i TABLE OF CONTENT TOPIC PAGE 1.0 INTRODUCTION 1 2.0 OBJECTIVE 3 3.0 PROCEDURE 4 4.0 RESULT 4.0.1 SAMPLE CALCULATION 4.0.2 INPUT POWER TABLE
5 5 6 5.0 DISCUSSION 8 6.0 CONCLUSION 9 REFERENCE 10
1 1.0 INTRODUCTION
There are two types of turbines, reaction and the impulse, the difference being the manner of head conversion. In the reaction turbine, the fluid fills the blade passages, and the head change or pressure drop occurs within the runner. An impulse turbine first converts the water head through a nozzle into a high-velocity jet, which then strikes the buckets at one position as they pass by. The runner passages are not fully filled, and the jet flow past the buckets is essentially at constant pressure. Impulse turbines are ideally suited for high head and relatively low power. The Pelton turbine used in this experiment is an impulse turbine. The Pelton turbine consists of three basic components as shown in Figure 1: a stationary inlet nozzle, a runner and a casing. The runner consists of multiple buckets mounted on a rotating wheel. The jet strikes the buckets and imparts momentum. The buckets are shaped in a manner to divide the flow in half and turn its relative velocity vector nearly 180°.
2 The primary feature of the impulse turbine is the power production as the jet is deflected by the moving buckets. Assuming that the speed of the exiting jet is zero (all of the kinetic energy of the jet is expended in driving the buckets), negligible head loss at the nozzle and at the impact with the buckets (assuming that the entire available head is converted into jet velocity), the energy equation applied to the control volume shown in Figure 1 provides the power extracted from the available head by the turbine
P availableQH available (1)
where Q is the discharge of the incoming jet, and Havailable is the available pressure head on the
nozzle. By applying the angular momentum equation (assuming negligible angular momentum for the exiting jet) to the same control volume about the axis of the turbine shaft the absolute value of the power developed by the turbine can be written as
P ωT 2 NT (2)
where ω is the angular velocity of the runner, T is the torque acting on the turbine shaft, and N is the rotational speed of the runner. The efficiency of the turbine is defined as the ratio between the powers developed by the turbine to the available water power
h
=
In general the efficiency of the turbine is provided as isoefficiency curves. They show the interrelationship among Q, w, and h. A typical isoefficiency plot is provided in Figure 2.
3 Figure 2: Isoefficiency curve for a laboratory-scale Pelton turbine.
Under ideal conditions the maximum power generated is about 85%, but experimental data shows that Pelton turbine are somewhat less efficient (approximately 80%) due to windage, mechanical friction, back splashing, and non uniform bucket flow.
2.0 OBJECTIVE
To learn the design and function of a Hydraulic turbine. To determine the impulse turbine characteristic
To determine the power curves characteristic
To produce the data of output power and torque against speed To test the output performance at different nozzle setting To determine the optimum efficiency point
To compare the mechanical & electrical power To determine the generator efficiency
4 3.0 PROCEDURE
The apparatus was set up with Pelton turbine mounted on the stainless steel frame. The control valve was ensured to be fully opened and slowly close the bypass valve. The nozzle jet was preset to be fully opened position for this experiment. The water from
the nozzle jet will make the turbine to rotate.
The pump was switched on to let the water flow into the nozzle.
The by-pass valve was adjusted slowly until the turbine reaches the maximum speed. The nozzle was adjusted to find out the maximum performance point (with suitable
speed, flow and pressure).
The reading for each meter was recorded.
Now, the Load On/off switch was switched on to load the generator.
The reading for each meter was recorded and the DC Ampere showed the ampere produce from generator.
The knob of rheostat was adjusted by turning anti-clockwise. The speed of generator was reduced. The reading for each meter was recorded. The reading for every 200 RPM decrement was recorded.
Test until the ampere meter show the maximum value, (HHHH). The by-pass valve was not adjusted during run the experiment.
The reading was put in table and the output power and efficiency of turbine was calculated.
The graph was plotted and the optimum working point was found. The experiment was repeated by different nozzle opening.
5 4.0 RESULTS
Table 1: Hydraulic Input Power (Without Load) NO. GENERATOR TORQUE (Nm) GENERATOR SPEED (rpm) WATER PRESSURE (bar) WATER PRESSURE (Pa) WATER FLOW RATE (lpm) WATER FLOW RATE (m3/s) VOLTAGE (Vdc) CURRENT (Adc) 1 0.03 2497 2.13 213000 44.5 0.000383 21.8 0.0 2 0.03 2300 1.82 182000 43.6 0.000406 20.7 0.0 3 0.03 2102 1.60 160000 42.4 0.000366 18.9 0.0 4 0.02 1903 1.38 138000 39.9 0.000342 15.2 0.0 5 0.02 1704 1.22 122000 36.4 0.000334 11.7 0.0 6 0.02 1503 1.05 105000 7 0.02 1300 0.89 89000 8 0.02 1101 0.75 75000 9 0.01 904 0.61 61000 10 0.01 704 0.50 50000 11 0.01 500 0.40 40000 12 0.01 302 0.31 31000 13 0.01 166 0.25 25000
Table 2: Hydraulic Input Power (With Load)
NO. GENERATOR TORQUE (Nm) GENERATOR SPEED (rpm) WATER PRESSURE (bar) WATER PRESSURE (Pa) WATER FLOW RATE (lpm) WATER FLOW RATE (m3/s) VOLTAGE (Vdc) CURRENT (Adc) 1 0.14 2031 1.74 174000 46.8 0.000354 21.9 0.9 2 0.25 1830 1.74 174000 46.6 0.000352 18.7 2.1 3 0.36 1627 1.74 174000 47.0 0.000355 15.6 3.0
6
4 0.47 1365 1.74 174000 46.3 0.000350 12.0 4.1
5 0.55 1169 1.75 175000 46.7 0.000353 9.3 4.8
4.0.1 SAMPLE OF CALCULATION
AVERAGE SPEED (rad/s) = Average speed (rpm) * 2π/60 = 2050*2π/60
= 214.68 (rad/s) TORQUE (Nm) = 0.02 Nm
4.0.2 INPUT POWER (HYDRAULIC) (W) Table 3: Turbine Equation (Without Load) Average speed (rad/s) Torque (Nm) Input Power (hydraulic) (W) Output Power (Mechanical) (W) Efficiency (Turbine) Output Power (Electrical) (W) Efficiency (Generator) 214.68 0.02 56.301 4.294 0.076 0.00 0.00 193.21 0.02 56.434 3.864 0.068 0.00 0.00 171.00 0.02 41.358 3.420 0.083 0.00 0.00 141.06 0.02 30.780 2.821 0.092 0.00 0.00 131.95 0.01 21.376 1.320 0.062 0.00 0.00 0 0.02 0.04 0.06 0.08 0.1 0 1 2 3 4 5
