US2804022A - Booster fuel pumps - Google Patents

Description

Aug. 27, 1957 H. E. ADAMS I 2,804,022

"BOOSTER FUEL PUMPS Filed March 29. 1955 2 Sheets-Sheet l I hil m' INVENTOR. Ham/d E Adams ATTORNEYS Aug. 27, 1957 H. E. ADAMS 2,804,022

\ BOOSTER FUEL PUMPS Filed March 29. 1955 2 {Sheets-Sheet 2 INVENTOR.

Harold fiAda/w ATTORNEYS United States Pate BOOSTER FUEL PUMPS Harold E. Adams, Norwalk, C0nn., assiguor to Nash Engineering Company, South Nor-walk, Conn., a corporation of Connecticut Application March 29, 1955, Serial No. 497,579

8 Claims. (Cl. 103-113) This invention relates to double suction impeller centrifugal pumps, and is in the nature of an improvement upon the pumping organization disclosed in my co-pending application for Letters Patent of the United States, Serial No. 270,614, filed February 8, 1952, for Fuel Booster Pumps.

In said application disclosure is made of a tank mounted fuel booster unit which comprises a double suction impeller centrifugal liquid pump and a priming vacuum pump of the liquid ring type. The centrifugal pump of that application includes separate, widely spaced fuel inlets in communication, respectively, with separate, but contiguous and merging pumping chambers at opposite sides of a partitioned double suction impeller.

Although the pumping chambers have separate suctions, they are arranged to deliver to a common outlet. Each chamber has a greater flow capacity than the common outlet, and each includes means for separating entrained gas and vapor from the liquid fuel. The vacuum pump is a two-lobed pump whose lobes are connected respectively to draw off air and vapor from the respective liquid pumping chambers of the centrifugal pump.

The pumping mechanism of said prior application has received a ready acceptance and is gaining in popular usage. It is of particular value because it will continue pumping when one of the suction inlets of the double suction impeller is uncovered, and this until thesecond suction inlet becomes uncovered also. The pump is especially valuable as an aircraft fuel pump because it takes care of the temporary shifting of fuel within the tank caused by unusual maneuvers such as diving, rolling, inversion or any conditions producing negative G acceleration.

When both the inlets of the pump referred to become uncovered, even briefly, however, the fuel in the .centrifugal pumping chambers is quickly exhausted to such an extent that the spinning liquid seal between them is broken, and the chambers are placed in free communication with one another.

The subsequent recovering of one of the inlets does not automatically lead to the reprinting of the pumping chamber served by that inlet. Since both chambers are exposed to free communication with the uncovered inlet, air can pass freely into both chambers, the liquid fuel cannot be sucked up into sealing position, and the entire lower half of the impeller must be flooded in order to seal off the impeller chambers so as to prevent the passage of air from one to another.

It is a primary object of the present invention tomaintain a segregating or sealing ring of spinning liquid between the two impeller pumpingchambers even after the 2,804,022 Patented Aug. 27, 1957 inlets of both chambers have been simultaneously exposed to the air.

It is a further object to enable a segregating or sealing ring of spinning liquid to be reestablished between the chambers when the seal has been broken, at a lower liquid supply level than has been possible heretofore.

To these ends, it is a feature of the invention that provision is made of a spring loaded valve, hereinafter referred to as a chamber segregating valve, which extends across the common outlet of the centrifugal pumping chambers and closes as soon as the discharge pressure of the centrifugal pump falls below a predetermined value. By this means a sufiicient quantity of liquid fuel is trapped and caused to act as a spinning liquid seal to prevent the passage of air from one of the pump chambers to the other. With this segregating or sealing ring maintained the mere resubmergence of one of the inlets closes off the pumping chamber served by it. The vacuum pump thereupon evacuates the air and vapor from the chamber thus closed off, causing the liquid to be sucked up into the chamber and to completely fill it. The pumping action of the chamber so filled is fully reestablished by that action.

Should the exposure of both inlets be maintained for a sufficient time to cause the sealing ring in the centrifugal pump and/or the pumping ring in the vacuum pump to become dissipated through evaporation or other cause, the chamber segregating valve will enable the seal to be reestablished as soon as the liquid rises far enough to reach the lower extremities of the impeller blades at the lower side of the impeller. The first liquid to reach the blades is caused to reestablish the sealing ring of the centrifugal pump and the pumping ring of the vacuum pump. Pumping through the single resubmerged inlet is thereupon reestablished as pointed out above.

