OCR Text |
Show liters/sec (0 - 21.2 ft3/min) for the combustion air. Natural gas is supplied to the system at a household pressure of 11" before being reduced to 1" - 3" of water pressure and injected into the combustion air. Compressed air at 25 psi (reduced to 0 to 1 0" inches of water pressure) is used to provide the swirl air. \ \ Flamrelocity I \~j/ \ \ Reaction Zone I I \~/ \ , Reactants Exit Tube ----7 Swirler Section 2" Pipe Cross Fuel Mixture : f-(--- I Quartz Cylinder Enclosure 52mm Exit Tube 52 mm diameter Figure 1: Schematic of Weak-Swirl burner and Enclosed System The operating principle of the WSB has been described in References 2 and 3. As the premixed fuel exits the system through the 5 cm (2") diameter exit tube, the centrifugal force due to the swirl flow causes the mixture to radially diverge as the fuel proceeds downstream. In order to conserve mass flux, the mixture velocity decreases as the mixture increases in area downstream. Unlike conventional swirl burners, our swirl intensities are not sufficient to generate flow recirculation. When the premixture is ignited, the propagating flame is stabilized at the location where the local turbulent burning velocity matches the local velocity of the reactants. This creates a stable flame, insensitive to perturbations in <p. If ~ (and thus the flame speed of the mixture) increases, the flame brush will move upstream. However, the flame will restabilize itself at the new location where the local velocity of the mixture again matches the higher flame speed. 4 |