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In this paper, the effect of direct diesel injection timing and engine speed on the performance and emissions of CI engine operating on RCCI (H2/diesel mixture) coupled with water injection have been numerically investigated and validated. The simulation have been carried out using GT-Power professional software. A single cylinder dual fuel compression ignition model has been built. The diesel fuel was injected directly to the cylinder. The hydrogen and water were injected to the engine intake manifold and engine port with constant mass flow rate and constant temperature for all engine speed. During the simulation the engine speed was varied from 1000 to 5000 rpm and the diesel injection timing was varied from (−5° to −25° CAD). In addition, the optimized diesel injection timing for specific engine operation parameters has also been performed.The results show that, for specific injection timing and constant hydrogen and water mass flow rate, the increase of engine speed results in an increase in the cylinder temperature, engine brake power, brake specific fuel consumption and NO emissions; but decreases brake thermal efficiency. Moreover, the analysis performed shows that, the advanced injection timing decreases the engine power, brake thermal efficiency and CO emissions; but increases NO emissions. Keywords: Reactivity controlled combustion, Water injection, Emissions, Engine simulation, Alternative fuel