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Aviation History
1948
1948 - 1952.PDF
6io FLIGHT NOVEMBER I-8TH, 1948 SOCEMA Aircraft Turbines tooling arrangement based on the ideasof M. Darrieus, Chief Engineer of the Cie Ele'ctro-Mecanique. These relate tothe protection of the blades by means of a boundary layer of cold air and we hadmade systematic tests on this scheme well before the war. It had enabled us tooperate a turbine at 900 deg C gas tem- perature without exceeding a blade tem-perature of 500 deg C. We applied this system only to the fixed blades and, asfull protection would have been excessive for a gas temperature of 800 deg C, welimited it to the under-surface Further- more, instead of a. continuous slot locatednear the leading edge, we provided a number of orifices in line. The air fromthe compressor outlet^cnters the hollow blade at th$ outer end, flows inwardsand cools the upper surface wall, then passes through an aperture in the base On the jet unit auxiliaries are mounted at the forward end. The annular combustion chamber has twenty interconnected flame tubes arranged in two concentric rings. The annular chamber accommodated anumber of flame tubes of different diameters"^isposed axially on two con-centrjcpi^gi^arcles. These tubes, circu- lar at*>l»e upstream end, were progres-siv^t_^eformed towards the downstream * ,<^>So that at their exit they againd an annular section. arrangement has several ad- t'aJenl applied for. Turbine nozz/e assembly for TGAR-1008. T/ie hollow sheet metal blades are drilled near the leading edge for the emission of a protecting layer of air. of the internal baffle plate to the under-surlace wall and feeds the orifices. With a protecting air flow of about one percent of the total, the nozzle blades work at a temperature 250 deg C lower thanthat of the gases after combustion. Fixed and moving blades are in JacobHoltzer Sirius HT, an austeiiitic steel with a creep of 0.5 per cent in 300 hoursat a stress of 9.52 tons/in2 at 700 deg C and 15.2 tons/in2 at 600 deg C. Fixedblades are naade from 1.5 mm sheet and the moving blades are machined fromstampings. The turbine disc is in Jacob Hortzer 1480 steel. The compressor iscompletely in light alloy; moving blades being stamped to finished size by theCompagnie Generate du Duralumin. v In 1945 the only example of anatomization combustion chamber we had was the Jumo 004, which was hardlyencouraging (duration 25 hours, unburnt proportion 12 per cent). At first we pro-vifled a vapourization combustion cham- ber 011 the same principle as that triedon the turbo-prop unit, but the problem was much more difficult. Vapourizationtould not be effected so simply in a coil surrounding the combustion chamberand we had to provide two coils" located in the turbine efflux. Injectors wereiitted behind the turbine to heat the coils initially and a start was achievedin about 30 seconds. In view of the drawbacks of thevapourization system we undertook the development of an atomization chamber. xl applied . Diagram showing path of cooling and protecting air through nozzle guide vanes. r'antages. By raising the gas tempera- ture of the outer tubes relative to the nner ones, the temperature at the roots of the moving blades is reduced andthermal stresses in the disc are lowered. The small inner tubes take 27 per centof the total flow and a temperature difference of ^00 deg C between the twozones would mean aii average tempera- ture only 50 deg C lower than the maxi-mum. This difference can be controlled and, if desired, could be varied withengine r.p.in. providing atomizers are fed with independent values of fuelpressure. At high altitude, if thrust is to be reduced to as low a value as pos-siale, the fuel supply to the larger tubes is c\t off and the supply to the smaller \jiA5s adjusted to a pressure sufficientrtvfoaintain a stable flame with minimum O^ichness. The unit then works almostin autorotation and it should be possible to avoid blow-out and ensure re-ignitionof all tubes when required. Control gear, though complicated, offers nodifficulties in principle. This chamber with separate flametubes is now enabling us to dispense with the turbine rear bearing and toreplace it with a front bearing, supported from the outer cylinder by arms crossingthe chamber through the secondary air flow betvveen the flame tubes. Our turbo-jet unit is regulated byr.p.m. The Societe Bonzavia undertook the design of the regulator, which isbased on that of the Jumo. Fuel supply is carried out by high-pressure gear pumpswhich, together with all controls and auxiliary drive gear, were manufacturedby the Societe Air-equipment. NOTTINGHAM U.A.S. DINNER SPEAKING at the Third AnnualDinner of the Nottingham Uni- . versity Air Squadron, A.V-M. R. O.Jones, C.B., A.F.C., recently appointed S.A.S.O. of Reserve Command, assuredmembers.^md guests that the C.-in-C. was very pleased with the progress ofthe quadion. During the past year the 26 Ticer and 36 Cadet members of theSquadron flew 1,340 hours in term time, and 800 hours;<iuring the summer camp. -Replying to the toast "The Guests,"proposed by the Commanding Officer. S/L. E. Cornish, Mr. B. L. Hallward,Vice-Chancellor of the University, ex- pressed confidence that members of the N.U.A.S. would appreciate their oppor-tunities to maintain the cheerful dis- cipline necessary in the Service after thepost-war lapse. Cadet Pilot I. M. Gifford, speaking for the members, men-tioned, their gratification that the com- bined U.A.S. Camps were in being, andsuggested that a rally of all University Squadrons, even if only for a week-endor so, would be a good thing. S/L. R. Hewitt, A.F.C., who succeeds S/L.Cornish as CO., promised that he would do all in his power to maintain thereputation of the Squadron. S/L. Cornish is leaving to take up an appoint-ment at Air Ministry. B 34
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