Energy loss and excitation characteristics of an axial waterjet pump with inlet guide vanes under different operating conditions

The waterjet pump with inlet guide vanes (IGVs) are widely used in propulsion systems of modern underwater vehicles. Understanding its complicated hydrodynamic characteristics is beneficial to improve the comprehensive performance. In this study, numerical simulations and experimental tests are carried out concurrently to investigate the flow field, energy losses and excitation characteristics of the waterjet pump. The results show that there is an obvious rotor-stator interaction between the IGVs wake and impeller blades, which leads to the thrust spectrum of the impeller is jointly dominated by the line spectrums located at the blade passing frequencies of impeller f_BPF and IGVs f_s. The negative pre-swirl flow induced by the IGVs could effectively offset the circumferential velocity at the impeller outlet, and this offset degree is closely related to the flowrate conditions. The quantification and visualization of the energy loss based on the diagnostic model derived from the mean kinetic energy equation shows that the impeller tip leakage flow and induced leakage vortex are the main sources for energy loss generation. The tip leakage flow also induces notable pressure pulsations dominated by the f_BPF. Under part-loading condition, the deteriorating unsteady flow within the waterjet pump leads to an increase in energy loss, and correlatively attributes obvious broadband features to the spectrums of pressure pulsation and unsteady forces as well as increased low frequency amplitudes.