Abstract: A variable geometry turbine comprises a turbine wheel and a primary inlet passage of variable axial width. The turbine has a secondary inlet passage provides a flow path for a working fluid which circumnavigates at least part of the primary inlet passage. A seal element and one or more apertures are cooperable to selectively allow or prevent fluid flow through the secondary inlet passage. The ratio of the minimum cross-sectional area of the flow path through the primary inlet passage to that of the secondary inlet passage is between 1.3 and 1.7.

Abstract: A variable geometry turbine comprises a turbine wheel and a primary inlet passage of variable axial width. The turbine has a secondary inlet passage provides a flow path for a working fluid which circumnavigates at least part of the primary inlet passage. A seal element and one or more apertures are cooperable to selectively allow or prevent fluid flow through the secondary inlet passage. The turbine wheel is of the radial-inflow axial-outflow type and secondary inlet passage has an outlet configured to direct working fluid to exit the secondary inlet passage in a direction which has an axial component in the opposite direction to the direction of axial outflow of the turbine wheel.

Abstract: A variable geometry turbine comprises a turbine wheel (9) supported in a housing (1) for rotation about an axis. A nozzle ring (5) is moveably mounted within a cavity (19) provided within the housing for adjustment of the width of an annular inlet passageway (4) extending radially inwards towards the turbine wheel (9). An array of inlet guide vanes (8) extends between a radial face of the nozzle ring (5) and an opposing wall of the inlet (4) defining a radial vane passage. A first circumferential array of apertures (25) is provided through the radial face, each of which lies substantially within the vane passage. A second circumferential array of apertures (24) is also provided in said radial face, each of lies substantially upstream or downstream of the first array (25) of apertures. The inlet (4) and cavity (19) are in fluid communication via both the first and second sets of apertures (25,24).

Abstract: A variable geometry turbine comprises a turbine wheel (9) supported in a housing (1) for rotation about an axis. A nozzle ring (5) is moveably mounted within a cavity (19) provided within the housing for adjustment of the width of an annular inlet passageway (4) extending radially inwards towards the turbine wheel (9). An array of inlet guide vanes (8) extends between a radial face of the nozzle ring (5) and an opposing wall of the inlet (4) defining a radial vane passage. A first circumferential array of apertures (25) is provided through the radial face, each of which lies substantially within the vane passage. A second circumferential array of apertures (24) is also provided in said radial face, each of lies substantially upstream or downstream of the first array (25) of apertures. The inlet (4) and cavity (19) are in fluid communication via both the first and second sets of apertures (25,24).