Patent ID: 6931849

Claim:
A variable geometry turbine comprising a turbine wheel supported in a housing for rotation about a turbine axis, an annular inlet passageway extending radially inwards towards the turbine wheel, the annular inlet passageway being defined between a radial wall of a moveable wall member and a facing wall of the housing, the moveable wall member being mounted within an annular cavity provided within the housing and having inner and outer annular surfaces, the wall member being moveable axially between first and second positions to vary the width of the inlet passage way, the second axial position being closer to said facing wall of the housing than the first axial position, the moveable wall member having a first annular flange extending axially from the radial wall into said cavity in a direction away from said facing wall of the housing, a first annular seal being disposed between said first annular flange and the adjacent inner or outer annular surface of the cavity, said first annular seal being mounted to one of said first annular flange or said adjacent annular surface of the cavity; wherein at least one inlet bypass passages is provided in the other of said first annular flange and said adjacent annular cavity surface, such that said first annular seal and said at least one bypass passage move axially relative to one another as the moveable wall member moves between said first and second positions; and wherein said first annular seal and said at least one inlet bypass passage are axially located such that with the annular wall member in said first position the seal prevents exhaust gas flow through the cavity but with said moveable wall member in the second position said at least one inlet bypass passage permits the flow of exhaust gas through said cavity to the turbine wheel thereby bypassing the annular inlet passageway.