A natural ventilation air cooling system and steam exhaust pipeline optimization method

Abstract

The present application relates to the field of industrial cooling technology, in particular to a natural ventilation air cooling system and a steam exhaust pipeline optimization method. The system comprises a steam turbine, an air cooling condenser and a steam exhaust pipe assembly composed of an air inlet main pipe, a mother pipe ring pipe and branch pipes. The air inlet main pipe is connected to the mother pipe ring pipe through a tee pipe fitting. The mother pipe ring pipe is composed of a first and a second circular arc pipe arranged horizontally and oppositely. Both pipes adopt a variable diameter structure with a gradually decreasing diameter from a self-connecting end to a closed end. The variable diameter sections are asymmetrically arranged. Multiple connection risers are asymmetrically arranged on the two circular arc pipes along the steam flow direction. A tee pipe fitting is additionally provided with a riser at the end of the first circular arc pipe for flow distribution. Each connection riser is connected to an upper layer branch pipe and a lower layer branch pipe with a first inclined shoulder part for guiding steam. The air cooling condenser is connected to the windward side and the leeward side of the ventilation tower. The present application can effectively reduce the flow difference between the upper and lower layer branch pipes, thereby significantly reducing the local resistance loss and improving the uniformity of flow distribution.

Description

Technical Field

[0001] This invention relates to the field of industrial cooling technology, and in particular to a natural ventilation air cooling system and an optimization method for exhaust pipes. Background Technology

[0002] The NDC system (Natural Draft Condenser) uses cold air drawn in by a natural draft tower to cool the turbine exhaust steam inside the air condenser. Large power plants using NDC technology have advantages such as low emissions, wide load range, deep peak shaving, and fast regulation. Compared with the exhaust system of conventional large generator sets, the exhaust pipe of the NDC system from the exhaust cylinder to the condenser has the following characteristics: (1) The exhaust pipe is long, the channel diameter is large, and the structure is complex; (2) Special structures must be adopted on the exhaust pipe to make the flow of the distribution channel uniform and the resistance reduced to ensure the economic operation of the unit; (3) There is condensation of steam in the exhaust pipe, the amount of condensation is affected by the environment, and the flow is a two-phase flow of a thin liquid film layer; (4) The whole system operates under negative pressure, and the vacuum affects the condensation effect and also makes the flow velocity in the pipe very high. If the guide vane is not designed properly, it will cause a very large impact on the entire device and destroy it.

[0003] Currently, thermal power plant units typically operate under conditions of significant variations (100%–20 mm%), large-scale back pressure variations (6–35 kPa), and extreme ambient temperature differences (-29–42°C). Meanwhile, changes in ambient wind direction and speed lead to significant differences in cooling airflow. Multiple constraints, multiple operating conditions, and complex flow patterns make it extremely difficult to achieve uniform steam distribution in large-diameter and variable-diameter, three-dimensional multi-branch exhaust pipes. This results in huge differences in pressure drop across different pipes, increases the difficulty of back pressure control, and directly affects the system's economy and stability. Summary of the Invention

[0004] The technical problem to be solved by the embodiments of the present invention is to provide a natural ventilation air cooling system and an optimization method for exhaust pipes, so as to solve the problems of uneven distribution of steam cooling flow and difficulty in back pressure control after the NDC system is scaled up in the prior art.

[0005] This invention discloses a natural ventilation air-cooling system, including a steam turbine, an air-cooled condenser, and an exhaust pipe assembly, wherein the exhaust pipe assembly includes an intake main pipe, a main pipe ring pipe, and branch pipes;

[0006] The main intake pipe is connected to the steam turbine and is connected to the main pipe ring pipe through a tee fitting;

[0007] The main pipe ring includes a first arc pipe and a second arc pipe arranged opposite to each other and horizontally. One end of the first arc pipe is closed, and the other end is connected to one end of the tee fitting. The pipe body of the first arc pipe has a variable diameter structure with multiple segments whose diameter decreases sequentially from its connecting end to its closed end. One end of the second arc pipe is closed, and the other end is connected to the other end of the tee fitting. The pipe body of the second arc pipe has a variable diameter structure with multiple segments whose diameter decreases sequentially from its connecting end to its closed end. The variable diameter segments of the first arc pipe and the variable diameter segments of the second arc pipe are arranged asymmetrically.

[0008] Multiple connecting risers are respectively provided on the first arc pipe and the second arc pipe along the steam flow direction, and the multiple connecting risers on the first arc pipe and the second arc pipe are asymmetrically distributed. A connecting riser is also provided at the end of the tee fitting that connects to the first arc pipe for diverting the steam on the inlet side of the first arc pipe.

[0009] The branch pipes are respectively installed on each of the connecting risers, including an upper branch pipe connected to the top of the connecting riser and a lower branch pipe connected to the middle of the connecting riser. The steam flow side of the lower branch pipe at the connection with the connecting riser forms a first inclined shoulder for oblique flow guidance. Each of the upper and lower branch pipes on the first arc pipe is connected to the air condenser preset on the leeward side of the ventilation tower. Each of the upper and lower branch pipes on the second arc pipe is connected to the air condenser preset on the windward side of the ventilation tower.

[0010] Optionally, the connecting riser includes a lower pipe body and an upper pipe body with decreasing diameter from bottom to top. The upper pipe body and the lower pipe body are connected by a first diameter-changing section, which is a tapered structure with a gradually changing pipe diameter.

[0011] The upper branch pipe is laid horizontally, and its diameter is the same as that of the upper pipe body. The top of the upper branch pipe and the upper pipe body are integrally formed, and an arc-shaped guide bend is formed at the joint.

[0012] The lower branch pipe is laid horizontally, and its diameter is smaller than that of the lower pipe body. A first docking hole is opened on the side wall of the lower pipe body. The end of the lower branch pipe that connects to the connecting riser is a first connecting end with a beveled surface on the steam flow side. The first connecting end is vertically fixed to the first docking hole, and the beveled surface of the first connecting end is obliquely docked with the first docking hole through the obliquely set first oblique shoulder.

[0013] All of the lower branch pipes are connected to the corresponding connecting risers through the first inclined shoulder, and the inclined direction of the first inclined shoulder is perpendicular to the inclined tangent direction of the first connecting end.

[0014] Optionally, the first arc tube is divided into a first weak cooling pipe section, a second weak cooling pipe section, and a third weak cooling pipe section with continuously varying diameters along the direction from its connecting end to its closed end.

[0015] The second arc pipe is divided into a first, second, third and fourth strongly cooled pipe sections with continuously varying diameters along the direction from its connecting end to its closed end.

[0016] The first weak cooling pipe section has the same pipe diameter as the first strong cooling pipe section, and the number of connecting risers distributed on the first weak cooling pipe section and the first strong cooling pipe section is the same.

[0017] The second weak cooling pipe section has the same pipe diameter as the second strong cooling pipe section, and the number of connecting risers distributed on the second weak cooling pipe section and the second strong cooling pipe section is the same.

[0018] The third weak cooling pipe section has the same pipe diameter as the third strong cooling pipe section, and the number of connecting risers distributed on the third weak cooling pipe section and the third strong cooling pipe section is the same.

[0019] The diameter of the fourth forced cooling pipe section is smaller than that of the third forced cooling pipe section, and a connecting riser is also provided on the fourth forced cooling pipe section.

[0020] Optionally, the connecting riser is vertically arranged and its diameter is smaller than that of the main pipe ring. A second docking hole is opened on the top pipe wall of the main pipe ring. Part of the connecting riser is connected to the main pipe ring at the end with a second connecting end with a beveled surface on the steam flow side. The second connecting end is vertically fixed to the second docking hole, and the second docking hole is provided with a beveled second shoulder that bevels at an angle to the beveled surface of the second connecting end.

[0021] The first strong cooling pipe section, the second strong cooling pipe section, the third strong cooling pipe section, and all the connecting risers on the first arc pipe are provided with a second inclined shoulder on the steam flow side of the end of the main pipe ring pipe.

[0022] Optionally, in the connecting riser where the second strong cooling pipe section is located on the end diameter change side and the second weak cooling pipe section is located on the end diameter change side, the angle between the chamfered surface of the second connecting end and the second chamfered shoulder is a first angle, and the first angle is less than a right angle.

[0023] The connecting risers on both sides of the diameter change point between the first weak cooling pipe section and the second weak cooling pipe section, the third weak cooling pipe section located at the first diameter change point, the first strong cooling pipe section and the second strong cooling pipe section on both sides of the diameter change point, and the third strong cooling pipe section located at the first diameter change point, have a second included angle between the chamfered surface of the second connecting end and the second chamfered shoulder, and the second included angle is smaller than the first included angle.

[0024] For all other connecting risers, the angle between the chamfered surface of the second connecting end and the second chamfered shoulder is a right angle.

