  Tubercles are modifications to the leading edge of an airfoil in the form of
blunt wave-like serrations. Several studies on the effect of tubercles on
isolated airfoils have shown a beneficial effect in the post-stall regime, as
reduced drag and increased lift, leading to a delay of stall. The prospect of
delaying stall is particularly attractive to designers of axial compressors in
gas turbines, as this leads to designs with higher loading and therefore higher
pressure rise with fewer number of stages. In the present study, experiments
were performed on a cascade of airfoils with NACA 65209 profile with different
tubercle geometries. The measurements were made over an exit plane using a
five-hole probe to compare the cascade performance parameters. Additionally,
hot-wire measurements were taken near the blade surface to understand the
nature of the flow in the region close to the tubercles. Oil-flow visualization
on the cascade end wall reveal the flow through the passage of blades with and
without tubercles. For the cascade considered, the estimated stall angle for
the best performing set of blades is found to increase up to 8.6{\deg} from
that of the unmodified blade of 6.0{\deg}. Application of such structures in
axial compressor blades may well lead to suppression of stall in axial
compressors and extend the operating range.
