Study On Water Hammer Protection Of Long Distance Pressure Pipeline Water Transmission Engineering

China is lack of water resource. The water resource amount per capita is small and the resource distribution is seriously uneven both in temporal and spatial over the country, meanwhile, a lot of water has been polluted. Therefore, to a great extent, the development of social economy and improvement of people's living standard are restricted. In order to satisfy water demand and promote the development of social economy, in our country, many long distance pressure pipeline water transimission projects have been built. Their pipileines are long and flow conditions are so complicated that complicated hydraulic transients easily occur. Although the duration of hydraulic transients is transient, serious engineering accidents may be caused. Several problems of the water hammer protection of long distance pressure pipeline water transimission are studied in this paper. The major contents are as follows:(1) Based on experiments in laboratory, hydraulic transients of pressure pipeline DN40 are measured, and the results of which are analyzed by method of characteristics. The anthor conludes that the results of Brunone unsteady friction model and traditional first-order model are consistent under the condition that closing speed of the valve is not too fast.(2) Air valves are widely used in water supply systems for their compact structure, low cost and convenient installation, etc. Air valves have the functions of air release during the pipeline being filled with water, air inbreathe and release during accidental or normal operation of the pumps and water hammer protection, etc. Differences between tested data and formula calculated results of air valve in hydraulic transient are analyzed in this paper, and the author puts forward that the air valve selection should be based on the tested data.(3) Experiments are carried out in laboratory. Dynamic local resistance coefficient of ball valve is preliminarily studied in this paper. Dynamic local resistance coefficient of ball valve is related to velocity rate of change. The minimum of the tested dynamic local resistance coefficient of ball valve and static local resistance coefficient of ball valve are consistent.(4) According to a real engineering project, after pumping station unit selection, flow rate and pipeline arrangement are determined, optimal design for long distance water supply pipeline by pump is performed by using linear programming method. Optimal design for pumping station is carried out with minimum annual cost. Then, hydraulic transients of the pipeline are analyzed and calculated, and reasonable water hammer protection measures are selected.