Active cooling structure design method for anti-deposition and clogging CMC materials

Abstract

This invention discloses a design method for an active cooling structure of CMC materials to prevent deposition and blockage. This anti-deposition, low-efficiency film cooling hole structure design is based on the key geometric features of the expanded film cooling holes in CMC material components. Building upon traditional fluid-structure interaction heat transfer simulation calculations, it incorporates a dispersed phase model to simulate the trajectory of dust particles in the fluid. A user-defined function is used to introduce a probability model of particle deposition, enabling an integrated design of the CMC material film cooling structure under dusty conditions. This results in a low-efficiency film cooling structure scheme for ceramic matrix composite components to prevent deposition, and its cooling effect before and after particle deposition is analyzed and evaluated. Therefore, by simulating and analyzing the impact of anti-deposition film cooling holes on the particle deposition rate on the wall surface, an evaluation method for the attenuation of film cooling efficiency after particle deposition is developed. This method can significantly reduce the attenuation of film cooling efficiency caused by particle deposition and improve the overall film cooling efficiency of CMC material components under long-term dusty service conditions.

Description

Technical Field

[0001] This invention relates to the field of engineering thermophysics, and in particular to a design method for an active cooling structure for CMC materials that resists deposition and blockage. Background Technology

[0002] The future combat capabilities of highly stealthy aircraft with superior penetration capabilities rely heavily on the core power support of high-performance aero engines. However, design requirements such as higher thermodynamic cycle parameters (gas temperature exceeding 2200K), longer component lifespan, and higher reliability (lifespan exceeding 6000 hours) pose significant challenges to the development of next-generation aero engines, especially high-temperature components such as turbine blades. Existing turbine blade design capabilities based on high-temperature alloys have reached their limits, and the application of composite materials, represented by ceramic matrix composites (CMC), offers the most likely and promising solution.

[0003] CMC materials have become a key solution for improving the temperature resistance of hot-end components in aero engines. However, their heat resistance limit is still lower than the gas temperature of high-performance aero engines above 2200K. In particular, the temperature resistance of domestically produced SiC fiber-reinforced CMC materials is currently around 1623K, which is still lower than that of foreign products. Therefore, efficient cooling technology is still needed to ensure the safe operation of high-temperature components made of CMC materials. At present, the cooling structure design of high-temperature components such as CMC turbine blades mostly adopts the approach of replacing metal blade cooling structures, using full film cooling on the leading edge and pressure surface of the blade, and using slit and turbulence-reducing structures on the trailing edge. However, for CMC material blades, on the one hand, their operating temperature is higher than that of traditional high-temperature alloys, approaching or exceeding the melting point of typical dust particles. When operating in dusty environments, the deposition rate of dust particles increases exponentially with temperature, and the deposition amount will be significantly higher than that of metal-based blades. On the other hand, CMC materials are heterogeneous structures composed of a matrix and toughening fibers, and their molding process is complex. Moreover, ceramic-based materials are difficult to process using traditional methods, resulting in a relatively rough surface of CMC material components, making it easier for dust particles to deposit on the rough surface. Therefore, it is necessary to conduct design and analysis of an anti-deposition blockage, low-attenuation, high-efficiency active cooling structure suitable for CMC turbine blades, taking into account the structural and process characteristics of braided CMC materials.

[0004] For CMC materials, due to the differences in the thermal properties of their internal fibers and matrix, as well as the anisotropy of the fibers themselves, the overall thermal conductivity of CMC materials exhibits significant anisotropy. The internal fiber weave structure and pore structure also significantly affect the heat transfer process of the cooling structure. Therefore, on the surface of CMC materials, there is a temperature dispersion distribution that varies with the weave structure, thus affecting the morphology of the deposited particles. Therefore, the designability of the material's microstructure can be fully utilized, combined with the characteristics of efficient cooling structures, to develop anti-deposition blockage, low-attenuation, and high-efficiency active cooling structures for CMC materials. Summary of the Invention

[0005] This invention addresses the risks of particle deposition and blockage in high-temperature ceramic matrix composite turbine blade cooling structures under dusty operating conditions, as well as the resulting reduction in cooling efficiency. It provides a design method for an active cooling structure using CMC materials to resist particle deposition and blockage. Based on adjustments to the shape of the film cooling orifice, the particle deposition characteristics and cooling efficiency resistance of the high-efficiency film cooling structure are investigated. This method significantly improves the coverage of the cooling film outflow, reduces the particle deposition rate near the orifice, and minimizes the overall cooling efficiency reduction of the film cooling structure after particle deposition.

