These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Combustion chemistry  

SciTech Connect

This research is concerned with the development and use of sensitivity analysis tools to probe the response of dependent variables to model input variables. Sensitivity analysis is important at all levels of combustion modeling. This group`s research continues to be focused on elucidating the interrelationship between features in the underlying potential energy surface (obtained from ab initio quantum chemistry calculations) and their responses in the quantum dynamics, e.g., reactive transition probabilities, cross sections, and thermal rate coefficients. The goals of this research are: (i) to provide feedback information to quantum chemists in their potential surface refinement efforts, and (ii) to gain a better understanding of how various regions in the potential influence the dynamics. These investigations are carried out with the methodology of quantum functional sensitivity analysis (QFSA).

Brown, N.J. [Lawrence Berkeley Laboratory, CA (United States)

1993-12-01

2

Hydrocarbon Fouling of SCR during PCCI combustion  

SciTech Connect

The combination of advanced combustion with advanced selective catalytic reduction (SCR) catalyst formulations was studied in the work presented here to determine the impact of the unique hydrocarbon (HC) emissions from premixed charge compression ignition (PCCI) combustion on SCR performance. Catalyst core samples cut from full size commercial Fe- and Cu-zeolite SCR catalysts were exposed to a slipstream of raw engine exhaust from a 1.9-liter 4-cylinder diesel engine operating in conventional and PCCI combustion modes. The zeolites which form the basis of these catalysts are different with the Cu-based catalyst made on a chabazite zeolite which las smaller pore structures relative to the Fe-based catalyst. Subsequent to exposure, bench flow reactor characterization of performance and hydrocarbon release and oxidation enabled evaluation of overall impacts from the engine exhaust. The Fe-zeolite NOX conversion efficiency was significantly degraded, especially at low temperatures (<250 C), after the catalyst was exposed to the raw engine exhaust. The degradation of the Fe-zeolite performance was similar for both combustion modes. The Cu-zeolite showed better tolerance to HC fouling at low temperatures compared to the Fe-zeolite but PCCI exhaust had a more significant impact than the exhaust from conventional combustion on the NOX conversion efficiency. Furthermore, chemical analysis of the hydrocarbons trapped on the SCR cores was conducted to better determine chemistry specific effects.

Prikhodko, Vitaly Y [ORNL; Pihl, Josh A [ORNL; Lewis Sr, Samuel Arthur [ORNL; Parks, II, James E [ORNL

2012-01-01

3

Predicting combustion properties of hydrocarbon fuel mixtures  

E-print Network

In this thesis, I applied computational quantum chemistry to improve the accuracy of kinetic mechanisms that are used to model combustion chemistry. I performed transition state theory calculations for several reactions ...

Goldsmith, Claude Franklin, III

2010-01-01

4

Determining Heats of Combustion of Gaseous Hydrocarbons  

NASA Technical Reports Server (NTRS)

Enrichment-oxygen flow rate-ratio related to heat of combustion. Technique developed for determining heats of combustion of natural-gas samples. Based on measuring ratio m/n, where m is (volmetric) flow rate of oxygen required to enrich carrier air in which test gas flowing at rate n is burned, such that mole fraction of oxygen in combustion-product gases equals that in carrier air. The m/n ratio directly related to heats of combustion of saturated hydrocarbons present in natural gas.

Singh, Jag J.; Sprinkle, Danny R.; Puster, Richard L.

1987-01-01

5

Global reaction schemes for hydrocarbon combustion  

Microsoft Academic Search

Global reaction schemes for the combustion of alkane hydrocarbons up to butane in mixtures with air in premixed and diffusion flames have been derived using analysis of flame structures. The schemes include two competing fuel breakdown reactions, and equilibrium assumptions have been used to derive initial estimates of the forms of the rate expressions. The deduced four-step reaction mechanism is

W. P. Jones; R. P. Lindstedt

1988-01-01

6

LOX/Hydrocarbon Combustion Instability Investigation  

NASA Technical Reports Server (NTRS)

The LOX/Hydrocarbon Combustion Instability Investigation Program was structured to determine if the use of light hydrocarbon combustion fuels with liquid oxygen (LOX) produces combustion performance and stability behavior similar to the LOX/hydrogen propellant combination. In particular methane was investigated to determine if that fuel can be rated for combustion instability using the same techniques as previously used for LOX/hydrogen. These techniques included fuel temperature ramping and stability bomb tests. The hot fire program probed the combustion behavior of methane from ambient to subambient temperatures. Very interesting results were obtained from this program that have potential importance to future LOX/methane development programs. A very thorough and carefully reasoned documentation of the experimental data obtained is contained. The hot fire test logic and the associated tests are discussed. Subscale performance and stability rating testing was accomplished using 40,000 lb. thrust class hardware. Stability rating tests used both bombs and fuel temperature ramping techniques. The test program was successful in generating data for the evaluation of the methane stability characteristics relative to hydrogen and to anchor stability models. Data correlations, performance analysis, stability analyses, and key stability margin enhancement parameters are discussed.

Jensen, R. J.; Dodson, H. C.; Claflin, S. E.

1989-01-01

7

Characteristics and combustion of future hydrocarbon fuels  

NASA Technical Reports Server (NTRS)

Changes in fuel properties that are expected in future hydrocarbon fuels for aircraft are discussed along with the principal properties of 'syncrudes' and the fuels that can be derived from them. The impact that the resultant potential changes in fuel properties may have on combustion and thermal stability characteristics is illustrated and discussed in terms of ignition, soot formation, carbon deposition, flame radiation, and emissions.

Rudey, R. A.; Grobman, J. S.

1978-01-01

8

Combustion chemistry of propane: A case study of detailed reaction mechanism optimization  

Microsoft Academic Search

Detailed chemical reaction mechanisms describing hydrocarbon combustion chemistry are conceptually structured in a hierarchical manner with H2 and CO chemistry at the base, supplemented as needed by elementary reactions of larger chemical species. While this structure gives a logical organization to com- bustion chemistry, the degree to which this organization reflects actual reactive fluxes in flames is not known. Moreover,

Zhiwei Qin; Vitali V. Lissianski; Huixing Yang; William C. Gardiner; Scott G. Davis; Hai Wang

2000-01-01

9

Combustion chemistry of solid propellants  

NASA Technical Reports Server (NTRS)

Several studies are described of the chemistry of solid propellant combustion which employed a fast-scanning optical spectrometer. Expanded abstracts are presented for four of the studies which were previously reported. One study of the ignition of composite propellants yielded data which suggested early ammonium perchlorate decomposition and reaction. The results of a study of the spatial distribution of molecular species in flames from uncatalyzed and copper or lead catalyzed double-based propellants support previously published conclusions concerning the site of action of these metal catalysts. A study of the ammonium-perchlorate-polymeric-fuel-binder reaction in thin films, made by use of infrared absorption spectrometry, yielded a characterization of a rapid condensed-phase reaction which is likely important during the ignition transient and the burning process.

Baer, A. D.; Ryan, N. W.

1974-01-01

10

Parallel Performance of a Combustion Chemistry Simulation Gregg Skinner  

E-print Network

combustion- generated pollutants, reducing knocking in internal combustion engines, studyingParallel Performance of a Combustion Chemistry Simulation Gregg Skinner Rudolf Eigenmann Center used a description of a combustion simulation'smathematicaland computationalmethods to develop

Padua, David

11

Effect of Hydrogen Enriched Hydrocarbon Combustion on Emissions and Performance  

Microsoft Academic Search

The principle of this mode of combustion is to add a percentage of hydrogen gas to the combustion reactions of either compression or spark ignition engines. The addition of hydrogen has been shown to decrease the formation of NOx, CO and unburned hydrocarbons. Studies have shown that added hydrogen in percentages as low as 5-10% percent of the hydrocarbon fuel

Jacob Wall

12

Basic Considerations in the Combustion of Hydrocarbon Fuels with Air  

NASA Technical Reports Server (NTRS)

Basic combustion research is collected, collated, and interpreted as it applies to flight propulsion. The following fundamental processes are treated in separate chapters: atomization and evaporation of liquid fuels, flow and mixing processes in combustion chambers, ignition and flammability of hydrocarbon fuels, laminar flame propagation, turbulent flames, flame stabilization, diffusion flames, oscillations in combustors, and smoke and coke formation in the combustion of hydrocarbon-air mixtures. Theoretical background, basic experimental data, and practical significance to flight propulsion are presented.

Barnett, Henry C; Hibbard, Robert R

1957-01-01

13

Theory and modeling in combustion chemistry  

SciTech Connect

This paper discusses four important problems in combustion chemistry. In each case, resolution of the problem focuses on a single elementary reaction. Theoretical analysis of this reaction is discussed in some depth, with emphasis on its unusual features. The four combustion problems and their elementary reactions are: (1) Burning velocities, extinction limits, and flammability limits: H+O{sub 2}{leftrightarrow}OH+O, (2) Prompt NO: CH+N{sub 2}{leftrightarrow}HCN+N, (3) the Thermal De-NO{sub x} Process: NH{sub 2}+NO{leftrightarrow}products, and (4) ``Ring`` formation in flames of aliphatic fuels and the importance of resonantly stabilized free radicals: C{sub 3}H{sub 3}{leftrightarrow}products.

Miller, J.A.

1996-10-01

14

Turbulent hydrocarbon combustions kinetics - Stochastic modeling and verification  

NASA Technical Reports Server (NTRS)

Idealized reactors, that are designed to ensure perfect mixing and are used to generate the combustion kinetics for complex hydrocarbon fuels, may depart from the ideal and influence the kinetics model performance. A complex hydrocarbon kinetics model that was established by modeling a jet-stirred combustor (JSC) as a perfectly stirred reactor (PSR), is reevaluated with a simple stochastic process in order to introduce the unmixedness effect quantitatively into the reactor system. It is shown that the comparisons of the predictions and experimental data have improved dramatically with the inclusion of the unmixedness effect in the rich combustion region. The complex hydrocarbon kinetics is therefore verified to be mixing effect free and be applicable to general reacting flow calculations.

Wang, T. S.; Farmer, R. C.; Tucker, Kevin

1989-01-01

15

Combustion kinetics and emission characteristics of polycyclic aromatic hydrocarbons from polylactic acid combustion.  

PubMed

This study investigates the combustion kinetics and emission factors of 16 U.S. Environmental Protection Agency priority polycyclic aromatic hydrocarbons (PAHs) in polylactic acid (PLA) combustion. Experimentally, two reactions are involved in the PLA combustion process that potentially result in the release of lactide, acetaldehyde, and n-hexaldehyde. The products may continuously be oxidized to form carbon dioxide (CO2) and some PAHs produced because of incomplete combustion. The analytical results indicate that the emission factors for PAHs are in the range of not detectable to 98.04 microg/g. The emission factors are much lower than those of poly(ethylene terephalate) (PET) and other combustion of plastics. Results from this work suggest that combustion is a good choice for waste PLA disposal. PMID:20681432

Chien, Yi-Chi; Liang, Chenju; Liu, Shou-Heng; Yang, Shu-Hua

2010-07-01

16

New method for determining heats of combustion of gaseous hydrocarbons  

NASA Technical Reports Server (NTRS)

As a spin off of a system developed for monitoring and controlling the oxygen concentration in the Langley 8-foot High Temperature Tunnel, a highly accurate on-line technique was developed for determining heats of combustion of natural gas samples. It is based on measuring the ratio m/n, where m is the (volumetric) flowrate of oxygen required to enrich the carrier air in which the test gas flowing at the rate n is burned, such that the mole fraction of oxygen in the combustion product gases equals that in the carrier air. The m/n ratio is directly related to the heats of combustion of the saturated hydrocarbons present in the natural gas. A measurement of the m/n ratio for the test gas can provide a direct means of determination of its heat of combustion by using the calibration graph relating the m/n values for pure saturated hydrocarbons with their heats of combustion. The accuracy of the technique is determine solely by the accuracy with which the flowrates m and n can be measured and is of the order of 2 percent in the present study. The theoretical principles and experimental results are discussed.

Singh, J. J.; Sprinkle, D. R.; Puster, R. L.

1985-01-01

17

Explosion-induced combustion of hydrocarbon clouds in a chamber  

SciTech Connect

The interaction of the detonation of a solid HE-charge with a non-premixed cloud of hydro-carbon fuel in a chamber was studied in laboratory experiments. Soap bubbles filled with a flammable gas were subjected to the blast wave created by the detonation of PETN-charges (0.2 g < mass < 0.5 g). The dynamics of the combustion system were investigated by means of high-speed photography and measurement of the quasi-static chamber pressure.

Neuwald, P; Reichenbach, H; Kuhl, A L

2001-02-06

18

Acceleration of the chemistry solver for modeling DI engine combustion using dynamic adaptive chemistry (DAC) schemes  

Microsoft Academic Search

Acceleration of the chemistry solver for engine combustion is of much interest due to the fact that in practical engine simulations extensive computational time is spent solving the fuel oxidation and emission formation chemistry. A dynamic adaptive chemistry (DAC) scheme based on a directed relation graph error propagation (DRGEP) method has been applied to study homogeneous charge compression ignition (HCCI)

Yu Shi; Long Liang; Hai-Wen Ge; Rolf D. Reitz

2010-01-01

19

Mach 2 combustion characteristics of hydrogen/hydrocarbon fuel mixtures  

NASA Technical Reports Server (NTRS)

The combustion of H2/CH4 and H2/C2H4 mixtures containing 10 to 70 vol pct hydrocarbon at combustor inlet Mach number 2 and temperatures 2000 to 4000 R is investigated experimentally, applying direct-connect test hardware and techniques similar to those described by Diskin and Northam (1987) in the facilities of the NASA Langley Hypersonic Propulsion Branch. The experimental setup, procedures, and data-reduction methods are described; and the results are presented in extensive tables and graphs and characterized in detail. Fuel type and mixture are found to have little effect on the wall heating rate measured near the combustor exit, but H2/C2H4 is shown to burn much more efficiently than H2/CH4, with no pilot-off blowout equivalence ratios greater than 0.5. It is suggested that H2/hydrocarbon mixtures are feasible fuels (at least in terms of combustion efficiency) for scramjet SSTO vehicles operating at freestream Mach numbers above 4.

Diskin, Glenn S.; Jachimowski, C. J.; Northam, G. Burton; Bell, Randy A.

1987-01-01

20

Mach 2 combustion characteristics of hydrogen/hydrocarbon fuel mixtures  

NASA Technical Reports Server (NTRS)

The combustion of H2/CH4 and H2/C2H4 mixtures containing 10-70 vol pct hydrocarbon at cumbustor inlet Mach number 2 and temperatures 2000-4000 R is investigated experimentally, applying direct-connect test hardware and techniques similar to those described by Diskin and Northam (1987) in the facilities of the NASA Langley Hypersonic Propulsion Branch. The experimental setup, procedures, and data-reduction methods are described; and the results are presented in extensive tables and graphs and characterized in detail. Fuel type and mixture are found to have little effect on the wall heating rate measured near the combustor exit, but H2/C2H4 is shown to burn much more efficiently than H2/CH4, with no pilot-off blowout at equivalence ratios greater than 0.5. It is suggested that H2/hydrocarbon mixtures are feasible fuels (at least in terms of combustion efficiency) for scramjet SSTO vehicles operating at freestream Mach numbers above 4.

Diskin, Glenn S.; Northam, G. Burton; Bell, Randy A.

1987-01-01

21

Investigation of the combustion kinetics and polycyclic aromatic hydrocarbon emissions from polycaprolactone combustion.  

PubMed

Polycaprolactone (PCL) is one of the most attractive biodegradable plastics that has been widely used in medicine and agriculture fields. Because of the large increase in biodegradable plastics usage, the production of waste biodegradable plastics will be increasing dramatically, producing a growing environmental problem. Generally, waste PCL is collected along with municipal solid wastes and then incinerated. This study investigates the combustion kinetics and emission factors of 16 US Environmental Protection Agency (EPA) priority polycyclic aromatic hydrocarbons (PAHs) in the PCL combustion. Experimentally, two reactions are involved in the PCL combustion process, possibly resulting in the emission of carbon dioxide, propanal, protonated caprolactone and very small amounts of PAH produced by incomplete combustion. The intermediate products may continuously be oxidized to form CO2. The emission factors for 16 US EPA priority PAHs are n.d. -2.95 microg/g, which are much lower than those of poly lactic acid and other plastics combustion. The conversion of PCL is 100%. Results from this work suggest that combustion is a good choice for the waste PCL disposal. PMID:23530325

Chien, Y C; Yang, S H

2013-01-01

22

Microwave enhanced combustion of laminar hydrocarbon flame fronts  

NASA Astrophysics Data System (ADS)

The X-43 missions in 2005 demonstrated the feasibility of a hydrogen fueled scramjet. Since that time, the cost, performance, and safety concerns surrounding the use of hydrogen have motivated researchers to investigate methods of enhancing the performance of easily stored hydrocarbon based fuels by improving their ignition, flammability, and flameholding characteristics. The microwave enhanced combustion testbed has demonstrated a significant increase in the laminar flame speed of a premixed CH4/air flame when 1.3 kW continuous wave (CW) microwave radiation is directed at the flame front in a high-Q resonant cavity. The main aspect of the research aimed to accurately quantify key combustion parameters in the microwave enhanced flame using laser diagnostics for improved spatial resolution and accuracy over invasive probe devices. Particle image velocimetry (PIV), filtered Rayleigh scattering (FRS), and planar laser induced fluorescence (PLIF) were used to measured flame speed, temperature, and OH radical concentrations, respectively. The PIV and FRS laser experiments measured increases in flame speed up to 20% and a deposition of only 30 W of microwave power into the flame. The temperature measurements show an increase of temperature within the flame front as well as in the post flame region that are not of large enough magnitude to account for the flame speed increase via simple joule heating. Alongside PLIF measurements of an enhanced concentration of OH in the flame zone, these results imply that the microwave enhanced combustion was a combined thermal joule heating and non-equilibrium interaction. By replacing the CW microwave source with a pulsed magnetron that is capable of generating 1 mus wide, 30 kW peak power pulses at 1000 pulses per second, similar flame speed enhancements were achieved with 40 times less power. This effort provides the first realistic approach towards incorporating the microwave enhanced combustion concept into a scramjet combustor.

Stockman, Emanuel Solomon

23

Stochastic atomistic simulation of polycyclic aromatic hydrocarbon growth in combustion.  

PubMed

Nanoparticles formed in gas phase environments, such as combustion, have an important impact on society both as engineering components and hazardous pollutants. A new software package, the Stochastic Nanoparticle Simulator (SNAPS) was developed, applying a stochastic chemical kinetics methodology, to computationally investigate the growth of nanoparticle precursors through trajectories of chemical reactions. SNAPS was applied to characterize the growth of polycyclic aromatic hydrocarbons (PAHs), important precursors of carbonaceous nanoparticles and soot, in a premixed laminar benzene flame, using a concurrently developed PAH growth chemical reaction mechanism, as well as an existing benzene oxidation mechanism. Simulations of PAH ensembles successfully predicted existing experimentally measured data and provided novel insight into chemical composition and reaction pathways. The most commonly observed PAH isomers in simulations showed the importance of 5-membered rings, which contrasts with traditionally assumed compositions involving primarily pericondensed 6-membered rings. In addition, the chemical growth of PAHs involved complex sequences of highly reversible reactions, rather than relatively direct routes of additions and ring closures. Furthermore, the most common reactions involved 5-membered rings, suggesting their importance to PAH growth. The framework developed in this work will facilitate future investigation of particle inception and soot formation and will benefit engineering of novel combustion technologies to mitigate harmful emissions. PMID:24647536

Lai, Jason Y W; Elvati, Paolo; Violi, Angela

2014-05-01

24

On-Line Measurement of Heat of Combustion of Gaseous Hydrocarbon Fuel Mixtures  

NASA Technical Reports Server (NTRS)

A method for the on-line measurement of the heat of combustion of gaseous hydrocarbon fuel mixtures has been developed and tested. The method involves combustion of a test gas with a measured quantity of air to achieve a preset concentration of oxygen in the combustion products. This method involves using a controller which maintains the fuel (gas) volumetric flow rate at a level consistent with the desired oxygen concentration in the combustion products. The heat of combustion is determined form a known correlation with the fuel flow rate. An on-line computer accesses the fuel flow data and displays the heat of combustion measurement at desired time intervals. This technique appears to be especially applicable for measuring heats of combustion of hydrocarbon mixtures of unknown composition such as natural gas.

Sprinkle, Danny R.; Chaturvedi, Sushil K.; Kheireddine, Ali

1996-01-01

25

Impact of retarded spark timing on engine combustion, hydrocarbon emissions, and fast catalyst light-off  

E-print Network

An experimental study was performed to determine the effects of substantial spark retard on engine combustion, hydrocarbon (HC) emissions, feed gas enthalpy, and catalyst light-off. Engine experiments were conducted at ...

Hallgren, Brian E. (Brian Eric), 1976-

2005-01-01

26

DIESEL OXIDATION CATALYST CONTROL OF HYDROCARBON AEROSOLS FROM REACTIVITY CONTROLLED COMPRESSION IGNITION COMBUSTION  

SciTech Connect

Reactivity Controlled Compression Ignition (RCCI) is a novel combustion process that utilizes two fuels with different reactivity to stage and control combustion and enable homogeneous combustion. The technique has been proven experimentally in previous work with diesel and gasoline fuels; low NOx emissions and high efficiencies were observed from RCCI in comparison to conventional combustion. In previous studies on a multi-cylinder engine, particulate matter (PM) emission measurements from RCCI suggested that hydrocarbons were a major component of the PM mass. Further studies were conducted on this multi-cylinder engine platform to characterize the PM emissions in more detail and understand the effect of a diesel oxidation catalyst (DOC) on the hydrocarbon-dominated PM emissions. Results from the study show that the DOC can effectively reduce the hydrocarbon emissions as well as the overall PM from RCCI combustion. The bimodal size distribution of PM from RCCI is altered by the DOC which reduces the smaller mode 10 nm size particles.

Prikhodko, Vitaly Y [ORNL] [ORNL; Parks, II, James E [ORNL; Barone, Teresa L [ORNL] [ORNL; Curran, Scott [ORNL] [ORNL; Cho, Kukwon [ORNL] [ORNL; Lewis Sr, Samuel Arthur [ORNL] [ORNL; Storey, John Morse [ORNL] [ORNL; Wagner, Robert M [ORNL] [ORNL

2011-01-01

27

A new comprehensive reaction mechanism for combustion of hydrocarbon fuels  

SciTech Connect

A detailed chemical kinetic model has been developed that accurately describes pyrolysis, ignition and oxidation of many small hydrocarbon fuels over a wide range of experimental conditions. Fuels include carbon monoxide and hydrogen methane, and other alkane species up to n-butane, ethylene, propene, acetylene, and oxygenated species such as methanol, acetaldehyde, and ethanol. Formation of some larger intermediate and product species including benzene, butadiene, large olefins, and cyclopentadiene has been treated in a semiempirical manner. The reaction mechanism has been tested for conditions that do not involve transport and diffusional processes, including plug flow and stirred reactors, batch reactors and shock tubes. The present kinetic model and its validation differ from previous comprehensive detailed reaction mechanisms in two important ways. First, in addition to conventional combustion data, experiments more commonly associated with chemical engineering problems such as oxidative coupling, oxidative pyrolysis and steam cracking are use to test the reaction mechanisms, making it even more general than previous models. In addition, H-atom abstraction and some other reaction rates, even for the smaller C[sub 2], C[sub 3], and C[sub 4] species, are treated using approximations that facilitate future extensions to larger fuels in a convenient manner. The construction of the reaction mechanisms and selected comparisons with experimental data are described that illustrate the generality of the model.

Ranzi, E.; Sogaro, A.; Gaffuri, P.; Pennati, G. (Politecnico di Milano (Italy). Dipt. di Chimica Industriale ed Ingegneria Chimica); Westbrook, C.K.; Pitz, W.J. (Lawrence Livermore National Lab., CA (United States))

1994-11-01

28

Carbon deposition model for oxygen-hydrocarbon combustion, volume 1  

NASA Technical Reports Server (NTRS)

Presented are details of the design, fabrication, and testing of subscale hardware used in the evaluation of carbon deposition characteristics of liquid oxygen and three hydrocarbon fuels for both main chamber and preburner/gas generator operating conditions. In main chamber conditions, the deposition of carbon on the combustion chamber wall was investigated at mixture ratios of 2.0 to 4.0 and at pressures of 1000 to 1500 psia. No carbon deposition on the chamber walls was detected at these main chamber mixture ratios. In preburner/gas generator operating conditions, the deposition of carbon on the turbine simulator tubes was evaluated at mixture ratios of 0.20 to 0.60 and at chamber pressures of 720 to 1650 psia. The results of the tests showed carbon deposition rate to be a strong function of mixture ratio and a weak function of chamber pressure. Further analyses evaluated the operational consequences of carbon deposition on preburner/gas generator performance. The report is in two volumes, of which this is Volume 1 covering the main body of the report plus Appendixes A through D.

Hernandez, R.; Ito, J. I.; Niiya, K. Y.

1987-01-01

29

Carbon Deposition Model for Oxygen-Hydrocarbon Combustion, Volume 2  

NASA Technical Reports Server (NTRS)

Presented are details of the design, fabrication, and testing of subscale hardware used in the evaluation of carbon deposition characteristics of liquid oxygen and three hydrocarbon fuels for both main chamber and preburner/gas generator operating conditions. In main chamber conditions, the deposition of carbon on the combustion chamber wall was investigated at mixture ratios of 2.0 to 4.0 and at chamber pressures of 1000 to 1500 psia. No carbon deposition on chamber walls was detected at these main chamber mixture ratios. In preburner/gas generator operating conditions, the deposition of carbon on the turbine simulator tubes was evaluated at mixture ratios of 0.20 to 0.60 and at chamber pressures of 720 to 1650 psia. The results of the tests showed carbon deposition rate to be a strong function of mixture ratio and a weak function of chamber pressure. Further analyses evaluated the operational concequences of carbon deposition on preburner/gas generator performance. This is Volume 2 of the report, which contains data plots of all the test programs.

Hernandez, R.; Ito, J. I.; Niiya, K. Y.

1987-01-01

30

A filtered tabulated chemistry model for LES of premixed combustion  

SciTech Connect

A new modeling strategy called F-TACLES (Filtered Tabulated Chemistry for Large Eddy Simulation) is developed to introduce tabulated chemistry methods in Large Eddy Simulation (LES) of turbulent premixed combustion. The objective is to recover the correct laminar flame propagation speed of the filtered flame front when subgrid scale turbulence vanishes as LES should tend toward Direct Numerical Simulation (DNS). The filtered flame structure is mapped using 1-D filtered laminar premixed flames. Closure of the filtered progress variable and the energy balance equations are carefully addressed in a fully compressible formulation. The methodology is first applied to 1-D filtered laminar flames, showing the ability of the model to recover the laminar flame speed and the correct chemical structure when the flame wrinkling is completely resolved. The model is then extended to turbulent combustion regimes by including subgrid scale wrinkling effects in the flame front propagation. Finally, preliminary tests of LES in a 3-D turbulent premixed flame are performed. (author)

Fiorina, B.; Auzillon, P.; Darabiha, N.; Gicquel, O.; Veynante, D. [EM2C - CNRS, Ecole Centrale Paris, 92295 Chatenay Malabry (France); Vicquelin, R. [EM2C - CNRS, Ecole Centrale Paris, 92295 Chatenay Malabry (France); GDF SUEZ, Pole CHENE, Centre de Recherche et d'Innovation Gaz et Energies Nouvelles, 93211 Saint-Denis la Plaine (France)

2010-03-15

31

Hydrocarbon-fueled internal combustion engines: "the worst form of vehicle propulsion... except for all the other forms"  

E-print Network

Hydrocarbon-fueled internal combustion engines: "the worst form of vehicle propulsion... except of Southern California, Los Angeles, CA 90089-1453 Introduction Hydrocarbon-fueled internal combustion engines system paradigm are discussed. First a definition of an internal combustion engine is needed

32

Combustion chemistry and an evolving transportation fuel environment.  

SciTech Connect

The world currently faces tremendous energy challenges stemming from the need to curb potentially catastrophic anthropogenic climate change. In addition, many nations, including the United States, recognize increasing political and economic risks associated with dependence on uncertain and limited energy sources. For these and other reasons the chemical composition of transportation fuels is changing, both through introduction of nontraditional fossil sources, such as oil sands-derived fuels in the US stream, and through broader exploration of biofuels. At the same time the need for clean and efficient combustion is leading engine research towards advanced low-temperature combustion strategies that are increasingly sensitive to this changing fuel chemistry, particularly in the areas of pollutant formation and autoignition. I will highlight the new demands that advanced engine technologies and evolving fuel composition place on investigations of fundamental reaction chemistry. I will focus on recent progress in measuring product formation in elementary reactions by tunable synchrotron photoionization, on the elucidation of pressure-dependent effects in the reactions of alkyl and substituted alkyl radicals with O{sub 2}, and on new combined efforts in fundamental combustion chemistry and engine performance studies of novel potential biofuels.

Taatjes, Craig A. (Org. 8353, Combustion Chemistry Department)

2010-05-01

33

Nonmethane hydrocarbon chemistry in the remote marine boundary layer  

NASA Technical Reports Server (NTRS)

A photochemical model of the remote marine boundary layer (MBL) is presented, with focus placed on the role of reactive nonmethane hydrocarbons (NMHC). A wide range of NMHC air-sea fluxes with various relative distributions of NMHC regions are considered. In particular, the flux magnitude at which NMHC emissions become significant, and then dominant, players in MBL chemistry is identified. Emphasis is placed on diurnal variability, diurnal ozone variations and sensitivity to NMHC emission fluxes, to CO, O3, H2O, and UV light, and to kinetics and isometric composition. Model runs indicate that, in the range consistent with current observations, the NMHCs may either dominate MBL chemistry, or simply be contributors at the 10-percent level. These model runs also show that existing observations of NMHCs in ocean water find them to scarce for fluxes from bulk-flux air-sea gas exchange models to be consistent with the fluxes needed in the proposed model to maintain the lowest observed MBL NMHC.

Donahue, Neil M.; Prinn, Ronald G.

1990-01-01

34

Computationally efficient implementation of combustion chemistry in parallel PDF calculations  

NASA Astrophysics Data System (ADS)

In parallel calculations of combustion processes with realistic chemistry, the serial in situ adaptive tabulation (ISAT) algorithm [S.B. Pope, Computationally efficient implementation of combustion chemistry using in situ adaptive tabulation, Combustion Theory and Modelling, 1 (1997) 41-63; L. Lu, S.B. Pope, An improved algorithm for in situ adaptive tabulation, Journal of Computational Physics 228 (2009) 361-386] substantially speeds up the chemistry calculations on each processor. To improve the parallel efficiency of large ensembles of such calculations in parallel computations, in this work, the ISAT algorithm is extended to the multi-processor environment, with the aim of minimizing the wall clock time required for the whole ensemble. Parallel ISAT strategies are developed by combining the existing serial ISAT algorithm with different distribution strategies, namely purely local processing (PLP), uniformly random distribution (URAN), and preferential distribution (PREF). The distribution strategies enable the queued load redistribution of chemistry calculations among processors using message passing. They are implemented in the software x2f_mpi, which is a Fortran 95 library for facilitating many parallel evaluations of a general vector function. The relative performance of the parallel ISAT strategies is investigated in different computational regimes via the PDF calculations of multiple partially stirred reactors burning methane/air mixtures. The results show that the performance of ISAT with a fixed distribution strategy strongly depends on certain computational regimes, based on how much memory is available and how much overlap exists between tabulated information on different processors. No one fixed strategy consistently achieves good performance in all the regimes. Therefore, an adaptive distribution strategy, which blends PLP, URAN and PREF, is devised and implemented. It yields consistently good performance in all regimes. In the adaptive parallel ISAT strategy, the type and extent of redistribution is determined "on the fly" based on the prediction of future simulation time. Compared to the PLP/ISAT strategy where chemistry calculations are essentially serial, a speed-up factor of up to 30 is achieved. The study also demonstrates that the adaptive strategy has acceptable parallel scalability.

Lu, Liuyan; Lantz, Steven R.; Ren, Zhuyin; Pope, Stephen B.

2009-08-01

35

Method and device for determining heats of combustion of gaseous hydrocarbons  

NASA Technical Reports Server (NTRS)

A method and device is provided for a quick, accurate and on-line determination of heats of combustion of gaseous hydrocarbons. First, the amount of oxygen in the carrier air stream is sensed by an oxygen sensing system. Second, three individual volumetric flow rates of oxygen, carrier stream air, and hydrocrabon test gas are introduced into a burner. The hydrocarbon test gas is fed into the burner at a volumetric flow rate, n, measured by a flowmeter. Third, the amount of oxygen in the resulting combustion products is sensed by an oxygen sensing system. Fourth, the volumetric flow rate of oxygen is adjusted until the amount of oxygen in the combustion product equals the amount of oxygen previously sensed in the carrier air stream. This equalizing volumetric flow rate is m and is measured by a flowmeter. The heat of combustion of the hydrocrabon test gas is then determined from the ratio m/n.

Singh, Jag J. (inventor); Sprinkle, Danny R. (inventor); Puster, Richard L. (inventor)

1988-01-01

36

Prediction of Carbon Monoxide and Hydrocarbon Emissions in Isooctane HCCI Engine Combustion Using Multi-Zone Simulations  

SciTech Connect

Homogeneous Charge Compression Ignitions (HCCI) engines show promise as an alternative to Diesel engines, yet research remains: development of practical HCCI engines will be aided greatly by accurate modeling tools. A novel detailed chemical kinetic model that incorporates information from a computational fluid mechanics code has been developed to simulate HCCI combustion. This model very accurately predicts many aspects of the HCCI combustion process. High-resolution computational grids can be used for the fluid mechanics portion of the simulation, but the chemical kinetics portion of the simulation can be reduced to a handful of computational zones (for all previous work 10 zones have been used). While overall this model has demonstrated a very good predictive capability for HCCI combustion, previous simulations using this model have tended to underpredict carbon monoxide emissions by an order of magnitude. A factor in the underprediction of carbon monoxide may be that all previous simulations have been conducted with 10 chemical kinetic zones. The chemistry that results in carbon monoxide emissions is very sensitive to small changes in temperature within the engine. The resolution in temperature is determined directly by the number of zones. This paper investigates how the number of zones (i.e. temperature resolution) affects the model's prediction of hydrocarbon and carbon monoxide emissions in an HCCI engine. Simulations with 10, 20, and 40 chemical kinetic zones have been conducted using a detailed chemical kinetic mechanism (859 species, 3606 reactions) to simulate an isooctane fueled HCCI engine. The results show that 10-zones are adequate to resolve the hydrocarbon emissions, but a greater numbers of zones are required to resolve carbon monoxide emissions. Results are also presented that explore spatial sources of the exhaust emissions within the HCCI engine combustion chamber.

Flowers, D; Aceves, S M; Martinez-Frias, J; Dibble, R

2002-05-02

37

Steam-enhanced regime for liquid hydrocarbons combustion: velocity distribution in the burner flame  

NASA Astrophysics Data System (ADS)

The lab-scale burner device with proprietary design was used for combustion of diesel fuel in a steam-enhanced regime. This operation mode ensures drastic intensification of liquid hydrocarbon combustion due to supply of superheated steam jet to the combustion zone. The particle image velocimetry technique was used for study of velocity field in the burner flame. The method of seeding of flow zone with new kind of tracers (micro-sized silica particles produced from silicon oil added to liquid fuel) was tested.

Alekseenko, S. V.; Anufriev, I. S.; Vigriyanov, M. S.; Dulin, V. M.; Kopyev, E. P.; Sharypov, O. V.

2014-06-01

38

UV absorption of CO2 for temperature diagnostics of hydrocarbon combustion applications  

E-print Network

UV absorption of CO2 for temperature diagnostics of hydrocarbon combustion applications J temperature, CO2 is transparent in the ultraviolet (UV) at wavelengths longer than 205 nm; however, at temperatures above 1000 K the CO2 absorption cross-section becomes significant in the region between 200

Lee, Tonghun

39

Applying an Additive Scheme to the Calculation of the Heat of Combustion of Saturated Hydrocarbons  

Microsoft Academic Search

+ + 1.5n + 0.5 () O2 n CO 2 n 1 + () H 2 O Q + + are basic physicochemical quantities used in thermo- chemical calculations and in the optimization of fuel composition. The heat of combustion has been measured for many, but not all, saturated hydrocarbons (3-10) (Table 1), and the accuracy of some of those

E. V. Sagadeev; R. A. Kafiatullin; V. V. Sagadeev; V. I. Sagadeev

2003-01-01

40

Chemical Kinetic Reaction Mechanisms for Combustion of Hydrocarbon and Other Types of Chemical Fuels  

DOE Data Explorer

Reaction mechanisms have been tested and validated extensively through comparisons between computed results and measured data from laboratory experiments (e.g., shock tubes, laminar flames, rapid compression machines, flow reactors, stirred reactors) and from practical systems (e.g., diesel engines, spark-ignition engines, homogeneous charge, compression ignition (HCCI) engines). These kinetic models are used to examine a wide range of combustion systems.[Taken from https://www-pls.llnl.gov/?url=science_and_technology-chemistry-combustion

41

Combustion characteristics of hydrogen–hydrocarbon hybrid fuels  

Microsoft Academic Search

A comparative study of the flame structure and characteristics of diffusion flames of the mixture of hydrogen–hydrocarbon (natural gas and propane) hybrid fuel in a slow co-flowing stream of air is presented. The volumetric content of natural gas and propane in the mixture was varied from 0–35%. The burner exit Reynolds number was varied from 150–3000. Measurements include flame length,

Ahsan R Choudhuri; S. R Gollahalli

2000-01-01

42

Comprehensive mechanisms for combustion chemistry: Experiment, modeling, and sensitivity analysis  

SciTech Connect

This research program is an integrated experimental/numerical effort to study pyrolysis and oxidation reactions and mechanisms for small-molecule hydrocarbon structures under conditions representative of combustion environments. The experimental aspects of the work are conducted in large diameter flow reactors, at pressures from one to twenty atmospheres, temperatures from 550 K to 1200 K, and with observed reaction times from 10{sup {minus}2} to 5 seconds. Gas sampling of stable reactant, intermediate, and product species concentrations provides not only substantial definition of the phenomenology of reaction mechanisms, but a significantly constrained set of kinetic information with negligible diffusive coupling. Analytical techniques used for detecting hydrocarbons and carbon oxides include gas chromatography (GC), and gas infrared (NDIR) and FTIR methods are utilized for continuous on-line sample detection of light absorption measurements of OH have also been performed in an atmospheric pressure flow reactor (APFR), and a variable pressure flow (VPFR) reactor is presently being instrumented to perform optical measurements of radicals and highly reactive molecular intermediates. The numerical aspects of the work utilize zero and one-dimensional pre-mixed, detailed kinetic studies, including path, elemental gradient sensitivity, and feature sensitivity analyses. The program emphasizes the use of hierarchical mechanistic construction to understand and develop detailed kinetic mechanisms. Numerical studies are utilized for guiding experimental parameter selections, for interpreting observations, for extending the predictive range of mechanism constructs, and to study the effects of diffusive transport coupling on reaction behavior in flames. Modeling using well defined and validated mechanisms for the CO/H{sub 2}/oxidant systems.

Dryer, F.L.; Yetter, R.A. [Princeton Univ., NJ (United States)

1993-12-01

43

Photographic combustion characterization of LOX/Hydrocarbon type propellants  

NASA Technical Reports Server (NTRS)

One hundred twenty-seven tests were conducted over a chamber pressure range of 125-1500 psia, a fuel temperature range of -245 F to 158 F, and a fuel velocity range of 48-707 ft/sec to demonstrate the advantages and limitations of using high speed photography to identify potential combustion anomalies such as pops, fuel freezing, reactive stream separation and carbon formations. Combustion evaluation criteria were developed to guide selection of the fuels, injector elements, and operating conditions for testing. Separate criteria were developed for fuel and injector element selection and evaluation. The photographic test results indicated conclusively that injector element type and design directly influence carbon formation. Unlike spray fan, impingement elements reduce carbon formation because they induce a relatively rapid near zone fuel vaporization rate. Coherent jet impingement elements, on the other hand, exhibit increased carbon formation.

Judd, D. C.

1980-01-01

44

Numerical simulation of combustion stability of liquid rocket engine based on chemistry dynamics  

Microsoft Academic Search

Combustion instability of O2\\/kerosene, O2\\/kerosene\\/hydrogen, and O2\\/kerosene\\/hydrogen spray flame is numerically studied. The numerical results of combustion self-oscillation are consistent\\u000a with the historical experiments. Hydrogen is helpful to stabilizing oxygen\\/hydrocarbon combustion. High gas injecting velocity\\u000a of the coaxial injector would increase the combustion stability. Contrary to the former expectation, the most sensitive region\\u000a for combustion instability is not where the

Yuhui Huang; Zhenguo Wang; Jin Zhou

2002-01-01

45

Vented explosion overpressures from combustion of hydrogen and hydrocarbon mixtures  

Microsoft Academic Search

Experimental data obtained for hydrogen mixtures in a room-size enclosure are presented and compared with data for propane and methane mixtures. This set of data was also used to develop a three-dimensional gasdynamic model for the simulation of gaseous combustion in vented enclosures. The experiments were performed in a 64m3 chamber with dimensions of 4.6×4.6×3.0m and a vent opening on

C. R. Bauwens; J. Chaffee; S. B. Dorofeev

2011-01-01

46

Geochemical evidence for combustion of hydrocarbons during the K-T impact event  

PubMed Central

It has been proposed that extensive wildfires occurred after the Cretaceous–Tertiary (K-T) impact event. An abundance of soot and pyrosynthetic polycyclic aromatic hydrocarbons (pPAHs) in marine K-T boundary impact rocks (BIRs) have been considered support for this hypothesis. However, nonmarine K-T BIRs, from across North America, contain only rare occurrences of charcoal yet abundant noncharred plant remains. pPAHs and soot can be formed from a variety of sources, including partial combustion of vegetation and hydrocarbons whereby modern pPAH signatures are traceable to their source. We present results from multiple nonmarine K-T boundary sites from North America and reveal that the K-T BIRs have a pPAH signature consistent with the combustion of hydrocarbons and not living plant biomass, providing further evidence against K-T wildfires and compelling evidence that a significant volume of hydrocarbons was combusted during the K-T impact event. PMID:19251660

Belcher, Claire M.; Finch, Paul; Collinson, Margaret E.; Scott, Andrew C.; Grassineau, Nathalie V.

2009-01-01

47

Investigating an annular nozzle on combustion products of hydrocarbon fuels  

NASA Astrophysics Data System (ADS)

Full-scale and computational experiments were used to investigate the flows in the jet thrust unit with annular nozzle and deflector in the form of a spherical segment. The used working gas was the combustion products of air mixtures with acetylene, gas-phase aviation kerosene, and natural gas. Experimental studies were carried out in a hot-shot wind tunnel in the range of stagnation pressure from 0.48 to 2.05 MPa. The calculations for the cases of combustion products outflow in terrestrial and high altitude conditions were performed with the original computer program that used the Euler and Navier-Stokes systems supplemented by equations of chemical kinetics. It was found that the thrust of the jet module with an annular nozzle at high altitude almost twice exceeds the sound nozzle thrust, but is lesser (about 25 %) than the thrust of the ideal calculated Laval nozzle; the difference therewith decreases markedly with the decrease of flight altitude and stagnation pressure.

Levin, V. A.; Afonina, N. E.; Gromov, V. G.; Smekhov, G. D.; Khmelevsky, A. N.; Markov, V. V.

2013-09-01

48

Photographic combustion characterization of LOX/hydrocarbon type propellants  

NASA Technical Reports Server (NTRS)

Single element injectors and two fuels were tested with the aim of photographically characterizing observed combustion phenomena. The three injectors tested were the O-F-O triplet, the transverse like on like (TLOL), and the rectangular unlike doublet (RUD). The fuels tested were RP-1 and propane. The hot firings were conducted in a specifically constructed chamber fitted with quartz windows for photographically viewing the impingement spray field. All LOX/HC testing demonstrated coking with the RP-1 fuel leaving far more soot than the propane fuel. No fuel freezing or popping was experienced under the test conditions evaluated. Carbon particle emission and combustion light brilliance increased with Pc for both fuels although RP-1 was far more energetic in this respect. The RSS phenomena appear to be present in the high Pc tests as evidenced by striations in the spray pattern and by separate fuel rich and oxidizer rich areas. The RUD element was also tested as a fuel rich gas generator element by switching the propellant circuits. Excessive sooting occurred at this low mixture ratio (0.55), precluding photographic data.

Judd, D. C.

1979-01-01

49

Spray Combustion Modeling with VOF and Finite-Rate Chemistry  

NASA Technical Reports Server (NTRS)

A spray atomization and combustion model is developed based on the volume-of-fluid (VOF) transport equation with finite-rate chemistry model. The gas-liquid interface mass, momentum and energy conservation laws are modeled by continuum surface force mechanisms. A new solution method is developed such that the present VOF model can be applied for all-speed range flows. The objectives of the present study are: (1) to develop and verify the fractional volume-of-fluid (VOF) cell partitioning approach into a predictor-corrector algorithm to deal with multiphase (gas-liquid) free surface flow problems; (2) to implement the developed unified algorithm in a general purpose computational fluid dynamics (CFD) code, Finite Difference Navier-Stokes (FDNS), with droplet dynamics and finite-rate chemistry models; and (3) to demonstrate the effectiveness of the present approach by simulating benchmark problems of jet breakup/spray atomization and combustion. Modeling multiphase fluid flows poses a significant challenge because a required boundary must be applied to a transient, irregular surface that is discontinuous, and the flow regimes considered can range from incompressible to highspeed compressible flows. The flow-process modeling is further complicated by surface tension, interfacial heat and mass transfer, spray formation and turbulence, and their interactions. The major contribution of the present method is to combine the novel feature of the Volume of Fluid (VOF) method and the Eulerian/Lagrangian method into a unified algorithm for efficient noniterative, time-accurate calculations of multiphase free surface flows valid at all speeds. The proposed method reformulated the VOF equation to strongly couple two distinct phases (liquid and gas), and tracks droplets on a Lagrangian frame when spray model is required, using a unified predictor-corrector technique to account for the non-linear linkages through the convective contributions of VOF. The discontinuities within the sharp interface will be modeled as a volume force to avoid stiffness. Formations of droplets, tracking of droplet dynamics and modeling of the droplet breakup/evaporation, are handled through the same unified predictor-corrector procedure. Thus the new algorithm is non-iterative and is flexible for general geometries with arbitrarily complex topology in free surfaces. The FDNS finite-difference Navier-Stokes code is employed as the baseline of the current development. Benchmark test cases of shear coaxial LOX/H2 liquid jet with atomization/combustion and impinging jet test cases are investigated in the present work. Preliminary data comparisons show good qualitative agreement between data and the present analysis. It is indicative from these results that the present method has great potential to become a general engineering design analysis and diagnostics tool for problems involving spray combustion.

Chen, Yen-Sen; Shang, Huan-Min; Liaw, Paul; Wang, Ten-See

1996-01-01

50

Characterisation of charged hydrocarbon sprays for application in combustion systems  

NASA Astrophysics Data System (ADS)

Phase Doppler anemometry measurements and flow visualizations are used to measure the structures of electrostatically atomized hydrocarbon fuel sprays, produced by charge injection nozzles. Due to the jet and drop breakup mechanisms that occur for electrostatically charged insulating liquids, these sprays contain relatively large numbers of small drops which are repelled away from the spray core region where the radial electric field component is high. The largest drops remain near the spray centreline and a radial stratification of the average diameter occurs, which can be advantageous for flame stabilisation. Droplet size reduces with increasing specific charge for the spray. Higher values of specific charge are obtained for reduction of orifice diameter, optimum positioning of the nozzle electrode, and increasing liquid flow rate. On the basis of the measurements, descriptions are given of the physics of processes both inside the atomizer and in the spray and the importance of operating the atomizing nozzle at electrohydrodynamically supercritical conditions is described.

Shrimpton, J. S.; Yule, A. J.

51

Combustion of two-phase hydrocarbon fuel clouds released into the atmosphere  

Microsoft Academic Search

Numerical modeling of the evolution, behavior, and combustion of two-phase hydrocarbon clouds released into the open atmosphere is presented. A Eulerian-Lagrangian model for transient flows of fuel vapor–droplet mixtures is formulated taking into account heat, mass, and momentum exchange between the gaseous and dispersed phases, soot formation, and radiative heat transfer. The calculations are performed for releases of pressure-liquefied propane;

G. M. Makhviladze; J. P. Roberts; S. E. Yakush

1999-01-01

52

Combustion performance and heat transfer characterization of LOX/hydrocarbon type propellants. Task 3: Data dump  

NASA Technical Reports Server (NTRS)

A preliminary characterization of Orbital Maneuvering System (OMS) and Reaction Control System (RCS) engine point designs over a range of thrust and chamber pressure for several hydrocarbon fuels is reported. OMS and RCS engine point designs were established in two phases comprising baseline and parametric designs. Interface pressures, performance and operating parameters, combustion chamber cooling and turboprop requirements, component weights and envelopes, and propellant conditioning requirements for liquid to vapor phase engine operation are defined.

Hart, S. W.

1982-01-01

53

Chemical kinetic models for combustion of hydrocarbons and formation of nitric oxide  

NASA Technical Reports Server (NTRS)

The formation of nitrogen oxides NOx during combustion of methane, propane, and a jet fuel, JP-4, was investigated in a jet stirred combustor. The results of the experiments were interpreted using reaction models in which the nitric oxide (NO) forming reactions were coupled to the appropriate hydrocarbon combustion reaction mechanisms. Comparison between the experimental data and the model predictions reveals that the CH + N2 reaction process has a significant effect on NO formation especially in stoichiometric and fuel rich mixtures. Reaction models were assembled that predicted nitric oxide levels that were in reasonable agreement with the jet stirred combustor data and with data obtained from a high pressure (5.9 atm (0.6 MPa)), prevaporized, premixed, flame tube type combustor. The results also suggested that the behavior of hydrocarbon mixtures, like JP-4, may not be significantly different from that of pure hydrocarbons. Application of the propane combustion and nitric oxide formation model to the analysis of NOx emission data reported for various aircraft gas turbines showed the contribution of the various nitric oxide forming processes to the total NOx formed.

