Abstract: Numerical research on the orifice-plate of a powerplant was carried out to analyse the discharge coefficient and pressure distribution at different sections. Results shows that the pressure measurement holes should be set at positions with the maximum pressure in the upstream and minimum pressure in the downstream. The downstream pressure measurement hole should be set at a distance 0.3D to 0.5D away from the plate center; while the upstream pressure measurement hole should be set at a distance 0.5D to 1.5D away from the plate center. Since the distance between the pressure measurement holes could seriously affect the measurement accuracy of flow rate, the installation of the orifice-plate flowmeter must be in strict accordance with the size of pressure hole, and the discharge coefficient should be corrected according to the actual position of measurement holes. There were obvious reflux at the downstream of the typical section, and the reflux flow rate accounted for 15% of the total flow rate. This research could provide reference for the pressure measurement, installation, test and adjustment of orifice-plate flowmeter.

Key words: flowmeter, orifice plate, CFX, differential pressure, calculations