| 摘要 |
A variable geometry turbine comprise a housing; a turbine wheel supported in the housing for rotation about a turbine axis: and an annular inlet passage upstream of said turbine wheel defined between respective inlet surfaces defined by an annular nozzle ring and a facing annular shroud. The nozzle ring and shroud are axially movable relative to one another to vary the size of the inlet passage; the nozzle ring having a circumferential array of inlet vanes extending across the inlet passage. The shroud covers the opening of a shroud cavity and defines a circumferential array of vane slots, each vane slot corresponding to an inlet vane, the vane slots and shroud cavity being configured to receive said inlet vanes to accommodate axial movement of the nozzle ring. At least one vane slot has a first side corresponding to a first side of the corresponding inlet vane and a second side corresponding to a second side of the corresponding inlet vane, the first side of the vane slot being located a shorter radial distance from the turbine wheel than the second side of the vane slot. The at least one vane slot has a leading end corresponding to a leading end of a corresponding inlet vane, and a trailing end downstream of the leading end, the trailing end corresponding to a trailing end of the inlet vane. A vane chord extends in a straight line between the a leading end tip and a trailing end tip of the inlet vane. The at least one vane slot has an increased clearance portion, the clearance between a portion of the at least one vane slot, which forms part of the increased clearance portion, and an adjacent portion of the inlet vane being greater than the clearance between a further portion of the at least one vane slot, which does not form part of the increased clearance portion, and an adjacent portion of the inlet vane. The increased clearance portion is located at the second side of the vane slot and extending from a trailing end tip of the trailing end of the vane slot to a point which is a distance from the trailing end of the vane slot, in the direction of the vane chord, that is greater than about 10% of the length of the vane chord. |
