多级火箭级间热分离数值模拟及参数不确定性研究

Numerical simulation of multistage rocket interstage thermal separation and research on parameter uncertainty

热分离作为火箭级间分离的主要方式,在提高分离过程的可靠性时,存在着级间区域喷流与外界来流耦合以及环境参数不确定性影响等问题。以某型两级火箭级间热分离过程为研究对象,针对上述2个方面问题,结合计算流体力学、统计学等研究手段,通过求解RANS方程与刚体运动方程,开展对火箭级间热分离过程的仿真模拟工作,讨论了分离载荷变化3个阶段的产生原因。并考察不同飞行速度、飞行高度和飞行攻角3个环境输入参数的不确定性,基于混沌多项式展开法(PCE)构建分离过程的不确定性分析模型,结合Sobol敏感性分析法量化了各个输入参数的影响程度。结果显示:3个环境参数分别主要通过影响作用于二子级的气动力、改变流场物性和抑制马赫盘发展影响分离过程;PCE法获得的一、二子级轴向速度的不确定带呈现不同的变化模式,其峰值分别达到50.1%和29.2%,表明二子级抗干扰的能力强。轴、径向运动参数对飞行速度的敏感性最强,敏感性指标分别达到0.36和0.30。研究获得的不确定性量化特征指标,为热分离过程姿态的预测、探索分离关键影响因素以及进一步优化设计提供了良好手段。

As the main method of interstage separation of rockets,thermal separation not only improves the reliability of the separation process,but also has problems such as the coupling of interstage regional jet and external incoming flow,and the influence of environmental parameter uncertainty is unknown.In this paper,taking the thermal separation process between a certain type of two-stage rocket stage as the research object,combined with computational fluid dynamics,statistics and other research methods,this paper carries out the simulation of the thermal separation process between rocket stages by solving the RANS equation and the rigid body motion equation,and discusses the causes of the three stages of separation load change.The uncertainty of the three environmental input parameters of different flight speed,flight altitude and flight angle of attack is investigated,and the uncertainty analysis model of the separation process is constructed based on the chaotic polynomial expansion method(PCE),and the influence degree of each input parameter is quantified by combining the Sobol sensitivity analysis method.The results show that the three environmental parameters mainly affect the separation process by influencing the aerodynamics of the second substage,changing the flow field and inhibiting the development of Mach disk.The uncertain bands of axial velocity of the first and second sub-stages obtained by PCE method show different change modes,and their peaks reach 50.1%and 29.2%,respectively,indicating that the second substage has strong anti-interference ability.The axial and radial motion parameters have the strongest sensitivity to flight speed,and the sensitivity indexes reach 0.36 and 0.30,respectively.The quantitative characteristics of uncertainty obtained in this study provide a good means for predicting the attitude of thermal separation process,exploring the key influencing factors of separation,and further optimizing the design.