2 Influence of inner wall coating on hydraulic friction coefficient
Therefore, when the absolute roughness of the inner wall of the pipe increases, the hydraulic friction coefficient will increase accordingly, and after the inner coating is used, the absolute roughness of the inner wall of the pipe will be significantly reduced, and the hydraulic friction coefficient will be finally reduced, and finally the flow performance of the medium is improved. Improve delivery efficiency and increase tube throughput.
3 Influence of inner wall coating on pipe transport capacity
The basic formula for the calculation of gas pipelines (the gas transport formula with an elevation difference of less than 200 m) is Q = C(p 2 1 - p 2) D 5 Z TL( 3) where: Q is the volume of natural gas under standard conditions. Flow, m 3 /s; p 1, p 2 are the calculated starting and ending pressures of the pipe section, MPa; D is the inner diameter of the pipe, m; T is the average temperature of the natural gas in the pipe, K; C is a constant; L is the end of the pipe Distance; Z is the natural gas compression factor.
Under the same conditions, the relationship between the output Q and the hydraulic friction coefficient can be obtained. Substituting the Colebrook formula into equation (3) yields Q 0 Q = 0 0 5 (4) where: a zero-mark indicates that there is an undercoat; and a no-corner indicates that there is no undercoat.
Substituting other friction coefficient calculation formulas, such as the Panhandle formula (= 1 11 81Re 0 146 1) into equation (3), can be obtained: Q 0 Q = 0 0 539 4 ( 5) The Soviet natural gas formula ( = 1 68 03Re 0 039 2) Substituting (3), you can get: Q 0 Q = 0 0 51 (6) It can be seen that no matter which formula is used, 0 < can be obtained, so Q 0 > Q. According to some literature reports For pipes with a roughness of 45 m before laying, when the roughness is reduced by 90%, the friction coefficient is reduced by 33%, and the output can be increased by 24%.
4 Influence of inner wall coating on the station spacing of booster station
In the case of the same volume, working pressure and other factors, from equation (3): L 0 L a = 0 (7) where L a is in the pipeline along the line, one of the booster stations and the next increase The distance between the stations is the same, because 0 < , so L a > L 0. With the use of the inner coating, the use distance increases, and the station spacing of the booster station increases accordingly, which can reduce the number of booster stations. According to foreign data, after using the inner coating on the gas pipeline, the number of booster stations can be reduced by 1/5.
5 Influence of inner wall coating on compressor power consumption
An important part of the gas transmission cost of the gas pipeline is the power consumption of the compressor, and the power consumption is calculated based on the power of the compressor. Generally, centrifugal compressors are used, and the reciprocating compressor should be used when the station pressure is high and the output is small. The centrifugal compressor is taken as an example to illustrate the effect of the inner coating on the compressor power.
When the gas pipeline compressor station uses a centrifuge, the compressor power can be calculated according to formula (8): N = 4 008 10 - 6 mm - 1 TBZB 1 qvm - 1 m - 1 (8) where: N is compression Machine power, kW; m is the variable index (m = 1 2 1 3); TB is the compressor suction temperature, K; ZB is the compression coefficient at the compressor suction; is the compressor efficiency; is the compressor pressure ratio, = 1 4 1 6.
From the flow formula (3), the relationship between the pipeline pressure and the friction coefficient can be obtained when the elevation difference is less than 200 m: p 2 1 - (p 2) 2 0 p 2 1 - p 2 = 0 (9) (9) The left numerator and the denominator are simultaneously divided by p 2 1 to obtain: 1- 1 2 0 1- 1 2 = 0 (10) The formula (10) can be obtained to obtain a compression ratio with an overcoat layer: 0 = 2( - 0) + 0(11) Therefore, it can be obtained that for a plain area with an elevation difference of less than 200 m, the ratio of the compressor power with or without the overcoat layer is N 0 N = m - 1 m 0 m - 1 m = m - 1 m 2( - 0) + 0 m - 1 2m - 1 m - 1 m - 1(12) Similarly, the formula for the volumetric uplift is Q = 1 051 < p 2 1 - p 2 (1+ h) >D 5 Z TL 1+ 2L ni= 1(hi + h i- 1)L i 0 5( 13)= 2g ZR T where: L is the length of the gas pipeline calculation section; R is air The gas constant, under standard conditions, R = 287 1 m 2 /( s 2 K); h is the difference between the end point of the gas pipeline and the starting point of the calculation section, m; n is the number of segments calculated along the gas pipeline; Hi is the end point elevation of each calculated segment, m; h i-1 is the starting point elevation of each calculated segment, m; L i is the length of each calculated segment, m; i indicates that the elevation of the terrain relief is h 1, h 2, h 3, i = 1, 2, .
Similarly, the ratio of the compressor power with or without the overcoat layer when the terrain is undulated according to equation (13) is N 0 N = m - 1 m 0 - 1 m - 1 m - 1 = m - 1 m C 2 ( - 0) + C 0 m - 1 2m - 1 m - 1 m - 1( 14)C= 1+ h It can be seen from equations (12) and (14) that after the use of the inner coating, the compressor The gas delivery power will decrease.
6 Conclusion
After the inner coating of the inner wall of the natural gas pipeline is laid, the flow characteristics of the natural gas in the pipeline can be effectively improved and improved; the number of compressor stations along the pipeline can be reduced; the power cost of the transportation and the pumping cost can be reduced; Pipe volume; can extend the pigging cycle; can reduce the transmission power consumption and pumping costs.
Therefore, the pipeline inner coating technology has good economic benefits, and this technology has been widely adopted in foreign natural gas pipelines, and has achieved good benefits. Domestically, we should also master and develop the inner coating technology of natural gas pipelines as soon as possible, which will benefit the development of the natural gas pipeline industry.
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