Development of pump geometry for engine cooling system

Abstract: The engine cooling system is an important part of the engine’s performance to achieve optimum temperatures in cylinders and provide cooling to subsystems. With increasing emission demands from legislation, further development of the cooling system is necessary. An important component in the engine cooling system is the pump that produces the necessary flow rate to cool down the components. The pump is connected to the drive shaft with a pulley so improvements in the pumps efficiency will directly affect the fuel efficiency of the vehicle. With more variations and increasingly complex system design different performance stages of the pump are necessary to provide desired flow rates depending on system design. To enable a rapid design of performance stages of pumps, a calculation model is constructed to predict the performance of an engine cooling pump based on the geometry of the impeller and pump casing. The model includes the main head losses that occur within a centrifugal pump both in the impeller and pump casing. The model is based on quasi one-dimensional calculations of velocity triangles in impeller and pump casing. The head losses are modelled with correlations from literature that are compared to test data from reference pumps. The developed model provides a pump - , hydraulic efficiency – and power curve based on main geometrical parameters. A design tool and procedure is constructed to suggest main geometry parameters for the impeller based on a desired operational point. The design tool is constructed on design coefficients based on reference pumps test data and correlations from literature. Together with the calculation model an impeller flow channel can be designed to achieve the desired operational point. Two impellers are designed and manufactured by rapid prototyping that are tested by an experimental test to verify the model and design tool. The result show that the calculation model captures the general behaviour of the pump curve and is within 1-10% accuracy. The calculation model and the design tool are designed to assess the performance of the main geometry parameters in the impeller and pump casing. Further optimization and studies of the complete flow field to assess secondary flows and cavitation behaviour can be done by numerical methods. The calculation model and design tool constructed provides a rapid way of designing new impellers and an easy method to perform parameter studies on changes in impeller geometry.