Annular Diffusers with Large Downstream Blockage Effects for Gas Turbine Combustion Applications

Abstract

., 2011.Annular diffusers with large downstream blockage effects for gas turbine combustion applications. Journal of Propulsion and Power, 27(6), pp. 1218-1230. Additional Information:• This paper was published in the Journal of Propulsion and In engineering applications, diffuser performance is significantly affected by its boundary conditions. In a gas turbine combustion system, the space envelope is limited, the inlet conditions are generated by upstream turbomachinery, and the downstream geometry is complex and in close proximity. Published work discusses the impact of compressor-generated inlet conditions, but little work has been undertaken on designing diffusers to accommodate a complex downstream geometry. This paper considers the design of an annular diffuser in the presence of a large downstream blockage. This is most applicable in the combustion system of a low-emission landbased aero-derivative gas turbine, where immediately downstream of the diffuser approximately 85% of the flow moves outboard and 15% moves inboard to supply the various flame-tube and turbine-cooling features. Several diffuser concepts are numerically developed and demonstrate 1) the interaction between the diffuser and downstream geometry and 2) how this varies with changes in diffuser geometry. A preferred concept is experimentally evaluated on a low-speed facility that simulates the combustion system and provides compressorgenerated inlet conditions. A conventionally designed aero-derivative diffuser system is also evaluated and, with reference to this datum, the system total pressure losses are reduced by between 20 and 35%.= mass flow rate N = rotor speed P, p = local total or static pressure R, r = radius T, t = local total or static temperature To 1 = total temperature in rig inlet U = velocity U blade = rotor midpassage blade speed Va = midpassage axial velocity y = dimensionless wall distance = kinetic energy coefficient = diffuser cant angle R = change in radius = total pressure loss coefficient = density = area-weighted spatially averaged mean valuẽ = mass-weighted spatially averaged mean value

Exhaust condensation through porous bed in the primary zone of novel dump diffuser geometry

“…Walker et al considered the design of an annular diffuser that consists of an outsized downstream obstruction. 11 On a low-speed facility that is provided with compressor-generated inlet conditions and a combustion system simulation, the design was experimentally tested. An integrated design concept was created using an iterative process after due deliberation of the flow field to accommodate the engagement between both the diffuser and flame tube.…”

Impact of a Cooled Cooling Air System on the External Aerodynamics of a Gas Turbine Combustion System

“…However, several studies have examined the effect of downstream blockage on the upstream pre-diffuser. For example, the work of Fishenden and Stevens [4], Bailey et al [5] and Walker et al [6] have shown that the pressure field generated by the flame tube can help to stabilize the diffuser flow and enable higher area ratios to be achieved. More recently the work of Impact of a Cooled Cooling Air System on the External Aerodynamics of a Gas Turbine Combustion System Walker et al [7,8] showed that for lean burn combustors the diffuser can be subjected to both circumferential and radial variations of the pressure field by the downstream geometry.…”