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主动冷却超燃冲压发动机一般使用碳氢化合物作为燃料,但是碳氢燃料存在点火延迟时间长,稳定燃烧范围窄等问题,这就迫切需要开展碳氢燃料点火和稳燃新方法的研究。脉冲燃烧可能是一种拓展超声速燃烧室工作范围的方式,但在超声速燃烧室内还没有开展相关研究。使用结构简单的脉冲火花塞(5Hz,50J/pulse),在马赫数2.5的直联式超声速燃烧室内,实验研究了乙烯和超临界煤油的超声速脉冲燃烧可能性、燃烧模式及影响因素。乙烯脉冲燃烧实验表明,在稳定燃烧范围以外存在脉冲燃烧,并能够提供有效的脉冲推力。乙烯脉冲燃烧主要存在于来流空气总温较低的条件下;随着总温的提高,脉冲燃烧将进一步引起稳定燃烧;当总温很高时,乙烯直接稳定燃烧,没有观测到脉冲燃烧现象。煤油的实验表明,本文所用的脉冲式能量补充无法实现超临界煤油的脉冲燃烧,煤油的脉冲燃烧可能需要更多的热量和自由基。
The active cooling scramjet generally uses hydrocarbon as the fuel, but the hydrocarbon fuel has a long ignition delay and a stable combustion range, which urgently needs to be studied on a new method for igniting and stabilizing the fuel. Pulsed combustion may be a way to expand the working range of supersonic combustors, but no studies have been conducted in supersonic combustors. The pulsed spark plugs (5Hz, 50J / pulse) with simple structure were used to investigate the supersonic pulse combustion possibility, combustion mode and influencing factors of ethylene and supercritical kerosene in a 2.5-sdirect supersonic combustor. Ethylene pulse combustion experiments show that there is pulsed combustion outside the stable combustion range and provide effective pulsed thrust. Ethylene pulse combustion mainly exists in the lower total air temperature conditions; with the increase of the total temperature, pulsed combustion will further lead to stable combustion; when the total temperature is high, the direct combustion of ethylene combustion, did not observe the phenomenon of pulsed combustion . Experiments on kerosene show that the pulsed energy supplement used in this paper can not achieve the pulse combustion of supercritical kerosene. The pulse combustion of kerosene may require more heat and free radicals.