Analysis of the wind tunnel test of a tilt rotor power force model

NASA Technical Reports Server (NTRS)

Marr, R. L.; Ford, D. G.; Ferguson, S. W.

1974-01-01

Two series of wind tunnel tests were made to determine performance, stability and control, and rotor wake interaction on the airframe, using a one-tenth scale powered force model of a tilt rotor aircraft. Testing covered hover (IGE/OCE), helicopter, conversion, and airplane flight configurations. Forces and moments were recorded for the model from predetermined trim attitudes. Control positions were adjusted to trim flight (one-g lift, pitching moment and drag zero) within the uncorrected test data balance accuracy. Pitch and yaw sweeps were made about the trim attitudes with the control held at the trimmed settings to determine the static stability characteristics. Tail on, tail off, rotors on, and rotors off configurations were testes to determine the rotor wake effects on the empennage. Results are presented and discussed.

Charts for Estimating Tail-rotor Contribution to Helicopter Directional Stability and Control in Low-Speed Flight

NASA Technical Reports Server (NTRS)

Amer, Kenneth B; Gessow, Alfred

1955-01-01

Theoretically derived charts and equations are presented by which tail-rotor design studies of directional trim and control response at low forward speed can be conveniently made. The charts can also be used to obtain the main-rotor stability derivatives of thrust with respect to collective pitch and angle of attack at low forward speeds. The use of the charts and equations for tail-rotor design studies is illustrated. Comparisons between theoretical and experimental results are presented. The charts indicate, and flight tests confirm, that the region of vortex roughness which is familiar for the main rotor is also encountered by the tail rotor and that prolonged operation at the corresponding flight conditions would be difficult.

Aeroelastic characteristics of the AH-64 bearingless tail rotor

NASA Technical Reports Server (NTRS)

Banerjee, D.

1988-01-01

The results of a wind tunnel test program to determine the performance loads and dynamic characteristics of the Composite Flexbeam Tail Rotor (CFTR) for the AH-64 Advanced Attack Helicopter are reported. The CFTR uses an elastomeric shear attachment of the flexbeam to the hub to provide soft-inplane S-mode and stiff-inplane C-mode configuration. The properties of the elastomer were selected for proper frequency placement and scale damping of the inplane S-mode. Kinematic pitch-lag coupling was introduced to provide the first cyclic inplane C-mode damping at high collective pitch. The CFTR was tested in a wind tunnel over the full slideslip envelop of the AH-64. It is found that the rotor was aeroelastically stable throughout the complete collective pitch range and up to rotor speeds of 1403 rpm. The dynamic characteristics of the rotor were found to be satisfactory at all pitch angles and rotor speeds of the tunnel tests. The design characteristics of the rotor which permit the high performance characteristics are discussed. Several schematic drawings and photographs of the rotor are provided.

Separation of Main and Tail Rotor Noise Sources from Ground-Based Acoustic Measurements Using Time-Domain De-Dopplerization

NASA Technical Reports Server (NTRS)

Greenwood, Eric II; Schmitz, Fredric H.

2009-01-01

A new method of separating the contributions of helicopter main and tail rotor noise sources is presented, making use of ground-based acoustic measurements. The method employs time-domain de-Dopplerization to transform the acoustic pressure time-history data collected from an array of ground-based microphones to the equivalent time-history signals observed by an array of virtual inflight microphones traveling with the helicopter. The now-stationary signals observed by the virtual microphones are then periodically averaged with the main and tail rotor once per revolution triggers. The averaging process suppresses noise which is not periodic with the respective rotor, allowing for the separation of main and tail rotor pressure time-histories. The averaged measurements are then interpolated across the range of directivity angles captured by the microphone array in order to generate separate acoustic hemispheres for the main and tail rotor noise sources. The new method is successfully applied to ground-based microphone measurements of a Bell 206B3 helicopter and demonstrates the strong directivity characteristics of harmonic noise radiation from both the main and tail rotors of that helicopter.

Conspicuity assessment of selected propeller and tail rotor paint schemes.

DOT National Transportation Integrated Search

1978-08-01

An investigation was conducted to rank the conspicuity of three paint schemes for airplane propellers and two schemes tail rotor blades previously recommended by the U.S. military and British Civil Aviation Authority. Thirty volunteer subjects with n...

Comparative lubrication studies of OH-58A tail rotor drive shaft bearings

NASA Technical Reports Server (NTRS)

Dietrich, M. W.; Parker, R. J.; Zaretsky, E. V.

1972-01-01

Comparative lubrication tests were run with OH-58A helicopter tail rotor drive shaft bearings. The tests were run in an outdoor environment with ambient temperatures ranging from 10 to 75 F. Dust was periodically applied to the bearings to simulate field conditions. The cause of bearing failure was associated with dust penetration. Rotor shaft failure was found to be caused by the shaft rotating in the standard rubber collar due to seizure of the bearings. Bearings with a positive rubbing seal having a MIL-G-81322 grease produced lives greater than with bearings having labyrinth seals and a mineral oil paste lubricant. An elongated collar prevented failure of the rotor shaft during bearing seizure. In a limited test, installation of tail boom shrouds over the bearings which excluded dust and water resulted in bearing lives in excess of 1800 hours or 1200 hours greater than the current 600 hours TBO, regardless of the lubricant-bearing combination used.

Flight investigation of the effect of tail boom strakes on helicopter directional control

NASA Technical Reports Server (NTRS)

Kelly, Henry L.; Crowell, Cynthia A.; Yenni, Kenneth R.; Lance, Michael B.

1993-01-01

A joint U.S. Army/NASA flight investigation was conducted utilizing a single-rotor helicopter to determine the effectiveness of horizontally mounted tail boom strakes on directional controllability and tail rotor power during low-speed, crosswind operating conditions. Three configurations were investigated: (1) baseline (strakes off), (2) single strake (strake at upper shoulder on port side of boom), and (3) double strake (upper strake plus a lower strake on same side of boom). The strakes were employed as a means to separate airflow over the tail boom and change fuselage yawing moments in a direction to improve the yaw control margin and reduce tail rotor power. Crosswind data were obtained in 5-knot increments of airspeed from 0 to 35 knots and in 30 deg increments of wind azimuth from 0 deg to 330 deg. At the most critical wind azimuth and airspeed in terms of tail rotor power, the strakes improved the pedal margin by 6 percent of total travel and reduced tail rotor power required by 17 percent. The increase in yaw control and reduction in tail rotor power offered by the strakes can expand the helicopter operating envelope in terms of gross weight and altitude capability. The strakes did not affect the flying qualities of the vehicle at airspeeds between 35 and 100 knots.

Performance and loads data from an outdoor hover test of a Lynx tail rotor

NASA Technical Reports Server (NTRS)

Signor, David B.; Yamauchi, Gloria K.; Smith, Charles A.; Hagen, Martin J.

1989-01-01

A Lynx tail rotor was tested in hover at the Outdoor Aerodynamic Research Facility at NASA Ames Research Center. The test objectives were to measure the isolated rotor performance to provide a baseline for subsequent testing, and to operate the rotor throughout the speed and collective envelope before testing in the NFAC 40- by 80-Foot Wind Tunnel. Rotor forces and blade bending moments were measured at ambient wind conditions from zero to 6.23 m/sec. The test envelope was limited to rotor speeds of 1550 to 1850 rpm and minus 13 deg to plus 20 deg of blade collective pitch. The isolated rotor performance and blade loads data are presented.

Induced Power of the Helicopter Rotor

NASA Technical Reports Server (NTRS)

Ormiston, Robert A.

2004-01-01

A simplified rotor model was used to explore fundamental behavior of lifting rotor induced power at moderate and high advance ratios. Several rotor inflow theories, including dynamic inflow theory and prescribed-wake vortex theory, together with idealized notional airfoil stall models were employed. A number of unusual results were encountered at high advance ratios including trim control reversal and multiple trim solutions. Significant increases in rotor induced power (torque) above the ideal minimum were observed for moderately high advance ratio. Very high induced power was observed near and above unity advance ratio. The results were sensitive to the stall characteristics of the airfoil models used. An equivalent wing analysis was developed to determine induced power from Prandtl lifting line theory and help interpret the rotor induced power behavior in terms of the spanwise airload distribution. The equivalent wing approach was successful in capturing the principal variations of induced power for different configurations and operating conditions. The effects blade root cutout were found to have a significant effect on rotor trim and induced power at high advance ratios.

An experimental investigation of the chopping of helicopter main rotor tip vortices by the tail rotor. Part 2: High speed photographic study

NASA Technical Reports Server (NTRS)

Cary, Charles M.

1987-01-01

The interaction of a free vortex and a rotor was recorded photographically using oil smoke and stroboscopic illumination. The incident vortex is normal to the plane of the rotor and crosses the rotor plane. This idealized aerodynamic experiment most nearly corresponds to helicopter flight conditions in which a tip vortex from the main rotor is incident upon the tail rotor while hovering. The high speed photographs reveal important features not observed using conventional photography where the image is the time average of varying instantaneous images. Most prominent is the strong interaction between the rotor tip vortex system and the incident vortex, resulting in the roll-up of the incident vortex around the (stronger) tip vortices and the resulting rapid destabilization of the deformed incident vortex. The viscous interaction is clearly shown also. Other forms of instabilities or wave-like behavior may be apparent from further analysis of the photographs.

Detailed Aerodynamic Analysis of a Shrouded Tail Rotor Using an Unstructured Mesh Flow Solver

NASA Astrophysics Data System (ADS)

Lee, Hee Dong; Kwon, Oh Joon

The detailed aerodynamics of a shrouded tail rotor in hover has been numerically studied using a parallel inviscid flow solver on unstructured meshes. The numerical method is based on a cell-centered finite-volume discretization and an implicit Gauss-Seidel time integration. The calculation was made for a single blade by imposing a periodic boundary condition between adjacent rotor blades. The grid periodicity was also imposed at the periodic boundary planes to avoid numerical inaccuracy resulting from solution interpolation. The results were compared with available experimental data and those from a disk vortex theory for validation. It was found that realistic three-dimensional modeling is important for the prediction of detailed aerodynamics of shrouded rotors including the tip clearance gap flow.

HARP model rotor test at the DNW. [Hughes Advanced Rotor Program

NASA Technical Reports Server (NTRS)

Dawson, Seth; Jordan, David; Smith, Charles; Ekins, James; Silverthorn, Lou

1989-01-01

Data from a test of a dynamically scaled model of the Hughes Advanced Rotor Program (HARP) bearingless model main rotor and 369K tail rotor are reported. The history of the HARP program and its goals are reviewed, and the main and tail rotor models are described. The test facilities and instrumentation are described, and wind tunnel test data are presented on hover, forward flight performance, and blade-vortex interaction. Performance data, acoustic data, and dynamic data from near field/far field and shear layer studies are presented.

Development in helicopter tail boom strake applications in the US

NASA Technical Reports Server (NTRS)

Wilson, John C.; Kelley, Henry L.; Donahue, Cynthia C.; Yenni, Kenneth R.

1988-01-01

The use of a strake or spoiler on a helicopter tail boom to beneficially change helicopter tail boom air loads was suggested in the United States in 1975. The anticipated benefits were a change of tail boom loads to reduce required tail rotor thrust and power and improve directional control. High tail boom air loads experienced by the YAH-64 and described in 1978 led to a wind tunnel investigation of the usefullness of strakes in altering such loads on the AH-64, UH-60, and UH-1 helicopters. The wind tunnel tests of 2-D cross sections of the tail boom of each demonstrated that a strake or strakes would be effective. Several limited test programs with the U.S. Army's OH-58A, AH-64, and UH-60A were conducted which showed the effects of strakes were modest for those helicopters. The most recent flight test program, with a Bell 204B, disclosed that for the 204B the tail boom strake or strakes would provide more than a modest improvement in directional control and reduction in tail rotor power.

Unconventional Rotor Power Response to Yaw Error Variations

DOE PAGES

Schreck, S. J.; Schepers, J. G.

2014-12-16

Continued inquiry into rotor and blade aerodynamics remains crucial for achieving accurate, reliable prediction of wind turbine power performance under yawed conditions. To exploit key advantages conferred by controlled inflow conditions, we used EU-JOULE DATA Project and UAE Phase VI experimental data to characterize rotor power production under yawed conditions. Anomalies in rotor power variation with yaw error were observed, and the underlying fluid dynamic interactions were isolated. Unlike currently recognized influences caused by angled inflow and skewed wake, which may be considered potential flow interactions, these anomalies were linked to pronounced viscous and unsteady effects.

Computational Study of Flow Interactions in Coaxial Rotors

NASA Technical Reports Server (NTRS)

Yoon, Seokkwan; Lee, Henry C.; Pulliam, Thomas H.

2016-01-01

Although the first idea of coaxial rotors appeared more than 150 years ago, most helicopters have used single main-rotor/tail-rotor combination. Since reactive moments of coaxial rotors are canceled by contra-rotation, no tail rotor is required to counter the torque generated by the main rotor. Unlike the single main rotor design that distributes power to both main and tail rotors, all of the power for coaxial rotors is used for vertical thrust. Thus, no power is wasted for anti-torque or directional control. The saved power helps coaxial rotors reach a higher hover ceiling than single rotor helicopters. Another advantage of coaxial rotors is that the overall rotor diameter can be reduced for a given vehicle gross weight because each rotor provides a maximum contribution to vertical thrust to overcome vehicle weight. However, increased mechanical complexity of the hub has been one of the challenges for manufacturing coaxial rotorcraft. Only the Kamov Design Bureau of Russia had been notably successful in production of coaxial helicopters until Sikorsky built X2, an experimental compound helicopter. Recent developments in unmanned aircraft systems and high-speed rotorcraft have renewed interest in the coaxial configuration. Multi-rotors are frequently used for small electric unmanned rotorcraft partly due to mechanical simplicity. The use of multiple motors provides redundancy as well as cost-efficiency. The multi-rotor concept has rarely been used until recently because of its inherent stability and control problems. However, advances in inexpensive electronic flight control systems have opened the floodgates for small drones using multirotors. Coaxial rotors have started to appear in some multi-rotor configurations. Small coaxial rotors have often been designed using a hundred year old approach that is "sketch, build, fly, and iterate." In that approach, there is no systematic way to explore trade-offs or determine logical next steps. It is neither possible to

V/STOL tilt rotor aircraft study. Volume 10: Performance and stability test of A 1-14.622 Froude scaled Boeing Vertol Model 222 tilt rotor aircraft (Phase 1)

NASA Technical Reports Server (NTRS)

Mchugh, F. J.; Eason, W.; Alexander, H. R.; Mutter, H.

1973-01-01

Wind tunnel test data obtained from a 1/4.622 Froude scale Boeing Model 222 with a full span, two prop, tilt rotor, powered model in the Boeing V/STOL wind tunnel are reported. Data were taken in transition and cruise flight conditions and include performance, stability and control and blade loads information. The effects of the rotors, tail surfaces and airframe on the performance and stability are isolated as are the effects of the airframe on the rotors.

Rotor-Fuselage Interaction: Analysis and Validation with Experiment

NASA Technical Reports Server (NTRS)

Berry, John D.; Bettschart, Nicolas

1997-01-01

The problem of rotor-fuselage aerodynamic interaction has to be considered in industry applications from various aspects. First, in order to increase helicopter speed and reduce operational costs, rotorcraft tend to be more and more compact, with a main rotor closer to the fuselage surface. This creates significant perturbations both on the main rotor and on the fuselage, including steady and unsteady effects due to blade and wake passage and perturbed inflow at the rotor disk. Furthermore,the main rotor wake affects the tail boom, empennage and anti-torque system. This has important consequences for helicopter control and vibrations at low speeds and also on tail rotor acoustics (main rotor wake-tail rotor interactions). This report describes the US Army-France MOD cooperative work on this problem from both the theoretical and experimental aspects. Using experimental 3D velocity field and fuselage surface pressure measurements, three codes that model the interactions of a helicopter rotor with a fuselage are compared. These comparisons demonstrate some of the strengths and weaknesses of current models for the combined rotor-fuselage analysis.

T700 power turbine rotor multiplane/multispeed balancing demonstration

NASA Technical Reports Server (NTRS)

Burgess, G.; Rio, R.

1979-01-01

Research was conducted to demonstrate the ability of influence coefficient based multispeed balancing to control rotor vibration through bending criticals. Rotor dynamic analyses were conducted of the General Electric T700 power turbine rotor. The information was used to generate expected rotor behavior for optimal considerations in designing a balance rig and a balance technique. The rotor was successfully balanced 9500 rpm. Uncontrollable coupling behavior prevented observations through the 16,000 rpm service speed. The balance technique is practical and with additional refinement it can meet production standards.

Performance and power regulation characteristics of two aileron-controlled rotors and a pitchable tip-controlled rotor on the Mod-O turbine

NASA Technical Reports Server (NTRS)

Corrigan, Robert D.; Ensworth, Clinton B. F., III; Miller, Dean R.

1987-01-01

Tests were conducted on the DOE/NASA mod-0 horizontal axis wind turbine to compare and evaluate the performance and the power regulation characteristics of two aileron-controlled rotors and a pitchable tip-controlled rotor. The two aileron-controlled rotor configurations used 20 and 38 percent chord ailerons, while the tip-controlled rotor had a pitchable blade tip. The ability of the control surfaces to regulate power was determined by measuring the change in power caused by an incremental change in the deflection angle of the control surface. The data shows that the change in power per degree of deflection angle for the tip-controlled rotor was four times the corresponding value for the 2- percent chord ailerons. The root mean square power deviation about a power setpoint was highest for the 20 percent chord aileron, and lowest for the 38 percent chord aileron.

Analysis and Prediction of Ice Shedding for a Full-Scale Heated Tail Rotor

NASA Technical Reports Server (NTRS)

Kreeger, Richard E.; Work, Andrew; Douglass, Rebekah; Gazella, Matthew; Koster, Zakery; Turk, Jodi

2016-01-01

When helicopters are to fly in icing conditions, it is necessary to consider the possibility of ice shed from the rotor blades. In 2013, a series of tests were conducted on a heated tail rotor at NASA Glenn's Icing Research Tunnel (IRT). The tests produced several shed events that were captured on camera. Three of these shed events were captured at a sufficiently high frame rate to obtain multiple images of the shed ice in flight that had a sufficiently long section of shed ice for analysis. Analysis of these shed events is presented and compared to an analytical Shedding Trajectory Model (STM). The STM is developed and assumes that the ice breaks off instantly as it reaches the end of the blade, while frictional and viscous forces are used as parameters to fit the STM. The trajectory of each shed is compared to that predicted by the STM, where the STM provides information of the shed group of ice as a whole. The limitations of the model's underlying assumptions are discussed in comparison to experimental shed events.

Rotor dynamic considerations for large wind power generator systems

NASA Technical Reports Server (NTRS)

Ormiston, R. A.

1973-01-01

Successful large, reliable, low maintenance wind turbines must be designed with full consideration for minimizing dynamic response to aerodynamic, inertial, and gravitational forces. Much of existing helicopter rotor technology is applicable to this problem. Compared with helicopter rotors, large wind turbines are likely to be relatively less flexible with higher dimensionless natural frequencies. For very large wind turbines, low power output per unit weight and stresses due to gravitational forces are limiting factors. The need to reduce rotor complexity to a minimum favors the use of cantilevered (hingeless) rotor configurations where stresses are relieved by elastic deformations.

An unsteady helicopter rotor: Fuselage interaction analysis

NASA Technical Reports Server (NTRS)

Lorber, Peter F.; Egolf, T. Alan

1988-01-01

A computational method was developed to treat unsteady aerodynamic interactions between a helicopter rotor, wake, and fuselage and between the main and tail rotors. An existing lifting line prescribed wake rotor analysis and a source panel fuselage analysis were coupled and modified to predict unsteady fuselage surface pressures and airloads. A prescribed displacement technique is used to position the rotor wake about the fuselage. Either a rigid blade or an aeroelastic blade analysis may be used to establish rotor operating conditions. Sensitivity studies were performed to determine the influence of the wake fuselage geometry on the computation. Results are presented that describe the induced velocities, pressures, and airloads on the fuselage and on the rotor. The ability to treat arbitrary geometries is demonstrated using a simulated helicopter fuselage. The computational results are compared with fuselage surface pressure measurements at several locations. No experimental data was available to validate the primary product of the analysis: the vibratory airloads on the entire fuselage. A main rotor-tail rotor interaction analysis is also described, along with some hover and forward flight.

Power method for calculating the far acoustic field of the helicopter lift rotor

NASA Astrophysics Data System (ADS)

Samokhin, V. F.

2011-05-01

A semiempirical method for calculating the far acoustic field of the lift rotor of a helicopter operating in the regime of oblique flow over it is described. The basic parametric relations for the acoustic radiation power of rotor noise components have been obtained on the basis of the Lamb idea that vortex-free motion arises under the action of a periodic force on an infinitely small volume of the medium. All sources of lift rotor noise are subdivided into two groups pertaining, respectively, to the inductive and profile parts of the total power supplied to the rotor. A comparison has been made between the results of calculation of the harmonic components of lift rotor noise made on the basis of the power method and the experimental data for the Mi-28 helicopter.

Open Rotor Aeroacoustic Installation Effects for Conventional and Unconventional Airframes

NASA Technical Reports Server (NTRS)

Czech, Michael J.; Thomas, Russell H.

2013-01-01

As extensive experimental campaign was performed to study the aeroacoustic installation effects of an open rotor with respect to both a conventional tube and wing type airframe and an unconventional hybrid wing body airframe. The open rotor rig had two counter rotating rows of blades each with eight blades of a design originally flight tested in the 1980s. The aeroacoustic installation effects measured in an aeroacoustic wind tunnel included those from flow effects due to inflow distortion or wake interaction and acoustic propagation effects such as shielding and reflection. The objective of the test campaign was to quantify the installation effects for a wide range of parameters and configurations derived from the two airframe types. For the conventional airframe, the open rotor was positioned in increments in front of and then over the main wing and then in positions representative of tail mounted aircraft with a conventional tail, a T-tail and a U-tail. The interaction of the wake of the open rotor as well as acoustic scattering results in an increase of about 10 dB when the rotor is positioned in front of the main wing. When positioned over the main wing a substantial amount of noise reduction is obtained and this is also observed for tail-mounted installations with a large U-tail. For the hybrid wing body airframe, the open rotor was positioned over the airframe along the centerline as well as off-center representing a twin engine location. A primary result was the documentation of the noise reduction from shielding as a function of the location of the open rotor upstream of the trailing edge of the hybrid wing body. The effects from vertical surfaces and elevon deflection were also measured. Acoustic lining was specially designed and inserted flush with the elevon and airframe surface, the result was an additional reduction in open rotor noise propagating to the far field microphones. Even with the older blade design used, the experiment provided

Aeroacoustic flowfield and acoustics of a model helicopter tail rotor at high advance ratio

NASA Technical Reports Server (NTRS)

Shenoy, Rajarama K.

1989-01-01

Some results, relevant to rotorcraft noise generation process at high advance ratio, are presented in this paper from schlieren flow visualization and acoustic tests of a model tail rotor. The measured in-plane noise trends are consistent with the growth of the tip supersonic region seen in the schlieren visuals. Schlieren flow visuals reveal a propagating pressure wave in the second quadrant. Simultaneously measured acoustic data and the results of two-dimensional transonic Blade-Vortex Interaction analysis code ATRAN-2 indicate that this pressure wave is attributable to BVI activity in the first quadrant. This paper establishes that the transonic Blade-Vortex Interactions contribute to noise at high advance ratio level flight conditions.

RSRA vertical drag test report. [rotor systems research aircraft

NASA Technical Reports Server (NTRS)

Flemming, R. J.

1981-01-01

The Rotor Systems Research Aircraft (RSRA), because of its ability to measure rotor loads, was used to conduct an experiment to determine vertical drag, tail rotor blockage, and thrust augmentation as affected by ground clearance and flight velocity. The RSRA was flown in the helicopter configuration at speeds from 0 to 15 knots for wheel heights from 5 to 150 feet, and to 60 knots out of ground effect. The vertical drag trends in hover, predicted by theory and shown in model tests, were generally confirmed. The OGE hover vertical drag is 4.0 percent, 1.1 percent greater than predicted. The vertical drag decreases rapidly as wheel height is reduced, and is zero at a wheel height of 6 feet. The vertical drag also decreases with forward speed, approaching zero at sixty knots. The test data show the effect of wheel height and forward speed on thrust, gross weight capability, and power, and provide the relationships for power and collective pitch at constant gross weight required for the simulation of helicopter takeoffs and landings.

14 CFR 29.547 - Main and tail rotor structure.

Code of Federal Regulations, 2012 CFR

2012-01-01

... AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Strength Requirements Main Component... designed to withstand the limit torque at any rotational speed, including zero. In addition: (1) The limit... structure, in either direction, by the rotor drive or by sudden application of the rotor brake; and (ii) For...

14 CFR 29.547 - Main and tail rotor structure.

Code of Federal Regulations, 2013 CFR

2013-01-01

... AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Strength Requirements Main Component... designed to withstand the limit torque at any rotational speed, including zero. In addition: (1) The limit... structure, in either direction, by the rotor drive or by sudden application of the rotor brake; and (ii) For...

14 CFR 29.547 - Main and tail rotor structure.

Code of Federal Regulations, 2011 CFR

2011-01-01

... AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Strength Requirements Main Component... designed to withstand the limit torque at any rotational speed, including zero. In addition: (1) The limit... structure, in either direction, by the rotor drive or by sudden application of the rotor brake; and (ii) For...

14 CFR 29.547 - Main and tail rotor structure.

Code of Federal Regulations, 2010 CFR

2010-01-01

... AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Strength Requirements Main Component... designed to withstand the limit torque at any rotational speed, including zero. In addition: (1) The limit... structure, in either direction, by the rotor drive or by sudden application of the rotor brake; and (ii) For...

14 CFR 29.547 - Main and tail rotor structure.

Code of Federal Regulations, 2014 CFR

2014-01-01

... AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Strength Requirements Main Component... designed to withstand the limit torque at any rotational speed, including zero. In addition: (1) The limit... structure, in either direction, by the rotor drive or by sudden application of the rotor brake; and (ii) For...

Hybrid Configuration of Darrieus and Savonius Rotors for Stand-alone Power Systems

NASA Astrophysics Data System (ADS)

Wakui, Tetsuya; Tanzawa, Yoshiaki; Hashizume, Takumi; Nagao, Toshio

The suitable hybrid configuration of Darrieus lift-type and Savonius drag-type rotors for stand-alone wind turbine-generator systems is discussed using our dynamic simulation model. Two types of hybrid configurations are taken up: Type-A installs the Savonius rotor inside the Darrieus rotor and Type-B installs the Savonius rotor outside the Darrieus rotor. The computed results of the output characteristics and the dynamic behaviors of the system operated at the maximum power coefficient points show that Type-A, which has fine operating behavior to wind speed changes and can be compactly designed because of a shorter rotational shaft, is an effective way for self-controlled stand-alone small-scale systems.

A Survey of Theoretical and Experimental Coaxial Rotor Aerodynamic Research

NASA Technical Reports Server (NTRS)

Coleman, Colin P.

1997-01-01

The recent appearance of the Kamov Ka-50 helicopter and the application of coaxial rotors to unmanned aerial vehicles have renewed international interest in the coaxial rotor configuration. This report addresses the aerodynamic issues peculiar to coaxial rotors by surveying American, Russian, Japanese, British, and German research. (Herein, 'coaxial rotors' refers to helicopter, not propeller, rotors. The intermeshing rotor system was not investigated.) Issues addressed are separation distance, load sharing between rotors, wake structure, solidity effects, swirl recovery, and the effects of having no tail rotor. A general summary of the coaxial rotor configuration explores the configuration's advantages and applications.

Numerical Modeling of Dependence of Separative Power of the Gas Centrifuge on the Length of Rotor

NASA Astrophysics Data System (ADS)

Bogovalov, S. V.; Borisevich, V. D.; Borman, V. D.; Tronin, I. V.; Tronin, V. N.

Numerical modelling and optimization of the gas flow and isotope separation in the Iguasu gas centrifuge (GC) for uranium enrichment have been performed for different lengths of the rotor. The calculations show that the specific separative power of the GC reduces with the length of the rotor. We show that the reduction of the specific separative power is connected with the growth of the pressure in the optimal regime and corresponding growth of temperature to prevent the working gas sublimation. The specific separative power remains constant with the growth of the rotor length provided that the temperature of the rotor is taken to be constant.

Application of the wide-field shadowgraph technique to rotor wake visualization

NASA Technical Reports Server (NTRS)

Norman, Thomas R.; Light, Jeffrey S.

1989-01-01

The wide field shadowgraph technique is reviewed along with its application to the visualization of rotor wakes. In particular, current experimental methods and data reduction requirements are discussed. Sample shadowgraphs are presented. These include shadowgraphs of model-scale helicopter main rotors and tilt rotors, and full scale tail rotors, both in hover and in forward flight.

Definition and analytical evaluation of a power management system for tilt-rotor aircraft

NASA Technical Reports Server (NTRS)

Morris, J. J.; Alexander, H. R.

1978-01-01

The paper reviews the special design criteria which apply to power management in a tilt-rotor aircraft. These include the need for accurate and fast control of rpm and thrust, while accounting for the dynamic interactions between rotor systems caused by cross-shafting and aircraft lateral/directional response. The power management system is also required to provide acceptable high speed sensitivity to longitudinal turbulence. It is shown that the criteria can best be met using a single governor adjusting the collective pitch by an amount proportional to a combination of the average rpm and the integral of the average rpm of the two rotors. This system is evaluated and compared with other candidate systems in hover and cruise flight.

Power law tails in phylogenetic systems.

PubMed

Qin, Chongli; Colwell, Lucy J

2018-01-23

Covariance analysis of protein sequence alignments uses coevolving pairs of sequence positions to predict features of protein structure and function. However, current methods ignore the phylogenetic relationships between sequences, potentially corrupting the identification of covarying positions. Here, we use random matrix theory to demonstrate the existence of a power law tail that distinguishes the spectrum of covariance caused by phylogeny from that caused by structural interactions. The power law is essentially independent of the phylogenetic tree topology, depending on just two parameters-the sequence length and the average branch length. We demonstrate that these power law tails are ubiquitous in the large protein sequence alignments used to predict contacts in 3D structure, as predicted by our theory. This suggests that to decouple phylogenetic effects from the interactions between sequence distal sites that control biological function, it is necessary to remove or down-weight the eigenvectors of the covariance matrix with largest eigenvalues. We confirm that truncating these eigenvectors improves contact prediction.

An Analysis of the Autorotative Performance of a Helicopter Powered by Rotor-Tip Jet Units

NASA Technical Reports Server (NTRS)

Gessow, Alfred

1950-01-01

The autorotative performance of an assumed helicopter was studied to determine the effect of inoperative jet units located at the rotor-blade tip on the helicopter rate of descent. For a representative ramjet design, the effect of the jet drag is to increase the minimum rate of descent of the helicopter from about 1,OO feet per minute to 3,700 feet per minute when the rotor is operating at a tip speed of approximately 600 feet per second. The effect is less if the rotor operates at lower tip speeds, but the rotor kinetic energy and the stall margin available for the landing maneuver are then reduced. Power-off rates of descent of pulse-jet helicopters would be expected to be less than those of ramjet. helicopters because pulse jets of current design appear to have greater ratios of net power-on thrust to power-off, drag than currently designed rain jets. Iii order to obtain greater accuracy in studies of autorotative performance, calculations in'volving high power-off rates of descent should include the weight-supporting effect of the fuselage parasite-drag force and the fact that the rotor thrust does not equal the weight of the helicopter.

Ice Shapes on a Tail Rotor

NASA Technical Reports Server (NTRS)

Kreeger, Richard E.; Tsao, Jen-Ching

2014-01-01

Testing of a thermally-protected helicopter rotor in the Icing Research Tunnel (IRT) was completed. Data included inter-cycle and cold blade ice shapes. Accreted ice shapes were thoroughly documented, including tracing, scanning and photographing. This was the first time this scanning capability was used outside of NASA. This type of data has never been obtained for a rotorcraft before. This data will now be used to validate the latest generation of icing analysis tools.

Structural analysis of wind turbine rotors for NSF-NASA Mod-0 wind power system

NASA Technical Reports Server (NTRS)

Spera, D. A.

1976-01-01

Preliminary estimates are presented of vibratory loads and stresses in hingeless and teetering rotors for the proposed NSF-NASA Mod-0 wind power system. Preliminary blade design utilizes a tapered tubular aluminum spar which supports nonstructural aluminum ribs and skin and is joined to the rotor hub by a steel shank tube. Stresses in the shank of the blade are calculated for static, rated, and overload operating conditions. Blade vibrations were limited to the fundamental flapping modes, which were elastic cantilever bending for hingeless rotor blades and rigid-body rotation for teetering rotor blades. The MOSTAB-C computer code was used to calculate aerodynamic and mechanical loads. The teetering rotor has substantial advantages over the hingeless rotor with respect to shank stresses, fatigue life, and tower loading. The hingeless rotor analyzed does not appear to be structurally stable during overloads.

Rotor performance characteristics from an aeroacoustic helicopter wind-tunnel test program

NASA Technical Reports Server (NTRS)

Hoad, D. R.; Elliott, J. W.; Orie, N. M.

1986-01-01

An investigation of helicopter rotor noise at model scale was conducted in the Langley 4 by 7 meter tunnel. The program described was the first of a planned three-phase project whose purpose was to examine the characteristic noise mechanism involved in main rotor/tail rotor interaction noise. This first phase was conducted with a main rotor only, in order to identify the characteristic noise generated by only the main rotor. The aerodynamic operating conditions of the rotor system were defined during the test. The acoustic data were properly referenced.

Power-Smoothing Scheme of a DFIG Using the Adaptive Gain Depending on the Rotor Speed and Frequency Deviation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Hyewon; Hwang, Min; Muljadi, Eduard

In an electric power grid that has a high penetration level of wind, the power fluctuation of a large-scale wind power plant (WPP) caused by varying wind speeds deteriorates the system frequency regulation. This paper proposes a power-smoothing scheme of a doubly-fed induction generator (DFIG) that significantly mitigates the system frequency fluctuation while preventing over-deceleration of the rotor speed. The proposed scheme employs an additional control loop relying on the system frequency deviation that operates in combination with the maximum power point tracking control loop. To improve the power-smoothing capability while preventing over-deceleration of the rotor speed, the gain ofmore » the additional loop is modified with the rotor speed and frequency deviation. The gain is set to be high if the rotor speed and/or frequency deviation is large. In conclusion, the simulation results based on the IEEE 14-bus system clearly demonstrate that the proposed scheme significantly lessens the output power fluctuation of a WPP under various scenarios by modifying the gain with the rotor speed and frequency deviation, and thereby it can regulate the frequency deviation within a narrow range.« less

Power-Smoothing Scheme of a DFIG Using the Adaptive Gain Depending on the Rotor Speed and Frequency Deviation

DOE PAGES

Lee, Hyewon; Hwang, Min; Muljadi, Eduard; ...

2017-04-18

In an electric power grid that has a high penetration level of wind, the power fluctuation of a large-scale wind power plant (WPP) caused by varying wind speeds deteriorates the system frequency regulation. This paper proposes a power-smoothing scheme of a doubly-fed induction generator (DFIG) that significantly mitigates the system frequency fluctuation while preventing over-deceleration of the rotor speed. The proposed scheme employs an additional control loop relying on the system frequency deviation that operates in combination with the maximum power point tracking control loop. To improve the power-smoothing capability while preventing over-deceleration of the rotor speed, the gain ofmore » the additional loop is modified with the rotor speed and frequency deviation. The gain is set to be high if the rotor speed and/or frequency deviation is large. In conclusion, the simulation results based on the IEEE 14-bus system clearly demonstrate that the proposed scheme significantly lessens the output power fluctuation of a WPP under various scenarios by modifying the gain with the rotor speed and frequency deviation, and thereby it can regulate the frequency deviation within a narrow range.« less

Low-speed wind tunnel test results of the Canard Rotor/Wing concept

NASA Technical Reports Server (NTRS)

Bass, Steven M.; Thompson, Thomas L.; Rutherford, John W.; Swanson, Stephen

1993-01-01

The Canard Rotor/Wing (CRW), a high-speed rotorcraft concept, was tested at the National Aeronautics and Space Administration (NASA) Ames Research Center's 40- by 80-Foot Wind Tunnel in Mountain View, California. The 1/5-scale model was tested to identify certain low-speed, fixed-wing, aerodynamic characteristics of the configuration and investigate the effectiveness of two empennages, an H-Tail and a T-Tail. The paper addresses the principal test objectives and the results achieved in the wind tunnel test. These are summarized as: i) drag build-up and differences between the H-Tail and T-Tail configuration, ii) longitudinal stability of the H-Tail and T-Tail configurations in the conversion and cruise modes, iii) control derivatives for the canard and elevator in the conversion and cruise modes, iv) aerodynamic characteristics of varying the rotor/wing azimuth position, and v) canard and tail lift/trim capability for conversion conditions.

14 CFR 29.1509 - Rotor speed.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Rotor speed. 29.1509 Section 29.1509....1509 Rotor speed. (a) Maximum power-off (autorotation). The maximum power-off rotor speed must be... minimum power-off rotor speed must be established so that it is not less than 105 percent of the greater...

14 CFR 27.1509 - Rotor speed.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Rotor speed. 27.1509 Section 27.1509... Rotor speed. (a) Maximum power-off (autorotation). The maximum power-off rotor speed must be established... minimum power-off rotor speed must be established so that it is not less than 105 percent of the greater...

14 CFR 29.1509 - Rotor speed.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Rotor speed. 29.1509 Section 29.1509....1509 Rotor speed. (a) Maximum power-off (autorotation). The maximum power-off rotor speed must be... minimum power-off rotor speed must be established so that it is not less than 105 percent of the greater...

14 CFR 27.1509 - Rotor speed.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Rotor speed. 27.1509 Section 27.1509... Rotor speed. (a) Maximum power-off (autorotation). The maximum power-off rotor speed must be established... minimum power-off rotor speed must be established so that it is not less than 105 percent of the greater...

The relationship between loads and power of a rotor and an actuator disc

NASA Astrophysics Data System (ADS)

van Kuik, Gijs A. M.

2014-12-01

Most state of the art rotor design methods are based on the actuator disc theory developed about one century ago. The actuator disc is an axisymmetric permeable surface carrying a load that represents the load on a real rotor with a finite number of blades N. However, the mathematics of the transition from a real rotor load to an axisymmetrically loaded disc is not yet presented in literature. By formulating an actuator disc equation of motion in which the Bernoulli constant H is expressed in kinematical terms, a comparison of the power conversion and load on the disc and rotor is possible. For both the converted power is expressed as a change of angular momentum times rotational speed. The limits for N → ∞ while the chord c → 0, the rotational speed Ω → ∞, the load F becoming uniform by ∂F/∂r → 0 and the thickness epsilon → 0 confirm that the classical disc represents the rotor with an infinite number of blades. Furthermore, the expressions for the blade load are compared to the expressions in current design and analysis tools. The latter do not include the load on chord-wise vorticity. Including this is expected to give a better modelling of the tip and root flow.

V/STOL tilt rotor aircraft study mathematical model for a real time simulation of a tilt rotor aircraft (Boeing Vertol Model 222), volume 8

NASA Technical Reports Server (NTRS)

Rosenstein, H.; Mcveigh, M. A.; Mollenkof, P. A.

1973-01-01

A mathematical model for a real time simulation of a tilt rotor aircraft was developed. The mathematical model is used for evaluating aircraft performance and handling qualities. The model is based on an eleven degree of freedom total force representation. The rotor is treated as a point source of forces and moments with appropriate response time lags and actuator dynamics. The aerodynamics of the wing, tail, rotors, landing gear, and fuselage are included.

SMART Rotor Development and Wind Tunnel Test

DTIC Science & Technology

2009-09-01

amplifier and control system , and data acquisition, processing, and display systems . Boeing�s LRTS (Fig. 2), consists of a sled structure that...Support Test Stand Sled Tail Sting Outrigger Arm Figure 2: System integration test at whirl tower Port Rotor Balance Main Strut Flap Tail...demonstrated. Finally, the reliability of the flap actuation system was successfully proven in more than 60 hours of wind tunnel testing

Predicting the long tail of book sales: Unearthing the power-law exponent

NASA Astrophysics Data System (ADS)

Fenner, Trevor; Levene, Mark; Loizou, George

2010-06-01

The concept of the long tail has recently been used to explain the phenomenon in e-commerce where the total volume of sales of the items in the tail is comparable to that of the most popular items. In the case of online book sales, the proportion of tail sales has been estimated using regression techniques on the assumption that the data obeys a power-law distribution. Here we propose a different technique for estimation based on a generative model of book sales that results in an asymptotic power-law distribution of sales, but which does not suffer from the problems related to power-law regression techniques. We show that the proportion of tail sales predicted is very sensitive to the estimated power-law exponent. In particular, if we assume that the power-law exponent of the cumulative distribution is closer to 1.1 rather than to 1.2 (estimates published in 2003, calculated using regression by two groups of researchers), then our computations suggest that the tail sales of Amazon.com, rather than being 40% as estimated by Brynjolfsson, Hu and Smith in 2003, are actually closer to 20%, the proportion estimated by its CEO.

Power Smoothing of a Variable-Speed Wind Turbine Generator in Association With the Rotor-Speed-Dependent Gain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Yeonhee; Kang, Moses; Muljadi, Eduard

This paper proposes a power-smoothing scheme for a variable-speed wind turbine generator (WTG) that can smooth out the WTG's fluctuating power caused by varying wind speeds, and thereby keep the system frequency within a narrow range. The proposed scheme employs an additional loop based on the system frequency deviation that operates in conjunction with the maximum power point tracking (MPPT) control loop. Unlike the conventional, fixed-gain scheme, its control gain is modified with the rotor speed. In the proposed scheme, the control gain is determined by considering the ratio of the output of the additional loop to that of themore » MPPT loop. To improve the contribution of the scheme toward maintaining the frequency while ensuring the stable operation of WTGs, in the low rotor speed region, the ratio is set to be proportional to the rotor speed; in the high rotor speed region, the ratio remains constant. The performance of the proposed scheme is investigated under varying wind conditions for the IEEE 14-bus system. The simulation results demonstrate that the scheme successfully operates regardless of the output power fluctuation of a WTG by adjusting the gain with the rotor speed, and thereby improves the frequency-regulating capability of a WTG.« less

Wind tunnel investigation of helicopter-rotor wake effects on three helicopter fuselage models

NASA Technical Reports Server (NTRS)

Wilson, J. C.; Mineck, R. E.

1975-01-01

The effects of rotor wake on helicopter fuselage aerodynamic characteristics were investigated in the Langley V/STOL tunnel. Force, moment, and pressure data were obtained on three fuselage models at various combinations of windspeed, sideslip angle, and pitch angle. The data show that the influence of rotor wake on the helicopter fuselage yawing moment imposes a significant additional thrust requirement on the tail rotor of a single-rotor helicopter at high sideslip angles.

Field Telemetry of Blade-rotor Coupled Torsional Vibration at Matuura Power Station Number 1 Unit

NASA Technical Reports Server (NTRS)

Isii, Kuniyoshi; Murakami, Hideaki; Otawara, Yasuhiko; Okabe, Akira

1991-01-01

The quasi-modal reduction technique and finite element model (FEM) were used to construct an analytical model for the blade-rotor coupled torsional vibration of a steam turbine generator of the Matuura Power Station. A single rotor test was executed in order to evaluate umbrella vibration characteristics. Based on the single rotor test results and the quasi-modal procedure, the total rotor system was analyzed to predict coupled torsional frequencies. Finally, field measurement of the vibration of the last stage buckets was made, which confirmed that the double synchronous resonance was 124.2 Hz, meaning that the machine can be safely operated. The measured eigen values are very close to the predicted value. The single rotor test and this analytical procedure thus proved to be a valid technique to estimate coupled torsional vibration.

Effect of rotor wake on aerodynamic characteristics of a 1/6 scale model of the rotor systems research aircraft. [in the Langley V/STOL tunnel

NASA Technical Reports Server (NTRS)

Mineck, R. E.

1977-01-01

Tests were conducted in the Langley V/STOL tunnel to determine the effect of the main-rotor wake on the aerodynamic characteristics of the rotor systems research aircraft. A 1/6-scale model with a 4-blade articulated rotor was used to determine the effect of the rotor wake for the compound configuration. Data were obtained over a range of angles of attack, angles of sideslip, auxiliary engine thrusts, rotor collective pitch angles, and rotor tip-path plane angles for several main-rotor advance ratios. Separate results are presented for the forces and moments on the airframe, the wing, and the tail. An analysis of the test data indicates significant changes in the aerodynamic characteristics. The rotor wake increases the longitudinal static stability, the effective dihedral, and the lateral static stability of the airframe. The rotor induces a downwash on the wing. This downwash decreases the wing lift and increases the drag. The asymmetrical rotor wake induces a differential lift across the wing and a subsequent rolling moment. These rotor induced effects on the wing become smaller with increasing forward speed.

Rotordynamic Feasibility of a Conceptual Variable-Speed Power Turbine Propulsion System for Large Civil Tilt-Rotor Applications

NASA Technical Reports Server (NTRS)

Howard, Samuel

2012-01-01

A variable-speed power turbine concept is analyzed for rotordynamic feasibility in a Large Civil Tilt-Rotor (LCTR) class engine. Implementation of a variable-speed power turbine in a rotorcraft engine would enable high efficiency propulsion at the high forward velocities anticipated of large tilt-rotor vehicles. Therefore, rotordynamics is a critical issue for this engine concept. A preliminary feasibility study is presented herein to address this concern and identify if variable-speed is possible in a conceptual engine sized for the LCTR. The analysis considers critical speed placement in the operating speed envelope, stability analysis up to the maximum anticipated operating speed, and potential unbalance response amplitudes to determine that a variable-speed power turbine is likely to be challenging, but not impossible to achieve in a tilt-rotor propulsion engine.

Numerical study on the power extraction performance of a flapping foil with a flexible tail

NASA Astrophysics Data System (ADS)

Wu, J.; Shu, C.; Zhao, N.; Tian, F.-B.

2015-01-01

The numerical study on the power extraction performance of a flapping foil with a flexible tail is performed in this work. A NACA0015 airfoil is arranged in a two-dimensional laminar flow and imposed with a synchronous harmonic plunge and pitch rotary motion. A flat plate that is attached to the trailing edge of the foil is utilized to model a tail, and so they are viewed as a whole for the purpose of power extraction. In addition, the tail either is rigid or can deform due to the exerted hydrodynamic forces. To implement numerical simulations, an immersed boundary-lattice Boltzmann method is employed. At a Reynolds number of 1100 and the position of the pitching axis at third chord, the influences of the mass and flexibility of the tail as well as the frequency of motion on the power extraction are systematically examined. It is found that compared to the foil with a rigid tail, the efficiency of power extraction for the foil with a deformable tail can be improved. Based on the numerical analysis, it is indicated that the enhanced plunging component of the power extraction, which is caused by the increased lift force, directly contributes to the efficiency improvement. Since a flexible tail with medium and high masses is not beneficial to the efficiency improvement, a flexible tail with low mass together with high flexibility is recommended in the flapping foil based power extraction system.

Power-law tails in the distribution of order imbalance

NASA Astrophysics Data System (ADS)

Zhang, Ting; Gu, Gao-Feng; Xu, Hai-Chuan; Xiong, Xiong; Chen, Wei; Zhou, Wei-Xing

2017-10-01

We investigate the probability distribution of order imbalance calculated from the order flow data of 43 Chinese stocks traded on the Shenzhen Stock Exchange. Two definitions of order imbalance are considered based on the order number and the order size. We find that the order imbalance distributions of individual stocks have power-law tails. However, the tail index fluctuates remarkably from stock to stock. We also investigate the distributions of aggregated order imbalance of all stocks at different timescales Δt. We find no clear trend in the tail index with respect Δt. All the analyses suggest that the distributions of order imbalance are asymmetric.

Flapping foil power generator performance enhanced with a spring-connected tail

NASA Astrophysics Data System (ADS)

Liu, Zhengliang; Tian, Fang-Bao; Young, John; Lai, Joseph C. S.

