| As a kind of flow measurement equipment,ultrasonic flow meter has a very wide range of applications in residential water,industrial production and agricultural irrigation.This is due to the advantages of ultrasonic flowmeters with high detection accuracy,small size,small pressure loss and low power consumption.Compared with traditional mechanical water meters,ultrasonic flowmeters have absolute advantages in flow measurement accuracy,but there are still many problems that need to be solved,such as the test results are not robust,and the detection accuracy is susceptible to pipeline fluid temperature changes and flow fields factors such as change.Therefore,in the field of ultrasonic flowmeter flow measurement,continuously improving the accuracy of flow measurement and overcoming the influence of pipeline fluid flow field and temperature changes on the measurement accuracy has always been the subject of continuous exploration by manufacturers and researchers.The ultrasonic flowmeter designed in this paper adopts the time difference method for the flow measurement principle.Based on the detection principle of the time difference method,a related compensation scheme is proposed,which solves the problem of affecting the detection accuracy due to the change of the pipeline fluid flow field and the temperature change.In the first and second chapters of this paper,the market application field and development process of ultrasonic flowmeters are described,and the current mainstream flow measurement and measurement principles of ultrasonic flowmeters are introduced.The methods based on its detection principle discuss the reasons that affect the accuracy of flow detection.From its root cause analysis,it is concluded that changes in pipeline fluid temperature and changes in pipeline fluid flow field are the main reasons affecting the accuracy of ultrasonic flowmeter flow measurement.Therefore,in the third chapter of this article,the research on the targeted compensation scheme is carried out according to the analysis conclusion of the previous chapter.With the help of Soild Works,this paper simulates the trajectory of pipeline fluids in different boundary layers under different flow fields.The simulation results provide experimental support for the application of microelement method and Newton's equilibrium law.Analyzing the simulation results,this paper gives the compensation coefficient K between the average surface velocity V_m and the average linear velocityV_L of the pipeline fluid under laminar and turbulent conditions.In view of the influence of pipeline fluid temperature changes on detection accuracy,this paper proposes two compensation schemes:temperature measurement look-up method and engineering empirical method with the help of TDC chip and temperature sensor,in order to overcome the pipeline fluid temperature change on ultrasonic flowmeter flow detection Influence of accuracy.This article is based on the DN20 ultrasonic flowmeter designed based on the principle of time difference detection.In the fourth and fifth chapters of this paper,the key chip components selection,hardware circuit schematic diagram and related functional programs are given respectively.This article takes the national ultrasonic water meter industry standard GB/T 778 2017 as the basic framework,with the main purpose of improving the precision measurement of ultrasonic flowmeters,designing ultrasonic flowmeters that meet national standards.The ultrasonic flowmeter designed in this paper has the following functions:LCD meter display,data storage,24-month historical flow accumulation query,pipeline fluid flow rate display,time and date display,battery voltage display,NB remote meter reading and temperature detection.This article uses the ultrasonic flowmeter calibration table experimental platform to verify the designed ultrasonic flowmeter.According to the compensation scheme proposed in this paper,the compensation principle is incorporated into the algorithm,and multiple experimental measurements are made on the pipeline fluid at different calibrated flows,and the experimental data is recorded,the measurement error is calculated,and the measurement error curve is fitted.By analyzing the corrected measurement error curve,it can be concluded that the compensated flow measurement error is within 2%,which meets the national requirements for ultrasonic flowmeter detection accuracy.Comparing the detection results before compensation,the detection accuracy has been significantly improved,confirming that the compensation scheme for pipeline flow field changes and temperature changes in this paper is effective,which is of great significance to the development of ultrasonic flowmeters. |
PDF Full Text Request