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Aviation History
1941
1941 - 1950.PDF
FLIGHT AUGUST 28TH, 1941, POSSIBILITIES OF water or a condensing plant. In the latter case some energy in the exhaust steam would be lost to propulsive effort. In 1939 the German aviation journal Flugsport issued a review of all designs dealing with thermal jet propulsion, by the German writer Gohlke. The article embodied many illustrations and leading particulars of the chief designs, including certain English patents. Early French Designs As in many other matters aeronautical, France took a leading part in attempts to adapt exhaust efflux to the propulsion of aircraft, Marconnet and Lorin having devised such schemes and explained their aims and objects as far back as 1909. Marconnet gave examples of a method in which the compression is effected by means of compressors or blowers; he differentiated at that early stage between systems with constant pressure and those with constant volume. Jet impulse reaction—that is, thrust provided by the extremely rapid ejection of gases from a suitably shaped nozzle—has progressed a long way in recent years. . Two months ago Lt. Col. J. T. C. Moore-Brabazon threw out a hint to a meeting of members of the Institution of Automobile Engineers, when he urged more original thought in design and experimentation, that future prime movers might be developed from an entirely different angle—some- thing basically different from the present power plants. Possibly the old problem of jet propulsion was in his mind in view of the activities of the world's scientists in this field of development. \ \\\ \ V, \ \ \ \ \ \ \ X\ \X \X X XX \N \\ XX // // // / // / / / / // / // // ',• / / / / / \ \ \ \ \ \ s \\ N.\ \\ XX X\ \\ \ V, \X X / X / N / X / X f \ / v / \ / X/ > / X / y, \ / J \ /, • \ .' 'j X // \ / • /' X / '• N' X v , \ /// X ', '/ N // 0 / , \T/• \ /' ' > .' "", \ '/y ^ / / X * Junkers jet reaction plant employing a multi-bank,air-cooled, two-stroke engine to drive the turbo-compressor. Additional fuel may be injected into the final expansionchambers to increase the propulsive effort. Jet Reaction—How It Works This briefly is how the system works. Air is the working fluid. Fuel, which for practical purposes will be any of the natural or synthetic liquid hydrocarbons which we use in engines to-day, is required for the addition of heat to the air. Air is drawn in, compressed into a heating chamber, and heat is added by the combustion of fuel. On re-expansion, sufficient energy is taken by a motive unit to drive the compressor, and the air, still capable of expan- sion, discharges to atmosphere as a high-velocity efflux from a nozzle or nozzles. This efflux, or jet, produces a reaction, in the nature of an axial thrust on the plant, which constitutes the propulsive effort. What is the real attraction of jet reaction units? Scientists claim that in its developed state it will provide a powerful thrust in proportion to its weight and make possible a higher speed than has been obtained up to the present with accepted type engines. Its efficiency should not be lowered by the reduced density of the air at high altitudes, and may even be enhanced owing to the low temperature prevailing in the upper atmosphere. Further- more, a complete plant will be of relatively simple con- struction, of convenient external form, and will operate with any fuel now in use. Means of regulation may include fuel control, gas flow control, control of compressor speed, or control of the power unit driving the compressor. For -manoeuvring the craft, the emission nozzle may be directionally controlled. One or more complete units may be employed on a single air- craft (a multi-unit design will be shown in our illustra- tions) and selectively operated either singly or in unison. When units are grouped, certain functions may be inter- dependent. For example, one turbine or reciprocating engine may drive the compressors for two units. '••.. Italian Projects „. •/../;>,.;:i. On August 27th of last year, according to the Popolo d'Italia, a high-speed Italian aircraft with jet propulsion to designs evolved by Engineer S. Campini, of the Caproni organisation (during its development frequently referred to), made a successful flight of ten minutes' -duration from the Forlanini aerodrome, Milan, in the presence of General Alberto Briganti, Commander of No. 1 Air Zone. The particulars of the machine quoted in a translation by the Ministry of Aircraft Production (R.T.P.) stated that the machine was built entirely of metal, had a gross weight of 8,800 lb., retractable landing gear and a pressure cabin. The machine was driven solely by the reaction of ejected gases, and was claimed to be the prelude to a revolution in the design of aircraft and power plant installations. The note added that Campini's work had finally led to the development of a power plant whose efficiency is not below that of the engine airscrew combination, even at conven- tional speeds. The report in the Popolo d'ltalia gave no details of the design of the propulsion plant, but probably this followed the lines suggested by Campini in 1932. In the projected design, illustrated on the previous page, Campini sought to employ jet propulsion for both sub-sonic and super- sonic speeds. The cabin, A, is of ovoid form and con- structed as a pressure unit for high-altitude operation. Air is admitted where the annular space between the cabin, A, and the enshrouding cylinder, B, has its smallest cross- section. This space widens out to the rear in order to con- vert the kinetic energy of the air into pressure energy. This compressed air then passes through a two-stage centrifugal compressor, C, driven by a radial engine, D, or possibly a gas turbine. Beyond the compressor it passes a radia- tor, E, which also acts as a rectifier, into the wide com- bustion space, F. Here, in an annular channel, G, of ven- turi shape, the air is supplied with fuel, and, after expan- sion, discharges through the nozzle, H. The nozzle unit is
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