| OCR Text |
Show Scaling the Low Swirl Burner from 15 k W to 600 kW D.T. Yegian, R.K. Cheng, Lawrence Berkeley National Laboratory, Combustion Research Group R.L. Hack, M . M . Miyasato, A. Chang, and G.S. Samuelsen University of California at Irvine, UCI Combustion Laboratory 1998 American/Japanese Flame Research Committees International Symposium October 11 -14,1998 ABSTRACT 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 a 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 have been investigated and found to be stable over an input power range from 100 to 600 k W . These tests demonstrate the validity of using the constant velocity approach in scaling the LSB. The non-dimensional swirl number for the larger L S B is constant for the input power range we have investigated. However, it is higher than that of the smaller burner. This is attributed to the fact that the swirl rate does not scale with velocity, instead, it scales with the residence time of the swirl air within the burner's exit tube. The N O x , C O and U H C emissions of the large L S B 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 <}> = 0.8 (25% excess air) at various input powers. The 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 is independent of burner size and combustion chamber geometry. On the other hand, the C O and U H C emission showed a strong dependence on burner chamber coupling. Both sets of data showed that a minimum input power is needed in order to keep C O emission below 25 ppm (corrected to 3 % O2) and U H C concentrations at the undetectable level. When operating above the minimum input power, the performance of the L S B is very encouraging. With N O x at 14 ppm, C O at 25 ppm, and U H C at an undetectable level, the L S B should be a prime candidate for use in natural-gas furnaces and boilers. 1 |
