Effect loss calculation method for comprehensively evaluating cooling performance of turbine blade air film

Abstract

The invention discloses an effect loss calculation method for comprehensively evaluating the gas film cooling performance of a turbine blade, and the method comprises the following steps: firstly, obtaining a main flow channel parameter and a gas film cooling gas parameter in a target calculation region of the turbine blade, and respectively calculating the gas film cooling efficiency, the total pressure loss coefficient and the high-temperature region cooling index; then establishing Pareto distribution relevance among the air film cooling efficiency, the total pressure loss coefficient and the mass flow ratio; and finally, the average air film cooling efficiency, the total pressure loss coefficient and the high-temperature area cooling index are combined in a power-exponential function combination form, an efficiency loss calculation coefficient is constructed, the comprehensive applicability of different cooling schemes is judged according to the coefficient, and a quantitative basis is provided for turbine blade air film cooling design optimization. The method can provide a scientific and comprehensive decision basis for the design of a high-performance turbine blade cooling structure, and has good engineering applicability and popularization value.

Description

Technical Field

[0001] This invention belongs to the field of aero-engine turbine blade cooling technology, and relates to the thermo-aerodynamic performance analysis technology of turbine blade film cooling system. Specifically, it is a method for comprehensively evaluating the performance loss of turbine blade film cooling, used to analyze and calculate the performance loss of blade cooling combined with losses. Background Technology

[0002] To increase thrust, aero-engine turbine inlet temperatures are constantly rising, leading to the wider application of film cooling (FSL) technology. However, FSL consumes up to 15% or even 20% of the cooling gas required for its operation, resulting in significant additional losses. Therefore, while developing and analyzing the effectiveness of FSL, it is also crucial to control these additional losses.

[0003] In the evaluation system of film cooling performance, film cooling efficiency is the most commonly used and convenient indicator for evaluating the quality of film cooling. It reflects the cooling effect through a dimensionless temperature ratio. This indicator has important guiding significance in blade cooling design, as it can intuitively characterize the isolation effect of the film cooling system on the mainstream high-temperature combustion gases. However, a simple evaluation of cooling efficiency ignores the impact of cold gas injection on the mainstream aerodynamic characteristics, especially on key aerodynamic parameters such as total pressure loss and mixing loss. Existing aerodynamic loss analyses under film cooling conditions are often based on aerodynamic analysis schemes without film cooling, using a variety of evaluation parameters, including pressure, kinetic energy, enthalpy, entropy increase, etc. Existing loss models make these parameters dimensionless to determine the loss changes under film cooling conditions.

[0004] However, while these loss calculation methods based on film cooling take into account the flow field changes caused by the cooling gas, the calculation results are still the original dimensionless loss quantities. They cannot be organically linked to the film cooling efficiency, and the two are relatively independent in evaluating the target film cooling design, sometimes leading to conflicts and trade-offs. Furthermore, some existing analytical methods have high requirements, making it difficult to transfer from numerical simulation to experiments. Practical measurement methods often fail to meet these requirements, making the verification of numerical simulation results difficult and limiting the application of these methods in practical engineering. For example, Chinese patent CN117610460A discloses a three-dimensional mixing loss assessment method for engine turbine blade film cooling. This method improves the accuracy of mixing loss calculation by establishing a three-dimensional flow model that considers the influence of secondary flow on the relative motion and interaction between the main flow and the jet. However, this method only addresses a single loss dimension, focusing primarily on the assessment of mixing loss, without forming a comprehensive evaluation with cooling efficiency. Moreover, this method relies on high-precision three-dimensional flow field parameters (such as velocity components and turbulent dissipation rate), which are difficult to obtain experimentally, and it cannot solve the trade-off between cooling and loss.

[0005] Furthermore, the optimization of film cooling hole design often requires considering multiple conflicting design objectives simultaneously, including maximizing cooling efficiency, minimizing aerodynamic losses, and ensuring cooling uniformity. Due to the lack of unified comprehensive evaluation criteria, the design process frequently relies on engineering experience and trial-and-error methods, making systematic optimization difficult. This situation not only affects design efficiency but also hinders the further development and application of film cooling technology.

[0006] In summary, existing air film cooling performance evaluation technologies suffer from several drawbacks. Firstly, the evaluation of cooling effect and aerodynamic loss are independent and lack a cohesive relationship. Secondly, they are significantly inadequate in terms of experimental operability and ease of engineering application. Therefore, a relatively simple calculation method that can comprehensively analyze both cooling and loss factors is needed to determine the rationality of specific air film cooling applications. This is a pressing technical problem that needs to be solved in the current performance evaluation of air film cooling systems. Summary of the Invention

[0007] (I) Purpose of the Invention

[0008] To address the aforementioned deficiencies and shortcomings of existing technologies, this invention aims to propose a method for comprehensively evaluating the performance of film cooling (FSC) of turbine blades. This method combines FSC efficiency (a cooling index) with total pressure loss coefficient (a loss index), and introduces a high-temperature cooling index as an auxiliary parameter, forming a multi-parameter FSC calculation method. By establishing a mathematical relationship between FSC efficiency, total pressure loss coefficient, and mass flow ratio, and constructing the FSC calculation coefficient using a power-law function, this invention achieves a unified evaluation of cooling effect and aerodynamic loss. For the same FSC technology or the same flow condition, the FSC calculation method can comprehensively calculate both cooling and loss changes. Based on the calculation results, it comprehensively judges whether the corresponding FSC technology is superior or more suitable for a certain operating condition, demonstrating broad application prospects and applicability to performance comparisons under various cooling orifice types, multi-region layouts, and different flow Mach numbers.

