Water Power: Building a Pelton Wheel - Renewable Energy - MOTHER EARTH NEWS Video Water Power: Building a Pelton Wheel If you're generating power from a flowing water source with a moderate head, a Pelton wheel is a good choice. By C.D. Bassett Tweet Example of a Pelton wheel that receives water through a pipe. While the penstock may be set up to provide either a precipitous or sloping fall, it should be of as large a diameter as possible, have minimum bends, and hold down flow friction to the least amount. ILLUSTRATION: POPULAR SCIENCE Print Email Though one of man's oldest prime movers, a water wheel generator is still a fascinating piece of machinery. Perhaps this is because it appears comprehensible at a glance (although an efficient wheel is actually a product of subtle and inconspicuous design refinements), and because it seems to be a way of getting power for nothing. The wheel we describe here, with accompanying technical diagram , was especially designed for this series on harnessing small streams, and will reward a careful craftsman by delivering years of constant service.

It's particularly suited for an installation having a moderate head (25' to 60') and relatively small flow (0.45 to 0.75 cubic feet per second). Subsequent installments will describe the construction of wheels suited for lesser heads of water and other varied conditions. The wheel is an impulse wheel, driven by the impulses produced as water strikes revolving blades or buckets. In a perfectly designed wheel, the water strikes at high speed, exhausts its energy in driving the wheel to which the bucket is attached, and then falls free of the wheel. Known as a Pelton wheel, this type developed from the "hurdy gurdy", a paddle wheel used in California by the forty-niners. The hurdy-gurdy was a wheel that rotated in a vertical plane, had flat vanes fixed around its circumference, and was driven by the force of water striking the vanes. It was not an efficient machine, but it was simple to construct. Then an engineer named Lester Pelton substituted a cup-shaped, divided bucket for each of the vanes, and by that step added a high degree of efficiency to the wheel's other virtues.

No single wheel will meet all operating requirements, but some will perform under a reasonably wide range of conditions. The following table indicates the r.p.m. and horsepower output that will be delivered by this wheel under given conditions of head and flow. The latter is measured in cubic feet per second: Head: 25' - Flow: 0.43; RPM: 350; HP: 1.0 Head: 30' - Flow: 0.51; RPM: 390; HP: 1.3 Head: 40' - Flow: 0.59; RPM: 450; HP: 2.0 Head: 50' - Flow: 0.66; RPM: 500; HP: 2.8 Head: 60' - Flow: 0.73; RPM: 550; HP: 3.75 Thus, if a survey of your stream indicates a head and flow close to these values, our Pelton wheel will fit neatly into your plans. Strictly speaking a water wheel is an engine powered by water, just as an automobile engine is powered by gasoline.

The important power-producing elements of the wheel are the buckets and the nozzle, and considerable care should be exercised to see that these parts are made correctly. The nozzle meters the correct amount of water to the wheel, and forms and directs the jet against the buckets. Both the inside diameter and the location of the nozzle with respect to the wheel are very important, since the jet must impinge upon each bucket at the correct wheel radius or lever arm. It must also be divided equally by the center ridge of each bucket. The function of the bucket is to convert the energy of the jet, represented by its high speed, into mechanical energy at the wheel shaft. To do this it must slow the water from its high speed in the jet to practically zero speed when it drops into the tail water. Maximum efficiency with this wheel will be obtained if the buckets have the proper form and size. This shape acts to slow the jet by turning it smoothly through 180 deg. The surface of each bucket must be as smooth as possible. A mirror finish is desirable on the inside, and even the back of each bucket should be ground and polished to minimize spray. Important also is the correct orientation of the bucket to the jet.

