Research On Flow Field Characteristics And Measurement Performance Of Turbine Flowmeter

With the increasing emphasis on the advancement and improvement of industrialization in recent years,the measurement of fluids needs to be more precise.As the main representative of speed flowmeter,turbine flowmeter is widely used in fluid measurement in various fields.However,its performance is susceptible to the state of the fluid being measured and its structure,resulting in excessive pressure loss or poor repeatability.In recent years.computer technology has developed rapidly,so it is meaningful to use modern fluid mechanics to analyze the internal flow characteristics of turbine flowmeters.Therefore,this paper intends to analyze the internal flow field of the turbine flow sensor by numerical simulation method,aiming to study the internal flow mechanism of the fluid.reduce the pressure loss of the flowmeter and improve the measurement performance of the flowmeter.In this paper,a large-diameter turbine flow sensor of a meter factory in Tianjin is taken as the research object.The simulation model is built according to the actual parameters,and the model is divided into structured grids by ANSYS ICEM CFD software.Using the steady-state simulation method,the pressure field of the sensor at the flow rate of 150m3/h is obtained:the pressure is at the leading edge of the blade,and the lowest pressure region near the inlet of the blade is located from the blade.The top penetrates to the root of the leaf.The pressure loss portion is mainly concentrated at the impeller and the rear deflector,and there is a recirculation zone at the end of the rear fluid,and the fluid pressure drop caused by the recirculation zone is small.The transient simulation method is used to calculate the sensor at the minimum flow point,which verifies that the Reynolds stress model(RSM)has higher simulation accuracy.It is found that the sensor under this flow is affected by the front deflector blades,and the impeller inlet speed changes periodically,which is also the root cause of the cyclical variation of the impeller torque.The impeller inlet speed at the maximum flow point is less affected by the leading flow guide vanes,and the change with the rotation time is slower,with better rotation stability.and greater pressure loss between the front and rear guide vanes under large flow.The model of different hub clearances,different tip clearances,and different blade trailing edge angles is calculated by the steady-state simulation method.It is concluded that the linearity error does not change much when the front and rear hub caps increase simultaneously and decrease by 2 mm.The K value of the meter coeffcient increases with the increase of the flow rate.Increasing the hub clearance increases the low velocity of the impeller,and the change is more pronounced at large flow points.Increasing the hub clearance at the same flow rate increases the pressure loss.and the relationship between the pressure loss and the flow rate is approximately a quadratic polynomial.The decrease ofthe tip clearance at low flow rate will result in uneven low velocity of the inflow section and the outflow section,which is not conducive to the stability of the impeller.In contrast,the impeller stability is better under large flow.The smallest tip clearance of the three structuires produces the largest linearity error.but results in a smaller pressure loss.The pressure loss caused by a 0.5 mm increase in the tip clearance at high flow is 10 times that of a small flow.Finally,the paper proposes that the trailing edge of the blade can be cut at two different positions.which reduces the linearity error.The meter coefficient of the 1/4-cut angle sensor is larger under the small flow rate.and the surface pressure of the blade is also higher.The sensor has a larger meter factor.but the blade surface pressure is lower.The 1/2 chamfered structure provides less pressure loss and better sensor performance.