Computational Fluid Dynamic Studies of Certain Ducted Bluff-Body Flowfields Relevant to Turbojet Combustors. Volume 2. Time-Averaged Flowfield Predictions for a Proposed Centerbody Combustor

摘要

The near-wake region in a ducted bluff-body combustor was investigated by finite-difference computations. The numerical predictions are based upon the time-independent, Reynolds-averaged Navier-Stokes equations and the k-epsilon turbulence model. The steady-state calculations address both nonreacting and reacting flowfields in a novel configuration to more realistically simulate some of the essential features of the primary zone of a gas turbine combustion chamber. This configuration is characterized by turbulent mixing and combustion in the recirculating near-wake region downstream of an axisymmetric bluff body due to two annular air streams--an outer swirl-free flow and an inner swirling flow--and a central fuel jet. The latter contains propane for reacting flows and carbon dioxide for nonreacting flows. In view of the large number of geometrical and flow parameters involved, the reported results are concerned with only a limited parametric examination with the major emphasis being on nonreacting flows. Questions addressed for a particular set of geometric parameters include the effects of variation of mass flow rates in all three streams and the influence of swirl in the middle stream. Reacting computations investigate the influence of swirl on combustion, as well as that of combustion on the flowfield. A careful consideration of the computed results of selected flow variables in terms of the global flowfield features, axial variations along the axis of symmetry, and radial profiles at different axial stations examines the implications of the present predictions and provides possible directions for ascertaining the validity of these predictions through future diagnostic measurements.