The results of detailed 2D numerical simulation of non-steady methane-air flame propagation in semi-closed tubes after ignition near the closed end are presented. Flame dynamics dependence on the tubes width for adiabatic and nonadiabatic walls is obtained. It is shown that main mechanism of front acceleration is flame surface perturbation due to hydrodynamic drag near the walls, which grows due to gas thermal expansion and flow acceleration. The mechanism of vortex formation in vicinity of the front bow point is demonstrated. The vortex is generated at the flame front velocities of the order of S-1 similar to 20 m/s and may become precursor for flow turbulization at later instants. The new theoretically possible regime of gas combustion in adiabatic conditions in narrow capillary is found. It is characterized by relatively low propagation velocity and incomplete combustion. (c) 2005 Elsevier Ltd. All rights reserved.