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Show 2.0 EXPERIMENTAL SYSTEMS The experimental systems shown in Figure 1 have been described in detail elsewhere (1, 2) and only the salient features will be presented below. Tunnel Furnace The downfired tunnel furnace was designed to allow utilization of commercially available spray nozzles and yet be capable of testing with artificial atmospheres. The combustor was 2.1 m long, 20 cm inside diameter and the walls consisted of insulating and high temperature castable refractories. The full load firing rate was 0.53 cc/sec, which corresponds to a nominal heat release of 20 kW. All airstreams were metered with precision rotameters. The main combustion air was preheated with an electric circulation heater; the atomization and secondary air streams were not preheated. In certain tests the "air" was enriched or replaced with varying amounts of carbon diozide, argon, and oxygen, all of which were supplied from high pressure cylinders. Fuel and air entered the combustion chamber through a burner with a shallow divergent exit (L/D = 5) and the combustion air was introduced axially (without swirl). The interchangeable fuel injection system consisted of a 19 mm diameter stainless steel tube which contained the atomizing air supply tube, the fuel oil supply tube, a cartridge heater for final oil temperature control, and a chromel-alumel thermocouple positioned in the injector tip prior to the nozzle for accurate oil temperature measurement. A commercial air-assisted ultrasonic oil atomizer (capacity 0.55 cc/sec) was used in this investigation because it provided adequate atomization of the heavy liquid fuels at relatively low flow rates. The tip of the fuel nozzle was positioned at the beginning of the burner divergent section and, in general, the visible flame front was displaced approximately one nozzle diameter from the nozzle tip. Boiler Simulator The large-scale combustion experiments were conducted in an axisymmetric combustor at a nominal firing rate of 900 kW. This combustor was 0.5 m in diameter, 4.5 m in total length, and divided into calorimetric sections cooled by heat transfer fluid. 7-5 |
