High-pressure oil-gas radial turbine structure considering axial force balance

Abstract

The application discloses a high-pressure oil-gas radial turbine structure considering axial force balance, relates to the technical field of turbomachinery engineering, and comprises a turbine front cover plate, an impeller and a turbine casing, wherein a back cover plate is arranged in the turbine casing, the back cover plate is connected with the motor casing, a motor casing side is fixedly connected with a mechanical seal shell through a countersunk screw, an expansion ring is arranged between the mechanical seal shell and the motor casing, the impeller is fixedly installed on a rotating shaft through interference fit, a shaft end baffle ring is arranged on one side of the rotating shaft, a shaft end nut is threadedly connected to the side of the rotating shaft away from the impeller, a shaft sleeve is installed on the side of the rotating shaft away from the shaft end nut through interference fit, and a Stelflex seal is arranged on the shaft sleeve. Through adoption of the arc-shaped blade, the annular through hole and the trapezoidal labyrinth structure, the pressure difference between the front and back discs of the impeller is reduced, the stress area of the front and back discs of the impeller is reduced, and the total axial force borne by the impeller is greatly reduced without changing the main flow direction.

Description

Technical Field

[0001] This invention relates to the field of turbomachinery engineering technology, specifically to a high-pressure oil-gas centrifugal turbine structure that takes into account axial force balance. Background Technology

[0002] "High heat and low power" is one of the key problems that urgently needs to be solved in the design of hypersonic vehicles. On the one hand, in hypersonic flight, the vehicle not only needs to withstand the heat dissipation of high-power airborne equipment and combustion heat load, but also faces external aerodynamic heat problems, making the "high heat" problem prominent. On the other hand, the diversification of the vehicle's functions leads to a surge in the power consumption of airborne equipment, but the vehicle can only carry a very limited amount of electricity. Moreover, since hypersonic vehicles lack rotating parts, the traditional solution of using a shaft to drive a generator is difficult to implement, thus the "low power" problem is very serious. To solve the "high heat and low power" problem of hypersonic vehicles, a feasible solution is to use the aviation kerosene carried by the vehicle to absorb a large amount of heat to reduce the thermal protection pressure of the vehicle. At the same time, the high-temperature and high-pressure mixed oil and gas generated after the aviation kerosene is cracked can drive the turbine to rotate and drive the generator to generate electricity. This power generation method is called "oil-gas turbine power generation".

[0003] Unlike conventional turbine power generation units, oil-gas turbine power generation faces a unique operating environment: the pressure of the mixed oil and gas after aviation kerosene cracking is typically as high as 5-6 MPa, and the gas pressure after expansion reaches 1-3 MPa. Under this high-pressure environment, the total axial force before and after the oil-gas turbine can reach approximately 2000 N, making bearing selection extremely difficult. Furthermore, due to the high pressure on the turbine's front and rear surfaces, the total axial force is highly sensitive to changes in the impeller structure; even slight changes in the impeller structure can lead to significant variations in the total axial force, or even cause the axial force to reverse.

[0004] In existing technologies, such as CN111255522.A, a balance disc is interference-fitted onto the high-pressure turbine disk to adjust the axial force of the high-pressure rotor system, and a grate-tooth sealing structure is provided at the top of the balance disc. By adjusting the grate tooth gap and the radial dimension of the balance disc, the pressure difference on both sides of the balance disc is changed, thereby adjusting the axial force of the system. However, the addition of the balance disc not only increases the weight of the turbine disk but also leads to turbine disk strength problems. While reducing the load, it also reduces the reliability of turbine components, making it unsuitable for oil and gas turbine power generation devices. Patent CN 102322443 A proposes a centrifugal pump impeller with a balance hole of a small diameter and a certain tilt angle, which can achieve axial force balance, but its application environment is limited. In the high-temperature environment (around 1000K) of oil and gas turbines, the turbine impeller will inevitably undergo significant deformation due to heat. The narrow gaps between the front pump cover and the front inlet ring, and between the rear cover plate inlet ring and the rear pump cover, as described in this patent, are difficult to guarantee, which will inevitably weaken its ability to balance axial force in oil and gas turbine power generation systems. Therefore, this invention designs an impeller and axial force balancing method for a single-stage centripetal turbine for cracked oil and gas media to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a high-pressure oil-gas centrifugal turbine structure that takes into account axial force balance, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a high-pressure oil-gas centrifugal turbine structure considering axial force balance, comprising a turbine front cover plate, an impeller, and a turbine casing. A wheel back cover plate is installed inside the turbine casing, and the wheel back cover plate is connected to a motor casing. A mechanical seal housing is fixedly connected to one side of the motor casing by countersunk screws. An expansion ring is placed between the mechanical seal housing and the motor casing. The impeller is fixedly mounted on a rotating shaft by an interference fit. A shaft end retaining ring is fitted on one side of the rotating shaft, and a shaft end nut is threadedly connected to the side of the rotating shaft away from the impeller. A shaft sleeve is fixedly connected to the side of the rotating shaft away from the shaft end nut by an interference fit. A step seal is fitted on the shaft sleeve, and the outer ring of the step seal is located inside the mechanical seal housing. A baffle is provided at the upper end of one side of the shaft sleeve, and the baffle is fixedly connected to the mechanical seal housing by countersunk screws, which can seal the airflow in the impeller back clearance.