[0006] This invention provides a method for designing an active cooling structure for CMC materials to resist deposition and blockage, comprising the following steps:

[0007] Step 1: Utilizing the designability of the woven CMC material prefabricated structure fiber, combined with the outflow characteristics and structural features of the expanded film vent, an integrated design of the expanded film vent and the material prefabricated structure is carried out. A CMC material component anti-deposition film cooling structure model and its fluid-structure interaction simulation model are constructed, and the material wall temperature distribution and the overall cooling effect of the film are calculated.

[0008] Step 2: For the anti-deposition film cooling structure model of CMC material components and its fluid-structure interaction simulation model in Step 1, a particle dispersion phase model is introduced to calculate the motion trajectory of dust particles in the flow field. At the same time, a particle deposition probability criterion model is introduced to obtain the wall particle deposition distribution under the simulation results of anti-deposition film pores.

[0009] Step 3: Based on the wall particle deposition distribution obtained from the anti-deposition film pore simulation results in Step 2, when the deposition layer thickness is greater than the preset threshold, the volume grid of the deposition layer is reconstructed by means of dynamic meshing or thickness extraction and remodeling. The wall temperature distribution including the influence of the deposition layer on flow heat transfer and the overall cooling effect of the film after particle deposition are calculated. When the deposition layer thickness is less than or equal to the preset threshold, the method of assigning thermal resistance to the deposition layer according to the thickness is used to calculate the wall temperature distribution including only the thermal resistance of the deposition layer and the overall cooling effect of the film after particle deposition.

[0010] Step 4: Compare the overall cooling effect of the gas film after particle deposition calculated in Step 3 with the material wall temperature distribution and overall cooling effect of the gas film calculated by the fluid-structure interaction simulation model in Step 1 without particle deposition to obtain the cooling effect attenuation. Evaluate the anti-deposition and low attenuation performance of the new gas film pores based on the cooling effect attenuation.

[0011] Optionally, in an embodiment of the present invention, step one specifically includes:

[0012] By utilizing the designability of the fibers in the prefabricated structure of CMC material, combined with the outflow characteristics and structural features of the expanded film vent, the fiber bundles are wound back into the reserved space of the vent region. At the same time, the number of local fibers is adjusted according to the vent characteristics. The integrated design of the expanded film vent and the prefabricated structure is carried out to form an expanded vent cooling structure. On both sides of the solid domain model of the film vent structure, a high-temperature main flow domain and a low-temperature secondary flow domain are constructed respectively, and connected through the film vent to form a CMC material component anti-deposition film cooling structure model and its fluid-structure interaction simulation model. The temperature distribution of the material wall and the comprehensive cooling effect of the film are calculated.

[0013] Optionally, in an embodiment of the present invention, step two specifically includes:

[0014] For the anti-deposition film cooling structure model of CMC material components and its fluid-structure interaction simulation model in step one, particle deposition calculation is introduced. The numerical simulation of particle deposition on the structural surface includes two aspects: the calculation of particle trajectory and the calculation of particle deposition on the structural surface. The particle trajectory is calculated by the Euler-Lagrange method. The particles are regarded as discrete phases, and the governing equation is established by the Lagrange method. The gas phase is solved by the Euler method. The dispersed phase model simulates the interaction between the two phases, gives the particle trajectory in the flow field, and describes the landing position of micro particles. After reaching the near wall, the particles will collide with the wall under the action of aerodynamic force, and then splashing, rebounding, spreading and adhesion phenomena will occur. Through the rebound adhesion model based on particle viscosity calculation, the ratio of the critical viscosity of a single particle to the viscosity value when impacting the wall is calculated as the deposition probability to determine whether the particle has deposited. Undeposited particles continue to move according to the rebound velocity calculated by the collision momentum equation. Deposited particles have their velocity set to zero, so that they are solidified on the wall surface, thus obtaining the particle deposition distribution on the wall surface under the simulation results of anti-deposition film pores.

