高空长航时无人机发动机工作稳定性研究

Stability of aero-engine for high altitude long endurance unmanned aerial vehicle

高空、低速飞行会对高空长航时无人机发动机压缩系统和燃烧室的稳定性产生不利影响。为评估高空长航时无人机发动机工作稳定性,采用无量纲分析法,对其燃烧稳定性和供油匹配性进行了研究。结果表明:随着飞行高度的增加,无量纲燃油流量逐渐增大,发动机转速变化引起的燃油流量变化越大,发动机越易进入不稳定工作区。该发动机停车时无量纲燃油流量严重偏离正常工作点,发动机富油熄火。无量纲转速为5.45时,发动机的富油稳定裕度为26%。相比于等高度减小法,利用无人机等状态爬升法进行主油路通断试飞,发动机的工作稳定性更高。无量纲分析法对高空长航时无人机工作稳定性分析及试飞方法设计具有重要意义。

The high altitude and low speed flight will have adverse effects on the stability of the engine com⁃pression system and combustion chamber of the High Altitude Long Endurance(HALE)UAV.In order to evaluate the working stability of the engine,the combustion stability and fuel supply matching of the engine were studied by the dimensionless analysis method.The results show that the dimensionless fuel flow gradu⁃ally increases with the increase of flight altitude,and the greater the change of engine fuel flow caused by the change of speed,the engine is more likely to enter the unstable working area.It is found that the dimen⁃sionless fuel flow deviates from the normal working point seriously when the engine stops,and the fule-rich engine flameout.It is calculated that when the dimensionless speed is 5.45,the fule-rich stability margin of the engine is 26%.At the same time,the analysis of dimensionless method shows that the engine works more stably when the UAV is used in the on-off test flight of the main fule circuit by the equal-state climb⁃ing method.Therefore,the dimensionless analysis method is of great significance to the working stability analysis and flight test method design of high altitude long endurance UAV.