When the full jet strikes, the bucket should be perpendicular to it. Both the nozzle and the buckets will wear under the action of the high-speed water, at a rate determined by the silt content and should therefore be made easily removable for replacement. Above all, buckets must be uniform. If you can get access to a metal-cutting handsaw, cut the blanks according to a single pattern. This pattern can be shaped so as to form the end bevels automatically when the blanks are bent, and the bending itself can be done in a jig or hammering form. This jig may be made of a piece of pipe of about 2" outside diameter mounted in hardwood endplates. Also provide a holding fixture that will slide in the table groove of the handsaw to assure that the slots for the end lugs are cut and spaced uniformly. A holding jig should also be made to line up the lugs and buckets for welding. On completion, balance the wheel by laying weld beads along the backs of any light buckets. Beads should be laid carefully and ground smooth. Ball bearings may be employed, but are not necessary since the wheel turns at comparatively low speeds.

If the builder prefers to use plain bearings, it will simplify machining the shaft, which should present a shoulder to the inside of the bearing so that the wheel may be positioned. If plain bearings are employed, babbitted linings are satisfactory, provided provision is made for proper lubrication. One vital job that the foundation must do is hold the wheel and the nozzle in correct relative positions. It should be placed on firm ground or piling so that it will not settle unevenly, and must, of course, take advantage of all the head possible. The penstock from the dam should have easy access to the nozzle, and the tail water easy escape to the stream. If possible use 4" or larger pipe for the penstock and lay it out to hold frictional losses to a minimum. The width of the foundation is such as to allow the water to fly clear of the buckets. The removable cover over the upper half of the wheel may fit more closely, since no water sprays from the buckets through this half of the revolution. The foundation may be made of such materials as timbers in a framework, masonry, or concrete, so long as it fulfills the above requirements.

The wheel and the machinery being driven may then be housed in any suitable, inexpensive shed. It's not wise to dispense with a gate valve, which is used to cut off or to throttle the water supply to the wheel. Since a gate valve cannot be operated rapidly, it is the best type, eliminating the risk of dangerous water hammer in the penstock. It is also well suited for throttling because fine adjustment is obtainable through the long operating screw. In throttling, the gate valve should be used together with a tachometer or revolution counter connected to the wheel shaft to secure the optimum speed and horsepower for the stream condition and load. Either fasten a tachometer permanently to the shaft, or keep a revolution counter handy in the wheel shed. Generally the head and volume of water flowing to the wheel will remain constant, resulting in a constant output. If the machinery driven by the wheel has a level power demand there will be little need for constant adjustment of the valve. The requisite piping, pipe fittings, steel sheet and rod bolts and nuts, and gaskets are available at building-supply houses houses or steel distributors. Machine screws, lock nuts bearings, and the like may be purchased from good-sized hardware distributors or mail-order houses.

One final point to keep in mind in making your calculations: head is defined as the vertical distance between the water surface behind the dam and the tail-water surface at the wheel. For an impulse wheel, however, which cannot operate submerged, the available head is measured from headwater to the center line of the nozzle. There is only 5" difference between the two definitions, but this can make some difference in output when working with the moderate heads for which this wheel is designed. While many details can be altered, the reader should beware of any that will affect operating characteristics. Thus stainless steel buckets and antifriction bearings would improve performance, involving only some extra work in building the wheel. Changes in the nozzle diameter, wheel radius, or effective head, however, should be undertaken only after careful consideration of the probable effect on performance. Reprinted courtesy of Popular Science Monthly, Popular Science Publishing Co. Inc. 1947 Power calculations for Pelton turbines MICRO-HYDRO INSTALLATION SIZING (PELTON AND TURGO WHEEL TURBINES) A friend of mine asked me to help size a micro-hydro installation that he was thinking of installing at his cottage.

Specifically he wanted to know how to calculate the flow rate of water through a pipe with a given vertical drop. This is a simple pump-sizing problem without a pump, so I thought I would give him a hand. It turned out to be a very interesting topic and I hope you will find it helpful in understanding the concept. A micro turbine is a wonderful way to generate you own electricity because it is so ecologically friendly. It has little or no impact on the environment and will provide continuous energy year round at low cost. Unfortunately, not many of us can access this resource since it usually requires a large track of land with a stream. For those of us who live in the country, it is possible that you could have a stream nearby on public land that you could access. In this case it may require a longer line (or penstock) to get the water from its source to your land where you will put your micro-turbine. This article is about how you can figure out how much energy will be available considering your terrain and water availability. This link will provide you with a pdf version of this web page. source of image: What is HEAD and why is it used?

