CN106649923B - Method and device for evaluating thermal damage of engine exhaust system - Google Patents
Method and device for evaluating thermal damage of engine exhaust system Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 26
- 230000003685 thermal hair damage Effects 0.000 title claims abstract description 23
- 230000006378 damage Effects 0.000 claims abstract description 68
- 238000010438 heat treatment Methods 0.000 claims abstract description 39
- 239000000463 material Substances 0.000 claims abstract description 33
- 238000004364 calculation method Methods 0.000 claims description 23
- 230000005855 radiation Effects 0.000 claims description 19
- 238000012546 transfer Methods 0.000 claims description 19
- 239000003570 air Substances 0.000 claims description 14
- 239000000203 mixture Substances 0.000 claims description 13
- 239000012080 ambient air Substances 0.000 claims description 8
- 230000003584 silencer Effects 0.000 claims description 8
- 239000003054 catalyst Substances 0.000 claims description 7
- 230000005540 biological transmission Effects 0.000 claims description 3
- 230000009429 distress Effects 0.000 claims description 2
- 238000005259 measurement Methods 0.000 abstract description 11
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- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 19
- 239000003546 flue gas Substances 0.000 description 19
- 238000011156 evaluation Methods 0.000 description 16
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- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N11/00—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity
- F01N11/002—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity the diagnostic devices measuring or estimating temperature or pressure in, or downstream of the exhaust apparatus
- F01N11/005—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity the diagnostic devices measuring or estimating temperature or pressure in, or downstream of the exhaust apparatus the temperature or pressure being estimated, e.g. by means of a theoretical model
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/10—Geometric CAD
- G06F30/15—Vehicle, aircraft or watercraft design
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
- G06F2119/08—Thermal analysis or thermal optimisation
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/40—Engine management systems
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Abstract
The invention discloses a method and a device for evaluating the thermal damage of an engine exhaust system, wherein the method comprises the following steps: acquiring exhaust parameters of the engine under a set rotating speed working condition; calculating surface temperature distribution information of the heat source component according to the exhaust parameters and the size structure parameters of the heat source component in the exhaust system; and calculating the heating temperature of the heat damage component according to the position and material parameters of the heat damage component and the surface temperature distribution information of the heat source component corresponding to the heat damage component so as to evaluate the heat damage of the heat damage component. The method simplifies the complex three-dimensional CAE simulation analysis in the vehicle heat management, avoids the contradiction that experimental measurement cannot be carried out in the stage without a sample vehicle, and avoids high experimental cost.
Description
Technical Field
The invention relates to the technical field of automobiles, in particular to a method and a device for evaluating heat damage of an engine exhaust system.
Background
In the vehicle development stage, thermal damage assessment needs to be carried out on components around the vehicle exhaust system because the exhaust temperature of the engine is high, which can cause thermal damage to the surrounding components and seriously affect the service life of the vehicle.
In the related art, simulation analysis is performed through Computer Aided Engineering (CAE), but the rapid analysis of the thermal hazard problem cannot be satisfied due to factors such as large workload, long time period, and complex calculation, and the Engineering requirements of vehicle development cannot be satisfied due to limitations of time effectiveness, cost, and period of a test experimental sample vehicle.
Disclosure of Invention
The present invention is directed to solving, at least to some extent, one of the technical problems in the related art.
Therefore, an object of the present invention is to provide a method for evaluating thermal damage of an engine exhaust system, which simplifies complex three-dimensional CAE simulation analysis in vehicle thermal management, avoids contradictions that experimental measurement cannot be performed in a vehicle-like-free stage, and avoids high experimental cost.
Another object of the present invention is to provide a thermal hazard assessment apparatus for an engine exhaust system.
In order to achieve the above object, an embodiment of an aspect of the present invention provides a method for evaluating thermal damage of an engine exhaust system, including the following steps: acquiring exhaust parameters of the engine under a set rotating speed working condition; calculating surface temperature distribution information of the heat source component according to the exhaust parameters and the size structure parameters of the heat source component in the exhaust system; and calculating the heating temperature of the heat damage component according to the position and material parameters of the heat damage component and the surface temperature distribution information of the heat source component corresponding to the heat damage component so as to evaluate the heat damage of the heat damage component.
