Research And Development Of Gas Flow Standard Device For Sonic Nozzle

With the rapid development of the economy in China,the energy crisis has become more and more serious.As a clean energy source,natural gas is very popular among people.On the long-distance pipeline of China's large-scale West-East Gas Pipeline Project,various gas flowmeters are used in large quantities,mainly for the safe transportation and trade settlement of natural gas.Therefore,it is necessary to ensure the instrument quality and accuracy in use.In the metrology of our country,the scope of measuring instruments that the state compulsion examines includes gas flowmeters.Therefore,before the gas flowmeter is manufactured and used,the metering performance on the flowmeter nameplate must be checked or calibrated in the gas flow standard device.In order to improve the calibrating accuracy and verification efficiency of the gas flow standard device,based on the introduction of the background of the gas flow standard device,the current situation at home and abroad,the development trend and the working principle,a gas flow standard device for the critical flow Venturi nozzle method is designed.The device mainly includes the vacuum gas source,the standard part,the test pipeline part and the upper computer system,the lower computer system and the data acquisition and processing,process control and verification software system.The device uses the upper computer(PC)and the lower computer(PLC)two level computer,the following computer(PLC)control unit as the core,carries on the data acquisition and processing of humidity,time,pressure,temperature,frequency,current and other parameters,and realizes the switching of the detection pipe,pump,valve group and other switching action control,and on the top of the device.Bit machine(PC)carries out information communication through RS485.The software system mainly consists of the software module of the upper computer,including the initialization module,the parameter setting module,the device test module,the traffic verification module,the verification reportmodule and the historical data query module.The upper computer is connected with the display,mouse,keyboard,printer and so on.The operator can control the hardware and software system of the device by operating the verification software system,and output,print and query the corresponding verification data.The device can automatically calibrate or calibrate 14 kinds of gas flowmeters with different calibre,and give the instrument coefficient or indication error and repeatability.Shaanxi Academy of Metrological Sciences,as the northwest measurement and testing center,not only undertakes the measurement and testing work in the province,but also undertakes the measurement and testing work in the whole northwest region.In recent years,the measurement volume of gas flowmeter has increased year by year.In order to meet the verification needs,Shaanxi Institute of Metrology has established a set of negative pressure critical flow Venturi nozzle method gas flow standard device.This device takes the atmosphere as the source,the advantage is that the gas source is stable,the system is relatively simple,and the investment and operation costs are relatively small.This paper chooses gas vortex flowmeter and gas turbine flowmeter to analyze the uncertainty of measurement results for the repeatability experiment and stability test of the device.