A design method for improving film cooling based on reserved expansion angle to prevent blockage

Abstract

This invention discloses a design method for improving film cooling based on a reserved expansion angle to prevent blockage, belonging to the field of high-efficiency cooling design for turbomachinery. The method includes the following steps: determining the structural parameters of the initial forward-inclined fan-shaped film cooling orifice; establishing a geometric model of the blockage at the outlet of the forward-inclined fan-shaped film cooling orifice; calculating the length of the extended portion of the film cooling orifice inclination angle in the flow-direction expansion section; calculating the length of the line connecting the expansion start position and the expansion end position on the symmetry plane of the film cooling orifice; establishing an optimization function for the flow-direction expansion angle based on the blockage geometric model and the blockage height; combining the calculated results of the line length with the functional relationship to construct a solution equation with the optimized flow-direction expansion angle as the only unknown; obtaining a numerical solution for the optimized flow-direction expansion angle; and using the optimized flow-direction expansion angle as the final design value to complete the design of the forward-inclined fan-shaped film cooling orifice. This invention solves the problem of coating accumulation at the outlet of the film cooling orifice during the thermal barrier coating spraying process, leading to obstructed cooling airflow and reduced cooling efficiency.

Description

Technical Field

[0001] This invention belongs to the field of efficient cooling design for turbomachinery, specifically relating to a design method for improving film cooling based on a reserved expansion angle to prevent blockage. Background Technology

[0002] High-pressure turbine guide vanes in aero-engines operate for extended periods in extremely high-temperature gas environments, resulting in exceptionally high thermal loads. Therefore, they rely on efficient external cooling technologies to ensure structural reliability and service life. Currently, the mainstream technology involves creating film cooling holes on the turbine blade surface and spraying a thermal barrier coating (TBC). This forms a heat-insulating, cool gas layer through the film cooling system, and the coating's low thermal conductivity adds additional thermal resistance, thus protecting the substrate material. However, these two external cooling methods interact, potentially preventing any single cooling method from fully realizing its cooling potential.

[0003] However, in actual manufacturing processes, to avoid the electrical conductivity requirements of EDM (Electrical Discharge Machining), a "hole-first, coating-later" process is commonly adopted. This process inevitably leads to the thermal barrier coating material entering the film cooling pores, especially in the outlet area, causing accumulation and blockage. This significantly reduces the effective cooling airflow outlet area, and the jet is more easily blown away from the wall at high airflow ratios, resulting in inaccurate cooling design. Therefore, adopting a design method that suppresses the cooling reduction caused by spray-applied pore blockage while considering the possibility of pore blockage is crucial to avoiding overestimating actual cooling performance and ensuring efficient turbine cooling.

[0004] Expansion film cooling (FSL) holes are widely used in aero-engine turbines. Clogging of these holes caused by spraying significantly impacts their cooling performance. In the paper "Effect of particle deposition on film cooling from fan-shaped holes" (International Journal of Heat and Mass Transfer, 2021, Vol. 181, Article No. 122028), the authors demonstrated the FSL performance after fan-shaped hole blockage. When the blockage reached or exceeded half the diameter of the FSL hole, significant shrinkage of the cooling zone and film blowing-off were observed, resulting in decreased film coverage efficiency, significantly deteriorated cooling performance, and in severe cases, even localized overheating, threatening blade safety.

[0005] In summary, given the potential for film cooling pore blockage due to thermal barrier coating application, existing technologies largely focus on passive structural expansion or pneumatic attachments, lacking a method based on predictive modeling that can quantify and compensate for the blockage's impact during the forward-looking design phase. Therefore, there is an urgent need in this field for a design method that can precisely reserve the expansion angle and ensure that the film cooling pore outlet area remains unchanged after blockage, thereby fundamentally guaranteeing the achievement of film cooling efficiency under design conditions. Summary of the Invention

[0006] The technical problem to be solved:

[0007] To overcome the shortcomings of existing technologies, this invention provides a design method for improving film cooling based on a reserved expansion angle to prevent clogging. Based on structural parameters such as the aperture, expansion initiation position, and inclination angle of the forward-tilted fan-shaped film cooling orifice, the geometry of the expanding film cooling orifice and the modeling method for the blockage are determined. A functional relationship between the flow-direction expansion angle after blockage and the height of the blockage is constructed. Using the condition of maintaining the same film cooling orifice outlet area, the corresponding equations are solved to obtain the flow-direction expansion angle after the reserved angle. This provides a basis for designing forward-tilted fan-shaped film cooling orifices to prevent cooling performance degradation caused by spray clogging. This invention, through a reserved expansion angle + mathematical model + iterative algorithm, predicts and compensates for the impact of thermal barrier coating blockage on the film cooling orifice outlet area during the design stage. This solves the problems of paint entering the film cooling orifice and accumulating at the outlet during thermal barrier coating spraying, leading to a reduction in effective flow area, obstructed cooling airflow, and decreased cooling efficiency.

