The effects of the dilution with inert gas on different combustion processes in confined space are investigated by utilizing a newly designed constant volume combustion bomb (CVCB) equipped with a perforated plate. Hydrogen-air mixture diluted with argon, nitrogen and carbon oxide of different proportions is employed in the present work. Combustion phenomena were all captured by high-speed Schlieren photography including flame propagation, compression wave formation as well as pressure oscillation. The results show that the dilution of inert gas slows down flame propagation in the combustion chamber. The velocity deficit increases in the order of Ar/N-2/CO2, which indicates that CO2 is a better inhibitor of flame propagation than Ar and N-2. The evaluated jet flow accelerates continuously driven by the forward spreading laminar flame and the velocities at different inert gas conditions decrease in the sequence of Ar/N-2/CO2. No shock wave occurs during the combustion process when inert gases are introduced into the chamber. The amplitude of pressure oscillations decreases with diluted mixture due to the absence of flame-shock interactions. Besides, the peak pressure shows difference among different inert gases. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.