Efficient air film cooling structure applied to turbine rotor outer ring

Abstract

The invention relates to the technical field of turbine blade cooling, and provides an efficient air film cooling structure applied to an outer ring of a turbine rotor, the efficient air film cooling structure comprises a plurality of cooling units, each cooling unit comprises an air film hole plate, and a plurality of rows of air film holes are formed in each air film hole plate; the air film holes are drop-shaped holes, and the outlet positions of the air film holes are provided with divergence angles in the flow direction; the compound angles of the air film holes are the same, and the inclination angles of the holes in the same row of air film holes are not completely the same. According to the invention, an optimized structure is adopted to systematically improve the internal flow path of the air film hole, and the momentum and speed of cold air outflow are obviously reduced by reducing flow separation and enlarging the outlet area; and the configuration of the water-drop-shaped hole is optimized from a traditional cylindrical hole to a water-drop-shaped hole which is expanded by 7 degrees in the flow direction, so that the comprehensive cooling efficiency can be greatly improved on the premise of not increasing the use amount of a cooling working medium.

Description

TECHNICAL FIELD

[0001] The application relates to the field of turbine blade cooling technology, in particular to a high-efficiency air film cooling structure applied to a turbine rotor outer ring. BACKGROUND

[0002] The turbine casing is the core bearing system of the engine and the boundary of the gas passage, directly bearing the severe scouring of high-temperature gas, huge gas pressure and complex mechanical load. The turbine outer ring, as a key component of the turbine casing, has a particularly special and critical function: it must maintain an accurate and stable tip clearance between the high-speed rotating rotor blades. The clearance directly determines the efficiency of the engine - if the clearance is too large, the gas will leak and the performance will decline; if the clearance is too small, the rotor and the casing may collide and cause catastrophic consequences. However, the working environment of the turbine outer ring is extremely harsh, as it not only has to withstand periodic high-temperature gas heat shock, but also faces mechanical load caused by dynamic clearance changes due to different thermal expansion coefficients of the casing and the rotor. Therefore, the cooling and thermal management of the turbine outer ring is one of the core challenges to ensure the reliability, efficiency and service life of modern aero-engines.

[0003] Currently, the impingement-air film combined cooling technology is considered one of the most effective solutions to this challenge. However, the final efficiency of this advanced cooling system is highly dependent on the efficiency of the last link - external air film cooling. If the air film cooling effect is poor, not only the heat insulation is ineffective, but also the cooling air and pressure loss of the previous impingement cooling and internal convection cooling are greatly wasted. Unfortunately, the traditional air film cooling structure currently applied to the turbine outer ring is the weakest link in the entire cooling chain, and its inherent defects are amplified rapidly under increasingly severe working conditions. It is extremely difficult and costly to fully reproduce the real high-temperature, high-pressure and high-speed environment of the engine in the laboratory. Therefore, using experimental modeling methods based on similarity criteria, through geometric scale-up, high-precision measurements at normal temperature and pressure have become a key means to study cooling characteristics. However, a large number of experimental studies have consistently shown that the simple structures commonly used in existing technologies, such as cylindrical holes and single inclination layouts, are difficult to provide efficient, uniform and stable cooling effects in the wide range of blowing ratios and Reynolds numbers covered by the modeling experiments. Its performance is sensitive to changes in working conditions, especially under high blowing ratio and high Reynolds number conditions, the cooling efficiency decays and becomes unstable.

[0004] In summary, although the impact-film cooling composite frame provides an excellent platform for solving the thermal protection of the turbine outer ring, its ultimate effectiveness is limited by the systemic deficiencies of traditional film cooling holes in terms of adhesion, coverage uniformity, multi-row coordination, and operational robustness. Existing technical solutions are mostly localized repairs to address single problems, lacking integrated and systematic innovative designs that consider hole shape, inclination angle, and overall arrangement.

