text:
Inlet manifold
From Wikipedia, the free encyclopedia
Jump to: navigation, search
Carburetors used as intake runners
A cutaway view of the intake of the original Fordson tractor (including the intake manifold, vaporizer, carburetor, and fuel lines).
In automotive engineering, an inlet manifold or intake manifold (in American English) is the part of an engine that supplies the fuel/air mixture to the cylinders. The word manifold comes from the Old English word manigfeald (from the Anglo-Saxon manig [many] and feald [repeatedly]) and refers to the multiplying of one (pipe) into many.[1]
In contrast, an exhaust manifold collects the exhaust gases from multiple cylinders into a smaller number of pipes – often down to one pipe.
The primary function of the intake manifold is to evenly distribute the combustion mixture (or just air in a direct injection engine) to each intake port in the cylinder head(s). Even distribution is important to optimize the efficiency and performance of the engine. It may also serve as a mount for the carburetor, throttle body, fuel injectors and other components of the engine.
Due to the downward movement of the pistons and the restriction caused by the throttle valve, in a reciprocating spark ignition piston engine, a partial vacuum (lower than atmospheric pressure) exists in the intake manifold. This manifold vacuum can be substantial, and can be used as a source of automobile ancillary power to drive auxiliary systems: power assisted brakes, emission control devices, cruise control, ignition advance, windshield wipers, power windows, ventilation system valves, etc.
This vacuum can also be used to draw any piston blow-by gases from the engine's crankcase. This is known as a positive crankcase ventilation system, in which the gases are burned with the fuel/air mixture.
The intake manifold has historically been manufactured from aluminum or cast iron, but use of composite plastic materials is gaining popularity (e.g. most Chrysler 4-cylinders, Ford Zetec 2.0, Duratec 2.0 and 2.3, and GM's Ecotec series).
Contents
[hide]
1 Turbulence
2 Volumetric efficiency
3 Variable-length intake manifold
4 See also
5 References
Turbulence[edit]
The carburetor or the fuel injectors spray fuel droplets into the air in the manifold. Due to electrostatic forces some of the fuel will form into pools along the walls of the manifold, or may converge into larger droplets in the air. Both actions are undesirable because they create inconsistencies in the air-fuel ratio. Turbulence in the intake causes forces of uneven proportions in varying vectors to be applied to the fuel, aiding in atomization. Better atomization allows for a more complete burn of all the fuel and helps reduce engine knock by enlarging the flame front. To achieve this turbulence it is a common practice to leave the surfaces of the intake and intake ports in the cylinder head rough and unpolished.
Only a certain degree of turbulence is useful in the intake. Once the fuel is sufficiently atomized additional turbulence causes unneeded pressure drops and a drop in engine performance.
Volumetric efficiency[edit]
This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (July 2008) (Learn how and when to remove this template message)
See also: Cylinder head porting
Comparison of a stock intake manifold for a Volkswagen 1.8T engine (top) to a custom-built one used in competition (bottom). In the custom-built manifold, the runners to the intake ports on the cylinder head are much wider and more gently tapered. This difference improves the volumetric efficiency of the engine's fuel/air intake.
The design and orientation of the intake manifold is a major factor in the volumetric efficiency of an engine. Abrupt contour changes provoke pressure drops, resulting in less air (and/or fuel) entering the combustion chamber; high-performance manifolds have smooth contours and gradual transitions between adjacent segments.
Modern intake manifolds usually employ runners, individual tubes extending to each intake port on the cylinder head which emanate from a central volume or "plenum" beneath the carburetor. The purpose of the runner is to take advantage of the Helmholtz resonance property of air. Air flows at considerable speed through the open valve. When the valve closes, the air that has not yet entered the valve still has a lot of momentum and compresses against the valve, creating a pocket of high pressure. This high-pressure air begins to equalize with lower-pressure air in the manifold. Due to the air's inertia, the equalization will tend to oscillate: At first the air in the runner will be at a lower pressure than the manifold. The air in the manifold then tries to equalize back into the runner, and the oscillation repeats. This process occurs at the speed of sound, and in most manifolds travels up and down the runner many times before the valve opens again.
The smaller the cross-sectional area of the runner, the higher the pressure changes on resonance for a given airflow. This aspect of Helmholtz resonance reproduces one result of the Venturi effect. When the piston accelerates downwards, the pressure at the output of the intake runner is reduced. This low pressure pulse runs to the input end, where it is converted into an over-pressure pulse. This pulse travels back through the runner and rams air through the valve. The valve then closes.
To harness the full power of the Helmholtz resonance effect, the opening of the intake valve must be timed correctly, otherwise the pulse could have a negative effect. This poses a very difficult problem for engines, since valve timing is dynamic and based on engine speed, whereas the pulse timing is static and dependent on the length of the intake runner and the speed of sound. The traditional solution has been to tune the length of the intake runner for a specific engine speed where maximum performance is desired. However, modern technology has given rise to a number of solutions involving electronically controlled valve timing (for example Valvetronic), and dynamic intake geometry (see below).
As a result of "resonance tuning", some naturally aspirated intake systems operate at a volumetric efficiency above 100%: the air pressure in the combustion chamber before the compression stroke is greater than the atmospheric pressure. In combination with this intake manifold design feature, the exhaust manifold design, as well as the exhaust valve opening time can be so calibrated as to achieve greater evacuation of the cylinder. The exhaust manifolds achieve a vacuum in the cylinder just before the piston reaches top dead center.[citation needed] The opening inlet valve can then—at typical compression ratios—fill 10% of the cylinder before beginning downward travel.[citation needed] Instead of achieving higher pressure in the cylinder, the inlet valve can stay open after the piston reaches bottom dead center while the air still flows in.[citation needed][vague]
