【作者】 谭超；

【导师】 董峰； 王江；

【作者基本信息】 天津大学 ， 检测技术与自动化装置， 2010， 博士

【摘要】 两相流是自然界与工业过程中十分常见的流动形态,由于流态的复杂性,对其过程参数的准确测量一直是科学研究与工业过程应用中亟待解决的重要课题。多传感器融合技术利用不同时间与空间的多传感器数据资源,通过对各局部测量信息的综合,消除多传感器信息之间可能存在的冗余和矛盾,并加以互补,降低其不确定性,实现比单一信息源对被测过程更完全、准确、可靠的测量和描述。本论文从两相流参数测量方法与流动机理出发,利用数值仿真技术,在研究V型内锥流量计与基于电学敏感原理的传感器用于两相流参数测量方法的基础上,建立各传感器两相流测量模型;结合数据级与特征级信息融合方法实现两相流流型的准确识别,以及质量流量、流速、分相含率和分相表观流速的测量。本研究主要完成的工作:1.从两相流参数测量方法与流动机理出发,开展水平管道油水与气水两相流的三维CFD(Computational Fluid Dynamics)非稳态仿真,分析两相流典型流动状态下,V型内锥流量计的测量特性,以及流动参数在预设测量截面处的变化。仿真结果表明,V型内锥对两相流流态有一定的干扰,但能在较短距离内恢复;实际取压位置与理想位置处的差别可以通过一个定值来补偿;锥体尾部出现回流区域形成较强烈的湍流,但尾部取压方式不受回流影响;气水两相流间歇流动结构有一定的速度和差压波动,因此在测量气水两相流时应考虑这种波动带来的影响;气水两相流的流速差别较大,在流动分析中应考虑滑动比或滑脱速度的影响。该仿真工作为V内锥测量模型与互相关测速提供了理论分析基础,并在此基础上设计并实现了基于电学敏感原理传感器的两相流流动参数测量系统。2.在对已有两相流差压测量关系式分析的基础上,引入Blasius系数,推导出油水两相流粘度对差压测量关系式的影响,提出一种考虑油水粘度影响的油水两相流质量流量关系式;实现了利用环形电导式传感器测量气水两相流的滑动比,并提出一种适用于研究工作实验范围的气水两相流质量流量测量关系式。测量结果表明:引入粘度的油水两相流质量流量关系式能够获得更准确的测量结果,而引入滑动比后的均相流模型测量结果较未考虑滑动比的均相流模型稳定,利用滑动比修正的Chisholm模型结合de Leeuw的分析结果选取相应的Blasius系数能获得更高的测量精度。从理论分析角度为差压流量计在两相流中的测量提供了一种理论与经验相结合的模型。3.结合两相流流动特性分析,提出一种能够在两相流流动特征信号中动态寻找信号段适用于互相关计算的方法,并建立了基于电学敏感原理的两相流混合流速测量以及分相含率的预测模型,实现了两相流双参数的同时测量。互相关结果表明,互相关方法测量到的油水与气水两相流结构性脉动传输与混合速度在不同的混合流动Froude数范围内存在分段线性关系,且参数拟合结果与数值仿真结果计算的参数值一致。相含率测量结果表明,油水两相流的混状流态满足Maxwell方程的假设条件,应用该方程测量油水两相流含水率的平均相对误差为8.1%。气水两相流离散流型可当作层流与满管流的交替处理,含水率测量结果的平均相对误差为10%。4.在各传感器测量模型与方法研究的基础上,实现了基于双截面电阻层析成像系统截面电极阵列间的数据级融合、特征级串行融合与并行融合;研究了基于V型内锥流量计与电阻层析成像系统测量数据特征级融合的水平管气水两相流流型识别方法;实现了基于V型内锥流量计与电学敏感原理传感器融合的两相流流速、相含率与滑动比的预测,以及两相流流量和各分相表观流速的准确测量。测量结果表明:利用同质传感器间自适应加权估计方法的数据级融合能够实现测量信息的最优化,达到单传感器的最优测量状态,而特征级融合能够提供额外的流动信息;利用融合方法计算的过程参数可比融合前更低的平均相对误差。更多还原

