Design method for preventing blockage and improving air film cooling based on reserved divergence angle

Abstract

The invention discloses a design method for anti-blocking lifting air film cooling based on a reserved divergence angle, and belongs to the field of efficient cooling design of turbomachinery. The method comprises the following steps: determining structural parameters of an initial forward-inclined fan-shaped air film hole; establishing a geometric model of the blockages at the outlet of the forward-inclined fan-shaped air film hole; calculating the length of the extension part of the gas film hole inclination angle in the flow direction expansion section; calculating the length of a connecting line between an expansion starting position and an expansion ending position on the film hole symmetry plane; establishing a flow direction divergence angle optimization function based on the obstruction geometric model and the obstruction height; according to the calculation result of the connecting line length and the function relation, a solving equation with the optimized flow direction divergence angle as a unique unknown number is constructed; obtaining a numerical solution for optimizing the flow direction divergence angle; and an optimized flow direction divergence angle is adopted as a final design value, and the design of the forward-inclined fan-shaped air film hole is completed. The problems that in the thermal barrier coating spraying process, paint is accumulated at an air film hole outlet, so that outflow of cooling airflow is blocked, and the cooling efficiency is reduced are solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of high-efficiency cooling design of turbomachinery, and particularly relates to a design method for preventing blockage and improving film cooling based on a reserved expansion angle. BACKGROUND

[0002] The high-pressure turbine guide vane of an aero-engine works in an extremely high-temperature gas environment for a long time, and has extremely high thermal load, so it must rely on efficient external cooling technology to ensure structural reliability and service life. At present, the mainstream technology is to open film holes on the surface of the turbine blade and spray thermal barrier coating (TBC), to form a heat-insulating cooling gas layer through the film, and to increase the additional thermal resistance by using the low thermal conductivity of the coating, so as to jointly protect the base material. The two external cooling methods interact with each other and may not fully exert the cooling effect of a single cooling method.

[0003] However, in the actual manufacturing process, in order to avoid the requirement of electrical discharge machining on the electrical conductivity of the coating, the process of "first making holes and then spraying" is generally adopted. This process inevitably causes the thermal barrier coating material to enter the inside of the film hole, especially to form a pile-up blockage at the outlet area, significantly reducing the outlet area of the effective cooling gas flow, and the jet is more likely to blow away from the wall under high blowing ratio, causing the cooling design to be inaccurate. Therefore, under the premise of considering hole blockage, the design method of suppressing hole blockage caused by spraying to reduce cooling is the key to avoiding overestimating the actual cooling performance and ensuring the efficient cooling of the turbine.

[0004] The turbine of an aero-engine widely adopts expansion-type film holes, and the hole blockage caused by spraying has a significant impact on the cooling performance of the expansion-type film hole. In "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 show the film cooling performance of the fan-shaped hole after blockage. When the height of the blockage in the hole reaches or exceeds half of the diameter of the film hole, a significant contraction of the cooling area and blowing off of the film can be observed, resulting in a decrease in film coverage efficiency and a significant deterioration of cooling performance, and in severe cases, even causing local overheating and threatening the safety of the blade.

[0005] In summary, under the background of thermal barrier coating spraying leading to film hole blockage, the existing technology is mostly focused on passive structure expansion or aerodynamic additional devices, and lacks a method based on predictive modeling that can quantitatively compensate for the impact of blockage at the foresight design stage. Therefore, there is an urgent need in the art for a design method that can accurately reserve the expansion angle and ensure that the outlet area of the film hole remains unchanged after blockage, so as to fundamentally guarantee the realization of the film cooling efficiency under the design condition. SUMMARY

[0006] Technical problems to be solved: In order to avoid the shortcomings of the prior art, the present application provides a design method for preventing blockage and improving gas film cooling based on a reserved expansion angle. According to the structural parameters of the initial forward-tilted fan-shaped gas film hole, such as the hole diameter, the expansion starting position, and the hole tilt angle, the geometry and the blockage modeling method of the expansion-type gas film hole are determined, and the functional relationship between the flow direction expansion angle after blockage and the blockage height is constructed to ensure that the same gas film hole outlet area is used to solve the equation set corresponding to the functional relationship to obtain the flow direction expansion angle after the reserved angle, and then provide a basis for preventing the blockage of the forward-tilted fan-shaped gas film hole caused by the cooling performance decline. The present application predicts and compensates the influence of the thermal barrier coating blockage on the gas film hole outlet area in the design stage by the method of reserved expansion angle + mathematical model + iterative algorithm, solves the problems that the coating will enter the gas film hole and accumulate at the outlet during the thermal barrier coating spraying process, resulting in a decrease in the effective flow area, a blockage of the cooling airflow, and a decrease in the cooling efficiency.

