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The Jumo 205
aircraft engine An aircraft engine, often referred to as an aero engine, is the power component of an aircraft propulsion system. Most aircraft engines are either piston engines or gas turbines, although a few have been rocket powered and in recent years ma ...
was the most famous of a series of
aircraft diesel engine An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines. ...
s produced by
Junkers Junkers Flugzeug- und Motorenwerke AG (JFM, earlier JCO or JKO in World War I, English: Junkers Aircraft and Motor Works) more commonly Junkers , was a major German aircraft and aircraft engine manufacturer. It was founded there in Dessau, Ge ...
. The Jumo 204 first entered service in 1932. Later engines of this type comprised the experimental Jumo 206 and Jumo 208, with the Jumo 207 produced in some quantity for the Junkers Ju 86P and -R high-altitude reconnaissance aircraft, and the 46-meter wingspan, six-engined
Blohm & Voss BV 222 The Blohm & Voss BV 222 ''Wiking'' (Pronounced "Veeking") was a large, six-engined German flying boat of World War II. Originally designed as a commercial transport, it was the largest German seaplane to attain production status during the war. ...
''Wiking'' flying boat. All three of these variants differed in stroke and bore and supercharging arrangements. In all, more than 900 of these engines were produced, in the 1930s and through most of
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
.


Design and development

These engines all used a
two-stroke cycle A two-stroke (or two-stroke cycle) engine is a type of internal combustion engine that completes a power cycle with two strokes (up and down movements) of the piston during one power cycle, this power cycle being completed in one revolution of t ...
with 12 pistons sharing six cylinders, piston crown to piston crown in an opposed configuration. This unusual configuration required 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. The intake ports were located at one end of the cylinder, whereas the exhaust ports were at the other end. This made one piston effectively control the intake, and the other control the exhaust. Two cam-operated injection pumps per cylinder were used, each feeding two nozzles, for four nozzles per cylinder in all. As is typical of two-stroke designs, the Jumos used no valves, but rather fixed intake and exhaust port apertures cut into the cylinder liners during their manufacture, which were uncovered when the pistons reached a certain point in their strokes. Normally, such designs have poor
volumetric efficiency Volumetric efficiency (VE) in internal combustion engine engineering is defined as the ratio of the mass density of the air-fuel mixture drawn into the cylinder at atmospheric pressure (during the intake stroke) to the mass density of the same volu ...
because both ports open and close at the same time and are generally located across from each other in the cylinder. This leads to poor scavenging of the burnt charge, which is why valveless two-strokes generally produce smoke and are inefficient. The Jumo solved this problem to a very large degree through clever arrangement of the ports. The intake port was located under the "lower" piston, while the exhaust port was under the "upper". The lower crankshaft ran 11° behind the upper, meaning that the exhaust ports opened, and even more importantly, closed first, allowing proper scavenging. This system made the two-stroke Jumos run as cleanly and almost as efficiently as four-stroke engines using valves, but with considerably less complexity. Some downside exists to this system, as well. For one, since matching pistons were not closing at quite the same time, but one ran "ahead" of the other, the engine could not run as smoothly as a true opposed-style engine. In addition, the power from the two opposing crankshafts had to be geared together, adding weight and complexity, a problem the design shared with
H-block Her Majesty's Prison Maze (previously Long Kesh Detention Centre, and known colloquially as The Maze or H-Blocks) was a prison in Northern Ireland that was used to house alleged paramilitary prisoners during the Troubles from August 1971 to Sept ...
engines. In the Jumo, these problems were avoided to some degree by taking power primarily from the "upper" shaft, somewhat offset upwards on the engine's front end. All of the accessories, such as fuel pumps, injectors and the
scavenging Scavengers are animals that consume dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a herbivorous feeding ...
compressor, were run from the lower shaft, meaning over half of its power was already used up. What was left over was then geared to the upper shaft, which ran the engine's propeller. In theory, the flat layout of the engine could have allowed it to be installed inside the thick wings of larger aircraft, such as
airliner An airliner is a type of aircraft for transporting passengers and air cargo. Such aircraft are most often operated by airlines. Although the definition of an airliner can vary from country to country, an airliner is typically defined as an ai ...
s and
bomber A bomber is a military combat aircraft designed to attack ground and naval targets by dropping air-to-ground weaponry (such as bombs), launching torpedoes, or deploying air-launched cruise missiles. The first use of bombs dropped from an air ...
s. Details of the oil scavenging system suggest this was not possible and the engine had to be run "vertically", as it was on all designs using it. Because the temperature of the exhaust gases of the Jumo diesel engines was substantially lower than that of comparable carburettor engines, it was easier to add a turbocharger for higher altitudes. This was explored in the Jumo 207 which used the energy of the exhaust gases to increase the power at high altitudes. The turbocharger was combined with a mechanically driven blower, so that the turbocharger creates the first stage of compression, and the mechanical blower the second stage. At low load and startup, the turbocharger does not contribute to supercharging the engine, but the mechanical blower provides enough air for the engine to operate. At high load, however, the turbocharger receives sufficient quantities of exhaust gas, which means that it alone can provide enough supercharging without the need of the inefficient mechanical blower. The addition of the turbocharger to the mechanical blower made the engine more powerful without significantly increasing its specific fuel consumption.


