Highly robust numerical calculation method for liquid-gas phase change transpiration cooling of turbine blades in porous media

Abstract

This invention discloses a highly robust numerical calculation method for liquid-gas phase-change transpiration cooling of porous media for turbine blades. The method includes model construction, medium property settings, multiphase flow settings, porous media domain settings, calculation configuration, control parameter settings, and boundary and monitoring configuration. By combining and optimizing the simulation conditions, the non-convergence problem during the simulation process is resolved, and the stability and accuracy of the simulation are improved. Through in-depth exploration and understanding of the transpiration cooling mechanism in porous media, this invention lays a solid theoretical and technical foundation for the industrial practice and application of porous media phase-change transpiration cooling technology, bringing innovative design ideas and solutions to related fields.

Description

Technical Field

[0001] The present invention relates to the field of cooling technology, in particular to a high-robustness numerical calculation method for liquid-gas phase change transpiration cooling of porous media of turbine blades. Background Art

[0002] Temperature management for turbine blades operating in high-temperature environments, such as aircraft engines, is crucial to ensuring engine performance and lifespan. Traditional turbine blade cooling methods, including gas and liquid cooling, are no longer sufficient to meet cooling requirements as operating temperatures continue to rise. Phase-change transpiration cooling, a novel cooling technology, has attracted attention due to its high cooling efficiency. This advanced cooling method utilizes the heat absorption and evaporation of liquid into gas within microporous channels within the blade. This phase change process effectively removes heat from the blade surface, thereby reducing blade temperature. However, the complex porous media within the model of phase-change transpiration cooling poses numerous challenges to the simulated fluid flow within the porous medium. These include the influence of porous media properties such as porosity and permeability on the fluid dynamics. Furthermore, the liquid-to-gas phase change process involves complex thermodynamic behavior, including the release of latent heat, the influence of temperature and pressure on the phase change process, and the heat conduction and convection mechanisms involved in the phase change process. These issues can reduce computational stability and increase the difficulty of simulations. In addition to computational difficulties, accurate simulation of the phase change transpiration cooling process usually requires very detailed meshing and high-precision numerical methods, resulting in high computational costs, especially for systems with complex internal structures. Summary of the Invention

[0003] In order to make up for the shortcomings of the existing technology and solve the problem of poor convergence in the numerical simulation research of phase change divergent cooling, the purpose of the present invention is to provide a highly robust numerical calculation method for liquid-gas phase change transpiration cooling of porous media of turbine blades. By combining and optimizing the simulation conditions, the non-convergence problem in the simulation process is solved, and the stability and accuracy of the simulation are improved, providing a more accurate numerical analysis method for the study of phase change transpiration cooling process.

[0004] The purpose of the present invention is achieved by adopting the following technical solutions:

[0005] A highly robust numerical calculation method for liquid-gas phase change transpiration cooling of a turbine blade is disclosed. The method is characterized by optimizing and combining simulation configurations to resolve non-convergence issues during the simulation process, improve simulation stability and accuracy, and provide a precise numerical analysis basis for the phase change transpiration cooling process. The method comprises the following steps:

[0006] Step 1: Model Construction: First, the geometric characteristics of the porous medium region and the coolant computational domain during the porous medium phase transition and divergent cooling process are clearly defined. The corresponding mesh file is generated and imported into the simulation software. To balance computational accuracy and computational complexity, the porous medium phase transition is divided into two independent computational stages. First, the main fluid domain is calculated to determine the heat transfer rate on the porous medium surface. Then, the domain between the porous medium and the coolant is simulated to determine the phase transition process of the coolant.

[0007] Step 2: Medium property setting: Add two additional media to the simulation software database: liquid water and water vapor, in addition to the standard gaseous air, and adjust the corresponding physical properties according to the research requirements, especially the density and viscosity parameters to improve the simulation accuracy.

[0008] Step 3: Multiphase Flow Settings: Select a volumetric fluid model and a mixed fluid model to improve stability, and add the three media you already configured. Adjust the phase transition settings for liquid water and water vapor, and select the phase transition temperature based on the relationship between pressure and boiling point.

[0009] Step 4: Porous Media Domain Setup: Use the κ-ωSST turbulence model, and consider using more complex turbulence models with high mesh quality. Select the Porous Domain option and set the porosity and porous media material according to the material parameters required for the study. In the Porous Media Setup, configure the ViscousResistance and Inertial Resistance parameters for air, liquid water, and water vapor, respectively, based on physical properties calculated from the literature.

[0010] Step 5: Computational Configuration: Use the couple algorithm to speed up convergence. If convergence is difficult, consider initially using a first-order upwind scheme to stabilize the computational field. Once this stabilizes, switch to a higher-order scheme, especially if the energy equation is difficult to converge.

[0011] Step 6: Control Parameter Settings: In the Control settings, keep the default parameters. Increase calculation stability by adjusting the turbulence and energy factors. Set limiters to set upper and lower limits for pressure and temperature to improve calculation stability. Adjust the time scale factor appropriately to accelerate convergence based on the calculation situation.

