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2014 
THE PELTON WHEEL 
TURBINE UNDER 
STUDY 
NYAGROWA MIMISA DICKENS 
EN251-0305/2011 
To study the variance of the power...
TOPIC 
PAGE 
ABSTRACT 3 
INTRODUCTION 3 
APPARATUS 6 
PROCEDURE 7 
THEORETICAL KNOWLEDGE 7 
PRESAUTIONS 12 
RESULTS 13 
CA...
PERFORMANCE TEST OF A PELTON WHEEL TURBINE 
3 
Aim 
To study the variance of the power output and overall efficiency again...
of the spear regulator along the axis of the nozzle which alters the annular space 
between the spear and the housing. A s...
Fig. General arrangement of the pelton wheel turbine 
5
FIG. Arrangement of Apparatus used in the Pelton Wheel Turbine Test 
6 
Apparatus used 
For the purpose of the study, the ...
7 
Procedure 
The sluice valve, V-2, was opened to supply water to the turbine, and the needle 
valve of the nozzle, N, wa...
Fig. Indication of actual state of operation of a pelton wheel turbine 
The amount of water striking the buckets is contro...
Figure below shows the pelton turbine. It consists of a circular disc (the runner) on the 
periphery of which a number of ...
Power supplied at the inlet of the turbine or the water horse power is given by the 
expression 
10 
ρgHQ 
750 
. 
Whe re ...
Performance characteristic curve of pelton turbines 
These are curves with the help of which the exact performance behavio...
A triangular weir is used to determine the discharge through the circuit. The water 
head through the weir is measured wit...
13 
Results 
Fundamental Data 
Properties of turbine 
Revolution speed (N) 900 rpm 
Pressure head on turbine 27 m 
Length ...
14 
Calculations 
a) The theoretical power input (Pth) of the turbine given by the expression: 
Pth = 
ρgHQ 
75 × 60 
HP 
...
Power Out (HP) efficiency (%) 
y = -1E+09x3 + 5E+06x2 - 2357.9x + 1.9629 
0.0012 0.0014 0.0016 0.0018 0.002 0.0022 
15 
ηo...
16 
Conclusion 
This experiment was carried out with an acceptable level of accuracy. It was 
generally a success as the r...
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Pelton wheel experiment

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an experimental approach on the study of the pelton wheel and how it operates

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Pelton wheel experiment

  1. 1. 2014 THE PELTON WHEEL TURBINE UNDER STUDY NYAGROWA MIMISA DICKENS EN251-0305/2011 To study the variance of the power output and overall efficiency against discharge with the head retained as a constant at normal speed MIMISA JOMO KENYATTA UNIVERSITY OF AGRICULTURE AND TECHNOLOGY 8/1/2014
  2. 2. TOPIC PAGE ABSTRACT 3 INTRODUCTION 3 APPARATUS 6 PROCEDURE 7 THEORETICAL KNOWLEDGE 7 PRESAUTIONS 12 RESULTS 13 CALCULATIONS 14 DISCUSION 15 CONCLUSION 16 REFERENCES 17 2
  3. 3. PERFORMANCE TEST OF A PELTON WHEEL TURBINE 3 Aim To study the variance of the power output and overall efficiency against discharge with the head retained as a constant at normal speed. Abstract The findings of an experiment carried out to study the properties and performance of a pelton wheel are herein discussed with much emphasis placed on the output measured. The resulting output was discussed against the theoretical output to determine presence and causes of a deviation. The results were presented in graphical method and the properties of the graph used to discuss the properties of the turbine under study. Flow was varied and head measured against each variance to indicate the power in the system. Other parameters necessary for the study were also measured and recorded for the study. The pelton wheel under study was of a smal ler scale though it acted as a representative of a similar system in large scale. The results were also used for the checking of scaling laws used for rturbines. Introduction A pelton wheel turbine is a tangential flow impulse hydraulic machine that is actively used for the production of power from kinetic energy of flowing water. It is the only form of impulse turbine in common industrial use. It is a robust and simple machine that is ideal for the production of power from low volume water flows at a high head with reasonable efficiency. The pelton wheel used in this experiment, although a model, reproduces all the characteristics of full size machines and allows an experimental program to determine the performance of a turbine and also to verify the theory of design. Impulse turbines operate through a mechanism that first converts head through a nozzle into high velocity, which strikes the buckets at single position as they pass by.jet flows past the buckets is quite essential at constant pressure thus runner passages are never fully filled. These turbines are suited for relatively low power and high head derivations. The pelton wheel turbine is comprised of three basic components that include the stationary inlet nozzle, the runner and the casing. The multiple buckets form the runner. They are mounted on a rotating wheel. They are shaped in a manner that divides the flow in half and turn in a velocity vector that is nearly 180degrees. The nozzle is positioned in a similar plane as the wheel and is arrange d so that the jet of water impinges tangentially on to the buckets. The nozzle is controlled by movement
