Smart Grid and Renewable Energy, 2012, 3, 239-245 Published Online August 2012 (
Performance Investigation of a Simple Reaction Water
Turbine for Power Generation from Low Head Micro
Hydro Resources
Abhijit Date, Ashwin Date, Aliakbar Akbarzadeh
School of Aerospace, Mechanical and Manufacturing Engineering, RMIT University, Melbourne, Australia.
Received January 30th, 2012; revised May 3rd, 2012; accepted May 10th, 2012
Theoretical investigation has shown a simple reaction water turbine would perform better when it spins faster. And for
the simple reaction turbine water turbine to spin faster under constant water head, its diameter should be smaller. This
paper reports on a performance analysis based on the experimental data collected from different performance tests car-
ried on two simple reaction water turbine prototypes. Two new designs of simple reaction water turbines and their
manufacturing methods are reported. The two turbines under investigation have different rotor diameters Φ 0.243 m and
Φ 0.122 m. In case of the simple reaction water turbine the water enters into the turbine axially and exits tangentially
through nozzles located on the outer periphery of the turbine. Further this paper will discuss the performance character-
istics of stationary turbine i.e. zero power produced and performance characteristics of turbine producing power. It was
found that rotor diameter affects the maximum rotational speed of the simple reaction turbine for constant supply head.
It was also found that faster the turbine spins its performance improves. The two turbines were tested between supply
head range of 1 m to 4 m.
Keywords: Barker’s Mill; Hydro Electric Low Head; Simple Reaction Turbine; Water Turbine
1. Introduction
The role of renewable energy in tomorrow’s world is of
great significance for the global environmental stability.
Sun, wind and flowing or stored hydro (water) are con-
sidered the most common renewable energy sources for
power generation. Out of these three renewable energy
resources, the advantage of hydro energy is that it can
continuously supply energy and can serve as a base
power. The annual global hydropower production is very
small as compared to the global power consumption.
However the technically exploitable hydro power poten-
tial available throughout the world is far more than is
actually been used as illustrated by the data from
Sterngerg Kaygusz and Taylor [1-3]. The world hydro
power scenario show that the technically exploitable po-
tential of hydro energy is about 14,000 TWh year and the
economically exploitable potential is about 8000 TWh
year, where as the present global hydro power generation
stands at 2800 TWh/year [2,4].
Looking at the above estimates it is clear that there is a
large potential of hydropower waiting to be exploited.
Further there is a large gap between technically exploit-
able and economically exploitable potential [5,6] which
creates a need for further research in hydropower tech-
nology to make it more economic and help to reduce this
gap. To date most of the large hydropower sites have
been exploited [7,8]. However, most of the small and
micro hydro sites are yet to be exploited.
Thus keeping in mind that the world currently is still
heavily dependent on non-renewable energy sources
(fossil fuels) such as coal, oil and natural gases, which
are rapidly diminishing and becoming increasingly more
expensive, the role of renewable energy has been recog-
nized to be significantly important in sustainable future
development. Hydropower is a good example of renew-
able energy; its present use and potential application to
future power generation cannot be underestimated.
The finding reported in this paper is based on the
theoretical and experimental investigations previously
reported by Date and Akbarzadeh [9,10]. Initially in this
paper theoretical performance analysis of a simple reac-
tion water turbine has been presented followed by the
design and fabrication method for split reaction water
turbine. Later the experimental set-up is discussed along
with the experimental procedures used. Further the ex-
perimental results are discussed with uncertainty analysis
presented for the experimental performance estimation.
Copyright © 2012 SciRes. SGRE
Performance Investigation of a Simple Reaction Water Turbine for Power Generation from Low
Head Micro Hydro Resources
parameters as a function of *T.
