面向一体化计算的整体式液体冲压发动机建模及性能评估

Integration algorithm oriented modeling and performance evaluation on integrated liquid fuel ramjet

为发展冲压发动机性能工程预估方法,建立了面向一体化计算的整体式液体冲压发动机性能计算模型,并使其兼容基团贡献算法,提高了拓展性。利用模型分析了冲压发动机在攻角0°~6°、高度0~18 km、马赫数2.0~3.5、余气系数1.0~2.9范围工况多维度连续变化下,比冲、推力系数和燃油质量流量的速度-高度特性、高度-节流特性、节流-速度特性以及攻角特性。研究结果表明:性能计算模型可在一体化计算条件下、基团贡献算法允许范围内,不依赖试验数据对冲压发动机性能预估,计算结果与技术参考值相比相对误差均小于14%。推力系数和比冲具有基本一致的速度-高度特性和相似的高度-节流特性,受燃气组分影响,推力系数和比冲的节流-速度特性差异明显。燃油质量流量的变化规律不同于比冲和推力系数,在进入平流层后呈现折缓趋势,而呈现连续性,速度越大、高度越低、余气系数越小,燃油质量流量越高,反之则越小。引入攻角以后,攻角越大,比冲和推力系数越低,进气道起动马赫数越高;攻角-起动马赫数曲线小范围内近似线性,攻角超过5.6°非线性加剧。

The engineering prediction method of ramjet performance was developed,and an integration algorithm oriented model of integrated liquid fuel ramjet was established,which was compatible with group contribution method.The velocity-altitude characteristic,altitude-throttle characteristic,throttle-velocity characteristic and angle of attack characteristic of the specific impulse,thrust coefficient and fuel mass flow rate of the ramjet at angles of attack 0°~6°,altitude 0~18 km,Mach number 2.0~3.5 and excess air coefficient 1.0~2.9 were analyzed.Results showed that,the model can predict the performance of ramjet engine without depending on the test data under the condition of integrated algorithm and within the allowable range of group contribution method.The relative error between the calculated results and the technical reference values was less than 14%.Thrust coefficient and specific impulse had basically the same velocity-altitude characteristics and similar altitude-throttle characteristics.The difference between throttle-velocity characteristics of thrust coefficient and specific impulse were obvious under the influence of gas composition.Different from the change of specific impulse and thrust coefficient showing a slowing trend after entering the stratosphere,fuel mass flow rate showed continuity.The higher the velocity,the lower the altitude and the smaller the excess air coefficient was,the higher the fuel mass flow rate was,and vice versa.Taking the angle of attack into account,the larger the angle of attack was,the lower the specific impulse,thrust coefficient and the higher the inlet start Mach number was.The angle of attack-start Mach number curve was approximately linear in a small range,and the non-linearity was intensified when the angle of attack exceeded 5.6°.