A single-stage high-speed pipeline turbine generator set for natural gas pipeline and design method

Abstract

A single-stage high-speed pipeline turbine generator set for natural gas pipeline and design method, the invention relates to a single-stage high-speed pipeline turbine generator set and design method, and belongs to the technical field of turbine expander power generation. In order to solve the problem that the auxiliary system of the natural gas overpressure turbine generator set in the prior art occupies a large proportion of the land area, the natural gas radial turbine expander and the high-speed permanent magnet synchronous generator are coaxially arranged, the natural gas radial turbine expander cooperates with the high-speed permanent magnet synchronous generator through a rotating shaft to generate power, and the natural gas radial turbine expander and the high-speed permanent magnet synchronous generator are installed on the natural gas pipeline. Natural gas turbine expander: thermal calculation is carried out, then three-dimensional modeling of the impeller is completed, analysis and optimization are carried out through CFD software, the key component impeller is made of titanium alloy, five-axis linkage high-speed milling is adopted for forming, motor selection is carried out according to the parameters of the expander, iteration optimization is carried out, and the generator design is completed.

Description

Technical Field

[0001] This invention relates to a single-stage high-speed pipeline turbine generator set and its design method, specifically to a single-stage high-speed pipeline turbine generator set and its design method for natural gas pipelines, belonging to the field of turbine expander power generation technology. Background Technology

[0002] Natural gas, as an important clean energy source, is also the most mature and widely utilized clean energy source. There has been a call to vigorously develop natural gas applications. With the construction of natural gas pipeline networks, the current global trend in gas pipeline development is towards long distances, large diameters, high pressures, and network connectivity. High-pressure natural gas transported from main pipelines needs to be depressurized at various receiving stations, gas storage facilities, and gas turbine power plants to meet the pressure demands of downstream users. During pressure regulation, high-pressure natural gas experiences a significant pressure drop, releasing a large amount of energy. If this pressure energy can be recovered and utilized appropriately, it will greatly improve energy efficiency and the economics of natural gas pipeline network operation. With the increasing use of natural gas in cities and the rapid expansion of natural gas pipeline networks, high-pressure natural gas pressure energy recovery and utilization technology has broad development prospects. Fully utilizing the residual pressure of natural gas is not only feasible and has significant economic benefits, but also contributes to the achievement of dual-carbon goals.

[0003] The future development direction of turboexpander generator sets is towards compactness, integration, and modularity, with the aim of reducing the equipment's footprint and enhancing its adaptability to various application scenarios. Traditional natural gas residual pressure turboexpander generator sets have a relatively large auxiliary system footprint. Adopting a direct-drive design between the turboexpander and the high-speed motor can reduce the unit's auxiliary equipment and footprint, while simultaneously improving equipment reliability. Summary of the Invention

[0004] In order to solve the problem that the auxiliary system of natural gas residual pressure turbine generator set occupies a large proportion of the floor space in the prior art, the present invention provides a single-stage high-speed pipeline turbine generator set and its design method for natural gas pipelines.

[0005] To address the aforementioned problems, the present invention provides the following technical solution:

[0006] A single-stage high-speed pipeline turbine generator set for natural gas pipelines includes a natural gas radial turbine expander and a high-speed permanent magnet synchronous generator; the natural gas radial turbine expander and the high-speed permanent magnet synchronous generator are coaxially arranged, and the natural gas radial turbine expander generates electricity by cooperating with the high-speed permanent magnet synchronous generator through a rotating shaft; the natural gas radial turbine expander and the high-speed permanent magnet synchronous generator are installed on the natural gas pipeline.

[0007] Furthermore, the natural gas centripetal turboexpander includes an outer shell, an inner shell, an impeller, and a generator main shaft;

[0008] The outer shell is fitted onto the inner shell, the natural gas outlet is installed at the outlet end of the outer shell, a natural gas passage chamber is provided between the outer shell and the inner shell, the generator main shaft is rotatably connected and installed inside the inner shell, and the impeller is fixedly installed on the generator main shaft 19.

[0009] Furthermore, the natural gas centripetal turboexpander includes a natural gas inlet and a natural gas outlet;

[0010] The natural gas inlet is installed at the inlet end of the outer shell, and the natural gas outlet is installed at the outlet end of the outer shell. A natural gas passage chamber is provided between the outer shell and the inner shell.

