Study And Design Of Critical Flow Meter

The critical flow meter is applied to flow measurement, flow control and calibration of flow meter. There are far-ranging studies for it with the methods of theory and experiment for a long time at home and abroad. Recently, along with the development of computer technology, the numerical simulation of critical flow meter is being more attentioned. And with regard to the secondary instrument of critical flow meter, the intelligent flow display instrument which is based on single-chip is being applied more and more.This study includes three parts. Initially, numerical simulation research for critical flow nozzle with software FLUENT was carried out, it mostly contains the influence of structured parameters on the actual flow and the influence of the expansion segment on the critical back pressure ratio.Then, according to the result as above, the figure structure and assembly method of critical flow nozzle were designed. The relationship between the discharge coefficient and the Reynolds number was calculated with software FLUENT. And curve formula was given.Thirdly, secondary instrument of critical flow meter based on MCS51 single-chip was designed. This equipment is made up of temperature sensor, pressure sensor, A/D converter, single-chip, fluid display screen and around circuit, with the functions of date collection, flow calculation and flow display.The results of numerical simulation indicate: the radius of convergence arc and the length's of throat column influence the actual flow obviously, not other parameters; The critical pressure ratio will enhance with the increase of expanding segment's length, decrease with the increase of expanding angle. The test of the secondary instrument of critical flow meter which was designed in this article indicates that it can complete the functions requested, and the tolerance can be accepted.