[0012] Step 7: Boundary and Monitoring Configuration: Because the porous media phase change is a two-step calculation, heat transfer must be added as a volume source term in the simulation software's exit boundary settings. Model convergence can be assessed by monitoring the water vapor distribution and the porous media surface temperature, paying attention to the unsteady nature of the phase change.

[0013] This paper improves physical models and numerical methods to more accurately simulate phase change and the flow and evaporation of the cooling medium. Through algorithm optimization and parallel computing technology, it reduces computing resource consumption and improves simulation efficiency. This also develops a numerical model with greater versatility and robustness to meet simulation requirements under diverse operating conditions.

[0014] The advantages of the present invention are:

[0015] 1. Improve computational stability and accuracy: Introducing improved physical models and highly robust numerical algorithms. This effectively overcomes computational divergence issues during simulation, improves the stability and accuracy of numerical simulations, makes simulation results more reliable and consistent with actual observations, and enhances the practical value and trustworthiness of the model.

[0016] 2. Optimize computing resource consumption: Adopting efficient algorithm optimization and parallel computing technology, this significantly reduces the demand for computing resources, including computing time and hardware resources, improves simulation efficiency, and makes large-scale and high-precision simulation possible.

[0017] 3. Enhance the model's applicability and flexibility: Developing a highly versatile simulation model enables the numerical calculation method to be applied to a wider range of porous media phase change transpiration cooling scenarios, encompassing diverse operating conditions and material properties. This improves the model's practicality and flexibility. This provides a powerful tool for understanding and exploring the mechanisms of porous media phase change transpiration cooling, promoting related scientific research and technological innovation.

[0018] By improving the stability, accuracy, efficiency and applicability of simulation, the present invention provides strong support for the research, design and optimization of porous medium phase change sweating cooling technology, and has important scientific research and engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a flow chart of the feasibility study of a highly robust numerical calculation method for phase change transpiration cooling in porous media according to the present invention.

[0020] Figure 2 Schematic diagram of the model structure of the porous medium phase change sweating cooling example of the present invention.

[0021] Figure 3 This is a cloud diagram of the liquid-gas boundary line in the porous medium at an injection rate of 0.15 according to the present invention.

[0022] Figure 4 This is a cloud diagram of the liquid-gas boundary line in the porous medium at an injection rate of 0.15 according to the present invention. DETAILED DESCRIPTION

[0023] The following will further describe the specific embodiments in detail with reference to the accompanying drawings of the embodiments of the present invention, and clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0024] The following further describes the specific technical implementation scheme of the present invention with reference to the accompanying drawings, so that those skilled in the art can further understand the present invention without limiting their rights.

[0025] Figure 1 This is a flow chart illustrating the feasibility study of a highly robust numerical calculation method for porous media phase change transpiration cooling. A highly robust numerical calculation method for porous media liquid-gas phase change transpiration cooling of turbine blades addresses non-convergence issues during the simulation process by optimizing and combining simulation configurations, improving simulation stability and accuracy, and providing a precise numerical analysis foundation for the phase change transpiration cooling process. The method includes the following steps:

[0026] Step 1: Model construction: First, the geometric characteristics of the porous medium region and the cooling medium calculation domain during the porous medium phase change and divergent cooling process are clearly studied, and the corresponding mesh file is generated and imported into the simulation software. In order to balance the calculation accuracy and the amount of calculation, the porous medium phase change region is set and the phase change process of the cooling medium is determined. Figure 2 As shown, the mainstream channel is used to pass high-temperature gas. The coolant enters from the bottom, first ensuring that the fluid is in a full liquid state in the liquid storage chamber, and then slowly penetrates into the porous medium, and a phase change process occurs in the porous medium area.

[0027] Step 2: Medium property setting: Add two additional media to the simulation software database: liquid water and water vapor, in addition to the standard gaseous air, and adjust the corresponding physical properties according to the research requirements, especially the density and viscosity parameters to improve the simulation accuracy.

[0028] Step 3: Multiphase flow settings: The VOF multiphase flow model is selected in the model to improve stability. The basic method of the VOF multiphase flow model is to define a function F as the water volume fraction function, which is used to represent the relative ratio of the water volume in the calculation area to the total calculation area. That is, when the calculation cell is full of gas, F = 0; when the calculation cell is completely liquid, F = 1. When the value of F is between 0 and 1, it means that there are multiple media in the calculation cell and there is a free surface. The direction of the external normal of the free surface is represented by the spatial gradient of F. The governing equation of F is as follows:

[0029]

[0030] Where: t——time; u i ——Velocity component; x i - Position component. Add the three media you've set. Adjust the phase transition settings for liquid water and water vapor. The phase transition temperature is selected based on the relationship between pressure and boiling point.

