Exploration On Fricition Head Loss Of Long-distance & Large-diameter Water Pipeline

With Chinese accelerating urbanization, the shortage of water resources seriously restrict the survival and development of city, water conveyance project become the main measure to solve the problem;Global warming, environmental pollution and other factors make long-distance and large-diameter pipeline win the designer’s pro- Lai.Piping materials are not limited to the traditional material(concrete pipe, steel pipe, cast iron pipe), and gradually turned to the new material(FRP pipe, prestressed concrete cylinder pipe(PCCP pipe), and so on).It was found that actual flow capacity of small trough inverted siphon and sangequan inverted siphon does not conform to the design standard in the north of Xinjiang water supply project since 2005.This paper explores the main causes of the problem;on the basis,researchs on hydraulic calculation method of large-diameter FRP pipe and PCCP pipe water, mainly for the friction head loss method; Equivalent roughness range and fricition coefficient(Hazen-Williams coefficient),which is suitable for different diameters during economic flow rate conditions,were given for the large-diameter FRP pipe and PCCP pipe engineering design.Conclusion:(1)After the small trough and sangequan inverted siphon prototype data analysis, neatening the pipeline hydraulic calculation method, identificating the flow pattern of pipeline under different flow rate; It is found that the flow pattern is in the turbulent transition zone, not generally considered rough area(square resistance region), but the turbulent flow roughness region calculation formula(Chezy formula) is used for the two kinds of inverted siphon hydraulic calculation. So the pipeline flow region judgment error is the main reasons,which caused "small trough inverted siphon flow is not enough, sangequan inverted siphon flow is surplus".(2)Through the identification on flow pattern of large-diameter pipe diameter size under different conditions, according to flow pattern to determine hydraulic calculation method,found that flow pattern of large-diameter pressure FRP pipe is the turbulent transition zone under normal conditions, not excluded the possibility that the turbulent smooth region; Large-diameter pressure PCCP pipe flow is also basically in turbulent transition region, but has the possibility to reach the turbulence rough region.(3) Jain,A.K formula and Harland formula are used to calculate the head loss value of small trough inverted siphon and sangequan inverted siphon; By comparing the calculation with the measured data, the results showed that: equivalent roughness values range of the large-diameter pressure FRP pipe should be 0.005~0.01 mm, PCCP large-diameter pipe range is 0.03~0.05 mm.(4)The Hazen-Williams formula is applied to hydraulic calculation of the small trough and sangequan inverted siphon; It is found that Hazen-Williams formula is no longer confined to the former’s experience theory(d<2.0 m, the pipe whose flow turbulent transition zone), but the formula can be suit for fricition head loss calculation of large-diameter pressure FRP pipe and PCCP pipe, and it can get more accurate results.