Similar articles

Abstract: A trapped air pocket can cause a partial air lock in the top of a hump pipe zone. It increases the resistance and decreases the hydraulic cross section, as well as the capacity of the water supply pipeline. A hydraulic model experiment is conducted to observe the deflection and movement of the trapped air pocket in the hump pipe zone. For various pipe flow velocities and air volumes, the head losses and the equilibrium slope angles are measured. The extra head losses are also obtained by reference to the original flow without the trapped air pocket. Accordingly, the equivalent sphere model is proposed to simplify the drag coefficients and estimate the critical slope angles. To predict the possibility and reduce the risk of a hump air lock, an empirical criterion is established using dimensional analysis and experimental fitting. Results show that the extra head losses increase with the increase of the flow velocity and air volume. Meanwhile, the central angle changes significantly with the flow velocity but only slightly with the air volume. An air lock in a hump zone can be prevented and removed by increasing the pipe flow velocity or decreasing the maximum slope of the pipe.

Influence of an air lock in the top of a hump pipe zone on a capacity of the water supply pipeline is discussed in the manuscript. The trapped air pocket can obstruct water flow due to increase in pressure losses. Although this problem is quite well recognized in the literature, it is still important from a practical point of view. The authors analyzed the influence of water flow rate in the pipe and the volume of an air pocket on both the friction and the critical equilibrium of the trapped air. The experiments were conducted for various pipe flow velocities and air volumes, to observe the deflection and movement of the trapped air pocket and to measure head losses. To describe the drag coefficients and estimate the critical slope angles Authors proposed a simplified model of trapped air pocket, called the Equivalent Sphere Model (ESM). Thus the calculations in the article relate to the assumed shape of the air pocket.

供水管路中驼峰气阻的临界平衡实验研究

[1]Brown, L., 2006. Understanding Gravity-Flow Pipelines Water Flow, Air Locks and Siphons. http://www.itacanet.org/understanding-gravity-flow-pipelines-water-flow-air-locks-and-siphons/

[2]Burch, T.M., Locke, A.Q., 2012. Air lock and embolism upon attempted initiation of cardiopulmonary bypass while using vacuum-assisted venous drainage. Journal of Cardiothoracic and Vascular Anesthesia, 26(3):468-470.

[3]Burrows, R., Qiu, D.Q., 1995. Effect of air pockets on pipeline surge pressure. Proceedings of the Institution of Civil Engineers-Water, Maritime and Energy, 112(4):349-361.

[4]Carlos, M., Arregui, F.J., Cabrera, E., et al., 2011. Understanding air release through air valves. Journal of Hydraulic Engineering, 137(4):461-469.

[5]Chaiko, M.A., Brinckman, K.W., 2002. Models for analysis of water hammer in piping with entrapped air. Journal of Fluids Engineering-Transactions of the Asme, 124(1):194-204.

[6]Epstein, M., 2008. A simple approach to the prediction of waterhammer transients in a pipe line with entrapped air. Nuclear Engineering and Design, 238(9):2182-2188.

[7]Escarameia, M., 2007. Investigating hydraulic removal of air from water pipelines. Proceedings of the Institution of Civil Engineers-Water Management, 160(1):25-34.

[8]Ferreri, G.B., Ciraolo, G., Lo Re, C., 2014. Storm sewer pressurization transient―an experimental investigation. Journal of Hydraulic Research, 52(5):666-675.

[9]Finnemore, E., Franzini, J., 2002. Fluid Mechanics with Engineering Applications (10th Edition). McGraw-Hill Education, Boston, USA, p.261-284.

[10]Greenshields, C.J., Leevers, P.S., 1995. The effect of air pockets on rapid crack propagation in pvc and polyethylene water pipe. Plastics, Rubber and Composites Processing and Applications, 24(1):7-12.

[11]Izquierdo, J., Fuertes, V.S., Cabrera, E., et al., 1999. Pipeline start-up with entrapped air. Journal of Hydraulic Research, 37(5):579-590.

[12]Lin, C., Liu, T., Yang, J., et al., 2015. Visualizing conduit flows around solitary air pockets by fvt and hspiv. Journal of Engineering Mechanics, 141(5):04014156

[13]Liu, T., Yang, J., 2013. Experimental studies of air pocket movement in a pressurized spillway conduit. Journal of Hydraulic Research, 51(3):265-272.

[14]Pothof, I., Clemens, F., 2010. On elongated air pockets in downward sloping pipes. Journal of Hydraulic Research, 48(4):499-503.

[15]Pothof, I., Clemens, F., 2011. Experimental study of air-water flow in downward sloping pipes. International Journal of Multiphase Flow, 37(3):278-292.

[16]Pozos, O., Gonzalez, C.A., Giesecke, J., et al., 2010. Air entrapped in gravity pipeline systems. Journal of Hydraulic Research, 48(3):338-347.

[17]Pozos-Estrada, O., Fuentes-Mariles, O.A., Pozos-Estrada, A., 2012. Gas pockets in a wastewater rising main: a case study. Water Science and Technology, 66(10):2265-2274.

[18]Pozos-Estrada, O., Pothof, I., Fuentes-Mariles, O.A., et al., 2015. Failure of a drainage tunnel caused by an entrapped air pocket. Urban Water Journal, 12(6):446-454.

[19]Reynolds, C., Yitayew, M., 1995. Low-head bubbler irrigation systems. Part ii: Air lock problems. Agricultural Water Management, 29(1):25-35.

[20]Vasconcelos, J.G., Leite, G.M., 2012. Pressure surges following sudden air pocket entrapment in storm-water tunnels. Journal of Hydraulic Engineering, 138(12):1081-1089.

[21]Yu, Y., 2015. Study of Critical Characteristic of Hump Air Resistor in Submarine Water Supply Pipeline. MS Thesis, Zhejiang University, Hangzhou, China (in Chinese).

[22]Zhou, F., Hicks, F., Steffler, P., 2004. Analysis of effects of air pocket on hydraulic failure of urban drainage infrastructure. Canadian Journal of Civil Engineering, 31(1):86-94.

[23]Zhou, L., Liu, D.Y., Karney, B., 2013. Investigation of hydraulic transients of two entrapped air pockets in a water pipeline. Journal of Hydraulic Engineering, 139(9):949-959.