Research On Characteristics Of The High Temperature Gaseous Hydrocarbon Fuel Expansion Power Generation System For Hypersonic Propulsion

Wide-range hypersonic propulsion system has broad application prospects and important significance in the future long-range,reusable aerospace transportation system.The fast,long-distance and reusable characteristics of hypersonic propulsion system lead to a huge power demand for its onboard equipments.Therefore,the onboard thermal power generation system has great significance for wide-speed-range operating hypersonic propulsion system.Aiming at the onboard thermal power generation for hypersonic propulsion system,the following works have been developed in this thesis:Thermal power generation schemes for wide-speed-range operating hypersonic propulsion were proposed and compared.The high temperature air and high temperature gaseous hydrocarbon fuel were compared at first.Consequently,power generation systems were constructed,including high temperature thermal power generation scheme and high temperature gaseous hydrocarbon fuel expansion power generation scheme.Evaluation of these two thermal power generation systems were conducted,performances of each scheme were brought.As a result,a combined thermal power generation system for wide-speed-range hypersonic propulsion system was constructed.With performance analysis of the combined thermal power generation system,necessity of performance improvement for high temperature gaseous hydrocarbon fuel expansion power generation system was put forward.In order to explore the expansion power generation capability of high temperature gaseous hydrocarbon fuel,the high temperature gaseous hydrocarbon fuel expansion thermal power generation test bench was developed.The results can not only be used to validate the expansion thermal power generation capacity,but also be used to explore possible performance improvement.The high temperature gaseous hydrocarbon fuel expansion thermal power generation test components and system structure was founded,and experiments of the high temperature gaseous hydrocarbon fuel and high temperature air were conducted.The results were analyzed and possible means to improve the performance were proposed.In addition,the experimental results in this chapter can also be used to validate the relevant performance evaluation models.In order to better evaluate performance of the expansion thermal power generation capability,the main component models of thermal power generation system were developed.Considering the large temperature increasing of hydrocarbon fuel in cooling channel and the accompanied pyrolysis,a thermophysical properties calculation model for high temperature thermal cracked hydrocarbon fuel was established.The RK-PR cubic equation of state and its mixing rules were adopted to calculate thermophysical properties such as density,specific heat,enthalpy and entropy.Meanwhile,the Chung method and the Ely-Hanley method were used to calculate the viscosity and thermal conductivity.The thermophysical properties calculation model was validated by REFPROP standard program.The results show that the calculation model can be used to predict the thermophysical properties of pyrolytic hydrocarbon fuel.Based on the thermophysical calculation model,a quasi-one-dimensional model of pyrolytic hydrocarbon fuel combined with flow,heat transfer and pyrolysis process was established for heating process in the active cooling channel.The model was validated by the related experimental results.What is more,a zero-dimensional high temperature hydrocarbon fuel expansion thermal power generation calculation model was established,and the validity of the model was verified by the experimental results of the high temperature gaseous hydrocarbon fuel.Finally,in order to study the dynaimc characteristics of high temperature gaseous hydrocarbon fuel thermal expansion power generation,a zero-dimensional dynamic model considering the thermo-mechanical coupling process of combustion-cooling-thermal power generation was established,and the model was validated by the dynamic heat transfer experimental results.The performance of high temperature gaseous hydrocarbon fuel thermal expansion power generation system was studied.By analyzing t influencing factors of thermal power generation performance of high temperature gaseous hydrocarbon fuel expansion system,the upper and lower limits of the thermal power generation system performance were defined.Aiming at the lower performance limit of power generation system,the expansion power generation capacity enhancement methods of partial mass flow high temperature gaseous hydrocarbon fuel capacity improvement method and catalytic steam reforming high temperature ga seous hydrocarbon fuel expansion power generation capacity improvement method were proposed.While,to imrpove the upper limit of power generation system performance,the method of power generation capacity enhancement by reheating of high temperature gaseous hydrocarbon fuel and catalytic steam reforming high temperature gaseous hydrocarbon fuel expansion were proposed.With the established analytical model,the feasibility of the above methods and the enhancement effect were evaluated.The influence of variable operating conditions of propulsion system on the performance of high temperature gaseous hydrocarbon fuel expansion power generation system was studied.Through qualitative analysis,the thermo-mechanical coupling process between the propulsion system and the high temperature gaseous hydrocarbon fuel expansion power generation system was defined.Through comparative analysis,it is clear that the thermo-mechanical coupling between the propulsion system and the high-temperature gaseous hydrocarbon fuel expansion power generation system makes the thermal dynamic process of high-temperature hydrocarbon fuel more complex.On this basis,the influence of engine inflow Mach number and fuel equivalence ratio on the steady-state characteristics of high temperature gaseous hydrocarbon fuel expansion power generation system was clarified.Based on the established dynamic model of high temperature gaseous hydrocarbon fuel expansion power generation system,the influence of variable operating conditions of propulsion system on the dynamic process of high temperature gaseous hydrocarbon fuel expansion power generation system was studied.Combining with the dynamic process of high temperature fuel thermodynamic power generation system under variable operating conditions of propulsion system,the dynamic change process of the relative change rate of fuel flow/pressure at the outlet of turbopump was given for the two structures of volumetric pump and centrifugal pump,and the flow control strategy based on the specific structure pump is put forward respectively.