Axial fan configurations, with three-to-nine controlled diffusion (CD) blades, have been examined using experimental methods. The initial measurements: pressure rise/flow rate, revealed distinct and opposite patterns: discontinuous pressure "jumps" for the 3-4 and 6-9 blade fans. The three, five and nine blade fans were selected for detailed examination using: i) time-mean surface pressure data from which the net lift force could be obtained and ii) X array hot-wire data (stationary probe) in the near wakes of the rotating blades. These data were processed to provide ensemble statistics. These data, plus the input shaft power were interpreted using the First Law of Thermodynamics in its control volume form. The results indicate that increasing the number of blades installed on the fan suppresses turbulent fluctuations in the wake of the fan. Additionally, similar phenomena in the flow field are observed at lower flow coefficient as the number of blades on the fan is increased.
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