Method for predicting particle deposition height and wall surface thermal coupling temperature

Abstract

The invention relates to the technical field of particle deposition thermal coupling, in particular to a method for predicting particle deposition height and wall surface thermal coupling temperature, which is suitable for predicting gas-solid two-phase flow and heat transfer behaviors in projects such as high-temperature heat flow equipment. According to the method, an unsteady heat-flow coupling field is established, and a migration track of particles in a flow field is released and tracked through a dispersed phase model; and after the particles are in contact with the wall surface, the deposition behavior of the particles is judged according to a particle deposition and rebound model, and deposition information of the deposited particles in the grid units is recorded. And a deposition layer area is identified in combination with the UDF, a transient heat conduction equation of the deposition layer is established, a deposition layer temperature field is iteratively solved, the solid wall surface temperature is updated, and a deposition-heat conduction-wall temperature feedback mechanism is formed. According to the method, the time-space evolution characteristics of the sedimentary layer and the influence of the time-space evolution characteristics on thermal load distribution are fully considered, and the precision of particle deposition thermal coupling prediction can be remarkably improved.

Description

Technical Field

[0001] The present invention relates to the field of particle deposition thermal coupling technology, and in particular to a method for predicting particle deposition height and wall thermal coupling temperature. Background Art

[0002] The phenomenon of particulate matter deposition on walls is widespread in fields such as aerospace, energy and power, industrial thermal engineering, and environmental control, significantly impacting heat load distribution and equipment reliability. For example, during the operation of aircraft engines or ground-based gas turbines, inhaled solid particles such as dust and volcanic ash, as well as fine particles such as fuel impurities, are easily transported into the combustion chamber and turbine components with high-temperature, high-speed airflow and deposited on high-temperature walls. In coal-fired boilers or industrial heat exchangers, ash entrained in flue gas can also deposit on heated surfaces, reducing heat transfer efficiency and increasing the risk of equipment wear. Furthermore, in environmental and biological systems, such as aerosol drug transport and filtration equipment operation, particle deposition on walls or filter materials is also a concern. Therefore, accurately predicting the morphology of particle deposition and its impact on the wall temperature field is crucial for the efficient design, operation, and maintenance of high-temperature heat flow equipment.

[0003] Existing studies mainly use a combination of numerical simulation and experimental testing to analyze particle deposition behavior. In terms of numerical simulation, discrete phase models (DPMs) are often used to track particle motion, and deposition criteria are set through user-defined functions (UDFs). However, traditional deposition simulation methods usually only focus on the adhesion probability after particle impact, and fail to effectively consider the feedback effect of the dynamic growth of the deposition layer on the flow field and thermal field. Especially under high-temperature conditions, the formation of the deposition layer will change the wall roughness, thermal conductivity and temperature distribution, thereby further affecting the secondary deposition behavior of the particles, which limits the prediction accuracy. In addition, existing methods often ignore the cumulative effect of particle deposition height, making it difficult to accurately describe the impact of the deposition layer on heat transfer characteristics after long-term operation. Therefore, there is an urgent need for a numerical calculation method that can simultaneously consider the evolution of deposition height and transient thermal coupling of the wall to improve the simulation accuracy of the particle deposition process. Summary of the Invention

[0004] In response to the technical problems raised above, a method for predicting the particle deposition height and the wall thermal coupling temperature is provided. The present invention establishes an unsteady thermal flow coupling field, and releases and tracks the migration trajectory of particles in the flow field through a discrete phase model (DPM); when the particles contact the wall, their deposition behavior is judged based on the particle deposition and rebound model, and the deposition quality, quantity and height information of the deposited particles are recorded in the grid unit. Combined with UDF to identify the deposition layer area, after meeting the thermal conductivity stability conditions, the transient heat conduction equation of the deposition layer is established, the deposition layer temperature field is iteratively solved, and the solid wall temperature is updated to form a deposition-heat conduction-wall temperature feedback mechanism.

[0005] The technical means adopted in the present invention are as follows:

[0006] A method for predicting particle deposition height and wall thermal coupling temperature, comprising:

[0007] Establish the geometric model of the cascade and perform structured meshing;

[0008] Numerical simulation of unsteady flow-thermal coupling, solving flow equations, energy equations and turbulence equations in unsteady flow fields;

[0009] Use discrete phase models to simulate the release of particles in the flow field and the migration trajectory of particles in the flow field;

[0010] Determine the motion state of particles after impacting the wall using a particle deposition model; the motion state includes deposition on the wall and returning to the flow field after rebounding;

[0011] If the particle's motion state after impacting the wall is to bounce back and return to the flow field, the migration trajectory will continue to be tracked. If the particle's motion state after impacting the wall is to deposit on the wall, the deposition information will be recorded in the corresponding unit grid.

