Automobile Engine 4 Stroke Cycle ENGS100.pdf

7/27/2019 Automobile Engine 4 Stroke Cycle ENGS100.pdf

http://slidepdf.com/reader/full/automobile-engine-4-stroke-cycle-engs100pdf 1/30

Automobile Engine

4 Stroke Cycle



Automobile: Main systems1. Engine – convert energy of fuel to energy of motion

2. Powertrain – transfer power from engine to driven wheels3. 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

place.

• 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

Chemical energy of

fuel and air

Engine

Convert chemical to

Kinetic energy

(energy of motion)Fuel

Air

System Boundary – automobile engine

Exhaust

Heat

Kinetic Energy

Engine RPM

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

motion.

• 4 –stroke cycle

• Otto cycle



Engine Construction• Basic “generic” Internal

Combustion AutomobileEngine.

• Start where air/fuel are

burned and work out from

there.

• Strip off components

• Engine put together in

two halves – Upper half = head

– Lower half = block

– Seal between upper and

lower = head gasket

Engine head

Engine

Engine block

Engine head

gasket



Engine Construction

• Look at single

cylinder • Most automobile

engines have more

than one cylinder • Same process in

each one



Engine: Main Parts1. Cylinder – contain burning air/fuel – hole in

metal block

2. Piston – convert pressure of burning air/fuelto 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



Valves



Crankshaft



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



Illustrations

• 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



Rings



Cams



Valve Trains (Cam Variation)



OHC and OHV



OHV and OHC Valve Trains



Timing

Connects crankshaft and camshaft

Coordinates valves and pistons

Gear Chain Belt



Timing Belt



Timing Chain



Timing Gear



Flywheel



Multi Valve Engines• Normal Innovation



Rotary Engine

http://upload.wikimedia.org/wikipedia/commons/f/fc/Wankel_Cycle_anim_en.gi

f

Automobile Engine 4 Stroke Cycle ENGS100.pdf

Documents

Transcript of Automobile Engine 4 Stroke Cycle ENGS100.pdf