A crossflow passage large rib spacing under the size air film cooling hole type

Abstract

The application belongs to the technical field of gas turbines, and provides a large-rib-spacing cross-flow passage large-small air film cooling hole type, a main flow passage is a flow direction passage, a cold gas passage is a cross-flow ribbed passage, each rib section includes two air film holes, which are a front-rib hole and a rear-rib hole, each air film hole includes a cold gas inlet, a cylindrical hole section, an expansion section and an air film hole outlet; one end of the cylindrical hole is communicated with the air film hole inlet, the other end is communicated with one end of the expansion section, the other end of the expansion section is communicated with the air film hole outlet, the air film hole inlet is connected with the cross-flow ribbed passage, and the air film hole outlet is connected with the main flow passage; based on the original large-rib-spacing cross-flow passage air film cooling hole type, the large-rib-spacing large-small air film hole type is obtained by adjusting the structural parameters of the front-rib hole and the rear-rib hole, the overall cooling performance of the air film hole is effectively improved, and the problem that the air film cooling effect of the large-rib-spacing air film hole is not ideal is solved.

Description

Technical Field

[0001] This invention belongs to the field of gas turbine technology, specifically relating to a type of large and small film cooling hole under the large rib spacing of a crossflow channel. Background Technology

[0002] Gas turbines, as power machines that use high-temperature, high-pressure gas generated from the combustion of fuels such as natural gas and syngas to drive turbine blades to rotate and perform work, are widely used in marine power, power generation, and propulsion. Increasing the turbine inlet temperature can effectively improve the efficiency and power output of a gas turbine. However, with the continuous increase in turbine inlet temperature, increasingly severe challenges are posed to the safe operation of gas turbines. Therefore, corresponding measures must be taken to keep the blade temperature below the allowable temperature of the material to ensure the safe operation of the gas turbine blades.

[0003] Film cooling (FS) technology plays a crucial role in the thermal protection of hot-end components of gas turbines. The principle of FFS is that jets of cool gas are ejected from discrete film orifices, interacting with the mainstream to form a film layer of mixed mainstream and cool gas that covers the blade surface, isolating the high-temperature mainstream and cooling the turbine blades. Previous FFS research typically treated two or more film orifices at the large fin spacing as a whole, adjusting their orifice design to improve FFS efficiency. However, in practical applications, the FFS cooling performance of the orifices before and after the fin spacing differs, and there is a phenomenon where the cooling efficiency of a single film orifice significantly decreases after design adjustments. Therefore, it is necessary to adjust the orifice design of the film orifices at the large fin spacing separately to improve FFS efficiency. This invention proposes a film cooling orifice design for both large and small film orifices at the large fin spacing in a crossflow channel to improve the overall cooling performance of the film orifices. Summary of the Invention

[0004] This invention provides a crossflow channel with a large rib spacing and a wide-sized film cooling orifice design to solve the problems in the prior art. The technical solution adopted by this invention is as follows:

[0005] A cross-flow channel with large rib spacing and large and small film cooling hole type, the main channel is a flow channel, the cold air channel is a cross-flow ribbed channel, each rib segment includes two film cooling holes, namely a front rib hole and a rear rib hole, each film cooling hole includes a cold air inlet, a cylindrical hole segment, an expansion segment and a film cooling hole outlet.

[0006] One end of the cylindrical hole is connected to the inlet of the film air hole, and the other end is connected to one end of the expansion section. The other end of the expansion section is connected to the outlet of the film air hole. The inlet of the film air hole is connected to the crossflow ribbed channel, and the outlet of the film air hole is connected to the mainstream channel.

[0007] Furthermore, the anterior rib hole and the posterior rib hole are respectively large and small film air holes. The film air hole closer to the side of the crossflow cold air is the posterior rib hole, and the film air hole farther away from the side of the crossflow is the anterior rib hole.

[0008] Furthermore, the length-to-diameter ratio L of the cylindrical section of the pre-rib hole m / D is 2.8, spanning angle β lat 13.4°, backslope angle β fwd The angle is 4.6°; the length-to-diameter ratio L of the cylindrical section of the rib hole is... m / D is 1.9, spanning angle β lat 12.8°, backslope angle β fwd The angle is 3°. The anterior rib aperture is an atmospheric film aperture, and the posterior rib aperture is a small atmospheric film aperture.

[0009] Furthermore, the length L of the cylindrical section of the air film aperture... m The length-to-diameter ratio L of the cylindrical hole diameter D m / D satisfies 1.5≤L m / D≤4, spanning angle 4°≤β lat ≤15°, backslope angle 0°≤β fwd ≤15°.

