1 summary

Now, the calibration that is used at the supersonic flowmeter with metric natural gas is as far as possible on discharge calibration device undertake. Since almost all these device use natural gas to had shed cop, connecting general reason condition to fall, impossible change affects the parameter of velocity of sound, for instance temperature, pressure, gas is comprised. When supersonic flowmeter is used if these parameter are alien the numerical value that leaves at calibration circumstance, can calibration still have effect?

The metabolic to supersonic flowmeter calibration effect that describes these parameter for mensurable ground, undertook a series of experiment of careful pilot calibration. The experiment of the first pace includes to be in southwest academy (SwRI) pressure 2.8MPa is used in high-pressured loop (400psi) calibration of natural gas medium a 200mm (8inch) with a 300mm (12inch) supersonic flowmeter. As additional referenced, the turbine flowmeter of 200mm and 300mm also applies in loop. Next nitrogen of fluid medium instead, velocity of sound changed 16% , numeric and classy effect at natural gas 4.6 MPa (677psi) pressure.

For the influence of further proof pressure to supersonic flowmeter calibration, in pressure from 1.4MPa (200psi) to 7MPa (1000psi) inside limits, the flowmeter of 300mm of diameter of use nitrogen speak or sing alternately undertook a series of statistical velocity of sound is measured. Measured value makes clear the 0.03% less than that the change in the velocity of sound inside this pressure limits is worth in computation.

In addition, to the change of the velocity of sound that the change of temperature and fluid medium brings about, had farther test. Be in with natural gas 21 ℃ (70 ℉) with 10 ℃ (50 ℉) have calibration test, be in with nitrogen 21 ℃ (70 ℉) with 32 ℃ (90 ℉) next undertaking. To the calibration of each series, curve of comparative and average calibration, reach change is opposite the influence of calibration. Below the device of contented expectation and flowmeter repeatability condition, the calibration to velocity of sound change of supersonic flowmeter, change of temperature and pressure does not have reaction. From natural gas when the fluid medium that is used at calibration change arrives when nitrogen, because to these two kinds of gas use condition equation differs,observed little change is.

If these test result prooves are supersonic the calibration order that flowmeter issues in a condition is feasible, it is OK also to be used below another conditions, include to use different aeriform medium.

2 foreword

The natural gas that is used at correlation to trade is metric the principle that uses supersonic flowmeter is the ultrasonic transmission time through measuring gas. Ultrasonic is in when with the fluid flow direction agrees, transmission time should is less than refluent the circumstance when. The transmission time difference below two kinds of condition is used at the average rate that computational gas flows. Real bulk flow can express with next type:
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