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Show S = 0.75 for> 75% of burner flow) produces an undesirably large IRZ and flow attachment to the combustion chamber walls. • The secondary fuel injection angle is critical for achieving low NOx and CO levels. An injection angle of between 0° and 15° to the axial direction appears to be optimum. If the angle is increased to 30°, the secondary fuel is entrained into the primary stage axial air flow, leading to high N0x- • The flame shape is affected by the choice of flue gas injection location. Adding flue gas to the swirled flow can increase the tangential momentum flux and create a large IRZ. Adding flue gas to the axial air stream produces a small IRZ and a temperature field that is below 1800 K. Prototype Burner Test Results Three sets of burner tests were conducted. The initial burner configuration was optimized at Power Flame's test facilities in Parsons, Kansas. Subsequently, a prototype burner was fabricated based on the optimum performance and configuration determined from the burner testing. The prototype burner was again tested and optimized at Power Flame before being shipped to Trane's test facilities in La Crosse, Wisconsin. At Trane, the burner was tested in a fully operational 300 ton chiller and was required to follow the load demands of the chilling system. Power Flame Test Arrangement: The initial burner configuration was fabricated by Power Flame and installed in an instrumented chiller combustion chamber. Figure 7 shows the burner installed at Power Flame's test facilities. Water was circulated in the test combustion chamber in place of the lithium bromide solution that is used in chilling systems. The chiller combustion chamber was approximately 0.66 M (26 inches) in diameter and approximately 1.8 M (6 feet) long. Design firing rate for the burner was 1.1 MW (3.8 MMBtu/hr), and the burner was tested over the range of 0.3 - 1.2 MW (1 - 4 MMBtu/hr). Air flow rate and pressure, primary and secondary fuel flow rates and pressures, flue gas recirculation rate, and stack NOx' CO and 02 concentrations were monitored during burner testing. The burner geometry and operating conditions were optimized during a comprehensive test campaign. Test Results: Sample data illustrating the relative effects of degree of fuel staging and flue gas recirculation rate on measured NOx emissions is shown in Figure 8. This data is for a fixed firing rate of 1.0 MW (3.5 MMBtu/hr) and an excess air level of about 15%. As expected, increasing the degree of fuel staging causes the NOx emissions to decrease, as the primary zone becomes leaner. This trend is observed both with and without flue gas recirculation. 13 |