CHARAGERIZATION OF THE DISCHARGE COEFFICIENT OF A SONIC VENTURI NOZZLE

Abstract

This paper identifles and determines the main parameters used to calculate the dlscharge coefficlent of a toroidal Venturl nozzle accordlng to the ISO Standard 9300, operating at the critical flow regime (sonlc). Thls study was conducted to investigate the effeds of the viscous stresses In the turbulent boundary layer, the wall thermal boundary condition, and the flow fleld curvature at the nucleus of the nozzle on the dlscharge coefflclent by means of a theoretical and numerlcal approach. Characterlzation of the dlscharge coefflclent in the Venturi sonlc nozzle was performed consldering the viscous and multidlmenslonal effects of the flujd flow as uncoupled phenomenon. As a result. each non-ideal mechanism can be  analyzed independently from the Inftuence of the other mechanlsm. We present a numerlcal procedure to characterlze the dlscharge coefflclent In the invlscld reglon of the ftow, by uslng the numerical simulation of the inviscld maln ftow by means of the commerclal CFD code. In the region of the vlscous stresses, the charaderlzation of thls coefflclent is based on the analytlcal theory of the turbulent boundary layer. Thls charaderization allowed obtalning a correlation of the dlscharge coefflclent that was valldated by dlred comparlson between the experimental correlations of the dlscharge coefflclent In turbulent boundary layer proposed by ISO-9300 and the Korea Research Institute of Standards and Sclence (KRISS). Thls valldation was carried out for throat Reynolds numbers from 1.4 to 2.6x10'. The agreement of the theoretical and measured dlscharge coefflclents by these correlations was better than  0.2%.