2017-12-01

The flexibility effects on the performance of a flapping foil power generator are numerically studied by using the immersed boundary-lattice Boltzmann method at a Reynolds number of 1100. The flapping foil system consists of a rigid NACA0015 foil undergoing harmonic pitch and plunge motions and a passively actuated flat plate pinned to the trailing edge of the rigid foil. The flexibility is modeled by a torsional spring model at the conjuncture of the rigid foil and the tail. Here, a parametric study on mass density and natural frequency is conducted under the optimum kinematic condition of the rigid system identified from the literature and numerical simulations made for reduced frequency f* = 0.04-0.24 and pitch amplitude θ0 = 40°-90°. Four typical cases are discussed in detail by considering time histories of hydrodynamic loads and tail deformations under the optimal and non-optimal kinematic conditions. Results show that under the rigid-system optimal kinematic condition, a tail with appropriate mass density (μ = 0.60) and resonant frequency ( fr*=1.18 ) can improve the maximum efficiency by 7.24% accompanied by an increase of 6.63% in power compared to those of a rigid foil with a rigid tail. This is because the deflection of the tail reduces the low pressure region on the pressure surface (i.e., the lower surface during the upstroke or the upper surface during the downstroke) caused by the leading edge vortex after the stroke reversal, resulting in a higher efficiency. At high flapping frequencies, a spring-connected tail ( fr*=0.13 ) eliminates the large spike in the moment observed in high stiffness cases, reducing the power required for the pitch motion, resulting in 117% improvement in efficiency over that with a rigid tail at a reduced frequency of 0.24.

MIDDLE GORGE POWER PLANT, OWENS RIVER STREAM FLOWING OVER TAIL ...

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

MIDDLE GORGE POWER PLANT, OWENS RIVER STREAM FLOWING OVER TAIL RACE OF POWER PLANT AND PENSTOCK HEADGATE TO LOWER GORGE CONTROL PLANT. A MINIMAL FLOW OF RIVER WATER IS REQUIRED TO MAINTAIN FISH LIFE - Los Angeles Aqueduct, Middle Gorge Power Plant, Los Angeles, Los Angeles County, CA

Development of a helicopter rotor/propulsion system dynamics analysis

NASA Technical Reports Server (NTRS)

Warmbrodt, W.; Hull, R.

1982-01-01

A time-domain analysis of coupled engine/drive train/rotor dynamics of a twin-engine, single main rotor helicopter model has been performed. The analysis incorporates an existing helicopter model with nonlinear simulations of a helicopter turboshaft engine and its fuel controller. System dynamic behavior is studied using the resulting simulation which included representations for the two engines and their fuel controllers, drive system, main rotor, tail rotor, and aircraft rigid body motions. Time histories of engine and rotor RPM response to pilot control inputs are studied for a baseline rotor and propulsion system model. Sensitivity of rotor RPM droop to fuel controller gain changes and collective input feed-forward gain changes are studied. Torque-load-sharing between the two engines is investigated by making changes in the fuel controller feedback paths. A linear engine model is derived from the nonlinear engine simulation and used in the coupled system analysis. This four-state linear engine model is then reduced to a three-state model. The effect of this simplification on coupled system behavior is shown.

Numerical Predictions of Wind Turbine Power and Aerodynamic Loads for the NREL Phase II and IV Combined Experiment Rotor

NASA Technical Reports Server (NTRS)

Duque, Earl P. N.; Johnson, Wayne; vanDam, C. P.; Chao, David D.; Cortes, Regina; Yee, Karen

1999-01-01

Accurate, reliable and robust numerical predictions of wind turbine rotor power remain a challenge to the wind energy industry. The literature reports various methods that compare predictions to experiments. The methods vary from Blade Element Momentum Theory (BEM), Vortex Lattice (VL), to variants of Reynolds-averaged Navier-Stokes (RaNS). The BEM and VL methods consistently show discrepancies in predicting rotor power at higher wind speeds mainly due to inadequacies with inboard stall and stall delay models. The RaNS methodologies show promise in predicting blade stall. However, inaccurate rotor vortex wake convection, boundary layer turbulence modeling and grid resolution has limited their accuracy. In addition, the inherently unsteady stalled flow conditions become computationally expensive for even the best endowed research labs. Although numerical power predictions have been compared to experiment. The availability of good wind turbine data sufficient for code validation experimental data that has been extracted from the IEA Annex XIV download site for the NREL Combined Experiment phase II and phase IV rotor. In addition, the comparisons will show data that has been further reduced into steady wind and zero yaw conditions suitable for comparisons to "steady wind" rotor power predictions. In summary, the paper will present and discuss the capabilities and limitations of the three numerical methods and make available a database of experimental data suitable to help other numerical methods practitioners validate their own work.

V/STOL tilt rotor aircraft study: Wind tunnel tests of a full scale hingeless prop/rotor designed for the Boeing Model 222 tilt rotor aircraft

NASA Technical Reports Server (NTRS)

Magee, J. P.; Alexander, H. R.

1973-01-01

The rotor system designed for the Boeing Model 222 tilt rotor aircraft is a soft-in-plane hingeless rotor design, 26 feet in diameter. This rotor has completed two test programs in the NASA Ames 40' X 80' wind tunnel. The first test was a windmilling rotor test on two dynamic wing test stands. The rotor was tested up to an advance ratio equivalence of 400 knots. The second test used the NASA powered propeller test rig and data were obtained in hover, transition and low speed cruise flight. Test data were obtained in the areas of wing-rotor dynamics, rotor loads, stability and control, feedback controls, and performance to meet the test objectives. These data are presented.

An investigation of rotor harmonic noise by the use of small scale wind tunnel models

NASA Technical Reports Server (NTRS)

Sternfeld, H., Jr.; Schaffer, E. G.

1982-01-01

Noise measurements of small scale helicopter rotor models were compared with noise measurements of full scale helicopters to determine what information about the full scale helicopters could be derived from noise measurements of small scale helicopter models. Comparisons were made of the discrete frequency (rotational) noise for 4 pairs of tests. Areas covered were tip speed effects, isolated rotor, tandem rotor, and main rotor/tail rotor interaction. Results show good comparison of noise trends with configuration and test condition changes, and good comparison of absolute noise measurements with the corrections used except for the isolated rotor case. Noise measurements of the isolated rotor show a great deal of scatter reflecting the fact that the rotor in hover is basically unstable.

Near-Field Acoustic Power Level Analysis of F31/A31 Open Rotor Model at Simulated Cruise Conditions, Technical Report II

NASA Technical Reports Server (NTRS)

Sree, Dave

2015-01-01

Near-field acoustic power level analysis of F31A31 open rotor model has been performed to determine its noise characteristics at simulated cruise flight conditions. The non-proprietary parts of the test data obtained from experiments in the 8x6 supersonic wind tunnel were provided by NASA-Glenn Research Center. The tone and broadband components of total noise have been separated from raw test data by using a new data analysis tool. Results in terms of sound pressure levels, acoustic power levels, and their variations with rotor speed, freestream Mach number, and input shaft power, with different blade-pitch setting angles at simulated cruise flight conditions, are presented and discussed. Empirical equations relating models acoustic power level and input shaft power have been developed. The near-field acoustic efficiency of the model at simulated cruise conditions is also determined. It is hoped that the results presented in this work will serve as a database for comparison and improvement of other open rotor blade designs and also for validating open rotor noise prediction codes.

Case Studies for the Statistical Design of Experiments Applied to Powered Rotor Wind Tunnel Tests

NASA Technical Reports Server (NTRS)

Overmeyer, Austin D.; Tanner, Philip E.; Martin, Preston B.; Commo, Sean A.

2015-01-01

The application of statistical Design of Experiments (DOE) to helicopter wind tunnel testing was explored during two powered rotor wind tunnel entries during the summers of 2012 and 2013. These tests were performed jointly by the U.S. Army Aviation Development Directorate Joint Research Program Office and NASA Rotary Wing Project Office, currently the Revolutionary Vertical Lift Project, at NASA Langley Research Center located in Hampton, Virginia. Both entries were conducted in the 14- by 22-Foot Subsonic Tunnel with a small portion of the overall tests devoted to developing case studies of the DOE approach as it applies to powered rotor testing. A 16-47 times reduction in the number of data points required was estimated by comparing the DOE approach to conventional testing methods. The average error for the DOE surface response model for the OH-58F test was 0.95 percent and 4.06 percent for drag and download, respectively. The DOE surface response model of the Active Flow Control test captured the drag within 4.1 percent of measured data. The operational differences between the two testing approaches are identified, but did not prevent the safe operation of the powered rotor model throughout the DOE test matrices.

Flywheel Rotor Safe-Life Technology

NASA Technical Reports Server (NTRS)

Ratner, J. K. H.; Chang, J. B.; Christopher, D. A.; McLallin, Kerry L. (Technical Monitor)

2002-01-01

Since the 1960s, research has been conducted into the use of flywheels as energy storage systems. The-proposed applications include energy storage for hybrid and electric automobiles, attitude control and energy storage for satellites, and uninterruptible power supplies for hospitals and computer centers. For many years, however, the use of flywheels for space applications was restricted by the total weight of a system employing a metal rotor. With recent technological advances in the manufacturing of composite materials, however, lightweight composite rotors have begun to be proposed for such applications. Flywheels with composite rotors provide much higher power and energy storage capabilities than conventional chemical batteries. However, the failure of a high speed flywheel rotor could be a catastrophic event. For this reason, flywheel rotors are classified by the NASA Fracture Control Requirements Standard as fracture critical parts. Currently, there is no industry standard to certify a composite rotor for safe and reliable operation forth( required lifetime of the flywheel. Technical problems hindering the development of this standard include composite manufacturing inconsistencies, insufficient nondestructive evaluation (NDE) techniques for detecting defects and/or impact damage, lack of standard material test methods for characterizing composite rotor design allowables, and no unified proof (over-spin) test for flight rotors. As part of a flywheel rotor safe-life certification pro-ram funded b the government, a review of the state of the art in composite rotors is in progress. The goal of the review is to provide a clear picture of composite flywheel rotor technologies. The literature review has concentrated on the following topics concerning composites and composite rotors: durability (fatigue) and damage tolerance (safe-life) analysis/test methods, in-service NDE and health monitoring techniques, spin test methods/ procedures, and containment options

T55 power turbine rotor multiplane-multispeed balancing study

NASA Technical Reports Server (NTRS)

Martin, M. R.

1982-01-01

A rotordynamic analysis of the T55-L-11C engine was used to evaluate the balancing needs of the power turbine and to optimize the balancing procedure. As a result, recommendations were made for implementation of a multiplane-multispeed balancing plan. Precision collars for the attachment of trial weights to a slender rotor were designed enabling demonstration balancing on production hardware. The quality of the balance was then evaluated by installing a high speed balanced power turbine in an engine and running in a test cell at the Corpus Christi Army depot. The engine used had been tested prior to the turbine changeout and showed acceptable overall vibration levels for the engine were significantly reduced, demonstrating the ability of multiplane-multispeed balancing to control engine vibration.

Utilization of rotor kinetic energy storage for hybrid vehicles

DOEpatents

Hsu, John S [Oak Ridge, TN

2011-05-03

A power system for a motor vehicle having an internal combustion engine, the power system comprises an electric machine (12) further comprising a first excitation source (47), a permanent magnet rotor (28) and a magnetic coupling rotor (26) spaced from the permanent magnet rotor and at least one second excitation source (43), the magnetic coupling rotor (26) also including a flywheel having an inertial mass to store kinetic energy during an initial acceleration to an operating speed; and wherein the first excitation source is electrically connected to the second excitation source for power cycling such that the flywheel rotor (26) exerts torque on the permanent magnet rotor (28) to assist braking and acceleration of the permanent magnet rotor (28) and consequently, the vehicle. An axial gap machine and a radial gap machine are disclosed and methods of the invention are also disclosed.

Performance Benefits for Wave Rotor-Topped Gas Turbine Engines

NASA Technical Reports Server (NTRS)

Jones, Scott M.; Welch, Gerard E.

1996-01-01

The benefits of wave rotor-topping in turboshaft engines, subsonic high-bypass turbofan engines, auxiliary power units, and ground power units are evaluated. The thermodynamic cycle performance is modeled using a one-dimensional steady-state code; wave rotor performance is modeled using one-dimensional design/analysis codes. Design and off-design engine performance is calculated for baseline engines and wave rotor-topped engines, where the wave rotor acts as a high pressure spool. The wave rotor-enhanced engines are shown to have benefits in specific power and specific fuel flow over the baseline engines without increasing turbine inlet temperature. The off-design steady-state behavior of a wave rotor-topped engine is shown to be similar to a conventional engine. Mission studies are performed to quantify aircraft performance benefits for various wave rotor cycle and weight parameters. Gas turbine engine cycles most likely to benefit from wave rotor-topping are identified. Issues of practical integration and the corresponding technical challenges with various engine types are discussed.

Calculated Dynamic Characteristics of a Soft-Inplane Hingeless Rotor Helicopter

NASA Technical Reports Server (NTRS)

Johnson, W.

1977-01-01

Calculated dynamic characteristics of a representative soft-inplane hingeless rotor helicopter are presented. The flight dynamics as a function of speed and gross weight are given. The requirements for accurate analytical modelling of this helicopter are established. The influence of the horizontal tail size, the rotor precone, the blade sweep, and the blade center of gravity/aerodynamic center offset on the calculated flight dynamics and aeroelastic stability are examined. The calculations show no evidence of an air resonance stability problem with this aircraft.

A wind-tunnel investigation of parameters affecting helicopter directional control at low speeds in ground effect

NASA Technical Reports Server (NTRS)

Yeager, W. T., Jr.; Young, W. H., Jr.; Mantay, W. R.

1974-01-01

An investigation was conducted in the Langley full-scale tunnel to measure the performance of several helicopter tail-rotor/fin configurations with regard to directional control problems encountered at low speeds in ground effect. Tests were conducted at wind azimuths of 0 deg to 360 deg in increments of 30 deg and 60 deg and at wind speeds from 0 to 35 knots. The results indicate that at certain combinations of wind speed and wind azimuth, large increases in adverse fin force require correspondingly large increases in the tail-rotor thrust, collective pitch, and power required to maintain yaw trim. Changing the tail-rotor direction of rotation to top blade aft for either a pusher tail rotor (tail-rotor wake blowing away from fin) or a tractor tail rotor (tail-rotor wake blowing against fin) will alleviate this problem. For a pusher tail rotor at 180 deg wind azimuth, increases in the fin/tail-rotor gap were not found to have any significant influence on the overall vehicle directional control capability. Changing the tail rotor to a higher position was found to improve tail-rotor performance for a fin-off configuration at a wind azimuth of 180 deg. A V-tail configuration with a pusher tail rotor with top blade aft direction of rotation was found to be the best configuration with regard to overall directional control capability.

Power-law tail probabilities of drainage areas in river basins

USGS Publications Warehouse

Veitzer, S.A.; Troutman, B.M.; Gupta, V.K.

2003-01-01

The significance of power-law tail probabilities of drainage areas in river basins was discussed. The convergence to a power law was not observed for all underlying distributions, but for a large class of statistical distributions with specific limiting properties. The article also discussed about the scaling properties of topologic and geometric network properties in river basins.

Acoustic Shielding for a Model Scale Counter-rotation Open Rotor

NASA Technical Reports Server (NTRS)

Stephens, David B.; Edmane, Envia

2012-01-01

The noise shielding benefit of installing an open rotor above a simplified wing or tail is explored experimentally. The test results provide both a benchmark data set for validating shielding prediction tools and an opportunity for a system level evaluation of the noise reduction potential of propulsion noise shielding by an airframe component. A short barrier near the open rotor was found to provide up to 8.5 dB of attenuation at some directivity angles, with tonal sound particularly well shielded. Predictions from two simple shielding theories were found to overestimate the shielding benefit.

Computational Assessment of the Aerodynamic Performance of a Variable-Speed Power Turbine for Large Civil Tilt-Rotor Application

NASA Technical Reports Server (NTRS)

Welch, Gerard E.

2011-01-01

The main rotors of the NASA Large Civil Tilt-Rotor notional vehicle operate over a wide speed-range, from 100% at take-off to 54% at cruise. The variable-speed power turbine offers one approach by which to effect this speed variation. Key aero-challenges include high work factors at cruise and wide (40 to 60 deg.) incidence variations in blade and vane rows over the speed range. The turbine design approach must optimize cruise efficiency and minimize off-design penalties at take-off. The accuracy of the off-design incidence loss model is therefore critical to the turbine design. In this effort, 3-D computational analyses are used to assess the variation of turbine efficiency with speed change. The conceptual design of a 4-stage variable-speed power turbine for the Large Civil Tilt-Rotor application is first established at the meanline level. The design of 2-D airfoil sections and resulting 3-D blade and vane rows is documented. Three-dimensional Reynolds Averaged Navier-Stokes computations are used to assess the design and off-design performance of an embedded 1.5-stage portion-Rotor 1, Stator 2, and Rotor 2-of the turbine. The 3-D computational results yield the same efficiency versus speed trends predicted by meanline analyses, supporting the design choice to execute the turbine design at the cruise operating speed.

Assessment of Aerodynamic Challenges of a Variable-Speed Power Turbine for Large Civil Tilt-Rotor Application

NASA Technical Reports Server (NTRS)

Welch, Gerand E.

2010-01-01

The main rotors of the NASA Large Civil Tilt-Rotor notional vehicle operate over a wide speed-range (100% at take-off to 54% at cruise). The variable-speed power turbine, when coupled to a fixed-gear-ratio transmission, offers one approach to accomplish this speed variation. The key aero-challenges of the variable-speed power turbine are related to high work factors at cruise, where the power turbine operates at 54% of take-off speed, wide incidence variations into the vane, blade, and exit-guide-vane rows associated with the power-turbine speed change, and the impact of low aft-stage Reynolds number (transitional flow) at 28 kft cruise. Meanline and 2-D Reynolds-Averaged Navier- Stokes analyses are used to characterize the variable-speed power-turbine aerodynamic challenges and to outline a conceptual design approach that accounts for multi-point operation. Identified technical challenges associated with the aerodynamics of high work factor, incidence-tolerant blading, and low Reynolds numbers pose research needs outlined in the paper

Homopolar motor with dual rotors

DOEpatents

Hsu, J.S.

1998-12-01

A homopolar motor has a field rotor mounted on a frame for rotation in a first rotational direction and for producing an electromagnetic field, and an armature rotor mounted for rotation on said frame within said electromagnetic field and in a second rotational direction counter to said first rotational direction of said field rotor. The two rotors are coupled through a 1:1 gearing mechanism, so as to travel at the same speed but in opposite directions. This doubles the output voltage and output power, as compared to a motor in which only the armature is rotated. Several embodiments are disclosed. 7 figs.

Rotor Performance at High Advance Ratio: Theory versus Test

NASA Technical Reports Server (NTRS)

Harris, Franklin D.

2008-01-01

Five analytical tools have been used to study rotor performance at high advance ratio. One is representative of autogyro rotor theory in 1934 and four are representative of helicopter rotor theory in 2008. The five theories are measured against three sets of well documented, full-scale, isolated rotor performance experiments. The major finding of this study is that the decades spent by many rotorcraft theoreticians to improve prediction of basic rotor aerodynamic performance has paid off. This payoff, illustrated by comparing the CAMRAD II comprehensive code and Wheatley & Bailey theory to H-34 test data, shows that rational rotor lift to drag ratios are now predictable. The 1934 theory predicted L/D ratios as high as 15. CAMRAD II predictions compared well with H-34 test data having L/D ratios more on the order of 7 to 9. However, the detailed examination of the selected codes compared to H-34 test data indicates that not one of the codes can predict to engineering accuracy above an advance ratio of 0.62 the control positions and shaft angle of attack required for a given lift. There is no full-scale rotor performance data available for advance ratios above 1.0 and extrapolation of currently available data to advance ratios on the order of 2.0 is unreasonable despite the needs of future rotorcraft. Therefore, it is recommended that an overly strong full-scale rotor blade set be obtained and tested in a suitable wind tunnel to at least an advance ratio of 2.5. A tail rotor from a Sikorsky CH-53 or other large single rotor helicopter should be adequate for this exploratory experiment.

Theoretical study of hull-rotor aerodynamic interference on semibuoyant vehicles

NASA Technical Reports Server (NTRS)

Spangler, S. B.; Smith, C. A.

1978-01-01

Analytical methods are developed to predict the pressure distribution and overall loads on the hulls of airships which have close coupled, relatively large and/or high disk loading propulsors for attitude control, station keeping, and partial support of total weight as well as provision of thrust in cruise. The methods comprise a surface-singularity, potential-flow model for the hull and lifting surfaces (such as tails) and a rotor model which calculates the velocity induced by the rotor and its wake at points adjacent to the wake. Use of these two models provides an inviscid pressure distribution on the hull with rotor interference. A boundary layer separation prediction method is used to locate separation on the hull, and a wake pressure is imposed on the separated region for purposes of calculating hull loads. Results of calculations are shown to illustrate various cases of rotor-hull interference and comparisons with small scale data are made to evaluate the method.

Homopolar motor with dual rotors

DOEpatents

Hsu, John S.

1998-01-01

A homopolar motor (10) has a field rotor (15) mounted on a frame (11) for rotation in a first rotational direction and for producing an electromagnetic field, and an armature rotor (17) mounted for rotation on said frame (11) within said electromagnetic field and in a second rotational direction counter to said first rotational direction of said field rotor (15). The two rotors (15, 17) are coupled through a 1:1 gearing mechanism (19), so as to travel at the same speed but in opposite directions. This doubles the output voltage and output power, as compared to a motor in which only the armature is rotated. Several embodiments are disclosed.

Interlayer toughening of fiber composite flywheel rotors

DOEpatents

Groves, Scott E.; Deteresa, Steven J.

1998-01-01

An interlayer toughening mechanism to mitigate the growth of damage in fiber composite flywheel rotors for long application. The interlayer toughening mechanism may comprise one or more tough layers composed of high-elongation fibers, high-strength fibers arranged in a woven pattern at a range from 0.degree. to 90.degree. to the rotor axis and bound by a ductile matrix material which adheres to and is compatible with the materials used for the bulk of the rotor. The number and spacing of the tough interlayers is a function of the design requirements and expected lifetime of the rotor. The mechanism has particular application in uninterruptable power supplies, electrical power grid reservoirs, and compulsators for electric guns, as well as electromechanical batteries for vehicles.

Wave rotor demonstrator engine assessment

NASA Technical Reports Server (NTRS)

Snyder, Philip H.

1996-01-01

The objective of the program was to determine a wave rotor demonstrator engine concept using the Allison 250 series engine. The results of the NASA LERC wave rotor effort were used as a basis for the wave rotor design. A wave rotor topped gas turbine engine was identified which incorporates five basic requirements of a successful demonstrator engine. Predicted performance maps of the wave rotor cycle were used along with maps of existing gas turbine hardware in a design point study. The effects of wave rotor topping on the engine cycle and the subsequent need to rematch compressor and turbine sections in the topped engine were addressed. Comparison of performance of the resulting engine is made on the basis of wave rotor topped engine versus an appropriate baseline engine using common shaft compressor hardware. The topped engine design clearly demonstrates an impressive improvement in shaft horsepower (+11.4%) and SFC (-22%). Off design part power engine performance for the wave rotor topped engine was similarly improved including that at engine idle conditions. Operation of the engine at off design was closely examined with wave rotor operation at less than design burner outlet temperatures and rotor speeds. Challenges identified in the development of a demonstrator engine are discussed. A preliminary design was made of the demonstrator engine including wave rotor to engine transition ducts. Program cost and schedule for a wave rotor demonstrator engine fabrication and test program were developed.

Wave rotor-enhanced gas turbine engines

NASA Technical Reports Server (NTRS)

Welch, Gerard E.; Scott, Jones M.; Paxson, Daniel E.

1995-01-01

The benefits of wave rotor-topping in small (400 to 600 hp-class) and intermediate (3000 to 4000 hp-class) turboshaft engines, and large (80,000 to 100,000 lb(sub f)-class) high bypass ratio turbofan engines are evaluated. Wave rotor performance levels are calculated using a one-dimensional design/analysis code. Baseline and wave rotor-enhanced engine performance levels are obtained from a cycle deck in which the wave rotor is represented as a burner with pressure gain. Wave rotor-toppings is shown to significantly enhance the specific fuel consumption and specific power of small and intermediate size turboshaft engines. The specific fuel consumption of the wave rotor-enhanced large turbofan engine can be reduced while operating at significantly reduced turbine inlet temperature. The wave rotor-enhanced engine is shown to behave off-design like a conventional engine. Discussion concerning the impact of the wave rotor/gas turbine engine integration identifies tenable technical challenges.

NASA Open Rotor Noise Research

NASA Technical Reports Server (NTRS)

Envia, Ed

2010-01-01

Owing to their inherent fuel burn efficiency advantage compared with the current generation high bypass ratio turbofan engines, there is resurgent interest in developing open rotor propulsion systems for powering the next generation commercial aircraft. However, to make open rotor systems truly competitive, they must be made to be acoustically acceptable too. To address this challenge, NASA in collaboration with industry is exploring the design space for low-noise open rotor propulsion systems. The focus is on the system level assessment of the open rotors compared with other candidate concepts like the ultra high bypass ratio cycle engines. To that end there is an extensive research effort at NASA focused on component testing and diagnostics of the open rotor acoustic performance as well as assessment and improvement of open rotor noise prediction tools. In this presentation and overview of the current NASA research on open rotor noise will be provided. Two NASA projects, the Environmentally Responsible Aviation Project and the Subsonic Fixed Wing Project, have been funding this research effort.

Method for cancelling expansion waves in a wave rotor

NASA Astrophysics Data System (ADS)

Paxson, Daniel E.

1994-03-01

A wave rotor system includes a wave rotor coupled to first and second end plates. Special ports are provided, one in each of the first and second end plates, to cancel expansion waves generated by the release of working fluid from the wave rotor. One of the expansion waves is reflected in the wave rotor from a reflecting portion, and provided to the special port in the second end plate. Fluid present at the special port in the second end plate has a stagnation pressure and mass flow which is substantially the same as that of the cells of the wave rotor communicating with such special port. This allows for cancellation of the expansion wave generated by the release of working fluid from the wave rotor. The special port in the second end plate has a first end corresponding substantially to the head of the expansion wave, and a second end corresponding substantially to the tail of the expansion wave. Also, the special port is configured to continually change along the circumference of the second end plate to affect expansion wave cancellation. An expansion wave generated by a second release of working fluid from the wave rotor is cancelled in a similar manner to that described above using a special port in the first end plate. Preferably the cycle of operation of the wave rotor system is designed so that the stagnation pressure and mass flow of the fluid present at the special ports is the same so that the special ports may be connected by a common duct.

Radial-radial single rotor turbine

DOEpatents

Platts, David A [Los Alamos, NM

2006-05-16

A rotor for use in turbine applications has a radial compressor/pump having radially disposed spaced apart fins forming passages and a radial turbine having hollow turbine blades interleaved with the fins and through which fluid from the radial compressor/pump flows. The rotor can, in some applications, be used to produce electrical power.

Apparatus and method for magnetically unloading a rotor bearing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sanders, Seth Robert

An apparatus and method for unloading a rotor bearing is described. The apparatus includes an electromagnet for levitating the rotor. In one embodiment, a sensor of the magnetic field near the electromagnet is used to control the current to levitate the rotor. In another embodiment, a method is provided that includes rotating the rotor, increasing the current to levitate the rotor and decrease the gap between electromagnet and rotor, and then reducing the current to levitate the rotor with a minimal amount of electric power to the electromagnet.

Interlayer toughening of fiber composite flywheel rotors

DOEpatents

Groves, S.E.; Deteresa, S.J.

1998-07-14

An interlayer toughening mechanism is described to mitigate the growth of damage in fiber composite flywheel rotors for long application. The interlayer toughening mechanism may comprise one or more tough layers composed of high-elongation fibers, high-strength fibers arranged in a woven pattern at a range from 0{degree} to 90{degree} to the rotor axis and bound by a ductile matrix material which adheres to and is compatible with the materials used for the bulk of the rotor. The number and spacing of the tough interlayers is a function of the design requirements and expected lifetime of the rotor. The mechanism has particular application in uninterruptable power supplies, electrical power grid reservoirs, and compulsators for electric guns, as well as electromechanical batteries for vehicles. 2 figs.

SMART Rotor Development and Wind-Tunnel Test

NASA Technical Reports Server (NTRS)

Lau, Benton H.; Straub, Friedrich; Anand, V. R.; Birchette, Terry

2009-01-01

Boeing and a team from Air Force, NASA, Army, Massachusetts Institute of Technology, University of California at Los Angeles, and University of Maryland have successfully completed a wind-tunnel test of the smart material actuated rotor technology (SMART) rotor in the 40- by 80-foot wind-tunnel of the National Full-Scale Aerodynamic Complex at NASA Ames Research Center, figure 1. The SMART rotor is a full-scale, five-bladed bearingless MD 900 helicopter rotor modified with a piezoelectric-actuated trailing-edge flap on each blade. The development effort included design, fabrication, and component testing of the rotor blades, the trailing-edge flaps, the piezoelectric actuators, the switching power amplifiers, the actuator control system, and the data/power system. Development of the smart rotor culminated in a whirl-tower hover test which demonstrated the functionality, robustness, and required authority of the active flap system. The eleven-week wind tunnel test program evaluated the forward flight characteristics of the active-flap rotor, gathered data to validate state-of-the-art codes for rotor noise analysis, and quantified the effects of open- and closed-loop active-flap control on rotor loads, noise, and performance. The test demonstrated on-blade smart material control of flaps on a full-scale rotor for the first time in a wind tunnel. The effectiveness and the reliability of the flap actuation system were successfully demonstrated in more than 60 hours of wind-tunnel testing. The data acquired and lessons learned will be instrumental in maturing this technology and transitioning it into production. The development effort, test hardware, wind-tunnel test program, and test results will be presented in the full paper.

Quincke rotors in colloidal suspensions

NASA Astrophysics Data System (ADS)

Xiao, Junjun; Huang, Jiping; Yu, Kin Wah; Gu, Guoqing

2004-03-01

When a polarized colloidal particle rotates in an applied electric field, the rotational motion of the particle leads to a displacement of the polarized charge on the surface of the particle. In this connection, the relaxation of the surface charge tends to restore the polarization, leading to a steady-state which is distinct from the equilibrium state in the absence of the rotational motion. There are three relevant cases, namely, rotating particles in a DC field[1, 2], particle rotation due to a rotating field[3, 4] as well as spontaneous rotation of particles in a DC field[5]. In this work, we have focused on the spontaneous rotation of colloidal particles in a DC field, which is known as Quincke rotation. In the collective behaviors of Quincke rotors, the mutual interactions between the individual rotors lead to the assembly of chain-like structures which make an angle with the applied field. We can solve the transient polarization relaxation of two approaching colloidal rotors numerically. More interestingly, we have been able to work out analytically the steady state of two nose-to-tail rotors, in an attempt to take into account the effect of the multipolar interaction between the rotors. As a result, we found that the multipolar interaction does not change the value of the induced dipole moment inside the rotor, but with one of the components of this dipole moment being reduced and the other being enhanced concomitantly. More results of interest have been reported as well. Based on the different dynamic behavior and interaction of Quincke rotors, a totally new class of material is expected to be designed. [1] J.T.K. Wan, K.W. Yu and G.Q. Gu, Phys. Rev. E 64, 061501 (2001). [2] J.T.K. Wan, K.W. Yu and G.Q. Gu, Phys. Rev. E 62, 6848 (2000). [3] J.P. Huang, K.W. Yu and G.Q. Gu, Phys. Rev. E 65, 021401 (2002). [4] J.P. Huang, K.W. Yu, G.Q. Gu and Mikko Karttunen, Phys. Rev. E 67, 051405 (2003). [5] G. Quinke, Ann. Phy. Chem 59, 417 (1896).

Wind-tunnel acoustic results of two rotor models with several tip designs

NASA Technical Reports Server (NTRS)

Martin, R. M.; Connor, A. B.

1986-01-01

A three-phase research program has been undertaken to study the acoustic signals due to the aerodynamic interaction of rotorcraft main rotors and tail rotors. During the first phase, two different rotor models with several interchangeable tips were tested in the Langley 4- by 7-Meter Tunnel on the U.S. Army rotor model system. An extensive acoustic data base was acquired, with special emphasis on blade-vortex interaction (BVI) noise. The details of the experimental procedure, acoustic data acquisition, and reduction are documented. The overall sound pressure level (OASPL) of the high-twist rotor systems is relatively insensitive to flight speed but generally increases with rotor tip-path-plane angle. The OASPL of the high-twist rotors is dominated by acoustic energy in the low-frequency harmonics. The OASPL of the low-twist rotor systems shows more dependence on flight speed than the high-twist rotors, in addition to being quite sensitive to tip-path-plane angle. An integrated band-limited sound pressure level, limited by 500 to 3000 Hz, is a useful metric to quantify the occurrence of BVI noise. The OASPL of the low-twist rotors is strongly influenced by the band-limited sound levels, indicating that the blade-vortex impulsive noise is a dominant noise source for this rotor design. The midfrequency acoustic levels for both rotors show a very strong dependence on rotor tip-path-plane angle. The tip-path-plane angle at which the maximum midfrequency sound level occurs consistently decreases with increasing flight speed. The maximum midfrequency sound level measured at a given location is constant regardless of the flight speed.

Vortex Core Size in the Rotor Near-Wake

NASA Technical Reports Server (NTRS)

Young, Larry A.

2003-01-01

Using a kinetic energy conservation approach, a number of simple analytic expressions are derived for estimating the core size of tip vortices in the near-wake of rotors in hover and axial-flow flight. The influence of thrust, induced power losses, advance ratio, and vortex structure on rotor vortex core size is assessed. Experimental data from the literature is compared to the analytical results derived in this paper. In general, three conclusions can be drawn from the work in this paper. First, the greater the rotor thrust, t h e larger the vortex core size in the rotor near-wake. Second, the more efficient a rotor is with respect to induced power losses, the smaller the resulting vortex core size. Third, and lastly, vortex core size initially decreases for low axial-flow advance ratios, but for large advance ratios core size asymptotically increases to a nominal upper limit. Insights gained from this work should enable improved modeling of rotary-wing aerodynamics, as well as provide a framework for improved experimental investigations of rotor a n d advanced propeller wakes.

14 CFR 27.33 - Main rotor speed and pitch limits.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Main rotor speed and pitch limits. 27.33... AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT Flight General § 27.33 Main rotor speed and pitch limits. (a) Main rotor speed limits. A range of main rotor speeds must be established that— (1) With power on...

14 CFR 29.33 - Main rotor speed and pitch limits.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Main rotor speed and pitch limits. 29.33... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Flight General § 29.33 Main rotor speed and pitch limits. (a) Main rotor speed limits. A range of main rotor speeds must be established that— (1) With power on...

14 CFR 29.33 - Main rotor speed and pitch limits.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Main rotor speed and pitch limits. 29.33... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Flight General § 29.33 Main rotor speed and pitch limits. (a) Main rotor speed limits. A range of main rotor speeds must be established that— (1) With power on...

14 CFR 27.33 - Main rotor speed and pitch limits.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Main rotor speed and pitch limits. 27.33... AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT Flight General § 27.33 Main rotor speed and pitch limits. (a) Main rotor speed limits. A range of main rotor speeds must be established that— (1) With power on...

Helicopter Fuselage Active Flow Control in the Presence of a Rotor

NASA Technical Reports Server (NTRS)

Martin, Preston B; Overmeyer, Austin D.; Tanner, Philip E.; Wilson, Jacob S.; Jenkins, Luther N.

2014-01-01

This work extends previous investigations of active flow control for helicopter fuselage drag and download reduction to include the effects of the rotor. The development of the new wind tunnel model equipped with fluidic oscillators is explained in terms of the previous test results. Large drag reductions greater than 20% in some cases were measured during powered testing without increasing, and in some cases decreasing download in forward flight. As confirmed by Particle Image Velocimetry (PIV), the optimum actuator configuration that provided a decrease in both drag and download appeared to create a virtual (fluidic) boat-tail fairing instead of attaching flow to the ramp surface. This idea of a fluidic fairing shifts the focus of 3D separation control behind bluff bodies from controlling/reattaching surface boundary layers to interacting with the wake flow.

Variable camber rotor study

NASA Technical Reports Server (NTRS)

Dadone, L.; Cowan, J.; Mchugh, F. J.

1982-01-01

Deployment of variable camber concepts on helicopter rotors was analytically assessed. It was determined that variable camber extended the operating range of helicopters provided that the correct compromise can be obtained between performance/loads gains and mechanical complexity. A number of variable camber concepts were reviewed on a two dimensional basis to determine the usefulness of leading edge, trailing edge and overall camber variation schemes. The most powerful method to vary camber was through the trailing edge flaps undergoing relatively small motions (-5 deg to +15 deg). The aerodynamic characteristics of the NASA/Ames A-1 airfoil with 35% and 50% plain trailing edge flaps were determined by means of current subcritical and transonic airfoil design methods and used by rotor performance and loads analysis codes. The most promising variable camber schedule reviewed was a configuration with a 35% plain flap deployment in an on/off mode near the tip of a blade. Preliminary results show approximately 11% reduction in power is possible at 192 knots and a rotor thrust coefficient of 0.09. The potential demonstrated indicates a significant potential for expanding the operating envelope of the helicopter. Further investigation into improving the power saving and defining the improvement in the operational envelope of the helicopter is recommended.

“Slimming” of power-law tails by increasing market returns

NASA Astrophysics Data System (ADS)

Sornette, D.

2002-06-01

We introduce a simple generalization of rational bubble models which removes the fundamental problem discovered by Lux and Sornette (J. Money, Credit and Banking, preprint at http://xxx.lanl.gov/abs/cond-mat/9910141) that the distribution of returns is a power law with exponent <1, in contradiction with empirical data. The idea is that the price fluctuations associated with bubbles must on average grow with the mean market return r. When r is larger than the discount rate rδ, the distribution of returns of the observable price, sum of the bubble component and of the fundamental price, exhibits an intermediate tail with an exponent which can be larger than 1. This regime r> rδ corresponds to a generalization of the rational bubble model in which the fundamental price is no more given by the discounted value of future dividends. We explain how this is possible. Our model predicts that, the higher is the market remuneration r above the discount rate, the larger is the power-law exponent and thus the thinner is the tail of the distribution of price returns.

14 CFR 23.1461 - Equipment containing high energy rotors.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Equipment containing high energy rotors. 23... Equipment Miscellaneous Equipment § 23.1461 Equipment containing high energy rotors. (a) Equipment, such as Auxiliary Power Units (APU) and constant speed drive units, containing high energy rotors must meet...

14 CFR 23.1461 - Equipment containing high energy rotors.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Equipment containing high energy rotors. 23... Equipment Miscellaneous Equipment § 23.1461 Equipment containing high energy rotors. (a) Equipment, such as Auxiliary Power Units (APU) and constant speed drive units, containing high energy rotors must meet...

14 CFR 23.1461 - Equipment containing high energy rotors.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Equipment containing high energy rotors. 23... Equipment Miscellaneous Equipment § 23.1461 Equipment containing high energy rotors. (a) Equipment, such as Auxiliary Power Units (APU) and constant speed drive units, containing high energy rotors must meet...

14 CFR 23.1461 - Equipment containing high energy rotors.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Equipment containing high energy rotors. 23... Equipment Miscellaneous Equipment § 23.1461 Equipment containing high energy rotors. (a) Equipment, such as Auxiliary Power Units (APU) and constant speed drive units, containing high energy rotors must meet...

14 CFR 23.1461 - Equipment containing high energy rotors.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Equipment containing high energy rotors. 23... Equipment Miscellaneous Equipment § 23.1461 Equipment containing high energy rotors. (a) Equipment, such as Auxiliary Power Units (APU) and constant speed drive units, containing high energy rotors must meet...

Stall induced instability of a teetered rotor

NASA Astrophysics Data System (ADS)

Glasgow, J. C.; Corrigan, R. D.

Recent tests on the 38m Mod-0 horizontal experimental wind turbine yielded quantitative information on stall induced instability of a teetered rotor. Tests were conducted on rotor blades with NACA 230 series and NACA 643-618 airfoils at low rotor speeds to produce high angles of attack at relatively low wind speeds and power levels. The behavior of the rotor shows good agreement with predicted rotor response based on blade angle of attack calculations and airfoil section properties. The untwisted blades with the 64 series airfoil sections had a slower rate of onset of rotor instability when compared with the twisted 230 series blades, but high teeter angles and teeter stop impacts were experienced with both rotors as wind speeds increased to produce high angles of attack on the outboard portion of the blade. The relative importance of blade twist and airfoil section stall characteristics on the rate of onset of rotor unstability with increasing wind speed was not established however. Blade pitch was shown to be effective in eliminating rotor instability at the expense of some loss in rotor performance near rated wind speed.

A prescribed wake rotor inflow and flow field prediction analysis, user's manual and technical approach

NASA Technical Reports Server (NTRS)

Egolf, T. A.; Landgrebe, A. J.

1982-01-01

A user's manual is provided which includes the technical approach for the Prescribed Wake Rotor Inflow and Flow Field Prediction Analysis. The analysis is used to provide the rotor wake induced velocities at the rotor blades for use in blade airloads and response analyses and to provide induced velocities at arbitrary field points such as at a tail surface. This analysis calculates the distribution of rotor wake induced velocities based on a prescribed wake model. Section operating conditions are prescribed from blade motion and controls determined by a separate blade response analysis. The analysis represents each blade by a segmented lifting line, and the rotor wake by discrete segmented trailing vortex filaments. Blade loading and circulation distributions are calculated based on blade element strip theory including the local induced velocity predicted by the numerical integration of the Biot-Savart Law applied to the vortex wake model.

REAR PROFILE OF TAIL FROM SECOND LEVEL OF TAIL DOCK ...

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

REAR PROFILE OF TAIL FROM SECOND LEVEL OF TAIL DOCK STAND, SHOWING AIRCRAFT NUMBER (319), HORIZONTAL STABILIZER, TAIL CONE AND COOLING CTS FOR THE AUXILIARY POWER UNIT (APU), MECHANIC PAUL RIDEOUT IS LOWERING THE BALANCE PANELS ON THE STABILIZERS FOR LUBRICATION AND INSPECTION. - Greater Buffalo International Airport, Maintenance Hangar, Buffalo, Erie County, NY

Empennage Noise Shielding Benefits for an Open Rotor Transport

NASA Technical Reports Server (NTRS)

Berton, Jeffrey J.

2012-01-01

NASA sets aggressive, strategic, civil aircraft performance and environmental goals and develops ambitious technology roadmaps to guide its research efforts. NASA has adopted a phased approach for community noise reduction of civil aircraft. While the goal of the near-term first phase focuses primarily on source noise reduction, the goal of the second phase relies heavily on presumed architecture changes of future aircraft. The departure from conventional airplane configurations to designs that incorporate some type of propulsion noise shielding is anticipated to provide an additional 10 cumulative EPNdB of noise reduction. One candidate propulsion system for these advanced aircraft is the open rotor engine. In some planned applications, twin open rotor propulsors are located on the aft fuselage, with the vehicle s empennage shielding some of their acoustic signature from observers on the ground. This study focuses on predicting the noise certification benefits of a notional open rotor aircraft with tail structures shielding a portion of the rotor noise. The measured noise of an open rotor test article--collected with and without an acoustic barrier wall--is the basis of the prediction. The results are used to help validate NASA s reliance on acoustic shielding to achieve the second phase of its community noise reduction goals. The noise measurements are also compared to a popular empirical diffraction correlation often used at NASA to predict acoustic shielding.

Numerical analysis of a variable camber rotor blade as a lift control device

NASA Technical Reports Server (NTRS)

Awani, A. O.; Stroub, R. H.

1984-01-01

A new rotor configuration called the variable camber rotor was numerically investigated as a lift control device. This rotor differs from a conventional (baseline) rotor only in the blade aft section. In this configuration, the aft section or flap is attached to the forward section by pin joint arrangement, and also connected to the rotor control system for the control of rotor thrust level and vectoring. Pilot action to the flap deflection controls rotor lift and tip path plane tilt. The drag due to flaps is presented and the theoretical result correlated with test data. The assessment of payoff for the variable camber rotor in comparison with conventional (baseline) rotor was examined in hover. The variable camber rotor is shown to increase hover power required by 1.35%, but such a minimal power penalty is not significant enough to be considered a negative result. In forward flight, the control needs of the variable camber rotor were evaluated.

System and method for cancelling expansion waves in a wave rotor

NASA Astrophysics Data System (ADS)

Paxson, Daniel E.

1993-12-01

A wave rotor system that is comprised of a wave rotor coupled to first and second plates is described. Special ports are provided, one in each of the first and second end plates, to cancel expansion waves generated by the release of working fluid from the wave rotor. One of the expansion waves is reflected in the wave rotor from a reflecting portion and provided to the special port in the second end plate. Fluid present at the special port in the second end plate has a stagnation pressure and mass flow which is the same as that of the cells of the wave rotor communicating with such special port. This allows for cancellation of the expansion wave generated by the release of working fluid from the wave rotor. The special port in the second end plate has a first end corresponding to the head of the expansion wave and a second end corresponding to the tail of the expansion wave. Also, the special port is configured to continually change along the circumference of the second end plate to affect expansion wave cancellation. An expansion wave generated by a second release of working fluid from the wave rotor is cancelled in a similar manner to that described above using a special port in the first end plate. The cycle of operation of the wave rotor system is designed so that the stagnation pressure and mass flow of the fluid present at the special ports is the same so that the special ports may be connected by a common duct.

Wind-tunnel Tests of a Cyclogiro Rotor

NASA Technical Reports Server (NTRS)

Wheatley, John B; Windler, Ray

1935-01-01

During an extensive study of all types of rotating wings, the NACA examined the cyclogiro rotor and made an aerodynamic analysis of that system (reference 1). The examination disclosed that such a machine had sufficient promise to justify an experimental investigation; a model with a diameter and span of 8 feet was therefore constructed and tested in the 20-foot wind tunnel during 1934. The experimental work included tests of the effect of the motion upon the rotor forces during the static-lift and forward-flight conditions at several rotor speeds and the determination of the relations between the forces generated by the rotor and the power required by it.

Effect of AFT Rotor on the Inter-Rotor Flow of an Open Rotor Propulsion System

NASA Technical Reports Server (NTRS)

Slaboch, Paul E.; Stephens, David B.; Van Zante, Dale E.

2016-01-01

The effects of the aft rotor on the inter-rotor flow field of an open rotor propulsion rig were examined. A Particle Image Velocimetry (PIV) dataset that was acquired phase locked to the front rotor position has been phase averaged based on the relative phase angle between the forward and aft rotors. The aft rotor phase was determined by feature tracking in raw PIV images through an image processing algorithm. The effect of the aft rotor potential field on the inter-rotor flow were analyzed and shown to be in good agreement with Computational Fluid Dynamics (CFD) simulations. It was shown that the aft rotor had no substantial effect on the position of the forward rotor tip vortex but did have a small effect on the circulation strength of the vortex when the rotors were highly loaded.

Single rotor turbine engine

DOEpatents

Platts, David A.

2002-01-01

There has been invented a turbine engine with a single rotor which cools the engine, functions as a radial compressor, pushes air through the engine to the ignition point, and acts as an axial turbine for powering the compressor. The invention engine is designed to use a simple scheme of conventional passage shapes to provide both a radial and axial flow pattern through the single rotor, thereby allowing the radial intake air flow to cool the turbine blades and turbine exhaust gases in an axial flow to be used for energy transfer. In an alternative embodiment, an electric generator is incorporated in the engine to specifically adapt the invention for power generation. Magnets are embedded in the exhaust face of the single rotor proximate to a ring of stationary magnetic cores with windings to provide for the generation of electricity. In this alternative embodiment, the turbine is a radial inflow turbine rather than an axial turbine as used in the first embodiment. Radial inflow passages of conventional design are interleaved with radial compressor passages to allow the intake air to cool the turbine blades.

NASA rotor systems research aircraft: Fixed-wing configuration flight-test results

NASA Technical Reports Server (NTRS)

Erickson, R. E.; Cross, J. L.; Kufeld, R. M.; Acree, C. W.; Nguyen, D.; Hodge, R. W.

