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Show Thus far, most of the work on evaluating the commercial potential of the L S B has been conducted at relatively low input powers below 100 k W . The test results are quite encouraging. With excess air at 4 3 % (equivalence ratio, (j> = 0.7) the N O x emission level is below 5 p p m (corrected to 3 % O2) in a 15 k W commercial spa heater [2]. To fire at the input powers needed for larger commercial products, w e need to explore the proper scaling approaches. The purpose of this study is to scale the L S B design to 6 0 0 K W and conduct preliminary evaluation of its performance in terms of stability, turndown, and emissions (NOx, C O and U H C ) . A large (10.16 c m exact ID) and a small (5.28 c m exact ID) L S B was constructed for evaluation in the furnace simulator and generic burner testing stations, respectively, at the U C Irvine Combustion Laboratory (UCICL). The two LSBs were tested successfully at input powers ranging from 146 k W to 585 k W for the 10 cm L S B and from 18 k W to 106 k W for the 5 c m LSB. This data allows for a better understanding of h ow to scale the L S B to larger capacities while maintaining operational stability and low emissions. BACKGROUND The use of strong swirl for flame stabilization is common in gas turbine injectors, dump combustors and industrial burners [3]. It is considered the most effective means by which to control flame intensity, size and shape for high speed flows. The primary function of the strong swirl is to create a torroidal recirculation zone (TRZ). In many conventional designs, a centered bluff body is used to form a T R Z in its wake. For non-premixed combustion, the T R Z promotes mixing of the fuel and air, and stabilizes the flame by recirculating the hot combustion products. For premixed combustion, the T R Z generates a zone of hot combustion products that enables the flame to anchor itself at either the upstream or the downstream stagnation points. Under near limit conditions, oscillation of the flame between the upstream and downstream stagnation points can cause instability and increased levels of noise. The mechanisms of TRZ flame stabilization have been the subject of numerous reviews [3, 4]. In Beer and Chigier [5], a swirl number for characterizing the swirl intensity is approximated as: R / R S = jUWr2dr/RJu2rdr (1) 0 / 0 W h e n tangential air injection is used, a geometric swirl number „ R *R*/z m-2 Sg^-^T (-f)2 (2) A0 m, has been defined [6, 7] to allow for the calculation of swirl intensity without the need to directly measure the angular and axial velocities. The term "strong swirl" is applied to those burners with Sg > 0.6 as the onset of recirculation occurs at this swirl intensity. 3 |