The difference in height between the water source and the turbine location is the key to generating power. This height is known as head or more precisely static head. Head is expressed in feet just like height; the difference is when we use the term head, we are actually talking about energy per pound of liquid displaced. So head is just another term for energy, specifically energy per unit weight of liquid displaced. How is this possible? Energy, or useful work can be expressed as pound-feet or lbf-ft in the Imperial system. If I divide this term by lbf, I obtain lbf-ft/lbf or feet (ft) and this is what is known as head. If I know how many pounds of liquid are displaced per unit time (this is proportional to flow rate in gallons per minute for example) then I know how much power is required since by multiplying head in lbf-ft/lbf by lbf/min, I get a unit of power in lbf-ft/min or foot-pounds per minute. We know there are 550 lbf-ft/s in a horsepower and 1.34 horsepower in a kilowatt.

Therefore, when we know the height difference, or static head, we can immediately get a good idea of how much energy will be available however the analysis is not complete without the flow rate. Typical micro-hydro installation The following image shows a typical system that I have seen and which I am familiar with. The stream is located on a hill or incline. The riverbed is accessible and you require some sort of structure that will hold your intake pipe solidly. Remember that heavy rains bring, high water levels and lots of activity within the stream, including the movement of large boulders that could disrupt, or destroy your intake if it is not built robustly enough. Intake design The intake structure shown could also be called a caisson and it is built of re-enforced concrete approximately 3 feet by 3 feet by 2.5 feet high with 6-inch walls. It is basically a thick frame with 4 concrete walls. This is robust enough to stay put in the stream even when the heavy waters come and provides a stable structure to which you can attach your intake pipe. You should provide some sort of filtration device at your pipe intake to prevent branches and other detritus from entering the pipe.

A heavy screen mesh is suitable and if you provide holes on the side of the pipe there will be more area for the water to enter the pipe, which causes less pressure drop. Your pipe intake should be sufficiently submerged to prevent a vortex forming at the surface that would allow air to enter the pipe and reduce the flow. The height required to avoid vortex formation depends on the size of the pipe and the flow rate, which has yet to be determined. For those of you who would like to calculate the submergence height see this applet: #applets10 . Typically for the flow rates that concern us an intake pipe end submergence of 2 feet is sufficient. Also you have to consider that the water level in the stream will vary throughout the year. It's important that the intake pipe be smoothly laid out from start to finish avoiding upward runs as much as possible. It may be impossible to avoid this but keep vertical excursions as small as possible. In particular near the intake you must avoid going above the water level prior to going downwards to the turbine. This is to avoid the possibility of getting an air lock (i.e. trapped air in the intake pipe) that could prevent water reaching the turbine.

If you are in the northern latitudes you will have to consider what to do about freezing temperatures. Small streams on a sharp incline flow throughout the year no matter the temperature. If you keep flow running through your line, you will experience the same effect, and will not get a frozen and possibly damaged line. This is something you should consider in your set up. The alternatives are to bury the line or use heat tracing both of which are expensive and time consuming. Let's get right to it and figure out what size pipe is suitable for our stream, what flow rate we can expect and how much power can be generated? Intake pipe size The intake pipe is the key to the whole installation and it will determine how much power can be generated. The other critical factor is the height or static head available between the surface of the stream and your turbine location. If the head is small, say 1 to 5 ft, then the amount of energy available will be very small and not worth the trouble. The other consideration is how much water is in the stream, and how much can you take without building a major infrastructure at the intake.

