dennis H.

    2000-01-01

    An engine includes a high pressure hydraulic system having a high pressure pump and at least one hydraulically-actuated device attached to an engine housing. A low pressure engine lubricating system is attached to the engine housing and includes a circulation conduit fluidly connected to an outlet from the high pressure pump.

  7. One-trip, multizone gravel-packing technique for low-pressure, shallow wells

    SciTech Connect

    Welrich, J.B.; Zaleski, T.E. Jr.; Tyler, S.L. )

    1990-11-01

    This paper describes a one-trip, multizone gravel-packing technique designed for use in short-zoned, shallow, low-pressure wells. The system, which allows several zones to be completed with a single gravel-pack assembly, has been adapted for use in both standard and thermal applications.

  8. Performance of a 13-Stage Development Compressor for the J40-WE-24 Engine at Equivalent Speeds from 30 to 112 Percent of Design

    NASA Technical Reports Server (NTRS)

    Hatch, James E.; Lucas, James G.; Finger, Harold B.

    1953-01-01

    The performance of a 13-stage development comressor for the J40-WE-24 engine has been determined at equivalent speeds from 30 to 112 percent of design. The design total-pressure ratio of 6.0 and the design weight flow of 164 pounds per second were not attained, An analysis was conducted to determine the reasons for the poor performance at the design and over-design speed. The analysis indicated that most of the difficulty could be attributed to the fact that the first stage was overcompromised to favor part-speed performance,

  9. First considerations on the structure and development of the Iberian thermal low-pressure system ()

    NASA Astrophysics Data System (ADS)

    Alonso, S.; Portela, A.; Ramis, C.

    1994-05-01

    During the summer a thermal low-pressure system is locked over the Iberian Peninsula. We present a first analysis of such a system using the potential vorticity approach. Our results show that its main characteristic is the existence of a negative potential vorticity (PV) dome and a funnel-like structure for potential temperature, both located at the centre of the low. The build-up and evolution of this PV dome can be understood in terms of the dot products of the absolute vorticity and the gradient of diabetic heating vectors and the curl of the friction forces and the gradient of potential temperature vectors. The inhibition of the Algerian Mediterranean cyclogenesis during the summer seems to bear some relation to the existence of this kind of low-pressure disturbance over the Iberian Peninsula.

  10. Exploring the limits: A low-pressure, low-temperature Haber-Bosch process

    NASA Astrophysics Data System (ADS)

    Vojvodic, Aleksandra; Medford, Andrew James; Studt, Felix; Abild-Pedersen, Frank; Khan, Tuhin Suvra; Bligaard, T.; Nørskov, J. K.

    2014-04-01

    The Haber-Bosch process for ammonia synthesis has been suggested to be the most important invention of the 20th century, and called the ‘Bellwether reaction in heterogeneous catalysis’. We examine the catalyst requirements for a new low-pressure, low-temperature synthesis process. We show that the absence of such a process for conventional transition metal catalysts can be understood as a consequence of a scaling relation between the activation energy for N2 dissociation and N adsorption energy found at the surface of these materials. A better catalyst cannot obey this scaling relation. We define the ideal scaling relation characterizing the most active catalyst possible, and show that it is theoretically possible to have a low pressure, low-temperature Haber-Bosch process. The challenge is to find new classes of catalyst materials with properties approaching the ideal, and we discuss the possibility that transition metal compounds have such properties.

  11. Heat pump employing optimal refrigerant compressor for low pressure ratio applications

    DOEpatents

    Ecker, Amir L.

    1982-01-01

    What is disclosed is a heat pump apparatus for conditioning a fluid characterized by a fluid handler for circulating the fluid in heat exchange relationship with a refrigerant fluid; two refrigerant heat exchangers; one for effecting the heat exchange with the fluid and a second refrigerant-heat exchange fluid heat exchanger for effecting a low pressure ratio of compression of the refrigerant; a rotary compressor for compressing the refrigerant with low power consumption at the low pressure ratio; at least one throttling valve connecting at the inlet side of heat exchanger in which liquid refrigerant is vaporized; a refrigerant circuit serially connecting the above elements; refrigerant in the circuit; a source of heat exchange fluid; heat exchange fluid circulating device and heat exchange fluid circuit for circulating the heat exchange fluid in heat exchange relationship with the refrigerant.

  12. Mixing unmixables: Unexpected formation of Li-Cs alloys at low pressure

    PubMed Central

    Desgreniers, Serge; Tse, John S.; Matsuoka, Takahiro; Ohishi, Yasuo; Tse, Justin J.

    2015-01-01

    Contrary to the empirical Miedema and Hume-Rothery rules and a recent theoretical prediction, we report experimental evidence on the formation of Li-Cs alloys at very low pressure (>0.1 GPa). We also succeeded in synthesizing a pure nonstoichiometric and ordered crystalline phase from an approximately equimolar mixture and resolved its structure using the maximum entropy method. The new alloy has a primitive cubic cell with the Li atom situated in the center and the Cs at the corners. This structure is stable to at least 10 GPa and has an anomalously high coefficient of thermal expansion at low pressure. Analysis of the valence charge density shows that electrons are donated from Cs to the Li “p”-orbitals, resulting in a rare formal oxidation state of −1 for Li. The observation indicates the diversity in the bonding of the seeming simple group I Li element. PMID:26601304

  13. Low-pressure airlift fermenter for single cell protein production. I. Design and oxygen transfer studies

    SciTech Connect

    Chen, N.Y.; Kondis, E.F.; Srinivasan, S.

    1987-03-01

    The energy consumption of a fermenter constitutes a major part of the operating expense of a single cell protein process. A low-pressure airlift fermenter was designed to reduce this cost. In this new design, the fermenter broth is kept below 120 cm in depth, and air alone is employed to fulfil the need of supplying oxygen, and cooling and agitating the broth. The use of low-pressure air from air blowers instead of air compressors lowers the capital cost of air delivery and reduces the energy consumption in the fermenter section to below 1 kWh/kg protein, a saving of over 70% as compared to a conventional stirred tank fermenter. It also eliminates the investment of mechanical agitators, heat exchangers, and air compressors. Sulfite oxidation studies confirmed the design concepts. 30 references.

  14. Effect of Coulomb scattering on low-pressure high-density electronegative discharges.

    PubMed

    Kawamura, E; Birdsall, C K

    2005-02-01

    For electronegative plasmas with low gas pressure and high ion densities, we expect Coulomb collisions between positive and negative ions to dominate over collisions between ions and neutrals. We incorporated Nanbu's cumulative small-angle collision method [K. Nanbu, Phys. Rev. E, 55, 4642 (1997)] into our one-dimensional three-velocity-component particle-in-cell code PDP1 in order to study the effect of Coulomb collisions on low pressure high density electronegative discharges. Nanbu's method treats a succession of small-angle binary collisions as a single binary collision with a large scattering angle, which is far faster than treating each individual small-angle collision. We find that Coulomb collisions between positive and negative ions in low-pressure high-density electronegative discharges significantly modify the negative ion flux, density, and kinetic energy profiles. PMID:15783425

  15. Effect of Coulomb scattering on low-pressure high-density electronegative discharges

    SciTech Connect

    Kawamura, E.; Birdsall, C.K.

    2005-02-01

    For electronegative plasmas with low gas pressure and high ion densities, we expect Coulomb collisions between positive and negative ions to dominate over collisions between ions and neutrals. We incorporated Nanbu's cumulative small-angle collision method [K. Nanbu, Phys. Rev. E, 55, 4642 (1997)] into our one-dimensional three-velocity-component particle-in-cell code PDP1 in order to study the effect of Coulomb collisions on low pressure high density electronegative discharges. Nanbu's method treats a succession of small-angle binary collisions as a single binary collision with a large scattering angle, which is far faster than treating each individual small-angle collision. We find that Coulomb collisions between positive and negative ions in low-pressure high-density electronegative discharges significantly modify the negative ion flux, density, and kinetic energy profiles.

  16. Finite Element Modeling and Analysis of Powder Stream in Low Pressure Cold Spray Process

    NASA Astrophysics Data System (ADS)

    Goyal, Tarun; Walia, Ravinderjit Singh; Sharma, Prince; Sidhu, Tejinder Singh

    2016-07-01

    Low pressure cold gas dynamic spray (LPCGDS) is a coating process that utilize low pressure gas (5-10 bars instead of 25-30 bars) and the radial injection of powder instead of axial injection with the particle range (1-50 μm). In the LPCGDS process, pressurized compressed gas is accelerated to the critical velocity, which depends on length of the divergent section of nozzle, the propellant gas and particle characteristics, and the diameters ratio of the inlet and outer diameters. This paper presents finite element modeling (FEM) of powder stream in supersonic nozzle wherein adiabatic gas flow and expansion of gas occurs in uniform manner and the same is used to evaluate the resultant temperature and velocity contours during coating process. FEM analyses were performed using commercial finite volume package, ANSYS CFD FLUENT. The results are helpful to predict the characteristics of powder stream at the exit of the supersonic nozzle.

  17. YBa2Cu3O7-δ superconducting films prepared by low pressure post-annealing

    NASA Astrophysics Data System (ADS)

    Wang, Lianhong; Liu, Chong; Fan, Jing

    2014-12-01

    YBa2Cu3O7-δ precursor films are deposited on 2″ LaAlO3 wafer by the co-evaporation technique using Y, BaF2 and Cu as evaporation sources. After deposition, the films are annealed at low-pressure atmosphere with the composition of oxygen and water vapour. Compared with the normal pressure annealing, it is shown that low pressure can greatly improve the superconducting properties of 2″ YBCO films with thickness larger than 500 nm, as the microcrack on films surface becomes unobservable the microwave surface resistance is greatly reduced. Furthermore, it is also revealed that the optimal processing window for making high quality superconducting YBCO films through ex-situ process is relatively small, therefore the ambient in annealing furnace is crucial important and should be precisely controlled.

  18. A thermal energy storage system for adsorbent low-pressure natural gas storage

    SciTech Connect

    Blazek, C.F.; Jasionowski, W.J.; Kountz, K.J.; Tiller, A.J.; Gauthier, S.W.; Takagishi, S.K.

    1992-12-31

    Carbon-based adsorbents were determined to be the best enhanced storage media that would store more natural gas at low pressures than achieved with compression only. Thermal energy storage (TES) was previously demonstrated to be a potentially promising technique to mitigate heat effects associated with low-pressure carbon adsorption systems for natural gas storage. Further investigations were conducted to develop information for the design of an optimized adsorption system that incorporates TES heat management. The selection of appropriate phase-change materials and nucleating agents, encapsulant materials, and corrosion inhibitors for a TES heat management system are discussed and the results of extended thermal cyclic behavior are presented. Engineering analyses and finite element analyses are employed to calculate adsorption rates, heat generation, temperatures, and heat transfer within the adsorbent bed. The size, volume, and arrangement of components for an operational TES system designed to accommodate fast-fill within a defined time limit is presented.

  19. A thermal energy storage system for adsorbent low-pressure natural gas storage

    SciTech Connect

    Blazek, C.F.; Jasionowski, W.J.; Kountz, K.J.; Tiller, A.J. ); Gauthier, S.W.; Takagishi, S.K. )

    1992-01-01

    Carbon-based adsorbents were determined to be the best enhanced storage media that would store more natural gas at low pressures than achieved with compression only. Thermal energy storage (TES) was previously demonstrated to be a potentially promising technique to mitigate heat effects associated with low-pressure carbon adsorption systems for natural gas storage. Further investigations were conducted to develop information for the design of an optimized adsorption system that incorporates TES heat management. The selection of appropriate phase-change materials and nucleating agents, encapsulant materials, and corrosion inhibitors for a TES heat management system are discussed and the results of extended thermal cyclic behavior are presented. Engineering analyses and finite element analyses are employed to calculate adsorption rates, heat generation, temperatures, and heat transfer within the adsorbent bed. The size, volume, and arrangement of components for an operational TES system designed to accommodate fast-fill within a defined time limit is presented.

  20. Finite Element Modeling and Analysis of Powder Stream in Low Pressure Cold Spray Process

    NASA Astrophysics Data System (ADS)

    Goyal, Tarun; Walia, Ravinderjit Singh; Sharma, Prince; Sidhu, Tejinder Singh

    2016-05-01

    Low pressure cold gas dynamic spray (LPCGDS) is a coating process that utilize low pressure gas (5-10 bars instead of 25-30 bars) and the radial injection of powder instead of axial injection with the particle range (1-50 μm). In the LPCGDS process, pressurized compressed gas is accelerated to the critical velocity, which depends on length of the divergent section of nozzle, the propellant gas and particle characteristics, and the diameters ratio of the inlet and outer diameters. This paper presents finite element modeling (FEM) of powder stream in supersonic nozzle wherein adiabatic gas flow and expansion of gas occurs in uniform manner and the same is used to evaluate the resultant temperature and velocity contours during coating process. FEM analyses were performed using commercial finite volume package, ANSYS CFD FLUENT. The results are helpful to predict the characteristics of powder stream at the exit of the supersonic nozzle.

  1. Instantaneous and efficient surface wave excitation of a low pressure gas or gases

    DOEpatents

    Levy, Donald J.; Berman, Samuel M.

    1988-01-01

    A system for instantaneously ionizing and continuously delivering energy in the form of surface waves to a low pressure gas or mixture of low pressure gases, comprising a source of rf energy, a discharge container, (such as a fluorescent lamp discharge tube), an rf shield, and a coupling device responsive to rf energy from the source to couple rf energy directly and efficiently to the gas or mixture of gases to ionize at least a portion of the gas or gases and to provide energy to the gas or gases in the form of surface waves. The majority of the rf power is transferred to the gas or gases near the inner surface of the discharge container to efficiently transfer rf energy as excitation energy for at least one of the gases. The most important use of the invention is to provide more efficient fluorescent and/or ultraviolet lamps.

  2. Properties of a low-pressure inductive RF discharge I: Experiment

    SciTech Connect

    Aleksandrov, A. F.; Vavilin, K. V.; Kral'kina, E. A.; Pavlov, V. B.; Rukhadze, A. A.

    2007-09-15

    Results are presented from experimental studies of low-pressure inductive RF discharges (including those with a capacitive component) employed in plasma technology. It is shown that both the RF power absorbed in the plasma and the electron density depend nonmonotonically on the external magnetic field. Discharge disruptions occurring at critical values of the magnetic field and the spatial redistribution and hysteresis of the plasma parameters were observed when varying the magnetic field and RF generator power. The parameters of the plasma of low-pressure (0.5-5 mTorr) inductive RF discharges were investigated, and the discharge properties related to the redistribution of the RF generator power between the plasma and the discharge external circuit were revealed. The experiments were performed with both conventional unmagnetized inductive plasma sources and plasma sources with a magnetic field.

  3. Energetic Ion Beam Production by a Low-Pressure Plasma Focus Discharge

    SciTech Connect

    Lim, L. K.; Yap, S. L.; Wong, C. S.

    2011-03-30

    Energetic ion beam emissions in a 3 kJ Mather type plasma focus operating at low-pressure regime are investigated. Deuterium gas is used and the discharge is operated in a low-pressure regime of below 1 mbar. Formation of the current sheath during the breakdown phase at the back wall is assisted by a set delayed trigger pulse. Energetic and intense ion beams with good reproducibility have been obtained for the operating pressure ranging from 0.05 mbar to 0.5 mbar. Deuteron beam is determined by time resolved measurement by making use of three biased ion collectors placed at the end on direction. The average energies of deuteron beams are resolved by using time-of flight method. Correlation between the ion emissions and the current sheath dynamics is also discussed.

  4. Germination of white radish, buckwheat and qing-geng-cai under low pressure in closed environment.

    PubMed

    Hinokuchi, Tsutomu; Oshima, Satoshi; Hashimoto, Hirofumi

    2004-11-01

    In order to cultivate plants under low pressure in closed environment, the germination rate of seeds of white radish was investigated under low pressure, low oxygen partial pressure and condition of pure oxygen. The result of these experiments showed that the germination rate was affected by the oxygen partial pressure. From this fact, it is possible to lower the total pressure by using only the pure oxygen in germination. Furthermore, the germination rates of seeds of buckwheat and qing-geng-cai were also investigated in pure oxygen for the comparison. Consequently, though tendency in germination rate of white radish was similar to qing-geng-cai, it was different from buckwheat. PMID:15858367

  5. Numerical Study of In-flight Particle Parameters in Low-Pressure Cold Spray Process

    NASA Astrophysics Data System (ADS)

    Ning, Xian-Jin; Wang, Quan-Sheng; Ma, Zhuang; Kim, Hyung-Jun

    2010-12-01

    A 2-D model of the low-pressure cold spray with a radial powder feeding was established using CFD software in this study. The flow field was simulated for both propellant gases of nitrogen and helium. To predict the in-flight particle velocity and temperature, discrete phase model was introduced to simulate the interaction of particle and the supersonic gas jet. The experimental velocity of copper powder with different sizes was used to validate the calculated one for low-pressure cold spray process. The results show that the computational model can provide a satisfactory prediction of the supersonic gas flow, which is consistent with the experimental Schlieren photos. It was found that similar velocity was obtained with the drag coefficient formula of Henderson and with that of Morsi and Alexander. As the shape factor was estimated, the reasonable prediction of velocity for non-spherical particle can be obtained, to compare with the experimental results.

  6. Low-pressure sustainment of surface-wave microwave plasma with modified microwave coupler

    NASA Astrophysics Data System (ADS)

    Sasai, Kensuke; Suzuki, Haruka; Toyoda, Hirotaka

    2016-01-01

    Sustainment of long-scale surface-wave plasma (SWP) at pressures below 1 Pa is investigated for the application of the SWP as an assisting plasma source for roll-to-roll sputter deposition. A modified microwave coupler (MMC) for easier surface-wave propagation is proposed, on the basis of the concept of the power direction alignment of the slot antenna and surface-wave propagation. The superiority of the MMC-SWP over conventional SWPs is shown at a sustainment pressure as low as 0.6 Pa and an electron density as high as 3 × 1017 m-3. A polymer film is treated with the MMC-SWP at a low pressure of 0.6 Pa, and surface modification at a low pressure is proved using Ar plasma. These results show the availability of the MMC-SWP as the surface treatment plasma source that is compatible with sputter deposition in the same processing chamber.

  7. Space shuttle low pressure auxiliary propulsion subsystem design definition: Design handbook

    NASA Technical Reports Server (NTRS)

    Bruns, A. E.; Gray, J. G.

    1971-01-01

    A detailed description of recommended low pressure auxiliary propulsion subsystems (APS) for a space shuttle orbiter and booster is presented. The APS designs are the product of a study to identify and evaluate APS concepts, and to perform in-depth design and performance analyses for the most attractive of these. Selected APS baselines use the main engine propellant tanks as low pressure gas accumulators. For the orbiter, propellants from separate liquid tanks are used for main engine tank resupply. Resupply propellants are first circulated through tubular, passive heat exchangers, where they are vaporized and superheated prior to injection into the main engine tanks. Warm propellant vapors from the main engine tanks are mixed with additional liquid propellants in a downstream liquid/vapor mixer and supplied to the engines at constant temperature and pressure (constant density). The booster APS requires no separate propellant storage, since propellant residuals, trapped in the main engine tanks following boost, are sufficient to meet APS propellant demands.

  8. Study of Boundary Layer Development in a Two-Stage Low-Pressure Turbine

    NASA Technical Reports Server (NTRS)

    Dorney, Daniel J.; Ashpis, David E.; Halstead, David E.; Wisler, David C.

    1999-01-01

    Experimental data from jet-engine tests have indicated that unsteady blade row interactions and separation can have a significant impact on the efficiency of low-pressure turbine stages. Measured turbine efficiencies at takeoff can be as much as two points higher than those at cruise conditions. Several recent studies have revealed that Reynolds number effects may contribute to the lower efficiencies at cruise conditions. In the current study numerical simulations have been performed to study the boundary layer development in a two-stage low-pressure turbine, and to evaluate the transition models available for low Reynolds number flows in turbomachinery. The results of the simulations have been compared with experimental data, including airfoil loadings and integral boundary layer quantities. The predicted unsteady results display similar trends to the experimental data, but significantly overestimate the amplitude of the unsteadiness. The time-averaged results show close agreement with the experimental data.

  9. Interplay between lattice dynamics and the low-pressure phase of simple cubic polonium

    NASA Astrophysics Data System (ADS)

    Zaoui, A.; Belabbes, A.; Ahuja, R.; Ferhat, M.

    2011-04-01

    Low-pressure structural properties of simple cubic polonium are explored through first-principles density-functional theory based relativistic total energy calculations using pseudopotentials and plane-wave basis set, as well as linear-response theory. We have found that Po undergoes structural phase transition at low pressure near 2 GPa, where the element transforms from simple cubic to a mixture of two trigonal phases namely, hR1 (α=86°) and hR2 (α=97.9°) structures. The lattice dynamics calculations provide strong support for the observed phase transition, and show the dynamical stability (instability) of the hR2 (hR1) phase.

  10. Low Pressure Experimental Simulation of Electrical Discharges Above and Inside a Cloud

    NASA Technical Reports Server (NTRS)

    Jarzembski, Maurice A.; Srivastava, Vandana

    1996-01-01

    A low pressure laboratory experiment to generate sporadic electrical discharges in either a particulate dielectric or air, representing a competing path of preferred electrical breakdown, was investigated. At high pressures, discharges occurred inside the dielectric particulate; at low pressures, discharges occurred outside the dielectric particulate; at a transition pressure regime, which depends on conductivity of the dielectric particulate, discharges were simultaneously generated in both particulate dielectric and air. Unique use of a particulate dielectric was critical for sporadic discharges at lower pressures which were not identical in character to discharges without the particulate dielectric. Application of these experimental results to the field of atmospheric electricity and simulation of the above-cloud type discharges that have recently been documented, called jets and sprites, are discussed.

  11. Mixing unmixables: Unexpected formation of Li-Cs alloys at low pressure.

    PubMed

    Desgreniers, Serge; Tse, John S; Matsuoka, Takahiro; Ohishi, Yasuo; Tse, Justin J

    2015-10-01

    Contrary to the empirical Miedema and Hume-Rothery rules and a recent theoretical prediction, we report experimental evidence on the formation of Li-Cs alloys at very low pressure (>0.1 GPa). We also succeeded in synthesizing a pure nonstoichiometric and ordered crystalline phase from an approximately equimolar mixture and resolved its structure using the maximum entropy method. The new alloy has a primitive cubic cell with the Li atom situated in the center and the Cs at the corners. This structure is stable to at least 10 GPa and has an anomalously high coefficient of thermal expansion at low pressure. Analysis of the valence charge density shows that electrons are donated from Cs to the Li "p"-orbitals, resulting in a rare formal oxidation state of -1 for Li. The observation indicates the diversity in the bonding of the seeming simple group I Li element. PMID:26601304

  12. Energy efficient engine: Low-pressure turbine subsonic cascade component development and integration program

    NASA Technical Reports Server (NTRS)

    Sharma, O. P.; Kopper, F. C.; Knudsen, L. K.; Yustinich, J. B.

    1982-01-01

    A subsonic cascade test program was conducted to provide technical data for optimizing the blade and vane airfoil designs for the Energy Efficient Engine Low-Pressure Turbine component. The program consisted of three parts. The first involved an evaluation of the low-chamber inlet guide vane. The second, was an evaluation of two candidate aerodynamic loading philosophies for the fourth blade root section. The third part consisted of an evaluation of three candidate airfoil geometries for the fourth blade mean section. The performance of each candidate airfoil was evaluated in a linear cascade configuration. The overall results of this study indicate that the aft-loaded airfoil designs resulted in lower losses which substantiated Pratt & Whitney Aircraft's design philosophy for the Energy Efficient Engine low-pressure turbine component.

  13. Growth Enhancement of Radish Sprouts Induced by Low Pressure O2 Radio Frequency Discharge Plasma Irradiation

    NASA Astrophysics Data System (ADS)

    Kitazaki, Satoshi; Koga, Kazunori; Shiratani, Masaharu; Hayashi, Nobuya

    2012-01-01

    We studied growth enhancement of radish sprouts (Raphanus sativus L.) induced by low pressure O2 radio frequency (RF) discharge plasma irradiation. The average length of radish sprouts cultivated for 7 days after O2 plasma irradiation is 30-60% greater than that without irradiation. O2 plasma irradiation does not affect seed germination. The experimental results reveal that oxygen related radicals strongly enhance growth, whereas ions and photons do not.

  14. Life modeling of atmospheric and low pressure plasma-sprayed thermal-barrier coating

    NASA Technical Reports Server (NTRS)

    Miller, R. A.; Argarwal, P.; Duderstadt, E. C.

    1984-01-01

    The cycles-to-failure vs cycle duration data for three different thermal barrier coating systems, which consist of atmospheric pressure plasma-sprayed ZrO2-8 percent Y2O3 over similarly deposited or low pressure plasma sprayed Ni-base alloys, are presently analyzed by means of the Miller (1980) oxidation-based life model. Specimens were tested at 1100 C for heating cycle lengths of 1, 6, and 20 h, yielding results supporting the model's value.

  15. Modelling Of Generation And Growth Of Nanoparticles In Low-Pressure Plasmas

    SciTech Connect

    Gordiets, B. F.

    2008-09-07

    Theoretical kinetic models of generation and growth of clusters and nanoparticles in low-pressure plasma are briefly rewired. The relatively simple kinetic model is discussed more detail. Simple formulas and equations are given for monomer density; cluster dimension distribution; critical cluster dimension; rate of particle production; particle density and average dimension as well as plasma characteristics. The analytical formula is also obtained for the time delay of the measured LIPEE signal in the 'Laser Induced Particle Explosive Evaporation' experimental method.

  16. CF6 jet engine performance improvement: low pressure turbine active clearance control

    SciTech Connect

    Beck, B.D.; Fasching, W.A.

    1982-06-01

    A low pressure turbine (LPT) active clearance control (ACC) cooling system was developed to reduce the fuel consumption of current CF6-50 turbofan engines for wide bodied commercial aircraft. The program performance improvement goal of 0.3% delta sfc was determined to be achievable with an improved impingement cooling system. The technology enables the design of an optimized manifold and piping system which is capable of a performance gain of 0.45% delta sfc.

  17. Observation of Quartz Cathode-Luminescence in a Low Pressure Plasma Discharge

    NASA Technical Reports Server (NTRS)

    Foster, John E.

    2004-01-01

    Intense, steady-state cathode-luminescence has been observed from exposure of quartz powder to a low pressure rf-excited argon plasma discharge. The emission spectra (400 to 850 nm) associated with the powder luminescence were documented as a function of bias voltage using a spectrometer. The emission was broad-band, essentially washing out the line spectra features of the argon plasma discharge.

  18. Study of the low-pressure plasma effect on polypropylene nonwovens

    SciTech Connect

    Lopez, R.; Pascual, M.; Calvo, O.

    2010-06-02

    In this work we have used low-pressure plasma with a gas based on methane and oxygen mixture to improve wettability and durability of a PP nonwoven fabrics. The obtained results show good durability with the use of methane-oxygen plasma mixture gas. The effects of the plasma are similar to a plasmapolymerization process but in this case we obtain hydrophilic properties with high durability. The surface does not suffer important changes and the roughness of the material remains constant.

  19. Low pressure arc discharge lamp apparatus with magnetic field generating means

    DOEpatents

    Grossman, M.W.; George, W.A.; Maya, J.

    1987-10-06

    A low-pressure arc discharge apparatus having a magnetic field generating means for increasing the output of a discharge lamp is disclosed. The magnetic field generating means, which in one embodiment includes a plurality of permanent magnets, is disposed along the lamp for applying a constant transverse magnetic field over at least a portion of the positive discharge column produced in the arc discharge lamp operating at an ambient temperature greater than about 25 C. 3 figs.

  20. Visible and near-ultraviolet spectra of low-pressure rare-gas microwave discharges

    NASA Technical Reports Server (NTRS)

    Campbell, J. P.; Spisz, E. W.; Bowman, R. L.

    1971-01-01

    The spectral emission characteristics of three commercial low pressure rare gas discharge lamps wire obtained in the near ultraviolet and visible wavelength range. All three lamps show a definite continuum over the entire wavelength range from 0.185 to 0.6 micrometers. Considerable line emission is superimposed on much of the continuum for wavelengths greater than 0.35 micrometers. These sources were used to make transmittance measurements on quartz samples in the near ultraviolet wavelength range.

  1. Low pressure arc discharge lamp apparatus with magnetic field generating means

    SciTech Connect

    Grossman, Mark W.; George, William A.; Maya, Jakob

    1987-01-01

    A low-pressure arc discharge apparatus having a magnetic field generating means for increasing the output of a discharge lamp is disclosed. The magnetic field generating means, which in one embodiment includes a plurality of permanent magnets, is disposed along the lamp for applying a constant transverse magnetic field over at least a portion of the positive discharge column produced in the arc discharge lamp operating at an ambient temperature greater than about 25.degree. C.

  2. Downhole steam generator using low-pressure fuel and air supply

    DOEpatents

    Fox, R.L.

    1981-01-07

    For tertiary oil recovery, an apparatus for downhole steam generation is designed in which water is not injected directly onto the flame in the combustor, the combustion process is isolated from the reservoir pressure, the fuel and oxidant are supplied to the combustor at relatively low pressures, and the hot exhaust gases is prevented from entering the earth formation but is used to preheat the fuel and oxidant and water. The combustion process is isolated from the steam generation process. (DLC)

  3. The CF6 Jet Engine Performance Improvement - Low Pressure Turbine Active Clearance Control

    NASA Technical Reports Server (NTRS)

    Beck, B. D.; Fasching, W. A.

    1982-01-01

    A low pressure turbine (LPT) active clearance control (ACC) cooling system was developed to reduce the fuel consumption of current CF6-50 turbofan engines for wide bodied commercial aircraft. The program performance improvement goal of 0.3% delta sfc was determined to be achievable with an improved impingement cooling system. The technology enables the design of an optimized manifold and piping system which is capable of a performance gain of 0.45% delta sfc.

  4. Low-pressure pulsed focused ultrasound with microbubbles promotes an anticancer immunological response

    PubMed Central

    2012-01-01

    Background High-intensity focused-ultrasound (HIFU) has been successfully employed for thermal ablation of tumors in clinical settings. Continuous- or pulsed-mode HIFU may also induce a host antitumor immune response, mainly through expansion of antigen-presenting cells in response to increased cellular debris and through increased macrophage activation/infiltration. Here we demonstrated that another form of focused ultrasound delivery, using low-pressure, pulsed-mode exposure in the presence of microbubbles (MBs), may also trigger an antitumor immunological response and inhibit tumor growth. Methods A total of 280 tumor-bearing animals were subjected to sonographically-guided FUS. Implanted tumors were exposed to low-pressure FUS (0.6 to 1.4 MPa) with MBs to increase the permeability of tumor microvasculature. Results Tumor progression was suppressed by both 0.6 and 1.4-MPa MB-enhanced FUS exposures. We observed a transient increase in infiltration of non-T regulatory (non-Treg) tumor infiltrating lymphocytes (TILs) and continual infiltration of CD8+ cytotoxic T-lymphocytes (CTL). The ratio of CD8+/Treg increased significantly and tumor growth was inhibited. Conclusions Our findings suggest that low-pressure FUS exposure with MBs may constitute a useful tool for triggering an anticancer immune response, for potential cancer immunotherapy. PMID:23140567

  5. Synthesis of Fullerenes in Low Pressure Benzene/Oxygen Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Hebgen, Peter; Howard, Jack B.

    1999-01-01

    The interest in fullerenes is strongly increasing since their discovery by Kroto et al. in 1985 as products of the evaporation of carbon into inert gas at low pressure. Due to their all carbon closed-shell structure, fullerenes have many exceptional physical and chemical properties and a large potential for applications such as superconductors, sensors, catalysts, optical and electronic devices, polymers, high energy fuels, and biological and medical materials. This list is still growing, because the research on fullerenes is still at an early stage. Fullerenes can be formed not only in a system containing only carbon and an inert gas, but also in premixed hydrocarbon flames under reduced pressure and fuel rich conditions. The highest yields of fullerenes in flames are obtained under conditions of substantial soot formation. There is a need for more information on the yields of fullerenes under different conditions in order to understand the mechanisms of their formation and to enable the design of practical combustion systems for large-scale fullerene production. Little work has been reported on the formation of fullerenes in diffusion flames. In order to explore the yields of fullerenes and the effect of low pressure in diffusion flames, therefore we constructed and used a low pressure diffusion flame burner in this study.

  6. Basalt catalyzed carbonate precipitation reactions using carbon dioxide at low temperatures and low pressures

    NASA Astrophysics Data System (ADS)

    Petrik-Huff, C.; Finkelstein, D. B.; Mabee, S. B.

    2011-12-01

    Increased attention is being paid to basalts as host formations for the geologic sequestration of anthropogenically produced CO2. Here, we present preliminary results of batch experiments conducted on basalts from the Hartford Basin, the Deerfield and the Holyoke Basalt, to better constrain the optimum conditions to maximize carbon sequestration through the precipitation of carbonate. The purpose of this work is to explore options for CO2 sequestration in a locality where there is a lack of large geologic reservoirs appropriate for storage. In these experiments, 10 grams of 400 micron Deerfield and Holyoke basalt was reacted with deionized water for three hours both at and below supercritical conditions. These experiments showed carbonate precipitation of 15% was consistent at low pressures of CO2 (800 psi) both at high (100 Celsius) and low (20 Celsius) temperatures. These ranges of carbonate precipitation were greatest (15%) when CO2 was at low pressures. Experiments conducted at supercritical conditions precipitated a maximum of 4.7% carbonate. This information is valuable when considering alternative sequestration mechanisms that could be operated adjacent to power generation facilities or more industrial pure sources of CO2. The possibility of low pressure/temperature sequestration reactors to be operated in areas where transport to regional or national sequestration facilities may be cost prohibitive is a parallel course of action that should also be considered. Additionally, it is important to consider how a small ex-situ carbon sequestration project can help increase public acceptance of carbon capture and sequestration.

  7. Capacitive micromachined ultrasonic transducer for ultra-low pressure measurement: Theoretical study

    NASA Astrophysics Data System (ADS)

    Li, Zhikang; Zhao, Libo; Jiang, Zhuangde; Akhbari, Sina; Ding, Jianjun; Zhao, Yihe; Zhao, Yulong; Lin, Liwei

    2015-12-01

    Ultra-low pressure measurement is necessary in many areas, such as high-vacuum environment monitoring, process control and biomedical applications. This paper presents a novel approach for ultra-low pressure measurement where capacitive micromachined ultrasonic transducers (CMUTs) are used as the sensing elements. The working principle is based on the resonant frequency shift of the membrane under the applied pressure. The membranes of the biased CMUTs can produce a larger resonant frequency shift than the diaphragms with no DC bias in the state-of-the-art resonant pressure sensors, which contributes to pressure sensitivity improvement. The theoretical analysis and finite element method (FEM) simulation were employed to study the relationship between the resonant frequency and the pressure. The results demonstrated excellent capability of the CMUTs for ultra-low pressure measurement. It is shown that the resonant frequency of the CMUT varies linearly with the applied pressure. A sensitivity of more than 6.33 ppm/Pa (68 kHz/kPa) was obtained within a pressure range of 0 to 100 Pa when the CMUTs were biased at a DC voltage of 90% of the collapse voltage. It was also demonstrated that the pressure sensitivity can be adjusted by the DC bias voltage. In addition, the effects of air damping and ambient temperature on the resonant frequency were also studied. The effect of air damping is negligible for the pressures below 1000 Pa. To eliminate the temperature effect on the resonant frequency, a temperature compensating method was proposed.

  8. Numerical Simulations of Steady and Unsteady Transition in Low-Pressure Turbine Blade Rows

    NASA Technical Reports Server (NTRS)

    Dorney, Daniel

    1998-01-01

    Transition plays an important role in the prediction of losses and performance in low-pressure turbines. The transition location on a turbine blade may vary significantly because of the wakes from upstream blade rows, and intermittent flow separation can also affect the transition process in an unsteady flow environment. In the present investigation, an unsteady Navier-Stokes analysis is used to predict transition in a low-pressure turbine cascade and a low-pressure turbine stage. The numerical flow analysis is third-order spatially accurate and second-order temporally accurate, and the equations of motion are integrated using an implicit time-marching procedure. The Baldwin-Lomax and k-epsilon turbulence models, in conjunction with several algebraic transition models, have been used to predict the location of transition. Predicted results include unsteady blade loadings, time-histories of the pressure, transition locations and boundary layer quantities, as well as performance quantities and comparisons with the available experimental/design data.

  9. 30 CFR 75.1106-6 - Exemption of small low pressure gas cylinders containing nonflammable or nonexplosive gas mixtures.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... STANDARDS-UNDERGROUND COAL MINES Fire Protection § 75.1106-6 Exemption of small low pressure gas cylinders... from a pressure which does not exceed 250 p.s.i.g., and which is manufactured and sold in conformance... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Exemption of small low pressure gas...

  10. 30 CFR 75.1106-6 - Exemption of small low pressure gas cylinders containing nonflammable or nonexplosive gas mixtures.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... STANDARDS-UNDERGROUND COAL MINES Fire Protection § 75.1106-6 Exemption of small low pressure gas cylinders... from a pressure which does not exceed 250 p.s.i.g., and which is manufactured and sold in conformance... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Exemption of small low pressure gas...

  11. 30 CFR 75.1106-6 - Exemption of small low pressure gas cylinders containing nonflammable or nonexplosive gas mixtures.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... STANDARDS-UNDERGROUND COAL MINES Fire Protection § 75.1106-6 Exemption of small low pressure gas cylinders... from a pressure which does not exceed 250 p.s.i.g., and which is manufactured and sold in conformance... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Exemption of small low pressure gas...

  12. 30 CFR 75.1106-6 - Exemption of small low pressure gas cylinders containing nonflammable or nonexplosive gas mixtures.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... STANDARDS-UNDERGROUND COAL MINES Fire Protection § 75.1106-6 Exemption of small low pressure gas cylinders... from a pressure which does not exceed 250 p.s.i.g., and which is manufactured and sold in conformance... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Exemption of small low pressure gas...

  13. 30 CFR 75.1106-6 - Exemption of small low pressure gas cylinders containing nonflammable or nonexplosive gas mixtures.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... STANDARDS-UNDERGROUND COAL MINES Fire Protection § 75.1106-6 Exemption of small low pressure gas cylinders... from a pressure which does not exceed 250 p.s.i.g., and which is manufactured and sold in conformance... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Exemption of small low pressure gas...

  14. Military Curriculum Materials for Vocational and Technical Education. Welding High and Low Pressure Lines, 3-26.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. National Center for Research in Vocational Education.

    This short course in welding high and low pressure lines was adapted from military curriculum materials for use in vocational education. The course is designed to teach safety requirements for work with high and low pressure pipelines; pipe welding requirements and specifications; special pipeline repair welding applications; layout of pipe…

  15. Low pressure and time storage influences on the electrets stability of HDPE composite films

    NASA Astrophysics Data System (ADS)

    Yovcheva, T.; Viraneva, A.; Galikhanov, M.

    2014-12-01

    The influence of both low pressure and time storage on the surface potential decay of high density polyethylene (HDPE) composite films with different weight concentrations of the zeolite particles - 0 wt.%, 2 wt.% and 6 wt.% were studied. The samples were charged in a corona discharge by means of a corona triode system for ' minute under room conditions. Positive or negative 5kV voltage was applied to the corona electrode and 1 kV voltage of the same polarity as that of the corona electrode was applied to the grid. After charging, the electret surface potential was measured by the method of the vibrating electrode with compensation. Two groups of tests were performed. In the first group after charging, the electrets were placed into a vacuum chamber where the pressure was reduced step by step in the range from 1000 mbar to 0.1 mbar. At each step the samples were stored for 1 minute. Then the electrets were removed from the vacuum chamber, the surface potential was measured again and the normalized surface potential was calculated. It was established that the low pressure had led to the surface potential decay of the electrets. The influence of the low pressure was analyzed by the equation that describes processes of desorption from the electret surface accompanied with surface diffusion. In the second group after charging, the electret surface potential was measured with the time of storage for two months. The experimental results obtained show a significant change in the electret behaviour of the composite films after the incorporation of zeolite particles with different concentration into the HDPE matrix. It was established that the surface potential decay depends on the corona polarity and the particle concentration.

  16. Study of Boundary Layer Development in a Two-Stage Low-Pressure Turbine

    NASA Technical Reports Server (NTRS)

    Dorney, Daniel J.; Ashpis, David E.; Halstead, David E.; Wisler, David C.

    1998-01-01

    Experimental data from jet-engine tests have indicated that unsteady blade row (wake) interactions and separation can have a significant impact on the efficiency of turbine stages. The effects of these interactions can be intensified in low-pressure turbine stages because of the low Reynolds number operating environment. Measured turbine efficiencies at takeoff can be as much as two points higher than those at cruise conditions. Thus, during the last decade a significant amount of effort has been put into determining the effects of transition and turbulence on the performance of low pressure turbine stages. Experimental investigations have been performed, for example, by Hodson et al. and Halstead et al. These investigations have helped identify/clarify the roles that factors such as the Reynolds number, free stream turbulence intensity, pressure gradient and curvature have in the generation of losses. In parallel to the experimental investigations, there have been significant analytical efforts to improve the modeling of transition. Examples of such efforts include the works of Mayle and Gostelow et al. These newer models show promise of providing accurate transition predictions over a wide range of flow conditions, although they have yet to be implemented into the numerical flow analyses used by the turbine design community. Some recent computational investigations of interest include the works of Chernobrovkin and Lakshminarayana and Eulitz and Engel. The focus of the current effort has been to -use a viscous, unsteady quasi-three-dimensional Navier-Stokes analysis to study boundary layer development in a two-stage low-pressure turbine. A two-layer algebraic turbulence model, along with a natural transition model and a bubble transition model, have been used, The geometry used in the simulations has been the subject of extensive experiments. The predicted results have been compared with experimental data, including airfoil loadings and time

  17. Low pressure drop filtration of airborne molecular organic contaminants using open-channel networks

    NASA Astrophysics Data System (ADS)

    Dallas, Andrew J.; Joriman, Jon; Ding, Lefei; Weineck, Gerald; Seguin, Kevin

    2007-03-01

    Airborne molecular contamination (AMC) continues to play a very decisive role in the performance of many microelectronic devices and manufacturing processes. Besides airborne acids and bases, airborne organic contaminants such as 1-methyl-2-pyrrolidinone (NMP), hexamethyldisiloxane (HMDSO), trimethylsilanol (TMS), perfluoroalkylamines and condensables are of primary concern in these applications. Currently, the state of the filtration industry is such that optimum filter life and removal efficiency for organics is offered by granular carbon filter beds. However, the attributes that make packed beds of activated carbon extremely efficient also impart issues related to elevated filter weight and pressure drop. Most of the lower pressure drop AMC filters currently offered are quite expensive and are simply pleated combinations of various adsorptive and reactive media. On the other hand, low pressure drop filters, such as those designed as open-channel networks (OCN's), offer good filter life and removal efficiency with the additional benefits of significant reductions in overall filter weight and pressure drop. Equally important for many applications, the OCN filters can reconstruct the airflow so as to enhance the operation of a tool or process. For tool mount assemblies and fan filter units (FFUs) this can result in reduced fan and blower speeds, which subsequently can provide reduced vibration and energy costs. Additionally, these low pressure drop designs can provide a cost effective way of effectively removing AMC in full fab (or HVAC) filtration applications without significantly affecting air-handling requirements. Herein, we will present a new generation of low pressure drop OCN filters designed for the removal of airborne organics in a wide range of applications.

  18. On the temperatures near and the motions of low-pressure centres in winter storms

    NASA Astrophysics Data System (ADS)

    Stewart, Ronald E.

    During the Canadian Atlantic Storm Program (CASP) field project, upper-air and surface data revealed that deep 0°C layers tended to occur ahead of low-pressure centres and that the low centres often tracked along the surface rain-snow boundary. These observations, as well as those reported in the literature in several other storm systems, are consistent with an hypothesis that the organization of some cyclonic storms is linked to the effects of melting snow. This hypothesis furthermore leads to a number of implications associated with tropospheric features and topographic effects.

  19. Palladium-Catalyzed Alkoxycarbonylation of Unactivated Secondary Alkyl Bromides at Low Pressure.

    PubMed

    Sargent, Brendon T; Alexanian, Erik J

    2016-06-22

    Catalytic carbonylations of organohalides are important C-C bond formations in chemical synthesis. Carbonylations of unactivated alkyl halides remain a challenge and currently require the use of alkyl iodides under harsh conditions and high pressures of CO. Herein we report a palladium-catalyzed alkoxycarbonylation of secondary alkyl bromides that proceeds at low pressure (2 atm CO) under mild conditions. Preliminary mechanistic studies are consistent with a hybrid organometallic-radical process. These reactions efficiently deliver esters from unactivated alkyl bromides across a diverse range of substrates and represent the first catalytic carbonylations of alkyl bromides with carbon monoxide. PMID:27267421

  20. Temporally and spatially integrated elemental analysis algorithm for low-pressure micro-LIBS measurements

    SciTech Connect

    Mungas, Greg

    2007-07-01

    Microscopic laser-induced breakdown spectroscopy (micro-LIBS) is a promising measurement technique for determining the relative elemental abundances of microscopic spots. Currently, the predominant source of measurement accuracy errors for micro-LIBS is shown to be based on a constant plasma temperature assumption. To reduce these measurement errors particularly in low-pressure applications (i.e.,extraterrestrial environments), a mathematical data analysis algorithm is presented that utilizes the many linear independent emission lines per element to estimate the time-integrated state of the plasma in the form of a plasma state matrix coupled with a vector of relative elemental abundances in the observed emission.

  1. Flow Control on Low-Pressure Turbine Airfoils Using Vortex Generator Jets

    NASA Technical Reports Server (NTRS)

    Volino, Ralph J.; Ibrahim, Mounir B.; Kartuzova, Olga

    2010-01-01

    Motivation - Higher loading on Low-Pressure Turbine (LPT) airfoils: Reduce airfoil count, weight, cost. Increase efficiency, and Limited by suction side separation. Growing understanding of transition, separation, wake effects: Improved models. Take advantage of wakes. Higher lift airfoils in use. Further loading increases may require flow control: Passive: trips, dimples, etc. Active: plasma actuators, vortex generator jets (VGJs). Can increased loading offset higher losses on high lift airfoils. Objectives: Advance knowledge of boundary layer separation and transition under LPT conditions. Demonstrate, improve understanding of separation control with pulsed VGJs. Produce detailed experimental data base. Test and develop computational models.

  2. Adapting optical technologies for low pressure measurements in the marine industry (1-10 bar)

    NASA Astrophysics Data System (ADS)

    Sanmartin, D. Rodriguez; Lawal, A.; Awcock, G.; Busbridge, S.; Cooper, P.; Spenceley, J.

    2013-05-01

    Optical sensing is a very attractive technology option to design transducers for applications, such as the measurement of liquid level in oil fuel tanks, which require intrinsic safety and electromagnetic compatibility. PSM Instrumentation Ltd., an UK firm specialised in instrumentation for liquid level measurement for the marine industry and the University of Brighton are currently collaborating in a 2 year research programme funded by the UK government scheme Knowledge Transfer Partnerships. This paper evaluates how optical technologies could be used in pressure transducers, and their potential benefits, such as intrinsic safety compliance and low cost cabling, for low pressure applications such as fuel tank gauging for applications in the marine industry.

  3. Insects at low pressure: applications to artificial ecosystems and implications for global windborne distribution

    NASA Technical Reports Server (NTRS)

    Cockell, C.; Catling, D.; Waites, H.

    1999-01-01

    Insects have a number of potential roles in closed-loop life support systems. In this study we examined the tolerance of a range of insect orders and life stages to drops in atmospheric pressure using a terrestrial atmosphere. We found that all insects studied could tolerate pressures down to 100 mb. No effects on insect respiration were noted down to 500 mb. Pressure toleration was not dependent on body volume. Our studies demonstrate that insects are compatible with plants in low-pressure artificial and closed-loop ecosystems. The results also have implications for arthropod colonization and global distribution on Earth.

  4. A laser and molecular beam mass spectrometer study of low-pressure dimethyl ether flames

    SciTech Connect

    Andrew McIlroy; Toby D. Hain; Hope A. Michelsen; Terrill A. Cool

    2000-12-15

    The oxidation of dimethyl ether (DME) is studied in low-pressure flames using new molecular beam mass spectrometer and laser diagnostics. Two 30.0-Torr, premixed DME/oxygen/argon flames are investigated with stoichiometries of 0.98 and 1.20. The height above burner profiles of nine stable species and two radicals are measured. These results are compared to the detailed chemical reaction mechanism of Curran and coworkers. Generally good agreement is found between the model and data. The largest discrepancies are found for the methyl radical profiles where the model predicts qualitatively different trends in the methyl concentration with stoichiometry than observed in the experiment.

  5. Track studies in water vapor using a low-pressure cloud chamber. II. Microdosimetric measurements.

    PubMed

    Stonell, G P; Marshall, M; Simmons, J A

    1993-12-01

    A low-pressure cloud chamber has been adapted to operate with pure water vapor. Photographs were obtained of tracks arising from the passage of ionizing radiation. The sources used were low-energy X rays, 242Cm alpha particles, and low-energy protons. Distributions of lineal energy, radial distances around an ion track, and interdroplet distances were measured and compared with the predictions of Monte Carlo calculations. After allowing for diffusion and the limitations of the geometry of the system, the measured and calculated distributions were found to be in good agreement. PMID:8278576

  6. Femtosecond filamentation in air at low pressures. Part II: Laboratory experiments

    NASA Astrophysics Data System (ADS)

    Méchain, G.; Olivier, T.; Franco, M.; Couairon, A.; Prade, B.; Mysyrowicz, A.

    2006-05-01

    We present experimental studies of filamentation of a femtosecond laser pulse in air at low pressures. The evolution of the filament has been studied by measuring along the propagation axis the conductivity and the sub-THz emission from the plasma channel. We show experimentally that the filamentation process occurs at pressures as low as 0.2 atm in agreement with numerical simulations. Experimental and numerical results [A. Couairon, M. Franco, G. Méchain, T. Olivier, B. Prade, A. Mysyrowicz, Opt. Commun., submitted for publication] are compared and the possible sources of discrepancy are discussed.

  7. Casting defects in low-pressure die-cast aluminum alloy wheels

    NASA Astrophysics Data System (ADS)

    Zhang, B.; Cockcroft, S. L.; Maijer, D. M.; Zhu, J. D.; Phillion, A. B.

    2005-11-01

    Defects in automotive aluminum alloy casting continue to challenge metallurgists and production engineers as greater emphasis is placed on product quality and production cost. A range of casting-related defects found in low-pressure die-cast aluminum wheels were examined metallographically in samples taken from several industrial wheel-casting facilities. The defects examined include macro- and micro- porosity, entrained oxide films, and exogenous oxide inclusions. Particular emphasis is placed on the impact of these defects with respect to the three main casting-related criteria by which automotive wheel quality are judged: wheel cosmetics, air-tightness, and wheel mechanical performance.

  8. Material uniformity of CdZnTe grown by low-pressure bridgman

    NASA Astrophysics Data System (ADS)

    Greaves, C. M.; Brunett, B. A.; Van Scyoc, J. M.; Schlesinger, T. E.; James, R. B.

    2001-02-01

    We have employed Low-Temperature Photoluminescence (LTPL) and Room-Temperature Photoluminescence Mapping (RTPLM) to explore the crystalline quality and material uniformity of Cadmium Zinc Telluride (CZT) radiation detector material grown by the Low-Pressure Bridgman (LPB) technique. We report on the differences in crystalline quality and uniformity of material supplied by eV Products Inc. and IMARAD Imaging Systems Ltd. In addition, we have examined the general detector response of the material supplied by IMARAD. We report on the uniformity of the detector response and the temperature dependence of this response when used as a detector.

  9. Reliability improvements and modernization of low pressure turbine cylinders for steam-turbine generator power plants

    SciTech Connect

    Aneja, I.K. )

    1990-01-01

    This paper presents the use of 2-D and 3-D finite element analysis to determine the cause of distress in certain components in the low pressure turbines for large power plants. The same finite element models are then used for parametric evaluation of various alternates to increase component fatigue life. Finally, the 3-D finite element model is used for designing a new cylinder which can withstand severe cyclic duty operation requirements and can also be used for modernization of existing old power plants.

  10. Energy efficient engine: Turbine intermediate case and low-pressure turbine component test hardware detailed design report

    NASA Technical Reports Server (NTRS)

    Leach, K.; Thulin, R. D.; Howe, D. C.

    1982-01-01

    A four stage, low pressure turbine component has been designed to power the fan and low pressure compressor system in the Energy Efficient Engine. Designs for a turbine intermediate case and an exit guide vane assembly also have been established. The components incorporate numerous technology features to enhance efficiency, durability, and performance retention. These designs reflect a positive step towards improving engine fuel efficiency on a component level. The aerodynamic and thermal/mechanical designs of the intermediate case and low pressure turbine components are presented and described. An overview of the predicted performance of the various component designs is given.

  11. Weak interactions between water and clathrate-forming gases at low pressures

    DOE PAGESBeta

    Thürmer, Konrad; Yuan, Chunqing; Kimmel, Greg A.; Kay, Bruce D.; Smith, R. Scott

    2015-07-17

    Using scanning probe microscopy and temperature programed desorption we examined the interaction between water and two common clathrate-forming gases, methane and isobutane, at low temperature and low pressure. Water co-deposited with up to 10–1 mbar methane or 10–5 mbar isobutane at 140 K onto a Pt(111) substrate yielded pure crystalline ice, i.e., the exposure to up to ~ 107 gas molecules for each deposited water molecule did not have any detectable effect on the growing films. Exposing metastable, less than 2 molecular layers thick, water films to 10–5 mbar methane does not alter their morphology, suggesting that the presence ofmore » the Pt(111) surface is not a strong driver for hydrate formation. This weak water–gas interaction at low pressures is supported by our thermal desorption measurements from amorphous solid water and crystalline ice where 1 ML of methane desorbs near ~ 43 K and isobutane desorbs near ~ 100 K. As a result, similar desorption temperatures were observed for desorption from amorphous solid water.« less

  12. Weak interactions between water and clathrate-forming gases at low pressures

    SciTech Connect

    Thurmer, Konrad; Yuan, Chunqing; Kimmel, Gregory A.; Kay, Bruce D.; Smith, R. Scott

    2015-11-01

    Using scanning probe microscopy and temperature programed desorption we examined the interaction between water and two common clathrate-forming gases, methane and isobutane, at low temperature and low pressure. Water co-deposited with up to 10-1 mbar methane or 10-5 mbar isobutane at 140 K onto a Pt(111) substrate yielded pure crystalline ice, i.e., the exposure to up to ~107 gas molecules for each deposited water molecule did not have any detectable effect on the growing films. Exposing metastable, less than 2 molecular layers thick, water films to 10-5 mbar methane does not alter their morphology, suggesting that the presence of the Pt(111) surface is not a strong driver for hydrate formation. This weak water-gas interaction at low pressures is supported by our thermal desorption measurements from amorphous solid water and crystalline ice where 1 ML of methane desorbs near ~43 K and isobutane desorbs near ~100 K. Similar desorption temperatures were observed for desorption from amorphous solid water.

  13. Flutter stability investigation of low-pressure steam turbine bladed disks

    SciTech Connect

    Omprakash, V.; Sarlashkar, A.V.; Lam, T.C.T.; Shuster, L.H.; McCloskey, T.H.

    1994-12-31

    This paper presents a numerical method to analyze flutter stability of low-pressure steam turbine blading. Any bladed disk normal vibration mode as well as the stage operating condition may be considered. The stability considerations are based on a quasi-steady power-per-vibration-cycle approach. The aerodynamic work per cycle of vibration of a bladed disk mode is calculated form the time integral of the product of the periodic time varying force and the specified harmonic vibration amplitude. The aerodynamic forces are obtained from the pressure distribution database generated from a separate 2-D cascade analysis for compressible inviscid flow for a wide range of flow angles. The method accounts for the kinematic corrections of instantaneous relative flow angle due to the vibratory motion. The non-linear material damping energy of the bladed disk as a function of the vibration amplitude is calculated using Lazan`s power law. The flutter stability is determined by the net power flow to the bladed disk at various amplitudes of vibration. Some results for the last stage of a low pressure steam turbine are presented.

  14. The aerodynamic design and performance of the NASA/GE E3 low pressure turbine

    NASA Technical Reports Server (NTRS)

    Cherry, D. G.; Dengler, R. P.

    1984-01-01

    The aerodynamic design and scaled rig test results of the low pressure turbine (LPT) component for the NASA/General Electric Energy Efficient Engine (E3) are presented. The low pressure turbine is a highly loaded five-stage design featuring high outer wall slope, controlled vortex aerodynamics, low stage flow coefficient, and reduced clearances. An assessment of its performance has been made based on a series of scaled air turbine tests which were divided into two phases: Block I (March through August, 1979) and Block II (June through September, 1981). Results from the Block II five-stage test, summarized in the paper, indicate that the E3 LPT will attain an efficiency level of 91.5 percent at the Mach 0.8/35,000 ft. max. climb altitude design point. This is relative to program goals of 91.1 percent for the E3 demonstrator engine and 91.7 percent for a fully developed flight propulsion system LPT.

  15. Quantitative and sensitive analysis of CN molecules using laser induced low pressure He plasma

    NASA Astrophysics Data System (ADS)

    Pardede, Marincan; Hedwig, Rinda; Abdulmadjid, Syahrun Nur; Lahna, Kurnia; Idris, Nasrullah; Jobiliong, Eric; Suyanto, Hery; Marpaung, Alion Mangasi; Suliyanti, Maria Margaretha; Ramli, Muliadi; Tjia, May On; Lie, Tjung Jie; Lie, Zener Sukra; Kurniawan, Davy Putra; Kurniawan, Koo Hendrik; Kagawa, Kiichiro

    2015-03-01

    We report the results of experimental study on CN 388.3 nm and C I 247.8 nm emission characteristics using 40 mJ laser irradiation with He and N2 ambient gases. The results obtained with N2 ambient gas show undesirable interference effect between the native CN emission and the emission of CN molecules arising from the recombination of native C ablated from the sample with the N dissociated from the ambient gas. This problem is overcome by the use of He ambient gas at low pressure of 2 kPa, which also offers the additional advantages of cleaner and stronger emission lines. The result of applying this favorable experimental condition to emission spectrochemical measurement of milk sample having various protein concentrations is shown to yield a close to linear calibration curve with near zero extrapolated intercept. Additionally, a low detection limit of 5 μg/g is found in this experiment, making it potentially applicable for quantitative and sensitive CN analysis. The visibility of laser induced breakdown spectroscopy with low pressure He gas is also demonstrated by the result of its application to spectrochemical analysis of fossil samples. Furthermore, with the use of CO2 ambient gas at 600 Pa mimicking the Mars atmosphere, this technique also shows promising applications to exploration in Mars.

  16. Comprehensive Validation of an Intermittency Transport Model for Transitional Low-Pressure Turbine Flows

    NASA Technical Reports Server (NTRS)

    Suzen, Y. B.; Huang, P. G.

    2005-01-01

    A transport equation for the intermittency factor is employed to predict transitional flows under the effects of pressure gradients, freestream turbulence intensities, Reynolds number variations, flow separation and reattachment. and unsteady wake-blade interactions representing diverse operating conditions encountered in low-pressure turbines. The intermittent behaviour of the transitional flows is taken into account and incorporated into computations by modifying the eddy viscosity, Mu(sub t), with the intermittency factor, gamma. Turbulent quantities are predicted by using Menter's two-equation turbulence model (SST). The onset location of transition is obtained from correlations based on boundary-layer momentum thickness, acceleration parameter, and turbulence intensity. The intermittency factor is obtained from a transport model which can produce both the experimentally observed streamwise variation of intermittency and a realistic profile in the cross stream direction. The intermittency transport model is tested and validated against several well documented low pressure turbine experiments ranging from flat plate cases to unsteady wake-blade interaction experiments. Overall, good agreement between the experimental data and computational results is obtained illustrating the predicting capabilities of the model and the current intermittency transport modelling approach for transitional flow simulations.

  17. An expression for the h l factor in low-pressure electronegative plasma discharges

    NASA Astrophysics Data System (ADS)

    Chabert, P.

    2016-04-01

    The positive ion flux exiting a low-pressure plasma discharge is a crucial quantity in global (volume-averaged) models. In discharges containing only electrons and positive ions (electropositive discharges), it is common to write this flux {Γ\\text{wall}}={{h}\\text{l}}{{n}\\text{i0}}{{u}\\text{B}} , where {{n}\\text{i0}} is the central positive ion density, {{u}\\text{B}} is the positive ion fluid speed at the sheath edge (the Bohm speed), and {{h}\\text{l}} is the positive ion edge-to-centre density ratio. There are well established formulae for {{h}\\text{l}} in electropositive discharges, but for discharges containing negative ions (electronegative discharges), the analysis is more complicated. The purpose of this paper is to propose a formula for the {{h}\\text{l}} factor in low-pressure electronegative discharges. We use the numerical solution of fluid equations with Boltzmann negative ions, including Poisson’s equation, as a guide to derive an analytical expression that can easily be incorporated in global models. The parameter space in which the derived expression is valid is discussed at the end of the paper.

  18. Controlling VUV photon fluxes in low-pressure inductively coupled plasmas

    NASA Astrophysics Data System (ADS)

    Tian, Peng; Kushner, Mark J.

    2015-06-01

    Low-pressure (a few to hundreds of millitorrs) inductively coupled plasmas (ICPs), as typically used in microelectronics fabrication, often produce vacuum-ultraviolet (VUV) photon fluxes onto surfaces comparable to or exceeding the magnitude of ion fluxes. These VUV photon fluxes are desirable in applications such as sterilization of medical equipment but are unwanted in many materials fabrication processes due to damage to the devices by the high-energy photons. Under specific conditions, VUV fluxes may stimulate etching or synergistically combine with ion fluxes to modify polymeric materials. In this regard, it is desirable to control the magnitude of VUV fluxes or the ratio of VUV fluxes to those of other reactive species, such as ions, or to discretely control the VUV spectrum. In this paper, we discuss results from a computational investigation of VUV fluxes from low-pressure ICPs sustained in rare gas mixtures. The control of VUV fluxes through the use of pressure, pulsed power, and gas mixture is discussed. We found that the ratio, β, of VUV photon to ion fluxes onto surfaces generally increases with increasing pressure. When using pulsed plasmas, the instantaneous value of β can vary by a factor of 4 or more during the pulse cycle due to the VUV flux more closely following the pulsed power.

  19. Evacuation of coal from hoppers/silos with low pressure pneumatic blasting systems

    NASA Technical Reports Server (NTRS)

    Fischer, J. S.

    1977-01-01

    The need for an efficient, economical, effective and quiet device for moving coal and other difficult bulk solids was recognized. Thus came the advent of the low pressure pneumatic blasting system - a very efficient means of using a small amount of plant air (up to 125 PSI) to eliminate the most troublesome material hang-ups in storage containers. This simple device has one moving part and uses approximately 3% of the air consumed by a pneumatic vibrator on the same job. The principle of operation is very simple: air stored in the unit's reservoir is expelled directly into the material via a patented quick release valve. The number, size, and placement of the blaster units on the storage vessel is determined by a series of tests to ascertain flowability of the problem material. These tests in conjunction with the hopper or silo configuration determine specification of a low pressure pneumatic blasting system. This concept has often proven effective in solving flow problems when all other means have failed.

  20. Characteristics of Ceramic Coatings Made by Thin Film Low Pressure Plasma Spraying (LPPS-TF)

    NASA Astrophysics Data System (ADS)

    Hospach, Andreas; Mauer, Georg; Vaßen, Robert; Stöver, Detlev

    2012-06-01

    The thin film low pressure plasma spray process (LPPS-TF) has been developed with the aim of efficient depositing uniform and thin coatings with large area coverage by plasma spraying. At high power input (~150 kW) and very low pressure (~100 Pa) the plasma jet properties change considerably and it is even possible to evaporate the powder feedstock material providing advanced microstructures of the deposits. This relatively new technique bridges the gap between conventional plasma spraying and physical vapor deposition. In addition, the resulting microstructures are unique and can hardly be obtained by other processes. In this paper, microstructures made by LPPS-TF are shown and the columnar layer growth by vapor deposition is demonstrated. In addition to the ceramic materials TiO2, Al2O3 or MgAl2O4, the focus of the research was placed on partially yttria-stabilized zirconia. Variations of the microstructures are shown and discussed concerning potential coating applications.

  1. Kinetic mechanism for low-pressure oxygen/methane ignition and combustion

    NASA Astrophysics Data System (ADS)

    Slavinskaya, N. A.; Wiegand, M.; Starcke, J. H.; Riedel, U.; Haidn, O. J.; Suslov, D.

    2013-03-01

    It is known that during a launch of a rocket, the interaction of the exhaust gases of rocket engines with the atmosphere causes a local depletion of the ozone layer. In order to study these chemical processes in detail, a chemical reaction mechanism of the methane oxidation appropriate for high- and low-pressure conditions and a chemical reactor network to reproduce operating conditions in rocket engines and in the environment have been developed. An earlier developed detailed chemical kinetic model for the high-pressure CH4/O2 combustion has been improved for the low pressure and low temperature methane combustion and augmented with a submodel for NOx formation. The main model improvements are related to the pressure depending reactions. The model has been validated for operating conditions of 0.02 < p < 100 atm, 300 < T < 1800 K and 0.5 < Φ < 3.0. The network of chemical reactors available in CHEMICAL WORKBENCH software has been successfully developed to simulate chemical processes in the convergent divergent rocket nozzle and in the exhaust-jet. Simulations performed have shown that the exhaust gases of a methane/oxygen propelled liquid rocket engine contain high amounts of active radicals, which can influence the formation of nitrogen compounds and consume ozone in the atmosphere.

  2. Microwave air plasmas in capillaries at low pressure I. Self-consistent modeling

    NASA Astrophysics Data System (ADS)

    Coche, P.; Guerra, V.; Alves, L. L.

    2016-06-01

    This work presents the self-consistent modeling of micro-plasmas generated in dry air using microwaves (2.45 GHz excitation frequency), within capillaries (<1 mm inner radius) at low pressure (300 Pa). The model couples the system of rate balance equations for the most relevant neutral and charged species of the plasma to the homogeneous electron Boltzmann equation. The maintenance electric field is self-consistently calculated adopting a transport theory for low to intermediate pressures, taking into account the presence of O‑ ions in addition to several positive ions, the dominant species being O{}2+ , NO+ and O+ . The low-pressure small-radius conditions considered yield very-intense reduced electric fields (∼600–1500 Td), coherent with species losses controlled by transport and wall recombination, and kinetic mechanisms strongly dependent on electron-impact collisions. The charged-particle transport losses are strongly influenced by the presence of the negative ion, despite its low-density (∼10% of the electron density). For electron densities in the range (1–≤ft. 4\\right)× {{10}12} cm‑3, the system exhibits high dissociation degrees for O2 (∼20–70%, depending on the working conditions, in contrast with the  ∼0.1% dissociation obtained for N2), a high concentration of O2(a) (∼1014 cm‑3) and NO(X) (5× {{10}14} cm‑3) and low ozone production (<{{10}-3}% ).

  3. Weak interactions between water and clathrate-forming gases at low pressures

    SciTech Connect

    Thürmer, Konrad; Yuan, Chunqing; Kimmel, Greg A.; Kay, Bruce D.; Smith, R. Scott

    2015-07-17

    Using scanning probe microscopy and temperature programed desorption we examined the interaction between water and two common clathrate-forming gases, methane and isobutane, at low temperature and low pressure. Water co-deposited with up to 10–1 mbar methane or 10–5 mbar isobutane at 140 K onto a Pt(111) substrate yielded pure crystalline ice, i.e., the exposure to up to ~ 107 gas molecules for each deposited water molecule did not have any detectable effect on the growing films. Exposing metastable, less than 2 molecular layers thick, water films to 10–5 mbar methane does not alter their morphology, suggesting that the presence of the Pt(111) surface is not a strong driver for hydrate formation. This weak water–gas interaction at low pressures is supported by our thermal desorption measurements from amorphous solid water and crystalline ice where 1 ML of methane desorbs near ~ 43 K and isobutane desorbs near ~ 100 K. As a result, similar desorption temperatures were observed for desorption from amorphous solid water.

  4. Quantitative and sensitive analysis of CN molecules using laser induced low pressure He plasma

    SciTech Connect

    Pardede, Marincan; Hedwig, Rinda; Abdulmadjid, Syahrun Nur; Lahna, Kurnia; Idris, Nasrullah; Ramli, Muliadi; Jobiliong, Eric; Suyanto, Hery; Marpaung, Alion Mangasi; Suliyanti, Maria Margaretha; Tjia, May On

    2015-03-21

    We report the results of experimental study on CN 388.3 nm and C I 247.8 nm emission characteristics using 40 mJ laser irradiation with He and N{sub 2} ambient gases. The results obtained with N{sub 2} ambient gas show undesirable interference effect between the native CN emission and the emission of CN molecules arising from the recombination of native C ablated from the sample with the N dissociated from the ambient gas. This problem is overcome by the use of He ambient gas at low pressure of 2 kPa, which also offers the additional advantages of cleaner and stronger emission lines. The result of applying this favorable experimental condition to emission spectrochemical measurement of milk sample having various protein concentrations is shown to yield a close to linear calibration curve with near zero extrapolated intercept. Additionally, a low detection limit of 5 μg/g is found in this experiment, making it potentially applicable for quantitative and sensitive CN analysis. The visibility of laser induced breakdown spectroscopy with low pressure He gas is also demonstrated by the result of its application to spectrochemical analysis of fossil samples. Furthermore, with the use of CO{sub 2} ambient gas at 600 Pa mimicking the Mars atmosphere, this technique also shows promising applications to exploration in Mars.

  5. In situ CF3 Detection in Low Pressure Inductive Discharges by Fourier Transform Infrared Spectroscopy

    NASA Technical Reports Server (NTRS)

    Kim, J. S.; Cappelli, M. A.; Sharma, S. P.; Arnold, J. O. (Technical Monitor)

    1998-01-01

    The detection of CF(x) (x=1-3) radicals in low pressure discharges using source gases such as CF4 and CHF3 is of importance to the understanding of their chemical structure and relevance in plasma based etching processes. These radicals are known to contribute to the formation of fluorocarbon polymer films, which affect the selectivity and anisotropy of etching. In this study, we present preliminary results of the quantitative measurement of trifluoromethyl radicals, CF3, in low pressure discharges. The discharge studied here is an inductively (transformer) coupled plasma (ICP) source in the GEC reference cell, operating on pure CF4 at pressures ranging from 10 - 100 mTorr, This plasma source generates higher electron number densities at lower operating pressures than obtainable with the parallel-plate capacitively coupled version of the GEC reference cell. Also, this expanded operating regime is more relevant to new generations of industrial plasma reactors being used by the microelectronics industry. Fourier transform infrared (FTIR) spectroscopy is employed to observe the absorption band of CF3 radicals in the electronic ground state X2Al in the region of 1233-1270/cm. The spectrometer is equipped with a high sensitivity HgCdTe (MCT) detector and has a fixed resolution of 0.125/cm. The CF3 concentrations are measured for a range of operating pressures and discharge power levels.

  6. Determination of the cathode and anode voltage drops in high power low-pressure amalgam lamps

    SciTech Connect

    Vasilyak, L. M.; Vasiliev, A. I. Kostyuchenko, S. V.; Sokolov, D. V.; Startsev, A. Yu.; Kudryavtsev, N. N.

    2011-12-15

    For the first time, cathode and anode drops of powerful low-pressure amalgam lamps were measured. The lamp discharge current is 3.2 A, discharge current frequency is 43 kHz, linear electric power is 2.4 W/cm. The method of determination of a cathode drop is based on the change of a lamp operating voltage at variation of the electrode filament current at constant discharge current. The total (cathode plus anode) drop of voltage was measured by other, independent ways. The maximum cathode fall is 10.8 V; the anode fall corresponding to the maximal cathode fall is 2.4 V. It is shown that in powerful low pressure amalgam lamps the anode fall makes a considerable contribution (in certain cases, the basic one) to heating of electrodes. Therefore, the anode fall cannot be neglected, at design an electrode and ballast of amalgam lamps with operating discharge current frequency of tens of kHz.

  7. Hydrogen negative-ion surface production on diamond materials in low-pressure H2 plasmas

    NASA Astrophysics Data System (ADS)

    Cartry, Gilles; Achkasov, Kostiantyn; Pardanaud, Cédric; Layet, Jean-Marc; Simonin, Alain; Gicquel, Alix; PIIM Collaboration; IRFM Collaboration; LSPM Collaboration

    2014-10-01

    Negative-ion sources producing H-current density of ~200 A/m2 are required for the heating of the fusion plasma of the international project ITER. The only up-to-date solution to reach such a high H-negative-ion current is the use of cesium (Cs). Deposition of Cs on the negative-ion source walls lowers the material work function and allows for high electron-capture efficiency by incident particles and thus, high negative ion yields. However, severe drawbacks to the use of Cs have been identified and its elimination from the fusion negative-ion sources would be highly valuable. Volume production is not efficient enough at low-pressure to reach the high current required. Therefore, we are working on alternative solutions to produce high yield of H-negative-ions on surfaces in Cs-free H2 plasmas. In this communication, we will detail the methodology employed to study negative-ion surface production. In particular we will describe how the negative-ions are extracted from the plasma, and how we can obtain information on surface production mechanisms from the measurement of the H-energy distribution functions. We will present some results obtained on diamond surfaces and show that diamond is a promising candidate as a negative-ion enhancer material in low-pressure H2 plasmas. EFDA, FR-FCM, ANR, PACA are acknowledged for their support.

  8. Low-pressure clathrate-hydrate formation in amorphous astrophysical ice analogs

    NASA Technical Reports Server (NTRS)

    Blake, D. F.; Allamandola, L. J.; Sandford, S.; Hudgins, D.; Freund, F.

    1991-01-01

    In modeling cometary ice, the properties of clathrate hydrates were used to explain anomalous gas release at large radial distances from the Sun, and the retention of particular gas inventories at elevated temperatures. Clathrates may also have been important early in solar system history. However, there has never been a reasonable mechanism proposed for clathrate formation under the low pressures typical of these environments. For the first time, it was shown that clathrate hydrates can be formed by warming and annealing amorphous mixed molecular ices at low pressures. The complex microstructures which occur as a result of clathrate formation from the solid state may provide an explanation for a variety of unexplained phenomena. The vacuum and imaging systems of an Hitachi H-500H Analytical Electron Microscope was modified to study mixed molecular ices at temperatures between 12 and 373 K. The resulting ices are characterized by low-electron dose Transmission Electron Microscopy (TEM) and Selected Area Electron Diffraction (SAED). The implications of these results for the mechanical and gas release properties of comets are discussed. Laboratory IR data from similar ices are presented which suggest the possibility of remotely observing and identifying clathrates in astrophysical objects.

  9. Weak interactions between water and clathrate-forming gases at low pressures

    NASA Astrophysics Data System (ADS)

    Thürmer, Konrad; Yuan, Chunqing; Kimmel, Greg A.; Kay, Bruce D.; Scott Smith, R.

    2015-11-01

    Using scanning probe microscopy and temperature programed desorption we examined the interaction between water and two common clathrate-forming gases, methane and isobutane, at low temperature and low pressure. Water co-deposited with up to 10- 1 mbar methane or 10- 5 mbar isobutane at 140 K onto a Pt(111) substrate yielded pure crystalline ice, i.e., the exposure to up to ~ 107 gas molecules for each deposited water molecule did not have any detectable effect on the growing films. Exposing metastable, less than 2 molecular layers thick, water films to 10- 5 mbar methane does not alter their morphology, suggesting that the presence of the Pt(111) surface is not a strong driver for hydrate formation. This weak water-gas interaction at low pressures is supported by our thermal desorption measurements from amorphous solid water and crystalline ice where 1 ML of methane desorbs near ~ 43 K and isobutane desorbs near ~ 100 K. Similar desorption temperatures were observed for desorption from amorphous solid water.

  10. Utilization of Low-Pressure Plasma to Inactivate Bacterial Spores on Stainless Steel Screws

    PubMed Central

    Stapelmann, Katharina; Fiebrandt, Marcel; Raguse, Marina; Awakowicz, Peter; Reitz, Günther

    2013-01-01

    Abstract A special focus area of planetary protection is the monitoring, control, and reduction of microbial contaminations that are detected on spacecraft components and hardware during and after assembly. In this study, wild-type spores of Bacillus pumilus SAFR-032 (a persistent spacecraft assembly facility isolate) and the laboratory model organism B. subtilis 168 were used to study the effects of low-pressure plasma, with hydrogen alone and in combination with oxygen and evaporated hydrogen peroxide as a process gas, on spore survival, which was determined by a colony formation assay. Spores of B. pumilus SAFR-032 and B. subtilis 168 were deposited with an aseptic technique onto the surface of stainless steel screws to simulate a spore-contaminated spacecraft hardware component, and were subsequently exposed to different plasmas and hydrogen peroxide conditions in a very high frequency capacitively coupled plasma reactor (VHF-CCP) to reduce the spore burden. Spores of the spacecraft isolate B. pumilus SAFR-032 were significantly more resistant to plasma treatment than spores of B. subtilis 168. The use of low-pressure plasma with an additional treatment of evaporated hydrogen peroxide also led to an enhanced spore inactivation that surpassed either single treatment when applied alone, which indicates the potential application of this method as a fast and suitable way to reduce spore-contaminated spacecraft hardware components for planetary protection purposes. Key Words: Bacillus spores—Contamination—Spacecraft hardware—Plasma sterilization—Planetary protection. Astrobiology 13, 597–606. PMID:23768085

  11. RAPID ASSOCIATION REACTIONS AT LOW PRESSURE: IMPACT ON THE FORMATION OF HYDROCARBONS ON TITAN

    SciTech Connect

    Vuitton, V.; Klippenstein, S. J. E-mail: yelle@lpl.arizona.edu E-mail: sjk@anl.gov

    2012-01-01

    Photochemical models of Titan's atmosphere predict that three-body association reactions are the main production route for several major hydrocarbons. The kinetic rate constants of these reactions strongly depend on density and are therefore only important in Titan's lower atmosphere. However, radiative association reactions do not depend on pressure. The possible existence of large rates at low density suggests that association reactions could significantly affect the chemistry of Titan's upper atmosphere and better constraints for them are required. The kinetic parameters of these reactions are extremely difficult to constrain by experimental measurements as the low pressure of Titan's upper atmosphere cannot be reproduced in the laboratory. However, in the recent years, theoretical calculations of kinetics parameters have become more and more reliable. We therefore calculated several radical-radical and radical-molecule association reaction rates using transition state theory. The calculations indicate that association reactions are fast even at low pressure for adducts having as few as four C atoms. These drastic changes have however only moderate consequences for Titan's composition. Locally, mole fractions can vary by as much as one order of magnitude but the column-integrated production and condensation rates of hydrocarbons change only by a factor of a few. We discuss the impact of these results for the organic chemistry. It would be very interesting to check the impact of these new rate constants on other environments, such as giant and extrasolar planets as well as the interstellar medium.

  12. Sensitive cesium measurement in liquid sample using low-pressure laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Wang, Zhen Zhen; Yan, Jun Jie; Liu, Ji Ping; Deguchi, Yoshihiro; Katsumori, Shunpei; Ikutomo, Akihiro

    2015-12-01

    The environmental pollution by trace heavy metals is a severe problem for the environment and human health. In this paper, the liquid jet of CsNO3 solution employed was introduced to the measurement chamber and detected using laser-induced breakdown spectroscopy (LIBS) directly at low pressure to determine the detection features of trace Cs element in liquid. The distinct and round plasma can be acquired when reducing the pressure. The interaction between the plasma core of the liquid jet and the surrounding gas can be controlled to enhance Cs detection ability. Cs emission was mainly in the surrounding area in the plasma. The influences of laser focal point and plasma measurement area on the measured signals were studied under low-pressure condition. When employing the defocus mode and varying the measurement area within a certain range, Cs signal and the signal-to-background ratio were improved. Cs detection limit can reach to 22.8 ppb (3σ/ms) at pressure of 26 kPa in this paper. According to the discussion, the detection limit will be enhanced when improving the experimental conditions using this method, which shows the great application potential of liquid sample measurement.

  13. Inactivation differences of microorganisms by low pressure UV and pulsed xenon lamps.

    PubMed

    Otaki, M; Okuda, A; Tajima, K; Iwasaki, T; Kinoshita, S; Ohgaki, S

    2003-01-01

    UV disinfection has been applied to water treatment in recent years with low-pressure and medium-pressure UV lamps mainly used as the light source. In general, UV disinfection is considered to be inefficient with water of high turbidity because of inhibition of light penetration. Additionally, photoreactivation may be a problem that should be considered in case a disinfected water is discharged to the environment where sunlight causes reactivation. Recently, other types of lamps have been proposed including a flush-type lamp (such as a pulsed-xenon lamp) that emits high energy and wide wavelength intermittently. In this study, the difference between inactivation efficiencies by low-pressure UV (LPUV) and pulsed-xenon (PXe) lamps was investigated using two coliphage types and three strains of Escherichia coli. PXe had a suppressive effect on photoreactivation rate of the E. coli strains even though there was no significant effect on inactivation rate and maximum survival ratio after photoreactivation. PXe also had a benefit when applied to high turbidity waters as no tailing phenomena were observed in the low survival ratio area although it was observed in LPUV inactivation. This efficiency difference was considered to be due to the difference in irradiated wavelength of both lamps. PMID:12639027

  14. Gas-phase reaction study of disilane pyrolysis: Applications to low pressure chemical vapor deposition

    SciTech Connect

    Johannes, J.E.; Ekerdt, J.G. . Dept. of Chemical Engineering)

    1994-08-01

    The gas-phase thermal reactions during disilane decomposition at low pressure chemical vapor deposition conditions were studied from 300 to 1,000 K using resonance enhanced multiphoton ionization (REMPI) and multiphoton ionization (MPI). REMPI of gas-phase Si, mass 28, was detected from 640 to 840 K and 1 to 10 Torr, with a maximum signal intensity between 700 to 720 K. During disilane decomposition, no SiH (427.8 nm), SiH[sub 2] (494-515 nm), or SiH[sub 3] (419.0 nm) was detected. MPI of higher silanes, silenes, and silylenes were detected through mass fragments 2, 32, and 60; these species reached a maximum signal intensity 20 degrees prior to the mass-28 maximum. Modeling studies that included a detailed low pressure gas-phase kinetic scheme predict relative gas-phase partial pressures generated during disilane pyrolysis. The model predicted experimental trends in the Si partial pressure and the higher silane, silene, and silylene partial pressures.

  15. Low-pressure, automated, sample packing unit for diffuse reflectance infrared spectrometry

    NASA Astrophysics Data System (ADS)

    Christy, Alfred A.; Tvedt, Jan Erik; Karstang, Terje V.; Velapoldi, Rance A.

    1988-03-01

    An automatic, low-pressure packing unit has been designed with control of packing time and pressure to prepare powder samples for diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). This unit also provides a polished packing surface that ensures constant measurement height of the sample in the spectrometer. Use of this unit coupled with sample rotation during measurement and control of particle size and size distribution, provides excellent precision in obtaining DRIFTS spectra. For example, repackings by a single person or by several untrained people gave coefficients of variation from 0.8% to 2.3% for each digital spectral value for a coal sample and from 1.3% to 3.7% for thymol blue, a sharp spectral featured organic, rather than the 15%-30% normally found for repackings of the same sample. Thus representative DRIFTS spectra can be obtained quickly and efficiently from a powder sample with a single spectrum using this low-pressure, mechanical packing device, control of particle parameters, and sample rotation as opposed to previous efforts requiring the repacking of several samples and averaging of the spectra.

  16. Simplified configuration for the combustor of an oil burner using a low pressure, high flow air-atomizing nozzle

    DOEpatents

    Butcher, Thomas A.; Celebi, Yusuf; Fisher, Leonard

    2000-09-15

    The invention relates to clean burning of fuel oil with air. More specifically, to a fuel burning combustion head using a low-pressure, high air flow atomizing nozzle so that there will be a complete combustion of oil resulting in a minimum emission of pollutants. The improved fuel burner uses a low pressure air atomizing nozzle that does not result in the use of additional compressors or the introduction of pressurized gases downstream, nor does it require a complex design. Inventors:

  17. Decomposition Characteristics of an Artificial Biogas in a Low-Pressure DC Glow Discharge

    NASA Astrophysics Data System (ADS)

    Itoh, Yasuhiro; Oshita, Takamasa; Satoh, Kohki; Itoh, Hidenori

    The decomposition characteristics of an artificial biogas, which is a mixture of CH4, CO2 and H2S, using a low pressure DC glow discharge have been investigated. It is found that H2, CO, C2H2, H2O, CS2 and COS are produced from the artificial biogas in the glow discharge. About 65 % of hydrogen atoms in CH4 are converted into H2 at the input energy of 800 J, at which CH4 is completely decomposed, and the decomposition characteristics of the artificial biogas has little dependency on H2S additive. Farther, H2S has a tendency to be decomposed earlier than the other components of the artificial biogas. When the glow discharge is generated in the artificial biogas with H2S, some of carbon atoms are found to deposit on electrodes and the wall of a discharge chamber.

  18. Remote catalyzation for growth of boron nitride nanotubes by low pressure chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Wang, Liangjie; Li, Taotao; Ling, Lin; Luo, Jie; Zhang, Kai; Xu, Yancui; Lu, Huifen; Yao, Yagang

    2016-05-01

    Direct deposition of high purity and quality boron nitride nanotubes (BNNTs) on Si substrate were obtained using low pressure chemical vapor deposition (LPCVD). We find Fe-Mg-O species may act as catalysts for growing BNNTs. This synthesis process conforms to vapor-liquid-solid (VLS) growth mechanism. As-grown BNNTs also show a large optical energy band gap of 6.12 eV, approaching to hexagonal phase BN single crystals. Meanwhile, as-grown BNNTs exhibit an intense UV-emission band located at 345 nm and a weak deep band at 237 nm. Their optoelectronic properties make them have promising for future nanoscale deep-UV light emitting devices.

  19. Mixture distributions for the statistical time delay in synthetic air at low pressure

    NASA Astrophysics Data System (ADS)

    Jovanović, Aleksandar P.; Popović, Biljana Č.; Marković, Vidosav Lj.; Stamenković, Suzana N.; Stankov, Marjan N.

    2014-08-01

    The mixture distributions for statistical time delay of electrical breakdown are proposed along with the generalized relation for the effective electron yield. The validity of the proposed model is tested by applying this distribution to experimental data measured in synthetic air at low pressure. Two samples without and with oxide surface are compared in order to determine physical processes leading to appearance of mixture distributions in the case of oxidized cathode. The obtained distributions are tested by Kolmogorov-Smirnov statistical hypothesis test in order to justify the use of mixture distributions. The physical interpretation of mixture distribution measured in the synthetic air is proposed, accompanied by the calculated values of the effective electron yield of initiating electrons in the gas gap.

  20. Ultrasensitive detection of explosives and chemical warfare agents by low-pressure photoionization mass spectrometry.

    PubMed

    Sun, Wanqi; Liang, Miao; Li, Zhen; Shu, Jinian; Yang, Bo; Xu, Ce; Zou, Yao

    2016-08-15

    On-spot monitoring of threat agents needs high sensitive instrument. In this study, a low-pressure photoionization mass spectrometer (LPPI-MS) was employed to detect trace amounts of vapor-phase explosives and chemical warfare agent mimetics under ambient conditions. Under 10-s detection time, the limits of detection of 2,4-dinitrotoluene, nitrotoluene, nitrobenzene, and dimethyl methyl phosphonate were 30, 0.5, 4, and 1 parts per trillion by volume, respectively. As compared to those obtained previously with PI mass spectrometric techniques, an improvement of 3-4 orders of magnitude was achieved. This study indicates that LPPI-MS will open new opportunities for the sensitive detection of explosives and chemical warfare agents. PMID:27260452

  1. On designing low pressure loss working spaces for a planar Stirling micromachine

    NASA Astrophysics Data System (ADS)

    Hachey, M.-A.; Léveillé, É.; Fréchette, L. G.; Formosa, F.

    2015-12-01

    In this paper, research was undertaken with the objective to design low pressure loss working spaces for a Stirling cycle micro heat engine operating from low temperature waste heat. This planar free-piston heat engine is anticipated to operate at the kHz level with mm3 displacement. Given the resonant nature of the free-piston configuration, the complexity of its working gas’ flow geometry and its projected high operating frequency, flow analysis is relatively complex. Design considerations were thus based on fast prototyping and experimentation. Results show that geometrical features, such as a sharp 90° corner between the regenerator and working spaces, are strong contributors to pressure losses. This research culminated into a promising revised working space configuration for engine start-up, as it considerably reduced total pressure losses, more than 80% at Re = 700, from the original design.

  2. Thermal equilibrium in gas-discharge plasma of low pressure mercury lamp

    NASA Astrophysics Data System (ADS)

    Gorbunkov, V. I.; Solomonov, V. I.

    2015-12-01

    A study was conducted emission spectra germicidal low pressure mercury lamp at currents 100-306 mA located in a closed opaque cavity. It is shown that the lamps located in the cavity with perfectly reflecting and absorbing internal surfaces, in the emission resonance line of mercury is dominant at λr = 253.65 nm. The same pattern is observed in the tube placed in a cavity with diffusely reflecting surface at a low current of about 100 mA. However the picture of spectrum changes at higher discharge current. The spectrum of the lamp with arc discharge at a current of 306 mA contains the maxima of the spectral lines. Its intensities are approximately described by Planck's radiation law at the temperature of 9270 +/- 230 K. The mechanisms of establish thermal equilibrium are discussed.

  3. Highly ionized physical vapor deposition plasma source working at very low pressure

    SciTech Connect

    Stranak, V.; Herrendorf, A.-P.; Drache, S.; Hippler, R.; Cada, M.; Hubicka, Z.; Tichy, M.

    2012-04-02

    Highly ionized discharge for physical vapor deposition at very low pressure is presented in the paper. The discharge is generated by electron cyclotron wave resonance (ECWR) which assists with ignition of high power impulse magnetron sputtering (HiPIMS) discharge. The magnetron gun (with Ti target) was built into the single-turn coil RF electrode of the ECWR facility. ECWR assistance provides pre-ionization effect which allows significant reduction of pressure during HiPIMS operation down to p = 0.05 Pa; this is nearly more than an order of magnitude lower than at typical pressure ranges of HiPIMS discharges. We can confirm that nearly all sputtered particles are ionized (only Ti{sup +} and Ti{sup ++} peaks are observed in the mass scan spectra). This corresponds well with high plasma density n{sub e} {approx} 10{sup 18} m{sup -3}, measured during the HiPIMS pulse.

  4. Highly ionized physical vapor deposition plasma source working at very low pressure

    NASA Astrophysics Data System (ADS)

    Stranak, V.; Herrendorf, A.-P.; Drache, S.; Cada, M.; Hubicka, Z.; Tichy, M.; Hippler, R.

    2012-04-01

    Highly ionized discharge for physical vapor deposition at very low pressure is presented in the paper. The discharge is generated by electron cyclotron wave resonance (ECWR) which assists with ignition of high power impulse magnetron sputtering (HiPIMS) discharge. The magnetron gun (with Ti target) was built into the single-turn coil RF electrode of the ECWR facility. ECWR assistance provides pre-ionization effect which allows significant reduction of pressure during HiPIMS operation down to p = 0.05 Pa; this is nearly more than an order of magnitude lower than at typical pressure ranges of HiPIMS discharges. We can confirm that nearly all sputtered particles are ionized (only Ti+ and Ti++ peaks are observed in the mass scan spectra). This corresponds well with high plasma density ne ˜ 1018 m-3, measured during the HiPIMS pulse.

  5. The effects of plasma inhomogeneity on the nanoparticle coating in a low pressure plasma reactor

    SciTech Connect

    Pourali, N.; Foroutan, G.

    2015-10-15

    A self-consistent model is used to study the surface coating of a collection of charged nanoparticles trapped in the sheath region of a low pressure plasma reactor. The model consists of multi-fluid plasma sheath module, including nanoparticle dynamics, as well as the surface deposition and particle heating modules. The simulation results show that the mean particle radius increases with time and the nanoparticle size distribution is broadened. The mean radius is a linear function of time, while the variance exhibits a quadratic dependence. The broadening in size distribution is attributed to the spatial inhomogeneity of the deposition rate which in turn depends on the plasma inhomogeneity. The spatial inhomogeneity of the ions has strong impact on the broadening of the size distribution, as the ions contribute both in the nanoparticle charging and in direct film deposition. The distribution width also increases with increasing of the pressure, gas temperature, and the ambient temperature gradient.

  6. Formation processes of nanometer sized particles in low pressure Ar/CH{sub 4} rf plasmas

    SciTech Connect

    Beckers, J.; Vacaresse, G. D. G. J.; Stoffels, W. W.

    2008-09-07

    In this paper, formation and growth processes of nanometer and micrometer sized dust particles in low pressure Ar/CH{sub 4} rf (13.56 MHz) plasmas are investigated as function of temperature in the range 25-100 deg. C. During experiments the pressure was typically 0.8 mbar and the forward power to the plasma was {approx}70 Watt. Measuring the fundamental voltage, current and phase angle together with their harmonics (up to the fourth) gives a good method to monitor the creation and growth of these dust particles in time. Furthermore, laser light scattering measurements are performed to give information about the dust particle density. It has been shown that dust particle formation in these conditions depends greatly on temperature.

  7. Growth Characteristics of Carbon Nanotubes on Oxidized Catalyst under Low-Pressure Condition

    NASA Astrophysics Data System (ADS)

    Sawaguchi, Daiki; Sato, Hideki; Hata, Koichi; Miyake, Hideto; Iida, Kazuo; Hiramatsu, Kazumasa

    2012-01-01

    Low-pressure alcohol catalytic chemical vapor deposition (LP-ACCVD), which is an ACCVD method at a lower pressure (<1 Pa) than that in the conventional method, has been attracting much interest because it enables the low-temperature growth of single-wall carbon nanotubes (CNTs). However, the growth rate of CNTs by LP-ACCVD is markedly low owing to its low growth pressure. To alleviate this problem, we have examined the influence of the catalyst preparation and CVD conditions on the properties of CNTs grown by LP-ACCVD. It has been found that the oxidation of catalyst enhances the growth of CNTs by LP-ACCVD. Furthermore, the low flow rate of the ethanol enhances the growth yield of CNTs at lower growth temperature, which is understood to be the result of sufficient gas heating on the substrate.

  8. Removal of C.I. Reactive Red 2 by low pressure UV/chlorine advanced oxidation.

    PubMed

    Wu, Qianyuan; Li, Yue; Wang, Wenlong; Wang, Ting; Hu, Hongying

    2016-03-01

    Azo dyes are commonly found as pollutants in wastewater from the textile industry, and can cause environmental problems because of their color and toxicity. The removal of a typical azo dye named C.I. Reactive Red 2 (RR2) during low pressure ultraviolet (UV)/chlorine oxidation was investigated in this study. UV irradiation at 254nm and addition of free chlorine provided much higher removal rates of RR2 and color than UV irradiation or chlorination alone. Increasing the free chlorine dose enhanced the removal efficiency of RR2 and color by UV/chlorine oxidation. Experiments performed with nitrobenzene (NB) or benzoic acid (BA) as scavengers showed that radicals (especially OH) formed during UV/chlorine oxidation are important in the RR2 removal. Addition of HCO3(-) and Cl(-) to the RR2 solution did not inhibit the removal of RR2 during UV/chlorine oxidation. PMID:26969069

  9. Fabrication of Planar Heterojunction Perovskite Solar Cells by Controlled Low-Pressure Vapor Annealing.

    PubMed

    Li, Yanbo; Cooper, Jason K; Buonsanti, Raffaella; Giannini, Cinzia; Liu, Yi; Toma, Francesca M; Sharp, Ian D

    2015-02-01

    A new method for achieving high efficiency planar CH3NH3I3-xClx perovskite photovoltaics, based on a low pressure, reduced temperature vapor annealing is demonstrated. Heterojunction devices based on this hybrid halide perovskite exhibit a top PCE of 16.8%, reduced J-V hysteresis, and highly repeatable performance without need for a mesoporous or nanocrystalline metal oxide layer. Our findings demonstrate that large hysteresis is not an inherent feature of planar heterojunctions, and that efficient charge extraction can be achieved with uniform halide perovskite materials with desired composition. X-ray diffraction, valence band spectroscopy, and transient absorption measurements of these thin films reveal that structural modifications induced by chlorine clearly dominate over chemical and electronic doping effects, without affecting the Fermi level or photocarrier lifetime in the material. PMID:26261969

  10. Low-pressure phase diagram of crystalline benzene from quantum Monte Carlo

    NASA Astrophysics Data System (ADS)

    Azadi, Sam; Cohen, R. E.

    2016-08-01

    We studied the low-pressure (0-10 GPa) phase diagram of crystalline benzene using quantum Monte Carlo and density functional theory (DFT) methods. We performed diffusion quantum Monte Carlo (DMC) calculations to obtain accurate static phase diagrams as benchmarks for modern van der Waals density functionals. Using density functional perturbation theory, we computed the phonon contributions to the free energies. Our DFT enthalpy-pressure phase diagrams indicate that the Pbca and P21/c structures are the most stable phases within the studied pressure range. The DMC Gibbs free-energy calculations predict that the room temperature Pbca to P21/c phase transition occurs at 2.1(1) GPa. This prediction is consistent with available experimental results at room temperature. Our DMC calculations give 50.6 ± 0.5 kJ/mol for crystalline benzene lattice energy.

  11. Monte Carlo Simulation of Laser-Ablated Particle Splitting Dynamic in a Low Pressure Inert Gas

    NASA Astrophysics Data System (ADS)

    Ding, Xuecheng; Zhang, Zicai; Liang, Weihua; Chu, Lizhi; Deng, Zechao; Wang, Yinglong

    2016-06-01

    A Monte Carlo simulation method with an instantaneous density dependent mean-free-path of the ablated particles and the Ar gas is developed for investigating the transport dynamics of the laser-ablated particles in a low pressure inert gas. The ablated-particle density and velocity distributions are analyzed. The force distributions acting on the ablated particles are investigated. The influence of the substrate on the ablated-particle velocity distribution and the force distribution acting on the ablated particles are discussed. The Monte Carlo simulation results approximately agree with the experimental data at the pressure of 8 Pa to 17 Pa. This is helpful to investigate the gas phase nucleation and growth mechanism of nanoparticles. supported by the Natural Science Foundation of Hebei Province, China (No. A2015201166) and the Natural Science Foundation of Hebei University, China (No. 2013-252)

  12. Low pressure process for continuous fiber reinforced polyamic acid resin matrix composite laminates

    NASA Technical Reports Server (NTRS)

    Druyun, Darleen A. (Inventor); Hou, Tan-Hung (Inventor); Kidder, Paul W. (Inventor); Reddy, Rakasi M. (Inventor); Baucom, Robert M. (Inventor)

    1994-01-01

    A low pressure processor was developed for preparing a well-consolidated polyimide composite laminate. Prepreg plies were formed from unidirectional fibers and a polyamic acid resin solution. Molding stops were placed at the sides of a matched metal die mold. The prepreg plies were cut shorter than the length of the mold in the in-plane lateral direction and were stacked between the molding stops to a height which was higher than the molding stops. The plies were then compressed to the height of the stops and heated to allow the volatiles to escape and to start the imidization reaction. After removing the stops from the mold, the heat was increased and 0 - 500 psi was applied to complete the imidization reaction. The heat and pressure were further increased to form a consolidated polyimide composite laminate.

  13. Performance of a low-pressure-ratio centrifugal compressor with four diffuser designs

    NASA Technical Reports Server (NTRS)

    Klassen, H. A.

    1973-01-01

    A low-pressure-ratio centrifugal compressor was tested with four different diffuser configurations. One diffuser had airfoil vanes. Two were pipe diffusers. One pipe diffuser had 7.5 deg cone diffusing passages. The other had trumpet-shaped passages designed for linear static-pressure rise from throat to exit. The fourth configuration had flat vanes with elliptical leading edges similar to those of pipe diffusers. The side walls were contoured to produce a linear pressure rise. Peak compressor efficiencies were 0.82 with the airfoil vane and conical pipe diffusers, 0.80 with the trumpet, and 0.74 with the flat-vane design. Surge margin and useful range were greater for the airfoil-vane diffuser than for the other three.

  14. Direct current-self-sustained non-ambipolar plasma at low pressure

    SciTech Connect

    Chen, Zhiying; Chen, Lee; Funk, Merritt

    2013-12-16

    For decades, non-ambipolar diffusion has been observed and studied in laboratory plasmas that contain a double layer. However, self-sustained non-ambipolar plasma has yet to be demonstrated. This article reports the method and results for achieving such a condition at low pressure, with a wide power range (as low as 6 W). The findings reveal that to achieve self-sustained non-ambipolar plasma, both the balance between electron and ion heating and the space-potential gradient are critical. The plasma reactor developed in this work has potential applications that include microelectronic surface processing and space propulsion, via space-charge-neutral plasma-beam thruster, when operated in the high power regime.

  15. Efficient swimmers use bending kinematics to generate low pressure regions for suction-based swimming thrust

    NASA Astrophysics Data System (ADS)

    Colin, Sean; Gemmell, Brad; Costello, John; Morgan, Jennifer; Dabiri, John

    2015-11-01

    A longstanding tenet in the conceptualization of animal swimming is that locomotion occurs by pushing against the surrounding water. Implicit in this perspective is the assumption that swimming involves lateral body accelerations that generate locally elevated pressures in the fluid, in order to achieve the expected downstream push of the surrounding water against the ambient pressure. Here we show that to the contrary, efficient swimming animals primarily pull themselves through the water by creating localized regions of low pressure via waves of body surface rotation that generate vortices. These effects are observed using laser diagnostics applied to normal and spinally-transected lampreys. The results suggest rethinking evolutionary adaptations observed in swimming animals as well as the mechanistic basis for bio-inspired underwater vehicles. NSF CBET (1510929).

  16. Pyrene measurements in sooting low pressure methane flames by jet-cooled laser-induced fluorescence.

    PubMed

    Wartel, M; Pauwels, J-F; Desgroux, P; Mercier, X

    2011-12-15

    This paper presents in detail the study we carried out concerning the pyrene measurement by jet-cooled laser-induced fluorescence (JCLIF) in different sooting low pressure methane flames. The aim of this paper is both to demonstrate the potentialities of this technique for the measurement of such moderately sized polycyclic aromatic hydrocarbons under sooting flame conditions and to provide new experimental data for the understanding and the development of chemical models of the soot formation processes. Several concentration profiles of pyrene measured in different sooting flame (various pressure and equivalence ratio) are presented. The validation of the JCLIF method for pyrene measurements is explained in detail as well as the calibration procedure, based on the standard addition method, which has been implemented for the quantification of the concentration profiles. Sensitivity lower than 1 ppb was obtained for the measurement of this species under sooting flame conditions. PMID:22029528

  17. Laser-induced fluorescence determination of temperatures in low pressure flames.

    PubMed

    Rensberger, K J; Jeffries, J B; Copeland, R A; Kohse-Höinghaus, K; Wise, M L; Crosley, D R

    1989-09-01

    Spatially resolved temperatures in a variety of low pressure flames of hydrogen and hydrocarbons burning with oxygen and nitrous oxide are determined from OH, NH, CH, and CN laser-induced fluorescence rotational excitation spectra. Systematic errors arising from spectral bias, time delay, and temporal sampling gate of the fluorescence detector are considered. In addition, we evaluate the errors arising from the influences of the optical depth and the rotational level dependence of the fluorescence quantum yield for each radical. These systematic errors cannot be determined through goodness-of-fit criteria and they are much larger than the statistical precision of the measurement. The severity of these problems is different for each radical; careful attention to the experimental design details for each species is necessary to obtain accurate LIF temperature measurements. PMID:20555739

  18. Experimental testing of cooling by low pressure adsorption in a zeolite

    SciTech Connect

    Redman, C.M.

    1985-01-01

    A small scale facility was designed, constructed, and utilized to test the use of zeolite adsorption of water vapor to augment chill storage in ice for conventional space cooling. The facility uses solar-derived energy, for the heat source and evaporatively chilled water for the heat sump. The product cooling uses sublimation of ice instead of melting. The ZCAT facility utilizes a heat pumping technique in which a water vapor adsorbent functions as the compressor and condenser. The design was based on use of 13X zeolite as the adsorber because of its high adsorbence at low pressures. However, it has been determined that other materials such as silica gel should give superior performance. While zeolite 13X holds more water in the pressure and temperature ranges of interest, silica gel cycles more water and has less residue water. Both points are very important in the design of an efficient and cost effective system.

  19. Comparison measurements of low-pressure between a laser refractometer and ultrasonic manometer

    NASA Astrophysics Data System (ADS)

    Egan, Patrick F.; Stone, Jack A.; Ricker, Jacob E.; Hendricks, Jay H.

    2016-05-01

    We have developed a new low-pressure sensor which is based on the measurement of (nitrogen) gas refractivity inside a Fabry-Perot cavity. We compare pressure determinations via this laser refractometer to that of well-established ultrasonic manometers throughout the range 100 Pa to 180 000 Pa. The refractometer demonstrates 10-6 ṡ p reproducibility for p > 100 Pa, and this precision outperforms a manometer. We also claim the refractometer has an expanded uncertainty of U(pFP) = [(2.0 mPa)2 + (8.8 × 10-6 ṡ p)2]1/2, as realized through the properties of nitrogen gas; we argue that a transfer of the pascal to p < 1 kPa using a laser refractometer is more accurate than the current primary realization.

  20. Erosion study of final stage blading of low pressure steam turbines

    NASA Astrophysics Data System (ADS)

    Dehouve, J.; Nardin, P.; Zeghmati, M.

    1999-04-01

    In order to increase our knowledge of erosion phenomena, the Steam Turbine Groupe (STG) of ALSTOM has been using an erosion test facility in the C.R.T.V. (Centre de Recherche Turbines à Vapeur). This test facility simulates erosion in low pressure steam turbine cylinders in order to compare the erosion resistance of various blade materials (12% chromium steel, titanium alloys, etc.) and their protection (superficial hardening, coatings, etc.). This test facility also allows us to understand the mechanism causing damage at a macroscopic level (impact energy of the droplets and the loss of eroded volume) and at a microscopic level (residual stress and metallurgic analysis) and therefore to determine an evolution law of material surface damage. In this paper, the behaviour of the materials (12% chromium steel and titanium alloys), which has been analysed by image production measurement methods, will be presented according to different impact velocities.

  1. Dynamics of cathode spots in low-pressure arc plasma removing oxide layer on steel surfaces

    NASA Astrophysics Data System (ADS)

    Tang, Z. L.; Yang, K.; Liu, H. X.; Zhang, Y. C.; Li, H.; Zhu, X. D.

    2016-03-01

    The dynamics of cathode spots has been investigated in low-pressure arc plasma for removing oxide layer on low carbon steel surfaces. The motion of cathode spots was observed with a high speed camera, and the arc voltage was analyzed by fast Fourier transform. The spots move on clean steel surface as a random walk, and the low-frequency components dominated the voltage waveform. However, the spots on steel surfaces with oxide layer tend to burn on the rim of the eroded area formed in the previous arcing, and the low-frequency components decrease correspondingly. The "color" of the colored random noise for arc voltage varies from the approximate brown noise for clean steel surface to pink noise for thick oxide layer, where the edge effect of boundary is considered to play a significant role.

  2. Photodecomposition of o-chloroaniline in aqueous solution with low pressure mercury lamp

    SciTech Connect

    Ishikawa, Seiichi; Baba, Kenzo; Hanada, Yoshifumi; Uchimura, Yutaka; Kido, Kozo

    1989-01-01

    Pollution of organochloric compounds has been a worldwide problem because of their toxicity, resistance to biodegradation and potential for accumulation in biological organisms. Several kinds of organochloric compounds had been detected in environmental samples and biological organisms. About 300 t of o-chloroaniline (o-CA) is produced in Japan annually. o-CA had been detected in river water and sediment. Decomposition by sunlight is a possible route for the environmental degradation of organochloric compounds and ultra violet ray (UV) irradiation is an effective treatment of them in natural water or wastewater. Therefore the authors are interested in the photochemical behavior of o-CA in aqueous solution. The disappearance of substrate and photodecomposition products by using a low pressure mercury lamp were examined.

  3. Effect of geometrical focusing on femtosecond laser filamentation with low pressure

    NASA Astrophysics Data System (ADS)

    Wang, Haitao; Jia, Wei; Fan, Chengyu

    2016-03-01

    The influence of geometrical focusing on the filamentation of femtosecond laser pulses at various low pressures (<1 atm) in air has been numerically demonstrated. The main peculiarities, such as filamentation dynamics, spatial-temporal evolution and supercontinuum generation manipulated by external geometrical focusing in the low atmospheric pressure regime, are analyzed by numerically solving a spatial-temporal equation for femtosecond laser pulse propagation in air. The results show that those important characteristics are more sensitive to the focal length than the variation of atmospheric pressure. It indicates that suitable design of the focal length will result in further amplitude uniformity and a lack of temporal aberrations in the compressed pulse. This theoretical modelling of pulse shaping optimization is a step to realization of high-energy femtosecond pulse delivery from the Earth's surface to altitudes of several kilometers up into the atmosphere.

  4. Low Pressure Plasma Sprayed Overlay Coatings for GRCop-84 Combustion Chamber Liners for Reusable Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Raj, S. V.; Barrett, C.; Ghosn, L. J.; Lerch, B.; Robinson,; Thorn, G.

    2005-01-01

    An advanced Cu-8(at.%)Cr-4%Nb alloy developed at NASA's Glenn Research Center, and designated as GRCop-84, is currently being considered for use as combustor chamber liners and nozzle ramps in NASA s future generations of reusable launch vehicles (RLVs). However, past experience has shown that unprotected copper alloys undergo an environmental attack called "blanching" in rocket engines using liquid hydrogen as fuel and liquid oxygen as the oxidizer. Potential for sulfidation attack of the liners in hydrocarbon-fueled engines is also of concern. Protective overlay coatings alloys are being developed for GRCop-84. The development of this coatings technology has involved a combination of modeling, coatings development and characterization, and process optimization. Coatings have been low pressure plasma sprayed on GRCop-84 substrates of various geometries and shapes. Microstructural, mechanical property data and thermophysical results on the coated substrates are presented and discussed.

  5. Low-pressure argon adsorption assessment of micropore connectivities in activated carbons.

    PubMed

    Zimny, T; Villieras, F; Finqueneisel, G; Cossarutto, L; Weber, J V

    2006-01-01

    Low-pressure argon adsorption has been used to study the energetic distribution of microporous activated carbons differing by their burn-off. The collected isotherms were analyzed using the derivative isotherm summation method. Some oscillations on the experimental curves for very low partial pressures were detected. The results are analyzed and discussed according to the literature and could be attributed to local overheating caused by spontaneous mass transfer of argon through constrictions between former pores and the new opening pore or deadend pores. We used the dynamic character of the experimental method and mainly the discrepancy of the quasi-equilibrium state to deduce key parameters related to the porosity topology. PMID:16112680

  6. Low-pressure microwave plasma nucleation and deposition of diamond films

    NASA Technical Reports Server (NTRS)

    Shing, Y. H.; Pool, F. S.; Rich, D. H.

    1992-01-01

    Low-pressure microwave plasma nucleation and deposition of diamond films were investigated in the pressure range 10-mtorr to 10 torr, at substrate temperatures 400-750 C and with CH4 and O2 concentrations in H2 plasma of 2-15 percent and 2-10 percent, respectively. The experiments were performed in a microwave plasma system consisting of a microwave plasma chamber, a downstream deposition chamber, and an RF induction heated sample stage. Scanning electron microscopy of diamond films deposited at 600 C with 5 percent CH4 and 5 percent O2 in H2 plasmas showed high-quality well faceted crystallites of 1/2 micron size. Cathodoluminescence measurements of these films showed very few nitrogen impurities and no detectable silicon impurities.

  7. Measuring OH and HO2 in the Troposphere by Laser-Induced Fluorescence at Low Pressure.

    NASA Astrophysics Data System (ADS)

    Brune, William H.; Stevens, Philip S.; Mather, James H.

    1995-10-01

    The hydroxyl radical OH oxidizes many lime gases in the atmosphere. It initiates and then participates in chemical reactions that lead to such phenomena as photochemical smog, acid rain, and stratospheric ozone depletion. Because OH is so reactive, its volume mixing ratio is less than 1 part per trillion volume (pptv) throughout the troposphere. Its close chemical cousin, the hydroperoxyl radical HO2, participates in many reactions as well. The authors have developed an instrument capable of measuring OH and HO2 by laser-induced fluorescence in a detection chamber at low pressure. This prototype instrument is able to detect about 1.4 × 105 molecules cm3 (0.005 pptv) of OH at the ground in a signal integration time of 30 s with negligible interferences. The absolute uncertainty is a factor of 1.5. This instrument is now being adapted to aircraft use for measurements throughout the troposphere.

  8. A 2-D Self-Consistent DSMC Model for Chemically Reacting Low Pressure Plasma Reactors

    SciTech Connect

    Bartel, Timothy J.; Economou, Demetre; Johannes, Justine E.

    1999-06-17

    This paper will focus on the methodology of using a 2D plasma Direct Simulation Monte Carlo technique to simulate the species transport in an inductively coupled, low pressure, chemically reacting plasma system. The pressure in these systems is typically less than 20 mtorr with plasma densities of approximately 10{sup 17} {number_sign}/m{sup 3} and an ionization level of only 0.1%. This low ionization level tightly couples the neutral, ion, and electron chemistries and interactions in a system where the flow is subsonic. We present our strategy and compare simulation results to experimental data for Cl{sub 2} in a Gaseous Electronics Conference (GEC) reference cell modified with an inductive coil.

  9. Comparison measurements of low-pressure between a laser refractometer and ultrasonic manometer.

    PubMed

    Egan, Patrick F; Stone, Jack A; Ricker, Jacob E; Hendricks, Jay H

    2016-05-01

    We have developed a new low-pressure sensor which is based on the measurement of (nitrogen) gas refractivity inside a Fabry-Perot cavity. We compare pressure determinations via this laser refractometer to that of well-established ultrasonic manometers throughout the range 100 Pa to 180 000 Pa. The refractometer demonstrates 10(-6) ⋅ p reproducibility for p > 100 Pa, and this precision outperforms a manometer. We also claim the refractometer has an expanded uncertainty of U(pFP) = [(2.0 mPa)(2) + (8.8 × 10(-6) ⋅ p)(2)](1/2), as realized through the properties of nitrogen gas; we argue that a transfer of the pascal to p < 1 kPa using a laser refractometer is more accurate than the current primary realization. PMID:27250398

  10. A search for chemical laser action in low pressure metal vapor flames. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Zwillenberg, M. L.