2. Theoretical Analysis of Simple Reaction
Water Turbine
Following the work done by Akbarzadeh [11] on para-
metric analysis of simple reaction water turbine, effi-
ciency and angular speed have been drawn as a function
of torque and shown in Figure 1. The universal charac-
teristics of this turbine are presented graphically in using
the dimensionless torque * as the independent vari-
able. Reducing the load torque applied to turbine from
the stationary to runaway condition corresponds to mov-
ing from right to left on the horizontal axis. Figure 1
shows the graphical representation of parameters
and *
as a function of non-dimensional torque.
The nature of an ideal simple reaction turbine as
shown in Figure 1 is illuminating, which shows how the
efficiency increases with increase in angular speed. Figure
1 further shows how a simple reactions turbine pumps
more water through the turbine as the angular speeds
increases due to centrifugal pumping effect. This cen-
trifugal pumping effect significantly increases the power
production capacity of this turbine and presents an op-
portunity to develop a compact water turbine for low
head hydro-power applications with low specific energy.
3. Simple Reaction Turbine and Specific
Specific speeds are commonly used as a tool for com-
parison of the characteristics of similar hydraulic ma-
chines. Here this tool is applied to simple reaction water
turbine, by using the formulation provided by Turton [12]
for the specific speed of turbines, the following relation
between specific speed and efficiency of a simple reac-
tion turbine has been derived as discussed by Akbar-
zadeh [11].
–3 4
Figure 1. Graphical presentationof dimensionles.
The effect of geometry on the relation between specific
speed and efficiency is expressed in terms of
However this can be changed to ratio of diameters i.e.
Dd where 2DR
and d is the diameter of the noz-
zle. Defining an equivalent exit nozzle diameter de as,
A (2)
Using the relation for the equivalent exit nozzle di-
ameter from Equation (2), we can re-write Equation (1)
as follows,
–3 4
It is not possible to present
as a function of
an explicit form [11]. However, the variation of
as a
function of
is presented for several values of diame-
ter ratio. It is seen in from Figure 2 that a simple reaction
turbine achieves higher efficiency for machines of higher
diameter ratio e
Dd , i.e. for a given diameter D, a
smaller nozzle exit area will improve efficiency. Since we
relate capacity of the turbine to the nozzle exit area, we
can then say that for the same specific speed and rotor
diameter, machines of smaller capacities would be more
efficient. It can be also seen from Figure 2 that efficiency
of a simple reaction turbine improves as the specific speed
increases. Considering the definition of
in Equa-
tion (3) this is equivalent to saying higher efficiencies are
achieved at high rotational speeds and higher flow rates.
This can be considered as an important conclusion in rela-
tion to the characteristics of simple reaction water turbine.
4. Design of Simple Reaction Water Turbine
This new design has very simple geometry, it can be
manufactured using a very basic skill set and can be
made from locally available materials (so low cost). The
Figure 2. Variation of efficiency with specific speed for
various diameter ratios.
Copyright © 2012 SciRes. SGRE
Performance Investigation of a Simple Reaction Water Turbine for Power Generation from Low
Head Micro Hydro Resources
split reaction turbine can produce power from very low
head hydro-sites (head range 0.3 m and flow rate of 10
litres per second). This simple reaction turbine is named
as “Split Reaction Turbine (SRT)” after its me- thod of
manufacturing [13,14]. Figure 3 shows the first SRT1
that has a diameter of 243 mm and height of 120 mm
with two exit nozzles each 6 mm wide. Therefore the
total exit area is 1440 mm². Figure 3 shows the second
SRT2 that has a diameter of 122 mm and height of 120
mm with two exit nozzles. The exit nozzle width of the
SRT2 could be varied in three steps 4.2 mm, 5.4 mm and
8 mm. Therefore the total exit area is 1440 mm². The exit
nozzle profile and the inner wall profile of the turbine
plays very important role in the efficiency of the turbine
and can be analyzed following the boundary layer and
viscous flow theory [15-20].
