A low pressure module suitable for large volume flow air turbines

Abstract

A low-pressure module suitable for large-capacity flow air turbine relates to the field of compressed air energy storage. The invention comprises a low-pressure outer cylinder, a low-pressure inner cylinder, a bearing box, a gas seal assembly and a corrugated joint. The inner and outer cylinders adopt a horizontal middle-embedded structure and are centered by three sets of adjusting shims. The low-pressure outer cylinder and the inner cylinder are provided with symmetric tangential double air inlets, cooperate with the bottom exhaust structure, and the size of a single air inlet is controllable, the flow field is uniform, and the pressure loss is small. The inner and outer cylinders are flexibly connected by the corrugated joint to absorb the thermal expansion difference; the outer cylinder is supported by the gravity of the base frame and provided with an anchor plate to form an expansion dead point. The inner cylinder adopts an integrated cast flow guide ring, the volute is provided with a flow guide rib plate, and the module adopts 4-stage thrust self-balancing blades. The invention solves the problems of large cylinder, poor sealing strength, and unstable shaft system caused by single air inlet under super large flow, has the advantages of high aerodynamic efficiency, good strength and rigidity, stable operation, and low cost, and is suitable for 350MW-660MW air turbine.

Description

Technical Field

[0001] This invention relates to the field of compressed air energy storage, and more specifically to a low-pressure module suitable for large-volume flow air turbines. Background Technology

[0002] Compressed air energy storage, as a new type of physical energy storage technology with large capacity, long life, and high safety, is a core piece of equipment for peak shaving, frequency regulation, and renewable energy consumption in new power systems. As energy storage systems develop towards ultra-high power outputs of 350MW to 660MW, low-pressure air turbine modules face prominent challenges such as a sharp increase in volumetric flow rate, high difficulty in balancing shaft thrust, large cylinder structure, and the difficulty in balancing aerodynamic performance and operational stability.

[0003] In the prior art, the invention patent with publication number CN120777075A discloses a 300MW secondary reheat side exhaust air turbine low-pressure module, which adopts a side exhaust structure, inner and outer cylinder nesting, integrated flow guide ring, corrugated expansion compensation and end gas seal integrated dynamic balance regulator and other designs, which to a certain extent improve the problems of exhaust swirl, large residual velocity loss and thrust balance difficulty, and improve the low-pressure cylinder efficiency.

[0004] However, this scheme has the following problems: it is only designed for the 300MW class and adopts a single-side single-intake structure. The size of the intake volute and cylinder block is still limited by the flow rate. When the power is increased to the 350MW-660MW class, the working fluid volume flow rate increases exponentially. If the single-intake scheme is used, the intake port diameter will exceed 2.5m, the volume and weight of the volute will increase dramatically, the ultra-large single-intake volute will significantly increase the difficulty of casting and machining, the cylinder block rigidity will decrease and it will be easy to deform. The cylinder strength and the sealing performance of the horizontal split surface will be difficult to guarantee. Moreover, the flow field uniformity will deteriorate, the airflow will be prone to deflection and eddies, the intake pressure loss will increase significantly, the aerodynamic efficiency will decrease, the cylinder block and volute size will exceed the standard, the bearing span will be forced to increase, the shaft vibration characteristics will deteriorate, and the rotor running stability will decrease.

[0005] Meanwhile, traditional low-pressure modules mostly adopt shaft-mounted or bottom-mounted structures. The bottom-mounted cylinder requires more bottom space, making the unit layout and maintenance difficult and costly. Although there are side-mounted structure solutions, they are all based on small and medium power and single air intake design. They are not optimized for ultra-large volume flow conditions by adopting dual tangential symmetrical air intake and dual-layer independent flow guidance, and cannot simultaneously meet the requirements of high strength, low flow resistance, high sealing, shaft system stability and low cost. Summary of the Invention

[0006] To address the problems of existing 300MW-class side-exhaust air turbine low-pressure modules using a single-intake structure, which cannot meet the ultra-large flow requirements of 350MW to 660MW, and suffer from issues such as large cylinder size, poor strength and sealing, large intake losses, large bearing span, and unstable shaft system, this invention provides a low-pressure module suitable for large-volume flow air turbines.

