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高超声速飞行器一体化设计中存在气动/热/推进/结构弹性相互耦合的问题,首先根据飞行器的机体/发动机一体化设计思想构造了二维高超声速飞行器模型,并基于激波/膨胀波原理和动量定理建立了气动力模型,采用Chavez和Schmidt建立的超燃冲压发动机推进系统模型;在飞行器结构方面,引入变截面和变质量分布的自由梁结构模型,并采用Eckert参考焓方法分析的气动加热过程中承力梁不同轴向位置温度随时间变化特征,在此基础上运用模态法计算了燃料消耗和气动加热条件下结构的固有频率和振型特征,获得结构弹性变形的模型;最后建立了考虑热气动弹性和推进系统作用的飞行动力学方程。研究结果表明:质量变化对结构弹性特性影响比较显著,而气动加热的影响主要表现在振动频率方面,且会随着加热过程的持续而逐渐增强;结构变形会改变飞行器静配平状态,特别是在机体质量较大的最初飞行阶段,气动加热会强化结构变形对配平特征的影响;线性化系统的动力学特征分析表明,质量减小和结构变形均会增加短周期模态和振荡模态的不稳定特性,而对高度特性的影响不大,气动加热效应会进一步增加飞行力学和气动弹性的耦合特征,并导致弹性模态的稳定性降低。
The integration of aerodynamic / thermal / propulsion / structural flexibility exists in the integrated design of hypersonic vehicles. Firstly, a two-dimensional hypersonic vehicle model is constructed according to the aircraft / engine integrated design concept. Based on the shock / expansion wave theory and Momentum theorem was used to establish the aerodynamic model and the model of propulsion system of scramjet was established by Chavez and Schmidt. In the aspect of aircraft structure, a free beam model with variable section and variable mass distribution was introduced and analyzed by Eckert reference enthalpy method In the process, the temperature of the bearing beam varies with time in different axial positions. On the basis of this, the natural frequencies and mode shapes of the structure under fuel consumption and aerodynamic heating are calculated by modal method, and the model of structural elastic deformation is obtained. Finally, The aerodynamic equation considering the thermo-dynamic elasticity and propulsion system. The results show that: the change of mass has a significant effect on the elastic characteristics of the structure, while the influence of aerodynamic heating is mainly in terms of vibration frequency and gradually increases with the duration of the heating process; the structural deformation will change the static balance of the aircraft, In the initial stage of flight, the aerodynamic heating will strengthen the effect of structural deformation on the trim characteristics. The analysis of the dynamic characteristics of the linearized system shows that mass reduction and structural deformation will increase the short-period modes and oscillation modes Stability characteristics, and has little effect on the height characteristics. The aerodynamic heating effect will further increase the coupling characteristics of aeromechanics and aeroelasticity, and lead to the decrease of the stability of the elastic modal.