[0008] The technical solution of this invention is: a design method for improving film cooling based on a reserved expansion angle to prevent blockage, comprising the following steps:

[0009] Determine the structural parameters of the initial forward-tilted fan-shaped air film orifice, including the diameter of the cylindrical section, aspect ratio, orifice inclination angle, initial flow direction expansion angle, and the proportion of the cylindrical section to the total orifice length.

[0010] The height of the blockage is determined based on the thickness of the thermal barrier coating, and a geometric model of the blockage at the outlet of the forward-tilted fan-shaped air film orifice is established.

[0011] Based on the structural parameters of the initial forward-tilted fan-shaped film air hole, the length of the extended portion of the inclination angle of the forward-tilted fan-shaped film air hole in the flow expansion section is calculated;

[0012] Based on the length of the extended portion, calculate the length of the line connecting the expansion start position and the expansion end position on the symmetry plane of the forward-tilted fan-shaped air film hole;

[0013] With the core constraint that the outlet area of ​​the blocked forward-tilted fan-shaped air film orifice remains equal to the initial forward-tilted fan-shaped air film orifice outlet area, the flow expansion angle after blockage is defined to be consistent with the initial flow expansion angle; the flow expansion angle after blockage is the angle between the line connecting the expansion start position to the outlet blockage and the axis of the cylindrical segment.

[0014] Based on the geometric model of the blockage and the height of the blockage, an optimization function for the flow direction expansion angle is established, that is, to optimize the functional relationship between the flow direction expansion angle and the length of the connecting line;

[0015] By combining the calculated results of the connecting line length with the functional relationship, a solution equation is constructed with the optimized flow direction expansion angle as the only unknown.

[0016] The above equations are solved by numerical iterative algorithm to obtain the numerical solution of the optimized flow direction expansion angle, that is, the forward-inclined fan-shaped air film orifice based on the reserved expansion angle;

[0017] The design of the forward-tilted fan-shaped film air hole was completed by using the optimized flow direction expansion angle as the final design value.

[0018] A further technical solution of the present invention is as follows: the method for establishing the geometric model of the blockage is to take the intersection of the vertical line from the upper end of the leeward side of the symmetry plane of the forward-tilted fan-shaped air film orifice and the flow expansion section as the starting position of the blockage, draw the outline of the blockage parallel to the wall of the flow expansion section through the intersection, and smoothly connect the starting position and the outline of the blockage through a tangent circular arc.

[0019] A further technical solution of the present invention is: the flow direction expansion angle optimization function is expressed as:

[0020]

[0021] In the formula, β 3 indicates the optimized flow direction expansion angle; β 1 represents the initial flow spread angle; h Indicates the height of the blockage; b This represents the length of the line connecting the starting and ending positions of the expansion within the symmetry plane of the forward-tilted fan-shaped film air hole. θ Indicates the inclination angle of the hole.

[0022] A further technical solution of the present invention is: the expression for the solution equation with the optimized flow direction expansion angle as the only unknown is:

[0023]

[0024] In the formula, D The diameter of the cylindrical section representing the forward-tilted fan-shaped film air hole; L d Indicates the aspect ratio; L cy This indicates the proportion of the cylindrical section to the total length of the hole; It indicates the length of the extended portion of the forward-tilted fan-shaped film air hole in the flow-expanding section.

[0025] A further technical solution of the present invention is: the numerical iteration algorithm includes an iteration termination determination step:

[0026] In each iteration, the actual flow expansion angle after blockage is calculated based on the flow expansion angle after the current reserved angle;

[0027] Calculate the relative deviation between the actual flow expansion angle and the initial flow expansion angle;

[0028] The iterative calculation terminates when the absolute value of the relative deviation is less than one percent.

[0029] A further technical solution of the present invention is: the numerical iteration algorithm adopts the Newton-Raphson method, the initial value of the iteration calculation is set as the initial flow direction expansion angle, the lower limit of the numerical range of the iteration solution is the initial flow direction expansion angle, and the upper limit is the orifice inclination angle.

[0030] A further technical solution of the present invention is to verify the final design value of the optimized flow direction expansion angle:

[0031] Based on the final determined optimized flow direction expansion angle and blockage geometry model, a gas film cooling flow calculation model including the blockage is established;

[0032] The cooling efficiency of the initial forward-tilted fan-shaped film air hole, the forward-tilted fan-shaped film air hole with blockage inside the hole, and the forward-tilted fan-shaped film air hole with reserved angle and blockage were calculated and compared through three-dimensional fluid dynamics simulation to verify the design effect.