Jachimowski, C. J.; Wilson, C. H.

1980-01-01

54

Speciated hydrocarbon emissions from the combustion of single component fuels. 1. Effect of fuel structure  

SciTech Connect

Speciated hydrocarbon emissions data have been collected for six single-component fuels run in a laboratory pulse flame combustor (PFC). The six fuels include n-heptane, isoctane (2,2,4-trimethylpentane), cyclohexane, 1-hexene, toluene, and methyl-t-butyl ether. Combustion of non-aromatic fuels in the PFC produced low levels of unburned fuel and high yields of methane and olefins irrespective of the molecular structure of the fuel. In contrast, hydrocarbon emissions from toluene combustion in the PFC were comprised predominantly of unburned fuel. With the PFC, low levels of 1,3-butadiene were observed from all the fuels except MTBE, for which no measurable level was detected; low levels of benzene were observed from isooctane, heptane, and 1-hexene, but significant levels from cyclohexane and toluene. No measurable amount of benzene was observed in the MTBE exhaust. For isooctane and toluene the speciated hydrocarbon emissions from a spark-ignited (SI) single-cylinder engine were also determined. HC emissions from the Si engine contained the same species as observed from the PFC, although the relative composition was different. For the non-aromatic fuel isooctane, unburned fuel represented a larger fraction of the HC emissions when run in the engine. HC emissions from toluene combustion in the engine were smaller to those from the PFC.

Siegel, W.O.; McCabe, R.W.; Chun, W.; Kaiser, E.W.; Perry, J.; Henig, Y.I.; Trinker, F.H.; Anderson, R.W. (Ford Motor Company, Dearborn, MI (United States))

1992-07-01

55

Hydrocarbon-fuel/combustion-chamber-liner materials compatibility  

NASA Technical Reports Server (NTRS)

The results of dynamic tests using methane and NASA-Z copper test specimen under conditions that simulate those expected in the cooling channels of a regeneratively cooled LOX/hydrocarbon booster engine operating at chamber pressures up to 3000 psi are presented. Methane with less than 0.5 ppm sulfur contamination has little or no effect on cooling channel performance. At higher sulfur concentrations, severe corrosion of the NASA-Z copper alloy occurs and the cuprous sulfide Cu2S, thus formed impedes mass flow rate and heat transfer efficiency. Therefore, it is recommended that the methane specification for this end use set the allowable sulfur content at 0.5 ppm (max). Bulk high purity liquid methane that meets this low sulfur requirement is currently available from only one producer. Pricing, availability, and quality assurance are discussed in detail. Additionally, it was found that dilute sodium cyanide solutions effectively refurbish sulfur corroded cooling channels in only 2 to 5 minutes by completely dissolving all the Cu2S. Sulfur corroded/sodium cyanide refurbished channels are highly roughened and the increased surface roughness leads to significant improvements in heat transfer efficiency with an attendant loss in mass flow rate. Both the sulfur corrosion and refurbishment effects are discussed in detail.

Homer, G. David

1991-01-01

56

Characteristics and combustion of future hydrocarbon fuels. [aircraft fuels  

NASA Technical Reports Server (NTRS)

As the world supply of petroleum crude oil is being depleted, the supply of high-quality crude oil is also dwindling. This dwindling supply is beginning to manifest itself in the form of crude oils containing higher percentages of aromatic compounds, sulphur, nitrogen, and trace constituents. The result of this trend is described and the change in important crude oil characteristics, as related to aircraft fuels, is discussed. As available petroleum is further depleted, the use of synthetic crude oils (those derived from coal and oil shale) may be required. The principal properties of these syncrudes and the fuels that can be derived from them are described. In addition to the changes in the supply of crude oil, increasing competition for middle-distillate fuels may require that specifications be broadened in future fuels. The impact that the resultant potential changes in fuel properties may have on combustion and thermal stability characteristics is illustrated and discussed in terms of ignition, soot formation, carbon deposition flame radiation, and emissions.

Rudey, R. A.; Grobman, J. S.

1978-01-01

57

The chemistry of minerals obtained from the combustion of Jordanian oil shale  

E-print Network

The chemistry of minerals obtained from the combustion of Jordanian oil shale Awni Y. Al was performed on the spent oil shale (oil shale ash) obtained from the combustion of Jordanian oil shale process, minimal fragmentation was encountered since Jordanian oil shale contains large proportions of ash

Shawabkeh, Reyad A.

58

Stabilization of liquid hydrocarbon fuel combustion by using a programmable microwave discharge in a subsonic airflow  

NASA Astrophysics Data System (ADS)

Under conditions of a programmable discharge (a surface microwave discharge combined with a dc discharge), plasma-enhanced combustion of alcohol injected into a subsonic ( M = 0.3-0.9) airflow in the drop (spray) phase is stabilized. It is shown that the appearance of the discharge, its current-voltage characteristic, the emission spectrum, the total emission intensity, the heat flux, the electron density, the hydroxyl emission intensity, and the time dependences of the discharge current and especially discharge voltage change substantially during the transition from the airflow discharge to stabilized combustion of the liquid hydrocarbon fuel. After combustion stabilization, more than 80% of liquid alcohol can burn out, depending on the input power, and the flame temperature reaches ˜2000 K.

Kopyl, P. V.; Surkont, O. S.; Shibkov, V. M.; Shibkova, L. V.

2012-06-01

59

Stabilization of liquid hydrocarbon fuel combustion by using a programmable microwave discharge in a subsonic airflow  

SciTech Connect

Under conditions of a programmable discharge (a surface microwave discharge combined with a dc discharge), plasma-enhanced combustion of alcohol injected into a subsonic (M = 0.3-0.9) airflow in the drop (spray) phase is stabilized. It is shown that the appearance of the discharge, its current-voltage characteristic, the emission spectrum, the total emission intensity, the heat flux, the electron density, the hydroxyl emission intensity, and the time dependences of the discharge current and especially discharge voltage change substantially during the transition from the airflow discharge to stabilized combustion of the liquid hydrocarbon fuel. After combustion stabilization, more than 80% of liquid alcohol can burn out, depending on the input power, and the flame temperature reaches {approx}2000 K.

Kopyl, P. V.; Surkont, O. S.; Shibkov, V. M.; Shibkova, L. V. [Moscow State University, Faculty of Physics (Russian Federation)

2012-06-15

60

Intermediates in the Formation of Aromatics in Hydrocarbon Combustion  

NASA Technical Reports Server (NTRS)

The formation of the first benzene ring is believed to be the rate limiting step in soot formation. Two different mechanisms have been proposed for formation of cyclic C6 species. The first involves the reaction of two acetylenes to give CH2CHCCH (vinyl acetylene), the loss of a H to give CHCHCCH (n-C41-13) or CH2CCCH (iso-C4H3), and addition of another acetylene to n-C4H3, followed by ring closure to give phenyl radical. Miller and Melius argue that only n-C4H3 leads to phenyl radical and since iso-C4H3 is more stable than n-C4H3 this mechanism is unlikely. An alternative mechanism proposed by them is formation of benzene from the dimerization of two CH2CCH (propargyl) radicals (formed by the reaction of singlet methylene with C2H2). We report reaction pathways and accurate energetics (from CASSCF/internally contracted CI calculations) for the reactions of CH(pi-2) and CH2-1 with acetylene, the reaction of vinylidene with acetylene, and the reaction of n-C4H3 and iso-C4H3 with acetylene. These calculations identify two new reactive intermediates CHCHCH ( a A"-2 ground state in Cs symmetry; spin coupling is a doublet from three singly occupied orbitals) and CHCCH (B-3 ground state in C2 symmetry) from the reaction of CH with acetylene. These species dimerize with no barrier to form benzene and para-benzyne, respectively. CHCCH is proposed as a reactive intermediate which can add to benzene to give higher polynuclear aromatic hydrocarbons or fullerenes. The addition of a C3H2 unit releases two C-C bond energies and thus the resulting addition product contains sufficient energy to break several CH bonds leading to a reduction in the H to C ratio as the cluster size increases. It is found that iso-C4H3 adds to acetylene to initially give a fulvene radical but that this species rearranges to phenyl radical. Thus, the reaction of acetylene with iso-C4H3 does lead to phenyl radical and the cyclization pathway may also contribute to formation of the initial benzene ring.

Walch, Stephen P.; Langhoff, S. R. (Technical Monitor)

1994-01-01

61

Determination of Combustion Product Radicals in a Hydrocarbon Fueled Rocket Exhaust Plume  

NASA Technical Reports Server (NTRS)

The identification of metallic effluent materials in a rocket engine exhaust plume indicates the health of the engine. Since 1989, emission spectroscopy of the plume of the Space Shuttle Main Engine (SSME) has been used for ground testing at NASA's Stennis Space Center (SSC). This technique allows the identification and quantification of alloys from the metallic elements observed in the plume. With the prospect of hydrocarbon-fueled rocket engines, such as Rocket Propellant 1 (RP-1) or methane (CH4) fueled engines being considered for use in future space flight systems, the contributions of intermediate or final combustion products resulting from the hydrocarbon fuels are of great interest. The effect of several diatomic molecular radicals, such as Carbon Dioxide , Carbon Monoxide, Molecular Carbon, Methylene Radical, Cyanide or Cyano Radical, and Nitric Oxide, needs to be identified and the effects of their band systems on the spectral region from 300 nm to 850 nm determined. Hydrocarbon-fueled rocket engines will play a prominent role in future space exploration programs. Although hydrogen fuel provides for higher engine performance, hydrocarbon fuels are denser, safer to handle, and less costly. For hydrocarbon-fueled engines using RP-1 or CH4 , the plume is different from a hydrogen fueled engine due to the presence of several other species, such as CO2, C2, CO, CH, CN, and NO, in the exhaust plume, in addition to the standard H2O and OH. These species occur as intermediate or final combustion products or as a result of mixing of the hot plume with the atmosphere. Exhaust plume emission spectroscopy has emerged as a comprehensive non-intrusive sensing technology which can be applied to a wide variety of engine performance conditions with a high degree of sensitivity and specificity. Stennis Space Center researchers have been in the forefront of advancing experimental techniques and developing theoretical approaches in order to bring this technology to a more mature stage.

Langford, Lester A.; Allgood, Daniel C.; Junell, Justin C.

2007-01-01

62

Development and Validation of ReaxFF Reactive Force Field for Hydrocarbon Chemistry Catalyzed by Nickel  

E-print Network

Development and Validation of ReaxFF Reactive Force Field for Hydrocarbon Chemistry Catalyzed as a function of temperature and pressure, we have developed the ReaxFF reactive force field to describe surface. The ReaxFF parameters were determined by fitting to the geometries and energy surfaces from

Goddard III, William A.

63

BP Oil Spill and Air Chemistry Crude oil contains various hydrocarbons  

E-print Network

BP Oil Spill and Air Chemistry Crude oil contains various hydrocarbons NOAA and CIRES here at CU went to the oil spill in an aircraft that was equipped with instruments to measure the air quality. 1/3 of the oil dissolved into the water column (methane completely, benzene and ethane almost completely) Showed

Toohey, Darin W.

64

Hydrocarbons. Independent Learning Project for Advanced Chemistry (ILPAC). Unit O1.  

ERIC Educational Resources Information Center

This unit on hydrocarbons is one of 10 first year units produced by the Independent Learning Project for Advanced Chemistry (ILPAC). The unit is divided into sections dealing with alkanes, alkenes, alkynes, arenes, and several aspects of the petroleum industry. Two experiments, exercises (with answers), and pre- and post-tests are included.…

Inner London Education Authority (England).

65

Combustion  

NASA Technical Reports Server (NTRS)

An overview of the emissions related research being conducted as part of the Fundamental Aeronautics Subsonics Fixed Wing Project is presented. The overview includes project metrics, milestones, and descriptions of major research areas. The overview also includes information on some of the emissions research being conducted under NASA Research Announcements. Objective: Development of comprehensive detailed and reduced kinetic mechanisms of jet fuels for chemically-reacting flow modeling. Scientific Challenges: 1) Developing experimental facilities capable of handling higher hydrocarbons and providing benchmark combustion data. 2) Determining and understanding ignition and combustion characteristics, such as laminar flame speeds, extinction stretch rates, and autoignition delays, of jet fuels and hydrocarbons relevant to jet surrogates. 3) Developing comprehensive kinetic models for jet fuels.

Bulzan, Dan

2007-01-01

66

Combustion and atmospheric oxidation of hydrocarbons: Theoretical study of the methyl peroxyl self-reaction  

Microsoft Academic Search

Alkyl peroxyls form in the atmospheric oxidation of hydrocarbons and in their combustion. When NO concentration is low, they can appreciably react with themselves. This reaction has both propagation and termination channels. Multireference second-order perturbative energy calculations CAS(16,12)-PT2\\/6-311G(2df,p) have been carried out on the CAS(8,8)-MCSCF\\/6-311G(d,p) geometries pertaining to the reaction pathways explored. The tetroxide intermediate put forward first by Russell

Giovanni Ghigo; Andrea Maranzana; Glauco Tonachini

2003-01-01

67

Systematic Reduction of Combustion Reaction Mechanisms of common Hydrocarbons and Oxygenated Fuels  

NASA Astrophysics Data System (ADS)

The aim of this work is the development of a numerical technique for the reduction of reaction mechanisms of common hydrocarbon and oxygenated fuels, such as methane, ethylene, propane, methanol and ethanol, using steady-state and partial equilibrium assumptions. Numerical tests are carried to establish the basic chain for each fuel as well as to determine the amount of small products of combustion, whose concentration depends on the turbulent mixing and needs to be controlled due to environmental restrictions. The results are in agreement with data in the literature.

de Bortoli, A. L.; Vaz, F. A.; Lorenzzetti, G. S.; Martins, I.

2010-09-01

68

Emissions of Parent, Nitro, and Oxygenated Polycyclic Aromatic Hydrocarbons from Residential Wood Combustion in Rural China  

PubMed Central

Residential wood combustion is one of the important sources of air pollution in developing countries. Among the pollutants emitted, parent polycyclic aromatic hydrocarbons (pPAHs) and their derivatives, including nitrated and oxygenated PAHs (nPAHs and oPAHs), are of concern because of their mutagenic and carcinogenic effects. In order to evaluate their impacts on regional air quality and human health, emission inventories, based on realistic emission factors (EFs), are needed. In this study, the EFs of 28 pPAHs (EFPAH28), 9 nPAHs (EFPAHn9) and 4 oPAHs (EFPAHo4) were measured for residential combustion of 27 wood fuels in rural China. The measured EFPAH28, EFPAHn9, and EFPAHo4 for brushwood were 86.7±67.6, 3.22±1.95×10?2, and 5.56±4.32 mg/kg, which were significantly higher than 12.7±7.0, 8.27±5.51×10?3, and 1.19±1.87 mg/kg for fuel wood combustion (p < 0.05). Sixteen U.S. EPA priority pPAHs contributed approximately 95% of the total of the 28 pPAHs measured. EFs of pPAHs, nPAHs, and oPAHs were positively correlated with one another. Measured EFs varied obviously depending on fuel properties and combustion conditions. The EFs of pPAHs, nPAHs, and oPAHs were significantly correlated with modified combustion efficiency and fuel moisture. Nitro-naphthalene and 9-fluorenone were the most abundant nPAHs and oPAHs identified. Both nPAHs and oPAHs showed relatively high tendencies to be present in the particulate phase than pPAHs due to their lower vapor pressures. The gas-particle partitioning of freshly emitted pPAHs, nPAHs and oPAHs was primarily controlled by organic carbon absorption. PMID:22765266

SHEN, Guofeng; TAO, Shu; WEI, Siye; ZHANG, Yanyan; WANG, Rong; WANG, Bin; LI, Wei; SHEN, Huizhong; HUANG, Ye; CHEN, Yuanchen; CHEN, Han; YANG, Yifeng; WANG, Wei; WANG, Xilong; LIU, Wenxin; SIMONICH, Staci L. M.

2012-01-01

69

A role of hydrocarbon reaction for NO{sub x} formation and reduction in fuel-rich pulverized coal combustion  

SciTech Connect

We have investigated an index for modeling a NO{sub x} reaction mechanism of pulverized coal combustion. The reaction mechanism of coal nitrogen was examined by drop-tube furnace experiments under various burning conditions. We proposed the gas phase stoichiometric ratio (SRgas) as a key index to evaluate NO{sub x} concentration in fuel-rich flames. The SRgas was defined as: SRgas {identical_to} amount of fuel required for stoichiometry combustion/amount of gasified fuel where, the amount of gasified fuel was defined as the amount of fuel which had been released to the gas phase by pyrolysis, oxidation and gasification reactions. When SRgas < 1.0, NO{sub x} concentration was strongly influenced by the value of SRgas. In this condition, the NO{sub x} concentration was hardly influenced by coal type, particle diameter, or reaction time. We developed a model to analyze NO{sub x} and XN(HCN, NH{sub 3}) concentrations for pulverized coal/air combustion and coal/CO{sub 2}/O{sub 2} combustion, based on the index. NO{sub x} and XN concentrations did not reproduce the experimental results without considering reactions between hydrocarbons and NO{sub x}. The hydrocarbon reaction was important for both NO{sub x} and XN, especially for air combustion. In the present model, an empirical formula was used to estimate the total concentration of hydrocarbons in coal flame. The reaction of heavy hydrocarbons which had plural aromatic rings was very important to analyze the reaction mechanism of hydrocarbons for coal combustion in detail. When burning temperature and SRgas were the same, total hydrocarbon concentration in a coal flame was larger than that of a light gaseous hydrocarbon flame. Total hydrocarbon concentration in oxy-fuel combustion was lower than that in air combustion. We verified the proposed model by experimental results obtained for a drop-tube furnace and a laboratory-scale furnace that had an installed low-NO{sub x} burner. (author)

Taniguchi, Masayuki; Kamikawa, Yuki; Okazaki, Teruyuki; Yamamoto, Kenji; Orita, Hisayuki [Energy and Environmental Systems Laboratory, Hitachi, Ltd. Power Systems Company, 7-2-1 Omika-cho, Hitachi-shi, Ibaraki-ken 319-1292 (Japan)

2010-08-15

70

Combustion  

NSDL National Science Digital Library

In this chemistry activity, learners discover that the weight of the product of combustion is greater than that of the starting material. Learners will compare the weight of steel wool before and after it is heated. Learners are asked to consider why the steel wool weighs more (oxidation) as well as write the balanced chemical equation for the burning of steel. This activity uses an open flame; adult supervision is recommended. The resource includes notes for educators and extension ideas.

House, The S.

2014-01-28

71

ON UPGRADING THE NUMERICS IN COMBUSTION CHEMISTRY CODES. (R824970)  

EPA Science Inventory

A method of updating and reusing legacy FORTRAN codes for combustion simulations is presented using the DAEPACK software package. The procedure is demonstrated on two codes that come with the CHEMKIN-II package, CONP and SENKIN, for the constant-pressure batch reactor simulati...

72

A filtered tabulated chemistry model for LES of premixed combustion  

E-print Network

and the correct chemical structure when the flame wrinkling is completely resolved. The model is then extended analysis of the dynamic behavior of the chemical system response. Alterna- tive approaches are Flame that the chemical flame structure can be described in a reduced phase subspace from elemen- tary combustion

Paris-Sud XI, Université de

73

Emission of oxygenated polycyclic aromatic hydrocarbons from indoor solid fuel combustion.  

PubMed

Indoor solid fuel combustion is a dominant source of polycyclic aromatic hydrocarbons (PAHs) and oxygenated PAHs (OPAHs) and the latter are believed to be more toxic than the former. However, there is limited quantitative information on the emissions of OPAHs from solid fuel combustion. In this study, emission factors of OPAHs (EF(OPAH)) for nine commonly used crop residues and five coals burnt in typical residential stoves widely used in rural China were measured under simulated kitchen conditions. The total EF(OPAH) ranged from 2.8 ± 0.2 to 8.1 ± 2.2 mg/kg for tested crop residues and from 0.043 to 71 mg/kg for various coals and 9-fluorenone was the most abundant specie. The EF(OPAH) for indoor crop residue burning were 1-2 orders of magnitude higher than those from open burning, and they were affected by fuel properties and combustion conditions, like moisture and combustion efficiency. For both crop residues and coals, significantly positive correlations were found between EFs for the individual OPAHs and the parent PAHs. An oxygenation rate, R(o), was defined as the ratio of the EFs between the oxygenated and parent PAH species to describe the formation potential of OPAHs. For the studied OPAH/PAH pairs, mean R(o) values were 0.16-0.89 for crop residues and 0.03-0.25 for coals. R(o) for crop residues burned in the cooking stove were much higher than those for open burning and much lower than those in ambient air, indicating the influence of secondary formation of OPAH and loss of PAHs. In comparison with parent PAHs, OPAHs showed a higher tendency to be associated with particulate matter (PM), especially fine PM, and the dominate size ranges were 0.7-2.1 ?m for crop residues and high caking coals and <0.7 ?m for the tested low caking briquettes. PMID:21375317

Shen, Guofeng; Tao, Shu; Wang, Wei; Yang, Yifeng; Ding, Junnan; Xue, Miao; Min, Yujia; Zhu, Chen; Shen, Huizhong; Li, Wei; Wang, Bin; Wang, Rong; Wang, Wentao; Wang, Xilong; Russell, Armistead G

2011-04-15

74

Bioavailability and potential carcinogenicity of polycyclic aromatic hydrocarbons from wood combustion particulate matter in vitro.  

PubMed

Due to increasing energy demand and limited fossil fuels, renewable energy sources have gained in importance. Particulate matter (PM) in general, but also PM from the combustion of wood is known to exert adverse health effects in human. These are often related to specific toxic compounds adsorbed to the PM surface, such as polycyclic aromatic hydrocarbons (PAH), of which some are known human carcinogens. This study focused on the bioavailability of PAHs and on the tumor initiation potential of wood combustion PM, using the PAH CALUX® reporter gene assay and the BALB/c 3T3 cell transformation assay, respectively. For this, both cell assays were exposed to PM and their respective organic extracts from varying degrees of combustion. The PAH CALUX® experiments demonstrated a concentration-response relationship matching the PAHs detected in the samples. Contrary to expectations, PM samples from complete (CC) and incomplete combustion (IC) provided for a stronger and weaker response, respectively, suggesting that PAH were more readily bioavailable in PM from CC. These findings were corroborated via PAH spiking experiments indicating that IC PM contains organic components that strongly adsorb PAH thereby reducing their bioavailability. The results obtained with organic extracts in the cell transformation assay presented the highest potential for carcinogenicity in samples with high PAH contents, albeit PM from CC also demonstrated a carcinogenic potential. In conclusion, the in vitro assays employed emphasize that CC produces PM with low PAH content however with a general higher bioavailability and thus with a nearly similar carcinogenic potential than IC PM. PMID:23796820

Gauggel-Lewandowski, Susanne; Heussner, Alexandra H; Steinberg, Pablo; Pieterse, Bart; van der Burg, Bart; Dietrich, Daniel R

2013-11-25

75

Recovery of resins and hydrocarbons by in situ combustion of resinous coals. Part VII: in situ gasification  

Microsoft Academic Search

A liquid resin and a hydrocarbon gas may be recovered from impermeable resinous coals by contact of the coal with steam at 550 to 800°F and 200 to 14,000 lb\\/sq in gage. A porous carbonaceous residue is left, suitable for combustion in situ.

E. M. Craighead; H. Purre

1959-01-01

76

Standard test method for heat of combustion of hydrocarbon fuels by bomb calorimeter (high-precision method)  

SciTech Connect

This method covers the determination of the heat of combustion of hydrocarbon fuels. It is designed specifically for use with aviation turbine fuels when the permissible difference between duplicate determinations is of the order of 0.1%. It can be used for a wide range of volatile and nonvolatile materials where slightly greater differences in precision can be tolerated. The heat of combustion is determined by burning a weighed sample in an oxygen-bomb calorimeter under controlled conditions. The temperature is measured by means of a platinum resistance thermometer. The heat of combustion is calculated from temperature observations before, during, and after combustion, with proper allowance for thermochemical and heat-transfer corrections. Either isothermal or adiabatic calorimeters may be used. The heat of combustion is a measure of the energy available from a fuel. A knowledge of this value is essential when considering the thermal efficiency of equipment for producing either power or heat.

Not Available

1980-01-01

77

Simulations of a turbulent non-premixed flame using combined dimension reduction and tabulation for combustion chemistry  

E-print Network

for combustion chemistry Zhuyin Ren a, , Graham M. Goldin b , Varun Hiremath c , Stephen B. Pope c a Department chemistry in simulations. " We demonstrate a method for accelerating chemistry calculations in CFD. " We flows. a r t i c l e i n f o Article history: Received 7 July 2012 Received in revised form 9 August

78

Regulated and speciated hydrocarbon emissions from a catalyst equipped internal combustion engine  

NASA Astrophysics Data System (ADS)

In the present work, the effect of engine operating conditions on its exhaust emissions and on catalytic converter operation is studied. A 4-cylinder OPEL 1.6 l internal combustion engine equipped with a hydraulic brake dynamometer was used in all the experiments. For exhaust emissions treatment a typical three-way catalyst was used. The highest hydrocarbon and carbon monoxide engine-out emissions were observed at engine power 2-4 HP. These emissions were decreased as the engine power was increased up to 20 HP. Among the various compounds detected in exhaust emissions, the following ones were monitored at engine and catalyst outlet: methane, hexane, ethylene, acetaldehyde, acetone, benzene, toluene and acetic acid. The concentration of each compound in the catalytic converter effluent was in the range 45-132, 5-12, 10-125, 15-22, 3-7, 3-12, 2-9, 0-6 ppm, respectively. After the required temperature for catalyst operation had been achieved, carbon monoxide tailpipe emissions were dramatically decreased and the observed hydrocarbon conversions were also high. Methane was the most resistant compound to oxidation while ethylene was the most degradable compound over the catalyst. The order from the easiest to the most resistant to oxidation compound was: Alkene>Aromatic>Aldehyde>Ketone>Alkane.

Poulopoulos, S. G.; Samaras, D. P.; Philippopoulos, C. J.

79

Characterization of polycyclic aromatic hydrocarbon particulate and gaseous emissions from polystyrene combustion  

SciTech Connect

The partitioning of polycyclic aromatic hydrocarbons (PAHs) between the particulate and gaseous phases resulting from the combustion of polystyrene was studied. A vertical tubular flow furnace was used to incinerate polystyrene spheres at different combustion temperatures to determine the effect of temperature and polystyrene feed size on the particulate and gaseous emissions and their chemical composition. The furnace reactor exhaust was sampled using real-time instruments (differential mobility particle sizer and/or optical particle counter) to determine the particle size distribution. For chemical composition analyses, the particles were either collected on Teflon filters or split into eight size fractions using a cascade impactor with filter media substrates, while the gaseous products were collected on XAD-2 adsorbent. Gas chromatography/mass spectroscopy was used to identify and quantify the specific PAH species, their partitioning between the gas and particulate phases, and their distribution as a function of emission particle size. The total mass and number of PAH species in both the particulate and gas phases were found to decrease with increasing incineration temperature and decreasing polystyrene feed size, while the mean diameter of the particles increases with increasing incineration temperature and decreasing feed size. In addition, the PAH species in the particulate phase were found to be concentrated in the smaller aerosol sizes.

Durlak, S.K.; Biswas, P. [Univ. of Cincinnati, OH (United States)] [Univ. of Cincinnati, OH (United States); Shi, J.; Bernhard, M.J. [Procter and Gamble, Cincinnati, OH (United States). Environmental Science Dept.] [Procter and Gamble, Cincinnati, OH (United States). Environmental Science Dept.

1998-08-01

80

Thermodynamic and transport combustion properties of hydrocarbons with air. Part 1: Properties in SI units  

NASA Technical Reports Server (NTRS)

Thermodynamic and transport combustion properties were calculated for a wide range of conditions for the reaction of hydrocarbons with air. Three hydrogen-carbon atom ratios (H/C = 1.7, 2.0, 2.1) were selected to represent the range of aircraft fuels. For each of these H/C ratios, combustion properties were calculated for the following conditions: Equivalence ratio: 0, 0.25, 0.5, 0.75, 1.0, 1.25 Water - dry air mass ratio: 0, 0.03 Pressure, kPa: 1.01325, 10.1325, 101.325, 1013.25, 5066.25 (or in atm: 0.01, 0.1, 1, 10, 50) Temperature, K: every 10 degrees from 200 to 900 K; every 50 degrees from 900 to 3000 K Temperature, R: every 20 degrees from 360 to 1600 R; very 100 degrees from 1600 to 5400 R. The properties presented are composition, density, molecular weight, enthalphy, entropy, specific heat at constant pressure, volume derivatives, isentropic exponent, velocity of sound, viscosity, thermal conductivity, and Prandtl number. Property tables are based on composites that were calculated by assuming both: (1) chemical equilibrium (for both homogeneous and heterogeneous phases) and (2) constant compositions for all temperatures. Properties in SI units are presented in this report for the Kelvin temperature schedules.

Gordon, S.

1982-01-01

81

Polycyclic aromatic hydrocarbon emission from straw burning and the influence of combustion parameters  

NASA Astrophysics Data System (ADS)

A simulated burning experiment was conducted in a tubular furnace system to examine the emission of polycyclic aromatic hydrocarbons (PAHs) from the burning of rice and bean straw, and the influence of combustion parameters was investigated. Total emission amounts of 16 PAHs (?PAHs) from the burning of rice and bean straw ranged from 9.29 to 23.6 ?g g -1 and from 3.13 to 49.9 ?g g -1, respectively, which increased with the increase of temperatures from 200 to 700 °C. The contribution of combustion to individual PAH yields was about 80.6-100%, which was generally increased with the increase of burning temperature. Moisture content in straw had a negative effect on PAH formation, especially on PAHs with low molecular weight. ?PAHs emission amounts decreased by 78.2% for bean straw with a moisture content of 30% in comparison with that for dried straw. In addition, PAH emission amounts increased with the increase of O 2 content in supplied air and then decreased, which showed a maximum emission at O 2 content of 40%. The source fingerprint of PAHs in emission from straw burning was established, which showed that naphthalene accounted for 35.0 ± 7.4% of ?PAHs. Based on the experimental data, emission amounts of ?PAHs from the burning of rice and bean straw were estimated to be 320-357 and 32.5-76.0 tons to ambient air per year in China, respectively.

Lu, Hao; Zhu, Lizhong; Zhu, Nali

82

On the Radiolysis of Ethylene Ices by Energetic Electrons and Implications to the Extraterrestrial Hydrocarbon Chemistry  

NASA Astrophysics Data System (ADS)

The chemical processing of ethylene ices (C2H4) by energetic electrons was investigated at 11 K to simulate the energy transfer processes and synthesis of new molecules induced by secondary electrons generated in the track of galactic cosmic ray particles. A combination of Fourier transform infrared spectrometry (solid state) and quadrupole mass spectrometry (gas phase) resulted in the identification of six hydrocarbon molecules: methane (CH4), the C2 species acetylene (C2H2), ethane (C2H6), the ethyl radical (C2H5), and—for the very first time in ethylene irradiation experiments—the C4 hydrocarbons 1-butene (C4H8) and n-butane (C4H10). By tracing the temporal evolution of the newly formed molecules spectroscopically online and in situ, we were also able to fit the kinetic profiles with a system of coupled differential equations, eventually providing mechanistic information, reaction pathways, and rate constants on the radiolysis of ethylene ices and the inherent formation of smaller (C1) and more complex (C2, C4) hydrocarbons involving carbon-hydrogen bond ruptures, atomic hydrogen addition processes, and radical-radical recombination pathways. We also discuss the implications of these results on the hydrocarbon chemistry on Titan's surface and on ice-coated, methane-bearing interstellar grains as present in cold molecular clouds such as TMC-1.

Zhou, Li; Maity, Surajit; Abplanalp, Matt; Turner, Andrew; Kaiser, Ralf I.

2014-07-01

83

Distribution of polycyclic aromatic hydrocarbons in fly ash during coal and residual char combustion in a pressurized fluidized bed  

SciTech Connect

To investigate the distribution of polycyclic aromatic hydrocarbons (PAHs) in fly ash, the combustion of coal and residual char was performed in a pressurized spouted fluidized bed. After Soxhlet extraction and Kuderna-Danish (K-D) concentration, the contents of 16 PAHs recommended by the United States Environmental Protection Agency (U.S. EPA) in coal, residual char, and fly ash were analyzed by a high-performance liquid chromatography (HPLC) coupled with fluorescence and diode array detection. The experimental results show that the combustion efficiency is lower and the carbon content in fly ash is higher during coal pressurized combustion, compared to the residual char pressurized combustion at the pressure of 0.3 MPa. Under the same pressure, the PAH amounts in fly ash produced from residual char combustion are lower than that in fly ash produced from coal combustion. The total PAHs in fly ash produced from coal and residual char combustion are dominated by three- and four-ring PAHs. The amounts of PAHs in fly ash produced from residual char combustion increase and then decrease with the increase of pressure in a fluidized bed. 21 refs., 1 fig., 4 tabs.

Hongcang Zhou; Baosheng Jin; Rui Xiao; Zhaoping Zhong; Yaji Huang [Nanjing University of Information Science and Technology, Nanjing (China)

2009-04-15

84

Nitro Polycyclic Aromatic Hydrocarbons in Particulate Matter Emitted by the Combustion of Diesel and Biodiesel  

NASA Astrophysics Data System (ADS)

The rapid population growth in large urban areas, has resulted in a precipitous increase in the consumption of fossil fuels, mainly by the transport sector, diesel vehicles are a significant source of air pollution by particulate matter emissions, damaging the population health, because of the size and composition of these particles, as they may contain carcinogenic organic compounds such as polycyclic aromatic hydrocarbons and their derivatives, nitro-PAH. This study focused on analysis of nitro-PAH contained in particles emitted from diesel engines fuelled with biodiesel blends (B5, B10 and B16.67) to different driving cycles (rpm and torque), and to compare their concentrations with emissions from current diesel. A diesel truck engine was used in the laboratory for collect particulate mass emitted directly from the exhaust. Mass of particles and nitro-PAH were determined by gas chromatography-mass spectrometry using negative chemical ionization. No reduction was observed in the particles mass per second by using biodiesel relative to diesel (p > 0.1). Seven nitro-PAH were observed in samples: 1-nitronaphthalene, 2-nitronaphthalene, 9-nitroanthracene, 3-nitrophenanthrene, 1,8-dinitronaphthalene, 1-nitropyrene and 1,6-dinitropyrene. 1-nitropyrene showed the highest mass concentration in diesel and in all blends of biodiesel, followed by 3-nitrophenanthrene. Emissions reduction in biodiesel combustion with respect to diesel combustion were observed for 1-nitropyrene: 50 %, in all blends (B5, B10 and B16.67) and for 3-nitrophenanthrene: 55 % in B5, 72 % in B10 and 64 % in B16.67.

Valle-Hernández, B. L.; Amador-Muñoz, O.; Jazcilevich, A. D.; Santos-Medina, G. L.; Hernández-Lopéz, E.; Villalobos-Pietrini, R.

2013-05-01

85

Small-Scale Abundance Variations in TMC-1: Dynamics and Hydrocarbon Chemistry  

NASA Astrophysics Data System (ADS)

We present high spectral resolution observations of eighteen molecules, including high-quality maps of CCS and HC7N in TMC-1, using NASA's Deep Space Network 70 m antenna to study the interaction between cloud dynamics and chemistry. Other molecules shown in our study are C18O, NH3, CS, C3S, C3H2, H2C3, H2C4, H2C6, HC3N, HC5N, DC5N, HC9N, C4H, C5H, C6H, and a successful detection of the rare C8H molecule. In addition, we have searched for and set meaningful abundance limits on several carbon chain and ring molecules such as C7H, H2C5, c-H2C5, and biogenic molecules such as pyrrole and glycine. All the species observed in TMC-1 show large spectral-line variations in both intensity and shape over extremely small scales (~0.03 pc). Maps of CCS and HC7N display abundance ratio variations of 3-5 along individual lines of sight. The high degree of clumpiness, transient nature of clumps, and gas-phase enrichment adequately explain the ``early-time'' chemistry and the molecular complexity in TMC-1. This enrichment has interesting implications for hydrocarbon chemistry in TMC-1, and presumably other clumpy, dark clouds. Specifically, the large number of clumps at various stages of early-time chemical evolution increases the chances for detection of complex hydrocarbons, since the probability of observing a clump at the time of peak abundance for a given molecular species is increased. We suggest two mechanisms for explaining the small-scale variations: (1) the passage of MHD waves in a clumpy medium and (2) grain impacts during clump-clump collisions. In the quiescent region far from any protostar, the MHD activity can be generated locally by clump collisions. The passage of MHD waves helps maintain early-time chemistry in the clumps. Both mechanisms provide enough energy to raise grain temperatures from 10 K to Tcrit~30 K, sufficient to cause reactive radical explosions in grain mantles and thermal desorption. In this manner, the mantle injection causes TMC-1 to exhibit some aspects of ``hot-core'' chemistry, as seen in more massive star-forming regions. The transient nature of the clumps and the mantle-driven chemistry make TMC-1 a good target for future searches of complex molecular species.

Dickens, J. E.; Langer, W. D.; Velusamy, T.

2001-09-01

86

Organo-sulfur chemistry in dense interstellar clouds via S(+)-hydrocarbon reactions  

NASA Astrophysics Data System (ADS)

Because S+ is predicted via current model calculations to be an abundant ion in dense interstellar clouds, it might be expected to play a role in the synthesis of organo-sulfur compounds via ion-molecule reactions. In particular, the newly observed interstellar molecule CCS is probably formed via a reaction sequence initiated by the reaction between S+ and acetylene (C2H2) to produce the organo-sulfur ion HC2S+ and H. Calculations based on models of dense interstellar clouds show that the abundance of CCS achieved via this synthesis may be only a factor of 6 - 7 below observation in TMC-1. In order to assess the importance of S+-hydrocarbon reactions in the chemistry of dense interstellar clouds, the authors have measured a variety of these reactions. In general, the results show that S+-hydrocarbon reactions sometimes exhibit a sulfur-insertion channel leading to organo-sulfur ionic species but that other channels, especially charge exchange, tend to dominate for the larger and more saturated hydrocarbons studied.

Smith, D.; Adams, N. G.; Giles, K.; Herbst, E.

1988-07-01

87

Combustion performance and heat transfer characterization of LOX/hydrocarbon type propellants  

NASA Technical Reports Server (NTRS)

An evaluation liquid oxygen (LOX) and various hydrocarbon fuels as low cost alternative propellants suitable for future space transportation system applications was done. The emphasis was directed toward low earth orbit maneuvering engine and reaction control engine systems. The feasibility of regeneratively cooling an orbit maneuvering thruster was analytically determined over a range of operating conditions from 100 to 1000 psia chamber pressure and 1000 to 10,000-1bF thrust, and specific design points were analyzed in detail for propane, methane, RP-1, ammonia, and ethanol; similar design point studies were performed for a film-cooled reaction control thruster. Heat transfer characteristics of propane were experimentally evaluated in heated tube tests. Forced convection heat transfer coefficients were determined. Seventy-seven hot firing tests were conducted with LOX/propane and LOX/ethanol, for a total duration of nearly 1400 seconds, using both heat sink and water-cooled calorimetric chambers. Combustion performance and stability and gas-side heat transfer characteristics were evaluated.

Michel, R. W.

1983-01-01

88

A Combustion Chemistry Analysis of Carbonate Solvents in Li-Ion Batteries  

SciTech Connect

Under abusive conditions Li-ion batteries can rupture, ejecting electrolyte and other flammable gases. In this paper we consider some of the thermochemical properties of these gases that will determine whether they ignite and how energetically they burn. We show that flames of carbonate solvents are fundamentally less energetic than those of conventional hydrocarbons. An example of this difference is given using a recently developed mechanism for dimethyl carbonate (DMC) combustion, where we show that a diffusion flame burning DMC has only half the peak energy release rate of an analogous propane flame. We find a significant variation among the carbonate solvents in the factors that are important to determining flammability, such as combustion enthalpy and vaporization enthalpy. This result suggests that thermochemical and kinetic factors might well be considered when choosing solvent mixtures.

Harris, S J; Timmons, A; Pitz, W J

2008-11-13

89

Carbon deposition model for oxygen-hydrocarbon combustion. Task 6: Data analysis and formulation of an empirical model  

NASA Technical Reports Server (NTRS)

The formation and deposition of carbon (soot) was studied in the Carbon Deposition Model for Oxygen-Hydrocarbon Combustion Program. An empirical, 1-D model for predicting soot formation and deposition in LO2/hydrocarbon gas generators/preburners was derived. The experimental data required to anchor the model were identified and a test program to obtain the data was defined. In support of the model development, cold flow mixing experiments using a high injection density injector were performed. The purpose of this investigation was to advance the state-of-the-art in LO2/hydrocarbon gas generator design by developing a reliable engineering model of gas generator operation. The model was formulated to account for the influences of fluid dynamics, chemical kinetics, and gas generator hardware design on soot formation and deposition.

Makel, Darby B.; Rosenberg, Sanders D.

1990-01-01

90

DNA ADDUCTS AS BIOMARKERS FOR ASSESSING EXPOSURE TO POLYCYCLIC AROMATIC HYDROCARBONS IN TISSUES FROM XUAN WEI WOMEN WITH HIGH EXPOSURE TO COAL COMBUSTION  

EPA Science Inventory

The high lung cancer raze in Xuan Wei, China, is associated with smoky coal use in unvented homes. moky coal combustion emits higher levels of polycyclic aromatic hydrocarbons (PAH) than wood combustion. his study used DNA adducts as a biomarker for human exposure to PAH from com...

91

Formation of soot from polycyclic aromatic hydrocarbons as well as fullerenes and carbon nanotubes in the combustion of hydrocarbon  

Microsoft Academic Search

  The eightieth anniversary of Academician, Lenin Prize Winner Rem Ivanovich Soloukhin is an important event for the scientific\\u000a association of investigators of combustion and detonation processes. R. I. Soloukhin has developed original gasdynamic laser\\u000a systems based on the selective thermal excitation and mixing in a supersonic flow: efficient high-power gas-flow lasers of\\u000a convective type with electric excitation and chemical lasers

Z. A. Mansurov

2011-01-01

92

Analysis of pyrolysis products from light hydrocarbons and kinetic modeling for growth of polycyclic aromatic hydrocarbons with detailed chemistry  

Microsoft Academic Search

Alternative chemical reaction pathways leading to polycyclic aromatic hydrocarbons (PAHs) in the pyrolysis of unsaturated light hydrocarbons were investigated to extend the previously proposed chemical kinetic model [K. Norinaga, O. Deutschmann, Ind. Eng. Chem. Res. 46 (2007) 3547–3557]. Although the previous model provided a reasonably good description of the pyrolysis behaviors observed in flow reactor experiments at 1073–1373K, the concentration

Koyo Norinaga; Olaf Deutschmann; Naomichi Saegusa; Jun-ichiro Hayashi

2009-01-01

93

Numerical investigation of a helicopter combustion chamber using LES and tabulated chemistry  

NASA Astrophysics Data System (ADS)

This article presents Large Eddy Simulations (LES) of a realistic aeronautical combustor device: the chamber CTA1 designed by TURBOMECA. Under nominal operating conditions, experiments show hot spots observed on the combustor walls, in the vicinity of the injectors. These high temperature regions disappear when modifying the fuel stream equivalence ratio. In order to account for detailed chemistry effects within LES, the numerical simulation uses the recently developed turbulent combustion model F-TACLES (Filtered TAbulated Chemistry for LES). The principle of this model is first to generate a lookup table where thermochemical variables are computed from a set of filtered laminar unstrained premixed flamelets. To model the interactions between the flame and the turbulence at the subgrid scale, a flame wrinkling analytical model is introduced and the Filtered Density Function (FDF) of the mixture fraction is modeled by a ? function. Filtered thermochemical quantities are stored as a function of three coordinates: the filtered progress variable, the filtered mixture fraction and the mixture fraction subgrid scale variance. The chemical lookup table is then coupled with the LES using a mathematical formalism that ensures an accurate prediction of the flame dynamics. The numerical simulation of the CTA1 chamber with the F-TACLES turbulent combustion model reproduces fairly the temperature fields observed in experiments. In particular the influence of the fuel stream equivalence ratio on the flame position is well captured.

Auzillon, Pierre; Riber, Eléonore; Gicquel, Laurent Y. M.; Gicquel, Olivier; Darabiha, Nasser; Veynante, Denis; Fiorina, Benoît

2013-01-01

94

Combustion of butanol isomers - A detailed molecular beam mass spectrometry investigation of their flame chemistry  

SciTech Connect

The combustion chemistry of the four butanol isomers, 1-, 2-, iso- and tert-butanol was studied in flat, premixed, laminar low-pressure (40 mbar) flames of the respective alcohols. Fuel-rich ({phi} = 1.7) butanol-oxygen-(25%)argon flames were investigated using different molecular beam mass spectrometry (MBMS) techniques. Quantitative mole fraction profiles are reported as a function of burner distance. In total, 57 chemical compounds, including radical and isomeric species, have been unambiguously assigned and detected quantitatively in each flame using a combination of vacuum ultraviolet (VUV) photoionization (PI) and electron ionization (EI) MBMS. Synchrotron-based PI-MBMS allowed to separate isomeric combustion intermediates according to their different ionization thresholds. Complementary measurements in the same flames with a high mass-resolution EI-MBMS system provided the exact elementary composition of the involved species. Resulting mole fraction profiles from both instruments are generally in good quantitative agreement. In these flames of the four butanol isomers, temperature, measured by laser-induced fluorescence (LIF) of seeded nitric oxide, and major species profiles are strikingly similar, indicating seemingly analog global combustion behavior. However, significant variations in the intermediate species pool are observed between the fuels and discussed with respect to fuel-specific destruction pathways. As a consequence, different, fuel-specific pollutant emissions may be expected, by both their chemical nature and concentrations. The results reported here are the first of their kind from premixed isomeric butanol flames and are thought to be valuable for improving existing kinetic combustion models. (author)

Osswald, Patrick; Gueldenberg, Hanna; Kohse-Hoeinghaus, Katharina [Department of Chemistry, Bielefeld University (Germany); Yang, Bin [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui (China); Department of Aerospace and Mechanical Engineering, University of Southern California, Los Angeles, CA (United States); Yuan, Tao; Qi, Fei [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui (China)

2011-01-15

95

Dynamic study of coupled heavy hydrocarbon pyrolysis and combustion. N. Gascoina*  

E-print Network

Hypersonic flight over Mach 5 should be achieved with Supersonic Combustion Ramjet. The regenerative cooling and Technology 184, 12 (2012) 2136-2153" DOI : 10.1080/00102202.2012.703729 #12;2/28 1. Introduction Hypersonic, 2010). The thermal management of the overall vehicle and more specifically of the combustion chamber

Boyer, Edmond

96

Combustion performance and heat transfer characterization of LOX/hydrocarbon type propellants, volume 2  

NASA Technical Reports Server (NTRS)

A data base which relates candidate design variables, such as injector type, acoustic cavity configuration, chamber length, fuel film-cooling, etc., to operational characteristics such as combustion efficiency, combustion stability, carbon deposition, and chamber gas-side heat flux was generated.

Schoenman, L.

1983-01-01

97

Reduction of light hydrocarbon combustion mechanisms and speciation study of industrial flares through computational fluid dynamics (CFD) methods  

NASA Astrophysics Data System (ADS)

Industrial ethylene flares are considered to be a probable major source of Volatile Organic Compounds (VOCs) such as formaldehyde. Due to the difficulty and cost of field measurements, currently on-line monitoring is not practical and other methods must be employed. Current methodologies for calculating speciated and total VOC emissions from flaring activities generally apply a simple mass reduction to the VOC species sent to the flare that does not consider the production of incomplete combustion or other intermediates. There arises a need of a speciation study for the inspection of these flares for their emissions. However, most of the detailed kinetic mechanisms for the speciation study of flaring events are too complex, and consist of large numbers of reactions and species, and also are computationally expensive. Thus a reduced mechanism will be desirable for improving computational efficiency. In this dissertation, a 50-species reduced mechanism for simulating ethylene flaring, namely LU1.0, is presented. Then, a 50-species mechanism for C 1-C3 hydrocarbons was developed through exhaustive search. These two algorithms were developed by reducing a detailed mechanism of 93 species and 600 reactions. The reduced mechanisms were validated successfully against literature results of various key performance indicators: laminar flame speeds, adiabatic flame temperature, ignition delay tests and burner stabilized flame. It is demonstrated that simulation results using this reduced mechanism are in good agreement with reported experimental results. This dissertation also presents a novel Run Time Combustion Zoning (RTCZ) technique based on the working principle of Eddy Dissipation Concept (EDC) for combustion modeling. This technique selectively chooses cells in which the full reaction mechanism needs to be solved. The selection criterion is based on the concept of differentiating between combustion and the non-combustion zone. With this approach, considerable reduction in computational load and stability of the solution was observed and even the number of iterations required to achieve a stable solution was significantly reduced.

Vaid, Hitesh S.

98

Simulations of a turbulent non-premixed flame using combined dimensionreduction and tabulation for combustion chemistry  

Microsoft Academic Search

The use of large chemical mechanisms of hydrocarbon fuels in turbulent\\u000d\\u000a\\u0009flame simulations is computationally expensive due to the large number\\u000d\\u000a\\u0009of chemical species and the wide range of chemical time scales involved.\\u000d\\u000a\\u0009The reduced description of reactive flows in combination with chemistry\\u000d\\u000a\\u0009tabulation can effectively reduce the simulation time when detailed\\u000d\\u000a\\u0009chemical kinetics is employed in multi-dimensional Computational\\u000d\\u000a\\u0009Fluid

Zhuyin Ren; Graham M. Goldin; Varun Hiremath; Stephen B. Pope

2012-01-01

99

Fundamental and Semi-Global Kinetic Mechanisms for Hydrocarbon Combustion. Final Report, March 1977-October 1980.  

National Technical Information Service (NTIS)

Over the past three and one half years, substantial research efforts of the Princeton Fuels Research Group have been directed towards the development of simplified mechanisms which would accurately describe the oxidation of hydrocarbons fuels. The objecti...

