CN115659863A - Method for improving in-cylinder EGR rate uniformity distribution - Google Patents
Method for improving in-cylinder EGR rate uniformity distribution Download PDFInfo
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- CN115659863A CN115659863A CN202211311647.7A CN202211311647A CN115659863A CN 115659863 A CN115659863 A CN 115659863A CN 202211311647 A CN202211311647 A CN 202211311647A CN 115659863 A CN115659863 A CN 115659863A
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Abstract
The invention provides a method for improving uniformity distribution of EGR (exhaust gas recirculation) rates in cylinders, which comprises the steps of obtaining bench calibration test data based on a bench calibration test database, establishing a GT-POWER one-dimensional thermodynamic model, calculating to obtain periodic boundary parameters required by CFD (computational fluid dynamics) calculation, building an air inlet pipeline and an EGR pipeline grid model by AVL FIRE (automatic voltage scaling) software, combining the obtained periodic boundary parameters, completing three-dimensional transient CFD (computational fluid dynamics) calculation by AVL FIRE software to obtain distribution of the EGR rates of air inlet of each cylinder, analyzing air flows in an air inlet manifold and the EGR pipeline, deriving result data of CFD analysis, further analyzing and calculating to obtain the EGR rate and the EGR rate of an outlet of each cylinder, further optimizing the EGR pipeline, reducing deviation rate of the EGR rate of each cylinder and improving distribution of the EGR rates in the cylinders. The method provided by the invention can verify the reasonability of the design of the air inlet pipeline and the EGR pipeline, provides direction guidance for the optimization design of the pipeline, and can effectively achieve the aim of optimal distribution of the EGR uniformity of each cylinder.
Description
Technical Field
The invention relates to the technical field of automobile exhaust gas circulation, in particular to a method for improving in-cylinder EGR rate uniformity distribution.
Background
With the continuous upgrading of engine emission regulations, the particle emission is reduced by one order of magnitude on the basis of the original emission, and the reduction amplitude of NOx emission is reduced by about 40% on the basis of the original emission, which is a difficult point for the upgrading and development of engine products, and one main method for reducing the NOx emission is an EGR technology.
In the engine ventilation process, the distribution uniformity of the recirculated exhaust gas in each cylinder directly influences the performance and emission of the engine, the improvement on the oil consumption has a remarkable effect, the NOx emission and the working stability of the engine are directly influenced, but an effective method for predicting the distribution uniformity and a reasonable optimization guidance idea are lacked.
When the EGR system is used for a four-cylinder engine, the distribution of the EGR rate of each cylinder is very uneven under the influence of pressure fluctuation of an intake manifold, and NOx emission of cylinders with high EGR rate and low EGR rate is increased for cylinders with high EGR rate. When the EGR rate deviation of each cylinder is checked to be a certain value, the requirement cannot be met, an air inlet manifold needs to be designed and optimized again, and the flow resistance of a pipeline is improved.
Disclosure of Invention
The invention aims to solve the problems, provides a method for improving the uniformity distribution of EGR rate in cylinders, analyzes the uniformity distribution state of EGR of each cylinder of a four-cylinder engine through the boundary input of a GT-POWER one-dimensional thermodynamic calculation model and based on a fluid flow CFD analysis theory method of AVL FIRE software, obtains the design rationality of an air inlet pipeline and an EGR pipeline based on an EGR rate and an EGR rate deviation rate calculation method, and provides a pipeline optimization design direction guide to achieve the aim of optimally distributing the EGR uniformity of each cylinder.
In order to achieve the above object, the present invention provides a method for improving in-cylinder EGR rate uniformity distribution, comprising the steps of:
and 6, optimizing the EGR pipeline according to the calculated EGR rate deviation rate, thereby reducing the EGR rate deviation rate of each cylinder and improving the in-cylinder EGR rate distribution.
Specifically, the calculation in step 2 obtains periodic boundary parameters required by the CFD calculation, where the periodic boundary parameters include mass flow curves of each air inlet, pressure curves, temperature curves, and mass flow curves at the EGR inlet.
Specifically, in step 5, the derived CFD analysis result data is further analyzed to obtain an EGR rate and an EGR rate deviation rate of each cylinder outlet, where the calculation formulas of the EGR rate and the EGR rate deviation rate are as follows:
EGR rate calculation formula:
in the above formula:
m i -mass flow at the ith cylinder outlet;
theta is the crank angle;
EGR iθ -EGR rate as a function of crank angle;
EGR i -the ith cylinder EGR rate;
EGR rate deviation rate calculation formula:
in the above formula:
ΔEGR i EGR Rate deviation Rate of the i-th Cylinder
EGR-Total EGR Rate.
