An analysis of the flow across an annular cascade of axial-flow inlet guide vanes was conducted in order to evaluate the role of sec¬ondary flows in causing discrepancies between design and observed velocity diagrams. A qualitative discussion of the general nature of -the secondary flows within the passages of stationary annular cas¬cades with radial design variations of circulation is presented for both the end-wall boundary-layer regions and the central potential-flow regions of the blade passage. Deviations from ideal mean outlet flows (as determined on the basis of blade-element performance) were shown to exist in the potential-flow region of the vanes because of conditions imposed by the end-wall boundaries, the displacement of the wall boundary-layer surfaces, and the irrotationality requirement. As a consequence of the existence of nonuniform radial flows across the blade spacing in the actual flow through cascades, it may not generally be possible to obtain any arbitrarily specified design variation of turning angle along the radial height of a blade row.nQuantitative evaluations of the variation of the actual mean flow leaving a row of inlet guide vanes were obtained by the method of singularities in which a distribution of vorticity directly proportional to the ideal circulation variation of the design was superimposed on the ideal blade-element flow. Induced turning-angle deflections were calculated from the induced velocities of the superimposed vortex system. With the use of an empirically determined correlation factor, good agreement was obtained between calculated and experimental radial variations of turning angle for several conventional inlet guide vanes for which accurate "blade-element turning-angle design data were avail¬able.
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