主控提前点火对复合推进剂慢速烤燃响应的影响

The study of slow cook-off of composite propellant containing ammonium perchlorate (AP) is the focus of the research on propellant safety, while the pre-ignition is a common and effective way to reduce the intensity of reaction in slow cook-off of engine. To investigate the effect of pre-ignition temperature on its response characteristics, a set of slow cook off experiments of composite propellant was designed and carried out, and the response characteristics of ignition at different temperatures were studied. The temperature distribution of the propellant and the thermal damage law of propellant microstructure before ignition were investigated by numerical simulation and thermal decomposition experiment. The results show that the engine spontaneously ignited with a reaction level of violent explosion, and the reaction level was burning when it was ignited at 120 ℃. The intensity of the reaction could be reduced effectively by pre-ignition when the propellant temperature was low before auto-ignition. The thermal decomposition process and thermal structure damage evolution of the propellant during slow cook-off were studied by thermogravimetry analysis combined with morphological characterization. As the heating temperature increased, some components of the propellant were decomposed, causing the internal temperature of the propellant to be higher than that of the shell, while the breakdown of binders and AP in the propellant resulted in a porous structure of the propellant charge, more likely leading to convection combustion after ignition and increasing the intensity of the reaction. Due to the autothermal reaction of the propellant, the highest temperature of the propellant reached 150 ℃ when the shell temperature was only 138 ℃. The highest temperature first appeared near the tail of the nozzle. Considering the influence of porous structure caused by AP decomposition on the intensity of reaction, the ignition temperature in advance should be lower than 138℃. In order to avoid the decomposition in the propellant to produce porous structure, which would cause severe reaction after ignition, some measures should be taken in igniting the propellant before the main propellant reaches auto-ignition temperature, which can effectively reduce the intensity of reaction.