Design Of Rocket Engine Plume Field Data Acquisition And Temperature Field Reconstruction System

The distribution of parameters such as temperature and gas component concentration in the plane of the rocket engine plume field has important reference value for establishing a reasonable propellant combustion model and evaluating and optimizing the performance of the rocket engine.Rocket engine plume field belongs to a special combustion flow field,with high temperature,high speed,and turbulent dynamic characteristics,traditional contact measurement methods can no longer meet the measurement needs of engine plume field.Tunable semiconductor laser absorption spectroscopy tomography(TDLAT)has the advantages of high sensitivity,fast response,and strong real-time performance,and can realize real-time monitoring of two-dimensional information such as temperature and gas component concentration in the plume field.Taking the rocket engine plume field monitoring system based on TDLAT technology as the practical application background,this paper aims to design a multichannel synchronous data acquisition system for plume field laser spectral data acquisition for the part of data acquisition and temperature field reconstruction in the system,and solve the problem that the existing data acquisition system cannot be directly applied to the plume field monitoring system.A temperature field reconstruction method is studied to realize the reconstruction of the temperature field in the upper software according to the collected data and solve the problem that the traditional reconstruction method cannot realize real-time monitoring of the temperature field due to the long time resolution.The specific work content of this article is as follows:(1)According to the measurement principle of TDLAT technology and the composition,technical indicators,and workflow of the plume field monitoring system,the technical indicators of the plume field data acquisition and temperature field reconstruction system were determined,and the overall scheme of the system was designed.(2)In order to solve the problem of mismatch between the existing data acquisition system and the plume field monitoring system,a set of multi-channel synchronous data acquisition systems dedicated to the plume field monitoring system is designed.According to the workflow of the plume field monitoring system and combined with the system design scheme,eight serial output ADCs with a resolution of 16 bit and a sampling rate of 1MSPS were used to design an 8-channel synchronous data acquisition module with "FPGA + ARM" as the control core.The data sampling logic,shift logic,and data storage logic are designed inside the FPGA,and the data cached by the dual-port RAM inside the FPGA is read by ARM and transmitted to the host computer through the Ethernet interface.By adopting the synchronous trigger method,two data acquisition modules are used to realize the synchronous acquisition of 16 laser spectral data.(3)Aiming at the problem that the time resolution of traditional reconstruction methods is too long,a temperature field reconstruction method based on the algebraic iteration(ART)algorithm is studied.Combined with the workflow of the rocket engine plume field monitoring system,the temperature field reconstruction model was established,and the implementation process of the ART algorithm was analyzed.According to the practical application background,the influence of different meshing numbers on the reconstruction effect of the ART algorithm was studied through numerical simulation,and the number of meshes was determined to be 15×15according to the index requirements of the system.Combined with the characteristics of data uploaded by the data acquisition system and the temperature field reconstruction model,the temperature field reconstruction upper computer software was designed.(4)The functions and indicators of the rocket plume field data acquisition and temperature field reconstruction system were tested and analyzed.Firstly,the data acquisition system is calibrated and analyzed by error,and the function of data acquisition is verified,and the experimental results show that the DC measurement accuracy of each channel of the data acquisition system is less than 0.03%.Then,the system designed in this paper is installed in the rocket engine plume field monitoring system,and the high-temperature flow field generated by the flat flame burner is used as the measurement target,and the plume field data acquisition and temperature field reconstruction experiments are simulated,and the functions and some indicators of the system are verified.The temperature field reconstruction results are compared with the B-type thermocouple measurement results,and the line means a relative error of the temperature field reconstruction is calculated.The average relative errors of the lines measured in the 1000 K temperature plane and 1800 K temperature plane were 2.72%and 1.31%,respectively,and the time resolution was 400ms～500ms,which met the requirements of the system index.