[0007] The technical solution of this invention is:

[0008] A low-pressure module suitable for large-volume flow air turbines, the low-pressure module includes a low-pressure outer cylinder and a low-pressure inner cylinder, a front bearing housing, a rear bearing housing, an air seal ring, a bellows, a low-pressure diaphragm sleeve, and a rotor.

[0009] The low-pressure inner cylinder is installed inside the low-pressure outer cylinder, so that the low-pressure inner cylinder and the low-pressure outer cylinder form a nested assembly structure to combine the low-pressure module body. Both the low-pressure inner cylinder and the low-pressure outer cylinder are horizontally split structures, and the horizontal split surfaces of the low-pressure inner cylinder and the low-pressure outer cylinder are aligned with each other.

[0010] The low-pressure outer cylinder and the low-pressure inner cylinder are aligned and positioned by adjusting shims. The front bearing housing and the rear bearing housing are located at the two ends of the axial direction of the low-pressure outer cylinder, and the front bearing housing and the rear bearing housing are connected to the rotor.

[0011] The low-pressure baffle is fixedly installed on the low-pressure inner cylinder. The air seal ring and the bellows form a steam seal assembly. The air seal ring is fixedly connected to the front bearing housing and the rear bearing housing respectively. The air seal ring is flexibly connected to the axial end of the low-pressure outer cylinder through the bellows to absorb the difference in thermal expansion deformation.

[0012] Furthermore, the low-pressure outer cylinder is provided with two air inlets for the upper half of the outer cylinder and the lower half of the outer cylinder, which are symmetrically arranged along the center of the cylinder body. An exhaust port is provided at the bottom of the low-pressure outer cylinder, and an inspection port is provided in the upper half of the low-pressure outer cylinder.

[0013] Furthermore, the low-pressure inner cylinder is provided with two air inlets, an upper half and a lower half, symmetrically arranged along the center of the cylinder body.

[0014] The upper and lower cylinder air inlets are tangentially arranged, and both inlets are equipped with a volute structure with a gradually decreasing cross-sectional area. A set of guide ribs is set inside the volute structure. The two guide ribs at the inlet end are arranged in parallel, and the two guide ribs inside the volute structure are curved guide ribs and are arranged in a centrally symmetrical manner.

[0015] Furthermore, the upper outer cylinder air inlet and the upper inner cylinder air inlet, and the lower outer cylinder air inlet and the lower inner cylinder air inlet are all coaxially arranged.

[0016] The upper outer cylinder air inlet and the upper inner cylinder air inlet, as well as the lower outer cylinder air inlet and the lower inner cylinder air inlet, are all flexibly connected by corrugated joints to absorb the difference in thermal expansion deformation between them.

[0017] Furthermore, the low-pressure outer cylinder has a horizontally split and welded structure, and the lower half of the cylinder body is provided with support plates around it. The support plates are supported on the steel base frame, and the low-pressure outer cylinder is fitted with the steel base frame, so that the low-pressure outer cylinder sits on the steel base frame.

[0018] Furthermore, the low-pressure outer cylinder is made of Q235A steel plate, steel pipe and shaped steel welded together. The outer cylinder shell of the low-pressure outer cylinder is formed by welding 40mm steel plate, and the outer wall is staggered with welded stiffening plates and T-shaped steel.

[0019] According to claim 3, the low-pressure module suitable for large-volume flow air turbines, the low-pressure inner cylinder is a horizontally split casting structure and is made of QT400-18A material.

[0020] The low-pressure inner cylinder is provided with a flange sealing structure on the horizontal split surface.

[0021] Furthermore, the low-pressure module also includes four stages of 2×2 thrust self-balancing blades, and the thrust self-balancing blades include two first-stage blades and two last-stage blades.

[0022] The first-stage blades are pre-twisted blades, and their stationary blades are fixed to the low-pressure inner cylinder by a low-pressure diaphragm. The last-stage blades are non-pre-twisted blades, and their stationary blades are mounted on the low-pressure inner cylinder by a welded diaphragm.

[0023] Furthermore, the low-pressure module also includes an inner cylinder guide ring and an outer cylinder guide ring;

[0024] The inner cylinder guide ring and the outlet end of the low-pressure inner cylinder are integrally cast. The inner cylinder guide ring and the outer cylinder guide ring are arranged in sequence along the airflow direction to form the exhaust guide channel of the low-pressure module.