1986-01-01

The fixed-wing, airplane configuration flight-test results of the Rotor System Research Aircraft (RSRA), NASA 740, at Ames/Dryden Flight Research Center are documented. Fourteen taxi and flight tests were performed from December 1983 to October 1984. This was the first time the RSRA was flown with the main rotor removed; the tail rotor was installed. These tests confirmed that the RSRA is operable as a fixed-wing aircraft. Data were obtained for various takeoff and landing distances, control sensitivity, trim and dynamics stability characteristics, performance rotor-hub drag, and acoustics signature. Stability data were obtained with the rotor hub both installed and removed. The speed envelope was developed to 261 knots true airspeed (KTAS), 226 knots calibrated airspeed (KCAS) at 10,000 ft density altitude. The airplane was configured at 5 deg. wing incidence with 5 deg. wing flaps as a normal configuration. Level-flight data were acquired at 167 KCAS for wing incidence from 0 to 10 deg. Step inputs and doublet inputs of various magnitudes were utilized to acquire dynamic stability and control sensitivity data. Sine-wave inputs of constantly increasing frequency were used to generate parameter identification data. The maximum load factor attained was 2.34 g at 206 KCAS.

A flight-dynamic helicopter mathematical model with a single flap-lag-torsion main rotor

NASA Technical Reports Server (NTRS)

Takahashi, Marc D.

1990-01-01

A mathematical model of a helicopter system with a single main rotor that includes rigid, hinge-restrained rotor blades with flap, lag, and torsion degrees of freedom is described. The model allows several hinge sequences and two offsets in the hinges. Quasi-steady Greenberg theory is used to calculate the blade-section aerodynamic forces, and inflow effects are accounted for by using three-state nonlinear dynamic inflow model. The motion of the rigid fuselage is defined by six degrees of freedom, and an optional rotor rpm degree of freedom is available. Empennage surfaces and the tail rotor are modeled, and the effect of main-rotor downwash on these elements is included. Model trim linearization, and time-integration operations are described and can be applied to a subset of the model in the rotating or nonrotating coordinate frame. A preliminary validation of the model is made by comparing its results with those of other analytical and experimental studies. This publication presents the results of research compiled in November 1989.

Performance of Single-Stage Turbine of Mark 25 Torpedo Power Plant with Two Nozzles and Three Rotor-Blade Designs

NASA Technical Reports Server (NTRS)

Schum, Harold J.; Whitney, Warren J.

1949-01-01

A single-stage modification of the turbine from a Mark 25 torpedo power plant was investigated to determine the performance with two nozzles and three rotor-blade designs. The performance was evaluated in terms of brake, rotor, and blade efficiencies at pressure ratios of 8, 15 (design), and 20. The blade efficiencies with the two nozzles are compared with those obtained with four other nozzles previously investigated with the same three rotor-blade designs. Blade efficiency with the cast nozzle of rectangular cross section (J) was higher than that with the circular reamed nozzle (K) at all speeds and pressure ratios with a rotor having a 0.45-inch 17 degree-inlet-angle blades. The efficiencies for both these nozzles were generally low compared with those of the four other nozzles previously investigated in combination with this rotor. At pressure ratios of 15 and 20, the blade efficiencies with nozzle K and the two rotors with 0.40-inch blades having different inlet angles were higher than with the four other nozzles, but the efficiency with nozzle J was generally low. Increasing the blade inlet angle from 17 degrees to 20 degrees had little effect on turbine performance, whereas changing the blade length from 0.40 to 0.45 inch had a marked effect. Although a slight correlation of efficiency with nozzle size was noted for the rotor with 0.45-inch 17 degree-inlet-angle blades, no such effect was discernible ,for the two rotors with 0.40-inch blades.Losses in the supersonic air stream resulting from the complex flow path in the small air passages are probably a large percentage of the total losses, and apparently the effects of changing nozzle size and shape within the limits investigated are of secondary importance.

Higher harmonic control analysis for vibration reduction of helicopter rotor systems

NASA Technical Reports Server (NTRS)

Nguyen, Khanh Q.

1994-01-01

An advanced higher harmonic control (HHC) analysis has been developed and applied to investigate its effect on vibration reduction levels, blade and control system fatigue loads, rotor performance, and power requirements of servo-actuators. The analysis is based on a finite element method in space and time. A nonlinear time domain unsteady aerodynamic model, based on the indicial response formulation, is used to calculate the airloads. The rotor induced inflow is computed using a free wake model. The vehicle trim controls and blade steady responses are solved as one coupled solution using a modified Newton method. A linear frequency-domain quasi-steady transfer matrix is used to relate the harmonics of the vibratory hub loads to the harmonics of the HHC inputs. Optimal HHC is calculated from the minimization of the vibratory hub loads expressed in term of a quadratic performance index. Predicted vibratory hub shears are correlated with wind tunnel data. The fixed-gain HHC controller suppresses completely the vibratory hub shears for most of steady or quasi-steady flight conditions. HHC actuator amplitudes and power increase significantly at high forward speeds (above 100 knots). Due to the applied HHC, the blade torsional stresses and control loads are increased substantially. For flight conditions where the blades are stalled considerably, the HHC input-output model is quite nonlinear. For such cases, the adaptive-gain controller is effective in suppressing vibratory hub loads, even though HHC may actually increase stall areas on the rotor disk. The fixed-gain controller performs poorly for such flight conditions. Comparison study of different rotor systems indicates that a soft-inplane hingeless rotor requires less actuator power at high speeds (above 130 knots) than an articulated rotor, and a stiff-inplane hingeless rotor generally requires more actuator power than an articulated or a soft-inplane hingeless rotor. Parametric studies for a hingeless rotor

Far-Field Acoustic Power Level and Performance Analyses of F31/A31 Open Rotor Model at Simulated Scaled Takeoff, Nominal Takeoff, and Approach Conditions: Technical Report I

NASA Technical Reports Server (NTRS)

Sree, Dave

2015-01-01

Far-field acoustic power level and performance analyses of open rotor model F31/A31 have been performed to determine its noise characteristics at simulated scaled takeoff, nominal takeoff, and approach flight conditions. The nonproprietary parts of the data obtained from experiments in 9- by 15-Foot Low-Speed Wind Tunnel (9?15 LSWT) tests were provided by NASA Glenn Research Center to perform the analyses. The tone and broadband noise components have been separated from raw test data by using a new data analysis tool. Results in terms of sound pressure levels, acoustic power levels, and their variations with rotor speed, angle of attack, thrust, and input shaft power have been presented and discussed. The effect of an upstream pylon on the noise levels of the model has been addressed. Empirical equations relating model's acoustic power level, thrust, and input shaft power have been developed. The far-field acoustic efficiency of the model is also determined for various simulated flight conditions. It is intended that the results presented in this work will serve as a database for comparison and improvement of other open rotor blade designs and also for validating open rotor noise prediction codes.

Flight Investigation of Effects of Transition, Landing Approaches, Partial-Power Vertical Descents, and Droop-Stop Pounding on the Bending and Torsional Moments Encountered by a Helicopter Rotor Blade

NASA Technical Reports Server (NTRS)

Ludi, LeRoy H.

1959-01-01

Flight tests have been conducted with a single-rotor helicopter, one blade of which was equipped at 14 percent and 40 percent of the blade radius with strain gages calibrated to measure moments rather than stresses, to determine the effects of transition, landing approaches, and partial-power vertical descents on the rotor-blade bending and torsional moments. In addition, ground tests were conducted to determine the effects of static droop-stop pounding on the rotor-blade moments. The results indicate that partial-power vertical descents and landing approaches produce rotor-blade moments that are higher than the moments encountered in any other flight condition investigated to date with this equipment. Decelerating through the transition region in level flight was found to result in higher vibratory moments than accelerating through this region. Deliberately induced static droop-stop pounding produced flapwise bending moments at the 14-percent-radius station which were as high as the moments experienced in landing approaches and partial-power vertical descents.

Prospects for development of wind turbines with orthogonal rotor

NASA Astrophysics Data System (ADS)

Gorelov, D. N.; Krivospitsky, V. P.

2008-03-01

The experimental data obtained previously on the investigation of power characteristics and the possibility of the self-start of the Darrieus rotor are anlysed. These results are used at the design of new two-tier wind turbines with straight blades. The full-scale tests of two design variants showed the prospects for the development of wind turbines with the Darrieus rotor. At a reasonable design, they do not need any devices for the rotor orientation and start-up, are little sensitive to wind gusts and can have a high level of power characteristics, which is not inferior to the best samples of the units of propeller type.

A two dimensional power spectral estimate for some nonstationary processes. M.S. Thesis

NASA Technical Reports Server (NTRS)

Smith, Gregory L.

1989-01-01

A two dimensional estimate for the power spectral density of a nonstationary process is being developed. The estimate will be applied to helicopter noise data which is clearly nonstationary. The acoustic pressure from the isolated main rotor and isolated tail rotor is known to be periodically correlated (PC) and the combined noise from the main and tail rotors is assumed to be correlation autoregressive (CAR). The results of this nonstationary analysis will be compared with the current method of assuming that the data is stationary and analyzing it as such. Another method of analysis is to introduce a random phase shift into the data as shown by Papoulis to produce a time history which can then be accurately modeled as stationary. This method will also be investigated for the helicopter data. A method used to determine the period of a PC process when the period is not know is discussed. The period of a PC process must be known in order to produce an accurate spectral representation for the process. The spectral estimate is developed. The bias and variability of the estimate are also discussed. Finally, the current method for analyzing nonstationary data is compared to that of using a two dimensional spectral representation. In addition, the method of phase shifting the data is examined.

Methods and apparatus for rotor load control in wind turbines

DOEpatents

Moroz, Emilian Mieczyslaw

2006-08-22

A wind turbine having a rotor, at least one rotor blade, and a plurality of generators, of which a first generator is configured to provide power to an electric grid and a second generator is configured to provide power to the wind turbine during times of grid loss. The wind turbine is configured to utilize power provided by the second generator to reduce loads on the wind turbine during times of grid loss.

14 CFR 27.923 - Rotor drive system and control mechanism tests.

Code of Federal Regulations, 2011 CFR

2011-01-01

... purpose of this paragraph, an affected power input includes all parts of the rotor drive system which can... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Rotor drive system and control mechanism... TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT Powerplant Rotor Drive System § 27...

14 CFR 27.923 - Rotor drive system and control mechanism tests.

Code of Federal Regulations, 2013 CFR

2013-01-01

... purpose of this paragraph, an affected power input includes all parts of the rotor drive system which can... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Rotor drive system and control mechanism... TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT Powerplant Rotor Drive System § 27...

Steady and Periodic Pressure Measurements on a Generic Helicopter Fuselage Model in the Presence of a Rotor

NASA Technical Reports Server (NTRS)

Mineck, Raymond E.; Gorton, Susan A.

2000-01-01

A wind tunnel test of a generic helicopter fuselage model with an independently mounted rotor has been conducted to obtain steady and periodic pressure data on the helicopter body. The model was tested at four advance ratios and three thrust coefficients. The periodic unsteady pressure coefficients are marked by four peaks associated with the passage of the four rotor blades. Blade passage effects are largest on the nose and tail boom of the model. The magnitude of the pulse increases with rotor thrust coefficient. Tabular listings of the unsteady pressure data are included to permit independent analysis. A CD-rom containing the steady and unsteady pressure data presented in the report is available from the authors.

Composite rotor blades for large wind energy installations

NASA Technical Reports Server (NTRS)

Kussmann, A.; Molly, J.; Muser, D.

1980-01-01

The design of large wind power systems in Germany is reviewed with attention given to elaboration of the total wind energy system, aerodynamic design of the rotor blade, and wind loading effects. Particular consideration is given to the development of composite glass fiber/plastic or carbon fiber/plastic rotor blades for such installations.

Synchronous Motor with Hybrid Permanent Magnets on the Rotor

PubMed Central

Slusarek, Barbara; Kapelski, Dariusz; Antal, Ludwik; Zalas, Pawel; Gwoździewicz, Maciej

2014-01-01

Powder metallurgy allows designers of electric motors to implement new magnetic circuit structures. A relatively new concept is the use of a magnet system consisting of various types of magnets on one rotor, for example sintered and bonded magnets. This concept has been applied to the design and manufacture of the four-pole rotor of a synchronous motor with 400 W power and a rotational speed of 1500 rpm. In this motor, the stator of an asynchronous motor type Sh 71-4B is applied. The application of the new construction of the rotor resulted in an increase in motor efficiency and power factor compared to an asynchronous motor with the same volume. PMID:25014102

Synchronous motor with hybrid permanent magnets on the rotor.

PubMed

Slusarek, Barbara; Kapelski, Dariusz; Antal, Ludwik; Zalas, Pawel; Gwoździewicz, Maciej

2014-07-10

Powder metallurgy allows designers of electric motors to implement new magnetic circuit structures. A relatively new concept is the use of a magnet system consisting of various types of magnets on one rotor, for example sintered and bonded magnets. This concept has been applied to the design and manufacture of the four-pole rotor of a synchronous motor with 400 W power and a rotational speed of 1500 rpm. In this motor, the stator of an asynchronous motor type Sh 71-4B is applied. The application of the new construction of the rotor resulted in an increase in motor efficiency and power factor compared to an asynchronous motor with the same volume.

Jet engine performance enhancement through use of a wave-rotor topping cycle

NASA Technical Reports Server (NTRS)

Wilson, Jack; Paxson, Daniel E.

1993-01-01

A simple model is used to calculate the thermal efficiency and specific power of simple jet engines and jet engines with a wave-rotor topping cycle. The performance of the wave rotor is based on measurements from a previous experiment. Applied to the case of an aircraft flying at Mach 0.8, the calculations show that an engine with a wave rotor topping cycle may have gains in thermal efficiency of approximately 1 to 2 percent and gains in specific power of approximately 10 to 16 percent over a simple jet engine with the same overall compression ratio. Even greater gains are possible if the wave rotor's performance can be improved.

Design of a Slowed-Rotor Compound Helicopter for Future Joint Service Missions

DTIC Science & Technology

2010-01-01

achieves a 208kt top speed at engine MCP and 11,000ft/ISA while having 216hp/ton installed power, based on engine MRP and MTOW. Figure 33...Intermediate rated power ISA International Standard Atmosphere MCP Maximum continuous power MRP Maximum rated power MTOW Maximum Takeoff Weight NDARC...NASA Design and Analysis of Rotorcraft SFC Specific fuel consumption SRC Slowed-Rotor Compound Symbols σ Rotor solidity (geometric) CD Drag

75 FR 69860 - Airworthiness Directives; Bell Helicopter Textron Canada Model 206L, 206L-1, and 206L-3 Helicopters

Federal Register 2010, 2011, 2012, 2013, 2014

2010-11-16

... the tailboom skin in the areas around the nutplates and in the areas of the tailboom drive shaft cover retention clips for cracks and corrosion using a 10-power or higher magnifying glass until the tailboom is... the tail rotor fairing and in the areas of the tail rotor drive shaft cover retention clips. The...

Navier-Stokes Simulation of a Heavy Lift Slowed-Rotor Compound Helicopter Configuration

NASA Technical Reports Server (NTRS)

Allan, Brian G.; Jenkins, Luther N.; Yao, Chung-Sheng; Bartram, Scott M.; Hallissy, Jim B.; Harris, Jerome; Noonan, Kevin W.; Wong, Oliver D.; Jones, Henry E.; Malovrh, Brendon D.;

Flow Structures within a Helicopter Rotor Hub Wake

NASA Astrophysics Data System (ADS)

Elbing, Brian; Reich, David; Schmitz, Sven

2015-11-01

A scaled model of a notional helicopter rotor hub was tested in the 48'' Garfield Thomas Water Tunnel at the Applied Research Laboratory Penn State. The measurement suite included total hub drag and wake velocity measurements (LDV, PIV, stereo-PIV) at three downstream locations. The main objective was to understand the spatiotemporal evolution of the unsteady wake between the rotor hub and the nominal location of the empennage (tail). Initial analysis of the data revealed prominent two- and four-per-revolution fluid structures linked to geometric hub features persisting into the wake far-field. In addition, a six-per-revolution fluid structure was observed in the far-field, which is unexpected due to the lack of any hub feature with the corresponding symmetry. This suggests a nonlinear interaction is occurring within the wake to generate these structures. This presentation will provide an overview of the experimental data and analysis with particular emphasis on these six-per-revolution structures.

Modeling Creep-Fatigue-Environment Interactions in Steam Turbine Rotor Materials for Advanced Ultra-supercritical Coal Power Plants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, Chen

2014-04-01

The goal of this project is to model creep-fatigue-environment interactions in steam turbine rotor materials for advanced ultra-supercritical (A-USC) coal power Alloy 282 plants, to develop and demonstrate computational algorithms for alloy property predictions, and to determine and model key mechanisms that contribute to the damages caused by creep-fatigue-environment interactions.

Assessment of Scaled Rotors for Wind Tunnel Experiments.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maniaci, David Charles; Kelley, Christopher Lee; Chiu, Phillip

2015-07-01

Rotor design and analysis work has been performed to support the conceptualization of a wind tunnel test focused on studying wake dynamics. This wind tunnel test would serve as part of a larger model validation campaign that is part of the Department of Energy Wind and Water Power Program’s Atmosphere to electrons (A2e) initiative. The first phase of this effort was directed towards designing a functionally scaled rotor based on the same design process and target full-scale turbine used for new rotors for the DOE/SNL SWiFT site. The second phase focused on assessing the capabilities of an already available rotor,more » the G1, designed and built by researchers at the Technical University of München.« less

Preliminary rotor wake measurements with a laser velocimeter

NASA Technical Reports Server (NTRS)

Hoad, D. R.; Rhodes, D. B.; Meyers, J. F.

1983-01-01

A laser velocimeter (LV) was used to determine rotor wake characteristics. The effect of various fuselage widths and rotor-fuselage spacings on time averaged and detailed time dependent rotor wake velocity characteristics was defined. Definition of time dependent velocity characteristics was attempted with the LV by associating a rotor azimuth position with each velocity measurement. Results were discouraging in that no apparent time dependent velocity characteristics could be discerned from the LV measurements. Since the LV is a relatively new instrument in the rotor wake measurement field, the cause of this lack of periodicity is as important as the basic research objectives. An attempt was made to identify the problem by simulated acquisition of LV-type data for a predicted rotor wake velocity time history. Power spectral density and autocorrelation function estimation techniques were used to substantiate the conclusion that the primary cause of the lack of time dependent velocity characteristics was the nonstationary flow condition generated by the periodic turbulence level that currently exists in the open throat configuration of the wind tunnel.

Wave-Rotor-Enhanced Gas Turbine Engine Demonstrator

NASA Technical Reports Server (NTRS)

Welch, Gerard E.; Paxson, Daniel E.; Wilson, Jack; Synder, Philip H.

1999-01-01

The U.S. Army Research Laboratory, NASA Glenn Research Center, and Rolls-Royce Allison are working collaboratively to demonstrate the benefits and viability of a wave-rotor-topped gas turbine engine. The self-cooled wave rotor is predicted to increase the engine overall pressure ratio and peak temperature by 300% and 25 to 30%. respectively, providing substantial improvements in engine efficiency and specific power. Such performance improvements would significantly reduce engine emissions and the fuel logistics trails of armed forces. Progress towards a planned demonstration of a wave-rotor-topped Rolls-Royce Allison model 250 engine has included completion of the preliminary design and layout of the engine, the aerodynamic design of the wave rotor component and prediction of its aerodynamic performance characteristics in on- and off-design operation and during transients, and the aerodynamic design of transition ducts between the wave rotor and the high pressure turbine. The topping cycle increases the burner entry temperature and poses a design challenge to be met in the development of the demonstrator engine.

Integration of a wave rotor to an ultra-micro gas turbine (UmuGT)

NASA Astrophysics Data System (ADS)

Iancu, Florin

2005-12-01

Wave rotor technology has shown a significant potential for performance improvement of thermodynamic cycles. The wave rotor is an unsteady flow machine that utilizes shock waves to transfer energy from a high energy fluid to a low energy fluid, increasing both the temperature and the pressure of the low energy fluid. Used initially as a high pressure stage for a gas turbine locomotive engine, the wave rotor was commercialized only as a supercharging device for internal combustion engines, but recently there is a stronger research effort on implementing wave rotors as topping units or pressure gain combustors for gas turbines. At the same time, Ultra Micro Gas Turbines (UmuGT) are expected to be a next generation of power source for applications from propulsion to power generation, from aerospace industry to electronic industry. Starting in 1995, with the MIT "Micro Gas Turbine" project, the mechanical engineering research world has explored more and more the idea of "Power MEMS". Microfabricated turbomachinery like turbines, compressors, pumps, but also electric generators, heat exchangers, internal combustion engines and rocket engines have been on the focus list of researchers for the past 10 years. The reason is simple: the output power is proportional to the mass flow rate of the working fluid through the engine, or the cross-sectional area while the mass or volume of the engine is proportional to the cube of the characteristic length, thus the power density tends to increase at small scales (Power/Mass=L -1). This is the so-called "cube square law". This work investigates the possibilities of incorporating a wave rotor to an UmuGT and discusses the advantages of wave rotor as topping units for gas turbines, especially at microscale. Based on documented wave rotor efficiencies at larger scale and subsidized by both, a gasdynamic model that includes wall friction, and a CFD model, the wave rotor compression efficiency at microfabrication scale could be estimated

Aeromechanical Evaluation of Smart-Twisting Active Rotor

NASA Technical Reports Server (NTRS)

Lim, Joon W.; Boyd, D. Douglas, Jr.; Hoffman, Frauke; van der Wall, Berend G.; Kim, Do-Hyung; Jung, Sung N.; You, Young H.; Tanabe, Yasutada; Bailly, Joelle; Lienard, Caroline;

Tail Shape Design of Boat Wind Turbines

NASA Astrophysics Data System (ADS)

Singamsitty, Venkatesh

Wind energy is a standout among the most generally utilized sustainable power source assets. A great deal of research and improvements have been happening in the wind energy field. Wind turbines are mechanical devices that convert kinetic energy into electrical power. Boat wind turbines are for the small-scale generation of electric power. In order to catch wind energy effectively, boat wind turbines need to face wind direction. Tails are used in boat wind turbines to alter the wind turbine direction and receive the variation of the incoming direction of wind. Tails are used to change the performance of boat wind turbines in an effective way. They are required to generate a quick and steady response as per change in wind direction. Tails can have various shapes, and their effects on boat wind turbines are different. However, the effects of tail shapes on the performance of boat wind turbines are not thoroughly studied yet. In this thesis, five tail shapes were studied. Their effects on boat wind turbines were investigated. The power extracted by the turbines from the air and the force acting on the boat wind turbine tail were analyzed. The results of this thesis provide a guideline of tail shape design for boat wind turbines.

Mach number scaling of helicopter rotor blade/vortex interaction noise

NASA Technical Reports Server (NTRS)

Leighton, Kenneth P.; Harris, Wesley L.

1985-01-01

A parametric study of model helicopter rotor blade slap due to blade vortex interaction (BVI) was conducted in a 5 by 7.5-foot anechoic wind tunnel using model helicopter rotors with two, three, and four blades. The results were compared with a previously developed Mach number scaling theory. Three- and four-bladed rotor configurations were found to show very good agreement with the Mach number to the sixth power law for all conditions tested. A reduction of conditions for which BVI blade slap is detected was observed for three-bladed rotors when compared to the two-bladed baseline. The advance ratio boundaries of the four-bladed rotor exhibited an angular dependence not present for the two-bladed configuration. The upper limits for the advance ratio boundaries of the four-bladed rotors increased with increasing rotational speed.

A theoretical study of the application of jet flap circulation control for reduction of rotor vibratory forces

NASA Technical Reports Server (NTRS)

Piziali, R. A.; Trenka, A. R.

1974-01-01

The results of a study to investigate the theoretical potential of a jet-flap control system for reducing the vertical and horizontal non-cancelling helicopter rotor blade root shears are presented. A computer simulation describing the jet-flap control rotor system was developed to examine the reduction of each harmonic of the transmitted shears as a function of various rotor and jet parameters, rotor operating conditions and rotor configurations. The computer simulation of the air-loads included the influences of nonuniform inflow and blade elastic motions. (no hub motions were allowed.) The rotor trim and total rotor power (including jet compressor power) were also determined. It was found that all harmonics of the transmitted horizontal and vertical shears could be suppressed simultaneously using a single jet control.

Performance of twist-coupled blades on variable speed rotors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lobitz, D.W.; Veers, P.S.; Laino, D.J.

1999-12-07

The load mitigation and energy capture characteristics of twist-coupled HAWT blades that are mounted on a variable speed rotor are investigated in this paper. These blades are designed to twist toward feather as they bend with pretwist set to achieve a desirable twist distribution at rated power. For this investigation, the ADAMS-WT software has been modified to include blade models with bending-twist coupling. Using twist-coupled and uncoupled models, the ADAMS software is exercised for steady wind environments to generate C{sub p} curves at a number of operating speeds to compare the efficiencies of the two models. The ADAMS software ismore » also used to generate the response of a twist-coupled variable speed rotor to a spectrum of stochastic wind time series. This spectrum contains time series with two mean wind speeds at two turbulence levels. Power control is achieved by imposing a reactive torque on the low speed shaft proportional to the RPM squared with the coefficient specified so that the rotor operates at peak efficiency in the linear aerodynamic range, and by limiting the maximum RPM to take advantage of the stall controlled nature of the rotor. Fatigue calculations are done for the generated load histories using a range of material exponents that represent materials from welded steel to aluminum to composites, and results are compared with the damage computed for the rotor without twist-coupling. Results indicate that significant reductions in damage are achieved across the spectrum of applied wind loading without any degradation in power production.« less

Hover and wind-tunnel testing of shrouded rotors for improved micro air vehicle design

NASA Astrophysics Data System (ADS)

Pereira, Jason L.

The shrouded-rotor configuration has emerged as the most popular choice for rotary-wing Micro Air Vehicles (MAVs), because of the inherent safety of the design and the potential for significant performance improvements. However, traditional design philosophies based on experience with large-scale ducted propellers may not apply to the low-Reynolds-number (˜20,000) regime in which MAVs operate. An experimental investigation of the effects of varying the shroud profile shape on the performance of MAV-scale shrouded rotors has therefore been conducted. Hover tests were performed on seventeen models with a nominal rotor diameter of 16 cm (6.3 in) and various values of diffuser expansion angle, diffuser length, inlet lip radius and blade tip clearance, at various rotor collective angles. Compared to the baseline open rotor, the shrouded rotors showed increases in thrust by up to 94%, at the same power consumption, or reductions in power by up to 62% at the same thrust. These improvements surpass those predicted by momentum theory, due to the additional effect of the shrouds in reducing the non-ideal power losses of the rotor. Increasing the lip radius and decreasing the blade tip clearance caused performance to improve, while optimal values of diffuser angle and length were found to be 10 and 50% of the shroud throat diameter, respectively. With the exception of the lip radius, the effects of changing any of the shrouded-rotor parameters on performance became more pronounced as the values of the other parameters were changed to degrade performance. Measurements were also made of the wake velocity profiles and the shroud surface pressure distributions. The uniformity of the wake was improved by the presence of the shrouds and by decreasing the blade tip clearance, resulting in lower induced power losses. For high net shroud thrust, a favorable pressure distribution over the inlet was seen to be more important than in the diffuser. Strong suction pressures were observed

Wireless Monitoring of Induction Machine Rotor Physical Variables

PubMed Central

Doolan Fernandes, Jefferson; Carvalho Souza, Francisco Elvis; de Paiva, José Alvaro

2017-01-01

With the widespread use of electric machines, there is a growing need to extract information from the machines to improve their control systems and maintenance management. The present work shows the development of an embedded system to perform the monitoring of the rotor physical variables of a squirrel cage induction motor. The system is comprised of: a circuit to acquire desirable rotor variable(s) and value(s) that send it to the computer; a rectifier and power storage circuit that converts an alternating current in a continuous current but also stores energy for a certain amount of time to wait for the motor’s shutdown; and a magnetic generator that harvests energy from the rotating field to power the circuits mentioned above. The embedded system is set on the rotor of a 5 HP squirrel cage induction motor, making it difficult to power the system because it is rotating. This problem can be solved with the construction of a magnetic generator device to avoid the need of using batteries or collector rings and will send data to the computer using a wireless NRF24L01 module. For the proposed system, initial validation tests were made using a temperature sensor (DS18b20), as this variable is known as the most important when identifying the need for maintenance and control systems. Few tests have shown promising results that, with further improvements, can prove the feasibility of using sensors in the rotor. PMID:29156564

Wireless Monitoring of Induction Machine Rotor Physical Variables.

PubMed

Doolan Fernandes, Jefferson; Carvalho Souza, Francisco Elvis; Cipriano Maniçoba, Glauco George; Salazar, Andrés Ortiz; de Paiva, José Alvaro

2017-11-18

With the widespread use of electric machines, there is a growing need to extract information from the machines to improve their control systems and maintenance management. The present work shows the development of an embedded system to perform the monitoring of the rotor physical variables of a squirrel cage induction motor. The system is comprised of: a circuit to acquire desirable rotor variable(s) and value(s) that send it to the computer; a rectifier and power storage circuit that converts an alternating current in a continuous current but also stores energy for a certain amount of time to wait for the motor's shutdown; and a magnetic generator that harvests energy from the rotating field to power the circuits mentioned above. The embedded system is set on the rotor of a 5 HP squirrel cage induction motor, making it difficult to power the system because it is rotating. This problem can be solved with the construction of a magnetic generator device to avoid the need of using batteries or collector rings and will send data to the computer using a wireless NRF24L01 module. For the proposed system, initial validation tests were made using a temperature sensor (DS18b20), as this variable is known as the most important when identifying the need for maintenance and control systems. Few tests have shown promising results that, with further improvements, can prove the feasibility of using sensors in the rotor.

Optimum performance of hovering rotors

NASA Technical Reports Server (NTRS)

Wu, J. C.; Goorjian, P. M.

1972-01-01

A theory for the optimum performance of a rotor hovering out of ground effect is developed. The performance problem is formulated using general momentum theory for an infinitely bladed rotor, and the effect of a finite number of blades is estimated. The analysis takes advantage of the fact that a simple relation exists between the radial distributions of static pressure and angular velocity in the ultimate wake, far downstream of the rotor, since the radial velocity vanishes there. This relation permits the establishment of an optimum performance criterion in terms of the ultimate wake velocities by introducing a small local perturbation of the rotational velocity and requiring the resulting ratio of thrust and power changes to be independent of the radial location of the perturbation. This analysis fully accounts for the changes in static pressure distribution and axial velocity distribution throughout the wake as the result of the local perturbation of the rotational velocity component.

High energy power-law tail in X-ray binaries and bulk Comptonization due to an outflow from a disk

NASA Astrophysics Data System (ADS)

Kumar, Nagendra

2018-02-01

We study the high energy power-law tail emission of X-ray binaries (XRBs) by a bulk Comptonization process which is usually observed in the very high soft (VHS) state of black hole (BH) XRBs and the high soft (HS) state of the neutron star (NS) and BH XRBs. Earlier, to generate the power-law tail in bulk Comptonization framework, a free-fall converging flow into BH or NS had been considered as a bulk region. In this work, for a bulk region we consider mainly an outflow geometry from the accretion disk which is bounded by a torus surrounding the compact object. We have two choices for an outflow geometry: (i) collimated flow and (ii) conical flow of opening angle θ _b and the axis is perpendicular to the disk. We also consider an azimuthal velocity of the torus fluids as a bulk motion where the fluids are rotating around the compact object (a torus flow). We find that the power-law tail can be generated in a torus flow having large optical depth and bulk speed (>0.75 c), and in conical flow with θ _b > ˜ 30° for a low value of Comptonizing medium temperature. Particularly, in conical flow the low opening angle is more favourable to generate the power-law tail in both the HS state and the VHS state. We notice that when the outflow is collimated, then the emergent spectrum does not have power-law component for a low Comptonizing medium temperature.

Wind tunnel investigation of rotor lift and propulsive force at high speed: Data analysis

NASA Technical Reports Server (NTRS)

Mchugh, F.; Clark, R.; Soloman, M.

1977-01-01

The basic test data obtained during the lift-propulsive force limit wind tunnel test conducted on a scale model CH-47b rotor are analyzed. Included are the rotor control positions, blade loads and six components of rotor force and moment, corrected for hub tares. Performance and blade loads are presented as the rotor lift limit is approached at fixed levels of rotor propulsive force coefficients and rotor tip speeds. Performance and blade load trends are documented for fixed levels of rotor lift coefficient as propulsive force is increased to the maximum obtainable by the model rotor. Test data is also included that defines the effect of stall proximity on rotor control power. The basic test data plots are presented in volumes 2 and 3.

Flow Environment Study Near the Empennage of a 15-Percent Scale Helicopter Model

NASA Technical Reports Server (NTRS)

Gorton, Susan Althoff; Berry, John D.; Hodges, W. Todd; Reis, Deane G.

2000-01-01

Development of advanced rotorcraft configurations has highlighted a need for high-quality experimental data to support the development of flexible and accurate analytical design tools. To provide this type of data, a test program was conducted in the Langley 14- by 22-Foot Subsonic Tunnel to measure the flow near the empennage of a 15-percent scale powered helicopter model with an operating tail fan. Three-component velocity profiles were measured with laser velocimetry (LV) one chord forward of the horizontal tail for four advance ratios to evaluate the effect of the rotor wake impingement on the horizontal tail angle of attack. These velocity data indicate the horizontal tail can experience unsteady angle of attack variations of over 30 degrees due to the rotor wake influence. The horizontal tail is most affected by the rotor wake above advance ratios of 0.10. Velocity measurements of the flow on the inlet side of the tail fan were made for a low-speed flight condition using conventional LV techniques. The velocity data show an accelerated flow near the tail fan duct, and vorticity calculations track the passage of main rotor wake vortices through the measurement plane.

Quasi-static rotor morphing concepts for rotorcraft performance improvements

NASA Astrophysics Data System (ADS)

Mistry, Mihir

The current research is focused on two separate quasi-static rotor morphing concepts: Variable span and variable camber. Both concepts were analyzed from the perspective of the performance improvements they allow for, as well as their design requirements. The goal of this body of work is to develop a comprehensive understanding of the benefits and implementation challenges of both systems. For the case of the variable span rotor concept, the effects on aircraft performance were evaluated for a UH-60A type aircraft. The parametric analysis included the performance effects of the rotor span and rotor speed variation, both individually as well as in combination. The design space considered the effect of three different gross weights (16000 lbs, 18300 lbs and 24000 lbs), for a window of +/-11% variation of the rotor speed and a range between +17% to --16% of radius variation (about the baseline) for a range of altitudes. The results of the analysis showed that variable span rotors by themselves are capable of reducing the power requirement of the helicopter by up to 20% for high altitude and gross weight conditions. However, when combined with rotor speed variation, it was possible to reduce the overall power required by the aircraft by up to 30%. Complimentary to the performance analysis, an analytical study of actuation concepts for a variable span rotor was also conducted. This study considered the design of two active actuation systems: Hydraulic pistons and threaded rods (jackscrews), and two passive systems which employed the use of an internal spring type restraining device. For all the configurations considered, it was determined that the design requirements could not be satisfied when considering the constraints defined. The performance improvements due to a variable camber system were evaluated for a BO-105 type rotor in hover. The design space considered included three different thrust levels (4800 lbs, 5500 lbs and 6400 lbs) for a range of altitudes and

Integrated technology rotor/flight research rotor concept definition study

NASA Technical Reports Server (NTRS)

Carlson, R. G.; Beno, E. A.; Ulisnik, H. D.

1983-01-01

As part of the Integrated Technology Rotor/Flight Research Rotor (ITR/FRR) Program a number of advanced rotor system designs were conceived and investigated. From these, several were chosen that best meet the started ITR goals with emphasis on stability, reduced weight and hub drag, simplicity, low head moment stiffness, and adequate strength and fatigue life. It was concluded that obtaining low hub moment stiffness was difficult when only the blade flexibility of bearingless rotor blades is considered, unacceptably low fatigue life being the primary problem. Achieving a moderate hub moment stiffness somewhat higher than state of the art articulated rotors in production today is possible within the fatigue life constraint. Alternatively, low stiffness is possible when additional rotor elements, besides the blades themselves, provide part of the rotor flexibility. Two primary designs evolved as best meeting the general ITR requirements that presently exist. An I shaped flexbeam with an external torque tube can satisfy the general goals but would have either higher stiffness or reduced fatigue life. The elastic gimbal rotor can achieve a better combination of low stiffness and high fatigue life but would be a somewhat heavier design and possibly exhibit a higher risk of aeromechanical instability.

A Note about Self-Induced Velocity Generated by a Lifting-Line Wing or Rotor Blade

NASA Technical Reports Server (NTRS)

Harris, Franklin D.

2006-01-01

This report presents an elementary analysis of the induced velocity created by a field of vortices that reside in the wake of a rotor blade. Progress achieved by other researchers in the last 70 years is briefly reviewed. The present work is presented in four stages of complexity that carry a lifting-line representation of a fixed wing into a single-blade rotor. The analysis leads to the conclusion that the lifting rotor's spiraling vortex wake structure has very high induced power when compared to the ideal wing. For an advanced ratio of one-half, induced power is on the order of 10 times that of the wing when the comparison is made at wingspan equal to rotor diameter and wing and rotor having equal lift.

Real-time simulator for helicopter rotor wind-tunnel operations

NASA Technical Reports Server (NTRS)

Talbot, P. D.; Peterson, R. L.; Graham, D. R.

1986-01-01

This paper describes the elements and operation of a simulator that is being used to train operators of the Rotor Test Apparatus (RTA) in the large-scale 40- by 80-Foot Wind Tunnel at Ames Research Center. The simulator, named TUTOR (for Tunnel Utilization Trainer with Operating Rotor) duplicates the controls of the rotor and its dynamic behavior, as well as the wind-tunnel controls. The simulation software uses a preexisting blade-element model of a four-bladed rotor with flapping and lead-lag degrees of freedom. Equations were developed for all hardware and controls of the RTA and of the wind tunnel that are normally required to perform a wind-tunnel test of a helicopter rotor. The simulator hardware consists of consoles designed to have the same appearance and functions as those in the control room of the 40- by 80-Foot Wind Tunnel, allowing input from three operators who normally establish the required operating conditions during a test run. Normal operating procedures can be practiced, as well as simulated emergencies such as rotor power failure.

Elastomer mounted rotors - An alternative for smoother running turbomachinery

NASA Technical Reports Server (NTRS)

Tecza, J. A.; Jones, S. W.; Smalley, A. J.; Cunningham, R. E.; Darlow, M. S.

1979-01-01

This paper describes the design of elastomeric bearing supports for a rotor built to simulate the power turbine of an advanced gas turbine engine which traverses two bending critical speeds. The elastomer dampers were constructed so as to minimize rotor dynamic response at the critical speeds. Results are presented of unbalance response tests performed with two different elastomer materials. These results showed that the resonances on the elastomer-mounted rotor were well damped for both elastomer materials and showed linear response to the unbalance weights used for response testing. Additional tests were performed using solid steel supports at either end (hand-mounted), which resulted in drastically increased sensitivity and nonlinear response, and with steel supports in one end of the rotor and the elastomer at the other, which yielded results which were between the soft- and hard-mounted cases. It is concluded that elastomeric supports are a viable alternative to other methods of mounting flexible rotors, that damping was well in excess of predictions and that elastomeric supports are tolerant of small rotor misalignments.

Integrated aerodynamic/dynamic optimization of helicopter rotor blades

NASA Technical Reports Server (NTRS)

Chattopadhyay, Aditi; Walsh, Joanne L.; Riley, Michael F.

1989-01-01

An integrated aerodynamic/dynamic optimization procedure is used to minimize blade weight and 4 per rev vertical hub shear for a rotor blade in forward flight. The coupling of aerodynamics and dynamics is accomplished through the inclusion of airloads which vary with the design variables during the optimization process. Both single and multiple objective functions are used in the optimization formulation. The Global Criteria Approach is used to formulate the multiple objective optimization and results are compared with those obtained by using single objective function formulations. Constraints are imposed on natural frequencies, autorotational inertia, and centrifugal stress. The program CAMRAD is used for the blade aerodynamic and dynamic analyses, and the program CONMIN is used for the optimization. Since the spanwise and the azimuthal variations of loading are responsible for most rotor vibration and noise, the vertical airload distributions on the blade, before and after optimization, are compared. The total power required by the rotor to produce the same amount of thrust for a given area is also calculated before and after optimization. Results indicate that integrated optimization can significantly reduce the blade weight, the hub shear and the amplitude of the vertical airload distributions on the blade and the total power required by the rotor.

Aerodynamic optimization of wind turbine rotor using CFD/AD method

NASA Astrophysics Data System (ADS)

Cao, Jiufa; Zhu, Weijun; Wang, Tongguang; Ke, Shitang

2018-05-01

The current work describes a novel technique for wind turbine rotor optimization. The aerodynamic design and optimization of wind turbine rotor can be achieved with different methods, such as the semi-empirical engineering methods and more accurate computational fluid dynamic (CFD) method. The CFD method often provides more detailed aerodynamics features during the design process. However, high computational cost limits the application, especially for rotor optimization purpose. In this paper, a CFD-based actuator disc (AD) model is used to represent turbulent flow over a wind turbine rotor. The rotor is modeled as a permeable disc of equivalent area where the forces from the blades are distributed on the circular disc. The AD model is coupled with a Reynolds Averaged Navier-Stokes (RANS) solver such that the thrust and power are simulated. The design variables are the shape parameters comprising the chord, the twist and the relative thickness of the wind turbine rotor blade. The comparative aerodynamic performance is analyzed between the original and optimized reference wind turbine rotor. The results showed that the optimization framework can be effectively and accurately utilized in enhancing the aerodynamic performance of the wind turbine rotor.

Blended Wing Body Concept Development with Open Rotor Engine Intergration

NASA Technical Reports Server (NTRS)

Pitera, David M.; DeHaan, Mark; Brown, Derrell; Kawai, Ronald T.; Hollowell, Steve; Camacho, Peter; Bruns, David; Rawden, Blaine K.

2011-01-01

The purpose of this study is to perform a systems analysis of a Blended Wing Body (BWB) open rotor concept at the conceptual design level. This concept will be utilized to estimate overall noise and fuel burn performance, leveraging recent test data. This study will also investigate the challenge of propulsion airframe installation of an open rotor engine on a BWB configuration. Open rotor engines have unique problems relative to turbofans. The rotors are open, exposed to flow conditions outside of the engine. The flow field that the rotors are immersed in may be higher than the free stream flow and it may not be uniform, both of these characteristics could increase noise and decrease performance. The rotors sometimes cause changes in the flow conditions imposed on aircraft surfaces. At high power conditions such as takeoff and climb out, the stream tube of air that goes through the rotors contracts rapidly causing the boundary layer on the body upper surface to go through an adverse pressure gradient which could result with separated airflow. The BWB / Open Rotor configuration must be designed to mitigate these problems.

Operation of a test bed axial-gap brushless dc rotor with a superconducting stator

DOE Office of Scientific and Technical Information (OSTI.GOV)

McKeever, J.W.; Sohns, C.W.; Schwenterly, S.W.

1993-08-01

A variable-speed axial-gap motor with a stator consisting of four liquid helium cooled superconducting electromagnets (two pole pairs) was built and proof tested up to 608 rpm in November 1990 as a tool for joint industry-laboratory evaluation of coils fabricated from high-temperature oxide superconductors. A second rotor was fabricated with improved materia winding configuration, and wire type, and the drive system was modified to eliminate current spiking. The modified motor was characterized to design speed, 188 rad/s (1800 rpm), to acquire a performance baseline for future comparison with that of high-temperature superconducting (HIS) wire. As it becomes commercially available, HTSmore » wire will replace the low-temperature electromagnet wire in a stator modified to control wire temperatures between 4 K and 77 K. Measurements of the superconducting electromagnetic field and locked rotor torque as functions of cryocurrent and dc current through two phases of the rotor, respectively, provided data to estimate power that could be developed by the rotor. Back emf and parasitic mechanical and electromagnetic drag torques were measured as functions of angular velocity to calculate actual rotor power developed and to quantify losses, which reduce the motor`s efficiency. A detailed measurement of motor power at design speed confirmed the developed power equation. When subsequently operated at the 33-A maximum available rotor current, the motor delivered 15.3 kill (20.5 hp) to the load. In a final test, the cryostat was operated at 2500 A, 200 A below its critical current. At rotor design current of 60 A and 2500 A stator current, the extrapolated developed power would be 44.2 kill (59.2 hp) with 94% efficiency.« less

Wind-Tunnel Investigation of Effects of Unsymmetrical Horizontal-Tail Arrangements on Power-on Static Longitudinal Stability of a Single-Engine Airplane Model

NASA Technical Reports Server (NTRS)

Purser, Paul E.; Spear, Margaret F.

1947-01-01

A wind-tunnel investigation has been made to determine the effects of unsymmetrical horizontal-tail arrangements on the power-on static longitudinal stability of a single-engine single-rotation airplane model. Although the tests and analyses showed that extreme asymmetry in the horizontal tail indicated a reduction in power effects on longitudinal stability for single-engine single-rotation airplanes, the particular "practical" arrangement tested did not show marked improvement. Differences in average downwash between the normal tail arrangement and various other tail arrangements estimated from computed values of propeller-slipstream rotation agreed with values estimated from pitching-moment test data for the flaps-up condition (low thrust and torque) and disagreed for the flaps-down condition (high thrust and torque). This disagreement indicated the necessity for continued research to determine the characteristics of the slip-stream behind various propeller-fuselage-wing combinations. Out-of-trim lateral forces and moments of the unsymmetrical tail arrangements that were best from consideration of longitudinal stability were no greater than those of the normal tail arrangement.

Optimization of an Active Twist Rotor Blade Planform for Improved Active Response and Forward Flight Performance

NASA Technical Reports Server (NTRS)

Sekula, Martin K; Wilbur, Matthew L.

2014-01-01

A study was conducted to identify the optimum blade tip planform for a model-scale active twist rotor. The analysis identified blade tip design traits which simultaneously reduce rotor power of an unactuated rotor while leveraging aeromechanical couplings to tailor the active response of the blade. Optimizing the blade tip planform for minimum rotor power in forward flight provided a 5 percent improvement in performance compared to a rectangular blade tip, but reduced the vibration control authority of active twist actuation by 75 percent. Optimizing for maximum blade twist response increased the vibration control authority by 50 percent compared to the rectangular blade tip, with little effect on performance. Combined response and power optimization resulted in a blade tip design which provided similar vibration control authority to the rectangular blade tip, but with a 3.4 percent improvement in rotor performance in forward flight.

