US2373037A - Carbon dioxide discharge system - Google Patents

Description

April 3, 1945. c. H. LINDSAY CARBON DIXIDE DISCHARGE SYSTEM Filed July 16, 1942 Patented Api.3, 1945 i CARBON DlOXlDE DISCHARGE SYSTEM Charles H. Lindsay, Elmira, N. TY., assignor to American-La France-Foamite Corporation, Elmira, N. Y., a corporation of New York y Application July 16, 1942, Serial No. 451,129

8 Claims. (Cl. 62-1) The invention relates to aircraft fuel systems and more particularly to'fsystems for delivering carbon dioxide gas into aircraft fuel tanks for the purpose of avoiding development of ignitible vapors in the space above the liquid fuel therein. Ordinary carbon dioxide discharging systems applied to this purpose have the objection that they do not function reliably because they store' the dioxide in the highly compressed liquid form, and,

when discharging through the fine orifice necessary to give the required slow rate are subject to stoppage from the freezing of any water with which the dioxide may be contaminated or which may find its way into the system. It is dlicult to obtain carbon dioxide entirely free from moisture, also to keep moisture from condensing within the tubing of the system, and even less than 1% can defeat a proper discharge for the purpose indicated, by clogging the fine nozzle orifice with Water ice. This may occur either from ice as fine particles frozen while suspended in the flowing dioxide, or as vapor, or as an ice film freezing on the inside of, and thereby closing the nozzle tip. The freezing temperature occurs from the rapid expansion of the dioxide as its pressure is relieved 'and as it changes from liquid to vapor form. lThe temperature drop is most pronounced at the nozzle tip, but water-freezing temperature can arise at any point along the line from the tip back to the storage flask during the discharge. It is of great importance that the discharge when started shall be complete and uninterrupted throughout the required period. These systems are put in use just before engaging in combat and their failure might mean disaster.

This invention is a liquid dioxide discharge system rendered free of all danger of ice-clogging. by virtue of a special construction and organization of the discharge passage which forestalls the movement oflwater, whether, in vapor, liquid, or

solid form, so far through the discharge lineas to reach the cold nozzle tip. As above indicated, the water may be present in liquid or vapor form, and it may also be in solution in the liquid dioxide. This latter fact, as well as theefact that the specic gravities of water and liquid dioxide.

are normally not very dierent, may account for the failure ofthe ordinary precautions, such as short dip-tubes, to prevent discharge ofthe way ter, in addition to which note must be taken of the ebullient condition of the liquid dioxide which begins on the instant of any release of pressure, as on discharge, so that if the water could be assumed to have collected as a pool in the bottom of the 'iiask the internal ebullient commotion would of course tend to scatter it throughout the mass of the dioxide, thus encouraging its entry into the discharge line. Proceeding on the theory that the Water and liquid dioxide are not susceptible of sharp separation for the reason mentioned, the discharge passage of this invention includes the combination of two different types of water-restraining agencies, one involv'- lng av labyrinthic entrance to the discharge line and the other a refrigerated eliminator at the other end, so that moisture in any of its forms is precluded from reaching the tip. This com@ blnation has been found consistently safe in operation and has been accepted as such, giving reliable discharges even in cases where water has been purposely added to the dioxide for test pur- -poses in amounts as high as 1.5% by weight and which of course is far greater than would be experienced in practice.

AThe accompanying drawing shows the preferred form of the new discharge passage, Fig. 1 being a diagrammatic section of the system, Fig. 2 an enlarged section of the labyrinthic receiving end of the passage, Fig. 3 an axial section of the 1,921,411, which is Well known to those skilled in .Y

and also to avoid excessive pressure within the nozzle and Fig. 4 a modified form of the waterdrainage provision.