[0007] The technical solution of the present application is: a design method for preventing blockage and improving gas film cooling based on a reserved expansion angle, comprising the following steps: Determine the structural parameters of the initial forward-tilted fan-shaped gas film hole, the structural parameters including the cylindrical segment diameter, the length-diameter ratio, the hole tilt angle, the initial flow direction expansion angle, and the proportion of the cylindrical segment to the total hole length of the initial forward-tilted fan-shaped gas film hole; Determine the blockage height based on the thermal barrier coating thickness, and establish a blockage geometry model at the outlet of the forward-tilted fan-shaped gas film hole; Based on the structural parameters of the initial forward-tilted fan-shaped gas film hole, calculate the length of the extension part of the forward-tilted fan-shaped gas film hole tilt angle in the flow direction expansion segment; According to the length of the extension part, calculate the length of the line connecting the expansion starting position and the expansion ending position on the symmetry plane of the forward-tilted fan-shaped gas film hole; With the core constraint condition that the outlet area of the blocked forward-tilted fan-shaped gas film hole remains equal to the outlet area of the initial forward-tilted fan-shaped gas film hole, the flow direction expansion angle after blockage is defined to remain consistent with the initial flow direction expansion angle; the flow direction expansion angle after blockage is the included angle between the line connecting the expansion starting position to the outlet blockage and the axis of the cylindrical segment; Based on the blockage geometry model and the blockage height, an optimization function of the flow direction expansion angle is established, i.e. the functional relationship between the optimized flow direction expansion angle and the line length; The calculation result of the line length and the functional relationship are combined to construct a solving equation with the optimized flow direction expansion angle as the only unknown; The numerical iterative algorithm is used to solve the above equation to obtain the numerical solution of the optimized flow direction expansion angle, i.e. the forward-tilted fan-shaped gas film hole based on the reserved expansion angle; The optimized flow direction expansion angle is used as the final design value to complete the design of the forward-tilting fan-shaped air film hole.

[0008] A further technical solution of the present application is that the method for establishing the blockage geometric model is that the intersection of the downward vertical line of the upper end point on the leeward side of the symmetric plane of the forward-tilting fan-shaped air film hole and the flow direction expansion segment is the starting position of the blockage, a blockage profile line parallel to the wall surface of the flow direction expansion segment is drawn through the intersection, and a tangent circular arc is used to smoothly connect the starting position and the blockage profile line.

[0009] A further technical solution of the present application is that the flow direction expansion angle optimization function is expressed as:

[0010] In the formula, β 3 represents the optimized flow direction expansion angle; β 1 represents the initial flow direction expansion angle; h H represents the blockage height; b L represents the length of the line between the expansion starting position and the expansion termination position in the symmetric plane of the forward-tilting fan-shaped air film hole; θ θ represents the hole inclination angle.

[0011] A further technical solution of the present application is that the solving equation with the optimized flow direction expansion angle as the only unknown is expressed as:

[0012] In the formula, D D represents the diameter of the cylindrical segment of the forward-tilting fan-shaped air film hole; L d L / D represents the length-diameter ratio; L cy D / L represents the proportion of the cylindrical segment in the total hole length; L represents the length of the extension part of the flow direction expansion segment.

[0013] A further technical solution of the present application is that the numerical iteration algorithm comprises an iteration termination determination step: In each iteration, the actual flow direction expansion angle after the blockage is calculated according to the flow direction expansion angle after the current reserved angle; The relative deviation between the actual flow direction expansion angle and the initial flow direction expansion angle is calculated; When the absolute value of the relative deviation is less than one percent, the iteration calculation is terminated.

[0014] A further technical solution of the present application is that 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, and the numerical range of the iteration solution is set as the lower limit of the initial flow direction expansion angle and the upper limit of the hole inclination angle.

[0015] A further technical solution of the present application is to verify the final design value of the optimized flow direction expansion angle. According to the final determined optimized flow direction expansion angle and the blockage geometric model, a gas film cooling flow calculation model containing the blockage is established; Through three-dimensional fluid dynamics simulation, the cooling efficiency of the initial forward-tilted fan-shaped film hole, the forward-tilted fan-shaped film hole with blockage in the hole, and the forward-tilted fan-shaped film hole with reserved angle and blockage is calculated and compared to verify the design effect.

