off line is already arranged as shown in the figure however the blow off line 13 may also be readily arranged at a point of the compressor at which no blow off line was arranged previously furthermore the blow off line 13 may adjoin an opening already existing but previously closed by a flange cover of the casing of the compressor 1 but if need be a new opening may also have been incorporated in the casing the new blow off line 13 then adjoining this new opening in addition a further blow off line 14 with a blow off valve 24 adjoins downstream of the compressor 1 and upstream of the combustion chamber 2 by blow off at this point the overall pressure ratio of the compressor is reduced which further reduces the risk of separation due to this modification a substantially larger mass flow overall can be passed through the blow off lines 11 12 13 and 14 while the invention has been described in detail with reference to exemplary embodiments thereof it will be apparent to one skilled in the art that various changes can be made and equivalents employed without departing from the scope of the invention the foregoing description of the preferred embodiments of the invention has been presented for purposes of illustration and description it is not intended to be exhaustive or to limit the invention to the precise form disclosed and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention the embodiments were chosen and described in order to explain the principles of the invention and its practical.