[0025] Furthermore, three sets of adjusting shims are provided between the low-pressure inner cylinder and the low-pressure outer cylinder. The three sets of adjusting shims are respectively used to achieve center alignment of the low-pressure inner cylinder relative to the low-pressure outer cylinder in the axial, vertical and horizontal directions and the left and right directions.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] This invention employs a dual-inlet structure with two symmetrically arranged sets of upper and lower inlets. Compared to a single inlet, under the same large-volume flow conditions, the flow rate and velocity of a single inlet can be controlled within a reasonable range, fundamentally avoiding the problem of excessive single-inlet diameter due to excessive flow. The dual-sided symmetrical inlet allows for uniform and synchronous airflow into the flow channel, improving the uniformity of the flow field distribution, suppressing airflow deviation, local eddies, and impact phenomena, reducing pressure loss in the inlet chamber and volute, and improving the overall aerodynamic efficiency. Simultaneously, the airflow counter-current effect optimizes the rotor's stress state, enhancing the unit's operational stability.

[0028] This invention employs a structure combining dual-side air intake and bottom exhaust. Compared to a single-intake, side-exhaust structure, it significantly reduces the overall size of the cylinder and volute, lowers casting and machining difficulty, and improves cylinder rigidity, structural strength, and the reliability of the horizontal split-face seal. With a smaller lateral cylinder dimension for the same power rating, it can shorten the bearing span, improve shaft vibration characteristics and operational stability, and solve the problem of insufficient shaft stability caused by the large size of high-flow-rate engines.

[0029] This invention employs a bottom-centralized exhaust system instead of a side exhaust system. During cylinder disassembly and maintenance, only the horizontal split bolts need to be removed and installed, eliminating the need to disassemble the exhaust pipe, effectively reducing maintenance workload and time. The load distribution around the cylinder body is uniform, and the exhaust side support is reliable, mitigating uneven stress on the support and foundation, and improving the cylinder structure's stability and operational safety. The number of blade stages can be flexibly set to two or more, offering strong structural versatility. Overall, it significantly improves aerodynamic efficiency, ease of assembly, maintenance costs, and operational stability. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of the present invention;

[0031] Figure 2 This is a schematic diagram of the low-pressure outer cylinder;

[0032] Figure 3 This is a schematic diagram of the low-pressure inner cylinder;

[0033] Figure 4 This is a schematic diagram of the assembly structure of the low-pressure outer cylinder and the low-pressure inner cylinder;

[0034] Figure 5 yes Figure 4 A schematic diagram of the bottom structure;

[0035] Figure 6 It is an assembly diagram of the bellows at the air inlet of the low-pressure outer cylinder and the low-pressure inner cylinder;

[0036] Figure 7 This is a schematic diagram of the structure of the present invention and its installation in the bearing housing;

[0037] Figure 8 yes Figure 7 Enlarged view of part A in the middle;

[0038] Figure 9 This is the assembly diagram of the adjusting shims for the low-pressure inner cylinder;

[0039] Figure 10 This is a cross-sectional view showing the connection between the low-pressure outer cylinder and the low-pressure inner cylinder.

[0040] Figure 11 It is the equivalent stress cloud diagram of the low-pressure inner cylinder;

[0041] Figure 12 This is a contact stress cloud diagram of the split surface of the low-pressure inner cylinder;

[0042] Figure 13 It is the equivalent stress cloud diagram of the low-pressure outer cylinder;

[0043] Figure 14 This is a contact stress cloud diagram of the split surface of the low-pressure outer cylinder;

[0044] Figure 15 This is a three-dimensional streamline diagram of the intake chamber of the low-pressure inner cylinder.

[0045] Figure 16 It is the static entropy cloud diagram of the intake chamber of the low-pressure inner cylinder;

[0046] Figure 17 This is a three-dimensional streamline diagram of the exhaust chamber of the low-pressure outer cylinder;

[0047] Figure 18 It is a cloud map of the total pressure distribution in the YZ plane of the low-pressure outer cylinder exhaust chamber;

[0048] Figure 19 It is a cloud map of the static entropy distribution in the YZ plane of the low-pressure outer cylinder exhaust chamber;

[0049] In the diagram: 1. Low-pressure outer cylinder, 2. Low-pressure inner cylinder, 3. Front bearing housing, 4. Rear bearing housing, 5. Air seal ring, 6. Bellows, 7. Low-pressure diaphragm sleeve, 8. Rotor, 9. First stage blade, 10. Last stage blade, 11. Inner cylinder guide ring, 12. Outer cylinder guide ring, 13. Gasket.

