A multi-scale modeling method for compressor blade fouling

Abstract

The present application relates to the field of compressor blade fouling modeling, in particular to a two-dimensional multiscale geometric modeling method considering the non-uniform characteristics of compressor blade fouling. First, according to the real compressor blade fouling distribution, the fouling is divided into a compact layer and a loose layer, then a mathematical model of the compact layer fouling size, position and region is established, while considering the rough characteristics of the loose layer fouling, a mathematical model of the loose layer fouling rough unit height, width and phase is established, and based on the grid requirements of CFD calculation and the judgment of whether the modeling result meets the requirements of the real fouling topography, a non-uniform multiscale geometric model of the fouling compressor blade is constructed. The multiscale modeling method of the compressor blade fouling provided by the present application does not need to rely on the rough wall surface model in the commercial CFD software, and can realize the real representation of the non-uniform multiscale characteristics of the compressor blade fouling topography in the modeling stage, providing a new tool and a new method for more accurately evaluating the aerodynamic performance degradation of the fouling compressor.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of compressor blade fouling modeling, and particularly relates to a two-dimensional multi-scale geometric modeling method considering non-uniform characteristics of compressor blade fouling. TECHNICAL BACKGROUND

[0002] During the frequent variable working condition flight process of the aircraft (take-off, climb, cruise, boost, low altitude, landing, etc.), suspended particulate matters (dust, soot, hydrocarbon aerosol, pollen and salt, etc.) in the atmosphere are inevitably sucked into the aero-engine, and part of the particulate matters are deposited and accumulated for a long time to form a fouling phenomenon on the surface of the compressor blade. The compressor blade is small in size and high in load, and its performance is extremely sensitive to the blade profile. The fouling not only changes the geometric shape of the compressor blade to cause an increase in flow loss, but also blocks the flow passage to cause a decrease in the through-flow capacity of the engine.

[0003] Considering the time and working condition differences of the aero-engine operation, the diversity of the compressor blade shape and the complexity of the gas flow inside the compressor, which will affect the deposition of the fouling particles on the blade, and the diversity of the flight area of the aircraft leads to the difference in the types and sizes of the impurity particles existing in the atmospheric environment, these factors ultimately cause the compressor fouling to present different thickness distribution forms and fouling geometric characteristics. The fouling on the surface of the blade presents a multi-scale and non-uniform topographic feature, mainly manifested as an increase in the fouling thickness and a change in the rough structure of the fouling, and the rough structure of the surface after the fouling is not a regular shape, but an irregular non-uniform rough concave-convex profile change.

[0004] There are related researches on blade fouling, mainly by simply increasing the blade thickness and roughness to simulate the blade fouling. The roughness representation method of the blade fouling is to modify the turbulence model parameters by using the equivalent sand model, to study the influence of the rough surface of the blade caused by the fouling on the flow field of the compressor, which is not a true geometric modeling, and this method cannot be used for high-fidelity solving of the influence mechanism of the micro-scale disturbance of the fouling compressor blade on the flow field. The representation of the fouling thickness usually gives the same value from the leading edge to the trailing edge, which cannot represent the non-uniform fouling thickness of the compressor blade caused by the influence of the flow and the blade shape during the actual operation of the compressor. Therefore, the method of simply increasing the thickness and roughness to simulate the fouling cannot reflect the multi-scale, non-uniform and random geometric topographic characteristics of the actual blade fouling.

[0005] The aerodynamic performance of the compressor is extremely sensitive to the blade profile, and the macroscopic non-uniform thickness and the microscopic multi-scale roughness characteristics of the blade fouling must be considered to establish the compressor blade fouling geometry model, so as to as accurately as possible evaluate the influence mechanism of the fouling on the aerodynamic performance degradation of the compressor. Therefore, fully considering the macroscopic non-uniform thickness and the microscopic roughness of the blade fouling, developing a non-uniform and multi-scale modeling method for the compressor blade fouling is the basis and prerequisite for further evaluating the aerodynamic performance degradation of the fouling compressor. SUMMARY

[0006] The purpose of the present application is to realize the real representation of the non-uniform multi-scale characteristics of the blade fouling morphology of the compressor without relying on the rough wall model in the commercial CFD software in the modeling stage, and to provide a research basis for evaluating the aerodynamic performance degradation of the fouling compressor.