[0011] Furthermore, the natural gas centrifugal turboexpander also includes a nozzle ring, which is disposed on the inner wall of the outer casing of the impeller, with the nozzle ring's outlet direction facing the impeller.

[0012] Furthermore, the nozzle ring is located at the gas outlet end between the outer shell and the inner shell, and the nozzle ring is used to adjust the gas outlet direction of natural gas.

[0013] Furthermore, the natural gas radial turbine expander also includes an axial magnetic bearing and a radial magnetic bearing;

[0014] The generator main shaft is rotatably connected to the inner housing via axial and radial magnetic levitation bearings.

[0015] Furthermore, the natural gas radial turbine expander also includes an axial end auxiliary bearing and a radial end auxiliary bearing;

[0016] The generator main shaft at the intake end is rotatably connected to the inner housing via an axial auxiliary bearing, and the generator main shaft near the exhaust end is rotatably connected to the inner housing via a radial auxiliary bearing. The axial auxiliary bearing and the radial auxiliary bearing are located on both sides of the axial magnetic levitation bearing 6 and the radial magnetic levitation bearing.

[0017] Furthermore, the natural gas centripetal turbine expander also includes tie rod bolts, through which the impeller is fixedly mounted on the generator main shaft.

[0018] Furthermore, the natural gas centripetal turbine expander also includes a balance disc, which is installed at the natural gas inlet, and the generator main shaft is in contact with the balance disc.

[0019] Furthermore, the high-speed permanent magnet synchronous generator includes a generator stator assembly and generator windings;

[0020] The generator stator assembly is fixedly mounted on the inner side wall of the inner housing, and the generator winding is fixedly mounted on the generator main shaft. The positions of the generator stator assembly and the generator winding are set accordingly.

[0021] A design method for a single-stage high-speed pipeline turbine generator set for natural gas pipelines, the method being implemented as follows:

[0022] Natural gas turbine expander: First, thermodynamic calculations are performed, then the three-dimensional model of the impeller is completed. Analysis and optimization are then conducted using CFD software, and the final design is determined based on the generator selection results. It can operate safely, stably, and efficiently under varying operating conditions, with natural gas flow rates ranging from 50% to 120%. The key component, the impeller, is made of titanium alloy, formed by five-axis linkage high-speed milling, and undergoes CAE analysis, 100% X-ray flaw detection, and a 115% overspeed test. High-speed permanent magnet synchronous generator: The generator is selected based on the expander parameters, and iterative optimization is performed to complete the generator design.

[0023] Step 1: Perform thermodynamic calculations on the natural gas turbine expander. The design parameters are as follows:

[0024] Design flow rate: 50,000 Nm3 / h

[0025] Expansion ratio: 1.34

[0026] Working medium: natural gas

[0027] The rotational speed of the turbine expander, the thermodynamic parameters at various characteristic points, the airflow parameters at the inlet and outlet of the turbine flow passage components, the basic dimensions of the nozzle and impeller, and the thermal efficiency and power of the turbine are determined by thermodynamic calculations.

[0028] Step 2: Aerodynamic calculations:

[0029] Based on thermal calculations, three-dimensional modeling is performed, flow field simulation calculations are conducted, and the flow passage components are optimized by combining three-dimensional CFD calculations to determine the power rating of the expander.

[0030] Step 3: Generator selection:

[0031] Based on the aerodynamic calculation results of the expander, the generator selection design is carried out, the temperature rise of natural gas after passing through the generator cooling channel is calculated, the impact of temperature rise on expander power and efficiency is verified, and after two rounds of iterative calculations and aerodynamic optimization design of the expander, and unit variable operating condition calculations are carried out, the aerodynamic design of the expander is completed, and the generator selection is determined.

[0032] Step 4: Connection of the natural gas radial turbine expander and the high-speed permanent magnet synchronous generator:

[0033] A high-speed permanent magnet synchronous generator using magnetic levitation bearings is directly connected to the impeller, eliminating the need for gear reduction devices, any other mechanical contact, and a lubrication system. It also eliminates wear and energy loss, as shown in the following formula:

[0034]

[0035] For torque,

[0036] For power,

[0037] n - is the rotational speed.

[0038] K – is the working condition coefficient.

[0039] The torque is calculated using the formula. The tooth profile and number of teeth on the end face are determined by calculating the inner diameter, pitch diameter, outer diameter, as well as parameters such as tooth profile angle, tooth pitch angle, and tooth space angle.

