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Pressure Change and Flame Characteristics in a Stretched, Rotating Flow
To investigate the pressure change and flame characteristics in a stretched, rotating flow, tubular flames of a lean hydrogen, methane, or propane-air mixture have been numerically simulated. Results show that, with rotation, the flame temperature of hydrogen and methane mixtures increases monotonically, while, that of a propane mixture decreases. With an increase of the fuel concentration, the position at which the reaction rate is maximum increases, and the temperature change becomes small. As seen in the pressure distribution, the pressure decreases around the center, and a pressure gradient is formed. This pressure gradient is steep near the center, but decreases as the radial distance is increased. The fuel flux decreases with the increase of circumferential velocities because of the decrease in the pressure gradient. For these reasons, this temperature change could be explained in terms of the pressure diffusion which results in mass transport due to the pressure gradient. However, it is also found that, with rotation, the pressure decreases and the density changes. The velocities increase due to flow expansion, resulting in an increase of flame stretch. Thus, the flame characteristic change with rotation is explained with the coupling of pressure diffusion and stretch effects.
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Graduate School of Engineering