A turbine based combined cycle(TBCC)propulsion system uses a turbine-based engine to accelerate the vehicle from takeoff to the mode transition flight condition,at which point,the propulsion system performs a“mode tr...A turbine based combined cycle(TBCC)propulsion system uses a turbine-based engine to accelerate the vehicle from takeoff to the mode transition flight condition,at which point,the propulsion system performs a“mode transition”from the turbine to ramjet engine.Smooth inlet mode transition is accomplished when flow is diverted from one flowpath to the other,without experiencing unstart or buzz.The smooth inlet mode transition is a complex unsteady process and it is one of the enabling technologies for combined cycle engine to become a functional reality.In order to unveil the unsteady process of inlet mode transition,the research of over/under TBCC inlet mode transition was conducted through a numerical simulation.It shows that during the mode transition the terminal shock oscillates in the inlet.During the process of inlet mode transition mass flow rate and Mach number of turbojet flowpath reduce with oscillation.While in ramjet flowpath the flow field is non-uniform at the beginning of inlet mode transition.The speed of mode transition and the operation states of the turbojet and ramjet engines will affect the motion of terminal shock.The result obtained in present paper can help us realize the unsteady flow characteristic during the mode transition and provide some suggestions for TBCC inlet mode transition based on the smooth transition of thrust.展开更多
To reduce the drag generated by the recirculation flow at the rocket base in a RocketBased Combined Cycle(RBCC)engine operating in the ramjet/scramjet mode,a novel annular rocket RBCC engine based on a central plug co...To reduce the drag generated by the recirculation flow at the rocket base in a RocketBased Combined Cycle(RBCC)engine operating in the ramjet/scramjet mode,a novel annular rocket RBCC engine based on a central plug cone was proposed.The performance loss mechanism caused by the recirculation flow at the rocket base and the influence of the plug cone configuration on the thrust performance were studied.Results indicated that the recirculation flow at the rocket base extended through the entire combustor,which creates an extensive range of the"low-kineticenergy zone"at the center and leads to an engine thrust loss.The plug cone serving as a surface structure had a restrictive effect on the internal flow of the engine,making it smoothly transit at the position of the large separation zone.The model RBCC engine could achieve a maximum thrust augmentation of 37.6%with a long plug cone that was twice diameter of the inner isolator.However,a shorter plug cone that was half diameter of the inner isolator proved less effective at reducing the recirculation flow for a supersonic flow and induced an undesirable flow fraction that diminished the thrust performance.Furthermore,the effectiveness of the plug cone increased with the flight Mach number,indicating that it could further broaden the operating speed range of the scramjet mode.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
文摘联合循环(Combined Cycle, CC)机组具有能源利用效率高、温室气体排放量低和运行方式灵活等特性,在电力系统中得到了越来越广泛的应用,积极参与到电力市场的竞价中。为了研究CC机组在日前电量市场中的竞价行为,文中提出了一种日前电量市场中CC机组竞价策略双层模型。上层模型为基于模式的CC机组竞价模型,下层模型为日前电量市场出清模型。该模型中的CC机组和独立系统运营商(Independent System Operator, ISO)通过电量市场出清得到的节点边际电价(Locational Marginal Prices, LMP)相互影响。CC机组向ISO提交报价同时影响电量市场的出清结果,并根据ISO进行的下层市场出清结果安排发电计划。利用Karush-Kuhn-Tucker(KKT)条件和对偶理论,将所提出的双层优化模型转化为均衡约束数学规划问题(Mathematical Program With Equilibrium Constraint, MPEC)。结果显示,文中所提出的竞价策略提高了CC机组在电量市场中的收益12.28%,降低市场的运行成本25.37%,验证了所提出模型的有效性。
基金The authors gratefully acknowledge the financial support received from the Aviation Foundation Project(Grant No.2012ZB52031)the Fundamental Research Funds for the Central Universities(Grant No.NJ20140021)for this project.
文摘A turbine based combined cycle(TBCC)propulsion system uses a turbine-based engine to accelerate the vehicle from takeoff to the mode transition flight condition,at which point,the propulsion system performs a“mode transition”from the turbine to ramjet engine.Smooth inlet mode transition is accomplished when flow is diverted from one flowpath to the other,without experiencing unstart or buzz.The smooth inlet mode transition is a complex unsteady process and it is one of the enabling technologies for combined cycle engine to become a functional reality.In order to unveil the unsteady process of inlet mode transition,the research of over/under TBCC inlet mode transition was conducted through a numerical simulation.It shows that during the mode transition the terminal shock oscillates in the inlet.During the process of inlet mode transition mass flow rate and Mach number of turbojet flowpath reduce with oscillation.While in ramjet flowpath the flow field is non-uniform at the beginning of inlet mode transition.The speed of mode transition and the operation states of the turbojet and ramjet engines will affect the motion of terminal shock.The result obtained in present paper can help us realize the unsteady flow characteristic during the mode transition and provide some suggestions for TBCC inlet mode transition based on the smooth transition of thrust.
基金supported by the National Natural Science Foundation of China(Nos.11925207 and 92252206)the Hunan Province Graduate Innovation Project,China(No.XJCX2023059)。
文摘To reduce the drag generated by the recirculation flow at the rocket base in a RocketBased Combined Cycle(RBCC)engine operating in the ramjet/scramjet mode,a novel annular rocket RBCC engine based on a central plug cone was proposed.The performance loss mechanism caused by the recirculation flow at the rocket base and the influence of the plug cone configuration on the thrust performance were studied.Results indicated that the recirculation flow at the rocket base extended through the entire combustor,which creates an extensive range of the"low-kineticenergy zone"at the center and leads to an engine thrust loss.The plug cone serving as a surface structure had a restrictive effect on the internal flow of the engine,making it smoothly transit at the position of the large separation zone.The model RBCC engine could achieve a maximum thrust augmentation of 37.6%with a long plug cone that was twice diameter of the inner isolator.However,a shorter plug cone that was half diameter of the inner isolator proved less effective at reducing the recirculation flow for a supersonic flow and induced an undesirable flow fraction that diminished the thrust performance.Furthermore,the effectiveness of the plug cone increased with the flight Mach number,indicating that it could further broaden the operating speed range of the scramjet mode.
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.