[0015] Optionally, in an embodiment of the present invention, step three specifically includes:

[0016] Based on the wall particle deposition distribution obtained from the anti-deposition film pore simulation results in step two, the wall temperature distribution and overall cooling effect considering the influence of the deposition layer on heat transfer are calculated. Taking into account both calculation speed and accuracy, a preset threshold is set for the maximum thickness of the deposition layer. The wall temperature and cooling effect after particle deposition are calculated using two schemes. When the deposition layer thickness is greater than the preset threshold, which will have a significant impact on the flow, the volume grid of the deposition layer is reconstructed by using dynamic meshing or extracting the deposition layer thickness and remodeling. After reassigning the grid properties of the deposition layer region according to the properties of the sediment, the calculation is iterated again to obtain the wall temperature distribution and overall cooling effect of the film pore that include the influence of the deposition layer on the flow heat transfer. When the deposition layer thickness is less than or equal to the preset threshold, the influence of the sediment on the flow is ignored. The method of assigning thermal resistance variables to the deposition layer according to the thickness is used to calculate the wall temperature distribution and overall cooling effect of the film pore that only includes the wall thermal resistance of the deposition layer.

[0017] Optionally, in an embodiment of the present invention, step four specifically includes:

[0018] The overall cooling effect calculated by the fluid-structure interaction simulation model in step one, which does not include particle deposition, is compared with that of the overall cooling effect on the downstream centerline of the film pore outlet and the surface average overall cooling effect in the vicinity of the film pore. The percentage of cooling effect attenuation in the characteristic area is obtained by comparing the cooling effect value before deposition. The anti-deposition low attenuation performance of the new film pore is evaluated based on the amount of cooling effect attenuation.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] This invention avoids the entrainment of particles by the eddy current at the outlet of the traditional circular film gas hole, improves the anti-deposition effect downstream of the film gas hole, significantly reduces the cooling efficiency decay after particle deposition, and improves the overall cooling efficiency of CMC material components after long-term service under particle deposition conditions.

[0021] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0022] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0023] Figure 1 A flowchart illustrating an active cooling structure design method for anti-deposition clogging CMC materials according to an embodiment of the present invention;

[0024] Figure 2 This is a schematic diagram of the expanded film pore structure according to an embodiment of the present invention;

[0025] Figure 3 This is a schematic diagram of a 2.5D woven CMC material expanded air film cooling plate model according to an embodiment of the present invention;

[0026] Figure 4 This is a computational domain model of a 2.5D braided CMC material flat plate according to an embodiment of the present invention;

[0027] Figure 5 This is a schematic diagram of the circular air film pore structure according to an embodiment of the present invention;

[0028] Figure 6 This is a schematic diagram of a 2.5D braided CMC material circular air film cooling plate model according to an embodiment of the present invention;

[0029] Figure 7 This invention provides a comparison of the film cooling effects of circular and expanded pore types in 2.5D woven CMC materials.

[0030] Figure 8 This is a comparison of the film deposition thickness of circular and expanded pore types in 2.5D woven CMC materials according to an embodiment of the present invention.

[0031] Figure 9 A comparison of the air film outflow streamlines of circular holes and expanded holes in 2.5D woven CMC materials according to an embodiment of the present invention;

[0032] Figure 10 A comparison of velocity distribution at the exit points of circular and expanded holes in 2.5D woven CMC materials according to an embodiment of the present invention;

[0033] Figure 11 This is a comparison of the vortex structures near circular holes and expanded holes in the 2.5D woven CMC material of this invention. Detailed Implementation

[0034] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0035] Figure 1 This is a flowchart illustrating an active cooling structure design method for anti-deposition and blockage CMC materials according to an embodiment of the present invention.

