Gas turbine gear box with low gear shaft elevation lifting amount

Abstract

A gas turbine gear box with low gear shaft elevation lifting quantity relates to the field of gear boxes and comprises a box body, a gear set system arranged in the box body and an oil spraying pipe used for spraying lubricating oil to the gear set system, the box body comprises an upper box body and a lower box body which are oppositely arranged, and the lower box body is divided into a connecting section and a sinking section from top to bottom. A mounting boss protruding out of the outer side face of the lower box body is arranged at the joint of the sinking section and the connecting section. An oil return cavity is formed in the lower box body, a connecting platform consistent with the mounting boss in height is arranged in the oil return cavity, the connecting platform is used for dividing the oil return cavity into a first oil return area on the upper portion and a second oil return area on the lower portion, the first oil return area is communicated with the second oil return area, and the width of the second oil return area is smaller than that of the first oil return area; an oil return opening is formed in the side wall of the sinking section, a gap is formed between the oil return liquid level of lubricating oil in the oil return cavity and a gear of the gear set system, and the elevation lifting amount of a gear shaft in the gear box can be reduced.

Description

Technical Field

[0001] The utility model relates to the field of gear boxes, in particular to a combustion engine gear box with a low gear shaft elevation. Background Art

[0002] A gas turbine is a power generation equipment that uses natural gas, hydrogen and other combustible gases as fuel to convert thermal energy into mechanical energy and finally into electrical energy. It is widely used in pipeline transportation, ship drive, distributed energy and other fields. It is also called a gas turbine. With the development of science and technology and the changing application environment, the size of gas turbines has become more compact and the structure has become more complex, and the requirements for the gearboxes that match them have become higher and higher.

[0003] The gear shaft elevation lift refers to the amount of movement of the gear shaft in the gear box from the start to the stable state in the vertical direction (i.e., elevation direction) relative to its original installation position. The engine is connected to the gear shaft in the gear box through a sleeve coupling. In order to improve the stability of the transmission connection, the elevation lift of the gear shaft in the gear box should be reduced as much as possible. For example, the elevation lift of the high-speed shaft of the gear box compatible with the G15 engine should be less than 0.1mm.

[0004] like Figure 6 As shown, in the prior art, the gear box body is mostly rectangular, and its bottom is the mounting surface 104 for mounting the gear box on the unit joint base. The unit joint base is fixed on a poured concrete foundation. As the lubricating oil for cooling the gear falls into the lower body of the gear box, the body will heat up and expand, thereby causing the gear shaft in the body to move upward, and the elevation of the gear shaft is difficult to reduce to an ideal level. Utility Model Content

[0005] The utility model aims to provide a combustion engine gear box with a low gear shaft elevation lift amount, so as to reduce the elevation lift amount of the gear shaft in the gear box.

[0006] In order to achieve the above-mentioned purpose, the specific scheme adopted by the utility model is as follows: a combustion engine gearbox with low gear shaft elevation lifting amount, comprising a box body, a gear set system arranged in the box body and an oil spray pipe for spraying lubricating oil to the gear set system, the box body comprises an upper box body and a lower box body arranged relatively, the lower box body is divided into a connecting section and a sinking section from top to bottom, and the width of the sinking section is smaller than the width of the connecting section, and a mounting boss protruding from the outer side surface of the lower box body is provided at the junction of the sinking section and the connecting section;

[0007] An oil return chamber is formed in the lower box body, and a connecting platform with the same height as the mounting boss is arranged in the oil return chamber, and the connecting platform is used to divide the oil return chamber into an upper first oil return area and a lower second oil return area, the first oil return area and the second oil return area are connected, and the width of the second oil return area is smaller than that of the first oil return area;

[0008] The side wall of the sinking section is provided with an oil return port communicating with the second oil return area, and a gap is formed between the lubricating oil return liquid level in the oil return cavity and the gears of the gear set system.

[0009] As a further optimization of the above technical solution: The gear set system includes a high-speed gear, an intermediate gear, and a low-speed gear. The intermediate gear includes an intermediate gear shaft, intermediate gear A and intermediate gear B arranged at both ends of the intermediate gear shaft. Intermediate gear A meshes with the high-speed gear, intermediate gear B meshes with the low-speed gear, and the high-speed gear and the low-speed gear are located on the same axis.

