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Internal Combustion Engine


Computer drawing of the Wright 1903 aircraft engine

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.

Computer drawing of the Wright 1903 aircraft engine operation

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:

Button to Download Applet

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.


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Editor: Nancy Hall
NASA Official: Nancy Hall
Last Updated: May 13 2021

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