CN109902319B - Method for analyzing air inlet temperature of automobile engine under urban working condition - Google Patents
Method for analyzing air inlet temperature of automobile engine under urban working condition Download PDFInfo
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Abstract
The invention relates to the technical field of automobile design auxiliary analysis, and discloses an analysis method for the inlet air temperature of an automobile engine under an urban working condition, which comprises the following steps: (1) Decomposing the working condition into a plurality of speed intervals, wherein the speed of each interval is V1 and V2 … Vn, and determining the time proportion P1 and P2 … Pn of each speed interval; (2) The heat dissipation capacity of the vehicle speed engine in each interval is arranged, and the heat exchange efficiency parameters of the front section cooling module are obtained; (3) CAE analysis is carried out on the engine intake temperature under the stable working condition of each vehicle speed interval; (4) And according to the engine inlet air temperature result of the stable working condition of each vehicle speed, carrying out weighted average through a time ratio to obtain the engine inlet air temperature T = T1P 1+ T2P 2+ … … + Tn Pn. According to the invention, the intake temperature of the urban working condition is evaluated by a time weighted average method, so that the working efficiency can be improved under the condition of ensuring the precision, and the development of the early automobile engineering is supported.
Description
Technical Field
The invention relates to the technical field of automobile design auxiliary analysis, in particular to an analysis method for the air inlet temperature of an automobile engine under urban working conditions.
Background
The urban working condition is a working condition with high driving frequency of customers, and the engine inlet air temperature of the vehicle under the working condition is very important. If the intake temperature does not meet the requirement, not only the driving safety is influenced, but also unnecessary loss in the later period is caused, so that the CAE analysis simulation of the engine intake temperature under the urban working condition is required in the early development period. Because the vehicle speed of the urban working condition changes rapidly along with the time and the duration is very long, the transient CAE analysis of the engine inlet air temperature under the working condition is very complex, the calculation time is very long, the workload is huge, and the calculation is difficult to complete through the transient CAE analysis at present.
Disclosure of Invention
In order to solve the technical problem, the invention provides an analysis method of the air inlet temperature of the automobile engine under the urban working condition, the air inlet temperature under the urban working condition is evaluated by a time weighted average method, the working efficiency can be improved under the condition of ensuring the precision, and the development of the automobile engineering at the early stage is supported.
Therefore, the technical scheme provided by one aspect of the invention is as follows:
an analysis method for the air inlet temperature of an automobile engine under urban working conditions comprises the following steps:
(1) Decomposing the working condition into a plurality of speed intervals, wherein the speed of each interval is V1 and V2 … Vn, and determining the time proportion P1 and P2 … Pn of each speed interval;
(2) The heat dissipation capacity of the engine at the vehicle speed of each interval is arranged, and the heat exchange efficiency parameters of the front-section cooling module are obtained;
(3) CAE analysis is carried out on the engine intake temperature under the stable working condition of the vehicle speed of each interval, and the analysis method comprises the following steps:
(31) Carrying out grid division on the whole vehicle;
(32) Setting boundary parameters;
(33) Setting a calculation model to carry out CAE calculation;
(34) Taking the average temperature of the cross section of the model engine air intake system at the position of a throttle valve as an engine air intake temperature result of the stable working condition of the vehicle speed of each interval;
(4) According to the engine inlet air temperature result of the stable working condition of the vehicle speed of each interval, carrying out weighted average through a time proportion, and obtaining the engine inlet air temperature result under the urban working condition through the following formula:
engine intake temperature T = T1 × P1+ T2 × P2+ … … + Tn × Pn,
wherein T1-Tn is the temperature result and P1-Pn is the time ratio.
According to one embodiment of the invention, the vehicle speed of the urban working condition is divided into 6 sections of 0-5kph,5-15kph,15-25kph,25-35kph,35-45kph and more than 45kph, and the representative vehicle speed of each section is V1, V2, V3, V4, V5, V6, the time ratio of the vehicle speed sections is P1, P2, P3, P4, P5, P6.
According to an embodiment of the present invention, the step (31) comprises: the method comprises the following steps of surface grid division and body grid division, wherein the type of a surface grid is a triangular grid, the body grid division is carried out on the basis of the surface grid division, and the type of the body grid is a tetrahedral grid.
According to one embodiment of the invention, the side length of the triangular mesh is less than or equal to 10mm, and the growth rate of the tetrahedral mesh is less than or equal to 1.6.
According to one embodiment of the invention, after the face mesh division, face mesh inspection is performed, the inspection requires that the minimum angle of the triangular mesh is not lower than 15 degrees, the maximum angle is not higher than 130 degrees, and the triangular mesh has no repetitive mesh and mesh which is intersected with each other.
According to one embodiment of the invention, after the volume mesh division, a volume mesh examination is performed, and the twist rate of all volume meshes is not higher than 0.95.