In some engines the intake runners are straight for minimal resistance. In most engines, however, the runners have curves...and some very convoluted to achieve desired runner length. These turns allow for a more compact manifold, with denser packaging of the whole engine, as a result. Also, these "snaked" runners are needed for some variable length/ split runner designs, and allow the size of the plenum to be reduced. In an engine with at least six cylinders the averaged intake flow is nearly constant and the plenum volume can be smaller. To avoid standing waves within the plenum it is made as compact as possible. The intake runners each use a smaller part of the plenum surface than the inlet, which supplies air to the plenum, for aerodynamic reasons. Each runner is placed to have nearly the same distance to the main inlet. Runners whose cylinders fire close after each other, are not placed as neighbors.
"180-degree intake manifolds"....Originally designed for carburetor V8 engines, the two plane, split plenum intake manifold separates the intake pulses which the manifold experiences by 180 degrees in the firing order. This minimizes interference of one cylinder's pressure waves with those of another, giving better torque from smooth mid-range flow. Such manifolds may have been originally designed for either two- or four-barrel carburetors, but now are used with both throttle-body and multi-point fuel injection. An example of the latter is the Honda J engine which converts to a single plane manifold around 3500 rpm for greater peak flow and horsepower.
"Heat Riser"....now obsolete, earlier manifolds ...with 'wet runners' for carbureted engines...used exhaust gas diversion through the intake manifold to provide vaporizing heat. The amount of exhaust gas flow diversion was controlled by a heat riser valve in the exhaust manifold, and employed a bi-metallic spring which changed tension according to the heat in the manifold. Today's fuel-injected engines do not require such devices.
Variable-length intake manifold[edit]
Lower intake manifold on a 1999 Mazda Miata engine, showing components of a variable length intake system.
Main article: Variable-length intake manifold
Variable-Length Intake Manifold (VLIM) is an internal combustion engine manifold technology. Four common implementations exist. First, two discrete intake runners with different length are employed, and a butterfly valve can close the short path. Second the intake runners can be bent around a common plenum, and a sliding valve separates them from the plenum with a variable length. Straight high-speed runners can receive plugs, which contain small long runner extensions. The plenum of a 6- or 8-cylinder engine can be parted into halves, with the even firing cylinders in one half and the odd firing cylinders in the other part. Both sub-plenums and the air intake are connected to an Y (sort of main plenum). The air oscillates between both sub-plenums, with a large pressure oscillation there, but a constant pressure at the main plenum. Each runner from a sub plenum to the main plenum can be changed in length. For V engines this can be implemented by parting a single large plenum at high engine speed by means of sliding valves into it when speed is reduced.
As the name implies, VLIM can vary the length of the intake tract in order to optimize power and torque, as well as provide better fuel efficiency.
There are two main effects of variable intake geometry:
Venturi effect - At low rpm, the speed of the airflow is increased by directing the air through a path with limited capacity (cross-sectional area). The larger path opens when the load increases so that a greater amount of air can enter the chamber. In dual overhead cam (DOHC) designs, the air paths are often connected to separate intake valves so the shorter path can be excluded by deactivating the intake valve itself.
Pressurization - A tuned intake path can have a light pressurizing effect similar to a low-pressure supercharger due to Helmholtz resonance. However, this effect occurs only over a narrow engine speed range which is directly influenced by intake length. A variable intake can create two or more pressurized "hot spots." When the intake air speed is higher, the dynamic pressure pushing the air (and/or mixture) inside the engine is increased. The dynamic pressure is proportional to the square of the inlet air speed, so by making the passage narrower or longer the speed/dynamic pressure is increased.
Many automobile manufacturers use similar technology with different names. Another common term for this technology is Variable Resonance Induction System (VRIS).
Vehicles using variable intake geometry [show]
Audi - 2.8-liter V6 gas engine (1991–98); 3.6- and 4.2-liter V8 engines, 1987–present
Alfa Romeo - 2.0 TwinSpark 16v - 155 ps(114 kW)
BMW DISA and DIVA systems
Dodge - 2.0 A588 - ECH (2001–2005) used in the 2001–2005 model year Dodge Neon R/T
Ferrari - 360 Modena, 550 Maranello
Ford VIS (Variable-resonance Intake System) - on their 2.9-liter 24V Cosworth (BOB) based on the Ford Cologne V6 engine in the later model Ford Scorpio.
Ford DSI (Dual-Stage Intake) - on their Duratec 2.5- and 3.0-liter V6s and it was also found on the Yamaha V6 in the Taurus SHO.
Ford - The Ford Modular V8 engines sport either the Intake Manifold Runner Control (IMRC) for 4V engines, or the Charge Motion Control Valve (CMCV) for 3V engines.
Ford - The 2.0L Split Port engine in the Ford Escort and Mercury Tracer feature an Intake Manifold Runner Control variable geometry intake manifold.
General Motors - 3.9L LZ8/LZ9 V6, 3.2L LA3 V6, and the 4.3L LF4 V6 in some second generation S10s and Sonomas
GM Daewoo - DOHC versions of E-TEC II engines
Holden - Alloytec
Honda - Integra, Legend, NSX, Prelude
Hyundai - XG V6
Isuzu - Isuzu Rodeo Used in the second generation V6, 3.2L (6VD1) Rodeos.
Jaguar - AJ-V6
Lancia VIS
Mazda VICS (Variable Inertia Charging System) is used on the Mazda FE-DOHC engine and Mazda B engine family of straight-4s, and VRIS (Variable Resistance Induction System) in the Mazda K engine family of V6 engines. An updated version of this technology is employed on the new Mazda Z engine, which is also used by Ford as the Duratec.