According to the method for evaluating the heat damage of the engine exhaust system, firstly, exhaust parameters of the engine under the working condition of set rotating speed are obtained, then, surface temperature distribution information of a heat source component is calculated according to the exhaust parameters and size structure parameters of the heat source component in the exhaust system, and finally, the heating temperature of the heat damage component is calculated according to the position and material parameters of the heat damage component and the surface temperature distribution information of the heat source component corresponding to the heat damage component, so that the heat damage component is evaluated. The method can not only realize reliable evaluation of the heat damage parts, but also simplify complex three-dimensional CAE simulation analysis in vehicle heat management, avoid the contradiction that experimental measurement cannot be carried out in a no-sample vehicle stage, and avoid high experimental cost.
According to an embodiment of the invention, the exhaust parameters comprise exhaust temperature, exhaust flow, exhaust pressure and exhaust composition at the inlet of the exhaust system and exhaust temperature, exhaust flow, exhaust pressure and exhaust composition at the outlet of the exhaust system.
According to one embodiment of the present invention, the heat source component includes one or more of an exhaust pipe, a muffler, a catalyst, a heat shield, and a fan, the dimensional structural parameters of the heat source component include one or more of an external dimension, an internal structural dimension, a pipe wall thickness, and material properties, the heat-harmful component includes one or more of a lifting lug, a wire harness, an ABS (Antilock Brake System), an oil pipe, a firewall, a sheath, a propeller shaft oil seal, a steering gear, a stay wire, and an oil pan, and the material parameters of the heat-harmful component include a dimension and material properties.
According to an embodiment of the present invention, the surface temperature distribution information of the heat source member is calculated by heat convection and heat conduction formulas, wherein the heat convection and heat conduction formulas are respectively:
wherein q is a convective heat transfer amount of the exhaust gas and the heat source part, h is a heat transfer coefficient of the heat source part, and tfIs the exhaust temperature, twThe surface temperature of the heat source part, phi, is the heat transfer rate of the heat source part, lambda1Is the thermal conductivity of the heat source component, A1Is a heat conducting area of the heat source part,
is a temperature gradient.
According to one embodiment of the invention, the heating temperature of the heat damage component is calculated by a radiation heating capacity formula and a forced convection heat release formula, wherein the radiation heating capacity formula and the forced convection heat release formula are respectively as follows:
wherein Q is1For heating by radiation, A2Surface area for the heat damage, d1Is the length of the heat source member, d2The heat damage partLength of member, sigma radiation constant, T1Surface temperature, T, of the heat source member2Is the heating temperature of the heat-damaged part, F12Angle coefficient of ε1Is the emissivity of the heat source part, epsilon2Emissivity of the heat-damaged part, Q2Lambda is air heat conductivity coefficient, U, for forced convection heat release∞Is the convection velocity of the ambient air, T∞Is the ambient temperature, upsilon air viscosity coefficient.
In order to achieve the above object, according to another aspect of the present invention, there is provided an apparatus for evaluating thermal damage of an engine exhaust system, comprising: the acquisition module is used for acquiring exhaust parameters of the engine under the working condition of set rotating speed; the first calculation module is used for calculating the surface temperature distribution information of the heat source component according to the exhaust parameters and the size and structure parameters of the heat source component in the exhaust system; and the second calculation module is used for calculating the heating temperature of the heat damage component according to the position and the material parameters of the heat damage component and the surface temperature distribution information of the heat source component corresponding to the heat damage component so as to evaluate the heat damage of the heat damage component.
According to the heat damage evaluation device of the engine exhaust system, firstly, the exhaust parameters of the engine under the working condition of the set rotating speed are obtained through the obtaining module, then, the first calculating module calculates the surface temperature distribution information of the heat source component according to the exhaust parameters and the size structure parameters of the heat source component in the exhaust system, and finally, the second calculating module calculates the heating temperature of the heat damage component according to the position and the material parameters of the heat damage component and the surface temperature distribution information of the heat source component corresponding to the heat damage component, so that the heat damage evaluation is carried out on the heat damage component. The device not only can realize the reliable evaluation of the heat damage parts, but also simplifies the complex three-dimensional CAE simulation analysis in the vehicle heat management, avoids the contradiction that experimental measurement cannot be carried out in the stage without a sample vehicle, and avoids high experimental cost.
