| In natural gas pipeline transportation process, changes of pressure, opening of valve and gas consumption have resulted changes in the operation of natural gas pipeline. Flow turns from steady to unstable, which has caused pulsatile flow and surge of pressure-regulating valve that influences safety and metering in natural gas production.Jidu-Heshu natural gas pipeline has been taken to fully reveal rules that surge of the downstream pressure-regulating valve influences on performance of orifice metering. Based on the basic equation of gas flow in pipeline and using the TVD difference schemes to simulate transient flow in natural gas pipeline. Analysis of pressure, flow and effects of orifice metering performance revealed that surge of pressure-regulating valve in HeShu station has resulted errors of orifice flowmeter. After 43.7 seconds, the pressure wave propagated to the upper entrance, which caused fluctuations of outlet pressure of orifice flowmeter. Owing to orifice function, the pressure wave superposed. At 48.74 seconds, outlet pressure of orifice flowmeter is larger than the inlet pressure, which caused counter current and errors of orifice metering. When actual flow reaches to 4701.7m3/d, the reactive error is 200%. Based on reasons and conditions, to install check valve in the HeShu station is the best way to ensure the accuracy of natural gas measurement. |
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