Experiments in a novel quasi-1D diffusion flame with variable bulk flow

TL;DR

This paper presents an improved quasi-1D diffusion flame burner with independent control of bulk flow, validated through experiments and modeling, enabling better study of flame stability and effects of flow direction.

Contribution

It introduces a novel burner design allowing independent control of flow parameters and validates a simplified theoretical model against experimental data.

Findings

Good approximation of 1-D diffusion flames achieved

Flow direction influences flame stability

Model aligns well with experimental concentration profiles

Abstract

The novel species injector of a recently developed research burner, consisting of an array of hypodermic needles, which allows to produce quasi one-dimensional unstrained diffusion flames has been improved. It is used in a new symmetric design with fuel and oxidizer injected through needle arrays which allows to independently choose both the magnitude and direction of the bulk flow through the flame. A simplified theoretical model for the flame position with variable bulk flow is presented which accounts for the transport properties of both reactants. The model results are compared to experiments with a CO2-diluted H2-O2 flame and variable bulk flow. The mixture composition throughout the burning chamber is monitored by mass spectrometry. The resulting concentration profiles are also compared to the simplified theory and demonstrate that the new burner configuration produces a good approximation of the 1-D chambered diffusion flame, which has been used extensively for the stability analysis of diffusion flames. Hence, the new research burner opens up new possibilities for the experimental validation of theoretical models developed in the idealized unstrained 1-D chambered flame configuration, in particular models concerning the effect of bulk flow magnitude and direction on flame stability. Some preliminary results are presented on the effect of bulk flow direction on the thermal-diffusive cellular flame instability.