Mercedes-Benz
MG - MG ZS 180 MG ZT 160, 180 and 190
Mitsubishi Cyclone is used on the 2.0L I4 4G63 engine family.
Nissan I4, V6, V8
Opel (or Vauxhall) TwinPort - modern versions of Ecotec Family 1 and Ecotec Family 0 straight-4 engines; a similar technology is used in 3.2 L 54° V6 engine
Peugeot 2.2 L I4, 3.0 L V6
Porsche VarioRam - 964, 993, 996, Boxster
Proton Campro CPS and VIM - Proton Gen-2 CPS and Proton Waja CPS; Proton Campro IAFM - 2008 Proton Saga 1.3
Renault - Clio 2.0RS
Rover - Rover 623 Rover 825 Rover 75 v6 Rover 45 v6
Subaru Legacy 1989–1994 JDM EJ20 2.0-liter naturally aspirated DOHC 16-valve flat-4
Subaru SVX 1992–1997 EG33 3.3-liter naturally aspirated DOHC 24-valve flat-6
Subaru Legacy and Subaru Impreza1999–2001 JDM EJ20 2.0-liter naturally aspirated DOHC 16-valve flat-4
Toyota T-VIS - (Toyota Variable Induction System) used in the early versions of the 3S-GE, 7M-GE, and 4A-GE engines, and ACIS - (Acoustic Control Induction System).
Volkswagen - 1.6 L I4, VR6, W8
Volvo - VVIS (Volvo Variable Induction System) Volvo B52 engine as found on the Volvo 850 and S70/V70 vehicles, and their successors. Longer inlet ducts used between 1500 and 4100 rpm at 80% load or higher.[2]
See also[edit]
Cylinder head porting
Fusible core injection molding
References[edit]
Wikimedia Commons has media related to Intake manifolds.
Jump up ^ manifold, (adv.) "in the proportion of many to one, by many times". AD1526 Oxford English Dictionary,
Jump up ^ Volvoclub UK: 850GLT Engine Info
[show]
v
t
e
Reciprocating engines and configurations
Type
Bourke
Orbital
Piston
Pistonless (Wankel)
Radial
Rotary
Split cycle
Stelzer
Tschudi
Stroke cycles
Two-stroke
Four-stroke
Five-stroke
Six-stroke
Two-and four-stroke
Configurations
& number of cylinders
Single cylinder
Single
Two cylinders
Split-single
I2
V2
F2
Inline / straight
I2
I3
I4
I5
I6
I7
I8
I9
I10
I12
I14
Flat
F2
F4
F6
F8
F10
F12
F16
V / Vee
V2
V3
V4
V5
V6
V8
V10
V12
V14
V16
V18
V20
V24
W
W8
W12
W16
W18
Other inline
H
U
Square four
VR
Opposed
X
X24
Junkers Jumo 222
Components
Valves
Cylinder head porting
Corliss
Intake
Exhaust
Multi
Overhead
Piston
Poppet
Side
Sleeve
Slide
Rotary valve
Variable valve timing
Camless
Desmodromic
Hydraulic tappet
Fuel supplies
Carburetor
Gasoline direct injection
Common rail
Mechanisms
Cam
Camshaft
Overhead camshaft
Connecting rod
Crank
Crankshaft
Scotch yoke
Swashplate
Rhombic drive
Linkages
Peaucellier–Lipkin
Watt's (parallel)
Other
Hemi
Recuperator
Turbo-compounding
[show]
v
t
e
Automotive engine
Part of the Automobile series
Basic terminology
Bore
Compression ratio
Crank
Cylinder
Dead centre
Diesel engine
Dry sump
Engine balance
Engine configuration
Engine displacement
Engine knocking
Firing order
Hydrolock
Petrol engine
Power band
Redline
Spark-ignition engine
Stroke
Stroke ratio
Wet sump
Main components
Connecting rod
Crankcase
Crankpin
Crankshaft
Crossflow cylinder head
Crossplane
Cylinder bank
Cylinder block
Cylinder head
Flywheel
Head gasket
Hypereutectic piston
Main bearing
Piston
Piston ring
Reverse-flow cylinder head
Starter ring gear
Sump
Valvetrain
Cam
Cam follower
Camshaft
Desmodromic valve
Hydraulic tappet
Multi-valve
Overhead camshaft
Overhead valve
Pneumatic valve springs
Poppet valve
Pushrod
Rocker arm
Sleeve valve
Tappet
Timing belt
Timing mark
Valve float
Variable valve timing
Aspiration
Air filter
Blowoff valve
Boost controller
Butterfly valve
Centrifugal-type supercharger
Cold air intake
Dump valve
Electronic throttle control
Forced induction
Inlet manifold
Intake
Intercooler
Manifold vacuum
Naturally aspirated engine
Ram-air intake
Scroll-type supercharger
Short ram air intake
Supercharger
Throttle
Throttle body
Turbocharger
Twin-turbo
Variable-geometry turbocharger
Variable-length intake manifold
Warm air intake
Fuel system
Carburetor
Common rail
Direct injection
Fuel filter
Fuel injection
Fuel pump
Fuel tank
Gasoline direct injection
Indirect injection
Injection pump
Lean-burn
Stratified charge engine
Turbo fuel stratified injection
Unit injector
Ignition
Contact breaker
Magneto
Distributor
Electrical ballast
High tension leads
Ignition coil
Spark plug
Wasted spark
Electrics and engine
management
Air–fuel ratio meter
Alternator
Automatic Performance Control
Car battery (lead–acid battery)
Crankshaft position sensor
Dynamo
Drive by wire
Electronic control unit
Engine control unit
Engine coolant temperature sensor
Glow plug
Idle air control actuator
MAP sensor
Mass flow sensor
Oxygen sensor
Starter motor
Throttle position sensor
Exhaust system
Automobile emissions control
Catalytic converter
Diesel particulate filter
Exhaust manifold
Glasspack
Muffler
Engine cooling
Air cooling
Antifreeze (ethylene glycol)
Core plug
Electric fan
Fan belt
Radiator
Thermostat
Water cooling
Viscous fan (fan clutch)
Other components
Balance shaft
Block heater
Combustion chamber
Cylinder head porting
Gasket
Motor oil
Oil filter
Oil pump
Oil sludge
PCV valve
Seal
Synthetic oil
Underdrive pulleys
Portal
Category
Retrieved from "https://en.wikipedia.org/w/index.php?title=Inlet_manifold&oldid=800136899"
Categories:
Engine technology
Auto parts
Hidden categories:
Articles needing additional references from July 2008
All articles needing additional references
All articles with unsourced statements
Articles with unsourced statements from July 2008
All Wikipedia articles needing clarification
Wikipedia articles needing clarification from February 2009
Navigation menu
Personal tools
Not logged in
Talk
Contributions
Create account
Log in
Namespaces
Article
Talk
Variants
Views
Read
Edit
View history
More
Search
Navigation
Main page
Contents
Featured content
Current events
Random article
Donate to Wikipedia
Wikipedia store
Interaction
Help
About Wikipedia
Community portal
Recent changes
Contact page
Tools
What links here
Related changes
Upload file
Special pages
Permanent link
Page information
Wikidata item
Cite this page
Print/export
Create a book
Download as PDF
Printable version
In other projects
Wikimedia Commons
Languages
Català
Dansk
Deutsch
Español
Français
Galego
Italiano
Nederlands
日本語
Polski
Português
Română
Slovenčina
Suomi
Svenska
Українська
Edit links
This page was last edited on 11 September 2017, at 18:24.
Text is available under the Creative Commons Attribution-ShareAlike License; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization.
Privacy policy
About Wikipedia
Disclaimers
Contact Wikipedia
Developers
Cookie statement
Mobile view
Enable previews

