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Show perturbations in $. The power output of a relatively small burner (exit diameter of 50 nun) is readily scaleable from 8 to 80 kW (30,000 to 300,000 Btu/hr.). Developed for fundamental research in turbulent combustion processes [2,3], the WSB is also applicable to commercial products. The work reported in this paper is a joint effort with Teledyne Laars of Moorpark, CA to evaluate the feasibility of using the lean burning WSB in water heaters. The results described here include an investigation of the swirl requirements for operating WSB in the open and in an enclosure. These experiments provided the necessary guidance for incorporating the burner in a typical water heater configuration. We have chosen the Teledyne Laars Telstar spa heater for evaluating the performance of the WSB. This natural gas heater operates at 15 kW (50,000 Btu/hr) with average thermal efficiency of 820/0. In our test station, the heat exchanger and the chimney assembly of the Telstar laboratory are mounted over a WSB. Tests were performed to determine the optimum operating condition for minimum emissions without sacrificing thermal efficiency. WEAK SWIRL BURNER The WSB currently used for this work (Figure 1) is fabricated from a 2" pipe cross filled with marbles to generate an even flow field at the entrance to the burner tube (5 cm in diameter by 5.5 cm in length). Two perforated screens (60% blockage ratio) are placed at each end of the burner tube. These act as flashback arrestors as well as generating turbulence in the premixture. Turbulence has the additional purpose of increasing the burning rate and creating a more compact flame. After the burner tube, the premixture enters the swirler section, where four tangentially mounted air jets (3.2 rom in diameter, inclined 20° from horizontal) inject compressed air into the outer edges of the premixture. This arrangement, tangential air injection, is one of the classical swirl generators suggested by Beer and Chigier [4]. The premixture and the swirl air then leave through the exit tube of length R. (as measured from the swirl jets). This tube has a 45° tapered rim to allow the pre mixture to smoothly diverge before reaching the reaction zone. A 1170 horsepower centrifugal blower with a controllable damper supplies up to 10 3 |