Research On Simulation Calculation About Combustion Performance Of Tubular Variable-burning-rate Gun Propellant

In this paper,the tubular variable burning rate propellant is studied,according to the layered structure,the tubular variable burning rate propellant is divided into two layers and three layers,and the three layers of tubular variable burning rate propellant can be divided into three web thickness conditions according to the relative web thickness of the internal and external flame retardant layer.The combustion physical model of the tubular variable burning rate propellant for each arc thickness condition is established,according to the combustion characteristics of each stage,the calculation formulas of the combustible mass fraction ? and the intensity of gas generation intensity ? in each stage are derived,and the values of time t and pressure p in the combustion process are calculated.The calculation program of combustion performance is compiled by using python language,and the functions of parameter input,situation discrimination,result output and graph drawing are realized.The combustion performance of tubular variable burning rate propellants with different sizes is compared and analyzed by theoretical calculation.Two-layer tubular variable burning rate propellant and three-layer tubular variable burning rate propellant with equal web thickness of internal and external flame retardant layers have only two combustion stages.The double-layer tubular variable burning rate propellant has progressive combustibility in the first stage of combustion,with the increase of burning rate ratio k,the step degree of ? value is greater than that of the three-layer tubular variable burning rate propellant with equal web thickness of internal and external flame retardant layers.The three-layer tubular variable burning rate propellant has three combustion stages under the condition of unequal web thickness of internal and external flame retardant layer.Under the condition that the web thickness of the external flame retardant layer is thicker than that of the internal flame retardant layer,it shows good progressive combustibility in the second combustion stage.Theoretical calculation results of combustion performance of three-layer tubular variable burning rate propellant under the condition that the external flame retardant layer is thicker than that of the internal flame retardant layer web thickness show that the burning rate ratio k and length-thickness ratio ? have great influence on combustion performance,and the combustion performance gradually becomes better with the increase of k and ?.The relative thickness of the external flame retardant layer a and the density ratio y also have influence on the combustion performance,but the density ratio y has little influence on the combustion performance.Compared with the experimental conditions of closed-bomb test,it is impossible for actual combustion of tubular propellant to achieve the same particle size and simultaneous ignition assumed in theoretical calculation.Therefore,the simulation calculation method is adopted,which divides the propellant into several parts with the same mass and the time interval of each step ignition is the same.By controlling the number of segments and the time interval between adj acent segments,the theoretical??? curves of tubular variable burning rate propellant under the condition of successive ignition are calculated.