According to an embodiment of the invention, the exhaust parameters comprise exhaust temperature, exhaust flow, exhaust pressure and exhaust composition at the inlet of the exhaust system and exhaust temperature, exhaust flow, exhaust pressure and exhaust composition at the outlet of the exhaust system.
According to one embodiment of the present invention, the heat source component includes one or more of an exhaust pipe, a muffler, a catalyst, a heat shield, and a fan, the dimensional structural parameters of the heat source component include an external dimension, an internal structural dimension, a pipe wall thickness, and material properties, the heat-harmful component includes one or more of a lifting lug, a wire harness, an ABS, an oil pipe, a firewall, a sheath, a propeller shaft oil seal, a steering gear, a wire harness, and an oil pan, and the material parameters of the heat-harmful component include a dimension and material properties.
According to an embodiment of the present invention, the first calculation module calculates the surface temperature distribution information of the heat source component by heat convection and heat conduction formulas, wherein the heat convection and heat conduction formulas are respectively:
wherein q is a convective heat transfer amount of the exhaust gas and the heat source part, h is a heat transfer coefficient of the heat source part, and tfIs the exhaust temperature, twThe surface temperature of the heat source part, phi, is the heat transfer rate of the heat source part, lambda1Is the thermal conductivity of the heat source component, A1Is a heat conducting area of the heat source part,
is a temperature gradient.
According to one embodiment of the invention, the second calculation module calculates the heating temperature of the heat-damaged component by a radiation heating capacity formula and a forced convection heat release formula, wherein the radiation heating capacity formula and the forced convection heat release formula are respectively as follows:
wherein Q is1For heating by radiation, A2Surface area for the heat damage, d1Is the length of the heat source member, d2Length of the heat-damaged part, sigma radiation constant, T1Surface temperature, T, of the heat source member2Is the heating temperature of the heat-damaged part, F12Angle coefficient of ε1Is the emissivity of the heat source part, epsilon2Emissivity of the heat-damaged part, Q2Lambda is air heat conductivity coefficient, U, for forced convection heat release∞Is the convection velocity of the ambient air, T∞Is the ambient temperature, upsilon air viscosity coefficient.
Drawings
FIG. 1 is a flow chart of a method of assessing thermal distress of an engine exhaust system according to an embodiment of the present disclosure;
FIG. 2 is a test platform for thermal hazard assessment of an engine exhaust system according to one embodiment of the present disclosure;
FIG. 3 is an interface for running a thermal hazard component thermal temperature calculation program according to one embodiment of the present invention;
FIG. 4 is a schematic view of a heat source component and a heat hazard component according to one embodiment of the invention;
FIG. 5 is a schematic view of a heat shield being added between a muffler and a lifting lug according to an embodiment of the present invention;
FIG. 6 is an operational interface of a computer program for verification after installation of a thermal shield according to one embodiment of the present invention; and
fig. 7 is a block diagram of a thermal damage evaluation apparatus of an engine exhaust system according to an embodiment of the present invention.
Reference numerals: the system comprises an engine 1, an inlet flow meter 2, an inlet temperature sensor 3, an inlet pressure sensor 4, an outlet temperature sensor 5, an outlet pressure sensor 6, an outlet flow meter 7, a catalytic grid 8, an outlet flue gas analyzer 9, an inlet flue gas analyzer 10, an exhaust gas measuring box 11, a communicating pipe 12, a data computer 13, a lifting lug 14, a silencer 15, ambient air flow 16 and a heat insulation plate 17.
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 or similar 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 drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
A method and apparatus for evaluating thermal damage of an engine exhaust system according to an embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a flow chart of a method of assessing thermal damage of an engine exhaust system according to an embodiment of the present invention. As shown in fig. 1, the method for evaluating the thermal damage of the engine exhaust system includes the steps of:
and S1, acquiring the exhaust parameters of the engine under the working condition of the set rotating speed.
In an embodiment of the invention, the exhaust parameters may include exhaust temperature, exhaust flow, exhaust pressure, and exhaust composition at an inlet of the exhaust system and exhaust temperature, exhaust flow, exhaust pressure, and exhaust composition at an outlet of the exhaust system.