[0033] A design system for film cooling based on a reserved expansion angle to prevent blockage includes:

[0034] The parameter determination module is used to determine the structural parameters of the initial forward-tilted fan-shaped air film orifice. The structural parameters include the diameter of the cylindrical section of the forward-tilted fan-shaped air film orifice, the aspect ratio, the orifice inclination angle, the initial flow direction expansion angle, and the proportion of the cylindrical section to the total orifice length.

[0035] The geometric modeling module determines the height of the blockage based on the thickness of the thermal barrier coating and establishes a geometric model of the blockage at the outlet of the forward-tilted fan-shaped film air hole.

[0036] The first calculation module, based on the structural parameters of the initial forward-tilted fan-shaped film air hole, calculates the length of the extended portion of the inclination angle of the forward-tilted fan-shaped film air hole in the flow expansion section;

[0037] The second calculation module calculates the length of the line connecting the starting position and the ending position of the expansion within the symmetry plane of the forward-tilted fan-shaped air film hole, based on the length of the extended portion.

[0038] The constraint setting module takes the equalization of the outlet area of ​​the forward-tilted fan-shaped air film orifice after blockage with the initial outlet area of ​​the forward-tilted fan-shaped air film orifice as the core constraint condition, and defines the flow expansion angle after blockage to be consistent with the initial flow expansion angle.

[0039] The function establishment module establishes a flow direction expansion angle optimization function based on the blockage geometry model and blockage height, that is, optimizes the functional relationship between the flow direction expansion angle and the connection length;

[0040] The equation construction module combines the calculation results of the connection length with the functional relationship to construct a solution equation with the optimized flow direction expansion angle as the only unknown.

[0041] The solution module uses a numerical iterative algorithm to solve the above equations and obtain a numerical solution for optimizing the flow direction expansion angle;

[0042] The output module uses the optimized flow direction expansion angle as the final design value to complete the design of the forward-tilted fan-shaped air film orifice.

[0043] A turbine blade has forward-inclined fan-shaped air film holes on its surface, designed and machined using a design method based on a reserved expansion angle to prevent blockage and enhance film cooling.

[0044] An aircraft engine, including the turbine blades.

[0045] Beneficial effects

[0046] The beneficial effects of this invention are as follows: The design method for improving film cooling based on a reserved expansion angle to prevent blockage can ensure that the outlet area of ​​the forward-tilted fan-shaped film cooling orifice does not change significantly even when the orifice is blocked due to the application of a thermal barrier coating, thereby avoiding a decrease in cooling performance. Specific advantages are as follows:

[0047] 1. This invention fundamentally and effectively suppresses the decline in cooling performance caused by the blockage of thermal barrier coatings: by pre-calculating and increasing the flow expansion angle (i.e., reserving the expansion angle) during the design stage, it actively compensates for the loss of flow area caused by the accumulation of coating material in the holes after spraying, ensuring that the outlet area of ​​the air film hole under actual blockage conditions is consistent with the design expectation, thereby fundamentally avoiding problems such as poor cooling airflow and jet blowing away from the wall surface caused by blockage, and stabilizing and improving the air film cooling efficiency.

[0048] 2. This invention achieves a paradigm shift from "passive response" to "active prediction and compensation": Unlike existing technologies that passively accommodate blockages by increasing cavity volume, this invention pioneers an active design method based on mathematical models and optimization algorithms. By establishing a geometric model of the blockage and using the strict constraint of "unchanged outlet area after blockage," precise mathematical relationships are constructed, enabling quantitative prediction and proactive compensation of the impact of blockages. This advanced design concept is demonstrated.

[0049] 3. This invention establishes a rigorous functional relationship and employs a numerical iterative algorithm (such as the Newton-Raphson method) to accurately calculate the required reserved expansion angle. The method sets explicit iteration termination conditions (such as a relative deviation of less than 1%), ensuring the accuracy and reliability of the design results and overcoming the uncertainties brought about by traditional empirical design or trial-and-error methods.

[0050] 4. The design method proposed in this invention is derived based on the core structural parameters of the forward-tilted fan-shaped film air hole (such as aperture, tilt angle, aspect ratio, etc.) and the predictable coating thickness (blockage height), and does not depend on a specific, fixed geometric configuration. Therefore, this method is applicable to the design of a series of forward-tilted fan-shaped film air holes of different sizes and angles, and has wide engineering applicability and flexibility.

