Addition of CNG and Reformer Gas to the Gasoline Fuelled SI-Engine 2004-01-0973
Addition of gaseous fuels to the gasoline fuelled SI-engine offers several potentials of improvements, like: cold start without enrichment, lower engine-out emissions, in certain cases better strategy of catalyst heating.
In the present work some results of investigations with addition of compressed natural gas CNG*) and of H2-containing reformer gases are presented. Two engines were fuelled with different compositions of H2-CO-CO2-N2 mixtures as model gases for methanol-, or gasoline- reformed fuels. The investigations were performed at warm, stationary, part load operation.
Due to the presence of hydrogen the reformer gas causes more advantages, than CNG. It lowers the gaseous emission components, shortens the combustion duration, increases the combustion stability and enables much more expanded lean-limits and EGR-limits.
The passive components of the reformer gas (CO2, N2) have similar influence on NOx-reduction as the internal EGR.
Due to a very low stoichiometric air requirement the reformer gas enables a dethrottling of the engine at part load and consequently an improvement of efficiency.