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    الصورة الرمزية حسن هادي
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    turbines ///التوربينات

    نقدم للاخوة الاعضاء ما تحت ايدينا من محاضرات ومواقع نت وغيرها حول التوربينات ونبدأ بالتوربين المائي ومن ثم يليها الانواع الاخرى مع كل احترامي
    Water turbine

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    Kaplan turbine and electrical generator cut-away view.



    The rotor of the small water turbine


    A water turbine is a rotary engine that takes energy from moving water.
    Water turbines were developed in the nineteenth century and were widely used for industrial power prior to electrical grids. Now they are mostly used for electric power generation. They harness a clean and renewable energy source.
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    [hide]
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    [edit] History


    [edit] Swirl

    Water wheels have been used for thousands of years for industrial power. Their main shortcoming is size, which limits the flow rate and head that can be harnessed.
    The migration from water wheels to modern turbines took about one hundred years. Development occurred during the Industrial revolution, using scientific principles and methods. They also made extensive use of new materials and manufacturing methods developed at the time.
    The word turbine was coined by the French engineer Claude Bourdin in the early 19th century and is derived from the Latin word for "whirling" or a "vortex". The main difference between early water turbines and water wheels is a swirl component of the water which passes energy to a spinning rotor. This additional component of motion allowed the turbine to be smaller than a water wheel of the same power. They could process more water by spinning faster and could harness much greater heads. (Later, impulse turbines were developed which didn't use swirl).

    [edit] Time line


    A Francis turbine runner, rated at nearly one million hp (750 MW), being installed at the Grand Coulee Dam



    A propeller-type runner rated 28,000 hp (21 MW)


    Ján Andrej Segner developed a reactive water turbine in the mid-1700s. It had a horizontal axis and was a precursor to modern water turbines. It is a very simple machine that is still produced today for use in small hydro sites. Segner worked with Euler on some of the early mathematical theories of turbine design.
    In 1820, Jean-Victor Poncelet developed an inward-flow turbine.
    In 1826 Benoit Fourneyron developed an outward-flow turbine. This was an efficient machine (~80%) that sent water through a runner with blades curved in one dimension. The stationary outlet also had curved guides.
    In 1844 Uriah A. Boyden developed an outward flow turbine that improved on the performance of the Fourneyron turbine. Its runner shape was similar to that of a Francis turbine.
    In 1849, James B. Francis improved the inward flow reaction turbine to over 90% efficiency. He also conducted sophisticated tests and developed engineering methods for water turbine design. The Francis turbine, named for him, is the first modern water turbine. It is still the most widely used water turbine in the world today.

    Inward flow water turbines have a better mechanical arrangement and all modern reaction water turbines are of this design. Also, as the swirling mass of water spins into a tighter rotation, it tries to speed up to conserve energy. This property acts on the runner, in addition to the water's falling weight and swirling motion. Water pressure decreases to zero as it passes through the turbine blades and gives up its energy.
    Around 1890, the modern fluid bearing was invented, now universally used to support heavy water turbine spindles. As of 2002, fluid bearings appear to have a mean time between failures of more than 1300 years.
    Around 1913, Victor Kaplan created the Kaplan turbine, a propeller-type machine. It was an evolution of the Francis turbine but revolutionized the ability to develop low-head hydro sites.

    [edit] A new concept


    Figure from Pelton's original patent (October 1880)


    All common water machines until the late 19th century (including water wheels) were reaction machines; water's pressure head acted on the machine and produced work. A reaction turbine needs to fully contain the water during energy transfer.
    In 1866, California millwright Samuel Knight invented a machine that worked off a completely different concept[1][2]. Inspired by the high pressure jet systems used in hydraulic mining in the gold fields, Knight developed a bucketed wheel which captured the energy of a free jet, which had converted a high head (hundreds of vertical feet in a pipe or penstock) of water to kinetic energy. This is called an impulse or tangential turbine. The water's velocity, roughly twice the velocity of the bucket periphery, does a u-turn in the bucket and drops out of the runner at 0 velocity.
    In 1879, Lester Pelton, experimenting with a Knight Wheel, developed a double bucket design, which exhausted the water to the side, eliminating some energy loss of the Knight wheel which exhausted some water back against the center of the wheel. In about 1895, William Doble improved on Pelton's half-cylindrical bucket form with an elliptical bucket that included a cut in it to allow the jet a cleaner bucket entry. This is the modern form of the Pelton turbine which today achieves up to 92% efficiency. Pelton had been quite an effective promoter of his design and although Doble took over the Pelton company he did not change the name to Doble because it had brand name recognition.
    Turgo and Crossflow turbines were later impulse designs.

