Hydropower water conveyance systam
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Transcript of Hydropower water conveyance systam
GAZIANTEP UNIVERSITY FACULTY OF ENGINEERING
DEPARTMENT OF CIVIL ENGINEERING
HYDROPOWER ENGINEERINGWATER CONVEYANCE SYSTEM
Submitted by: KHABAT STAR MOHAMMED MARIF MAHMOOD KARIM
ISRAA NAJAT JABBARYASIR SHAKIR MAHMOOD
Submitted to :Doç.Dr.Aytaç Güven
Water Conveyance system
Introduction
Any structure that conveys water from one location to another.
Hydropower Block Diagram
Plan ( 1 )
Plan ( 2 )
Intake
Definition of diversion head work
A structure constructed across a river to raise the normal water level and drive the required supply in to main canal or power canal
Diversion Head work
Fig. ( 1 )
Components of diversion head work
1. Barrage or weir 2. Canal head regulator3. Divide wall4. Fish ladder 5. Under sluice portion 6. Silt excluder 7. Marginal bunds 8. Guide bank
Weir Barrage
Canal head regulator
Function of head work 1. A head work raises the water level in the
river.2. It regulates the intake of water into the canal.3. It also controls the entry of silt into the canal.4. A headwork can also store water for small
periods of time.5. Reduces fluctuations in the level of supply in
river.
What is intake
A hydraulic-engineering installation for obtaining water from a source of supply (river, lake, reservoir, and so on) for purposes of hydroelectric power engineering, water supply, or irrigation.
Intake
Elements of intake
1. Trash rack and supporting structure.2. Smolt screens. 3. Bell mouth entrance. 4. Gate slot closing devices with air vents.5. Ice, log trash boom.6. Silt excluders and silt ejectors. 7. Under sluices.
1- Trash rack 2- screen
• A trash rack is a wooden or metal structure, that prevents water-borne debris (such as logs, boats, animals, masses of cut waterweed, etc.) from entering the intake of a water mill, pumping station or water conveyance. This protects penstock, and sluice gates from destruction during floods..
• Usually positioned in forebay or intake structure.
Trash Rack
Trash rack Trash rack
Removing or cleaning process to trash rack
Smolt Screen
3- Bell mouth entrance .
4 – gate slot closing It is control regulates the entry of water into the intake.
Gates
5- ICE,LOG,AND TRASH BOOMS
Floating boom use to perform one or more of the following functions
1. Deflection of logs and trash from the intake screens.
2. Deflection of ice away from the intake.3. Prevention of the boats form being carried into
the intake
Trash Boom .
6- silt excluders and silt ejectors
• Silt Control Devices A. Silt Excluder: The silt excluder is located on
the u/s of diversion weir and in front of the head regulator and the object is to remove silt that has entered in the stilling basin through scouring sluices.
B.Silt Ejector: Silt Ejector is located in the canal take off from the diversion weir it ejects the silt that has entered in the canal
Silt control
Silt excluder Silt Ejector
LOCATION OF INTAKE The various factors influencing the choice of location of intake structure are:1- Type of storage reservoir2- Location and type of dam/weir3- Type of water conductor system that is canal or tunnel4- Topographical features of the river.5- should not be located on curves or at least on shape curves 6- should remain easily accessible during floods.7- located at place from where can draw water even during the driest period of the year
TYPE OF INTAKE
•Depending on the function served and the range in reservoir head under which it is to operate, •The discharging capacity and frequency of the reservoir drawdown, intake for hydroelectric projects or more elaborate structure raised as a tower above maximum reservoir level.
Type of Intake
PLAN ( 3 )
A- According to source
1- River Intake
River intake
2- Reservoir intake
3- Lake intake
4 - Canal intake
B- According to position of intake
• An Intake structure which remains entirely under water during its operation is termed as submerged intake.
• It is provided where the structure serves only as an entrance to the outlet required.
• The conduct intake may be inclined, vertical or horizontal in accordingly with the intake requirements.
• An inclined intake may be provided with gates and operated on the upstream slopes of a low dam.
1-submerged intake
submerged intake
2- Exposed intake
• Is in the form of well or tower constructed near the bank of river or in some cases even away from the bank of river, they are more common due to ease in operation and maintenance .
