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Show These observations based on the predictions of our model agree well with all the experimental indications of our work. Besides the evidence from normal operation of the furnace, there was also clear visual corroboration from running the furnace cold with the nearfield door open. Air infiltrating through the nearfield door and being entrained by the fuel jets then made those jets visible as turbulent diffusion flames. At 0\ = 65°, these flames were observed to head virtually straight for the furnace roof and floor, upon which they impinged. 8.3.6. The extent of aerodynamic farfield development As pointed out in § 8.2, if given enough space, the multi-jet flow from a burner coalesces into a single round jet, whereupon the aerodynamic farfield of this system is entered. Under relatively simple conditions, such as constant-density flow, the farfield structure is virtually independent of the initial conditions. W e will now examine the question of the extent to which farfield development is possible within a typical furnace space. The first step is to calculate the effective source diameter, Db,s of the burner. W e have Di, = 4w2 / npjjx± = 4(wfl + mf )2 / np„(Ga cos02 + Gf cosfl,) (ma + mf)2 A . W J KpaD-f)cos<92 + (m) I NpfD2)cos0] ,2 . p (\ + wf(Pfy = ND2^- tZJ4-, • (21) p„ cos<92 +(cos0x)Wf<pfpa Ipf Since normally Wfcpf < 0.0608 when burning our natural gas, and, we assume, p^ = pe, this approximates D2 bs = ND2(MJe/MJa)/cos02. (22) Consider N=1,D2= 19.05, 02 = 10°, Ta = 400 °C = 673 K, and Te = 1200 °C = 1473 K. Setting Ma = 28.96 kg/kmol and Me = 27.77 kg/kmol, we get Db,s = 76.7 m m. If the air port axes were parallel (02 = 0), then, according to the results of Yimer, Grandmaison and Becker (1996), we would find, approximately: 1. The jets from the air ports would neck in to a "vena contracta" at around JC = 3 D ^ = 230 m m. 2. The virtual origin of the single, round, farfield jet would lie around x = 4Dbj = 307 m m. 3. In respect to the mean velocity field, the farfield would begin around x = 20 Db,s = 1534 m m. In our case, with 02= 10°, these distances must all be somewhat greater. However, it does appear that for the conditions of our CGRI burner trials in the C A G C T furnace, the vena and the farfield virtual origin were likely located upstream of x = 500 m m , and the furnace space (a 3 m run from burner wall to opposite sidewall) is just great enough for the farfield to begin, but no more. 20 |