汽轮机变工况级内盐析颗粒沉积特性研究

Deposition characteristics of salting-out particles in steam turbine stage with variable working conditions

为了深入了解汽轮机变工况时盐析颗粒的微观行为,本文应用计算流体力学与群体平衡模型耦合的方法,对汽轮机变工况时盐析颗粒的速度、粒子数及粒径的分布特性进行模拟分析。结果表明:随着负荷的降低,低速区在盐析流场入口处不断扩大,逐渐扩散到整个入口截面,动叶尾缘处反向漩涡在负荷降低到60%时消失;随着汽轮机负荷的降低,静叶前缘处粒子数为6.5×1016的盐析颗粒沉积带区域逐渐缩小,汽轮机叶片上的颗粒粒子数也在不断减少;随着汽轮机负荷的降低,静叶片的盐析颗粒粒径基本为0.1?m并且分布比较均匀,变化不明显,而动叶上的盐析颗粒粒径则不断增长。将本文模拟结果与文献结果、电厂实际汽轮机叶栅表面盐沉积图片进行对比,验证本文模拟结果可信。以上结论对寻求减少汽轮机叶栅表面盐沉积的方法、提高汽轮机运行效率和可靠性,具有重要的意义。

To have a better understanding of microscopic behavior of salting-out particles under variable working conditions in a steam turbine, the salting-out particle velocity, particle number and particle diameter distribution under variable working conditions were simulated using coupling method of computational fluid dynamics and population balance model （CFD-PBM）. The results show that, as the turbine load decreases, the area with low velocity at inlet of the salting-out flow field continuously extends, and gradually spreads to the whole cross section of the entrance area, the reverse vortex of the tailed-edge of rotor blade disappears when the turbine load is reduced to 60%. As the turbine load decreases, the deposition belt of salting-out particles with particle number of 6.5 × 10 16 at the leading edge of the stator blade gradually shrinks, and the particle number in the steam turbine blade also gradually reduces. As the turbine load decreases, the particle diameter of the salting-out particles on the stator blade is about 0.1 μm and its distribution is relatively uniform and varies not obviously, while the particle diameter of the salting-out particles on the rotor blade continuously increases. The simulation results are compared with the literatures＇ results and the pictures of salt deposition on the actual surface of turbine blades, it proves the simulation results are credible. The above conclusions are of important significance to searching methods to reduce the salt deposition on the steam turbine cascades and improving the efficiency and reliability of steam turbines.