I assume the gasoline is burnt to power the engine, or does it contain a chemical which creates a reaction? What’s the whole process?
In: Technology
I’m gonna make this an extremely short answer because I’m sure someone will explain it better. So those pistons/cylinders in the engine systems subject to the ideal gas law, PV=nRT. With gas, it obviously has a hot combustion point that would overheat an engine quickly if all the energy was released at once. You don’t want that. So you want the change in temperature for each reaction to be very slow. This gets accomplished by changing both the pressure and volume inversely to each other so that the energy of the system doesn’t change much. The other part of how that is accomplished is by having a very small amount of the substance, n, to the point where it is close enough to 0 to a relatively insignificant increase in temperature per reaction. This is called an [adiabatic process or reaction](https://en.wikipedia.org/wiki/Adiabatic_process) It’s why engines warm up slowly as well. The pistons are also synchronized in some way that one reaction will transfer some of its energy to the mechanical energy of the piston, starting that reaction and so on…
**tl;dr**: use a miniscule amount of gas, piston pump it to raise the pressure and lower the volume so the reactions slowly and efficiently happen and some of that mechanical energy gets transferred in a cascade to the other pistons to continue getting that power.
Certain chemicals have a great deal of energy, and when ignited, burn with oxygen in the air, creating a lot of heat and also waste exhaust fumes, which is the end product of the two substances burning. In the case of gasoline in an engine, it works like this:
– When the piston is all the way at the bottom, two valves open, and air and fuel are injected into the cylinder. These valves then close shut so the piston cylinder is sealed.
– The piston, which is already moving up and down, starts to move all the way back up. This means that the air-fuel mix is compressed to a very high pressure, which makes the explosion more powerful.
– When it reaches the top and the mixture is at it’s maximum pressure, the sparkplug creates a spark that ignites the fuel and air, causing a huge explosion in the cylinder, which immediately forces the piston all the way back down with a great deal of force.
– Forcing this piston down turns the crankshaft, which turns the wheels.
– As it reaches the bottom again, the valves open to let exhaust gasses out, so the chamber is empty, and air and fuel back in to start the process again.
The entire process means that for the engine to work, the engine already needs to be in motion, because how else is the piston going to move all the way back up? This is why cars have batteries. An electric motor makes the pistons turn a few times to kickstart the process.
So, in short, it’s taking the chemical energy that’s inside gasoline, and releasing it in a quick chemical reaction by igniting it, causing it to burn and release energy, which we then turn into mechanical energy with a fast-moving piston.
Its a controlled explosion.
Your car has a few cylinders, likely 4, 6 or 8.
Gas is injected into a cylinder, and a spark plug ignites the gasoline. That forces the piston down, and the piston turns a crankshaft. This crankshaft will rotate around 3,000 revolutions per minute. (your car may have an Tachometer that tells you how fast your crankshaft is rotating. That energy is then used to turn the transmission, which is then used to turn the wheels.
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