Automobile Engine 4 Stroke Cycle ENGS100

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Automobile Engine 4 Stroke Cycle ENGS100 Powered By Docstoc
					Automobile Engine

   4 Stroke Cycle
           Automobile: Main systems
1.       Engine – convert energy of fuel to energy of motion
2.       Powertrain – transfer power from engine to driven wheels
3.       Brakes – slow and stop vehicle
4.       Steering – control direction of travel
5.       Suspension
     –      Absorb bumps
     –      Maintain alignment
     –      Keep wheels in contact with road
6.       Electrical – generate and distribute electricity
7.       Body – protect occupants (
      Automobile: Main Theme
• Visually apparent how form follows function.
• Visually Accessible.
• How it works is there to see if look in the right
• Components performing specific function in
  overall system also very apparent.
• Systems and subsystems of components
  contributing to overall operation also readily
  apparent in automobile.
                             Engine                Exhaust
Chemical energy of     Convert chemical to
fuel and air                                       Heat
                         Kinetic energy
                       (energy of motion)
     Fuel                                          Kinetic Energy
                                                  Engine RPM

            System Boundary – automobile engine

            Start at location where air and fuel
            are burned and work out from there.

            Put the car together starting with
            the combustion
  Engine: Underlying Principle
• Internal combustion engine
  – Energy conversion device
  – Heat engine
  – Heat -> Work
• Converts energy of fuel into energy of
• 4 –stroke cycle
• Otto cycle
           Engine Construction
• Basic “generic” Internal
  Combustion Automobile
• Start where air/fuel are
  burned and work out from
• Strip off components        Engine
• Engine put together in      Engine head
  two halves
   – Upper half = head          Engine block
   – Lower half = block
   – Seal between upper and    Engine head
     lower = head gasket       gasket
        Engine Construction
• Look at single
• Most automobile
  engines have more
  than one cylinder
• Same process in
  each one
                     Engine: Main Parts
1.   Cylinder – contain burning air/fuel – hole in
     metal block
2.   Piston – convert pressure of burning air/fuel
     to force – metal plug
3.   Crank – convert linear to rotary motion –
     crank-shaped metal
4.   Connecting Rod – Transfer force from piston
     to crank – metal bar
5.   Spark plug – Ignite air/fuel mixture –
     Insulated gap
6.   Intake port – allow air/fuel into cylinder –
     hole in engine head
7.   Intake valve – control flow through intake
     port – upside down metal T
8.   Exhaust port – allow exhaust to exit cylinder
     – hole in engine head
9.   Exhaust valve – control flow through
     exhaust port – upside down metal T
4-Stroke Cycle
4-Stroke Cycle
                       4-Stroke Cycle Details
•   Cams
     –      Open and close intake and exhaust valves.
     –      Camshaft: several cams connected together.
     –      OHC: Over head Cam, cam is above valves, allows higher engine speeds.
     –      DOHC: Double Overhead Cam, separate control of intake and exhaust valve to optimize performance.

•   Timing Belt (also timing chain, timing gears)
     –      Connects crankshaft to camshaft
     –      Coordinates opening and closing of valves with up and down motion of pistons.
     –      Insures that valves are opened and closed at proper time.

•   Flywheel
     –      Heavy metal disk at the end of the crankshaft.
     –      Helps to smooth out surges from the power strokes to keep engine rotating at a uniform rate.

•   Rings
     –      Help seal pistons to cylinder walls

•   Firing Order
     –      Each cylinder in different part of the cycle
     –      Insures always one cylinder pushing the others
     –      Smooths out vibrations
     –      Distributes heat input to engine block

•   Multi valve engines
     –      Small valves move quicker
• Form following function
• More than one design possible
  – Valve trains
  – Timing
    Firing Order

1   2   3   4
P   E   C   I
E   I   P   C
I   C   E   P
C   P   I   E
Valve Trains (Cam Variation)
OHV and OHC Valve Trains
Gear                                Belt

Connects crankshaft and camshaft
Coordinates valves and pistons
Timing Belt
Timing Chain
Timing Gear
Multi Valve Engines
          • Normal Innovation
                     Rotary Engine