The upstream effect on back pressure ratio Chunhui Li, lich@nim.ac.cn NIM, P. R. China

Background

The experimental system

Reynolds number effect sonic nozzles Orifice plate SN throat diameter flow Reynolds number apertures [mm] [m3/h] [/] 8601 4.0250 8.80 5.25×104 18.218 8602 5.9090 19.20 7.76×104 8603 7.0020 26.90 9.14×104 8604 7.9820 35.30 1.05×105 30.708 8605 9.0855 45.30 1.19×105 8606 9.9360 54.50 1.31×105 8607 11.0320 67.50 1.46×105 8608 12.4440 85.00 1.64×105 8609 13.6740 104.00 1.81×105

Type I-SN.8601

Type II-SN.8602

Geometrical effect Sonic nozzle Orifice plate SN Throat diameter [mm] Diffuser angle [°] Reynolds number apertures 01 10.021 6 1.34×105 30.708 02 10.020 4 03 10.018 2.5 04 5.006 6.69×104 18.218 05 5.038 6.74×104 06 5.010 6.70×104

10mm-6。

Conclusions The upstream condition or flow condition effect can be positive or negative, which may be related with the ration of the tube diameter to the throat diameter? The measurement of CBPR on site may be necessary?

Discharge coefficient in transition region How to relate the discharge coefficient and Reynolds number during the transition region!