Stirling Engines

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Stirling EnginesElectric Motors
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A Stirling Engine which runs of a coffee
cuphttp//jlnlabs.imars.com/html/stirling.htm

• created on January 31, 2001 - JLN Labs - Last
  update February 2, 2001, All informations and
  diagrams are published freely (freeware) and are
  intended for a private use and a non commercial
  use.

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Stirling-cycle engines

• They has been patented in 1816 by Robert
  Stirling, a Scottish engineer.
• The Stirling-cycle engine runs on the expansion
  and contraction of a gas forced between separate
  hot and cold chambers.
• The resulting change in volume is then used to
  drive a piston, which can then be used to power
  external devices.
• Imagine a compact, quiet power plant that
  delivers some kilowatts of electricity-plus hot
  water for heating. Let's say this power source is
  also virtually pollution-free, able to burn most
  fuels, and requires minimal maintenance.
• I have purchased my own Stirling Engine model at
  the American Stirling Company, the model is the
  "Coffee Cup Stirling Engine MM-1".
• This model works very well and turn at a high
  speed on a simple coffee cup filled with water
  and heated in a simple microwaves oven...

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• When the air inside the engine is heated it
  expands and pushes up on the piston.
• Then when the air is cooled, it contracts and
  pulls down on the piston.

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See the video of the Stirling engine MM-1
inaction

• Video Amination Using RealPlayer
  F\???????\???\stirling.rm

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How a Stirling Engine Works-http//www.infiniacor
p.com/technology/how_stirling_works.htm,

• Originally developed by Robert Stirling in 1816,
  the Stirling cycle uses a working fluid
  (typically Helium, Nitrogen or Hydrogen gas) in a
  closed cylinder containing a piston.
• Heated on one end and cooled on the other, the
  expansion and cooling of the gas drives the
  piston back and forth in the cylinder.
• Amination piston_engine1.swf (Courtesy of NASA)

Animation of a 55 We Stirling TDC
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How a Stirling Engine Works-http//www.infiniacor
p.com/technology/how_stirling_works.htm,

• The work performed by this piston-motion is used
  to drive a generator (in Infinias case, a
  patented linear alternator) or to create pressure
  waves to drive a compression process.
• The cycle can be operated in reverse by using the
  generator as a motor to drive the piston.
• In this case, the continuous expansion and
  cooling of the working fluid caused by the piston
  motion creates a cooling effect.
• These types of systems are called Stirling
  coolers (also referred to as cryocoolers) and can
  maintain temperatures as low as 10 Kelvin
  (-263C, and 442 F)
• The partners at the NASA Glenn Research Center,
  have put together some excellent educational
  materials about the science of the Stirling
  Cycle. Learn More.

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Various Stirling cycle configurations in
operation -http//www.grc.nasa.gov/WWW/tmsb/stirl
ing/doc/stirling_animation.html

• The following animations illustrate various
  Stirling cycle configurations in operation. Click
  on the image to view the animation. They take a
  while to load.
• The 55 We Stirling TDC operating in a vertical
  orientation created by Jeff Schreiber.
• Amination piston_engine1.swf
• (Courtesy of NASA)

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Dual opposed 55 We Stirling TDCs-Created by Jeff
Schreiber

• Stirling Animation - Dual Opposed obtained from
  NASA Glenn Research Center Thermo-Mechanical
  Systems Branch
• http//www.grc.nasa.gov/WWW/tmsb/stirling/animatio
  n/anim_2.html

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Stirling Rhombic drive

• http//www.grc.nasa.gov/WWW/tmsb/stirling/animatio
  n/anim_3.html
• Created by Salvatore Oriti, 5490 co-op student

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Stirling Rhombic drive
http//www.grc.nasa.gov/WWW/tmsb/stirling/animatio
n/anim_4.html Created by Jeff Schreiber
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Stirling Animation - Beta Configuration-Created
by Salvatore Oriti, 5490 co-op student

• Amination file animation_dual_opposed_with_rods_j
  eff.gif
• Last Revision March 20, 2002

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Stirling Animation Gamma (L) Beta (R)
Configurations-Created by Kyle Schneider, 5490
summer student
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HyperPhysics-Educational Web site

• http//hyperphysics.phy-astr.gsu.edu/hbase/electri
  c/dccircon.htmlc1

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How Does an Electric Motor Work?

• http//hyperphysics.phy-astr.gsu.edu/hbase/magneti
  c/mothow.htmlc1

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DC Motor Operation

• This is an active graphic. Click on bold type for
  further illustration.

