Unsteady Flow Field in a Turbomachinery

Computational Fluid Dynamics analysis has been used to solve the unsteady three-dimensional viscous flow in the entire impeller and volute casing of a centrifugal pump.

The numerical calculations are carried out with a multiple frame of reference approach, whereby the impeller flow field is solved in a rotating frame and the casing in a fixed one.

The results of numerical simulation provide detailed information of the unsteady three-dimensional viscous flow field in the entire Turbomachinery.

The animation shows the unsteady pressure field at the midspan of the impeller and volute casing at over load condition.

According to the animation the flow is due to the interaction between impeller blades and the tongue of the volute casing characterized by pressure fluctuations, which are strong at the impeller outlet and in the vicinity of the tongue. These pressure fluctuations are reduced in the casing as the advancement angle increases. These reduced pressure fluctuations are spread to the discharge nozzle. Since the flow is incompressible, strong pressure fluctuations at the impeller outlet caused by the interaction between the blades and tongue of the volute casing, are reflected upstream to the impeller inlet.