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Aviation History
1954
1954 - 1398.PDF
14 May 1954 619 TURBO-WASP DISSECTED More News of the J57 Two-spool Turbojet AFTER much research, the Pratt and Whitney Aircraft Division of the United Aircraft Corporation put the L first turbojet of their own design into production in February last year. At that time the entire American industry had begun to look upon this engine, the J57, as the most promising of all their "home-grown" turbojets, and it has now become accepted as the standard power unit of many of America's most important aircraft—among which can be named the following: Fighters, North American F-100 Super Sabre, Convair F-102, McDonnell F-101 Voodoo, McDonnell F3H Demon, Douglas F4D Skyray, Chance Vought F8U, and Grumman F11F; Bombers, Boeing B-52 Stratofortress, and Douglas A3D Skywarrior; and Transports, Boeing 707 (367-80) Stratoliner and Stratotanker, Douglas DC-8 and various projects. A first description of the J57 appeared in our issue of November 27th last. The engine can be briefly summed-up as an all-steel, high-compression, two-spool turbojet giving about 10,000 lb thrust, or 15,000 lb with a Pratt and Whitney- designed afterburner. The weight is, in comparison with British engines of equal thrust, high at 4,100/4,400 lb; on the other hand, the specific fuel consumption is unusually good, at around 0.76 lb/hr/lb at full power. As the J57 is a two-spool engine, the starter motor drives the high-pressure rotating assembly, consisting of the rear, seven-stage compressor and its single-stage turbine, the two being connected by a large-diameter hollow drive-shaft. This assembly accelerates rapidly and generates sufficient airflow for combustion to start; after a few seconds the gas flow through the two low-pressure turbines is sufficient to drive the low-pressure (front) compressor as well; the low-pressure axial drum carries nine rows of blades, and is tapered acutely as can be seen by the side-view photograph. The low-pres sure turbines drive this compressor via a shaft which passes through the centre of the high-pressure turbines, hollow drive-shaft and rear compressor. The main bearings are in line with "E," in the annotated photograph below; this is the diffuser between the two compressors, and bearings for both compressors are mounted on central rings held by the large guide-vanes, the position of the vanes being visible in the photograph. The "six o'clock" vane of this diffuser is a hollow fairing for the drive-shaft linking the main rotating components with First engine to be officially'rated at 10,000 lb thrust, the J57 is here seen from the left side. The key is as follows: A, oil return line; 8, anti-icing gate-valve actuator; C, breather pipe; D, oil tank; E, engine mounting flanges; F, high- pressure casing; G, breather line; H, diffuser; I, combustion cham ber; ], turbine section; K, thermo couple harness; L, oil scavenge line; M, inter-compressor bleed valve; N, anti-windmilling brake; O, inter-compressor bleed control- valve governor; P, anti-icing air pipe; Q, oil pipe. Looking out of the eductor tube into a J57 test cell at Ford's Chicago plant. It is worth noting that the floor is completely clear. the engine accessories. This shaft transmits the drive from the starter motor to the front of the rear compressor. The starter motor itself is an air-turbine unit driven by a com pressed-air supply obtained either from a ground truck or, in a multi-engined aircraft, from the compressors of engines already started. It is housed beneath the sheet-metal cowling lying under the waisted middle-portion of the engine, and is fed from an air intake on the front of the left-hand side. This cowling also houses the fuel and oil pumps; the oil filter is adjacent to it, and the shaft drive is carried forward beneath the compressor case to a power-operated clutch or brake which quickly brings the engine to rest after shut-down or mechanical failure in the air. Such brakes are mandatory in the American Services to prevent windmilling under the influence of ram air. Airframe accessories are remotely positioned and are driven by turbines fed on compressor air tapped off around the diffuser section; an exception is the main alternator, which is driven off the front compressor as shown (U), with a hydraulic constant-speed coupling. It is noteworthy that the engine is built up from nine prin cipal steel-drum assemblies, all of which are bolted together
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