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Aviation History
1943
1943 - 2323.PDF
SEPTEMBER 23RD, 1943 DEVELOPMENT OF THE AIRCRAFT SUPERCHARGER caused by poor balance or synchronous vibration. The rather unique conditions under which the irripeller- shaft bearings work called for the development of par- ticular bearing types, and an investigation into the method of^their mounting and the srfte and supply of their lubrication. The pro- blem of lubrication was fur- ther aggravated by the high depression around the impeller shaft, particularly at small throttle angles; this depression tended to draw the oil from the adjacent bearings, thus calling for carefully de- signed oil retainers. Mechanical and metallurgical problems, promoted by exhaust-gas temperature, have been responsible for the non- appearance of the exhaust-gas turbine blower until recent years. The First Single-speed. Superchargers _ The distinction of having been the first supercharged engine in service goes to the Armstrong Siddeley Jaguar Mark 4S, as fitted in 1926 to the Armstrong Whitworth Siskin, Mark 3A, single->«eater fighter. The 4S Jaguar had a rated altitude of 9,500 feet and a rated boost of minus £ lb./sq. in. The impeller ran at approximately 13 times engine speed and had a tip-speed of 860 ft./sec. at the rated r.p.m. This was quickly followed into service by the Bristol Bulldog Mark 1 with a Jupiter Mark 7 FLIGHT 343 The * Armstrong-Whitworth Siskin IIIB fitted with geared and supercharged Siddeley Jaguar engine. engine. The latter had a rated altitude of 12,000 feet and a rated boost of minus i£ lb./sq. in. Nos. 3 and 17 Squad- rons were among the first to be equipped with this aircraft. Both the Jaguar Mark 4S and Jupiter Mark 7 weie fitted with a "gated throttle." The "gate" consisted of a spring-loaded stop on the throttle quadrant, which pre- vented thye throttle being opened without conscious effort past the setting which gave maximum permissible boost at ground level. In this way the throttle could be opened quickly in the event of an emergency at ground level. It is of interest to note that the gated throttle was also used on normally-aspirated, high-compression engines; the Jupiter Marie 6A will be remembered in this respect and later the Rolls-Royce Kestrel as fitted to the Hawker Hart. In 1930 the Jupiter Mark 7F, as installed in the Bristol Bulldog Mark 2A and supplied to No. 56 Squadron, was fitted with an automatic boost control—the first to appear in service. This engine had a rated altitude of 9,000 feet, the boost having been increased to zero lb./sq. in.. __OW-OFF VALVE FOR GOVERNING SECOND STAGEIMPELLOR TURBINE & . IMPELLOR ON WTERCOOLER '" -ITFD-HP i aiAuc INTAKB SAME SHAFT (AJRJ Diagrammatic layout of four two-stage supercharger arrangements. (Top left) Rolls-Royce Merlin 61. (Top right) Societe Rateau. (Bottom left) High alti'.ude Bristol Pegasus. (Bottom right) Lockheed XC-35.
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