INVESTIGATION OF FLOW AERODYNAMICS FOR OPTIMAL FUEL PLACEMENT AND MIXING IN THE RADIAL SWIRLER SLOT OF A DRY LOW EMISSION GAS TURBINE COMBUSTION CHAMBER

摘要

This paper presents the results of a detailed investigation of the fuel-air mixing processes that take place within the radial swirler slot of a dry low emission combustion system. The aerodynamics of the flow within the slot is complex and this, together with the placement of the fuel holes with cross injection, controls the mixing of the fuel and air. Computational fluid dynamics (CFD) with the Shear Stress Transport (k-ω) turbulence model was used for flow and mixing predictions within the radial swirler slot and for conducting a CFD-based Design of Experiments (DOE) optimisation study, in which different parameters related to the fuel injection holes were varied. The optimisation study was comprised of 25 orthogonal design configurations in a Taguchi L25 orthogonal array. The test domain for the CFD, and its experimental validation, was a large-scale representation of a swirler slot from a Siemens proprietary DLE combustion system. The DOE study showed that the number of fuel holes, injection hole diameter and inter-hole distance are the most influential parameters for determining optimal fuel mixing. Consequently, the optimised mixing configuration obtained from the above study was experimentally tested on an atmospheric test facility. The mixing patterns from experiments at various axial locations across the slot are in good agreement with the mixing predictions from the optimal CFD model. The optimised fuel injection design improved mixing compared with the original design by about 60%.