DE2144977A1 - Pumping arrangement - Google Patents

Description

DIPL.-ING Λ. GRÜNECKER 8000 MUNICH 22

MoxImilicnslraBe 43

D R.-! N GH KIN KELDEY _{To | Rfon2} ", _mmiJU

DR.-ING. VV. STOCKMAIR, Ae. E. (cauf.inst.oi ^ techn). TelegramsMonapatMönJien

Telex 05-28300

PATE MTA N WALTE

2HA977

P ^; M? 9 September 8, 1971

27 / Ha

CHANDLaR EVANS INC

Charter Or.k Boulevard

West Hartford, Connecticut 06101, USA

Pumping arrangement

The invention relates to a pump arrangement with an inlet and an outlet.

Lie pumping arrangement according to the invention is particularly suitable for fuel regulators. At a. Pump arrangement according to of the invention is a hydrodynamic and a forced VBrdrdrungopuape intended; the latter can be designed as a gear pump with a circumferential seal that can be lifted off.

Hydrodynamic pumps (semi-axial and axial centrifugal pumps) are not self-priming at low speeds. Furthermore, an outlet pressure to be noted can be a hydroaynamischon ioimpe e.g. at the highest speeds of a drive turbines can only be avoided, but will be dispensed with is to use the pump only to generate the pressures, required to feed fuel to the engine at low engine speeds.

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In general, aircraft gas turbine engines require self-priming fuel pumps which can generate a high discharge pressure and so can meet the conditions necessary to start the engine and operate it at low speeds. Therefore, it has been used in fuel regulators Zwangsverdrängungepumpen, particularly gear pumps are self-priming and leave during start w can generate high pressure.

Given the latest developments in auxiliary equipment, such as fuel controls, for the operation of modern engines with high efficiency and high speeds can, however, positive displacement pumps in the Do not use the entire speed range of the engine or only use it with serious disadvantages because in In this case, high power losses and warming occur, which can be traced back to the large overflow volumes that occur with positive displacement pumps, and on the fluid and mechanical friction in the fc high-speed machines.

One arrangement for avoiding the difficulties noted above is disclosed in U.S. Patent Application Ser. ? 67 293 of October 14, 1968 with the title "Fluid Pump and Delivery System" is given. Fuel consumption of the engine in all its Br ^o © hzahlbereich can be satisfied "This pump arrangement

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contains a circuit with a positive displacement pump for starting and running at low speed, a second circuit with a centrifugal pump intended for normal operation and one for cruising in large high specific third circuit with a steam core centrifugal pump. The positive displacement pump stops delivering fuel to the engine as soon as the Centrifugal pump generates the required fuel pressure The pump arrangement enables the positive displacement pump to be relieved when the centrifugal pump is fueling delivers to the engine under the required pressure. As a result, the large overflows avoided that otherwise occur with positive displacement pumps. However, the arrangement is complex and overall not trouble-free in operation.

An important object of the invention is to provide a pump arrangement intended for a gas turbine engine in which large overflow quantities and the difficulties associated therewith are avoided in a simple manner.

In a pump arrangement of the type mentioned, the invention provides that a centrifugal pump and a positive displacement pump provided with a circumferential seal are connected in series and that a device for relieving the positive displacement pump provided with a circumferential seal is provided.

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The pump arrangement according to the invention preferably comprises in one structural unit a centrifugal pump and a positive displacement pump, in particular designed as a gear pump, with 'a circumferential seal in the form of a' sealing block. Furthermore, a device is provided which, at a predetermined outlet pressure of the centrifugal pump, moves the sealing block away from the gears of the gear pump provided with the head gasket.

According to the invention, a hydrodynamic pump and a positive displacement pump provided with a circumferential seal are thus combined with one another. The pump provided with the circumferential seal generates the pressure at low speeds and the hydrodynamic pump generates the pressure at high speeds. The invention therefore uses a basic arrangement similar to that given in the aforementioned patent application.

