CN108090299B - Design method for pre-arching shape of photo-thermal heat absorber prestressed tube bundle or tube panel - Google Patents
Design method for pre-arching shape of photo-thermal heat absorber prestressed tube bundle or tube panel Download PDFInfo
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Abstract
The invention provides a method for designing a pre-arching shape of a pre-stressed tube bundle or a tube panel of a photo-thermal heat absorber, and belongs to the technical field of pre-stress design. The design method comprises the following steps: solving the temperature field, solving the deformation shape of the tube bundle or tube panel, and solving the stress sigma of the normal temperature state without considering energy flow inputPDetermining an adjustment coefficient k and determining an arching curve of the tube bundle or tube panel. The design method can quickly and accurately design the bending pre-arching shape of the tube bundle or the tube panel of the photothermal heat absorber, and the pre-arching shape curve calculated according to the design method applies prestress to the tube bundle or the tube panel of the photothermal heat absorber, so that the capability of the tube bundle or the tube panel of the photothermal heat absorber for bearing the maximum heat flux density can be effectively improved, and the strength requirement of the photothermal heat absorber at the actual working temperature during illumination can be met.
Description
Technical Field
The invention belongs to the technical field of prestress design, particularly relates to a design of prestress of a unilaterally heated photo-thermal heat absorber, and particularly relates to a design method of a pre-arching shape of a pre-stressed tube bundle or a tube panel of the photo-thermal heat absorber.
Background
Under the irradiation of maximum energy flux density, the single-side heated heat absorber, especially the photothermal heat absorber, generates higher temperature difference between the light side and the backlight side of the tube bundle or tube panel. If the lateral displacement of the tube bundle or tube panel is limited, high thermal stresses will be generated. By the prestress method, the highest stress of the tube bundle or tube panel can be reduced, and the capacity of the tube panel or tube bundle capable of bearing the peak value of the heat flux density can be improved. The method comprises the steps of firstly arching and bending a tube bundle or a tube panel in advance, carrying out heat treatment, and finally assembling to form prestress. How to rapidly calculate the reasonable bending shape of the tube bundle or the tube panel aiming at the heating characteristics of the photo-thermal heat absorber is the key for designing the prestress.
Disclosure of Invention
The invention aims to provide a design method for the pre-arching shape of a unilateral heat-receiving prestressed tube bundle or a tube panel of a photo-thermal heat absorber and the like.
The purpose of the invention is realized by the following technical scheme:
the design method of the invention is mainly realized by two stages: 1. calculating the free bending shape of the tube bundle or the tube panel under the action of temperature gradient to be an initial bending shape through the input of energy flow density; 2. and adjusting the initial bending shape by a numerical simulation method to finally determine the bending and arching shape. The specific implementation mode is as follows:
a design method for a pre-arching shape of a pre-stressed tube bundle or a tube panel of a photo-thermal heat absorber comprises the following steps:
A. solving a temperature field
Calculating the temperature field of the tube bundle or the tube panel according to the actual heat flux density input and the medium flow of the tube wall of the photo-thermal heat absorber;
B. solving tube bundle or tube panel deformation shape
Reading the temperature field result obtained in the step A into analysis software, setting constraints at the upper end and the lower end of the tube bundle or the tube panel, not setting any constraint point in the middle, and solving the deformation shape of the tube bundle or the tube panel;
C. solving stress sigma of normal temperature state without considering energy flow inputp
And D, reversing the deformation shape obtained in the step B to obtain a shape which is symmetrical and opposite to the deformation shape of the deformation shape and is used as an initial arching shape curve, selecting a prestress supporting point of the tube bundle or the tube panel, setting upper and lower end constraints, and applying displacement to the axial position of the straight tube at the prestress supporting point0Solving the stress σ at normal temperature regardless of the input of energy flowp；
D. Determining an adjustment factor k
The stress sigma at normal temperature obtained in the step CpSolving an adjustment coefficient k:
wherein C is an intensity adjustment coefficient; [ sigma ]]tAllowable stress value of the material at the working temperature;
E. determining pre-arching curves for tube bundles or tube panels
Displacing the displacement obtained in the step 3)0Multiplying the displacement by an adjusting coefficient k to obtain the actual displacement required to be applied by the pre-arching of the tube bundle or the tube panelp＝k0(ii) a Multiplying the initial arching shape curve obtained in the step 3) by an adjusting coefficient k to obtain the pre-arching shape curve of the tube bundle or the tube panel.
