Device for controlling clearance in a gas turbine

A device for controlling clearance between the tips of rotary blades and a stationary ring assembly in a gas turbine, said device comprising a circular control box surrounding said stationary ring assembly,

• wherein said control box comprises:
• at least two annular air circulation strips spaced apart from each other in the axial direction and each having a plurality of perforations for modifying the temperature of the stationary ring assembly by discharging air;
• an annular air feed channel radially spaced from said air circulation strip;
• at least one air duct for feeding said feed channel with air;
• and
• a plurality of hollow distribution spacers connecting said air feed channel to said air circulation strips in order to feed the strips with air while allowing the air that has been discharged against the stationary ring assembly to flow between said feed channel and said circulation strips in order to be exhausted therefrom.