碳氢燃料超声速脉冲燃烧实验研究

Pulse Combustion of Hydrocarbon Fuels in a Supersonic Model Combustor

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。

Hydrocarbon fuel is used in the regenerative cooled scramjet. Due to its disadvantages in ignition delay time and stable combustion range,it is desirable to develop new technology for igniting and stabilizing the hydrocarbon flame. Pulse combustion may be a potential method,but its study in the scramjet combustor has not been paid attention. In this work,pulse combustion of hydrocarbon fuels,ethylene and kerosene,in a Mach 2.5 supersonic model combustor was experimentally investigated using a pulse spark igniter(5Hz,50J/pulse) located in the center of a cavity,respectively. The results indicate that pulse combustion of ethylene exists outside the stable combustion range,which can provide effective pulse thrust. Pulse combustion of ethylene appears mainly at low air stagnation temperature. Pulse combustion can further induce the stable combustion with increase of air stagnation temperature. No pulse combustion is observed at high air stagnation. Pulse spark igniter in this work is unable to induce pulse combustion of supercritical kerosene,which maybe requires more energy and radicals.