Specifically, the temperature, flow, pressure and flue gas composition before and after the flue gas is catalyzed can be collected through a flowmeter, a temperature sensor, a pressure sensor and a flue gas analyzer. The flowmeter can adopt a vortex flowmeter with higher reliability and accuracy, the pressure sensor can adopt a piezoelectric sensor with higher accuracy, and the flue gas analyzer evaluates the heat change before and after the catalytic reaction of the flue gas by analyzing the contents of three harmful substances of CO, HC and NOx in the flue gas.
It should be noted that the catalytic reaction of the flue gas can be completed by a catalytic grid, and the three harmful substances of CO, HC and NOx in the flue gas can be converted into harmless substances by the catalytic grid, and the structure of the catalytic grid is a honeycomb grid carrier to be coated with metal glass, rhodium and palladium.
In practical application, as shown in fig. 2, the flow meter, the temperature sensor, the pressure sensor, the flue gas analyzer and the catalytic grating may be disposed in an exhaust gas measurement box, and a vacuum heat insulation layer and a heat insulation asbestos layer are disposed on an inner wall of the exhaust gas measurement box to avoid energy loss of flue gas, and data communication ports of the sensors are reserved on the exhaust gas measurement box so that data can be directly transmitted to a data computer through communication lines. During testing, the engine is connected with the exhaust gas measuring box through the communicating pipe, then the rotating speed working condition of the engine is set according to the running state of the vehicle, each sensor in the exhaust gas measuring box acquires the flow, the temperature, the pressure and the smoke components under the working condition, and data are transmitted to the data computer through the communication line.
And S2, calculating the surface temperature distribution information of the heat source component according to the exhaust parameters and the size structure parameters of the heat source component in the exhaust system.
According to one embodiment of the invention, the heat source components may include one or more of an exhaust pipe, a muffler, a catalyst, a heat shield, a fan, and are not limited thereto since the components in each exhaust system are different. Dimensional and structural parameters of the heat source component may include physical dimensions, internal structural dimensions, tube wall thickness, and material properties (e.g., surface roughness, emissivity, thermal conductivity, etc.).
Specifically, the heat transfer relationship from gas to solid to gas and the corresponding heat formula can be used: and Q is C m delta t, evaluating the energy loss of each heat source component after the smoke enters the exhaust system of the engine, and calculating the surface temperature of each heat source component, wherein Q is the heat release quantity, C is the specific heat capacity, m is the mass, and delta t is the temperature variation.
Further, according to an embodiment of the present invention, the surface temperature distribution information of the heat source member may be calculated by heat convection and heat conduction formulas, wherein the heat convection and heat conduction formulas are respectively:
wherein q is the convective heat transfer rate of the exhaust gas and the heat source component, h is the heat transfer coefficient of the heat source component, and tfIs the exhaust temperature, twSurface temperature of the heat source member, phi is heat transfer rate of the heat source member, lambda1Is the thermal conductivity of the heat source component, A1Is a heat conducting area of the heat source part,
is a temperature gradient.
Specifically, an exhaust pipe is taken as an example. The exhaust pipe can be divided into a plurality of sections with smaller length, the surface temperature of the exhaust pipe is considered to be the same in each section, the temperature of the surface of the exhaust pipe of the section, which is transmitted by the flue gas, is calculated according to the formula (1), and then the surface temperature of the exhaust pipe of the next section is calculated. Because the heat of the flue gas can be partially dissipated due to the last section of the exhaust pipe, the surface temperature of the next section of the exhaust pipe can be calculated according to the surface temperature of the last section of the exhaust pipe. And sequentially calculating until the calculation of the surface temperature of the whole exhaust pipe is completed.
In order to simplify the testing task of the tester, the tester can be compiled into a window-type calculation program in advance according to the formula (1), and the tester can quickly and conveniently complete the calculation of the surface temperature of the heat source component by only inputting the size and structure parameters of the heat source component and the exhaust parameters of the engine. It will be appreciated that the engine exhaust parameters may also be directed directly into the calculation routine without the need for human input.
And S3, calculating the heating temperature of the heat damage component according to the position and the material parameters of the heat damage component and the surface temperature distribution information of the heat source component corresponding to the heat damage component so as to evaluate the heat damage of the heat damage component.
