| Waterjet propulsion has good operation performance and cavitation resistance ability, high efficiency, simple transmission mechanism, easily maintenance, large load range,which is widely applied in modern high speed vessel. Waterjet pump and inlet duct as the most important components of the waterjet propulsor are related to the whole performance of the propulsion system. The efficiency and flow field of waterjet pump are affected by the flow field of tip clearance of blade and axial gap between impeller and guide blade body. The outlet of duct is the inlet of waterjet propulsor, the shape and area of the water inlet of inlet duct directly affect the flow field in duct, thus affect Waterjet pump flow field. Researching the coupling of different tip clearance and axial gap, optimizing water inlet area of inlet duct have important reference value to the design of waterjet propulsion. In this paper, a high-speed vessel waterjet pump is used as the research object. The following several aspects have been completed mainly:Firstly, the three-dimensional geometric model of the waterjet pump and fluid model was established by using UG. Three kinds of tip clearance model 0.5mm(2.6%D), 1mm(5.1%D), 1.5mm(7.6%D, D is impeller diameter) and three kinds of axis gap model 5.6mm,11.2mm,16.8mm(Pump's original gap is 8.7 mm) have been established, nine models are got by coupling tip clearance with axis gap. Hexahedron mesh grids of the blocking fluid model were structured by ICEM.Secondly, numerical simulation is calculated by ANSYS CFX and use experiment to verify its reliability. The calculation of model is reliable, proved by experimental. 9 different conditions are calculated on each model. The pressure distribution of blade and tip clearance and differential pressure curve of tip clearance which conclusively effect tip clearance flow field have been got.Thirdly, the calculation results show that the tip clearance and the axial gap mainly influence in small flow condition. The increase of the axial gap make the negative pressure zone for cavitation increase on blade suction surface but the tip clearance increasing makes it decrease. The increasing of tip clearance and axis gap make the negative pressure zone for cavitation on blade suction surface decrease, the high pressure zone on the margin of the blade outlet decrease at the rated flow condition. The increase of tip clearance and axis gap make the negative pressure zone and high pressure zone decrease, the increase of tip clearance make the high pressure zone on the margin of the blade outlet increase at large flow condition. With the increase of tip clearance, the different pressure is effected by axis gap extend from outlet to inlet when axis gap increases. With the axial gap increasing,it weakens the tip clearance effects on clearance differential pressure. The increase of flow will weak the influence of tip clearance and axis gap on the clearance differential pressureFourth, changing the longitudinal length of the water inlet of inlet duct, four different inlet areas are obtained and a series of numerical simulation calculations are carried out under the condition of four kinds of different IVR. The flow performance of inlet duct is analyzed from pessure distribution on outlet section, weighting average angle, pressure distribution of upper and low wall on different, pressure distribution on the section of duct, the flow loss. When the IVR is small with water inlet area of inlet duct increasing, the simulation calculated results show that: Pressure distributes uniform on outlet section. Weighting average angle increases 1°~2°. The pressure coefficient of upper and low wall increases and the cavitation resistance of inlet duct decreases. The pressure distributes uniform on the section of duct. The flow loss decrease. When the IVR is large, the increasing of water inlet area optimize the flow field of inlet duct is less. |
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