| Due to the main monitoring local parameters including the main steam pressure and temperature, reheat steam temperature, back pressure, heater terminal temperature difference, etc. deviating from the design values frequently during unit practical operation, it affects unit thermal economics. According to the layout and structure of the actual thermodynamic system in power plant, thermodynamic system state equation including thermodynamic system steam-water distribution equation,turbine power equation and boiler absorbed heat equation is established,meanwhile, energy-efficiency distribution matrix equation which is easy to partial quantitative analysis on thermodynamic system and suitable for computer programming is also constructed. In this thesis, the variable condition theory of steam turbine is introduced emphatically, the calculation principle of governing stage characteristic curves and its application in variable condition are profoundly researched. By proposing a new judge algorithm of quality flux to estimate fluid class of last stage, a sequential calculation mothod of final stage at partial load is built to get the exhaust enthalpy. Unconsidering thermodynamic system under the premise of variable condition, the valve opening level of governing stage remains unchanged, based on Flugel formula and the variable condition theory of turbine, the variable condition calculation models for local parameters of steam turbine are established. Considering the varying condition of regenerative system,the variable condition calculation models for heater terminal temperature difference are also established. Taking a 600 MW condensing turbine as an example, the influences of the local parameters on unit energy consumption are qualitative analysed, and the correction curves are fitted by the modles.Using the IFC function,calculation program of variable condition is generated by MATLAB.Comparing with the correction curves provided by the manufacture,the error between the calculated value and the standard value is very small under the same condition. It can fully satisfy the practical needs, verify the accuracy of the calculation models and provide a reference for field operators to fast check unit heat consumption. |
