CN111611635A - Design method of high-low temperature test platform of ballastless track of high-speed railway - Google Patents
Design method of high-low temperature test platform of ballastless track of high-speed railway Download PDFInfo
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Abstract
The invention provides a design method of a high-low temperature test platform of a ballastless track of a high-speed railway. The method comprises the following steps: establishing a high-low temperature test platform model of a ballastless track of a high-speed railway by using finite element software, wherein the model comprises a test box library body model, a test box base model, a working space fluid model and a ballastless track model, the test box library body model is fixedly arranged on the test box base model, and the ballastless track model is fixedly arranged in the test box library body model; adjusting the component structure in the high-low temperature test platform model of the ballastless track of the high-speed railway according to the heat preservation effect, stability and applicability performance indexes of the high-low temperature test platform model of the ballastless track of the high-speed railway, and realizing the design and optimization of the high-low temperature test platform of the ballastless track. The method has the advantages of high visualization degree, flexible modeling configuration and comprehensive consideration of design factors, and can provide a systematic and complete design method for establishing the high-low temperature test platform of the ballastless track of the high-speed railway.
Description
Technical Field
The invention relates to the technical field of high-speed railway ballastless track tests, in particular to a design method of a high-low temperature test platform of a high-speed railway ballastless track.
Background
The method is characterized in that the regions of China are wide, the climate condition difference is large, the ballastless track of the high-speed railway is used as a concrete structural project placed in a natural environment, the influence of the change of various natural environment conditions is suffered, the temperature of each point on the surface and inside of the ballastless track changes at any time, and temperature deformation and ballastless track diseases are generated due to the change of the temperature, a large number of field analyses show that the diseases of the ballastless track are mostly caused by temperature load at present, and deformation imbalance under the action of the temperature load is a main cause of the ballastless track diseases.
Aiming at the problem of diseases of ballastless tracks, at present, most scholars at home and abroad carry out outdoor tests, the outdoor tests not only need to consume a large amount of time, manpower and material resources, but also only study the influence of a temperature field on the stress of track parts aiming at a certain work point, and do not consider the influence of extreme high and low temperature, temperature circulation and the like on the generation and development of the diseases of the track parts. The test box of the ballastless track of the high-speed railway can carry out an extremely high-low temperature and temperature cycle development indoor test aiming at the ballastless track so as to solve the test requirement which cannot be achieved outdoors, but the test box of the ballastless track of the high-speed railway aiming at the indoor test is not established at present, the platform construction is still in an early stage, and the design of the test box of the ballastless track of the high-speed railway is still without a systematic method.
Disclosure of Invention
The embodiment of the invention provides a design method of a high-low temperature test platform of a high-speed railway ballastless track, which aims to overcome the problems in the prior art.
In order to achieve the purpose, the invention adopts the following technical scheme.
A design method of a high and low temperature test platform of a high-speed railway ballastless track comprises the following steps:
establishing a high-low temperature test platform model of a ballastless track of a high-speed railway by using finite element software, wherein the high-low temperature test platform model comprises a test box library body model, a test box base model, a working space fluid model and a ballastless track model, the test box library body model is fixedly arranged on the test box base model, the working space fluid model is a fluid space which is not occupied by an object and needs to be heated or cooled in the test platform model, and the ballastless track model is fixedly arranged in the test box library body model;
adjusting the component structure in the high-low temperature test platform model of the ballastless track of the high-speed railway according to the heat preservation effect, stability and applicability performance indexes of the high-low temperature test platform model of the ballastless track of the high-speed railway, and realizing the design and optimization of the high-low temperature test platform of the ballastless track.
Preferably, the test box body model is characterized in that the body plate of the test box body model is of a three-layer structure including an inner container, a middle heat-insulating layer and an outer container, the inner container is made of a stainless steel plate, the outer container is made of a color steel plate, the middle heat-insulating layer is made of a heat-insulating material, and the inner container, the middle heat-insulating layer and the outer container are simulated by adopting entity units.
Preferably, the test box base model is in a steel plate and concrete base or integral concrete base structure form and is positioned at the bottom of the test box library model.
Preferably, the ballastless track model comprises steel rails, fastener units, track plates, mortar layers, supporting layers and wide and narrow joints, wherein the steel rails are simulated by the beam units, the fastener units are simulated by the spring units, the track plates, the mortar layers and the supporting layers are simulated by the solid units, longitudinal constraint of the longitudinally-connected ballastless track is realized at the constraint end of the ballastless track model by arranging reaction walls and jacks, the reaction walls and the jacks are simulated by the solid units, and the pre-pressure of the jacks is realized by heating the jack parts.