[0016] A design system for preventing blockage and improving gas film cooling based on reserved expansion angle, comprising: A parameter determination module is configured to determine the structural parameters of the initial forward-tilted fan-shaped film hole, wherein the structural parameters include the diameter of the cylindrical section of the forward-tilted fan-shaped film hole, the length-diameter ratio, the hole inclination angle, the initial flow direction expansion angle, and the proportion of the cylindrical section in the total hole length. A geometric modeling module is configured to determine the height of the blockage based on the thickness of the thermal barrier coating, and to establish a blockage geometric model at the outlet of the forward-tilted fan-shaped film hole. A first calculation module is configured to calculate the length of the extended part of the forward-tilted fan-shaped film hole inclination angle in the flow direction expansion section based on the structural parameters of the initial forward-tilted fan-shaped film hole. A second calculation module is configured to calculate the length of the line segment between the start position and the end position of the expansion in the symmetry plane of the forward-tilted fan-shaped film hole based on the length of the extended part. A constraint setting module is configured to define the constraint condition that the outlet area of the blocked forward-tilted fan-shaped film hole remains equal to the outlet area of the initial forward-tilted fan-shaped film hole, and to define the constraint condition that the flow direction expansion angle after blockage remains consistent with the initial flow direction expansion angle. A function establishing module is configured to establish an optimization function of the flow direction expansion angle based on the blockage geometric model and the height of the blockage, i.e., a function relationship between the optimized flow direction expansion angle and the length of the line segment. An equation construction module is configured to construct a solving equation with the optimized flow direction expansion angle as the only unknown variable by combining the calculation result of the length of the line segment and the function relationship. A solving module is configured to solve the above equation using a numerical iteration algorithm to obtain a numerical solution of the optimized flow direction expansion angle. An output module is configured to use the optimized flow direction expansion angle as the final design value to complete the design of the forward-tilted fan-shaped film hole.

[0017] A turbine blade having a surface provided with a forward-tilted fan-shaped film hole designed and processed based on a design method for preventing blockage and improving gas film cooling based on reserved expansion angle.

[0018] An aero-engine comprising the turbine blade.

[0019] Advantages The beneficial effects of the present application are as follows: the design method for preventing blockage and improving gas film cooling based on the reserved expansion angle can ensure that the outlet area of the forward-tilted fan-shaped gas film hole does not change significantly to avoid a decrease in cooling performance in the case of blockage in the hole caused by spraying thermal barrier coating. The specific advantages are as follows: 1. The present application fundamentally suppresses the decrease in cooling performance caused by thermal barrier coating blockage: by calculating and increasing the flow direction expansion angle (i.e. the reserved expansion angle) in the design stage, the loss of flow area caused by the accumulation of coating material in the hole after spraying is actively compensated, ensuring that the outlet area of the gas film hole under the actual blockage condition is consistent with the design expectation, thereby fundamentally avoiding problems such as poor outflow of cooling gas and jet blowing away from the wall caused by blockage, and stabilizing and improving the gas film cooling efficiency.

[0020] 2. The present application realizes the design paradigm change from "passive response" to "active prediction and compensation": unlike the structural improvement idea in the prior art which passively accommodates the blockage by enlarging the hole volume, the present application initiates an active design method based on mathematical models and optimization algorithms. By establishing a geometric model of the blockage and taking "unchanged outlet area after blockage" as a strict constraint, an accurate mathematical relationship is constructed, realizing the quantitative prediction and forward compensation of the blockage effect, and the design concept is advanced.

[0021] 3. The present application can accurately calculate the required reserved expansion angle by establishing a strict functional relationship and using a numerical iterative algorithm (such as the Newton-Raphson method) for solving. The method sets a clear iteration termination condition (such as a relative deviation of less than 1%), ensuring the accuracy and reliability of the design results, and overcoming the uncertainty brought by traditional empirical design or trial-and-error method.

[0022] 4. The design method proposed by the present application is based on the core structural parameters (such as hole diameter, inclination angle, aspect ratio, etc.) of the forward-tilted fan-shaped gas film hole and the predictable coating thickness (blockage height), and does not depend on specific and fixed geometric configurations. Therefore, this method is suitable for the design of a series of forward-tilted fan-shaped gas film holes with different sizes and angles, and has wide engineering applicability and flexibility.

