WO2024029027A1

WO2024029027A1 - Triple gear pump

Info

Publication number: WO2024029027A1
Application number: PCT/JP2022/029919
Authority: WO
Inventors: 精鋭増田
Original assignee: 株式会社Ihi
Priority date: 2022-08-04
Filing date: 2022-08-04
Publication date: 2024-02-08

Abstract

This triple gear pump comprises one driving gear, and a first and a second driven gear that each engage with the driving gear and that respectively constitute a first and a second gear pump; moreover, said triple gear pump discharges a fluid used as fuel. This triple gear pump comprises: a housing that surrounds the first gear pump and the second gear pump; a driving shaft that is linked with the driving gear so as to rotate integrally with the same, and that is drawn out of the housing; a driving shaft bearing that rotatably supports the driving shaft, that is capable of floating in the axial direction, and that receives pressure from the fluid and abuts the driving gear; a mechanical seal that is interposed between the driving shaft and the housing and that prevents the fluid from leaking outside of the housing; and a seal that is interposed between the driving shaft bearing and the mechanical seal and that prevents the pressure of the fluid from being transmitted to the mechanical seal.

Description

triple gear pump

The present disclosure relates to a floating bearing type triple gear pump that pressurizes and discharges fluid by rotating gears, and particularly relates to a triple gear pump that can be operated stably not only in series and parallel modes but also in no-load mode.

A gear pump usually includes a pair of gears that mesh with each other and a housing that houses the gears, and pressurizes and discharges fluid by rotating the pair of gears in a flow path defined by the housing. It is used in fuel supply devices for reciprocating engines and jet engines.

Floating bearings are often used in gear pumps. In a floating bearing type gear pump, the bearing not only supports the gear shaft, but is also slightly movable in the axial direction and comes into contact with and supports the side surface of the gear. The fluid passing through the gear pump is used not only to lubricate the bearing, but also to pressurize the bearing to press it against the side of the gear.

A triple gear pump has been proposed in which two gear pumps are driven simultaneously by one drive shaft. According to the triple gear pump, a relatively small flow rate can be achieved by operating two gear pumps in series, and a relatively large flow rate can be achieved by operating two gear pumps in parallel.

Patent Documents 1 and 2 disclose related technologies.

Japanese Patent Application Publication No. 2008-50979 International Publication WO2017/009994A1

Floating bearings require pressurization, and in order to ensure smooth operation of the gear pump and prevent fluid leakage from the side of the gear, it is necessary to manage the pressurization within an appropriate range. In triple gear pumps, the pressure of the fluid around the floating bearing has non-negligible fluctuations depending on the operating mode, so the technical difficulty increases as the number of supported operating modes increases. Resulting in.

The present disclosure relates to a triple gear pump that can stably operate not only in series and parallel modes but also in no-load mode.

A triple gear pump according to one aspect includes a driving gear, and first and second driven gears meshing with the driving gear and forming first and second gear pumps, respectively, and is used as fuel. discharge the fluid. Such a triple gear pump includes a housing surrounding the first gear pump and the second gear pump, a housing coupled to the drive gear so as to rotate together, a drive shaft pulled out from the housing, and a housing that rotates the drive shaft. a drive shaft bearing that is axially floating and abuts the drive gear under pressure from the fluid; and a drive shaft bearing that is interposed between the drive shaft and the housing so that the fluid can flow outside the housing and a seal interposed between the drive shaft bearing and the mechanical seal to prevent the pressure of the fluid from propagating to the mechanical seal.

A triple gear pump is provided that can operate stably not only in series and parallel modes but also in no-load mode.

FIG. 1 is a schematic block diagram of a system for supplying fuel to an aircraft engine according to one embodiment. FIG. 2 is a cross-sectional plan view of a triple gear pump according to one embodiment. FIG. 3 is a schematic cross-sectional view of the triple gear pump. FIG. 4 is an enlarged cross-sectional plan view mainly showing the area around the floating bearing in the triple gear pump. FIG. 5 is a schematic block diagram illustrating series mode, parallel mode and no-load mode.

Some exemplary embodiments will be described below with reference to the accompanying drawings. Throughout the following description and appended claims, the terms "axial" and "periaxial" are used in a shaft-specific manner.

Referring to FIG. 1, a triple gear pump 1 according to the present embodiment is used, for example, by being incorporated into a system that supplies fuel to an aircraft engine 10. pressurizes and discharges a fluid such as

Fluid is supplied from the tank through the flow path _F1 , pressurized by the triple gear pump 1, and discharged. Another low pressure pump 3 may be interposed on the flow path _F1 for system startup or other purposes. Although the low pressure pump 3 is not necessarily limited to this, a centrifugal pump can be used.

