The flow-field of a propane-air diffusion flame combustor with interior and exterior conjugate heat transfers was numerically studied.Results obtained from four combustion models,combined with the re-normalization gro...The flow-field of a propane-air diffusion flame combustor with interior and exterior conjugate heat transfers was numerically studied.Results obtained from four combustion models,combined with the re-normalization group(RNG) k-ε turbulence model,discrete ordinates radiation model and enhanced wall treatment are presented and discussed.The results are compared with a comprehensive database obtained from a series of experimental measurements.The flow patterns and the recirculation zone length in the combustion chamber are accurately predicted,and the mean axial velocities are in fairly good agreement with the experimental data,particularly at downstream sections for all four combustion models.The mean temperature profiles are captured fairly well by the eddy dissipation(EDS),probability density function(PDF),and laminar flamelet combustion models.However,the EDS-finite-rate combustion model fails to provide an acceptable temperature field.In general,the flamelet model illustrates little superiority over the PDF model,and to some extent the PDF model shows better performance than the EDS model.展开更多
This article aims to investigate the effects of using an alternative fuel on the emissions of carbon dioxide (CO_(2)) and carbon monoxide (CO) in a reactive flow spraying inside a model combustor. The study highlights...This article aims to investigate the effects of using an alternative fuel on the emissions of carbon dioxide (CO_(2)) and carbon monoxide (CO) in a reactive flow spraying inside a model combustor. The study highlights the trade-offs between CO_(2) and CO emissions, encouraging further investigation into alternative fuels, considering their environmental impact. The bio-synthetic fuel comprises Jatropha Bio-Synthetic Paraffinic Kerosene (JSPK) blended with Jet-A at five different weight ratios to make the alternative fuels. The two-phase flow of the fuel and air mixture is assessed by the Eulerian-Lagrangian approach. The realizable κ-ε model is employed to model the turbulent flow. The discrete ordinates method is applied to model radiative heat transfer, and the steady flamelet combustion model is utilized to model combustion. The distributions of mean mixture fraction and mole fractions of CO_(2) and CO at the combustion chamber outlet are presented. Results reveal that variations in fuel properties affect the emission of pollutants since adding JSPK increases the emission rate of the mean mixture fraction and the mole fraction of CO and decreases the mole fraction of CO_(2) at the combustor outlet. Also, employing a weight ratio of 80% Jet-A with 20% JSPK leads to achieving the lowest mean mixture fraction and mole fraction of CO with a maximum reduction of 25% relative to utilizing only the base fuel. In addition, the lowest amount of CO_(2) is obtained for 70% Jet-A / 30% JSPK, which is about 15% less than other weight ratios.展开更多
This paper experimentally studied the effect of CO_(2) opposing multiple jets on the thermoacoustic instability and NO_(x) emissions in a lean-premixed model combustor.The feasibility was verified from three variables...This paper experimentally studied the effect of CO_(2) opposing multiple jets on the thermoacoustic instability and NO_(x) emissions in a lean-premixed model combustor.The feasibility was verified from three variables:the CO_(2) jet flow rate,hole numbers,and hole diameters of the nozzles.Results indicate that the control effect of thermoacoustic instability and NO_x emissions show a reverse trend with the increase of open area ratio on the whole,and the optimal jet flow rate range is 1-4 L/min with CO_(2) opposing multiple jets.In this flow rate range,the amplitude and frequency of the dynamic pressure and heat release signals CH~* basically decrease as the CO_(2) flow rate increases,which avoids high-frequency and high-amplitude thermoacoustic instability.The amplitude-damped ratio of dynamic pressure and CH*can reach as high as 98.75% and 93.64% with an optimal open area ratio of 3.72%.NO_(x) emissions also decrease as the jet flow rate increases,and the maximum suppression ratio can reach 68.14%.Besides,the flame shape changes from a steep inverted "V" to a more flat "M",and the flame length will become shorter with CO_(2) opposing multiple jets.This research achieved the synchronous control of thermoacoustic instability and NO_(x) emissions,which could be a design reference for constructing a safer and cleaner combustor.展开更多
