Development of the GE Quiet Combustor and Other Design Changes to Benefit Air Quality

Abstract

The attractiveness of gas turbines in cogeneration facilities and combined-cycle (Brayton-Rankine) power plants is linked to high specific work; power per unit mass flow. Manufacturers have, over the years, increased gas turbine firing temperature to increase specific work, hence combined-cycle efficiency. High firing temperatures, insofar as they are related to high adiabatic stoichiometric flame temperatures, have brought higher NOx emissions along with high efficiency. Furthermore, efforts to combat smoke have also driven flame temperatures higher. As combustors evolved to produce higher firing temperatures, and design matured in order to lower smoke emissions and control these NOx emissions, dynamic pressure oscillation activity within the combustor, noise, has increased; increasing wear and necessitating more frequent maintenance. Many different concepts were built and tested as described in this paper and others are in research. At this point, the staged combustor operates in the lean/lean and premixed modes and the multi-nozzle quiet combustor operating with diluent injection offer more immediate prospects for achieving the NOx levels demanded today with natural gas and distillate oils.