Development of a five-step global methane oxidation NO formation mechanismfor lean-premixed gas turbine combustion

It is known that many of the previously published global methane oxidation mechanisms used in conjunction with computational fluid dynamics (CFD) code s do not accurately predict CH4 and CO concentrations under typical lean-pr emixed combustion turbine operating conditions. In an effort to improve the accuracy of the global oxidation mechanism under these conditions, an opti mization method for selectively adjusting the reaction rate parameters of t he global mechanisms (e.g., pre-exponential factor, activation temperature, and species concentration exponents) using chemical reactor modeling is de veloped herein. Traditional global mechanisms involve only hydrocarbon oxid ation: that is, they do not allow for the prediction of NO directly from th e kinetic mechanism. In this work, a two-step global mechanism for NO forma tion is proposed to be used in combination with a three-step oxidation dire ctly from the kinetic mechanism. In this work, a two-step global mechanism for mechanism. The resulting five-step global mechanism can be used with CF D codes to predict CO, CO2, and NO emission directly. Results of the global mechanism optimization method are shown for a pressure of 1 atmosphere and for pressures of interest for gas turbine engines. CFD results showing pre dicted CO and NO emissions using the five-step global mechanism developed f or elevated pressures are presented and compared to measured data.