Trapped Vortex Combustor Development for Military Aircraft

Abstract

Tomorrow's military aircraft will require improved durability leading to life-cycle cost reductions and reduced emission levels while demanding higher performance. A combustor concept that is being developed with these goals in mind is the Trapped Vortex Combustor (TVC). Early testing at AFRL showed that the TVC has the potential to deliver exceptional performance and low emissions. Based on its potential for highpower performance, the TVC was chosen as the ATEGG Phase 3 combustor. Although the ATEGG Phase 3 program has stopped, development of the TVC continues through a joint technology development effort between GE Aircraft Engines, the Navy, and ESTCP.This development program will take the TVC from the laboratory test stage through design and fabrication of engine worthy combustor hardware. Once the hardware fabrication is complete, the current program provides for one full annular test with an option for a second full annular test. The schedule in Figure-1 shows the TVC development timeline with completed items in gray. The first full annular design of a TVC completed testing in April 2007. Ultimate plans are for the TVC to be transitioned into a demonstration engine to achieve a Technology Readiness Level (TRL) of 6.The TVC has been designed to fit within an existing engine architecture, and all TVC goals and objectives are benchmarked against the production combustor. Specific goals for the TVC, relative to the production combustor include:• 50% reduction in high-power Nitrogen Oxides (NOx)• 60% reduction in low-power Carbon Monoxide (CO)• 80% reduction in low-power HydroCarbons (HC) Objectives are in place to improve altitude relight, lean-blow-out, and durability while maintaining cost, weight and combustor exit temperature profile.What makes the Trapped Vortex Combustor so unique is the use of driven cavities incorporated into the combustor liners. The concept being developed differs from the ATEGG Phase 3 TVC in that it uses a rich-quench-lean design approach. All of the fuel is introduced into the cavities where it evaporates and mixes with a portion of the total combustor air, partially burns, and eventually leaves the cavities. Main air chutes through the dome are used to trap the vortices in the cavities increasing the mixing time, and provide additional air to mix with the partially burned gases to complete combustion and quench NOx formation prior to reaching the exhaust plane. Figure-2 provides a schematic illustration of this process.