According to the invention are a centrifugal pump and one with Gear pump provided with a circumferential seal, in particular in a single pumping circuit arranged one behind the other. If * the pump fitted with the circumferential seal does not have any pressure needs to generate, the sealing block is provided with the peripheral seal by means of an actuating device Pump moved away from the circumference of the gears. In contrast to the pump arrangement according to the aforementioned patent application only a single pump circuit is used here. Furthermore, a novel device is used, the sealing block

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moved away from the circumference of the gears when the with the pump provided with the circumferential seal no longer needs to generate pressure.

The pump arrangement according to the invention has a housing in which a pump cavity is formed, which has an inlet opening and an outlet opening, also 2 two gear wheels rotatably mounted in the cavity and meshing with one another, a sealing block which is movably mounted in the cavity, an outlet chamber and two Has arc-shaped sealing surfaces and is held in firm contact with the circumference of the gearwheels under the action of a fluid pressure, furthermore a first line connecting the inlet of the pump arrangement with the inlet opening of the cavity, in which the fluid supplied to the gearwheels is in series with to increase the pressure the gears a hydrodynamic .Pump is arranged, a second line which connects the outlet opening of the cavity with the outlet of the pump arrangement, a.Schalteinrichtung which is in operative connection with the housing and by means of which the fluid pressure can be changed, which the sealing block against n gears suppressed, an at least partially disposed in the cavity, pressure-exerting of the fluid pressurized pressing device by means of which the sealing block at the gears bar and that the moving away of the sealing block of the gears by acting directly on it flow "

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medium pressure forces, and a third line, which connects the switching device and the pressing device to one another in such a way that the latter of the fluid pressure can be relieved, so that the fluid pressure forces acting directly on the sealing block move it away from the gears.

"Other features, details and benefits of the

Invention emerge from the following description of embodiments of the invention with reference to the drawing. It shows:

1 shows a schematic sectional view of an embodiment of a pump arrangement according to the invention, Fig. 2 is a schematic sectional view of another. - Embodiment of a pump arrangement according to the invention and

Pig. 3 shows a schematic sectional view of a further embodiment of the pump arrangement according to the invention .

In all the figures of the drawing, the same reference symbols denote the same parts. Fig «I shows a pumping arrangement 10, primarily for use in the fuel system is intended for a gas turbine engine and can form part of the fuel regulator itself. The invention is but not limited to pumps for fuel systems, but generally applicable to pumping arrangements

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The pump arrangement 10 has an inlet 12 and an outlet 14. It conveys from the inlet 12 to the outlet 14 via a main line section 16. This is formed by a first line section 18 and a second line section 21. A hydrodynamic pump 20 is arranged in the line section 18 of the main line branch 16, which is designed here as a centrifugal inducer pump and receives _{fluid under a low pressure P 1 from a suitable fuel supply via the inlet 12.} At the outlet of the centrifugal pump 20, fluid emerges under a pressure PD. This fluid flows through the line piece 18 into a cavity 22 in which a positive displacement gear pump 24 is arranged, which is provided with a circumferential seal. _{The fluid has a pressure Pj 1} at the outlet 26 of the pump 24 and flows through the line section 21 to the outlet 14. A cleaning filter 27 is arranged in the line section 21, from which the cleaned fluid is fed to the bearings of the pump and the cleaned control fluid gives away. The fluid discharged from the cleaning filter 27 can also be used to flush the valves in a fuel regulator to which the pump arrangement is assigned.

A pressure relief line 28 connects the outlet 26 of the positive displacement gear pump 24 with the line piece 18. A check valve 50 arranged in line 28 is set so that

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it opens and allows a flow from the outlet 26 to the line _{piece 18 when the pressure difference Pj 1} -Pg between the outlet and the inlet of the positive displacement gear pump 24 exceeds a predetermined value. As a result, during operation of the gear pump, excess fluid flows through the valve 30 is essentially a safety device; it does not open during normal operation.

