High-pressure gas turbine for turbomachine and turbomachine

A high-pressure gas turbine for a turbomachine (10) extending around a longitudinal axis (X), the turbine comprising:

• a nozzle guide vane assembly (30) comprising an internal annular platform (34) and an annular array of fixed vanes (32), each fixed vane (32) being connected, radially inwards, to the internal annular platform (34),
• an annular array of movable blades (40) mounted downstream of the nozzle guide vane assembly (30), comprising a disc (41) from which blades (42) extend radially outwards,
• an upstream sealing element (50) applied against a downstream face of the nozzle guide vane assembly (30), and a downstream sealing element (43) applied against an upstream face of the disc (41) of the annular array of movable blades (40),
• the upstream sealing element (50) comprising an annular portion (52) from which a downstream annular deflector (54) extends longitudinally downstream, said annular portion (52) having a radially outer portion comprising a upstream annular cavity (56), said upstream cavity (56) being open at a radially outer annular clearance (58) delimited between the downstream face of the nozzle guide vane assembly (30) and the upstream sealing element (50),
• the downstream sealing element (43) comprising a first upstream deflector (47) arranged, at least in part, radially internally to the internal annular platform (34) of the nozzle guide vane assembly (30) and radially externally to the downstream deflector (54) of the upstream sealing element (50), said downstream sealing element (43) further comprising a second upstream deflector (48) arranged, at least in part, radially internally to the downstream deflector (54), the downstream deflector (54) extending, at least in part, radially facing the first and second upstream deflectors (47, 48), the first and second upstream deflectors (47, 48) and the downstream deflector (54) defining a double baffle;
• wherein the upstream annular cavity (56) of the upstream sealing element (50) is delimited longitudinally by a downstream radial face (36a) of the nozzle guide vane assembly (30) and by a downstream radial wall (60) of the upstream sealing element (50) extending radially outwards from the annular portion (52) of the upstream sealing element (50), and delimited radially by an annular end surface (52a) located at a radially outer end of said annular portion (52) and by a longitudinal wall (62) extending longitudinally upstream from the radially outer end of the downstream radial wall (60) parallel to an inner annular face (34a) of internal annular platform (34), said external annular clearance (58) being formed longitudinally between the downstream radial face (36a) of the nozzle guide vane assembly (30) and the upstream end of said longitudinal wall (62).