key: html

type: local

value: div

attrs: id class

values: mw-page-base noprint

values: mw-head-base noprint

attrs: id class style

value: a

attrs: id class lang

values: firstHeading firstHeading en

values: siteSub noprint

values: jump-to-nav mw-jump

value: img

attrs: alt src width height class srcset data-file-width data-file-height

attrs: href class

attrs: href class title

attrs: href title

values: /wiki/Carburetor#Vaporizers Carburetor

values:
/wiki/Manifold_(engineering)
mw-redirect
Manifold (engineering)

values:
/wiki/Spark_ignition
mw-redirect
Spark ignition

values:
/wiki/Piston_engine
mw-redirect
Piston engine

values:
/wiki/Automobile_ancillary_power
mw-redirect
Automobile ancillary power

values:
/wiki/Windshield_wiper
mw-redirect
Windshield wiper

values:
/wiki/Air-fuel_ratio
mw-redirect
Air-fuel ratio

attrs: alt src width height srcset data-file-width data-file-height

values: Help:Introduction to referencing with Wiki Markup/1

values: plainlinks metadata ambox ambox-content ambox-Unreferenced

values: This claim needs references to reliable sources. (July 2008)

values:
noprint Inline-Template Template-Fact
white-space:nowrap;

values: This information is too vague. (February 2009)

values:
/wiki/Multi-point_fuel_injection
mw-redirect
Multi-point fuel injection

values: Edit section: Variable-length intake manifold

values:
/wiki/Dual_overhead_cam
mw-redirect
Dual overhead cam

values:
/wiki/Ferrari_360_Modena
mw-redirect
Ferrari 360 Modena

values:
/wiki/Ferrari_550_Maranello
mw-redirect
Ferrari 550 Maranello

values:
/wiki/Yamaha_Motor_Corporation
mw-redirect
Yamaha Motor Corporation

values:
/wiki/GM_High_Value_Engine
mw-redirect
GM High Value Engine

values:
/wiki/GM_54-Degree_V6_engine
mw-redirect
GM 54-Degree V6 engine

values:
/wiki/Jaguar_(car)
mw-redirect
Jaguar (car)

values:
/wiki/Mitsubishi_4G63_engine
mw-redirect
Mitsubishi 4G63 engine

values:
/wiki/Ecotec_Family_1
mw-redirect
Ecotec Family 1

values:
/wiki/Ecotec_Family_0
mw-redirect
Ecotec Family 0

values:
/wiki/Porsche_Boxster
mw-redirect
Porsche Boxster

values:
/wiki/Proton_(carmaker)
mw-redirect
Proton (carmaker)

