Axial unloading closed centripetal oil-gas turbine

Abstract

The invention relates to the field of aero-engine power systems, and provides an axially-unloaded closed centripetal oil-gas turbine which comprises a turbine moving blade disc (4) comprising a plurality of moving blades spaced from one another to form a plurality of flow channels; the turbine outer cover plate (1) covers one side of a movable blade of the turbine movable blade disc (4); the back assembly is arranged on the side, away from the turbine outer cover plate (1), of the turbine movable blade disc (4). And the multiple turbine stationary blades (3) are arranged at the peripheral edge of the turbine movable blade disc (4) and configured to guide airflow into a flow channel of the turbine movable blade disc (4), a through hole (41) except a shaft hole is formed in the center of the turbine movable blade disc (4), and the through hole (41) is configured to enable one side of the back assembly to be in fluid communication with the outlet side of the turbine movable blade disc (4). According to the axial unloading closed centripetal oil-gas turbine, the total axial force of the centripetal turbine can be reduced, the service life of the bearing is prolonged, and the running safety of the whole machine is improved.

Description

Technical Field

[0001] The invention relates to the field of aero-engine power systems, and in particular to an axially unloaded closed centripetal oil-gas turbine. Background Art

[0002] Hypersonic vehicles are often accompanied by the problem of "more heat and less electricity" when working. Given that scramjet engines lack rotating parts that can be directly used to drive generators to generate electricity, how to convert excess heat into electrical energy to achieve continuous power supply for airborne equipment has become a technical problem that cannot be ignored in the airborne energy management of hypersonic vehicles. Among various thermoelectric conversion technologies, oil and gas turbine power generation technology can use high-temperature and high-pressure oil and gas to drive the rotor parts in the turbine to rotate to output mechanical energy, and then drive the generator to generate electricity. This technology can make full use of the excess waste heat in the oil and gas to continuously provide electrical energy for the airborne equipment of hypersonic vehicles, and is expected to solve the technical problems mentioned above.

[0003] When designing an oil-gas turbine, considering that a large amount of bleed air will lead to a reduction in the efficiency of the engine's main cycle, the turbine intake volume will be constrained according to the required output power, and it is expected that the oil-gas turbine can provide sufficient output power while its size and mass are small, so as to minimize the space occupied by the whole machine, increase the payload of the hypersonic aircraft, and ensure that the power generation device can provide sufficient electricity. At present, the choice of oil-gas turbines is mainly divided into two categories: centrifugal turbines and axial flow turbines. The centrifugal turbine works through the action of centrifugal force and Coriolis inertial force, and can still achieve high power and high efficiency under the conditions of low intake volume and high speed. It also has the advantages of light weight and compact structure. Therefore, when designing an oil-gas turbine, a single-stage centrifugal turbine solution is often used.

[0004] In the design process of the centripetal oil-gas turbine, the axial force balance problem is a major difficulty. In aircraft, in order to avoid the film boiling of the fuel in the cooling channel and thus the deterioration of heat transfer, and to ensure that the fuel is well mixed in the combustion chamber, it is generally necessary for the pressure in the cooling channel to exceed the critical pressure of the fuel. Since the fuel is cracked at high temperature, the pressure in the cooling channel will continue to rise, and eventually the inlet pressure of the oil-gas turbine will reach 6MPa or even higher. The pressure of the cracked oil and gas after expansion in the turbine can also reach 1-3MPa. In this high-pressure environment, even if the turbine size is small and the total force area is small, the total axial force (pointing to the front disk of the turbine) it receives will reach more than 1000N. There is no coaxial component in the oil-gas turbine power generation device that supplies a similar magnitude of reverse axial force to the turbine. Most of the axial force will be transmitted to the casing through the bearing. Under the condition of long-term axial load overload, the working life of the bearing is greatly reduced, and the safety of the whole machine operation is seriously threatened. In summary, high absolute pressure and high load bring great challenges to the axial force balance of the turbine. Therefore, it is very necessary to design a centripetal turbine with a small total axial force.

