Junkers Jumo 213

The Junkers Jumo 213 was a World War II-era V-12 liquid-cooled aircraft engine, a development of Junkers Motoren's earlier design, the Jumo 211. The design added two features, a pressurized cooling system that required considerably less cooling fluid that allowed the engine to be built smaller and lighter, and a number of improvements that allowed it to run at higher RPM. These changes boosted power by over 500 hp and made the 213 one of the most sought-after Axis engine designs in the late-war era.

Design and development

When the Jumo 211 entered production in the late 1930s it used an unpressurized liquid cooling system based on an "open cycle". Water was pumped through the engine to keep it cool, but the system operated at atmospheric pressure, or only slightly higher. Since the boiling point of water decreases with altitude (pressure) this meant that the temperature of the cooling water had to be kept quite low to avoid boiling at high altitudes, which in turn meant that the water removed less heat from the engine before flowing into the radiator to cool it.

Junkers Jumo 204

The Junkers Jumo 204 was the second in a series of German aircraft Diesel engines. The Jumo 204 first entered service in 1932. Later engines in the series were designated Jumo 205, Jumo 206, Jumo 207 and Jumo 208, they differed in stroke and bore and supercharging arrangements.

Design and development

Development of the Junkers diesel engines started in the 1920s with the Junkers Fo3 and Junkers Fo4/Junkers SL1. The Fo4 was re-designated Junkers 4, which in turn was re-designated Junkers Jumo 204 by the Reichsluftfahrtministerium (RLM).

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. Intake and exhaust ports were duplicated at both ends of the block. There were two cam-operated injection pumps per cylinder, each feeding two nozzles, totaling four nozzles per cylinder.

Junkers Jumo 211

The Jumo 211 was an inverted V-12 aircraft engine, Junkers Motoren's primary aircraft engine of World War II. It was the direct competitor to the famous Daimler-Benz DB 601 and closely paralleled its development. While the Daimler-Benz engine was mostly used in single-engined and twin-engined fighters, the Jumo engine was primarily used in bombers such as Junkers' own Ju 87 and Ju 88, and Heinkel's H-series examples of the Heinkel He 111 medium bomber. It was the most-produced German aero engine of the war, with almost 70,000 examples completed.

Design and development

The Jumo 211 was developed by Dr. Franz Josef Neugebauer as scaled-up successor to the earlier Jumo 210. In 1934, even before the new Jumo 210 had completed its acceptance tests, the RLM sent out a request for a new 1,000 PS-class engine of about 500 kg weight. Both Jumo and Daimler-Benz responded, and in order to reach service before the new Daimler-Benz DB 600, the Jumo team decided to make their new design as similar as possible to their 210H model, currently in testing.

Junkers Jumo 223

The Junkers Jumo 223 was an experimental 24-cylinder aircraft engine based on the Junkers Jumo 205. Like the Jumo 205, it was an opposed piston two-stroke diesel engine. It had four banks of six cylinders in a rhomboid configuration, with four crankshafts one at each vertex of the rhombus, and 48 pistons. It was designed for a power of 2,500 horsepower at 4,400 rpm, and weighed around 2,370 kg.

Only one example is known to have been built. It is rumoured to have been taken to Moscow after the war, where development may have continued.

Jumo 224

In 1942 the 223 was abandoned in favour of an even larger engine, the Jumo 224 with an intended output power of 4,500 horsepower.

The Jumo 223 series was influential to the successful three-crankshaft Napier Deltic engine.

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