[0040] Based on the end face tooth design results and the maximum torque transmitted, calculate the required preload, determine the tie rod bolt size, select a suitable material, and perform strength verification calculations to complete the tie rod bolt design.

[0041] Step 5: Structural Design

[0042] FEA finite element structural analysis will perform finite element analysis on rotating components such as impellers and nozzle blades, fully considering factors such as stress field, strain field, deformation, and vibration characteristics, to evaluate the static strength of structures such as impellers and nozzle blades, and analyze the fatigue life characteristics of structures such as impellers and nozzle blades under typical working conditions. It will also calculate parameters such as mass, center of gravity, moment of inertia, and axial thrust of the shaft system, providing data input for rotor dynamics calculations, obtaining the critical speed, modal, and unbalance response characteristics of the shaft system, and drawing Campbell diagrams and interferograms to ensure the stability of the structure.

[0043] Step 6: Rotor dynamics analysis and calculation:

[0044] After completing the aerodynamic design and strength verification of the natural gas radial turbine, and taking into full account factors such as the operating parameters and working fluid characteristics of the natural gas turbine, the focus is on key technical issues such as the rotor's operational stability. Rotor dynamics calculations are performed to determine key parameters such as journal size, support position, bearing span, and counterweight mass, so as to obtain a design scheme with good rotor dynamics characteristics.

[0045] Compared with the prior art, the present invention has the following advantages:

[0046] This invention designs the main shafts of the natural gas radial turbine expander and the high-speed permanent magnet synchronous generator to be the same, and uses natural gas as the cooling medium for the generator, eliminating the need for a dry gas sealing device, reducing the shaft length, increasing the shaft rigidity, and improving the safety and stability of the shaft system. By installing a magnetic levitation bearing between the housing and the generator main shaft, the vibration value and noise of the unit can be greatly reduced, and ultra-high speed can be achieved to fully utilize the rotor performance. This invention eliminates the need for a gearbox and lubrication station, resulting in a small footprint. The equipment of this invention has a high degree of integration and can effectively improve the power generation efficiency of the entire equipment. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the overall structure of the present invention. Detailed Implementation

[0048] Combination Figure 1 This embodiment describes a single-stage high-speed pipeline turbine generator set for natural gas pipelines, comprising a natural gas radial turbine expander and a high-speed permanent magnet synchronous generator; the natural gas radial turbine expander and the high-speed permanent magnet synchronous generator are coaxially arranged, and the natural gas radial turbine expander generates electricity by cooperating with the high-speed permanent magnet synchronous generator through a rotating shaft; the natural gas radial turbine expander and the high-speed permanent magnet synchronous generator are installed on the natural gas pipeline.

[0049] This invention directly connects a natural gas centrifugal turbine expander and a high-speed permanent magnet synchronous generator, using process gas (natural gas) to cool the generator. The generator employs electromagnetic bearings, and the expander and generator are sealed within a natural gas pipeline. Electrical connection is achieved only through sealed connectors, eliminating the need for traditional intake volutes, dry gas sealing systems, gearboxes, and lubrication systems. This results in a highly integrated, single-unit design with a small footprint. Because natural gas has a higher specific heat capacity than air, it saves cooling space for the generator. Simultaneously, the natural gas's temperature rise during generator cooling increases the unit's power output, reducing losses and improving efficiency.

[0050] Combination Figure 1 As shown, the natural gas radial turbine expander includes an outer shell 4, an inner shell 5, an impeller 17, and a generator main shaft 19;

[0051] The outer shell 4 is fitted onto the inner shell 5. The natural gas outlet 15 is installed at the outlet end of the outer shell 4. A natural gas passage chamber is provided between the outer shell 4 and the inner shell 5. The generator main shaft 19 is rotatably connected and installed inside the inner shell 5. The impeller 17 is fixedly installed on the generator main shaft 19.

[0052] Combination Figure 1 As shown, the natural gas centrifugal turboexpander includes a natural gas inlet 1 and a natural gas outlet 15;

[0053] The natural gas inlet 1 is installed at the inlet end of the outer shell 4, and the natural gas outlet 15 is installed at the outlet end of the outer shell 4. A natural gas passage chamber is provided between the outer shell 4 and the inner shell 5.

