Effects of small- and large-scale structures in a piloted jet diffusion flame

Abstract

Laser Doppler Anemometry (LDA) and Planar Laser-Induced Fluorescence (PLIF) measurements have been performed in a turbulent nonpremixed jet flame. One of the features of this configuration is a central co-axial fuel jet surrounded by a turbulent annular air flow. The whole is placed within a low-speed coflowing air stream. This three-flow system with turbulent primary air differs from flow systems used for nonpremixed jet flames reported in the literature and is very useful for obtaining information on the mixing process between fuel and primary air. Next to the characterization of the velocity field, special attention has been paid to the conditional seeding of the central fuel jet and of the annular air flow. Together with visualizations of the OH radical, an important combustion intermediate which is formed during combustion, and the NO radical, which is seeded to the central jet flow, the resulting statistics reveal the properties of small- and large-scale structures in the flame.