Flows Through Axial Compressor - Turbomachinery Aerodynamics - Lecture Slides, Slides of Turbomachinery

Download Flows Through Axial Compressor - Turbomachinery Aerodynamics - Lecture Slides and more Slides Turbomachinery in PDF only on Docsity!

1

3-D Flows in Blade Passages of Axial Flow Compressors

3-D Flows through axial compressor

• Axial flow acquires rotational component on entering the blades
• Axial compressors blades are normally highly twisted
• Airfoils used may significantly vary in camber and stagger settings from hub to tip
• Solidity and spacing between the airfoils vary from root to tip
• As a result of the above, Cp distributions on the blade surfaces vary from root to tip

3-D blade shapes

Top View

Fabricated Blades

The flow, in passing through the curved, twisted blades, develop asymetric boundary layers on its bounding surface, which promote strong passage vortex development

In certain blade shapes the flow, in passing through the blades, develop two passage vortices

Boundary layer development at casing and hub (due to adverse pressure gradient of main flow) further contributes to 3-D flow development

End-wall Boundary layer development

• Tip cross flow is opposite in motion to the rotation of the rotor blades
• Blade tip scrubs through casing boundary layer

Scrubbing

• Flow entering the stages downstream of the first stage becomes more and more non-axial
• Boundary layers are developed at the two ends of the blades – casing and hub ends
• The growing end wall boundary layers also act as “blockage” and reduces the main flow rate

Flow across blade tip

3-D Flow development in rotor blades

3-D Flow development in rotor blades

Next Class -----

3-D Flow Analysis – Simple Radial Equilibrium theory