Research On Forming Control Method Of Porosity Of Solid Rocket Motor Propellant During Core-Inserting

Nowadays,Solid Rocket Motor has been widely used in aerospace,national defense,military and other fields,but there are still many problems in its grain-forming process,which need to be improved and sloved.Solid Rocket Motor grain molding needs to go through three processes: mixing,pouring(core-inserting)and vulcanization,in which the pouring(core-inserting)is the most important process.Pouring(core-inserting)refers to the process that the mandrel enters the propellant slurry through the pressing-plate.In the process of core-inserting,the air on the surface of the mandrel will enter the propellant slurry with the movement of the mandrel,resulting in pore defects,which will result in the reduction of the propellant grain quality.In order to solve the problem of pore defect of Solid Rocket Motor grain during the core-inserting process,based on a pressing plate assembly used to reduce the porosity of propellant grain proposed by the research group,the optimal matching parameters of pressing plate assembly and mandrel structure were studied,the specific research contents include:(1)Shear viscosity test and rheological property analysis of propellant.On the basis of making the condiations of propellant used for general testing,the items that must be tested before pouring and the storage conditions of raw materials before pouring,the test scheme of propellant shear viscosity is designed,the propellant slurry is prepared,and the shear viscosity data of propellant slurry is tested and collected by Anton Paar MCR rheocompass rheometer software.Based on the experimental data,the relationship between temperature,shear rate and shear viscosity of solid propellant slurry was explored,and the internal mechanism of the relationship was deeply studied,which laid the foundation for selecting the constitutive model to characterize the rheological properties of solid propellant slurry.(2)Optimal selection of the constitutive model characterizing the rheological properties of solid propellant slurry was completed.According to the experimental data and rules,the Power-law model,Carreau model and Cross model with temperature dependent rate were fitted by the shear viscosity of propellant slurry from the mathematical point of view to obtain the relevant parameters of the constitutive model;The Power-law equation,Carreau equation and Cross equation were used for correlation analysis,and the reasonable constitutive model was selected to characterize the rheological properties of solid propellant slurry.The significance of the selected constitutive model is tested to confirm whether it is universal.(3)Numerical simulation of propellant core-inserting process.Based on the constitutive model of propellant slurry optimized selected,VOF model and dynamic grid technology are used to simulate the core-inserting process.The effects of the gap between the mandrel and the pressing-plate and the shape of the mandrel on the quantity of air brought into the propellant slurry are analyzed.The main factors of reducing the porosity of Solid Rocket Motor grain are determined,which can provide guidance for the design of the mandrel and pressing plate components during the core-inserting pouring process.