Qian Jiangbo, Gu Qingfeng, Yao Hao, Zeng Wei
National Thermal Power Engineering & Technology Research Center, North China Electric Power University, 071003, Baoding, China.
Eur Phys J E Soft Matter. 2019 Feb 21;42(2):22. doi: 10.1140/epje/i2019-11783-1.
The last stages of most steam turbines operate in wet steam, resulting in water erosion of the rotor blades and the reduction of turbine efficiency. Accurate measurement of steam wetness is the key to ensure an efficient and stable operation of steam turbines. The equivalent complex permittivity model of wet steam was established by Maxwell-Wagner non-homogeneous dielectric theory, and the complex permittivity distribution of frequency and temperature changes of saturated water, dry saturated steam, and wet steam was derived. The measurement experiments verified the above properties of dry saturated steam and wet steam. The complex permittivity of the wet steam is similar to that for the dry saturated steam. The real part increases with increasing frequency and temperature. When the frequency is large or the temperature is low, the real part approaches 1. The imaginary part increases first and then decreases with the increase of frequency. In addition, with the increase of temperature, the imaginary part becomes larger. When the temperature is low, the imaginary part is close to 0, which is independent of the frequency.
大多数蒸汽轮机的最后阶段在湿蒸汽中运行，这会导致转子叶片受到水蚀并降低汽轮机效率。准确测量蒸汽湿度是确保蒸汽轮机高效稳定运行的关键。基于麦克斯韦-瓦格纳非均匀介质理论建立了湿蒸汽的等效复介电常数模型，并推导了饱和水、干饱和蒸汽和湿蒸汽的复介电常数随频率和温度变化的分布情况。测量实验验证了干饱和蒸汽和湿蒸汽的上述特性。湿蒸汽的复介电常数与干饱和蒸汽的相似。实部随频率和温度的升高而增加。当频率较大或温度较低时，实部接近1。虚部随频率的增加先增大后减小。此外，随着温度的升高，虚部变大。当温度较低时，虚部接近0，且与频率无关。
