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Aviation History
1955
1955 - 1123.PDF
FLIGHT, 12 August 1955 235 DEVELOPMENT ON THE GRAND SCALE . . . in the previously mentioned separate control rooms, with theflow conditions needed for the tests. Observation, which takes place in enclosed steel cells, is effected through the medium ofa TV screen. All the equipment is designed for continuous operation andthe test cells may be used for type-tests of 150 hours' duration or more. The cells can be lengthened to take additional equip-ment, such as afterburners or exhaust cooling devices. Test data obtained will be rapidly processed by a large digital-typecomputing machine. Consisting of a group of supersonic and hypersonic windtunnels, the gas dynamics facility will be used solely for the development testing of models of aircraft, projectiles and missilesdesigned to operate at extremely high speeds. Occupying an area approximately 400ft by 500ft, the facility, also based on aGerman design, comprises three small wind tunnels. These are E-l, a small 12inxl2in tunnel with a Mach range of 1.2 to5.0; Tunnel A, a 40in x 40in installation with a Mach range of from 1.2 to 5.5; and Tunnel B, another 40inx40in equipmentwith a Mach range of from 4.5 to 10. With the completion of the facility by adding three or four more tunnels, A.E.D.C.expect to reach Mach 18. When Tunnel B is completed it will be the largest tunnel in the world capable of testing in the Machrange of from 5 to 10. Incidental to testing at Mach 10, it is necessary to heat the air to 1,500 deg F to prevent solidification—i.e., to prevent the occurrence of an actual snowstorm in the test section.A and B are continuous-flow tunnels and air is provided to them from a battery of 12 compressors through eight stages ofcompression. This primary air mover is an extremely versatile plant consisting of six axial compressors and six centrifugalcompressors, driven by electric motors totalling almost 100,000 h.p. By using this size of tunnel, and as a result of the economicaland convenient method of increasing the air pressure to more than 100 atmospheres at high Mach numbers, Reynolds numbersnear to those of missiles in flight will be attained. Tunnel E-l is an intermittent-type tunnel and is supplied withair from a huge 5,200 cu ft capacity high-pressure storage bottle, in which the air is stored at a pressure of 4,000 lb/sq in. With aninside diameter of 4ft this bottle takes the form of a tube, 720ft in length, and replaces many manifolded bottles usually usedfor such high-pressure air storage. Air is supplied from an auxiliary compressor group, which includes vacuum pumps andcentrifugal and reciprocating compressors. After passing through the Tunnel E-l test-section, the air is discharged to a 72ft-diameter vacuum sphere with walls 1 Jin thick. Much of the air ducting and most of the air heating, coolingand drying equipment of the gas dynamics facility is exposed in a large area lying between the compressor building and the tunnelbuildings. A feature of this installation is its flexible power system, whichwill permit testing over widely varying speed, altitude and temperature conditions, so that the full-scale flight characteristicsof the test models can be readily ascertained. Consisting of two continuous-flow closed-circuit wind tunnels,one transonic and one supersonic, each 16ft square, and a scale model of the test section of each, the propulsion wind tunnelfacility is designed to carry out development testing of full-scale operating ramjet and turbojet powerplants installed in missilesor aircraft. It will be able to handle material of about 4ft diameter and up to about 30ft in length. In addition, full-scaleairscrews and aerodynamic models can be tested. Both tunnels are powered by a common-drive motor system of One of the four main motors providing power for the closed-circuit tunnels; two are of 25,000 h.p. and two of 83,000 h.p.—a total of 216,000 h.p. Scale is given by the man standing on the bedplate. High-altitude test cell of the engine test facility. Engines can be tested in simulated altitudes of up to about 80,000ft. 216,000 h.p. capacity and the whole airtight tube of speciallyfabricated steel is about 60ft in diameter at its maximum cross- section. Each circuit has its own set of compressors, whichmake up the largest installation of rotating machinery in America. The main drive and compressor system is so arranged that bothtunnels can operate simultaneously up to half power, or indi- vidually up to full power. Thus, model installation and instru-mentation can proceed in one circuit, while test programmes are being conducted in the other. The tunnel has an altitude range,under certain conditions, of 8,000 to 100,000ft, with tempera- tures and pressures to correspond to the altitudes and velocitiesthrough most of the test range. The Mach number range covers an area of between Mach 0.8 and Mach 3.5. Each tunnel will be provided with a completely adjustableflexible nozzle to cover its entire operating Mach number range. Several interchangeable test-sections will be completely remov-able from the tunnel circuit and may be transported from the tunnels to the model-installation building. A scavenging systemfor the elimination of contaminated air and a make-up system for replenishing the circuits with clean, dry air is provided, whichutilizes the exhauster and blower capacity of the engine test facility and its ramjet addition. Construction is being accomplished in two stages, the first ofwhich will put the transonic circuit in operation, and this is scheduled for completion this year. Shakedown and calibrationtests will take about six months. The supersonic circuit will then be built without seriously interrupting the test work being carriedout in the transonic circuit. Measuring 16ft x 16ft x 40ft long, the transonic-circuit test sec-tion is of the closed-circuit single-return type. Flow will be controlled by an adjustable Laval nozzle, the nozzle walls beingcontoured by fifteen pairs of motor driven jacks per wall. These jacks will be positioned remotely by an operator in the transonic-control room. Movement of the flexible walls will be in the horizontal plane, while the top and bottom walls willremain fixed. Several 40ft test-section carts are provided for the operationof the transonic circuit, and test articles may be completely installed and made ready for test without interfering with testinggoing on in the tunnel circuit. The range of the supersonic circuit will overlap the upperMach number limit of the transonic circuit by beginning at Mach number 1.4. The supersonic velocity in the test section is con-trolled by a nozzle with flexible walls 16ft high and 57ft long. The pressure in the tunnel circuits can be varied from twoatmospheres to that equivalent to an altitude of 100,000ft, while temperature and altitude conditions matching those obtained inactual flight, through a wide range of speeds, can be provided. Coolers installed within the tunnel circuits provide a means ofsimulating standard altitude temperatures. At maximum flow rates, these coolers will use water at a rate equivalent to that of acity the size of Washington, D.C. The supersonic circuit is scheduled for completion in 1957. Built for the U.S. Air Force at the East Pittsburgh plant ofthe Westinghouse Electric Corporation, the four motors installed are claimed to be the most powerful electric motors ever built.Two are rated at 83,000 h.p. each and a smaller pair are rated at 25,000 h.p. each. The five compressors which the motors willdrive are also by Westinghouse. Each of the larger motors stands 21jft high and weighs 225tons. The rotors spin at 600 r.p.m. and some 31 miles of copper
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