This can be hard to evaluate, and sometimes you just have to take a stab at it, and use this as a basis for calculating your power availability. You can then determine how this impacts the size of your intake structure, versus the size of the streambed. All streams are different and the shape of the streambed varies considerably from one location to another. However, as a guideline use this table as a starting point for sizing your intake pipe. Stream width (ft) - fittings including valve loss (negligible) - pipe length loss (to determine) = HF - nozzle loss (negligible) The intake filter friction loss depends on the mesh size, the open area, etc. If we make a very tight screen we will have a high pressure drop and therefore high friction loss. It is possible to build an acceptable filter with a low friction loss, say 1 ft or less. You are probably wondering why I am expressing the filter loss in feet and not in psi for example. While it is possible and often done, it is simpler to use feet everywhere so that all the units are compatible. For those of you who want to know what the correspondence between feet and psi is, go to this link: #gl39 The fittings (i.e.

elbows, tees, y's, etc.) friction loss in this case will be quite low and negligible, I don't expect we will have more than 2-3 elbows and this will offer very little resistance, less than 1 ft. The same applies to the valve that is located near the turbine; the resistance it offers when it is fully open is negligible. The pipe friction loss HF can be determined in several ways. You can use the applet that I have on my web site, which is what I will use in this example, or you can use tables or equations. For more information see this link: . Calculations In this section you can do your own calculations using a couple of equations and an applet on my web site. If you just need to get an idea of how much power you could generate with typical installation with 100, 500 or 1000 feet, see the charts that summarizes these calculations in Appendix A. To calculate the pipe friction loss using the pipe friction loss applet, go to this link .

You must have Java Run Time installed on your computer for this applet to work as is explained at the top of the web page, there are also instructions how to obtain if you do not have it installed. On the menu titled "Applets on this page", select applet no. 13, you should see a screen like this: Figure 6 You can put any pipe diameter size you wish for the calculation. Normally you want to use the inside diameter of the pipe as the pipe diameter. Depending on the construction and the pipe material, the inside diameter can be slightly smaller than the nominal size. So that a 3" pipe will vary between 2.9 to 3". I have used the nominal size as the inside diameter in all the calculations. Let's start with a value of 200 gpm, 3" pipe diameter, 10 feet of head and a pipe length of 100 feet. We will assume that the piping will be made of steel, polyethylene or PVC or something equivalent. The type of material determines the roughness, the rougher the pipe the higher the friction.

The materials mentioned all have a low roughness of approximately the same value, so leave the default values for roughness as in the applet. Make sure you have 200 gpm in the flow rate text box and that all the other values are as shown in Figure 6 and then press the Calculate button. You will get a value for total friction loss HF of 9.92 ft. Using 200 gpm we can calculate the velocity in the pipe based on the pipe diameter using equation (1), or we get directly from the applet 9.1 ft/s. This is the velocity in the pipe, the velocity v2 is at the outlet of the nozzle which has a 1.5 in diameter outlet. Therefore we use equation (1) to calculate v2: So now we put these values into equation (2) We calculate v2 to be 2.3 ft/s and our assumption based on 200 gpm is 36.3 ft/s so that means that our assumption is wrong and we need to decrease the flow rate to get a better match.

The following table shows a series of calculations that converge on the correct value: q (USgpm) 20.7 Table 2. Flow rate calculation for 10 ft of head and a 3" pipe. As you can see from the results in the above table the velocity in the pipe is quite low. This means that we may have a larger pipe than we need considering the available head. What would happen if we repeated this exercise with a smaller pipe size, say a 2" keeping the length the same at 100 feet. Also this time we will look at the amount of power provided by each of these scenarios. We will discuss later how power is calculated. q (USgpm) 10 Table 3. Flow rate calculation for different pipe sizes at 10 ft of head. As you can see, we can save money on the pipe purchase due to the smaller diameter, but the power produced is also going down significantly. The 2" diameter pipe would not be a viable proposition. The results of these calculations have been plotted and presented in three charts in Appendix A.

Power available Now that we know the velocity and the flow rate at the end of the nozzle, we can calculate the energy available, and therefore the power that is energy per unit time, or Watts. There are two possible ways to calculate the power at the turbine wheel; one is with the water jet velocity and the flow with equation (3); the other with the head and the flow using equation (4). Both will give the same results. The head h in equation (4) is the difference between the static head (z1 - z2), and the friction loss, so that it is the net head at the water jet. Rather than interrupt this article if you want to know where these equations come from see this pdf document . Our available power is 0.064 kilowatt or 64 watts. The effect of static head As you can see 10 feet of head does not provide a lot of energy. With more head, we can increase the flow rate through the pipe, and increase the velocity at the nozzle outlet, and thus provide more power.

