火箭冲压组合发动机亚燃模态流道匹配特性分析

Analysis on Matching Relationship in Full Flowpath of Rocket Based Combined Cycle Engine at Ramjet Mode

为获得喷注规律对RBCC工作特性的影响,开展Ma_∞=3~6条件下火箭冲压组合发动机亚燃模态的全流道一体化数值分析,比较了不同来流条件下燃烧组织方式与进排气之间的匹配关系。研究发现,随着飞行马赫数的增加,隔离段压比提高,需相应调整燃料喷注位置和当量比,前移主释热区,最大化利用预燃激波串的匹配特性;在低马赫数下,则需将释热区转移至燃烧室后部扩张比较大区域,扩展流道后部压力范围,最大化利用热力壅塞的匹配特性,在不同马赫数下,通过分布式释热的方法实现宽裕较优工作。除此以外,关闭火箭也可以使得预燃激波串后移,改善进气道工作状态,发动机平均比冲性能提高10%以上,此时可以适当增加燃烧室前部喷油量,以保证低马赫数下整体的推力性能。

Numerical analysis of full flow path in RBCC engine on matching relationship between combustion organization,air intake and exhaust was carried out from Mach number 3 to 6 at ramjet mode to reflect effects of different injection position and equivalence ratio on operating characteristic. With flight Mach number increasing,pressure ratio in the isolator was improved which led main reaction zone moved forward and injection law was adjusted to maximize the function of pre-combustion train. At low Mach flight conditions,main reaction zone need to move backward and broaden high pressure range in the rear part with great expansion to maximize the function of thermal choking. Through heat released in different zones,performance was optimized at a wide range.Besides,closure of rocket moved pre-combustion shock train backwards which improved the condition of inlet and overall impulse performance more than 10%. Meanwhile equivalence ratio should be increased to ensure the overall thrust performance at low Mach flight condition.