[0007] In order to achieve the above purpose, the present application provides a multi-scale and non-uniform compressor blade fouling modeling method, comprising the following steps:

[0008] Step 1: According to the morphology characteristics of the blade fouling, the blade fouling is divided into two parts of a compact layer and a loose layer, the compact layer changes smoothly and non-uniformly along the blade profile, and the loose layer has non-uniform multi-scale roughness characteristics along the blade profile, the compact layer fouling and the loose layer fouling are both defined as functions changing along the blade profile curve, and are respectively denoted as H0(x) and H1(x), x represents the position of the blade profile curve, and the size of the fouling y is defined as H0(x)+H1(x);

[0009] Step 2: According to the real blade fouling distribution area, the clean blade profile coordinates are divided into a plurality of areas, and each divided blade profile area coordinate is normalized, that is, x∈[0,1], in order to as accurately as possible describe the multi-scale roughness characteristics of the blade fouling, and at the same time meet the grid division requirements, l1μm≤x i+1 -x i ≤l2μm, so as to establish a model of different fouling distributions at different positions of the blade under the real condition, and facilitate the implementation of steps 3 and 4.

[0010] Step 3: Compact layer fouling establishment: the Hicks-Henne function is used to represent the non-uniform distribution characteristics of the compact layer H0(x) of the fouling blade, a series of control parameters are given to adapt to different compact layer fouling distributions, A0 controls the size of the compact layer of the fouling blade, t1 controls the position of the maximum value of the compact layer fouling, and t2 represents the change range of the compact layer fouling along the arc length on the blade surface;

[0011] Step 4: Loose layer fouling establishment: based on the superposition method of multiple cosine functions, the geometric model of the loose layer fouling is established, the variable A k is the height of the rough structure of the fouling in the kth function, and w kThe width of the fouling rough structure in the kth function is x, and x is the coordinate value in the horizontal direction, In order to avoid coupling a given random phase, the subscript k represents the serial number of the variable in the function, n is the number of multiple cosine functions, and the tight layer fouling size H1(x) is calculated;

[0012] Step 5, superimposing the tight layer fouling H0(x) and the loose layer fouling H1(x) at the same profile line position of the blade, the fouling size y at the corresponding profile line position is obtained;

[0013] Step 6, step 5 is the calculation of the fouling blade coordinate point, which specifically includes:

[0014] Step 6.1, selecting two coordinate points A and B on the clean blade which are close in distance to form a vector First, the modulus of the vector is taken as the minimum value l1μm, and the angle θ between the vector and the axial chord direction is calculated;

[0015] Step 6.2, based on the fouling size y at the coordinate point A and the angle θ, the vector perpendicular to the vector is calculated, and the fouling blade coordinate point on the vector is solved.

[0016] Step 6.3, repeating step 6.1 and step 6.2 until the fouling blade coordinate of all positions on the clean blade is obtained,

[0017] Step 6.4, all fouling coordinates are smoothly connected to obtain the profile of the fouling blade.

[0018] Step 7, output all the coordinates of the fouling blade in the format of geomturbo or dat file, import into Autogrid5 or ICEM software, check whether the fouling blade geometry file is continuous, and determine whether the grid file can meet the requirements of CFD calculation and be sufficient to describe the fouling blade, otherwise increase Δx=x i+1 -x i , repeat step 6 until the fouling compressor blade two-dimensional geometric model meeting the requirements is generated.

[0019] Compared with the prior art, the beneficial effects of the present application are:

[0020] (1) The present application considers the fouling distribution characteristics of the real compressor blade, and the fouling blade model established has the non-uniform and multi-scale roughness characteristics of the real compressor blade fouling.

[0021] (2) The application realizes the real representation of the non-uniform multi-scale characteristics of the fouling morphology of the compressor blade in the modeling stage, and the fouling compressor aerodynamic performance degradation research can be carried out without the rough wall solving algorithm of any commercial CFD solver, thereby providing a basic geometric model for the influence mechanism of the high-fidelity numerical solution of the fouling compressor blade on the flow field.