F. L. Dryer, I. Glassman, K. Brezinsky

1981-01-01

100

Chemistry in the Center for Catalytic Hydrocarbon Functionalization: An Energy Frontier Research Center  

E-print Network

such as hydrocarbons, dioxygen, water, carbon dioxide and dihydrogen are central to new technologies for the use new methods to rearrange the bonds of hydrocarbons, activate and transform water and carbon dioxide. Keywords Carbon dioxide Á Catalysis Á Energy Á Fuel cell Á Functionalization Á Hydrocarbon Á Methane Á

Goddard III, William A.

101

Effect of Hydrocarbon Emissions from PCCI-type Combustion on the Performance of Selective Catalytic Reduction Catalysts  

SciTech Connect

Core samples cut from full size commercial Fe- and Cu-zeolite selective catalytic reduction catalysts were exposed to a slipstream of raw engine exhaust from a 1.9-liter 4-cylinder diesel engine operating in conventional and premixed charge compression ignition (PCCI) combustion modes. Subsequently, the NO{sub x} reduction performance of the exposed catalysts was evaluated on a laboratory bench-reactor fed with simulated exhaust. The Fe-zeolite NO{sub x} conversion efficiency was significantly degraded, especially at low temperatures (<250 C), after the catalyst was exposed to the engine exhaust. The degradation of the Fe-zeolite performance was similar for both combustion modes. The Cu-zeolite was much more resistant to hydrocarbon (HC) fouling than the Fe-zeolite catalyst. In the case of the Cu-zeolite, PCCI exhaust had a more significant impact than the exhaust from conventional combustion on the NO{sub x} conversion efficiency. For all cases, the clean catalyst performance was recovered after heating to 600 C. Gas chromatography mass spectrometry analysis of the HCs adsorbed to the catalyst surface provided insights into the observed NO{sub x} reduction performance trends.

Prikhodko, Vitaly Y [ORNL; Pihl, Josh A [ORNL; Lewis Sr, Samuel Arthur [ORNL; Parks, II, James E [ORNL

2012-01-01

102

An experimental and numerical investigation on hydrogen-hydrocarbon composite fuel combustion  

Microsoft Academic Search

An experimental and numerical study on the combustion characteristics of turbulent diffusion flames of natural gas-hydrogen composite fuel is presented. Three mixtures (90--10%, 80--20% and 65--35% by volume) of natural gas and hydrogen were used. The results are compared with the combustion characteristics of a pure natural gas flame. The following parameters were measured: (i) flame stability (blowout velocity, and

Ahsan Reza Choudhuri

2000-01-01

103

Analysis of pollutant chemistry in combustion by in situ pulsed photoacoustic laser diagnostics  

NASA Astrophysics Data System (ADS)

A technique for gas analysis based on pulsed-laser-induced photoacoustic spectroscopy in the UV and the visible is presented. The laser-based technique and the associated analysis probe have been developed for the analysis of pollutant chemistry in fluidized beds and other combustion environments with limited or no optical access. The photoacoustic-absorption spectrum of the analyzed gas is measured in a test cell located at the end of a tubular probe. This test cell is subject to the prevailing temperature and pressure in the combustion process. The instrument response has been calibrated for N2O, NO, NO2, NH3, SO2, and H2 S at atmospheric pressure between 20 and 910 deg C. The response of the probe was found to increase with pressure for N2O, NO, NH 3, and NO2 up to 1.2 MPa pressure. The method and the probe have been used for detection and ranging of gas concentrations in a premixed methane flame. Some preliminary tests in a large 12-MW circulating bed boiler have also been done.

Stenberg, Jari; Hernberg, Rolf; Vattulainen, Juha

1995-12-01

104

Theoretical performance analysis of a constant velocity MHD generator for combustion products of hydrocarbon and air  

Microsoft Academic Search

Calculations are performed along a constant velocity, dc, MHD generator utilizing stoichiometric products of hydrocarbon and air. The gas is assumed to be in thermal equilibrium and representable by a Boltzman distribution so that the degree of ionization can be determined by means of the Saha equation. Variations in pressure, temperature, gaseous electrical conductivity, density, entropy, enthalpy, number density, degree

Blecher

1961-01-01

105

Sampling and analysis of hydrocarbons in combustion gases. Quarterly report, October-December 1980  

Microsoft Academic Search

The purpose of these studies is to develop a methodology for the chemical analysis of ultratrace levels of polycyclic organic compounds in the flue gases from fluidized-bed combustors. Extant methodology in the literature for the chemical analysis of polycyclic aromatic hydrocarbons (PAHs) present in stack emissions at ultratrace levels is described and critically evaluated. In the measurement of organic matter

I. Johnson; K. M. Myles; A. A. Siczek; D. C. Fee

1981-01-01

106

Supersonic combustion and mixing characteristics of hydrocarbon fuels in screamjet engines  

NASA Astrophysics Data System (ADS)

The combustion characteristics of gaseous propane in supersonic airflow using the rearward-facing step that is swept inward from both end sides is studied. The effect of sweeping the step on the flow field features of propane combustion is investigated. The study of the supersonic combustion of ethylene is carried out using different combustor configurations, different main fuel equivalence ratios, and different pilot fuel equivalence ratios. The swept step shows the ability to hold the propane flame in the supersonic air stream without extinction. It was found that the side sweeping of the combustor exhibits the high temperature and combustion products concentration in the far field domain while the area downstream of the normal injection location characterizes lower temperature and products concentration. It is recommended to optimize the combustor length to ensure the complete combustion and consequently the full liberation of the chemical energy stored in the fuel before the fuel exits the combustor. The main findings from the ethylene study can be summarized in the following points. The step configuration with no pilot injection can afford the flame holding mechanism in the supersonic air stream by creating the flow recirculations in the step base area and featuring permanent high temperature regions surrounding the normal fuel injection. The step configuration showed good mixing capabilities in the far field domain. The wedge configuration proved superiority over the generic rearward-facing step configuration in holding the ethylene flame in the supersonic airstreams, producing overall higher temperature medium throughout the combustor, and exhibiting lower flow losses and higher combustor efficiency. The increase in the equivalence ratio of the ethylene normal fuel injection enhances the general flow field features and energy field characteristics in the combustor except in the step base area where the lower equivalence ratio features better temperature distribution and higher combustion efficiency. Although the wedge with no pilot injection configuration presents the highest level of temperature distribution in the cavity and downstream regions, the 0.02-pilot equivalence ratio increases the temperature of the upstream face of the normal injection and enhances the flame holding mechanism. The 0.02-pilot equivalence ratio presented the optimum pilot injection case that can promote the flame holding mechanism and keep good combustion and flow field qualities. While further increase of the pilot injection equivalence ratio quenches the high temperature gases in the cavity region, which leads to the deficiency in the flame holding mechanism, the excessive pilot fuel injection shows its positive effect by increasing the average flow field static temperature and absolute pressure in the far field domain. (Abstract shortened by UMI.)

Taha, Ahmed Aly

107

Formation of Combustible Hydrocarbons and H2 during Photocatalytic Decomposition of Various Organic Compounds under Aerated and Deaerated Conditions.  

PubMed

A possibility of photocatalytic production of useful aliphatic hydrocarbons and H2 from various organic compounds, including acetic acid, methanol, ethanol and glucose, over Fe-modified TiO2 is discussed. In particular, the influence of the reaction atmosphere (N2, air) was investigated. Different gases were identified in the headspace volume of the reactor depending on the substrate. In general, the evolution of the gases was more effective in air compared to a N2 atmosphere. In the presence of air, the gaseous phase contained CO2, CH4 and H2, regardless of the substrate used. Moreover, formation of C2H6 and C3H8 in the case of acetic acid and C2H6 in the case of ethanol was observed. In case of acetic acid and methanol an increase in H2 evolution under aerated conditions was observed. It was concluded that the photocatalytic decomposition of organic compounds with simultaneous generation of combustible hydrocarbons and hydrogen could be a promising method of "green energy" production. PMID:25432013

Mozia, Sylwia; Ku?agowska, Aleksandra; Morawski, Antoni W

2014-01-01

108

Dispersion modeling of polycyclic aromatic hydrocarbons from combustion of biomass and fossil fuels and production of coke in Tianjin, China.  

PubMed

A USEPA, procedure, ISCLT3 (Industrial Source Complex Long-Term), was applied to model the spatial distribution of polycyclic aromatic hydrocarbons (PAHs) emitted from various sources including coal, petroleum, natural gas, and biomass into the atmosphere of Tianjin, China. Benzo[a]pyrene equivalent concentrations (BaPeq) were calculated for risk assessment. Model results were provisionally validated for concentrations and profiles based on the observed data at two monitoring stations. The dominant emission sources in the area were domestic coal combustion, coke production, and biomass burning. Mainly because of the difference in the emission heights, the contributions of various sources to the average concentrations at receptors differ from proportions emitted. The shares of domestic coal increased from approximately 43% at the sources to 56% at the receptors, while the contributions of coking industry decreased from approximately 23% at the sources to 7% at the receptors. The spatial distributions of gaseous and particulate PAHs were similar, with higher concentrations occurring within urban districts because of domestic coal combustion. With relatively smaller contributions, the other minor sources had limited influences on the overall spatial distribution. The calculated average BaPeq value in air was 2.54 +/- 2.87 ng/m3 on an annual basis. Although only 2.3% of the area in Tianjin exceeded the national standard of 10 ng/m3, 41% of the entire population lives within this area. PMID:16913110

Tao, Shu; Li, Xinrong; Yang, Yu; Coveney, Raymond M; Lu, Xiaoxia; Chen, Haitao; Shen, Weiran

2006-08-01

109

The effect of thermal radiation and radiation models on hydrogen–hydrocarbon combustion modelling  

Microsoft Academic Search

This paper presents numerical simulation results from the modelling of a turbulent non-premixed hydrogen (H2) and hydrogen–hydrocarbon flame with and without radiation models. CFD studies using Fluent code were carried out for three cases; without radiation model, with the P-1 radiation model and with the discrete transfer radiation model. The model results from these three cases are compared with each

Mustafa Ilbas

2005-01-01

110

Polycyclic aromatic hydrocarbon and particulate emissions from two-stage combustion of polystyrene: the effect of the primary furnace temperature.  

PubMed

A study is presented on laboratory-scale combustion of polystyrene (PS) to identify staged-combustion conditions that minimize emissions. Batch combustion of shredded PS was conducted in fixed beds placed in a bench-scale electrically heated horizontal muffle furnace. In most cases, combustion of the samples occurred by forming gaseous diffusion flames in atmospheric pressure air. The combustion effluent was mixed with additional air, and it was channeled to a second muffle furnace (afterburner) placed in series. Further reactions took place in the secondary furnace at a residence time of 0.7 s. The gas temperature of the primary furnace was varied in the range of 500-1,000 degrees C, while that of the secondary furnace was kept fixed at 1,000 degrees C. Sampling for CO, CO2, O2, soot, and unburned hydrocarbon emissions (volatile and semivolatile, by GC-MS) was performed at the exits of the two furnaces. Results showed that the temperature of the primary furnace, where PS gasifies, is of paramount importance to the formation and subsequent emissions of organic species and soot. Atthe lowesttemperatures explored, mostly styrene oligomers were identified at the outlet of the primary furnace, but they did not survive the treatment in the secondary furnace. The formation and emission of polycyclic aromatic hydrocarbons (PAH) and soot were suppressed. As the temperature in the first furnace was raised, increasing amounts of a wide range of both unsubstituted and substituted PAH containing up to at least seven condensed aromatic rings were detected. A similar trend was observed for total particulate yields. The secondary furnace treatment reduced the yields of total PAH, but it had an ambiguous effect on individual species. While most low molecular mass PAH were reduced in the secondary furnace, concentrations of some larger PAH increased under certain conditions. Thus, care in the selection of operating conditions of both the primary furnace (gasifier/ burner) and the secondary furnace (afterburner) must be exercised to minimize the emission of hazardous pollutants. The emissions of soot were also reduced in the afterburner but not drastically. This indicates that soot is indeed resistant to oxidation; thus, it would be best to avoid its formation in the first place. An oxidative pyrolysis temperature of PS in the vicinity of 600 degrees C appears to accomplish exactly that. An additional afterburner treatment at a sufficiently high temperature (1,000 degrees C) may be a suitable setting for minimization of most pollutants. To obtain deeper understanding of chemical processes, the experimental results were qualitatively compared with preliminary predictions of a detailed kinetic model that describes formation and destruction pathways of chemical species including most PAH observed in the present work. The modeling was performed forthe secondary furnace assuming plug-flow conditions therein. The experimentally determined chemical composition at the outlet of the primary furnace was part of the input parameters of the model calculation. PMID:11563660

Wang, J; Levendis, Y A; Richter, H; Howard, J B; Carlson, J

2001-09-01

111

Chemistry of internal combustion engine deposits. I. Microanalysis, thermogravimetric analysis, and infrared spectroscopy  

SciTech Connect

The deposits examined in this study were generated by six-cylinder engines employing various unleaded fuel and lube combinations. The entire deposit mass (piston top and head area of all cylinders) was combined; while obvious artifacts such as paint and bristles from brushes were removed, ferromagnetic impurities were not. Elemental analysis was performed by Galbraith Laboratories (Knoxville, TN) using the techniques indicated: carbon and hydrogen (Pragel), nitrogen (Dumas), oxygen (LECO), and inorganics (wet chemistry/atomic absorption). The weight of the sample as a function of time was determined using a Dupont 951 thermogravimetric analyzer interfaced to a Dupont 990 thermal analyzer. Typical sample sizes were 20 mg, and temperatures between ambient and 1000/sup 0/C were recorded with a chromel/alumel thermocouple. Infrared spectra of deposits were run in pellet form (about 1 mg in KBr) on a Digilab FTS-14. The analyses show that combustion chamber deposits are volatile carbonaceous materials, having more in common with bituminous coals than with graphite. A unifying trait among the deposits is the presence of approximately 25 wt % oxygen, which is distributed among a variety of chemical functionalities, including -OH, C=O, and C-O. Chemical titration of these deposits is difficult.

Ebert, L.B.; Davis, W.H. Jr.; Mills, D.R.; Dennerlein, J.D.

1981-03-01

112

HYDROCARBON AND OXIDANT CHEMISTRY OBSERVED AT A SITE NEAR ST. LOUIS  

EPA Science Inventory

Integrated quantitative gas chromatographic measurements of the nearly one hundred individual hydrocarbons present in ambient air were made to deternime the total non-methane organic burden at a midwest rural site in coordination with halocarbon, oxidant and local meteorological ...

113

Comprehensive Mechanisms for Combustion Chemistry: An Experimental and Numerical Study with Emphasis on Applied Sensitivity Analysis  

SciTech Connect

This project was an integrated experimental/numerical effort to study pyrolysis and oxidation reactions and mechanisms for small-molecule hydrocarbon structures under conditions representative of combustion environments. The experimental aspects of the work were conducted in large-diameter flow reactors, at 0.3 to 18 atm pressure, 500 to 1100 K temperature, and 10-2 to 2 seconds reaction time. Experiments were also conducted to determine reference laminar flame speeds using a premixed laminar stagnation flame experiment and particle image velocimetry, as well as pressurized bomb experiments. Flow reactor data for oxidation experiments include: (1)adiabatic/isothermal species time-histories of a reaction under fixed initial pressure, temperature, and composition; to determine the species present after a fixed reaction time, initial pressure; (2)species distributions with varying initial reaction temperature; (3)perturbations of a well-defined reaction systems (e.g. CO/H2/O2 or H2/O2)by the addition of small amounts of an additive species. Radical scavenging techniques are applied to determine unimolecular decomposition rates from pyrolysis experiments. Laminar flame speed measurements are determined as a function of equivalence ratio, dilution, and unburned gas temperature at 1 atm pressure. Hierarchical, comprehensive mechanistic construction methods were applied to develop detailed kinetic mechanisms which describe the measurements and literature kinetic data. Modeling using well-defined and validated mechanisms for the CO/H2/Oxidant systems and perturbations of oxidation experiments by small amounts of additives were also used to derive absolute reaction rates and to investigate the compatibility of published elementary kinetic and thermochemical information. Numerical tools were developed and applied to assess the importance of individual elementary reactions to the predictive performance of the developed mechanisms and to assess the uncertainties in elementary rate constant evaluations.

Dryer, Frederick L.

2009-04-10

114

Sampling and analysis of hydrocarbons in combustion gases. Annual report, October 1979-September 1980  

SciTech Connect

The purpose of these studies is to develop a method for the chemical analysis of ultratrace levels of polycyclic organic compounds in the flue gases from fluidized-bed combustors. Methods which have the potential for real time analysis have been studied. Two methods, double mass spectrometry and laser ionization mass spectrometry, appear to be promising. A brief review of current analytical methods has been made. A brief examination of fly ash from fluidized-bed combustion revealed no carcinogenic species although samples collected during fluidized-bed combustor startup were found to be mutagenic.

Johnson, I.; Myles, K.M.; Siczek, A.A.

1981-04-01

115

Combustion efficiency and altitude operational limits of three liquid hydrocarbon fuels having high volumetric energy content in a J33 single combustor  

NASA Technical Reports Server (NTRS)

Combustion efficiency and altitude operational limits were determined in a J33 single combustor for AN-F-58 fuel and three liquid hydrocarbon fuels having high volumetric energy content (decalin, tetralin, and monomethylnaphthalene) at simulated altitude and combustor inlet-air conditions. At the conditions investigated, the combustion efficiency for the four fuels generally decreased with an increase in volumetric energy content. The altitude operational limits for decalin and tetralin fuels were higher than for AN-F-58 fuel; monomethylnaphthalene fuel gave the lowest altitude operational limit.

Stricker, Edward G

1950-01-01

116

Structural characteristics of polycyclic aromatic hydrocarbon isomers in coal tars and combustion products  

SciTech Connect

Isomeric polycyclic aromatic hydrocarbons (PAH) with two to six rings in coal-derived products and in a carbon black were separated, identified, and quantified by using capillary column gas chromatography and gas chromatography-mass spectrometry. A newly synthesized smectic liquid-crystalline polysiloxane and a conventional polymethylsiloxane were utilized as stationary phases. Many previously difficult to separate isomeric PAH (i.e., methylphenanthrenes/methylanthracenes, triphenylene/chrysene, methylchrysenes, benzofluoranthenes, and pentaphene/benzo(b)chrysene) were identified). The relative abundances of the PAH in these samples were compared and correlated to the reaction conditions during their production. The relationship between abundance and structure for the identified PAH was also discussed. 26 references, 5 figures, 1 table.

Nishioka, M.; Chang, H.C.; Lee, M.L.

1986-10-01

117

Radiocarbon apportionment of fossil versus biofuel combustion sources of polycyclic aromatic hydrocarbons in the Stockholm metropolitan area.  

PubMed

Source-diagnostic markers and the isotopic composition of polycyclic aromatic hydrocarbons (PAHs) were examined in surface sediments from the greater Stockholm waterways to deduce the contribution from biomass sources to the environmental PAH load. The summed concentration of 20 PAHs ranged from 0.8 to 45.1 microg/g (dry weight) and exhibited a steep decline with increasing distance from the city center evidencing that sources within the metropolitan area of Stockholm dominate its PAH burden. Several diagnostic PAH ratios indicated an overwhelming predominance of pyrogenic sources over the petrogenic ones, while retene and 1,7-dimethylphenanthrene were unable to correctly evaluate the contribution from biomass combustion. The stable carbon isotope composition (delta13C) of individual PAHs ranged from -24.8 to -27.0% but also was proved inefficient to discriminate between different types of fuels due to the overlapping signals in various sources. The delta14C values of PAHs ranged between -550.4 and -934.1%, indicating a clear predominance of fossil fuel sources. By using an isotopic mass balance approach, we estimated that on average 17+/-9% of PAHs derived from biomass combustion. This radiocarbon apportionment, in conjunction with detailed energy statistics for the Stockholm region, revealed that the ambient PAH burden is roughly similar, per unit energy produced, from fossil fuels and biofuels. Societies' shifting energy policies toward a larger reliance on biofuels may thus not lead to further deterioration of air quality and respiratory ailments for the urban population. PMID:15543735

Mandalakis, Manolis; Gustafsson, Orjan; Reddy, Christopher M; Xu, Li

2004-10-15

118

Influence of combustion parameters on the formation of polychlorinated dibenzo-p-dioxins, dibenzofurans, benzenes, and biphenyls and polyaromatic hydrocarbons in a pilot incinerator  

Microsoft Academic Search

A laboratory-scale fluidized-bed incinerator was used to study the influence of several combustion parameters with respect to the emission of important aromatic contaminants including polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), polychlorinated benzenes (PCBz), polyaromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs). The parameters studied include bed temperature, O[sub 2]-concentration, variations in HCl and H[sub 2]O, and temperature and residence time in

Ingrid Faengmark; Bert van Bavel; Stellan Marklund; C. Rappe; B. Stroemberg; N. Berge

1993-01-01

119

Emissions of parent, nitrated, and oxygenated polycyclic aromatic hydrocarbons from indoor corn straw burning in normal and controlled combustion conditions.  

PubMed

Emission factors (EFs) of parent polycyclic aromatic hydrocarbons (pPAHs), nitrated PAHs (nPAHs), and oxygenated PAHs (oPAHs) were measured for indoor corn straw burned in a brick cooking stove under different burning conditions. The EFs of total 28 pPAHs, 6 nPAHs and 4 oPAHs were (7.9 +/- 3.4), (6.5 +/- 1.6) x 10(-3), and (6.1 +/- 1.4) x 10(-1) mg/kg, respectively. Fuel charge size had insignificant influence on the pollutant emissions. Measured EFs increased significantly in a fast burning due to the oxygen deficient atmosphere formed in the stove chamber. In both restricted and enhanced air supply conditions, the EFs of pPAHs, nPAHs and oPAHs were significantly higher than those measured in normal burning conditions. Though EFs varied among different burning conditions, the composition profiles and calculated isomer ratios were similar, without significant differences. The results from the stepwise regression model showed that fuel burning rate, air supply amount, and modified combustion efficiency were the three most significant influencing factors, explaining 72%-85% of the total variations. PMID:24494494

Shen, Guofeng; Xue, Miao; Wei, Siye; Chen, Yuanchen; Wang, Bin; Wang, Rong; Lv, Yan; Shen, Huizhong; Li, Wei; Zhang, Yanyan; Huang, Ye; Chen, Han; Wei, Wen; Zhao, Qiuyue; Li, Bing; Wu, Haisuo; Tao, Shu

2013-10-01

120

Combustion rate limits of hydrogen plus hydrocarbon fuel: Air diffusion flames from an opposed jet burner technique  

NASA Technical Reports Server (NTRS)

Combustion of H2/hydrocarbon (HC) fuel mixtures may be considered in certain volume-limited supersonic airbreathing propulsion applications. Effects of HC addition to H2 were evaluated, using a recent argon-bathed, coaxial, tubular opposed jet burner (OJB) technique to measure the extinction limits of counterflow diffusion flames. The OJB flames were formed by a laminar jet of (N2 and/or HC)-diluted H2 mixture opposed by a similar jet of air at ambient conditions. The OJB data, derived from respective binary mixtures of H2 and methane, ethylene, or propane HCs, were used to characterize BLOWOFF and RESTORE. BLOWOFF is a sudden breaking of the dish-shaped OJB flame to a stable torus or ring shape, and RESTORE marks sudden restoration of the central flame by radial inward flame propagation. BLOWOFF is a measure of kinetically-limited flame reactivity/speed under highly stretched, but relatively ideal impingement flow conditions. RESTORE measures inward radial flame propagation rate, which is sensitive to ignition processes in the cool central core. It is concluded that relatively small molar amounts of added HC greatly reduce the reactivity characteristics of counterflow hydrogen-air diffusion flames, for ambient initial conditions.

Pellett, Gerald L.; Guerra, Rosemary; Wilson, Lloyd G.; Reeves, Ronald N.; Northam, G. Burton

1987-01-01

121

Symposium (International) on Combustion, 19th, Technion Israel Institute of Technology, Haifa, Israel, August 8-13, 1982, Proceedings  

NASA Technical Reports Server (NTRS)

Topics discussed are related to elementary reactions, reaction mechanisms and modeling, laminar flames, flame chemistry, turbulent reacting shear flows, turbulent premixed flames, turbulent combustion measurements, continuous combustors, detonation, detonation and explosion, heterogeneous detonation, propellant combustion, fire-ignition and thermal degradation, fire-flame spread and burning, fire-modeling, spray combustion, and droplet combustion. Coal combustion kinetics and mechanisms are considered along with coal combustion mechanisms and pyrolysis, coal combustion techniques, NOx in coal combustion, gaseous pollutants, soot and PAH, soot and inorganic pollutants, I.C. engine combustion, and ignition and extinction. Attention is given to intricate paths and simple steps in chemical kinetics and combustion, the formation of polycyclic aromatic hydrocarbons by combustion, turbulent flame structure and speed in spark ignition engines, and unresolved problems in SOx, NOx, and soot control in combustion.

1982-01-01

122

Combustion performance and heat transfer characterization of LOX/hydrocarbon type propellants, volume 1  

NASA Technical Reports Server (NTRS)

A program to evaluate liquid oxygen and various hydrocarbon fuel as low cost alternative propellants suitable for future space transportation system applications is discussed. The emphasis of the program is directed toward low earth orbit maneuvering engine and reaction control engine systems. The feasibility of regeneratively cooling an orbit maneuvering thruster was analytically determined over a range of operating conditions from 100 to 1000 psia chamber pressure and 1000 to 10,000-1bF thrust, and specific design points were analyzed in detail for propane, methane, RP-1, ammonia, and ethanol; similar design point studies were performed for a filmcooled reaction control thruster. Heat transfer characteristics of propate were experimentally evaluated in heated tube tests. Forced convection heat transfer coefficients were determined over the range of fluid conditions encompassed by 450 to 1800 psia, -250 to +250 F, and 50 to 150 ft/sec, with wall temperatures from ambient to 1200 F. Seventy-seven hot firing tests were conducted with LOX/propane and LOC/ethanol, for a total duration of nearly 1400 seconds, using both heat sink and water-cooled calorimetric chambers.

Michel, R. W.

1983-01-01

123

Effect of fuel nitrogen and hydrogen content on emissions in hydrocarbon combustion  

NASA Technical Reports Server (NTRS)

How the emissions of nitrogen oxides and carbon monoxide are affected by: (1) the decreased hydrogen content and (2) the increased organic nitrogen content of coal derived fuels is investigated. Previous CRT experimental work in a two stage flame tube has shown the effectiveness of rich lean two stage combustion in reducing fuel nitrogen conversion to nitrogen oxides. Previous theoretical work gave preliminary indications that emissions trends from the flame tube experiment could be predicted by a two stage, well stirred reactor combustor model using a detailed chemical mechanism for propane oxidation and nitrogen oxide formation. Additional computations are reported and comparisons with experimental results for two additional fuels and a wide range of operating conditions are given. Fuels used in the modeling are pure propane, a propane toluene mixture and pure toluene. These give hydrogen contents 18, 11 and 9 percent by weight, respectively. Fuel bound nitrogen contents of 0.5 and 1.0 percent were used. Results are presented for oxides of nitrogen and also carbon monoxide concentrations as a function of primary equivalence ratio, hydrogen content and fuel bound nitrogen content.

Bittker, D. A.; Wolfbrandt, G.

1981-01-01

124

An investigation on polycyclic aromatic hydrocarbon emissions from pulverized coal combustion systems  

PubMed

Results from a series of tests conducted to study the emission of polynuclear or polycyclic aromatic hydrocarbons (PAHs) from bench-scale and small industrial, water-tube boiler are discussed. A Middle Kittanning, and Upper Freeport seam coals were used in the study. Samples were extracted from the reactor outlet and from the inlet and outlet sides of the research boiler's (RB) baghouse using EPA promulgated methods.Only acenaphthene and fluoranthene were detected in down-fired combustor (DFC) samples. In addition to these two, naphthalene was detected in the RB samples. Emission factors ranged from 80 to 320 &mgr;g/kg of fuel fired. Although there were minor trends in the emissions' data, given the reproducibility limits for PAH compounds, no significant differences were found in the emissions with respect to the fuel type or form (pulverized coal (PC) vs. coal-water slurry fuel (CWSF), and raw vs. cleaned coal) and firing conditions (high and low excess air). The PAH emissions showed a decrease with increase in the firing rate.A bench-scale drop-tube reactor (DTR) was used to study the effects of temperature and residence time on PAH formation. The results revealed near constant PAH concentrations in the solid-phase samples, while the PAH concentrations in the vapor-phase samples increased as a function of temperature. At a temperature of around 1300 degrees C, the rate of PAH formation was exceeded by the rate of PAH oxidation, and PAH concentrations in the vapor phase began to decrease. PMID:10781720

Pisupati; Wasco; Scaroni

2000-05-29

125

A Complete Understanding of Hydrocarbon Chemistry in Titan's Atmosphere: from C-1 to C-3  

NASA Astrophysics Data System (ADS)

Propene (C3H6) has been missing from detection in Titan’s stratosphere for nearly 30 years until recently it is unveiled by the Composite Infrared Spectrometer (CIRS) onboard Cassini spacecraft (Nixon et al., 2013). A one-dimensional photochemical model of Titan with an updated eddy diffusion profile (Li. et al., 2014) is used to study its vertical profile. We find that the stratospheric mixing ratio of propene peaks at 100 km with a value of 3×10^(-9), which is in good agreement with the Cassini observation. Another important species that is missing from the hydrocarbon family in Titan’s stratosphere is allene (CH2CCH2), which is an isomer of propyne. Based on the photochemical model, we provide the evidence that its abundance is on the margin of detection limit. We suggest further effort in detecting allene, which will complete the family of C-3 hydrocarbons.

Li, Cheng; Zhang, Xi; Yung, Yuk L.

2014-11-01

126

Improved Recovery Boiler Performance Through Control of Combustion, Sulfur, and Alkali Chemistry  

SciTech Connect

This project involved the following objectives: 1. Determine black liquor drying and devolatilization elemental and total mass release rates and yields. 2. Develop a public domain physical/chemical kinetic model of black liquor drop combustion, including new information on drying and devolatilization. 3. Determine mechanisms and rates of sulfur scavenging in recover boilers. 4. Develop non-ideal, public-domain thermochemistry models for alkali salts appropriate for recovery boilers 5. Develop data and a one-dimensional model of a char bed in a recovery boiler. 6. Implement all of the above in comprehensive combustion code and validate effects on boiler performance. 7. Perform gasification modeling in support of INEL and commercial customers. The major accomplishments of this project corresponding to these objectives are as follows: 1. Original data for black liquor and biomass data demonstrate dependencies of particle reactions on particle size, liquor type, gas temperature, and gas composition. A comprehensive particle submodel and corresponding data developed during this project predicts particle drying (including both free and chemisorbed moisture), devolatilization, heterogeneous char oxidation, char-smelt reactions, and smelt oxidation. Data and model predictions agree, without adjustment of parameters, within their respective errors. The work performed under these tasks substantially exceeded the original objectives. 2. A separate model for sulfur scavenging and fume formation in a recovery boiler demonstrated strong dependence on both in-boiler mixing and chemistry. In particular, accurate fume particle size predictions, as determined from both laboratory and field measurements, depend on gas mixing effects in the boilers that lead to substantial particle agglomeration. Sulfur scavenging was quantitatively predicted while particle size required one empirical mixing factor to match data. 3. Condensed-phase thermochemistry algorithms were developed for salt mixtures and compared with sodium-based binary and higher order systems. Predictions and measurements were demonstrated for both salt systems and for some more complex silicate-bearing systems, substantially exceeding the original scope of this work. 4. A multi-dimensional model of char bed reactivity developed under this project demonstrated that essentially all reactions in char beds occur on or near the surface, with the internal portions of the bed being essentially inert. The model predicted composition, temperature, and velocity profiles in the bed and showed that air jet penetration is limited to the immediate vicinity of the char bed, with minimal impact on most of the bed. The modeling efforts substantially exceeded the original scope of this project. 5. Near the completion of this project, DOE withdrew the BYU portion of a multiparty agreement to complete this and additional work with no advanced warning, which compromised the integration of all of this material into a commercial computer code. However, substantial computer simulations of much of this work were initiated, but not completed. 6. The gasification modeling is nearly completed but was aborted near its completion according to a DOE redirection of funds. This affected both this and the previous tasks.

Baxter, Larry L.

2008-06-09

127

Polar sunrise experiment 1995: hydrocarbon measurements and tropospheric Cl and Br-atoms chemistry  

Microsoft Academic Search

As part of the Polar Sunrise Experiments (PSE) 1995, we report our results on measurement of non-methane hydrocarbons (NMHC) collected at Alert, Northwest Territories, Canada (82.5° N, 62.3° W) from Julian days 57 to 113, 1995 along with our data on continuous methane and ozone measurements during the same period. The concentration of NMHCs such as alkanes correlated well with

Parisa A. Ariya; Hiromi Niki; Geoffrey W. Harris; Kurt G. Anlauf; Douglas E. J. Worthy

1999-01-01

128

Rate constants for the homogeneous gas-phase Al/HCl combustion chemistry  

E-print Network

, *, Laurent Catoireb , Benjamin Legrandc , Iskender Go¨kalpc , Claude Paillardb a Department of Chemical most chemical kinetics experiments have been conducted at much lower pressures. The aims of this work). Combustion and Flame 132 (2003) 91­101 0010-2180/03/$ ­ see front matter © 2003 The Combustion Institute. All

Swihart, Mark T.

129

Determination of the Heat of Combustion of Biodiesel Using Bomb Calorimetry: A Multidisciplinary Undergraduate Chemistry Experiment  

ERIC Educational Resources Information Center

Biodiesel was synthesized by transesterification of waste vegetable oil using common glassware and reagents, and characterized by measuring heat of combustion, cloud point, density and measuring the heat of combustion and density together allows the student the energy density of the fuel. Analyzing the biodiesel can serve as a challenging and…

Akers, Stephen M.; Conkle, Jeremy L.; Thomas, Stephanie N.; Rider, Keith B.

2006-01-01

130

Molecular dynamics study of shock-induced chemistry in small condensed-phase hydrocarbons  

Microsoft Academic Search

Molecular dynamics simulations using an empirical bond order potential have been performed to investigate shock-induced chemistry in solid acetylene, ethylene, and methane. Acetylene was found to undergo significant polymerization reactions for flyer plate impact speeds above 10 km\\/s. These conditions are similar to those which would be experienced upon planetary impact of comets, which are known to contain condensed-phase acetylene.

M. L. Elert; S. V. Zybin; C. T. White

2003-01-01

131

Extended Lagrangian quantum molecular dynamics simulations of shock-induced chemistry in hydrocarbons  

SciTech Connect

A set of interatomic potentials for hydrocarbons that are based upon the self-consistent charge transfer tight-binding approximation to density functional theory have been developed and implemented into the quantum molecular dynamics code ''LATTE''. The interatomic potentials exhibit an outstanding level of transferability and have been applied in molecular dynamics simulations of tert-butylacetylene under thermodynamic conditions that correspond to its single-shock Hugoniot. We have achieved precise conservation of the total energy during microcanonical molecular dynamics trajectories under incomplete convergence via the extended Lagrangian Born-Oppenheimer molecular dynamics formalism. In good agreement with the results of a series of flyer-plate impact experiments, our SCC-TB molecular dynamics simulations show that tert-butylactylene molecules polymerize at shock pressures around 6.1 GPa.

Sanville, Edward J [Los Alamos National Laboratory; Bock, Nicolas [Los Alamos National Laboratory; Challacombe, William M [Los Alamos National Laboratory; Cawkwell, Marc J [Los Alamos National Laboratory; Niklasson, Anders M N [Los Alamos National Laboratory; Dattelbaum, Dana M [Los Alamos National Laboratory; Sheffield, Stephen [Los Alamos National Laboratory; Sewell, Thomas D [UNIV OF MISSOURI

2010-01-01

132

Experimental investigation of the atmospheric chemistry of aromatic hydrocarbons and long-chain alkanes. Final report  

SciTech Connect

The interaction of volatile organic compounds (VOCs) and oxides of nitrogen in the presence of sunlight leads to the formation of ozone and other manifestations of photochemical air pollution. There are, however, significant uncertainties in our knowledge of the products and mechanisms of the atmospheric reactions of alkanes and aromatic hydrocarbons, important constituents of ambient air in urban areas, with the hydroxyl (OH) radical. A series of product studies of the OH radical-initiated reactions of selected alkanes, ketones and alcohols have been carried out to obtain further insights into alkoxy radical isomerization. Product studies of the OH radical reaction with 4-methyl-2-pentanone, 2,6-dimethyl-4-heptanone, 2,4-dimethyl-2-pentanol and 3,5-dimethyl-3-hexanol in the presence of NOx have provided unambiguous evidence for alkoxy radical isomerization and these studies have provided rate constant ratios for the isomerization reaction versus alkoxy radical decomposition and reaction with O2.

Atkinson, R.; Arey, J.; Tuazon, E.C.; Aschmann, S.M.; Bridier, I.

1994-08-01

133

Linking molecular level chemistry to macroscopic combustion behavior for nano-energetic materials with halogen containing oxides  

NASA Astrophysics Data System (ADS)

Coupling molecular scale reaction kinetics with macroscopic combustion behavior is critical to understanding the influences of intermediate chemistry on energy propagation, yet bridging this multi-scale gap is challenging. This study integrates ab initio quantum chemical calculations and condensed phase density functional theory to elucidate factors contributing to experimentally measured high flame speeds (i.e., >900 m/s) associated with halogen based energetic composites, such as aluminum (Al) and iodine pentoxide (I2O5). Experiments show a direct correlation between apparent activation energy and flame speed suggesting that flame speed is directly influenced by chemical kinetics. Toward this end, the first principle simulations resolve key exothermic surface and intermediate chemistries contributing toward the kinetics that promote high flame speeds. Linking molecular level exothermicity to macroscopic experimental investigations provides insight into the unique role of the alumina oxide shell passivating aluminum particles. In the case of Al reacting with I2O5, the alumina shell promotes exothermic surface chemistries that reduce activation energy and increase flame speed. This finding is in contrast to Al reaction with metal oxides that show the alumina shell does not participate exothermically in the reaction.

Farley, Cory W.; Pantoya, Michelle L.; Losada, Martin; Chaudhuri, Santanu

2013-08-01

134

The solubility of 40Ar in liquid hydrocarbons: implications for Titan's chemistry and evolution  

NASA Astrophysics Data System (ADS)

The solubility of argon in liquid methane and ethane has been experimentally determined at 94 K. The solubilities are very large: 47% in methane and 15% in ethane, making the lakes of Titan an important potential reservoir of 40Ar. The amount of argon in the Titan lakes can be several times the atmospheric amount. After describing the experimental results, we will compare them with available models for vapor-liquid equilibria in the CH4-N2-Ar system. Using the data obtained on the solubility of argon in ethane, we will also derive implications for calculating the vapor-liquid equilibria in the C2H6-N2-Ar system. We eventually discuss the reasons for such high solubilities in terms of Hildebrand solubility parameters and the implications for Titan's surface chemistry and evolution.

Hodyss, R. P.; Beauchamp, P. M.; Choukroun, M.; Sotin, C.

2011-12-01

135

Parsing pyrogenic polycyclic aromatic hydrocarbons: forensic chemistry, receptor models, and source control policy.  

PubMed

A realistic understanding of contaminant sources is required to set appropriate control policy. Forensic chemical methods can be powerful tools in source characterization and identification, but they require a multiple-lines-of-evidence approach. Atmospheric receptor models, such as the US Environmental Protection Agency (USEPA)'s chemical mass balance (CMB), are increasingly being used to evaluate sources of pyrogenic polycyclic aromatic hydrocarbons (PAHs) in sediments. This paper describes the assumptions underlying receptor models and discusses challenges in complying with these assumptions in practice. Given the variability within, and the similarity among, pyrogenic PAH source types, model outputs are sensitive to specific inputs, and parsing among some source types may not be possible. Although still useful for identifying potential sources, the technical specialist applying these methods must describe both the results and their inherent uncertainties in a way that is understandable to nontechnical policy makers. The authors present an example case study concerning an investigation of a class of parking-lot sealers as a significant source of PAHs in urban sediment. Principal component analysis is used to evaluate published CMB model inputs and outputs. Targeted analyses of 2 areas where bans have been implemented are included. The results do not support the claim that parking-lot sealers are a significant source of PAHs in urban sediments. PMID:24265245

O'Reilly, Kirk T; Pietari, Jaana; Boehm, Paul D

2014-04-01

136

Terascale High-Fidelity Simulations of Turbulent Combustion with Detailed Chemistry  

SciTech Connect

The TSTC project is a multi-university collaborative effort to develop a high-fidelity turbulent reacting flow simulation capability utilizing terascale, massively parallel computer technology. The main paradigm of our approach is direct numerical simulation (DNS) featuring highest temporal and spatial accuracy, allowing quantitative observations of the fine-scale physics found in turbulent reacting flows as well as providing a useful tool for development of sub-models needed in device-level simulations. The code named S3D, developed and shared with Chen and coworkers at Sandia National Laboratories, has been enhanced with new numerical algorithms and physical models to provide predictive capabilities for spray dynamics, combustion, and pollutant formation processes in turbulent combustion. Major accomplishments include improved characteristic boundary conditions, fundamental studies of auto-ignition in turbulent stratified reactant mixtures, flame-wall interaction, and turbulent flame extinction by water spray. The overarching scientific issue in our recent investigations is to characterize criticality phenomena (ignition/extinction) in turbulent combustion, thereby developing unified criteria to identify ignition and extinction conditions. The computational development under TSTC has enabled the recent large-scale 3D turbulent combustion simulations conducted at Sandia National Laboratories.

Hong G. Im; Arnaud Trouve; Christopher J. Rutland; Jacqueline H. Chen

2009-02-02

137

Terascale High-Fidelity Simulations of Turbulent Combustion with Detailed Chemistry  

SciTech Connect

The TSTC project is a multi-university collaborative effort to develop a high-fidelity turbulent reacting flow simulation capability utilizing terascale, massively parallel computer technology. The main paradigm of our approach is direct numerical simulation (DNS) featuring highest temporal and spatial accuracy, allowing quantitative observations of the fine-scale physics found in turbulent reacting flows as well as providing a useful tool for development of sub-models needed in device-level simulations. The code named S3D, developed and shared with Chen and coworkers at Sandia National Laboratories, has been enhanced with new numerical algorithms and physical models to provide predictive capabilities for spray dynamics, combustion, and pollutant formation processes in turbulent combustion. Major accomplishments include improved characteristic boundary conditions, fundamental studies of auto-ignition in turbulent stratified reactant mixtures, flame-wall interaction, and turbulent flame extinction by water spray. The overarching scientific issue in our recent investigations is to characterize criticality phenomena (ignition/extinction) in turbulent combustion, thereby developing unified criteria to identify ignition and extinction conditions. The computational development under TSTC has enabled the recent large-scale 3D turbulent combustion simulations conducted at Sandia National Laboratories.

Im, Hong G [University of Michigan] [University of Michigan; Trouve, Arnaud [University of Maryland] [University of Maryland; Rutland, Christopher J [University of Wisconsin] [University of Wisconsin; Chen, Jacqueline H [Sandia National Laboratories] [Sandia National Laboratories

2012-08-13

138

Constraints on emissions of hydrocarbons and combustion tracers in the Colorado Front Range using observations of 14CO2 at the Boulder Atmospheric Observatory (BAO)  

NASA Astrophysics Data System (ADS)

Bottom-up inventories of trace gases formed as a byproduct of fossil fuel combustion have significant uncertainty associated with them because of the difficulty in quantifying the relationship between the mass of fuel consumed and the mass emitted; this is in contrast to the near stoichiometric production of CO2 from the combustion of hydrocarbons. Emissions of species such as CO, CH4, acetylene, and benzene depend greatly on a number of variables including fuel type, combustion temperature, oxidant-to-fuel ratio, and post-combustion tail-pipe or flue-stack "scrubbing". Given the impact of many of these combustion by-products on air quality, human health, and climate, atmospheric observations are necessary in order to critically evaluate bottom-up emissions estimates. Atmospheric radiocarbon (14C) represents an important observational constraint on emissions of fossil-fuel derived carbon into the atmosphere due to the near absence of 14C in fossil fuel reservoirs. The high sensitivity and precision that accelerator mass spectrometry (AMS) affords in atmospheric 14C analysis has greatly increased the potential for using such measurements to verify bottom-up emissions inventories of fossil fuel CO2 (CO2ff), as well as other co-emitted species. Here we use observations of 14CO2 and a series of hydrocarbons and combustion tracers from the Boulder Atmospheric Observatory (BAO; Lat: 40.050o, Lon: -105.004o) to derive emission ratios of each species to CO2. From these emission ratios, we estimate absolute emission fluxes of these species by using an existing CO2ff inventory. Among the species considered are CO, CH4, acetylene (C2H2), benzene (C6H6), and C3-C5 alkanes. Comparisons of top-down emissions estimates are made to existing inventories of these species for the region, where available, as well as to previous efforts to estimate emissions from atmospheric observations in the Colorado Front Range.We find that CO is overestimated in the NEI 2008 by a factor of ~2; a close evaluation of the inventory suggests that the CO emissions per unit fuel burned from on-road gasoline vehicles is likely significantly over-estimated. Emissions estimates of CH4 and the C3-C5 alkanes from gas and oil drilling and processing operations to the north and east of the BAO tower are in good agreement with previous top-down estimates for the region.

LaFranchi, B. W.; Petron, G.; Miller, J. B.; Lehman, S. J.; Andrews, A. E.; Dlugokencky, E. J.; Miller, B. R.; Montzka, S. A.; Turnbull, J. C.; Tans, P. P.; Guilderson, T. P.

2011-12-01

139

Chemistry  

NSDL National Science Digital Library

Finds ChemEd DL resources related to the sections of the General Chemistry textbook, Chemistry, by Kenneth W. Whitten, Raymond E. Davis, M. Larry Peck, George G. Stanley published by Brooks/Cole, 2010.

140

Distribution of hydrocarbons between oils and associated fine-grained sedimentary rocks: physical chemistry applied to petroleum geochemistry. II  

Microsoft Academic Search

Amounts and ratios of hydrocarbons in nonreservoir rocks (potential source rocks) can be compared with associated oils if, in relatively old and stable geologic situations, the hydrocarbons reach or closely approach a distribution equilibrium between source rock and reservoir. A distribution-equilibrium equation makes possible the calculation of the composition of a hypothetical oil expected from the composition of the hydrocarbons

A. Young; R. D. McIver

1977-01-01

141

Terascale High-Fidelity Simulations of Turbulent Combustion with Detailed Chemistry  

SciTech Connect

This SciDAC project enabled a multidisciplinary research consortium to develop a high fidelity direct numerical simulation (DNS) software package for the simulation of turbulent reactive flows. Within this collaboration, the authors, based at CMU's Pittsburgh Supercomputing Center (PSC), focused on extensive new developments in Sandia National Laboratories' "S3D" software to address more realistic combustion features and geometries while exploiting Terascale computational possibilities. This work significantly advances the state-of-the-art of DNS of turbulent reacting flows.

Raghurama Reddy; Roberto Gomez; Junwoo Lim; Yang Wang; Sergiu Sanielevici

2004-10-15

142

A flame tabulated chemistry approach for premixed combustion using industrial CFD codes  

Microsoft Academic Search

A flame tabulated model to account for detailed chemistry is used along with a presumed PDF approach to simulate a lean turbulent premixed flame stabilized behind a conical bluff body. Here, the FPI model is retained to build the chemical database. The resulting look-up tables are then coupled with CEDRE, the ONERA code for aerothermochemistry problems. The coupling between CEDRE

J. Savre; N. Bertier; D. Gaffié

143

Chemical Kinetic Data Base for Combustion Chemistry. Part I. Methane and Related Compounds  

Microsoft Academic Search

This document contains evaluated data on the kinetics and thermodynamic properties of species that are of importance in methane pyrolysis and combustion. Specifically, the substances considered include H, H2, O, O2, OH, HO2, H2O2, H2O, CH4, C2H6, HCHO, CO2, CO, HCO, CH3, C2H5, C2H4, C2H3, C2H2, C2H, CH3CO, CH3O2, CH3O, singlet CH2, and triplet CH2. All possible reactions are considered.

W. Tsang; R. F. Hampson

1986-01-01

144

Comparison of numerical techniques for integration of stiff ordinary differential equations arising in combustion chemistry  

NASA Technical Reports Server (NTRS)

The efficiency and accuracy of several algorithms recently developed for the efficient numerical integration of stiff ordinary differential equations are compared. The methods examined include two general-purpose codes, EPISODE and LSODE, and three codes (CHEMEQ, CREK1D, and GCKP84) developed specifically to integrate chemical kinetic rate equations. The codes are applied to two test problems drawn from combustion kinetics. The comparisons show that LSODE is the fastest code currently available for the integration of combustion kinetic rate equations. An important finding is that an interactive solution of the algebraic energy conservation equation to compute the temperature does not result in significant errors. In addition, this method is more efficient than evaluating the temperature by integrating its time derivative. Significant reductions in computational work are realized by updating the rate constants (k = at(supra N) N exp(-E/RT) only when the temperature change exceeds an amount delta T that is problem dependent. An approximate expression for the automatic evaluation of delta T is derived and is shown to result in increased efficiency.

Radhakrishnan, K.

1984-01-01

145

Terascale High-Fidelity Simulations of Turbulent Combustion with Detailed Chemistry: Spray Simulations  

SciTech Connect

The Terascale High-Fidelity Simulations of Turbulent Combustion (TSTC) project is a multi-university collaborative effort to develop a high-fidelity turbulent reacting flow simulation capability utilizing terascale, massively parallel computer technology. The main paradigm of the approach is direct numerical simulation (DNS) featuring the highest temporal and spatial accuracy, allowing quantitative observations of the fine-scale physics found in turbulent reacting flows as well as providing a useful tool for development of sub-models needed in device-level simulations. Under this component of the TSTC program the simulation code named S3D, developed and shared with coworkers at Sandia National Laboratories, has been enhanced with new numerical algorithms and physical models to provide predictive capabilities for turbulent liquid fuel spray dynamics. Major accomplishments include improved fundamental understanding of mixing and auto-ignition in multi-phase turbulent reactant mixtures and turbulent fuel injection spray jets.

Rutland, Christopher J.

