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Show 686 287 H 10 2 54 457 .2 CH4 Nozzle Details Top Heater Connection 4 Shroud Diameter: 101 .6 Electrical Insulator Heated Burner Tube Quartz Alignment Tube Dimensions in mm 5 W Argon Ion Laser Fig. 1 Burner Details Focusing Lens Exhaust Air+Oxygen --========r- Methane Transmitted Li ght Photodiode Burner on Traverse Burner and Extinction Schematic Radiant fluxes were measured using a Land radiometer Type RADIP positioned 0.73m distant from the central axis of the flame. By considering each flame to be basically cylindrical with dimensions of length and radius determined photographically, the total radiant fluxes were obtained for each flame via the application of the appropriate view factor (7). An extinction technique has been developed to measure soot volume fractions in flames (Fig. 1). A 5 Watt argon ion laser (Lexel 3500) was employed and focused in the flame using a 0.5 m focal length lens. The initial and transmitted beams were monitored by splitting off a small fraction from the main beam and delivering these through polaroid and bandpass filters, centred at /.-.=488 nm to two photodiodes. The soot attenuation measurements were achieved by ratioing the signals derived from these two vertically polarised beams so as to minimise small fluctuations in the laser power. The centre line beam attenuation was measured at various heights up the flames to determine the maximum sooting location. The burner was then moved horizontally so as to achieve radial attenuation distributions at the maximum sooting height. These line of sight measurements were deconvoluted via an Abel inversion technique (8) to yield local extinction coefficients (1q) and local soot volume fractions (fvi) ' The value of complex refractive index (m) was assumed to be 1.6-0.6i for all flames investigated (9-10). I' 2k, J VI - 36nF(2) (3) F(2) = nK [(n2 - ,,' +2)' +4n2,,2] (4) m = n - iK (5) On-line analysis for nitrogen oxides, carbon dioxide and oX1'gen was performed, on a dry gas basis, using a chemiluminescent Signal 4000 NOx analyser a Signal 2000 C02 analyser and a Servomex 580A 02 analyser. The samples were taken along the flame axis between 1.5 and 2 times the visible flame length above the burner nozzle. The sample probe was manufactured from 6 mm diameter stainless steel tubing formed into a 50 mm dIameter ring. On the inside and outside of the ring series of 0.5 mm diameter holes were drilled so that a uniform sample could be obtained from the post flame |