  4. 4. of the spear regulator along the axis of the nozzle which alters the annular space between the spear and the housing. A static pressure tapping is provided to enable the measurement of the water pressure in the inlet. Fig. The configuration of the nozzle and buckets in a Pelton wheel turbine The nozzle is controlled by movement of the spear regulator along the axis of the nozzle which alters the annular space between the spear and the housing, the spear being shaped so as to induce the fluid to coalesce into a circular jet of varying diameter according to the position of the spear. A friction dynamometer consists of a 60mm diameter brake wheel fitted with a fabric brake band which is tensioned by a weight hanger and masses with the fixed end being secures via a spring balance to the support frame. A tachometer may be used to measure the speed of the turbine. 4
  5. 5. Fig. General arrangement of the pelton wheel turbine 5
  6. 6. FIG. Arrangement of Apparatus used in the Pelton Wheel Turbine Test 6 Apparatus used For the purpose of the study, the following system of apparatus were used V- 1,2,3 List of apparatus as labeled in the diagram above :Sluice valve X :Balance N :Nozzle G :Hook Gauge NV :Needle valve PG- 2 :Pressure gauge PB :Plony brake T :Main tank W :Waterway TW :Triangular weir A thermometer was also used for the determination of the water temperature. The tachometer was used optically in the determination of the speed of the turbine so as to retain the speed at 900rpm.
  7. 7. 7 Procedure The sluice valve, V-2, was opened to supply water to the turbine, and the needle valve of the nozzle, N, was opened manually by the handle, MV, to allow the water flow. As the turbine rotated cooling water was supplied into the plony brake. Importance was taken such that the temperature did not exceed 60º C for the most efficient operation. Initially the needle valve was fully opened, and the sluice was adjusted to bring the pressure head on the turbine to 27m. The pressure head was maintained at 27m throughout the experiment period, and was monitored by the pressure gauge-PG -2. To maintain the turbine speed at 900rpm, the adjusting screw of the plony brake, Z, was tightened and when the arm of the plony brake got. At that speed, the spring balance, X, reading (Kg) was recorded as the load on the plony brake. The experiment was performed several times (15 times) by shutting the needle valve in bits. It was noted that for each revolution the needle advanced 1.25mm. As a precautionary measure the needle valve, NV, was not shut completely before shutting off the sluice valve, V-2, because the pump water pressure might break some of the vinyl tubes between the sluice valve and the needle valve. Theoretical Knowledge pertaining to the experiment The efficiency of the turbine is defined as the ratio between the power developed by the turbine to the available water power. Figure below shows the layout of a hydro-electric power plant in which the turbine is pelton wheel. Water from the reservoir flows through the penstock at the outlet of which is fitted a nozzle. The nozzle increases the kinetic energy of the water jets. These water jets strike the bucket of the runner making it rotate. The two main parts of the pelton turbine are: i. the nozzle and the flow regulating arrangement ii. the runner with the buckets
  8. 8. Fig. Indication of actual state of operation of a pelton wheel turbine The amount of water striking the buckets is controlled by providing a spear in the nozzle as shown in Figure below. The spear is a conical needle which is operated either by a band wheel or automatically in an axial direction depending on the size of the unit. When the spear is pushed forward into the nozzle, the amount of water striking the runner is reduced, where as if the spear is pushed back the amount of water is increased. 8 Fig. Velocity Analysis
