Research On Performance Of Brayton Cycle Integrated System Of Scramjet Engine

With the increasing Mach number and flight time,the aerospace industry is advancing rapidly,but at the same time,the power supply and engine thermal protection requirements of hypersonic vehicles are also increasing,and the traditional on-board power generation and thermal protection methods are not applicable,and only the energy transfer but not the energy conversion is realized.In order to solve the problems of power supply and cooling of hypersonic vehicles simultaneously,this paper proposes a new closed regenerative Brayton cycle(CRBC)integrated engine cooling system,taking into account the characteristics of today’s major thermoelectric conversion technologies and the flight requirements of hypersonic vehicles.In order to investigate the cooling power generation potential,dynamic response law and practical application feasibility of the CRBC system,firstly,a steady-state mathematical model of the CRBC system is established,and the thermal performance of the CRBC integrated system under ideal and restricted conditions is calculated using MATLAB software successively,and the Supercritical Carbone Dioxide(S-CO2)CRBC integrated engine cooling system is calculated.(S-CO2)CRBC integrated system(referred to as S-CRBC)and helium(Helium,He)CRBC integrated system(referred to as H-CRBC)are compared and analyzed.In order to predict the dynamic characteristics of the integrated system,a dynamic simulation model of the integrated system is created using the SIMULINK platform,and the dynamic response law of the S-CRBC system is obtained by applying a perturbation.Finally,the second law of thermodynamics was applied to analyze and evaluate the quality of the system in the endangered system.The analysis shows that 1)the system thermal efficiency and power generation are better for S-CRBC under ideal conditions,and the optimal working thermal efficiencies of S-CRBC and H-CRBC are 40% and 42.26%,respectively,and the net system cycle work is 253.58 k W and 222.97 k W,respectively,and the wall temperature drop is 198.69 K and 260.93 K,respectively,under the limiting conditions.2)Improving the compressor inlet temperature,pressure and flow rate can reduce the system power generation performance.Increasing the inlet temperature can reduce the fuel flow demand,and increasing the outlet pressure can effectively improve the thermal protection performance of the engine.The system thermal efficiency rises gradually with the increase of heat source power,and is more sensitive to the decrease of heat source power.Under the dual disturbance of cold and heat sources,the fluctuation of wall temperature and thermal efficiency are affected by the direction,magnitude and frequency of the change of cold and heat source parameters at the same time,and the stability of cold and heat source parameters is crucial for the stable operation of S-CRBC system.3)The system heat loss is mainly concentrated in the heat exchanger part,accounting for 65.54%of the whole system,and the system heat efficiency is high,about 29.21%.It is calculated that the specific power of S-CRBC system can reach 0.44 k W/kg,which is significantly better than the traditional on-board battery(0.06～0.58 k W/kg)and fuel cell(0.22～0.33 k W/kg)power supply methods with smaller mass penalty.The proposed S-CRBC system with good power generation cooling effect and low mass penalty meets the practical application requirements of hypersonic vehicles and has more room for future enhancement.