Simultaneous measurement of air flow conditions and resultant blade and gearbox loading at large-scale cooling system fans

[摘要] ENGLISH ABSTRACT: Axial flow fans used in large-scale air-cooled steam condensers (ACSCs) may operateunder distorted inflow conditions. These conditions occur due to the prevailing windconditions, the presence of buildings, and the location of the fan within the ACSC. Fanslocated on the periphery of the ACSC are affected the most due to their exposure tostrong winds and the inner fans drawing in air past them. Distorted inflow conditionscause varying fan blade and gearbox loading conditions.The purpose of the investigation was to simultaneously measure the inlet air flowand the resultant blade and gearbox loading conditions of a single fan located on theperiphery of a large-scale ACSC. Inlet and heat exchanger bundle outlet air flow velocitieswere measured using a combination of ultrasonic and propeller anemometers whileblade loading was measured with strain gauges attached at the neck of the specific bladebeing monitored. Strain gauges were also attached to the low-speed fan shaft to measuregearbox loading.Measurements were recorded over a period of 8 days where it was found that increasedwind resulted in increased air flow in the axial direction of the fan, which thencaused a reduction in average blade loading. This was due to a decreased static pressurerise over the fan. The fan blade was found to vibrate at its own natural frequency of6 Hz when excited by the variable aerodynamic loading. The aerodynamic loading wasextracted from the measured data and was found to correlate well with previous experimentalwork performed by Bredell et al. (2006a). Shaft bending stresses and torque werefound to oscillate at the fan's rotational frequency of 2Hz with a large torque exerted onthe shaft during fan start-up.

[发布机构] Stellenbosch University