According to an embodiment of the present invention, the step (32) of setting the boundary parameter includes the steps of:
(321) Magnifying the grid model units from millimeters to meters;
(322) Performing material assignment on different fluid domains and solid domains by adopting a standard turbulence k-epsilon double-course calculation model;
(323) Setting fluid domain attributes and endowing the parts with material attributes;
(324) Setting the whole vehicle inlet speed of each interval at the vehicle speed, the exhaust temperature and the exhaust flow rate of the vehicle at the vehicle speed, setting the speed of an engine air inlet at the vehicle speed, and setting the heat dissipation capacity of the engine under the vehicle speed working condition.
According to an embodiment of the invention, before the step (33), determining a CAE calculation model and parameter settings, wherein the parameters include a relaxation factor, a convergence factor and a calculation step number.
According to one embodiment of the invention, the CAE calculation model is a standard model, and the number of calculation steps is greater than or equal to 3000.
According to one embodiment of the invention, before the step (4), the method further comprises a step of checking the calculation result, firstly checking whether the speed field of the whole vehicle meets the requirement, secondly checking whether the speed field of the engine intake system is correct, and extracting the calculation result if the speed field of the whole vehicle is correct and the speed field of the engine intake system is correct.
The beneficial effects of the invention include:
(1) By utilizing a CFD analysis theory and based on the analysis of actual urban working conditions, a CAE analysis method and a CAE analysis flow of the engine inlet air temperature under the urban working conditions are formulated, and the requirement of an analysis department on the inlet air temperature at the early stage is met;
(2) The inlet air temperature under the urban working condition can be analyzed under the condition of meeting the precision, so that the method has better practical value and can be better used for early-stage engineering development;
(3) The feedback speed of the simulation analysis department to the design department is accelerated, and the design progress of the designer to the part structure is greatly improved.
Drawings
FIG. 1 is a schematic flow chart of a method for analyzing an intake air temperature of an automobile engine under urban conditions according to one aspect of the present invention.
FIG. 2 is a time and vehicle speed map for an urban condition.
Detailed Description
The following describes in detail a specific embodiment of an analysis method for an intake temperature of an automobile engine under urban conditions according to an aspect of the present invention with reference to the accompanying drawings.
According to one aspect of the invention, the method for analyzing the intake temperature of the automobile engine under the urban working condition comprises the following steps:
(1) Decomposing the working condition into a plurality of speed intervals, wherein the speed of each interval is V1 and V2 … Vn, and determining the time proportion P1 and P2 … Pn of each speed interval;
(2) The heat dissipating capacity of the engine under the vehicle speed of each interval is arranged, and the heat exchange efficiency parameters of the front section cooling module are obtained;
(3) CAE analysis is carried out on the engine intake temperature under the stable working condition of the vehicle speed of each interval, and the analysis method comprises the following steps:
(31) Carrying out grid division on the whole vehicle;
(32) Setting boundary parameters;
(33) Setting a calculation model for CAE calculation;
(34) Taking the average temperature of the cross section of the air inlet system of the model engine at the position of a throttle valve as the result of the air inlet temperature of the engine under the stable working condition of the vehicle speed of each interval;
(4) According to the engine inlet air temperature result of the stable working condition of the vehicle speed of each interval, carrying out weighted average through a time proportion, and obtaining the engine inlet air temperature result under the urban working condition through the following formula:
engine intake temperature T = T1 × P1+ T2 × P2+ … … + Tn × Pn, where T1-Tn are the temperature results and P1-Pn are the time ratios.
In one embodiment, the vehicle speed of the urban working condition is divided into six sections of 0-5kph,5-15kph,15-25kph,25-35kph,35-45kph and more than 45kph, and the representative vehicle speed of each section is V1, V2, V3, V4, V5, V6, the time ratio of the vehicle speed sections is P1, P2, P3, P4, P5, P6. Finally, through analysis of six working conditions, the engine intake temperature is obtained:
T=T1*P1+T2*P2+T3*P3+T4*P4+T5*P5+T6*P6。
the technical solution proposed by the present invention is described in more detail below with reference to fig. 1.
According to the CAE analysis requirement of the engine inlet air temperature and the characteristics of urban working conditions, the CAE analysis flow information is as follows.