In the step C, two prestressed supporting points are provided, and the vertical distance between the two prestressed supporting points and the upper and lower ends of the tube bundle or the tube panel is 1/4L-1/3L, where L is the vertical length of the projection of the whole tube bundle or the tube panel in the axial direction.
As a specific embodiment of the method for designing the pre-arching shape of the pre-stressed tube bundle or tube panel of the photothermal heat absorber, in step a, the temperature field is calculated by using fluid mechanics (CFD) analysis software.
As a specific embodiment of the method for designing the pre-arching shape of the pre-stressed tube bundle or tube panel of the photothermal heat absorber, in the step a, the medium is one or more of air, water, steam, heat transfer oil, liquid metal and molten salt.
As a specific embodiment of the method for designing the pre-arching shape of the pre-stressed tube bundle or tube panel of the photothermal heat absorber, in step B, the analysis software is Finite Element (FEA) structural analysis software.
As a specific embodiment of the method for designing the pre-arching shape of the pre-stressed tube bundle or tube panel of the photothermal heat absorber, in step C, the initial arching shape may be fitted according to the characteristics of the process to determine the initial arching shape as a rough shape.
In step D, a value range of C is 0.5 < C < 1, and a value of C is 0.9.
As a specific embodiment of the method for designing the pre-arching shape of the pre-stressed tube bundle or the tube panel of the photo-thermal heat absorber, in step E, the pre-arching shape curve of the tube bundle or the tube panel can be fitted into a bent tube or a bent-line bent tube according to a factory manufacturing process.
As a specific embodiment of the method for designing the pre-arching shape of the pre-stressed tube bundle or the tube panel of the photothermal heat absorber, in step E, the specific fitting process of curve fitting the pre-arching shape of the tube bundle or the tube panel into the polygonal-line bent tube includes:
step C, applying the displacement to the axial line position of the straight pipe at the position of the obtained prestress fulcrum0While obtaining the vertical displacement of the middle point of the tube bundle or the tube panel from the axial position of the straight tube, namely the displacement of the middle positionc；
The radius of the bent pipe in the bent line bent pipe is calculated by the following formula:
in the above formula: l is the vertical length of the whole tube bundle or the projection of the tube bundle in the axial direction; l is1The vertical length of the projection of the distance between the prestress branch point and the upper end and the lower end of the tube bundle or the tube panel on the axial direction is shown;cp＝kc；p＝k0。
in the specific factory manufacturing process, the length and slope of the broken line are according to the displacementpAnd L1Determining, and finally using the calculated radius of the bent pipe as an arc, wherein a curve obtained between the radius of the bent pipe and the intersection point of the bent pipe and the broken lines on the two sides is the bent pipe obtained by fitting, and a curve obtained by overlapping and fitting the bent pipe and the broken lines on the two sides is the bent pipeThe method is used for fitting the obtained pre-arching curve of the bent pipe with the broken line according to the factory manufacturing process.
The specific embodiment of the method for designing the pre-arching shape of the pre-stressed tube bundle or tube panel of the photothermal heat absorber provided by the invention comprises the following steps:
A. solving tube bundle temperature field under working condition
Calculating a tube bundle temperature field under a working condition through fluid mechanics (CFD) analysis software according to the actual heat flux density input and the medium flow of the tube wall of the photothermal heat absorber; wherein the mass flow of a single tube bundle is 2.466kg/s, and the inlet temperature is 290 ℃;
B. solving free deformation shape of tube bundle at working temperature
B, introducing the temperature obtained in the step A into Finite Element (FEA) structure analysis software, setting upper and lower end constraints of the tube bundle, not setting any constraint point in the middle, and solving the obtained tube bundle deformation shape;
C. solving the prestress sigma under the initial arching shapep
Reversing the deformed shape obtained in the step B to obtain a shape which is symmetrical and opposite to the deformed shape of the deformed shape and is used as an initial arching shape curve; two prestress fulcrums are arranged at positions which are respectively arranged at the positions with the vertical distance of 1/4L-1/3L from the upper end and the lower end of the tube bundle, after the prestress fulcrums are arranged, the constraint of the upper end and the lower end is well arranged, and displacement towards the axial line position of the straight tube is exerted at the prestress fulcrums0＝2.33m；
Solving and obtaining the normal temperature state sigma without considering the input of energy flow by utilizing finite element structural analysis softwarep＝280.37MPa；
D. Determining an adjustment factor k
Obtaining σ according to step C abovepDetermining an adjusting coefficient k;
k＝C×[σ]t/σp＝0.9×280/280.37＝0.899；
wherein: c is 0.9; [ sigma ]]t＝280MPa；σp＝280.37MPa；
E determining a pre-arching curve of a tube bundle or tube panel
The product obtained in the step C isDisplacement of0Multiplying the displacement by an adjusting coefficient k to obtain the actual displacement required to be applied by the pre-arching of the tube bundle or the tube panelp：
p＝k0＝0.899×2.33m＝2.095
And D, multiplying the initial arching shape curve obtained in the step C by an adjusting coefficient k to obtain the pre-arching shape curve of the tube bundle or the tube panel.