[0050] 1-1. Upper half of the outer cylinder intake port; 1-2. Lower half of the outer cylinder intake port; 1-3. Exhaust port; 1-4. Inspection port; 1-5. Support plate.

[0051] 2-1. Upper cylinder intake port; 2-2. Lower cylinder intake port; 2-3. Volute structure; 2-4. Guide ribs. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention. Specific implementation method one:

[0054] Combination Figure 1 — Figure 10 This embodiment describes a low-pressure module suitable for large-volume flow air turbines. The low-pressure module is used as the final flow unit in a 350MW to 660MW compressed air energy storage system.

[0055] The low-pressure module includes a low-pressure outer cylinder 1, a low-pressure inner cylinder 2, a front bearing housing 3, a rear bearing housing 4, an air seal ring 5, a bellows 6, a low-pressure partition sleeve 7, and a rotor 8.

[0056] The low-pressure inner cylinder 2 is installed in the internal cavity of the low-pressure outer cylinder 1 in a coaxial nesting manner. The two are combined to form a double-layer cylinder structure, which together constitute the main pressure-bearing and flow-passing components of the low-pressure module.

[0057] Both the low-pressure inner cylinder 2 and the low-pressure outer cylinder 1 adopt a horizontal split structure, that is, they are divided into an upper cylinder and a lower cylinder along the horizontal plane of the rotor axis. During assembly, the split surface of the low-pressure inner cylinder 2 and the split surface of the low-pressure outer cylinder 1 are kept aligned to ensure the coaxiality of the flow passage and the consistency of the sealing surface. The low-pressure inner cylinder 2 and the low-pressure outer cylinder 1 are precisely centered and positioned by three sets of adjusting shims 13. The three sets of shims respectively constrain the positional deviation of the inner cylinder relative to the outer cylinder in the axial direction, the vertical direction, and the horizontal direction, eliminating the eccentricity error caused by machining and assembly.

[0058] The front bearing housing 3 and the rear bearing housing 4 are respectively arranged on the outer sides of the axial ends of the low-pressure outer cylinder 1. Both bearing housings are independent support structures and are not rigidly connected to the low-pressure outer cylinder 1 or the low-pressure inner cylinder 2. The front bearing housing 3 and the rear bearing housing 4 jointly support the rotor 8.

[0059] The low-pressure baffle sleeve 7 is fixedly installed on the inner wall of the low-pressure inner cylinder 2 as the mounting carrier of the first stage stationary vane; the air seal ring 5 and the bellows 6 together form the end air seal assembly. The air seal ring 5 is fastened to the inner ring position of the front bearing housing 3 and the rear bearing housing 4 by bolts and positioning structure respectively, and remains centered and fixed with the bearing housing.

[0060] The outer ring of the air seal ring 5 is flexibly connected to the axial end flange of the low-pressure outer cylinder 1 through a bellows 6. The bellows 6 can generate elastic deformation in the axial and radial directions to absorb the relative displacement caused by the thermal expansion of the low-pressure outer cylinder 1, prevent the rotor 8 from rubbing against the air seal ring 5, and ensure the sealing effect at the axial end. Specific Implementation Method Two:

[0062] Knot Figure 1 — Figure 10 This embodiment describes a low-pressure module suitable for large-capacity air turbines. The overall dimensions of the low-pressure outer cylinder 1 are: length 5560mm × width 7150mm × height 7440mm, and the bearing span is 5480mm, which meets the stability requirements of the shaft system of large-capacity turbines.

[0063] The low-pressure outer cylinder 1 is a horizontally split welded structure, which is formed by welding Q235A steel plates, steel pipes and structural steel. The main shell is welded from Q235A steel plates with a thickness of 40mm. The outer wall surface is welded with reinforcing ribs and T-shaped steel in an alternating manner along the axial and circumferential directions to form a grid-like reinforcing structure, which improves the strength, rigidity and deformation resistance of the cylinder.

