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Show flow are supplied by the same fueVair source at a fixed~ . CO emissions of the vaneswirled WSB range from a high of 56 ppm at ~ = 0.85, to a minimum of 12 ppm around <P = 0.75 before rising again at lower~ . As the thermal efficiency of the system does not appear to be compromised when ~ ~0.75 , the CO "valley" and the corresponding NO emissions is used as the ideal operating conditions for the prototype WSB. Due to fuel supply constraints, the laboratory experiments were limited to a maximum of 90,000 BtuIhr. Further tests have been completed at Teledyne Laars' testing facilities in Moorpark, California to find the maximum operating range for the 53 mm diameter WSB. Instead of fitting the swirler with our customized screens, the vaneswirler tested at Teledyne Laars used wire mesh screen and metal foam sheets. These materials are more easily available then our screens and do not increase production cost. The vane-swider was found to operate reliably from 40,000 to 400,000 BtuIhr in the open, with ~ ranging from 0.6 to 1.0. However, it should be emphasized that 400,00 Btulhr is not highest possible firing rate of the WSB. Rather, it only represents the maximum currently achieved, as tests at Teledyne Laars were limited by the air supply system. When operating in a prototype heat exchanger at 250,000 BtuIhr, CO levels were comparable to those in Figure 7. The work completed at Teledyne Laars demonstrated the feasibility of operating a single size vane-swirled WSB at higher power ranges for a variety of units. Future Plans Although the scope of this work is limited to conditions of interest to developing water heaters, our results implies that vane-swirled WSBs can be adopted for use in many practical applications. More testing will be performed using different geometries (R, Rh, U, and vane length) and flow velocities (Uinf, Uc, and UJ to characterize the stable operating range of the vane-swirled WSB versus ~ and firing rates. These studies will show if the operating range of vane-swirler with different geometries fall within a narrow range of Sy. One these operational range are defined, it might be possible to express the operation range, through the use of the Sv expression, in terms of a blockage parameter instead of an empirical ratio U /U a. This would enable a burner engineer to design a vane- 11 |