values:
/wiki/Proton_Gen-2
mw-redirect
Proton Gen-2

values:
/wiki/Campro_engine#Campro_IAFM_engine
mw-redirect
Campro engine

values:
/wiki/Japanese_Domestic_Market
mw-redirect
Japanese Domestic Market

values:
/wiki/Subaru_SVX#Engines
mw-redirect
Subaru SVX

values:
/wiki/Toyota_4A-GE
mw-redirect
Toyota 4A-GE

values:
/wiki/Volvo_B52_engine
mw-redirect
Volvo B52 engine

values: text-align: left; display: none; background: transparent;

values:
NavFrame collapsed
border:none;
NavFrame1

values:
reflist mw-references-wrap
list-style-type: decimal;

values: Template talk:Piston engine configurations

values:
/wiki/Orbital_engine
mw-redirect
Orbital engine

values:
/wiki/Tschudi_engine
mw-redirect
Tschudi engine

values:
/wiki/Intake_valve
mw-redirect
Intake valve

values: nowraplinks collapsible autocollapse navbox-inner

values:
/wiki/Throttle_body
mw-redirect
Throttle body

values:
/wiki/Mechanical_fan
mw-redirect
Mechanical fan

values:
navbox-abovebelow hlist
2
font-weight:bold;

values: Category:Articles needing additional references from July 2008

values: Category:All articles needing additional references

values: Category:All articles with unsourced statements

values: Category:Articles with unsourced statements from July 2008

values: Category:All Wikipedia articles needing clarification

values: Category:Wikipedia articles needing clarification from February 2009

values: Discussion about edits from this IP address [ctrl-alt-n]

values: A list of edits made from this IP address [ctrl-alt-y]

values: You are encouraged to create an account and log in; however, it is not mandatory

values: You're encouraged to log in; however, it's not mandatory. [ctrl-alt-o]

values:
/wiki/Inlet_manifold
View the content page [ctrl-alt-c]
c

values: Discussion about the content page [ctrl-alt-t]

values: p-namespaces navigation vectorTabs p-namespaces-label

values:
p-variants
navigation
vectorMenu emptyPortlet
p-variants-label

values: Past revisions of this page [ctrl-alt-h]

values: p-views navigation vectorTabs p-views-label

values:
p-cactions
navigation
vectorMenu emptyPortlet
p-cactions-label

values:
mw-wiki-logo
/wiki/Main_Page
Visit the main page

values:
/wiki/Main_Page
Visit the main page [ctrl-alt-z]
z

values: Featured content – the best of Wikipedia

values: Find background information on current events

values:
/wiki/Special:Random
Load a random article [ctrl-alt-x]
x

values: portal navigation p-navigation p-navigation-label

values: Guidance on how to use and edit Wikipedia

values: About the project, what you can do, where to find things

values: A list of recent changes in the wiki [ctrl-alt-r]

values: portal navigation p-interaction p-interaction-label

values: List of all English Wikipedia pages containing links to this page [ctrl-alt-j]

values: Recent changes in pages linked from this page [ctrl-alt-k]

values:
/wiki/Wikipedia:File_Upload_Wizard
Upload files [ctrl-alt-u]
u

values: A list of all special pages [ctrl-alt-q]

values: Permanent link to this revision of the page

values: Link to connected data repository item [ctrl-alt-g]

values: Printable version of this page [ctrl-alt-p]

values: portal navigation p-wikibase-otherprojects p-wikibase-otherprojects-label

values:
uls-settings-trigger
Language settings
0
button
true

values: インテークマニホールド – Japanese

values:
https://fi.wikipedia.org/wiki/Imusarja
Imusarja – Finnish
fi
fi
interlanguage-link-target

values: Впускний колектор – Ukrainian

values: mediawiki ltr sitedir-ltr mw-hide-empty-elt ns-0 ns-subject page-Inlet_manifold rootpage-Inlet_manifold skin-vector action-view


