Influence of the return channel geometry on the performance stability of a centrifugal pump

The paper reports on fluid-dynamical investigations of large-scale instabilities in a radial multistage pump with a vaneless return channel. To establish a relation between the flow field structure at high/partial load and acoustic radiation, numerical analyses were carried out by means of the commercial code CFX 12.0 on the entire machine so as to study the unsteady phenomena developing in the pump. All the computations were performed using the unsteady “transient” model. The time step for the calculation will be chosen according to a rotation of the runner of about 1 degree. Turbulence will be modelled by DES model. To validate the numerical analysis, numerical pressure signals were compared with experimental signals. Further numerical analyses were also carried out on simplified configurations in order to determine the geometrical and fluid-dynamical parameters affecting the development of the identified unsteady phenomena.