Sunday, May 22, 2011

Pollution? How car engines work

How many of you have cars, I’m sure more than 80% do, but how many really know how the engine works, I’m gonna address just a small kind of engine, Gasoline non-electronical-injection engines. My knowledge is not wide about it but I’m going to share what I know.

The mechanics of an engine is not very complex, just a well timed and precise dance involving all parts to get the most of the combustion power of the fuel. The complex part is the thermodynamics of the process, as I had a low grade on that subject in the university (barely passed) I’m not gonna go further on it.

Im using some gif images to explain it better, mostly ‘cause I suck in flash and failed in my attempts to make good ones, and wikipedia’s are good enough ^^.

Engine Parts

Here are the main parts of the engine

Picture of the general parts of an engine
  • Combustion Chamber
  • Piston
  • Intake and Exhaust Valves
  • Spark Plug
  • Crankshaft
Most car engines work on 4 stroke cycles:
  • Intake Stroke
  • Compression Stroke
  • Combustion Stroke
  • Exhaust Stroke
Engine dance
Animation gif for the stroke of a piston on an engine
The first stroke starts with the piston on top, as the piston goes down the intake valve opens and lets in a mixture of Gasoline and Air. This mixture consists mostly of Air (around 80% or more in volume).

The piston then moves back to the top to compress the mixture; this compression helps the explosion to become more powerful.

As soon the piston is again at the top, the spark plug releases a spark and ignites the fuel and explodes forcing the piston to go back down with force.

As soon the piston has reached the bottom, it moves back up again and the exhaust valve opens to allow the combustion gases leave the body of the engine starting the cycle again.
engine function animation engine
Chemist Approach
A chemist doesn’t worry too much about the mechanics of the cycle, but the combustion phase of it.
Gasoline consists of hydrocarbons with between 4+ carbon atoms (up to 10 sometimes), most of them are aliphatic alcane hydrocarbons.
I will made a comparison with C4 (Butane) and C5 (Pentane) components of gasoline with some “Environment-friendly” substitutes of gasoline.

Regular Gasoline

Gasoline Substitutes

Natural Gas, that consists of Methane (C1) around 85%
CO2 is a pollutant, and its generated in high amounts by motor engines, as you can see in the reactions above, carbon dioxide is generated except on the Hydrogen combustion, the more amount of carbon molecules the fuel has, it generates more CO2.

Some countries started to use Natural Gas instead of gasoline, this a good choice because Methane doesn’t generate a high amount of CO2, BUT still it does generate some.
The perfect fuel in my opinion :D, Hydrogen, as you can see it generates none CO2.

If you want more information related to Combustion reactions or engines just leave me a message.


Xenototh said...

So we don't get to have any fun stats on energy being lost as heat and system efficiency? :P Even so, still really detailed, wasn't expecting the chem aspect.

Vav said...

Nice visual representation! Love your explanations too.

ReMs said...

hahaha xD no xenototh, but from what i know, engines only use like around 15% of total energy generated, a big part of the rest is gone with heat dissipation on the engine's body; didnt want to go further on that subject 'cause i HATE thermodynamics ^^

CPH said...

Very interesting! I never really knew much about this.

Dejch said...

thanks for the info cos i am driving a car but don't really know how the engine works

Moobeat said...


Pentele said...

Isn't methane like 10 times worse than CO2?

ReMs said...

it is, but only if its released into the atmosphere as it is, on engines it is burned into CO2, but you are right its dangerous thats why gas fuel cars need to have well sealed tanks and certified modifications on the engine to avoid any ruptures and leaks

Prototape said...

Very cool post, never really knew the whole process.

Gaberabtic said...

Very informative post man Keep on bloggen.I really didn't know this stuff thanks

Pool Fool said...

the production of hybrids costs much more pollution.

Xzib1t said...

Very informative post!

Genj0 said...

Nice information, is always good to know a little more

Splendid TV said...

Nice helpful post with good information, thanks!

BojanCo said...

Absolutly fantastic post! Thnaks

Noises said...

great work

Azurikai said...

its nice figuring out how the internal combustion engine actually works!

Anonymous said...

very descriptive post on how the internal combustion engine works.

Vague Raconteur said...

Very good... but chemists would never but 6 and a half :O we'd ramp it all the way up to 13, and double everything else too. In the hatred of fractions.

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