| OCR Text |
Show TESTING PROCEDURE AND DEFINITION OF PERFORMANCE FUNCTION To study the mechanisms responsible for V O C formation and to relate the V O C emissions to previous studies of the burner's performance [13], five conditions were tested at constant load. Cases 1 through 4 used the superior performance counter-swirl injector with the burner operating at different combinations of V and S'. Case 5 was conducted using the poorer performance co-swirl injector. The motivating reasons, previously discussed in [14], for selecting each point are as follows: Case 1 Low V and low S': This run, characterized by high N O x and low CO, was designed to determine the effect of high temperature on V O C emissions. Case 2 Low V and high S': Because higher swirl should increase the recirculation zone size, this condition was selected to provide an indication of the effect of quenching on V O C formation. Case 3 High V and lowS': This case represents a high performance condition for the counter-swirl nozzle (Le., low N O x and high combustion efficiency). Hence, case 3 represents the potential of V O C release at an otherwise optimal operating condition. Case 4 High Vs and high S': Characterized by a larger recirculation zone and increased O2 levels, this condition was selected to reveal the combined effect of quenching and oxidation on V O C formation. Case 5 High V and high S' (Co-swirl nozzle): Similar to case 4, this test condition was chosen to help identify the combined effects of quenching, oxidation, and instability, exacerbated by poor overall efficiency, on V O C emissions. Fig. 3 shows a performance map of the burner over its stability limits for the co-swirl and counter-swirl injectors. The test conditions, accompanied by a photograph of the actual reaction, are identified on the map. Most of the test cases lie near the stability limits of the burner where there exists the possibility of "localized" flame-out resulting in unburned fuel emissions. 6 |