According to an embodiment of the present invention, the heat-harmful member may include one or more of a lifting lug, a wire harness, ABS, an oil pipe, a firewall, a sheath, a transmission shaft oil seal, a steering gear, a stay wire, and an oil pan, and particularly, without limitation, the material parameter of the heat-harmful member may include a size (e.g., a distance from the heat source member, a heat receiving area, etc.) and a material physical property (e.g., an absorption rate, a thermal conductivity, etc.).
According to one embodiment of the invention, the heating temperature of the heat-damaged component can be calculated by a radiation heating capacity formula and a forced convection heat release formula, wherein the radiation heating capacity formula and the forced convection heat release formula are respectively as follows:
wherein Q is1For heating by radiation, A2Surface area for the heat damage, d1Is the length of the heat source member, d2Length of the heat-damaged part, sigma radiation constant, T1Surface temperature, T, of the heat source member2Is the heating temperature of the heat-damaged part, F12Angle coefficient of ε1Is the emissivity of the heat source part, epsilon2Emissivity of the heat-damaged part, Q2Lambda is air heat conductivity coefficient, U, for forced convection heat release∞Is the convection velocity of the ambient air, T∞Is the ambient temperature, upsilon air viscosity coefficient.
Similarly, the calculation program can be compiled into a window type calculation program in advance according to the formula (2), and the tester can quickly and conveniently complete the calculation of the heating temperature of the heat-damage component only by inputting the surface temperature of the heat source component and the position and material parameters of the heat-damage component.
In actual testing, in order to optimize the defect that the error of the calculation result of the complete theoretical formula is large, calculation can be performed by combining related experimental data, which is specifically shown in fig. 3. The corresponding parameters of the working condition one are a database which is arranged in an experiment, and the summarized experimental data of the relevant heat damage parts are used as a reference standard; and the parameters corresponding to the working condition II are input parameters obtained by the method, and the finally calculated temperature Tx is the surface temperature of the heat damage component. f is the form coefficient ratio in the formula, and e is the speed ratio coefficient in the formula.
The following further illustrates the entire testing process using a heat source component muffler and a thermally damaged component lifting lug (as shown in fig. 4) as examples.
First, the exhaust port of an engine (2.0L natural suction) was connected to an exhaust gas measurement box via a communication pipe, and a test bench was constructed. Then, a working condition that the target rotating speed is 3500rpm is set for the engine, the flow, the temperature, the pressure and the components of the flue gas before being catalyzed are measured through an exhaust measuring box and are respectively 0.5L/s, 900 ℃ and 9.6bar, and the flow, the temperature, the pressure and the components of the flue gas after being catalyzed by a catalytic grid are respectively 0.4L/s, 950 ℃ and 8 bar. Then, the enthalpy value of the smoke discharged by the engine is estimated by the data computer according to the contents of three harmful substances of CO, HC and NOx in the smoke before and after catalysis and the parameters, and the heat quantity of the engine exhaust is 30 kw.
It should be noted that, according to the gas enthalpy calculation formula, the enthalpy of the ambient air around the exhaust pipe is used as a reference to calculate the enthalpy of the flue gas in unit time:
h＝(C1+C2d/1000)t+Q*d/1000 (3)
wherein h is the enthalpy value of the smoke in unit time, C1Average constant pressure specific heat capacity for ambient air, C2Is the constant pressure specific heat capacity of the water vapor, d is the flue gas humidity, t is the flue gas temperature, and Q is the latent heat of vaporization of water at ambient temperature.
When the smoke with the heat (30kw) is introduced into the exhaust system, according to the heat transfer process from the gas to the pipeline solid and then to the outside air, with reference to the heat transfer mode in heat transfer science, the parameters and the dimensional structure parameters of each heat source component in the exhaust system are input into the self-edited energy flow analysis program, the flow change of the energy of the smoke of the engine in the process of passing through the exhaust system is calculated, and therefore the surface temperature of the muffler of the heat source component is calculated to be 300 ℃.
After the surface temperature of the heat source component silencer is calculated, the position, the size and the material physical properties of the lug and the temperature of the corresponding heat source component are led into temperature solver software, and therefore the surface temperature of the lug is calculated to be 126 ℃.
