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Aviation History
1945
1945 - 1809.PDF
13TH- F LIGHT 283 The first-jet-propelled heavy bomber, the Junkers 287. L of development, as will be seen from the illustration. It i axial mducer, a compressor with one radial outflow and GERMAN JET RIVALRY lever position and compensated by thepitot head pressure. The projected 012 unit, intended forthe Ju .287 bomber, had an eleven-stage axial compressor and a two-stage turbine.The -designed thrust was, 6,000 to 6,.400 lb. with a specific consumption ofabout 1.2 lb./hr./]b. • The total weight was 4,400 lb. and overall length about17ft. Up to the time of the German col- lapse this unit had not been tested. The only other concern to be creditedwith an operational unit was the Bayer- ische Motoren Werke\ . Preliminarystudios were undertaken in' 1934. work on the B.M.W. 003 was commenced in 1939, and the unit firstran in August, 1940. Instead 01 the designed static thrust of jet i positions for idling and power. In emergency this unit ] operated on diesel oil instead of the German standard Iht diesei oil." tobably the most highly developed and certainly the most kiy used jet unit was the Junkers 004. The sectional illus- ou shows the 004 B version, which-is representative of all models from A to E and their sub-types. After initial in- flations commencing in 1937, Junkers began full-scale towards the end of 1939, and the first unit was run in kmber, 1940. Flight tests wore made in an Me no, and Inmcntal craft a year, later, and in the summer of 1943 they : installed in a prototype Me 262. Owing to our bombing full-scale production was not., achieved until the ner of 1944. • , • •.. Eight-stag *ige Compressor lie tight-stage axial compressor delivers air to six inter-sected combustion chambers into which the fuel is injected trcam. Combustion chambers are of aluminised mild steeltaad are free to slide at their forward ends to accommodate _nai expansion. The single-stage turbine rotor has sixty-fllades of heat-resistant steel ot 30 per cent, nickel and 15 [cent, chromium composition. Cooling air is bled offiteen the fourth and fifth compressor stages and is led to the skin surrounding the combustion chamber assembly.;i quantity of this air passes into the space between the Ibustion chambers and the inner wall, but most of it passes•- one oi the exhaust cone struts to circulate inside the cone ,ass through small holes to the downstream face of the;ne disc. Some of "it passes into a double skin extending lithin about 2ft. of the discharge nozzle.- After the last com-Bor stage, air is bled off internally to . _..-.' Eels in two of the casting ribs to cool • • , ' • [upstream face of the turbine disc.icr air is taken through three tunnels be central .casting to the spacejreen the two diaphragms forward of [turbine disc, whence it passes intonollow entry vanes of the turbine and Jischarged through slits in the trailingof the vanes. Turbine blades originally solid, but, due to diffi-es of material supply, hollow blades ned from sheet metal were subse-tly employed. • with the other two main Germans, Heinkel-Hirth and BMW, the •ing system employs a Riedel flat-, two-stroke petrol engine, which is ;'ted in the air intake coaxial with I main shaft. On the ground it can bei'i by means of a cable and pulley, i:i the air it is started electricallyl» the cockpit. Uuel for the main pulsiou unit is light diesel oil. Gon-• "f the discharge nozzle is. by a ullet" operated from the trtrottle the Heinkel-Hirth on" unit two-stttge turoine. Below, the 003 unit with ' seven-stage compressor. v on page 284. Component features of the B.M.W. unit, shownin an illustration, are an axial compressor in seven stages, a single annular combustion chamber furnished with sixteen fuelsprayers and a single-stage axial turbine with hollow, air-cooled rotor and stator blades. Economy of Critical Metals Control of the discharge nozzle is by the usual •" bullet"arranged with four positions for starting, take-off, high speed and cruising. The fuel is light diesel oil or, if necessary, 87octane petrol. In this design the utmost care was taken to economise inalloy steels and, in fact, the latest unit only required 1.3 lb. nickel. Similar to other concerns, B.M.W. had big ideas. Oneproject was for a unit having a twelve-stage compressor, a combustion chamber with twenty-four fuel sprays, and a three-stage turbine. This giant, B.M.W. 018, was to develop a static thrust of 7,500 lb., but it was not completed at thecessation of hostilities. The 007 turbo jet unit was developed by Prof. Leist fortiie Daimler-Benz concern. One unit was built and run under test in the autumn oi 1943. It was of exceptional interest asit possessed a number oi unusual features. The compressor and a ducted fan wore arranged on two contra-rotating drums.The inner drum had nine stages of compressor blading, whilst the outer drum carried internally eight stages of compressorblading and externally three stages of fan blading. Four tubu- lar combustion-chambers were provided, and the turbine rotorwas cooled over 30 per cent, of its circumference by air drawn from the ducted fan circuit, whilst the remaining 70 per cent,oi the circumference received the working gases.
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