[0023] 5. The present application guarantees the life of the hot end of the turbine blade and the reliability of the engine. The gas film hole designed by this method can still maintain excellent cooling effect after spraying thermal barrier coating, effectively controlling the working temperature of the turbine blade, and has great significance for improving the service life, operation safety and overall reliability of the hot end components such as high-pressure turbine of an aero-engine. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1The figure is a schematic view of the symmetry plane of the forward-leaning fan-shaped gas film hole in the embodiment of the present application. Figure 2 The figure is a schematic view of the blockage geometry model of the outlet of the forward-leaning fan-shaped gas film hole in the embodiment of the present application. Figure 3 The figure is a schematic view of the structure of the initial forward-leaning fan-shaped gas film hole, the forward-leaning fan-shaped gas film hole blocked in the hole, and the forward-leaning fan-shaped gas film hole blocked with a reserved angle in the embodiment of the present application. Figure 4 The figure is a schematic view of the flat plate gas film cooling calculation domain of the blocked forward-leaning fan-shaped gas film hole in the embodiment of the present application. Figure 5 The figure is a comparison chart of the gas film cooling effect of the initial forward-leaning fan-shaped gas film hole, the forward-leaning fan-shaped gas film hole blocked in the hole, and the forward-leaning fan-shaped gas film hole blocked with a reserved angle in the embodiment of the present application. Figure 6 The figure is a comparison chart of the average gas film cooling effect of the initial forward-leaning fan-shaped gas film hole, the forward-leaning fan-shaped gas film hole blocked in the hole, and the forward-leaning fan-shaped gas film hole blocked with a reserved angle in the embodiment of the present application. DETAILED DESCRIPTION

[0025] The embodiments described below with reference to the drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0026] At present, several structural improvements have been proposed to solve the problems existing in the prior art. For example, a patent with the publication number CN220226986U proposes a gas film hole structure with double diverging sections and a recessed back wall, which increases the space near the outlet to accommodate coating deposition, thereby reducing the impact of blockage. Although this scheme expands the flow area to some extent, it still has obvious limitations: first, its design relies on specific geometric configurations and does not provide universal design criteria and parameter quantification methods; second, it fails to establish a mathematical model between the blockage degree and the structural parameters, making it impossible to accurately predict and compensate for different hole diameters, inclination angles, coating thicknesses, etc. In addition, another prior art (CN112324517B) focuses on introducing a Coanda bulge structure downstream of the gas film hole to improve the gas flow adhesion, which belongs to the category of aerodynamic optimization and does not involve the fundamental process problem of blockage prevention.

[0027] Based on the problems existing in the prior art, the present application proposes a design method for preventing blockage and improving gas film cooling based on a reserved expansion angle, which establishes a functional relationship between the outlet flow expansion angle and the geometric parameters after blockage based on the gas film hole structure parameters and the blockage modeling method. By solving the corresponding equation set, the flow expansion angle after the reserved angle can be accurately calculated. The specific technical scheme is as follows: The present application proposes a design method for preventing blockage and improving gas film cooling based on a reserved expansion angle, which includes the following steps: determining the structural parameters of the initial forward-tilted fan-shaped air film hole, the structural parameters including the diameter of the cylindrical section of the forward-tilted fan-shaped air film hole, the length-diameter ratio, the hole tilt angle, the initial flow direction expansion angle, and the proportion of the cylindrical section in the total hole length; determining the blockage height based on the thermal barrier coating thickness, and establishing a blockage geometry model at the outlet of the forward-tilted fan-shaped air film hole; based on the structural parameters of the initial forward-tilted fan-shaped air film hole, calculating the length of the extended part of the forward-tilted fan-shaped air film hole tilt angle in the flow direction expansion section; based on the length of the extended part, calculating the length of the line segment between the expansion start position and the expansion end position on the symmetry plane of the forward-tilted fan-shaped air film hole; taking the equal outlet area of the blocked forward-tilted fan-shaped air film hole and the outlet area of the initial forward-tilted fan-shaped air film hole as the core constraint condition, and defining that the blocked flow direction expansion angle is consistent with the initial flow direction expansion angle; the blocked flow direction expansion angle is the included angle between the line segment from the expansion start position to the outlet blockage and the axis of the cylindrical section; based on the blockage geometry model and the blockage height, establishing a flow direction expansion angle optimization function, i.e. a function relationship between the optimized flow direction expansion angle and the length of the line segment; combining the calculation result of the length of the line segment and the function relationship, constructing a solving equation taking the optimized flow direction expansion angle as the only unknown quantity; solving the above equation by using a numerical iteration algorithm to obtain the numerical solution of the optimized flow direction expansion angle, i.e. obtaining the forward-tilted fan-shaped air film hole based on the reserved expansion angle; taking the optimized flow direction expansion angle as the final design value to complete the design of the forward-tilted fan-shaped air film hole.

