A turbine assembly of an engine is disclosed. The turbine assembly includes a nozzle ring for receiving exhaust gases from a combustion chamber having a plurality of guide vanes for guiding the exhaust gases, a stator ring disposed downstream to the nozzle ring, and a rotor disposed circumferentially within the stator ring. The stator ring includes a plurality of stator vanes adapted to receive the exhaust gases through the guide vanes of the nozzle ring. The stator ring is axially movable between a first position and a second position along at least one cross-key pin disposed between the stator ring and a turbine casing. Each of the plurality of stator vanes moves into a throat plane of each pair of the plurality of guide vanes in the first position of the stator ring, and moves out of the throat plane in the second position of the stator ring.