2009-04-26

146

On the effects of hydrocarbon and sulphur-containing compounds on the CCN activation of combustion particles  

NASA Astrophysics Data System (ADS)

The European PartEmis project (''Measurement and prediction of emissions of aerosols and gaseous precursors from gas turbine engines'') was focussed on the characterisation and quantification of exhaust emissions from a gas turbine engine. A comprehensive suite of aerosol, gas and chemi-ion measurements were conducted under different combustor operating conditions and fuel sulphur concentrations. Combustion aerosol characterisation included on-line measurements of mass and number concentration, size distribution, mixing state, thermal stability of internally mixed particles, hygroscopicity, cloud condensation nuclei (CCN) activation potential, and off-line analysis of chemical composition. Modelling of CCN activation of combustion particles was conducted using microphysical and chemical properties obtained from the measurements as input data. Based on this unique data set, the role of sulphuric acid coatings on the combustion particles, formed in the cooling exhaust plume through either direct condensation of gaseous sulphuric acid or coagulation with volatile condensation particles nucleating from gaseous sulphuric acid, and the role of the organic fraction for the CCN activation of combustion particles was investigated. It was found that particles containing a large fraction of non-volatile organic compounds grow significantly less at high relative humidity than particles with a lower content of non-volatile OC. Also the effect of the non-volatile OC fraction on the potential CCN activation is significant. While a coating of water-soluble sulphuric acid increases the potential CCN activation, or lowers the activation diameter, respectively, the non-volatile organic compounds, mainly found at lower combustion temperatures, can partially compensate this sulphuric acid-related enhancement of CCN activation of carbonaceous combustion aerosol particles.

Petzold, A.; Gysel, M.; Vancassel, X.; Hitzenberger, R.; Puxbaum, H.; Vrochticky, S.; Weingartner, E.; Baltensperger, U.; Mirabel, P.

2005-05-01

147

Evaluation of joint probability density function models for turbulent nonpremixed combustion with complex chemistry  

NASA Technical Reports Server (NTRS)

Two types of mixing sub-models are evaluated in connection with a joint-scalar probability density function method for turbulent nonpremixed combustion. Model calculations are made and compared to simulation results for homogeneously distributed methane-air reaction zones mixing and reacting in decaying turbulence within a two-dimensional enclosed domain. The comparison is arranged to ensure that both the simulation and model calculations a) make use of exactly the same chemical mechanism, b) do not involve non-unity Lewis number transport of species, and c) are free from radiation loss. The modified Curl mixing sub-model was found to provide superior predictive accuracy over the simple relaxation-to-mean submodel in the case studied. Accuracy to within 10-20% was found for global means of major species and temperature; however, nitric oxide prediction accuracy was lower and highly dependent on the choice of mixing sub-model. Both mixing submodels were found to produce non-physical mixing behavior for mixture fractions removed from the immediate reaction zone. A suggestion for a further modified Curl mixing sub-model is made in connection with earlier work done in the field.

Smith, N. S. A.; Frolov, S. M.; Bowman, C. T.

1996-01-01

148

Chemistry Notes.  

ERIC Educational Resources Information Center

Presents background information, laboratory procedures, classroom materials/activities, and experiments for chemistry. Topics include superheavy elements, polarizing power and chemistry of alkali metals, particulate carbon from combustion, tips for the chemistry laboratory, interesting/colorful experiments, behavior of bismuth (III) iodine, and…

School Science Review, 1982

1982-01-01

149

The Effect of Fuel and Oil Structure on Hydrocarbon Emissions from Oil Layers during Closed Vessel Combustion  

Microsoft Academic Search

The effects of fuel and oil structure on the product gas emissions from a combustion bomb are studied for various fuel-oil systems. Five oils (a synthetic motor oil, a petroleum-based motor oil, an oxypolypropylene oil, an oxypolyethylene-polypropylene oil, and glycerol) were tested in combination with two fuel blends (ethane-ethanol and ethane-methanol). Gas samples from the reactor were analyzed by gas

ANDREW A. ADAMCZYK; WALTER G. ROTHSCHILD; E. W. KAISER

1985-01-01

150

Effect of Hydrocarbon Emissions From PCCI-Type Combustion On The Performance of Selective Catalytic Reduction Catalysts  

SciTech Connect

Core samples cut from full size commercial Fe-and Cu-zeolite SCR catalysts were exposed to a slipstream of raw engine exhaust from a 1.9-liter 4-cylinder diesel engine operating in conventional and PCCI combustion modes. Subsequently, the NOx reduction performance of the exposed catalysts was evaluated on a laboratory bench- reactor fed with simulated exhaust. The Fe-zeolite NOx conversion efficiency was significantly degraded, especially at low temperatures (<250 C), after the catalyst was exposed to the engine exhaust. The degradation of the Fe-zeolite performance was similar for both combustion modes. The Cu-zeolite was much more resistant to HC fouling than the Fe-zeolite catalyst. In the case of the Cu-zeolite, PCCI exhaust had a more significant impact than the exhaust from conventional combustion on the NOx conversion efficiency. For all cases, the clean catalyst performance was recovered after heating to 600 C. GC-MS analysis of the HCs adsorbed to the catalyst surface provided insights into the observed NOx reduction performance trends.

Prikhodko, Vitaly Y [ORNL] [ORNL; Pihl, Josh A [ORNL] [ORNL; Lewis Sr, Samuel Arthur [ORNL] [ORNL; Parks, II, James E [ORNL

2011-01-01

151

Interrogating Hydrocarbon Radicals  

NASA Astrophysics Data System (ADS)

Motivated by astrophysical problems (and a sense of fun) for some years my research group has been obtaining new spectra of hitherto unobserved hydrocarbon radicals. We employ the complementary techniques of resonant ionization and laser induced fluorescence to rigorously identify radicals by matching their ground state vibrational frequencies to those obtained using density functional theory (DFT). While some radicals were made to order in our pulsed electrical discharge source, others of particular chemical importance have been found lurking in the congested forest of dicarbon and tricarbon fluorescence. Using a 2-dimensional fluorescence (2df) map, we have extracted pure spectra, unpolluted by C_2 and C_3, from a benzene discharge. One spectrum was first presented at this symposium in 2006, but at that stage was not identified. Subsequent measurement of a matching resonant ionization spectrum revealed a mass of 115, much higher than the benzene precursor. With the aid of DFT calculations, the species was positively identified, giving clues to hydrocarbon-building chemistry of relevance to combustion; planetary atmospheres; and the interstellar and circumstellar space. Further experiments revealed other surprising additions to the radical zoo, also identified with the help of 2df. Along the way we have also identified two new band systems of C_2, the first involving the hidden c^3?_u^+ state, and have ventured into the world of larger molecules, such as hexabenzocoronene, C42H18.

Schmidt, Timothy W.

2010-06-01

152

An analytical study of nitrogen oxides and carbon monoxide emissions in hydrocarbon combustion with added nitrogen, preliminary results  

NASA Technical Reports Server (NTRS)

The effect of combustor operating conditions on the conversion of fuel-bound nitrogen (FBN) to nitrogen oxides NO sub x was analytically determined. The effect of FBN and of operating conditions on carbon monoxide (CO) formation was also studied. For these computations, the combustor was assumed to be a two stage, adiabatic, perfectly-stirred reactor. Propane-air was used as the combustible mixture and fuel-bound nitrogen was simulated by adding nitrogen atoms to the mixture. The oxidation of propane and formation of NO sub x and CO were modeled by a fifty-seven reaction chemical mechanism. The results for NO sub x and CO formation are given as functions of primary and secondary stage equivalence ratios and residence times.

Bittker, D. A.

1979-01-01

153

Reductions in emissions of carbonaceous particulate matter and polycyclic aromatic hydrocarbons from combustion of biomass pellets in comparison with raw fuel burning.  

PubMed

Biomass pellets are emerging as a cleaner alternative to traditional biomass fuels. The potential benefits of using biomass pellets include improving energy utilization efficiency and reducing emissions of air pollutants. To assess the environmental, climate, and health significance of replacing traditional fuels with biomass pellets, it is critical to measure the emission factors (EFs) of various pollutants from pellet burning. However, only a few field measurements have been conducted on the emissions of carbon monoxide (CO), particulate matter (PM), and polycyclic aromatic hydrocarbons (PAHs) from the combustion of pellets. In this study, pine wood and corn straw pellets were burned in a pellet burner (2.6 kW), and the EFs of CO, organic carbon, elemental carbon, PM, and PAHs (EF(CO), EF(OC), EF(EC), EF(PM), and EF(PAH)) were determined. The average EF(CO), EF(OC), EF(EC), and EF(PM) were 1520 ± 1170, 8.68 ± 11.4, 11.2 ± 8.7, and 188 ± 87 mg/MJ for corn straw pellets and 266 ± 137, 5.74 ± 7.17, 2.02 ± 1.57, and 71.0 ± 54.0 mg/MJ for pine wood pellets, respectively. Total carbonaceous carbon constituted 8 to 14% of the PM mass emitted. The measured values of EF(PAH) for the two pellets were 1.02 ± 0.64 and 0.506 ± 0.360 mg/MJ, respectively. The secondary side air supply in the pellet burner did not change the EFs of most pollutants significantly (p > 0.05). The only exceptions were EF(OC) and EF(PM) for pine wood pellets because of reduced combustion temperatures with the increased air supply. In comparison with EFs for the raw pine wood and corn straw, EF(CO), EF(OC), EF(EC), and EF(PM) for pellets were significantly lower than those for raw fuels (p < 0.05). However, the differences in EF(PAH) were not significant (p > 0.05). Based on the measured EFs and thermal efficiencies, it was estimated that 95, 98, 98, 88, and 71% reductions in the total emissions of CO, OC, EC, PM, and PAHs could be achieved by replacing the raw biomass fuels combusted in traditional cooking stoves with pellets burned in modern pellet burners. PMID:22568759

Shen, Guofeng; Tao, Shu; Wei, Siye; Zhang, Yanyan; Wang, Rong; Wang, Bin; Li, Wei; Shen, Huizhong; Huang, Ye; Chen, Yuanchen; Chen, Han; Yang, Yifeng; Wang, Wei; Wei, Wen; Wang, Xilong; Liu, Wenxing; Wang, Xuejun; Masse Simonich, Staci L y

2012-06-01

154

Reductions in Emissions of Carbonaceous Particulate Matter and Polycyclic Aromatic Hydrocarbons from Combustion of Biomass Pellets in Comparisonwith Raw Fuel Burning  

PubMed Central

Biomass pellets are emerging as a cleaner alternative to traditional biomass fuels. The potential benefits of using biomass pellets include improving energy utilization efficiency and reducing emissions of air pollutants. To assess the environmental, climate, and health significance of replacing traditional fuels with biomass pellets, it is critical to measure the emission factors (EFs) of various pollutants from pellet burning. However, only a few field measurements have been conducted on the emissions of carbon monoxide (CO), particulate matter (PM), and polycyclic aromatic hydrocarbons (PAHs) from the combustion of pellets. In this study, pine wood and corn straw pellets were burned in a pellet burner (2.6 kW) and the EFs of CO, organic carbon, elemental carbon, PM, and PAHs (EFCO, EFOC, EFEC, EFPM, and EFPAH) were determined. The average EFCO, EFOC, EFEC, and EFPM were 1520±1170, 8.68±11.4, 11.2±8.7, and 188±87 mg/MJ for corn straw pellets, and 266±137, 5.74±7.17, 2.02±1.57, and 71.0±54.0 mg/MJ for pine wood pellets, respectively. Total carbonaceous carbon constituted 8 to 14% of the PM mass emitted. The measured values of EFPAH for the two pellets were 1.02±0.64 and 0.506±0.360 mg/MJ, respectively. The secondary side air supply in the pellet burner did not change the EFs of most pollutants significantly (p > 0.05). The only exceptions were EFOC and EFPM for pine wood pellets because of reduced combustion temperatures with the increased air supply. In comparison with EFs for the raw pine wood and corn straw, EFCO, EFOC, EFEC, and EFPM for pellets were significantly lower than those for raw fuels (p < 0.05). However, the differences in EFPAH were not significant (p > 0.05). Based on the measured EFs and thermal efficiencies, it was estimated that 95, 98, 98, 88, and 71% reductions in the total emissions of CO, OC, EC, PM, and PAHs could be achieved by replacing the raw biomass fuels combusted in traditional cooking stoves with pellets burned in modern pellet burners. PMID:22568759

SHEN, Guofeng; TAO, Shu; WEI, Siye; ZHANG, Yanyan; WANG, Rong; WANG, Bin; LI, Wei; SHEN, Huizhong; HUANG, Ye; CHEN, Yuanchen; CHEN, Han; YANG, Yifeng; WANG, Wei; WEI, Wen; WANG, Xilong; LIU, Wenxing; WANG, Xuejun; SIMONICH, Staci L. Massey

2012-01-01

155

Tropospheric chemistry of natural hydrocarbons, aldehydes, and peroxy radicals: Their connections to sulfuric acid production and climate effects  

Microsoft Academic Search

Recent work has shown that natural hydrocarbon emissions can significantly affect the levels of urban and regional tropospheric ozone. We report on the reactivities of these biogenic trace gases, particularly, isoprene, focusing on their importance in the production of aldehydes and peroxy radicals, leading to increased levels of hydrogen over regional forests. Hydrogen peroxide can lead to the wet oxidation

J. S. Gaffney; N. A. Marley

1993-01-01

156

Rate constants for the reaction of C4H radical with various hydrocarbons at very low temperatures (15 K - 300K) relevant to the atmospheric chemistry of Titan  

NASA Astrophysics Data System (ADS)

Modelling the chemistry of planetary atmospheres requires the knowledge of a large number of physical and chemical data among which chemical rate coefficients. Of particular interest is the understanding of how complex molecules and unstable hydrocarbons can be formed and survive in such extreme environments. Many organic compounds have been detected in Titan's atmosphere, and the active photochemistry taking place in the upper atmosphere is thought to be responsible for the haze that hides Titan's surface. According to photochemical models, diacetylene (C4 H2 ) production is initiated by the photodissociation of acetylene C2 H2 (a product of methane photolysis). Diacetylene is the first of the series of polyynes proposed as a formation route for the haze particles present in the upper atmosphere. Photolysis of diacetylene can lead to a large amount of radicals, including C4 H that can react to form species containing longer carbon chains. As major discrepancies have been found between models and observations concerning hydrocarbon ratios in the stratosphere of Titan, we have undertaken a close collaboration with our colleagues of the LISA (Créteil) to determine accurate experimental data to improve the understanding of the chemistry and the photochemistry of polyynes, and more specifically diacetylene in Titan's atmosphere. In Rennes, we have used the CRESU (Cinétique de Réaction en Ecoulement Supersonique Uniforme or Reaction Kinetics in a Uniform Supersonic Flow) technique to study the reactivity of the the butadiynyl radical, C4 H, with a series of small hydro- carbons observed in the atmosphere of Titan. Rate constants have been derived over a wide range of temperatures (15 K - 300 K). Many of these reactions have been found to be fast (k ? 10-10 cm3 molecule-1 s-1 ), with a rate coefficient increasing when the temperature was lowered. Spectroscopic aspects of these studies and consequences of these new data on the models have been undertaken by our colleagues of Créteil.

Berteloite, C.; Le Picard, S. D.; Canosa, A.; Sims, I. R.; Benilan, Y.; Gazeau, M.-C.

157

The Influence of Hydrocarbon and CO2 on the Reversibility of Li-O2 Chemistry Using In Situ Ambient Pressure X-ray Photoelectron Spectroscopy  

SciTech Connect

Identifying fundamental barriers that hinder reversible lithium oxygen (Li O2) redox reaction is essential for developing efficient and long lasting rechargeable Li O2 batteries. Addressing these challenges is being limited by parasitic reactions in the carbon based O2 electrode with aprotic electrolytes. Understanding the mechanisms of these parasitic reactions is hampered by the complexity that multiple and coupled parasitic reactions involving carbon, electrolytes, and Li O2 reaction intermediates/products can occur simultaneously. In this work, we employed solid state cells free of carbon and aprotic electrolytes to probe the influence of surface adventitious hydrocarbons and carbon dioxide (CO2) on the reversibility of the Li O2 redox chemistry using in situ synchrotron based ambient pressure X ray photoelectron spectroscopy. Direct evidence was provided, for the first time, that surface hydrocarbons and CO2 irreversibly react with Li O2 reaction intermediates/ products such as Li2O2 and Li2O, forming carboxylate and carbonate based species, which cannot be removed fully upon recharge. The slower Li2O2 oxidation kinetics was correlated with increasing coverage of surface carbonate/ carboxylate species. Our work critically points out that materials design that mitigates the reactivity between Li O2 reaction products and common impurities in the atmosphere is needed to achieve long cycle life Li O2 batteries.

Lu, Yi-chun [Massachusetts Institute of Technology (MIT)] [Massachusetts Institute of Technology (MIT); Crumlin, Ethan [Massachusetts Institute of Technology (MIT)] [Massachusetts Institute of Technology (MIT); Carney, Thomas J [ORNL] [ORNL; Baggetto, Loic [ORNL] [ORNL; Veith, Gabriel M [ORNL] [ORNL; Dudney, Nancy J [ORNL] [ORNL; Liu, Zhi [Lawrence Berkeley National Laboratory (LBNL)] [Lawrence Berkeley National Laboratory (LBNL); Shao-Horn, Yang [Massachusetts Institute of Technology (MIT)] [Massachusetts Institute of Technology (MIT)

2013-01-01

158

Minor and trace authigenic components as indicators of pore fluid chemistry during maturation and migration of hydrocarbons. Final report  

SciTech Connect

Variations in mineralogy and composition of late authigenic sulfur-bearing minerals in upper Smackover limestones recorded diagenetic events associated with hydrocarbon migration. Uranium concentration, as revealed by fission track imaging and instrumental neutron activation analyses, varies on a microscopic and regional scale in the upper Smackover limestones. Uranium is locally concentrated in stylolites and fine grained opaque material. Comparison of uranium and thorium concentrations in stylolites suggests these elements are insoluble residue of the pressure solution process. Regionally, uranium concentration varies with clay content of the host limestone indicating that sorption plays a major role in the geochemical behavior of uranium in the subsurface. Comparison of uranium ratios of upper Smackover limestones to those of black shales from the Gray Sands tentatively suggests that uranium was redistributed from hydrocarbon source rocks to reservoir rocks. However, better understanding of the association of uranium with organic-rich rocks and the role of sorption are required before uranium can be used reliably as a pore fluid tracer. Late authigenic sulfur-bearing minerals are excellent indicators of late-stage diagenetic events and evolution of pore fluids associated with hydrocarbons. Study of these minerals in the upper Smackover limestones has provided the first concrete evidence of migration of late-stage pore fluids into these rocks along faults and has shown that this flow was focussed in specific areas. This knowledge allows a clearer and more specific interpretation of previous authors observations and data.

Tieh, T.T.; Denham, M.E.

1993-02-01

159

Minor and trace authigenic components as indicators of pore fluid chemistry during maturation and migration of hydrocarbons  

SciTech Connect

Variations in mineralogy and composition of late authigenic sulfur-bearing minerals in upper Smackover limestones recorded diagenetic events associated with hydrocarbon migration. Uranium concentration, as revealed by fission track imaging and instrumental neutron activation analyses, varies on a microscopic and regional scale in the upper Smackover limestones. Uranium is locally concentrated in stylolites and fine grained opaque material. Comparison of uranium and thorium concentrations in stylolites suggests these elements are insoluble residue of the pressure solution process. Regionally, uranium concentration varies with clay content of the host limestone indicating that sorption plays a major role in the geochemical behavior of uranium in the subsurface. Comparison of uranium ratios of upper Smackover limestones to those of black shales from the Gray Sands tentatively suggests that uranium was redistributed from hydrocarbon source rocks to reservoir rocks. However, better understanding of the association of uranium with organic-rich rocks and the role of sorption are required before uranium can be used reliably as a pore fluid tracer. Late authigenic sulfur-bearing minerals are excellent indicators of late-stage diagenetic events and evolution of pore fluids associated with hydrocarbons. Study of these minerals in the upper Smackover limestones has provided the first concrete evidence of migration of late-stage pore fluids into these rocks along faults and has shown that this flow was focussed in specific areas. This knowledge allows a clearer and more specific interpretation of previous authors observations and data.

Tieh, T.T.; Denham, M.E.

1993-02-01

160

Carbon black enriched combustion  

SciTech Connect

A process for combustion of carbon black enriched gaseous hydrocarbon fuels is described comprising: entraining a plurality of carbon black particles in a carrier fluid, forming a carbon black/carrier fluid mixture; injecting said carbon black/carrier fluid mixture through a center nozzle of a fluid injector into a combustion chamber, said fluid injector having an outer nozzle concentrically disposed around said center nozzle forming an annular chamber between said center nozzle and said outer nozzle; injecting at least a first portion of a gaseous hydrocarbon fuel through said annular chamber into said combustion chamber forming a carbon black enriched gaseous hydrocarbon fuel; mixing said carbon black enriched gaseous hydrocarbon fuel with combustion air, forming a fuel/air mixture; and igniting said fuel/air mixture.

Joshi, M.L.; Tester, M.E.

1993-06-29

161

Forensic Chemistry  

NASA Astrophysics Data System (ADS)

Forensic chemistry is unique among chemical sciences in that its research, practice, and presentation must meet the needs of both the scientific and the legal communities. As such, forensic chemistry research is applied and derivative by nature and design, and it emphasizes metrology (the science of measurement) and validation. Forensic chemistry has moved away from its analytical roots and is incorporating a broader spectrum of chemical sciences. Existing forensic practices are being revisited as the purview of forensic chemistry extends outward from drug analysis and toxicology into such diverse areas as combustion chemistry, materials science, and pattern evidence.

Bell, Suzanne

2009-07-01

162

Sandia Combustion Research: Technical review  

SciTech Connect

This report contains reports from research programs conducted at the Sandia Combustion Research Facility. Research is presented under the following topics: laser based diagnostics; combustion chemistry; reacting flow; combustion in engines and commercial burners; coal combustion; and industrial processing. Individual projects were processed separately for entry onto the DOE databases.

NONE

1995-07-01

163

Igniting Chemistry in Fireworks  

NSDL National Science Digital Library

Students learn about the concepts of spectral chemistry, combustion, and the nature of fire through the use of visually rich fireworks resources. Optional resources address chemical reactions for those who want a more advanced chemistry lesson.

Foundation, Wgbh E.

2004-01-29

164

FUNDAMENTAL COMBUSTION RESEARCH APPLIED TO POLLUTION FORMATION. VOLUME 1. FCR PROGRAM OVERVIEW AND GAS-PHASE CHEMISTRY  

EPA Science Inventory

The report is the first in a series of four, documenting research performed under EPA's Fundamental Combustion Research (FCR) program. It is divided in two: Part A is a program overview and an introduction to the series; and Part B documents research performed in the gas-phase ch...

165

Combustor nozzle for a fuel-flexible combustion system  

DOEpatents

A combustor nozzle is provided. The combustor nozzle includes a first fuel system configured to introduce a syngas fuel into a combustion chamber to enable lean premixed combustion within the combustion chamber and a second fuel system configured to introduce the syngas fuel, or a hydrocarbon fuel, or diluents, or combinations thereof into the combustion chamber to enable diffusion combustion within the combustion chamber.

Haynes, Joel Meier (Niskayuna, NY); Mosbacher, David Matthew (Cohoes, NY); Janssen, Jonathan Sebastian (Troy, NY); Iyer, Venkatraman Ananthakrishnan (Mason, OH)

2011-03-22

166

Tripropellant combustion process  

NASA Technical Reports Server (NTRS)

The addition of small amounts of hydrogen to the combustion of LOX/hydrocarbon propellants in large rocket booster engines has the potential to enhance the system stability. Programs being conducted to evaluate the effects of hydrogen on the combustion of LOX/hydrocarbon propellants at supercritical pressures are described. Combustion instability has been a problem during the development of large hydrocarbon fueled rocket engines. At the higher combustion chamber pressures expected for the next generation of booster engines, the effect of unstable combustion could be even more destructive. The tripropellant engine cycle takes advantage of the superior cooling characteristics of hydrogen to cool the combustion chamber and a small amount of the hydrogen coolant can be used in the combustion process to enhance the system stability. Three aspects of work that will be accomplished to evaluate tripropellant combustion are described. The first is laboratory demonstration of the benefits through the evaluation of drop size, ignition delay and burning rate. The second is analytical modeling of the combustion process using the empirical relationship determined in the laboratory. The third is a subscale demonstration in which the system stability will be evaluated. The approach for each aspect is described and the analytical models that will be used are presented.

Kmiec, T. D.; Carroll, R. G.

1988-01-01

167

A quantum chemistry study on thermochemical properties of high energy-density endothermic hydrocarbon fuel JP-10.  

PubMed

The density functional theory (DFT) calculations at the M06-2X/6-31++G(d,p) level have been performed to explore the molecular structure, electronic structure, C-H bond dissociation enthalpy, and reaction enthalpies for five isodesmic reactions of a high energy-density endothermic hydrocarbon fuel JP-10. On the basis of the calculations, it is found that the carbonium ion C-6 isomer formed from the catalytic cracking at the C? site of JP-10 has the lowest energy, and the R-5 radical generated from the thermal cracking at the C? site of JP-10 is the most stable isomer. Furthermore, a series of hypothetical and isodesmic work reactions containing similar bond environments are used to calculate the reaction enthalpies for target compounds. For the same isodesmic reaction, the reaction enthalpy of each carbon site radical has also been calculated. The present work is of fundamental significance and strategic importance to provide some valuable insights into the component design and energy utilization of advanced endothermic fuels. PMID:24633778

Qin, Xiao-Mei; Xie, Hu-Jun; Yue, Lei; Lu, Xiao-Xing; Fang, Wen-Jun

2014-04-01

168

A Dual-Line Detection Rayleigh Scattering Diagnostic Technique for the Combustion of Hydrocarbon Fuels and Filtered UV Rayleigh Scattering for Gas Velocity Measurements  

NASA Technical Reports Server (NTRS)

Non-intrusive techniques for the dynamic measurement of gas flow properties such as density, temperature and velocity, are needed in the research leading to the development of new generation high-speed aircraft. Accurate velocity, temperature and density data obtained in ground testing and in-flight measurements can help understand the flow physics leading to transition and turbulence in supersonic, high-altitude flight. Such non-intrusive measurement techniques can also be used to study combustion processes of hydrocarbon fuels in aircraft engines. Reliable, time and space resolved temperature measurements in various combustor configurations can lead to a better understanding of high temperature chemical reaction dynamics thus leading to improved modeling and better prediction of such flows. In view of this, a research program was initiated at Polytechnic University's Aerodynamics Laboratory with support from NASA Lewis Research Center through grants NAG3-1301 and NAG3-1690. The overall objective of this program has been to develop laser-based, non-contact, space- and time-resolved temperature and velocity measurement techniques. In the initial phase of the program a ND:YAG laser-based dual-line Rayleigh scattering technique was developed and tested for the accurate measurement of gas temperature in the presence of background laser glare. Effort was next directed towards the development of a filtered, spectrally-resolved Rayleigh/Mie scattering technique with the objective of developing an interferometric method for time-frozen velocity measurements in high-speed flows utilizing the uv line of an ND:YAG laser and an appropriate molecular absorption filter. This effort included both a search for an appropriate filter material for the 266 nm laser line and the development and testing of several image processing techniques for the fast processing of Fabry-Perot images for velocity and temperature information. Finally, work was also carried out for the development of a new laser-based strain-rate and vorticity technique for the time-resolved measurement of vorticity and strain-rates in turbulent flows.

Otugen, M. Volkan

1997-01-01

169

POLYCYCLIC AROMATIC HYDROCARBON (PAH) SIZE DISTRIBUTIONS IN AEROSOLS FROM APPLIANCES OF RESIDENTIAL WOOD COMBUSTION AS DETERMINED BY DIRECT THERMAL DESORPTION - GC/MS  

EPA Science Inventory

The paper describesd a direct thermal desorption (TDS) approach to determine the PAH composition (MW = 202-302 amu) in size-segregated aerosols from residential wood combustion (RWC). Six combustion tests are performed with two highly available wood fuel varieties, Douglas-fir (P...

170

High Temperature Chemical Kinetic Combustion Modeling of Lightly Methylated Alkanes  

SciTech Connect

Conventional petroleum jet and diesel fuels, as well as alternative Fischer-Tropsch (FT) fuels and hydrotreated renewable jet (HRJ) fuels, contain high molecular weight lightly branched alkanes (i.e., methylalkanes) and straight chain alkanes (n-alkanes). Improving the combustion of these fuels in practical applications requires a fundamental understanding of large hydrocarbon combustion chemistry. This research project presents a detailed high temperature chemical kinetic mechanism for n-octane and three lightly branched isomers octane (i.e., 2-methylheptane, 3-methylheptane, and 2,5-dimethylhexane). The model is validated against experimental data from a variety of fundamental combustion devices. This new model is used to show how the location and number of methyl branches affects fuel reactivity including laminar flame speed and species formation.

Sarathy, S M; Westbrook, C K; Pitz, W J; Mehl, M

2011-03-01

171

Critical influence of finite rate chemistry and unmixedness on ignition and combustion of supersonic H2-air streams  

NASA Technical Reports Server (NTRS)

Good agreement has been obtained between published profiles of composition and pitot pressure and the calculated results from a computer program in which finite rate chemistry was used. Significant differences are noted between results calculated using 7 species and 8 reactions and those calculated using 12 species and 25 reactions. Differences are also found between results in which the effect of unmixedness on reaction in turbulent flow is applied or is not applied.

Evans, J. S.; Schexnayder, C. J., Jr.

1979-01-01

172

Health effects of combustion-generated soot and polycyclic aromatic hydrocarbons. Progress report, May 1, 1979-April 30, 1980. [Lead abstract  

SciTech Connect

Mutagen studies on soot and soot components are reported in aspects dealing from quantitative chemical analyses of samples and mutagenesis of cells and microorganisms exposed to mutagens, to bioassay developments and techniques. Several polycyclic aromatic hydrocarbons are characterized and discussed.

Thilly, W. G.

1980-05-01

173

Comparison, limitations and uncertainty of wet chemistry techniques, loss on ignition and dry combustion in soil organic carbon analysis  

NASA Astrophysics Data System (ADS)

Soil organic carbon (SOC) has an important role in natural processes (carbon cycle, global climate change and plant growth), agriculture, soil protection and biodiversity. Determination of SOC is usually based on the oxidation of soil organic matter (SOM). Many methods are available, each with advantages and disadvantages in terms of accuracy, costs, convenience and repeatability. Therefore, it is necessary to make a comprehensive overview in order to select appropriate method with the purpose of accurate SOC determination. Most errors in SOC stocks assessment and SOC monitoring occur due to differences in analytical approaches and procedures. This can be a key factor in making incorrect conclusions. The purpose of this research was to compare methods for SOC determination and highlight the strengths and weaknesses of individual methods. The research was conducted on soil samples collected from different soil types and different land uses of temperate region. The concentration of SOC in every sample was determined by the following methods: Tyrin's method, Tyrin's method without addition of AgSO4, Kotzmann's method, loss on ignition (LOI) method, Walkley-Black method, dry combustion by CHN analyzer with pretreatment with HCl and subtraction of volumetrically determined soil inorganic carbon (SIC) from dry combustion by CHN analyzer without pretreatment. Each of the applied methods demonstrated specific limitations. The average SOC concentration determined by different methods ranged from 16.1-28.5 g kg-1. It has been established that different methods for the determination of total SOC recovered 76-157% of SOC compared to the reference dry combustion method by CHN analyzer. The correlation coefficients between applied methods ranged from 0.74-0.98. The Tyrin's method without addition of AgSO4 can be recommended as the most suitable method for the determination of SOC, with mandatory use of the correction factor 1.14. For the purpose of reducing the difference between results obtained by CHN analyzer and other applied methods, linear regression equations for the recalculation of SOC concentration were developed.

?iri?, Vladimir; Manojlovi?, Maja; Beli?, Milivoj; Neši?, Ljiljana; Švarc-Gaji?, Jaroslava; Sitaula, Bishal K.

2014-05-01

174

QUANTITATIVE ANALYSIS OF POLYNUCLEAR AROMATIC HYDROCARBONS IN LIQUID FUELS  

EPA Science Inventory

Polynuclear aromatic hydrocarbons (PNAs), formed in combustion processes with liquid hydrocarbon fuels, contribute to mobile source exhaust emissions. Because correlation between PNA levels in automobile exhaust and pre-existent PNAs in fuel has been demonstrated in previous work...

175

The History of Chemistry. The Case of the Supposed Isomerism of the Hydrocarbon Ethane in the Construction of Knowledge: Implications for Chemical Education.  

ERIC Educational Resources Information Center

Contends that chemical education proposals for changing the conception of chemistry literacy should include making explicit the relationship between chemistry as science and chemistry as technology. Illustrates the importance of distinguishing between scientific and technological activities by explaining the events and processes that are…

Cross, Roger T.; Price, Ronald F.

2001-01-01

176

DEVELOPMENT OF RELATIVE POTENCY ESTIMATES FOR PAHS AND HYDROCARBON COMBUSTION PRODUCT FRACTIONS COMPARED TO BENZO[A]PYRENE AND THEIR USE IN CARCINOGENIC RISK ASSESSMENTS  

EPA Science Inventory

As an extension of the work started in a previous contract (EPA 68-02-4403, April 1988), various approaches for estimating the carcinogenic potency of polycyclic aromatic hydrocarbons (PAH) mixtures were investigated. he approach uses the two-stage model described in the previous...

177

Modeling the combustion behavior of hazardous waste in a rotary kiln incinerator.  

PubMed

Hazardous wastes have complex physical forms and chemical compositions and are normally incinerated in rotary kilns for safe disposal and energy recovery. In the rotary kiln, the multifeed stream and wide variation of thermal, physical, and chemical properties of the wastes cause the incineration system to be highly heterogeneous, with severe temperature fluctuations and unsteady combustion chemistry. Incomplete combustion is often the consequence, and the process is difficult to control. In this article, modeling of the waste combustion is described by using computational fluid dynamics (CFD). Through CFD simulation, gas flow and mixing, turbulent combustion, and heat transfer inside the incinerator were predicted and visualized. As the first step, the waste in various forms was modeled to a hydrocarbon-based virtual fuel mixture. The combustion of the simplified waste was then simulated with a seven-gas combustion model within a CFD framework. Comparison was made with previous global three-gas combustion model with which no chemical behavior can be derived. The distribution of temperature and chemical species has been investigated. The waste combustion model was validated with temperature measurements. Various operating conditions and the influence on the incineration performance were then simulated. Through this research, a better process understanding and potential optimization of the design were attained. PMID:16194906

Yang, Yongxiang; Pijnenborg, Marc J A; Reuter, Markus A; Verwoerd, Joep

2005-01-01

178

Stack contamination effects during small-scale combustion testing of synthetic fuels  

SciTech Connect

The Analytical Chemistry Branch at the Pittsburgh Energy Technology Center has undertaken the assessment of the possible environmental impact of substituting synfuels for petroleum-based fuels in utility and industrial boilers. The assessment is based on a study of results obtained from the analysis of trace organic compounds present in the exaust gases of a fully instrumented 20-hp firetube boiler. The stack gases from petroleum-based fuels, synfuels, and methanol combustion tests have been sampled and analyzed by combined gas chromatography/mass spectrometry. The stack gas sampled during the combustion of methanol showed the presence of saturated and aromatiic hydrocarbons as well as detectable amounts of organic sulfur compounds, such as dibenzothiophene. The presence of these compounds could not be explained on the basis of methanol showed the presence of saturated and aromatic hydrocarbons as well as detectable amounts of organic sulfur compounds, such as dibenzothiophene. The presence of these compounds could not be explained on the basis of methanol combustion but suggests contamination of the 20-hp combustor-exhaust system from earlier tests using petroleum or coal-derived fuels. The previously established exhaust stack protocol was reviewed by the Combustion Technology Branch and the Analytical Chemistry Branch. It was decided that a more exhaustive protocol was required. When this revised protocol was instituted, cross-contamination and memory effects disappeared, and sampling integrity was reestablished, thus allowing the analytical data to be properly interpreted. 5 references, 7 figures, 5 tables.

Douglas, L.J.; Gibbon, G.A.; White, C.M.

1984-01-01

179

Determination of the temperature and concentrations for the products of combustion of a hydrocarbon fuel on the basis of their infrared self-radiation  

Microsoft Academic Search

A measuring system has been developed and a procedure has been proposed for determining the temperature of gas flows and the concentrations of the products of combustion of organic fuels on the basis of the spectral “radiation–absorption” method. A gas multi-wavelength (1.8–4.8?m) pyrometer–photometer has been created for measuring the self-radiation of gas flows and transmission of probing radiation from a

E Vitkin; O Zhdanovich; V Tamanovich; V Senchenko; V Dozhdikov; M Ignatiev; I Smurov

2002-01-01

180

Combustion of JP8 in Laminar Premixed Flames.  

National Technical Information Service (NTIS)

Experimental and numerical studies are carried out to develop a surrogate that can reproduce selected aspects of combustion of JP-8. Surrogate fuels are defined as mixtures of few hydrocarbon compounds with combustion characteristics similar to those of c...

K. Seshadri

2008-01-01

181

Chemical kinetic simulation of hydrocarbon oxidation through the exhaust port of a spark ignition engine  

SciTech Connect

The oxidation of unburned hydrocarbons, remaining in the cylinder of a spark-ignited engine after the main combustion event, takes place both in-cylinder and in the exhaust port. Hydrocarbons emerging from engine tailpipes consist of unburned fuel as well as products of incomplete combustion. This paper addresses the extent of oxidation and the production of nonfuel species in the exhaust port of a single-cylinder spark-ignition engine. Simulations of the unsteady thermal and composition state of the gases emerging from the cylinder were coupled to detailed chemistry models of the oxidation of hydrocarbons (propane, isooctane, methane, and ethane) to determine the change in the average composition of the gas as it passes through the exhaust port. The results are compared to previously measured speciated compositions of the exhaust gases at the exhaust port inlet and outlet. A stratification parameter to represent the growth of the thermal boundary layer due to heat transfer is added to the simplified unsteady plug flow simulation. Comparisons between model and experiment show that the concentration of products of incomplete combustion can only be adequately reproduced if stratification effects are taken into account.

Wu, K.C.; Hochgreb, S. [Massachusetts Inst. of Technology, Cambridge, MA (United States). Mechanical Engineering Dept.] [Massachusetts Inst. of Technology, Cambridge, MA (United States). Mechanical Engineering Dept.

1996-12-01

182

Characterisation of polycyclic aromatic hydrocarbons in flue gas and residues of a full scale fluidized bed combustor combusting non-hazardous industrial waste.  

PubMed

This paper studies the fate of PAHs in full scale incinerators by analysing the concentration of the 16 EPA-PAHs in both the input waste and all the outputs of a full scale Fluidized Bed Combustor (FBC). Of the analysed waste inputs i.e. Waste Water Treatment (WWT) sludge, Refuse Derived Fuel (RDF) and Automotive Shredder Residue (ASR), RDF and ASR were the main PAH sources, with phenanthrene, fluoranthene and pyrene being the most important PAHs. In the flue gas sampled at the stack, naphthalene was the only predominant PAH, indicating that the PAHs in FBC's combustion gas were newly formed and did not remain from the input waste. Of the other outputs, the boiler and fly ash contained no detectable levels of PAHs, whereas the flue gas cleaning residue contained only low concentrations of naphthalene, probably adsorbed from the flue gas. The PAH fingerprint of the bottom ash corresponded rather well to the PAH fingerprint of the RDF and ASR, indicating that the PAHs in this output, in contrast to the other outputs, were mainly remainders from the PAHs in the waste inputs. A PAH mass balance showed that the total PAH input/output ratio of the FBC ranged from about 100 to about 2600 depending on the waste input composition and the obtained combustion conditions. In all cases, the FBC was clearly a net PAH sink. PMID:25002370

Van Caneghem, J; Vandecasteele, C

2014-11-01

183

Fuel property effects on engine combustion processes. Final report  

SciTech Connect

A major obstacle to improving spark ignition engine efficiency is the limitations on compression ratio imposed by tendency of hydrocarbon fuels to knock (autoignite). A research program investigated the knock problem in spark ignition engines. Objective was to understand low and intermediate temperature chemistry of combustion processes relevant to autoignition and knock and to determine fuel property effects. Experiments were conducted in an optically and physically accessible research engine, static reactor, and an atmospheric pressure flow reactor (APFR). Chemical kinetic models were developed for prediction of species evolution and autoignition behavior. The work provided insight into low and intermediate temperature chemistry prior to autoignition of n-butane, iso-butane, n-pentane, 1-pentene, n-heptane, iso-octane and some binary blends. Study of effects of ethers (MTBE, ETBE, TAME and DIPE ) and alcohols (methanol and ethanol) on the oxidation and autoignition of primary reference fuel (PRF) blends.

Cernansky, N.P.; Miller, D.L.

1995-04-27

184

Studies in combustion dynamics  

SciTech Connect

The goal of this program is to develop a fundamental understanding and a quantitative predictive capability in combustion modeling. A large part of the understanding of the chemistry of combustion processes comes from {open_quotes}chemical kinetic modeling.{close_quotes} However, successful modeling is not an isolated activity. It necessarily involves the integration of methods and results from several diverse disciplines and activities including theoretical chemistry, elementary reaction kinetics, fluid mechanics and computational science. Recently the authors have developed and utilized new tools for parallel processing to implement the first numerical model of a turbulent diffusion flame including a {open_quotes}full{close_quotes} chemical mechanism.

Koszykowski, M.L. [Sandia National Laboratories, Livermore, CA (United States)

1993-12-01

185

Real-time quantitative analysis of combustion-generated polycyclic aromatic hydrocarbons by resonance-enhanced multiphoton ionization time-of-flight mass spectrometry  

SciTech Connect

We have combined resonance-enhanced multiphoton ionization (REMPI) time-of-flight mass spectrometry with on-line flame sampling to determine the centerline concentrations of naphthalene, fluorene, and anthracene in a pure methane + oxygen/argon (1:5) diffusion flame. Naphthalene concentrations between 100 parts per billion by volume (ppbV) and 6 parts per million by volume (ppmV) and fluorene concentrations below 50 ppbV are determined using one-color REMPI on jet-cooled samples extracted from the flame; anthracene concentrations in the 5-40 ppbV range are determined using two-color REMPI. The REMPI ion signals are converted to absolute concentrations in real time by performing gas-phase standard additions to the flame sample. Isomer-selective detection of larger polycyclic aromatic hydrocarbons, such as perylene and benzo[a]pyrene, is possible using the two-color REMPI approach. 38 refs., 8 figs.

Gittins, C.M.; Rohlfing, E.A. [Sandia National Lab., Livermore, CA (United States)] [Sandia National Lab., Livermore, CA (United States); Castaldi, M.J.; Senkan, S.M. [Univ. of California, Los Angeles, CA (United States)] [Univ. of California, Los Angeles, CA (United States)

1997-02-01

186

Real-Time Quantitative Analysis of Combustion-Generated Polycyclic Aromatic Hydrocarbons by Resonance-Enhanced Multiphoton Ionization Time-of-Flight Mass Spectrometry.  

PubMed

We have combined resonance-enhanced multiphoton ionization (REMPI) time-of-flight mass spectrometry with on-line flame sampling to determine the centerline concentrations of naphthalene, fluorene, and anthracene in a pure methane + oxygen/argon (1:5) diffusion flame. Naphthalene concentrations between 100 parts per billion by volume (ppbV) and 6 parts per million by volume (ppmV) and fluorene concentrations below 50 ppbV are determined using one-color REMPI on jet-cooled samples extracted from the flame; anthracene concentrations in the 5-40 ppbV range are determined using two-color REMPI. The REMPI ion signals are converted to absolute concentrations in real time by performing gas-phase standard additions to the flame sample. Isomer-selective detection of larger polycyclic aromatic hydrocarbons, such as perylene and benzo[a]pyrene, is possible using the two-color REMPI approach. PMID:21639183

Gittins, C M; Castaldi, M J; Senkan, S M; Rohlfing, E A

1997-02-01

187

The effect of strain rate on polycyclic aromatic hydrocarbon (PAH) formation in acetylene diffusion flames  

SciTech Connect

Acetylene is a ubiquitous combustion intermediate that is also believed to be the major precursor for aromatic, polycyclic aromatic hydrocarbon (PAH), and soot formation in both hydrocarbon and halogenated hydrocarbon flames. However, in spite of its important role as a flame intermediate, the detailed chemical structures of acetylene diffusion flames have not been studied in the past. Here the detailed chemical structures of counterflow diffusion flames of acetylene at strain rates of 37.7 and 50.3 s{sup -1} are presented. Both flames possessed the same carbon density of 0.37 g/L corresponding to an acetylene mole fraction of 0.375 in argon on the fuel side, and an oxygen mole fraction of 0.22 in argon on the oxidizer side. Concentration profiles of a large number of major, minor, and trace species, including a wide spectrum of aromatics and PAH, have been determined by direct sampling from flames using a heated quartz microprobe coupled to an online gas chromatograph/mass selective detector (GC/MSD). Temperature profiles were made using a thermocouple and the rapid insertion technique. Although the major species concentrations were nearly the same in the two flames, the mole fraction profiles of trace combustion by-products were significantly lower in the higher-strain-rate flame, by nearly two orders of magnitude for PAH. These comparative results provide new information on the trace chemistries of acetylene flames and should be useful for the development and validation of detailed chemical kinetic mechanisms describing the formation of toxic by-products in the combustion of hydrocarbons and halogenated hydrocarbons. (author)

Yamamoto, Manabu; Duan, Shici; Senkan, Selim [Department of Chemical Engineering, University of California, Los Angeles, CA 90095 (United States)

2007-11-15

188

The influence of galactic cosmic rays on ion-neutral hydrocarbon chemistry in the upper atmospheres of free-floating exoplanets  

NASA Astrophysics Data System (ADS)

Cosmic rays may be linked to the formation of volatiles necessary for prebiotic chemistry. We explore the effect of cosmic rays in a hydrogen-dominated atmosphere, as a proof-of-concept that ion-neutral chemistry may be important for modelling hydrogen-dominated atmospheres. In order to accomplish this, we utilize Monte Carlo cosmic ray transport models with particle energies of 106 eVchemistry is then applied to a Drift-Phoenix model of a free-floating giant gas planet. Our results suggest that the activation of ion-neutral chemistry in the upper atmosphere significantly enhances formation rates for various species, and we find that C2H2, C2H4, NH3, C6H6 and possibly C10H are enhanced in the upper atmospheres because of cosmic rays. Our results suggest a potential connection between cosmic-ray chemistry and the hazes observed in the upper atmospheres of various extrasolar planets. Chemi-ionization reactions are briefly discussed, as they may enhance the degree of ionization in the cloud layer.

Rimmer, P. B.; Helling, Ch.; Bilger, C.

2014-04-01

189

Measurements of C{sub 2}-C{sub 6} hydrocarbons during the Polar Sunrise 1992 Experiment: Evidence for Cl atom and Br atom chemistry  

SciTech Connect

The authors report the results of grab samples made in the Arctic winter atmosphere, which were analyzed for the presence of nonmethane hydrocarbons (C{sub 2} - C{sub 6}). The normal removal reactions for such species are due to OH radical reactions, which are expected to be strongly suppressed in winter months. The nonmethane hydrocarbons were observed to correlate well with methane during most of the winter. In April, during low ozone periods, additional depletions of acetylene were observed, which could be correlatied at least in part with Cl concentrations. Not all the variations could be accounted for due to chlorine reactions, and the authors argue that this could be the result of bromine reactions, whose presence would also correlate well with the observed ozone depletions.

Jobson, B.T.; Niki, H. [York Univ., Ontario (Canada)] [York Univ., Ontario (Canada); Yokouchi, Y. [National Institute for Environmental Studies, Ibaraki (Japan)] [and others] [National Institute for Environmental Studies, Ibaraki (Japan); and others

1994-12-20

190

The energetics and structures of some highly unsaturated alicyclic hydrocarbons and their derivatives: a comparison of experiment, quantum chemistry and estimation  

NASA Astrophysics Data System (ADS)

Making use of results derived from calorimetric, electron diffraction and microwave measurements, quantum chemical calculations at the MP2/6-31G*//MP2/6-31G* level (with zeropoint energies at the HF/6-31G* level) and assorted estimation methodologies, structures and enthalpies of formation are presented for some highly unsaturated alicyclic hydrocarbons (cyclopropene, cyclobutene, cyclopentadiene, 1,4- and 1,3-cyclohexadiene, and cycloheptatriene) and their keto- and exo-methylene derivatives.

Liebman, Joel F.; Skancke, Anne

191

Measurements of C2-C6 hydrocarbons during the Polar Sunrise 1992 Experiment: Evidence for Cl atom and Br atom chemistry  

Microsoft Academic Search

Grab samples for nonmethane hydrocarbons (NMHCs) were collected from three sites: daily at Alert, Northwest territories (82.5°N, 62.3°W) from January 21 to April 19, daily at an ice flow 150 km north of Alert from April 9 to 25, and on an aerial survey conducted in April over the Arctic archipelago. In situ measurements of n-butane and i-pentane were also

B. T. Jobson; H. Niki; Y. Yokouchi; J. Bottenheim; F. Hopper; R. Leaitch

1994-01-01

192

Measurements of C 2 –C 7 hydrocarbons during the Polar Sunrise Experiment 1994: Further evidence for halogen chemistry in the troposphere  

Microsoft Academic Search

Air samples for nonmethane hydrocarbon (NMHC) analysis were collected at two ground-based sites: Alert, Northwest Territories (82.5øN, 62.3øW) and Narwhal ice camp, an ice floe 140 km northwest of Alert, from Julian days 90 to 117, 1994, and on a 2-day aerial survey conducted on Julian days 89 and 90, 1994 over the Arctic archipelago. Several ozone depletion events and

P. A. Ariya; B. T. Jobson; R. Sander; H. Niki; G. W. Harris; J. F. Hopper; K. G. Anlauf

1998-01-01

193

Probing flame chemistry with MBMS, theory, and modeling  

SciTech Connect

The objective is to establish kinetics of combustion and molecular-weight growth in C{sub 3} hydrocarbon flames as part of an ongoing study of flame chemistry. Specific reactions being studied are (1) the growth reactions of C{sub 3}H{sub 5} and C{sub 3}H{sub 3} with themselves and with unsaturated hydrocarbons and (2) the oxidation reactions of O and OH with C{sub 3}`s. This approach combines molecular-beam mass spectrometry (MBMS) experiments on low-pressure flat flames; theoretical predictions of rate constants by thermochemical kinetics, Bimolecular Quantum-RRK, RRKM, and master-equation theory; and whole-flame modeling using full mechanisms of elementary reactions.