[0010] A design method for large and small film cooling orifice types under large rib spacing in a crossflow channel includes: selecting a range of design variables based on empirical data from literature; constructing an initial sample library from 25 sets of data using the Latin hypercube sampling method; performing CFD calculations on the sample library; and determining η. ave, M and Nu / Nu 0ave,M As the optimization objective, a nonlinear surrogate model between multiple inputs and multiple outputs is constructed using a radial basis function neural network. Then, multi-objective artificial hummingbird optimization is performed based on the surrogate model to obtain a set of Pareto optimal solutions. The numerical simulation results are compared with the optimization prediction results to determine whether the absolute value of their error is less than 2%. If it is less than 2%, the optimization design is complete. Otherwise, the optimization design variable values ​​and calculation results are added to the sample library as samples for retraining until the convergence deviation criterion is met. Finally, the TOPSIS method is used to obtain the optimal solution.

[0011] The present invention has the following beneficial effects:

[0012] The average area cooling efficiency of the air film cooling holes after the design adjustment in this invention is improved by 7.25%, 14.81%, 14.37%, and 2.68% respectively compared with the reference holes at blowing ratios M=0.5, 1.0, 1.5, and 2.0. The air film cooling hole design with large rib spacing in the crossflow channel proposed in this invention is simple and significantly improves the air film cooling performance, showing certain practical application prospects. Based on the original air film cooling hole design with large rib spacing in the crossflow channel, this invention obtains air film cooling hole designs with large rib spacing by adjusting the structural parameters of the holes before and after the ribs, effectively improving the overall cooling performance of the air film holes and solving the problem of unsatisfactory air film cooling effect of air film holes with large rib spacing. Attached Figure Description

[0013] Figure 1 The existing technology uses a cross-flow ribbed channel and a large rib spacing in the cross-flow channel with a film cooling hole layout structure.

[0014] Figure 2 This is a schematic diagram of the air film cooling holes under large rib spacing;

[0015] Figure 3 Top view of the air film cooling hole arrangement;

[0016] Figure 4 Schematic diagram of the cross-section of the film pore. Figure 1 ;

[0017] Figure 5 Schematic diagram of the cross-section of the film pore. Figure 2 ;

[0018] Figure 6 Schematic diagram of the cross-section of the film pore. Figure 3 ;

[0019] Figure 7 For reference, see the schematic diagram of the film pore structure;

[0020] Figure 8 This is a schematic diagram of the structure of an embodiment of the present invention;

[0021] Figure 9 The reference air film cooling efficiency is compared with that of the embodiment when the air blowing ratio M = 1.0.

[0022] Figure 10 The reference air film cooling efficiency is compared with that of the embodiment when the air blowing ratio M = 2.0.

[0023] Figure 11 To compare the average cooling efficiency of the cooling hole area of ​​the large and small film cooling holes and the reference film cooling holes under different air blowing ratios and the large rib spacing of the crossflow channel. Detailed Implementation

[0024] The following will be based on embodiments of the present invention. Figures 1-11 The technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0025] This invention proposes a type of large and small film cooling hole with a large rib spacing in a crossflow channel, such as... Figures 1-3 The mainstream flow region shown is the mainstream channel, and the cold air flow region is a crossflow ribbed channel. Each rib segment includes two film vents: a pre-rib vent and a post-rib vent. Figures 4-6 As shown, each air film vent includes a cold air inlet A. inlet Cylindrical hole section L m Expansion segment L fwd and air film outlet A exit .

[0026] One end of the cylindrical hole is connected to the inlet of the film air hole, and the other end is connected to one end of the expansion section. The other end of the expansion section is connected to the outlet of the film air hole. The inlet of the film air hole is connected to the crossflow ribbed channel, and the outlet of the film air hole is connected to the mainstream channel.

[0027] Furthermore, the anterior and posterior air film holes are of different sizes, with the posterior air film hole being closer to the side of the crossflow cold air inlet and the anterior air film hole being farther away from the inlet.

[0028] Furthermore, the length-to-diameter ratio L of the cylindrical section of the pre-rib hole m / D is 2.8, spanning angle β lat 13.4°, backslope angle β fwd The angle is 4.6°; the length-to-diameter ratio L of the cylindrical section of the rib hole is... m / D is 1.9, spanning angle β lat 12.8°, backslope angle β fwd The angle is 3°. The anterior rib aperture is an atmospheric film aperture, and the posterior rib aperture is a small atmospheric film aperture.