Tank mounted pumps of this nature are used for two general purposes in an airplane, first, for discharging into a line directly connected to the suction of the main engine pump and, second, in transferring fuel from one tank into another tank or another airplane, such as in aerial refueling. Where the booster pump discharge line is directly connected to the suction of a main engine pump, the failure of the booster pump will result not only in an immediate loss of pressure, but also in a reduction in pressure below ambient pressure. This negative pressure is induced by the suction of the main engine pump, which endeavors to draw fuel whether or not the booster pump is operating effectively. In normal applications it is the custom to add a by-pass valve, which is a check valve, so disposed that the main engine pump can draw fuel into the fuel line through the by-pass valve, directly from the fuel tank. The presence of such a by-pass valve provides a possible alternate fuel supply path to the main engine pump when the booster ptunp fails to deliver fuel.

In the present organization, however, the by-pass valve is made to perform an additional function. By providing a substantially lighter spring-loading for the by-pass valve than for the priming valve, a limitation is put upon the negative pressure which can be developed in the feed line to the main fuel pump. In this way the development by the main fuel pump of a suction sufiicient to open the chamber segregating valve when the booster pump is not delivering fuel is guarded against and the maintenance of the segregating or sealing ring is assured.

When the present pump is used as a fuel transfer pump vails when only one pump inlet is submerged.

The pumping structure of Figures 1 and 2 is in principle the same as the pumping structure of Serial No. 270,614, save that a priming valve and a by-pass valve have been added. The mechanism shown constitutes a unit which is adapted to be mounted within an aircraft fuel tank. Casing members 10, 12, 14 and 16 jointly enclose a motor 18, a motor shaft 20, a vacuum pump rotor 22 and a centrifugal pump impeller 24, the rotor and impeller being fast on the shaft 20. A two-lobed housing member 26 is provided for the vacuum pump rotor 22.

The impeller 24 includes a partition 37 which divides the centrifugal pump into separate but contiguous and merging upper and lower pumping chambers 28 and 30, both of which chambers discharge to a common volute 32. The upper chamber 28 communicates with an intake member 34 whose mouth or inlet 34a is illustrated as being remote from the pump. The lower chamber 30 communicates with an intake member 36 whose mouth or inlet 36a is remote from the inlet 34a. The pump and inlet pipes do not necessarily have to be disposed as shown in the drawings and there is no intent to be limited by this type of installation. The pump can be mounted at an angle or horizontal and the inlets can be directed, as desired, to different parts of the tank. The centrifugal pump has all the physical characteristics and advantages of the pump of Serial No. 270,614. The impeller has separate blades at the upper and lower sides of the partition or center shroud 37. The pump parts are designed to separate entrained air and vapor from the liquid fuel. Air'and vapor separated by centrifugal action in the upper chamber 28 are delivered to an annular groove 38 and are thence drawn off through a passage 40 to a first lobe 42 of the liquid ring vacuum pump. Air and vapor separated by centrifugal action in the lower chamber 30 are delivered to an annular groove 44 and are thence drawn off through passages 46, 48 and 50 to a second lobe 42a of the liquid ring vacuum pump. Both lobes 42 and 42a of the vacuum pump discharge through a common discharge pipe 52 into the tank. The lobes of the vacuum pump serve not only as independent suction means for drawing off separated air and vapor from the respective chambers of the centrifugal pump, but also as independent primers for said chambers.

The housing member is formed with a port 54 through which the volute 32 discharges into a fitting 56 which forms a part of the fuel line leading to the main engine pump (not shown). An elbow 58 which forms a further section of said fuel line is connected to the fitting 56 by a cap screw 60, being clamped within a flange 64 and against a seat 66 by pressure exerted through tightening of the screw.

The fitting 56 is provided interiorly with a guiding and abutment member 68, which, as shown, is desirably integral with the body of the fitting 56. A chamber segregating valve 70 is shown in Figure 1 as bearing against a valve seat of the casing member 10 which surrounds the port 54. The valve 74) is equipped with a stem 72, which is guided in a bore 74 formed in the member 68. A rabbeted disc 76 surrounds the portion of the member 68 in which the bore 74 is formed, bears against a shoulder of the member 68, and serves as an abutment for one end of a compression coil spring 78. The spring 78 bears at its opposite end against the valve 71) to urge the valve yieldingly toward its seat.

