Research On The Working Process Of Solid Rocket Motor Based On Conjugate Heat Transfer Phenomenon

The working process of the solid rocket motor is a complex flow process accompanied by chemical and physical reactions,and its thermal-fluid-solid coupling conjugate heat transfer process directly affects engine performance.The research on the conjugate heat transfer phenomenon of solid rocket motor by numerical simulation methods is of practical significance to improve the performance of the solid rocket motor.In the experiments of actual solid rocket motors,three phases,including solid,condensed and gas phase,appear during the process of combustion.In this paper,taking the combustion of solid propellant as the background and Fluent as the platform,a coupling algorithm that combines the heat transfer calculation with Level-set and MDF(minimum distance function)is established through a secondary development for Fluent.Combining the N-S equation,a conjugate heat transfer model is established.And the conjugate heat transfer phenomenon of solid rocket engine from ignition to the grain surface regression are simulated.The main contents are as follow.(1)During the combustion of propellant in the solid rocket engine,the solid phase changes into condensed phase on the burning surface and combustion gas is produced.Polynomial function,arctangent function,Boltzmann function and Dose Resp function are used to fit the changing density,and the Boltzmann function with a better fitting effect is obtained.The change in density is used to simulate the three phase states,namely solid phase,condensed phase and gas phase,in the propellant combustion process.Combined with N-S equation,a conjugate heat transfer is established.The process of mass,energy and momentum transfer and chemical reaction during the work of solid rocket motor are simulated in the model.(2)Taking the standard test solid rocket motor as the research object,the accuracy of the algorithm is verified by the small error of comparing the numerical results of temperature and pressure in the combustion chamber with cylindrical-grain of internal combustion with the theoretical calculation and experiments results.The grain surface regression and the phenomenon of conjugate heat transfer are analyzed under the condition of various propellants and nozzles with different throat sizes and divergence ratios.The small errors of comparing the numerical results of temperature and pressure in the combustion chambers with the theoretical calculation and experiments results provides the evidence of the universality of the algorithm.(3)By integrating the numerical simulation of solid rocket motor ignition pressure building process and the grain surface regression,the conjugate heat transfer phenomenon between igniting powder,combustion gas and propellant during solid rocket motor working process is analyzed,and the simulation of the working process of the motors of different propellants are realized.Through the validation of accuracy and universality,the coupling algorithm combining heat transfer calculation with level-set and MDF method and the conjugate heat transfer three phases model established in this paper provide a reference to investigate the conjugate heat transfer phenomenon in the solid rocket motor and makes it a step closer to the realization of thermal-fluid-solid coupling simulation of the solid rocket motor.