The blades is called the set of blades of a compressor and a turbine. A distinction is made between rotor and stator blades. A ring of moving blades with the associated ring of guide blades is called a stage. The blades of the turbine or compressor can be multi-level.

The guide vanes are incorporated in the housing of the compressor or the turbine and directing the working fluid at an optimum angle to the blades, located on the rotatable shafts. About the blades is the coupling of the mechanical usable performance between machine and fluid instead of ( iA turbines drive a connected machine to work, usually a generator, a compressor is driven by a motor iA ).

When specifying the number of stages of a compressor or a turbine rotor blade rings the number of instructions: A five-stage compressor has five rotor blade rings. The guide vane compressors are in most cases associated with the preceding blade ring in turbines usually the subsequent moving blade ring.

## Fluid Mechanics

In the guide vanes depending on the level of unreacted enthalpy is implemented either in whole or in part in flow energy. In the impellers, the flow energy is converted by the deflection in a circumferential force. Generally less steps are required as for the construction of the same slope in a compressor for the degradation of enthalpy in a turbine. This is connected with that the accelerated flow of a turbine is much less danger of a stall than the delayed stream in a compressor.

The ratio of sales in the blades of a turbine stage into flow energy enthalpy to the total enthalpy of a turbine stage is called the degree of reaction. Usually, in reaction turbines, a reaction rate of 0.5 is realized. In constant-pressure turbines is the reaction degree 0; the total enthalpy is reacted in one stage in the guide vane flow energy, the pressure in the rotor blades of the speed remains constant.

The rotor blades of a turbine are exposed to particular stresses. Critical is especially high operating temperatures, in combination with the tensile stresses in the radial direction. These stresses cause in the long run the so-called creep of the blades. The blades in the course of their lives are getting longer. It can touch the outer cage of the turbine, causing the turbine is blocked in the worst case the shovel. Critical are also vibration stress: The blade falls into the " flutter". This can lead to material fatigue.

The high loads make highly resilient materials required. The materials of the blades presently limit the efficiency of the turbine, since they allow only a limited operating temperature. High operating temperatures have a positive effect on the Carnot efficiency.

## Materials

Turbine blades are made of titanium alloys, nickel superalloy or tungsten -molybdenum alloys. The blades are as erosion such as pitting, also known as " pitting corrosion ", protected for higher resistance to temperatures by coatings. The coating on the heat shield is called thermal barrier coating or TBC shortly. Further measures to make the blades more resistant to heat, exist in sophisticated cooling channel systems. This technique is applied in both the conductivity and in the blades.

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