Hi-Q Rotor - Low Wind Speed Technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Todd E. Mills; Judy Tatum

The project objective was to optimize the performance of the Hi-Q Rotor. Early research funded by the California Energy Commission indicated the design might be advantageous over state-of-the-art turbines for collecting wind energy in low wind conditions. The Hi-Q Rotor is a new kind of rotor targeted for harvesting wind in Class 2, 3, and 4 sites, and has application in areas that are closer to cities, or 'load centers.' An advantage of the Hi-Q Rotor is that the rotor has non-conventional blade tips, producing less turbulence, and is quieter than standard wind turbine blades which is critical to themore » low-wind populated urban sites. Unlike state-of-the-art propeller type blades, the Hi-Q Rotor has six blades connected by end caps. In this phase of the research funded by DOE's Inventions and Innovation Program, the goal was to improve the current design by building a series of theoretical and numeric models, and composite prototypes to determine a best of class device. Development of the rotor was performed by aeronautical engineering and design firm, DARcorporation. From this investigation, an optimized design was determined and an 8-foot diameter, full-scale rotor was built and mounted using a Bergey LX-1 generator and furling system which were adapted to support the rotor. The Hi-Q Rotor was then tested side-by-side against the state-of-the-art Bergey XL-1 at the Alternative Energy Institute's Wind Test Center at West Texas State University for six weeks, and real time measurements of power generated were collected and compared. Early wind tunnel testing showed that the cut-in-speed of the Hi-Q rotor is much lower than a conventional tested HAWT enabling the Hi-Q Wind Turbine to begin collecting energy before a conventional HAWT has started spinning. Also, torque at low wind speeds for the Hi-Q Wind Turbine is higher than the tested conventional HAWT and enabled the wind turbine to generate power at lower wind speeds. Based on the data collected, the

Magnetic resonance imaging of DNP enhancements in a rotor spinning at the magic angle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perras, Frederic A.; Kobayashi, Takeshi; Pruski, Marek

Simulations performed on model, static, samples have shown that the microwave power is non-uniformly distributed in the magic angle spinning (MAS) rotor when using conventional dynamic nuclear polarization (DNP) instrumentation. Here, we applied the stray-field magic angle spinning imaging (STRAFI–MAS) experiment to generate a spatial map of the DNP enhancements in a full rotor, which is spun at a low rate in a commercial DNP–MAS NMR system. Notably, we observed that the enhancement factors produced in the center of the rotor can be twice as large as those produced at the top of the rotor. Surprisingly, we observed that themore » largest enhancement factors are observed along the axis of the rotor as opposed to against its walls, which are most directly irradiated by the microwave beam. We lastly observed that the distribution of enhancement factors can be moderately improved by degassing the sample and increasing the microwave power. The inclusion of dielectric particles greatly amplifies the enhancement factors throughout the rotor. Furthermore, the STRAFI–MAS approach can provide useful guidance for optimizing the access of microwave power to the sample, and thereby lead to further increases in sensitivity of DNP–MAS NMR.« less

Magnetic resonance imaging of DNP enhancements in a rotor spinning at the magic angle

DOE PAGES

Perras, Frederic A.; Kobayashi, Takeshi; Pruski, Marek

2016-02-23

Simulations performed on model, static, samples have shown that the microwave power is non-uniformly distributed in the magic angle spinning (MAS) rotor when using conventional dynamic nuclear polarization (DNP) instrumentation. Here, we applied the stray-field magic angle spinning imaging (STRAFI–MAS) experiment to generate a spatial map of the DNP enhancements in a full rotor, which is spun at a low rate in a commercial DNP–MAS NMR system. Notably, we observed that the enhancement factors produced in the center of the rotor can be twice as large as those produced at the top of the rotor. Surprisingly, we observed that themore » largest enhancement factors are observed along the axis of the rotor as opposed to against its walls, which are most directly irradiated by the microwave beam. We lastly observed that the distribution of enhancement factors can be moderately improved by degassing the sample and increasing the microwave power. The inclusion of dielectric particles greatly amplifies the enhancement factors throughout the rotor. Furthermore, the STRAFI–MAS approach can provide useful guidance for optimizing the access of microwave power to the sample, and thereby lead to further increases in sensitivity of DNP–MAS NMR.« less

Investigation of Rotor Performance and Loads of a UH-60A Individual Blade Control System

NASA Technical Reports Server (NTRS)

Yeo, Hyeonsoo; Romander, Ethan A.; Norman, Thomas R.

2011-01-01

Wind tunnel measurements of performance, loads, and vibration of a full-scale UH-60A Black Hawk main rotor with an individual blade control (IBC) system are compared with calculations obtained using the comprehensive helicopter analysis CAMRAD II and a coupled CAMRAD II/OVERFLOW 2 analysis. Measured data show a 5.1% rotor power reduction (8.6% rotor lift to effective-drag ratio increase) using 2/rev IBC actuation with 2.0 amplitude at = 0.4. At the optimum IBC phase for rotor performance, IBC actuator force (pitch link force) decreased, and neither flap nor chord bending moments changed significantly. CAMRAD II predicts the rotor power variations with the IBC phase reasonably well at = 0.35. However, the correlation degrades at = 0.4. Coupled CAMRAD II/OVERFLOW 2 shows excellent correlation with the measured rotor power variations with the IBC phase at both = 0.35 and = 0.4. Maximum reduction of IBC actuator force is better predicted with CAMRAD II, but general trends are better captured with the coupled analysis. The correlation of vibratory hub loads is generally poor by both methods, although the coupled analysis somewhat captures general trends.

Investigation of Rotor Performance and Loads of a UH-60A Individual Blade Control System

NASA Technical Reports Server (NTRS)

Yeo, Hyeonsoo; Romander, Ethan A.; Norman, Thomas R.

2011-01-01

Wind tunnel measurements of performance, loads, and vibration of a full-scale UH-60A Black Hawk main rotor with an individual blade control (IBC) system are compared with calculations obtained using the comprehensive helicopter analysis CAMRAD II and a coupled CAMRAD II/OVERFLOW 2 analysis. Measured data show a 5.1% rotor power reduction (8.6% rotor lift to effective-drag ratio increase) using 2/rev IBC actuation with 2.0. amplitude at u = 0.4. At the optimum IBC phase for rotor performance, IBC actuator force (pitch link force) decreased, and neither flap nor chord bending moments changed significantly. CAMRAD II predicts the rotor power variations with IBC phase reasonably well at u = 0.35. However, the correlation degrades at u = 0.4. Coupled CAMRAD II/OVERFLOW 2 shows excellent correlation with the measured rotor power variations with IBC phase at both u = 0.35 and u = 0.4. Maximum reduction of IBC actuator force is better predicted with CAMRAD II, but general trends are better captured with the coupled analysis. The correlation of vibratory hub loads is generally poor by both methods, although the coupled analysis somewhat captures general trends.

Fabrication and Testing of High-Speed-Single-Rotor and Compound-Rotor Systems

DTIC Science & Technology

2016-05-04

pitch link loads, hub loads, rotor wakes and performance of high -speed single-rotor and compound-rotor systems to support 1. REPORT DATE (DD-MM-YYYY) 4...Public Release; Distribution Unlimited UU UU UU UU 05-04-2016 14-Jul-2014 13-Jan-2016 Final Report: Fabrication and Testing of High -Speed Single- Rotor and...Final Report: Fabrication and Testing of High -Speed Single-Rotor and Compound-Rotor Systems Report Title The Alfred Gessow Rotorcraft Center has

Fabrication and Testing of High-Speed Single-Rotor and Compound-Rotor Systems

DTIC Science & Technology

2016-04-05

pitch link loads, hub loads, rotor wakes and performance of high -speed single-rotor and compound-rotor systems to support 1. REPORT DATE (DD-MM-YYYY) 4...Public Release; Distribution Unlimited UU UU UU UU 05-04-2016 14-Jul-2014 13-Jan-2016 Final Report: Fabrication and Testing of High -Speed Single- Rotor and...Final Report: Fabrication and Testing of High -Speed Single-Rotor and Compound-Rotor Systems Report Title The Alfred Gessow Rotorcraft Center has

Applying Dynamic Wake Models to Induced Power Calculations for an Optimum Rotor

DTIC Science & Technology

2009-08-01

versions being special cases of the general one. Although the rotor blade may be moving at transonic speeds near the tip, the rotor wake is...The effect of a finite number of blades incurs an additional loss in wake energy due to the individual vortex sheets from each blade . In 1929... blades . Up to this point, previous developments have been able to achieve the full description of the wake in all ranges of flight regime

Power-law tails and non-Markovian dynamics in open quantum systems: An exact solution from Keldysh field theory

NASA Astrophysics Data System (ADS)

Chakraborty, Ahana; Sensarma, Rajdeep

2018-03-01

The Born-Markov approximation is widely used to study the dynamics of open quantum systems coupled to external baths. Using Keldysh formalism, we show that the dynamics of a system of bosons (fermions) linearly coupled to a noninteracting bosonic (fermionic) bath falls outside this paradigm if the bath spectral function has nonanalyticities as a function of frequency. In this case, we show that the dissipative and noise kernels governing the dynamics have distinct power-law tails. The Green's functions show a short-time "quasi"-Markovian exponential decay before crossing over to a power-law tail governed by the nonanalyticity of the spectral function. We study a system of bosons (fermions) hopping on a one-dimensional lattice, where each site is coupled linearly to an independent bath of noninteracting bosons (fermions). We obtain exact expressions for the Green's functions of this system, which show power-law decay ˜|t - t'|-3 /2 . We use these to calculate the density and current profile, as well as unequal-time current-current correlators. While the density and current profiles show interesting quantitative deviations from Markovian results, the current-current correlators show qualitatively distinct long-time power-law tails |t - t'|-3 characteristic of non-Markovian dynamics. We show that the power-law decays survive in the presence of interparticle interaction in the system, but the crossover time scale is shifted to larger values with increasing interaction strength.

Affect of Brush Seals on Wave Rotor Performance Assessed

NASA Technical Reports Server (NTRS)

1995-01-01

The NASA Lewis Research Center's experimental and theoretical research shows that wave rotor topping can significantly enhance gas turbine engine performance levels. Engine-specific fuel consumption and specific power are potentially enhanced by 15 and 20 percent, respectively, in small (e.g., 400 to 700 hp) and intermediate (e.g., 3000 to 5000 hp) turboshaft engines. Furthermore, there is potential for a 3- to 6-percent specific fuel consumption enhancement in large (e.g., 80,000 to 100,000 lbf) turbofan engines. This wave-rotor-enhanced engine performance is accomplished within current material-limited temperature constraints. The completed first phase of experimental testing involved a three-port wave rotor cycle in which medium total pressure inlet air was divided into two outlet streams, one of higher total pressure and one of lower total pressure. The experiment successfully provided the data needed to characterize viscous, partial admission, and leakage loss mechanisms. Statistical analysis indicated that wave rotor product efficiency decreases linearly with the rotor to end-wall gap, the square of the friction factor, and the square of the passage of nondimensional opening time. Brush seals were installed to further minimize rotor passage-to-cavity leakage. The graph shows the effect of brush seals on wave rotor product efficiency. For the second-phase experiment, which involves a four-port wave rotor cycle in which heat is added to the Brayton cycle in an external burner, a one-dimensional design/analysis code is used in conjunction with a wave rotor performance optimization scheme and a two-dimensional Navier-Stokes code. The purpose of the four-port experiment is to demonstrate and validate the numerically predicted four-port pressure ratio versus temperature ratio at pressures and temperatures lower than those that would be encountered in a future wave rotor/demonstrator engine test. Lewis and the Allison Engine Company are collaborating to investigate

Investigation of Maximum Blade Loading Capability of Lift-Offset Rotors

NASA Technical Reports Server (NTRS)

Yeo, Hyeonsoo; Johnson, Wayne

2013-01-01

Maximum blade loading capability of a coaxial, lift-offset rotor is investigated using a rotorcraft configuration designed in the context of short-haul, medium-size civil and military missions. The aircraft was sized for a 6600-lb payload and a range of 300 nm. The rotor planform and twist were optimized for hover and cruise performance. For the present rotor performance calculations, the collective pitch angle is progressively increased up to and through stall with the shaft angle set to zero. The effects of lift offset on rotor lift, power, controls, and blade airloads and structural loads are examined. The maximum lift capability of the coaxial rotor increases as lift offset increases and extends well beyond the McHugh lift boundary as the lift potential of the advancing blades are fully realized. A parametric study is conducted to examine the differences between the present coaxial rotor and the McHugh rotor in terms of maximum lift capabilities and to identify important design parameters that define the maximum lift capability of the rotor. The effects of lift offset on rotor blade airloads and structural loads are also investigated. Flap bending moment increases substantially as lift offset increases to carry the hub roll moment even at low collective values. The magnitude of flap bending moment is dictated by the lift-offset value (hub roll moment) but is less sensitive to collective and speed.

Analysis of the aerodynamic performance of the multi-rotor concept

NASA Astrophysics Data System (ADS)

Chasapogiannis, Petros; Prospathopoulos, John M.; Voutsinas, Spyros G.; Chaviaropoulos, Takis K.

2014-06-01

The concept of a large (~20MW) multi-rotor wind turbine intended for offshore installations is analysed with respect to its aerodynamic performance. The effect of closely clustering rotors on a single actuator disk is estimated using two different modelling approaches: a CFD solver in which the rotors are simulated as distinct actuator disks and a vortex based solver in which the blade geometry is exactly considered. In the present work, a system of 7 rotors is simulated with a centre to centre spacing of 1.05D. At nominal conditions (tip speed ratio=9) both models predict an increase in power of ~3% alongside with an increase in thrust of ~1.5%. The analysis of the flow field indicates that in the 7 rotor system the individual wakes merge into one wake at ~2D and that flow recovery starts at approximately the same downstream distance as in the single rotor case. As regards the dynamic implications of the close spacing of the rotors it was found that there is an increase in the loading amplitude ranging from 0.30-2.13% at blade level in rated conditions.

Adhesive quality inspection of wind rotor blades using thermography

NASA Astrophysics Data System (ADS)

Li, Xiaoli; Sun, Jiangang; Shen, Jingling; Wang, Xun; Zhang, Cunlin; Zhao, Yuejin

2018-04-01

Wind power is playing an increasingly important role in ensuring electrical safety for human beings. Because wind rotor blades are getting larger and larger in order to harvest wind energy more efficiently, there is a growing demand for nondestructive testing. Due to the glue structure of rotor blades, adhesive quality evaluation is needed. In this study, three adhesive samples with a wall thickness of 13mm, 28mm or 31mm were each designed with a different adhesive situation. The transmission thermography was applied to inspect the samples. The results illustrate that this method is effective to inspect adhesive quality of wind rotor blades.

Aerodynamic loads and rotor performance for the Darrieus wind turbines

NASA Astrophysics Data System (ADS)

Paraschivoiu, I.

1981-12-01

Aerodynamic blade loads and rotor performance are studied for the Darrieus windmill by using a double-multiple streamtube model. The Darrieus is represented as a pair of actuator disks in tandem at each level of the rotor, with upstream and downstream half-cycles. An equilibrium velocity exists in the center plane, and the upwind velocity is higher than the downwind velocity; lift and drag coefficients are calculated from the Reynolds number and the local angle of attack. Half-rotor torque and power are found by averaging the contributions from each streamtube at each position of the rotor in the upwind cycle. An example is provided for a 17 m Darrieus employing NACA blades. While the method is found to be suitable for predicting blade and rotor performance, the need to incorporate the effects of dynamic stall in the model is stressed as a means to improve accuracy.

Halbach Magnetic Rotor Development

NASA Technical Reports Server (NTRS)

Gallo, Christopher A.

2008-01-01

The NASA John H. Glenn Research Center has a wealth of experience in Halbach array technology through the Fundamental Aeronautics Program. The goals of the program include improving aircraft efficiency, reliability, and safety. The concept of a Halbach magnetically levitated electric aircraft motor will help reduce harmful emissions, reduce the Nation s dependence on fossil fuels, increase efficiency and reliability, reduce maintenance and decrease operating noise levels. Experimental hardware systems were developed in the GRC Engineering Development Division to validate the basic principles described herein and the theoretical work that was performed. A number of Halbach Magnetic rotors have been developed and tested under this program. A separate test hardware setup was developed to characterize each of the rotors. A second hardware setup was developed to test the levitation characteristics of the rotors. Each system focused around a unique Halbach array rotor. Each rotor required original design and fabrication techniques. A 4 in. diameter rotor was developed to test the radial levitation effects for use as a magnetic bearing. To show scalability from the 4 in. rotor, a 1 in. rotor was developed to also test radial levitation effects. The next rotor to be developed was 20 in. in diameter again to show scalability from the 4 in. rotor. An axial rotor was developed to determine the force that could be generated to position the rotor axially while it is rotating. With both radial and axial magnetic bearings, the rotor would be completely suspended magnetically. The purpose of this report is to document the development of a series of Halbach magnetic rotors to be used in testing. The design, fabrication and assembly of the rotors will be discussed as well as the hardware developed to test the rotors.

Noise reduction experience at Hughes Helicopter, Inc.

NASA Technical Reports Server (NTRS)

Janakiram, D. S.

1982-01-01

Noise reduction is mostly limited to light helicopters whose noise signature is dominated by their tail rotors. It is primarily hardware oriented. Well known noise reduction techniques such as reduction of rotor speeds with an accompanying increase in solidity to maintain performance, engine noise reduction with the use of exhaust mufflers, and acoustic blanketing of transmission and engine compartment are used. The concept of blade phasing as a means of reducing tail rotor noise is also used. Engine noise (exhaust noise), power train noise and airframe noise becomes important at low rotor tip speeds and means must be found to reduce these noise sources if further noise reductions are desired. The use of a special test rig aids in isolating the various noise sources and arriving at the penalties (performance or payload) involved in quieting them. Significant noise reduction are achieved for the light helicopter with minimum performance or weight penalties because of the dominance of a single noise source (the tail rotor).

Noise reduction experience at Hughes Helicopter, Inc.

NASA Astrophysics Data System (ADS)

Janakiram, D. S.

1982-07-01

Noise reduction is mostly limited to light helicopters whose noise signature is dominated by their tail rotors. It is primarily hardware oriented. Well known noise reduction techniques such as reduction of rotor speeds with an accompanying increase in solidity to maintain performance, engine noise reduction with the use of exhaust mufflers, and acoustic blanketing of transmission and engine compartment are used. The concept of blade phasing as a means of reducing tail rotor noise is also used. Engine noise (exhaust noise), power train noise and airframe noise becomes important at low rotor tip speeds and means must be found to reduce these noise sources if further noise reductions are desired. The use of a special test rig aids in isolating the various noise sources and arriving at the penalties (performance or payload) involved in quieting them. Significant noise reduction are achieved for the light helicopter with minimum performance or weight penalties because of the dominance of a single noise source (the tail rotor).

Coupled rotor/fuselage dynamic analysis of the AH-1G helicopter and correlation with flight vibrations data

NASA Technical Reports Server (NTRS)

Corrigan, J. C.; Cronkhite, J. D.; Dompka, R. V.; Perry, K. S.; Rogers, J. P.; Sadler, S. G.

1989-01-01

Under a research program designated Design Analysis Methods for VIBrationS (DAMVIBS), existing analytical methods are used for calculating coupled rotor-fuselage vibrations of the AH-1G helicopter for correlation with flight test data from an AH-1G Operational Load Survey (OLS) test program. The analytical representation of the fuselage structure is based on a NASTRAN finite element model (FEM), which has been developed, extensively documented, and correlated with ground vibration test. One procedure that was used for predicting coupled rotor-fuselage vibrations using the advanced Rotorcraft Flight Simulation Program C81 and NASTRAN is summarized. Detailed descriptions of the analytical formulation of rotor dynamics equations, fuselage dynamic equations, coupling between the rotor and fuselage, and solutions to the total system of equations in C81 are included. Analytical predictions of hub shears for main rotor harmonics 2p, 4p, and 6p generated by C81 are used in conjunction with 2p OLS measured control loads and a 2p lateral tail rotor gearbox force, representing downwash impingement on the vertical fin, to excite the NASTRAN model. NASTRAN is then used to correlate with measured OLS flight test vibrations. Blade load comparisons predicted by C81 showed good agreement. In general, the fuselage vibration correlations show good agreement between anslysis and test in vibration response through 15 to 20 Hz.

A Sequential Shifting Algorithm for Variable Rotor Speed Control

NASA Technical Reports Server (NTRS)

Litt, Jonathan S.; Edwards, Jason M.; DeCastro, Jonathan A.

2007-01-01

A proof of concept of a continuously variable rotor speed control methodology for rotorcraft is described. Variable rotor speed is desirable for several reasons including improved maneuverability, agility, and noise reduction. However, it has been difficult to implement because turboshaft engines are designed to operate within a narrow speed band, and a reliable drive train that can provide continuous power over a wide speed range does not exist. The new methodology proposed here is a sequential shifting control for twin-engine rotorcraft that coordinates the disengagement and engagement of the two turboshaft engines in such a way that the rotor speed may vary over a wide range, but the engines remain within their prescribed speed bands and provide continuous torque to the rotor; two multi-speed gearboxes facilitate the wide rotor speed variation. The shifting process begins when one engine slows down and disengages from the transmission by way of a standard freewheeling clutch mechanism; the other engine continues to apply torque to the rotor. Once one engine disengages, its gear shifts, the multi-speed gearbox output shaft speed resynchronizes and it re-engages. This process is then repeated with the other engine. By tailoring the sequential shifting, the rotor may perform large, rapid speed changes smoothly, as demonstrated in several examples. The emphasis of this effort is on the coordination and control aspects for proof of concept. The engines, rotor, and transmission are all simplified linear models, integrated to capture the basic dynamics of the problem.

Hover performance tests of full scale variable geometry rotors

NASA Technical Reports Server (NTRS)

Rorke, J. B.

1976-01-01

Full scale whirl tests were conducted to determine the effects of interblade spatial relationships and pitch variations on the hover performance and acoustic signature of a 6-blade main rotor system. The variable geometry rotor (VGR) variations from the conventional baseline were accomplished by: (1) shifting the axial position of alternate blades by one chord-length to form two tip path planes; and (2) varying the relative azimuthal spacing from the upper rotor to the lagging hover rotor in four increments from 25.2 degrees to 62.1 degrees. For each of these four configurations, the differential collective pitch between upper and lower rotors was set at + or - 1 deg, 0 deg and -1 deg. Hover performance data for all configurations were acquired at blade tip Mach numbers of 0.523 and 0.45. Acoustic data were recorded at all test conditions, but analyzed only at 0 deg differential pitch at the higher rotor speed. The VGR configurations tested demonstrated improvements in thrust at constant power as high as 6 percent. Reductions of 3 PNdb in perceived noise level and of 4 db in blade passage frequency noise level were achieved at the higher thrust levels. Consistent correlation exists between performance and acoustic improvements. For any given azimuth spacing, performance was consistently better for the differential pitch condition of + or - 1 degree, i.e. with the upper rotor pitch one degree higher than the lower rotor.

Design of an Advanced Wood Composite Rotor and Development of Wood Composite Blade Technology

NASA Technical Reports Server (NTRS)

Stroebel, Thomas; Dechow, Curtis; Zuteck, Michael

1984-01-01

In support of a program to advance wood composite wind turbine blade technology, a design was completed for a prototype, 90-foot diameter, two-bladed, one-piece rotor, with all wood/epoxy composite structure. The rotor was sized for compatibility with a generator having a maximum power rating of 4000 kilowatts. Innovative features of the rotor include: a teetering hub to minimize the effects of gust loads, untwisted blades to promote rotor power control through stall, joining of blades to the hub structure via an adhesive bonded structural joint, and a blade structural design which was simplified relative to earlier efforts. The prototype rotor was designed to allow flexibility for configuring the rotor upwind or downwind of the tower, for evaluating various types of teeter dampers and/or elastomeric stops, and with variable delta-three angle settings of the teeter shaft axis. The prototype rotor was also designed with provisions for installing pressure tap and angle of attack instrumentation in one blade. A production version rotor cost analysis was conducted. Included in the program were efforts directed at developing advanced load take-off stud designs for subsequent evaluation testing by NASA, development of aerodynamic tip brake concepts, exploratory testing of a wood/epoxy/graphite concept, and compression testing of wood/epoxy laminate, with scarf-jointed plies.

Pre-design study for a modern four-bladed rotor for the Rotor System Research Aircraft (RSRA). [integrating the YAH-64 main rotor

NASA Technical Reports Server (NTRS)

Hughes, C. W.; Logan, A. H.

1981-01-01

Various candidate rotor systems were compared in an effort to select a modern four-bladed rotor for the RSRA. The YAH-64 rotor system was chosen as the candidate rotor system for further development for the RSRA. The process used to select the rotor system, studies conducted to mate the rotor with the RSRA and provide parametric variability, and the development plan which would be used to implement these studies are presented. Drawings are included.

Rotor-to-stator Partial Rubbing and Its Effects on Rotor Dynamic Response

NASA Technical Reports Server (NTRS)

Muszynska, Agnes; Franklin, Wesley D.; Hayashida, Robert D.

1991-01-01

Results from experimental and analytical studies on rotor to stationary element partial rubbings at several locations and their effects on rotor dynamic responses are presented. The mathematical model of a rubbing rotor is given. The computer program provides numerical results which agree with experimentally obtained rotor responses.

Evaluation of the operating resource of the most loaded rotor element of the additional steam turbine with steam-hydrogen overheat of the working fluid at a nuclear power station

NASA Astrophysics Data System (ADS)

Bairamov, A. N.

2017-11-01

The operation of a nuclear power plant with a hydrogen energy complex and a constantly operating low capacity additional steam turbine makes it possible to improve the reliability of the power supply to the needs of a nuclear power plant in the face of major systemic accidents. In this case, the additional steam turbine is always in operation. This determines the alternation of the operating conditions of the additional steam turbine, and, at the same time, the alternation of the loads attributable to the rotor, which affects its working life. The aim of the article is to investigate the effect of cyclic loads on the number of cycles before the destruction of the most important elements of the rotor of an additional steam turbine due to the alternation of operating conditions when entering the peak load and during unloading at night. The article demonstrates that the values of the stress range intensity index for the most important elements of the rotor of an additional steam turbine lie in the area of the threshold values of the fatigue failure diagram. For this region, an increase in the frequency of loading is associated with the phenomenon of closure of the fatigue crack and, as a consequence, a possible slowing of its growth. An approximate number of cycles before failure for the most loaded element of the rotor is obtained.

Design of the NASA Lewis 4-Port Wave Rotor Experiment

NASA Technical Reports Server (NTRS)

Wilson, Jack

1997-01-01

Pressure exchange wave rotors, used in a topping stage, are currently being considered as a possible means of increasing the specific power, and reducing the specific fuel consumption of gas turbine engines. Despite this interest, there is very little information on the performance of a wave rotor operating on the cycle (i.e., set of waves) appropriate for use in a topping stage. One such cycle, which has the advantage of being relatively easy to incorporate into an engine, is the four-port cycle. Consequently, an experiment to measure the performance of a four-port wave rotor for temperature ratios relevant to application as a topping cycle for a gas turbine engine has been designed and built at NASA Lewis. The design of the wave rotor is described, together with the constraints on the experiment.

Engineering science research issues in high power density transmission dynamics for aerospace applications. [rotorcraft geared rotors

NASA Technical Reports Server (NTRS)

Singh, Rajendra; Houser, Donald R.

1993-01-01

This paper discusses analytical and experimental approaches that will be needed to understand dynamic, vibro-acoustic and design characteristics of high power density rotorcraft transmissions. Complexities associated with mathematical modeling of such systems will be discussed. An overview of research work planned during the next several years will be presented, with emphasis on engineering science issues such as gear contact mechanics, multi-mesh drive dynamics, parameter uncertainties, vibration transmission through bearings, and vibro-acoustic characteristics of geared rotor systems and housing-mount structures. A few examples of work in progress are cited.

Thermoelastic steam turbine rotor control based on neural network

NASA Astrophysics Data System (ADS)

Rzadkowski, Romuald; Dominiczak, Krzysztof; Radulski, Wojciech; Szczepanik, R.

2015-12-01

Considered here are Nonlinear Auto-Regressive neural networks with eXogenous inputs (NARX) as a mathematical model of a steam turbine rotor for controlling steam turbine stress on-line. In order to obtain neural networks that locate critical stress and temperature points in the steam turbine during transient states, an FE rotor model was built. This model was used to train the neural networks on the basis of steam turbine transient operating data. The training included nonlinearity related to steam turbine expansion, heat exchange and rotor material properties during transients. Simultaneous neural networks are algorithms which can be implemented on PLC controllers. This allows for the application neural networks to control steam turbine stress in industrial power plants.

Optimization of wave rotors for use as gas turbine engine topping cycles

NASA Technical Reports Server (NTRS)

Wilson, Jack; Paxson, Daniel E.

1995-01-01

Use of a wave rotor as a topping cycle for a gas turbine engine can improve specific power and reduce specific fuel consumption. Maximum improvement requires the wave rotor to be optimized for best performance at the mass flow of the engine. The optimization is a trade-off between losses due to friction and passage opening time, and rotational effects. An experimentally validated, one-dimensional CFD code, which includes these effects, has been used to calculate wave rotor performance, and find the optimum configuration. The technique is described, and results given for wave rotors sized for engines with sea level mass flows of 4, 26, and 400 lb/sec.

Description of the US Army small-scale 2-meter rotor test system

NASA Technical Reports Server (NTRS)

Phelps, Arthur E., III; Berry, John D.

1987-01-01

A small-scale powered rotor model was designed for use as a research tool in the exploratory testing of rotors and helicopter models. The model, which consists of a 29 hp rotor drive system, a four-blade fully articulated rotor, and a fuselage, was designed to be simple to operate and maintain in wind tunnels of moderate size and complexity. Two six-component strain-gauge balances are used to provide independent measurement of the rotor and fuselage aerodynamic loads. Commercially available standardized hardware and equipment were used to the maximum extent possible, and specialized parts were designed so that they could be fabricated by normal methods without using highly specialized tooling. The model was used in a hover test of three rotors having different planforms and in a forward flight investigation of a 21-percent-scale model of a U.S. Army scout helicopter equipped with a mast-mounted sight.

Physical space and long-tail markets

NASA Astrophysics Data System (ADS)

Bentley, R. Alexander; Madsen, Mark E.; Ormerod, Paul

2009-03-01

The Internet is known to have had a powerful impact on on-line retailer strategies in markets characterised by long-tail distribution of sales [C. Anderson, Long Tail: Why the Future of Business is Selling Less of More, Hyperion, New York, 2006]. Such retailers can exploit the long tail of the market, since they are effectively without physical limit on the number of choices on offer. Here we examine two extensions of this phenomenon. First, we introduce turnover into the long-tail distribution of sales. Although over any given period such as a week or a month, the distribution is right-skewed and often power law distributed, over time there is considerable turnover in the rankings of sales of individual products. Second, we establish some initial results on the implications for shelf-space and physical retailers in such markets.

Dynamic Calibration of the NASA Ames Rotor Test Apparatus Steady/Dynamic Rotor Balance

NASA Technical Reports Server (NTRS)

Peterson, Randall L.; vanAken, Johannes M.

1996-01-01

The NASA Ames Rotor Test Apparatus was modified to include a Steady/Dynamic Rotor Balance. The dynamic calibration procedures and configurations are discussed. Random excitation was applied at the rotor hub, and vibratory force and moment responses were measured on the steady/dynamic rotor balance. Transfer functions were computed using the load cell data and the vibratory force and moment responses from the rotor balance. Calibration results showing the influence of frequency bandwidth, hub mass, rotor RPM, thrust preload, and dynamic loads through the stationary push rods are presented and discussed.

Aerodynamic Evaluation of Two Compact Radial-Inflow Turbine Rotors

NASA Technical Reports Server (NTRS)

Simonyi, P. Susan; Roelke, Richard J.; Stabe, Roy G.; Nowlin, Brentley C.; Dicicco, Danielle

1995-01-01

The aerodynamic evaluation of two highly loaded compact radial turbine rotors was conducted at the NASA Lewis Research Center Small Engine Component Test Facility (SECTF). The experimental results were used for proof-of-concept, for modeling radial inflow turbine rotors, and for providing data for code verification. Two rotors were designed to have a shorter axial length, up to a 10-percent reduced diameter, a lighter weight, and equal or higher efficiencies with those of conventional radial inflow turbine rotors. Three configurations were tested: rotor 1, having a 40-percent shorter axial length, with the design stator (stator 1); rotor 1 with the design stator vanes closed down (stator 2); and rotor 2, slightly shorter axially and having higher loading, with stator 2. The stator had 36 vanes and the rotors each had 14 solid blades. Although presently uncooled, the rotor blades were designed for thicknesses which would allow cooling passages to be added. The overall stage performance measurements and the rotor and stator exit flow field surveys were obtained. Measurements of steady state temperatures, pressures, mass flow rates, flow angles, and output power were made at various operating conditions. Data were obtained at corrected speeds of 80, 90, 100, 110, and 120 percent of design over a range of equivalent inlet-to-exit pressure ratios of 3.5, 4.0, 4.5, and 5.0, the maximum pressure ratio achieved. The test showed that the configuration of rotor 1 with stator 1 running at the design pressure ratio produced a flow rate which was 5.6 percent higher than expected. This result indicated the need to close down the stator flow area to reduce the flow. The flow area reduction was accomplished by restaggering the vanes. Rotor 1 was retested with the closed-down stator vanes and achieved the correct mass flow. Rotor 2 was tested only with the restaggered vanes. The test results of the three turbine configurations were nearly identical. Although the measured

Tipjet 80-inch Model Rotor Hover Test: Test No. 1198

DTIC Science & Technology

1993-09-01

primarily working papers Intended for internal use. They I carry an Identifying number which indicates their type and the numerical code of the oriwginatn...rotor lifting system, while exhbitin the highes aumntbnratio eve recorded for a CC rotor, sufer an induced power penalty due to the norilifting regon...INFORMATION This work was conducted by the Ship Systems and Programs DirectorateI (Code 22) of the Carderock Division, Naval Surface Warfare Center

Rotor vibration caused by external excitation and rub

NASA Technical Reports Server (NTRS)

Matsushita, O.; Takagi, M.; Kikuchi, K.; Kaga, M.

1982-01-01

For turbomachinery with low natural frequencies, considerations have been recently required for rotor vibrations caused by external forces except unbalance one, such as foundation motion, seismic wave, rub and so forth. Such a forced vibration is investigated analytically and experimentally in the present paper. Vibrations in a rotor-bearing system under a harmonic excitation are analyzed by the modal technique in the case of a linear system including gyroscopic effect. For a nonlinear system a new and powerful quasi-modal technique is developed and applied to the vibration caused by rub.

Electric generator using a triangular diamagnetic levitating rotor system.

PubMed

Ho, Joe Nhut; Wang, Wei-Chih

2009-02-01

This paper describes a feasibility study of creating a small low friction and low maintenance generator using a diamagnetically stabilized levitating rotor. The planar rotor described in this paper uses a triangular configuration of magnets that generates emf by passing over coils placed below the rotor. Equations were developed to predict the generated emf from coils with two different coil geometries. Additionally, this paper provides a method for estimating optimal coil size and position for the planar rotor presented for both segmental arc and circular coils to obtain maximum power output. Experiments demonstrated that the emf generated in the coils matches well with the predicted wave forms for each case, and the optimization theory gives good prediction to outcome of induced waveforms. For the segmental arc coil design, the induced emf was 1.7 mV at a radial frequency of 21.8 rad/s. For the circular coil design, the emf was 1.25 mV at a radial frequency of 28.1 rad/s.

The importance of dynamic stall in aerodynamic modeling of the Darrieus rotor

NASA Astrophysics Data System (ADS)

Fraunie, P.; Beguier, C.; Paraschivoiu, I.

The CAARDEX program is defined for analyzing the behavior of Darrieus wind turbines in terms of the Reynolds number, the geometrical characteristics of the wind turbine and the spreading of the stream tubes traversing the rotor volume. It is demonstrated that the maximum power conversion efficiency of the Darrieus rotor is 0.4, with the energy capture being divided at a 4:1 ratio upstream to downstream rotor. The model shows that the velocity induced on the rotor is a function of the specific velocity and solidity, and that previous stream tube theories are valid only at low values of these parameters. CARDAAX treats the rotor disk in terms of horizontal slices of stream tubes modeled separately for the upstream and downstream segments. Account is taken of the velocity profile in the atmospheric boundary layer, which can vary significantly in the case of large wind turbines, i.e., several hundred feet high. When applied to predicting the performance of a 1 kW, 2.6 m diam prototype Darrieus wind turbine in a 10 mps flow, fair agreement is obtained for power capture/wind velocity and cyclic aerodynamic forces. Additional flow visualization data is provided to illustrate the production of turbulence in the form of vortices shed between the blades.

Blade tip, finite aspect ratio, and dynamic stall effects on the Darrieus rotor

NASA Astrophysics Data System (ADS)

Paraschivoiu, I.; Desy, P.; Masson, C.

1988-02-01

The objective of the work described in this paper was to apply the Boeing-Vertol dynamic stall model in an asymmetric manner to account for the asymmetry of the flow between the left and right sides of the rotor. This phenomenon has been observed by the flow visualization of a two-straight-bladed Darrieus rotor in the IMST water tunnel. Also introduced into the aerodynamic model are the effects of the blade tip and finite aspect ratio on the aerodynamic performance of the Darrieus wind turbine. These improvements are compatible with the double-multiple-streamtube model and have been included in the CARDAAV computer code for predicting the aerodynamic performance. Very good agreement has been observed between the test data (Sandia 17 m) and theoretical predictions; a significant improvement over the previous dynamic stall model was obtained for the rotor power at low tip speed ratios, while the inclusion of the finite aspect ratio effects enhances the prediction of the rotor power for high tip speed ratios. The tip losses and finite aspect ratio effects were also calculated for a small-scale vertical-axis wind turbine, with a two-straight-bladed (NACA 0015) rotor.

Numerical modelling of the flow and isotope separation in centrifuge Iguasu for different lengths of the rotor

NASA Astrophysics Data System (ADS)

Bogovalov, S. V.; Borisevich, V. D.; Borman, V. D.; Tronin, I. V.; Tronin, V. N.

2016-06-01

Numerical modelling and optimization of the gas flow and isotope separation in the Iguasu gas centrifuge (GC) for uranium enrichment have been performed for different lengths of the rotor. The calculations show that the specific separative power of the GC reduces with the length of the rotor. We show that the reduction of the specific separative power is connected with the growth of the pressure in the optimal regime and corresponding growth of temperature to prevent the working gas sublimation. The specific separative power remains constant with the growth of the rotor length provided that the temperature of the gas is taken to be constant.

Numerical modelling of the flow and isotope separation in centrifuge Iguasu for different lengths of the rotor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bogovalov, S. V.; Borisevich, V. D.; Borman, V. D.

Numerical modelling and optimization of the gas flow and isotope separation in the Iguasu gas centrifuge (GC) for uranium enrichment have been performed for different lengths of the rotor. The calculations show that the specific separative power of the GC reduces with the length of the rotor. We show that the reduction of the specific separative power is connected with the growth of the pressure in the optimal regime and corresponding growth of temperature to prevent the working gas sublimation. The specific separative power remains constant with the growth of the rotor length provided that the temperature of the gasmore » is taken to be constant.« less

Loss of efficiency in a coaxial arrangement of a pair of wind rotors

NASA Astrophysics Data System (ADS)

Okulov, V. L.; Naumov, I. V.; Tsoy, M. A.; Mikkelsen, R. F.

2017-07-01

The efficiency of a pair of wind turbines is experimentally investigated for the case when the model of the second rotor is coaxially located in the wake of the first one. This configuration implies the maximum level of losses in wind farms, as in the rotor wakes, the deceleration of the freestream is maximum. As a result of strain gauge measurements, the dependences of dimensionless power characteristics of both rotors on the distances between them were determined for different modes at different tip speed ratios. The obtained results are of interest for further development of aerodynamics of wind turbines, for optimizing the work of existing wind farms and reducing their power losses due to interactions with wakes of other wind turbines during design and calculation.

Rotor meandering contributes to irregularity in electrograms during atrial fibrillation.

PubMed

Zlochiver, Sharon; Yamazaki, Masatoshi; Kalifa, Jérôme; Berenfeld, Omer

2008-06-01

Radiofrequency ablation therapy of atrial fibrillation (AF) recently incorporated the analysis of dominant frequency (DF) and/or electrogram fractionation for guidance. However, the relationships between DF, fractionation, and spatiotemporal characteristics of the AF source remain unclear. We hypothesize that a meandering reentrant AF source contributes to the wave fractionation and is reflected in the power spectrum of local electrograms elsewhere in the rotor's surroundings. Meandering rotors as AF sources were simulated in 2-dimensional models of human atrial tissue and recorded in isolated sheep hearts. Nondominant elements of the signals were differentiated from the dominant elements using singular value decomposition, whereby the purely periodic constituent (PC) relating to the rotor's DF was eliminated rendering a residual constituent (RC) that consisted of all other activity. Spectral analysis of the decomposed constituents revealed peaks corresponding to the meandering frequency of the rotor tip, the magnitudes of which were proportional to the size of and the distance to the rotor core. Similar analyses on epicardial optical signals and electrograms from isolated sheep hearts, as well as human complex fractionated atrial electrograms, showed applicability of the approach. Increased meandering of the rotor driving AF reduces activation periodicity and increases fractionation. The spectral manifestation of the rotor activity beyond the meandering region makes it possible to characterize AF source stability, as well as DF in humans using electrode mapping.

Integrated technology rotor/flight research rotor hub concept definition

NASA Technical Reports Server (NTRS)

Dixon, P. G. C.

1983-01-01

Two variations of the helicopter bearingless main rotor hub concept are proposed as bases for further development in the preliminary design phase of the Integrated Technology Rotor/Flight Research Rotor (ITR/FRR) program. This selection was the result of an evaluation of three bearingless hub concepts and two articulated hub concepts with elastomeric bearings. The characteristics of each concept were evaluated by means of simplified methodology. These characteristics included the assessment of stability, vulnerability, weight, drag, cost, stiffness, fatigue life, maintainability, and reliability.

Structural Considerations of a 20MW Multi-Rotor Wind Energy System

NASA Astrophysics Data System (ADS)

Jamieson, P.; Branney, M.

2014-12-01

The drive to upscale offshore wind turbines relates especially to possiblereductions in O&M and electrical interconnection costs per MW of installed capacity.Even with best current technologies, designs with rated capacity above about 3 MW are less cost effective exfactory per rated MW(turbine system costs) than smaller machines.Very large offshore wind turbines are thereforejustifiedprimarily by overall offshore project economics. Furthermore, continuing progress in materials and structures has been essential to avoid severe penalties in the power/mass ratio of large multi-MW machines.The multi-rotor concept employs many small rotors to maximise energy capture area withminimum systemvolume. Previous work has indicated that this can enablea very large reduction in the total weight and cost of rotors and drive trains compared to an equivalent large single rotor system.Thus the multi rotor concept may enable rated capacities of 20 MW or more at a single maintenancesite. Establishing the cost benefit of a multi rotor system requires examination of solutions for the support structure and yawing, ensuring aerodynamic losses from rotor interaction are not significant and that overall logistics, with much increased part count (more reliable components) and less consequence of single failuresare favourable. This paper addresses the viability of a support structure in respect of structural concept and likely weight as one necessary step in exploring the potential of the multi rotor concept.

Rotor compound concept for designing an industrial HTS synchronous motor

NASA Astrophysics Data System (ADS)

Kashani, M.; Hosseina, M.; Sarrafan, K.; Darabi, A.

2013-06-01

Recently, producing power with smaller amount of losses become as a goal in our daily life. Today, large amount of energy waste in power networks all around the world. The main reason is “resistive electric equipments” of power networks. Since early 1980s, simultaneous with the development of high temperature superconductive (HTS) technology, superconductors gently attracted the mankind attentions. Using superconductive equipments instead of conventional resistive ones are result in salient electric loss reduction in power systems. Especially to reduce losses in power networks superconductive industrial rotating machines can potentially perform a significant role. In early recent century, first generation of HTS rotating machines was born. But unfortunately they have long way to penetrate the commercial markets yet. In HTS rotating machines the conventional copper made windings are replaced with the HTS superconductors. In this paper an industrial HTS synchronous motor with YBCO coated conductor field windings was designed. As a new approach, model was equipped with a compound rotor that includes both magnetic and non-magnetic materials. So, large amount of heavy iron made part was replaced by light non-magnetic material such as G-10 fiberglass. Furthermore, in this structure iron loss in rotor could be reduced to its lowest value. Also less weight and more air gap energy density were the additional advantages. Regarding zero electric loss production in field windings and less iron loss in rotor construction, this model potentially is more effective than the other iron made HTS motors.

Open Rotor Development

NASA Technical Reports Server (NTRS)

Van Zante, Dale E.; Rizzi, Stephen A.

2016-01-01

The ERA project executed a comprehensive test program for Open Rotor aerodynamic and acoustic performance. System studies used the data to estimate the fuel burn savings and acoustic margin for an aircraft system with open rotor propulsion. The acoustic measurements were used to produce an auralization that compares the legacy blades to the current generation of open rotor designs.

Quantum-rotor-induced polarization.

PubMed

Meier, Benno

2018-07-01

Quantum-rotor-induced polarization is closely related to para-hydrogen-induced polarization. In both cases, the hyperpolarized spin order derives from rotational interaction and the Pauli principle by which the symmetry of the rotational ground state dictates the symmetry of the associated nuclear spin state. In quantum-rotor-induced polarization, there may be several spin states associated with the rotational ground state, and the hyperpolarization is typically generated by hetero-nuclear cross-relaxation. This review discusses preconditions for quantum-rotor-induced polarization for both the 1-dimensional methyl rotor and the asymmetric rotor H 2 17 O@C 60 , that is, a single water molecule encapsulated in fullerene C 60 . Experimental results are presented for both rotors. Copyright © 2018 John Wiley & Sons, Ltd.

Advanced Flywheel Composite Rotors: Low-Cost, High-Energy Density Flywheel Storage Grid Demonstration

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

2010-10-01

GRIDS Project: Boeing is developing a new material for use in the rotor of a low-cost, high-energy flywheel storage technology. Flywheels store energy by increasing the speed of an internal rotor —slowing the rotor releases the energy back to the grid when needed. The faster the rotor spins, the more energy it can store. Boeing’s new material could drastically improve the energy stored in the rotor. The team will work to improve the storage capacity of their flywheels and increase the duration over which they store energy. The ultimate goal of this project is to create a flywheel system thatmore » can be scaled up for use by electric utility companies and produce power for a full hour at a cost of $100 per kilowatt hour.« less

A moving hum filter to suppress rotor noise in high-resolution airborne magnetic data

USGS Publications Warehouse

Xia, J.; Doll, W.E.; Miller, R.D.; Gamey, T.J.; Emond, A.M.

2005-01-01

A unique filtering approach is developed to eliminate helicopter rotor noise. It is designed to suppress harmonic noise from a rotor that varies slightly in amplitude, phase, and frequency and that contaminates aero-magnetic data. The filter provides a powerful harmonic noise-suppression tool for data acquired with modern large-dynamic-range recording systems. This three-step approach - polynomial fitting, bandpass filtering, and rotor-noise synthesis - significantly reduces rotor noise without altering the spectra of signals of interest. Two steps before hum filtering - polynomial fitting and bandpass filtering - are critical to accurately model the weak rotor noise. During rotor-noise synthesis, amplitude, phase, and frequency are determined. Data are processed segment by segment so that there is no limit on the length of data. The segment length changes dynamically along a line based on modeling results. Modeling the rotor noise is stable and efficient. Real-world data examples demonstrate that this method can suppress rotor noise by more than 95% when implemented in an aeromagnetic data-processing flow. ?? 2005 Society of Exploration Geophysicists. All rights reserved.

Development of flexible rotor balancing criteria

NASA Technical Reports Server (NTRS)

Walter, W. W.; Rieger, N. F.

1979-01-01

Several studies in which analytical procedures were used to obtain balancing criteria for flexible rotors are described. General response data for a uniform rotor in damped flexible supports were first obtained for plain cylindrical bearings, tilting pad bearings, axial groove bearings, and partial arc bearings. These data formed the basis for the flexible rotor balance criteria presented. A procedure by which a practical rotor in bearings could be reduced to an equivalent uniform rotor was developed and tested. It was found that the equivalent rotor response always exceeded to practical rotor response by more than sixty percent for the cases tested. The equivalent rotor procedure was then tested against six practical rotor configurations for which data was available. It was found that the equivalent rotor method offered a procedure by which balance criteria could be selected for practical flexible rotors, using the charts given for the uniform rotor.

Development of Improved Design and 3D Printing Manufacture of Cross-Flow Fan Rotor

DTIC Science & Technology

2016-06-01

the design study, each solver run was monitored. Plotting the value of the mass flows, as well as the torque on the rotor blades , allowed a simple...DISTRIBUTION CODE A 13. ABSTRACT (maximum 200 words) This study determined the optimum blade stagger angle for a cross-flow fan rotor and evaluated the...parametric study determined optimum blade stagger angle using thrust, power, and thrust-to-power ratio as desired output variables. A MarkForged Mark One 3D

Rotor design optimization using a free wake analysis

NASA Technical Reports Server (NTRS)

Quackenbush, Todd R.; Boschitsch, Alexander H.; Wachspress, Daniel A.; Chua, Kiat

1993-01-01

The aim of this effort was to develop a comprehensive performance optimization capability for tiltrotor and helicopter blades. The analysis incorporates the validated EHPIC (Evaluation of Hover Performance using Influence Coefficients) model of helicopter rotor aerodynamics within a general linear/quadratic programming algorithm that allows optimization using a variety of objective functions involving the performance. The resulting computer code, EHPIC/HERO (HElicopter Rotor Optimization), improves upon several features of the previous EHPIC performance model and allows optimization utilizing a wide spectrum of design variables, including twist, chord, anhedral, and sweep. The new analysis supports optimization of a variety of objective functions, including weighted measures of rotor thrust, power, and propulsive efficiency. The fundamental strength of the approach is that an efficient search for improved versions of the baseline design can be carried out while retaining the demonstrated accuracy inherent in the EHPIC free wake/vortex lattice performance analysis. Sample problems are described that demonstrate the success of this approach for several representative rotor configurations in hover and axial flight. Features that were introduced to convert earlier demonstration versions of this analysis into a generally applicable tool for researchers and designers is also discussed.