[0025] Optionally, a third docking hole is provided on the top wall of the main pipe ring, and the bottom end of part of the connecting riser is connected to the third docking hole through a second diameter changing part, wherein the second diameter changing part is a tapered structure with a gradually changing pipe diameter.

[0026] The end of the tee fitting and the connecting riser on the fourth cooling pipe section are both connected to the main pipe ring pipe through the second reducing part.

[0027] Optionally, the tee fitting includes a first pipe end that connects to the main intake pipe, and a second pipe end and a third pipe end that are symmetrically and parallel to each other along the central axis of the first pipe end. An oblique pipe section extends from the first pipe end and connects to the second pipe end and the third pipe end respectively.

[0028] The connecting end of the first arc tube is perpendicularly connected to and communicates with the connecting end of the second tube. Inside the perpendicular connection between the first arc tube and the connecting end of the second tube, a plurality of arc-shaped first guide vanes are arranged side by side along its width direction. A guide gap is formed between two adjacent first guide vanes to guide the steam in the main intake pipe into the first arc tube.

[0029] The connecting end of the second arc tube is perpendicularly connected to and communicates with the third tube connection end. Inside the part where the second arc tube is perpendicularly connected to the third tube connection end, multiple arc-shaped second guide vanes are arranged side by side along its width direction. A guide gap is formed between two adjacent second guide vanes to guide the steam in the main intake pipe into the second arc tube.

[0030] Optionally, the connecting riser on the end of the tee fitting is located on the second pipe connection end, and the upper branch pipe and the lower branch pipe on the corresponding branch are both located on the central axis of the first pipe connection end.

[0031] This invention also discloses a method for optimizing exhaust pipes, used to optimize the exhaust pipe assembly in the aforementioned natural ventilation air-cooled system. The method for optimizing exhaust pipes includes:

[0032] Establish a flow field simulation model of the initial structure of the exhaust pipe assembly. The initial structure includes the preset diameter variation dimensions of each section of the main pipe ring pipe, and the preset direct connection method for connecting each pipe.

[0033] The flow distribution deviation between the upper branch pipe and the corresponding lower branch pipe in each branch of the initial structure is obtained by flow field simulation, and the proportion of all branch pipes is divided according to the degree of deviation.

[0034] The effects of individually adjusting the diameter of the main pipe ring pipe and individually setting the first inclined shoulder on the steam inlet side of the lower branch pipe on the flow distribution deviation of each path were compared by flow field simulation, and the structural optimization sequence was determined based on the comparison results.

[0035] According to the determined structural optimization sequence, a first inclined shoulder is provided on the steam flow side of the connection between all the lower branch pipes and the corresponding connecting risers, and the connecting riser at the end of the tee fitting is connected to the main pipe ring pipe through a tapered reducing part to obtain the primary optimized structure;

[0036] Based on the initial optimization structure, the diameter of the main pipe ring pipe is iteratively adjusted, and the optimized diameter of each section of the main pipe ring pipe is determined after the proportion of the flow distribution deviation of each path approaches the optimal ratio through flow field simulation verification.

[0037] Optionally, the exhaust pipe optimization method further includes optimizing the diameter variation dimensions of each section of the main pipe ring pipe, and then structuring the flow distribution between the main pipe ring pipe and the connecting risers of each branch, including:

[0038] The primary optimized structure is obtained by adjusting the main pipe ring pipe in the primary optimized structure according to the optimized diameter size, and a secondary optimized structure is obtained. For all the connecting risers in the secondary optimized structure, a second inclined shoulder is provided on the steam flow side at the connection between the main pipe ring pipe and the riser.

[0039] Based on all the connecting risers with the second inclined shoulder, the inclined shoulder angle at the diameter change point of each section of the main pipe ring is iteratively adjusted, and the flow field simulation is used to verify until the proportion of the flow distribution deviation of each path reaches the preset target proportion, thereby determining the optimized angle and optimized position of the second inclined shoulder;

[0040] The connecting riser at the end of the second arc pipe is connected to the main pipe ring pipe through a tapered diameter reducing part, and the secondary optimization structure is adjusted according to the optimized angle and optimized position of the second inclined shoulder to obtain the target optimized structure.

[0041] Compared with the prior art, the natural ventilation air-cooling system and exhaust pipe optimization method provided by the embodiments of the present invention have the following advantages:

[0042] The main intake pipe and the main ring pipe are efficiently connected via a tee fitting. The asymmetrical diameter-changing structure of the main ring pipe, employing first and second circular arc pipes, ensures smoother steam flow and reduces local resistance losses. The asymmetrically arranged diameter-changing sections and the asymmetrically distributed connecting risers work together to ensure uniform steam distribution within the main ring pipe, preventing a significant increase in steam flow at the front connecting riser when steam flows through the first and second circular arc pipes. Furthermore, the first sloping shoulder on the lower branch pipes effectively reduces the flow difference between upper and lower branch pipes, significantly reducing local resistance losses and improving the uniformity of flow distribution. This allows steam to flow smoothly through the exhaust pipe and be evenly distributed to the air-cooled condensers on the leeward and windward sides of the ventilation tower, improving the overall system's cooling efficiency, economy, and operational stability. Attached Figure Description

[0043] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0044] Figure 1 This is a schematic diagram of the overall structure of the exhaust pipe assembly in a natural ventilation air-cooling system provided in an embodiment of the present invention;

[0045] Figure 2 This is a schematic diagram of the structure of the first and second oblique shoulders in conjunction with each other, provided in an embodiment of the present invention.

[0046] Figure 3 This is a schematic diagram of the structure of the first oblique shoulder and the second variable diameter part in accordance with an embodiment of the present invention;

[0047] Figure 4 This is a schematic diagram of the structure of the tee fitting provided in an embodiment of the present invention;

[0048] Figure 5 The diagram shows the flow distribution comparison curves of the upper and lower branch pipes in the simulation of the optimized structure thirteen and the initial structure provided in the embodiments of the present invention.

[0049] The markings in the attached diagram are as follows:

[0050] 1. Main intake pipe; 2. First arc pipe; 21. First weak cooling pipe section; 22. Second weak cooling pipe section; 23. Third weak cooling pipe section; 3. Second arc pipe; 31. First strong cooling pipe section; 32. Second strong cooling pipe section; 33. Third strong cooling pipe section; 34. Fourth strong cooling pipe section; 4. T-fitting; 41. First pipe connection end; 42. Second pipe connection end; 43. Third pipe connection end; 44. First guide vane; 45. Second guide vane; 5. Connecting riser; 51. Lower pipe body; 52. Upper pipe body; 53. First diameter reducing section; 54. Guide bend; 55. Second connecting end; 56. Second sloping shoulder; 57. Second diameter reducing section; 6. Upper branch pipe; 7. Lower branch pipe; 71. First sloping shoulder; 72. First connecting end. Detailed Implementation

[0051] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0052] This invention discloses a natural ventilation air cooling system, such as Figure 1 and Figure 2 As shown, it includes a steam turbine, an air-cooled condenser, and an exhaust pipe assembly. The exhaust pipe assembly includes an intake main pipe 1, a main pipe ring pipe, and branch pipes.

[0053] The main intake pipe 1 is connected to the steam turbine and is connected to the main pipe ring pipe through the tee fitting 4;

[0054] The main pipe ring includes a first arc pipe 2 and a second arc pipe 3 arranged horizontally and opposite to each other. One end of the first arc pipe 2 is closed and the other end is connected to one end of a tee fitting 4. The pipe body of the first arc pipe 2 has a variable diameter structure with multiple segments whose diameter decreases sequentially from its connecting end to its closed end. One end of the second arc pipe 3 is closed and the other end is connected to the other end of the tee fitting 4. The pipe body of the second arc pipe 3 has a variable diameter structure with multiple segments whose diameter decreases sequentially from its connecting end to its closed end. The variable diameter segments of the first arc pipe 2 and the variable diameter segments of the second arc pipe 3 are arranged asymmetrically.

[0055] Multiple connecting risers 5 are respectively provided on the first arc pipe 2 and the second arc pipe 3 along the steam flow direction, and the multiple connecting risers 5 on the first arc pipe 2 and the second arc pipe 3 are asymmetrically distributed. A connecting riser 5 is also provided at the end of the tee fitting 4 that connects to the first arc pipe 2, for diverting the steam on the inlet side of the first arc pipe 2.

[0056] Branch pipes are respectively installed on each connecting riser 5, including an upper branch pipe 6 connected to the top of the connecting riser 5 and a lower branch pipe 7 connected to the middle of the connecting riser 5. The steam flow side of the lower branch pipe 7 and the connecting riser 5 is formed with a first inclined shoulder 71 for oblique flow guidance. Each upper branch pipe 6 and lower branch pipe 7 on the first arc pipe 2 is connected to an air condenser pre-installed on the leeward side of the ventilation tower. Each upper branch pipe 6 and lower branch pipe 7 on the second arc pipe 3 is connected to an air condenser pre-installed on the windward side of the ventilation tower.

