Out-flow radial turbine

Radial means that the fluid is flowing in radial direction that is either from inward to outward or from outward to inward, with respect to the runner shaft axis. If the fluid is flowing from inward to outward then it is called outflow radial turbine.

Most practical radial outflow turbines are Reaction-type turbines, whereas the converse, radial inflow turbines can be either reaction type, impulse type (in the case of a typical turbo-supercharger), or intermediate (in the case of Francis turbines for example.)
 * 1) In this turbine, the working fluid enters around the axis of the wheel and then flows outwards (i.e., towards the outer periphery of the wheel).
 * 2) The guide vane mechanism is typically surrounded by the runner/turbine.
 * 3) In this turbine, the inner diameter of the runner is the inlet and outer diameter is an outlet.

Components of Out-flow Turbine
The Main Components of Reaction Turbine are :


 * Casing/ Involute: Typically the Runner shaft bearings, rotating seals, guide vane assembly and inlet tube are mounted to the casing
 * Guide Vanes: In liquid turbines these are also sometimes referred to as Wicket gates. These convert some of the pressure energy into momentum energy, but their main functions are to control the flow rate and impart an average tangential velocity on the fluid greater than or equal to the tangential velocity of the runner inlets. In an OFRT these are typically mounted concentrically, within in the same plane as the turbine. However the guide vanes can also be designed in an axial or diagonal/mixed configuration.
 * Runner/Turbine: The passage between the blades has a converging-diverging profile. The majority of the head loss or pressure drop occurs as the working fluid passes through the turbine in radial outflow design. The runner is connected to the shaft which rotates along with it and thus this can be used for power production. Depending on the design, the flow through the turbine may be strictly planar, or it may enter the turbine axially and undergo a 90° turn therein.
 * Draft Tube: It is connected to outlet of the turbine which assists fluid exiting the spiral casing. It is used because the exit pressure may becomes less than the stagnation pressure within the tail race and thus it may become difficult for the fluid to proceed downstream causing choked-flow. To make it exit from the tail race/involute it's necessary to provide diverging cross section so that the pressure can increase while the linear velocity greatly decreases.

Advantages
Some of the advantages of radial outflow turbine are:

Radial flow turbines are generally more preferred in small turbines because of simpler construction. Radial flow turbine rotor does not use aerofoil sections, as a result of which the rotor of radial flow turbine has a shape very similar to a centrifugal compressor and it uses 3D shape for energy extraction. They are more conducive to being produced from a single casting or round billet as a Bladed-disk or "blisk."
 * The configuration of radial flow turbine is simple, similar to a centrifugal compressor.
 * 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.
 * Because the high pressure side is near the rotational axis (at low radius), it is possible to keep leakage losses lower than with other reaction turbines (Ljungström, axial or in-flow radial). This is more important in small turbines where complex rotating seal systems aren't cost effective.