Performance of a reduced NOx diffusion flame combustor for the MS5002 gas turbine

This paper describes a reduced NOx diffusion flame combustor that has been developed for the MS5002 gas turbine. Laboratory tests have shown that when firing with natural gas, without water or steam injection, NOx emissions f rom the new combustor are about 40 percent loser than NOx emissions from th e standard MS5002 combustor. CO emissions are virtually unchanged at base l end, bur increase at part load conditions. The laboratory results were conf irmed in 1997 by a commercial demonstration test at a British Petroleum sit e in Prudhoe Bay, Alaska. The standard MS5002 gas turbine is equipped with a conventional, swirl stabilized diffusion flame combustion system. The twe lve standard combustors in an MS5002 turbine are cylindrical cans, approxim ately 27 cm (10.5 in.) in diameter and 112 cm (44 in.) long. A small, annul ar, vortex generator surrounds the single fuel nozzle that is centered at t he inlet to each can. The walls of the cans are louvered for cooling, and c ontain an array of mixing and dilution holes that provide the air needed to complete combustion and dilute the burned gas to the desired turbine inlet temperature, The new, reduced NOx emissions combustor (referred to as a "l ean head end'' or LHE, combustor) retains all of the key features of the co nventional combustor: the only significant difference is the arrangement of the mixing and dilution holes in the cylindrical combustor can. By optimiz ing the number, diameter and location of these holes. NOx emissions were su bstantially reduced. The materials of construction, fuel nozzle, and total combustor air flow were unchanged. The differences in NOx emissions between the standard and LHE combustors, as well as the variations in NOx emission s with firing temperature, were well correlated using turbulent flame lengt h arguments. Details of this correlation are also presented.