1. Analyzing the urban working condition vehicle speed:
the speed of the city working condition changes rapidly along with the time, and the time length is long, about 53 minutes, as shown in figure 2. According to the vehicle speed, the urban working conditions are divided into six sections of 0-5kph,5-15kph,15-25kph,25-35kph,35-45kph and more than 45kph, the representative vehicle speed of each section is V1, V2, V3, V4, V5 and V6, and the sections are used as the vehicle speed working conditions of CAE steady state analysis. And counting the time proportions P1, P2, P3, P4, P5 and P6 occupied by each vehicle speed interval in the whole urban working condition for time weighted average processing. As shown in table 1 below:
| speed interval | Representing vehicle speed | Time ratio | The result of the calculation |
| 0-5kph | V1 | P1 | T1 |
| 5-15kph | V2 | P2 | T2 |
| 15-25kph | V3 | P3 | T3 |
| 25-35kph | V4 | P4 | T4 |
| 35-45kph | V5 | P5 | T5 |
| Over 45kph | V6 | P6 | T6 |
2. CAE steady state analysis at various vehicle speeds:
the method comprises the steps of arranging calculation parameters such as heat dissipation capacity of engines representing vehicle speeds (V1, V2, V3, V4, V5 and V6), heat exchange efficiency of a front section cooling module and the like, adopting CFD software to analyze engine inlet air temperature CAE representing stable working conditions under the vehicle speeds, and enabling an analysis flow of each stable working condition to comprise the following steps.
And 2.1, dividing a surface grid, wherein the surface grid is divided according to the geometric model of the whole vehicle, the type of the surface grid is triangular, and the grid division size is 10mm.
And 2.2, checking the surface mesh, namely checking the divided surface mesh, wherein the minimum angle of the triangular mesh is not less than 15 degrees, and the maximum angle is not more than 130 degrees. All grids cannot have repetitive grids and grids that cross each other.
And 2.3, carrying out body meshing on the face mesh passing the inspection. The type of the volume mesh is a tetrahedral mesh, and the growth rate is 1.6.
2.4, checking the volume meshes, wherein the torsion rate of all the volume meshes is required to be not higher than 0.95, and if the torsion rate is exceeded, the volume meshes are divided again.
2.5, setting boundary conditions, importing the divided volume grids into CAE software, and setting the boundary conditions, specifically comprising:
a) Expanding the grid model unit from millimeters (mm) to meters (m);
b) The calculation model adopts a standard k-epsilon dual equation, and an energy and radiation model is opened;
c) Assigning material values to the different fluid and solid domains;
d) Setting fluid domain attributes including hole site attributes of an air filter of an engine air intake system;
e) Assigning material properties to the part;
f) Setting internal unit attributes for the relevant parts;
g) Setting the inlet speed of the whole vehicle at the vehicle speed, the exhaust temperature and the exhaust flow at the vehicle speed, setting the speed of an air inlet of the engine at the vehicle speed, and setting the heat dissipation capacity of the engine under the working condition of the vehicle speed.
2.6, calculating a model and parameter setting, wherein the calculating model is SIMPLE, and the relaxation factor is as follows: pressure = R1, density = R2, body Forces = R3, momentum = R4, turbo Kinetic Energy = R5, turbo dispersion Rate = R6, turbo visual = R7, energy = R8, and differential order = R9; the convergence factor is set to: continuity =0.000001, x-velocity =0.000001, y-velocity =0.000001, z-velocity =0.000001, k =0.000001, epsilon =0.000001, energy =0.000001, do-intensity =0.000001; the number of steps is 3000.
And 2.7, checking a calculation result, namely checking whether the speed field of the whole vehicle meets the requirement or not, and checking whether the speed field of an air inlet system of the engine is correct or not. The calculation result is extracted in the case where both are correct.
And 2.8, extracting the result, and taking the average temperature of the cross section at the position of the throttle valve of the air inlet system of the engine as the temperature result under the condition of representing the vehicle speed.
3. And (4) processing results:
according to the engine intake temperature results of each stable working condition representing the vehicle speed, weighted average is carried out according to the time proportion in the table 1, and finally the engine intake temperature result under the urban working condition is obtained, wherein the calculation formula is as follows:
the engine intake air temperature T = T1 × P1+ T2 × P2+ T3 × P3+ T4 × P4+ T5 × P5+ T6 × P6.
The following table lists a specific example, and the final plate dividing result value of the inlet air temperature is obtained by the method of the invention and is better used for early engineering development by the feedback of a design department.
The above is only one embodiment of the present invention, and it should be noted that, for those skilled in the art, a plurality of modifications and amendments can be made without departing from the principle of the present invention, and these modifications and amendments are also included in the protection scope of the present invention.
