【作者】 程玉强；

【导师】 吴建军；

【作者基本信息】 国防科学技术大学 ， 航空宇航科学与技术， 2009， 博士

【摘要】 本文针对我国发展可重复使用液体火箭发动机技术的需求,以某新型液氧煤油发动机为研究对象,对发动机减损控制技术所涉及的发动机系统动力学建模与仿真、关键部件结构动力学与损伤动力学建模与仿真、发动机减损控制律综合分析方法、基于模糊逻辑的在线减损控制方法等主要方面进行了系统深入的研究。所发展的可重复使用液体火箭发动机减损控制理论与方法,对改进和提高发动机系统可靠性、结构部件耐用性以及发动机工作寿命具有重要作用,相关研究结果也可为可重复使用液体火箭发动机起动过程、转工况过程和关机过程的方案设计提供重要参考。论文建立了某型液氧煤油发动机低频集中参数系统动力学模型,基于Matlab/ Simulink平台,开发实现了具有一定通用性的发动机系统动力学仿真软件,该仿真软件可以对液氧煤油发动机工作全过程进行数值仿真。基于该仿真软件,对发动机起动过程、转工况过程和关机过程进行了大量的数值模拟。研究发现,流量调节器起动流量、流量调节器转级速率、末端流量等参量的设置对发动机瞬变过程具有重要影响。对于可重复使用液体火箭发动机而言,这些参量的设置不仅影响发动机动态特性,而且直接影响关键部件损伤的发展。建立了发动机冷却夹套隔片和涡轮叶片的结构动力学模型和损伤动力学模型,系统地探究了发动机系统起动、转工况和关机等过程中冷却夹套隔片和涡轮叶片损伤发展规律。研究发现:发动机在稳态工况下,冷却夹套隔片和主涡轮叶片损伤发展缓慢;发动机在起动过程、由高工况向低工况转变过程和关机过程等瞬变过程中所产生的冷却夹套隔片损伤增量较大;发动机在起动过程和由额定工况向高工况转变过程中所产生的主涡轮叶片损伤增量较大。研究结果表明,进行发动机减损控制,需要重点针对瞬变过程进行减损。通过对材料性能和冷却通道结构对冷却夹套隔片损伤影响的研究,以及瞬变过程中流量调节器流量和转级速率对冷却夹套隔片和主涡轮叶片损伤影响的研究,发现:不同的起动方案和工况调节方案所引起的关键部件损伤增量差异很大,对这些方案进行优化设计,对提高关键部件耐用性和发动机可靠性十分有益。系统地研究了液体火箭发动机减损控制律的综合分析问题,发展并实现了基于多目标粒子群算法的发动机减损控制方法。指出发动机减损控制律的综合分析问题可转换为由发动机系统性能目标函数、冷却夹套隔片损伤目标函数、主涡轮叶片损伤目标函数等构成的多目标优化问题,优化得到的控制输入序列即为发动机减损控制律。研究结果表明:(1)在发动机起动、由额定工况向高工况转变和由高工况向低工况转变等瞬变过程中,通过合理选取优化后的控制输入序列,在系统性能损失不明显的情况下,可以不同程度地减少发动机瞬变过程中冷却夹套隔片和主涡轮叶片损伤增量;(2)在发动机起动过程中,通过牺牲发动机系统性能,不一定能减少冷却夹套隔片损伤增量,但可以较大幅度地减少主涡轮叶片损伤增量。针对发动机在线减损控制问题,提出了一种基于模糊逻辑的智能减损控制方案,设计实现了能够同时减少冷却夹套隔片和主涡轮叶片两个关键部件损伤增量的模糊减损控制器。研究结果表明:(1)设计的模糊减损控制器能够在线判断冷却夹套隔片和主涡轮叶片损伤情况,并自主采取合适的减损控制策略,具有一定智能性;(2)在发动机起动、由额定工况向高工况转变和由高工况向低工况转变等不同的瞬变过程中,模糊减损控制器的减损效果略有差异,但都达到减损的目的,且发动机系统性能损失不明显;关键部件损伤越大,应用模糊减损控制器后,关键部件损伤增量减少越明显。更多还原

【Abstract】 In order to develop the concerned techniques about reusable liquid-propellant rocket engines, taking certain LOX/Kerosene rocket engine as the object investigated, some main aspects of engine damage-mitigating control (DMC) such as system dynamics modeling and simulating, critical components’structural dynamics and damage dynamics modeling and simulating, synthesis of the rocket engine DMC law and on-line DMC method based on fuzzy logic have been studied in this dissertation. The theory and techniques developed in the dissertation can be used to improve and enhance engine’s system reliability, structural durability of critical components, and service life of the rocket engine. The results can also provide valuable reference for optimizing the scheme of startup process, state regulating process and shutdown process of reusable liquid-propellant rocket engines.The system dynamics model of the LOX/Kerosene rocket engine was built by using standard lumped parameter methods. Based on the model, a universal simulation software for the rocket engine based on Matlab/Simulink was developed which can be applied to simulate the whole process of the rocket engine. Different operating schemes of the startup process, state regulating process and shutdown process were simulated by using the software. The results show that the setup of flow regulator’s startup mass flow-rate, flow regulator’s change rate and end mass flow-rate has an important influence on characteristics of the transient process of rocket engine. The influence of these factors on the reusable liquid-propellant rocket engine is not only dynamic performance, but also damage evolving process of the critical components.The structural and damage dynamics models of coolant channel ligaments (CCL) and turbine blades (TB) were also built. Based on these models, CCL and TB damage evolution law during the startup process, state regulating process and shutdown process were investigated. Some important results have been obtained. For examples, the damage of CCL and TB evolving is slow during steady state, while the damage accumulation of CCL during startup process, HTL process (a regulating process from high operating condition preseted to low operating condition preseted) and shutdown process is very obvious. In addition, the damage accumulation of TB during startup process and RTH process (a regulating process from rated condition to high working condition preseted) is also obvious. The results indicate that DMC of the rocket engine should put emphasis on the transient processes. The effects of material property and geometrical dimensions of CCL on damage evolution of CCL, the effects of flow regulator’s mass flow-rate and change rate on damage evolution of CCL and TB, were all studied. The results show that different schemes of startup and state regulation can make distinct damage accumulation of CCL and TB. Optimizing these schemes is very valuable to improve reliability and structural durability of critical components.It is presented and clarified that analysis and synthesis of DMC law can be dealt as a muti-objectives optimization. For DMC of liquid-propellant rocket engines, three objective functions including performance function, damage of CCL function and damage of TB function can be constructed. The optimized control input sequences are the DMC laws. The theory and methodology of analysis and synthesis on the DMC law based on multi-objective particle swarm optimization is clarified and discussed with simulation computation. The results show that: (i) the optimized control input sequences can reduce the damage accumulation of CCL and TB during the transient process such as startup process, RTH process and HTL process by insignificant sacrifice on the system performance; (ii) appreciable loss on the system performance can considerably reduce damage accumulation of TB during startup process, but it may not work to CCL.In order to develop on-line damage-mitigating control method, the design and realization of the intelligent damage-mitigating controller (DMCer) based on fuzzy logic, which can reduce both CCL and TB’s damage accumulation, were also discussed and studied. The results of simulating computation with the DMCer for the rocket engine show that: (i) the DMCer can monitor the damage of the CCL and TB, and take proper DMC law in time if necessary; (ii) the DMCer can reduce the damage accumulation of CCL and TB during startup process, RTH process and HTL process with insignificant loss on system performance, and the effect of damage reduction will be more obvious along with the damage evolving.更多还原