Reduced and Validated Kinetic Mechanisms for Hydrogen-CO-sir Combustion in Gas Turbines

Abstract

Rigorous experimental, theoretical, and numerical investigation of various issues relevant to the development of reduced, validated kinetic mechanisms for synthetic gas combustion in gas turbines was carried out -including the construction of new radiation models for combusting flows, improvement of flame speed measurement techniques, measurements and chemical kinetic analysis of H 2 /CO/CO 2 /O 2 /diluent mixtures, revision of the H 2 /O 2 kinetic model to improve flame speed prediction capabilities, and development of a multi-time scale algorithm to improve computational efficiency in reacting flow simulations. Executive SummaryRigorous experimental, theoretical, and numerical investigation of various issues relevant to the development of reduced, validated kinetic mechanisms for synthetic gas combustion in gas turbines was carried out -including the construction of new radiation models for combusting flows, improvement of flame speed measurement techniques, measurements and chemical kinetic analysis of H 2 /CO/CO 2 /O 2 /diluent mixtures, revision of the H 2 /O 2 kinetic model to improve flame speed prediction capabilities, and development of a multi-time scale algorithm to improve computational efficiency in reacting flow simulations.An accurate spectral dependent radiation model is developed to predict flame speed and flammability of H 2 /CO/CO 2 /H 2 O/Air mixtures. The results showed that radiation reabsorption significantly extended the flammability limits. It was also demonstrated that accurate prediction of coal syngas flammability is not possible without appropriate consideration of radiation absorption by CO 2 and H 2 O.Methodologies to improve flame speed measurement were developed by experimental and theoretical investigation of the effect of non-spherical (i.e. cylindrical) bomb geometry on the evolution of outwardly propagating flames and the determination of laminar flame speeds. The cylindrical chamber boundary modifies the propagation rate through the interaction of the wall with the flow induced by thermal expansion across the flame (even with constant pressure), which leads to significant distortion of the flame surface for large flame radii. It was determined that these departures from the unconfined case, especially the resulting non-zero burned gas velocities, can lead to significant errors in flame speeds calculated using the conventional assumptions, especially for large flame sizes.The methodology to estimate the effect of nonzero burned gas velocities is applied to correct the flame speed for non-zero burned gas speeds, in order to extend the range of flame radii useful for flame speed measurements. Under the proposed scaling, the burned gas speed can be well approximated as a function of only flame radius for a given chamber geometry -i.e. the correction function need only be determined once for an apparatus and then it can be used for any mixture. Results indicate that the flow correction can be used to extract flame speeds for flame radii up to 0.5 times the wall radius wi...