Claims (9)
1. An analysis method for the air inlet temperature of an automobile engine under an urban working condition is characterized by comprising the following steps:
(1) Decomposing the working condition into a plurality of speed intervals, wherein the speed of each interval is V1 and V2 … Vn, and determining the time proportion P1 and P2 … Pn of each speed interval;
(2) The heat dissipation capacity of the engine under the vehicle speed of each interval is arranged, and the heat exchange efficiency parameters of the front section cooling module are obtained;
(3) CAE analysis is carried out on the engine intake temperature under the stable working condition of the vehicle speed of each interval, and the analysis method comprises the following steps:
(31) Carrying out grid division on the whole vehicle;
(32) Setting boundary parameters, which include:
(321) Magnifying the grid model units from millimeters to meters;
(322) Performing material assignment on different fluid domains and solid domains by adopting a standard turbulence k-epsilon double-course calculation model;
(323) Setting fluid domain attributes and endowing the parts with material attributes;
(324) Setting the whole vehicle inlet speed, the exhaust temperature and the exhaust flow rate of the vehicle at the vehicle speed of each interval, setting the speed of an engine air inlet at the vehicle speed, and setting the heat dissipation capacity of the engine under the vehicle speed working condition;
(33) Setting a calculation model for CAE calculation;
(34) Taking the average temperature of the cross section of the model engine air intake system at the position of a throttle valve as an engine air intake temperature result of the stable working condition of the vehicle speed of each interval;
(4) According to the engine inlet air temperature result of the stable working condition of the vehicle speed of each interval, carrying out weighted average through a time proportion, and obtaining the engine inlet air temperature result under the urban working condition through the following formula:
engine intake temperature T = T1 × P1+ T2 × P2+ … … + Tn × Pn,
wherein T1-Tn are the temperature results and P1-Pn are the time ratios.
2. The method for analyzing the intake air temperature of the automobile engine under the urban working condition according to claim 1, wherein the method comprises the following steps: the vehicle speed under the urban working condition is divided into 6 sections of 0-5kph,5-15kph,15-25kph,25-35kph,35-45kph and more than 45kph, and the representative vehicle speed of each section is V1, V2, V3, V4, V5, V6, and the time proportion P1, P2, P3, P4, P5, P6 of the vehicle speed section.
3. The method for analyzing the intake air temperature of the automobile engine under the urban working condition according to claim 1, wherein the method comprises the following steps: the step (31) includes: the method comprises the following steps of surface grid division and body grid division, wherein the type of a surface grid is a triangular grid, the body grid division is carried out on the basis of the surface grid division, and the type of the body grid is a tetrahedral grid.
4. The method for analyzing the intake air temperature of the automobile engine under the urban working condition according to claim 3, wherein the method comprises the following steps: the side length of the triangular mesh is less than or equal to 10mm, and the growth rate of the tetrahedral mesh is less than or equal to 1.6.
5. The method for analyzing the intake air temperature of the automobile engine under the urban working condition according to claim 3, wherein the method comprises the following steps: and after the face meshes are divided, checking the face meshes, wherein the checking requires that the minimum angle of the triangular meshes is not lower than 15 degrees, the maximum angle is not more than 130 degrees, and the triangular meshes do not have repetitive meshes and mutually crossed meshes.
6. The method for analyzing the intake air temperature of the automobile engine under the urban working condition according to claim 3, wherein the method comprises the following steps: after the body grid division, body grid inspection is carried out, and the torsion rate of all the body grids is not higher than 0.95.
7. The method for analyzing the intake air temperature of the automobile engine under the urban condition according to any one of claims 1 to 6, characterized in that: and before the step (33), determining a CAE calculation model and parameter settings, wherein the parameters comprise a relaxation factor, a convergence factor and a calculation step number.
8. The method for analyzing the intake air temperature of the automobile engine under the urban working condition according to claim 7, wherein the method comprises the following steps: the CAE calculation model is a standard model, and the number of calculation steps is greater than or equal to 3000.
9. The method for analyzing the intake air temperature of the automobile engine under the urban condition according to any one of claims 1 to 6, wherein the method comprises the following steps: and (5) before the step (4), checking a calculation result, namely checking whether the speed field of the whole vehicle meets the requirement or not, checking whether the speed field of an air inlet system of the engine is correct or not, and extracting the calculation result under the condition that the speed field of the whole vehicle and the speed field of the air inlet system of the engine are both correct.
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| CN102622490A (en) * | 2012-03-28 | 2012-08-01 | 奇瑞汽车股份有限公司 | Method for analyzing uniformity of exhaust gas recirculation (EGR) of engine air |
| CN106649923A (en) * | 2016-09-14 | 2017-05-10 | 北京汽车股份有限公司 | Thermal damage assessment method and device for engine exhaust system |
| CN106844899A (en) * | 2016-12-31 | 2017-06-13 | 华晨汽车集团控股有限公司 | The detection method of exhaust manifold Steady-State Thermal Field |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102622490A (en) * | 2012-03-28 | 2012-08-01 | 奇瑞汽车股份有限公司 | Method for analyzing uniformity of exhaust gas recirculation (EGR) of engine air |
| CN106649923A (en) * | 2016-09-14 | 2017-05-10 | 北京汽车股份有限公司 | Thermal damage assessment method and device for engine exhaust system |
| CN106844899A (en) * | 2016-12-31 | 2017-06-13 | 华晨汽车集团控股有限公司 | The detection method of exhaust manifold Steady-State Thermal Field |
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