CN115034053A - Simulation analysis method and device for simulating residual exhaust gas of two-stroke engine - Google Patents

Abstract

The invention discloses a simulation analysis method and a simulation analysis device for simulating residual exhaust gas of a two-stroke engine, wherein the method comprises the following steps: obtaining size parameters of the engine, constructing an engine solid model according to the size parameters, and performing meshing on the engine solid model to output a mesh model file; building an engine one-dimensional performance simulation model according to the conditions and control parameters of the engine, and resolving through the engine one-dimensional performance simulation model to obtain boundary conditions required by an engine entity model; reading a grid model file, setting an initialization condition for carrying out numerical simulation on the boundary condition, carrying out numerical simulation calculation, and analyzing the result of the numerical simulation calculation to obtain simulation result image data in an engine cylinder; and carrying out a plurality of times of numerical simulation calculation based on the simulation result image data to obtain the residual change value of the exhaust gas in the engine cylinder. The invention simplifies the design process of the air exchange structure of the two-stroke engine, and reduces the manufacturing time and cost for designing the engine body.

Description

Simulation analysis method and device for simulating residual exhaust gas of two-stroke engine

Technical Field

The invention relates to the technical field of internal combustion engine testing, in particular to a simulation analysis method and device for simulating residual exhaust gas of a two-stroke engine.

Background

Under the condition of the same displacement, the two-stroke engine has the advantages of higher geometric compression ratio than the four-stroke engine, simple structure, mature technology, low cost and the like due to the dynamic property and the technical maturity, and is relatively wide in the practical application of agriculture and forestry. Since the gas flow organization system in the cylinder of the two-stroke gasoline engine is complex, researchers never stop researching the gas flow in the cylinder since the middle of the last century, and a numerical simulation method for the combustion and the gas flow organization in the cylinder of the engine is developed to observe the flowing state and the component distribution of the gas in the cylinder more intuitively, so that the aim of reorganizing the gas flow in the cylinder can be achieved by optimizing the parameters of a scavenging port and an exhaust port, and the aims of reducing oil consumption and optimizing emission are fulfilled. On a two-stroke engine air exchange structure, transverse flow scavenging and reflux scavenging are two common modes, scavenging passages of the transverse flow scavenging are distributed on opposite surfaces of an exhaust port, and in the scavenging process, air flow of fresh working media drives waste gas from the lower part to the upper part from the scavenging port; the scavenging passage for scavenging by backflow is distributed at two sides of the exhaust passage, and fresh working medium airflow collides from two sides and drives waste gas from bottom to top in the scavenging process. Therefore, the size and the position of the scavenging passage and the exhaust passage are designed to be important directions for improving the fuel economy of the engine and optimizing the emission.

In the actual design process of the engine, the basic size and the position of the scavenging passage and the exhaust passage are redesigned every time the direction of scavenging airflow is adjusted, the time and the cost required by the design and the production of the engine are increased by reworking the size and the position of an engine body including the scavenging passage and the exhaust passage, and therefore, the scavenging of the engine needs to be considered before the design and the production so as to carry out numerical simulation to optimize the structure.

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, the invention aims to provide a simulation analysis method for simulating residual exhaust gas of a two-stroke engine, which is simplified in the design process of a two-stroke engine ventilation structure and reduces the manufacturing time and cost for designing an engine body.

Another object of the present invention is to provide a simulation analysis device for simulating the residual exhaust gas of a two-stroke engine.

In order to achieve the above object, in one aspect, the present invention provides a simulation analysis method for simulating residual exhaust gas of a two-stroke engine, including:

obtaining size parameters of an engine, constructing an engine entity model according to the size parameters, and performing meshing on the engine entity model to output a mesh model file; building an engine one-dimensional performance simulation model according to the conditions and the control parameters of the engine, and resolving through the engine one-dimensional performance simulation model to obtain boundary conditions required by the engine entity model; reading the grid model file, setting the initialization condition of numerical simulation on the boundary condition, carrying out numerical simulation calculation, and analyzing the result of the numerical simulation calculation to obtain the simulation result image data in the engine cylinder; and carrying out multiple times of numerical simulation calculation based on the simulation result image data to obtain the residual change value of the exhaust gas in the engine cylinder.