[0029] Furthermore, the length L of the cylindrical section of the air film aperture... m The length-to-diameter ratio L of the cylindrical hole diameter D m / D satisfies 1.5≤L m / D≤4, spanning angle 4°≤β lat ≤15°, backslope angle 0°≤β fwd ≤15°.

[0030] In the process of realizing the concept of this invention, it was found that the cooling effect of the air film cooling holes under the large rib spacing of the crossflow channel is different. After conventional parameter design, two different results will occur. The first is that the cooling efficiency of the front hole and the rear hole of the rib is improved at the same time, but the improvement is not large. The second is that the cooling efficiency of one of the air film holes of the front hole and the rear hole of the rib is improved, while the cooling efficiency of the other is improved by a small margin or negatively.

[0031] This invention innovatively constructs a novel design framework for film cooling holes with large rib spacing in crossflow channels. It integrates open-source Latin hypercube sampling, radial basis function (RBF) neural networks, and the multi-objective artificial hummingbird optimization algorithm (MOAHA) into a single process. The framework uses Latin hypercube sampling to uniformly distribute samples, builds a high-precision surrogate model using RBF neural networks, and uses the MOAHA algorithm to globally search for the optimal solution, thereby synergistically improving the film cooling performance of the holes behind and in front of the ribs. This method is the first of its kind in this field. The specific process is as follows: based on literature and empirical data, a range of design variables is selected; an initial sample library is constructed using 25 sets of data using the Latin hypercube sampling method; CFD calculations are performed on the sample library; and η is... ave, M and Nu / Nu 0ave,M As the optimization objective, a nonlinear surrogate model between multiple inputs and multiple outputs is constructed using a radial basis function neural network. Then, multi-objective artificial hummingbird optimization is performed based on the surrogate model to obtain a set of Pareto optimal solutions. The numerical simulation results are compared with the optimization prediction results to determine if the absolute value of the error is less than 2%. If it is less than 2%, the optimization design is complete; otherwise, the optimization design variable values ​​and calculation results are added to the sample library as samples for retraining until the convergence deviation criterion is met. Finally, the TOPSIS method is used to obtain the optimal solution to simultaneously improve the film cooling performance of the rear and front rib holes.

[0032] A comparative analysis of the air film cooling hole type under the large rib spacing of the crossflow channel in the prior art and the air film cooling efficiency of the large and small air film cooling holes under the large rib spacing of the crossflow channel in the specific embodiment of the present invention shows that the two are identical in all structural parameters except for the air film hole parameters.

[0033] The film air vents closer to the inflow side of the cross-flow cold air are called rear rib vents, and those farther away are called front rib vents. Each film air vent consists of a cylindrical section and an expansion section. The diameter of the film air vent is D = 3 mm, the total length is L / D = 6, and the length-to-diameter ratio of the cylindrical section is L. m / D is 2.5, spanning angle β lat 7° and backslope angle β fwd It is 7°.

[0034] Boundary conditions: Both the mainstream gas and the crossflow cold gas are set to ideal air. The mainstream inlet temperature is set to 300 K, the inlet velocity to 25 m / s, the turbulence intensity to 5%, the outlet static pressure to 1 atm, and the mainstream channel wall is set to adiabatic no-slip. The mainstream Reynolds number based on the orifice size is approximately 5500. The crossflow channel inlet temperature is set to 196 K, the inlet velocity to 12.5 m / s, and the turbulence intensity to 0.9%. The set blowing ratio is obtained by varying the crossflow outlet mass flow rate, ranging from 0.5 to 2.0. The crossflow channel inlet Reynolds number is 33000.

[0035] like Figures 1-3 For the overall computational domain of the numerical simulation, the parameters are set as follows: the main channel cross-section is 12D×30D, and the total length is 180D. The distance from the main channel inlet plane to the center of the film gas outlet is 70D, and the distance from the outlet plane to the center of the film gas outlet is 110D. The crossflow cooling gas channel is a rectangular channel with a cross-section of 8D×8D and a total length of 200D. The orifice spacing is 6D, the film gas outlet incident angle is 30°, and the rib spacing is 12D, twice the orifice spacing. In the crossflow ribbed channel, the rib height and rib width are both 1.8D.

[0036] like Figures 4-6 This is a diagram of the air film cooling hole structure under the reference crossflow channel with large rib spacing. The length of the cylindrical section, the diameter of the air film hole, the spanwise expansion angle, and the back tilt angle are represented by L. m D, β lat β fwd express.