The invention has the following beneficial effects:
the design method can quickly and accurately design the bending pre-arching shape of the tube bundle or the tube panel of the photothermal heat absorber, and the pre-arching shape curve calculated according to the design method applies prestress to the tube bundle or the tube panel of the photothermal heat absorber, so that the capability of the tube bundle or the tube panel of the photothermal heat absorber for bearing the maximum heat flux density can be effectively improved, and the strength requirement of the photothermal heat absorber at the actual working temperature during illumination can be met.
Drawings
FIG. 1 is a schematic flow chart of a method for designing a pre-arching shape of a pre-stressed tube bundle or a tube panel of a photothermal heat absorber according to the present invention;
FIG. 2 is a graph of energy flow density for illumination and shape without regard to bundle camber as simulated in step A of example 1;
FIG. 3 is a tube bundle deformation shape solved according to the upper and lower end constraint points in step B of example 1;
FIG. 4 is an initial arching shape obtained after step B in example 1 is reversely symmetrical according to the deformed shape of the tube bundle;
FIG. 5 is a graph showing distribution of prestressed pivot setting, prestressed pivot displacement, and intermediate position displacement in step C of example 1;
FIG. 6 is a comparison of the adjusted pre-arching curve of the tube bundle and the initial arching shape curve of example 1;
FIG. 7 is a graph of pre-arching curves for a dog leg elbow in example 1, according to the factory fabrication process.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The method for designing the pre-arching shape of the pre-stressed tube bundle or tube panel of the photothermal heat absorber is described in detail below by combining specific principles and calculation processes.
The invention discloses a method for designing a pre-arching shape of a pre-stressed tube bundle or a tube panel of a photo-thermal heat absorber, which has a specific flow shown in figure 1 and comprises the following steps:
step A of solving the temperature field
And calculating the temperature field of the tube bundle or the tube panel according to the actual heat flux density input and the medium flow of the tube wall of the photothermal heat absorber.
The purpose of solving the temperature field in the step A is to obtain the deformation shape of the tube bundle or the tube panel in actual work according to the result of the temperature field.
Specifically, according to the actual heat flow density input and medium flow of the wall of the photothermal heat absorber, calculating the temperature field of the tube bundle or the tube panel through fluid dynamics (CFD) analysis software;
further, the fluid mechanics (CFD) analysis software is preferably one or more of Fluent, CFX, Star-CD, and phoenicics, and those skilled in the art may select the software according to specific use requirements and conditions, as long as the software can calculate the temperature field according to the heat flow density and the medium flow rate, and the calculation process and the use method using the software are routine and easy for those skilled in the art to implement, and are not specifically illustrated and limited herein.
Furthermore, the medium is air, water, steam, heat conduction oil, liquid metal, molten salt and the like, and for the concentrating solar power generation system, the molten salt working medium has good stability due to the characteristics of moderate heat conductivity and large specific heat, and can be used as a good high-temperature heat conduction medium and a good heat storage medium. Further, the molten salt is preferably NaNO3-KNO3Binary molten salt and NaNO2-KNO3-NaNO3The specific gravity of each component of the ternary molten salt is different, which directly influences the performance of the molten salt and is determined according to the requirementsThe usage requirements of the body are selected.
