03-05: Vibration Control: New Fan Blade Tip Reduces Pulsation

This paper describes the test method and test results of a research project into the effect of tip speed and blade angle of the cooling tower fan on the pulsation forces exercised on the fan stack. Pulsation on the fan ring is directly caused by the movement of the cooling tower fan, and occurs at blade passing frequency. The pulsation force is a combination of the aerodynamically generated pressure difference between the upstream and downstream side of the fan blade and the velocity (under) pressure generated by the surface of the blade tip. The extent of this effect has been confirmed by extensive measurements.