The Research On The Axial Flow Impeller Cavitation

Pump is the one of most widely used general-purpose machine in our lives, but during the course of society production, the cases of the axial flow pump operating conditions deviate from the design condition would happen, because the water level of the intake sump and outlet sump changs. That would inevitably cause the occurrence of the phenomenon of cavitation. When cavitation occurs, the cavity may take a great interference on the flow field and its distribution, such as a fallen flow and head, a lower efficiency, vibration and noise, which affect the safety and reliability of the pump operation. So it requires that we should consider the influence of cavitation at the design stage to ensure the axial flow pump has a high cavitation performance, and reduce its design and operation costs at the same time.This article is based on combining the experiments and numerical simulation, seeking the location and size of low-pressure area, establishing the relationship between external characteristics of head, power, efficiency and the cavitation, trying to find an appropriate algorithm for the numerical simulation of axial flow pump cavitation performance. The article uses ANSYS-ICEM, TurboGrid on the axial inlet and impeller modeling and mesh generation, then calculates the inner flow field of axial flow pump with commercial software CFX 10.0 on this basis. In the three-dimensional cavitation flow calculation, both a two-phase homogeneous mixed fluid continuity equation and Reynold time-average N-S equation are used as the physical model, supplying with RNG k-εturbulence model, plus a cavitation model to describe the cavitation process. The finite volume method is adopted as the numerical methods on unstructured hexahedral grid to discrete the control equations, numerical results can simulate the cavitation on the blades of axial flow pump surface well.In comparison the CFX-Post analysis and model test, it finds that:(1) two-phase mixture model can predict cavitation occurrence and its development; (2) the prediction of cavitation position and shape at different operating points corresponds with the experimental results; (3) the gap cavitation occurs at the outer edge of the blade and the impeller room clearance, with a reducing effective cavitation allowance and a volume and speed of reflux increasing trend; (4) the locations of cavitation are in agreement with and the non-cavitation model calculated minimum pressure points, but compared to the inlet side area where the lowest pressure point occurs, the highest bubble phase volume fraction point is further back. This is possibly because the water brings bubble there; (5) compared the computed result with the model experiment, carries on the cavitation simulating calculation using the runner 0°cavitation test data, the data result is found to have the uniformity in the tendency, but the accuracy still needs to be improved and a further study.