Measurement of Combustion Air to a Typical Cyclone Burner With a Common Wind Box and Pressure Loss Effects on the Cyclone Due to Inlet Configuration

To maintain proper fuel air ratio and minimize NOx during combustion, air and coal flow into a cyclone burner must be measured. Due to the large length to width ratio of the air inlet to some burners, often greater than 7, accurate measurement has proven to be difficult; in fact, measurement with a ratio greater than 2 to 1 has proven to be difficult. A typical cyclone burner system was analyzed with a premium CFD modeling package, with particular attention being given to the location which would be considered “worst case”. If this location can be measured accurately, then we can assume that the less stringent locations will also be measured accurately. Additionally, a “best case” was also analyzed to compare pressure loss due to the measurement. The worst case location was chosen based on a cross flow condition of the air just going around the corner at the entrance, where the flow velocity is the highest. See Figure A. The “best case” condition was chosen as the air flow entering the inlet normal to the plane of the inlet, although this condition may not actually exist in the example wind box chosen. Three inlet configurations were analyzed, (1) three optimally designed Oval High Betas across the inlet, (2) two optimally designed Oval High Betas across the inlet and (3) the flow distribution across the inlet as is, with no method to break up the large length to width ratio. Of particular interest, once the analysis for both the “worst case” and “best case” were done for the three inlet configurations, one configuration, proved best for both measurement and pressure loss—condition (1), the three optimally designed Oval High Betas.