The purpose of this project was to calculate the dimensions of a centrifugal pump, for a determined application, to write a report and then to make an oral presentation, in English, to an auditorium. Therefore, this is a complete project from the choice of the specifications with documented research to the design of the pump. The first thing was to define the field of application and the specifications of the pump: water flow, engine rotation speed and characteristics of ducts before and after the pump. The entire pump installation has to be studied in order to calculate the total pressure drop in the system: length, radius and roughness of ducts, the eventual presence of elbows which increase local pressure drop, etc. We then use, for the calculation of the characteristics, an Excel software which is very simple to use and efficient. The second aspect was to work in groups, to divide the tasks into different parts. Then, at the end of the project, take stock of the situation and to compare our work with our initial aim.
[...] An ANSIMAG centrifugal pump Pump location What is expected: Water Flow 200 m3/h = 0.056 m3/s ( 792,5 GPM Head of water 220 m ( 721,8 ft Pressure 10 bars ( 145 PSI Canal characteristics Water Temperature T = 15°C ( 60 Voluminous mass ( = 999,17 kg/m3 ( 0.0360912 lb/in3 Dynamic viscosity ( = 0,00126 Pl Ducts characteristics Length L = 40 m ( 131,2 ft Diameter D = 100 mm ( 0.328084 ft Roughness ( = 0,1 mm Pump characteristics Engine rotation 2900 tr/mn ( 303,69 rad/s speed Materials : Suction and discharge casing in ductile iron Diffuser and impeller in cast iron Shaft in stainless steel Part two : the theory Phenomenons to avoid Cavitation The formation and subsequent collapse of vapor-filled cavities in a liquid due to dynamic action is called cavitation. [...]
[...] Calculation of the available NPSH : Calculation of the required NPSH : with Calculation of the maximum value of suction without cavitation : with This is a non-linear equation with the HaMAX as unknown. Algorithm Arbitrary values In fact, the algorithm used for the pump characteristics calculation is simple but repetitive, that is why we need a software. When the algorithm has converged, it gives us results. Before using the algorithm, we must calculate the number of stages we need for our pump. In this aim of view, we used the specific speed ns (also called Brauer number) and is fixed to 25. [...]
[...] The last part shows the results of the calculation with few graphs: head of water, efficiency and power of the pump (in function of the flow) and compares our pump with those of the industry. A brief conclusion will end this report. The last page sum up data about the fluid, ducts, the pump . Part one : Presentation Pump operating principle General information. Pumps are used to add energy to the fluid. Fluid machines can be divided into two main categories: positive displacement machines (denoted as the static type) and turbo-machines (denoted as the dynamic type). [...]
[...] For large centrifugal pumps, a diffuser is used to guide vanes surround the impeller. The diffuser vanes decelerate the flow as the fluid is directed into the pump casing. The casing shape is designed to reduce the velocity as the fluid leaves the impeller, and this decrease in kinetic energy is converted into an increase in pressure. Pump impellers can be single or double section. For the single-suction impeller, the fluid enters through the eye on one only side of the impeller, whereas for the double-suction impeller the fluid enters the impeller along its axis from both sides. [...]
[...] jc is the pressure drop due to impact of the fluid on the wheel : jc = Va with jf is the pressure drop due to the friction : Jf = with = 6816,6 Then this formula will give us Hu : Hu = Hth jf jc = Hth - - Va Then Hu = Hth jf jc Part three : results Graphs The following graph is a summary of the different characteristics of the pump in function of the water flow. [...]
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