ψ The pump 24 has two intermeshing £ aiiK. ~

wheels 32 and 34, which are mounted in a known manner on a shaft 36 and 38, respectively. The shaft 'j> and J & \ ~ rei seipumpe sina 20 with a drive 40 Zöhnkrana au operating ε-connected can be coupled with the transmission of a guest \ ~ irbinea engine. The shafts 36 »38 are rotatably mounted in suitable bearings with a small running clearance so that the axes of rotation of the shafts 36» 38 in the. run essentially parallel. There is therefore an entry area 42 to the left of the area of engagement between the gears 32, 34- and an exit area 44 to the right of this area of engagement. Fluid is transported in the tooth gaps between the adjacent teeth of each gear from the inlet area 42 into the outlet area 44 and is released from these tooth gaps into the outlet area 44 in the part of the outlet area adjoining the meshing area.

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> ORIGINAL BATHROOM

2H4977

In the exit area 44, a sealing block 46 engages with sealing surfaces 48 and 50 on the circumference of each gearwheel. The sealing surfaces 48 and 50 are grounded by means of a compression spring 2 acting on the rear or right-hand side of the sealing block 46 and under the action of the pressure in the volume-changing chamber 54 located on the rear or right-hand side of the sealing block 46 against at least two Teeth of each gear pressed. The lateral büv /. The upper and lower parts of the sealing block are connected to one another by a web $ 6 , which has a channel or an opening 58 through which the outlet pressure is transmitted to the volume-changing chamber 54-. The design of the sealing block 46 is known per se to the person skilled in the art.

A pressure relief line 60 is connected to the right part of the pump cavity 22, that is to say also to the variable volume Chamber 54 in connection and is used to control the. <3 pressure in the variable-volume chamber 54. The depressurization of the volumetric Chamber y + is switched by a slide 62 between the gear pump 24 and the centrifugal pump 20 controlled.

The switchover slide 62 has a housing 64 with two chambers 66 and 6ö. In one chamber 66 there is a diaphragm ′ / 0 through which fluid can pass from the line 60 to the suction side of the pump 20 via a line which connects the diaphragm ′ / 0 and the inlet cables of the pump 20 at a point 73. The two

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BATH ORIGINAL

2U4977

the. Chambers 66, 68 are connected by a bore in which a cylindrical slide piston 75 is slidably arranged. The slide piston 74 is provided with a flange or a disk 76. The left end face of the slide body 74 can cover the screen 70 and thereby prevent a flow from the line 60 to the point 73. At the periphery of the flange 76 an evacuated bellows 78 is fixed ψ, which causes the position of the slider body 74 is a function of the pressure in the chamber 68 is. " A line 80 connects the chamber 68 and the annular space surrounding the cleaning filter 26, so that the pressure present in this annular space 81 acts on the chamber 68. The pressure in the annular space 81 surrounding the cleaning filter 26 is equal to the outlet pressure (Ppj of the gear pump 24 minus the pressure loss at the filter.

When starting, the spring force of the bellows 78 presses the slide piston 74- against the orifice 70.When the pressure in the chamber 68 is so high that it overcomes the spring force exerted by the bellows 78 on the flange 76, the slide piston 74 is shifted to the right so that the aperture 70 is exposed. The pressure in the variable-volume chamber 54 is equal to the pump outlet pressure Pj ₁ when the slide piston 74 covers the orifice 70. This outlet pressure P ^, is transmitted from the outlet area 44 of the pump 24 via the passage 58 in the web 56 to the chamber 54. When closed

■ 201) 0 l'3 / 107 2

21U977

BIcucjo 70 is therefore the lower or right surface of the Dichtbjockes 46 a dependent on the outlet pressure Subjected to force that assists the force exerted by the spring 52.