[0010] As a further optimization of the above technical solution: Both ends of the high-speed gear shaft of the high-speed gear extend out of the high-speed gear, and a high-speed support bearing is arranged at the end facing the low-speed gear, and a high-speed support thrust bearing is arranged at the end opposite to the low-speed gear.

[0011] As a further optimization of the above technical solution: The high-speed support thrust bearing includes a support bearing and a thrust bearing that are detachably connected.

[0012] As a further optimization of the above technical solution: A high-speed oil seal sheet, a high-speed oil seal body, a high-speed wind blocking plate, and a high-speed end cover are sequentially installed on the high-speed gear shaft outside the high-speed support thrust bearing from inside to outside.

[0013] As a further optimization of the above technical solution: Both ends of the low-speed gear shaft of the low-speed gear extend out of the low-speed gear, and a low-speed support bearing is arranged at the end facing the high-speed gear, and a low-speed support thrust bearing is arranged at the end opposite to the high-speed gear.

[0014] As a further optimization of the above technical solution: A low-speed oil seal and a low-speed wind blocking plate are sequentially installed on the low-speed gear shaft outside the low-speed support thrust bearing from inside to outside.

[0015] As a further optimization of the above technical solution: An intermediate support thrust bearing is arranged on the intermediate gear shaft outside intermediate gear A, and an intermediate support bearing is arranged on the intermediate gear shaft outside intermediate gear B.

[0016] As a further optimization of the above technical solution: Spray oil pipes are arranged on both the upper and lower sides of the high-speed gear.

[0017] As a further optimization of the above technical solution: A breather cap and an upper end cover are arranged on the upper box body.

[0018] Compared with the prior art, the utility model has the following beneficial effects:

[0019] 1. In the present utility model, the mounting boss of the gearbox is arranged on the side wall of the lower box body, and a connecting platform with the same height as the mounting boss is arranged in the oil return cavity, so as to reduce the center height of the gearbox and then reduce the elevation increase of the gear shaft caused by the thermal expansion of the box body, and reduce the elevation difference of the gear shaft in the gearbox under cold and hot environments. At the same time, the lower box body is set as a sunken structure with a connecting section and a sunken section, and a gap is formed between the oil return liquid level of the lubricating oil in the oil return cavity and the gears of the gear set system, and the gears do not contact the oil return liquid level of the lubricating oil, which not only reduces the elevation increase amount of the gear shaft caused by the thermal expansion amount, but also does not affect the operation performance of the gearbox itself, and controls the elevation increase amount of the high-speed shaft of the gearbox below 0.1 mm.

[0020] 2. The high-speed support thrust bearing is set as a detachable thrust bearing and a support bearing. When the gearbox is separately subjected to a no-load test, the thrust bearing and the support bearing are installed at the same time to bear the axial force generated by the rotation of the high-speed gear through the thrust bearing; when the gearbox is installed on the G15 gas turbine unit, the thrust bearing is first removed to reserve an axial position for the installation of the high-speed sleeve coupling on the high-speed gear shaft, so as to realize the assembly of the gearbox and the G15 gas turbine unit.

[0021] 3. Since the rotational speed of the high-speed gear is relatively high and the heat generation is large, spray oil pipes are arranged on both the upper and lower sides of the high-speed gear to effectively cool the high-speed gear and reduce the thermal expansion of the high-speed gear. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is an exploded view of the gas turbine gearbox of the present utility model;

[0023] Figure 2 is a side view of the gas turbine gearbox of the present utility model;

[0024] Figure 3 is a side view sectional view of the lower box body in the gas turbine gearbox of the present utility model;

[0025] Figure 4 is a top view of the lower box body (including the gear set system) of the gas turbine gearbox of the present utility model;

[0026] Figure 5 is an exploded view of the high-speed thrust bearing in the gas turbine gearbox of the present utility model;

[0027] Figure 6 is a side view of the gearbox structure in the prior art;