5. Experimental Test Rig and Test
Figure 4 shows the picture of the water turbine test rig
used for the performance analysis of the simple reaction
turbine prototypes. This test rig is divided into two main
sections: 1) Hydraulic power input unit, which is com-
prised of water pump, flow meter, pressure gauge, deliv-
ery pipe, and flow control system; 2) Power output unit
comprised the simple reaction water turbine with the
inlet rotary seal arrangement, the electric generator, the
DC electronic load, the tachometer.
Figure 3. Pictures of two split reaction water turbines.
DC generator
Electronic DC
Tachometer Supply pressure
Flow meter
Flow control
Figure 4. Water turbine test rig.
Here the water stored in the water tank (tank capacity 0.5
m³) is pressurized with the water pump and then this pres-
surized water is supplied to the turbine. After the water tur-
bine extracts the mechanical power from the water, it is
discharged back into the water tank for re-circulation
through the systems. The mechanical power produced by
the turbine is transmitted to the electric generator through
the solid flange coupling. Then the electric power pro-
duced by the generator is dumped into the DC electronic
load. The voltage and current are measured this helps to
estimate the electrical power output.
The stationary test is carried under different hydro-
static supply heads. This technique helps to estimate the
stationary torque produced by the turbine. The stationary
torque is equivalent to the maximum torque that turbine
can produce at a certain hydrostatic supply head. It also
helps to estimate the stationary water flow rate through
the turbine. This is equivalent to the minimum water
flow rate that a constant hydrostatic supply head can
produce. Finally, this test technique helps to estimate the
stationary discharge coefficient of the turbine.
Both the turbine prototypes discussed in Section 4
have been tested with this technique. Figure 5 shows the
experimental set-up used in the stationary test. During
the stationary test, torque arm is connected to the turbine
shaft and the force sensor (Dana Load cell capacity 20
kgf), the force sensor measures the tangential force at the
torque arm and this is used to estimate the stationary
torque. The force sensor is secured rigidly to the test rig
frame as shown in Figure 5. From this measurement, the
torque is deduced and hence the total reaction force of
the exiting water jets. Here water is supplied at constant
hydrostatic head, the supply pressure/head is monitored
on the pressure gauge, the flow rate is monitored on the
flow meter and the force (proportional to torque) is
monitored on the force sensor indicator (strain indicator),
at the same time all these parameters are also recorded.
In the stationary test, the flow rate is only dependent on
Load Cell (Force sensor)
Torque arm
Strain Indicato
Figure 5. Stationary torque and flow rate measurement
Copyright © 2012 SciRes. SGRE
Performance Investigation of a Simple Reaction Water Turbine for Power Generation from Low
Head Micro Hydro Resources
the supplied hydrostatic head as there is no centrifugal
pumping effect present that could alter the flow rate.
The relative velocity of the water jet at both the exit
nozzles is equal to the total volume flow rate of water
supplied to the turbine divided by the total exit nozzle
area. Ideally the torque produced at the turbine shaft
should be equal to the estimated torque, here estimated
torque is equal to product of absolute velocity, total mass
flow rate and mean turbine radius (when the turbine is
stationary the absolute velocity is equal to the relative
velocity). The turbine shaft torque is equal to the product
of the measured force (value of force in Newton) at the
turbine shaft times the torque arm length (in meters). The
stationary test results for both the turbine prototypes are
analyzed and discussed in next section.
Power test is used to measure and estimate the overall
performance of the turbine prototypes. During this test
the hydrostatic supply head is kept constant while the
load on the turbine is varied. This technique helps to es-
timate the maximum power produced by a turbine for a
constant hydrostatic head and the maximum energy con-
version efficiency (overall efficiency) of the hydroelec-
tric unit. It also helps to estimate the water flow rate
while turbine is rotating. Here the flow rate increases
with the increase in rotational speed due to centrifugal
pumping effect as discussed in Section 2 and illustrated
by Figure 1. Further, this test technique helps to carry
out the overall energy balance analysis of the hydroelec-
tric unit.
