Method for controlling blade top clearance of ORC (organic Rankine cycle) turbine unit

The invention discloses a blade top clearance control method for an ORC (organic Rankine cycle) turbine unit, the ORC turbine unit comprises a bearing box, an air inlet volute, a flow guide casing, a stator assembly composed of a first-stage stationary blade casing and a second-stage stationary blade casing, and a rotor assembly composed of a main shaft, a first-stage bladed disc and a second-stage bladed disc, the rotor assembly is arranged in the stator assembly, and the main shaft is arranged in the stator assembly. The blade top gaps are the gaps between the first-stage stationary blade machine shell and the top of the first-stage blade disc and between the second-stage stationary blade machine shell and the top of the second-stage blade disc. The control method for the blade top clearance specifically comprises the steps of judging whether the calculation clearance of the blade top clearance conforms to the design clearance or not, drilling and reaming positioning pin holes of two adjacent components in