US2300332A - Fuel feed device for aircraft - Google Patents

Description

Oct. 27, 1942.

R. AVIGDOR FUEL FEED DEVICE FOR AIRCRAFT Original Filed Feb. 13, 1939 Patented Oct. 27, 1942 UNITED FUEL-FEED DEVICE FOR AIRCRAFT Rifat Avigdor, Toronto, Ontario, Canada Original application February 13, 1939, Serial No.

256,157.- Divided and this application April 28, 1941, Serial No. 390,817. In Germany September 2, 1938 9 Claims.

This application is a division of Patent No. 2,263,864, granted Nov. 25, 1941, entitled Fuel feed device for aircraft.

The invention relates to an arrangement in fuel feeding devices for aircraft. The liquid fuel required for the operation of the internal combustion engine of an aeroplane is fed to the engine by means of a pump from one or more tanks arranged at suitable places in the aeroplane. This pump is preferably arranged as a so-called submersible pump set within the fuel tank or tanks. The pump is driven by an electro-motor, which in a suitable way is mounted in the casing of the pump. The arrangement is such that the pump is located in close proximity to the tank bottom and is suspended from the upper cover plate of the tank.

The tank may have thick walls, which, if necessary, are either covered by insulating material or consist of non metallic substances.

Now it has occurred in practice that tanks of this type behave as heat-accumulators so that the fuel within the tank is heated and accumulates the heat absorbed for a considerable time. The heating is. during the summer months, a-consequence of the sun rays and the outside temperature. Now as soon as an aeroplane with a fuel heated in this way ascends to considerable height the fuel in the tank will begin to evaporate and gasify due to the decreasing air pressure. The ef feet thereof is that the pump can no longer satisfactorily feed the fuel to the engine since generally a blade pump is used, the feeding action of which will stop as soon as trapped gases or vapors of the fuel occur in the feed path of the pump. A cooling of the fuel within the tank is impossible by reason of the insulating effect of the walls, in particular since the ascending of an aeroplane to considerable height takes place in a short time. The fuel supply is therefore uncertain and the case may occur that the supply is entirely interrupted.

When the fuel within the tank is heated gases and vapors are trapped, in particular closely above the bottom of the tank. Now, since the inlet of the feed pump is located at this place within the tank it may occur that the fuel supply is already stopped in the case of a small increase of the temperature of the fuel. Moreover, just at the inlet zone of the pump a somewhat reduced pressure is created by the suction of the pump rotor as compared with the pressure in the surrounding mass of liquid, whereby the evaporation or gasification of the fuel will occur still earlier or more intensively.

These disadvantagesare removed, according to the invention, by effecting a cooling of the fuel by circulation from the tank through an outside cooler and back to the tank. This circulation of the fuel may according to the invention, be' produced by means of a submersible pump in the tank. Preferably the return flow of the fuel from the cooler is to enter at or in the vicinity, of the inlet of the pump feeding the fuel to the motor.

Instead of a submersible pump maintaining the circulation for the cooling of the fuel, according to the invention use may also be made of the pump feeding the fuel to the engine. In this case, part of the fuel delivered by the engine feed pump is branched off and passed through a cooler, located outside the tank. The, return flow of the fuel preferably enters again at or in the vicinityof the inlet of the feed pump supplying the motor. I

The cooler is arranged at a convenient place on the aeroplane preferably so as to be subjected to the air current. A cooler of this nature need have but'relatively small dimensions since the outside temperature at considerable height is'very low and moreover the strong air current caused by the flight produces a vigorous cooling.

Since for devices of the type described above pumps are used which always have a feeding capacity which is greater than the fuel consumption of the engine; the branching off of part of the fuel for the circulation through a cooler for the cooling of the fuel contents of the tank may be carried out without taking any further steps.

The fuel returning from. the cooler is introduced into the inlet of, thefeed-pump at a certain pressure or at a certain speed so that the pump will have to produce less power than if the fuel were flowing to the pump only at the pressure head of the fluid column in the tank. The energy used for the circulation of the fuel to cool the fuel is therefore partially compensated by the smaller amount of energy to be produced by the pump. The cooling device'as such therefore consumes relatively little power.

It is especially advantageous to construct in accordance with the invention the outlet end of the return conduit so as to form an injector for to effectively cool in a short time the contents of a fuel tank by circulation; so that in the hot test season and under very strongradiation of the sun the temperature of the fuel is kept so low that no evaporation or gasiflcation can occur.

The invention is illustrated in the drawing schematically and by way of example.

Figure 1 is an elevation of an embodiment of the device according to the invention.

Figure 2 is an'elevation, partly sectional, of the lower portionof the feed-pump, and

Figure 3 is a view similar to Figure 2 illustrating a modification.

i denotes the tank of an aeroplane in which the submersible pump 2 is suspended. The fuel in the tank flows to the pump through the strainer 3 constituting the lower end of the pump. The fuel is fed throughthe pipe conduit 4 to the internal combustion engine in the direction of the arrow 5. g

In the embodiment shown in Figure 1 another pump 6 is arranged in the tank I to which pump the fuel flows-through a strainer I mounted on the pump 6. The pump 8 feeds the fuel through a pipe conduit 8 into a cooler S. .The cooler is mounted on the aeroplane in such a manner that it is subjected to'the air current or is exposed in such a manner that the fuel is effectively cooled.

