SIDE CHANNEL SELF PRIMING FUEL PUMP HAVING RESERVOIR

Abstract: A side channel pump (10) has a pumping cavity (26) which includes an inlet port (78), a discharge port (80) and side channels (72,74). An impeller (54) is mounted for rotation in the pumping cavity. A reservoir (20) holds an ample supply of liquid for pump priming and pump cooling during periods of gas pumping. A bypass suction duct (24) carries liquid from the reservoir to the pumping cavity during priming, gas pumping and normal operating and a bypass return duct (22) returns some discharged liquid to the reservoir during gas pumping and normal operation. The reservoir acts as a heat sink to enable the liquid ring formed during gas pumping operation to absorb more heat and provide pump cooling.

Description: Technical Field This invention relates to a side-channel pump of the type recited in the head clause of claim 1. Disclosure of Invention Side-channel pumps of this type are known from GB-A-898,257 and DE-B-1,056,937, and similar pumps are known from U.S Patents Nos. 1,920,484 and 3,007,417. Side-channel pumps are inherently capable of efficiently handling gases, liquids or a mixture of gas and liquid and are somewhat self-priming. Gases in the liquid entering a side-channel pump or the evaluation of gases from volatile liquids (such as aircraft fuel) will not cause the pump to lose its prime and stop pumping. However, the term "self-priming" as applied to a conventional side channel pump is slightly misdescriptive in that the pump must be filled with liquid before it is started for the first time. Thereafter, the residual charge of liquid which remains in the pump will obviate further priming, provided, however, that the liquid does not evaporate as may be occasioned if the liquid is hot or volatile. The known side channel pumps suffer from a prominent drawback which limits the range of applications in which such pumps may be utilized viz. : they have a tendency to overheat while pumping gases when little or no liquid flow is present to remove the heat. Obviously, excessive heat generation by a pump can produce undesirable consequences with regard to pump life or even possibly create a hazardous condition. Accordingly, it is object of the invention to provide a side-channel pump which is self priming in the absence of sufficient fuel in the pump casing and is to be cooled during prolonged gas pumping operation. FIGURE 1 is a schematic diagram of a side-channel pump according to the invention. FIGURE 2 is a longitudinal sectional view of a side-channel pump according to the invention. FIGURES 3 and 4 are sectional views of the pump of FIGURE 2, taken substantially along the lines 3-3 and 4-4, respectively. FIGURE 5 is a schematic representation of the development of the channels. FIGURE 6 is a front elevational view of the impeller, per se. Referring to the drawings, wherein like reference characters refer to like parts throughout the several figures, a side-channel pump 10 is depicted in FIGURE 1. Flow from an inlet conduit 12 enters a pump inlet 14 and proceeds thence through the pump to a pump outlet 16. Flow from outlet 16 enters a discharge conduit 18 for delivery to a fluid consuming load such as an aircraft gas turbine engine. A portion of the discharge flow, destined to enter or already within the discharge conduit 18, is diverted to a reasonably sized reservoir 20 through a bypass return duct 22. Liquid in the reservoir 20 is drawn into a bypass suction duct 24 which supplies liquid to a suction area of the pump 10 via a secondary inlet port, thereby completing a bypass loop. During normal operation and gas pumping operation when flow demand is minimal there will always be flow in the bypass loop, albeit of a small magnitude. FIGURES 2,3 and 4 show a preferred embodiment of a pump 10. A pumping cavity 26 is formed within a housing 28, 30, 32 by two housing walls 28 and 30 and a ring-shaped spacer 32 interposed therebetween in abutting relationship therewith. The housing walls 28 and 30 are held in firm engagement with the spacer 32 by a plurality of bolts 34 and maintained in proper angular relationship by a plurality of dowels 36 which are received within aligned bores in the housing walls 28 and 30 and spacer 32. Housing walls 28 and 30 have portions 42 and 44 of sufficient width to allow the inclusion of aligned bores 46 and 48. A pair of fixed bearings 50 and 52 are respectively mounted within the bores 46 and 48. An impeller