| OCR Text |
Show burner designs were tested with circular and slotted discharge nozzles (ref. Figure 5). The results of this test work are shown in Figure 8. The entrainment data is plotted against normalized distance from the jet exhaust. All data were measured at a distance of 37" from the burner discharge. The variation in normalized length is due to the change in hydraulic diameter. The two straight lines represent the non-reacting 20 T results (with density change) from Ricou and Spalding5, and reacting flow from Dahm6. The data, in general, lies between the reacting and non-reacting predictions. There is considerable variation however, between the round and slotted burner jets. Burner family A shows little difference between the round and slotted, although the slotted data is closer to the reacting flow prediction. Burner family B shows improvement in entrainment of the slotted shape but the data is further from the predicted results. There are test conditions which may account for the entrainment diversity shown in Figure 8. The greatest perhaps is that the velocity profile of the burner exit was not symmetrical, as visible flame was observed favoring one side of the nozzle exit. The outer region, or mixing layer, of the jet is most critical to determining entrainment. It is in this region that the measured velocity pressures at the exit were the smallest, and very sensitive to experimental error (i.e. tilting of the pitot tube, boundary effects along the test rig wall, etc.). The burner flame holder design, particularly of burner family A, lends itself to stabilizing flame to one side. Orientation of the slotted nozzle, or varying the air and fuel piping arrangement, also had some impact on asymmetry of the jet. Also, the test rig obstructed radial flow into the burner jet. The jet in this instance 15-- m „ + m a 10 -- m, X = 37 inches O - Burner Family A (round) D - Burner Family A (slot) • - Burner Family B (round) • - Burner Family B (slot) 5- Ricou and Spalding (non-reacting flow) 10 20 X/dh 30 40 Figure 8 Entrainment Results Using High Velocity Burners 7 |