[0022] (3) The fouling blade model established in the application is not limited by the shape of the compressor blade, and provides a more accurate and reliable new method for evaluating the aerodynamic performance degradation of the fouling compressor, and has wider applicability. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a schematic diagram of a fouling blade;

[0024] Figure 2 is a non-uniform multi-scale fouling modeling flowchart;

[0025] Figure 3 is a schematic diagram of a non-uniform multi-scale fouling superposition method;

[0026] Figure 4 is a schematic diagram of non-uniform multi-scale fouling blade modeling results (different models of tight layer fouling distribution);

[0027] Figure 5 is a schematic diagram of non-uniform multi-scale fouling blade modeling results (different models of loose layer fouling distribution);

[0028] Figure 6 is a non-uniform multi-scale fouling blade modeling aerodynamic performance evaluation diagram (different models of tight layer fouling distribution);

[0029] Figure 7 is a non-uniform multi-scale fouling blade aerodynamic performance evaluation diagram (different models of loose layer fouling distribution). DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the application clearer, the following further describes the application in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the application and not to limit the application. In addition, the technical features involved in each embodiment of the application described below can be combined with each other as long as they do not conflict with each other.

[0031] Next, taking the pressure surface leading edge fouling thickness as an example, a two-dimensional non-uniform multi-scale model of the fouling blade is established.

[0032] Step 1, according to the morphology of the fouling, first in the normal direction, according to the fouling scale, it is divided into two parts of the tight layer (H0>0.1mm) and the loose layer (10μm≤H1≤100μm), the value is based on the existing blade fouling particle deposition results;

[0033] Step 2, in this example, the leading edge point and the trailing edge point are taken as the demarcation points, the blade profile is divided into the suction surface and the pressure surface two parts, and the blade profile coordinates from the leading edge point to the trailing edge point are normalized, that is, x∈[0,1], in order to as accurately as possible describe the multi-scale roughness characteristics of the blade fouling, Δx is taken as 10μm≤x i+1 -x i ≤100μm;

[0034] Step 3, the establishment of the tight layer fouling model: the specific calculation formula of the tight layer fouling is, Based on the actual compressor blade fouling, A0, t1, t2 are given to control the size, position and variation range of the tight layer. In this example, three different tight layer fouling sizes are given to evaluate the aerodynamic performance degradation of the different fouling blades, that is, A0=0.1, 0.15, 0.2, the tight layer fouling H0 maximum thickness position control parameter t1=0.1, which ensures that the maximum value position of the tight layer fouling is at 10% arc length position, t2=10 ensures that the tight layer changes in the entire pressure surface. Finally, the non-uniform distribution of the tight layer fouling from the leading edge to the trailing edge of the pressure surface is calculated.

[0035] Step 4, the establishment of the loose layer fouling model: the specific calculation formula of the loose layer fouling is, It is calculated and verified that n=3 can better describe the multi-scale roughness random characteristics of the loose layer fouling. The control parameters A k , ω k and are used to control the size, roughness unit peak valley width and phase of the loose layer fouling, so as to achieve the modeling purpose of the multi-scale characteristics of the loose layer fouling. In this example, a set of reference values of the control parameters are given for the modeling of the loose layer fouling, and the influence of different loose layer scales on the aerodynamic performance degradation of the fouling blade is evaluated.

[0036] Table 1 control parameter values of loose layer multi-scale modeling

[0037]

[0038] Step 5, the tight layer fouling and the loose layer fouling established in steps 3 and 4 are accumulated at the same profile position, that is, the fouling size

[0039] Step 6, the fouling profile coordinate points of the entire fouling area are calculated from the leading edge point as the starting point, which is specifically:

[0040] Step 6.1. Take the starting point as the first point A and the nearest point to the first point as the second point B to form a vector In order to describe the multi-scale roughness characteristics of the blade fouling as accurately as possible, first, the vector of the module is taken as the starting point A to draw a horizontal line, and the angle θ between the horizontal line and the vector is obtained, and the specific calculation formula is

[0041] Step 6.2. Based on the fouling size y of point A and the angle θ obtained, the fouling profile coordinate point C(z0, y0) at position A is calculated, and the specific calculation formula is as follows. The positive and negative in the specific calculation are based on the solution area.