    1975-01-01

    Optical emissions were studied from low pressure (approximately 1 torr) dilute diffusion flames of Ca and Mg vapor with O2, N2O and mixtures of CCl4 and O2. The Ca flames with O2 and N2O revealed high vibrational excitation of the product CaO molecule (up to v=30). The flames with CCl4 revealed extreme nonequilibrium metal atom electronic excitation, up to the metal atom ionization limit (6.1 eV for Ca, 7.6 eV for Mg). The metal atom excited electronic state populations did not follow a Boltzmann distribution, but the excitation rates ('pumping rate') were found to obey an Arrhenius-type expression, with the electronic excitation energy playing the role of activation energy and a temperature of about 5000 K for triplet excited states and 2500 K for singlets (vs. approximately 500 K translational temperature).

  11. Performance and control study of a low-pressure-ratio turbojet engine for a drone aircraft

    NASA Technical Reports Server (NTRS)

    Seldner, K.; Geyser, L. C.; Gold, H.; Walker, D.; Burgner, G.

    1972-01-01

    The results of analog and digital computer studies of a low-pressure-ratio turbojet engine system for use in a drone vehicle are presented. The turbojet engine consists of a four-stage axial compressor, single-stage turbine, and a fixed area exhaust nozzle. Three simplified fuel schedules and a generalized parameter fuel control for the engine system are presented and evaluated. The evaluation is based on the performance of each schedule or control during engine acceleration from a windmill start at Mach 0.8 and 6100 meters to 100 percent corrected speed. It was found that, because of the higher acceleration margin permitted by the control, the generalized parameter control exhibited the best dynamic performance.

  12. Gas/gas and gas/wall average energy transfer from very low-pressure pyrolysis

    NASA Astrophysics Data System (ADS)

    Gilbert, Robert G.; King, Keith D.

    1980-07-01

    It is shown that data obtained using very low-pressure pyrolysis (VLPP) on the pressure and temperature dependence of unimolecular rate coefficients of reactants with several reaction channels yield average energies transferred in gas/gas and gas/wall collisions (the wall being seasoned quartz at 800-1200 K). The downward average energy transferred, «Δ Eå, for chlorocyclobutane/ethylene collisions is found to be 1600 cm -1 at 970 K; «Δ Eå for chlorocyclobutane/wall collisions varies from 5000 cm -1 (wall efficiency β w = 0.8) at 930 K to 3500 cm -1 (β w = 0.4) at 1150 K; similar values are found from published data on cycloheptatriene and cyclopropane- d2. This indicates that the assumption of unit wall efficiency usually used in fitting VLPP experiments to RRKM theory needs revision.

  13. Three-electrode low pressure discharge apparatus and method for uniform ionization of gaseous media

    DOEpatents

    McLellan, Edward J.

    1983-01-01

    Uniform, transverse electrical discharges are produced in gaseous media without the necessity of switching the main discharge voltage with an external device which carries the entire discharge current. A three-electrode low pressure discharge tube is charged across its anode (1) and cathode (2) to below breakdown voltage using a dc voltage source (3). An array of resistors (4) or capacitors can be made to discharge to the wire screen anode by means of a low energy high voltage pulse circuit (5) producing sufficient preionization in the region between the anode and cathode to initiate and control the main discharge. The invention has been demonstrated to be useful as a CO.sub.2 laser oscillator and pulse-smoother. It can be reliably operated in the sealed-off mode.

  14. Low pressure plasma discharges for the sterilization and decontamination of surfaces

    NASA Astrophysics Data System (ADS)

    Rossi, F.; Kylián, O.; Rauscher, H.; Hasiwa, M.; Gilliland, D.

    2009-11-01

    The mechanisms of sterilization and decontamination of surfaces are compared in direct and post discharge plasma treatments in two low-pressure reactors, microwave and inductively coupled plasma. It is shown that the removal of various biomolecules, such as proteins, pyrogens or peptides, can be obtained at high rates and low temperatures in the inductively coupled plasma (ICP) by using Ar/O2 mixtures. Similar efficiency is obtained for bacterial spores. Analysis of the discharge conditions illustrates the role of ion bombardment associated with O radicals, leading to a fast etching of organic matter. By contrast, the conditions obtained in the post discharge lead to much lower etching rates but also to a chemical modification of pyrogens, leading to their de-activation. The advantages of the two processes are discussed for the application to the practical case of decontamination of medical devices and reduction of hospital infections, illustrating the advantages and drawbacks of the two approaches.

  15. Research program: The investigation of heat transfer and fluid flow at low pressure

    NASA Astrophysics Data System (ADS)

    El-Genk, M. S.; Philbin, J. S.; Foushee, F. C.

    1986-04-01

    This paper gives an overview of a multiyear joint research program being conducted at the University of New Mexico (UNM) with support from Sandia National Laboratories and GA Technologies. This research focuses on heat removal and fluid dynamics in flow regimes characterized by low pressure and low Reynolds number. The program was motivated by a desire to characterize and analyze cooling in a broad class of TRIGA-type reactors under: (1) typical operating conditions, (2) anticipated, new operating regimes, and (3) postulated accident conditions. It has also provided experimental verification of analytical tools used in design analysis. The paper includes descriptions of the UNM thermal-hydraulics test facility and the experimental test sections. During the first two years experiments were conducted using single, electrically heated rod in water and air annuli. This configuration provides an observable and serviceable simulation of a fuel rod and its coolant channel.

  16. Low Pressure High Density Plasma Development on a Small Helicon Plasma Experiment (HPX)*

    NASA Astrophysics Data System (ADS)

    James, R. W.; Allen, L. A.; Paolino, R. N.; Thayer, N.; Romano, B.; Stutzman, B. S.; Welicka, C.; Coast Guard Plasma Lab Team

    2011-10-01

    Small helicon plasmas have been employed in various capacities from industry to spacecraft propulsion. At the Coast Guard Academy Plasma Lab (CGAPL), a small Helicon Plasma Experiment (HPX) is being developed to utilize the reputed high densities (1013 cm-3 and higher) at low pressure (.01 T), in high temperature and density diagnostic development for future laboratory investigations. HPX is designed to operate at these high densities and pressure to create repeatedly stable Capacitively Coupled Plasma (CCP) and Inductively Coupled Plasma (ICP) plasmas induced by an RF frequency in the 10 to 70 MHz range. Progress on the development of the RF coupling system, and qualitative observations from the optical and electric diagnostics are to be reported.

  17. Study of flow fields induced by surface dielectric barrier discharge actuator in low-pressure air

    SciTech Connect

    Che, Xueke E-mail: st@mail.iee.ac.cn; Nie, Wansheng; Tian, Xihui; Hou, Zhiyong; He, Haobo; Zhou, Penghui; Zhou, Siyin; Yang, Chao; Shao, Tao E-mail: st@mail.iee.ac.cn

    2014-04-15

    Surface dielectric barrier discharge (SDBD) is a promising method for a flow control. Flow fields induced by a SDBD actuator driven by the ac voltage in static air at low pressures varying from 1.0 to 27.7 kPa are measured by the particle image velocimetry method. The influence of the applied ac voltage frequency and magnitude on the induced flow fields is studied. The results show that three different classes of flow fields (wall jet flow field, complex flow field, and vortex-shape flow field) can be induced by the SDBD actuator in the low-pressure air. Among them, the wall jet flow field is the same as the tangential jet at atmospheric pressure, which is, together with the vertical jet, the complex flow field. The vortex-shape flow field is composed of one vertical jet which points towards the wall and two opposite tangential jets. The complex and the vortex-shape flow fields can be transformed to the wall jet flow field when the applied ac voltage frequency and magnitude are changed. It is found that the discharge power consumption increases initially, decreases, and then increases again at the same applied ac voltage magnitude when the air pressure decreases. The tangential velocity of the wall jet flow field increases when the air pressure decreases. It is however opposite for the complex flow field. The variation of the applied ac voltage frequency influences differently three different flow fields. When the applied ac voltage magnitude increases at the same applied ac voltage frequency, the maximal jet velocity increases, while the power efficiency increases only initially and then decreases again. The discharge power shows either linear or exponential dependences on the applied ac voltage magnitude.

  18. The role of transition in high-lift low-pressure turbines for aeroengines

    NASA Astrophysics Data System (ADS)

    Hodson, Howard P.; Howell, Robert J.

    2005-08-01

    The fan of a high bypass ratio turbo fan engine produces up to 80% of the total thrust of the engine. It is the low-pressure (LP) turbine that drives the fan and, on some engines, a number of compressor stages. The unsteady aerodynamics of the LP turbine, and in particular, the role of unsteady flow in laminar-turbulent transition, is the subject of this paper. The flow in turbomachines is unsteady due to the relative motion of the rows of blades. In the LP turbine, the wakes from the upstream blade rows provide the dominant source of unsteadiness. Because much of the blade-surface boundary-layer flow is laminar, one of the most important consequences of this unsteadiness is the interaction of the wakes with the suction-side boundary layer of a downstream blade. This is important because the blade suction-side boundary layers are responsible for most of the loss of efficiency and because the combined effects of random (wake turbulence) and periodic disturbances (wake velocity defect and pressure fields) cause the otherwise laminar boundary layer to undergo transition and eventually become turbulent. This paper discusses the development of unsteady flows in LP turbines and the process of wake-induced boundary-layer transition in low-pressure turbines and the loss generation that results. Particular emphasis will be placed on unsteady separating flows and how the effects of wakes may be exploited to control loss generation in the laminar-turbulent transition processes. This control has allowed the successful development of the latest generation of ultra-high-lift LP turbines. More recent developments, which harness the effects of surface roughness in conjunction with the wakes, are also presented.

  19. On the theory of intensity distributions of tornadoes and other low pressure systems

    NASA Astrophysics Data System (ADS)

    Schielicke, Lisa; Névir, Peter

    Approaching from a theoretical point of view, this work presents a theory which unifies intensity distributions of different low pressure systems, based on an energy of displacement. Resulting from a generalized Boltzmann distribution, the expression of this energy of displacement is obtained by radial integration over the forces which are in balance with the pressure gradient force in the horizontal equation of motion. A scale analysis helps to find out which balance of forces prevail. According to the prevailing balances, the expression of the energy of displacement differs for various depressions. Investigating the system at the moment of maximum intensity, the energy of displacement can be interpreted as the work that has to be done to generate and finally eliminate the pressure anomaly, respectively. By choosing the appropriate balance of forces, number-intensity (energy of displacement) distributions show exponential behavior with the same decay rate β for tornadoes and cyclones, if tropical and extra-tropical cyclones are investigated together. The decay rate is related to a characteristic (universal) scale of the energy of displacement which has approximately the value Eu = β- 1 ≈ 1000 m 2s - 2 . In consequence, while the different balances of forces cause the scales of velocity, the energy of displacement scale seems to be universal for all low pressure systems. Additionally, if intensity is expressed as lifetime minimum pressure, the number-intensity (pressure) distributions should be power law distributed. Moreover, this work points out that the choice of the physical quantity which represents the intensity is important concerning the behavior of intensity distributions. Various expressions of the intensity like velocity, kinetic energy, energy of displacement and pressure are possible, but lead to different behavior of the distributions.

  20. Wall thinning criteria for low temperature-low pressure piping. Task 91-030-1

    SciTech Connect

    Mertz, G.E.

    1993-01-01

    This acceptance criteria is intended to prevent gross rupture or rapidly propagating failure during normal and abnormal operating conditions. Pitting may be present in the carbon steel piping. While the acceptance criteria have provisions to preclude gross rupture through a pitted region, they do not protect against throughwall pit growth and subsequent leakage. Potential leakage through a pit in low pressure piping is less than the post-DBE design basis leakage. Both the uniform thinning and LTA criteria protect against leakage, since their potential for leakage is larger. The acceptance criteria protects against gross rupture due to general wall thinning, local wall thinning (LTA`s), pitting, and fracture through weld defects. General wall thinning calculations are based on the restart criteria, SEP-24. LTA criteria for hoop stresses are based on ASME Code Case N-480 {open_quotes}Examination Requirements for Pipe Wall Thinning Due to Single Phase Erosion and Corrosion{close_quotes}. The LTA criteria for axial stress is based on an effective average thickness concept, which prevents plastic collapse of a locally thinned pipe. Limits on pit density, based on an effective cross section concept, are used to prevent gross rupture through a group of pits. The CEGB R-6 failure assessment diagram is used in the fracture evaluation, along with postulated weld defects. This criteria is intended for low temperature, low pressure piping systems. Corrosion and/or weld defects increase the peak stresses during normal operation and may lead to a reduction in fatigue life. Piping systems subject to significant thermal or mechanical fatigue will require additional analysis which is beyond the scope of this document.

  1. Ultrasonic nebulization extraction/low pressure photoionization mass spectrometry for direct analysis of chemicals in matrices.

    PubMed

    Liu, Chengyuan; Zhu, Yanan; Zhou, Zhongyue; Yang, Jiuzhong; Qi, Fei; Pan, Yang

    2015-09-01

    A novel ultrasonic nebulization extraction/low-pressure photoionization (UNE-LPPI) system has been designed and employed for the rapid mass spectrometric analysis of chemicals in matrices. An ultrasonic nebulizer was used to extract the chemicals in solid sample and nebulize the solvent in the nebulization cell. Aerosols formed by ultrasonic were evaporated by passing through a transferring tube, and desolvated chemicals were ionized by the emitted light (10.6 eV) from a Krypton discharge lamp at low pressure (∼68 Pa). First, a series of semi/non-volatile compounds with different polarities, such as polycyclic aromatic hydrocarbons (PAHs), amino acids, dipeptides, drugs, nucleic acids, alkaloids, and steroids were used to test the system. Then, the quantification capability of UNE-LPPI was checked with: 1) pure chemicals, such as 9,10-phenanthrenequinone and 1,4-naphthoquinone dissolved in solvent; 2) soil powder spiked with different amounts of phenanthrene and pyrene. For pure chemicals, the correlation coefficient (R(2)) for the standard curve of 9,10-phenanthrenequinone in the range of 3 ng-20 μg mL(-1) was 0.9922, and the measured limits of detection (LOD) was 1 ng ml(-1). In the case of soil powder, linear relationships for phenanthrene and pyrene from 10 to 400 ng mg(-1) were obtained with correlation coefficients of 0.9889 and 0.9893, respectively. At last, the feasibility of UNE-LPPI for the detection of chemicals in real matrices such as tablets and biological tissues (tea, Citrus aurantium peel and sage (Salvia officinalis) leaf) were successfully demonstrated. PMID:26388379

  2. Unsteady flows in a two-dimensional linear cascade with low-pressure turbine blades

    NASA Astrophysics Data System (ADS)

    Murawski, Christopher Gabriel

    Experimental studies of unsteady flow phenomena in a low pressure turbine linear cascade are presented. Turbine engine flow passages contain numerous loss mechanisms. The loss mechanisms investigated in this study are low Reynolds number and freestream turbulence effects, secondary flows and wake interactions. Also, a method is implemented which decreases the profile losses due to low Reynolds number effects. The results are presented in three segments. First, the effects of Reynolds number and freestream turbulence intensity on the low-pressure turbine cascade blade are investigated. The condition of the blade's boundary layer is the leading factor controlling the level of profile loss. The losses from the airfoil decrease as the Reynolds number and freestream turbulence increase due to a decrease in the size of the separation zone on the suction side of the turbine airfoil. Boundary layer separation occurs on the suction surface of the turbine. Changes to this region are achieved when attaching different length tail sets to the turbine airfoils which alters the axial chord of each blade. A clear improvement on suction side boundary layer behavior at low Reynolds numbers was seen when the tail extensions were shorter than about 9% of axial chord. Finally, the effect wake disturbance frequency on the secondary flow vortex structure in a turbine cascade is studied. Cylinders are traversed across the front of the blade row to simulate turbine blade disturbances. The response of the secondary flow structure to the movement of the wake generator shuttle with zero, one and multiple wake generator rods are presented. Multiple wake disturbance frequencies are varied from 12 Hz to 52 Hz. Multiple wake disturbance frequency below the axial chord flow frequency enable the secondary flow vortex structure to re-establish itself between each wake disturbance event. Axial chord flow frequency is defined as the axial velocity in the cascade divided by the axial chord length of

  3. Measurements in a Transitional Boundary Layer Under Low-Pressure Turbine Airfoil Conditions

    NASA Technical Reports Server (NTRS)

    Simon, Terrence W.; Qiu, Songgang; Yuan, Kebiao; Ashpis, David (Technical Monitor); Simon, Fred (Technical Monitor)

    2000-01-01

    This report presents the results of an experimental study of transition from laminar to turbulent flow in boundary layers or in shear layers over separation zones on a convex-curved surface which simulates the suction surface of a low-pressure turbine airfoil. Flows with various free-stream turbulence intensity (FSTI) values (0.5%, 2.5% and 10%), and various Reynolds numbers (50,000, 100,000 200,000 and 300,000) are investigated. Reynold numbers in the present study are based on suction surface length and passage exit mean velocity. Flow separation followed by transition within the separated flow region is observed for the lower-Re cases at each of the FSTI levels. At the highest Reynolds numbers and at elevated FSn, transition of the attached boundary layer begins before separation, and the separation zone is small. Transition proceeds in the shear layer over the separation bubble. For both the transitional boundary layer and the transitional shear layer, mean velocity, turbulence intensity and intermittency (the fraction of the time the flow is turbulent) distributions are presented. The present data are compared to published distribution models for bypass transition, intermittency distribution through transition, transition start position, and transition length. A model developed for transition of separated flows is shown to adequately predict the location of the beginning of transition, for these cases, and a model developed for transitional boundary layer flows seems to adequately predict the path of intermittency through transition when the transition start and end are known. These results are useful for the design of low-pressure turbine stages which are known to operate under conditions replicated by these tests.

  4. DEVELOPMENT OF A LOW PRESSURE, AIR ATOMIZED OIL BURNER WITH HIGH ATOMIZER AIR FLOW

    SciTech Connect

    BUTCHER,T.A.

    1998-01-01

    This report describes technical advances made to the concept of a low pressure, air atomized oil burner for home heating applications. Currently all oil burners on the market are of the pressure atomized, retention head type. These burners have a lower firing rate limit of about 0.5 gallons per hour of oil, due to reliability problems related to small flow passage sizes. High pressure air atomized burners have been shown to be one route to avoid this problem but air compressor cost and reliability have practically eliminated this approach. With the low pressure air atomized burner the air required for atomization can be provided by a fan at 5--8 inches of water pressure. A burner using this concept, termed the Fan-Atomized Burner or FAB has been developed and is currently being commercialized. In the head of the FAB, the combustion air is divided into three parts, much like a conventional retention head burner. This report describes development work on a new concept in which 100% of the air from the fan goes through the atomizer. The primary advantage of this approach is a great simplification of the head design. A nozzle specifically sized for this concept was built and is described in the report. Basic flow pressure tests, cold air velocity profiles, and atomization performance have been measured. A burner head/flame tube has been developed which promotes a torroidal recirculation zone near the nozzle for flame stability. The burner head has been tested in several furnace and boiler applications over the tiring rate range 0.2 to 0.28 gallons per hour. In all cases the burner can operate with very low excess air levels (under 10%) without producing smoke. Flue gas NO{sub x} concentration varied from 42 to 62 ppm at 3% 0{sub 2}. The concept is seen as having significant potential and planned development efforts are discussed.

  5. Graphite thermometry in a low-pressure contact aureole, Halifax, Nova Scotia

    NASA Astrophysics Data System (ADS)

    Hilchie, L. J.; Jamieson, R. A.

    2014-11-01

    Intrusion of the late Devonian South Mountain Batholith, southern Nova Scotia, produced a low-pressure contact metamorphic aureole in its metasedimentary host rocks. The effects of contact metamorphism are particularly well developed in pelitic rocks of the Halifax Group on the eastern margin of the batholith. Contact metamorphic isograds and mineral assemblages suggest low-pressure metamorphism, with P-T conditions at the contact estimated at 2.5-3.0 kbar and ca. 650 °C. In this study, Raman spectroscopy of carbonaceous material (RSCM) was used to obtain temperatures from graphite, which is common throughout the contact aureole. Temperature estimates range from ca. 360 °C just outside the cordierite-in isograd to ca. 640 °C in the sillimanite-K-feldspar zone near the contact, the latter consistent with the temperature estimated from the corresponding silicate mineral assemblage. Three different RSCM calibrations produced very similar results except at the high-temperature end of the observed range. A thermal profile constructed from the RSCM data was used to constrain a 2D numerical model for post-intrusion conductive cooling of the batholith along its eastern margin. Comparison of RSCM vs model thermal profiles suggest that observed differences between the thermal structure of the inner and outer aureole were controlled by the subsurface geometry of the pluton contact. The model predicts that peak temperatures in country rocks within 1 km of the contact were reached within 50 ka of intrusion, but that the outer part of the aureole took 250-500 ka to reach peak temperatures. The results confirm the utility of RSCM thermometry for acquiring temperature data over a range of metamorphic grades.

  6. Particle modelling of magnetically confined oxygen plasma in low pressure radio frequency discharge

    SciTech Connect

    Benyoucef, Djilali; Yousfi, Mohammed

    2015-01-15

    The main objective of this paper is the modelling and simulation of a radio frequency (RF) discharge in oxygen at low pressure and at room temperature, including the effect of crossed electric and magnetic fields for generation and confinement of oxygen plasma. The particle model takes into account one axial dimension along the electric field axis and three velocity components during the Monte Carlo treatment of the collisions between charged particles and background gas. The simulation by this developed code allows us not only to determine the electrodynamics characteristics of the RF discharge, but also to obtain kinetics and energetic description of reactive oxygen plasma at low pressure. These information are very important for the control of the deep reactive-ion etching technology of the silicon to manufacture capacitors with high density and for the deposition thick insulating films or thick metal to manufacture micro-coils. The simulation conditions are as follows: RF peak voltage of 200 V, frequency of 13.56 MHz, crossed magnetic field varying from 0 to 50 Gauss, and oxygen pressure of 13.8 Pa. In the presence of magnetic field, the results show an increase of the plasma density, a decrease of the electron mean energy, and also a reduction of the ratio between electron density and positive ion density. Finally in order to validate, the results are successfully compared with measurements already carried out in the literature. The conditions of comparison are from 100 to 300 V of the peak voltage at 13.56 MHz under a pressure of 13.8 Pa and a gap distance of 2.5 cm.

  7. Comparative mortality of diapausing and nondiapausing larvae of Plodia interpunctella (Lepidoptera: Pyralidae) exposed to monoterpenoids and low pressure.

    PubMed

    Mbata, George N; Pascual-Villalobos, Marie J; Payton, Mark E

    2012-04-01

    Monoterpenoids and low pressure have each been demonstrated to cause mortality of stored-product insect pests. The current report investigated the prospects of integrating the two methods in the management of diapausing and nondiapausing larvae of Plodia interpunctella (Hübner). In a separate experiment, the larvae were exposed to 35.5 mmHg in Erlenmeyer flasks at 19 and 28 degrees C for times ranging from 30 min to 96 h. Another set of experiments was conducted to investigate the toxicity of exposing P. interpunctella larvae to monoterpenoids including E-anethole, estragole, S-carvone, linalool, L-fenchone, geraniol, gamma-terpinene, and DL-camphor alone or in combination with low pressure (50 mmHg). Lethal times (LT) determined by subjecting time-mortality data to probit analyses were shortened to half when both diapausing and nondiapausing larvae were exposed to low pressure at 28 degrees C compared with 19 degrees C. Exposure of diapausing larvae to a monoterpenoid alone, with the exception of DL-camphor and estragole, at a concentration of 66.7 microl/1L of volume required > 30 h to generate 99% mortality at 19.0 +/- 0.8 degrees C. However, the LT99 values for diapausing and nondiapausing larvae exposed to combinations of DL-camphor or estragole and low pressure were considerably shortened. Combinations involving the rest of the monoterpenoids investigated and low pressure did not generate LT99 that were shorter than those of the control, which was low pressure only. These results suggest that integrating low pressure with DL-camphor or estragole could be a new method for the control of diapausing larvae of P. interpunctella at cooler temperatures. PMID:22606841

  8. A comparison of low-pressure and supercharged operation of polymer electrolyte membrane fuel cell systems for aircraft applications

    NASA Astrophysics Data System (ADS)

    Werner, C.; Preiß, G.; Gores, F.; Griebenow, M.; Heitmann, S.

    2016-08-01

    Multifunctional fuel cell systems are competitive solutions aboard future generations of civil aircraft concerning energy consumption, environmental issues, and safety reasons. The present study compares low-pressure and supercharged operation of polymer electrolyte membrane fuel cells with respect to performance and efficiency criteria. This is motivated by the challenge of pressure-dependent fuel cell operation aboard aircraft with cabin pressure varying with operating altitude. Experimental investigations of low-pressure fuel cell operation use model-based design of experiments and are complemented by numerical investigations concerning supercharged fuel cell operation. It is demonstrated that a low-pressure operation is feasible with the fuel cell device under test, but that its range of stable operation changes between both operating modes. Including an external compressor, it can be shown that the power demand for supercharging the fuel cell is about the same as the loss in power output of the fuel cell due to low-pressure operation. Furthermore, the supercharged fuel cell operation appears to be more sensitive with respect to variations in the considered independent operating parameters load requirement, cathode stoichiometric ratio, and cooling temperature. The results indicate that a pressure-dependent self-humidification control might be able to exploit the potential of low-pressure fuel cell operation for aircraft applications to the best advantage.

  9. Method to Remove Particulate Matter from Dusty Gases at Low Pressures

    NASA Technical Reports Server (NTRS)

    Calle, Carlos; Clements, J. Sid

    2012-01-01

    Future human exploration of Mars will rely on local Martian resources to reduce the mass, cost, and risk of space exploration launched from Earth. NASA's In Situ Resource Utilization (ISRU) Project seeks to produce mission consumables from local Martian resources, such as atmospheric gas. The Martian atmosphere, however, contains dust particles in the 2-to-10 -micrometer range. These dust particles must be removed before the Martian atmospheric gas can be processed. The low pressure of the Martian atmosphere, at 5 to 10 mbars, prevents the development of large voltages required for a standard electrostatic precipitator. If the voltage is increased too much, the corona transitions into a glow/streamer discharge unsuitable for the operation of a precipitator. If the voltage is not large enough, the dust particles are not sufficiently charged and the field is not strong enough to drive the particles to the collector. A method using electrostatic fields has been developed to collect dust from gaseous environments at low pressures, specifically carbon dioxide at pressures around 5 to 10 mbars. This method, commonly known as electrostatic precipitation, is a mature technology in air at one atmosphere. In this case, the high voltages required for the method to work can easily be achieved. However, in carbon dioxide at low pressures, such as those found on Mars, large voltages are not possible. The innovation reported here consists of two concentric cylindrical electrodes set at specific potential difference that generate an electric field that produces a corona capable of imparting an electrostatic charge to the incoming dust particles. The strength of the field is carefully balanced so as to produce a stable charging corona at 5 to 10 mbars, and is also capable of imparting a force to the particles that drives them to the collecting electrode. There are only two possible ways that dust can be removed from Martian atmospheric gas intakes: with this electrostatic

  10. Compilation of cross sections for kinetic models of low pressure hydrogen discharges

    NASA Astrophysics Data System (ADS)

    Phelps, A. V.

    2011-10-01

    We report an initial compilation of cross sections that have been used to model,the collisional kinetics of low-pressure discharges in H2. Processes that are considered include electron momentum transfer, excitation, and ionization collisions with H2; momentum transfer, Hα excitation, ionization, and charged pair formation in collisions of H+, H2+,H3+,H, H2,and H- with H2; collisions of electrons, H+, H2+,H3+,H, H2, and H- with graphite and Cu surfaces resulting in secondary electrons, particle reflection, and negative ion formation. For each major category, the compilation includes a section reviewing data sources. The recommendations are expressed as analytic formulas expected to be good to +/- 10 % . This compilation is expected to be refined from time to time. As part of the Plasma Data Exchange Project, the compilation will be made available at http://www.lxcat.laplace.univ-tlse.fr/ and/or http://www.icecat.laplace.univ-tlse.fr/. We report an initial compilation of cross sections that have been used to model,the collisional kinetics of low-pressure discharges in H2. Processes that are considered include electron momentum transfer, excitation, and ionization collisions with H2; momentum transfer, Hα excitation, ionization, and charged pair formation in collisions of H+, H2+,H3+,H, H2,and H- with H2; collisions of electrons, H+, H2+,H3+,H, H2, and H- with graphite and Cu surfaces resulting in secondary electrons, particle reflection, and negative ion formation. For each major category, the compilation includes a section reviewing data sources. The recommendations are expressed as analytic formulas expected to be good to +/- 10 % . This compilation is expected to be refined from time to time. As part of the Plasma Data Exchange Project, the compilation will be made available at http://www.lxcat.laplace.univ-tlse.fr/ and/or http://www.icecat.laplace.univ-tlse.fr/. A. V. Phelps, Phys. Rev. E 79, 066401 (2009).

  11. Safety, tolerability, and efficacy of endoscopic low-pressure liquid nitrogen spray cryotherapy in the esophagus

    PubMed Central

    Greenwald, Bruce D.; Dumot, John A.; Horwhat, J. David; Lightdale, Charles J.; Abrams, Julian A.

    2011-01-01

    SUMMARY Endoscopic cryotherapy is a new technique for ablation of esophageal dysplasia and neoplasia. Preliminary studies have shown it to be safe and effective for this indication. The objective of this study is to characterize safety, tolerability, and efficacy of low-pressure liquid nitrogen endoscopic spray cryotherapy ablation in a large cohort across multiple study sites. Parallel prospective treatment studies at four tertiary care academic medical centers in the U.S. assessed spray cryotherapy in patients with Barrett’s esophagus with or without dysplasia, early stage esophageal cancer, and severe squamous dysplasia who underwent cryotherapy ablation of the esophagus. All patients were contacted between 1 and 10 days after treatment to assess for side effects and complications of treatment. The main outcome measurement was the incidence of serious adverse events and side effects from treatment. Complete response for high-grade dysplasia (HGD) (CR-HGD), all dysplasia (CR-D), intestinal metaplasia (CR-IM) and cancer (CR-C) were assessed in patients completing therapy during the study period. A total of 77 patients were treated for Barrett’s high-grade dysplasia (58.4%), intramucosal carcinoma (16.9%), invasive carcinoma (13%), Barrett’s esophagus without dysplasia (9.1%), and severe squamous dysplasia (2.6%). Twenty-two patients (28.6%) reported no side effects throughout treatment. In 323 procedures, the most common complaint was chest pain (17.6%) followed by dysphagia (13.3%), odynophagia (12.1%), and sore throat (9.6%). The mean duration of any symptoms was 3.6 days. No side effects were reported in 48% of the procedures (155/323). Symptoms did not correlate with age, gender, diagnosis, or to treatment early versus late in the patient’s or site’s experience. Logit analysis showed that symptoms were greater in those with a Barrett’s segment of 6 cm or longer. Gastric perforation occurred in one patient with Marfan’s syndrome. Esophageal

  12. Solid oxide fuel cell electrolytes produced via very low pressure suspension plasma spray and electrophoretic deposition

    NASA Astrophysics Data System (ADS)

    Fleetwood, James D.

    Solid oxide fuel cells (SOFCs) are a promising element of comprehensive energy policies due to their direct mechanism for converting the oxidization of fuel, such as hydrogen, into electrical energy. Both very low pressure plasma spray and electrophoretic deposition allow working with high melting temperature SOFC suspension based feedstock on complex surfaces, such as in non-planar SOFC designs. Dense, thin electrolytes of ideal composition for SOFCs can be fabricated with each of these processes, while compositional control is achieved with dissolved dopant compounds that are incorporated into the coating during deposition. In the work reported, sub-micron 8 mole % Y2O3-ZrO2 (YSZ) and gadolinia-doped ceria (GDC), powders, including those in suspension with scandium-nitrate dopants, were deposited on NiO-YSZ anodes, via very low pressure suspension plasma spray (VLPSPS) at Sandia National Laboratories' Thermal Spray Research Laboratory and electrophoretic deposition (EPD) at Purdue University. Plasma spray was carried out in a chamber held at 320 - 1300 Pa, with the plasma composed of argon, hydrogen, and helium. EPD was characterized utilizing constant current deposition at 10 mm electrode separation, with deposits sintered from 1300 -- 1500 °C for 2 hours. The role of suspension constituents in EPD was analyzed based on a parametric study of powder loading, powder specific surface area, polyvinyl butyral (PVB) content, polyethyleneimine (PEI) content, and acetic acid content. Increasing PVB content and reduction of particle specific surface area were found to eliminate the formation of cracks when drying. PEI and acetic acid content were used to control suspension stability and the adhesion of deposits. Additionally, EPD was used to fabricate YSZ/GDC bilayer electrolyte systems. The resultant YSZ electrolytes were 2-27 microns thick and up to 97% dense. Electrolyte performance as part of a SOFC system with screen printed LSCF cathodes was evaluated with peak

  13. Simulation of low-pressure inductively coupled plasmas: Non-local effects and pulsed power operation

    NASA Astrophysics Data System (ADS)

    Ramamurthi, Badri

    For modeling of low-pressure Inductively Coupled Plasma (ICP) discharges, a number of approaches have been proposed with varying degree of complexity. A self-consistent 1-D model was developed in this work to study the effects of non-local electron conductivity on power absorption and plasma density profiles in a planar inductively coupled argon discharge at low pressures (< 10 mTorr). The self-consistent kinetic description of the discharge included three modules: (1) an EEDF module to compute a non-Maxwellian EEDF, (2) a non-local electron conductivity module which predicted current distribution in the plasma as an integral over the electric field and solved Maxwell's equations to find the self-consistent electric field as well as the non-local power deposition profile and (3) a Heavy Species Transport (HST) module which solved for the ion and metastable atom density and velocity. Results from the full model were then compared with those obtained by using a local conductivity model (Ohm's law) for the RF current. For 10 mTorr, the EEDF was found to be almost Maxwellian with electron temperature ˜ 3 V. As a result, the plasma density profiles obtained from the local and non-local cases were almost identical for the same total power. Interestingly, a similar result was obtained even for a pressure of 1 mTorr where the EEDF was non-Maxwellian. This suggests that as far as species density and flux are concerned, local conductivity models, with lesser computational expense, can be employed even in the non-local regime. Comparisons between simulation and experiment for RF field and current density showed better agreement for non-local model compared with local model. A two-dimensional (r,z) continuum model was then developed to study the spatio-temporal dynamics of a pulsed power (square-wave modulated) discharge in argon (electropositive) and chlorine (electronegative) sustained in an inductively coupled plasma (ICP) reactor with a planar coil. The self

  14. Fracturing of Etnean and Vesuvian rocks at high temperatures and low pressures

    NASA Astrophysics Data System (ADS)

    Rocchi, Valentina; Sammonds, P. R.; Kilburn, C. R. J.

    2004-04-01

    The mechanical properties of volcanic rocks at high temperatures and low pressures are key properties in the understanding of a range of volcanological problems, in particular lava flow dynamics. The measurement of these properties on extrusive volcanic samples under the appropriate pressure and temperature conditions has a direct application in the assessment of volcanic hazards. A new triaxial deformation cell has been designed to obtain mechanical strength data on rock samples at temperatures up to 1000°C and pressures up to 30 MPa. Significantly, the cell uses large cylindrical rock specimens, 25 mm diameter by 75 mm long, never previously employed in such a high-temperature apparatus. The large specimen size is necessary to test volcanic rocks with their large crystals and vesicles. The design of this novel apparatus is presented. Its operating temperature and pressure range encompasses the conditions of an advancing flow from the vent to the front, as well as the conditions of the volcanic rocks hosting magma at equivalent depths of up to 2 km. Experimental results are presented for tests on Vesuvian and Etnean rocks. Results show that the Vesuvius and the Etnean rocks remain fully brittle up to 600°C with typical strengths of 90 MPa and 100 MPa and Young's moduli of 60 GPa and 40 GPa, respectively. Above these temperatures the elastic modulus and compressive strength decreases steadily in both the Vesuvian and Etnean rocks, reaching 10% of the original values at 900°C and 800°C, respectively, when partial melting occurred. Full melting occurs at 1100°C in the Vesuvian rock and at 1040°C in the Etnean rock. Results also show that confining pressure has only a small effect on the strength of the rock at these low pressures, and that strain rates are important at high temperatures. Fracture energy release rates have been calculated and show an inversely proportional relationship with temperature. Results reveal why fracturing is important on the crust of

  15. Physical Insights, Steady Aerodynamic Effects, and a Design Tool for Low-Pressure Turbine Flutter

    NASA Astrophysics Data System (ADS)

    Waite, Joshua Joseph

    The successful, efficient, and safe turbine design requires a thorough understanding of the underlying physical phenomena. This research investigates the physical understanding and parameters highly correlated to flutter, an aeroelastic instability prevalent among low pressure turbine (LPT) blades in both aircraft engines and power turbines. The modern way of determining whether a certain cascade of LPT blades is susceptible to flutter is through time-expensive computational fluid dynamics (CFD) codes. These codes converge to solution satisfying the Eulerian conservation equations subject to the boundary conditions of a nodal domain consisting fluid and solid wall particles. Most detailed CFD codes are accompanied by cryptic turbulence models, meticulous grid constructions, and elegant boundary condition enforcements all with one goal in mind: determine the sign (and therefore stability) of the aerodynamic damping. The main question being asked by the aeroelastician, "is it positive or negative?'' This type of thought-process eventually gives rise to a black-box effect, leaving physical understanding behind. Therefore, the first part of this research aims to understand and reveal the physics behind LPT flutter in addition to several related topics including acoustic resonance effects. A percentage of this initial numerical investigation is completed using an influence coefficient approach to study the variation the work-per-cycle contributions of neighboring cascade blades to a reference airfoil. The second part of this research introduces new discoveries regarding the relationship between steady aerodynamic loading and negative aerodynamic damping. Using validated CFD codes as computational wind tunnels, a multitude of low-pressure turbine flutter parameters, such as reduced frequency, mode shape, and interblade phase angle, will be scrutinized across various airfoil geometries and steady operating conditions to reach new design guidelines regarding the influence

  16. Heat and mass transfer of a low-pressure Mars greenhouse: Simulation and experimental analysis

    NASA Astrophysics Data System (ADS)

    Hublitz, Inka

    Biological life support systems based on plant growth offer the advantage of producing fresh food for the crew during a long surface stay on Mars. Greenhouses on Mars are also used for air and water regeneration and waste treatment. A major challenge in developing a Mars greenhouse is its interaction with the thin and cold Mars environment. Operating a Mars greenhouse at low interior pressure reduces the pressure differential across the structure and therefore saves structural mass as well as reduces leakage. Experiments were conducted to analyze the heating requirements as well as the temperature and humidity distribution within a small-scale greenhouse that was placed in a chamber simulating the temperatures, pressure and light conditions on Mars. Lettuce plants were successfully grown inside of the Mars greenhouse for up to seven days. The greenhouse atmosphere parameters, including temperature, total pressure, oxygen and carbon dioxide concentration were controlled tightly; radiation level, relative humidity and plant evapo-transpiration rates were measured. A vertical stratification of temperature and humidity across the greenhouse atmosphere was observed. Condensation formed on the inside of the greenhouse when the shell temperature dropped below the dew-point. During the night cycles frost built up on the greenhouse base plate and the lower part of the shell. Heat loss increased significantly during the night cycle. Due to the placement of the heating system and the fan blowing warm air directly on the upper greenhouse shell, condensation above the plants was avoided and therefore the photosynthetically active radiation at plant level was kept constant. Plant growth was not affected by the temperature stratification due to the tight temperature control of the warmer upper section of the greenhouse, where the lettuce plants were placed. A steady state and a transient heat transfer model of the low pressure greenhouse were developed for the day and the night

  17. Progress in Development of Low Pressure High Density Plasmas on a Small Helicon Plasma Experiment (HPX)

    NASA Astrophysics Data System (ADS)

    James, Royce; Lopez, M.; Nolan, S.; Page, E. L.; Schlank, C.; Sherman, J.; Stutzman, B. S.; Zuniga, J.

    2012-10-01

    At the Coast Guard Academy Plasma Lab (CGAPL), a small Helicon Plasma Experiment (HPX) is being developed to utilize the reputed high densities (10^13 cm-3 and higher) at low pressure (.01 T) [1], for eventual high temperature and density diagnostic development in future laboratory investigations. HPX is designed to create repeatedly stable plasmas induced by an RF frequency in the 10 to 70 MHz range and employs an electromagnet to provide the external energy in the plasma's magnetic field to transition from the H-Mode to the Helicon Mode. An acceleration coil, currently under construction, will place the plasma in the vacuum chamber for optical and particle probing. With the initial construction phase complete and first plasmas attained, HPX is constructing triple and mach particle probes, magnetic probes, and a single point 300 W Thompson Scattering system backed by a 32-channel DAQ system capable 12 bits of sampling precision at 2 MS/s for plasma property investigations. Progress on the development of the RF coupling system, magnetic coils, and qualitative observations from the optical and electric diagnostics are to be reported. [4pt] [1] K. Toki, et al., Thin Solid Films 506-507 (2005).

  18. Progress on Development of Low Pressure High Density Plasmas on the Helicon Plasma Experiment (HPX)

    NASA Astrophysics Data System (ADS)

    James, Royce; Azzari, Phillip; Duke-Tinson, Omar; Frank, John; Karama, Jackson; Hopson, Jordan; Paolino, Richard; Sandri, Eva; Sherman, Justin; Wright, Erin; Turk, Jeremy

    2015-11-01

    The small Helicon Plasma Experiment (HPX) at the Coast Guard Academy Plasma Lab (CGAPL), continues to progress toward utilizing the reputed high densities (1013 cm-3 and higher) at low pressure (.01 T) [1] of helicons, for eventual high temperature and density diagnostic development in future laboratory investigations. HPX is designed to create repeatedly stable plasmas (~ 20 - 30 ns) induced by an RF frequency in the 10 to 70 MHz range. HPX is constructing RF field corrected Langmuir probe raw data will be collected and used to measure the plasma's density, temperature, and potentially the structure and behavior during experiments. Our 2.5 J YAG laser Thomson Scattering system backed by a 32-channel Data Acquisition (DAQ) system is capable 12 bits of sampling precision at 2 MS/s for HPX plasma property investigations. Progress on the development of the RF coupling system, Helicon Mode development, magnetic coils, and observations from the Thomson Scattering, particle, and electromagnetic scattering diagnostics will be reported. Supported by U.S. DEPS Grant [HEL-JTO] PRWJFY15.

  19. Progress on Development of Low Pressure High Density Plasmas on the Helicon Plasma Experiment (HPX)

    NASA Astrophysics Data System (ADS)

    James, R. W.; Duke-Tinson, O.; Nolan, S.; Page, E. J.; Lopez, M.; Karama, J.; Paolino, R. N.; Schlank, C.; Sherman, J.; Stutzman, B. S.; Crilly, P. B.

    2013-10-01

    At the Coast Guard Academy Plasma Lab (CGAPL), a small Helicon Plasma Experiment (HPX) is being developed to utilize the reputed high densities (1013 cm-3 and higher) at low pressure (.01 T), for eventual high temperature and density diagnostic development in future laboratory investigations. HPX is designed to create repeatedly stable plasmas induced by an RF frequency in the 10 to 70 MHz range. We employ a 400 to 1000 Gauss electromagnet that promotes energy conservation in the plasma via external energy production in the magnetic field facilitated by decreased inertial effects, in order to reach the Helicon Mode. With the initial construction phase complete and repeatable plasmas attained, HPX is constructing triple and mach particle probes, magnetic probes, and a single point 300 W Thompson Scattering system backed by a 32-channel Data Acquisition (DAQ) system capable 12 bits of sampling precision at 2 MS/s for HPX plasma property investigations. Progress on the development of the RF coupling system, Helicon Mode development, magnetic coils, and observations from the optical, particle, and electromagnetic scattering diagnostics will be reported. Supported by U.S. DEPS Grant [HEL-JTO] PRWJFY12.

  20. Development of Low Pressure High Density Plasmas on the Helicon Plasma Experiment (HPX)

    NASA Astrophysics Data System (ADS)

    James, Royce; Azzari, Phillip; Crilly, Paul; Duke-Tinson, Omar; Karama, Jackson; Paolino, Richard; Schlank, Carter; Sherman, Justin

    2014-10-01

    The small Helicon Plasma Experiment (HPX) at the Coast Guard Academy Plasma Lab (CGAPL), continues to progress toward utilizing the reputed high densities (10 cm-3 and higher) at low pressure (.01 T) of helicons, for eventual high temperature and density diagnostic development in future laboratory investigations. HPX is designed to create repeatedly stable plasmas induced by an RF frequency in the 10 to 70 MHz range. We employ a 400 to 1000 Gauss electromagnet that promotes energy conservation in the plasma via external energy production in the magnetic field facilitated by decreased inertial effects, in order to reach the Helicon Mode. HPX is completing construction of triple and mach particle probes, magnetic probes, and is designing a single point 300 W Thompson Scattering system backed by a 32-channel Data Acquisition (DAQ) system capable 12 bits of sampling precision at 2 MS/s for HPX plasma property investigations. Progress on the development of the RF coupling system, Helicon Mode development, magnetic coils, and observations from the optical, particle, and electromagnetic scattering diagnostics will be reported. Supported by U.S. DEPS Grant [HEL-JTO] PRWJFY13.

  1. Multifunctional Low-Pressure Turbine for Core Noise Reduction, Improved Efficiency, and Nitrogen Oxide (NOx) Reduction

    NASA Technical Reports Server (NTRS)

    Miller, Christopher J.; Shyam, Vikram; Rigby, David L.

    2013-01-01

    This work studied the feasibility of using Helmholtz resonator cavities embedded in low-pressure-turbine (LPT) airfoils to (1) reduce core noise by damping acoustic modes; (2) use the synthetic jets produced by the liner hole acoustic oscillations to improve engine efficiency by maintaining turbulent attached flow in the LPT at low-Reynolds-number cruise conditions; and (3) reduce engine nitrogen oxide emissions by lining the internal cavities with materials capable of catalytic conversion. Flat plates with embedded Helmholtz resonators, designed to resonate at either 3000 or at 400 Hz, were simulated using computational fluid dynamics. The simulations were conducted for two inlet Mach numbers, 0.25 and 0.5, corresponding to Reynolds numbers of 90 000 and 164 000 based on the effective chordwise distance to the resonator orifice. The results of this study are (1) the region of acoustic treatment may be large enough to have a benefit; (2) the jets may not possess sufficient strength to reduce flow separation (based on prior work by researchers in the flow control area); and (3) the additional catalytic surface area is not exposed to a high velocity, so it probably does not have any benefit.

  2. Computer Modeling of an Ion Trap Mass Analyzer, Part I: Low Pressure Regime

    NASA Astrophysics Data System (ADS)

    Nikolić, Dragan; Madzunkov, Stojan M.; Darrach, Murray R.

    2015-12-01

    We present the multi-particle simulation program suite Computational Ion Trap Analyzer (CITA) designed to calculate the ion trajectories within a Paul quadrupole ion trap developed by the Jet Propulsion Laboratory (JPL). CITA uses an analytical expression of the electrodynamic field, employing up to six terms in multipole expansion and a modified velocity-Verlet method to numerically calculate ion trajectories. The computer code is multithreaded and designed to run on shared-memory architectures. CITA yields near real-time simulations with full propagation of 26 particles per second per core. As a consequence, a realistic numbers of trapped ions (100+ million) can be used and their trajectories modeled, yielding a representative prediction of mass spectrometer analysis of trace gas species. When the model is compared with experimental results conducted at low pressures using the conventional quadrupole and dipole excitation modes, there is an excellent agreement with the observed peak shapes. Owing to the program's efficiency, CITA has been used to explore regions of trapping stability that are of interest to experimental research. These results are expected to facilitate a fast and reliable modeling of ion dynamics in miniature quadrupole ion trap and improve the interpretation of observed mass spectra.

  3. Efficacy of hybrid adsorption/membrane pretreatment for low pressure membrane.

    PubMed

    Malczewska, B; Benjamin, M M

    2016-08-01

    Fouling by natural organic matter (NOM) is a major obstacle when water from natural sources is treated using low-pressure membranes. Prior research by our group has demonstrated that passing natural water through a thin, pre-deposited layer of heated aluminum oxide particles (HAOPs) can remove substantial amounts of NOM from the feed and thereby reduce the fouling rate of downstream membranes. The work reported here explored the technical efficacy of such a pretreatment process under more challenging (and therefore realistic) conditions than reported earlier. Several analytical techniques were applied to the feed and permeate in an attempt to identify the key fouling components. The results demonstrate that a HAOPs layer can be pre-deposited on a stainless steel mesh and then be readily washed off at the end of a filtration cycle with very little irreversible fouling due to residual NOM or HAOPs left on the mesh. In addition, the pretreatment step removes enough foulant to allow a downstream UF membrane to operate at significantly higher fluxes than when conventional pretreatment is applied. HAOPs pretreatment also reduced the formation of chlorinated and brominated trihalomethanes (THM4) by more than 67% and of haloacetic acids (HAA9) by 64%-88% in simulated distribution system (SDS) tests. PMID:27174606

  4. Diamond synthesis from carbon nanofibers at low temperature and low pressure

    PubMed Central

    Luo, Chengzhi; Qi, Xiang; Pan, Chunxu; Yang, Wenge

    2015-01-01

    In this article, we report a new route to synthesize diamond by converting “solid” carbon nanofibers with a Spark Plasma Sintering system under low temperature and pressure (even at atmospheric pressure). Well-crystallized diamond crystals are obtained at the tips of the carbon nanofibers after sintering at 1500 °C and atmospheric pressure. Combining with scanning electron microscopy, transmission electron microscopy, electron-energy loss spectroscopy and Raman spectroscopy observations, we propose the conversion mechanism as follows: the disorder “solid” carbon nanofibers → well crystallined carbon nanofibers → bent graphitic sheets → onion-liked rings → diamond single crystal → the bigger congregated diamond crystal. It is believed that the plasma generated by low-voltage, vacuum spark, via a pulsed DC in Spark Plasma Sintering process, plays a critical role in the low temperature and low pressure diamond formation. This Spark Plasma Sintering process may provide a new route for diamond synthesis in an economical way to a large scale. PMID:26351089

  5. Low-pressure hydrocracking of coal-derived Fischer-Tropsch waxes to diesel

    SciTech Connect

    Dieter Leckel

    2007-06-15

    Coal-derived low-temperature Fischer-Tropsch (LTFT) wax was hydrocracked at pressures of 3.5-7.0 MPa using silica-alumina-supported sulfided NiW/NiMo and an unsulfided noble metal catalyst, modified with MoO{sub 3}. A low-pressure operation at 3.5 MPa produced a highly isomerized diesel, having low cloud points (from -12 to -28{sup o}C) combined with high cetane numbers (69-73). These properties together with the extremely low sulfur ({lt}5 ppm) and aromatic ({lt}0.5%) contents place coal/liquid (CTL) derived distillates as highly valuable blending components to achieve Eurograde diesel specifications. The upgrading of coal-based LTFT waxes through hydrocracking to high-quality diesel fuel blend components in combination with commercial-feasible coal-integrated gasification combined cycle (coal-IGCC) CO{sub 2} capture and storage schemes should make CTL technology more attractive. 28 refs., 7 figs., 8 tabs.

  6. Effect of confining wall potential on charged collimated dust beam in low-pressure plasma

    SciTech Connect

    Kausik, S. S.; Kakati, B.; Saikia, B. K.

    2013-05-15

    The effect of confining wall potential on charged collimated dust beam in low-pressure plasma has been studied in a dusty plasma experimental setup by applying electrostatic field to each channel of a multicusp magnetic cage. Argon plasma is produced by hot cathode discharge method at a pressure of 5×10{sup −4} millibars and is confined by a full line cusped magnetic field confinement system. Silver dust grains are produced by gas-evaporation technique and move upward in the form of a collimated dust beam due to differential pressure maintained between the dust and plasma chambers. The charged grains in the beam after coming out from the plasma column enter into the diagnostic chamber and are deflected by a dc field applied across a pair of deflector plates at different confining potentials. Both from the amount of deflection and the floating potential, the number of charges collected by the dust grains is calculated. Furthermore, the collimated dust beam strikes the Faraday cup, which is placed above the deflector plates, and the current (∼pA) so produced is measured by an electrometer at different confining potentials. The experimental results demonstrate the significant effect of confining wall potential on charging of dust grains.

  7. Uniform Thermal Nanoimprinting at Low Pressure by Improved Heat Transfer Using Hydrofluoroethers

    NASA Astrophysics Data System (ADS)

    Mekaru, Harutaka; Hiroshima, Hiroshi

    2013-06-01

    We propose a low-pressure process of thermal nanoimprinting by improved heat transfer. In poly(ethylene terephthalate) (PET; Tg=75 °C), poly(methyl methacrylate) (PMMA; Tg=105 °C), and polycarbonate (PC; Tg=150 °C), in which fine pattern transfer can be performed at 12.9 MPa, if the imprinting pressure is reduced to one-third, poor transfer occurs at the edges of the patterned area, and the uniformity of the entire patterned area degrades. However, it turned out that moldability can be improved significantly by introducing hydrofluoroether (HFE) between the mold and the surface of thermoplastic sheets. A dispensing method using a pipette was chosen to introduce HFE, and three types of HFE liquid, namely, Novec 7100 (bp=61 °C), Novec 7200 (bp=76 °C), and Novec 7300 (bp=98 °C), were tested. It was confirmed that the uniformity was greatly improved by combinations of PET and Novec 7100, PMMA and Novec 7200, and PC and Novec 7300. The heat of the mold spread efficiently onto the surface of thermoplastics via the HFE liquid, and it seems to result in the same effect as a preliminary heating process before the mold comes into contact with the thermoplastic sheet.

  8. Nanostructure protein repellant amphiphilic copolymer coatings with optimized surface energy by Inductively Excited Low Pressure Plasma.

    PubMed

    Bhatt, Sudhir; Pulpytel, Jérome; Ceccone, Giacomo; Lisboa, Patricia; Rossi, François; Kumar, Virendra; Arefi-Khonsari, Farzaneh

    2011-12-01

    Statistically designed amphiphilic copolymer coatings were deposited onto Thermanox, Si wafer, and quartz crystal microbalance (QCM) substrates via Plasma Enhanced Chemical Vapor Deposition of 1H,1H,2H,2H-perfluorodecyl acrylate and diethylene glycol vinyl ether in an Inductively Excited Low Pressure Plasma reactor. Plasma deposited amphiphilic coatings were characterized by Field Emission Scanning Electron Microscopy, X-ray Photoelectron Spectroscopy, Atomic Force Microscopy, and Water Contact Angle techniques. The surface energy of the coatings can be adjusted between 12 and 70 mJ/m(2). The roughness of the coatings can be tailored depending on the plasma mode used. A very smooth coating was deposited with a CW (continuous wave) power, whereas a rougher surface with R(a) in the range of 2 to 12 nm was deposited with the PW (pulsed wave) mode. The nanometer scale roughness of amphiphilic PFDA-co-DEGVE coatings was found to be in the range of the size of the two proteins namely BSA and lysozyme used to examine for the antifouling properties of the surfaces. The results show that the statistically designed surfaces, presenting a surface energy around 25 mJ/m(2), present no adhesion with respect to both proteins measured by QCM. PMID:22029599

  9. A microfluidic reactor for rapid, low-pressure proteolysis with on-chip electrospray ionization.

    PubMed

    Liuni, Peter; Rob, Tamanna; Wilson, Derek J

    2010-02-01

    A microfluidic reactor that enables rapid digestion of proteins prior to on-line analysis by electrospray ionization mass spectrometry (ESI-MS) is introduced. The device incorporates a wide (1.5 cm), shallow (10 microm) reactor 'well' that is functionalized with pepsin-agarose, a design that facilitates low-pressure operation and high clogging resistance. Electrospray ionization is carried out directly from a short metal capillary integrated into the chip outlet. Fabrication, involving laser ablation of polymethyl methacrylate (PMMA), is exceedingly straightforward and inexpensive. High sequence coverage spectra of myoglobin (Mb), ubiquitin (Ub) and bovine serum albumin (BSA) digests were obtained after <4 s of residence time in the reactor. Stress testing showed little loss of performance over approximately 2 h continuous use at high flow rates (30 microL/min). The device provides a convenient platform for a range of applications in proteomics and structural biology, i.e. to enable high-throughput workflows or to limit back-exchange in spatially resolved hydrogen/deuterium exchange (HDX) experiments. PMID:20049884

  10. Deuterium analysis in zircaloy using ps laser-induced low pressure plasma

    SciTech Connect

    Marpaung, Alion Mangasi; Lie, Zener Sukra; Niki, Hideaki; Kagawa, Kiichiro; Fukumoto, Ken-ichi; Ramli, Muliadi; Abdulmadjid, Syahrun Nur; Idris, Nasrullah; Hedwig, Rinda; Tjia, May On; Pardede, Marincan; Suliyanti, Maria Margaretha; Jobiliong, Eric; Kurniawan, Koo Hendrik

    2011-09-15

    An experimental study on picosecond laser induced plasma spectroscopy of a zircaloy sample with low-pressure surrounding helium gas has been carried out to demonstrate its potential applicability to three-dimensional quantitative micro-analysis of deuterium impurities in zircaloy. This was achieved by adopting the optimal experimental condition ascertained in this study, which is specified as 7 mJ laser energy, 1.3 kPa helium pressure, and 50 {mu}s measurement window, and which was found to result in consistent D emission enhancement. Employing these operational parameters, a linear calibration line exhibiting a zero intercept was obtained from zircaloy-4 samples doped with various concentrations of D impurity, regarded as surrogates for H impurity. An additional measurement also yielded a detection limit of about 10 {mu}g/g for D impurity, well below the acceptable threshold of damaging H concentration in zircaloy. Each of these measurements was found to produce a crater size of only 25 {mu}m in diameter, promising its application for performing less-destructive measurements. The result of this study has thus paved the way for conducting a further experiment with hydrogen-doped zircaloy samples and the further technical development of a three-dimensional quantitative micro-analysis of detrimental hydrogen impurity in zircaloy vessels used in nuclear power plants.

