Engine oil warm-up through heat recovery on exhaust gases – Emissions reduction assessment during homologation cycles

Fuel saving is currently the most important technology driver in the development of low-emissions internal combustion engines. As known, friction is responsible for losses during engine operation, leading to an increased fuel consumption and ultimately increased emissions. Among all options for friction reduction, the oil thermal management has not yet received the attention it deserves, despite the fact that its potential compares to the one of other more consolidated techniques. Such a lack of interest appears even worse, when the impact of an accelerated oil warm up on the emissions reduction during reference homologation cycles is considered: in standard NEDC cycles, the oil viscosity reaches its design value only during the final part of the cycle, i.e. once the most part of harmful emissions has already occurred. This is due to a delayed thermal stabilization of the lubricant oil and poor friction reduction performances during the NEDC early phases. In this paper, the Authors investigate the effectiveness of the waste heat recovery on the exhaust gases, to speed up the lubricant oil warm up, effective immediate after engine ignition and thus, with little or no delay on the start of NEDC homologation cycle. The experimental activity, performed on a turbocharged engine (F1C 3L IVECO), starts with the setting up of a proper oil circuit and exhaust line layout, to allow the exhaust tailpipe to include a shell and tube heat exchanger for heat recovery. The unsteady heat availability on the exhaust gases, along with the variability the mass flowrate experiences during the NEDC cycle represents a major variable to account for in the heat exchanger selection and design. All interactions between the modified oil circuit, engine, coolant circuit and the exhaust line needed to be evaluated as well. Significant reduction of fuel consumption and pollutant emissions have been experimentally demonstrated.