Simplified methodology to assess the use of alternative fuels at fuel flexible gas turbine combustion chamber design stage using thermokinetic equilibrium and nearlyglobal mechanisms

Abstract

Modern combustion turbines have several applications: power stations, naval, aeronautical and oil industry. Aeronautical applications seek reduction of pollutant emissions using mixtures of conventional Jet fuels with biofuels and synthetic fuels. Due to the restrictions of natural gas and other oil fuels supply for the generation of electricity, the use of alternative fuels in stationary gas turbines is being seriously considered. Generally, all liquid and gaseous fuels from biomass, syngas, biogas, refinery gas and other unconventional sources are considered as alternative fuels. In the last years, with the objective of making the industrial and aeronautical process in harmony with the current environmental laws around the world, much research on the use of these alternative fuels in gas turbines is in progress. Gas turbines are thermal machines with the great advantage
of being capable of successfully burning a large variety of fuels in a continuous combustion process. Gas turbine combustion chambers with this ability are referred as “Fuel Flexible Gas Turbine Combustor”. This paper aims at describing a methodology for sizing fuel flexible gas turbine combustors and, additionally, analyzing the reacting flow in these designed combustion chambers. The design of the fuel flexible gas turbine combustors is based on the thermokinetic equilibrium, nearly-global mechanisms, zero and one-dimensional approaches simultaneously with numerical methods as Newton-Raphson, LU factorization and inverse Lagrange polynomials. A computational tool has been developed for the combustor sizing. The zero and onedimensional models are based on the methodology developed by Lefebvre, Melconian e Modak. The thermokinetic
equilibrium, flammability limit and nearly-global mechanisms models are based on the methodology developed by Gordon and McBride. The study of the combustion efficiency for the studied fuels and its influence on the production of pollutant emissions under several operating conditions is presented. Useful information is generated at the design stage of a fuel flexible gas turbine combustion chamber, which may be used to alter the pollutant emissions at very early stage of the design.