Since energy extracted from, for example, a turbine of the engine 10 is used to power the triple gear pump 1, the discharge amount of the triple gear pump 1 is normally proportional to or at least dependent on the rotation speed of the turbine. For example, when cruising at high altitude, the engine speed may be relatively high but the fuel consumption may be low, so the discharge amount does not necessarily match the required amount of the engine 10. Of the fluid discharged there, a portion exceeding the required amount is divided by the fuel control unit 5 and returned to the flow path _F1 through the reflux path _F3 , and only the required amount is supplied to the engine ₁₀ through the flow path F5. be done.

Since the lubricating oil L circulates within the engine 10 and is heated, the discharge fluid is also used for cooling it. That is, the flow path _F5 is connected to the oil cooler 9, which cools the lubricating oil L, and after the fluid itself is preheated, it is introduced into the combustion chamber 7 of the engine 10 via the supply path _F7 , where it is combusted. served.

The triple gear pump 1 itself generates heat, and part of the heat returns to the triple gear pump 1 through the return path _F3 , resulting in a considerable temperature rise in the fluid in the flow path _F5 . Therefore, the cooling capacity of the oil cooler 9 is often not balanced with the temperature rise of the lubricating oil L. Therefore, an air-cooled oil cooler 11 that uses air A extracted from a bypass passage of the engine 10 is used as an auxiliary aid. As the reflux through the reflux path _F3 increases and the temperature of the discharge fluid increases, and the load on the air-cooled oil cooler 11 increases, the thermal stress on each part of the system increases, and thermal energy is wasted. Energy efficiency will decrease. Conventional triple gear pumps enable series and parallel modes to increase or decrease the discharge volume and minimize the return volume.

According to the triple gear pump 1 according to the present embodiment, by enabling not only series and parallel modes but also no-load mode, it is possible to further increase/decrease the discharge amount and improve energy efficiency. . That is, for example, when the aircraft is idling on the ground or cruising at high altitude, the series and parallel modes are used, and when a large flow rate is required, such as during takeoff, the triple gear pump 1 is left unloaded. This enables switching such that fuel is supplied exclusively by the centrifugal pump 3. The problem is that in the no-load mode, high pressure is applied to the entire triple gear pump 1, making it difficult to control pressurization. The solution will become clear from the following explanation.

Combining FIGS. 2 and 3 and mainly referring to FIG. 3, the triple gear pump 1 generally includes a drive gear 23 driven by one drive shaft 21, and first and second gears meshing with the drive gear 23, respectively. The combination of the drive gear 23 and the first driven gear 27 constitutes the first gear pump _G1 , and the combination of the drive gear 23 and the second driven gear 31 constitutes the first gear pump G1. It constitutes a gear pump _G2 . Since the housing 41 surrounds these and is in close contact with the tips of the teeth of each gear, the

spaces

43, 45, and 47 surrounded by the gear teeth and the housing 41 serve to transport the fluid while pressurizing it in accordance with the rotation of the gears. do. The housing 41 also includes an inlet 49 and an outlet 51 that communicate with the first gear pump _G1 , and an inlet 53 and an outlet 55 that communicate with the second gear pump _G2 . When the drive gear 23 rotates around its axis by an external power source, the first and second gear pumps G ₁ and G ₂ operate in parallel, and the fluid sucked in from the suction port 49 at a pressure P ₁ is transferred to the discharge port. 51 at a pressure P ₃ , and the fluid sucked in from the suction port 53 at a pressure P ₅ is discharged to the discharge port 55 at a pressure P ₇ . Typically, the discharge pressures P ₃ and P ₇ are higher than the suction pressures P ₁ and P ₅ , respectively, but as explained below, this depends on the operating mode.

Mainly referring to FIG. 2, the drive shaft 21 is pulled out of the housing 41 for coupling with a power source, but the

shafts

25, 29 of the first and second driven

gears

27, 31 are It is enclosed within 41. Each

shaft

21, 25, 29 is rotatably supported by a pair of

floating bearings

33, 35, 37, respectively. Each floating bearing 33, 35, 37 also sandwiches a

gear

23, 27, 31, respectively. The

floating bearings

33, 35, and 37 can float slightly in the axial direction, and come into contact with both side surfaces of the

gears

23, 27, and 31, respectively, under appropriate pressurization.

A gap is maintained between both ends of the first and second driven

shafts

25, 29 and

floating bearings

35, 37, respectively, and the housing 41, and fluid can flow in by communicating with the

suction ports

49, 53, respectively. , the fluid in the gap is pressurized at each end by suction pressures P ₁ and P ₅ . This pressurization is used to press the

floating bearings

35 and 37 against the first and second driven

gears

27 and 31, respectively. For example, the first and second driven

shafts

25 and 29 are hollow in order to spread the fluid across both ends and apply uniform pressure. Further, in order to apply this pressurization to the floating bearing 33 of the drive shaft 21, a communication passage 67 is interposed between the floating bearing 37 and the floating bearing 33 to provide fluid communication therebetween.