' flows at a certain speed or at a certain pressure outlet end ii ofsaid conduitis located within a tapering hollow member I! and together therewith forms' an injector. By the fuel leaving. the 4 outlet I [in thedirection of the arrow It the fuel surrounding the injector isdrawn and carried along in the direction of the arrows I9. At the same time the fuel carried along by the action of the-injector is in this way cooled, while the pressure head of the return conduit at the 10 same time'promotes the feed. Now, the fuel to the rotor I! of the feed pump, so that the advantages referred to above are obtained,

opens at H into the inlet strainer 3 of the feedpump 2 or into the vicinity thereof.

The operationof this embodiment is as followsz The pump 6 feeds fuel continuously through the conduit 8 into the cooler 9. In the cooler the warm fuel coming from the tank is cooled and flows in this cooled condition through the conduitv i0 back to the tank. Part of the fuel leaving the outlet endll of 'the conduit III is mixed with the warm fuel in the tank I and already thereby reduces gradually the temperature of the fuel. A further portion of the fuel leaving the outlet end II flows directly into the inlet strainer 3 and is supplied to the engine through the conduit 4 by the main feed pump 2.

After a short time the total amount of fuel contained in the tank I has passed through the cooler 9 whereby a rapid cooling of the fuel obtained. so that no evaporation or gasiiication due to the heat accumulating walls of the tank can occur.

Now in order to utilize the pressure head of I the circulating fuel resulting from the operation of the pump and the position of the cooler 9, the outlet end of'the return conduit of the fuel is formed .as an injector as shown in the embodiment according to Figure 2. The casing of the pump, through which the fuel is fed to the engine, is again denoted by 21.

the conduit 4 to the engine. Similarly as in the embodiment according to Figure 1 the conduit it of the ,retumflow of the cooler s enters underneath the inlet of the feed pump. The conduit l0 is provided with a special heat insulating layer I 6, so that the fuel is supplied to the feed. pump at the lowest possible. temperature. The 7 motor feed P mp wl h m fil from said The injector device is shown in Figure 2 only schematically. In the existing pumps provided with an" inlet strainer, it is preferred to use a plurality of injectors arranged in a circle around the inlet strainer in the form of an injectorannulusm The cooler '9 is shown in thedrawing only schematically and acoil cooler or a cooler of any other typ may be used for the same purpose.

I claim} a Y 1. A fuel feed device for aircraft comprising a fuel tank,- a cooler located outside the tank, a

submersible motor feed pump-unit in the tank for withdrawing fuel from said tank, an additional submersible pump unit in the-tank for withdrawing fuel-from said tank the feed con duit of which is connected to the cooler and a return conduit from the cooler to the inlet of the motor feed pump unit to return the cooled fuel to said pump unit. 7

2 A fuel feed device for aircraft comprising a fuel tank, a cooler located outside the tank, a submersible motor feed pump unit in the tank for withdrawing fuel from said tank, an additional submersible pump unit in the tank for withdrawing fuel from said tank the feed conduit of whichis connected to the cooler and a return conduit from the cooler tothe vicinity of the inletof the motor feed pump unit to return the cooled fuel to said pump unit.

3. A fuel feed device for aircraft comprising a fuel tank, a cooler located outside the tank, a submersible motor feed pump unit in the tank for withdrawing fuel from said tank, an additional submersible pump unit in the tank for withdrawlngfuel from said tank the feed conduit of which is connected to the cooler and a a return conduit from the cooler to the inlet of the motor feed pump unit to return the cooled fuel to said pump unit, the outlet end of said return conduit beingfformed as an injector open ing into the, fuel surroimding said outlet end.

4. .A-fuel feeding device for aircraft comprisinga fuel tank, a cooler located outside said tank, an engine feed pump in said tank for withdrawing fuel from said tank, means independent ofsaid feed pump. for feedingfuel from said tank to said cooler and vmeans for returning the fuel -.at;fl= w cooled by said cooler. to said tank of the inlet ofsaid pump.-

5. A'fuel mam; device for "eaeeamsam nrst'named pump.

6; A fuel feed device for aircraft comprising a fuel tank, a cooler located outside said tank, a

tank, a second pump for withdrawing fuel from said tank having its discharge conduit connected to said cooler and a return conduit from said cooler to the inlet of said motor feed pump to feed the cooled fuel to said motor feed pump.

'7. A fuel feed device for aircraft comprising a fuel tank, a cooler located outside said tank, a motor feed pump for withdrawing fuel from said tank, a second pump for withdrawing fuel from said tank having its discharge conduit connected to said cooler and a return conduit from said cooler to the vicinity of the inlet of said motor feed pump to feed the cooled fuel to said motor feed pump.

8. A fuel feed device for aircraft comprising a fuel tank, a cooler located outside said tank, a motor feed pump for withdrawing fuel from said tank, a second pump for withdrawing fuel said tank having its feed conduit connected to said cooler and a return conduit from said cooler to the inlet of said motor feed pump to feed the cooled fuel to said motor feed pump, said return conduit terminating in annuiarly arranged injectors at the inlet of said fuel pump.

RIFAT AVIGDOR.

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