[0009] (II) Technical Solution

[0010] To achieve the objective of this invention and solve its technical problems, the present invention adopts the following technical solution:

[0011] A method for comprehensively evaluating the performance of film cooling in turbine blades is provided. This method is used to quantitatively assess the combined performance of film cooling efficiency and aerodynamic losses caused by cooling in the optimization of film cooling design or the evaluation of operational adaptability of aero-engine turbine blades. The method includes at least the following steps:

[0012] S100. Basic Parameter Acquisition:

[0013] Obtain the mainstream channel parameters and film cooling gas parameters within the target computational region of the turbine blades. The mainstream channel parameters include at least the inlet temperature T of the mainstream gas in the turbine blade channel. g,in Import total pressure P tg,in Total export pressure P tg,out Outlet static pressure P g,out and mainstream mass flow m g The air film cooling parameters include at least the cooling air temperature T at the inlet of the cooling system. c Total air conditioning pressure P tc , static pressure of cold air P c and the mass flow rate of the cooling air (m) c Simultaneously, the adiabatic wall temperature or local surface temperature T of the turbine blade surface under film cooling is obtained. aw And based on the cold air mass flow rate m c and mainstream mass flow rate m g Calculate the mass flow ratio φ = m c / m g ;

[0014] S200. Calculation of film cooling efficiency:

[0015] Based on the mainstream inlet temperature T g,in Air conditioning temperature T c and blade surface temperature T aw The local film cooling efficiency η was calculated using the temperature difference ratio to characterize the isolation and protection effect of the cooling film on the mainstream high-temperature combustion gas. The film cooling efficiency within the study area was linearly averaged, and then averaged over each flow direction to obtain the average film cooling efficiency of the target area. Used to characterize the overall level of cooling effect;

[0016] S300. Total pressure loss coefficient calculation:

[0017] Based on mainstream mass flow rate m g With cooling air mass flow rate m c The proportion of the total inlet pressure P of the mainstream gas tg,in and total air conditioning pressure P tc The weighted calculation yields the total mixing pressure P of the mains and the cooling air. mix This is used to characterize the pressure state of the mainstream gas and the film cooling gas before mixing, and is combined with the total pressure P at the mainstream outlet. tg,out and outlet static pressure P g,out The total pressure loss coefficient ξ is calculated using the pressure difference ratio to characterize the mixing loss caused by cold gas injection.

[0018] S400. Cooling index Λ in high-temperature zone:

[0019] Extract the highest temperature T within the target computational region.max Combined with the air conditioning temperature T c The high-temperature cooling index Λ is determined by the mass flow ratio φ. It is expressed as an index with the temperature ratio as the base and the index is φ. The high-temperature cooling index Λ is used to characterize the degree of optimization in the limited area of ​​the air film cooling effect and can fine-tune and correct the final calculation results to a certain extent.

[0020] S500. Construct the Pareto distribution expression between η and φ:

[0021] Based on the isenthalpic mixing assumption, a Pareto distribution expression between η and φ is constructed, and a nonlinear distribution function of ξ and φ is constructed to reveal the variation law of loss with cold air volume. Correlation modeling reflects the corresponding characteristics and trends of η to ξ to mass flow rate ratio φ.

[0022] S600. Comprehensive Calculation of Performance Loss Calculation Coefficient:

[0023] The average film cooling efficiency is calculated using a combination of power functions. The total pressure loss coefficient ξ and the high-temperature zone cooling index Λ are combined to construct the effect loss calculation coefficient E. The larger the value of E, the better the cooling effect of the evaluated air film cooling scheme and the smaller the additional loss.

[0024] S700. Comprehensive performance evaluation judgment:

[0025] For cooling schemes with different film cooling orifice types, orifice positions, orifice diameters, injection angles, cold gas mass flow ratios, or flow conditions, the efficiency loss calculation coefficient E is calculated for each scheme. Based on this coefficient, different cooling schemes are compared and analyzed. The comprehensive applicability of different cooling schemes in the target area is determined according to the value of E, providing a quantitative basis for the optimization of turbine blade film cooling design.

[0026] (III) Technical Effects

[0027] The efficiency calculation method for comprehensively evaluating the film cooling performance of turbine blades in this invention relates the film cooling efficiency η to the total pressure loss coefficient ξ and the mass flow rate ratio φ of the mainstream cooling gas. Based on the simplified assumption of film detachment, the Pareto distribution laws of φ-η and φ-ξ are obtained. Based on these laws, the numerical distributions of both and their influence on the air-cooled turbine are comprehensively considered to ultimately determine the overall performance of film cooling. This method has the following advantages:

[0028] (1) The performance loss calculation method is expressed as a dimensionless quantity in the range of 0 to 1, and its monotonicity is affected by the combined changes of four sub-items. Each sub-item is derived from commonly used judgment criteria and is reasonable. Its final expression is reasonable and does not rely on empirical coefficients. Moreover, most of the parameters involved in the performance loss calculation method are easy to obtain. Apart from the parameters involving the inherent properties of the gas, there are only mass flow rate, temperature and pressure. The method is also easy to implement in both numerical simulation and actual experiments.

