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Show CALIBRATION MIRROR FLAME DETECTION MIRROR IR-UV CALIBRATION SOURCES CALIBRATION MOVEABLE "'"""::::::::::::- ---=::........:---____ B..~",__.",....:.... MIRROR BEAM SPLITTER Fig. 1 - Schematic of the SFA Optical Unit wheel provide the timing signals for synchronizing the electronics. In order to calibrate the system, a movable mirror directs light from the calibration sources into the optical system and simultaneously blocks the light from the flame. The radiation from the calibration sources allows the four signal levels and their ratios to be adjusted. The SFA has been designed with two separate detectors. The detectors are mounted on separate optical axes so that band limiting filters can be used. A special silicon beam-splitting mirror is positioned at a 45-degree angle in front of the IR detector. The silicon beam splitter passes IR wavelengths, but reflects UV wavelengths with a high reflectivity. The UV detector is positioned at right angles to the IR detector and is located at the same distance from the mirror as the IR detector. Thus, the optical system focuses the IR in the beam onto the IR detector and the UV on the UV detector. This optical design for the detectors allows bandpass filters to be placed in front of either detector to limit the radiation waveband falling on the detector. The optical system focuses the flame radiation at the plane of the aperture through a 45- degree mirror. The focused beam is then reflected by another 45-degree mirror onto a focusing mirror which concentrates the radiation onto the detectors through a beam splitter. The optical enclosure is water-cooled so that it can be installed close to the boiler front. The microprocessor unit consists of a Motorola Model 6800 microprocessor and the necessary support chips. The design incorporates 8 K of program memory, 2 K of RAM memory, four analog outputs, a display, four digital outputs for controlling system functions, and six counters (four are used for the signals and two for future analog inputs). The microprocessor program controls all the functions of the SFA system. Its basic function is to collect the count data from the four counters connected to the two detector signal inputs, and generate two ratios from these signals. The values obtained for these input data and the calculated ratios are then displayed on the front panel. In addition, four of these signals are converted to analog outputs, using four digitalto- analog converters (DAC), which are wired to a connector on the electronics enclosure. The input signals from the detectors are in 223 the form of counts over a period of 0.10 second. The program averages these O.IO-second counts over either 1 second or 10 seconds, depending on the speed of response that is required. The average value is then displayed. The linear range of the system is 0 to 1800 counts on the display, or 0 to 4.98 Vdc on the analog outputs. The ratio readings and outputs are calculated from the two IR and the two UV signals. MIT COMBUSTION RESEARCH FACILITY An overall arrangement of the MIT-CRF is shown schematically in Figure 2. The 3-MW thermal pilot plant MIT-CRF is designed to permit close simulation of the thermal environment of large, industrial-type, turbulent diffusion flames. The flames produced in this facility are studied primarily by means of water-cooled, "inflame" probes, most of which are based on designs originated at the International Flame Research Foundation (IFRF). The CRF is a 4-ft x 4-ft cross section, about 35 ft long, combustion tunnel made up of 30 interchangeable, separate, l-ft-wide wall sections, all of which are water-cooled and instrumented to obtain a sectional heat balance. Fifteen of the wall sections are refractory-lined to permit hot-wall operation of up to 3000°F face temperature, and the remainder of the sections have bare metal surfaces permitting cold-wall operation (212°F face temperature). The interchangeability of these wall sections permits variable furnace length and variable heat sink distribution. The CRF is equipped with a single burner of up to 3 MW thermal, multifuel firing capability; the burner assembly is of IFRF design and contains an interchangeable, centrally located gas or liquid fuel/coal slurry gun which carries the appropriate mechanical, steam, or air atomizing nozzles for liquid fuel/coal slurry injection. The combustion air is supplied to an annular throat surrounding the fuel gun via a variable swirl generator which permits the ratio of tangential to axial momentum in the combustion a i r to be varied over a wide range. The variation in combustion air swirl permits significant changes in flame flow pattern and overall aerodynamics to be obtained. The fuel handling and preparation system is designed to permit use of gaseous fuels and a range of liquid fuels including mixtures of solids and liquids, i.e., coal-oil mixtures and coal-water slurries. The facility also operates with pulverized coal as the fuel, using pneumatic transportation of the coal particles. All of the measurement and monitoring systems for both inputs to the furnace and experimental variables are interfaced to a computerized data acquisition and handling system. This system permits rapid evaluation of all process variables and also rapid processing of all "inflame" measurements, many of which may need to be further analyzed to provide guidance on input parameter selection for continuation of the measurements program. |