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
In this paper the ignition characteristics of gaseous ethylene hydrocarbon fuel is investigated in the supersonic clean airstreams experimental facility with a resistance heater. The generic cavity flame holder is use...In this paper the ignition characteristics of gaseous ethylene hydrocarbon fuel is investigated in the supersonic clean airstreams experimental facility with a resistance heater. The generic cavity flame holder is used to create recirculation and promote the fuel/air mixing at the lower wall of the combustor. Three different injection concepts are considered in this research : ( 1 ) ethylene injection upstream of the cavity ; (2) ethylene and hydrogen injection upstream of the cavity simultaneously; ( 3 )ethylene injection preceded by pilot hydrogen injection. The pilot injection showed to be a supportive tool for holding the flame of the main normal ethylene fuel injection. Therefore, using pilot hydrogen injection and cavity configuration necessitates optimizing the combustor length to ensure the complete combustion and the full liberation of the chemical energy stored in the fuel before exiting the combustor.The present study proved the possibility of igniting the ethylene and maintaining its flame in the supersonic airstreams.展开更多
In order to investigate the effects of fuel injection distribution on the scrarnjet combustor performance, there are conducted three sets of test on a hydrocarbon fueled direct-connect scramjet test facility. The resu...In order to investigate the effects of fuel injection distribution on the scrarnjet combustor performance, there are conducted three sets of test on a hydrocarbon fueled direct-connect scramjet test facility. The results of Test A, whose fuel injection is carried out with injectors located on the top-wall and the bottom-wall, show that the fuel injection with an appropriate close-front and centralized distribution would be of much help to optimize combustor performances. The results of Test B, whose fuel injection is performed at the optimal injection locations found in Test A, with a given equivalence ratio and different injection proportions for each injector, show that this injection mode is of little benefit to improve combustor performances. The results of Test C with a circumferential fuel injection distribution displaies the possibility of ameliorating combustor performance. By analyzing the effects of injection location parameters on combustor performances on the base of the data of Test C, it is clear that the injector location has strong coupled influences on combustor performances. In addition, an irmer-force synthesis specific impulse is used to reduce the errors caused by the disturbance of fuel supply and working state of air heater while assessing combustor performances.展开更多
The mixing and combustion characteristics in a cavity flameholding combustor under inlet Mach number 2.92 are numerically investigated with ethylene injection.Dimensionless distance is defined as the ratio of the actu...The mixing and combustion characteristics in a cavity flameholding combustor under inlet Mach number 2.92 are numerically investigated with ethylene injection.Dimensionless distance is defined as the ratio of the actual distance to the height of the combustor entrance.The cavity shear-layer mode,the lifted cavity shear-layer mode,and jet wake mode with upstream separation are observed respectively with dimensionless distance equals to 1.5,4.5,and 7.5.In both non-reacting and reacting flow fields,the numerical results are essentially in agreement with the schlieren photography,flame chemiluminescence images,and wall pressure,which verify the reliability of the numerical method.The results of non-reacting flow fields show that the BackwardFacing Step(BFS)can promote the flow separation downstream at a fixed distance.The more forward the separation position is,the larger the separation zone is in the non-reacting flow field.Furthermore,the larger the separation zone is,the higher the intensity of combustion in the reacting flow field is.A reasonable distance can reduce the total pressure loss generated by the shock waves in the combustor.The flame presents remarkable three-dimensional characteristics in the reacting flow fields.When dimensionless distance equals to 4.5,there are flames near the side wall above the cavity and it is difficult for the flame stabilization in the center of the combustor,while the combustion intensity in the center of the combustor is higher than that near the side wall when dimensionless distance equals to 7.5.In the cavity flameholding combustors with a backward-facing step,the higher combustion intensity may bring much total pressure loss to the combustor.Thus,it is a good choice to achieve better thrust performance when dimensionless distance equals to 4.5 compared to the other two combustors.展开更多