[0054] Natural gas inlet 1 and natural gas outlet 15 are connected to the natural gas pipeline via flanges.

[0055] Combination Figure 1 As shown, the natural gas centripetal turbine expander also includes a nozzle ring 18, which is disposed on the inner wall of the outer inner casing 5 of the impeller 17, and the outlet direction of the nozzle ring 18 is directed toward the impeller 17.

[0056] The nozzle ring 18 blows natural gas toward the impeller 17, which in turn drives the impeller 17 and the generator main shaft 19 on the impeller 17 to rotate.

[0057] Combination Figure 1 As shown, the nozzle ring 18 is located at the gas outlet end between the outer shell 4 and the inner shell 5, and the nozzle ring 18 is used to adjust the gas outlet direction of natural gas.

[0058] Combination Figure 1 As shown, the natural gas radial turbine expander also includes an axial magnetic bearing 6 and a radial magnetic bearing 11;

[0059] The generator main shaft 19 is rotatably connected to the inner housing 5 via an axial end magnetic levitation bearing 6 and a radial end magnetic levitation bearing 11.

[0060] Combination Figure 1 As shown, the natural gas radial turbine expander also includes an axial end auxiliary bearing 3 and a radial end auxiliary bearing 14;

[0061] The generator main shaft 19 at the intake end is rotatably connected to the inner housing 5 via the axial auxiliary bearing 3. The generator main shaft 19 near the exhaust end is rotatably connected to the inner housing 5 via the radial auxiliary bearing 14. The axial auxiliary bearing 3 and the radial auxiliary bearing 14 are located on both sides of the axial magnetic levitation bearing 6 and the radial magnetic levitation bearing 11.

[0062] Combination Figure 1 As shown, the natural gas centripetal turbine expander also includes tie rod bolts 16, and the impeller 17 is fixedly mounted on the generator main shaft 19 by the tie rod bolts 16.

[0063] Combination Figure 1 As shown, the natural gas centripetal turbine expander also includes a balance disc 2, which is installed at the natural gas inlet 1, and the generator main shaft 19 is in contact with the balance disc 2.

[0064] When the axial thrust impeller of a natural gas radial turbine expander is working, the gas pressure difference generates a huge axial force. The balance disc 2 uses reverse gas pressure to counteract most of the axial force. This protects the thrust bearing, significantly reducing its load, wear, and heat generation, and extending its lifespan. It also reduces axial vibration, ensuring balanced axial force, smoother operation, and minimizing unit vibration and abnormal noise.

[0065] Combination Figure 1 As shown, the high-speed permanent magnet synchronous generator includes a generator stator assembly 9 and generator windings;

[0066] The generator stator assembly 9 is fixedly installed on the inner side wall of the inner housing 5, and the generator winding is fixedly installed on the generator main shaft 19. The positions of the generator stator assembly 9 and the generator winding are set accordingly.

[0067] The generator's main shaft 19 rotates, generating electricity by cutting magnetic field lines.

[0068] In this invention, natural gas enters the unit from the natural gas inlet 1, and the airflow is evenly distributed to the nozzle ring 18 through the airflow channel chamber between the outer shell 4 and the inner shell 5, minimizing energy loss. The airflow accelerates through the nozzle ring, driving the impeller 17 to rotate, thereby driving the generator main shaft 19 to rotate and generate electricity.

[0069] In a preferred embodiment, the generator main shaft 19 is rotatably connected to the inner housing 5 via an axial magnetic levitation bearing 6 and a radial magnetic levitation bearing 11. Axial auxiliary bearings 3 and radial auxiliary bearings 14 are respectively provided on both sides of the axial magnetic levitation bearing 6 and the radial magnetic levitation bearing 11. By installing the axial magnetic levitation bearing 6, the radial magnetic levitation bearing 11, the axial auxiliary bearings 3, and the radial auxiliary bearings 14, the transmission part can achieve completely non-contact levitation operation, achieving true lubrication-free operation and a compact structure.

[0070] Further optimization involves the impeller 17 of the natural gas turbine expander being rotatably connected to the generator main shaft 19 via tie rod bolts 16; and the nozzle ring 18 of the natural gas turbine expander being connected to the inner casing 4 and the outer casing 4 of the unit.