In the specific solving process of the temperature field in this step, a person skilled in the art can input specific media types according to actual heat flow densities, and solve the temperature field of the tube bundle or the tube panel by combining with fluid mechanics (CFD) analysis software, and the specific calculation process is routine and easy to be implemented by the person skilled in the art.
Step B, solving the deformation shape of the tube bundle or the tube panel
And C, reading the temperature field result obtained in the step A into analysis software, setting constraints at the upper end and the lower end of the tube bundle or the tube panel, and solving the deformation shape of the tube bundle or the tube panel without setting any constraint point in the middle.
And B, solving the deformation shape of the tube bundle or the tube panel according to the temperature field result obtained in the step A, and inputting the temperature field result into specific analysis software to obtain the deformation shape of the tube bundle or the tube panel in actual work.
Specifically, reading the temperature field result obtained in the step A into Finite Element (FEA) structure analysis software, setting constraints at the upper end and the lower end of the tube bundle or the tube panel, not setting any constraint point in the middle, and solving the deformation shape of the tube bundle or the tube panel.
Further, the Finite Element (FEA) structure analysis software is preferably one or more of Ansys, ABAQUS, HyperWorks, Nastran and the like. The software can be selected by those skilled in the art according to specific use requirements and situations, as long as the software can calculate the deformed shape of the tube bundle or the tube panel according to the result of the temperature field, and the calculation process and the use method using the software are routine and easy for those skilled in the art, and are not specifically described and limited herein.
The purpose of setting the constraints of the upper end and the lower end of the tube bundle or the tube panel and not setting any constraint point in the middle is to solve the deformation shape of the tube bundle only under the action of temperature, and the deformation is used as the initial shape of the bending shape after being reversely adjusted. In order to solve the bending deformation caused by the simple temperature effect, the tube bundle cannot be restrained too much, so the invention preferably sets the restraint at the upper end and the lower end of the tube panel or the tube bundle and does not set any restraint point in the middle. Common constraints are implemented as (without limitation): the translational freedom degrees of one end in three directions are restricted, but the rotational freedom degrees of the end in the bending direction cannot be limited, and the translational freedom degrees of the other end are restricted, but the axial freedom degrees of the tube bundle or the tube panel and the rotational freedom degrees of the tube bundle or the tube panel in the bending direction cannot be limited. The specific restraining arrangements of the tube bundles or tube panels of the present invention are conventional and readily achievable by those skilled in the art, as is the operation of conventional restraint.
Step C, solving the stress sigma of the normal temperature state without considering the input of energy flowp
And D, reversing the deformation shape obtained in the step B to obtain a shape which is symmetrical and opposite to the deformation shape of the deformation shape and is used as an initial arching shape curve, selecting a prestress supporting point of the tube bundle or the tube panel, setting upper and lower end constraints, and applying displacement to the axial position of the straight tube at the prestress supporting point0Solving the stress σ at normal temperature regardless of the input of energy flowp。
Specifically, the deformed shape obtained in the step B is reversed, a shape which is symmetrical and opposite to the deformed shape is obtained and is used as an initial arching shape curve, and fitting can be carried out according to the characteristics of process manufacturing to determine the shape as an approximate shape; then selecting a prestress supporting point of the tube bundle or the tube panel, setting upper and lower end point constraints, and applying displacement along the light-facing surface at the prestress supporting point0Solving the stress σ at normal temperature regardless of the input of energy flowp。
Specifically, fitting is performed according to the characteristics of the process manufacturing, and the initial arching shape curve is determined to be an approximate shape, so that the obtained initial arching shape curve can meet the requirements of the production process, a person skilled in the art can fit the initial arching shape curve into a bent pipe or a bent line bent pipe which is more convenient for producing actual requirements according to the fitting method of the step E of the present invention, fitting can also be performed according to a fitting manner which can be realized by the person skilled in the art and the actual production, and no specific limitation is imposed here as long as the requirements of the production process can be met.
