强预冷发动机新型热力循环布局及性能分析

Thermodynamic performance analysis of anovel precooled airbreathing engine layout

为兼顾高超声速强预冷发动机的比冲及系统复杂度,提出了一种耦合闭式氦循环的强预冷发动机新型热力循环布局。该热力循环采用空气适度预冷,闭式氦循环采用较为简单的二支路分流冷却压缩方式。在支路1中,使用较少的液氢即可保证氦被冷却至低温以便于压缩,可提高闭式循环增压比进而增加闭式循环输出功率;在支路2中,利用温度相对较低的氢气对预冷器出口分流的部分高温氦冷却,保证支路1和支路2掺混后的氦温度满足预冷器要求。对该新型强预冷发动机的设计点性能进行了参数化影响分析及优化设计,马赫数5工作点比冲可达3287 s。通过旁路冲压当量比和喷管喉道面积的调节,可保证进气道、预冷涡轮通道和旁路冲压通道的匹配工作,且能实现冷却与燃烧所需燃料量的平衡;通过对闭式氦循环基准压力的调节可实现发动机推力的有效调节,且各主要部件均能匹配稳定工作。沿典型飞行轨迹的发动机总体性能计算表明,在马赫数0~5工作范围内,该新型强预冷发动机具有较高的推力和比冲性能;且闭式氦循环较为简单,利于工程实现,该新型热力循环布局可为高超声速强预冷发动机设计提新的思路。

In order to consider the specific impulse and system complexity at the same time,a new hypersonic precooled airbreathing engine thermodynamic cycle layout which coupled with closed-loop helium cycle was proposed.This thermodynamic cycle layout adopts moderate air precooling,and a relatively simple two branch splitting,cooling and recompression pattern is adopted in the closed-loop helium cycle.In the first branch,less liquid hydrogen is used to ensure that helium was chilled to lower temperature,making helium easy to be compressed,so as to increase the pressure ratio of closed-loop cycle and then increase the output power of the closed-loop cycle.In the second branch,the hydrogen with relatively lower temperature is further used to cool the high-temperature helium form the precooler to ensure that the helium temperature after mixing meets the requirements of the precooler.Firstly,the parametric analysis and optimization of the design point performance of precooled airbreathing engine were carried out,and the engine specific impulse at Mach 5 working point can reach 3287 s.By adjusting the equivalence ratio of bypass ramjet combustor and nozzle throat area,matched working of the intake,precooled turbine channel and bypass ramjet channel can be achieved,and the amount of fuel for cooling and combustion can be balanced.The engine thrust can be effectively regulated by adjusting the base pressure of closed-loop helium cycle,and all the main components can work stably.The overall engine performance calculated along a typical flight trajectory shows that this new precooled airbreathing engine has high thrust and specific impulse in the working range of Mach 0~5.The closed-loop helium cycle layout is relatively simple and easier to achieve engineering realization.Thus this new thermodynamic cycle layout can offer a new idea for the design of hypersonic precooled airbreathing engine.