Design Of Transient Thermal Liquid Crystal Calibration System And Multi Factor Error Analysis Of Temperature Measurement

In order to obtain higher thermal efficiency of gas turbines,the inlet temperature of turbine blades is getting higher and higher,and the working environment is getting worse and worse.To ensure the safety operation of the gas turbines,it is necessary to understand the temperature distribution and heat transfer in the high temperature region,so as to take effective cooling measures.Because of its unique characteristics,thermal liquid crystals have been widely used in the research of heat transfer.But in China,only a small number of units and universities engaged in this area.Thermal liquid crystal presents color-temperature monotony in a certain temperature range.The heat transfer coefficient can be obtained through the one-dimensional semi-infinite plate heat conduction equation and it has important practical significance in heat transfer experiments.Therefore,it is important to analysis the regular between color and temperature of thermal liquid crystal,and the factors influencing the color display.So as to learn the method to reduce the experimental error and optimize the cooling structure of turbine blades.In this paper,the narrow band SNP100/R39C1W thermal liquid crystal was used as research object,the uncertainty of heat transfer coefficient was analyzed by theory,and the characteristics and influencing factors of thermal liquid crystal was researched by means of experiments.Studied the heat transfer characteristics of the smooth channel experiment units,which was made of methyl methacrylate.Specific research contains the following several aspects:1.The heat transfer experiments of thermal liquid crystal is based on digital image processing technology.Firstly,the color changing principle,color space theory,heat transfer experiment principle,the relationship between calibration experiment and heat transfer experiment was discussed.Calculation shows that the experiment section's thickness meet the heat penetration time requirements,so the technology of transient thermal liquid crystal can be used in this paper.2.The theory of transient thermal liquid crystal technology is one-dimensional semi-infinite plate heat conduction equation,theoretical analyzed the uncertain of heat transfer coefficient E_h,and gives the appropriate experiment temperature T_m,in order to improve the experiment accuracy.3.The principle of thermal liquid crystal calibration experiments is to form a linear temperature gradient distribution,and recording different temperature corresponding color information.The numerical calculation showed that the self-designed aluminum calibration block meets the requirements.Designed and built calibration test bench,and studied the influence factors on the characteristic curve,including fine processing,coating thickness,camera shooting angle,light source intensity and placing time.4.Designed and built the heat exchanging test bench,introduced experimental equipment,experimental process and matters needing attention.The self-designed welder-wire mesh heating system can raise the temperature above 60?in seconds,and meets the requirements of transient experiment.5.The calculation area of the same size as the experimental piece is established.Based on the selection of turbulence models and the verification of grid independence,the results of heat transfer experiment and numerical calculation are compared and analyzed.Because of manufacturing error,assembly accuracy and other reasons,there exists lower heat exchange area on the surface.With the increase of Re,Nu increases,and the relative error of Nu obtained by experiment and numerical calculation also increases.