Study On Condensed Phase Flow State In Solid Engine Nozzle

The internal flow field of modern solid rocket engines is a typical two-phase flow,and the calculation and analysis of two-phase flow in the nozzle has always been one of the focuses of engine performance research.However,the condensed phase products generated by solid propellant combustion exhibit polymerization and phase transition phenomena in the flow process inside the nozzle.Therefore,it is of great significance to understand the performance of the engine and analyze and study the condensed phase flow process inside the engine nozzle.This article will study the polymerization and phase transition process of condensed alumina particles in the nozzle of a solid rocket motor.Firstly,conduct experiments to measure the transmittance of solid rocket motor plumes and the parameters of condensed particles,measuring the total pressure of the engine,average temperature at the nozzle outlet,and particle size distribution.The measurement results indicate that the higher the total pressure,the higher the average temperature at the nozzle outlet.The temperature of the gas in the combustion chamber continuously decreases through the nozzle,but remains above the melting point temperature of the alumina.The measurement results of the particle size distribution at the nozzle outlet show that the particle size distribution of condensed phase in the engine plume presents a bimodal distribution distribution,and the increase of the engine total pressure will make the overall particle size distribution smaller.The thermal calculation method was used to calculate the high-energy propellant and HTPB propellant,and the gas parameters,total temperature,and condensed phase product content were determined.Secondly,the simulation method of coupling the particle group equilibrium model with the dual fluid model was used to analyze the polymerization process of alumina particles under different total pressures,expansion ratios,and propellant parameters.It was found that as the total pressure increased,the average particle radial small-scale mode direction shifted,and the overall particle size distribution became smaller;As the expansion ratio of the nozzle increases,the overall distribution of particle size decreases;Compared with high-energy propellants,in the case of HTPB propellants,the small particle fraction at the nozzle outlet increases,while the large particle fraction decreases,resulting in a smaller overall particle size distribution.Finally,the simulation method of equivalent specific heat method was used to analyze the phase transition process of alumina particles in a large-sized nozzle.Under different expansion ratios and propellant conditions,the phase transition of alumina particles in the nozzle and the influence of particle phase transition on the flow field and thrust were analyzed and studied.It was found that as the expansion ratio increased,the particle size range and degree of phase transition of the particles increased,and the thrust of the nozzle increased,resulting in an increase in the thrust enhancement value caused by particle phase transition.Under the same expansion ratio conditions,compared with high-energy propellants,HTPB propellants are more prone to phase transition of particles in the nozzle,with a higher degree of particle phase transition.The thrust generated under HTPB propellants is smaller,but the thrust increase caused by particle phase transition is greater,and the proportion of increase is greater.