An Investigation Into the Performance of Two Inlet Nozzles for Flow Measurement

The discharge coefficients for two inlet nozzles with different contraction shapes were studied experimentally together with the behavior of the boundary layer on the nozzle wall. For the inlet nozzle which has the same contraction shape as the ISA 1932 nozzle, it was found that boundary-layer transition with an intermediary separation bubble is responsible for the occurrence of a large hump in the discharge coefficients. The well-rounded inlet nozzle showed a satisfactory performance. The effect of pressure tap size and that of the proximity of a wall to the inlet on discharge coefficients were quantified experimentally.