Numerical Simulation of Unstable Flow in Cooling Pump of Internal Combustion Engine

Cooling pump is an important device to ensure the reliable and stable working of the internal combustion engine. As the size of the structure is limited by space, its internal flow is complex. To explore the internal flow of cooling pump, the numerical simulation of the full flow field of the model pump under different flow conditions is carried out by using the Detached-Eddy Simulation (DES) model, and the unstable flow characteristics in the flow-path are analyzed. The results show that the intensity of pressure fluctuation near the tongue is the highest and the flow deterioration is the most serious. Under the condition of small flow rate, the area of flow separation is from the tongue to the outlet, return vortices and rotating stall occur in the impeller flow-path, and the outlet vortices dominate the vibration characteristics of the cooling pump. The lowest non-uniformity coefficient of impeller inlet corresponds to the 0.7Q(d) working point in high efficiency area, but the vertical degree of outflow is same, which is close to the ideal flow direction, and the velocity distribution of flow-path section becomes more uniform with the increase of flow rate. The change of flow rate will affect the unstable degree of the inlet flow, thus affecting the flow rate of the working fluid flowing into the impeller. The unstable degree of the inlet is more serious when the cooling pump works under the condition of small flow rate. The research results can provide some theoretical reference for the structural design of cooling pump.