CFD Modeling of Annulus/Port Flows

Abstract

CFD predictions are reported of the flow–field associated with the interaction of an annulus flow with a single row of plain radial holes drilled in the inner annulus surface, creating radially inward jets penetrating an inner core–flow. This situation is typical of annulus air admission port geometries found in all gas turbine combustors. The emphasis of the work is placed on an examination of different levels of geometrical approximation of the hole geometry. Both castellated and hole–fitted methods are studied using a general non–orthogonal body–fitted mesh, and a CFD code based on a pressure–correction methodology combined with a k–ε turbulence model. Noticeable differences are observed between the two approaches in terms of jet entry angle, impingement strength of the resulting radial jets, upstream vortex size, and annulus flow details downstream of the hole. These changes are mainly brought about by variations in the predicted velocity profile over the hole open area, particularly at the edges of the hole. The hole–fitted approach is also used to investigate the predicted differences between a round and a D–shaped hole. Small changes are observed in jet penetration behaviour; also the origin of the vortex in the wake of the jet is predicted to shift due to the addition of a corner in the hole shape.