一种基于有限体积法计算汽轮机汽缸轴向膨胀的新方法

汽缸与转子轴向相对膨胀是影响汽轮机启动速度及机组运行安全的重要因素之一,目前对汽缸膨胀的计算与模拟尚不能用于电厂机组运行的实时监测。该文在圆筒壁非稳态导热的基础上,给出了圆筒壁温度分布的解析解,提出有限体积法计算汽缸轴向膨胀。定义了体积膨胀特征温度,将汽缸沿轴向分成若干段,每段简化成圆筒壁,在此基础上,计算有限体积的膨胀特征温度,分别计算各段的膨胀量,然后累加。对理论模型进行了有限元验证,计算结果与有限元结果误差较小,满足工程计算的需要。通过该计算方法,结合已有转子膨胀计算方法可以实现汽缸轴向胀差的实时监测。

A New Method Based on Finite Volume Method to Estimate Axial Thermal Expansion of Steam Turbine Cylinder

The comparative axial thermal expansion of cylinder and rotor was one factor effecting steam turbine start-up time and generator unit security. Now, it couldn't be carried out that monitoring expansion of cylinder on line. It was presented that using finite volume method to estimate axial expansion of cylinder, which is based on cylinder transient heat conduction, and expansion reference temperature (ERT) was defined to describe the capability of cylinder expansion. The cylinder was divided into several parts and their heat expansions were calculated. A good coincidence between the results calculated according to the theoretical model presented in this paper and the results of finite element calculation can be observed. By this calculating method, it can be carried out that monitor and measure on-line to axial differential expansion of steam turbines.