Junkers Jumo 222
The Junkers Jumo 222 was a planned German aircraft engine from the time of the Second World War . However, due to the course of the war, quarrels and wrong decisions in the bureaucracy of the Reich Aviation Ministry (RLM), it was never made ready for use.
history
As early as 1936, considerations were made about a new large aircraft engine in the 2000 to 3000 hp class. For this purpose, a liquid-cooled in-line star engine with six rows (cylinder banks) of four cylinders each (= 24 cylinders) was planned. The expansion by two cylinders per row to a total of 36 cylinders was also planned. On April 4, 1938, the RLM awarded the development contract with the project name "Jumo 222". The engine was to be used in Bomber B , this project was followed by the Junkers Ju 288 . However, problems and delays in development meant that the first flight of the Ju 288 with the Jumo 222 could not take place until October 1941. During these first test flights, there were repeated damage to the crankshaft bearings, and the Daimler-Benz DB 603 was now preferred in the RLM . Thus, at the end of December 1941, the decision was made to pursue the program with a lower level of urgency. With the deterioration of the war situation and the relocation of production to fighter planes , the project had to be ended in the summer of 1943.
technical features
The engine had the appearance of an in-line radial engine, but ran with a different firing order - more like a triple V-engine . As a result, uniform ignition intervals (every 30 ° crankshaft rotation) were not possible. The cylinders were arranged in such a way that the intake and exhaust ports of adjacent cylinder banks were next to each other. This simplified the design of the gas ducts from the rear-mounted mechanical supercharger and only required three exhaust pipes. Each cylinder had two intake valves and a sodium-cooled exhaust valve, its own high-pressure injection between the intake valves and two spark plugs.
- Four-stroke Otto in-line star engine , six rows with four cylinders each
- Overpressure liquid cooling for cylinders and cylinder heads (120 ° C at 0.4 bar overpressure)
- Three-valve cylinder heads, each with an overhead camshaft , two inlet valves and one outlet valve
- Direct petrol injection with three injection pumps ; an injection pump for two cylinder banks (= 8 cylinders)
- Reduction gear as planetary gear with helical teeth
- Charging with a centrifugal charger, experimental versions with an additional exhaust gas turbocharger
Technical specifications
Jumo 222 A / B
- Type: In-line radial engine 6 × 4 = 24 cylinders
- Bore: 135 mm
- Stroke: 135 mm
- Displacement: 46.4 liters
- Compression ratio: 6.5: 1
- Dry matter: 1084 kg
- Starting power: 2000 hp / 1470 kW at 2900 min -1
- Mass-power ratio: 0.54 kg / hp
- Full pressure altitude: 5500 m
Versions
- Jumo 222 A / B-1: first version bore x stroke (135 × 135) = 46,380 cm³, 1470 kW (2000 hp) at 3200 min -1 , single-stage two-speed loader, zero series, flight tested
- Jumo 222 A / B-2: enlarged variant, larger valve cross-sections, bore × stroke 140 × 135 = 49,880 cm³, 2500 hp at 2900 min −1 , single-stage two-speed charger, pilot series, flight-tested
- Jumo 222 A / B-3: like A / B-2, but improved loader, full pressure altitude: 6000 m, pilot series, flight-tested
- Jumo 222C / D: variant enlarged again, bore × stroke 145 × 140 = 55,480 cm³, 3000 hp at 3200 min −1 , full pressure height: 10,000 m, well designed, V models being assembled
- Jumo 222 E / F: like A / B-3, with two-stage two-speed charger and charge air cooling , full pressure altitude: 9400 m, pilot series, flight-tested
- Jumo 222 turbo: such as A / B-3, ATL and charge-air cooling, solid printing height: m 12,300, 2400 hp at 3200 min -1 , only test
- Jumo 222 G / 225: , projected, magnified version with 6 × 6 = 36 cylinder bore x stroke cc 135 x 135 = 69,570, 3500 hp at 3000 min -1 , and speed charging increasable
The direction of rotation of the propeller shaft was indicated by the letter - A, C and E turned to the left, while B, D and F turned to the right. The crankshaft always ran uniformly to the right; the propeller direction was varied exclusively via different gears.
Since the Junkers Jumo 222 has six cylinders per star, it is one of the so-called hexagon engines. Other examples of hexagon motors are rare - for example the 24-cylinder and water-cooled Dobrynin WD-4K and the 12-cylinder, air-cooled Curtiss H-1640 Chieftain . Similarly, there were also octagon engines like the Bristol Hydra with two air-cooled 8-cylinder stars lying one behind the other.
swell
- Reinhard Müller: Junkers Flugtriebwerke , AVIATIC Verlag, 2006, ISBN 3-925505-79-2 .
- Holger Lorenz: Kennzeichen Junkers , Druck- und Verlagsgesellschaft Marienberg mbH, 2005, ISBN 3-931770-57-5 .