[0005] Chinese patent application CN202310600265.4 (publication number CN117569871A) provides a high-pressure oil and gas centripetal turbine structure that takes into account the balance of axial force. It is also the applicant's application. It provides a solution for axial unloading of open turbines. The applicant has tried to apply the centripetal turbine structure to closed turbines in order to achieve the same effect of reducing axial force, but it was not satisfactory. There are relatively large differences between the two turbines. The same annular through hole is used in the center of the turbine impeller, and comb teeth are set at the mid-diameter position of the impeller. The test results cannot meet the requirements. For this reason, it is necessary to provide a solution for reducing the axial load specifically for closed centripetal oil and gas turbines. In view of this, the present invention is proposed. Summary of the invention

[0006] The object of the present invention is to at least partially overcome the defects of the prior art and provide a closed centripetal oil-gas turbine with axial unloading.

[0007] Another object of the present invention is to provide a closed centripetal oil-gas turbine with axial unloading, so as to reduce the total axial force of the centripetal turbine.

[0008] Another object of the present invention is to provide a closed centripetal oil-gas turbine with axial unloading to increase the service life of the bearing.

[0009] The present invention also aims to provide a closed centripetal oil-gas turbine with axial unloading to improve the operating safety of the whole machine.

[0010] To achieve the above purpose or one of the purposes, the technical solution of the present invention is as follows:

[0011] A closed centripetal oil and gas turbine with axial unloading, the oil and gas turbine comprising:

[0012] A turbine blade disk, comprising a plurality of blades spaced apart from one another to form a plurality of flow passages, wherein the flow passages are configured such that a circumferential airflow entering from an edge of the turbine blade disk flows through the blades and then flows out axially from a center of the turbine blade disk;

[0013] A turbine outer cover plate, which is arranged on one side of the moving blades of the turbine moving blade disk;

[0014] A back assembly is arranged on a side of the turbine blade disk away from the turbine outer cover plate; and

[0015] A plurality of turbine vanes are disposed at the outer peripheral edge of the turbine blade disk and are configured to guide airflow into the flow channel of the turbine blade disk.

[0016] A through hole other than the shaft hole is opened at the center of the turbine impeller, and the through hole is configured to allow one side of the back component to be in fluid communication with the outlet side of the turbine impeller.

[0017] According to a preferred embodiment of the present invention, the oil and gas turbine further comprises a turbine wheel cover, the turbine wheel cover is located between the moving blades of the turbine impeller and the turbine outer cover plate, and is sealed on the moving blades of the turbine impeller, so that the plurality of flow channels are closed on one side;

[0018] The turbine wheel cover and the turbine impeller are relatively fixed, so that the turbine wheel cover and the turbine impeller can rotate together.

[0019] According to a preferred embodiment of the present invention, there are multiple through holes.

[0020] According to a preferred embodiment of the present invention, a cross section of each through hole perpendicular to the axial direction of the oil-gas turbine is elliptical.

[0021] According to a preferred embodiment of the present invention, an extending direction of the through hole is parallel to the axial direction of the oil and gas turbine.

[0022] According to a preferred embodiment of the present invention, the through hole is configured such that the through hole twists along the circumferential direction of the turbine impeller during the process of extending from the side close to the back assembly to the outlet side of the turbine impeller.

[0023] According to a preferred embodiment of the present invention, there is a gap between the turbine outer cover plate and the turbine wheel cover, and comb teeth are arranged in the gap.

[0024] According to a preferred embodiment of the present invention, the comb teeth are arranged at a position close to the outlet side of the turbine rotor blade disk.

[0025] According to a preferred embodiment of the present invention, the comb teeth are provided on a side of the turbine wheel cover facing the turbine outer cover plate; or

[0026] The comb teeth are arranged on a side of the turbine outer cover plate facing the turbine wheel cover; or

[0027] The comb teeth are arranged on the sides of the turbine wheel cover and the turbine outer cover plate facing each other.