[0029] (2) Based on the calculation results, the design of film cooling will comprehensively consider the cooling effect and its impact on losses, and can balance the situation of high cooling and high losses. This is of positive significance for controlling losses and reducing energy consumption. The efficiency loss calculation method has wide applicability because the pressure, temperature and other parameters used are key and common parameters in various environments. It is not limited by changes in low and high speed flow conditions. It can evaluate the applicability of film cooling for the same cooling area by distinguishing the film cooling settings such as orifice type and angle, as well as subsonic and supersonic flow conditions. Attached Figure Description

[0030] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings, wherein:

[0031] Figure 1 This is a flowchart of a method for calculating the effectiveness of film cooling performance of turbine blades.

[0032] Figure 2 This is a schematic diagram of a turbine blade with film cooling holes.

[0033] Explanation of reference numerals in the attached figures:

[0034] m c - Cooling mass flow rate, m g -Mainstream quality traffic, P c -Cold air static pressure, P tc - Total air conditioning pressure, P g2 -Mainstream export static pressure, P tg,in -Mainstream imported total pressure, P tg,out - Mainstream outlet total pressure, A1- Film cooling hole, A2- Cooling chamber, A3- Blade suction surface, A4- Blade pressure surface, A5- Blade leading edge, A6- Blade trailing edge, A7- Measurement area for film cooling efficiency and high-temperature cooling index. Detailed Implementation

[0035] This invention aims to propose a method for comprehensively evaluating the performance of film cooling (FSC) in turbine blades. This method is used in the optimization of FSC design or the evaluation of operational adaptability of aero-engine turbine blades to quantitatively assess the combined performance of FSC efficiency and aerodynamic losses caused by cooling. To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be described in more detail below with reference to the accompanying drawings. The described embodiments are some, but not all, of this invention, and are exemplary, intended to explain the invention, and should not be construed as limiting the invention.

[0036] Example 1: Comprehensive Evaluation Method for Film Cooling Performance of Turbine Blades

[0037] As a specific example, such as Figure 1 As shown in the embodiments of the present invention, the method for calculating the performance loss of turbine blade film cooling provides a comprehensive evaluation method that mainly includes the following steps during implementation:

[0038] S100. Basic Parameter Acquisition:

[0039] Obtain the mainstream channel parameters and film cooling gas parameters within the target computational region of the turbine blades. The mainstream channel parameters include at least the inlet temperature T of the mainstream gas in the turbine blade channel. g,in Import total pressure P tg,in Total export pressure P tg,out Outlet static pressure P g,out and mainstream mass flow m g The air film cooling parameters include at least the cooling air temperature T at the inlet of the cooling system. c Total air conditioning pressure P tc , static pressure of cold air P c and the mass flow rate of the cooling air (m) c Simultaneously, the adiabatic wall temperature or local surface temperature T of the turbine blade surface under film cooling is obtained. aw And based on the cold air mass flow rate m c and mainstream mass flow rate m g Calculate the mass flow ratio φ = m c / m g .

[0040] Preferably, the acquisition of the above-mentioned basic parameters adopts a hierarchical and progressive data extraction strategy. First, the flow field distribution data of the turbine blade passage is obtained through numerical simulation or experimental testing. Then, a spatial coordinate system for parameter extraction is established within a specified target computational region. The acquisition locations of the main channel parameters are defined as follows: inlet parameters are obtained by area-weighted averaging on the inlet section within the range of 0.5 to 1.5 times the chord length upstream of the blade leading edge; outlet parameters are obtained by mass-weighted averaging on the outlet section within the range of 0.3 to 0.6 times the chord length downstream of the blade trailing edge. g The parameters of the film cooling gas are obtained by integrating the density-velocity product of the inlet cross-section; T is the value of the film cooling gas. c The measurement location is set at the inlet of the cold air chamber, P tc and P c The value was obtained by using the average volume of the cold air chamber, m c The mass flow rate at the inlet of the cold air chamber is used to ensure that the parameters of each film cooling gas can represent the true state of the cold air; T aw The mass flow rate φ is obtained by calculating the boundary conditions of the adiabatic wall in numerical simulation, and by measuring it using an infrared thermal imager or a surface-embedded thermocouple in the experiment; and the calculation of the mass flow rate φ must ensure that m g and m c For steady-state measurements taken at the same time reference, time averaging is used for unsteady operating conditions. This hierarchical extraction method ensures the accuracy and consistency of the basic parameters, while establishing a standardized process for parameter acquisition to guarantee the comparability of evaluation results between different cooling schemes.

[0041] S200. Calculation of film cooling efficiency:

[0042] Based on the mainstream inlet temperature T g,in Air conditioning temperature T c and blade surface temperature T aw The local film cooling efficiency η was calculated using the temperature difference ratio to characterize the isolation and protection effect of the cooling film on the mainstream high-temperature combustion gas. The film cooling efficiency within the study area was linearly averaged, and then averaged over each flow direction to obtain the average film cooling efficiency of the target area. Used to characterize the overall level of cooling effect.