  9. 9. Figure below shows the pelton turbine. It consists of a circular disc (the runner) on the periphery of which a number of buckets evenly spaced are fixed. The shape of the buckets is a double hemispherical cup or bowl. Each bucket is divided into two symmetrical parts by a dividing wall which is known as a splitter. The jet of water strikes the splitter which then divides the jet into two equal parts and the jet comes out at the outer edge of the bucket. The buckets are shaped in such a way the jet gets deflected through 160° or 170°. 9 Definition of terms 1. Total Head: The difference between the head race level and the tail race level when no water is flowing is known as Total Head (Hg). 2. Net Head: It is also called the effective head and is the available head at the inlet of the turbine. When water is flowing from head race to turbine, there is head loss due to friction between the water and the penstocks. There could also be minor head losses such as loss due to bends, pipe fittings and entrance loss of penstock etc. If hf is the total head loss, then net head on the turbine is given by H = Hg − hf Pelton turbine is best suited to operating under very high heads compared with other types of turbines. 3. Overall Efficiency: The overall efficiency of a pelton turbine is the ratio of the useful power output to the power input. Mathematically, Overall efficiency(ηov) = Power available to the shaft Power suppied at the inlet
  10. 10. Power supplied at the inlet of the turbine or the water horse power is given by the expression 10 ρgHQ 750 . Whe re ρ = density of wate r (kg/m3), g = acceleration due to gravity (9.81m2/sec), Q = discharge, H = net head (m). The power losses that occur within a turbine are attributed to volumetric, mechanical and hydraulic losses. Volumetric losses ## some of the volume of the water is discharged to the # without striking the runner buckets. Thus the ratio of the volume of the water # striking the runner to the volume of the water supplied to the turbine is defined as the volumetric efficiency. Mathematically, Volumetric efficiency(ηv) = volume of water striking the bucket volume of water supplied to the turbine The shaft horse power (SHP) output is less than power input due to power consumed in overcoming mechanical friction at bearings and stuffing boxes. The ratio of the power available at the shaft of the turbine to the power developed by the runner is calle d the me chanical e fficiency (ηm) of the turbine. Mathematically, ηm = Power at the shaft of the turbine Power developed by the runner The water head actually utilized by a turbine is less than that available because of frictional losses as water flows across the buckets. The water power at the inlet of the turbine due to hydraulic losses as the vanes are not smooth and water jet is not completely turned back. The ratio of the power developed by the runner to the available powe r at the inlet is known as the hydraulic e fficiency (η h) of the pelton turbine. Mathematically, ηh = Power developed by the runner Power available at the inlet Normal overall efficiency (ηov) = ηv ∙ ηm ∙ ηh
  11. 11. Performance characteristic curve of pelton turbines These are curves with the help of which the exact performance behavior of the turbines under different working conditions can be ascertained. The curves are plotted from the results of the tests performed on turbines under different working conditions. The quantities that can be varied during a test on a turbine are: speed, head, discharge, power, overall efficiency and gate opening. If the speed and water head of a pelton turbine are maintained at constant values, then the curves obtained by plotting the discharge (Q) against both the power outputs and the overall efficiencies are called the operating characteristic curves of the pelton turbine. 11 Preparation of the Experiment The asbestos of the plony brake (PB) (details as shown in Figure 4) should be oiled before the experiment is started. This ensures easier reading of the load on the spring balance. The sluice valves, V-1, 2, 3 are put in closed positions. Before the pump is started ensure that it is filled up with water i.e. primary and once started it should not be allowed to run for long before opening any of the valves V-1, 2, 3. This is to prevent it from getting overheated. Figure: Details of the plony brake
  12. 12. A triangular weir is used to determine the discharge through the circuit. The water head through the weir is measured with a hook gauge; first the zero water head is measured. This is done as follows: Kee ping the water flowing over the weir, observe reflection of the end of the weir ‘V’ on the water from the upper stream side. Open the cork valve (V-8) positioned under the waterway, to lower the surface water level and then read the water head with the hook gauge when the end of the weir ‘V’ coincide s with end of the shade ‘V’ re flecte d on the surface of the water. This reading is recorded as the zero water head. Then close cork valve (V-8) to prepare for the other readings. The other water heads are read when the point of the hook gauge coincides with the reflection itself in the water through a glass window. In every case allow the water to settle before recording the reading i.e. waits for about 5 minutes after the flow adjustment before you take the next reading. 12 Precautions taken 1. It was ensured that the centrifugal pump that supplies water in this system is primed first before the mortar is started. 2. The gate openings were set carefully and throughout each gate opening, the spear wheel and the delivery valve were not changed.
