Numerical investigations of flow characteristics of a pumpjet propulsor in oblique inflow

摘要

In this study, a detailed analysis of hydrodynamic performance of a pumpjet propulsor (PJP) in different oblique inflow angles (beta = 0 degrees , 5 degrees , 10 degrees , 15 degrees , 20 degrees, 25 degrees, 30 degrees, 40 degrees) and different rotational speeds (n= 3000rpm, 3600rpm, 4200rpm) is investigated numerically. The SST k-omega turbulence model and sliding mesh technology based on the Reynolds Averaged Navier-Stokes (RANS) method are employed. The structured grids are adopted to the whole computational domain. The grid independent inspection is carried out and verified. A ducted propeller (the Ka470 propeller in 19A duct) is selected to validate the numerical method by comparison of its results with experimental data. Based on the numerical method, it can be found that the propulsor efficiency decreased with the increasing of different beta. The propulsor efficiency changes tinily in little oblique angle and decreases significantly when the oblique angle is larger than 20 degrees. The thrust coefficient and torque coefficient of PJP are obtained. The increase of beta has a negative impact on the balance performance of PJP. The pressure distributions of pressure and suction side of rotor blade with different beta are analyzed. Owing to the influence of beta, the pressure of the upper left region of rotor blade drops significantly. The enlargement of the local load on pressure side and the appearance and expansion of the low-pressure region on suction side occour at the bottom right region of rotor blade. The radial distributions of the axial velocity (V-z) and the tangential velocity (V-t) with different Span and beta along the axial direction are investigated. The increase of beta resultes in a severe oscillatory behavior of the flow velocity, which easily induces the occurrence of cavitation phenomenon and mechanical vibration. The velocity contours of the axial cross section with different beta are presented. Due to the change of beta, the flows are blocked by the flow-guide and duct, there are obvious high-velocity and low-velocity regions of the flows.