[0043] Specifically, the local film cooling efficiency η is expressed as a ratio of temperature differences, and its mathematical expression is as follows:

[0044]

[0045] Based on this, the average film cooling efficiency was further calculated. First, n measurement lines extending from the blade root to the blade tip along the spanwise direction are equally spaced on the surface of the turbine blade in the target calculation region (e.g., ...). Figure 2 As shown in the figure, each measurement line contains multiple measurement points evenly distributed along the span. The number of measurement points is determined based on the blade span height. The line-average efficiency of each measurement line is calculated by arithmetic averaging. Where m is the number of measuring points on the i-th measuring line, η ij Let be the local film cooling efficiency at the j-th measurement point on the i-th line; then, the flow-direction average of the line average efficiency of all measurement lines is calculated to obtain the overall average film cooling efficiency of the target area. This dual averaging method comprehensively considers the spanwise and flowwise variation characteristics of the air film cooling distribution on the turbine blade surface, effectively eliminating the impact of local cooling inhomogeneity on the overall evaluation, and providing a standardized calculation benchmark for quantitative comparison of different cooling schemes.

[0046] S300. Total pressure loss coefficient calculation:

[0047] Based on mainstream mass flow rate m g With cooling air mass flow rate m c The proportion of the total inlet pressure P of the mainstream gas tg,in and total air conditioning pressure P tc The weighted calculation yields the total mixing pressure P of the mains and the cooling air. mix This is used to characterize the pressure state of the mainstream gas and the film cooling gas before mixing, and is combined with the total pressure P at the mainstream outlet. tg,out and outlet static pressure P g,out The total pressure loss coefficient ξ is calculated using the pressure difference ratio to characterize the mixing loss caused by cold gas injection. ξ is a dimensionless quantity in the range of 0 to 1, with the closer it is to 0, the smaller the loss.

[0048] Specifically, the total pressure loss coefficient ξ is calculated using the pressure difference ratio, and its mathematical expression is as follows:

[0049]

[0050] Where P mix The total mixing pressure P is the pressure of the main gas and the cooling gas before mixing. mix The calculation uses a weighted average of the mass flow rate of the mains and the cooling air, and its mathematical expression is as follows:

[0051]

[0052] Total pressure of blending P mix The calculation method is based on momentum conservation and a simplified isentropic mixing assumption, which can effectively characterize the additional pressure loss caused by perturbation structure, velocity gradient, and density difference during the mixing and convergence of mainstream gas and cold gas. This is achieved by introducing P... mix As a reference pressure benchmark, and thus related to P tg,out P g,outBy forming a proportional expression, the pressure loss variation characteristics under different cold air injection intensities can be effectively normalized.

[0053] S400. Calculation of Cooling Index in High-Temperature Zone:

[0054] Extract the highest temperature T within the target computational region. max Combined with the air conditioning temperature T c The high-temperature cooling index Λ is determined by the mass flow rate ratio φ. It is expressed as an index with the temperature ratio as the base and the index is φ. The high-temperature cooling index Λ is used to characterize the degree of optimization in the limited area of ​​the air film cooling effect and can fine-tune and correct the final calculation results to a certain extent.

[0055] Specifically, the cooling index Λ in the high-temperature zone is calculated using an exponential form with the temperature ratio as the base, and its algorithm formula is as follows:

[0056]

[0057] Among them, T max To obtain the highest temperature in the target area, This represents the average cooling efficiency of the area. The expression measures the variation in cooling effect in areas with relatively poor cooling by the relative deviation between the cold air temperature and the highest temperature. When there is no high-temperature zone and the cooling effect is completely uniform, the Λ value approaches 1. When the distribution is extremely uneven, the Λ value will be slightly lower, but with the correction of φ, the difference is slight. This index can effectively identify the integrity and continuity of the air film coverage, indicating the changes in the uncovered high-temperature zone while fine-tuning the final calculation results, providing an evaluation basis for optimizing the air film orifice layout and injection parameters.

[0058] S500. Construct the Pareto distribution expression between η and φ:

[0059] Based on the isenthalpic mixing assumption, a Pareto distribution expression between η and φ is constructed, and a nonlinear distribution function of ξ and φ is constructed to reveal the variation law of loss with cold air volume. Correlation modeling reflects the corresponding characteristics and trends of η to ξ to mass flow rate ratio φ.

[0060] S600. Comprehensive Calculation of Performance Loss Calculation Coefficient:

[0061] The average film cooling efficiency is calculated using a combination of power functions. The total pressure loss coefficient ξ and the high-temperature zone cooling index Λ are combined to construct the effect loss calculation coefficient Ε. The larger the value of Ε, the better the cooling effect of the evaluated air film cooling scheme and the smaller the additional loss.

[0062] Specifically, the efficiency loss calculation coefficient E is constructed using a combination of double power-exponential functions, and its mathematical expression is as follows:

[0063]

[0064] In the formula, η is averaged, specifically by first averaging the terms and then averaging the flow direction. E is a dimensionless quantity in the range of 0 to 1. When the film cooling efficiency η and the high-temperature cooling index Λ are high and the total pressure loss coefficient ξ is low, the calculated value of E is obviously higher, and the overall performance of film cooling is better. When the four sub-terms cannot be better at the same time and need to be selected, the closer the value is to 1, the better the corresponding film cooling or the overall performance of the film cooling is. More specifically, in formula (5) This represents the spanwise average film cooling efficiency on the i-th measurement line, where n is the number of measurement lines. All parameters are averaged in both spanwise and flowwise directions within the target calculation region to ensure the spatial representativeness of the statistical results.

