Turbomachine comprising a system for cooling the downstream face of an impeller of a centrifugal compressor

A turbomachine, comprising a diffuser—distributor assembly arranged at the outlet of the impeller of a centrifugal compressor and supplying an annular combustion chamber with air and means for injecting air for ventilating a turbine, this diffuser—distributor assembly comprising an annular downstream end-piece connected at its downstream end to the injection means and delimiting, with the downstream face of the impeller, an annular cavity for the circulation of ventilation air taken from the outlet of the compressor, which comprises means for drawing off from the injection means, a fraction of said turbine ventilation airflow, and means for guiding the drawn-off air to the radially internal portion of the downstream face of the impeller, so that this airflows radially from inside to outside along the downstream face of the impeller and mixes with the air taken from the outlet of the compressor in order to reduce the temperature of the air in the annular cavity.