[0057] Through the implementation of the above-described natural ventilation air-cooling system embodiment, the main intake pipe 1 is connected to the main ring pipe via a tee fitting 4, allowing the steam discharged from the turbine to be evenly distributed to the first arc pipe 2 and the second arc pipe 3. The first arc pipe 2 and the second arc pipe 3 adopt a multi-section variable diameter structure, which conforms to the characteristic of natural flow rate decay during the steam flow along the main ring pipe, and maintains the stability of the flow velocity inside the pipe through gradual diameter reduction. Preferably, the variable diameter sections are connected by variable diameter heads with gradually changing pipe diameters, which can reduce the increase in local resistance caused by sudden changes in pipe diameter and ensure the continuity of steam flow in the circumference of the ring pipe. Based on this, the asymmetrical structure of the variable diameter sections of the first arc pipe 2 and the second arc pipe 3 is used to address the difference in operating conditions between the windward and leeward sides of the ventilation tower: the windward side has sufficient airflow and high cooling efficiency, while the leeward side is prone to forming a low-pressure area and has weak cooling capacity. Therefore, the asymmetrical structure of the variable diameter sections of the first circular arc pipe 2 and the second circular arc pipe 3 is achieved by adjusting the flow resistance on both sides in a differentiated manner. For example, the first circular arc pipe 2 on the leeward side can use fewer variable diameter sections (relatively gentle pipe diameter changes) to appropriately increase the flow resistance of this path and limit excessive steam flow to areas with weak cooling capacity; while the second circular arc pipe 3 on the windward side optimizes steam distribution through more variable diameter sections (more rapid pipe diameter changes) to fully utilize the potential of high cooling efficiency areas. This dynamic adaptation mechanism can effectively balance the system back pressure and prevent local flow overload or insufficient flow caused by uneven environmental wind field.

[0058] As described above, the asymmetrical distribution of the connecting risers 5 on the first arc pipe 2 and the second arc pipe 3 further refines the flow distribution strategy. For example, the dense riser layout on the second arc pipe 3 can receive and disperse a large steam flow, distributing it evenly to each air-cooled condenser (cooling triangle); the sparse riser layout on the first arc pipe 2 matches the lower cooling demand on the leeward side. Combined with the connecting riser 5 added to the end of the tee fitting 4, the steam about to enter the first arc pipe 2 (leeward side) is pre-diverted. This independent connecting riser 5 directly guides some steam away from the first arc pipe 2, effectively reducing the steam flow load in the first arc pipe 2 and preventing excessive steam from flooding into the leeward side area with limited cooling capacity. This structure appears to add a connecting riser 5 on the leeward side, but in fact it reduces the flow pressure of the main ring pipe on the leeward side by localizing the flow, indirectly causing more steam to flow naturally through the tee fitting 4 to the windward side where the risers are dense, i.e., into the second arc pipe 3. Thus, at the system level, the steam is optimized to the high cooling efficiency area, so as to maintain the stability of the system back pressure when the ambient wind field changes.

[0059] Furthermore, the branch pipes optimize the steam distribution efficiency within the single-path connecting riser 5 through the coordinated operation of the upper branch pipe 6 and the lower branch pipe 7. Specifically, a first inclined shoulder 71 is formed on the steam inflow side at the junction of the lower branch pipe 7 and the connecting riser 5. This structure guides the steam flow line through a smooth inclined surface, significantly reducing velocity changes and flow separation at bends, effectively minimizing local resistance losses. This guiding effect significantly suppresses the flow difference between the upper and lower branch pipes 7, ensuring uniform steam distribution to the cooling triangle of the same air condenser.

[0060] Therefore, the natural ventilation air-cooling system of this embodiment of the invention forms a complete flow control system through the initial flow diversion of the tee fitting 4, the variable diameter flow stabilization of the main pipe ring, the macroscopic adjustment of the asymmetric riser layout, and the flow guidance optimization of the first inclined shoulder 71 of the lower branch pipe 7. This system, in particular, further optimizes the flow uniformity at the branch pipe level through the inclined flow guidance design of the first inclined shoulder 71, effectively solving the problems of uneven steam distribution and back pressure control faced by large-scale natural ventilation direct air-cooling systems. This achieves spatial matching between steam supply and cooling demand, significantly improving the system's operational economy, stability, and reliability under varying operating conditions and extreme environments.

[0061] Furthermore, the connecting riser 5 includes a lower pipe body 51 and an upper pipe body 52 with decreasing pipe diameter from bottom to top. The upper pipe body 52 and the lower pipe body 51 are connected by a first diameter changing part 53, which is a tapered structure with a gradually changing pipe diameter.

[0062] The upper branch pipe 6 is laid horizontally, and its diameter is the same as that of the upper pipe body 52. ​​The top of the upper branch pipe 6 and the upper pipe body 52 are integrally formed, and an arc-shaped guide bend 54 is formed at the joint.

[0063] The lower branch pipe 7 is laid horizontally, and its diameter is smaller than that of the lower pipe body 51. A first docking hole is opened on the side wall of the lower pipe body 51. The end of the lower branch pipe 7 that connects to the riser pipe 5 is a first connecting end 72 with a beveled surface on the steam flow side. The first connecting end 72 is vertically fixed to the first docking hole, and the beveled surface of the first connecting end 72 is obliquely docked with the first docking hole through the obliquely set first oblique shoulder 71.

[0064] All the lower branch pipes 7 are connected to the corresponding connecting risers 5 through the first oblique shoulder 71, and the oblique direction of the first oblique shoulder 71 is perpendicular to the oblique tangent direction of the first connecting end 72.

[0065] Through the implementation of the above-described natural ventilation air-cooling system embodiment, the connecting riser 5 is divided into an upper pipe body 52 and a lower pipe body 51 with different diameters. This is designed to accommodate the pressure decrease and velocity change of steam flowing from bottom to top in the connecting riser 5, in order to maintain the principle of constant velocity. Furthermore, the tapered structure of the first diameter-changing section 53 achieves a smooth and gradual change in pipe diameter, reducing local resistance loss caused by abrupt changes in cross-section and promoting a stable fluid transition.

[0066] As described above, by integrally forming the upper branch pipe 6 with the upper pipe body 52 and creating an arc-shaped guide bend 54 at the joint, the steam turning process at the top of the connecting riser 5 can be optimized to minimize eddies and secondary flow phenomena. Furthermore, the first inclined shoulder 71 optimizes the fluid velocity distribution at the bend in the flow to the lower branch pipe 7, significantly reducing the flow rate difference between the upper and lower branch pipes 7 and improving the overall flow distribution uniformity. Specifically, the inclined direction of the first inclined shoulder 71 is perpendicular to the inclined tangent direction of the first connecting end 72. This angle is precisely optimized through flow field simulation to ensure optimal orthogonal matching with the mainstream flow direction when the fluid enters, minimizing flow separation and energy dissipation, thereby significantly reducing local resistance and improving flow distribution uniformity. Finally, by providing the first inclined shoulder 71 on all lower branch pipes 7, the flow rate difference between the upper and lower branch pipes 7 on each branch is systematically reduced, facilitating precise back pressure control and optimized cooling effect for the entire system.

[0067] Furthermore, looking back Figure 1 The first circular arc pipe 2 is divided into a first weak cooling pipe section 21, a second weak cooling pipe section 22 and a third weak cooling pipe section 23 with continuously changing diameters along the direction from its connecting end to its closed end;

[0068] The second circular arc pipe 3 is divided into a first strong cooling pipe section 31, a second strong cooling pipe section 32, a third strong cooling pipe section 33 and a fourth strong cooling pipe section 34 with continuously changing diameters along the direction from its connecting end to its closed end.

[0069] The diameter of the first weak cooling pipe section 21 is the same as that of the first strong cooling pipe section 31, and the number of connecting risers 5 distributed on the first weak cooling pipe section 21 and the first strong cooling pipe section 31 is the same.

[0070] The second weak cooling pipe section 22 and the second strong cooling pipe section 32 have the same pipe diameter, and the number of connecting risers 5 distributed on the second weak cooling pipe section 22 and the second strong cooling pipe section 32 is the same.

[0071] The diameter of the third weak cooling pipe section 23 is the same as that of the third strong cooling pipe section 33, and the number of connecting risers 5 distributed on the third weak cooling pipe section 23 and the third strong cooling pipe section 33 is the same.

[0072] The diameter of the fourth strong cooling pipe section 34 is smaller than that of the third strong cooling pipe section 33, and a connecting riser 5 is also installed on the fourth strong cooling pipe section 34.