Preferably, an air inlet part model and an air outlet part model are arranged at the junction of the test box library body model and the working space fluid model, and the air inlet part model and the air outlet part model are cube fluid space parts with the side length of 0.5 m.
Preferably, the method comprises:
establishing a space coupling heat transfer model of a high-low temperature test platform of a ballastless track of a high-speed railway by using finite element software, wherein the space coupling heat transfer model specifically comprises the following steps:
(1) the specific length, width and height of the high-low temperature test box body are determined by considering the elastic modulus, Poisson ratio, density, expansion coefficient, heat conductivity coefficient and specific heat of the material;
(2) the length, the width and the height of the base of the test box are specifically determined, and the elastic modulus, the Poisson ratio, the density, the expansion coefficient, the heat conductivity coefficient and the specific heat of the material are considered;
(3) the working space fluid component is used for determining the size of an internal cuboid fluid space under the non-zero load condition based on the size of a platform and a ballastless track structure for test laid in a test box, establishing the working space fluid component under the non-zero load condition and considering the density, the expansion coefficient, the thermal conductivity, the specific heat and the dynamic viscosity coefficient of air fluid;
(4) and the air inlet and outlet part is a cubic fluid space part with a certain size according to design requirements, is placed at the edge of the platform box body, and considers the density, the expansion coefficient, the heat conductivity, the specific heat and the dynamic viscosity coefficient of air fluid.
(5) The ballastless track structure for the test considers longitudinal constraints at two ends and modeling by considering the actual heat transfer material property and the geometric dimension of the ballastless track structure.
Preferably, the working space fluid model is used for calculating the distribution of the internal air temperature field under the heating condition and the cooling condition, and the positions of the air inlet and the air outlet, the air inlet and the air outlet modes, the air inlet speed and the temperature set value are adjusted so as to meet the requirements of the heat preservation and heat insulation performance of the test platform.
Preferably, under the condition of the same thickness of the box structure layer, the lower the thermal conductivity coefficient of the heat-insulating layer material, the higher the thermal resistance of the box structure, the lower the average thermal conductivity coefficient of the box, and the better the heat-insulating performance of the test platform model.
Preferably, when the test platform model is used for a temperature rise test, the air inlet and the air return opening are arranged on the same side of the test box body, and the air inlet is arranged above the air return opening.
Preferably, the top library body plate of the test box body is a top plate, the vertical displacement of the top plate is calculated by adopting a static analysis method under the condition of only considering the self weight of the structure, the thickness of inner and outer structure layers of the top plate is increased or a plurality of pairs of side supporting columns are arranged in a contrasting manner to support the test box library body model, so that the vertical displacement of the top plate under the action of the self gravity load is reduced.
According to the technical scheme provided by the embodiment of the invention, the design method of the high-low temperature test platform of the ballastless track of the high-speed railway has the advantages of high visualization degree, flexible modeling configuration and comprehensive design factor consideration, can provide a systematic and complete design method for establishing the high-low temperature test platform of the ballastless track of the high-speed railway, and solves the early working problem of the test platform.
Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a perspective view of a high and low temperature test platform model of a ballastless track of a high-speed railway according to an embodiment of the invention;
FIG. 2 is a schematic diagram of a finite element model of a test chamber library body model and a test chamber base model according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a workspace fluid model provided by an embodiment of the invention;
FIG. 4 is a schematic diagram of an inlet model and an outlet model according to an embodiment of the present invention;
fig. 5 is a structural model diagram of a ballastless track in a test box according to an embodiment of the present invention;
FIG. 6 is a schematic view of vertical displacement of a top plate of a box body before improvement design under the action of self weight according to an embodiment of the present invention;
fig. 7 is a schematic view illustrating a change in vertical displacement of a roof slab according to an embodiment of the present invention;
FIG. 8 is a schematic diagram illustrating vertical displacement of a top plate after arrangement of a support post according to an embodiment of the present invention;
FIG. 9 is a schematic diagram illustrating a comparison of thermal resistances of a case body with different insulating layer materials for a thermal insulating layer according to an embodiment of the present invention;
FIG. 10 is a schematic diagram showing the comparison of the average thermal conductivity of the box body when different insulating layer materials are adopted for the thermal insulating layer according to the embodiment of the present invention;
fig. 11 is a schematic diagram of the temperature of the outer wall of a thermal insulation layer provided by an embodiment of the present invention when the thermal insulation layer is made of different materials for the thermal insulation layer in low temperature operation;
fig. 12 is a schematic diagram of three alternative air inlet and outlet manners, namely, upper air inlet, lower air return, lower air inlet, upper air return, left air inlet, and right air return, under a temperature rise condition according to an embodiment of the present invention;
FIG. 13 is a schematic diagram of selecting horizontal planes with different heights in the vertical direction in a test chamber according to an embodiment of the present invention;
fig. 14 is a schematic diagram of a selected position of a temperature node No. 1 on each height horizontal plane in a test chamber according to an embodiment of the present invention;
FIG. 15 is a schematic diagram illustrating a vertical temperature gradient of air when the temperature of the air is raised by upper air intake and lower air return according to an embodiment of the present invention;
FIG. 16 is a schematic diagram illustrating a vertical temperature gradient of air when a temperature raising mode of downward air intake and upward air return is adopted according to an embodiment of the present invention;
fig. 17 is a schematic diagram of a vertical temperature gradient change curve of air in a temperature rising manner using left air intake and right air return according to an embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.
