The Junkers Jumo 205 aircraft engine was the most famous of a series of diesel engines that were the first, and for more than half a century, the only successful diesel aircraft engines. The Jumo 204 first entered service in 1932. Later engines in the series were styled Jumo 206, Jumo 207 and Jumo 208, and differed in stroke and bore and supercharging arrangements. In all more than 900 of these engines were produced. For the Prussian/German landowning classes, see junker. The name Junkers (IPA: /ˈjunkeɺs/) is well known in connection with aircraft, which were produced under this name for the Luftwaffe during World War II. In particular the Ju 87 Stuka and Ju 52 Tante Ju were common symbols of the Nazi... The term aircraft engine, for the purposes of this article, refers to aircraft reciprocating, or rotary, internal combustion engines as opposed to jet engines or turboprops. ... The diesel engine is a type of internal combustion engine; more specifically, it is a compression ignition engine, in which the fuel is ignited by being suddenly exposed to the high temperature and pressure of a compressed gas containing oxygen (usually atmospheric air), rather than a separate source of ignition...

These engines all used a two-stroke cycle with six cylinders and twelve pistons, in an opposed piston configuration with two crankshafts, one at the bottom of the cylinder block and the other at the top, geared together. The pistons moved towards each other during the operating cycle. Junkers Jumo 205 engine cutaway. ... Junkers Jumo 205 engine cutaway. ... The two-stroke cycle of an internal combustion engine differs from the more common four-stroke cycle by having only two strokes (linear movements of the piston) instead of four, although the same four operations (intake, compression, power, exhaust) still occur. ... This article is about existing engine designs. ...

The lower crankshaft ran eleven degrees behind the upper, providing superior port timing and meaning that more power was transmitted to the upper crankshaft. All ancillary equipment was run from the lower crankshaft, so that three quarters of the power delivered to the output shaft came from the upper crankshaft, which was geared directly to the output shaft, and in turn to the propellers.

Some of the efficiency of the engine was robbed by the complex and heavy gearing between the two crankshafts, a problem the design shared with the H block engines. This was offset to a large degree by the high compression ratios and the superior thermodynamic efficiency of the Diesel cycle. Cover of Road & Track magazine, showing BRM H16 engine. ...

Intake and exhaust manifolds were duplicated on both sides of the block. There were two cam-operated injection pumps per cylinder, each feeding two nozzles, for 4 nozzles per cylinder in all.

In theory the flat layout of the engine could have allowed it to be installed inside thick wings of larger aircraft, such as airliners and bombers. An airliner of Air Jamaica, the Airbus A340 An airliner is a type of aircraft initially designed for the transport of paying passengers. ... A bomber is a military aircraft designed to attack ground targets, primarily by dropping bombs. ...

The Jumo 205 powered the early versions of the Junkers Ju 86 bomber, but was found too unresponsive for combat and liable to failure when used at maximum power as is common for combat aircraft. Later versions of the design also used the engine for extreme high-altitude use. It was far more successful as a power unit for airships, for which its characteristics were ideal, and for non-combat applications such as the Blohm & Voss Ha 139 airliner. Junkers Ju 86 Junkers Ju 86 The Junkers Ju 86 was a German monoplane bomber and civilian plane. ... Akron in flight, 2 November 1931 An airship is a buoyant (lighter-than-air) aircraft that can be steered and propelled through the air. ... The Blohm + Voss Ha 139 was an all-metal float seaplane flown by Deutsche Luft Hansa on transatlantic routes between 1937 and 1939. ...

A twelve cylinder version, the Jumo 218, was designed but never built, while a single example of the 24-cylinder 4-crankshaft Junkers Jumo 223 was built and tested. The Junkers Jumo 223 was an experimental 24-cylinder aircraft engine based on the Junkers Jumo 205. ...

External links

• Opposed piston engines (http://www.histomobile.com/histomob/tech/1/120.htm) (in French).
• Jumo 205 (http://www.dundee.ac.uk/museum/MECHENG/3001.htm) description and cutaway view.