US2780999A - Fuel booster pump - Google Patents

Description

Feb. 12, 1957 J. A. COMPTON ETAL 2,780,999

FUEL BOOSTER PUMP 2 Sheets-Sheet 1 Filed Dec. 12, 1951 fnuerzz o rts: James 0. Compi'oro 1 Feb. 12, 1957 J, A, COMPTON ErAL 2,780,999

FUEL BOOSTER PUMP 2 Sheets-Sheet 2 Filed Dec. 12, 1953 /a,oa0 20,000

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United States Patent FUEL BOOSTER PUMP James A. Compton, South Euclid, and Albert Paul, Cleveland, Ohio, assignors to Borg-Warner Corporation, Clucago, Ill., a corporation of Illinois Application December 12, 1951, Serial No. 261,296

4 Claims. (Cl. 103-113) This invention relates to a fuel booster pump, and more particularly to an arrangement for facilitating vapor elimination in a centrifugal type fuel booster pump.

Because the vapor pressure of the high octane fuel used in aircraft is relatively high, that is, on the order of 6 to 7 p. s. i. at 100 F., as an aircraft rises from ground level to higher altitudes where the surrounding air pressure becomes relatively low and possibly lower than the vapor pressure of the fuel, the fuel is subject to boiling and vaporization. This causes formation of bubbles in the fuel tank and at the pump inlet and it renders exceedingly difiicult pumping of the fuel from the tank to the aircraft motor. To some extent, this undesirable condition can be mitigated by pressurizing the fuel in the tank, but this is considered dangerous and is particularly undesirable in military aircraft.

Rather than pressurize the fuel in the tank, another approach has been used in some instances, and that is to effect, insofar as feasible, :1 separation of the liquid and occluded gas and vapor, and to provide means for returning to the tank the occluded gas and vapor. One method of accomplishing this is disclosed in Burns Patent No. 2,513,992, wherein a propeller type pump is employed in tandem with a centrifugal pump, the propeller agitating the fuel and causing return to the fuel tank of occluded air and vapor-thereby providing a supply of fuel to the centrifugal pump which is substantially free of occluded air and vapor bubbles and thus the centrifugal pump does not fail by cavitation and is able to develop the required pressure to the main fuel pump associated with the aircraft carburetor or fuel injection system. However, in this latter type of arrangement a considerable portion of the fuel is also returned to the fuel tank, and furthermore, because of the unavoidable low output of the propeller type pump, the fuel supplied to the centrifugal pump is still at or very near the boiling point so that the performance of the centrifugal pump is limited by the adverse inlet conditrons.

Another arrangement which has been used in meeting this problem has been to employ a centrifugal type pump in combination with a liquid ring type pump, such as illustrated in Jennings Patent 1,718,294 and Adams Patent 2,362,954, the liquid ring pump being employed for the purpose of removing occluded gas and vapor gathering at the inlet or eye of the centrifugal pump. Unless this vapor which tends to gather in a bubble at the inlet of the centrifugal pump is removed, the centrifugal pump is very likely to fail.

With systems such as the two just described, efliciency is relatively low since a considerable portion of the fuel is returned to the fuel tank and furthermore, because of the necessity of providing a second pumping arrangement, the system is naturally heavier and more expensive than a system wherein a centrifugal pump alone would be able to supply the final fuel pressure.

In accordance with the present invention, as applied in a fuel booster pump of the type employing a centrif- "ice ugal pump as the fuel pressure boosting mechanism, a sleeve is located in the inlet port formed in the housing of the centrifugal pump and projects axially inwardly toward the impeller to define with the adjacent wall of the pump inlet port an annular chambered area adjacent the lower extremities of the centrifugal pump impeller. During the operation of the centrifugal pump occluded air, gas and vapor entrained with the liquid fuel entering the pump inlet are forced into the annular chamber so provided. A venting passage communicated to the fuel tank or to a suitable gas handling pump, is connected to this annular chamber and permits escape of the gas, air and vapor which accumulate therein under moderate pressure.

