The effects of skew parameter on the water jet propulsion pump with special emphasis on transient performances

The skew has a significant impact on performance of waterjet propulsion pumps used in marine engineering. The objective of this paper is to investigate the influence of skew parameter especially on transient performances by modifying the skew distribution based on a prototype jet propulsion pump. The numerical methods were used to investigate the steady and transient characteristics of several types of pumps with different skew parameter based on the prototype pump. It is found that the increased skew enhances the head and efficiency at high flow rate, while the performance of the pump with decreased skew is reduced across nearly all operating conditions. The C-type pump has the best comprehensive performance among the others. The head of the C-type pump with increased skew is up to 21 % higher than that of the A-type pump, and the efficiency is increased by up to 5.43 %. This enhancement can be attributed to the suppression of secondary flow, which results in changes in the circumferential vorticity and the distribution of potential rotor enthalpy. Regarding the transient characteristics, the flow capacity is improved and an ideal velocity component is achieved by the C-type pump with increased skew. Additionally, the amplitude of pressure pulsations at the rotor-stator boundary is significantly reduced by up to 61 %, and the potential for vibration and noise reduction is demonstrated to be stronger. The conclusion is of certain value for the analysis and improvement of water jet propulsion pumps.