Numerical simulations were performed to model the non-reacting and reacting flow behind a rearward step flameholder in Mach 1.6 supersonic flow with fuel injection at the step base.The combustor geometry was based on ...Numerical simulations were performed to model the non-reacting and reacting flow behind a rearward step flameholder in Mach 1.6 supersonic flow with fuel injection at the step base.The combustor geometry was based on the University of Florida scramjet experimental facility.Turbulence was modeled using k-u shear stress transport(SST),laminar flamelet was used for combustion modeling.Wall static pressure showed good agreement with experimental data for non-reacting and reacting flow.For non-reacting flow,dummy fuel helium mole fraction distribution in the recirculation region behind the step was validated with planar laser induced fluorescence(PLIF)images in experiments.To improve the combustion characteristics,air was injected in tandem with hydrogen at step base using various configurations.With all fuel injection as baseline,the case with 2 air jets around each fuel jet and air injected at 2 times the stagnation pressure of fuel showed the most improvement compared to other cases.It was most effective in reducing the local fuel richness,shortening the flame length and increasing combustion efficiency.展开更多
The flame-holding mechanism in hypersonic propulsion technology is the most important factor in prolonging the duration time of hypersonic vehicles.The two-dimensional coupled implicit Reynolds-averaged Navier-Stokes ...The flame-holding mechanism in hypersonic propulsion technology is the most important factor in prolonging the duration time of hypersonic vehicles.The two-dimensional coupled implicit Reynolds-averaged Navier-Stokes equations,the shear-stress transport k-ω turbulence model and the finite-rate/eddy-dissipation reaction models were used to simulate the combustion flow field of a typical strut-based scramjet combustor.We investigated the effects of the hydrogen-air reaction mechanism and fuel injection temperature and pressure on the parametric distributions in the combustor.The numerical results show qualitative agreement with the experimental data.The hydrogen-air reaction mechanism makes only a slight difference in parametric distributions along the walls of the combustor,and the expansion waves and shock waves exist in the combustor simultaneously.Furthermore,the expansion wave is formed ahead of the shock wave.A transition occurs from the shock wave to the normal shock wave when the injection pressure or temperature increases,and the reaction zone becomes broader.When the injection pressure and temperature both increase,the waves are pushed out of the combustor with subsonic flows.When the waves are generated ahead of the strut,the separation zone is formed in double near the walls of the combustor because of the interaction of the shock wave and the boundary layer.The separation zone becomes smaller and disappears with the disappearance of the shock wave.Because of the horizontal fuel injection,the vorticity is generated near the base face of the strut,and this region is the main origin for turbulent combustion.展开更多
A numerical investigation has been performed on supersonic mixing of hydrogen with air in a Scramjet (Supersonic Combustion Ramjet) combustor and its flame holding capability by solving Two-Dimensional full Navier-Sto...A numerical investigation has been performed on supersonic mixing of hydrogen with air in a Scramjet (Supersonic Combustion Ramjet) combustor and its flame holding capability by solving Two-Dimensional full Navier-Stokes equations. The main flow is air entering through a finite width of inlet and gaseous hydrogen is injected perpendicularly from the side wall. An explicit Harten-Yee Non-MUSCL Modified-flux-type TVD scheme has been used to solve the system of equations, and a zero-equation algebraic turbulence model to calculate the eddy viscosity coefficient. In this study the enhancement of mixing and good flame holding capability of a supersonic combustor have been investigated by varying the distance of injector position from left boundary keeping constant the backward-facing step height and other calculation parameters. The results show that the configuration for small distance of injector position has high mixing efficiency but the upstream recirculation can not evolved properly which is an important factor for flame holding capability. On the other hand, the configuration for very long distance has lower mixing efficiency due to lower gradient of hydrogen mass concentration on the top of injector caused by the expansion of side jet in both upstream and downstream of injector. For moderate distance of injector position, large and elongated upstream recirculation can evolve which might be activated as a good flame holder.展开更多
The high-temperature non-equilibrium effect is a novel and significant issue in the flows over a high Mach number(above Mach 8)air-breathing vehicle.Thus,this study attempts to investigate the high-temperature non-equ...The high-temperature non-equilibrium effect is a novel and significant issue in the flows over a high Mach number(above Mach 8)air-breathing vehicle.Thus,this study attempts to investigate the high-temperature non-equilibrium flows of a curved compression two-dimensional scramjet inlet at Mach 8 to 12 utilizing the two-dimensional non-equilibrium RANS calculations.Notably,the thermochemical non-equilibrium gas model can predict the actual high-temperature flows,and the numerical results of the other four thermochemical gas models are only used for comparative analysis.Firstly,the thermochemical non-equilibrium flow fields and work performance of the inlet at Mach 8 to 12 are analyzed.Then,the influences of high-temperature non-equilibrium effects on the starting characteristics of the inlet are investigated.The results reveal that a large separation bubble caused by