[0036] like Figure 1 As shown, the active cooling structure design method for anti-deposition clogging CMC materials includes the following steps:

[0037] Step 1: Utilizing the designability of the woven CMC material prefabricated structure fiber, combined with the outflow characteristics and structural features of the expanded film vent, an integrated design of the expanded film vent and the material prefabricated structure is carried out. A CMC material component anti-deposition film cooling structure model and its fluid-structure interaction simulation model are constructed, and the material wall temperature distribution and the overall cooling effect of the film are calculated.

[0038] Step 2: For the anti-deposition film cooling structure model of CMC material components and its fluid-structure interaction simulation model in Step 1, a particle dispersion phase model is introduced to calculate the motion trajectory of dust particles in the flow field. At the same time, a particle deposition probability criterion model is introduced to obtain the wall particle deposition distribution under the simulation results of anti-deposition film pores.

[0039] Step 3: Based on the wall particle deposition distribution obtained from the anti-deposition film pore simulation results in Step 2, when the deposition layer thickness is greater than the preset threshold, the volume grid of the deposition layer is reconstructed by means of dynamic meshing or thickness extraction and remodeling. The wall temperature distribution including the influence of the deposition layer on flow heat transfer and the overall cooling effect of the film after particle deposition are calculated. When the deposition layer thickness is less than or equal to the preset threshold, the method of assigning thermal resistance to the deposition layer according to the thickness is used to calculate the wall temperature distribution including only the thermal resistance of the deposition layer and the overall cooling effect of the film after particle deposition.

[0040] Step 4: Compare the overall cooling effect of the gas film after particle deposition calculated in Step 3 with the material wall temperature distribution and overall cooling effect of the gas film calculated by the fluid-structure interaction simulation model in Step 1 without particle deposition to obtain the cooling effect attenuation. Evaluate the anti-deposition and low attenuation performance of the new gas film pores based on the cooling effect attenuation.

[0041] Optionally, in an embodiment of the present invention, step one specifically includes:

[0042] By utilizing the designability of the fibers in the prefabricated structure of CMC material, combined with the outflow characteristics and structural features of the expanded film vent, the fiber bundles are wound back into the reserved space of the vent region. At the same time, the number of local fibers is adjusted according to the vent characteristics. The integrated design of the expanded film vent and the prefabricated structure is carried out to form an expanded vent cooling structure. On both sides of the solid domain model of the film vent structure, a high-temperature main flow domain and a low-temperature secondary flow domain are constructed respectively, and connected through the film vent to form a CMC material component anti-deposition film cooling structure model and its fluid-structure interaction simulation model. The temperature distribution of the material wall and the comprehensive cooling effect of the film are calculated.

[0043] Optionally, in an embodiment of the present invention, step two specifically includes:

[0044] For the anti-deposition film cooling structure model of CMC material components and its fluid-structure interaction simulation model in step one, particle deposition calculation is introduced. The numerical simulation of particle deposition on the structural surface includes two aspects: the calculation of particle trajectory and the calculation of particle deposition on the structural surface. The particle trajectory is calculated by the Euler-Lagrange method. The particles are regarded as discrete phases, and the governing equation is established by the Lagrange method. The gas phase is solved by the Euler method. The dispersed phase model simulates the interaction between the two phases, gives the particle trajectory in the flow field, and describes the landing position of micro particles. After reaching the near wall, the particles will collide with the wall under the action of aerodynamic force, and then splashing, rebounding, spreading and adhesion phenomena will occur. Through the rebound adhesion model based on particle viscosity calculation, the ratio of the critical viscosity of a single particle to the viscosity value when impacting the wall is calculated as the deposition probability to determine whether the particle has deposited. Undeposited particles continue to move according to the rebound velocity calculated by the collision momentum equation. Deposited particles have their velocity set to zero, so that they are solidified on the wall surface, thus obtaining the particle deposition distribution on the wall surface under the simulation results of anti-deposition film pores.

