|Fig. 3-11 Methods of securing blades to disc.|
|Fig. 3-10 Rotors of drum and disc|
24. In compressor designs (fig. 3-10) the rotational speed is such that a disc is required to support the centrifugal blade load. Where a number of discs are fitted onto one shaft they may be coupled and secured together by a mechanical fixing but generally the discs are assembled and welded together, close to their periphery, thus forming an integral drum.
25. Typical methods of securing rotor blades to the disc are shown in fig. 3-11, fixing may be circumferential or axial to suit special requirements of the stage. In general the aim is to design a securing feature that imparts the lightest possible load on the supporting disc thus minimizing disc weight. Whilst most compressor designs have separate blades for manufacturing and maintainability requirements, it becomes more difficult on the smallest engines to design a practical fixing. However this may be overcome by producing blades integral with the disc; the so called ’blisk’.