Numerical Study Of Particle Erosion In Solid Rocket Motor Nozzle

Ablation in solid rocket motors(SRMs)has always been a hot area of design and research.Ablation can be divided into three categories: the thermal-flow erosion,the particle erosion and the chemical ablation.In certain propellant charge forms or high-load working conditions,the particle erosion caused by the high concentration two phase flow usually dominates in the SRM nozzle ablation.In order to prevent launch failure caused by the damage of nozzle thermal protection layer during the working process of the SRM,and to provide some references for the nozzle design with little ablation,a study of particle erosion in the SRM nozzle has been carried out for better understanding of the position and extent of the ablation.The Fluent code was used to simulate the particle ablation in the SRM nozzle in this thesis.The Euler-Lagrange method was used to simulate the whole internal flow conditions and the particle distribution.The realizable k-epsilon model is used for the turbulent gas flow calculation,and the fixed walk DPM model was used to calculate the parameters of the condensed phase.The particle ablation model proposed by Oka was interpreted as an UDF program,which was imported into the Fluent software to change the conditions to calculate the ablation rate.The spring layer smoothing method was used in the dynamic mesh model because the ablation is relatively small.It is found that: the nozzle mass flow rate,particle size distribution,particle injection position and nozzle convergent angle all have relatively large influence to the particle ablation rate in the nozzle.The greater the nozzle mass flow rate,the more homogeneous the particle size distribution,the greater the ablation rate.The particles injected from the top face of the SRM cause larger ablation rate than the particles injected from the side faces,and the ablation rate is a maximum when the nozzle convergent angle is 45°.Mean while,the ablation process changes significantly over time.When the SRM ignites,the particles do not ablate the nozzle throat,but only the nozzle convergent section.Due to this ablation,the shape of the nozzle convergence section was changed,result in trajectory change of the particles,which will ablate the nozzle throat at some time after the SRM work.As time increases,the throat ablation become more and more serious,the ablation region become larger too.But when the ablation rate reaches a certain value,its changing rate will become slow.The results in this thesis will offer technique references for the thermal protection design of the SRM nozzle.