In order to introduce a pressure P ₉ different from the suction pressures P ₁ and P ₅ from the outside and apply it to the floating

bearings

35 and 37, for example, both side surfaces of the housing 41 may each be provided with an introduction pipe. In order to receive such pressure _P9 , the floating

bearings

35, 37 have a reduced diameter on the end side, and may be provided with a step on the shoulder thereof, and the inner end of the introduction tube may be open toward the shoulder. . The stepped surface can be used as a surface that receives the pressure _P9 . A suitable seal, such as a gasket, should be interposed between the end face and the shoulder to suppress the propagation of mutual pressure. Such an inlet pipe can also communicate, for example, with the

outlet

51 or 55, in which case the pressure P ₉ applied to the step surface corresponds in principle to the outlet pressure P ₃ or P ₇ . In order to further adjust the pressurization, a pressurizing means such as a spring 39 may be interposed between the shoulder and the housing 41, for example. These are used to adjust the pressurization of the floating

bearings

35 and 37.

Seals

61 and 63 are interposed between the housing 41 and the drive shaft 21 to prevent internal fluid from leaking. One or both of the

seals

61 and 63 may be a mechanical seal that presses the seal surfaces against each other using, for example, a spring force. A seal 65 that prevents fluid pressure from propagating is interposed between the above-mentioned communication path 67 and the seal 61 so that excessive pressure does not apply to the mechanical seal. For example, a labyrinth seal can be applied to such a seal 65.

The housing 41 may further include an inlet passage 69 to collect fluid leaking from the labyrinth seal and to apply an appropriate pressure P ₁₁ to the mechanical seal 61 . For example, a flow path F ₁ can be connected to the introduction path 69 , so that the pressure of the fluid before being pressurized by the triple gear pump 1 can be applied to the mechanical seal 61 . Of course, other appropriate channels may be connected.

Referring to FIG. 4 in combination with FIG. 2, a force _f1 originating from the suction pressure _P5 acts on the upper ends of the upper floating

bearings

33, 37, and therefore the upper floating

bearings

33, 37 and is pressed against the second driven gear 31 by a downward force f _d . Since the lower floating bearing 37 has the communication passage 67, the force _f1 derived from the suction pressure _P5 acts on the lower floating bearing 33, and therefore the lower floating

bearing

33 , 37 are pressed against the drive gear 23 and the second driven gear 31 by an upward force _fu . Since the common pressure is applied, the forces f _d and f _u are balanced, and the driving gear 23 and the second driven gear 31 are stably supported. Also, a force _f2 different from these (usually larger) is used to adjust the upward force _fu , thereby preventing the floating bearing 37 from disengaging from the second driven gear 31. can do.

Although the above description relates exclusively to the second gear pump _G2 , a similar force balance also holds true for the first gear pump _G1 .

The triple gear pump 1 is operated by being connected to a fuel supply system as shown in FIG. That is, the flow path F ₁ is branched into two and connected to an inflow path F ₁₁ and an inflow path F ₁₇ . A check valve V ₁ may be interposed between the flow path F ₁ and the inflow path F ₁₁ . The inflow paths F ₁₁ and F ₁₇ are connected to suction

ports

49 and 53 of the first and second gear pumps G ₁ and G ₂ , respectively. The

respective discharge ports

51 and 55 are connected to the outflow paths F ₁₃ and F ₁₉ , respectively. The inflow path _F11 also branches into two, one of which communicates with the outflow path _F15 via the valve _V3 , and after merging with the outflow paths _F13 and _F19 , the flow path _F21 . It is connected to the. Flow path F ₂₁ is connected to flow path F ₅ of the fuel supply system.

Referring to FIG. 5(a) in combination with FIGS. 2 to 4, when valve _V3 is closed, triple gear pump 1 operates in series mode. At this time, a comparison using the flow path F1 is made in both the inflow path _F11 communicating with the suction port 49 of the first gear pump _G1 and the inflow path _F17 communicating with the suction port 53 of _{the second} gear pump _G2. A low pressure is applied. At this time, the pressures P ₁ and P ₅ are both low pressures, and the vertical forces f _d and f _u of each of the floating

bearings

33, 35, and 37 are balanced. The pressurized fluid discharged from the discharge port 51 passes through the flow paths F ₁₃ and F ₁₅ , and the fluid discharged from the discharge port 55 passes through the flow path F ₁₉ and merges in the flow path F ₂₁ to form the engine 10 . supplied to