[0028] Reference numerals: 1, lower box body; 101, connecting section; 102, sunken section; 103, oil return port; 104, mounting plane; 105, mounting boss; 106, lubricating oil return liquid level; 107, oil return cavity; 1071, first oil return area; 1072, second oil return area; 108, connecting platform; 2, low-speed air baffle; 3, low-speed air baffle spacer; 4, low-speed oil seal; 5, low-speed support thrust bearing; 6, low-speed support bearing; 7, low-speed gear; 8, low-speed oil injection pipe; 9, high-speed lower oil injection pipe; 10, high-speed gear; 11, high-speed upper oil injection pipe; 12, high-speed support bearing; 13, high-speed support thrust bearing; 1301, support bearing; 1302, thrust bearing; 1303, hexagon socket head cap screw; 14, high-speed oil seal piece; 15, high-speed oil seal body; 16, high-speed air baffle spacer; 17, high-speed air baffle; 18, high-speed end cover; 19, intermediate blanking cover A; 20, intermediate support thrust bearing; 21, intermediate gear A; 22, intermediate gear shaft; 23, intermediate gear B; 24, intermediate support bearing; 25, intermediate blanking cover B; 26, upper box body; 27, upper end cover A; 28, breather cap A; 29, breather cap B; 30, upper end cover B. Detailed implementation manners

[0029] The technical solution of the present utility model will be further elaborated in detail below in combination with specific embodiments. For parts that are not detailedly recorded and disclosed in the following embodiments of the present utility model, they should all be understood as the prior art known or should be known to those skilled in the art, such as the installation methods of bearings, blanking covers, air baffles, air baffle spacers, oil seals, etc. on the corresponding gear shafts and box bodies, the conveying and spraying methods of lubricating oil in the gearbox, the external discharge path of the lubricating oil return of the lower box body, etc.

[0030] Please refer to Figure 1-2 , the present utility model discloses a gas turbine gearbox with a low elevation lift of the gear shaft, which includes a box body, a gear set system arranged in the box body, and an oil injection pipe for spraying lubricating oil to the gear set system. The outer contour of the box body is rectangular, including an upper box body 26 and a lower box body 1 arranged oppositely. The gear set system is located at the docking position of the upper box body 26 and the lower box body 1 and is supported on the upper end surface of the lower box body 1. A plurality of connecting plates parallel to the width direction of the box body are arranged in both the upper box body 26 and the lower box body 1. Arc-shaped grooves are opened on the side walls of the upper box body 26, the side walls of the lower box body 1, and the connecting plates in the box body. The arc-shaped grooves of the upper box body 26 and the lower box body 1 correspond one by one and have opposite openings to install and fix the gear set system.

[0031] The lower box body 1 is divided into a connecting section 101 and a sunken section 102 from top to bottom. The outer contours of the connecting section 101 and the sunken section 102 are both rectangular, and the width of the sunken section 102 is smaller than the width of the connecting section 101.

[0032] At the connection between the sinking section 102 and the connecting section 101, there are mounting bosses 105 protruding from the outer side of the lower box body 1. There are two mounting bosses 105, which are symmetrically arranged on both sides of the lower box body 1 and extend along the length direction of the lower box body 1.

[0033] As Figure 3 shown, an oil return cavity 107 is formed inside the lower box body 1. Two connecting platforms 108 are oppositely arranged in the oil return cavity 107. The connecting platforms 108 extend along the length direction of the lower box body 1. The connecting platforms 108 are used to divide the oil return cavity 107 into a first oil return area 1071 in the upper part and a second oil return area 1072 in the lower part. Both the first oil return area 1071 and the second oil return area 1072 are rectangular, and the width of the first oil return area 1071 is greater than the width of the second oil return area 1072. The distance between the two connecting platforms 108 in the horizontal direction is the width of the second oil return area 1072. The first oil return area 1071 and the second oil return area 1072 are connected to each other, so that the lubricating oil sprayed on the gear set system can fall into the second oil return area 1072 after passing through the first oil return area 1071. Rib plates (not shown in the figure) are arranged in the first oil return area 1071 and the second oil return area 1072 to ensure the structural stability of the oil return cavity 107.

[0034] The connecting platform 108 is at the same height as the mounting boss 105, and the connecting platform 108 and the mounting boss 105 are integrally formed. The bottom surface of the connecting platform 108 is flush with the bottom surface of the mounting boss 105, and they jointly form a mounting plane 104 for mounting the gearbox.

