Rough set theory is a powerful tool in dealing with vague and uncertain information . in this paper , by analyzing the fault characteristics of liquid rocket engine and the rough set method , rough set theory was applied to mine the hot - firing test data of liquid rocket engine 粗糙集是一种处理模糊和不确定知识的数学工具,在分析液体火箭发动机故障和粗糙集理论特点的基础上,将粗糙集理论应用于液体火箭发动机试车数据挖掘中。
When an engine works under the vacuum condition . so existing experimental products can be proof - tested by it and all test results obtained will be used for reference for the aero craft . accordingly , the technology studied in the thesis is quite significative to improve the efficiency of the engines of space propulsion system , economize limited resources on the spacecrafts , and prolong their lives 其目的是建立一个能满足小推力液体火箭发动机动态推力测试的系统,以便能够根据空间推进系统对发动机越来越高的工作性能要求,真实有效地反映发动机在真空环境下的工作状态等,对已经设计和生产出的发动机在高空模拟条件下进行实际测试,从而提供发动机的动态性能指标,为发动机的定型提供试验数据和依据。
Comparing to the direct drain cool - down process used in china , the natural precooling cycle , which may save the propellant of the precooling , simplify the prestart program , delay the ignition of the rocket and be more safe in the process of precooling as well is employed in this paper 国外在该项领域的技术已经在实际火箭发射场得以应用，相比之下，我国仍采用排放式的预冷方法。因此，需要研究低温液体火箭发动机循环预冷的方法，尽快实现赶超发达国家的目标。
The channel scale on transpiration cooling for the platelet thrust chamber of liquid propellant rocket engine is approaching micron dimension . it is very possible that micro - scale effects will occur in the flow and heat transfer of the channel . in the past , researchs on flow and heat transfer in the platelet micro - channel are mostly based on macro - scale theory 液体火箭发动机推力室壁面发汗冷却通道的尺度已达微米量级,通道内的流动与换热很可能存在微尺度效应,以前的相关研究都以宏观尺度的理论为依据,其研究结果的合理性需要进行微尺度效应的分析。
The thesis focuses on the basic principles of fault diagnosis , qualitative modeling of lre , qualitative reasoning techniques and diagnosis mechanism for lre . in the thesis , the theoretical foundation of diagnosis based on component is expounded . on the basis of above works , a relation - based diagnosis method is proposed by considering the practical diagnosis problems for lre , and a diagnosis example is demonstrated 本文首先对基于定性模型诊断方法的分类、特点和研究现状进行了评述，接着分别研究了基于部件模型的诊断方法、基于定性键合图模型的诊断方法、基于时间因果图模型的诊断方法在液体火箭发动机上的应用，其内容涉及故障诊断基本理论与原理、发动机定性建模技术、定性推理技术以及针对液体火箭发动机的故障诊断机制和策略。
Disigning coolant channel on the firebox of liquid rocket engine to loxodrome ( equal - angle helix ) groove can improve firebox coolant capability greatly . because the width dimension of loxodrome groove is narrow and the depth is deep , some machining methods are incapable , such as end - milling or electrochemistry . according to the peculiarities , a cnc disk - cutter - milling method which is composed of five motion axes with four simultaneously interpolated ones is researched . because most firebox generatrix is composed of complex curves , it is very difficult to get cnc cutting program with manual means . in order to deal with the problem , the loxodrome mathematics model is studied , and an auto - programming software system is developed . the software system can generate cnc cutting program of loxodrome on many kinds of turned surface . the constriction - distension segment of firebox is the most representative workpiece . the sharp changing of its generatrix slope makes loxodrome milling difficult . with the theory analyzing and practice cutting experiment , some applied techniques , which include milling mode and direction , choosing cutter diameter and cutting start point setting , are developed . adopting the technology above , tens regular workpiece have been manufacturing . the two - year manufacture practice has confirmed the validity and feasibility of developed loxodrome coolant channel milling method . the developed technology is also worth to be referenced to other similar workpiece 将液体火箭发动机燃烧室的冷却通道设计为斜航线(等倾角螺旋线)槽形,可以大幅度改善燃烧室的冷却性能.