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Aviation History
1947
1947 - 0203.PDF
FEBRUARY 6TH, 1947 fc chamber comprises a branched dome of light alloy, flanged and bolted to a mild-steel outer casing. The dome bolts directly to the rear face of the diffuser, whilst the remote end of the outer casing makes a sliding joint with the turbine nozzle junction ring to permit thermal'expansion. Co-axially within the chamber is an assembly consisting of a flame tube capped by a colander. Fabricated from Wiggins Nimonic 75 heat-resistant alloy, the assembly is positioned from the dome bv three cast lugs and three inserted Starboard side view with insulating cuff removed. •FACE COOLING AIR TO TURBINE REAR FACE- MUFF FOR,AIRCRAFT WARMING INSULATING AIR SHROUD THERMOCOUPLE PROPULSION NOZZLE Maximum diameter Standard length Dry weight Maximum revs. 53 in. Static thrust 5.000 Ib. 122 in. Fuel consumption (.04/b./lb./hr. 2,011 Ib. Oil consumption t.Spt.jhr 10,000 r.p.m. Air mass flow 88/b./sec radial supports. One of the latter is constituted by the tubular member by which all chambers are interconnected to effect a pressure balance and permit propagation of the flame from one chamber to another when starting-up. The burner is entered between the branches of the dome, passes through the metering orifice in the outer cone of the colander and is centred in a ring of swirl vanes in the inner cone of the colander. Of the air entering the dome, approximately 30 per cent passes the metering orifice and swirl vanes for primary combustion of h fuel at a ratio *of about 18 : 1. The rfiajor portion, however, flows between the flame tube and the outer casing and is fed to the interior of the flame tube by way of a multiple series of holes to dilute the combustion pro- ducts and lower the heat of the gas to a temperature that can be with- stood by the turbine blades. A small portion of this secondary air continues to the end of the flame tube and passes through segmental slots cut in the terminal flange of the outer casing. The oveiall air to fuel ratio is of the order of 60: 1 but these figures will vary somewhat in accordance with altitude and operating regime. In the event of a " wet start," when fuel is injected but ignition does not occur, fuel in the lower run of the chambers will tend to flow back and be collected in the domes. As a safety measure, there- fore, the lower cylinders are interconnected by a drain pipe by which such fuel can be jettisoned. It is the aim of the com- bustion engineer to achieve complete combustion of the fuel without any restriction or impedance of the mass flow. If this were possible the specific pressure at the exit of the combustion cham- ber would be the same as at the entrance! As some de- gree of turbulence is essential to consume fuel at a high rate, this ideal is unattain- able. Credit attaches to those responsible for the design of the Ghost chamber, however, as the pressure drop from entry to discharge is only 2.8 lb/sq. in. Temperature contour diagrams, taken at the turbine nozzle junction BULLET immediately aft of the com- bustion chamber, show remarkably even thermal distribution and the variation from peak to meau temperature is ouly 84 deg. C. Turbine Assembly The nozzle junction, fabricated from stainless steel, re- ceives the discharge ends of the ten combustion chambers and is supported by a deeply dished diaphragm mounted on the housing of the rear bearing. Flanged to the rear of the nozzle junction is the stator ring having 84 blades which direct the gases to the appropriate angle of attack for the blades on the turbine wheel. Stator blades are stampings of Jessop's G.18 B steel and each is secured by two integral pins riveted through the inner ring and a tongue peened in the shroud ring. After the blades are built in, the shroud ring is divided into ten segments to permit radial expansion without distortion. To the rear of the statoi ring is bolted the shroud ring for the turbine wheel and together these three components, nozzle junction, stator ring and turbine shroud, form a drum. A complete combustion chamber and, alongside, the main components. The burner is secured between the branches of the dome.
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