Of course the topography of the land must lend itself to this, the steeper the stream the better, so that you can get maximum elevation drop, for the shortest length of pipe. The following table looks at these scenarios for different heads using a 4" pipe with static head varying between 25 and 150 feet and a pipe length of 500 feet with a nozzle diameter of 1.5": Static Head (ft) Table 4. Head available vs. power generated for a 4" pipe. KiloWatt-hours It is interesting to know how much power you are producing and this is useful information to size the turbine, generator, and the electric cable. What is this power worth? The utility company charges vary but in my area they charge $0.07 per kW-h. In the scenario we studied you will be producing 64 watts on a constant basis. This means that every 24 hours, you are producing 64 X 24 = 1.54 kW-hours or in a 30 day month 46.1 kW-h. This would cost you $3.23 per month.

Table 5 gives a calculation for the power that your installation could produce at the generator shaft. It is based on the power of the water jet due to its mass flow rate, velocity and, the turbine wheel design, with its losses. This does not include the power loss at the generator or the normally negligible transmission loss through electrical cables (if sized correctly). Static Head (ft) $182.74 Table 5. Power generated for a 4" pipe vs static head available. Turbines are available with a number of nozzles varying from 1 to 4. The nozzle diameter determines the jet velocity. The main advantage of multiple nozzles is to reduce the velocity through each nozzle since there are many to share the total flow rate thereby diminishing wear due to high-velocity induced erosion. The power generated remains about the same. Turbine speed As explained earlier the Pelton turbine wheel is designed to run at half the water jet velocity, as this is where it will generate its maximum power. The turbine diameter must be matched to the jet velocity to achieve the proper rotational speed of the turbine wheel that turns the generator. Based on the jet velocity the turbine rpm will be given by: where d is the turbine diameter.

In this case the turbine speed is: Assuming the turbine diameter is 6 in, the turbine will turn at 1230 rpm with 100 feet of static head, 4" pipe and 355 gpm. This is a suitable speed for a permanent magnet generator. See this link to see how this equation was determined. Turbine wheels come in different sizes and it is important to choose the right combination of diameter with the number of nozzles to obtain a suitable rpm for the generator to operate efficiently.

All these calculations have been pre-programmed in an Excel spreadsheet that you can download at this address: The equation used for calculating friction loss is the Swamee-Jain formula and you can find out about it at this web address: All these calculations have been pre-programmed in an Excel spreadsheet that you can download at this address: You can also use this applet to do the complete calculations: and in metric: and for those of you interested about how the applet solves for flow using the Newton-Raphson iteration technique, see this document: Solving the gravity flow equation for flow rate using The Newton-Raphson iteration technique Turbine discharge The water coming out of the turbine casing needs to be returned to the stream. It is in your interest to have a short distance, as this will reduce the pipe size required and minimize cost. This should be considered in you choice of location of the turbine. Again make sure that the pipe is layed out with a continuous slope towards the discharge and generously sized to avoid water build up in the turbine casing. You can use similar calculations to determine this pipe size, with the difference that there is no nozzle to consider. Turgo wheel turbine The Turgo wheel turbine is a variation on the Pelton turbine.

The wheel looks like the Pelton wheel cut in half. Because the water jet interferes less with the wheel than the Pelton design it can handle more flow. They typically have 1 or 2 nozzles that are inclined at an angle with the plane (perpendicular to the shaft) of the wheel. Because the blade design is less complicated to manufacture it can be less expensive than the Pelton design. The application range is somewhere between 90 and 600 feet of head at the turbine. Pipe pressure rating This is a topic where there are some misconceptions. On many web sites the amount of power available is compared to the pressure at the bottom of the pipe due to the static head. This does not occur during the operation of a micro-hydro system because all the pressure energy due to height is converted to velocity (kinetic) energy, or friction loss. If you put a pressure gauge just ahead of the nozzle, you will read the pressure drop that occurs across the nozzle, since one end of the nozzle is at zero pressure. Depending on the design of this nozzle, the pressure drop can be negligible and there will be very little pressure at the bottom of the pipe, while the turbine is in operation.