A ported ring member 80 is secured in an opening of the fitting 56 and may serve as an alternative channel of communication between the tank and the interior of the fitting 56. A by-pass valve 82 normally bears against a seat provided on the ring member 80. The valve 82 has a stem 84 which is slidingly received in a bore 86 of the member 68. A compression coil spring 88, lodged in the bore 86, bears against the inner end of the stem 84 to thrust the valve 82 yieldingly outward toward its seat. The spring 88 is a weaker spring than the spring 78, the relationship being such that the valve 82 will always open before the valve 70 when a negative pressure occurs in the interior of fitting 56.

When the tank is full of liquid fuel, both inlet members 34 and 36 will be fully submerged and both sides of the impeller 24 will act simultaneously to pump fuel. If the mouth of the inlet member 34, which for illustration is here shown at higher elevation than the mouth of inlet 36, is uncovered, a condition like that illustrated in Figure 2 will then prevail. The liquid contained in the upper inlet member and in the upper chamber of the centrifugal pump will soon become exhausted, except that a sufficient resistance to fuel discharge will be developed and maintained in the volute 32, by pressure developed in the lower chamber of the centrifugal pump, to maintain an undischarged revolving ring 90 of liquid fuel in the upper chamber. Since this ring is constantly driven by the impeller it is maintained in the location and form shown by centrifugal action, and serves effectively to seal off communication of air or vapor between the upper and lower chambers of the centrifugal pump. In this situation it is only necessary for the mouth of the intake member 36 to be barely submerged in order for the lower half of the centrifugal pump to be maintained fully efiective. The lower intake member 36 and the lower chamber of the centrifugal pump start full of liquid, and as liquid is forced out through the volute 32 other liquid is drawn in through the mouth of the inlet member 36 to replace it. The operation as thus far described would occur with or without the chamber segregating valve 70 being present.

If the airplane should become inverted, or negative G conditions should develop, as in a very steep dive, with the tank full or nearly full, and that condition should continue until the mouth of the inlet member 36 has become uncovered, the reverse condition to that described above would prevail. The intake member 36 and the chamber 30 would become emptied except for a sealing ring 90, but what is normally the upper half of the impeller could continue to function unimpaired.

If it is desired to place a pump in a tank that normally may be only partially full and if under these circumstances such maneuvers as driving, tipping, inversion or other unusual attitudes be undertaken, it will frequently happen that the mouths of both inlet memberswill be temporarily uncovered, even though enough fuel be present to keep at least one inlet mouth covered under conditions of normal flight. Under these conditions there is temporarily a total failure of liquid fuel supply to the pump. As the liquid in the active chamber becomes depleted the mass of the spinning liquid is diminished, causing the centrifugal discharge pressure to be diminished. The pressure in the line to the main fuel pump and in the volute 32 also fall. Without the chamber segregating valve all the spinning liquid in the active chamber of the centrifugal pump would be discharged into the volute or would flow back into the tank, and the two chambers 30 and 32 would no longer be sealed off against the passage of air from one to another of them. As previously noted, when this condition has occurred in pumps which have no chamber segregating valve the resumption of pumping cannot be achieved until the liquid has risen, without the aid of suction, to substantially the level of the impeller partition.

With the chamber segregating valve present, however, the lowering of the pump discharge pressure in response escapee to depletion of the spinning body of liquid in the centrifugal pump permits the valve 70 to be closed by the spring 78 when there is still a sufiicient segregating or sealing ring 90 of revolving liquid in the centrifugal pump (as shown in Figure 1) to maintain the chambers 28 and 30 sealed oif from one another. With the seal thus maintained it is necessary only for the mouth of the inlet member 34 or 36 to be barely submerged, as illustrated in the case of the inlet 36 in Figure 2, in order for pumping through the submerged inlet mouth to be reestablished. As soon as the mouth of the inlet member 36, for example, is fully covered, the priming lobe 42a of the vacuum pump which acts through the passages 46, 48, 50 evacuates the air and gas from the inlet member 36 and the chamber 30 to suck the liquid fuel up into the field of action of the lower half of the impeller. All air and gas are quickly Withdrawn from the inlet member 36 and the chamber 3%, so that the pumping of air-free and gas-free liquid fuel through the chamber 3!). as illustrated in Figure 2, is quickly reestablished.