The"liquid dioxide container or flask and its operating head l will be recognized as conven tional and will be understood to confine the liquid under a pressure in the neighborhood of 850 lbs. at normal temperatures. An example of such operating heads will be found in Patent No.

this art. On opening the operating head, as by perforating the sealing disc therein as customary, liquid dioxide ows upwardly through the dip tube structure 2 and thence through the piping v3 to the nozzle 4 in the fuel tank 5 to be protected. It will be understood that the discharge passage starts at the foot or entrance to the dip tube structure and ends at the nozzle orifice,

which is of smaller size than customary in dioxide systems, being in he order of from .025 inch to .040 inch diameter. Such ne holes are required in order to prolong the discharge period gardless of variation in the lengths of different flasks with which it may be used, thereby insuring a maximum liquid evacuation of the flask when discharged, and at the `same time steadying the structure against vibration,

The lower telescopic section 6 contains or constitutes the labyrinthic receiving entrance above referred to. It comprises an inner inserted cylindrical member or tube 8 appropriately mounted therein to form therewith an annular chamber or passage 9, which is shallow in proportion to its circumference and width. The entrance thereto is at its lowest point, provided by a ring of radial holes Ill andthe exit therefrom is by radial outlet holes II at its top leading into the interior of the inserted member 8. Liquid dioxide enters the lower holes by horizontal flow in the flask proper and then flows first upwardly through this shallow passage, thence inwardly through the radial holes II and thence upwardly again into the upper section 2 and onwardly through the piping 3 toward the nozzle. The cross sections of the annular chamber 9 and of its entrance and exit holes are substantially equal to the cross section of the tube 2, or at any rate equal to that of the perforation made in the sealing disc so that the flow occurs without any particular restriction or choking effect at this point. The construction constitutes a water-restraining means, functioning apparently by the impingement of the liquid on the surfaces of the shallow passage, which holds thewater or some of it back, by causing it to adhere to such surfaces. After the discharge is over the water so retained can be found, usually then frozen,. in the labyrinthic passage.

From thiswaterjrestraining means the dioxide Y good conductor of heat and preferably in tubular form. One end of` this screen is attached (at I3) around the interior neck of the nozzle tip I4 and preferably by' soldering it thereto so as to establish a good thermal connection therewith. The tubular screen is of extended length, many times its own diameter, and being closed at its freev end all of the dioxide must pass through it in order to reach the nozzle.v

At the time of discharge the nozzle tip instant-l ly acquires a sub-zero temperature as the effect of the abrupt expansion through its orice, and the soldered connection transmits this low temperature to the screen so that water. even in so ne a state as to be'regarded as dissolved in the dioxide, encountering this cold metal mesh is promptly frozen thereon and therefore does not reach thetip. At the same time such particles of water or water vapor as may have become frozen in the piping before reaching the screen are also .caught by it and thereby kept from plugging thetip. The screen thus lserves as amoisture eliminator both by its refrigerating action on dissolved or liquid water and by itsl mechanical screening action. In the latter respect of continuoudischarge during the effective discharge period and notwithstanding the fine size of the discharge outlet with which these systems must be provided.

I have found that the refrigerated screen tends to collect less frost when the dioxide entranceinto the dip tube or into a shallow chamber therein, such'as the chamber 9. is by horizontal flow as through the radial holes I0, rather than by way of a dip tube that is open-ended at its foot, indicating that such direction of entering is a factor in the result, and also that it is still further reduced .by locating a flange Il immediately below such radial holes, and I accordingly prefer this construction of the receiving entrance.

Since it is obviously desirable that no water should remain over in the ask when recharged with dioxide, provision for the` removal of any such water is provided by forming the inner or impingement member 8 of the dip tube with a tubular extension I6 closed at its end and constituting the very 'foot of the dip tube, pressed against the ask bottom by the telescope spring as above pointed out. This extension is in line with the axis of the dip-tube and provided with a lateral port normally closed by a ball valve I1 and spring I8. By inserting a proper suction tube through the flask head and pushing it into this extension, the ball I1 can be unseated, letting any water in the flask bottom iiow into the extension, so that it can be sucked up by the tube, thus removing any residuum of water in the flask before recharging it with dioxide. This is much easier than unscrewing the discharge head to drain out water.