[0073] Through the implementation of the above-described natural ventilation air-cooling system embodiment, the smooth and gradual change in diameter of the first arc pipe 2 and the second arc pipe 3 effectively reduces local resistance loss and promotes the stability of steam flow. Secondly, the first weakly cooled pipe section 21 and the first strongly cooled pipe section 31 have the same pipe diameter and the same number of connecting risers 5, ensuring the basic symmetry of flow distribution on both sides of the tee fitting 4 and reducing flow deviation caused by environmental differences. The consistent design of the second weakly cooled pipe section 22 and the second strongly cooled pipe section 32, and the third weakly cooled pipe section 23 and the third strongly cooled pipe section 33 further enhances flow balance and reduces deviation between branches. The fourth strongly cooled pipe section 34 has a smaller pipe diameter than the third strongly cooled pipe section 33, and by adding an additional connecting riser 5, it compensates for the flow attenuation at the end of the second arc pipe 3, optimizing the overall distribution uniformity.

[0074] The aforementioned structure matches the cooling requirements of the windward and leeward sides through differentiated diameter changes, and combines the first inclined shoulder 71 set on all lower branch pipes 7 to reduce vortices and secondary flow, thereby achieving precise back pressure control and improved cooling efficiency.

[0075] Furthermore, combined Figure 1 and Figure 2 As shown, the connecting riser 5 is vertically arranged, and its diameter is smaller than that of the main pipe ring pipe. A second docking hole is opened on the top pipe wall of the main pipe ring pipe. The end of the connecting riser 5 that connects to the main pipe ring pipe is a second connecting end 55 with a beveled surface on the steam flow side. The second connecting end 55 is vertically fixed to the second docking hole, and a beveled second shoulder 56 is provided on the second docking hole, which is obliquely docked with the beveled surface of the second connecting end 55.

[0076] Among them, the first strong cooling pipe section 31, the second strong cooling pipe section 32, the third strong cooling pipe section 33, and all connecting risers 5 on the first arc pipe 2 are provided with a second inclined shoulder 56 on the steam flow side of the connecting mother pipe ring pipe end.

[0077] Through the implementation of the above-described natural ventilation air-cooling system embodiment, the connecting riser 5 is designed with a vertical layout and a diameter smaller than that of the main pipe ring pipe. The vertical spatial layout of the connecting riser 5 promotes natural steam diffusion, while the difference in pipe diameter creates a reasonable flow velocity gradient. Secondly, a second connecting hole is opened on the top wall of the main pipe ring pipe, so that the second connecting end 55 of the connecting riser 5 with the beveled surface is vertically fixed to it. Combined with the beveled connecting structure of the second beveled shoulder 56, the flow separation phenomenon when steam flows horizontally from the ring pipe to the vertical direction of the riser is effectively reduced, and the total flow rate of the branch at this point can be significantly increased, thereby uniformly distributing the low flow rate branch pipes.

[0078] As described above, the first three strong cooling sections (first strong cooling section 31, second strong cooling section 32, and third strong cooling section 33) of the second arc pipe 3 are mainly distributed at the front and middle parts of the windward side. Due to the high steam pressure and sufficient kinetic energy within these sections, and their corresponding areas of strongest cooling capacity, the connecting risers 5 at these locations utilize the second inclined shoulder 56 as a streamlined guide port. This efficiently and smoothly guides the high-speed steam from the main pipe ring pipe into the corresponding branch's connecting riser 5, allowing the steam to flow smoothly and quickly with low resistance, matching its powerful cooling capacity. The fourth strong cooling section 34, located at the end of the second arc pipe 3, has steam whose pressure and kinetic energy have dropped to their lowest point after a long journey and multiple diversions. This is the "most unfavorable operating point" where flow separation and stall are most likely to occur. Therefore, if the second inclined shoulder 56 is still used for guiding the flow at this location, the steam distribution effect will be unsatisfactory, requiring other technical means.

[0079] Meanwhile, the first arc pipe 2 adopts the second sloping shoulder 56 along its entire length. The uniform sloping shoulder structure can ensure that the steam entering the first arc pipe 2 is evenly distributed to the connecting riser 5 of each branch, thereby achieving basic and uniform condensation to prevent local complete failure or local excessive congestion.

[0080] The specific layout of the aforementioned sloping shoulder structure is determined based on flow field simulation, which makes the steam flow more smoothly when it enters the connecting riser 5, reduces the generation of eddies and energy dissipation, and provides a continuous and stable steam supply for the upper branch pipe 6 and the lower branch pipe 7, thereby enhancing the flow balance between the upper and lower branch pipes 7 on each branch, and ultimately achieving the optimal operation of the natural ventilation direct air cooling system in the entire operating range.

[0081] Furthermore, the connecting riser 5 on the end of the second strong cooling pipe section 32 and the second weak cooling pipe section 22 is located on the end of the diameter change side, and the angle between the oblique surface of the second connecting end 55 and the second oblique shoulder 56 is the first angle, and the first angle is less than a right angle.

[0082] The connecting risers 5 at the diameter change points of the first weak cooling pipe section 21 and the second weak cooling pipe section 22, the third weak cooling pipe section 23 located at the diameter change point at the first end, the first strong cooling pipe section 31 and the second strong cooling pipe section 32, and the third strong cooling pipe section 33 located at the diameter change point at the first end, have a second included angle between the oblique surface of the second connecting end 55 and the second oblique shoulder 56, which is smaller than the first included angle.

[0083] For all other connecting risers 5, the angle between the chamfered surface of the second connecting end 55 and the second chamfered shoulder 56 is a right angle.

[0084] In implementing the above-described natural ventilation air-cooling system embodiment, to further optimize the flow distribution of steam from the main pipe ring pipe into the connecting riser 5, the angle of the second inclined shoulder 56 needs to be adjusted. However, adjusting the second inclined shoulder 56 of each connecting riser 5 one by one is not conducive to engineering construction. Therefore, the second inclined shoulder 56 is specially set on both sides of the diameter change points of each section of the main pipe ring pipe (including the first weak cooling pipe section 21 and the second weak cooling pipe section 22, the second weak cooling pipe section 22 and the third weak cooling pipe section 23, the first strong cooling pipe section 31 and the second strong cooling pipe section 32, and the second strong cooling pipe section 32 and the third strong cooling pipe section 33). By utilizing the inherent velocity change characteristics of the diameter change area, the local flow field distribution is optimized through the inclined shoulder structure, significantly improving the steam throughput capacity in the branch connecting riser 5. This targeted arrangement maintains the flow regulation effect, avoids the engineering complexity of the entire system's inclined shoulder modification through precise optimization of key parts, and makes the steam distribution in the diameter change area more uniform, ultimately achieving synergistic optimization of system resistance reduction and back pressure stability control.

[0085] As described above, the connecting risers 5 at different locations are provided with second oblique shoulders 56 arranged at different angles. For example, at the connecting risers 5 where the second strong cooling pipe section 32 is located at the end of the diameter change side and the second weak cooling pipe section 22 is located at the end of the diameter change side, a first included angle of 75° is adopted. By increasing the inclination angle between the oblique surface and the second oblique shoulder 56, a smoother flow channel transition is formed, which effectively reduces the tendency of high-velocity steam to flow separation at the end of the pipe, and allows steam in the area with the lowest system pressure to enter the branch pipe more smoothly.

[0086] At the connecting risers 5 located on both sides of the diameter change between the first weakly cooled pipe section 21 and the second weakly cooled pipe section 22, on the first diameter change side of the third weakly cooled pipe section 23, on both sides of the diameter change between the first strongly cooled pipe section 31 and the second strongly cooled pipe section 32, and on the first diameter change side of the third strongly cooled pipe section 33, a second included angle of 60° is adopted. This moderately angled guide surface balances the acceleration effect and resistance loss caused by the abrupt change in cross-section in the diameter change region, ensuring necessary flow guidance while avoiding excessive pressure drop. The right-angled connecting risers 5 at other locations ensure structural simplicity and engineering economy in the stable flow field region.

[0087] The aforementioned three-level angle configuration system based on pipe segment functional positioning forms a systematic local resistance control mechanism: the 75° angle mainly serves to ensure flow stability in the low-pressure area at the end of the system, the 60° angle focuses on optimizing energy loss in the transition zone of diameter changes, and the right-angle design is suitable for conventional stable flow field regions. Particularly at key locations such as the end of the second strong cooling pipe segment 32, the streamlined design of the first angle significantly improves the re-acceleration capability of steam in the kinetic energy decay zone, preventing eddy current generation. In multiple diameter-change junction areas, the precise setting of the second angle weakens the longitudinal velocity gradient and controls the development of lateral secondary flow, making the circumferential pressure distribution of the main pipe more balanced. This differentiated sloping angle strategy, by matching the fluid dynamic characteristics of different pipe segments, achieves precise adaptation of the local resistance coefficient to the overall flow demand, ultimately enabling a dynamic balance between the steam distribution ratio and actual cooling capacity between the strong cooling and weak cooling regions, thereby improving the system's adaptability under varying operating conditions.