[0028] According to a preferred embodiment of the present invention, the turbine outer cover plate has two bent edges, and the two bent edges respectively cover two ends of the turbine wheel cover.

[0029] According to a preferred embodiment of the present invention, the oil and gas turbine further comprises a rotating shaft, and the turbine impeller is mounted on the rotating shaft in an interference fit manner.

[0030] According to a preferred embodiment of the present invention, the back side assembly comprises:

[0031] Bearings;

[0032] turbine casing;

[0033] A turbine back plate, the turbine back plate being installed inside the turbine casing;

[0034] a motor casing connected to a turbine back plate; and

[0035] The mechanical seal shell is fixedly connected to one side of the motor casing.

[0036] According to a preferred embodiment of the present invention, the portion of the rotating shaft close to the back assembly is fixedly connected to a sleeve by means of interference fit, and a step seal is provided on the sleeve;

[0037] The outer ring of the step seal is arranged in the mechanical seal housing, and a baffle is fixedly connected to a side of the mechanical seal housing away from the turbine impeller.

[0038] According to a preferred embodiment of the present invention, an expansion ring is provided between the motor casing and the mechanical seal housing.

[0039] According to the axially unloaded closed centripetal oil and gas turbine of the present invention, high-temperature and high-pressure oil and gas enter the oil and gas turbine through the turbine stator blade inlet port, the stator blade outlet port is connected to the turbine impeller disk inlet port, and the oil and gas will be divided into three air flows after passing through the stator blade. The main flow of oil and gas flows into the flow channel of the turbine impeller as the first airflow, and converts its kinetic energy and thermal energy into mechanical work of the turbine shaft in the turbine impeller by pushing the turbine impeller to rotate, and then flows out of the flow channel of the turbine impeller; a small part of the airflow (the second airflow) flows to the impeller cavity due to the influence of oil and gas leakage, so that a large pressure is generated at the impeller back disc (the side of the back component). Due to the pressure difference between the back disc and the turbine front disc (the side of the turbine outer cover plate), an axial force pointing to the turbine front disc will be generated. By performing elliptical through-hole treatment on the turbine impeller near the disc center, the impeller cavity of the turbine impeller is connected to the outlet of the turbine impeller, and the front and rear pressure difference of the turbine impeller is reduced. In addition, due to the existence of the elliptical through-hole, the total force-bearing area of ​​the front and rear discs of the turbine impeller is reduced at the same time, so that the total axial force on the turbine impeller is reduced, so that the total axial force of the oil and gas turbine is reduced.

[0040] Furthermore, the turbine impeller is processed with an elliptical through hole, which is more suitable for a closed turbine and achieves the purpose of reducing the axial load better than a circular or annular through hole. In addition, the elliptical through hole can better adjust its shape, reduce the total force area of ​​the turbine as much as possible, increase the through hole area, and reduce its total mass; if the structural strength design requirements are not met, the requirements can be met by adjusting the shape of the through hole. Furthermore, the design of the elliptical through hole provides additional geometric parameters (aspect ratio), which provides designers with more freedom to adapt to specific application requirements and operating conditions. When the structural strength design requirements are not met, the requirements can be met by processing the ratio of the major and minor axes of the ellipse, and this processing method can more conveniently adjust its knot. The elliptical through hole helps to achieve a more uniform stress distribution on the wheel disc, because the stress distribution in the major and minor axis directions of the ellipse may be different, and the curvature of the elliptical through hole helps to disperse these stress concentration points, thereby reducing local stress and offsetting uneven stress. The elliptical through holes are evenly distributed axially, and the number can be 4 or 6. The preferred number of the present invention is 6.