[0051] 5. This invention ensures the hot-end life of turbine blades and the reliability of the engine. The film cooling holes designed by this method can maintain excellent cooling effect after the thermal barrier coating is applied, effectively controlling the operating temperature of the turbine blades. This is of great significance for improving the service life, operational safety and overall reliability of hot-end components such as high-pressure turbines of aero engines. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the symmetry plane of the forward-tilted fan-shaped air film hole in an embodiment of the present invention;

[0053] Figure 2 This is a schematic diagram of the geometric model of the blockage at the outlet of the forward-tilted fan-shaped air film orifice in an embodiment of the present invention;

[0054] Figure 3 This is a schematic diagram of the structure of the initial forward-tilted fan-shaped air film hole, the forward-tilted fan-shaped air film hole blocked inside the hole, and the forward-tilted fan-shaped air film hole with reserved angle and blocked, in an embodiment of the present invention.

[0055] Figure 4 This is a schematic diagram of the calculation domain for flat plate air film cooling with blocked forward-tilting fan-shaped air film holes in an embodiment of the present invention;

[0056] Figure 5 This is a comparison diagram of the air film cooling effect of the initial forward-tilted fan-shaped air film hole, the forward-tilted fan-shaped air film hole blocked inside the hole, and the forward-tilted fan-shaped air film hole with reserved angle and blocked in the embodiment of the present invention.

[0057] Figure 6 This is a comparison diagram of the average air film cooling effect of the initial forward-tilted fan-shaped air film hole, the forward-tilted fan-shaped air film hole blocked inside the hole, and the forward-tilted fan-shaped air film hole with reserved angle and blocked, in an embodiment of the present invention. Detailed Implementation

[0058] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0059] Several structural improvements have been proposed to address the problems existing in the prior art. For example, patent CN220226986U proposes a film membrane orifice structure with a double-expanding section and a concave rear wall, which reduces the impact of blockage by increasing the space near the outlet to accommodate coating deposition. Although this solution expands the flow area to some extent, it still has obvious limitations: first, its design relies on a specific geometric configuration and does not provide universal design principles or parameter quantification methods; second, it fails to establish a mathematical model between the degree of blockage and structural parameters, making it impossible to accurately predict and compensate for different orifice diameters, inclination angles, coating thicknesses, etc. In addition, another prior art (CN112324517B) focuses on introducing a Coanda bulge structure downstream of the film membrane orifice to improve airflow adhesion. Its technical approach belongs to the category of aerodynamic optimization and does not address the fundamental process problem of blockage prevention.

[0060] To address the problems existing in current technologies, this invention proposes a design method for improving film cooling based on a reserved expansion angle to prevent blockage. Based on the film cooling pore structure parameters and blockage modeling methods, a functional relationship is established between the outlet flow expansion angle after blockage and geometric parameters. By solving the corresponding equations, the flow expansion angle after the reserved angle is accurately calculated. The specific technical solution is as follows:

[0061] This invention proposes a design method for improving film cooling based on a reserved expansion angle to prevent blockage, comprising the following steps:

[0062] Determine the structural parameters of the initial forward-tilted fan-shaped air film orifice, including the diameter of the cylindrical section of the forward-tilted fan-shaped air film orifice, the aspect ratio, the orifice inclination angle, the initial flow direction expansion angle, and the proportion of the cylindrical section to the total orifice length.

[0063] The height of the blockage is determined based on the thickness of the thermal barrier coating, and a geometric model of the blockage at the outlet of the forward-tilted fan-shaped air film orifice is established.

[0064] Based on the structural parameters of the initial forward-tilted fan-shaped film air hole, the length of the extended portion of the inclination angle of the forward-tilted fan-shaped film air hole in the flow expansion section is calculated;

[0065] Based on the length of the extended portion, calculate the length of the line connecting the expansion start position and the expansion end position on the symmetry plane of the forward-tilted fan-shaped air film hole;

[0066] With the core constraint that the outlet area of ​​the blocked forward-tilted fan-shaped air film orifice remains equal to the initial forward-tilted fan-shaped air film orifice outlet area, the flow expansion angle after blockage is defined to be consistent with the initial flow expansion angle; the flow expansion angle after blockage is the angle between the line connecting the expansion start position to the outlet blockage and the axis of the cylindrical segment.

[0067] Based on the geometric model of the blockage and the height of the blockage, an optimization function for the flow direction expansion angle is established, that is, to optimize the functional relationship between the flow direction expansion angle and the length of the connecting line;

[0068] By combining the calculated results of the connecting line length with the functional relationship, a solution equation is constructed with the optimized flow direction expansion angle as the only unknown.

