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CFD simulations have been conducted to study Homogeneous Charge Compression Ignition (HCCI) combustion in a single-cylinder poppet valve Direct-Injection 2-stroke gasoline engine using the Ricardo engine CFD code VECTIS. Multi-domain, multi-cycle simulations were performed to determine the trapped conditions, in particular the high residual gas content and charge distribution. The HCCI ignition and combustion were modelled using the Livengood-Wu ignition integral combined with the Ricardo Two-Zone Flamelet combustion model. Good agreements have been achieved between simulation and engine test data. The ignition points and in-cylinder pressures were predicted with good accuracy. The paper demonstrates that in 2-stroke engine operation the in-cylinder charge inhomogeneity is significant. The multi-domain, multi-cycle CFD simulation is an effective approach to study the charge inhomogeneity and its effect on HCCI engine combustion.