[0064] Two air inlets are provided on the side wall of the low-pressure outer cylinder 1, which are arranged symmetrically along the center of the cylinder body. They are the upper outer cylinder air inlet 1-1 and the lower outer cylinder air inlet 1-2. Both air inlets adopt tangential air intake, and the air intake direction is matched with the tangential direction of the inner cylinder volute. This is used to achieve uniform air intake with large volume flow rate, replacing the traditional single air inlet ultra-large diameter pipe structure. The diameter of a single air inlet is controlled at 1750mm and the flow velocity is 58m / s, avoiding the problems of insufficient strength, sealing difficulties and high cost caused by excessive pipe diameter.

[0065] The bottom center of the low-pressure outer cylinder 1 is provided with a lower exhaust port 1-3, which adopts a bottom centralized exhaust structure. The exhaust direction is vertically downward and the exhaust channel is integrally formed with the lower half of the outer cylinder to avoid the problems of uneven flow field and asymmetrical force on the cylinder body caused by lateral exhaust.

[0066] Two inspection ports 1-4 are provided on the top of the upper cylinder body of the low-pressure outer cylinder 1. When the machine is stopped for maintenance, the staff can directly remove the cover plate of the inspection port 1-4 and enter the interior of the outer cylinder through the inspection port 1-4 for inspection. There is no need to lift the upper part of the outer cylinder, which reduces the difficulty of on-site maintenance and the construction period.

[0067] The lower half of the low-pressure outer cylinder 1 extends outward to form a ring of support plates 1-5. The low-pressure outer cylinder 1 sits on the steel base frame as a whole through the support plates 1-5. The low-pressure outer cylinder 1 and the steel base frame are only attached by their own weight, without any rigid connecting parts such as bolts. Furthermore, a lubricating oil groove is opened on the mating surface of the two, and lubricating oil is introduced to form a lubrication interface, ensuring that the outer cylinder can slide and expand freely in the axial and lateral directions when heated.

[0068] Four anchor plates are installed on the lower half of the low-pressure outer cylinder 1, located below the two air inlets and on both sides of the axial direction. The anchor plates are embedded in the concrete foundation and together form the axial and lateral expansion dead points of the low-pressure cylinder. This allows the outer cylinder to expand evenly from the dead points to the surrounding areas with a symmetrical distribution of expansion, ensuring that the center position of the cylinder is always fixed and preventing rotor rubbing due to expansion deviation. Specific implementation method three:

[0070] Combination Figure 1 — Figure 10 This embodiment describes a low-pressure module suitable for large-volume flow air turbines. The low-pressure inner cylinder 2 is a horizontally split integral casting structure, made of QT400-18A ductile iron.

[0071] The low-pressure inner cylinder 2 is divided into an upper inner cylinder and a lower inner cylinder. A high-precision flange sealing surface is machined on the horizontal split surface, and high-strength connecting bolts are installed. The low-pressure inner cylinder 2 corresponds to the dual air inlets of the low-pressure outer cylinder 1, and is provided with two tangential air inlets arranged symmetrically along the center of the cylinder body, namely the upper inner cylinder air inlet 2-1 and the lower inner cylinder air inlet 2-2. Both air inlets are tangential air inlet structures, and the airflow enters along the tangential direction of the inner cylinder circumference to avoid flow loss caused by radial impact.

[0072] The inner sides of the upper inner cylinder inlet 2-1 and the lower inner cylinder inlet 2-2 are both connected to a gradually narrowing volute structure 2-3. The volute flow channel gradually narrows from the inlet to the flow passage, so that the airflow smoothly changes from tangential flow to axial flow, and the flow channel streamline is smooth. Four guide ribs 2-4 are set inside the volute structure 2-3. The guide ribs 2-4 are arranged parallel to the airflow direction, with one end connected to the inner wall of the volute structure 2-3 and the other end extending to the flow passage inlet. They not only strengthen the strength of the volute structure 2-3 and prevent deformation of the large-sized volute, but also guide and equalize the flow, so that the velocity distribution of the flow field is uniform, without eddies, without flow separation, and without significant entropy increase. According to three-dimensional aerodynamic calculation, the pressure loss of the intake volute is less than 1%, and the aerodynamic efficiency is excellent.

[0073] The outlet end of the low-pressure inner cylinder 2 is provided with an inner cylinder guide ring 11. The inner cylinder guide ring 11 is integrally cast with the body of the low-pressure inner cylinder 2, without splicing seams, flange connections, or bolt fixing structures. Compared with the traditional split guide ring, it eliminates the air leakage gap at the joint surface, improves the flow efficiency, and reduces on-site installation procedures and assembly difficulty.