[0041] In addition, the turbine wheel cover is connected to the rim of the turbine impeller, and the turbine outer cover plate covers the outside of the turbine wheel cover. A small part of the oil and gas (the third airflow) will flow into the gap between the turbine wheel cover and the turbine outer cover plate. A grate is provided at the oil and gas outlet of the turbine wheel cover. The grate preferably has an angle of about 60° with the horizontal direction. The oil and gas are compressed by the flow channel in the tooth gap between the grate of the turbine wheel cover and the turbine outer cover plate (the gap between the tooth tip of the grate and the turbine outer cover plate), resulting in increased speed and reduced pressure, while in the tooth cavity As the flow channel suddenly expands, a strong vortex appears in the oil and gas. Therefore, the kinetic energy of the oil and gas is lost to a certain extent each time it passes through a tooth gap and tooth cavity, and its speed is continuously reduced. The sealing effect brought by the grate teeth on the turbine wheel cover is gradually improved. The grate tooth structure near the outlet end of the turbine impeller forms a high-efficiency throttling effect on the working medium in the gap between the turbine wheel cover and the turbine outer cover plate, which increases the pressure on the top surface of the turbine outer cover plate and generates an axial force pointing to the direction of the turbine back plate, which greatly reduces the total axial force of the turbine.

[0042] Therefore, the closed centripetal oil-gas turbine with axial unloading of the present invention reduces the total axial force of the centripetal turbine, thereby eliminating the need for the bearing to bear overload, thereby increasing the service life of the bearing and improving the operating safety of the entire machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 A cross-sectional schematic diagram of a closed centripetal oil-gas turbine with axial unloading according to an embodiment of the present invention;

[0044] Figure 2It is a partial three-dimensional view of a closed centripetal oil-gas turbine with axial unloading according to an embodiment of the present invention, wherein the positional relationship between the turbine outer cover plate and the turbine rotor blade disk is shown;

[0045] Figure 3 It is a partial three-dimensional view of a closed centripetal oil-gas turbine with axial unloading according to an embodiment of the present invention, wherein the turbine outer cover plate is removed, and the positional relationship between the turbine wheel cover and the turbine rotor blade disk is shown;

[0046] Figure 4 It is a stereoscopic view of a turbine rotor blade disk of an axially unloaded closed centripetal oil and gas turbine according to an embodiment of the present invention. DETAILED DESCRIPTION

[0047] Exemplary embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the same or similar reference numerals represent the same or similar elements. In addition, in the detailed description below, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the disclosed embodiments. However, it is apparent that one or more embodiments may also be implemented without these specific details. In other cases, known structures and devices are embodied in a schematic manner to simplify the accompanying drawings.

[0048] In order to solve the problem of the difficulty in balancing the axial force of the centripetal oil-gas turbine in the aircraft mentioned in the above background technology, the present invention proposes a closed centripetal oil-gas turbine for high absolute pressure working fluids, which takes into account the problem of the difficulty in balancing the axial force of the closed centripetal oil-gas turbine, greatly reduces the total axial force of the centripetal turbine, and alleviates the problem of the difficulty in balancing the axial force of the oil-gas turbine to a certain extent. The following is a detailed description of the closed centripetal oil-gas turbine with axial unloading (balancing axial force) of the embodiment of the present invention in conjunction with the accompanying drawings. Figure 1 As shown, the oil and gas turbine includes a turbine outer cover plate 1, a turbine wheel cover 2, a turbine stator blade 3, a turbine moving blade disk 4, a shaft end nut 5, a shaft end retaining ring 6, a rotating shaft 7, a step seal 8, a shaft sleeve 9, a baffle 10, a mechanical seal housing 11, a countersunk screw 12, a motor casing 13, a turbine back plate 14, and a turbine casing 15.

[0049] The turbine impeller 4 includes a plurality of impeller blades spaced apart from each other to form a plurality of flow passages, such as Figure 4 As shown, the flow channel is configured so that the circumferential airflow entering from the edge of the turbine impeller 4 flows through the impeller blades and then flows out from the central axial direction of the turbine impeller 4; the turbine outer cover plate 1 is arranged on one side of the impeller blades of the turbine impeller 4; the turbine wheel cover 2 is located between the impeller blades of the turbine impeller 4 and the turbine outer cover plate 1, and is sealed on the impeller blades of the turbine impeller 4, so that the multiple flow channels are closed on one side, and the turbine wheel cover 2 is relatively fixed to the turbine impeller 4, so that the turbine wheel cover 2 and the turbine impeller 4 can rotate together.