[0035] An oil return port 103 communicating with the second oil return area 1072 is opened on the side wall of the sinking section 102. There is a gap between the lubricating oil return liquid level 106 in the oil return cavity 107 and the gears of the gear set system, so as to prevent the gears in the gear set system from contacting the lubricating oil in the oil return cavity 107, causing the gears to expand due to heat and resulting in the elevation of the gear shaft elevation.

[0036] In the process of evaluating the elevation amount of the gear shaft in the gearbox, it is usually considered that the distance between the mounting plane 104 and the gear shaft in the gearbox is the center height (as Figure 6 shown). In the present invention, by arranging the mounting boss 105 on the side wall of the lower box body 1, the mounting plane 104 is lifted compared with the prior art, that is, the center height of the gearbox is reduced, thereby reducing the elevation of the gear shaft caused by the thermal expansion of the box body. At the same time, the bottom surface of the lower box body 1 is moved downward to be set as a sunken structure. A gap is formed between the lubricating oil return liquid level in the oil return cavity and the gears of the gear set system, which can ensure that the gears do not contact the lubricating oil return liquid level 106. The lubricating oil in the oil return cavity 107 is located in the second oil return area 1072, which not only reduces the elevation amount of the high-speed shaft of the gearbox caused by the thermal expansion amount, but also does not affect the operating performance of the gearbox.

[0037] As shown Figure 1 、 2 As shown in Fig. 4, the gear set system includes a high-speed gear 10, an intermediate gear, and a low-speed gear 7. The intermediate gear includes an intermediate gear shaft 22, an intermediate gear A21 and an intermediate gear B23 arranged at both ends of the intermediate gear shaft 22. The intermediate gear A21 meshes with the high-speed gear 10, and the intermediate gear B23 meshes with the low-speed gear 7. The high-speed gear 10 and the low-speed gear 7 are located on the same axis, realizing a two-stage parallel shaft arrangement structure with no power split for the input / output of the gearbox. The rotation directions of the input shaft and the output shaft are the same, meeting the assembly requirements of the gas turbine.

[0038] The high-speed gear 10 is located on the high-speed gear shaft and transmits torque through meshing with the intermediate gear A21. The high-speed gear 10 is a single helical tooth, involute, and hard tooth surface gear. Both ends of the high-speed gear shaft extend out of the high-speed gear 10 and are respectively provided with a sliding bearing. The type is a tilting pad bearing. The bearing arranged towards the low-speed gear 7 is the high-speed support bearing 12, and the bearing arranged opposite to the low-speed gear 7 is the high-speed support thrust bearing 13. Combined Figure 4 、 5 As shown in Fig., the high-speed support thrust bearing 13 includes a support bearing 1301 and a thrust bearing 1302 that are detachably connected. The support bearing 1301 and the thrust bearing 1302 are detachably connected by an internal hexagonal bolt 1303.

[0039] When the gearbox is separately subjected to an unloaded test, the thrust bearing 1302 must be installed to bear the axial force generated by the gears. When the gas turbine unit is installed and operated, the thrust bearing 1302 in the high-speed support thrust bearing 13 needs to be removed, and the high-speed sleeve coupling is installed by moving the axial position of the high-speed shaft. The support bearing 1301 and the high-speed support bearing 12 provide support stiffness for the operation of the high-speed gear shaft, and the thrust bearing 1302 can bear the axial force generated during gear meshing.

[0040] On the high-speed gear shaft outside the high-speed support thrust bearing 13, a high-speed oil seal piece 14, a high-speed oil seal body 15, a high-speed wind blocking plate 17, and a high-speed end cover 18 are sequentially installed from inside to outside. A high-speed wind blocking plate spacer 16 is also arranged between the high-speed wind blocking plate 17 and the high-speed oil seal body 15. The high-speed end cover 18 is convenient for removing the thrust bearing 1302. The high-speed oil seal body 15 and the high-speed oil seal piece 14 are of a labyrinth non-contact seal to prevent the lubricating oil inside the gearbox from flowing out. The high-speed wind blocking plate 17 and the high-speed wind blocking plate spacer 16 can effectively weaken the "siphon" effect generated during the high-speed rotation of the sleeve coupling and avoid the seepage of the lubricating oil at the oil seal.

