Experimental Study on Self-Ignition of Hydrogen Injection into High Temperature Supersonic Airstream

在高温/高速风洞（最高驻点温度1500 K，马赫数1.8），已被调查。通过高温喷氢和等离子体炬化学自由基喷入的燃烧试验，发现在1400 K的气流中，喷入温度升高到950 K对近喷燃烧有明显的影响，但对下游火焰的影响不大。但发现其对主气流温度相当敏感。试验段内形成的火焰与冲击波有强烈的相互作用趋势，在相应的相互作用点处燃烧得到加强。等离子体炬采用氩气为载气，氧气为二次添加气体，在1000 K的气流中工作。但在800 K时实现了点火，远低于通常的自燃温度1300 K，同时发现氧自由基的加入使点火温度进一步降低到600 K，表现出一定的不稳定性。在这种情况下，由于与试验段内的冲击波相互作用，整体火焰也得到了增强。

Supersonic cmbustion of hydrogen gas, which was injected transversely from a circular hole flush to the wall of a high temperature/high speed wind tunnel (stagnation temperature 1500K max., Mach number 1.8), has been investigated. The experimental study consists of combustion tests due to (1) hydrogen injection with elevated temperature (2) chemical radicals injection using a plasma torch.The effect of elevating injectant temperature up to 950K by using a heater system has been recognized upon the near-injector combustion in the airstream of 1400K.The bulk flame downstream, homever, was not much affected by this injectant temperature, but found to be rather sensitive to the main airflow temperature. The flame formed inside the test section showed a tendency of strong interaction with the shock waves, which enhanced the combustion at the corresponding interaction point.The plasma torch employed Argon as the carrier gas and Oxygen as the secondary additive gas, which operated in the airflow of 1000K.The combustion tests were not successful for the torch to be located upstream of the fuel injector, but realized the ignition at the temperature of 800K,that is, far below the usual self-ignition temperature of 1300K.It has been also shown that the additive Oxygen radicals further lowered the ignition temperature to 600K,which showed a little unstable feature. The bulk flame in this case is also enhanced due to the interaction with the shock waves inside the test sectoon.