差压装置流量测量范围度扩展方法研究与实验
发布时间：2018-10-08 17:22
【摘要】：流量是过程检测涉及的主要参数之一,其测量值的准确性、有效性与设备的安全性和运行的经济性直接相关。热力发电厂生产过程中管内工质大多属于高温高压流体,目前对这类流体流量在用的测量方法是差压式流量测量装置,而此类装置的局限性在于其范围度为3：1最多4：1,这就意味着在生产过程中,如果管流流量低于测量上限的1/或1/流量以0计。正是这种局限性导致热电厂与用户之间产生计量争议,而作为国家标准规定的流量测量方法,差压式流量测量装置具有法定地位,技术监督部门也无其他依据对上述争议进行仲裁。因此,寻求一种既严格遵守国家标准GB/T 2624.1～4—2006“用差压装置测量圆形截面管道中的满管流体流量”的规定,又具有较大范围度的流量测量解决方案不但具有工程实用价值,更兼有理论意义。本文从分析造成小流量工况下测量误差大的原因出发,揭示差压式流量测量装置范围度小的的实质在于差压变送器的允许误差在小流量时形成的相对误差过大所致。解决问题的合理设想之一是：在小流量时使一次装置输出的差压对应的变送器输出亦为较大值,然而实际的情况是无论一次装置输出差压为何值,变送器输出电流都将差压成比例地转换成4-20mADC电流,除非将输出差压分成多段分别测量,即将一次装置输出差压由多个差压变送器按段分别转换成4—20mA电流。由此随之而来的是流出系数C必须按段分别计算,工控机信号处理系统根据不同差压段选择不同流出系数。遵循着这一设想,对于差压流量测量装置设计命题,本论文提出的解决方案如下：第一步,按GB/ 2624.1-4—2006“用差压装置测量圆形截面管道中的满管流体流量”附录A(资料性附录)给出的第二类命题计算方法对流量测量装置进行设计,设计结果包含最大流量qmmax对应一次装置输出差压ΔPmax、常用流量qmch对应一次装置的输出差压ΔPch、最小流量qmmin对应一次装置的输出差压ΔPmin、流出系数C、一次装置的开孔直径比β；第二步,采用两台差压变送器同时对一次装置的输出差压进行测量,其中差压变送器DP1的量程为0-ΔPmax,差压变送器DP2的量程为0～APmin,流量信号处理系统根据差压值选择其中之一进行处理；ΔPmin-△Pmax之间的差压由差压变送器DP1成比例地转换成4-20mADC电流信号,0-APmin之间的差压由差压变送器DP2成比例地转换成4-20mADC电流。一次装置输出0～ΔPmin之间的差压时所对应的流出系数cmin由第一类命题求解方法得到。于是该解决方案在完全遵循GB/T 2624.1-4—2006的前提下,装置的范围度由3：1到4：1提高到9：1到16：1。本论文设计了基于上述技术路线的实验方案,建造了实验装置,以实验证明了解决方案原理的正确性和可行性。
[Abstract]:Flow rate is one of the main parameters involved in process detection. The accuracy and effectiveness of the measurement value are directly related to the safety of the equipment and the economy of operation. Most of the working fluids in the pipe are high temperature and high pressure fluids in the production process of thermal power plant. At present, the method of measuring the flow rate of this kind of fluid is the differential pressure type flow measuring device. The limitation of this type of device is that its range is up to 4: 1 at 3:1, which means that in the production process, if the flow rate of the pipe is less than 1 / 1 / 1 / 1 of the upper limit of the measurement, the flow rate is zero. It is this limitation that leads to a dispute over measurement between the thermal power plant and the user. As a national standard flow measurement method, the differential pressure flow measuring device has the legal status. The technical supervision department also does not have other basis to carry on the arbitration to the above dispute. Therefore, it is not only of engineering practical value to seek a solution that not only strictly complies with the national standard GB/T 2624.1 / 4-2006 "using differential pressure device to measure the flow rate of the full pipe in a circular section pipe", but also has a large range of flow measurement solutions. It also has theoretical significance. Based on the analysis of the causes of large measurement errors under small flow conditions, this paper reveals that the essence of the small range of differential pressure flow measuring devices lies in the relative error caused by the allowable errors of differential pressure transmitters when the flow rate is small. One of the reasonable ideas to solve the problem is that the output of the transmitter corresponding to the differential pressure output of the primary unit is also larger when the flow rate is small, but the actual situation is that no matter what the value of the differential pressure output of the primary device is, The output current of the transmitter is converted proportionally to the 4-20mADC current, unless the output differential voltage is divided into multiple sections and measured separately, that is, the output differential voltage of the primary unit is converted from multiple differential pressure transmitters to the 4-20mA current by segment. Therefore, the outflow coefficient C must be calculated according to the section, and the signal processing system of the industrial control computer chooses different outflow coefficient according to the different differential pressure section. Following this assumption, for the design proposition of differential pressure flow measurement device, the solution proposed in this paper is as follows: the first step, According to the second type propositional calculation method given in Appendix A (Information Appendix) of GB/ 2624.1-4-2006, "measuring the flow rate of full pipe in circular section pipe with differential pressure device", the design of flow measuring device is carried out. The design results include that the maximum flow rate qmmax corresponds to the primary unit output differential pressure 螖 Pmax, qmch corresponding to the primary unit output differential pressure 螖 Pch, minimum flow rate qmmin corresponding to the output differential pressure 螖 Pmin, outflow coefficient C of the primary unit, the opening diameter ratio of the primary unit to 尾; the second step, Two differential pressure transmitters are used to measure the output differential pressure of the primary device simultaneously. The differential pressure transmitter DP1 has a measuring range of 0- 螖 Pmax, differential pressure transmitter DP2, and the flow signal processing system selects one of them according to the differential pressure value to process. The differential pressure between 螖 Pmin- Pmax is converted proportionally from differential pressure transmitter (DP1) to 4-20mADC current signal (0-APmin) from differential pressure transmitter (DP2) to 4-20mADC current. The outflow coefficient cmin corresponding to the differential pressure between 0 ~ 螖 Pmin is obtained from the first class propositional solution method. Under the premise of GB/T 2624.1-4-2006, the range of the device was raised from 3:1 to 4:1 to 9:1 to 16: 1. In this paper, the experimental scheme based on the above technical route is designed and the experimental device is built to prove the correctness and feasibility of the principle of the solution.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TH814