Westmoreland, P.R. [Univ. of Massachusetts, Amherst (United States)

1993-12-01

194

Radiation Chemistry  

NASA Astrophysics Data System (ADS)

Ionizing radiation causes chemical changes in the molecules of the interacting medium. The initial molecules change to new molecules, resulting in changes of the physical, chemical, and eventually biological properties of the material. For instance, water decomposes to its elements H2 and O2. In polymers, degradation and crosslinking take place. In biopolymers, e.g., DNS strand breaks and other alterations occur. Such changes are to be avoided in some cases (radiation protection), however, in other cases they are used for technological purposes (radiation processing). This chapter introduces radiation chemistry by discussing the sources of ionizing radiation (radionuclide sources, machine sources), absorption of radiation energy, techniques used in radiation chemistry research, and methods of absorbed energy (absorbed dose) measurements. Radiation chemistry of different classes of inorganic (water and aqueous solutions, inorganic solids, ionic liquids (ILs)) and organic substances (hydrocarbons, halogenated compounds, polymers, and biomolecules) is discussed in concise form together with theoretical and experimental backgrounds. An essential part of the chapter is the introduction of radiation processing technologies in the fields of polymer chemistry, food processing, and sterilization. The application of radiation chemistry to nuclear technology and to protection of environment (flue gas treatment, wastewater treatment) is also discussed.

Wojnárovits, L.

195

Combustion Fundamentals Research  

NASA Technical Reports Server (NTRS)

The various physical processes that occur in the gas turbine combustor and the development of analytical models that accurately describe these processes are discussed. Aspects covered include fuel sprays; fluid mixing; combustion dynamics; radiation and chemistry and numeric techniques which can be applied to highly turbulent, recirculating, reacting flow fields.

1984-01-01

196

A comprehensive detailed chemical kinetic reaction mechanism for combustion of n-alkane hydrocarbons from n-octane to n-hexadecane  

SciTech Connect

Detailed chemical kinetic reaction mechanisms have been developed to describe the pyrolysis and oxidation of nine n-alkanes larger than n-heptane, including n-octane (n-C{sub 8}H{sub 18}), n-nonane (n-C{sub 9}H{sub 20}), n-decane (n-C{sub 10}H{sub 22}), n-undecane (n-C{sub 11}H{sub 24}), n-dodecane (n-C{sub 12}H{sub 26}), n-tridecane (n-C{sub 13}H{sub 28}), n-tetradecane (n-C{sub 14}H{sub 30}), n-pentadecane (n-C{sub 15}H{sub 32}), and n-hexadecane (n-C{sub 16}H{sub 34}). These mechanisms include both high temperature and low temperature reaction pathways. The mechanisms are based on previous mechanisms for the primary reference fuels n-heptane and iso-octane, using the reaction classes first developed for n-heptane. Individual reaction class rules are as simple as possible in order to focus on the parallelism between all of the n-alkane fuels included in the mechanisms. These mechanisms are validated through extensive comparisons between computed and experimental data from a wide variety of different sources. In addition, numerical experiments are carried out to examine features of n-alkane combustion in which the detailed mechanisms can be used to compare reactivities of different n-alkane fuels. The mechanisms for these n-alkanes are presented as a single detailed mechanism, which can be edited to produce efficient mechanisms for any of the n-alkanes included, and the entire mechanism, with supporting thermochemical and transport data, together with an explanatory glossary explaining notations and structural details, is available for download from our web page. (author)

Westbrook, Charles K.; Pitz, William J.; Herbinet, Olivier; Silke, Emma J. [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Curran, Henry J. [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); University College of Ireland, Galway (Ireland)

2009-01-15

197

Combustion aerosols: factors governing their size and composition and implications to human health.  

PubMed

Particulate matter (PM) emissions from stationary combustion sources burning coal, fuel oil, biomass, and waste, and PM from internal combustion (IC) engines burning gasoline and diesel, are a significant source of primary particles smaller than 2.5 microns (PM2.5) in urban areas. Combustion-generated particles are generally smaller than geologically produced dust and have unique chemical composition and morphology. The fundamental processes affecting formation of combustion PM and the emission characteristics of important applications are reviewed. Particles containing transition metals, ultrafine particles, and soot are emphasized because these types of particles have been studied extensively, and their emissions are controlled by the fuel composition and the oxidant-temperature-mixing history from the flame to the stack. There is a need for better integration of the combustion, air pollution control, atmospheric chemistry, and inhalation health research communities. Epidemiology has demonstrated that susceptible individuals are being harmed by ambient PM. Particle surface area, number of ultrafine particles, bioavailable transition metals, polycyclic aromatic hydrocarbons (PAH), and other particle-bound organic compounds are suspected to be more important than particle mass in determining the effects of air pollution. Time- and size-resolved PM measurements are needed for testing mechanistic toxicological hypotheses, for characterizing the relationship between combustion operating conditions and transient emissions, and for source apportionment studies to develop air quality plans. Citations are provided to more specialized reviews, and the concluding comments make suggestions for further research. PMID:11055157

Lighty, J S; Veranth, J M; Sarofim, A F

2000-09-01

198

Assembling gas-phase reaction mechanisms for high temperature inorganic systems based on quantum chemistry calculations and reaction rate theories  

NASA Astrophysics Data System (ADS)

Detailed chemical kinetic modeling based on computational quantum chemistry has been quite successful in making quantitative predictions about some systems, particularly the combustion of small hydrocarbons and certain areas of atmospheric chemistry. The gas phase chemistry of many processes in high-temperature inorganic systems, from materials synthesis to propulsion to waste incineration, could in principle be modeled with equal or greater success using detailed chemical kinetic modeling. This contribution provides examples from our own work of how computational quantum chemistry can be used in developing gas phase reaction mechanisms for modeling of high temperature materials processing. In the context of CVD of silicon from dichlorosilane, CVD of alumina from AlCl3/H2/CO2 mixtures, and particle nucleation from silane, this detailed chemical kinetic modeling has given us insight into gas phase reaction pathways that we would not likely have gained by other means.

Swihart, Mark T.

2005-02-01

199

Differential mechanisms of cell death induced by nitro-polycyclic aromatic hydrocarbons.  

E-print Network

??Polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs are environmental pollutants formed during incomplete combustion of organic material, found attached to particulate matter (PM) in ambient air.… (more)

Asare, Nana Y. O.

2009-01-01

200

Nitrogen oxide pollution abatement using catalytic combustion  

SciTech Connect

A process is claimed for purifying nitric acid plant tail gases in which there is catalytic combustion of a hydrogen containing gas with the oxygen contained in the tail gases, the improvement in which heat produced from the catalytic combustion is used for catalytic reforming of a stream of hydrocarbon and steam to produce the hydrogen containing gas.

James, G.

1980-04-15

201

Research avenues in combustion aerodynamics  

SciTech Connect

Practical combustion systems incorporate interdependent phenomena of three-dimensional multicomponent flow fields with complex multiphase chemical kinetics, evaporation and heat transfer processes all occurring simultaneously. An overview is presented here of the prospects for improved understanding of combustion processes, with particular emphasis on fluid dynamics and modeling, as applied to practical combustion systems. Extensive measurements should cover a wide range of physical variables, and include mean and time-dependent data and correlations obtained nonintrusively, so as to aid the modeler. Regarding combustion studies, after success with fluid dynamic model laws with a given fuel, extension to a wider range of fuels is required. Applied combustion research needs include the clean and efficient combustion of fossil fuels and future low-grade liquid and solid fuels, and the associated reduction of pollution through combustion control. Fundamental combustion research needs to be done in the areas of interactions between turbulence and kinetics, nonintrusive optical diagnostics, computer model development, gas and solid phase kinetics, droplet/particle cloud combustion, soot formation and chemistry, and flame structure. Both experimental and theoretical combustion engineers need greater understanding of combustion processes.

Lilley, D.G. [Oklahoma State Univ., Stillwater, OK (United States). School of Mechanical and Aerospace Engineering

1994-12-31

202

Preliminary assessment of combustion modes for internal combustion wave rotors  

NASA Technical Reports Server (NTRS)

Combustion within the channels of a wave rotor is examined as a means of obtaining pressure gain during heat addition in a gas turbine engine. Several modes of combustion are considered and the factors that determine the applicability of three modes are evaluated in detail; premixed autoignition/detonation, premixed deflagration, and non-premixed compression ignition. The last two will require strong turbulence for completion of combustion in a reasonable time in the wave rotor. The compression/autoignition modes will require inlet temperatures in excess of 1500 R for reliable ignition with most hydrocarbon fuels; otherwise, a supplementary ignition method must be provided. Examples of combustion mode selection are presented for two core engine applications that had been previously designed with equivalent 4-port wave rotor topping cycles using external combustion.

Nalim, M. Razi

1995-01-01

203

Resonance ionization detection of combustion radicals  

SciTech Connect

Fundamental research on the combustion of halogenated organic compounds with emphasis on reaction pathways leading to the formation of chlorinated aromatic compounds and the development of continuous emission monitoring methods will assist in DOE efforts in the management and disposal of hazardous chemical wastes. Selective laser ionization techniques are used in this laboratory for the measurement of concentration profiles of radical intermediates in the combustion of chlorinated hydrocarbon flames. A new ultrasensitive detection technique, made possible with the advent of tunable VUV laser sources, enables the selective near-threshold photoionization of all radical intermediates in premixed hydrocarbon and chlorinated hydrocarbon flames.

Cool, T.A. [Cornell Univ., Ithaca, NY (United States)

1993-12-01

204

The Mechanism of High Temperature Combustion of Propane and Butane  

Microsoft Academic Search

By combination of a mechanism describing lean and moderately rich combustion of alkanes and alkenes with a mechanism describing rich combustion and formation of soot pre-cursors in acetylene flames, a general reaction scheme is developed for the simulation of lean and rich high-temperature combustion of hydrocarbons up to C4 - species. Results of these simulations are compared to experimental data,

JÜRGEN WARNATZ

1983-01-01

205

Hydrocarbon pneumonia  

MedlinePLUS

... polish , paint thinner, or other oily materials or solvents. These hydrocarbons have a very low viscosity. This ... will give you further instructions. This is a free and confidential service. All local poison control centers ...

206

Hydrocarbon Transport  

NSF Publications Database

... EAM NSF Org: OD / OPP Date : December 04, 1991 File : opp93039 DIVISION OF POLAR PROGRAMS OFFICE OF ... on Hydrocarbon Transport in Polar Soils) To: Files (Environment - S.7) (Hazardous Wastes - S.7.1 ...

207

Accelerating the Computation of Detailed Chemical Reaction Kinetics for Simulating Combustion of Complex Fuels  

SciTech Connect

Combustion of hydrocarbon fuels has been a very challenging scientific and engineering problem due to the complexity of turbulent flows and hydrocarbon reaction kinetics. There is an urgent need to develop an efficient modeling capability to accurately predict the combustion of complex fuels. Detailed chemical kinetic models for the surrogates of fuels such as gasoline, diesel and JP-8 consist of thousands of chemical species and Arrhenius reaction steps. Oxygenated fuels such as bio-fuels and heavier hydrocarbons, such as from newer fossil fuel sources, are expected to have a much more complex chemistry requiring increasingly larger chemical kinetic models. Such models are beyond current computational capability, except for homogeneous or partially stirred reactor type calculations. The advent of highly parallel multi-core processors and graphical processing units (GPUs) promises a steep increase in computational performance in the coming years. This paper will present a software framework that translates the detailed chemical kinetic models to high- performance code targeted for GPU accelerators.

Grout, Ray W [ORNL

2012-01-01

208

Accelerating the Computation of Detailed Chemical Reaction Kinetics for Simulating Combustion of Complex Fuels  

SciTech Connect

Combustion of hydrocarbon fuels has been a very challenging scientific and engineering problem due to the complexity of turbulent flows and hydrocarbon reaction kinetics. There is an urgent need to develop an efficient modeling capability to accurately predict the combustion of complex fuels. Detailed chemical kinetic models for the surrogates of fuels such as gasoline, diesel and JP-8 consist of thousands of chemical species and Arrhenius reaction steps. Oxygenated fuels such as bio-fuels and heavier hydrocarbons, such as from newer fossil fuel sources, are expected to have a much more complex chemistry requiring increasingly larger chemical kinetic models. Such models are beyond current computational capability, except for homogeneous or partially stirred reactor type calculations. The advent of highly parallel multi-core processors and graphical processing units (GPUs) promises a steep increase in computational performance in the coming years. This paper will present a software framework that translates the detailed chemical kinetic models to high-performance code targeted for GPU accelerators.

Sankaran, R.; Grout, R.

2012-01-01

209

Department of Chemistry & Biochemistry UCLA Chemistry, Biochemistry & Chemistry Material Science  

E-print Network

Department of Chemistry & Biochemistry UCLA Chemistry, Biochemistry & Chemistry Material Science ...........................................................................................................................................4 Chemistry & Biochemistry Undergraduate Office..............................................................................................6 Majors in Chemistry & Biochemistry

Levine, Alex J.

210

ENVIRONMENTAL CARCINOGENIC POLYCYCLIC AROMATIC HYDROCARBONS: PHOTOCHEMISTRY AND PHOTOTOXICITY  

Microsoft Academic Search

Polycyclic aromatic hydrocarbons (PAHs) are a class of environmental contaminants that has long been of interest in the fields of organic chemistry, theoretical chemistry, physical chemistry, environmental science, toxicology, cancer research, and energy sciences. Concerning environmental science and cancer research, majority of the research has focused on the occurrence, environmental fate, degradation\\/remediation, chemical transformation, genotoxicity, metabolism and metabolic activation, DNA

Hongtao Yu

2002-01-01

211

Hydrocarbon-enhanced particulate filter regeneration via microwave ignition  

SciTech Connect

A regeneration method for a particulate filter includes estimating a quantity of particulate matter trapped within the particulate filter, comparing the quantity of particulate matter to a predetermined quantity, heating at least a portion of the particulate filter to a combustion temperature of the particulate matter, and introducing hydrocarbon fuel to the particulate filter. The hydrocarbon fuel facilitates combustion of the particulate matter to regenerate the particulate filter.

Gonze, Eugene V. (Pinckney, MI); Brown, David B. (Brighton, MI)

2010-02-02

212

Combustion noise  

NASA Technical Reports Server (NTRS)

A review of the subject of combustion generated noise is presented. Combustion noise is an important noise source in industrial furnaces and process heaters, turbopropulsion and gas turbine systems, flaring operations, Diesel engines, and rocket engines. The state-of-the-art in combustion noise importance, understanding, prediction and scaling is presented for these systems. The fundamentals and available theories of combustion noise are given. Controversies in the field are discussed and recommendations for future research are made.

Strahle, W. C.

1977-01-01

213

In-Cylinder Reaction Chemistry and Kinetics During Negative Valve Overlap Fuel Injection Under Low-Oxygen Conditions  

SciTech Connect

Fuel injection into the negative valve overlap (NVO) period is a common method for controlling combustion phasing in homogeneous charge compression ignition (HCCI) as well as other forms of advanced combustion. During this event, at least a portion of the fuel hydrocarbons can be converted to products containing significant levels of H2 and CO, as well as other short chain hydrocarbons by means of thermal cracking, water-gas shift, and partial oxidation reactions, depending on the availability of oxygen and the time-temperature-pressure history. The resulting products alter the autoignition properties of the combined fuel mixture for HCCI. Fuel-rich chemistry in a partial oxidation environment is also relevant to other high efficiency engine concepts (e.g., the dedicated EGR (D-EGR) concept from SWRI). In this study, we used a unique 6-stroke engine cycle to experimentally investigate the chemistry of a range of fuels injected during NVO under low oxygen conditions. Fuels investigated included iso-octane, iso-butanol, ethanol, and methanol. Products from NVO chemistry were highly dependent on fuel type and injection timing, with iso-octane producing less than 1.5% hydrogen and methanol producing more than 8%. We compare the experimental trends with CHEMKIN (single zone, 0-D model) predictions using multiple kinetic mechanisms available in the current literature. Our primary conclusion is that the kinetic mechanisms investigated are unable to accurately predict the magnitude and trends of major species we observed.

Kalaskar, Vickey B [ORNL] [ORNL; Szybist, James P [ORNL] [ORNL; Splitter, Derek A [ORNL] [ORNL; Pihl, Josh A [ORNL] [ORNL; Gao, Zhiming [ORNL] [ORNL; Daw, C Stuart [ORNL] [ORNL

2013-01-01

214

Combustion engine. [for air pollution control  

NASA Technical Reports Server (NTRS)

An arrangement for an internal combustion engine is provided in which one or more of the cylinders of the engine are used for generating hydrogen rich gases from hydrocarbon fuels, which gases are then mixed with air and injected into the remaining cylinders to be used as fuel. When heavy load conditions are encountered, hydrocarbon fuel may be mixed with the hydrogen rich gases and air and the mixture is then injected into the remaining cylinders as fuel.

Houseman, J. (inventor)

1977-01-01

215

Combustion of High-Energy-High-Density Fuels  

Microsoft Academic Search

Quantitative analyses of combustion products of a High Energy\\/High Density (HED) hydrocarbon, Methylated Pentacycloundecane Alkene Dinner (MPCU), are presented. This compound is a large molecule, C24H28, which dissolves in large proportions in existing liquid hydrocarbons, such as JP-10, forming stable blends to 50% w\\/w. These blends exhibited a five-fold larger burning rate compared with pure JP-10 droplets. Identification of combustion

C. SEGAL; S. PETHE; K. R. WILLIAMS

2001-01-01

216

Kinetic data base for combustion modeling  

SciTech Connect

The aim of this work is to develop a set of evaluated rate constants for use in the simulation of hydrocarbon combustion. The approach has been to begin with the small molecules and then introduce larger species with the various structural elements that can be found in all hydrocarbon fuels and decomposition products. Currently, the data base contains most of the species present in combustion systems with up to four carbon atoms. Thus, practically all the structural grouping found in aliphatic compounds have now been captured. The direction of future work is the addition of aromatic compounds to the data base.

Tsang, W.; Herron, J.T. [National Institute of Standards and Technology, Gaithersburg, MD (United States)

1993-12-01

217

Fundamental studies of fuel chemistry as related to internal combustion engine phenomena. Technical progress report, July 1, 1988--June 30, 1989  

SciTech Connect

The present research effort was initiated with the intent of providing substantially improved insights (through homogeneous gas phase kinetic studies at different constant pressures) to the fuel chemistry issues important to autoignition in engines. The conditions of the proposed experiments were chosen to represent those similar to the engine parameters under knocking conditions: temperatures in the range of 700--1,100K, pressures from one to approximately 20 atmospheres and stoichiometries around one. A major part of the proposed research has been to design and construct a variable pressure flow reactor facility in which a range of reaction pressures, and in fact, lower reaction temperatures could be accessed. The reactor facility design and construction are nearly complete, and initial testing has begun to compare the overall experimental operating characteristics of the reactor with the design parameters. Experiments on Isobutene/oxygen mixtures have also been conducted in the existing atmospheric pressure flow reactor at about 1,150 K and in an equivalence ratio range of pyrolysis with about 100 ppm oxygen background to 0.42. A detailed kinetic model has been developed to interpret the pyrolysis and oxidation characteristics. 89 refs.

Dryer, F.L.; Brezinsky, K.

1989-07-01

218

Emissions from syngas combustion  

SciTech Connect

Gasification technology has matured to the point that previously-held hesitations regarding performance and availability have given way to acceptance of the technology for energy generation. Indeed, the past few years have seen a significant increase in the number of gasifiers installed for generation of power and heat, and the number of installations is expected to increase dramatically over the next several decades as demand for efficient and environmentally sound energy generation increases. It is valuable to consider the environmental impact of this new generation of energy production systems, specifically release of gaseous emissions from combustion of the synthesis gas produced by gasification. Emissions from syngas combustion in turbines, engines and boilers are discussed in this review. The types of emissions considered include the unburned fuel components and partially oxidized species, nitrogen and sulfur-containing gases, volatile organic compounds, and other trace elements. Combustion of synthesis gas, in general, produces lower emissions for heat and power generation than conventional liquid and solid fuels. The composition of the syngas strongly influences the level of emissions. Hydrogen and carbon monoxide in synthesis gases results in elevated combustion temperature that facilitates the thermal formation of NO and NO{sub 2}. In contrast, higher temperatures promote complete combustion and reduce the emission of organic volatiles, which are formed mainly from minor fractions of hydrocarbons in synthesis gases. Particulate matter, metallic compounds and other undesired pollutants are usually removed before firing synthesis gases for heat and power production. Therefore, integrated gasification and combined cycle systems are more environmentally friendly than conventional power generation systems.

Whitty, K.J.; Zhang, H.R.; Eddings, E.G. [University of Utah, Salt Lake City, UT (United States). Inst. for Clean & Secure Energy

2008-07-01

219

Kinetic double-layer model of aerosol surface chemistry and gas-particle interactions (K2-SURF): degradation of polycyclic aromatic hydrocarbons exposed to O3, NO2, H2O, OH and NO3  

NASA Astrophysics Data System (ADS)

We present a kinetic double-layer surface model (K2-SURF) that describes the degradation of polycyclic aromatic hydrocarbons (PAHs) on aerosol particles exposed to ozone, nitrogen dioxide, water vapor, hydroxyl and nitrate radicals. The model is based on multiple experimental studies of PAH degradation and on the PRA framework (Pöschl et al., 2007) for aerosol and cloud surface chemistry and gas-particle interactions. For a wide range of substrates, including solid and liquid organic and inorganic substances (soot, silica, sodium chloride, octanol/decanol, organic acids, etc.), the concentration- and time-dependence of the heterogeneous reaction between PAHs and O3 can be efficiently described with a Langmuir-Hinshelwood-type mechanism. Depending on the substrate material, the Langmuir adsorption constants for O3 vary over three orders of magnitude (Kads,O3?10-15-10-13 cm3), and the second-order rate coefficients for the surface layer reaction of O3 with different PAH vary over two orders of magnitude (kSLR,PAH,O3?10-18-10-17 cm2 s-1). The available data indicate that the Langmuir adsorption constants for NO2 are similar to those of O3, while those of H2O are several orders of magnitude smaller (Kads,H2O?10-18-10-17 cm3). The desorption lifetimes and adsorption enthalpies inferred from the Langmuir adsorption constants suggest chemisorption of NO2 and O3 - possibly in the form of O atoms - and physisorption of H2O. The K2-SURF model enables the calculation of ozone uptake coefficients, ?O3, and of PAH concentrations in the quasi-static particle surface layer. Competitive adsorption and chemical transformation of the surface (aging) lead to a strong non-linear dependence of ?O3 on time and gas phase composition, with different characteristics under dilute atmospheric and concentrated laboratory conditions. Under typical ambient conditions, ?O3 of PAH-coated aerosol particles are expected to be in the range of 10-6-10-5. At ambient temperatures, NO2 alone does not efficiently degrade PAHs, but it was found to accelerate the degradation of PAHs exposed to O3. The accelerating effect can be attributed to highly reactive NO3 radicals formed in the gas phase or on the surface. Estimated second-order rate coefficients for O3-NO2 and PAH-NO3 surface layer reactions are in the range of 10-17-10-16 cm2 s-1 and 10-15-10-12 cm2 s-1, respectively. The chemical half-life of PAH is expected to range from a few minutes on the surface of soot to multiple hours on organic and inorganic solid particles and days on liquid particles. On soot, the degradation of particle-bound PAHs in the atmosphere appears to be dominated by a surface layer reaction with adsorbed ozone. On other substrates, it is likely dominated by gas-surface reactions with OH or NO3 radicals (Eley-Rideal-type mechanism). To our knowledge, K2-SURF is the first atmospheric process model describing multiple types of parallel and sequential surface reactions between multiple gaseous and particle-bound chemical species. It illustrates how the general equations of the PRA framework can be simplified and adapted for specific reaction systems, and we suggest that it may serve as a basis for the development of a general master mechanism of aerosol and cloud surface chemistry.

Shiraiwa, M.; Garland, R. M.; Pöschl, U.

2009-09-01

220

Kinetic double-layer model of aerosol surface chemistry and gas-particle interactions (K2-SURF): Degradation of polycyclic aromatic hydrocarbons exposed to O3, NO2, H2O, OH and NO3  

NASA Astrophysics Data System (ADS)

We present a kinetic double-layer surface model (K2-SURF) that describes the degradation of polycyclic aromatic hydrocarbons (PAHs) on aerosol particles exposed to ozone, nitrogen dioxide, water vapor, hydroxyl and nitrate radicals. The model is based on multiple experimental studies of PAH degradation and on the PRA framework (Pöschl-Rudich-Ammann, 2007) for aerosol and cloud surface chemistry and gas-particle interactions. For a wide range of substrates, including solid and liquid organic and inorganic substances (soot, silica, sodium chloride, octanol/decanol, organic acids, etc.), the concentration- and time-dependence of the heterogeneous reaction between PAHs and O3 can be efficiently described with a Langmuir-Hinshelwood-type mechanism. Depending on the substrate material, the Langmuir adsorption constants for O3 vary over three orders of magnitude (Kads,O3 ? 10-15-10-13 cm3), and the second-order rate coefficients for the surface layer reaction of O3 with different PAH vary over two orders of magnitude (kSLR,PAH,O3 ? 10-18-10-17 cm2 s-1). The available data indicate that the Langmuir adsorption constants for NO2 are similar to those of O3, while those of H2O are several orders of magnitude smaller (Kads,H2O ? 10-18-10-17 cm3). The desorption lifetimes and adsorption enthalpies inferred from the Langmuir adsorption constants suggest chemisorption of NO2 and O3 and physisorption of H2O. Note, however, that the exact reaction mechanisms, rate limiting steps and possible intermediates still remain to be resolved (e.g., surface diffusion and formation of O atoms or O3- ions at the surface). The K2-SURF model enables the calculation of ozone uptake coefficients, ?O3, and of PAH concentrations in the quasi-static particle surface layer. Competitive adsorption and chemical transformation of the surface (aging) lead to a strong non-linear dependence of ?O3 on time and gas phase composition, with different characteristics under dilute atmospheric and concentrated laboratory conditions. Under typical ambient conditions, ?O3 of PAH-coated aerosol particles are expected to be in the range of 10-6-10-5. At ambient temperatures, NO2 alone does not efficiently degrade PAHs, but it was found to accelerate the degradation of PAHs exposed to O3. The accelerating effect can be attributed to highly reactive NO3 radicals formed in the gas phase or on the surface. Estimated second-order rate coefficients for O3-NO2 and PAH-NO3 surface layer reactions are in the range of 10-17-10-16 cm2 s-1 and 10-15-10-12 cm2 s-1, respectively. The chemical half-life of PAHs is expected to range from a few minutes on the surface of soot to multiple hours on organic and inorganic solid particles and days on liquid particles. On soot, the degradation of particle-bound PAHs in the atmosphere appears to be dominated by a surface layer reaction with adsorbed ozone. On other substrates, it is likely dominated by gas-surface reactions with OH or NO3 radicals (Eley-Rideal-type mechanism). To our knowledge, K2-SURF is the first atmospheric process model describing multiple types of parallel and sequential surface reactions between multiple gaseous and particle-bound chemical species. It illustrates how the general equations of the PRA framework can be simplified and adapted for specific reaction systems, and we suggest that it may serve as a basis for the development of a general master mechanism of aerosol and cloud surface chemistry.

Shiraiwa, M.; Garland, R. M.; Pöschl, U.

2009-12-01

221

Hydrocarbon and nonhydrocarbon derivatives of cyclopropane  

NASA Technical Reports Server (NTRS)

The methods used to prepare and purify 19 hydrocarbon derivatives of cyclopropane are discussed. Of these hydrocarbons, 13 were synthesized for the first time. In addition to the hydrocarbons, six cyclopropylcarbinols, five alkyl cyclopropyl ketones, three cyclopropyl chlorides, and one cyclopropanedicarboxylate were prepared as synthesis intermediates. The melting points, boiling points, refractive indices, densities, and, in some instances, heats of combustion of both the hydrocarbon and nonhydrocarbon derivatives of cyclopropane were determined. These data and the infrared spectrum of each of the 34 cyclopropane compounds are presented in this report. The infrared absorption bands characteristic of the cyclopropyl ring are discussed, and some observations are made on the contribution of the cyclopropyl ring to the molecular refractions of cyclopropane compounds.

Slabey, Vernon A; Wise, Paul H; Gibbons, Louis C

1953-01-01

222

Toward solar fuels: photocatalytic conversion of carbon dioxide to hydrocarbons.  

PubMed

The past several decades have seen a significant rise in atmospheric carbon dioxide levels resulting from the combustion of hydrocarbon fuels. A solar energy based technology to recycle carbon dioxide into readily transportable hydrocarbon fuel (i.e., a solar fuel) would help reduce atmospheric CO2 levels and partly fulfill energy demands within the present hydrocarbon based fuel infrastructure. We review the present status of carbon dioxide conversion techniques, with particular attention to a recently developed photocatalytic process to convert carbon dioxide and water vapor into hydrocarbon fuels using sunlight. PMID:20141175

Roy, Somnath C; Varghese, Oomman K; Paulose, Maggie; Grimes, Craig A

2010-03-23

223

Spherical combustion clouds in explosions  

NASA Astrophysics Data System (ADS)

This study explores the properties of spherical combustion clouds in explosions. Two cases are investigated: (1) detonation of a TNT charge and combustion of its detonation products with air, and (2) shock dispersion of aluminum powder and its combustion with air. The evolution of the blast wave and ensuing combustion cloud dynamics are studied via numerical simulations with our adaptive mesh refinement combustion code. The code solves the multi-phase conservation laws for a dilute heterogeneous continuum as formulated by Nigmatulin. Single-phase combustion (e.g., TNT with air) is modeled in the fast-chemistry limit. Two-phase combustion (e.g., Al powder with air) uses an induction time model based on Arrhenius fits to Boiko's shock tube data, along with an ignition temperature criterion based on fits to Gurevich's data, and an ignition probability model that accounts for multi-particle effects on cloud ignition. Equations of state are based on polynomial fits to thermodynamic calculations with the Cheetah code, assuming frozen reactants and equilibrium products. Adaptive mesh refinement is used to resolve thin reaction zones and capture the energy-bearing scales of turbulence on the computational mesh (ILES approach). Taking advantage of the symmetry of the problem, azimuthal averaging was used to extract the mean and rms fluctuations from the numerical solution, including: thermodynamic profiles, kinematic profiles, and reaction-zone profiles across the combustion cloud. Fuel consumption was limited to ˜ 60-70 %, due to the limited amount of air a spherical combustion cloud can entrain before the turbulent velocity field decays away. Turbulent kinetic energy spectra of the solution were found to have both rotational and dilatational components, due to compressibility effects. The dilatational component was typically about 1 % of the rotational component; both seemed to preserve their spectra as they decayed. Kinetic energy of the blast wave decayed due to the pressure field. Turbulent kinetic energy of the combustion cloud decayed due to enstrophy overline{? 2} and dilatation overline{? 2}.

Kuhl, A. L.; Bell, J. B.; Beckner, V. E.; Balakrishnan, K.; Aspden, A. J.

2013-05-01

224

Jovian Auroral Chemistry  

NASA Astrophysics Data System (ADS)

Recent STIS data indicate that the jovian aurora occasionally deposits an energy flux of several W/m2 into the upper atmosphere, most of which penetrates the homopause into hydrocarbon-rich layers. The energetic electrons which carry this flux are thought to initiate the formation of complex hydrocarbons and soot-like aerosols which settle into and blanket the polar stratosphere. Because of the large number of important species and reactions involved, until recently there has been little attention paid to the problem of simulating jovian auroral chemistry. We have modified the Caltech/JPL KINETICS code for general atmospheric chemistry for the investigation of jovian auroral chemistry. Building on the recent work by Perry et al. (J. Geophys. Res., 104, 16,451, 1999), Wong et al. (Astrophys. J., 534, L215, 2000), and Moses et al. (Icarus, 143, 244, 2000; J. Geophys. Res., 105, 7013, 2000), we have updated and included several hundred neutral-neutral and ion-neutral reactions to provide a basis for studying the effects of energetic electron impact on the auroral region atmosphere of Jupiter. We present here the initial results from this study, concentrating on the main ion-neutral pathways for producing complex hydrocarbons, and examining the role of the simplest aromatic compound, c-C3H3+.

Gladstone, G. R.; Majeed, T.; Moses, J. I.; Waite, J. H., Jr.; Allen, M. A.; Yung, Y. L.; Pryor, W. R.

2000-10-01

225

On-line measurement of heat of combustion  

NASA Technical Reports Server (NTRS)

An experimental method for an on-line measurement of heat of combustion of a gaseous hydrocarbon fuel mixture of unknown composition is developed. It involves combustion of a test gas with a known quantity of air to achieve a predetermined oxygen concentration level in the combustion products. This is accomplished by a feedback controller which maintains the gas volumetric flow rate at a level consistent with the desired oxygen concentration in the products. The heat of combustion is determined from a known correlation with the gas volumetric flow rate. An on-line microcomputer accesses the gas volumetric flow data, and displays the heat of combustion values at desired time intervals.

Chaturvedi, S. K.; Chegini, H.

1988-01-01

226

Combustion of droplets and sprays  

NASA Astrophysics Data System (ADS)

The combustion of liquid hydrocarbon fuels in internal combustion engines and gas turbines for energy production and aircraft propulsion is intrinsically tied to the formation of pollutants. Apart from aiming for the highest combustion efficiencies in order to lower the operational costs and the emission of CO2, the reduction of poisonous and environmentally harmful exhaust constituents is a challenging task for scientists and engineers. The most prominent pollutants are soot, identified to trigger respiratory diseases and cancer, and nitric oxides such as NO and NO2, which promote the formation of ozone affecting the cardiovascular system when released in the lower atmosphere. Soot and nitric oxides are greenhouse pollutants in the upper atmosphere. Even though only 2-3% of the anthropogenic emission of nitric oxides are contributed by aircraft, it is the only emission at high altitudes. Unfortunately, it has the greatest impact on climate there and it does not matter whether the fuels are fossil or, in the future, biomass.

Eigenbrod, Christian; Sattelmayer, Thomas; Bäßler, Stefan; Mauss, Fabian; Meisl, Jürgen; Oomens, Bas; Rackwitz, Leif; Tait, Nigel; Angelberger, Christian; Eilts, Peter; Magnusson, Ingemar; Lauvergne, Romain; Tatschl, Reinhard

2005-10-01

227

Chemical kinetics and combustion modeling  

SciTech Connect

The goal of this program is to gain qualitative insight into how pollutants are formed in combustion systems and to develop quantitative mathematical models to predict their formation rates. The approach is an integrated one, combining low-pressure flame experiments, chemical kinetics modeling, theory, and kinetics experiments to gain as clear a picture as possible of the process in question. These efforts are focused on problems involved with the nitrogen chemistry of combustion systems and on the formation of soot and PAH in flames.

Miller, J.A. [Sandia National Laboratories, Livermore, CA (United States)

1993-12-01

228

Sandia Combustion Research Program: Annual report, 1986  

SciTech Connect

This report presents research results of the past year, divided thematically into some ten categories. Publications and presentations arising from this work are included in the appendix. Our highlighted accomplishment of the year is the announcement of the discovery and demonstration of the RAPRENOx process. This new mechanism for the elimination of nitrogen oxides from essentially all kinds of combustion exhausts shows promise for commercialization, and may eventually make a significant contribution to our nation's ability to control smog and acid rain. The sections of this volume describe the facility's laser and computer system, laser diagnostics of flames, combustion chemistry, reacting flows, liquid and solid propellant combustion, mathematical models of combustion, high-temperature material interfaces, studies of engine/furnace combustion, coal combustion, and the means of encouraging technology transfer. 182 refs., 170 figs., 12 tabs.

Not Available

1986-01-01

229

Advanced Chemistry Basins Model  

SciTech Connect

The objective of this project is to: (1) Develop a database of additional and better maturity indicators for paleo-heat flow calibration; (2) Develop maturation models capable of predicting the chemical composition of hydrocarbons produced by a specific kerogen as a function of maturity, heating rate, etc.; assemble a compositional kinetic database of representative kerogens; (3) Develop a 4 phase equation of state-flash model that can define the physical properties (viscosity, density, etc.) of the products of kerogen maturation, and phase transitions that occur along secondary migration pathways; (4) Build a conventional basin model and incorporate new maturity indicators and data bases in a user-friendly way; (5) Develop an algorithm which combines the volume change and viscosities of the compositional maturation model to predict the chemistry of the hydrocarbons that will be expelled from the kerogen to the secondary migration pathways; (6) Develop an algorithm that predicts the flow of hydrocarbons along secondary migration pathways, accounts for mixing of miscible hydrocarbon components along the pathway, and calculates the phase fractionation that will occur as the hydrocarbons move upward down the geothermal and fluid pressure gradients in the basin; and (7) Integrate the above components into a functional model implemented on a PC or low cost workstation.

Blanco, Mario; Cathles, Lawrence; Manhardt, Paul; Meulbroek, Peter; Tang, Yongchun

2003-02-13

230

Composition, distribution, and characterization of polycyclic aromatic hydrocarbons in soil in Linfen, China  

SciTech Connect

A total of 10 surface soil samples representing the entire area of Linfen City were collected and analyzed for the presence of 16 polycyclic aromatic hydrocarbons. The total polycyclic aromatic hydrocarbon concentration ranged from 1.1 to 63.7 {mu} g g{sup -1}. Analysis of the sources of contamination revealed that polycyclic aromatic hydrocarbons in the soil were derived from combustion sources. Specifically, the primary source of polycyclic aromatic hydrocarbons was coal combustion, but the samples were also effected to varying degrees by traffic emissions. Furthermore, increased levels of contamination were observed in northeast Linfen due to the distribution of industrial plants.

Fu, S.; Cheng, H.X.; Liu, Y.H.; Xia, X.J.; Xu, X.B. [Chinese Academy of Sciences, Beijing (China)

2009-02-15

231

Numerical simulation of turbulent combustion: Scientific challenges  

NASA Astrophysics Data System (ADS)

Predictive simulation of engine combustion is key to understanding the underlying complicated physicochemical processes, improving engine performance, and reducing pollutant emissions. Critical issues as turbulence modeling, turbulence-chemistry interaction, and accommodation of detailed chemical kinetics in complex flows remain challenging and essential for high-fidelity combustion simulation. This paper reviews the current status of the state-of-the-art large eddy simulation (LES)/prob-ability density function (PDF)/detailed chemistry approach that can address the three challenging modelling issues. PDF as a subgrid model for LES is formulated and the hybrid mesh-particle method for LES/PDF simulations is described. Then the development need in micro-mixing models for the PDF simulations of turbulent premixed combustion is identified. Finally the different acceleration methods for detailed chemistry are reviewed and a combined strategy is proposed for further development.

Ren, ZhuYin; Lu, Zhen; Hou, LingYun; Lu, LiuYan

2014-08-01

232

Design and operation of a real-time polynuclear aromatic hydrocarbon (PAH) monitor for the analysis of combustion products formed in the incineration of navy colored smoke compositions. Final report December 1982-October 1983  

SciTech Connect

This publication describes the design and construction of a fluorescence-based polynuclear aromatic hydrocarbon (PAH) monitor and calibration system. It also covers the installation and operation of this real-time monitor system during the incineration testing of Navy colored smoke compositions at the Los Alamos National Laboratory Controlled Air Incinerator facility, Los Alamos, N. Mex. During these tests, no PAHs were found to be present in the incinerator effluent gases at a concentration level > approx 1 ppm (the approximate gas-phase detection limit of the monitor). Recommendations are listed for future system improvements.

Loda, R.T.

1984-08-01

233

Biofuels Combustion  

NASA Astrophysics Data System (ADS)

This review describes major features of current research in renewable fuels derived from plants and from fatty acids. Recent and ongoing fundamental studies of biofuel molecular structure, oxidation reactions, and biofuel chemical properties are reviewed, in addition to combustion applications of biofuels in the major types of engines in which biofuels are used. Biofuels and their combustion are compared with combustion features of conventional petroleum-based fuels. Two main classes of biofuels are described, those consisting of small, primarily alcohol, fuels (particularly ethanol, n-butanol, and iso-pentanol) that are used primarily to replace or supplement gasoline and those derived from fatty acids and used primarily to replace or supplement conventional diesel fuels. Research efforts on so-called second- and third-generation biofuels are discussed briefly.

Westbrook, Charles K.

2013-04-01

234

Biofuels combustion.  

PubMed

This review describes major features of current research in renewable fuels derived from plants and from fatty acids. Recent and ongoing fundamental studies of biofuel molecular structure, oxidation reactions, and biofuel chemical properties are reviewed, in addition to combustion applications of biofuels in the major types of engines in which biofuels are used. Biofuels and their combustion are compared with combustion features of conventional petroleum-based fuels. Two main classes of biofuels are described, those consisting of small, primarily alcohol, fuels (particularly ethanol, n-butanol, and iso-pentanol) that are used primarily to replace or supplement gasoline and those derived from fatty acids and used primarily to replace or supplement conventional diesel fuels. Research efforts on so-called second- and third-generation biofuels are discussed briefly. PMID:23298249

Westbrook, Charles K

2013-01-01

235

Determination of stable carbon and hydrogen isotopes of light hydrocarbons  

Microsoft Academic Search

A combined system for the measurement of ¹³C\\/¹²C and D\\/H ratios on light hydrocarbons (Câ-Câ) and COâ is described. The system is designed for natural gas and sediment gas analyses. It comprises gas chromatographic separation with online combustion of hydrocarbons to COâ and HâO, reduction of HâO to Hâ on zinc in closed ampules, and mass spectrometric determination of isotope

Ingolf. Dumke; Eckhard. Faber; Juergen. Poggenburg

1989-01-01

236

Plantwide Energy Management for Hydrocarbon and Petrochemical Industry  

E-print Network

PLANTWIDE ENERGY MANAGEMENT FOR HYDROCARBON AND PETROCHEMICAL INDUSTRY Anwar Ahmed Combustion Engineering Australia Pty. LId. Box HiI~ Victoria, Australia ABSTRACT Within the hydrocarbon and petrochemical industry the generation... and utilization of various forms of energy is a highly complex and dynamic process. The process plant normally generates steam and fuel in the form of process off-gas. The same process plant also requires fuel, steam, and electricity, which is supplied from...

Ahmed, A.; Clinkscales, T.

237

Electrically heated particulate filter regeneration using hydrocarbon adsorbents  

SciTech Connect

An exhaust system that processes exhaust generated by an engine is provided. The system generally includes a particulate filter (PF) that filters particulates from the exhaust wherein an upstream end of the PF receives exhaust from the engine. A grid of electrically resistive material selectively heats exhaust passing through the upstream end to initiate combustion of particulates within the PF. A hydrocarbon adsorbent coating applied to the PF releases hydrocarbons into the exhaust to increase a temperature of the combustion of the particulates within the PF.

Gonze, Eugene V [Pinckney, MI

2011-02-01

238

Combustion & Health  

E-print Network

FFCOMBUSTION & HEALTH Winifred J. Hamilton, PhD, SM Clear Air Through Energy Efficiency (CATEE) Galveston, TX October 9?11, 2012 FFCOMBUSTION & HEALTH FFCOMBUSTION: THE THREAT ? Biggest threat to world ecosystems (and to human health...) ? Combustion of fossil fuels for ? Electricity ? Industrial processes ? Vehicle propulsion ? Cooking and heat ? Other ? Munitions ? Fireworks ? Light ? Cigarettes, hookahs? FFCOMBUSTION & HEALTH FFCOMBUSTION: THE THREAT ? SCALE (think health...

Hamilton, W.

2012-01-01

239

Turbulent combustion  

SciTech Connect

Turbulent combustion is the dominant process in heat and power generating systems. Its most significant aspect is to enhance the burning rate and volumetric power density. Turbulent mixing, however, also influences the chemical rates and has a direct effect on the formation of pollutants, flame ignition and extinction. Therefore, research and development of modern combustion systems for power generation, waste incineration and material synthesis must rely on a fundamental understanding of the physical effect of turbulence on combustion to develop theoretical models that can be used as design tools. The overall objective of this program is to investigate, primarily experimentally, the interaction and coupling between turbulence and combustion. These processes are complex and are characterized by scalar and velocity fluctuations with time and length scales spanning several orders of magnitude. They are also influenced by the so-called {open_quotes}field{close_quotes} effects associated with the characteristics of the flow and burner geometries. The authors` approach is to gain a fundamental understanding by investigating idealized laboratory flames. Laboratory flames are amenable to detailed interrogation by laser diagnostics and their flow geometries are chosen to simplify numerical modeling and simulations and to facilitate comparison between experiments and theory.

Talbot, L.; Cheng, R.K. [Lawrence Berkeley Laboratory, CA (United States)

1993-12-01

240

Properties of Diazocarbene [CNN] and the Diazomethyl Radical [HCNN] via Ion Chemistry and Spectroscopy  

E-print Network

endothermic, rxnH0 ) 1.6 ( 0.7 kcal mol-1 . I. Introduction In an internal combustion engine, air known1 for some time that "thermal" NO is generated in the post- combustion region by the Zeldovich mechanism involving O atoms and N2. In most combustion processes, hydrocarbons are degraded to produce

Ellison, Barney

241

Polycyclic aromatic hydrocarbon exhaust emissions from different reformulated diesel fuels and engine operating conditions  

NASA Astrophysics Data System (ADS)

The study of light-duty diesel engine exhaust emissions is important due to their impact on atmospheric chemistry and air pollution. In this study, both the gas and the particulate phase of fuel exhaust were analyzed to investigate the effects of diesel reformulation and engine operating parameters. The research was focused on polycyclic aromatic hydrocarbon (PAH) compounds on particulate phase due to their high toxicity. These were analyzed using a gas chromatography-mass spectrometry (GC-MS) methodology. Although PAH profiles changed for diesel fuels with low-sulfur content and different percentages of aromatic hydrocarbons (5-25%), no significant differences for total PAH concentrations were detected. However, rape oil methyl ester biodiesel showed a greater number of PAH compounds, but in lower concentrations (close to 50%) than the reformulated diesel fuels. In addition, four engine operating conditions were evaluated, and the results showed that, during cold start, higher concentrations were observed for high molecular weight PAHs than during idling cycle and that the acceleration cycles provided higher concentrations than the steady-state conditions. Correlations between particulate PAHs and gas phase products were also observed. The emission of PAH compounds from the incomplete combustion of diesel fuel depended greatly on the source of the fuel and the driving patterns.

Borrás, Esther; Tortajada-Genaro, Luis A.; Vázquez, Monica; Zielinska, Barbara

2009-12-01

242

Green Chemistry  

NSDL National Science Digital Library

This special feature page from the American Chemical Society (ACS) showcases the up-and-coming field of "green chemistry," that is, the development of chemical products and processes that eliminate or reduce the use and generation of hazardous substances. A list of principles behind green chemistry, a searchable bibliography of green chemistry references, green chemistry links (including conferences), and an online preview of the ACS-published book Real-World Cases in Green Chemistry are all found at the site. Five video clips on green chemistry from the standpoint of academia, industry, and small business are also featured (Windows Media Player). This page comes from ACS's Green Chemistry Project, a three-year educational project to develop and disseminate green chemistry educational materials for graduate and undergraduate chemistry students. Check back often for updates.

2002-01-01

243

Turbulent Combustion in SDF Explosions  

SciTech Connect

A heterogeneous continuum model is proposed to describe the dispersion and combustion of an aluminum particle cloud in an explosion. It combines the gas-dynamic conservation laws for the gas phase with a continuum model for the dispersed phase, as formulated by Nigmatulin. Inter-phase mass, momentum and energy exchange are prescribed by phenomenological models. It incorporates a combustion model based on the mass conservation laws for fuel, air and products; source/sink terms are treated in the fast-chemistry limit appropriate for such gasdynamic fields, along with a model for mass transfer from the particle phase to the gas. The model takes into account both the afterburning of the detonation products of the C-4 booster with air, and the combustion of the Al particles with air. The model equations were integrated by high-order Godunov schemes for both the gas and particle phases. Numerical simulations of the explosion fields from 1.5-g Shock-Dispersed-Fuel (SDF) charge in a 6.6 liter calorimeter were used to validate the combustion model. Then the model was applied to 10-kg Al-SDF explosions in a an unconfined height-of-burst explosion. Computed pressure histories are compared with measured waveforms. Differences are caused by physical-chemical kinetic effects of particle combustion which induce ignition delays in the initial reactive blast wave and quenching of reactions at late times. Current simulations give initial insights into such modeling issues.

Kuhl, A L; Bell, J B; Beckner, V E

2009-11-12

244

DOES FOSSIL FUEL COMBUSTION LEAD TO GLOBAL WARMING? Stephen E. Schwartz  

E-print Network

DOES FOSSIL FUEL COMBUSTION LEAD TO GLOBAL WARMING? Stephen E. Schwartz Environmental Chemistry--Fri, Dec 1, 2006 DOES FOSSIL FUEL COMBUSTION LEAD TO GLOBAL WARMING? Stephen E. Schwartz Environmental Chemistry Division Brookhaven National Laboratory Upton NY 11973 USA [Abstract] Tropospheric sulfate

Schwartz, Stephen E.

245

Infrared multiphoton ignition and combustion enhancement of natural gas  

Microsoft Academic Search

The unique chemistry of methane combustion, including strong C-H bond energy, leads to difficulties in use of natural gas as an engine fuel. Problems include low combustion efficiency, knocking, unreliable ignition (misfiring), and NOx emission. It is well established that improvement of the above-mentioned combustion phenomena requires the presence of high concentration of chain-initiating and chain-branching reactive radicals. This project

Moshe Lavid; Arthur T. Poulos; Suresh K. Gulati

1993-01-01

246

Online and offline experimental techniques for polycyclic aromatic hydrocarbons recovery and measurement  

NASA Astrophysics Data System (ADS)

The implementation of techniques aimed at improving engine performance and reducing particulate matter (PM) pollutant emissions is strongly influenced by the limited understanding of the polycyclic aromatic hydrocarbons (PAH) formation chemistry, in combustion devices, that produces the PM emissions. New experimental results which examine the formation of multi-ring compounds are required. The present investigation focuses on two techniques for such an experimental examination by recovery of PAH compounds from a typical combustion oriented experimental apparatus. The online technique discussed constitutes an optimal solution but not always feasible approach. Nevertheless, a detailed description of a new online sampling system is provided which can serve as reference for future applications to different experimental set-ups. In comparison, an offline technique, which is sometimes more experimentally feasible but not necessarily optimal, has been studied in detail for the recovery of a variety of compounds with different properties, including naphthalene, biphenyl, and iodobenzene. The recovery results from both techniques were excellent with an error in the total carbon balance of around 10% for the online technique and an uncertainty in the measurement of the single species of around 7% for the offline technique. Although both techniques proved to be suitable for measurement of large PAH compounds, the online technique represents the optimal solution in view of the simplicity of the corresponding experimental procedure. On the other hand, the offline technique represents a valuable solution in those cases where the online technique cannot be implemented.