However, if you close the turbine intake valve then the pipe will be under pressure due to the static head, and this produces the maximum pressure at the bottom. For 100 feet of head the pressure will be 100/2.31 = 43 psi. Therefore you should verify the pipe material maximum working pressure if the head of your system is above 100 feet. The pressure rating of the pipe should be at least the static head converted to pressure plus a reasonable safety factor. Manufacturers of micro-hydro turbines The Pelton turbine is one of the designs that is suitable for this type of application. The following images show the products offered by two manufacturers Harris and Hydro Power. Harris offers a range of turbine generators between 700 and 2500 watts. Harris Hydroelectric is one manufacturer, see this web site Figure 7. Harris turbine. Figure 8. Harris turbine view of the Pelton turbine wheel from below. Figure 9. Hydro Power turbine view of the Pelton turbine wheel from below. Appendix A Analysis of the graphs of Power vs. Pipe diameter The plots of power vs.

pipe diameter are split into 4 graphs for systems that can be built with 100, 500, 1000 and 2000 feet of pipe. Single nozzles were used in the analysis and their diameter was optimized to give the maximum power for each static head and pipe size. The maximum nozzle diameter used was 1.5 inch. Figure 14. Power vs, pipe diameter at 10-50 feet of head and 100 feet of pipe. Figure 15. Power vs, pipe diameter at 25-150 feet of head and 500 feet of pipe. Figure 16. Power vs, pipe diameter at 50-150 feet of head and 1000 feet of pipe. Figure 17. Power vs, pipe diameter at 50-150 feet of head and 2000 feet of pipe. Free power from a recycled washing machine, generating enough to live off the grid - YouTube Free power from a recycled washing machine, generating enough to live off the grid Want to watch this again later? Sign in to add this video to a playlist. Need to report the video?

Sign in to report inappropriate content. Rating is available when the video has been rented. This feature is not available right now. Please try again later. Published on Oct 30, 2012 A step by step guide showing how to convert a smartdrive washing machine into a pelton wheel dc generator making 780 watts, the power is fed into a small battery bank & inverter - generating enough power to live off the grid. All you need is a head of water. I am using water from my stream to spin the turbine.

Follow this link for the video showing how to rewire the stator Category The Pelton Wheel Experiment | Dickens Mimisa - Academia.edu The Pelton Wheel Experiment Dickens Mimisa 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 2014 MIMISA JOMO KENYATTA UNIVERSITY OF AGRICULTURE AND TECHNOLOGY 8/1/2014 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 3 PERFORMANCE TEST OF A PELTON WHEEL TURBINE 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 smaller 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 arranged so that the jet of water impinges tangentially on to the buckets. The nozzle is controlled by movement 4 Fig. The configuration of the nozzle and buckets in a Pelton wheel turbine 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. 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. 5 Fig. General arrangement of the pelton wheel turbine 6 FIG.

Arrangement of Apparatus used in the Pelton Wheel Turbine Test 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 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 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. Fig. Velocity Analysis 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°. 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 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, ( ) 10 Power supplied at the inlet of the turbine or the water horse power is given by the expression .

Where = density of water (kg/m 3 ), g = acceleration due to gravity (9.81m 2 /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, ( ) 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 called the mechanical efficiency (m) of the turbine. Mathematically, 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 power at the inlet is known as the hydraulic efficiency (h) of the pelton turbine. Mathematically, ( ) 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. 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 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: Keeping 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’ coincides with end of the shade ‘V’ reflected 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. 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 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) Spring balance reading (w) kg Actual power ( ) Overall Efficie ncy (ηov) % Reading m Head (HV) m Discharge (Q) Temperatu re °C Density () kg/m 3 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 9

6.266 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 Calculations a) The theoretical power input (Pth

) of the turbine given by the expression: Where = density of water (depends on the water temperature and atmospheric pressure), Q = discharge, H = net water head on the turbine (given H=27m).

