Numerical Investigation on Combustion Behaviors of Direct-Injection Spark Ignition Engine Fueled with CNG-Hydrogen Blends

This paper deals with the subject of natural gas-Hydrogen blends as alternative fuel for spark ignition engine. First, a brief overview on previous works in this field was presented. Then, a numerical investigation focusedon the effect of hydrogen addition on the performances and emissions was also presented. A CFD approach using CONVERGE CFD Code was applied on a direct injection spark ignition engine at low regime and lean mixtures. A detailed chemistry associated with AMR (Adaptive Mesh Refinement) technique was adopted. To illustrate the effect of hydrogen addition to natural gas, three hydrogen fractions are considered 0%, 10% and 18%. The obtained results showthatthe promotion of the chemical reaction with hydrogen addition is mainly due to the increase of free radicals H, O, OH in the flame as a result of hydrogen addition. Hence, the heat release rate starting is advanced with the increase of hydrogen fraction while the combustion duration decreases. It is observed that the heat release rate and the maximum in cylinder temperature increase when hydrogen is added. Exhaust CO emissions decreases with the increase of hydrogen fraction, while NOx emissions increase. Hydrogen addition could give a great potential to reduce soot formation.