Exposed intake
C – According to presence of water in the tower
• In dry intake tower the entry ports are directly connected with the withdrawal conduit and water inside the tower when gates are in a closed position.
• Dry Intake tower has a merit that the intake tower being dry is made accessible for inspection and operation besides that the water can be withdrawn from any level by opening the port at that level.
1- Dry intake tower
2- Wet Intake Tower
• A wet intake tower has entry ports at various levels and the vertical shaft is filled with water up to reservoir level.
• It differs from the dry intake tower is that the water enters from the ports into the tower and then into the withdrawal conduct through separate gated openings.
Wet intake tower
QUALITY WATER
1- Location of intake is required to be such as to draw the best quality of water from the reservoir.
2- Depth of water at intake is important.
3- Quality of water varies at different levels in the reservoir and it is necessary to draw water fromdifferent elevation of the reservoir at different seasons of the Year for which multi-level intakes are frequently provided.
Water conveyance systemThe main components are :A. Open channel flow systemB. Pressure flow system
Open channel flow and pressure flow systems
What is Open channel?A covered or uncovered conduit in which liquid (usually water) flows with its top surface bounded by the atmosphere. Typical open channels are rivers, streams, canals, flumes, or sewers, and water-supply or hydropower aqueducts
Classification of open channel
Based on : 1. shape 2. natural / artificial (man made) 3. change in cross section and slope 4. boundary characteristic
Classification based on a shape
1.Rectangular2.Trapezoidal 3. Triangular4. semi-Circular5.Parabolic6.Compound
Trapezoidal open channel
Rectangularopen channel
semi-circular open channel
Triangularopen channel
Compound open channel
Parabolic open channel
Open channel geometric relationships for varies cross-section
Classification based on
• Natural channel All watercourses that exist naturally on the
earth like Brooke ,creeks , tidal• Artificial channel Those constructed to perform various project
requirements and termed canals Flumes , culverts
Natural channel Artificial channel
Classification based on change in slope and cross section
Prismatic : a channel in which cross section shape and size also the bottom slope are constant , most of man-made channels(artificial) are prismatic channels like rectangular ,trapezoidal , triangular ,circular channels
• Non – prismatic : slope or cross section changes, all natural channels generally have varying in cross section and consequently are non- prismatic.
Classification based on boundary characteristic
Mobile boundary channel Rigid boundary channel
Forebay
• A forebay is an artificial pool of water in which located before and connected with penstocks
• Provided in case of run-off- river plants • The major use of forebay was to distribution Flow of water in to penstocks , store water
which is rejected by hydropower plant , Containing a trash rack and bye-pass channel.
Forebay connecting with penstock and Containing a trash rack and bye-pass channel
Forebay in nature
Trashrack that which used to prevent undesirable material (planate , dead animals) for entering to penstock that may choke the system
BANK AND CHANNEL PROTECTIVE LINING
Lining are Protective layer artificial or natural material which placed in a channel bottom and banks that may be used to: • prevent erosion resulting from high velocities of water • breaking down resulting from entering water in Cracks and gaps• shapely appearance and proper
Lining classification The main classifications of open channel linings are based on the material which that covered the channel and we have two items :
• Rigid Linings
• Flexible linings
Rigid LiningsRigid linings are generally constructed of concrete, pvc, or concrete blocks pavement they are more expensive , prevent infiltration and Require periodic maintenancewhose smoothness offers a higher capacity for a given cross-sectional area and Higher VelocitiesThe following are examples of Rigid Linings:
Pri –cast concrete channel
concrete blocks channel Pvc channel
Flexible liningsFlexible linings have several advantages compared to rigid linings They are generally less expensive, permit infiltration and exhilaration and can be vegetated to have a natural appearance, have self-healing qualities which reduce maintenance In many cases flexible linings are designed to provide only transitional protection against erosion
The following are examples of Flexible linings:
Grasses or natural vegetation
Grass linings are suitable for applications where they will be exposed to periodic relatively slow flow of water This type of lining has a pleasing appearance, is economical and is not subject to damage as a result of undermining or settlement of the supporting soils
Rubble riprap
Wire-enclosed riprap
B:Pressure flow system1- Low-pressure conduits and tunnels2- High-pressure conduits, commonly called the
penstocks
TunnelsTunnels can be designed as underground passages made without removing the overlying rock or soil.