Wind Tunnel Interference Effects on Tilt Rotor Testing Using Computational Fluid Dynamics

NASA Technical Reports Server (NTRS)

Koning, Witold J. F.

2015-01-01

Experimental techniques to measure rotorcraft aerodynamic performance are widely used. However, most of them are either unable to capture interference effects from bodies, or require an extremely large computational budget. The objective of the present research is to develop an XV-15 Tilt Rotor Research Aircraft rotor model for investigation of wind tunnel wall interference using a novel Computational Fluid Dynamics (CFD) solver for rotorcraft, RotCFD. In RotCFD, a mid-fidelity URANS solver is used with an incompressible flow model and a realizable k-e turbulence model. The rotor is, however, not modeled using a computationally expensive, unsteady viscous body-fitted grid, but is instead modeled using a blade element model with a momentum source approach. Various flight modes of the XV-15 isolated rotor, including hover, tilt and airplane mode, have been simulated and correlated to existing experimental and theoretical data. The rotor model is subsequently used for wind tunnel wall interference simulations in the National Full-Scale Aerodynamics Complex (NFAC) at NASA Ames Research Center in California. The results from the validation of the isolated rotor performance showed good correlation with experimental and theoretical data. The results were on par with known theoretical analyses. In RotCFD the setup, grid generation and running of cases is faster than many CFD codes, which makes it a useful engineering tool. Performance predictions need not be as accurate as high-fidelity CFD codes, as long as wall effects can be properly simulated. For both test sections of the NFAC wall interference was examined by simulating the XV-15 rotor in the test section of the wind tunnel and with an identical grid but extended boundaries in free field. Both cases were also examined with an isolated rotor or with the rotor mounted on the modeled geometry of the Tiltrotor Test Rig (TTR). A 'quasi linear trim' was used to trim the thrust for the rotor to compare the power as a unique

Analysis of a Multi-Flap Control System for a Swashplateless Rotor

NASA Technical Reports Server (NTRS)

Sekula, Martin K.; Wilbur, Matthew L.

2011-01-01

An analytical study was conducted examining the feasibility of a swashplateless rotor controlled through two trailing edge flaps (TEF), where the cyclic and collective controls were provided by separate TEFs. This analysis included a parametric study examining the impact of various design parameters on TEF deflections. Blade pitch bearing stiffness; blade pitch index; and flap chord, span, location, and control function of the inboard and outboard flaps were systematically varied on a utility-class rotorcraft trimmed in steady level flight. Gradient-based optimizations minimizing flap deflections were performed to identify single- and two-TEF swashplateless rotor designs. Steady, forward and turning flight analyses suggest that a two-TEF swashplateless rotor where the outboard flap provides cyclic control and inboard flap provides collective control can reduce TEF deflection requirements without a significant impact on power, compared to a single-TEF swashplateless rotor design.

Rotor/Wing Interactions in Hover

NASA Technical Reports Server (NTRS)

Young, Larry A.; Derby, Michael R.

2002-01-01

Hover predictions of tiltrotor aircraft are hampered by the lack of accurate and computationally efficient models for rotor/wing interactional aerodynamics. This paper summarizes the development of an approximate, potential flow solution for the rotor-on-rotor and wing-on-rotor interactions. This analysis is based on actuator disk and vortex theory and the method of images. The analysis is applicable for out-of-ground-effect predictions. The analysis is particularly suited for aircraft preliminary design studies. Flow field predictions from this simple analytical model are validated against experimental data from previous studies. The paper concludes with an analytical assessment of the influence of rotor-on-rotor and wing-on-rotor interactions. This assessment examines the effect of rotor-to-wing offset distance, wing sweep, wing span, and flaperon incidence angle on tiltrotor inflow and performance.

The effect of solidity on the performance of H-rotor Darrieus turbine

NASA Astrophysics Data System (ADS)

Hassan, S. M. Rakibul; Ali, Mohammad; Islam, Md. Quamrul

2016-07-01

Utilization of wind energy has been investigated for a long period of time by different researchers in different ways. Out of which, the Horizontal Axis Wind Turbine and the Vertical Axis Wind Turbine have now advanced design, but still there is scope to improve their efficiency. The Vertical Axis Wind Turbine (VAWT) has the advantage over Horizontal Axis Wind Turbine (HAWT) for working on omnidirectional air flow without any extra control system. A modified H-rotor Darrieus type VAWT is analysed in this paper, which is a lift based wind turbine. The effect of solidity (i.e. chord length, no. of blades) on power coefficient (CP) of H-rotor for different tip speed ratios is numerically investigated. The study is conducted using time dependent RANS equations using SST k-ω model. SIMPLE scheme is used as pressure-velocity coupling and in all cases, the second order upwind discretization scheme is chosen for getting more accurate solution. In results, different parameters are compared, which depict the performance of the modified H-rotor Darrieus type VAWT. Double layered H-rotor having inner layer blades with longer chord gives higher power coefficient than those have inner layer blades with smaller chord.

V/STOL tilt rotor aircraft study. Volume 5: Definition of stowed rotor research aircraft

NASA Technical Reports Server (NTRS)

Soule, V. A.

1973-01-01

The results of a study of folding tilt rotor (stowed rotor) aircraft are presented. The effects of design cruise speed on the gross weight of a conceptual design stowed rotor aircraft are shown and a comparison is made with a conventional (non-folding) tilt rotor aircraft. A flight research stowed rotor design is presented. The program plans, including costs and schedules, are shown for the research aircraft development and a wind tunnel plan is presented for a full scale test of the aircraft.

COMETBOARDS Can Optimize the Performance of a Wave-Rotor-Topped Gas Turbine Engine

NASA Technical Reports Server (NTRS)

Patnaik, Surya N.

1997-01-01

A wave rotor, which acts as a high-technology topping spool in gas turbine engines, can increase the effective pressure ratio as well as the turbine inlet temperature in such engines. The wave rotor topping, in other words, may significantly enhance engine performance by increasing shaft horse power while reducing specific fuel consumption. This performance enhancement requires optimum selection of the wave rotor's adjustable parameters for speed, surge margin, and temperature constraints specified on different engine components. To examine the benefit of the wave rotor concept in engine design, researchers soft coupled NASA Lewis Research Center's multidisciplinary optimization tool COMETBOARDS and the NASA Engine Performance Program (NEPP) analyzer. The COMETBOARDS-NEPP combined design tool has been successfully used to optimize wave-rotor-topped engines. For illustration, the design of a subsonic gas turbine wave-rotor-enhanced engine with four ports for 47 mission points (which are specified by Mach number, altitude, and power-setting combinations) is considered. The engine performance analysis, constraints, and objective formulations were carried out through NEPP, and COMETBOARDS was used for the design optimization. So that the benefits that accrue from wave rotor enhancement could be examined, most baseline variables and constraints were declared to be passive, whereas important parameters directly associated with the wave rotor were considered to be active for the design optimization. The engine thrust was considered as the merit function. The wave rotor engine design, which became a sequence of 47 optimization subproblems, was solved successfully by using a cascade strategy available in COMETBOARDS. The graph depicts the optimum COMETBOARDS solutions for the 47 mission points, which were normalized with respect to standard results. As shown, the combined tool produced higher thrust for all mission points than did the other solution, with maximum benefits

Development of a Highly Loaded Rotor Blade for Steam Turbines

NASA Astrophysics Data System (ADS)

Segawa, Kiyoshi; Shikano, Yoshio; Tsubouchi, Kuniyoshi; Shibashita, Naoaki

Turbine manufacturers have been concerned about efficient utilization of limited energy resources and prevention of environmental pollution. For steam turbine power plants, a higher efficiency gain is necessary to reduce the fuel consumption rate. Blade configurations have been studied for reductions of profile loss and endwall loss that lead to decreased steam turbine internal efficiency, by applying recent aerodynamic technologies based on advanced numerical analysis methods. This paper discusses increase of pitch-chord ratio by 14% (reduction of rotor blade numbers by 14%) and increased blade aerodynamic loading without deterioration of performance. A new rotor cascade is found which improves blade performance, especially at the root section where the reduction in the energy loss coefficient is about 40%. This rotor blade also provides lower manufacturing cost.

Investigation of rotor blade element airloads for a teetering rotor in the blade stall regime

NASA Technical Reports Server (NTRS)

Dadone, L. U.; Fukushima, T.

1974-01-01

A model of a teetering rotor was tested in a low speed wind tunnel. Blade element airloads measured on an articulated model rotor were compared with the teetering rotor and showed that the teetering rotor is subjected to less extensive flow separation. Retreating blade stall was studied. Results show that stall, under the influence of unsteady aerodynamic effects, consists of four separate stall events, each associated with a vortex shed from the leading edge and sweeping over the upper surface of the rotor blade. Current rotor performance prediction methodology was evaluated through computer simulation.

Aeromechanical stability of helicopters with composite rotor blades in forward flight

NASA Technical Reports Server (NTRS)

Smith, Edward C.; Chopra, Inderjit

1992-01-01

The aeromechanical stability, including air resonance in hover, air resonance in forward flight, and ground resonance, of a helicopter with elastically tailored composite rotor blades is investigated. Five soft-inplane hingeless rotor configurations, featuring elastic pitch-lag, pitch-flap and extension-torsion couplings, are analyzed. Elastic couplings introduced through tailored composite blade spars can have a powerful effect on both air and ground resonance behavior. Elastic pitch-flap couplings (positive and negative) strongly affect body, rotor and dynamic inflow modes. Air resonance stability is diminished by elastic pitch-flap couplings in hover and forward flight. Negative pitch-lag elastic coupling has a stabilizing effect on the regressive lag mode in hover and forward flight. The negative pitch-lag coupling has a detrimental effect on ground resonance stability. Extension-torsion elastic coupling (blade pitch decreases due to tension) decreases regressive lag mode stability in both airborne and ground contact conditions. Increasing thrust levels has a beneficial influence on ground resonance stability for rotors with pitch-flap and extension-torsion coupling and is only marginally effective in improving stability of rotors with pitch-lag coupling.

Flexible rotor dynamics analysis

NASA Technical Reports Server (NTRS)

Shen, F. A.

1973-01-01

A digital computer program was developed to analyze the general nonaxisymmetric and nonsynchronous transient and steady-state rotor dynamic performance of a bending- and shear-wise flexible rotor-bearing system under various operating conditions. The effects of rotor material mechanical hysteresis, rotor torsion flexibility, transverse effects of rotor axial and torsional loading and the anisotropic, in-phase and out-of-phase bearing stiffness and damping force and moment coefficients were included in the program to broaden its capability. An optimum solution method was found and incorporated in the computer program. Computer simulation of experimental data was made and qualitative agreements observed. The mathematical formulations, computer program verification, test data simulation, and user instruction was presented and discussed.

Integrated Technology Rotor/Flight Research Rotor (ITR/FRR) concept definition study

NASA Technical Reports Server (NTRS)

Hughes, C. W.

1983-01-01

Studies were conducted by Hughes Helicopters, Inc. (HHI) for the Applied Technology Laboratory and Aeromechanics Laboratory, U.S. Army Research and Technology Laboratories (AVRADCOM) and the Ames Research Center, National Aeronautics and Space Administration (NASA). Results of predesign studies of advanced main rotor hubs, including bearingless designs, are presented in this report. In addition, the Government's rotor design goals and specifications were reviewed and evaluated. Hub concepts were designed and qualitatively evaluated in order to select the two most promising concepts for further development. Various flexure designs, control systems, and pitchcase designs were investigated during the initial phases of this study. The two designs selected for additional development were designated the V-strap and flat-strap cruciform hubs. These hubs were designed for a four bladed rotor and were sized for 18,400 pounds gross weight with the same diameter (62 feet) and solidity (23 inch chord) as the existing rotor on the Rotor Systems Research Aircraft (RSRA).

Noise comparison of two 1.2-pressure-ratio fans with 15 and 42 rotor blades

NASA Technical Reports Server (NTRS)

Woodward, R. P.; Glaser, F. W.; Wazyniak, J. A.

1973-01-01

Two 1.829-m-(6-ft-) diameter fans suitable for a quiet engine for future short-takeoff-and-landing (STOL) aircraft were compared. Both fans were designed for a 1.2 pressure ratio with similar weight flows, thrusts, and tip speeds. The first fan, designated QF-9, had 15 rotor blades and 11 stator blades. The rotor was highly loaded and the tip solidity was less than 1. The QF-9 rotor blades had an adjustable pitch feature which can be used for thrust reversal. The second fan, designated QF-6, operated at a moderate loading with a rotor tip solidity greater than 1. Fan QF-6 had 42 rotor blades and 50 stator blades. The low number of rotor blades for QF-9 reduced the frequency of the blade-passage tone below the range of maximum annoyance. In addition to this difference, the QF-9 fan had a somewhat smaller rotor-stator separation than the QF-6 fan. In terms of sound pressure level and sound power level, QF-9 was the noisier fan, with the power level results for QF-9 being about 1 db above those for QF-6 at equivalent operating points as determined by similar stage pressure ratios. At the same equivalent operating points, the maximum perceived noise along a 152.5-m (500-ft) sideline for QF-9 was about 2.5 PNdb below that for QF-6, which indicated that QF-9 was less objectionable to human hearing.

Parametric study of laminated composite material shaft of high speed rotor-bearing system

NASA Astrophysics Data System (ADS)

Gonsalves, Thimothy Harold; Kumar, G. C. Mohan; Ramesh, M. R.

2018-04-01

In this paper some of the important parameters that influence the effectiveness of composite material shaft of high speed rotor-bearing system on rotor dynamics are analyzed. The type of composite material composition, the number of layers along with their stacking sequences are evaluated as they play an important role in deciding the best configuration suitable for the high-speed application. In this work the lateral modal frequencies for five types of composite materials shaft of a high-speed power turbine rotor-bearing system and stresses due to operating torque are evaluated. The results are useful for the selection of right combination of material, number of layers and their stacking sequences. The numerical analysis is carried out using the ANSYS Rotor dynamic analysis features.

Preliminary simulation of an advanced, hingless rotor XV-15 tilt-rotor aircraft

NASA Technical Reports Server (NTRS)

Mcveigh, M. A.

1976-01-01

The feasibility of the tilt-rotor concept was verified through investigation of the performance, stability and handling qualities of the XV-15 tilt rotor. The rotors were replaced by advanced-technology fiberglass/composite hingless rotors of larger diameter, combined with an advanced integrated fly-by-wire control system. A parametric simulation model of the HRXV-15 was developed, model was used to define acceptable preliminary ranges of primary and secondary control schedules as functions of the flight parameters, to evaluate performance, flying qualities and structural loads, and to have a Boeing-Vertol pilot conduct a simulated flight test evaluation of the aircraft.

Wind Tunnel Interference Effects on Tilt Rotor Testing Using Computational Fluid Dynamics

NASA Technical Reports Server (NTRS)

Koning, Witold J. F.

2016-01-01

for the rotor to compare the power as a unique variable. Power differences between free field and wind tunnel cases were found from -7 to 0 percent in the 80- by 120-Foot Wind Tunnel and -1.6 to 4.8 percent in the 40- by 80-Foot Wind Tunnel, depending on the TTR orientation, tunnel velocity, and blade setting. The TTR will be used in 2016 to test the Bell 609 rotor in a similar fashion to the research in this report.

An analytical study for the design of advanced rotor airfoils

NASA Technical Reports Server (NTRS)

Kemp, L. D.

1973-01-01

A theoretical study has been conducted to design and evaluate two airfoils for helicopter rotors. The best basic shape, designed with a transonic hodograph design method, was modified to meet subsonic criteria. One airfoil had an additional constraint for low pitching-moment at the transonic design point. Airfoil characteristics were predicted. Results of a comparative analysis of helicopter performance indicate that the new airfoils will produce reduced rotor power requirements compared to the NACA 0012. The hodograph design method, written in CDC Algol, is listed and described.

Application of a High-Fidelity Icing Analysis Method to a Model-Scale Rotor in Forward Flight

NASA Technical Reports Server (NTRS)

Narducci, Robert; Orr, Stanley; Kreeger, Richard E.

2012-01-01

An icing analysis process involving the loose coupling of OVERFLOW-RCAS for rotor performance prediction and with LEWICE3D for thermal analysis and ice accretion is applied to a model-scale rotor for validation. The process offers high-fidelity rotor analysis for the noniced and iced rotor performance evaluation that accounts for the interaction of nonlinear aerodynamics with blade elastic deformations. Ice accumulation prediction also involves loosely coupled data exchanges between OVERFLOW and LEWICE3D to produce accurate ice shapes. Validation of the process uses data collected in the 1993 icing test involving Sikorsky's Powered Force Model. Non-iced and iced rotor performance predictions are compared to experimental measurements as are predicted ice shapes.

Sound radiation from a subsonic rotor subjected to turbulence

NASA Technical Reports Server (NTRS)

Sevik, M.

1974-01-01

The broadband sound radiated by a subsonic rotor subjected to turbulence in the approach stream has been analyzed. The power spectral density of the sound intensity has been found to depend on a characteristic time scale-namely, the integral scale of the turbulence divided by the axial flow velocity-as well as several length-scale ratios. These consist of the ratio of the integral scale to the acoustic wavelength, rotor radius, and blade chord. Due to the simplified model chosen, only a limited number of cascade parameters appear. Limited comparisons with experimental data indicate good agreement with predicted values.

Ground states of linear rotor chains via the density matrix renormalization group

NASA Astrophysics Data System (ADS)

Iouchtchenko, Dmitri; Roy, Pierre-Nicholas

2018-04-01

In recent years, experimental techniques have enabled the creation of ultracold optical lattices of molecules and endofullerene peapod nanomolecular assemblies. It was previously suggested that the rotor model resulting from the placement of dipolar linear rotors in one-dimensional lattices at low temperature has a transition between ordered and disordered phases. We use the density matrix renormalization group (DMRG) to compute ground states of chains of up to 100 rotors and provide further evidence of the phase transition in the form of a diverging entanglement entropy. We also propose two methods and present some first steps toward rotational spectra of such molecular assemblies using DMRG. The present work showcases the power of DMRG in this new context of interacting molecular rotors and opens the door to the study of fundamental questions regarding criticality in systems with continuous degrees of freedom.

Tilt rotor hover aeroacoustics

NASA Technical Reports Server (NTRS)

Coffen, Charles David

1992-01-01

The methodology, results, and conclusions of a study of tilt rotor hover aeroacoustics and aerodynamics are presented. Flow visualization and hot wire velocity measurement were performed on a 1/12-scale model of the XV-15 Tilt Rotor Aircraft in hover. The wing and fuselage below the rotor cause a complex recirculating flow. Results indicate the physical dimensions and details of the flow including the relative unsteadiness and turbulence characteristics of the flow. Discrete frequency harmonic thickness and the loading noise mechanism were predicted using WOPWOP for the standard metal blades and the Advanced Technology Blades. The recirculating flow created by the wing below the rotor is a primary sound mechanism for a hovering tilt rotor. The effects of dynamic blade response should be included for fountain flow conditions which produce impulsive blade loading. Broadband noise mechanisms were studied using Amiet's method with azimuthally varying turbulence characteristics derived from the measurements. The recirculating fountain flow with high turbulence levels in the recirculating zone is the dominant source of broadband noise for a hovering rotor. It is shown that tilt rotor hover aeroacoustic noise mechanisms are now understood. Noise predictions can be made based on reasonably accurate aerodynamic models developed here.

FUN3D Airload Predictions for the Full-Scale UH-60A Airloads Rotor in a Wind Tunnel

NASA Technical Reports Server (NTRS)

Lee-Rausch, Elizabeth M.; Biedron, Robert T.

2013-01-01

An unsteady Reynolds-Averaged Navier-Stokes solver for unstructured grids, FUN3D, is used to compute the rotor performance and airloads of the UH-60A Airloads Rotor in the National Full-Scale Aerodynamic Complex (NFAC) 40- by 80-foot Wind Tunnel. The flow solver is loosely coupled to a rotorcraft comprehensive code, CAMRAD-II, to account for trim and aeroelastic deflections. Computations are made for the 1-g level flight speed-sweep test conditions with the airloads rotor installed on the NFAC Large Rotor Test Apparatus (LRTA) and in the 40- by 80-ft wind tunnel to determine the influence of the test stand and wind-tunnel walls on the rotor performance and airloads. Detailed comparisons are made between the results of the CFD/CSD simulations and the wind tunnel measurements. The computed trends in solidity-weighted propulsive force and power coefficient match the experimental trends over the range of advance ratios and are comparable to previously published results. Rotor performance and sectional airloads show little sensitivity to the modeling of the wind-tunnel walls, which indicates that the rotor shaft-angle correction adequately compensates for the wall influence up to an advance ratio of 0.37. Sensitivity of the rotor performance and sectional airloads to the modeling of the rotor with the LRTA body/hub increases with advance ratio. The inclusion of the LRTA in the simulation slightly improves the comparison of rotor propulsive force between the computation and wind tunnel data but does not resolve the difference in the rotor power predictions at mu = 0.37. Despite a more precise knowledge of the rotor trim loads and flight condition, the level of comparison between the computed and measured sectional airloads/pressures at an advance ratio of 0.37 is comparable to the results previously published for the high-speed flight test condition.

Performance optimization for rotors in hover and axial flight

NASA Technical Reports Server (NTRS)

Quackenbush, T. R.; Wachspress, D. A.; Kaufman, A. E.; Bliss, D. B.

1989-01-01

Performance optimization for rotors in hover and axial flight is a topic of continuing importance to rotorcraft designers. The aim of this Phase 1 effort has been to demonstrate that a linear optimization algorithm could be coupled to an existing influence coefficient hover performance code. This code, dubbed EHPIC (Evaluation of Hover Performance using Influence Coefficients), uses a quasi-linear wake relaxation to solve for the rotor performance. The coupling was accomplished by expanding of the matrix of linearized influence coefficients in EHPIC to accommodate design variables and deriving new coefficients for linearized equations governing perturbations in power and thrust. These coefficients formed the input to a linear optimization analysis, which used the flow tangency conditions on the blade and in the wake to impose equality constraints on the expanded system of equations; user-specified inequality contraints were also employed to bound the changes in the design. It was found that this locally linearized analysis could be invoked to predict a design change that would produce a reduction in the power required by the rotor at constant thrust. Thus, an efficient search for improved versions of the baseline design can be carried out while retaining the accuracy inherent in a free wake/lifting surface performance analysis.

Impact of number of co-existing rotors and inter-electrode distance on accuracy of rotor localization.

PubMed

Aronis, Konstantinos N; Ashikaga, Hiroshi

Conflicting evidence exists on the efficacy of focal impulse and rotor modulation on atrial fibrillation ablation. A potential explanation is inaccurate rotor localization from multiple rotors coexistence and a relatively large (9-11mm) inter-electrode distance (IED) of the multi-electrode basket catheter. We studied a numerical model of cardiac action potential to reproduce one through seven rotors in a two-dimensional lattice. We estimated rotor location using phase singularity, Shannon entropy and dominant frequency. We then spatially downsampled the time series to create IEDs of 2-30mm. The error of rotor localization was measured with reference to the dynamics of phase singularity at the original spatial resolution (IED=1mm). IED has a significant impact on the error using all the methods. When only one rotor is present, the error increases exponentially as a function of IED. At the clinical IED of 10mm, the error is 3.8mm (phase singularity), 3.7mm (dominant frequency), and 11.8mm (Shannon entropy). When there are more than one rotors, the error of rotor localization increases 10-fold. The error based on the phase singularity method at the clinical IED of 10mm ranges from 30.0mm (two rotors) to 96.1mm (five rotors). The magnitude of error of rotor localization using a clinically available basket catheter, in the presence of multiple rotors might be high enough to impact the accuracy of targeting during AF ablation. Improvement of catheter design and development of high-density mapping catheters may improve clinical outcomes of FIRM-guided AF ablation. Copyright © 2017 Elsevier Inc. All rights reserved.

Comparison of individual pitch and smart rotor control strategies for load reduction

NASA Astrophysics Data System (ADS)

Plumley, C.; Leithead, W.; Jamieson, P.; Bossanyi, E.; Graham, M.

2014-06-01

Load reduction is increasingly seen as an essential part of controller and wind turbine design. On large multi-MW wind turbines that experience high levels of wind shear and turbulence across the rotor, individual pitch control and smart rotor control are being considered. While individual pitch control involves adjusting the pitch of each blade individually to reduce the cyclic loadings on the rotor, smart rotor control involves activating control devices distributed along the blades to alter the local aerodynamics of the blades. Here we investigate the effectiveness of using a DQ-axis control and a distributed (independent) control for both individual pitch and trailing edge flap smart rotor control. While load reductions are similar amongst the four strategies across a wide range of variables, including blade root bending moments, yaw bearing and shaft, the pitch actuator requirements vary. The smart rotor pitch actuator has reduced travel, rates, accelerations and power requirements than that of the individual pitch controlled wind turbines. This benefit alone however would be hard to justify the added design complexities of using a smart rotor, which can be seen as an alternative to upgrading the pitch actuator and bearing. In addition, it is found that the independent control strategy is apt at roles that the collective pitch usually targets, such as tower motion and speed control, and it is perhaps here, in supplementing other systems, that the future of the smart rotor lies.

The effect of solidity on the performance of H-rotor Darrieus turbine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hassan, S. M. Rakibul, E-mail: rakibulhassan21@gmail.com; Ali, Mohammad, E-mail: mali@me.buet.ac.bd; Islam, Md. Quamrul, E-mail: quamrul@me.buet.ac.bd

Utilization of wind energy has been investigated for a long period of time by different researchers in different ways. Out of which, the Horizontal Axis Wind Turbine and the Vertical Axis Wind Turbine have now advanced design, but still there is scope to improve their efficiency. The Vertical Axis Wind Turbine (VAWT) has the advantage over Horizontal Axis Wind Turbine (HAWT) for working on omnidirectional air flow without any extra control system. A modified H-rotor Darrieus type VAWT is analysed in this paper, which is a lift based wind turbine. The effect of solidity (i.e. chord length, no. of blades)more » on power coefficient (C{sub P}) of H-rotor for different tip speed ratios is numerically investigated. The study is conducted using time dependent RANS equations using SST k-ω model. SIMPLE scheme is used as pressure-velocity coupling and in all cases, the second order upwind discretization scheme is chosen for getting more accurate solution. In results, different parameters are compared, which depict the performance of the modified H-rotor Darrieus type VAWT. Double layered H-rotor having inner layer blades with longer chord gives higher power coefficient than those have inner layer blades with smaller chord.« less

Aeroelastic considerations for torsionally soft rotors

NASA Technical Reports Server (NTRS)

Mantay, W. R.; Yeager, W. T., Jr.

1986-01-01

A research study was initiated to systematically determine the impact of selected blade tip geometric parameters on conformable rotor performance and loads characteristics. The model articulated rotors included baseline and torsionally soft blades with interchangeable tips. Seven blade tip designs were evaluated on the baseline rotor and six tip designs were tested on the torsionally soft blades. The designs incorporated a systemmatic variation in geometric parameters including sweep, taper, and anhedral. The rotors were evaluated in the NASA Langley Transonic Dynamics Tunnel at several advance ratios, lift and propulsive force values, and tip Mach numbers. A track sensitivity study was also conducted at several advance ratios for both rotors. Based on the test results, tip parameter variations generated significant rotor performance and loads differences for both baseline and torsionally soft blades. Azimuthal variation of elastic twist generated by variations in the tip parameters strongly correlated with rotor performance and loads, but the magnitude of advancing blade elastic twist did not. In addition, fixed system vibratory loads and rotor track for potential conformable rotor candidates appears very sensitive to parametric rotor changes.

Rotor bore and turbine rotor wheel/spacer heat exchange flow circuit

DOEpatents

Caruso, Philip M.; Eldrid, Sacheverel Quentin; Ladhani, Azad A.; DeMania, Alan Richard; Palmer, Gene David; Wilson, Ian David; Rathbun, Lisa Shirley; Akin, Robert Craig

2002-01-01

In a turbine having closed-circuit steam-cooling passages about the rim of the rotor during steady-state operation, compressor discharge air is supplied to the rotor bore for passage radially outwardly into the wheel space cavities between the wheels and spacers. Communicating slots and channels in the spacers and wheels at circumferentially spaced positions enable egress of the compressor discharge air into the hot gas flow path. At turbine startup, cooling air flows through the closed-circuit steam passages to cool the outer rim of the rotor while compressor discharge air pre-warms the wheels and spacers. At steady-state, cooling steam is supplied in the closed-circuit steam-cooling passages and compressor discharge air is supplied through the bore and into the wheel space cavities to cool the rotor.

Rotor systems research aircraft predesign study. Volume 2: Conceptual study report

NASA Technical Reports Server (NTRS)

Schmidt, S. A.; Linden, A. W.

1972-01-01

The overall feasibility of the technical requirements and concepts for a rotor system research aircraft (RSRA) was determined. The designs of two aircraft were then compared against the RSRA requirements. One of these is an all new aircraft specifically designed as an RSRA vehicle. A new main rotor, transmission, wings, and fuselage are included in this design. The second aircraft uses an existing Sikorsky S-61 main rotor, an S-61 roller gearbox, and a highly modified Sikorsky S-67 airframe. The wing for this aircraft is a new design. Both aircraft employ a fan-in-fin anti-torque/yaw control system, T58-GE-16 engines for rotor power, and TF34-GE-2 turbofans for auxiliary thrust. Each aircraft meets the basic requirements and goals of the program. The all new aircraft has inflight variable main rotor shaft tilt, a side-by-side cockpit seating arrangement, and is slightly faster in the compound mode. It is also somewhat lighter since it uses new dynamic components specifically designed for the RSRA. Preliminary development plans, including schedules and costs, were prepared for both of these aircraft.

A rotor-mounted digital instrumentation system for helicopter blade flight research measurements

NASA Technical Reports Server (NTRS)

Knight, V. H., Jr.; Haywood, W. S., Jr.; Williams, M. L.

1978-01-01

A rotor mounted flight instrumentation system developed for helicopter rotor blade research is described. The system utilizes high speed digital techniques to acquire research data from miniature pressure transducers on advanced rotor airfoils which are flight tested on an AH-1G helicopter. The system employs microelectronic pulse code modulation (PCM) multiplexer digitizer stations located remotely on the blade and in a hub mounted metal canister. As many as 25 sensors can be remotely digitized by a 2.5 mm thick electronics package mounted on the blade near the tip to reduce blade wiring. The electronics contained in the canister digitizes up to 16 sensors, formats these data with serial PCM data from the remote stations, and transmits the data from the canister which is above the plane of the rotor. Data are transmitted over an RF link to the ground for real time monitoring and to the helicopter fuselage for tape recording. The complete system is powered by batteries located in the canister and requires no slip rings on the rotor shaft.

Air and ground resonance of helicopters with elastically tailored composite rotor blades

NASA Technical Reports Server (NTRS)

Smith, Edward C.; Chopra, Inderjit

1993-01-01

The aeromechanical stability, including air resonance in hover, air resonance in forward flight, and ground resonance, of a helicopter with elastically tailored composite rotor blades is investigated. Five soft-inplane hingeless rotor configurations, featuring elastic pitch-lag, pitch-flap and extension-torsion couplings, are analyzed. Elastic couplings introduced through tailored composite blade spars can have a powerful effect on both air and ground resonance behavior. Elastic pitch-flap couplings (positive and negative) strongly affect body, rotor and dynamic inflow modes. Air resonance stability is diminished by elastic pitch-flap couplings in hover and forwrad flight. Negative pitch-lag elastic coupling has a stabilizing effect on the regressive lag mode in hover and forward flight. The negative pitch-lag coupling has a detrimental effect on ground resonance stability. Extension-torsion elastic coupling (blade pitch decreases due to tension) decreases regressive lag mode stability in both airborne and ground contact conditions. Increasing thrust levels has a beneficial influence on ground resonance stability for rotors with pitch-flap and extension-torsion coupling and is only marginally effective in improving stability of rotors with pitch-lag coupling.

Macroscopic balance model for wave rotors

NASA Technical Reports Server (NTRS)

Welch, Gerard E.

1996-01-01

A mathematical model for multi-port wave rotors is described. The wave processes that effect energy exchange within the rotor passage are modeled using one-dimensional gas dynamics. Macroscopic mass and energy balances relate volume-averaged thermodynamic properties in the rotor passage control volume to the mass, momentum, and energy fluxes at the ports. Loss models account for entropy production in boundary layers and in separating flows caused by blade-blockage, incidence, and gradual opening and closing of rotor passages. The mathematical model provides a basis for predicting design-point wave rotor performance, port timing, and machine size. Model predictions are evaluated through comparisons with CFD calculations and three-port wave rotor experimental data. A four-port wave rotor design example is provided to demonstrate model applicability. The modeling approach is amenable to wave rotor optimization studies and rapid assessment of the trade-offs associated with integrating wave rotors into gas turbine engine systems.

The dynamics of a flexible bladed disc on a flexible rotor in a two-rotor system

NASA Technical Reports Server (NTRS)

Gallardo, V. C.; Stallone, M. J.

1984-01-01

This paper describes the development of the analysis of the transient dynamic response of a bladed disk on a flexible rotor. The rotating flexible bladed disk is considered as a module in a complete turbine engine structure. The analysis of the flexible bladed disk (FBD) module is developed for the non-equilibrated one-diameter axial mode. The FBD motion is considered as a sum of two standing axial waves constrained to the rotor. The FBD is coupled inertially and gyroscopically to its rotor support, and indirectly through connecting elements, to the adjacent rotor and/or other supporting structures. Incorporated in the basic Turbine Engine Transient Response Analysis program (TETRA), the FBD module is demonstrated with a two-rotor model where the FBD can be excited into resonance by an unbalance in the adjacent rotor and at a frequency equal to the differential rotor speed. The FBD module also allows the analysis of two flexible bladed disks in the same rotor.

Open Rotor Aeroacoustic Modeling

NASA Technical Reports Server (NTRS)

Envia, Edmane

2012-01-01

Owing to their inherent fuel efficiency, there is renewed interest in developing open rotor propulsion systems that are both efficient and quiet. The major contributor to the overall noise of an open rotor system is the propulsor noise, which is produced as a result of the interaction of the airstream with the counter-rotating blades. As such, robust aeroacoustic prediction methods are an essential ingredient in any approach to designing low-noise open rotor systems. To that end, an effort has been underway at NASA to assess current open rotor noise prediction tools and develop new capabilities. Under this effort, high-fidelity aerodynamic simulations of a benchmark open rotor blade set were carried out and used to make noise predictions via existing NASA open rotor noise prediction codes. The results have been compared with the aerodynamic and acoustic data that were acquired for this benchmark open rotor blade set. The emphasis of this paper is on providing a summary of recent results from a NASA Glenn effort to validate an in-house open noise prediction code called LINPROP which is based on a high-blade-count asymptotic approximation to the Ffowcs-Williams Hawkings Equation. The results suggest that while predicting the absolute levels may be difficult, the noise trends are reasonably well predicted by this approach.

Open Rotor Aeroacoustic Modelling

NASA Technical Reports Server (NTRS)

Envia, Edmane

2012-01-01

Owing to their inherent fuel efficiency, there is renewed interest in developing open rotor propulsion systems that are both efficient and quiet. The major contributor to the overall noise of an open rotor system is the propulsor noise, which is produced as a result of the interaction of the airstream with the counter-rotating blades. As such, robust aeroacoustic prediction methods are an essential ingredient in any approach to designing low-noise open rotor systems. To that end, an effort has been underway at NASA to assess current open rotor noise prediction tools and develop new capabilities. Under this effort, high-fidelity aerodynamic simulations of a benchmark open rotor blade set were carried out and used to make noise predictions via existing NASA open rotor noise prediction codes. The results have been compared with the aerodynamic and acoustic data that were acquired for this benchmark open rotor blade set. The emphasis of this paper is on providing a summary of recent results from a NASA Glenn effort to validate an in-house open noise prediction code called LINPROP which is based on a high-blade-count asymptotic approximation to the Ffowcs-Williams Hawkings Equation. The results suggest that while predicting the absolute levels may be difficult, the noise trends are reasonably well predicted by this approach.

Development of an Open Rotor Cycle Model in NPSS Using a Multi-Design Point Approach

NASA Technical Reports Server (NTRS)

Hendricks, Eric S.

2011-01-01

NASA's Environmentally Responsible Aviation Project and Subsonic Fixed Wing Project are focused on developing concepts and technologies which may enable dramatic reductions to the environmental impact of future generation subsonic aircraft (Refs. 1 and 2). The open rotor concept (also referred to as the Unducted Fan or advanced turboprop) may allow the achievement of this objective by reducing engine emissions and fuel consumption. To evaluate its potential impact, an open rotor cycle modeling capability is needed. This paper presents the initial development of an open rotor cycle model in the Numerical Propulsion System Simulation (NPSS) computer program which can then be used to evaluate the potential benefit of this engine. The development of this open rotor model necessitated addressing two modeling needs within NPSS. First, a method for evaluating the performance of counter-rotating propellers was needed. Therefore, a new counter-rotating propeller NPSS component was created. This component uses propeller performance maps developed from historic counter-rotating propeller experiments to determine the thrust delivered and power required. Second, several methods for modeling a counter-rotating power turbine within NPSS were explored. These techniques used several combinations of turbine components within NPSS to provide the necessary power to the propellers. Ultimately, a single turbine component with a conventional turbine map was selected. Using these modeling enhancements, an open rotor cycle model was developed in NPSS using a multi-design point approach. The multi-design point (MDP) approach improves the engine cycle analysis process by making it easier to properly size the engine to meet a variety of thrust targets throughout the flight envelope. A number of design points are considered including an aerodynamic design point, sea-level static, takeoff and top of climb. The development of this MDP model was also enabled by the selection of a simple power

Investigation of Rotor-Airframe Interaction Noise Associated with Small-Scale Rotary-Wing Unmanned Aircraft Systems

NASA Technical Reports Server (NTRS)

Zawodny, Nikolas S.; Boyd, D. Douglas, Jr.

2017-01-01

In this study, hover acoustic measurements are taken on isolated rotor-airframe configurations representative of smallscale, rotary-wing unmanned aircraft systems (UAS). Each rotor-airframe configuration consists of two fixed-pitch blades powered by a brushless motor, with a simplified airframe geometry intended to represent a generic multicopter arm. In addition to acoustic measurements, CFD-based aeroacoustic predictions are implemented on a subset of the experimentally tested rotor-airframe configurations in an effort to better understand the noise content of the rotor-airframe systems. Favorable agreements are obtained between acoustic measurements and predictions, based on both time- and frequency-domain post-processing techniques. Results indicate that close proximity of airframe surfaces result in the generation of considerable tonal acoustic content in the form of harmonics of the rotor blade passage frequency (BPF). Analysis of the acoustic prediction data shows that the presence of the airframe surfaces can generate noise levels either comparable to or greater than the rotor blade surfaces under certain rotor tip clearance conditions. Analysis of the on-surface Ffowcs Williams and Hawkings (FW-H) source terms provide insight as to the predicted physical noise-generating mechanisms on the rotor and airframe surfaces.

Effects of rotor parameter variations on handling qualities of unaugmented helicopters in simulated terrain flight

NASA Technical Reports Server (NTRS)

Talbot, P. D.; Dugan, D. D.; Chen, R. T. N.; Gerdes, R. M.

1980-01-01

A coordinated analysis and ground simulator experiment was performed to investigate the effects on single rotor helicopter handling qualities of systematic variations in the main rotor hinge restraint, hub hinge offset, pitch-flap coupling, and blade lock number. Teetering rotor, articulated rotor, and hingeless rotor helicopters were evaluated by research pilots in special low level flying tasks involving obstacle avoidance at 60 to 100 knots airspeed. The results of the experiment are in the form of pilot ratings, pilot commentary, and some objective performance measures. Criteria for damping and sensitivity are reexamined when combined with the additional factors of cross coupling due to pitch and roll rates, pitch coupling with collective pitch, and longitudinal static stability. Ratings obtained with and without motion are compared. Acceptable flying qualities were obtained within each rotor type by suitable adjustment of the hub parameters, however, pure teetering rotors were found to lack control power for the tasks. A limit for the coupling parameter L sub q/L sub p of 0.35 is suggested.

A new hybrid observer based rotor imbalance vibration control via passive autobalancer and active bearing actuation

NASA Astrophysics Data System (ADS)

Jung, DaeYi; DeSmidt, Hans

2018-02-01

Many researchers have explored the use of active bearings, such as non-contact Active Magnetic Bearings (AMB), to control imbalance vibration in rotor systems. Meanwhile, the advantages of a passive Auto-balancer device (ABD) eliminating the imbalance effect of rotor without using other active means have been recently studied. This paper develops a new hybrid imbalance vibration control approach for an ABD-rotor system supported by a normal passive bearing in augmented with an AMB to enhance the balancing and vibration isolation capabilities. Essentially, an ABD consists of several freely moving eccentric balancing masses mounted on the rotor, which, at supercritical operating speeds, act to cancel the rotor's imbalance at steady-state. However, due to the inherent nonlinearity of the ABD, the potential for other, non-synchronous limit-cycle behavior exists resulting in increased rotor vibration. To address this, the algorithm of proposed hybrid control is designed to guarantee globally asymptotic stability of the synchronous balanced condition. This algorithm also incorporates with a "Luenberger-like" observer that continuously estimates the states of a balancer ball circulating around within ABD. In particular, it is shown that the balanced equilibrium can be made globally attractive under the hybrid control strategy, and that the control power levels of AMB are significantly reduced via the addition of the ABD because the control is designed such that it is only switched on for the abnormal operation of ABD and will be disengaged otherwise. Moreover, unlike other imbalance vibration control applications based upon ABD such as rotor speed regulator [21,22], this approach enables the controller to achieve the desirable performance without altering rotor speed once the rotor initially reaches the target speed. These applications are relevant to limited power applications such as in satellite reaction wheels, flywheel energy storage batteries or CD-ROM application.

An Experimental Determination of Losses in a 3-Port Wave Rotor

NASA Technical Reports Server (NTRS)

Wilson, Jack

1996-01-01

Wave rotors, used in a gas turbine topping cycle, offer a potential route to higher specific power and lower specific fuel consumption. In order to exploit this potential properly, it is necessary to have some realistic means of calculating wave rotor performance, taking losses into account, so that wave rotors can be designed for good performance. This in turn requires a knowledge of the loss mechanisms. The experiment reported here was designed as a statistical experiment to identify the losses due to finite passage opening time, friction, and leakage. For simplicity, the experiment used a 3-port, flow divider, wave cycle, but the results should be applicable to other cycles. A 12 inch diameter rotor was used, with two different lengths, 9 inches and 18 inches, and two different passage widths, 0.25 inch and 0.54 inch, in order to vary friction and opening time. To vary leakage, moveable end-walls were provided so that the rotor to end-wall gap could be adjusted. The experiment is described, and the results are presented, together with a parametric fit to the data. The fit shows that there will be an optimum passage width for a given wave rotor, since, as the passage width increases, friction losses decrease, but opening-time losses increase, and vice-versa. Leakage losses can be made small at reasonable gap sizes.

A theoretical study of the application of jet flap circulation control for reduction of rotor vibratory forces, addendum

NASA Technical Reports Server (NTRS)

Renka, A. R.

1975-01-01

The theoretical potential of a jet flap control system for reducing the vertical and horizontal non-cancelling helicopter rotor blade root shears was investigated. It was determined that the dominant contributor to the rotor power requirements is the requirement to maintain moment trim as well as force trim. It was also found that the requirement to maintain moment trim does not entail a power penalty.

Updated Assessment of an Open Rotor Airplane Using an Advanced Blade Design

NASA Technical Reports Server (NTRS)

Hendricks, Eric S.; Berton, Jeffrey J.; Haller, William J.; Tong, Michael T.; Guynn, Mark D.

2013-01-01

Application of open rotor propulsion systems (historically referred to as "advanced turboprops" or "propfans") to subsonic transport aircraft received significant attention and research in the 1970s and 1980s when fuel efficiency was the driving focus of aeronautical research. Recent volatility in fuel prices and concern for aviation's environmental impact have renewed interest in open rotor propulsion, and revived research by NASA and a number of engine manufacturers. Over the last few years, NASA has revived and developed analysis capabilities to assess aircraft designs with open rotor propulsion systems. These efforts have been described in several previous papers along with initial results from applying these capabilities. The initial results indicated that open rotor engines have the potential to provide large reductions in fuel consumption and emissions. Initial noise analysis indicated that current noise regulations can be met with modern baseline blade designs. Improved blades incorporating low-noise features are expected to result in even lower noise levels. This paper describes improvements to the initial assessment, plus a follow-on study using a more advanced open rotor blade design to power the advanced singleaisle transport. The predicted performance and environmental results of these two advanced open rotor concepts are presented and compared.

Modern rotor balancing - Emerging technologies

NASA Technical Reports Server (NTRS)

Zorzi, E. S.; Von Pragenau, G. L.

1985-01-01

Modern balancing methods for flexible and rigid rotors are explored. Rigid rotor balancing is performed at several hundred rpm, well below the first bending mode of the shaft. High speed balancing is necessary when the nominal rotational speed is higher than the first bending mode. Both methods introduce weights which will produce rotor responses at given speeds that will be exactly out of phase with the responses of an unbalanced rotor. Modal balancing seeks to add weights which will leave other rotor modes unaffected. Also, influence coefficients can be determined by trial and error addition of weights and recording of their effects on vibration at speeds of interest. The latter method is useful for balancing rotors at other than critical speeds and for performing unified balancing beginning with the first critical speed. Finally, low-speed flexible balancing permits low-speed tests and adjustments of rotor assemblies which will not be accessible when operating in their high-speed functional configuration. The method was developed for the high pressure liquid oxygen turbopumps for the Shuttle.

Helicopter rotor and engine sizing for preliminary performance estimation

NASA Technical Reports Server (NTRS)

Talbot, P. D.; Bowles, J. V.; Lee, H. C.

1986-01-01

Methods are presented for estimating some of the more fundamental design variables of single-rotor helicopters (tip speed, blade area, disk loading, and installed power) based on design requirements (speed, weight, fuselage drag, and design hover ceiling). The well-known constraints of advancing-blade compressibility and retreating-blade stall are incorporated into the estimation process, based on an empirical interpretation of rotor performance data from large-scale wind-tunnel tests. Engine performance data are presented and correlated with a simple model usable for preliminary design. When approximate results are required quickly, these methods may be more convenient to use and provide more insight than large digital computer programs.

Performance optimization of helicopter rotor blades

NASA Technical Reports Server (NTRS)

Walsh, Joanne L.

1991-01-01

As part of a center-wide activity at NASA Langley Research Center to develop multidisciplinary design procedures by accounting for discipline interactions, a performance design optimization procedure is developed. The procedure optimizes the aerodynamic performance of rotor blades by selecting the point of taper initiation, root chord, taper ratio, and maximum twist which minimize hover horsepower while not degrading forward flight performance. The procedure uses HOVT (a strip theory momentum analysis) to compute the horse power required for hover and the comprehensive helicopter analysis program CAMRAD to compute the horsepower required for forward flight and maneuver. The optimization algorithm consists of the general purpose optimization program CONMIN and approximate analyses. Sensitivity analyses consisting of derivatives of the objective function and constraints are carried out by forward finite differences. The procedure is applied to a test problem which is an analytical model of a wind tunnel model of a utility rotor blade.

Rotor blade assembly having internal loading features

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soloway, Daniel David

Rotor blade assemblies and wind turbines are provided. A rotor blade assembly includes a rotor blade having exterior surfaces defining a pressure side, a suction side, a leading edge and a trailing edge each extending between a tip and a root, the rotor blade defining a span and a chord, the exterior surfaces defining an interior of the rotor blade. The rotor blade assembly further includes a loading assembly, the loading assembly including a weight disposed within the interior and movable generally along the span of the rotor blade, the weight connected to a rotor blade component such that movementmore » of the weight towards the tip causes application of a force to the rotor blade component by the weight. Centrifugal force due to rotation of the rotor blade biases the weight towards the tip.« less

Improved motors for utility applications: Volume 6, Squirrel-cage rotor analysis: Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Griffith, J.W.; McCoy, R.M.

