浅析音速喷嘴装置中喷嘴间的相互影响

目前采用音速喷嘴作为传递标准的气体流量标准装置被国内外检测机构广泛使用。在使用时,将根据需要的流量使用单个或多个喷嘴组合。与国外音速喷嘴的实际应用相比较,国内装置在喷嘴的安装方式、结构排列和上游设计方面多有不同。在对装置进行不确定度评定时,需要考虑喷嘴间相互影响(包括数量和位置等)对流量不确定度的影响。本文基于国内两套音速喷嘴法气体流量标准装置,利用单个、多个喷嘴的组合,测得两组相近流量点下涡轮流量计仪表系数,计算出不同组合的仪表系数偏差。本文考虑了实验时各组实际体积流量差值的影响,利用曲线拟合的方法,拟合出涡轮流量计仪表系数特性曲线,给出拟合方程式。将流量不同带来的影响剔除,最终给出喷嘴间相互影响带来的偏差,两套装置得出由此影响带来的不确定度为0.02%和0.07%。因此,在对音速喷嘴装置进行不确定度分析时应考虑这一分量。此外,通过相近流量不同喷嘴的组合对流量计进行检测,可以发现和找出喷嘴的问题,也是一种装置期间核查的好办法。

Interaction Between Sonic Nozzles in Device

At present, the nozzle as gas flow transfer standard device is widely used in domestic and foreign testing organizations. In application, the selection of a single nozzle, a couple of nozzles or several nozzles depends on the required flow. Compared with the practical application of sonic nozzles abroad, domestic plants are different in such aspects as nozzle installation method, structure arrangement and the upstream design. In uncertainty evaluation, the interaction (numbers and positions) between nozzles should be considered. Two sets of sonic nozzle gas flow standard device from Beijing and Henan are chosen to measure two groups of similar flow points with turbine flow meter and calculate the deviation coefficients of different combinations of instruments. The uncertainty from this phenomenon is 0.02% and 0.07% respectively. Obviously, because of the nozzle processing, installation and use, two sets of sonic nozzle by means of experimental results are quite different. So the uncertainty analysis for the sonic nozzle device should consider this component. The job for evaluation of the standard device can be more scientific and accurate in this way.