Large Coal-fired Power Generating Units Turbine System Simulation Modeling And The Variable Working Condition Characteristics

Currently, thermal power is the core of national energy structure. It is a significanttask that to research on operation characteristics and energy consumption distribution of thepower plant system. As the core of thermal power station, steam turbine system animportant part. The study on its performance characteristic and economical efficiency is theprimary task when doing the research on power plant thermal system. In the operationprocess of the system, state change of the equipment is inevitable. At this time, theoperating working conditions would deviate from the design working conditions. Thevariable working condition of the entire system can not be evaluated by conventionalmethods. In this article, the fundamental starting point of the research task is to usesimulation modeling technology to create a turbine system simulation model of all workingconditions, in order to understand the variable working condition of steam turbine systemoperating characteristics through study this model.The article expounds the related methods and theories on calculation of variableworking conditions for steam turbine, mainly focused on the widely used Flugel formula,which states a viewpoint that the Flugel formula has weaknesses on working conditioncalculation because its great calculation error, also it is unable to meet some requirement ofaccident working condition calculation. Therefore this article does a textual research on theorigin of Flugel formula, then explain the reason why it is not appropriate for this model.This paper mainly research a600MW supercritical unit, analyzes the composition andvariable working characteristic of its steam turbine system. According to the sectionalmodular modeling theory, models for each part of steam turbine system have established.According to design data, under the condition which ruled out the classic Flugel formula,there are simple function relationships between the unit pressure ratio and the functionwith Mach numberM aand adiabatic coefficient k. By using the relationship, the new simulation model of steam turbine proper established and has been calculated and verified.According to the sectional modular modeling theory, divide the steam turbine bypasssystem into throttling decompression and spray desuperheating. Therefore the simulationmodel of steam turbine bypass system established. Based on all the established models, thesteam turbine system model is completed and the variable working condition has beencalculated. The research takes heat rate as the main object, calculates the variable workingconditions and operating characteristics including unit load change, main single reheatsteam parameters change, main stream pressure and temperature coupling variableconditions, regenerative heater heat transfer coefficient change, removal of regenerativeheater, terminal difference changes l of regenerative heater, and reheat accident spray unit.The article also sorts and analyzes the value and trend of system heat rate changes undervarious working conditions, pointing out the effect of those changes on energy consumptionof steam turbine changes. In order to verify the correctness of the calculation results of thismodel, it does a comparative study between operating working conditions and designworking conditions.