CAJ | 학술논문

为了研究回流涡空化特性，对一台螺旋离心泵内部的空化流动进行了可视化研究，在一定的工况下该泵内部发生了回流涡空化，捕捉到了不同流量下螺旋离心泵内部回流涡空化形态，发现回流漩涡空化中存在2个旋转的空化云，并且随着流量的减小，回流涡空化云体积逐渐减小；对该泵进行了数值模拟，发现随着流量的减小，泵进口外部形成的回流区域变小，从而导致回流涡空化云体积逐渐减小。该文对螺旋离心泵内回流涡空化体积演变机理的深入研究提供了参考。
위료연구회류와공화특성，대일태라선리심빙내부적공화류동진행료가시화연구，재일정적공황하해빙내부발생료회류와공화，포착도료불동류량하라선리심빙내부회류와공화형태，발현회류선와공화중존재2개선전적공화운，병차수착류량적감소，회류와공화운체적축점감소；대해빙진행료수치모의，발현수착류량적감소，빙진구외부형성적회류구역변소，종이도치회류와공화운체적축점감소。해문대라선리심빙내회류와공화체적연변궤리적심입연구제공료삼고。
Screw centrifugal pump has swirling backflow under a wide range of flow rates. The backflow vortex structure occurs in the shear layer between the main flow and the swirling backflow. The pressure at the core of a backflow vortex is lower than the ambient pressure due to the centrifugal force on the vertical flow which results in cavitation if the core pressure becomes lower than the vapor pressure. This is called backflow vortex cavitation. In order to study the backflow vortex cavitation, a screw centrifugal pump was designed for experimental studies. The clearance between vane rim and cover plate was 2.9 mm in this screw centrifugal pump. By using the high speed video picture, we observed two backflow vortex cavitation clouds extending upstream from the tip at the screw centrifugal pump inlet, covering a wide range of flow rates. We also found that under a certain net positive suction head (NPSH), i.e., when the flow rate was decreased, the volume of the two backflow vortex cavitation cloud was decreased. Experimental studies on the backflow vortex cavitation from this screw centrifugal pump have provided novel insight of the characteristics of backflow vortex cavitation, but the limited information has not lead to the complete understanding of the phenomena. In addition to blade surface and backflow vortex cavitations, tip leakage cavitation occurred for screw centrifugal pump with tip clearance. With these types of cavitation, the flow in a screw centrifugal pump presented a very complicated three-dimensional structure. Since experiment results give limited information, numerical simulation plays an important role to further understand such complicate flow phenomena. Using the CFD code, the fundamental characteristics of the backflow vortex cavitation was investigated in detail. It was found that the backflow vortices were formed in a circumferentially twisted manner at the boundary between the swirling backflow and the straight inlet flow. When the flow rate was decreased, the screw centrifugal pump inlet flow velocity increased, but the static pressure of fluid at screw centrifugal pump inlet region decreased. As the screw centrifugal pump inlet fluid static pressure was decreased, the static pressure of suction side of vane region near by vane tip at screw centrifugal pump inlet decreased. Meanwhile, the pressure of pressure side of vane region near by vane tip at screw centrifugal pump inlet was about vapor pressure. With the decreased flow rate, the pressure difference of pressure side of vane and suction side of vane reduced. The backflow region reduced upstream due to the decreased pressure difference of pressure side of vane and suction side of vane, which is the main reason of the two backflow vortex cavitation volume decreased with the flow rate decreased in screw centrifugal pump. When the clearance between vane rim and cover plate was less than 1.3 mm in the screw centrifugal pump, the screw centrifugal pump inlet region had no backflow occurred. It indicated that the size of clearance between vane rim and cover plate have influences on backflow vortex cavitation occurred in screw centrifugal pump inlet. The purpose of the present study is to obtain a further understanding of backflow vortex cavitation.