液体火箭发动机高压混合燃气涡轮绝热功计算方法

Calculation method of insulation power of high pressure hybrid gas turbine for liquid rocket engine

在高压补燃循环液体火箭发动机的设计中,涡轮绝热功是影响发动机推力的重要设计参数,其计算的准确性直接影响涡轮设计的有效性。高压下,真实气体效应突出,对绝热功的计算有较大影响,必须考虑其作用。对比分析了Soave-Redlich-Kwong(SRK)、Peng-Robinson(PR)和Redlich-Kwong-Peng-Robinson(RK-PR)3种立方型状态方程描述氧气、甲烷和氢气的热力学性质的准确性。结果表明SRK方程的准确性较高,与NIST数据最大误差不超过2%。高压涡轮燃气为多元混合物,其绝热功的计算应考虑混合规则。假设涡轮等熵膨胀,分别推导了理想气体假设和考虑混合规则下的SRK方程的涡轮绝热功的计算公式,发现理想气体绝热功的计算与真实气体偏差近10%。提出了一种可以在工程上计算各型号发动机高压涡轮绝热功的算法,即利用进出口平均压缩因子计算高压涡轮近似绝热功,该方法与理论方法的最大误差不超过3%。

In the design of liquid rocket engine,the thermal insulation work of the turbine is an important design parameter that affects the engine thrust,and the accuracy of the calculation directly affects the efficiency of the turbine design.Under high pressure,the effect of real gas is prominent,which affects the accuracy of adiabatic work calculation and must be taken into account.This paper compares and analyzes the accuracy of three cubic equation[Soave-Redlich-Kwong(SRK),Peng-Robinson(PR),Redlich-Kwong-Peng-Robinson(RK-PR)]of state describing the thermodynamic properties of oxygen,methane and hydrogen.The results show that the accuracy of SRK equation is the best,the maximum error with NIST's data is less than 2%.Besides,the high-pressure turbine's gas is a multi-component mixture,and the calculation of the adiabatic work should consider the mixing rule.Assuming the expansion of the turbine is isentropic,the formulas of the ideal gas hypothesis and the turbine adiabatic work considering the equation under the mixing rule are derived respectively.And it is proved that the calculation's error of the ideal gas adiabatic work is much higher than the real gas.Finally,an algorithm for calculating the thermal insulation work of high-pressure turbo-engines is presented,which is calculating the approximate adiabatic work of high-pressure turbine by compressing factor,and the maximum error between the method and the theoretical method is less than 3%.