Flameless oxidation modelling: on application to gas turbine combustors

Abstract

Interest in the 'flameless oxidation' (FO) concept has escalated over the last decade because it has proved to be an effective method for reducing thermal NOx emissions from, and for improving combustion efficiency in, high temperature thermal processes. Thus far, the main areas of application have been in the steel, chemical and ceramic industries, where the technology has shown that NOx emissions can be lowered significantly while maintaining high efficiency. These advantages and other additional benefits are beginning to attract the attention of the gas turbine community in the power generation and aircraft industry sectors. In general, FO embodies partially premixed and diffusion reaction. Therefore, a validated methodology is needed, which can handle this complication in a manner enabling gas turbine combustor design calculations to be efficiently performed. The present paper concerns the validation of such a methodology and its application to a prototype gas turbine design. It follows a previous validation study of proposed FO modelling, covering a wide range of FO laboratory scale combustion facilities. Very useful agreement was demonstrated. In the first part of the present study, predictions of a recently constructed afterburner device, operated under gas turbine FO conditions, are performed to assess the validity of the model for gas turbine application. Thereafter, the method is applied to a new gas turbine combustor design. The conditions required to secure the FO regime therein are identified. Simulation of the new combustor shows encouraging results that demonstrate the potential for NOx reduction and improved pattern factors offered by FO combustion.