Stability Characteristics and Emission Levels of a Laboratory Hot Water Heater Utilizing a Weak-Swirl Burner

This paper reports the test results of a collaboration between Lawrence Berkeley National Laboratory and Teledyne Laars to assess the viability of incorporating the Weak-Swirl Burner (WSB) into a 15 kW (50,000 Btu/hour) Telstar spa heater. By stabilizing premixed lean combustion down to equivalence ratios $ ~ 0.6, the WSB greatly reduces NOx levels by minimizing thermally generated NOx through the Zeldovich mechanism. The first set of experiments focus on establishing the WSB's minimum and maximum swirl requirement (corresponding to blowoff and flashback) for varying $, power levels, burner size, and enclosure. The second set of experiments evaluates the performance of a laboratory water heater where the WSB is incorporated into a Telstar heat exchanger. I t was found that the laboratory test station achieves "low" « 50 ppm) and "ultra-low" « 25 ppm) NOx emissions without compromising the thermal efficiency. The optimum operating condition is for $ = 0.8 at 18 kW (60,000 Btu/hr) where NOx < 25 ppm and CO < 50 ppm (both corrected to 30/0 02). The results will be used as design guideline for using the low emission WSB in a prototype. The stable operation we found for enclosed WSB demonstrates the potential for its use in other combustion applications as well.