Model Parameterized Assessment of a Thermal Storage Unit for Engine Oil Warm-up Improvement

Despite the attention paid to components downsizing and down weighting, as well as to combustion control and exhaust gases after-treatment, friction reduction remains a promising area of intervention when it comes to the reduction of the environmental impact of internal combustion engines. The larger gain must be sought at cold starts, when the viscosity of the lubricant oil is higher and does not allow proper friction reduction. Moreover, during the first phases of engine operation, the metallic masses are not yet warm and do not contribute to the thermal stabilization of the lubricant. Further consequences of unfavourable thermal conditions are increased specific fuel consumption and pollutant emissions. Proper thermal management could effectively speed up the reaching of the design operating temperature of the oil and positively affect both homologation and on-road operation. The abundance of waste thermal energy during normal operation supports the option of on-board thermal storage for faster oil heating: water, heated by exhaust gases or residual thermal energy from previous use or by a combination of the two, can be stored inside a thermally insulated tank and serve as heating fluid in a dedicated water/oil heat exchanger. The paper presents a model based evaluation of this opportunity. The model has been validated thanks to an experimental activity carried out on an IVECO 3.0 L light-duty diesel engine, during a transient cycle (i.e., homologation one) reproduced on a dynamometric test bench. Different configurations in terms of hot storage volume, hot storage initial temperature, and the flow rate of the hot water during operation have been studied, producing optimized values for the hot water and storage unit design.