the cowl shock/lower wall boundary layer interaction appears upstream of the shoulder,at Mach 8.The separation zone size is smaller,and its location is closer to the downstream area while the thermal process changes from frozen to non-equilibrium and then to equilibrium.With the increase of inflow Mach number,the thermochemical non-equilibrium effects in the whole inlet flow field gradually strengthen,so their influences on the overall work performance of the high Mach number inlet are more obvious.The vibrational relaxation or thermal non-equilibrium effects can yield more visible influences on the inlet performance than the chemical non-equilibrium reactions.The inlet in the thermochemical non-equilibrium flow can restart more easily than that in the thermochemical frozen flow.This work should provide a basis for the design and starting ability prediction of the high Mach number inlet in the wide operation range.展开更多
The impulse and self starting characteristics of a mixed-compression hypersonic inlet designed at Mach number of 6.5 are studied by applying the unsteady computational fluid dynamics (CFD) method. The full Navier–S...The impulse and self starting characteristics of a mixed-compression hypersonic inlet designed at Mach number of 6.5 are studied by applying the unsteady computational fluid dynamics (CFD) method. The full Navier–Stokes equations are solved with the assumption of viscous perfect gas model, and the shear-stress transport (SST) k–x two-equation Reynolds averaged Navier– Stokes (RANS) model is used for turbulence modeling. Results indicate that during impulse starting, the flow field is divided into three zones with different aerodynamic parameters by primary shock and upstream-facing shock. The separation bubble on the shoulder of ramp undergoes a generating, growing, swallowing and disappearing process in sequence. But a separation bubble at the entrance of inlet exists until the freestream velocity is accelerated to the starting Mach number during self starting. The mass flux distribution of flow field is non-uniform because of the interaction between shock and boundary layer, so that the mass flow rate at throat is unsteady during impulse starting. The duration of impulse starting process increases almost linearly with the decrease of freestream Mach number but rises abruptly when the freestream Mach number approaches the starting Mach number. The accelerating performance of booster almost has no influence on the self starting ability of hypersonic inlet.展开更多
A two-dimensional Reynolds averaged Navier Stokes(RANS)simulation of a dual mode ramjet(DMRJ)combustor is performed,modeling the University of Michigan dual-mode combustor experimental setup operating in reacting mode...A two-dimensional Reynolds averaged Navier Stokes(RANS)simulation of a dual mode ramjet(DMRJ)combustor is performed,modeling the University of Michigan dual-mode combustor experimental setup operating in reacting mode with different equivalence ratios(4).The simulations are carried out using a k-u SST turbulence model and a steady diffusion flamelet model for non-premixed combustion.Air enters the isolator at Mach 2.2,stagnation pressure and temperature of 549.2 kPa and 1400 K respectively.Hydrogen is injected transverse to the flow direction and upstream of the cavity flame holder to simulate ramjet(4 Z 0.29)and scramjet(4 Z 0.19)modes of operation.Wall static pressure plots are used to validate numerical results against experimental data.Analysis of flow separation in ramjet mode due to the presence of a shock train in the isolator is carried out by means of numerical Schlieren images overlapped with contours of negative axial velocity,showing the effects of shock wave boundary layer interaction(SWBLI).Active control through wall normal boundary layer bleed in the separated flow region is implemented,which weakens the shock train and moves it downstream closer to the cavity.Bleed results in an improved stagnation pressure recovery in ramjet mode,with a marginal increase in combustion efficiency.展开更多
The solid-fueled Scramjet is an interesting option for supersonic combustion ramjet.It shows significant advantages such as simple fuel supply and compactness,avoiding the complex system of tanks and pipelines that en...The solid-fueled Scramjet is an interesting option for supersonic combustion ramjet.It shows significant advantages such as simple fuel supply and compactness,avoiding the complex system of tanks and pipelines that encountered in liquid-fueled Scramjets.The solid-fueled Scramjet could be the simplest air-breathing engine for the hypersonic flight regime.This paper presents a comprehensive and systematic review of the research progress on solid-fueled Scramjet in various institutes and universities.It summarizes a progress overview of three types of the solid-fueled Scramjet,which covers a wealth of landmark numerical and experimental results.Based on this,several relevant key technologies are proposed.Several inherent scientific issues are refined,such as the mixing mechanism of multi-phase flow and supersonic airflow,ignition and combustion mechanism of the condensed phase in a supersonic airflow,and coupling mechanism of gas and solid phase in a supersonic flow.Finally,the historical development trend is clarified,and some recommendations are provided for future solid-fueled Scramjet.展开更多
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.
