Vanes and shrouds for a turbo-machine

A turbocharger comprising a turbine comprising:

• (i) a turbine wheel,
• (ii) a turbine housing for defining a chamber for receiving the turbine wheel for rotation of the turbine wheel about an axis, the turbine housing further defining a gas inlet, and an annular inlet passage from the gas inlet to the chamber,
• (iii) a ring-shaped shroud defining a plurality of slots and encircling the axis;
• (iv) a nozzle ring supporting a plurality of vanes which extend from the nozzle ring parallel to the axis, and project through respective ones of the slots, the shroud and nozzle ring being positioned on opposite sides of the inlet passage, one of the shroud and the nozzle ring being rotatable relative to the turbine housing about the axis by at least 0.1 degree;
• and
• (v) a rotation mechanism for, in use, rotating the one of the shroud and nozzle ring around the axis.

A ring-shaped shroud defining a plurality of slots, the shroud being for installation in a turbine, the ring-shaped shroud comprising:

• a plurality of gas interaction elements upstanding from a land surface of a face of the shroud, each gas interaction element including at least one wall surface, the shroud being for installation in a turbine comprising:
• (i) a turbine wheel,
• (ii) a turbine housing for defining a chamber for receiving the turbine wheel for rotation of the turbine wheel about an axis, the turbine housing further defining a gas inlet, and an annular inlet passage from the gas inlet to the chamber, and being configured for supporting the shroud with the shroud encircling the axis and rotatable relative to the turbine housing about the axis by at least 0.1 degree, and
• (iii) a nozzle ring supporting a plurality of vanes which extend from the nozzle ring parallel to the axis, and project through respective ones of the slots,
• wherein the at least one wall surface of each gas interaction element is configured to develop a rotational force in use due to flow of the gas against the gas interaction element.