Furthermore, the number of the prestressed supporting points is two, the vertical distance between the prestressed supporting points and the upper end and the lower end of the tube bundle or the tube panel is 1/4L-1/3L, wherein L is the vertical length of the projection of the whole tube bundle or the tube panel in the axial direction; the distance between the prestress support point and the upper end and the lower end of the tube panel is only the vertical length of the axial projection of the prestress support point and the end point on the tube bundle or the tube panel. The reason for this arrangement of the prestressed pivot is: the energy flow density of illumination is approximately in normal distribution, the temperature near the middle section of the tube bundle or the tube panel is highest, the bending moment near the middle section is largest, and the stress is highest; in the prestressed structure, the back pressure of the fulcrum can form reverse bending moment to offset bending moment caused by temperature so as to reduce stress. Two back pressure points are arranged near the regions 1/3-1/4, the formed prestress bending moment is trapezoidal, the magnitude of the prestress bending moment can be well controlled, and the stress offset is easier to control.
In addition, the specific operation of setting the upper and lower end point constraints in the step is similar to the specific operation of setting the constraints of the upper and lower ends of the tube bundle or the tube panel in the step B, and the operation is carried out according to the implementation mode of the step B.
In this step, the stress σ at normal temperature state is not considered in consideration of the energy flow inputpThe finite element software is adopted for solving, and the solving formula and the solving process are conventional and easy to realize for the technicians in the field, according to the related introduction of the invention, and the finite element analysis software and the solving formula are combined, the stress sigma of the normal temperature state without considering the input energy can be realizedpAnd (4) solving.
Step D determining an adjustment factor k
The stress sigma at normal temperature obtained in the step CpSolving an adjustment coefficient k:
wherein C is an intensity adjustment coefficient;
[σ]tallowable stress value of the material at the working temperature;
c is a strength adjustment coefficient, specifically an adjustment coefficient of a safety factor considered according to a stress change caused by manufacturing deviation, material stress relaxation and creep, and a specific value thereof is related to the manufacturing process and the characteristics of the material itself, and a person skilled in the art can set the strength adjustment coefficient according to the characteristics of the manufacturing process and the material itself in a specific setting process, which is conventional and easy to implement for the person skilled in the art. Further, the value range of C is more than 0.5 and less than 1; still more preferably 0.9.
[σ]tThe allowable stress value of the material at the working temperature can be obtained by searching the material standard.
Step E, determining a pre-arching curve of the tube bundle or tube panel
Shifting the obtained step C0Multiplying the displacement by an adjusting coefficient k to obtain the actual displacement required to be applied by the pre-arching of the tube bundle or the tube panelp＝k0(ii) a And D, multiplying the initial arching shape curve obtained in the step C by an adjusting coefficient k to obtain the pre-arching shape curve of the tube bundle or the tube panel.
Further, the pre-arching shape curve of the tube bundle or tube panel is fitted into a bent tube or a fold-line bent tube according to the factory manufacturing process. Under illumination, the deformation shape of the tube bundle or the tube panel is complex, is related to illumination distribution, the flowing state of an internal medium and pivot constraint, is difficult to express by a curve equation, can only be approximately fitted, and can be approximated by a bent tube or a folded tube in order to meet the requirement of factory manufacturing. The realization method is to extract the deformation data of the finite element software and fit the data with the data processing software. Or intercepting a finite element software deformation result graph in a ratio of 1:1, reading in CAD software, and drawing and approximately fitting.
Furthermore, according to the factory manufacturing process, the pre-arching curve obtained by the method is fitted into a polygonal line bent pipe as a final pre-arching curve, and the specific fitting process is as follows:
applying a displacement along the light-facing surface at the position where the prestress fulcrum is obtained according to the step C0While obtaining the vertical displacement of the middle point of the tube bundle or the tube panel from the axial position of the straight tube, namely the displacement of the middle positionc；
The radius of the bent pipe in the bent line bent pipe is calculated by the following formula:
in the above formula: l is the vertical length of the whole tube bundle or the projection of the tube bundle in the axial direction; l is1The vertical length of the projection of the distance between the prestress branch point and the upper end and the lower end of the tube bundle or the tube panel on the axial direction is shown;cp＝kc；p＝k0。
in the specific factory manufacturing process, the length and slope of the broken line are according to the displacementpAnd L1And finally, taking the radius of the bent pipe obtained by calculation as an arc, wherein a curve obtained between the radius of the bent pipe and the intersection point of the bent pipe and the broken lines on the two sides is the bent pipe obtained by fitting, and a curve obtained by superposing and fitting the bent pipe and the broken lines on the two sides is the pre-arching curve of the bent pipe with the broken lines obtained by fitting according to the factory manufacturing process.
