A method for predicting comprehensive cooling efficiency under high temperature conditions using similarity principle

Abstract

The present invention discloses a method for predicting the comprehensive cooling efficiency under high-temperature conditions using the similarity principle. The medium and low temperature test conditions ensure that the parameters such as the temperature ratio and Reynolds number ratio are similar to those under high-temperature conditions. A dimensionless parameter expression of the comprehensive cooling efficiency is determined using a one-dimensional coupled heat transfer model. The Nusselt numbers inside and outside the blade and the thermal conductivity of the air are obtained using an empirical formula to estimate the heat transfer coefficient ratio and the temperature rise coefficient. The wall thermal conductivity is calculated based on the outer wall temperature distribution, thereby calculating the Biot number distribution. The film cooling efficiency is inferred based on the numerical values ​​of each parameter. or Finally, based on the high-temperature boundary conditions and the known cooling efficiency under low-temperature conditions, the internal-external heat transfer coefficient ratio, temperature rise coefficient, and solid Biot number are corrected to accurately estimate the overall cooling efficiency under high-temperature conditions. This invention utilizes similar principles to correct parameters such as the heat transfer coefficient ratio, temperature rise coefficient, and solid Biot number under medium- and low-temperature conditions, improving the accuracy of the high-temperature turbine's overall cooling efficiency derived from medium- and low-temperature tests.

Description

Technical Field

[0001] The present invention belongs to the field of turbine blade cooling efficiency prediction, and in particular relates to a method for predicting comprehensive cooling efficiency under high temperature conditions by utilizing similarity principles. Background Art

[0002] For aircraft engines, increasing the turbine inlet temperature is an important means to improve the thrust-to-weight ratio and efficiency of aircraft engines. However, the current demand for increasing the turbine inlet temperature is always higher than the development of the high-temperature resistance of blade materials. Therefore, turbine cooling technology is an important means to effectively reduce the temperature of turbine blades, and comprehensive cooling efficiency has become an important criterion for evaluating cooling characteristics.

[0003] Aircraft engine turbines often operate at extremely high temperatures and pressures. Maintaining consistent temperature and pressure parameters throughout testing would incur significant research costs. Therefore, researchers typically utilize similarity modeling theory to reduce testing costs by mimicking the operating conditions of high-pressure, high-temperature experiments to medium-temperature, medium-pressure conditions. Through experimental modeling, researchers hope to obtain reliable and realistic turbine blade cooling efficiency under laboratory conditions.

[0004] To ensure thermal and motion similarity, many existing simulation experiments consider the primary-to-secondary flow temperature ratio and the primary-to-secondary flow Reynolds number to be the two most important parameters in experimental modeling. However, some simulation schemes, on the one hand, overlook the influence of the primary-side Biot number on turbine blade cooling efficiency. On the other hand, even under laboratory conditions, even when the importance of the Biot number is acknowledged, it is difficult to accurately determine the distribution of the Biot number without first determining the overall cooling efficiency. Furthermore, even when the Biot number is known, it is difficult to arbitrarily select solid materials with appropriate thermal conductivity to achieve a matching Biot number. This results in discrepancies between the overall cooling efficiency obtained from experimental simulation schemes at low and medium temperatures and that at high temperatures, making it difficult to understand the true cooling effect of the blade. Summary of the Invention

[0005] In order to solve the problem that the temperature difference between medium and low temperature working conditions and high temperature working conditions changes the solid thermal conductivity coefficient and makes the mainstream side Biot number inconsistent, the present invention provides a method for predicting the comprehensive cooling efficiency under high temperature conditions using the similarity principle. By continuously correcting the mainstream side Biot number, calculating the new comprehensive cooling efficiency, and further correcting the wall temperature and thermal conductivity coefficient, the comprehensive cooling efficiency of high temperature working conditions can be accurately predicted.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A method for predicting comprehensive cooling efficiency under high temperature conditions using similarity principle is characterized by the following specific steps:

[0008] Step 1: Set the boundary conditions for high-temperature and medium-low temperature conditions. The high-temperature boundary condition is the actual working environment of the turbine blade. The medium-low temperature condition ensures that the temperature ratio and Reynolds number ratio parameters are consistent with those of the high-temperature condition. Obtain the outer wall temperature distribution and the corresponding comprehensive cooling efficiency under the medium-low temperature condition.

