A Study of Turbulent Combustion Mechanism in a High Temperature, High-Pressure, and Low-Oxygen Environment

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This project aims to extend the research of high-pressure and high-temperature turbulent combustion to the low oxygen concentration combustion in terms of utilizing for new premix-type gas turbine combustors with an exhaust gas recirculation. Turbulent premixed flames and turbulent non-premixed flames using oxidizer diluted with N_2 and CO_2 were investigated. Observation and analysis of instantaneous flame structure using OH-PLIF and CH-PLIF were conducted. Measurements of turbulence characteristics, NOx emission, and turbulent burning velocity were also performed.For turbulent non-premixed flames, oxidizer preheated up to 1300 K, whose oxygen concentration was 4 vol % minimum diluted with CO_2 and N_2 were visualized using CH-PLIF. It has been proved that bubble-like flame structures are formed especially in the case of lifted flames. Low NOx emission has been also confirmed even for non-lifted flame using a NOx analyzer.For turbulent premixed flames, flame stabilization for the meth … More ane-air mixture preheated up to 573 K diluted with CO_2 at pressure up to 1.0 MPa has been succeeded. The oxygen concentration of the mixture could be reduced up to 10 vol % simulating the condition of premix-type gas turbine combustors with exhaust gas recirculation. Instantaneous OH-PLIF images were obtained and fractal analysis was performed to explore the effects of intrinsic flame instability on CO_2 diluted premixed flames. Moreover, Turbulent burning velocity and time-averaged production rate of product species were determined. As a result, turbulent premixed flames for low oxygen concentration due to CO_2 dilution at high pressure and high temperature increases the volume of heat release region and reduces the time averaged production rate of combustion products, leading to mild heat releasing. These characteristics are an important factor for reducing combustion instability of premix-type gas turbine combustors and profitable features in terms of realizing new premix-type gas turbine combustors with exhaust gas recirculation proposed in this research project. Less