Numerical Simulation Of Propellant In Channel Considering Wall Slip

Nitroguanidine gun propellants are widely used in artillery with high energy,low ablation characteristics.However,the extrusion molding crafts of nitroguanidine gun propellant are mainly depends on experiment and simulation.the defects of long period and high cost can't meet the manufacturing precision of nitroguanidine gun propellant at this stage.In order to solve the problems existing in the extrusion molding of nitroguanidine gun propellant.the rheological law,extrusion process and mold structure optimization of propellant were studied on the basis of considering the wall slip of gun propellant,Which improving the molding precision of numerical simulation of nitroguanidine gun propellant,shorting the development cycle and saving the cost.Based on the mechanism wall slip,the rheological properties at different temperatures were measured.The modified Bingham model,Cross model,power law model and general Naver's slip model were used to study the rheological behavior of the propellant in the flow channel.The results show that the power model combined with the generalized Naver's slip model can accurately describe the flow properties of the gun propellant in the inner flow channel.The mathematical model of the single-hole nitroguanidine gun propellant considering wall slip correction in extrusion process was established.The influence of slip coefficient on the pressure field,velocity field and shear rate field of single-hole gun propellant was analyzed by numerical calculation.The results show that the smaller the slip coefficient,the smaller the inlet pressure,the smaller the change of the shear rate in the flow channel and the smaller the change of the velocity.The mathematical model of the seven-hole nitroguanidine gun propellant extrusion molding process thinking about wall slip correction was established.The effects of wall slip on pressure field,velocity vector field,velocity field of the seven-hole nitroguanidine gun propellant were analyzed by numerical calculation.The comparison between simulation size and actual results shows that the error of the seven-hole propellant parameters are less than 3%.A 7 hole propellant die is taken as the object.The inward flow channel model with different aperture and arc thickness were established respectively.The numerical calculation was used to analyze the influence of the aperture and arc thickness difference on the parameters in the flow channel.The optimum scheme of the designed scheme is determined.The experimental results show that the arc thickness is zero and the machining quality is good.