at 54 having radial vanes 55 is carried by an integral hollow shaft 56 journaled in the bearings 50 and 52. Impeller 54 is sized to have minimum running clearance between itself and the confronting surfaces of the pumping cavity 26, viz.: walls 58 and 60 which are respectively defined by the housing walls 28 and 30 and the radial interior periphery 62 of the spacer 32. Internal splines 64 within the shaft 56 are drivingly engaged by external splines on the head 66 of a pump drive shaft 68 to provide a driving connection therebetween, whereby rotation may be imparted to the impeller 54. A shaft seal 70 is interposed between the drive shaft 68 and the housing wall 30 to prevent leakage from the interior of the housing 28, 30, 32 to the exterior of the housing 28, 30, 32. The walls 58 and 60 of the pumping cavity 26 are relieved to form segmental, circumferential side channels 72 and 74 which are coextensive and mirror images. As best seen in FIGURES 2 and 3, the outer radius of the channels 72 and 74 is substantially equal to the radius of the impeller 54 and the channels 72 and 74 have a central angle of about three hundred degrees, whereby the ends of each channel 72, 74 are circumferentially spaced. The channels 72 and 74, which have segments 72A, 72B, 72C, 74A, 74B and 74C, are open only towards the impeller 54 throughout their length and are gradually reduced in depth at both of their ends, as shown in the respective profiles of FIGURE 5, so as to respectively merge with the walls 58 and 60. Such channel geometry with gradual increases and decreases in depth at both ends causes gradual liquid withdrawal or liquid return to pockets 76 formed between the vanes 55 (See FIGURE 6). From FIGURES 2 and 3, it will be observed that the radially outer sides of the vanes 55 pass directly over the channels 72 and 74, thereby insuring continuous communication between the pockets 76 and the channels 72 and 74. As is apparent from FIGURE 3, the impeller 54 rotates in a counterclockwise direction such that the vanes 55 travel from the suction area of the pump 10 (where channel segment 72A has a depth which progressively increases) to a discharge area of the pump 10 (where channel segment 72B has depth which progressively decreases). Housing wall 28 is provided with a main inlet port 78 in the suction area through which incoming fluid is directed into the pumping cavity 26 between the housing walls 28 and 30 and spacer 32, whereas housing wall 30 incorporates a main discharge port 80 (FIGURE 4) in the discharge area of the pump 10 from where fluid finds egress from the pumping cavity 26. Main inlet port 78 and main discharge port 80 are respectively fluidly connected to the pump inlet conduit 12 and the pump outlet 16 by means of suitable passages (not shown). While it is unnecessary to describe the detailed operation of conventional side channel pumps since their operation is well understood by those skilled in the art, it simply should be noted that the energy increment of liquid flowing through such a pump, which is produced by the interchange of impulses between the liquid in the pockets and the liquid in the side-channels, is so large that the total head for this type of pump may be between two and three times greater than that of an ordinary impeller pump with similar parameters. This together with its gas pumping capabilities, may render such a pump suitable for use in association with aircraft gas turbine engine controls. As previously noted, as pumping for a long period of time by a side channel pump, with little or no liquid being pumped, is liable to overheat the pump. To prevent such an occurrence, reservoir 20 functions as a heat sink. From FIGURES 2,3 and 4, it will be seen that the reservoir 20 is formed in an extension of the housing 26, 28, 30 by confronting cavities 82 and 84 in the housing walls 28 and 30, respectively. The bypass suction duct 24 (shown partially by dashed lines) defined in the housing wall 28 communicates with the liquid residing in the reservoir 20 via a suction duct inlet port 86. The other end of the suction duct 24 communicates with a secondary inlet port 88 to pumping cavity 26 which is formed in the wall 58. With reference to FIGURE 4, the bypass return duct 22 (shown by dashed lines) fluidly interconnects the discharge port 80 with the reservoir 20 by means of a secondary discharge port 90 formed in the housing wall 30 adjacent the discharge port 80. In a traditional side