[0045] Optionally, in an embodiment of the present invention, step three specifically includes:

[0046] Based on the wall particle deposition distribution obtained from the anti-deposition film pore simulation results in step two, the wall temperature distribution and overall cooling effect considering the influence of the deposition layer on heat transfer are calculated. Taking into account both calculation speed and accuracy, a preset threshold is set for the maximum thickness of the deposition layer. The wall temperature and cooling effect after particle deposition are calculated using two schemes. When the deposition layer thickness is greater than the preset threshold, which will have a significant impact on the flow, the volume grid of the deposition layer is reconstructed by using dynamic meshing or extracting the deposition layer thickness and remodeling. After reassigning the grid properties of the deposition layer region according to the properties of the sediment, the calculation is iterated again to obtain the wall temperature distribution and overall cooling effect of the film pore that include the influence of the deposition layer on the flow heat transfer. When the deposition layer thickness is less than or equal to the preset threshold, the influence of the sediment on the flow is ignored. The method of assigning thermal resistance variables to the deposition layer according to the thickness is used to calculate the wall temperature distribution and overall cooling effect of the film pore that only includes the wall thermal resistance of the deposition layer.

[0047] Optionally, in an embodiment of the present invention, step four specifically includes:

[0048] The overall cooling effect calculated by the fluid-structure interaction simulation model in step one, which does not include particle deposition, is compared with that of the overall cooling effect on the downstream centerline of the film pore outlet and the surface average overall cooling effect in the vicinity of the film pore. The percentage of cooling effect attenuation in the characteristic area is obtained by comparing the cooling effect value before deposition. The anti-deposition low attenuation performance of the new film pore is evaluated based on the amount of cooling effect attenuation.

[0049] The present invention will be further described below with reference to embodiments and comparative examples.

[0050] Example:

[0051] Figure 2 A schematic diagram of an anti-deposition, low-attenuation, expanding gas film pore structure according to an embodiment of the present invention is provided. Figure 2 A schematic diagram of a 2.5D woven CMC material anti-deposition low-attenuation expansion film cooling plate model is given. The overall size of the plate is 50*6.68*3.45mm, in which the fiber bundle cross section is hexagonal, the warp spacing is 0.35mm, and the weft spacing is 0.35mm. Figure 3 The computational domain model for flat-plate film cooling involved in the simulation is presented. The computational domain is divided into three parts: the mainstream gas flow domain, with a height of 90mm above the plate, and a 45° bend in front of the plate to improve particle collision efficiency in the simulation; the secondary cold gas flow domain, with dimensions of 50*6.68*5.6mm; and the solid plate domain, with dimensions as shown below. Figure 3 As shown in the image.

[0052] During the modeling process, the conventional 2.5D woven warp yarns are first manipulated. The bottom layer of warp yarns is fixed, and the upper layer of warp yarns are moved backward a certain distance based on the previous layer. This distance should correspond to the angle requirements of the air film aperture, including but not limited to the moving distance and air film aperture angle mentioned in this article. Then, at the air film aperture location, the weft yarns are wound back to reserve space for the forward-tilting expansion type air film aperture. Based on this, the top layer of warp yarns downstream of the air film aperture is removed to reserve more space for air film aperture operation. A new forward-tilting expansion type air film aperture is formed by cutting 0.75mm vertically behind the forward-tilting expansion type air film aperture.

[0053] The numerical study utilized non-isothermal flow and coupled heat transfer models in the FLUENT software, while also introducing the DPM dispersed phase model and particle deposition UDF function to calculate particle trajectories and deposition criteria. The thermal properties of the flat solid domain were introduced from the microscale woven structure, specifically isotropic thermal conductivity for the matrix and anisotropic thermal conductivity for the fiber bundles. The anisotropic thermal conductivity matrix was used to characterize the variation of the fiber bundle thermal conductivity with the fiber bundle direction.

