Research On Ultrasonic Temperature Measurement System Based On Acoustic Tomography

As an important part of rockets,missiles and aerospace vehicles,monitoring the temperature distribution characteristics of rocket engine tail flame is helpful to analyze the combustion performance of fuel and the uniformity of power distribution.It is of great significance to the research and development and finalization of rocket power system.However,the tail flame of rocket engine has the characteristics of high upper temperature limit,fast change process and difficult to obtain the internal temperature distribution characteristics.Aiming at these problems in the process of measuring the temperature of the tail flame,this paper proposes a temperature field measurement scheme based on acoustic tomography technology,which mainly completes the following work:Firstly,this paper studies the basic theory of acoustic tomography technology,and analyzes the echo extraction algorithm and two-dimensional field reconstruction algorithm that affect the accuracy of temperature measurement.The key design scheme of temperature measurement system is demonstrated,including sensor layout scheme and embedded control system scheme,and the overall implementation method of the system is described.Secondly,in order to realize the accurate measurement of high-temperature tail flame in the interference environment,this paper optimizes the hardware transceiver circuit,including signal driving circuit,multi-level amplification circuit,band-pass filter circuit,etc.,and designs the driving and control functions on FPGA + arm heterogeneous system.Then,in order to capture the transient temperature characteristics of the high-temperature tail flame temperature field,the non blocking transceiver timing is studied in order to reduce the minimum time delay and improve the response rate of the temperature acquisition system.A multi-channel data acquisition unit is designed to receive multi-channel ultrasonic echo data.In order to enhance the portability and expansibility of the function of the temperature measurement system,the Linux operating system is integrated in zynq,the DMA kernel driver is designed,the acquisition and transmission control program is designed,and a great quantity of echo data is uploaded to the computer through the high-speed transmission interface.Finally,the cross-correlation algorithm with high precision and strong noise suppression ability is used to extract the flight time of ultrasonic driving signal and echo signal,and the reconstruction effect of two-dimensional temperature field is simulated and tested by the least square method.The acquisition accuracy and error of the temperature measurement system are analyzed by comparative experiments.The test results show that the acoustic tomography temperature measurement system has the characteristics of wide temperature measurement range,fast response rate and the preferable ability of noise suppression,and can retrieve the section temperature details of combustion tail flame through two-dimensional field reconstruction algorithm.It provides a feasible solution for the measurement of rocket plume temperature field.