Large Eddy Simulation of Periodic Transient Pressure Fluctuation in a Centrifugal Pump Impeller at Low Flow Rate

Abstract

This paper presents a large eddy simulation of a centrifugal pump impeller during a transient condition. The flow rate is sinusoidal and oscillates between 0.25Qd (Qd indicates design load) and 0.75Qd when the rotating speed is maintained. Research shows that in one period, the inlet flow rate will twice reach 0.5Qd, and among the impeller of one moment is a stall state, but the other is a non-stall state. In the process of flow development, the evolution of low-frequency pressure fluctuation shows an obviously sinusoidal form, whose frequency is insensitive to the monitoring position and equals to that of the flow rate. However, inside the impeller, the phase and amplitude in the stall passages lag behind more and are stronger than that in the non-stall passages. Meanwhile, the strongest region of the high-frequency pressure fluctuation appears in the stall passages at the transient rising stage. The second dominant frequency in stall passages is 2.5 times to that in non-stall passages. In addition, similar to the pressure fluctuation, the evolution of the low-frequency head shows a sinusoidal form, whose phase is lagging behind that by one-third of a period in the inlet flow rate.

Effects of oscillation frequency on the flow characteristics of a centrifugal pump impeller with sinusoidal flow rate

“…The detailed simulation schemes and boundary conditions can be found in Kuang et al 41 Here is a brief introduction. The finite volume method was used to discrete the governing equations, and the DSM model 42 was employed to calculate the internal flow.…”

“…Kuang et al 41 obtained the pressure fluctuation in the impeller mid-height at the inlet impeller passage under transient condition. They found that pressure fluctuations include low and high-frequency components.…”

“…Kuang et al 41 conducted LES on a centrifugal pump impeller with sinusoidal flow rate. The similarity and differences in pressure fluctuation characteristics between transient and quasi-steady conditions were investigated.…”

“…Figure 3. Grids of the centrifugal pump impeller: (a) view of centrifugal pump impeller, (b) blade front view, and (c) blade middle view 41. …”

Vortex structure and pressure fluctuation of a pump-turbine in pump mode using large Eddy simulation

“…In these schemes, the y + on average in the runner and guide vanes is less than 5, which meets the calculation requirements. 26–28 Scheme 5 is selected for numerical simulation.

Figure 3.Grid refinement research.

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