[0054] The mainstream inlet boundary in the calculation is defined as follows: inlet temperature 1300-2400K, mainstream velocity 60m / s. The secondary flow inlet boundary is defined as follows: inlet temperature 790K, blowing ratio 0.5. The secondary flow enters the secondary flow channel through the secondary flow inlet, then enters the mainstream channel through the film gas vents. After mixing with the mainstream, it flows out through the pressure outlet boundary, with an absolute pressure of 101325Pa at the outlet. Particles are released from the mainstream inlet, with the following particle properties: melting point 1478K, diameter 1-40μm, density 1980kg / m³. 3The computational domain is bounded by periodic boundaries on both sides; the other boundaries are adiabatic boundary conditions.

[0055] In this study, FLUENT software was used to mesh the computational model. The woven CMC flat plate portion was meshed using a polyhedral mesh, with surface meshing used for refinement at the fiber-matrix interface. A boundary layer mesh was constructed in the fluid domain near the gas combustion sidewall.

[0056] Comparative example:

[0057] Meanwhile, to compare the deposition characteristics and cooling effect attenuation differences between the 2.5D braided CMC material anti-deposition low-attenuation expanded film cooling pores of this invention and traditional circular film cooling pores, the same simulation method was used in the comparative example to simulate and analyze particle deposition and cooling effect of the circular film cooling structure of the 2.5D braided CMC material. The computational domain model and dimensions of the circular film cooling plate are also included. Figure 4 Same as above. Figure 5 A schematic diagram of a circular air film cooling hole structure with a diameter of 0.8 mm is provided as a comparative example of the present invention. Figure 6 A schematic diagram of a 2.5D woven CMC material circular film cooling plate model is provided. To calculate the deposition characteristics between the film pores, it includes two complete film pores. The overall dimensions of the plate are 50*6.68*3.45mm, with hexagonal fiber bundle cross-sections, a warp spacing of 0.35mm, and a weft spacing of 0.35mm. Furthermore, the anisotropic thermal conductivity settings, DPM particle settings, mesh generation, and boundary condition settings involved in the simulation calculations in the comparative example are the same as those in the embodiment.

[0058] Figure 7 A comparison of the overall cooling efficiency distribution cloud maps of the film-film covered wall surface without particle deposition is presented in the example (anti-deposition low-attenuation film-film orifice) and the comparative example (circular film-film orifice). As can be seen from the figures, compared with the circular film-film orifice, the anti-deposition low-attenuation film-film orifice significantly improves the downstream film coverage effect, including the film cooling efficiency value within the high film cooling efficiency region. Within the 0-10D range downstream of the film-film orifice, the average overall cooling efficiencies of the circular film-film orifice and the anti-deposition low-attenuation film-film orifice are 0.15 and 0.24, respectively.

[0059] Figure 8 Comparative cloud maps of deposition thickness distribution on the wall surface are provided for the examples and comparative examples. As can be seen from the figures, compared to circular film vents, the deposition thickness downstream of the anti-deposition low-attenuation film vents is significantly lower, including both the film cooling efficiency value and the high film cooling efficiency region. Within a 0-10D range downstream of the film vents, the average deposition thicknesses of the circular film vents and the anti-deposition low-attenuation film vents are 0.516 mm and 0.335 mm, respectively.

[0060] Figure 9Comparative airflow diagrams of two 2.5D braided CMC material air film cooling structures are provided in the examples and comparative examples. As can be seen from the figures, compared to circular air film holes, the expanded holes in the 2.5D braided CMC material significantly improve the downstream air film coverage effect.

[0061] Figure 10 A comparison of velocity distribution at the outlet of circular and expanded holes in 2.5D braided CMC materials is presented. As can be seen from the figure, the flow velocity at the outlet of the circular air film hole is high, and it is entrained towards the wall on both sides in the high-speed region; the flow velocity at the outlet of the expanded hole is lower, and the outflow is close to the wall and the distribution is more uniform in the spanwise direction.