In the present paper,a sensitivity analysis of pollutants and pattern factor in a model combustor due to changes in the geometrical characteristics of stabilizing jets has been carried out.The exhaust pollutants inclu...In the present paper,a sensitivity analysis of pollutants and pattern factor in a model combustor due to changes in the geometrical characteristics of stabilizing jets has been carried out.The exhaust pollutants including NO_(x),CO and soot have been chosen due to their harmful effect on the environment.The pattern factor has been also considered owing to its impact on turbine blades.The geometrical characteristics comprise diameter,angle and position of stabilizing jets.Eulerian-Lagrangian approach has been employed to model liquid fuel injection and distribution,breakup and evaporation of droplets.For the analysis of reactive-spray flow characteristics,RANS approach,realizable k-εturbulence model,discrete ordinates radiative heat transfer model and steady flamelet combustion model together with the chemical reaction mechanism of diesel fuel(C_(10)H_(22))have been applied.NO_(x) modeling has been performed via post-processing.Sensitivity analysis is such that by making variations in the problem inputs(diameter,angle and position of jets)in an organized manner,the effects on the outputs(NO_(x),CO,soot and pattern factor)are predicted.The number and order of simulations are predicted by design of experiments and full factorial model.Results have been analyzed using analysis of variance.It has been observed that if interactions among the characteristics of jets are considered,it is possible to analyze the exhaust pollutants more accurately.In fact,by using the interactions,it is likely to find a point where all output parameters are improved.Results show that by considering interactions of stabilizing jet characteristics,the maximum values of NO_(x),CO,soot and pattern factor change from 13.927 ppm,11.198%mole fraction,2.877 ppm and 0.043 to 26.233 ppm,14.693%mole fraction,142.357 ppm and 0.060,respectively.Furthermore,the minimum values change from 5.819 ppm,7.568%mole fraction,0.013 ppm and 0.029 to 6.098 ppm,5.987%mole fraction,0.002 ppm and 0.027,respectively.展开更多
By combining the three-dimensional model software and grid generation software,the combustor parametric model and high quality and high speed gridding in the full flow field has been realized.Based on the research of ...By combining the three-dimensional model software and grid generation software,the combustor parametric model and high quality and high speed gridding in the full flow field has been realized.Based on the research of the parametric modeling,an optimizing design,CFD analysis and performance prediction of the combustor have been accomplished,and the rule of the combustor performance variation with structural parameters was presented.The results show that the combustor capability has no significant change with the radial swirler parameters and the primary holes area.The combustor capability has significant change with position and profile of the primary holes and dilution holes,and the combustor outlet temperature profile and emission change greatly when the total hole area of the burnerinnerliner changes.The parametric model method is helpful to provide a fast design method for the aero-engine combustor design.展开更多
The flame quenching process in combustors was observed by high speed camera and Schlieren system, at the inflow conditions of Ma = 2.64, To = 1483K, P0 = 1.65 MPa, T = 724 K and P -- 76.3 kPa. Changing process of the ...The flame quenching process in combustors was observed by high speed camera and Schlieren system, at the inflow conditions of Ma = 2.64, To = 1483K, P0 = 1.65 MPa, T = 724 K and P -- 76.3 kPa. Changing process of the flame and shock structure in the combustor was clearly observed. The results revealed that the precom- bustion shock disappeared accompanied with the process in which the flame was blown out and withdrawed from the mainflow into the cavity and vanished after a short while. The time of quenching process was extended by the cavity flame holder, and the ability of flame holding was enhanced by arranging more cavities in the downstream as well. The flame was blown from the upstream to the downstream, so the flame in the downstream of the cavity was quenched out later than that in the upstream.展开更多