[0012] Calculate the minimum spatial step size and the number of virtual network layers in the deposition layer;

[0013] Determine whether the deposition height at each location on the wall satisfies the stability conditions of the unsteady-state heat transfer equation. If not, the wall temperature is not updated. If it is, the temperature field is iteratively solved based on the thermal conductivity parameters of the deposition. Once thermal equilibrium is reached, the wall temperature is updated.

[0014] Furthermore, a pressure-velocity coupling algorithm is used to process fluid flow during the unsteady flow-heat coupling numerical simulation.

[0015] Furthermore, the discrete phase model combines models of multiple forces, including gravity, thermophoretic force, bidirectional coupling force between particles and fluid, and Saffman lift caused by shear force.

[0016] Furthermore, the particle deposition model uses a critical viscosity model, and the deposition probability P s (T p ) Determine the motion state of the particle after impacting the wall:

[0017]

[0018] Among them, μ critical represents the viscosity of the particles at the critical temperature, μ Tp Indicates the viscosity of the particle at the current temperature.

[0019] Furthermore, the deposition information includes: deposition quantity, deposition quality, grid unit area and density; the deposition height is calculated using the deposition information:

[0020]

[0021] Where C is a constant, m particle represents the mass of a single particle, ρ particle Represents the density of a single particle, A cell Indicates the area of ​​the grid cell corresponding to the deposition location.

[0022] Furthermore, the calculation of the minimum spatial step size and the number of virtual network layers of the deposition layer specifically includes:

[0023] Minimum spatial step size F O Need to meet:

[0024]

[0025] Where α is the thermal diffusivity, Δt is the time step, and Δx is the space step;

[0026] Calculate the number of virtual grid layers in the sedimentary layer:

[0027]

[0028] Where n is the number of virtual grid layers.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] The method for predicting particle deposition height and wall thermal coupling temperature provided by the present invention couples the particle motion, deposition layer growth, and wall heat transfer processes, does not require redundant mesh operations, and is applicable to more complex geometric appearance models. The gas-solid-solid (3D / 1D / 3D) transient heat transfer model proposed in the present invention can more accurately reproduce the particle deposition characteristics and their impact on the wall heat transfer performance in high-temperature heat flow equipment under high-temperature gas environments.

[0031] The method for predicting particle deposition height and thermally coupled wall temperature provided by this invention can be used to predict the impact of particle deposition on blade surface heat loads. It is suitable for studying gas-solid two-phase flow and heat transfer in gas turbines, high-temperature thermal flow equipment, and related engineering applications. In engineering applications, this method can be used to predict maintenance cycles for particle flow equipment, assess the impact of deposition layers on cooling efficiency, provide a basis for blade cleaning and replacement, and support the efficient gas-thermal optimization design of high-temperature components.

[0032] Based on the above reasons, the present invention can be widely promoted in the fields of particle deposition thermal coupling and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0034] Figure 1 This is a flow chart of the method for predicting particle deposition height and wall thermal coupling temperature in the present invention.

[0035] Figure 2 Schematic diagram of the gas-solid-solid boundary in an embodiment of the present invention.

[0036] Figure 3 Schematic diagram of the gas-solid-solid transient heat transfer model (3D / 1D / 3D) in an embodiment of the present invention.

[0037] Figure 4 This is a comparison chart of experimental measurement and numerical prediction results of the deposit height on the center line of the target surface after flat plate impact cooling particle deposition in an embodiment of the present invention. DETAILED DESCRIPTION

[0038] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0039] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0040] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0041] Unless otherwise specified, the relative arrangement of the parts and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be clear that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to actual proportional relationships. The technology, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be considered as a part of the specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of the exemplary embodiments can have different values. It should be noted that similar numbers and letters represent similar items in the following drawings, and therefore, once an item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0042] In the description of the present invention, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "horizontal, vertical, vertical, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention: the directional words "inside and outside" refer to the inside and outside relative to the outline of each component itself.