It will be observed that the valve 70 has an area considerably greater than the area of the port 54 (more than twice as great, as shown) and that the valve seats against an annular flange or boss 92 immediately adjacent to the opening 54. The spring 78 is proportioned to hold the valve 70 closed on the seat boss 92 against the low pressure exerted by the peripheral sealing ring 90. This pressure is relatively low compared to that generated by the full impeller when operating normally. As soon as the impeller is primed and filled with liquid, it generates the higher normal discharge pressure and easily lifts valve 70 off its seat 92. Immediately after the valve lifts from its seat, the full area of the valve 70 is exposed to the pump discharge pressure, which is held back because of the close clearance between the outer diameter of valve 70 and the smaller diameter at 93 of body 56. This relationship occurs immediately after the initial opening movement of valve 70.

It will be noted that this pressure, which is at this time considerably greater than the pressure required by the spring to hold valve 70 on the smaller area seat 92, is additionally exerted over the larger area of the valve disc 70 so that it further multiplies the force acting on the valve against the relatively weak spring 78.

As the result of this combination of forces, valve '70 pops open to a position opposite the larger diameter at 94 of the casing 56. From position 70a to position 7%, the casing gradually enlarges from 93 to 94 so as to increase the opening between the edges of the valve 70 and the casing to permit flow from the pump to pass through the larger area with a minimum of pressure drop. Actually, the pressure drop under the full open position of the valve and with full flow is no greater than the initial low pressure difference required to hold valve 70 closed against the smaller seat 92.

As has been noted, the by-pass valve is designed to open more readily than the chamber segregating valve under the pumping condition of the booster pump illustrated in Figure 1. Since the by-pass valve limits the suction which can be built up Within the fitting 56, the priming valve can never be opened until pumping by the booster pump is resumed.

Should the mouths of both intake members 34 and 36 become uncovered and remain uncovered for a sufiicient length of time to permit the liquid segregating and sealing ring 90 and the liquid pumping ring of the vacuum pump to be dissipated, the restoration of pumping would not occur in response merely to the resubmersion of the mouth of one of the inlet members. It would be reestablished however by submerging one of the inlet members just far enough to cause the liquid level to reach the lower tips of the impeller blades. A portion of the first liquid to reach contact with the impeller blades would be thrown outward to reestablish the segregating and sealing ring in the centrifugal pump, this result being achieved because the immediate discharge of the liquid into the main pump fuel line is prevented by the chamber segregating valve. Another portion of the first liquid reaching the impeller blades is driven by them into the vacuum pump to reestablish the pumping ring in the vacuum pump. With these two rings reestablished the priming of the chamber whose inlet is covered is quickly completed and the delivery of liquid fuel through that chamber is quickly resumed.

I have described what I believe to be the best embodiments of my invention. I do not wish, however, to be confined to the embodiments shown, but what I desire to cover by Letters Patent is set forth in the appended claims.

What is claimed is:

1. A booster fuel pump unit comprising, in combination, a double suction impeller centrifugal liquid pump, having two contiguous, merging pumping chambers in which. opposite halves of the impeller are respectively contained, intake members providing separate, widely spaced inlets to the respective chambers, and a common discharge member including a port adapted for communication with the inlet of a main fuel pump, vacuum pumping mechanism connected separately to the pumping chambers of the centrifugal pump and including means for removing air and vapor from each chamber independently of the other chamber, and a spring loaded chamber segregating valve constructed and arranged to cover and close the port of said discharge member when the fuel delivery pressure of the centrifugal pump falls below a predetermined value, said chamber segregating valve serving to retain a centrifugally maintained sealing or segregating ring of spinning liquid at the junction of the merging pumping chambers of the centrifugal liquid pump when the supply of liquid at the inlets of both chambers fails, thereby to prevent the transmission of air from one pumping chamber to the other. 2. A booster fuel pump unit comprising, in combination, a double suction impeller centrifugal liquid pump, having two contiguous, merging pumping chambers in which opposite halves of the impeller are respectively contained, intake members providing separate, widely spaced inlets to the pumping chambers at opposite sides of the impeller, and means providing a common discharge volute in communication with both chambers, said volute having a single outlet port, vacuum pumping mechanism connected separately to the two pumping chambers of the centrifugal pump and including means for removing air and vapor from each chamber independently of the other chamber, and a spring loaded chamber segregating valve constructed and arranged to cover and close the outlet port of said volute when the fuel delivery pressure of said centrifugal pump falls below a predetermined value, and to open said port automatically when the pumping of liquid fuel in volume is resumed, said chamber segregating valve serving to retain a centrifugally maintained sealing or segregating ring of spinning liquid at the junction of the merging chambers of the centrifugal liquid pump when the supply of liquid at the inlets of both chambers fails, thereby to prevent the transmission of air from one pumping chamber to the other.

