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Show IFRF Doc N o K 70/y/113 IJmuiden, April 1997 -6- A F R C Spring meeting 1997 mechanism to be fully effective, before mixing of the combustion air with the primary/reburn zone products, and/or that the reburn fuel is not injected at the optimum location. Further analysis of this flame is given in a separate report, [13] where predictions of the flow field, chemistry and temperature using the C F D code F L U E N T is validated against detailed in-flame measurements. Sec air So' = 1 11 Tert. air So' = 0 55 500 400 300 200 100 . D 8 • • - • - • O O A • • A • 8 i S e c air 7 19 40 7 20 39 6 19 . O 8 • Velocity (m/s) A • Tert air Reburn fuel 74 59 29 74 59 29 74 59 i . 74 radial injection 74 radial injection 74 radial injection 13.5 axial injection 13.5 axial injection 13.5 axial injection 13.5 axially with rebum swrter 13.5 axially with rebum swirler I . I . 0.2 0.4 0.6 0.8 Primary stoichiometry (k ) 10 1.2 Figure 3.1 Effect of the rebum fuel velocity and injection mode on N O , 600 500 - primary fuel: Gotteibom - rebum fuel: Natural Gas 300 - 100 • • 1 ' 1- CBO • - - ' § o 1 I o J X , «Q.9 pvtnarY a o a v internal 12 hole-classical 6 note - classical turbine - classical D o A ' 20 Rebum fuel fraction 30 Figure 3.2 Effect of internal and "classical" reburning on N O x Furthermore, Figure 3.2 directly compares the technique of internal fuel staging with "classical" reburning with reburn fuel fractions in the range 5%-30%. It is clear that N O x reduction with internal fuel staging is as good as the classical technique in the Rff range of 5 - 20%. With a Rff of 30%, the classical technique, using a six hole nozzle shows overall the best performance with flue gas N O x c |