Prediction Meter Factor of Turbine Meter Considering the Effects of Cavitation

Turbine meters are wildly used in many fields for flow measurement with high accuracy and good repeatability, but the curve between meter factor and flow rates is affected by cavitation flow inside the meter. Cavitation is the main physical phenomenon which will have great effects on meter factor of turbine meters, especially at large flow rate. The meter factor will change at different cavitation number and will increase when the cavitation number decreases. In order to study its effects on meter factor, transient unsteady numerical simulation is carried out with RNG turbulence model and UDFs (User Defined Functions) based on torque balance equation in FLUENT software. The condensation/evaporation Cavitation Model is included at the simulation process. The results showed that the meter factor increased with the decrease of the cavitation number, and the meter factor is larger than at non-cavitation condition. Also the dynamic characteristics of the turbine flow meter impeller are obtained for the prediction of its meter factor and pressure distributions are obtained by the unsteady numerical simulation. The bearing friction drag is included in the torque balance equation, which is deduced from the theory of bearing.