Efficiency vs output power
turbine generator
7 Graph 3: Efficiency vs output power for without load (Turbine and Generator).
Table 4: Turbine Equation (With Load) Average speed (rad/s) Torque (Nm) Input Power (hydraulic) (W) Output Power (Mechanical) (W) Efficiency (Turbine) Output Power (Electrical) (W) Efficiency (Generator) 212.68 0.14 60.60 29.78 0.49 19.71 0.66 191.64 0.25 61.25 47.91 0.78 39.27 0.82 170.38 0.36 61.77 61.34 0.99 46.80 0.76 142.94 0.47 60.90 67.18 1.10 49.20 0.73 122.42 0.55 61.78 67.33 1.08 44.64 0.66
Graph 4: Efficiency vs output power for with load (Turbine and Generator)
Optimum Working point
8 5.0 DISCUSSION
Based on graph 3, for the turbine without load, it shows that the higher efficiency at 141.6 rad/s which is 0.092 or 9.2% efficiency. Thus at average speed 141.6 rad/s gave the best performance for turbine. Besides that, for graph 4 which is turbine with load, it shows that the higher efficiency occur at average speed of 170.38 rad/s that is with the efficiency of 0.99 or 99%. It can be conclude that the best performance for turbine with load occur at average speed of 170.38 rad/s.
For the maximum power, based on graph 3 for without load turbine showed that maximum power was at 4.294 W and for without load gave 67.33 W for maximum power produced. To know the performance effect of the turbines, we can look in two aspects. First is the nozzle setting and second is guide vane setting. For the nozzle setting, the decrement of the nozzle opening gave the increment of the flow velocity while for the guide vane setting by opening the angle of 180° gave the higher momentum for the turbine to rotate at highest speed. The function of nozzle and vane use in this experiment is the nozzle jet strikes the buckets and imparts momentum. The buckets are shaped in a manner to divide the flow in half and turn its relative velocity vector nearly 180°.
The working principle of this experiment is turbines convert fluid energy into rotational mechanical energy. For the Francise turbine, It is an inward-flow reaction turbine that combines radial and axial flow concepts. It mostly used in electrical power production. For the Pelton turbine, the high speed water jets emerging from the nozzles strike the buckets at splitters, placed
9 at the middle of a bucket, from where jets are divided into two equal streams. These stream flow along the inner curve of the bucket and leave it in the direction opposite to that of incoming jet. The high speed water jets running the Pelton Wheel Turbine are obtained by expanding the high pressure water through nozzles to the atmospheric pressure. The high pressure water can be obtained from any water body situated at some height or streams of water flowing down the hills. For the Kaplan turbine, The working head of water is low so large flow rates are allowed in the Kaplan Turbine. The water enters the turbine through the guide vanes which are aligned such as to give the flow a suitable degree of swirl determined according to the rotor of the turbine. The flow from guide vanes pass through the curved passage which forces the radial flow to axial direction with the initial swirl imparted by the inlet guide vanes which is now in the form of free vortex.
The axial flow of water with a component of swirl applies force on the blades of the rotor and loses its momentum, both linear and angular, producing torque and rotation (their product is power) in the shaft. The scheme for production of hydroelectricity by Kaplan Turbine is same as that for Francis Turbine. The difference between Francis, Pelton and Kaplan turbine are Pelton turbines are most suitable for high head situations, for which the head can be converted into a high speed jet. Francis turbines are used for intermediate heads, and Kaplan for the lowest heads.
6.0 CONCLUSION
The best performance of the turbine can be known from the average speed of the turbine, for the turbine with the load need higher average speed compared to turbine without load to get the best performance of the turbine. For the maximum power of the turbine produced showed that with load in turbine can get higher power compared to the turbine without load. For the three difference turbines, even this turbines got each specialty but the aim of this use of turbines were to convert fluid or gas energy into rotational mechanical energy and electrical energy.
10 REFERENCE
1) Robertson, J.A. and Crowe, C.T. (1993). Engineering Fluid Mechanics, 5th edition, Houghton
Mifflin, Boston, MA.
2) White, F.M. (1994). Fluid Mechanics, 3rd edition, McGraw-Hill, Inc., New York, NY.
3)
http://www.knowenergysolutions.com/conventional-energy/oil-and-gas/mechanical-engineering/the-pelton-turbine/
4)
http://www.knowenergysolutions.com/conventional-energy/oil-and-gas/mechanical-engineering/kaplan-turbine/
5) Layton, Edwin T. "From Rule of Thumb to Scientific Engineering: James B. Francis and the Invention of the Francis Turbine," NLA Monograph Series. Stony Brook, NY: Research Foundation of the State University of New York, 1992.
