wearing material 19 fixed to stator 6 i e made of a soft material in which they form recesses as a function of differential expansions at the various machine speeds the air pressure forces air outside the chamber 16 and into an annular and divergent guide duct 20 contiguous with part of the bottom of the chamber 28 over a large part of its length and from which air exits through upper injectors 36 which lead into an external radial ring 22 of the turbine disk 2 actually forming part of the surface of side 29 of flange 13 rigidly attached to this disk the air in the second ventilation circuit significantly cools the external ring 22 by coming into contact with this area close to the combustion gases and therefore heated to a higher temperature the need to cool the entire disk 2 and particularly its periphery justifies the doubling up of cooling circuits which use air that may originate from other parts of the machine however the design is such that part of the air in the first ventilation circuit does not pass through orifices 12 but instead bypasses flange 13 on the outside and passes through a labyrinth or brush seal 23 fairly similar to the previous seal 17 and like it composed of lipseals 24 erected on the side flange 13 and a layer of wearing material 25 welded to a surface of the stator.