[0074] The inner cylinder guide ring 11 and the outer cylinder guide ring 12 are arranged coaxially along the exhaust direction to form a double-layer guide exhaust channel, which guides the airflow after power to smoothly flow into the exhaust chamber and finally discharges from the lower exhaust port, resulting in excellent overall aerodynamic performance. Specific implementation method four:

[0076] Combination Figure 1 — Figure 10 This embodiment describes a low-pressure module suitable for large-volume flow air turbines, wherein the upper outer cylinder inlet 1-1 and the upper inner cylinder inlet 2-1, and the lower outer cylinder inlet 1-2 and the lower inner cylinder inlet 2-2 are all coaxially arranged.

[0077] The upper outer cylinder air inlet 1-1 and the upper inner cylinder air inlet 2-1, and the lower outer cylinder air inlet 1-2 and the lower inner cylinder air inlet 2-2 are all connected by air inlet bellows 6 to achieve flexible sealing. One end flange of bellows 6 is fixed to the outer cylinder air inlet, and the other end flange is fixed to the inner cylinder air inlet. The bellows body is a multi-wave metal elastic structure, which can effectively absorb the thermal expansion difference, vibration displacement and assembly deviation between the inner and outer cylinders, while ensuring the airtightness of the air inlet chamber and preventing high-pressure gas from leaking out. Specific implementation method five:

[0079] Combination Figure 1 — Figure 10 This embodiment describes a low-pressure module suitable for large-volume flow air turbines. The low-pressure module adopts a 4-stage (2×2) thrust self-balancing blade structure, including two first-stage blades 9 and two last-stage blades 10. The two first-stage blades 9 and the two last-stage blades 10 are arranged symmetrically in opposite directions. The airflow counteracts each other to achieve axial thrust self-balancing, which greatly reduces the load on the thrust bearing.

[0080] The first-stage blade 9 is a pre-twisted blade, and its stationary blade is fixedly installed on the positioning step on the inner wall of the low-pressure inner cylinder 2 by the low-pressure diaphragm sleeve 7. The diaphragm sleeve and the inner cylinder are positioned by a stop and fastened with bolts to ensure the installation accuracy of the stationary blade.

[0081] The final stage blade 10 is a non-pre-twisted blade. Its stationary blade adopts a welded partition structure, which is directly mounted on the support step on the inner wall of the low-pressure inner cylinder 2 and fixed by welding. The structure is simple and highly reliable. Specific implementation method six:

[0083] Combination Figure 1 — Figure 10 This embodiment describes a low-pressure module suitable for large-volume flow air turbines, wherein the low-pressure module further includes an inner cylinder guide ring 11 and an outer cylinder guide ring 12;

[0084] The inner cylinder guide ring and the outlet end of the low-pressure inner cylinder 2 are integrally cast. The inner cylinder guide ring 11 and the outer cylinder guide ring 12 are arranged in sequence along the airflow direction to form the exhaust guide channel of the low-pressure module. Specific implementation method seven:

[0086] Combination Figure 11 and Figure 12 This embodiment describes a low-pressure module suitable for large-volume flow air turbines. The low-pressure inner cylinder 2 is internally pressurized with gas, and the axial force generated by the partition sleeve, along with the overall weight of the low-pressure inner cylinder 2, are calculated to obtain the equivalent stress cloud diagram of the inner cylinder, as shown below. Figure 11 As shown.

[0087] The equivalent stress of the low-pressure inner cylinder 2 is qualified, the stress test of each path is qualified, and the cylinder strength is qualified.

[0088] With a bolt preload of 310 MPa applied, the contact pressure at the split surface of the low-pressure inner cylinder 2 was obtained through analysis, as shown below. Figure 12 . Detailed implementation method eight:

[0090] Combination Figure 13 and Figure 14 This embodiment describes a low-pressure module suitable for large-volume flow air turbines.

[0091] Gas pressure is applied inside the low-pressure outer cylinder 1. The equivalent stress cloud diagram of the outer cylinder, calculated based on the weight of the low-pressure outer cylinder 1, is shown below. Figure 13 As shown.

