Numerical Simulation Of The Nozzle Ablation Process In Solid Rocket Motors

Solid rocket motors have important applications in human exploration of deep space and military fields.As the core device of the engine,the nozzle is the most important part of the engine design.Due to the extremely harsh working environment,the nozzle ablation problem has been widely concerned by scholars at home and abroad.Previous scholars mostly used steady-state calculations for numerical simulation of nozzle ablation,ignoring the effects of thermal conductivity and profile changes of the nozzle wall.The purpose of this paper is to use the transient simulation method to comprehensively consider the heat transfer and mass transfer between the solid wall of the nozzle and the gas,and the effect of changes in the shape of the inner wall of the nozzle on the ablation of the nozzle,and to study the ablation process of the engine nozzle..In this paper,the numerical simulation method is used to study the ablation process of the 70-lb BATES engine nozzle based on the FLUENT software.The transient calculation of the thermal chemical ablation of the carbon-based nozzle is performed,the main part is the chemical reaction between nozzle wall and the oxidizing components H₂O?CO₂.On this basis,the heat transfer between the gas and the solid wall is considered,and the effects of the incoming flow temperature,pressure,and radiation heat transfer on the ablation performance of the nozzle are discussed.In order to study the effect of wall surface ablation in the ablation process of the nozzle,a dynamic mesh method was used.First,the flow field was calculated,the ablation amount of the nozzle was calculated by the flow field information,and then though the calculated ablation amount of the nozzle,the grid node of the nozzle wall is controlled by the user-defined macro“DEFINE_GRID_MOTION”;the two-way coupling calculation of the movement and flow field of the moving grid node is realized,that is,the flow field determines the retreat of the grid node,and the node retreats again.In turn affecting the distribution of the flow field,the calculation simultaneously considers the influence of the product generated by the wall ablation on the flow field enhancement.Through dynamic mesh technology,nozzle ablation calculations under different working conditions?15%and 21%aluminum-containing propellants?were performed.The numerical simulation of the nozzle profile,the pressure field in the nozzle and the change of the thrust of the nozzle caused by ablation was realized.The results showed that due to the presence of ablation,the nozzle profile will shift during operation.This shift will occur mainly at the converging section and the throat of the nozzle.The small changes in the size of the throat will directly affect the distribution of flow field and interior ballistic characteristics in the motors.