  2. [2]
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    [edit] Theory of operation

    Flowing water is directed on to the blades of a turbine runner, creating a force on the blades. Since the runner is spinning, the force acts through a distance (force acting through a distance is the definition of work). In this way, energy is transferred from the water flow to the turbine.
    Water turbines are divided into two groups; reaction turbines and impulse turbines.
    The precise shape of water turbine, whatever its design, is driven by the supply pressure of water.

    [edit] Reaction turbines

    Reaction turbines are acted on by water, which changes pressure as it moves through the turbine and gives up its energy. They must be encased to contain the water pressure (or suction), or they must be fully submerged in the water flow.
    Newton's third law describes the transfer of energy for reaction turbines.
    Most water turbines in use are reaction turbines. They are used in low and medium head applications.

    [edit] Impulse turbines

    Impulse turbines change the velocity of a water jet. The jet impinges on the turbine's curved blades which reverse the flow. The resulting change in momentum (impulse) causes a force on the turbine blades. Since the turbine is spinning, the force acts through a distance (work) and the diverted water flow is left with diminished energy.
    Prior to hitting the turbine blades, the water's pressure (potential energy) is converted to kinetic energy by a nozzle and focused on the turbine. No pressure change occurs at the turbine blades, and the turbine doesn't require a housing for operation.
    Newton's second law describes the transfer of energy for impulse turbines.
    Impulse turbines are most often used in very high head applications.

    [edit] Power

    The power available in a stream of water is;

    where:
    • P = power (J/s or watts)
    • η = turbine efficiency
    • ρ = density of water (kg/m3)
    • g = acceleration of gravity (9.81 m/s2)
    • h = head (m). For still water, this is the difference in height between the inlet and outlet surfaces. Moving water has an additional component added to account for the kinetic energy of the flow. The total head equals the pressure head plus velocity head.
    • = flow rate (m3/s)

    [edit] Pumped storage

    Some water turbines are designed for Pumped storage hydroelectricity. They can reverse flow and operate as a pump to fill a high reservoir during off-peak electrical hours, and then revert to a turbine for power generation during peak electrical demand. This type of turbine is usually a Deriaz or Francis in design.

    [edit] Efficiency

    Large modern water turbines operate at mechanical efficiencies greater than 90% (not to be confused with thermodynamic efficiency).

    [edit] Types of water turbines

    Reaction turbines:
    Impulse turbines:

    [edit] Design and application


    Turbine selection is based mostly on the available water head, and less so on the available flow rate. In general, impulse turbines are used for high head sites, and reaction turbines are used for low head sites. Kaplan turbines are well-adapted to wide ranges of flow or head conditions, since their peak efficiency can be achieved over a wide range of flow conditions.
    Small turbines (mostly under 10 MW) may have horizontal shafts, and even fairly large bulb-type turbines up to 100 MW or so may be horizontal. Very large Francis and Kaplan machines usually have vertical shafts because this makes best use of the available head, and makes installation of a generator more economical. Pelton wheels may be either vertical or horizontal shaft machines because the size of the machine is so much less than the available head. Some impulse turbines use multiple water jets per runner to increase specific speed and balance shaft thrust.

    [edit] Typical range of heads


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  3. [3]
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    Specific speed
    The specific speed, ns , of a turbine characterizes the turbine's shape in a way that is not related to its size. This allows a new turbine design to be scaled from an existing design of known performance. The specific speed is also the main criteria for matching a specific hydro site with the correct turbine type.
    The specific speed of a turbine can also be defined as the speed of an ideal, geometrically similar turbine, which yields one unit of power for one unit of head.
    The specific speed of a turbine is given by the manufacturer (along with other ratings) and will always refer to the point of maximum efficiency. This allows accurate calculations to be made of the turbine's performance for a range of heads and flows.

    Image adapted from European Community's 'Layman's Guidebook (on how to develop a small hydro site)'




    (dimensioned parameter), n = rpm (dimensionless parameter),
    Ω = angular velocity (radians/second) Example; Given a flow and head for a specific hydro site, and the rpm requirement of the generator, calculate the specific speed. The result is the main criteria for turbine selection.
    The specific speed is also the starting point for analytical design of a new turbine. Once the desired specific speed is known, basic dimensions of the turbine parts can be easily calculated.
    Affinity Laws allow the output of a turbine to be predicted based on model tests. A miniature replica of a proposed design, about one foot (0.3 m) in diameter, can be tested and the laboratory measurements applied to the final application with high confidence. Affinity laws are derived by requiring similitude between the test model and the application.
    Flow through the turbine is controlled either by a large valve or by wicket gates arranged around the outside of the turbine runner. Differential head and flow can be plotted for a number of different values of gate opening, producing a hill diagram used to show the efficiency of the turbine at varying conditions.