[0069] The above equations are solved by numerical iterative algorithm to obtain the numerical solution of the optimized flow direction expansion angle, that is, the forward-inclined fan-shaped air film orifice based on the reserved expansion angle;

[0070] The design of the forward-tilted fan-shaped film air hole was completed by using the optimized flow direction expansion angle as the final design value.

[0071] In one embodiment, the method for establishing the geometric model of the blockage is as follows: the intersection of the vertical line from the upper end of the leeward side of the symmetry plane of the forward-tilted fan-shaped air film orifice downward with the flow expansion section is taken as the starting position of the blockage. A blockage outline parallel to the wall of the flow expansion section is drawn through this intersection point, and the starting position and the blockage outline are smoothly connected by a tangent circular arc.

[0072] In one embodiment: the flow direction expansion angle optimization function is expressed as:

[0073]

[0074] In the formula, β 3 indicates the optimized flow direction expansion angle; β 1 represents the initial flow spread angle; h Indicates the height of the blockage; b This represents the length of the line connecting the starting and ending positions of expansion in the symmetry plane of the forward-tilted fan-shaped air film aperture. θ Indicates the inclination angle of the hole;

[0075] In one embodiment: the solution equation with the optimized flow direction expansion angle as the only unknown is expressed as:

[0076]

[0077] In the formula, D The diameter of the cylindrical section representing the forward-tilted fan-shaped film air hole; L d Indicates the aspect ratio; L cy This indicates the proportion of the cylindrical section to the total length of the hole; It indicates the length of the extended portion of the forward-tilted fan-shaped film air hole in the flow-expanding section.

[0078] In one embodiment: the numerical iteration algorithm includes an iteration termination determination step:

[0079] In each iteration, the actual flow expansion angle after blockage is calculated based on the flow expansion angle after the current reserved angle;

[0080] Calculate the relative deviation between the actual flow expansion angle and the initial flow expansion angle;

[0081] The iterative calculation terminates when the absolute value of the relative deviation is less than one percent.

[0082] In one embodiment: the numerical iteration algorithm adopts the Newton-Raphson method, the initial value for iterative calculation is set as the initial flow expansion angle, the lower limit of the numerical range of the iterative solution is the initial flow expansion angle, and the upper limit is the orifice inclination angle.

[0083] In one embodiment: the final design value of the optimized flow spread angle is verified:

[0084] Based on the final determined optimized flow direction expansion angle and blockage geometry model, a gas film cooling flow calculation model including the blockage is established;

[0085] The cooling efficiency of the initial forward-tilted fan-shaped film air hole, the forward-tilted fan-shaped film air hole with blockage inside the hole, and the forward-tilted fan-shaped film air hole with reserved angle and blockage were calculated and compared through three-dimensional fluid dynamics simulation to verify the design effect.

[0086] This invention also proposes a design system for film cooling based on a reserved expansion angle to prevent blockage, comprising:

[0087] The parameter determination module is used to determine the structural parameters of the initial forward-tilted fan-shaped air film orifice. The structural parameters include the diameter of the cylindrical section of the forward-tilted fan-shaped air film orifice, the aspect ratio, the orifice inclination angle, the initial flow direction expansion angle, and the proportion of the cylindrical section to the total orifice length.

[0088] The geometric modeling module determines the height of the blockage based on the thickness of the thermal barrier coating and establishes a geometric model of the blockage at the outlet of the forward-tilted fan-shaped film air hole.

[0089] The first calculation module, based on the structural parameters of the initial forward-tilted fan-shaped film air hole, calculates the length of the extended portion of the inclination angle of the forward-tilted fan-shaped film air hole in the flow expansion section;

[0090] The second calculation module calculates the length of the line connecting the starting position and the ending position of the expansion within the symmetry plane of the forward-tilted fan-shaped air film hole, based on the length of the extended portion.

[0091] The constraint setting module takes the equalization of the outlet area of ​​the forward-tilted fan-shaped air film orifice after blockage with the initial outlet area of ​​the forward-tilted fan-shaped air film orifice as the core constraint condition, and defines the flow expansion angle after blockage to be consistent with the initial flow expansion angle.

[0092] The function establishment module establishes a flow direction expansion angle optimization function based on the blockage geometry model and blockage height, that is, optimizes the functional relationship between the flow direction expansion angle and the connection length;

[0093] The equation construction module combines the calculation results of the connection length with the functional relationship to construct a solution equation with the optimized flow direction expansion angle as the only unknown.

[0094] The solution module uses a numerical iterative algorithm to solve the above equations and obtain a numerical solution for optimizing the flow direction expansion angle;

[0095] The output module uses the optimized flow direction expansion angle as the final design value to complete the design of the forward-tilted fan-shaped air film orifice.

