scholarly journals Semianalytical Correlations for NOx, CO, and UHC Emissions

1992 ◽  
Author(s):  
N. K. Rizk ◽  
H. C. Mongia
Keyword(s):  
Kinetic Scheme ◽  
Large Data ◽  
Chemical Kinetic ◽  
Reaction Scheme ◽  
Emission Model ◽  
Future Goals ◽  
Unburned Hydrocarbon ◽  
Annular Combustor ◽  
Analytical Approaches ◽  
Detailed Chemical

To meet the future goals of reduced emissions produced by gas turbine combustors, a better understanding of the process of formation of various pollutants is required. Both empirical and analytical approaches are used to provide the exhaust concentrations of pollutants of interest such as NOx, CO, and unburned hydrocarbon with varying degrees of success. In the present investigation, an emission model that simulates the combustor by a number of reactors representing various combustion zones is proposed. A detailed chemical kinetic scheme was used to provide a fundamental basis for the derivation of a number of expressions that simulate the reaction scheme. The model addresses the combined effects of spray evaporation and mixing in the reaction zone. The model validation included the utilization of a large data base obtained for an annular combustor of a modern turbopropulsion engine. In addition to the satisfactory agreement with the measurements, the model provided insight into the regions within the combustor that could be responsible for the excessive formation of emissions. Methods to reduce the emissions may be implemented in light of such information.

Semianalytical Correlations for NOx, CO, and UHC Emissions

1993 ◽  
Vol 115 (3) ◽  
pp. 612-619 ◽  
Author(s):  
N. K. Rizk ◽  
H. C. Mongia
Keyword(s):  
Kinetic Scheme ◽  
Large Data ◽  
Chemical Kinetic ◽  
Reaction Scheme ◽  
Emission Model ◽  
Future Goals ◽  
Unburned Hydrocarbon ◽  
Annular Combustor ◽  
Analytical Approaches ◽  
Detailed Chemical

To meet the future goals of reduced emissions produced by gas turbine combustors, a better understanding of the process of formation of various pollutants is required. Both empirical and analytical approaches are used to provide the exhaust concentrations of pollutants of interest such as NOx, CO, and unburned hydrocarbon with varying degrees of success. In the present investigation, an emission model that simulates the combustor by a number of reactors representing various combustion zones is proposed. A detailed chemical kinetic scheme was used to provide a fundamental basis for the derivation of a number of expressions that simulate the reaction scheme. The model addresses the combined effects of spray evaporation and mixing in the reaction zone. The model validation included the utilization of a large data base obtained for an annular combustor of a modern turbopropulsion engine. In addition to the satisfactory agreement with the measurements, the model provided insight into the regions within the combustor that could be responsible for the excessive formation of emissions. Methods to reduce the emissions may be implemented in light of such information.

Regional and Business Aircraft Mission Emissions

1994 ◽  
Author(s):  
Nader K. Rizk ◽  
Duane A. Smith
Keyword(s):  
Ambient Pressure ◽  
Kinetic Scheme ◽  
Chemical Kinetic ◽  
Engine Emissions ◽  
Calculation Technique ◽  
Fuel Flow ◽  
Annular Combustor ◽  
Conventional Methods ◽  
Semianalytical Method ◽  
Detailed Chemical