[0009] Step 2: Use the one-dimensional coupled heat transfer model to obtain the dimensionless parameters and temperature expressions related to the comprehensive cooling efficiency, and obtain the definition of each parameter in the expression;

[0010] Step 3: First, determine the primary and secondary flow Reynolds numbers and Prandtl numbers for high-temperature and medium-low-temperature conditions. Second, estimate the Nusselt numbers for high-temperature gas and cold air convection heat transfer based on the classic Dittus-Boelter criterion for channel convection heat transfer. Estimate the thermal conductivity of gas and cold air under the two conditions using the air thermal conductivity-temperature correlation formula. Finally, use the calculated Nusselt number and thermal conductivity to estimate the internal and external heat transfer coefficient ratio H and temperature rise coefficient R under the low-temperature condition of the test. c ;

[0011] Step 4: Create a uniformly distributed grid on the outer wall surface. Map the outer wall temperature obtained from the test condition in step 1 to the grid to obtain the outer wall temperature of each grid node. Then, calculate the thermal conductivity of each grid node on the outer wall based on the relationship between temperature and thermal conductivity. Finally, estimate the Biot number of each grid node on the outer wall based on the definition of the mainstream side Biot number.

[0012] Step 5: Determine the film cooling efficiency η based on the comprehensive cooling efficiency results under low temperature conditions and the numerical results of various parameters;

[0013] Step 6: To estimate the comprehensive cooling efficiency under high-temperature conditions, calculate the corrected internal and external heat transfer coefficient ratio, temperature rise coefficient, and solid Biot number based on the high-temperature boundary conditions and the known comprehensive cooling efficiency under medium and low-temperature conditions. Then, use the corrected dimensionless parameters to deduce the comprehensive cooling efficiency under high-temperature conditions. Repeat the calculation iteratively until the error is minimized.

[0014] In step 1, in order to meet the thermal similarity between the low temperature working condition and the high temperature working condition, the temperature ratio T c / T g and heat transfer coefficient ratio H = h c / h g Consistent, where T c With T g are the air conditioning temperature and gas temperature, respectively, h c With h g are the heat transfer coefficients on the cold air side and the gas side respectively; to meet the similarity of motion and power, the Reynolds number ratio Re c / Re g is consistent with the Mach number Ma, where Rec With Re g where c and g represent the cooling gas and high-temperature gas, respectively, η is the adiabatic film cooling efficiency, Re is the Reynolds number, Ma is the Mach number, H is the ratio of the internal and external heat transfer coefficients, and h is the heat transfer coefficient.

[0015] In step 2, the one-dimensional coupled heat transfer model is used to obtain the dimensionless parameters and temperature expressions related to the comprehensive cooling efficiency, and the definition formula of each parameter in the expression is obtained.

[0016] The dimensionless parameter and temperature expression of the comprehensive cooling efficiency in the present invention are:

[0017]

[0018] Where Big is the mainstream measured Biot number, R c is the temperature rise coefficient. The definition of each parameter is as follows:

[0019]

[0020]

[0021] Where m c is the cooling air flow rate, A c is the cooling area on the air side, c pc is the specific heat capacity of the cooling air, t m is the thickness of the film cooling solid domain, k s is the solid thermal conductivity, T aw is the wall temperature when the outer wall is adiabatic, T c，e is the outlet temperature of the cold air from the film hole.

[0022] In step 3, first, determine the primary and secondary flow Reynolds numbers and Prandtl numbers for high temperature and medium and low temperature conditions. Then, estimate the Nusselt number Nu for high temperature gas and cold gas convection heat transfer based on the classic Dittus-Boelter criterion for channel convection heat transfer: Nu = 0.023Re 0.8 Pr n When the fluid is heated, n = 0.4, and when the fluid is cooled, n = 0.3.

[0023] The thermal conductivity of high-temperature fuel gas and cooling gas under high-temperature and medium-low-temperature conditions is estimated using the temperature correlation formula of air thermal conductivity. The temperature correlation formula is as follows:

[0024] k=0.00393+(0.0000765448)T+(-0.0000000121525)T 2

[0025] Where k is the thermal conductivity and T is the gas temperature.

