Experimental study on spray, combustion and emission characteristics of pine oil/diesel blends in a multi-cylinder diesel engine

Abstract

Pine oil has a high calorific value, which makes it an appropriate biofuel for diesel engines. In this paper, spray characteristics such as spray morphology, spray penetration and spray cone angle of pine oil-diesel blends were investigated under various injection pressures using a constant volume spray chamber. The effects of the injection pressure on the combustion and emission characteristics of pine oil-diesel blends were experimentally investigated in a four-cylinder diesel engine under medium EGR (24.6%). Four different fuels including pure diesel (P0), three blends of pine oil and diesel fuel denoted as P20 (20% pine oil and 80% diesel in volume), P40 (40% pine oil and 60% diesel in volume), and P50 (50% pine oil and 50% diesel in volume) were tested. Our results indicate that, as the injection pressure increases, the spray penetration of blended fuels increase, while the spray cone angle shows slightly change. And with the increasing of injection pressure, the peak values of heat release rate and in-cylinder pressure during the combustion of the four blended fuels increase, the BSFC slightly increase, the emissions of soot, CO and THC decrease, however NOx emissions increase. The effects of the increase of injection pressure on soot emissions of pure diesel are greater than that of blended fuels. When the mixing ratio of pine oil exceeds 40%, the beneficial effects of injection pressure on soot emissions from the combustion of blended fuels are weakened. At the same injection pressure, the BSFC of P20 almost equals the value of P0. As the mixing ratio of pine oil increases, the spray penetration and the spray cone angle of blended fuels increase, which enhanced the atomization process and fuel evaporation. With the increase ratio of pine oil, the peak values of in-cylinder pressure and heat release rate increase, the emissions of NOx, CO and THC increase and soot emissions decrease dramatically. For the combustion of the tested fuels, the number concentration and mass concentration of total PMs can be reduced by increasing the injection pressure or the amount of pine oil in the blends. At an injection pressure of 100MPa, the total PM number concentration and mass concentration of P50 are respectively lower 86.30% and 96.55% than the values for pure diesel.