Analysis of combustion of methane and hydrogen-methane blends in small DISI engine using advanced diagnostics

In the last years, even more attention was paid to the alternative fuels which allow both reducing the fuel consumption and the pollutant emissions. Gaseous fuels like methane and hydrogen are the most interesting in terms of engine application. This paper reports a comparison between standard gasoline fuel and CH4 and different CH4/H2 mixtures in a transparent small single-cylinder Direct Injection spark ignition (DI SI) engine operating under steady state conditions. It is representative of the small displacement gasoline engine for automotive application. . Engine performance and exhaust emissions were evaluated at different engine speeds. Moreover, 2D-digital cycle resolved imaging was performed with high spatial resolution in the combustion chamber. In particular, 2D-digital imaging measurements allowed the characterization of the gaseous and liquid injection and flame propagation in terms of mean radius and velocity. Moreover, the interaction of turbulence with the spray and the local flame were evaluated. The combustion promotion due to methane and hydrogen addition and contribution to the reduction of pollutant formation were estimated.