1986-11-01

An analysis of squirrel cage induction motor rotors was undertaken in response to an Industry Assessment Study finding 10% of motor failures to be rotor related. The analysis focuses on evaluating rotor design life. The evaluation combines state-of-the-art electromagnetic, thermal, and structural solution techniques into an integrated analysis and presents a simple summary. Finite element techniques are central tools in the analysis. The analysis is applied to a specific forced draft fan drive design. Fans as a category of application have a higher failure rate than other categories of power station auxiliary motor applications. Forced-draft fan drives are one ofmore » the major fan drives which accelerate a relatively high value of rotor load inertia. Various starting and operating conditions are studied for this forced-draft fan drive motor including a representative application duty cycle.« less

Patterns of the Rotor-over-Stator Rolling under Change in the Damping Components

NASA Astrophysics Data System (ADS)

Shatokhin, V. F.

2018-03-01

As experimental studies show, the rubbing of the rotor against the structure usually excites harmonics of different frequencies. In high-frequency regions, the power of the vibration signal appears to be considerable. The rotor—supports—stator system is in an unstable equilibrium state during the contact interaction between the rotor and the stator. The forces exerted on the rotor facilitate the excitation of the asynchronous rolling and its damping. The forces have been determined that facilitate the excitation of the progressive and retrograde rotor precession. The consideration of these forces in the algorithm for modeling the rotor-over-stator rolling development allows investigation of the impact of the components of the above forces on the behavior of the rotor system. The initial excitation—disturbance of the normal operation—of the rotor and subsequent unsteady oscillations of it result from sudden imbalance in the second span. The results of numerical modeling of the rubbing in the second span and the rotor-over-stator rolling upon change in the damping components of secondary (gyroscopic) components b ij ( i ≠ j) of the damping matrix are presented for the rotor on three bearing-supports considering the synergetic effect of the forces of various types exerted on the rotor. It is shown that change in one of the parameters of the excitation forces leads to ambiguity of the pattern (manifestation form) of the asynchronous rotor-over-stator rolling and proves the existence of more than one states towards which the rotor—supports—stator system tends. In addition to the rolling with a constant rotor—stator contact, oscillations of the rotor develop in the direction perpendicular to the common trajectory of the precession motion of the rotor's center with transition to the vibro-impact motion mode. The oscillations of the rotor tend towards the symmetry center of the system (the stator bore center). The reason is the components of the stiffness

Field Balancing and Harmonic Vibration Suppression in Rigid AMB-Rotor Systems with Rotor Imbalances and Sensor Runout.

PubMed

Xu, Xiangbo; Chen, Shao

2015-08-31

Harmonic vibrations of high-speed rotors in momentum exchange devices are primary disturbances for attitude control of spacecraft. Active magnetic bearings (AMBs), offering the ability to control the AMB-rotor dynamic behaviors, are preferred in high-precision and micro-vibration applications, such as high-solution Earth observation satellites. However, undesirable harmonic displacements, currents, and vibrations also occur in the AMB-rotor system owing to the mixed rotor imbalances and sensor runout. To compensate the rotor imbalances and to suppress the harmonic vibrations, two control methods are presented. Firstly, a four degrees-of-freedom AMB-rotor model with the static imbalance, dynamic imbalance, and the sensor runout are described. Next, a synchronous current reduction approach with a variable-phase notch feedback is proposed, so that the rotor imbalances can be identified on-line through the analysis of the synchronous displacement relationships of the geometric, inertial, and rotational axes of the rotor. Then, the identified rotor imbalances, which can be represented at two prescribed balancing planes of the rotor, are compensated by discrete add-on weights whose masses are calculated in the vector form. Finally, a repetitive control algorithm is utilized to suppress the residual harmonic vibrations. The proposed field balancing and harmonic vibration suppression strategies are verified by simulations and experiments performed on a control moment gyro test rig with a rigid AMB-rotor system. Compared with existing methods, the proposed strategies do not require trial weights or an accurate model of the AMB-rotor system. Moreover, the harmonic displacements, currents, and vibrations can be well-attenuated simultaneously.

Field Balancing and Harmonic Vibration Suppression in Rigid AMB-Rotor Systems with Rotor Imbalances and Sensor Runout

PubMed Central

Xu, Xiangbo; Chen, Shao

2015-01-01

Harmonic vibrations of high-speed rotors in momentum exchange devices are primary disturbances for attitude control of spacecraft. Active magnetic bearings (AMBs), offering the ability to control the AMB-rotor dynamic behaviors, are preferred in high-precision and micro-vibration applications, such as high-solution Earth observation satellites. However, undesirable harmonic displacements, currents, and vibrations also occur in the AMB-rotor system owing to the mixed rotor imbalances and sensor runout. To compensate the rotor imbalances and to suppress the harmonic vibrations, two control methods are presented. Firstly, a four degrees-of-freedom AMB-rotor model with the static imbalance, dynamic imbalance, and the sensor runout are described. Next, a synchronous current reduction approach with a variable-phase notch feedback is proposed, so that the rotor imbalances can be identified on-line through the analysis of the synchronous displacement relationships of the geometric, inertial, and rotational axes of the rotor. Then, the identified rotor imbalances, which can be represented at two prescribed balancing planes of the rotor, are compensated by discrete add-on weights whose masses are calculated in the vector form. Finally, a repetitive control algorithm is utilized to suppress the residual harmonic vibrations. The proposed field balancing and harmonic vibration suppression strategies are verified by simulations and experiments performed on a control moment gyro test rig with a rigid AMB-rotor system. Compared with existing methods, the proposed strategies do not require trial weights or an accurate model of the AMB-rotor system. Moreover, the harmonic displacements, currents, and vibrations can be well-attenuated simultaneously. PMID:26334281

Intrinsic and Extrinsic Temperature-Dependency of Viscosity-Sensitive Fluorescent Molecular Rotors

PubMed Central

Howell, Sarah; Dakanali, Marianna; Theodorakis, Emmanuel A.; Haidekker, Mark A.

2011-01-01

Molecular rotors are a group of environment-sensitive fluorescent probes whose quantum yield depends on the ability to form twisted intramolecular chargetransfer (TICT) states. TICT formation is dominantly governed by the solvent's microviscosity, but polarity and the ability of the solvent to form hydrogen bonds play an additional role. The relationship between quantum yield ϕF and viscosity η is widely accepted as a power-law, ϕF = C · ηx. In this study, we isolated the direct influence of the temperature on the TICT formation rate by examining several molecular rotors in protic and aprotic solvents over a range of temperatures. Each solvent's viscosity was determined as a function of temperature and used in the above power-law to determine how the proportionality constant C varies with temperature. We found that the power-law relationship fully explains the variations of the measured steady-state intensity by temperature-induced variations of the solvent viscosity, and C can be assumed to be temperature-independent. The exponent x, however, was found to be significantly higher in aprotic solvents than in protic solvents. We conclude that the ability of the solvent to form hydrogen bonds has a major influence on the relationship between viscosity and quantum yield. To use molecular rotors for the quantitative determination of viscosity or microviscosity, the exponent x needs to be determined for each dye-solvent combination. PMID:21947609

The Anatomy of AP1000 Mono-Block Low Pressure Rotor Forging

NASA Astrophysics Data System (ADS)

Jin, Jia-yu; Rui, Shou-tai; Wang, Qun

AP1000 mono-block low pressure (LP) rotor forgings for nuclear power station have maximum ingot weight, maximum diameter and the highest technical requirements. It confronts many technical problems during manufacturing process such as composition segregation and control of inclusion in the large ingot, core compaction during forging, control of grain size and mechanical performance. The rotor forging were anatomized to evaluate the manufacturing level of CFHI. This article introduces the anatomical results of this forging. The contents include chemical composition, mechanical properties, inclusions and grain size and other aspects from the full-length and full cross-section of this forging. The fluctuation of mechanical properties, uniformity of microstructure and purity of chemical composition were emphasized. The results show that the overall performance of this rotor forging is particularly satisfying.

Cluster Tails for Critical Power-Law Inhomogeneous Random Graphs

NASA Astrophysics Data System (ADS)

van der Hofstad, Remco; Kliem, Sandra; van Leeuwaarden, Johan S. H.

2018-04-01

Recently, the scaling limit of cluster sizes for critical inhomogeneous random graphs of rank-1 type having finite variance but infinite third moment degrees was obtained in Bhamidi et al. (Ann Probab 40:2299-2361, 2012). It was proved that when the degrees obey a power law with exponent τ \\in (3,4), the sequence of clusters ordered in decreasing size and multiplied through by n^{-(τ -2)/(τ -1)} converges as n→ ∞ to a sequence of decreasing non-degenerate random variables. Here, we study the tails of the limit of the rescaled largest cluster, i.e., the probability that the scaling limit of the largest cluster takes a large value u, as a function of u. This extends a related result of Pittel (J Combin Theory Ser B 82(2):237-269, 2001) for the Erdős-Rényi random graph to the setting of rank-1 inhomogeneous random graphs with infinite third moment degrees. We make use of delicate large deviations and weak convergence arguments.

Research on Aerodynamic Characteristics of Composite powered Unmanned Airship

NASA Astrophysics Data System (ADS)

Chen, Yu; Wang, Yun; Wang, Lu; Ma, Chengyu; Xia, Jun

2017-10-01

The main structure of the composite powered unmanned airship is consists of airbags and four-rotor system, which airbag increases the available lift, and has more advantages in terms of load and flight when compared with the traditional four-rotor. In order to compare the aerodynamic performance of the composite powered unmanned airship and the traditional four-rotor, the SIMPLE algorithm and the RNG k-epsilon model method are be used. The energy consumption of the composite powered unmanned airship is lesser than the traditional four-rotor under the same load and range was found.

Navier-Stokes flowfield computation of wing/rotor interaction for a tilt rotor aircraft in hover

NASA Technical Reports Server (NTRS)

Fejtek, Ian G.

1993-01-01

The download on the wing produced by the rotor-induced downwash of a tilt rotor aircraft in hover is of major concern because of its severe impact on payload-carrying capability. A method has been developed to help gain a better understanding of the fundamental fluid dynamics that causes this download, and to help find ways to reduce it. In particular, the method is employed in this work to analyze the effect of a tangential leading edge circulation-control jet on download reduction. Because of the complexities associated with modeling the complete configuration, this work focuses specifically on the wing/rotor interaction of a tilt rotor aircraft in hover. The three-dimensional, unsteady, thin-layer compressible Navier-Stokes equations are solved using a time-accurate, implicit, finite difference scheme that employs LU-ADI factorization. The rotor is modeled as an actuator disk which imparts both a radical and an azimuthal distribution of pressure rise and swirl to the flowfield. A momentum theory blade element analysis of the rotor is incorporated into the Navier-Stokes solution method. Solution blanking at interior points of the mesh has been shown here to be an effective technique in introducing the effects of the rotor and tangential leading edge jet. Results are presented both for a rotor alone and for wing/rotor interaction. The overall mean characteristics of the rotor flowfield are computed including the flow acceleration through the rotor disk, the axial and swirl velocities in the rotor downwash, and the slipstream contraction. Many of the complex tilt rotor flow features are captured including the highly three-dimensional flow over the wing, the recirculation fountain at the plane of symmetry, wing leading and trailing edge separation, and the large region of separated flow beneath the wing. Mean wing surface pressures compare fairly well with available experimental data, but the time-averaged download/thrust ratio is 20-30 percent higher than the

Static-thrust Investigation of Full-scale PV-2 Helicopter Rotors Having NACA 0012.6 and 23012.6 Airfoil Sections

NASA Technical Reports Server (NTRS)

Lipson, Stanley

1946-01-01

An investigation was conducted to compare the performance of two 25-ft-diam rotors which had identical dimensions and were similar in construction but different in blade airfoil-sections. Tests were conducted at indicated blade pitch angles from 3 degrees to 11.5 degrees and rotor speeds of 200, 290, and 371 rpm. The 23012.6 rotor required 2 percent less power to hover than the 0012.6. At thrust coefficients above design, the performance of the 23012.6 became better than the 0012.6 rotor.

Sizing Power Components of an Electrically Driven Tail Cone Thruster and a Range Extender

NASA Technical Reports Server (NTRS)

Jansen, Ralph H.; Bowman, Cheryl; Jankovsky, Amy

2016-01-01

The aeronautics industry has been challenged on many fronts to increase efficiency, reduce emissions, and decrease dependency on carbon-based fuels. This paper provides an overview of the turboelectric and hybrid electric technologies being developed under NASA's Advanced Air Transportation Technology (AATT) Project and discusses how these technologies can impact vehicle design. The discussion includes an overview of key hybrid electric studies and technology investments, the approach to making informed investment decisions based on key performance parameters and mission studies, and the power system architectures for two candidate aircraft. Finally, the power components for a single-aisle turboelectric aircraft with an electrically driven tail cone thruster and for a hybrid-electric nine-passenger aircraft with a range extender are parametrically sized, and the sensitivity of these components to key parameters is presented.

A study of sound generation in subsonic rotors, volume 2

NASA Technical Reports Server (NTRS)

Chalupnik, J. D.; Clark, L. T.

1975-01-01

Computer programs were developed for use in the analysis of sound generation by subsonic rotors. Program AIRFOIL computes the spectrum of radiated sound from a single airfoil immersed in a laminar flow field. Program ROTOR extends this to a rotating frame, and provides a model for sound generation in subsonic rotors. The program also computes tone sound generation due to steady state forces on the blades. Program TONE uses a moving source analysis to generate a time series for an array of forces moving in a circular path. The resultant time series are than Fourier transformed to render the results in spectral form. Program SDATA is a standard time series analysis package. It reads in two discrete time series and forms auto and cross covariances and normalizes these to form correlations. The program then transforms the covariances to yield auto and cross power spectra by means of a Fourier transformation.

Design of plywood and paper flywheel rotors

NASA Astrophysics Data System (ADS)

Erdman, A. G.; Hagen, D. L.; Gaff, S. A.

1982-05-01

Technical and economic design factors of cellulosic rotors are compared with conventional materials for stationary flywheel energy storage systems. Wood species, operation in a vacuum, assembly and costs of rotors are evaluated. Wound kraft paper, twine and plywood rotors are examined. Two hub attachments are designed. Support stiffness is shown to be constrained by the material strength, rotor configuration and speed ratio. Preliminary duration of load tests was performed on vacuum dried hexagonal birch plywood. Dynamic and static rotor hub fatigue equipment is designed. Moisture loss rates while vacuum drying plywood cylinders were measured, and the radial and axial diffusion coefficients were evaluated. Diffusion coefficients of epoxy coated plywood cylinders were also obtained. Economics of cellulosic and conventional rotors were examined. Plywood rotor manufacturing costs were evaluated. The optimum economic shape for laminated rotors is shown to be cylindrical. Vacuum container costs are parametrically derived and based on material properties and costs. Containment costs are significant and are included in comparisons. The optimum design stress and wound rotor configuration are calculated for seventeen examples. Plywood rotors appear to be marginally competitive with the steel hose wire or E glass rotors. High performance oriented kraft paper rotors potentially provide the lowest energy storage costs in stationary systems.

A flight investigation of performance and loads for a helicopter with NLR-1T main-rotor blade sections

NASA Technical Reports Server (NTRS)

Morris, C. E. K., Jr.; Tomaine, R. L.; Stevens, D. D.

1979-01-01

Data on performance and rotor loads for a teetering-rotor, AH-1G helicopter flown with a main rotor that had the NLR-1T airfoil as the blade-section contour are presented. The test envelope included hover, forward-flight speed sweeps from 35 to 85 m/sec, and collective-fixed maneuvers at about 0.25 tip-speed ratio. The data set for each test point described vehicle flight state, control positions, rotor loads, power requirements, and blade motions. Rotor loads are reviewed primarily in terms of peak-to-peak and harmonic content. Lower frequency components predominated for most loads and generally increased with increased airspeed, but not necessarily with increased maneuver load factor.

Estimation of dynamic rotor loads for the rotor systems research aircraft: Methodology development and validation

NASA Technical Reports Server (NTRS)

Duval, R. W.; Bahrami, M.

1985-01-01

The Rotor Systems Research Aircraft uses load cells to isolate the rotor/transmission systm from the fuselage. A mathematical model relating applied rotor loads and inertial loads of the rotor/transmission system to the load cell response is required to allow the load cells to be used to estimate rotor loads from flight data. Such a model is derived analytically by applying a force and moment balance to the isolated rotor/transmission system. The model is tested by comparing its estimated values of applied rotor loads with measured values obtained from a ground based shake test. Discrepancies in the comparison are used to isolate sources of unmodeled external loads. Once the structure of the mathematical model has been validated by comparison with experimental data, the parameters must be identified. Since the parameters may vary with flight condition it is desirable to identify the parameters directly from the flight data. A Maximum Likelihood identification algorithm is derived for this purpose and tested using a computer simulation of load cell data. The identification is found to converge within 10 samples. The rapid convergence facilitates tracking of time varying parameters of the load cell model in flight.

An unsteady rotor/fuselage interaction method

NASA Technical Reports Server (NTRS)

Egolf, T. Alan; Lorber, Peter F.

1987-01-01

An analytical method has been developed to treat unsteady helicopter rotor, wake, and fuselage interaction aerodynamics. An existing lifting line/prescribed wake rotor analysis and a source panel fuselage analysis were modified to predict vibratory fuselage airloads. The analyses were coupled through the induced flow velocities of the rotor and wake on the fuselage and the fuselage on the rotor. A prescribed displacement technique was used to distort the rotor wake about the fuselage. Sensitivity studies were performed to determine the influence of wake and body geometry on the computed airloads. Predicted and measured mean and unsteady pressures on a cylindrical body in the wake of a two-bladed rotor were compared. Initial results show good qualitative agreement.

Morphing Downwind-Aligned Rotor Concept Based on a 13-MW Wind Turbine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ichter, Brian; Steele, Adam; Loth, Eric

To alleviate the mass-scaling issues associated with conventional upwind rotors of extreme-scale wind turbines (>/=10 MW), a morphing downwind-aligned rotor (MoDaR) concept is proposed herein. The concept employs a downwind rotor with blades whose elements are stiff (no intentional flexibility) but with hub-joints that can be unlocked to allow for moment-free downwind alignment. Aligning the combination of gravitational, centrifugal and thrust forces along the blade path reduces downwind cantilever loads, resulting in primarily tensile loading. For control simplicity, the blade curvature can be fixed with a single morphing degree of freedom using a near-hub joint for coning angle: 22 degreesmore » at rated conditions. The conventional baseline was set as the 13.2-MW Sandia 100-m all glass blade in a three-bladed upwind configuration. To quantify potential mass savings, a downwind load-aligning, two-bladed rotor was designed. Because of the reduced number of blades, the MoDaR concept had a favorable 33% mass reduction. The blade reduction and coning led to a reduction in rated power, but morphing increased energy capture at lower speeds such that both the MoDaR and conventional rotors have the same average power: 5.4 MW. A finite element analysis showed that quasi-steady structural stresses could be reduced, over a range of operating wind speeds and azimuthal angles, despite the increases in loading per blade. However, the concept feasibility requires additional investigation of the mass, cost and complexity of the morphing hinge, the impact of unsteady aeroelastic influence because of turbulence and off-design conditions, along with system-level Levelized Cost of Energy analysis.« less

Development of an active twist rotor blade with distributed actuation and orthotropic material

NASA Astrophysics Data System (ADS)

Wierach, Peter; Riemenschneider, Johannes; Keye, Stefan

2005-05-01

Individual blade control (IBC) as well as higher harmonic control (HHC) for helicopter rotors promises to be a method to increase flight performance and to reduce vibration and noise. For those controls, an additional twist actuation of the rotor blade is needed. The developed concept comprises the implementation of distributed piezoelectric actuation into the rotor blade skin. In order to maximize the twist within given constraints, as torsional rigidity and given actuator design, the concept takes advantage of an orthotropic rotor blade skin. That way, a combination of shear actuation with orthotropic coupling generates more twist than each one of these effects alone. Previous approaches with distributed actuation used actuators operating in +/-45° direction with quasi-isotropic composites. A FE-Model of the blade was developed and validated using a simplified demonstrator. The objective of this study was to identify the effects of various geometric and material parameters to optimize the active twist performance of the blades. The whole development was embedded in an iterative process followed by an objective assessment. For this purpose a detailed structural model on the basis of the BO105 model rotor blade was developed, to predict the performance with respect to rotor dynamics, stability, aerodynamics and acoustics. Rotor dynamic simulations provided an initial overview of the active twist rotor performance. In comparison to the BO105 baseline rotor a noise reduction of 3 dB was predicted for an active twist of 0.8° at the blade tip. Additionally, a power reduction of 2.3% at 87m/s based on a 2.5 to BO105 was computed. A demonstrator blade with a rotor radius of 2m has been designed and manufactured. This blade will be tested to prove, that the calculated maximum twist can also be achieved under centrifugal loads.

Induction generators for Wind Energy Conversion Systems. Part I: review of induction generator with squirrel cage rotor. Part II: the Double Output Induction Generator (DOIG). Progress report, July-December 1975

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jayadev, T.S.

1976-02-01

The application of induction generators in Wind Energy Conversion Systems (WECS) is described. The conventional induction generator, which is an induction machine with a squirrel cage rotor, had been used in large wind power plants in Europe, but has not caught much attention until now by designers of large systems in this country. The induction generator with a squirrel cage rotor is described and useful design techniques to build induction generators for wind energy application are outlined. The Double Output Induction Generator (DOIG) - so called because power is fed into the grid from the stator, as well as themore » rotor is described. It is a wound rotor induction machine with power electronics to convert rotor slip frequency power to that of line frequency.« less

The identification of helicopter noise using a neural network

NASA Technical Reports Server (NTRS)

Cabell, Randolph H.; Fuller, Chris R.; O'Brien, Walter F.

1990-01-01

Experiments were carried out to demonstrate the ability of an artificial neural network (ANN) system to distinguish between the noise of two helicopters. The ANN is taught to identify helicopters by using two types of features: one that is associated with the ratio of the main-rotor to tail-rotor blade passage frequency (BPF), and the ohter that describes the distribution of peaks in the main-rotor spectrum, which is independent of the tail-rotor. It is shown that the ability of the ANN to identify helicopters is comparable to that of a conventional recognition system using the ratio of the main-rotor BPF to the tail-rotor BPF (when both the main- and the tail-rotor noise are present), but the performoance of ANN exceeds the conventional-method performance when the tail-rotor noise is absent. In addition, the results of ANN can be obtained as a function of propagation distance.

Impact of number of co-existing rotors and inter-electrode distance on accuracy of rotor localization☆,☆☆

PubMed Central

Aronis, Konstantinos N.; Ashikaga, Hiroshi

2018-01-01

Background Conflicting evidence exists on the efficacy of focal impulse and rotor modulation on atrial fibrillation ablation. A potential explanation is inaccurate rotor localization from multiple rotors coexistence and a relatively large (9–11 mm) inter-electrode distance (IED) of the multi-electrode basket catheter. Methods and results We studied a numerical model of cardiac action potential to reproduce one through seven rotors in a two-dimensional lattice. We estimated rotor location using phase singularity, Shannon entropy and dominant frequency. We then spatially downsampled the time series to create IEDs of 2–30 mm. The error of rotor localization was measured with reference to the dynamics of phase singularity at the original spatial resolution (IED = 1 mm). IED has a significant impact on the error using all the methods. When only one rotor is present, the error increases exponentially as a function of IED. At the clinical IED of 10 mm, the error is 3.8 mm (phase singularity), 3.7 mm (dominant frequency), and 11.8 mm (Shannon entropy). When there are more than one rotors, the error of rotor localization increases 10-fold. The error based on the phase singularity method at the clinical IED of 10 mm ranges from 30.0 mm (two rotors) to 96.1 mm (five rotors). Conclusions The magnitude of error of rotor localization using a clinically available basket catheter, in the presence of multiple rotors might be high enough to impact the accuracy of targeting during AF ablation. Improvement of catheter design and development of high-density mapping catheters may improve clinical outcomes of FIRM-guided AF ablation. PMID:28988690

Flow-driven rotor simulation of vertical axis tidal turbines: A comparison of helical and straight blades

NASA Astrophysics Data System (ADS)

Le, Tuyen Quang; Lee, Kwang-Soo; Park, Jin-Soon; Ko, Jin Hwan

2014-06-01

In this study, flow-driven rotor simulations with a given load are conducted to analyze the operational characteristics of a vertical-axis Darrieus turbine, specifically its self-starting capability and fluctuations in its torque as well as the RPM. These characteristics are typically observed in experiments, though they cannot be acquired in simulations with a given tip speed ratio (TSR). First, it is shown that a flow-driven rotor simulation with a two-dimensional (2D) turbine model obtains power coefficients with curves similar to those obtained in a simulation with a given TSR. 3D flowdriven rotor simulations with an optimal geometry then show that a helical-bladed turbine has the following prominent advantages over a straight-bladed turbine of the same size: an improvement of its self-starting capabilities and reduced fluctuations in its torque and RPM curves as well as an increase in its power coefficient from 33% to 42%. Therefore, it is clear that a flow-driven rotor simulation provides more information for the design of a Darrieus turbine than a simulation with a given TSR before experiments.

Rotor balance system

NASA Technical Reports Server (NTRS)

Novotny, Rudolph J. (Inventor)

1989-01-01

A balance ring (18) which is shrunk fit within each disk (12) of a rotor is selectively ground for detail balance. A plurality of openings (20) through the outer edge of the balance ring receive weights during the asssembly balance of the rotor. A snap ring (42) retains the weights within the openings.

Research on a new magnetic-field-modulated brushless double-rotor machine with sinusoidal-permeance modulating ring

NASA Astrophysics Data System (ADS)

Zheng, Ping; Liu, Jiaqi; Bai, Jingang; Song, Zhiyi; Liu, Yong

2017-05-01

The magnetic-field-modulated brushless double-rotor machine (MFM-BDRM), composed of a stator, a modulating ring rotor, and a PM rotor, is a kind of power-split device for hybrid electric vehicles (HEVs). In this paper, a new MFM-BDRM with sinusoidal-permeance modulating ring named Sinusoidal-Permeance-Modulating-Ring Brushless Double-Rotor Machine (SPMR-BDRM) is proposed to solve the problem of poor mechanical strength and large iron loss. The structure and the operating principle of the MFM-BDRM are introduced. The design principle of the sinusoidal-permeance modulating ring is analyzed and derived. The main idea of that is to minimize the harmonic permeance of air gap, thereby the harmonic magnetic fields can be restrained. There are comparisons between a MFM-BDRM with sinusoidal-permeance modulating ring and a same size MFM-BDRM with traditional modulating ring, including magnetic field distributions and electromagnetic performances. Most importantly, the iron losses are compared under six different conditions. The result indicates that the harmonic magnetic fields in the air gap are restrained; the electromagnetic torque and power factor are almost the same with same armature current; the torque ripples of the modulating ring rotor and the PM rotor are reduced; the stator loss is reduced by 13% at least and the PM loss is reduced by 20% at least compared with the same size traditional MFM-BDRM under the same operating conditions.

Helicopter rotor noise investigation during ice accretion

NASA Astrophysics Data System (ADS)

Cheng, Baofeng

measured high-frequency broadband noise increases significantly with increasing surface roughness heights, which indicates that it is feasible to quantify helicopter rotor ice-induced surface roughness through acoustic measurements. Comprehensive broadband noise measurements based on different accreted ice roughness at AERTS are then used to form the data base from which a correlation between the ice-induced surface roughness and the broadband noise level is developed. Two parameters, the arithmetic average roughness height, Ra, and the averaged roughness height, based on the integrated ice thickness at the blade tip, are introduced to describe the ice-induced surface roughness at the early stage of the ice accretion. The ice roughness measurements are correlated to the measured broadband noise level. Strong correlations (absolute mean deviations of 9.3% and 11.2% for correlation using Ra and the averaged roughness height respectively) between the ice roughness and the broadband noise level are obtained, which can be used as a tool to determine the accreted ice roughness in the AERTS facility through acoustic measurement. It might be possible to use a similar approach to develop an early ice accretion detection tool for helicopters, as well as to quantify the ice-induced roughness at the early stage of rotor ice accretion. Rotor broadband noise source identification is conducted and the broadband noise related to ice accretion is argued to be turbulent boundary layer - trailing edge (TBL-TE) noise. Theory suggests TBL-TE noise scales with Mach number to the fifth power, which is also observed in the experimental data. The trailing edge noise theories developed by Ffowcs Williams and Hall, and Howe both identify two important parameters: boundary layer thickness and turbulence intensity. Numerical studies of 2-D airfoils with different ice-induced surface roughness heights are conducted to investigate the extent that surface roughness impacts the boundary layer thickness

Definition of Forces on Turbomachinery Rotors. Task B Report: Dynamic Analysis of Rotors

NASA Technical Reports Server (NTRS)

Childs, D. W.

1983-01-01

The rotordynamic characteristics of turbomachinery are known to depend on the forces developed due to relative motion between the rotor and the housing. For example, the critical speed locations generally depend on the bearing stiffnesses, seal dampling influences rotor stability and bearing reaction amplitudes near critical speeds, etc. A systematic examination of the influence of changes in the forces acting on rotors is studied. More specifically, the sensitivity of the rotordynamic characteristics to changes in rotor forces is analyzed. Rotordynamic characteristics of the HPOTP (High Pressure Oxygen Turbopump) and HPFTP (High Pressure Fuel Turbopump) of the SSME (Space Shuttle Main Engine) are investigated. Because of their markedly different rotordynamic characteristics, these units are considered to be representative of a range of possible future liquid rocket engine turbomachinery.

Full scale hover test of a 25 foot tilt rotor

NASA Technical Reports Server (NTRS)

Helf, S.; Broman, E.; Gatchel, S.; Charles, B.

1973-01-01

The tilt rotor underwent a hover performance test on the Aero Propulsion Laboratory whirl stand at Wright-Patterson Air Force Base. The maximum thrust over density ratio measured at the design tip speed of 740 feet per second was 10,016 pounds. This occurred when the power over density ratio was 1721 horsepower. At the hover overspeed rpm, the thrust and power, over density ratio, were 11,008 pounds and 1866 horsepower. During the test, the maximum measured thrust coefficient was 0.177, and the rotor figure of merit exceeded 0.81. Measured lifting efficiency was 8.35 pounds per horsepower at the thrust a 13,000-pound aircraft would require for hover at sea level on a standard day. No effect of compressibility on performance is discernible in the test results (the range of tip Mach numbers tested was 0.55 to 0.71).

Hovering and Low-Speed Performance and Control Characteristics of the Kaman Helicopter Rotor System as Determined on the Langley Helicopter Tower. TED No. NACA DE 205

NASA Technical Reports Server (NTRS)

Carpenter, Paul J.; Paulnock, Russell S.

1949-01-01

An investigation has been conducted with the Langley helicopter tower to obtain basic performance and control characteristics of the Raman rotor system. Blade-pitch control is obtained in this configuration by utilizing an auxiliary flap to twist the blades. Rotor thrust and power required were measured for the hovering condition and over a range of wind velocities from 0 to 30 miles per hour. The control characteristics and the transient response of the rotor to various control movements were also measured. The hovering-performance data are presented as a survey of the wake velocities and the variation of torque coefficient with thrust coefficient. The power required for the test rotor to hover at a thrust of 1350 pounds and a rotor speed of 240 rpm is approximately 6.5 percent greater than that estimated for a conventional rotor of the same diameter and solidity. It is believed that most of this difference is caused by th e flap servomechanism. The reduction in total power required for sustentation of the single-rotor configuration tested at various wind velocities and at the normal operating rotor thrust was found to be similar to the theoretical and experimental results for ro tors with conventionally actuated pitch. The control effectiveness was determined as a function of rotor speed. Sufficient control was available to give a thrust range of 0 to 1500 pounds and a rotor tilt of plus or minus 7 degrees. The time lag between flap motion and blade-pitch response is approximately 0.02 to 0.03 second. The response of the rotor following the blade-pitch response is similar to that of a rotor with conventionally actuated pitch changes. The over-all characteristics of the rotor investigated indicate that satisfactory performance and control characteristics were obtained.

Transonic airfoil design for helicopter rotor applications

NASA Technical Reports Server (NTRS)

Hassan, Ahmed A.; Jackson, B.

1989-01-01

Despite the fact that the flow over a rotor blade is strongly influenced by locally three-dimensional and unsteady effects, practical experience has always demonstrated that substantial improvements in the aerodynamic performance can be gained by improving the steady two-dimensional charateristics of the airfoil(s) employed. The two phenomena known to have great impact on the overall rotor performance are: (1) retreating blade stall with the associated large pressure drag, and (2) compressibility effects on the advancing blade leading to shock formation and the associated wave drag and boundary-layer separation losses. It was concluded that: optimization routines are a powerful tool for finding solutions to multiple design point problems; the optimization process must be guided by the judicious choice of geometric and aerodynamic constraints; optimization routines should be appropriately coupled to viscous, not inviscid, transonic flow solvers; hybrid design procedures in conjunction with optimization routines represent the most efficient approach for rotor airfroil design; unsteady effects resulting in the delay of lift and moment stall should be modeled using simple empirical relations; and inflight optimization of aerodynamic loads (e.g., use of variable rate blowing, flaps, etc.) can satisfy any number of requirements at design and off-design conditions.

Flapping inertia for selected rotor blades

NASA Technical Reports Server (NTRS)

Berry, John D.; May, Matthew J.

1991-01-01

Aerodynamics of helicopter rotor systems cannot be investigated without consideration for the dynamics of the rotor. One of the principal properties of the rotor which affects the rotor dynamics is the inertia of the rotor blade about its root attachment. Previous aerodynamic investigation have been performed on rotor blades with a variety of planforms to determine the performance differences due to blade planform. The blades tested for this investigation have been tested on the U.S. Army 2 meter rotor test system (2MRTS) in the NASA Langley 14 by 22 foot subsonic tunnel for hover performance. This investigation was intended to provide fundamental information on the flapping inertia of five rotor blades with differing planforms. The inertia of the bare cuff and the cuff with a blade extension were also measured for comparison with the inertia of the blades. Inertia was determined using a swing testing technique, using the period of oscillation to determine the effective flapping inertia. The effect of damping in the swing test was measured and described. A comparison of the flapping inertials for rectangular and tapered planform blades of approximately the same mass showed the tapered blades to have a lower inertia, as expected.

Some perspective decisions for the regeneration system equipment of the thermal and nuclear power plants decreasing the probability of water ingress into the turbine and rotor acceleration by return steam flow

NASA Astrophysics Data System (ADS)

Trifonov, N. N.; Svyatkin, F. A.; Sintsova, T. G.; Ukhanova, M. G.; Yesin, S. B.; Nikolayenkova, E. K.; Yurchenko, A. Yu.; Grigorieva, E. B.

2016-03-01

The regeneration system heaters are one of the sources of possible ingress of the water into the turbine. The water penetrates into the turbine either at the heaters overflow or with the return flow of steam generated when the water being in the heater boils up in the dynamic operation modes or at deenergization of the power-generating unit. The return flow of steam and water is dangerous to the turbine blades and can result in the rotor acceleration. The known protective devices used to prevent the overflow of the low-pressure and high-pressure heaters (LPH and HPH), of the horizontal and vertical heaters of heating-system water (HWH and VWH), as well as of the deaerators and low-pressure mixing heaters (LPMH) were considered. The main protective methods of the steam and water return flows supplied by the heaters in dynamic operation modes or at deenergization of the power-generating unit are described. Previous operating experience shows that the available protections do not fully prevent water ingress into the turbine and the rotor acceleration and, therefore, the development of measures to decrease the possibility of ingress of the water into the turbine is an actual problem. The measures allowing eliminating or reducing the water mass in the heaters are expounded; some of them were designed by the specialists of OAO Polzunov Scientific and Development Association on Research and Design of Power Equipment (NPO CKTI) and are efficiently introduced at heat power plants and nuclear power plants. The suggested technical solutions allow reducing the possibility of the water ingress into the turbine and rotor acceleration by return steam flow in the dynamic operation modes or in the case of power generating unit deenergization. Some of these solutions have been tested in experimental-industrial exploitation and can be used in industry.

The NASA modern technology rotors program

NASA Technical Reports Server (NTRS)

Watts, M. E.; Cross, J. L.

1986-01-01

Existing data bases regarding helicopters are based on work conducted on 'old-technology' rotor systems. The Modern Technology Rotors (MTR) Program is to provide extensive data bases on rotor systems using present and emerging technology. The MTR is concerned with modern, four-bladed, rotor systems presently being manufactured or under development. Aspects of MTR philosophy are considered along with instrumentation, the MTR test program, the BV 360 Rotor, and the UH-60 Black Hawk. The program phases include computer modelling, shake test, model-scale test, minimally instrumented flight test, extensively pressure-instrumented-blade flight test, and full-scale wind tunnel test.

A Novel Numerical Approach for Generation and Propagation of Rotor-Stator Interaction Noise

NASA Astrophysics Data System (ADS)

Patel, Krishna

As turbofan engine designs move towards bypass ratios ≥12 and corresponding low pressure ratios, fan rotor blade tip Mach numbers are reduced, leading to rotor-stator interaction becoming an important contributor to tonal fan noise. For future aircraft configurations employing boundary layer ingestion, non-uniform flow enters the fan. The impact of such non-uniform flows on the generation and propagation of rotor-stator interaction tones has yet to be assessed. In this thesis, a novel approach is proposed to numerically predict the generation and propagation of rotor-stator interaction noise with distorted inflow. The approach enables a 42% reduction in computational cost compared to traditional approaches employing a sliding interface between the rotor and stator. Such an interface may distort rotor wakes and can cause non-physical acoustic wave reflections if time steps are not sufficiently small. Computational costs are reduced by modelling the rotor using distributed, volumetric body forces. This eliminates the need for a sliding interface and thus allows a larger time step size. The force model responds to local flow conditions and thus can capture the effects of long-wavelength flow distortions. Since interaction noise is generated by the incidence of the rotor wakes onto the stator vanes, the key challenge is to produce the wakes using a body force field since the rotor blades are not directly modelled. It is shown that such an approach can produce wakes by concentrating the viscous forces along streamtubes in the last 15% chord. The new approach to rotor wake generation is assessed on the GE R4 fan from NASA's Source Diagnostic Test, for which the computed overall aerodynamic performance matches the experiment to within 1%. The rotor blade wakes are generated with widths in excellent agreement and depths in fair agreement with the experiment. An assessment of modal sound power levels computed in the exhaust duct indicates that this approach can be used

System for Controlling a Magnetically Levitated Rotor

NASA Technical Reports Server (NTRS)

Morrison, Carlos R. (Inventor)

2006-01-01

In a rotor assembly having a rotor supported for rotation by magnetic bearings, a processor controlled by software or firmware controls the generation of force vectors that position the rotor relative to its bearings in a "bounce" mode in which the rotor axis is displaced from the principal axis defined between the bearings and a "tilt" mode in which the rotor axis is tilted or inclined relative to the principal axis. Waveform driven perturbations are introduced to generate force vectors that excite the rotor in either the "bounce" or "tilt" modes.

Aeroelastic considerations for torsionally soft rotors

NASA Technical Reports Server (NTRS)

Mantay, W. R.; Yeager, W. T., Jr.

1985-01-01

A research study was initiated to systematically determine the impact of selected blade tip geometric parameters on conformable rotor performance and loads characteristics. The model articulated rotors included baseline and torsionally soft blades with interchangeable tips. Seven blade tip designs were evaluated on the baseline rotor and six tip designs were tested on the torsionally soft blades. The designs incorporated a systemmatic variation in geometric parameters including sweep, taper, and anhedral. The rotors were evaluated in the NASA Langley Transonic Dynamics Tunnel at several advance ratios, lift and propulsive force values, and tip Mach numbers. A track sensitivity study was also conducted at several advance ratios for both rotors. Based on the test results, tip parameter variations generated significant rotor performance and loads differences for both baseline and torsionally soft blades.

Rotor Meandering Contributes to Irregularity in Electrograms during Atrial Fibrillation

PubMed Central

Zlochiver, Sharon; Yamazaki, Masatoshi; Kalifa, Jerome; Berenfeld, Omer

2010-01-01

Radiofrequency ablation therapy of atrial fibrillation (AF) recently incorporated the analysis of dominant frequency (DF) and/or electrogram fractionation for guidance. However, the relationships between DF, fractionation and spatio-temporal characteristics of the AF source remain unclear. We hypothesize that meandering reentrant AF source contributes to the wave fractionation and is reflected in the power spectrum of local electrograms elsewhere in the rotor’s surroundings. Methods Meandering rotors as AF sources were simulated in 2D models of human atrial tissue and recorded in isolated sheep hearts. Non-dominant elements of the signals were differentiated from the dominant elements using singular value decomposition, whereby the purely periodic constituent (PC) relating to the rotor’s DF was eliminated rendering a residual constituent (RC) that consisted of all other activity. Results Spectral analysis of the decomposed constituents revealed peaks corresponding to the meandering frequency of the rotor tip, the magnitudes of which were proportional to the size of, and the distance to the rotor core. Similar analyses on epicardial optical signals and electrograms from isolated sheep hearts, as well as human complex fractionated atrial electrograms demonstrated applicability of the approach. Conclusion Increased meandering of the rotor driving AF reduces activation periodicity and increases fractionation. The spectral manifestation of the rotor activity beyond the meandering region makes it possible to characterize AF source stability, as well as DF in humans using electrode mapping. PMID:18534369

Further Examination of the Vibratory Loads Reduction Results from the NASA/ARMY/MIT Active Twist Rotor Test

NASA Technical Reports Server (NTRS)

Wilbur, Matthew L.; Yeager, William T., Jr.; Sekula, Martin K.

2002-01-01

The vibration reduction capabilities of a model rotor system utilizing controlled, strain-induced blade twisting are examined. The model rotor blades, which utilize piezoelectric active fiber composite actuators, were tested in the NASA Langley Transonic Dynamics Tunnel using open-loop control to determine the effect of active-twist on rotor vibratory loads. The results of this testing have been encouraging, and have demonstrated that active-twist rotor designs offer the potential for significant load reductions in future helicopter rotor systems. Active twist control was found to use less than 1% of the power necessary to operate the rotor system and had a pronounced effect on both rotating- and fixed-system loads, offering reductions in individual harmonic loads of up to 100%. A review of the vibration reduction results obtained is presented, which includes a limited set of comparisons with results generated using the second-generation version of the Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics (CAMRAD II) rotorcraft comprehensive analysis.

75 FR 55453 - Airworthiness Directives; Sikorsky Aircraft Corporation Model S-76A, S-76B, and S-76C Helicopters

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-13

... track-and-balance of the tail rotor. Finally, this AD requires installing a vertical stabilizer..., track- and-balance of the tail rotor. Accomplishing the tail rotor track-and- balance would involve both...'' state-- almost to the point of takeoff, and the mechanic would accomplish the vibration measurements...

Does climate have heavy tails?

NASA Astrophysics Data System (ADS)

Bermejo, Miguel; Mudelsee, Manfred

2013-04-01

When we speak about a distribution with heavy tails, we are referring to the probability of the existence of extreme values will be relatively large. Several heavy-tail models are constructed from Poisson processes, which are the most tractable models. Among such processes, one of the most important are the Lévy processes, which are those process with independent, stationary increments and stochastic continuity. If the random component of a climate process that generates the data exhibits a heavy-tail distribution, and if that fact is ignored by assuming a finite-variance distribution, then there would be serious consequences (in the form, e.g., of bias) for the analysis of extreme values. Yet, it appears that it is an open question to what extent and degree climate data exhibit heavy-tail phenomena. We present a study about the statistical inference in the presence of heavy-tail distribution. In particular, we explore (1) the estimation of tail index of the marginal distribution using several estimation techniques (e.g., Hill estimator, Pickands estimator) and (2) the power of hypothesis tests. The performance of the different methods are compared using artificial time-series by means of Monte Carlo experiments. We systematically apply the heavy tail inference to observed climate data, in particular we focus on time series data. We study several proxy and directly observed climate variables from the instrumental period, the Holocene and the Pleistocene. This work receives financial support from the European Commission (Marie Curie Initial Training Network LINC, No. 289447, within the 7th Framework Programme).

Magic angle spinning NMR with metallized rotors as cylindrical microwave resonators.

PubMed

Scott, Faith J; Sesti, Erika L; Choi, Eric J; Laut, Alexander J; Sirigiri, Jagadishwar R; Barnes, Alexander B

2018-04-19

We introduce a novel design for millimeter wave electromagnetic structures within magic angle spinning (MAS) rotors. In this demonstration, a copper coating is vacuum deposited onto the outside surface of a sapphire rotor at a thickness of 50 nm. This thickness is sufficient to reflect 197-GHz microwaves, yet not too thick as to interfere with radiofrequency fields at 300 MHz or prevent sample spinning due to eddy currents. Electromagnetic simulations of an idealized rotor geometry show a microwave quality factor of 148. MAS experiments with sample rotation frequencies of ω r /2π = 5.4 kHz demonstrate that the drag force due to eddy currents within the copper does not prevent sample spinning. Spectra of sodium acetate show resolved 13 C J-couplings of 60 Hz and no appreciable broadening between coated and uncoated sapphire rotors, demonstrating that the copper coating does not prevent shimming and high-resolution nuclear magnetic resonance spectroscopy. Additionally, 13 C Rabi nutation curves of ω 1 /2π = 103 kHz for both coated and uncoated rotors indicate no detrimental impact of the copper coating on radio frequency coupling of the nuclear spins to the sample coil. We present this metal coated rotor as a first step towards an MAS resonator. MAS resonators are expected to have a significant impact on developments in electron decoupling, pulsed dynamic nuclear polarization (DNP), room temperature DNP, DNP with low-power microwave sources, and electron paramagnetic resonance detection. Copyright © 2018 John Wiley & Sons, Ltd.

User's Manual for Computer Program ROTOR. [to calculate tilt-rotor aircraft dynamic characteristics

NASA Technical Reports Server (NTRS)

Yasue, M.

1974-01-01

A detailed description of a computer program to calculate tilt-rotor aircraft dynamic characteristics is presented. This program consists of two parts: (1) the natural frequencies and corresponding mode shapes of the rotor blade and wing are developed from structural data (mass distribution and stiffness distribution); and (2) the frequency response (to gust and blade pitch control inputs) and eigenvalues of the tilt-rotor dynamic system, based on the natural frequencies and mode shapes, are derived. Sample problems are included to assist the user.

Double-ended ceramic helical-rotor expander

DOEpatents

Mohr, Peter B.; Myers, Wendell B.

1995-01-01

A ceramic helical rotor expander using a double-ended or tandem herringbone type rotor arrangement with bearing and seal assemblies remote from the hot gas inlets and especially capable of operating at an inlet temperature of above 1100.degree. C. The rotors are solid or hollow and bonded to hollow metal shafts, and mounted in a composite or simple prismatic casing. The rotors, casing and shafts are constructed from low expansivity materials. In the preferred embodiment the rotors are constructed of silicon nitride and the shafts constructed of an molybdenum alloy, with the metal shafts being supported in bearings and secured to synchronizing gears. The rotors and casing may be provided with coolant channels therein, and are constructed to eliminate the problem of end leakages at inlet temperature and pressure, and the need for high temperature bearings and seals.

Double-ended ceramic helical-rotor expander

DOEpatents

Mohr, P.B.; Myers, W.B.

1995-02-28

A ceramic helical rotor expander is disclosed using a double-ended or tandem herringbone type rotor arrangement with bearing and seal assemblies remote from the hot gas inlets and especially capable of operating at an inlet temperature of above 1,100 C. The rotors are solid or hollow and bonded to hollow metal shafts, and mounted in a composite or simple prismatic casing. The rotors, casing and shafts are constructed from low expansivity materials. In the preferred embodiment the rotors are constructed of silicon nitride and the shafts constructed of an molybdenum alloy, with the metal shafts being supported in bearings and secured to synchronizing gears. The rotors and casing may be provided with coolant channels therein, and are constructed to eliminate the problem of end leakages at inlet temperature and pressure, and the need for high temperature bearings and seals. 3 figs.

