摘要
涡轮流量计的准确度受被测介质及其运动粘度变化的影响。使用体积流量和仪表系数无法从变粘度实验中取得形态一致且可预测的标定结果。应用量纲分析导出雷诺数和斯特劳哈尔数作为描述涡轮流量计性能的无量纲参数。通过改变丙二醇-水溶液的体积浓度得到5个不同运动粘度的介质,分别用于标定一台DN25涡轮流量计。对比结果表明,不同粘度下的标定曲线在雷诺数小于7400区域出现分离,标定数据最大相差0.9%。随着雷诺数增加,仪表系数中轴承阻滞部分的影响相对减小,标定曲线簇由分散趋于聚拢,标定数据差异小于0.1%。叶片表面的流动边界层发生层湍转捩时阻力的突变导致标定曲线出现驼峰,运动粘度越低,驼峰趋于平缓。轴承阻滞中的静态阻力部分是造成相同雷诺数下仪表系数差异的主要原因,这种差异随雷诺数减小而增加,所以,当校准介质和工作介质的运动粘度有显著差异时,涡轮流量计要避免工作在低雷诺数区域。
The accuracy of the turbine meter is influenced by the measured medium and its changing kinematic viscosity.Predictability and consistency of calibrating meter factor against volume flow rate are unable to be achieved with various viscous liquids.The method of dimensional analysis is applied to derive Reynolds and Strouhal numbers to describe the performance of the turbine meter.A DN25 turbine meter is calibrated with five different mixtures of propylene glycol and water,respectively.The comparison results show that the calibration data for varied kinematic viscosity vary up to 0.9%at Reynolds number lower than 7400.The scattered calibration curves tend to be collapsed as the Reynolds number increases,and the calibration data vary less than 0.1%.The rise of skin friction drag occurs at the boundary layer transition from laminar flow to turbulent flow on the rotor blade surface,which is responsible for a hump-shaped calibration curve.When the kinematic viscosity is lower,the hump is flatter.The bearing static drag is the main reason for scattered meter factors,and the discrepancy tends to increase with decreasing Reynolds number.Therefore,the turbine meter should not be used for low Reynolds numbers when the kinematic viscosities of the calibration medium and the working medium are significantly different.
作者
刘夷平
梁艳争
朱碧玉
马力
Liu Yiping;Liang Yanzheng;Zhu Biyu;Ma Li(Shanghai Institute of Measurement and Testing Technology,Shanghai 201203,China;Shanghai Key Laboratory of On⁃line Testing and Control Technology,Shanghai 201203,China)
出处
《仪器仪表学报》
EI
CAS
CSCD
北大核心
2022年第2期100-107,共8页
Chinese Journal of Scientific Instrument
基金
国家市场监督管理总局科技计划(2017QK081)项目资助
关键词
涡轮流量计
标定曲线
运动粘度
雷诺数
turbine meter
calibration curve
kinematic viscosity
Reynolds number
