Study On Measuring Technology Of Rarefied Aerodynamic Heating In Wind Tunnel

With the rapid development of the hypersonic flight vehicle nearing space,the aerodynamic heating of flight vehicle in transitional flow are getting more and more attention.The wind tunnel experiment is an important means of research about rarefied aerodynamic heating in hypersonic low density Wind tunnel.In the second chapter,infrared thermography technology is improved.Such problems as surface temperature measurement under great measurement angle,the measurement accuracy,the corresponding relation between model spatial coordinates and the pixels etc.,are studied in heating rate measurement by infrared thermography.As a result,the solutions to the problems will push forward infrared thermography to the engineering and practical application.Then,the common thin-skin calorimeter design was introduced and modified according to the measurement requirements of new wind tunnel's model,which led to a novel variable-thickness thin-skin temperature measurement structure.The variable-thickness thin-skin structure depressed effectively the lateral heat conduction losses due to the temperature difference between the thin-skin and the surrounding shell during long-time test,therefore a longer effective measurement time was obtained.Heat flux data was obtained using a one dimensional heat flux identification method based on the variable-thickness thin-skin flight data,which improved the response time in comparison with the thin-skin calorimetric method.In the third chapter,the hypersonic low density wind tunnel,infrared camera and other equipment are introduced.The operating principle of wind tunnel is described.The Knudsen simulation criteria are introduced and analyzed.To validate these above-mentioned techniques,a sphere-cylinder model is measured using infrared thermograpy and thermocouple.The test data is compared with the result obtained by theoretical calculation method.The two results are agree well with each other.The studies are summarized and some improved and optimized methods are given at last.Then the author carried out the infrared image processing software debugging through XX model wind tunnel experiment.At last,the flight test results measured with the variable-thickness thin-skin calorimeter are analyzed.The thin-skin calorimeter structure was proved reliable by the flight test.In this paper,a complete infrared thermography technology system for low density wind tunnel is established.This system can control the test quality effectively.On the other hand,a novel variable-thickness thin-skin calorimeter for hypersonic low density wind tunnel was developed.A longer effective measurement time can be obtained using this new structure calorimeter.Both of these technologies are used in china for the first time and have innovative above.