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This paper investigates the flame morphological characteristics (flame height, flame horizontal length and flame tilt angle) of diffusion combustion with or without near-wall constraint in cross-wind. Experiments are carried out using propane as fuel for 10, 15, 20 cm square burners at various heat release rates. Two air entrainment conditions are performed: with near-wall (simulated by a mica board) constraint or in free space (without near-wall). The cross-wind is provided by a wind tunnel up to 3.5 m/s. The evolution of flame height, flame horizontal length and flame tilt angle are measured for a total of 240 test conditions. It is found that the flame height of near-wall condition is higher while the flame tilt angle is lower than that of free condition, both changing monotonously with cross-wind speed. The flame horizontal length is first relatively smaller then larger for near-wall condition than that of free condition with increase in cross-wind speed, however, for both air entrainment conditions it increases first then decreases with cross-wind speed. Three independent length scales are proposed based on the analysis of competition of combustion buoyancy and cross-wind momentum and the inherent physics. General formulas are proposed, based on dimensionless parameters derived according to the derived length scales, to represent the flame morphological characteristics for both with or without near-wall conditions in cross-wind. [ABSTRACT FROM AUTHOR]

• Flame pulsation frequencies of free-, wall- and corner buoyant flames quantified. • Effect of wall on flame pulsation frequency revealed. • Correlation for flame pulsation frequency established. • Characteristic length scale for the flame pulsation frequency proposed. This work studies the flame pulsation frequency f of free-, wall- and corner buoyant turbulent diffusion flames. Five square gaseous burners with the burner side length of 10, 15, 20, 25 and 30 cm are used to produce the three types of flames. In addition, five rectangular gaseous burners with dimensions of 30 cm × 15 cm, 25 cm × 12.5 cm, 20 cm × 10 cm, 15 cm × 7.5 cm, 10 cm × 5 cm (aspect ratio of 2:1 with half surface area of the square burners) are also used to produce wall flames. Propane is used as fuel. Results show that heat release rates have no significant effect on f. The flame pulsation frequency of free flames is larger than that of wall flames, which is further larger than that of corner flames. For all types of flames, the flame pulsation frequency decreases with the increasing of the burner size. The classic 1/2 power law correlation, i.e., f ~(g / D)0.5 for flame pulsation frequency of free flame can well describe the data of all types of flames (square, rectangular; free flame, wall flame and corner flame) on the basis of the "mirror" approach, and the perimeter-equivalent diameter is used as the appropriate length scale. [ABSTRACT FROM AUTHOR]