Air injection casing for a turbomachine

A cooling-air injection casing having an annular shape around a longitudinal axis defining an axial direction and comprising a casing upstream end, a casing downstream end and a casing main wall which connects the upstream casing end with the downstream casing end, the casing main wall having an annular shape with a diameter that increases from upstream to downstream, the casing further comprising:

• an air mixing cavity, bounded axially by the casing main wall from its upstream end and radially by an injector wall integral with the casing main wall and which extends toward the longitudinal axis, the injector wall being connected to a substantially axial wall-which radially bounds the air mixing cavity;
• an air intake cavity, bounded upstream by the injector wall and downstream by a high-pressure rotor disk, the air intake cavity being in fluid communication with the air upstream of the casing main wall via an air injector which has at least one air injector inlet made in the casing main wall and an air injector outlet made in the injector wall;
• an air bleeding cavity bounded by a high-pressure rotor disk and a substantially radial wall connected to the casing main wall, the substantially radial wall being further connected to the substantially radial wall;
• a first sealing gasket separating the air mixing cavity and the air intake cavity;
• a second sealing gasket separating the air intake cavity and the air bleeding cavity;
• the injection casing further having an air passage cavity bounded by the substantially radial wall, the casing main wall and the substantially axial wall, the air passage cavity being in fluid communication with the air mixing cavity via apertures made in the substantially axial wall, and in that the air passage cavity is in fluid communication with the air bleeding cavity by means of apertures made in the substantially radial wall and wherein the apertures made in the substantially axial wall-have an inclination-to the axial direction comprised between 45° and 70°.