Scale model testing of JEA Northside Units 1 and 2 primary air distribution system and windbox

Primary air flow is supplied to the windbox of a 300 MW Circulating Fluidized-Bed (CFB) boiler by means of three primary air ducts connected to a common plenum. A flow rate measurement is performed in each duct using an Annubar flow meter. Due to the tight configuration of the piping and the associated turbulence, the measured flows in the three ducts were not consistent, resulting in improper air flow distribution in the boiler. A primary air duct flow study was performed in an effort to improve measurement accuracy, which will lead to improved combustion efficiency and low load cycling by allowing precision air flow control in the furnace.;One objective of this project was to employ a 1/10 scale model test to determine the best method to improve the flow upstream of each Annubar flow meter. Flow visualization and measurements using a five-hole directional velocity probe were performed. It was determined that mounting 50% open area screens in the primary air duct of the scale model had the effect of significantly reducing both yaw and pitch angles across the Annubar measurement plane and notably flattened the velocity profiles in the flow direction.;This project also employed a 1/10 scale model test of the windbox to verify computational fluid dynamics (CFD) predictions which were used to determine the type of diffuser plate to be placed in the CFB boiler for optimal uniformity in air distribution. Detailed local velocity measurements on the model were performed using a TSI AVM430 Velometer air velocity meter. Although these results did not closely match the corresponding CFD results due to various reasons, flow uniformity trends duplicated those predicted using CFD analysis. Uniformity was deemed independent of Reynolds number in both experimental and CFD results lending credence to the CFD predictions.