By taking the low pressure(LP) module of a turbine with independent structure as the research object

the deformation of the LP cylinder inner casing and shaft sealing in vacuum raising stage is numerically analyzed.In order to clarify the influence of gravity

vacuum force and thermal effect on shaft sealing clearance of the LP cylinder

the above three loads are added on the LP cylinder step by step for finite element analysis. The results show that

under the action of gravity

the LP cylinder inner casing will sink as a whole and tilt at both ends. Under the action of vacuum force

the shaft sealing sinks further with the cylinder

and the bottom gap becomes larger.When the LP cylinder runs with water spraying

the high temperature sealing steam heats the shaft sealing and LP cylinder inner casing

the shaft sealing rises with the cylinder as a whole

and the bottom clearance decreases. Under the combined action of vacuum force and heat effect

the bottom clearance of the shaft sealing reduces by 0.061～0.105 mm. In the case of water spraying

the whole vacuum raising stage has little effect on the clearance of the LP shaft sealing.