As is known, the combustion chamber of the turbine engine is located in an annular space defined by an internal housing and an external housing, in which the internal housing supports the diffuser of which the inlet is aligned with the outlet of the compressor, which is radial when the last stage of the compressor is centrifugal.
The air leaving the diffuser is intended, primarily, to enter the combustion chamber and to be mixed with fuel and then burned, and, secondarily, to bypass the combustion chamber in order to supply primary orifices for dilution of the chamber and means for injecting ventilation air in particular of the wheel of the first stage of the high-pressure turbine, located downstream of the combustion chamber.
A small portion of the air flow leaving the compressor is taken to cool the impeller of the last compressor stage. This air then flows downstream in an annular space defined by the internal housing of the chamber and a substantially cylindrical rotor or rotating wall extending radially inside the internal housing and injection means and connecting the impeller of the compressor to the turbine wheel, then passes into the high-pressure turbine blades in order to cool them.
The injection means include an annular duct of which the air outlet leads axially downstream for the injection of air onto the turbine wheel, through orifices of a flange mounted upstream of said wheel. These injection means also include substantially radial bypass ducts for the passage of a major portion of the air flow for cooling the impeller of the compressor, which has flowed downstream into the aforementioned annular space to the injection means.
A labyrinth-type seal is mounted between the injection means and the upstream flange of the turbine wheel, which seal comprises blocks of corrodible material attached to the outlet of the injection means and cooperating with annular lips borne by the upstream flange. A small portion of the air flow for cooling the impeller of the compressor is intended to axially pass through this seal.
The remaining portion of the air flow for cooling the impeller passes through the bypass ducts of the injection means and is intended to ventilate the upstream flange of the high-pressure turbine wheel, then injected into the channel of the turbine.
This technology enables the upstream flange of the turbine wheel to be well ventilated, but the air flow used for this ventilation is then directly injected into the channel of the turbine and does not therefore participate in the thermodynamic cycle of the engine, which is detrimental in terms of the performance of the turbine engine.