[0028] In one embodiment: the method for establishing the blockage geometry model is to take the intersection point of the downward perpendicular line from the upper end point on the leeward side in the symmetry plane of the forward-tilted fan-shaped air film hole and the flow direction expansion section as the start position of the blockage, draw a blockage contour line parallel to the wall surface of the flow direction expansion section through the intersection point, and smoothly connect the start position and the blockage contour line through a tangent circular arc.

[0029] In one embodiment: the flow direction expansion angle optimization function has the expression:

[0030] In the formula, β 3 represents the optimized flow direction expansion angle; β 1 represents the initial flow direction expansion angle; h represents the blockage height; b represents the length of the line segment between the expansion start position and the expansion end position in the symmetry plane of the forward-tilted fan-shaped air film hole; θ represents the hole tilt angle; In one embodiment: the expression of the equation for solving the flow direction expansion angle as the only unknown variable is:

[0031] In the formula, D D represents the diameter of the cylindrical section of the forward-tilted fan-shaped air film hole; L d L / D represents the length-diameter ratio; L cy D / L represents the proportion of the cylindrical section to the total hole length; D represents the length of the extended part of the flow direction expansion section of the forward-tilted fan-shaped air film hole.

[0032] In one embodiment: the numerical iterative algorithm comprises an iteration termination determination step: In each iteration, the actual flow direction expansion angle after plugging is calculated according to the current flow direction expansion angle after reserving; The relative deviation between the actual flow direction expansion angle and the initial flow direction expansion angle is calculated; When the absolute value of the relative deviation is less than one percent, the iteration calculation is terminated.

[0033] In one embodiment: the numerical iterative algorithm adopts the Newton-Raphson method, and the initial value of the iteration calculation is set as the initial flow direction expansion angle, and the lower limit of the numerical range of the iteration solution is the initial flow direction expansion angle, and the upper limit is the hole inclination angle.

[0034] In one embodiment: the final design value of the optimized flow direction expansion angle is verified: According to the final determined optimized flow direction expansion angle and the plugging geometry model, a gas film cooling flow calculation model containing the plugging is established; Through three-dimensional fluid dynamics simulation, the cooling efficiency of the initial forward-tilted fan-shaped air film hole, the forward-tilted fan-shaped air film hole with plugging in the hole and the forward-tilted fan-shaped air film hole with reserving angle and plugging is calculated and compared to verify the design effect.

[0035] The application also provides a design system for preventing plugging and improving gas film cooling based on a reserved expansion angle, comprising: A parameter determination module is configured to determine the structure parameters of the initial forward-tilted fan-shaped air film hole, wherein the structure parameters include the diameter of the cylindrical section of the forward-tilted fan-shaped air film hole, the length-diameter ratio, the hole inclination angle, the initial flow direction expansion angle and the proportion of the cylindrical section to the total hole length; A geometry modeling module is configured to determine the height of the plugging based on the thermal barrier coating thickness, and establish a plugging geometry model at the outlet of the forward-tilted fan-shaped air film hole; A first calculation module is configured to calculate the length of the extended part of the flow direction expansion section of the forward-tilted fan-shaped air film hole based on the structure parameters of the initial forward-tilted fan-shaped air film hole; A second calculation module is configured to calculate a length of a line between an expansion start position and an expansion end position in a symmetric plane of the forward-tilted fan-shaped air film hole according to the length of the extended portion; A constraint setting module is configured to define, as a core constraint condition, that an outlet area of the blocked forward-tilted fan-shaped air film hole is equal to an initial outlet area of the forward-tilted fan-shaped air film hole, and to define that a flow direction expansion angle after blocking is consistent with an initial flow direction expansion angle; A function establishing module is configured to establish, based on the blocking object geometric model and the blocking object height, a flow direction expansion angle optimization function, that is, a function relationship between the optimized flow direction expansion angle and the length of the line; An equation constructing module is configured to construct, by combining the calculation result of the length of the line and the function relationship, a solving equation with the optimized flow direction expansion angle as the only unknown quantity; A solving module is configured to solve the above equation by using a numerical iteration algorithm to obtain a numerical solution of the optimized flow direction expansion angle; An output module is configured to use the optimized flow direction expansion angle as a final design value to complete the design of the forward-tilted fan-shaped air film hole.