In addition, the simulation analysis method for simulating the residual exhaust gas of the two-stroke engine according to the embodiment of the invention can also have the following additional technical characteristics:

further, in one embodiment of the present invention, the dimension parameters include: the engine may include a plurality of engine bore sizes, scavenge passage sizes and locations, exhaust passage sizes and locations, piston sizes and locations, scavenge port sizes, and exhaust port sizes.

Further, in one embodiment of the present invention, the condition and control parameters include: the sizes and the arrangement modes of the air inlet passage and the air outlet passage, the compression ratio, the ignition advance angle and the air-fuel ratio.

Further, in an embodiment of the present invention, after reading the mesh model file, the method further includes: setting a mathematical model, a dynamic grid model and a grid interaction surface of the engine solid model; wherein the mathematical model comprises an energy transfer model, a turbulence model, and a component transport model; the grid interaction surface comprises an interaction surface of the piston and the exhaust passage and an interaction surface of the piston and the scavenging passage.

Further, in an embodiment of the present invention, the boundary condition includes: scavenge port pressure and exhaust port pressure.

Further, in an embodiment of the present invention, the setting of the initialization condition for the numerical simulation includes: and dividing the pressure, the temperature and the initial component mass fraction of the scavenging passage, the combustion chamber and the exhaust pipe.

Further, in an embodiment of the present invention, after the performing the plurality of numerical simulation calculations, the method further includes: adjusting the position and size of a scavenging passage, the shape of a combustion chamber and the position and size of an exhaust passage of the engine according to parameters; and adjusting parameters of the dynamic grid model and the scavenging port pressure of the boundary condition.

The simulation analysis method for simulating the residual exhaust gas of the two-stroke engine provided by the embodiment of the invention realizes guidance on the structural design of the engine through the simulation analysis method, and reduces the economic cost and time investment caused by repeated design and processing.

In order to achieve the above object, according to another aspect of the present invention, there is provided a simulation analysis apparatus for simulating residual exhaust gas of a two-stroke engine, comprising:

the model division module is used for acquiring size parameters of the engine, constructing an engine solid model according to the size parameters, and performing meshing on the engine solid model to output a mesh model file;

the condition calculation module is used for building an engine one-dimensional performance simulation model according to the construction parameters of the engine, and calculating the boundary conditions required by the engine entity model through the engine one-dimensional performance simulation model;

the data analysis module is used for reading the grid model file, setting the initialization condition of numerical simulation on the boundary condition, carrying out numerical simulation calculation, and analyzing the result of the numerical simulation calculation to obtain the simulation result image data in the engine cylinder;

and the calculation output module is used for carrying out numerical simulation calculation for multiple times based on the simulation result image data to obtain the residual change value of the exhaust gas in the engine cylinder.

The simulation analysis device for simulating the residual exhaust gas of the two-stroke engine, disclosed by the embodiment of the invention, can be used for guiding the structural design of the engine by a simulation analysis method, and reducing the economic cost and time investment caused by repeated design and processing.

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

The foregoing and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a flow chart of a method for simulation analysis of residual exhaust gas from a simulated two-stroke engine according to an embodiment of the present invention;

FIG. 2 is a flow chart of a simulation analysis method for simulating residual exhaust gas of a two-stroke engine based on Fluent according to an embodiment of the invention;

FIG. 3 is a block diagram of an engine according to an embodiment of the invention;

FIG. 4 is a graph of calculated scavenging path pressures according to an embodiment of the present invention;

FIG. 5 is an in-cylinder CO obtained after calculation of the results according to an embodiment of the present invention ₂ A concentration distribution cloud chart.

Fig. 6 is a schematic structural diagram of a simulation analysis device for simulating residual exhaust gas of a two-stroke engine according to an embodiment of the invention.

Detailed Description

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.

In order to make the technical solutions of the present invention better understood, 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 only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Hereinafter, a simulation analysis method and apparatus for simulating residual exhaust gas of a two-stroke engine 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 for simulation analysis of residual exhaust gas from a simulated two-stroke engine in accordance with one embodiment of the present invention.

As shown in fig. 1, the method includes, but is not limited to, the steps of:

s1, obtaining size parameters of the engine, constructing an engine solid model according to the size parameters, and performing meshing on the engine solid model to output a mesh model file;

s2, building an engine one-dimensional performance simulation model according to the conditions and control parameters of the engine, and resolving through the engine one-dimensional performance simulation model to obtain boundary conditions required by an engine entity model;

s3, reading the grid model file, setting the initialization condition of numerical simulation for the boundary condition, carrying out numerical simulation calculation, and analyzing the result of the numerical simulation calculation to obtain the simulation result image data in the engine cylinder;

and S4, performing a plurality of times of numerical simulation calculation based on the simulation result image data to obtain the residual change value of the exhaust gas in the engine cylinder.

