热式流量计的误差分析及精度提升方法研究

发布时间：2018-09-11 13:18

【摘要】：热式质量流量计(Thermal Mass Flowmeter)是利用传热原理实现流量测量的仪表,其成本低,原理、结构简单,无可动部件,压力损失小,测量范围大,是当前质量流量计的研究热点,广泛用于汽车电子、半导体工业、能源与环保等领域,但目前对热式流量计的误差理论研究不足,国内市场的热式质量流量计普遍测量精度不高,另外,对热式流量计传感器深入的理论研究也很少,而传感器作为直接感知流量信号的元件,其热学特性对整个流量计的精度也有着重大影响。针对热式质量流量计测量精度不高的问题,本文主要研究工作如下：1) 研究了常用类型的热式流量传感器,通过深入分析传感器的特性,提出一项应用于流量测量时的技术指标：测速响应时间,并设计实验进行了分析研究；2) 从测量原理、数据处理、元器件性能等方面分析了热式质量流量计的测量不确定度来源,对主要测量不确定度来源气体温度变化、插入深度偏差进行重点研究,给出了相应的测量不确定度传播系数；3) 详细分析研究目前的恒温控制和温度补偿方法,指出目前所用方法的缺点和不足,在此基础上提出了一种精度提升方法——数字闭环恒温控制及数字化温度补偿方法；4) 设计并搭建实验平台,进行热式质量流量计样机的标定实验,拟合标定数据得到不同温度点下的流量计特性曲线以及特性曲线系数与温度的函数,并设计实验验证提出的精度提升方法的有效性与准确性。
[Abstract]:Thermal mass Flowmeter (Thermal Mass Flowmeter) is an instrument that uses heat transfer principle to realize flow measurement. Its cost is low, its principle is simple, its structure is simple, it has no moving parts, its pressure loss is small, its measurement range is large, and it is the research hotspot of mass Flowmeter at present. Widely used in automotive electronics, semiconductor industry, energy and environmental protection, but the error theory of thermal Flowmeter is not enough, the domestic market thermal mass Flowmeter measurement accuracy is not high, in addition, As a component of direct sensing flow signal, the thermal characteristics of the sensor have a significant impact on the accuracy of the Flowmeter. In order to solve the problem that the measurement accuracy of thermal mass Flowmeter is not high, the main research work in this paper is as follows: 1) the common types of thermal flow sensors are studied, and the characteristics of the sensors are deeply analyzed. A technical index used in flow measurement: response time of velocity measurement is put forward, and the experiment is designed to analyze and study the measurement principle and data processing. The sources of measurement uncertainty of thermal mass Flowmeter are analyzed in terms of the performance of components and components. The variation of gas temperature and the deviation of insertion depth from the main sources of measurement uncertainty are studied emphatically, and the transmission coefficient of measurement uncertainty is given. 3) the current methods of constant temperature control and temperature compensation are analyzed and studied in detail, and the shortcomings and shortcomings of the current methods are pointed out. On the basis of this, a method of improving precision is proposed, which is digital closed loop constant temperature control and digital temperature compensation. 4) designing and building the experimental platform, carrying on the calibration experiment of the thermal mass Flowmeter prototype, fitting the calibration data to get the characteristic curve of the Flowmeter at different temperature points and the function of the coefficient of the characteristic curve and the temperature. Experiments are designed to verify the effectiveness and accuracy of the proposed method.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TH814

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