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In order to meet future requirements for emission reduction and fuel economy a variety of concepts are available for gasoline engines. In the recent past new pathways have been found using alternative fuels and fuel combinations to establish cost optimized solutions. The presented concept for a SI-engine consists of combined injection of gasoline and hydrogen. A hydrogen enriched gas mixture is being injected additionally to gasoline into the engine manifold. The gas composition represents the output of an onboard gasoline reformer. The simulations and measurements show substantial benefits to improve the combustion process resulting in reduced cold start and warm up emissions and optimized part load operation. The replacement of gasoline by hydrogen-rich gas during engine start leads to zero hydrocarbons in the exhaust gas.

Addition of hydrogen-rich gas to gasoline in internal combustion engines is gaining increasing interest, as it seems suitable to reach near-zero emission combustion, able to easily meet future stringent regulations. Bottled gas was used to simulate the output of an on-board reformer (21%H2, 24%CO, 55%N2). Measurements were carried out on a 4-stroke, 2-cylinder, 0.5-liter engine, with EGR, in order to calculate the heat release rate through a detailed two-zone model. A quasi-dimensional model of the flame was developed: it consists of a geometrical estimate of the flame surface, which is then coupled with the heat release rate. The turbulent flame speed can then be inferred. The model was then applied to blends of gasoline with hydrogen-rich gas, showing the effect on the flame speed and transition from laminar to turbulent combustion.