Research On Metering And Differential Control Of Urban Gas Pipeline Network

As to the city gas company, gas transmission error is an important economic index, which has a great impact on the cost of transportation and economic benefits of enterprise. As the expansion of city gas pipeline network, the problem of transmission error has attracted people’s attentation. For example, the annual total amout of city gas supply is442.4million cubic meters inChengduShuangliu in2006, but the amount of error has reached47.6million cubic meters and the error rate is2.98%. The annual total amout of city gas supply is29.34million cubic meters in a city gas company in the south of Sichuan province in2010, but the amount of error has reached9.48million cubic meters and the error rate is32.2%. The annual transmission amount of Huayou Natural Gas Company is60million cubic meters per day, if the error rate is1%(the unit price of natural gas is1.2yuan per cubic meter), so the possible gas loss is0.6million cubic meters per day, which causes0.72million economic loss per day and262.8million per year. So it is necessary to carry out the research of city gas pipeline network trasmission error to low the error rate.Main reasons to cause the city gas trasmission error are analysed from the angle of trasmission error components. The feature and current state of city gas metering are analysed. As a participator the new type cone flowmeter is designed, also the construction diagram. The modes of new type cone flowmeter and orific flwmeter are established basing on the software of FLUENT to contrast the straight pipe requirment, pressure loss, and capacity of resisting disturbance of new type cone flowmeter and orifice flowmeter. As a participator to design the performance contrasting experiments among turbine flowmeter, vortex precession flowmeter, orific flowmeter from the aspects of accuracy, pressure loss, interference capacity of flow state. The current state of city gas metering system management and the existing problems are analysed.It has been shown that the measurement deviation of city gas metering system is the main reason to transmission error, namely, the metering error is the main part of transmission error. The simulation results have shown performance advantage of the new type of cone flowmeter, which has shorter straight length, smaller pressure loss and less affecting by blent pipe. The flow coefficients and expansion coefficients of different orific and aperture ratio of new type cone flowmeter have obtained by the calibration experiments of new type cone flowmeter. The contrasting experiment results of new type flowmeter with other three types flowmeters show that the new type cone flowmeter has the feature of high precision and more stable, smaller pressure loss (β>0.55) and strong interference capacity (β=0.45). The scientific methods to choose metering instruments and management are introduced. The calculation method of city gas transmisson error index is proposed, which provide operation guidance to the city gas metering error.