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Show swirler based strictly on the physical parameters of the swirler geometry to operate at the ideal condition of ~ = 0.75 - 0.80. CONCLUSION Our results illustrate the successful development of an economical and simple vane-swirler that can replace the air-swirler used in previous versions of the Weak -Swirl Burner. The vane-swirler produces the necessary diverging flow field to stabilize a lean premixed flame above the exit of the burner tube. The unique feature of our vane-swirler is a center tube that allows a portion of the premixture to pass through without being affected by swirl vanes fitted in the annular region. The center tube is the key element in generating the necessary .flow divergence for stabilization by a WSB. This design differs from conventional vane-swirlers that emphasize the generation of recirculation zones. The vane swirler helps to simplify the design of WSB because is does not require two separate flow controls. A new expression was developed that takes into account the contribution of the flow momentum from the undisturbed core flow. In terms of performance, the WSB using a vane-swirler improves CO emissions while achieving the same thermal efficiency and low NO emissions. At the optimum operating condition of $ = 0.80 (achievable by the four screens shown in Figure 6), NO emissions are less than a fifth of the proposed regulation limits of 40 Jlg/J, CO is a tenth of the 400 ppm limit, and thermal efficiency is uncompromised. With the successful development of a vane swirler to replace the air-injected swirler, an important milestone has been reached in the commercialization of an economical, durable, and reliable premixed weak-swirl burner. ACKNOWLEDGEMENT This work was supported by the Department of Energy, Energy Research Laboratory Technology Transfer through a Cooperative Research and Development Agreement with Teledyne Laars, Moorpark, California. The authors would like to thank Mr. Gary Hubbard for developing the computer software, Mr. Ken Hom for fabricating burner and swirler components. 12 |