Comandini, A.; Malewicki, T.; Brezinsky, K.

2012-03-01

247

Combustion instability modeling and analysis  

SciTech Connect

It is well known that the two key elements for achieving low emissions and high performance in a gas turbine combustor are to simultaneously establish (1) a lean combustion zone for maintaining low NO{sub x} emissions and (2) rapid mixing for good ignition and flame stability. However, these requirements, when coupled with the short combustor lengths used to limit the residence time for NO formation typical of advanced gas turbine combustors, can lead to problems regarding unburned hydrocarbons (UHC) and carbon monoxide (CO) emissions, as well as the occurrence of combustion instabilities. The concurrent development of suitable analytical and numerical models that are validated with experimental studies is important for achieving this objective. A major benefit of the present research will be to provide for the first time an experimentally verified model of emissions and performance of gas turbine combustors. The present study represents a coordinated effort between industry, government and academia to investigate gas turbine combustion dynamics. Specific study areas include development of advanced diagnostics, definition of controlling phenomena, advancement of analytical and numerical modeling capabilities, and assessment of the current status of our ability to apply these tools to practical gas turbine combustors. The present work involves four tasks which address, respectively, (1) the development of a fiber-optic probe for fuel-air ratio measurements, (2) the study of combustion instability using laser-based diagnostics in a high pressure, high temperature flow reactor, (3) the development of analytical and numerical modeling capabilities for describing combustion instability which will be validated against experimental data, and (4) the preparation of a literature survey and establishment of a data base on practical experience with combustion instability.

Santoro, R.J.; Yang, V.; Santavicca, D.A. [Pennsylvania State Univ., University Park, PA (United States); Sheppard, E.J. [Tuskeggee Univ., Tuskegee, AL (United States). Dept. of Aerospace Engineering

1995-12-31

248

Detailed modeling of size distribution functions and hydrogen content in combustion-formed particles  

SciTech Connect

A kinetic modeling approach is proposed to delve into the nature and chemistry of combustion-produced particles. A sectional method is used for the first time on this purpose. It is based on modeling of gas-to-particle transitions by sections containing 125 lumped species with C numbers ranging from 24 to 4 x 10{sup 8} and H/C ratio ranging from 0 to 1. This allows not only the mass evolution of particles, but also their hydrogen content to be followed. The model is tested in an atmospheric pressure premixed flat flame of ethylene/oxygen with C/O = 0.8 and cold gas flow velocity of 4 cm/s. Comparison of modeled results with experimental data is satisfying in terms of species concentrations and H/C ratio of the particles. Analysis of model results in comparison with the experimental data has shown that it is possible to distinguish different precursors of particles moving from the exit of the burner into the post-oxidation region of the flame. At particle inception, i.e. just downstream from the flame front, gas-phase PAHs are responsible for particle nucleation and oligomers of aromatic hydrocarbons and small pericondensed hydrocarbons are predominantly present. Then the dehydrogenation process takes place and soot formation starts; in this zone large pericondensed and stacked structures are produced. Further up soot maturation generally linked with dehydrogenation is present, but still a few particles with higher H/C and with low coagulation efficiency are produced and remain present along the flame. The model, in accordance with experimental structural soot analysis, shows that in soot particles condensed structures typical of clusters of large pericondensed hydrocarbons are present whereas high-molecular mass condensed species mainly comprise oligomers of small aromatic compounds of clusters of small pericondensed hydrocarbons. (author)

Sirignano, Mariano; D'Anna, Andrea [Dipartimento di Ingegneria Chimica, Universita di Napoli ''Federico II'', Napoli (Italy); Kent, John [School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney, Sydney (Australia)

2010-06-15

249

Combustion control  

Microsoft Academic Search

This patent describes an improved method of operating in a combustion process which is regulated by maintaining a preselected feed forward relationship of fuel input and air input. It comprises: establishing a fuel\\/air input peak relationship for the approximately stoichiometric condition which produces the maximum infrared radiation; selecting a desired operating fuel\\/air ratio based on a result of the fuel\\/air

Zabielski

1990-01-01

250

Advanced Combustion  

SciTech Connect

The activity reported in this presentation is to provide the mechanical and physical property information needed to allow rational design, development and/or choice of alloys, manufacturing approaches, and environmental exposure and component life models to enable oxy-fuel combustion boilers to operate at Ultra-Supercritical (up to 650{degrees}C & between 22-30 MPa) and/or Advanced Ultra-Supercritical conditions (760{degrees}C & 35 MPa).

Holcomb, Gordon R. [NETL

2013-03-11

251

Constant-Pressure Combustion Charts Including Effects of Diluent Addition  

NASA Technical Reports Server (NTRS)

Charts are presented for the calculation of (a) the final temperatures and the temperature changes involved in constant-pressure combustion processes of air and in products of combustion of air and hydrocarbon fuels, and (b) the quantity of hydrocarbon fuels required in order to attain a specified combustion temperature when water, alcohol, water-alcohol mixtures, liquid ammonia, liquid carbon dioxide, liquid nitrogen, liquid oxygen, or their mixtures are added to air as diluents or refrigerants. The ideal combustion process and combustion with incomplete heat release from the primary fuel and from combustible diluents are considered. The effect of preheating the mixture of air and diluents and the effect of an initial water-vapor content in the combustion air on the required fuel quantity are also included. The charts are applicable only to processes in which the final mixture is leaner than stoichiometric and at temperatures where dissociation is unimportant. A chart is also included to permit the calculation of the stoichiometric ratio of hydrocarbon fuel to air with diluent addition. The use of the charts is illustrated by numerical examples.

Turner, L Richard; Bogart, Donald

1949-01-01

252

Alkene and arene combustion on Pd(111)  

SciTech Connect

Palladium-catalyzed combustion reactions can play a significant role in the control of auto emissions in the three-way catalytic converter. Oxidation reactions of ethene, propene, 1-butene, 1,3-butadiene, benzene, and toluene were studied on oxygen-precovered Pd(111) (0.25 ML--1.2 ML) using temperature-programmed reaction spectroscopy (TPRS). Combustion is the sole reaction pathway; no partial oxidation products are formed. Comparison of these results with those from Pd(100) demonstrates that the structure of the metal surface does not significantly affect the mechanism of catalytic oxidation of most of the olefins or aromatic hydrocarbons studied, although, in general, combustion occurs at higher temperatures on Pd(111). Only for benzene combustion is there an appreciable structure sensitivity. For all the hydrocarbons studied the CO{sub 2} and CO yields are maximized for an oxygen precoverage of 0.34 oxygen atoms per surface palladium atom. Abrupt increases in carbon oxide production at specific oxygen coverages indicate that oxygen-induced surface reconstructions may play a role in the combustion activity.

Harris, T.D.; Madix, R.J. [Stanford Univ., CA (United States)] [Stanford Univ., CA (United States)

1998-09-10

253

Formation and reduction of nitric oxide in fixed-bed combustion of straw  

Microsoft Academic Search

Mechanisms of nitric oxide (NO) formation and reduction in fixed-bed combustion of straw have been modeled mathematically and verified experimentally. The model for the straw combustion and nitrogen chemistry consists of sub-models for evaporation, pyrolysis, tar and char combustion, nitrogen conversion, and energy and mass conservation. Twenty chemical reactions are included, of which 12 belong to the fuel nitrogen reaction

H. Zhou; A. D. Jensen; P. Glarborg; A. Kavaliauskas

2006-01-01

254

Advanced modeling of large-scale oxy-fuel combustion processes  

E-print Network

radiative heat transfer and combustion chemistry are two of the fundamental issues. Efforts are made in bothAdvanced modeling of large-scale oxy-fuel combustion processes Chungen Yin Department of Energy Technology, Aalborg University, DK-9220 Aalborg, Denmark, chy@et.aau.dk Introduction Oxy-fuel combustion

Yin, Chungen

255

ENVIRONMENTAL CHEMISTRY  

EPA Science Inventory

Environmental chemistry is applied to estimating the exposure of ecosystems and humans to various chemical environmental stressors. Among the stressors of concern are mercury, pesticides, and arsenic. Advanced analytical chemistry techniques are used to measure these stressors ...

256

Chemistry Notes  

ERIC Educational Resources Information Center

Described are eight chemistry experiments and demonstrations applicable to introductory chemistry courses. Activities include: measure of lattice enthalpy, Le Chatelier's principle, decarboxylation of soap, use of pocket calculators in pH measurement, and making nylon. (SL)

School Science Review, 1976

1976-01-01

257

Chemistry Notes.  

ERIC Educational Resources Information Center

Presents background information, laboratory procedures, classroom materials/activities, and chemistry experiments. Topics include sublimation, electronegativity, electrolysis, experimental aspects of strontianite, halide test, evaluation of present and future computer programs in chemistry, formula building, care of glass/saturated calomel…

School Science Review, 1983

1983-01-01

258

Chemistry Notes  

ERIC Educational Resources Information Center

Thirteen ideas are presented that may be of use to chemistry teachers. Topics covered include vitamin C, industrial chemistry, electrical conductivity, electrolysis, alkali metals, vibration modes infra-red, dynamic equilibrium, and some new demonstrations in gaseous combinations. (PS)

School Science Review, 1972

1972-01-01

259

Comprehensive kinetic model for the low-temperature oxidation of hydrocarbons  

SciTech Connect

The oxidation chemistry in the low- and intermediate-temperature regimes (600--900 K) is important and plays a significant role in the overall combustion process. Autoignition in diesel engines as well as end-gas autoignition and knock phenomena in s.i. engines are initiated at these low temperatures. The low-temperature oxidation chemistry of linear and branched alkanes is discussed with the aim of unifying their complex behavior in various experimental systems using a single detailed kinetic model. New experimental data, obtained in a pressurized flow reactor, as well as in batch- and jet-stirred reactors, are useful for a better definition of the region of cool flames and negative temperature coefficient (NTC) for pure hydrocarbons from propane up to isooctane. Thermochemical oscillations and the NTC region of the reaction rate of the low-temperature oxidation of n-heptane and isooctane in a jet-stirred flow reactor are reproduced quite well by the model, not only in a qualitative way but in terms of the experimental frequencies and intensities of cool flames. Very good agreement is also observed for fuel conversion and intermediate-species formation. Irrespective of the experimental system, the same critical reaction steps always control these phenomena. The results contribute to the definition of a limited set of fundamental kinetic parameters that should be easily extended to model heavier alkanes.

Gaffuri, P.; Faravelli, T.; Ranzi, E. [Politecnico di Milano (Italy)] [Politecnico di Milano (Italy); Cernansky, N.P.; Miller, D. [Drexel Univ., Philadelphia, PA (United States). Dept. of Mechanical Engineering and Mechanics] [Drexel Univ., Philadelphia, PA (United States). Dept. of Mechanical Engineering and Mechanics; d`Anna, A.; Ciajolo, A. [CNR, Napoli (Italy). Ist. di Richerche sulla Combustione] [CNR, Napoli (Italy). Ist. di Richerche sulla Combustione

1997-05-01

260

Molecular and isotopic records of the combustion inputs to the environment over the last 250 yrs  

E-print Network

The most ubiquitous source of polycyclic aromatic hydrocarbons (PAHs) to the environment is incomplete combustion. This study generated a high-resolution historical record of pyrogenic PAH emissions since pre-industrial ...

Lima, Ana Lúcia Cessel de, 1969-

2004-01-01

261

Characteristics of hydrogen–hydrocarbon composite fuel turbulent jet flames  

Microsoft Academic Search

The characteristics (flame length, pollutant emission, radiative heat loss fraction, and volumetric soot concentration) of hydrogen–hydrocarbon composite fuel turbulent jet diffusion flames are presented. A correlation of flame length with hydrogen concentration in the fuel mixture is shown. The reactivity of fuel mixture increases with the increase of hydrogen concentration, which ultimately shortens the combustion time, and thereby reduces the

Ahsan R. Choudhuri; S. R. Gollahalli

2003-01-01

262

Fundamental spectroscopic studies of carbenes and hydrocarbon radicals  

SciTech Connect

Highly reactive carbenes and carbon-chain radicals are studied at millimeter wavelengths by observing their rotational spectra. The purpose is to provide definitive spectroscopic identification, accurate spectroscopic constants in the lowest vibrational states, and reliable structures of the key intermediates in reactions leading to aromatic hydrocarbons and soot particles in combustion.

Gottlieb, C.A.; Thaddeus, P. [Harvard Univ., Cambridge, MA (United States)

1993-12-01

263

Chemistry Links  

NSDL National Science Digital Library

This compiled site contains titles and links to over 40 sites, journal articles, course and tutorial materials, simulations, batteries, and other resources. Definitions of chemistry, theoretical chemistry, organic, physical and nuclear chemistry are integrated with the links to outside materials. A number of useful keywords are included to help users navigate the materials.

Charnine, Michael

2011-04-01

264

Propellant Chemistry for CFD Applications  

NASA Technical Reports Server (NTRS)

Current concepts for reusable launch vehicle design have created renewed interest in the use of RP-1 fuels for high pressure and tri-propellant propulsion systems. Such designs require the use of an analytical technology that accurately accounts for the effects of real fluid properties, combustion of large hydrocarbon fuel modules, and the possibility of soot formation. These effects are inadequately treated in current computational fluid dynamic (CFD) codes used for propulsion system analyses. The objective of this investigation is to provide an accurate analytical description of hydrocarbon combustion thermodynamics and kinetics that is sufficiently computationally efficient to be a practical design tool when used with CFD codes such as the FDNS code. A rigorous description of real fluid properties for RP-1 and its combustion products will be derived from the literature and from experiments conducted in this investigation. Upon the establishment of such a description, the fluid description will be simplified by using the minimum of empiricism necessary to maintain accurate combustion analyses and including such empirical models into an appropriate CFD code. An additional benefit of this approach is that the real fluid properties analysis simplifies the introduction of the effects of droplet sprays into the combustion model. Typical species compositions of RP-1 have been identified, surrogate fuels have been established for analyses, and combustion and sooting reaction kinetics models have been developed. Methods for predicting the necessary real fluid properties have been developed and essential experiments have been designed. Verification studies are in progress, and preliminary results from these studies will be presented. The approach has been determined to be feasible, and upon its completion the required methodology for accurate performance and heat transfer CFD analyses for high pressure, tri-propellant propulsion systems will be available.

Farmer, R. C.; Anderson, P. G.; Cheng, Gary C.

1996-01-01

265

Multi-Dimensional Measurements of Combustion Species in Flame Tube and Sector Gas Turbine Combustors  

NASA Technical Reports Server (NTRS)

The higher temperature and pressure cycles of future aviation gas turbine combustors challenge designers to produce combustors that minimize their environmental impact while maintaining high operation efficiency. The development of low emissions combustors includes the reduction of unburned hydrocarbons, smoke, and particulates, as well as the reduction of oxides of nitrogen (NO(x)). In order to better understand and control the mechanisms that produce emissions, tools are needed to aid the development of combustor hardware. Current methods of measuring species within gas turbine combustors use extractive sampling of combustion gases to determine major species concentrations and to infer the bulk flame temperature. These methods cannot be used to measure unstable combustion products and have poor spatial and temporal resolution. The intrusive nature of gas sampling may also disturb the flow structure within a combustor. Planar laser-induced fluorescence (PLIF) is an optical technique for the measurement of combustion species. In addition to its non-intrusive nature, PLIF offers these advantages over gas sampling: high spatial resolution, high temporal resolution, the ability to measure unstable species, and the potential to measure combustion temperature. This thesis considers PLIF for in-situ visualization of combustion species as a tool for the design and evaluation of gas turbine combustor subcomponents. This work constitutes the first application of PLIF to the severe environment found in liquid-fueled, aviation gas turbine combustors. Technical and applied challenges are discussed. PLIF of OH was used to observe the flame structure within the post flame zone of a flame tube combustor, and within the flame zone of a sector combustor, for a variety of fuel injector configurations. OH was selected for measurement because it is a major combustion intermediate, playing a key role in the chemistry of combustion, and because its presence within the flame zone can serve as a qualitative marker of flame temperature. All images were taken in the environment of actual engines during flight, using actual jet fuel. The results of the PLIF study led directly to the modification of a fuel injector.

Hicks, Yolanda Royce

1996-01-01

266

NASA Microgravity Combustion Science Program  

NASA Technical Reports Server (NTRS)

Combustion has been a subject of increasingly vigorous scientific research for over a century, not surprising considering that combustion accounts for approximately 85% of the world's energy production and is a key element of many critical technologies used by contemporary society. Although combustion technology is vital to our standard of living, it also poses great challenges to maintaining a habitable environment. A major goal of combustion research is production of fundamental (foundational) knowledge that can be used in developing accurate simulations of complex combustion processes, replacing current "cut-and-try" approaches and allowing developers to improve the efficiency of combustion devices, to reduce the production of harmful emissions, and to reduce the incidence of accidental uncontrolled combustion. With full understanding of the physics and chemistry involved in a given combustion process, including details of the unit processes and their interactions, physically accurate models which can then be used for parametric exploration of new combustion domains via computer simulation can be developed, with possible resultant definition of radically different approaches to accomplishment of various combustion goals. Effects of gravitational forces on earth impede combustion studies more than they impede most other areas of science. The effects of buoyancy are so ubiquitous that we often do not appreciate the enormous negative impact that they have had on the rational development of combustion science. Microgravity offers potential for major gains in combustion science understanding in that it offers unique capability to establish the flow environment rather than having it dominated by uncontrollable (under normal gravity) buoyancy effects and, through this control, to extend the range of test conditions that can be studied. It cannot be emphasized too strongly that our program is dedicated to taking advantage of microgravity to untangle complications caused by gravity, allowing major strides in our understanding of combustion processes and in subsequent development of improved combustion devices leading to improved quality of life on Earth. Fire and/or explosion events aboard spacecraft could be devastating to international efforts to expand the human presence in space. Testing to date has shown that ignition and flame spread on fuel surfaces (e.g., paper, wire insulation) behave quite differently under partial gravity and microgravity conditions. In addition, fire signatures-i.e., heat release, smoke production, flame visibility, and radiation-are now known to be quite different in reduced gravity environments; this research has provided data to improve the effectiveness of fire prevention practices, smoke and fire detectors, and fire extinguishment systems. The more we can apply our scientific and technological understanding to potential fire behavior in microgravity and partial gravity, the more assurance can be given to those people whose lives depend on the environment aboard spacecraft or eventually on habitats on the Moon or Mars.

King, Merrill K.

1999-01-01

267

Problems of providing completeness of the methane-containing block-jet combustion in a rocket-ramjet engine's combustion chamber  

NASA Astrophysics Data System (ADS)

Some problems of methane-containing hydrocarbon fuel combustion are discussed. It seems that reduction of methane burnout zone length is one from main problems of designing new type engine. It is very important at the creation of combustion chambers of a rocket-ramjet engine for prospective space shuttle launch vehicles.

Timoshenko, Valeriy I.; Belotserkovets, Igor S.; Gusinin, Vjacheslav P.

2009-11-01

268

Chemical Kinetic Models for HCCI and Diesel Combustion  

SciTech Connect

Hydrocarbon fuels for advanced combustion engines consist of complex mixtures of hundreds or even thousands of different components. These components can be grouped into a number of chemically distinct classes, consisting of n-paraffins, branched paraffins, cyclic paraffins, olefins, oxygenates, and aromatics. Biodiesel contains its own unique chemical class called methyl esters. The fractional amounts of these chemical classes are quite different in gasoline, diesel fuel, oil-sand derived fuels and bio-derived fuels, which contributes to the very different combustion characteristics of each of these types of combustion systems. The objectives of this project are: (1) Develop detailed chemical kinetic models for fuel components used in surrogate fuels for diesel and HCCI engines; (2) Develop surrogate fuel models to represent real fuels and model low temperature combustion strategies in HCCI and diesel engines that lead to low emissions and high efficiency; and (3) Characterize the role of fuel composition on low temperature combustion modes of advanced combustion engines.

Pitz, W J; Westbook, C K; Mehl, M

2008-10-30

269

CLUSTER CHEMISTRY  

SciTech Connect

Metal cluster chemistry is one of the most rapidly developing areas of inorganic and organometallic chemistry. Prior to 1960 only a few metal clusters were well characterized. However, shortly after the early development of boron cluster chemistry, the field of metal cluster chemistry began to grow at a very rapid rate and a structural and a qualitative theoretical understanding of clusters came quickly. Analyzed here is the chemistry and the general significance of clusters with particular emphasis on the cluster research within my group. The importance of coordinately unsaturated, very reactive metal clusters is the major subject of discussion.

Muetterties, Earl L.

1980-05-01

270

Computational Chemistry for Chemistry Educators  

NSDL National Science Digital Library

This is a 15-session course on the technologies, techniques, and tools of computational chemistry. By using the same computational tools as research computational chemists, educators will have the opportunity to study chemistry in a manner very different than traditional teaching and education in chemistry.

Institute, Shodor C.

271

Chemical Kinetic Modeling of Biofuel Combustion  

NASA Astrophysics Data System (ADS)

Bioalcohols, such as bioethanol and biobutanol, are suitable replacements for gasoline, while biodiesel can replace petroleum diesel. Improving biofuel engine performance requires understanding its fundamental combustion properties and the pathways of combustion. This study's contribution is experimentally validated chemical kinetic combustion mechanisms for biobutanol and biodiesel. Fundamental combustion data and chemical kinetic mechanisms are presented and discussed to improve our understanding of biofuel combustion. The net environmental impact of biobutanol (i.e., n-butanol) has not been studied extensively, so this study first assesses the sustainability of n-butanol derived from corn. The results indicate that technical advances in fuel production are required before commercializing biobutanol. The primary contribution of this research is new experimental data and a novel chemical kinetic mechanism for n-butanol combustion. The results indicate that under the given experimental conditions, n-butanol is consumed primarily via abstraction of hydrogen atoms to produce fuel radical molecules, which subsequently decompose to smaller hydrocarbon and oxygenated species. The hydroxyl moiety in n-butanol results in the direct production of the oxygenated species such as butanal, acetaldehyde, and formaldehyde. The formation of these compounds sequesters carbon from forming soot precursors, but they may introduce other adverse environmental and health effects. Biodiesel is a mixture of long chain fatty acid methyl esters derived from fats and oils. This research study presents high quality experimental data for one large fatty acid methyl ester, methyl decanoate, and models its combustion using an improved skeletal mechanism. The results indicate that methyl decanoate is consumed via abstraction of hydrogen atoms to produce fuel radicals, which ultimately lead to the production of alkenes. The ester moiety in methyl decanoate leads to the formation of low molecular weight oxygenated compounds such as carbon monoxide, formaldehyde, and ketene. The study concludes that the oxygenated molecules in biofuels follow similar combustion pathways to the hydrocarbons in petroleum fuels. The oxygenated moiety's ability to sequester carbon from forming soot precursors is highlighted. However, the direct formation of oxygenated hydrocarbons warrants further investigation into the environmental and health impacts of practical biofuel combustion systems.

Sarathy, Subram Maniam

272

Gas turbine combustion and emission control  

NASA Astrophysics Data System (ADS)

The fundamentals of combustion are discussed in the context of gaseous and liquid fuels and gas turbine fuels. Methods for reducing the emission of pollutants in gas turbines are considered. These emissions are carbon monoxide, unburnt hydrocarbons, smoke/soot, nitrogen oxides, sulphur oxides, and carbon dioxide. The focus is on nitrogen oxides. The general principles of combustor and burner design are considered: aero/can type combustors, silo combustors, and annular combustors. Premix and diffusion flames are discussed.

Schetter, B.

273

HOMOGENEOUS CATALYSTS FOR THE PARTIAL-OXYGENATION OF SATURATED HYDROCARBONS WITH HYDROGEN PEROXIDE  

EPA Science Inventory

The development of catalysts with the capacity to activate green oxidants, such as hydrogen peroxide and molecular oxygen, can offer an environmentally sound pathway for hydrocarbon oxidation. Furthermore, by including the concepts of green chemistry and pollution prevention one ...

274

Molecular and Biochemical Characterization of Hydrocarbon Production in the Green Microalga Botryococcus braunii  

E-print Network

Botryococcus braunii (Chlorophyta, Botryococcaceae) is a colony-forming green microalga that produces large amounts of liquid hydrocarbons, which can be converted into transportation fuels. While B. braunii has been well studied for the chemistry...

Weiss, Taylor Leigh

2012-10-19

275

Mechanisms for the formation of exhaust hydrocarbons in a single cylinder spark-ignition engine, fueled with deuterium-labeled ortho-, meta-, and para-xylene  

SciTech Connect

Combustion studies in engines have investigated the chemistry leading to the formation in the exhaust of aromatic hydrocarbons from deuterium-labeled isomeric xylenes. These fuels were: ortho-xylene-d{sub 0} and ortho-xylene=d{sub 10} (1:1); para-xylene-d{sub 0} and para-xylene-d{sub 10} (1:1); and meta-xylene-2,4,5,6-d{sub 4}. Isotopic distributions within the exhausted hydrocarbons establish the postflame chemistry involved. There is an isotope effect in the consumption of residual fuel in the postflame region. The residual fuel from each experiment exhibits minimal H-D exchange. Toluene is an intermediate in the formation of ethylbenzene, and is produced through X{sup {sm_bullet}} atom (X{sup {sm_bullet}} = H or D) displacement of methyl radicals from the xylene fuel. Benzene is formed by direct demethylation, but there are other routes. Styrene from o- and p-xylene fuels is formed intramolecularly, probably involving xylylene and methylcycloheptatetraene intermediates. Ethyltoluene is formed by combination of methyl and methylbenzyl radicals.

Gregory, D.; Jackson, R.A. [Univ. of Sussex, Brighton (United Kingdom). School of Chemistry, Physics and Environmental Science] [Univ. of Sussex, Brighton (United Kingdom). School of Chemistry, Physics and Environmental Science; Bennett, P.J. [BP Oil, Sunbury-on-Thames (United Kingdom)] [BP Oil, Sunbury-on-Thames (United Kingdom)

1999-08-01

276

Apparatus for recovering hydrocarbons from air-hydrocarbon vapor mixtures  

Microsoft Academic Search

An improved process and apparatus for recovering hydrocarbons from an air-hydrocarbon vapor mixture such as the mixture of air and vaporized light hydrocarbon compounds expelled as a result of loading gasoline or the like into storage tanks and tank trucks. The air-hydrocarbon vapor mixture is caused to flow through a bed of solid adsorbent whereby the hydrocarbons are removed from

H. L. Dinsmore; G. W. Long; D. J. Peters; R. E. Schwartz

1981-01-01

277

Trace Chemistry  

NASA Technical Reports Server (NTRS)

The goals of the trace chemistry group were to identify the processes relevant to aerosol and aerosol precursor formation occurring within aircraft gas turbine engines; that is, within the combustor, turbine, and nozzle. The topics of discussion focused on whether the chemistry of aerosol formation is homogeneous or heterogeneous; what species are important for aerosol and aerosol precursor formation; what modeling/theoretical activities to pursue; what experiments to carry out that both support modeling activities and elucidate fundamental processes; and the role of particulates in aerosol and aerosol precursor formation. The consensus of the group was that attention should be focused on SO2, SO3, and aerosols. Of immediate concern is the measurement of the concentration of the species SO3, SO2, H2SO4 OH, HO2, H2O2, O, NO, NO2, HONO, HNO3, CO, and CO2 and particulates in various engines, both those currently in use and those in development. The recommendation was that concentration measurements should be made at both the combustor exit and the engine exit. At each location the above species were classified into one of four categories of decreasing importance, Priority I through IV, as follows: Combustor exit: Priority I species - SO3:SO2 ratio, SO3, SO2, and particulates; Priority II species: OH and O; Priority III species - NO and NO2; and Priority IV species - CO and CO2. For the Engine exit: Priority I species - SO3:SO2 ratio, SO3, SO2,H2SO4, and particulates; Priority II species: OH,HO2, H2O2, and O; Priority III species - NO, NO2, HONO, and HNO3; and Priority IV species - CO and CO2. Table I summarizes the anticipated concentration range of each of these species. For particulate matter, the quantities of interest are the number density, size distribution, and composition. In order to provide data for validating multidimensional reacting flow models, it would be desirable to make 2-D, time-resolved measurements of the concentrations of the above species and, in addition, of the pressure, temperature, and velocity. A near term goal of the experimental program should be to confirm the nonlinear effects of sulfur speciation, and if present, to provide an explanation for them. It is also desirable to examine if the particulate matter retains any sulfur. The recommendation is to examine the effects on SOx production of variations in fuel-bound sulfur and aromatic content (which may affect the amount of particulates formed). These experiments should help us to understand if there is a coupling between particulate formation and SO, concentration. Similarly, any coupling with NOx can be examined either by introducing NOx into the combustion air or by using fuel-bound nitrogen. Also of immediate urgency is the need to establish and validate a detailed mechanism for sulfur oxidation/aerosol formation, whose chemistry is concluded to be homogeneous, because there is not enough surface area for heterogeneous effects. It is envisaged that this work will involve both experimental and theoretical programs. The experimental work will require, in addition to the measurements described above, fundamental studies in devices such as flow reactors and shock tubes. Complementing this effort should be modeling and theoretical activities. One impediment to the successful modeling of sulfur oxidation is the lack of reliable data for thermodynamic and transport properties for several species, such as aqueous nitric acid, sulfur oxides, and sulfuric acid. Quantum mechanical calculations are recommended as a convenient means of deriving values for these properties. Such calculations would also help establish rate constants for several important reactions for which experimental measurements are inherently fraught with uncertainty. Efforts to implement sufficiently detailed chemistry into computational fluid dynamic codes should be continued. Zero- and one-dimensional flow models are also useful vehicles for elucidating the minimal set of species and reactions that must be included in two- and three-dimensional modeling studies.

Radhakrishnan, Krishnan; Whitefield, Philip

1999-01-01

278

Remote detection of polynuclear aromatic hydrocarbons using laser-induced fluorescence. Interim report January 82-August 84  

SciTech Connect

This publication discusses the feasibility of remotely detecting gas-phase polynuclear aromatic hydrocarbons (PAHs) that might be produced during the combustion of propellant, explosive, and pyrotechnic (PEP) materials. Laboratory scale and remote laser-induced fluorescence measurements are presented.

Loda, R.T.

1985-01-01

279

FORMATION OF POLYCYCLIC AROMATIC HYDROCARBONS AND THEIR GROWTH TO SOOT -A REVIEW OF CHEMICAL REACTION PATHWAYS. (R824970)  

EPA Science Inventory

The generation by combustion processes of airborne species of current health concern such as polycyclic aromatic hydrocarbons (PAH) and soot particles necessitates a detailed understanding of chemical reaction pathways responsible for their formation. The present review discus...

280

for Undergraduate CHEMISTRY MAJORS  

E-print Network

Technology, Colloid and Surface Chemistry, Consumer Products, Food and Flavor Chemistry, Forensic ChemistryHANDBOOK for Undergraduate CHEMISTRY MAJORS DEPARTMENT OF CHEMISTRY Fall 2010 #12;#12;TABLE OF CONTENTS A Career in Chemistry - What It Means ___________________________________________ 4 What do

Stuart, Steven J.

281

Analytical Chemistry  

NSDL National Science Digital Library

This document contains a list of detailed lecture notes covering a wide range of topics including equilibrium, titrations, sample preparation, acids and bases, buffers, spectrophotometry, potentiometry and chromatography. This site is part of a collection of notes from a general chemistry course taught at the State University of West Georgia. This document gives supplementary material that could be useful to intermediate chemistry majors in an analytical chemistry course or new faculty developing a course.

Henderson, David E.

2011-06-01

282

Integrated self-cleaning window assembly for optical transmission in combustion environments  

DOEpatents

An integrated window design for optical transmission in combustion environments is described. The invention consists of an integrated optical window design that prevents and removes the accumulation of carbon-based particulate matter and gaseous hydrocarbons through a combination of heat and catalysis. These windows will enable established optical technologies to be applied to combustion environments and their exhaust systems.

Kass, Michael D [Oak Ridge, TN

2007-07-24

283

Combustion and emissions performance of a hybrid hydrogen–gasoline engine at idle and lean conditions  

Microsoft Academic Search

Due to the narrow flammability of gasoline, pure gasoline-fueled spark-ignited (SI) engines always encounter partial burning or even misfire at lean conditions. Gasoline engines tend to suffer poor combustion and expel large emissions at idle conditions because of the high variation in the intake charge and low combustion temperature. Comparatively, hybrid hydrogen engines (HHE) fueled with the mixtures of hydrocarbon

Changwei Ji; Shuofeng Wang

2010-01-01

284

Infrared multiphoton ignition and combustion enhancement of natural gas. Final report, November 1989October 1992  

Microsoft Academic Search

This research program has demonstrated the feasibility of using Infrared Multiphoton (IRMP) processes for reliable ignition and combustion enhancement of natural gas. Hydrocarbon constituents of natural gas are excited with focused, pulsed infrared lasers tuned to discrete resonant frequencies causing their dissociation to very reactive radicals. These radicals participate in chain-branching and chain-propagating reactions significantly improving the combustion of natural

M. Lavid; A. T. Poulos; S. K. Gulati; J. G. Stevens; W. R. Lempert

1993-01-01

285

Doing Chemistry  

NSDL National Science Digital Library

This website includes over 150 chemistry experiments in the following areas: Atomic Structure, Bonding, Chemical Reactions, Colligative Properties, Condensed States, Electrochemistry, Equilibrium Gases, Instrumentation, Limiting Reactant and more.

Brooks, David W.

2010-05-25

286

Chemistry Notes  

ERIC Educational Resources Information Center

Twelve new chemistry expermiments are described. Broad areas covered include atomic structure, solubility, gaseous diffusion, endothermic reactions, alcohols, equilibrium, atomic volumes, and some improvised apparatus. (PS)

School Science Review, 1972

1972-01-01

287

Chemical kinetic modelling of hydrocarbon ignition  

SciTech Connect

Chemical kinetic modeling of hydrocarbon ignition is discussed with reference to a range of experimental configurations, including shock tubes, detonations, pulse combustors, static reactors, stirred reactors and internal combustion engines. Important conditions of temperature, pressure or other factors are examined to determine the main chemical reaction sequences responsible for chain branching and ignition, and kinetic factors which can alter the rate of ignition are identified. Hydrocarbon ignition usually involves complex interactions between physical and chemical factors, and it therefore is a suitable and often productive subject for computer simulations. In most of the studies to be discussed below, the focus of the attention is placed on the chemical features of the system. The other physical parts of each application are generally included in the form of initial or boundary conditions to the chemical kinetic parts of the problem, as appropriate for each type of application being addressed.

Westbrook, C.K.; Pitz, W.J.; Curran, H.J.; Gaffuri, P.; Marinov, N.M.

1995-08-25

288

Spectroscopy, Kinetics, and Dynamics of Combustion Radicals  

SciTech Connect

Spectroscopy, kinetics and dynamics of jet cooled hydrocarbon transients relevant to the DOE combustion mission have been explored, exploiting i) high resolution IR lasers, ii) slit discharge sources for formation of jet cooled radicals, and iii) high sensitivity detection with direct laser absorption methods and near the quantum shot noise limit. What makes this combination powerful is that such transients can be made under high concentrations and pressures characteristic of actual combustion conditions, and yet with the resulting species rapidly cooled (T ?10-15K) in the slit supersonic expansion. Combined with the power of IR laser absorption methods, this provides novel access to spectral detection and study of many critical combustion species.

Nesbitt, David J. [Research/Professor

2013-08-06

289

Aliphatic hydrocarbon and polycyclic aromatic hydrocarbon geochemistry of twelve major rivers in the Northwest Territories  

SciTech Connect

Suspended sediment and water samples collected from twelve major rivers in the Northwest Territories were analyzed for aliphatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) to assess the sources and transport of hydrocarbons entering the Arctic Ocean. Three stations on the Mackenzie River and one station near the mouth of eleven other northern rivers were selected for sampling. Samples were collected on the Mackenzie River on four occasions to characterize spring, summer and fall flow conditions and once on the remaining eleven rivers during high flow conditions. The Mackenzie River is distinctively different then the other eleven rivers. Naturally occurring hydrocarbons predominate in the river. These hydrocarbons include biogenic alkanes, diagenic PAHs, petrogenic alkanes, and PAHs from oil seeps and/or bitumens. Anthropogenic inputs of PAHs are low as indicated by low concentrations of combustion PAHs. Alkyl PAH distributions indicate that a significant component of the lower molecular weight PAH fraction is petrogenic. The majority of the high molecular weight PAHs, together with the petrogenic PAHs have a principal source in the Mackenzie River.

Backus, S. [Backus Consulting, Stoney Creek, Ontario (Canada); Swyripa, M.; Peddle, J. [Department of Indian and Northern Development, Yellowknife, Northwest Territories (Canada); Jeffries, D.S. [National Water Research Inst., Burlington, Ontario (Canada)

1995-12-31

290

Near-threshold absolute photoionization cross-sections of some reaction intermediates in combustion  

NASA Astrophysics Data System (ADS)

The use of photoionization mass spectrometry for the development of quantitative kinetic models for the complex combustion chemistry of both conventional hydrocarbon fuels and oxygenated biofuels requires near-threshold measurements of absolute photoionization cross-sections for numerous reaction intermediates. Near-threshold absolute cross-sections for molecular and dissociative photoionization for 20 stable reaction intermediates (methane, ethane, propane, n-butane, cyclopropane, methylcyclopentane, 1-butene, cis-2-butene, isobutene, 1-pentene, cyclohexene, 3,3-dimethyl-1-butene, 1,3-hexadiene, 1,3-cyclohexadiene, methyl acetate, ethyl acetate, tetrahydrofuran, propanal, 1-butyne, 2-butyne) are presented. Previously measured total photoionization cross-sections for 9 of these molecules are in good agreement with the present results. The measurements are performed with photoionization mass spectrometry (PIMS) using a monochromated VUV synchrotron light source with an energy resolution of 40 meV (fwhm) comparable to that used for flame-sampling molecular beam PIMS studies of flame chemistry and reaction kinetics.

Wang, Juan; Yang, Bin; Cool, Terrill A.; Hansen, Nils; Kasper, Tina

2008-02-01

291

The design and operation of a combustion tube for investigation of combustion oil recovery  

E-print Network

of Distance from Burning Front and Time for C = 0. 045 . 20 Computed Steady State Temperature Distribution as a Function of Distance from Burning Front and Heat Loss Constant . 23 Schematic Diagram of the Combustion Tube Apparatus . 26 The Combustion...- quires that in-place oil be ignited and supplied with sufficient oxygen to move a burning front in the direction of gas flow through a porous and permeable, hydrocarbon-bearing formation. The thermal energy released by the burning zone is in turn...

Penberthy, Walter Lawren

2012-06-07

292

Plant hydrocarbon recovery  

Microsoft Academic Search

A process for production and recovery of hydrocarbons from whole plants in a form suitable for use as chemical feedstocks or as hydrocarbon energy sources comprises: pulverizing by grinding or chopping the plants to a suitable particle size, drying and preheating the particles in a reducing atmosphere under positive pressure, passing the particles through a thermal conversion zone containing a

T. A. Weil; P. M. Dzadzic; C. C. J. Shih; M. C. Price

1982-01-01

293

Hydrocarbon Spectral Database  

National Institute of Standards and Technology Data Gateway

SRD 115 Hydrocarbon Spectral Database (Web, free access)   All of the rotational spectral lines observed and reported in the open literature for 91 hydrocarbon molecules have been tabulated. The isotopic molecular species, assigned quantum numbers, observed frequency, estimated measurement uncertainty and reference are given for each transition reported.

294

Geology of Hydrocarbons Visualizations  

NSDL National Science Digital Library

This site has over two dozen animations about hydrocarbons as energy sources, including where resources are found, the amount of each energy source/type used in the US and in the world, how hydrocarbons are formed, and how they are found by exploration geologists.

US Geological Survey Western Earth Surface Processes Team; National Park Service.

295

HYDROCARBON OXIDATION OVER VANADIUM PHOSPHORUS OXIDE CATALYST USING HYDROGEN PEROXIDE  

EPA Science Inventory

Selective oxidation of hydrocarbons is one of the very important and challenging areas in industrial chemistry due to the wide ranging utility of the resulting oxygenates in fine chemical synthesis. Most of the existing processes for their oxidations employ toxic and often stoich...

296

Quantum interference in polycyclic hydrocarbon molecular wires Derek Walter a  

E-print Network

, anthracene or tetracene molecule a large peak appears in the electron transmission probability spectrumQuantum interference in polycyclic hydrocarbon molecular wires Derek Walter a , Daniel Neuhauser, Los Angeles, CA 90095-1569, USA b Institute of Chemistry and the Lise Meitner Center for Quantum

Baer, Roi

297

Chemistry Notes.  

ERIC Educational Resources Information Center

Outlines laboratory procedures, demonstrations, teaching suggestions, and content information related to chemistry. Topics include polarizing power; calorimetry and momentum; microcomputers in school chemistry; a constant-volume dispenser for liquids, floating magnets, and crystal lattices; preparation of chromium; and solvent polarity and…

School Science Review, 1981

1981-01-01

298

Atmospheric Chemistry of Acenaphthalene and Acenaphthylene  

NASA Astrophysics Data System (ADS)

Polycyclic aromatic hydrocarbons (PAHs) are released into the atmosphere as a by-product of combustion processes and have been detected in ambient air at urban locations around the world. In the atmosphere, PAHs containing two and three rings are found predominantly in the gas-phase, whilst those containing six or more rings principally adsorb to particles. PAHs with four or five rings are found in both phases. The gas-phase PAHs can be chemically transformed in the lower troposphere via reaction with hydroxyl (OH) and nitrate (NO3) radicals and ozone. These reactions lead to the formation of a range of oxidation products including phenols, nitro-PAHs and carbonyls, in addition to other pollutants such as ozone and secondary organic aerosol (SOA). Despite their importance, relatively little is known about the atmospheric chemistry of the PAHs, mainly because of the difficulty of working with these compounds and also the variety and complexity of the reaction products formed. Up to now only one kinetic study on the reaction of acenaphthalene and acenaphthylene with OH, NO3 and ozone has been reported in the peer-reviewed literature. In this study, we have determined rate coefficients for the gas-phase reactions of acenaphthalene and acenaphthylene with OH, NO3 and ozone using the relative rate method. The results are compared with previous measurements and used to provide estimates of the tropospheric lifetimes of these compounds. A recently developed denuder-filter sampling technique was used to investigate the gas and particle phase products arising from the photooxidation of the PAHs. Chemical analysis was performed using gas chromatography - mass spectrometry using O-(2,3,4,5,6- pentafluorobenzyl)-hydroxylamine (PFBHA) and pentafluorobenzyl bromide (PFBBr) as derivatizing agents for carbonyls and phenols respectively. The results provide new data on the gas-particle partitioning behavior of the oxidation products and useful information on the products likely to be involved in secondary organic aerosol formation from the PAHs.

Zhou, S.; Wenger, J. C.

2009-04-01

299

A laboratory scale supersonic combustive flow system  

SciTech Connect

A laboratory scale supersonic flow system [Combustive Flow System (CFS)] which utilizes the gaseous products of methane-air and/or liquid fuel-air combustion has been assembled to provide a propulsion type exhaust flow field for various applications. Such applications include providing a testbed for the study of planar two-dimensional nozzle flow fields with chemistry, three-dimensional flow field mixing near the exit of rectangular nozzles, benchmarking the predictive capability of various computational fluid dynamic codes, and the development and testing of advanced diagnostic techniques. This paper will provide a detailed description of the flow system and data related to its operation.

Sams, E.C.; Zerkle, D.K.; Fry, H.A.; Wantuck, P.J.

1995-02-01

300

Combustion Fundamentals Research  

NASA Technical Reports Server (NTRS)

Increased emphasis is placed on fundamental and generic research at Lewis Research Center with less systems development efforts. This is especially true in combustion research, where the study of combustion fundamentals has grown significantly in order to better address the perceived long term technical needs of the aerospace industry. The main thrusts for this combustion fundamentals program area are as follows: analytical models of combustion processes, model verification experiments, fundamental combustion experiments, and advanced numeric techniques.

1983-01-01

301

Correlation of physical properties with molecular structure for some dicyclic hydrocarbons having high thermal-energy release per unit volume  

NASA Technical Reports Server (NTRS)

As part of a program to study the correlation between molecular structure and physical properties of high-density hydrocarbons, the net heats of combustion, melting points, boiling points, densities, and kinematic viscosities of some hydrocarbons in the 2-n-alkylbiphenyl, 1,1-diphenylalkane, diphenylalkane, 1,1-dicyclohexylalkane, and dicyclohexylalkane series are presented.

Wise, P H; Serijan, K T; Goodman, I A

1951-01-01

302

Improved bioavailability and biodegradation of a model polyaromatic hydrocarbon by a biosurfactant producing bacterium of marine origin  

Microsoft Academic Search

Polyaromatic hydrocarbons (PAHs) are organic pollutants mostly derived from the processing and combustion of fossil fuels and cause human health hazards. In the present study a marine biosurfactant producing strain of Bacillus circulans was used to increase the bioavailability and consequent degradation of a model polyaromatic hydrocarbon, anthracene. Although the organism could not utilize anthracene as the sole carbon source,

Palashpriya Das; Soumen Mukherjee; Ramkrishna Sen

2008-01-01

303

Exhaust gas recirculation system for an internal combustion engine  

Microsoft Academic Search

An exhaust gas recirculation system for an internal combustion engine includes an exhaust gas recirculation passage for communicating an exhaust port with an intake passage through a recirculation flow control valve. The recirculation system according to the invention comprises a timing valve in the recirculation passage adapted to open at specified moments for extracting exhaust gases containing highly concentrated hydrocarbons.

H. Aihara; Y. Matsumoto; Y. Nakagawa; S. Suzuki

1981-01-01

304

New insight into the hydrocarbon-pool chemistry of the methanol-to-olefins conversion over zeolite H-ZSM-5 from GC-MS, solid-state NMR spectroscopy, and DFT calculations.  

PubMed

Over zeolite H-ZSM-5, the aromatics-based hydrocarbon-pool mechanism of methanol-to-olefins (MTO) reaction was studied by GC-MS, solid-state NMR spectroscopy, and theoretical calculations. Isotopic-labeling experimental results demonstrated that polymethylbenzenes (MBs) are intimately correlated with the formation of olefin products in the initial stage. More importantly, three types of cyclopentenyl cations (1,3-dimethylcyclopentenyl, 1,2,3-trimethylcyclopentenyl, and 1,3,4-trimethylcyclopentenyl cations) and a pentamethylbenzenium ion were for the first time identified by solid-state NMR spectroscopy and DFT calculations under both co-feeding ([(13) C6 ]benzene and methanol) conditions and typical MTO working (feeding [(13) C]methanol alone) conditions. The comparable reactivity of the MBs (from xylene to tetramethylbenzene) and the carbocations (trimethylcyclopentenyl and pentamethylbenzium ions) in the MTO reaction was revealed by (13) C-labeling experiments, evidencing that they work together through a paring mechanism to produce propene. The paring route in a full aromatics-based catalytic cycle was also supported by theoretical DFT calculations. PMID:25178472

Wang, Chao; Chu, Yueying; Zheng, Anmin; Xu, Jun; Wang, Qiang; Gao, Pan; Qi, Guodong; Gong, Yanjun; Deng, Feng

2014-09-22

305

Numerical Simulations of Self-Ignition of Hydrogen-Hydrocarbons Mixtures in a Hot Supersonic Air Flow  

Microsoft Academic Search

1 Abstract The present paper, carried out in the framework of the French Promethee Program, deals with the comparative study of the self-ignition of hydrogen and hydrocarbons\\/hydrogen mixtures jets in co-stream vitiated Mach 2 airflow. Here, ethylene and methane are used as surrogate combustible for hydrocarbons fuels. Experimental studies have been performed to obtain a large database of hydrocarbons\\/hydrogen mixtures

Erwin George; Philippe Magre; Vladimir Sabel' nikov

306

ORGANIC CHEMISTRY UCLA Organic Chemistry Faculty  

E-print Network

ORGANIC CHEMISTRY UCLA Organic Chemistry Faculty perform research in molecular machines, exotic CHEMISTRY FACULTY RESEARCH INTERESTS Anne M. Andrews, Professor-in-Residence: Understanding how areas of interest include cross- coupling reactions, green chemistry, heterocycle synthesis, and natural

Levine, Alex J.

307

Modeling complex chemical effects in turbulent nonpremixed combustion  

NASA Technical Reports Server (NTRS)

Virtually all of the energy derived from the consumption of combustibles occurs in systems which utilize turbulent fluid motion. Since combustion is largely related to the mixing of fluids and mixing processes are orders of magnitude more rapid when enhanced by turbulent motion, efficiency criteria dictate that chemically powered devices necessarily involve fluid turbulence. Where combustion occurs concurrently with mixing at an interface between two reactive fluid bodies, this mode of combustion is called nonpremixed combustion. This is distinct from premixed combustion where flame-fronts propagate into a homogeneous mixture of reactants. These two modes are limiting cases in the range of temporal lag between mixing of reactants and the onset of reaction. Nonpremixed combustion occurs where this lag tends to zero, while premixed combustion occurs where this lag tends to infinity. Many combustion processes are hybrids of these two extremes with finite non-zero lag times. Turbulent nonpremixed combustion is important from a practical standpoint because it occurs in gas fired boilers, furnaces, waste incinerators, diesel engines, gas turbine combustors, and afterburners etc. To a large extent, past development of these practical systems involved an empirical methodology. Presently, efficiency standards and emission regulations are being further tightened (Correa 1993), and empiricism has had to give way to more fundamental research in order to understand and effectively model practical combustion processes (Pope 1991). A key element in effective modeling of turbulent combustion is making use of a sufficiently detailed chemical kinetic mechanism. The prediction of pollutant emission such as oxides of nitrogen (NO(x)) and sulphur (SO(x)) unburned hydrocarbons, and particulates demands the use of detailed chemical mechanisms. It is essential that practical models for turbulent nonpremixed combustion are capable of handling large numbers of 'stiff' chemical species equations.

