Numerical simulation of performance of marine waterjet propulsion system
Luo Can1, Cheng Li1, Liu Chao1, Qi Weijun2, Shang Yi′nan1
1.School of Hydraulic, Energy and Power Engineering, Yangzhou University, Yangzhou, Jiangsu 225009, China; 2.Nanjing Water Planning and Designing Institute Co. Ltd., Nanjing, Jiangsu 210006, China
Abstract:To analyse the hydraulic performance of the mixed-flow pump with vaned diffuser in a waterjet propulsion system more accurately, CFX code is used to simulate the steady turbulent flow in the system, which consists of a pump, entry duct, water body below the vessel and nozzle, at various flow rates by means of the standard k-ε turbulence model. The hydraulic loss distribution, hydraulic performance, axial thrust and flow field features are exploited. Because the geometry of entry duct is relatively complex where its rectangular section at the inlet needs to be transformed into a circular one at the outlet, the hydraulic loss takes a maximum proportion in the entry duct, especially at a low flow rate. In that case, the proportion exceeds 90%. However, this proportion reduces with increasing flow rate, and the hydraulic loss proportions in the other components increase accordingly. The system is subject to the hydraulic instability around 0.50Qd. The high efficiency zone exists in the range of 0.76Qd and 1.10Qd. The axial thrust generated by the pump diminishes when the flow rate rises. At a small flow rate, the flow pattern in the impeller is complicated, and the spanwise vortex, radial vortex and leakage vortex are evident. Fortunately, these vortices are shrunk until disappear with increasing flow rate.
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