  11. Design and Application of a High Sensitivity Piezoresistive Pressure Sensor for Low Pressure Conditions

    PubMed Central

    Yu, Huiyang; Huang, Jianqiu

    2015-01-01

    In this paper, a pressure sensor for low pressure detection (0.5 kPa–40 kPa) is proposed. In one structure (No. 1), the silicon membrane is partly etched to form a crossed beam on its top for stress concentration. An aluminum layer is also deposited as part of the beam. Four piezoresistors are fabricated. Two are located at the two ends of the beam. The other two are located at the membrane periphery. Four piezoresistors connect into a Wheatstone bridge. To demonstrate the stress concentrate effect of this structure, two other structures were designed and fabricated. One is a flat membrane structure (No. 2), the other is a structure with the aluminum beam, but without etched silicon (No. 3). The measurement results of these three structures show that the No.1 structure has the highest sensitivity, which is about 3.8 times that of the No. 2 structure and 2.7 times that of the No. 3 structure. They also show that the residual stress in the beam has some backside effect on the sensor performance. PMID:26371001

  12. Diagnostics of surface wave driven low pressure plasmas based on indium monoiodide-argon system

    NASA Astrophysics Data System (ADS)

    Ögün, C. M.; Kaiser, C.; Kling, R.; Heering, W.

    2015-06-01

    Indium monoiodide is proposed as a suitable alternative to hazardous mercury, i.e. the emitting component inside the compact fluorescent lamps (CFL), with comparable luminous efficacy. Indium monoiodide-argon low pressure lamps are electrodelessly driven with surface waves, which are launched and coupled into the lamp by the ‘surfatron’, a microwave coupler optimized for an efficient operation at a frequency of 2.45 GHz. A non intrusive diagnostic method based on spatially resolved optical emission spectroscopy is employed to characterize the plasma parameters. The line emission coefficients of the plasma are derived by means of Abel’s inversion from the measured spectral radiance data. The characteristic plasma parameters, e.g. electron temperature and density are determined by comparing the experimentally obtained line emission coefficients with simulated ones from a collisional-radiative model. Additionally, a method to determine the absolute plasma efficiency via irradiance measurements without any goniometric setup is presented. In this way, the relationship between the plasma efficiency and the plasma parameters can be investigated systematically for different operating configurations, e.g. electrical input power, buffer gas pressure and cold spot temperature. The performance of indium monoiodide-argon plasma is compared with that of conventional CFLs.

  13. Transport of low pressure electronegative SF6 plasma through a localized magnetic filter

    NASA Astrophysics Data System (ADS)

    Levko, D.; Garrigues, L.; Hagelaar, G. J. M.

    2014-08-01

    The generation of an ion-ion plasma where only few electrons are present in the discharge could be appropriated in the context of ion plasma source applications. We present in this paper results obtained with a one-dimensional fluid model in the context of low pressure electronegative SF6 plasma. Without magnetic field, results show that the electron density is still large in the discharge. With a localized magnetic filter, where the magnetic field strength is such that the transport of the electrons is affected while the transport of ion species remains unmagnetized, we show that a region with a negative-positive ion plasma is found downstream the magnetic filter. The negative ions are produced in the filter due to the decrease of electron temperature. We also find conditions when the plasma sheath near the biased electrode collapses and the negative ion extraction from the plasma becomes possible. In addition, the influence of E × B electron transport on the one-dimensional model results is discussed.

  14. Slowing Down Times and dE/dX for Surface μ^+ in Low Pressure Gases

    NASA Astrophysics Data System (ADS)

    Senba, Masayoshi; Fleming, Donald; Arseneau, Donald; Pan, James; Mayne, Howard

    2000-05-01

    The times taken for surface muons to slow down from initial energies of ~ 2 MeV to the energy of the last charge exchange cycle, ~ 10 eV, has been measured using a novel technique in low pressure gases, from the phase of the μSR signal and its dependence on pressure. To our knowledge there are no other such data for postive muons in this energy range. These times can be converted to stoping powers, dE/dX, providing a unique test of the velocity dependence in the historic Bethe-Bloch equation, from a comparison of μ^+ and proton stopping powers. Calculations of the time spent in the charge-exchange regime have been carried out by an appropriate scaling of the atomic cross sections for proton charge exchange. The final thermalization time of the Mu atom, from about 10 eV to k_BT, has also been calculated in H2 gas, from cross sections determined from Quasi Classical Trajectories.

  15. Low-Pressure Microwave Excited Microplasmas as Sources of VUV Photons and Metastable Excited Atoms: Modeling

    NASA Astrophysics Data System (ADS)

    Kushner, Mark; Cooley, James; Xue, Jun; Urdhal, Randall

    2011-10-01

    Low pressure plasmas sustained in rare gases and rare gas mixtures can be efficient sources of VUV light from resonant optical transitions. Many applications would benefit from having small, inexpensive sources of plasma produced VUV light. To address this need, microwave wave excited microplasma sources in rare gases operating at pressures of <10 Torr are being developed. The microplasmas are sustained in ceramic cavities having cross sectional dimensions of <=1 mm, excited by a split-ring resonator antenna operated at 2.45 GHz. Power deposition is a few W. Hybrid computer modeling of microplasmas sustained in Ar has been performed to develop scaling laws for increasing the efficiency of VUV light production. The model includes a Monte Carlo simulation for the electron energy distribution and for radiation transport. Results from those studies will be discussed for plasma densities, electron energy distributions, VUV light production and excited state densities as a function of power, pressure and aspect ratio of the microplasma cavities. Modeling results will be compared to laser absorption spectroscopy of Ar excited state densities. Work supported by Agilent Technologies.

  16. Amine Enrichment of Thin-Film Composite Membranes via Low Pressure Plasma Polymerization for Antimicrobial Adhesion.

    PubMed

    Reis, Rackel; Dumée, Ludovic F; He, Li; She, Fenghua; Orbell, John D; Winther-Jensen, Bjorn; Duke, Mikel C

    2015-07-15

    Thin-film composite membranes, primarily based on poly(amide) (PA) semipermeable materials, are nowadays the dominant technology used in pressure driven water desalination systems. Despite offering superior water permeation and salt selectivity, their surface properties, such as their charge and roughness, cannot be extensively tuned due to the intrinsic fabrication process of the membranes by interfacial polymerization. The alteration of these properties would lead to a better control of the materials surface zeta potential, which is critical to finely tune selectivity and enhance the membrane materials stability when exposed to complex industrial waste streams. Low pressure plasma was employed to introduce amine functionalities onto the PA surface of commercially available thin-film composite (TFC) membranes. Morphological changes after plasma polymerization were analyzed by SEM and AFM, and average surface roughness decreased by 29%. Amine enrichment provided isoelectric point changes from pH 3.7 to 5.2 for 5 to 15 min of plasma polymerization time. Synchrotron FTIR mappings of the amine-modified surface indicated the addition of a discrete 60 nm film to the PA layer. Furthermore, metal affinity was confirmed by the enhanced binding of silver to the modified surface, supported by an increased antimicrobial functionality with demonstrable elimination of E. coli growth. Essential salt rejection was shown minimally compromised for faster polymerization processes. Plasma polymerization is therefore a viable route to producing functional amine enriched thin-film composite PA membrane surfaces. PMID:26083007

  17. Simulation study of nanoparticle coating in a low pressure plasma reactor

    SciTech Connect

    Pourali, N.; Foroutan, G.

    2015-02-15

    A self-consistent combination of plasma fluid model, nanoparticle heating model, and surface deposition model is used to investigate the coating of nanosize particles by amorphous carbon layers in a low pressure plasma reactor. The numerical results show that, owing to the net heat release in the surface reactions, the particle temperature increases and its equilibrium value remains always 50 K above the background gas temperature. The deposition rate decreases with increasing of the particle temperature and the corresponding time scale is of the order of 10 ms. The deposition rate is also strongly affected by the change in plasma parameters. When the electron temperature is increased, the deposition rate first increases due to the enhanced ion and radical generation, shows a maximum and then declines as the particle temperature rises above the gas temperature. An enhancement in the background gas pressure and/or temperature leads to a reduction in the deposition rate, which can be explained in terms of the enhanced etching by atomic hydrogen and particle heating by the background gas.

  18. Crater effects on H and D emission from laser induced low-pressure helium plasma

    SciTech Connect

    Pardede, Marincan; Lie, Tjung Jie; Kurniawan, Koo Hendrik; Maruyama, Tadashi; Kagawa, Kiichiro; Tjia, May On

    2009-09-15

    An experimental study has been performed on the effects of crater depth on the hydrogen and deuterium emission intensities measured from laser plasmas generated in low-pressure helium ambient gas from zircaloy-4 samples doped with different H and D impurity concentrations as well as a standard brass sample for comparison. The results show that aside from emission of the host atom, the emission intensities of other ablated atoms of significantly smaller masses as well as that of the He atom generally exhibit relatively rapid initial decline with increasing crater depth. This trend was found to have its origin in the decreasing laser power density arriving at the crater bottom and thereby weakened the shock wave generated in the crater. As the crater deepened, the declining trend of the intensity appeared to level off as a result of compensation of the decreasing laser power density by the enhanced plasma confinement at increasing crater depth. Meanwhile, the result also reveals the significant contribution of the He-assisted excitation process to the doped hydrogen and deuterium emission intensities, leading to similar crater-depth dependent variation patterns in contrast to that associated with the surface water, with growing dominance of this common feature at the later stage of the plasma expansion. Therefore, a carefully chosen set of gate delay and gate width which are properly adapted to the crater-depth dependent behavior of the emission intensity may produce the desired intrinsic emission data for quantitative depth profiling of H impurity trapped inside the zircaloy wall.

  19. Investigation of Low-Pressure Ultraviolet Radiation on Inactivation of Rhabitidae Nematode from Water

    PubMed Central

    DEHGHANI, Mohammad Hadi; JAHED, Gholam-Reza; ZAREI, Ahmad

    2013-01-01

    Background: Rhabditidae is a family of free-living nematodes. Free living nematodes due to their active movement and resistance to chlorination, do not remove in conventional water treatment processes thus can be entered to distribution systems and cause adverse health effects. Ultraviolet radiation (UV) can be used as a method of inactivating for these organisms. This cross sectional study was done to investigate the efficiency of ultraviolet lamp in the inactivation of free living nematode in water. Methods: The effects of radation time, turbidity, pH and temperature were invistigated in this study. Ultraviolet lamp used in this study was a 11 W lamp and intensity of this lamp was 24 μw / cm2. Results: Radiation time required to achieve 100% efficiency for larvae nematode and adults was 9 and 10 minutes respectively. There was a significant correlation between the increase in radiation time, temperature rise and turbidity reduction with inactivation efficiency of lamp (P<0.001). Increase of turbidity up 25 NTU decreased inactivation efficiency of larvae and adult nematodes from 100% to 66% and 100% to 64% respectively. Change in pH range from 6 to 9 did not affect the efficiency of inactivation. With increasing temperature inactivation rate increased. Also the effect of the lamp on inactivation of larvae nematod was mor than adults. Conclusions: It seems that with requiring the favorable conditions low-pressure ultraviolet radiation systems can be used for disinfection of water containing Rhabitidae nematode. PMID:23641409

  20. Endoscopic third ventriculostomy as adjunctive therapy in the treatment of low-pressure hydrocephalus in adults

    PubMed Central

    Foster, Kimberly A.; Deibert, Christopher P.; Choi, Phillip A.; Gardner, Paul A.; Tyler-Kabara, Elizabeth C.; Engh, Johnathan A.

    2016-01-01

    Background: Treatment of low-pressure hydrocephalus (LPH) may require prolonged external ventricular drainage (EVD) at sub-zero pressures to reverse ventriculomegaly. Endoscopic third ventriculostomy (ETV) has been used in the treatment of noncommunicating hydrocephalus; however, indications for ETV are expanding. Methods: Patients with the diagnosis of LPH as defined by the Pang and Altschuler criteria who underwent sub-zero drainage treatment over an 8-year period were included. Patients were divided into two cohorts based on whether or not ETV was employed during their treatment. Time from EVD placement to internalization of shunt was recorded for both groups; time from ETV to placement of shunt was recorded for the patients undergoing ETV. Results: Sixteen adult patients with LPH were managed with sub-zero drainage method. Ten (62.5%) patients did not undergo ETV and the average time from first ventriculostomy to shunting was 73 days (range 14–257 days). Six (37.5%) patients underwent ETV during the course of their treatment; average time from initial ventriculostomy to shunt was 114 days (range 0–236 days) (P = 0.16). Time from development of LPH to ETV ranged from 28 days to 6.5 months. In the ETV group, of the 4 patients who underwent shunting, the average time to shunting following ETV was 15.25 days. Conclusions: ETV can be used successfully in the management of refractory LPH to decrease the duration of EVD. PMID:27069743

  1. Energy efficient engine. Low pressure turbine test hardware detailed design report

    NASA Technical Reports Server (NTRS)

    Cherry, D. G.; Gay, C. H.; Lenahan, D. T.

    1982-01-01

    The low pressure turbine for the energy efficient engine is a five-stage configuration with moderate aerodynamic loading incorporating advanced features of decambered airfoils and extended blade overlaps at platforms and shrouds. Mechanical integrity of 18,000 hours on flowpath components and 36,000 hours on all other components is achieved along with no aeromechanical instabilities within the steady-state operating range. Selection of a large number (156) of stage 4 blades, together with an increased stage 4 vane-to-blade gap, assists in achieving FAR 36 acoustic goals. Active clearance control (ACC) of gaps at blade tips and interstage seals is achieved by fan air cooling judiciously applied at responsive locations on the casing. This ACC system is a major improvement in preventing deterioration of the 0.0381 cm (0.015 in.) clearances required to meet the integrated-core/low-spool turbine efficiency goal of 91.1% and the light propulsion system efficiency goal of 91.7%.

  2. NASA/GE Energy Efficient Engine low pressure turbine scaled test vehicle performance report

    NASA Technical Reports Server (NTRS)

    Bridgeman, M. J.; Cherry, D. G.; Pedersen, J.

    1983-01-01

    The low pressure turbine for the NASA/General Electric Energy Efficient Engine is a highly loaded five-stage design featuring high outer wall slope, controlled vortex aerodynamics, low stage flow coefficient, and reduced clearances. An assessment of the performance of the LPT has been made based on a series of scaled air-turbine tests divided into two phases: Block 1 and Block 2. The transition duct and the first two stages of the turbine were evaluated during the Block 1 phase from March through August 1979. The full five-stage scale model, representing the final integrated core/low spool (ICLS) design and incorporating redesigns of stages 1 and 2 based on Block 1 data analysis, was tested as Block 2 in June through September 1981. Results from the scaled air-turbine tests, reviewed herein, indicate that the five-stage turbine designed for the ICLS application will attain an efficiency level of 91.5 percent at the Mach 0.8/10.67-km (35,000-ft), max-climb design point. This is relative to program goals of 91.1 percent for the ICLS and 91.7 percent for the flight propulsion system (FPS).

  3. Low-pressure systems and extreme precipitation in central India: sensitivity to temperature changes

    NASA Astrophysics Data System (ADS)

    Sørland, Silje Lund; Sorteberg, Asgeir

    2015-10-01

    Extreme rainfall events in the central Indian region are often related to the passage of synoptic scale monsoon low-pressure systems (LPS). This study uses the surrogate climate change method on ten monsoon LPS cases connected to observed extreme rainfall events, to investigate how sensitive the precipitation and runoff are to an idealized warmer and moister atmosphere. The ten cases are simulated with three different initial and lateral boundary conditions: the unperturbed control run, and two sets of perturbed runs where the atmospheric temperature is increased uniformly throughout the atmosphere, the specific humidity increased according to Clausius Clapeyron's relation, but the large-scale flow is unchanged. The difference between the control and perturbed simulations are mainly due to the imposed warming and feedback influencing the synoptic flow. The mean precipitation change with warming in the central Indian region is 18-20 %/K, with largest changes at the end of the LPS tracks. The LPS in the warmer runs are bringing more moisture further inland that is released as precipitation. In the perturbed runs the precipitation rate is increasing at all percentiles, and there is more frequent rainfall with very heavy intensities. This leads to a shift in which category that contributes most to the total precipitation: more of the precipitation is coming from the category with very heavy intensities. The runoff changes are similar to the precipitation changes, except the response in intensity of very heavy runoff, which is around twice the change in intensity of very heavy precipitation.

  4. Pressure boosting technology recovers reserves in low pressure oil and gas fields

    SciTech Connect

    Sarshar, M.M.

    1999-01-01

    Fragmentation of reservoirs or production from different zones often results in oil or gas wells having different flowing wellhead pressures (FWHP). In many fields, the wells flow to a manifold, then the oil and gas is transported by pipeline to a processing plant. Production from the low-pressure (LP) wells is often restricted because of the backpressure imposed by the high-pressure (HP) wells or by the transportation pipeline. To minimize the production restrictions from LP wells, HP wells are usually choked down and their high energy is thus wasted through the choke. A team of engineers from CALTEC, the oil and gas division of BHR Group, have developed a system which harnesses the energy from HP wells to boost production from LP wells. The system is called WELLCOM, short for WELL COMmingling system. This patented system has won the 1998 British Royal Society Esso Energy award for an outstanding contribution to the advancement of science or engineering or technology that leads to a more efficient mobilization, conservation, or use of energy sources.

  5. Improved ultrathin oxynitride formed by thermal nitridation and low pressure chemical vapor deposition process

    NASA Astrophysics Data System (ADS)

    Maiti, Bikas; Hao, Ming Yin; Lee, Insup; Lee, Jack C.

    1992-10-01

    In this letter, we will present the electrical and reliability characteristics of ultrathin oxynitrides (65-73 Å) formed by thermal nitridation of silicon substrate followed by deposition of silicon dioxide by low pressure chemical vapor deposition (LPCVD) technique. The dielectric integrity has been compared to those of the conventional thermal oxide and reoxidized nitrided oxides. It has been found that the new oxynitrides have lower electron trapping, higher charge-to-breakdown, and lower interface state generation under electrical stress even in comparison to reoxidized nitrided oxides with the same thermal budget. The improved characteristics are believed to be due to the combination of the nitrogen-rich layer at the Si/SiO2 interface, the higher quality of LPCVD oxides over thermally grown oxides, and the reduced hydrogen concentration in the dielectrics in comparison to conventional nitrided oxides. The results indicate that these new oxynitride films may be promising for ultra large scale integrated metal-oxide-semiconductor device applications, especially in cases where low thermal budget processes are desirable.

  6. Synthetic Vortex Generator Jets Used to Control Separation on Low-Pressure Turbine Airfoils

    NASA Technical Reports Server (NTRS)

    Ashpis, David E.; Volino, Ralph J.

    2005-01-01

    Low-pressure turbine (LPT) airfoils are subject to increasingly stronger pressure gradients as designers impose higher loading in an effort to improve efficiency and lower cost by reducing the number of airfoils in an engine. When the adverse pressure gradient on the suction side of these airfoils becomes strong enough, the boundary layer will separate. Separation bubbles, particularly those that fail to reattach, can result in a significant loss of lift and a subsequent degradation of engine efficiency. The problem is particularly relevant in aircraft engines. Airfoils optimized to produce maximum power under takeoff conditions may still experience boundary layer separation at cruise conditions because of the thinner air and lower Reynolds numbers at altitude. Component efficiency can drop significantly between takeoff and cruise conditions. The decrease is about 2 percent in large commercial transport engines, and it could be as large as 7 percent in smaller engines operating at higher altitudes. Therefore, it is very beneficial to eliminate, or at least reduce, the separation bubble.

  7. Controlling Ion and UV/VUV Photon Fluxes in Pulsed Low Pressure Plasmas for Materials Processing

    NASA Astrophysics Data System (ADS)

    Tian, Peng; Kushner, Mark J.

    2012-10-01

    UV/VUV photon fluxes in plasma materials processing have a variety of effects ranging from damaging to synergistic. To optimize these processes, it is desirable to have separate control over the fluxes of ions and photons, or at least be able to control their relative fluxes or overlap in time. Pulsed plasmas may provide such control as the rates at which ion and photon fluxes respond to the pulse power deposition are different. Results from a computational investigation of pulsed plasmas will be discussed to determine methods to control the ratio of ion to photon fluxes. Simulations were performed using a 2-dimensional plasma hydrodynamics model which addresses radiation transport using a Monte Carlo Simulation. Radiation transport is frequency resolved using partial-frequency-redistribution algorithms. Results for low pressure (10s of mTorr) inductively and capacitively coupled plasmas in Ar/Cl2 mixtures will be discussed while varying duty cycle, reactor geometry, gas mixture and pressure. We found that the time averaged ratio of VUV photon-to-ion fluxes in ICPs can be controlled with duty cycle of the pulsed power. Even with radiation trapping, photon fluxes tend to follow the power pulse whereas due to their finite response times, fluxes of ions tend to average the power pulse. Due to the overshoot in electron temperature that occurs at the start of low-duty-cycle pulses, disproportionately large photon fluxes (compared to ion fluxes) can be generated.

  8. Review of recent developments and applications in low-pressure (vacuum outlet) gas chromatography.

    PubMed

    Sapozhnikova, Yelena; Lehotay, Steven J

    2015-10-29

    The concept of low pressure (LP) vacuum outlet gas chromatography (GC) was introduced more than 50 years ago, but it was not until the 2000s that its theoretical applicability to fast analysis of GC-amenable chemicals was realized. In practice, LPGC is implemented by placing the outlet of a short, wide (typically 10-15 m, 0.53 mm inner diameter) analytical column under vacuum conditions, which speeds the separation by reducing viscosity of the carrier gas, thereby leading to a higher optimal flow rate for the most separation efficiency. To keep the inlet at normal operating pressures, the analytical column is commonly coupled to a short, narrow uncoated restriction capillary that also acts as a guard column. The faster separations in LPGC usually result in worse separation efficiency relative to conventional GC, but selective detection usually overcomes this drawback. Mass spectrometry (MS) provides highly selective and sensitive universal detection, and nearly all GC-MS instruments provide vacuum outlet conditions for implementation of LPGC-MS(/MS) without need for adaptations. In addition to higher sample throughput, LPGC provides other benefits, including lower detection limits, less chance of analyte degradation, reduced peak tailing, increased sample loadability, and more ruggedness without overly narrow peaks that would necessitate excessively fast data acquisition rates. This critical review summarizes recent developments in the application of LPGC with MS and other detectors in the analysis of pesticides, environmental contaminants, explosives, phytosterols, and other semi-volatile compounds. PMID:26547491

  9. The Effects of Blade Count on Boundary Layer Development in a Low-Pressure Turbine

    NASA Technical Reports Server (NTRS)

    Dorney, Daniel J.; Flitan, Horia C.; Ashpis, David E.; Solomon, William J.

    2000-01-01

    Experimental data from jet-engine tests have indicated that turbine efficiencies at takeoff can be as much as two points higher than those at cruise conditions. Recent studies have shown that Reynolds number effects contribute to the lower efficiencies at cruise conditions. In the current study numerical simulations have been performed to study the boundary layer development in a two-stage low-pressure turbine, and to evaluate the models available for low Reynolds number flows in turbomachinery. In a previous study using the same geometry the predicted time-averaged boundary layer quantities showed excellent agreement with the experimental data, but the predicted unsteady results showed only fair agreement with the experimental data. It was surmised that the blade count approximation used in the numerical simulations generated more unsteadiness than was observed in the experiments. In this study a more accurate blade approximation has been used to model the turbine, and the method of post-processing the boundary layer information has been modified to more closely resemble the process used in the experiments. The predicted results show improved agreement with the unsteady experimental data.

  10. Transport of low pressure electronegative SF{sub 6} plasma through a localized magnetic filter

    SciTech Connect

    Levko, D.; Garrigues, L.; Hagelaar, G. J. M.

    2014-08-15

    The generation of an ion-ion plasma where only few electrons are present in the discharge could be appropriated in the context of ion plasma source applications. We present in this paper results obtained with a one-dimensional fluid model in the context of low pressure electronegative SF{sub 6} plasma. Without magnetic field, results show that the electron density is still large in the discharge. With a localized magnetic filter, where the magnetic field strength is such that the transport of the electrons is affected while the transport of ion species remains unmagnetized, we show that a region with a negative–positive ion plasma is found downstream the magnetic filter. The negative ions are produced in the filter due to the decrease of electron temperature. We also find conditions when the plasma sheath near the biased electrode collapses and the negative ion extraction from the plasma becomes possible. In addition, the influence of E × B electron transport on the one-dimensional model results is discussed.

  11. Inactivation of Pathogenic Bacteria on Seeds by Active Oxygen Species Generated in Low-Pressure Plasma

    NASA Astrophysics Data System (ADS)

    Ono, Reoto; Uchida, Shohei; Hayashi, Nobuya; Kosaka, Rina; Soeda, Yasutaka

    2015-09-01

    The inactivation of bacteria on seeds by active oxygen species generated by a low-pressure oxygen plasma is investigated. Species of active oxygen contributing to the inactivation of bacteria are attempted to be identified. Cylindrical stainless chamber with the internal volume of 17 L is used and RF antenna is set inside the chamber. The oxygen gas pressure is 20-100 Pa. RF power of 13.56 MHz is supplied to RF antenna and CCP is generated. After irradiation, bacteria are extracted from seeds and cultivated on nutrient agars. The number of colonies on these agars is counted after 48 h incubation. The number of bacteria on seeds decreases to less than 10-3 after plasma irradiation for 45 min comparing with that of control. The tendency of the reduction rate of bacteria on seeds has positive correlation with that of the light emission intensity of the singlet excited oxygen molecule as the oxygen gas pressure is varied. It is supposed that the singlet excited oxygen molecule would be one of the major factors for the inactivation of bacteria on seeds.

  12. Pulsed Discharge Effects on Bacteria Inactivation in Low-Pressure Radio-Frequency Oxygen Plasma

    NASA Astrophysics Data System (ADS)

    Vicoveanu, Dragos; Ohtsu, Yasunori; Fujita, Hiroharu

    2008-02-01

    The sporicidal effects of low-pressure radio frequency (RF) discharges in oxygen, produced by the application of continuous and pulsed RF power, were evaluated. For all cases, the survival curves showed a biphasic evolution. The maximum efficiency for bacteria sterilization was obtained when the RF power was injected in the continuous wave mode, while in the pulsed mode the lowest treatment temperature was ensured. The inactivation rates were calculated from the microorganism survival curves and their dependencies on the pulse characteristics (i.e., pulse frequency and duty cycle) were compared with those of the plasma parameters. The results indicated that the inactivation rate corresponding to the first phase of the survival curves is related to the time-averaged intensity of the light emission by the excited neutral atoms in the pulsed plasma, whereas the inactivation rate calculated from the second slope of the survival curves and the time-averaged plasma density have similar behaviors, when the pulse parameters were modified.

  13. Kinetic interpretation of resonance phenomena in low pressure capacitively coupled radio frequency plasmas

    NASA Astrophysics Data System (ADS)

    Wilczek, Sebastian; Trieschmann, Jan; Eremin, Denis; Brinkmann, Ralf Peter; Schulze, Julian; Schuengel, Edmund; Derzsi, Aranka; Korolov, Ihor; Hartmann, Peter; Donkó, Zoltán; Mussenbrock, Thomas

    2016-06-01

    Low pressure capacitive radio frequency (RF) plasmas are often described by equivalent circuit models based on fluid approaches that predict the self-excitation of resonances, e.g., high frequency oscillations of the total current in asymmetric discharges, but do not provide a kinetic interpretation of these effects. In fact, they leave important questions open: How is current continuity ensured in the presence of energetic electron beams generated by the expanding sheaths that lead to a local enhancement of the conduction current propagating through the bulk? How do the beam electrons interact with cold bulk electrons? What is the kinetic origin of resonance phenomena? Based on kinetic simulations, we find that the energetic beam electrons interact with cold bulk electrons (modulated on a timescale of the inverse local electron plasma frequency) via a time dependent electric field outside the sheaths. This electric field is caused by the electron beam itself, which leaves behind a positive space charge, that attracts cold bulk electrons towards the expanding sheath. The resulting displacement current ensures current continuity by locally compensating the enhancement of the conduction current. The backflow of cold electrons and their interaction with the nonlinear plasma sheath cause the generation of multiple electron beams during one phase of sheath expansion and contribute to a strongly non-sinusoidal RF current. These kinetic mechanisms are the basis for a fundamental understanding of the electron power absorption dynamics and resonance phenomena in such plasmas, which are found to occur in discharges of different symmetries including perfectly symmetric plasmas.

  14. A preliminary stage configuration for a low pressure nuclear thermal rocket (LPNTR)

    SciTech Connect

    Leyse, C.F.; Madsen, W.W.; Neuman, J.E.; Ramsthaler, J.H.; Schnitzler, B.G.

    1990-01-01

    A low pressure nuclear thermal rocket (LPNTR) is configured to meet the requirements of a nuclear stage for manned Mars exploration. Safety, reliability and performance are given equal consideration in selecting the stage configuration. Preliminary trade studies are conducted to size the engine thrust and determine the thrust chamber pressure. A weight breakdown and mechanical configuration for the selected LPNTR concept are defined. A seven engine stage configuration is selected which gives a two engine out capability and eliminates the need for engine gimbaling. The stage can be ground assembled and launched as a unit including tankage for trans Earth injection and Earth orbital capture. The tankage is configured to eliminate the need for an inert shield. The small engine will be cheaper to develop than a single engine providing full thrust, and will be compatible with stages for Earth orbital, Lunar and deep space missions. Mission analyses are presented with engine operation in a high thrust mode and in a dual range high thrust-low thrust mode. Mass savings over a reference NERVA stage are projected to be 45--55% for the high thrust operating mode and 50--60% for the dual range mode. Potential exists for further increases in performance by optimizing the thrust chamber/nozzle design. 6 refs., 10 figs., 5 tabs.

  15. Precipitation response of monsoon low-pressure systems to an idealized uniform temperature increase

    NASA Astrophysics Data System (ADS)

    Sørland, Silje Lund; Sorteberg, Asgeir; Liu, Changhai; Rasmussen, Roy

    2016-06-01

    The monsoon low-pressure systems (LPSs) are one of the most rain-bearing synoptic-scale systems developing during the Indian monsoon. We have performed high-resolution, convection-permitting experiments of 10 LPS cases with the Weather Research and Forecasting regional model, to investigate the effect of an idealized uniform temperature increase on the LPS intensification and precipitation. Perturbed runs follow a surrogate climate change approach, in which a uniform temperature perturbation is specified, but the large-scale flow and relative humidity are unchanged. The differences between control and perturbed simulations are therefore mainly due to the imposed warming and moisture changes and their feedbacks to the synoptic-scale flow. Results show that the LPS precipitation increases by 13%/K, twice the imposed moisture increase, which is on the same order as the Clausius-Clapeyron relation. This large precipitation increase is attributed to the feedbacks in vertical velocity and atmospheric stability, which together account for the high sensitivity. In the perturbed simulations the LPSs have higher propagation speeds and are more intense. The storms intensification to the uniform temperature perturbation can be interpreted in terms of the conditional instability of second kind mechanism where the condensational heating increases along with low-level convergence and vertical velocity in response to temperature and moisture increases. As a result, the surface low deepens.

  16. NOM fractionation and fouling of low-pressure membranes in microgranular adsorptive filtration.

    PubMed

    Cai, Zhenxiao; Benjamin, Mark M

    2011-10-15

    Membrane fouling by natural organic matter (NOM) was investigated in microgranular adsorptive filtration (μGAF) systems, in which a thin layer of adsorbent is predeposited on low-pressure membranes. The adsorbents tested included heated aluminum oxide particles (HAOPs), ion exchange (IX) resin, and powdered activated carbon (PAC). Size exclusion chromatography (SEC) separated the NOM into four apparent MW fractions with significant UV₂₅₄. HAOPs and the IX resin performed almost identically with respect to removal of these fractions, and differently from PAC. However, while HAOPs and PAC reduced fouling substantially, IX resin did not, indicating that fouling could not be attributed to the NOM fractions detected by SEC. Rather, the key foulants appear to comprise a very small fraction of the NOM with almost no UV₂₅₄ absorbance. Alginate, a strongly fouling surrogate for natural polysaccharides, is adsorbed effectively by HAOPs, but not by IX resin or PAC, suggesting that polysaccharides sometimes play a key role in membrane fouling by NOM. PMID:21905711

  17. Track studies in water vapor using a low-pressure cloud chamber. I. Macroscopic measurements.

    PubMed

    Stonell, G P; Marshall, M; Simmons, J A

    1993-12-01

    Techniques have been developed to operate a low-pressure cloud chamber with pure water vapor. Photographs have been obtained of the tracks arising in this medium from the passage of ionizing radiation. The sources used were low-energy X rays, 242Cm alpha particles, and low-energy protons. Track lengths of the electrons were similar to those found previously in tissue-equivalent gas. W values of 35.6 +/- 0.4 and 32.6 +/- 0.6 eV per ion pair for carbon and aluminum X rays also compare closely with those in tissue-equivalent gas, but are somewhat higher than the predictions of Monte Carlo calculations. Differential w values were obtained: for alpha particles of energy 5.3 MeV the value was 33.0 +/- 3.0 eV per ion pair; for protons of energy 390, 230, and 85 keV the values were 30.6 +/- 1.9, 31.9 +/- 2.0, and 33.6 +/- 3.4 eV per ion pair. The energy losses of protons in water vapor were measured in a second (dummy) chamber used for energy calibration. Results support Janni's values of stopping power for protons in the energy range 40-480 keV. PMID:8278575

  18. Electronic structure of low-pressure and high-pressure phases of silicon disulfide

    NASA Astrophysics Data System (ADS)

    Bletskan, D. I.; Vakulchak, V. V.; Glukhov, K. E.

    2014-07-01

    Self-consistent density functional theory calculations of band spectra, densities of states as well as the spatial distribution of valence electron charge density were carried out for the low-pressure α-phase and the high-pressure β-phase of SiS2. Group-theoretical analysis performed for both phases enabled the symmetry of wave functions in a number of high-symmetry points of the Brillouin zone as well as the structure of valence band representations to be found. Based on the calculations of the band structure, the orthorhombic α-phase of SiS2 was determined to be an indirect-gap semiconductor with the band gap E gi = 2.44 eV (T 1 → X 8 transition), while the β-phase was shown to be direct gap with E gd = 2.95 eV (Г 3 → Г 2 transition). The calculated energy distribution of the total density of states in the valence band of α-SiS2 qualitatively and quantitatively correlates with the main experimental features of the X-ray photoelectron spectrum.

  19. NCO quantitative measurement in premixed low pressure flames by combining LIF and CRDS techniques.

    PubMed

    Lamoureux, Nathalie; Mercier, Xavier; Pauwels, Jean-François; Desgroux, Pascale

    2011-06-01

    NCO is a short-lived species involved in NO(x) formation. It has never been quantitatively measured in flame conditions. In the present study, laser-induced fluorescence (LIF) and cavity ring-down spectroscopy (CRDS) were combined to measure NCO radical concentrations in premixed low-pressure flames (p = 5.3 kPa). NCO LIF excitation spectrum and absorption spectrum (using CRDS) measured in a stoichiometric CH(4)/O(2)/N(2)O/N(2) flame were found in good agreement with a simulated spectrum using PGOPHER program that was used to calculate the high-temperature absorption cross section of NCO in the A(2)Σ(+)-X(2)Π transition around 440.479 nm. The relative NCO-LIF profiles were measured in stoichiometric CH(4)/O(2)/N(2)O/N(2) flames where the ratio N(2)O/O(2) was progressively decreased from 0.50 to 0.01 and in rich CH(4)/O(2)/N(2) premixed flames. Then, the LIF profiles were converted into NCO mole fraction profiles from the absorption measurements using CRDS in a N(2)O-doped flame. PMID:21548555

  20. Numerical simulation of turbulent flow in the throttle of the MBIR reactor's low-pressure chamber

    NASA Astrophysics Data System (ADS)

    Yarunichev, V. A.; Orlova, E. E.; Lemekhov, Yu. V.; Shpanskii, V. A.

    2015-08-01

    This work in devoted to numerical calculation of turbulent flow in a labyrinth-type throttle. A system of such throttles is installed at the inlet to the MBIR reactor's low-pressure chamber and serves for setting up the required pressure difference and coolant flow rate. MBIR is a multipurpose fourthgeneration fast-neutron research reactor intended for investigating new kinds of nuclear fuel, structural materials, and coolants. The aim of this work is to develop a verified procedure for carrying out 3D calculation of the throttle using CFD modeling techniques. The investigations on determining the throttle hydraulic friction coefficient were carried out in the range of Reynolds numbers Re = 52000-136000. The reactor coolant (liquid sodium) was modeled by tap water. The calculations were carried out using high-Reynolds-number turbulence models with the near-wall functions k-ɛ and RNG k-ɛ, where k is the turbulent pulsation kinetic energy and ɛ is the turbulence kinetic energy dissipation rate. The obtained results have shown that the calculated value of hydraulic friction coefficient differs from its experimental value by no more than 10%. The developed procedure can be applied in determining the hydraulic friction coefficient of a modified labyrinth throttle design. The use of such calculation will make it possible to predict an experiment with the preset accuracy.

  1. Glow Discharge Plasma Active Control of Separation at Low Pressure Turbine Conditions.

    NASA Astrophysics Data System (ADS)

    Hultgren, Lennart S.; Ashpis, David E.

    2002-11-01

    Active flow control of boundary-layer separation using glow-discharge plasma actuators is studied experimentally. Separation is induced on a flat plate installed in a closed-circuit wind tunnel by a shaped insert on the opposite wall. The flow conditions represent flow over the suction surface of a modern low-pressure-turbine airfoil. The Reynolds number, based on wetted plate length and nominal exit velocity, is varied from 50,000 to 300,000, covering cruise to takeoff conditions. Low (0.2%) and high (2.5%) free-stream turbulence intensities are set using passive grids. The base flow includes closed separation bubbles and non-reattaching separated flow, and is thoroughly documented using single-wire constant-temperature anemometry and static surface pressure measurements. A spanwise-oriented phased-plasma-array actuator, fabricated on a printed circuit board, is surface-flush-mounted upstream of the separation point and can provide forcing in a wide frequency range. Static surface pressure measurements and hot-wire anemometry of the controlled flow are performed and indicate that the glow-discharge plasma actuator is an effective device for separation control.

  2. Operation of a THGEM-based detector in low-pressure Helium

    NASA Astrophysics Data System (ADS)

    Cortesi, M.; Yurkon, J.; Stolz, A.

    2015-02-01

    In view of a possible application as a charge-particle track readout for an Active Target Time Projection Chamber (AT-TPC), the operating properties of THick Gaseous Electron Multipliers (THGEM) in pure low-pressure Helium were investigated. This paper includes the effective gain dependence on pressure for different detector configurations (single-, double-, triple-cascade setup), long-term gain stability and energy resolution from tracks of 5.5 MeV alpha particles. Stable operational conditions and maximum detector gains of 104-107 have been achieved in pure Helium at pressure ranging from 100 torr up to 760 torr. Energy resolution of 6.65% (FWHM) for 690 keV of energy deposited by 5.5 MeV alpha particles at 350 torr was measured. The expected energy resolution for the full track is around 2.4% (FWHM). These results, together with the robustness of THGEM electrodes against spark damage, make THGEM structures highly competitive compared to other technologies considered for TPC applications in an active target operating with pure noble gases, requiring a high dynamic range and a wide operating pressure range down to few hundred torr.

  3. Destruction of methane in low-pressure, electrodeless radio frequency plasma on quartz walls

    NASA Astrophysics Data System (ADS)

    Mozetic, Miran; Vesel, Alenka; Alegre, Daniel; Tabares, Francisco L.

    2011-09-01

    The destruction of methane in a low pressure, electrodeless radiofrequency discharge was studied by mass spectrometry. Plasmas were created in a quartz tube with the inner diameter of 3.6 cm. A coil with 6 turns was fixed onto the tube and connected to radio frequency (RF) generator via a matching network. Methane flows between 1.16 and 3.30 mbar.l/s and various RF powers up to 1200 W were used. Depending on gas flow and RF power, the discharge was either in E or H mode. The evolution of different hydrocarbon species versus discharge power was measured systematically by a differentially pumped mass spectrometer. No carbon deposit on the quartz walls was seen during the scans. The results showed that the destruction of methane depended on the flow rate as well as the discharge power and was accomplished already in the E mode. Well-pronounced maxima in the formation of both ethane and acetylene were observed at low gas flow rates. The observed products from radical recombination evolved with plasma conditions, and their contribution to the global carbon balance strongly decreased at high power-per-particle density. The functionality of secondary hydrocarbon formation with respect to the experimental parameters has been analyzed and a simple kinetic model is proposed in order to account for the observed trends.

  4. A large-volume microwave plasma source based on parallel rectangular waveguides at low pressures

    NASA Astrophysics Data System (ADS)

    Zhang, Qing; Zhang, Guixin; Wang, Shumin; Wang, Liming

    2011-02-01

    A large-volume microwave plasma with good stability, uniformity and high density is directly generated and sustained. A microwave cavity is assembled by upper and lower metal plates and two adjacently parallel rectangular waveguides with axial slots regularly positioned on their inner wide side. Microwave energy is coupled into the plasma chamber shaped by quartz glass to enclose the space of working gas at low pressures. The geometrical properties of the source and the existing modes of the electric field are determined and optimized by a numerical simulation without a plasma. The calculated field patterns are in agreement with the observed experimental results. Argon, helium, nitrogen and air are used to produce a plasma for pressures ranging from 1000 to 2000 Pa and microwave powers above 800 W. The electron density is measured with a Mach-Zehnder interferometer to be on the order of 1014 cm-3 and the electron temperature is obtained using atomic emission spectrometry to be in the range 2222-2264 K at a pressure of 2000 Pa at different microwave powers. It can be seen from the interferograms at different microwave powers that the distribution of the plasma electron density is stable and uniform.

  5. Vapors and Droplets Mixture Deposition of Metallic Coatings by Very Low Pressure Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Vautherin, B.; Planche, M.-P.; Bolot, R.; Quet, A.; Bianchi, L.; Montavon, G.

    2014-04-01

    In recent years, the very low pressure plasma-spraying (VLPPS) process has been intensely developed and implemented to manufacture thin, dense and finely structured ceramic coatings for various applications, such as Y2O3 for diffusion barriers, among other examples. This paper aims at presenting developments carried out on metallic coatings. Aluminum was chosen as a demonstrative material due to its "moderate" vaporization enthalpy (i.e., 38.23 KJ cm-3) compared to the one of copper (i.e., 55.33 KJ cm-3), cobalt (i.e., 75.03 KJ cm-3), or even tantalum (i.e., 87.18 KJ cm-3). The objective of this work is primarily to better understand the behavior of a solid precursor injected into the plasma jet leading to the formation of vapors and to better control the factors affecting the coating structure. Nearly dense aluminum coatings were successfully deposited by VLPPS at 100 Pa with an intermediate power plasma torch (i.e., Sulzer Metco F4 type gun with maximum power of 45 kW). Optical emission spectroscopy (OES) was implemented to study and analyze the vapor behavior into the plasma jet. Simplified CFD modeling allowed better understanding of some of the thermo-physical mechanisms. The effect of powder-size distribution, substrate temperature and spray distance were studied. The phase composition and microstructural features of the coatings were characterized by XRD and SEM. Moreover, Vickers microhardness measurements were implemented.

  6. Thermodynamics of methane adsorption on copper HKUST-1 at low pressure

    SciTech Connect

    Wu, Di; Guo, Xiaofeng; Sun, Hui; Navrotsky, Alexandra

    2015-06-11

    Metal–organic frameworks (MOFs) can be engineered as natural gas storage materials by tuning the pore structures and surface properties. Here we report the direct measurement of CH₄ adsorption enthalpy on a paddlewheel MOF (Cu HKUST-1) using gas adsorption calorimetry at 25 °C at low pressures (below 1 bar). In this pressure region, the CH₄–CH₄ intermolecular interactions are minimized and the energetics solely reflects the CH₄–MOF interactions. Our results suggest moderately exothermic physisorption with an enthalpy of -21.1 ± 1.1 kJ/mol CH₄ independent of coverage. The calorimetric investigation complements previous computational and crystallographic studies by providing zero coverage enthalpies of CH₄ adsorption. The analysis of the new and literature data suggests that in initial stages of adsorption the CH₄–HKUST-1 interaction tends to be more sensitive to the pore dimension than to the guest polarizability, suggesting a less specific chemical binding role for the open Cu site.

  7. Low pressure cesium and potassium Diode Pumped Alkali Lasers: pros and cons

    NASA Astrophysics Data System (ADS)

    Zhdanov, Boris V.; Rotondaro, Matthew D.; Shaffer, Michael K.; Knize, Randall J.

    2015-10-01

    This paper based on the talk presented at the Security plus Defence 2015 Conference held at Toulouse, France in September 2015. In this paper we present the results of our experiments on a comparative study of Cesium and Potassium based DPALs aimed to determine which of these two lasers has better potential for scaling to high powers. For both lasers we have chosen a so called "low pressure DPAL approach", which uses buffer gas pressure of about 1 Atm for spin-orbit mixing of the exited states of alkali atoms to provide population inversion in the gain medium. The goal of this study was to determine power limiting effects, which affect performance of these DPALs, and find out how these limiting effects can be mitigated. The experiments were performed using both static and flowing gain medium. In our experiments, we studied the performance of both lasers in CW and pulsed modes with different pulse duration and observed output power degradation in time from the initial value to the level corresponding to the CW mode of operation. As a result of this study, we revealed some essential positive and negative features of both DPALs, which should be taken into account for power scaling experiments.

  8. Influence of Forbidden Processes on Similarity Law in Argon Glow Discharge at Low Pressure

    NASA Astrophysics Data System (ADS)

    Fu, Yang-Yang; Luo, Hai-Yun; Zou, Xiao-Bing; Wang, Xin-Xin

    2014-07-01

    The similarity law of gas discharge is not always valid due to the occurrence of some elementary processes, such as the stepwise ionization process, which are defined as the forbidden processes. To research the influence of forbidden processes on the similarity law, physical parameters (i.e., the electric field, electron density, electron temperature) in similar gaps are investigated based on the fluid model of gas discharge. The products of gas pressure p and dimensions are kept to be constant in similar gaps and the discharge model is solved with and without the forbidden processes, respectively. Discharges in similar gaps are identified as glow discharges and the typical similarity relations all are investigated. The results show that the forbidden processes cause significant deviations of similarity relations from the theoretical ones and the deviations are enlarged as the scaled-down factor k increases. If the forbidden processes are excluded from the model, the similarity law will be valid in argon glow discharge at low pressure.

  9. Design of an Ion Source for {sup 3}He Fusion in a Low Pressure IEC Device

    SciTech Connect

    Piefer, Gregory R.; Santarius, John F.; Ashley, Robert P.; Kulcinski, Gerald L.

    2005-05-15

    Recent developments in helicon ion sources and Inertial Electrostatic Confinement (IEC) device performance at UW-Madison have enabled low pressure (< 50 {mu}torr, 6.7 mPa) operating conditions that should allow the {sup 3}He-{sup 3}He fusion reaction to be observed in an IEC device. An ion source capable of delivering a {approx} 10 mA {sup 3}He ion beam into an IEC device with minimal neutral gas flow has been designed and tested. Furthermore, a new IEC device that has never been operated with deuterium has been constructed to avoid D-{sup 3}He protons from obstructing the {sup 3}He-{sup 3}He reaction product spectrum, and to minimize Penning ionization of deuterium by excited helium, which in the past is suspected to have limited the ionized density of He. These developments make it possible to study beam-background {sup 3}He-{sup 3}He fusion reactions with > 300 mA recirculating ion currents.

  10. Low pressure fractionation in arc volcanoes: an example from Augustine Volcano, Alaska

    SciTech Connect

    Daley, E.E.; Swanson, S.E.

    1985-01-01

    Augustine Volcano, situated between the Cook and Katmai segments of the Eastern Aleutian Volcanic Arc, has erupted 5 times since its discovery in 1778. Eruptions are characterized by early vent-clearing eruptions with accompanying pyroclastic flows followed by dome-building and more pyroclastic flows. Bulk rock chemistry of historic and prehistoric lavas shows little variability. The lavas are calc-alkaline, low to medium K, porphyritic acid andesites, rare basalt, and minor dacite pumice. FeO*/MgO averages 1.6 over this silica range. Plagioclase phenocrysts show complicated zoning patterns, but olivine, orthopyroxene, and clinopyroxene phenocrysts show little compositional variation. Hornblende, where present, is ubiquitously oxidized and was clearly out of equilibrium during the last stages of fractionation. Evolved liquid compositions of vitriophyric domes are rhyolitic, and of pumices are slightly less evolved suggesting that individual eruptions become more fractionated with time. Comparison of glass compositions with experimental results is consistent with low pressure fractionation of a relatively dry silicate melt. Disequilibrium of amphiboles and the evolved nature of glasses indicate that shallow level fractionation plays a significant role in the evolution of Augustine magmas. This model is consistent with a shallow magma chamber inferred from geophysical models of the Augustine system and also with its simple, predictable eruption pattern.

  11. Experimental Investigation on Electromagnetic Attenuation by Low Pressure Radio-Frequency Plasma for Cavity Structure

    NASA Astrophysics Data System (ADS)

    He, Xiang; Zhang, Yachun; Chen, Jianping; Chen, Yudong; Zeng, Xiaojun; Yao, Hong; Tang, Chunmei

    2016-01-01

    This paper reports on an experiment designed to test electromagnetic (EM) attenuation by radio-frequency (RF) plasma for cavity structures. A plasma reactor, in the shape of a hollow cylinder, filled with argon gas at low pressure, driven by a RF power source, was produced by wave-transmitting material. The detailed attenuations of EM waves were investigated under different conditions: the incident frequency is 1-4 GHz, the RF power supply is 13.56 MHz and 1.6-3 kW, and the argon pressure is 75-200 Pa. The experimental results indicate that 5-15 dB return loss can be obtained. From a first estimation, the electron density in the experiment is approximately (1.5-2.2) × 1016 m-3 and the collision frequency is about 11-30 GHz. The return loss of EM waves was calculated using a finite-difference time-domain (FDTD) method and it was found that it has a similar development with measurement. It can be confirmed that RF plasma is useful in the stealth of cavity structures such as jet-engine inlet. supported by National Natural Science Foundation of China (No. 51107033) and the Fundamental Research Funds for the Central Universities of China (No. 2013B33614)

  12. Impact of effluent organic matter on low-pressure membrane fouling in tertiary treatment.

    PubMed

    Ayache, C; Pidou, M; Croué, J P; Labanowski, J; Poussade, Y; Tazi-Pain, A; Keller, J; Gernjak, W

    2013-05-15

    This study aims at comparing low-pressure membrane fouling obtained with two different secondary effluents at bench and pilot-scale based on the determination of two fouling indices: the total fouling index (TFI) and the hydraulically irreversible fouling index (HIFI). The main objective was to investigate if simpler and less costly bench-scale experimentation can substitute for pilot-scale trials when assessing the fouling potential of secondary effluent in large scale membrane filtration plants producing recycled water. Absolute values for specific flux and total fouling index for the bench-scale system were higher than those determined from pilot-scale, nevertheless a statistically significant correlation (r(2) = 0.63, α = 0.1) was obtained for the total fouling index at both scales. On the contrary no such correlation was found for the hydraulically irreversible fouling index. Advanced water characterization tools such as excitation-emission matrix fluorescence spectroscopy (EEM) and liquid chromatography with organic carbon detection (LC-OCD) were used for the characterization of foulants. On the basis of statistical analysis, biopolymers and humic substances were found to be the major contribution to total fouling (r(2) = 0.95 and r(2) = 0.88, respectively). Adsorption of the low molecular weight neutral compounds to the membrane was attributed to hydraulically irreversible fouling (r(2) = 0.67). PMID:23541121

  13. Low-pressure line-shape study in molecular oxygen with absolute frequency reference

    NASA Astrophysics Data System (ADS)

    Domysławska, J.; Wójtewicz, S.; Cygan, A.; Bielska, K.; Lisak, D.; Masłowski, P.; Trawiński, R. S.; Ciuryło, R.

    2013-11-01

    We present a line-shape analysis of the rovibronic R1 Q2 transition of the oxygen B band resolved by the Pound-Drever-Hall-locked frequency-stabilized cavity ring-down spectroscopy technique in the low pressure range. The frequency axis of the spectra is linked by the ultra-narrow diode laser to the optical frequency comb in order to measure the absolute frequency at each point of the recorded spectra. Experimental spectra are fitted with various line-shape models: the Voigt profile, the Galatry profile, the Nelkin-Ghatak profile, the speed-dependent Voigt profile, and the speed-dependent Nelkin-Ghatak profile with quadratic and hypergeometric approximations for the speed dependence of collisional broadening and shifting. The influences of Dicke narrowing, speed-dependent effects, and correlation between phase- and velocity-changing collisions on the line shape are investigated. Values of line-shape parameters, including the absolute frequency of the transition 435685.24828(46) GHz, are reported.

  14. Flow Separation Control for Low-Pressure Turbine Blade using Vortex Generator Jets

    NASA Astrophysics Data System (ADS)

    Kasliwal, Amit

    2005-11-01

    Numerical study of flow separation control is conducted employing Vortex-Generator Jets. This strategy is first tested for the flow past a cylinder at Reynolds number (Re) of 13,400, and then applied to flow in a low-pressure turbine (LPT) cascade for the PAK-B blade geometry at Re = 25,000. A fourth-order accurate compact-difference scheme is used along with sixth-order filtering (C4F6). FDL3DI, a research code developed at WPAFB, is used as the flow solver. A blowing ratio of 2.0 with a skew angle of 90^o and a pitch angle of 30^o is employed in the simulations for the aforementioned configurations. The control jets are pulsed with F^+ = 1.0 for the case of the cylinder, and with F^+ = 2.33 for the LPT case. The results show a significant decrease in drag on the cylinder after the jets are turned on. The total-pressure loss is calculated in the wake region, at x/D = 3.0, and a reduction of 10% is observed. For the LPT case, the implemented flow separation control strategy totally eliminates the separation and leads to 27.5% reduction in wake total-pressure loss.

  15. Two dimensional analysis of low pressure flows in the annulus region between two concentric cylinders.

    PubMed

    Al-Kouz, Wael; Alshare, Aiman; Alkhalidi, Ammar; Kiwan, Suhil

    2016-01-01

    A numerical simulation of the steady two-dimensional laminar natural convection heat transfer for the gaseous low-pressure flows in the annulus region between two concentric horizontal cylinders is carried out. This type of flow occurs in "evacuated" solar collectors and in the receivers of the solar parabolic trough collectors. A finite volume code is used to solve the coupled set of governing equations. Boussinesq approximation is utilized to model the buoyancy effect. A correlation for the thermal conductivity ratio (k r = k eff/k) in terms of Knudsen number and the modified Rayleigh number is proposed for Prandtl number (Pr = 0.701). It is found that as Knudsen number increases then the thermal conductivity ratio decreases for a given Rayleigh number. Also, it is shown that the thermal conductivity ratio k r increases as Rayleigh number increases. It appears that there is no consistent trend for varying the dimensionless gap spacing between the inner and the outer cylinder ([Formula: see text]) on the thermal conductivity ratio (k r) for the considered spacing range. PMID:27186493

  16. Experimental Investigation of Boundary Layer Behavior in a Simulated Low Pressure Turbine

    NASA Technical Reports Server (NTRS)

    Shyne, Rickey J.; Sohn, Ki-Hyeon; DeWitt, Kenneth J.

    1999-01-01

    A detailed investigation of the flow physics occurring on the suction side of a simulated Low Pressure Turbine (LPT) blade was performed. A contoured upper wall was designed to simulate the y pressure distribution of an actual LPT blade onto a flat plate. The experiments were carried out at Reynolds numbers of 100,000 and 250,000 with three levels of freestream turbulence. The main emphasis in this paper is placed on flow field surveys performed at a y Reynolds number of 100,000 with levels of freestream turbulence ranging from 0.8% to 3%. Smoke-wire flow visualization data was used to confirm that the boundary layer was separated and formed a bubble. The transition process over the separated flow region is observed to be similar to a laminar free shear layer flow with the formation of a large coherent eddy structure. For each condition, the locations defining the separation bubble were determined by careful examination of pressure and mean velocity profile data. Transition onset location and length determined from intermittency profiles decrease as freestream turbulence levels increase. Additionally, the length and height of the laminar separation bubbles were observed to be inversely proportional to the levels of freestream turbulence.

  17. Conceptual design of a low-pressure micro-resistojet based on a sublimating solid propellant

    NASA Astrophysics Data System (ADS)

    Cervone, Angelo; Mancas, Alexandru; Zandbergen, Barry

    2015-03-01

    In the current and future trend towards smaller satellite missions, the development of a simple and reliable propulsion system with performance and characteristics in line with the typical requirements of nano-satellites and CubeSats plays a crucial role for enhancing the capabilities of this type of missions. This paper describes the design of a micro-resistojet using water stored in the frozen state (ice) as propellant, operating under sublimation conditions at low pressure. The low operating pressure allows for using the vapor pressure of ice as the only method of propellant feeding, thereby allowing for extremely low thrust and electric power usage. The results of an extensive set of numerical simulations for optimizing the thruster geometry in terms of power ratio and specific impulse produced are discussed. In addition, the design of the complete propulsion system is described. It makes use of a limited number of moving parts and two power sources, one in the thruster to increase the propellant temperature and one in the tank to maintain the propellant storage conditions. Results show that the proposed design represents an alternative option capable of meeting the typical requirements of small satellite missions by means of an intrinsically green propellant such as water, with the pressure inside the system never exceeding 600 Pa. Optimization results showed an optimum thrust to power ratio in range 0.2-1.2 mN/W for an expansion slot aspect ratio of 2.5.

