Propulsion performance and unsteady forces of a pump-jet propulsor with different pre-swirl stator parameters

Rotor-stator interaction of a pump-jet propulsor can induce strong pressure fluctuations and vibrations, which may deteriorate the vibration and acoustic performance and cause damage to the propulsion system at some severe working conditions. In this paper, the role of stator parameters, such as the prewhirl angle, the rotor-stator spacing and the chord length of the stator blades, in the propulsion performance and unsteady forces of a pump-jet propulsor is investigated through a numerical simulation. The shear-stress transport (SST) k-omega turbulence model together with the sliding mesh technique are employed to simulate the three-dimensional unsteady flow. The propulsion performance is obtained from the steady simulation at nine advance ratios. Take the steady result as the initial flow field, the convergence usually occurs in one revolution of the rotor in the unsteady computations. For the unsteady computation analysis, the line-spectrum amplitudes of the unsteady rotor forces are analyzed, and a method based on time domain statistics is employed to reflect the fluctuating amplitude characteristic of the unsteady pressures on the whole blade surface of the rotor. Since the pitch angle of the rotor blade decreases sharply along the radial direction, the velocity circumferential angle is corrected based on the blade pitch angle to reflect the fluctuation of rotor incidence angle in the circumferential direction.