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Aviation History
1940
1940 - 0134.PDF
JANUARY 18, 1940. THE JUNKERS PETROL INJECTION GENERATOR ELCCTRIC MOTOR FOR VARYING A18SCRCW PITCH AIR SNTAKT FUEL PUMP FEEDING INdECTSON PUMPS Starboard side of the inverted Junkers engine, showing the cantilever supporting beams, and disposition of accessories.The sparking plugs on the outside of the cylinder banks are easily reached, but those on the inside, together with the fuel injectors, are very inaccessible. IT is now possible to reveal the eagerly awaited detailsof the Junkers engine fitted with direct petrol injectionpumps Our readers may recall that toward the end of last year a Heinkel He III K Mark V twin-engined bomber was forced down by R.A.F. fighters, and after receiving damage from gun fire made a pancake landing with its landing gear in the retracted position on the Lammermuir Hills near the Firth of Forth. This machine was fitted with Junkers Jumo 211 A in- verted twelve-cylinder engines, one of which has since been removed and subjected to a thorough examination and calibration tests by the Rolls-Royce Co. The second engine is the subject of investigation. Although the tests have not been finally completed, by the courtesy of the Air Ministry Technical Department and the Rolls-Royce Co., representatives of Flight have been accorded an oppor- tunity of studying one of the engines in detail and to have access to the very full amount of information and data available. The Junkers engine removed from the Heinkel received a comparatively small amount of damage as a result of its forced landing, and this was mainly the shifting of the petrol injection pump unit fitted between the cylinders, and therefore on the underside of the engine. The super- charger casing also developed a fault, but the defects were easily remedied and the engine at the present moment is in full working order on a test bench in one of the engine test houses. Undoubtedly the chief interest in this German power unit is the system of direct petrol injection into each cylin- der from a specially designed pump unit, which is remin- iscent of a diesel pump. The rated h.p. of the engine is 1,050 at 2,300 crankshaft r.p.m. and 14,000ft. altitude. The bore and stroke, 150 mm. by 165 mm. respectively, give a total capacity of 35 litres, and there are two inlets and one exhaust valve per cylinder. The cylinder banks are set at 60 deg., whilst the weight of the engine, fitted with ^tarter and generator, is 1,525 lb. A two-speed supercharger is employed, and the fuel, as taken from the Heinkel tanks and subjected to analysis, was 87 octane with a content of 4.4 c.c. of lead per Imperial gallon. The nature of the fuel used is of interest in view of certain suppositions that one of the main attractions to Germany in adopting direct-injection engines is the possi- bility of successfully employing low-grade fuel. The Direct Injection System Air only is forced under pressure by the supercharger through the branched induction manifold to the two banks of cylinders. It is controlled by a barrel-type throttle located on the pressure side of the supercharger. The air pressure is not only governed by the throttle, but also by the two speeds of the supercharger itself, according to altitude requirements. The resulting changes in the The engine from the port side. Rubber mountings in thecantilever arms absorb engine vibration and provide a flexible support.
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