Influence of Hydrogen-Rich-Gas Addition on Combustion, Pollutant Formation and Efficiency of an IC-SI Engine

The addition of hydrogen-rich gas to gasoline in an Internal Combustion Engine seems to be particularly suitable to arrive at a near-zero emission Otto engine, which would be able to easily meet the most stringent regulations.

In order to simulate the output of an on-board reformer that partially oxidizes gasoline, providing the hydrogen-rich gas, a bottled gas has been used.

Detailed results of our measurements are here shown, such as fuel consumption, engine efficiency, exhaust emissions, analysis of the heat release rates and combustion duration, for both pure gasoline and blends with reformer gas. Additionally simulations have been performed to better understand the engine behaviour and NOx formation.

Results show that:

• When running at λ=1 and without EGR, addition of hydrogen-rich gas produces a significant shortening of the very first phase of combustion (inflammation phase) rather than of the remaining combustion process;
• Addition of hydrogen-rich gas allows to run the engine at extremely high λ or EGR rate;
• When running at the highest possible λ or EGR (limited by COV increase) the duration of all phases of combustion remains almost unaffected by the diluents;
• In all conditions a significant decrease of UHC and NOx emissions has been observed;
• In all conditions a significant increase of engine efficiency has been measured, which seems to be enough to compensate and overcome the losses due to the partial oxidation of Gasoline in the Reformer.