text:
Hydraulic head
From Wikipedia, the free encyclopedia
Jump to: navigation, search
Available difference in hydraulic head across a hydroelectric dam, before head losses due to turbines, wall friction and turbulence.
Fluid flows from the tank at the top to the basin at the bottom under the pressure of the hydraulic head.
Hydraulic head or piezometric head is a specific measurement of liquid pressure above a geodetic datum.[1][2]
It is usually measured as a liquid surface elevation, expressed in units of length, at the entrance (or bottom) of a piezometer. In an aquifer, it can be calculated from the depth to water in a piezometric well (a specialized water well), and given information of the piezometer's elevation and screen depth. Hydraulic head can similarly be measured in a column of water using a standpipe piezometer by measuring the height of the water surface in the tube relative to a common datum. The hydraulic head can be used to determine a hydraulic gradient between two or more points.
Contents
[hide]
1 "Head" in fluid dynamics
2 Components of hydraulic head
2.1 Fresh water head
3 Hydraulic gradient
4 Hydraulic head in groundwater
4.1 Atmospheric pressure
5 Head loss
6 Analogs to other fields
7 See also
8 Notes
9 References
"Head" in fluid dynamics[edit]
In fluid dynamics, head is a concept that relates the energy in an incompressible fluid to the height of an equivalent static column of that fluid. From Bernoulli's Principle, the total energy at a given point in a fluid is the energy associated with the movement of the fluid, plus energy from static pressure in the fluid, plus energy from the height of the fluid relative to an arbitrary datum. Head is expressed in units of height such as meters or feet.
The static head of a pump is the maximum height (pressure) it can deliver. The capability of the pump at a certain RPM can be read from its Q-H curve (flow vs. height).
A common misconception is that the head equals the fluid's energy per unit weight, while, in fact, the term with pressure does not represent any type of energy (in the Bernoulli equation for an incompressible fluid this term represents work of pressure forces). Head is useful in specifying centrifugal pumps because their pumping characteristics tend to be independent of the fluid's density.
There are four types of head used to calculate the total head in and out of a pump:
Velocity head is due to the bulk motion of a fluid (kinetic energy). Its pressure head correspondent is the dynamic pressure.
Elevation head is due to the fluid's weight, the gravitational force acting on a column of fluid.
Pressure head is due to the static pressure, the internal molecular motion of a fluid that exerts a force on its container.
Resistance head (or friction head or Head Loss) is due to the frictional forces acting against a fluid's motion by the container.
Components of hydraulic head[edit]
A mass free falling from an elevation z > 0 {\displaystyle z\,>\,0\,} (in a vacuum) will reach a speed
v = 2 g z , {\displaystyle v={\sqrt {{2g}{z}}},} when arriving at elevation z=0, or when we rearrange it as a head: h = v 2 2 g {\displaystyle h={\frac {v^{2}}{2g}}}
where
g {\displaystyle g} is the acceleration due to gravity
The term v 2 2 g {\displaystyle {\frac {v^{2}}{2g}}} is called the velocity head, expressed as a length measurement. In a flowing fluid, it represents the energy of the fluid due to its bulk motion.
The total hydraulic head of a fluid is composed of pressure head and elevation head.[1][2] The pressure head is the equivalent gauge pressure of a column of water at the base of the piezometer, and the elevation head is the relative potential energy in terms of an elevation. The head equation, a simplified form of the Bernoulli Principle for incompressible fluids, can be expressed as:
h = ψ + z {\displaystyle h=\psi +z\,}
where
h {\displaystyle h} is the hydraulic head (Length in m or ft), also known as the piezometric head.
ψ {\displaystyle \psi } is the pressure head, in terms of the elevation difference of the water column relative to the piezometer bottom (Length in m or ft), and
z {\displaystyle z} is the elevation at the piezometer bottom (Length in m or ft)
In an example with a 400 m deep piezometer, with an elevation of 1000 m, and a depth to water of 100 m: z = 600 m, ψ = 300 m, and h = 900 m.
The pressure head can be expressed as:
ψ = P γ = P ρ g {\displaystyle \psi ={\frac {P}{\gamma }}={\frac {P}{\rho g}}}
where
P {\displaystyle P} is the gauge pressure (Force per unit area, often Pa or psi),
γ {\displaystyle \gamma } is the unit weight of the liquid (Force per unit volume, typically N·m−3 or lbf/ft³),
ρ {\displaystyle \rho } is the density of the liquid (Mass per unit volume, frequently kg·m−3), and
g {\displaystyle g} is the gravitational acceleration (velocity change per unit time, often m·s−2)
Fresh water head[edit]
The pressure head is dependent on the density of water, which can vary depending on both the temperature and chemical composition (salinity, in particular). This means that the hydraulic head calculation is dependent on the density of the water within the piezometer. If one or more hydraulic head measurements are to be compared, they need to be standardized, usually to their fresh water head, which can be calculated as:
h f w = ψ ρ ρ f w + z {\displaystyle h_{\mathrm {fw} }=\psi {\frac {\rho }{\rho _{\mathrm {fw} }}}+z}
where
h f w {\displaystyle h_{\mathrm {fw} }\,} is the fresh water head (Length, measured in m or ft), and
ρ f w {\displaystyle \rho _{\mathrm {fw} }\,} is the density of fresh water (Mass per unit volume, typically in kg·m−3)
Hydraulic gradient[edit]
The hydraulic gradient is a vector gradient between two or more hydraulic head measurements over the length of the flow path. For groundwater, it is also called the 'Darcy slope', since it determines the quantity of a Darcy flux or discharge. It also has applications in open-channel flow where it can be used to determine whether a reach is gaining or losing energy. A dimensionless hydraulic gradient can be calculated between two points with known head values as:
i = d h d l = h 2 − h 1 l e n g t h {\displaystyle i={\frac {dh}{dl}}={\frac {h_{2}-h_{1}}{\mathrm {length} }}}
where
i {\displaystyle i} is the hydraulic gradient (dimensionless),
d h {\displaystyle dh} is the difference between two hydraulic heads (Length, usually in m or ft), and
d l {\displaystyle dl} is the flow path length between the two piezometers (Length, usually in m or ft)
The hydraulic gradient can be expressed in vector notation, using the del operator. This requires a hydraulic head field, which can only be practically obtained from a numerical model, such as MODFLOW for groundwater or standard step or HEC-RAS for open channels. In Cartesian coordinates, this can be expressed as:
∇ h = ( ∂ h ∂ x , ∂ h ∂ y , ∂ h ∂ z ) = ∂ h ∂ x i + ∂ h ∂ y j + ∂ h ∂ z k {\displaystyle \nabla h=\left({\frac {\partial h}{\partial x}},{\frac {\partial h}{\partial y}},{\frac {\partial h}{\partial z}}\right)={\frac {\partial h}{\partial x}}\mathbf {i} +{\frac {\partial h}{\partial y}}\mathbf {j} +{\frac {\partial h}{\partial z}}\mathbf {k} }
This vector describes the direction of the groundwater flow, where negative values indicate flow along the dimension, and zero indicates 'no flow'. As with any other example in physics, energy must flow from high to low, which is why the flow is in the negative gradient. This vector can be used in conjunction with Darcy's law and a tensor of hydraulic conductivity to determine the flux of water in three dimensions.
Hydraulic head in groundwater[edit]
Relation between heads for a hydrostatic case and a downward flow case.
The distribution of hydraulic head through an aquifer determines where groundwater will flow. In a hydrostatic example (first figure), where the hydraulic head is constant, there is no flow. However, if there is a difference in hydraulic head from the top to bottom due to draining from the bottom (second figure), the water will flow downward, due to the difference in head, also called the hydraulic gradient.
Atmospheric pressure[edit]
Even though it is convention to use gauge pressure in the calculation of hydraulic head, it is more correct to use total pressure (gauge pressure + atmospheric pressure), since this is truly what drives groundwater flow. Often detailed observations of barometric pressure are not available at each well through time, so this is often disregarded (contributing to large errors at locations where hydraulic gradients are low or the angle between wells is acute.)
The effects of changes in atmospheric pressure upon water levels observed in wells has been known for many years. The effect is a direct one, an increase in atmospheric pressure is an increase in load on the water in the aquifer, which increases the depth to water (lowers the water level elevation). Pascal first qualitatively observed these effects in the 17th century, and they were more rigorously described by the soil physicist Edgar Buckingham (working for the United States Department of Agriculture (USDA)) using air flow models in 1907.
Head loss[edit]
In any real moving fluid, energy is dissipated due to friction; turbulence dissipates even more energy for high Reynolds number flows. This dissipation, called head loss, is divided into two main categories, "major losses" associated with energy loss per length of pipe, and "minor losses" associated with bends, fittings, valves, etc. The most common equation used to calculate major head losses is the Darcy–Weisbach equation. Older, more empirical approaches are the Hazen–Williams equation and the Prony equation.
For relatively short pipe systems, with a relatively large number of bends and fittings, minor losses can easily exceed major losses. In design, minor losses are usually estimated from tables using coefficients or a simpler and less accurate reduction of minor losses to equivalent length of pipe.
Analogs to other fields[edit]
Hydraulic head is a measure of energy, and has many analogs in physics and chemistry, where the same mathematical principles and rules apply:
Hydraulic head is analogous to:
magnetic monopole
electric charge
heat (i.e., temperature)
concentration
A continuous field of the hydraulic head is analogous to:
an electric field
a magnetic field
Similar differential operators can be applied to the fields, to find:
the gradient, or the direction of flow
the divergence of flow
the curl, or if the field is rotating
See also[edit]
Borda–Carnot equation
Dynamic pressure
Total dynamic head
[hide]
v
t
e
Physical aquifer properties used in hydrogeology
hydraulic head
hydraulic conductivity
storativity
permeability
porosity
water content
[show]
v
t
e
Hydropower
Hydroelectricity generation
Dam
List of conventional hydroelectric power stations
Pumped-storage hydroelectricity
Small hydro
Micro hydro
Pico hydro
Hydroelectricity equipment
Francis turbine
Kaplan turbine
Tyson turbine
Gorlov helical turbine
Pelton wheel
Turgo turbine
Cross-flow turbine
Water wheel
Notes[edit]
^ Jump up to: a b Mulley, Raymond (2004), Flow of Industrial Fluids: Theory and Equations, CRC Press, ISBN 0849327679 , 410 pages. See pp. 43–44.
^ Jump up to: a b Chanson, Hubert (2004), Hydraulics of Open Channel Flow: An Introduction, Butterworth–Heinemann, ISBN 0750659785 , 650 pages. See p. 22.
References[edit]
Bear, J. 1972. Dynamics of Fluids in Porous Media, Dover. ISBN 0-486-65675-6.
for other references which discuss hydraulic head in the context of hydrogeology, see that page's further reading section

