Secondary Flow in Axial-Flow Turbomachinery

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Abstract
A method is presented by which one can include the principal effects of secondary flow in the design of multi-stage axial-flow turbomachinery. The method uses the conventional axial-symmetry solution as a basic flow picture from which the induced turning and radial velocities characteristic to the secondary flow can be deduced. Frictional effects, such as the growth of boundary layers on the blades, are excluded from the analysis, but the disposition of the fluid which comes from boundary layers on the hub and casing surfaces upstream of a blade row can be accounted for in an approximate manner by assuming that the fluid is frictionless while in the blading. To get a first-order approximation of the secondary flow in a blade row, it is necessary to know only the number of blades in the row and the axisymmetric-flow solution. The principal assumption involved in this approximation is that the distortion of the flow surfaces due to the secondary velocities is small. The method is sufficiently accurate for predicting the secondary flows which occur as a result of nonuniform blade loading, but solutions for boundary-layer flows must be considered only qualitative because of the large flow-surface distortions which are associated with these flows.

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