[0031] Step 4: Porous Media Domain Settings: Use the k-ωSST turbulence model and consider using more complex turbulence models under high mesh quality conditions. Check the Porous Domain option and set the porosity and porous media material according to the material parameters required for the study. In the porous media settings, configure the ViscousResistance and InertialResistance parameters for air, liquid water, and water vapor, respectively. These parameters are calculated based on the physical properties in the paper "Experimental Investigation of Transpiration Cooling with Phase Change for Sintered Porous Plates."

[0032] Step 5: Computational Configuration: Use the couple algorithm to speed up convergence. If convergence is difficult, consider initially using a first-order upwind scheme to stabilize the computational field. Once this stabilizes, switch to a higher-order scheme, especially if the energy equation is difficult to converge.

[0033] Step 6: Control Parameter Settings: In the Control settings, keep the default parameters. Increase calculation stability by adjusting the turbulence and energy factors. Set limiters to set upper and lower limits for pressure and temperature to improve calculation stability. Adjust the time scale factor appropriately to accelerate convergence based on the calculation situation.

[0034] Step 7: Boundary and monitoring configuration: Since the porous media phase change is calculated in two steps, heat transfer needs to be added in the form of volume source terms in the outlet boundary settings. Evaluate whether the model has converged by monitoring the water vapor distribution and the temperature change on the porous media surface, and pay attention to the unsteady characteristics of the phase change. Figure 3 and Figure 4 It can be seen that for different coolant injection rates, when the mainstream temperature and flow rate remain consistent, there are obvious differences in the changes in the porous medium temperature.

[0035] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A highly robust numerical calculation method for liquid-gas phase change cooling of porous media in turbine blades, characterized by: By optimizing the simulation configuration, the non-convergence problem in the simulation process is resolved, the stability and accuracy of the simulation are improved, and a precise numerical analysis basis is provided for the phase change sweating cooling process. The following steps are included: Step 1: Model construction: determine the phase change process of the cooling medium; Step 2: Medium property settings: Add two media to the simulation software database: liquid water and water vapor, and adjust the corresponding physical properties, including density and viscosity parameters, according to research requirements; Step 3: Multiphase flow settings: A volumetric fluid model and a mixed fluid model are used to improve stability. The three media (air, liquid water, and water vapor) are added. The phase transition settings for liquid water and water vapor are adjusted, and the phase transition temperature is selected based on the relationship between pressure and boiling point. Step 4: Porous media domain settings: Use the k-ωSST turbulence model and use the turbulence model under high mesh quality conditions. Check the porous domain option and set the porosity and porous media material according to the material parameters. Step 5: Calculation configuration: Use the couple algorithm to improve convergence speed; Step 6: Control parameter settings: In the Control settings, keep the default parameters and adjust the turbulence and energy factor values ​​to increase the calculation stability. Set limiters to limit the upper and lower limits of pressure and temperature to improve the calculation stability. Adjust the time scale factor to accelerate the convergence process. Step 7: Boundary and monitoring configuration: Since the phase change of porous media is calculated in two steps, heat transfer is added as a volume source term in the outlet boundary settings. The model convergence is evaluated by monitoring the water vapor distribution and the temperature change on the porous media surface.

2. The highly robust numerical calculation method for liquid-gas phase change transpiration cooling of porous media for turbine blades according to claim 1, characterized in that: Step 1 is as follows: 1) Clarify the geometric characteristics of the porous medium region and the cooling medium calculation domain during the porous medium phase change and divergent cooling process, generate the corresponding mesh file and import it into the simulation software; 2) To balance computational accuracy and computational complexity, the porous medium phase change is divided into two independent calculation segments. First, the main fluid domain is calculated to obtain the heat transfer rate on the porous medium surface; then, the domain between the porous medium and the cooling medium is simulated to determine the phase change process of the cooling medium.

3. The highly robust numerical calculation method for liquid-gas phase change transpiration cooling of turbine blade porous media according to claim 1, characterized in that: In step 3, the VOF multiphase flow model is selected to improve stability. The basic method of the VOF multiphase flow model is to define a function F as the water volume fraction function to represent the relative ratio of the water volume in the calculation area to the total calculation area. That is, when the calculation unit is full of gas, F = 0; when the calculation unit is completely liquid, F = 1. When the value of F is between 0 and 1, it means that there are multiple media in the calculation unit and there is a free surface. The direction of the external normal of the free surface is represented by the spatial gradient of F. The control equation of F is as follows: Where: t—time; u i —Velocity component; x i —position component, and add the three media that have been set, adjust the phase change settings of liquid water and water vapor, and select the phase change temperature based on the relationship between pressure and boiling point.

4. The highly robust numerical calculation method for liquid-gas phase change transpiration cooling of porous media for turbine blades according to claim 1, characterized in that: In step 4, in the porous media settings, configure the Viscous Resistance and Inertial Resistance parameters for the three media: air, liquid water, and water vapor.

5. The highly robust numerical calculation method for liquid-gas phase change transpiration cooling of turbine blade porous media according to claim 1, characterized in that: In step 5, if convergence difficulties are encountered, the first-order upwind format is used to stabilize the computational field, and after initial stabilization, it is switched to a higher-order format.

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