Referring to FIG. 5(b) instead of FIG. 5(a), when valve _V3 is opened, triple gear pump 1 operates in parallel mode. The outlet pressure P ₃ of the first gear pump G ₁ passes through the valve V ₃ into the inlet channel F ₁₁ , as a result of which the suction pressure P ₁ increases to match the outlet pressure P ₃ . The presence of the non-return valve _V1 prevents the fluid from flowing back towards the flow path _F1 . At this time as well, the common pressure P ₁ is applied to both floating bearings 35, so the vertical forces f _d and f _u are balanced. Also, changes in pressure _P1 do not affect floating

bearings

33, 37. At this time, the first gear pump _G1 idles (does no work), and only the discharge from the second gear pump _G2 contributes to the supply of fluid.

Note that the valve _V3 is not an on-off valve, but a control valve such as a variable throttle valve that can continuously change the flow rate can be used. In this case, the valve _V3 may have an intermediate state other than fully closed (the state shown in FIG. 5(a)) and fully open (the state shown in FIG. 5(b)), but in any of the intermediate states, However, the balance of forces with respect to the floating

bearings

33, 35, 37 is not lost.

Referring to FIG. 5(c) instead of FIGS. 5(a) and 5(b), a no-load mode is possible according to this embodiment. At this time, the valve _V3 remains open (or may be closed) and increases the discharge amount of the centrifugal pump 3. Then, high pressure from the centrifugal pump 3 is applied to both gear pumps G ₁ and G ₂ . As can be understood from the above explanation, not only the vertical forces f _d and f _u are balanced on the floating

bearings

35 and 37, but also the pressure is applied to the floating bearing 33 of the drive shaft 21 by the communication passage 67, so that the floating The vertical forces f _d and _fu of the bearing 33 are also balanced. Although high pressure is applied to the floating bearing 33, the labyrinth seal 65 prevents this pressure from reaching the mechanical seal 61. Fluid will not leak out from the mechanical seal 61 or the smooth operation of the mechanical seal 61 will not be impaired.

In the no-load mode, both gear pumps G ₁ , G ₂ do virtually no work, and only the centrifugal pump 3 contributes exclusively to the fluid supply. The centrifugal pump can efficiently discharge a large volume of fluid, especially when the engine 10 exerts high output. As can be understood with reference to FIG. 1 again, the triple gear pump 1 does virtually no work, and the reflux of fluid through the reflux path _F3 can be minimized, so that the flow of fluid supplied to the flow path _F5 is minimized. Temperature rise can be suppressed. The cooling capacity of the oil cooler 9 can be fully utilized, and the load on the air-cooled oil cooler 11 can be suppressed.

For example, the parallel mode is used when the engine 10 requires high output even at low rotation speed, the parallel mode is used when cruising at high altitude, and the centrifugal pump is exclusively used in the no-load mode when particularly high output is required, such as during takeoff. According to this embodiment, an optimal mode can be selected and used. This embodiment can achieve high energy efficiency in both cases.

Although several embodiments have been described, it is possible to modify or transform the embodiments based on the content disclosed above.

Claims

A triple gear pump that discharges fluid used as fuel, and includes a first driving gear and first and second driven gears that mesh with the driving gear and constitute first and second gear pumps, respectively. And,
a housing surrounding the first gear pump and the second gear pump;
a drive shaft coupled to the drive gear so as to rotate together and pulled out from the housing;
a drive shaft bearing that rotatably supports the drive shaft, is able to float in the axial direction, and comes into contact with the drive gear under pressure from the fluid;
a mechanical seal interposed between the drive shaft and the housing to prevent the fluid from leaking out of the housing;
a seal interposed between the drive shaft bearing and the mechanical seal that prevents the pressure of the fluid from propagating to the mechanical seal;
Triple gear pump with.
a driven shaft coupled to the second driven gear;
a floating bearing rotatably supporting the driven shaft, floating in the axial direction, and abutting the second driven gear in the axial direction;
a communication passage that fluidly communicates the drive shaft bearing and the floating bearing within the housing;
The triple gear pump according to claim 1, wherein the seal is interposed between the communication path and the mechanical seal.
further comprising an inlet opened in the housing and communicating with the second gear pump for introducing the fluid into the second gear pump;
3. The triple gear pump of claim 2, wherein the inlet is in fluid communication with the drive shaft bearing, the floating bearing, and the communication passageway to apply the pressure to the drive shaft bearing and the floating bearing.
an introduction path for introducing the fluid before being pressurized from the outside of the housing to the mechanical seal;
The triple gear pump according to claim 1, further comprising:
The triple gear pump according to any one of claims 1 to 4, wherein the seal is a labyrinth seal.