Both the prototypes were tested with power test tech-
nique at different hydrostatic supply pressures/heads
(range 1 m to 4 m) to estimate their performance charac-
teristics. At the beginning of a power test, the turbine is
allowed to rotate free without any electric load or some
times with very small electrical load, while the supply
pressure is held constant. At the same time parameters
like flow rate, rotational speed, output voltage, and out-
put current are recorded. Then the electric load is gradu-
ally increased in steps, this tends to decrease the rota-
tional speed of the turbine. This decrease in rotational
speed reduces the centrifugal pumping effect causing the
supply pressure to increase slightly. The supply pressure
is then adjusted to its original value with the flow control
device (3 phase frequency controller) connected to the
water pump as shown in Figure 4. The parameters like
supply pressure, flow rate, rotational speed, output volt-
age and output current are recorded for each step when
load is increased. The increase in load is continued till
the turbine slows down to about quarter of no-load rota-
tional speed. This procedure is repeated for different
supply pressures to analysis the performance characteris-
tics of both turbine prototypes.
The mechanical power produced by the turbine is
equal to sum of electrical power output, plus the power
lost in DC generator, plus the power lost in overcoming
turbine air drag plus the power lost in friction at the ro-
tary seal. For a permanent magnet DC motor/generator
only a few constants and equations linking them are
needed to describe the relationship between speed, torque
and current [21]. The DC motor torque constant t
defined as the ratio between the torque and the current.
The DC motor/generator constant t
is estimated by
using the equations and the performance data provided in
the Baldor DC motor catalogue and the numerical value
of t
is estimated as 0.902.
The electrical power output from the DC motor/gen-
(Watts) can be estimated using following
tg g
I is the generator output current (Amp) and
V is the generator output voltage (Volts) ad both are
measured during the power test. Finally the turbine out-
put power (i.e. the actual mechanical power output from
turbine before any bearing frictional loss, mechanical
seal frictional loss and turbine drag loss) (Watts) is
estimated using following equation,
The power loss loss in overcoming the turbine air
drag plus the power loss in friction at the rotary seal was
measured using the procedure discussed in the earlier
publications [10,13]. The turbine efficiency is the ratio of
the actual mechanical output power divided by the rate at
which potential energy is supplied to the turbine.
6. Experimental Results and Discussion
Stationary tests have shown that the discharge coefficient
for both SRT prototypes is quite similar and it varies
between a numerical value of 0.96 to 0.98. Figure 6
shows the variation of discharge coefficient for SRT 1
and SRT 2 with respect to flow rate of water flowing
through the turbine. This shows that both turbine proto-
types have similar fluid frictional losses when the turbine
is held stationary.
Figures 7 and 8 show the relationship between y-axis.
Overall it can be seen that for both the turbines the fric-
tional power loss increases as the rotational speed. 800
rpm as can be seen from Figure 8. From experiments it
was observed that the air drag increases as the turbine
exit nozzle width of increase, this was due to shape of
turbine drifting away from a perfect circle to more ellip-
tical as the exit nozzle width is increased. In addition
Copyright © 2012 SciRes. SGRE
Performance Investigation of a Simple Reaction Water Turbine for Power Generation from Low
Head Micro Hydro Resources
Figure 3. Discharge coefficients against the flow rate.
Figure 4. Measured and estimated performance parameters
for SRT 1.
Figure 5. Measured and estimated performance parameters
for SRT 2.
