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Although the primary purpose of ASHRAE research project 1010 was to investigate the effects of inlet disturbances on the air and sound performance of axial fans, two interesting phenomena were revealed in the narrow band (1/24th octave) acoustic data for undisturbed inlets. These phenomena are discussed in this paper. The influence of operating point on the shape of the acoustic spectrum, especially on the tonality, is discussed. The second interesting phenomenon is the vortex shedding, which occurs for most of the fans tested. This behavior is analyzed and explained. [ABSTRACT FROM AUTHOR]

This experimental study determined the degradation in performance of large axial fans caused by close inlet walls. Three fans with hub to tip ratios of 0.39, 0.49. and 0.74 were each tested at four blade angles and over the flow rate range of wide open to near shutoff The closest walls, 0.5D front clearance and OD side clearance, caused only modest loss in flow rate, up to 3²%. and less than a 5% loss of efficiency in the 0.49 H/T fan. The other two fans had only minor decreases in flow rate and in efficiency for the closest walls. No significant losses were found for any of the test fans when tested with clearances larger than the minimum. [ABSTRACT FROM AUTHOR]

The air performance effects expected due to inlet velocity distortion for axial fans is predicted based on basic airfoil data. This expectation is compared with the test data gathered in RP-1010. Sound data for various inlet configurations are also presented to help understand the test data. [ABSTRACT FROM AUTHOR]