[0043] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used herein to describe the spatial positional relationship of a device or feature to other devices or features as shown in the figures. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figures. For example, if the device in the drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below their position devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0044] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0045] like Figure 1As shown, the present invention provides a method for predicting particle deposition height and wall thermal coupling temperature, comprising:

[0046] Establish the geometric model of the blade cascade and perform structured meshing. In the implementation, the vertical blade cascade model is used as the research object, and the ICEM is used to perform structured meshing on the model. At the same time, the boundary layer is reasonably applied according to the actual operating conditions. A sufficient number of boundary layers are divided around the blades. The number of boundary layer grid layers and the height of the first layer grid must meet the Y of the steady-state calculation. + (y-plus) value is less than or equal to 1, Y + The (y-plus) value is a dimensionless wall distance parameter used to assess whether the mesh resolution near the wall is sufficiently accurate to capture the boundary layer properties:

[0047]

[0048] Where ρ is the fluid density, u τ is the friction velocity, y is the distance from the wall to the first calculation point, and μ is the fluid dynamic viscosity.

[0049] The unsteady flow-thermal coupling method is used to numerically simulate the flow, energy, and turbulence equations in the unsteady flow field. The SST k-omega turbulence model is used for simulation, and a suitable time step is selected for calculation.

[0050] In specific implementation, as a preferred embodiment of the present invention, a pressure-velocity coupling algorithm is used to process fluid flow during the unsteady flow-heat coupling numerical simulation.

[0051] During implementation, the particle release is simulated after the numerical simulation results of the continuous phase fluid converge. This moment is marked as t = 0, where t is the time of the unsteady calculation. The interaction between the particles and the flow field is considered in the two-phase flow, tracking the migration trajectory of the particles in the flow field and simultaneously obtaining the collision parameters of the particles on the wall.

[0052] The discrete phase model (DPM) in Fluent is used to simulate the release of particles in the flow field and the migration trajectory of particles in the flow field;

[0053] In specific implementation, as a preferred embodiment of the present invention, the discrete phase model combines models of multiple forces, including gravity, thermophoretic force, bidirectional coupling force between particles and fluid, and Saffman lift caused by shear force, taking into account the influence of multiple forces on the particles themselves.

[0054] In order to save computing power and obtain deposition characteristics as quickly as possible, the accelerated deposition method was used in the calculation. The particle concentration was multiplied by the amplification factor. However, the amplified particle concentration must satisfy the requirement that the volume fraction of particles in the flow field is less than 10% to ensure sparse multiphase flow.

[0055] Determine the motion state of particles after impacting the wall using a particle deposition model; the motion state includes deposition on the wall and returning to the flow field after rebounding;

[0056] In specific implementation, as a preferred embodiment of the present invention, the particle deposition model uses the critical viscosity model, and the deposition probability P s (T p ) Determine the motion state of the particle after impacting the wall:

[0057]

[0058] Among them, μ critical represents the viscosity of the particles at the critical temperature, μ Tp Indicates the viscosity of the particle at the current temperature.

[0059] If the particle's motion state after impacting the wall is to bounce back and return to the flow field, the migration trajectory will continue to be tracked. If the particle's motion state after impacting the wall is to deposit on the wall, the deposition information will be recorded in the corresponding unit grid.

[0060] In specific implementation, as a preferred embodiment of the present invention, the deposition information includes: deposition quantity, deposition quality, grid unit area and density; the deposition height is calculated using the deposition information:

[0061]

[0062] Among them, C is a constant, is a parameter regulator, and m particle represents the mass of a single particle, ρ particle Represents the density of a single particle, A cell Indicates the area of ​​the grid cell corresponding to the deposition location.

[0063] During implementation, deposition information is recorded through UDM. UDM (User-Defined Memory) is a user-defined memory, a function used to store custom data, allowing users to define additional storage variables on mesh cells, surfaces, or nodes.

[0064] Calculate the minimum spatial step size and the number of virtual network layers in the deposition layer;

[0065] In specific implementation, as a preferred embodiment of the present invention, the calculation of the minimum spatial step size and the number of virtual network layers of the deposition layer specifically includes:

[0066] Minimum spatial step size FO Need to meet:

[0067]

[0068] Where α is the thermal diffusivity, Δt is the time step, and Δx is the space step;

[0069]

[0070] Where λ is the thermal conductivity, ρ is the fluid density, C P is the specific heat capacity at constant pressure.

[0071] Calculate the number of virtual grid layers in the sedimentary layer:

[0072]

[0073] Where n is the number of virtual grid layers. The value of the spatial step length Δx is based on the minimum characteristic thickness caused by particle deposition.

[0074] Determine whether the deposition height at each location on the wall satisfies the stability conditions of the unsteady-state heat transfer equation. If not, the wall temperature is not updated. If it is, use the UDF to calculate the flow field data outside the deposition layer and determine the boundary conditions of the equation. It iteratively solves the temperature field based on the thermal conductivity and other physical properties of the deposition. After reaching thermal equilibrium, the wall temperature is updated and the calculation proceeds to the next time step.