[0065] S700. Comprehensive performance evaluation judgment:

[0066] For cooling schemes with different film cooling orifice types, orifice positions, orifice diameters, injection angles, cold gas mass flow ratios, or flow conditions, the efficiency loss calculation coefficient E is calculated for each scheme. Based on this coefficient, different cooling schemes are compared and analyzed. The comprehensive applicability of different cooling schemes in the target area is determined according to the value of E, providing a quantitative basis for the optimization of turbine blade film cooling design.

[0067] As a preferred option, a grading evaluation standard for film cooling schemes is established based on the value of the efficiency loss calculation coefficient E. When E ≥ 0.9, it is rated as excellent, indicating that the cooling effect and aerodynamic loss are well balanced; when 0.8 ≤ E < 0.9, it is rated as good, indicating that the overall performance meets the requirements of engineering applications; when 0.6 ≤ E < 0.8, it is rated as average, indicating that there is room for performance improvement; when E < 0.6, it is rated as poor, and the cooling scheme needs to be redesigned.

[0068] The above-described method for calculating the efficiency loss of turbine blade film cooling performance in this embodiment of the invention may further include steps S501 to S504 in step S500 for establishing Pareto distribution correlation, namely, establishing the Pareto distribution relationship between film cooling efficiency η and mass flow ratio φ, which reflects the regularity of film cooling efficiency changing with mass flow ratio; simultaneously establishing the Pareto distribution correlation between total pressure loss coefficient ξ and mass flow ratio φ, through the total pressure of the cooling gas P tc The functional relationship between the mass flow rate ratio φ and the mass flow rate ratio φ is realized to ensure that the main evaluation parameters have consistent distribution and mathematical correlation.

[0069] Specifically, the film cooling efficiency η and the total pressure loss coefficient ξ are the main parameters. The determination of the main parameters follows a Pareto distribution, the original form of which is shown in equation (6), where N Pareto Describing the distribution of the target, A Paretoand b Pareto X represents a constant. Pareto The index 'a' represents a quantity exceeding a certain standard. Pareto The value is in the range of 1 to 2. This distribution was originally used to describe and predict income distribution, and with development, it has gradually evolved to include distributions related to other natural or social phenomena. The main parameters will be shown in equations (7) to (13) under what conditions they follow a Pareto distribution.

[0070]

[0071] Equation (7) represents the mixing temperature T. mix The assumption, T mix This is based on an approximate isenthalpic mixing form, but with an added coefficient k1, where k1 = 1 when the isenthalpic assumption is fully followed. Subsequent coefficients in some processes all use positive coefficients k. i In the form of i = 1, 2, ...

[0072] (m g +m c )T mix =k1(m g T g,in +m c T c (7)

[0073] Therefore, based on this linear approximation of isenthalpy, the film cooling efficiency η can be transformed from equation (1) to equation (8), where φ is the ratio of the cold gas mass flow rate to the mainstream mass flow rate (φ = m c / m g Equation (8) shows that it is related to the mass flow rate ratio and is based on the assumption of linear approximation of isenthalpy, and η is expressed as a generalized Pareto distribution.

[0074]

[0075] In the total pressure loss coefficient ξ, it is assumed that when studying the influence of changes in film cooling, the mainstream operating conditions are generally determined, that is, the mainstream relevant parameters are constant values, and the mixing pressure P mix Simultaneously, the mass flow ratio φ and the total cooling pressure P tc The relevant information is shown in equation (9):

[0076]

[0077] For the total pressure of the air conditioner P tc Referring to common mass flow meters, the flow rate is proportional to the square root of the pressure. Therefore, the relationship between the total pressure of the cold air and the mass flow rate can be expressed as equation (10). tg,in Replace with k6, and then P mix Represented as equation (11):

[0078] P tc =k4·φ 2 +k5 (10)

[0079]

[0080] Substituting into ξ, P tg,out and P g,out Replacing k7 and k8 respectively, equation (2) can be expressed as equation (12):

[0081]

[0082] The derivative of ξ with respect to the mass flow ratio φ is shown in equation (13), where the constants k6>k7>k8. Analysis of its monotonicity reveals that under different k5 values, ξ monotonically increases or decreases first and then increases in the range φ>0. This phenomenon can explain some situations: in film cooling of a portion of the blade, the total pressure loss coefficient decreases with increasing cooling air volume at a small blowing ratio. However, when the cooling air volume is large, the total pressure loss increases with increasing cooling air volume, i.e., increasing mass flow ratio.

[0083]

[0084] Since the actual simulation and experiment are conducted for single holes, single rows of holes or a small number of rows of holes, the mass flow rate of the cold air is small and φ always remains at a low value. Therefore, the higher-order terms can be ignored, and ξ can be expressed as equation (14):

[0085]

[0086] At this point, the flow-pressure curve of the cold air still needs to be considered, i.e., equation (110). The positive coefficient has the following cases: (1) k5>k6>k7>k8: ξ follows an inverse Pareto distribution, and this part of the loss increases with the increase of φ; (2) k6>k5>k7>k8 or k6>k7>k5>k8: ξ conforms to a generalized Pareto distribution, but this part of the loss decreases slightly with the increase of φ; (3) k6>k7>k8>k5: ξ exhibits an inverse Pareto distribution, and this part of the loss decreases slightly with the increase of φ. It can be seen that the main parameters η and ξ basically conform to the Pareto distribution. Combining the two has the consistency of distribution. Analyzing them together with the mass flow rate of the cold air can reveal the changing law of cooling and loss in film cooling.

