Performance of Vane-Type CO2 Expander and Characteristics of Transcritical Expansion Process
Performance of Vane-Type CO2 Expander and Characteristics of Transcritical Expansion Process
复制标题
DOI：
10.1080/10789669.2009.10390859
复制
发表时间：
2009-07
期刊：
影响因子：
--
通讯作者：
M. Fukuta;T. Yanagisawa;M. Higashiyama;Y. Ogi
中科院分区：
文献类型：
--
作者：
M. Fukuta;T. Yanagisawa;M. Higashiyama;Y. Ogi
二氧化碳（CO2）是用于制冷或热泵循环的氢氟碳制冷剂的替代品之一。由于风冷式CO2循环的固有COP低于氢氟碳化物循环，建议使用膨胀器作为膨胀装置，以提高CO2循环的循环性能。膨胀机的性能对循环性能的提高有很大的影响。此外，膨胀过程是复杂的，因为在典型条件下运行的膨胀机发生的膨胀过程是从超临界到亚临界的。因此，弄清膨胀机的性能和膨胀过程是十分重要的。本文研制了一种小型叶片式膨胀机，并对其性能进行了测试。原型叶片式膨胀机泄漏损失大，通过改变叶片背压供给方式改善了性能。此外，还对膨胀机中的膨胀过程进行了实验和分析。采用带玻璃窗的简易活塞-气缸膨胀机构，对跨临界膨胀过程进行了详细的研究。结果表明，与进口温度小于40℃时的理想情况相比，跨临界膨胀过程中压力变化的拐点出现了一定的时间延迟。CO2分子的团簇结构在进入亚临界区后仍保持较长时间。
Carbon dioxide (CO2) is one candidate for alternatives to hydrofluorocarbon refrigerants for refrigeration or heat-pump cycles. Since the inherent COP of an air-cooled CO2 cycle is lower than that of HFCs, the use of an expander as an expansion device is recommended to improve the cycle performance of the CO2 cycle. The performance of the expander greatly influences the improvement of the cycle performance. Moreover, an expansion process is complicated, since the expansion process occurring in the expander operated under a typical condition proceeds from supercritical to subcritical. Therefore, it is important to clarify both the expander performance and the expansion process in the expander. In this study, a small vane-type expander is developed, and the performance of the expander is measured. The prototype vane expander has a large leakage loss, and the performance is improved by changing the way of supplying a vane back pressure. Additionally, the expansion process in the expander is examined experimentally and analytically. The transcritical expansion process is also investigated in detail by using a simple piston-cylinder expansion mechanism with a glass window. It is shown that an inflection point of the pressure change under the transcritical expansion process appears with a certain time delay in comparison with an ideal case when the inlet temperature is less than about 40°C. A cluster structure of a CO2 molecule remains for a long time after entering the subcritical region.