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).