直流锅炉蒸汽压力与中间点温度耦合特性分析

Coupling Characteristics of Steam Pressure and Intermediate Point Temperature for Once-through Boiler

汽轮机调门开度扰动实验得到的超临界直流炉蓄热系数其数值明显小于锅炉设计参数的计算值和直接能量平衡协调控制系统的调试值。分析发现,直流炉与汽包炉蓄热利用的机制存在差异:直流炉压力变化时只能利用汽水部分蓄热,中间点温度变化时才能利用金属部分蓄热。将直流炉汽水系统横向划分为传热区和容积区,分别建立传热区金属与容积区汽水蓄热过程能量平衡方程,可建立微分方程形式的直流炉汽水系统核心模型,也能籍此定量分析蒸汽压力与中间点温度的耦合特性。将机组实际燃料量–给水流量–汽轮机高调阀开度引入模型,变工况下中间点温度–机前压力–发电负荷模型输出值与机组实际值很好吻合,显示模型有足够的准确度。

The experiment value of heat storage coefficient for supercritical once-through boiler is obviously lower than the computation value based on design parameters and lower than the debugging value of direct energy balance（DEB） coordinated control system under the opening disturbance of governor valve in turbine. Analysis results show that there is difference of heat storage usage mechanism between once-through boiler and drum boiler. The difference is that the change of steam pressure can only use the heat storage of steam and water in once-through boiler, and the variation of intermediate point temperature can use the heat storage of metal. So the steam and water system of once-through boiler was divided into heat transfer region and volume region. Energy balance equation for heat storage process of metal in heat transfer region and for heat storage process of steam and water in volume region were constructed. Then the kernel model described by differential equations for steam and water system in once-through boiler was constructed. Based on the kernel model, the coupling characteristics between steam pressure and intermediate temperature can be quantitatively analyzed. The real operation data of fuel flow, feed water flow and governor valve opening of high pressure cylinder in turbine were introduced into the model as inputs signals, the experiments results showed that the model outputs of intermediate point temperature, throttle pressure and generation load can agree very well with the real outputs of units under varying operation conditions. The model has enough accuracy.