[0026] Using the Nusselt number and thermal conductivity calculation results and the dimensionless parameter definition formula, the internal and external heat transfer coefficient ratio H and the temperature rise coefficient R under the low temperature conditions of the test are estimated. c The definition and empirical formula of heat transfer coefficient ratio and temperature rise coefficient are as follows:

[0027]

[0028] Where, L g With L c are the characteristic scales of the primary and secondary flows, respectively, k g With k c are the thermal conductivity of the mainstream and secondary gas respectively

[0029] In step 4, first, a uniformly distributed grid is created on the outer wall (created according to the wall coordinates). The outer wall temperature obtained from the test condition in step 1 is mapped to the grid through the interpolation function to obtain the outer wall temperature of each grid node. Then, the thermal conductivity of the outer wall is calculated based on the relationship between temperature and thermal conductivity:

[0030] K s =a+b×T w_experiment

[0031] Where a and b are constants obtained from the fitting.

[0032] Finally, the distribution of the Biot number on the outer wall is estimated based on the definition and empirical formula of the Biot number on the mainstream side:

[0033]

[0034] where t m is the thickness of the solid domain for film cooling.

[0035] In step 5, the low temperature result Φ is obtained by comprehensive cooling efficiency. experiment And the film cooling efficiency η can be inferred from the values ​​of various parameters:

[0036]

[0037] Step 6: To estimate the comprehensive cooling efficiency under high temperature conditions, the comprehensive cooling efficiency Φ under high temperature boundary conditions and medium and low temperature conditions is calculated. experiment , the corrected internal and external heat transfer coefficient ratio, temperature rise coefficient and solid Biot number can be calculated, and then the comprehensive cooling efficiency of high temperature conditions can be calculated based on the corrected dimensionless parameters. The iterative calculation is carried out until the error is minimized.

[0038] The beneficial effects of the present invention are:

[0039] The importance of the Biot number on the mainstream side is often ignored in traditional test modeling schemes, that is, the influence of the temperature difference between low-temperature conditions and high-temperature conditions on the thermal conductivity of solids is ignored, which leads to a large difference in the Biot number on the mainstream side. The present invention is a method that uses the similarity principle to correct the comprehensive cooling efficiency of the turbine under medium and low-temperature test conditions to the cooling efficiency under high-temperature conditions. By using the similarity principle and the temperature correction method based on the original similarity theory, a better correction is made for the influence of temperature on the thermal conductivity. By updating the outer wall temperature on the mainstream side, the Biot number is corrected, and a new comprehensive cooling efficiency is calculated. Then, a new outer wall temperature is obtained according to the new cooling efficiency, and the Biot number is corrected again. The iterative update is repeated until the error is minimized, and the comprehensive cooling efficiency of the high-temperature condition predicted by the low-temperature condition can be obtained. After correction by similarity, the accuracy of the comprehensive cooling efficiency prediction can be increased to 99.5%, which effectively compensates for the error caused by the previous modeling scheme due to ignoring or failing to match the Biot number. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Comprehensive cooling efficiency distribution diagram for high temperature, medium and low temperature working conditions.

[0041] Figure 2 Distribution diagram of the difference ΔΦ between the comprehensive cooling efficiency of high temperature and medium and low temperature conditions.

[0042] Figure 3 Biot number distribution diagram for medium and low temperature conditions.

[0043] Figure 4 Graph of Biot number correction results.

[0044] Figure 5 Flowchart of the temperature correction method.

[0045] Figure 6 Correction results of the comprehensive cooling efficiency of the outer wall.

[0046] Figure 7 The difference between the comprehensive cooling efficiency of high temperature working condition and the correction result ΔΦ fix Distribution map.

[0047] Figure 8 ΔΦ fix Schematic diagram of the lateral average comparison of the ΔΦ comprehensive cooling efficiency.

[0048] Figure 9 It is a schematic diagram of matching parameters between medium and low temperature working conditions and high temperature working conditions. DETAILED DESCRIPTION

[0049] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention, but should not be construed as limiting the present invention.

[0050] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0051] A method for correcting the turbine comprehensive cooling efficiency under medium and low temperature test conditions to the cooling efficiency under high temperature conditions using similar principles is as follows:

[0052] Step 1: Boundary conditions for high temperature and medium and low temperature conditions are required (including the inlet flow rate and temperature of the mainstream and cold air, and the outlet pressure). The boundary condition for the high temperature condition is the actual working environment of the turbine blade, and the medium and low temperature condition ensures that the temperature ratio and Reynolds number ratio and other parameters are consistent with the high temperature condition. Tests are carried out according to the boundary conditions to obtain the outer wall temperature distribution T under the medium and low temperature conditions. w_experiment And its corresponding comprehensive cooling efficiency Φ experiment . Ensure that the temperature is higher than T c / T g and heat transfer coefficient ratio H = h c / h g Consistent, where T c With T g are the air conditioning temperature and gas temperature, respectively, h c With h g are the heat transfer coefficients on the cold air side and the gas side respectively; to meet the similarity of motion and power, the Reynolds number ratio Re c / Re g is consistent with the Mach number Ma, where Re c With Re g are the cooling air Reynolds number and the gas Reynolds number, respectively. Figure 9 It is a schematic diagram of matching parameters between medium and low temperature working conditions and high temperature working conditions.