[0092] Depend on Figure 13 It can be seen that the outer cylinder is subjected to relatively small forces, with a maximum equivalent stress of 166MPa. The equivalent stress test is qualified, and the strength of the outer cylinder can meet the operating requirements.

[0093] With a bolt preload of 310 MPa applied, the contact pressure at the split surface of the low-pressure outer cylinder 1 was obtained through analysis, as shown below. Figure 14 As shown, the contact pressure at the split surface of the low-pressure outer cylinder 1 is greater than 1.5 times the pressure difference between the inside and outside, and the airtightness of the horizontal split surface of the cylinder is qualified, which can meet the requirements for safe operation. It performs excellently in terms of strength, rigidity, and split surface sealing. Specific implementation method nine:

[0095] Combination Figure 15 and Figure 16 This embodiment describes a low-pressure module suitable for large-volume flow air turbines. The exhaust chamber of this low-pressure module is a large cavity. The working fluid enters from the intake volute, passes through the blades on both sides, enters the exhaust chamber, and is finally discharged from the bottom of the cylinder. The aerodynamic calculations mainly examine the pressure loss in the intake and exhaust chambers.

[0096] The overall three-dimensional streamline diagram and static entropy cloud diagram of the intake chamber are as follows: Figure 15 and Figure 16 As shown, the airflow enters the intake volute from the intake duct, where it changes from tangential to axial flow before entering the turbine stage. The streamlines are generally smooth, with no significant vortices or entropy increase inside the volute, indicating that the internal guide vanes have minimal impact on the flow field. Calculations show that the pressure loss in the intake volute is less than 1%, indicating good overall performance of the intake chamber. Specific Implementation Method Ten:

[0098] Combination Figure 17 — Figure 19This embodiment describes a low-pressure module suitable for large-volume flow air turbines.

[0099] The overall three-dimensional streamline diagram of the exhaust chamber is as follows: Figure 17 As shown, the overall flow in the exhaust chamber is relatively turbulent, which is determined by the complex shape of the exhaust chamber. Most of the airflow generates vortex motion after contacting the inner wall of the outer cylinder, and is eventually discharged from the lower part of the cylinder.

[0100] To more intuitively observe the pressure loss in the exhaust chamber, a detailed analysis was conducted using the YZ plane of the exhaust chamber. Figure 18 YZ plane total pressure distribution cloud map and Figure 19 The static entropy distribution cloud map shows that the airflow is relatively uniform in the exhaust direction.

[0101] Calculations show that the pressure loss in the exhaust chamber is about 2%. Since the exhaust pressure is atmospheric pressure, the pressure loss is about 2 kPa, which is relatively small. The overall performance of the exhaust chamber is good.

[0102] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent substitutions, and improvements made to the above embodiments without departing from the scope of the present invention, based on the technical essence of the present invention and within the spirit and principles of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A low-pressure module suitable for large-volume flow air turbines, characterized in that, The low-pressure module includes a low-pressure outer cylinder (1) and a low-pressure inner cylinder (2), a front bearing housing (3), a rear bearing housing (4), an air seal ring (5), a bellows (6), a low-pressure partition sleeve (7), and a rotor (8). The low-pressure inner cylinder (2) is installed inside the low-pressure outer cylinder (1), so that the low-pressure inner cylinder (2) and the low-pressure outer cylinder (1) form a nested assembly structure to combine the main body of the low-pressure module. Both the low-pressure inner cylinder (2) and the low-pressure outer cylinder (1) are horizontal split structures, and the horizontal split surfaces of the low-pressure inner cylinder (2) and the low-pressure outer cylinder (1) are aligned with each other. The low-pressure outer cylinder (1) and the low-pressure inner cylinder (2) are aligned and positioned by adjusting shims. The front bearing housing (3) and the rear bearing housing (4) are located at the two ends of the axial direction of the low-pressure outer cylinder (1), respectively. The low-pressure partition sleeve (7) is fixedly installed on the low-pressure inner cylinder (2). The air seal ring (5) and the bellows (6) form an air seal assembly. The air seal ring (5) is fixedly connected to the front bearing housing (3) and the rear bearing housing (4) respectively. The air seal ring (5) is flexibly connected to the axial end of the low-pressure outer cylinder (1) through the bellows (6) to absorb the thermal expansion deformation difference.

