Research On Flow Measurement Of Eccentric Venturi Tube Based On Flow-3D

The throat diameter reduction ratio of eccentric venturi is the main structural parameter affecting its flow measurement performance.In this paper,the numerical simulation method is used to analyze the discharge coefficient,pressure head loss and flow field characteristics of eccentric venturi flowmeter.Considering the three factors of flow measurement accuracy,pressure head loss and the required length of straight pipe section at downstream outlet of eccentric venturi flowmeter,the appropriate diameter reduction ratio of eccentric Venturi flowmeter in DN200 to DN500 is proposed.In the numerical simulation of eccentric venturi,the geometric model of DN200 to DN500 eccentric venturi was built with Solidworks software,taking the reducing ratio of 0.35 to 0.90 as the variation range,and then the flow situation of water in eccentric venturi was simulated with Flow-3D software,and the numerical simulation results of outflow coefficient,pressure loss and flow field characteristics were analyzed.The results show that the average range of discharge coefficient of DN200 to DN500 eccentric venturi is 0.958 to 0.981,the average range of local head loss coefficient is 0.14 to 0.24,and the recommended suitable reducing ratio ranges are 0.45 to 0.80,0.45 to 0.80,0.45 to 0.80,0.45 to 0.80,0.45 to 0.80,0.45 to 0.80,0.45 to 0.70 and 0.45 to 0.70,respectively.When the flow measurement accuracy is required to be high,the eccentric venturi with small reduction ratio should be selected;when the pressure loss is required to be small and the outlet straight pipe section is required to be short,the eccentric venturi with large reduction ratio should be selected.Compared with the classical venturi,the flow measurement performance is analyzed and it is found that the outflow coefficient error of the eccentric venturi is slightly larger than that of the classical venturi,but both errors are within the acceptable range of 5%.In terms of pressure loss,for the eccentric venturi with DN300 diameter and 0.45 to 0.80 reduction ratio,the pressure loss is 6%to 14%more than that of the classical venturi,and the highest head loss is 0.05m,which is several times higher In the aspect of flow field characteristics,the flow field of classical venturi tube is symmetrical and smooth,and there is only slight backflow around the back of the diffusion section close to the tube wall,forming a small range of backflow area;the backflow phenomenon of the back of the eccentric venturi tube near the upper tube wall is more obvious,the range of the backflow area is larger,and the streamline returns to a stable state The length of the downstream straight pipe needed for the steady state will be slightly longer than that of the classical venturi.In a word,the eccentric venturi is slightly inferior to the classical venturi in measurement stability,measurement error,head loss and the required length of straight pipe section at downstream outlet,but the difference is small and almost negligible.However,the anti clogging performance of eccentric venturi pipe is better than that of classical venturi pipe,so it will have a broad application prospect in the field of low-pressure pipeline water delivery and irrigation with many sediment impurities.