Turbine as well as active clearance control method, and clearance control system and mechanism thereof

The invention provides a turbine as well as an active clearance control method, a clearance control system and a clearance control mechanism thereof. The clearance control mechanism comprises a fixed outer ring, a plurality of movable ring blocks and a plurality of sealing assemblies, wherein the fixed outer ring is provided with a plurality of guide holes; the movable ring blocks are arranged around the fixed outer ring on the peripheral side of the fixed outer ring; each movable ring block corresponds to one sealing assembly; each sealing assembly comprises a plurality of sealing units; each sealing unit comprises a slender sealing piece; the sealing pieces slidably penetrate through the guide holes of the fixed outer ring; the outer ends of the sealing pieces are fixed to the movable ring blocks; the inner ends of the sealing pieces are located on the inner side of the fixed outer ring; the inner ends of all the sealing pieces of the sealing assembly corresponding to each movable ring block define a variab