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Show Table 1 - Recent LOA Appl1cat10ns at Combustton Engtneertng Ash Velocity Distribution in Pneumatic Transport Pipes. In-flame Measurements 1n Coal/Water Mtxture Combustors. Parttcle Velocity Measurements for Ash Erosion Research. Settltng Velocities and Drag Coefflctent/Shape Factor Determination. Air Flow Measurements In Nuclear Fuel Bundle Models. As shown in Figure 2, a laser anemometer Is composed of three basic components: a laser light source, an optical system, and an electronic signal processing system. When a light wave inferacts with a moving particle In the fluid stream, the frequency of scattered Hght is altered. Laser anemometry is based on the measurement of this frequency, which is directly proportional to the instantaneous velocity of the particle. There are two possible ways to explain the basic physlcl principles of laser anemometry. First, when the differential frequency of the scattered llght is measured, tt can be considered as being caused by the Doppler shift of ltght scattered by the particle traversing the volume. Or, alternatively, the t~o beams ca~ be considered to form a set of mterference frmges, and that l1ght is scattered by the particles as they cross each interference fringe. In both cases the differential frequency is measured, so either of these basic explanations may be used. LOA operation is based on the assumption that the particles suspended ~n the flow move Voftth ~he same velocity as the flU1d whose velocity 1S bemg measured. Thus laser anemometry depends on the presence of material in the fluid to act as scattering centers. In the case of gases, the scatterers are liquid or solid particles which must be small enough to follow the local gas velocity, yet not so small that they have appreciable thermal (Brownian) motion- particles of 0.1 to 1 micron are usually used. In most casesJ the flow must be seeded. A relatively new velocity measurement technique that shows promise is called Speckle Photography. As reported by Suzuk 1, e.t. a 1. (21), this technfQue is basically an extens1!>n of the proven double spark photography technlQue. The advantage of this technique is that through the use of a laser TV camera, and micro computer, two dimensional velocity magni~ude ~nd directional information can be ootamed w1th minimal test facl11ty time (For example, as compared to the time required for a double spark photograph). This technique is currently ltmited by the need to inject particles into the flow model that are small enough to follow the gas flow patterns and not experience sltp, yet large enough to be photographed. Because of thls reQufrement, the technique is currently ltmtted tr small models. 119 L.ON' S.~OI L "hi coNoei IOf\ ,'OUU'", or,o",.",e'" I,.t,,,, Fig. 2 - Laser Doppler Anemometer Flow Mixing Measurement Techniques - The mixing of two or more input streams is a key performance variable in a large number of ut11tty and industrial combustor systems. In addition, the residence time of certain components within the furnace system is important. Practical model1ng appllcattons range from fuel-air mixing within the furnace to the mixing of the flue gases and injected reheat a1r at the entrance to the exhaust stack. In the isothermal model1ng of such systems It is common practice to seea one of the input streams with a tracer gas or inject It at an elevated temperature. By traversing the model and measuring the local gas concentration or air temperature distribution, mixing levels and efficiencies can be determined. The used of heated injection air combtned with thermocouple traverses 1n modeltng systems is discussed by Thompson, et. al. (8). Gaseous tracer concentration techniques in the past have been l1mited by the need to extract a sample of gas from the flow model for later laboratory analysts. This technique was improved with the use of on-l1ne hel1um concentration measurement devices. The application of such a device to an isothermal flow model of a two stage coal gasifier is discussed by Bianca, Bauver, and McGowan (4). This technique obtained accurate results, but d1d require approximately 10 minutes to zero and to obtain a steady state concentrat 10n readlng. |