[0071] The generator is connected to the natural gas pipeline via a flange at natural gas inlet 1, and the natural gas turbine expander is connected to the natural gas pipeline via a flange at natural gas outlet 15. During operation, the working gas enters the gas flow channel chamber between the outer shell 4 and the inner shell 5 from natural gas inlet 1, and is sprayed onto the impeller 17 through nozzle ring 18, causing the impeller 17 to rotate. This rotation drives the generator main shaft 19. When the generator main shaft 19 and impeller 17 rotate together, the high-pressure natural gas passes through the turbine expander, drives the generator windings to perform work, and is delivered to the high-speed permanent magnet synchronous generator. The pressure energy is recovered and converted into electrical energy, and the expanded low-pressure natural gas meets the needs of downstream users. As an energy recovery device, it replaces the pressure regulating valve on the natural gas pipeline, converting the enthalpy of the pressurized natural gas in the pipeline into mechanical energy and completing the depressurization process. The mechanical energy is output axially through the expander, driving the generator to generate electricity.

[0072] The specific implementation steps of a design method for a single-stage high-speed pipeline turbine generator set for generating electricity by recovering residual pressure from natural gas pipelines are as follows:

[0073] Natural gas turbine expander: First, thermodynamic calculations are performed, then the three-dimensional model of the impeller is completed. Analysis and optimization are then conducted using CFD software, and the final design is determined based on the generator selection results. It can operate safely, stably, and efficiently under varying operating conditions, with natural gas flow rates ranging from 50% to 120%. The key component, the impeller, is made of titanium alloy, formed by five-axis linkage high-speed milling, and undergoes CAE analysis, 100% X-ray flaw detection, and a 115% overspeed test. High-speed permanent magnet synchronous generator: The generator is selected based on the expander parameters, and iterative optimization is performed to complete the generator design.

[0074] Step 1: Perform thermodynamic calculations on the natural gas turbine expander. The design parameters are as follows:

[0075] Design flow rate: 50,000 Nm3 / h

[0076] Expansion ratio: 1.34

[0077] Working medium: natural gas

[0078] The rotational speed of the turbine expander, the thermodynamic parameters at various characteristic points, the inlet and outlet airflow parameters of the turbine flow passage components, the basic dimensions of the nozzle and impeller, and the thermal efficiency and power of the turbine are determined by thermodynamic calculations.

[0079] Step 2: Aerodynamic calculations:

[0080] Based on thermal calculations, three-dimensional modeling is performed, flow field simulation calculations are conducted, and the flow passage components are optimized by combining three-dimensional CFD calculations to determine the power rating of the expander.

[0081] Step 3: Generator selection:

[0082] Based on the aerodynamic calculation results of the expander, the generator selection design is carried out, the temperature rise of natural gas after passing through the generator cooling channel is calculated, the impact of temperature rise on expander power and efficiency is verified, and after two rounds of iterative calculations and aerodynamic optimization design of the expander, and variable operating condition calculations of the unit are carried out, the aerodynamic design of the expander is completed, and the generator selection is determined.

[0083] Step 4: Connection of the natural gas radial turbine expander and the high-speed permanent magnet synchronous generator:

[0084] A high-speed permanent magnet synchronous generator using magnetic levitation bearings is directly connected to the impeller, eliminating the need for gear reduction devices, any other mechanical contact, and a lubrication system. It also eliminates wear and energy loss, as shown in the following formula:

[0085]

[0086] For torque,

[0087] Power (kW),

[0088] n - is the rotational speed (r / min);

[0089] K – is the working condition coefficient (1.25 to 1.5).

[0090] The torque is calculated using the formula. The tooth profile and number of teeth on the end face are determined by calculating the inner diameter, middle diameter, outer diameter, as well as parameters such as tooth profile angle, tooth profile pitch angle, and tooth groove angle.

[0091] Based on the end face tooth design results and the maximum torque transmitted, calculate the required preload, determine the tie rod bolt size, select a suitable material, and perform strength verification calculations to complete the tie rod bolt design.

[0092] Step 5: Structural Design

[0093] FEA finite element structural analysis will perform finite element analysis on rotating components such as impellers and nozzle blades, fully considering factors such as stress field, strain field, deformation, and vibration characteristics. It will evaluate the static strength of structures such as impellers and nozzle blades, analyze the fatigue life characteristics of structures such as impellers and nozzle blades under typical working conditions, calculate parameters such as mass, center of gravity, moment of inertia, and axial thrust of the shaft system, provide data input for rotor dynamics calculation, obtain the critical speed, modal, and unbalance response characteristics of the shaft system, and draw Campbell diagrams and interferograms to ensure the stability of the structure.

