Entropy production analysis for the clocking effect between inducer and impeller in a high-speed centrifugal pump

The clocking effect between the inducer and the impeller has a certain impact on the performance of the high-speed centrifugal pump, which however, is often ignored by designers. In the present study, three-dimensional numerical simulation based on Reynolds-averaged Navier-Stokes method is adopted to evaluate the influence of this clocking effect on the performance of a full-scale liquid rocket engine oxygen turbopump. A novel entropy production method with the correction of wall effects was introduced to evaluate the energy loss generated in the pump and to clarify the formation mechanism of this clocking effect from the perspective of the second law of thermodynamics. Results show that the best performance is captured when the relative circumferential angle between the inducer blade trailing edge and the impeller blade leading edge was set as 0 degrees and the maximum difference in pump efficiency is approximately 1.5% at different clocking positions. The entropy production analysis of each component of the pump reveals that the clocking effect on the pump performance mainly originates from the turbulent dissipation in the impeller and the diffuser. The study of the local entropy production rate and the streamline distributions shows that the formation of this clocking effect is owing to the different extent of the separation vortices in the impeller passage near the shroud and the impeller blade wake in the diffuser inlet as well as the backflow vortices in the diffuser blade passage near the volute tongue.