Experimental Investigation and Comparison of a Decalin/Butylcyclohexane Based Naphthenic Bio-Blendstock Surrogate Fuel in a Compression Ignition Engine

Many efforts have been made in recent years to find renewable replacements for fossil fuels that can reduce the carbon footprint without compromising combustion performance. Bio-blendstock oil developed from woody biomass using a reliable thermochemical conversion method known as catalytic fast pyrolysis (CFP), along with hydrotreating upgrading has the potential to deliver on this renewable promise. To further our understanding of naphthenic-rich bio-blendstock oils, an improved formulation surrogate fuel (SF), SF1.01, featuring decalin and butylcyclohexane naphthenic content was devised and blended with research-grade No.2 diesel (DF2) at various volume percentages. The blends were experimentally evaluated in a single-cylinder Ricardo Hydra compression ignition engine to quantify engine and emissions performance of SF1.01/DF2 blends. Injection timing events were varied from knock limit to misfire limit at the same operating conditions for all blends. A decrease in the engine power output was observed as the SF content was increased due to lower combustion efficiency, yielding slightly higher CO and THC emissions. Higher SF content also correlated with a significant decrease in the PM emissions. NOx emissions were minimal as they fell below detectable limits. A comparison is also presented between DF2 and previously published SF1/DF2 blends that featured only decalin as the naphthenic content. It was found that butylcyclohexane is more desirable from a combustion performance and emissions characteristic than decalin for the composition of the naphthenic content. A bio-blendstock oil of similar composition to the evaluated SF would be a good candidate for displacing fossil-derived heavy petroleum distillate fuels in engine applications.