发射光谱诊断电弧加热器漏水故障的试验研究

电弧加热器是飞行器热防护系统地面考核试验的首选设备。电弧加热器在运行时，由于其电极工作在高温环境，普遍采用高压水进行冷却，试验中存在着由于电极烧穿漏水导致加热器严重烧损的风险。由于高温气流的恶劣环境，目前尚无有效监测手段。本文作者建立一套以氢原子Hα（656.28nm）和氧原子（777.19nm）发射谱线作为目标谱线的发射光谱监测系统，通过分析电弧加热器故障条件和正常运行下高温流场中的发射光谱特性，诊断某高焓电弧加热器因烧蚀出现的电极漏水故障，并在考虑温度误差的前提下对该光谱测量系统测量灵敏度进行评估，获得了A、B两种试验状态下的漏水探测极限:A状态下约为1.85～0.94g/s；B状态下，2.12～0.98g/s。试验结果表明，发射光谱应用于电弧加热器漏水故障诊断是切实可行的。

Experimental study on leak detection of cooling water in arc heater based on emission spectroscopy

High-enthalpy arc heaters play an important role in the development of thermal protection materials and heat shield structures for entry vehicles because they are capable of producing longtime and representative flow environments. Owing to the large heat flux loading on the electrode, the erosion of the electrode is inevitable. Generally, high pressure water is used for cooling of the electrode. The arc heater may suffer serious damage caused by electrode leak, especially for hundreds or even thousands of seconds aerodynamic heating tests. Therefore, it is necessary to develop fast response diagnostic technique to monitor the operating status of the facility and determine the initial time of water leakage to avoid costly arc-heater failure. Because of the extreme conditions inside the arc-heater section, options for measurements of the test gases are limited, and optical spectroscopy-based measurements present a diagnostic opportunity. Optical Emission Spectroscopy (OES) is widely used for measuring gas parameters of high-temperature flow field because it is non-intrusive, high sensitive, and just constituted of simple instruments. In our studies, the 656.28 nm emission spectral line of the atomic hydrogen and the 777.19 nm emission spectral line of the atomic oxygen are utilized for routinely in situ monitoring the operating status and determining the initial time of water leakage at a high-enthalpy arc heater. According to the intensity ratio of the two emission spectral lines, the mass fluxes of the water leakage can be derived, which are 1.85~0.94g/s and 2.12~0.98g/s, corresponding to equilibrium temperatures equal to 6000~8000K and 5500~7500K under two different test conditions, respectively. The current test results of this study illustrate the feasibility and potential of the OES technology in high-enthalpy arc heater safety diagnosis, especially on the water leakage diagnosis.