An alternate method of water-drainage, as indicated by Fig. 4, may in some cases represent the preferred form, as for instance where the dip-tube is curved or otherwise obstructed against the use of a suction tube. Insuch cases this same water drainage valve can be located at or in the head itself, as indicated at I9 inthis figure. When such valve is pressed open by a suitable tool introduced through the opened head, the

flask being inverted, any water can be drained 'closedat both its ends and provided with lateral hpies near its lower end to receive dioxide and lateralvholes near its upper end through which dioxide passes in its course toward ysaid nozzle, the cross area of said shallow chamber and the aggregate areas of said holes being not substantially less than 'that' of the discharge passage elsewhere.

2. A carbon dioxide discharge system comprising a flask of liquid dioxide having a discharge passage comprising a dip-tube within the flask connected to a discharge nozzle through which such liquid expands to vapor. phase and means for retarding the passage of water in the dioxide to said nozzle comprising said dip-tube closed at its lower end, aradially projecting flange on said closed end and lateral dioxide entrance holes leading into such tube just above said flange.

' 3. A carbon dioxide system comprising a flask of liquid dioxide having a discharge passage inV cluding. an interior tubularv conduit and means for y l 9,873,087 removing any water retained in the yflask comprising a valve port in said conduit, a valve normally closing such port, said valve being operable mentl introduced through said dip-tube and` adapted to allow water'in the flask to enter said dip-tube below the holes therein.

5. A carbon dioxide system comprising a ask oi liquid dioxide having a discharge head iormed with a tubular part projecting into the ask, a port in such part and a valve for said port located to be openable by an instrument inserted through the discharge head, whereby water collecting in said flask can be drained out through said head.

6. A carbon dioxide system for slow discharge into a lfuel tank comprising a ask of liqueed carbon dioxide having a discharge passage comprising a tube within the flask and piping connecting such tube to a nozzle within said tank, said tube having its only entrance organized in the form of labyrinthically related holes and located in the lower part of the ask to cause said passage to conduct only liquid dioxide during the effective part of the discharge period, such entrance holes being of such area as to offer. no greater resistance to iiow than any other part of such discharge passage and said nozzle having a i'lne orifice suited for discharging into a fuel I l l l 7. carbon dioxide discharge system f/or slow discharge into a fuel tan comprising a nozzle inA said tank, a flask of liquid dioxide having a discharge passage including a. tube within the flask organized to receive only liquid therefrom during the effective part of the discharge period and piping connecting such tube to the nozzle in the tank having a restricted oriice through which the liquid dioxideexpands to vapor phase, said orifice constituting the point of maximum restriction to the outflowof the liquid dioxide and said passage including a water-restraining means associated with the' foot of said interior tube in the flask and a second kwater-restraining means constituting part of said nozzle capable of \re taining water vaporv closely associated with said orifice in the'nozzle, and means at the head of the flask normally coniining the liquid dioxide therein adapted 'to be opened to permit immediate unrestricted flow through said discharge passage.

8. A carbon dioxide system for slow discharge t into a fuel tank comprising a'nozzle in said tank,

a ask of liquefied carbon dioxide having a dl's.

charge passage comprising a tube within the iiask and piping connecting such tube to a nozzle within said tank, said tube being closed-ended and having its only entrance organized in the form of holes in the side wall of said tube located in the lower part of the flask to cause said passage to receive only liquid from the ask during the ef fective part of the discharge period, such entrance holes being of such area as to oer no greater resistance to flow than' any other part of `such discharge passage and said nozzle having a fine oriiicesulted for slowly discharging into.

a fuel tank and containing a fine screen partaking of the subzero temperature at said 4orifice and intercepting the flow thereto, said screen having suiiicient area to freeze and retain thereon any water encountering it without itself becoming a stoppage to flow.

:CHS H. LINDSAY.

Images