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Aviation History
1951
1951 - 0897.PDF
(Above) dt Hovilland Ghost turbojet. (Right) Metrovick Beryl turbojet. DESIGNS OF A DECADE compressor; not only in general terms, but more specifically, in ad- vocating the single-sided centrifugal type. The Goblin can to some extent be regarded as a linear descendent of the early Whittle concept of the turbojet, and is delightfully simple in basic layout. Elliptical-nostril intakes give direct into the eye of the single-sided centrifugal compressor, the delivery from which is distributed between 16 combustion chambers. These feed the single-stage turbine which drives the compressor through a tubular shaft, the compressor and turbine forming a single rotating assembly mounted on only two bearings. It must be recorded that the Goblin passed an official type approval test in January, 1945, and, as a result, holds Type Certificate No. 1 for a turbine unit for aircraft propulsion. Following on from the Goblin, and resembling it in fundamental layout, the Ghost was the next unit produced by the company. It was first run in October, 1945, and early the following year was developing its rated output of 5,000 1b thrust. In order to keep down the diameter as much as possible, cascade vanes are fitted in the compressor-diffuser to turn the air axially as it leaves the diffuser vanes. Each of the ten combustion chambers which, understandably, are of considerably greater volume than those of the Goblin, receives air from the compressor-diffuser through twin branch pipes. It says much for the design of the combustion system that a compression ratio of 4.26:1 is achieved and that the specific fuel consumption of the unit is 1.06 lb/hr/lb. Metropolitan-Vlckers, Ltd., were perhaps the first com- mercial company to engage in the gas-turbine field, for in 1938 they collaborated with the R.A.E. in designing a power unit, known as the B. 10, which embodied a nine-stage axial com- pressor driven by a four-stage turbine. The company have, of course, an immense background of experience in the design and manufacture of steam turbines, and in view of this it is only natural that, in connection with gas-turbine design, their attention should have been focused on the axial-flow type of unit. In 1940 they started the development of a unit which, designated F.2, embodied a nine-stage axial compressor, an annular combustion chamber and a two-stage turbine. The power unit passed a 25-hour special category test in November, 1942, with a thrust rating of 1,800 lb, and a year later a pair of these units, installed in a modified Gloster F 9/40 (the forerunner of the Meteor) made possible the first flight of a British aircraft propelled by axial-flow rurbojets. The F.2/4 was developed into the Metrovick Beryl, modifications including a ten-stage axial-flow compressor and 3 single-stage turbine. For a weight of 1,750 lb, the Beryl gave a take-off thrust of 3,500 lb, at which the specific fuel consumption was 1.05 lb/hr/lb. This last figure, however, was reduced to 1.00 lb/hr/lb at the cruise rating of 3,000 lb static thrust at sea level. Interesting developments undertaken by the company in the thrust-augmentation field were seen in the F.3 and F.5 power units. The F.3 was basically an F.2 turbojet, modified to incor- porate a four-stage turbine immediately downstream of the normal two-stage (compressor-dflfing) turbine, the new four-stage unit Metrovick F.2/3 turbojet with ducted fan thrust-augmenter.
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