[0053] Attachment Figure 1 The comprehensive cooling efficiency distribution diagram for high temperature design and medium and low temperature test conditions is shown in Figure 2, where X / D represents the ratio of the distance along the flow direction of the fluid to the diameter of the air film hole, and Y / D represents the ratio of the spanwise distance to the diameter of the air film hole. Figure 1 It can be seen that the simulation results using traditional similarity theory are quite different from those under high temperature conditions, and the cooling effect under high temperature conditions is underestimated. Figure 2 The difference in comprehensive cooling efficiency between high temperature and medium and low temperature conditions (ΔΦ=Φ design -Φ experiment ) distribution map, from the attached Figure 2 It can be seen more clearly that the prediction accuracy of the leading edge is the lowest while the middle is more accurate. The maximum error of the cooling efficiency is 0.025, which exceeds 4.1%.

[0054] Step 2: Use the one-dimensional coupled heat transfer model to obtain the dimensionless parameters and temperature expressions related to the comprehensive cooling efficiency, and obtain the definition formula of each parameter in the expression.

[0055] The dimensionless parameter and temperature expression of the comprehensive cooling efficiency in the present invention are:

[0056]

[0057] Where Big is the mainstream measured Biot number, R c is the temperature rise coefficient. The definition of each parameter is as follows:

[0058]

[0059] Where m c is the cooling air flow rate, A c is the cooling area on the air side, c pc is the specific heat capacity of the cooling air, t m is the thickness of the film cooling solid domain, k s is the solid thermal conductivity, T aw is the wall temperature when the outer wall is adiabatic, T c，e is the outlet temperature of the cold air from the film hole.

[0060] Step 3: First, determine the primary and secondary flow Reynolds numbers and Prandtl numbers for high-temperature and medium-low-temperature conditions. The primary characteristic length can be selected as the gas inlet hydraulic diameter, and the secondary characteristic length can be the film hole diameter. Next, estimate the Nusselt number Nu for high-temperature gas and cold gas convective heat transfer based on the classic Dittus-Boelter criterion for channel convective heat transfer:

[0061] Nu=0.023Re 0.8 Pr n

[0062] Where n = 0.4 when the fluid is heated, and n = 0.3 when the fluid is cooled.

[0063] The thermal conductivity of high-temperature fuel gas and cooling gas under high-temperature and medium-low-temperature conditions is estimated using the temperature correlation formula of air thermal conductivity. The temperature correlation formula is as follows:

[0064] k=0.00393+(0.0000765448)T+(-0.0000000121525)T 2

[0065] Using the Nusselt number and thermal conductivity calculation results and the dimensionless parameter definition formula, the internal and external heat transfer coefficient ratio H and the temperature rise coefficient R under the low temperature conditions of the test are estimated. c The definition and empirical formula of heat transfer coefficient ratio and temperature rise coefficient are as follows:

[0066]

[0067] Step 4 First, create a uniformly distributed grid on the outer wall (created according to the wall coordinates), map the outer wall temperature obtained from the test condition in step 1 to the grid through the interpolation function, and obtain the outer wall temperature of each grid node. Then, use the relationship between solid thermal conductivity and temperature to calculate the thermal conductivity of the solid domain at the outer wall:

[0068] K s =a+b×T w_experiment

[0069] Where a and b are constants obtained from the fitting.

[0070] Finally, the distribution of the Biot number on the outer wall is estimated based on the definition and empirical formula of the Biot number on the mainstream side. Figure 3 This is the Biot number distribution diagram.

[0071] The definition and empirical formula of the mainstream side Biot number are as follows:

[0072]

[0073] where t m is the thickness of the solid domain for film cooling.

