差分式层流流量传感技术研究

Research on the Differential Type Laminar Flow Sensor

层流流量计非常适合于纯净气体微小流量测量,但是常规层流流量测量方法为了保证较好的流量-差压线性关系,其毛细管需要很长,导致层流流量计存在压损大的问题。提出一种差分式层流流量传感技术,该技术中层流流量传感器包括两段长度不同的毛细管组,工作时,分别测量两段毛细管组两端的差压,并取两个差压之差,即差压差分值,用于流量计算。通过差压差分,毛细管进出口局部损失和层流起始段流动损失等非线性压降被抵消掉,差压差分值与流量之间具有理想的线性关系。介绍了差分式层流流量传感技术原理,分析了传感元件中沿流道的压降特性,设计了模型传感器并进行了实验测试。实验结果表明,在(0.016~2.500)m 3/h的流量测试范围内,差分式层流流量传感器流量测量误差在±1%以内,证明了这一新型层流流量传感方法的正确性。

Laminar flow meter is very suitable for the small flow rate measurement of pure gases.However,conventional laminar flow measurement method requires long capillary tubes in order to ensure a good linear relationship between flow rate and differential pressure,which leads to a problem of large pressure loss.This paper presents a differential type laminar flow sensor,which consists of two capillary tube bundles with different lengths.The differential pressure at both ends of the two capillary tube bundles is measured respectively,and the difference of the two differential pressures,namely the differential pressure difference value,is taken for flow calculation.By getting difference of the differential pressures,nonlinear pressure drops such as local loss of the capillary inlet and outlet and the flow resistance loss of the initial flow are inter-neutralized,and there is an ideal linear relationship between the differential pressure difference and the flow rate.The principle of the differential type laminar flow sensing technique is introduced,the pressure drop characteristics along the flow passageway in the sensor element is analyzed,a model sensor unit is designed and tested.Experimental results show that the flow measurement error of the differential type laminar flow sensor is less than±1%within the flow measurement range of(0.016~2.500)m 3/h,which verifies this new laminar flow sensing technique.