Fan performance characteristic tests on axial flow fans provide information on the global flow field, based on stable inlet flow field distribution. More information is often required on the local flow distribution existing in the vicinity of the fan blades. A 1.543 m diameter scale model of an axial flow fan, termed the M-Fan is tested in an ISO 5801, type A, test facility. The M-fan was specifically designed for low-pressure, high flowrate application in air-cooled or hybrid condensers. As such, the scaled version of the fan is designed to have a fan static pressure rise of 116.7 Pa at a flow rate of 14.2 m³/s. Two specially constructed M-Fan blades with thirty-five pressure taps at five radial locations are manufactured to conduct blade surface pressure measurements on the fan blades at their operating point. The fan blades are equipped with 2 mm diameter tubes that run down the length of the fan blades in order to convey the measured pressure. Piezoresistive pressure transducers, located on the hub of the fan, measure the static pressure distribution on the blades and the data is transferred to a stationary computer using a wireless telemetry setup. Because of the centrifugal acceleration of the air in the measured tubes, provision has to be made for subtracting this effect from the measured data. The use of the blade pressure measurements set-up is qualified by testing and comparing to previous experimental results obtained on the B-fan. The experimental M-fan results are compared against a periodic numerical model of a fan blade modelled in an ISO 5801, type A test facility configuration, which was simulated using ANSYS^â^ Fluent. The simulations are performed at the designed flow rate of 14.2 m³/s. Due to adjustments that had to be made to accommodate the blade measurement set-up, the hub configuration modelled for the fan differed from the configuration used in the test facility. The experimental tests and numerical model correlate well with each other, although it was found that the pressure data is particularly sensitive to the selected operating point. The blade surface pressure measurements have a maximum root mean square error (RMSE) of 95.51 Pa (average 47.95 Pa, minimum 17.36 Pa) and minimum Pearson correlation of 0.941 (average 0.977). The experimental method used to measure the blade surface pressure is however shown to be reliable and accurate. This, together with the numerical model, can be used as an effective method to provide further understanding on local flow distribution existing in the vicinity of an axial flow fan.


Blade Surface Pressure Measurements on a Low Pressure Rise Axial Flow Fan

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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