Effects of Exhaust Gas Recirculation on Fuel Consumption

Abstract

The effects of EGR on fuel consumption were analysed quantitatively in terms of factors improving and deteriorating fuel economy through experiments as well as thermodynamic calculations. To examine the effects of combustion duration on fuel economy under heavy EGR, experiments were performed with three engine variations. In calculation models, changes in specific heats, heat transfer rate, and dissociation rate caused by changes in gas temperature were considered. In conclusion, it may be stated that reductions of pumping loss, cooling loss, and dissociation were found to be improving factors, where the contribution ratio was approximately 4.5:4.0:1.5. The sum of calculated fuel economy gain increased steadily as the EGR increased, and reached more than 10 per cent at a 20 per cent EGR under light load condition. On the other hand, a major deteriorating factor was found to be a combustion fluctuation. This combustion fluctuation could be significantly reduced by achieving a ‘fast burn’ through increased turbulence and/or dual point ignition.