Investigation of the Suitable Ignition Point for Determination of Confined Deflagration Characteristics

Abstract

In this study, we investigated the effects of ignition position on the deflagration characteristics of flammable gases by using constant volume vessels with similar cylindrical shapes. Ion probes equipped on the top and bottom walls of the vessels were used to record arrival time of propagating flames to the walls in order to evaluate effects of buoyancy on flame growth. As a result, it was confirmed that explosion index, K_G, which is one of the important indices for explosion venting, varied depending on the ignition position especially in the case of flammable gases with slow laminar burning velocity. When the maximum K_G value was obtained at an ignition position located between the top and bottom walls, the propagating flames reached both walls almost at the same time. On the other hand, when the K_G value increased monotonically at the lower ignition position, the maximum K_G value was obtained at the bottom ignition position. Therefore, in cases where there is noticeable effect of buoyancy on flame growth, K_G should be determined at suitable ignition positions in consideration of arrival time of propagating flames to combustion vessel walls.