[0005] Therefore, there is an urgent need in this field for a highly efficient film cooling structure for next-generation high-performance engines, which must be able to fundamentally solve the aforementioned bottlenecks. Summary of the Invention

[0006] This invention proposes a high-efficiency film cooling structure for turbine rotor outer rings. Guided by the complex flow and heat transfer mechanisms revealed by experimental modeling methods, it achieves efficient utilization of cold air and uniform and stable film coverage over a wide range of blowing ratios and Reynolds numbers, while possessing excellent anti-blowing capability. This ensures that the potential of the impact-film composite cooling system is fully realized, providing a reliable guarantee for the safe operation of turbine outer rings under turbine inlet temperatures above 2000K.

[0007] To achieve the above objectives, the present invention proposes a high-efficiency film cooling structure for use on the outer ring of a turbine rotor, comprising multiple cooling units, wherein each cooling unit includes a film cooling perforated plate with multiple film cooling holes formed thereon. The air film orifice is a teardrop-shaped orifice, and the outlet position of the air film orifice has an expansion angle along the flow direction; The composite angle of each of the air film pores is the same, but the inclination angles of each pore in the same air film pore are not exactly the same. The dimensionless hole spacing between adjacent exhaust membrane holes is 8D; In the same exhaust film hole, the dimensionless hole spacing between the holes is non-uniform.

[0008] Furthermore, the expansion angle at the outlet position of the air film pore is 7°.

[0009] Furthermore, the composite angle of the air film pore is 18°.

[0010] Furthermore, the diameter of the air film pore is 1.2 mm.

[0011] Furthermore, the thickness of the air film perforated plate is 8.33D.

[0012] Furthermore, the air film holes on the air film perforated plate are arranged in a periodic manner with cooling units, and each cooling unit contains thirty-nine air film holes.

[0013] Furthermore, in each of the cooling units, the air film holes are divided into multiple rows, and the tilt angle parameters of each air film hole are set differently according to its position in the row and column.

[0014] Furthermore, the tilt angle parameters of the air film holes in the cooling unit are specifically as follows: First row: 70°, 60°, 40°, 35°, 30°, 30°, 30°, 30°; Second row: 70°, 60°, 50°, 35°, 30°, 30°, 30°, 30°, 30°; Third row: 70°, 60°, 40°, 35°, 30°, 30°, 30°, 30°; Fourth row: 70°, 50°, 30°, 30°, 30°, 30°, 30°; Fifth row: 70°, 50°, 30°, 30°, 30°, 30°, 30°.

[0015] Furthermore, the multiple cooling units are arranged along the axial direction of the air film pores to form a complete air film cooling area.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The teardrop-shaped orifice structure, with its unique outlet expansion angle design, effectively reduces the normal momentum component of the cooling jet, significantly suppressing the "blowing" phenomenon of cool air. This structure allows the cooling airflow to adhere more fully to the wall surface, forming a continuous and stable low-temperature film layer, thereby greatly improving film cooling efficiency. The non-uniform tilt angle film orifice layout design allows for targeted optimization based on the flow characteristics and cooling requirements of different regions. This design enables a more reasonable distribution of the cooling film on the turbine outer ring surface, effectively avoiding the generation of localized overheating areas and improving the uniformity of the wall temperature field. This cooling structure maintains high cooling efficiency across a wide operating range, from low to high airflow ratios, demonstrating excellent anti-blowing capability and adaptability. By optimizing the orifice spacing to 8D, the interaction between the outflow from the front and rear film orifices is enhanced, producing a significant superimposed cooling effect. This compact layout maximizes the cooling effect within a limited space, improving overall cooling performance. This structure maintains stable cooling performance even under high Reynolds number conditions, which meets the actual operating conditions of modern aero engines and has good engineering applicability and practical value. Attached Figure Description