This paper describes the numerical calculations of gaseous reaction flows in a model of gas turbine combustors. The profiles of hydrodynamic and thermodynamic patterns in a three-dimensional combustor model are obtain...This paper describes the numerical calculations of gaseous reaction flows in a model of gas turbine combustors. The profiles of hydrodynamic and thermodynamic patterns in a three-dimensional combustor model are obtained by solving the governing differential transport equations. The well-established numerical prediction algorithm SIMPLE, the modified k-ε turbulence model and k-ε-g turbulent diffusion flame model have been adopted in computations. The β function has been selected as probability density function. The effect of combustion process on flow patterns has been investigated. The calculated results have been verified by experiments. They are in remarkably good agreement.展开更多
文摘The flow-field of a propane-air diffusion flame combustor with interior and exterior conjugate heat transfers was numerically studied.Results obtained from four combustion models,combined with the re-normalization group(RNG) k-ε turbulence model,discrete ordinates radiation model and enhanced wall treatment are presented and discussed.The results are compared with a comprehensive database obtained from a series of experimental measurements.The flow patterns and the recirculation zone length in the combustion chamber are accurately predicted,and the mean axial velocities are in fairly good agreement with the experimental data,particularly at downstream sections for all four combustion models.The mean temperature profiles are captured fairly well by the eddy dissipation(EDS),probability density function(PDF),and laminar flamelet combustion models.However,the EDS-finite-rate combustion model fails to provide an acceptable temperature field.In general,the flamelet model illustrates little superiority over the PDF model,and to some extent the PDF model shows better performance than the EDS model.
文摘This article aims to investigate the effects of using an alternative fuel on the emissions of carbon dioxide (CO_(2)) and carbon monoxide (CO) in a reactive flow spraying inside a model combustor. The study highlights the trade-offs between CO_(2) and CO emissions, encouraging further investigation into alternative fuels, considering their environmental impact. The bio-synthetic fuel comprises Jatropha Bio-Synthetic Paraffinic Kerosene (JSPK) blended with Jet-A at five different weight ratios to make the alternative fuels. The two-phase flow of the fuel and air mixture is assessed by the Eulerian-Lagrangian approach. The realizable κ-ε model is employed to model the turbulent flow. The discrete ordinates method is applied to model radiative heat transfer, and the steady flamelet combustion model is utilized to model combustion. The distributions of mean mixture fraction and mole fractions of CO_(2) and CO at the combustion chamber outlet are presented. Results reveal that variations in fuel properties affect the emission of pollutants since adding JSPK increases the emission rate of the mean mixture fraction and the mole fraction of CO and decreases the mole fraction of CO_(2) at the combustor outlet. Also, employing a weight ratio of 80% Jet-A with 20% JSPK leads to achieving the lowest mean mixture fraction and mole fraction of CO with a maximum reduction of 25% relative to utilizing only the base fuel. In addition, the lowest amount of CO_(2) is obtained for 70% Jet-A / 30% JSPK, which is about 15% less than other weight ratios.
基金supported by the National Science Fund for Distinguished Young Scholars (Grant No. 51825605)。
文摘This paper experimentally studied the effect of CO_(2) opposing multiple jets on the thermoacoustic instability and NO_(x) emissions in a lean-premixed model combustor.The feasibility was verified from three variables:the CO_(2) jet flow rate,hole numbers,and hole diameters of the nozzles.Results indicate that the control effect of thermoacoustic instability and NO_x emissions show a reverse trend with the increase of open area ratio on the whole,and the optimal jet flow rate range is 1-4 L/min with CO_(2) opposing multiple jets.In this flow rate range,the amplitude and frequency of the dynamic pressure and heat release signals CH~* basically decrease as the CO_(2) flow rate increases,which avoids high-frequency and high-amplitude thermoacoustic instability.The amplitude-damped ratio of dynamic pressure and CH*can reach as high as 98.75% and 93.64% with an optimal open area ratio of 3.72%.NO_(x) emissions also decrease as the jet flow rate increases,and the maximum suppression ratio can reach 68.14%.Besides,the flame shape changes from a steep inverted "V" to a more flat "M",and the flame length will become shorter with CO_(2) opposing multiple jets.This research achieved the synchronous control of thermoacoustic instability and NO_(x) emissions,which could be a design reference for constructing a safer and cleaner combustor.