【Abstract】 Two-phase flow is commonly encountered and of paramount significance in both natural and industrial processes, and yet its rheological complexity makes the accurate measurement on its process parameters difficult to achieve and hence presents an urgent issue to scientific researchers and industrial engineers. Multi-sensor fusion techniques combine data and related information from spatially and temporally distributed sensors to achieve more complete, specific and reliable inferences than could be achieved by using a single, independent sensor. The integration or fusion of data from each local sensor eliminates possible redundancy and contradictions and consequently improves accuracy and uncertainty of the measurement.In light of the parametric measuring techniques and flow mechanism of two-phase flow, the measuring models of V-cone meters and electrically sensitive sensors are established through numerical simulations; the process parameters of two-phase flow, such as flow regime, mass flowrate, and flow velocity as well as the phase concentration are jointly determined with data fusion and feature fusion methods. The main works accomplished are as follows:1. Based on the parametric measuring techniques and flow mechanism of two-phase flow, typical flow conditions of oil-water and gas-water two-phase flow were studied through CFD unstable simulations. The simulation results show that the flow condition is disturbed by the V-cone meter but will recover in a short distance; the pressure difference due to tapping position can be compensated with a constant ratio; the turbulence occurred at the cone tail has no influence upon the pressure tapping means; the segregated flow condition of gas-water two-phase flow involves fluctuations of velocity and differential pressure, which must be taken into consideration in velocity measurement; the velocity ratio between gas and water unavoidably influences the flow model development. The simulation work lays a theoretical foundation for the development of V-cone measuring correlation and cross-correlation model, and the measuring systems of electrically sensitive sensors were built on simulation basis.2. The influence of viscosity of oil-water two-phase flow upon the differential pressure model is derived in view of the existing models for two-phase flow, from which a correlation of measuring the mass flowrate of oil-water two-phase flow is presented in consideration of the viscosity character. Besides, a slip ratio based measuring correlation for gas-water two-phase flow mass flowrate measurement is presented by introducing the slip ratio with conductivity rings. The results indicate that a better accuracy is achieved by introducing viscosity character of oil phase into the measuring model, and the velocity ratio based homogeneous model is more stable in parametric measurement than the normal model, in addition, the velocity ratio based Chisholm correlation in conjunction with de Leeuw’s selection on Blasius parameter evidently improves the measuring accuracy. This work provides a theory and experience integrated model for the differential pressure meters in two-phase flow measurement.3. With the analysis on flowing properties of two-phase fluids, a method of dynamically seeking suitable signal segment for cross-correlating measured signals from two-phase flow is proposed, in addition the prediction models of mixture velocity and phase concentration by using electrically sensitive sensors were established to achieve the simultaneous measurement on these two parameters. Cross-correlation results show that the cross-correlated velocity is a kind of structural velocity within two-phase flow, and can be piecewisely fitted into the mixture velocity within different range of Froude number. The prediction of phase concentration indicates that the flow condition of oil-water mixture meets the assumption of Maxwell equation and hence by using this equation achieves 8.1% average relative error in water holdup measurement of oil-water two-phase flow; the gas-water two-phase flow can be treated as the alternatively flow of full pipe and stratified flow and the average relative error is 10%.4. Based on the independent measuring model and methodology of above measuring systems, the information from each sensing plane of a Dual-plane ERT system is fused at data level and feature level respectively, moreover, the measurement data from a V-cone meter and an ERT system is also fused at feature level. And the performance of each fusion method is analyzed and discussed with the flow regime identification on gas-water two-phase flow in a horizontal pipe. At last, the flow velocity, phase concentration and slip ratio as well as the flow rate and superficial velocity of each phase are measured in acceptable accuracy by fusing the information from a V-cone meter and the electrically sensitive sensors. The results show that the data fusion with adaptive weighted estimation optimizes the measuring performance and feature fusion achieves higher accuracy by introducing additional information, and that the fusion based results have more accurate measurement than each independent sensor.更多还原