点火具能量释放过程数值仿真分析

Numerical Simulation Analysis of the Energy-Released Process for the Ignition Transient

为了探索某小型固体火箭发动机尾部点火具射流性能,在工程实际应用项目的基础上,建立了连接件接连点火器和喷管的物理结构。使用经典内弹道理论计算点火器内2#小粒黑火药的燃烧过程,得出点火具的压力输出规律,作为Fluent燃气流动动力学仿真的压力入口条件,利用UDF接口编入计算,建立圆柱体台阶式收缩通道的三维瞬态数理模型,通过改变连接件收缩通道的长度,模拟了点火具内的温度、压力、速度分布。结果表明:在圆柱体台阶式收缩连接件的结构下,由于分界壁的阻碍作用,强化了燃气射流在圆柱室内径向的湍流掺混效应,能量发生耗散,燃气温度和速度降低,使得点火延迟增大,但同时扩张容积起到了蓄能调节作用,降低点火压力峰值,保障点火具可靠工作;存在一个最佳搭配比,既有效缩短点火时间,又可保障点火安全可靠进行。

The physical model of ignition system which is composed of an igniter,a connector and a nozzle is established to explore the properties of jet gas of a small rocket motor with rear ignition.Firstly,the output mechanism of pressure of igniter with No.2 small-grain black powder is obtained on the classical interior ballistics model.The secondary development based on FLUENT software is implemented using UDF interface program in which the output law of pressure of igniter is simulated with profile.It numerically simulated the 3D axisymmetric flow field of a small solid rocket motor rear.The distribution maps of temperature,pressure and velocity were obtained.The results indicate that the turbulent mixing effect of gas jet along radial direction in a cylindrical chamber is enhanced due to resistance of the boundary wall.And the energy dissipation is strengthened.The ignition delay is lengthened with the decreased of temperature and velocity of gas jet.But at the same time,the expansion capacity plays a certain role in energy storage,reducing the peak value of ignition pressure and ensuring the reliable operation of ignition devices.Therefore,there is an optimal matching ratio,which can effectively shorten the ignition time and ensure the ignition safety and reliability.