  18. Thermodynamics of methane adsorption on copper HKUST-1 at low pressure

    DOE PAGESBeta

    Wu, Di; Guo, Xiaofeng; Sun, Hui; Navrotsky, Alexandra

    2015-06-11

    Metal–organic frameworks (MOFs) can be engineered as natural gas storage materials by tuning the pore structures and surface properties. Here we report the direct measurement of CH₄ adsorption enthalpy on a paddlewheel MOF (Cu HKUST-1) using gas adsorption calorimetry at 25 °C at low pressures (below 1 bar). In this pressure region, the CH₄–CH₄ intermolecular interactions are minimized and the energetics solely reflects the CH₄–MOF interactions. Our results suggest moderately exothermic physisorption with an enthalpy of -21.1 ± 1.1 kJ/mol CH₄ independent of coverage. The calorimetric investigation complements previous computational and crystallographic studies by providing zero coverage enthalpies of CH₄more » adsorption. The analysis of the new and literature data suggests that in initial stages of adsorption the CH₄–HKUST-1 interaction tends to be more sensitive to the pore dimension than to the guest polarizability, suggesting a less specific chemical binding role for the open Cu site.« less

  19. Enhancement of emission currents in plasma electron sources based on a low-pressure arc discharge

    NASA Astrophysics Data System (ADS)

    Koval, T. V.; Devyatkov, V. N.; Hung, Nguyen Bao

    2015-11-01

    The paper reports on a theoretical and experimental study of the discharge plasma generation with an enhanced electron emission current in a plasma electron source based on a low-pressure arc discharge with a grid-stabilized plasma emission boundary. The source operates at a pressure in the working chamber of p = 0.02-0.05 Pa (Ar), accelerating voltage of up to Ua = 10 kV, and longitudinal magnetic field for electron beam transport of up to Bz = 0.1 T. The experiments show that in the mode of electron emission from the plasma, the voltage Ud between the cathode and grid electrode changes its sign. The numerical simulation demonstrates that the plasma potential and voltage Ud depend on the electric field penetrating from the acceleration gap into the discharge region through the grid meshes, and on the discharge current, gas pressure, geometric transparency of the grid, and gas kind. It is shown that the main mechanisms responsible for the increase in the discharge current and electron emission current from the plasma are associated with secondary ion-electron emission from the emission electrode and with positive feedback between the region of cathode plasma generation and the channel of electron beam transport.

  20. Low-pressure cesium and potassium diode pumped alkali lasers: pros and cons

    NASA Astrophysics Data System (ADS)

    Zhdanov, Boris V.; Rotondaro, Matthew D.; Shaffer, Michael K.; Knize, Randall J.

    2016-02-01

    This paper presents the results of our experiments on a comparative study of cesium and potassium diode pumped alkali lasers (DPALs) aimed to determine which of these two lasers has more potential to scale to high powers. For both lasers, we have chosen a "low-pressure DPAL approach," which uses buffer gas pressure of about 1 atm for spin-orbit mixing of the excited states of alkali atoms to provide population inversion in the gain medium. The goal of this study was to determine power-limiting effects, which affect the performance of these DPALs, and find out how these limiting effects can be mitigated. We studied the performance of both lasers in CW and pulsed modes using both static and flowing gain medium and pump with different pulse duration. We observed output power degradation in time from the initial value to the level corresponding to the CW mode of operation. As a result of this study, some essential positive and negative features of both DPALs were revealed, which should be taken into account for power-scaling experiments.

  1. Production and Study of Titan's Aerosols Analogues with A RF Low Pressure Plasma Discharge

    NASA Astrophysics Data System (ADS)

    Szopa, C.; Cernogora, G.; Correia, J. J.; Boufendi, L.; Jolly, A.

    2005-10-01

    The atmosphere of Titan, the biggest satellite of Saturn, contains aerosols produced by the organic chemistry induced by the photochemistry of N2 and CH4, the major gaseous atmospheric compounds. In spite of their importance for the properties of the Titan's atmosphere, and for organic chemistry, only few direct information are available about them because of the limitations of the observational techniques, and their processes of formation and growth are not understood. In order to bring answers to these questions, we developed a new type of laboratory simulation to produce analogues of Titan's aerosols (known as tholins) with a low pressure Radio Frequency plasma discharge. The main originality of this experiment (named PAMPRE) comes from its ability to produce particles in volume, as they are maintained in levitation by electrostatic forces compensating gravity, whereas the other experiments produce tholins on the reactors walls or a substrate. We initiated our investigations by a study of the properties of the produced particles as a function of the plasma operating conditions (i.e. amount of CH4 in N2, injected RF power, pressure, and gas flow). We here present the results of this study.

  2. Characterization of Yttria-Stabilized Zirconia Coatings Deposited by Low-Pressure Plasma Spraying

    NASA Astrophysics Data System (ADS)

    He, Peng-jiang; Yin, Shuo; Song, Chen; Lapostolle, Frédéric; Liao, Han-lin

    2016-02-01

    The research presented here aimed to apply plasma spraying at a low pressure of 100 Pa for fabricating the columnar structure or dense coatings. These coatings with different structures were elaborated from the vapor condensation and molten droplets, respectively, using the agglomerated YSZ powders and a relatively low power commercial F4-VB torch. It was shown that the crystallite size of coating deposited from the vapor condensation at a spraying distance of 200 mm was reduced to 17.1 nm from 43.7 nm of the feedstock. Observations indicated that a thin columnar structured coating was produced out of the line of sight of projection. In the line of sight of projection, the hybrid structured coating was obtained. The relatively dense coating was fabricated using a specifically designed extended nozzle. Investigations by means of optical emission spectroscopy were performed to analyze the nature of the plasma jet with YSZ powders. The Vickers microhardness was also conducted. It was found that the relatively dense coating showed a higher value in comparison to the hybrid structure coating, up to 1273 ± 56 Hv100g.

  3. Chemistry in low-pressure cold plasmas: ions of astrophysical interest

    NASA Astrophysics Data System (ADS)

    Carrasco, E.; Jiménez-Redondo, M.; Tanarro, I.; Herrero, V. J.

    2012-12-01

    The ionic chemistry of various hydrogen mixtures (H2/N2, H2/O2, and H2/air) has been studied in low-pressure hollow cathode discharges. The major ions identified in the different discharges (H_3^+ , N2H+, H3O+ and NH_4^+ ) have been also found in astronomical observations or predicted in astrochemical models. The relative stability of the protonated ions in the various mixtures has been investigated in detail. In discharges of H2 with small amounts of N2, O2 and air, appreciable amounts of NH3 and H2O were formed at the reactor walls. The preponderance of the protonated ions in these plasmas was found to be largely dictated by the proton affinity of their respective molecular precursors. Even for small amounts of water and ammonia, proton transfer reactions tend to concentrate the positive charge in H3O+ and, especially, in NH_4^+ ions. These results support the predictions of some astrochemical models indicating that these ions could be dominant in warm astronomical environments where H2O and NH3 molecules evaporate from dust grain mantels.

  4. Experimental calculations of droplet diffusion in a low-pressure cloud chamber.

    PubMed

    Briden, P E; Holt, P D; Simmons, J A

    1994-11-01

    A low-pressure cloud chamber was used for several years to display the tracks created by the passage of ionizing particles through vapors of interest. The spatial distributions of the ions that were formed were of special interest, but the accuracy with which these distributions could be determined was reduced by the presence of diffusion. This meant that the droplets, when photographed, had moved significantly away from the point of creation of the parent ion. In the present investigation photographs obtained by previous workers have been analyzed in an attempt to quantify the extent to which the droplets had diffused. The results suggest that the diffusion, when converted to standard density (1000 kg/m3), was independent of the pressure inside the cloud chamber and the mixture used. It could be represented by a one-dimensional root-mean-square diffusion distance whose value was calculated to be 2.42 +/- 0.04 nm. Values for the diffusion of thermalized electrons (< approximately 4 eV) before capture to form negative ions were also calculated. They appeared to lie in the range 3.5-5.0 nm, and were again independent of the pressure and nature of the mixture. The magnitude of the diffusion was large enough to mask any measurable prediffusion structure for a distance in the region of 10 nm radially around the track path of the alpha-particle and proton tracks analyzed. PMID:7938472

  5. Influence of emitter temperature on the energy deposition in a low-pressure plasma

    NASA Astrophysics Data System (ADS)

    Levko, Dmitry; Raja, Laxminarayan L.

    2016-03-01

    The influence of emitter temperature on the energy deposition into low-pressure plasma is studied by the self-consistent one-dimensional Particle-in-Cell Monte Carlo Collisions model. Depending on the emitter temperature, different modes of discharge operation are obtained. The mode type depends on the plasma frequency and does not depend on the ratio between the densities of beam and plasma electrons. Namely, plasma is stable when the plasma frequency is small. For this plasma, the energy transfer from emitted electrons to plasma electrons is inefficient. The increase in the plasma frequency results first in the excitation of two-stream electron instability. However, since the thermal velocity of plasma electrons is smaller than the electrostatic wave velocity, the resonant wave-particle interaction is inefficient for the energy deposition into the plasma. Further increase in the plasma frequency leads to the distortion of beam of emitted electrons. Then, the electrostatic wave generated due to two-stream instability decays into multiple slower waves. Phase velocities of these waves are comparable with the thermal velocity of plasma electrons which makes possible the resonant wave-particle interaction. This results in the efficient energy deposition from emitted electrons into the plasma.

  6. Vibrational kinetics in Cl2 and O2 low-pressure inductively-coupled plasmas

    NASA Astrophysics Data System (ADS)

    Booth, Jean-Paul; Foucher, Mickael; Marinov, Daniil; Chabert, Pascal; Annusova, Anna; Guerra, Vasco; Agarwal, Ankur; Rauf, Shahid

    2015-09-01

    Low energy electron interactions with molecules via resonances can cause vibrational excitation (affecting chemical kinetics), electron energy loss and modification of the EEDF. However, with the exception of N2 and H2 plasmas, very little attention has been paid to this subject. We have implemented a novel high-sensitivity ultra-broadband UV absorption bench, allowing spectra to be recorded with noise as low as 2×10-5 over a 250 nm wavelength range, and recording of complete vibronic bands. We applied this to radiofrequency inductively-coupled plasmas in low pressure (5-50 mTorr) pure O2 and pure Cl2. In O2 plasmas we surprisingly observe highly vibrationally excited O2 (v'' up to 18) via B-X Schumann-Runge bands. Cl2 molecules show a broad UV absorption spectrum in the region 250-400 nm, with distinctly different absorption spectra for vibrationally excited molecules. However, only a small fraction of the Cl2 molecules were observed in vibrationally excited states and the vibrational temperature is close to equilibrium with the local gas translational temperature (up to 1000 K), in contrast to O2. We are currently working on global models with vibrational kinetics to explain these results. Work supported by LABEX Plas@par (ANR-11-IDEX-0004-02), and Applied Materials.

  7. Experimental Investigation of Boundary Layer Behavior in a Simulated Low Pressure Turbine

    NASA Technical Reports Server (NTRS)

    Sohn, Ki-Hyeon; Shyne, Rickey J.; DeWitt, Kenneth J.

    1998-01-01

    A detailed investigation of the flow physics occurring on the suction side of a simulated Low Pressure Turbine (LPT) blade was performed. A contoured upper wall was designed to simulate the pressure distribution of an actual LPT blade onto a flat plate. The experiments were carried out at Reynolds numbers of 100,000 and 250,000 with three levels of freestream turbulence. The main emphasis in this paper is placed on flow field surveys performed at a Reynolds number of 100,000 with levels of freestream turbulence ranging from 0.8% to 3%. Smoke-wire flow visualization data was used to confirm that the boundary layer was separated and formed a bubble. The transition process over the separated flow region is observed to be similar to a laminar free shear layer flow with the formation of a large coherent eddy structure. For each condition, the locations defining the separation bubble were determined by careful examination of pressure and mean velocity profile data. Transition onset location and length determined from intermittency profiles decrease as freestream turbulence levels increase. Additionally, the length and height of the laminar separation bubbles were observed to be inversely proportional to the levels of freestream turbulence.

  8. Intermittent operation of low pressure UF membranes for sewage reuse at household level.

    PubMed

    Diamantis, Vasileios I; Anagnostopoulos, Konstantinos; Melidis, Paraschos; Ntougias, Spyridon; Aivasidis, Alexander

    2013-01-01

    A household-scale wastewater treatment system was operated with domestic sewage. The system could recover gardening/irrigation water from raw sewage or secondary effluent by low pressure ultrafiltration (UF). The UF membranes (surface area = 3.5 m(2), pore size = 0.04 μm) were operated at constant transmembrane pressure (0.13 bar). The proposed technology was examined for approximately 2 months without membrane cleaning. Membrane operation was performed periodically (one or two times per week), simulating water usage for gardening irrigation. During raw sewage filtration (chemical oxygen demand (COD) total = 242 ± 71 mg L(-1), COD soluble = 105 ± 51 mg L(-1), suspended solids = 188 ± 58 mg L(-1)), low permeate COD was achieved (52 ± 25 mg L(-1)), whereas nitrogen and phosphorus were recovered in the permeate. The water recovered during 1 h of operation displayed a gradual decrease from 42 to 22 L m(-2)h(-1) during the 50-d time period. For the secondary effluent filtration, the UF module achieved consistently a recovery rate of 39.6 ± 8.0 L m(-2)h(-1), with an average permeate COD of 37 mg L(-1). In this case, the fouling layer (cake layer) was completely reversible after the relaxation period, rendering the process suitable for unattended household applications. PMID:23985509

  9. Experimental investigations of driving frequency effect in low-pressure capacitively coupled oxygen discharges

    SciTech Connect

    Liu, Jia; Liu, Yong-Xin; Liu, Gang-Hu; Gao, Fei; Wang, You-Nian

    2015-04-14

    The effect of driving frequency on the electron density is investigated in low-pressure capacitively coupled oxygen plasmas by utilizing a floating hairpin probe. The power absorbed by the plasma is investigated and it is found that the power lost in the matching network can reach 50% or higher under certain conditions. The effect of driving frequency on the electron density is studied from two aspects, i.e., constant absorbed power and electrode voltage. In the former case, the electron density increases with the driving frequency increasing from 13.56 to 40.68 MHz and slightly changes depending on the gas pressures with the frequency further increasing to 100 MHz. In the latter case, the electron density rapidly increases when the driving frequency increases from 13.56 to 40.68 MHz, and then decreases with the frequency further increasing to 100 MHz. The electron series resonance is observed at 40.68 MHz and can be attributed to the higher electron density. And the standing wave effect also plays an important role in increasing electron density at 100 MHz and 2.6 Pa.

  10. Analysis based on global model of nitrogen plasma produced by pulsed microwave at low pressure

    SciTech Connect

    Qiu, Feng; Yan, Eryan Meng, Fanbao; Ma, Hongge; Liu, Minghai

    2015-07-15

    This paper analyzes certain evolution processes in nitrogen plasmas discharged using pulsed microwaves at low pressure. Comparing the results obtained from the global model incorporating diffusion and the microwave transmission method, the temporal variation of the electron density is analyzed. With a discharge pressure of 300 Pa, the results obtained from experiments and the global model calculation show that when the discharge begins the electron density in the plasma rises quickly, to a level above the critical density corresponding to the discharge microwave frequency, but falls slowly when the discharge microwave pulse is turned off. The results from the global model also show that the electron temperature increases rapidly to a peak, then decays after the electron density reaches the critical density, and finally decreases quickly to room temperature when the discharge microwave pulse is turned off. In the global model, the electron density increases because the high electron temperature induces a high ionization rate. The decay of the electron density mainly comes from diffusion effect.

  11. [Experimental study on closed plasma discharging under low pressure and spectroscopic diagnosis].

    PubMed

    Lin, Min; Xu, Hao-jun; Su, Chen; Liang, Hua

    2014-06-01

    Closed plasma can overcome difficulties of maintaining plasma and excessive energy consumption in open environment. For plasma stealth technology, a closed plasma generator was designed. Using microsecond pulse generator and argon as working gas, discharge experiments were carried out under low pressure environment. The emission spectrum of Ar at different position in discharge chamber was measured. By using collisional-radiative modal (CRM), the distribution of plasma parameters was studied. At a given electron temperature and density with specified discharge parameters, corresponding population distribution could be obtained by CRM. By comparing the line ratio of argon 2p levels acquired from CRM with the line ratio from spectrum measured, the plasma parameters were confirmed after obtaining the minimum difference value. Using the line ratio of argon 2p9 to 2p1 from CRM while the range of electron density was 1-5 eV, the calculating error was analyzed. The results reveal that, the electron density of the closed plasma reaches a magnitude of 10(11) cm(-3) and shows a gradient distribution with small variational amplitude, and the distribution is beneficial to the application of plasma stealth. PMID:25358170

  12. Effects of feed solution chemistry on low pressure reverse osmosis filtration of cesium and strontium.

    PubMed

    Ding, Shiyuan; Yang, Yu; Huang, Haiou; Liu, Hengchen; Hou, Li-an

    2015-08-30

    The objective of this study was to identify the removal mechanisms of radionuclides by reverse osmosis (RO) membranes under conditions relevant to full-scale water treatment. For this purpose, the effects of feed solution chemistry on the removal of Cs and Sr by a low pressure RO system was investigated by systematically varying membrane surface charge, ionic composition, and organic matter concentrations. The results showed that the effects of solution chemistry on the filtration of Cs and Sr were related to their hydrated ionic radius, resulting in the predominance of the Donnan's effect and electrostatic interactions, respectively. Consequently, the rejection of Cs increased more pronouncedly than Sr with the increases of feed concentration. Due to the Donnan's effect, different anions decreased the rejection of Cs to different extents in accordance to the order of anions' radii as SO4(2-)>Cl(-)>NO3(-)>F(-). The variations in Sr rejection were influenced by the electrostatic interactions between Sr(2+) and the membrane. In addition, humic acid (HA) lowered the rejection of Cs and caused significant membrane flux decline, but did not change the rejection of Sr. Sr also aggravated HA fouling of the membrane. PMID:25841084

  13. Experimental investigations of driving frequency effect in low-pressure capacitively coupled oxygen discharges

    NASA Astrophysics Data System (ADS)

    Liu, Jia; Liu, Yong-Xin; Liu, Gang-Hu; Gao, Fei; Wang, You-Nian

    2015-04-01

    The effect of driving frequency on the electron density is investigated in low-pressure capacitively coupled oxygen plasmas by utilizing a floating hairpin probe. The power absorbed by the plasma is investigated and it is found that the power lost in the matching network can reach 50% or higher under certain conditions. The effect of driving frequency on the electron density is studied from two aspects, i.e., constant absorbed power and electrode voltage. In the former case, the electron density increases with the driving frequency increasing from 13.56 to 40.68 MHz and slightly changes depending on the gas pressures with the frequency further increasing to 100 MHz. In the latter case, the electron density rapidly increases when the driving frequency increases from 13.56 to 40.68 MHz, and then decreases with the frequency further increasing to 100 MHz. The electron series resonance is observed at 40.68 MHz and can be attributed to the higher electron density. And the standing wave effect also plays an important role in increasing electron density at 100 MHz and 2.6 Pa.

  14. Diamond synthesis from carbon nanofibers at low temperature and low pressure

    NASA Astrophysics Data System (ADS)

    Luo, Chengzhi; Qi, Xiang; Pan, Chunxu; Yang, Wenge

    2015-09-01

    In this article, we report a new route to synthesize diamond by converting “solid” carbon nanofibers with a Spark Plasma Sintering system under low temperature and pressure (even at atmospheric pressure). Well-crystallized diamond crystals are obtained at the tips of the carbon nanofibers after sintering at 1500 °C and atmospheric pressure. Combining with scanning electron microscopy, transmission electron microscopy, electron-energy loss spectroscopy and Raman spectroscopy observations, we propose the conversion mechanism as follows: the disorder “solid” carbon nanofibers → well crystallined carbon nanofibers → bent graphitic sheets → onion-liked rings → diamond single crystal → the bigger congregated diamond crystal. It is believed that the plasma generated by low-voltage, vacuum spark, via a pulsed DC in Spark Plasma Sintering process, plays a critical role in the low temperature and low pressure diamond formation. This Spark Plasma Sintering process may provide a new route for diamond synthesis in an economical way to a large scale.

  15. Infrared Cavity Ringdown Laser Absorption Spectroscopy (IR-CRLAS) in low pressure flames

    SciTech Connect

    Scherer, J.J.; Rakestraw, D.J.

    1996-12-31

    The authors have employed Infrared Cavity Ringdown Laser Absorption Spectroscopy (IR-CRLAS) as a diagnostic tool for combustion chemistry studies. High resolution rovibrational absorption spectra have been obtained in low pressure laminar flames in the mid-infrared employing a pulsed single mode optical parametric oscillator (OPO) laser system. The high sensitivity and generality of IR-CRLAS for combustion studies is demonstrated in a variety of flames and is shown to be robust even in sooting environments with high temperature gradients. The ability to obtain spatially resolved data is also demonstrated in one dimensional laminar flame studies. These preliminary results indicate the potential of IR-CRLAS as a combustion diagnostic which is capable of obtaining absolute concentrations of reactants, intermediates, and products simultaneously within a narrow spectral region. In this demonstration, two information rich mid-infrared spectral regions (1.6 and 3-4 microns) have been probed at Doppler-limited resolution with an effective laser bandwidth of < 0.007 cm{sup -1}.

  16. Quantitative deuterium analysis of titanium samples in ultraviolet laser-induced low-pressure helium plasma.

    PubMed

    Abdulmadjid, Syahrun Nur; Lie, Zener Sukra; Niki, Hideaki; Pardede, Marincan; Hedwig, Rinda; Lie, Tjung Jie; Jobiliong, Eric; Kurniawan, Koo Hendrik; Fukumoto, Ken-Ichi; Kagawa, Kiichiro; Tjia, May On

    2010-04-01

    An experimental study of ultraviolet (UV) laser-induced plasma spectroscopy (LIPS) on Ti samples with low-pressure surrounding He gas has been carried out to demonstrate its applicability to quantitative micro-analysis of deuterium impurities in titanium without the spectral interference from the ubiquitous surface water. This was achieved by adopting the optimal experimental condition ascertained in this study, which is specified by 5 mJ laser energy, 10 Torr helium pressure, and 1-50 mus measurement window, which resulted in consistent D emission enhancement and effective elimination of spectral interference from surface water. As a result, a linear calibration line exhibiting a zero intercept was obtained from Ti samples doped with various D impurity concentrations. An additional measurement also yielded a detection limit of about 40 ppm for D impurity, well below the acceptable threshold of damaging H concentration in Ti and its alloys. Each of these measurements was found to produce a crater size of only 25 mum in diameter, and they may therefore qualify as nondestructive measurements. The result of this study has therefore paved the way for conducting further experiments with hydrogen-doped Ti samples and the technical implementation of quantitative micro-analysis of detrimental hydrogen impurity in Ti metal and its alloys, which is the ultimate goal of this study. PMID:20412619

  17. Optimal time duration for low-pressure controlled reperfusion to efficiently protect ischemic rat heart.

    PubMed

    Bopassa, J C; Nemlin, C; Sebbag, L; Rodriguez, C; Ovize, M; Ferrera, R

    2007-10-01

    Previous studies have shown the capacity of low-pressure (LP) reperfusion to protect the ischemic heart. The present study sought to determine the optimal time for the application of LP reperfusion. Isolated rat hearts (n = 30) were exposed to 40 minutes of global warm ischemia followed by 70 minutes of reperfusion. Reperfusion was performed under LP (LP = 70 cm H(2)O) for 0 (control group), 5 (group LP-5), 10 (group LP-10), 30 (group LP-30), or 60 (group LP-60) minutes. Following the LP period the hearts were reperfused with normal pressure (100 cm H(2)O) until the end of reperfusion. Cardiac function was assessed during reperfusion using the Langendorff model. Myocardial necrosis was assessed by measuring LDH leakage in the coronary effluents. Functional recovery was reduced among the control and LP-5 groups with rate-pressure products (RPP) averaging 3788 +/- 499 and 5333 +/- 892 mm Hg/min, respectively. RPP was significantly improved in other groups with RPP averaging 7363 +/- 1159, 7441 +/- 863, and 7269 +/- 692 mm Hg/min in LP-10, LP-30, and LP-60 (P < .01). Similarly, necrosis measured by LDH leakage was significantly reduced in LP-10, LP-30, and LP-60 hearts (P < .01). This study demonstrated that LP reperfusion improves postischemic contractile dysfunction and attenuates necrosis when applied for at least 10 minutes. PMID:17954191

  18. Low pressure catalytic co-conversion of biogenic waste (rapeseed cake) and vegetable oil.

    PubMed

    Giannakopoulou, Kanellina; Lukas, Michael; Vasiliev, Aleksey; Brunner, Christoph; Schnitzer, Hans

    2010-05-01

    Zeolite catalysts of three types (H-ZSM-5, Fe-ZSM-5 and H-Beta) were tested in the catalytic co-conversion of rapeseed cake and safflower oil into bio-fuel. This low pressure process was carried out at the temperatures of 350 and 400 degrees Celsius. The yields and compositions of the product mixtures depended on the catalyst nature and the process temperatures. The produced organic phases consisted mainly of hydrocarbons, fatty acids and nitriles. This mixture possessed improved characteristics (e.g. heating value, water content, density, viscosity, pH) compared with the bio-oils, making possible its application as a bio-fuel. The most effective catalyst, providing the highest yield of organic liquid phase, was the highly acidic/wide-pore H-Beta zeolite. The products obtained on this catalyst demonstrated the highest degree of deoxygenation and the higher HHV (Higher Heating Value). The aqueous liquid phase contained water-soluble carboxylic acids, phenols and heterocyclic compounds. PMID:20060714

  19. Low Pressure Phase Transitions in Wurtzite CdSe Quantum Dots

    NASA Astrophysics Data System (ADS)

    Meulenberg, Robert W.; Strouse, Geoffrey F.

    2001-03-01

    Over the last several years, significant efforts in understanding the effects of high pressures on quantum dots (QDs) have been reported. It has been shown that the high-pressure phase transition from wurtzite (WZ) to rock-salt for CdSe QDs is doubled (3 - 6 GPa), but the energy dependence of the absorption edge is near that of the bulk value (partialE/partialP 45 meV/GPa). Upon release of pressure, mixtures of both hexagonal and cubic (WZ and zinc blende (ZB), respectively) structures are seen, due to the low energy of interconversion of the lattice. Surprisingly, ZB is rarely observed for II-VI nanomaterials although it is thermodynamically preferred and moderate to low pressures should induce a WZ -> ZB phase transition. Experiments with pressures in lower pressure ranges (< 1 GPa) have been ignored and may give insight into these types of low energy phase transitions. We report findings of QD size dependent pressure coefficients and postulate that changes in the band structure of quantum confined semiconductors (which lead to these changes in the pressure coefficient) are a function of the compressibility and defect nature of the material, which induce surface reconstruction events. We present optical absorption and photoluminescence data, as well as time-resolved luminescence data to infer to the mechanism of the pressure dependence.

  20. Exhaust Aftertreatment and Low Pressure Loop EGR Applied to an Off-Highway Engine

    SciTech Connect

    Baumgard, Kirby; Triana, Antonio; Johnson, John; Yang, Song; Premchand, Kiran

    2006-01-30

    The goal of the project was to demonstrate that low pressure loop EGR incorporating a diesel oxidation catalyst (DOC) and a diesel particulate filter (DPF) can be applied to an off-highway engine to meet Tier 3 (Task I) and Interim Tier 4 (Task II) off-road emissions standards. Task I data was collected using a John Deere 8.1 liter engine modified with a low pressure loop EGR system. The engine and EGR system was optimized and final data over the ISO 8178 eight mode test indicated the NOx emissions were less than 4 g/kWh and the PM was less than 0.02 g/kWh which means the engine met the Tier 3 off-road standard. Considerable experimental data was collected and used by Michigan Tech University to develop and calibrate the MTU-Filter 1D DPF model. The MTU-Filter 1D DPF code predicts the particulate mass evolution (deposition and oxidation) in the diesel particulate filter (DPF) during simultaneous loading and during thermal and NO{sub 2}-assisted regeneration conditions. It also predicts the pressure drop across the DPF, the flow and temperature fields, the solid filtration efficiency and the particle number distribution downstream of the DPF. A DOC model was also used to predict the NO{sub 2} upstream of the DPF. The DPF model was calibrated to the experimental data at temperatures from 230 C to 550 C, and volumetric flow rates from 9 to 39 actual m{sup 3}/min. Model predictions of the solid particulate mass deposited in the DPF after each loading and regeneration case were in agreement within +/-10g (or +/-10%) of experimental measurements at the majority of the engine operating conditions. The activation temperatures obtained from the model calibration are in good agreement with values reported in the literature and gave good results in the model calibration by using constant pre-exponential factors throughout the entire range of conditions evaluated. The average clean filter permeability was 2.372 x 10{sup -13} m{sup 2}. Estimates of the solid particulate mass

  1. Deuterium analysis in zircaloy using ps laser-induced low pressure plasma

    NASA Astrophysics Data System (ADS)

    Marpaung, Alion Mangasi; Lie, Zener Sukra; Niki, Hideaki; Kagawa, Kiichiro; Fukumoto, Ken-ichi; Ramli, Muliadi; Abdulmadjid, Syahrun Nur; Idris, Nasrullah; Hedwig, Rinda; Tjia, May On; Pardede, Marincan; Suliyanti, Maria Margaretha; Jobiliong, Eric; Kurniawan, Koo Hendrik

    2011-09-01

    An experimental study on picosecond laser induced plasma spectroscopy of a zircaloy sample with low-pressure surrounding helium gas has been carried out to demonstrate its potential applicability to three-dimensional quantitative micro-analysis of deuterium impurities in zircaloy. This was achieved by adopting the optimal experimental condition ascertained in this study, which is specified as 7 mJ laser energy, 1.3 kPa helium pressure, and 50 μs measurement window, and which was found to result in consistent D emission enhancement. Employing these operational parameters, a linear calibration line exhibiting a zero intercept was obtained from zircaloy-4 samples doped with various concentrations of D impurity, regarded as surrogates for H impurity. An additional measurement also yielded a detection limit of about 10 μg/g for D impurity, well below the acceptable threshold of damaging H concentration in zircaloy. Each of these measurements was found to produce a crater size of only 25 μm in diameter, promising its application for performing less-destructive measurements. The result of this study has thus paved the way for conducting a further experiment with hydrogen-doped zircaloy samples and the further technical development of a three-dimensional quantitative micro-analysis of detrimental hydrogen impurity in zircaloy vessels used in nuclear power plants.

  2. Design and Application of a High Sensitivity Piezoresistive Pressure Sensor for Low Pressure Conditions.

    PubMed

    Yu, Huiyang; Huang, Jianqiu

    2015-01-01

    In this paper, a pressure sensor for low pressure detection (0.5 kPa-40 kPa) is proposed. In one structure (No. 1), the silicon membrane is partly etched to form a crossed beam on its top for stress concentration. An aluminum layer is also deposited as part of the beam. Four piezoresistors are fabricated. Two are located at the two ends of the beam. The other two are located at the membrane periphery. Four piezoresistors connect into a Wheatstone bridge. To demonstrate the stress concentrate effect of this structure, two other structures were designed and fabricated. One is a flat membrane structure (No. 2), the other is a structure with the aluminum beam, but without etched silicon (No. 3). The measurement results of these three structures show that the No.1 structure has the highest sensitivity, which is about 3.8 times that of the No. 2 structure and 2.7 times that of the No. 3 structure. They also show that the residual stress in the beam has some backside effect on the sensor performance. PMID:26371001

  3. Thermodynamics of Methane Adsorption on Copper HKUST-1 at Low Pressure.

    PubMed

    Wu, Di; Guo, Xiaofeng; Sun, Hui; Navrotsky, Alexandra

    2015-07-01

    Metal-organic frameworks (MOFs) can be engineered as natural gas storage materials by tuning the pore structures and surface properties. Here we report the direct measurement of CH4 adsorption enthalpy on a paddlewheel MOF (Cu HKUST-1) using gas adsorption calorimetry at 25 °C at low pressures (below 1 bar). In this pressure region, the CH4-CH4 intermolecular interactions are minimized and the energetics solely reflects the CH4-MOF interactions. Our results suggest moderately exothermic physisorption with an enthalpy of -21.1 ± 1.1 kJ/mol CH4 independent of coverage. This calorimetric investigation complements previous computational and crystallographic studies by providing zero coverage enthalpies of CH4 adsorption. The analysis of the new and literature data suggests that in initial stages of adsorption the CH4-HKUST-1 interaction tends to be more sensitive to the pore dimension than to the guest polarizability, suggesting a less specific chemical binding role for the open Cu site. PMID:26266715

  4. Computer Modeling of an Ion Trap Mass Analyzer, Part I: Low Pressure Regime.

    PubMed

    Nikolić, Dragan; Madzunkov, Stojan M; Darrach, Murray R

    2015-12-01

    We present the multi-particle simulation program suite Computational Ion Trap Analyzer (CITA) designed to calculate the ion trajectories within a Paul quadrupole ion trap developed by the Jet Propulsion Laboratory (JPL). CITA uses an analytical expression of the electrodynamic field, employing up to six terms in multipole expansion and a modified velocity-Verlet method to numerically calculate ion trajectories. The computer code is multithreaded and designed to run on shared-memory architectures. CITA yields near real-time simulations with full propagation of 26 particles per second per core. As a consequence, a realistic numbers of trapped ions (100+ million) can be used and their trajectories modeled, yielding a representative prediction of mass spectrometer analysis of trace gas species. When the model is compared with experimental results conducted at low pressures using the conventional quadrupole and dipole excitation modes, there is an excellent agreement with the observed peak shapes. Owing to the program's efficiency, CITA has been used to explore regions of trapping stability that are of interest to experimental research. These results are expected to facilitate a fast and reliable modeling of ion dynamics in miniature quadrupole ion trap and improve the interpretation of observed mass spectra. Graphical Abstract ᅟ. PMID:26286456

  5. Comparing geophysical measurements to theoretical estimates for soil mixtures at low pressures

    SciTech Connect

    Wildenschild, D; Berge, P A; Berryman, K G; Bonner, B P; Roberts, J J

    1999-01-15

    The authors obtained good estimates of measured velocities of sand-peat samples at low pressures by using a theoretical method, the self-consistent theory of Berryman (1980), using sand and porous peat to represent the microstructure of the mixture. They were unable to obtain useful estimates with several other theoretical approaches, because the properties of the quartz, air and peat components of the samples vary over several orders of magnitude. Methods that are useful for consolidated rock cannot be applied directly to unconsolidated materials. Instead, careful consideration of microstructure is necessary to adapt the methods successfully. Future work includes comparison of the measured velocity values to additional theoretical estimates, investigation of Vp/Vs ratios and wave amplitudes, as well as modeling of dry and saturated sand-clay mixtures (e.g., Bonner et al., 1997, 1998). The results suggest that field data can be interpreted by comparing laboratory measurements of soil velocities to theoretical estimates of velocities in order to establish a systematic method for predicting velocities for a full range of sand-organic material mixtures at various pressures. Once the theoretical relationship is obtained, it can be used to estimate the soil composition at various depths from field measurements of seismic velocities. Additional refining of the method for relating velocities to soil characteristics is useful for development inversion algorithms.

  6. Studies on hydrogen plasma and dust charging in low-pressure filament discharge

    SciTech Connect

    Kakati, B. Kalita, D.; Kausik, S. S.; Saikia, B. K.; Bandyopadhyay, M.

    2014-08-15

    The effect of working gas pressure and dust charging on electron energy probability function has been studied for hydrogen plasma in a multi-dipole dusty plasma device. A cylindrical Langmuir probe is used to evaluate the plasma parameters and electron energy probability function (EEPF) for different working pressures. For lower energy range (below 10 eV), the EEPF follows a bi-Maxwellian shape at very low pressure (6 × 10{sup −5} mbar), while elevating the working pressure up to ∼2 × 10{sup −3} mbar, the shape of the EEPF transforms into a single Maxwellian. Some dip structures are observed at high energy range (ε > 10 eV) in the EEPF of hydrogen plasma at all the working conditions. In presence of dust particles, it is observed that the shape of the EEPF changes due to the redistribution of the high and low-energy electron populations. Finally, the effect of working pressure on charge accumulation on dust particles is studied with the help of a Faraday cup and electrometer. From the observations, a strong influence of working pressure on plasma parameters, EEPF and dust charging is observed.

  7. Steam wetness measurement using CCD imaging methods in low-pressure turbine

    NASA Astrophysics Data System (ADS)

    Wu, Wei; Qin, Shiqiao; Huang, Zhuqing; Wang, Xingshu; Hu, Chunsheng

    2010-11-01

    The steam flow in low-pressure turbine contained abundant water droplets, which will decrease the work efficiency and pose potential threaten to operation safety, so measurement of steam wetness has brought great interest in electricity generation industry. In this paper, a new measuring method using CCD (Charge Coupled Device) imaging technique was proposed to determine the wetness in steam turbine based on the forward small angle light scattering theory. A simulated steam turbine facility was designed to generate the wet steam, and light scattering experiments were carried out at various working conditions in this device. The steam wetness parameters and droplet size distribution were obtained by means of numerical inversion of the light intensity distribution based on Mie scattering theory. The results demonstrate that the obtained data from the present analysis is in good agreement with the results of the theory analysis and previous study, and the proposed method is proved to be suitable for steam wetness measuring and monitoring by further development.

  8. Low-pressure systems and extreme precipitation in central India: sensitivity to temperature changes

    NASA Astrophysics Data System (ADS)

    Sørland, Silje Lund; Sorteberg, Asgeir

    2016-07-01

    Extreme rainfall events in the central Indian region are often related to the passage of synoptic scale monsoon low-pressure systems (LPS). This study uses the surrogate climate change method on ten monsoon LPS cases connected to observed extreme rainfall events, to investigate how sensitive the precipitation and runoff are to an idealized warmer and moister atmosphere. The ten cases are simulated with three different initial and lateral boundary conditions: the unperturbed control run, and two sets of perturbed runs where the atmospheric temperature is increased uniformly throughout the atmosphere, the specific humidity increased according to Clausius Clapeyron's relation, but the large-scale flow is unchanged. The difference between the control and perturbed simulations are mainly due to the imposed warming and feedback influencing the synoptic flow. The mean precipitation change with warming in the central Indian region is 18-20 %/K, with largest changes at the end of the LPS tracks. The LPS in the warmer runs are bringing more moisture further inland that is released as precipitation. In the perturbed runs the precipitation rate is increasing at all percentiles, and there is more frequent rainfall with very heavy intensities. This leads to a shift in which category that contributes most to the total precipitation: more of the precipitation is coming from the category with very heavy intensities. The runoff changes are similar to the precipitation changes, except the response in intensity of very heavy runoff, which is around twice the change in intensity of very heavy precipitation.

  9. Evaluation of HFC-245ca for commercial use in low pressure chillers. Final report, Volume I

    SciTech Connect

    Keuper, E.F.

    1996-03-01

    Federal regulations banned the production of CFC-11 on January 1, 1996. HCFC-123, the only commercial alternative, will be limited to service applications after January 1, 2020 and will be eliminated from production on January 1, 2030. HFC-245ca has been identified as a potential replacement for CFC-11 in retrofit applications and for HCFC-123 in new chillers, but the marginal flammability of HFC-245ca is a major obstacle to its commercial use as a refrigerant in the United States. This report assesses the commercial viability of HFC-245ca based on its experimental performance in a direct drive low pressure centrifugal chiller exclusive of its flammability characteristics. Three different impeller diameters were tested in the chiller, with all impellers having identical discharge blade angles. Experimental work included tests in a 200 ton 3 stage direct drive chiller with 3 impeller sets properly sized for each of three refrigerants, CFC-11, HCFC-123, and HFC-245ca. The commercial viability assessment focused on both retrofit and new product performance and cost.

  10. Measurements in Separated and Transitional Boundary Layers Under Low-Pressure Turbine Airfoil Conditions

    NASA Technical Reports Server (NTRS)

    Volino, Ralph J.; Hultgren, Lennart .

    2000-01-01

    Detailed velocity measurements were made along a flat plate subject to the same dimensionless pressure gradient as the suction side of a modern low-pressure turbine airfoil. Reynolds numbers based on wetted plate length and nominal exit velocity were varied from 50,000 to 300,000, covering cruise to takeoff conditions. Low and high inlet free-stream turbulence intensities (0.2% and 7%) were set using passive grids. The location of boundary-layer separation does not depend strongly on the free-stream turbulence level or Reynolds number, as long as the boundary layer remains non-turbulent prior to separation. Strong acceleration prevents transition on the upstream part of the plate in all cases. Both free-stream turbulence and Reynolds number have strong effects on transition in the adverse pressure gradient region. Under low free-stream turbulence conditions transition is induced by instability waves in the shear layer of the separation bubble. Reattachment generally occurs at the transition start. At Re = 50,000 the separation bubble does not close before the trailing edge of the modeled airfoil. At higher Re, transition moves upstream, and the boundary layer reattaches. With high free-stream turbulence levels, transition appears to occur in a bypass mode, similar to that in attached boundary layers. Transition moves upstream, resulting in shorter separation regions. At Re above 200,000, transition begins before separation. Mean velocity, turbulence and intermittency profiles are presented.

  11. Diamond synthesis from carbon nanofibers at low temperature and low pressure.

    PubMed

    Luo, Chengzhi; Qi, Xiang; Pan, Chunxu; Yang, Wenge

    2015-01-01

    In this article, we report a new route to synthesize diamond by converting "solid" carbon nanofibers with a Spark Plasma Sintering system under low temperature and pressure (even at atmospheric pressure). Well-crystallized diamond crystals are obtained at the tips of the carbon nanofibers after sintering at 1500 °C and atmospheric pressure. Combining with scanning electron microscopy, transmission electron microscopy, electron-energy loss spectroscopy and Raman spectroscopy observations, we propose the conversion mechanism as follows: the disorder "solid" carbon nanofibers→well crystallined carbon nanofibers→bent graphitic sheets→onion-liked rings→diamond single crystal→the bigger congregated diamond crystal. It is believed that the plasma generated by low-voltage, vacuum spark, via a pulsed DC in Spark Plasma Sintering process, plays a critical role in the low temperature and low pressure diamond formation. This Spark Plasma Sintering process may provide a new route for diamond synthesis in an economical way to a large scale. PMID:26351089

  12. Ablative material testing for low-pressure, low-cost rocket engines

    NASA Technical Reports Server (NTRS)

    Richter, G. Paul; Smith, Timothy D.

    1995-01-01

    The results of an experimental evaluation of ablative materials suitable for the production of light weight, low cost rocket engine combustion chambers and nozzles are presented. Ten individual specimens of four different compositions of silica cloth-reinforced phenolic resin materials were evaluated for comparative erosion in a subscale rocket engine combustion chamber. Gaseous hydrogen and gaseous oxygen were used as propellants, operating at a nominal chamber pressure of 1138 kPa (165 psi) and a nominal mixture ratio (O/F) of 3.3. These conditions were used to thermally simulate operation with RP-1 and liquid oxygen, and achieved a specimen throat gas temperature of approximately 2456 K (4420 R). Two high-density composition materials exhibited high erosion resistance, while two low-density compositions exhibited approximately 6-75 times lower average erosion resistance. The results compare favorably with previous testing by NASA and provide adequate data for selection of ablatives for low pressure, low cost rocket engines.

  13. Reynolds-Averaged Navier-Stokes Studies of Low Reynolds Number Effects on the Losses in a Low Pressure Turbine

    NASA Technical Reports Server (NTRS)

    Dorney, Daniel J.

    1996-01-01

    Experimental data from jet-engine tests have indicated that unsteady blade-row interaction effects can have a significant impact on the efficiency of low-pressure turbine stages. Measured turbine efficiencies at takeoff can be as much as two points higher than those at cruise conditions. Preliminary studies indicate that Reynolds number effects may contribute to the lower efficiencies at cruise conditions. In the current study, numerical experiments have been performed to quantify the Reynolds number dependence of unsteady wake/separation bubble interaction on the performance of a low-pressure turbine.

  14. Optical emission spectroscopy for simultaneous measurement of plasma electron density and temperature in a low-pressure microwave induced plasma

    SciTech Connect

    Konjevic, N.; Jovicevic, S.; Ivkovic, M.

    2009-10-15

    The simple optical emission spectroscopy technique for diagnostics of low pressure microwave induced plasma (MIP) in hydrogen or in MIP seeded with hydrogen is described and tested. This technique uses the Boltzmann plot of relative line intensities along Balmer spectral series in conjunction with the criterion for partial local thermodynamic equilibrium for low electron density (N{sub e}) plasma diagnostics. The proposed technique is tested in a low pressure MIP discharge for simultaneous determination of electron density N{sub e} (10{sup 17}-10{sup 18} m{sup -3}) and temperature T{sub e}.

  15. Simplified Configuration for the Combustor of an oil Burner using a low Pressure, high flow air-atomizing Nozzle

    SciTech Connect

    Butcher, Thomas; Celebi, Yusuf; Fisher, Leonard

    1998-09-28

    The invention relates to clean burning of fuel oil with air. More specifically, to a fuel burning combustion head using a low-pressure, high air flow atomizing nozzle so that there will be a complete combustion oil resulting in a minimum emission of pollutants. The inventors have devised a fuel burner that uses a low pressure air atomizing nozzle. The improved fuel burner does not result in the use of additional compressors or the introduction of pressurized gases downstream, nor does it require a complex design.

  16. Production of a low-pressure processing plasma with ion beam injection for thin-film preparation

    NASA Astrophysics Data System (ADS)

    Fujita, Hiroharu; Yagura, Shinya

    1988-06-01

    A low-pressure processing plasma production with an ion beam injection is presented by applying microwave and rf discharges in a low-pressure gas for thin-film preparation. Electrostatic ion energy analyzer and emissive probe techniques are used in the plasma of a nonreactive gas to get plasma characteristics. The measurement reveals that an energy of ion beam injected into a reactor is controllable by adjusting a bias potential applied between the two plasmas, and electric fields at the steady state are affected by a configuration of a magnetic field applied for an enhancement of a microwave plasma production.

  17. Study of dust re-suspension at low pressure in a dedicated wind-tunnel

    NASA Astrophysics Data System (ADS)

    Rondeau, Anthony; Sabroux, Jean-Christophe; Chassefière, Eric

    2015-04-01

    The atmosphere of several telluric planets or satellites are dusty. Such is the case of Earth, Venus, Mars and Titan, each bearing different aeolian processes linked principally to the kinematic viscosity of the near-surface atmosphere. Studies of the Martian atmosphere are particularly relevant for the understanding of the dust re-suspension phenomena at low pressure (7 mbar). It turns out that operation of fusion reactors of the tokamak design produces significant amount of dust through the erosion of plasma-facing components. Such dust is a key issue, both regarding the performance and the safety of a fusion reactor such as ITER, under construction in Cadarache, France. Indeed, to evaluate the explosion risk in the ITER fusion reactor, it is essential to quantify the re-suspended dust fraction as a function of the dust inventory that can be potentially mobilized during a loss of vacuum accident (LOVA), with air or water vapour ingress. A complete accident sequence will encompass dust re-suspension from near-vacuum up to atmospheric pressure. Here, we present experimental results of particles re-suspension fractions measured at 1000, 600 and 300 mbar in the IRSN BISE (BlowIng facility for airborne releaSE) wind tunnel. Both dust monolayer deposits and multilayer deposits were investigated. In order to obtain experimental re-suspension data of dust monolayer deposits, we used an optical microscope allowing to measure the re-suspended particles fraction by size intervals of 1 µm. The deposits were made up of tungsten particles on a tungsten surface (an ubiquitous plasma facing component) and alumina particles on a glass plate, as a surrogate. A comparison of the results with the so-called Rock'nRoll dust re-suspension model (Reeks and Hall, 2001) is presented and discussed. The multilayer deposits were made in a vacuum sedimentation chamber allowing to obtain uniform deposits in terms of thickness. The re-suspension experimental data of such deposits were obtained

  18. Flow Control Under Low-Pressure Turbine Conditions Using Pulsed Jets: Experimental Data Archive

    NASA Technical Reports Server (NTRS)

    Volino, Ralph J.; Ibrahim, Mounir B.

    2012-01-01

    This publication is the final report of research performed under an NRA/Cooperative Interagency Agreement, and includes a supplemental CD-ROM with detailed data. It is complemented by NASA/CR-2012-217416 and NASA/CR-2012-217417 which include a Ph.D. Dissertation and an M.S. thesis respectively, performed under this contract. In this study the effects of unsteady wakes and flow control using vortex generator jets (VGJs) were studied experimentally and computationally on the flow over the L1A low pressure turbine (LPT) airfoil. The experimental facility was a six passage linear cascade in a low speed wind tunnel at the U.S. Naval Academy. In parallel, computational work using the commercial code FLUENT (ANSYS, Inc.) was performed at Cleveland State University, using Unsteady Reynolds Averaged Navier Stokes (URANS) and Large Eddy Simulations (LES) methods. In the first phase of the work, the baseline flow was documented under steady inflow conditions without flow control. URANS calculations were done using a variety of turbulence models. In the second phase of the work, flow control was added using steady and pulsed vortex generator jets. The VGJs successfully suppressed separation and reduced aerodynamic losses. Pulsed operation was more effective and mass flow requirements are very low. Numerical simulations of the VGJs cases showed that URANS failed to capture the effect of the jets. LES results were generally better. In the third phase, effects of unsteady wakes were studied. Computations with URANS and LES captured the wake effect and generally predicted separation and reattachment to match the experiments. Quantitatively the results were mixed. In the final phase of the study, wakes and VGJs were combined and synchronized using various timing schemes. The timing of the jets with respect to the wakes had some effect, but in general once the disturbance frequency was high enough to control separation, the timing was not very important. This is the supplemental CD-ROM

  19. A Shock-Tube Study of the CO + OH Reaction Near the Low-Pressure Limit.

    PubMed

    Nasir, Ehson F; Farooq, Aamir

    2016-06-01

    Rate coefficients for the reaction between carbon monoxide and hydroxyl radical were measured behind reflected shock waves over 700-1230 K and 1.2-9.8 bar. The temperature/pressure conditions correspond to the predicted low-pressure limit of this reaction, where the channel leading to carbon dioxide formation is dominant. The reaction rate coefficients were inferred by measuring the formation of carbon dioxide using quantum cascade laser absorption near 4.2 μm. Experiments were performed under pseudo-first-order conditions with tert-butyl hydroperoxide (TBHP) as the OH precursor. Using ultraviolet laser absorption by OH radicals, the TBHP decomposition rate was measured to quantify potential facility effects under extremely dilute conditions used here. The measured CO + OH rate coefficients are provided in Arrhenius form for three different pressure ranges: kCO+OH(1.2-1.6 bar) = (9.14 ± 2.17) × 10(-13) exp(-(1265 ± 190)/T) cm(3) molecule(-1) s(-1); kCO+OH(4.3-5.1 bar) = (8.70 ± 0.84) × 10(-13) exp(-(1156 ± 83)/T) cm(3) molecule(-1) s(-1); and kCO+OH(9.6-9.8 bar) = (7.48 ± 1.92) × 10(-13) exp(-(929 ± 192)/T) cm(3) molecule(-1) s(-1). The measured rate coefficients are found to be lower than the master equation modeling results by Weston et al. [J. Phys. Chem. A, 2013, 117, 821] at 819 K and in closer agreement with the expression provided by Joshi and Wang [Int. J. Chem. Kinet., 2006, 38, 57]. PMID:27182716

  20. Fracture toughness of low-pressure chemical-vapor-deposited polycrystalline silicon carbide thin films

    NASA Astrophysics Data System (ADS)

    Hatty, V.; Kahn, H.; Trevino, J.; Zorman, C. A.; Mehregany, M.; Ballarini, R.; Heuer, A. H.

    2006-01-01

    The fracture toughness of thin-film polycrystalline silicon carbide (poly-SiC) deposited on silicon (Si) wafers via low-pressure chemical-vapor deposition (LPCVD) has been measured on a scale useful for micromachined devices; the results are compared to previous studies on poly-SiC thin films deposited by atmospheric pressure chemical-vapor deposition (APCVD) [Bellante et al., Appl. Phys. Lett. 86, 071920 (2005)]. Samples in this study included those with and without silicon dioxide (SiO2) sacrificial release layers. The LPCVD processing technique induces residual tensile stresses in the films. Doubly clamped microtensile specimens were fabricated using standard micromachining processes, and microindentation was used to initiate atomically sharp precracks. The residual stresses in the films create stress intensity factors K at the crack tips; upon release, the precracks whose K exceeded a critical value, KIC, propagated to failure. The fracture toughness KIC was the same for both types of devices, 2.9+/-0.2 MPa m1/2 for the SiC on Si samples and 3.0+/-0.2 MPa m1/2 for the SiC on SiO2/Si samples, and similar to that found for APCVD poly-SiC, 2.8<=KIC<=3.4 MPa m1/2 [Bellante et al., Appl. Phys. Lett. 86, 071920 (2005)], indicating that KIC is truly a structure-insensitive material property. The fracture toughness of poly-SiC compares favorably with that for polysilicon, 0.85+/-0.05 MPa m1/2 [Kahn et al., Science 298, 1215 (2002)].

  1. Ice-melt rates during volcanic eruptions within water-drained, low-pressure subglacial cavities

    NASA Astrophysics Data System (ADS)

    Woodcock, D. C.; Lane, S. J.; Gilbert, J. S.

    2016-02-01

    Subglacial volcanism generates proximal and distal hazards including large-scale flooding and increased levels of explosivity. Direct observation of subglacial volcanic processes is infeasible; therefore, we model heat transfer mechanisms during subglacial eruptions under conditions where cavities have become depressurized by connection to the atmosphere. We consider basaltic eruptions in a water-drained, low-pressure subglacial cavity, including the case when an eruption jet develops. Such drained cavities may develop on sloping terrain, where ice may be relatively shallow and where gravity drainage of meltwater will be promoted. We quantify, for the first time, the heat fluxes to the ice cavity surface that result from steam condensation during free convection at atmospheric pressure and from direct and indirect radiative heat transfer from an eruption jet. Our calculations indicate that the direct radiative heat flux from a lava fountain (a "dry" end-member eruption jet) to ice is c. 25 kW m-2 and is a minor component. The dominant heat transfer mechanism involves free convection of steam within the cavity; we estimate the resulting condensation heat flux to be c. 250 kW m-2. Absorption of radiation from a lava fountain by steam enhances convection, but the increase in condensing heat flux is modest at c. 25 kW m-2. Overall, heat fluxes to the ice cavity surface are likely to be no greater than c. 300 kW m-2. These are comparable with heat fluxes obtained by single phase convection of water in a subglacial cavity but much less than those obtained by two-phase convection.

  2. Polydiagnostic calibration performed on a low pressure surface wave sustained argon plasma

    NASA Astrophysics Data System (ADS)

    de Vries, N.; Palomares, J. M.; Iordanova, E. I.; van Veldhuizen, E. M.; van der Mullen, J. J. A. M.

    2008-10-01

    The electron density and electron temperature of a low pressure surface wave sustained argon plasma have been determined using passive and active (laser) spectroscopic methods simultaneously. In this way the validity of the various techniques is established while the plasma properties are determined more precisely. The electron density, ne, is determined with Thomson scattering (TS), absolute continuum measurements, Stark broadening and an extrapolation of the atomic state distribution function (ASDF). The electron temperature, Te, is obtained using TS and absolute line intensity (ALI) measurements combined with a collisional-radiative (CR) model for argon. At an argon pressure of 15 mbar, the ne values obtained with TS and Stark broadening agree with each other within the error bars and are equal to (4 ± 0.5) × 1019 m-3, whereas the ne value (2 ± 0.5) × 1019 m-3 obtained from the continuum is about 30% lower. This suggests that the used formula and cross-section values for the continuum method have to be reconsidered. The electron density determined by means of extrapolation of the ASDF to the continuum is too high (~1020 m-3). This is most probably related to the fact that the plasma is strongly ionizing so that the extrapolation method is not justified. At 15 mbar, the Te values obtained with TS are equal to 13 400 ± 1100 K while the ALI/CR-model yields an electron temperature that is about 10% lower. It can be concluded that the passive results are in good or fair agreement with the active results. Therefore, the calibrated passive methods can be applied to other plasmas in a similar regime for which active diagnostic techniques cannot be used.

  3. Inactivation of Single-Celled Ascaris suum Eggs by Low-Pressure UV Radiation

    PubMed Central

    Brownell, Sarah A.; Nelson, Kara L.

