However, as demonstrated in the present paper, such an assumption is not realistic for the usual numerical configuration of a flame propagating in an "ideal" tube with no heat transfer to the walls.
In contrast, even a small effect of conduction along this surface leads to significantly higher minimum M. Comparison is made with an alternative configuration of a flame stabilized at the exit of a tube, where heat recirculation occurs via conduction through tube wall; it is found that the counter-current exchanger configuration provides superior performance under similar operating conditions.
Interestingly, these trends match those observed on other configurations of diffusion flames, further strengthening the consistency of the YSI methodology.
To this end, a turbulent nonpremixed jet flame (Reynolds number 15,200 and CH4/H2/N2 fuel composition) is considered, representing a benchmark flame configuration of the International Workshop on Measurement and Computation of Turbulent Nonpremixed Flames (TNF Workshop).
We consider the simple geometric configuration of a planar diffusion flame situated in a channel at the interface between a fuel being supplied from below, and oxidant diffusing in from a stream above.
This demonstrates, the possibility for burner and boiler manufacturers to use numerical simulations to predict relatively complex configurations in terms of flame structure and pollutant emissions.
As expected, unsteady partial premixing results in a fluctuating double-flame configuration: a premixed flame and a diffusion flame.
The pressure time histories are also presented together with the regimes of combustion for all flow configurations during the course of flame propagation.
Four different types of flame configurations, including two attached flames, inner lifted/outer attached flames, inner attached/outer lifted flames, and twin lifted flames, were successfully simulated depending on the flow conditions.
The "chaotic flame" configuration characterizes a flame not necessarily attached to the burner that exhibits a disordered geometry that leads to aperiodicity of its motion.