3. A booster fuel pump unit comprising, in combination, a double suction impeller centrifugal liquid pump, having two contiguous, merging pumping chambers, a partitioned impeller having separate sets of blades in the respective chambers, intake members providing separate, widely spaced inlets to the respective chambers, and means providing a common discharge passage in communication with both chambers, said passage having a single outlet port, a two lobed vacuum pump of the liquid ring type having its respective lobes in communication with the respective centrifugal pumping chambers in the regions of the impeller blade tips remote from the partition, for removing air and vapor from each chamber independently of the other, and a spring loaded chamber segregating valve constructed and'arranged to cover and close the port of such discharge passage when the fuel delivery pressure of said centrifugal pump falls below a predetermined value in response to a failure of liquid fuel supply, and to open automatically when the pumping of liquid fuel in volume is resumed, said chamber segregating valve serving to retain a centrifugally maintained sealing or segregating ring of spinning liquid at the junction of the merging pumping chambers of the centrifugal liquid pump during such failure of liquid supply at both inlets, thereby to promote the independent priming of either chamber when liquid supply to its inlet is re-established.

4. A booster fuel pump unit comprising, in combination, a double suction impeller centrifugal liquid pump, having two contiguous, merging pumping chambers and a common discharge passage in communication with both chambers, which passage has a single outlet port, a partitioned impeller having separate sets of blades in the respective chambers designed to pump liquid but to separate entrained air and vapor from the liquid, each chamber having a flow capacity greater than that of the common discharge passage and having an air and vapor collection channel in the region of the impeller blade tips remote from the partition, 21 two lobed vacuum pump of the liquid ring type having its respective lobes in communication with the respective air and vapor collecting channels in the centrifugal pump chambers, and a spring loaded chamber segregating valve constructed and arranged to cover and close the single outlet port of said discharge passage when the fuel delivery pressure of said centrifugal pump falls below a predetermined value in response to a simultaneous failure of liquid fuel supply at both inlets, and to open automatically when the pumping of liquid fuel through either chamber is resumed, said chamber segregating valve serving to retain a centrifugally maintained sealing or segregating ring of spinning liquid at the junction of the merging pumping chambers of the centrifugal liquid pump during such failure of liquid supply at both inlets, thereby to promote the independent priming of either chamber when liquid supply to its inlet is re-established.

5. A booster fuel pump unit comprising, in combination, a double suction impeller centrifugal liquid pump, having two contiguous, merging pumping chambers and a common discharge passage in communication with both chambers, which passage includes a single outlet port, a partitioned impeller having separate sets of blades in the respective chambers designed to pump liquid but to separate entrained air and vapor from the liquid, vacuum pumping mechanism including means for withdrawing air and vapor from the respective chambers independently of one another, a hollow fitting disposed to cover said single outlet port and adapted for communication with the inlet of a main engine pump, and a spring loaded chamber segregating valve in said fitting constructed and arranged to cover and close said port when the discharge pressure of said centrifugal pump falls below a predetermined value in response to a simultaneous failure of fuel supply at the inlets of both chambers, through the retaining of a centrifugally maintained sealing or segregating ring of spinning liquid at the junction of the merging pumping chambers of the centrifugal liquid pump during such failure of liquid supply at both inlets, thereby to promote the independent priming of either chamber when liquid supply to its inlet is re-established, and to reopen automatically when pumping is resumed through either chamber.