channel pump, the pumping cavity must be supplied with liquid before pumping operation can commence. Thereafter, impeller rotation causes liquid to be thrown outwardly into the side channels, thereby forming a free space around the hub which draws air from the inlet conduit via the inlet port. Concurrently therewith, the diminishing channel depth occasions a return of liquid to the pockets in the impeller, thereby resulting in a discharge through the discharge port of the air originally drawn into the pumping cavity. After repeated revolutions of the impeller, air or gas will be evacuated from the inlet conduit whereby the pump will draw in and discharge liquid from the inlet port and discharge port, respectively. The operation of the aforedescribed pump 10 is, of course, fundamentally similar, except that priming can be effectuated solely by the liquid in the reservoir 20. When pump 10 attains a sufficient speed after initial starting, fuel in the reservoir 20 will be drawn through the bypass suction duct 24 and enter pumping cavity 26 through the secondary inlet port 88. After repeated revolutions of the impeller 54, a peripheral liquid ring will develop, thereby creating gas pumping geometry as would exist in a traditional side channel pump after priming. Eventually, the liquid rotating with the impeller 54 forms a seal between the inlet port 78 and the discharge port 80 as in a traditional side channel pump; and finally, after the all air is expelled from the inlet conduit 12, only fuel is drawn into the pumping cavity 26 and pumped therefrom. During gas pumping operation, a traditional side channel pump and a pump of the invention will develop a liquid ring. The typical kidney-shaped outline of such a ring is shown in phantom in FIGURE 3, it being understood that gas lies within the boundaries thereof. Substantial heat will be generated by the pumping operation should gas pumping continue for a period of time; and the heat generation will cause a temperature rise in the liquid ring. However, in a pump 10 of the invention, liquid in the ring will be constantly exchanged for liquid in the reservoir by the flow through the secondary inlet port 88 and the secondary discharge port 90. Hence, the heat generated during gas pumping, which is absorbed by the liquid ring, will be rejected to the reservoir 20, which acts as a heat sink, thereby cooling the pump 10. The design and location of the reservoir 20 admits of many variations. However, it will be understood that the reservoir should be capable of collecting and preserving liquid for a long period of time and have a sufficient capacity to act as a heat sink.

Claims: A side channel pump (10) of the type comprising: a pump housing (28, 30, 32) having an inlet (14) and an outlet (16) and a pumping cavity (26) therein; the pumping cavity (26) having a wall (28) with an inlet port (78) in a suction area of the wall (28) and a discharge port (80) in a discharge area of a wall (30) and a circumfeerential side channel (72, 74), the inlet (14) being fluidly connected to the inlet port (78) for supplying fluid thereto and the discharge port (80) being fluidly connected to the outlet (16) for supplying fluid thereto; and an impeller (54) mounted in the housing (28, 30, 32) for rotation in the pumping cavity (26) comprising a reservoir (20) for containing a supply of liquid, a bypass suction duct (24) for carrying liquid from the reservoir (20) to the pumping cavity (26), and a suction duct (24) inlet port (86) in the reservoir (20) for conducting liquid in the reservoir (20) to the bypass suction duct (24), a secondary inlet port (88) in the pumping cavity (26) wall (28) in the suction area thereof for conducting liquid in the bypass suction duct (24) to the pumping cavity (26), characterized by means (22, 90) to conduct liquid in the discharge area of the pumping cavity (26) wall to the reservoir (20). The pump (10) according to claim 1, characterized in that the liquid conducting means (22, 90) comprises: a bypass return duct (22), and a secondary outlet port (90) in fluid communication with the discharge port (80) for conducting flow from the discharge port (80) to the bypass return duct (22). The pump (10) according to claim 1, characterized in that the reservoir (20) is formed in an extension of the pump housing (28, 30, 32).

Inventors: NASVYTIS, PIUS J.
Applicants: COLTEC INDUSTRIES INC
Application year: 1988
Main classification: F04D5
IPC codes: F04D5, F04D9