本文编号：2257633
[Abstract]:Flow rate is one of the main parameters involved in process detection. The accuracy and effectiveness of the measurement value are directly related to the safety of the equipment and the economy of operation. Most of the working fluids in the pipe are high temperature and high pressure fluids in the production process of thermal power plant. At present, the method of measuring the flow rate of this kind of fluid is the differential pressure type flow measuring device. The limitation of this type of device is that its range is up to 4: 1 at 3:1, which means that in the production process, if the flow rate of the pipe is less than 1 / 1 / 1 / 1 of the upper limit of the measurement, the flow rate is zero. It is this limitation that leads to a dispute over measurement between the thermal power plant and the user. As a national standard flow measurement method, the differential pressure flow measuring device has the legal status. The technical supervision department also does not have other basis to carry on the arbitration to the above dispute. Therefore, it is not only of engineering practical value to seek a solution that not only strictly complies with the national standard GB/T 2624.1 / 4-2006 "using differential pressure device to measure the flow rate of the full pipe in a circular section pipe", but also has a large range of flow measurement solutions. It also has theoretical significance. Based on the analysis of the causes of large measurement errors under small flow conditions, this paper reveals that the essence of the small range of differential pressure flow measuring devices lies in the relative error caused by the allowable errors of differential pressure transmitters when the flow rate is small. One of the reasonable ideas to solve the problem is that the output of the transmitter corresponding to the differential pressure output of the primary unit is also larger when the flow rate is small, but the actual situation is that no matter what the value of the differential pressure output of the primary device is, The output current of the transmitter is converted proportionally to the 4-20mADC current, unless the output differential voltage is divided into multiple sections and measured separately, that is, the output differential voltage of the primary unit is converted from multiple differential pressure transmitters to the 4-20mA current by segment. Therefore, the outflow coefficient C must be calculated according to the section, and the signal processing system of the industrial control computer chooses different outflow coefficient according to the different differential pressure section. Following this assumption, for the design proposition of differential pressure flow measurement device, the solution proposed in this paper is as follows: the first step, According to the second type propositional calculation method given in Appendix A (Information Appendix) of GB/ 2624.1-4-2006, "measuring the flow rate of full pipe in circular section pipe with differential pressure device", the design of flow measuring device is carried out. The design results include that the maximum flow rate qmmax corresponds to the primary unit output differential pressure 螖 Pmax, qmch corresponding to the primary unit output differential pressure 螖 Pch, minimum flow rate qmmin corresponding to the output differential pressure 螖 Pmin, outflow coefficient C of the primary unit, the opening diameter ratio of the primary unit to 尾; the second step, Two differential pressure transmitters are used to measure the output differential pressure of the primary device simultaneously. The differential pressure transmitter DP1 has a measuring range of 0- 螖 Pmax, differential pressure transmitter DP2, and the flow signal processing system selects one of them according to the differential pressure value to process. The differential pressure between 螖 Pmin- Pmax is converted proportionally from differential pressure transmitter (DP1) to 4-20mADC current signal (0-APmin) from differential pressure transmitter (DP2) to 4-20mADC current. The outflow coefficient cmin corresponding to the differential pressure between 0 ~ 螖 Pmin is obtained from the first class propositional solution method. Under the premise of GB/T 2624.1-4-2006, the range of the device was raised from 3:1 to 4:1 to 9:1 to 16: 1. In this paper, the experimental scheme based on the above technical route is designed and the experimental device is built to prove the correctness and feasibility of the principle of the solution.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TH814
【参考文献】
相关期刊论文 前3条
1 周人;;大量程比的流量测量方案[J];石油化工自动化;2011年03期
2 纪亮;;国家质检总局对差压式流量计的范围进行界定[J];中国计量;2006年09期
3 黄咏梅,张宏建,胡赤鹰,韩冬;新DFT递推算法在涡街流量信号处理中的应用[J];浙江大学学报(工学版);2003年01期
，本文编号：2257633
本文链接：https://www.wllwen.com/kejilunwen/yiqiyibiao/2257633.html