Specifically, in step 6, the EGR pipeline is optimized according to the calculated EGR rate deviation ratio, and when the calculated EGR rate deviation ratio is greater than 5%, the EGR pipeline needs to be optimized, where the optimization direction is to optimize the pipeline diameter at the interface between the EGR pipe and the intake manifold.
Compared with the prior art, the invention has the beneficial effects that:
the invention discloses a method for improving in-cylinder EGR rate uniformity distribution, which analyzes the EGR uniformity distribution state of each cylinder of a four-cylinder engine through the boundary input of a GT-POWER one-dimensional thermodynamic calculation model and a fluid flow CFD analysis theory method based on AVL FIRE software, obtains the design rationality of an air inlet pipeline and an EGR pipeline based on the EGR rate and an EGR rate deviation rate calculation method, and provides a pipeline optimization design direction guide to achieve the aim of optimal distribution of EGR uniformity of each cylinder.
Drawings
FIG. 1 is a schematic diagram of an in-cylinder EGR rate and an EGR rate deviation rate before optimization in an embodiment of the invention;
FIG. 2 is a diagram illustrating an optimized in-cylinder EGR rate and EGR rate deviation rate in an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without any inventive step, are within the scope of the present invention.
The invention provides a method for improving uniformity distribution of EGR rate in a cylinder, which comprises the following steps:
EGR rate calculation formula:
in the above formula:
m i -mass flow at the ith cylinder outlet;
theta-crank angle;
EGR iθ -EGR rate as a function of crank angle;
EGR i -the ith cylinder EGR rate;
EGR rate deviation rate calculation formula:
in the above formula:
ΔEGR i ——EGR rate deviation ratio of i-th cylinder
EGR-Total EGR Rate.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the structure of the present invention in any way. Any simple modification, equivalent change and modification of the above embodiments according to the technical spirit of the present invention are within the technical scope of the present invention.
Claims (4)
1. A method of improving in-cylinder EGR rate uniformity distribution, comprising the steps of:
step 1, acquiring bench calibration test data based on a bench calibration test database, and establishing a GT-POWER one-dimensional thermodynamic model;
step 2, calculating to obtain periodic boundary parameters required by CFD calculation according to the established GT-POWER one-dimensional thermodynamic model;
step 3, constructing a CAD model of the flow entity of the intake manifold and the inner cavity of the EGR circulation pipeline based on CATIA software;
step 4, according to the CAD model of the flow entity of the inner cavities of the intake manifold and the EGR circulation pipeline constructed in the step 3, further building a grid model of the intake pipeline and the EGR pipeline by AVL FIRE software, and combining the periodic boundary parameters required by the CFD calculation obtained in the step 2, completing three-dimensional transient CFD calculation by the AVL FIRE software to obtain the distribution of the intake EGR rate of each cylinder, analyzing the gas flow in the intake manifold and the EGR pipeline, and exporting the result data of the CFD analysis;
step 5, further analyzing and calculating the derived CFD analysis result data to obtain the EGR rate and the EGR rate deviation rate of each cylinder outlet;
and 6, optimizing the EGR pipeline according to the calculated EGR rate deviation rate, thereby reducing the EGR rate deviation rate of each cylinder and improving the in-cylinder EGR rate distribution.
2. The method of claim 1, wherein the calculating in step 2 is to derive periodic boundary parameters required for CFD calculation, and the periodic boundary parameters comprise mass flow curves at each inlet, pressure curves, temperature curves, and mass flow curves at the EGR inlet.
3. The method of claim 1, wherein the CFD analysis result data derived in step 5 is further analyzed to obtain the EGR rate and the EGR rate deviation rate of each cylinder outlet, wherein the EGR rate and the EGR rate deviation rate are calculated as follows: EGR rate calculation formula:
in the above formula:
m i -mass flow at the ith cylinder outlet;
theta-crank angle;
EGR iθ -EGR rate as a function of crank angle;
EGR i -the ith cylinder EGR rate;
EGR rate deviation rate calculation formula:
in the above formula:
ΔEGR i EGR Rate deviation Rate of the ith Cylinder
EGR-Total EGR Rate.
4. The method for improving the uniformity distribution of the EGR rate in the cylinder according to claim 1, wherein the EGR pipeline is optimized according to the deviation rate of the calculated EGR rate in step 6, when the deviation rate of the calculated EGR rate is greater than 5%, the EGR pipeline needs to be optimized, and the optimization direction is to optimize the diameter of the pipeline at the interface between the EGR pipe and the intake manifold.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202211311647.7A CN115659863A (en) | 2022-10-25 | 2022-10-25 | Method for improving in-cylinder EGR rate uniformity distribution |
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| CN202211311647.7A CN115659863A (en) | 2022-10-25 | 2022-10-25 | Method for improving in-cylinder EGR rate uniformity distribution |
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