斜航线冷却槽的槽宽尺寸较小而槽深尺寸较大,所以无法使用棒铣刀铣削、电化学等加工方式.针对这些特点,提出了五轴控制、四轴联动的数控片铣刀铣削加工方法.由于燃烧室外表面的母线轮廓复杂,手工编制数控加工程序难度大.为了解决数控加工程序的编制问题,研究了斜航线的数学模型,开发了自动编程软件系统.使用该系统,可以生成多种母线轮廓回转体外表面上的斜航线数控加工程序.燃烧室收敛-扩张段的母线斜率变化大,加工难度大,是斜航线冷却通道加工的最典型工件.经过理论分析和实际切削实验,研究了针对该类型工件的片铣刀直径选择、铣削方式和方向、刀具调整和起刀点的设置等多项实际的加工方案.采用上述的一系列技术,已经成功地加工了数十个合格工件.经过两年多的实际生产过程应用,验证了所开发的斜航线冷却通道加工方法的正确性和可行性.这些加工技术的研制成功,对其他相似类型零件的加工亦具有参考意义
To overcome the disadvantages of diagnosis methods based on static models , a new diagnosis method for lre based on temporal causal graph ( tcg ) is developed . the tcg model of lre is set up , and based on this model the qualitative simulation and diagnosis analysis under abnormal conditions for lre are carried out . the results show that the theory and methods proposed and discussed provide a theoretical basis for the design and realiz ation of practical lre fault diagnosis from qualitative point of view 本文阐述了基于部件模型诊断方法的基本理论与原理，给出了求解该诊断问题的算法，在该理论的基础上，结合发动机实际诊断问题，提出了基于关系模型的诊断方法，并对空间推进系统进行了诊断实例分析；鉴于键合图在系统建模方面的优势，研究了大型泵压式液体火箭发动机基于定性键合图的诊断方法，建立了发动机的键合图模型，给出了诊断机制，进行了实例分析；为克服目前基于静态模型方法的不足之处，本文提出了液体火箭发动机基于时间因果图模型的诊断方法，建立了发动机的时间因果图模型，对发动机在故障状态下的动态特性进行了定性仿真，并进行了诊断分析。
Liquid rocket engine is a thermal kinetic system , it runs under extremely strict physical conditions , such as high temperature , high pressure , strong erosion , high density of energy release , strong components parameters coupling . it is very difficult to establish accurate dynamic mathematical model 液体火箭发动机是一种在极端的物理条件(如高温、高压、强腐蚀和高密度的能量释放等)下运行的复杂的流体-热动力系统,部件参数强烈耦合,很难建立精确的动态数学模型。
In this thesis , the qualitative - model - based fault diagnosis methods for a liquid - propellant rocket engine ( lre ) are studied in order to provide ones with novel approaches to build the fault diagnosis system , which possesses good robustness , real - time operating ability and practicability . the qualitative - model - based fault diagnosis methods hopefully substitute for quantitative - model - based methods for their limitations of computational complexity , robustness and practicability , and for the traditional rule - based method for its limitations of the acquisition of knowledge and flexibility 本文主要研究液体火箭发动机基于定性模型的故障诊断方法，其目的是为建立具有良好鲁棒性、实时性和实用性的发动机诊断系统提供一条新的技术途径，以期克服定量模型方法计算复杂、鲁棒性差、不便应用的缺陷，克服传统的基于规则方法知识获取困难和灵活性差的缺点。
In this thesis the theory and method of intelligent fault diagnosis for a large turbo - pump fed liquid - propellant rocket engine ( lre ) is innovatively proposed and developed , based on the hybrid reasoning strategy and the hybrid knowledge models including mathematical model , logic model , graphic model and qualitative model . the theory and method are constructed in the way of intelligent modeling technique and creative application of knowledge engineering , and focus on the difficult problems and critical techniques such as the unified treatment of lre knowledge ( experience , facts , rules , graph , system structure , behavior , model knowledge and measured data ) , the integration and translation of qualitative and quantitative knowledge , and the knowledge - based intelligent fault diagnosis reasoning methods . firstly , besides the correlation of different knowledge , the concept and the types of lre diagnosis knowledge are systematically described 本文以某大型泵压式液体火箭发动机为研究对象，以智能建模技术和知识工程的创造性应用为主要技术手段，围绕着发动机知识(经验、事实、规则、图形、结构、行为、模型知识与测量数据信息等)的统一处理技术、定性定量知识的集成与转化和基于知识的智能故障诊断推理等关键技术和难点，创新地研究发展了发动机基于混合知识模型(数学模型、逻辑模型、图形模型及定性模型)和混合推理策略的智能故障诊断理论和方法。
