Experimental and computational results which document mixing of passage flow and
leakage flow in a rotor stage of a high pressure turbine are presented. Of specific focus
are the effects of hub endwall contour geometries on mixing of the two flows and on film
cooling coverage by the leakage flow over the endwall. The understanding of fluid
physics in this area has received increased interest recently due to higher endwall heat
loads as a result of new combustor designs.
The setting is a linear, stationary cascade which represents many features of the
actual engine, such as geometry, Reynolds number, approach flow turbulence level and
scale, and leakage mass flow rates. Rotation, density gradient, and upstream airfoil row
effects are not represented. Two hub endwall geometries which give quite different
acceleration profiles in the airfoil row entry plane region are examined. The flow field in
the leakage flow delivery plenum, important to the mixing process, is characterized by
measurements and computation.
The effects of leakage flow injection on the passage aerodynamic losses are also measured and computed. The loss pattern at the passage exit shows the effects of
boundary layers on the pressure surface, the suction surface, and the two endwalls.
Passage secondary flow features, such as remnants of the passage, horseshoe, and corner
vortices are visible in the exit passage loss data. The effects of changes in leakage flow
injection rate on the losses are found to be minimal for the cases studied.
Measurements of adiabatic effectiveness on the contoured endwall show coverage
only over the upstream portion of the passage, with concentration on the suction side. The
effects of the horseshoe and corner vortices on mixing of the leakage and passage flows
are evident in the effectiveness pattern. Computed effectiveness distributions show
similar trends to those seen in the measurements; however, measured effectiveness values are generally lower than computed values, indicating the more rapid dissipation of
turbulent transport in the computations than in reality. Comparison of effectiveness
distributions shows that the contoured endwall geometry referred to as the “dolphin nose”
leads to better overall film cooling coverage on the endwall.
University of Minnesota M.S. thesis. April 2010. Major: Mechanical Engineering. Advisor: Terrence W. Simon. 1 computer file (PDF); xv, 163 pages, appendix A. Ill. (some col.)
Erickson, Ryan David.
Experimental investigation of disc cavity leakage flow and hub endwall contouring in a linear rotor cascade..
Retrieved from the University of Minnesota Digital Conservancy,
Content distributed via the University of Minnesota's Digital Conservancy may be subject to additional license and use restrictions applied by the depositor.