Thermodynamic analysis of energy dissipation and unsteady flow characteristic in a centrifugal dredge pump under over-load conditions

Abstract

The present paper aims to investigate the energy dissipation related to unsteady flow phenomena inside a three-bladed impeller of a centrifugal dredge pump under over-load operating conditions. Three-dimensional unsteady numerical simulations of the centrifugal pump are performed by adopting the SAS SST-curvature correction turbulence model with the total energy equation. The simulating results are verified by comparing the performance results and pressure fluctuation with available experimental data. The unsteady flow patterns and energy dissipation in the rotating impeller are analysed by entropy distribution and pressure fluctuation spectra. A high-entropy area appears in the impeller flow passage when the discharge increases. It is indicated in the unsteady simulation results that a vortex flow with high entropy generates and detaches periodically, which causes the hydraulic energy loss under over-load operating conditions. In numerical simulations, a frequency as 3.3 times of rotating frequency is found in the pressure spectral analysis at 1.45 Q0 operating condition, which is related to the unsteady flow structure. The secondary flow near the volute tongue is found at 1.45 Q0 operating condition due to the large angle of attack when discharge increases.