LES of an Advancing Helicopter Rotor, and Near to Far Wake Assessment

NASA Astrophysics Data System (ADS)

Caprace, Denis-Gabriel; Duponcheel, Matthieu; Chatelain, Philippe; Winckelmans, Grégoire

2017-11-01

Helicopter wake physics involve complex, unsteady vortical flows which have been only scarcely addressed in past studies. The present work focuses on LES of the wake flow behind an advancing rotor, to support the investigation of rotorcraft wake physics and decay mechanisms. A hybrid Vortex Particle-Mesh (VPM) method is employed to simulate the wake of an articulated four-bladed rotor in trimmed conditions, at an advance ratio of 0.41. The simulation domain extends to 30 rotor diameters downstream. The coarse scale aerodynamics of the blades are accounted for through enhanced immersed lifting lines. The vorticity generation mechanisms, the roll-up of the near wake and the resulting established far wake are described (i) qualitatively in terms of vortex dynamics using rotor polar plots and 3D visualizations; (ii) quantitatively using classical integral diagnostics. The power spectra measured by velocity probes in the wake are also presented. The analysis shows that the wake reaches a fully turbulent equilibrium state at a distance of about 30 diameters downstream. This work is supported by the Belgian french community F.R.S.-FNRS.

Rotor Wake/Stator Interaction Noise Prediction Code Technical Documentation and User's Manual

NASA Technical Reports Server (NTRS)

Topol, David A.; Mathews, Douglas C.

2010-01-01

This report documents the improvements and enhancements made by Pratt & Whitney to two NASA programs which together will calculate noise from a rotor wake/stator interaction. The code is a combination of subroutines from two NASA programs with many new features added by Pratt & Whitney. To do a calculation V072 first uses a semi-empirical wake prediction to calculate the rotor wake characteristics at the stator leading edge. Results from the wake model are then automatically input into a rotor wake/stator interaction analytical noise prediction routine which calculates inlet aft sound power levels for the blade-passage-frequency tones and their harmonics, along with the complex radial mode amplitudes. The code allows for a noise calculation to be performed for a compressor rotor wake/stator interaction, a fan wake/FEGV interaction, or a fan wake/core stator interaction. This report is split into two parts, the first part discusses the technical documentation of the program as improved by Pratt & Whitney. The second part is a user's manual which describes how input files are created and how the code is run.

Hover Testing of the NASA/Army/MIT Active Twist Rotor Prototype Blade

NASA Technical Reports Server (NTRS)

Wilbur, Matthew L.; Yeager, William T., Jr.; Wilkie, W. Keats; Cesnik, Carlos E. S.; Shin, Sangloon

2000-01-01

Helicopter rotor individual blade control promises to provide a mechanism for increased rotor performance and reduced rotorcraft vibrations and noise. Active material methods, such as piezoelectrically actuated trailing-edge flaps and strain-induced rotor blade twisting, provide a means of accomplishing individual blade control without the need for hydraulic power in the rotating system. Recent studies have indicated that controlled strain induced blade twisting can be attained using piezoelectric active fiber composite technology. In order to validate these findings experimentally, a cooperative effort between NASA Langley Research Center, the Army Research Laboratory, and the MIT Active Materials and Structures Laboratory has been developed. As a result of this collaboration an aeroelastically-scaled active-twist model rotor blade has been designed and fabricated for testing in the heavy gas environment of the Langley Transonic Dynamics Tunnel (TDT). The results of hover tests of the active-twist prototype blade are presented in this paper. Comparisons with applicable analytical predictions of active-twist frequency response in hovering flight are also presented.

Rotor damage detection by using piezoelectric impedance

NASA Astrophysics Data System (ADS)

Qin, Y.; Tao, Y.; Mao, Y. F.

2016-04-01

Rotor is a core component of rotary machinery. Once the rotor has the damage, it may lead to a major accident. Thus the quantitative rotor damage detection method based on piezoelectric impedance is studied in this paper. With the governing equation of piezoelectric transducer (PZT) in a cylindrical coordinate, the displacement along the radius direction is derived. The charge of PZT is calculated by the electric displacement. Then, by the use of the obtained displacement and charge, an analytic piezoelectric impedance model of the rotor is built. Given the circular boundary condition of a rotor, annular elements are used as the analyzed objects and spectral element method is used to set up the damage detection model. The Electro-Mechanical (E/M) coupled impedance expression of an undamaged rotor is deduced with the application of a low-cost impedance test circuit. A Taylor expansion method is used to obtain the approximate E/M coupled impedance expression for the damaged rotor. After obtaining the difference between the undamaged and damaged rotor impedance, a rotor damage detection method is proposed. This method can directly calculate the change of bending stiffness of the structural elements, it follows that the rotor damage can be effectively detected. Finally, a preset damage configuration is used for the numerical simulation. The result shows that the quantitative damage detection algorithm based on spectral element method and piezoelectric impedance proposed in this paper can identify the location and the severity of the damaged rotor accurately.

Hot gas ingestion effects on fuel control surge recovery and AH-1 rotor drive train torque spikes

NASA Technical Reports Server (NTRS)

Tokarski, Frank; Desai, Mihir; Books, Martin; Zagranski, Raymond

1994-01-01

This report summarizes the work accomplished through computer simulation to understand the impact of the hydromechanical turbine assembly (TA) fuel control on rocket gas ingestion induced engine surges on the AH-1 (Cobra) helicopter. These surges excite the lightly damped torsional modes of the Cobra rotor drive train and can cause overtorqueing of the tail rotor shaft. The simulation studies show that the hydromechanical TA control has a negligible effect on drive train resonances because its response is sufficiently attenuated at the resonant frequencies. However, a digital electronic control working through the TA control's separate, emergency fuel metering system has been identified as a solution to the overtorqueing problem. State-of-the-art software within the electronic control can provide active damping of the rotor drive train to eliminate excessive torque spikes due to any disturbances including engine surges and aggressive helicopter maneuvers. Modifications to the existing TA hydromechanical control are relatively minor, and existing engine sensors can be utilized by the electronic control. Therefore, it is concluded that the combination of full authority digital electronic control (FADEC) with hydromechanical backup using the existing TA control enhances flight safety, improves helicopter performance, reduces pilot workload, and provides a substantial payback for very little investment.

Periodic control of the individual-blade-control helicopter rotor

NASA Technical Reports Server (NTRS)

Mckillip, R. M., Jr.

1985-01-01

This paper describes the results of an investigation into methods of controller design for linear periodic systems utilizing an extension of modern control methods. Trends present in the selection of various cost functions are outlined, and closed-loop controller results are demonstrated for two cases: first, on an analog computer simulation of the rigid out of plane flapping dynamics of a single rotor blade, and second, on a 4 ft diameter single-bladed model helicopter rotor in the MIT 5 x 7 subsonic wind tunnel, both for various high levels of advance ratio. It is shown that modal control using the IBC concept is possible over a large range of advance ratios with only a modest amount of computational power required.

Performance and wake conditions of a rotor located in the wake of an obstacle

NASA Astrophysics Data System (ADS)

Naumov, I. V.; Kabardin, I. K.; Mikkelsen, R. F.; Okulov, V. L.; Sørensen, J. N.

2016-09-01

Obstacles like forests, ridges and hills can strongly affect the velocity profile in front of a wind turbine rotor. The present work aims at quantifying the influence of nearby located obstacles on the performance and wake characteristics of a downstream located wind turbine. Here the influence of an obstacle in the form of a cylindrical disk was investigated experimentally in a water flume. A model of a three-bladed rotor, designed using Glauert's optimum theory at a tip speed ratio λ = 5, was placed in the wake of a disk with a diameter close to the one of the rotor. The distance from the disk to the rotor was changed from 4 to 8 rotor diameters, with the vertical distance from the rotor axis varied 0.5 and 1 rotor diameters. The associated turbulent intensity of the incoming flow to the rotor changed 3 to '6% due to the influence of the disk wake. In the experiment, thrust characteristics and associated pulsations as a function of the incoming flow structures were measured by strain gauges. The flow condition in front of the rotor was measured with high temporal accuracy using LDA and power coefficients were determine as function of tip speed ratio for different obstacle positions. Furthermore, PIV measurements were carried out to study the development of the mean velocity deficit profiles of the wake behind the wind turbine model under the influence of the wake generated by the obstacle. By use of regression techniques to fit the velocity profiles it was possible to determine velocity deficits and estimate length scales of the wake attenuation.

Full-scale hingeless rotor performance and loads

NASA Technical Reports Server (NTRS)

Peterson, Randall L.

1995-01-01

A full-scale BO-105 hingeless rotor system was tested in the NASA Ames 40- by 80-Foot Wind Tunnel on the rotor test apparatus. Rotor performance, rotor loads, and aeroelastic stability as functions of both collective and cyclic pitch, tunnel velocity, and shaft angle were investigated. This test was performed in support of the Rotor Data Correlation Task under the U.S. Army/German Memorandum of Understanding on Cooperative Research in the Field of Helicopter Aeromechanics. The primary objective of this test program was to create a data base for full-scale hingeless rotor performance and structural blade loads. A secondary objective was to investigate the ability to match flight test conditions in the wind tunnel. This data base can be used for the experimental and analytical studies of hingeless rotor systems over large variations in rotor thrust and tunnel velocity. Rotor performance and structural loads for tunnel velocities from hover to 170 knots and thrust coefficients (C(sub T)/sigma) from 0.0 to 0.12 are presented in this report. Thrust sweeps at tunnel velocities of 10, 20, and 30 knots are also included in this data set.

Wave Rotor Research and Technology Development

NASA Technical Reports Server (NTRS)

Welch, Gerard E.

1998-01-01

Wave rotor technology offers the potential to increase the performance of gas turbine engines significantly, within the constraints imposed by current material temperature limits. The wave rotor research at the NASA Lewis Research Center is a three-element effort: 1) Development of design and analysis tools to accurately predict the performance of wave rotor components; 2) Experiments to characterize component performance; 3) System integration studies to evaluate the effect of wave rotor topping on the gas turbine engine system.

[Treatment of organic waste gas by adsorption rotor].

PubMed

Zhu, Run-Ye; Zheng, Liang-Wei; Mao, Yu-Bo; Wang, Jia-De

2013-12-01

The adsorption rotor is applicable to treating organic waste gases with low concentration and high air volume. The performance of adsorption rotor for purifying organic waste gases was investigated in this paper. Toluene was selected as the simulative gaseous pollutant and the adsorption rotor was packed with honeycomb modified 13X molecular sieves (M-13X). Experimental results of the fixed adsorption and the rotor adsorption were analyzed and compared. The results indicated that some information on the fixed adsorption was useful for the rotor adsorption. Integrating the characteristics of the adsorbents, waste gases and the structures of the rotor adsorption, the formulas on optimal rotor speed and cycle removal efficiency of the adsorption rotor were deduced, based on the mass and heat balances of the adsorbing process. The numerical results were in good agreement with the experimental data, which meant that the formulas on optimal rotor speed and cycle removal efficiency could be effectively applied in design and operation of the adsorption rotor.

A flight investigation of performance and loads for a helicopter with 10-64C main rotor blade sections

NASA Technical Reports Server (NTRS)

Morris, C. E. K.; Tomaine, R. L.; Stevens, D. D.

1980-01-01

A flight investigation produced data on performance and rotor loads for a teetering rotor, AH-1G helicopter flown with a main rotor that had the NLR-1T airfoil as the blade section contour. The test envelope included hover, forward flight speeds from 34 to 83 m/sec (65 to 162 knots), and collective fixed maneuvers at about 0.25 tip speed ratio. The data set for each test point describes vehicle flight state, control positions, rotor loads, power requirements, and blade motions. Rotor loads are reviewed primarily in terms of peak to peak and harmonic content. Lower frequency components predominated for most loads and generally increased with increased airspeed, but not necessarily with increased maneuver load factor. Detailed data for an advanced airfoil on an AH-1G are presented.

A novel type of rim thrust motor with Halbach array permanent magnet rotor

NASA Astrophysics Data System (ADS)

Cao, Haichuan; Chen, Weihu

2018-05-01

The Rim-driven Thruster (RDT) is a new type of marine electric thruster proposed in recent years. In this paper, the author proposed a new type of permanent magnet synchronous rim thrust motor (RTM). The motor uses a Halbach array permanent magnet rotor, which can improve the torque density of the propulsion motor by utilizing the unilateral magnetic field of the Halbach array. In this paper, the electromagnetic properties of the motor were measured and compared with that of the ordinary magnetic pole motor through numerical analysis. The results show that at the same power, the new motor can significantly reduce the thickness of the rotor's permanent magnet and yoke core, and has obvious advantages in power density, moment of inertia, dynamic performance, and cost.

Computational Analysis of Multi-Rotor Flows

NASA Technical Reports Server (NTRS)

Yoon, Seokkwan; Lee, Henry C.; Pulliam, Thomas H.

2016-01-01

Interactional aerodynamics of multi-rotor flows has been studied for a quadcopter representing a generic quad tilt-rotor aircraft in hover. The objective of the present study is to investigate the effects of the separation distances between rotors, and also fuselage and wings on the performance and efficiency of multirotor systems. Three-dimensional unsteady Navier-Stokes equations are solved using a spatially 5th order accurate scheme, dual-time stepping, and the Detached Eddy Simulation turbulence model. The results show that the separation distances as well as the wings have significant effects on the vertical forces of quadroror systems in hover. Understanding interactions in multi-rotor flows would help improve the design of next generation multi-rotor drones.

Substantially parallel flux uncluttered rotor machines

DOEpatents

Hsu, John S.

2012-12-11

A permanent magnet-less and brushless synchronous system includes a stator that generates a magnetic rotating field when sourced by polyphase alternating currents. An uncluttered rotor is positioned within the magnetic rotating field and is spaced apart from the stator. An excitation core is spaced apart from the stator and the uncluttered rotor and magnetically couples the uncluttered rotor. The brushless excitation source generates a magnet torque by inducing magnetic poles near an outer peripheral surface of the uncluttered rotor, and the stator currents also generate a reluctance torque by a reaction of the difference between the direct and quadrature magnetic paths of the uncluttered rotor. The system can be used either as a motor or a generator

The calculation of rotor/fuselage interaction for two-dimensional bodies

NASA Technical Reports Server (NTRS)

Stremel, Paul M.

1990-01-01

Unsteady rotor wake interactions with the empennage, tail boom, and other aerodynamic surfaces have a significant influence on the aerodynamic performance of the helicopter, ride quality, and vibration. A Computational Fluid Dynamic (CFD) method for computing the aerodynamic interaction between an interacting vortex wake and the viscous flow about arbitrary 2-D bodies was developed to address this helicopter problem. The vorticity and flow field velocities are calculated on a body-fitted computational mesh using an uncoupled iterative solution. The interacting vortex wake is represented by an array of discrete vortices which, in turn, are represented by a finite core model. The evolution of the interacting vortex wake is calculated by Lagrangian techniques. The flow around circular and elliptic cylinders in the absence of an interacting vortex wake was calculated. These results compare very well with other numerical results and with results obtained from experiment and thereby demonstrate the accuracy of the viscous solution. The interaction of a simulated rotor wake with the flow about 2-D bodies, representing cross sections of fuselage components, was calculated to address the vortex interaction problem. The vortex interaction was calculated for the flow about a circular and an elliptic cylinder at 45 and 90 degrees incidence. The results demonstrate the significant variation in lift and drag on the 2-D bodies during the vortex interaction.

14 CFR 27.547 - Main rotor structure.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Main rotor structure. 27.547 Section 27.547... structure. (a) Each main rotor assembly (including rotor hubs and blades) must be designed as prescribed in this section. (b) [Reserved] (c) The main rotor structure must be designed to withstand the following...

Method for manufacturing a rotor having superconducting coils

DOEpatents

Driscoll, David I.; Shoykhet, Boris A.

2001-01-01

A method and apparatus for manufacturing a rotor for use with a rotating machine is provided that employs a superconducting coil on the rotor. An adhesive is applied to an outer surface of the rotor body, which may include a groove disposed within an outer surface of the rotor body. A superconducting coil is then mounted onto the rotor body such that the adhesive bonds the superconducting coil to the rotor body.

Rotor design for maneuver performance

NASA Technical Reports Server (NTRS)

Berry, John D.; Schrage, Daniel

1986-01-01

A method of determining the sensitivity of helicopter maneuver performance to changes in basic rotor design parameters is developed. Maneuver performance is measured by the time required, based on a simplified rotor/helicopter performance model, to perform a series of specified maneuvers. This method identifies parameter values which result in minimum time quickly because of the inherent simplicity of the rotor performance model used. For the specific case studied, this method predicts that the minimum time required is obtained with a low disk loading and a relatively high rotor solidity. The method was developed as part of the winning design effort for the American Helicopter Society student design competition for 1984/1985.

Rotor Current Control of DFIG for Improving Fault Ride - Through Using a Novel Sliding Mode Control Approach

NASA Astrophysics Data System (ADS)

Cai, Guowei; Liu, Cheng; Yang, Deyou

2013-11-01

The doubly fed induction generators (DFIG) have been recognized as the dominant technology used in wind power generation systems with the rapid development of wind power. However, continuous operation of DFIG may cause a serious wind turbine generators tripping accident, due to destructive over-current in the rotor winding which is caused by the power system fault or inefficient fault ride-through (FRT) strategy. A new rotor current control scheme in the rotor-side converter (RSC) ispresented to enhance FRT capacities of grid-connected DFIG. Due to the strongly nonlinear nature of DFIG and insensitive to DFIG parameter's variations, a novel sliding mode controller was designed. The controller combines extended state observer (ESO) with sliding model variable structure control theory. The simulation is carried out to verify the effectiveness of the proposed control approach under various types of grid disturbances. It is shown that the proposed controller provides enhanced transient features than the classic proportional-integral control. The proposed control method can effectively reduce over-current in the RSC, and the transient pulse value of electromagnetic torque is too large under power grid fault.

Hover performance tests of baseline metal and Advanced Technology Blade (ATB) rotor systems for the XV-15 tilt rotor aircraft

NASA Technical Reports Server (NTRS)

Bartie, K.; Alexander, H.; Mcveigh, M.; Lamon, S.; Bishop, H.

1986-01-01

Rotor hover performance data were obtained for two full-scale rotor systems designed for the XV-15 Tilt Rotor Research Aircraft. One rotor employed the rectangular planform metal blades (rotor solidity = 0.089) which were used on the initial flight configuration of the XV-15. The second rotor configuration examined the nonlinear taper, composite-construction, Advanced Technology Blade (ATB), (rotor solidity = 0.10) designed to replace the metal blades on the XV-15. Variations of the baseline ATB tip and cuff shapes were also tested. A new six-component rotor force and moment balance designed to obtain highly accurate data over a broad range of thrust and torque conditions is described. The test data are presented in nondimensional coefficient form for the performance results, and in dimensional form for the steady and alternating loads. Some wake and acoustic data are also shown.

Prediction of the Aero-Acoustic Performance of Open Rotors

NASA Technical Reports Server (NTRS)

VanZante, Dale; Envia, Edmane

2014-01-01

The rising cost of jet fuel has renewed interest in contrarotating open rotor propulsion systems. Contemporary design methods offer the potential to maintain the inherently high aerodynamic efficiency of open rotors while greatly reducing their noise output, something that was not feasible in the 1980's designs. The primary source mechanisms of open rotor noise generation are thought to be the front rotor wake and tip vortex interacting with the aft rotor. In this paper, advanced measurement techniques and high-fidelity prediction tools are used to gain insight into the relative importance of the contributions to the open rotor noise signature of the front rotor wake and rotor tip vortex. The measurements include three-dimensional particle image velocimetry of the intra-rotor flowfield and the acoustic field of a model-scale open rotor. The predictions provide the unsteady flowfield and the associated acoustic field. The results suggest that while the front rotor tip vortex can have a significant influence on the blade passing tone noise produced by the aft rotor, the front rotor wake plays the decisive role in the generation of the interaction noise produced as a result of the unsteady aerodynamic interaction of the two rotors. At operating conditions typical of takeoff and landing operations, the interaction noise level is easily on par with that generated by the individual rotors, and in some cases is even higher. This suggests that a comprehensive approach to reducing open rotor noise should include techniques for mitigating the wake of the front rotor as well as eliminating the interaction of the front rotor tip vortex with the aft rotor blade tip.

Blood Pump Having a Magnetically Suspended Rotor

NASA Technical Reports Server (NTRS)

Antaki, James F. (Inventor); Paden, Bradley (Inventor); Burgreen, Gregory (Inventor); Groom, Nelson J. (Inventor)

2002-01-01

A blood pump preferably has a magnetically suspended rotor that rotates within a housing. The rotor may rotate about a stator disposed within the housing. Radial magnetic bearings may be defined within the stator and the rotor in order to suspend the rotor. The radial magnetic bearings may be passive magnetic bearings that include permanent magnets disposed within the stator and the rotor or active magnetic bearings. The pump may further include an axial magnetic bearing that may be either a passive or an active magnetic bearing. A motor that drives the rotor may be disposed within the housing in order to more easily dissipate heat generated by the motor. A primary flow path is defined between the rotor and the stator, and a secondary flow path is defined between the stator and the rotor. Preferably, a substantial majority of blood passes through the primary flow path. The secondary flow path is large enough so that it provides adequate flushing of the secondary flow path while being small enough to permit efficient operation of the radial magnet bearings across the secondary flow path.

Blood Pump Having a Magnetically Suspended Rotor

NASA Technical Reports Server (NTRS)

Antaki, James F. (Inventor); Paden, Bradley (Inventor); Burgreen, Gregory (Inventor); Groom, Nelson J. (Inventor)

2001-01-01

A blood pump preferably has a magnetically suspended rotor that rotates within a housing. The rotor may rotate about a stator disposed within the housing. Radial magnetic bearings may be defined within the stator and the rotor in order to suspend the rotor. The radial magnetic bearings may be passive magnetic bearings that include permanent magnets disposed within the stator and the rotor or active magnetic bearings. The pump may further include an axial magnetic bearing that may be either a passive or an active magnetic bearing. A motor that drives the rotor may be disposed within the housing in order to more easily dissipate heat generated by the motor. A primary flow path is defined between the rotor and the stator, and a secondary flow path is defined between the stator and the rotor. Preferably, a substantial majority of blood passes through the primary flow path. The secondary flow path is large enough so that it provides adequate flushing of the secondary flow path while being small enough to permit efficient operation of the radial magnet bearings across the secondary flow path.

Design Optimization of a Variable-Speed Power Turbine

NASA Technical Reports Server (NTRS)

Hendricks, Eric S.; Jones, Scott M.; Gray, Justin S.

2014-01-01

NASA's Rotary Wing Project is investigating technologies that will enable the development of revolutionary civil tilt rotor aircraft. Previous studies have shown that for large tilt rotor aircraft to be viable, the rotor speeds need to be slowed significantly during the cruise portion of the flight. This requirement to slow the rotors during cruise presents an interesting challenge to the propulsion system designer as efficient engine performance must be achieved at two drastically different operating conditions. One potential solution to this challenge is to use a transmission with multiple gear ratios and shift to the appropriate ratio during flight. This solution will require a large transmission that is likely to be maintenance intensive and will require a complex shifting procedure to maintain power to the rotors at all times. An alternative solution is to use a fixed gear ratio transmission and require the power turbine to operate efficiently over the entire speed range. This concept is referred to as a variable-speed power-turbine (VSPT) and is the focus of the current study. This paper explores the design of a variable speed power turbine for civil tilt rotor applications using design optimization techniques applied to NASA's new meanline tool, the Object-Oriented Turbomachinery Analysis Code (OTAC).

Rotor burst protection program: Statistics on aircraft gas turbine engine rotor failures that occurred in US commercial aviation during 1975

NASA Technical Reports Server (NTRS)

Delucia, R. A.; Mangano, G. J.

1977-01-01

Statistics on gas turbine rotor failures that have occurred in U.S. commercial aviation during 1975 are presented. The compiled data were analyzed to establish: (1) The incidence of rotor failures and the number of contained and uncontained rotor bursts; (2) The distribution of rotor bursts with respect to engine rotor component; i.e., fan, compressor or turbine; (3) The type of rotor fragment (disk, rim or blade) typically generated at burst; (4) The cause of failure; (5) The type of engines involved; and (6) The flight condition at the time of failure.

Flight Investigation of Effects of Selected Operating Conditions on the Bending and Torsional Moments Encountered by a Helicopter Rotor Blade

NASA Technical Reports Server (NTRS)

Ludi, LeRoy H.

1961-01-01

Flight tests have been conducted with a single-rotor helicopter to determine the effects of partial-power descents with forward speed, high-speed level turns, pull-outs from autorotation, and high-forward-speed high-rotor-speed autorotation on the flapwise bending and torsional moments of the rotor blade. One blade of the helicopter was equipped at 14 percent and 40 percent of the blade radius with strain gages calibrated to measure moments rather than stresses. The results indicate that the maximum moments encountered in partial-power descents with forward speed tend to be generally reduced from the maximum moments encountered during partid-power descents at zero forward speed. High-speed level turns and pull-outs from auto-rotation caused retreating-blade stall which produced torsional moments (values up to 2,400 inch-pounds). at the 14-percent-radius station that were as large as those encountered during the previous investigations of retreating-blade stall (values up t o 2,500 inch-pounds). High-forward- speed high-rotor-speed autorotation produced flapwise bending moments (values up to 7,200 inch-pounds) at the 40-percent-radius station which were as large as the flapwise bending moments (values up to 7,800 inch-pounds) a t the 14-percent-radius station encountered during partial - power vertical descents. The results of the present investigation (tip-speed ratios up to 0.325 and an unaccelerated level-flight mean lift coefficient of about 0.6), in combination with the related results of at zero forward speed produce the largest rotor-blade vibratory moments. However, inasmuch as these large moments occur only during 1 percent of the cycles and 88 percent of the cycles are at moment values less than 70 percent of these maximum values in partial-power descents, other conditions, such as high-speed flight where the large moments are combined with large percentages of time spent,must not be neglected in any rotor-blade service-life assessment.

Investigations on bending-torsional vibrations of rotor during rotor-stator rub using Lagrange multiplier method

NASA Astrophysics Data System (ADS)

Mokhtar, Md Asjad; Kamalakar Darpe, Ashish; Gupta, Kshitij

2017-08-01

The ever-increasing need of highly efficient rotating machinery causes reduction in the clearance between rotating and non-rotating parts and increase in the chances of interaction between these parts. The rotor-stator contact, known as rub, has always been recognized as one of the potential causes of rotor system malfunctions and a source of secondary failures. It is one of few causes that influence both lateral and torsional vibrations. In this paper, the rotor stator interaction phenomenon is investigated in the finite element framework using Lagrange multiplier based contact mechanics approach. The stator is modelled as a beam that can respond to axial penetration and lateral friction force during the contact with the rotor. It ensures dynamic stator contact boundary and more realistic contact conditions in contrast to most of the earlier approaches. The rotor bending-torsional mode coupling during contact is considered and the vibration response in bending and torsion are analysed. The effect of parameters such as clearance, friction coefficient and stator stiffness are studied at various operating speeds and it has been found that certain parameter values generate peculiar rub related features. Presence of sub-harmonics in the lateral vibration frequency spectra are prominently observed when the rotor operates near the integer multiple of its lateral critical speed. The spectrum cascade of torsional vibration shows the presence of bending critical speed along with the larger amplitudes of frequencies close to torsional natural frequency of the rotor. When m × 1/n X frequency component of rotational frequency comes closer to the torsional natural frequency, stronger torsional vibration amplitude is noticed in the spectrum cascade. The combined information from the stator vibration and rotor lateral-torsional vibration spectral features is proposed for robust rub identification.

Open Rotor - Analysis of Diagnostic Data

NASA Technical Reports Server (NTRS)

Envia, Edmane

2011-01-01

NASA is researching open rotor propulsion as part of its technology research and development plan for addressing the subsonic transport aircraft noise, emission and fuel burn goals. The low-speed wind tunnel test for investigating the aerodynamic and acoustic performance of a benchmark blade set at the approach and takeoff conditions has recently concluded. A high-speed wind tunnel diagnostic test campaign has begun to investigate the performance of this benchmark open rotor blade set at the cruise condition. Databases from both speed regimes will comprise a comprehensive collection of benchmark open rotor data for use in assessing/validating aerodynamic and noise prediction tools (component & system level) as well as providing insights into the physics of open rotors to help guide the development of quieter open rotors.

Wind energy converter with high-speed vertical axis rotor and straight rotor blades

NASA Astrophysics Data System (ADS)

Zelck, G.

1982-11-01

Complete documents for a wind energy converter with a vertical axis rotor and straight blades (H-rotor) were developed. The 2 blade rotor with rigid and rectangular air foils in wooden construction reaches the nominal output of 75 KVA from 11,4 m/sec. wind velocity onwards. The development activities are supported by wind tunnel and component tests. The final design selected was based upon previous development work. Trade offs show that the design is more advantageous compared to other designs. The use of wood as a material for the rotary and horizontal blade supports gives positive result.

Windage Power Loss in Gas Foil Bearings and the Rotor-Stator Clearance of High Speed Generators Operating in High Pressure Environments

NASA Technical Reports Server (NTRS)

Bruckner, Robert J.

2009-01-01

Closed Brayton Cycle (CBC) and Closed Supercritical Cycle (CSC) engines are prime candidates to convert heat from a reactor into electric power for robotic space exploration and habitation. These engine concepts incorporate a permanent magnet starter/generator mounted on the engine shaft along with the requisite turbomachinery. Successful completion of the long-duration missions currently anticipated for these engines will require designs that adequately address all losses within the machine. The preliminary thermal management concept for these engine types is to use the cycle working fluid to provide the required cooling. In addition to providing cooling, the working fluid will also serve as the bearing lubricant. Additional requirements, due to the unique application of these microturbines, are zero contamination of the working fluid and entirely maintenance-free operation for many years. Losses in the gas foil bearings and within the rotor-stator gap of the generator become increasingly important as both rotational speed and mean operating pressure are increased. This paper presents the results of an experimental study, which obtained direct torque measurements on gas foil bearings and generator rotor-stator gaps. Test conditions for these measurements included rotational speeds up to 42,000 revolutions per minute, pressures up to 45 atmospheres, and test gases of nitrogen, helium, and carbon dioxide. These conditions provided a maximum test Taylor number of nearly one million. The results show an exponential rise in power loss as mean operating density is increased for both the gas foil bearing and generator windage. These typical "secondary" losses can become larger than the total system output power if conventional design paradigms are followed. A nondimensional analysis is presented to extend the experimental results into the CSC range for the generator windage.

Aeromechanics of a High Speed Coaxial Helicopter Rotor

NASA Astrophysics Data System (ADS)

Schmaus, Joseph Henry

The current work seeks to understand the aeromechanics of lift offset coaxial rotors in high speeds. Future rotorcraft will need to travel significantly faster that modern rotorcraft do while maintaining hovering efficiency and low speed maneuverability. The lift offset coaxial rotor has been shown to have those capabilities. A majority of existing coaxial research is focused on hovering performance, and few studies examine the forward flight performance of a coaxial rotor with lift offset. There are even fewer studies of a single rotor with lift offset. The current study used comprehensive analysis and a new set of wind tunnel experiments to explore the aeromechanics of a lift offset coaxial rotor in high speed forward flight. The simulation was expanded from UMARC to simultaneously solve multiple rotors with coupled aerodynamics. It also had several modifications to improve the aerodynamics of the near-wake model in reverse flow and improve the modeling of blade passages. Existing coaxial hovering tests and flight test data from the XH-59A were used to validate the steady performance and blade loads of the comprehensive analysis. It was used to design the structural layout of the blades used in the wind tunnel experiment as well as the test envelope and testing procedure. The wind tunnel test of a model rotor developed by the University of Texas at Austin and the University of Maryland was performed in the Glenn L Martin Wind Tunnel. The test envelope included advance ratios 0.21-0.53, collectives 4°- 8°, and lift offsets 0%-20% for both rotors tested in isolation and as a coaxial system operating at 900 RPM. Rotating frame hub loads, pushrod loads, and pitch angle were recorded independently for each rotor. Additional studies were performed at 1200 RPM to isolate Reynold effects and with varying rotor-to-rotor phase to help quantify aerodynamic interactions. Lift offset fundamentally changes the lift distribution around the rotor disk, doing so increases the

Aerodynamic Performance of a 0.27-Scale Model of an AH-64 Helicopter with Baseline and Alternate Rotor Blade Sets

NASA Technical Reports Server (NTRS)

Kelley, Henry L.

1990-01-01

Performance of a 27 percent scale model rotor designed for the AH-64 helicopter (alternate rotor) was measured in hover and forward flight and compared against and AH-64 baseline rotor model. Thrust, rotor tip Mach number, advance ratio, and ground proximity were varied. In hover, at a nominal thrust coefficient of 0.0064, the power savings was about 6.4 percent for the alternate rotor compared to the baseline. The corresponding thrust increase at this condition was approx. 4.5 percent which represents an equivalent full scale increase in lift capability of about 660 lbs. Comparable results were noted in forward flight except for the high thrust, high speed cases investigated where the baseline rotor was slightly superior. Reduced performance at the higher thrusts and speeds was likely due to Reynolds number effects and blade elasticity differences.

Filter type rotor for multistation photometer

DOEpatents

Shumate, II, Starling E.

1977-07-12

A filter type rotor for a multistation photometer is provided. The rotor design combines the principle of cross-flow filtration with centrifugal sedimentation so that these occur simultaneously as a first stage of processing for suspension type fluids in an analytical type instrument. The rotor is particularly useful in whole-blood analysis.

Analysis and Design of Rotors at Ultra-Low Reynolds Numbers

NASA Technical Reports Server (NTRS)

Kunz, Peter J.; Strawn, Roger C.

2003-01-01

Design tools have been developed for ultra-low Reynolds number rotors, combining enhanced actuator-ring / blade-element theory with airfoil section data based on two-dimensional Navier-Stokes calculations. This performance prediction method is coupled with an optimizer for both design and analysis applications. Performance predictions from these tools have been compared with three-dimensional Navier Stokes analyses and experimental data for a 2.5 cm diameter rotor with chord Reynolds numbers below 10,000. Comparisons among the analyses and experimental data show reasonable agreement both in the global thrust and power required, but the spanwise distributions of these quantities exhibit significant deviations. The study also reveals that three-dimensional and rotational effects significantly change local airfoil section performance. The magnitude of this issue, unique to this operating regime, may limit the applicability of blade-element type methods for detailed rotor design at ultra-low Reynolds numbers, but these methods are still useful for evaluating concept feasibility and rapidly generating initial designs for further analysis and optimization using more advanced tools.

The Tail-Elicited Tail Withdrawal Reflex of "Aplysia" Is Mediated Centrally at Tail Sensory-Motor Synapses and Exhibits Sensitization across Multiple Temporal Domains

ERIC Educational Resources Information Center

Philips, Gary T.; Sherff, Carolyn M.; Menges, Steven A.; Carew, Thomas J.

2011-01-01

The defensive withdrawal reflexes of "Aplysia californica" have provided powerful behavioral systems for studying the cellular and molecular basis of memory formation. Among these reflexes the (T-TWR) has been especially useful. In vitro studies examining the monosynaptic circuit for the T-TWR, the tail sensory-motor (SN-MN) synapses, have…

Rotor assembly and assay method

DOEpatents

Burtis, C.A.; Johnson, W.F.; Walker, W.A.

1993-09-07

A rotor assembly for carrying out an assay includes a rotor body which is rotatable about an axis of rotation, and has a central chamber and first, second, third, fourth, fifth, and sixth chambers which are in communication with and radiate from the central chamber. The rotor assembly further includes a shuttle which is movable through the central chamber and insertable into any of the chambers, the shuttle including a reaction cup carrying an immobilized antigen or an antibody for transport among the chambers. A method for carrying out an assay using the rotor assembly includes moving the reaction cup among the six chambers by passing the cup through the central chamber between centrifugation steps in order to perform the steps of: separating plasma from blood cells, binding plasma antibody or antigen, washing, drying, binding enzyme conjugate, reacting with enzyme substrate and optically comparing the resulting reaction product with unreacted enzyme substrate solution. The movement of the reaction cup can be provided by attaching a magnet to the reaction cup and supplying a moving magnetic field to the rotor. 34 figures.

Rotor assembly and assay method

DOEpatents

Burtis, Carl A.; Johnson, Wayne F.; Walker, William A.

1993-01-01

A rotor assembly for carrying out an assay includes a rotor body which is rotatable about an axis of rotation, and has a central chamber and first, second, third, fourth, fifth, and sixth chambers which are in communication with and radiate from the central chamber. The rotor assembly further includes a shuttle which is movable through the central chamber and insertable into any of the chambers, the shuttle including a reaction cup carrying an immobilized antigen or an antibody for transport among the chambers. A method for carrying out an assay using the rotor assembly includes moving the reaction cup among the six chambers by passing the cup through the central chamber between centrifugation steps in order to perform the steps of: separating plasma from blood cells, binding plasma antibody or antigen, washing, drying, binding enzyme conjugate, reacting with enzyme substrate and optically comparing the resulting reaction product with unreacted enzyme substrate solution. The movement of the reaction cup can be provided by attaching a magnet to the reaction cup and supplying a moving magnetic field to the rotor.

Acoustic Reflection and Transmission of 2-Dimensional Rotors and Stators, Including Mode and Frequency Scattering Effects

NASA Technical Reports Server (NTRS)

Hanson, Donald B.

1999-01-01

A reduced order modeling scheme has been developed for the unsteady acoustic and vortical coupling between blade rows of a turbomachine. The essential behavior of the system is governed by modal scattering coefficients (i.e., reflection and transmission coefficients) of the rotor, stator, inlet and nozzle, which are calculated as if they were connected to non-reflecting ducts. The objective of this report is to identify fundamental behavior of these scattering coefficients for a better understanding of the role of blade row reflection and transmission in noise generation. A 2D flat plate unsteady cascade model is used for the analysis with the expectation that the general behavior presented herein will carry over to models that include more realistic flow and geometry. It is shown that stators scatter input waves into many modes at the same frequency whereas rotors scatter on frequency, or harmonic order. Important cases are shown here the rotor reflection coefficient is greater than unity; a mode at blade passing frequency (BPF) traveling from the stator with unit sound power is reflected by the rotor with more than unit power at 2xBPF and 3xBPE Analysis is presented to explain this unexpected phenomenon. Scattering curves are presented in a format chosen for design use and for physical interpretation. To aid in interpretation of the curves, formulas are derived for special condition where waveforms are parallel to perpendicular to the rotor.

Experimental studies of the rotor flow downwash on the Stability of multi-rotor crafts in descent

NASA Astrophysics Data System (ADS)

Veismann, Marcel; Dougherty, Christopher; Gharib, Morteza

2017-11-01

All rotorcrafts, including helicopters and multicopters, have the inherent problem of entering rotor downwash during vertical descent. As a result, the craft is subject to highly unsteady flow, called vortex ring state (VRS), which leads to a loss of lift and reduced stability. To date, experimental efforts to investigate this phenomenon have been largely limited to analysis of a single, fixed rotor mounted in a horizontal wind tunnel. Our current work aims to understand the interaction of multiple rotors in vertical descent by mounting a multi-rotor craft in a low speed, vertical wind tunnel. Experiments were performed with a fixed and rotationally free mounting; the latter allowing us to better capture the dynamics of a free flying drone. The effect of rotor separation on stability, generated thrust, and rotor wake interaction was characterized using force gauge data and PIV analysis for various descent velocities. The results obtained help us better understand fluid-craft interactions of drones in vertical descent and identify possible sources of instability. The presented material is based upon work supported by the Center for Autonomous Systems and Technologies (CAST) at the Graduate Aerospace Laboratories of the California Institute of Technology (GALCIT).

Dynamics of the line-start reluctance motor with rotor made of SMC material

NASA Astrophysics Data System (ADS)

Smółka, Krzysztof; Gmyrek, Zbigniew

2017-12-01

Design and control of electric motors in such a way as to ensure the expected motor dynamics, are the problems studied for many years. Many researchers tried to solve this problem, for example by the design optimization or by the use of special control algorithms in electronic systems. In the case of low-power and fractional power motors, the manufacture cost of the final product is many times less than cost of electronic system powering them. The authors of this paper attempt to improve the dynamic of 120 W line-start synchronous reluctance motor, energized by 50 Hz mains (without any electronic systems). The authors seek a road enabling improvement of dynamics of the analyzed motor, by changing the shape and material of the rotor, in such a way to minimize the modification cost of the tools necessary for the motor production. After the initial selection, the analysis of four rotors having different tooth shapes, was conducted.

Previous Open Rotor Research in the US

NASA Technical Reports Server (NTRS)

VanZante, Dale

2011-01-01

Previous Open Rotor noise experience in the United States, current Open Rotor noise research in the United States and current NASA prediction methods activities were presented at a European Union (EU) X-Noise seminar. The invited attendees from EU industries, research establishments and universities discussed prospects for reducing Open Rotor noise and reviewed all technology programs, past and present, dedicated to Open Rotor engine concepts. This workshop was particularly timely because the Committee on Aviation Environmental Protection (CAEP) plans to involve Independent Experts in late 2011 in assessing the noise of future low-carbon technologies including the open rotor.

Two-Dimensional Fourier Transform Analysis of Helicopter Flyover Noise

NASA Technical Reports Server (NTRS)

SantaMaria, Odilyn L.; Farassat, F.; Morris, Philip J.

1999-01-01

A method to separate main rotor and tail rotor noise from a helicopter in flight is explored. Being the sum of two periodic signals of disproportionate, or incommensurate frequencies, helicopter noise is neither periodic nor stationary. The single Fourier transform divides signal energy into frequency bins of equal size. Incommensurate frequencies are therefore not adequately represented by any one chosen data block size. A two-dimensional Fourier analysis method is used to separate main rotor and tail rotor noise. The two-dimensional spectral analysis method is first applied to simulated signals. This initial analysis gives an idea of the characteristics of the two-dimensional autocorrelations and spectra. Data from a helicopter flight test is analyzed in two dimensions. The test aircraft are a Boeing MD902 Explorer (no tail rotor) and a Sikorsky S-76 (4-bladed tail rotor). The results show that the main rotor and tail rotor signals can indeed be separated in the two-dimensional Fourier transform spectrum. The separation occurs along the diagonals associated with the frequencies of interest. These diagonals are individual spectra containing only information related to one particular frequency.

Performance of Single-Stage Turbine of Mark 25 Torpedo Power Plant with Two Special Nozzles. II; Efficiency with 20 Degrees-Inlet-Angle Rotor Blades

NASA Technical Reports Server (NTRS)

Schum, Harold J.; Whitney, Warren J.

1949-01-01

A single-stage modification of the turbine from a Mark 25 torpedo power plant was investigated to determine the performance with two nozzle designs in combination with special rotor blades having a 20 inlet angle. The performance is presented in terms of blade, rotor, and brake efficiency as a function of blade-jet speed ratio for pressure ratios of 8, 15 (design), and 20. The blade efficiency with the nozzle having circular pas- sages (K) was equal to or higher than that with the nozzle having rectangular passages (J) for all pressure ratios and speeds investigated. The maximum blade efficiency of 0.571 was obtained with nozzle K at a pressure ratio of 8 and a blade-jet speed ratio of 0.296. The difference in blade efficiency was negligible at a pressure ratio of 8 at the low speeds; the maxim difference was 0.040 at a pressure ratio of 20 and a blade-jet speed ratio of 0.260.

Energy characteristics of Darrieus rotor ( review)

NASA Astrophysics Data System (ADS)

Gorelov, D. N.

2010-09-01

Presented below is the review of the results of experimental studies of energy characteristics of Darrieus rotor with vertical rotation axis. Influence of main geometry parameters of the rotor on its energy characteristics has been analyzed. It is shown that Darrieus rotor may have the higher level of energy characteristics than the best propeller wind turbines.

Tuned mass damper for integrally bladed turbine rotor

NASA Technical Reports Server (NTRS)

Marra, John J. (Inventor)

1994-01-01

The invention is directed to a damper ring for damping the natural vibration of the rotor blades of an integrally bladed rocket turbine rotor. The invention consists of an integral damper ring which is fixed to the underside of the rotor blade platform of a turbine rotor. The damper ring includes integral supports which extend radially outwardly therefrom. The supports are located adjacent to the base portion and directly under each blade of the rotor. Vibration damping is accomplished by action of tuned mass damper beams attached at each end to the supports. These beams vibrate at a predetermined frequency during operation. The vibration of the beams enforce a local node of zero vibratory amplitude at the interface between the supports and the beam. The vibration of the beams create forces upon the supports which forces are transmitted through the rotor blade mounting platform to the base of each rotor blade. When these forces attain a predetermined design frequency and magnitude and are directed to the base of the rotor blades, vibration of the rotor blades is effectively counteracted.

Sizing Power Components of an Electrically Driven Tail Cone Thruster and a Range Extender

NASA Technical Reports Server (NTRS)

Jansen, Ralph H.; Bowman, Cheryl; Jankovsky, Amy

2016-01-01

The aeronautics industry has been challenged on many fronts to increase efficiency, reduce emissions, and decrease dependency on carbon-based fuels. The NASA Aeronautics Research Mission Directorate has identified a suite of investments to meet long term research demands beyond the purview of commercial investment. Electrification of aviation propulsion through turboelectric or hybrid electric propulsion is one of many exciting research areas which has the potential to revolutionize the aviation industry. This paper will provide an overview of the turboelectric and hybrid electric technologies being developed under NASAs Advanced Air Transportation Technology (AATT) Project, and how these technologies can impact vehicle design. An overview will be presented of vehicle system studies and the electric drive system assumptions for successful turboelectric and hybrid electric propulsion in single aisle size commercial aircraft. Key performance parameters for electric drive system technologies will be reviewed, and the technical investment made in materials, electric machines, power electronics, and integrated power systems will be discussed. Finally, power components for a single aisle turboelectric aircraft with an electrically driven tail cone thruster and a hybrid electric nine passenger aircraft with a range extender will be parametrically sized.

Performance of Single-Stage Turbine of Mark 25 Torpedo Power Plant with Two Special Nozzles. III; Efficiency with Standard Rotor Blades

NASA Technical Reports Server (NTRS)

Schum, Harold J.; Whitney, Warren J.

1949-01-01

A Mark 25 torpedo power plant modified to operate as a single-stage turbine was investigated to determine the performance with two nozzle designs and a standard first-stage rotor having 0.40-inch blades with a 17O met-air angle. Both nozzles had smaller port cross-sectional areas than those nozzles of similar design, which were previously investigated. The performance of the two nozzles was compared on the basis of blade, rotor, and brake efficiencies as a function of blade-jet speed ratio for pressure ratios of 8, 15 (design), and 20. At pressure ratios of 15 and 20, the blade efficiency obtained with the nozzle having circular passages (K) was higher than that obtained with the nozzle having rectangular passages (J). At a pressure ratio of 8, the efficiencies obtained with the two nozzles were comparable for blade-jet speed ratios of less than 0.260. For blade-jet speed ratios exceeding this value, nozzle K yielded slightly higher efficiencies. The maximum blade efficiency of 0.569 was obtained with nozzle K at a pressure ratio of 8 and a blade-jet speed ratio of 0.295. At design speed and pressure ratio, nozzle K yielded a maximum blade efficiency of 0.534, an increase of 0.031 over that obtained with nozzle J. When the blade efficiencies of the two nozzles were compared with those of four other nozzles previously investigated, the maximum difference for the six nozzles with this rotor was 0.050. From, this comparison, no specific effect of nozzles size or shape on over-all performance was discernible.

Broadband rotor noise analyses

NASA Technical Reports Server (NTRS)

George, A. R.; Chou, S. T.

1984-01-01

The various mechanisms which generate broadband noise on a range of rotors studied include load fluctuations due to inflow turbulence, due to turbulent boundary layers passing the blades' trailing edges, and due to tip vortex formation. Existing analyses are used and extensions to them are developed to make more accurate predictions of rotor noise spectra and to determine which mechanisms are important in which circumstances. Calculations based on the various prediction methods in existing experiments were compared. The present analyses are adequate to predict the spectra from a wide variety of experiments on fans, full scale and model scale helicopter rotors, wind turbines, and propellers to within about 5 to 10 dB. Better knowledge of the inflow turbulence improves the accuracy of the predictions. Results indicate that inflow turbulence noise depends strongly on ambient conditions and dominates at low frequencies. Trailing edge noise and tip vortex noise are important at higher frequencies if inflow turbulence is weak. Boundary layer trailing edge noise, important, for large sized rotors, increases slowly with angle of attack but not as rapidly as tip vortex noise.