[0007] In a further embodiment, the wheel back cover plate is interference-fitted with both the turbine casing and the motor casing, and the axial positioning of the motor casing and the wheel back cover plate is achieved by means of a boss.

[0008] In a further embodiment, an annular through hole is provided near the center of the impeller. The annular through hole is evenly distributed circumferentially and communicates with the turbine back disk cavity and the turbine outlet. Its main function is to reduce the weight of the impeller disk to increase the load capacity. By balancing the pressure in the disk cavity at the low radius of the impeller, the effect of the front and rear axial forces of the impeller is reduced. The annular through hole is evenly distributed circumferentially to prevent large eccentric vibrations caused by uneven mass distribution during impeller rotation.

[0009] In a further embodiment, trapezoidal grates are provided at the middle diameter of the impeller. The main function is to facilitate the formation of a vortex aerodynamic structure after the airflow in the back gap enters the grates, thereby playing a certain role in obstructing the airflow and preventing too much airflow from entering the annular through hole through the back gap, thus improving the turbine aerodynamic performance.

[0010] In a further embodiment, the impeller's median diameter grate is an axial grate structure. By effectively throttling the airflow in flow path b, the airflow pressure can be reduced, thereby further reducing the axial force on the turbine backplate.

[0011] In a further embodiment, the impeller is provided with multiple arc-shaped blades at equal intervals. Their main function is to ensure that the blades contact the airflow at the guide vane outlet with an optimal blade angle, avoiding strong flow separation and significant secondary flow losses at the turbine blade suction surface, thus improving energy conversion efficiency. To prevent structural strength issues with the blades after material removal, the bottom of the arc-shaped blades is more biased towards the turbine blade suction surface to prevent significant stress concentration at the blade root when the airflow pushes the blades. Furthermore, the back of the impeller is also thickened to further prevent turbine blade flutter.

[0012] Compared with the prior art, the beneficial effects of the present invention are:

[0013] The key point of this invention is to change the impeller structure to adjust the airflow and force-bearing area inside the turbine, thereby reducing the total axial force and avoiding complicating the structure of the oil-gas turbine.

[0014] 1. By using arc-shaped blades, the pressure difference between the front and rear discs of the impeller is reduced and the force-bearing area of ​​the front and rear discs of the impeller is reduced without changing the main flow direction, thereby significantly reducing the total axial force of the impeller.

[0015] 2. Multiple annular through holes are designed between the front and rear impeller discs to facilitate communication between the airflow on the impeller back disc and the airflow at the turbine outlet, further reducing the airflow pressure on the turbine back disc and the weight of the impeller, and effectively reducing the total axial force and load.

[0016] 4. The trapezoidal grates are located near the impeller's median diameter, completely avoiding the high-temperature area near the turbine inlet. This greatly reduces the centrifugal force on the impeller and significantly reduces the deformation of the grates, thus ensuring that the grates maintain a sufficiently small sealing gap during operation and achieve a good sealing effect under most working conditions. Attached Figure Description

[0017] Figure 1 This is a cross-sectional view of the axial force balance scheme for a single-stage radial turbine of the present invention.

[0018] Figure 2 A front view of the impeller structure for the invention;

[0019] Figure 3 This is a rotating cross-sectional view of the impeller of the present invention;

[0020] Figure 4 This is a three-dimensional view of the impeller of the present invention.

[0021] In the diagram: 1. Shaft end nut; 2. Shaft end retaining ring; 3. Rotating shaft; 4. Impeller; 41. Annular through hole; 42. Trapezoidal grate teeth; 43. Arc-shaped blade; 5. Shaft sleeve; 6. Step seal; 7. Baffle; 8. Countersunk screw; 9. Mechanical seal housing; 10. Motor casing; 11. Wheel back cover plate; 12. Turbine casing; 13. Guide vane; 14. Turbine front cover plate. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1

[0024] Please see Figure 1-4 This embodiment provides a high-pressure oil-gas centrifugal turbine structure that considers axial force balance. The main structure includes: shaft end nut 1, shaft end retaining ring 2, rotating shaft 3, impeller 4, shaft sleeve 5, step seal 6, baffle 7, countersunk screw 8, mechanical seal housing 9, motor housing 10, wheel back cover plate 11, turbine housing 12, guide vane 13, and turbine front cover plate 14.