According to the simulation analysis method for simulating the residual exhaust gas of the two-stroke engine, the structural design of the engine is guided by the simulation analysis method, and the economic cost and time investment caused by repeated design and processing are reduced.

FIG. 2 is a flow chart of a simulation analysis method for simulating residual exhaust gas of a two-stroke engine based on Fluent, according to an embodiment of the present invention, as shown in FIG. 2.

Step 201, obtaining the basic size of the engine according to a mechanical design drawing of the selected engine, establishing an entity model of the engine by utilizing three-dimensional software such as UG (Unigraphics) and the like, and exporting an IGS file;

step 202, importing the x.igs file output in the step 201 into ICEM, designing grid parameters, dividing grids, and exporting an x.msh file;

step 203, building a GT-Power one-dimensional model according to the structure of the engine, solving boundary conditions and initial conditions of the engine through the GT-Power model, and compiling Profiles files;

step 204, reading the msh file generated in the step 202 by using Fluent software, setting a mathematical model, a dynamic grid model and a grid interaction surface of the engine entity model, setting boundary conditions of the engine model according to the Profiles file compiled in the step 203, setting initialization conditions of numerical simulation, starting numerical simulation calculation to obtain a calculation result, and exporting the calculation result into a tec dat file;

step 205, opening the xtec. dat file generated in the step 204 by Tecplot software to obtain simulated image data inside the engine, wherein the simulated image data comprises a residual exhaust gas concentration distribution cloud map;

step 206, outputting the residual exhaust gas concentration distribution cloud chart in the step 205;

step 207, repeating the steps 201-206, performing numerical simulation for multiple times, and only changing basic size parameters of the engine in the step 201 and the dynamic grid model and boundary conditions in the step 203 before carrying out simulation for each time;

and step 208, comparing the residual exhaust gas concentration distribution cloud charts output in the step 206, summarizing and analyzing to obtain the optimal structure and parameter conditions for scavenging the engine.

And obtaining an optimal structure for scavenging the engine and providing optimization guidance for the scavenging design of the engine according to the residual exhaust gas concentration distribution cloud chart obtained in the step 208.

Specifically, in step 201, the basic dimensions of the engine include the bore size of the engine, the scavenging path size and position, the exhaust path size and position, the piston size and position, the scavenging port size, and the exhaust port size.

Specifically, in step 202, the engine model is gridded, and the number of grids is at least 50 ten thousand.

Specifically, the structure of the engine comprises the sizes of an air inlet passage and an air outlet passage, the arrangement mode of the air inlet passage and the air outlet passage, the compression ratio, the ignition advance angle and the air-fuel ratio.

Specifically, in step 204, the included mathematical models include an energy transfer model, a turbulence model, and a component transport model. The turbulence model uses an achievable k-epsilon model; the component transportation model uses a gasoil-air model; the Mesh Method In the dynamic grid model uses a Ratio based model In Layering, and the Options use an In-cylinder model. The grid interaction surface comprises an interaction surface of the piston and the exhaust passage, and an interaction surface of the piston and the scavenging passage. The boundary conditions include scavenging port pressure, exhaust port pressure. And carrying out simulation calculation for the SIMPLE algorithm by adopting an algorithm of numerical simulation calculation.

Specifically, in step 204, the Initialization conditions of the numerical simulation are the pressure, temperature and initial component mass fraction of the scavenging path, combustion chamber, exhaust pipe divided by the Patch function in Solution Initialization in Fluent.

Specifically, in step 207, the changed basic engine size includes the position and size of the scavenging path, the shape of the combustion chamber, and the position and size of the exhaust path, the basis for changing the dynamic grid model is the engine speed, and the changed boundary condition is the scavenging port pressure.