基金This paper is supported by the Doctorate Foundation of Northwestern Polytechnical University under Grant No.W016107
文摘In this paper the ignition characteristics of gaseous ethylene hydrocarbon fuel is investigated in the supersonic clean airstreams experimental facility with a resistance heater. The generic cavity flame holder is used to create recirculation and promote the fuel/air mixing at the lower wall of the combustor. Three different injection concepts are considered in this research : ( 1 ) ethylene injection upstream of the cavity ; (2) ethylene and hydrogen injection upstream of the cavity simultaneously; ( 3 )ethylene injection preceded by pilot hydrogen injection. The pilot injection showed to be a supportive tool for holding the flame of the main normal ethylene fuel injection. Therefore, using pilot hydrogen injection and cavity configuration necessitates optimizing the combustor length to ensure the complete combustion and the full liberation of the chemical energy stored in the fuel before exiting the combustor.The present study proved the possibility of igniting the ethylene and maintaining its flame in the supersonic airstreams.
文摘In order to investigate the effects of fuel injection distribution on the scrarnjet combustor performance, there are conducted three sets of test on a hydrocarbon fueled direct-connect scramjet test facility. The results of Test A, whose fuel injection is carried out with injectors located on the top-wall and the bottom-wall, show that the fuel injection with an appropriate close-front and centralized distribution would be of much help to optimize combustor performances. The results of Test B, whose fuel injection is performed at the optimal injection locations found in Test A, with a given equivalence ratio and different injection proportions for each injector, show that this injection mode is of little benefit to improve combustor performances. The results of Test C with a circumferential fuel injection distribution displaies the possibility of ameliorating combustor performance. By analyzing the effects of injection location parameters on combustor performances on the base of the data of Test C, it is clear that the injector location has strong coupled influences on combustor performances. In addition, an irmer-force synthesis specific impulse is used to reduce the errors caused by the disturbance of fuel supply and working state of air heater while assessing combustor performances.
基金supported by the National Natural Science Foundation of China(Nos.11925207 and 12002381)the Scientific Research Plan of the National University of Defense Technology in 2019,China(No.ZK19-02)the Science and Technology Foundation of State Key Laboratory,China(No.6142703200311).
文摘The mixing and combustion characteristics in a cavity flameholding combustor under inlet Mach number 2.92 are numerically investigated with ethylene injection.Dimensionless distance is defined as the ratio of the actual distance to the height of the combustor entrance.The cavity shear-layer mode,the lifted cavity shear-layer mode,and jet wake mode with upstream separation are observed respectively with dimensionless distance equals to 1.5,4.5,and 7.5.In both non-reacting and reacting flow fields,the numerical results are essentially in agreement with the schlieren photography,flame chemiluminescence images,and wall pressure,which verify the reliability of the numerical method.The results of non-reacting flow fields show that the BackwardFacing Step(BFS)can promote the flow separation downstream at a fixed distance.The more forward the separation position is,the larger the separation zone is in the non-reacting flow field.Furthermore,the larger the separation zone is,the higher the intensity of combustion in the reacting flow field is.A reasonable distance can reduce the total pressure loss generated by the shock waves in the combustor.The flame presents remarkable three-dimensional characteristics in the reacting flow fields.When dimensionless distance equals to 4.5,there are flames near the side wall above the cavity and it is difficult for the flame stabilization in the center of the combustor,while the combustion intensity in the center of the combustor is higher than that near the side wall when dimensionless distance equals to 7.5.In the cavity flameholding combustors with a backward-facing step,the higher combustion intensity may bring much total pressure loss to the combustor.Thus,it is a good choice to achieve better thrust performance when dimensionless distance equals to 4.5 compared to the other two combustors.
