凹腔结构对超声速燃烧室中横向燃料喷流流动与燃烧的影响

Influence of cavity geometry on flow and combustion of transverse fuel jets in a supersonic combustor

在超声速燃烧室的壁面上安装具有不同长深比、深度以及后壁倾角的凹腔,在凹腔上游壁面横向喷注燃料射流。分别利用掺有丙酮蒸气的氦气和氢气模拟不燃烧和燃烧两种情况下的横向燃料喷流,利用平面激光诱导荧光技术分别对流场中不同截面上的丙酮和氢氧基进行成像,同时对不燃烧情况下的喷流流场进行了数值仿真。研究发现:凹腔结构主要通过影响由凹腔后壁高压区向凹腔前壁传播高压扰动的行为来影响凹腔内部的静压分布,从而影响燃料的流动过程;凹腔长深比减小、深度或后壁倾角增大都有助于高压扰动的前传,导致燃料不易向凹腔内部偏转以及进入凹腔的燃料质量减少;凹腔长深比和深度的增加可增大凹腔内低速回流区的范围,有助于增强凹腔内部的燃烧以及火焰稳定能力;凹腔后壁倾角对燃料燃烧的影响不显著。

Several cavities with different geometry parameters including the length-to-depth ratio （L/D）, depth （D） and aft ramp angle （θ） were placed inside a supersonic duct just downstream of the fuel injection port, respectively. A helium jet adulterated with acetone vapor and a hydrogen jet were employed to simulate the fuel jet under non-combusting and combusting conditions. Acetone and hydroxyl radical fluorescence images at different planes of the flowfield were imaged by the planar laser-induced fluorescence （PLIF） technique. The non-combusting flowfield was simulated numerically. The results show that cavity geometry parameters can affect the static pressure distribution in the cavity through influencing the transmitting characteristics of the high-pressure disturbance from the cavity back wall to the cavity front wall and then affect the flow of the fuel jet. Less LiD or deeper （ larger D） or steeper （ larger θ） cavities are helpful in transmitting the high-pressure disturbance that can cause the fuel not easy to turn to the cavity and prevent the fuel mass from entering the cavity. Larger LiD and deeper cavities can increase the range of the low speed back flowing regions in the cavity which can enhance the combustion in the cavity and the flame-holding ability. It seems that the cavity aft ramp angle has little influence on the combustion of the fuel.