Luminous Flame Height Correlation Based on Fuel Mass Flow for a Laminar to Transition-to-Turbulent Regime Diffusion Flame

TL;DR

This study develops a flame-height correlation for diffusion flames transitioning from laminar to turbulent regimes, validated through experimental imaging and numerical simulations, offering improved predictive accuracy for flame behavior.

Contribution

The paper introduces a new flame-height correlation applicable across laminar and transition-to-turbulent regimes, validated with experimental and numerical methods, with reduced adjustment variation.

Findings

Correlation has 16.9% adjustment variation in laminar regime

5.54% adjustment variation compared to existing correlations

Numerical results align with experimental flame zones

Abstract

This paper presents a flame-height correlation for laminar to transition-to-turbulent regime diffusion flames. Flame-height measurements are obtained by means of numerical and experimental studies in which three high definition cameras were employed to take frontal, lateral and 45{\deg} angled images simultaneously. The images were analysed using an image-processing algorithm to determine the flame-height through indirect measurement. To locate an overall chemical-flame-length, numerical simulations were conducted with the unsteady Reynolds-Averaged Navier-Stokes technique. The eddy-dissipation model was also implemented to calculate chemical reaction rate. The experiments show that this proposed correlation has an adjustment variation of luminous flame-height for the laminar regime of 16.9%, which indicates that, without the use of the intermittent buoyant flame-height correlation, it globally best represents the flame-height in this regime. For the laminar and transition-to-turbulence regime the adjustment variations are 5.54% compared to the most accepted flame-height correlations, thus providing an acceptably good fitting. The numerical results show that the proposed range for the chemical-flame-length is located between the luminous and flickering flame zone compared to the experimental flame images. These results agree with the chemical length zone reported in the literature. Therefore, the correlation can be used for laminar and transition-to-turbulent combustion regimes.