For the forty years following the
of the Wright brothers, airplanes used
internal combustion engines
Today, most general aviation or private airplanes are still
powered by propellers and internal combustion engines, much like your
On this page we will discuss the fundamentals of the
internal combustion engine using the
Wright brothers' 1903 engine, shown in the figure, as an example.
The brothers' design is very simple by today's standards, so it is a good
engine for students to study to learn the fundamentals of
engine operation. This type of
internal combustion engine
is called a
engine because there are four movements
of the piston before the entire engine firing sequence is repeated.
In the figure, we have colored the
fuel/air intake system
green, and the
blue. We also represent the fuel/air mixture and the exhaust gases by small
colored balls to show how these gases move through the engine.
Since we will be referring to the movement of various engine parts, here is
a figure showing the names of the parts:
with the intake stroke as the piston is
pulled towards the crankshaft (to the left in the figure).
The intake valve is open, and fuel and air are drawn past the valve
and into the combustion chamber and cylinder
from the intake manifold located on top of the combustion chamber.
The exhaust valve is closed and the electrical contact switch is open.
The fuel/air mixture is at a relatively low
and is colored blue in this figure. At the end of the intake stroke,
the piston is located at the far left and begins to move back towards the
The cylinder and combustion chamber are full of the low pressure fuel/air mixture
and, as the piston begins to move to the right, the intake valve closes
to begin the
The intake stroke takes place at a nearly constant atmospheric pressure
because the inlet valve is open to the intake manifold throughout
There is (theoretically) no
done on the fuel air mixture during this process.
The random motion of the gas fills
the increasing volume as the piston moves to the left.
The pressure and temperature ratios are both 1.0 during the intake stroke.
- Beginner's Guide Home Page