【作者】 韩振兴；

【导师】 刘石；

【作者基本信息】 中国科学院研究生院（工程热物理研究所） ， 工程热物理， 2005， 博士

【摘要】 作为一种有效测温手段,热敏液晶测温技术在国外已被大量应用于传热领域的研究。在国内这项技术处于起步阶段。热敏液晶测温技术具有测量精度高、响应速度快、适合对流换热面温度测量等优点。在本文中,以美国Hallcrest公司生产的SPN/R35C10W型可喷涂热敏液晶材料为基础,建立了基于色调技术的热敏液晶定量测温系统,并把其应用于平板气膜冷却实验中。 热敏液晶所呈现色彩的色调与温度之间的关系可以用六次多项式进行拟合。经误差分析测量精度在95%置信区间内可达0.8℃。实验研究表明相机轴线和待测平面法线之间夹角是影响标定数据分布的重要因素,在央角小于30°的条件下,可以忽略其带来的影响。在有效测温区间内,不同的光强条件对标定数据的影响可以忽略,光强设定应以取得良好色彩呈现效果为佳。热敏液晶在重新喷涂或者放置一段时间后,为提高测量精度应对其进行重新标定。 气膜冷却是燃气轮机涡轮叶片的一种重要冷却方法。在建立平板气膜冷却实验台的基础上,应用热敏液晶测量技术测量射流孔下游的壁面温度分布。本文中讨论了不同吹风比、不同射流孔长径比、不同射流注入角、不同复合角条件等因素对射流孔下游冷却特性的影响。绝热气膜冷却效率被作为衡量不同条件下气膜冷却性能优劣的重要参数。 在低吹风比条件下,与主流相比,射流动量较低。受主流影响,射流容易贴附在射流孔下游表面,射流孔近孔区域取得良好的冷却效果。高吹风比条件下,由于射流动量较高,在冷却孔下游容易发生“吹离”和“再附”现象。在低射流孔长径比条件下(L/D=2),由于射流未能在孔内充分发展,不同吹风比条件下射流孔下游冷却效率等值线的分布特点相似。通过设置不同的射流注入角条件来考察不同垂直方向速度分量对射流孔下游冷却特性的影响。即使在只有垂直方向速度的条件下,低吹风比时冷却孔下游近孔区域等值线依然呈现锥形分布的特点。高吹风比条件下,等值线近似直线分布。通过引入不同复合角考察在存在横向速度分量的条件下对射流孔下游冷却特性的影响。实验结果显示复合角条件下的冷却性能要优于简单角条件,孔间区域获得了较好的冷却效果。更多还原

【Abstract】 As an effective method of temperature measurement, liquid crystal thermography has been widely used in the field of heat transfer in many developed countries. This technique is just at the beginning of its applications in our country. It has the following advantages: high accuracy, fast response to temperature variations, suitable for temperature measurement on convective surface, etc. In this paper, a system of quantitative temperature measurement is based on the definition of hue. The type of the sprayable thermo-chromic liquid crystal for the experiment is SPN/R35C10W, made by Hallcrest Company in USA. This temperature measurement system is applied in the experiments of film cooling on flat plates for the first time interiorly.The relation between the hue of the color of the thermo-chromic liquid crystal and the temperature can be fitted with a six-order poly-nominal function. An error analysis shows that the measurement accuracy can be 0.8° C in the 95% confidence region. The calibration data show that the visual angle is an important factor to influence the calibration curve, however, this effect can be neglected when the visual angel is smaller than 30°. In the valid measurement region of temperature, light intensity has little effect on the calibration data, thus it can be set to achieve the best color appearance. The thermochromic liquid crystal should be re-calibrated when it is re-sprayed or deposited for a period of time.Film cooling is an important measure used to protect the blade in gas turbines. We configure our experimental setup of film cooling on flat plates, and utilize thermo-chromic liquid crystal to measure the temperature distributions downstream of the injection holes. In the thesis, we discuss the influences on film cooling brought by different blowing ratio, different injection hole length to diameter ratios, different injection angles and different compound angles. The adiabatic film cooling effectiveness is regarded as an important parameter to weigh the cooling performance at different experimental conditions.At a low blowing ratio, the secondary injection flow has low momentumcompared to the mainstream, so it is easily suppressed by the mainstream to a region near the cooper plate surface. Better cooling performance can be achieved in the region immediately out of the injection holes. When the blowing ratio increases, the phenomenon of "blowing off’ and "re-attachment" happen downstream of the injection holes. At a low hole length to diameter ratio (L/D=2), the air flow cannot fully develop in the hole. The distribution characteristics of the adiabatic film cooling effectiveness are similar at different blowing ratios. The effect on the cooling performance due to different vertical velocity component is considered through experiments with different injection angles. The results show that the isolines still appear in a taper shape in the nearby region of the injection hole at a low blowing ratio when only vertical velocity exists, and the isolines change to near beelines at high blowing ratios. Different lateral velocity component can be produced through the introduction of compound angles. Its effect on film cooling is studied through experiments at three compound angles. The results indicate that a proper compound angle can yield better cooling performance than that of a simple angle. The regions between holes receive better cooling.更多还原