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Study on Instability of Subcooled Cryogenic Cavitating Flows

过冷低温空化流的不稳定性研究

基本信息

批准号：
16560156
负责人：
OIKE Mamoru
金额：
$ 2.37万
依托单位：
Ishinomaki Senshu University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2005
项目状态：
已结题

项目摘要

In this study, the experimental research was carried out about the cavitating flow of liquid nitrogen both at normal boiling point (NBP) and subcooled densified condition, and some knowledge about subcooled cryogenic fluid has been obtained.The experiments were performed at cryogenic two phase flow test equipment. A cylindrical converging-diverging nozzle is installed in the test section, which has 2.2mm throat diameter and a 1.21/25 contraction area ratio. During the experiment, pressures and temperatures at both upstream and downstream of the throat were measured, as well as volume flow rate and kinetic pressure.In the case of subcooled condition, from the results of experimental measurements and observations, the fluid of higher flow rate was allowed to be passed through the throat without cavitation, compared with NBP conditions. The flow rate of subcooled condition at 68K reaches three times as much as that of NBP condition. Also, the different types of cavitating flow were observed in subcooled conditions. The cavitation occurrence was intermittently, that is, cavitating flow could not stay long time period and it shifted back to the single phase liquid flow. This is explained by choked flow at the throat caused by reduced acoustic velocity. This intermittent occurrence of cavitation was not only interesting phenomena, but also important in engineering application. While the cavitation occurred intermittently, the large amplitude of oscillations was induced at the same time. The pressure fluctuation amplitude reaches a maximum 35% of the base pressure, and seems to be a dangerous phenomenon in engineering applications.These phenomena about subcooled cavitating flow are governed by acoustic velocity and cavitation number which change with temperature conditions. In this research, the relationship between the flow appearance and cavitation number or acoustic velocity was shown for predicting the cavitating flow phenomena of subcooled cryogenic fluids.

本研究在低温两相流实验装置上，对液氮在常沸点和过冷致密条件下的空化流动进行了实验研究，获得了对过冷低温流体的一些认识。试验段安装圆柱形收敛-扩张喷管，喉部直径2.2 mm，收缩面积比1.21/25。在实验过程中，测量了喉部上下游的压力和温度，以及体积流量和动压。在过冷情况下，从实验测量和观察的结果来看，与NBP条件相比，允许更高流量的流体通过喉部而不产生空化。在68K时，过冷条件下的流量是NBP条件下的3倍。在过冷条件下，观察到了不同类型的空化流动。空化的发生是间歇性的，即空化流不能长时间停留，而是移回单相液流。这是由于声速降低导致喉部流动受阻造成的。这种间歇性空化现象不仅是一种有趣的现象，而且在工程应用中也具有重要意义。在间歇性空化发生的同时，也诱发了较大幅度的振荡。压力波动幅度最大可达基础压力的35%，在工程应用中似乎是一种危险现象，这种现象由声速和空化数控制，并随温度条件变化。为了预测过冷低温流体的空化流动现象，给出了流态与空化数或声速的关系。