Other objects and advantages of the present invention will be apparent from the following detailed description thereof taken in conjunction with the drawings wherein Fig. l is a vertical sectional view, partly in elevation, showing a combined centrifugal-liquid ring type booster pump having associated with the inlet thereof a sleeve in accordance with the present invention,

Fig. 2 is a transverse sectional view taken substantially along the line 2-2 of Fig. 1,

Fig. 3 is a graph indicating relative performance characteristics of a pump of the type illustrated in Fig. l with and without the inlet sleeve of this invention, and

Fig. 4 is a fragmentary view, similar to Fig. 1, illustrating the incorporation of the inlet sleeve of this invention in a simple, centrifugal booster pump.

Referring now to Fig. 1, a combined centrifugalliquid ring type booster pump is there illustrated comprising generally a motor 5 for driving a shaft 6 to which is ailixed a liquid ring impeller 7 and a centrifugal impeller 8, the whole being enclosed within a housing 9 and located, in the embodiment illustrated, within a tank it A suitable mounting plate 11 is -provided for securing the housing 9 in position in the tank. The motor 5 ordinarily is an electric motor and is controlled remotely, as is well known in the art. Fluid entering this bootser pump from the tank passes through a screen 12 mounted about the open lower portion of the housing of the pump and moves at first radially inwardly and then upwardly through the inlet port opening 13 of the centrifugal portion of the pump, entering the lower portion of the volute chamber 14, forming the pumping chamber of the centrifugal portion of the pump. Fluid under pressure is discharged through volute passage 15 which is connected by a suitable conduit (not illustrated) to the engine or other apparatus with which this booster pump may be associated in use.

Since the occluded air and vapor entering the centrifugal pump with the fuel tends to collect at the eye, that is, the center of the inlet of the centrifugal pump, it is sometimes the practice, as pointed out hereinbefore, to provide a liquid ring impeller type pump, such as the pump 7, for the purpose of evacuating the entrained vapor and gas. Communication is afforded between the liquid ring pump and the eye of the centrifugal impeller 8 by a suitable passage 16 provided in the pump housing, connected to chamber 17 enclosing the liquid ring impeller 7. In prior art arrangements this passage 16 has been connected directly to the inlet area of the impeller 8.

However, it has been found in accordance with the present invention that elimination of gas and vapor is more complete and at the same time segregation or separation of the gas and vapor from the liquid portion of fuel is more nearly perfect if there be provided at the inlet of the pump a sleeve, indicated at 20, whereby gas and vapor tending to move in a direction opposite to the direction of movement of the fuel (the gas and vapor being lighter) may be collected and segregated.

Referringmore in detail than-to Fig. 1', it will be seen of gaseous materials.

' that at the inlet of the ce gal puns there mounted portion 21 and a lower outwardly flanged portion 22 ereby the s eeve i ecurely ocate a the entrance to the centri u l pump chamber. Th lower inn r orn r. 22;; afth sleeve is rounded o pro ide desirable fl w n it ns h radi lly enter si e f the upper portion 21 of the sle 20 defines ith the djac n Wall of he n r tus Pump hamber an an ular cham er 23 of ri ngula r ssct on, int which chambe 23 as and vapor are f rced under Pres ure during the perat on o h ent ifugal phrnphus, rather; tha ha e th ga an ap r e n to the eye of th Pump an he aga Pa ial y ith he fue n isuid stat nt ring he pump, t e a and apor are tram d the ann lar hamb r and PYIi1 i from ret rning to he inlet of the centrifugal pump. It will be apparent that in the sen of sl e .0 ir andaas ent ain d with he fu l o ld nd no on y to gathe a in at the inle of h ntr fuga P mp and part thereof be retrieved by h liquid r n mp 7 u @1 9 se ne ould be mix d a a with t e f er e c ntrifugal Pui-npehd h c rri d along with the liquid portion of the fuel discharged through the velute passa e 5 To the ex e t tha this tendency to em n an be m n mized, h etfieiehsy of the pump is directly increased. Thus by preventing re-entrance of the segregated gas and'vapor by means of the sleeve 2%, a m r mpr e h it'ih ef iciency provided.

