Abstract
Reducing the noise of the underwater propulsor is gaining more and more attention in the marine industry. The pump-jet propulsor (PJP) is an extraordinary innovation in marine propulsion applications. This paper inspects the effects of blade number on a pre-swirl stator pump-jet propulsor (PJP) quantitatively and qualitatively. The numerical calculations are conducted by IDDES and ELES, where the ELES is only adopted to capture the vortical structures after refining the mesh. The numerical results show good agreement with the experiment. Detailed discussions of the propulsion, the features of thrust fluctuation in time and frequency domains, and the flow field are involved. Based on the ELES results, the vortices in the PJP flow field and the interactions between the vortices of the stator, rotor, and duct are presented. Results suggest that, though changing the blade number under a constant solidity does not affect the propulsion, it has considerable effects on the thrust fluctuation of PJP. The wakes of the stator and rotor are also notably changed. Increasing the stator blade numbers has significantly weakened the high-intensity vortices in the stator wake and, hence, the interaction with the rotor wake vortices. The hub vortices highly depend upon the wake vortices of the rotor. The hub vortices are considerably broken by upstream wake vortices when the load per rotor blade is high. In summary, the blade number is also vital for the further PJP design, particularly when the main concerns are exciting force and noise performance.
Highlights
Nowadays, the pump-jet propulsor (PJP) has been widely equipped in torpedos and submarines owing to its high efficiency and outstanding noise resistance
Results show that the tip clearance between the rotor blade tip and the duct is the easiest cavitation place
The effects of blade number on the propulsion, flow, and vortices of a pre-swirl stator pump-jet propulsor are concerned under constant solidities
Summary
The pump-jet propulsor (PJP) has been widely equipped in torpedos and submarines owing to its high efficiency and outstanding noise resistance. PJP is a multicomponent underwater propulsor consisting of a duct and a stator and rotor vane cascades inside the duct. The stator can be installed either upstream or downstream of the rotor, whose installed position categorizes the PJPs into two main forms: the pre-swirl stator form and the rear stator form. The PJP hydrodynamics sets the characteristic performance of the underwater vehicles, and the PJP is receiving increased attention. The propulsion features and flow of PJPs have been widely studied through both numerical approaches and experiments. Suryanarayana et al [3] obtained the cavitation performance of a PJP. Results show that the tip clearance between the rotor blade tip and the duct is the easiest cavitation place
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