As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may also be present. Further, "connected" or "coupled" as used herein may include wirelessly connected or coupled. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
For the convenience of understanding the embodiments of the present invention, the following description will be further explained by taking several specific embodiments as examples in conjunction with the drawings, and the embodiments are not to be construed as limiting the embodiments of the present invention.
The embodiment of the invention applies large-scale general finite element software to establish a ballastless track test box model of the high-speed railway and a ballastless track space coupling heat transfer analysis model for internal tests, and designs the test box of the ballastless track of the high-speed railway.
The embodiment of the invention provides a design method of a high-low temperature test platform of a ballastless track of a high-speed railway based on a design principle from outside to inside. The method comprises the steps of establishing a high-low temperature test platform model of the ballastless track of the high-speed railway by using finite element software, wherein the high-low temperature test platform model comprises a test box library body model, a test box base model, a working space fluid model and a ballastless track model, the test box library body model is fixedly arranged on the test box base model, the working space fluid model is a fluid space which is not occupied by an object and needs to be heated or cooled in the test platform model, and the ballastless track model is fixedly arranged in the test box library body model. The specific implementation method can apply ABAQUS large finite element software.
Adjusting the component structure in the high-low temperature test platform model of the ballastless track of the high-speed railway according to the heat preservation effect, stability and applicability performance indexes of the high-low temperature test platform model of the ballastless track of the high-speed railway, and realizing the design and optimization of the high-low temperature test platform of the ballastless track.
The method of the embodiment of the invention adopts the means of static analysis, modal analysis, harmonic response analysis and the like to design the structural stability and the safety of the test box library model and the test box foundation; designing the heat preservation and insulation performance of the test box library body model through the structural heat transfer model of the test box library body model; designing test parameters such as an air inlet and outlet mode, an air inlet speed, a test temperature set value and the like based on air temperature field uniformity analysis by utilizing a working space Fluid model analysis model established by a finite element CFD (Computational Fluid Dynamics) module; an indoor constraint mode of the ballastless track for the test is designed through the ballastless track model for the test, and a ballastless track temperature loading mode during the test is designed based on the heat convection and heat radiation principles. Based on the finite element model, the steps of the method are adopted, so that the design and optimization of the ballastless track test box are realized.
The structure diagram of the high and low temperature test platform model of the ballastless track of the high-speed railway provided by the embodiment of the invention is shown in fig. 1 and comprises a test box library body model, a test box base model, a working space fluid model and a ballastless track model. The test box base body model is fixedly arranged on the test box base model, and the ballastless track model is fixedly arranged in the test box base body model.
The schematic diagram of the finite element model of the test box library body model and the test box base model provided by the embodiment of the invention is shown in fig. 2, the high and low temperature test box library body model is a design main body, a multilayer structure is adopted, and a solid unit is adopted for modeling. The body plate of the high and low temperature test box body model adopts a three-layer structure form of an inner container, a middle heat insulation layer and an outer container, the inner container is made of a stainless steel plate, the outer container is made of a color steel plate, the middle heat insulation layer is made of heat insulation materials such as polyurethane hard foaming materials, and the model is simulated by adopting entity units.
The test box base model adopts two structural forms of a steel plate, a concrete base and an integral concrete foundation and is positioned at the bottom of the test box base model, and solid units are adopted in the model for modeling.
Fig. 3 is a schematic diagram of a workspace fluid model according to an embodiment of the present invention, and fig. 4 is a schematic diagram of an intake component model and an outlet component model according to an embodiment of the present invention. As shown in fig. 3 and 4, the working space fluid model is a fluid space which is not occupied by an object and needs to be heated or cooled in the test platform model, the air inlet component and the air outlet component are located at the junction of the test box library body model and the working space fluid model, and the simulation is performed by using an 8-node hexahedral cell FC3D8 which is commonly used for fluid simulation.
