Structural Optimization And Characteristics Of Inner And Outer Pipe Differential Pressure Flowmeter

Flow measurement is a significant component of metrology science and technology.It has an intimate relationship with national life,international trade,national defense construction and environmental protection.Differential pressure flowmeter is considered the most widely used type of flowmeter.It is used to measure gas and liquid flow in industrial production frequently.This article is based on the original inner and outer pipe differential pressure flowmeter to improve the flowmeter's sensitivity,accuracy and energy-saving.Finally,the inner and outer pipe differential pressure flowmeter is modified from throttle structure and the pressure method.A new type of inner and outer pipe differential pressure flowmeter throttle structure is proposed.Namely,the inlet tube section and the contraction tube section are added at the front of the inner tube of the inner and outer tube differential pressure flowmeter,so that the fluid entering the inner tube is accelerated and then decelerated.Meanwhile,the fluid entering between the inner and outer tubes is subjected to a rapid expansion and shrinkage deceleration.The maximum differential pressure value can be obtained where the difference between the fluid speeds of the inner and outer tubes is maximum,that is,the pressure of the middle pipe section with the largest pressure difference.By applying three-dimensional CFD simulation software,the internal and external pipe differential pressure flowmeters with different shrinkage angles,expansion angles and equivalent throttling ratios were simulated,and the performances of differential pressure flowmeters with different internal and external pipe diameters were compared and analyzed.The optimized new differential pressure flowmeter inside and outside the tube is selected to compare with the original internal and external differential pressure flowmeter with the same internal diameter and the differential flowmeter with opposite flow inside and outside the tube.Under the condition that the inlet velocity is 3m/s,the new type of inside and outside Pipe differential pressure flow meter differential pressure value is 3.4 times as much as the differential pressure value of the original inner and outer tube differential pressure flowmeter,is 2.6 times as much as the differential pressure value of the reverse flow inner and outer tube differential pressure flowmeter,the sensitivity has been greatly improved;new type of inner and outer tube differential pressure flowmeter pressure loss ratio is the original inner and outer pipe differential pressure flowmeter pressure loss ratio of 1/5,reverse flow internal and external differential pressure flowmeter pressure loss ratio of 1/4,energy efficiency has greatly improved.The structure of the throttle was optimized,meanwhile a new differential pressure flowmeter pressure-receiving method was proposed.The method of symmetrically taking pressure from the same section of the original inner-outer tube differential pressure flowmeter was optimized to be the same section and pressure tube in the same location.Single-ended pressure taking method for the inner pressure tube.The optimized new pressure-taking model ensures that the pressure-taking surface has the same height when the flowmeter is used for vertical measurement or horizontal measurement,eliminates the measurement error caused by the difference in the level of the pressure-receiving line,and the pressure-removing pipeline is simplified.The complexity of the connection makes it easier to connect with a differential pressure transmitter.On the basis of optimizing the structure of the internal and external pipe differential pressure meter throttles and the way of taking pressure,a new type of internal and external pipe differential pressure flowmeter experimental prototype was fabricated,the water flow and air flow experiments were performed respectively.Water flow experiment is ranged 2m3/h~24m3/h flow,selecting 12 working points and repeating the measurement three times.The experimental results show that this type of inner and outer pipe differential pressure flowmeter has stable performance in the large flow stage,the outflow coefficient is stably near 1.0,the pressure loss ratio is near 0.15,which has a good energy saving.Data processing software is selected to fit the water flow outflow coefficient curve,combining a fitting model of the water flow outflow coefficient C.This model is combined with a new type of flow calculation model for the differential pressure flowmeter of the inner and outer tubes to obtain the differential flow rate of the new inner and outer tubes,water flow measurement model.It has been verified that the relative error of the water flow measurement model is within ±0.7%.The air flow experiment selects six operating points within the flow range of 50m3/h~280m3/h,repeating the measurement three times.It is deemed that the data processing software is used to fit the curve of the air flow outflow coefficient,and the new type of differential pressure flowmeter is obtained.It has been verified that the relative error of the air flow measurement model is within ±1.4%.