Simultaneous Measurement of Air Flow and Blade Loading Conditions in an Air-Cooled Steam Condenser Fan

B2 - HVAC and Condenser Fans

Axial flow fans used in large-scale air-cooled steam condensers (ACSCs) may operate under distorted inflow conditions. These conditions occur due to the prevailing wind conditions, the presence of buildings, and the location of the fan in the ACSC. Fans located on the periphery of the ACSC are affected the most due to their exposure to strong winds and the inner fans drawing in air past them. The distorted inflow causes cyclic blade loading conditions.

The purpose of the investigation is to simultaneously measure the inlet flow and the blade loading conditions of a single fan located on the periphery of a large-scale ACSC. The measurements were taken in real-time in order to compare any air flow variations with structural loads experienced by the fan system.

To measure the inlet flow a combination of ultrasonic and propeller anemometers along with thermocouples were used. One of each sensor was attached to six separate frames which were placed on the safety grid at the fan inlet. The anemometers were used to create a three-dimensional velocity vector for the air flow while the thermocouples measured the air temperature. These inlet flow measurements were coupled to measurements taken from eight propeller anemometers attached at the outlets of the heat exchanger bundles.

Blade loading was measured with strain gauges attached at the neck of the blade being monitored. Two sets of strain gauges were used to measure the bending in the flap-wise direction and the direction of rotation while another set was used to measure the torsion at the neck of the blade. The strain gauge data was transmitted to a base station which was synchronized with the flow measurements. Strain gauges were also attached to the fan's driveshaft to determine the load being transferred to the gearbox. These strain gauges also measured bending in two directions as well as torsion and were attached to the same wireless bridge amplifier.

To simplify the data capturing system all signals were converted to standard analogue voltages or currents. This simplification enabled the use of data capturing hardware with a large amount of channels, which in turn enabled easy synchronization of the multitude of sensor signals.

When installed, the system sufficiently captured data from the array of sensors and was able to perform autonomously for several hours at a time. During testing the ambient conditions were recorded using a weather mast located in the vicinity of the ACSC.