Spring and pressure force together form a cumulative force which acts on the right surface of the sealing block 46 and the arc-shaped sealing surfaces 48, 50 against the circumference of the gears 34 b & w. 32 presses. When the centrifugal pump 20 and the gear pump 24 have reached a sufficient speed, the pressure in the chamber 68 acting on the left surface of the flange 76 is so high that it can overcome the spring force exerted by the bellows 78 on the flange 76, so that the slide piston 74 is displaced to the right and the diaphragm 70 is released. Fluid flows out of the chamber 54 via the lines 60, the diaphragm 70 and the line to the inlet side of the pump 20. This flow relieves the sealing block 46 of the force that is exerted on the right side of the sealing block as a result of the pressure drop at the diaphragm 58 is exercised. As a result of this relief, the compressive forces acting on the left side of the web and the arcuate sealing surfaces can push the sealing block 46 to the right against the force of the loading springs 52. When the sealing block 46 is shifted to the right, so that the arcuate sealing surfaces are moved away from the teeth of the gears, the pump 24 no longer acts as a pressure generator arranged in the pumping circuit;

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2UA97-7

However, it continues to deliver fluid from the "inlet area 42" to the outlet area 44. This state remains Maintained as long as the pressure generated by the centrifugal pump 20 meets the requirements of the system. In Tests have shown that when the gear pump is relieved, the pressure P ^ on a. Value, something drops below P-g. This is attributed to the fact that the flow path acts as a throttle point between the teeth of the gears and the removed 'arcuate sealing surfaces. Of the Discharge pressure at which the pump 24 is relieved must of course be appropriate to the intended use the pump arrangement can be selected. If this is assigned, for example, to a fuel regulator for a gas turbine engine is, the relief should take place in the range of the * idling speed of the engine.

The one in Pig. I illustrated pump arrangement has the following W e curiously white.

When starting, the rotating drive tooth drives) ring 40 includes pumps 24 and 20 which are drivingly connected to one another in a suitable manner (not shown), for example by a shaft are. The spring 52 first presses the sealing block 46 against the circumference of the gears. With increasing The speed of the pump 24 supports the pressure in the variable-volume chamber 54 that of the spring 52 force exerted on the sealing block 46 so that the sealing

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block 46 now with a stronger force to the perimeter of gears 32 and 34 is printed.

Once the speed of the pumps is so high that the pump 20 has the required amount of fluid below the Can deliver prescribed pressure, the pressure in the chamber 68 overcomes that of the bellows 78 on the slide piston 74 specified pressure, so that the diaphragm 70 is released When the aperture 70 is open, the fluid flows out of the variable volume chamber 54 to the entry side the centrifugal pump 20, whereby the voluntenvariable chamber 54 is relieved of pressure. Now push the acting on the sealing surfaces of the sealing block 46 and the web 56 Pressure forces the sealing block 46 to the right. Therefore, the gear pump 24 no longer generates pressure. This has the consequence that after the aperture 70 has been released by the slide piston 74, a larger flow rate occurs through the aperture than through the passage 58, so that between the variable volume Chamber 54 and the outlet area 44 a pressure difference is available. Since the sealing surfaces of the sealing block 46 only when operating at low speed with the The circumference of the gears are in contact, the service life of the gear pump 24 is extended accordingly.

The embodiment of FIG. 2 has a similar operation as the embodiment of FIG. 1, but are According to FIG. 2, the sealing block and the device used to actuate it are configured somewhat differently. The sealing block 100 has two converging inclined surfaces 102 and 104 on its right or lower side, each with one

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Inclined wedge 106 or 108 are in sliding contact. Each of these wedges has the shape of a right triangle, its hypotenuse with the associated Inclined surface of the sealing block 100 is in sliding contact and causes the arcuate sealing surfaces 50 and 48 against the circumference of the gears 32 and 34 to be printed. From the underside of the short leg of each wedge 106 or 108 there is a rod 110 or which acts as a piston in the manner explained below. Between the perimeter of the chamber and the short ones At the base of the wedges 106 and 108 there is a compression spring 114 and 118, respectively. These press when starting The wedges spring against the sealing block 100 and thus the sealing surfaces 48 and 50 against the circumference of the gears 34 or 32.

