旋流组合稳焰的宽范围亚燃冲压燃烧室性能研究

Performance of a wide-range ramjet combustor with swirl-combined flame-holding methods

关键词:  亚燃冲压发动机  旋流  火焰稳定  宽范围  点火边界

Key words:  Ramjet engine  Swirl  Flame stability  Wide range  Ignition boundary

摘要:

拓宽冲压发动机的稳定工作范围对于发展组合循环发动机技术意义重大。为兼顾火焰稳定和总压恢复性能，在亚燃冲压燃烧室中提出局部旋流组合稳焰方式。在燃烧室入口前加装2个总阻塞比仅为9.6%的旋流器，与突扩结构共同作为火焰稳定装置。在Ma1.5和Ma3的来流条件下，对不同的煤油喷注方式、点火位置、喉部面积和运行当量比对燃烧室特性的影响进行了实验研究。结果表明，相较于无旋流器时，旋流稳焰以1%左右的总压损失为代价，Ma1.5时使得点火边界下降了64.7%，联焰边界下降了14.8%，成功下拓了亚燃冲压燃烧室的点火和火焰稳定范围。旋流器单独供油还能使得点火当量比进一步下拓至0.13，下降幅度达到74.5%。对于点火边界来说，受煤油穿透和分布影响，单外喷优于单内喷，点火位置对单内喷的点火有一定影响，而喉部面积对点火影响不大。对于联焰边界来说，单内喷和单外喷很难实现联焰；内外都喷时，随着当量比增加，火焰实现联焰且长度明显增大。对于燃烧效率而言，单外喷燃烧效率最高，随当量比的增加燃烧效率呈下降趋势，而Ma=3时，来流总温的升高使得燃烧效率提高至η>0.87。

Abstract:

Expanding the working range of ramjet engines is of great significance for the development of combined cycle engines. To balance the performance of flame stability and total pressure recovery， the local swirl-combined flame-holding method has been proposed in the ramjet combustor. Two swirlers were installed in front of the inlet of the combustor， with a blockage ratio of only 9.6%. Together with the sudden expansion structure， they serve as a flame-holding apparatus. Under the inflow conditions of Ma1.5 and Ma3， different kerosene injection patterns， ignition positions， throat areas， and operating equivalence ratios were experimentally investigated. Results show that compared to the cases without swirler， the swirl flame-holding method achieved a 64.7% reduction in ignition boundary and a 14.8% reduction in flame connection boundary at the cost of about 1% total pressure loss at Ma1.5， successfully expanding the ignition and stability range of the ramjet combustor. The fuel supply of swirler can further reduce the ignition equivalence ratio to 0.13， with a decline of 74.5%. For the ignition boundary， the external injection is superior to the internal injection due to the penetration and distribution of kerosene. The ignition position has a certain impact on the ignition of the internal injection， while the throat area has little effect on the ignition. For the flame connection boundary， it is difficult to achieve flame connection by the external injection or the internal injection. When kerosene is injected simultaneously from both the internal and external holes， flame connection can be achieved and the length increases with the increase in equivalence ratio. The external injection has the highest combustion efficiency， and the combustion efficiency shows a decreasing trend with the increase of the equivalence ratio. When Ma=3， the rise in the total temperature of the incoming flow increases the combustion efficiency to η>0.87.