The influence of design operating conditions on engine coolant pump absorption in real driving scenarios. 2024-37-0015

Reducing CO2 emissions in on-the-road transport is important to limit global warming and follow a green transition towards net zero Carbon by 2050. In a long-term scenario, electrification will be the future of transportation. However, in the mid-term, the priority should be given more strongly to other technological alternatives (e.g., decarbonization of the electrical energy and battery recharging time). In the short- to mid-term, the technological and environmental reinforcement of ICEs could participate in the effort of decarbonization, also matching the need to reduce harmful pollutant emissions, mainly during traveling in urban areas. Engine thermal management represents a viable solution considering its potential benefits and limited implementation costs compared to other technologies. A variable flow coolant pump actuated independently from the crankshaft represents the critical component of a thermal management system. Adjusting the flow rate independently from the engine allows the control of coolant flow according to engine thermal needs, eventually leading to shorter warm-ups, higher efficiency, and lower emissions. In addition, this feature adds a degree of freedom in the design phase, allowing the adoption of smaller pumps with higher efficiencies in the most frequent operating conditions and low space requirements. Increasing efficiency would decrease the energy absorbed by the pump during usual driving and homologation cycles, ensuring lower specific CO2 emissions. This latter aspect has been investigated in the present study to understand the impact of various design conditions on pump energy absorption during real driving. A reference small vehicle has been considered, and its gasoline turbocharged engine has been preliminarily tested to measure the hydraulic characteristics of all the cooling fluid branches as a function of the thermostat lift. Different electrically actuated coolant pumps with best efficiency points located at different flow rates and pressure heads have been experimentally characterized. The reference vehicle has been run in several real driving mission profiles, collecting data from the ECU. From previous experimental activity, flow rates and pressure delivered on all the branches have been derived as they really happened during driving, as well as the mechanically actuated OEM pump efficiency. The thermostat's real status during driving has also been considered. Considering as reference datum the energy absorbed during a real driving from the existing pump, the differently designed water pumps have been virtually substituted to the mechanical one. They were virtually electrically operated on board, reproducing the same flow rates circulating when the conventional pump operated in a real driving. The potential mechanical energy to drive the redesigned pumps was calculated and compared with the reference one. The influence of the mechanical energy absorbed by the pump with respect to that of the propulsion has been assessed, allowing the evaluation of the CO2 saving potential due to a newly designed pump. The outcomes of the study clearly show the benefits of a new design rule for pumps, re-orienting the design point to a pump operation with a greater probability of occurrence during real driving.