OH-PLIF investigation of wall effects on the flame quenching in a slit burner

Abstract

To examine the effects of the wall on flame quenching, an OH-PLIF investigation of a premixed methane/air flame was conducted with a slit burner between two parallel walls. Three types of materials, i.e., stainless steel 304, silicon, and zirconia ceramics, were tested at wall temperatures of 300 and 600°C. The quenching process, captured by an intensified charge-coupled device (ICCD) camera, showed different critical distances for stable flames that became unstable and were quenched for the three materials at the same temperature. It is interesting to note that, at a higher wall temperature, the flame is lifted before finally quenching, while this did not happen at 300°C. By analyzing the maximum OH fluorescence intensity in the flame extracted from the OH image, we have not found a distinct relation between the maximum OH fluorescence intensity and the quenching distance. In some cases, the flame can sustain a very weak OH intensity. Conversely, we also obtained the OH fluorescence intensity close to wall and within 0.6mm from the surface. We found that the trend of the OH fluorescence intensity close to wall correlates with the quenching characteristics very well. At the same wall temperature, a greater OH intensity close to wall results in a shorter quenching distance and vice versa. The wall made of zirconia ceramics demonstrates the greatest OH intensity close to the wall and, thus, the shortest quenching distance, while of the quenching distance in the case of STS 304 demonstrates the opposite trend. Additionally, we also calculated the non-dimensional chemical action of the surface based on the OH-PLIF data, which can demonstrate the differences in the chemical quenching characteristics for the three types of materials.