Numerical simulation and experimental test of dual fuel operated diesel engines

In this article the authors discuss the effect of different fuel ratios on the performance and pollutant fractions of a common rail diesel engine supplied with both natural gas and diesel oil. The study of the dual fuel NG/diesel operation is carried out on a CFD basis, with an engine numerical simulation that includes the gas exchange periods and it aims at a comprehensive analysis of both the combustion development and the pollutant formation under different conditions induced by different choices of the operating parameters and fuel. Preliminary calculations have been performed to individuate the correct setting of some injection models, in order to determine the most appropriate setup of the injection timing when varying the CNG ratio in the fuel blend. The calculations are compared with some experimental data obtained on a light duty direct injection diesel engine at steady state test bench. In particular, a comparison between diesel and dual fuel diesel/ CNG operation has been made, in terms of performance and pollutant levels