A line 118 contains an orifice 120 and is in communication with another line 122, so that filtered Fluid, which is substantially at exit pressure P-ni 3, to the outer ends of the rods and 112 arrives. Another line 124 is connected to line 122, so that the latter and thus the outer ends of the rods 110, 112 with the chamber 66 are in communication.

Now does the spool? 4 release orifice 70, so the outlet pressure acts on the outer ends of the

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Rods 110 and 112, the wedges 106,108 are against the Sealed "block 100 pressed and therefore support the from force exerted on springs 114, 116. When the discharge pressure of the pump 24 is high enough, the slide piston will 74 shifted to the right in the manner explained above, so that it exposes the diaphragm? 0 and thereby reduces the application pressure of the rods 110,112 because a pressure drop occurs at the throttle point 120. As a result, the forces acting on the sealing block 100 can counteract the force of the loading springs 114, Slide 116 to the right. This movement of the sealing block 100 to the right causes sliding contact between the Inclined surfaces 102,104 and the hypotenuses of the wedges 106, 108. If necessary, the entire surface of the Sealing block 100 be designed as an inclined surface on which a single wedge engages.

In the embodiment of a pump arrangement according to the invention shown in FIG. 3, the sealing block 200 is somewhat T-shaped. Its lower or right part has a channel 202 which is in communication with the chamber 47 and in which a diaphragm 204 is arranged. It should be noted that the channel 202 does not lead through the right end or the base surface of the sealing block 200, but ends just in front of this surface. Side channels 206 and 208 are formed in the sealing block 200, which are in communication with the channel at a point which lies between its end adjacent to the base of the sealing block 200 and the diaphragm 204.

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In each of the side channels 206, 208 a hollow piston 210 1, or 212 is slidably arranged, which protrudes from the channel 202 to the outside. A compression spring 214 is arranged in the hollow parts of the pistons and transversely passes through the channel 202 between the pistons. The outer end cfer pistons 210 and 212 engage the sides of struts 216 and 218, respectively, and press them against the sealing block 200. The lower or right-hand surfaces of the struts 216, 218 are bevelled to match the sloping profile of the housing 17 and are in with it Sliding contact. Such is also at the free ends of the struts 216, 218 with side surfaces 220 and 222 located between the ends of the sealing block 200 Line 226 is connected to the chamber 66 of the switching slide 62.

When the gear pump 24 in FIG. 3 is running slowly, therefore, the one in the channel 202 assists downstream of the Orifice 204 existing, high pressure the spring forces acting on the hollow pistons 210, 212, so that these pistons exert an increased force on the struts 216 and 218, respectively. From Fig. 3 it can be seen that these struts under the Effect of the force exerted by the pistons 210,212 slide along the inclined surfaces of the housing 17 so that

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the sealing block 200 is pressed firmly against the periphery of the gears. Once the aperture 70 is in the above Is exposed, the pressure present downstream of the orifice 204 · decreases and that on the Pressure forces acting on the sealing block can push the sealing block to the right. As a result of the displacement of the sealing block 200 to the right, the struts 216, 218 slide along the housing 17; therefore, pistons 210 and 212 moved inward and the gear pump 24 is relieved as in the previously described embodiments.

The pumps shown here can also be fitted with side plates Be mistaken. Side plates suitable for use in the specified pump arrangement are, for example U.S. Patents 2,420,622, 2,74-2,862, 2,996,999, 3,292,550, and 3,4-27,985.

The exemplary embodiments described above can be varied in many ways within the scope of the concept of the invention will. All of the claims, the description and the drawing features and Advantages of the invention, including structural details, spatial arrangements and method steps, can be essential to the invention both individually and in any combination.

