Effects of acoustic excitation on pinch-off flame structure and NOx emissions in H2/CH4 flame

Abstract

The flame structure and exhaust emissions of pinch-off flames, in which flames are separated under acoustic excitation conditions, were studied. Flame structure analysis was performed using OH∗ chemiluminescence measurements, and exhaust emissions analysis was performed with a gas analyzer. Structure analysis of the pinch-off flame for acoustic excitation was performed basis the OH∗ images, and various structures were confirmed according to the forcing frequency and velocity perturbation intensity. To analyze the correlation between the flame structure and NO x emission, the flame residence time and emission index of NO x (EINO x ) were analyzed according to the Strouhal number. The flame residence time and EINO x decreased as the velocity perturbation intensity increased; analyzing the NO x emission characteristics is limited when based only on the flame residence time. 1/2-power scaling was followed by EINO x analysis and the Strouhal number was normalized to the flame residence time. • Investigation of dynamic and exhaust emission characteristics of pinch-off flames. • Pinch-off flame structure is defined by detailed NO x emissions analysis. • Flame height decreases relative to an increase in the velocity perturbation. • Reduction of flame height reduces the flame residence time. • The τ res alone is insufficient for analyzing NO x emissions.