A schematic diagram of a ballastless track model provided by an embodiment of the invention is shown in fig. 5. The slab ballastless track model comprises steel rails, fastener units, a track slab, a mortar layer, a supporting layer and wide and narrow joints, wherein the steel rails are simulated by adopting beam units, the fastener units are simulated by adopting spring units, and the track slab, the mortar layer and the supporting layer are simulated by adopting entity units.
The inner length, width and height dimensions of the test chamber body are respectively set to be 26m, 5m and 3m by considering the geometrical dimensions of the structural components of the test chamber and the applicability design of materials. The modulus of elasticity, poisson's ratio, density, coefficient of expansion, thermal conductivity, specific heat of the material used are considered.
The length, width and height dimensions of the test chamber base model were set to 27m, 7m and 2m, respectively. The modulus of elasticity, poisson's ratio, density, coefficient of expansion, thermal conductivity, specific heat of the material used are considered.
A cuboid fluid space with the length, width and height of 26m, 5m and 3m is set under the condition that the test chamber is unloaded. Under the non-no-load condition, namely, the ballastless track model structure paved in the test box occupies the indoor space, and the working space fluid model component under the non-no-load condition can be established according to the size of the ballastless track model. The density, expansion coefficient, thermal conductivity, specific heat and kinetic viscosity coefficient of the air fluid are taken into account. The air inlet part and the air outlet part are set as cubic fluid space parts with side length of 0.5m for visual representation, namely the sectional area of the air inlet and the air outlet is 0.25m 2. The density, expansion coefficient, thermal conductivity, specific heat and kinetic viscosity coefficient of the air fluid are taken into account.
A CRTS II plate type ballastless track model for a test is laid in the center of the interior of the test box, the ballastless track model comprises structures such as steel rails, fasteners, track plates, CA mortar layers, supporting layers, wide and narrow joints and the like, and the actual material property, the geometric dimension and the constraint at two ends are considered. The longitudinal restraint of the longitudinally-connected ballastless track is realized by arranging a counterforce wall and a jack at the restraint end part of the ballastless track, the counterforce wall and the jack are simulated by adopting a solid unit, and the pre-pressure of the jack is realized by heating a jack part.
Considering the safety design of the test platform, adopting finite element static force calculation, and calculating the vertical displacement of the top plate under the condition of only considering the dead weight of the structure. Simulating the characteristics of main modes of each order of the structure in a frequency range which is easy to be influenced by adopting mode analysis in a finite element, and judging the actual vibration response of the structure under the action of a vibration source in the frequency band; the method comprises the steps of adopting harmonic response analysis in a finite element to determine the steady-state response of a structure when the structure bears a load which changes along the simple harmonic rule along with time, only calculating the steady-state forced vibration of the structure in the analysis process, not considering the transient vibration when the vibration excitation starts, calculating the displacement-frequency curve of the structure under several frequencies, predicting the continuous dynamic characteristic of the structure, and verifying whether the design can overcome the harmful effects caused by resonance, fatigue and other forced vibrations. Thus, the structural stability and the vibration characteristic of the test platform are judged; the structural stability of the test platform is optimized by methods of arranging a support column for supporting, adjusting the thickness of a steel plate and the like.
Considering the design of the heat insulation performance of the test box, heating the indoor air of the test box, transferring the heat to the inner surface of the test box warehouse model in the air convection heat transfer and heat radiation modes after the temperature rises, transferring the heat to the outer surface of the warehouse from the inner surface of the warehouse in the heat conduction mode, judging the heat insulation capacity of the test box enclosure structure by calculating the heat conductivity coefficient, the heat flow density, the box heat resistance and the box outer wall temperature, adjusting the thickness of the box enclosure structure according to the heat insulation capacity, judging whether a heat insulation layer is arranged or not, and selecting a proper heat insulation layer material.
Considering the uniform design of the air temperature in the test box, the air inlet of the working space fluid model is provided with fluid inflow with speed and temperature, the air outlet is provided with fluid outflow with zero pressure, the working space fluid model analysis model established by the finite element CFD module is used for calculating the internal air temperature field distribution under the heating condition and the cooling condition, and the air inlet and outlet mode, the air inlet speed and the temperature set value are adjusted to obtain the optimal air temperature uniformity in the test box.
