在稀薄气流中用红外热图测量中低量值热流

在分析高高空热流测量需求基础上，针对高超声速飞行器稀薄气流地面试验热流量值小等特点，从满足模型壁面定常热流假设和一维半无限大假设条件、减小试验模型侧向导热误差和控制试验模型表面温升等方面分析了试验模型加热时间对热流测量的影响。其次选择较低热扩散系数模型绝热材料、采用瞬变平面热源法提高试验模型材料热物性参数标定精度、采用漫反射补偿等提高发射率测量精度等手段，提高中低量值热流测量精度。最后，在利用薄壁量热法获得模型表面热流时，测量MW/m2量级热流是把热电偶焊接在试验模型内壁面，而用红外热图及测量几kW/m2到几百kW/m2量级热流是测量模型外壁面热流，为了对这三者结果进行比较，在马赫数 Ma 为 12、试验总压 P₀ 为4.2 MPa、试验总温 T₀ 为700 K的试验状态下，用热电偶与红外热图同时测量了双锥薄壁模型不同点的热流，结果表明:红外测热结果与热电偶测量外壁面结果更接近，热电偶布置在外壁面位置所获得的热流大于布置在内壁面位置所获得的热流，模型加热时间对不同量值热流测量的影响是不同的。

Measurement of mid-low order of magnitude of heat transfer rate using infrared thermography in rarefied flow

Based on the analysis of demand for measuring heat transfer of hypersonic vehicle at high attitude, aimed at the characteristic of mid-low order of magnitude of heat transfer rate at ground test for simulating rarefied flow, various factors of the influence on measurement accuracy of mid-low order of magnitude of heat transfer were analyzed. Firstly, the influence of model heating time on heat transfer measurement was analyzed from reducing lateral error of experiment model to controlling temperature rise of model surface, which was based on a steady heat transfer of model surface and one-dimensional and semi-infinite hypothesis. Secondly, model adiabat materials with low thermal diffusivity were put to use. Transient Plane Source Method was introduced so as to calibrate thermal physical parameter(density, specific heat ratio and thermal conductivity) of model material with high accuracy. Kinds of method, such as diffusing compensation and phase-locked method, were adopted to raise measurement accuracy of model surface emittance. Finally, when using thin-wall calorimetry to obtain model surface heat transfer rate, thermocouple was welded on the inner surface of test model to measure heat transfer rate such as MW/m2 order of magnitude, while one was done on the outer surface of model to measure that with several kW/m2 to several hundred kW/m2 by thermocouple or by infrared thermography. In order to compare these results, on the experimental condition of Mach number 12, total pressure 4.2 MPa and total temperature 700 K, heat transfer rate at different points of the double cone thin-wall model was measured by thermocouple and infrared thermography simultaneously. The results indicated that the heat transfer rate measured with infrared thermometry was approaching to that done with thermocouple on the outer surface of model, that heat transfer rate by thermocouple on the outer surface of model was greater than that by thermocouple on the inner surface of test model, and that the influence of model heating time on the measurement of heat transfer rate with different order of magnitude was different.