DID YOU KNOW? DTIC has over 3.5 million final reports on DoD funded research, development, test, and evaluation activities available to our registered users. Click HERE
to register or log in.
A Visualization Study of Secondary Flows in Cascades
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION HAMPTON VA LANGLEY RESEARCH CENTER
Pagination or Media Count:
Flow-visualization techniques are employed to ascertain the stream-line patterns of the nonpotential, secondary flows in the boundary layers of cascades, thereby providing a basis for more extended analyses in turbomachines. The three-dimensional deflection of the end-wall boundary layer results in the formation of a vortex well up in each cascade passage. The size and tightness of the vortex generated depend upon the main flow turning in the cascade passage. Once formed, a vortex resists turning in subsequent blade rows. This results in unfavorable angles of attack and possible flow disturbances on the pressure surfaces of subsequent blade rows when the vortices impinge on these surfaces. Two major tip-clearance effects are observed the formation of a tip-clearance vortex, and the scraping effect of a blade with relative motion past the wall boundary layer. The flow patterns indicate methods for improving the blade-tip loading characteristics of compressors and of low- and high-speed turbines.
APPROVED FOR PUBLIC RELEASE