Investigation Of the Pump, Dissipation and Inverse Turbine Operating Modes Using the CATHARE-3 One-Dimensional Rotodynamic Pump Model.

International audience4-quadrant behavior of rotodynamic pumps topic is investigated in the frame of hydropower plants operation (electricity production or storage) and also in the nuclear field, where accidental operating conditions are supposed when doing reactors safety analyses. A predictive transient one-dimensional rotodynamic pump model is currently developed into the CATHARE-3 thermal-hydraulic system code at CEA Saclay, France. This is done in partnership with ArianeGroup, Electricite De France, Cetim, Framatome and the Laboratory of Fluid Mechanics of Lille (LMFL). Flow is computed in each part of the pump (suction, impeller, diffuser, volute and discharge pipe) based on the definition of a mean stream line. Several cells are used to mesh each part of the rotodynamic pump, what makes this model different from usually called “1D models”. One-phase or two-phase flows can be simulated taking into account mechanical and thermal disequilibria by the use of a 6-balance-equation model. During year 2018, this predictive pump model has been qualified on a low specific speed centrifugal pump geometry (DERAP facility at LMFL, France) by predicting its performance curves and the evolution of head and torque as functions of time during a fast start-up transient. Pump-loop interaction has also been studied and qualified with a system-scale approach, which is the main destination of the CATHARE-3 thermal-hydraulic code. In this study, the model is tested on a medium specific speed centrifugal pump in every operating modes encountered in the first quadrant (positive flow rate and rotational speed). Starting from a normal pump operating mode, the flow rate is gradually increased to reach the dissipation region. Head becomes negative but some torque is still consumed by the machine (it is given to the fluid). Flow rate is increased again till the inverse turbine operating mode is reached. Pump is then making pressure loss but gives energy to the shaft. This inverse turbine mode is not as efficient as the normal turbine mode encountered in the thir