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Show 1660 r 5.0 Results and Discussion Experimental Results The first series of test results were made in the small furnace having seven thermocouples positioned 12" apart, and in line with the burner. The test burner was positioned 12" above the furnace floor and fired with approximately 610,000 BTUH (with 1 5 0 % excess air). The thermocouples were located along the floor, against one of the furnace side walls. The furnace was fired to approximately 1600°F. Recessing the burner into the furnace wall decreased the slope of the temperature profile as shown in Figure 6. The burner was recessed in a 10" x 10" cavity. Two recesses were tested: 6" and 12". In both cases the temperature distribution along the length of the flame was more uniform compared to the burner fired flush at the furnace hot face. The temperature was higher near the furnace wall as a result of recessing. A burner having a rectangular (slotted) discharge (AR = 3.6) was tested at similar 12" Recess Rush With Wall 20 40 60 80 Distance From Burner (Inches) Figure 6 Recessing High Velocity Burners * 1640 100 1620 Slotted Nozzle Round Nozzle 20 40 60 Distance From Burner (inches) 60 Figure 7 Round vs. Slotted Nozzles capacity and excess air, and showed a similar improvement in temperature distribution (see Figure 7). The slot was sized for an 1 8 % increase in velocity. Recessing the slotted burner further improved the temperature distribution and reduced the temperature near the wall. A round nozzle was resized to increased the velocity by 7 8 % and also improved the temperature distribution, but not nearly as much as the above tests. The furnace experiments showed that simple modifications to the burner nozzle shape and location can significantly flatten the temperature distribution parallel to the burning flame. The tests further showed that combining such modifications compound the improvement. In the best case the temperature distribution improved by nearly 5 0 %. The second series of experiments were done to investigate burner entrainment. High velocity burners were down-fired in ambient air conditions into a cylindrical test rig. The firing arrangement was selected to negate buoyancy effects. Velocity pressure and temperature were measured at the exit of the test rig to determine total flow. Air and fuel flow to the burner was metered. The test burners were lower in capacity (330,000 to 500,000 BTUH) than prior tests, and were fired near stoichiometric conditions. Two existing high velocity 100 6 |