In this paper, numerical investigations of an axial flow pump with different tip clearances (0.6, 1.2, 1.8, 2.4, 3.0 mm) at different flow rates (0.42 ∼ 0.5 m3/s) are carried out. The SST k-ω turbulence model together with the sliding grid technique are adopted. The uncertainty analysis is carried out with a tip clearance of 0.6 mm to verify the accuracy of the numerical solver. The comparisons of hydrodynamic performance for the axial flow pump with different tip clearances are presented in detail. As the tip clearance increases, the thrust and propulsion efficiency of the axial flow pump can be reduced significantly.
The axial flow pump is a kind of highly specific speed pump with a large flow rate and low head, which is the core power component of marine water-jet propulsion system. The axial flow pump is widely used in many fields of great significance, such as the industrial circulating water systems, waterjet propulsion, large-scale water diversion and so on (Guan, 2009). When the axial flow pump is operating, there is a tip clearance between the rotor blade and the surface of duct. The tip clearance has a great influence in the hydrodynamic performance of the axial flow pump. Therefore, it is very important to investigate the impact of tip clearance on the axial flow pump. With the rapid development of computational methods, CFD (Computational Fluid Dynamics) method is widely used in complex flow. It is practical and reliable for the investigation of tip clearance.
Studies on tip clearance of turbomachinery have already been presented (Xiao et al., 2001). Many of the studies about the flow of tip clearance are aimed at duct propeller. For example, Lee et al. studied the flow of tip clearance of the ducted propeller by solving the three-dimensional RANS (Reynolds Averaged Navier-Stokes) equations. The calculated results are in good agreement with experimental results. It is shown that the numerical method is feasible for the study of tip clearance flow (Lee, 2003). Ji et al. investigated the unsteady cavitating turbulent flow around a full-scale marine propeller operated in non-uniform ship wake (Ji; Luo; Wu; Liu, 2010).