Smith, Nigel S. A.

1995-01-01

308

Natural hydrocarbons, urbanization, and urban ozone  

NASA Technical Reports Server (NTRS)

The combined effects of emission control and urbanization, with its concomitant intensification of the urban heat island, on urban ozone concentrations are studied. The effect of temperature on ozone is considered, and attention is given to the temperature effect on ozone photochemistry. Model calculations suggest that ozone concentration enhancements are caused by the effect of temperature on the atmospheric chemistry of peroxyacetyl nitrate, as well as the temperature dependence of natural and anthropogenic hydrocarbon emissions. It is pointed out that, because of the sensitivity of urban ozone to local climatic conditions and the ability of trees to moderate summertime temperatures, the inadvertent removal of trees from urbanization can have an adverse effect on urban ozone concentration, while a temperature increase in the urban heat island caused by urbanization can essentially cancel out the ozone-reducing benefits obtained from a 50-percent reduction in anthropogenic hydrocarbon emissions.

Cardelino, C. A.; Chameides, W. L.

1990-01-01

309

The combustion program at CTR  

NASA Technical Reports Server (NTRS)

Understanding and modeling of turbulent combustion are key problems in the computation of numerous practical systems. Because of the lack of analytical theories in this field and of the difficulty of performing precise experiments, direct numerical simulation (DNS) appears to be one of the most attractive tools to use in addressing this problem. The general objective of DNS of reacting flows is to improve our knowledge of turbulent combustion but also to use this information for turbulent combustion models. For the foreseeable future, numerical simulation of the full three-dimensional governing partial differential equations with variable density and transport properties as well as complex chemistry will remain intractable; thus, various levels of simplification will remain necessary. On one hand, the requirement to simplify is not necessarily a handicap: numerical simulations allow the researcher a degree of control in isolating specific physical phenomena that is inaccessible in experiments. CTR has pursued an intensive research program in the field of DNS for turbulent reacting flows since 1987. DNS of reacting flows is quite different from DNS of non-reacting flows: without reaction, the equations to solve are clearly the five conservation equations of the Navier Stokes system for compressible situations (four for incompressible cases), and the limitation of the approach is the Reynolds number (or in other words the number of points in the computation). For reacting flows, the choice of the equations, the species (each species will require one additional conservation equation), the chemical scheme, and the configuration itself is more complex.

Poinsot, Thierry J.

1993-01-01

310

"Doing Chemistry."  

ERIC Educational Resources Information Center

Summarizes papers presented at the Sixth Biennial Conference on Chemical Education in the area of "Doing Chemistry," i.e., demonstrations and student experiments. A bibliography of 21 presented papers in this area is attached. (CS)

Journal of Chemical Education, 1981

1981-01-01

311

Cooperative Chemistry  

NSDL National Science Digital Library

Concept mapping in the organic chemistry laboratory can supplant cookbook activities with higher cognitive exercises. The common thread of most organic lab experiments is the synthesis, isolation, purification, and characterization of a carbon compound. T

Gahr, Allan A.

2003-02-01

312

Catalytic Chemistry.  

ERIC Educational Resources Information Center

Describes an approach for making chemistry relevant to everyday life. Involves the study of kinetics using the decomposition of hydrogen peroxide by vegetable juices. Allows students to design and carry out experiments and then draw conclusions from their results. (JRH)

Borer, Londa; And Others

1996-01-01

313

Chemistry Notes.  

ERIC Educational Resources Information Center

Describes equipment, activities, and experiments useful in chemistry instruction, including among others, a rapid method to determine available chlorine in bleach, simple flame testing apparatus, and a simple apparatus demonstrating the technique of flash photolysis. (SK)

School Science Review, 1980

1980-01-01

314

Chemistry Notes.  

ERIC Educational Resources Information Center

Describes 13 activities, experiments and demonstrations, including the preparation of iron (III) chloride, simple alpha-helix model, investigating camping gas, redox reactions of some organic compounds, a liquid crystal thermometer, and the oxidation number concept in organic chemistry. (JN)

School Science Review, 1981

1981-01-01

315

Radioanalytical Chemistry  

NSDL National Science Digital Library

This website provides a course on the use of radionuclides in analytical chemistry. Types of radioactive decay are discussed as well as the techniques of scintillation counting, neutron activation analysis, and gamma spectroscopy.

Hardy, James K.

2010-07-01

316

Chemistry Tutorials  

NSDL National Science Digital Library

The California State University Stanislaus developed these interactive chemistry Web tutorials to assist college students in mass spectrometry, proton NMR chemical shifts, and more. With the many animations and figures, visitors will find assistance with the subtraction and absorption of light and with infrared absorption frequencies for numerous compounds. The titration tutorials simulate laboratory experiments without the hazards of dealing with chemicals. Students will also find a very informative lesson describing how to use Excel to record and analyze their chemistry data.

317

Membrane separation of hydrocarbons  

DOEpatents

Mixtures of heavy oils and light hydrocarbons may be separated by passing the mixture over a polymeric membrane which comprises a polymer capable of maintaining its integrity in the presence of hydrocarbon compounds at temperature ranging from about ambient to about 100.degree. C. and pressures ranging from about 50 to about 1000 psi. The membranes which possess pore sizes ranging from about 10 to about 500 Angstroms are cast from a solvent solution and recovered.

Funk, Edward W. (Highland Park, IL); Kulkarni, Sudhir S. (Hoffman Estates, IL); Chang, Y. Alice (Des Plaines, IL)

1986-01-01

318

Turbulent Methane-Air Combustion  

NASA Technical Reports Server (NTRS)

This study is aimed at enhancing the understanding of turbulent premixed methane-air combustion. Such understanding is essential since: (1) many industries are now pursuing lighter hydrocarbon alternative fuels and the use of premixed flames to reduce pollutant emissions, and (2) the characteristic dimensions and flow rates of most industrial combustors are often large for flows to be turbulent. The specific objectives of the study are: (1) to establish the effects of process variables (e.g., flow rate, fuel/air ratio, chlorinated hydro-carbons, and pressure) on the emissions and flow structure (velocity distribution, streamlines, vorticity and flame shape), and (2) to develop a mechanistic model to explain the observed trends. This includes the acquisition of Dantec FlowMap Particle Image Velocimeter. The design and fabrication of the premixed burner has also been completed. The study is now at the stage of testing of equipment and analytical instruments. The presentation will give details on the tasks completed and on the current and future plans. The project is progressing well and all activities are on schedule. The outlook for the success of the project is bright.

Yaboah, Yaw D.; Njokwe, Anny; James, LaShanda

1996-01-01

319

Nitrogen release during coal combustion  

SciTech Connect

Experiments in entrained flow reactors at combustion temperatures are performed to resolve the rank dependence of nitrogen release on an elemental basis for a suite of 15 U.S. coals ranging from lignite to low-volatile bituminous. Data were obtained as a function of particle conversion, with overall mass loss up to 99% on a dry, ash-free basis. Nitrogen release rates are presented relative to both carbon loss and overall mass loss. During devolatilization, fractional nitrogen release from low-rank coals is much slower than fractional mass release and noticeably slower than fractional carbon release. As coal rank increases, fractional nitrogen release rate relative to that of carbon and mass increases, with fractional nitrogen release rates exceeding fractional mass and fractional carbon release rates during devolatilization for high-rank (low-volatile bituminous) coals. At the onset of combustion, nitrogen release rates increase significantly. For all coals investigated, cumulative fractional nitrogen loss rates relative to those of mass and carbon passes through a maximum during the earliest stages of oxidation. The mechanism for generating this maximum is postulated to involve nascent thermal rupture of nitrogen-containing compounds and possible preferential oxidation of nitrogen sites. During later stages of oxidation, the cumulative fractional loss of nitrogen approaches that of carbon for all coals. Changes in the relative release rates of nitrogen compared to those of both overall mass and carbon during all stages of combustion are attributed to a combination of the chemical structure of coals, temperature histories during combustion, and char chemistry.

Baxter, L.L.; Mitchell, R.E.; Fletcher, T.H.; Hurt, R.H.

1995-02-01

320

CHEMISTRY 320 PHYSICAL CHEMISTRY I  

E-print Network

), physical transformations (including phase transitions), solutions, electrochemistry, and chemical kinetics of the physical principles of chemistry. Goals/ Objectives: CHEM 320 presents chemical principles from, internal energy, enthalpy and entropy), chemical thermodynamics (Gibbs free energy and chemical potentials

Findley, Gary L.

321

Computational Chemistry for Chemistry Educators  

NSDL National Science Digital Library

In this paper we describe an ongoing project where the goal is to develop competence and confidence among chemistry faculty so they are able to utilize computational chemistry as an effective teaching tool. Advances in hardware and software have made research-grade tools readily available to the academic community. Training is required so that faculty can take full advantage of this technology, begin to transform the educational landscape, and attract more students to the study of science.

Sendlinger, Shawn C.; Metz, Clyde R.

322

Polycyclic Aromatic Hydrocarbons Residues in Sandstorm Depositions in Beijing, China  

Microsoft Academic Search

This study was conducted to determine the concentration of 16 polycyclic aromatic hydrocarbons (PAHs) in sandstorm depositions\\u000a in Beijing, China. The PAH concentrations in 13 samples collected in Beijing ranged from 0.18 to 3.52 ?g g?1. Analysis of the sources of contamination revealed that the PAHs were derived from a coal combustion source, although various\\u000a effects of traffic emissions were also observed.

S. Fu; K. Li; X. J. Xia; X. B. Xu

2009-01-01

323

The combustion process  

NASA Technical Reports Server (NTRS)

The effect of thermodynamic, chemical, and physical properties on the combustion of materials is discussed. The mechanisms which produce and support combustion of various materials are examined. The effects of free radical reactions, convection and gravitational effects on combustion rates, and changes in flame propagation due to size and shape of surfaces are described.

Downs, W. R.

1971-01-01

324

BOOK REVIEW: Turbulent Combustion  

Microsoft Academic Search

The book Turbulent Combustion by Norbert Peters is a concise monograph on single-phase gaseous low Mach number turbulent combustion. It is compiled from the author's review papers on this topic plus some additional material. Norbert Peters characterizes turbulent combustion both by the way fuel and air are mixed and by the ratio of turbulent and chemical time scales. This approach

Norbert Peters

2001-01-01

325

Combustion synthesis and nanomaterials  

Microsoft Academic Search

The recent developments and trends in combustion science towards the synthesis of nanomaterials are discussed. Different modifications made to conventional combustion approaches for preparation of nanomaterials are critically analyzed. Special attention is paid to various applications of combustion synthesized nanosized products.

Singanahally T. Aruna; Alexander S. Mukasyan

2008-01-01

326

Interstellar Grain Surface Chemistry  

NASA Technical Reports Server (NTRS)

Chemistry on grain surfaces plays an Important role in the formation of interstellar Ices, It can also influence the composition of the gas phase through outgassing near luminous, newly formed stars. This paper reviews the chemical processes taking place on Interstellar grain surfaces with the emphasis on those transforming CO into other hydrocarbons. At low, molecular cloud temperatures (approximately equal to 10K), physisorption processes dominate interstellar grain surface chemistry and GO is largely hydrogenated through reactions with atomic H and oxidized through reactions with atomic O. The former will lead to the formation of H2CO and CH3OH ices, while the latter results in CO2 ice. The observational evidence for these ices in molecular clouds will be discussed. Very close to protostars, the gas and grain temperatures are much higher (approximately equal to 500K) and chemisorption processes, including catalytic surface reactions, becomes important. This will be illustrated based upon our studies of the Fischer-Tropsch Synthesis of CH4 from CO on metallic surfaces. Likely, this process has played an important role in the early solar nebula. Observational consequences will be pointed out.

Tielens, Alexander G. G. M.; Cuzzi, Jeffrey N. (Technical Monitor)

1995-01-01

327

Measurement of adsorption and cracking of hydrocarbons over processed oil shale particles  

Microsoft Academic Search

A parallel reactor system was used to monitor adsorption, desorption and\\/or cracking of vapour-phase hydrocarbons over processed oil shale with short contact times at elevated temperatures. Hydrocarbons ranging from benzene to n-decane were passed across samples of pyrolysed, gasified and combusted shales at 300–650 C. The gasified shale exhibited the greatest adsorption capacity at low temperatures and the highest cracking

Darrell N. Taulbee

1995-01-01

328

Kitchen Chemistry  

NSDL National Science Digital Library

There is a great deal of chemistry going on in every kitchen, even though most cooks may not be cognizant of the various interactions going on in the pot, wok, or oven. MIT's popular OpenCourseWare Initiative has recently made the contents of Dr. Patricia Christie's course on kitchen chemistry available on this site. Visitors to the site can download the syllabus, take in some assigned readings (and recipes), and look over the assignments. The assignments include investigations that involve emulsifiers, ice cream, peer teaching, and pancakes, among other things. The site also includes links to helpful readings, such as those on chocolate, the health benefits of capsicum, and the world of gluten. For people who wish to bring back the frayed connective tissue between chemistry and the culinary arts, this site is absolutely essential.

Christie, Patricia

2006-01-01

329

Chemistry & Industry  

NSDL National Science Digital Library

Chemistry and Industry Magazine, a bimonthly product of the Society of Chemical Industry, provides selected full-text articles from the print magazine in the areas of news, commentary, features, latest results from chemical literature, and highlights from the latest European patents. In addition, there is a searchable and browsable archive of past issues, a daily news section, and searchable jobs and meetings databases. The Society of Chemical Industry is "an international association of about 6000 members aimed at furthering applied chemistry." One of the highlights of its web site is its publication section, where, under "electronic publications," readers can find updated daily news, jobs and meetings listings on chemistry, pharmaceuticals, biotechnology, and the environment.

2006-01-11

330

Position: Assistant Professor of Chemistry, Physical Chemistry  

E-print Network

John Grey Position: Assistant Professor of Chemistry, Physical Chemistry Email: jkgrey@unm.edu Phone: 505.277.1658; Fax: 505.277.2609 Office: Clark Hall B70 Homepage: http://chemistry.unm.edu/faculty_web/jgrey Education B.S. in Chemistry, 1999, Michigan Technological University, Houghton, MI Ph.D. in Chemistry

331

Synthetic fuel combustion: pollutant formation. Soot initiation mechanisms in burning aromatics. First quarterly report, 19 September31 December 1980  

Microsoft Academic Search

Although considerable progress has been made in recent years in understanding the phenomenology of soot formation in the combustion of hydrocarbon fuels, relatively little attention has been focused upon aromatic fuels of the types commonly found in coal liquids. In particular, the effects of gas-phase free radicals, formed during combustion, on the kinetics of formation of incipient soot particles have

W. T. Rawlins; T. Tanzawa

1981-01-01

332

Combustion Enhancement Using a Silent Discharge Plasma Reactor  

NASA Astrophysics Data System (ADS)

Electric fields affect flame propagation speed, stability, and combustion chemistry. External electrodes, arc discharges, and plasma jets have been used to combust gas mixtures outside their flammability limits. Experiments with silent electrical discharges (SEDs) and propagating flames have shown that flame propagation velocity is actually decreased (combustion retarded) when an SED is applied directly to the flame region, but velocity is increased (combustion promoted) when applied to the unburned gas mixture upstream of a flame. More recent work has proposed electric arc/microwave-driven plasma-generating fuel nozzles to produce dissociated fuel or ionized fuel for aircraft gas turbine engine combustor mixers. In contrast to prior works, we have used a silent discharge plasma (SDP) reactor to break up large fuel molecules into smaller molecules and create free radicals/active species in a gas stream before the fuel is mixed with an oxidizer and combusted. A cylindrical SDP reactor was used to 'activate' propane before mixing it with air and igniting the combustible gas mixture. With the plasma, the physical appearance of the flame changes and substantial changes in mass spectrometer fragmentation peaks for fuel and combustion products are observed (i.e., combustion is enhanced). Results of changes in the degree of combustion will be discussed in terms of variations in the plasma specific energy.

Rosocha, Louis; Platts, David; Coates, Don; Stange, Sy

2003-10-01

333

Polycyclic aromatic hydrocarbon (PAH) emissions from a coal-fired pilot FBC system  

Microsoft Academic Search

Due to the extensive amount of data suggesting the hazards of these compounds, 16 polycyclic aromatic hydrocarbons (PAHs) are on the Environmental Protection Agency (EPA) Priority Pollutant List. Emissions of these PAHs in the flue gas from the combustion of four coals were measured during four 1000h combustion runs using the 0.1MW heat-input (MWth) bench-scale fluidized bed combustor (FBC). An

Kunlei Liu; Wenjun Han; Wei-Ping Pan; John T. Riley

2001-01-01

334

Thermogravimetric-mass spectrometric analysis on combustion of lignocellulosic biomass.  

PubMed

Combustion characteristics of biomass main components and three lignocellulosic biomass (fir wood, eucalyptus wood and pine bark) were investigated by thermogravimetric analysis coupled with mass spectrometry. The combustion of biomass was divided into two main steps, devolatilization and char oxidation stage. Heating rate effect was also studied. Generally, the higher the heating rate, the higher the decomposition temperature. Furthermore, the weight loss rate decreased due to particle temperature gradients. Combustion kinetics were studied. Models based on reaction order (Oi), nucleation (Ni) and diffusion (Di) achieved the best fitting to the experimental data. Cellulose oxidation presented the highest activation energies. CO, CO2 and H2O were the main components evolved from combustion. Additionally, light hydrocarbons (CH4 and C2H5) were also present. Finally, nitrogen compounds were in a higher proportion than sulfur compounds being released as primary amines and NOx. PMID:23835261

López-González, D; Fernandez-Lopez, M; Valverde, J L; Sanchez-Silva, L

2013-09-01

335

Studies of combustion kinetics and mechanisms  

SciTech Connect

The objective of the current research is to gain new quantitative knowledge of the kinetics and mechanisms of polyatomic free radicals which are important in hydrocarbon combustion processes. The special facility designed and built for these (which includes a heatable tubular reactor coupled to a photoionization mass spectrometer) is continually being improved. Where possible, these experimental studies are coupled with theoretical ones, sometimes conducted in collaboration with others, to obtain an improved understanding of the factors determining reactivity. The decomposition of acetyl radicals, isopropyl radicals, and n-propyl radicals have been studied as well as the oxidation of methylpropargyl radicals.

Gutman, D. [Catholic Univ. of America, Washington, DC (United States)

1993-12-01

336

/6582 Biophysical Chemistry Fall Biophysical Chemistry  

E-print Network

/6582 Biophysical Chemistry Fall 1 CHEM /6582 Biophysical Chemistry Course meeting place concepts in biophysical chemistry. You will develop an understanding of how thermodynamics, kinetics literature concerning the application of biophysical techniques to characterize biological molecules

Sherrill, David

337

Accumulation of polycyclic aromatic hydrocarbons in acid sensitive lakes  

SciTech Connect

Polycyclic aromatic hydrocarbon concentrations and fluxes were measured in {sup 210}Pb dated sediment cores taken from nine lakes in four regions identified as susceptible to acidification. Calculated PAH accumulations were compared with historic S emissions, accumulation of sedimentary S, and anthropogenic metal accumulations to determine if PAH could be used as an indicator of combustion-derived sulfate deposition. Comparisons between regions indicated that the Adirondacks have a significantly higher burden of PAH than do northern New England, the northern Great Lakes States, and northern Florida. This difference likely results from significant upwind PAH sources to the Adirondack lakes. Detailed investigation of the largest lake in the study set, Big Moose Lake, indicates that PAH may serve as conservative, combustion indicators in large lakes. In this lake, PAH fluxes and concentrations were significantly correlated with historical S emission rates. These data suggest that PAH measured in sediment cores from large lakes can serve as indicators of past combustion production deposition.

Furlong, E.T.; Cessar, L.R.; Hites, R.A. (Indiana Univ., Bloomington (USA))

1987-11-01

338

Green Chemistry  

NSDL National Science Digital Library

This audio segment from PRI's The World Science Podcast explores the science of Green Chemistry. Hear about companies that are developing greener chemicals, and learn why they are fast becoming an attractive alternative for the multi-billion dollar chemical industry.

Foundation, Wgbh E.

2010-02-12

339

Confectionary Chemistry.  

ERIC Educational Resources Information Center

Presents activities and demonstrations that enable teachers to use various types of confections as tactile experiences to spark chemistry students' interest and generate enthusiasm for learning. Presents uses of candy in teaching about atomic structure, spontaneous nuclear decay, chemical formulas, fractoluminescence, the effect of a molecular…

Levine, Elise Hilf

1996-01-01

340

Bad Chemistry  

NSDL National Science Digital Library

This site from the Princeton Section of the American Chemical Society consists of articles about common chemical misconceptions along with examinations of the scientific explanation. The purpose of this page is to reveal common misconceptions in the field of Chemistry. The intended audience is secondary school students and their teachers. The page is at present just beginning, and additions are welcome.

Lehmann, Kevin; University, Princeton

341

Atmospheric Chemistry  

NSDL National Science Digital Library

This set of links provides access to resources on atmospheric chemistry, especially acid deposition, air pollution, and air quality. The sites include personal and government pages, universities and research groups, non-governmental organizations and meetings, and products and services. There are also links to related search topics.

342

Definition Chemistry  

E-print Network

1 · Definition · Chemistry · Factors · Mitigation MinE 422 Acid Rock Drainage Online `Gard Guide is a great source of information Terminology · acid rock drainage (ARD) · saline drainage (SD) · acid mine or acid and metalliferous drainage (AMD) · mining influenced water (MIW) · neutral mine drainage (NMD

Boisvert, Jeff

343

Nuclear Chemistry  

NSDL National Science Digital Library

This page, from the University of North Carolina - Chapel Hill Chemistry Fundamentals program and the Shodor Education Foundation, discusses five different types of radioactive decay: alpha, beta negative, gamma, positron emission, and electron capture. After examining the numerous equations, students can test their dating skills by solving three practice problems. Solutions are included.

2008-03-12

344

Analytical Chemistry  

NSDL National Science Digital Library

This site features lecture notes for first and second level courses in analytical chemistry. Topics include titrations, gravimetry, kinetics and electrochemistry (redox). Potentiometry, coulometry, voltammetry, spectroscopic and separation methods are presented as well, and are illustrated with QuickTime animations.

Hardy, James K.

2011-03-30

345

Chemistry Notes.  

ERIC Educational Resources Information Center

Describes some laboratory apparatus, chemistry experiments and demonstrations, such as a Kofler block melting point apparatus, chromatographic investigation of the phosphoric acid, x-ray diffraction, the fountain experiment, endothermic sherbet, the measurement of viscosity, ionization energies and electronic configurations. (GA)

School Science Review, 1978

1978-01-01

346

Polycyclic Aromatic Hydrocarbons  

NSDL National Science Digital Library

The featured molecules for the month of February are a number of polycyclic aromatic hydrocarbons (PAHs) discussed in the article "Fluorescence, Absorption, and Excitation Spectra of Polycyclic Aromatic Hydrocarbons as a Tool for Quantitative Analysis". PAHs are ubiquitous in air, soils, and water as a result of both direct and indirect emissions. PAHs are discharged into environments as byproducts of the combusion of fossil fuels used for transportation and generation of electricity. Other sources of PAH emissions include industrial processes, biomass burning, waste incineration, oil spills, and cigarette smoke.

347

Quantitative Hydrocarbon Surface Analysis  

NASA Technical Reports Server (NTRS)

The elimination of ozone depleting substances, such as carbon tetrachloride, has resulted in the use of new analytical techniques for cleanliness verification and contamination sampling. The last remaining application at Rocketdyne which required a replacement technique was the quantitative analysis of hydrocarbons by infrared spectrometry. This application, which previously utilized carbon tetrachloride, was successfully modified using the SOC-400, a compact portable FTIR manufactured by Surface Optics Corporation. This instrument can quantitatively measure and identify hydrocarbons from solvent flush of hardware as well as directly analyze the surface of metallic components without the use of ozone depleting chemicals. Several sampling accessories are utilized to perform analysis for various applications.

Douglas, Vonnie M.

2000-01-01

348

Hydrocarbon Impacts Database  

NSDL National Science Digital Library

The Hydrocarbon Impacts (HI) database is a subset of the University of Calgary's Arctic Institute of North America's Arctic Science and Technology Information System database. More than 5,100 records describe "publications and research projects about the environmental impacts, socio-economic effects and regulation of hydrocarbon exploration, development and transportation in northern Canada." Users can search by record type, keyword, subject code, geographic code, author, and year, as well as an advanced search feature to locate the information. Well designed and easy to use, the database provides those interested in this narrow subject field a helpful resource.

349

The effect of insulated combustion chamber surfaces on direct-injected diesel engine performance, emissions, and combustion  

NASA Technical Reports Server (NTRS)

The combustion chamber of a single-cylinder, direct-injected diesel engine was insulated with ceramic coatings to determine the effect of low heat rejection (LHR) operation on engine performance, emissions, and combustion. In comparison to the baseline cooled engine, the LHR engine had lower thermal efficiency, with higher smoke, particulate, and full load carbon monoxide emissions. The unburned hydrocarbon emissions were reduced across the load range. The nitrous oxide emissions increased at some part-load conditions and were reduced slightly at full loads. The poor LHR engine performance was attributed to degraded combustion characterized by less premixed burning, lower heat release rates, and longer combustion duration compared to the baseline cooled engine.

Dickey, Daniel W.; Vinyard, Shannon; Keribar, Rifat

1988-01-01

350

Combustion characteristics of gas turbine alternative fuels  

NASA Technical Reports Server (NTRS)

An experimental investigation was conducted to obtain combustion performance values for specific heavyend, synthetic hydrocarbon fuels. A flame tube combustor modified to duplicate an advanced gas turbine engine combustor was used for the tests. Each fuel was tested at steady-state operating conditions over a range of mass flow rates, fuel-to-air mass ratio, and inlet air temperatures. The combustion pressure, as well as the hardware, were kept nearly constant over the program test phase. Test results were obtained in regards to geometric temperature pattern factors as a function of combustor wall temperatures, the combustion gas temperature, and the combustion emissions, both as affected by the mass flow rate and fuel-to-air ratio. The synthetic fuels were reacted in the combustor such that for most tests their performance was as good, if not better, than the baseline gasoline or diesel fuel tests. The only detrimental effects were that at high inlet air temperature conditions, fuel decomposition occurred in the fuel atomizing nozzle passages resulting in blockage. And the nitrogen oxide emissions were above EPA limits at low flow rate and high operating temperature conditions.

Rollbuhler, R. James

1987-01-01

351

Chemistry Newsletter # 7  

NSF Publications Database

... the Division of Chemistry Don Burland to retire from the Division of Chemistry Mathematical and ... WITHIN THE DIVISION OF CHEMISTRY The Division of Chemistry has completed its national search and is ...

352

CHEMISTRY DEPARTMENT HANDBOOKFOR STUDENTS  

E-print Network

/ENVIRONMENTAL, Bachelor of Science in Chemistry with Option in Environmental Chemistry 27 BS CHEM/NANOTECHNOLOGY, Bachelor in Biochemistry 85 Minor in Environmental Chemistry 86 1st, 2nd and 3rd Floor Maps of the Chemistry Rooms

Hardy, Christopher R.

353

Simplified Modeling of Oxidation of Hydrocarbons  

NASA Technical Reports Server (NTRS)

A method of simplified computational modeling of oxidation of hydrocarbons is undergoing development. This is one of several developments needed to enable accurate computational simulation of turbulent, chemically reacting flows. At present, accurate computational simulation of such flows is difficult or impossible in most cases because (1) the numbers of grid points needed for adequate spatial resolution of turbulent flows in realistically complex geometries are beyond the capabilities of typical supercomputers now in use and (2) the combustion of typical hydrocarbons proceeds through decomposition into hundreds of molecular species interacting through thousands of reactions. Hence, the combination of detailed reaction- rate models with the fundamental flow equations yields flow models that are computationally prohibitive. Hence, further, a reduction of at least an order of magnitude in the dimension of reaction kinetics is one of the prerequisites for feasibility of computational simulation of turbulent, chemically reacting flows. In the present method of simplified modeling, all molecular species involved in the oxidation of hydrocarbons are classified as either light or heavy; heavy molecules are those having 3 or more carbon atoms. The light molecules are not subject to meaningful decomposition, and the heavy molecules are considered to decompose into only 13 specified constituent radicals, a few of which are listed in the table. One constructs a reduced-order model, suitable for use in estimating the release of heat and the evolution of temperature in combustion, from a base comprising the 13 constituent radicals plus a total of 26 other species that include the light molecules and related light free radicals. Then rather than following all possible species through their reaction coordinates, one follows only the reduced set of reaction coordinates of the base. The behavior of the base was examined in test computational simulations of the combustion of heptane in a stirred reactor at various initial pressures ranging from 0.1 to 6 MPa. Most of the simulations were performed for stoichiometric mixtures; some were performed for fuel/oxygen mole ratios of 1/2 and 2.

Bellan, Josette; Harstad, Kenneth

2008-01-01

354

UCLA CHEMISTRY & BIOCHEMISTRY  

E-print Network

UCLA CHEMISTRY & BIOCHEMISTRY ORIENTATION HANDBOOK 2012-2013 #12;Table of Contents Introduction .............................................................................................................................................2 Chemistry & Biochemistry Undergraduate Office ................................................................................................................................................4 Biochemistry

Levine, Alex J.

355

Plant hydrocarbon recovery  

SciTech Connect

A process for production and recovery of hydrocarbons from whole plants in a form suitable for use as chemical feedstocks or as hydrocarbon energy sources comprises: pulverizing by grinding or chopping the plants to a suitable particle size, drying and preheating the particles in a reducing atmosphere under positive pressure, passing the particles through a thermal conversion zone containing a reducing atmosphere and with a residence time of 1 s to approximately 30 min at approximately 200-1000 degrees, and separately recovering the condensable vapors as liquids and the noncondensable gases in a condition suitable for use as chemical feedstocks or as hydrocarbon fuels. Thus 1 g of dried Euphorbia marginata was thermally decomposed at 950/sup 0/. The respective yields of char, liquid products, CO, CO/sub 2/, CH/sub 4/, acetylene, ethylene, and total hydrocarbons were 31.1, 12.6, 13.3, 17.7, 3.9, 1.1, 4.0, and 21.6%.

Weil, T.A.; Dzadzic, P.M.; Shih, C.C.J.; Price, M.C.

1982-01-26

356

Optrode for sensing hydrocarbons  

DOEpatents

A two-phase system employing the Fujiwara reaction is provided for the fluorometric detection of halogenated hydrocarbons. A fiber optic is utilized to illuminate a column of pyridine trapped in a capillary tube coaxially attached at one end to the illuminating end of the fiber optic. A strongly alkaline condition necessary for the reaction is maintained by providing a reservoir of alkali in contact with the column of pyridine, the surface of contact being adjacent to the illuminating end of the fiber optic. A semipermeable membrane caps the other end of the capillary tube, the membrane being preferentially permeable to the halogenated hydrocarbon and but preferentially impermeable to water and pyridine. As the halogenated hydrocarbon diffuses through the membrane and into the column of pyridine, fluorescent reaction products are formed. Light propagated by the fiber optic from a light source, excites the fluorescent products. Light from the fluorescence emission is also collected by the same fiber optic and transmitted to a detector. The intensity of the fluorescence gives a measure of the concentration of the halogenated hydrocarbons. 5 figs.

Miller, H.; Milanovich, F.P.; Hirschfeld, T.B.; Miller, F.S.

1988-09-13

357

Hydrocarbons from lignocellulosic residues  

Microsoft Academic Search

Although there has been much interest in the search for a universal solution, e.g., fermentation alcohol, to meeting liquid engine fuel needs from biomass materials, it is argued that specific fuel needs of agricultural and forestry operations may dictate a diversity of approaches. Several options for producing fuels such as ethanol, methanol, and hydrocarbons are reviewed. Recent work in biomass

Soltes

1983-01-01

358

Zeroing in on hydrocarbons  

SciTech Connect

The increasing costs of remediating contaminated sites has stimulated research for cost-reducing techniques in soil investigation and cleanup techniques. MAP Environmental Research has developed a technology using ground penetrating radar in combination with in house developed software to locate and define the extent of hydrocarbon contamination. This article discusses the new technology. 2 figs.

Roest, I.P.B. van der; Brasser, D.J.S.; Wagebaert, A.P.J.; Stam, P.H. [MAP Environmental Research BV, Arnhem (Netherlands)

1997-05-01

359

Hydrocarbon in Catalyst in  

E-print Network

#12;Hydrocarbon in Steam in Catalyst in Vent 1 Vent 2 Product out Tank Pressure controller Computer operator Inform #12;Explosion Pressure toohigh PRV1 doesnotopen PRV2 doesnotopen Valve failure Computer(Product) + Temperature(Product) + FixedVolume Quantity(Steam) +,TIME Quantity(HC) +,TIME+,TIME+,TIME Temperature(Steam

Ladkin, Peter B.

360

Optrode for sensing hydrocarbons  

DOEpatents

A two-phase system employing the Fujiwara reaction is provided for the fluorometric detection of halogenated hydrocarbons. A fiber optic is utilized to illuminate a column of pyridine trapped in a capillary tube coaxially attached at one end to the illuminating end of the fiber optic. A strongly alkaline condition necessary for the reaction is maintained by providing a reservoir of alkali in contact with the column of pyridine, the surface of contact being adjacent to the illuminating end of the fiber optic. A semipermeable membrane caps the other end of the capillary tube, the membrane being preferentially permeable to the halogenated hydrocarbon and but preferentially impermeable to water and pyridine. As the halogenated hydrocarbon diffuses through the membrane and into the column of pyridine, fluorescent reaction products are formed. Light propagated by the fiber optic from a light source, excites the fluorescent products. Light from the fluorescence emission is also collected by the same fiber optic and transmitted to a detector. The intensity of the fluorescence gives a measure of the concentration of the halogenated hydrocarbons.

Miller, Holly (Bethel Island, CA); Milanovich, Fred P. (Lafayette, CA); Hirschfeld, Tomas B. (Livermore, CA); Miller, Fred S. (Bethel Island, CA)

1987-01-01

361

Optrode for sensing hydrocarbons  

DOEpatents

A two-phase system employing the Fujiwara reaction is provided for the fluorometric detection of halogenated hydrocarbons. A fiber optic is utilized to illuminate a column of pyridine trapped in a capillary tube coaxially attached at one end to the illuminating end of the fiber optic. A strongly alkaline condition necessary for the reaction is maintained by providing a reservoir of alkali in contact with the column of pyridine, the surface of contact being adjacent to the illuminating end of the fiber optic. A semipermeable membrane caps the other end of the capillary tube, the membrane being preferentially permeable to the halogenated hydrocarbon and but preferentially impermeable to water and pyridine. As the halogenated hydrocarbon diffuses through the membrane and into the column of pyridine, fluorescent reaction products are formed. Light propagated by the fiber optic from a light source, excites the fluorescent products. Light from the fluorescence emission is also collected by the same fiber optic and transmitted to a detector. The intensity of the fluorescence gives a measure of the concentration of the halogenated hydrocarbons.

Miller, Holly (Bethel Island, CA); Milanovich, Fred P. (Lafayette, CA); Hirschfeld, Tomas B. (Livermore, CA); Miller, Fred S. (Bethel Island, CA)

1988-01-01

362

Acetoxylation of unsaturated hydrocarbons  

SciTech Connect

Acetoxylation is a method for one-step introduction of ester groups into molecules of unsaturated hydrocarbons. Subsequent processing of esters formed may allow an easy preparation of alkanediols and dicarboxylic and polyfunctional carboxylic acids with the required number of carbon atoms.

Vekki, A.V. de [Scientific-Research Institute of Petrochemical Processes, St. Petersburg (Russian Federation)

1994-06-10

363

NATURAL MARINE HYDROCARBON SEEPAGE  

E-print Network

. Using 3.5 kHz sonar data, seep distribution offshore of Coal Oil Point was mapped forAugust 1996, July in the environment (Hovland et al., 1993; Hornafius et al., 1999). Natural marine hydrocarbon seeps offshore of Coal. 1). Farther offshore, seepage passes through overlying Sisquoc Formation cap rock and includes both

Luyendyk, Bruce

364

Chemistry 675 Advanced Organic Chemistry  

E-print Network

. Chisholm 4-006 CST jdchisho@syr.edu 443-6894 Office Hours: By appointment, between 9 AM and 5 PM Course in my office (CST 4-006) or my mailbox in the chemistry office (CST 1-014). Late problem sets will have

Doyle, Robert

365

Environmental Chemistry II (Atmospheric Chemistry)  

E-print Network

Seinfeld, J. H. and Pandis, S. N. Atmospheric Chemistry and Physics: From Air Pollution to Climate Change Monday, December 16 at 4:00 p.m. (Climate Change and comprehensive) Exams I and II are planned as two for undergraduate students than graduate students. Grading Scale 85 -100% at least an A- 75 - 84% at least a B- 65

Dibble, Theodore

366

Unravelling combustion mechanisms through a quantitative understanding of elementary reactions  

Microsoft Academic Search

This review of the role of reaction kinetics in combustion chemistry traces the historical evolution and present state of qualitative and quantitative understanding of a number of reaction systems. Starting from the H2–O2 system, in particular from the reaction between H and O2, mechanisms and key reactions for soot formation, for the appearance of NOx, and for processes of peroxy

James A. Miller; Michael J. Pilling; Jürgen Troe

2005-01-01

367

Modeling chemical flame structure and combustion dynamics in LES  

Microsoft Academic Search

In turbulent premixed combustion, the instantaneous flame thickness is typically thinner that the grid size usually retained in Large Eddy Simulations (LES), requiring adapted models. Two alternatives to couple chemical databases with LES balance equations, the Thickened Flame (TFLES) and the Filtered Tabulated Chemistry (F-TACLES) models, are investigated here and compared in terms of chemical flame structure and dynamics. To

P. Auzillon; B. Fiorina; R. Vicquelin; N. Darabiha; O. Gicquel; D. Veynante

2011-01-01

368

Fuel effects on gas turbine combustion-ignition, stability, and combustion efficiency  

SciTech Connect

An analytical study is made of the substantial body of experimental data acquired during recent Wright-Patterson Aero Propulsion Laboratory sponsored programs on the effects of fuel properties on the performance and reliability of several gas turbine combustors, including J79-17A, J79-17C (Smokeless), F101, TF41, TF39, J85, TF33, and F100. Quantitative relationships are derived between certain key aspects of combustion, notably combustion efficiency, lean blowout limits and lean light-off limits, and the relevant fuel properties, combustor design features, and combustor operating conditions. It is concluded that combustion efficiency, lean blowout limits, and lean lightoff limits are only slightly dependent on fuel chemistry, but are strongly influenced by the physical fuel properties that govern atomization quality and spray evaporation rates.

Lefebvre, A.H.

1984-06-01

369

Fuel effects on gas turbine combustion-ignition, stability, and combustion efficiency  

SciTech Connect

An analytical study is made of the substantial body of experimental data acquired during recent Wright-Patterson Aero Propulsion Laboratory sponsored programs on the effects of fuel properties on the performance and reliability of several gas turbine combustors, including J79-17A, J79-17C (Smokeless), F101, TF41, TF39, J85, TF33, and F100. Quantitative relationships are derived between certain key aspects of combustion, notably combustion efficiency, lean blowout limits and lean light-off limits, and the relevant fuel properties, combustor design features, and combustor operating conditions. It is concluded that combustion efficiency, lean blowout limits, and lean lightoff limits are only slightly dependent on fuel chemistry, but are strongly influenced by the physical fuel properties that govern atomization quality and spray evaporation rates.

Lefebvre, A.H.

1985-01-01

370

Irradiation chemistry in the outer solar system  

NASA Astrophysics Data System (ADS)

The dark, reddish tinged surfaces of icy bodies in the outer solar are usually attributed to the long term irradiation of simple hydrocarbons such as methane leading to the loss of hydrogen and the production of long carbon chains. While methane is stable and detected on the most massive bodies in the Kuiper belt, evidence of active irradiation chemistry is scant except for the presence of ethane on methane-rich Makemake and possible detections of ethane on more methane-poor Pluto and Quaoar. We have obtained deep high signal-to-noise spectra of Makemake from 1.5 to 2.5 microns in an attempt to trace the radiation chemistry in the outer solar system beyond the initial ethane formation. We present the first astrophysical detections of solid ethylene, acetylene, and possibly propane -- all expected products of the continued irradiation of methane, and use these species to map the chemical pathway from methane to long-chain hydrocarbons.

Brown, Michael E.

2014-11-01

371

Combustion of Micropowdered Biomass  

NASA Astrophysics Data System (ADS)

Combustion of finely powdered biomass has the potential to replace heating oil, which accounts for a significant fraction of US oil consumption, in heating, cooling and local power generation applications. When ground to 30-150 micron powders and dispersed in air, wood and other biomass can undergo deflagrating combustion, as occurs with gaseous and dispersed liquid fuels. Combustion is very nearly complete, and in contrast to sugar/starch or cellulose-derived ethanol, nearly all of the available plant mass is converted to usable energy so the economics are much more promising. We are exploring the fundamental combustion science of biomass powders in this size range. In particular, we are examining how powder size, powder composition (including the fraction of volatile organics) and other parameters affect the combustion regime and the combustion products.

Geil, Ethan; Thorne, Robert

2009-03-01

372

Hydrocarbonization research: completion report  

SciTech Connect

Hydrocarbonization is a relatively simple process used for producing oil, substitute natural gas, and char by heating coal under a hydrogen-rich atmosphere. This report describes studies that were performed in a bench-scale hydrocarbonization system at Oak Ridge National Laboratory (ORNL) during the period 1975 to 1978. The results of mock-up studies, coal metering valve and flowmeter development, and supporting work in an atmospheric hydrocarbonization system are also described. Oil, gas, and char yields were determined by hydrocarbonization of coal in a 0.1-m-diam fluidized-bed reactor operated at a pressure of 2170 kPa and at temperatures ranging from 694 to 854 K. The nominal coal feed rate was 4.5 kg/h. Wyodak subbituminous coal was used for most of the experiments. A maximum oil yield of approx. 21% based on moisture- and ash-free (maf) coal was achieved in the temperature range of 810 to 840 K. Recirculating fluidized-bed, uniformly fluidized-bed, and rapid hydropyrolysis reactors were used. A series of operability tests was made with Illinois No. 6 coal to determine whether caking coal could be processed in the recirculating fluidized-bed reactor. These tests were generally unsuccessful because of agglomeration and caking problems; however, these problems were eliminated by the use of chemically pretreated coal. Hydrocarbonization experiments were carried out with Illinois No. 6 coal that had been pretreated with CaO-NaOH, Na/sub 2/CO/sub 3/, and CaO-Na/sub 2/CO/sub 3/. Oil yields of 14, 24, and 21%, respectively, were obtained from the runs with treated coal. Gas and char yield data and the composition of the oil, gas, and char products are presented.

Youngblood, E.L.; Cochran, H.D. Jr.; Westmoreland, P.R.; Brown, C.H. Jr.; Oswald, G.E.; Barker, R.E.

1981-01-01

373

EFFECT OF HYDROCARBON COMPOSITION ON OXIDANT-HYDROCARBON RELATIONSHIPS. PHASE II. BLEND OF TOTAL HYDROCARBON EMISSIONS  

EPA Science Inventory

To assess the formation of atmospheric oxidants resulting from exhaust emitted by catalyst-equipped vehicles, chamber irradiations were conducted using a hydrocarbon blend representing total hydrocarbon emissions (exhaust, refueling and evaporation). Results were compared with pr...

374

[Retention of selenium volatility using lime in coal combustion].  

PubMed

For understanding the volatility of selenium, the effect of the contents of exchangeable cations of coal on it, and the retention of selenium using CaO in coal combustion, the sequential chemistry extraction, the fixed bed and circulating fluidized bed (CFB) combustion, X-ray diffraction (XRD) and atomic fluorescence spectrometry (AFS) were undertaken. The results showed that the volatility of selenium was more than 97% in coal combustion at 815 degrees C, and the volatility of selenium was affected by the content of exchangeable cations of coal in low-middle temperature. It was identified that lime can restrain the volatility of selenium. In fixed bed combustion of coal, the retention rates of selenium volatility were between 11.6% and 50.7% using lime. In circulating fluidized bed combustion of coal, partitioning of selenium changed very much in ash of different size fraction between without lime and with lime. Comparing with combustion without lime, the content of selenium in ash from chimney was less than fourth times and that in leaching water from chimney decreased by two orders of magnitude using lime. Retention of selenium volatility using lime is so effective in coal combustion, especially in CFB combustion of coal. PMID:11507891

Zhang, J; Ren, D; Zhong, Q; Xu, F; Zhang, Y; Yin, J

2001-05-01

375

Environmental Chemistry  

NSDL National Science Digital Library

In this activity with several mini experiments, learners explore the chemistry that helps scientists learn about the environment and how they can help save it. Learners will determine if pollutants that have entered the ground water can also enter plants. Then, learners examine fossils to see if any changes have occurred over time in a particular species of sea mollusks. Finally, learners act as chemists to recycle paper by making paper from toilet paper.

Shaw, Maisie; Gomez, Maria

2010-01-01

376

Circumstellar chemistry  

NASA Technical Reports Server (NTRS)

Recent theoretical studies of circumstellar chemistry are discussed for both red-giant and protostellar winds. The generalized photochemical model is able to account for the recently discovered silicon-bearing molecules in the prototypical, C-rich, AGB star IRC + 10216. The surprising occurrence of CO in protostellar winds that are largely atomic is interpreted to be the result of the high density and the rapid decrease of the temperature with distance that is expected for such winds.

Glassgold, A. E.; Mamon, G. A.

1991-01-01

377

[Homolytic activation of hydrocarbons and hydrogen by persistent radicals  

SciTech Connect

New synthetic methods for preparing persistent transition metal- centered radicals have been developed, based on ligand addition reactions of triphenylmethyl complexes. Preliminary study indicate that they will react under mild conditions with substrates such as hydrogen and certain hydrocarbons. The chemistry has been extended to biradicals. Mechanism and selectivity of the novel reactions are being studied. Extensions and modification of synthetic method to provide addition persistent radicals are proposed; more general methodologies including the reduction of metal halides are also being developed.

Not Available

1993-01-01

378

Chemistry 411/611 Inorganic Chemistry (2011)  

E-print Network

1 Chemistry 411/611 Inorganic Chemistry (2011) Instructor: Assistant Professor Mathew M. Maye Chemistry", 5th Edition, Freeman Press. Available at SU bookstore. The solution manual is optional. (Suggested for CHE611 Students pursuing Inorganic) Huheey, "Inorganic Chemistry: Principles of Structure

Mather, Patrick T.

379

Molten salt pyrolysis of latex. [synthetic hydrocarbon fuel production using the Guayule shrub  

NASA Technical Reports Server (NTRS)

Latex-rich plants such as Guayule or extracts thereof are pyrolyzed in an inert nitrogen atmosphere inorganic salt melts such as a LiCl/KCl eutectic at a temperature of about 500 C. The yield is over 60% of a highly aromatic, combustible hydrocarbon oil suitable for use as a synthetic liquid fuel.

Bauman, A. J. (inventor)

1981-01-01

380

Diversity of ndo Genes in Mangrove Sediments Exposed to Different Sources of Polycyclic Aromatic Hydrocarbon Pollution  

Microsoft Academic Search

Polycyclic aromatic hydrocarbon (PAH) pollutants originating from oil spills and wood and fuel combustion are pollutants which are among the major threats to mangrove ecosystems. In this study, the composition and relative abundance in the sediment bacterial communities of naphthalene dioxygenase (ndo) genes which are important for bacterial adaptation to environmental PAH contamination were investigated. Three urban mangrove sites which

Newton C. Marcial Gomes; Ludmila R. Borges; Rodolfo Paranhos; Fernando N. Pinto; Ellen Krogerrecklenfort; Leda C. S. Mendonca-Hagler; Kornelia Smalla

2007-01-01

381

Mathematical Modeling of Carbon Dioxide Injection in the Subsurface for Improved Hydrocarbon Recovery and Sequestration  

E-print Network

Mathematical Modeling of Carbon Dioxide Injection in the Subsurface for Improved Hydrocarbon Recovery and Sequestration Philip C. Myint, Laurence Rongy, Kjetil B. Haugen, Abbas Firoozabadi Department. Combustion of fossil fuels contributes to rising atmospheric carbon dioxide (CO2) levels that have been

Firoozabadi, Abbas

382

Catalyst of uranium, platinum and rhodium for converting carbon monoxide, hydrocarbons and nitrogen oxides  

SciTech Connect

A catalytic composite suitable for use in the continuous and simultaneous conversion of carbon monoxide, hydrocarbons, and nitrogen oxides contained in hot gases particularly from hot gases from an internal combustion engine is disclosed. The catalytic composite comprises uranium and a metal selected from the group consisting of platinum, palladium, rhodium, or mixtures thereof.

Joy III., G. C.

1985-07-02

383

2007-01-0472 Particulate and Hydrocarbon Emissions from a Spray Guided  

E-print Network

temperatures and heats of vaporization are given in Table 3. Combustion of alcohols is also known to produce-out emissions. In this work, the effect of blending methanol and ethanol with gasoline on unburned hydrocarbon are a key enabler to reducing CO2 emissions and improving fuel efficiency. Methanol and ethanol can

384

THE ADVANCED CHEMISTRY BASINS PROJECT  

SciTech Connect

In the next decades, oil exploration by majors and independents will increasingly be in remote, inaccessible areas, or in areas where there has been extensive shallow exploration but deeper exploration potential may remain; areas where the collection of data is expensive, difficult, or even impossible, and where the most efficient use of existing data can drive the economics of the target. The ability to read hydrocarbon chemistry in terms of subsurface migration processes by relating it to the evolution of the basin and fluid migration is perhaps the single technological capability that could most improve our ability to explore effectively because it would allow us to use a vast store of existing or easily collected chemical data to determine the major migration pathways in a basin and to determine if there is deep exploration potential. To this end a the DOE funded a joint effort between California Institute of Technology, Cornell University, and GeoGroup Inc. to assemble a representative set of maturity and maturation kinetic models and develop an advanced basin model able to predict the chemistry of hydrocarbons in a basin from this input data. The four year project is now completed and has produced set of public domain maturity indicator and maturation kinetic data set, an oil chemistry and flash calculation tool operable under Excel, and a user friendly, graphically intuitive basin model that uses this data and flash tool, operates on a PC, and simulates hydrocarbon generation and migration and the chemical changes that can occur during migration (such as phase separation and gas washing). The DOE Advanced Chemistry Basin Model includes a number of new methods that represent advances over current technology. The model is built around the concept of handling arbitrarily detailed chemical composition of fluids in a robust finite-element 2-D grid. There are three themes on which the model focuses: chemical kinetic and equilibrium reaction parameters, chemical phase equilibrium, and physical flow through porous media. The chemical kinetic scheme includes thermal indicators including vitrinite, sterane ratios, hopane ratios, and diamonoids; and a user-modifiable reaction network for primary and secondary maturation. Also provided is a database of type-specific kerogen maturation schemes. The phase equilibrium scheme includes modules for primary and secondary migration, multi-phase equilibrium (flash) calculations, and viscosity predictions.