Through the established test box and the built internal plate type ballastless track space coupling heat transfer model, the internal temperature field of the ballastless track for the test is calculated by adopting methods such as thermal convection, thermal radiation and the like as boundary conditions of the model temperature load, and then the temperature loading mode of the ballastless track for the test is designed.
The effectiveness of the invention is further illustrated below with reference to the figures and examples:
example 1
In the embodiment, the structural safety is analyzed, and an optimized design scheme of the ballastless track test box is provided by adopting the method for enhancing the structural stability.
The box body of the test box is mainly composed of an inner and outer structural layer steel plate and a middle heat insulation layer, the design of an inner container of 30mm, a heat insulation layer of 100mm and an outer container of 20mm is adopted, and a top base plate of the box body of the test box is a top plate. Through calculation of a finite element static analysis module, it is found that because the top plate is long and the inner and outer structural layers are thin, fig. 6 is a schematic diagram of vertical displacement of the top plate of the box body before improvement design under the action of self weight, as shown in fig. 6, the middle part of the top plate maximally generates 11.83mm vertical displacement under the action of gravity, the sinking amount is large, and the structural stability is poor. The solution of providing a plurality of pairs of lateral support columns for supporting or adjusting the thickness of the top plate of the box is considered to enhance the structural stability of the test box, wherein the support columns are arranged schematically as shown in fig. 1. Fig. 8 is a schematic diagram of the vertical displacement of the top plate after the arrangement of the support columns according to the embodiment of the present invention, and it can be seen from fig. 8 that after the arrangement of the vertical support columns, the vertical displacement of the top plate is reduced to a certain extent, and because the bending rigidity of the top plate itself is small, the reduction of the vertical displacement of the top plate after the arrangement of the support columns is not large, and the reduction of the vertical displacement of the top plate after the arrangement of 3 pairs of support columns is only reduced by 3.84 mm.
Fig. 7 is a schematic view of a change of vertical displacement of a roof slab along with the thickening of the roof slab according to an embodiment of the present invention, as can be seen from fig. 7, the vertical displacement of the roof slab under the self gravity load is gradually reduced along with the increase of the thickness of the structural layer steel plate, because the larger the thickness of the steel plate is, the larger the bending rigidity is, and the smaller the central sinking amount is under the gravity load. When the thickening amount is 15mm, compared with the original situation, the displacement of the top plate is reduced by about 9mm, and the effect is obvious. Meanwhile, the reduction rate of the vertical displacement of the top plate is gradually reduced along with the thickening of the structural layer, and the vertical displacement is reduced by 6.1mm when the thickening amount is increased from 0mm to 5 mm; when the thickening amount is increased from 15mm to 20mm, the vertical displacement is reduced by only 0.52 mm.
In conclusion, it can be known from the calculation of the method that the thickness of the structural layer of the top plate is increased, namely the bending rigidity of the top plate is increased, so that the vertical displacement of the top plate is controlled more effectively, the reinforcing effect and the material utilization rate can be comprehensively considered during actual design, and the inner structural layer and the outer structural layer of the top plate are thickened by 15mm respectively.
Example 2
In the embodiment, the heat insulation performance of the building envelope is analyzed, the heat insulation capacity of the test box body is enhanced, and an optimal design scheme from a ballastless track to a low-temperature test box is provided through the method.
Establishing a space coupling heat transfer model of a high-low temperature test platform of a ballastless track of a high-speed railway by using finite element software, wherein the space coupling heat transfer model specifically comprises the following steps:
(1) the specific length, width and height of the high-low temperature test box body are determined by considering the elastic modulus, Poisson ratio, density, expansion coefficient, heat conductivity coefficient and specific heat of the material;
(2) the length, the width and the height of the base of the test box are specifically determined, and the elastic modulus, the Poisson ratio, the density, the expansion coefficient, the heat conductivity coefficient and the specific heat of the material are considered;
(3) the working space fluid component is used for determining the size of an internal cuboid fluid space under the non-zero load condition based on the size of a platform and a ballastless track structure for test laid in a test box, establishing the working space fluid component under the non-zero load condition and considering the density, the expansion coefficient, the thermal conductivity, the specific heat and the dynamic viscosity coefficient of air fluid;
(4) and the air inlet and outlet part is a cubic fluid space part with a certain size according to design requirements, is placed at the edge of the platform box body, and considers the density, the expansion coefficient, the heat conductivity, the specific heat and the dynamic viscosity coefficient of air fluid.
(5) The ballastless track structure for the test considers longitudinal constraints at two ends and modeling by considering the actual heat transfer material property and the geometric dimension of the ballastless track structure.
