Local Deformation And Strength Analysis Of Ultra Supercritical Steam Turbine In The Balance Piston Movement Structure

The current steam turbine parameters has reached 26.25MPa/600 degrees,compared to Subcritical Units,the efficiency has been greatly improved,but at the same time,the high temperature and high pressure environment makes the tensile strength and toughness are decreased,and the friction phenomenon is found in the high pressure cylinder balancing piston and cylinder or regional seal structure between the rotor radial rub,which seriously affected the normal operation of the unit,so it is necessary to study the regional balance piston movement structure gap,the structural strength,and the research of fatigue-creep coupling start stop condition damage for ultra supercritical steam turbine high pressure cylinder,at the same time the service life is needed,to guarantee the safe operation of high pressure cylinder structure in the service period.In this paper,an ultra supercritical steam turbine(inlet parameters 26.25MPa/600 ?)is as the research object,using the finite element software ABAQUS,establishing the thermodynamic coupling model,analyzing the creep strength of the steady state for high pressure cylinder components,and using continuum damage mechanics theory to evaluate creep fatigue under coupling life during start-stop process,and analyzing the radial clearance between the piston movement trend of regional balance structure for the unit of the rub phenomenon,in order to evaluate the service conditions.The Norton-Bailey creep constitutive equation is introduced to analyze the temperature field,stress field,uniaxial and multiaxial creep strain field of the high pressure cylinder structure in the steady state for 200 thousand hours,results show that the stress field showed relaxation for the high pressure cylinder structure in the process of creep;multi axial creep strain is checked by ASME specification,and the results meet the standard assessment.Based on the start-stop curve,the temperature field,stress field and displacement field of the high-pressure cylinder during start-up and shutdown process are analyzed.It is found that there is great fluctuation in temperature and stress at the initial stage of start-up.The clearance between dynamic and static structure in the balance piston area is analyzed during the start and stop process.The results show that the minimum clearance near the end of the balanced piston inlet at the end of steady state operation,but no rubbing has yet occurred.The creep fatigue coupling damage analysis of HP cylinder is based on continuous damage mechanics model.The post processing program of Python is applied to calculate the creep fatigue coupling damage of high pressure cylinder,and the safety life is checked,which ensures the safe operation of high pressure cylinder with multiple structures.