[0094] Step 6: Rotor dynamics analysis and calculation:

[0095] After completing the aerodynamic design and strength verification of the natural gas radial turbine, and taking into full account factors such as the operating parameters and working fluid characteristics of the natural gas turbine, the focus is on key technical issues such as the rotor's operational stability. Rotor dynamics calculations are performed to determine key parameters such as journal size, support position, bearing span, and counterweight mass, so as to obtain a design scheme with good rotor dynamics characteristics.

[0096] Evaluation criteria: The rotor design requires calculation of the rotor's critical speed and unbalanced response. The avoidance rate, vibration amplitude, and stability requirements must meet the API-684 and API-617 standards. The bearing selection scheme must meet the relevant requirements of API-610 and ISO-281 regarding DN value, life, and axial thrust.

Claims

1. A single-stage high-speed pipeline turbine generator set for natural gas pipelines, characterized in that: It includes a natural gas radial turbine expander and a high-speed permanent magnet synchronous generator; the natural gas radial turbine expander and the high-speed permanent magnet synchronous generator are coaxially arranged, and the natural gas radial turbine expander generates electricity by cooperating with the high-speed permanent magnet synchronous generator through a rotating shaft. The natural gas radial turbine expander and the high-speed permanent magnet synchronous generator are installed on the natural gas pipeline.

2. A single-stage high-speed pipeline turbine generator set for natural gas pipelines according to claim 1, characterized in that: The natural gas radial turboexpander includes a natural gas inlet (1), an outer shell (4), an inner shell (5), a natural gas outlet (15), an impeller (17), and a generator main shaft (19). The outer shell (4) is fitted onto the inner shell (5). The natural gas outlet (15) is installed at the outlet end of the outer shell (4). A natural gas passage chamber is provided between the outer shell (4) and the inner shell (5). The generator main shaft (19) is rotatably connected and installed inside the inner shell (5). The impeller (17) is fixedly installed on the generator main shaft (19). The natural gas inlet (1) is installed at the inlet end of the outer shell (4). The natural gas outlet (15) is installed at the outlet end of the outer shell (4). A natural gas passage chamber is provided between the outer shell (4) and the inner shell (5).

3. A single-stage high-speed pipeline turbine generator set for natural gas pipelines according to claim 2, characterized in that: The natural gas centripetal turbine expander also includes a nozzle ring (18), which is located on the inner wall of the outer casing (5) of the impeller (17), and the outlet direction of the nozzle ring (18) is facing the impeller (17).

4. A single-stage high-speed pipeline turbine generator set for natural gas pipelines according to claim 3, characterized in that: The nozzle ring (18) is located at the gas outlet end between the outer shell (4) and the inner shell (5), and the nozzle ring (18) is used to adjust the gas outlet direction of natural gas.

5. A single-stage high-speed pipeline turbine generator set for natural gas pipelines according to claim 2, characterized in that: The natural gas radial turbine expander also includes an axial end magnetic levitation bearing (6) and a radial end magnetic levitation bearing (11). The generator main shaft (19) is rotatably connected to the inner housing (5) through an axial end magnetic levitation bearing (6) and a radial end magnetic levitation bearing (11).

6. A single-stage high-speed pipeline turbine generator set for natural gas pipelines according to claim 5, characterized in that: The natural gas radial turbine expander also includes an axial end auxiliary bearing (3) and a radial end auxiliary bearing (14). The generator main shaft (19) at the intake end is rotatably connected to the inner housing (5) through the axial auxiliary bearing (3), and the generator main shaft (19) near the exhaust end is rotatably connected to the inner housing (5) through the radial auxiliary bearing (14). The axial auxiliary bearing (3) and the radial auxiliary bearing (14) are located on both sides of the axial magnetic levitation bearing (6) and the radial magnetic levitation bearing (11).

7. A single-stage high-speed pipeline turbine generator set for natural gas pipelines according to claim 2, characterized in that: The natural gas centrifugal turbine expander also includes tie rod bolts (16), and the impeller (17) is fixedly mounted on the generator main shaft (19) by tie rod bolts (16).

