Development of models enabling research of effect of temperature stratifi-cation across flanges of cylinder casing on operation of thermal expansion system of steam turbine

Abstract

The authors propose a generalized scheme of interaction between some steam turbine cylinder, a corresponding bearing pedestal and a turbine unit base (feather tongues). Based on this scheme, a simplified analytical model has been developed with methods of theoretical mechanics and strength of materials. It enables determination of the value of friction force applied at the feather tongues at the temperature difference between the left and right flanges of turbine case horizontal joint (temperature stratification).To verify assumptions of the analy­tical model, the authors have developed a model of interaction between the cylinder, bearing pedestal and feather tongues based on the finite element method.

Comparative calculations considering both models have proved that the values of friction forces at
the feather tongues – bearing pedestal couple with the temperature stratification at flanges of the horizontal joint of the turbine high-pressure cylinder are almost the same for an actual operational range of temperature stratification. An analytical model provides with somewhat overestimated results.

The modeling results may be used for evaluation of friction forces at feather tongues of a front bearing pedestal under conditions of temperature stratification across the flanges of the conjugated high-pressure cylinder of the steam turbine. With the models proposed, designers of multi-cylinder steam turbines can make justified decisions when specifying the gap values for the feather tongues – bearing pedestal couple