Retrieved from "https://en.wikipedia.org/w/index.php?title=Hydraulic_head&oldid=809043691"
Categories:
Aquifers
Water
Hydrology
Fluid dynamics
Water wells
Navigation menu
Personal tools
Not logged in
Talk
Contributions
Create account
Log in
Namespaces
Article
Talk
Variants
Views
Read
Edit
View history
More
Search
Navigation
Main page
Contents
Featured content
Current events
Random article
Donate to Wikipedia
Wikipedia store
Interaction
Help
About Wikipedia
Community portal
Recent changes
Contact page
Tools
What links here
Related changes
Upload file
Special pages
Permanent link
Page information
Wikidata item
Cite this page
Print/export
Create a book
Download as PDF
Printable version
Languages
Català
Deutsch
Español
Français
Italiano
עברית
ქართული
Қазақша
Bahasa Melayu
Nederlands
日本語
Русский
Simple English
ไทย
Українська
中文
Edit links
This page was last edited on 6 November 2017, at 20:13.
Text is available under the Creative Commons Attribution-ShareAlike License; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization.
Privacy policy
About Wikipedia
Disclaimers
Contact Wikipedia
Developers
Cookie statement
Mobile view
Enable previews

values: mw-page-base noprint

values: mw-head-base noprint

values: firstHeading firstHeading en

values: siteSub noprint

values: jump-to-nav mw-jump

values:
/wiki/Hydroelectric_dam
mw-redirect
Hydroelectric dam

attrs: class style

value: b

values:
/wiki/Bernoulli%27s_Principle
mw-redirect
Bernoulli's Principle

values:
/wiki/Datum_(geodesy)
mw-redirect
Datum (geodesy)