[0036] The application further provides a turbine blade, which is provided with a forward-tilted fan-shaped air film hole designed and formed by the design method for preventing blocking of the air film cooling based on the reserved expansion angle.

[0037] The application further provides an aero-engine, characterized in that the aero-engine comprises the turbine blade.

[0038] The above technical solutions are further described in detail below with reference to the drawings: In one embodiment, the design method for preventing blocking of the air film cooling based on the reserved expansion angle comprises the following steps: Step 1: referring to Figure 1 , the structure parameters of the initial forward-tilted fan-shaped air film hole are determined, including that the diameter of the cylindrical section of the forward-tilted fan-shaped air film hole is 1 mm, the length-diameter ratio is 6, the hole tilt angle is 30°, the spanwise expansion angle is 7°, the initial flow direction expansion angle is 4°, and the proportion of the cylindrical section in the total hole length is ; Step 2: referring to Figure 2 , the blocking object modeling method for spraying blocking is determined, the intersection point of the vertical line downward from the upwind side end point on the symmetric plane of the forward-tilted fan-shaped air film hole and the flow direction expansion section is the start position of the blocking object, the blocking object height is 0.25 mm, which is the same as the coating thickness, the blocking object contour line parallel to the flow direction expansion section is drawn, and the start position and the blocking object contour line are connected by a tangent circular arc to complete the modeling of the blocking object at the outlet of the forward-tilted fan-shaped air film hole; Step 3: in the flow direction expansion part, the length of the extended portion of the forward-tilted fan-shaped air film hole tilt angle in the expansion section is calculated from the expansion start position as the starting point; The length of the extended portion of the forward-tilted fan-shaped air film hole tilt angle in the expansion section is calculated according to the following formula:

[0039] Step 4: In the flow direction expansion part, the distance length of the line connecting the expansion start position and the expansion end position of the forward-leaning fan-shaped air film hole on the symmetry plane is calculated; The length of the line connecting the expansion start position and the expansion end position is calculated as follows:

[0040] Wherein, β 3 represents the optimized flow direction expansion angle, b is the length of the line connecting the expansion start position and the expansion end position in the symmetry plane of the forward-leaning fan-shaped air film hole; Step 5: By reserving the flow direction expansion angle, it is ensured that the flow direction expansion angle of the forward-leaning fan-shaped air film hole after the occurrence of the blockage is consistent with the initial flow direction expansion angle, both being 4°, so as to ensure that the outlet area of the forward-leaning fan-shaped air film hole after spraying is unchanged. At this time, the included angle between the line connecting the expansion start position and the outlet blockage and the axis of the cylindrical section is defined as the flow direction expansion angle after the blockage; Wherein, the specific mathematical expression of the outlet area of the same forward-leaning fan-shaped air film hole is as follows: A 2= A 1 β 1= β 2=4° Wherein, A 1 is the initial outlet area of the forward-leaning fan-shaped air film hole, A 2 is the outlet area of the forward-leaning fan-shaped air film hole after the blockage, β 1 is the initial flow direction expansion angle, β 2 is the flow direction expansion angle after the blockage; Step 6: According to the requirement that the flow direction expansion angle after the blockage is the same as the initial flow direction expansion angle in step 5, and in combination with the modeling method of the blockage and the blockage height proposed in step 2, the flow direction expansion angle of the forward-leaning fan-shaped air film hole after the reservation angle, i.e. the optimized flow direction expansion angle, is determined; Wherein, the calculation formula of the optimized flow direction expansion angle is as follows:

[0041] Wherein, β 3 is the optimized flow direction expansion angle, h is the height of the blockage; Step 7: The optimized flow direction expansion angle is solved by simultaneously solving the calculation formula and the calculation result of the key structural parameters of the forward-leaning fan-shaped air film hole after the blockage in steps 3, 4 and 6; Wherein, the calculation equation group for solving the optimized flow direction expansion angle is as follows:

[0042] Step 8: The only unknown quantities in the equations are the length of the line connecting the expansion start and end positions and the optimized flow expansion angle. Substitute into the equation In the equation , the optimized flow expansion angle can be obtained by solving the equation; The equation is as follows:

