汽轮机湿蒸汽特性的超声衰减测量技术

Ultrasonic attenuation measurement technology of wet steam characteristics of steam turbine

针对核电站二回路汽轮机末级中,湿蒸汽工质夹带的液滴会威胁核电厂的经济性与安全性的问题,本文基于长波区简化模型对超声波在气液两相流中超声衰减系数、声速与体积浓度、液滴粒径关系进行数值模拟。利用超声衰减法,对气液两相流中100 kHz、160 kHz、200 kHz超声衰减系数进行测量,结合长波区简化模型对两相流液滴体积浓度进行反演计算。使用称重法对两相流中液滴体积浓度进行标定,将计算结果与标定的体积浓度进行对比分析。结果表明:超声衰减法可以对气液两相流液滴体积浓度进行在线测量,并且蒸汽液滴体积浓度变化0.01%超声幅值衰减可以达到25%而声速变化量为0.5%,超声衰减法更适合用于核电厂二回路蒸汽浓度测量。

The entrainment of liquid droplets by a wet steam working medium in the final stage of secondary loop turbine in nuclear power plants threatens the economy and safety of these power plants.This article is based on ECAH.The long waveform model numerically simulates the relationship between ultrasonic attenuation coefficient,sound velocity,volume concentration,and droplet size in a gas-liquid two-phase flow.The ultrasonic attenuation method is used to measure two-phase flow to obtain the ultrasonic attenuation coefficients at 100,160,and 200 kHz in a gas-liquid two-phase flow.Combined with the simplified ECAH model,the volume concentration of droplets in a two-phase flow was retrieved and calculated.The weighing method is used to calibrate the volume concentration of the two-phase flow,and the calibrated volume concentration is compared and analyzed with the calculated results.Results show that the ultrasonic attenuation method can be used to measure the volume concentration of droplets in an online gas-liquid two-phase flow,and the ultrasonic amplitude attenuation can reach 25%with changes of 0.01%of the vapor droplet volume concentration and 0.5%of sound speed.The ultrasonic attenuation method is suitable for the secondary loop steam concentration measurement in nuclear power plants.