The hydraulic performances of the centrifugal pumps are well-known as long as considering normal pump operating conditions but the abnormal operating conditions as energy dissipators or as turbines are less studied. The complete pump characteristics can be reported on a single four-quadrant representation and can be used to predict the behaviour of the machine during the transient operations or to explain the accidental scenarios. This study which is supported by the French manufacturers aims to explore the four quadrant operating conditions of a testing centrifugal pump using experimental and numerical approaches. In the one hand, the experimental test rig afford to perform a series of constant-speed runs varying from negative to positive values in the normal or reverse direction. The range of flowrates is included between -200 to +300 per cent and differs following the rotational speeds. Head, efficiency and torque are measured for all cases, negative or positive discharges. On the other hand, numerical modelling of the same centrifugal pump is performed. CFD computations for a large range of flow rates are analysed. According to the operating conditions, steady state or transient rotor-stator approaches are used to obtain realistic predictions and a discussion concerning the domain of validity of steady state modelling is proposed. Finally, the pump behaviour in the four quadrants obtained by the transient numerical simulations based on two equation turbulence models are in good agreement with the experimental results.
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