This week’s picture comes from the Valiant Air Command Warbird Museum in Titusville, Florida. It’s of an Allison J-33 jet engine –one of the first jet engines ever produced in the U.S.:
You may have noticed that this beast looks nothing like the kind of engine you’d see on a modern plane. In fact, it’s a very direct descendant of Frank Whittle’s early Rolls-Royce Derwent engine — essentially just being scaled up for greater thrust. The J-33’s relatively plump profile comes from its use of a centrifugal compressor, which compresses incoming air by accelerating it outward, at right angles to the engine’s long axis. Most modern jet engines use axial compressors instead, essentially sequential series of fan blades — these are heavier and more expensive than centrifugal units, but can be scaled up to feed engines with greater thrust.
To get you oriented, air entered the engine on the left (through the trusswork), was compressed / mixed with fuel / ignited in the burners (gray cone-shaped pieces), then exhausted out to the right.
The J-33 was originally designed by General Electric, based on its work with Whittle during WWII. But the production contract for the engine was given to the Allison division of General Motors in 1945 when it became obvious that they could produce the engine more quickly and at a lower cost. Allison would go on to build nearly 7,000 J-33 engines until its production was stopped in 1955; it would be used to power the U.S.’ first production jet fighter (the P-80 Shooting Star), as well as trainers, guided missiles, and experimental aircraft. If your memory’s good, you might recall that a P-80 shot down a MiG-15 in the world’s first jet-on-jet dogfight.