制冷与热泵循环中膨胀部件的理论与试验研究

发布时间：2018-03-05 21:26

本文选题：节能　切入点：二级孔板　出处：《天津大学》2014年博士论文　论文类型：学位论文

【摘要】：我国能源形势的严峻已成为不争的事实，为了解决我国的能源问题，关键在于节能，节约优先，效率为本。针对制冷行业，进一步提高循环效率是关键。由于膨胀节流过程节能潜力巨大，而且作为制冷与热泵系统中的研究薄弱环节，本文主要对膨胀部件进行研究，通过理论分析、数值计算和试验研究相结合，从耗散型节流装置孔板到回收型节流装置膨胀机开展研究。孔板是一种结构简单、造价低廉、并有一定控制性能的膨胀部件，可作为膨胀机在启动、非标工况下工作或故障应急的备用装置。本文对耗散型节流装置二级孔板进行了相关研究。提出了二级孔板的设计方法，并设计加工了孔板样板，通过试验对比分析了各样板的节流特性。二级孔板的设计重点在于第二级多孔孔板，主要设计思路为通过开孔率转化为相应尺寸标准孔板的设计。对各样板的试验结果表明，各级孔板孔径的变化对其节流特性的影响不同；二级孔板能够实现流量调节作用，其中以第二级孔板对流量的调节作用为主。多孔孔板的设计参数为多孔孔板的设计以及节流效应的试验提供了比较基础，其中，疏密度和开孔率是影响多孔孔板节流效应的主要因素。对于给出的二级孔板设计模型，第一级孔板的理论压降与试验值之间的相对误差在±15%以内；而第二级孔板的理论压降由于受到各种半经验公式的误差累积的影响，其与试验值之间的相对误差在±30%以内，有必要对模型进行修正。针对常规工质膨胀比较大的特点，设计了回收型节流装置双转子滚动活塞式膨胀机，分析了膨胀机的基本结构及工作过程，建立了膨胀机的不可逆损失模型。通过对膨胀机运动部件之间相对运动及各泄漏通道的分析，分别建立了膨胀机的流体泄漏模型与摩擦损失模型，并分析了润滑油含量对物性的影响以及不同泄漏间隙下膨胀机的泄漏损失情况。通过对泄漏模型与摩擦损失模型的分析与模拟计算，提出了减小膨胀机不可逆损失的有效方法。根据建立的膨胀机模型，对膨胀机在不同工况下的运行情况进行了模拟计算。结果表明，工质进口压力与干度对膨胀机效率的影响较大。在设计工况下膨胀机的理论效率为72.0%，理论输出功为4.87kW。而膨胀机转速为设计转速1500rpm，进口压力在1.0MPa至2.0MPa范围内变化时，其理论输出功在2.55~6.92kW之间，理论效率可以保持在63.4%~74.1%之间。讨论了膨胀相变过程中的亚稳平衡状态，定性分析了相变延迟现象对膨胀机性能的影响，探讨了改善相变延迟现象的方法，讨论了初始参数对膨胀相变过程的影响，并分析了快速降压过程中汽泡的成长情况。由于制冷剂在膨胀机内的膨胀相变过程为亚稳平衡态的相变，为打破亚稳平衡状态需要足够尺度的扰动，初始温度或压力较高时将有助于这一过程的进行。而相变延迟现象对膨胀机的影响存在一定阈值，只有相变延迟时间超过这一阈值时，膨胀过程才会受到比较明显的影响。对膨胀腔内的液体实现有效扰动，将有助于改善相变延迟现象的发生。一旦汽核形成，膨胀过程中压力的变化将成为促进其成长的动力，使相变过程快速进行。成功研制了双转子滚动活塞式膨胀机样机，并对其进行了试运转与试验测试。结果表明，膨胀机在两相进口条件下运转平稳，并输出一定的膨胀功；同时也发现，转子式膨胀机实现过冷液膨胀受到了一定的限制。其中膨胀机效率与回收功受进口工质干度的影响较大，基本随干度的增加呈增加趋势。同时，膨胀机的试验结果也验证了膨胀功的来源，主要以膨胀相变功为主。能实现膨胀机正常运转的进口工质干度最低为0.3。试验过程中随进口工质干度由0.3增加至0.7，实现的膨胀机名义效率由最低0.6%可增加至超过80%。膨胀机的转速集中在250~370rpm之间。回收的膨胀功在进口干度约0.7时约达到1200W，而当膨胀机进口气态工质比例更高时，将可以得到更多的膨胀功。说明膨胀机的设计有成功的一面，也存在许多没有预料到的地方，为进一步提高膨胀机回收功，，提出了改进方案。
[Abstract]:China's energy situation has become an indisputable fact, in order to solve the energy problem in our country, the key lies in energy conservation, conservation priority, efficiency oriented. In the refrigeration industry, to further improve the circulation efficiency is the key. The throttling process due to the expansion potential of energy saving, but also as a study of refrigeration and heat pump system in the weak link. Mainly study on the expansion of components, through theoretical analysis, numerical calculation and experimental study of a combination of machine, carried out the research from the dissipative type orifice plate throttling device to recovery type expansion throttling device.
The orifice plate is a kind of simple structure, low cost, and has a certain expansion member control performance, can be used as the expander in starting, non-standard working conditions or emergency standby equipment fault. Based on dissipative type throttling device two hole plate was studied. Put forward the design method of two hole plate. Design and plate processing model, the model of throttling characteristics are analyzed through experiments. Two design key hole plate is second orifice plate, the main design ideas through the opening rate into the corresponding size design of standard orifice plate. The experimental results of the model show that changes in levels of orifice the aperture Throttling Characteristics of different; two hole board to achieve flow control, the second orifices of flow regulation function. The design parameters for the design of the orifice plate orifice plate and throttling effect test Experience provides a basis for comparison, the density and porosity are the main factors influencing multi orifice plate throttling effect. For a level two hole plate design model is given, and the first level test between the theory of pressure drop orifice value of relative error is less than 15%; and second hole plate theory due to the cumulative effect of pressure drop the error by various semi empirical formulas, and the relative error between experimental value is less than 30%, it is necessary to revise the model.
