Effect Of Thermal Stimulation On Charge Response Characteristics Of Solid Propellant

In order to study the thermal safety of solid rocket motors filled with HTPE composite propellants,in this paper,the thermal response characteristics of small HTPE composite propellant cook-off bombs under thermal stimulation were studied by cook-off experiment and numerical simulation.On the basis of this,the thermal response characteristics of solid rocket motor with different charge structure and its changing regulation are studied by numerical simulation method.The main research contents are as follows:(1)The cook-off tests were carried out on the small-sized HTPE propellant cook-off bomb by using the self-designed cook-off experimental device at a heating rate of 1℃/min and 2℃/min While using a thermocouple multi-point temperature.The results showed that the response levels are combustion at this two heating rates.The heating rate basically has no effects on the response temperature of the charge center point,but has impacts on the outer wall response temperature of cook-off bomb.With the decrease of the heating rate,the response temperature of the outer wall is also decreasing.(2)A cook-off model of propellant was established for small size cook-off experiment.The numerical simulation was carried out on the propellant cook-off bombs at different heating rates(3.3℃ /h ~ 2 ℃ /min)by Fluent software.The propellant Chemical kinetics parameters were determined.And the effect of heating rate on the response characteristics of HTPE composite propellant was studied.The results show that the heating rate ranging from 3.3℃/h ~ 2℃/min is slow cook-off,in which the ignition position of HTPE composite propellant cook-off bomb is in the cylinder center.And the ignition temperature is basically 232.2 ℃.With the decrease of the heating rate,the ignition time of the cook-off bomb decreases exponentially,and the response temperature outside the ignition point increases logarithmically.(3)According to the solid rocket motor composite charge structure,the motor cook-off model was established.The cook-off numerical simulation was carried out on the solid rocket motor at different heating rates(3.3℃/h ~ 2℃/min)by Fluent software.The effect of heating rate on the cook-off characteristics of solid rocket motor was studied.The results show that the change trend of the ignition time and the response temperature of the outer wall of the HTPE composite propellant is basically the same as the small cook-off bomb.That is,the charge size and structure don’t affect the regulation of the ignition time and the outer wall response temperature with heating rate.but the absolute value of them have a great relationship with the charge size and structure.The strict division of fast or slow cook-off must be combined charge size,charge structure and other factors.We can’t ignore the effect of natural convection heat transfer on the coo-off response characteristics of the motor.(4)The cook-off numerical simulation was carried out on the solid rocket motors with mono tube and star tube structure at different heating rates(3.3℃/h ~ 2℃/min)by Fluent software.The effect of charge structure on the cook-off response characteristics of motor was studied.The results show that the charge structure has an effect on the cook-off characteristics of the solid rocket motor.The influence of the ignition location on the ignition rate is the critical heating rate.And the influence of the ignition position has a critical heating rate of a jumping change.Under the conditions of this study,Under the condition of this study,the critical heating rate of the ignition position jump of star tube motor is 0.3℃/min and 0.5℃/min.The above research results have important reference value for the thermal safety analysis and structural design of solid rocket motor.