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The difference between axial and radial turbines consists in the way the fluid flows through the components (compressor and turbine). Whereas for an axial turbine the rotor is 'impacted' by the fluid flow, for a radial turbine, the flow is smoothly oriented perpendicular to the rotation axis, and it drives the turbine in the same way water ...
An axial turbine has a similar construction as an axial compressor, but it operates in the reverse, converting flow of the fluid into rotating mechanical energy. A set of static guide vanes or nozzle vanes accelerates and adds swirl to the fluid and directs it to the next row of turbine blades mounted on a turbine rotor.
Radial flow turbines are mechanically robust compared to axial turbines and they are easy to configure. As a result of that they were considered for the application before axial turbine. They are more tolerant of overspeed and temporary temperature extremes. Radial flow turbines have higher energy extraction capability in one single stage.
The radial component of the fluid velocity is negligible. Since there is no change in the direction of the fluid, several axial stages can be used to increase power output. A Kaplan turbine is an example of an axial flow turbine. In the figure: U = Blade velocity, V f = Flow velocity, V = Absolute velocity, V r = Relative velocity,
From an energy exchange point of view axial compressors are reversed turbines. Steam-turbine designer Charles Algernon Parsons, for example, recognized that a turbine which produced work by virtue of a fluid's static pressure (i.e. a reaction turbine) could have its action reversed to act as an air compressor, calling it a turbo compressor or pump.
V f = flow velocity (axial component in case of axial machines, radial component in case of radial machines). The following angles are encountered during the analysis: α = absolute angle is an angle made by V with the plane of the machine (usually the nozzle angle or the guide blade angle) i.e. angle made by absolute velocity V and the ...
Axial momentum theory demonstrates how the wind turbine imparts an influence on the wind which in-turn decelerates the flow and limits the maximum power. For more details see Betz's law . Since this effect is the same for both lift and drag-based machines it can be ignored for comparison purposes.
Turbines are sometimes differentiated on the basis of the type of inlet flow, whether the inlet velocity is in axial direction, radial direction or a combination of both. . The Francis turbine is a mixed hydraulic turbine (the inlet velocity has Radial and tangential components) while the Kaplan turbine is an axial hydraulic turbine (the inlet velocity has only axial velocity componen