An experimental investigation of a large scale engine cooling fan with an aerodynamic shroud has been conducted to assess the effectiveness of this active flow control technique. The experimental study was motivated by the desire to increase the performance and efficiency of this axial fan which is intended for use in an off highway application. The aerodynamic shroud utilizes a Coanda jet that is: (i) delivered from a pressurized plenum, and (ii) introduced along the surface of the shroud upstream of the fan inlet. This annular jet delivers high momentum fluid into the blade tip clearance region.; Experimental data were acquired to quantify the effect of the aerodynamic shroud. Integral quantities including pressure rise, flow rate, and input power were measured for a reference baseline condition and for several powered shroud conditions. The results show that the inception of fan stall is delayed to a lower flow rate (higher pressure rise) as compared to the baseline condition. Further insight into the effect of the aerodynamic shroud is provided by detailed velocity measurements in the wake of the fan. Specifically, a double-X hot-wire probe was used to resolve three components of velocity at a single axial location and various radial locations. The phase averaged data show that the aerodynamic shroud affects the "tip vortex" and the velocity field at the measurement location. Time averaged and phase averaged in-plane PIV measurements support these data.
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