[0074] Step 5: Calculate the low temperature result Φ by comprehensive cooling efficiency experiment And the film cooling efficiency η can be inferred from the values ​​of various parameters:

[0075]

[0076] Step 6: To estimate the comprehensive cooling efficiency under high temperature conditions, the corrected internal and external heat transfer coefficient ratio H can be calculated based on the high temperature boundary conditions (primary and secondary flow temperatures and primary and secondary flow rates, etc.). fix , temperature rise coefficient R c_fix , it is worth noting that since the Reynolds number ratio of the primary and secondary flows is matched, only the Prandtl number is corrected in the heat transfer coefficient ratio. According to the primary and secondary flow temperatures under high temperature conditions and the comprehensive cooling efficiency Φ under known low temperature conditions experiment The outer wall temperature T after the first correction can be obtained w_fix , the specific method is:

[0077] T w_fix =T g_design -φ experimet *(T g_design -T c_design )

[0078] According to T w_fix The corrected thermal conductivity K is obtained s_fix , and use the new thermal conductivity to calculate the corrected Biot number Bi g_fix The modified Biot number distribution is shown in the attached figure. Figure 4 Finally, according to the corrected H _fix , R c_fix ,Bi g_fix The comprehensive cooling efficiency Φ under high temperature conditions is calculated by combining the air film cooling efficiency η fix , and then according to the new cooling efficiency Φ fix The new outer wall temperature is obtained, and then the Biot number is corrected again, and the iterative update is repeated until the error is minimized. The specific temperature correction method process is shown in the attached figure. Figure 5 shown.

[0079] Attachment Figure 6 The final modified distribution cloud diagram of the comprehensive cooling efficiency of the outer wall is attached. Figure 7 The difference between the comprehensive cooling efficiency of high temperature working condition and the correction result (ΔΦ fix =Φ design -Φ fix ). It can be seen that the correction effect is obvious. In a large range, the prediction results are almost the same as those under high temperature conditions, with an error of no more than 0.6%. Figure 8 is ΔΦ fix Compared with the lateral average of the ΔΦ comprehensive cooling efficiency, the overall error has been reduced compared with the previous prediction results, among which the leading edge accuracy has reached 98.3%.

[0080] The average area results of each parameter during the correction process are shown in the following table:

[0081]

[0082] The average value of the comprehensive cooling efficiency area under high-temperature conditions is 0.6066. Therefore, the overall average error before correction reaches 1.78%. After temperature correction using the high-temperature similarity principle, the average error is only 0.46%, and the prediction accuracy is greatly improved.

Claims

1. A method for predicting comprehensive cooling efficiency under high temperature conditions using similarity principle, characterized in that The specific steps are as follows: Step 1: Set the boundary conditions for high-temperature and medium-low temperature conditions. The high-temperature boundary condition is the actual working environment of the turbine blade. The medium-low temperature condition ensures that the temperature ratio and Reynolds number ratio parameters are consistent with those of the high-temperature condition. Obtain the outer wall temperature distribution and its corresponding comprehensive cooling efficiency under medium and low temperature conditions; Step 2: Use the one-dimensional coupled heat transfer model to obtain the dimensionless parameters and temperature expressions related to the comprehensive cooling efficiency, and obtain the definition of each parameter in the expression; Step 3: First, determine the primary and secondary flow Reynolds numbers and Prandtl numbers for high-temperature and medium-low-temperature conditions. Second, estimate the Nusselt numbers for high-temperature gas and cold air convection heat transfer based on the classic Dittus-Boelter criterion for channel convection heat transfer. Estimate the thermal conductivity of gas and cold air under the two conditions using the air thermal conductivity-temperature correlation formula. Finally, use the calculated Nusselt number and thermal conductivity to estimate the internal and external heat transfer coefficient ratio H and temperature rise coefficient R under the medium-low temperature condition of the test. c ; Step 4: Create a uniformly distributed grid on the outer wall surface, map the outer wall surface temperature obtained from the test condition in step 1 to the grid, and obtain the outer wall surface temperature of each grid node; Then, the thermal conductivity of each grid node on the outer wall is calculated based on the relationship between temperature and thermal conductivity. Finally, the Biot number of each grid node on the outer wall is estimated based on the definition of the Biot number on the mainstream side. Step 5: Determine the film cooling efficiency η based on the comprehensive cooling efficiency results under medium and low temperature conditions and the numerical results of various parameters; Step 6: To estimate the comprehensive cooling efficiency under high-temperature conditions, calculate the corrected internal and external heat transfer coefficient ratio, temperature rise coefficient, and solid Biot number based on the high-temperature boundary conditions and the known comprehensive cooling efficiency under medium and low-temperature conditions. Then, use the corrected dimensionless parameters to deduce the comprehensive cooling efficiency under high-temperature conditions. Repeat the calculation iteratively until the error is minimized.