The wall heat-insulating material commonly used in the construction industry at present comprises rigid polyurethane foam materials, polystyrene foam boards (EPS boards), extruded polystyrene boards (XPS boards), glass wool boards, foam glass and the like, and the heat conductivity coefficients of the materials are shown in table 1.
TABLE 1 thermal conductivity of common insulating layer materials/(W.m-1. K-1)
Aiming at the box body structure of the test box, the design of 30mm of an inner container, 100mm of a heat preservation layer and 20mm of an outer container is adopted in the embodiment, and the heat insulation capability under the steady-state heat transfer of the box body is calculated under the condition of only changing the type of the heat preservation layer material of the middle layer by utilizing the heat transfer analysis and calculation of the method.
Fig. 9 is a schematic diagram showing comparison of thermal resistances of the box body with different insulating layer materials for the thermal insulating layer according to the embodiment of the present invention, and fig. 10 is a schematic diagram showing comparison of average thermal conductivity of the box body with different insulating layer materials for the thermal insulating layer. As can be seen from fig. 9 and 10, the influence of different insulating layer materials on the thermal insulation performance of the box body is mainly attributed to the thermal conductivity of the insulating layer material itself. Under the condition of the same thickness of the box structure layer, the lower the self heat conductivity coefficient of the heat-insulating layer material is, the larger the thermal resistance of the box structure is, the smaller the average heat conductivity coefficient of the box is, and the better the heat-insulating property is. Under the same thickness of the structural layer, the thermal resistance of the box body made of different heat-insulating layer materials and the average thermal conductivity of the box body are in an inverse proportion relation.
The related technical requirements stipulate a method for testing the heat preservation performance of a box body of a test box: stabilizing the temperature of the test box at the highest working temperature point for 2 hours, and using a surface thermometer to check the temperature of the outer wall of the test box, so as to ensure that the temperature of the part which is easy to touch outside the test box is not higher than 50 ℃ during high-temperature test; the temperature of the test box is stabilized at the lowest working temperature for 2 hours, and the condition of the outer surface of the box body is observed, so that the condensation phenomenon can be avoided when the low-temperature test and the environment temperature are 15-35 ℃ and the relative humidity is less than or equal to 85%.
In order to ensure that the box body of the actual test box meets the test requirements, namely the outer wall of the box body meets the requirement that the condensation phenomenon does not occur when the room temperature is 20 ℃ and the relative humidity is 85%, the temperature of the outer wall of the box body which adopts different heat-insulating layer materials under the low-temperature working condition of the test box is calculated by the method and is obtained as shown in fig. 11. As can be seen from fig. 11, when the thickness of the thermal insulation layer is 100mm, the hard foam polyurethane and the XPS board with lower thermal conductivity coefficient of the materials are used as the thermal insulation layer materials, so that the requirement of non-condensation on the outer wall can be met; if the EPS board, the glass wool board and the foam glass are used as the heat insulation layer materials of the box body, the thickness of the heat insulation layer needs to be correspondingly increased so as to meet the heat insulation requirement of the box body.
In conclusion, the calculation of the method shows that the heat preservation layer with the thickness of 100mm can meet the requirement of the heat preservation performance of the box body by selecting the hard foam polyurethane as the material, and the heat preservation effect is optimal in the selection scheme.
Example 3
In the embodiment, the distribution of the internal air temperature field under the temperature rise condition is calculated, the heating effects of different air inlet and outlet modes can be compared, and an optimal design scheme from the ballastless track to the low-temperature test box is provided by the method.
Under the no-load condition of the test box, the air inlet speed is ensured to be constant, and the temperature distribution of the indoor air is analyzed aiming at the temperature rise operation. In the case of temperature rise, the temperature is set to 70 ℃ and the air speed of the inlet air is 1 m/s. The following three air inlet and outlet modes are arranged, the temperature rise time is set to be 1h, and the change of the indoor air temperature field of the experimental box along with the temperature rise time in each air inlet mode is researched.
The method comprises the following steps of (1) air intake from the upper part and air return from the lower part: the air inlet and the air outlet are positioned at the same side of the test box body, and the air inlet is positioned above the air return inlet;
secondly, air intake from the bottom and air return from the top: the air inlet and the air outlet are positioned at the same side of the test box body, and the air inlet is positioned below the air return inlet;
thirdly, left air inlet and right air return: the air inlet and the air outlet are positioned on different sides of the test box body and are positioned on the same horizontal plane.
Fig. 12 is a schematic view of each air inlet and outlet mode.