to the air drag the mechanical power loss also contains the
power loss due to friction in the V-ring lip seal. It was
observed from the power loss tests that the power loss due
to V-ring lip seal sharply increased at higher rotational
speeds. The testing procedure used for measurement of
the power loss with V-ring seals was based on the previ-
ous work [10]. Figure 9 shows the relationship between
the turbine efficiency and the rotational speed. The tur-
bine efficiency is defined as the energy conversion effi-
ciency from potential energy in the water to mechanical
energy at the turbine. Here the considered inefficiency is
only due to the fluid frictional losses. It can be seen from
the Figure 9 that SRT2 has higher turbine efficiency then
SRT 1 and as discussed earlier in Sections 2 and 3, this
increase in efficiency can be attributed to the higher rota-
tional speeds of the turbine. The effect of reduced air
drag of SRT 2 is not considered in estimating the turbine
7. Uncertainty Analysis
Uncertainty analysis of the measured and estimated pa-
rameters was carried out following the law of error
propagation [22]. The uncertainty analysis of the ex-
perimental data from stationary test shows that the esti-
mated torque has a relative uncertainty of ±4.41% and
the measured torque has a relative uncertainty of ±1.13%.
The uncertainty in the measured volume flow rate is
about ±2.5% and the uncertainty in the estimated dis-
charge coefficient Cd is only ±2.53%. This shows that
the experimental procedure and instrumentation used has
a good level of confidence and reliability.
The relative uncertainty in the estimation of the total
output power is estimated as maximum ±5.02%. The
relative uncertainty in the estimation of the rate of poten-
tial energy supplied to the turbine is estimated as ±2.70%.
From these calculated quantities of the relative uncer-
tainties it is confirmed that the experimental procedures
used for conducting the performance power test on the
simple reaction turbines in this research have very high
level of confidence and reliability.
8. Conclusion
Most of the low head hydro turbines are large and bulky
Figure 6. Estimated turbine efficiency for SRT 1 and SRT
Copyright © 2012 SciRes. SGRE
Performance Investigation of a Simple Reaction Water Turbine for Power Generation from Low
Head Micro Hydro Resources
as they have to handle large volume flow rates to pro-
duce reasonable power and then have low efficiency. The
above analysis shows that the simple reaction water with
small diameter can efficiently produce power without
having to be large and bulky. The energy conversion
efficiency of a simple reaction water turbine increases
with the increase in the rotational speed. The theoretical
analysis also shows that the turbine efficiency approaches
its maximum value as the load torque approaches the
50% of the stationary torque. Theoretical analysis also
shows that a simple reaction water turbine will spin faster
as the turbine diameter is reduced. From the experimental
analysis it was confirmed that a turbine with smaller di-
ameter tends to rotate faster in comparison with a turbine
with larger diameter, when both are supplied with same
hydro static head. Additionally the small diameter rotor
will have less air drag power losses. The theoretical pre-
dictions have shown that a simple reaction water turbine
would have higher efficiency at higher rotational speeds.
SRT 2 (Φ 0.122 m) has approximately half the diameter
as compared to SRT 1 (Φ 0.243 m) and the test results
have shown that SRT 2 rotates twice as fast as SRT1
under same hydro static head. Further the test results
have shown that SRT 2 has higher turbine efficiency as
compared with SRT 1. So it can be concluded that the
higher turbine efficiency is due to the fact that turbine
rotates at higher rotational speeds and is supported by the
theoretical predictions. The uncertainty analysis has
shown that the experimentally measured results and the
estimated results have reasonable relative uncertainties
and so the findings of this study can be used as a basis
for future investigation. Future work should involve ex-
perimental investigation of SRT’s with even smaller di-
ameters and smoother nozzle profiles.
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Performance Investigation of a Simple Reaction Water Turbine for Power Generation from Low
Head Micro Hydro Resources
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Nomenclature R Radius of the turbine (m)
T Torque (N-m)
Total exit area (m2)
Actual mechanical output power (W)
C Discharge coefficient
Angular speed of the rotor (radian/s)
d Exit nozzle diameter (m)
Density of water (kg/m3)
D Equivalent exit nozzle diameter (m)
Turbine Efficiency
Turbine diameter (m) SRT Split reaction turbine
Acceleration due to gravity (m/s2) SRT 1 Rotor diameter Φ 243mm
Supply head (m) SRT 2 Rotor Diameter Φ 122mm
Specific speed of turbine
Mass flow rate of water through the turbine