[0096] The present invention also proposes a turbine blade, the surface of which is provided with a forward-inclined fan-shaped air film cooling hole designed and machined based on a design method for improving film cooling by reserving an expansion angle to prevent blockage.

[0097] The present invention also proposes an aero-engine, characterized in that it includes the turbine blades.

[0098] The above technical solution will be further described in detail below with reference to the accompanying drawings:

[0099] In one embodiment, a design method for improving film cooling based on reserved expansion angle to prevent blockage includes the following steps:

[0100] Step 1: Refer to Figure 1 The structural parameters of the initial forward-tilted fan-shaped film air hole were determined, including: the diameter of the cylindrical section of the forward-tilted fan-shaped film air hole is 1 mm, the length-to-diameter ratio is 6, the hole inclination angle is 30°, the spanwise expansion angle is 7°, the initial flow-wise expansion angle is 4°, and the proportion of the cylindrical section to the total hole length is... ;

[0101] Step 2: Refer to Figure 2 To determine the modeling method for the blockage in the spray-coated plug, the starting position of the blockage is the intersection of the vertical line from the upper end of the leeward side of the symmetrical plane of the forward-inclined fan-shaped air film hole and the flow expansion section. The height of the blockage is 0.25mm, the same as the coating thickness. The outline of the blockage is drawn parallel to the flow expansion section. The starting position and the outline of the blockage are connected by a tangent circular arc to complete the modeling of the blockage at the outlet of the forward-inclined fan-shaped air film hole.

[0102] Step 3: In the expansion section, taking the expansion start position as the starting point, calculate the length of the extended portion of the forward-tilted fan-shaped film orifice in the expansion section;

[0103] The formula for calculating the length of the extended portion of the expansion section, where the inclination angle of the forward-tilted fan-shaped film air hole is located, is as follows:

[0104]

[0105] Step 4: In the flow expansion section, calculate the distance between the line connecting the starting and ending positions of the forward-tilted fan-shaped film vents on the plane of symmetry;

[0106] The formula for calculating the length of the line connecting the starting and ending positions of the expansion is as follows:

[0107]

[0108] in, β 3 indicates the optimized flow expansion angle. b The length of the line connecting the starting and ending positions of expansion in the symmetry plane of the forward-tilted fan-shaped air film aperture;

[0109] Step 5: By reserving a flow expansion angle, ensure that the flow expansion angle of the forward-tilted fan-shaped air film orifice remains consistent with the initial flow expansion angle of 4° after blockage, thus ensuring that the outlet area of ​​the forward-tilted fan-shaped air film orifice remains unchanged after spraying. At this time, the angle between the line connecting the expansion start position to the outlet blockage and the axis of the cylindrical section is defined as the flow expansion angle after blockage;

[0110] The specific mathematical expression for the outlet area of ​​the same forward-tilted fan-shaped film air hole is as follows:

[0111] A 2= A 1 β 1= β 2=4°

[0112] in, A 1 represents the initial forward-tilted fan-shaped air film orifice outlet area. A 2 represents the outlet area of ​​the forward-tilting fan-shaped film air hole after blockage. β 1 represents the initial flow expansion angle. β 2 represents the flow expansion angle after blockage;

[0113] Step 6: Based on the requirement in Step 5 that the flow expansion angle after blockage is the same as the initial flow expansion angle, and combined with the blockage modeling method and blockage height proposed in Step 2, determine the flow expansion angle of the forward-tilted fan-shaped film orifice after reserving the angle, that is, optimize the flow expansion angle;

[0114] The formula for calculating the optimized flow expansion angle is as follows:

[0115]

[0116] in, β 3. To optimize the flow direction expansion angle, h The height of the blockage;

[0117] Step 7: Based on the calculation formulas and results of the key structural parameters of the forward-tilting fan-shaped film pore after blockage in Steps 3, 4 and 6, solve the optimization flow direction expansion angle simultaneously;

[0118] The equations for calculating the optimal flow spread angle are as follows:

[0119]

[0120] Step 8: The only unknowns remaining in the equation system are the length of the line connecting the starting and ending positions of the expansion and the optimized flow direction and expansion angle. Substitute into the equation The equation can be obtained from this. The optimal flow spread angle can be obtained by solving the equation; The equation is as follows:

[0121]

[0122] Step 9: The equation contains inverse trigonometric functions and trigonometric functions, making a theoretical solution impossible. The Newton-Raphson method is used iteratively to obtain a numerical solution. The initial values ​​for the iteration and the range of the optimized flow direction expansion angle are set to 4° and [4°, 30°], respectively, as detailed below:

[0123] The Newton-Raphson numerical iteration algorithm will use the function In the initial value β 3,0 Taylor's expansion:

[0124] ;

[0125] make f ( β 3) = 0, that is:

[0126] ;

[0127] The next iteration point is obtained:

[0128] ;

[0129] This process iterates continuously until the accuracy requirements are met:

[0130] ;

[0131] Step 10: Refer to Figure 3 As shown, the termination condition for the iterative calculation of the optimized flow expansion angle is that the calculation can be terminated when the actual flow expansion angle after the reserved angle and the blockage deviates from the initial flow expansion angle by less than 1%.

