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Aviation History
1955
1955 - 1402.PDF
514 FLIGHT Largest outlet silencers in Britain, the twin Mk 6 Detuners never get hotter than 150 deg C. The only obvious indication of running is the shimmering effluent, aural indications being insignificant. GYRON TEST-BED ... the original open bed, a visitor was singularly unimpressed byseeing a pair of thrustmeters each reading 7,500 1b, and refused to believe that the true reading was the sum. The late MajorHalford is reported to have ordered the present arrangement to prevent a repetition of such an occurrence.) The control room is a model of cleanliness, ordered layout andreasonable working space. As the drawing shows, it has been designed to permit a second bed—a mirror-image of the first—tobe built alongside, the manometers for this bed being already in position. From the outset it has been the aim to incorporateeverything that could possibly be required now, or at any future date. From the control station the engine is clearly visible throughlarge windows, it being possible to see exactly what is going on in the cell and to check for even the slightest leak. As a safety pre-caution the windows have two layers of Jin armour glass and one 2in layer, and a ring of fin boiler plate surrounds the Gyronturbine section. Air for the Gyron is drawn in through an enormous intakethrough which flow velocity is never sufficient to draw in much extraneous material (there is a wire fence about five feet high),although leaves from surrounding trees do get picked up. The vertical splitters are of a new, hexagonal form, which tune outa greater range of frequencies than the conventional pattern. Even at full power (at current ratings) the depression inside the celldoes not exceed one inch of water, and disturbance to the numerous pipes and wires is trivial. For every pound of airpassing through the Gyron, just under \\ 1b is entrained by the bell-mouth cooling intake behind the propelling nozzle. Thisresults in metal temperatures being incredibly low; in fact, the window in the outlet duct (for looking up the jetpipe of theengine itself) has a Perspex window. The first 15ft of duct is telescopic, and can be adjusted to suitdifferent types of Gyron, with or without afterburner. If even longer engines develop, a six-foot section of duct can be removedbodily by an electric hoist. Beyond the test cell proper is a second chamber into which the first exhaust duct discharges. The latter points into the entry of the outlet silencer, and entrainsa further mass of air (just over 150 per cent of the engine mass flow) through a roof intake and splitter panels. Thus, the twu-stage air entraintnent, with a 3 : 1 ratio over the engine flow, keeps the outlet ducting cool enough for it to be touched, and it ;scertain that no water cooling will be needed even with a 30,000 lb- thrust Gyron with afterburner. No stainless steel is used any-where in the outlet ducting. From the secondary cell there leads a diffuser, a parallel section,a breeches-piece dividing the flow into two and, finally, a pair of Cullum Mk 6 Detuners with upturned outlets. The Mk 6is a well-known unit, and the use of a pair has made possible the accommodation of what may be the greatest flow of hot gas yethandled anywhere without having to develop a new Detuner. Each Detuner is anchored near the bifurcation, and expands foreand aft from this point, each section being roller-mounted on steel plates carried upon brick walls. Detuners were described in ourissue of September 5th, 1952; an associated company, H. J. W. Cullum and Co., Ltd., provided sound-proofing throughout theGyron bed, and—having experience of over 30 turbojet test instal- lations in several countries—we consider the Gyron facility thequietest yet, in spite of the massive throughput. The latter may, in fact, tend to reduce apparent noise, owing to a reductionin mean frequency of sound. Precautions against fire are naturally comprehensive. The entiretest cell is continuously exhausted by two large fans mounted at the base of the Detuner silencing duct. These fans extract airfrom the cell through individual ducts, and remove all dangerous fumes which might result from the starting cycle or from brokenpiping. Spilt fluids are run off into an anti-flash sump and thence to a drain outside the building. In addition to various handextinguishers there is an elaborate and automatically controlled extinguishing system. In the event of fire breaking out in the test cell, the operationof a single switch on the main control console causes the fuel pump (low-pressure) to be shut off and the main fuel inlet valveto be closed. At the same time, the extractor fans are switched off and heavy steel roller shutters are run down over the mainair intake to the bed. A second shutter can be run down across the entry to the outlet silencer. While all this is going on, thefire is kept in check by the discharge of a primary shot of carbon dioxide from nozzles around the engine (some of which arevisible in the heading photograph). When the test cell is sealed off, a second (and larger) CO2 discharge is made, sufficient to floodthe cell completely. In the highly unlikely event of a fire still persisting after this treatment, a manual switch can release athird, very large, volume of CO,. As it is at present, the Gyron test facility has cost somethingof the order of £140,000, all of which has been paid by the de Havilland Enterprise. Chief contractors, in addition toDetuners, Ltd., and Cullums, have been such firms as Minneapolis- Honeywell-Brown, Barnet Instruments, Rotameter, Rellumit andTannoy. A Gyron first went on test in the bed in May of this year, and it is now in use day and night, without any disturbanceto anyone. This "Flight" copyright drawing emphasizesthe straight-through flow in the Gyron bed. (1) Main air intake, (2) acoustic splitters,(3) roller shutters, (4) trolley rails, (5) fire-sup- pression nozzles, (6) thrust pads, (7) three-pointsuspension, (8) telescopic section, (9) removable section, (10) tailpipe inspection window, (11).econdary air intake, (1Z) instrument panel, (13) control panel and observation window, (14)manometer panels for existing and future bed. (15) twin Detuners, (16) fuel storage tanks.
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