values:
/wiki/Velocity_head
mw-redirect
Velocity head

values:
/wiki/Gravitational_force
mw-redirect
Gravitational force

values: Edit section: Components of hydraulic head

values: vertical-align: -0.338ex; width:6.542ex; height:2.176ex;

values: vertical-align: -1.171ex; width:10.636ex; height:3.509ex;

values: vertical-align: -2.338ex; width:7.594ex; height:6.176ex;

values: vertical-align: -0.671ex; width:1.126ex; height:2.009ex;

values:
/wiki/Term_(mathematics)
mw-redirect
Term (mathematics)

values: vertical-align: -2.338ex; width:3.135ex; height:6.176ex;

values:
/wiki/Gauge_(engineering)
mw-redirect
Gauge (engineering)

values: vertical-align: -0.671ex; width:10.318ex; height:2.509ex;

values: vertical-align: -0.338ex; width:1.349ex; height:2.176ex;

values: vertical-align: -0.671ex; width:1.524ex; height:2.509ex;

values: vertical-align: -0.338ex; width:1.099ex; height:1.676ex;

values: vertical-align: -2.338ex; width:13.508ex; height:5.843ex;

values: \psi = \frac{P}{\gamma} = \frac{P}{\rho g}

values: vertical-align: -0.338ex; width:1.756ex; height:2.176ex;

values: vertical-align: -0.838ex; width:1.273ex; height:2.176ex;

values:
/wiki/Unit_weight
mw-redirect
Unit weight

values: vertical-align: -0.838ex; width:1.212ex; height:2.176ex;

values: vertical-align: -2.338ex; width:16.071ex; height:5.343ex;

values: h_\mathrm{fw} = \psi \frac{\rho}{\rho_\mathrm{fw}} + z

values: vertical-align: -0.671ex; width:3.782ex; height:2.509ex;

values: vertical-align: -0.838ex; width:3.645ex; height:2.176ex;

values: vertical-align: -2.505ex; width:18.952ex; height:6.009ex;

values: i = \frac{dh}{dl} = \frac{h_2 - h_1}{\mathrm{length}}

values: vertical-align: -0.338ex; width:0.813ex; height:2.176ex;

values: vertical-align: -0.338ex; width:2.576ex; height:2.176ex;

values: vertical-align: -0.338ex; width:1.93ex; height:2.176ex;

values:
/wiki/Cartesian_coordinates
mw-redirect
Cartesian coordinates

values: vertical-align: -2.505ex; width:44.831ex; height:6.176ex;

values:
\nabla h = \left(
{\frac{\partial h}{\partial x}},
{\frac{\partial h}{\partial y}},
{\frac{\partial h}{\partial z}}
\right) =
{\frac{\partial h}{\partial x}}\mathbf{i} +
{\frac{\partial h}{\partial y}}\mathbf{j} +
{\frac{\partial h}{\partial z}}\mathbf{k}

values: Edit section: Hydraulic head in groundwater

values:
/wiki/Fluid_pressure
mw-redirect
Fluid pressure

values:
/wiki/Gauge_pressure
mw-redirect
Gauge pressure

values:
/wiki/Barometric_pressure
mw-redirect
Barometric pressure

values: nowraplinks collapsible show navbox-inner

values:
navbox-image
2
width:1px;padding:0px 0px 0px 2px

values: nowraplinks hlist collapsible autocollapse navbox-inner

values: navigation navbox Hydropower padding:3px

values:
catlinks mw-normal-catlinks
catlinks mw-normal-catlinks
interface

values: Discussion about edits from this IP address [ctrl-alt-n]

values: A list of edits made from this IP address [ctrl-alt-y]

values: You are encouraged to create an account and log in; however, it is not mandatory

values: You're encouraged to log in; however, it's not mandatory. [ctrl-alt-o]

values:
/wiki/Hydraulic_head
View the content page [ctrl-alt-c]
c

values: Discussion about the content page [ctrl-alt-t]

values: p-namespaces navigation vectorTabs p-namespaces-label

values:
p-variants
navigation
vectorMenu emptyPortlet
p-variants-label

values: Past revisions of this page [ctrl-alt-h]

values: p-views navigation vectorTabs p-views-label

values:
p-cactions
navigation
vectorMenu emptyPortlet
p-cactions-label

values:
mw-wiki-logo
/wiki/Main_Page
Visit the main page

values:
/wiki/Main_Page
Visit the main page [ctrl-alt-z]
z

values: Featured content – the best of Wikipedia

values: Find background information on current events

values:
/wiki/Special:Random
Load a random article [ctrl-alt-x]
x

values: עומד הידראולי – Hebrew

values: დაწნევა – Georgian

values: Арын (Химия) – Kazakh

values: ไฮดรอลิกเฮด – Thai

values: /static/images/wikimedia-button-1.5x.png 1.5x, /static/images/wikimedia-button-2x.png 2x

values: /static/images/poweredby_mediawiki_132x47.png 1.5x, /static/images/poweredby_mediawiki_176x62.png 2x

values:
suggestions
display: none; font-size: 13px;

values: mediawiki ltr sitedir-ltr mw-hide-empty-elt ns-0 ns-subject page-Hydraulic_head rootpage-Hydraulic_head skin-vector action-view