[0050] The baffle 10, the mechanical seal housing 11, the motor casing 13, the turbine back plate 14, and the turbine casing 15 together serve as a back assembly, and are arranged on the side of the turbine impeller 4 away from the turbine outer cover plate 1; a plurality of turbine stationary blades 3 are arranged at the outer peripheral edge of the turbine impeller 4, and are configured to guide the airflow into the flow channel of the turbine impeller 4. Among them, the air outlet port of the stationary blade 3 is connected to the air inlet port of the turbine impeller 4, the turbine wheel cover 2 is connected to the wheel rim of the turbine impeller 4, and the turbine outer cover plate 1 covers the outer side of the turbine wheel cover 2, and the two are not connected.

[0051] Preferably, the turbine outer cover plate 1 has two bent edges, and the two bent edges cover the two ends of the turbine wheel cover 2 respectively. Figure 1 shown.

[0052] Since the fully enclosed turbine wheel cover is connected to the moving blades of the present invention, when the airflow flows into the moving blade flow channel, the turbine wheel cover can provide good sealing performance to reduce gas leakage. Compared with an open turbine, the moving blades in the present invention reduce gap leakage losses and can achieve higher efficiency.

[0053] The turbine wheel cover is connected to the rim of the turbine blades, completely enclosing the turbine flow channel and providing a continuous geometric structure. The uninterrupted structure helps to maintain the overall stiffness, thereby exhibiting higher bending and torsion resistance in mechanical properties; the wheel cover and the blades form a seamless whole, so that the mechanical stress and thermal stress acting on the turbine can be evenly distributed on the entire wheel disc, reducing local stress concentration; the closed turbine exhibits lower dynamic imbalance and vibration response when rotating at high speed, which helps to improve the stability and reliability of the turbine in long-term operation. The structural integrity and uniform stress distribution of the closed turbine help to extend the service life of the turbine and reduce the risk of damage and failure due to fatigue.

[0054] The rotating shaft 7 is a stepped rotating shaft, forming multiple rotating shaft sections with different diameters, and the turbine impeller 4 is installed on the middle section of the rotating shaft 7 in an interference fit manner. The portion of the rotating shaft 7 close to the back assembly is fixedly connected with a sleeve 9 by means of an interference fit. The back assembly mainly includes a bearing, a turbine casing 15, a turbine back plate 14, a motor casing 13 and a mechanical seal housing 11. The bearing is arranged on the sleeve 9, the turbine casing 15 forms a housing surrounding the back assembly, the turbine back plate 14 is installed inside the turbine casing 15, the motor casing 13 is connected to the turbine back plate 14, and the mechanical seal housing 11 is fixedly connected to one side of the motor casing 13 by a countersunk screw 12, and an expansion ring is arranged between the motor casing 13 and the mechanical seal housing 11. The rotating shaft 7 is installed with a shaft end retaining ring 6 on the outlet side close to the turbine impeller 4, and a shaft end nut 5 is connected to the side of the shaft end retaining ring 6 away from the turbine impeller 4. The shaft sleeve 9 is provided with a step seal 8, an outer ring of the step seal 8 is provided in a mechanical seal housing 11, and a baffle 10 is fixedly connected to the side of the mechanical seal housing 11 away from the turbine impeller 4 to seal the airflow at the gap of the back side component.

[0055] In particular, a through hole 41 is provided in the center of the turbine impeller 4 in addition to the shaft hole, and the through hole 41 is configured to allow one side of the back component to be fluidically connected to the outlet side of the turbine impeller 4, such as Figure 1 Advantageously, the number of the through holes 41 is multiple. In the illustrated embodiment, the number of the through holes 41 is six, but the through holes 41 may have other numbers, such as 3, 4, 5 or more, among which six through holes 41 are preferred.