The location of trapping groove or recess 23 is importent n e it m be lo ated so hat the a vapor and air separated from the liquid 'pgrtion of the fucl by the centrifugal pumping action will tend to gather therein. It has been determined that the trapping recess 23 should be located as nearly as possible at the narrowest diam ter f the centrifugal pumping Chamber, that is, in practice, immediately adjacent the eye of the impeller, The depth of chamber 23, in general, is best determined by actual test and experimentation. However, it will be evident that the tubular portion 21 must extend a substantial distance beyond the inner edge of the inlet port sp as to define an effective trapping area. It must, on the other hand, not extend so far as to interfere with thedischarge of liquid from the centrifugal pump. In the embodiment illustrated in Fig. l, the lower portion of the impeller S is actually centrally recessed as indicated at 81; to rcceive the pp rm t Po ti n o t e sl e in ot er WQIQS, h r m y h a s i h er p of th s ee e and of the impeller.

In h em dime il ust ted in Figi apo and gas in rapp c s .23 re coll ed n a drain P ssa e 24, formed he l er pert n o he h usin and 5 9mmunicating with the lower side of the recess 23, and are i hd a rom th pa s ge by e q id n pump,

which, as is well known, is well adapted to the pumping Passage 24 communicates at its left, upper end with passage 16 leading to the inlet of the liquid ring impeller. The liquid ring pump discharges directly into the tank 10.

It will be noted that a narrow cross-section, drain passage is formed in the housing on the opposite side of the inlet from the passage leading to the liquid ring pump and communicates with the lower side of chamber 23. This small passage is provided to drain liquid, particularly water, which may gather in the chamber 23 and under freezing conditions prevent operation of the centrifugal pump after a period of nonoperation, and is required because of the incorporation of the sleeve 20 in the nle of the Pump, since t u the s ee e, iquid ac umulating at the inlet would run back in the tank. Passage 25 i p f a y mad qu t smal n c ess seet-i n to avoid interfer nce With the opera ion o t e pump- Referring now to the graph presented in Fig. 3, the dotted line curve A indicates the prcssureoutpnt or performance of a pump such as that illustrated-in Fig. 1

a esee ithout the idet slee e of this in ention.- reih curv A it will be apparent that the pump begins to fail at approximately 15,000 ft. and failure is substantially complete at approximately 17,500 ft. In most instances such failure is due to the accumulation of air, gas and vapor at the inlet of the centrifugal pump more rapidly than it can effectively be removed by the scavenging liquid ring pump. It will be noted that curve A has been shown as commencing again and the pressure output rising to the approximate value attained prior to failure. This recovery phenomenon is due to the fact that if the primary pump with which the booster pump is associated continues to e driven t en this pump may pump the ai and ap accumulating at the inlet 9f the centrifugal pump through the fuel line and in this manner clear the'centrifugal pump. Ultimately, the liquid ring pump might be able to accomplish this also. This does not necessarily occur but does occur sometimes. However, even under ideal conditions ending to ma e f r ah recov pe o m n the e will be a substantial period of time during which no fuel is actually pumped. If this period is of suiiicient duration, then where such a boosterpump is employed with a jet engine, it will be apparent that a flame out, that is, extinction of thejet flame, may occur with resultant total failure of the engine. 'In any event, such intermittent operation is extremely dangerous and particularly so since once the necessary conditions are present it will occur not once bu pea ed The continuous curved line B represents the performance of a fuel pump of the type shown in Fig. 1 provided with the inlet sleeve 20. From curve B it will be evident that there is no failure and that the pressure is continuous. Fluctuations represented in curve B are actual and not theoretical, being due to flight conditions including change in the pressure against the fuel in the tank by the air as the aircraft goes to higher altitudes and changes in the temperature of the fuel being pumped due to the 7. It has been determined that due to the pressure developed by the centrifugal pump in the centrifugal pumping chamber, which pressure is exerted to some extent against the air and gas trapped in the annular chamber 23, under many operating conditions'this pressure is of itself .eliective to cause return to the tank of air and gas trapped in chamber 23 without the necessity of providing'the gas evacuating pump shown in Fig. 1. This embodiment, of course, has a real advantage over the embodiment shown in Fig. 1 in that the pump is both lighter and cheaper.