文摘In the present paper,a sensitivity analysis of pollutants and pattern factor in a model combustor due to changes in the geometrical characteristics of stabilizing jets has been carried out.The exhaust pollutants including NO_(x),CO and soot have been chosen due to their harmful effect on the environment.The pattern factor has been also considered owing to its impact on turbine blades.The geometrical characteristics comprise diameter,angle and position of stabilizing jets.Eulerian-Lagrangian approach has been employed to model liquid fuel injection and distribution,breakup and evaporation of droplets.For the analysis of reactive-spray flow characteristics,RANS approach,realizable k-εturbulence model,discrete ordinates radiative heat transfer model and steady flamelet combustion model together with the chemical reaction mechanism of diesel fuel(C_(10)H_(22))have been applied.NO_(x) modeling has been performed via post-processing.Sensitivity analysis is such that by making variations in the problem inputs(diameter,angle and position of jets)in an organized manner,the effects on the outputs(NO_(x),CO,soot and pattern factor)are predicted.The number and order of simulations are predicted by design of experiments and full factorial model.Results have been analyzed using analysis of variance.It has been observed that if interactions among the characteristics of jets are considered,it is possible to analyze the exhaust pollutants more accurately.In fact,by using the interactions,it is likely to find a point where all output parameters are improved.Results show that by considering interactions of stabilizing jet characteristics,the maximum values of NO_(x),CO,soot and pattern factor change from 13.927 ppm,11.198%mole fraction,2.877 ppm and 0.043 to 26.233 ppm,14.693%mole fraction,142.357 ppm and 0.060,respectively.Furthermore,the minimum values change from 5.819 ppm,7.568%mole fraction,0.013 ppm and 0.029 to 6.098 ppm,5.987%mole fraction,0.002 ppm and 0.027,respectively.
文摘By combining the three-dimensional model software and grid generation software,the combustor parametric model and high quality and high speed gridding in the full flow field has been realized.Based on the research of the parametric modeling,an optimizing design,CFD analysis and performance prediction of the combustor have been accomplished,and the rule of the combustor performance variation with structural parameters was presented.The results show that the combustor capability has no significant change with the radial swirler parameters and the primary holes area.The combustor capability has significant change with position and profile of the primary holes and dilution holes,and the combustor outlet temperature profile and emission change greatly when the total hole area of the burnerinnerliner changes.The parametric model method is helpful to provide a fast design method for the aero-engine combustor design.
基金supported by the National Natural Science Foundation of China (10902124)
文摘The flame quenching process in combustors was observed by high speed camera and Schlieren system, at the inflow conditions of Ma = 2.64, To = 1483K, P0 = 1.65 MPa, T = 724 K and P -- 76.3 kPa. Changing process of the flame and shock structure in the combustor was clearly observed. The results revealed that the precom- bustion shock disappeared accompanied with the process in which the flame was blown out and withdrawed from the mainflow into the cavity and vanished after a short while. The time of quenching process was extended by the cavity flame holder, and the ability of flame holding was enhanced by arranging more cavities in the downstream as well. The flame was blown from the upstream to the downstream, so the flame in the downstream of the cavity was quenched out later than that in the upstream.
文摘This paper describes the numerical calculations of gaseous reaction flows in a model of gas turbine combustors. The profiles of hydrodynamic and thermodynamic patterns in a three-dimensional combustor model are obtained by solving the governing differential transport equations. The well-established numerical prediction algorithm SIMPLE, the modified k-ε turbulence model and k-ε-g turbulent diffusion flame model have been adopted in computations. The β function has been selected as probability density function. The effect of combustion process on flow patterns has been investigated. The calculated results have been verified by experiments. They are in remarkably good agreement.