[0087] More specifically, in step S500, the establishment of the Pareto distribution correlation includes at least the following sub-steps:

[0088] S501. Pareto distribution modeling of film cooling efficiency η:

[0089] Based on the linear approximate isenthalpic mixing assumption, the mixing temperature T is established. mixThe linear model, its mathematical expression is (m g +m c )T mix =k1(m g T g,in +m c T c ), where k1 is the mixing correction coefficient, and k1 = 1 when the isenthalpic assumption is fully followed; the film cooling efficiency is expressed mathematically as The expression is in the form of η, where k2 and k3 are positive coefficients determined by the relationship between temperature and mass flow rate. This expression reflects the generalized Pareto distribution relationship between η and mass flow rate ratio φ, and reflects the nonlinear law of η changing with φ. When φ is small, η increases significantly with the increase of φ. When φ increases to a certain threshold, η tends to saturate, and the marginal improvement of cooling efficiency weakens.

[0090] S502. Pareto distribution modeling of the total pressure loss coefficient ξ:

[0091] Establish the relationship between total cooling air pressure and mass flow rate ratio P tc =k4·φ 2 +k5, where k4 and k5 are system characteristic parameters determined based on the relationship between pressure and mass flow rate; the total blending pressure is expressed as... The form is where k6 represents the main import total pressure P. tg,in A simplified expression for the total pressure loss coefficient is derived mathematically. k7 and k8 represent the main outlet total pressure and static pressure, respectively. This expression reflects the Pareto distribution characteristics under the condition of small mass flow ratio.

[0092] S503. Determining the Pareto distribution type of the total pressure loss coefficient ξ:

[0093] The Pareto distribution type of ξ can be determined based on the relationship between the coefficients. When k5>k6>k7>k8, ξ follows an inverse Pareto distribution and increases with increasing φ; when k6>k5>k7>k8 or k6>k7>k5>k8, ξ conforms to a generalized Pareto distribution but decreases slightly with increasing φ; when k6>k7>k8>k5, ξ exhibits an inverse Pareto distribution and decreases slightly with increasing φ.

[0094] S504. Distribution Consistency Verification and Parameter Correlation:

[0095] By comparing the Pareto distributions of the film cooling efficiency η and the total pressure loss coefficient ξ, the consistency and mathematical correlation of the two main parameters are verified. This ensures that, under the same mass flow rate ratio, the variation law of cooling effect and aerodynamic loss follows a unified statistical distribution principle, providing a reliable mathematical basis and parameter coupling relationship for the comprehensive calculation of subsequent efficiency and loss calculation coefficients, and realizing a coordinated evaluation of cooling and loss.

[0096] In summary, the performance loss calculation method for comprehensively evaluating the film cooling performance of turbine blades proposed in this invention has a wide range of applications. Since its applicability to experimental environments was a key consideration in its construction, the performance loss calculation method utilizes mass flow rate, pressure, and temperature data. These data are readily available in experimental environments, allowing the method to be applied in both numerical simulations and experimental settings to evaluate the applicability and suitable operating conditions of the target film cooling technology. Regarding the applicable operating conditions of the performance loss calculation method, the film cooling efficiency, total pressure loss coefficient, and high-temperature cooling index are only calculated using measured parameters. These parameters change with increasing flow rate, and this change is reflected in the calculation results. Therefore, the performance loss calculation method can also demonstrate the difference between subsonic and transonic film cooling applications through calculated values, thus determining the applicable environment of the target film cooling system. However, when applying this method, the analysis should be performed on the same area covered by film cooling. For example, a comprehensive evaluation of film cooling with different orifice types on the pressure surface should be considered, or a comprehensive evaluation of film cooling with the same orifice type on the suction surface under different working conditions should be performed.

[0097] Example 2: Application Case

[0098] Based on Example 1 above, Example 2 provides a detailed application example illustrating how to calculate post-processing mixing losses using completed numerical calculation cases or experimental data, thereby achieving a comprehensive evaluation of the turbine blade film cooling performance. In Example 2, the post-processing mixing loss calculation is based on a completed CFX numerical calculation case. First, the mainstream mass flow rate m in the channel is recorded. g The mass flow rate at the inlet is used as the integral. Then, the mass flow rate (m) of the cold air is calculated based on the cold air inlet. c ,like Figure 2 The example includes a cold air chamber A2. According to the law of mass conservation, the mass flow rate of the cold air is equal to the inlet mass flow rate of the cold air chamber. Based on the calculation results, the temperature parameters can also be calculated, based on the mainstream temperature T. g Air conditioning temperature T c and the temperature of the insulating wall T aw The local film cooling efficiency can be obtained, and the calculation method is shown in equation (1). Figure 2 By performing line averaging on regions A7 with equal flow intervals, and then averaging at each interval, the average film cooling efficiency of this measurement region can be obtained. Similarly, according to equation (4), the highest surface temperature T in the target area is... max The cooling index of the high-temperature zone in the measurement area can be obtained by calculating the cooling temperature Tc and the mass flow rate ratio φ in area A7. The calculation of cooling-related parameters for the effect loss calculation method is now complete.

