【作者】 肖根福；

【导师】 刘国平；

【作者基本信息】 南昌大学 ， 机械电子工程， 2013， 博士

【摘要】 涡旋压缩机没有往复运动机构,体积小、重量轻、易损件少,在中小容量的压缩机中具有很大的性能优势,是高性能压缩机的主要发展方向之一。无油涡旋压缩机在结构上排除了工作介质接触润滑油的可能,可以满足医疗、食品等行业的特殊需求,但是排气量大、使用寿命长的无油涡旋压缩机制造尚存在困难。为了深入了解涡旋压缩机的运行机理,从原理上指导涡旋压缩机的设计,分析无油涡旋压缩机的内部流动过程显得非常重要。本课题运用热力学理论和计算流体力学方法研究了涡旋压缩机的内部流动过程,获得了涡旋压缩机压缩腔内压力、温度、流速的瞬态分布,为高性能涡旋压缩机的设计提供参考。本文首先介绍了无油涡旋压缩机的结构和工作原理,根据压缩腔的几何形状,将热力学和传热学作为理论基础,用质量守恒和能量守恒等定律,分析了无油涡旋压缩机压缩腔的容积变化过程和热力工作过程,建立了一种全面考虑了压缩过程中的换热和泄漏现象且适用于无油涡旋压缩机的实用热力学仿真模型,并用实验验证了该数学模型的准确性。然后通过分析涡旋压缩机流场模拟的数学模型和数值计算方法,将涡旋压缩机排气过程视为准静态过程,用计算流体力学的稳态方法来分析涡旋压缩机。选定了合理的排气过程几何模型,检验了网格的无关性,用湍流模型模拟了排气流动过程。该模拟给出了无油涡旋压缩机压缩腔内不同轴向截面内的速度场、不同涡旋转角时的速度场及包含排气管在内的三维速度场。再将涡旋压缩机进行几何简化,用二维模型研究了压缩腔内部的动态流动过程。克服了涡旋压缩机压缩腔几何形状复杂的困难,获得了适合涡旋压缩机内流场仿真的网格形式。该模拟采用了基于局部弹性变形与网格重划的CFD动网格技术,以理想气体为工作介质,满足流体控制方程及气体状态方程,采用了RNG κ-ε湍流模型。该模拟详细展示了二维涡旋压缩机吸气、压缩、排气过程的压缩腔内压力、温度、速度的分布情况,对比了不同转速时的温度、压力、速度的变化规律。用实验数据验证了数值模拟的正确性,保证了结果的真实有效。最后,设计了涡旋压缩机的三维简化几何模型,通过网格性能对比获得了适合三维涡旋压缩机内流场模拟的三棱柱网格,利用动网格技术及交界面技术完成了涡旋压缩机的三维瞬态模拟。该模拟形象地揭示了三维涡旋压缩机的内部流动规律,给出了温度、压力、流速在每个转角位置的变化过程。与实验值及二维仿真值进行了对比,分析了误差原因。无油涡旋压缩机内流场仿真形象地揭示了涡旋压缩机的内部流动规律,为深入研究无油涡旋压缩机机理,解决无油涡旋压缩机使用寿命短、排气量难以提高等问题提供了理论参考。同时,动网格技术在涡旋压缩机内流场动态模拟中的应用,探索了计算流体力学技术应用的一个新领域,拓宽了动网格技术的工程应用范围。更多还原

【Abstract】 Scroll compressors are small size, light weight, less wearing parts and without reciprocating mechanism and own. They have great performance advantages in small and medium capacity compressors. They are main development direction of high performance compressors. The structure of oil-free scroll compressor precludes the possibility that working medium contacts with lubricants, which meet the specific needs of medical, food and other industry. However, the manufacturer of large displacement, long life oil-free scroll compressor is still difficult. In order to deeply understand the operation of the scroll compressor, and guide the design of the scroll compressor based on the principle, the analysis of the flow process in scroll compressor is very important. The thermodynamic and computational fluid dynamics theory are applied to study the scroll compressor’s internal flow process in this paper, and the transient distribution of pressure, temperature, flow velocity is gain for the design reference of high performance compressors.Firstly, the oil-free scroll compressor’s structure and working principle are introduced. According to the compression chamber geometry, based on the theory of thermodynamics and heat transfer, by Laws of mass and energy conservation, the volume change and thermodynamic process in the compression chamber are analyzed in detail. In this paper, the oil-free scroll compressor thermodynamic simulation models taking full account of the heat exchanger and the compression process leaks are proposed. The accuracy of mathematical models has been verified by the actul measured value.Then the flow field mathematical model and numerical simulation method are analyzed. The discharge process of scroll compressor is deemed as quasi-static process and the scoll compressor is analyzed by steady-state method of computational fluid dynamics. The reasonable geometric model of exhaust model is selected. The mesh independence is verigied in tests and last the exhaust process is simulated based turbulence theory. This simulation shows the velocity field in scroll compressor at different axial cross section and different vortex angular as well as the three-dimensional velocity field including exhaust pipe.And then the geometric model of scroll compressor is simplified. The compression chamber internal flow simulation is realized by using two-dimensional geometric model. Althought the geomety of scroll compressor is very complex, a suitable mesh form for scroll compressor flow field simulation is found. During the simulation, local deformation coupled with remeshing in CFD dynamicmesh technique is applied, under the condition of a compressible ideal gas, and the flow governing equations as well as the equation of gas state is followed. The RNG κ-ε model is used for turbulent model. This simulation detailedly displays the distribution of the compression chamber pressure, temperature, velocity distribution in the course of suction, compression, and exhaust in two-dimensional scroll compressor. The temperature, pressure, velocity variation at different speed is compared. The experimental results verify the correctness and validity of simulation.Finally,three-dimensional simplified geometric model of scroll compressor is designed. The triple prism mesh that is suitable for3-D scroll compressor flow field simulation is identified by comparing other meshes. The3-D transient simulation is achieved by using dynamic mesh and interface technology. The simulation vividly reveals3-D flow law within the scroll compressor and the temperature, pressure, flow velocity at each angular are given. The3-D results are compared with both2-D results and actual values, meanwhile, the reasons for the error difference are analyzed.The internal flow field simulation vividly reveals the flow law in scroll compressor. It’s important theoretical reference for in-depth study of the oil-free scroll compressor mechanism and solving the oil-free scroll compressor problems of short life and low displacement. Meanwhile, a new application area of CFD technique is explored due to the application of dynamic mesh technology for internal flow flield. It widens the application area of dynamic mesh technology.更多还原