The answer is C.) Install baffles (inter-pole baffles)
The selected solution was to install the inter-pole baffles as this addressed the root cause of the axial flow imbalance. The model indicated that the bottom fan was supplying all of the air, while the top fan was only maintaining the pressure (operation at shut-off pressure). As a result, nearly 75% of the total stator vent air flow was through the top half of the stator. The root cause of the flow imbalance was the low resistance to axial air flow through the inter-polar spaces. Installation of the inter-pole baffles increased the resistance to axial air flow and balanced the flow through the stator vents to within a few percent as predicted by the model, and then confirmed by measurement.
Options B.) and D.) were also presented to the customer as additional modifications that could be implemented with the pole baffle installation to increase the overall air flow through the stator vents. The customer elected to reduce the amount of the up-rate, and as a result the additional corrective actions were not required. Additionally, the performance was significantly improved through installation of the inter-pole baffles, further reducing the need for additional corrective action. One of the units has been operating for about 20 years with the new inter-polar baffles.
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