FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1942
1942 - 0918.PDF
422 FLIGHT APRIL 30TH, 194? NEW IDEAS ON PROPULSION French and American Schemes Employing Steam Turbines NEWS has now reached us that the Breguet Aircraft works at Toulouse is building an experimental jet-propelled machine to the designs of R. Leduc. This French engineer is well known for his work in connection with the problem of jet propulsion. As reported in the fourth article on the subject appearing in the October 9th, 1941, issue of Flight, Leduc patented a thermal jet system in the year 1933.' According to Inter Avia, the new experi mental type is basically similar in principle to the Caproni- Campini machine, but with one important exception. Whereas the Italian craft uses a standard type of air-cooled radial engine to drive the air compressor unit, Leduc em ploys a steam turbine for this purpose. Of the VUIA type running at 3,000 r.p.m. under a steam pressure of 1,910 lb. per sq. in., the turbine is estimated to develop 1,200 h.p. Experiments, presumably on the test bed, are claimed to have given satisfactory results. No details are yet avail able, however, of either the boiler or the necessary con denser plant. Obviously, the steam system would have to operate on a closed cycle. Condensing raises further prob lems which are not easy of solution in an aircraft instal lation. The condenser would, most likely be placed in -the main air stream so that heat transferred from the steam would be usefully absorbed for the pro pulsive jet. The development of a jet-propelled aircraft employ ing such a system will be watched with intense interest by designers throughout the world. According to present-day standards it would not seem pos sible for the rate of fuel con sumption to be as low as that of an internal combustion engine doing the same work. The pro jected speed of the new machine is estimated to be in excess of 310 miles an hour. Earlier- Projects Leduc's earlier designs were all of the compressorless type in which a divergent duct was employed to raise the pressure of the "relative wind" admitted when the machine was in motion. Fuel was introduced through a comparatively large number of nozzles disposed across the main stream, as shown in the diagram (Fig. 1). Combus tion of the fuel would therefore be relatively inefficient owing to the low degree of compression attainable, and consumption might be expected to be inordinately high. Fig. 2 is a sketch ot the model of a Leduc design which was exhibited at the Paris Salon de 1'Aviation in 1938. This mid-wing monoplane with a fuselage of streamline form was a somewhat fanciful conception of "the machine ot the future." The descriptive notice exhibited alongside the model, with the characteristically light-hearted abandon of the Gallic race, informed the visitor to the Salon that with i wing area of 16 sq. metres, a weight of 2,000 kilogrammes and an output of 14,000 h.p., the machine would have a speed of 1,000 kilometres per hour and a ceijing of 30 kil«.** metres. There is no evidence that this design was taken beyond the model stage. In the Flight article referred to earlier, it was suggested that Ituch compressorless schemes of propulsion, whilst admittedly ingenious, were somewhat impracticable ideas of obtaining something for nothing. Some form of mechanically-driven compressor appears to be necessary, and the latest project of M. Leduc is a striking confirma tion of this point of view. Ambitious American Schemes Four different arrangements of power units are disclosed in a recently published American patent in the names of Igor I. Sikorsky, M. E. Gluharefi and R. W. Griswold and assigned to the United Aircraft Corporat'on. The declared objects are to con serve engine power by the utili sation of waste heat, to improve engine cooling, and to enhance the aerodynamic characteristics of the wing section. Fig. 3 shows a typical layout, while other arrangements include a similar scheme for a V-type, liquid-cooled engine, a method of returning the power generated by the waste heat to th^ main engine, and the use of the auxiliary power to drive an electric generator for cabin heating. Referring to the illustration, the radial engine A is enclosed in a cowling and the cooling air is drawn in by way of the central forward aperture by the suction of blower B. The air passes between the cylinders to remove excess heat, and is led into a chamber C formed by the leading-edge of the wing. Here it may be passed along the leading-edge to impart heat and prevent ice formation. The blower is driven by means of an exhaust gas turbine D and a steam turbine E operating on a common shaft. The gas turbine is connected directly to the exhaust conduit of the engine, whilst the steam turbine is driven by steam supplied from a boiler F heated by the efflux of the gas turbine. Steam leaving the turbine is passed through a condenser G and the condensed fluid is returned by pump H to a storage tank or directly to the boiler, as shown. From the leading-edge chamber the blower delivers the air to a mid-wing chamber J, where it is forced through the condenser into an in ternal duct K. This communicates with • a spanwise slot L located to the rear of the upper surface of the wing. It is claimed that such an arrangement con verts practically all the heat of the exhaust g.is into mechanical energy which is utilised for
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
