With the tendency of high-speed flight and economic cruise, combustion mode in a scramjet engine will transfer from diffusion combustion mode to premixed combustion mode because of the decrease of Damköhler Number in combustor. In order to study the fuel equivalence ratio conditions for the establishment of premixed combustion mode and corresponding combustion mechanism, series of direct-connected experiments with gaseous ethylene as fuel were conducted. The total temperature of Mach 2.0 incoming flow ranged from 1200 K to 1700 K. Wall pressure of the combustor was collected to analyze related combustion mode and planar laser induced fluorescence (PLIF) was adopted to research combustion mechanism of corresponding combustion mode. Results showed that with the increment of fuel equivalence ratio ER, combustion mode transited from premixed combustion mode to partially premixed combustion mode and finally diffusion combustion mode. Bilateral injection scheme was more advantageous for premixed combustion to establish due to better fuel/air mixing and further downstream reaction position originating from diluted fuel in height position and corresponding low flame speed. Besides, total temperature of inflow had effect on the combustion characteristics in different aspects. On one hand, higher inflow total temperature brought lower lean fuel blow-off ER limit. On the other hand, the stabilization equivalence ratio range of premixed combustion mode would widen with the increment of inflow total temperature in the variation of 1200 K–1700 K which could be attributed to the coupling result of inflow temperature (affecting flame speed) and inflow velocity, indicating inevitability of appearance of premixed combustion mode in high-speed economic cruise with high inflow total temperature.

随着高速飞行和经济巡航的发展趋势，超燃冲压发动机的燃烧方式由于燃烧室中达姆克勒数的减少，将从扩散燃烧方式向预混燃烧方式转变。为研究建立预混燃烧模式的燃料当量比条件及相应的燃烧机理，以气态乙烯为燃料进行了一系列直联实验。2.0马赫来流总温度范围为1200K～1700K。采集燃烧室壁压分析相关燃烧模式，采用平面激光诱导荧光（PLIF）研究相应燃烧模式的燃烧机理。结果表明，随着燃料当量比ER的增加，燃烧方式从预混燃烧方式过渡到部分预混燃烧方式，最后是扩散燃烧方式。由于更好的燃料/空气混合以及来自高度位置的稀释燃料和相应的低火焰速度的进一步下游反应位置，双边喷射方案更有利于建立预混燃烧。此外，流入总温度对燃烧特性有不同的影响。一方面，较高的流入总温度带来较低的稀薄燃料排放ER限制。另一方面，在1200 K~1700 K的变化范围内，预混燃烧模式的稳定当量比范围会随着流入总温度的增加而扩大，这可能是由于流入温度（影响火焰速度）和流入的耦合结果。速度，表明在高流入总温度的高速经济巡航中出现预混燃烧模式的必然性。