[0041] The low-speed gear 7 is located on the low-speed gear shaft and transmits torque by meshing with the intermediate gear B23. The low-speed gear 7 is a single helical tooth, involute, and hard tooth surface gear. Both ends of the low-speed gear shaft extend out of the low-speed gear 7 and are provided with two sliding bearings. The bearing type is a split bearing. The bearing towards the high-speed gear 10 is the low-speed support bearing 6, and the bearing opposite to the high-speed gear 10 is the low-speed support thrust bearing 5. Outside the low-speed support thrust bearing 5, a low-speed oil seal 4 and a low-speed wind baffle 2 are sequentially arranged from inside to outside. A low-speed wind baffle spacer 3 is also arranged between the low-speed wind baffle 2 and the low-speed oil seal 4. The support bearings in the low-speed support bearing 6 and the low-speed support thrust bearing 5 provide support stiffness for the operation of the low-speed gear 7, and the thrust bearing in the low-speed support thrust bearing 5 can bear the axial force generated during gear meshing. The low-speed oil seal 4 is a labyrinth non-contact seal to prevent the lubricating oil inside the gearbox from flowing out. The low-speed wind baffle 2 and the low-speed wind baffle spacer 3 can effectively weaken the "siphon" effect generated during the high-speed rotation of the coupling and avoid the leakage of lubricating oil at the oil seal.

[0042] Both ends of the intermediate gear shaft 22 extend out of the corresponding intermediate gear A21 and intermediate gear B23, and are respectively provided with a sliding bearing and an intermediate blind cover. The bearing type is a split bearing, as Figure 1 shown. The bearing arranged on the right side of the intermediate gear A21 is the intermediate support thrust bearing 20, and an intermediate blind cover A19 is arranged outside the intermediate support thrust bearing 20. The bearing arranged on the left side of the intermediate gear B23 is the intermediate support bearing 24, and an intermediate blind cover B25 is arranged outside the intermediate support bearing 24. The support bearings in the intermediate support thrust bearing 20 and the intermediate support bearing 24 provide support stiffness for the operation of the intermediate gear shaft 22. The thrust bearing in the intermediate support thrust bearing 20 can bear the axial force generated during the meshing of the intermediate gear A21 and the intermediate gear B23. The intermediate blind cover A19 and the intermediate blind cover B25 can prevent the lubricating oil from flowing out of the gearbox interior.

[0043] The intermediate gear shaft 22 meshes with the high-speed gear 10 and the low-speed gear 7 respectively through the intermediate gear A21 and the intermediate gear B23 to transmit torque. It is set that the meshing between the intermediate gear A21 and the high-speed gear 10 is the first-stage gear meshing, and the intermediate gear A21 and the high-speed gear 10 form a first-stage gear pair. The meshing between the intermediate gear B23 and the low-speed gear 7 is the second-stage gear meshing, and the intermediate gear B23 and the low-speed gear 7 form a second-stage gear pair. An oil spraying pipe is arranged in the gearbox to spray lubricating oil to the gear set system. Since the linear velocity of the first-stage gear pair is relatively high, a high-speed upper oil spraying pipe 11 is arranged on its upper side and a high-speed lower oil spraying pipe 9 is arranged on its lower side. The high-speed upper oil spraying pipe 11 is located on the meshing-in side of the first-stage gear pair. The lubricating oil enters with the gear meshing and mainly provides lubrication for the first-stage gear pair. The high-speed lower oil spraying pipe 9 is located on the meshing-out side of the first-stage gear pair. The lubricating oil does not enter with the gear meshing and mainly dissipates heat for the first-stage gear pair. A low-speed oil spraying pipe 8 is arranged on the upper side of the second-stage gear pair, and the low-speed oil spraying pipe 8 dissipates heat and lubricates the second-stage gear pair.

