development of the optimal design model of water transmission pipeline (Case study: transmission line of outside of river bed Biston dam)

Due to the high cost of designing, construction and operation of dam reservoirs and related facilities, Optimization in the construction of reservoirs and related facilities to increase productivity and reduce costs has been considered by designers. In this regard, the development of computer software can be a great help to design engineers in such a way that boring manual calculations and calculation errors are reduced For this purpose, the main goal of the present study is to prepare and develop a computer model based on genetic algorithm in which the objective function that is the sum of the fixed and current costs of the transmission system during the useful life of the project, considering the velocity and pressure constrain was minimized. Simulation water hammer in the optimal system with and without control facilities is one of the secondary goals of this research.

In this study, the optimal design of the pumping station and transmission line is performed based on optimizing using the binary genetic algorithm with the objective function of minimizing fixed and current costs of the transmission system and pumping station during the useful life of the project. The study area is the pump station and water transmission line of Biston dam that is located in the outside of Gamasiab river bed in Kermanshah province. In order to optimize the unit length price of 24 pipes of different materials from nominal diameter 110 to 2000 mm as well as the specifications of all domestic manufacturing pumps and some imported pumps were defined as a database in the model. The type of pump and suitable pipes of conveyance line are selected by minimizing the cost function by observing the pressure and velocity constraints.

Model validation results in design of conveyance line by three case: 1- Reservoir - pipe system with end valve, 2- Pipeline with side branches on the slope and 3- Transmission line between two points with irregular topography indicated that the model optimize the transmission line by observing the pressure and velocity constraints in such a way that even in the design of a part of transmission line that placed on downhill slop (case 3) by selecting the optimal smaller diameter prevent overpressure along the transmission line. Then results of the design of the Biston Dam transmission line showed that the diameter of the 1600 mm steel transmission pipe and the centrifugal pump model of 200-50-500 have the lowest cost during useful life of 20 years. The water hammer simulation results on optimal system showed that an Air chamber with a radius of 3 meters and a height of about 5.5 meters that in the initial conditions, it is half full of water and its air pressure is about 86, It keeps the pipeline safe from the point of view of water hammer and sudden shutdown of the pumping station.

Reducing the constant and annual costs of conveyance line and pumping station of outside of river bed dams as much as possible can be effective in the economic explanation of the projects. In this research, in order to reduce the mentioned cost, optimal design of conveyance line and pumping station of outside of river bed Biston dams was considered. In this project it is necessary to transfer 3500 l/s water from Gamasyab river to Biston dam reservoirs during 6 months of the year (November to May) by the optimal transmission pipe line. For this purpose, a computer model was prepared and developed in which based on optimization by binary genetic algorithm method the transmission system is optimized. Model validation was performed using it for optimal design of several different cases and successful results were obtained. Then the optimization of the Biston dam transmission line was done. The result showed that use of 21 centrifugal pump model of 200-50-500 devices (84% efficiency and 78.5 m operating pressure) with steel pipe with a diameter of 1600 is optimal along the entire path. In this situation, the cost of purchase and piping the Biston water transfer project is 1,681,952$.