小流量离心式制冷压缩机流动机理及设计研究

发布时间：2018-04-28 07:07

本文选题：离心压缩机 + 小流量　；参考：《北京建筑大学》2017年硕士论文

【摘要】：离心式制冷压缩机由于其稳定性和高效性一直在大流量蒸发循环系统中占据重要地位,而在小流量应用领域,其运行效率远远低于大流量下效率指标。小流量离心式压缩机设计难点在于分析其内部粘性气体复杂流动造成的流动损失,本文以小流量离心式制冷压缩机作为研究对象,通过搭建压缩机性能测试试验台对设计样机进行性能测试,根据其内部结构参数绘制等比例流道三维模型,并调用Fluent模拟软件中NIST Real Gas模型选取R134a真实气体物性参数进行CFD数值仿真计算,并结合样机试验测试数据,对模拟结果及方法进行了验证,然后对压缩机内部气体流动机理进行分析研究。经测试所设计的样机整机效率在50%左右,内部流动尚有较大优化空间,同时试验结果也验证了模拟方法的可行性和模拟结果的准确性;模拟结果表明在所研究工况下,叶轮进口靠近压力面存在明显的二次流现象,制冷剂气体以与叶片存在冲角的方向进入叶轮子午面流道并与轮盘发生撞击,之后气体流动出现盖面分离现象。气体在叶轮出口处气流方向与扩压器叶片存在冲角,导致气流不能平稳流入扩压器流道。整机模型中流动损失主要集中在“级”内,故在进行流动优化时优先考虑“级”内损失;研究不同结构参数对压缩机流动效率的影响,发现针对所设计的小流量离心制冷压缩机,在设计工况下原模型的叶轮出口处流动较为平稳,效率相对较高;匹配圆弧通道扩压器和直壁通道扩压器对本次设计模型效率并无本质影响;叶片数为12时的叶轮模型效率最优。本文对小流量离心式压缩机模型仿真得出的计算结果可为今后小流量离心式制冷压缩机结构优化设计提供指导。同时,为探究不同结构参数对内部流动的影响,模型对比数量仍需进一步提高。
[Abstract]:Centrifugal refrigeration compressor has been playing an important role in large flow evaporative circulation system because of its stability and efficiency, but in the field of small flow application, its operational efficiency is far lower than the efficiency index under large flow rate. The difficulty in the design of small flow centrifugal compressor is to analyze the flow loss caused by the complex flow of viscous gas inside the compressor. This paper takes the small flow centrifugal compressor as the research object. The performance of the designed prototype was tested by setting up the compressor performance test rig, and the three-dimensional model of proportional flow channel was drawn according to its internal structure parameters. Using the NIST Real Gas model in Fluent simulation software, the real gas physical property parameters of R134a are selected for CFD numerical simulation, and the simulation results and methods are verified by combining the test data of prototype test. Then the gas flow mechanism inside the compressor is analyzed and studied. The efficiency of the prototype designed by the test is about 50%, and there is still much room for optimization of the internal flow. At the same time, the feasibility of the simulation method and the accuracy of the simulation results are verified by the test results. There is an obvious secondary flow phenomenon in the impeller inlet near the pressure surface. The refrigerant gas enters the impeller meridional flow channel in the direction of the angle of attack with the blade and impinges on the wheel, and then the gas flow appears the cover surface separation phenomenon. The air flow direction at the outlet of the impeller has an angle of incidence with the diffuser blade, which results in the airflow not flowing smoothly into the diffuser channel. In the whole model, the flow loss is mainly concentrated in the "grade", so the "grade" loss is given priority in the optimization of the flow, and the influence of different structural parameters on the flow efficiency of the compressor is studied. It is found that the flow of the impeller outlet of the original model is relatively stable and the efficiency is relatively high under the design conditions for the designed centrifugal compressor with small flow rate. The matching arc channel diffuser and the straight wall channel diffuser have no essential influence on the efficiency of the design model, and the impeller model efficiency is optimal when the blade number is 12:00. In this paper, the results obtained from the model simulation of the centrifugal compressor with small flow can provide guidance for the optimization design of the structure of the centrifugal compressor with small flow in the future. At the same time, in order to explore the influence of different structural parameters on internal flow, the number of model contrast needs to be further improved.
【学位授予单位】：北京建筑大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB652

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