Joseph Wolf, age 14, of Louville Ky., for his questions
What is an internal combustion engine?
An engine is a gadget for putting energy to work,. Combustion means burning and many different engines run on heat energy. There is energy in expanding steam. It forces the lid of a boiling pot to bob up and down. Steam energy is used to run a steam engine. It is a heat engine but because the steam is not made inside the Engine it is not an. internal combustion engine. An automobile is an internal combustion engine because the heat energy is manufactured right inside the engine.
The car, of course, uses gasoline fuel and the fuel is converted into energy inside the engines cylinders. This energy is then carried by various mechanical parts to turn the wheels. The cylinders are all alike, so lets see how one of them works.
The cylinder parts are made of strong, sturdy metal for they must be able to stand tremendous pressure. The main art is like a tin can, open at one end. A solid plug called a piston fits snugly into this open end and moves up and down. The cylinder is topped with valves and a spark plug.
The inside of the cylinder is a sealed chamber of air and gases. When the piston is lowered, the chamber is bigger. When the piston rises up inside the cylinder, the chamber is smaller an the gases squeezed or compressed. Gasoline vapor mixed with air fills the chamber when the piston is down. Then the piston rises and the explosive mixture is compressed.
The gases now occupy/one sixth of their original space and at this moment they are ignited by a spark from the spark plug. The combustion or burning of the gases happens in an instant explosion.
The force of the explosion thumps down on the piston with perhaps a tonand a half of pressure and down it goes.
One valve in the top of the cylinder lets out the waste exhaust gases from the explosion. Another valve lets in a new charge of air and gasoline vapor to refill the chamber. Then the piston starts up again and the cycle repeats itself. The car is driven by a series of these explosions happening in the sturdy cylinders,
We can see that the piston is driven down by the force of the explosion. But what forces it back up into the cylinder? This is done by the mechanical parts which also translate the up and down motion of the piston to the rotary motion which turns the wheels.
The piston is fixed to a strong metal connecting rod by an elbow which is a small metal rod called the piston rod. The connecting rod is joined with a crankpin on the engine’s crankshaft. The up and down motion of piston is turned into rotary motion by these mechanical parts and the rotary motion pushes the descending piston back into the cylinder after each explosion: