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Show pollutants for a variety of applications. One of the latest S C A Q M D rules curtails, for the first time, N O x emissions from large water heaters and small boilers of 22 to 585 kW. Depending on the particular classification of the product, N O x will be limited to below 30 ppm for n e w products ranging from 117 to 585 k W , and below 55 p p m for products ranging from 22 to 117 k W . A s these regulations will begin to take effect on January 1, 2000, manufacturers have less than 15 months to bring their new products into compliance with S C A Q M D 1146.2 or risk being barred from that market [15-17]. As these small to medium systems were previously unregulated, there will be a need for low N O x burner technologies that are simple and low cost. A s the test results show, the L S B is a very promising burner concept for these systems because it has been demonstrated that the L S B can easily meet S C A Q M D 1146.2. Moreover, w e also have gained confidence in scaling this burner to meet different capacity needs. However, transferring laboratory knowledge to practical situations is non-trivial. W e are planning to continue the research and development of this burner. Future investigations will focus on exploring the operating regime of the large L S B at different equivalence ratios and up to an input power of 3 M W . The stability, size, and combustion intensities under the optimum operating conditions will also be investigated. The ultimate goal of these laboratory studies will be to obtain the necessary background knowledge to develop a prototype with an industrial partner for field testing. SUMMARY AND CONCLUSIONS The lean premixed low swirl burner (LSB) concept has been successful scaled to input powers of up to 600 k W . Using a constant velocity approach, the design of the large capacity L S B (10.16 c m ID) is a linear scaled-up version of a smaller L S B (5.28 c m ID) developed previously for smaller water heaters of up to 18 k W . The operating regimes of the large burner has been investigated and was found to be stable over an input power range from 150 to 600 k W corresponding to 4:1 turndown. These successful tests demonstrate the validity of using the constant velocity approach in scaling the L S B to different sizes and capacities. The swirl requirement of the larger L S B is almost constant for the input power range w e have investigated. However, it is higher than that of the smaller burner. This is attributed to the fact that swirl rate does not scale with velocity, instead, it scales with the residence time of the swirl air within the burner tube. The NOx, CO and UHC emissions of the large LSB were investigated in a furnace simulator and compared to those of a small L S B operating in a burner evaluation facility. The test matrix was limited to (j) = 0.8 at various input power. The <f) = 0.8 test condition was chosen based on the results obtained in a water heater simulator with a small LSB. Previous results show that the emissions of N O x and C O at <|) = 0.8 should be about 15 and 50 p p m respectively (both at 3 % O2). Our test results showed that the N O x emissions of both the large and the small LSBs average about 14 p p m ( 3 % O2) over the entire input power range of 15 to 600 k W . Therefore, N O x emissions from the L S B are independent of burner size and combustion chamber geometry. O n the other hand, the C O and U H C emission showed a strong dependence on burner chamber coupling. Both sets of data 9 |