[0025] A turbine casing 12 houses a wheel back cover plate 11, and a motor casing 10 is installed inside the wheel back cover plate 11. A mechanical seal housing 9 is fixedly connected to one side of the motor casing 10 by countersunk screws 8. An expansion ring is placed between the mechanical seal housing 9 and the motor casing 10. The impeller 4 is fixedly mounted on the shaft 3 by an interference fit. A shaft end retaining ring 2 is fitted on one side of the shaft 3, and a shaft end nut 1 is threadedly connected to the side of the shaft 3 away from the impeller 4. A shaft sleeve 5 is fixedly connected to the side of the shaft 3 away from the shaft end nut 1 by an interference fit. A step seal 6 is fitted on the shaft sleeve 5, and the outer ring of the step seal 6 is located inside the mechanical seal housing 9. A baffle 7 is provided at the upper end of one side of the shaft sleeve 5, and the baffle 7 is fixedly connected to the mechanical seal housing 9 by countersunk screws 8, which can seal the airflow in the wheel back gap of the impeller 4.

[0026] A guide vane 13 is provided between the turbine front cover plate 14 and the turbine casing 12, and the gap between the turbine front cover plate 14 and the impeller 4 forms the main flow path a and the guide airflow b.

[0027] The guide vane 13, turbine casing 12, wheel back cover 11 and turbine front cover 14 serve to guide the airflow in the main flow path a.

[0028] Specifically, after the airflow enters the turbine rotor channel from the guide vane 13, it is divided into two airflows. One is the main flow path airflow a, which flows along the turbine blades. Under the guidance of the wheel back cover plate 11 and the turbine front cover plate 14, the mixed oil and gas in the main flow path expands and does work to drive the impeller 4 to rotate, and then flows out of the turbine blade channel. The other is the airflow in the wheel back gap flow path b, which enters the annular through hole 41 after being throttled by the trapezoidal grate teeth 42. Afterward, it will merge with the main flow path airflow a and be discharged from the turbine. During this period, the motor casing 10, the mechanical seal housing 9, the step seal 6, and the bushing 5 will guide and seal the airflow b.

[0029] Example 2

[0030] Please see Figure 1-3 Further improvements were made based on Example 1:

[0031] The annular through holes 41 are evenly distributed circumferentially and are connected to the turbine back disk cavity and turbine outlet, which can reduce the axial force in front and behind the impeller 4.

[0032] An annular through-hole 41 is provided near the center of the impeller 4. Its main function is to reduce the weight of the impeller disc, thereby increasing the load capacity, and to balance the pressure in the disc cavity at the low radius of the impeller 4, thus reducing the axial force on the front and rear of the impeller 4. Compared with a circular through-hole, the shape of the annular through-hole 41 can be adjusted more easily during the design process, minimizing the self-weight of the impeller 4 as much as possible. In particular, by adjusting the radius of the corners around the annular through-hole, the structure of the impeller 4 can be optimized more easily, thereby meeting the impeller strength design requirements.

[0033] Trapezoidal grates 42 are also provided at the middle diameter position of the impeller 4. The trapezoidal grates 42 maintain an inclination angle of about 60° to 70° with the horizontal direction. Their main function is to facilitate the formation of a vortex structure after the airflow in the back gap enters the grates, thereby playing a certain role in obstructing the airflow and preventing too much airflow from entering the annular through hole 41, thus improving the turbine aerodynamic performance.

[0034] The impeller's intermediate diameter grate adopts an axial grate structure. Compared with radial grates, it can reduce the axial force on the turbine back plate to a greater extent while achieving the same throttling effect, thus improving the overall axial force control.

[0035] The number of trapezoidal grates 42 can be set to 3-5, with 3 being the preferred number. The number and size of the annular through holes 41 will affect the stress area of ​​the turbine disk and the airflow through the trapezoidal grates 42. Therefore, the specific design selection can be combined with the structural strength calculation of the turbine disk and the airflow obstruction effect of the trapezoidal grates 42.

[0036] By positioning the trapezoidal grate 42 at the middle diameter of the impeller 4, the huge centrifugal force generated when the trapezoidal grate 42 is located at the rim of the impeller 4 avoids additional structural strength problems for the impeller 4. It also prevents the trapezoidal grate 42 from being subjected to strong thermal loads and causing large thermal deformation in the high-temperature area at the inlet of the impeller 4.

