Influence of diffuser angle on discharge coefficient of sonic nozzles for flow-rate measurements

摘要

A series of numerical simulations were conducted to investigate the influence of diffuser angle on discharge coefficient of sonic nozzles for gas flow-rate measurements satisfied with the regulation of ISO-9300 and operated at atmospheric condition with throat diameter from 0.15 to 5 mm and 2.0 × 10~3 ≤ Re_d ≤ 6.6 × 10~4. When throat diameters are larger than 1 mm, the discharge coefficients are almost the same for nozzles with different diffuser angles, while they increase with increasing diffuser angle for smaller nozzles. A concept or effective critical flow was introduced to explore the effect of diffuser angle on discharge coefficient. Using a new parameter, effective throat diameter or deviation of effective throat diameter from the minimum effective diameter 8, a very good description is derived to discuss the effect of diffuser angle on the discharge coefficient.