2. The low-pressure module suitable for large-volume flow air turbines according to claim 1, characterized in that, The low-pressure outer cylinder (1) is provided with two upper half outer cylinder air inlets (1-1) and lower half outer cylinder air inlets (1-2) symmetrically arranged along the center of the cylinder body. The bottom of the low-pressure outer cylinder (1) is provided with an exhaust port (1-3). The upper half of the low-pressure outer cylinder (1) is provided with an inspection port (1-4).

3. The low-pressure module suitable for large-volume flow air turbines according to claim 1, characterized in that, The low-pressure inner cylinder (2) is provided with two upper half inner cylinder air inlets (2-1) and lower half inner cylinder air inlets (2-2) arranged symmetrically along the center of the cylinder body. The upper cylinder intake (2-1) and the lower cylinder intake (2-2) are tangentially arranged, and both inlets are equipped with a volute structure (2-3) with a gradually decreasing cross-sectional area. A set of guide ribs (2-4) are set inside the volute structure (2-3). The two guide ribs (2-4) at the inlet end are arranged in parallel, and the two guide ribs (2-4) inside the volute structure (2-3) are curved guide ribs and are arranged in a centrally symmetrical manner.

4. The low-pressure module suitable for large-volume flow air turbines according to claim 2 or 3, characterized in that, The upper outer cylinder air inlet (1-1) and the upper inner cylinder air inlet (2-1), and the lower outer cylinder air inlet (1-2) and the lower inner cylinder air inlet (2-2) are all coaxially arranged. The upper outer cylinder air inlet (1-1) and the upper inner cylinder air inlet (2-1), and the lower outer cylinder air inlet (1-2) and the lower inner cylinder air inlet (2-2) are all flexibly connected by corrugated joints (6) to absorb the difference in thermal expansion deformation between the two.

5. The low-pressure module suitable for large-volume flow air turbines according to claim 2, characterized in that, The low-pressure outer cylinder (1) is a horizontally split welded structure, and the lower half of the cylinder body of the low-pressure outer cylinder (1) is provided with support plates (1-5) around it. The support plates are supported on the steel base frame, and the low-pressure outer cylinder (1) is attached to the steel base frame, so that the low-pressure outer cylinder (1) sits on the steel base frame.

6. The low-pressure module suitable for large-volume flow air turbines according to claim 5, characterized in that, The low-pressure outer cylinder (1) is made of Q235A steel plate, steel pipe and section steel welded together. The outer cylinder shell of the low-pressure outer cylinder (1) is formed by welding 40mm steel plate, and the outer wall is welded with staggered stiffening plates and T-shaped steel. The low-pressure outer cylinder (1) is provided with a flange sealing structure on the horizontal split surface.

7. The low-pressure module suitable for large-volume flow air turbines according to claim 3, characterized in that, The low-pressure inner cylinder (2) is a horizontally split casting structure, made of QT400-18A material; The low-pressure inner cylinder (2) is provided with a flange sealing structure on the horizontal split surface.

8. The low-pressure module suitable for large-volume flow air turbines according to claim 1, characterized in that, The low-pressure module also includes four stages of 2×2 thrust self-balancing blades, and the thrust self-balancing blades include two first-stage blades (9) and two last-stage blades (10). The first stage blade (9) is a pre-twisted blade, and its stationary blade is fixed on the low-pressure inner cylinder (2) by a low-pressure partition sleeve (7). The last stage blade (10) is a non-pre-twisted blade, and its stationary blade is mounted on the low-pressure inner cylinder (2) by a welded partition.

9. The low-pressure module for large-volume flow air turbines according to claim 8, characterized in that, The low-pressure module also includes an inner cylinder guide ring (11) and an outer cylinder guide ring (12). The inner cylinder guide ring and the outlet end of the low-pressure inner cylinder (2) are integrally cast. The inner cylinder guide ring (11) and the outer cylinder guide ring (12) are arranged in sequence along the airflow direction to form the exhaust guide channel of the low-pressure module.

10. The low-pressure module for large-volume flow air turbines according to claim 1, characterized in that, Three sets of adjusting shims (13) are provided between the low-pressure inner cylinder (2) and the low-pressure outer cylinder (1). The three sets of adjusting shims (13) are used to achieve the centering and positioning of the low-pressure inner cylinder (2) relative to the low-pressure outer cylinder (1) in the axial, vertical and horizontal directions and left and right directions, respectively.

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