A New Design Rule of Engine Coolant Pump in ICEs Focused to Energy Consumption Reduction

Engine thermal management systems represent a promising solution to improve the efficiency of current Internal Combustion Engines (ICE) and sustain the transition towards a net zero scenario. The core component of an engine thermal management system is the electric pump, which can adjust the coolant flow rate according to the engine thermal needs. This possibility opens to newer design choices, which can contribute to non-negligible energy savings. In this study, three electric coolant pumps with different maximum efficiencies have been investigated to understand the influence of the design operating conditions on the pump energy absorption. A reference vehicle equipping a 130 HP downsized gasoline engine has been considered. An experimental test bench with a copy of the engine and its cooling circuit has been reproduced, and the electric pumps have been tested at a wide range of rotational speeds and thermostat lifts to obtain their characteristic maps. Once their performances were known, the vehicle was run in three driving cycles consisting of different shares of rural, urban and highway sections, acquiring data from the Electronic Control Unit (ECU). These data have been used to calculate the operating condition and energy absorption of the mechanical pump originally equipped by the vehicle and the electric pumps. The results have been evaluated using a statistical approach, normalizing the instantaneous efficiency by using their maximum efficiency values. The results show that all the electric pumps have lower energy absorption compared to the conventional mechanical actuation, with a reduction of up to 77% of the energy absorption. Considering the vehicle's fuel consumption and the lower heating value of gasoline, the potential reduction of CO2 specific emissions is 1 g/km. The statistical analysis approach showed that the design operating conditions have a higher influence than the maximum pump efficiency. The best performances are achieved through the electric pump with the lowest efficiency, showing a decrease in energy absorption between 10 % and 50% compared to the other electric prototypes, depending on the driving profile.