【作者】 孙向东；

【导师】 李斌；

【作者基本信息】 上海大学 ， 控制理论与控制工程， 2010， 博士

【摘要】 在目前的流量测量领域,测量的可靠性和精确度都要求很高,电磁流量计被认为是最可靠和精确的流量仪表之一。特别是大口径电磁流量计的应用也越来越广泛,如水库引水、源水进水厂、自来水出厂、污水处理和污水排放等领域,可作为供水结算和计量仪表。随着城市化的发展,用水量和排放量的增加,大口径流量仪表的需求量也不断增加,在大口径测量中电磁流量计相比传统流量计在原理上有显著的优势。目前电磁流量计基本上都是采用实流校准,但是电磁流量计在校准设备上需要有相当大的投入,而大口径的电磁流量计实流校准装置投入尤其巨大(1000mm口径的装置约达300多万),对应的校准方法及其装置问题阻碍了大口径电磁流量计的生产和发展。因此,研究一种低成本的有效的校准方法及其装置成为流量仪表领域的重要课题之一。本论文工作是以电磁流量计传感器原理中微流元与权重函数的关系为基础,提出并研究了一种不需要高投入的大口径电磁流量计校准方法,即是一种基于单位元的干校准方法。进而研究了对应干校准方法的校准基准传递关系和精度分析方法,实现了对应校准方法的装置,并通过实验验证了对应方法及其装置的可行性。论文的主要研究工作和成果有如下几个方面:(1)以电磁流量计基本原理及其权重函数理论为基础,深入研究了电磁流量计传感器和转换器的校准与成套基本形式以及参数基本关系,分析得出了在校准与成套关系下的传感器系数组成特点以及导致系数不一致性的基本原因,给出了传感器系数和转换器系数在校准与成套中的基本关系模型。(2)在对已有电磁流量计干校准方法的原理和特点的研究基础上,以流体微元与电磁流量计权重函数理论为依据,用小流量单位元在大口径传感器中的权重函数关系作为干校准基本数据,从流体微元及其单位元干校准模型和权重函数关系出发,提出了一种基于单位元的干校准方法及其理论关系,并讨论研究了基于单位元的干校准方法的基本实施框架。(3)从单位元原理及其传感器感应电势信号的基本公式出发,研究建立了从校准基准到被校准参数的计算与分析关系,通过引入实际传感器测量管流速分布和仪表测量零点问题,得出了干校准方法的综合计算方法,给出了基于单位元的干校准方法实施步骤。同时,研究了干校准方法实施中的实际流速、单位元口径与步长、流速测量精度、磁场与权重函数的空间关系、采样定位精度、单位元电极水平倾斜度、电极高度偏移、水力学口径偏差等对干校准精度可能产生的影响,为后续干校准装置的研究与实验提供基本依据。(4)论文研究设计了包括流量稳定的小流量供给装置、定位系统、数据采集处理系统、单位元等组成的干校准装置,具体实现了基于单位元的干校准装置,设计了装置的运行方法和事实校准运行的8个具体步骤,并分析比较了新型干校准装置的效益。(5)对基于单位元的干校准方法进行了验证性的实验研究工作。讨论了实验的传感器流量值基准传递方法和基准传感器的校准数据获取方法,设计和实施了对应干校准实验的条件和步骤,给出了具体的干校准实验数据和干校准装置稳定性试验数据,验证了基于单位元的干校准方法及其装置的基本可行性。更多还原

【Abstract】 In the current field of flow measurement,reliability and accuracy are very demanding, electro-magnetic flowmeter is considered to be one of the most reliable and accurate instrument. The application of electromagnetic flowmeter especially large diameter are increasingly being used,such as the reservoir water, the source of water into the water plant, water supply factory, sewage treatment and effluent disposal areas,it can be used as water supply billing and metering instrumentation. With the development of urbanization and the increase in water consumption,the demand of large diameter flowmeter increasing quickly,Electromagnetic flowmeter have significantly advantages compared to the traditional flowmeter. At present electromagnetic flowmeters are basically using the actual flow calibration. But the need for calibration of electromagnetic flowmeters adds considerably to the cost of these instruments especially in the larger sizes(about $3million for 1000mm in diameter). The problem of calibration equipment obstructs the development of large diameter flowmeters. Study of an inexpensive and effective calibration method has become one of the most important task in the field of flowmeter.This paper is based on the relationship between unit element and weighting function, raised and discussed a technique for calibration of large electromagnetic flowmeters which avoids the need for a calibration flow rig, which is called dry calibration of large electromagnetic flowmeters based on unit element. Then we discussed the transfer of calibrate standard and method of accuracy analysis. The task and achievement of this thesis is as follow:I. Based on basic principles of electromagnetic flowmeter and its weight function, the paper in-depth studied of the electromagnetic flowmeter calibration of sensors and converters,also studied of the fundamental mode of the complete and its parameter fundamental relation, find out the coefficient composition characteristics of sensor and the basic reasons leading to inconsistent coefficient, given the basic relational model of sensors coefficient and converters coefficient in calibration and set.II. On the basis of the principles and characteristics of currently existing dry calibration methods,according to unit element and weighting function of electromagnetic flowmeter, and take the weighting function of the unit element in large-diameter sensor as basic data of dry calibration, the paper raised a dry calibration method based on unit element and discussed its basic framework.III. According to the basic formula of induced electromotive force,established the calculation and analysis method of the calibration reference,by the introduction of the velocity distribution and zero point,we get the integrated calculating method of dry calibration, and given the implementation steps of unit element dry calibration method. Also the paper studied several factors which may have impact on the accuracy in dry calibration, such as the actual velocity, aperture and step size of unit element, velocity measurement accuracy, the spatial relationships of magnetic fields and weighting function, positioning accuracy, the inclination and height offset of unit element electrodes and diameter deviation of electromagnetic flowmeter.IV. This thesis researched and designed of the dry calibration equipment including small flow supply equipment, positioning system, data acquisition and processing system, and unit element. Recently we concrete realized the dry calibration equipment and given the operation method of dry calibration equipment, then analyzed and compared the effectiveness of the new dry calibration equipment.V. Conducted a confirmatory experimental research work for the new dry calibration method. This thesis discussed the baseline transfer method and the calibration data acquisition method of reference sensor. By implemented the dry calibration experiment under the given conditions and steps, we get the dry calibration experimental data and stability test data of dry calibration equipment, verified the feasibility of the new dry calibration method and equipment.更多还原