[0056] Specifically, the through hole 41 is an elliptical through hole, which is a special shape used for the closed turbine. Through experimental comparison, the elliptical through hole better achieves the purpose of reducing the axial load, that is, the cross section of each through hole 41 perpendicular to the axial direction of the oil and gas turbine is elliptical. In order to make the side of the back component communicate with the fluid on the outlet side of the turbine impeller 4, the extension direction of the through hole 41 is most directly set to be parallel to the axial direction of the oil and gas turbine. However, the applicant found that the through hole 41 can also be configured so that the through hole 41 twists along the circumference of the turbine impeller 4 during the process of extending from the side close to the back component to the outlet side of the turbine impeller 4. When the twisting direction of the through hole 41 is consistent with the twisting direction of the blades of the turbine impeller 4, the fluid connection effect is better. For this purpose, the twisting directions of multiple through holes 41 can be set to be the same and synchronized with the twisting angle of the blades of the turbine impeller 4.

[0057] The turbine impeller is a device that converts the kinetic energy and thermal energy of the oil and gas from the stationary blades into mechanical work of the turbine shaft. It is treated with elliptical through holes near the center of the disc. The through holes are evenly distributed along the axial direction, which can reduce the weight of the turbine, increase the effective load, and connect the impeller cavity with the outlet side of the turbine impeller. The front and rear force-bearing surfaces of the turbine are reduced and the front and rear pressures are balanced to reduce the total axial force of the turbine.

[0058] As an extended embodiment of the present invention, the twisting directions of adjacent through holes 41 among the multiple through holes 41 are opposite, and in the through holes 41 twisted in the same direction, the twisting angles of the through holes 41 are gradually increased in sequence. In this way, it can be ensured that when the turbine impeller 4 is driven to rotate at different rotational speeds, both the back component side and the outlet side of the turbine impeller 4 have better pressure-passing effects.

[0059] Further, there is a gap between the turbine outer cover plate 1 and the turbine wheel cover 2, and a grate 21 is provided in the gap, and preferably, the grate 21 is provided at a position close to the outlet side of the turbine impeller 4. Specifically, the grate 21 is provided on the side of the turbine wheel cover 2 facing the turbine outer cover plate 1; or the grate 21 is provided on the side of the turbine outer cover plate 1 facing the turbine wheel cover 2; or the grate 21 is provided on the sides of the turbine wheel cover 2 and the turbine outer cover plate 1 facing each other.

[0060] When the turbine wheel cover is a wheel cover structure with comb teeth near the outlet end of the moving blades, the throttling of oil and gas generates a wheel cover axial force that can offset the axial force of the turbine back, so that the total axial force of the turbine is lower than the total axial force of the oil and gas turbine without a wheel cover. In addition, the turbine outer cover plate covers and is fixed to the outer side of the turbine wheel cover, and cooperates with the turbine wheel cover to generate a force that can offset the axial force of the turbine back.

[0061] In practical applications, the comb teeth are trapezoidal comb teeth, and the number of trapezoidal comb teeth is usually 3 to 5. However, due to different working conditions, such as changes in temperature, pressure, flow rate and other factors, the total axial force exerted on the turbine will also be different. This requires that when designing the comb teeth, adjustments should be made according to specific working conditions. The size of the elliptical through hole of the turbine impeller in the present invention is also an important factor affecting the total axial force. When designing the comb teeth, it is necessary to comprehensively consider the influence of the elliptical through hole of the turbine impeller and the specific needs of the turbine, and determine the most suitable comb tooth size and number through precise calculation and simulation analysis.

