Impulse turbines use jets of water that make contact with turbine blades to turn the runner. Examples include Pelton wheels for high heads, Turgo turbines for medium heads, and Jonval wheels where water is directed sideways onto curved vanes. Pelton wheels can generate up to 200 MW and are best for heads from 15-1800m. Turgo turbines are a modified Pelton design used for heads from 15-30m. Calculations are provided for determining the speed and power output of a Pelton wheel turbine based on variables like water flow rate and velocity.

1. 2012
Impulse Turbines
Mo’tasem Abushanap
TUTO
11/4/2012

2. 4/11/2012 Mo`tasem Ash
Impulse Turbines
Definition
In an impulse turbine the runner operates in air, and is turned by one or multiple jets of water
which make contract with the blade. A nozzle converts the pressurized low velocity water into a
high speed jet much like you might use with a garden hose nozzle. The nozzle is aligned so that it
provides maximum force on the blades; they can be used for medium and high heads.
Examples of this type are:
a- Pelton Wheel: it is suitable for high heads and low flows, best operating heads 15-
1800m, it can generate up to 200 MW.
b- Turgo: it is a modification of Pelton wheel where the runner is a cast wheel whose shape
generally resembles a fan blade that is closed on the outer edges. The water stream is
applied on one side, goes across the blades and exits on the other side, it used for medium
heads, its head range 15-30m.
c- Jonval Wheel: in which water descends through fixed curved guide vanes which direct
the flow sideways onto curved vanes on the runner
d- Water wheel: a machine for converting the energy of free-flowing or falling water into
useful forms of power, often in a watermill. A water wheel consists of a large wooden or
metal wheel, with a number of blades or buckets arranged on the outside rim forming the
driving surface. Most commonly, the wheel is mounted vertically on a horizontal axle,
but the tub or Norse wheel is mounted horizontally on a vertical shaft. Vertical wheels
can transmit power either through the axle or via a ring gear and typically drive belts or
gears; horizontal wheels usually directly drive their load.
Impulse
Turbines
Pelton
Wheel
Whater
Jonval Turgo
Wheel
Figure 1.1 Impulse Turbines
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3. 4/11/2012 Mo`tasem Ash
Figure 1.3 Impulse Turbines
Calculation of Pelton Wheel
ηs=√ …………………………………………………………………1
P.E=m.g.h………………………………………………………………….2
K.E= m.V2…………………………………………………………………3
Vi=√ ………………………………………………………….……….4
 Assume that al velocity vectors are parallel to each other.
 Define speed of the runner as (u).
Vi-u = initial velocity relative to runner speed.
Vf=(-Vi+u)+u= -Vi+2u……………………………………………….……5
If Vf=0, then we have Ideal speed
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4. 4/11/2012 Mo`tasem Ash
u=Vi/2…………………………………………………………….……….6
which means that all the kinetic energy in the jet is transferred to the wheel.
By applying newton’s 2nd and 3rd laws
F = -m(Vf-Vi)
= -ρQ[(-Vi+2u)-Vi]
= -ρQ(-2Vi+2u)
=2ρQ(Vi-u)……………………..……………………………….……….7
T= F(D/2)
=ρQD(Vi-u)……………………………………………………..………..8
P=ω.T
=F.u
=2ρQ(Vi-u)*u………………………………………………….…………9
Assume Vf=0,
Pmax= ρQVi2/2
Pmax= ρgHQ…………………………………………………..………….10
η= 4u(Vi-u)/Vi……………………………………………….…..………11
References
1. http://en.wikipedia.org/wiki/Hydraulics
2. http://www.turbinesinfo.com/what-is-a-turbine/
3. http://www.wisegeek.com/what-is-a-turbine.htm
4. http://www.thermopedia.com/content/859/
5. http://en.wikipedia.org/wiki/Turbine#Types
6. http://hassam.hubpages.com/hub/Types-Of-Turbines
7. http://www.ehow.com/list_7453448_types-hydraulic-turbines.html
8. http://www.energybible.com/water_energy/water_turbines.html
9. http://en.wikipedia.org/wiki/Pelton_wheel
10. http://www.frenchriverland.com/pelton_wheel.htm
11. http://www.microhydropower.com/our-products/pelton-wheel/
12. http://en.wikipedia.org/wiki/Turgo_turbine
13. http://www1.eere.energy.gov/water/hydro_turbine_types.html
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5. 4/11/2012 Mo`tasem Ash
14. http://en.wikipedia.org/wiki/Jonval_turbine
15. http://en.wikipedia.org/wiki/Water_wheel
16. https://d2t1xqejof9utc.cloudfront.net/screenshots/pics/ebbc86d5d057cef74fb3c8d59d697
9e3/medium.jpg
17. http://www.hydrogenappliances.com/pelton_wheel_diagram.gif
18. http://upload.wikimedia.org/wikipedia/commons/thumb/5/5e/Turgo_turbine.png/220px-
Turgo_turbine.png
19. http://upload.wikimedia.org/wikipedia/commons/3/3f/Waterwheel_2.png
20. http://upload.wikimedia.org/wikipedia/commons/thumb/5/53/Overshot_water_wheel_sch
ematic.svg/220px-Overshot_water_wheel_schematic.svg.png
21. http://www.british-hydro.org/mini-hydro/images/turgo-sketch.gif
22. http://upload.wikimedia.org/wikipedia/commons/thumb/7/7c/Schiffbau_jonval2.jpg/200p
x-Schiffbau_jonval2.jpg
23. http://www.pioneer-sys.net/images/microhydro/micro_7.gif
24. http://www.pumpfundamentals.com/micro-hydro.htm
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