[0088] The angle combination of the second connection end 55 and the second oblique shoulder 56 of all the connecting risers 5 together constitutes a spatially distributed flow resistance adjustment network. Through the carefully designed local loss characteristics at each node, the pressure distribution pattern in the main pipe ring is actively shaped, laying the fluid dynamic foundation for uniform steam distribution at the branch pipe level, thereby achieving the coordinated optimization of back pressure control and cooling efficiency at the system level.

[0089] Furthermore, combined Figure 1 and Figure 3 As shown, a third docking hole is provided on the top pipe wall of the mother pipe ring pipe. The bottom end of part of the connecting riser 5 is connected to the third docking hole through the second diameter changing part 57. The second diameter changing part 57 is a tapered structure with a gradually changing pipe diameter.

[0090] Among them, the end of the tee fitting 4 and the connecting riser 5 on the fourth strong cooling pipe section 34 are both connected to the main pipe ring pipe through the second reducing part 57.

[0091] By implementing the above-described natural ventilation air-cooling system embodiment, connecting a portion of the riser 5 to the third connecting hole on the main pipe ring pipe via the second diameter reducing part 57 can achieve a smooth transition in pipe diameter, thereby reducing local resistance loss and fluid turbulence caused by abrupt changes in cross-section. Specifically, connecting the riser 5 at the end of the tee fitting 4 to the main pipe ring pipe via the second diameter reducing part 57 can effectively reduce local resistance loss during the pre-diversion process, allowing more steam to be smoothly guided away from the first arc pipe 2 through this independent diversion path, and effectively suppressing the backflow vortex generated after the steam positively impacts the tee blind plate; at the same time, connecting the riser 5 on the fourth forced cooling pipe section 34 to the main pipe ring pipe via the second diameter reducing part 57 eliminates the flow separation phenomenon caused by the velocity decay at the end of the main pipe ring pipe, allowing the steam at the end of the second arc pipe 3 to smoothly transition to the riser 5 of this path. The conical transition structure at these two key locations reduces the local resistance peaks in the high-speed impact zone and the low-pressure end through streamlined flow guidance, making the pressure distribution of steam in the inlet and end sections of the main pipe ring system more balanced, thereby improving the overall uniformity of flow distribution in the upper and lower branch pipes.

[0092] Furthermore, combined Figure 1 and Figure 4 As shown, the three-way fitting 4 includes a first pipe end 41 that connects to the intake main pipe 1, and a second pipe end 42 and a third pipe end 43 that are symmetrically and parallelly arranged along the central axis of the first pipe end 41. An inclined pipe section extends from the first pipe end 41 and connects to the second pipe end 42 and the third pipe end 43 respectively.

[0093] The connecting end of the first arc pipe 2 is perpendicularly connected to and communicates with the second pipe end 42. Inside the perpendicular connection between the first arc pipe 2 and the second pipe end 42, multiple arc-shaped first guide vanes 44 are arranged side by side along its width direction. A guide gap is formed between two adjacent first guide vanes 44 to guide the steam in the intake main pipe 1 into the first arc pipe 2.

[0094] The connecting end of the second arc tube 3 is perpendicularly connected to and communicates with the third tube end 43. Inside the perpendicular connection between the second arc tube 3 and the third tube end 43, multiple arc-shaped second guide vanes 45 are arranged side by side along its width direction. A guide gap is formed between two adjacent second guide vanes 45 to guide the steam in the intake main tube 1 into the second arc tube 3.

[0095] Furthermore, looking back Figure 1 The connecting riser 5 at the end of the tee fitting 4 is located on the second pipe connection end 42, and the upper branch pipe 6 and the lower branch pipe 7 of this route are both located on the central axis of the first pipe connection end 41.

[0096] Through the implementation of the above-described natural ventilation air-cooling system embodiment, the symmetrical extension structure of the inclined pipe section in the tee fitting 4 achieves natural flow diversion of the steam stream, ensuring a balanced initial distribution of the incoming flow from the main intake pipe 1 at the second pipe joint 42 and the third pipe joint 43. Multiple arc-shaped first guide vanes 44, positioned at the perpendicular connection between the first arc pipe 2 and the second pipe joint 42, form a gradually narrowing guide gap, causing the steam to undergo moderate pre-swirl upon entering the first arc pipe 2, effectively eliminating vortex formation in the blind end region of the tee fitting. Simultaneously, the second guide vanes 45, positioned at the second arc pipe 3 and the third pipe joint 43, form matching flow conditions at symmetrical positions through the same guide gap. This symmetrical guide vane layout maintains the dynamic balance of the flow field at the inlet of the left and right annular pipes and, through the special curvature design of the arc-shaped guide surface, converts some dynamic pressure into static pressure, significantly reducing local resistance loss.

[0097] Furthermore, the connecting riser 5 located on the second pipe joint 42 has its upper branch pipe 6 and lower branch pipe 7 symmetrically arranged along the central axis of the first pipe joint 41, forming an independent flow distribution channel. This connecting riser 5 works synergistically with the first guide vane 44: the mainstream steam guided by the first guide vane 44 diffuses uniformly circumferentially along the first arc pipe 2, while the connecting riser 5 directly diverts a portion of the steam through the second pipe joint 42. This dual distribution mechanism allows for precise control of the steam load on the first arc pipe 2 (corresponding to the leeward side). When ambient wind causes a decrease in cooling capacity on the leeward side, this structure diverts some steam to other areas in advance through the connecting riser 5, preventing excessive steam from lingering in the leeward side system. Simultaneously, the first guide vane 44 ensures that the remaining steam maintains a stable flow state within the first arc pipe 2, preventing flow separation due to reduced flow rate. This combined flow guidance and diversion structure ensures that the system maintains optimal flow distribution characteristics under varying operating conditions.

[0098] As described above, the symmetrical guide vanes inside the tee fitting 4 ensure a balanced basic flow field, while the dedicated connecting riser 5 on the second pipe joint 42 provides dynamic adjustment capability. Together, they constitute a composite solution to address the impact of ambient wind. The entire structure minimizes pressure loss through refined flow field design, significantly reducing the total pressure drop of steam in the tee area. Furthermore, the flow deviation between the left and right ring pipes can be stably controlled within 3%, significantly improving the operational stability and economy of the natural ventilation direct air-cooling system under complex wind field conditions.

[0099] This invention also discloses a method for optimizing exhaust pipes, used to optimize the exhaust pipe assembly in the above-mentioned natural ventilation air-cooled system. The exhaust pipe optimization method includes:

[0100] Establish a flow field simulation model of the initial structure of the exhaust pipe assembly. The initial structure includes the preset diameter variation dimensions of each section of the main pipe ring pipe, and the preset direct connection method for connecting each pipe.

[0101] The flow distribution deviation between the upper branch pipe 6 and the corresponding lower branch pipe 7 of each branch in the initial structure is obtained by flow field simulation, and the proportion of each branch pipe is divided according to the degree of deviation.

[0102] The effects of individually adjusting the diameter of the main pipe ring pipe and individually setting the first inclined shoulder 71 on the steam inflow side of the lower branch pipe 7 on the flow distribution deviation of each path were compared by flow field simulation, and the structural optimization sequence was determined based on the comparison results.

[0103] According to the determined structural optimization sequence, a first inclined shoulder 71 is set on the steam flow side of the connection between all lower branch pipes 7 and the corresponding connecting riser pipes 5, and the connecting riser pipe 5 at the end of the tee fitting 4 is connected to the main pipe ring pipe through a tapered reducing part to obtain the primary optimized structure;

[0104] Based on the initial optimization structure, the diameter of the main pipe ring pipe is iteratively adjusted, and the optimized diameter of each section of the main pipe ring pipe is determined after the proportion of the flow distribution deviation of each path approaches the optimal ratio through flow field simulation verification.

[0105] Furthermore, the exhaust pipe optimization method also includes optimizing the diameter variation dimensions of each section of the main pipe ring pipe, and then structuring the flow distribution between the main pipe ring pipe and each branch connecting riser 5, including:

[0106] Based on the optimized diameter adjustment of the main pipe ring pipe in the primary optimization structure, a secondary optimization structure is obtained, and a second inclined shoulder 56 is provided on the steam flow side of all connecting risers 5 in the secondary optimization structure at their connection with the main pipe ring pipe.

[0107] Based on all the connecting risers 5 with the second inclined shoulder 56, the inclined shoulder angle at the diameter change of each section of the main pipe ring pipe is iteratively adjusted, and the flow field simulation is used to verify until the proportion of the flow distribution deviation of each path reaches the preset target proportion, and the optimized angle and optimized position of the second inclined shoulder 56 are determined.

