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Aviation History
1940
1940 - 0140.PDF
JANUARY 18, 1940. JUNKERS PETROL INJECTION ENGINE (CONTINUED) * The starboard exhaust pipe on the invertedJunkers engine has a by-pass pipe for cock- pit heating near the main exhaust exit. connected to the light alloy manifolds bolted on the inner faces of each cylinder bank. For starting purposes, manual in- jection is effected by the pilot through a pipe and nipple which dopes the induction manifold with petrol. Briefly considered, the injection and . supercharging system simply comprises a supercharger which forces pure air into the cylinders in a volume governed by the im- peller whether in low or high gear and by the throttle setting. The pressure of air, or boost, automatically controls the delivery of petrol into the cylinders, and thus the fuel-air ratio for combustion is maintained automatically. Obviously, the mainten- tenance of the ratio is of the greatest im- portance for economical running and the avoidance of weak mixture effects, and it will be interesting to know eventually what the effects of sudden movements of the throttle have on the fuel-air ratio in the system generally. Final Comment Although this article deals primarily with the details of the complicated injection system, a few further remarks may be made as regards the engine itself. The internal finish of the engine as regards bearing sur- faces, gears, bearings, etc., is of a high order, but the external appearance does not approach the high standard of British engines. Certainly, finesse in detail work and general artistry is not comparable with the perfection of the Rolls-Royce Merlin, for example. Of light alloy, the main part of the crankcase and cylinder water jackets of both banks are cast in one piece, which exhibits advanced foundry technique. The cylinders proper are thin shells held to a common alloy combustion chamber by a series of long studs, one head with its set of cylinder shells forming one bank of cylinders. A single overhead camshaft is mounted on each head and operates the double inlet and single exhaust valves through rockers fitted with roller cam followers. DISC CLUTCH CONTROL MULTI-tHSC CLUTCH HIGH SPEED DRIVE FREE WHEEL CLUTCH LOW SPEED DRIVE SELF -ALIGNING BEARINGS SLIPPER CLUTCH Two-speed clutch and gear drive of the supercharger impeller.The centrifugal slipper clutch absorbs shock to the drive on engine acceleration from idling. Arrangement of the blower, throttle and induction pipe at therear of the engine. The balanced crankshaft is geared to the airscrew shaft to provide a reduction speed of 0.648 to 1, while the engine, as a whole, is supported at four points in rubber mountings to the neat light alloy supporting girders of the engine- carrying structure. The V.D.M. airscrew is electrically controlled from the pilot's cockpit, and is mounted on a hub shaft which is flange mounted with radial serrations to the flange on the reduction gear shaft. Water is employed for engine cooling, with a 40 per cent, content of Glycol as an anti-freeze agent. A single pump at the rear of the engine circulates water through the cylinder jackets from a retractable radiator, the header tank being arranged as a circular unit fitting around the airscrew reduction gear casing. A shallow saddle radiator for oil cooling is mounted over the crankcase at the rear of the engine. The engine idles and runs well at various throttle open- ings under test, comparable with the performance of normal supercharged engines fitted with carburetters. M. A. M. SUPERCHARGER AIR INTAKE RPE" • DETACHED / SUPERC THROTTLE BOOST CONTROL H PETROL PUMP FEEDING INJECTOR PUMPS
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