The effects of biodiesel on the spatial distribution of soot during combustion in a diesel engine-generator group

The soot emission is one of the main limiting factors in the Diesel engine performance, due to the heat losses caused during its formation. Studies show that the formation of this product can be reduced by adding oxygenated fuels to replace part of fossil fuels. There is a growing demand for computational models of engines powered by renewable fuels, capable of predicting operational characteristics in different conditions. The objective of this work is to determine, by using computational fluid dynamics (CFD) model, the effects of different percentages of biodiesel on the spatial distributions of soot inside the combustion chamber. Performance and emissions, as well as spatial distributions of soot and temperature were evaluated simulating cases with 8%, 10%, 13%, 15%, 50%, and 100% for mixtures of biodiesel. The numerical modeling was based on the physical parameters of a MWM 229 Diesel engine generator and validated through experimental tests using 8% of biodiesel on the diesel composition. A three-dimensional model of one of the engine cylinders was developed. The simulations were carried out in the closed combustion cycle, between 150 ° CA BPMS and 150 ° CA APMS. The amount of fuel injected for each simulation case was configured to assure the same amount of energy inside the cylinder, taking into account the calorific value of each fuel. The results of the numerical model showed a trend to reduce the soot emission with the increase of the biodiesel percentage. The highest concentration of soot was observed in regions close to the cylinder and the piston walls in the spray fuel direction.