The Effect of Diesel Fuel Properties on Engine-out Emissions and Fuel Efficiency at Mid-Load Conditions

The influence of various diesel fuel properties on the steady state emissions and performance of a Cummins light-duty (ISB) engine modified for single cylinder operation has been studied at the mid-load “cruise” operating condition. Designed experiments involving independent manipulation of both fuel properties and engine control parameters have been used to build statistical engine response models. The models were then applied to optimize for the minimum fuel consumption subject to specific constraints on emissions and mechanical limits and also to estimate the optimum engine control parameter settings and fuel properties. The study reveals that under the high EGR, diffusion-burn dominated conditions encountered during the experiments, NOx is impacted by cetane number and the distillation characteristics. Lower T50 (mid-distillation temperature) resulted in simultaneous reductions in both NOx and smoke, and higher cetane number provided an additional small NOx benefit. The optimum fuel properties appeared to provide a better NOx-fuel consumption tradeoff than that achieved by a representative #2 ultra-low sulphur diesel blend (ULSD). The model was also applied to simulate fluctuations in emissions and fuel consumption caused by expected variations in market diesel fuel properties.