For the conventional refrigerant expansion characteristics of relatively large, design recovery type throttling device of double rotor rolling piston expander, analyzes the basic structure and working process of the expander, a model of irreversible loss of expander. The expander between the moving parts and the relative motion of leakage channel analysis, are established. The expander fluid leakage model and friction loss model, and analyzed the influence of oil content on the physical properties and the different leakage gap expansion machine leakage loss. Through calculation and simulation analysis of leakage model and friction loss model, and puts forward some effective methods to reduce the irreversible loss of expander. The expander based on model the operation of the expander under different working conditions were simulated. The results show that the refrigerant inlet pressure and dry degree on expander efficiency in the design greatly. Under the working condition, the theoretical efficiency of the expander is 72%, the theoretical output power is 4.87kW., and the expander speed is 1500rpm of design speed. When the inlet pressure varies from 1.0MPa to 2.0MPa, the theoretical output power is between 2.55~6.92kW, and the theoretical efficiency can be kept between 63.4%~74.1%.
The expansion of metastable equilibrium state during the phase change process, the qualitative analysis of the influence of phase change delay phenomenon on the expander performance, discusses the methods to improve the phase delay phenomenon, the influence of initial parameters on the thermal expansion process are discussed, and analyze the growth of bubble rapid depressurization process. Because phase refrigerant in the expansion process of thermal expansion the machine is metastable, to break the disturbance of metastable equilibrium states need enough scale, the initial temperature or high pressure will contribute to this process. There are some phenomena and phase change delay threshold of the expander, only the phase delay time exceeds this threshold, the expansion process will be affected obviously. Effective disturbance of the fluid cavity expansion, will help improve the phase delay phenomenon. Once the nuclear steam formed during the expansion process of pressure change It will be the motive force to promote its growth and make the process of phase transition rapidly.
The successful development of the dual rotor rolling piston expander prototype, and has carried on the test run and test. The results show that the expansion machine operates smoothly in two-phase inlet conditions, and the output of the expansion work; it is also found that the rotor type expansion machine realizes the supercooled liquid expansion by a certain limit. The expander efficiency and power recovery by imported refrigerant of large dry, with dry degree increased. At the same time, the expander test results also verify the source of the expansion work, mainly by the thermal expansion of power. To achieve the normal operation of the expander imported refrigerant dryness for a minimum of 0.3. test in the process with imported refrigerant dryness increased from 0.3 to 0.7, the name of the expander efficiency can be increased to more than 0.6% of the minimum 80%. expander speed ranged from 250~370rpm. The recovery of the expansion work in the import dry degree of about 0.7 to about 1200W, and when the ratio of the inlet gaseous working medium of the expander is higher, more expansion work can be obtained. This shows that the design of the expander is successful and there are many unforeseen points. In order to further improve the recovery work of the expander, an improvement plan is put forward.

【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TB653

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