This study proposes a quantitative evaluation framework to assess the performance of boundary layer injection(BLI)technology,establishing standardized metrics for integration into performance analysis of scramjets.We ...This study proposes a quantitative evaluation framework to assess the performance of boundary layer injection(BLI)technology,establishing standardized metrics for integration into performance analysis of scramjets.We comparatively evaluate inert gas and fuel BLI strategies under typical combustor inflow conditions through systematic numerical investigations employing this evaluation framework.Key findings reveal that fuel injection demonstrates superior skin friction reduction efficacy compared to inert gases,especially hydrogen,achieving skin friction reduction performance up to 600 s at Mach 8+conditions with an injection equivalence ratio(ER)of 0.1.Hydrogen’s advantage arises from its inherently low density,coupled with combustion-induced density reduction in the log-law region.This dual mechanism suppresses turbulent momentum transport and attenuates skin friction through large-scale flow restructuring.However,when benchmarked against reacting mainstream flows without BLI,fuel injection efficacy diminishes significantly(100 s level)—local density reduction effects induced by boundary layer combustion are attenuated by mainstream heat release,limiting further momentum transport suppression and reducing drag reduction performance to inert gas levels.These results underscore the critical influence of ambient combustion conditions on BLI effectiveness,emphasizing that BLI implementation must prioritize non-reacting or weakly reacting flow environments.The proposed standardized metrics address this operational dependency,enabling BLI optimization within full-engine design paradigms to prevent counterproductive“pseudo-optimization.”展开更多
Ejector mode is a unique and critical phase of wide-range rocket-based combined cycle(RBCC)engine.In this paper,a quasi-one-dimensional thermodynamic performance modeling method,with more detailed model treatments for...Ejector mode is a unique and critical phase of wide-range rocket-based combined cycle(RBCC)engine.In this paper,a quasi-one-dimensional thermodynamic performance modeling method,with more detailed model treatments for the inlet-diffuser system,pri-mary/secondaryflow interaction,and pressure feedback matching,was developed for operating characteristics studies and multi-objective optimization analysis of the ejector mode of an actual RBCC engine.A series of three-dimensional simulations of separate inlet and fullflowpath was completed to validate the modeling study and provide further insight into the operating charac-teristics.The primary/secondary equilibrium pressure ratio functions a significant effect on ejector mode performance,a higher performance augmentation can be obtained by lower rocket pressure ratio,larger mixing section area ratio,smaller throttling throat and higher equivalence ratio,within an appropriate range.The positive performance augmentation can be realized at lowflight Mach conditions,the coordination and trade-off relationships between specific im-pulse,performance augmentation ratio and thrust-to-area ratio during ejector mode are present by the Pareto-front from MOP analysis.It is further verified by CFD simulation that,the operating back-pressure at the exit of inlet-diffuser system functions a decisive influence on the airbreathing characteristics,the pressure feedback and matching should be well-controlled for secondaryflowrate and performance augmentation.The thermodynamic modeling analysis re-sults are basically consistent with those of numerical simulation,to validate the rationality and effectiveness of the modeling method.展开更多
Experimental studies were conducted in order to improve the understanding of the thrust generation and the pressure/flame reverse propagation of the air-breathing pulse detonation engines(APDEs)with self-designed inle...Experimental studies were conducted in order to improve the understanding of the thrust generation and the pressure/flame reverse propagation of the air-breathing pulse detonation engines(APDEs)with self-designed inlets and valves structures.The present experimental research utilized a gasoline/air APDE(with 68 mm inner-diameter,2050 mm length and maximum operating frequency not less than 40 Hz which was as a benchmark structure)at different operating frequencies,with freestream air inflow of 1.1 atm and 0℃.The theoretical equivalence ratio of gasoline/air was 1.Two kinds of inlets with centerbody or without were considered and combined with two kinds of self-designed valves(the elastic-valve and the convergent aero-valve)specially designed for comparative experiments.During the test,the inflow parameters,the pressure along the longitudinal direction inside the engine and the thrust force were measured for the APDE operating characteristic analysis,including the detonation combustion,the aerodynamic drag,the pressure/flame reverse propagation and the thrust generation.The research results indicate that:The inlet centerbody does not increase drag but plays a positive effect on airflow stability and operation matching.The elastic-valve and the convergent aero-valve,though increase the inlet aerodynamic drag,have obvious effects on suppressing the detonation wave and pressure forward propagation,resulting in effective thrust increase.Effects of the convergent aero-valve are the best when the flow choked,while the effects of elastic-valve are better and continuously stable in a wider range of frequency.The wmaximum nondimensional thrust increases with the elastic-valve is reached about 1.12 at the frequency of 8-9 Hz,and about 0.97 with the convergent aero-valve at the frequency of 7 Hz.The maximum fuel specific impulse is 2514.6 s when using the convergent aerovalve.And this study provides technical reserve for the APDE optimization design.展开更多
基金supported by the National Key Laboratory of Ramjet,Beijing Power Machinery Research Institute,Beijing,China.(No.WDZC6142703202202).
