The effect of turbulence on unsteady premixed flame propagation and associated pressure rise during explosion of stoichiometric CH4/air in closed spherical vessels of different size was investigated by means of CFD simulation. Computations were run by varying the vessel volume from 20 I to 200 I and to 1 m(3). Numerical results have shown that, at fixed initial conditions, the turbulence kinetic energy induced by the propagating flame increases with increasing vessel volume. It has been demonstrated that the cubic relationship does not apply. Under the conditions investigated, a correction to the cubic relationship has been proposed to take into account the effect of the vessel volume on turbulence. (C) 2016 Elsevier Ltd. All rights reserved.