[0044] A breather cap and an upper end cap are arranged on the top of the upper housing 26. Among them, the breather cap includes a breather cap A28 and a breather cap B29, and the upper end cap includes an upper end cap A27 and an upper end cap B30. Both the upper end cap A27 and the upper end cap B30 are square and are arranged at intervals along the length direction of the upper housing 26. The breather cap A28 and the breather cap B29 are located between the upper end cap A27 and the upper end cap B30, and the breather cap A28 and the breather cap B29 are arranged along the width direction of the upper housing 26. Both the breather cap A28 and the breather cap B29 are circular. Both the upper end cap A27 and the upper end cap B30 are made of transparent materials such as glass and acrylic plates to facilitate observing the meshing state of the first-stage gear pair and the second-stage gear pair. Vent holes adapted to the breather cap A28 and the breather cap B29 are provided on the upper housing 26. The breather cap A28 and the breather cap B29 are both covered on the vent holes and can be removed from the vent holes, which can make the inside of the gearbox communicate with the outside atmosphere, balance the pressure difference inside and outside the gearbox, and prevent the lubricating oil inside the gearbox from leaking out.

[0045] The gas turbine gearbox described in the present utility model can be used on the current G15 gas turbine. The G15 gas turbine generates heat energy by burning combustible gas to drive the gas turbine rotor to rotate. The gas turbine rotor drives the high-speed gear shaft to rotate synchronously through a sleeve coupling. The high-speed gear 10 transmits torque to the intermediate gear A21 through the first-stage gear meshing, and then the intermediate gear B23 transmits torque to the low-speed gear 7 through the second-stage gear meshing. The low-speed gear shaft drives the generator rotor to rotate synchronously through a diaphragm coupling to generate electric energy.

[0046] In the gas turbine gearbox of the present utility model, the high-speed support thrust bearing 13 is composed of a thrust bearing 1302 and a support bearing 1301 that are detachably connected. When the gearbox is separately subjected to an unloaded test, the thrust bearing 1302 must be installed to bear the axial force generated by the gears. When the G15 gas turbine unit is installed and operated, the thrust bearing 1302 is removed, and the high-speed sleeve coupling is installed by moving the axial position of the high-speed gear shaft to meet the installation and operation requirements of the G15 gas turbine. Moreover, by adopting the layout type of three gear shafts in the present utility model, the high-speed gear 10 meshes with the intermediate gear A21, and the low-speed gear 7 meshes with the intermediate gear B23. The high-speed gear shaft and the low-speed gear shaft are on the same axis, and the input / output of the gearbox adopts a power non-split two-stage parallel shaft layout structure, and the rotation directions of the input shaft and the output shaft are the same, ensuring the installation and operation of the gas turbine.

[0047] In the present utility model, by arranging the mounting boss 105 of the gearbox on the side wall of the lower housing 1, the mounting plane 104 of the gearbox is raised, thereby reducing the center height of the gearbox. At the same time, the lower housing 1 is set as a sunken structure, and a gap is formed between the gear and the lubricating oil return liquid level 106, ensuring that the gear does not contact the lubricating oil return liquid level 106, reducing the contact between the relatively high-temperature lubricating liquid returning oil in the lower housing 1 and the side wall of the housing above the mounting plane 104, avoiding the thermal expansion caused by the contact between the gear and the lubricating oil in the oil return cavity, reducing the elevation difference of the gear shafts in the gearbox under hot and cold environments, and controlling the elevation increase of the high-speed shaft of the gearbox below 0.1 mm.

[0048] It can be understood that due to the high rotational speed of the high-speed shaft in the gearbox, affected by the double factors of the housing elevation and the thermal expansion of the gear itself, the elevation increase of the high-speed shaft is more obvious than that of other shafts. By reducing the elevation increase of the high-speed shaft in the present utility model, the elevation increases of other gear shafts such as the low-speed shaft in the gearbox can be effectively reduced. When the elevation increase of the high-speed shaft of the gearbox is lower than 0.1 mm, the elevation increases of other gear shafts can all be lower than 0.1 mm.

[0049] Application test:

[0050] Basic parameters of the gearbox: rated power 16500 KW, low-speed output speed 4800 rpm, high-speed input speed 9713 rpm, center height of the gearbox 800 mm, distance from the mid-plane of the gearbox to the bottom surface of the sunken part 1120 mm, linear velocity of the high-speed gear pair 147.6 m / s, linear velocity of the low-speed gear pair 107.6 m / s. After the gearbox operates at the rated speed for 4 hours, the elevation increase of the high-speed gear shaft is 0.08 mm.

