液化空气循环对组合发动机性能影响的研究

Influence of Air Liquefaction Cycle on Performance of Combined Cycle Engine

本文研究了氧、氮不分离的液化空气循环对SERJ组合发动机性能影响的规律,并与采用氧、氮分离液化空气循环的组合发动机性能进行了分析比较。结论表明,空气液化后不分离的组合发动机性能明显优于分离情况下的发动机性能;同时还发现,不论氧、氮是否分离,采用液化空气循环都能改善组合发动机比冲性能,但均使推力有所下降。分析表明,液化空气产生的冲压阻力,液氮冷却外机体形成的旁路阻力和流量损失是导致推力下降的主要原因。

This paper studies the effect of LACE (Air Liquefaction Cycle) onperformance of SERJ (Supercharged Ejector Ramjet) combined cycle engine.To the authors' best knowledge, there existed only the papers by Weng [3]and Bendot [5] on this subject. The authors studied the subject further [4].Compared with Refs. [3-5], the new findings of this paper are as follows: 1. LACE improves specific impulse but lowers thrust. At design pointof engine operation, the specific impulse of SERJ combined cycle enginewithout LACE is only 375s but its thrust is as large as 1478kN [3]. 2. Performance of engine with LACE without separation of air into O_2and N_2 is much better than performance of engine with LACE with airseparation. At design point, the specific impulse of engine with LACE is 613swith air separation but is 999s without air separation. Again at design point,the thrust of engine with LACE is 491kN with air separation but is 798kNwithout air separation. 3. The thrust loss of engine with LACE is mainly the result of threefactors: ramjet drag caused by air liquefaction, bypass drag caused by thecooling of aircraft structure by liquid nitrogen, and mass flow loss of theengine. 4. For two operating modes of SERJ combined cycle engine with LACEwithout air separation, curves are given relating the specific impulse andthrust to Mach number and altitude. The above findings were obtained through computer simulation.