文摘Numerical simulations were performed to model the non-reacting and reacting flow behind a rearward step flameholder in Mach 1.6 supersonic flow with fuel injection at the step base.The combustor geometry was based on the University of Florida scramjet experimental facility.Turbulence was modeled using k-u shear stress transport(SST),laminar flamelet was used for combustion modeling.Wall static pressure showed good agreement with experimental data for non-reacting and reacting flow.For non-reacting flow,dummy fuel helium mole fraction distribution in the recirculation region behind the step was validated with planar laser induced fluorescence(PLIF)images in experiments.To improve the combustion characteristics,air was injected in tandem with hydrogen at step base using various configurations.With all fuel injection as baseline,the case with 2 air jets around each fuel jet and air injected at 2 times the stagnation pressure of fuel showed the most improvement compared to other cases.It was most effective in reducing the local fuel richness,shortening the flame length and increasing combustion efficiency.
基金supported by the National Natural Science Foundation of China (90816027 and 61004094)the Excellent Graduate Student Innovative Project of the National University of Defense Technology (B070101)+1 种基金the Hunan Provincial Innovation Foundation for Post graduate (3206)the Chinese Scholarship Council (2009611036)
文摘The flame-holding mechanism in hypersonic propulsion technology is the most important factor in prolonging the duration time of hypersonic vehicles.The two-dimensional coupled implicit Reynolds-averaged Navier-Stokes equations,the shear-stress transport k-ω turbulence model and the finite-rate/eddy-dissipation reaction models were used to simulate the combustion flow field of a typical strut-based scramjet combustor.We investigated the effects of the hydrogen-air reaction mechanism and fuel injection temperature and pressure on the parametric distributions in the combustor.The numerical results show qualitative agreement with the experimental data.The hydrogen-air reaction mechanism makes only a slight difference in parametric distributions along the walls of the combustor,and the expansion waves and shock waves exist in the combustor simultaneously.Furthermore,the expansion wave is formed ahead of the shock wave.A transition occurs from the shock wave to the normal shock wave when the injection pressure or temperature increases,and the reaction zone becomes broader.When the injection pressure and temperature both increase,the waves are pushed out of the combustor with subsonic flows.When the waves are generated ahead of the strut,the separation zone is formed in double near the walls of the combustor because of the interaction of the shock wave and the boundary layer.The separation zone becomes smaller and disappears with the disappearance of the shock wave.Because of the horizontal fuel injection,the vorticity is generated near the base face of the strut,and this region is the main origin for turbulent combustion.
文摘A numerical investigation has been performed on supersonic mixing of hydrogen with air in a Scramjet (Supersonic Combustion Ramjet) combustor and its flame holding capability by solving Two-Dimensional full Navier-Stokes equations. The main flow is air entering through a finite width of inlet and gaseous hydrogen is injected perpendicularly from the side wall. An explicit Harten-Yee Non-MUSCL Modified-flux-type TVD scheme has been used to solve the system of equations, and a zero-equation algebraic turbulence model to calculate the eddy viscosity coefficient. In this study the enhancement of mixing and good flame holding capability of a supersonic combustor have been investigated by varying the distance of injector position from left boundary keeping constant the backward-facing step height and other calculation parameters. The results show that the configuration for small distance of injector position has high mixing efficiency but the upstream recirculation can not evolved properly which is an important factor for flame holding capability. On the other hand, the configuration for very long distance has lower mixing efficiency due to lower gradient of hydrogen mass concentration on the top of injector caused by the expansion of side jet in both upstream and downstream of injector. For moderate distance of injector position, large and elongated upstream recirculation can evolve which might be activated as a good flame holder.
基金co-supported by the China Scholarship Council(No.202206840048)the Training Fund for Excellent Doctoral Candidates of Nanjing University of Science and Technology,China+4 种基金the Opening Foundation of State Key Laboratory of High Temperature Gas Dynamics,Institute of Mechanics,China(No.2021KF07)the National Key Laboratory Fund,China(No.2022-JCJQ-LB-020-01)the Foundation of Key Laboratory of Hypersonic Aerodynamic Force and Heat Technology,AVIC Aerodynamics Research Institute,China(No.XFX20220104)the China Postdoctoral Science Foundation(No.BX20200070)the Fundamental Research Foundation of the Central Universities,China(No.2022CDJXY012)。
文摘The high-temperature non-equilibrium effect is a novel and significant issue in the flows over a high Mach number(above Mach 8)air-breathing vehicle.Thus,this study attempts to investigate the high-temperature non-equilibrium flows of a curved compression two-dimensional scramjet inlet at Mach 8 to 12 utilizing the two-dimensional non-equilibrium RANS calculations.Notably,the thermochemical non-equilibrium gas model can predict the actual high-temperature flows,and the numerical results of the other four thermochemical gas models are only used for comparative analysis.Firstly,the thermochemical non-equilibrium flow fields and work performance of the inlet at Mach 8 to 12 are analyzed.Then,the influences of high-temperature non-equilibrium effects on the starting characteristics of the inlet are investigated.The results reveal that a large separation bubble caused by the cowl shock/lower wall boundary layer interaction appears upstream of the shoulder,at Mach 8.The separation zone size is smaller,and its location is closer to the downstream area while the thermal process changes from frozen to non-equilibrium and then to equilibrium.With the increase of inflow Mach number,the thermochemical non-equilibrium effects in the whole inlet flow field gradually strengthen,so their influences on the overall work performance of the high Mach number inlet are more obvious.The vibrational relaxation or thermal non-equilibrium effects can yield more visible influences on the inlet performance than the chemical non-equilibrium reactions.The inlet in the thermochemical non-equilibrium flow can restart more easily than that in the thermochemical frozen flow.This work should provide a basis for the design and starting ability prediction of the high Mach number inlet in the wide operation range.
