Accurate Calculation Method And Applied Research On Thermal Performance Of Steam Turbine Depth Off-design Conditions

At present in China, energy supply shortage is growing, construction of the poweris developing rapidly, the demand of electricity is also increasing, which inevitablycause the electricity structure to produce bigger change, and unit is often at off-designconditions even depth off-design conditions. In order to ensure the safe and economicoperation of steam turbine, the thermodynamic calculation of steam turbine off-designmust be worked out. In addition, through the off-design conditions calculation, it ispossible to get the change of operation conditions of various economic index, tooptimize the operation modes and to realize energy saving and consumption reducing.But at present the off-design theory development of steam turbine is relatively laggardin our country, which has already become one of the main factors that prevent powerplant safety and economic operation from achieving automatic management.This treatise attempts to study the thermal characteristics of the steam turbinedepth off-design conditions accurate calculation method and its application incoal-fired power plant. Firstly, the calculation purpose and significance of steamturbine depth off-design conditions were introduced systematically, then the off-designperformance analysis and calculation instance of the steam turbine governing stage,middle stage and the final stage were carred out. In the governing stage off-designconditions calculation, according to the original data and field test data (includingsteam parameters of the steam turbine, geometic size of the governing stage), theenthalpy, reaction degree, power and efficiency of the governing stage off-designconditions were calculated, and its characteristic curves were drawn. In the middlestages off-design conditions, the feature of the characteristic flow area was expounded,the expression of the characteristic flow area of steam turbine and the relationship ofpressure, temperature and flow were got. The characteristic flow area were calculatedby thermal equilibrium diagram data of the stage group design condition, and detailoff-design condition calculations of middle stage group were completed based on thefeature of the characteristic flow area is unchanged in different conditions. Thecalculation results include the characteristic flow area, flow, relative internalefficiency and internal power of stage group. In the final stage of steam turbineoff-design calculations, the inner power and relative internal efficiency were carred outby a general calculation method of steam turbine incremental output, and the relevant curves were given. Finally, according to the variable condition calculation principleand method, the application software was exploited, and good results were obtained.