Variants

;Jumo 205: ;Jumo 206: An experimental version. Development halted in favour of the Jumo 208. ;Jumo 207A: High-altitude version with two inline centrifugal superchargers and a precooler. ;Jumo 207 B-3 had an improved turbocharger and featured
GM-1 {{unreferenced, date=September 2008 GM-1 (''Göring Mischung'' 1) was a system for injecting nitrous oxide (laughing gas) into aircraft engines that was used by the '' Luftwaffe'' in World War II. This increased the amount of oxygen in the fuel ...
nitrous oxide Nitrous oxide (dinitrogen oxide or dinitrogen monoxide), commonly known as laughing gas, nitrous, or nos, is a chemical compound, an oxide of nitrogen with the formula . At room temperature, it is a colourless non-flammable gas, and ha ...
injection. ;Jumo 207 C: optimised for medium altitude. Produced in small series for the Blohm & Voss BV 222. ;Jumo 207 D: optimised for medium altitude. Cylinder diameter increased from 105 mm to 110 mm. Maximum power at ground level was 1,200 hp (880 kW). Prototypes only. ;Jumo 207 E: similar to the 207 C but greater performance at high altitude. Project only. ;Jumo 207 F: optimised for higher altitude. Two-stage turbocharger. Development stopped in 1942.Reinhard Mueller (2006) Junkers Flugtriebwerke. ;Jumo 208: with greater displacement, resulting in a maximum power of 1,500 hp (1,100 kW) at medium altitude. Bench tested but not produced. ;Jumo 218: A 12-cylinder version, the Jumo 218, was designed but never built. ; Jumo 223: A single 24-cylinder four-crankshaft Jumo 223 was built and tested. ;Jumo 224: Larger than the Jumo 223 by combining 4 Jumo 207 C engines. ;CLM Lille 6As: A license-built version from CLM Lille, delivering (CLM was the predecessor to the engine maker, a sister company to
Peugeot Peugeot (, , ) is a French brand of automobiles owned by Stellantis. The family business that preceded the current Peugeot companies was founded in 1810, with a steel foundry that soon started making hand tools and kitchen equipment, and then ...
) ;CLM Lille 6BrS: A developed version of the 6As used to power the Bernard 86


