POWER

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POWER
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Power

• Power measures how quickly work is done
• Power systems are the machines that use energy to
  perform work
• They are found in automobiles, jet airplanes and
  the tape drive of a cassette player
• 1 hp 550 ft lbs/sec or 1 hp 33,000 ft
  lbs/min
• 1 hp 746 Watts

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Power Systems

• They have two major parts --- engine and
  transmission
• An engine is a machine that uses energy to create
  mechanical force and motion --- automobiles,
  trucks, jet aircraft, submarines and home
  appliances
• A transmission, or drive, is a device that
  transfers force from one place to another or
  changes its direction --- belts, pulleys, chains
  and gears
• A transmission may also increase/decrease the
  force or divide it into smaller parts
• People in around 600 BC used simple engines using
  the energy of animals and the wind --- grinding
  grain, pumping water
• Today, engines uses the energy in fuels. They
  change the energy stored in fuels into mechanical
  force and motion
• The fuel in todays engines is portable

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Transmission
Engine
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Engines

• Automobiles, rockets, factories
• Types external, internal combustion engines,
  reaction engines, electrical motors and nuclear
  reactors
• External Combustion Engines
• The fuel is burned in a separate chamber
• Expanding gas builds up pressure and applies
  force on a piston or turbine
• Force on a piston gives a back-and-forth
  (reciprocating) motion
• Force on a turbine gives a rotational (turning)
  motion
• A flywheel and connecting rod are used to change
  the movement of the piston into rotary motion
• The flywheel builds up momentum and smoothes out
  the rotary motion
• In a railroad locomotive, the drive wheels are
  connected to steam pistons

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Engines

• Internal Combustion Engines
• First successful engine was invented by Otto in
  1876
• Fuel is burned in a closed chamber --- combustion
  chamber
• Burning fuel becomes expanding gas and pushes a
  piston
• Piston is connected by a rod to a crankshaft
• Crankshaft changes the pistons reciprocating
  motion into rotary motion
• Small engines are used in lawn mowers, portable
  generators and snow throwers etc
• No spark plugs is used in a diesel engine. They
  are used in large trucks and ships etc
• When the piston or flywheel makes an object (the
  load) move, work is done. In this way, the engine
  delivers power

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Engines

• Internal Combustion Engines
• Four Stroke Cycle
• Intake Stroke
• Compression Stroke
• Power Stroke
• Exhaust Stroke