An innovative triple-screw pump for engine cooling in the road transportation sector

The efficiency improvement of Internal Combustion Engines (ICEs) is still necessary, providing them a valid contribution to the future of road propulsion, increasingly governed by regulations aimed at curbing CO2 emissions. In this context, technologies related to engine thermal management, and more specifically to the cooling pump, offer a good potential. Screw-type cooling pumps, notably triple-screw pumps (TSP), emerge as a solution, demonstrating superior efficiency compared to centrifugal pumps at design and off-design operating conditions. A TSP optimized in terms of efficiency for the cooling system of a turbocharged gasoline engine was investigated. The requested high speed of rotation suitable for engine cooling to reduce size and weight led to the introduction of a new screws' arrangement, which improved pump durability and mechanical efficiency, but enhanced the impact of clearances on the so-called blowhole backflow, usually negligible for bigger pump sizes. Hence, a refined mathematical model capable to predict the new screw pump's performances was developed and experimentally validated. A stable and high mechanical efficiency (>80 %), and a global efficiency greater than 50 % even very far from the design point, were reached. This feature applies in engine cooling, but can be useful also in industrial applications requiring high pump efficiency.