Study On Determination Of The Optimum Temperature Rising Rate For Hot Startup Of Large Thermal Power Units

Large thermal power cycling units need frequent startup and shutdown whichparticipate in two-shift peak regulating,which sets a still higher demand on timelinessof startup response. As the background of establishing one regional wind and firetransaction peaking mechanism,this text determines the optimum temperature rise rateof startup to increase startup speed to meet the dual requirements of timeliness andeconomy.First of all, on the basis of referencing operating rules, the text analies the basischaracteristics of all stages of HP-IP cylinders unite start-up combined with fieldpractical startup operation steps, and grasps the working mechanism of correlationsystem. calculation formulas of heat transfer coefficient and steam parameters isprogramed by C language in order to output boundary condition results of differentparts of steam turbine rotor in all of start-up stages automatically.Secondly, on the basis of turbine rotor unsteady temperature field, stress fieldmathematical model and finite element theory, the geometry established by CAD isintroduced into the finite element analysis software ANSYS, and technology of localgrid refinement processing has been applied to mesh. Then boundary conditionsgetted by the C language calculation program are applied according to operation steps,unsteady temperature field and thermal stress field of different start-up stages arecalculated. the distribution and variation of temperature field and stress field indifferent stages of start-up are analied according to finite element resluts.Finally, this paper takes hot startup of one introduced350MW turbine unit forexample, studies out five optimization schemes preliminarily, which are simulatednumerically one by one. thermal stress result is obtained at the focal monitoringpoints of rotor by calculating and arranging data, thermal stress variation withtemperature rising rate is analyzed, low cycle fatigue life consumption of steam turbine rotor is calculated by symmetric cycle method and the optimum startuptemperature rising rate is determined in the process of hot startup according to theanalysis of calculated results, and the startup optimization scheme is getted. Itsresearch and application are of much reference value for large thermal power unitsdepth peak load cycling.