    [edit] Runaway speed

    The runaway speed of a water turbine is its speed at full flow, and no shaft load. The turbine will be designed to survive the mechanical forces of this speed. The manufacturer will supply the runaway speed rating.

    [edit] Maintenance


    A Francis turbine at the end of its life showing cavitation pitting, fatigue cracking and a catastrophic failure. Earlier repair jobs that used stainless steel weld rods are visible.


    Turbines are designed to run for decades with very little maintenance of the main elements; overhaul intervals are on the order of several years. Maintenance of the runners and parts exposed to water include removal, inspection, and repair of worn parts.
    Normal wear and tear is pitting from cavitation, fatigue cracking, and abrasion from suspended solids in the water. Steel elements are repaired by welding, usually with stainless steel rod. Damage areas are cut or ground out, then welded back up to their original or an improved profile. Old turbine runners may have a significant amount of stainless steel added this way by the end of their lifetime. Elaborate welding procedures may be used to achieve the highest quality repairs.[3]
    Other elements requiring inspection and repair during overhauls include bearings, packing box and shaft sleeves, servomotors, cooling systems for the bearings and generator coils, seal rings, wicket gate linkage elements and all surfaces. [4]


    [edit] Environmental impact

    Water turbines have had both positive and negative impacts on the environment.
    They are one of the cleanest producers of power, replacing the burning of fossil fuels and eliminating nuclear waste. They use a renewable energy source and are designed to operate for decades. They produce significant amounts of the world's electrical supply.
    Historically there have also been negative consequences. The rotating blades or gated runners of water turbines can interrupt the natural ecology of rivers, killing fish, stopping migrations, and disrupting peoples' livelihoods. For example, American Indian tribes in the Pacific Northwest had livelihoods built around salmon fishing, but aggressive dam-building destroyed their way of life. Since the late 20th century, it has been possible to construct hydropower systems that divert fish and other organisms away from turbine intakes without significant damage or loss of power; such systems require less cleaning but are substantially more expensive to construct. In the United States, it is now illegal to block the migration of fish so fish ladders must be provided by dam builders.

    [edit] See also


    [edit] References

    1. <LI id=_note-0>^ W. A. Doble, The Tangential Water Wheel, Transactions of the American Institute of Mining Engineers, Vol. XXIX, 1899. <LI id=_note-1>^ W. F. Durrand, The Pelton Water Wheel, Stanford University, Mechanical Engineering, 1939. <LI id=_note-2>^ Cline, Roger:Mechanical Overhaul Procedures for Hydroelectric Units (Facilities Instructions, Standards, and Techniques, Volume 2-7); United States Department of the Interior Bureau of Reclamation, Denver, Colorado, July 1994 (800KB pdf).
    2. ^ United States Department of the Interior Bureau of Reclamation; Duncan, William (revised April 1989): Turbine Repair (Facilities Instructions, Standards & Techniques, Volume 2-5) (1.5 MB pdf).

    [edit] External links


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  4. [4]
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    عضو متميز
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    Water Turbines

    Power has been extracted from moving water by humans for many purposes and for many centuries, and water turbines have been used in electricity generation for well over a century. Many water turbine designs have been developed over that time, and these designs continue to be further optimized with the aid of advanced simulation software from ANSYS.

    In this demanding simulation environment, where small incremental design improvements translate into substantial savings, ANSYS tools are repeatedly called upon to enhance the performance of all components of all varieties of water turbines. From multi-phase flows in Pelton turbines to non-linear stress analysis of Kaplan runners, ANSYS is the CAE provider of choice for water turbine design optimization.


    Pelton Turbine courtesy of
    VA Tech Hydro
    Kaplan Turbine courtesy of Turboinštitut, Republic of Slovenia

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  5. [5]
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    Our web address has changed, please click here to go to www.steamcycle.com.



    Steam Turbine Blade Bath Design and Analysis

    Using a new sophisticated computer code, the design and analysis of steam turbine flow path or individual stages, evaluation of proposed unit upgrades and load range changes, or analysis of units being considered for repowering to a combined cycle unit is provided.


