The Research Of Level Set Method Application To The Inner Flow Field Simulation Of Solid Rocket Motor

The accurate prediction of the internal ballistic performance of solid rocket motors is of great significance to the engine design work.In solid rocket motors with large aspect ratios,the charge is prone to erosion combustion,and the burning rate of the charge wake increases.The internal ballistic parameters calculated using the parallel layer assumption have large errors with the experimental values,and considering the erosion combustion of the propellant in the calculation of the internal flow field of the engine operating process can predict the internal ballistic performance of the engine more accuratelyThis paper uses the level set method to calculate the non-uniform regression process of charge burning surface,analyzes the accuracy of the level set method to calculate the area of non-uniform regression burning surface,and combines the propellant erosion combustion model to calculate the internal flow field for the working process of solid rockets with different charge types,the main contents of the paper are as follows:The calculation procedure for non-uniform combustion surface regression is developed based on this combined level set method by modifying the re-initialization step of the level set method with the minimum distance function method.The calculation error of the procedure is kept within 3% for the special cases of tilt,depression and bulge.The feasibility of accelerating the calculation of the regression of three-dimensional burning surfaces of different grain shapes is analyzed,and the step interval of reinitialization can be enlarged appropriately in the case of parallel layer regression of burning surfaces,and for the case of non-uniform regression,the step interval of reinitialization should be limited to two time steps.Three propellant erosion combustion burning rate prediction models,Lenoir-Robiliard model,Guo Guangyun formula and Mukunda-Paul model,are applied to the level set method to numerically calculate the engine working process.The comparison with the experimental values shows that the Lenoir-Robiliard model is less accurate than the other two models and does not reflect the threshold phenomenon of erosive burning.The internal ballistic performance variation trend calculated by Guangyun Guo’s formula is the most similar to the experimental value,but the generality of the model is poor.although the Mukunda-Paul model sacrifices some calculation accuracy,the model excludes the influence of experimental coefficients as much as possible and is more general.The error of calculating the internal ballistic performance by the level set method combined with the Mukunda-Paul model is smaller than the error of calculating the internal ballistic performance by the minimum distance function method and the immersed boundary method.The calculation method of internal flow field in the working process of solid rocket motor is used to calculate the working process of star-shaped charge motor,finocyl charge motor and slotted tube charge motor.At the beginning of the engine working,the combustion effect of erosion is strongest,the burning rate of the charge increases,the burning surface of the charge column tilts to different degrees,and the pressure of the combustion chamber increases at the beginning of the engine working.The time of stable engine working stage is shortened,the trailing stage of pressure time curve appears earlier,the trailing stage lasts longer,and the internal ballistic performance of engine working process is significantly different from the theoretical prediction of parallel layer assumption.This paper analyzes the accuracy of the level-set method to calculate the working process of solid rocket motors with erosion combustion,and describes the effect of erosion combustion on the ballistic performance inside the engine,which provides a reference for the design of large aspect ratio engines.