Analysis of shift in discharge coefficient for contaminated multihole orifice flow meter

The aim of this paper is to provide a comprehensive numerical study of influence of contamination and multihole orifice (MHO) flow meter geometry on shift in discharge coefficient. In this research, authors analyzed steady, three-dimensional, turbulent flow of dry air through MHO flow meter with 3 different beta parameters. Shift in discharge coefficient was calculated for 29 different combinations of contamination parameters for 7 contamination angles, 3 different Reynolds numbers and 3 beta parameters. Numerical method that was used was finite volume method with SIMPLE algorithm and standard k-epsilon turbulence model. Grid sensitivity study was performed on four systematically refined numerical grids for MHO with contamination for all values of Reynolds number, all values of beta parameters and 3 values of contamination angle. Obtained results were grid independent. Numerical results for MHO without contamination were compared with the experimental results found in the literature. It was found that contamination angle has most influence on shift in discharge coefficient. Also it was found that the contamination has influence on the change of pressure drop values, which directly affects the change of other parameters. Pressure drop and singular pressure loss coefficient of the orifice with contamination are smaller compared to the values for a pure orifice, whereby the measurement accuracy was reduced. It was found that the multi-hole orifice meter was less sensitive to the pressure drop changes due to the increasing of contamination angle in regards to the single-hole orifice meters.