[0099] Then, the average total inlet pressure P of the main flow face of the entire channel is calculated. tg1 and the total pressure P of the air conditioning inlet tc The total blending pressure P can be obtained by combining the mass flow rate and equation (3). mix Then, the total pressure loss coefficient ξ can be obtained. Here, ξ takes into account the influence of the cooling air and can reflect the impact of changes in cooling air on the loss. At this point, the calculation of loss-related parameters is complete.

[0100] Based on three parts—the film cooling efficiency η, the total pressure loss coefficient ξ, and the high-temperature zone cooling index Λ—the final efficiency loss calculation coefficient Ε can be formed. During calculation, in the same measurement area, for example, by setting film cooling holes of different shapes or angles upstream of the suction surface region A7, these film cooling holes can be compared, and flow conditions can be adjusted, such as the mainstream Mach number or the blowing ratio, to calculate and comprehensively judge the applicability of various film cooling holes under different flow conditions. Similarly, different measurement areas can be located at the pressure surface, leading edge, trailing edge, etc., as long as the control condition has the same measurement area.

[0101] In the experiment, this calculation method is also quite convenient. Temperature parameters can be obtained using an infrared thermal imager or thermocouples in the measurement area. Combining the supply temperatures of the mains and the cold air, the film cooling efficiency η and the cooling index Λ in the high-temperature zone can be obtained. Pressure parameters can be measured using pressure probes before and after the grid, so the total pressure loss coefficient ξ can also be calculated. Therefore, based on these three parameters, Ε can also be calculated. During operation, the specific measurement method depends on the characteristics of the experiment itself and is not affected by the efficiency loss calculation method; it is only necessary to ensure that the required mass flow rate, pressure, and temperature parameters are measured.

[0102] The objectives of this invention have been fully and effectively achieved through the above embodiments. Those skilled in the art will understand that this invention includes, but is not limited to, the contents described in the accompanying drawings and the specific embodiments described above. Although the invention has been described with reference to what is currently considered the most practical and preferred embodiments, it should be understood that the invention is not limited to the disclosed embodiments, and any modifications that do not depart from the functional and structural principles of the invention will be included within the scope of the claims.

Claims

1. A method for calculating the performance loss of a turbine blade film cooling system, characterized in that, It should include at least the following steps: S100. Obtain the mainstream channel parameters and film cooling gas parameters within the target area of ​​the turbine blade, wherein the mainstream channel parameters include at least the inlet temperature T of the mainstream gas in the turbine blade channel. g,in Import total pressure P tg,in Total export pressure P tg,out Outlet static pressure P g,out and mainstream mass flow m g The parameters for film cooling should at least include the air temperature T at the inlet of the cooling system. c Total air conditioning pressure P tc , static pressure of cold air P c and the mass flow rate of the cooling air (m) c Simultaneously, the adiabatic wall temperature or local surface temperature T of the turbine blade surface is obtained. aw And based on the cold air mass flow rate m c and mainstream mass flow rate m g Calculate the mass flow rate ratio φ = m c / m g ; S200. Based on T g,in T c and T aw The local film cooling efficiency η is calculated using the temperature difference ratio, and the average film cooling efficiency of the target area is obtained by averaging along the flow direction and averaging over the region. S300. Based on the mass flow ratio φ, the main inlet total pressure P tg,in and total air conditioning pressure P tc The total blending pressure P was obtained by weighted calculation. mix And combined with the mainstream export total pressure P tg,out and outlet static pressure P g,out Calculate the total pressure loss coefficient ξ; S400. Extract the highest temperature T in the cooling zone. max Air conditioning temperature T c Using the mass flow ratio φ as the base and the temperature ratio as the exponent, a high-temperature cooling index Λ is constructed. The high-temperature cooling index characterizes the degree of optimization in the limited area of ​​the air film cooling effect and is used to fine-tune the calculation results. S500. Based on the isenthalpic mixing assumption, a Pareto distribution expression between η and φ is constructed, and a nonlinear distribution function of ξ and φ is constructed to reveal the law of loss variation with cold air volume. Correlation modeling reflects the corresponding characteristics and trends of η to ξ to mass flow rate ratio φ. S600. Employs a power-law function combination to calculate the average film cooling efficiency. The total pressure loss coefficient ξ and the high-temperature zone cooling index Λ are combined to construct the efficiency loss calculation coefficient E; S700. Calculate the efficiency loss calculation coefficient E for different cooling schemes, and determine the overall applicability of different cooling schemes in the target area based on the value of E.

2. The method for calculating the performance loss of turbine blade film cooling according to claim 1, characterized in that, In step S100, the acquisition locations of the mainstream channel parameters are defined as follows: inlet parameters are obtained by area-weighted averaging on the inlet cross-section within the range of 0.5 to 1.5 times the chord length upstream of the blade leading edge; outlet parameters are obtained by mass-weighted averaging on the outlet cross-section within the range of 0.3 to 0.6 times the chord length downstream of the blade trailing edge. g The parameters of the film cooling gas are obtained by integrating the density-velocity product of the inlet cross-section; T is the value of the film cooling gas. c The measurement location is set at the inlet of the cold air chamber, P tc and P c The value was obtained by using the average volume of the cold air chamber, m c T is obtained based on the mass flow rate at the inlet of the cold air chamber. aw The values ​​are obtained by calculating the boundary conditions of the adiabatic wall in numerical simulation, and by measuring them in experiments using an infrared thermal imager or a surface-embedded thermocouple.