文摘This study proposes a quantitative evaluation framework to assess the performance of boundary layer injection(BLI)technology,establishing standardized metrics for integration into performance analysis of scramjets.We comparatively evaluate inert gas and fuel BLI strategies under typical combustor inflow conditions through systematic numerical investigations employing this evaluation framework.Key findings reveal that fuel injection demonstrates superior skin friction reduction efficacy compared to inert gases,especially hydrogen,achieving skin friction reduction performance up to 600 s at Mach 8+conditions with an injection equivalence ratio(ER)of 0.1.Hydrogen’s advantage arises from its inherently low density,coupled with combustion-induced density reduction in the log-law region.This dual mechanism suppresses turbulent momentum transport and attenuates skin friction through large-scale flow restructuring.However,when benchmarked against reacting mainstream flows without BLI,fuel injection efficacy diminishes significantly(100 s level)—local density reduction effects induced by boundary layer combustion are attenuated by mainstream heat release,limiting further momentum transport suppression and reducing drag reduction performance to inert gas levels.These results underscore the critical influence of ambient combustion conditions on BLI effectiveness,emphasizing that BLI implementation must prioritize non-reacting or weakly reacting flow environments.The proposed standardized metrics address this operational dependency,enabling BLI optimization within full-engine design paradigms to prevent counterproductive“pseudo-optimization.”
基金supported by the National Natural Science Foundation of China (Grant No.52076094).
文摘Ejector mode is a unique and critical phase of wide-range rocket-based combined cycle(RBCC)engine.In this paper,a quasi-one-dimensional thermodynamic performance modeling method,with more detailed model treatments for the inlet-diffuser system,pri-mary/secondaryflow interaction,and pressure feedback matching,was developed for operating characteristics studies and multi-objective optimization analysis of the ejector mode of an actual RBCC engine.A series of three-dimensional simulations of separate inlet and fullflowpath was completed to validate the modeling study and provide further insight into the operating charac-teristics.The primary/secondary equilibrium pressure ratio functions a significant effect on ejector mode performance,a higher performance augmentation can be obtained by lower rocket pressure ratio,larger mixing section area ratio,smaller throttling throat and higher equivalence ratio,within an appropriate range.The positive performance augmentation can be realized at lowflight Mach conditions,the coordination and trade-off relationships between specific im-pulse,performance augmentation ratio and thrust-to-area ratio during ejector mode are present by the Pareto-front from MOP analysis.It is further verified by CFD simulation that,the operating back-pressure at the exit of inlet-diffuser system functions a decisive influence on the airbreathing characteristics,the pressure feedback and matching should be well-controlled for secondaryflowrate and performance augmentation.The thermodynamic modeling analysis re-sults are basically consistent with those of numerical simulation,to validate the rationality and effectiveness of the modeling method.
基金the National Natural Science Foundation of China(91441201)the Fundamental Research Funds for the Central Universities(5003123003)for financial supports of this work.
文摘Experimental studies were conducted in order to improve the understanding of the thrust generation and the pressure/flame reverse propagation of the air-breathing pulse detonation engines(APDEs)with self-designed inlets and valves structures.The present experimental research utilized a gasoline/air APDE(with 68 mm inner-diameter,2050 mm length and maximum operating frequency not less than 40 Hz which was as a benchmark structure)at different operating frequencies,with freestream air inflow of 1.1 atm and 0℃.The theoretical equivalence ratio of gasoline/air was 1.Two kinds of inlets with centerbody or without were considered and combined with two kinds of self-designed valves(the elastic-valve and the convergent aero-valve)specially designed for comparative experiments.During the test,the inflow parameters,the pressure along the longitudinal direction inside the engine and the thrust force were measured for the APDE operating characteristic analysis,including the detonation combustion,the aerodynamic drag,the pressure/flame reverse propagation and the thrust generation.The research results indicate that:The inlet centerbody does not increase drag but plays a positive effect on airflow stability and operation matching.The elastic-valve and the convergent aero-valve,though increase the inlet aerodynamic drag,have obvious effects on suppressing the detonation wave and pressure forward propagation,resulting in effective thrust increase.Effects of the convergent aero-valve are the best when the flow choked,while the effects of elastic-valve are better and continuously stable in a wider range of frequency.The wmaximum nondimensional thrust increases with the elastic-valve is reached about 1.12 at the frequency of 8-9 Hz,and about 0.97 with the convergent aero-valve at the frequency of 7 Hz.The maximum fuel specific impulse is 2514.6 s when using the convergent aerovalve.And this study provides technical reserve for the APDE optimization design.
