Design and Simulation of the Distributer and Nozzle of a Micro Hydro Pelton Turbine
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Date
2018-03
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Addis Ababa University
Abstract
Pelton turbine is a type of hydraulic turbine in which energy carried by water is converted into
kinetic energy by providing nozzle at the end of the penstock. The performance of this turbine
depends on the nozzle shape and the distributer. In this paper attempts were made to study the
effect of different nozzle shapes, nozzle angle, distributer bend, split angle, spear shape and
spear angle.
CATIA V5 and Ansys Fluent software were used to design and analysis of the numerical
simulation for all the models developed. For the design and simulation of nozzle and
distributer, a jet diameter of 54.4mm, flow rate of 0.14m
3
/s and the total head of 50m were
taken. And also the nozzle angle of (30-45) in degree and the spear angle of (20-25) in degrees
were fed to Ansys and then it generates 82 samples. So, the effect of each angle in the range
was analyzed. The value obtained from Ansys parameter correlation depicts that nozzle angle
of 30 degree and spear angle of 20 degree gives maximum efficiency. And finally the variation
of blocking distance on efficiency and performance of the intended result was critical, sample
values in mm from (0-93) was evaluated and best performance was found at blocking distance
of 80mm. And more over, as the flow rate varies seasonally or due to flow rate regulation,
ranges of flow rate in m
3
/s from 0.1 up to 0.009 per single nozzle was considered for the
baseline and optimal design.
Results obtained from numerical simulation on contours of static pressure, contours of velocity
magnitude, and velocity vectors were colored inside the fluid interior for all models. So the
comparison and analysis made on the model is based on the color magnitude on the legend bar
of velocity and pressure. The result showed that, increasing the pipe diameter of distributer
results in the reduction of head loss. However, since the optimal diameter is 142 mm, further
increment in pipe diameter increases the cost of pipe. The other critical and notable factor to
mention from the study was the nozzle angle and nozzle efficiency. i.e. As the nozzle angle
increases the nozzle efficiency decreases due to back flow at the exit of the nozzle. In the end,
increasing pipe diameter of distributer decreases the hydraulic energy inside the nozzle.
The performance of the nozzle at different flow rate and different closing distance were
analyzed and efficiency of 96.8 % was achieved. Finally after the nozzle and distributer
optimized separately, then by integrating both components i.e. distributer and nozzle and their
simulation were analyzed and 96.5% efficiency was obtained.
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Keywords
micro-hydro Pelton turbine, distributer, nozzle, spear, CFD, optimization