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Show -12- obvious relation between the viscosity at a shear rate of 100 s " and the ease of atomization with the slurries tested. Once the atomizing air rate was set to an optimum value, and using o 300 C air preheat, all seven slurries could be fired into the 3/4 insulated furnace (50% heat extraction) without gas support. Under the input conditions and with the slurries made with high or medium volatile~~cQals, burnout levels in the range 95-99% were measured as shown in figure 12» These burnout levels are similar to those measured with dry pulverized coal of a similar grind fired into the same furnace conditions. In general the slurries made with high volatile bituminous coals, and those with the finest particle size distribution gives the most flexibility regarding ignition particularly when operating without air preheat or under high flame heat extraction rate conditions. The same slurries giving the most flexibility regarding ignition also gave the highest coal burnout levels. The preliminary work in collaboration with Hoogovens [ 13 ], had already confirmed the absolute necessity of a strong, high temperature internal recirculation zone in order to achieve stable iginition. The burner design characteristics necessary to achieve this end relate particularly to the fundamental studies described in the following section. STUDIES ON THE NEAR FIELD AERODYNAMICS OF SWIRL BURNERS An important aspect of flame research which had been the subject of an investigation prior to the end of 1982 was that of scaling of combustion systems [ 1 5 ]. This work involved a multiscale experimental study, one of the objects of which was to compare constant residence time and constant velocity burner scaling techniques. This investigation was an extremely good example of the possibilities for collaboration between two laboratories within the |