The preliminary calculation shows that the temperature change trend and the amplitude of each node are basically consistent on each horizontal plane, which shows that the air temperature at the same height in the box body is basically the same at the same time, so that the air temperature change in the vertical direction only needs to be compared.
Fig. 13 is a schematic diagram of selecting horizontal planes with different heights in the vertical direction in the test chamber according to the embodiment of the present invention, fig. 14 is a schematic diagram of a selected position of a temperature node No. 1 on each height horizontal plane in the test chamber, and as shown in fig. 13 and fig. 14, in order to visually see the change of the air temperature in the vertical direction in the space of the test chamber body, an upper horizontal plane, a middle horizontal plane, and a lower horizontal plane are selected in the vertical direction, and the node No. 1 in the middle of the three horizontal planes is respectively defined as an air top plane (D11), a vertical middle plane (D21), and an air bottom plane (D31).
Fig. 15 is a schematic diagram of a vertical temperature gradient curve of air when a temperature rising method of upper intake air and lower return air is adopted according to an embodiment of the present invention, and as shown in fig. 15, a vertical temperature gradient curve of air when a temperature rising method of upper intake air and lower return air is adopted.
Fig. 16 is a schematic diagram of a vertical temperature gradient curve of air when a temperature rising method of lower intake air and upper return air is adopted according to an embodiment of the present invention, and as shown in fig. 16, a vertical temperature gradient curve of air when a temperature rising method of lower intake air and upper return air is adopted.
Fig. 17 is a schematic diagram of a vertical temperature gradient change curve of air when a temperature rising method of left air intake and right air return is adopted according to an embodiment of the present invention, and as shown in fig. 17, a vertical temperature gradient change curve of air when a temperature rising method of left air intake and right air return is adopted.
The calculation shows that the temperature of the air in the test chamber is faster at the upper part and slower at the lower part. Compared with the heating modes of upper air inlet and lower air return, the heating rates of the air of the other two heating modes are greatly reduced, and the bottom surface temperature only reaches 54.9 ℃ and 66.2 ℃ at the moment of heating time of 1 h.
In comparison, under the condition of temperature rise, the rapid temperature rise and the temperature distribution uniformity of indoor air are considered, the upper air inlet mode and the lower air return mode are adopted as the air inlet and outlet modes, air fluid in the box body is more uniform, and the temperature change uniformity performance of the test platform model is better.
In conclusion, the high-low temperature test platform of the high-speed railway ballastless track designed by the method provided by the embodiment of the invention has the advantages of high visualization degree, flexible modeling configuration and comprehensive design factor consideration, can provide a systematic and complete design method for establishing the high-low temperature test platform of the high-speed railway ballastless track, solves the early-stage working problem of the test platform, and provides a simple, feasible, high visualization degree and comprehensive systematic design method of the high-speed railway ballastless track test box.
The high-low temperature test platform for the ballastless track of the high-speed railway designed by the method provided by the embodiment of the invention is a multifunctional step-in artificial environment composite simulation durability test device, has stable and balanced heating performance, can control the temperature and humidity with high precision and high temperature, can simulate the service state of the ballastless track under real and complex climatic conditions, is a large-scale basic research and application basic scientific research test platform capable of carrying out comprehensive research and detection evaluation on structural scientificity, reliability and safety, and has the characteristics of commonality, universality, open sharing and the like.
The high-low temperature test platform for the ballastless track of the high-speed railway designed by the method can be used for carrying out structural fatigue tests, structural temperature and humidity cycle tests, ballastless track open joint and arch up tests, monitoring equipment and sensor performance test researches, ballastless track surface coating technology test researches, relevant tests of track disease treatment materials/methods, roadbed frost heaving and other relevant tests. In addition, the device can also be applied to relevant tests and tests of various structures, components and equipment in other fields such as bridges, roadbeds, pavements, materials and the like.
Those of ordinary skill in the art will understand that: the figures are merely schematic representations of one embodiment, and the blocks or flow diagrams in the figures are not necessarily required to practice the present invention.
Those of ordinary skill in the art will understand that: the components in the devices in the embodiments may be distributed in the devices in the embodiments according to the description of the embodiments, or may be correspondingly changed in one or more devices different from the embodiments. The components of the above embodiments may be combined into one component, or may be further divided into a plurality of sub-components.