[0037] The trapezoidal grate 42 is located at the center of the turbine diameter, which ensures that the trapezoidal grate 42 structure maintains sufficient sealing clearance during operation, achieving the sealing effect required by the design.

[0038] Multiple arc-shaped blades 43 are equidistantly arranged on the impeller 4, with blade angles of 50°-80°, preferably 55.6°. The turbine blades are arc-shaped blades, also known as backward-curved blades. Their main function is to enable the blades to contact the outlet airflow of the guide vane 13 at the optimal blade angle, thereby avoiding significant flow separation and large secondary flow losses on the suction surface of the turbine blades and improving energy conversion efficiency.

[0039] Furthermore, there is a V-shaped groove between two adjacent arc blades 43, and the root of the groove is slightly biased towards the suction surface, so that the root of the pressure surface of the arc blade 43 has sufficient thickness to ensure that the arc blade 43 can withstand greater tensile stress during operation, reducing the force-bearing area in front and behind the impeller 4, thereby reducing the difference in axial force between the front and back of the turbine.

[0040] To prevent structural strength issues in the curved blade 43 after material removal, the bottom of the V-shaped deep groove is more biased towards the suction surface of the turbine blade, so as to prevent large stress concentration at the root of the curved blade 43 when the airflow pushes it.

[0041] In addition, to prevent the arc-shaped blades 43 of the impeller 4 from experiencing severe chattering during high-speed rotation, the arc-shaped blades are appropriately thickened towards the back cover plate 11 in this invention to improve the stiffness of the arc-shaped blades 43 and avoid severe chattering of the turbine blades.

[0042] The specific usage method is as follows: After the guide vane 13 ejects a high-temperature and high-pressure airflow into the impeller 4, it splits into two flow paths: the main flow path a and the gap flow path b of the impeller back cover plate 11. In the main flow path a, the airflow enters the main flow channel along the arc-shaped blade 43 and expands in the flow channel, doing work to drive the impeller 4 to rotate. The airflow exerts a backward axial force on the arc-shaped blade 43 and the hub surface of the impeller 4, and generates a forward axial force on the impeller back of the impeller 4. Conventional impellers 4 will generate a large pressure difference between the impeller back gap and the main flow channel, thus generating a large axial force. However, by using the arc-shaped blade 43, the pressure difference before and after the V-shaped deep groove is greatly reduced, thus significantly reducing the axial force near the V-shaped deep groove. In the impeller back gap flow path b, the airflow follows the arc-shaped blade... After the slit enters the trapezoidal grate 42, it forms a vortex within the slit, which can impede the airflow in flow path b. This prevents more airflow from flowing out of the impeller 4 through the trapezoidal grate 42 and the annular through hole 41, thus ensuring the aerodynamic performance of the turbine. The airflow after exiting the trapezoidal grate 42 flows out of the impeller 4 through the annular through hole 41. The setting of the annular through hole 41 reduces the pressure difference between the back clearance at the low radius of the impeller 4 and the turbine outlet, so that the pressure in the back clearance in flow path b is always at a low level, thereby further reducing the forward axial force of the impeller back plate.

[0043] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-pressure oil-gas radial turbine structure considering axial force balance, comprising a turbine front cover plate (14), an impeller (4), and a turbine casing (12), characterized in that: The turbine casing (12) is equipped with a wheel back cover plate (11), and the wheel back cover plate (11) is connected to a motor casing (10). The motor casing (10) is fixedly connected to a mechanical seal housing (9) by countersunk screws (8) on one side. An expansion ring is placed between the mechanical seal housing (9) and the motor casing (10). The impeller (4) is mounted on the shaft (3) by interference fit. A shaft end retaining ring (2) is sleeved on one side of the shaft (3), and a shaft end nut (1) is threaded on the side of the shaft (3) away from the impeller (4). A shaft sleeve (5) is installed on the side of the shaft (3) away from the shaft end nut (1) by interference fit. A step seal (6) is sleeved on the shaft sleeve (5), and the step seal (6) is located inside the mechanical seal housing (9). A baffle (7) is provided at the upper end of one side of the shaft sleeve (5), and the baffle (7) is fixedly connected to the mechanical seal housing (9) by countersunk screws (8). The impeller (4) is provided with an annular through hole (41) near the center of the disk. The annular through hole (41) is evenly distributed in the circumference and communicates with the back disk cavity of the turbine and the turbine outlet. The impeller (4) is also provided with trapezoidal grating teeth (42) at the middle diameter position. The impeller (4) is provided with multiple arc-shaped blades (43) at equal intervals, and the back of the impeller (4) is thickened.

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