Junkers Jumo 222
| Jumo 222 | |
|---|---|
 |
|
| Preserved Jumo 222E, with aftercoolers fitted | |
| Type | Multiple bank in-line piston aero-engine |
| Manufacturer | Junkers |
| First run | 1939 |
| Major applications |
Junkers Ju 288 Focke-Wulf Fw 191 |
| Number built | 289 |
The Jumo 222 was a high-power multiple bank in-line piston aircraft engine design from Junkers, designed under the management of Ferdinand Brandner of the Junkers Motorenwerke. Such was the performance of the engine compared to contemporary designs that many developments of wartime Luftwaffe piston-engined aircraft designs were based on it, at least as an option. The design failed to mature even after years of intensive development, dooming the entire Bomber B program along with it. Only a small number were built, never leaving the prototype phase, but the design nevertheless continued appearing, endlessly, on proposals for new Luftwaffe multi-engined designs long after most had given up hope it would ever work.
Design work on the Jumo 222 started in 1937. The engine was configured with six inline cylinder banks spaced at equal angles around the crankcase, each bank having four cylinders. The engine looked like a radial due to the arrangement — this was evident from a cross-sectional drawing of the original version, using a master connecting rod with five additional conrods pivoted from the master rod's crankpin end casting, as with a single-row radial — but the internal workings were designed to operate more like a V engine with each adjacent pair of cylinder banks, each with a crossflow head, and it was liquid-cooled like most inlines. Looking at a complete Jumo 222 from a "nose-on" view, the half-dozen cylinder banks were arranged at 60° equal angles from each other, such that neighbouring banks had their exhaust ports (at the "60°, 180° & 300°" spaces) and intake ports (at the "0°, 120° & 240°" spaces) facing each other, resulting in simpler "plumbing" from the rear-mounted supercharger and resulting in only three sets of exhaust headers. The trio of exhaust header sets would have been most likely present at the bottom of an engine nacelle, and on the upper quarters to either side (appearing like the exhausts for many Allied "upright" V-style aviation engines) for the shortest possible exhaust outlet routing. The four-cylinder-long multibank design also engendered a shorter (by roughly 80 cm/31 in), larger cross-section cylindrical nacelle design somewhat like the Ju 88A used (and in comparison to them), which could still use an enlarged-diameter variety of annular radiator to cool the 222's cylinders and motor oil, and which for the Junkers Ju 288, intended to use pairs of the in-house multibank powerplants (spinning their propellers in opposing directions, like the He 177A), mounting each annular radiator directly ahead of a Jumo 222's multibank crankcase (as with the Jumo 211s used on the Ju 88A) and using hollow ducted spinners with each of its four-blade propellers, to pass the air rearwards into the annular radiators.
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