The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for apparatus or system embodiments, since they are substantially similar to method embodiments, they are described in relative terms, as long as they are described in partial descriptions of method embodiments. The above-described embodiments of the apparatus and system are merely illustrative, and the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. A design method of a high and low temperature test platform of a high-speed railway ballastless track is characterized by comprising the following steps:
establishing a high-low temperature test platform model of a ballastless track of a high-speed railway by using finite element software, wherein the high-low temperature test platform model comprises a test box library body model, a test box base model, a working space fluid model and a ballastless track model, the test box library body model is fixedly arranged on the test box base model, the working space fluid model is a fluid space which is not occupied by an object and needs to be heated or cooled in the test platform model, and the ballastless track model is fixedly arranged in the test box library body model;
adjusting the component structure in the high-low temperature test platform model of the ballastless track of the high-speed railway according to the heat preservation effect, stability and applicability performance indexes of the high-low temperature test platform model of the ballastless track of the high-speed railway, and realizing the design and optimization of the high-low temperature test platform of the ballastless track.
2. The method as claimed in claim 1, wherein the test box library body model is characterized in that the library body plate is of a three-layer structure of an inner container, an intermediate insulating layer and an outer container, the inner container is made of stainless steel plates, the outer container is made of color steel plates, the intermediate insulating layer is made of heat insulating materials, and the inner container, the intermediate insulating layer and the outer container are simulated by using solid units.
3. The method of claim 1, wherein the test chamber base model is in the form of a steel plate plus concrete base or a monolithic concrete foundation structure at the bottom of the test chamber base model.
4. The method according to claim 1, wherein the ballastless track model comprises steel rails, fastener units, track plates, mortar layers, supporting layers and wide and narrow joints, wherein the steel rails are simulated by using beam units, the fastener units are simulated by using spring units, the track plates, the mortar layers and the supporting layers are simulated by using solid units, longitudinal constraint of the longitudinally-connected ballastless track is realized by arranging a counterforce wall and a jack at a constraint end of the ballastless track model, the counterforce wall and the jack are simulated by using the solid units, and pre-pressure of the jack is realized by heating the top of a jack piece.
5. The method of claim 1, wherein an air inlet part model and an air outlet part model are provided at the intersection of the test box library body model and the working space fluid model, and the air inlet part model and the air outlet part model are cubic fluid space parts with a side length of 0.5 m.
6. The method according to any one of claims 1 to 5, wherein the method comprises:
establishing a space coupling heat transfer model of a high-low temperature test platform of a ballastless track of a high-speed railway by using finite element software, wherein the space coupling heat transfer model specifically comprises the following steps:
(1) the specific length, width and height of the high-low temperature test box body are determined by considering the elastic modulus, Poisson ratio, density, expansion coefficient, heat conductivity coefficient and specific heat of the material;
(2) the length, the width and the height of the base of the test box are specifically determined, and the elastic modulus, the Poisson ratio, the density, the expansion coefficient, the heat conductivity coefficient and the specific heat of the material are considered;
(3) the working space fluid component is used for determining the size of an internal cuboid fluid space under the non-zero load condition based on the size of a platform and a ballastless track structure for test laid in a test box, establishing the working space fluid component under the non-zero load condition and considering the density, the expansion coefficient, the thermal conductivity, the specific heat and the dynamic viscosity coefficient of air fluid;
(4) and the air inlet and outlet part is a cubic fluid space part with a certain size according to design requirements, is placed at the edge of the platform box body, and considers the density, the expansion coefficient, the heat conductivity, the specific heat and the dynamic viscosity coefficient of air fluid.
(5) The ballastless track structure for the test considers longitudinal constraints at two ends and modeling by considering the actual heat transfer material property and the geometric dimension of the ballastless track structure.
7. The method as claimed in claim 6, wherein the working space fluid model is used for calculating the distribution of the internal air temperature field under the heating condition and the cooling condition, and the positions of the air inlet and the air outlet, the air inlet and the air outlet modes, the air inlet speed and the temperature set value are adjusted to meet the requirements of the heat preservation and heat insulation performance of the test platform.
8. The method as claimed in claim 7, wherein the lower the thermal conductivity of the insulation layer material, the higher the thermal resistance of the box structure, and the lower the average thermal conductivity of the box, the better the insulation performance of the test platform model.
9. The method as claimed in claim 7, wherein when the test platform model is used for a temperature rise test, the air inlet and the air return inlet are arranged on the same side of the test box body, and the air inlet is arranged above the air return inlet.
10. The method as claimed in any one of claims 1 to 5, wherein the top library plate of the test box body is a top plate, the vertical displacement of the top plate is calculated by a static analysis method under the condition of only considering the self weight of the structure, the thickness of inner and outer structural layers of the top plate is increased or a plurality of pairs of side supporting columns are arranged in contrast to support the test box library model, so that the vertical displacement of the top plate under the action of self gravity load is reduced.
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