The method for designing the pre-arching shape of the pre-stressed tube bundle or tube panel of the photothermal heat absorber of the invention is explained and illustrated below by referring to specific examples.
Example 1
The CFD software of this example 1 employs ANSYS Fluent 14.5
The FEA software adopts ANSYS Mechanical 14.5
This example illustrates the design and application of the pre-arched shape of the pre-stressed tube bundle or tube panel of the photothermal heat absorber of the present invention using a single tube bundle. Wherein the allowable stress [ sigma ] of the material at the working temperature]t＝280MPa。
The specific design process of the pre-arching curve is as follows:
a solving of tube bundle temperature field under working condition
Specifically, according to the actual heat flux density input and medium flow of the tube wall of the photothermal heat absorber, calculating a tube bundle temperature field under a working condition through fluid dynamics (CFD) analysis software;
FIG. 2 is a graph of simulated energy flow density without regard to tube bundle camber and illumination in example 1, wherein the individual tube bundle mass flow was 2.466kg/s, the inlet temperature was 290 ℃, and the tube bundle temperature field was calculated by ANSYS Fluent 14.5 software.
B, solving the free deformation shape of the tube bundle at the working temperature
And D, introducing the temperature field obtained by the solution in the step A into ANSYS Mechanical 14.5 finite element structure analysis software, setting the upper end constraint and the lower end constraint of the tube bundle, and not setting any constraint point in the middle. The shape of the tube bundle deformation obtained by solving the constraint points of the upper end and the lower end is shown in fig. 3.
C solving the prestress sigma under the initial arching shapep
The deformed shape obtained in the above step B is inverted to obtain a shape symmetrically opposite to the deformed shape as an initial arching shape curve, as shown in fig. 4. The two prestress supporting points are respectively arranged at the positions which are 1/4L-1/3L away from the upper end and the lower end of the tube bundle, and L is the vertical length of the projection of the whole tube bundle in the axial direction.
After the prestressed supporting point is set, the upper and lower end point constraints are set. And applying displacement to the axial position of the straight pipe at the prestressed supporting point0Meanwhile, the vertical displacement of the middle point of the tube bundle from the axis position of the straight tube, namely the displacement c of the middle position can be obtained, the arrangement of the prestress fulcrum, the displacement of the prestress fulcrum and the displacement distribution of the middle position are shown in figure 5, and the displacement of the prestress fulcrum is obtained by calculation02.33m, displacement of the intermediate positionc＝3.198m。
Solving and obtaining the maximum value sigma of the equivalent stress of the Von-Mises at the normal temperature state without considering the input of energy flow by utilizing finite element structural analysis softwarep＝280.37MPa。
D determining an adjustment factor k
Obtaining the maximum value sigma of the Von-Mises equivalent stress according to the step Cp(-280.37 MPa), the adjustment factor k is determined.
k＝C×[σ]t/σp＝0.9×280/280.37＝0.899
Wherein: c is 0.9; [ sigma ]]t＝280MPa；σp＝280.37MPa
E determining a pre-arching curve of a tube bundle
Shifting the obtained step C0Multiplying the displacement by an adjusting coefficient k to obtain the actual displacement required to be applied for pre-arching the tube bundleP：
＝k0＝0.899×2.33m＝2.095
And D, multiplying the initial arching shape curve obtained in the step C by an adjusting coefficient k to obtain a tube bundle pre-arching shape curve. The comparison of the adjusted pre-arching curve of the tube bundle and the initial arching shape curve is shown in fig. 6. In fig. 6, a curve a (Z-direction deformation displacement) is a deformation displacement curve of the tube bundle subjected to illumination calculated in the second step, and a curve b (initial arching curve) is an initial arching curve adopted in the third step, and is a curve obtained by mirroring the curve a on the plane of the tube bundle; the curve c (final camber curve after adjustment) is the final camber curve obtained by multiplying the curve b by the adjustment coefficient k.