[0062] Figure 11 The isosurfaces of Q Criterion = 0.1 near the outlet of the two film cooling structures in the embodiments and comparative examples are given to illustrate the vortex structure. As can be seen from the figure, due to the high flow velocity at the outlet of the circular film cooling hole, the generated vortex intensity is large and the vortex duration is longer. Under the entrainment effect of the vortex, low-diameter particles collide with the wall surface, resulting in a higher local deposition at the end of the vortex. In contrast, the outlet flow velocity of the anti-deposition low-attenuation film cooling hole is lower, the film coverage is wider, the vortex intensity on both sides of the outlet of the film cooling hole is lower, and the geometric scale is smaller, so that the particles do not concentrate and collide with the wall surface, thereby reducing the deposition rate.

[0063] On the one hand, due to the lower outflow velocity of the expanded film vent, the jet is more longitudinally dispersed and adheres better to the wall, resulting in weaker mixing eddies between the cooling airflow and the mainstream combustion gas. This makes it less likely for smaller dust particles to collide with the wall surface due to the entrainment effect of the eddies, reducing the collision rate of particles downstream of the film vent and thus reducing the deposition rate. On the other hand, the cooling airflow of the expanded film vent covers a larger area of ​​the downstream wall surface, allowing the wall surface to maintain a lower temperature over a larger area. Since the probability of particles colliding with the wall surface and being deposited is positively correlated with temperature, the particle deposition rate of the expanded film vent is lower than that of the circular film vent in the area covered by the cooling airflow downstream of the film vent.

[0064] In summary, the present invention establishes a design method for anti-deposition and low-attenuation film cooling pores based on braided ceramic matrix composites (CMC), which can significantly improve the overall film cooling efficiency of braided CMC material components, reduce the deposition rate of particles on the wall surface, and reduce the attenuation of film cooling efficiency after long-term service in a particle deposition environment.

[0065] The active cooling structure design method for anti-deposition and clogging CMC materials proposed in this invention, based on the key geometric features of the expanded film cooling pores of CMC material components, combines traditional fluid-structure interaction heat transfer simulation calculations with a dispersed phase model to simulate the trajectory of dust particles in the fluid. A user-defined function is used to introduce a probability model of particle deposition, enabling the integrated design of the CMC material film cooling structure under dusty conditions. This results in a low-attenuation film cooling structure scheme for anti-deposition cooling efficiency of ceramic matrix composite components, and its cooling effect before and after particle deposition is analyzed and evaluated. Therefore, by simulating and analyzing the influence of anti-deposition film cooling pores on the particle deposition rate on the wall surface, an evaluation method for the attenuation of film cooling efficiency after particle deposition is developed. This method can significantly reduce the attenuation of film cooling efficiency caused by particle deposition and improve the overall film cooling efficiency of CMC material components under long-term dusty service conditions.

[0066] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0067] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "N" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0068] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or N executable instructions for implementing custom logic functions or processes, and the scope of preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.

Claims

1. A method for designing an active cooling structure for CMC materials to resist deposition and blockage, characterized in that, Includes the following steps: Step 1: Utilizing the designability of the woven CMC material prefabricated structure fiber, combined with the outflow characteristics and structural features of the expanded film vent, an integrated design of the expanded film vent and the material prefabricated structure is carried out. A CMC material component anti-deposition film cooling structure model and its fluid-structure interaction simulation model are constructed, and the material wall temperature distribution and the overall cooling effect of the film are calculated. Step 2: For the anti-deposition film cooling structure model of CMC material components and its fluid-structure interaction simulation model in Step 1, a particle dispersion phase model is introduced to calculate the motion trajectory of dust particles in the flow field. At the same time, a particle deposition probability criterion model is introduced to obtain the wall particle deposition distribution under the simulation results of anti-deposition film pores. Step 3: Based on the wall particle deposition distribution obtained from the anti-deposition film pore simulation results in Step 2, when the deposition layer thickness is greater than the preset threshold, the volume grid of the deposition layer is reconstructed by means of dynamic meshing or thickness extraction and remodeling. The wall temperature distribution including the influence of the deposition layer on flow heat transfer and the overall cooling effect of the film after particle deposition are calculated. When the deposition layer thickness is less than or equal to the preset threshold, the method of assigning thermal resistance to the deposition layer according to the thickness is used to calculate the wall temperature distribution including only the thermal resistance of the deposition layer and the overall cooling effect of the film after particle deposition. Step 4: Compare the overall cooling effect of the gas film after particle deposition calculated in Step 3 with the material wall temperature distribution and overall cooling effect of the gas film calculated by the fluid-structure interaction simulation model in Step 1 without particle deposition to obtain the cooling effect attenuation. Evaluate the anti-deposition and low attenuation performance of the new gas film pores based on the cooling effect attenuation.