[0132] The specific termination determination for optimizing the flow direction expansion angle is as follows:

[0133] The pre-reserved angle obtained through iterative calculation is the flow expansion angle. β 3 = 6.91°, the reserved angle and the flow expansion angle after blockage are β 2 = 4.03°, which meets the accuracy requirements of the iteration. ;

[0134] Step 11: Refer to Figure 4 As shown, by using the blockage modeling method and optimizing the flow direction expansion angle in steps 2 and 10, a flat film cooling computational domain with a blockage height of 0.25 mm and the same outlet area as the initial forward-tilted fan-shaped film cooling hole is obtained.

[0135] Step 12: Mesh and perform 3D simulation calculations for the flat-plate film cooling computational domain to obtain the film cooling efficiency of the initial forward-tilted fan-shaped film cooling holes, the forward-tilted fan-shaped film cooling holes with blockage inside, and the forward-tilted fan-shaped film cooling holes with reserved angles and blockage, as detailed below:

[0136] The computational domain was divided using tetrahedral elements, and the independence of the mesh generation was verified and relevant computational conditions were set. Specifically, the turbulence model selected was SST. γ-θ The model, in its mainstream form, adopts a velocity inlet and a pressure outlet, while the cooling air adopts a mass flow inlet, with a cooling air blowing ratio of 0.5 and 1.0;

[0137] Step 13: Refer to Figure 5 and Figure 6 As shown, the present invention obtained a pre-angled and blocked forward-tilted fan-shaped air film orifice and compared it with the air film cooling effect and average air film cooling effect of the initially blocked forward-tilted fan-shaped air film orifice. After increasing the flow direction tilt angle, the negative effect of blockage on air film cooling under the two blowing ratio conditions was almost completely eliminated.

[0138] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A design method for improving film cooling based on a reserved expansion angle to prevent blockage, characterized in that, Includes the following steps: Determine the structural parameters of the initial forward-tilted fan-shaped air film orifice, including the diameter of the cylindrical section, aspect ratio, orifice inclination angle, initial flow direction expansion angle, and the proportion of the cylindrical section to the total orifice length. The height of the blockage is determined based on the thickness of the thermal barrier coating, and a geometric model of the blockage at the outlet of the forward-tilted fan-shaped air film orifice is established. Based on the structural parameters of the initial forward-tilted fan-shaped film air hole, the length of the extended portion of the inclination angle of the forward-tilted fan-shaped film air hole in the flow expansion section is calculated; Based on the length of the extended portion, calculate the length of the line connecting the expansion start position and the expansion end position on the symmetry plane of the forward-tilted fan-shaped air film hole; With the core constraint that the outlet area of ​​the blocked forward-tilted fan-shaped air film orifice remains equal to the initial forward-tilted fan-shaped air film orifice outlet area, the flow expansion angle after blockage is defined to be consistent with the initial flow expansion angle; the flow expansion angle after blockage is the angle between the line connecting the expansion start position to the outlet blockage and the axis of the cylindrical segment. Based on the geometric model of the blockage and the height of the blockage, an optimization function for the flow direction expansion angle is established, that is, to optimize the functional relationship between the flow direction expansion angle and the length of the connecting line; By combining the calculated results of the connecting line length with the functional relationship, a solution equation is constructed with the optimized flow direction expansion angle as the only unknown. The above equations are solved by numerical iterative algorithm to obtain the numerical solution of the optimized flow direction expansion angle, that is, the forward-inclined fan-shaped air film orifice based on the reserved expansion angle; The design of the forward-tilted fan-shaped film air hole was completed by using the optimized flow direction expansion angle as the final design value.

2. The design method for film cooling based on a reserved expansion angle to prevent blockage, as described in claim 1, is characterized in that: The method for establishing the geometric model of the blockage is as follows: the intersection of the vertical line from the upper end of the leeward side of the symmetry plane of the forward-tilted fan-shaped air film orifice downward with the flow expansion section is taken as the starting position of the blockage. The outline of the blockage parallel to the wall of the flow expansion section is drawn through this intersection point, and the starting position and the outline of the blockage are smoothly connected by a tangent circular arc.