In the embodiment illustrated in Fig. 4, therefore, instead of providing the passage 16 through the housing connecting the drainage passage 24 with the liquid ring impeller, a port 26 is formed in the housing and the drainage passage 24 is connected thereto, the port 26 opening into the tank 19 and permitting direct return Since during the operation or of trapped air and gas. the booster pump, the fuel in the tank is under suction whereas the air, vapor and gas collected in the recess 23 is under some pressure above the inlet pressure value, it will be apparent that there is no danger of fuel being sucked into the pump through the port 26, but rather that there will be a return flow from the pump trapping area 23 to the tank.

An additional advantage obtained through the use of the sleeve 20 is that the inlet condition to the centrifugal impeller is materially improved. In the absenceof the sleeve the centrifugal impeller tips agitate the fuelas it enters this pump and this produces turbulence which in turn reduces the overall pumping efliciency of the centrifugal pump.

Where herein the various parts of this invention have been referred to as being located in a right or a left position or in an upper or lower position, it will be understood that this is done solely for the purpose of facilitating description and that such references relate only to the relative positions of the parts as shown in the accompanying drawings.

While but two embodiments of this invention have been shown and described it will be understood that many changes and modifications may be made therein without departing from the scope of the present invention.

What is claimed is:

1. A combined fuel booster and vapor eliminating pump for pumping volatile fuels, including a pump casing having a centrifugal pumping chamber formed therein and an inlet and an outlet port connected to said chamber, a centrifugal impeller rotatably mounted in said chamber and having blades conforming to the contour of said chamber, an elongated sleeve mounted in said inlet port and providing at its inner surface an inlet throat, a portion of said sleeve extending into said chamber in overlapping relation with said impeller to prevent the return of vapor to the center of said impeller, the outer wall of said portion of said sleeve defining with the adjacent inner Wall of said casing a vapor trapping recess, a portion of said blades extending into said trapping recess to provide communication between said recess and the remainder of said blades, and passage defining means for permitting vapor trapped in said recess to escape therefrom, said trapping recess being located radially inwardly of the maximum diameter of said chamber.

2. A combined fuel booster and vapor eliminating pump for pumping volatile fuels, including a pump casing having a centrifugal pumping chamber formed therein and an inlet and an outlet port connected to said chamber, a centrifugal impeller rotatably mounted in said chamber and having blades conforming to the contour of said chamber, an elongated sleeve mounted in said inlet port and providing at its inner surface an inlet throat, a portion of said sleeve extending into said chamber in overlapping relation with said impeller to prevent the return of vapor to the center of said impeller, the outer wall of said portion of said sleeve defining with the adjacent inner wall of said casing a vapor trapping recess, a pottion of said blades extending into said trapping recess to provide communication between said recess and the remainder of said blades, and passage defining means for permitting vapor trapped in said recess to escape thereform, said trapping recess being located radially inwardly of the widest portion of said chamber.

3. A combined fuel booster and vapor elminating pump for pumping volatile fuels, including a pump casing having a centrifugal pumping chamber formed therein and an inlet and an outlet port connected to said chamber, a centrifugal impeller rotatably mounted in said chamber and having blades conforming to the contour of said chamber, an elongated sleeve mounted in said inlet port and providing at its inner surface an inlet throat, a portion of said sleeve extending into said chamber, the outer Wall of said portion of said sleeve defining with the adjacent inner wall of said casing a vapor trapping recess, a portion of said blades extending into said trapping recess to provide communication between said recess and the remainder of said blades, and passage defining means for permitting vapor trapped in said recess to escape therefron and a drain passage connected to said recess for preventing accumulation of liquid therein.

4. in a fuel booster pump including a housing having a pumping chamber formed therein and an inlet and an outlet port communicating with said chamber, a centrifugal impeller rotatably disposed in said chamber for pumping liquid from said inlet port to said outlet port and having blades conforming to the contour of said chamber, an inner sleeve located at said inlet port and defining within said housing a trapping chamber, a portion of said blades extending into said trapping chamber for providing opening communication between the chamer and the remainder of said blades, and a vent passage defining means connected to said trapping chamber.

References Cited in the file of this patent UNITED STATES PATENTS 1,139,042 Lehne et al May 11, 1915 2,306,300 Curtis Dec. 22, 1942 2,581,828 Adams Jan. 8, 1952 FOREIGN PATENTS 597,751 Great Britain Feb. 3, 1946 630,932 Germany May 14, 1936 695,713 Germany Aug. 31, 1940

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