History of aicraft piston engines

The twin rotors are m ounted on a single shaft change

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Unformatted text preview: Rateau, and e xperimental models were tested during the war, but none was put into service use. Laboratory work on gear-driven superchargers was conducted d uring the war by the RAF at Farnborough, England. Intensive development of supercharging equipment began both in England and the United S tates in 1918. R.-R. MERLIN "SIXTY-ONE" H V ERTICAL COOLINC FINS ™ P ASSAGES INLET BRANCH O F INTERCOOLER B OOST CONTROL U NIT Perspective drawing of the new two-stage two-speed supercharger of the Rolls-Royce Merlin 61 engine. The twin rotors are m ounted on a single shaft. Change of speed of the supercharger drive is effected by a hydraulic pump. FULL GEAR C LUTCH & CEAR DRIVE T WO-SPEED CHANCE OPERATINC. P UMP AMAL FUEL PRESSURE R EDUCING VALVE Figure 64.—A two-stage two-speed geared supercharger with intercooler and aftercooler, as installed on the Rolls-Royce Merlin 61 engine of 1942, the first of its kind to be used in service. (From Flight, vol. 4 2, p. 656, Dec. 17, 1942) 68 M any types of compressors have been considered, but only one, t he centrifugal type, ever got beyond the experimental stage. The Royal Aircraft Factory had Armstrong-Siddeley construct a radial engine with a b uilt-in geared centrifugal supercharger in 1916, but the design was unsuccessful, probably because of torsional vibration in the drive system. Siddeley did not produce a successful geared supercharger until that used in 1926 in the Jaguar (see fig. 38). G eared superchargers were built experimentally by Curtiss and by W right Aeronautical Corporation in 1925, b ut the first United States production engine to be so equipped was the Pratt & Whitney Wasp of 1927, a y ear later than the Jaguar. After 1930 all military and transport engines w ere equipped with geared centrifugal superchargers, and in all cases some kind of flexible coupling was introduced in the gear train to prevent c ritical torsional vibration. The culmination of the geared centrifugal type is represented by the 2-stage, 2-speed supercharger of the Rolls-Royce M erlin (fig. 64). I n 1918 t he Engineering Division of the Army Air Service contracted w ith the General Electric Company to develop turbo-superchargers of the R ateau type. The man in charge of this development for GE was Dr. Sanford A. Moss, who remained in this position for over twenty years. E xperimental models applied to the Liberty engine were tested at the t op of Pikes Peak in 1918, and in flight at McCook Field in 1919. F igure 65 shows an installation of this early type of General Electric s upercharger on a Liberty engine. A Le Pere airplane with this equipment h eld the world's altitude record for the years 1920, 1921, and 1922. S upercharging was hard on an engine not originally designed for it, and I remember when Major Schroeder, who made the 1920 record, returned from a flight with the Liberty engine and its nacelle cut in two by a failed c onnecting rod at the third crank from the front end. The only elements h olding the four forward cylinders an...
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