[0037] Figure 7 It is a structural diagram of the air film pore. Figure 8 This is a structural diagram of the large and small film cooling orifice patterns under the large rib spacing in the crossflow channel. Compared with the reference large rib spacing film cooling orifice pattern, the front and rear holes in this invention have different parameter designs. The length of the cylindrical section of the front hole is slightly increased, the spanwise expansion angle is increased by 6.4°, and the back tilt angle is decreased by 2.4°; the length of the cylindrical section of the rear hole is reduced, the spanwise expansion angle is increased by 5.8°, and the back tilt angle is decreased by 4°.

[0038] Figure 9 , Figure 10 The embodiments demonstrate varying degrees of improvement in spanwise average film cooling efficiency at air-to-air ratios M=1.0 and M=2.0. At an air-to-air ratio M=1.0, the embodiments show a significant improvement in spanwise average film cooling efficiency across the cooling plane. At an air-to-air ratio M=2.0, the embodiments show improved film cooling performance within the coordinate range of 0≤X / D≤13, while exhibiting a slight decrease in film cooling performance downstream of X / D=13.

[0039] Figure 11The embodiments demonstrate the area-average film cooling efficiency at airflow ratios M = 0.5, 1.0, 1.5, and 2.0. The area-average film cooling efficiency improved by 7.3% at M = 0.5; by 14.81% at M = 1.0; by 14.37% at M = 1.5; and by 2.7% at M = 2.0. The improvement in area-average film cooling efficiency was particularly significant at M = 1.0.

[0040] The above results indicate that the large and small film cooling hole patterns with large rib spacing in the crossflow channel proposed in this invention can effectively improve the film cooling efficiency of the fan-shaped film cooling holes in the crossflow ribbed channel.

[0041] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications, alterations, substitutions, or variations made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention shall fall within the protection scope defined by the claims of the present invention.

Claims

1. A type of large and small film cooling orifice with a large rib spacing in a crossflow channel, characterized in that: The main channel is a flow channel, and the cold air channel is a cross-flow ribbed channel. Each rib section includes two air film holes, namely a front rib hole and a rear rib hole. Each air film hole includes a cold air inlet, a cylindrical hole section, an expansion section, and an air film hole outlet. One end of the cylindrical hole is connected to the inlet of the film air hole, and the other end is connected to one end of the expansion section. The other end of the expansion section is connected to the outlet of the film air hole. The inlet of the film air hole is connected to the crossflow ribbed channel, and the outlet of the film air hole is connected to the mainstream channel. The anterior rib opening is an atmospheric film opening, and the posterior rib opening is a small atmospheric film opening; Length of the cylindrical section of the air film aperture L m With the diameter of the cylindrical hole D Aspect Ratio L m / D Satisfying 1.5≤ L m / D ≤4, spanning angle 4°≤ b lat ≤15°, backslope angle 0°≤ b fwd ≤15°; The film vents closer to the inflow side of the crossflow cold air are called posterior rib vents, while the film vents farther from the inflow side are called anterior rib vents.

2. The crossflow channel with large rib spacing and large and small film cooling hole type according to claim 1, characterized in that, The length-to-diameter ratio of the cylindrical section of the front hole of the rib L m / D 2.8, spanwise expansion angle β lat 13.4°, lean angle β fwd The angle is 4.6°; the length-to-diameter ratio of the cylindrical section of the rib hole is 4.6°. L m / D 1.9, spanning angle β lat 12.8°, lean angle β fwd It is 3.0°.

3. A method for designing large and small film cooling orifices under a large rib spacing in a crossflow channel, applied to the large and small film cooling orifice design under a large rib spacing in a crossflow channel as described in claim 1, characterized in that, include: Based on literature and empirical data, the range of design variables was selected, and the Latin hypercube sampling method was used to construct an initial sample library for 25 sets of data. CFD calculations were then performed on the sample library. Will η ave,M and Nu / Nu 0ave,M As the optimization objective, a nonlinear surrogate model between multiple inputs and multiple outputs is constructed using a radial basis function neural network. Then, multi-objective artificial hummingbird optimization is performed based on the surrogate model to obtain a set of Pareto optimal solutions. The numerical simulation results are compared with the optimization prediction results to determine whether the absolute value of their error is less than 2%. If it is less than 2%, the optimization design is complete. Otherwise, the optimization design variable values ​​and calculation results are added to the sample library as samples for retraining until the convergence deviation criterion is met. Finally, the TOPSIS method is used to obtain the optimal solution. η ave,M It is the average film cooling efficiency of the cooling wall surface under a specified airflow ratio M. Nu / Nu 0ave,M It is the average relative Nusselt number of the cooling wall surface under a specified airflow ratio M.

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