Turbomachinery

A turbomachine is a fluid energy machine in which the energy transfer between the fluid and machine is in an open space by a flow according to the laws of fluid dynamics through the detour of the kinetic energy.

Operation and demarcation

The energy transmission takes place usually by means of rotor blades, vanes or blades which are profiled in such a way that the flow around the pressure difference between front and back is formed ( airfoil ).

The counterpart of the turbomachine is the displacement takes place (also piston engine ), in which the energy transfer in a ( similar by valves ) closed space of variable volume according to the laws of fluid statics.

The applications of flow and displacement machines differ mainly by the fact that at high flow rates usually outweigh the advantages of flow machines, in which the small displacement machines.

The effect of flow machines is linked to the flow rate of the fluid; when the engine is running too slow, no energy transfer takes place, and since the fluid is not included, it escapes from the machine. In an ideal displacement (see below ), however, the fluid is to be included; it can not escape, and the energy transfer can be carried out theoretically infinitely slowly, without the action of the machine is reduced.

An often incorrectly called defining criterion for flow machines is a rotating motion or a stationary, non -timed process. But this is not always true; There are also rotating and continuously operating positive displacement ( rotary machines such as Roots blower, etc.) and there are also translationally oscillating flow machines ( Hubflügelmaschinen, Fan Machine, etc. - derived from wings and fins from the animal world ).

A special form of flow machines are those which no housing for the steering of the fluid need as the propeller of domestic fans, aircraft engines and propellers, rotors of wind turbines or agitators.

Classification of turbomachines in species and groups

Fluid machines are classified into the following types and groups according to the type of the fluid, the energy flow direction and the structure:

Note: Colloquially, a " fan " called electrical appliances are to be found in the table above as a propeller, because ( as a protection against injury ) have no case other than a grid. Stand or tower fans but are centrifugal fans with housing and therefore can also be found in the table as fans.

Dimensionless parameters for describing of turbomachines

The following dimensionless parameters are often used for the characterization of flow machines. They allow a comparison of flow machines in different dimensions and boundary conditions.

• Diameter number δ
• Print number ψ
• Flow coefficient φ (including delivery or volume number called )
• COP λ
• Run number σ

Diameter number

The diameter number is calculated as follows: