OCR Text |
Show sample ("mole fractions, wet basis"). In the literature, the term "volume fraction" still frequently appears, a vestige of the classical Orsat analysis (the result, of course, is the same so long as ideal gas behaviour prevails). Like others, w e herein sometimes use non-SI multipliers, expressing X, in p p m (the fraction times 106) when small and in % (the fraction times 100) when large. Where not otherwise specified, X, is always in the standard form, a fraction. 6. Experimental design Four series of trials were performed: 1. Series 1-XBM1-T/F. Single-burner trials with the X B M 1 burner in the Bl sidewall position, some with a tunnel-type combustion chamber made by installing appropriate brick walls within the furnace and some with the full furnace combustion chamber. These were the first trials to be done, and amounted to a preliminary exploration. Because of considerable ignorance about what to look for and expect, they were not as well managed as the subsequent trials but in the end it was seen that the results supported what the later trials more clearly revealed. 2. Series 1-XBM2-T. Single-burner trials with the X B M 2 in the Bl sidewall position, with a tunnel-type combustion chamber, with a variety of fuel and air port sizes and fuel port angles 3. Series 3-XBM2-F. Three-burner trials with X B M 2 burners, with the full furnace combustion chamber and a single combination of fuel and air port sizes and fuel port angle 4. Series 1-XBM2-F. Single-burner trials with the X B M 2 burner in the Bl sidewall position, with the full furnace combustion chamber and a single combination of fuel and air port sizes and fuel port angle. These trials were particularly utilized to map gas-composition fields, giving measures of flame size and shape under various operating conditions The manipulated operating variables were: 1. The firing rate, varied from the maximum attainable to as low as 1/5 the maximum (thus a turndown as high as 5:1). The maximum, 300 to 400 k W combustion heat release per burner, depending on the air nozzle diameters employed and the air preheat, was determined by the maximum delivery pressure of the combustion air blower, ca. 8700 Pa, around half of which was consumed on the way to the burners by line losses and orifice metering.. 2. The excess air level, varied from -2.5 to 27 %. 3. The air preheat, varied from 190 to 500 °C. Because the preheat was obtained with recuperators, the preheat temperature was significantly coupled with the exhaust-gas temperature. This, though unavoidable, was unfortunate for the experimental design. It would have been better if the preheat could have been set quite independently 4. The furnace load, manipulated through the cold-sink exposure. A s explained in Sect. 3, the entire floor of the furnace combustion chamber consists of water-cooled panels. Numbers of panels, ranging from none to all, were covered with 25 m m thick mineral-fiber blanket insulation. The ratio of cold sink area to total boundary area of the combustion chamber thus ranged from 0 to 0.321. 5. The employment of the pilot flame (on or off). 6 |