William Goddard; Peter Meulbroek; Yongchun Tang; Lawrence Cathles III

2004-04-05

385

Opposed Jet Burner Approach for Characterizing Flameholding Potentials of Hydrocarbon Scramjet Fuels  

NASA Technical Reports Server (NTRS)

Opposed Jet Burner (OJB) tools have been used extensively by the authors to measure Flame Strength (FS) extinction limits of laminar H2/N2 air and (recently) hydrocarbon (HC) air Counterflow Diffusion Flames (CFDFs) at one atm. This paper details normalization of FSs of N2- diluted H2 and HC systems to account for effects of fuel composition, temperature, pressure, jet diameter, inflow Reynolds number, and inflow velocity profile (plug, contoured nozzle; and parabolic, straight tube). Normalized results exemplify a sensitive accurate means of validating, globally, reduced chemical kinetic models at approx. 1 atm and the relatively low temperatures approximating the loss of non-premixed idealized flameholding, e.g., in scramjet combustors. Laminar FS is defined locally as maximum air input velocity, U(sub air), that sustains combustion of a counter-jet of g-fuel at extinction. It uniquely characterizes a fuel. And global axial strain rate at extinction (U(sub air) normalized by nozzle or tube diameter, D(sub n or (sub t)) can be compared directly with computed extinction limits, determined using either a 1-D Navier Stokes stream-function solution, using detailed transport and finite rate chemistry, or (better yet) a detailed 2-D Navier Stokes numerical simulation. The experimental results define an idealized flameholding reactivity scale that shows wide ranging (50 x) normalized FS s for various vaporized-liquid and gaseous HCs, including, in ascending order: JP-10, methane, JP-7, n-heptane, n-butane, propane, ethane, and ethylene. Results from H2 air produce a unique and exceptionally strong flame that agree within approx. 1% of a recent 2-D numerically simulated FS for a 3 mm tube-OJB. Thus we suggest that experimental FS s and/or FS ratios, for various neat and blended HCs w/ and w/o additives, offer accurate global tests of chemical kinetic models at the Ts and Ps of extinction. In conclusion, we argue the FS approach is more direct and fundamental, for assessing, e.g., idealized scramjet flameholding potentials, than measurements of laminar burning velocity or blowout in a Perfectly Stirred Reactor, because the latter characterize premixed combustion in the absence of aerodynamic strain. And FS directly measures a chemical kinetic characteristic of non-premixed combustion at typical flameholding temperatures. It mimics conditions where gfuels are typically injected into a subsonic flameholding recirculation zone that captures air, where the effects of aerodynamic strain and associated multi-component diffusion become important.

Pellett, Gerald L.; Convery, Janet L.; Wilson, Lloyd G.

2006-01-01

386

Particulate polycyclic aromatic hydrocarbons in the Atlantic and Indian Ocean atmospheres during the Indian Ocean Experiment and Aerosols99: Continental sources to the marine atmosphere  

Microsoft Academic Search

Polycyclic aromatic hydrocarbons (PAHs), mutagenic compounds predominantly derived from combustion, have been used as markers of combustion sources to the atmosphere. Marine aerosol collected aboard the NOAA R\\/V Ronald Brown during the Aerosols99 and the Indian Ocean Experiment (INDOEX) projects was analyzed for PAHs to assess the continental impact of combustion-derived particulate matter on the Atlantic and Indian Ocean atmospheres.

Bernard S. Crimmins; Russell R. Dickerson; Bruce G. Doddridge; Joel E. Baker

2004-01-01

387

Hydrocarbon conversion process  

SciTech Connect

1. A combination process is described for producing high octane blending components for gasolines which consists of (a) contacting a mixture of methanol and an olefinic C/sub 4/ cut comprising isobutene, 1-butene, and 2-butenes under etherification conditions to produce methyltertiarybutyl ether and unreacted C/sub 4/ olefinic hydrocarbons, (b) contacting the unreacted C/sub 4/ olefinic hydrocarbons with a molecular sieve to selectively adsorb 2-butenes leaving a stream comprising 1-butene, (c) subjecting at least a portion of the 1-butene stream to skeletal isomerization to form isobutene, (d) subjecting the remainder of the 1-butene stream to double bond isomerization to form 2-butenes, and (e) passing the 2-butenes formed by isomerization and an isoparaffin to alkylation to form alkylate.

Hutson, T. Jr.; Hann, P.D.

1986-04-08

388

Frozen Hydrocarbons in Comets  

NASA Astrophysics Data System (ADS)

Recent investigations of the luminescence of frozen hydrocarbon particles of icy cometary halos have been carried out. The process of luminescence of organic icy particles in a short-wavelength solar radiation field is considered. A comparative analysis of observed and laboratory data leads to 72 luminescent emission lines in the spectrum of the comet 153P/Ikeya-Zhang. The concept of cometary relict matter is presented, and the creation of a database of unidentified cometary emission lines is proposed.

Simonia, Irakli

2011-02-01

389

Modification of liquid hydrocarbons  

SciTech Connect

Improved rate of dissolution in liquid hydrocarbon fuels, of specified tert-butylstyrene copolymers capable of imparting anti-misting characteristics to the fuel, is obtained when the copolymer, following its production by aqueous emulsion polymerization of the monomers, is isolated from the resulting latex by a process of flocculation, separation, washing and drying at moderate temperatures. The copolymer thus isolated is advantageously incorporated in the liquid fuel in the form of a slurry with a hydroxylic liquid and an amine.

Roberts, T. S.; Waite, F. A.

1985-09-24

390

Biogeochemistry of Halogenated Hydrocarbons  

NASA Astrophysics Data System (ADS)

Halogenated hydrocarbons originate from both natural and industrial sources. Whereas direct anthropogenic emissions to the atmosphere and biosphere are often easy to assess, particularly when they are tied to major industrial activities, the attribution of emissions to other human activities (e.g., biomass burning), diffuse sources (e.g., atmospheric discharge, run off), and natural production (e.g., soils, fungi, algae, microorganisms) are difficult to quantify. The widespread occurrence of both alkyl and aryl halides in groundwater, surface water, soils, and various trophic food chains, even those not affected by known point sources, suggests a substantial biogeochemical cycling of these compounds (Wania and Mackay, 1996; Adriaens et al., 1999; Gruden et al., 2003). The transport and reactive fate mechanisms controlling their reactivity are compounded by the differences in sources of alkyl-, aryl-, and complex organic halides, and the largely unknown impact of biogenic processes, such as enzymatically mediated halogenation of organic matter, fungal production of halogenated hydrocarbons, and microbial or abiotic transformation reactions (e.g., Asplund and Grimvall, 1991; Gribble, 1996; Watling and Harper, 1998; Oberg, 2002). The largest source may be the natural halogenation processes in the terrestrial environment, as the quantities detected often exceed the amount that can be explained by human activities in the surrounding areas ( Oberg, 1998). Since biogeochemical processes result in the distribution of a wide range of halogenated hydrocarbon profiles, altered chemical structures, and isomer distributions in natural systems, source apportionment (or environmental forensics) can often only be resolved using multivariate statistical methods (e.g., Goovaerts, 1998; Barabas et al., 2003; Murphy and Morrison, 2002).This chapter will describe the widespread occurrence of halogenated hydrocarbons, interpret their distribution and biogeochemical cycling in light of natural and anthropogenic sources, biotic and abiotic reactivity, and prevailing cycling mechanisms. Specific emphasis will be placed on the potential role of biotic and abiotic transformation reactions in soil, water, and sediment environments resulting in environmental sequestration and phase transfer.

Adriaens, P.; Gruden, C.; McCormick, M. L.

2003-12-01

391

School of Chemistry CHEM3100: Chemistry at a Molecular Level  

E-print Network

School of Chemistry CHEM3100: Chemistry at a Molecular Level Tutorial Groups 2013/14 Name Programme Tutor Ahmed, Zacher Medicinal Chemistry Arif, Saboor Chemistry Bagnall, Samuel Chemistry Barbara, David Chemistry Beaumont, Nicholas Chemistry Quinn, Michael J Chemistry Bennett, Matthew Chemistry Booth, Natalie

Rzepa, Henry S.

392

ASRM combustion instability studies  

NASA Technical Reports Server (NTRS)

The objectives of this task were to measure and compare the combustion response characteristics of the selected propellant formulation for the Space Shuttle Advanced Solid Rocket Motor (ASRM) with those of the current Redesigned Solid Rocket Motor (RSRM) formulation. Tests were also carried out to characterize the combustion response of the selected propellant formulation for the ASRM igniter motor.

Strand, L. D.

1992-01-01

393

Fifteenth combustion research conference  

SciTech Connect

The BES research efforts cover chemical reaction theory, experimental dynamics and spectroscopy, thermodynamics of combustion intermediates, chemical kinetics, reaction mechanisms, combustion diagnostics, and fluid dynamics and chemically reacting flows. 98 papers and abstracts are included. Separate abstracts were prepared for the papers.

NONE

1993-06-01

394

Radical cations in radiation chemistry of liquid hydrocarbons  

SciTech Connect

The state of knowledge concerning radical cations in liquid alkanes is discussed with particular emphasis on those which exhibit high mobility. Uncertainty has existed in the interpretation of previous results with respect to the nature and reactivity of high mobility ions, especially for cyclohexane. Recent time-resolved studies on pulse radiolysis/transient absorption, photoconductivity, and magnetic resonance in these systems have led us to propose new mechanisms for the high mobility ions. In decalins, scavenging of these ions by solutes is a pseudo-first-order reaction. In cyclohexane, the behavior is more complex and is indicative of the involvement of two species. This bimodality is rationalized in terms of a dynamic equilibrium between two conformers of the solvent radical cation. Several experimental tests supporting these views include a recent study on two-color laser photoionization in cyclohexane.

Trifunac, A.D.; Sauer, M.C., Jr.; Shkrob, I.A.; Werst, D.W.

1996-07-01

395

Methyl Substitution in Hydrocarbon Discharge Chemistry: Diagnosis by Laser Spectroscopy  

E-print Network

of a molecular beam combined with a linear time-of-flight (TOF) mass analyzer (resolution of 900 at mass 200 18, 2003 The spectra of C8H4 and C10H5 were observed in a butadiyne/argon discharge under the same members of this series have been confirmed to exist in space.2,3 Optical and microwave spectra have been

Maier, John Paul

396

Industrial Chemistry  

NSDL National Science Digital Library

This Web site addresses Professor Dr. J. Gmehling's research group activities in "the synthesis and design of chemical processes with an emphasis on thermal separation processes." Ranging from the development of thermodynamic models to the construction of software tools and data banks, their research at the University of Oldenburg, covers a broad range in the field of Industrial Chemistry. Students and educators can view informative figures and images such as the Isothermal Flow Calorimeter and the Gas-Liquid Chromatography. Users can download the free software, Dortmund Data Bank (DDB), which searches the literature for experimental information.

397

(Pesticide chemistry)  

SciTech Connect

This report summarizes a trip by L. W. Barnthouse of the Environmental Sciences Division (ESD), Oak Ridge National Laboratory (ORNL), to Hamburg, Federal Republic of Germany (FRG), where he participated in the 7th International Congress of Pesticide Chemistry. He chaired a workshop on experimental systems for determining effects of pesticides on nontarget organisms and gave an oral presentation at a symposium on pesticide risk assessment. Before returning to the United States, Dr. Barnthouse visited the Netherlands Institute for Sea Research in Texel, the Netherlands.

Barnthouse, L.W.

1990-09-04

398

Chemistry References  

NSDL National Science Digital Library

This site highlights chemistry resources that we consider essentiala fabulous periodic table, a database of chemical compounds, a set of demonstrations of chemical reactions that are just plain spectacular, and, dont forget, laboratory safety. Articles from the web sites Whats That Stuff? and Science News for Kids can be used as supplemental reading all through the year. This site explains the history and characteristics of over 20 substances, such as sunscreen, Cheese Whiz, baseballs, fluoride, new car smell, ink, lipstick, bug spray, and licorice. The individual articles are nontechnical for the most part and are presented in a fun way that readers will enjoy. Also, if a ...

Kim

2007-08-08

399

CHEMISTRY CURRICULUM SEMESTER I  

E-print Network

CHEMISTRY CURRICULUM SEMESTER ­ I Chemistry-I: Physical principles (2:1) Atomic structure-state approximation, Arrhenius equation and collision theory and catalysis. SEMESTER ­ II Chemistry-II: Structure orbital theory: polyatomic molecules - Walsh diagram; Main group chemistry: periodic properties, chemistry

Srinivasan, N.

400

GOM Deepwater Horizon Oil Spill: A Time Series Analysis of Variations in Spilled Hydrocarbons  

NASA Astrophysics Data System (ADS)

An estimated amount of 210 million gallons of crude oil was released into the Gulf of Mexico (GOM) from April 20th to July 15th 2010 during the Deepwater Horizon oil rig explosion. The spill caused a tremendous financial, ecological, environmental and health impact and continues to affect the GOM today. Variations in hydrocarbons including alkanes, hopanes and poly-cyclic aromatic hydrocarbons (PAHs) can be analyzed to better understand the oil spill and assist in oil source identification. Twenty-one sediment samples*, two tar ball samples and one surface water oil sample were obtained from distinct locations in the GOM and within varying time frames from May to December 2010. Each sample was extracted through the ASE 200 solvent extractor, concentrated down under nitrogen gas, purified through an alumina column, concentrated down again with nitrogen gas and analyzed via GC X GC-TOF MS. Forty-one different hydrocarbons were quantified in each sample. Various hydrocarbon 'fingerprints,' such as parental :alkylate PAH ratios, high molecular weight PAHs: low molecular weight alkane ratios, and carbon preference index were calculated. The initial objective of this project was to identify the relative hydrocarbon contributions of petrogenic sources and combustion sources. Based on the calculated ratios, it is evident that the sediment core taken in October of 2010 was greatly affected by combustion sources. Following the first month of the spill, oil in the gulf was burned in attempts to contain the spill. Combustion related sources have quicker sedimentation rates, and hydrocarbons from a combustion source essentially move into deeper depths quicker than those from a petrogenic source, as was observed in analyses of the October 2010 sediment. *Of the twenty-one sediment samples prepared, nine were quantified for this project.

Palomo, C. M.; Yan, B.

2013-12-01

401

Liquid Oxygen Cooling of Hydrocarbon Fueled Rocket Thrust Chambers  

NASA Technical Reports Server (NTRS)

Rocket engines using liquid oxygen (LOX) and hydrocarbon fuel as the propellants are being given serious consideration for future launch vehicle propulsion. Normally, the fuel is used to regeneratively cool the combustion chamber. However, hydrocarbons such as RP-1 are limited in their cooling capability. Another possibility for the coolant is the liquid oxygen. Combustion chambers previously tested with LOX and RP-1 as propellants and LOX as the collant demonstrated the feasibility of using liquid oxygen as a coolant up to a chamber pressure of 13.8 MPa (2000 psia). However, there was concern as to the effect on the integrity of the chamber liner if oxygen leaks into the combustion zone through fatigue cracks that may develop between the cooling passages and the hot gas side wall. In order to study this effect, chambers were fabricated with slots machined upstream of the throat between the cooling passage wall and the hot gas side wall to simulate cracks. The chambers were tested at a nominal chamber pressure of 8.6 MPa (1247 psia) over a range of mixture ratios from 1.9 to 3.1 using liquid oxygen as the coolant. The results of the testing showed that the leaking LOX did not have a deleterious effect on the chambers in the region of the slots. However, there was unexplained melting in the throat region of both chambers, but not in line with the slots.

Armstrong, Elizabeth S.

1989-01-01

402

Combustion of volatile matter during the initial stages of coal combustion  

SciTech Connect

Both the secondary pyrolysis and combustion of the volatiles from a bituminous coal will be studied. Devolatilization and secondary pyrolysis experiments will be conducted in a novel flow reactor in which secondary pyrolysis of the volatiles occurs after devolatilization is complete. This allows unambiguous measurements of the yields from both processes. Measurements will be made for reactor temperatures from 1500 to 1700 K, and a nominal residence time of 200 msec. These conditions are typical of coal combustion. Yields of tar, soot, H{sub 2}, CO, CH{sub 4}, and C{sub 2} and C{sub 3} hydrocarbons will be determined as a function of reactor temperature. The yields will be reported as a function of the temperature of the reactor. The instrumentation for temperature measurements will be developed during future studies. Combustion studies will be conducted in a constant volume bomb, which will be designed and constructed for this study. Tar and soot will be removed before introducing the volatiles to the bomb, so that only the combustion of the light gas volatiles will be considered. The burning velocities of light gas volatiles will be determined both as functions of mixture stoichiometry and the temperature at which the volatiles are pyrolysed. 90 refs., 70 figs., 13 tabs.

Marlow, D.; Niksa, S.; Kruger, C.H.

1990-08-01

403

Problems connected with the analysis of halocarbons and hydrocarbons in the non-urban atmosphere.  

PubMed

The problems connected with the measurement of hydrocarbons outside urban areas are considerable: The atmospheric mixing ratios of most of the hydrocarbons are very low--from a few ppb down to some ppt; the mixture of hydrocarbons is extremely complex, ranging from light n-alkanes to alkyl benzenes and terpenes; for measurements in remote areas the logistic conditions often restrict the instrumentation which can be used for sample collection or in situ measurements (such as lack of electric power supply, weight restrictions etc.). Nevertheless, sensitive and sufficiently reliable measurements of hydrocarbons in the non-urban atmosphere are important. Hydrocarbons are important factors in the tropospheric photochemistry (e.g. ozone formation) and can be used as valuable tracers for man-made atmospheric pollutants etc. Other useful tracers for anthropogenic emission are halocarbons such as dichlormethane, tri- and tetrachloroethen etc. The impact of man-made hydrocarbons on the chemistry of the troposphere can only be understood if the extent of natural (biogenic) contributions is known. From measurements of a large variety of hydrocarbons and halocarbons it is often possible to obtain information about the sources of the most important atmospheric hydrocarbon species, even for trace gases with both significant anthropogenic and biogenic sources. In this presentation some of the problems and their solutions connected with such measurements of atmospheric hydrocarbons and halocarbons are presented and discussed. Some of the results obtained by several series of measurements are described, indicating that man-made as well as biogenic hydrocarbons can be important factors for the chemistry of the atmosphere. PMID:3793365

Rudolph, J; Johnen, F J; Khedim, A

1986-01-01

404

Ultra-lean combustion at high inlet temperatures  

NASA Technical Reports Server (NTRS)

Combustion at inlet air temperatures of 1100 to 1250 K was studied for application to advanced automotive gas turbine engines. Combustion was initiated by the hot environment, and therefore no external ignition source was used. Combustion was stabilized without a flameholder. The tests were performed in a 12 cm diameter test section at a pressure of 2.5 x 10 to the 5th power Pa, with reference velocities of 32 to 60 m/sec and at maximum combustion temperatures of 1350 to 1850 K. Number 2 diesel fuel was injected by means of a multiple source fuel injector. Unburned hydrocarbons emissions were negligible for all test conditions. Nitrogen oxides emissions were less than 1.9 g NO2/kg fuel for combustion temperatures below 1680 K. Carbon monoxide emissions were less than 16 g CO/kg fuel for combustion temperatures greater than 1600 K, inlet air temperatures higher than 1150 K, and residence times greater than 4.3 microseconds.

Anderson, D. N.

1981-01-01

405

Investigation on fuel-rich premixed flames of monocyclic aromatic hydrocarbons: Part I. Intermediate identification and mass spectrometric analysis  

SciTech Connect

Fuel-rich premixed flames of seven monocyclic aromatic hydrocarbons (MAHs) including benzene, toluene, styrene, ethylbenzene, ortho-xylene, meta-xylene, and para-xylene were studied at the pressure of 30 Torr and comparable flame conditions (C/O = 0.68). The measurement of photoionization efficiency (PIE) spectra facilitated the comprehensive identification of combustion intermediates from m/z = 15 to 240, while mass spectrometric analysis was performed to gain insight into the flame chemistry. Features of the sidechain structure in fuel molecule affect the primary decomposition and aromatics growth processes, resulting in different isomeric structures or compositions of some primary products. This effect becomes weaker and weaker as both processes proceed. The results indicate that most intermediates are identical in all flames, leading to similar intermediate pools of these fuels. Consequently the chemical structures of flames fueled by different MAHs are almost identical, subsequent to the initial fuel-specific decomposition and oxidation that produce the primary intermediates. On the other hand, special features of the sidechain structure can affect the concentration levels of PAHs by increasing the concentrations of the key intermediates including the benzyl radical and phenylacetylene. Therefore, the total ion intensities of the PAH intermediates in the flames were observed to increase in the order of: benzene < toluene and styrene < four C{sub 8}H{sub 10}, which implies the same order of the sooting tendency. (author)

Li, Yuyang [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029 (China); Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544 (United States); Zhang, Lidong; Yuan, Tao; Zhang, Kuiwen; Yang, Jiuzhong; Yang, Bin; Qi, Fei [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029 (China); Law, Chung K. [Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544 (United States)

2010-01-15

406

Low temperature formation of naphthalene and its role in the synthesis of PAHs (Polycyclic Aromatic Hydrocarbons) in the interstellar medium  

PubMed Central

Polycyclic aromatic hydrocarbons (PAHs) are regarded as key molecules in the astrochemical evolution of the interstellar medium, but the formation mechanism of even their simplest prototype—naphthalene (C10H8)—has remained an open question. Here, we show in a combined crossed beam and theoretical study that naphthalene can be formed in the gas phase via a barrierless and exoergic reaction between the phenyl radical (C6H5) and vinylacetylene (CH2 = CH-C ? CH) involving a van-der-Waals complex and submerged barrier in the entrance channel. Our finding challenges conventional wisdom that PAH-formation only occurs at high temperatures such as in combustion systems and implies that low temperature chemistry can initiate the synthesis of the very first PAH in the interstellar medium. In cold molecular clouds, barrierless phenyl-type radical reactions could propagate the vinylacetylene-mediated formation of PAHs leading to more complex structures like phenanthrene and anthracene at temperatures down to 10 K. PMID:22198769

Zhang, Fangtong; Kim, Y. Seol; Kaiser, Ralf I.; Landera, Alexander; Kislov, Vadim V.; Mebel, Alexander M.; Tielens, A. G. G. M.

2012-01-01

407

Numerical modeling of hydrogen-fueled internal combustion engines  

SciTech Connect

The planned use of hydrogen as the energy carrier of the future introduces new challenges and opportunities, especially to the engine design community. Hydrogen is a bio-friendly fuel that can be produced from renewable resources and has no carbon dioxide combustion products; and in a properly designed ICE, almost zero NO{sub x} and hydrocarbon emissions can be achieved. Because of the unique properties of hydrogen combustion - in particular the highly wrinkled nature of the laminar flame front due to the preferential diffusion instability - modeling approaches for hydrocarbon gaseous fuels are not generally applicable to hydrogen combustion. This paper reports on the current progress to develop a engine design capability based on KIVA family of codes for hydrogen-fueled, spark-ignited engines in support of the National Hydrogen Program. A turbulent combustion model, based on a modified eddy-turnover model in conjunction with an intake flow valve model, is found to describe well the efficiency and NO{sub x} emissions of this engine satisfy the Equivalent Zero Emission Vehicle (EZEV) standard established by the California Resource Board. 26 refs., 10 figs., 1 tab.

Johnson, N.L.; Amsden, A.A.

1996-12-31

408

The photochemistry of anthropogenic nonmethane hydrocarbons in the troposphere  

NASA Technical Reports Server (NTRS)

A lumped, nonmethane hydrocarbon (NMHC) chemical mechanism is presently applied to a one-dimensional photochemical model of the troposphere. The profiles of OH, HO2, NO(x), and HNO3, showed only slight changes when NMHC chemistry was added. The integrated column of peroxyacetylnitrate (PAN), when NMHC chemistry was included, comprised 17 percent of the odd nitrogen budget. Advection is noted as an important possible mechanism for the removal of PAN at midlatitudes. The inclusion of such intermediate lifetime species as aldehydes and olefins has both provided additional sources of short-lived NMHC radicals, such as the peroxyacetyl radical that is the radical precursor of PAN, and offered a more detailed description of the concentrations of short-lived species and the overall NMHC chemistry.

Brewer, D. A.; Augustsson, T. R.; Levine, J. S.

1983-01-01

409

Hydrocarbon biodegradation in intertidal wetland sediments.  

PubMed

Intertidal wetlands, primarily salt marsh, mangrove and mudflats, which provide many essential ecosystem services, are under threat on numerous fronts; a situation that is made worse by crude-oil pollution. Microbes are the main vehicle for remediation of such sediments, and new discoveries, such as novel biodegradation pathways, means of accessing oil, multi-species interactions, and community-level responses to oil addition, are helping us to understand, predict and monitor the fate of oil. Despite this, there are many challenges, not least because of the heterogeneity of these ecosystems and the complexity of crude oil. For example, there is growing awareness about the toxicity of the oxygenated products that result from crude-oil weathering, which are difficult to degrade. This review highlights how developments in areas as diverse as systems biology, microbiology, ecology, biogeochemistry and analytical chemistry are enhancing our understanding of hydrocarbon biodegradation and thus bioremediation of oil-polluted intertidal wetlands. PMID:24863896

McGenity, Terry J

2014-06-01

410

Laser ignition in internal-combustion engines: Sparkless initiation  

NASA Astrophysics Data System (ADS)

Laser ignition has been implemented in a single-cylinder internal combustion engine fueled by gasoline. Indicator diagrams (cylinder pressure versus crank angle) were obtained for laser ignition with nano- and microsecond pulses of an Nd:YAG laser. The maximum power of microsecond pulses was below critical for spark initiation, while the radiation wavelength was outside the spectral range of optical absorption by hydrocarbon fuels. Apparently, the ignition starts due to radiation absorption by the oil residues or carbon deposit in the combustion chamber, so that the ability of engine to operate is retained. This initiation of spark-free ignition shows the possibility of using compact semiconductor quantum-cascade lasers operating at wavelengths of about 3.4 ?m (for which the optical absorption by fuel mixtures is high) in ignition systems of internal combustion engines.

Andronov, A. A.; Gurin, V. A.; Marugin, A. V.; Savikin, A. P.; Svyatoshenko, D. E.; Tukhomirov, A. N.; Utkin, Yu. S.; Khimich, V. L.

2014-08-01

411

APPROXIMATE CHEMISTRY 113  

E-print Network

APPROXIMATE CHEMISTRY 113 Spring 2014 Forensic Science Professors James T. Spencer (jtspence SKILLS: Chemistry 113, Forensic Science, is focused upon the application of scientific methods specifically relevant to crime detection and analysis will be presented. No prior chemistry instruction

Doyle, Robert

412

Sawyer Environmental Chemistry Research  

E-print Network

1 Sawyer Environmental Chemistry Research Laboratory Sawyer Environmental Research Center University of Maine #12;2 Mission Statement The Sawyer Environmental Chemistry Research Laboratory is a multi industry. The Sawyer Environmental Chemistry Research Laboratory employs advanced analytical techniques

Thomas, Andrew

413

Why Teach Environmental Chemistry?  

ERIC Educational Resources Information Center

Discusses the importance of teaching environmental chemistry in secondary school science classes, and outlines five examples of environmental chemistry problems that focus on major concepts of chemistry and have critical implications for human survival and well-being. (JR)

Gardner, Marjorie H.

1974-01-01

414

Computational Chemistry List  

NSDL National Science Digital Library

The Computational Chemistry List (CCL) was established as an independent electronic forum for chemistry researchers and educators from around the world. The discussions cover all aspects of computational chemistry.

415

Gas turbine combustion instability  

SciTech Connect

Combustion oscillations are a common problem in development of LPM (lean premix) combustors. Unlike earlier, diffusion style combustors, LPM combustors are especially susceptible to oscillations because acoustic losses are smaller and operation near lean blowoff produces a greater combustion response to disturbances in reactant supply, mixing, etc. In ongoing tests at METC, five instability mechanisms have been identified in subscale and commercial scale nozzle tests. Changes to fuel nozzle geometry showed that it is possible to stabilize combustion by altering the timing of the feedback between acoustic waves and the variation in heat release.

Richards, G.A.; Lee, G.T.

1996-09-01

416

Hexacyclic monoaromatic hydrocarbons of petroleum  

SciTech Connect

This paper is concerned with a new group of petroleum compounds: hexacyclic C/sub 32/-C/sub 35/ hydrocarbons--alkylbenzotrisnorhopanes, which contain an aromatic ring. Investigations have shown these hydrocarbons to be closely related structurally and, apparently, genetically to hydrocarbons of hopane series. They are often present in the highest concentrations in crude oils with relatively high concentrations of C/sub 32/ and higher hopanes. The authors found two such crude oils: the Tertiary crude oil of Shakarlyk (Central Asia) and a Devonian crude oil of Ostashkovich deposit. These hydrocarbons were identified in a number of other crude oils at lower concentrations.

Ostroukhov, S.B.; Aref'yev, O.A.; Petrov, Al.A.

1983-01-01

417

Aspiration toxicology of hydrocarbons and lamp oils studied by in vitro technology.  

PubMed

Medical literature regularly reports on accidental poisoning in children after aspiration of combustibles such as lamp oils which usually contain hydrocarbons or rape methyl esters (RMEs). We aimed to analyze the toxic potential of alkanes and different combustible classes in vitro with regard to biologic responses and mechanisms mediating toxicity. Two different in vitro models were used, i.e. (i) a captive bubble surfactometer (CBS) to assess direct influence of combustibles on biophysical properties of surfactant film and (ii) cell cultures (BEAS-2B and R3/1 cells, primary macrophages, re-differentiated epithelia) closely mimicking the inner lung surface. Biological endpoints included cell viability, cytotoxicity and inflammatory mediator release. CBS measurements demonstrate that combustibles affect film dynamics, i.e. the surface tension/area characteristics during compression and expansion, in a dose and molecular chain length dependent manner. Cell culture results confirm the dose dependent toxicity. Generally, cytotoxicity and cytokine release are higher in short-chained alkanes and hydrocarbon-based combustibles than in long-chained substances, e.g. highest inducible cytotoxicity in BEAS-2B was for hexane 84.6%, decane 74% and hexadecane 30.8%. Effects of RME-based combustibles differed between the cell models. Our results confirm data from animal experiments and give new insights into the mechanisms underlying the adverse health effects observed. PMID:23376439

Schneider, S; Schürch, D; Geiser, M

2013-04-01

418

Environmental chemistry. Seventh edition  

SciTech Connect

This book presents a basic understanding of environmental chemistry and its applications. In addition to providing updated materials in this field, the book emphasizes the major concepts essential to the practice of environmental chemistry. Topics of discussion include the following: toxicological chemistry; toxicological chemistry of chemical substances; chemical analysis of water and wastewater; chemical analysis of wastes and solids; air and gas analysis; chemical analysis of biological materials and xenobiotics; fundamentals of chemistry; and fundamentals of organic chemistry.

Manahan, S.E. [Univ. of Missouri, Columbia, MO (United States)

1999-11-01

419

Hydrocarbon conversion process  

SciTech Connect

Processes are claimed for the production of highly aromatic petroleum fractions from various petroleum feedstocks suitable for catalytic cracking in a fluidized catalytic cracking unit and for producing needle coke from various hydrocarbon cracking stocks. The heavy gas oil from a first fluidized catalytic cracking unit is subjected to further catalytic cracking in a separate fluid catalytic cracking unit at temperatures in the range of 565/sup 0/ to 650/sup 0/ C producing light olefins and a heavy gas oil consisting essentially of aromatic components suitable for the production of needle coke.

Lionetti, T.A.; Schrader, C.H.

1983-06-14

420

Application of Density Functional Theory to the Study of the Reaction of NO with Char-Bound Nitrogen during Combustion  

E-print Network

in fluidized beds, so that it is important to understand the N2O formation and reduction mechanism during coal combustion.1 The chemistry of the formation of nitrogen oxides during coal combustion is complex and many four model structures to represent the nitrogen left with the char when coal is devolatilized

Truong, Thanh N.

421

Large eddy simulation modelling of combustion for propulsion applications.  

PubMed

Predictive modelling of turbulent combustion is important for the development of air-breathing engines, internal combustion engines, furnaces and for power generation. Significant advances in modelling non-reactive turbulent flows are now possible with the development of large eddy simulation (LES), in which the large energetic scales of the flow are resolved on the grid while modelling the effects of the small scales. Here, we discuss the use of combustion LES in predictive modelling of propulsion applications such as gas turbine, ramjet and scramjet engines. The LES models used are described in some detail and are validated against laboratory data-of which results from two cases are presented. These validated LES models are then applied to an annular multi-burner gas turbine combustor and a simplified scramjet combustor, for which some additional experimental data are available. For these cases, good agreement with the available reference data is obtained, and the LES predictions are used to elucidate the flow physics in such devices to further enhance our knowledge of these propulsion systems. Particular attention is focused on the influence of the combustion chemistry, turbulence-chemistry interaction, self-ignition, flame holding burner-to-burner interactions and combustion oscillations. PMID:19531515

Fureby, C

2009-07-28

422

Science Update: Inorganic Chemistry.  

ERIC Educational Resources Information Center

Describes areas of inorganic chemistry which have changed dramatically in the past year or two, including photochemistry, electrochemistry, organometallic complexes, inorganic reaction theory, and solid state chemistry. (DS)

Rawls, Rebecca

1981-01-01

423

Biology 3515/Chemistry 3515 Biological Chemistry Laboratory  

E-print Network

Biology 3515/Chemistry 3515 Biological Chemistry Laboratory Spring 2013 (Draft Syllabus, 23 August 2012) Course Description and Objectives: This course is intended for students who have taken Biology and function, particularly for enzymes. Prerequisites: Biology 3510 or Chemistry 3510 Instructor: David P

Simons, Jack

424

A USM turbulence-chemistry model for simulating NOx formation in turbulent combustionq  

E-print Network

A USM turbulence-chemistry model for simulating NOx formation in turbulent combustionq L.X. Zhou*, L. Qiao, X.L. Chen, J. Zhang Department of Engineering Mechanics, State Key Laboratory of Clean Coal-order moment (USM) turbulence-chemistry model for simulating NOx formation in turbulent combustion is proposed

Qiao, Li

425

Combustion Technology Outreach  

NASA Technical Reports Server (NTRS)

Lewis' High Speed Research (HSR) Propulsion Project Office initiated a targeted outreach effort to market combustion-related technologies developed at Lewis for the next generation of supersonic civil transport vehicles. These combustion-related innovations range from emissions measurement and reduction technologies, to diagnostics, spray technologies, NOx and SOx reduction of burners, noise reduction, sensors, and fuel-injection technologies. The Ohio Aerospace Institute and the Great Lakes Industrial Technology Center joined forces to assist Lewis' HSR Office in this outreach activity. From a database of thousands of nonaerospace firms considered likely to be interested in Lewis' combustion and emission-related technologies, the outreach team selected 41 companies to contact. The selected companies represent oil-gas refineries, vehicle/parts suppliers, and manufacturers of residential furnaces, power turbines, nonautomobile engines, and diesel internal combustion engines.

1995-01-01

426

COMBUSTION - RISK MANAGEMENT  

EPA Science Inventory

This research involves the characterization of waste combustion systems and their emissions along with the development and evaluation of techniques to prevent emissions formation and/or control their release. This area addresses incinerators and industrial systems burning wastes...

427

Fluidized coal combustion  

NASA Technical Reports Server (NTRS)

Fluidized-bed coal combustion process, in which pulverized coal and limestone are burned in presence of forced air, may lead to efficient, reliable boilers with low sulfur dioxide and nitrogen dioxide emissions.

Moynihan, P. I.; Young, D. L.

1979-01-01

428

Synthesis of PNA hydrocarbons  

SciTech Connect

The synthesis of PNA hydrocarbons usually includes ring construction, aromatization, removal of oxygen or other heteroatoms and in some cases specific placement of alkyl or aryl groups. These topics are of current interest in our laboratory. We have examined the regioselectivity of the Haworth sequence (Scheme I, Table I) and chromic acid oxidation at the benzylic position (Scheme II) as routes to 1-tetralones which in turn can become parent aromatic hydrocarbons or alkyl substituted ones (Scheme III). Simultaneous aromatization and deoxygenation can be accomplished in a single step by heating 1-tetralones in the presence of alkali (Scheme IV, Table VI). The deoxidative coupling of substituted acetophenones to stilbene types using active titanium species as coupling agents and subsequent photocyclization (Scheme IX) has provided a convenient route to polymethylphenathrenes. The maleic anhydride (Diels-Alder) route to ring construction (Scheme X) can be improved through use of Pd/C or PbO/sub 2/ as a reagent for bis-decarboxylation of vicinal anhydrides.

Eisenbraun, E.J.; Premasagar, V.; Holba, A.G.; Keen, G.W.

1980-08-01

429

Symposium /International/ on Combustion, 17th, Leeds University, Leeds, England, August 20-25, 1978, Proceedings  

NASA Technical Reports Server (NTRS)

The Symposium focused on deflagration to detonation transition, coal combustion, turbulent-combustion interactions, kinetics, furnace combustion, inhibition and ignition, flame structure and chemistry, combustion studies, measurement techniques, fire and explosion, engine combustion, soot, and propellants and explosives. Papers were presented on numerical modeling of the deflagration-to-detonation transition, the interaction between turbulence and combustion, turbulent flame propagation in premixed gases, spray evaporation in recirculating flow, dissociation of nitric oxide in shock waves, pollutant emissions from partially mixed turbulent flames, energy transfer and quenching rates of laser-pumped electronically excited alkalis in flames, a study of flammability limits using counterflow flames, the unified theory of explosions with fuel consumption, and the dynamics and radiant intensity of large hydrogen flames.

1979-01-01

430

Fundamental combustion and diagnostics research at Sandia. Progress Report from January-March 1980  

SciTech Connect

The combustion research at Sandia Laboratories sponsored by the Office of Basic Energy Sciences (OBES) emphasizes basic research into fundamental problems associated with combustion. Special emphasis is placed on the development and application of advanced research methods. The overall program addresses: (1) detailed chemistry of combustion, (2) fundamental processes associated with laminar and turbulent flames, (3) development of research techniques specifically applicable to combustion environments, and (4) operation of the user-oriented Combustion Research Facility. This report presents status reports on the research sponsored by OBES. The first section contains activities in Combustion Research, the second section contains activities in Molecular Physics and Spectroscopy, and the third section contains activities in Diagnostics Research.

Hartley, D.L.; Gusinow, M.A.

1980-06-01

431

Coal combustion system  

DOEpatents

In a coal combustion system suitable for a gas turbine engine, pulverized coal is transported to a rich zone combustor and burned at an equivalence ratio exceeding 1 at a temperature above the slagging temperature of the coal so that combustible hot gas and molten slag issue from the rich zone combustor. A coolant screen of water stretches across a throat of a quench stage and cools the combustible gas and molten slag to below the slagging temperature of the coal so that the slag freezes and shatters into small pellets. The pelletized slag is separated from the combustible gas in a first inertia separator. Residual ash is separated from the combustible gas in a second inertia separator. The combustible gas is mixed with secondary air in a lean zone combustor and burned at an equivalence ratio of less than 1 to produce hot gas motive at temperature above the coal slagging temperature. The motive fluid is cooled in a dilution stage to an acceptable turbine inlet temperature before being transported to the turbine.

Wilkes, Colin (Lebanon, IN); Mongia, Hukam C. (Carmel, IN); Tramm, Peter C. (Indianapolis, IN)

1988-01-01

432

Supersonic Combustion of Kerosene\\/H2Mixtures in a Model Scramjet Combustor  

Microsoft Academic Search

Liquid hydrocarbon supersonic combustion has been experimentally investigated. Kerosene was burnt in a steady. vitiated Mach 2.15 - air flow of a model scramjet combustor. The fuel is injected into the supersonic air stream by means of pylons. The effervescent atomisation method has been employed such that the liquid fuel is injected as a spray. By means of the Mie

C. Gruenig; F. Mayinger

1999-01-01

433

Experimental investigation of fuel combustion in counterflowing high-temperature air flow  

Microsoft Academic Search

The possibility of using high-energy synthetic hydrocarbon fuels, borane fuels, as well as borohydrocarbon fuels are currently being studied for use by various kinds of aircraft with jet engines. The problem addressed in this work included experimental determination of the geometric characteristics of the vaporization and combustion zones of borohydrocarbon fuel sprayed in a counterflowing air flow and comparing them

Y. M. Annushkin; A. N. Knyazev; N. S. Loshenkova

1983-01-01

434

Small scales, many species and the manifold challenges of turbulent combustion  

E-print Network

Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY 14853, USA tools, and well short of what has been achieved in other disciplines, such as solid mechanics and fluid are posed by the small scales, the many chemical species involved in hydrocarbon combustion, and the coupled

435

ANALYSIS OF A FUEL-AIR COMBUSTION MIXTURE BY INFRARED SPECTROSCOPY. Progress Report  

Microsoft Academic Search

A method of analysis is described for the products resulting from the ; incomplete combustion of a mixture of liquid hydrocarbon fuel and excess air. ; Gas sample generally is found to consist of air, unburned fuel, carbon dioxide, ; carbon monoxide, ethylene, and acetylene. These are first determined ; simultaneously by infrared absorptiometry. Then the sample is passed nitrogen

J. S. Whittick; R. F. Muraca

1959-01-01

436

Heavy Lift Launch Capability with a New Hydrocarbon Engine  

NASA Technical Reports Server (NTRS)

The Advanced Concepts Office at NASA's George C. Marshall Space Flight Center was tasked to define the thrust requirement of a new liquid oxygen rich staged combustion cycle hydrocarbon engine that could be utilized in a launch vehicle to meet NASA s future heavy lift needs. Launch vehicle concepts were sized using this engine for different heavy lift payload classes. Engine out capabilities for one of the heavy lift configurations were also analyzed for increased reliability that may be desired for high value payloads or crewed missions. The applicability for this engine in vehicle concepts to meet military and commercial class payloads comparable to current ELV capability was also evaluated.

Threet, Grady E., Jr.; Holt, James B.; Philips, Alan D.; Garcia, Jessica A.

2011-01-01

437

Polycyclic aromatic hydrocarbons residues in sandstorm depositions in Beijing, China  

SciTech Connect

This study was conducted to determine the concentration of 16 polycyclic aromatic hydrocarbons (PAHs) in sandstorm depositions in Beijing, China. The PAH concentrations in 13 samples collected in Beijing ranged from 0.18 to 3.52 {mu} g g{sup -1}. Analysis of the sources of contamination revealed that the PAHs were derived from a coal combustion source, although various effects of traffic emissions were also observed. Furthermore, the PAH levels in Beijing tended to be higher in the southeast. Finally, the Nemerow composite index revealed that the degree of pollution in the sandstorm depositions varied widely among sampling sites.

Fu, S.; Li, K.; Xia, X.J.; Xu, X.B. [Chinese Academy of Sciences, Beijing (China)

2009-02-15

438

Process for producing benzene by hydrodealkylation of a hydrocarbon fraction comprising alkylaromatic hydrocarbons, olefinic hydrocarbons and sulfur compound  

SciTech Connect

A stabilized hydrocarbon fraction comprising toluene, xylene, sulfur and olefinic hydrocarbons is converted to benzene by catalytic hydrodesulfurization, hydrodealkylation and catalytic hydrogenation.

Derrien, M.; Cosyns, J.

1984-07-31

439

Condensation of hydrocarbons – A review  

Microsoft Academic Search

Hydrocarbons are one of the candidates for refrigerants of next generation heat pump and refrigeration systems. Although the hydrocarbons have superior thermophysical properties as a refrigerant to fluorocarbons and are widely used in domestic refrigerators, their flammability prevents their wide application to larger systems, such as residential and packaged air conditioners, car air conditioners, heat pumps, etc. In this paper,

Akio Miyara

2008-01-01

440

Biomass burning in the tropics: impact on atmospheric chemistry and biogeochemical cycles.  

PubMed

Biomass burning is widespread, especially in the tropics. It serves to clear land for shifting cultivation, to convert forests to agricultural and pastoral lands, and to remove dry vegetation in order to promote agricultural productivity and the growth of higher yield grasses. Furthermore, much agricultural waste and fuel wood is being combusted, particularly in developing countries. Biomass containing 2 to 5 petagrams of carbon is burned annually (1 petagram = 10(15) grams), producing large amounts of trace gases and aerosol particles that play important roles in atmospheric chemistry and climate. Emissions of carbon monoxide and methane by biomass burning affect the oxidation efficiency of the atmosphere by reacting with hydroxyl radicals, and emissions of nitric oxide and hydrocarbons lead to high ozone concentrations in the tropics during the dry season. Large quantities of smoke particles are produced as well, and these can serve as cloud condensation nuclei. These particles may thus substantially influence cloud microphysical and optical properties, an effect that could have repercussions for the radiation budget and the hydrological cycle in the tropics. Widespread burning may also disturb biogeochemical cycles, especially that of nitrogen. About 50 percent of the nitrogen in the biomass fuel can be released as molecular nitrogen. This pyrdenitrification process causes a sizable loss of fixed nitrogen in tropical ecosystems, in the range of 10 to 20 teragrams per year (1 teragram = 10(12) grams). PMID:17734705

Crutzen, P J; Andreae, M O

1990-12-21

441

Biomass Burning in the Tropics: Impact on Atmospheric Chemistry and Biogeochemical Cycles  

NASA Astrophysics Data System (ADS)

Biomass burning is widespread, especially in the tropics. It serves to clear land for shifting cultivation, to convert forests to agricultural and pastoral lands, and to remove dry vegetation in order to promote agricultural productivity and the growth of higher yield grasses. Furthermore, much agricultural waste and fuel wood is being combusted, particularly in developing countries. Biomass containing 2 to 5 petagrams of carbon is burned annually (1 petagram = 1015 grams), producing large amounts of trace gases and aerosol particles that play important roles in atmospheric chemistry and climate. Emissions of carbon monoxide and methane by biomass burning affect the oxidation efficiency of the atmosphere by reacting with hydroxyl radicals, and emissions of nitric oxide and hydrocarbons lead to high ozone concentrations in the tropics during the dry season. Large quantities of smoke particles are produced as well, and these can serve as cloud condensation nuclei. These particles may thus substantially influence cloud microphysical and optical properties, an effect that could have repercussions for the radiation budget and the hydrological cycle in the tropics. Widespread burning may also disturb biogeochemical cycles, especially that of nitrogen. About 50 percent of the nitrogen in the biomass fuel can be released as molecular nitrogen. This pyrodenitrification process causes a sizable loss of fixed nitrogen in tropical ecosystems, in the range of 10 to 20 teragrams per year (1 teragram = 1012 grams).

Crutzen, Paul J.; Andreae, Meinrat O.

1990-12-01

442

PRECIPITATION CHEMISTRY OF MAGNESIUM SULFITE HYDRATES IN MAGNESIUM OXIDE SCRUBBING  

EPA Science Inventory

The report gives results of laboratory studies defining the precipitation chemistry of MgSO3 hydrates. The results apply to the design of Mg-based scrubbing processes for SO2 removal from combustion flue gas. In Mg-based scrubbing processes, MgSO3 precipitates as either trihydrat...

443

A second-generation reactive empirical bond order (REBO) potential energy expression for hydrocarbons  

Microsoft Academic Search

A second-generation potential energy function for solid carbon and hydrocarbon molecules that is based on an empirical bond order formalism is presented. This potential allows for covalent bond breaking and forming with associated changes in atomic hybridization within a classical potential, producing a powerful method for modelling complex chemistry in large many-atom systems. This revised potential contains improved analytic functions

Donald W. Brenner; Olga A. Shenderova; Judith A. Harrison; Steven J. Stuart; Boris Ni; Susan B. Sinnott

2002-01-01

444

STABLE CARBON ISOTOPE BIOGEOCHEMISTRY OF A SHALLOW SAND AQUIFER CONTAMINATED WITH FUEL HYDROCARBONS  

EPA Science Inventory

Ground-water chemistry and the stable C isotope composition ( 13CDIC) of dissolved C (DIC) were measured in a sand aquifer contaminated with JP-4 fuel hydrocarbons. Results show that ground water in the upgradient zone was characterized by DIC content of 14-20 mg C/L and 13CDIC...

445

Hydrocarbon sensors and materials therefor  

DOEpatents

An electrochemical hydrocarbon sensor and materials for use in sensors. A suitable proton conducting electrolyte and catalytic materials have been found for specific application in the detection and measurement of non-methane hydrocarbons. The sensor comprises a proton conducting electrolyte sandwiched between two electrodes. At least one of the electrodes is covered with a hydrocarbon decomposition catalyst. Two different modes of operation for the hydrocarbon sensors can be used: equilibrium versus non-equilibrium measurements and differential catalytic. The sensor has particular application for on-board monitoring of automobile exhaust gases to evaluate the performance of catalytic converters. In addition, the sensor can be utilized in monitoring any process where hydrocarbons are exhausted, for instance, industrial power plants. The sensor is low cost, rugged, sensitive, simple to fabricate, miniature, and does not suffer cross sensitivities.

Pham, Ai Quoc (San Jose, CA); Glass, Robert S. (Livermore, CA)

2000-01-01

446

Molecular Tracers of Saturated and Polycyclic Aromatic Hydrocarbon Inputs into Central Park Lake, New York City  

PubMed Central

Saturated hydrocarbons (SH) and polycyclic aromatic hydrocarbons (PAHs) have been quantified in a sediment core obtained from Central Park Lake, New York City. Radionuclides 210Pb and 137Cs were used to assign approximate dates to each individual section in the core. The dating profil