An integrated computational fluid dynamic (CFD) and chemical kinetics framework is applied to a two dimensional section of a four stroke spark ignition (SI) engine in ANSYS Fluent 2024 R1 to investigate the effects of H₂ enrichment (0 %, 5 %, 10 %, 20 %, 30 % by volume) on in-cylinder combustion and emissions over a full 360o–1080o crank angle (CA) cycle at 2000 revolutions per minute (rpm). A CHEMKIN mechanism of 57 species and 269 reactions defined as fuel, characterizes gasoline as a surrogate fuel. Turbulence closures (k-ε & k-ω) and radiation treatments (P1 & Rosseland) are compared. The results obtained demonstrate that an increase in H2 content results in a corresponding increase in peak in cylinder temperatures and velocity peaks. The CO and soot emissions are reduced by over 70% and 43%, respectively, while there is an approximate 85% increase in thermal NOₓ emissions due to elevated combustion temperatures. The k-ε model and the Rosseland approximation are determined to best represent turbulent mixing and radiative losses under the studied conditions. The results also show that a 20% H₂ blend results in almost optimal reduction of CO and soot with an acceptable increase in NOₓ that is a good balance of the combustion efficiency improvement and emission disadvantages. The results of this thesis give quantitative indications for H₂ gasoline dual fuel strategies in engines and also reveal the choosing the correct physical models for accurate CFD predictions.