Operability and Efficiency Performance of Ultra-Compact, High Gravity (g) Combustor Concepts

Abstract

Future gas turbine engines are required to be more capable than their predecessors. This often implies severe demands on the engine that translate into increasing compressor and combustor exit temperatures, higher combustion pressures and higher fuel/air ratio combustors with greater turn-down ratios (wider operating limits between idle and maximum power conditions). Major advances in combustor technology are required to meet the conflicting challenges of improving performance, increasing durability and maintaining cost. Unconventional combustor configurations are one promising approach to address these challenges. Ultra-short combustors to minimize residence time, with special flame-holding mechanisms to cope with increased through-velocities are likely in the future. Engine cycles other than the standard Brayton cycle may also be used for special applications in order to avoid the use of excessive combustion temperatures, and to extract additional power from the system. This paper focuses on vortex-stabilized combustor technologies that can enable the design of compact, high-performance combustion systems. Compact combustors weigh less and take up less volume in space-limited turbine engine for aero applications. This paper presents a parametric design study of the Ultra-Compact Combustor (UCC), a novel design based on TVC work that uses high swirl in a circumferential cavity to enhance reaction rates via high cavity g-loading on the order of 3000 g’s. Increase in reaction rates translates to a reduced combustor volume. Three combustor geometric features were varied during experiments which included (1) high-g cavity flame-holding method, (2) high-g cavity to main airflow transport method, and (3) fuel injection method. Experimental results are presented for these combustor configurations and results have shown promise for advanced engine applications. Lean blowout fuel-air ratio limits at 25–50% the value of current systems were demonstrated. Combustion efficiency was measured over a wide range of UCC operating conditions. This data begins to build the design space required for future engine designs that may use these novel, compact, high-g combustion systems.