[0108] The connecting riser 5 at the end of the second arc pipe 3 is connected to the main pipe ring pipe through a tapered variable diameter section. The secondary optimization structure is adjusted according to the optimized angle and optimized position of the second inclined shoulder 56 to obtain the target optimized structure.

[0109] The exhaust pipe optimization method of this invention will be further illustrated by specific simulation experiments:

[0110] 1. Set the unit operating conditions, as shown in Table 1:

[0111] Table 1 Unit Operating Conditions Table

[0112]

[0113] In Table 1, THA (Turbine Heat Acceptance) is used to evaluate the system's efficiency and flow distribution under standard conditions; TRL (Turbine Rated Load) is used to verify whether the exhaust pipe can maintain good flow uniformity under high pressure differential when the cooling capacity is worst (such as the leeward effect caused by strong summer winds), preventing some branches from being "blocked" due to excessive back pressure; VWO (Valve Wide Open) and TMCR (Turbine Maximum Continuous Rating) are used to verify the exhaust pipe's pressure resistance, vibration, and whether it can still maintain flow distribution uniformity at high flow rates under maximum steam flow.

[0114] 2. For the initial structure of the exhaust pipe assembly, the diameter of the main pipe ring is a gradually changing structure, with design diameter values ​​of 6020mm, 4220mm, 3020mm, and 2020mm. For ease of analysis, as follows... Figure 1 As shown, the branch lines containing each connecting riser 5 are numbered in a counter-clockwise direction. Connecting riser 5 number 1 is located at the T-junction at the tower entrance; connecting risers 5 numbered 2-8 correspond to the first strong cooling pipe section 31, with a pipe diameter of 6020mm; connecting risers 5 numbered 9-13 correspond to the second strong cooling pipe section 32, with a pipe diameter of 4220mm; connecting risers 5 numbered 16-19 correspond to the third strong cooling pipe section 33, with a pipe diameter of 3020mm; connecting riser 5 numbered 20 correspond to the fourth strong cooling pipe section 34, with a pipe diameter of 2020mm; connecting risers 5 numbered 21-26 correspond to the third weak cooling pipe section 23, with a pipe diameter of 3020mm; connecting risers 5 numbered 27-31 correspond to the second weak cooling pipe section 22, with a pipe diameter of 4220mm; connecting risers 5 numbered 32-38 correspond to the first weak cooling pipe section 21, with a pipe diameter of 6020mm.

[0115] Simulation results show that the initial structure of the exhaust pipe assembly includes 76 branch pipes (38 upper branch pipes 6 and 38 lower branch pipes 7). The relative flow deviation between the upper and lower branch pipes 7 exceeds 10% in 53% (40 branch pipes), is controlled between 5% and 10% in 38% (29 branch pipes), and is controlled within 5% in 9% (7 branch pipes). Overall, the flow rate of the upper and lower branch pipes 7 is lower than that of the upper branch pipe 6 in each branch. Therefore, the initial structure of the exhaust pipe assembly has considerable room for optimization.

[0116] 3. Based on the operational experience of ACC (AirCooled Condenser, direct air-cooled system), the optimization objectives for the NDC exhaust piping are shown in Table 2:

[0117] Table 2 Structural Optimization Objectives

[0118]

[0119] Therefore, the purpose of the exhaust pipe optimization method in this embodiment of the invention is to provide an exhaust pipe assembly structure for a natural ventilation air-cooled system, so as to solve the problems of uneven flow distribution and back pressure control in the steam cooling system after the NDC system is scaled up.

[0120] 4. Optimize Structure 1:

[0121] The optimization divides the main pipe ring into zones based on pipe diameter according to the principle of constant flow velocity. First, the pipe diameter of each zone is adjusted. In the first optimization structure, the pipe diameter of the main pipe ring is changed from 6020mm, 4220mm, 3020mm, 2020mm to 5820mm, 4720mm, 3520mm, 2020mm.

[0122] Simulation results show that the flow field distribution in optimized structure one is generally similar to that of the initial structure. The pressure decreases and the flow velocity increases at the constriction of the main intake pipe 1. In optimized structure one: the relative flow deviation of the upper and lower branch pipes 7 exceeds 10% for 57% (43 paths), is controlled within 5%-10% for 24% (18 paths), and is controlled within 5% for 19% (15 paths). Compared with the initial structure, the flow distribution is somewhat more uniform, but the overall difference is still significant.

[0123] 5. Optimize Structure Two:

[0124] Based on the optimized structure one, a first inclined shoulder 71 is set on all lower branch pipes 7, and the pipe diameter of the main pipe ring pipe is the same as that of the optimized structure one.

[0125] Simulation results show that the flow field distribution in optimized structure two is generally similar to that in the initial structure. The concave surface of the guide vanes in the tee fitting 4 exhibits higher pressure, while the convex surface shows lower pressure. The pressure decreases and the flow velocity increases at the constriction of the main intake pipe 1. In optimized structure two: the relative flow deviation of the upper and lower branch pipes 7 exceeds 10% for 9% (7 lines); the relative flow deviation of the upper and lower branch pipes 7 is controlled within 5%-10% for 28% (21 lines); and the relative flow deviation of the upper and lower branch pipes 7 is controlled within 5% for 63% (48 lines).

[0126] 6. Optimize Structure Three:

[0127] Optimized Structure 3 is based on Optimized Structure 1, and simply verifies the impact of pipe diameter adjustment on the flow distribution of each branch. The pipe diameter of the main pipe ring pipe is changed from 6020mm, 4220mm, 3020mm, 2020mm to 5820mm, 4520mm, 3220mm, 2020mm, while the rest is the same as the initial structure.

[0128] Simulation results show that the flow field distribution in optimized structure three is generally similar to that in the initial structure. The concave surface of the guide vanes in the tee fitting 4 exhibits higher pressure, while the convex surface shows lower pressure. The pressure decreases and the flow velocity increases at the constriction of the main intake pipe 1. In optimized structure three: the relative flow deviation of the upper and lower branch pipes 7 exceeds 10% for 56% (42 lines), is controlled within 5%-10% for 18% (14 lines), and is controlled within 5% for 26% (20 lines).

[0129] 7. Optimize Structure Four:

[0130] Optimized Structure Four is based on Optimized Structure Two, except that the connecting riser 5 of No. 20 is equipped with a second diameter reducing section 57, and the diameter of the main pipe ring is 5820mm, 4520mm, 3220mm, and 2020mm (same as Optimized Structure Three).

[0131] Simulation results show that the flow field distribution in optimized structure four is generally similar to that of the initial structure. The concave surface of the guide vanes in the tee fitting 4 exhibits higher pressure, while the convex surface pressure is lower. The pressure decreases and the flow velocity increases at the constriction of the main intake pipe 1. In optimized structure four: the relative flow deviation of the upper and lower branch pipes 7 exceeds 10% for 6% (5 lines), is controlled within 5%-10% for 25% (19 lines), and is controlled within 5% for 69% (52 lines). The second diameter reducer 57, installed in the No. 20 connecting riser 5, significantly reduces the uneven flow distribution in this line.

[0132] 8. Optimize Structure Five:

[0133] Optimized Structure 5 further adjusts the pipe diameter based on Optimized Structure 4. The pipe diameter of the main pipe ring pipe changes from 6020mm, 4220mm, 3020mm, 2020mm to 5820mm, 4520mm, 3220mm, 2020mm, while the rest is the same as Optimized Structure 4.

[0134] Simulation results show that the flow field distribution in optimized structure five is generally similar to that of the initial structure. The concave surface of the guide vanes inside the tee fitting 4 exhibits higher pressure, while the convex surface shows lower pressure. The pressure decreases and the flow velocity increases at the constriction of the main intake pipe 1. In optimized structure five: the relative flow deviation of the upper and lower branch pipes 7 exceeds 10% for 49% (37 lines); the relative flow deviation of the upper and lower branch pipes 7 is controlled within 5%-10% for 18% (14 lines); and the relative flow deviation of the upper and lower branch pipes 7 is controlled within 5% for 33% (25 lines).

[0135] 9. Optimize Structure Six:

[0136] Optimization Structure Six adjusts the pipe diameter based on Optimization Structure Four. The diameter of the main pipe and ring pipe changes from 6020mm, 4220mm, 3020mm, and 2020mm to 5620mm, 4720mm, 3420mm, and 2220mm, while the rest remains the same as Optimization Structure Four.

[0137] Simulation results show that the optimized flow field distribution is generally similar to the initial structure. The concave surface of the guide vanes inside the tee fitting 4 exhibits higher pressure, while the convex surface shows lower pressure. The pressure decreases and the flow velocity increases at the constriction of the main intake pipe 1. In optimized structure six: the relative flow deviation of the upper and lower branch pipes 7 exceeds 10% for 10% (8 lines); the relative flow deviation of the upper and lower branch pipes 7 is controlled within 5%-10% for 25% (19 lines); and the relative flow deviation of the upper and lower branch pipes 7 is controlled within 5% for 65% (49 lines).

