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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.
Mixed flow turbomachines – When axial and radial flow are both present and neither is negligible, the device is termed a mixed flow turbomachine. [9] It combines flow and force components of both radial and axial types. A Francis turbine is an example of a mixed-flow turbine.
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.
In the axial compressor the air flows parallel to the axis of rotation. Axial compressors are made to be multi-staged. A stage consists of a row of rotating blades called the rotor, which are connected to the central shaft and a row of stationary or fixed blades called stator. In axial flow compressor, the air flows from stage to stage.
These understandings apply to all dynamic, continuous-flow, axisymmetric pumps, fans, blowers, and compressors in axial, mixed-flow and radial/centrifugal configurations. This relationship is the reason advances in turbines and axial compressors often find their way into other turbomachinery including centrifugal compressors.
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.
As stated above, some of the air is deflected away from the turbine. This causes the air passing through the rotor plane to have a smaller velocity than the free stream velocity. The ratio of this reduction to that of the air velocity far away from the wind turbine is called the axial induction factor. It is defined as where a is the axial ...