    2006-01-01

    Intact and decorticated single-celled Ascaris suum eggs were exposed to UV radiation from low-pressure, germicidal lamps at fluences (doses) ranging from 0 to 8,000 J/m2 for intact eggs and from 0 to 500 J/m2 for decorticated eggs. With a UV fluence of 500 J/m2, 0.44- ± 0.20-log inactivation (mean ± 95% confidence interval) (63.7%) of intact eggs was observed, while a fluence of 4,000 J/m2 resulted in 2.23- ± 0.49-log inactivation (99.4%). (The maximum quantifiable inactivation was 2.5 log units.) Thus, according to the methods used here, Ascaris eggs are the most UV-resistant water-related pathogen identified to date. For the range of fluences recommended for disinfecting drinking water and wastewater (200 to 2,000 J/m2), from 0- to 1.5-log inactivation can be expected, although at typical fluences (less than 1,000 J/m2), the inactivation may be less than 1 log. When the eggs were decorticated (the outer egg shell layers were removed with sodium hypochlorite, leaving only the lipoprotein ascaroside layer) before exposure to UV, 1.80- ± 0.32-log reduction (98.4%) was achieved with a fluence of 500 J/m2, suggesting that the outer eggshell layers protected A. suum eggs from inactivation by UV radiation. This protection may have been due to UV absorption by proteins in the outer layers of the 3- to 4-μm-thick eggshell. Stirring alone (without UV exposure) also inactivated some of the Ascaris eggs (∼20% after 75 min), which complicated determination of the inactivation caused by UV radiation alone. PMID:16517669

  4. Experimental and numerical study of chemiluminescent species in low-pressure flames

    NASA Astrophysics Data System (ADS)

    Kathrotia, T.; Riedel, U.; Seipel, A.; Moshammer, K.; Brockhinke, A.

    2012-06-01

    Chemiluminescence has been observed since the beginning of spectroscopy, nevertheless, important facts still remain unknown. Especially, reaction pathways leading to chemiluminescent species such as OH∗, CH∗, C2^{*}, and CO2^{*} are still under debate and cannot be modeled with standard codes for flame simulation. In several cases, even the source species of spectral features observed in flames are unknown. In recent years, there has been renewed interest in chemiluminescence, since it has been shown that this radiation can be used to determine flame parameters such as stoichiometry and heat release under some conditions. In this work, we present a reaction mechanism which predicts the OH∗, CH∗ (in A- and B-state), and C2^{*} emission strength in lean to fuel-rich stoichiometries. Measurements have been performed in a set of low-pressure flames which have already been well characterized by other methods. The flame front is resolved in these measurements, which allows a comparison of shape and position of the observed chemiluminescence with the respective simulated concentrations. To study the effects of varying fuels, methane flame diluted in hydrogen are measured as well. The 14 investigated premixed methane-oxygen-argon and methane-hydrogen-oxygen-argon flames span a wide parameter field of fuel stoichiometry ( ϕ=0.5 to 1.6) and hydrogen content (H2 vol%=0 to 50). The relative comparison of measured and simulated excited species concentrations shows good agreement. The detailed and reliable modeling for several chemiluminescent species permits correlating heat release with all of these emissions under a large set of flame conditions. It appears from the present study that the normally used product of formaldehyde and OH concentration may be less well suited for such a prediction in the flames under investigation.

  5. CH2Cl2 thin film formation on low-pressure DC plasma discharge

    NASA Astrophysics Data System (ADS)

    Martinez, H.; Flores, O.; Campillo, B.; Gomez, A.; Salazar-Flores, L.; Poveda, J. C.

    2012-08-01

    Low-pressure DC plasma discharges sustained in a glow discharge of CH2Cl2 are studied. The plasma conditions were: 1.0 Torr, 20 W and 12 l/min. The electron temperature and ion density were estimated to be 5.47±0.27 eV and (1.57±0.06)×1016 m-3, using a double Langmuir probe. The diagnostic of the species was made by optical emission spectroscopy using a spectrometer. The main species identified were at 339.61, 358.60 and 377.96 nm for C2(c'1Πg-b1Πu); at 392.50 nm for C3('Πu-' ? ); at 431.42 nm for CH(A2Δ-X2Π); at 778.28 nm for Cl; at 657.80 nm for C+; at 471.90 and 487.30 nm for H2; at 380.61 nm for CH+(A'Π-X'Σ) and at 317.73 nm for HCl+(A2Σ-X2Π). Special attention was given to the behavior of material deposited on the electrode and the time discharge dependence was also investigated. The material deposited was analyzed with the aid of a scanning electron microscope (SEM) and Fourier transform infrared spectroscopy. The SEM observation shows an increment in the particle size which is in agreement with the observation of less bands in the infrared spectra.

  6. Experimental Study of Transitional Flow Behavior in a Simulated Low Pressure Turbine

    NASA Technical Reports Server (NTRS)

    Sohn, Ki Hyeon; DeWitt, Kenneth J.

    2007-01-01

    A detailed investigation of the flow physics occurring on the suction side of a simulated Low Pressure Turbine (LPT) blade was performed. A contoured upper wall was designed to simulate the pressure distribution of an actual LPT airfoil onto a flat lower plate. The experiments were carried out for the Reynolds numbers of 35,000, 70,000, 100,000, and 250,000 with four levels of freestream turbulence ranging from 1 to 4 percent. For the three lower Reynolds numbers, the boundary layer on the flat plate was separated and formed a bubble. The size of laminar separation bubble was measured to be inversely proportional to the freestream turbulence levels and Reynolds numbers. However, no separation was observed for the Re = 250,000 case. The transition on a separated flow was found to proceed through the formation of turbulent spots in the free shear layer as evidenced in the intermittency profiles for Re = 35,000, 70,000, and 100,000. Spectral data show no evidence of Kelvin-Helmholtz of Tollmien-Schlichting instability waves in the free shear layer over a separation bubble (bypass transition). However, the flow visualization revealed the large vortex structures just outside of the bubble and their development to turbulent flow for Re = 50,000, which is similar to that in the free shear layer (separated-flow transition). Therefore, it is fair to say that the bypass and separated-flow transition modes coexist in the transition flows over the separation bubble of certain conditions. Transition onset and end locations and length determined from intermittency profiles decreased as Reynolds number and freestream turbulence levels increase.

  7. Investigations on the stability of the low pressure positive column in oxygen

    NASA Astrophysics Data System (ADS)

    Testrich, H.; Pasedag, D.; Navrátil, Z.; May, B.; Reimer, R.; Wilke, C.; Wagner, H.-E.

    2009-07-01

    The stability of the low pressure positive column in oxygen was investigated in a pressure range from 0.5 to 0.9 Torr within a discharge current interval from 0.5 to 90 mA. The transition between the well-known T- and H-modes has been studied. The H- to T-mode transition showed a marked hysteresis in the E(I) characteristic which is affected by wall processes. For the first time temporally resolved electric field measurements were realized. At small discharge current the electric field showed a significant modulation, characterized by incoherent fluctuations with a broadband Fourier spectrum. With increasing current the discharge operates in the T-mode, where a mode selection with high modulation degree occurred, resulting in a periodic oscillation of the electric field at a discrete frequency spectrum. The dynamic state in the T-mode is expressed by T-waves moving from the cathode to the anode. It seems that they were excited by oscillations in the cathode region. The waves were damped in the direction of the anode and show no dispersion. The discharge stability was studied using a hydrodynamic model considering electrons, positive and negative ions as well as metastable O2(a 1Δg) molecules. Here the negative O--ions play a crucial role. In good agreement with the experiments the transition between the H-and T-modes was explained as a linear unstable equilibrium state where the energy dependence of the corresponding rate coefficients is the driving mechanism (attachment-induced instability).

  8. Experimental Study of Transitional Flow Behavior in a Simulated Low Pressure Turbine

    NASA Technical Reports Server (NTRS)

    Sohn, Ki Hyeon; DeWitt, Kenneth J.

    1998-01-01

    A detailed investigation of the flow physics occurring on the suction side of a simulated Low Pressure Turbine (LPT) blade was performed. A contoured upper wall was designed to simulate the pressure distribution of an actual LPT airfoil onto a flat lower plate. The experiments were carried out for the Reynolds numbers of 35,000, 70,000, 100,000 and 250,000 with four levels of freestream turbulence ranging from 1% to 4%. For the three lower Reynolds numbers, the boundary layer on the flat plate was separated and formed a bubble. The size of laminar separation bubble was measured to be inversely proportional to the freestream turbulence levels and Reynolds numbers. However, no separation was observed for the Re = 250,000 case. The transition on a separated flow was found to proceed through the formation of turbulent spots in the free shear layer as evidenced in the intermittency profiles for Re = 35,000, 70,000 and 100,000. Spectral data show no evidence of Kelvin-Helmholtz or Tollmien-Schlichting instability waves in the free shear layer over a separation bubble (bypass transition). However, the flow visualization revealed the large vortex structures just outside of the bubble and their development to turbulent flow for Re = 50,000, which is similar to that in the free shear layer (separated-flow transition). Therefore, it is fair to say that the bypass and separated-flow transition modes coexist in the transitional flows over the separation bubble for certain conditions. Transition onset and end locations and length determined from intermittency profiles decrease as Reynolds number and freestream turbulence levels increase.

  9. Identification of effluent organic matter fractions responsible for low-pressure membrane fouling.

    PubMed

    Filloux, Emmanuelle; Gallard, Hervé; Croue, Jean-Philippe

    2012-11-01

    Anion exchange resin (AER), powder activated carbon (PAC) adsorption and ozonation treatments were applied on biologically treated wastewater effluent with the objective to modify the effluent organic matter (EfOM) matrix. Both AER and PAC led to significant total organic carbon (TOC) removal, while the TOC remained nearly constant after ozonation. Liquid Chromatography-Organic Carbon Detection (LC-OCD) analysis showed that the AER treatment preferentially removed high and intermediate molecular weight (MW) humic-like structures while PAC removed low MW compounds. Only a small reduction of the high MW colloids (i.e. biopolymers) was observed for AER and PAC treatments. Ozonation induced a large reduction of the biopolymers and an important increase of the low MW humic substances (i.e. building blocks). Single-cycle microfiltration (MF) and ultrafiltration (UF) tests were conducted using commercially available hollow fibres at a constant flux. After reconcentration to their original organic carbon content, the EfOM matrix modified by AER and PAC treatments exhibited higher UF membrane fouling compared to untreated effluent; result that correlated with the higher concentration of biopolymers. On the contrary, ozonation which induced a significant degradation of the biopolymers led to a minor flux reduction for both UF and MF filtration tests. Based on a single filtration, results indicate that biopolymers play a major role in low pressure membrane fouling and that intermediate and low MW compounds have minor impact. Thus, this approach has shown to be a valid methodology to identify the foulant fractions of EfOM. PMID:22884373

  10. Compressible DNS of transitional and turbulent flow in a low pressure turbine cascade

    NASA Astrophysics Data System (ADS)

    Ranjan, Rajesh; Deshpande, Suresh; Narasimha, Roddam

    2015-11-01

    Direct numerical simulation (DNS) of flow in a low pressure turbine cascade at high incidence is performed using a new in-house code ANUROOP. This code solves compressible Navier-Stokes equations in conservative form using finite volume technique and uses kinetic-energy consistent scheme for the flux calculations. ANUROOP is capable of handling flow past complex geometries using hybrid grid approach (separate grid topologies for the boundary layer and rest of the blade passage). This approach offers much more control in mesh spacing and distribution compared to elliptic grid technique, which is used in many previous studies. Also, in contrast to previous studies, focus of the current work is mainly on the boundary layer flow. The flow remains laminar on the pressure side of the blade, but separates in the aft region of the suction side leading to transition. Separation bubbles formed at this region are transient in nature and we notice multiple bubbles merging and breaking in time. In the mean flow however, only one bubble is seen. Velocity profiles very near to the leading edge of the suction side suggest strong curvature effect. Higher-order boundary layer theory that includes effect of curvature is found to be necessary to characterize the flow in this region. Also, the grid convergence study reveals interesting aspects of numerics vital for accurate simulation of this kind of complex flows. We would like to thank the Gas Turbine Enabling Technology (GATET) Program for funding this project. We also thank C-DAC, Pune and CSIR-4PI, Bangalore for providing computational resources.

  11. Influence of two-phase flow characteristic on critical heat flux in low pressure

    SciTech Connect

    Inoue, Akira; Lee, Sangryoul

    1996-08-01

    Estimation of the critical heat flux (CHF) in a boiling two-phase flow is one of the important subjects for the safety of water-cooled reactors and other energy systems. In the case of a boiling two-phase flow at low pressure, flow pattern and void fraction are easy to change by the power input and the flow becomes more complex due to low density of gas phase. The CHF is affected by the flow pattern. In this study, the CHFs were measured over wide quality range from the subcooled boiling to the annular-mist flow. By using Pyrex glass tube as a test channel, the two-phase flow situation was observed. Graphite rod or stainless steel tube was used as a heater rod and installed at the center of the glass tube. Two-phase flow was formed by steam injection to circulating water at an upstream region of the test section. The flow pattern was kept nearly constant over the length of test section due to the low input power density into the fluid. Then, the characteristics of CHF could be investigated at each flow patterns of bubbly, slug, annular and annular-mist flow. In the subcooled boiling region of bubbly flow, the CHF decreased with increase of quality and was less sensitive to flow rate. In the slug flow region, the CHF showed a minimum value. With more increase of quality in the annular flow, the CHF increased and reached a peak value at a certain quality depending on a flow rate. The peak of CHF occurred almost at a constant vapor mass velocity. In the annular-mist flow region, the CHF decreased with increase of quality. In the region, the effect of heated length on the CHF was systematically measured and validity of an analytical model considering dryout of liquid film based on formation of a dry patch was investigated.

  12. Experimental Study of the Effects of Periodic Unsteady Wakes on Flow Separation in Low Pressure Turbines

    NASA Technical Reports Server (NTRS)

    Ozturk, Burak; Schobeiri, Meinhard T.

    2009-01-01

    The present study, which is the first of a series of investigations of low pressure turbine (LPT) boundary layer aerodynamics, is aimed at providing detailed unsteady boundary layer flow information to understand the underlying physics of the inception, onset, and extent of the separation zone. A detailed experimental study on the behavior of the separation zone on the suction surface of a highly loaded LPT-blade under periodic unsteady wake flow is presented. Experimental investigations were performed on a large-scale, high-subsonic unsteady turbine cascade research facility with an integrated wake generator and test section unit. Blade Pak B geometry was used in the cascade. The wakes were generated by continuously moving cylindrical bars device. Boundary layer investigations were performed using hot wire anemometry at Reynolds number of 110,000, based on the blade suction surface length and the exit velocity, for one steady and two unsteady inlet flow conditions, with the corresponding passing frequencies, wake velocities, and turbulence intensities. The reduced frequencies cover the entire operation range of LP-turbines. In addition to the unsteady boundary layer measurements, blade surface pressure measurements were performed at Re = 50,000, 75,000, 100,000, 110,000, and 125,000. For each Reynolds number, surface pressure measurements are carried out at one steady and two periodic unsteady inlet flow conditions. Detailed unsteady boundary layer measurement identifies the onset and extension of the separation zone as well as its behavior under unsteady wake flow. The results, presented in ensemble-averaged and contour plot forms, help to understand the physics of the separation phenomenon under periodic unsteady wake flow.

  13. Final Report: Comparison of the primary (national) standards of low-pressure gas flow

    NASA Astrophysics Data System (ADS)

    Benková, Miroslava; Makovnik, Stefan; Mickan, Bodo

    2015-01-01

    The EURAMET.M.FF-K6 comparison was organized for the purpose of determination of the degree of equivalence of the primary (national) standards for low-pressure gas flow measurement over the range (2 to 100) m3/h and was performed simultaneously with CCM.FF-K6.2011 with the same transfer standard. A rotary gas meter G65 was used as a transfer standard. The measurements were provided by prescribed reference conditions. Fifteen laboratories from EURAMET participated in this key comparison - SMU, Slovakia; PTB, Germany; CEM, Spain; LNE-LADG, France; VSL, Netherlands; CMI, Czech Republic; BEV, Austria; MKEH, Hungary; GUM Poland; SP, Sweden; METAS, Switzerland; DMDM, Serbia; TUBITAK-UME, Turkey; EIM, Greece; IMBiH, Bosnia-Herzegovina. The EURAMET.M.FF-K6 is linked to the CCM.FF-K6.2011 by correcting the results of three linking laboratories (Slovakia SMU, Germany PTB and France LNE LADG). This correction provides an estimate of what would have been the result from the EURAMET.M-FF-K6 participants, if they had actually participated in CCM.FF-K6.2011. According to the evaluation 93.7 % of the results were consistent with KCRV, 3.4 % of the results were in the warning level and 2.9 % of the results were inconsistent. The results of this comparison can be used for review of the CMC tables. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

  14. Glow Discharge Plasma Demonstrated for Separation Control in the Low-Pressure Turbine

    NASA Technical Reports Server (NTRS)

    Ashpis, David e.; Hultgren, Lennart S.

    2004-01-01

    Flow separation in the low-pressure turbine (LPT) is a major barrier that limits further improvements of aerodynamic designs of turbine airfoils. The separation is responsible for performance degradation, and it prevents the design of highly loaded airfoils. The separation can be delayed, reduced, or eliminated completely if flow control techniques are used. Successful flow control technology will enable breakthrough improvements in gas turbine performance and design. The focus of this research project was the development and experimental demonstration of active separation control using glow discharge plasma (GDP) actuators in flow conditions simulating the LPT. The separation delay was shown to be successful, laying the foundation for further development of the technologies to practical application in the LPT. In a fluid mechanics context, the term "flow control" means a technology by which a very small input results in a very large effect on the flow. In this project, the interest is to eliminate or delay flow separation on LPT airfoils by using an active flow control approach, in which disturbances are dynamically inserted into the flow, they interact with the flow, and they delay separation. The disturbances can be inserted using a localized, externally powered, actuating device, examples are acoustic, pneumatic, or mechanical devices that generate vibrations, flow oscillations, or pulses. A variety of flow control devices have been demonstrated in recent years in the context of the external aerodynamics of aircraft wings and airframes, where the incoming flow is quiescent or of a very low turbulence level. However, the flow conditions in the LPT are significantly different because there are high levels of disturbances in the incoming flow that are characterized by high free-stream turbulence intensity. In addition, the Reynolds number, which characterizes the viscous forces in the flow and is related to the flow speed, is very low in the LPT passages.

  15. Flow Control Under Low-Pressure Turbine Conditions Using Pulsed Jets

    NASA Technical Reports Server (NTRS)

    Volino, Ralph J.; Ibrahim, Mounir B.

    2012-01-01

    This publication is the final report of research performed under an NRA/Cooperative Interagency Agreement, and includes a supplemental CD-ROM with detailed data. It is complemented by NASA/CR-2012-217416 and NASA/CR-2012-217417 which include a Ph.D. Dissertation and an M.S. thesis respectively, performed under this contract. In this study the effects of unsteady wakes and flow control using vortex generator jets (VGJs) were studied experimentally and computationally on the flow over the L1A low pressure turbine (LPT) airfoil. The experimental facility was a six passage linear cascade in a low speed wind tunnel at the U.S. Naval Academy. In parallel, computational work using the commercial code FLUENT (ANSYS, Inc.) was performed at Cleveland State University, using Unsteady Reynolds Averaged Navier Stokes (URANS) and Large Eddy Simulations (LES) methods. In the first phase of the work, the baseline flow was documented under steady inflow conditions without flow control. URANS calculations were done using a variety of turbulence models. In the second phase of the work, flow control was added using steady and pulsed vortex generator jets. The VGJs successfully suppressed separation and reduced aerodynamic losses. Pulsed operation was more effective and mass flow requirements are very low. Numerical simulations of the VGJs cases showed that URANS failed to capture the effect of the jets. LES results were generally better. In the third phase, effects of unsteady wakes were studied. Computations with URANS and LES captured the wake effect and generally predicted separation and reattachment to match the experiments. Quantitatively the results were mixed. In the final phase of the study, wakes and VGJs were combined and synchronized using various timing schemes. The timing of the jets with respect to the wakes had some effect, but in general once the disturbance frequency was high enough to control separation, the timing was not very important.

  16. Experimental Studies of Low-Pressure Turbine Flows and Flow Control

    NASA Technical Reports Server (NTRS)

    Volino, Ralph J.

    2012-01-01

    This report summarizes research performed in support of the NASA Glenn Research Center (GRC) Low-Pressure Turbine (LPT) Flow Physics Program. The work was performed experimentally at the U.S. Naval Academy faculties. The geometry corresponded to "Pak B" LPT airfoil. The test section simulated LPT flow in a passage. Three experimental studies were performed: (a) Boundary layer measurements for ten baseline cases under high and low freestream turbulence conditions at five Reynolds numbers of 25,000, 50,000, 100,000, 200,000, and 300,000, based on passage exit velocity and suction surface wetted length; (b) Passive flow control studies with three thicknesses of two-dimensional bars, and two heights of three-dimensional circular cylinders with different spanwise separations, at same flow conditions as the 10 baseline cases; (c) Active flow control with oscillating synthetic (zero net mass flow) vortex generator jets, for one case with low freestream turbulence and a low Reynolds number of 25,000. The Passive flow control was successful at controlling the separation problem at low Reynolds numbers, with varying degrees of success from case to case and varying levels of impact at higher Reynolds numbers. The active flow control successfully eliminated the large separation problem for the low Reynolds number case. Very detailed data was acquired using hot-wire anemometry, including single and two velocity components, integral boundary layer quantities, turbulence statistics and spectra, turbulent shear stresses and their spectra, and intermittency, documenting transition, separation and reattachment. Models were constructed to correlate the results. The report includes a summary of the work performed and reprints of the publications describing the various studies.

  17. Millimeter-size single-crystal graphene by suppressing evaporative loss of Cu during low pressure chemical vapor deposition.

    PubMed

    Chen, Shanshan; Ji, Hengxing; Chou, Harry; Li, Qiongyu; Li, Hongyang; Suk, Ji Won; Piner, Richard; Liao, Lei; Cai, Weiwei; Ruoff, Rodney S

    2013-04-11

    Millimeter-size single-crystal monolayer graphene is synthesized on polycrystalline Cu foil by a method that involves suppressing loss by evaporation of the Cu at high temperature under low pressure. This significantly diminishes the number of graphene domains, and large single crystal domains up to ∼2 mm in size are grown. PMID:23386288

  18. A Computational Fluid Dynamics Study of Transitional Flows in Low-Pressure Turbines under a Wide Range of Operating Conditions

    NASA Technical Reports Server (NTRS)

    Suzen, Y. B.; Huang, P. G.; Ashpis, D. E.; Volino, R. J.; Corke, T. C.; Thomas, F. O.; Huang, J.; Lake, J. P.; King, P. I.

    2007-01-01

    A transport equation for the intermittency factor is employed to predict the transitional flows in low-pressure turbines. The intermittent behavior of the transitional flows is taken into account and incorporated into computations by modifying the eddy viscosity, mu(sub p) with the intermittency factor, gamma. Turbulent quantities are predicted using Menter's two-equation turbulence model (SST). The intermittency factor is obtained from a transport equation model which can produce both the experimentally observed streamwise variation of intermittency and a realistic profile in the cross stream direction. The model had been previously validated against low-pressure turbine experiments with success. In this paper, the model is applied to predictions of three sets of recent low-pressure turbine experiments on the Pack B blade to further validate its predicting capabilities under various flow conditions. Comparisons of computational results with experimental data are provided. Overall, good agreement between the experimental data and computational results is obtained. The new model has been shown to have the capability of accurately predicting transitional flows under a wide range of low-pressure turbine conditions.

  19. A radial differential mobility analyzer for the size-classification of gas-phase synthesized nanoparticles at low pressures

    NASA Astrophysics Data System (ADS)

    Nanda, K. K.; Kruis, F. E.

    2014-07-01

    Differential mobility analyzers (DMAs) are commonly used to generate monodisperse nanoparticle aerosols. Commercial DMAs operate at quasi-atmospheric pressures and are therefore not designed to be vacuum-tight. In certain particle synthesis methods, the use of a vacuum-compatible DMA is a requirement as a process step for producing high-purity metallic particles. A vacuum-tight radial DMA (RDMA) has been developed and tested at low pressures. Its performance has been evaluated by using a commercial NANO-DMA as the reference. The performance of this low-pressure RDMA (LP-RDMA) in terms of the width of its transfer function is found to be comparable with that of other NANO-DMAs at atmospheric pressure and is almost independent of the pressure down to 30 mbar. It is shown that LP-RDMA can be used for the classification of nanometer-sized particles (5-20 nm) under low pressure condition (30 mbar) and has been successfully applied to nanoparticles produced by ablating FeNi at low pressures.

  20. Assessing the effectiveness of low-pressure ultraviolet light for inactivating Mycobacterium avium complex (MAC) micro-organisms

    EPA Science Inventory

    Aims: To assess low-pressure ultraviolet light (LP-UV) inactivation kinetics of Mycobacterium avium complex (MAC) strains in a water matrix using collimated beam apparatus. Methods and Results: Strains of M. avium (n = 3) and Mycobacterium intracellulare (n = 2) were exposed t...

  1. Test beam results of a low-pressure micro-strip gas chamber with a secondary-electron emitter

    SciTech Connect

    Kwan, S.; Anderson, D.F.; Zimmerman, J.; Sbarra, C.; Salomon, M.

    1994-10-01

    We present recent results, from a beam test, on the angular dependence of the efficiency and the distribution of the signals on the anode strips of a low-pressure microstrip gas chamber with a thick CsI layer as a secondary-electron emitter. New results of CVD diamond films as secondary-electron emitters are discussed.

  2. SEPARATION OF HAZARDOUS ORGANICS BY LOW PRESSURE MEMBRANES: TREATMENT OF SOIL-WASH RINSE-WATER LEACHATES

    EPA Science Inventory

    Soil washing is a promising technology for treating contaminated soils. In the present work, low-pressure, thin-film composite membranes were evaluated to treat the soil-wash leachates so that the treated water could be recycled back to the soil washing step. Experiments were don...

  3. "Virtual IED sensor" at an rf-biased electrode in low-pressure plasma

    NASA Astrophysics Data System (ADS)

    Bogdanova, M. A.; Lopaev, D. V.; Zyryanov, S. M.; Rakhimov, A. T.

    2016-07-01

    Energy distribution and the flux of the ions coming on a surface are considered as the key-parameters in anisotropic plasma etching. Since direct ion energy distribution (IED) measurements at the treated surface during plasma processing are often hardly possible, there is an opportunity for virtual ones. This work is devoted to the possibility of such indirect IED and ion flux measurements at an rf-biased electrode in low-pressure rf plasma by using a "virtual IED sensor" which represents "in-situ" IED calculations on the absolute scale in accordance with a plasma sheath model containing a set of measurable external parameters. The "virtual IED sensor" should also involve some external calibration procedure. Applicability and accuracy of the "virtual IED sensor" are validated for a dual-frequency reactive ion etching (RIE) inductively coupled plasma (ICP) reactor with a capacitively coupled rf-biased electrode. The validation is carried out for heavy (Ar) and light (H2) gases under different discharge conditions (different ICP powers, rf-bias frequencies, and voltages). An EQP mass-spectrometer and an rf-compensated Langmuir probe (LP) are used to characterize plasma, while an rf-compensated retarded field energy analyzer (RFEA) is applied to measure IED and ion flux at the rf-biased electrode. Besides, the pulsed selfbias method is used as an external calibration procedure for ion flux estimating at the rf-biased electrode. It is shown that pulsed selfbias method allows calibrating the IED absolute scale quite accurately. It is also shown that the "virtual IED sensor" based on the simplest collisionless sheath model allows reproducing well enough the experimental IEDs at the pressures when the sheath thickness s is less than the ion mean free path λi (s < λi). At higher pressure (when s > λi), the difference between calculated and experimental IEDs due to ion collisions in the sheath is observed in the low energy range. The effect of electron impact ionization

  4. Ultra high efficiency/low pressure supercritical fluid chromatography with superficially porous particles for triglyceride separation.

    PubMed

    Lesellier, E; Latos, A; de Oliveira, A Lopes

    2014-01-31

    This paper reports the development of the separation of vegetable oil triglycerides (TG) in supercritical chromatography (SFC), using superficially porous particles (SPPs). The SPP, having a small diameter (2-3μm), provide a higher theoretical plate number (N), which allows to improve separation of critical pairs of compounds. However, compared to fully porous particles of larger diameter (5μm), the pressure drop is also increased. Fortunately, supercritical fluids have a low viscosity, which allows coupling several columns to achieve high N values, while maintaining flow rate above 1ml/min, ensuring a ultra high efficiency (UHE) at low pressure (LP) (below 40MPa), with regards to the one reached with liquid and sub-two micron particles (around 100MPa). The use of two detector systems (UV and ELSD) connected in series to the UHE-LP-SFC system provides complementary responses, due to their specific detection principles. Working in a first part with three coupled Kinetex C18 columns (45cm total length), the effect of modifier nature and percentage were studied with two reference oils, argan and rapeseed, chosen for their different and well-known TG composition. The analytical method was developed from previous studies performed with fully porous particles (FPP). Optimized conditions with three Kinetex were as follows: 17°C, 12% of ACN/MeOH (90/10; v/v). With these conditions, and by using an increased length of Kinetex C18 column (60cm), another additional column was selected from ten different commercial SPP C18 bonded phases, by applying a Derringer function on varied parameters: theoretical plate number (TPN), separation index (SI) for critical pairs of peaks (the peaks of compounds difficult to separate due to subtle structural differences), the analysis duration, and the total peak number. This function normalizes the values of any parameters, between 0 and 1, from the worst value to the better, allowing to take account of various parameters in the final

  5. On the Physics of Flow Separation Along a Low Pressure Turbine Blade Under Unsteady Flow Conditions

    NASA Technical Reports Server (NTRS)

    Schobeiri, Meinhard T.; Ozturk, Burak; Ashpis, David E.

    2003-01-01

    The present study, which is the first of a series of investigations dealing with specific issues of low pressure turbine (LPT) boundary layer aerodynamics, is aimed at providing detailed unsteady boundary flow information to understand the underlying physics of the inception, onset, and extent of the separation zone. A detailed experimental study on the behavior of the separation zone on the suction surface of a highly loaded LPT-blade under periodic unsteady wake flow is presented. Experimental investigations were performed at Texas A&M Turbomachinery Performance and Flow Research Laboratory using a large-scale unsteady turbine cascade research facility with an integrated wake generator and test section unit. To account for a high flow deflection of LPT-cascades at design and off-design operating points, the entire wake generator and test section unit including the traversing system is designed to allow a precise angle adjustment of the cascade relative to the incoming flow. This is done by a hydraulic platform, which simultaneously lifts and rotates the wake generator and test section unit. The unit is then attached to the tunnel exit nozzle with an angular accuracy of better than 0.05 , which is measured electronically. Utilizing a Reynolds number of 110,000 based on the blade suction surface length and the exit velocity, one steady and two different unsteady inlet flowconditions with the corresponding passing frequencies, wake velocities and turbulence intensities are investigated using hot-wire anemometry. In addition to the unsteady boundary layer measurements, blade surface pressure measurements were performed at Re=50,000, 75,000, 100,000, and 125,000 at one steady and two periodic unsteady inlet flow conditions. Detailed unsteady boundary layer measurement identifies the onset and extent of the separation zone as well as its behavior under unsteady wake flow. The results presented in ensemble-averaged and contour plot forms contribute to understanding the

  6. Design and validation of a high-lift low-pressure turbine blade

    NASA Astrophysics Data System (ADS)

    McQuilling, Mark Wayne

    This dissertation is a design and validation study of the high-lift low-pressure turbine (LPT) blade designated L2F. High-lift LPTs offer the promise of reducing the blade count in modern gas turbine engines. Decreasing the blade count can reduce development and maintenance costs and the weight of the engine, but care must be taken in order to maintain turbine section performance with fewer blades. For an equivalent amount of work extracted, lower blade counts increase blade loading in the LPT section. The high-lift LPT presented herein allows 38% fewer blades with a Zweifel loading coefficient of 1.59 and maintains the same inlet and outlet blade metal angles of conventional geometries in service today while providing an improved low-Reynolds number characteristic. The computational design method utilizes the Turbine Design and Analysis System (TDAAS) developed by John Clark of the Air Force Research Laboratory. TDAAS integrates several government-funded design utilities including airfoil and grid generation capability with a Reynolds-Averaged Navier-Stokes flow solver into a single, menu-driven, Matlab-based system. Transition modeling is achieved with the recently developed model of Praisner and Clark, and this study validates the use of the model for design purposes outside of the Pratt & Whitney (P&W) design system where they were created. Turbulence modeling is achieved with the Baldwin and Lomax zero-equation model. The experimental validation consists of testing the front-loaded L2F along with a previously designed, mid-loaded blade (L1M) in a linear turbine cascade in a low-speed wind tunnel over a range of Reynolds numbers at 3.3% freestream turbulence. Hot-wire anemometry and pressure measurements elucidate these comparisons, while a shear and stress sensitive film (S3F) also helps describe the flow in areas of interest. S3F can provide all 3 components of stress on a surface in a single measurement, and these tests extend the operational envelope of the

  7. Advanced Research on the Electrode Area of a Low Pressure Hg-Ar Discharge Lamp

    NASA Astrophysics Data System (ADS)

    Shi, Jianou

    The phenomenon of electrical discharge in low pressure Hg-Ar vapor has been under continuous investigation since it was first discovered. Because much work has been done in the positive column, it is, therefore, that the electrode area of the lamp is the main focus of this thesis. To simulate the interface phenomena on a electrode surface, samples, with optically smooth tungsten-barium interfaces were fired in a high vacuum furnace at different temperatures. Measurements were made using surface characterization techniques. It is found that no Ba_3WO _6 is formed on the surface as previously reported in the powder mixing experiments, and the interface consists mainly of BaWO_4. It was discovered in the early 1950's that vaporization of the barium from the cathode in a fluorescent lamp could be reduced tremendously with the addition of 5% of ZrO _2 to the coating mix. However, the reason for this is poorly understood. A possible explanation has been found, and number of tests have been completed to simulate the formation of BaZO_3 under different lamp operating conditions. The measurements and simulation of barium atom and ion number densities are presented. Barium emitted from the electrode surface has a strong interaction with the local plasma. The number density distributions depend mainly on the discharge conditions. A Monte Carlo computer simulation for the barium ion number density is described and the results from the simulation compared to the experimental results obtained by absorption method. It is clear that the ion distribution and phosphor contamination in the electrode area are two closely related issues. XPS is used to measure the chemical composition on the phosphor surface of the lamp. A discussion of calibration methods and the possible compounds forming on the phosphors is then presented. A number of questions have been raised concerning the safety of the lamp and its affects on health related to radiation generated in the electrode area. Typically

  8. Investigation of the DSMC Approach for Ion/neutral Species in Modeling Low Pressure Plasma Reactor

    SciTech Connect

    Deng Hao; Li, Z.; Levin, D.; Gochberg, L.

    2011-05-20

    Low pressure plasma reactors are important tools for ionized metal physical vapor deposition (IMPVD), a semiconductor plasma processing technology that is increasingly being applied to deposit Cu seed layers on semiconductor surfaces of trenches and vias with the high aspect ratio (e.g., >5:1). A large fraction of ionized atoms produced by the IMPVD process leads to an anisotropic deposition flux towards the substrate, a feature which is critical for attaining a void-free and uniform fill. Modeling such devices is challenging due to their high plasma density, reactive environment, but low gas pressure. A modular code developed by the Computational Optical and Discharge Physics Group, the Hybrid Plasma Equipment Model (HPEM), has been successfully applied to the numerical investigations of IMPVD by modeling a hollow cathode magnetron (HCM) device. However, as the development of semiconductor devices progresses towards the lower pressure regime (e.g., <5 mTorr), the breakdown of the continuum assumption limits the application of the fluid model in HPEM and suggests the incorporation of the kinetic method, such as the direct simulation Monte Carlo (DSMC), in the plasma simulation.The DSMC method, which solves the Boltzmann equation of transport, has been successfully applied in modeling micro-fluidic flows in MEMS devices with low Reynolds numbers, a feature shared with the HCM. Modeling of the basic physical and chemical processes for ion/neutral species in plasma have been developed and implemented in DSMC, which include ion particle motion due to the Lorentz force, electron impact reactions, charge exchange reactions, and charge recombination at the surface. The heating of neutrals due to collisions with ions and the heating of ions due to the electrostatic field will be shown to be captured by the DSMC simulations. In this work, DSMC calculations were coupled with the modules from HPEM so that the plasma can be self-consistently solved. Differences in the Ar

  9. Turbulent transition behavior in a separated and attached-flow low pressure turbine passage

    NASA Astrophysics Data System (ADS)

    Memory, Curtis L.

    Various time accurate numerical simulations were conducted on the aft-loaded L1A low pressure turbine airfoil operating at Reynolds numbers presenting with fully-stalled, non-reattaching laminar separation. The numerical solver TURBO was modified from its annular gas turbine simulation configuration to conduct simulations based on a linear cascade wind tunnel facility. Simulation results for the fully separated flow fields revealed various turbulent decay mechanisms. Separated shear layer decay, in the form of vortices forming between the shear layer and the blade wall, was shown to agree with experimental particle image velocimetry (PIV) data in terms of decay vortex size and core vorticity levels. These vortical structures eventually mix into a large recirculation zone which dominates the blade wake. Turbulent wake ex- tent and time-averaged velocity distributions agreed with PIV data. Steady-blowing vortex generating jet (VGJ) flow control was then applied to the flow fields. VGJ-induced streamwise vorticity was only present at blowing ratios above 1.5. VGJs actuated at the point of flow separation on the blade wall were more effective than those actuated downstream, within the separation zone. Pulsed-blowing VGJs at the upstream blade wall position were then actuated at various pulsing frequencies, duty cycles, and blowing ratios. These condition variations yielded differing levels of separation zone mitigation. Pulsed VGJs were shown to be more effective than steady blowing VGJs at conditions of high blowing ratio, high frequency, or high duty cycle, where blowing ratio had the highest level of influence on pulsed jet efficacy. The characteristic "calm zone" following the end of a given VGJ pulse was observed in simulations exhibiting high levels of separation zone mitigation. Numerical velocity fields near the blade wall during this calm zone was shown to be similar to velocity fields observed in PIV data. Instantaneous numerical vorticity fields indicated

  10. Numerical modeling of transition to turbulence in low-pressure axial gas turbines

    NASA Astrophysics Data System (ADS)

    Flitan, Horia Constantin

    2002-09-01

    Experimental data from modern turbofan engines indicate that the low-pressure turbine stages experience a significant drop in efficiency as the aircraft reaches its cruise conditions at high altitude. Under these circumstances, the low Reynolds number flow allows the apparition of a boundary layer which is no longer turbulent but transitional in nature. A further decrease in velocity may lead to the separation of the highly unstable laminar portion accompanied by a dramatic growth in aerodynamic losses. The methods for numerically simulating the transitional flows occurring over turbine blades were reviewed. Two large categories were identified as suitable for numerical implementation into a fully-implicit, finite-difference, Navier-Stokes code. The first involved a Baldwin-Lomax turbulence model corrected for attached flow transition with an intermittency factor distribution. The general expression of Solomon, Walker and Gostelow was added to the code, in parallel with the zero-pressure gradient form of Narasimha, used for reference. In both cases transition inception is detected with the Abu-Ghannam Shaw correlation. Whenever laminar separation takes place, Robert's correlation for short bubble transition is activated. The second category comprised the two-equation, low Reynolds number turbulence models of Chien and Launder-Sharma. They have a certain ability to predict bypass transition and seem to better comprehend the physics of wake-induced transition. For the approximate factorization solution algorithm, the implicit part of the Launder-Sharma system was expressed in an original form. Also, the Kato-Launder correction was added to be used as an option. Numerical investigations of attached flow bypass transition and separated flow short bubble transitions were performed on two cascade geometries. The Abu-Ghannam Shaw criterion proved to be inaccurate for curved surfaces. The Solomon, Walker Gostelow distribution did not perform better than Narasimha

  11. On the Physics of Flow Separation Along a Low Pressure Turbine Blade Under Unsteady Flow Conditions

    NASA Technical Reports Server (NTRS)

    Schobeiri, Meinhard T.; Ozturk, Burak; Ashpis, David E.

    2005-01-01

    The present study, which is the first of a series of investigations dealing with specific issues of low pressure turbine (LPT) boundary layer aerodynamics, is aimed at providing detailed unsteady boundary flow information to understand the underlying physics of the inception, onset, and extent of the separation zone. A detailed experimental study on the behavior of the separation zone on the suction surface of a highly loaded LPT-blade under periodic unsteady wake flow is presented. Experimental investigations were performed at Texas A&M Turbomachinery Performance and Flow Research Laboratory using a large-scale unsteady turbine cascade research facility with an integrated wake generator and test section unit. To account for a high flow deflection of LPT-cascades at design and off-design operating points, the entire wake generator and test section unit including the traversing system is designed to allow a precise angle adjustment of the cascade relative to the incoming flow. This is done by a hydraulic platform, which simultaneously lifts and rotates the wake generator and test section unit. The unit is then attached to the tunnel exit nozzle with an angular accuracy of better than 0.05 , which is measured electronically. Utilizing a Reynolds number of 110,000 based on the blade suction surface length and the exit velocity, one steady and two different unsteady inlet flow conditions with the corresponding passing frequencies, wake velocities and turbulence intensities are investigated using hot-wire anemometry. In addition to the unsteady boundary layer measurements, blade surface pressure measurements were performed at Re=50,000, 75,000, 100,000, and 125,000 at one steady and two periodic unsteady inlet flow conditions. Detailed unsteady boundary layer measurement identifies the onset and extent of the separation zone as well as its behavior under unsteady wake flow. The results presented in ensemble-averaged and contour plot forms contribute to understanding the

  12. Calibration of the modified Electrical Low-Pressure Impactor (ELPI) for use with pressurized pharmaceutical aerosols.

    PubMed

    Kotian, Reshma; Peart, Joanne; Bryner, Joan; Byron, Peter R

    2009-03-01

    The modified Electrical Low Pressure Impactor (ELPI) is currently being used in several laboratories to determine inherent electrostatic charge of pharmaceutical aerosols as a function of their particle size. However, the ELPI appears to underestimate the aerodynamic particle size distributions (aPSDs) of pressurized metered dose inhalers (pMDIs), casting doubt upon the manufacturer's calibration. In the present study, four commercially available pMDIs with a range of aPSDs were used to recalibrate cutoff diameters (d50s) of the ELPI stages using a reference ACI. Particle size analyses were performed in a mensurated ACI and a calibrated modified ELPI (n = 5); stage coating was employed in both instruments. The ACI data were fitted to a lognormal cumulative distribution function by nonlinear regression analysis. Best estimates for mass median aerodynamic diameter (MMAD) and geometric standard deviation (GSD) for each pMDI were obtained and used in combination with impaction results from the modified ELPI to determine new d50s for each of the ELPI stages by numerical methods. Ventolin HFA was employed to validate the new ELPI d50 values. The curve-fitting procedure produced excellent fits of the ACI data for all the calibration pMDIs, which were well modeled as mono-modal and lognormally distributed. The mean d50s obtained following recalibration of the modified ELPI were found to deviate increasingly from the manufacturer-supplied values as aerodynamic diameter decreased. Ventolin HFA's MMAD determined using the modified ELPI with the manufacturer-supplied d50s was 2.06 +/- 0.08 microm. The MMAD calculated using the recalibrated d50s was 2.63 +/- 0.09 microm, which was statistically indistinguishable (p = 0.0852) from that determined for Ventolin HFA using the ACI (2.73 +/- 0.09 microm). In the absence of a comprehensive recalibration of the ELPI using monodisperse aerosols, the mean d50s for stages 4-12 of ELPI reported offer a practical way of analyzing the a

  13. Thermal Shock Properties of Yttria-Stabilized Zirconia Coatings Deposited Using Low-Energy Very Low Pressure Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Zhu, Lin; Zhang, Nannan; Bolot, Rodolphe; Liao, Hanlin; Coddet, Christian

    2015-08-01

    Yttria-stabilized zirconia (YSZ) coatings have been frequently used as a thermal protective layer on the metal or alloy component surfaces. In the present study, ZrO2-7%Y2O3 thermal barrier coatings (TBCs) were successfully deposited by DC (direct current) plasma spray process under very low pressure conditions (less than 1 mbar) using low-energy plasma guns F4-VB and F100. The experiments were performed to evaluate the thermal shock resistance of different TBC specimens which were heated to 1373 K at a high-temperature cycling furnace and held for 0.5 h, followed by air cooling at room temperature for 0.2 h. For comparison, a corresponding atmospheric plasma spray (APS) counterpart was also elaborated to carry out the similar experiments. The results indicated that the very low pressure plasma spray (VLPPS) coatings displayed better thermal shock resistance. Moreover, the failure mechanism of the coatings was elucidated.

  14. Modeling the Rapid Boil-Off of a Cryogenic Liquid When Injected into a Low Pressure Cavity

    NASA Technical Reports Server (NTRS)

    Lira, Eric

    2016-01-01

    Many launch vehicle cryogenic applications require the modeling of injecting a cryogenic liquid into a low pressure cavity. The difficulty of such analyses lies in accurately predicting the heat transfer coefficient between the cold liquid and a warm wall in a low pressure environment. The heat transfer coefficient and the behavior of the liquid is highly dependent on the mass flow rate into the cavity, the cavity wall temperature and the cavity volume. Testing was performed to correlate the modeling performed using Thermal Desktop and Sinda Fluint Thermal and Fluids Analysis Software. This presentation shall describe a methodology to model the cryogenic process using Sinda Fluint, a description of the cryogenic test set up, a description of the test procedure and how the model was correlated to match the test results.

  15. Improving the shape and compliance characteristics of a high-volume, low-pressure cuff improves tracheal seal.

    PubMed

    Young, P J; Blunt, M C

    1999-12-01

    A prototype design of a compliant latex, high-volume, low-pressure cuffed tracheal tube cuff (CHVLP) was compared with the Mallinckrodt Hi-Lo, Sheridan preformed and Portex Profile high-volume, low-pressure (HVLP) cuffed tracheal tubes for leakage of dye placed above the cuff in a benchtop mechanical ventilation model and in five isolated pig tracheas. There was no leakage in the ventilation model or in the pig tracheas with the prototype CHVLP. There was rapid leakage in the ventilation model and in all the pig tracheas for the Mallinckrodt Hi-Lo, the Sheridan preformed and the Portex Profile cuffs. This benchtop study suggests that improved HVLP cuff compliance characteristics may be beneficial in the prevention of leakage of fluid to the lungs known to occur with HVLP cuffs. PMID:10700788

  16. The NASA Low-Pressure Turbine Flow Physics Program: A Review

    NASA Technical Reports Server (NTRS)

    Ashpis, David E.

    2002-01-01

    An overview of the NASA Glenn Low-Pressure Turbine (LPT) Flow Physics Program will be presented. The flow in the LPT is unique for the gas turbine. It is characterized by low Reynolds number and high freestream turbulence intensity and is dominated by interplay of three basic mechanisms: transition, separation and wake interaction. The flow of most interest is on the suction surface, where large losses are generated due to separation. The LPT is a large, multistage, heavy, jet engine component that suffers efficiency degradation between takeoff and cruise conditions due to decrease in Reynolds number with altitude. The performance penalty is around 2 points for large commercial bypass engines and as much as 7 points for small, high cruise altitude, military engines. The gas-turbine industry is very interested in improving the performance of the LPT and in reducing its weight, part count and cost. Many improvements can be accomplished by improved airfoil design, mainly by increasing the airfoil loading that can yield reduction of airfoils and improved performance. In addition, there is a strong interest in reducing the design cycle time and cost. Key enablers of the needed improvements are computational tools that can accurately predict LPT flows. Current CFD tools in use cannot yet satisfactorily predict the unsteady, transitional and separated flow in the LPT. The main reasons are inadequate transition & turbulence models and incomplete understanding of the LPT flow physics. NASA Glenn has established its LPT program to answer these needs. The main goal of the program is to develop and assess models for unsteady CFD of LPT flows. An approach that consists of complementing and augmenting experimental and computational work elements has been adopted. The work is performed in-house and by several academic institutions, in cooperation and interaction with industry. The program was reviewed at the Minnowbrook II meeting in 1997. This review will summarize the progress

  17. Magmatic Volatiles and Low Pressure Degassing at a Mafic Shield Volcano (Belknap) in the Oregon Cascades

    NASA Astrophysics Data System (ADS)

    Mordensky, S. P.; Ruscitto, D. M.; Wallace, P. J.; Cashman, K. V.

    2011-12-01

    Cinder cones and shield volcanoes frequently coexist in volcanic fields. Despite their proximity, cinder cones often erupt as monogenetic (single) events, whereas shield volcanoes are polygenetic (multiple eruptive events). Why some vents erupt once for a relatively short period of time (months) but others nearby remain active enough to build up as shields (over hundreds or thousands of years) remains ambiguous. To better understand the magma ascent conditions associated with these disparate eruption styles, we contrast the volatile concentrations within olivine-hosted melt inclusions of tephra deposits from the late-stage eruptions of a mafic shield volcano with those from nearby cinder cones. Belknap Crater is a shield volcano in the Central Oregon High Cascades that grew through repeated eruptions from ~2800 to 1500 years BP (Sherrod et al., 2004). Volatile contents from late-stage ash collected on the flanks of the summit cone range from 0.1 to 2.4 wt% H2O and <50 to 770 ppm CO2. The most volatile-rich inclusions record vapor saturation pressures of ~2 kbar, equivalent to ~7 km depth in the crust, whereas inclusions with the lowest volatile contents indicate very low pressures of formation. Given that the height of the volcano is roughly 540 meters above the surrounding ground level, many of the inclusions with relatively low H2O values and CO2 values, which are often below detection limits, likely reflect olivine crystallization within the volcano itself. In contrast, melt inclusions from nearby short-lived cinder cones (e.g. Collier Cone and 4-in-1 Cone) of similar age, < 2900 years BP, contain 2-4 wt% H2O and 500-1200 ppm CO2. These inclusions lack the low H2O, low CO2 values found at Belknap - even in deposits representing the final stages of explosive activity - and record crystallization at pressures between ~1-2 kbar, equivalent depth of ~4-8 km depth in the crust. H2O-CO2 patterns in inclusions from Belknap are similar to those observed in the late

  18. Effect of low-pressure plasma treatment on the color and oxidative stability of raw pork during refrigerated storage.

    PubMed

    Ulbin-Figlewicz, Natalia; Jarmoluk, Andrzej

    2016-06-01

    The effect of low-pressure plasma on quality attributes of meat is an important aspect, which must be considered before application in food. The aim of this study was to determine the color, fatty acid composition, lipid oxidation expressed as thiobarbituric acid reactive substances and total antioxidant capacity of raw pork samples exposed to helium low-pressure plasma treatment (20 kPa) for 0, 2, 5, and 10 min during the storage period. The thiobarbituric acid reactive substance concentrations of all plasma-treated samples during storage were in the range from 0.26 to 0.61 mg malondialdehyde/kg. Exposure time caused significant changes only in total color difference, hue angle, and chroma after 10 min of treatment. Ferric reducing ability of plasma values of meat samples decreased from 1.93 to 1.40 mmol Trolox Eq/kg after 14 days of storage. The storage period significantly affected proportion of polyunsaturated fatty acids, with an increase about 3% after 14 days of refrigeration storage while the content of saturated fatty acids was at the same level. Helium low-pressure plasma does not induce oxidative processes. Application of this decontamination technique while maintaining product quality is possible in food industry. PMID:26223879

  19. Graphene chemical vapor deposition at very low pressure: The impact of substrate surface self-diffusion in domain shape

    SciTech Connect

    Cunha, T. H. R.; Ek-Weis, J.; Lacerda, R. G.; Ferlauto, A. S.

    2014-08-18

    The initial stages of graphene chemical vapor deposition at very low pressures (<10{sup −5 }Torr) were investigated. The growth of large graphene domains (∼up to 100 μm) at very high rates (up to 3 μm{sup 2} s{sup −1}) has been achieved in a cold-wall reactor using a liquid carbon precursor. For high temperature growth (>900 °C), graphene grain shape and symmetry were found to depend on the underlying symmetry of the Cu crystal, whereas for lower temperatures (<900 °C), mostly rounded grains are observed. The temperature dependence of graphene nucleation density was determined, displaying two thermally activated regimes, with activation energy values of 6 ± 1 eV for temperatures ranging from 900 °C to 960 °C and 9 ± 1 eV for temperatures above 960 °C. The comparison of such dependence with the temperature dependence of Cu surface self-diffusion suggests that graphene growth at high temperatures and low pressures is strongly influenced by copper surface rearrangement. We propose a model that incorporates Cu surface self-diffusion as an essential process to explain the orientation correlation between graphene and Cu crystals, and which can clarify the difference generally observed between graphene domain shapes in atmospheric-pressure and low-pressure chemical vapor deposition.

  20. Growth of Carnobacterium spp. from permafrost under low pressure, temperature, and anoxic atmosphere has implications for Earth microbes on Mars

    PubMed Central

    Nicholson, Wayne L.; Krivushin, Kirill; Gilichinsky, David; Schuerger, Andrew C.

    2013-01-01

    The ability of terrestrial microorganisms to grow in the near-surface environment of Mars is of importance to the search for life and protection of that planet from forward contamination by human and robotic exploration. Because most water on present-day Mars is frozen in the regolith, permafrosts are considered to be terrestrial analogs of the martian subsurface environment. Six bacterial isolates were obtained from a permafrost borehole in northeastern Siberia capable of growth under conditions of low temperature (0 °C), low pressure (7 mbar), and a CO2-enriched anoxic atmosphere. By 16S ribosomal DNA analysis, all six permafrost isolates were identified as species of the genus Carnobacterium, most closely related to C. inhibens (five isolates) and C. viridans (one isolate). Quantitative growth assays demonstrated that the six permafrost isolates, as well as nine type species of Carnobacterium (C. alterfunditum, C. divergens, C. funditum, C. gallinarum, C. inhibens, C. maltaromaticum, C. mobile, C. pleistocenium, and C. viridans) were all capable of growth under cold, low-pressure, anoxic conditions, thus extending the low-pressure extreme at which life can function. PMID:23267097

  1. Columnar-Structured Thermal Barrier Coatings (TBCs) by Thin Film Low-Pressure Plasma Spraying (LPPS-TF)

    NASA Astrophysics Data System (ADS)

    Hospach, Andreas; Mauer, Georg; Vaßen, Robert; Stöver, Detlev

    2011-01-01

    The very low-pressure plasma Spray (VLPPS) process has been developed with the aim of depositing uniform and thin coatings with coverage of a large area by plasma spraying. At typical pressures of 100-200 Pa, the characteristics of the plasma jet change compared to conventional low-pressure plasma-spraying processes (LPPS) operating at 5-20 kPa. The combination of plasma spraying at low pressures with enhanced electrical input power has led to the development of the LPPS-TF process (TF = thin film). At appropriate parameters, it is possible to evaporate the powder feedstock material providing advanced microstructures of the deposits. This technique offers new possibilities for the manufacturing of thermal barrier coatings (TBCs). Besides the material composition, the microstructure is an important key to reduce thermal conductivity and to increase strain tolerance. In this regard, columnar microstructures deposited from the vapor phase show considerable advantages. Therefore, physical vapor deposition by electron beam evaporation (EB-PVD) is applied to achieve such columnar-structured TBCs. However, the deposition rate is low, and the line-of-sight nature of the process involves specific restrictions. In this article, the deposition of TBCs by the LPPS-TF process is shown. How the evaporation of the feedstock powder could be improved and to what extent the deposition rates could be increased were investigated.

  2. Landau Damping and Anomalous Skin Effect in Low-pressure Gas Discharges: Self-consistent Treatment of Collisionless Heating

    SciTech Connect

    Igor D. Kaganovich; Oleg V. Polomarov; Constantine E. Theodosiou

    2004-01-30

    In low-pressure discharges, where the electron mean free path is larger or comparable with the discharge length, the electron dynamics is essentially nonlocal. Moreover, the electron energy distribution function (EEDF) deviates considerably from a Maxwellian. Therefore, an accurate kinetic description of the low-pressure discharges requires knowledge of the nonlocal conductivity operator and calculation of the non-Maxwellian EEDF. The previous treatments made use of simplifying assumptions: a uniform density profile and a Maxwellian EEDF. In the present study a self-consistent system of equations for the kinetic description of nonlocal, nonuniform, nearly collisionless plasmas of low-pressure discharges is reported. It consists of the nonlocal conductivity operator and the averaged kinetic equation for calculation of the non-Maxwellian EEDF. This system was applied to the calculation of collisionless heating in capacitively and inductively coupled plasmas. In particular, the importance of accounting for the nonuniform plasma density profile for computing the current density profile and the EEDF is demonstrated. The enhancement of collisionless heating due to the bounce resonance between the electron motion in the potential well and the external radio-frequency electric field is investigated. It is shown that a nonlinear and self-consistent treatment is necessary for the correct description of collisionless heating.

  3. Effects of the nozzle design on the properties of plasma jet and formation of YSZ coatings under low pressure conditions

    NASA Astrophysics Data System (ADS)

    Sun, Chengqi; Gao, Yang; Yang, Deming; Fu, Yingqing

    2016-06-01

    How to control the quality of the coatings has become a major problem during the plasma spraying. Because nozzle contour has a great influence on the characteristic of the plasma jet, two kinds of plasma torches equipped with a standard cylindrical nozzle and a converging-diverging nozzle are designed for low pressure plasma spraying(LPPS) and very low pressure plasma spraying(VLPPS). Yttria stabilized zirconia(YSZ) coatings are obtained in the reducing pressure environment. The properties of the plasma jet without or with powder injection are analyzed by optical emission spectroscopy, and the electron temperature is calculated based on the ratio of the relative intensity of two Ar I spectral lines. The results show that some of the YSZ powder can be vaporized in the low pressure enlarged plasma jet, and the long anode nozzle may improve the characteristics of the plasma jet. The coatings deposited by LPPS are mainly composed of the equiaxed grains and while the unmelted powder particles and large scalar pores appear in the coatings made by VLPPS. The long anode nozzle could improve the melting of the powders and deposition efficiency, and enhance the coatings' hardness. At the same time, the long anode nozzle could lead to a decrease in the overspray phenomenon. Through the comparison of the two different size's nozzle, the long anode is much more suitable for making the YSZ coatings.

  4. Growth of Carnobacterium spp. from permafrost under low pressure, temperature, and anoxic atmosphere has implications for Earth microbes on Mars.

