Development of a Dry Ultra Low NOx Double Swirler Staged Gas Turbine Combustor

This paper describes the development of an ultra-low NOx gas turbine combustor for cogeneration systems. The combustor, called a double swirler staged combustor, utilizes three-staged premixed combustion for low NOx emission. The unique feature of the combustor is its tertiary premix nozzles located downstream of the double swirler premixing nozzles around the combustor liner. Engine output is controlled by simply varying the fuel gas flow, and therefore employs no complex variable geometries for air flow control. Atmospheric combustion tests have demonstrated the superior performance of the combustor. NOx level is maintained at less than 3 ppm (O₂=15%) over the range of engine output between 50% and 100%. Assuming the general relationship that NOx emission is proportional to the square root of operating pressure, the NOx level is estimated at less than 9 ppm (O₂=15%) at the actual pressure of 0.91 MPa (abs.). Atmospheric tests have also shown high combustion efficiency; more than 99.9% over the range of engine output between 60% and 100%. Emissions of CO and UHC are maintained at 0 and 1 ppm (O₂=15%), respectively, at the full engine load.