Noise Benefits of Rotor Trailing Edge Blowing for a Model Turbofan

NASA Technical Reports Server (NTRS)

Woodward, Richard P.; Fite, E. Brian; Podboy, Gary G.

2007-01-01

An advanced model turbofan was tested in the NASA Glenn 9- by 15-Foot Low Speed Wind Tunnel (9x15 LSWT) to explore far field acoustic effects associated with rotor Trailing-Edge-Blowing (TEB) for a modern, 1.294 stage pressure ratio turbofan model. The TEB rotor (Fan9) was designed to be aerodynamically similar to the previously tested Fan1, and used the same stator and nacelle hardware. Fan9 was designed with trailing edge blowing slots using an external air supply directed through the rotor hub. The TEB flow was heated to approximate the average fan exit temperature at each fan test speed. Rotor root blockage inserts were used to block TEB to all but the outer 40 and 20% span in addition to full-span blowing. A configuration with full-span TEB on alternate rotor blades was also tested. Far field acoustic data were taken at takeoff/approach conditions at 0.10 tunnel Mach. Far-field acoustic results showed that full-span blowing near 2.0% of the total flow could reduce the overall sound power level by about 2 dB. This noise reduction was observed in both the rotor-stator interaction tones and for the spectral broadband noise levels. Blowing only the outer span region was not very effective for lowering noise, and actually increased the far field noise level in some instances. Full-span blowing of alternate blades at 1.0% of the overall flow rate (equivalent to full-span blowing of all blades at 2.0% flow) showed a more modest noise decrease relative to full-span blowing of all blades. Detailed hot film measurements of the TEB rotor wake at 2.0% flow showed that TEB was not every effective for filling in the wake defect at approach fan speed toward the tip region, but did result in overfilling the wake toward the hub. Downstream turbulence measurements supported this finding, and support the observed reduction in spectral broadband noise.

Predesign study for a modern 4-bladed rotor for the NASA rotor systems research aircraft

NASA Technical Reports Server (NTRS)

Bishop, H. E.; Burkam, J. E.; Heminway, R. C.; Keys, C. N.; Smith, K. E.; Smith, J. H.; Staley, J. A.

1981-01-01

Trade-off study results and the rationale for the final selection of an existing modern four-bladed rotor system that can be adapted for installation on the Rotor Systems Research Aircraft (RSRA) are reported. The results of the detailed integration studies, parameter change studies, and instrumentation studies and the recommended plan for development and qualification of the rotor system is also given. Its parameter variants, integration on the RSRA, and support of ground and flight test programs are also discussed.

Tunneling of coupled methyl quantum rotors in 4-methylpyridine: Single rotor potential versus coupling interaction

NASA Astrophysics Data System (ADS)

Khazaei, Somayeh; Sebastiani, Daniel

2017-11-01

We study the influence of rotational coupling between a pair of methyl rotators on the tunneling spectrum in condensed phase. Two interacting adjacent methyl groups are simulated within a coupled-pair model composed of static rotational potential created by the chemical environment and the interaction potential between two methyl groups. We solve the two-dimensional time-independent Schrödinger equation analytically by expanding the wave functions on the basis set of two independent free-rotor functions. We investigate three scenarios which differ with respect to the relative strength of single-rotor and coupling potential. For each scenario, we illustrate the dependence of the energy level scheme on the coupling strength. It is found that the main determinant of splitting energy levels tends to be a function of the ratio of strengths of coupling and single-rotor potential. The tunnel splitting caused by coupling is maximized for the coupled rotors in which their total hindering potential is relatively shallow. Such a weakly hindered methyl rotational potential is predicted for 4-methylpyridine at low temperature. The experimental observation of multiple tunneling peaks arising from a single type of methyl group in 4-methylpyridine in the inelastic neutron scattering spectrum is widely attributed to the rotor-rotor coupling. In this regard, using a set of first-principles calculations combined with the nudged elastic band method, we investigate the rotational potential energy surface (PES) of the coaxial pairs of rotors in 4-methylpyridine. A Numerov-type method is used to numerically solve the two-dimensional time-independent Schrödinger equation for the calculated 2D-density functional theory profile. Our computed energy levels reproduce the observed tunneling transitions well. Moreover, the calculated density distribution of the three methyl protons resembles the experimental nuclear densities obtained from the Fourier difference method. By mapping the

Tunneling of coupled methyl quantum rotors in 4-methylpyridine: Single rotor potential versus coupling interaction.

PubMed

Khazaei, Somayeh; Sebastiani, Daniel

2017-11-21

We study the influence of rotational coupling between a pair of methyl rotators on the tunneling spectrum in condensed phase. Two interacting adjacent methyl groups are simulated within a coupled-pair model composed of static rotational potential created by the chemical environment and the interaction potential between two methyl groups. We solve the two-dimensional time-independent Schrödinger equation analytically by expanding the wave functions on the basis set of two independent free-rotor functions. We investigate three scenarios which differ with respect to the relative strength of single-rotor and coupling potential. For each scenario, we illustrate the dependence of the energy level scheme on the coupling strength. It is found that the main determinant of splitting energy levels tends to be a function of the ratio of strengths of coupling and single-rotor potential. The tunnel splitting caused by coupling is maximized for the coupled rotors in which their total hindering potential is relatively shallow. Such a weakly hindered methyl rotational potential is predicted for 4-methylpyridine at low temperature. The experimental observation of multiple tunneling peaks arising from a single type of methyl group in 4-methylpyridine in the inelastic neutron scattering spectrum is widely attributed to the rotor-rotor coupling. In this regard, using a set of first-principles calculations combined with the nudged elastic band method, we investigate the rotational potential energy surface (PES) of the coaxial pairs of rotors in 4-methylpyridine. A Numerov-type method is used to numerically solve the two-dimensional time-independent Schrödinger equation for the calculated 2D-density functional theory profile. Our computed energy levels reproduce the observed tunneling transitions well. Moreover, the calculated density distribution of the three methyl protons resembles the experimental nuclear densities obtained from the Fourier difference method. By mapping the

Measured and predicted rotor performance for the SERI advanced wind turbine blades

NASA Astrophysics Data System (ADS)

Tangler, J.; Smith, B.; Kelley, N.; Jager, D.

1992-02-01

Measured and predicted rotor performance for the Solar Energy Research Institute (SERI) advanced wind turbine blades were compared to assess the accuracy of predictions and to identify the sources of error affecting both predictions and measurements. An awareness of these sources of error contributes to improved prediction and measurement methods that will ultimately benefit future rotor design efforts. Propeller/vane anemometers were found to underestimate the wind speed in turbulent environments such as the San Gorgonio Pass wind farm area. Using sonic or cup anemometers, good agreement was achieved between predicted and measured power output for wind speeds up to 8 m/sec. At higher wind speeds an optimistic predicted power output and the occurrence of peak power at wind speeds lower than measurements resulted from the omission of turbulence and yaw error. In addition, accurate two-dimensional (2-D) airfoil data prior to stall and a post stall airfoil data synthesization method that reflects three-dimensional (3-D) effects were found to be essential for accurate performance prediction.

Flywheels Would Compensate for Rotor Imbalance

NASA Technical Reports Server (NTRS)

Hrastar, J. A. S.

1982-01-01

Spinning flywheels within rotor can null imbalance forces in rotor. Flywheels axes are perpendicular to each other and to rotor axis. Feedback signals from accelerometers or strain gages in platform control flywheel speeds and rotation directions. Concept should be useful for compensating rotating bodies on Earth. For example, may be applied to large industrial centrifuge, particularly if balance changes during operation.

Influence of rubbing on rotor dynamics, part 1

NASA Technical Reports Server (NTRS)

Muszynska, Agnes; Bently, Donald E.; Franklin, Wesley D.; Hayashida, Robert D.; Kingsley, Lori M.; Curry, Arthur E.

1989-01-01

The results of analytical and experimental research on rotor-to-stationary element rubbing in rotating machines are presented. A characterization of physical phenomena associated with rubbing, as well as a literature survey on the subject of rub is given. The experimental results were obtained from two rubbing rotor rigs: one, which dynamically simulates the space shuttle main engine high pressure fuel turbopump (HPFTP), and the second one, much simpler, a two-mode rotor rig, designed for more generic studies on rotor-to-stator rubbing. Two areas were studied: generic rotor-to-stator rub-related dynamic phenomena affecting rotating machine behavior and applications to the space shuttle HPFTP. An outline of application of dynamic stiffness methodology for identification of rotor/bearing system modal parameters is given. The mathematical model of rotor/bearing/seal system under rub condition is given. The computer program was developed to calculate rotor responses. Compared with experimental results the computed results prove an adequacy of the model.

Stabilization and control of quad-rotor helicopter using a smartphone device

NASA Astrophysics Data System (ADS)

Desai, Alok; Lee, Dah-Jye; Moore, Jason; Chang, Yung-Ping

2013-01-01

In recent years, autonomous, micro-unmanned aerial vehicles (micro-UAVs), or more specifically hovering micro- UAVs, have proven suitable for many promising applications such as unknown environment exploration and search and rescue operations. The early versions of UAVs had no on-board control capabilities, and were difficult for manual control from a ground station. Many UAVs now are equipped with on-board control systems that reduce the amount of control required from the ground-station operator. However, the limitations on payload, power consumption and control without human interference remain the biggest challenges. This paper proposes to use a smartphone as the sole computational device to stabilize and control a quad-rotor. The goal is to use the readily available sensors in a smartphone such as the GPS, the accelerometer, the rate-gyros, and the camera to support vision-related tasks such as flight stabilization, estimation of the height above ground, target tracking, obstacle detection, and surveillance. We use a quad-rotor platform that has been built in the Robotic Vision Lab at Brigham Young University for our development and experiments. An Android smartphone is connected through the USB port to an external hardware that has a microprocessor and circuitries to generate pulse-width modulation signals to control the brushless servomotors on the quad-rotor. The high-resolution camera on the smartphone is used to detect and track features to maintain a desired altitude level. The vision algorithms implemented include template matching, Harris feature detector, RANSAC similarity-constrained homography, and color segmentation. Other sensors are used to control yaw, pitch, and roll of the quad-rotor. This smartphone-based system is able to stabilize and control micro-UAVs and is ideal for micro-UAVs that have size, weight, and power limitations.

Computer Code for Interpreting 13C NMR Relaxation Measurements with Specific Models of Molecular Motion: The Rigid Isotropic and Symmetric Top Rotor Models and the Flexible Symmetric Top Rotor Model

DTIC Science & Technology

2017-01-01

unlimited. 13. SUPPLEMENTARY NOTES 14. ABSTRACT: Carbon-13 nuclear magnetic resonance (13C NMR) spectroscopy is a powerful technique for...FLEXIBLE SYMMETRIC TOP ROTOR MODEL 1. INTRODUCTION Nuclear magnetic resonance (NMR) spectroscopy is a tremendously powerful technique for...application of NMR spectroscopy concerns the property of molecular motion, which is related to many physical, and even biological, functions of molecules in

Active-Twist Rotor Control Applications for UAVs

NASA Technical Reports Server (NTRS)

Wilbur, Matthew L.; Wilkie, W. Keats

2004-01-01

The current state-of-the-art in active-twist rotor control is discussed using representative examples from analytical and experimental studies, and the application to rotary-wing UAVs is considered. Topics include vibration and noise reduction, rotor performance improvement, active blade tracking, stability augmentation, and rotor blade de-icing. A review of the current status of piezoelectric fiber composite actuator technology, the class of piezoelectric actuators implemented in active-twist rotor systems, is included.

Anisotropic Electron Tail Generation during Tearing Mode Magnetic Reconnection

NASA Astrophysics Data System (ADS)

Dubois, Ami

2017-10-01

Magnetic reconnection (MR) plays an important role in particle transport, energization, and acceleration in space, astrophysical, and laboratory plasmas. In the MST RFP, discrete MR events release large amounts of energy from the equilibrium magnetic field, a large fraction of which is transferred to the ions in a non-collisional process. Key features are anisotropic heating, mass and charge dependence, and energetic ion tail formation. Unlike the ions, the thermal electron temperature decreases at MR events, which is consistent with enhanced electron heat transport due to increased magnetic stochasticity. However, new high-speed x-ray spectrum measurements reveal transient formation of a non-Maxwellian energetic electron tail during MR. The energetic tail is characterized by a power-law, E-γ, with the spectral index (γ) decreasing from 4.2 to 2.2 at MR, and then increasing rapidly to 6.8 due to increased stochastic transport. The x-ray emission peaks in a radial view and is symmetric in the toroidal direction, indicating an anisotropic electron tail is generated. The toroidal symmetry of the electron tail implies runaway acceleration is not a dominant process, consistent with the net emf, ηJll, being smaller than the Dreicer field. Modeling of bremsstrahlung emission shows that a power-law electron tail distribution that is localized near the magnetic axis will yield strong perpendicular anisotropy, consistent with x-ray measurements in the radial and toroidal views. A strong correlation between high energy x-ray flux and tearing mode dynamics suggests a turbulent mechanism is active. This implies that the electron tail formation most likely results from a turbulent wave-particle interaction. This work is supported by the US DOE and NSF.

Acoustic Scattering by Three-Dimensional Stators and Rotors Using the SOURCE3D Code. Volume 1; Analysis and Results

NASA Technical Reports Server (NTRS)

Meyer, Harold D.

1999-01-01

This report provides a study of rotor and stator scattering using the SOURCE3D Rotor Wake/Stator Interaction Code. SOURCE3D is a quasi-three-dimensional computer program that uses three-dimensional acoustics and two-dimensional cascade load response theory to calculate rotor and stator modal reflection and transmission (scattering) coefficients. SOURCE3D is at the core of the TFaNS (Theoretical Fan Noise Design/Prediction System), developed for NASA, which provides complete fully coupled (inlet, rotor, stator, exit) noise solutions for turbofan engines. The reason for studying scattering is that we must first understand the behavior of the individual scattering coefficients provided by SOURCE3D, before eventually understanding the more complicated predictions from TFaNS. To study scattering, we have derived a large number of scattering curves for vane and blade rows. The curves are plots of output wave power divided by input wave power (in dB units) versus vane/blade ratio. Some of these plots are shown in this report. All of the plots are provided in a separate volume. To assist in understanding the plots, formulas have been derived for special vane/blade ratios for which wavefronts are either parallel or normal to rotor or stator chords. From the plots, we have found that, for the most part, there was strong transmission and weak reflection over most of the vane/blade ratio range for the stator. For the rotor, there was little transmission loss.

Time histories of horizontal-tail loads, elevator loads, and deformations on a jet-powered bomber airplane during abrupt pitching maneuvers at approximately 20,000 feet

NASA Technical Reports Server (NTRS)

Wiener, Bernard; Harris, Agnes E

1950-01-01

Time histories are presented of horizontal-tail loads, elevator loads, and deformations on a jet-powered bomber during abrupt pitching maneuvers at a pressure altitude of approximately 20,000 feet. The normal and pitching accelerations measured varied from -0.90b to 3.41g and from -0.73 to 0.80 radian per second per second (sic), respectively, with a Mach number variation of from 0.40 to o.75. The maximum horizontal-tail load measured was 17,250 pounds down. The maximum elevator load was 1900 pounds up. The stabilizer twisted a maximum of 0.76 degrees leading edge down at the tip. The greatest fuselage deflection at the tail was about 1.7 inches down.

Rotor for a line start permanent magnet machine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Melfi, Mike; Schiferl, Rich; Umans, Stephen

A rotor comprises laminations with a plurality of rotor bar slots with an asymmetric arrangement about the rotor. The laminations also have magnet slots equiangularly spaced about the rotor. The magnet slots extend near to the rotor outer diameter and have permanent magnets disposed in the magnet slots creating magnetic poles. The magnet slots may be formed longer than the permanent magnets disposed in the magnets slots and define one or more magnet slot apertures. The permanent magnets define a number of poles and a pole pitch. The rotor bar slots are spaced from adjacent magnet slots by a distancemore » that is at least 4% of the pole pitch. Conductive material is disposed in the rotor bar slots, and in some embodiments, may be disposed in the magnet slot apertures.« less

Rotor component displacement measurement system

DOEpatents

Mercer, Gary D.; Li, Ming C.; Baum, Charles R.

2003-05-27

A measuring system for measuring axial displacement of a tube relative to an axially stationary component in a rotating rotor assembly includes at least one displacement sensor adapted to be located normal to a longitudinal axis of the tube; an insulated cable system adapted for passage through the rotor assembly; a rotatable proximitor module located axially beyond the rotor assembly to which the cables are connected; and a telemetry system operatively connected to the proximitor module for sampling signals from the proximitor module and forwarding data to a ground station.

Integration of Rotor Aerodynamic Optimization with the Conceptual Design of a Large Civil Tiltrotor

DTIC Science & Technology

2010-01-01

Rotor MCP Maximum Continuous Power MRP Maximum Rated Power (take-off power) NDARC NASA Design and Analysis of Rotorcraft OEI One Engine Inoperative...OGE Out of Ground Effect SFC Specific Fuel Consumption SNI Simultaneous Non-Interfering approach STOL Short Takeoff and Landing VTOL Vertical...that are assembled into a complete aircraft model. NDARC is designed for high computational efficiency. Performance is calculated with physics- based

Design of plywood and paper flywheel rotors

NASA Astrophysics Data System (ADS)

Hagen, D. L.

Technical and economic design factors of cellulosic rotors are compared with conventional materials for stationary flywheel energy storage systems. Wood species, operation in a vacuum, assembly and costs of plywood rotors are evaluated. Wound kraft paper, twine and veneer rotors are examined. Two bulb attachments are designed. Support stiffness is shown to be constrained by the material strength, rotor configuration and speed ratio. Plywood moisture equilibrium during manufacture and assembly is critical. Disk shaping and rotor assembly are described. Potential self-centering dynamic balancing methods and equipment are described. Detailed measurements of the distribution of strengths, densities and specific energy of conventional Finnish Birch plywood and of custom made hexagonal Birch plywood are detailed. High resolution tensile tests were performed while monitoring the acoustic emissions with micoprocessor controlled data acquisition. Preliminary duration of load tests were performed on vacuum dried hexagonal birch plywood. Economics of cellulosic and conventional rotors were examined.

Energy and momentum management of the Space Station using magnetically suspended composite rotors

NASA Technical Reports Server (NTRS)

Eisenhaure, D. B.; Oglevie, R. E.; Keckler, C. R.

1985-01-01

The research addresses the feasibility of using magnetically suspended composite rotors to jointly perform the energy and momentum management functions of an advanced manned Space Station. Recent advancements in composite materials, magnetic suspensions, and power conversion electronics have given flywheel concepts the potential to simultaneously perform these functions for large, long duration spacecraft, while offering significant weight, volume, and cost savings over conventional approaches. The Space Station flywheel concept arising out of this study consists of a composite-material rotor, a large-angle magnetic suspension (LAMS) system, an ironless armature motor/generator, and high-efficiency power conversion electronics. The LAMS design permits the application of appropriate spacecraft control torques without the use of conventional mechanical gimbals. In addition, flywheel systems have the growth potential and modularity needed to play a key role in many future system developments.

Empirical study of the tails of mutual fund size

NASA Astrophysics Data System (ADS)

Schwarzkopf, Yonathan; Farmer, J. Doyne

2010-06-01

The mutual fund industry manages about a quarter of the assets in the U.S. stock market and thus plays an important role in the U.S. economy. The question of how much control is concentrated in the hands of the largest players is best quantitatively discussed in terms of the tail behavior of the mutual fund size distribution. We study the distribution empirically and show that the tail is much better described by a log-normal than a power law, indicating less concentration than, for example, personal income. The results are highly statistically significant and are consistent across fifteen years. This contradicts a recent theory concerning the origin of the power law tails of the trading volume distribution. Based on the analysis in a companion paper, the log-normality is to be expected, and indicates that the distribution of mutual funds remains perpetually out of equilibrium.

Design of automatic rotor blades folding system using NiTi shape memory alloy actuator

NASA Astrophysics Data System (ADS)

Ali, M. I. F.; Abdullah, E. J.

2016-10-01

This present paper will study the requirements for development of a new Automatic Rotor Blades Folding (ARBF) system that could possibly solve the availability, compatibility and complexity issue of upgrading a manual to a fully automatic rotor blades folding system of a helicopter. As a subject matter, the Royal Malaysian Navy Super Lynx Mk 100 was chosen as the baseline model. The aim of the study was to propose a design of SMART ARBF's Shape Memory Alloy (SMA) actuator and proof of operating concept using a developed scale down prototype model. The performance target for the full folding sequence is less than ten minutes. Further analysis on design requirements was carried out, which consisted of three main phases. Phase 1 was studying the SMA behavior on the Nickel Titanium (NiTi) SMA wire and spring (extension type). Technical values like activation requirement, contraction length, and stroke- power and stroke-temperature relationship were gathered. Phase 2 was the development of the prototype where the proposed design of stepped-retractable SMA actuator was introduced. A complete model of the SMART ARBF system that consisted of a base, a main rotor hub, four main rotor blades, four SMA actuators and also electrical wiring connections was fabricated and assembled. Phase 3 was test and analysis whereby a PINENG-PN968s-10000mAh Power Bank's 5 volts, which was reduced to 2.5 volts using LM2596 Step-Down Converter, powered and activated the NiTi spring inside each actuator. The bias spring (compression type), which functions to protract and push the blades to spread position, will compress together with the retraction of actuators and pull the blades to the folding position. Once the power was removed and SMA spring deactivated, the bias spring stiffness will extend the SMA spring and casing and push the blades back to spread position. The timing for the whole revolution was recorded. Based on the experimental analysis, the recorded timing for folding sequence is

Inward rectifier potassium channels control rotor frequency in ventricular fibrillation.

PubMed

Jalife, José

2009-11-01

Ventricular fibrillation (VF) is the most important cause of sudden cardiac death. While traditionally thought to result from random activation of the ventricles by multiple independent wavelets, recent evidence suggests that VF may be determined by the sustained activation of a relatively small number of reentrant sources. In addition, recent experimental data in various species as well as computer simulations have provided important clues about its ionic and molecular mechanisms, particularly in regards to the role of potassium currents in such mechanisms. The results strongly argue that the inward rectifier current, I(K1,) is an important current during functional reentry because it mediates the electrotonic interactions between the unexcited core and its immediate surroundings. In addition, I(K1) is a stabilizer of reentry due to its ability to shorten action potential duration and reduce conduction velocity near the center of rotation. Increased I(K1) prevents wave front-wave tail interactions and thus averts rotor destabilization and breakup. Other studies have shown that while the slow component of the delayed rectifier potassium current I(Ks) does not significantly modify rotor frequency or stability, it plays a major role in postrepolarization refractoriness and wave break formation. Therefore, the interplay between I(K1) and the rapid sodium inward current (I(Na)) is a major factor in the control of cardiac excitability and thus the stability and frequency of reentry, while I(Ks) is an important determinant of fibrillatory conduction.

Rectification of the background potassium current: a determinant of rotor dynamics in ventricular fibrillation.

PubMed

Samie, F H; Berenfeld, O; Anumonwo, J; Mironov, S F; Udassi, S; Beaumont, J; Taffet, S; Pertsov, A M; Jalife, J

2001-12-07

Ventricular fibrillation (VF) is the leading cause of sudden cardiac death. Yet, the mechanisms of VF remain elusive. Pixel-by-pixel spectral analysis of optical signals was carried out in video imaging experiments using a potentiometric dye in the Langendorff-perfused guinea pig heart. Dominant frequencies (peak with maximal power) were distributed throughout the ventricles in clearly demarcated domains. The fastest domain (25 to 32 Hz) was always on the anterior left ventricular (LV) wall and was shown to result from persistent rotor activity. Intermittent block and breakage of wavefronts at specific locations in the periphery of such rotors were responsible for the domain organization. Patch-clamping of ventricular myocytes from the LV and the right ventricle (RV) demonstrated an LV-to-RV drop in the amplitude of the outward component of the background rectifier current (I(B)). Computer simulations suggested that rotor stability in LV resulted from relatively small rectification of I(B) (presumably I(K1)), whereas instability, termination, and wavebreaks in RV were a consequence of strong rectification. This study provides new evidence in the isolated guinea pig heart that a persistent high-frequency rotor in the LV maintains VF, and that spatially distributed gradients in I(K1) density represent a robust ionic mechanism for rotor stabilization and wavefront fragmentation.

Initial design of 12S-10P outer-rotor field excitation flux switching motor with different rotor width

NASA Astrophysics Data System (ADS)

Othman, Syed Muhammad Naufal bin Syed; Sulaiman, Erwan bin; Husin, Zhafir Aizat; Khan, Faisal; Mazlan, Mohamed Mubin Aizat

2015-05-01

This paper proposes an initial design of 12 slot, 10 pole outer-rotor field-excitation flux switching motor (FEFSM) with two different rotor width based from 2 different formula to design the rotor width. Hence, initial design include the three coil test to determine the U, W, V-phase, the flux strengthening and weakening, flux at various armature coil and field-excitation coil current, and finally the torque at various JA and JE. As for the materials, the stator and rotor consists of steel sheets made of electromagnetic steels, copper for armature coils and field excitation coils as the only field for magnetic flux source. There will be some design specification and restriction on outer-rotor FEFSM based on 2D-Finite Element Analysis will be applied to design the proposed machine.

Labyrinth seal forces on a whirling rotor

NASA Technical Reports Server (NTRS)

Wright, D. V.

1983-01-01

An experimental investigation of air labyrinth seal forces on a subsynchronously whirling model rotor is described and test results are given for diverging, converging, and straight two-strip seals. The effects of pressure drop, provide basic experimental data needed in the development of design methods for predicting and preventing self-excited whirl of turbine rotors and other machines having labyrinth seals. The total dynamic seal forces on the whirling model rotor are measured accurately by means of an active damping and stiffness system that is adjusted to obtain neutral whirl stability of the model rotor system. In addition, the whirling pressure pattern in the seal annulus is measured for a few test conditions and the corresponding pressure forces on the rotor are compared with the total measured forces. This comparison shows that either radial and axial pressure gradients in the seal annulus or drag forces on the rotor are significant. Comparisons made between the measured seal forces and theoretical results show that present theory is inadequate.

Load and stability measurements on a soft-inplane rotor system incorporating elastomeric lead-lag dampers

NASA Technical Reports Server (NTRS)

Weller, W. H.

1977-01-01

An experimental investigation was conducted of the dynamic response and inplane stability associated with a new soft-inplane helicopter rotor. The unique feature of this rotor was the use of an internal elastomeric damper to restrain the blade inplane motion about the lead-lag hinge. The properties of the elastomer were selected to provide both a nominal first inplane frequency ratio of 0.65 and sufficient damping to eliminate the need for additional external damping sources to prevent ground resonance on a typical fuselage structure. For this investigation a 1/5-scale aeroelastic model was used to represent the rotor. The four-blade model had a diameter of 3.05 m (10 ft) and a solidity of 0.103. The first out-of-plane frequency ratio was 1.06. The model was tested in hover and in forward flight up to an advance ratio of 0.45. At each forward speed the rotor lift was varied up to simulated maneuver conditions. The measured rotor loads and response were within acceptable limits, and no adverse response qualities were observed. Moderate out-of-plane hub moments were measured, even for zero lift, to indicate the beneficial control power available for this design. Blade inplane stability testing indicated that the rotor system damping remained at moderate levels throughout the operating envelope.

Theoretical study of the effect of ground proximity on the induced efficiency of helicopter rotors

NASA Technical Reports Server (NTRS)

Heyson, H. H.

1977-01-01

A study of rotors in forward flight within ground effect showed that the ground-induced interference is an upwash and a decrease in forward velocity. The interference velocities are large, oppose the normal flow through the rotor, and have large effects on the induced efficiency. Hovering with small ground clearances may result in significant blade stall. As speed is increased from hover in ground effect, power initially increases rather than decreases. At very low heights above the ground, the power requirements become nonlinear with speed as a result of the streamwise interference. The streamwise interference becomes greater as the wake approaches the ground and eventually distorts the wake to form the ground vortex which contributes to certain observed directional stability problems.

Design of helicopter rotors to noise constraints

NASA Technical Reports Server (NTRS)

Schaeffer, E. G.; Sternfeld, H., Jr.

1978-01-01

Results of the initial phase of a research project to study the design constraints on helicopter noise are presented. These include the calculation of nonimpulsive rotor harmonic and broadband hover noise spectra, over a wide range of rotor design variables and the sensitivity of perceived noise level (PNL) to changes in rotor design parameters. The prediction methodology used correlated well with measured whirl tower data. Application of the predictions to variations in rotor design showed tip speed and thrust as having the most effect on changing PNL.

Rotor internal friction instability

NASA Technical Reports Server (NTRS)

Bently, D. E.; Muszynska, A.

1985-01-01

Two aspects of internal friction affecting stability of rotating machines are discussed. The first role of internal friction consists of decreasing the level of effective damping during rotor subsynchronous and backward precessional vibrations caused by some other instability mechanisms. The second role of internal frication consists of creating rotor instability, i.e., causing self-excited subsynchronous vibrations. Experimental test results document both of these aspects.

Flowfield analysis of modern helicopter rotors in hover by Navier-Stokes method

NASA Technical Reports Server (NTRS)

Srinivasan, G. R.; Raghavan, V.; Duque, E. P. N.

1991-01-01

The viscous, three-dimensional, flowfields of UH60 and BERP rotors are calculated for lifting hover configurations using a Navier-Stokes computational fluid dynamics method with a view to understand the importance of planform effects on the airloads. In this method, the induced effects of the wake, including the interaction of tip vortices with successive blades, are captured as a part of the overall flowfield solution without prescribing any wake models. Numerical results in the form of surface pressures, hover performance parameters, surface skin friction and tip vortex patterns, and vortex wake trajectory are presented at two thrust conditions for UH60 and BERP rotors. Comparison of results for the UH60 model rotor show good agreement with experiments at moderate thrust conditions. Comparison of results with equivalent rectangular UH60 blade and BERP blade indicates that the BERP blade, with an unconventional planform, gives more thrust at the cost of more power and a reduced figure of merit. The high thrust conditions considered produce severe shock-induced flow separation for UH60 blade, while the BERP blade develops more thrust and minimal separation. The BERP blade produces a tighter tip vortex structure compared with the UH60 blade. These results and the discussion presented bring out the similarities and differences between the two rotors.

Relativistic kicked rotor.

PubMed

Matrasulov, D U; Milibaeva, G M; Salomov, U R; Sundaram, Bala

2005-07-01

Transport properties in the relativistic analog of the periodically kicked rotor are contrasted under classically and quantum mechanical dynamics. The quantum rotor is treated by solving the Dirac equation in the presence of the time-periodic delta-function potential resulting in a relativistic quantum mapping describing the evolution of the wave function. The transition from the quantum suppression behavior seen in the nonrelativistic limit to agreement between quantum and classical analyses in the relativistic regime is discussed. The absence of quantum resonances in the relativistic case is also addressed.

Strong, Ductile Rotor For Cryogenic Flowmeters

NASA Technical Reports Server (NTRS)

Royals, W. T.

1993-01-01

Improved magnetic flowmeter rotor resists cracking at cryogenic temperatures, yet provides adequate signal to magnetic pickup outside flowmeter housing. Consists mostly of stainless-steel alloy 347, which is ductile and strong at low temperatures. Small bead of stainless-steel alloy 410 welded in groove around circumference of round bar of stainless-steel alloy 347; then rotor machined from bar. Tips of rotor blades contain small amounts of magnetic alloy, and passage of tips detected.

Rotor Re-Design for the SSME Fuel Flowmeter

NASA Technical Reports Server (NTRS)

Marcu, Bogdan

1999-01-01

The present report describes the process of redesigning a new rotor for the SSME Fuel Flowmeter. The new design addresses the specific requirement of a lower rotor speed which would allow the SSME operation at 1 15% rated power level without reaching a blade excitation by the wakes behind the hexagonal flow straightener upstream at frequencies close to the blade natural frequency. A series of calculations combining fleet flowmeters test data, airfoil fluid dynamics and CFD simulations of flow patterns behind the flowmeter's hexagonal straightener has led to a blade twist design alpha = alpha (radius) targeting a kf constant of 0.8256. The kf constant relates the fuel volume flow to the flowmeter rotor speed, for this particular value 17685 GPM at 3650 RPM. Based on this angle distribution, two actual blade designs were developed. A first design using the same blade airfoil as the original design targeted the new kf value only. A second design using a variable blade chord length and airfoil relative thickness targeted simultaneously the new kf value and an optimum blade design destined to provide smooth and stable operation and a significant increase in the blade natural frequency associated with the first bending mode, such that a comfortable margin could be obtained at 115% RPL. The second design is a result of a concurrent engineering process, during which several iterations were made in order to achieve a targeted blade natural frequency associated with the first bending mode of 1300 Hz. Water flow tests preliminary results indicate a kf value of 0.8179 for the f-irst design, which is within 1% of the target value. The second design rotor shows a natural frequency associated with the first bending mode of 1308 Hz, and a water-flow calibration constant of kf 0.8169.

The response of turbine engine rotors to interference rubs

NASA Technical Reports Server (NTRS)

Kascak, A. F.

1980-01-01

A method was developed for the direct integration of a rotor dynamics system experiencing a blade loss induced rotor rub. Both blade loss and rotor rub were simulated on a rotor typical of a small gas turbine. A small change in the coefficient of friction (from 0.1 to 0.2) caused the rotor to change from forward to backward whirl and to theoretically destroy itself in a few rotations. This method provides an analytical capability to study the susceptibility of rotors to rub induced backward whirl problems.

Software for System for Controlling a Magnetically Levitated Rotor

NASA Technical Reports Server (NTRS)

Morrison, Carlos R. (Inventor)

2004-01-01

In a rotor assembly having a rotor supported for rotation by magnetic bearings, a processor controlled by software or firmware controls the generation of force vectors that position the rotor relative to its bearings in a 'bounce' mode in which the rotor axis is displaced from the principal axis defined between the bearings and a 'tilt' mode in which the rotor axis is tilted or inclined relative to the principal axis. Waveform driven perturbations are introduced to generate force vectors that excite the rotor in either the 'bounce' or 'tilt' modes.

Vibration limiting of rotors by feedback control

NASA Technical Reports Server (NTRS)

Lewis, D. W.; Moore, J. W.; Bradley, P. L.; Allaire, P. E.

1982-01-01

Experimental findings of a three mass rotor with four channels of feedback control are reported. The channels are independently controllable with force being proportional to the velocity and/or instantaneous displacement from equilibrium of the shaft at the noncontacting probe locations (arranged in the vertical and horizontal attitudes near the support bearings). The findings suggest that automatic feedback control of rotors is feasible for limiting certain vibration levels. Control of one end of a rotor does afford some predictable vibration limiting of the rotor at the other end.

Aeroelastic characteristics of composite bearingless rotor blades

NASA Technical Reports Server (NTRS)

Bielawa, R. L.

1976-01-01

Owing to the inherent unique structural features of composite bearingless rotors, various assumptions upon which conventional rotor aeroelastic analyses are formulated, are violated. Three such features identified are highly nonlinear and time-varying structural twist, structural redundancy in bending and torsion, and for certain configurations a strongly coupled low frequency bending-torsion mode. An examination of these aeroelastic considerations and appropriate formulations required for accurate analyses of such rotor systems is presented. Also presented are test results from a dynamically scaled model rotor and complementary analytic results obtained with the appropriately reformulated aeroelastic analysis.

Understanding the heavy-tailed dynamics in human behavior

NASA Astrophysics Data System (ADS)

Ross, Gordon J.; Jones, Tim

2015-06-01

The recent availability of electronic data sets containing large volumes of communication data has made it possible to study human behavior on a larger scale than ever before. From this, it has been discovered that across a diverse range of data sets, the interevent times between consecutive communication events obey heavy-tailed power law dynamics. Explaining this has proved controversial, and two distinct hypotheses have emerged. The first holds that these power laws are fundamental, and arise from the mechanisms such as priority queuing that humans use to schedule tasks. The second holds that they are statistical artifacts which only occur in aggregated data when features such as circadian rhythms and burstiness are ignored. We use a large social media data set to test these hypotheses, and find that although models that incorporate circadian rhythms and burstiness do explain part of the observed heavy tails, there is residual unexplained heavy-tail behavior which suggests a more fundamental cause. Based on this, we develop a quantitative model of human behavior which improves on existing approaches and gives insight into the mechanisms underlying human interactions.

Soft hub for bearingless rotors

NASA Technical Reports Server (NTRS)

Dixon, Peter G. C.

1991-01-01

Soft hub concepts which allow the direct replacement of articulated rotor systems by bearingless types without any change in controllability or need for reinforcement to the drive shaft and/or transmission/fuselage attachments of the helicopter were studied. Two concepts were analyzed and confirmed for functional and structural feasibility against a design criteria and specifications established for this effort. Both systems are gimballed about a thrust carrying universal elastomeric bearing. One concept includes a set of composite flexures for drive torque transmittal from the shaft to the rotor, and another set (which is changeable) to impart hub tilting stiffness to the rotor system as required to meet the helicopter application. The second concept uses a composite bellows flexure to drive the rotor and to augment the hub stiffness provided by the elastomeric bearing. Each concept was assessed for weight, drag, ROM cost, and number of parts and compared with the production BO-105 hub.

A strategy for advancing tilt-rotor technology

NASA Technical Reports Server (NTRS)

Morlok, Edward K.; Schoendorfer, David L.

1985-01-01

Tilt-rotor technology has many features which make it a very promising development in aviation which might have application to a wide variety of transportation and logistics situations. However, aside from military applications and rather specialized industrial applications, little is known regarding the potential of tilt-rotor for commercial transportation and hence it is difficult to plan a development program which would gain support and be likely to produce a stream of significant benefits. The purpose is to attempt to provide some of this information in a manner that would be useful for preparing a strategy for development of tilt-rotor aircraft technology. Specifically, the objectives were: to identify promising paths of development and deployment of tilt-rotor aircraft technology in the air transportation system considering both benefits and disbenefits, and to identify any particular groups that are likely to benefit significantly and propose plans for gaining their support of research and development of this technology. Potential advantages of the tilt-rotor technology in the context of air transportation as a door-to-door system were identified, and then promising paths of development of such tilt-rotor systems were analyzed. These then lead to recommendations for specific studies, information dissemination and development of awareness of the tilt-rotor among specific transport-related groups.

Development of a Rotor-Body Coupled Analysis for an Active Mount Aeroelastic Rotor Testbed. Degree awarded by George Washington Univ., May 1996

NASA Technical Reports Server (NTRS)

Wilbur, Matthew L.

1998-01-01

At the Langley Research Center an active mount rotorcraft testbed is being developed for use in the Langley Transonic Dynamics Tunnel. This testbed, the second generation version of the Aeroelastic Rotor Experimental System (ARES-II), can impose rotor hub motions and measure the response so that rotor-body coupling phenomena may be investigated. An analytical method for coupling an aeroelastically scaled model rotor system to the ARES-II is developed in the current study. Models of the testbed and the rotor system are developed in independent analyses, and an impedance-matching approach is used to couple the rotor system to the testbed. The development of the analytical models and the coupling method is examined, and individual and coupled results are presented for the testbed and rotor system. Coupled results are presented with and without applied hub motion, and system loads and displacements are examined. The results show that a closed-loop control system is necessary to achieve desired hub motions, that proper modeling requires including the loads at the rotor hub and rotor control system, and that the strain-gauge balance placed in the rotating system of the ARES-II provided the best loads results.

WTG Energy Systems' Rotor: Steel at 80 Feet

NASA Technical Reports Server (NTRS)

Barrows, R. E.

1979-01-01

The design, specifications, and performance of the 80 foot diameter fixed pitch rotor operating on the MP1-200 wind turbine generator installed as part of the Island of Cuttyhunk's electric power utility grid system are described. This synchronous generating system rated 200 kilowatts at 28 mph wind velocity, and produces constant 60 Hz, 480 VAC current at +/- 1 percent accuracy throughout the machine's operating range. Future R & D requirements and suggestions are included with cost data.

XV-15 tilt rotor ship #1 and #2 parked on NASA ramp

NASA Image and Video Library

1981-04-03

The XV-15 tilt rotor ships #1 and #2 parked on the NASA Dryden Flight Research Center ramp. The XV-15s, manufactured by Bell, were involved in limited research at Dryden in 1980 and 1981. The development of the XV-15 Tiltrotor research aircraft was initiated in 1973 with joint Army/NASA funding as a "proof of concept", or "technology demonstrator" program, with two aircraft being built by Bell Helicopter Textron (BHT) in 1977. The aircraft are powered by twin Lycoming T-53 turboshaft engines that are connected by a cross-shaft and drive three-bladed, 25 ft diameter metal rotors (the size extensively tested in a wind tunnel). The engines and main transmissions are located in wingtip nacelles to minimize the operational loads on the cross-shaft system and, with the rotors, tilt as a single unit. For takeoff, the proprotors and their engines are used in the straight-up position where the thrust is directed downward. The XV-15 then climbs vertically into the air like a helicopter. In this VTOL mode, the vehicle can lift off and hover for approximately one hour. Once off the ground, the XV-15 has the ability to fly in one of two different modes. It can fly as a helicopter, in the partially converted airplane mode. The XV-15 can also then convert from the helicopter mode to the airplane mode. This is accomplished by continuous rotation of the proprotors from the helicopter rotor position to the conventional airplane propeller position. During the ten to fifteen second conversion period, the aircraft speed increases and lift is transferred from the rotors to the wing. To land, the proprotors are rotated up to the helicopter rotor position and flown as a helicopter to a vertical landing.

Rotor blade boundary layer measurement hardware feasibility demonstration

NASA Technical Reports Server (NTRS)

Clark, D. R.; Lawton, T. D.

1972-01-01

A traverse mechanism which allows the measurement of the three dimensional boundary layers on a helicopter rotor blade has been built and tested on a full scale rotor to full scale conditions producing centrifugal accelerations in excess of 400 g and Mach numbers of 0.6 and above. Boundary layer velocity profiles have been measured over a range of rotor speeds and blade collective pitch angles. A pressure scanning switch and transducer were also tested on the full scale rotor and found to be insensitive to centrifugal effects within the normal main rotor operating range. The demonstration of the capability to measure boundary layer behavior on helicopter rotor blades represents the first step toward obtaining, in the rotating system, data of a quality comparable to that already existing for flows in the fixed system.

Stochastic modeling of the migration of Cs-137 in the soil considering a power law tailing in space

NASA Astrophysics Data System (ADS)

Oka, Hiroki; Hatano, Yuko

2016-04-01

We develop a theoretical model to reproduce the measured data of Cs-137 in the soil due to the Fukushima Daiichi NPP accident. In our past study, we derived the analytic solution under the generalized Robin boundary condition (Oka-Yamamoto solution). This is a generalization of the He-Walling solution (1996). We compared our solution with the Fukushima soil data of for 3 years after the accident and found that the concentration of Cs-137 has a discrepancy from our solution, specifically in a deep part because the depth profiles have a power law tailing. Therefore, we improved our model in the following aspect. When Cs particle (or Cs solution) migrate in the soil, the diffusion coefficient should be the results of many processes in the soil. These processes include the effect of various materials which constitute the soil (clay, litter, sand), or the variations of pore size in the soil. Hence we regard the diffusion coefficient as the stochastic variable, we derive the model. Specifically, we consider the solution of ADE to be the conditional probability C(x,t|D) in terms of the diffusion coefficient D and calculate C(x,t)=∫_(0~∞) C(x,t|D)*f(D)*dD, where f(D) is the probability density function of D. This model has a power law tailing in space like the space-fractional ADE.

Rotors and the Dynamics of Cardiac Fibrillation

PubMed Central

Pandit, Sandeep V.; Jalife, José

2013-01-01

The objective of this article is to present a broad review on the role of cardiac electrical rotors and their accompanying spiral waves in the mechanism of cardiac fibrillation. At the outset, we present a brief historical overview regarding reentry, and then discuss the basic concepts and terminologies pertaining to rotors and their initiation. Thereafter, the intrinsic properties of rotors and spiral waves, including phase singularities, wavefront curvature and dominant frequency maps are discussed. The implications of rotor dynamics for the spatio-temporal organization of fibrillation, independent of the species being studied are touched upon next. The knowledge gained regarding the role of cardiac structure in the initiation and/or maintenance of rotors and the ionic bases of spiral waves in the last two decades, and its significance for drug therapy is reviewed subsequently. We conclude by looking at recent evidence suggesting that rotors are critical in sustaining both atrial and ventricular fibrillation (AF, VF) in the human heart, and its implications for treatment with radio-frequency ablation. PMID:23449547

Use of active control systems to improve bending and rotor flapping response of a tilt rotor VTOL airplane

NASA Technical Reports Server (NTRS)

Whitaker, H. P.; Cheng, Y.

1975-01-01

The results are summarized of an analytical study of the use of active control systems for the purpose of reducing the root mean square response of wing vertical bending and rotor flapping to atmospheric turbulence for a tilt-rotor VTOL airplane. Only the wing/rotor assembly was considered so that results of a wind tunnel test program would be applicable in a subsequent phase of the research. The capabilities and limitations of simple single feedback configurations were identified, and the most promising multiloop feedback configurations were then investigated. Design parameters were selected so as to minimize either wing bending or rotor flapping response. Within the constraints imposed by practical levels of feedback gains and complexity and by considerations of safety, reduction in response due to turbulence of the order of 30 to 50 percent is predicted using the rotor longitudinal cyclic and a trailing edge wing flap as control effectors.

Signal Separation of Helicopter Radar Returns Using Wavelet-Based Sparse Signal Optimisation

DTIC Science & Technology

2016-10-01

RR–0436 ABSTRACT A novel wavelet-based sparse signal representation technique is used to separate the main and tail rotor blade components of a...helicopter from the composite radar returns. The received signal consists of returns from the rotating main and tail rotor blades , the helicopter body...component signal com- prising of returns from the main body, the main and tail rotor hubs and blades . Temporal and Doppler characteristics of these

Overview of the Novel Intelligent JAXA Active Rotor Program

NASA Technical Reports Server (NTRS)

Saito, Shigeru; Kobiki, Noboru; Tanabe, Yasutada; Johnson, Wayne; Yamauchi, Gloria K.; Young, Larry A.

2010-01-01

The Novel Intelligent JAXA Active Rotor (NINJA Rotor) program is a cooperative effort between JAXA and NASA, involving a test of a JAXA pressure-instrumented, active-flap rotor in the 40- by 80-Foot Wind Tunnel at Ames Research Center. The objectives of the program are to obtain an experimental database of a rotor with active flaps and blade pressure instrumentation, and to use that data to develop analyses to predict the aerodynamic and aeroacoustic performance of rotors with active flaps. An overview of the program is presented, including a description of the rotor and preliminary pretest calculations.

Psychoacoustic Testing of Modulated Blade Spacing for Main Rotors

NASA Technical Reports Server (NTRS)

Edwards, Bryan; Booth, Earl R., Jr. (Technical Monitor)

2002-01-01

Psychoacoustic testing of simulated helicopter main rotor noise is described, and the subjective results are presented. The objective of these tests was to evaluate the potential acoustic benefits of main rotors with modulated (uneven) blade spacing. Sound simulations were prepared for six main rotor configurations. A baseline 4-blade main rotor with regular blade spacing was based on the Bell Model 427 helicopter. A 5-blade main rotor with regular spacing was designed to approximate the performance of the 427, but at reduced tipspeed. Four modulated rotors - one with "optimum" spacing and three alternate configurations - were derived from the 5 bladed regular spacing rotor. The sounds were played to 2 subjects at a time, with care being taken in the speaker selection and placement to ensure that the sounds were identical for each subject. A total of 40 subjects participated. For each rotor configuration, the listeners were asked to evaluate the sounds in terms of noisiness. The test results indicate little to no "annoyance" benefit for the modulated blade spacing. In general, the subjects preferred the sound of the 5-blade regular spaced rotor over any of the modulated ones. A conclusion is that modulated blade spacing is not a promising design feature to reduce the annoyance for helicopter main rotors.