Investigation Of Hydrocarbon-Fueled Scramjet Feed System Scheme

The scramjet is an ideal power system and the key component of hydrocarbon vehicle, and critical technologies of scramjet have been developed with a significant progress, but the feed system of scramjet has not caught enough attention. Based on the active regenerative cooling scramjet, a scheme of the turbo-pump feed system based on expansion cycle is designed.Firstly, based on the long time operation scramjet, a general design method of the scramjet's feed system is presented, a detailed design model is established and a feed system scheme of the scramjet is designed. The study results show that there is an optimal pressure of driving gas at the turbine inlet to make the consumption of driving gas minimal in starting process; the driving gas consumption decreases as the temperature of driving gas increases, but its effect gradually weakens as the temperature of driving gas increases; when each scheme is in their optimal pressure of driving gas at the turbine inlet and the same driving gas temperature, the schme which employs helium to start consumes the minimum driving gas.Secondly, after introducing a universal method of analyzing the static characteristics of feed system, the mathematical model built which is used to analyse the static characteristics of the scheme employing helium to start, the engine parameters is calculated and the effects of interference factors on the engine performace is analysed. The results indicate that combustion efficiency has the greatest impact on engine performance; the efficiency of turbo-pump components, the flow discharge coefficient and the fuel density has a great influence on engine performance; the ratio between the pressures at the outlet and inlet of the turbine has a small effect on engine performance and the fuel pressure at the pump inlet has a minimal impact on engine performance.Finally, the analysis method of start process of scramjet feed system is presented, and the dynamic mathmetical model of turbo-pump components, the one dimentional calculation model and the heat transfer model are established. Besides, considering the effect of the fuel flow velocity in coolant channel, the calculaton method of coolant heating process is presented. Based on the scheme employing helium to start, the start process of the feed system is simulated. The results show that it is shorter than the time to reach the power equilibrium of the turbine pump assembly to reach the thermal equilibrium; the time when the coolant enters the cooling channel has a little impact on the equilibrium time but a great effect on the maximum temperature the chamber wall can reach and the temperature of the fuel at the cooling channel outlet; increasing the aspect ratio of the height and the width of the cooling channel can enhance the heat transfer within a certain range.