双级延伸喷管高空展开过程动力学耦合仿真研究

Coupling simulation of dynamics on the expansion process of double extendible nozzle at high altitude

带有延伸喷管的固体火箭发动机一般采用热分离方式进行级间分离,要求延伸喷管按照先点火、后展开的时序进行工作。因此,延伸喷管的展开过程实质上为一个燃气流动与延伸锥运动相互耦合影响的过程。为了详细分析和评估在燃气流场和延伸喷管展开相互耦合影响下尾流的变化和延伸锥的展开情况,根据Fluent软件中的用户自定义函数(UDF)功能提出了一种耦合仿真方法,并据此对某型双级延伸喷管的展开过程进行了耦合仿真研究,得到了在延伸喷管展开过程中尾流的变化以及延伸锥的运动和气动力等参数随时间的变化情况。计算结果表明,在延伸喷管展开过程中,延伸锥及其展开机构所在的空腔内的温度出现短时剧烈波动,需对其进行一定的热防护;在高空工况下,流场气动力对延伸锥的展开主要为阻碍作用且影响较大,当气瓶初始压强低于1.0 MPa时,延伸锥可能出现无法展开的情况;耦合仿真结果可反映出发动机工作时延伸锥的实际展开情况,可对延伸喷管能源系统输入参数等设计提供指导。

The solid rocket motor with extendible nozzle generally adopts the thermal separation method for its stage separation,thus the extendible nozzle is required to work according to the timing of the first ignition and then the expansion.Therefore,essen?tially the expansion process of the extendible nozzle is a intercoupling process of the gas flow and the movement of extension cone.In order to analyze and evaluate the change of wake flow and the expansion of extension cone under the intercoupling effect of gas flow and the expansion of extendible nozzle,the coupling simulation study on the expansion process of a certain type of double extendible nozzle was carried out according to the user?defined functions of Fluent.The flow field of the extendible nozzle and the motion param?eters and the axial aerodynamic force change with time of extension cone were obtained.The results show that in the deployment process of the extendible nozzle,the temperature of cavity where extension cone and its deployment mechanism are varies dramatical?ly,which should be thermally protected;The aerodynamic force has a greater influence on impeding the expansion process of the ex?tension cone at the high altitude,and when the initial pressure of gas bottle is lower than 1.0 MPa,the extension cone may be failed to deploy at ordered position;The coupling simulation results can reflect the real motion of the extension cone,which can provide guidance to the parameter design of energy system of the extendible nozzle.