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Show lean premixed flames on a conventional burner. The technology is simple and could be easily retrofitted into existing appliances. LABORATORY SETUP Details of the experimental setup have previously been described in detail [2] and will be only briefly reviewed here. Flows of natural gas and air are metered, measured, and then mixed before being injected into the bottom of the burner. Glass beads in the base of the burner break up the incoming jet of reactants and disperse it evenly. A fine gauge wire mesh on top of the beads prevents shedding of large scale vortices from the beads, ensuring quiescent flow. The flow of premixed reactants is then accelerated through a contraction section and out through the nozzle of the burner where the flame is stabilized. The burner nozzle is shown in Figure 1. The base case for comparison is the traditional rim stabilized burner which is shown on the left in Figure 1. Here the flame is thermally anchored to burner rim as described in detail in Lewis and von Elbe [3]. The inner diameter of the rim is 32 mm and the length of the exit section along to flow axis is 25 mm. At the end of the contraction section, at the base of the exit section, there is a provision for a turbulence generator. A perforated plate with 3 mm holes and 50 % blockage ratio was used to induce turbulence. Turbulence intensity at the burner exit was approximately 11.5 %. The ring stabilized burner, the focus of this research, is shown on the right in Figure 1. Rings of different diameters and cross-sections can be placed in the flow to aerodynamically anchor the flame. The rings, which were made of stainless steel or aluminum, were held in place by three small spindles 0.5 mm in diameter which were anchored to the burner rim. Several different rings with a variety of diameters and cross sectional areas were investigated as summarized in Table 1. The most influential parameter in determining the performance of a ring stabilizer was found to be the gap size which is 3 |