Of course, the obtained pre-arching curve can be readjusted and fitted to be a broken-line bent pipe curve according to the factory manufacturing process to serve as the required pre-stress arching curve. The specific process of the fitting of the broken line bent pipe is as follows:
the radius of the bent pipe in the bent line bent pipe is calculated by the following formula:
in the above formula: l is the vertical length of the whole tube bundle projected in the axial direction; l is1The vertical length of the projection of the distance between the prestress branch point and the upper end and the lower end of the tube bundle in the axial direction is shown;cp＝kc；p＝k0。
in this example, L is 17.6m, L1＝4.4m，p＝2.330m，c＝3.198m，k＝0.899，p＝2.095m，cpCalculated bend radius R of 2.875mp＝11.795m。
Length and slope of broken line according to displacementpAnd L1And finally, taking the radius of the bent pipe obtained by calculation as an arc, wherein a curve obtained between the radius of the bent pipe and the intersection point of the bent pipe and the broken lines on the two sides is the bent pipe obtained by fitting, and a curve obtained by superposing and fitting the bent pipe and the broken lines on the two sides is the pre-arching curve of the bent pipe with the broken lines obtained by fitting according to the factory manufacturing process. The example fitting the resulting equationThe wire sweep is shown in figure 7.
Example 1 comparison of a prestressed and non-arched bundle of tubes Using a Pre-arched shape
The tube bundle of example 1 was prestressed with a pre-arched shape and the tube bundle of non-arched shape (without prestressing) was placed under the same illumination intensity, and the maximum value of the equivalent stress was examined. Wherein, the maximum value of Von-Mises equivalent stress of the non-arch structure tube bundle without adopting the pre-arching shape in the illumination intensity table is 330MPa, which exceeds the yield strength of the material by 280 MPa; the maximum value of the Von-Mises equivalent stress of the tube bundle of the example 1 is 164MPa after prestress is applied to the tube bundle according to the pre-arching shape, so that the stress level is greatly reduced.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (10)
1. A design method for a pre-arching shape of a pre-stressed tube bundle or a tube panel of a photo-thermal heat absorber is characterized by comprising the following steps:
A. solving a temperature field
Calculating the temperature field of the tube bundle or the tube panel according to the actual heat flux density input and the medium flow of the tube wall of the photo-thermal heat absorber;
B. solving tube bundle or tube panel deformation shape
Reading the temperature field result obtained in the step A into analysis software, setting constraints at the upper end and the lower end of the tube bundle or the tube panel, not setting any constraint point in the middle, and solving the deformation shape of the tube bundle or the tube panel;
C. solving stress sigma of normal temperature state without considering energy flow inputp
Inverting the deformed shape obtained in the step B to obtainThe symmetrical and opposite deformation shape is used as an initial arch camber curve, a prestress fulcrum of a tube bundle or a tube panel is selected, upper and lower end constraints are set, and displacement to the axial line position of a straight tube is applied at the prestress fulcrum0Solving the stress σ at normal temperature regardless of the input of energy flowp；
D. Determining an adjustment factor k
The stress sigma at normal temperature obtained in the step CpSolving an adjustment coefficient k:
wherein C is an intensity adjustment coefficient;
[σ]tallowable stress value of the material at the working temperature;
E. determining pre-arching curves for tube bundles or tube panels
Shifting the obtained step C0Multiplying the displacement by an adjusting coefficient k to obtain the actual displacement required to be applied by the pre-arching of the tube bundle or the tube panelp＝k0(ii) a And D, multiplying the initial arching shape curve obtained in the step C by an adjusting coefficient k to obtain the pre-arching shape curve of the tube bundle or the tube panel.
2. The design method of the pre-arching shape of the pre-stressed tube bundle or tube panel of the photothermal heat absorber according to claim 1, wherein in step C, the number of the pre-stressed pivot points is two, and the vertical distance between the two pre-stressed pivot points and the upper end and the lower end of the tube bundle or tube panel is 1/4L to 1/3L, wherein L is the vertical length of the whole tube bundle or tube panel projected in the axial direction.
3. The method for designing the pre-arching shape of the pre-stressed tube bundle or the tube panel of the photothermal heat absorber according to claim 1, wherein in step a, the temperature field is calculated by using fluid mechanics (CFD) analysis software.
4. The method for designing the pre-arching shape of the pre-stressed tube bundle or the tube panel of the photothermal heat absorber according to claim 1, wherein in the step a, the medium is one or more of air, water, steam, heat transfer oil, liquid metal and molten salt.
5. The method for designing the pre-arching shape of the pre-stressed tube bundle or the tube panel of the photothermal heat absorber according to claim 1, wherein in step B, the analysis software is Finite Element (FEA) structural analysis software.
