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Show This persists until the two regions have merged in the upper flame zone. Note that this region corresponds to that shown in Fig. 10 as having strong radial penetration of the fuel jet into the air jet. The other region where a difference in the fluctuation of the components exists is along the shear region between the internal recirculation zone and the fuel jet. In this region (where the flow is predominantly axial) the axial component exhibits enhanced fluctuations. These data help to account for what appears to be a much higher level of fluctuation in the data of Figs. 6 and 7 (radial and tangential components) as compared to Fig. 5 (axial component). These data show that the width of the velocity distributions for the three components are about the same, but when scaled with the mean value of each component (as in Figs. 5-7) they appear to be much larger for the radial and tangential cases. Inlet Air Flow Figure 12 shows the three components of velocity at the furnace entrance plane. Axial and radial velocities exhibit fairly flat profiles across most of the throat area but are then strongly peaked approaching the centerline. The tangential velocity behaves in the opposite fashion, dropping off as the centerline is approached. The behavior of the axial and radial components is consistent with existence of a low pressure region in the center of the flowfield. They are augmented by virtue ofaxiaVradial pressure gradients in this region. In the discussion of Figs. 5 and 6, it was postulated that this low pressure region is the result of entrainment by the fuel jet. Figures 13 through 15 support this hypothesis by showing the velocity profiles under three conditions with varying degrees of entrainment. The first condition is the full flow under burning conditions (as shown in the previous figure). The second is with the spray shut off, but with the atomizing air still present (no flame, half the mass flowrate in the "fuel" jet). The third is the main air flow only (no spray or atomizing air, no flame). As evident in the figures, the extent to which the velocity components are augmented depends directly on the entrainment ability of the central fuel jet. This interplay of the jets must be carefully considered when modeling a flow field such as this, since one might otherwise be tempted to specify the inlet conditions for the two jets independently (i.e., to use the "main air only" profile as the throat inlet condition). Figure 16 shows the fluctuations in the three components across the entrance plane. All three components are of similar order, but the tangential component fluctuations are somewhat lower than those of the axial and radial components. CONCLUSIONS Six distinct regions were observed in the structure of the flow: (1) The fuel jet-a swirling two-phase flow with velocities of order 25 m/s and a very broad range of fluctuations. This jet persists until approximately 100 mm downstream of the nozzle after which it is indistinguishable from the main air jet. This region contains a high number density of droplets and the velocity data acquired in it are biased by the detection abilities of the laser doppler instrument The fuel jet is conical in shape, mixing on the inner edge with the internal recirculation zone and on the outer edge with the main air jet. In mixing with these two regions, the fuel jet entrains both hot product gases that have been recirculated from the upper flame regions, and fresh air from the main air jet. (2) The main air jet-a swirling air jet with velocity of order 4 m/s and initially modest fluctuations of about 20% of the mean. This jet mixes with the fuel jet on its inner - 9- |