[0042] z0=z1±sin(θ·y)

[0043] y0=y1±sin(θ·y)

[0044] Step 6.3. Steps 6.1 and 6.2 are performed on all coordinate points of the entire fouling profile area until all coordinate points of the fouling profile are calculated.

[0045] Step 6.4. The obtained all fouling profile coordinates are connected with smooth curves to obtain the profile line of the fouling profile.

[0046] Step 7. The obtained coordinate of the fouling profile is output in the format of geomturbo file, imported into Autogrid5 or ICEM software, the continuity of the fouling profile geometry file is checked, and it is judged whether the grid file conforming to the CFD calculation requirements and sufficient to describe the fouling profile can be established, otherwise Δx i+1 = Δx i +100μm, repeat step 6 until the required fouling compressor blade two-dimensional geometric model is finally generated.

[0047] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any skilled person in the art can easily think of various equivalent modifications or replacements within the technical range disclosed by the present application, and these modifications or replacements should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A multi-scale modeling method for compressor blade fouling, characterized in that, Includes the following steps: Step 1: Based on the morphological characteristics of the blade fouling, the blade fouling is divided into two parts: a compact layer and a loose layer. The compact layer is smooth and non-uniformly varied along the blade profile, while the loose layer has non-uniform multi-scale roughness along the blade profile. Both the compact layer fouling and the loose layer fouling are defined as functions that vary along the blade profile arc, denoted as H0(x) and H1(x) respectively, where x represents the position of the blade profile arc, and the fouling size is defined as y = H0(x) + H1(x). Step 2: Based on the actual distribution area of ​​blade fouling, divide the clean blade shape coordinates into several regions, and normalize the coordinates of each divided blade shape region, i.e., x∈[0,1]. In order to describe the multi-scale roughness characteristics of blade fouling as accurately as possible, and at the same time meet the mesh generation requirements of numerical calculation, ensure that l1μm≤x i+1 -x i ≤12μm, which facilitates the implementation of steps 3 and 4; Step 3, Establishment of the compact layer fouling: The Hicks-Henne function is used to characterize the non-uniform distribution of the compact layer H0(x) on the fouled blade. A series of control parameters are given to adapt to different compact layer fouling distributions. A0 controls the size of the compact layer on the fouled blade; t1 controls the location of the maximum value of the compact layer fouling; t2 characterizes the range of variation of the compact layer fouling along the arc length on the blade surface. The formula for calculating the compact layer fouling is defined as: Step 4, Establishment of loose deposits: A geometric model of loose deposits is established based on the multiple cosine function superposition method, with variable A. k w represents the height of the rough structure due to buildup in the k-th function. k Let x represent the width of the roughened structure in the k-th function, and x be the horizontal coordinate value. To avoid coupling with a given random phase, the subscript k represents the index of the variable in the function, and n is the number of multiple cosine functions. The size of the densely deposited fouling, H1(x), is calculated. The formula for calculating the loosely deposited fouling is defined as: Step 5: Superimpose the densely deposited scale H0(x) and the loosely deposited scale H1(x) at the same blade profile position to obtain the scale size y at the corresponding profile position; Step 6, Step 6 is the calculation of the coordinate points of the scale buildup blade, specifically including: Step 6.1: Select two relatively close coordinate points A and B on the clean leaf shape to form a vector. Calculate vectors The angle θ between the axial direction and the chord length direction; Step 6.2: Based on the obtained size y of the dirt accumulation at coordinate point A and the included angle θ, calculate the vector... Perpendicular vectors Solving vectors The coordinate points of the scale buildup on the blade shape; Step 6.3: Repeat steps 6.1 and 6.2 until the coordinates of the airfoil after all locations on the clean airfoil have accumulated dirt are obtained. Step 6.4: Smoothly connect all the scale coordinates to obtain the profile of the scale blade. Step 7: Output the coordinates of all fouling blade profiles in GeoMurbo or DAT file format, import them into Autogrid5 or ICEM software, check if the fouling blade profile geometry file is continuous, and determine if a mesh file that meets the CFD calculation requirements and is sufficient to describe the fouling blade profile can be created; otherwise, increase Δx = x. i+1 -x i Repeat step 6 until a two-dimensional geometric model of the fouled compressor blade that meets the requirements is generated.

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