【作者】 孙伟；

【导师】 何国庚；

【作者基本信息】 华中科技大学 ， 制冷及低温工程， 2021， 博士

【摘要】 采用制冷剂喷射技术的低温空气源热泵可以有效地解决传统单级压缩热泵系统在寒冷季节存在的排气温度过高,系统性能衰减和制热量不足的问题。喷射增焓压缩机是喷射增焓技术的关键,为了提高喷射效率和热泵系统性能,本文对喷射增焓滚动转子压缩机在小型低温空气源热泵中的应用进行了深入研究。首先,基于喷射增焓滚动转子压缩机的运行特性,对其压缩和喷射过程进行了理论分析,建立了用于闪蒸器和经济器系统的喷射增焓滚动转子压缩机性能理论计算模型及CFD模拟模型。其次,对喷射增焓滚动转子压缩机在经济器和闪蒸器系统中的性能进行了实验测试和对比。实验结果显示,使用喷射增焓滚动转子压缩机的闪蒸器和经济器系统均能有效的提高热泵系统的制热量和COP,但经济器系统喷射的制冷剂可以为气液两相状态,其有利于降低压缩机的排气温度。在相同喷射压力条件下,当喷射制冷剂均为气相状态时,闪蒸器和经济器系统的性能相当;当经济器系统喷射的制冷剂为气液两相状态时,闪蒸器系统的性能高于经济器系统。随后对气相喷射增焓滚动转子压缩机的流动特性进行了CFD仿真模拟,并通过理论和实验结果验证了CFD模拟模型的可靠性。分析发现了实验用压缩机存在严重的吸气和喷射回流现象。根据压缩机的几何结构及运行特性,通过CFD模拟探讨了不同喷射口位置对喷射增焓压缩机吸气回流和喷射回流的影响。通过对气液两相喷射增焓滚动转子压缩机的流动特性进行了理论分析和CFD模拟。分析发现传统经济器系统存在喷射干度不可调节的缺陷,进而提出了一种新型可调节喷射干度的经济器热泵循环系统。通过对不同喷射干度下喷射增焓滚动转子压缩机的性能分析发现,该系统可以有效解决压缩机排气温度过高的问题,使得热泵系统在极端恶劣的环境温度下也可以正常高效运行。最后,通过理论和CFD模拟相结合的方法,对喷射支路不带止回阀的端面喷射口的结构及喷射条件进行了优化。结果显示,喷射口最佳喷射起始角度为0°,而最佳喷射结束角与设定的打开喷射支路时的最高蒸发温度密切相关。此外,当喷射压力略高于喷射结束时压缩腔的压力时,几乎不会产生喷射回流现象。并且相较于传统无喷射口的热泵系统,在保证制热量的同时,使用优化后的喷射增焓转子压缩机热泵系统的运行工况可以向下扩展约10℃。本文研究的喷射增焓滚动转子压缩机不仅在喷射支路不用设置止回阀,而且可以在低温工况下极大提高系统的制热量和系统性能,这对低温空气源热泵的产品设计开发及应用推广具有重要意义。更多还原

【Abstract】 The low temperature air source heat pumps using refrigerant injection technique can effectively solve the problems of high discharge temperature,system performance degradation and insufficient heating capacity in the traditional single-stage compression heat pump system in the cold seasons.The injection compressor is the key to the refrigerant injection technique.In order to improve the injection efficiency and the performance of the heat pump system,this paper conducts an in-depth study on the application of the injection rotary compressors in the small low temperature air source heat pumps.Firstly,based on the operating characteristics of the injection rotary compressor,the compression and injection process were theoretically analyzed,and the theoretical calculation model and CFD simulation model for the performance of the flash tank and internal heat exchanger cycle system using the injection rotary compressor were proposed.Secondly,the performance of internal heat exchanger cycle and flash tank cycle using an injection rotary compressor was tested and compared.The results of experiments showed that both the internal heat exchanger cycle and flash tank cycle can effectively improve the heating capacity and COP,and for the internal heat exchanger cycle,the injected refrigerant can be in a two-phase state,which is beneficial to reduce the discharge temperature of the compressor.Under the same injection pressure condition,when the injected refrigerant is in the vapor phase,the performance of internal heat exchanger cycle and flash tank cycle are equivalent;when the injected refrigerant of the internal heat exchanger cycle is in the two-phase state,the performance of the flash tank cycle is higher than the internal heat exchanger cycle.Then,the CFD simulation was carried out on the flow characteristics of the vapor injection rotary compressor,and the reliability of the CFD simulation results was verified by theoretical and experimental results.It is found that there are serious suction backflow and injection backflow during the operation process of the experimental compressor.According to the geometric structure and operating characteristics of the injection rotary compressor,the influence of different injection port positions on the suction and injection backflow of the injection compressor is discussed through CFD simulation.In addition,theoretical analysis and CFD simulation of the flow characteristics of the twophase injection rotary compressor were carried out.It is found that the injection quality of traditional internal heat exchanger cycle can not be controlled,and a novel internal heat exchanger cycle which can adjust the injection quality was proposed.Through the performance analysis of the novel internal heat exchanger cycle under different injection quality,it is found that this system can effectively solve the problem that the compressor discharge temperature is too high,so that the air source heat pump can run normally and efficiently under extreme environment temperature.Finally,by combining theory and CFD simulation,the structure of the injection port and the injection conditions of the system were optimized.The results show that the optimal start of injection rotation angle is 0°,and the optimal end of injection rotation angle is closely related to the maximum evaporation temperature when the injection path is opened.In addition,the injection pressure can be slightly higher than the pressure of the compression chamber at the end of the injection,which will only produce negligible injection backflow.And compared with the traditional heat pump system without injection path,the operating conditions of the heat pump system using the optimized injection rotary compressor can be extended down by about 10℃ while ensuring the heating capacity.The injection rotary compressor studied in this paper not only does not need to set a check valve in the injection path,but also can greatly improve the heating capacity and system performance of the heat pump under low temperature conditions,which is of great significance to the product design and promotion of low temperature air source heat pumps.更多还原