  13. 13. 13 Results Fundamental Data Properties of turbine Revolution speed (N) 900 rpm Pressure head on turbine 27 m Length of the handle of the plony brake 0.130 m Properties of V-notch Half angle of V-notch (θ) 45° Coefficient of discharge (CdV) 0.576 Coefficient (KV) 1.360 Crest level (hook gauge) 0.21805 m Operation Data Stag e V-notch Properties of water Theoretic al power input (Pth) HP Spring balance reading (w) kg Actual power (Pa) HP Overall Efficie ncy (ηov) % Reading m Head (HV) m Discharge (Q) × 10−3m3 /s Temperatu re °C Density (ρ) kg/m3 1 0.17020 0.04785 0.681 18.0 998.595 2.401 14 2.287 95.248 2 0.16280 0.05525 0.976 19.5 998.305 3.439 20 3.267 95.007 3 0.15645 0.06160 1.281 19.5 998.305 4.514 27 4.411 97.717 4 0.15255 0.06550 1.493 20.0 998.203 5.262 32 5.228 99.345 5 0.14865 0.06940 1.726 20.0 998.203 6.081 36 5.881 96.717 6 0.14700 0.07105 1.830 20.0 998.203 6.449 38 6.208 96.266 7 0.14525 0.07280 1.945 20.0 998.203 6.853 40 6.535 95.353 8 0.14400 0.07405 2.029 20.0 998.203 7.151 40 6.535 91.379 9 0.14265 0.07540 2.123 20.0 998.203 7.481 41 6.698 89.528 10 0.14180 0.07625 2.183 20.0 998.203 7.694 41 6.698 87.053
  14. 14. 14 Calculations a) The theoretical power input (Pth) of the turbine given by the expression: Pth = ρgHQ 75 × 60 HP Whe re ρ = density of water (de pends on the water temperature and atmospheric pressure), Q = discharge, H = net water head on the turbine (given H=27m). Example: Pth = 998.595 ∗ 9.81 ∗ 27 ∗ 0.681 75 × 60 HP Pth =2.401W b) The actual power output (Pa) of the turbine is obtained from the expression: Pa = 2πxNw 75 × 60 HP Where x = length of the handle of the plony brake (given as 0.130m), N = revolution per minute of the turbine (supposed to be 900rpm), w = load exerted by the plony brake (kg) read on the spring balance. Example Pa = 2π ∗ 0.13 ∗ 900 ∗ 14 75 × 60 HP Pa =2.287 HP c) The ove rall e fficiency of the pe lton turbine (η ov) is given by the formula: ηov = Pa Pth × 100% Calculate the overall efficiencies of the pelton turbine at each discharge Example:
  15. 15. Power Out (HP) efficiency (%) y = -1E+09x3 + 5E+06x2 - 2357.9x + 1.9629 0.0012 0.0014 0.0016 0.0018 0.002 0.0022 15 ηov = 2.287 2.401 × 100% =95.248% Discussion From the above calculations the values of actual power output are slightly lower than the values of theoretical power output of the turbine and thus from this a relationship between the discharge, actual output and efficiency can be shown using a graph as indicated below. y = -2E+07x2 + 39797x + 73.253 109 104 99 94 89 84 7 6 5 4 3 2 1 0 From this relationship, it is possible to prove that the higher the power output of a turbine, the higher the efficiency. These are functions of the discharge. It is also correct to indicaate that efficiency of the system increases with increase in the specific speed of the pelton wheel. This has been derived from the relationship of the values collected, tabulated and graphed as herein. Efficiency (%) Power out (HP) Discharge (m3/s)
  16. 16. 16 Conclusion This experiment was carried out with an acceptable level of accuracy. It was generally a success as the results obtained were useful for the analysis of the properties of the machine. From the experimental results, it became possible for the real picture of the operational basis of the machine to be displayed in such a way that the characteristics of the turbine were visible in the graphical analysis used. The experiment was not fully accurate due to several errors that resulted from several misdoings. The greatest being that it became really difficult to acquire readings from the spring balance since the setup was vibrating as result of the operation of the machine. As such, this explains the slight deviation of the results obtained in the experiment that were later reflected in the graphs drawn to represent the work. Other errors may have resulted from unseen leakages in the system and observational and computational errors. The experiment was, however, carried out with a great level of keenness to reduce the occurrence of such errors. References 1. Rajput, R. K. (2005). Elements of mechanical engineering. New Delhi, India: Laxmi Publications 2. Agar, D., & Rasi, M. (2008). On the use of a laboratory-scale Pelton wheel water turbine in renewable energy education. Renewable Energy, 33(7), 1517-1522. 3. Zhang, Z. (2007). Flow interactions in Pelton turbines and the hydraulic efficiency of the turbine system. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 221(3), 343-355. 4. Arndt, R. E. (1991). Hydraulic turbines. Energy, 2, 2

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