The Wind Tunnel used in these investigations has a four-blade linear cascade test section as shown above. Flow enters the test section from the contraction at the left. Ahead of the blade section are sections for adding turbulence generating devices to generate high free stream turbulence as found in real turbine systems.
The flow that passes through the test blades exits into the room air. For this test section, we use tailboards and bleeds to adjust the flow through the blade passages. By moving the tailboards and bleeds we can "balance" the flow in each of the three blade passages. Our measurements are made in the central passage (ie. on the convex side of Blade 2 and the concave side of Blade 3).
When we do mass transfer tests, a naphthalene-coated blade replaces Blade 2 or 3, depending on which side we are measureing. During a run, only a few mils of the naphthalene surface will sublime away, which means that the blade shape does not change enough to affect the flow situation.