3. The method for calculating the performance loss of turbine blade film cooling according to claim 1, characterized in that, In step S200, the local film cooling efficiency η is calculated using the temperature difference ratio, and its mathematical expression is: n measurement lines extending longitudinally are equally spaced along the flow direction on the turbine blade surface of the target calculation region. Each measurement line contains multiple measurement points. First, the line-average efficiency of each measurement line is calculated based on the arithmetic mean. m is the number of measuring points on the i-th measuring line, η ij The local film cooling efficiency at the j-th measurement point on the i-th line is given. Then, the flow-direction average efficiency of the line average efficiency across all measurement lines is calculated to obtain the overall average film cooling efficiency for the target area.

4. The method for calculating the performance loss of turbine blade film cooling according to claim 1, characterized in that, In step S300, the total pressure loss coefficient ξ is calculated using the pressure difference ratio, and its mathematical expression is as follows: Where P mix The total mixing pressure P is the pressure of the mainstream gas and the film cooling gas before mixing. mix The calculation uses a weighted average of mainstream and cooling air mass flow rates, and its mathematical expression is as follows:

5. The method for calculating the performance loss of turbine blade film cooling according to claim 1, characterized in that, In step S400, the cooling index Λ of the high-temperature zone is calculated using a normalized exponential form, and its mathematical expression is: Where T max This represents the highest temperature measured in the target area.

6. The method for calculating the performance loss of turbine blade film cooling according to claim 1, characterized in that, The Pareto distribution correlation establishment in step S500 will be divided into detailed steps S501 to S504. Based on the linear approximate isenthalpic mixing assumption, the Pareto distribution relationship between the film cooling efficiency η and the mass flow rate ratio φ will be established; simultaneously, the Pareto distribution correlation between the total pressure loss coefficient ξ and the mass flow rate ratio φ will be established, through the total cooling gas pressure P. tc The functional relationship between the mass flow rate ratio φ and the mass flow rate ratio is realized.

7. The method for calculating the performance loss of turbine blade film cooling according to claim 6, characterized in that, In step S500, establishing the Pareto distribution correlation includes at least the following: S501. Pareto distribution modeling of film cooling efficiency η: Based on the linear approximate isenthalpic mixing assumption, a mixing temperature T is established. mix The linear model, its mathematical expression is (m g +m c )T mix =k1(m g T g,in +m c T c ), where k1 is the mixing correction coefficient, and k1 = 1 when the isenthalpic assumption is fully followed; the film cooling efficiency is expressed mathematically as The expression is in the form of η, where k2 and k3 are positive coefficients determined by the relationship between temperature and mass flow rate. This expression reflects the generalized Pareto distribution relationship between η and the mass flow rate ratio φ. S502. Pareto distribution modeling of total pressure loss coefficient ξ: Establishing the relationship between total cooling pressure and mass flow rate ratio P tc =k4·φ 2 +k5, k4, and k5 are coefficients determined based on the relationship between pressure and mass flow rate; the total blending pressure is expressed as... In the form of k6, the main imported total pressure P tg,in A simplified expression for the total pressure loss coefficient is derived mathematically. k7 and k8 represent the main outlet total pressure and static pressure, respectively. This expression reflects the Pareto distribution characteristics under the condition of small mass flow ratio. S503. Pareto Distribution Type Determination of Total Pressure Loss Coefficient ξ: The Pareto distribution type of ξ is determined based on the relationship between the coefficients. When k5>k6>k7>k8, ξ follows an inverse Pareto distribution and increases with increasing φ; when k6>k5>k7>k8 or k6>k7>k5>k8, ξ conforms to a generalized Pareto distribution but decreases slightly with increasing φ; when k6>k7>k8>k5, ξ exhibits an inverse Pareto distribution and decreases slightly with increasing φ. S504. Distribution Consistency Verification and Parameter Correlation: By comparing the Pareto distribution forms of η and ξ, the consistency and mathematical correlation of the two main parameters are verified, ensuring that under the same mass flow ratio, the variation law of cooling effect and aerodynamic loss follows a unified statistical distribution principle.

8. The method for calculating the performance loss of turbine blade film cooling according to claim 1, characterized in that, In step S600, the efficiency loss calculation coefficient E is constructed using a combination of double power functions, and its mathematical expression is as follows: This represents the spanwise average film cooling efficiency on the i-th measurement line, where n is the number of measurement lines. All parameters are averaged in both spanwise and flowwise directions within the target calculation region.

9. The method for calculating the performance loss of turbine blade film cooling according to claim 1, characterized in that, In step S700, a grading evaluation standard is established based on the value of E. When E ≥ 0.9, it is rated as excellent, indicating that the cooling effect and aerodynamic loss are well balanced; when 0.8 ≤ E < 0.9, it is rated as good, indicating that the overall performance meets the requirements of engineering applications; when 0.6 ≤ E < 0.8, it is rated as average, indicating that there is room for performance improvement; when E < 0.6, it is rated as poor, and the cooling scheme needs to be redesigned.

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