Applications

The Jumo 205 powered early versions of the Junkers Ju 86 bomber, but was found too unresponsive for combat and liable to failure at maximum power, common for combat aircraft. Later versions of the design also used the engine for extreme high-altitude use, as with the Ju 86P and -R versions for high-altitude reconnaissance over the British Isles. In January 1940, the Luftwaffe tested the
prototype A prototype is an early sample, model, or release of a product built to test a concept or process. It is a term used in a variety of contexts, including semantics, design, electronics, and software programming. A prototype is generally used to ...
Ju 86P with Jumo 207A-1
turbocharged In an internal combustion engine, a turbocharger (often called a turbo) is a forced induction device that is powered by the flow of exhaust gases. It uses this energy to compress the intake gas, forcing more air into the engine in order to pr ...
diesel engine The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is a so-cal ...
s. It was far more successful as a power unit for
airship An airship or dirigible balloon is a type of aerostat or lighter-than-air aircraft that can navigate through the air under its own power. Aerostats gain their lift from a lifting gas that is less dense than the surrounding air. In early ...
s, for which its characteristics were ideal, and for noncombat applications such as the
Blohm & Voss Ha 139 The Blohm & Voss Ha 139 was a German all-metal inverted gull wing floatplane. With its four engines it was at the time one of the largest float-equipped seaplanes that had been built. The inboard engines were mounted at the joint between the in ...
airliner. Its more fuel-efficient operation lent itself for use on Germany's few
maritime patrol {{Unreferenced, date=March 2008 Maritime patrol is the task of monitoring areas of water. Generally conducted by military and law enforcement agencies, maritime patrol is usually aimed at identifying human activities. Maritime patrol refers to ac ...
flying-boat designs during World War II, such as the
BV 138 The Blohm & Voss BV 138 ''Seedrache'' (Sea Dragon), but nicknamed ''Der Fliegende Holzschuh'' ("flying clog",Nowarra 1997, original German title of the Schiffer book. from the side-view shape of its fuselage, as well as a play on the title of th ...
and
BV 222 The Blohm & Voss BV 222 ''Wiking'' (Pronounced "Veeking") was a large, six-engined German flying boat of World War II. Originally designed as a commercial transport, it was the largest German seaplane to attain production status during the war. ...
.


Applications list

*
Blohm & Voss BV 138 The Blohm & Voss BV 138 ''Seedrache'' (Sea Dragon), but nicknamed ''Der Fliegende Holzschuh'' ("flying clog",Nowarra 1997, original German title of the Schiffer book. from the side-view shape of its fuselage, as well as a play on the title of th ...
*
Blohm & Voss Ha 139 The Blohm & Voss Ha 139 was a German all-metal inverted gull wing floatplane. With its four engines it was at the time one of the largest float-equipped seaplanes that had been built. The inboard engines were mounted at the joint between the in ...
*
Blohm & Voss BV 222 The Blohm & Voss BV 222 ''Wiking'' (Pronounced "Veeking") was a large, six-engined German flying boat of World War II. Originally designed as a commercial transport, it was the largest German seaplane to attain production status during the war. ...
*
Dornier Do 18 The Dornier Do 18 was a development of the Do 16 flying boat. It was developed for the ''Luftwaffe'', but ''Luft Hansa'' received five aircraft and used these for tests between the Azores and the North American continent in 1936 and on their ma ...
*
Dornier Do 24 The Dornier Do 24 is a 1930s German three-engine flying boat designed by the Dornier Flugzeugwerke for maritime patrol and search and rescue. A total of 279 were built among several factories from 1937 to 1945. Design and development The Dorni ...
(V1 and V2 prototypes) *
Dornier Do 26 The Dornier Do 26 was an all-metal gull-winged flying boat produced before and during World War II by ''Dornier Flugzeugwerke'' of Germany. It was operated by a crew of four and was intended to carry a payload of 500 kg (1,100 lb) o ...
* Junkers Ju 86


Specifications (Jumo 205E)