[0017] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. In the drawings: Figure 1 This is a schematic diagram of the planar structure of the high-efficiency air film cooling structure proposed in this invention; Figure 2 This is a schematic diagram of the original film cooling structure. Figure 3 This is a schematic diagram of the teardrop-shaped hole planar structure of the high-efficiency air film cooling structure of the present invention; Figure 4 This is a comparison chart of the average overall cooling efficiency of the optimized structure and the original structure of this invention; Figure 5 This is a bar chart showing the average area of ​​the optimized structure and the original structure of this invention. Among them, 1. Air film pore I, 2. Air film pore II, 3. Air film orifice plate. Detailed Implementation

[0018] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0019] This embodiment proposes a high-efficiency film cooling structure for the outer ring of a turbine rotor, which includes multiple cooling units. Three cooling units are arranged along the axial direction of the film cooling hole I1 to form a high-efficiency film cooling structure. like Figure 1 As shown, a cooling unit specifically includes: There are thirty-nine air-film pores I1, which are teardrop-shaped and have a 7° inclination angle at the pore outlet. The composite angle of all air-film pores I1 is 18°, but the inclination angle of each period of pores is not exactly the same. Figure 2 Compared to the original structure, the shape of the air film pore I1 has been changed from cylindrical to teardrop-shaped, and the dimensionless pore spacing (L / D) between adjacent air film pores has been changed from 15D to 8D. The dimensionless pore spacing (P / D) is non-uniform.

[0020] Among them, such as Figure 3The teardrop-shaped planar structure shown, taking the fourth row as an example, has air film holes with inclination angles of 70°, 50°, 30°, 30°, 30°, 30°, and 30°, and hole spacings of 7.2, 5.1, 13.9, 15.8, 17.8, and 17.8, respectively.

[0021] In some embodiments, the angle between the straight line containing the perforation row and the main flow is 18°, the composite angle of each multi-row perforation is 18°, and the inclination angle of each periodic perforation is not exactly the same. The inclination angles of each perforation are shown in Table 1 below (parameters of periodic structure perforations): Table 1

[0022] In some embodiments, the dimensionless hole spacing (L / D) is 8D, and the dimensionless hole spacing (P / D) is non-uniform.

[0023] In some embodiments, the air film orifice D = 1.2 mm, and the thickness of the air film orifice plate is 8.33D.

[0024] In the high-efficiency film cooling structure of this invention, the cooling airflow passes through the impact orifice plate, exits at high speed from the impact holes, enters the impact channel, and undergoes intense impact heat transfer on the target surface. Subsequently, this cooling airflow enters the core of this invention—the high-efficiency film cooling orifice I1. Finally, the cooling airflow exits from the high-efficiency film cooling orifice I1, forming a complete, dense, and tough high-performance heat-insulating film on the outer wall of the film cooling orifice plate. This invention abandons the traditional cylindrical orifice and adopts a structurally optimized teardrop-shaped film cooling orifice, and changes the orifice spacing. Experimental results show that, under the same flow conditions, the teardrop-shaped orifice produces significantly better film cooling efficiency than the cylindrical orifice, allowing the cooling airflow to better adhere to the wall surface after exiting, forming a more uniform, stable, and wider-coverage cold film.

[0025] Example 2 This example relates to a high-efficiency film cooling structure applied to the outer ring of a turbine rotor. The most direct results are obtained through rigorous experimental comparison between the original and optimized structures. This embodiment focuses on the differences between the two in the key aspect of film cooling structure and the resulting performance leap. The film cooling plate 3, with one cooling unit comprising thirty-nine teardrop-shaped film holes I1, has a 7° inclination angle at the hole outlet. The angle between the straight line containing the hole rows and the main flow is 18°, and the composite angle of each multi-row film cooling hole I1 is 18°, although the inclination angle of each periodic hole is not entirely the same. The dimensionless hole row spacing (L / D) is 8D, and the dimensionless hole spacing (P / D) is non-uniform. The diameter of the film cooling hole I1 is D = 1.2 mm, and the thickness of the film cooling plate is 8.33D.