6. The method for designing the pre-arching shape of the pre-stressed tube bundle or the tube panel of the photothermal heat absorber according to claim 1, wherein in the step C, the initial arching shape can be fitted according to characteristics of process manufacturing.
7. The method for designing the pre-arching shape of the pre-stressed tube bundle or the tube panel of the photothermal heat absorber according to claim 1, wherein in the step D, the value range of C is 0.5 < C < 1.
8. The method for designing the pre-arching shape of the pre-stressed tube bundle or the tube panel of the photothermal heat absorber according to claim 1, wherein in step E, the pre-arching shape curve of the tube bundle or the tube panel can be fitted into a bent tube or a bent-line bent tube according to a factory manufacturing process.
9. The method for designing the pre-arching shape of the pre-stressed tube bundle or the tube panel of the photothermal heat absorber according to claim 8, wherein in the step E, the concrete fitting process of curve fitting of the pre-arching shape of the tube bundle or the tube panel into the polygonal-line bent tube comprises:
step C, applying the displacement to the axial line position of the straight pipe at the position of the obtained prestress fulcrum0While obtaining the vertical displacement of the middle point of the tube bundle or the tube panel from the axial position of the straight tube, namely the displacement of the middle positionc；
The radius of the bent pipe in the bent line bent pipe is calculated by the following formula:
in the above formula: l is the vertical length of the whole tube bundle or the projection of the tube bundle in the axial direction; l is1The vertical length of the projection of the distance between the prestress branch point and the upper end and the lower end of the tube bundle or the tube panel on the axial direction is shown;cp＝kc；p＝k0；
in the specific factory manufacturing process, the length and slope of the broken line are according to the displacementpAnd L1And finally, taking the radius of the bent pipe obtained by calculation as an arc, wherein a curve obtained between the radius of the bent pipe and the intersection point of the bent pipe and the broken lines on the two sides is the bent pipe obtained by fitting, and a curve obtained by superposing and fitting the bent pipe and the broken lines on the two sides is the pre-arching curve of the bent pipe with the broken lines obtained by fitting according to the factory manufacturing process.
10. The design method of the pre-arching shape of the pre-stressed tube bundle or the tube panel of the photothermal heat absorber according to claim 1 is characterized by comprising the following steps:
A. solving tube bundle temperature field under working condition
Calculating a tube bundle temperature field under a working condition through fluid mechanics (CFD) analysis software according to the actual heat flux density input and the medium flow of the tube wall of the photothermal heat absorber; wherein the mass flow of a single tube bundle is 2.466kg/s, and the inlet temperature is 290 ℃;
B. solving free deformation shape of tube bundle at working temperature
B, introducing the temperature obtained in the step A into Finite Element (FEA) structure analysis software, setting upper and lower end constraints of the tube bundle, not setting any constraint point in the middle, and solving the obtained tube bundle deformation shape;
C. solving the prestress sigma under the initial arching shapep
Reversing the deformed shape obtained in the step B to obtain a shape which is symmetrical and opposite to the deformed shape of the deformed shape and is used as an initial arching shape curve; two prestressed supporting points are arranged and respectively arranged at the positions which are 1/4L-1/3L away from the upper end and the lower end of the tube bundle, and after the prestressed supporting points are arranged, the prestressed supporting points are arrangedThe upper and lower end point constraints are well arranged, and displacement to the axial line position of the straight pipe is applied at the prestressed supporting point0＝2.33m；
Solving and obtaining the normal temperature state sigma without considering the input of energy flow by utilizing finite element structural analysis softwarep＝280.37MPa；
D. Determining an adjustment factor k
Obtaining σ according to step C abovepDetermining an adjusting coefficient k;
k＝C×[σ]t/σp＝0.9×280/280.37＝0.899；
wherein: c is 0.9; [ sigma ]]t＝280MPa；σp＝280.37MPa；
E. Determining pre-arching curves for tube bundles or tube panels
Shifting the obtained step C0Multiplying the displacement by an adjusting coefficient k to obtain the actual displacement required to be applied by the pre-arching of the tube bundle or the tube panelp：
p＝k0＝0.899×2.33m＝2.095
And D, multiplying the initial arching shape curve obtained in the step C by an adjusting coefficient k to obtain a pre-arching shape curve of the tube bundle or the tube panel.
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