Study On Structure Strength For 1200MW USC Steam Turbine Intermediate Pressure Inner Casing

As atmospheric pollution problem increasingly obvious in China,increasing cycle efficiency of coal-fired power generation,limiting emission of CO₂,SO₂ and NO_x,developing high efficiency and clean coal-fired power generation technology are becoming the main development directions of power generation industry in our country now.The parameters of new developed 1200MW USC steam turbine is 28Mpa/600℃/620℃.The inlet steam temperature of the intermediate pressure（IP）casing is 620℃.The size of the IP casing is 20%larger than the active service casing of 1000MW unit.In order to ensure the safety and reliability of IP inner casing during its service duration under high temperature environment,it is necessary to calculate and analyze the creep strength and fatigue strength of new design IP inner casing,In this paper,the new design IP inner casing of 1200MW USC steam turbine is the analysis object.Conduct comparative analysis of temperature,stress and strain distribution of different structure design of IP inner casing under stable operating conditions.By introducing the Norton-Bailey creep constitutive equations and Cocks-Ashby multiaxial toughness factor,assess the creep strength of IP inner casing after long term stable operation.And assess the sealing performance on the horizontal joint of IP inner casing.By using Manson-Coffin formula,analyze the fatigue damage of IP inner casing due to start up and shut off.The results disclosed:the new design IP inner casing meets the requirements of high temperature creep strength and safe operation in design service period.