Example: 2.401W b) The actual power output (Pa) of the turbine is obtained from the expression: 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 2.287 HP c) The overall efficiency of the pelton turbine (ov) is given by the formula: Calculate the overall efficiencies of the pelton turbine at each discharge Example: 15 =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. 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. y = -1E+09x 3 + 5E+06x 2 - 2357.9x + 1.9629 y = -2E+07x 2 + 39797x + 73.253 84 89 94 99 104 109 0 1 2 3 4 5 6 7 0.0012 0.0014 0.0016 0.0018 0.002 0.0022 E f f i c i e n c y ( % ) P o w e r o u t ( H P ) Discharge (m3/s) Power Out (HP) efficiency (%) 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 READ PAPER 1000+ images about Hydroelectric on Pinterest | Pump, Power generator and Old washing machine Forward 8.10.14 - Why Are We Not Building the Voith Wells Generator Wave Energy Converter Everywhere? - "This wave energy device concept from Voith is as ingenious as it is simple. It is a shore based concrete bunker like installation that allows water to enter a chamber from a submerged opening as the waves move up and down. The water in the chamber rises and falls with the waves pushing a column of air trapped above the water level through a wells turbine generator that makes clean electricity." See More Turbines-classification | VENKITARAJ KONERY PURUSHOTHAMAN - Academia.edu V. Konery Purusho...

ME 405 Hydraulic Machinery Turbines Module-II TURBINES A hydraulic machine is a device in which mechanical energy is transferred from the liquid flowing through the machine to its operating member (runner, piston and others) or from the operating member of the machine to the liquid flowing through it. Hydraulic machines in which, the operating member receives energy from the liquid flowing through it and the inlet energy of the liquid is greater than the outlet energy of the liquid are referred as hydraulic turbines. Hydraulic machines in which energy is transmitted from the working member to the flowing liquid and the energy of the liquid at the outlet of the hydraulic machine is less than the outlet energy are referred to as pumps. It is well known from Newton’s Law that to change momentum of fluid, a force is required. Similarly, when momentum of fluid is changed, a force is generated. This principle is made use in hydraulic turbine. In a turbine, blades or buckets are provided on a wheel and directed against water to alter the momentum of water. As the momentum is changed with the water passing through the wheel, the resulting force turns the shaft of the wheel performing work and generating power. A hydraulic turbine uses potential energy and kinetic energy of water and converts it into usable mechanical energy.

The mechanical energy made available at the turbine shaft is used to run an electric power generator which is directly coupled to the turbine shaft The electric power which is obtained from the hydraulic energy is known as hydroelectric energy. Hydraulic turbines belong to the category of rotodynamic machinery. The hydraulic turbines are classified according to type of energy available at the inlet of turbine, direction of flow through vanes, head at the inlet of the turbines and specific speed of the turbines. According to the type of energy at inlet: Impulse turbine: - In the impulse turbine, the total head of the incoming fluid is converted in to a large velocity head at the exit of the supply nozzle. That is the entire available energy of the water is converted in to kinetic energy. Although there are various types of impulse turbine designs, perhaps the easiest to understand is the Pelton wheel turbine. It is most efficient when operated with a large head and lower flow rate. VENKITARAJ K P DEPT.MECH.ENGG, CE ADOOR Page 1 ME 405 Hydraulic Machinery Turbines Module-II Reaction turbine: Reaction turbines on the other hand, are best suited -for higher flow rate and lower head situations.