[0026] The cooling structure of this invention, with the perforated film cooling plate 3 and its surface-distributed precision perforations I1 as its core, forms the final thermal barrier against high-temperature combustion gases. In the original structure, the perforations II2 adopt a traditional cylindrical configuration with a perforation spacing of 15D. This layout represents the current conventional design level and provides a reliable benchmark for performance evaluation. In the optimized structure, this embodiment features a systematic and innovative design. First, the perforation configuration is improved from a cylindrical shape to a teardrop-shaped perforation that expands 7° along the flow direction. This unique configuration effectively improves the outlet flow characteristics of the cold air. Simultaneously, the perforations I1 are concentrated in a key area closer to the upstream of the main flow direction, and the perforation spacing is optimized to 8D. This series of improvements, through the synergistic optimization of layout and configuration, achieves the reorganization and distribution of cooling airflow. This innovative design concept breaks through the limitations of traditional film cooling. Through the dual optimization of configuration and layout, the cooling airflow forms a more uniform and stable protective layer on the wall surface, ultimately achieving a significant breakthrough in cooling efficiency. The optimized structure not only achieves a qualitative leap in cooling efficiency, but also reaches a new level in the utilization efficiency of cooling airflow, providing an innovative solution for thermal protection technology of high-temperature components.

[0027] Furthermore, in this embodiment, the film cooling orifice I1 adopts a geometric configuration with a rounded leading edge and a gradually expanding tail. To evaluate its cooling performance, this embodiment experimentally measured key parameters at different blowing ratios M and compared them with those of a traditional cylindrical orifice. Performance evaluation is based on experimental data, using NHFR as the core indicator, and its expression is:

[0028] Furthermore, under the same blowing ratio, the water-droplet structure exhibits a significantly higher measured film cooling efficiency (η) than the cylindrical orifice due to its superior film coverage capability. Simultaneously, the convective heat transfer coefficient ratio (h) is also higher. f The measured data ( / h0) show that the water-droplet orifice effectively suppresses jet stripping and avoids the adverse increase in local heat transfer intensity. Based on the experimental data and the NHFR formula, it is calculated that under typical operating conditions, the NHFR value of the water-droplet orifice scheme is higher than that of the cylindrical orifice. All performance conclusions are based on the measured data recorded in the experimental report, confirming the superiority of the water-droplet film orifice in reducing wall heat load.

[0029] This embodiment compares the original structure with the optimized structure, such as... Figure 4As shown in the cooling efficiency cloud diagram, the gas film generated by the cylindrical orifice exhibits typical jet characteristics, with a narrow spanwise coverage and obvious low-efficiency regions between orifices, resulting in poor gas film uniformity. The gas film generated by the teardrop-shaped expanding orifice, however, is significantly wider and more continuous in its spanwise distribution, effectively eliminating the shortcomings of the original structure and forming a complete and uniform cold gas coverage layer. This confirms the significant advantages of the optimized structure in improving temperature distribution uniformity and suppressing local overheating.

[0030] like Figure 5 As shown, the average overall cooling efficiency of the optimized structure's film cooling plate is significantly improved compared to the original structure. Figure 5 As shown, at Re=2000 and different airflow ratios, the area-average cooling efficiency of the optimized structure is higher than that of the original structure. At M=0.3, 0.6, and 0.9, compared to the original structure, the area-average efficiency of the optimized structure increases by 23.4%, 49.1%, and 44.1%, respectively. This quantitative result directly proves that the optimized film cooling structure can significantly improve thermal protection performance, with an overall cooling effect improvement of over 20% under typical operating conditions, providing more reliable and efficient thermal protection for the turbine outer ring.