6. A booster fuel pump unit comprising, in combination, a double suction impeller centrifugal liquid pump, having two contiguous, merging pumping chambers and a common discharge passage in communication with both chambers, which passage includes a single outlet port, a partitioned impeller having separate sets of blades in the respective chambers designed to pump liquid but to separate entrained air and vapor from the liquid, vacuum pumping mechanism including means for withdrawing air and vapor from the respective chambers independently of one another, a hollow fitting disposed to cover said single outlet port and adapted for communication with the inlet of a main engine pump, a spring loaded chamber segregating valve in said fitting constructed and arranged to cover and close said port when the discharge pressure of said centrifugal pump falls below a predetermined value in response to a simultaneous failure of fuel supply at the inlets of both chamhers, a centrifugually maintained sealing or segregating ring of spinning liquid at the junction of the merging pumping chambers of the centrifugal liquid pump during such failure of liquid supply at both inlets, thereby to promote the independent priming of either chamber when liquid supply to its inlet is re-established and to reopen automatically when pumping is resumed through either chamber, and a spring loaded by-p-ass valve in said fitting for admitting fuel, air or vapor to the fitting independently of the centrifugal pump when the chamber segregating valve is closed, the bypass valve being more lightly loaded than the chamber segregating valve to prevent development in the fitting of a sufficient suction to pull the priming valve open when the delivery of liquid fuel by the centrifugal pump is interrupted.

7. A booster fuel pump unit comprising, in combination, a double suction impeller centrifugal liquid pump, having two contiguous, merging pumping chambers and a common discharge passage in communication with both chambers, which passage includes a single outlet port, a partitioned impeller having separate sets of blades in the respective chambers designed. to pump liquid but to separate entrained air and vapor from the liquid, vacuum pumping mechanism including means for Withdrawing air and vapor from the respective chambers independently of one another, a hollow fitting disposed to cover said single outlet port and adapted for communi cation with the inlet of a main engine pump, and a spring loaded chamber segregating valve in said fitting constructed and arranged to cover and close said port when the discharge pressure of said centrifugal pump falls below a predetermined value in response to a simultaneous failure of fuel supply at the inlets of both chambers, a centrifugally maintained sealing or segregating ring of spinning liquid at the junction of the merging pumping chambers of the centrifugal liquid pump during such failure of liquid supply at both inlets, thereby to promote the independent priming of either chamber when liquid supply to its inlet is re-established and to reopen automatically when pumping in volume is resumed through either chamber, the chamber segregating valve having an area substantially greater than the port which it covers so that the valve will expose far less working area to the discharge pressure of the centrifugal pump when the valve is closed than when the valve is opened.

8. A booster fuel pump unit comprising, in combination, a double suction impeller centrifugal liquid pump, having two contiguous, merging pumping chambers and a common discharge passage in communication with both chambers, which passage includes a single outlet port, a partitioned impeller having separate sets of blades in the respective chambers designed to pump liquid but to separate entrained air and vapor from the liquid,

vacuum pumping mechanism including means for with-' drawing air and vapor from the respective chambers independently of one another, a hollow fitting disposed to cover said single outlet port and adapted for communication with the inlet of a main engine pump, and a spring loaded chamber segregating valve in said fitting constructed and arranged to cover and close said port when the discharge pressure of said centrifugal pump falls below a predetermined value in response to a simultaneous failure of fuel supply at the inlets of both chambers, a centrifugally maintained sealing or segregating ring 10 of spinning liquid at the junction of the merging pumpthe discharge pressure of the centrifugal pump when the ing chambers of the centrifugal liquid pump during such valve is closed than when the valve is opened. failure of l1qu1d supply at both inlets, thereby to promote References Cited in the file of this patent the independent priming of either chamber when liquid supply to its inlet is re-established and to reopen auto- 5 UNITED STATES PATENTS matically when pumping in volume is resumed through 1,090,606 Epps Mar. 17, 1914 either chamber, the chamber segregating valve having 2,553,066 Southern May 15, 1951 an area at least twice as great as the port which it covers 2,581,828 Adams Jan. 8, 1952 so that the valve will expose far less working area to 2,612,844 Grise Oct. 7, 1952

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