Abstract:
Cascade tests have been made to obtain information on the related questions of whether simpler sections than the normal aerofoil C4 can be used without loss o~ efficiency, and whether a particular section should be constructed on a circular-arc or a parabolic-arc camber-line. Of the large possible number of simple shapes, three only were chosen for comparison with the aerofoil. They were a flat plate with rounded leading and trailing edges, a flat plate with sharpened leading and trailing edges, and an approximately biconvex shape. A representative cascade shape was chosen (blade inlet angle 55 deg, outlet angle 30 deg, and pitch/chord ratio 0.75) and four cascades with the four sections mentioned above mounted on circular-arc camber-lines were made up. In addition, to provide data on the relative advantage of circular-arc and parabolic-arc camber-line, two cascades were made up on parabolic-arcs. The main conclusions to be drawn are that the approximately biconvex profile, which is a very simple shape to make, is superior to the aerofoil at Mach numbers above 0.75, and that the circular-arc camber-line is on the whole superior to the parabolic-arc. The 'plate' blades with blunt leading and trailing edges are poor in performance, but the 'plate with sharpened edges' is reasonably good. It is suggested that very thin blades of the 'plate' type may have certain applications.