To meet the design requirements of next generation aircraft engines and the expected trends of more stringent emissions regulations, better calculation methods for aircraft mission emissions need to be established. In the present investigation, a number of steps were taken to define an appropriate calculation technique. The data obtained for a full-scale annular combustor rig were compared with engine emissions to illustrate that the level of rig-to-engine agreement was good enough to use the rig data to formulate a proposed mission NOx calculation technique. Conventional methods were then used to correlate the rig data in terms of various operating parameters. It was demonstrated that the level of agreement with data was improved by including both combustion and geometrical aspects in the correlations of NOx, CO, UHC, and smoke. A semianalytical approach, which was based on detailed chemical kinetic scheme and simulated the combustor by a number of reactors representing various combustion zones, was used to correlate the data of the annular combustor. The results illustrated that better estimates of emissions were obtained over conventional methods. Two mission profiles that represented the operation of turbofan-powered regional and business aircrafts were selected to evaluate their mission emissions using the semianalytical method. An approach that utilized only the four ICAO test points in the semianalytical method was formulated to provide the total aircraft mission emissions. Results obtained by this approach were comparable to those calculated using correlations based on extensive testing of the combustor; thus, by using such a method considerable savings in cost and effort could be achieved during combustor development. The results also demonstrated the possibility of correlating the emissions in terms of ambient pressure and temperature and fuel flow rate; thus, accurate estimates of altitude emissions could be obtained.

Chemical Kinetic Research on Flame Characteristics of Ethylene under High CO2 Concentration Atmosphere

2014 ◽  
Vol 1070-1072 ◽  
pp. 512-516
Author(s):  
Dan Dan Zhou ◽  
Chong Jiu Li ◽  
Ran Zhao ◽  
Dong Sheng Xia
Keyword(s):  
Numerical Study ◽  
Laboratory Data ◽  
Flame Temperature ◽  
Chemical Kinetic ◽  
Reaction Scheme ◽  
Main Reaction ◽  
Flame Propagation Velocity ◽  
Elementary Reactions ◽  
Air Atmosphere ◽  
Detailed Chemical

A numerical study was conducted to understand the flame characteristics of ethylene under O2/CO2 atmosphere by detailed chemical kinetic models. Special interest is focused on the effects of CO2 on flame propagation velocity and ignition delay. A modified reaction mechanism was established, and the ability of the reaction scheme was evaluated through comparison with well-defined laboratory data in the literature. A key result of the study is that the flame temperature and flame speed are significantly reduced because of the chemical and thermal effects of CO2. The most important reactions as well as the dominant reaction steps under both O2/CO2 atmosphere and air atmospheres were also studied. It can be concluded that although the main reaction paths of fuel oxidation under both atmospheres are quite similar, the most important elementary reactions are different from each other. Besides, the same reactions assume great importance for ignition under air atmosphere become less qualified under O2/CO2 atmosphere.

Three-Dimensional Gas Turbine Combustor Emissions Modeling

1992 ◽  
Author(s):  
N. K. Rizk ◽  
H. C. Mongia
Keyword(s):  
Three Dimensional ◽  
Kinetic Scheme ◽  
Reaction Rates ◽  
Chemical Kinetic ◽  
Emission Model ◽  
Pollutant Formation ◽  
Emissions Modeling ◽  
Pollutant Concentrations ◽  
Mathematical Expressions ◽  
And Performance

An emission model that combines the analytical capabilities of 3-D combustor performance codes with mathematical expressions based on detailed chemical kinetic scheme is formulated. The expressions provide the trends of formation and/or the consumption of NOx, CO, and UHC in various regions of the combustor utilizing the details of the flow and combustion characteristics given by the 3-D analysis. By this means, the optimization of the combustor design to minimize pollutant formation and maintain satisfactory stability and performance could be achieved. The developed model was used to calculate the emissions produced by several engine combustors that varied significantly in design and concept, and operated on both conventional and high density fuels. The calculated emissions agreed well with the measurements. The model also provided insight into the regions in the combustor where excessive emissions were formed, and helped to understand the influence of the combustor details and air admission arrangement on reaction rates and pollutant concentrations.

