Developments of High-Efficiency and Low-Emission Gas Turbine Combustors by Diode-laser Absorption Measurements

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In this study, diode laser absorption measurements and effective control factors of combustion noise, combustion oscillations and emissions of CO_2 and NO_x are investigated to develop high-efficiency and low emission gas turbine combustors. Direct numerical simulations of hydrogen/air and hydro-carbon/air turbulent premixed flames are conducted by taking into account detailed kinetic mechanisms and temperature dependence of transport and thermal properties. By using the results of direct numerical simulation, simulations of diode laser absorption measurements are conducted and the accuracy of those is clarified. It is shown that accuracy of diode laser absorption measurements is enough if it was applied in the burnt gas. Based on the numerical simulations, measurement systems based on the diode laser absorption are developed for H_2O and CO_2 absorption. Measurements are conducted in fundamental laboratory buners to verify accuracy such as species concentration, temperature and time resolutions. From this study, advantages and limitations of the diode laser absorption measurement are shown. From the results of direct numerical simulations, relations between NO_x production rate and local flame structure such as local heat release rate, curvature of the flame front and strain rate are also investigated to develop the effective control scheme of emission. It is shown that CH concentration will be a good control factor of NO_x because the local NO_x production rate is well correlated with the local heat release and CH concentration. To identify the effective control factors of combustion noise and combustion oscillations, direct numerical simulations of sound in chemically reacting turbulence are also conducted. From the results of DNS, sound generation mechanism form turbulent combustion is investigated and prediction method of far field sound is developed.