Post on 21-Dec-2015
Secondary Flows in Turbine Cascades & Consequences
P M V SubbaraoProfessor
Mechanical Engineering Department
Finite Length of Blade Generates more Physical Boundaries and vorticity.……
Parts of A Current Turbine Rotor
Losses Contributed by EndWalls
More Geometrical Features of A Turbine Blade
Modular Concept of Blade Design & Construction
The Profile of A 3D Blade
• A 3D blade works along with its endwalls.
• Endwall flows originate from specifically developing endwall boundary layers.
• These are associated with the presence of longitudinal vortices with a dominant streamwise component of the vorticity.
• These are generally known as and secondary flows.
• They are driven by transverse static pressure gradients and mass forces acting on fluid elements in curvilinear motion through the blade-to-blade passage.
Understanding the complex development of endwall flows is a part of betterment of blade profile !!!
Impact of Endwall Flows
• Endwall flows are also an important source of losses in turbines.
• More serious impact on cascades with short-height blading and high flow turning.
• Due to the complex nature of endwall boundary layer flows/secondary flows, the evaluation of endwall losses is not an easy task.