【作者】 董颖怀；

【导师】 王振龙；

【作者基本信息】 哈尔滨工业大学 ， 机械制造及其自动化， 2009， 博士

【摘要】 以MEMS(Micro Electro Mechanical Systems)技术为基础的微飞行器是目前航空航天领域最具吸引力的产品之一,而动力装置的微型化问题则是性能更强更灵活的新型微飞行器的关键技术。近年来,在国外,尤其是美国,相继开展了微动力机电系统和微发动机的研究工作。目前硅刻蚀技术已经成功的应用于微型发动机的研制中。微型发动机的发展也从平面的二维结构到复杂的三维自由曲面,从MEMS传统的硅基材料到具有更高性能的合金材料,这都迫切地需要更加多样化的微细加工方法。微细加工技术的发展促进了微型发动机技术的进步,同时微型发动机的进一步发展也同样对加工技术提出了更高的要求。本文分析了微型涡轮发动机的工作原理,论述了其工作过程和热循环模式。通过比较微型发动机与传统发动机的工作过程,针对微型发动机的特点和技术难点,提出了一种新型的分布式微型发动机结构,将燃烧腔与涡轮转动本体分离,可由一个燃烧腔提供动力,供给多个涡轮转子转动,大大简化了微型发动机的设计,燃烧室内空气与燃料混合燃烧后传递给涡轮转动部件的热量大大减少,使得转子的工作环境改善,使用寿命增加。为了使得转子获得更好的转动性能和气动特性,本文设计了具有微三维结构的微型压气机和涡轮结构,并通过流体力学仿真软件对压气机和涡轮的内部流场进行了分析。在微型发动机中,由于尺寸很小,使得装配的难度大大增加,尤其是对于转动部件,在装配后,由于存在着装配误差,使得旋转的精度降低,转子转动的稳定性减小,转动过程中转子偏心的影响大大制约了微型发动机的性能,所以提高转动轴与涡轮和压气机叶轮的同轴度是微型发动机研究中的一个难题。本文对发动机的转动部件采用涡轮压气机一体式转子结构设计,中间的旋转轴与涡轮和压气机叶轮是一体的,这样既能减少发动机部件的数量,又可保证轴与转动部件的同轴度,可大大提高动叶轮在高速转动过程中的稳定性。同时,涡轮和压气机与旋转轴的连接强度增大,可靠性大大增加。由于微型发动机的旋转轴半径尺寸很小,并且转动叶轮高速旋转运动,普通的滚动轴承已经无法满足需要,本文设计了一种新型的微型径向动压气浮轴承结构,将气浮轴承与微型发动机外壳集成在一起,即简化了总体结构,又降低了装配时的难度。通过使用FLUENT软件,建立了微型径向动压气浮轴承的轴间气体流动的仿真模型,对气体在气浮轴承内部的流动情况进行了仿真与分析,验证了所设计微型径向动压气浮轴承结构的合理性,并进一步根据仿真计算的结果对所设计的微型径向动压气浮轴承结构进行了优化设计。由于传统MEMS加工技术的限制,目前在微型发动机的研究中,其关键部件涡轮和压气机转子的叶片造型通常为二维结构,并且通常只能使用硅基材料,这大大限制了微型发动机的发展和潜力。由于微型发动机的尺寸只有几厘米甚至几毫米大小,传统的MEMS技术目前还很难加工出具有自由曲面的微细结构。而微细电火花加工技术其具有无宏观切削作用力、设备简单和真三维加工能力等特点,同时其所能处理的材料非常广泛,不仅可以加工各种性能优良的金属、合金,还可以加工硅等半导体材料、陶瓷等,使得微细电火花加工技术成为最适合加工本文所提出的微三维结构的微型发动机的方法。目前微细电火花铣削加工中不可避免的问题是电极的损耗,这也是限制微细电火花铣削能力的主要因素之一,为此,本文将深入分析微细电火花铣削加工过程中电极损耗的特点,提出了在线实时测量补偿策略,并以此为基础开发出微细电火花铣削专用的CAM(Computer Aided Manufacturing)系统,解决使用微细电火花铣削技术加工制造微型发动机转子所遇到的问题。在充分挖掘微细电火花加工技术特点的基础上,根据微型涡轮发动机的结构特点,采用微细电火花加工技术为主要的加工手段对微型发动机的关键部件进行加工制造。使用微细电火花磨削技术加工涡轮压气机一体式转子结构的旋转轴;使用微细电火花铣削技术在高温镍合金材料上加工出了具有微三维结构的压气机和涡轮叶片;使用微细电火花线切割技术加工出了微型气浮轴承。通过外部气源模拟微型燃烧室提供动力,本文所设计并加工制造的微型涡轮发动机可以最高达到4×104RPM的转速,达到了预期的设计要求。研究了进气压强和进气口距叶片距离对转速的影响,并测试了其在工作时的噪音。本文对微型涡轮发动机的整体结构进行了设计仿真,以微细电火花加工技术为主要手段,完成微型发动机关键部件的加工制造,实现了具有高转速的微型涡轮发动机原型,为微型涡轮发动机的实用化奠定了基础。更多还原

