Peggy Brennan, Age 12, Of Newport News, Va., for her question:
How does a carburetor burn fuel?
An automobile is run by an internal combustion engine. The fire power or combustion is produced internally, inside the engine. In a steam engine, the combustion is produced outside the engine. The carburetor is but one of the vital parts which help to produce the combustion inside an automobile engine.
The carburetor in an automobile engine merely helps to burn the fuel. The actual. Burning of the fuel is called combustion. It is a series of explosions which takes place inside the cylinders of the engine. The fuel which is exploded is gasoline vapor mixed with air. The carburetor is a sort of atomizer which sprays the gasoline fuel where it is needed.
A supply of gasoline passes into the carburetor from where it passes into a small tube. It reaches a larger tube of rushing air. The liquid gasoline is dragged along in the draft and blown to droplets and finer droplets. It becomes a fine, misty spray.
In this form, the gasoline soon evaporates and becomes mixed with the draft of air. The job of the carburetor is now finished. It cannot burn the carburetor fuel. But it can change the liquid gasoline into vapor which is mixed with a current of moving air. In this form, the fuel can be burned by the cylinders of the engine.
The draft of air and gasoline vapor pass by the valves at the top of the cylinders. Each cylinder is built like a sturdy round drum. The bottom is plugged with a heavy moving part called the piston. At the top, each cylinder has a spark plug and two valves, one to let in a supply of air and gasoline vapor fuel and an exhaust valve to let out the waste materials.
The gaseous fuel passes into a cylinder through the intake valve. The piston is now at the bottom of the cylinder, and the sturdy little chamber fills up with gas. Then the intake valve closes and the piston pushes up to compress the trapped gasoline fuel. When the piston reaches the top, the fuel may be squeezed or compressed to one sixth of its original volume. Now the spark plug sets off an electric spark, and the gasoline mixture explodes with a force strong enough to force dawn the piston again.
The moving piston is connected to moving parts, and, as it moves, it forces them to move, too. The explosion in the cylinder is passed along from one moving part of the engine to another. Finally it reaches the wheels of the car and makes them turn. Many vital parts are needed to power an engine, and the job of the carburetor is to turn the liquid gasoline into vaporous gasoline which can be burned in the car's cylinders.