A numerical simulation on flow characteristics of fluid passing through a plain dump combustor and modified dump combustors

In this paper, a numerical simulation on flow characteristics for a plain dump combustor and modified dump combustors with central restriction of fillet, rectangular and vertical ellipsoidal dome shape have been done. Flow characteristics, i.e., streamline contour, casing wall pressure and axial velocity profiles have been studied under highly turbulent flow conditions for the Reynolds number ranging from 10 × 103 to 162 × 103. The size of the re-circulating bubble increases with the increase in Reynolds number for all considered configurations. In plain dump combustor, re-circulating bubbles generate only near the corner at the throat region and spreads in the flow direction. However, in the modified dump combustors, re-circulating bubbles generate at corner, central and exit regions. For the considered modified dump combustor configurations, at first the static pressure along the upper casing wall decreases slightly up to the entry of the restriction. Then, it sharply increases, reaches maximum value at a certain point. After that, wall pressure gradually decreases. This high downstream pressure helps in better mixing of the fuel air mixture. Fluctuation of reversed velocity in radial direction is more in modified dump combustor with central restriction of vertical ellipsoidal shape. This reversed velocity creates an adverse pressure gradient and forms re-circulating zone near the casing wall. Magnitudes of width and strength of re-circulation zone are noted to increase with increase in Reynolds number.