A Semi-Analytical Emission Model for Diffusion Flame, Rich/Lean and Premixed Lean Combustors

1995 ◽  
Vol 117 (2) ◽  
pp. 290-301 ◽  
Author(s):  
N. K. Rizk ◽  
H. C. Mongia
Keyword(s):  
Gas Turbine ◽  
Diffusion Flame ◽  
Kinetic Scheme ◽  
Reaction Rates ◽  
Chemical Kinetic ◽  
Operating Conditions ◽  
Development Effort ◽  
Emission Model ◽  
Performance And Emissions ◽  
And Performance

To enhance gas turbine combustor performance and emissions characteristics, better design methods need to be developed. In the present investigation, an emission model that simulates a detailed chemical kinetic scheme has been developed to provide the rate of reactions of the parent fuel, an intermediate hydrocarbon compound, CO, and H2. The intermediate fuel has variable carbon and hydrogen contents depending on operating conditions, that were selected in the development effort to simulate actual operation of rich/lean, diffusion flame, and lean combustor concepts. The developed reaction rate expressions address also the limited reaction rates that may occur in the near-wall regions of the combustor due to the admittance of radial air jets and cooling air in these regions. The validation effort included the application of the developed model to a combustor simulated by a multiple-reactor arrangement. The results indicate the accurate duplication of the calculations obtained from the detailed kinetic scheme using the developed model. This illustrates the great potential of using such a unified approach to guide the design of various types of combustor to meet the more stringent approach to guide the design of various types of combustor to meet the more stringent emissions and performance requirements of next-generation gas turbine engines.

The Combustion of Lean Mixtures of Methane and Air—A Kinetic Investigation

1986 ◽  
Vol 108 (4) ◽  
pp. 336-342 ◽  
Author(s):  
M. Hanna ◽  
G. A. Karim
Keyword(s):  
Combustion Process ◽  
Kinetic Scheme ◽  
Reaction Rates ◽  
Chemical Kinetic ◽  
Energy Utilization ◽  
Wide Range ◽  
Lean Mixtures ◽  
The Times ◽  
Combustion Processes ◽  
Detailed Chemical

The combustion of lean mixtures of methane, representing natural gas, in air is examined analytically employing a detailed chemical kinetic scheme involving 14 species and made up of 32 reaction steps that proceed simultaneously. The changes with time in the concentrations of the major relevant reactive species are determined throughout, right from the commencement of the preignition reactions to the time of achieving near equilibrium conditions. The results of such an approach to the combustion process are considered over a wide range of temperature (1200 K–2200 K) and equivalence ratios (from 0.20 to the stoichiometric value). Information is then presented in relation to some important combustion parameters that included the ignition delay, overall reaction rates and the times needed for completing the combustion process. Some guidelines are suggested for effecting eventually improved energy utilization and reduced environmental pollution from combustion processes involving lean mixtures of methane and air.

scholarly journals A Semianalytical Emission Model for Diffusion Flame, Rich/Lean, and Premixed Lean Combustors

1993 ◽  
Author(s):  
N. K. Rizk ◽  
H. C. Mongia
Keyword(s):  
Gas Turbine ◽  
Diffusion Flame ◽  
Kinetic Scheme ◽  
Reaction Rates ◽  
Chemical Kinetic ◽  
Operating Conditions ◽  
Development Effort ◽  
Emission Model ◽  
Turbine Engine ◽  
Performance And Emissions

To enhance gas turbine combustor performance and emissions characteristics better design methods need to be developed. In the present investigation, an emission model that simulates a detailed chemical kinetic scheme has been developed to provide the rate of reactions of the parent fuel, an intermediate hydrocarbon compound, CO, and H2. The intermediate fuel has variable carbon and hydrogen contents depending on operating conditions, that were selected in the development effort to simulate actual operation of rich/lean, diffusion flame, and lean combustor concepts. The developed reaction rate expressions address also the limited reaction rates that may occur in the near wall regions of the combustor due to the admittance of radial air jets and cooling air in these regions. The validation effort included the application of the developed model to a combustor simulated by a multiple-reactor arrangement. The results indicate the accurate duplication of the calculations obtained from the detailed kinetic scheme using the developed model. This illustrates the great potential of using such a unified approach to guide the design of various types of combustors to meet the more stringent emissions and performance requirements of next generation gas turbine engine.

