Research And Analysis On Water Hammer Protection In Long-distance And Multistage Pressurized Supply Heating Water Pipe Network

In recent years, the constructions of the city central heating system is experiencing a rapid development, the most obvious features are the bigger heating scale, the higher heat medium parameters and the longer transport distance. Water hammer, as a physical problem in supply heating water pipe network, has significant harms, for a slight water hammer could cause the pipe leakage, increase water supplement and results in unstable operation. It could also seriously effect the heating supplies for residents, even threats people’s lives and properties,thus the importance of water hammer can not be ignored. Especially in large scale projects such as long-distance and multistage pressurized supply heating water pipe network, its probability of the occurrence of water hammer will be higher, and the destructive force will be greater. It’s an urgent problem that how to ensure the safe operation in long-distance and multistage pressurized supply heating water pipe network and how to protect the network from water hammer damage, and this is the focus of this thesis.Based on the fundamental theories of water hammer and according to the characteristics of long-distance and multistage pressurized supply heating water pipe network, this thesis introduces the difficulties and methods of water hammer protection. It not only gives the boundary conditions which is commonly used in this kind of supply heating water pipe network and establishes the corresponding mathematical model of water hammer calculation,but also compares and analyzes the advantages and disadvantages of several water hammer protection devices, and gives a detailed description of its working principle and boundary conditions. Based on the example of the long-distance and multistage pressurized supply heating water pipe network project of Gujiao Xingneng power plant to Taiyuan, by using Microsoft Visual C++ program to carry out numerical simulation for the unsteady flow in pump-stopping water hammer, the thesis compares and analyzes the water hammer protection effect under different conditions when respectively using over-pressure relief valve、one-way surge tank、air pressure tank and box-type two-way surge tank, founding that installing the two-phase closed slowly-closing check valve at the outlet of the water pump, and the box-type two-way surge tank in the specified pile number could effectively reduce the water hammer pressure in the pipeline, which might be the best water hammer protection scheme.Through the analysis of the above contents, this thesis draws some conclusions and suggestions which can better promote the research and development of water hammer protection in long-distance and multistage pressurized supply heating water pipe network.These conclusions and suggestions may have a certain reference value on how to avoid the water hammer occurrence in long-distance and multistage pressurized supply heating water pipe network in design, construction, commissioning, and operation.