According to the method for evaluating the thermal damage of the engine exhaust system, firstly, the designed exhaust measuring box is utilized to complete the collection of the engine exhaust parameters (temperature, flow, pressure and components), the parameters are input into a self-edited energy flow analysis program, the flow change of the energy of the engine exhaust in the process of passing through the exhaust system is calculated, the evaluation of the surface temperature distribution of each heat source component (such as an exhaust pipe, a silencer, a catalyst and the like) in the exhaust system is completed, then, the thermal damage problem existing in the peripheral components of the exhaust system in the whole vehicle state is rapidly and effectively calculated according to a self-edited thermal damage temperature solver, and the thermal damage problem evaluation in the whole vehicle state is completed. The method simplifies the complex three-dimensional CAE simulation analysis in vehicle heat management, is more accurate, simple and convenient compared with CAE simulation analysis, has short calculation period and high calculation speed, effectively avoids the contradiction that experimental measurement cannot be carried out in a vehicle-like-free stage and high experimental cost, and provides reference for the service life of the vehicle and the design of the vehicle.
Further, after the evaluation of the thermal hazard problem in the vehicle state is completed, optimization measures can be provided for the evaluation result and verified, for example, the convection velocity (blowing rate) of air on the surface of the thermal hazard component can be changed, the thermal hazard distance can be changed, and a heat-resistant material can be replaced or a heat-insulating plate can be added to shield the heat source component. In addition, in the development of projects, the structures and positions of components are changed, heat insulation is added, and verification can be carried out at the moment.
Specifically, the heat source part muffler and the thermally harmful part lug are still taken as examples for further explanation.
As shown in fig. 5, a heat insulation plate can be added between the silencer and the lifting lug to shield the influence of the silencer on the lifting lug; an aluminum foil heat insulation cover can also be additionally arranged on the lifting lug; the distance between the silencer and the lifting lug can be adjusted from 70mm to 120 mm; the air flow velocity around the lifting lug can also be adjusted from 3m/s to 5 m/s. Verification may then be performed by self-editing verification software, as shown in FIG. 6. After verification, after the aluminum foil heat insulation cover is additionally arranged, the surface temperature of the lifting lug is 85 ℃; after the distance is adjusted from 70mm to 120mm, the surface temperature of the lifting lug is 105 ℃; after the air flow speed is adjusted from 3m/s to 5m/s, the surface temperature of the lifting lug is 99 ℃. Therefore, whether the optimization measure achieves an ideal result or not can be judged according to the verification result.
In one embodiment of the present invention, the surface temperature of the heat source part and the heat receiving temperature of the heat-damaged part are shown in table 1.
TABLE 1
In summary, according to the method for evaluating the thermal damage of the engine exhaust system of the embodiment of the invention, firstly, the exhaust parameters of the engine under the condition of the set rotation speed are obtained, then, the surface temperature distribution information of the heat source component is calculated according to the exhaust parameters and the size structure parameters of the heat source component in the exhaust system, and finally, the heating temperature of the heat-damaged component is calculated according to the position and material parameters of the heat-damaged component and the surface temperature distribution information of the heat source component corresponding to the heat-damaged component, so as to evaluate the thermal damage of the heat-damaged component. The method can not only realize reliable evaluation of the heat damage parts, but also simplify complex three-dimensional CAE simulation analysis in vehicle heat management, avoid the contradiction that experimental measurement cannot be carried out in a no-sample vehicle stage, and avoid high experimental cost.
Fig. 7 is a block diagram of a thermal damage evaluation apparatus of an engine exhaust system according to an embodiment of the present invention. As shown in fig. 7, the thermal damage evaluation device of the engine exhaust system includes: an acquisition module 10, a first calculation module 20 and a second calculation module 30.
The obtaining module 10 is configured to obtain an exhaust parameter of the engine under a set rotation speed condition.
According to one embodiment of the invention, the exhaust parameters include exhaust temperature, exhaust flow, exhaust pressure and exhaust composition at the inlet of the exhaust system and exhaust temperature, exhaust flow, exhaust pressure and exhaust composition at the outlet of the exhaust system.
The first calculation module 20 is used for calculating the surface temperature distribution information of the heat source component according to the exhaust gas parameters and the size structure parameters of the heat source component in the exhaust system.