【Abstract】 The micro aerocraft with MEMS (Micro Electro Mechanical Systems) technology is one of the most attractively fields of aerospace field. The micromation of power plant is the key technology of micro aerocraft. In recent years, the power MEMS and micro engine have been researched by the foreign countries, especially int the United States. The Silicon etching technology has been successfully applied to the development of micro-engines. The development of micro engine is from two-dimensional structure to complex three-dimensional free-form, from traditional silicon-based MEMS materials to a more high-performance alloy materials. The more micro fabrication technologies are needed for the development micro engine.The principle of micro-turbine engine is analysed. The working peocess and thermal cycling are discussed. To compare the working process with micro-turbine engine and tradition turbine engine, a new distributed structure of micro-turbine engine was developed ccording to the characteristics of micro engine. The combustion chamber and rotor was separated, more than one micro-turbine engine was supplied by one combustion chamber. The design of micro-turbine was simpleness. The heat of mciro combustion chamber is less transferring to the turbineA micro turbine and compressor with micro three-dimensional structures was designed for the better capability. The internal flow of turbine and compressor was analysied by the Computational Fluid Dynamics software. The assembly of micro-turbine is difficult because of the small size. The rotation accuracy and stability of rotor will be reduced. Improving the coaxial accuracy is a key technology. In this paper, an integrated of turbine-shaft-compressor structure was designed. It can reduce component number and improve the stability of rotor. And the joint strength and reliability will increase.The dimension of micro turbine engine is usually only few millimeters, the rolling bearing is not suitable. A new mciro radial dynamic compression gas bearing was designed and and verified the reasonable of this new structure with FLUENT sofaware. According the simulation results, the parameters of gas bearing was optimized.The blade of the turbine and compressor of mciro engine is two- dimensional structure and used with Si-based materials because of the limitation of tradition MEMS technology. Due to the size of micro-turbine engine, it’s still difficult to machine free-form structures by traditional MEMS technology. The mciro EDM machining technology has the characteristic of no macroscopic cutting force, simple device and ture three-dimensional process capacity with multifarious materals cantans metal and semiconductor materials. So the micro EDM machining technology is well suitable for the fabrication micro turbine engine with three-dimensional structures.Electrode wear is a major problem of micro-EDM milling. Based on the characteristic of micro-EDM milling, a new compensation with fixed length real time was put forward. A mciro EDM milling CAM system was developed based on the Unigraphics software plant. A mciro chess and face with complex thres- dimensional structure was machined by this CAM system.The key components of mciro turbine engine were fabricated by micro EDM machining technology. A rotation axis was machined by mciro electric discharge grinding; the blade of turbine and compressor with micro three- dimensional structure were machined by mciro EDM milling; the gas bearing was machined by mciro wire electrical discharge machining.The power source was supplied by the external air source. The speed of rotor was reached 4×104RPM. The influence of inlet pressure and distance of inlet nozzle were researched.In this paper, a new micro turbine engine was designed and simulation. The key components of mciro turbine engine were fabricated by micro EDM machining technology. A micro turbine engine protype was realized with high rotation speed, which lays the foundation to realize pratical mciro power engine.更多还原