辐射输运与功率损失对空气感应耦合等离子体流动特性的影响机理研究

In this study, the inductively coupled plasma (ICP) wind tunnel which is used to study the thermal protection system of aircraft in the aerospace field is taken as the research object. Regarding the incorrect flow-field simulation results under the low-pressure condition for the air ICP, we systematically study the mechanism of the influences of radiation transport and power loss on flow properties for air ICP. In our study, the energy transport, the inductive discharge, Joule effect and the internal energy exchange of chemical particles are fully simulated on the basis of the coupling among radiation-field, electromagnetic-field, chemical-field and thermodynamic-field with the consideration of flow power loss. The modeling accuracy of the flow can be highly improved. Finally, the flow-field properties such as the radiation heat flux density, particle density, temperature, velocity, electric field, Lorentz force, power loss, thermal efficiency etc. can be obtained for the 10kW, 110kW and 1.2MW ICP wind tunnels. Through the comparative cases, we analyze the influence of radiation heat transfer and power loss on the temperature distribution, conductivity distribution, Lorentz force distribution for air ICP. The mechanism of the effects of radiation transport and power loss on heat transfer, the electron generation, thermal motion and the flow characteristics can be made clear for the air ICP. In addition, the main species and the wavelength range of air which dominate the radiation heat transfer, and the key factors that affect the thermal efficiency for the air ICP can be revealed. The present study can provide high precision and low cost computing tools for the development of aircraft thermal protection systems.

本课题以航天领域中研究飞行器热防护系统的感应耦合等离子体（ICP）风洞为研究对象，针对低压空气ICP仿真流场失真问题系统地研究辐射输运与功率损失对空气ICP流动特性的影响机理。研究中，基于辐射场-流场-电磁场-化学场-热力场多场耦合，并考虑气流功率损失，全面模拟空气ICP的能量转化、感应放电、焦耳效应、粒子内能交换等过程，全面提高流场模拟精度。最终准确获得10kW、110kW与1.2MW级ICP风洞内气流的辐射热流量密度、粒子数密度、温度、速度，电场，洛伦兹力，功率损失、热效率等。通过对比算例，分析辐射传热与功率损失对空气ICP的温度分布、电导率分布、洛伦兹力分布等的影响，阐明辐射输运与功率损失对空气ICP热量传递、电子生成机制、粒子热运动和流场特性的影响机理，揭示主导辐射传热的粒子种类及波长范围，阐明影响空气ICP热效率的关键因素。为开发飞行器热防护系统提供高精度低成本的计算工具。

本项目以感应耦合等离子体（ICP）风洞为研究对象，通过流场-电磁场-化学场-热力场-辐射场多场耦合模型研究辐射传热与功率损失对ICP流动特性的影响机理，最终准确获得10千瓦、100千瓦和1.2兆瓦级ICP风洞典型工况下空气等离子体的电子温度、粒子数密度、洛伦兹力、焦耳加热率、速度、压强、电场强度、辐射热流量密度等的分布规律，为开发再入飞行器热防护材料提供基础数据和理论指导。通过研究发现：洛伦兹力对感应线圈区空气粒子的动量传递和电子热运动起着控制作用，且径向洛伦兹力的最大值比轴向洛伦兹的峰值高10.5倍；电场强度虚部的最大值比其实部的峰值大2.9倍，负的电场虚部主要由外加高频电流产生，而正的电场虚部则是由等离子体内部自由电子产生；主导ICP辐射传热的粒子为N原子和O原子；以100千瓦ICP风洞为例，通过辐射与导热传递到石英管壁面并散失的热量占面板输入功率的18.5%；高频电路的功率损失占输入功率的46.4%，它是总功率损失的主要部分；等离子体最大温度随工作压力的增大而减小；当放电管直径增大时，感应线圈区等离子体气流的最大温度减小。