Model-Based Design and Numerical Analysis of a Downsized Centrifugal Pump for Engine Cooling Applications

<div class="section abstract"><div class="htmlview paragraph">The water pump is the crucial component of the engine cooling system. It is usually designed considering as rated conditions the ones evaluated when the engine delivers its maximum power. This results in an overdesign of the pump, considering that almost never the engine delivers the maximum power, in usual operation. At these conditions, in fact, flow rate and pressure delivered reach the maximum values, which are not needed to cool the engine in most probable operating conditions. In fact, considering the real operating conditions during a typical driving mission or a homologation cycle, the mechanical power is far away from the maximum datum, as well as the cooling flow rate and pressure delivered by the pump. To a so unbalanced design for the pump corresponds a low efficiency of it, being the technology oriented to use a centrifugal type, whose efficiency is quite dependent on speed of revolution and flow rate delivered. Hence, modifying the design point of the pump causes a mechanical energy saving, improving the organic efficiency and reducing the efficiency penalization when it operates, as it happens always, at off design conditions.</div><div class="htmlview paragraph">In this work, a model-based procedure to design a centrifugal pump in a more suitable engine working point from the point of view of the energy absorbed is considered. The procedure starts with an estimation of the engine thermal needs in different working conditions and on a driving cycle. Hence, a flow rate is targeted, and a pressure drop of the cooling circuit estimated, to have the specifics of the pump design. The model is able to evaluate all the hydraulic losses of the pump in its impeller and volute. The geometry generated has been refined and finally investigated through numerical CFD analysis. Subsequently, the turbulent flow field of the pump was analyzed in terms of static pressure, velocity, and kinetic energy distribution. The pump head and flow rate delivered were simulated using CFD techniques and compared with experimental results, assessing also the efficiency of the pump and the loss distribution. Finally, the pump performance has been evaluated along a driving cycle, to assess the energy absorbed during a real operating condition.</div></div>