[0043] Step 9: The equation contains inverse trigonometric and trigonometric functions, and a theoretical solution is not available. Therefore, the Newton-Raphson method is used to iteratively solve the equation. The initial value of the iteration and the range of the optimized flow expansion angle are set to 4° and [4°, 30°], respectively, as follows: The Newton-Raphson numerical iterative algorithm converts the function At the initial value β 3,0 Taylor expansion: ; make f ( β 3)=0, that is: ; Solve for the next iteration point: ; This process is iterated until the accuracy requirements are met: ; Step 10: Reference Figure 3 As shown in Figure 2, the termination judgment condition for the iterative calculation of the optimized flow expansion angle is that when the relative deviation between the reserved angle and the actual flow expansion angle after blockage and the initial flow expansion angle is less than 1%, the calculation can be terminated. The iterative termination judgment for optimizing the flow expansion angle is as follows: The flow expansion angle after iterative calculation of the reserved angle is: β 3=6.91°, the reserved angle and the flow expansion angle after blocking are β 2=4.03°, which meets the accuracy requirements of iteration ; Step 11: Reference Figure 4 As shown, the blockage modeling method and optimized flow expansion angle in steps 2 and 10 are used to obtain a flat film cooling calculation domain with a blockage height of 0.25 mm and the same outlet area as the initial forward-inclined fan-shaped film hole; Step 12: meshing and three-dimensional simulation calculation are carried out for the flat plate gas film cooling calculation domain to obtain the gas film cooling effect of the initial forward-tilted fan-shaped gas film hole, the forward-tilted fan-shaped gas film hole with hole blockage and the forward-tilted fan-shaped gas film hole with reserved angle and blockage, and the specific steps are as follows: The calculation domain is divided by tetrahedron unit, and the irrelevance verification of meshing and relevant calculation condition setting are completed, wherein: the turbulent flow model is selected as SST γ-θ Model, the main flow adopts velocity inlet and pressure outlet, the cooling gas adopts mass flow inlet, and the blowing ratio of the cooling gas is 0.5 and 1.0; Step 13: as shown in Figs. Figure 5 and Figure 6 , the forward-tilted fan-shaped gas film hole with reserved angle and blockage is obtained by the present application, and the gas film cooling effect of the initial forward-tilted fan-shaped gas film hole with hole blockage and the average gas film cooling effect are compared, and the negative effect of blockage on the gas film cooling under two blowing ratios is almost completely eliminated after increasing the flow direction angle.

[0044] Although the embodiments of the present application have been shown and described above, it can be understood that the above-mentioned embodiments are exemplary and cannot be understood as limiting the present application, and the ordinary skilled in the art can change, modify, replace and modify the above-mentioned embodiments within the scope of the present application without departing from the principles and purposes of the present application.

Claims

1. A design method for improving film cooling based on reserved expansion angle anti-blocking, characterized in that: The following steps are involved: Determining structural parameters of the initial forward-inclined fan-shaped air film hole, the structural parameters including the diameter of the cylindrical section of the initial forward-inclined fan-shaped air film hole, the aspect ratio, the hole inclination angle, the initial flow direction expansion angle, and the proportion of the cylindrical section to the total hole length; The blockage height is determined based on the thickness of the thermal barrier coating, and a geometric model of the blockage at the outlet of the forward-inclined fan-shaped air film hole is established; Based on the structural parameters of the initial forward-inclined fan-shaped air film hole, the length of the extended portion of the forward-inclined fan-shaped air film hole in the flow direction expansion section is calculated; According to the length of the extended part, calculate the length of the line between the expansion start position and the expansion end position on the symmetry plane of the forward-inclined fan-shaped air film hole; The core constraint condition is that the outlet area of ​​the forward-inclined fan-shaped air film hole after blockage should be equal to the outlet area of ​​the initial forward-inclined fan-shaped air film hole. The flow expansion angle after blockage is defined as the angle between the line connecting the expansion starting position to the outlet blockage and the axis of the cylindrical segment. Based on the blockage geometry model and blockage height, a flow expansion angle optimization function is established, that is, the functional relationship between the flow expansion angle and the connection length is optimized; The calculation results of the connection length and the functional relationship are combined to construct a solution equation with the optimized flow expansion angle as the only unknown variable; The numerical iterative algorithm is used to solve the above equations to obtain the numerical solution of the optimized flow expansion angle, that is, the forward-inclined fan-shaped air film hole based on the reserved expansion angle is obtained; The optimized flow expansion angle is used as the final design value to complete the design of the forward-inclined fan-shaped air film hole.

