【作者】 王振；

【导师】 张涛；

【作者基本信息】 天津大学 ， 检测技术与自动化装置， 2008， 博士

【摘要】 涡轮流量传感器是一种速度式流量传感器,它具有精度高、重复性好、量程范围宽、体积小等优点,因此被广泛应用于石油、化工、冶金、轻工、食品等工业领域中。由于涡轮流量传感器应用现场条件复杂,被测流体流动情况也不尽相同,因此研究涡轮流量传感器在不同流体条件下的测量性能,对扩大涡轮流量传感器应用领域具有重要现实意义。本论文主要完成以下工作:1.提出了环形通道内混合流体的虚拟速度剖面指数,分析了混合流体中气泡对叶片的阻力影响,建立了涡轮流量传感器测量泡状流的数学模型,得出虚拟速度剖面指数随体积含气率变化的规律。通过理论结果与实验结果的比较,证明该模型具有较好的预测精度。2.采用气液两相混合模型对涡轮流量传感器测量体积含气率低于10%的水平气液两相泡状流进行了数值仿真,根据流场分析得出的结论,提出以现有传感器与改进传感器的仪表系数迁移量仿真值的对比为判定依据,对现有传感器进行了改进设计。实流实验结果表明,改进传感器测量气液两相流的性能优于现有传感器,从而验证了该改进方法的有效性。3.以涡轮流量传感器量程范围内线性度误差最小为目标函数,根据四个叶轮特征参数和传感器测量单相流的数学模型,采用多变量非线性规划优化算法,提出了降低涡轮流量传感器线性度误差的优化设计方法。以50 mm和25 mm口径的传感器为例进行优化设计,通过优化前、后传感器实流实验结果比较,验证了该优化设计方法的有效性。4.分别采用S-A模型、标准k-ε模型、RNG k-ε模型、Realizable k-ε模型和标准k-ω模型五种湍流模型,对涡轮流量传感器测量单相流进行了仿真研究,结果显示使用标准k-ω模型可以更加准确地反映传感器内部流场,预测传感器仪表系数和特性曲线。5.对3台具有不同导程叶轮的涡轮流量传感器,测量体积含气率低于10%的水平气液两相泡状流的特性进行了实验研究。得出了不同含气率下传感器的两相流量特性曲线与仪表系数迁移量曲线,同时得出叶轮导程值大小影响着传感器测量误差值。对体积含气率变化影响涡轮流量传感器特性的物理机理以及造成传感器测量特性改变与误差的原因进行了分析讨论。更多还原

【Abstract】 Turbine flowmeter is a kind of velocity-type flowmeter with advantages of high accuracy, good repeatability, wide flow range, and small volume. So it is widely applied in chemical industry, petroleum, metallurgy, light industry, food industry and other flow industry. Because the industry field conditions for turbine flowmeter working is complex, and the flow regime is diversity, it is significant for extending the application field of turbine flowmeter to research on the performance of turbine flowmeter under different flow conditions.The main research works of this dissertation are as following:1. The index number of virtual velocity profile of mixed fluid in the annulus pipe was presented. Based on the analysis of the influence for bubble of mixed fluid to blade by the drag force, the mathematic model of measuring gas-liquid two-phase bubble flow with turbine flowmeter was established. The curve between the index number of virtual velocity profile and gas volume fraction were obtained. The validity of mathematic model was verified by experiments.2. Based on the mixture model, the numerical simulation on gas-liquid two-phase bubble flow (GVF<10%) in a turbine flowmeter was investigated. According to the conclusion of flow field analysis, a method, which can evaluate the performance of turbine flowmeter by simulative value of meter factor variation, was put forward. The rotor’s structure of existed flowmeter was improved. It was showed by physical experiment that the performance of the improved meter was better than that of existed meter. The validity of the method of improving design for turbine flowmeter was verified.3. The object function was the minimum of linearity errors of the measurement range. According to four characteristic parameters, the turbine flowmeter’s mathematic model and the multivariable nonlinear programming algorithm, a method was presented for reducing the linearity error of a turbine flowmeter. The turbine flowmeters of 50 mm and 25 mm caliber were optimized. The turbine flowmeter with optimal rotor and existed rotor were evaluated on a water flow calibration facility. Through the comparisons of linearity error between the meters with optimal rotor and the meter with existed rotor, the validity of the design reducing the linearity error of turbine flowmeter was verified. 4. Five kinds of turbulence model, S-A model, standard k-εmodel, RNG k-εmodel, Realizable k-εmodel and standard k-ωmodel were applied separately to numerically simulate a turbine flowmeter for measuring liquid. The comparisons between the numerical results and the data of physical experiment showed that standard k-ωmodel was more suitable for 3D numerical simulation on the internal flow fields of the turbine flow sensor and the prediction of the meter factor.5. Three turbine flowmeters, with different lead of rotors, were investigated to measure horizontal gas-liquid two-phase bubble flow on the gas-liquid two-phase flow facility. Results showed that the characteristics curve, measurement relative error and repeatability error were clearly changed with the variation of gas volume fraction. The performance of turbine flowmeter with smaller lead of rotor was better than those of the other two flowmeters. The reasons of the change of measurement performance and error were analyzed and discussed. The physical mechanics that the turbine flowmeter measurement performance was affected by gas volume fraction was also analyzed.更多还原