利用节流孔板提高液氨计量表计量准确度的试验研究

EXPERIMENTAL RESEARCH ON IMPROVING THE MEASURE CCURACY OF ANHYDROUS AMMONIA METER WITH RESTRICTION ORIFICE

液氨计量表示值误差，主要受液氨介质在流经计量表时产生汽化形成气液二相流的影响。作者对研制的液氨计量表在出口处设置节流孔板以建立背压、提高和维持液氨的液相压力、降低示值误差进行了理论分析、试验设计和探索性试验，建立了压力与节流孔径间的函数关系式和压力随节流孔径变化率的函数式。通过对二种介质（水、液氨）的计量试验检测和数据处理分析，得出了影响液氨计量表主要性能指标（示值误差及压力损失）的关键因素的主次、优水平、优水平组合及置信度。

The anhydrous ammonia meter(AAM)is one of important instruments in straw ammo-niation system. The indication error of the AAM that is a main function index of the AAM,is affected by anhydrous ammonia gasification forming gas-liquid fluid when it flows themeter. In order to reduce the indication error of the AAM , the restriction orifice is put at theAAM exit,that in use for establishing the back pressure of the AAM,raising and keeping theliquid state pressure of anhydrous ammonia. In this paper , the functional relation betweenpressure and diameter of the restriction orifice , the relationship of the pressure changed fol-lowing different diameter of the restriction orifice are set up by theoretical analysis. Accord-ing to the experiment design plan and the exploratory tests ,the major-minor key factorsthat influence the main function indexes of the AAM,the optimum level and its assemblageand the believing degree of these are obtained by means of experiment with two kinds ofmedium, water and anhydrous ammonia,and processing the experimental data. The resultsof test indicate that the gasification of anhydrous ammonia in the AAM could be reduced, theflowing state of anhydrous ammonia in the AAM could be improved and the measure accura-cy of the AAM could be raised by the restriction orifice.