High-intensity turbulent premixed combustion: General correlations of turbulent burning velocities in a new cruciform burner

A methodology was developed to investigate general correlations of turbulent burning velocities for high-intensity premixed turbulent combustion. The burner consists of two vessels with a cruciform shape. The long vertical vessel provides a stable, downward-propagating premixed flame, while the horizontal vessel is equipped with a pair of counter-rotating fans and perforated plates at each end to generate highintensity isotropic turbulence. Using a pair of specially designed ion-probe sensors, turbulent burning velocities of both methane-air and propane-air mixtures are quantitatively measured over a greater parameter range than hitherto measured. These turbulent burning rates are then compared with earlier results using different burners. When Bradley's dimensionless correlations in terms of the Lewis, turbulent Karlovitz, and Reynolds numbers are used to analyze the present data, great caution in smoothing large scattering data of S_T/S_L against u'/S_L is required. Our present S_T/S_L data are generally smaller than that of Bradley by a factor of 2 at any fixed u'/S_L. Interestingly, when the Lewis number is less than unity, no global quenching of turbulent premixed flames is observed event at u'/S_L ≈ 50, a value significantly higher than hitherto used. Finally, a general correlation of the form (S_T - S_L)/u' ≈ 0.05 Da^0.61, is proposed, where Da is the Damkohler number. This correlation is better than previous correlations, which covers both distributed (small Da) and corrugated flamelet (large Da) regimes.