    PubMed

    Nicholson, Wayne L; Krivushin, Kirill; Gilichinsky, David; Schuerger, Andrew C

    2013-01-01

    The ability of terrestrial microorganisms to grow in the near-surface environment of Mars is of importance to the search for life and protection of that planet from forward contamination by human and robotic exploration. Because most water on present-day Mars is frozen in the regolith, permafrosts are considered to be terrestrial analogs of the martian subsurface environment. Six bacterial isolates were obtained from a permafrost borehole in northeastern Siberia capable of growth under conditions of low temperature (0 °C), low pressure (7 mbar), and a CO(2)-enriched anoxic atmosphere. By 16S ribosomal DNA analysis, all six permafrost isolates were identified as species of the genus Carnobacterium, most closely related to C. inhibens (five isolates) and C. viridans (one isolate). Quantitative growth assays demonstrated that the six permafrost isolates, as well as nine type species of Carnobacterium (C. alterfunditum, C. divergens, C. funditum, C. gallinarum, C. inhibens, C. maltaromaticum, C. mobile, C. pleistocenium, and C. viridans) were all capable of growth under cold, low-pressure, anoxic conditions, thus extending the low-pressure extreme at which life can function. PMID:23267097

  5. Modeling the Effects of Ice Accretion on the Low Pressure Compressor and the Overall Turbofan Engine System Performance

    NASA Technical Reports Server (NTRS)

    Veres, Joseph P.; Jorgenson, Philip C. E.; Wright, William B.

    2011-01-01

    The focus of this study is on utilizing a mean line compressor flow analysis code coupled to an engine system thermodynamic code, to estimate the effects of ice accretion on the low pressure compressor, and quantifying its effects on the engine system throughout a notional flight trajectory. In this paper a temperature range in which engine icing would occur was assumed. This provided a mechanism to locate potential component icing sites and allow the computational tools to add blockages due to ice accretion in a parametric fashion. Ultimately the location and level of blockage due to icing would be provided by an ice accretion code. To proceed, an engine system modeling code and a mean line compressor flow analysis code were utilized to calculate the flow conditions in the fan-core and low pressure compressor and to identify potential locations within the compressor where ice may accrete. In this study, an "additional blockage" due to the accretion of ice on the metal surfaces, has been added to the baseline aerodynamic blockage due to boundary layer, as well as the blade metal blockage. Once the potential locations of ice accretion are identified, the levels of additional blockage due to accretion were parametrically varied to estimate the effects on the low pressure compressor blade row performance operating within the engine system environment. This study includes detailed analysis of compressor and engine performance during cruise and descent operating conditions at several altitudes within the notional flight trajectory. The purpose of this effort is to develop the computer codes to provide a predictive capability to forecast the onset of engine icing events, such that they could ultimately help in the avoidance of these events.

  6. Surface chemistry and optical property of TiO{sub 2} thin films treated by low-pressure plasma

    SciTech Connect

    Dhayal, Marshal Jun, Jin; Gu, Hal Bon; Hee Park, Kyung

    2007-10-15

    The low temperature RF plasma treatment was used to control the surface chemistry and optical property of TiO{sub 2} thin films deposited by RF magnetron sputtering with a very good uniformity at 300 deg. C substrate heating temperature. The XRD pattern indicates the crystalline structure of the film could be associated to amorphous structure of TiO{sub 2} in thin film. The plasma treatment of TiO{sub 2} film can increase the proportion of Ti{sup 3+} in Ti2p and decrease in carbon atoms as alcohol/ether group in C1s at the surface. The optical transmittance of the film was enhanced by 50% after the plasma treatment. The surface structure and morphology remain the same for untreated and low-pressure plasma-treated films. Therefore, increase in the optical transmission could be due to change in surface chemistry and surface cleaning by plasma treatment. - Graphical abstract: The surface chemistry and surface states of TiO{sub 2} films was modified using low-pressure RF plasma treatment. The surface roughness and crystalline structure remain unchanged for low-pressure plasma-treated films. There was an increase in the Ti{sup 3+} surface states of Ti2p at the surface and this can be useful to increase the photocatalytic activities of TiO{sub 2} films. The proportion of carbon atoms as carboxyl group in C1s was also increased after plasma treatment. All the plasma-treated films show a higher optical transmittance when untreated and it was increased when the power was increased. The increase in the optical transmission could be due to surface cleaning of films by plasma treatment and possibly due to change in the surface chemistry.

  7. Crystal Defects in CdZnTe Crystals Grown by the Modified Low-Pressure Bridgman Method

    SciTech Connect

    Bolotnikov A.; Marchini, L.; Zappettini, M.; Zha, M.; Zambelli, N.; Camarda, G.S.; James, R.B.

    2012-04-13

    Cadmium Zinc Telluride (CZT) is among the most promising materials for room-temperature X- and gamma-ray detectors. However, crystal defects such as Te inclusions and subgrain boundaries significantly hamper their performances. In this work, we evaluated CZT crystals grown by the modified low-pressure Bridgman technique at the IMEM Institute, Parma. We characterized the crystals by IR microscopy to identify the sizes and concentrations of the Te inclusions, along with high spatial resolution X-ray response mapping to measure the uniformity of their charge-transport properties. In addition, we employed white X-ray beam diffraction topography to analyze their crystalline structure.

  8. Effect of inducer inlet and diffuser throat areas on performance of a low pressure ratio sweptback centrifugal compressor

    NASA Technical Reports Server (NTRS)

    Klassen, H. A.

    1975-01-01

    A low-pressure-ratio centrifugal compressor was tested with nine combinations of three diffuser throat areas and three impeller inducer inlet areas which were 75, 100, and 125 percent of design values. For a given inducer inlet area, increases in diffuser area within the range investigated resulted in increased mass flow and higher peak efficiency. Changes in both diffuser and inducer areas indicated that efficiencies within one point of the maximum efficiency were obtained over a compressor specific speed range of 27 percent. The performance was analyzed of an assumed two-spool open-cycle engine using the 75 percent area inducer with a variable area diffuser.

  9. Vessel failure time for a low-pressure short-term station blackout in a BWR-4

    SciTech Connect

    Carbajo, J.J. )

    1993-01-01

    A low-pressure, short-term station blackout severe accident sequence has been analyzed using the MELCOR code, version 1.8.1, in a boiling water reactor (BWR)-4. This paper presents a sensitivity study evaluating the effect of several MELCOR input parameters on vessel failure time. Results using the MELCOR/CORBH package and the BWRSAR code are also presented and compared to the MELCOR results. These calculated vessel failure times are discussed, and a judgment is offered as to which is the most realistic.

  10. Modernization of exhaust hood of low-pressure cylinder of a cogeneration turbine T-250/300-23.5

    NASA Astrophysics Data System (ADS)

    Solodov, V. G.; Khandrymailov, A. A.; Kultishev, A. Yu.; Stepanov, M. Yu.; Yamaltdinov, A. A.

    2015-12-01

    An option of modernization of an exhaust hood for a low-pressure cylinder of a T-250/300-23.5 series turbine is presented in order to increase its effectiveness in a wide regimes range. An influence of a number of design decisions on gas-dynamic and energy characteristics of an exhaust compartment is considered. The investigation is carried out by the numerical simulation of a viscous wet steam flow through the exhaust compartment consisting of a last stage and an exhaust hood. A comparison of the calculated and experimental data is presented.

  11. Negative-ion yield in low-pressure radio frequency discharges in hydrogen: Particle modeling and vibrational kinetics

    SciTech Connect

    Diomede, P.; Longo, S.; Capitelli, M.

    2006-03-15

    A theoretical study of the complex interplay between the vibrational kinetics and the plasma dynamics in low-pressure hydrogen plasmas produced by radio frequency discharges is performed. The study is realized by means of a one-dimensional particle model with five species (e, H{sup +}, H{sub 2}{sup +}, H{sub 3}{sup +}, and H{sup -}) while the vibrational/dissociation kinetics is based on a continuum model and the two are self-consistently coupled. In particular, we analyze the influence of pressure.

  12. Kinetics of low pressure CVD growth of SiO2 on InP and Si

    NASA Technical Reports Server (NTRS)

    Iyer, R.; Lile, D. L.

    1988-01-01

    The kinetics of low pressure CVD growth of SiO2 from SiH4 and O2 has been investigated for the case of an indirect (remote) plasma process. Homogeneous (gas phase) and heterogeneous operating ranges have been experimentally identified. The process was shown to be consistent within the heterogeneous surface-reaction dominated range of operation. A kinetic rate equation is given for growth at 14 W RF power input and 400 mtorr total pressure on both InP and Si substrates. The process exhibits an activation energy of 8.4 + or - 0.6 kcal/mol.

  13. Transport Equations Resolution By N-BEE Anti-Dissipative Scheme In 2D Model Of Low Pressure Glow Discharge

    SciTech Connect

    Kraloua, B.; Hennad, A.

    2008-09-23

    The aim of this paper is to determine electric and physical properties by 2D modelling of glow discharge low pressure in continuous regime maintained by term constant source. This electric discharge is confined in reactor plan-parallel geometry. This reactor is filled by Argon monatomic gas. Our continuum model the order two is composed the first three moments the Boltzmann's equations coupled with Poisson's equation by self consistent method. These transport equations are discretized by the finite volumes method. The equations system is resolved by a new technique, it is about the N-BEE explicit scheme using the time splitting method.

  14. Note: High turn density magnetic coils with improved low pressure water cooling for use in atom optics

    NASA Astrophysics Data System (ADS)

    McKay Parry, Nicholas; Baker, Mark; Neely, Tyler; Carey, Thomas; Bell, Thomas; Rubinsztein-Dunlop, Halina

    2014-08-01

    We describe a magnetic coil design utilizing concentrically wound electro-magnetic insulating (EMI) foil (25.4 μm Kapton backing and 127 μm thick layers). The magnetic coils are easily configurable for different coil sizes, while providing large surfaces for low-pressure (0.12 bar) water cooling. The coils have turn densities of ˜5 mm-1 and achieve a maximum of 377 G at 2.1 kW driving power, measured at a distance 37.9 mm from the axial center of the coil. The coils achieve a steady-state temperature increase of 36.7°C/kW.

  15. NASA CF6 jet engine diagnostics program: Long-term CF6-6D low-pressure turbine deterioration

    NASA Technical Reports Server (NTRS)

    Smith, J. J.

    1979-01-01

    Back-to-back performance tests were run on seven airline low pressure turbine (LPT) modules and four new CF6-6D modules. Back-to-back test cell runs, in which an airline LPT module was directly compared to a new production module, were included. The resulting change, measured in fuel burn, equaled the level of LPT module deterioration. Three of the LPT modules were analytically inspected followed by a back-to-back test cell run to evaluate current refurbishment techniques.

  16. Highly oriented NdFeCoB nanocrystalline magnets from partially disproportionated compacts by reactive deformation under low pressure

    SciTech Connect

    Zheng, Qing; Li, Jun; Liu, Ying Yu, Yunping; Lian, Lixian

    2014-05-07

    In the present investigation, we take advantage of the ultrafine grain size of NdFeCoB partially hydrogen-disproportionated phases, and prepare anisotropic nanocrystalline magnets with full density and homogenous microstructure and texture by reactive deformation under low pressure. Our results suggest that the pressure could properly promote an occurrence of desorption-recombination reaction due to a shorter-range rearrangement of the atoms, and the newly recombined Nd{sub 2}Fe{sub 14}B grains with fine grain size could undergo deformation immediately after the phase transformation, and then an obvious anisotropy and uniform alignment would be obtained. The maximum magnetic properties, (BH){sub max} = 25.8 MGOe, Br = 11.8 kG, H{sub cj} = 5.5 kOe, were obtained after being treated for 5 min at 820 °C in vacuum. The present study highlights the feasibility to prepare anisotropic nanocrystalline magnets with homogeneous microstructure and a strong (00l) texture of uniform grain size under low pressure.

  17. E-H mode transition in low-pressure inductively coupled nitrogen-argon and oxygen-argon plasmas

    NASA Astrophysics Data System (ADS)

    Lee, Young Wook; Lee, Hye Lan; Chung, T. H.

    2011-06-01

    This work investigates the characteristics of the E-H mode transition in low-pressure inductively coupled N2-Ar and O2-Ar discharges using rf-compensated Langmuir probe measurements and optical emission spectroscopy (OES). As the ICP power increases, the emission intensities from plasma species, the electron density, the electron temperature, and the plasma potential exhibit sudden changes. The Ar content in the gas mixture and total gas pressure have been varied in an attempt to fully characterize the plasma parameters. With these control parameters varying, the changes of the transition threshold power and the electron energy distribution function (EEDF) are explored. In N2-Ar and O2-Ar discharges at low-pressures of several millitorr, the transition thresholds are observed to decrease with Ar content and pressure. It is observed that in N2-Ar plasmas during the transition, the shape of the EEDF changes from an unusual distribution with a flat hole near the electron energy of 3 eV in the E mode to a Maxwellian distribution in the H mode. However, in O2 -Ar plasmas, the EEDFs in the E mode at low Ar contents show roughly bi-Maxwellian distributions, while the EEDFs in the H mode are observed to be nearly Maxwellian. In the E and H modes of O2-Ar discharges, the dissociation fraction of O2 molecules is estimated using optical emission actinometry. During the E-H mode transition, the dissociation fraction of molecules is also enhanced.

  18. Online spectrophotometric determination of Fe(II) and Fe(III) by flow injection combined with low pressure ion chromatography.

    PubMed

    Chen, Shujuan; Li, Nan; Zhang, Xinshen; Yang, Dongjing; Jiang, Heimei

    2015-03-01

    A simple and new low pressure ion chromatography combined with flow injection spectrophotometric procedure for determining Fe(II) and Fe(III) was established. It is based on the selective adsorption of low pressure ion chromatography column to Fe(II) and Fe(III), the online reduction reaction of Fe(III) and the reaction of Fe(II) in sodium acetate with phenanthroline, resulting in an intense orange complex with a suitable absorption at 515nm. Various chemical (such as the concentration of colour reagent, eluant and reductive agent) and instrumental parameters (reaction coil length, reductive coil length and wavelength) were studied and were optimized. Under the optimum conditions calibration graph of Fe(II)/Fe(III) was linear in the Fe(II)/Fe(III) range of 0.040-1.0mg/L. The detection limit of Fe(III) and Fe(II) was respectively 3.09 and 1.55μg/L, the relative standard deviation (n=10) of Fe(II) and Fe(III) 1.89% and 1.90% for 0.5mg/L of Fe(II) and Fe(III) respectively. About 2.5 samples in 1h can be analyzed. The interfering effects of various chemical species were studied. The method was successfully applied in the determination of water samples. PMID:25523043

  19. Low-pressure plasma enhanced immobilization of chitosan on low-density polyethylene for bio-medical applications

    NASA Astrophysics Data System (ADS)

    Pandiyaraj, K. Navaneetha; Ferraria, Ana Maria; Rego, Ana Maria Botelho do; Deshmukh, Rajendra. R.; Su, Pi-Guey; Halleluyah Mercy, Jr.; Halim, Ahmad Sukari

    2015-02-01

    With the aim of improving blood compatibility of low density polyethylene (LDPE) films, an effective low-pressure plasma technology was employed to functionalize the LDPE film surfaces through in-situ grafting of acrylic acid (AAc). Subsequently, the molecules of poly(ethylene glycol) (PEG) and chitosan (CHI) were immobilized on the surface of grafted LDPE films. The unmodified and modified LDPE films were analyzed using various characterization techniques such as contact angle, atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR) and X-ray photo electron spectroscopy (XPS) to understand the changes in surface properties such as hydrophilicity, surface topography and chemical composition, respectively. Furthermore, LDPE films have been subjected to an ageing process to determine the durability of the plasma assisted surface modification. The blood compatibility of the surface modified LDPE films was confirmed by in vitro tests. It was found that surface modified LDPE films show better hydrophilic behavior compared with the unmodified one. FTIR and XPS results confirm the successful immobilization of CHI on the surface of LDPE films. LDPE films showed marked morphological changes after grafting of AAc, PEG and CHI which were confirmed through AFM imaging. The in vitro blood compatibility tests have clearly demonstrated that CHI immobilized LDPE films exhibit remarkable anti thrombogenic nature compared with other modified films. Surface modified LDPE films through low-pressure plasma technique could be adequate for biomedical implants such as artificial skin substrates, urethral catheters or cardiac stents, among others.

  20. Online spectrophotometric determination of Fe(II) and Fe(III) by flow injection combined with low pressure ion chromatography

    NASA Astrophysics Data System (ADS)

    Chen, Shujuan; Li, Nan; Zhang, Xinshen; Yang, Dongjing; Jiang, Heimei

    2015-03-01

    A simple and new low pressure ion chromatography combined with flow injection spectrophotometric procedure for determining Fe(II) and Fe(III) was established. It is based on the selective adsorption of low pressure ion chromatography column to Fe(II) and Fe(III), the online reduction reaction of Fe(III) and the reaction of Fe(II) in sodium acetate with phenanthroline, resulting in an intense orange complex with a suitable absorption at 515 nm. Various chemical (such as the concentration of colour reagent, eluant and reductive agent) and instrumental parameters (reaction coil length, reductive coil length and wavelength) were studied and were optimized. Under the optimum conditions calibration graph of Fe(II)/Fe(III) was linear in the Fe(II)/Fe(III) range of 0.040-1.0 mg/L. The detection limit of Fe(III) and Fe(II) was respectively 3.09 and 1.55 μg/L, the relative standard deviation (n = 10) of Fe(II) and Fe(III) 1.89% and 1.90% for 0.5 mg/L of Fe(II) and Fe(III) respectively. About 2.5 samples in 1 h can be analyzed. The interfering effects of various chemical species were studied. The method was successfully applied in the determination of water samples.

  1. Correction factors for saturation effects in white light and laser absorption spectroscopy for application to low pressure plasmas

    SciTech Connect

    Briefi, S.; Wimmer, C.; Fantz, U.

    2012-05-15

    In white light absorption spectroscopy, the broadening of the absorption signal due to the apparatus profile of the spectrometer may lead to an underestimation of the determined density as one measures an apparent optical depth. This is in particular true for high optical depth where saturation effects of the transmitted intensity occur. Provided that the line profile of the absorption line is known, the apparent optical depth effect can be accounted for by introducing a correction factor. The impact of the saturation and the approach of considering the effect are demonstrated for argon and indium lines in low pressure plasmas where correction factors of one order of magnitude or even higher are reached very easily. For the indium line, the hyperfine splitting has been taken into account. In laser absorption, the line profile is resolved. However, the weak but rather broad background emission of the laser diode can cause a saturation signal at the photo diode resulting also in an underestimation of the density obtained from the analysis. It is shown that this can be taken into account by fitting the theoretical line profile to the measured absorption signal which yields also a correction factor. The method is introduced and demonstrated at the example of the cesium resonance line including the hyperfine splitting. Typical correction factors around two are obtained for the cesium ground state density at conditions of a low pressure negative hydrogen ion source in which cesium is evaporated to enhance the negative ion production.

  2. Comments on "Sensitive analysis of carbon, chromium and silicon in steel using picosecond laser induced low pressure helium plasma"

    NASA Astrophysics Data System (ADS)

    Zaytsev, Sergey M.; Popov, Andrey M.; Zorov, Nikita B.; Labutin, Timur A.

    2016-04-01

    In the paper "Sensitive analysis of carbon, chromium and silicon in steel using picosecond laser induced low pressure helium plasma" by Syahrun Nur Abdulmadjid, Nasrullah Idris, Marincan Pardede, Eric Jobiliong, Rinda Hedwig, Zener Sukra Lie, Hery Suyanto, May On Tjia, Koo Hendrik Kurniawan and Kiichiro Kagawa [Spectrochim. Acta Part B 114 (2015) 1-6], the authors presented experimental study to demonstrate the sensitive detection of C, Cr and Si in low-alloy steels under low pressure He atmosphere. Although the use of only UV-VIS spectral range for determination of these elements seems to be a beneficial, the point that needs to be commented is the result of carbon determination with the use of C I 247.856 nm line. Thermodynamic modeling based on the NIST and R. Kurucz data for the different excitation conditions in plasma demonstrates that it is hardly possible to distinguish any carbon signal due to significantly intensive iron line Fe II 247.857 nm. Authors are kindly requested to re-consider this part of their study.

  3. Coupled fluid-thermal analysis of low-pressure sublimation and condensation with application to freeze-drying

    NASA Astrophysics Data System (ADS)

    Ganguly, Arnab

    Freeze-drying is a low-pressure, low-temperature condensation pumping process widely used in the manufacture of bio-pharmaceuticals for removal of solvents by sublimation. The goal of the process is to provide a stable dosage form by removing the solvent in such a way that the sensitive molecular structure of the active substance is least disturbed. The vacuum environment presents unique challenges for understanding and controlling heat and mass transfer in the process. As a result, the design of equipment and associated processes has been largely empirical, slow and inefficient. A comprehensive simulation framework to predict both, process and equipment performance is critical to improve current practice. A part of the dissertation is aimed at performing coupled fluid-thermal analysis of low-pressure sublimation-condensation processes typical of freeze-drying technologies. Both, experimental and computational models are used to first understand the key heat transfer modes during the process. A modeling and computational framework, validated with experiments for analysis of sublimation, water-vapor flow and condensation in application to pharmaceutical freeze-drying is developed. Augmented with computational fluid dynamics modeling, the simulation framework presented here allows to predict for the first time, dynamic product/process conditions taking into consideration specifics of equipment design. Moreover, by applying the modeling framework to process design based on a design-space approach, it has demonstrated that there is a viable alternative to empiricism.

  4. Design and evaluation of a Laval-type supersonic atomizer for low-pressure gas atomization of molten metals

    NASA Astrophysics Data System (ADS)

    Si, Chao-run; Zhang, Xian-jie; Wang, Jun-biao; Li, Yu-jun

    2014-06-01

    A Laval-type supersonic gas atomizer was designed for low-pressure gas atomization of molten metals. The principal design objectives were to produce small-particle uniform powders at lower operating pressures by improving the gas inlet and outlet structures and optimizing structural parameters. A computational fluid flow model was developed to study the flow field characteristics of the designed atomizer. Simulation results show that the maximum gas velocity in the atomization zone can reach 440 m·s-1; this value is independent of the atomization gas pressure P 0 when P 0 > 0.7 MPa. When P 0 = 1.1 MPa, the aspiration pressure at the tip of the delivery tube reaches a minimum, indicating that the atomizer can attain the best atomization efficiency at a relatively low atomization pressure. In addition, atomization experiments with pure tin at P 0 = 1.0 MPa and with 7055Al alloy at P 0 = 0.8 and 0.4 MPa were conducted to evaluate the atomization capability of the designed atomizer. Nearly spherical powders were obtained with the mass median diameters of 28.6, 43.4, and 63.5 μm, respectively. Compared with commonly used atomizers, the designed Laval-type atomizer has a better low-pressure gas atomization capability.

  5. Predictions of Separated and Transitional Boundary Layers Under Low-Pressure Turbine Airfoil Conditions Using an Intermittency Transport Equation

    NASA Technical Reports Server (NTRS)

    Suzen, Y. B.; Huang, P. G.; Hultgren, Lennart S.; Ashpis, David E.

    2003-01-01

    A new transport equation for the intermittency factor was proposed to predict separated and transitional boundary layers under low-pressure turbine airfoil conditions. The intermittent behavior of the transitional flows is taken into account and incorporated into computations by modifying the eddy viscosity, t , with the intermittency factor, y. Turbulent quantities are predicted by using Menter s two-equation turbulence model (SST). The intermittency factor is obtained from a transport equation model, which not only can reproduce the experimentally observed streamwise variation of the intermittency in the transition zone, but also can provide a realistic cross-stream variation of the intermittency profile. In this paper, the intermittency model is used to predict a recent separated and transitional boundary layer experiment under low pressure turbine airfoil conditions. The experiment provides detailed measurements of velocity, turbulent kinetic energy and intermittency profiles for a number of Reynolds numbers and freestream turbulent intensity conditions and is suitable for validation purposes. Detailed comparisons of computational results with experimental data are presented and good agreements between the experiments and predictions are obtained.

  6. Predictions of Separated and Transitional Boundary Layers Under Low-Pressure Turbine Airfoil Conditions Using an Intermittency Transport Equation

    NASA Technical Reports Server (NTRS)

    Suzen, Y. Bora; Huang, P. G.; Hultgren, Lennart S.; Ashpis, David E.

    2001-01-01

    A new transport equation for the intermittency factor was proposed to predict separated and transitional boundary layers under low-pressure turbine airfoil conditions. The intermittent behavior of the transitional flows is taken into account and incorporated into computations by modifying the eddy viscosity, mu(sub t), with the intermittency factor, gamma. Turbulent quantities are predicted by using Menter's two-equation turbulence model (SST). The intermittency factor is obtained from a transport equation model, which not only can reproduce the experimentally observed streamwise variation of the intermittency in the transition zone, but also can provide a realistic cross-stream variation of the intermittency profile. In this paper, the intermittency model is used to predict a recent separated and transitional boundary layer experiment under low pressure turbine airfoil conditions. The experiment provides detailed measurements of velocity, turbulent kinetic energy and intermittency profiles for a number of Reynolds numbers and freestream turbulent intensity conditions and is suitable for validation purposes. Detailed comparisons of computational results with experimental data are presented and good agreements between the experiments and predictions are obtained.

  7. Modeling the Deterioration of Engine and Low Pressure Compressor Performance During a Roll Back Event Due to Ice Accretion

    NASA Technical Reports Server (NTRS)

    Veres, Joseph P.; Jorgenson, Philip, C. E.; Jones, Scott M.

    2014-01-01

    The main focus of this study is to apply a computational tool for the flow analysis of the engine that has been tested with ice crystal ingestion in the Propulsion Systems Laboratory (PSL) of NASA Glenn Research Center. A data point was selected for analysis during which the engine experienced a full roll back event due to the ice accretion on the blades and flow path of the low pressure compressor. The computational tool consists of the Numerical Propulsion System Simulation (NPSS) engine system thermodynamic cycle code, and an Euler-based compressor flow analysis code, that has an ice particle melt estimation code with the capability of determining the rate of sublimation, melting, and evaporation through the compressor blade rows. Decreasing the performance characteristics of the low pressure compressor (LPC) within the NPSS cycle analysis resulted in matching the overall engine performance parameters measured during testing at data points in short time intervals through the progression of the roll back event. Detailed analysis of the fan-core and LPC with the compressor flow analysis code simulated the effects of ice accretion by increasing the aerodynamic blockage and pressure losses through the low pressure compressor until achieving a match with the NPSS cycle analysis results, at each scan. With the additional blockages and losses in the LPC, the compressor flow analysis code results were able to numerically reproduce the performance that was determined by the NPSS cycle analysis, which was in agreement with the PSL engine test data. The compressor flow analysis indicated that the blockage due to ice accretion in the LPC exit guide vane stators caused the exit guide vane (EGV) to be nearly choked, significantly reducing the air flow rate into the core. This caused the LPC to eventually be in stall due to increasing levels of diffusion in the rotors and high incidence angles in the inlet guide vane (IGV) and EGV stators. The flow analysis indicating

  8. First occurrence of very low pressure ultra-high temperatures metamorphism in the Khondalite Belt, North China Craton.

    NASA Astrophysics Data System (ADS)

    Lobjoie, Cyril; Lin, Wei; Trap, Pierre; Goncalves, Philippe; Marquer, Didier

    2016-04-01

    This study report the first occurrence of very low pressure (<0.4GPa) ultra-high temperatures metamorphism within the Paleoproterozoic Khondalite Belt of the North China Craton. This high grade orogenic domain is mostly composed of garnet +/- spinel +/- sapphirine-bearing migmatites, numerous Grt-bearing granites and marbles. These rocks are intruded by numerous metric to kilometric mafic intrusions. Petrological analyses and phase equilibria diagram modeling were performed on garnet and spinel-bearing and olivine-bearing migmatites. Garnet and spinel-bearing migmatites show a quartz, ternary feldspar, garnet, biotite sillimanite and spinel main assemblage. Pseudosection diagram calculations give suprasolidus P-T conditions around ca. 0.7GPa for ca. 900°C that correspond to the peak temperature conditions. Thermometry using ternary feldspar thermometry gives temperatures estimations at ca. 950-1015°C for a pressure of 0.7GPa. The Olivine-bearing migmatite, located at the contact with a mafic intrusion, shows two main assemblages. The first assemblage that makes the rock matrix consists of a micrographic quartz and feldspar domains associated with biotite, sillimanite and spinel. The second assemblage appears within mm-scale pockets with a complex symplectitic texture. Careful investigation revealed that theses pockets formed after garnet pseudomorphosis, with the development of an Opx-Sp-Crd association. Within this assemblage, an olivine-cordierite and Opx-Crd-Bi-Qtz assemblage occurred as smaller pockets. The petrogenetic grid and pseudosection calculations made for this olivine-bearing migmatite give P-T conditions around 0.35GPa for ca. 950°C that correspond to the peak temperature conditions recorded by the olivine-cordierite assemblage. The succession of reactions with garnet pseudomorphosis into an Opx-Spl-Crd followed by the crystallization of an Ol-Crd assemblage is modelled in the petrogenetic grid calculation and correspond to an isobaric clockwise P

  9. An aircraft instrument design for in situ tropospheric OH measurements by laser induced fluorescence at low pressures

    NASA Technical Reports Server (NTRS)

    Brune, William H.; Stevens, Philip S.; Mather, James H.

    1993-01-01

    The hydroxyl radical (OH) is important for many processes involved in tropospheric chemistry. For instance, it initiates the photochemical degradation of gases that cause global climate change, such as methane and the chlorofluorocarbon substitutes (HCFCs). Because of its reactivity, its abundances are less than 0.1 pptv. Thus, OH has been very difficult to measure accurately, despite its importance. Techniques have evolved, however, so that good measurements of tropospheric OH abundances are now possible. One of these techniques that is adaptable to aircraft measurements is the laser induced fluorescence detection of the OH radical in a detection chamber at low pressures. The current ground-based instrument, which can be readily adapted to aircraft, can detect OH abundances of 1.4 x 10 exp 5 OH molecules/cu cm with S/N = 2 in 30 sec, and 5 x 10 exp 4/cu cm in 5 min.

  10. Experimental investigation of supersonic low pressure air plasma flows obtained with different arc-jet operating conditions

    SciTech Connect

    Lago, Viviana; Ndiaye, Abdoul-Aziz

    2012-11-27

    A stationary arc-jet plasma flow at low pressure is used to simulate some properties of the gas flow surrounding a vehicle during its entry into celestial body's atmospheres. This paper presents an experimental study concerning plasmas simulating a re-entry into our planet. Optical measurements have been carried out for several operating plasma conditions in the free stream, and in the shock layer formed in front of a flat cylindrical plate, placed in the plasma jet. The analysis of the spectral radiation enabled the identification of the emitting species, the determination of the rotational and vibrational temperatures in the free-stream and in the shock layer and the determination of the distance of the shock to the flat plate face. Some plasma fluid parameters like, stagnation pressure, specific enthalpy and heat flux have been determined experimentally along the plasma-jet axis.

  11. Measurement of vibrational populations in low-pressure hydrogen plasma by coherent anti-Stokes Raman scattering

    NASA Astrophysics Data System (ADS)

    Pealat, M.; Taran, J. P. E.; Taillet, J.; Bacal, M.; Bruneteau, A. M.

    1981-04-01

    Vibrational populations in a low-pressure H2 plasma have been measured by coherent anti-Stokes Raman scattering (CARS). The plasma generator is described, and some particulars of the optical arrangement are given. The CARS system is a commercial spectrometer, whose original optical system has been slightly modified for this study, by eliminating the Polarex arrangement for the YAG laser oscillator and by adding a YAG amplifier stage. This has resulted in improved beam quality and enhanced peak power. For an electron density of 2 x 10 to the 11th cm to the 0.001 and a total pressure of 0.13 m bar, the rotational temperature was found to be 475 K. The populations of the vibrational states v equals 0, 1, and 2 have also been measured. Their distribution is non-Boltzmann. The influence of pressure and discharge parameters is discussed.

  12. Development of a chromatographic low pressure flow injection system using amperometric detection: Application to the analysis of niacin in coffee.

    PubMed

    Santos, João Rodrigo; Rangel, António O S S

    2015-11-15

    In this work, an analytical flow system able to perform low pressure chromatography with amperometric detection is presented. As case study, the determination of niacin (vitamin B3) in coffee brewed samples was selected. The manifold comprised a 1.0 cm length monolithic column coated with didecyldimethylammonium bromide, a laboratory-made boron doped diamond electrode, and featured in-line ionic strength adjustment of the mobile phase. The figures of merit concerning the selected case study namely, detection limit, 7.90 × 10(-7) M, determination rate, ca. 10 samplesh(-1), mobile phase and ISA solution consumption, ca. 2.6 mL per analysis, and CV, below 5% for retention time and peak height, showed the competitiveness of this analytical strategy comparing to the described HPLC methods for niacin determination. The strategy displays a simple configuration, low cost, fast and easy assembling, foreseeing its use to general purpose applications. PMID:25977010

  13. Design criteria for semi-central sanitation with low pressure network and membrane bioreactor-the ENREM project.

    PubMed

    Gnirss, Regina; Luedicke, Carsten; Vocks, Martin; Lesjean, Boris

    2008-01-01

    MBR-technology is able to fulfil similar or even higher standard for nutrients removal than conventional activated sludge processes. This paper presents the optimisation of the membrane bioreactor technology, together with a low pressure sewer, to equip a remote and yet unsewered area of Berlin requiring high quality wastewater treatment. The hydraulic flow pattern of the entire system has to be studied carefully due to the small collection system (no time delay between wastewater discharge and treatment to minimise the daily profile). The pollutant concentrations in the wastewater exhibit also stronger variations. In order to flatten out the hydraulic and load profile, and therefore to reduce the size of the biological reactor and the membrane surface, a buffer tank was installed before the MBR-plant. A full analysis of the influent hydraulic flow and wastewater characterisation is provided for the demonstration MBR-plant. PMID:18309219

  14. Filament wound pressure vessels - Effects of using liner tooling of low pressure vessels for high pressure vessels development

    NASA Astrophysics Data System (ADS)

    Lal, Krishna M.

    High performance pressure vessels have been recently demanded for aerospace and defense applications. Filament wound pressure vessels consist of a metallic thin liner, which also acts as a mandrel, and composite/epoxy overwrap. Graphite/epoxy overwrapped vessels have been developed to obtain the performance ratio, PV/W, as high as one million inches. Under very high pressure the isotropic metallic liner deforms elasto-plastically, and orthotropic composite fibers deform elastically. Sometimes, for the development of ultra high pressure vessels, composite pressure vessels industry uses the existing liner tooling developed for low burst pressure capacity composite vessels. This work presents the effects of various design variables including the low pressure liner tooling for the development of the high burst pressure capacity Brilliant Pebbles helium tanks. Advance stress analysis and development of an ultra high pressure helium tank.

  15. High voltage instrument transformers for outdoor service with an insulation of low pressure SF6 gas and plastic foils

    NASA Astrophysics Data System (ADS)

    Brand, U.

    1985-04-01

    Gas-insulated failsafe high voltage instrument transformers with system voltages in the range of 123 to 420 kV for outdoor service were developed. The basic physics and high power tests performed on gas-filled instrument transformer housings are discussed. Construction and design of gas-insulated voltage transformers are explained. The insulation of the 123 kV model consists of low pressurized SF6 gas and plastic foils. The 245 kV unit has the same principal design; however, a higher SF6 pressure is used and the apparatus is fitted with a hollow composite insulator made of a fiber reinforced plastics tube and silicone casing. For the 420 kV model the same insulator type is used and a design for the voltage grading along the insulator is developed. The transformers show good performance in service; they are a safe and environment-protecting alternative to oil insulated equipment.

  16. Microstructure and Oxidation Resistance of NiCoCrAlYTa Coating by Low Pressure Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Liang, X.-H.; Zhou, K. S.; Liu, M.; Hong, R. J.; Deng, C. G.; Luo, S.; Chen, Z. K.

    The NiCoCrAlYTa coating was prepared on Ni-based single crystal super-alloys by low pressure plasma spraying (LPPS). The phases and microstructures for the coatings were characterized by X-ray diffraction and scanning electron microscopy, and the fracture toughness and micro-hardness for both coatings and substrate were also investigated. The relationship between coating properties and oxidation was analyzed. The result shows that elementary distribution of NiCoCrAlYTa coatings, which consists of γ-Ni, β-NiAl, γ'-Ni3Al, and CrCoTa phases, is much homogeneous. The composition changes with depth from the surface to substrate for the coatings. The micro-hardness of coatings is 350.8 HV0.3 and fracture toughness is 2.73 MPa m1/2. The oxidation resistance of coatings excelled than Ni-based single crystal super-alloys.

  17. LIBS-based detection of geological samples at low pressures (<0.001 torr) for moon and asteroid exploration.

    SciTech Connect

    Harris, R. D.; Cremers, D. A.; Khoo, C.; Benelli, K. M.

    2005-01-01

    LIBS is under development for future use on surface probes to Mars. Under simulated Mars atmospheric composition and pressure (7 torr, predominately CO{sub 2}), LIBS has been shown useful for qualitative and quantitative analysis of geological samples at close and stand-off distances (19 m). Because of its many advantages compared to previously deployed and current in-use methods of elemental analysis (e.g. x-ray fluorescence, APXS), LIBS has potential for application to other planetary bodies. Of particular interest are the Moon and asteroids having very low ambient gas pressures at the surface. Because the laser plasma used by LIBS is sensitive to the surrounding atmosphere, it is important to determine analysis capabilities under these conditions. The results of a study of LIBS capabilities at low pressure is presented here for both in-situ and stand-off analysis.

  18. Analysis of the low-pressure plasma pretreated polymer surface in terms of acid-base approach

    NASA Astrophysics Data System (ADS)

    Kraus, Eduard; Orf, Lukas; Baudrit, Benjamin; Heidemeyer, Peter; Bastian, Martin; Bonenberger, Ramona; Starostina, Irina; Stoyanov, Oleg

    2016-05-01

    We demonstrate the use of a modern wetting method for determining the acid-base properties of treated polymer surfaces for different plastics and adhesives. The effect of the surface treatment with low pressure plasma was evaluated from the viewpoint of acid-base approach with plastics polyoxymethylene (POM) and polyetheretherketone (PEEK). The correlations between the acid-base properties and the identified mechanical tensile strengths of adhesive bonded joints were evaluated and discussed. In the investigated range the determination coefficients for POM and PEEK were calculated to R2 = 0.93 and R2 = 0.97, respectively. These relatively high determination coefficients showed a good correlation between the mechanical strength and the acidity parameter ΔDshort for use in bonding technology for surface pretreatment of polymers with LPP.

  19. Photocatalytic abatement of NOx by C-TiO2/polymer composite coatings obtained by low pressure cold gas spraying

    NASA Astrophysics Data System (ADS)

    Robotti, M.; Dosta, S.; Fernández-Rodríguez, C.; Hernández-Rodríguez, M. J.; Cano, I. G.; Melián, E. Pulido; Guilemany, J. M.

    2016-01-01

    In the present work, we study the photocatalytic activity of carbon-modified TiO2 (C-TiO2)/polymer composite coatings obtained by low pressure cold gas spraying (LP-CGS). To produce the novel coatings, C-TiO2 was mixed with a ductile material, the polymer ECTFE, by means of a low energy ball milling (LEBM) process. The LEBM system permits the mechanical anchoring of small TiO2 aggregates around the large ductile polymeric particles. A well-bonded coating with good mechanical coupling was formed between the ball-milled mixture and the substrate. Photocatalytic tests showed that the LP-CGS nano-TiO2 coatings actively photodegraded NO and the by-product, NO2. Compared to commercial paint, the as-prepared coatings presented here enhanced photocatalytic performance.

  20. An Assessment of the Residual Stresses in Low Pressure Plasma Sprayed Coatings on an Advanced Copper Alloy

    NASA Technical Reports Server (NTRS)

    Raj, S. V.; Ghosn, L. J.; Agarwal, A.; Lachtrupp, T. P.

    2002-01-01

    Modeling studies were conducted on low pressure plasma sprayed (LPPS) NiAl top coat applied to an advanced Cu-8(at.%)Cr-4%Nb alloy (GRCop-84) substrate using Ni as a bond coat. A thermal analysis suggested that the NiAl and Ni top and bond coats, respectively, would provide adequate thermal protection to the GRCop-84 substrate in a rocket engine operating under high heat flux conditions. Residual stress measurements were conducted at different depths from the free surface on coated and uncoated GRCop-84 specimens by x-ray diffraction. These data are compared with theoretically estimated values assessed by a finite element analysis simulating the development of these stresses as the coated substrate cools down from the plasma spraying temperature to room temperature.

  1. Laser-fluorescence measurements of nitric oxide in low-pressure H2/O2/NO flames

    NASA Technical Reports Server (NTRS)

    Cattolica, R. J.; Mataga, T. G.; Cavolowsky, J. A.

    1989-01-01

    The concentration profiles of NO in low-pressure (76 Torr) H2/O2/Ar flames to which nitric oxide is added are measured by pulsed laser-induced fluorescence. Temporally resolved fluorescence measurements are used to determine the collisional deexcitation rates needed to convert time-integrated fluorescence signal into oxide concentration. Five flames are studied with H2/O2 equivalence ratios of 0.88, 0.98, 1.22, 1.37, and 1.50. In these flames the collisional deexcitation rate decreases rapidly above the burner surface as the density decreases with increasing temperature. A 20 percent decrease is observed for the lean flames, and a 30 percent decrease for the rich flames. Within the precision of the measurement technique (+ or - 10 percent), no significant removal of nitric oxide is observed in these flames.

  2. High T(c) superconducting films of Y-Ba-Cu oxides prepared by low-pressure plasma spraying

    NASA Astrophysics Data System (ADS)

    Tachikawa, K.; Watanabe, I.; Kosuge, S.; Kabasawa, M.; Suzuki, T.

    1988-03-01

    A low-pressure plasma spraying technique for depositing high T(c) Y-Ba-Cu-O thick films has been developed. Films with a thickness range of 20-100 microns have been prepared by using Y(0.3)Ba(0.7)CuO(x) powders. After post-annealing in oxygen for 1 h at 950 C, the flims, which were deposited on a nimonic alloy substrate heated at 650 C during spraying, exhibited a zero resistance temperature of 90.6 K, with a transition width (90-10 percent) of 2 K and a critical current density (77 K, 0 T) of 690 A/sq cm.

  3. Modelling of NO destruction in a low-pressure reactor by an Ar plasma jet: species abundances in the reactor

    NASA Astrophysics Data System (ADS)

    Kutasi, Kinga

    2011-03-01

    The destruction of NO molecules by an Ar plasma jet in a low-pressure (0.2 Torr) reactor is investigated by means of a 3D hydrodynamic model. The density distribution of species created through molecular kinetics triggered by the collision of Ar+ with NO is calculated, showing that in the case of the most abundant species a quasi-homogeneous density distribution builds up in a large part of the reactor. The conversion of NO into stable O2 and N2 molecules is followed under different plasma jet conditions and NO gas flows, and the effect of N2 addition on NO destruction is studied. It is shown that in the present system the reproduction of NO molecules on the surface through surface-assisted recombination of N and O atoms becomes impossible due to the fast disappearance of N atoms in the jet's inlet vicinity.

  4. Modernization of exhaust hoods of low-pressure sections of steam turbines manufactured by the Ural Turbine Works

    NASA Astrophysics Data System (ADS)

    Yamaltdinov, A. A.; Sakhnin, Yu. A.; Ryabchikov, A. Yu.; Evdokimov, S. Yu.; Sergach, S. V.

    2014-12-01

    Issues of modernizing the current exhaust hoods of low-pressure sections for steam turbines manufactured by the Ural Turbine Works and designing new ones with the use of modern methods of computational fluid dynamics (ANSYS CFX) are considered. A flow in the exhaust hood is simulated numerically. Verification of obtained data is performed. The use of the finite volume method allowed the three-dimensional flow in the exhaust hood of turbines of the T-100 series to be analyzed and a simple variant for improvement of its characteristics to be developed. The project data on the novel design of the exhaust hood for the T-125/150-12.8 turbine are given.

  5. The manufacture of replacement low pressure carrier casings and associated stationary guide vane blading through on site component sample measurement

    SciTech Connect

    Fraser, M.J.

    1996-12-31

    In today`s competitive utility market place, the manufacture of replacement components by alternate manufacturing has become an increasingly important available option for turbine operators seeking to achieve substantive cost and lead time reductions in spare part purchasing. Essential to this strategy--in the absence of a total redesign of the component(s) or their assemblies--is the provision or access to the selected alternate manufacture of the necessary sample parts. This paper details the manufacture by reverse engineering of 3 replacement low pressure carrier guide vane blade casings for a 60 MW steam turbine complete with their associated blading and ancillary parts where the necessary sample parts and assemblies could not be released from site due to outage constraints.

  6. Plasma diagnostics of low pressure high power impulse magnetron sputtering assisted by electron cyclotron wave resonance plasma

    SciTech Connect

    Stranak, Vitezslav; Herrendorf, Ann-Pierra; Drache, Steffen; Bogdanowicz, Robert; Hippler, Rainer; Cada, Martin; Hubicka, Zdenek; Tichy, Milan

    2012-11-01

    This paper reports on an investigation of the hybrid pulsed sputtering source based on the combination of electron cyclotron wave resonance (ECWR) inductively coupled plasma and high power impulse magnetron sputtering (HiPIMS) of a Ti target. The plasma source, operated in an Ar atmosphere at a very low pressure of 0.03 Pa, provides plasma where the major fraction of sputtered particles is ionized. It was found that ECWR assistance increases the electron temperature during the HiPIMS pulse. The discharge current and electron density can achieve their stable maximum 10 {mu}s after the onset of the HiPIMS pulse. Further, a high concentration of double charged Ti{sup ++} with energies of up to 160 eV was detected. All of these facts were verified experimentally by time-resolved emission spectroscopy, retarding field analyzer measurement, Langmuir probe, and energy-resolved mass spectrometry.

  7. The validity of the one-dimensional fluid model of electrical breakdown in synthetic air at low pressure

    NASA Astrophysics Data System (ADS)

    Jovanović, A. P.; Stankov, M. N.; Marković, V. Lj.; Stamenković, S. N.

    2013-12-01

    In this letter the validity of the fluid model used to simulate the electrical breakdown in air at low pressure is discussed. The new method for the determination of the ionization source term for the mixed gases is proposed. Paschen's curve obtained by the fluid model is compared to the available experimental data. The electron and ions density profiles calculated by the fluid model are presented. Based on Ohm's law, the current and voltage waveforms are calculated and compared to the ones measured by the oscilloscope in the synthetic-air filled tube with stainless-steel electrodes. It is shown that the one-dimensional fluid model can be used for modeling the electrical breakdown at pd values higher than Paschen's minimum and to determine stationary values of electron and ions densities.

  8. Very low pressure plasma sprayed yttria-stabilized zirconia coating using a low-energy plasma gun

    NASA Astrophysics Data System (ADS)

    Zhu, Lin; Zhang, Nannan; Bolot, Rodolphe; Planche, Marie-Pierre; Liao, Hanlin; Coddet, Christian

    2011-12-01

    In the present study, a more economical low-energy plasma source was used to perform a very low pressure plasma-spray (VLPPS) process. The plasma-jet properties were analyzed by means of optical emission spectroscopy (OES). Moreover, yttria-stabilized zirconia coating (YSZ) was elaborated by a F100 low-power plasma gun under working pressure of 1 mbar, and the substrate specimens were partially shadowed by a baffle-plate during plasma spraying for obtaining different coating microstructures. Based on the SEM observation, a column-like grain coating was deposited by pure vapor deposition at the shadowed region, whereas, in the unshadowed region, the coating exhibited a binary microstructure which was formed by a mixed deposition of melted particles and evaporated particles. The mechanical properties of the coating were also well under investigation.

  9. Gemini: A hybrid plasma modelling capability for low pressure systems. User`s manual - V.1.7

    SciTech Connect

    Johannes, J.; Bartel, T.; Sears, D.; Payne, J.

    1996-10-01

    Gemini is the coupling of Icarus, the Sandia National Laboratories (SNL) 2-D Direct Simulation Monte Carlo (DMSC) code, to MPRES, the University of Houston 2-D finite element plasma reactor code. Thus, Gemini is not a stand alone code. The primary application of Gemini is the simulation of inductively coupled plasma reactors that operate at low pressures (< 10mtorr) where continuum formulations of the transport equations begin to break down. Plasma parameters (electron density (ne), electron temperature (Te) and electrostatic fields (Er and Ez)) are computed in MPRES and interpolated onto the DSMC grid. This allows transport of the neutrals and ions to be performed using the DSMC method while including electron impact reactions and field transport effects. A sample calculation including appropriate input files is given.

  10. Experimental investigation of supersonic low pressure air plasma flows obtained with different arc-jet operating conditions

    NASA Astrophysics Data System (ADS)

    Lago, Viviana; Ndiaye, Abdoul-Aziz

    2012-11-01

    A stationary arc-jet plasma flow at low pressure is used to simulate some properties of the gas flow surrounding a vehicle during its entry into celestial body's atmospheres. This paper presents an experimental study concerning plasmas simulating a re-entry into our planet. Optical measurements have been carried out for several operating plasma conditions in the free stream, and in the shock layer formed in front of a flat cylindrical plate, placed in the plasma jet. The analysis of the spectral radiation enabled the identification of the emitting species, the determination of the rotational and vibrational temperatures in the free-stream and in the shock layer and the determination of the distance of the shock to the flat plate face. Some plasma fluid parameters like, stagnation pressure, specific enthalpy and heat flux have been determined experimentally along the plasma-jet axis.

  11. Note: High turn density magnetic coils with improved low pressure water cooling for use in atom optics.

    PubMed

    McKay Parry, Nicholas; Baker, Mark; Neely, Tyler; Carey, Thomas; Bell, Thomas; Rubinsztein-Dunlop, Halina

    2014-08-01

    We describe a magnetic coil design utilizing concentrically wound electro-magnetic insulating (EMI) foil (25.4 μm Kapton backing and 127 μm thick layers). The magnetic coils are easily configurable for different coil sizes, while providing large surfaces for low-pressure (0.12 bar) water cooling. The coils have turn densities of ~5 mm(-1) and achieve a maximum of 377 G at 2.1 kW driving power, measured at a distance 37.9 mm from the axial center of the coil. The coils achieve a steady-state temperature increase of 36.7°C/kW. PMID:25173328

  12. Low pressure CO₂ hydrogenation to methanol over gold nanoparticles activated on a CeOx/TiO₂ interface

    DOE PAGESBeta

    Yang, Xiaofang; Boscoboinik, J. Anibal; Kattel, Shyam; Senanayake, Sanjaya D.; Nie, Xiaowa; Graciani, Jesus; Rodriguez, Jose A.; Liu, Ping; Stacchiola, Dario J.; Chen, Jingguang G.

    2015-07-28

    Capture and recycling of CO₂ into valuable chemicals such as alcohols could help mitigate its emissions into the atmosphere. Due to its inert nature, the activation of CO₂ is a critical step in improving the overall reaction kinetics during its chemical conversion. Although pure gold is an inert noble metal and cannot catalyze hydrogenation reactions, it can be activated when deposited as nanoparticles on the appropriate oxide support. In this combined experimental and theoretical study, it is shown that an electronic polarization at the metal–oxide interface of Au nanoparticles anchored and stabilized on a CeOx/TiO₂ substrate generates active centers formore » CO₂ adsorption and its low pressure hydrogenation, leading to a higher selectivity toward methanol. In conclusion, this study illustrates the importance of localized electronic properties and structure in catalysis for achieving higher alcohol selectivity from CO₂ hydrogenation.« less

  13. Operation of gas electron multiplier (GEM) with propane gas at low pressure and comparison with tissue-equivalent gas mixtures

    NASA Astrophysics Data System (ADS)

    De Nardo, L.; Farahmand, M.

    2016-05-01

    A Tissue-Equivalent Proportional Counter (TEPC), based on a single GEM foil of standard geometry, has been tested with pure propane gas at low pressure, in order to simulate a tissue site of about 1 μm equivalent size. In this work, the performance of GEM with propane gas at a pressure of 21 and 28 kPa will be presented. The effective gas gain was measured in various conditions using a 244Cm alpha source. The dependence of effective gain on the electric field strength along the GEM channel and in the drift and induction region was investigated. A maximum effective gain of about 5×103 has been reached. Results obtained in pure propane gas are compared with gas gain measurements in gas mixtures commonly employed in microdosimetry, that is propane and methane based Tissue-Equivalent gas mixtures.

  14. Effect of Reynolds number, turbulence level and periodic wake flow on heat transfer on low pressure turbine blades.

    PubMed

    Suslov, D; Schulz, A; Wittig, S

    2001-05-01

    The development of effective cooling methods is of major importance for the design of new gas turbines blades. The conception of optimal cooling schemes requires a detailed knowledge of the heat transfer processes on the blade's surfaces. The thermal load of turbine blades is predominantly determined by convective heat transfer which is described by the local heat transfer coefficient. Heat transfer is closely related to the boundary layer development along the blade surface and hence depends on various flow conditions and geometrical parameters. Particularly Reynolds number, pressures gradient and turbulence level have great impact on the boundary layer development and the according heat transfer. Therefore, in the present study, the influence of Reynolds number, turbulence intensity, and periodic unsteady inflow on the local heat transfer of a typical low pressure turbine airfoil is experimentally examined in a plane cascade. PMID:11460633

  15. Remote temperature measurements of a cold start-up on a low pressure steam turbine using phosphor thermography

    SciTech Connect

    Allison, S.W.; Beshears, D.L.; Cates, M.R.; Cunningham, G.T.; Puri, A.; Schuster, L.

    1995-12-31

    The feasibility of using a noncontact, optical method for temperature measurement based on thermographic phosphors was explored during the cold start-up of a low pressure turbine rotor at the TVA Cumberland Steam Plant. A simple optical system delivered low power laser light to a segment of the balance rim and balance weight holes which were coated with phosphor. From analysis of the laser induced fluorescence, temperatures ranging from 37C (99 F) to 121 C (250 F) were determined. There was no discernible condensation of steam on the viewing port optics. This transient temperature history at the exit end of the LP rotor may help to determine the root cause of a recent blade failure experienced in the L-0 blade row of a unit at this plant during an overspeed test.

  16. Interplanetary magnetic field polarity and the size of low-pressure troughs near 180 deg W longitude

    NASA Technical Reports Server (NTRS)

    Wilcox, J. M.; Duffy, P. B.; Schatten, K. H.; Svalgaard, L.; Scherrer, P. H.; Roberts, W. O.; Olson, R. H.

    1979-01-01

    The relationship between interplanetary magnetic field polarity and the area of low pressure (300 mbar) troughs near 180 deg W longitude is examined. For most of the winters from 1951 to 1973, the trough size, as indicated by the vorticity area index, is found to be significantly greater when the interplanetary magnetic field is directed away from the sun than when the field is directed towards the sun. This relationship is shown to hold for various combinations of winters and for most months within a winter, and be most pronounced at the time when polarity was determined. It is suggested that the phenomenon is caused by merging of interplanetary magnetic field lines, when polarity is directed away from the sun, with geomagnetic field lines in the Northern Hemisphere (where these measurements were made), allowing energetic particle fluxes to have access to the north polar region

  17. A propagation time difference evaluation for a clamp-on ultrasonic flowmeter for low-pressure gas

    NASA Astrophysics Data System (ADS)

    Nishiguchi, Hiroshi; Sawayama, Toshiyuki; Nagamune, Kouki

    2016-07-01

    We have been studying the development of a clamp-on ultrasonic flowmeter for measuring the gas flow rate, especially at low-pressure gas such as atmospheric pressure. In this study, we evaluated the propagation time difference of ultrasonic wave for measuring the airflow at atmospheric pressure. We placed a pair of ultrasonic transducers outside a pipe and generated ultrasonic waves aslant to the flow direction. We observed the propagation time difference of the ultrasonic wave as a function of the gas flow velocity, and found that the difference was proportional to the gas flow. Therefore, it was shown that we were able to measure the atmospheric pressure gas flow rate with a clamp-on ultrasonic flowmeter. Moreover, we evaluated the dependency of ultrasonic wave intensity on gas pressure.

  18. Development of compact high voltage switched mode power supply for microwave plasma sources supply for low pressure plasma

    NASA Astrophysics Data System (ADS)

    Kerdtongmee, P.; Srinoum, D.; Nisoa, M.

    2011-08-01

    Although microwave induced plasmas are well known as high efficiency plasma sources, their uses in laboratories are limited since the microwave power systems are complicated and expensive. The output power of commercially available low-cost microwave ovens is fixed and discontinuous resulting from the high voltage doubler topology of the magnetron tube power supply. In this paper, a high voltage switched mode power supply of forward topology has been developed for continuous microwave power radiation. The forward converter can generate a no-load high voltage output maximum of 7 kV. When driving the magnetron tube, the microwave output power could be varied from 0 to 35 W while the high voltage output level was constantly regulated at -3.4 kV. A microwave induced plasma system was setup to investigate the plasma produced. A low pressure argon plasma was produced with only 2 W over a wide range of pressures.

  19. A Concept for a Low Pressure Noble Gas Fill Intervention in the IFE Fusion Test Facility (FTF) Target Chamber

    SciTech Connect

    Gentile, C. A.; Blanchard, W. R.; Kozub, T. A.; Aristova, M.; McGahan, C.; Natta, S.; Pagdon, K.; Zelenty, J.