[0138] 10. Optimize Structure Seven:

[0139] Optimized Structure Seven adjusts the pipe diameter based on Optimized Structure Four. The diameter of the main pipe ring pipe changes from 6020mm, 4220mm, 3020mm, and 2020mm to 5820mm, 4520mm, 3220mm, and 2020mm. All lower branch pipes 7 are equipped with a first inclined shoulder 71.

[0140] Simulation results show that the flow field distribution in optimized structure 7 is generally similar to that of the initial structure. The concave surface of the guide vanes in the tee fitting 4 exhibits higher pressure, while the convex surface shows lower pressure. The pressure decreases and the flow velocity increases at the constriction of the main intake pipe 1. In optimized structure 7: the relative flow deviation of the upper and lower branch pipes 7, accounting for 8% (6 channels), exceeds 10%; the relative flow deviation of the branch pipes (22 channels) is controlled within 5%-10%; and the relative flow deviation of the branch pipes (48 channels) is controlled within 5%.

[0141] 11. Optimize the structure eight:

[0142] The diameter of the main pipe in the optimized structure 8 is selected as 5720mm, 4520mm, 3120mm, and 2020mm. All lower branch pipes 7 are equipped with a first inclined shoulder 71. Each branch connecting riser 5 is directly connected to the main pipe ring pipe. The rest is the same as the optimized structure 7.

[0143] Simulation results show that the flow field distribution in optimized structure eight is generally similar to that of the initial structure. The concave surface of the guide vanes in the tee fitting 4 exhibits higher pressure, while the convex surface shows lower pressure. The pressure decreases and the flow velocity increases at the constriction of the main intake pipe 1. In optimized structure eight: the relative flow deviation of the upper and lower branch pipes 7, accounting for 10% (8 channels), exceeds 10%; the relative flow deviation of the branch pipes (21 channels) is controlled within 5%-10%; and the relative flow deviation of the branch pipes (47 channels) is controlled within 5%.

[0144] 12. Optimize Structure Nine:

[0145] For optimized structure nine, the diameter of the main pipe ring pipe is 5820mm, 4520mm, 3220mm, and 2020mm. A second sloping shoulder 56 with a height of 710mm is made at 90 degrees on the connecting risers 5 at No. 8, 13, 27, and 32. A second diameter reducing part 57 is set on the connecting riser 5 at No. 19. The rest is the same as optimized structure seven.

[0146] Simulation results show that the flow field distribution in optimized structure nine is generally similar to that of the initial structure. The concave surface of the guide vanes in the tee fitting 4 exhibits higher pressure, while the convex surface shows lower pressure. The pressure decreases and the flow velocity increases at the constriction of the main intake pipe 1. In optimized structure nine: the relative flow deviation of the upper and lower branch pipes 7 exceeds 10% for 10% (8 lines); the relative flow deviation of the upper and lower branch pipes 7 is controlled within 5%-10% for 23% (17 lines); and the relative flow deviation of the upper and lower branch pipes 7 is controlled within 5% for 67% (51 lines).

[0147] 13. Optimize the structure ten:

[0148] Based on optimized structure nine, optimized structure ten adopts a second sloping shoulder 56 with a height of 350mm for connecting risers 5 of No. 8, 13, 27 and 32, and a second diameter reducing part 57 for connecting riser 5 of No. 19. The rest are the same as optimized structure nine.

[0149] Simulation results show that the flow field distribution in optimized structure 10 is generally similar to that of the initial structure. The concave surface of the guide vanes in the tee fitting 4 exhibits higher pressure, while the convex surface shows lower pressure. The pressure decreases and the flow velocity increases at the constriction of the main intake pipe 1. In optimized structure 10: the relative flow deviation of the upper and lower branch pipes 7 exceeds 10% for 4% (3 lines); the relative flow deviation of the upper and lower branch pipes 7 is controlled within 5%-10% for 24% (18 lines); and the relative flow deviation of the upper and lower branch pipes 7 is controlled within 5% for 72% (55 lines).

[0150] 14. Optimize the structure eleventh:

[0151] Based on Optimized Structure IX, Optimized Structure XI adopts a second inclined shoulder 56 with a height of 350mm for connecting risers 5 of No. 8, 13, 27 and 32, and a second diameter reducing part 57 for connecting riser 5 of No. 19. The rest are the same as Optimized Structure IX.

[0152] Simulation results show that the flow field distribution in optimized structure eleven is generally similar to that of the initial structure. The concave surface of the guide vanes in the tee fitting 4 exhibits higher pressure, while the convex surface shows lower pressure. The pressure decreases and the flow velocity increases at the constriction of the main intake pipe 1. In optimized structure eleven: the relative flow deviation of the upper and lower branch pipes 7, accounting for 3% (2 lines), exceeds 10%; the relative flow deviation of the branch pipes, accounting for 22% (17 lines), is controlled within 5%-10%; and the relative flow deviation of the branch pipes, accounting for 75% (57 lines), is controlled within 5%.

[0153] 15. Optimize Structure Twelve:

[0154] Based on optimized structure nine, optimized structure twelve further reduces the second inclined shoulder 56 of the connecting risers 5 of pipes 8 and 32, 9 and 31, 13 and 27, and 14 and 26 to 60 degrees with a height of 350 mm, and the connecting riser 5 of pipe 19 is equipped with a second diameter reducing part 57.

[0155] Simulation results show that the flow field distribution of optimized structure 12 is generally similar to that of the initial structure. The concave surface of the guide vanes inside the tee fitting 4 exhibits higher pressure, while the convex surface exhibits lower pressure. The pressure decreases and the flow velocity increases at the constriction of the main intake pipe 1. In optimized structure 12: the relative flow deviation of the upper and lower branch pipes 7 exceeds 10% for 1% (path 1), is controlled within 5%-10% for 15% (path 11), and is controlled within 5% for 83% (path 64).

[0156] 16. Optimize Structure Thirteen:

[0157] Based on the optimization of structure nine, structure 13 adopts a 75-degree second inclined shoulder 56 for connecting risers 53 of No. 13 and No. 27, and a 60-degree second inclined shoulder 56 for connecting risers 5 of No. 8 and No. 32, No. 9 and No. 31, and No. 14 and No. 26. The connecting risers 5 of No. 1 and No. 19 are equipped with a second diameter reducing section 57.

[0158] Simulation results show that the flow field distribution of optimized structure thirteen is generally similar to the initial structure. The concave surface of the guide vane inside the tee fitting 4 has higher pressure, while the convex surface has lower pressure. The pressure decreases and the flow velocity increases at the constriction of the main intake pipe 1. In optimized structure thirteen: the relative flow deviation of the upper and lower branch pipes 7 exceeds 10% for 0% (0 paths), is controlled within 5%-10% for 11% (8 paths), and is controlled within 5% for 89% (68 paths). After adjusting and optimizing the diameter of the main pipe ring pipe and the slopes at various points, this structure can limit the flow deviation of most of the upper and lower branch pipes 7 to within 5%, and the overall flow change between the connecting risers 5 of each branch is also relatively smooth (see...). Figure 5 The pressure drop of optimized structure thirteen under various operating conditions is summarized in Table 3.

[0159] Table 3 Summary of Pressure Drop under Various Operating Conditions

[0160]

[0161] As shown in Table 3, the back pressure of optimized structure thirteen is lower than the target value, and the structural optimization achieved the expected results. Therefore, the structure of optimized structure thirteen is used as the final optimization scheme in this embodiment of the invention.

[0162] It should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Those skilled in the art can modify the technical solutions described in the above embodiments, or make equivalent substitutions for some of the technical features; and all such modifications and substitutions should fall within the protection scope of the present invention.

Claims

1. A natural ventilation air-cooling system, characterized in that, The natural ventilation air-cooling system includes a steam turbine, an air-cooled condenser, and an exhaust pipe assembly, wherein the exhaust pipe assembly includes an intake main pipe, a main pipe ring pipe, and branch pipes. The main intake pipe is connected to the steam turbine and is connected to the main pipe ring pipe through a tee fitting; The main pipe ring includes a first arc pipe and a second arc pipe arranged opposite to each other and horizontally. One end of the first arc pipe is closed, and the other end is connected to one end of the tee fitting. The pipe body of the first arc pipe has a multi-segment diameter-decreasing variable diameter structure along the direction from its connecting end to its closed end. One end of the second arc pipe is closed, and the other end is connected to the other end of the tee fitting. The pipe body of the second arc pipe has a multi-segment diameter-decreasing variable diameter structure along the direction from its connecting end to its closed end. The variable diameter segments of the first arc pipe and the variable diameter segments of the second arc pipe are arranged asymmetrically, and the number of variable diameter segments of the second arc pipe is greater than the number of variable diameter segments of the first arc pipe. Multiple connecting risers are respectively provided on the first arc pipe and the second arc pipe along the steam flow direction. The multiple connecting risers on the first arc pipe and the second arc pipe are asymmetrically distributed, and the number of connecting risers on the second arc pipe is greater than the number of connecting risers on the first arc pipe. A connecting riser is also provided at the end of the tee fitting that connects to the first arc pipe for diverting the steam on the inlet side of the first arc pipe. The branch pipes are respectively installed on each of the connecting risers, including an upper branch pipe connected to the top of the connecting riser and a lower branch pipe connected to the middle of the connecting riser. The steam flow side of the lower branch pipe at the connection with the connecting riser forms a first inclined shoulder for oblique flow guidance. Each of the upper and lower branch pipes on the first arc pipe is connected to the air condenser preset on the leeward side of the ventilation tower. Each of the upper and lower branch pipes on the second arc pipe is connected to the air condenser preset on the windward side of the ventilation tower.