TBM: also known as a "mole", is a machine used to excavate tunnels with a circular cross section through a variety of soil and rock strata. They may also be used for micro tunneling. They can bore through anything from hard rock to sand.
Layout of a tunnel alignmentThe first aspect that needs to be decided for a tunnel is the alignment .
Hydropower tunnel•
Hydraulic tunnels can be divided into the following categories:
1- Pressure tunnels2- Free flowing tunnelsDepending on their shape, tunnels may be classified as:1- D-shaped2- Horse-shoe shaped 3- Circular shaped4- Egg Shaped and Egglipse Sections
Tunnel section
Cross – section of a tunnel depends on the following factors:1- Geological conditions prevailing along the alignment,2- Structural considerations, and3- Hydraulic requirements,4- Functional requirements.
D-SHAPED SECTION:• D-shaped section is found to be suitable in tunnels located
in good quality, intact sedimentary rocks and massive external igneous, hard ,compacted , metamorphic rocks where the external or internal pressures.
Horse-Shoe sectionThis sections are strong in their resistance to external pressure. Quality of rock and adequate rock cover in terms of the internal pressure to which the tunnel is subjected govern the use of these sections. This section offers the advantage of flat base for constructional ease and change over to circular section with minimum additional expenditure in reaches of inadequate rock cover and poor rock formation.
Note: For tunnel excavated to horse -shoe section and concreted to circular section.
Modify horse shoe section
Egg Shaped and Egglipse Sections• Where the rock is stratified soft and very closely laminated (as
laminated sand stones, slates, micaceous schists , etc) and where the external pressure and tensile forces in the crown are likely to be high so as to cause serious rock falls, those sections should be considered.
Circular sectionThe circular section is most suitable from structural consideration. It is difficult to excavation where cross-sectional area is small. In case where the tunnel is subjected to high internal pressure, but does not have good quality of rock and/or adequate rock cover around it. circular section is considered to be most suitable.
Steel supports These are built of steel sections, usually I-sections, either shaped or welded in pieces in the form of a curve or a straight section
Installing steel supports
ROOF BOLTS OF ROCK• Rock bolts were used to support the roof and walls of major structures
such as tunnels and power stations• These steel bolts, of different length and spacing, were inserted into the
rock where they were found to be an excellent anchorage for the rock.
Tunnel Lining• Tunnel linings: main types. Tunnel linings are grouped into three
main forms some or all of which may be used in the construction of a tunnel.
• Temporary ground support• Primary lining• Secondary lining • Temporary ground support: In rock tunnels where the ground has
insufficient stand-up time to allow the construction of the primary lining some distance behind the face.
• Primary lining. A primary lining is the main structural component of the tunnel support system which is required to sustain the loads and deformations that the ground may induce during the tunnel's intended working life.
• Secondary lining. Various tunnels require smooth bore profiles for their intended use, eg sewer and water tunnels or aesthetic finishes for public usage, eg highway and pedestrian tunnels.
Arch steel support
Shotcrete in tunnel
Tunnel Grouting: This is a cement mortar with proportion of cement, sand and water in the ratio 1:1:1 by weight usually, though it may be modified suitably according to site
conditions.types of grouting:• Back-fill grouting :to fill spaces between initial lining and
rock.• − Contact grouting: to fill gaps between initial lining and plug
concrete.• − Consolidation grouting: to improve the quality of the
surrounding rock.• − Curtain grouting: To preventing water seepage from the
waterway end portion.
• Grouting
• Grouting process
• Pattern of Holes for Grouting• Backfill or Contact Grouting - Backfill grouting is limited to
the arch portion of the tunnel. The number of holes normally three in each section, the pattern being staggered in each subsequent sections located 3 m center to center.
Consolidation or Pressure Grouting -• Consolidation grouting is done to consolidate the shattered rock
all around the cavity. The pattern of holes is such that these are distributed all along the periphery but staggered in alternate sections space 3 m center to center. The number of holes may be four for smaller tunnels six for bigger tunnels.
Consolidation or Pressure Grouting 6 holes
What is surge tankSurge tank is located between the headrace pressure conduit and the steeply sloping penstock pipe and is designed either as a chamber excavated in the mountain or as a tower raising high above the surrounding terrain.
