For the forty years following the
first flight
of the Wright brothers, airplanes used
internal combustion engines
to turn
propellers
to generate
thrust.
Today, most general aviation or private airplanes are still
powered by propellers and internal combustion engines, much like your
automobile engine.
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.
When discussing engines, we must consider both the
mechanical operation of the
machine and the
thermodynamic
processes that enable the machine to produce useful
work.
The basic mechanical design of the Wright engine is
remarkably similar to modern,
four-stroke,
four cylinder
automobile engines.
As the name implies, the
combustion process
of an internal combustion engine takes place in an enclosed
cylinder. Inside the cylinder is a moving
piston which
compresses
a mixture of fuel and air before combustion and is then forced back
down the cylinder following combustion. On the
power stroke
the piston turns a crank which converts the linear motion of the
piston into circular motion. The turning
crankshaft
is then used to turn the aircraft propeller. The
motion of the piston is repeated in a
thermodynamic cycle
called the
Otto Cycle
which was developed by the German, Dr. N. A. Otto, in 1876
and is still used today.
While there are some important differences between modern
aircraft engines and the Wright 1903 engine,
the simplicity of the Wright engine design
makes it a good starting point for students.
Individual web pages for all of the major systems and
parts
are provided so that
you can study each item in some detail.
Here's a Java program that you can use to look at the engine from a
variety of locations:
You can download your own copy of this applet by pushing the following button:
The program is downloaded in .zip format. You must save the file to disk and
then "Extract" the files. Click on
"Engine.html" to run the program off-line.