[0051] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present utility model. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present utility model. Therefore, the present utility model will not be limited to the embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A combustion engine gearbox with low gear shaft elevation, comprising a housing, a gear set system arranged in the housing, and an oil spray pipe for spraying lubricating oil to the gear set system, wherein the housing comprises an upper housing (26) and a lower housing (1) arranged opposite to each other, characterized in that: The lower box body (1) is divided from top to bottom into a connecting section (101) and a sinking section (102), and the width of the sinking section (102) is smaller than the width of the connecting section (101). A mounting boss (105) protruding from the outer side surface of the lower box body (1) is provided at the junction of the sinking section (102) and the connecting section (101); An oil return chamber (107) is formed in the lower housing (1), and a connecting platform (108) is provided in the oil return chamber (107) at the same height as the mounting boss (105). The connecting platform (108) is used to divide the oil return chamber (107) into an upper first oil return area (1071) and a lower second oil return area (1072). The first oil return area (1071) and the second oil return area (1072) are connected, and the width of the second oil return area (1072) is smaller than the width of the first oil return area (1071). The side wall of the sinking section (102) is provided with an oil return port (103) connected to the second oil return area (1072), and a gap is formed between the lubricating oil return liquid level (106) in the oil return chamber (107) and the gears of the gear set system.

2. A gas turbine gearbox with low gear shaft elevation as claimed in claim 1, characterized in that: The gear set system comprises a high-speed gear (10), an intermediate gear and a low-speed gear (7), wherein the intermediate gear comprises an intermediate gear shaft (22), an intermediate gear A (21) and an intermediate gear B (23) arranged at both ends of the intermediate gear shaft (22), the intermediate gear A (21) meshes with the high-speed gear (10), the intermediate gear B (23) meshes with the low-speed gear (7), and the high-speed gear (10) and the low-speed gear (7) are located on the same axis.

3. A gas turbine gearbox with low gear shaft elevation as claimed in claim 2, characterized in that: Both ends of the high-speed gear shaft of the high-speed gear (10) extend out of the high-speed gear (10), and a high-speed support bearing (12) is arranged at one end facing the low-speed gear (7), and a high-speed support thrust bearing (13) is arranged at one end opposite to the low-speed gear (7).

4. A gas turbine gearbox with low gear shaft elevation as claimed in claim 3, characterized in that: The high-speed support thrust bearing (13) comprises a support bearing (1301) and a thrust bearing (1302) which are detachably connected.

5. A gas turbine gearbox with low gear shaft elevation as claimed in claim 3, characterized in that: A high-speed oil seal sheet (14), a high-speed oil seal body (15), a high-speed wind blocking plate (17) and a high-speed end cover (18) are sequentially installed on the high-speed gear shaft located outside the high-speed support thrust bearing (13) from the inside to the outside.

6. A gas turbine gearbox with low gear shaft elevation as claimed in claim 2, characterized in that: Both ends of the low-speed gear shaft of the low-speed gear (7) extend out of the low-speed gear (7), and a low-speed support bearing (6) is arranged at one end facing the high-speed gear (10), and a low-speed support thrust bearing (5) is arranged at one end facing away from the high-speed gear (10).

7. A gas turbine gearbox with low gear shaft elevation as claimed in claim 6, characterized in that: A low-speed oil seal (4) and a low-speed wind blocking plate (2) are sequentially installed on the low-speed gear shaft located outside the low-speed support thrust bearing (5) from the inside to the outside.

8. A gas turbine gearbox with low gear shaft elevation as claimed in claim 2, characterized in that: An intermediate support thrust bearing (20) is arranged on the intermediate gear shaft (22) located outside the intermediate gear A (21), and an intermediate support bearing (24) is arranged on the intermediate gear shaft (22) located outside the intermediate gear B (23).

9. A gas turbine gearbox with low gear shaft elevation as claimed in claim 2, characterized in that: Oil injection pipes are arranged on both upper and lower sides of the high-speed gear (10).

10. A gas turbine gearbox with low gear shaft elevation as claimed in claim 1, characterized in that: The upper box body (26) is provided with a ventilating cover and an upper end cover.

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