超声速气流点火助燃用等离子体火炬的试验研究

Experimental Investigation on Plasma Torch for Supersonic Flowfield Ignition and Combustion

关键词:  等离子体火炬  超声速气流  纹影技术  发射光谱  激波

Key words:  Plasma torch  Supersonic flow  Schlieren technology  Emission spectroscopy  Shock wave

摘要:

对一种用于超声速气流点火助燃的高频率电弧等离子体发生器的工作特性进行了试验研究。首先采用CCD高速相机、光谱分析仪对静止空气条件下的等离子体喷射过程进行了试验，获得了不同种类、不同工作气喷注压力下等离子体射流的活性粒子种类和能量分布特性； 其次，采用纹影技术对超声速横向射流条件下的等离子体喷射流场结构进行了分析。研究结果表明，等离子体射流能量集中于等离子体射流的中心轴附近，并且在中心轴下游 2cm 左右达到了最大衰减。等离子体的喷注压力对等离子体射流的能量分布和光谱特性影响较大。当等离子体的工作介质为 N2 时，喷注压力由 0.3 MPa 增大至 0.5MPa，等离子体射流具有比较好的能量交换过程。通过光谱分析发现，氮气等离子体的组成是氮原子和氧原子，其强度随着与喷嘴距离的增大而减小，随着工作压力的增大而增大。等离子射流横向喷入超声速流场对主流的阻碍作用导致弓形激波的形成，它能有效促进活性粒子和来流的掺混过程。

Abstract:

The experimental study for high frequency arc discharge plasma torch designed for supersonic flow ignition and combustion enhancement was conducted. Firstly，the process of plasma injection into quiescent air was investigated through CCD high speed camera and emission spectrometry device. Plasma jet active particle information and energy distribution property were obtained under several working conditions: different working gas and different injection pressure. Secondly，the typical flow-field structure with plasma injection vertically into supersonic flow was analyzed by Schlieren technology. The results show that plasma jet energy is concentrated near the jet axis，which has the maximum attenuation in the downstream as far as 2cm from the outlet. The working gas and injection pressure have great effects on plasma energy distribution and emission spectrometry property. In the case of working gas as N2，when the injection pressure increases from 0.3 MPa to 0.5 MPa，the plasma jet shows better energy exchange performance. From emission spectroscopy，it is shown that plasma from nitrogen is mainly consisted of nitrogen and oxygen atom，whose intensity decreases with increasing distance from the nozzle，while it increases with the increase of injection pressure. When plasma is vertically injected into supersonic flow-field，its hinder function to mainstream results in the formation of the bow shock wave，which can enhance the mixing process of active particle and incoming air.