    2010-01-14

    An engineering evaluation has been initiated to investigate conceptual engineering methods for implementing a viable gas shield strategy in the Fusion Test Facility (FTF) target chamber. The employment of a low pressure noble gas in the target chamber to thermalize energetic helium ions prior to interaction with the wall could dramatically increase the useful life of the first wall in the FTF reactor1. For the purpose of providing flexibility, two target chamber configurations are addressed: a five meter radius sphere and a ten meter radius sphere. Experimental studies at Nike have indicated that a low pressure, ambient gas resident in the target chamber during laser pulsing does not appear to impair the ability of laser light from illuminating targets2. In addition, current investigations into delivering, maintaining, and processing low pressure gas appear to be viable with slight modification to current pumping and plasma exhaust processing technologies3,4. Employment of a gas fill solution for protecting the dry wall target chamber in the FTF may reduce, or possibly eliminate the need for other attenuating technologies designed for keeping He ions from implanting in first wall structures and components. The gas fill concept appears to provide an effective means of extending the life of the first wall while employing mostly commercial off the shelf (COTS) technologies. Although a gas fill configuration may provide a methodology for attenuating damage inflicted on chamber surfaces, issues associated with target injection need to be further analyzed to ensure that the gas fill concept is viable in the integrated FTF design5. In the proposed system, the ambient noble gas is heated via the energetic helium ions produced by target detonation. The gas is subsequently cooled by the chamber wall to approximately 800oC, removed from the chamber, and processed by the chamber gas processing system (CGPS). In an optimized scenario of the above stated concept, the chamber

  20. Note: High turn density magnetic coils with improved low pressure water cooling for use in atom optics

    SciTech Connect

    McKay Parry, Nicholas Neely, Tyler; Carey, Thomas; Bell, Thomas; Rubinsztein-Dunlop, Halina; Baker, Mark

    2014-08-15

    We describe a magnetic coil design utilizing concentrically wound electro-magnetic insulating (EMI) foil (25.4 μm Kapton backing and 127 μm thick layers). The magnetic coils are easily configurable for different coil sizes, while providing large surfaces for low-pressure (0.12 bar) water cooling. The coils have turn densities of ∼5 mm{sup −1} and achieve a maximum of 377 G at 2.1 kW driving power, measured at a distance 37.9 mm from the axial center of the coil. The coils achieve a steady-state temperature increase of 36.7°C/kW.

  1. DNS of Flow in a Low-Pressure Turbine Cascade Using a Discontinuous-Galerkin Spectral-Element Method

    NASA Technical Reports Server (NTRS)

    Garai, Anirban; Diosady, Laslo Tibor; Murman, Scott; Madavan, Nateri

    2015-01-01

    A new computational capability under development for accurate and efficient high-fidelity direct numerical simulation (DNS) and large eddy simulation (LES) of turbomachinery is described. This capability is based on an entropy-stable Discontinuous-Galerkin spectral-element approach that extends to arbitrarily high orders of spatial and temporal accuracy and is implemented in a computationally efficient manner on a modern high performance computer architecture. A validation study using this method to perform DNS of flow in a low-pressure turbine airfoil cascade are presented. Preliminary results indicate that the method captures the main features of the flow. Discrepancies between the predicted results and the experiments are likely due to the effects of freestream turbulence not being included in the simulation and will be addressed in the final paper.

  2. Collisional quenching of CH(A), OH(A), and NO(A) in low pressure hydrocarbon flames

    SciTech Connect

    Tamura, Masayuki; Berg, P.A.; Harrington, J.E.; Lique, J.; Jeffries, J.B.; Smith, G.P.; Crosley, D.R.

    1998-08-01

    Excited state lifetimes have been measured for the A-states of CH, OH, and NO in a number of low-pressure, premixed, laminar flow methane flames. From these lifetimes, collisional quenching rates were determined as a function of height above the burner and thus as a function of flame temperature and composition. The results were compared with values calculated using a model of the flame chemistry to predict collider mole fractions, together with parameterizations of quenching rate coefficients and modeled flame composition data. This indicates that collisional quenching corrections for laser-induced fluorescence measurements can be calculated from knowledge of major species mole fractions and gas temperature. Predicted quenching rates for CH range from agreement with measured values to 27% higher than measured values. This discrepancies suggest insufficient knowledge of high temperature quenching by H{sub 2}O and N{sub 2}.

  3. Development of a Low Pressure, Air Atomized Oil Burner with High Atomizer Air Flow: Progress Report FY 1997

    SciTech Connect

    Butcher, T.A.

    1998-01-01

    This report describes technical advances made to the concept of a low pressure, air atomized oil burner for home heating applications. Currently all oil burners on the market are of the pressure atomized, retention head type. These burners have a lower firing rate limit of about 0.5 gallons per hour of oil, due to reliability problems related to small flow passage sizes. High pressure air atomized burners have been shown to be one route to avoid this problem but air compressor cost and reliability have practically eliminated this approach. With the low pressure air atomized burner the air required for atomization can be provided by a fan at 5-8 inches of water pressure. A burner using this concept, termed the Fan-Atomized Burner or ''FAB'' has been developed and is currently being commercialized. In the head of the FAB, the combustion air is divided into three parts, much like a conventional retention head burner. This report describes development work on a new concept in which 100% of the air from the fan goes through the atomizer. The primary advantage of this approach is a great simplification of the head design. A nozzle specifically sized for this concept was built and is described in the report. Basic flow pressure tests, cold air velocity profiles, and atomization performance have been measured. A burner head/flame tube has been developed which promotes a toroidal recirculation zone near the nozzle for flame stability. The burner head has been tested in several furnace and boiler applications over the firing rate range 0.2 to 0.28 gallons per hour. In all cases the burner can operate with very low excess air levels (under 10%) without producing smoke. Flue gas NO{sub x} concentration varied from 42 to 62 ppm at 3% O{sub 2}. The concept is seen as having significant potential and planned development efforts are discussed.

  4. CFD Study of the Hydrocarbon Boost Low-Pressure Inducer and Kicker in the Presence of a Circumferential Groove

    NASA Technical Reports Server (NTRS)

    Coker, Robert

    2011-01-01

    Results are presented of a computational fluid dynamics (CFD) study done in support of Marshall Space Flight Center's (MSFC) sub-scale water flow experiments of the Hydrocarbon Boost (HCB) Oxidizer Turbopump (OTP) being developed by the Air Force Research Laboratory (AFRL) and Aerojet. A circumferential groove may be added to the pump to reduce synchronous cavitation and subsequent bearing loads at a minimal performance cost. However, the energy may reappear as high order cavitation (HOC) that spans a relatively large frequency range. Thus, HOC may have implications for the full-scale OTP inducer in terms of reduced structural margin at higher mode frequencies. Simulations using the LOCI/Stream CFD program were conducted in order to explore the fluid dynamical impact of the groove on the low-pressure inducer and kicker. It was found that the circumferential groove has minimal head performance impact, but causes back-flowing high-swirl fluid to interact with the nearly-axial incoming fluid just above the inducer blades. The high-shear interface between the fluids is Kelvin-Helmholtz unstable, resulting in trains of low pressure regions or 'pearls' forming near the upstream edge of the groove. When the static pressure in these regions becomes low enough and they get cut by the blade leading edge, HOC is thought to occur. Although further work is required, the numerical models indicate that HOC will occur in the runbox of the AFRL/Aerojet HCB OTP. Comparisons to the ongoing water flow experiments will be discussed, as well as possible designs that may mitigate HOC while continuing to reduce synchronous cavitation. December 2011 MSS/LPS/SPS Joint Subcommittee Meeting ABSTRACT SUBMITTAL FORM

  5. E-H mode transition in low-pressure inductively coupled nitrogen-argon and oxygen-argon plasmas

    SciTech Connect

    Lee, Young Wook; Lee, Hye Lan; Chung, T. H.

    2011-06-01

    This work investigates the characteristics of the E-H mode transition in low-pressure inductively coupled N{sub 2}-Ar and O{sub 2}-Ar discharges using rf-compensated Langmuir probe measurements and optical emission spectroscopy (OES). As the ICP power increases, the emission intensities from plasma species, the electron density, the electron temperature, and the plasma potential exhibit sudden changes. The Ar content in the gas mixture and total gas pressure have been varied in an attempt to fully characterize the plasma parameters. With these control parameters varying, the changes of the transition threshold power and the electron energy distribution function (EEDF) are explored. In N{sub 2}-Ar and O{sub 2}-Ar discharges at low-pressures of several millitorr, the transition thresholds are observed to decrease with Ar content and pressure. It is observed that in N{sub 2}-Ar plasmas during the transition, the shape of the EEDF changes from an unusual distribution with a flat hole near the electron energy of 3 eV in the E mode to a Maxwellian distribution in the H mode. However, in O{sub 2} -Ar plasmas, the EEDFs in the E mode at low Ar contents show roughly bi-Maxwellian distributions, while the EEDFs in the H mode are observed to be nearly Maxwellian. In the E and H modes of O{sub 2}-Ar discharges, the dissociation fraction of O{sub 2} molecules is estimated using optical emission actinometry. During the E-H mode transition, the dissociation fraction of molecules is also enhanced.

  6. Improved outcome with novel device for low-pressure PTCA in de novo and in-stent lesions

    SciTech Connect

    Ischinger, Thomas A.; Solar, Ronald J.; Hitzke, Evelyn

    2003-03-01

    Purpose: Complex lesion morphology requiring the use of high pressure to effect lumen expansion and in-stent restenosis (ISR) remain two indications that challenge conventional PTCA balloons. We report on a new PTCA device that is designed to provide precise, low-pressure dilatation of both de novo and in-stent lesions. Methods: The FX miniRAIL catheter (FX) has an integral wire positioned external to a dilating balloon and a short, 12-mm guidewire lumen distal to the balloon. The balloon inflates against the guidewire and the external wire to prevent slippage and to introduce high focal longitudinal stresses at low inflation pressures. In this initial study, the FX was used in 37 lesions (25 de novo, 12 in-stent; vessel reference diameter=2.73{+-}0.49 mm) in 30 patients. A stepwise inflation protocol and QCA were used to determine the balloon pressure at which the stenosis was resolved (stenosis resolution pressure, SRP). Results: All lesions (100%) were easily reached, crossed and dilated without complication. The SRP was 4.5{+-}2.9 atm, and no balloon slippage was observed. Residual stenosis after FX was 26.39{+-}13.29%. Minor dissections (Types A and B) were observed in eight lesions (21.6%). Target lesion revascularization (TLR) and target vessel revascularization (TVR) at follow-up (8.1{+-}1.5 months) were 8.3% and 12.5%, respectively. Conclusion: The design of the FX is versatile and appears to provide for a safe, effective and improved low-pressure PTCA technique in de novo and in-stent lesions.

  7. Chemical structures of low-pressure premixed methylcyclohexane flames as benchmarks for the development of a predictive combustion chemistry model

    SciTech Connect

    Skeen, Scott A.; Yang, Bin; Jasper, Ahren W.; Pitz, William J.; Hansen, Nils

    2011-11-14

    The chemical compositions of three low-pressure premixed flames of methylcyclohexane (MCH) are investigated with the emphasis on the chemistry of MCH decomposition and the formation of aromatic species, including benzene and toluene. The flames are stabilized on a flat-flame (McKenna type) burner at equivalence ratios of φ = 1.0, 1.75, and 1.9 and at low pressures between 15 Torr (= 20 mbar) and 30 Torr (= 40 mbar). The complex chemistry of MCH consumption is illustrated in the experimental identification of several C7H12, C7H10, C6H12, and C6H10 isomers sampled from the flames as a function of distance from the burner. Three initiation steps for MCH consumption are discussed: ring-opening to heptenes and methyl-hexenes (isomerization), methyl radical loss yielding the cyclohexyl radical (dissociation), and H abstraction from MCH. Mole fraction profiles as a function of distance from the burner for the C7 species supplemented by theoretical calculations are presented, indicating that flame structures resulting in steeper temperature gradients and/or greater peak temperatures can lead to a relative increase in MCH consumption through the dissociation and isomerization channels. Trends observed among the stable C6 species as well as 1,3-pentadiene and isoprene also support this conclusion. Relatively large amounts of toluene and benzene are observed in the experiments, illustrating the importance of sequential H-abstraction steps from MCH to toluene and from cyclohexyl to benzene. Furthermore, modeled results using the detailed chemical model of Pitz et al. (Proc. Combust. Inst.2007, 31, 267–275) are also provided to illustrate the use of these data as a benchmark for the improvement or future development of a MCH mechanism.

  8. Chemical structures of low-pressure premixed methylcyclohexane flames as benchmarks for the development of a predictive combustion chemistry model

    DOE PAGESBeta

    Skeen, Scott A.; Yang, Bin; Jasper, Ahren W.; Pitz, William J.; Hansen, Nils

    2011-11-14

    The chemical compositions of three low-pressure premixed flames of methylcyclohexane (MCH) are investigated with the emphasis on the chemistry of MCH decomposition and the formation of aromatic species, including benzene and toluene. The flames are stabilized on a flat-flame (McKenna type) burner at equivalence ratios of φ = 1.0, 1.75, and 1.9 and at low pressures between 15 Torr (= 20 mbar) and 30 Torr (= 40 mbar). The complex chemistry of MCH consumption is illustrated in the experimental identification of several C7H12, C7H10, C6H12, and C6H10 isomers sampled from the flames as a function of distance from the burner.more » Three initiation steps for MCH consumption are discussed: ring-opening to heptenes and methyl-hexenes (isomerization), methyl radical loss yielding the cyclohexyl radical (dissociation), and H abstraction from MCH. Mole fraction profiles as a function of distance from the burner for the C7 species supplemented by theoretical calculations are presented, indicating that flame structures resulting in steeper temperature gradients and/or greater peak temperatures can lead to a relative increase in MCH consumption through the dissociation and isomerization channels. Trends observed among the stable C6 species as well as 1,3-pentadiene and isoprene also support this conclusion. Relatively large amounts of toluene and benzene are observed in the experiments, illustrating the importance of sequential H-abstraction steps from MCH to toluene and from cyclohexyl to benzene. Furthermore, modeled results using the detailed chemical model of Pitz et al. (Proc. Combust. Inst.2007, 31, 267–275) are also provided to illustrate the use of these data as a benchmark for the improvement or future development of a MCH mechanism.« less

  9. Buoyancy induced limits for nanoparticle synthesis experiments in horizontal premixed low-pressure flat-flame reactors

    NASA Astrophysics Data System (ADS)

    Weise, C.; Faccinetto, A.; Kluge, S.; Kasper, T.; Wiggers, H.; Schulz, C.; Wlokas, I.; Kempf, A.

    2013-06-01

    Premixed low-pressure flat-flame reactors can be used to investigate the synthesis of nanoparticles. The present work examines the flow field inside such a reactor during the formation of carbon (soot) and iron oxide (from Fe(CO)5) nanoparticles, and how it affects the measurements of nanoparticle size distribution. The symmetry of the flow and the impact of buoyancy were analysed by three-dimensional simulations and the nanoparticle size distribution was obtained by particle mass spectrometry (PMS) via molecular beam sampling at different distances from the burner. The PMS measurements showed a striking, sudden increase in particle size at a critical distance from the burner, which could be explained by the flow field predicted in the simulations. The simulation results illustrate different fluid mechanical phenomena which have caused this sudden rise in the measured particle growth. Up to the critical distance, buoyancy does not affect the flow, and an (almost) linear growth is observed in the PMS experiments. Downstream of this critical distance, buoyancy deflects the hot gas stream and leads to an asymmetric flow field with strong recirculation. These recirculation zones increase the particle residence time, inducing very large particle sizes as measured by PMS. This deviation from the assumed symmetric, one-dimensional flow field prevents the correct interpretation of the PMS results. To overcome this problem, modifications to the reactor were investigated; their suitability to reduce the flow asymmetry was analysed. Furthermore, 'safe' operating conditions were identified for which accurate measurements are feasible in premixed low-pressure flat-flame reactors that are transferrable to other experiments in this type of reactor. The present work supports experimentalists to find the best setup and operating conditions for their purpose.

  10. Synthesis of highly transparent ultrananocrystalline diamond films from a low-pressure, low-temperature focused microwave plasma jet

    PubMed Central

    2012-01-01

    This paper describes a new low-temperature process underlying the synthesis of highly transparent ultrananocrystalline diamond [UNCD] films by low-pressure and unheated microwave plasma jet-enhanced chemical vapor deposition with Ar-1%CH4-10%H2 gas chemistry. The unique low-pressure/low-temperature [LPLT] plasma jet-enhanced growth even with added H2 and unheated substrates yields UNCD films similar to those prepared by plasma-enhanced growth without addition of H2 and heating procedure. This is due to the focused plasma jet which effectively compensated for the sluggish kinetics associated with LPLT growth. The effects of pressure on UNCD film synthesis from the microwave plasma jet were systematically investigated. The results indicated that the substrate temperature, grain size, surface roughness, and sp3 carbon content in the films decreased with decreasing pressure. The reason is due to the great reduction of Hα emission to lower the etching of sp2 carbon phase, resulting from the increase of mean free path with decreasing pressure. We have demonstrated that the transition from nanocrystalline (80 nm) to ultrananocrystalline (3 to 5 nm) diamond films grown via microwave Ar-1%CH4-10%H2 plasma jets could be controlled by changing the pressure from 100 to 30 Torr. The 250-nm-thick UNCD film was synthesized on glass substrates (glass transition temperature [Tg] 557°C) using the unique LPLT (30 Torr/460°C) microwave plasma jet, which produced UNCD films with a high sp3 carbon content (95.65%) and offered high optical transmittance (approximately 86% at 700 nm). PMID:22260391

  11. Laser-induced incandescence technique to identify soot nucleation and very small particles in low-pressure methane flames

    NASA Astrophysics Data System (ADS)

    Mouton, Thomas; Mercier, Xavier; Wartel, Maxime; Lamoureux, Nathalie; Desgroux, Pascale

    2013-09-01

    This paper presents the study we carried out on the formation of soot particles in low-pressure premixed CH4/O2/N2 flames by using Laser-Induced Incandescence (LII). Flames were stabilised at 26.6 kPa (200 torr). Four different equivalence ratios were tested (Φ = 1.95, 205, 2.15 and 2.32), Φ = 1.95 corresponding to the equivalence ratio for which LII signals begin to be measurable along the flame. The evolution of the LII signals with laser fluence (fluence curve), time (temporal decay) and emission wavelength is reported at different heights above the burner. We specifically took advantage of the low-pressure conditions to probe with a good spatial resolution the soot inception zone of the flames. Significant different behaviours of the fluence curves are observed according to the probed region of the flames and Φ. In addition, while the surface growth process is accompanied by an increase in the LII decay-times (indicator of the primary particle diameter) at higher Φ, decay-times become increasingly short at lower Φ reaching a constant value along the flame at Φ = 1.95. These behaviours are consistent with the detection of the smallest incandescent particles in the investigated flames, these particles having experienced very weak surface growth. Flame modelling including soot formation has been implemented in flames Φ = 2.05 and 2.32. Experimental quantitative soot volume fraction profiles were satisfactorily reproduced by adjusting the fraction of reactive soot surface available for reactions. The qualitative variation of the computed soot particle diameter and the relative weight of surface growth versus nucleation were consistent with the experimental observations.

  12. Understanding of the importance of the spore coat structure and pigmentation in the Bacillus subtilis spore resistance to low-pressure plasma sterilization

    NASA Astrophysics Data System (ADS)

    Raguse, Marina; Fiebrandt, Marcel; Denis, Benjamin; Stapelmann, Katharina; Eichenberger, Patrick; Driks, Adam; Eaton, Peter; Awakowicz, Peter; Moeller, Ralf

    2016-07-01

    Low-pressure plasmas have been evaluated for their potential in biomedical and defense purposes. The sterilizing effect of plasma can be attributed to several active agents, including (V)UV radiation, charged particles, radical species, neutral and excited atoms and molecules, and the electric field. Spores of Bacillus subtilis were used as a bioindicator and a genetic model system to study the sporicidal effects of low-pressure plasma decontamination. Wild-type spores, spores lacking the major protective coat layers (inner, outer, and crust), pigmentation-deficient spores or spore impaired in encasement (a late step in coat assembly) were systematically tested for their resistance to low-pressure argon, hydrogen, and oxygen plasmas with and without admixtures. We demonstrate that low-pressure plasma discharges of argon and oxygen discharges cause significant physical damage to spore surface structures as visualized by atomic force microscopy. Spore resistance to low-pressure plasma was primarily dependent on the presence of the inner, and outer spore coat layers as well as spore encasement, with minor or less importance of the crust and spore pigmentation, whereas spore inactivation itself was strongly influenced by the gas composition and operational settings.

  13. Turbofan engine with a low pressure turbine driven supercharger in a bypass duct operated by a fuel rich combustor and an afterburner

    NASA Technical Reports Server (NTRS)

    Bartos, James W. (Inventor)

    1999-01-01

    A multiple bypass turbofan engine includes a core Brayton Cycle gas generator with a fuel rich burning combustor and is provided with a variable supercharged bypass duct around the gas generator with a supercharging means in the supercharged bypass duct powered by a turbine not mechanically connected to the gas generator. The engine further includes a low pressure turbine driven forward fan upstream and forward of an aft fan and drivingly connected to a low pressure turbine by a low pressure shaft, the low pressure turbine being aft of and in serial flow communication with the core gas generator. A fan bypass duct is disposed radially outward of the core engine assembly and has first and second inlets disposed between the forward and aft fans. An inlet duct having an annular duct wall is disposed radially inward of the bypass duct and connects the second inlet to the bypass duct. A supercharger means for compressing air is drivingly connected to the low pressure turbine and is disposed in the inlet duct. A secondary combustor or augmentor is disposed in an exhaust duct downstream of and in fluid flow communication with the bypass duct and the gas generator.

  14. Low Pressure Radio-Frequency Oxygen Plasma Induced Oxidation of Titanium – Surface Characteristics and Biological Effects

    PubMed Central

    Tseng, Wan-Yu; Hsu, Sheng-Hao; Huang, Chieh-Hsiun; Tu, Yu-Chieh; Tseng, Shao-Chin; Chen, Hsuen-Li; Chen, Min-Huey; Su, Wei-Fang; Lin, Li-Deh

    2013-01-01

    Objective This research was designed to investigate the effects of low pressure radio-frequency (RF) oxygen plasma treatment (OPT) on the surface of commercially pure titanium (CP-Ti) and Ti6Al4V. Surface topography, elemental composition, water contact angle, cell viability, and cell morphology were surveyed to evaluate the biocompatibility of titanium samples with different lengths of OP treating time. Materials and Methods CP-Ti and Ti6Al4V discs were both classified into 4 groups: untreated, treated with OP generated by using oxygen (99.98%) for 5, 10, and 30 min, respectively. After OPT on CP-Ti and Ti6Al4V samples, scanning probe microscopy, X-ray photoelectron spectrometry (XPS), and contact angle tests were conducted to determine the surface topography, elemental composition and hydrophilicity, respectively. The change of surface morphology was further studied using sputtered titanium on silicon wafers. 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay and F-actin immunofluorescence stain were performed to investigate the viability and spreading behavior of cultivated MG-63 cells on the samples. Results The surface roughness was most prominent after 5 min OPT in both CP-Ti and Ti6Al4V, and the surface morphology of sputtered Ti sharpened after the 5 min treatment. From the XPS results, the intensity of Ti°, Ti2+, and Ti3+ of the samples’ surface decreased indicating the oxidation of titanium after OPT. The water contact angles of both CP-Ti and Ti6Al4V were increased after 5 min OPT. The results of MTT assay demonstrated MG-63 cells proliferated best on the 5 min OP treated titanium sample. The F-actin immunofluorescence stain revealed the cultivated cell number of 5 min treated CP-Ti/Ti6Al4V was greater than other groups and most of the cultivated cells were spindle-shaped. Conclusions Low pressure RF oxygen plasma modified both the composition and the morphology of titanium samples’ surface. The CP-Ti/Ti6Al4V treated with 5 min

  15. Characterization of Dust-Plasma Interactions In Non-Thermal Plasmas Under Low Pressure and the Atmospheric Pressure

    NASA Astrophysics Data System (ADS)

    Bilik, Narula

    This dissertation research focuses on the experimental characterization of dust-plasma interactions at both low and atmospheric pressure. Its goal is to fill the knowledge gaps in (1) the fundamental research of low pressure dusty plasma electrons, which mainly relied on models with few experimental results; and (2) the nanoparticle synthesis process in atmospheric pressure uniform glow plasmas (APGDs), which is largely unexplored in spite of the economical advantage of APGDs in nanotechnology. The low pressure part of the dissertation research involves the development of a complete diagnostic process for an argon-siline capacitively-coupled RF plasma. The central part of the diagnostic process is the Langmuir probe measurement of the electron energy probability function (EEPF) in a dusty plasma, which has never been measured before. This is because the dust particles in the plasma cause severe probe surface contamination and consequently distort the measurement. This problem is solved by adding a solenoid-actuated shield structure to the Langmuir probe, which physically protects the Langmuir probe from the dust particle deposition to ensure reliable EEPF measurements. The dusty plasma EEPFs are characterized by lower electron density and higher electron temperature accompanied by a drop in the low energy electron population. The Langmuir probe measurement is complemented with other characterizations including the capacitive probe measurement, power measurement, and dust particle collection. The complete diagnostic process then gives a set of local plasma parameters as well as the details of the dust-electron interactions reflected in the EEPFs. This set of data serves as input for an analytical model of nanoparticle charging to yield the time evolution of nanoparticle size and charge in the dusty plasma. The atmospheric pressure part of the dissertation focuses on the design and development of an APGD for zinc oxide nanocrystal synthesis. One of the main

  16. Ethylene Decomposition Initiated by Ultraviolet Radiation from Low Pressure Mercury Lamps: Kinetics Model Prediction and Experimental Verification.

    NASA Astrophysics Data System (ADS)

    Jozwiak, Zbigniew Boguslaw

    1995-01-01

    Ethylene is an important auto-catalytic plant growth hormone. Removal of ethylene from the atmosphere surrounding ethylene-sensitive horticultural products may be very beneficial, allowing an extended period of storage and preventing or delaying the induction of disorders. Various ethylene removal techniques have been studied and put into practice. One technique is based on using low pressure mercury ultraviolet lamps as a source of photochemical energy to initiate chemical reactions that destroy ethylene. Although previous research showed that ethylene disappeared in experiments with mercury ultraviolet lamps, the reactions were not described and the actual cause of ethylene disappearance remained unknown. Proposed causes for this disappearance were the direct action of ultraviolet rays on ethylene, reaction of ethylene with ozone (which is formed when air or gas containing molecular oxygen is exposed to radiation emitted by this type of lamp), or reactions with atomic oxygen leading to formation of ozone. The objective of the present study was to determine the set of physical and chemical actions leading to the disappearance of ethylene from artificial storage atmosphere under conditions of ultraviolet irradiation. The goal was achieved by developing a static chemical model based on the physical properties of a commercially available ultraviolet lamp, the photochemistry of gases, and the kinetics of chemical reactions. The model was used to perform computer simulations predicting time dependent concentrations of chemical species included in the model. Development of the model was accompanied by the design of a reaction chamber used for experimental verification. The model provided a good prediction of the general behavior of the species involved in the chemistry under consideration; however the model predicted lower than measured rate of ethylene disappearance. Some reasons for the model -experiment disagreement are radiation intensity averaging, the experimental

  17. Self-Consistent System of Equations for a Kinetic Description of the Low-Pressure Discharges Accounting for the Nonlocal and Collisionless Electron Dynamics

    SciTech Connect

    Igor D. Kaganovich; Oleg Polomarov

    2003-05-19

    In low-pressure discharges, when the electron mean free path is larger or comparable with the discharge length, the electron dynamics is essentially non-local. Moreover, the electron energy distribution function (EEDF) deviates considerably from a Maxwellian. Therefore, an accurate kinetic description of the low-pressure discharges requires knowledge of the non-local conductivity operator and calculation of the non-Maxwellian EEDF. The previous treatments made use of simplifying assumptions: a uniform density profile and a Maxwellian EEDF. In the present study a self-consistent system of equations for the kinetic description of nonlocal, non-uniform, nearly collisionless plasmas of low-pressure discharges is derived. It consists of the nonlocal conductivity operator and the averaged kinetic equation for calculation of the non-Maxwellian EEDF. The importance of accounting for the non-uniform plasma density profile on both the current density profile and the EEDF is demonstrated.

  18. Global model analysis of negative ion generation in low-pressure inductively coupled hydrogen plasmas with bi-Maxwellian electron energy distributions

    SciTech Connect

    Huh, Sung-Ryul; Kim, Nam-Kyun; Jung, Bong-Ki; Chung, Kyoung-Jae; Hwang, Yong-Seok; Kim, Gon-Ho

    2015-03-15

    A global model was developed to investigate the densities of negative ions and the other species in a low-pressure inductively coupled hydrogen plasma with a bi-Maxwellian electron energy distribution. Compared to a Maxwellian plasma, bi-Maxwellian plasmas have higher populations of low-energy electrons and highly vibrationally excited hydrogen molecules that are generated efficiently by high-energy electrons. This leads to a higher reaction rate of the dissociative electron attachment responsible for negative ion production. The model indicated that the bi-Maxwellian electron energy distribution at low pressures is favorable for the creation of negative ions. In addition, the electron temperature, electron density, and negative ion density calculated using the model were compared with the experimental data. In the low-pressure regime, the model results of the bi-Maxwellian electron energy distributions agreed well quantitatively with the experimental measurements, unlike those of the assumed Maxwellian electron energy distributions that had discrepancies.

  19. Mass spectrometry of positive ions in capacitively coupled low pressure RF discharges in oxygen with water impurities

    NASA Astrophysics Data System (ADS)

    Stefanović, Ilija; Stojanović, Vladimir; Boulmer-Leborgne, Chantal; Lecas, Thomas; Kovacevic, Eva; Berndt, Johannes

    2016-07-01

    A capacitively coupled RF oxygen discharge is studied by means of mass spectroscopy. Mass spectra of neutral and positive species are measured in the mid plane between the electrodes at different distances between plasma and mass-spectrometer orifice. In the case of positive ions, as expected, the largest flux originates from \\text{O}2+ . However, a significant number of impurities are detected, especially for low input powers and larger distances. The most abundant positive ions (besides \\text{O}2+ ) are \\text{N}{{\\text{O}}+}, \\text{NO}2+ , {{\\text{H}}+}≤ft({{\\text{H}}2}\\text{O}\\right) , and {{\\text{H}}+}{{≤ft({{\\text{H}}2}\\text{O}\\right)}2} . In particular, for the case of hydrated hydronium ions {{\\text{H}}+}{{≤ft({{\\text{H}}2}\\text{O}\\right)}n} (n  =  1, 2) a surprisingly large flux (for low pressure plasma conditions) is detected. Another interesting fact concerns the {{\\text{H}}2}{{\\text{O}}+} ions. Despite the relatively high ammount of water impurities {{\\text{H}}2}{{\\text{O}}+} ions are present only in traces. The reaction mechanisms leading to the production of the observed ions, especially the hydrated hydronium ions are discussed.

  20. Evidence for Skill Level Differences in the Thought Processes of Golfers During High and Low Pressure Situations

    PubMed Central

    Whitehead, Amy E.; Taylor, Jamie A.; Polman, Remco C. J.

    2016-01-01

    Two studies examined differences in the cognition of golfers with differing levels of expertise in high and low pressure situations. In study 1, six high skill and six low skill golfers performed six holes of golf, while verbalizing their thoughts using Think Aloud (TA) protocol. Higher skilled golfers’ cognitive processes centered more on planning in comparison to lower skilled golfers. Study 2 investigated whether thought processes of golfers changed in response to competitive pressure. Eight high skill and eight moderate skilled golfers, completed a practice round and a competition round whilst verbalizing thoughts using TA. To create pressure in the competition condition, participants were instructed that monetary prizes would be awarded to the top three performers and scores of all golfers would be published in a league table in the club house. When performing under competitive pressure, it was found that higher skilled golfers were more likely to verbalize technical rules compared to practice conditions, especially during putting performance. This shift in cognition toward more technical aspects of motor performance was strongly related to scores on the Decision Specific Reinvestment Scale, suggesting individuals with a higher propensity for reinvestment show the largest changes in cognition under pressure. From a practical perspective, TA can aid a player, coach or sport psychologist by allowing thought processes to be identified and investigate a performer’s thoughts when faced with the pressure of a competition. PMID:26779085

  1. A Simple Ion Flux Estimation in a Low Pressure R.F. Plasma (13.56MHz)

    NASA Astrophysics Data System (ADS)

    Grenier, I.; Massereau, V.; Celerier, A.; Machet, J.

    1997-04-01

    A new application of the sputtering rate measurement is given in this paper. In fact, by measuring the sputtering rate of different materials fixed on the radio frequency (r.f.) biased electrode, it is possible to determine easily ion flux that falls onto this biased electrode. This study is realized in a low pressure (0.4 Pa) argon planar r.f. discharge system (13.56 MHz). This sputtering method is interesting to have informations about the deposition process in physical vapour deposition. In order to demonstrate the validity of this method, experiments have been carried out in two reactors, each one with different geometrical parameters and the results obtained have been compared and confirmed using the Child-Langmuir law. The ion flux increases as a function of the incident r.f power (0 300 W). The values obtained range from 10^{18} to 10^{19} ions m^{-2} s^{-1}. These results in an argon plasma are applied to estimate incident ion flux in a nitrogen atmosphere. Finally, we show that it is possible to evaluate the incident ion flux by measuring the sputtering rate when the plasma is densified using either an auxiliary hot cathode discharge or an additional magnetic field. These experimental cases correspond respectively to r.f. triode ion plating or r.f. magnetron sputtering.

  2. On the effect of ion-neutral collisions on dust grain screening in a low-pressure gas discharge plasma

    NASA Astrophysics Data System (ADS)

    Semenov, I. L.; Zagorodny, A. G.; Krivtsun, I. V.

    2012-04-01

    The effect of ion-neutral collisions on charging of micrometer-sized dust grains immersed in a low-pressure argon discharge plasma is studied on the basis of the Vlasov-Bhatnagar-Gross-Krook kinetic equations. The equations are solved numerically using the method described in our previous work [I. L. Semenov et al., Phys. Plasmas 18, 103707 (2011)]. A modified version of the numerical method is proposed to reduce the required computational time. Numerical calculations are carried out for typical plasma parameters used in laboratory investigations of dusty plasma. On the basis of the obtained results, the influence of collisions on the ion flux and grain charge is analyzed. A comparison of our results with those obtained using different analytical models proposed earlier is presented. In addition, applicability of simple kinetic models describing the influence of collisions on the electric potential around a dust grain [S. A. Khrapak et al., Phys. Rev. Lett. 100, 225003 (2008); A. G. Zagorodny et al. Ukr. J. Phys. 54, 1089 (2009)] is examined. The influence of ion-neutral collisions on the distribution of plasma macroparameters near the grain surface is also demonstrated.

  3. Effects of N2-O2 Gas Mixture Ratio on Microorganism Inactivation in Low-Pressure Surface Wave Plasma

    NASA Astrophysics Data System (ADS)

    Zhao, Ying; Ogino, Akihisa; Nagatsu, Masaaki

    2011-08-01

    In this study, the effect of N2/O2 gas mixture ratio on low-pressure surface wave plasma inactivation of spore-forming bacteria was investigated. It was experimentally confirmed from the quadrupole mass spectrometry measurements that the spores were etched by atomic oxygen via converting the hydrogen atoms constituting microorganisms into H2O and the carbon into CO2. On the basis of results of plasma diagnostics by optical emission spectroscopy and the results of inactivation efficiency by colony-forming units and scanning electron microscope, we found that although there is the highest ultraviolet (UV) emission intensity in pure N2 plasma and the highest etching efficiency in 90% O2/10% N2 plasma, the inactivation rate of microorganisms was not so efficient. The best inactivation result was obtained in 30-80% O2 gas mixture ratios after 60 s plasma irradiation. The present results indicated that more efficient inactivation is achieved by the synergetic effects between atomic oxygen etching and the vacuum ultraviolet (VUV)/UV emission by combining both effects via optimizing N2/O2 gas mixture ratio.

  4. Electrical characterization of low-pressure chemical-vapor-deposited silicon dioxide metal-oxide-silicon structures

    NASA Astrophysics Data System (ADS)

    Ang, S. S.; Shi, Y. J.; Brown, W. D.

    1993-03-01

    The electrical characteristics of as-deposited and oxygen-annealed low-pressure chemical-vapor-deposited (LPCVD) silicon dioxide (SiO2) metal-oxide-silicon (MOS) structures were investigated. As-deposited LPCVD SiO2 MOS structures exhibit a high oxide fixed charge density in the mid-1011 cm-2 and an interface state density in the low-1011 cm-2 eV-1 due to the large number of oxygen and silicon dangling bonds. A low electron barrier height in these structures (1.2 eV) is presumed to be due to lowering of the barrier by excess silicon microclusters. Oxygen-annealed LPCVD SiO2 MOS structures exhibit oxide fixed charge and interface state densities in the mid-1010 cm-2 and mid-1010 cm-2 eV-1, respectively. Both the as-deposited and annealed devices exhibit turnaround in flatband voltage shift with avalanche electron injection. However, the direction of shift is opposite for the two devices with the annealed device being very similar to that of thermally grown SiO2 MOS structures. Apparently, oxygen annealing restructures and oxidizes the partial SiOx in the as-deposited LPCVD oxide into stochiometric SiO2. However, the residual nonstochiometric SiO2 microclusters in the bulk result in an electron barrier height of only 2.3 eV.

  5. Solid oxide fuel cell electrolytes produced by a combination of suspension plasma spray and very low pressure plasma spray.

    SciTech Connect

    Slamovich, Elliot; Fleetwood, James; McCloskey, James F.; Hall, Aaron Christopher; Trice, Rodney Wayne

    2010-07-01

    Plasma spray coating techniques allow unique control of electrolyte microstructures and properties as well as facilitating deposition on complex surfaces. This can enable significantly improved solid oxide fuel cells (SOFCs), including non-planar designs. SOFCs are promising because they directly convert the oxidization of fuel into electrical energy. However, electrolytes deposited using conventional plasma spray are porous and often greater than 50 microns thick. One solution to form dense, thin electrolytes of ideal composition for SOFCs is to combine suspension plasma spray (SPS) with very low pressure plasma spray (VLPPS). Increased compositional control is achieved due to dissolved dopant compounds in the suspension that are incorporated into the coating during plasma spraying. Thus, it is possible to change the chemistry of the feed stock during deposition. In the work reported, suspensions of sub-micron diameter 8 mol.% Y2O3-ZrO2 (YSZ) powders were sprayed on NiO-YSZ anodes at Sandia National Laboratories (SNL) Thermal Spray Research Laboratory (TSRL). These coatings were compared to the same suspensions doped with scandium nitrate at 3 to 8 mol%. The pressure in the chamber was 2.4 torr and the plasma was formed from a combination of argon and hydrogen gases. The resultant electrolytes were well adhered to the anode substrates and were approximately 10 microns thick. The microstructure of the resultant electrolytes will be reported as well as the electrolyte performance as part of a SOFC system via potentiodynamic testing and impedance spectroscopy.

  6. Enhanced Optical Properties of Chemical Vapor Deposited Single Crystal Diamond by Low-Pressure/High-Temperature Annealing

    SciTech Connect

    Meng, Y.; Yan, C; Lai, Y; Krasnicki, S; Shu, H; Yu, T; Liang, Q; Mao, H; Hemley, R

    2008-01-01

    Single crystal diamond produced by chemical vapor deposition (CVD) at very high growth rates (up to 150 em/h) has been successfully annealed without graphitization at temperatures up to 2200 C and pressures <300 torr. Crystals were annealed in a hydrogen environment by using microwave plasma techniques for periods of time ranging from a fraction of minute to a few hours. This low-pressure/high-temperature (LPHT) annealing enhances the optical properties of this high-growth rate CVD single crystal diamond. Significant decreases are observed in UV, visible, and infrared absorption and photoluminescence spectra. The decrease in optical absorption after the LPHT annealing arises from the changes in defect structure associated with hydrogen incorporation during CVD growth. There is a decrease in sharp line spectral features indicating a reduction in nitrogen-vacancy-hydrogen (NVH-) defects. These measurements indicate an increase in relative concentration of nitrogen-vacancy (NV) centers in nitrogen-containing LPHT-annealed diamond as compared with as-grown CVD material. The large overall changes in optical properties and the specific types of alterations in defect structure induced by this facile LPHT processing of high-growth rate single-crystal CVD diamond will be useful in the creation of diamond for a variety of scientific and technological applications.

  7. Comparison of ultraviolet light-emitting diodes and low-pressure mercury-arc lamps for disinfection of water.

    PubMed

    Sholtes, Kari A; Lowe, Kincaid; Walters, Glenn W; Sobsey, Mark D; Linden, Karl G; Casanova, Lisa M

    2016-09-01

    Ultraviolet (UV) light-emitting diodes (LEDs) emitting at 260 nm were evaluated to determine the inactivation kinetics of bacteria, viruses, and spores compared to low-pressure (LP) UV irradiation. Test microbes were Escherichia coli B, a non-enveloped virus (MS-2), and a bacterial spore (Bacillus atrophaeus). For LP UV, 4-log10 reduction doses were: E. coli B, 6.5 mJ/cm(2); MS-2, 59.3 mJ/cm(2); and B. atrophaeus, 30.0 mJ/cm(2). For UV LEDs, the 4-log10 reduction doses were E. coli B, 6.2 mJ/cm(2); MS-2, 58 mJ/cm(2); and B. atrophaeus, 18.7 mJ/cm(2). Microbial inactivation kinetics of the two UV technologies were not significantly different for E. coli B and MS-2, but were different for B. atrophaeus spores. UV LEDs at 260 nm are at least as effective for inactivating microbes in water as conventional LP UV sources and should undergo further development in treatment systems to disinfect drinking water. PMID:26888599

  8. Low-pressure effective fluorescence lifetimes and photo-physical rate constants of one- and two-ring aromatics

    NASA Astrophysics Data System (ADS)

    Benzler, Thorsten; Faust, Stephan; Dreier, Thomas; Schulz, Christof

    2015-12-01

    One- and two-ring aromatics such as toluene and naphthalene are frequently used molecular tracer species in laser-induced fluorescence (LIF) imaging diagnostics. Quantifying LIF signal intensities requires knowledge of the photo-physical processes that determine the fluorescence quantum yield. Collision-induced and intramolecular energy transfer processes in the excited electronic state closely interact under practical conditions. They can be separated through experiments at variable low pressures. Effective fluorescence lifetimes of gaseous toluene, 1,2,4-trimethylbenzene, anisole, naphthalene, and 1-methylnaphthalene diluted in CO2 were measured after picosecond laser excitation at 266 nm and time-resolved detection of fluorescence intensities. Measurements in an optically accessible externally heated cell between 296 and 475 K and 0.010-1 bar showed that effective fluorescence lifetimes generally decrease with temperature, while the influence of the bath-gas pressure depends on the respective target species and temperature. The results provide non-radiative and fluorescence rate constants and experimentally validate the effect of photo-induced cooling.

  9. The Switch from Low-Pressure Sodium to Light Emitting Diodes Does Not Affect Bat Activity at Street Lights

    PubMed Central

    Rowse, Elizabeth G.; Harris, Stephen; Jones, Gareth

    2016-01-01

    We used a before-after-control-impact paired design to examine the effects of a switch from low-pressure sodium (LPS) to light emitting diode (LED) street lights on bat activity at twelve sites across southern England. LED lights produce broad spectrum ‘white’ light compared to LPS street lights that emit narrow spectrum, orange light. These spectral differences could influence the abundance of insects at street lights and thereby the activity of the bats that prey on them. Most of the bats flying around the LPS lights were aerial-hawking species, and the species composition of bats remained the same after the switch-over to LED. We found that the switch-over from LPS to LED street lights did not affect the activity (number of bat passes), or the proportion of passes containing feeding buzzes, of those bat species typically found in close proximity to street lights in suburban environments in Britain. This is encouraging from a conservation perspective as many existing street lights are being, or have been, switched to LED before the ecological consequences have been assessed. However, lighting of all spectra studied to date generally has a negative impact on several slow-flying bat species, and LED lights are rarely frequented by these ‘light-intolerant’ bat species. PMID:27008274

  10. Population transfer and rapid passage effects in a low pressure gas using a continuous wave quantum cascade laser

    NASA Astrophysics Data System (ADS)

    McCormack, E. A.; Lowth, H. S.; Bell, M. T.; Weidmann, D.; Ritchie, G. A. D.

    2012-07-01

    A continuous wave quantum cascade laser (cw-QCL) operating at 10 μm has been used to record absorption spectra of low pressure samples of OCS in an astigmatic Herriott cell. As a result of the frequency chirp of the laser, the spectra show clearly the effects of rapid passage on the absorption line shape. At the low chirp rates that can be obtained with the cw-QCL, population transfer between rovibrational quantum states is predicted to be much more efficient than in typical pulsed QCL experiments. This optical pumping is investigated by solving the Maxwell Bloch equations to simulate the propagation of the laser radiation through an inhomogeneously broadened two-level system. The calculated absorption profiles show good quantitative agreement with those measured experimentally over a range of chirp rates and optical thicknesses. It is predicted that at a low chirp rate of 0.13 MHz ns-1, the population transfer between rovibrational quantum states is 12%, considerably more than that obtained at the higher chirp rates utilised in pulsed QCL experiments.

  11. Film analysis employing subtarget effect using 355 nm Nd-YAG laser-induced plasma at low pressure

    NASA Astrophysics Data System (ADS)

    Hedwig, Rinda; Budi, Wahyu Setia; Abdulmadjid, Syahrun Nur; Pardede, Marincan; Suliyanti, Maria Margaretha; Lie, Tjung Jie; Kurniawan, Davy Putra; Kurniawan, Koo Hendrik; Kagawa, Kiichiro; Tjia, May On

    2006-12-01

    The applicability of spectrochemical analysis for liquid and powder samples of minute amount in the form of thin film was investigated using ultraviolet Nd-YAG laser (355 nm) and low-pressure ambient air. A variety of organic samples such as commercial black ink usually used for stamp pad, ginseng extract, human blood, liquid milk and ginseng powder was prepared as film deposited on the surface of an appropriate hard substrate such as copper plate or glass slide. It was demonstrated that in all cases studied, good quality spectra were obtained with very low background and free from undesirable contamination by the substrate elements, featuring ppm or even sub-ppm sensitivity and worthy of application for quantitative analysis of organic samples. The proper preparation of the films was found to be crucial in achieving the high quality spectra. It was further shown that much inferior results were obtained when the atmospheric-pressure (101 kPa) operating condition of laser-induced breakdown spectroscopy or the fundamental wavelength of the Nd-YAG laser was employed due to the excessive or improper laser ablation process.

  12. Characterization of low-pressure microwave and radio frequency discharges in oxygen applying optical emission spectroscopy and multipole resonance probe

    NASA Astrophysics Data System (ADS)

    Steves, Simon; Styrnoll, Tim; Mitschker, Felix; Bienholz, Stefan; Nikita, Bibinov; Awakowicz, Peter

    2013-11-01

    Optical emission spectroscopy (OES) and multipole resonance probe (MRP) are adopted to characterize low-pressure microwave (MW) and radio frequency (RF) discharges in oxygen. In this context, both discharges are usually applied for the deposition of permeation barrier SiOx films on plastic foils or the inner surface of plastic bottles. For technological reasons the MW excitation is modulated and a continuous wave (cw) RF bias is used. The RF voltage produces a stationary low-density plasma, whereas the high-density MW discharge is pulsed. For the optimization of deposition process and the quality of the deposited barrier films, plasma conditions are characterized using OES and MRP. To simplify the comparison of applied diagnostics, both MW and RF discharges are studied separately in cw mode. The OES and MRP diagnostic methods complement each other and provide reliable information about electron density and electron temperature. In the MW case, electron density amounts to ne = (1.25 ± 0.26) × 1017 m-3, and kTe to 1.93 ± 0.20 eV, in the RF case ne = (6.8 ± 1.8)×1015 m-3 and kTe = 2.6 ± 0.35 eV. The corresponding gas temperatures are 760±40 K and 440±20 K.

  13. Experimental studies of the kinetics of the reaction of hydroxyl (OH) radicals with 3-methylfuran at low pressure

    NASA Astrophysics Data System (ADS)

    Liljegren, J. A.; Stevens, P. S.

    2011-12-01

    In addition to anthropogenic origins from fossil fuel combustion and biomass burning, 3-methylfuran is an atmospheric constituent of interest due to biogenic origins from the OH-initiated oxidation of isoprene. Although the yield of 3-methylfuran produced from the OH-initiated oxidation of isoprene is relatively small (approximately 5%), 3-methylfuran could contribute significantly to atmospheric chemistry due to the high emission rate of isoprene to the atmosphere. A knowledge of the rate constant for the reaction of OH radicals with 3-methylfuran under a variety of conditions is important for determining the overall impact of isoprene emissions on atmospheric chemistry. The rate constant for the reaction of OH with 3-methylfuran has been measured as a function of temperature at low pressure using discharge-flow techniques coupled with laser induced fluorescence detection of OH. These absolute measurements at room temperature will be compared to previous measurements using relative rate techniques. The measurements of the temperature dependence for this reaction are the first to be reported.

  14. An Approach to the Prototyping of an Optimized Limited Stroke Actuator to Drive a Low Pressure Exhaust Gas Recirculation Valve.

    PubMed

    Gutfrind, Christophe; Dufour, Laurent; Liebart, Vincent; Vannier, Jean-Claude; Vidal, Pierre

    2016-01-01

    The purpose of this article is to describe the design of a limited stroke actuator and the corresponding prototype to drive a Low Pressure (LP) Exhaust Gas Recirculation (EGR) valve for use in Internal Combustion Engines (ICEs). The direct drive actuator topology is an axial flux machine with two air gaps in order to minimize the rotor inertia and a bipolar surface-mounted permanent magnet in order to respect an 80° angular stroke. Firstly, the actuator will be described and optimized under constraints of a 150 ms time response, a 0.363 N·m minimal torque on an angular range from 0° to 80° and prototyping constraints. Secondly, the finite element method (FEM) using the FLUX-3D(®) software (CEDRAT, Meylan, France) will be used to check the actuator performances with consideration of the nonlinear effect of the iron material. Thirdly, a prototype will be made and characterized to compare its measurement results with the analytical model and the FEM model results. With these electromechanical behavior measurements, a numerical model is created with Simulink(®) in order to simulate an EGR system with this direct drive actuator under all operating conditions. Last but not least, the energy consumption of this machine will be estimated to evaluate the efficiency of the proposed EGR electromechanical system. PMID:27213398

  15. High temperature tensile and creep behaviour of low pressure plasma-sprayed Ni-Co-Cr-Al-Y coating alloy

    NASA Technical Reports Server (NTRS)

    Hebsur, M. G.; Miner, R. V.

    1986-01-01

    The high temperature tensile and creep behavior of low pressure plasma-sprayed plates of a typical Ni-Co-Cr-Al-Y alloy has been studied. From room temperature to 800 K, the Ni-Co-Cr-Al-Y alloy studied has nearly a constant low ductility and a high strength. At higher temperatures, it becomes weak and highly ductile. At and above 1123 K, the behavior is highly dependent on strain rate and exhibits classic superplastic characteristics with a high ductility at intermediate strain rates and a strain rate sensitivity of about 0.5. At either higher or lower strain rates, the ductility decreases and the strain rate sensitivities are about 0.2. In the superplastic deformation range, the activation energy for creep is 120 + or - 20 kJ/mol, suggesting a diffusion-aided grain boundary sliding mechanism. Outside the superplastic range, the activation energy for creep is calculated to be 290 + or - 20 kJ/mol.

  16. Experimental and numerical investigations of electron density in low-pressure dual-frequency capacitively coupled oxygen discharges

    SciTech Connect

    Liu, Jia; Wen, De-Qi; Liu, Yong-Xin; Gao, Fei; Lu, Wen-Qi; Wang, You-Nian

    2013-11-15

    The electron density is measured in low-pressure dual-frequency (2/60 MHz) capacitively coupled oxygen discharges by utilizing a floating hairpin probe. The dependence of electron density at the discharge center on the high frequency (HF) power, low frequency (LF) power, and gas pressure are investigated in detail. A (1D) particle-in-cell/Monte Carlo method is developed to calculate the time-averaged electron density at the discharge center and the simulation results are compared with the experimental ones, and general agreements are achieved. With increasing HF power, the electron density linearly increases. The electron density exhibits different changes with the LF power at different HF powers. At low HF powers (e.g., 30 W in our experiment), the electron density increases with increasing LF power while the electron density decreases with increasing LF power at relatively high HF powers (e.g., 120 W in our experiment). With increasing gas pressure the electron density first increases rapidly to reach a maximum value and then decreases slowly due to the combined effect of the production process by the ionization and the loss processes including the surface and volume losses.

  17. Hot Corrosion Behavior of Low-Pressure Cold-Sprayed CoNiCrAlY Coatings

    NASA Astrophysics Data System (ADS)

    Zhang, L. W.; Ning, X. J.; Lu, L.; Wang, Q. S.; Wang, L.

    2016-02-01

    CoNiCrAlY coatings were deposited by low-pressure cold spraying and pre-oxidized in a vacuum environment, and its hot corrosion behavior in pure Na2SO4 and 75 wt.% Na2SO4 + 25 wt.% NaCl salts was investigated. The pre-oxidation treatment resulted in the formation of a dense and continuous α-Al2O3 scale on the coating surface. After being corroded for 150 h at 900 °C, the pre-oxidized coating exhibited better corrosion resistance to both salts than the as-sprayed coating. The presence of preformed Al2O3 scale reduced the consumption rate of aluminum, by delaying the formation of internal oxides and sulfides and promoting the formation of a denser and more adherent Al2O3 scale. Moreover, we investigated the corrosion mechanism of cold-sprayed CoNiCrAlY coatings in the two salts and discussed the effect of the pre-oxidation treatment.

  18. 2D fluid-analytical simulation of electromagnetic effects in low pressure, high frequency electronegative capacitive discharges

    NASA Astrophysics Data System (ADS)

    Kawamura, E.; Lichtenberg, A. J.; Lieberman, M. A.; Marakhtanov, A. M.

    2016-06-01

    A fast 2D axisymmetric fluid-analytical multifrequency capacitively coupled plasma (CCP) reactor code is used to study center high nonuniformity in a low pressure electronegative chlorine discharge. In the code, a time-independent Helmholtz wave equation is used to solve for the capacitive fields in the linearized frequency domain. This eliminates the time dependence from the electromagnetic (EM) solve, greatly speeding up the simulations at the cost of neglecting higher harmonics. However, since the code allows up to three driving frequencies, we can add the two most important harmonics to the CCP simulations as the second and third input frequencies. The amplitude and phase of these harmonics are estimated by using a recently developed 1D radial nonlinear transmission line (TL) model of a highly asymmetric cylindrical discharge (Lieberman et al 2015 Plasma Sources Sci. Technol. 24 055011). We find that at higher applied frequencies, the higher harmonics contribute significantly to the center high nonuniformity due to their shorter plasma wavelengths.

  19. Acoustic performance of low pressure axial fan rotors with different blade chord length and radial load distribution

    NASA Astrophysics Data System (ADS)

    Carolus, Thomas

    The paper examines the acoustic and aerodynamic performance of low-pressure axial fan rotors with a hub/tip ratio of 0.45. Six rotors were designed for the same working point by means of the well-known airfoil theory. The condition of an equilibrium between the static pressure gradient and the centrifugal forces is maintained. All rotors have unequally spaced blades to diminish tonal noise. The rotors are tested in a short cylindrical housing without guide vanes. All rotors show very similar flux-pressure difference characteristics. The peak efficiency and the noise performance is considerably influenced by the chosen blade design. The aerodynamically and acoustically optimal rotor is the one with the reduced load at the hub and increased load in the tip region under satisfied equilibrium conditions. It runs at the highest aerodynamic efficiency, and its noise spectrum is fairly smooth. The overall sound pressure level of this rotor is up to 8 dB (A) lower compared to the other rotors under consideration.

  20. The use of biodegradable polymeric nanoparticles in combination with a low-pressure gene gun for transdermal DNA delivery.

    PubMed

    Lee, Po-Wei; Peng, Shu-Fen; Su, Chun-Jen; Mi, Fwu-Long; Chen, Hsin-Lung; Wei, Ming-Cheng; Lin, Hao-Jan; Sung, Hsing-Wen

    2008-02-01

    Gold particles have been used as a carrier for transdermal gene delivery, which may cause adverse side effects when accumulated. In this study, biodegradable nanoparticles, composed of chitosan (CS) and poly-gamma-glutamic acid (gamma-PGA), were prepared by an ionic-gelation method for transdermal DNA delivery (CS/gamma-PGA/DNA) using a low-pressure gene gun. The conventional CS/DNA without the incorporation of gamma-PGA was used as a control. Small-angle X-ray scattering (SAXS) was used to examine the internal structures of test nanoparticles, while identification of their constituents was conducted by Fourier transformed infrared (FT-IR) spectroscopy. The CS/gamma-PGA/DNA were spherical in shape with a relatively homogeneous size distribution. In contrast, CS/DNA had a heterogeneous size distribution with a donut, rod or pretzel shape. Both test nanoparticles were able to effectively retain the encapsulated DNA and protect it from nuclease degradation. As compared with CS/DNA, CS/gamma-PGA/DNA improved their penetration depth into the mouse skin and enhanced gene expression. These observations may be attributed to the fact that CS/gamma-PGA/DNA were more compact in their internal structures and had a greater density than their CS/DNA counterparts, thus having a larger momentum to penetrate into the skin barrier. The results revealed that CS/gamma-PGA/DNA may substitute gold particles as a DNA carrier for transdermal gene delivery. PMID:18001831