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

3. The design method for improving film cooling based on a reserved expansion angle to prevent blockage according to claim 2, characterized in that: The flow expansion angle optimization function is expressed as: Where, β 3 represents the optimized flow expansion angle; β 1 represents the initial flow expansion angle; h Indicates the height of the blockage; b It represents the length of the line between the expansion start position and the expansion end position in the symmetry plane of the forward-inclined fan-shaped air film hole; θ Indicates the hole inclination angle.

4. The design method for improving film cooling based on a reserved expansion angle to prevent blockage according to claim 3, characterized in that: The expression for solving the equation with the optimized flow expansion angle as the only unknown is: Where, D Indicates the diameter of the cylindrical section of the forward-inclined fan-shaped air film hole; L d represents the aspect ratio; L cy Indicates the proportion of cylindrical segment to total hole length; It indicates the length of the extended part of the forward-inclined fan-shaped air film hole in the flow direction expansion section.

5. The design method for improving film cooling based on a reserved expansion angle to prevent blockage according to claim 4, characterized in that: The numerical iterative algorithm includes the following steps to determine the termination of the iteration: In each iteration, the actual flow expansion angle after blockage is calculated based on the flow expansion angle after the current reserved angle; Calculating the relative deviation between the actual flow expansion angle and the initial flow expansion angle; When the absolute value of the relative deviation is less than one percent, the iterative calculation is terminated.

6. The design method for improving film cooling based on a reserved expansion angle to prevent blockage according to claim 5, characterized in that: The numerical iteration algorithm adopts the Newton-Raphson method, the initial value of the iterative calculation is set to 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 hole inclination angle.

7. The design method for improving film cooling based on a reserved expansion angle to prevent blockage according to claim 6, characterized in that: Verify the final design value of the optimized flow expansion angle: Based on the final optimized flow expansion angle and the blockage geometry model, a film cooling flow calculation model including the blockage is established; Through three-dimensional fluid dynamics simulation, the cooling efficiency of the initial forward-inclined fan-shaped air film hole, the forward-inclined fan-shaped air film hole blocked inside the hole, and the forward-inclined fan-shaped air film hole with a reserved angle and blocked is calculated and compared to verify the design effect.

8. A design system for preventing blockage and improving film cooling based on a reserved expansion angle, implementing the design method for preventing blockage and improving film cooling based on a reserved expansion angle according to any one of claims 1 to 7; characterized in that: include: a parameter determination module for determining the structural parameters of the initial forward-inclined fan-shaped air film hole, wherein the structural parameters include the cylindrical section diameter, aspect ratio, hole inclination angle, initial flow direction expansion angle, and the proportion of the cylindrical section to the total hole length of the forward-inclined fan-shaped air film hole; The geometric modeling module determines the blockage height based on the thickness of the thermal barrier coating and establishes the blockage geometric model at the outlet of the forward-inclined fan-shaped air film hole; The first calculation module calculates the length of the extended portion of the inclination angle of the forward-inclined fan-shaped air film hole in the flow direction expansion section based on the structural parameters of the initial forward-inclined fan-shaped air film hole; The second calculation module calculates the length of the line between the expansion start position and the expansion end position in the symmetry plane of the forward-inclined fan-shaped air film hole according to the length of the extended portion; The constraint setting module uses the core constraint condition that the outlet area of ​​the forward-inclined fan-shaped air film hole after blockage should be equal to the initial outlet area of ​​the forward-inclined fan-shaped air film hole, and defines the flow expansion angle after blockage to be consistent with the initial flow expansion angle; The function establishment module establishes a flow expansion angle optimization function based on the blockage geometry model and blockage height, that is, optimizes the functional relationship between the flow 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 expansion angle as the only unknown variable; The solution module uses a numerical iterative algorithm to solve the above equations and obtain the numerical solution for the optimized flow expansion angle; The output module uses the optimized flow expansion angle as the final design value to complete the design of the forward-inclined fan-shaped air film hole.

9. A turbine blade, characterized in that: Its surface is provided with forward-inclined fan-shaped air film holes designed and processed based on the design method of reserving expansion angle to prevent blockage and enhance air film cooling as described in any one of claims 1-7.

10. An aircraft engine, characterized in that: Including the turbine blade according to claim 9.

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