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Show IFRF D o c N o K 70/y/113 IJmuiden, April 1997 -12- A F R C Spring meeting 1997 The figure shows that for type II flames, N O x is reduced (relative to the baseline case with no coal through bluff body) with increase in the fuel fraction that is injected via the bluff body. It was found that the solid 90 ° bluff body or swirler located in the central fuel gun was superior to the solid 30 ° bluff body. For type I flames there was very little difference between the bluff body types. However, best performance was achieved when 20 % of the blend was injected through the central gun with a 90 ° bluff body with holes. Results with the solid 90 ° bluff body, show that N O x increases with increased fuel fraction, as the flame changed in shape from the typical type I to that of the type II. o 800 700 600 500 400 300 200 100 Type I • o A A -•- X gun position -20 60 -20 60 -20 60 60 Muff body 4 7 m m (verier 47mm svarter 30° solid 30° solid »0°sobd SO" solid 90°*rth notes 10 20 30 40 Fuel Fraction of Blend through bluff body [ % ] 50 Figure 3.9 The Effect of Fuel Fraction on N O x 3.3.2 High Velocity Air In addition to the effects on N O x with types of bluff body, the investigation also examined ways of segregating the swirled secondary air from the axially injected tertiary air. This was achieved by introducing a jet of air termed High Velocity Air ( H V A ) between the two air streams. The results from these tests are shown in figure 3.10. |