4. Internal Combustion Engines
The internal combustion engine is
an engine in which the
combustion of fuel-oxidizer
mixture occurs in a confined space
applied in:
automotive
rail transportation
power generation
ships
aviation
garden appliances
7. Internal Combustion Engines
– two stroke -
1. Power / Exhaust 2. Intake / Compression
a. ignition
b. piston moves downward
compressing fuel-air mixture
in the crankcase
c. exhaust port opens
a. inlet port opens
b. compressed fuel-air mixture
rushes into the cylinder
c. piston upward movement
provides further compression
8. Internal Combustion Engines
– two stroke -
Advantages:
•lack of valves, which simplifies construction and
lowers weight
•fire once every revolution, which gives a
significant power boost
•can work in any orientation
•good power to weight ratio
Drawbacks:
•lack of a dedicated lubrication system makes
the engine to wear faster.
•necessity of oil addition into the fuel
•low efficiency
•produce a lot of pollution
9. Internal Combustion Engines
– four stroke -
starting position
a. piston starts moving
down
b. intake valve opens
c. air-fuel mixture
gets in
1. intake
a. piston moves up
b. both valves closed
c. air-fuel mixture
gets compressed
2. compression
10. Internal Combustion Engines
– four stroke -
ignition
a. air-fuel mixture
explodes driving the
piston down
3. power
a. piston moves up
b. exhaust valve opens
c. exhaust leaves the
cylinder
4. exhaust
11. Internal Combustion Engines
– four stroke -
Advantages:
•dedicated lubrication system makes to engine
more wear resistant
•better efficiency that 2-stroke engine
•no oil in the fuel – less pollution
Drawbacks:
•complicated constriction
•should work in horizontal position due to
lubrication
14. COMPARISON of PETROL/GASOLINE vs DIESEL
engine (in technical views)
Inlet stroke
> In petrol engines the mixture of air and petrol is drawn in by the falling
piston
> In diesel engines only air is drawn in by the falling piston
Compression stroke
> In petrol engine, the mixture is compressed upto about 1/8th to 1/12th of its
original size.
> In diesel engine, only air is compressed upto about 1/14th to 1/25th of its
original size.
Expansion stroke
> In petrol engine, the air and fuel mixture is ignited using a spark plug and
burns expanding and forcing the piston down.
> In diesel engine, fuel is injected at a high pressure into the hot, compressed
air in the cylinder, causing it to burn and force the piston down. No spark is
required.
15. COMPARISON of PETROL/GASOLINE vs DIESEL
engine (in technical views)
Exhaust stroke
➢ In both petrol and diesel engines, the burned mixture of air and fuel is pushed out of
the cylinder by the rising piston.
A diesel engine is also known as a "compression ignition" engine. Since the air is
compressed to very high pressure raising its temperature and then diesel is injected in a
very fine spray which causes the diesel to ignite and explode. Whereas a petrol engine is
known as a "spark ignition" engine. Since a spark plug is required to ignite the mixture
of petrol and air in the combustion chamber.
LUBRICANTS COMSUMPTION COMPARISON
Petrol destroys lubrication and burns the engine whereas diesel doesn't. So a diesel
engine would last longer than a petrol engine.
WEIGHT COMPARISON
Petrol engines are lighter than diesel engines.
16. COMPARISON of PETROL/GASOLINE vs DIESEL
engine (in technical views)
TORQUE COMPARISON
Diesel engines have higher torque than petrol engines. What does this mean?
Well, this means that a diesel engine would pull heavy loads easily than a petrol
engine. Though the pickup of a petrol engine would be much more than that of a
diesel engine, the diesel engine would be steady and carry heavier loads to longer
distances.
FUEL EFFICIENCY COMPARISON
Diesel engines have better fuel efficiency as compared to petrol due to the fact that
they have higher compression ratio.
DURABILITY COMPARISON
Diesel engines don't need an ignition system, which reduces their complexity. But
they are more noisy and may require frequent maintenance as compared to petrol
engines. Also they are more durable.
17. COMPARISON of PETROL/GASOLINE vs DIESEL
engine (in technical views)
• SPARK PLUGS
Diesel engines may also need glow plugs in extreme cold conditions which
heat up the cylinder so that a cold engine can start easily.
FUEL ECONOMY COMPARISON
And now the most important part, fuel economy. Diesel wins in both ways.
Diesel engines give better mileage than petrol engines and In Malaysia diesel
is much cheaper than petrol. So running on diesel would make you go farther
at a lower cost than running on petrol.
COMPRESSION RATIO COMPARISON
Engine breaking is tougher in the diesel due to the 22:1 compression ratio. But
a petrol engine is more likely to start than a diesel one. You do need a good
battery to start the second motor.
18. COMPARISON of PETROL/GASOLINE vs DIESEL
engine (in technical views)
• REV COMPARISON
Petrol cars rev up to 7-8 thousand, while diesel ones go up to 5 thousand.
SPEED COMPARISON
If you take two cars with same cylindrical capacity, one diesel one petrol with
same horse power and if we consider that the drivers of both of the cars are
experts, 0-60mph and ¼ mile , the petrol fueled one is always going to win.
Both diesel engines and gasoline engines covert fuel into energy through a
series of small explosions or combustions. The major difference between
diesel and gasoline is the way these explosions happen. In a gasoline engine,
fuel is mixed with air, compressed by pistons and ignited by sparks from spark
plugs. In a diesel engine, however, the air is compressed first, and then the fuel
is injected. Because air heats up when it's compressed, the fuel ignites.
28. Internal Combustion Engines
Wankel rotary engine
Advantages:
•higher power output
•no reciprocating mass
•simpler and lighter construction
Drawbacks:
•increased wear of rubbing parts
•higher fuel consumption
•requirement for better materials
