The Research Of Model Skin Friction Measurement Technology In Hypersonic Wind Tunnel

The skin friction takes a large proportion in total drag force for hypersonic vehicle,and its precise measurement is one of the key technical problems which must be peremptorily solved for the development of modern hypersonic vehicles.MEMS skin friction sensor is very important to development of hypersonic vehicles and investigations on various phenomena and problems of hypersonic flows.MEMS skin friction sensor has not been successfully applied to measure hypersonic skin friction.There are still many problems must be studied.This project will systematically research on direct measurement principles and methods of hypersonic skin friction,review the influences of direct measurement based skin friction sensor on aerodynamic performances of measured surface,and provide novel measuring methods and sensing structures of MEMS-based hypersonic skin friction measurement.Based on the existing sensing structure,design theory and key fabrication techniques of MEMS skin friction sensor will be researched,MEMS skin friction sensor prototypes will be developed,and the sensor prototypes will be calibrated.The main works of this paper are listed as below.Through the review of the literature to grasp the development status of domestic and foreign skin friction measurement technology,expounds the urgent needs of reduction of skin friction measurement of hypersonic vehicle,the applicability and feasibility of skin friction measurement using MEMS technology have been advanced.The skin friction mechanism is introduced and numerical simulation on the flow of flat and aerodynamic characteristics of hypersonic MEMS skin friction sensors are carried out.Skin friction measurement range of flat model,vertical load 100 Pa and resolution ratio 1Pa are obtained.The effects of the gap of sensor floating-element and different horizontal position between floating-element and shell are studied.The conclusion could be used for the reference of the skin friction sensor design.The structure and working principle of the skin friction sensor are described,the digital interface is designed,and detection of weak capacitance is realized.MEMS skin friction sensor prototypes are made.Calibration test is carried out to verify the performance of MEMS skin friction sensor.Calibration data and theoretical analysis results are compared to evaluate the sensor performance.The results show that the novel MEMS skin friction sensor prototypes' measurement range are 100 Pa,and resolution ratio are 1Pa.Most of them have the advantages of high sensitivity,stable and static response linearity are higher than 2%,repeatability precision are better than1.5%.Verification testing of MEMS skin friction sensor is conducted in the ?0.5m hypersonic wind tunnel.Through two stages repeated test and high kinetic pressure test.Better prototypes are used in repeated test;the test repeatability precision of 6# skin friction sensor prototype is 1.38%;the sensor's structural strength and sensitivity meet the design requirements in the high kinetic pressure test.This thesis developed a technique of skin friction measurement based on MEMS sensor,research results show that the structure and working principle of the skin friction sensor are able to apply to hypersonic wind tunnel;MEMS friction sensor prototypes have the advantages of fast response,high sensitivity,stable and reliable,which meet the needs of skin friction measurement experiment.