Material selection compressor rotor

Selection of construction materials for rotors and casings is more limited than for centrifugal compressors. 

Cast iron is the standard material used to construct the cylindrical housing, but other materials may be used if corrosive conditions exist. The rotor is usually a continuous piece of steel that includes the shaft and is made from bar stock. Special materials can be selected for corrosive applications. Occasionally, the rotor may be a separate iron casting keyed to a shaft. On most standard air compressors, the rotor-shaft seals are semi-metallic packing in... 

As the observed power deficit had been explained to a very large extent, several measures were identified to enable its reduction. One measure would be to optimize the flow conditions for the inflow and outflow areas of the compressor and turbine sections in order to minimize the pressure drop losses and to achieve an optimum inflow into the blading. Moreover, a reduction of the blade gap losses would be required. That could be achieved by a reduction in rotor vibration and better selection of materials. The materials for both the rotor and the stationary blade carrier should be selected to optimize thermal expansions to achieve minimum gaps at operating conditions. One approach would be the replacement of the non-cooled austenitic stationary blade carrier in favor of a ferritic one, with cooling provided at necessary locations. Preferably no cooling at 750 C should be provided at all, taking into account possible improvements in avaible blade and rotor materials. A third approach that seems to be possible would be a further optimization of the stationary blade profiles and rotor blade profiles. 

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