396 / 2018-12-21 10:31:48

Influence of blade surface heating on wet steam condensation characteristics in nucleation stage of steam turbine/叶片表面加热对汽轮机成核级湿蒸汽冷凝特性的影响

steam turbine, nucleation stage, wet steam, condensation flow, blade surface heating/汽轮机；成核级；湿蒸汽；凝结流动；叶片表面加热

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The steam flow state in the nucleation stage will affect the thermodynamic and aerodynamic characteristics of the steam turbine. In order to reduce the wetness losses, the effect of blade surface volume heating on condensation characteristics is studied. Based on thermodynamic theory, nucleation model and droplet growth model were studied. A two-fluid model of homogeneous condensation was established from the point of view of volume average, and the accuracy of the model was verified. The effects of stator blade surface volume heating, rotor blade surface volume heating and coupling heating on wet steam condensation characteristics were analyzed. The research shows that the stator blade surface volume heating can prevent steam condensation very well. When the stator blade surface volume heating rate is 0.375 J /(mm2·s), the average outlet wetness of the stage is 0.0158, which decreases 69.34% compared with the non-heating condition, and the entropy increase is only 6.8% higher than the non-heating condition. When the blade surface heating method is adopted, the primary water droplets on the blade surface will be evaporated before forming water film, thus eliminating the secondary water droplet resistance loss, braking loss and weakening the thermodynamic loss. The blade surface heating can inhibit steam condensation very well and improve the turbine efficiency to a certain extent.
成核阶段的蒸汽流动状态直接影响汽轮机的热力学特性和气动特性。为了减少湿损失，研究了叶片表面加热对冷凝特性的影响。基于热力学理论，首先对比研究了不同成核模型和水滴生长模型。随后，从体积平均的观点出发，建立了均相凝结的两流体模型，并验证了模型的准确性。分析了静叶表面加热、动叶表面加热和耦合加热对湿蒸汽凝结特性的影响。研究表明，静叶表面加热和耦合加热都可以很好地防止蒸汽凝结，但静叶表面加热的效果更好。当静叶表面积加热速率为0.375J/(mm2·s)时，级平均出口湿度为0.0158，与不加热工况相比降低了69.34%，熵增加仅比不加热工况高6.8%。采用叶片表面加热方法后，叶片表面的一次水滴在形成水膜之前将被蒸发，从而阻止了二次水滴的生成。叶片表面加热可以很好地抑制蒸汽凝结，消除二次水滴阻力损失、制动损失并削弱了热力学损失，在一定程度上提高了汽轮机效率。