Experimental Investigation of Flame Structure and Combustion Limit During Premixed Methane/Air Jet Flame and Sidewall Interaction

Abstract

The effects of inlet gas parameters and sloping sidewall angle on the flame structure and combustion limit with and without sidewall were experimentally investigated. Flame height and impact angle were obtained by chemiluminescence intensity analysis of CH* distribution. First, the combustion characteristics of flame with and without sidewall at different equivalence ratios were explored; then, the influence of Reynolds number and inlet gas temperature on flame structure and combustion limit of v-shaped flame with sidewall were analyzed, and the results with sidewall were compared with those without sidewall. Finally, the variation trend of flame parameters with different sloping sidewall angles was analyzed. The experimental results show that the existence of sidewall makes flame shape change from “M-shaped” to “inverted N-shaped”, and conical shape to trapezoidal shape. The inhibition effect of sidewall on flame stretching downstream is strengthened with the increase in Reynolds number; but as the temperature of the inlet gas increases, the inhibitory effect is obviously weakened. When sloping sidewall angle decreases from 90° to 55° at 5° intervals, flame height and impact angle of v-shaped flame reach the extreme value when β = 80°. Compared with the case without sidewall, the range of v-shaped flame with sidewall has no obvious trend of broadening or shrinking when inlet gas temperature is increased; however, as sloping sidewall angle decreases, the range of the v-shaped flame shrinks obviously and flammability limit increases significantly.