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Aviation History
1943
1943 - 2102.PDF
-228 FLIGHT AUGUST 26TH, 1943 The Junkers Junto 211 Series Captured Heinkel He IIIH and Junkers Ju 88A.1 Power Plants Examined1I LLUSTRATED descriptions of the GermanJumo 21 IA aircraft engine have previously appeared in Flight, the most importantbeing a detailed and fully illustrated description of the main feature of interest, viz., direct-fuel injection, in ourissue dated January 18th, 1940. In our issue of August 5th, 1943, we published briefresults of bench tests which the Ministry of Aircraft Pro- duction has had made on Jumo 21 ID engines taken froma Heinkel Hem. Following is an abstract from M.A.P. reports on the engine. The 2HA engine, fitted with a two-speed supercharger,has 12 cylinders, arranged in inverted-Vee formation, and is liquid-cooled (Glysantin-water mixture), with direct-fuelinjection into the cylinders and spark ignition. The air- screw is driven through spur reduction gearing, both thedriving and driven gears being splined to the shafts and centralised by split bronze cones. The driven shaft ismounted on a roller race at the rear and on a combined roller and thrust race at the front housing cover. Pro-vision is made for a cannon firing through the airscrew shaft. Auxiliaries and accessories are driven through atrain of gears in a wheelcase at the rear of the engine. A combinad hand and electric starter is fitted. The general design follows established practice, but in-teresting features worthy of notice are the cylinder heads incorporating cooled exhaust ports and exhaust valveguides, and also the method of attaching the cylinder liners to the head, the position of the supercharger, the designof oil scraper piston rings and the use of single-piece split- cone cotters for valve-spring caps. Dealing with these in the above order, the cylinder headfor each bank is a single-piece aluminium-alloy casting in The engine mounting is of magnesium alloy forgings supported by tubular steel struts. Cooling the exhaust. The exhaust port is completelyjacketed, and cored passages are provided around the exhaust-valve guide. which the camshaft bearing pedestals are cast integrally.The combustion chambers are flat-topped and have two inlet and one exhaust valve per cylinder. Bronze valveguides are inserted ; the exhaust valve guide passes through the water space and is a press fit in the opening into ttoecombustion chamber. The pressure joint is made on Sc aluminium washer under the shoulder of the guide. Waferleakage at the camshaft end of the guide is prevented by a rubber ring in an annular groove. The steel valve-seating rings are conical externally and are pressed into the head and rolled into a taper at the inner end; theexhaust-valve rings appear to be " Stellite "-faced. Provision for Four Plugs Two sparking-plug holes are provided on each side of the cylinder head, although two plugs only are fitted. The fuel-injection nozzle is situated on the centre line, at right angles to the crankshaft. The nozzle is screwed into the cylinder head and is liquid-cooled. The intricate nature of the cylinder-head casting is illustrated, and its will be noticed that the exhaust port is completely jacketed, and that cored passages are provided around the exhaust-valve guide and injection nozzle. Preliminary examina- tion of the casting sug- gests that it is of good quality and that con- siderable skill is neces- sary for its manufac- ture. Liners of 45-ton steel are bolted to the cylin- der head by four long studs of 60-ton steel, the head itself being secured to the cylinder block by fourteen studs. The engine is fitted with a two-speed centri- fugal supercharger, the air intake of which faces forward and is protected only by a gauze screen. An un- Cylinder liner. Fourlong studs draw the liner against the cylin-der head into which the liner is spigoted.
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