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Electric Current in DC Motor
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Magnetic Field in DC Motor Operation
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Commutator and Brushes on DC Motor

• To keep the torque on a DC motor from reversing
  every time the coil moves through the plane
  perpendicular to the magnetic field, a split-ring
  device called a commutator is used to reverse the
  current at that point.
• The electrical contacts to the rotating ring are
  called "brushes" since copper brush contacts were
  used in early motors. Modern motors normally use
  spring-loaded carbon contacts, but the historical
  name for the contacts has persisted.

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Torque in DC Motor
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Torque Variation in DC Motor
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Electricity Magnetism
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Concepts of Magnetic Forces
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Applications of Magnetic Force
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AC Generator

• The turning of a coil in a magnetic field
  produces motional emfs in both sides of the coil
  which add.
• Since the component of the velocity perpendicular
  to the magnetic field changes sinusoidally with
  the rotation, the generated voltage is sinusoidal
  or AC.
• This process can be described in terms of
  Faraday's law when you see that the rotation of
  the coil continually changes the magnetic flux
  through the coil and therefore generates a
  voltage.

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How Does an Electric Generator Work?http//hyperp
hysics.phy-astr.gsu.edu/hbase/magnetic/genhow.html
c1
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Magnetic Force on Moving Charge

• This is an active graphic. Click on highlighted
  text for further detail.

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Lorentz Force Law

• Both the electric field and magnetic field can be
  defined from the Lorentz force law

• The electric force is straightforward, being in
  the direction of the electric field if the charge
  q is positive, but the direction of the magnetic
  part of the force is given by the right hand
  rule.

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Voltage Generated in a Moving Wire
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AC Generator

• The turning of a coil in a magnetic field
  produces motional emfs in both sides of the coil
  which add.

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Generator and Motor

• A hand-cranked generator can be used to generate
  voltage to turn a motor. This is an example of
  energy conversion from mechanical to electrical
  energy and then back to mechanical energy.

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AC Motor

• As in the DC motor case, a current is passed
  through the coil, generating a torque on the
  coil. Since the current is alternating, the motor
  will run smoothly only at the frequency of the
  sine wave. It is called a synchronous motor. More
  common is the induction motor, where electric
  current is induced in the rotating coils rather
  than supplied to them directly. One of the
  drawbacks of this kind of AC motor is the high
  current which must flow through the rotating
  contacts. Sparking and heating at those contacts
  can waste energy and shorten the lifetime of the
  motor. In common AC motors the magnetic field is
  produced by an electromagnet powered by the same
  AC voltage as the motor coil. The coils which
  produce the magnetic field are sometimes referred
  to as the "stator", while the coils and the solid
  core which rotates is called the "armature". In
  an AC motor the magnetic field is sinusoidally
  varying, just as the current in the coil varies.

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Magnetic Force

• The magnetic field B is defined from the Lorentz
  Force Law, and specifically from the magnetic
  force on a moving charge

The implications of this expression
include 1. The force is perpendicular to both
the velocity v of the charge q and the magnetic
field B. 2. The magnitude of the force is F qvB
sin? where ? is the angle lt 180 degrees between
the velocity and the magnetic field. This implies
that the magnetic force on a stationary charge or
a charge moving parallel to the magnetic field is
zero. 3. The direction of the force is given by
the right hand rule. The force relationship above
is in the form of a vector product.
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Magnetic Force

• The magnetic field B is defined from the Lorentz
  Force Law, and specifically from the magnetic
  force on a moving charge

• From the force relationship above it can be
  deduced that the units of magnetic field are
  Newton seconds /(Coulomb meter) or Newtons per
  Ampere meter.
• This unit is named the Tesla. It is a large unit,
  and the smaller unit Gauss is used for small
  fields like the Earth's magnetic field.
• A Tesla is 10,000 Gauss.
• The Earth's magnetic field is on the order of
  half a Gauss.

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Right Hand Rule

• A useful mnemonic for visualizing the direction
  of a magnetic force as given by the Lorentz force
  law.
• The diagrams above are two of the forms used to
  visualize the force on a moving positive charge.
  The force is in the opposite direction for a
  negative charge moving in the direction shown.
  One fact to keep in mind is that the magnetic
  force is perpendicular to both the magnetic field
  and the charge velocity, but that leaves two
  possibilities. The right hand rule just helps you
  pin down which of the two directions applies.

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Right Hand Rule

• The right hand rule is a useful mnemonic for
  visualizing the direction of a magnetic force as
  given by the Lorentz force law.
• The diagrams above are two of the forms used to
  visualize the force on a moving positive charge.
• The force is in the opposite direction for a
  negative charge moving in the direction shown.
• One fact to keep in mind is that the magnetic
  force is perpendicular to both the magnetic field
  and the charge velocity, but that leaves two
  possibilities.
• The right hand rule just helps you pin down which
  of the two directions applies.
• For applications to current-carrying wires, the
  conventional electric current direction can be
  substituted for the charge velocity v in the
  above digram.