2. The method for predicting comprehensive cooling efficiency under high temperature conditions using the similarity principle according to claim 1, characterized in that: In step 1, in order to meet the thermal similarity between the low temperature working condition and the high temperature working condition, the temperature ratio T c / T g and heat transfer coefficient ratio H = h c / h g Consistent, where T c With T g are the air conditioning temperature and gas temperature, respectively, h c With h g are the heat transfer coefficients on the cold air side and the gas side respectively; to meet the similarity of motion and power, the Reynolds number ratio Re c / Re g is consistent with the Mach number Ma, where Re c With Re g are the cooling air Reynolds number and the gas Reynolds number, respectively.

3. The method for predicting comprehensive cooling efficiency under high temperature conditions using the similarity principle according to claim 1, characterized in that: In step 2, the dimensionless parameter and temperature expression of the comprehensive cooling efficiency are: In the formula Bi g The mainstream measurement of Biot number, R c is the temperature rise coefficient, subscripts c and g represent cold air and high-temperature gas respectively, η is the adiabatic film cooling efficiency, H is the ratio of internal and external heat transfer coefficients, and the definitions of the parameters are as follows: Where m c is the cooling air flow rate, A c is the cooling area on the air side, c pc is the specific heat capacity of the cooling air, t m is the thickness of the film cooling solid domain, k s is the solid thermal conductivity, T aw is the wall temperature when the outer wall is adiabatic, T c，e is the outlet temperature of the cold air from the film hole.

4. The method for predicting comprehensive cooling efficiency under high temperature conditions using similarity principle according to claim 1, characterized in that: In step 3, first, determine the primary and secondary flow Reynolds numbers and Prandtl numbers for high temperature and medium and low temperature conditions; second, estimate the Nusselt number Nu for high temperature gas and cold gas convection heat transfer based on the classic Dittus-Boelter criterion for channel convection heat transfer: Nu = 0.023Re 0.8 Pr n ; Wherein, n = 0.4 when the fluid is heated, and n = 0.3 when the fluid is cooled; The thermal conductivity of high-temperature gas and cold air under high-temperature conditions and medium-low-temperature conditions is estimated using the temperature correlation formula of air thermal conductivity. The temperature correlation formula is as follows: k=0.00393+(0.0000765448)T+(-0.0000000121525)T 2 Where k is the thermal conductivity and T is the gas temperature; Using the Nusselt number and thermal conductivity calculation results and the dimensionless parameter definition formula, the internal and external heat transfer coefficient ratio H and the temperature rise coefficient R under low temperature conditions in the experiment are estimated. c , the definition and empirical formula of heat transfer coefficient ratio and temperature rise coefficient are as follows: Where, L g With L c are the characteristic scales of the primary and secondary flows, respectively, k g With k c are the thermal conductivity of the mainstream and secondary gas flows, respectively.

5. The method for predicting comprehensive cooling efficiency under high temperature conditions using similarity principle according to claim 1, characterized in that: The process in step 6 is as follows: On the basis of steps 3 to 5, in order to estimate the comprehensive cooling efficiency under high-temperature conditions, first, the corrected internal and external heat transfer coefficient ratio and temperature rise coefficient are calculated according to the primary and secondary flow temperatures and primary and secondary flow flow rates of the high-temperature boundary conditions; secondly, the first corrected outer wall temperature is calculated according to the primary and secondary flow temperatures of the high-temperature conditions and the comprehensive cooling efficiency under known medium and low-temperature conditions, and then the corrected thermal conductivity is obtained based on the outer wall temperature, and the corrected Biot number is calculated using the new thermal conductivity; finally, the corrected comprehensive cooling efficiency is obtained using the corrected heat transfer coefficient ratio, temperature rise coefficient, Biot number and adiabatic film cooling efficiency, and then the new outer wall temperature is obtained based on the new comprehensive cooling efficiency, and then the Biot number is corrected again, and the iterative update is repeated until the error is minimized.

6. The method for predicting comprehensive cooling efficiency under high temperature conditions using similarity principle according to claim 1, characterized in that: In step 1, the boundary conditions for high temperature and medium and low temperature working conditions include the inlet flow rate and temperature of the mainstream and secondary flows, and the outlet pressure.

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