[0031] In summary, due to structural limitations, traditional cylindrical film cooling orifices often eject cooling airflow as a high-momentum, concentrated jet, which easily penetrates the mainstream boundary layer and detaches from the wall, resulting in a so-called "blowing-away" phenomenon. This not only prevents the cold air from effectively adhering to the wall for thermal insulation protection but also leads to rapid dissipation of the cooling gas, resulting in low overall cooling utilization. To address these issues, this embodiment employs an optimized structure to systematically improve the internal flow path of the film cooling orifice. By reducing flow separation and expanding the outlet area, the momentum and velocity of the cold air outflow are significantly reduced. Based on this optimization, the flow behavior of the cooling airflow achieves a crucial shift from high-momentum concentrated jetting to low-momentum wall-adhering spreading, thereby forming a more stable and uniformly covered film protective layer on the wall. The synergistic effect of the above structural optimization and flow control significantly enhances the wall adhesion and lateral diffusion performance of the film, ultimately forming a high-quality film layer that is uniform, stable, and widely covered, which is difficult to achieve with traditional structures.

[0032] Through systematic experimental comparisons, the high-efficiency film cooling structure proposed in this invention exhibits significant advantages in both macroscopic performance and microscopic mechanisms. Experimental results show that by focusing the film cooling hole layout on high heat load regions and optimizing its configuration from traditional cylindrical holes to teardrop-shaped holes expanding 7° along the flow direction, a significant improvement in overall cooling efficiency can be achieved without increasing the amount of coolant used. Under multiple blowing ratio conditions, the optimized structure improves the area-average cooling efficiency by 23.4%, 49.1%, and 44.1% respectively compared to the original structure, with the overall cooling effect improvement generally exceeding 20%. This technological breakthrough marks a significant advancement in film cooling from a coarse-fiber injection mode to a fine-grained coverage mode, providing turbine outer ring components with thermal protection performance far exceeding that of the benchmark solution, fully demonstrating the advanced nature, high efficiency, and significant value of this design in engineering applications.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A high-efficiency film cooling structure applied to the outer ring of a turbine rotor, characterized in that, It includes multiple cooling units, each of which includes a perforated air film plate with multiple air film holes. The air film orifice is a teardrop-shaped orifice, and the outlet position of the air film orifice has an expansion angle along the flow direction; The composite angle of each of the air film pores is the same, but the inclination angles of each pore in the same air film pore are not exactly the same. The dimensionless hole spacing between adjacent exhaust membrane holes is 8D; In the same exhaust film hole, the dimensionless hole spacing between the holes is non-uniform.

2. The high-efficiency gas film cooling structure according to claim 1, characterized in that, The expansion angle at the outlet of the air film vent is 7°.

3. The high-efficiency gas film cooling structure according to claim 1, characterized in that, The composite angle of the air film pore is 18°.

4. The high-efficiency gas film cooling structure according to claim 1, characterized in that, The diameter of the air film pore is 1.2 mm.

5. The high-efficiency gas film cooling structure according to claim 1, characterized in that, The thickness of the air film perforated plate is 8.33D.

6. The high-efficiency gas film cooling structure according to claim 1, characterized in that, The air film holes on the air film perforated plate are arranged in a periodic manner according to the cooling units, and each cooling unit contains thirty-nine air film holes.

7. The high-efficiency film cooling structure according to claim 6, characterized in that, In each of the cooling units, the air film holes are divided into multiple rows, and the tilt angle parameters of each air film hole are set differently according to its position in the row and column.

8. The high-efficiency film cooling structure according to claim 7, characterized in that, The tilt angle parameters of the air film holes in the cooling unit are as follows: First row: 70°, 60°, 40°, 35°, 30°, 30°, 30°, 30°; Second row: 70°, 60°, 50°, 35°, 30°, 30°, 30°, 30°, 30°; Third row: 70°, 60°, 40°, 35°, 30°, 30°, 30°, 30°; Fourth row: 70°, 50°, 30°, 30°, 30°, 30°, 30°; Fifth row: 70°, 50°, 30°, 30°, 30°, 30°, 30°.

9. The high-efficiency film cooling structure according to claim 1, characterized in that, Multiple cooling units are arranged along the axis of the air film pores to form a complete air film cooling area.

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