恒流式射频辉光放电等离子体高超声速流场测量机理及方法研究

With the significant advantages of small spatial volume, high frequency response, no temperature compensation, high signal to noise ratio and easy to calibrate, plasma anemometer becomes one of the most promising approach for hypersonic flow measurement, especially for the researching of the hypersonic boundary layer turbulence characteristics. In view of the key limitations of existing plasma anemometer, research works based on the constant current radio frequency glow discharge plasma anemometer are planned to be carried out as followings: Researching on coupled affect mechanism between the hypersonic flow and radio frequency glow discharge plasma; Solving the real-time control method that could realize the const loop current of the radio frequency discharge in the environment of dynamic flow field; Studying on the method for extracting and processing the signal of constant current radio frequency glow discharge plasma anemometer. The theoretical model of the measurement method will be established, meanwhile, the approaches for enhancing the stability of radio frequency glow discharge and improving precision for the feature extracting are proposed, meanwhile, the method for plasma anemometer based on the radio frequency glow discharge is achieved, which could be applied in the hypersonic flow field at Mach 5 and the frequency response of the plasma anemometer could be more than 500Hz.

等离子体风速计具有空间分辨率高、频响高、无需温度补偿、信噪比高、校准方便等显著优势，是目前高超声速流场实验研究颇具前途的测量方法之一，特别适用于高超声速边界层湍流特性研究。本项目以恒流式射频辉光放电等离子体风速测量机理与方法为对象，针对制约其发展的关键问题开展如下研究工作：高超声速流场及射频辉光放电等离子体耦合作用机理研究；动态流场下射频辉光放电等离子体回路电流恒定实时控制方法研究；恒流式辉光放电等离子体风速测量系统信号提取及处理方法研究。建立辉光放电等离子风速测量的理论模型，增强辉光放电等离子体风速计工作稳定性并实现高精度流场特征信号提取，获得可用于5马赫流场、500Hz以上带宽的射频辉光放电等离子体风速测量方法。

目前， 高超声速研究在航空航天领域的地位日益显著，已经成为各个强国争相占据的制高点。而湍流是高超声速研究中最为棘手的问题之一，急需一种高精度、应用范围广的流动测量技术，以便明确高超声速流体的湍流边界和转换机制，建立准确湍流模型。一种基于射频辉光放电的等离子体风速测量技术具有动态响应高、信噪比高、结构紧凑等诸多优势，满足高超声速流体测量要求。本项目以辉光放电等离子体风速测量技术为研究对象，针对制约其发展的关键问题开展了如下工作：气体流场与射频辉光放电等离子体耦合作用机理研究；动态流场下辉光放电等离子体风速测量数值仿真与电学建模研究；辉光放电等离子体风速测量实验研究。搭建出了等离子体风速测量数值仿真平台与实验系统，开展了相关的仿真与实验研究，此外，建立了实验系统的电路模型，进行了电学建模。通过仿真结果发现：射频条件下，负载放电间距越小且放电频率在2MHz-3.56MHz之间时，测量效果较好。通过实验结果发现：负载电压或电流有效值均与风速值有着良好的线性关系，都可用于风速的标定。本项目取得的成果能够促进等离子体风速测量技术的推广，并加快等离子体风速计的实用化进程。