Abstract
Previous studies show that the tip clearance loss limits the improvement of turbomachinery performance, and it is roughly in close relation with the gap size. In this study, a pumpjet propulsor (PJP) with different sizes of tip clearances ([Formula: see text], 0.5, 1, 2, 3[Formula: see text]mm) has been presented to investigate the influence of tip clearances on PJP. This analysis is based on computational fluid dynamic (CFD) method, and the SST k-[Formula: see text] turbulence model is applied. Calculations are carried out with a worldwide employed ducted propeller (the Ka4-70 propeller in 19A duct) to verify the numerical simulation. And the grid independence validation is discussed. The numerical simulation of PJP flow with different tip clearances is carried out. Results show that the open water efficiency decreases gradually with the increase of tip clearance. The efficiency decreasing is caused by the tip flow loss. The shape of tip vortex of PJP which consisted of tip-separation vortex and tip-leakage vortex is presented. Furthermore, the formation and spread process of tip vortex at different tip clearances are discussed. Then, the effect of different tip clearances on the pressure field of rotor blade is investigated. The main pressure area affected by different tip clearances is mainly concentrated in the area above 0.9 spanwise of the suction side of rotor blade. Beyond that, the effects of different tip clearances on the velocity field of PJP has been studied.
Highlights
Pumpjet propulsor is a new type of underwater propulsion system, which adopts single-rotor propulsion and decelerating duct
Ivanell [2001] uses computational fluid dynamics method (CFD) to calculate the hydrodynamic performance of the torpedo with pump jet, and the rationality of the method is verified by comparing with the experimental results
Ducted propeller and turbomachinery are different with pumpjet propulsor, the results of duct propeller and axial flow pump researches have a good reference to the research of tip clearance flow of pumpjet propulsor
Summary
Pumpjet propulsor is a new type of underwater propulsion system, which adopts single-rotor propulsion and decelerating duct. Suryanarayana et al [2010] make experiment on hydrodynamic performance of the underwater vehicle equipped with pumpjet propulsor They verify the advantages of the rear stator pumpjet propulsor and indicate that the rear stator can absorb the rotational energy of the rotor, reduce the radial component in the wake, and improve the efficiency of the propulsion. Ducted propeller and turbomachinery are different with pumpjet propulsor, the results of duct propeller and axial flow pump researches have a good reference to the research of tip clearance flow of pumpjet propulsor. Numerical Investigation of Different Tip Clearances Effect numerical simulation, based on the sliding grid technique, the numerical simulation of three-dimensional full channel steady turbulent flow is carried out. The numerical simulation of PJP flow with different tip clearances is carried out. The effect of different tip clearances on the hydrodynamic performance of Pumpjet Propulsor is researched. The research conclusion will be important to improve the efficiency of Pumpjet Propulsor and help the design of it
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