[0062] According to the axially unloaded closed centripetal oil and gas turbine of the present invention, high-temperature and high-pressure oil and gas enter the oil and gas turbine through the turbine stator blade inlet port, the stator blade outlet port is connected to the turbine impeller disk inlet port, and the oil and gas will be divided into three air flows after passing through the stator blade. The main flow of oil and gas flows into the flow channel of the turbine impeller as the first airflow, and converts its kinetic energy and thermal energy into mechanical work of the turbine shaft in the turbine impeller by pushing the turbine impeller to rotate, and then flows out of the flow channel of the turbine impeller; a small part of the airflow (the second airflow) flows to the impeller cavity due to the influence of oil and gas leakage, so that a large pressure is generated at the impeller back disc (the side of the back component). Due to the pressure difference between the back disc and the turbine front disc (the side of the turbine outer cover plate), an axial force pointing to the turbine front disc will be generated. By performing elliptical through-hole treatment on the turbine impeller near the disc center, the impeller cavity of the turbine impeller is connected to the outlet of the turbine impeller, and the front and rear pressure difference of the turbine impeller is reduced. In addition, due to the existence of the elliptical through-hole, the total force-bearing area of ​​the front and rear discs of the turbine impeller is reduced at the same time, so that the total axial force on the turbine impeller is reduced, so that the total axial force of the oil and gas turbine is reduced.

[0063] Furthermore, the turbine impeller is processed with an elliptical through hole, which is more suitable for a closed turbine and achieves the purpose of reducing the axial load better than a circular or annular through hole. In addition, the elliptical through hole can better adjust its shape, reduce the total force area of ​​the turbine as much as possible, increase the through hole area, and reduce its total mass; if the structural strength design requirements are not met, the requirements can be met by adjusting the shape of the through hole. Furthermore, the design of the elliptical through hole provides additional geometric parameters (aspect ratio), which provides designers with more freedom to adapt to specific application requirements and operating conditions. When the structural strength design requirements are not met, the requirements can be met by processing the ratio of the major and minor axes of the ellipse, and this processing method can more conveniently adjust its knot. The elliptical through hole helps to achieve a more uniform stress distribution on the wheel disc, because the stress distribution in the major and minor axis directions of the ellipse may be different, and the curvature of the elliptical through hole helps to disperse these stress concentration points, thereby reducing local stress and offsetting uneven stress. The elliptical through holes are evenly distributed axially, and the number can be 4 or 6. The preferred number of the present invention is 6.

[0064] In addition, the turbine wheel cover is connected to the rim of the turbine impeller, and the turbine outer cover plate covers the outside of the turbine wheel cover. A small part of the oil and gas (the third airflow) will flow into the gap between the turbine wheel cover and the turbine outer cover plate. A grate is provided at the oil and gas outlet of the turbine wheel cover. The grate preferably has an angle of about 60° with the horizontal direction. The oil and gas are compressed by the flow channel in the tooth gap between the grate of the turbine wheel cover and the turbine outer cover plate (the gap between the tooth tip of the grate and the turbine outer cover plate), resulting in increased speed and reduced pressure, while in the tooth cavity As the flow channel suddenly expands, a strong vortex appears in the oil and gas. Therefore, the kinetic energy of the oil and gas is lost to a certain extent each time it passes through a tooth gap and tooth cavity, and its speed is continuously reduced. The sealing effect brought by the grate teeth on the turbine wheel cover is gradually improved. The grate tooth structure near the outlet end of the turbine impeller forms a high-efficiency throttling effect on the working medium in the gap between the turbine wheel cover and the turbine outer cover plate, which increases the pressure on the top surface of the turbine outer cover plate and generates an axial force pointing to the direction of the turbine back plate, which greatly reduces the total axial force of the turbine.

[0065] Therefore, the closed centripetal oil-gas turbine with axial unloading of the present invention reduces the total axial force of the centripetal turbine, thereby eliminating the need for the bearing to bear overload, thereby increasing the service life of the bearing and improving the operating safety of the entire machine.

[0066] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made to these embodiments without departing from the principles and spirit of the present invention. The scope of application of the present invention is defined by the appended claims and their equivalents.