[0075] Example

[0076] like Figure 1 As shown, the present invention provides a method for predicting particle deposition height and wall thermal coupling temperature. The present invention can be used to predict the impact of particle deposition process on solid surface heat load, and is suitable for gas-solid two-phase flow and heat transfer research in gas turbines, high-temperature heat flow equipment and related engineering applications.

[0077] In this embodiment, the thermal boundary is regarded as a gas-solid-solid heat transfer boundary, such as Figure 2 As shown, a 3D / 1D / 3D transient heat transfer model is introduced, such as Figure 3 As shown in the figure, the particle deposition layer is simplified into a 1D heat conduction region perpendicular to the wall, and n computational units are divided into it. Note that this 1D region is only used as a heat conduction calculation region and not a physical geometric structure. The upstream gas and the downstream blade solid are connected at both ends to realize a three-segment heat conduction link. The temperature T of the adjacent unit on the wall is extracted from the 3D flow field. g , as the upper surface boundary condition of the 1D model; and extract the bottom temperature T from the blade solid structure blade , as the bottom boundary condition of the 1D model.

[0078] In order to finally verify the reliability, accuracy and practicality of the method of the present invention, the shock cooling structure in the flat plate shock cooling particle deposition experiment conducted by Bowen and Bons was used as the research object, and two areas were selected on the back side of the target surface just below the center line of the shock tube, with diameters of 1 and 2 times the diameter of the shock tube, respectively, and recorded as Z1 and Z2. Figure 4 The simulated predicted values ​​of the target surface average temperature in the two regions were quantitatively compared with the experimental measured values. The results show that the method proposed in the present invention has good reliability, accuracy and effectiveness.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for predicting particle deposition height and wall thermal coupling temperature, characterized in that: include: Establish the geometric model of the cascade and perform structured meshing; Numerical simulation of unsteady flow-thermal coupling, solving flow equations, energy equations and turbulence equations in unsteady flow fields; Use discrete phase models to simulate the release of particles in the flow field and the migration trajectory of particles in the flow field; Determine the motion state of particles after impacting the wall using a particle deposition model; the motion state includes deposition on the wall and returning to the flow field after rebounding; If the particle's motion state after impacting the wall is to bounce back and return to the flow field, the migration trajectory will continue to be tracked. If the particle's motion state after impacting the wall is to deposit on the wall, the deposition information will be recorded in the corresponding unit grid. Calculate the minimum spatial step size and the number of virtual network layers in the deposition layer; Determine whether the deposition height at each location on the wall satisfies the stability conditions of the unsteady-state heat transfer equation. If not, the wall temperature is not updated. If it is, the temperature field is iteratively solved based on the thermal conductivity parameters of the deposition. Once thermal equilibrium is reached, the wall temperature is updated.

2. The method for predicting particle deposition height and wall thermal coupling temperature according to claim 1, characterized in that: During the unsteady flow-heat coupling numerical simulation, a pressure-velocity coupling algorithm is used to process the fluid flow.

3. The method for predicting particle deposition height and wall thermal coupling temperature according to claim 1, characterized in that: The discrete phase model combines models of multiple forces, including gravity, thermophoretic force, bidirectional coupling force between particles and fluid, and Saffman lift caused by shear force.

4. The method for predicting particle deposition height and wall thermal coupling temperature according to claim 1, characterized in that: The particle deposition model adopts the critical viscosity model through the deposition probability P s (T p ) Determine the motion state of the particle after impacting the wall: Among them, μ critical represents the viscosity of the particles at the critical temperature, μ Tp Indicates the viscosity of the particle at the current temperature.

5. The method for predicting particle deposition height and wall thermal coupling temperature according to claim 1, characterized in that: The deposition information includes: deposition quantity, deposition quality, grid unit area and density; the deposition height is calculated using the deposition information: Where C is a constant, m particle represents the mass of a single particle, ρ particle Represents the density of a single particle, A cell Indicates the area of ​​the grid cell corresponding to the deposition location.

6. The method for predicting particle deposition height and wall thermal coupling temperature according to claim 1, characterized in that: The calculation of the minimum spatial step size and the number of virtual network layers of the deposition layer specifically includes: Minimum spatial step size F O Need to meet: Where α is the thermal diffusivity, Δt is the time step, and Δx is the space step; Calculate the number of virtual grid layers in the sedimentary layer: Where n is the number of virtual grid layers.

Images