Operation of T-250/300-240 turbines without working blades in the last stages of the low-pressure cylinder

Abstract

The current operating regimes for turbines of this type and their possible long-term uses affect the choice of a rational option for the modernization of the low-pressure cylinder (using a three stage rotor with reduced lengths of the working blades in the last stage or removal of working blades in the last stages), which should be made taking into account the specific conditions at each given heating and electric power plant. Studies of T-250/300-240 turbines at the heating and electric power plant TETs-23 of JSC “Mosenergo” operating without working blades in the last stages of the low-pressure cylinder are described. These demonstrate increased efficiency during both summer and winter operation under the conditions at this plant. The condition of the trailing edges of the working blades in stages 30 and 39 is found to be excellent, but erosion of the steam inlet deflector cone in the region of the feedthrough for the low-pressure cylinder along the direction of the twist in the flow is observed. It is proposed that an alignment module be installed at the outlet of the low-pressure cylinder for protection from overload, the compressor effect, and root eddies. For further increases in efficiency it is proposed to examine the feasibility of raising the maximum allowable temperature of the exhaust at the low-pressure cylinder of the modernized turbine.