Measurement of Turbulent Flame Velocity

Unlike laminar combustion, turbulent flame velocities depend not only on fuel properties, but, to a greater extent, on the turbulence field characteristics. Therefore, quantification of the turbulent field is a necessary condition for turbulent flame velocity measurement. An informative method of turbulent combustion investigation has been proposed in [1]. A spherical container with four fans installed symmetrically along the container perimeter was used in the experiments. Conditions for w pulsating velocity controllability have been created in the central part of the container  

Gelfand et al., Thermo-Gas Dynamics of Hydrogen Combustion and Explosion, Shock Wave and High Pressure Phenomena, 

Heat-loss anemometers with Wollaston filaments [2] and laser heat-loss anemometers [3, 4] were used for turbulent field calibration depending on the fans rotary speed. The experiments revealed that the turbulent intensity (pulsating velocity) in the central part of the field is in direct proportion to the fans rotary speed. Maximum values of the pulsating velocities obtained were about m = 10 m/s with a 10% non-uniformity. The Lagrangian scale is about 10 mm. In the experiments [5,6] the turbulent intensity resulted mu = 16 m/s. 

The turbulent flame velocities in the container with fans have been measured by two methods. In the first method, the front boundary displacement of the turbulent flame in the Schlieren photos was observed, similar to the case of the laminar flame the equivalent spherical front radius was found by a mathematical treatment (planimetry, for example). The up-dated Schlieren photography devices have allowed registration in two projections for calculating the flame source volume with better accuracy. 

The method applied in [1, 2] is based on the ascertained fact that the quantity of combustion products is uniquely dependent on the pressure in a spherical container. The advantage of this method is that it allows measuring the turbulent velocity even in the case of deformed or fragmented sources of combustion. 

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