The main functions of a surge tank are:• Reduces the amplitude of pressure
fluctuations by reflecting the incoming pressure waves.
• Improves the regulating characteristics of a hydraulic turbine because; it reduces the water starting time of a hydropower scheme.
• Surge tanks, which are used to dissipate water hammer pressure
Water Hammer
• Water Hammer is a pressure surge or wave that occurs when there is a sudden momentum change of a fluid (the motion of a fluid is abruptly forced to stop or change direction) within an enclosed space (Water Hammer).
• This commonly occurs in pipelines when a valve is closed suddenly at the end of a pipeline where the velocity of the fluid is high. The pressure wave created will propagate within the pipeline.
Depending upon its configuration, a surge tank may be classified as follows;
• 1- Simple surge tank: A simple surge tank is a shaft connected to pressure tunnel directly or by a short connection of cross-sectional area not less than the area of the head race tunnel.
2- Orifice surge tank: if the entrance to the surge tank is restricted by means of an orifice, it is called an orifice tank.
3- Differential surge tank: an orifice tank having a riser is called differential tank.
4-Closed surge tank:If the top of the tank is closed and there is compressed air between the water surface and the top of the tank, then the tank is called closed surge tank, a tank with air cushion.
5-Surge Tank with Spilling Chamber
PENSTOCK
What is penstock ?•A penstock is one of the parts of conveyance system that construct from a steel or reinforced concrete to resist high pressure in the water conveyance system
• What is the Function of penstock?
• It’s function is conveying water from for bay or surge tank to the turbine in the power hous and it’s help to increase the kinetic energy of water that comes from the end of head race.
Type of penstock
1. Buried penstocks 2. Exposed penstocks
Buried penstocks:
are supported continuously on the soil at the bottom of a trench backfilled after placing the pipe. The thickness of the cover over the pipe should be about 1.o to 1.2 m.
Advantage:• The soil cover protects the penstock against effect of
temperature variations,• It protects the conveyed water against freezing.• Buried pipes do not spoil the landscape.• They are safer against rock slides, avalanches and falling
trees.
Disadvantage:
• the inspection and faults cannot be determined easily.• It’s installation expensive Especially For large diameters and
rocky soils.• On steep hillsides, especially if the friction coefficient of the
soil is low, such pipes may slide.• Maintenance and repair of the pipe is difficult.
are installed above the terrain surface and supported on piers (briefly called supports or saddles). Consequently, there is no
contact between the terrain and the pipe itself, and the support is not continuous but confined piers.
Advantage:•The possibility of continuous and adequate inspection during operation.•Its installation is less expensive in case of large diameters of rocky terrain.•Safety against sliding may be ensured by properly designed anchorages.•Such pipes are readily accessible and maintenance and repair operations can be carried out easily
Exposed penstocks:
Disadvantage:
• Full exposure to external variations in temperature.• The water conveyed may freeze.• Owing to the spacing of supports and anchorages
significant longitudinal stresses may develop especially in pipes of large diameters designed for low internal pressures
Design of penstock:
• According to the Bureau of Indian Standards code IS: 11625-1986 “Criteria for hydraulic design of penstocks” The determination of penstock diameter based on the following losses may be expected for a penstock:
a. Head loss at trash rock .b. Head loss at intake entrance .c. Friction losses, and .d. Other losses as at bends, bifurcations, transitions,
values, etc.
Bends Depending on topography, the alignment of the penstock is often
required to be changed, in direction, to obtain the most economical profile.
Reducer piece:In the case of very long penstocks, it is often necessary to reduce the diameter
of the pipe as the head on the pipe increases. This reduction from one diameter to another should be effected gradually by introducing a special pipe piece called reducer piece.
Branch pipe: Depending upon the number of units a single penstock feeds.
Expansion joints :are installed in exposed penstocks to prevent longitudinal expansion or contraction when changes in temperature occur.
Manholes: Manholes are provided in the course of the penstock length to provide access to the pipe interior for inspection, maintenance and repair.
Air vents and valves: These are provided on the immediate downstream side of the control gate or valve to facilitate connection with the atmosphere.
How hydropower system work ?
• Tailraces: After passing through the turbine the water
returns to the river trough a short canal called a tailrace.
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