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Aviation History
1921
1921 - 0541.PDF
AUGUST II, 1921 fitted with oil-receptacles, cut off obliquely at the open ends The fuel installation (Fig. 28), which has been constructed rnnSf C?nCelVed af,ter ma*y y^rs of practical experienceconsists of a principal reservoir, a, with an auxiliary reservoir b, built beside it, a fuel-pump, c, worked by the engine a hand- vaive'/SrS a scaven§er> «> and7 super gCompreSs?c.n valve f in the pressure pipe of the pump ; from valve f, the feed-pipe equipped with a manometer, g, is conducted into the carburettor. The principal reservoir is filled with fuel from the auxiliary tank, and is likewise under pressure ofSnsT ft r T' T^tin CaS6Of damage by g^fire-or similar cause, it cannot discharge its contents too quickly If thecontents of the principal tank have run out, however a safe landing may be effected by means of the contents'of the ThTamTunfsuppL'd bv'rWnT5 ^ be'fed h/ ei£eT tank'than thaSSKn PTf 1S co,nsiderably greater than that required by the engine. The surplus passes through Sip 3d. Outer 71/ie Auxi/io/~y Air 7 CARBURCTOR Auxiliary Avx/'/ior 'Prthcipo/iVozze/. //he Dr/lli'ngs Outer Tube Scovenoer S/eve */"if. 33 Section of. i/mt Contro/ 34. Section C"JO. to 34- supercompression valve / into a receiver, from which it either flows back into the auxiliary tank or into the principal tank, according to the manner of its adjustment. This disposal of the fuel leaves each fuel pump free to act independently of the other, the functioning of the whole being thus assured even when the engine pump may be out of order. The fuel is therefore always supplied to the carburettor under constant super-compression, in which respect it has the advantage over the ordinary device with auxiliary tank, in which the fuel pressure at the carburettor varies considerably in accord- ance with the angle of the aeroplane and the building-in of the auxiliary tank. The fuel pump (Fig. 29) consists of an ordinary piston-pump with an aluminium case, a, bronze bearings, b, and slightly adjusted piston, c, to which the fuel flows over a combined sieve-scavenger and water separator, d, the bottom of which can be unscrewed, and an intake ventilator, e, borne down by its own weight. The pump is slowly driven by the control- wheels of the engine, by means of a transmission screw. In its original form, as used on the 220 h.p. aircraft engine, it was worked with glycerine as auxiliary fluid. Duration tests soon prove, however, that there is perfect safety in workingeven when the piston inducts the fuel directly, though the interior of the piston must, in such cases, be filled from time totime with viscous oil Every time it descends, the piston pump drives the sucked-in quantity of fuel-mixture over the ventilator /, which is similarly loaded by its own weight, into the so-called super-compression ventilator (see Fig. 30),which simultaneously compensates the pulsations of the fuel-pump, somewhat asan air tank. The cap-like body of the ventilator is inverted over the free end of the exhaust-pipe ; the caulked rim of theventilator being held down by a spring, the tension of which can be so regulated by means of the screw lid that the com-pression of the fuel at the carburetter amounts to about 0-2 to 0.25. Any surplus supplied by the fuel-pump over theamount required to maintain that pressure and supply the consumption in the carburettor flows down obliquely into thetank (see Fig. 28) surrounding the super-compression valve, which is conducted to the open air. Any marked variationin the fuel pressure is a sign that the air contained in the air- tank has escaped. When working empty, it is necessaryonly to open an air-tap in the intake piping for a time to enable the air-tank to be refilled with air. The carburettors (see Figs. 31 to 34) are welded togetherin pairs and covered with a water-jacket ; they adjoin the super-compression valve in the same direction as the fuelpiping. In the float chamber a, the fuel is taken at b and scavenged through a fine sieve, c, and kept at a constant heightin the usual manner. At this height, it also becomes station- ary in the principal nozzle d (see Fig. 34) of the carburettor,which is connected with the float tank by the calibrated boring e of the bottom screw. In its starting position, the throttlevalve / (see Fig. 33) releases only one auxiliary bore, g, of the case ; a finely bored auxiliary nozzle, h, directly supplied -with fuel from the carburettor penetrates into the bore g, and the strong aspiration thus engendered at the upper edgeof the auxiliary nozzle (which may easily be adjusted by chang- ing the position of the air valve) enables the fuel to be wellinducted and pulverised even when the engine is working slowly. As the pressure on the upper edge of the principalnozzle d augments, through the widening of the throttle opening and increasing engine speed, the fuel becomes so muchthe more highly aspirated and pulverised in proportion and auxiliary air enters through the aperture i between the pipesk and / (Fig. 34), penetrates to the principal nozzle through fine borings m and thereby promotes the pulverisation of thefuel and prevents the mixture from becoming too rich in fuel. The method of carburettor-construction above described is based on the French Claudel carburettor model, and has many recommendations. It is easy of access, and the nozzle can be easily adjusted and taken out from above ; its main air stream is perpendicular to the main nozzle, so that the fuel stream branches off at right angles and pulverises well. The fuel-supply which collects at the bottom of the principal nozzle when the engine works slowly, also makes it possible for the throttle to open to its full extent suddenly after a gliding flight until it is quite near the ground, without there being any risk of the engine's " jibbing " before the fuel has time to flow in through the bottom opening of the principal nozzle. Another advantage lies in the fact of there being no need for the usual auxiliary air apertures, controlled by the throttle-valve and limited by curves, as such apertures can never be quite accurately adjusted, and each separate carburettor must therefore be adapted to the engine for which it is intended. The double spark plugs attached to each cylinder for reasons of safety are independently charged by two dynamos (Robert Bosch Co., Ltd., Stuttgart) with 12 plates of 12 poles. The dynamos are driven obliquely from the rear end of the engine by means of ordinary spring coupling (see Fig. 3). They are symmetrically ranged and constructed for anti-clockwise rotation, and a very simple method is obtained for adjusting the sparking-point by means of the rods. The cooling water pump is installed at the end of the gear wheel intended for the auxiliary command at the back of the engine, that is, at a spot where the entire contents of the water-jacket and pipes can be discharged. The shaft of the pump is set in ball bearings at the upper end supported by a special block, while the lower end, terminating in a bronze bearing, supports a fixed wheel secured by a pin. The pump has an opening in the middle pipe, and two outlet pipes ; it conveys the cooling water on each side of the engine into a main pipe, and this again conveys the principal stream •• directly through the adjacent cylinder-heads, so that the valve-heads are most effectively cooled. A weaker auxiliary stream of cooling water penetrates the cyUnder-jacket from 541
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