[0067] List of reference numerals:

[0068] 1. Turbine outer cover;

[0069] 2. Turbine wheel cover;

[0070] 21. Comb teeth;

[0071] 3. Turbine stator blades;

[0072] 4. Turbine impeller;

[0073] 41. Through hole;

[0074] 5. Shaft end nut;

[0075] 6. Shaft end retaining ring;

[0076] 7. Rotating shaft;

[0077] 8. Stephon;

[0078] 9. Bushing;

[0079] 10. Baffle;

[0080] 11. Mechanical seal housing;

[0081] 12. Countersunk screws;

[0082] 13. Motor casing;

[0083] 14. Turbine back plate;

[0084] 15. Turbine casing.

Claims

1. A closed centripetal oil and gas turbine with axial unloading, characterized in that: The oil and gas turbine comprises: A turbine impeller (4) comprising a plurality of impeller blades spaced apart from one another to form a plurality of flow passages, wherein the flow passages are configured such that a circumferential airflow entering from an edge of the turbine impeller (4) flows through the impeller blades and then flows out axially from a center of the turbine impeller (4); A turbine outer cover plate (1) is arranged to cover one side of the moving blades of the turbine moving blade disk (4); A back assembly is arranged on a side of the turbine impeller (4) away from the turbine outer cover plate (1); and A plurality of turbine stator blades (3) are arranged at the outer peripheral edge of the turbine impeller (4) and are configured to guide airflow into the flow channel of the turbine impeller (4). A through hole (41) other than the shaft hole is opened at the center of the turbine impeller (4), and the through hole (41) is configured to allow one side of the back component to be fluidically connected to the outlet side of the turbine impeller (4).

2. The closed centripetal oil-gas turbine with axial unloading according to claim 1, characterized in that: The oil and gas turbine further comprises a turbine wheel cover (2), wherein the turbine wheel cover (2) is located between the moving blades of the turbine impeller (4) and the turbine outer cover plate (1), and covers the moving blades of the turbine impeller (4), so that the plurality of flow channels are closed on one side; The turbine wheel cover (2) and the turbine impeller (4) are relatively fixed, so that the turbine wheel cover (2) and the turbine impeller (4) can rotate together.

3. The closed centripetal oil-gas turbine with axial unloading according to claim 2, characterized in that: The number of the through holes (41) is plural.

4. The closed centripetal oil-gas turbine with axial unloading according to claim 3 is characterized in that: The cross section of each through hole (41) perpendicular to the axial direction of the oil-gas turbine is elliptical.

5. The closed centripetal oil-gas turbine with axial unloading according to claim 4, characterized in that: The extending direction of the through hole (41) is parallel to the axial direction of the oil and gas turbine.

6. The closed centripetal oil-gas turbine with axial unloading according to claim 4, characterized in that: The through hole (41) is configured such that the through hole (41) twists along the circumferential direction of the turbine impeller (4) in the process of extending from the side close to the back component to the outlet side of the turbine impeller (4).

7. The closed centripetal oil-gas turbine with axial unloading according to claim 4, characterized in that: There is a gap between the turbine outer cover plate (1) and the turbine wheel cover (2), and (21) is arranged in the gap.

8. The axially unloaded closed centripetal oil-gas turbine according to claim 7, characterized in that: The comb teeth (21) are arranged at a position close to the outlet side of the turbine impeller (4).

9. The closed centripetal oil-gas turbine with axial unloading according to claim 7, characterized in that: The comb teeth (21) are arranged on a side of the turbine wheel cover (2) facing the turbine outer cover plate (1); or The comb teeth (21) are arranged on a side of the turbine outer cover plate (1) facing the turbine wheel cover (2); or The comb teeth (21) are both arranged on the sides of the turbine wheel cover (2) and the turbine outer cover plate (1) facing each other.

10. The closed centripetal oil-gas turbine with axial unloading according to any one of claims 2 to 9, characterized in that: The turbine outer cover plate (1) has two bent edges, and the two bent edges respectively cover two ends of the turbine wheel cover (2).

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