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Aviation History
1956
1956 - 1656.PDF
818-819 FLIGHT, 23 November 1956 Sir George Cayley Memorial Lecture Mr. F. H. Owner on Engine Development The lecturer (right) with Mr. N. E. Rowe, Blackburn technical director and president of Brough R.Ae.S. Branch. EACH year at Brough, the memory of Sir George Cayley,father of British aviation and one of the earliest researchersinto the problem of aerodynamics, is commemorated by a lecture to the local branch of the Royal Aeronautical Society. Inkeeping with the spirit of the occasion, the lectures are largely retrospective in context and presented by authorities whose longexperience specially qualifies them to both review'past achieve- ments and to determine the trend of development in the yearsahead. The lecture this year, entitled A Survey of the Developmentof Aircraft Engines, was to have been given by A. Cdre. Banks, but because of his unavoidable absence abroad the subject wastackled—extempore, yet with a most pleasing and eloquent fluency —at very short notice by Mr. F. H. Owner, C.B.E., M.Sc,F.R.Ae.S., M.I.Mech.E., the deputy chief engineer of the de Havilland Engine Co. Recalling that Henry Ford had once said "history is bunk,"Mr. Owner asked how else, except by a study of history, was it possible for the trend of events to be gauged?He underlined his point by projecting a series of slides depict- ing the development of the turbine power unit. DiscussingHero's steam turbine of 150 B.C. he unwittingly gave his audi- ence an insight into the inquiring mind of a senior engineer.The bearings of the chamber, he remarked, were apparently steam-lubricated—a concept that was now repeated in the modernpractice of gas lubrication. Surveying the historical background to the modern turbojet,Mr. Owner touched upon the accelerating development stages to which the turbine power unit had been subjected: Branca'sfirst appreciation of the value of high turbine rim speed in 1629; Barber's realization of the necessity of cooling by water-injectionin 1791 and the important patents on the Parsons gas turbine which were taken out in 1884. At the turn of the century thepace of progress quickened; Sir Charles Curtis had built a non- self-sustaining turbine with straight-through combustion, and awater-cooled axial turbine in 1894. This was followed by the Ammengaud and Lemale steam turbine in Paris—of about threeper cent overall thermal efficiency—and the Karavoden and Hotsworth turbines as interesting variations on methods ofcompression. In 1920 a considerable—if theoretical—advance into gas-tur-bine technology was made by W. J. Stern, whose report The Status of the Aeronautical Gas Turbine was one of the firstinvestigations into the thermal and pressure cycles in a turbine, and reviewed the materials and stress levels that would berequired in a 1,000 h.p. unit with a 7:1 compression ratio. But such an engine, the lecturer recalled, was dismissed as impracticaluntil the time that better materials could be developed. The next step forward was the result of Dr. A. A. Griffith'sresearches (he achieved a compressor efficiency of 90 per cent) into free-vortex theory in 1926. An engine based on this theory Fig. 1. Classification of aircraft propulsion systems. was the counter-rotating^ counter-flow engine, examples ofwhich were built by Rolls-Royce and Armstrong Siddeley in 1939. In this engine each compressor stage is powered by anadjacent turbine stage and the residual gases for jet propulsion are exhausted at the forward, intake end of the engine. Perhaps it was this feature, and the unexpectedly hi^h leakagelosses which occurred between the compressor and turbine stages, that contributed to its demise: but a more potent factor wasthe advent of a new name and of new ideas. Frank Whittle's developments were beginning to overshadow every other project. It is always interesting to hear the authoritative opinions ofthose who are able to pronounce on the abilities of great men. Mr. Owner knew Frank Whittle in the early 1930s and had studiedthe famous patent 347203 (a number, it may be added, that the lecturer required no notes to remember) which was taken out in1930. It was Whittle, the lecturer said, who recognized that "the crux of the problem was to operate the turbine at a high enoughtemperature" and even at this time he was proposing the use of ceramic blades. It is to the lecturer's credit that he now readily 0OXTT Fig. 2. Ducted rocket. admits that he was among those who scoffed—or at least wassceptical—at this idea. A new name to most of the audience was that of the HungarianJendrassik. Before the war this inventor had developed an aero engine with a ten-stage axial compressor giving a compressionratio of 2.2:1 and revolving at 18,500 r.p.m. The Campini jet was more familiar; although not particularly successful, thisdesign—which made use of a reciprocating engine-driven com- pressor—was one of the very earliest to fly. Wartime development of the gas turbine—hampered at firstby the intensive effort devoted to attaining technical superiority with the piston engine—eventually proceeded apace. But theintensive work and rapid strides that were made during the forties were perforce glossed over by Mr. Owner. The subject is vast,and lecture time not unlimited; his audience had to be content with a reference to the "unparalleled" effort that Whittle devotedto improving the efficiency of the neglected combustion chamber. Present-day efficiencies, Mr. Owner assured his listeners with anot-too-deceptive earnestness, were often calculated to be 102 per cent. Reproduced on this page (Fig. 1) is the table that the lecturerused to sum up the many forms of aircraft propulsion systems. The major division of systems into those which are air-swallowingand those which carry their own oxidant have been intermingled and exchanged to form composite (separate propulsion systems)or compound (integrated system) aircraft propulsion units. The eight final systems are those which are most suitable for transonicor supersonic flight in different Mach number regimes. Discussing some of the systems shown in the diagram, thespeaker mentioned that propulsive ducts—which in aircraft require air launching or assisted take-off devices—have beenunder development in France since 1925. Rockets were chiefly exploited by the Germans, who used them in their He 176 andMe 163 intercepters. The development of practical rocket-pro- pulsion aircraft caused some headaches, he recalled: the manag-ing director was ordered to act as test pilot on the second Me 163
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