Abstract
In order to elucidate the effect of wall temperature on a diffusion flame–wall interaction, an acetylene diffusion flame in a head-on quenching type was investigated. Direct photography, two-color thermometry, soot-LII (laser-induced incandescence), OH-LIF (laser-induced fluorescence) and numerical simulation with detailed reaction mechanisms were employed to find out the influence mechanism of wall temperature on near-wall combustion performance and emission characteristics. It is clearly shown through optical diagnostics and computation fluid dynamics (CFD) simulation that, compared with cold wall, the high temperature zone for hot wall becomes wider, and the smaller quenching layer is formed due to the higher wall heat flux. High-concentration soot emission is formed primarily near the outer flame far from the wall. CH2O, CO and HC emissions are decreased as wall temperature rises, while the formation of soot and A4 is increased. A diffusion flame–wall interaction structure is proposed to reveal the influence mechanism of wall temperature.
Highlights
In some spatially confined combustion environments, such as an engine combustion chamber [1,2,3,4], flame–wall interaction (FWI) will occur
According to the relative position relation between flame propagation direction and wall surface, wall quenching can be divided into two types: head-on quenching (HOQ), where flame propagation is perpendicular to the wall, and side-wall quenching (SWQ), where the flame burns parallel to the wall [11]
Wang et al [14] studied the questions of turbulent fuel–air–temperature mixing, flame extinction, and wall-surface heat transfer using direct numerical simulation (DNS) for an ethylene–air diffusion flame–wall interaction
Summary
In some spatially confined combustion environments, such as an engine combustion chamber [1,2,3,4], flame–wall interaction (FWI) will occur. Wang et al [14] studied the questions of turbulent fuel–air–temperature mixing, flame extinction, and wall-surface heat transfer using direct numerical simulation (DNS) for an ethylene–air diffusion flame–wall interaction. They proposed a modified flame extinction criterion that combines the concepts of mixture fraction and excess enthalpy. The results showed that both 2D and 3D FGM simulations could predict the flame structure and major characteristics correctly, such as the temperature, the flame–wall interaction parameter and the reduced quenching distance It had limitations in predicting CO mass fraction distribution near the wall. The study is significant to understand the flame–wall interaction
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