Method for modifying a multistage compressor

1. A method for increasing the absorption capacity in a multistage compressor, the compressor comprising rotor blades of a first compressor rotor blade row with a defined blade leaf profile, the rotor blades having a fixed blade angle in a flow direction, and blades of at least one further blade row arranged downstream of a second compressor stage having a defined blade leaf profile and, in the flow direction, a fixed blade angle, substantially identical to the blade angle of the first compressor rotor blade row, the compressor rotor blade row and at the least one further blade row arranged downstream of the second stage, are exchanged with different blade rows that include unchanged blade leaf profiles, and operate with a different blade angle, as compared with the fixed blade angles, and the blade angles of the at least one further blade row are selected as a function of the blade angle, modified for a greater absorption capacity, of the first compressor rotor blade row.

2. The method as claimed in claim 1 , wherein the blade geometry of the guide blade row of the first compressor stage is maintained unchanged.

3. The method as claimed in claim 1 , wherein the rotor blades of the second compressor rotor blade row are exchanged for modified rotor blades which have an identical blade leaf profile to the original rotor blades and the blade angle of which is different from the blade angle of the original rotor blades.

4. The method as claimed in claim 3 , wherein the blade geometry of the guide blade row of the second compressor stage is maintained unchanged.

5. The method as claimed in claim 1 , wherein the further blade row is a rotor blade row.

6. The method as claimed in claim 1 , wherein the further blade row is a guide blade row.

7. The method as claimed in claim 1 , wherein, in at least one compressor stage arranged downstream of the second compressor stage, both the blades of the rotor blade row and the blades of the guide blade row are exchanged for modified blades which have an identical blade leaf profile to the original blades and the blade angle of which is different from that of the original blades.

8. The method as claimed in claim 1 , wherein the blades of at least one of the blade rows of each compressor stage arranged downstream of the second compressor stage are exchanged for modified blades which have an identical blade leaf profile to the original blades and the blade angle of which is different from that of the original blades.

9. The method as claimed in claim 1 , wherein the blade angles in the blade rows, the blades of which are exchanged for modified blades, are coordinated with one another in such a way that a relative enthalpy build-up in the individual compressor stages is kept essentially constant.

10. The method as claimed in claim 1 , wherein the blade angle of the modified blades is greater than the blade angle of the original blades, in such a way that chords of the blade leaf profiles of the modified blades are oriented to a greater extent in a direction of the compressor axis as a function of the increased mass flow.

11. The method as claimed in claim 1 , wherein the compressor mass flow is increased.

12. A multistage compressor comprising, rotor blades of a first compressor rotor blade row with a defined blade leaf profile, the rotor blades having a fixed blade angle in a flow direction, and blades of at least one further blade row arranged downstream of a second compressor stage having a defined blade leaf profile and, in the flow direction, a fixed blade angle, substantially identical to the blade angle of the first compressor rotor blade row, the compressor rotor blade row and the at least one further blade row, arranged downstream of the second stage, wherein replacement blade rows include unchanged blade leaf profiles, and operate with a different blade angle, as compared with the fixed blade angles, and the blade angles of the at least one further blade row are selected as a function of the blade angle, modified for a greater absorption capacity, of the first compressor rotor blade row.

13. The compressor as claimed in claim 12 , comprising at least three axial compressor stages.

14. The compressor as claimed in claim 13 , wherein the compressor is a purely axial multistage compressor.

15. A gas turbo group, comprising a compressor as claimed in claim 12 .

16. A device for increasing an absorption capacity in a multistage compressor, the compressor comprising rotor blades of a first compressor rotor blade row with a defined blade leaf profile, the rotor blades having a fixed blade angle in the flow direction, and blades of at least one further blade row arranged downstream of a second compressor stage having a defined blade leaf profile and, in the flow direction, a fixed blade angle, substantially identical to the blade angle of the first compressor rotor blade row, the compressor rotor blade row and the at least one further blade row are arranged downstream of the second compressor stage, the device comprising replacement blade rows for the first compressor rotor blade row and the at least one further blade row, the replacement blade rows have replacement blades with unchanged blade leaf profiles and a different blade angle, as compared with the fixed blade angles, and the blade angles of the replacement blades of the at least one further blade row are selected as a function of the blade angle, modified for a greater absorption capacity, of the replacement blades of the first compressor rotor blade row.