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Claims (8)

21U977 Pat ent a η spr üc.he Q. J Pump arrangement has an inlet and an outlet, characterized by a housing in which a pump cavity (22) is formed which has an inlet opening (42) and an outlet (44), furthermore two gear wheels (36, 38) rotatably mounted in the cavity (22) and meshing with one another, a sealing block (46; 100; 200), which is movably mounted in the cavity (22), an outlet chamber (47) and two arc-shaped sealing surfaces (48,50) possessed and under the action of fluid pressure is held firmly in contact with the circumference of the gears (36, 38), and also a first, the inlet (12) the pump arrangement with the inlet opening (42) of the cavity (22) connecting line (18), in which to increase the pressure of the fluid supplied to the gears (36, 38) in series with the gears (36, 38) is hydrodynamic Pump (20) is arranged, a second line (21) which the outlet opening (44) of the cavity (22) with the outlet of the pump arrangement (10) connects a switching device (62) which is in operative connection with the housing stands and by means of which the fluid pressure can be changed, which the sealing block (46; 100; 200) against the gears (36,38) pushes, an at least partially arranged in the cavity (22), acted upon by the fluid pressure Pressure device (52-56; 102-116; 210-218), by means of which the sealing block (46; 100; 200) is attached to the gear wheels 209813/1072 C56, JS) can be pressed and which the moving away of the Sealing block (46; 100; 200) from the gears (36,38) by means of fluid pressure forces acting directly on it> and a third. Line (60; 122,124; 226), which the switching device (62) and the pressing device (52-56; 102-116, 210-218) with each other connects that the latter can be relieved of the fluid pressure, so that the directly on-the ^ sealing block (46; 100; 200; acting flow mean pressure forces him from the Gears (36,38) can move away. 2. Pump arrangement according to claim 1, characterized in that the pressing device (52-56) has a web (56) which is integral with the sealing block and is penetrated by a passage (58) and in the cavity (22) delimits a variable-volume chamber (54), with which is connected to the third line (60). 3 · Pump arrangement according to claim 1 or 2, characterized in that the pressing device (102-1 ^ 6) has an inclined wedge (106,108) of which a rod (112, 110) arranged displaceably in the third line (122, 124) extends, and the sealing block (100) has an inclined surface (102,104) at its base with which the inclined wedge (106,108) is in sliding contact stands· 209813/1072 21U977 4 ·. Pump arrangement according to one of Claims A to 3 »characterized by a line arrangement (80, .118) which connects the second line (21) to the third line (122, 124) and contains a diaphragm (120). 5 · Pump arrangement according to at least one of the claims 1 to 4, characterized in that the pressing device has a piston (210, 212), which is mounted in the sealing block (200) relative to this laterally displaceable that the sealing block (200) a with the outlet chamber (4-7) communicating channel (202) which contains a diaphragm (204), downstream of which the piston (210, 212) is arranged, which is in communication with the channel (202), that the sealing block (200) has a sideways surface (220,222) and the cavity (22) has an inclined surface and that with the piston (210,212) a movable strut (216,218) is in contact, which is located between the sideways Surface (220,222) and the inclined surface of the cavity (22) extends and engages on these surfaces. 6. Fump arrangement according to at least one of claims Λ to 5 »characterized in that the switching device (62) has a housing (64) with a first and a second chamber (66 and 68) that in the first chamber (66) a Aperture (70) is arranged and the. first chamber <66) with the third line (60} 122, 124; 226) is in connection that in the second chamber (68) a 209813/1072 pressure-dependent device (78) is arranged and in the housing (64) of the switching device (62) between the chambers (66,68) a contact piece (7 ^) is arranged displaceably, which is in one piece with the pressure-dependent device (78) and under its action with respect to the diaphragm (70) in e-ine open and closed positions can be moved. 7. Pump arrangement according to Claim 6, characterized by a line arrangement (72), which the first Chamber (66) with the first line (.18) connects, and through a line arrangement (80), which the second chamber (68) with the second line (21) connects. 8. Pump arrangement according to claim 6 or 7? characterized in that the pressure-dependent device an evacuated bellows (78) attached to the wall of the second chamber (68). 209813/1072 Blank page