Research On Thermodynamic Cycle And Regulating Law Of The Precooled Engine

Precooled engine is one of the most efficient propulsion system for the hypersonic airplane, and is promising to be the propulsion system of the SSTO spaceplane or the booster of TSTO. The essential distinction between the precooled engine and the traditional one is that the heat transmission is added to the main dynamic cycle of the engine by precooler or the injection process for the first time. While the precooler broadens the flight envelop, the complexity, safety boundary and key controlled variables are also increased. All those increments result in a problem that the traditional cycle analysis and research of the control method of the turbo-jet engine are not directly suitable for the precooled engine. Based on those considerations above, a research about the thermodynamic cycle and control method is developed in this paper.Firstly, the thermodynamic cycle of the precooled engine has been studied. The precooled ATREX has been chosen as the selected object engine to be studied. By fomulating the cycle of that engine, the results show that the cycle is different from the Brayton cycle, both air and fuel should be taken into consideration, and cycle precooled ratio has been added into the cycle main parameters.Secondly, the thermodynamic cycle performance has been studied. It has been proved that the five cycle variables are fan compression ratio, gas-oil ratio, thermal load of the precooler, total thermal load and total pressure recovery of the heat exchange. And their effect on the engine performance were calculated and analysized. The result shows that the heat exchange amount in the combustion chamber has little infulence on the engine performance. Aiming at the different effects of those cycle variables on the engine performance, a constrained multi-optimization was given to get an optimized set of the variables to maximum the performance. The optimized result provided a great reference of the designed point of the engine model. By applying sensitive analysis of other cycle parameters, a way to improve the engine performance was put forward by enhancing the fan efficiency.Thirdly, the concept of “precooled depth” was proposed. Based on that concept, the safety boundaries were analysized and the sequence of those boundaries was cleared. By comparing the precooled air-turbo rocket and the traditional air-turbo rocket, the reason of the phenomenon that the flight envelop was extended and the degree of the extendion was clear. And the precooled one could ultilize a compressor with higher compression ratio. By comparing the precooled air-turbo rocket and the precooled turbojet, the suitable flight envelop of each engine was analysized. By modeling the dynamic model of the shaft and precooler, it was clear that the const time of the precooler was so much smaller than the shaft that it could be ignored. The engine could be simplified into a one order system.Finally, the model of the precooled air-turbo rocket was developed, which includes the dynamic parts of the engine and could present the variable performance of the components, and the operating characteristic was studied. The control method of the precooled engine was preliminarily studied. The new problems of the precooled engine were analysized. The collaborating function of the precooled air-turbo rocket was derivated and the result shows that the precooled air-turbo rocket has one more degree of freedom. Based on the research above, the combined regulating law based on the relative corrected parameters was put forward. As for the selecting gist of controled variables and the demarcation points of the regulating law, an example of the regulating law of the maximum working state was given.