OCR Text |
Show 3-4. Gas/air mixture (Figure 12) l) Gas/air mixture Uniformity of gas/air mixture has a large influence on flame stability and N O x emissions characteristics. Figure 12 shows the method of gas/air mixing at the time of starting the test. In this method, combustion itself could not be continued. But in the method shown in Figure 4, a uniform gas/air mixing seemed to be achieved. However, in this case, the pressure drop is as large as approx.2.9 kPa at the rated combustion with O 2=4%. This is our future subject to be solved. 3-5. Convection heat transfer of furnace Unlike the conventional combustion, convection heat transfer of this cyclonic combustion shows as large as 10.5 % of total heat input at rated. This value was obtained from the difference between the calculated value and measured value. 3-6. Multiple nozzle structure (Figure 13,14) W e hereby report the test result of the burner with multiple nozzle structure, in which three air mixture nozzles are arranged in furnace axis direction. Figure 13 shows burner structure while Figure 14 shows the combustion characteristics. The NOx emissions was as low as 18 ppm at rated load with O 2= 5%. By arranging multiple nozzles like these, the flame stability increased. W e think this reduction of N O x emissions is the effect of flame cooling owing to multi-nozzle arrangement. - 1 0 - PILOT BURNER "A" AAiP - Gas/Air |G** Mixture Eb flfr-l » LJJ. r- ~r *A--'A*SECTION FIGURE 12. PRIMARY GAS/AIR MIXING UNIT |