双模态发动机的模态鉴别方法

双模态冲压发动机的不同燃烧模态具有不同的稳焰机制和流态特征,并且在模态转换时伴随着显著的推力变化. 因此,准确判断燃烧模态,对于捕捉发动机的燃烧区位置/范围、释热分布特征,以及为进一步优化燃烧室的设计(流道结构和供油布局) 具有重要意义. 目前尚无鉴别模态的有效试验方法,本文提出了一种模态鉴别的试验方法,并在超燃直连台上开展验证试验. 试验中使用的测量技术包括:壁面静压、高速阴影/纹影、多通道可调谐二极管吸收光谱和高能态碳氢自由基CH^* 自发光成像. 利用多种测量方法的组合,可以同时获得燃烧室中气流静温、速度、马赫数分布,释热分布以及燃烧区位置/范围. 这些试验数据能够用于判别模态,并获得不同模态的流动和火焰特征.

EXPERIMENTAL STUDY ON JUDGMENT METHOD OF COMBUSTION MODE ON DUAL-MODE SCRAM JET

For a dual-mode scramjet engine, different combustion modes present different flame-stability mechanisms and different flow characteristics. Besides, thrust varies remarkably when mode transition occurs. Therefore, it is extremely important to discriminate combustion mode accurately, so as to capture flame location, measure the distribution of heat release and further optimize combustor design (i.e., configuration and fuel supplying). Since there is no effective experimental method to estimate combustion mode, a new judgment method is proposed in this paper and validation experiments were implemented in a direct-connected scramjet test facility. Multi-diagnostics, including wall pressure, high frame-rate schlieren, CH^* chemiluminescence imaging, and TDLAS (tunable diode laser absorption spectroscopy), were used in these experiments. Distributions of temperature, velocity, Mach number and heat release were obtained simultaneously. These data can be used to discriminate combustion mode and relate different flow/combustion characteristic swith different combustion modes.