scholarly journals Evaluation of Emission Model for Diffusion Flame, Rich/Lean, and Premixed Lean Combustors

1993 ◽  
Author(s):  
N. K. Rizk ◽  
H. C. Mongia
Keyword(s):  
Diffusion Flame ◽  
Variable Structure ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Reaction Scheme ◽  
Emission Model ◽  
Nox Formation ◽  
Model Calculations ◽  
Lean Combustion ◽  
Wide Range

A recently developed emission model was used to predict the emission characteristics of a gas turbine combustor. The model involves a multiple-step reaction scheme that addresses the breakup of the fuel into an intermediate hydrocarbon compound of variable structure. The reaction rate expressions developed in the present approach simulated the results obtained using a detailed chemical kinetic mechanism over a wide range of operation that is typically encountered in a conventional diffusion flame combustor, as well as low NOx rich/quench/lean, and premixed/prevaporized lean combustion concepts. The modeling of the combustor involves dividing the combustor into a number of reactors representing various combustion and near wall regions of the combustor. The calculations showed that the fuel reaction could proceed at a completely different rate depending on the conditions prevailing in each region of the combustor. The model results also indicated that at idle power mode the initial rate of NOx formation was high. However, due to the subsequent admission of air, no further addition to the NOx concentration was predicted at downstream locations. At high power levels, the fuel rich region near the combustor dome inhibits the formation of NOx. The admission of air in this case brings the fuel/air mixture close to the stoichiometric value causing a significant amount of NOx to form. The model calculations agreed quite well with the measured data of the combustor.

An Analytical Examination of the Partial Oxidation of Rich Mixtures of Methane and Oxygen

1992 ◽  
Vol 114 (2) ◽  
pp. 152-157 ◽  
Author(s):  
G. A. Karim ◽  
A. S. Hanafi
Keyword(s):  
Partial Oxidation ◽  
Equivalence Ratio ◽  
Kinetic Scheme ◽  
Reaction Rates ◽  
Chemical Kinetic ◽  
Operating Conditions ◽  
Wide Range ◽  
Rich Mixtures ◽  
Detailed Chemical

The uncatalyzed partial oxidation of rich mixtures of methane and oxygen is examined analytically, primarily with the view of hydrogen and/or synthesis gas (hydrogen plus carbon monoxide) production while employing a detailed chemical kinetic scheme of 108 simultaneous reactions and 28 species. The role of various operating conditions in establishing the yield of hydrogen and other products, the corresponding ignition delay periods and reaction rates is examined over a wide range of temperature, equivalence ratio and pressure. Correlations in terms of simple overall Arrhenius expressions are also provided.

Three-Dimensional Gas Turbine Combustor Emissions Modeling

1993 ◽  
Vol 115 (3) ◽  
pp. 603-611 ◽  
Author(s):  
N. K. Rizk ◽  
H. C. Mongia
Keyword(s):  
Three Dimensional ◽  
Kinetic Scheme ◽  
Reaction Rates ◽  
Chemical Kinetic ◽  
Emission Model ◽  
Pollutant Formation ◽  
Emissions Modeling ◽  
Pollutant Concentrations ◽  
Mathematical Expressions ◽  
And Performance

An emission model that combines the analytical capabilities of three-dimensional combustor performance codes with mathematical expressions based on detailed chemical kinetic scheme is formulated. The expressions provide the trends of formation and/or the consumption of Nox, CO, and UHC in various regions of the combustor utilizing the details of the flow and combustion characteristics given by the three-dimensional analysis. By this means, the optimization of the combustor design to minimize pollutant formation and maintain satisfactory stability and performance could be achieved. The developed model was used to calculate the emissions produced by several engine combustors that varied significantly in design and concept, and operated on both conventional and high-density fuels. The calculated emissions agreed well with the measurements. The model also provided insight into the regions in the combustor where excessive emissions were formed, and helped to understand the influence of the combustor details and air admissions arrangement on reaction rates and pollutant concentrations.

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