Other notable opposed-piston engines

*
Commer TS3 The Commer TS3 was a diesel engine fitted in Commer trucks built by the Rootes Group in the 1950s and 1960s. It was the first diesel engine used by the company. Development Rootes' intention for the engine was for it to fit under the QX "cab forwa ...
the "Commer Knocker" commercial vehicle engine *
Leyland L60 The Leyland L60 was a British vertical six-cylinder opposed-piston two-stroke multi-fuel diesel engine designed by Leyland Motors in the late 1950s/early 1960s for the Chieftain main battle tank (MBT). The engine was also used in the Vic ...
tank engine, used in the Chieftain tank, was similar in layout to the Junkers Jumo 205 and Napier Culverin. *
Rolls-Royce Rolls-Royce (always hyphenated) may refer to: * Rolls-Royce Limited, a British manufacturer of cars and later aero engines, founded in 1906, now defunct Automobiles * Rolls-Royce Motor Cars, the current car manufacturing company incorporated in ...
K60 engine was used in the
FV430 The FV430 series covers a number of armoured fighting vehicles of the British Army, all built on the same chassis. The most common is the FV432 armoured personnel carrier. Although the FV430 series has been in service since the 1960s, and som ...
series of
armoured fighting vehicles An armoured fighting vehicle (AFV) is an armed combat vehicle protected by armour, generally combining operational mobility with offensive and defensive capabilities. AFVs can be wheeled or tracked. Examples of AFVs are tanks, armoured c ...
and Swedish tank Strv 103. * Napier Deltic *Soviet engine 5TDF was used in
T-64 The T-64 is a Soviet tank manufactured in Kharkiv, and designed by Kharkiv Morozov Machine Building Design Bureau. The tank was introduced in the early 1960s. It was a more advanced counterpart to the T-62: the T-64 served in tank divisions, whil ...
tank. *Soviet engine 6TD was used in
T-80UD The T-80 is a main battle tank (MBT) that was designed and manufactured in the former Soviet Union and manufactured in Russia. The T-80 is based on the T-64, while incorporating features from the later T-72. The chief designer of the T-80 was S ...
, T-84, and Al-Khalid tanks. * Fairbanks Morse 38 8 1/8


See also

*
Charomskiy ACh-30 The Charomskiy ACh-30 was a Soviet aircraft diesel engine developed during World War II. The initial version was not very satisfactory and it was cancelled when its factory was forced to evacuate in the autumn of 1941. Production was reinitiated i ...
and
Charomskiy M-40 The Charomskiy M-40 was a Soviet turbocharged aircraft diesel engine developed during World War II. It was used in a few Petlyakov Pe-8 heavy bombers until August 1941 when it was removed, because it was unreliable at high altitudes. The engines w ...
: Soviet
four stroke A four-stroke (also four-cycle) engine is an internal combustion (IC) engine in which the piston completes four separate strokes while turning the crankshaft. A stroke refers to the full travel of the piston along the cylinder, in either directi ...
V12 diesel aero engines produced in the 1940s. *
Packard DR-980 The Packard DR-980 is an American nine-cylinder air-cooled aircraft Diesel engine first certificated in 1930. The engine was unpopular despite its economy and reliability due to the unpleasant nature of its diesel exhaust fumes an ...
: American 9-cylinder radial diesel aero engine first flown in 1929. *
List of aircraft engines This is an alphabetical list of aircraft engines by manufacturer. 0–9 2si *2si 215 *2si 230 * 2si 430 *2si 460 *2si 500 * 2si 540 * 2si 690 3W ''Source: RMV'' *3W 106iB2 *3W-110 *3W-112 *3W-170 *3W-210 *3W-220 A Abadal (Fra ...


References


Further reading

* * * *


External links


Multi-crankshafts opposed piston engines (french)description and cutaway viewRoyal Air Force Museum - Jumo 205YouTube video of restored/operable Jumo 205 Diesel on test standOpposedPistonEngines.com's Jumo 205 PageOpposedPistonEngines.com's Jumo 207 Page
{{Junkers Jumo aeroengines Two-stroke diesel engines Aircraft diesel engines Opposed piston engines Junkers aircraft engines 1930s aircraft piston engines