8. A single-stage high-speed pipeline turbine generator set for natural gas pipelines according to claim 3, characterized in that: The natural gas centripetal turbine expander also includes a balance disc (2), which is installed at the natural gas inlet (1) and the generator main shaft (19) is in contact with the balance disc (2).

9. A single-stage high-speed pipeline turbine generator set for natural gas pipelines according to claim 2, characterized in that: The high-speed permanent magnet synchronous generator includes a generator stator assembly (9) and generator windings; The generator stator assembly (9) is fixedly installed on the inner side wall of the inner housing (5), and the generator winding is fixedly installed on the generator main shaft (19). The generator stator assembly (9) and the generator winding are positioned accordingly.

10. A design method for a single-stage high-speed pipeline turbine generator set for natural gas pipelines according to any one of claims 1 to 9, characterized in that: The method is implemented in the following manner: Natural gas turbine expander: First, thermodynamic calculations are performed, then the three-dimensional model of the impeller is completed. Analysis and optimization are then conducted using CFD software, and the final design is determined based on the generator selection results. It can operate safely, stably, and efficiently under varying operating conditions, with natural gas flow rates ranging from 50% to 120%. The key component, the impeller, is made of titanium alloy, formed by five-axis linkage high-speed milling, and undergoes CAE analysis, 100% X-ray flaw detection, and a 115% overspeed test. High-speed permanent magnet synchronous generator: Based on the expander parameters, the generator is selected and iteratively optimized to complete the generator design. Step 1: Perform thermodynamic calculations on the natural gas turbine expander. The design parameters are as follows: Design flow rate: 50,000 Nm3 / h Expansion ratio: 1.34 Working medium: natural gas The rotational speed of the turbine expander, the thermodynamic parameters at various characteristic points, the airflow parameters at the inlet and outlet of the turbine flow passage components, the basic dimensions of the nozzle and impeller, and the thermal efficiency and power of the turbine are determined by thermodynamic calculations. Step 2: Aerodynamic calculations: Based on thermal calculations, three-dimensional modeling is performed, flow field simulation calculations are conducted, and the flow passage components are optimized by combining three-dimensional CFD calculations to determine the power rating of the expander. Step 3: Generator selection: Based on the aerodynamic calculation results of the expander, the generator selection design is carried out, the temperature rise of natural gas after passing through the generator cooling channel is calculated, the impact of temperature rise on expander power and efficiency is verified, and after two rounds of iterative calculations and aerodynamic optimization design of the expander, and unit variable operating condition calculations are carried out, the aerodynamic design of the expander is completed, and the generator selection is determined. Step 4: Connection of the natural gas radial turbine expander and the high-speed permanent magnet synchronous generator: A high-speed permanent magnet synchronous generator using magnetic levitation bearings is directly connected to the impeller, eliminating the need for gear reduction devices, any other mechanical contact, and a lubrication system. It also eliminates wear and energy loss, as shown in the following formula: For torque, For power, n - is the rotational speed. K – is the working condition coefficient. The torque is calculated using the formula. The tooth profile and number of teeth on the end face are determined by calculating the inner diameter, pitch diameter, outer diameter, as well as parameters such as tooth profile angle, tooth pitch angle, and tooth space angle. Based on the end face tooth design results and the maximum torque transmitted, calculate the required preload, determine the tie rod bolt size, select a suitable material, and perform strength verification calculations to complete the tie rod bolt design. Step 5: Structural Design FEA finite element structural analysis will perform finite element analysis on rotating components such as impellers and nozzle blades, fully considering factors such as stress field, strain field, deformation, and vibration characteristics, to evaluate the static strength of structures such as impellers and nozzle blades, and analyze the fatigue life characteristics of structures such as impellers and nozzle blades under typical working conditions. It will also calculate parameters such as mass, center of gravity, moment of inertia, and axial thrust of the shaft system, providing data input for rotor dynamics calculations, obtaining the critical speed, modal, and unbalance response characteristics of the shaft system, and drawing Campbell diagrams and interferograms to ensure the stability of the structure. Step 6: Rotor dynamics analysis and calculation: After completing the aerodynamic design and strength verification of the natural gas radial turbine, and taking into full account factors such as the operating parameters and working fluid characteristics of the natural gas turbine, the focus is on key technical issues such as the rotor's operational stability. Rotor dynamics calculations are performed to determine key parameters such as journal size, support position, bearing span, and counterweight mass, so as to obtain a design scheme with good rotor dynamics characteristics.

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