Elucidation and Modeling of Turbulent Premixed Combustion Phenomena in a High-Pressure and High-Temperature Environment

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This research aimed to explore turbulent combustion phenomena at high pressure and high temperature. Turbulent premixed flames for preheated mixture stabilized in a high-pressure chamber were investigated. Precise observations of the flame and measurement of turbulent burning velocity and the smallest scales of flame wrinkling due to Darrieus-Landau hydrodynamic instability were performed. Effects of pressure and preheating were examined and the turbulent combustion model at high pressure and high temperature was developed.Electrical heater of the air was developed and installed in the high-pressure chamber for the present experiment. The maximum pressure and temperature were 1.0 MPa and 573 K because of the limitation of high-temperature seals. Methane/air mixtures were used for the experiments. The fractal inner cutoff of OH-PLIF images as the smallest scale of flame wrinkles was analyzed, and it was clarified that the significant correlation between the smallest wrinkling scale and … More characteristic scale of Darrieus-Landau hydrodynamic instability even at 573 K for large turbulence Reynolds number. Precise measurement of the energy spectrum of turbulence showed that Kolmogorov's similarity law for nondimensional energy spectrums of flow turbulence at high pressure and high temperature was confirmed, and a characteristic scale equivalent to the average vortex-tube diameter, which is about 10 times larger than the Kolmogorov scale can be considered as a scale corresponding to the largest wavenumber of initial flow disturbances. It was also shown that the smallest wrinkling scale becomes constant when this turbulence scale becomes smaller than the instability scale because of the effect of the Darrieus-Landau hydrodynamic instability. Measurements of laminar burning velocity at high-pressure and high-temperature were performed using simultaneous PIV and OH-PLIF methods developed in this research. Experiments for stoichiometric H2/O2/He mixture were performed first and then methane/air mixture was examined. Modification of the reaction mechanism was also performed. The numerical and experimental data were used for the analysis of the turbulent combustion.Finally, measurements of turbulent burning velocity based on image processing of OH-PLIF images were conducted and the model to estimate turbulent burning velocity at high-pressure and high-temperature based on turbulent Reynolds number was developed. Less