完全氧化DZ125的双向反射特性实验研究

作为燃气轮机的核心部件，涡轮叶片长期在上千度的高温下工作，为了保证叶片安全可靠地运行，需要对其温度进行实时的监测。辐射测温是目前涡轮叶片非接触式测温的主流方法，其测温精度与叶片材料反射特性关系密切，如何预测不同方向反射能量的大小，减小反射辐射对测温结果的影响是目前研究的难点。为了预测叶片反射能量大小，提高辐射测温的准确性，对涡轮叶片常见材料——完全氧化DZ125的双向反射分布函数(BRDF)进行研究。采用对比法作为实验测量的方法，先分析了BRDF对比法测量原理及数据处理方法，之后自主搭建了试验台，在温度分别为25, 900和1 100℃,波长分别为1 060, 1 550和1 908 nm的条件下，控制入射天顶角及反射天顶角在0°～60°范围变化，方位角在0°～180°范围变化，测量计算出了多组BRDF值，分析了各种因素对完全氧化DZ125的BRDF的影响。最后采用Modified Phong模型对BRDF测量值进行了拟合，并与实验测量结果进行了对比，得到了较好的结果。研究结果表明，温度、波长对完全氧化DZ125的BRDF影响较小，在涡轮叶片工作的温度范围变化不大，辐射波长变化不大时，...

Study on Reflection Characteristics of Completely Oxidized DZ125

As the core component of a gas turbine, the turbine blade works at a high temperature of thousands of degrees for a long time. In order to ensure the safe and reliable bladeoperation, its temperature needs to be monitored in real-time. Radiation temperature measurement is currently the mainstream method of non-contact temperature measurement of gas turbine blades. Its temperature measurement accuracy is closely related to the reflection characteristics of blade materials. The difficulty of current research isto predict the reflected energy in different directions and reduce the impact of reflected radiation on temperature measurement. In order to predict the reflected energy of the turbine blade and improve the accuracy of radiation temperature measurement, the bidirectional reflection distribution function (BRDF) of completely oxidized DZ125, a common material of turbine blade, is studied in this paper.The reference method is used as the experimental measurement method. Firstly, the measurement principle and data processing method of the BRDF comparison method is analyzed. After that, the experiment platform was built independently. Under the conditions of 25, 900 and 1 100 ℃ and wavelength of 1 060, 1 550 and 1 908 nm, the incident zenith angle and reflection zenith angle were controlled to change in the range of 0° to 60°, and the azimuth angle changed in the range of 0° to 180°. Several groups of the BRDF values were measured and calculated, and the effects of various factors on BRDF of completely oxidized DZ125 were analyzed. Finally, the modified Phong model is used to fit the measured values of BRDF. The fitting results can be accepted accordingto the comparison with the experimental results. The results show that temperature and wavelength have little effect on BRDF of fully oxidized DZ125. As long as the temperature range of the turbine blade and the radiation wavelength does not change strongly, the effect of both on BRDF can be ignored.The incident zenith angle, reflection zenith angle and azimuth angle greatly affect BRDF. The closer the incident zenith angle and reflection zenith angle are,and the closer the azimuth angle is 180°, the closer the position of the measuring probe is to the specular reflection direction. Then the specular reflection characteristics of the sample are more significant, and the BRDF is large. On the contrary, diffuse reflection dominates when the probe is far away from the specular reflection direction, and BRDF decays rapidly. The experimental results show that completely oxidized DZ125 has strong specular reflection characteristics. The modified Phong model fitting results show the bidirectional reflection characteristics of fully oxidized DZ125. This model is simple and suitable for using Monte Carlo simulation to predict the distribution of the total energy of DZ125 oxidation.It provides a theoretical basis for the subsequent study of the radiation temperature measurement of turbine blades.