In this type of turbines, the rotation of runner or rotor (rotating part of the turbine) is partly due to impulse action and partly due to change in pressure over the runner blades; therefore, it is called as reaction turbine. For, a reaction turbine, the penstock pipe feeds water to a row of fixed blades through casing. These fixed blades convert a part of the pressure energy into kinetic energy before water enters the runner. The water entering the runner of a reaction turbine has both pressure energy and kinetic energy. Water leaving the turbine is still left with some energy (pressure energy and kinetic energy). Since, the flow from the inlet to tail race is under pressure, casing is absolutely necessary to enclose the turbine. In general, Reaction turbines are medium to low-head, and high-flow rate devices. The reaction turbines in use are Francis and Kaplan According to the direction of flow through runner: Tangential flow turbines: In this type of turbines, the water strikes the runner in the direction of tangent to the wheel. Example: Pelton wheel turbine. Radial flow turbines: In this type of turbines, the water strikes in the radial direction. accordingly, it is further classified as, a.

Inward flow turbine: The flow is inward from periphery to the centre (centripetal type). Example: old Francis turbine. b. Outward flow turbine: The flow is outward from the centre to periphery (centrifugal type). Example: Fourneyron turbine. Axial flow turbine: The flow of water is in the direction parallel to the axis of the shaft. Example: Kaplan turbine and propeller turbine. Mixed flow turbine: The water enters the runner in the radial direction and leaves in axial direction. Example: Modern Francis turbine. According to the head at inlet of turbine: High head turbine: In this type of turbines, the net head varies from 150m to 2000m or even more, and these turbines require a small quantity of water. Example: Pelton wheel turbine. these turbines require moderate quantity of water. Example: Francis turbine. VENKITARAJ K P DEPT.MECH.ENGG, CE ADOOR Page 2 ME 405 Hydraulic Machinery Turbines Module-II Low head turbine: The net head is less than 30m and also these turbines require large quantity of water. Example: Kaplan turbine.

According to the specific speed of the turbine similar turbine that would develop unit power when working under a unit head (1m head). Low specific speed turbine: The specific speed is less than 50. (varying from 10 to 35 for single jet and up to 50 for double jet ) Example: Pelton wheel turbine. Medium specific turbine: The specific speed is varies from 50 to 250. Example: Francis turbine. High specific turbine: the specific speed is more than 250. Example: Kaplan turbine. Radial flow turbines the water flows in radial direction. The water may flow radically from outwards to inwards or from inwards to outwards. turbine is known as inward radial flow turbine. If the water flows from inwards to outwards, the turbine is known as outward radial flow turbine. kinetic energy as well as pressure energy. Casing: - The water from penstocks enters the casing which is of spiral shape in which area of cross section of casing goes on decreasing gradually. The casing completely surrounds the runner of the turbine. Guide mechanism: - It consists of stationary circular wheel all round the runner of the turbine. The stationary guide vanes are fixed on guide mechanism.

The guide vanes allow the water to strike the vanes fixed on the runner without shock at inlet. Runner: - It is a circular wheel on which a series of radial curved vanes are fixed. The surfaces of the vanes are made very smooth. The radial curved are so shaped that the water enters and leaves without shock. VENKITARAJ K P DEPT.MECH.ENGG, CE ADOOR Page 3 ME 405 Hydraulic Machinery Turbines Module-II Draft tube: - The pressure at the exit of the runner of reaction turbine is generally less than atmospheric pressure. The water exit cannot be directly discharged to the tail race. A tube or pipe of gradually increasing area is used for discharging water from the exit of turbine to the tailrace. This tube of increasing area is called draft tube. Axial flow turbines turbine is known as axial flow turbine. kinetic energy and during the flow of water through runner a part of pressure energy is converted into kinetic energy, the turbine is known as reaction turbine. The lower end of the shaft is made larger which is known as hub. The vanes are fixed on the hub and hence hub acts as runner for axial flow reaction turbine. 1. Propeller turbine 2.

Kaplan turbine able, the turbine is known as propeller turbine. This turbine is suitable where a large quantity of water at low heads is available. VENKITARAJ K P DEPT.MECH.ENGG, CE ADOOR Page 4 ME 405 Hydraulic Machinery Turbines Module-II VENKITARAJ K P DEPT.MECH.ENGG, CE ADOOR Page 5 READ PAPER

Question: A Pelton wheel converts what power into usable energy?
Answer: Water