Fuel conservation and emission reduction through novel waste heat recovery for internal combustion engines

Abstract Lubrication systems of combustion engines offer a large potential for energy conservation and reduction of emissions. Different approaches include variable oil pumps to adjust oil pressure and flow rates to the engines requirements or thermal management to reduce the viscosity of the engine oil. For both of these systems the fuel conservation during physical tests is typically much smaller than the predictions through computations. The root cause of these differences between simulations and test results are analysed in this paper with specific focus on the heat transfer from the engine to the lubrication oil and the effects of water condensation in the exhaust. The analysis resulted in different waste heat recovery system configurations that are presented. Vehicle test results for one system with a gasoline engine demonstrate a fuel conservation potential of over 7% together with two digit reductions of several emission components. For another more effective but also more simple system configuration a similar improvement potential is shown. Risks and benefits of such novel waste heat recovery systems are discussed. Further benefits are the positive effects on performance, reduction of wear and the potential of extended oil change intervals.