With the concern of the foreseen reduction in fossil fuel resources and stringent environmental constraints, the demand of improving internal combustion (IC) engine efficiency and emissions has become more and more pressing. Hydrogen has been proved to be a promising renewable energy that can be used on IC engines. In this paper an evaluation and assessment of numerical and experimental investigations on performance and exhaust emission with hydrogen added to a spark ignited gasoline engine fuelled with gasoline and natural gas are performed. The experimental results showed that thermal efficiency, combustion performance, NOx emissions improved with the increase of hydrogen addition level. The HC and CO emissions first decrease with the increasing hydrogen enrichment level, but when hydrogen energy fraction exceeds 12.44%, it begins to increase again at idle and stoichiometric conditions. Numerical results showed that there is an increase in engine efficiency only if Maximum Brake Torque (MBT) spark advance is used for each fuel. Moreover, an economic analysis has been carried out to determine the optimum percentage of hydrogen in such blends, showing percent increments by using these fuels about between 10 and 34%.

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