1937
Turbojet Engine
Frank Whittle (1907–1996)
The ramjet engine is about as simple as engines get. It is basically a tube traveling through the air like an arrow. At the front opening, air rams into the tube because of the tube’s velocity. An inlet cone aids the process, providing compression. In the middle of the tube, fuel sprays into the air stream and burns in the combustion area, assisted by a flame holder. The burning fuel creates heat, expanding the air significantly. Since air is ramming in the front of the tube, the expanding gas rushes out the back, creating thrust. The problem is that a ramjet engine does not work when it is standing still. Frank Whittle, a British engineer air officer, produced a solution to this in the late 1930s, which lead to the first successful turbojet engine appearing in 1937.
A turbojet engine has a powerful fan at the front inlet. The fan moves air through the engine even when standing still. Engineers developing Whittle’s initial concept evolved this idea to a multistage compressor—a series of fans and blades. By compressing incoming air by a factor of 10 or more, the engine can burn additional fuel and create more thrust. An electric motor could turn the compressor, but engineers realized that another turbine in the exhaust stream is a better approach. The exhaust turbine connects to the compressor with a shaft running through the center of the engine: a very efficient design.
However, the exhaust turbine is sitting in an extremely hot airstream. Materials scientists and engineers solved this problem by creating new alloys and techniques to prevent meltdown. Second, the shaft is turning at high rpm, so it is important for the system to be balanced and lubricated.
By using the shaft’s rotation to additionally turn a large bypass fan, the efficient turbofan engine was born in 1943. With the turbofan’s efficiency, engineers make air travel affordable for millions. By adding a power takeoff shaft, the gas turbine engine seen in the Apache Helicopter and M1 tank is born.
SEE ALSO Jet Engine Testing (1951), M1 Tank (1980), Apache Helicopter (1986).