【作者】 赵丽；

【导师】 李敏霞；

【作者基本信息】 天津大学 ， 工程热物理， 2010， 硕士

【摘要】 常规工质逆循环中,包括压缩机、换热器及系统控制等在内的各部分都得到了较为完善的发展,唯独节流部件是例外。原因是多方面的。但是不得不看到的是,将逆循环装置中取代节流阀的膨胀机应用于大中型制冷与热泵机组时,可回收的膨胀功比较可观。而其可观前景与推广应用的关键就是开发出高效膨胀机。针对逆循环中取代节流阀的双转子膨胀机,本文通过理论分析与数值计算,分析了膨胀机的设计要点,讨论了工作过程中膨胀相变机理以及内部各不可逆损失的能流分析与相关模拟计算。论文以课题组研发CO₂滚动活塞膨胀机的经验为基础,开展了常规工质取代节流阀的双转子膨胀机的设计研究。分析了针对不同工质,转子式膨胀机相应的侧重点。给出了膨胀机结构特征尺寸的设计依据,并讨论了膨胀机的运动规律。取代节流阀的膨胀机工作过程中,回收的有用能主要来自膨胀过程中的相变功。尽可能回收这部分功是提高膨胀机效率的关键。为此,论文详细讨论了膨胀机工作过程中的相关相变机理。液体的极限过热度、汽化核心的形成以及汽泡的生长模式是相变过程中比较重要的过程,尤以汽化核心的形成为相变过程顺利进行的关键。论文以已有理论研究为基础,提出了汽核形成模型,并分析与总结了纯工质情形下过热液极限过热度以及汽泡的生长模型。为了不断优化设计取代节流阀的常规工质双转子膨胀机,在设计与分析膨胀机结构与运动的基础上,对膨胀机进行了建模分析,主要探讨了膨胀机工作过程中的摩擦与泄漏情况。分析了各部件之间的受力情况,并对相关各力的作用效果进行了便于理解的合理的解释。讨论了常规工质双转子膨胀机的主要泄漏通道及泄漏模型,并建立了膨胀机的摩擦损失模型与泄漏损失模型。模拟结果表明,摩擦损失对膨胀机效率影响较大,是提高膨胀机效率关键应解决的问题。最后,对常规制冷逆循环中取代节流阀的膨胀机可实现的试验方式进行了探讨。由于直接在大中型系统中测试较为不便,现提出三角循环模式进行膨胀机的试验与测试。更多还原

【Abstract】 In conventional reverse cycle, all parts including compressor, heat exchanger and system control etc., have been got a more perfect development. Just throttle part is an exception with many reasons. But what have to see is that the recoverable work is substantial when a expander, in a medium or large refrigeration and heat pump units, has been used to replace the throttle in a conventional reverse cycle. And the key to its prospects and promote its application is to develop a highly efficient expander. To the two rolling piston expander which been used to replace throttle in conventional reverse cycle, through theoretical analysis and numerical calculation, the paper have discussed the design elements of the expander, analysed the phase transition mechanism during its expansion process and the irreversible loss of energy and related simulation.Based on our work group’experience of CO₂ rolling piston expander, this paper have carried out the design of conventional two rolling piston expander which been used to replace throttle, analyzed the corresponding focus in rotor expander of different working refrigerants, given the design basis of the structure size of expander, and discussed the motion discipline of the expander.During the work process of expander of which replace throttle, the recoverable useful energy is mainly the phase transition work in expansion process. Maximize the recovery of this work is the key to improving the efficiency of expander. To this end, the paper have discussed in detail the related phase change mechanism in the work process of expander. What is more important during the phase transition process is the limit of liquid superheat, the formation of the vaporization core and the model of vaporization bubble growth, particularly the formation of the vaporization core is the key to the smoothly run of phase transition. Basing on the existing theoretical research, thesis has been proposed the formation of the vaporization core,as well as, analyzed and summarized the limit of liquid superheat and the growth model of bubble in the case of pure refrigerant.In order to optimize the design of conventional two rolling piston expander which would replace throttle, under the design and analysis of the structure and movement of expander, modeling analysis have been conducted and the analysis of friction and leakage is the main work. The forces between various components have been analysed and a reasonable explanation of the effect related to each force have been given to facilitate understanding. The main leakage channel and leakage model of working fluid was discussed. Then the friction loss model and leakage loss model was established. The results show that the friction loss has a greater impact on the expander efficiency and is key problems to be solved to improve the efficiency of expander.Finally, the realisable testing of expander has been discussed. As the too much trouble when carry out a direct test in large systems, triangular model has been proposed.更多还原