3. The design method for film cooling based on a reserved expansion angle to prevent blockage, as described in claim 2, is characterized in that: The optimization function for the flow direction expansion angle is expressed as follows: In the formula, β 3 indicates the optimized flow direction expansion angle; β 1 represents the initial flow spread angle; h Indicates the height of the blockage; b This represents the length of the line connecting the starting and ending positions of the expansion within the symmetry plane of the forward-tilted fan-shaped film air hole. θ Indicates the inclination angle of the hole.

4. The design method for film cooling based on a reserved expansion angle to prevent blockage, as described in claim 3, is characterized in that: The solution equation with the optimized flow spread angle as the only unknown is expressed as follows: In the formula, D The diameter of the cylindrical section representing the forward-tilted fan-shaped film air hole; L d Indicates the aspect ratio; L cy This indicates the proportion of the cylindrical section to the total length of the hole; It indicates the length of the extended portion of the forward-tilted fan-shaped film air hole in the flow-expanding section.

5. The design method for film cooling based on a reserved expansion angle to prevent blockage, as described in claim 4, is characterized in that: The numerical iteration algorithm includes an iteration termination determination step: In each iteration, the actual flow expansion angle after blockage is calculated based on the flow expansion angle after the current reserved angle; Calculate the relative deviation between the actual flow expansion angle and the initial flow expansion angle; The iterative calculation terminates when the absolute value of the relative deviation is less than one percent.

6. The design method for film cooling based on a reserved expansion angle to prevent blockage, as described in claim 5, is characterized in that: The numerical iterative algorithm adopts the Newton-Raphson method. The initial value for iterative calculation is set as the initial flow expansion angle, and the lower limit of the numerical range of the iterative solution is the initial flow expansion angle, while the upper limit is the orifice inclination angle.

7. The design method for film cooling based on a reserved expansion angle to prevent blockage, as described in claim 6, is characterized in that: The final design value of the optimized flow direction expansion angle was verified: Based on the final determined optimized flow direction expansion angle and blockage geometry model, a gas film cooling flow calculation model including the blockage is established; The cooling efficiency of the initial forward-tilted fan-shaped film air hole, the forward-tilted fan-shaped film air hole with blockage inside the hole, and the forward-tilted fan-shaped film air hole with reserved angle and blockage were calculated and compared through three-dimensional fluid dynamics simulation to verify the design effect.

8. A design system for film cooling based on reserved expansion angle to prevent blockage, comprising the design method for film cooling based on reserved expansion angle to prevent blockage as described in any one of claims 1-7; characterized in that, include: The parameter determination module is used to determine the structural parameters of the initial forward-tilted fan-shaped air film orifice. The structural parameters include the diameter of the cylindrical section of the forward-tilted fan-shaped air film orifice, the aspect ratio, the orifice inclination angle, the initial flow direction expansion angle, and the proportion of the cylindrical section to the total orifice length. The geometric modeling module determines the height of the blockage based on the thickness of the thermal barrier coating and establishes a geometric model of the blockage at the outlet of the forward-tilted fan-shaped film air hole. The first calculation module, based on the structural parameters of the initial forward-tilted fan-shaped film air hole, calculates the length of the extended portion of the inclination angle of the forward-tilted fan-shaped film air hole in the flow expansion section; The second calculation module calculates the length of the line connecting the starting position and the ending position of the expansion within the symmetry plane of the forward-tilted fan-shaped air film hole, based on the length of the extended portion. The constraint setting module takes the equalization of the outlet area of ​​the forward-tilted fan-shaped air film orifice after blockage with the initial outlet area of ​​the forward-tilted fan-shaped air film orifice as the core constraint condition, and defines the flow expansion angle after blockage to be consistent with the initial flow expansion angle. The function creation module establishes a flow direction expansion angle optimization function based on the blockage geometry model and blockage height, that is, optimizes the functional relationship between the flow direction expansion angle and the connection length; The equation construction module combines the calculation results of the connection length with the functional relationship to construct a solution equation with the optimized flow direction expansion angle as the only unknown. The solution module uses a numerical iterative algorithm to solve the above equations and obtain a numerical solution for optimizing the flow direction expansion angle; The output module uses the optimized flow direction expansion angle as the final design value to complete the design of the forward-tilted fan-shaped air film orifice.

9. A turbine blade, characterized in that, Its surface is provided with a forward-inclined fan-shaped air film hole designed and processed by the design method of the pre-reserved expansion angle anti-blockage and air film cooling as described in any one of claims 1-7.

10. An aircraft engine, characterized in that, Includes the turbine blade as described in claim 9.

Images