2. The natural ventilation air-cooling system according to claim 1, characterized in that: The connecting riser includes a lower pipe body and an upper pipe body with decreasing diameter from bottom to top. The upper pipe body and the lower pipe body are connected by a first diameter-changing section, which is a tapered structure with a gradually changing diameter. The upper branch pipe is laid horizontally, and its diameter is the same as that of the upper pipe body. The top of the upper branch pipe and the upper pipe body are integrally formed, and an arc-shaped guide bend is formed at the joint. The lower branch pipe is laid horizontally, and its diameter is smaller than that of the lower pipe body. A first docking hole is opened on the side wall of the lower pipe body. The end of the lower branch pipe that connects to the connecting riser is a first connecting end with a beveled surface on the steam flow side. The first connecting end is vertically fixed to the first docking hole, and the beveled surface of the first connecting end is obliquely docked with the first docking hole through the obliquely set first oblique shoulder. All of the lower branch pipes are connected to the corresponding connecting risers through the first inclined shoulder, and the inclined direction of the first inclined shoulder is perpendicular to the inclined tangent direction of the first connecting end.

3. The natural ventilation air-cooling system according to claim 1, characterized in that: The first arc pipe is divided into a first weak cooling pipe section, a second weak cooling pipe section and a third weak cooling pipe section with continuously changing diameter along the direction from its connecting end to its closed end. The second arc pipe is divided into a first, second, third and fourth strongly cooled pipe sections with continuously varying diameters along the direction from its connecting end to its closed end. The first weak cooling pipe section has the same pipe diameter as the first strong cooling pipe section, and the number of connecting risers distributed on the first weak cooling pipe section and the first strong cooling pipe section is the same. The second weak cooling pipe section has the same pipe diameter as the second strong cooling pipe section, and the number of connecting risers distributed on the second weak cooling pipe section and the second strong cooling pipe section is the same. The third weak cooling pipe section has the same pipe diameter as the third strong cooling pipe section, and the number of connecting risers distributed on the third weak cooling pipe section and the third strong cooling pipe section is the same. The diameter of the fourth forced cooling pipe section is smaller than that of the third forced cooling pipe section, and a connecting riser is also provided on the fourth forced cooling pipe section.

4. The natural ventilation air-cooling system according to claim 3, characterized in that: The connecting riser is vertically arranged and its diameter is smaller than that of the main pipe ring pipe. A second docking hole is opened on the top pipe wall of the main pipe ring pipe. The end of the connecting riser that connects to the main pipe ring pipe is a second connecting end with a beveled surface on the steam flow side. The second connecting end is vertically fixed to the second docking hole, and a beveled second shoulder is provided on the second docking hole to be obliquely docked with the beveled surface of the second connecting end. The first strong cooling pipe section, the second strong cooling pipe section, the third strong cooling pipe section, and all the connecting risers on the first arc pipe are provided with a second inclined shoulder on the steam flow side of the end of the main pipe ring pipe.

5. The natural ventilation air-cooling system according to claim 4, characterized in that: The connecting riser where the second strong cooling pipe section is located on the end diameter change side and the second weak cooling pipe section is located on the end diameter change side has a first included angle between the chamfered surface of the second connecting end and the second chamfered shoulder, and the first included angle is less than a right angle. The connecting risers on both sides of the diameter change point between the first weak cooling pipe section and the second weak cooling pipe section, the third weak cooling pipe section located at the first diameter change point, the first strong cooling pipe section and the second strong cooling pipe section on both sides of the diameter change point, and the third strong cooling pipe section located at the first diameter change point, have a second included angle between the chamfered surface of the second connecting end and the second chamfered shoulder, and the second included angle is smaller than the first included angle. For all other connecting risers, the angle between the chamfered surface of the second connecting end and the second chamfered shoulder is a right angle.

6. The natural ventilation air-cooling system according to claim 4, characterized in that: The top wall of the main pipe ring is provided with a third docking hole, and the bottom end of part of the connecting riser is connected to the third docking hole through a second diameter changing part, which is a tapered structure with a gradually changing pipe diameter. The end of the tee fitting and the connecting riser on the fourth cooling pipe section are both connected to the main pipe ring pipe through the second reducing part.

7. The natural ventilation air-cooling system according to claim 1, characterized in that: The tee fitting includes a first pipe end that connects to the main intake pipe, and a second pipe end and a third pipe end that are symmetrically and parallel to each other along the central axis of the first pipe end. An oblique pipe section extends from the first pipe end and connects to the second pipe end and the third pipe end respectively. The connecting end of the first arc tube is perpendicularly connected to and communicates with the connecting end of the second tube. Inside the perpendicular connection between the first arc tube and the connecting end of the second tube, a plurality of arc-shaped first guide vanes are arranged side by side along its width direction. A guide gap is formed between two adjacent first guide vanes to guide the steam in the main intake pipe into the first arc tube. The connecting end of the second arc tube is perpendicularly connected to and communicates with the third tube connection end. Inside the part where the second arc tube is perpendicularly connected to the third tube connection end, multiple arc-shaped second guide vanes are arranged side by side along its width direction. A guide gap is formed between two adjacent second guide vanes to guide the steam in the main intake pipe into the second arc tube.

8. The natural ventilation air-cooling system according to claim 7, characterized in that: The connecting riser at the end of the tee fitting is located on the second pipe connection end, and the upper branch pipe and the lower branch pipe on the corresponding branch are both located on the central axis of the first pipe connection end.

9. A method for optimizing exhaust pipes, used to optimize the exhaust pipe assembly in the natural ventilation air-cooled system according to any one of claims 1-8, characterized in that, The exhaust pipe optimization method includes: An initial structural flow field simulation model of the exhaust pipe assembly is established. The initial structure includes the preset diameter variation dimensions of each section of the main pipe ring pipe, and the preset direct connection method for connecting each pipe. The flow distribution deviation between the upper branch pipe and the corresponding lower branch pipe in each branch of the initial structure is obtained by flow field simulation, and the proportion of all branch pipes is divided according to the degree of deviation. The effects of individually adjusting the diameter of the main pipe ring pipe and individually setting the first inclined shoulder on the steam inlet side of the lower branch pipe on the flow distribution deviation of each path were compared by flow field simulation, and the structural optimization sequence was determined based on the comparison results. According to the determined structural optimization sequence, a first inclined shoulder is provided on the steam flow side of the connection between all the lower branch pipes and the corresponding connecting risers, and the connecting riser at the end of the tee fitting is connected to the main pipe ring pipe through a tapered reducing part to obtain the primary optimized structure; Based on the initial optimization structure, the diameter of the main pipe ring pipe is iteratively adjusted, and the optimized diameter of each section of the main pipe ring pipe is determined after the proportion of the flow distribution deviation of each path approaches the optimal ratio through flow field simulation verification.

10. The exhaust pipe optimization method according to claim 9, characterized in that, The exhaust pipe optimization method further includes optimizing the diameter variation dimensions of each section of the main pipe ring pipe, and then structuring the flow distribution between the main pipe ring pipe and the connecting risers of each branch, including: The primary optimized structure is obtained by adjusting the main pipe ring pipe in the primary optimized structure according to the optimized diameter size, and a secondary optimized structure is obtained. For all the connecting risers in the secondary optimized structure, a second inclined shoulder is provided on the steam flow side at the connection between the main pipe ring pipe and the riser. Based on all the connecting risers with the second inclined shoulder, the inclined shoulder angle at the diameter change point of each section of the main pipe ring is iteratively adjusted, and the flow field simulation is used to verify until the proportion of the flow distribution deviation of each path reaches the preset target proportion, thereby determining the optimized angle and optimized position of the second inclined shoulder; The connecting riser at the end of the second arc pipe is connected to the main pipe ring pipe through a tapered diameter reducing part, and the secondary optimization structure is adjusted according to the optimized angle and optimized position of the second inclined shoulder to obtain the target optimized structure.

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