等离子体对超燃燃烧室凹腔性能影响的数值研究

Numerical Study of Effects of Plasma on Performance of Scramjet Combustor Cavity

关键词:  超燃燃烧室  等离子体  凹腔  输入电功率  数值模拟 

Key words:  Scramjet combustor  Plasma  Cavity  Electrical input power  Numerical simulation

摘要:

在超燃燃烧室凹腔上游及其底部近前壁面处布置电极产生丝状等离子体,基于准直流电弧放电热阻塞原理,采用数值模拟方法研究了等离子体对燃烧室均温、凹腔均温、剪切层、凹腔阻力以及质量交换率的影响。结果显示:等离子体对燃烧室整体的温升效应可以忽略,但能够明显提高凹腔内平均温度；受丝状等离子体对凹腔的预热及对剪切层的“切割”作用,剪切层中沿流动方向的涡强度降低,从而降低了凹腔前缘及后缘撞击激波强度,使其附近压力分布更平滑；丝状等离子体存在时,凹腔阻力系数明显下降,质量交换率也大幅提高,但增大等离子体输入功率对改善控制效果的影响不明显。 

Abstract:

The quasi-DC discharge plasma filament actuator electrodes were located near the upstream of the back-wise wallstep and at the bottom of the cavity. The effects of plasma on the scramjet combustor cavity including the mean temperature of combustor and cavity, shear layer, cavity drag and mass exchange rate were numerically investigated based on the dominant thermal blocking mechanism. The results show that when plasma works, the temperature in cavity increases obviously but the whole combustor flow field is not impacted. Because of the pre-heating effect in the cavity and the ‘Cut’ effect on the shear layer due to the plasma filament, the movement of vortex in shear layer along streamwise is blocked, which leads to that the leading edge shock waves are weakened and so do the shock waves from the rear wall induced by the shear layer, thus the pressure distribution appears more smoothly around the cavity. The cavity drag coefficient drops apparently while the rate of mass exchange increases a lot due to plasma filament. As the electrical input power increases, the control effect is not improved further markedly. 