文摘The impulse and self starting characteristics of a mixed-compression hypersonic inlet designed at Mach number of 6.5 are studied by applying the unsteady computational fluid dynamics (CFD) method. The full Navier–Stokes equations are solved with the assumption of viscous perfect gas model, and the shear-stress transport (SST) k–x two-equation Reynolds averaged Navier– Stokes (RANS) model is used for turbulence modeling. Results indicate that during impulse starting, the flow field is divided into three zones with different aerodynamic parameters by primary shock and upstream-facing shock. The separation bubble on the shoulder of ramp undergoes a generating, growing, swallowing and disappearing process in sequence. But a separation bubble at the entrance of inlet exists until the freestream velocity is accelerated to the starting Mach number during self starting. The mass flux distribution of flow field is non-uniform because of the interaction between shock and boundary layer, so that the mass flow rate at throat is unsteady during impulse starting. The duration of impulse starting process increases almost linearly with the decrease of freestream Mach number but rises abruptly when the freestream Mach number approaches the starting Mach number. The accelerating performance of booster almost has no influence on the self starting ability of hypersonic inlet.
文摘A two-dimensional Reynolds averaged Navier Stokes(RANS)simulation of a dual mode ramjet(DMRJ)combustor is performed,modeling the University of Michigan dual-mode combustor experimental setup operating in reacting mode with different equivalence ratios(4).The simulations are carried out using a k-u SST turbulence model and a steady diffusion flamelet model for non-premixed combustion.Air enters the isolator at Mach 2.2,stagnation pressure and temperature of 549.2 kPa and 1400 K respectively.Hydrogen is injected transverse to the flow direction and upstream of the cavity flame holder to simulate ramjet(4 Z 0.29)and scramjet(4 Z 0.19)modes of operation.Wall static pressure plots are used to validate numerical results against experimental data.Analysis of flow separation in ramjet mode due to the presence of a shock train in the isolator is carried out by means of numerical Schlieren images overlapped with contours of negative axial velocity,showing the effects of shock wave boundary layer interaction(SWBLI).Active control through wall normal boundary layer bleed in the separated flow region is implemented,which weakens the shock train and moves it downstream closer to the cavity.Bleed results in an improved stagnation pressure recovery in ramjet mode,with a marginal increase in combustion efficiency.
基金supported by the China Scholarship Council and the National Natural Science Foundation of China(Nos.2020JJ4665,51706241).
文摘The solid-fueled Scramjet is an interesting option for supersonic combustion ramjet.It shows significant advantages such as simple fuel supply and compactness,avoiding the complex system of tanks and pipelines that encountered in liquid-fueled Scramjets.The solid-fueled Scramjet could be the simplest air-breathing engine for the hypersonic flight regime.This paper presents a comprehensive and systematic review of the research progress on solid-fueled Scramjet in various institutes and universities.It summarizes a progress overview of three types of the solid-fueled Scramjet,which covers a wealth of landmark numerical and experimental results.Based on this,several relevant key technologies are proposed.Several inherent scientific issues are refined,such as the mixing mechanism of multi-phase flow and supersonic airflow,ignition and combustion mechanism of the condensed phase in a supersonic airflow,and coupling mechanism of gas and solid phase in a supersonic flow.Finally,the historical development trend is clarified,and some recommendations are provided for future solid-fueled Scramjet.