According to one embodiment of the invention, the heat source component may include one or more of an exhaust pipe, a muffler, a catalyst, a heat shield, and a fan, and the dimensional structural parameters of the heat source component may include an outer dimension, an inner structural dimension, a wall thickness, and material properties.
According to an embodiment of the present invention, the first calculation module 20 may calculate the surface temperature distribution information of the heat source part through a heat convection and heat conduction equation as shown in the above equation (1).
The second calculation module 30 is used for calculating the heating temperature of the heat damage component according to the position and material parameters of the heat damage component and the surface temperature distribution information of the heat source component corresponding to the heat damage component so as to perform heat damage evaluation on the heat damage component.
According to one embodiment of the present invention, the heat-harmful member may include one or more of a lifting lug, a wire harness, ABS, an oil pipe, a firewall, a sheath, a propeller shaft oil seal, a steering gear, a stay wire, and an oil pan, and the material parameters of the heat-harmful member may include a size and material physical properties.
According to an embodiment of the present invention, the second calculating module 30 may calculate the heating temperature of the heat-damaged component by a radiant heating capacity formula and a forced convection heat release formula, wherein the radiant heating capacity formula and the forced convection heat release formula are shown in the above formula (2).
It should be noted that, the details that are not disclosed in the device for evaluating the thermal damage of the engine exhaust system according to the embodiment of the present invention are referred to the details that are disclosed in the method for evaluating the thermal damage of the engine exhaust system according to the embodiment of the present invention, and detailed description thereof is omitted.
According to the heat damage evaluation device of the engine exhaust system, firstly, the exhaust parameters of the engine under the working condition of the set rotating speed are obtained through the obtaining module, then, the first calculating module calculates the surface temperature distribution information of the heat source component according to the exhaust parameters and the size structure parameters of the heat source component in the exhaust system, and finally, the second calculating module calculates the heating temperature of the heat damage component according to the position and the material parameters of the heat damage component and the surface temperature distribution information of the heat source component corresponding to the heat damage component, so that the heat damage evaluation is carried out on the heat damage component. The device not only can realize the reliable evaluation of the heat damage parts, but also simplifies the complex three-dimensional CAE simulation analysis in the vehicle heat management, avoids the contradiction that experimental measurement cannot be carried out in the stage without a sample vehicle, and avoids high experimental cost.
In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (4)
1. A method of assessing thermal distress of an engine exhaust system, comprising the steps of:
acquiring exhaust parameters of the engine under a set rotating speed working condition;
calculating surface temperature distribution information of the heat source component according to the exhaust parameters and the size structure parameters of the heat source component in the exhaust system; and
calculating the heating temperature of the heat damage component according to the position and material parameters of the heat damage component and the surface temperature distribution information of the heat source component corresponding to the heat damage component so as to evaluate the heat damage of the heat damage component;
wherein,
the exhaust parameters include exhaust temperature, exhaust flow, exhaust pressure, and exhaust composition at an inlet of the exhaust system and exhaust temperature, exhaust flow, exhaust pressure, and exhaust composition at an outlet of the exhaust system;
the heat source component comprises one or more of an exhaust pipe, a silencer, a catalyst, a heat shield and a fan;
calculating surface temperature distribution information of the heat source component by a heat convection and heat conduction formula, wherein the heat convection and heat conduction formula is respectively as follows:
wherein q is a convective heat transfer amount of the exhaust gas and the heat source part, h is a heat transfer coefficient of the heat source part, and tfIs the exhaust temperature, twThe surface temperature of the heat source part, phi, is the heat transfer rate of the heat source part, lambda1Is the thermal conductivity of the heat source component, A1Is a heat conducting area of the heat source part,
is a temperature gradient;
the heat damage part comprises one or more of a lifting lug, a wiring harness, an ABS (anti-lock braking system), an oil pipe, a firewall, a sheath, a transmission shaft oil seal, a steering engine, a stay wire and an oil pan;
calculating the heating temperature of the heat damage component through a radiation heating capacity formula and a forced convection heat release formula, wherein the radiation heating capacity formula and the forced convection heat release formula are respectively as follows:
wherein Q is1Is heated by radiationAmount, A2Is the surface area of the heat-damaged part, d1Is the length of the heat source member, d2Length of the heat-damaged part, sigma radiation constant, T1Surface temperature, T, of the heat source member2Is the heating temperature of the heat-damaged part, F12Angle coefficient of ε1Is the emissivity of the heat source part, epsilon2Emissivity of the heat-damaged part, Q2Lambda is air heat conductivity coefficient, U, for forced convection heat release∞Is the convection velocity of the ambient air, T∞Is the ambient temperature, upsilon air viscosity coefficient.
