Design And Research Of A Dynamic Calibration System For Visual Shock Tube

As an important measure to evaluate the damage power of weapons and ammunition,testing for shock wave overpressure has received more and more attention,and it is very important to improve the precision of testing.Shock tube is often used as a calibration device for shock wave overpressure because of its good step pressure signal.At this stage,shock tube is only used to calibrate pressure sensors dynamically,and it is impossible to observe the variation of flowing field of shock wave around sensors.There are many different shapes of pressure sensors in free field such as pen,rod and disc.Obviously the flowing linearity of different structures and different installation angles is different,and it will have a certain impact on the testing results of shock wave overpressure.In order to improve the precision of calibration for pressure sensors in free field,it is necessary to analyze the variation of flowing field of shock wave.So in this paper,a dynamic calibration system for visual shock tube is designed to record the changes of pressure value and flowing field of shock wave at the same time.The main research work is as follows:?1?To analyze the flowing relationship of gases in the shock tube,the influences of different kinds of gas sources such as the air,N₂,CO₂ and H₂ on shock wave are compared by theoretical calculations and experimental tests.It is found that different kinds of gas sources can only affect the pressure amplitude of shock wave,and cannot affect the dynamic characteristics index.Using the relationship between the maximum duration of constant flowing and the position of gases in the shock tube,the calculation method of optimal length for the high and low pressure regions of shock tube is deduced.?2?In order to realize the visualization of shock tube,an optical observation system combining a schlieren apparatus and a high-speed camera is designed.In order to ensure that the images of flowing field are not distorted,a plane observation window is designed.Therefore,the installation area of sensors in the low pressure region?2m at the end?is designed as a square tube,and the square tube and the front-end cylindrical tube are connected in an external manner.The rationality of the design is verified by numerical simulation.?3?A set of test subsystems of calibration system for shock tube is designed,mainly including:speed measuring subsystem and pressure measuring subsystem.The systematic errors are analyzed by the actual test,and the measurement error of the system is within 1%.?4?Before the actual shock tube platform has been built,the numerical simulation of different shapes and different installation angles of sensors is carried out by using the theoretical basis of fluid mechanics,which provides a reference for the construction of the actual platform,and has a certain guiding role in the follow-up platform calibration test.