The full-cavitation model without considering the effect of the undissolved gas in water on cavitation was applied to study the transient hydraulic characteristics of the cavitation process in centrifugal pumps. The numerical simulation on vapor-liquid two-phase turbulence within whole flow passage of a centrifugal pump was performed by the computational fluid dynamics software CFX
and the comparison between the simulation results and the experimental data was conducted. The results show that the simulation results are in reasonable agreement with the experimental data. In the process of cavitation
the gas volume fraction at the blade back increases with the decrease in net positive suction head(NPSH). However
when the gas volume fraction at the working surface of the blade is greater than zero
the bubbles begin to clog the impeller channel
thus affecting the energy exchange and transfer in the impeller. The velocity within the impeller fluctuates irregularly due to the vortex caused by cavitation
leading to the increase in the velocity and load near the region of the vortex and in the channel of the blade working surface. Head decreases slowly to a certain extent and then declines sharply with the decrease in NPSH. In addition
the head fluctuation amplitude is different under different conditions and has a maximum value at the lower flow rate.
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references
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