    Suitable for fossil, nuclear, and industrial units and applicable to all geometric turbine stage configurations including: Rateau and Curtis Control Stages, impulse and reaction HP, IP, and LP staging, including the long last row LP blades, and multiple steam inlets, such as in combined cycle units.


    Using this modeling software, the following is determined:


    kW output for each stage and the entire turbine

    Individual stage and overall turbine efficiency

    Stage pressures, temperatures, and enthalpies

    Stage velocities, mach numbers, and flow angles

    Stage moisture level

    Blade loadings and rotor axial thrust

    Turbine mass flow rate for a given geometry and bounding steam conditions

    The effects of rotor blade and stator vane surface finish (roughness) as a function of local blade path flow conditions

    The effects of moisture removal on turbine performance; primarily applicable to nuclear LPs

    Effects of blade deposits on MW output and efficiency

    Effects of blade erosion on kW output and efficiency

    Effects of baffle plate replacing a stage

    Effects of turbine extractions
    Major Program Attributes

    The computer model is based on a multi-stream tube approach to flow field design and analysis, i.e., axi-symmetric (2 dimensional). It assumes a simplified radial equilibrium at stator exit (with streamline curvature option) and conservation of angular momentum between stator exit and rotor inlet (mass flows may be different).


    The program has the following customizations that allow modeling of most flow phenomena:


    Very low flow rates can be accommodated - down to no load flow. Blade flow reversal regions are determined wherein affected stages may act as a compressor delivering energy to the blade path flow

    All seal discharge coefficients are determined internally, the number of seals is arbitrary, 1 to >40, they may be straight through or stepped

    The Rateau axial seal and disc balance hole discharge coefficients are also determined internally

    Seal leakage and flow directions can reverse due to the effects of negative reaction or very low flow rates

    The control stage and Rateau stages can be partially admitted; Curtis stage admissions can be different

    Inlet steam conditions can be maintained at prescribed levels, such as consistent with given throttle conditions and inlet pressure loss characteristics

    The turbine's exhaust pressure may be held constant or may be determined as a function of a pressure-flow curve or by means of a defined flow number

    Interstage total pressure losses can be defined, such as those due to piping losses

    Several blade loss options are available including a design loss model, secondary flow losses, and incidence losses

    An efficiency modifier is also available for study purposes

    A maximum of three feedwater heaters can be accommodated, two closed heaters with or without drain coolers, and one deaerator

    Converging-diverging blade passages can be incorporated in the last rotor blade



    Inquiries as to application and/or lease of this Steam Turbine Design and Analysis Computer Program can be made to the program's developer (Turboflow International, Inc.) through Jonas, Inc.



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  6. [6]
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    Water is a renewable resource that is an important source of electricity in California and the Northwest. The potential energy of water is harnessed to produce mechanical energy which can be used directly, or used to generate electricity.
    Moving Water -- Moving Blades

    You can make a small water turbine model by taping cardboard strips on a cork. Put pins in the ends for axles and make a U-shaped holder for it. You can also slip metal or plastic fins into the slits made in the cork. This will turn as fast as the water stream is moving, so generally turbines have high speed jets directed toward them.

    An Overshot Waterwheel

    This model is like the old waterwheels used for grinding grain or running machines. Great power and slow speed were needed to turn the heavy grinding stones at an even speed.

    This device could use a relatively small stream. It is the weight of the water in the buckets that causes the wheel to overbalance and turn. You can equip your wheel with a string and bucket and find out how much weight the mechanism can lift.


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  7. [7]
    AbuMaha
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    صراحه موضوع غني جدا واحتاج الكثير من الوقت لاستفيد منه مشكوووووور

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  8. [8]
    حسن هادي
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    اقتباس المشاركة الأصلية كتبت بواسطة AbuMaha مشاهدة المشاركة
    صراحه موضوع غني جدا واحتاج الكثير من الوقت لاستفيد منه مشكوووووور
    نحن بخدمة جميع الاعضاء وشكرا على مروركم وان شاء الله سنضيف مشاركات حول التوربينات الاخرى

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  9. [9]
    حسن هادي
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    Kaplan turbine and electrical generator cut-away view.

    A water turbine is a rotary engine that takes energy from moving water.
    Water turbines were developed in the nineteenth century and were widely used for industrial power prior to electrical grids. Now they are mostly used for electric power generation. They harness a clean and renewable energy source.
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