2. The method of claim 1, wherein the dimensional structural parameters of the heat source component include external dimensions, internal structural dimensions, tube wall thickness, and material properties, and the material parameters of the heat-damaged component include dimensions and material properties.
3. An apparatus for assessing thermal damage of an engine exhaust system, comprising:
the acquisition module is used for acquiring exhaust parameters of the engine under the working condition of set rotating speed;
the first calculation module is used for calculating the surface temperature distribution information of the heat source component according to the exhaust parameters and the size and structure parameters of the heat source component in the exhaust system; and
the second calculation module is used for calculating the heating temperature of the heat damage component according to the position and the material parameters of the heat damage component and the surface temperature distribution information of the heat source component corresponding to the heat damage component so as to evaluate the heat damage of the heat damage component;
wherein,
the exhaust parameters include exhaust temperature, exhaust flow, exhaust pressure, and exhaust composition at an inlet of the exhaust system and exhaust temperature, exhaust flow, exhaust pressure, and exhaust composition at an outlet of the exhaust system;
the heat source component comprises one or more of an exhaust pipe, a silencer, a catalyst, a heat shield and a fan;
the first calculation module calculates surface temperature distribution information of the heat source component by heat convection and heat conduction formulas, wherein the heat convection and heat conduction formulas are respectively:
wherein q is a convective heat transfer amount of the exhaust gas and the heat source part, h is a heat transfer coefficient of the heat source part, and tfIs the exhaust temperature, twThe surface temperature of the heat source part, phi, is the heat transfer rate of the heat source part, lambda1Is the thermal conductivity of the heat source component, A1Is a heat conducting area of the heat source part,
is a temperature gradient;
the heat damage part comprises one or more of a lifting lug, a wiring harness, an ABS (anti-lock braking system), an oil pipe, a firewall, a sheath, a transmission shaft oil seal, a steering engine, a stay wire and an oil pan;
the second calculation module calculates the heating temperature of the heat damage component through a radiation heating capacity formula and a forced convection heat release formula, wherein the radiation heating capacity formula and the forced convection heat release formula are respectively as follows:
wherein Q is1For heating by radiation, A2Is the surface area of the heat-damaged part, d1Is the length of the heat source member, d2Length of the heat-damaged part, sigma radiation constant, T1Surface temperature, T, of the heat source member2Is the heating temperature of the heat-damaged part, F12Angle coefficient of ε1Is the emissivity of the heat source part, epsilon2Emissivity of the heat-damaged part, Q2Lambda is air heat conductivity coefficient, U, for forced convection heat release∞Is the convection velocity of the ambient air, T∞Is the ambient temperature, upsilon air viscosity coefficient.
4. The apparatus of claim 3, wherein the dimensional structural parameters of the heat source component include external dimensions, internal structural dimensions, tube wall thickness, and material properties, and the material parameters of the heat-damaged component include dimensions and material properties.
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| CN108052784A (en) * | 2018-01-31 | 2018-05-18 | 北京汽车股份有限公司 | Crew module's temperature simulation method and system |
| CN108491676B (en) * | 2018-06-29 | 2021-10-22 | 北京汽车股份有限公司 | Heat insulation performance simulation analysis method and system of heat shield |
| CN109145388B (en) * | 2018-07-25 | 2023-02-28 | 中国航发沈阳发动机研究所 | Thermal analysis method for aircraft engine component |
| CN111523176B (en) * | 2020-04-13 | 2023-02-28 | 东风汽车集团有限公司 | Construction method and system for thermal hazard test working condition of passenger car |
| CN113094768A (en) * | 2021-04-01 | 2021-07-09 | 中汽研（天津）汽车工程研究院有限公司 | Thermal management-thermal runaway joint simulation method for power battery system |
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