| Coal is playing the dominant role in our national industry because of the current development status of China and will continue to influence the national economy in a strategic position. Since the air pollution especially the NOx emission caused by coal-burning power plants becomes increasingly prominent, the clean coal-fired generation is of great urgency. The most effective methods in China to realize the in-combustion control is developing high efficient and low NOx burner.In this paper, reaction mechanism and control methods of NOx were described with examples of typical low NOx burner, and HT-NR3 low NOx swirling burner was chosen as study object. The cold-flow experiment was carried out on reduced model of HT-NR3 burner within the ratio of 1:4 according to similarity theory. This burner include 3 different air ducts, which are straight primary air duct, straight internal secondary air duct and swirling outer secondary air duct. Under 11 operational conditions on different wind speed and swirling intensity, experiments were carried out to study their influence on aerodynamic fields. Further more, numerical simulations were conducted based on refined grids in GAMBIT to eliminate false diffusionBoth experiment and numerical simulation results indicate that when the primary air speed decreases, it had obviously enlarged the back-flow areas; the impact was minor by changing the internal secondary air speed; outer secondary air had the most effects on back-flow area. When the the speed of outer secondary air changed from big to small and finally to no swirl at all, the back-flow area show the decreasing trend accordingly. The range of primary air was shortened by enhancing the swirling intensity and back-flow area was affected. |
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