The Allison Engine Company has been developing a low emission, can-annular combustion system for the 501K industrial gas turbine engine to satisfy increasingly stringent environmental requirements. This paper describes the progress achieved, over that previously reported by Razdan et al. (1994), through subsequent design evolution, bench testing, and engine evaluation. Allison’s goal is to develop a retrofittable, can-annular combustion system that limits emission levels to less than 25 ppm nitrogen oxide (NOx), 50 ppm carbon monoxide (CO), and 20 ppm unburned hydrocarbon (UHC), while operating at full load conditions. The interim emissions goals for the combustion system are 37 ppm NOx, 80 ppm CO, and 20 ppm UHC (all dry 15% O2 corrected).

The combustion system under development employs a dual mode combustion approach to meet engine operability requirements and high power emission targets without the use of combustor diluent injection or postcombustor exhaust treatment. A lean premixed combustion mode is used to minimize combustion zone temperature and limit NOx production during high power engine operation. The lean premix mode is augmented with a diffusion flame pilot mode for engine starting and low power operation.

Initial engine testing showed a dry low NOx combustion system, designed to meet a 37 ppm NOx limit, produced less than 34 ppm NOx and less than 10 ppm CO and UHC in test stand verification test. Continued burner rig testing with modified primary combustion zone stoichiometry has demonstrated NOx less than 25 ppm, CO less than 50 ppm, and UHC less than 20 ppm with simulated engine conditions representing 20 to 100% power. Development activity continues on the combustion system as engine field evaluation trials proceed.

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