2. The method according to claim 1, characterized in that, Step one specifically includes: By utilizing the designability of the fibers in the prefabricated structure of CMC material, combined with the outflow characteristics and structural features of the expanded film vent, the fiber bundles are wound back into the reserved space of the vent region. At the same time, the number of local fibers is adjusted according to the vent characteristics. The integrated design of the expanded film vent and the prefabricated structure is carried out to form an expanded vent cooling structure. On both sides of the solid domain model of the film vent structure, a high-temperature main flow domain and a low-temperature secondary flow domain are constructed respectively, and connected through the film vent to form a CMC material component anti-deposition film cooling structure model and its fluid-structure interaction simulation model. The temperature distribution of the material wall and the comprehensive cooling effect of the film are calculated.

3. The method according to claim 1, characterized in that, Step two specifically includes: For the anti-deposition film cooling structure model of CMC material components and its fluid-structure interaction simulation model in step one, particle deposition calculation is introduced. The numerical simulation of particle deposition on the structural surface includes two aspects: the calculation of particle trajectory and the calculation of particle deposition on the structural surface. The particle trajectory is calculated by the Euler-Lagrange method. The particles are regarded as discrete phases, and the governing equation is established by the Lagrange method. The gas phase is solved by the Euler method. The dispersed phase model simulates the interaction between the two phases, gives the particle trajectory in the flow field, and describes the landing position of micro particles. After reaching the near wall, the particles will collide with the wall under the action of aerodynamic force, and then splashing, rebounding, spreading and adhesion phenomena will occur. Through the rebound adhesion model based on particle viscosity calculation, the ratio of the critical viscosity of a single particle to the viscosity value when impacting the wall is calculated as the deposition probability to determine whether the particle has deposited. Undeposited particles continue to move according to the rebound velocity calculated by the collision momentum equation. Deposited particles have their velocity set to zero, so that they are solidified on the wall surface, thus obtaining the particle deposition distribution on the wall surface under the simulation results of anti-deposition film pores.

4. The method according to claim 1, characterized in that, Step three specifically includes: Based on the wall particle deposition distribution obtained from the anti-deposition film pore simulation results in step two, the wall temperature distribution and overall cooling effect considering the influence of the deposition layer on heat transfer are calculated. Taking into account both calculation speed and accuracy, a preset threshold is set for the maximum thickness of the deposition layer. The wall temperature and cooling effect after particle deposition are calculated using two schemes. When the deposition layer thickness is greater than the preset threshold, which will have a significant impact on the flow, the volume grid of the deposition layer is reconstructed by using dynamic meshing or extracting the deposition layer thickness and remodeling. After reassigning the grid properties of the deposition layer region according to the properties of the sediment, the calculation is iterated again to obtain the wall temperature distribution and overall cooling effect of the film pore that include the influence of the deposition layer on the flow heat transfer. When the deposition layer thickness is less than or equal to the preset threshold, the influence of the sediment on the flow is ignored. The method of assigning thermal resistance variables to the deposition layer according to the thickness is used to calculate the wall temperature distribution and overall cooling effect of the film pore that only includes the wall thermal resistance of the deposition layer.

5. The method according to claim 1, characterized in that, Step four specifically includes: The overall cooling effect calculated by the fluid-structure interaction simulation model in step one, which does not include particle deposition, is compared with that of the overall cooling effect on the downstream centerline of the film pore outlet and the surface average overall cooling effect in the vicinity of the film pore. The percentage of cooling effect attenuation in the characteristic area is obtained by comparing the cooling effect value before deposition. The anti-deposition low attenuation performance of the new film pore is evaluated based on the amount of cooling effect attenuation.

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