Complex Wake-Blade and Wake-Wake Interactions in a Multistage Turbomachine

 

Joseph Katz

Whiting School Mechanical Engineering Professor

Department of Mechanical Engineering

The johns Hopkins University

Baltimore, MD 21218

 

The flow structure and spatial distribution of turbulence around a rotor blade within a multistage axial turbomachines are inherently affected by interaction with wakes shed by upstream blades. Several associated phenomena are investigated experimentally by performing PIV measurements in a facility that has refractive index matched blades and fluid, which enables unobstructed view of the entire flow field. The presentation provides a few striking examples of wake-blade and wake-wake interactions, such as:

i.                     Substantial modifications to the turbulence with incoming wake due to exposure to the strain field generated by the blade, including effects of rapid straining, compression, wall blockage and highly inhomogeneous production.

ii.                   Periodic changes to the velocity profile and thickness of the blade boundary layer, which are caused by wake impingement.

iii.                  Shearing of the rotor wake by the non-uniform flow field, the resulting inhomogeneous turbulence production and formation of turbulent hot spots.

iv.                 Modifications to the flow near the tip of one blade due to impingement of a tip vortex generated by another blade in the same rotor.