Investigation of universal conditions of stability of thermal expansion system of steam turbines to external actions

Abstract

The analysis of various designs (both traditional and alternative) for outboard bearing housing joints with cylinders of steam turbines of medium and high power. Taking into account the identified similarities in the interaction of elements of the considered structures, a generalized kinematic model of the thermal expansion system of a steam turbine is presented. In the assumed model, the thermal expansion system is presented in the form of a multi-link hinged system consisting of one or more “basic” modules. Based on the developed model, the stability conditions (the absence of self-braking on the guiding longitudinal keys) against external influences are studied for the thermal expansion system of a steam turbine. According to the simulation results, it is shown that the magnitude of the turbine cylinder rotation angle change relative to the bearing housing in the junction must be limited. It was revealed that for stability of a system with one outboard bearing housing, it is sufficient that the maximum rotation angle at the junction of the turbine cylinder and the bearing housing does not exceed the maximum rotation angle of the bearing housing relative to the longitudinal keys. For stability of a system with several sequentially moving outboard bearing housings (multi-cylinder turbine), it is necessary that the limiting angle of rotation at all junctions of the turbine cylinders with bearing housings does not exceed the value of the smallest limiting angle of rotation for all bearing housings. The results of the study can be applied in the design of new steam turbines and in the reconstruction of thermal expansion systems for equipment in operation.

Keywords

• turbine unit
• heat expansion
• bearing case
• longitudinal spline
• transversal spline