The Research and Application of Critical-Flow-Subsonic Venturi Nozzle (The Extended Application of the ISO 9300 Critical Flow Venturi Nozzle)

摘要

The ISO 9300 Critical Flow Venturi Nozzle can be operated properly only in critical flow. If critical flow is not obtained, either a wrong measurement results, or the measurement is stopped if U>Ukp is confirmed. In addition, the measuring range of the Venturi nozzle is limited by the working pressure of the air source, therefore, the range of the measurement is small. Per the ISO 9300 standard, the critical flow Venturi nozzle is transformed into a critical-flow-subsonic Venturi nozzle with function of taking pressure on the throat. A high accurate differential pressure convertor and the corresponding software are introduced, the multi-measuring range intelligent flowmeter with the function of determination of critical pressure ratio is constituted. During the measurement, the flow state is judged automatically. If U≤Ukp, the flow is critical. The calculation of the flow volume and the accuracy of measurement are completely same as the ISO 9300 critical flow Venturi nozzle type. If U>Ukp, the flow is subsonic. The pressure converter engaged in the calculation of flow volume, and a high accuracy of measurement is ensure.