Further, the engine exhaust gas residue is analyzed based on Fluent software, and the method comprises the following steps:

step 301, obtaining the basic size of the engine according to the mechanical design drawing of the selected engine, establishing a solid model of the engine by utilizing UG and other three-dimensional software, and exporting an IGS file;

step 302, the engine solid model is shown in fig. 3 and comprises a scavenging passage 1, a secondary scavenging passage 2, a piston 3, a combustion chamber 4 and an exhaust pipe 5;

step 303, reading the msh file generated in step 202 by using Fluent software, setting a mathematical model, a dynamic grid model and a grid interaction surface of an engine entity model, and writing the msh file into a profile file according to the scavenging port pressure curve calculated in step 203, as shown in fig. 4, setting boundary conditions of the engine model, setting initialization conditions of numerical simulation, carrying out simulation calculation to obtain a calculation result, and exporting the msh file into a star _ tec.dat file;

step 304, opening the tec _ dat file generated in the step 204 by Tecplot software to obtain simulated image data of the interior of the engine, wherein the simulated image data comprises a residual exhaust gas concentration distribution cloud map;

as an example, the in-cylinder residual exhaust gas concentration distribution cloud obtained in step 205, as shown in fig. 5, may visually reflect the scavenging effect in the engine cylinder.

Step 305, outputting the exhaust gas concentration distribution cloud chart in the step 205;

step 306, changing the relevant parameters of step 201 includes: the position and the size of a scavenging passage, the shape of a combustion chamber, the position and the size of an exhaust passage, the rotating speed of an engine and the pressure of a scavenging port are repeated, the steps 202, 203, 204, 205 and 206 are repeated, a residual exhaust gas concentration distribution cloud chart of a simulation result is compared, and the effect after the structural parameters are adjusted is analyzed;

307. and obtaining the optimal structure of the scavenging of the engine and providing optimization guidance for the scavenging design of the engine according to the exhaust gas concentration distribution cloud map obtained in the step 208.

According to the simulation analysis method for simulating the residual exhaust gas of the two-stroke engine, the structural design of the engine is guided by the simulation analysis method, and the economic cost and time investment caused by repeated design and processing are reduced.

In order to implement the above embodiment, as shown in fig. 6, a simulation analysis device 10 for simulating residual exhaust gas of a two-stroke engine is further provided in the present embodiment, wherein the device 10 includes: the model partitioning module 100, the condition solving module 200, the data analysis module 300, and the calculation output module 400.

The model division module 100 is used for obtaining size parameters of the engine, constructing an engine entity model according to the size parameters, and performing meshing on the engine entity model to output a mesh model file;

the condition calculating module 200 is used for building an engine one-dimensional performance simulation model according to the conditions and the control parameters of the engine, and calculating the boundary conditions required by the engine entity model through the engine one-dimensional performance simulation model;

the data analysis module 300 is configured to read a mesh model file, perform numerical simulation on the boundary conditions by setting initialization conditions, perform numerical simulation calculation, and analyze results of the numerical simulation calculation to obtain simulation result image data in an engine cylinder;

and the calculation output module 400 is used for carrying out multiple times of numerical simulation calculation on the basis of the simulation result image data to obtain the residual change value of the exhaust gas in the engine cylinder.

Further, after the data obtaining module 100, the method further includes: and the preprocessing module is used for preprocessing the index data, wherein the preprocessing comprises multiple data processing of deduplication, verification and desensitization.

Further, after the data analysis module 300, the method further includes:

the model setting module is used for setting a mathematical model, a dynamic grid model and a grid interaction surface of the engine solid model; wherein the mathematical model comprises an energy transfer model, a turbulence model and a component transport model; and the grid interaction surface comprises an interaction surface of the piston and the exhaust passage and an interaction surface of the piston and the scavenging passage.

Further, the calculation output module 400 further includes:

the first parameter adjusting module is used for adjusting the position and the size of a scavenging passage, the shape of a combustion chamber and the position and the size of an exhaust passage of the engine; and the number of the first and second groups,

and the second parameter adjusting module is used for adjusting the parameters of the dynamic grid model and the scavenging port pressure of the boundary condition.

According to the simulation analysis device for simulating the residual exhaust gas of the two-stroke engine, the structural design of the engine is guided by a simulation analysis method, and the economic cost and time investment caused by repeated design and processing are reduced.

It should be noted that the above explanation of the embodiment of the simulation analysis method for simulating the residual exhaust gas of the two-stroke engine is also applicable to the simulation analysis device for simulating the residual exhaust gas of the two-stroke engine of the embodiment, and is not repeated herein.

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 to implicitly indicate 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 explicitly specified otherwise.

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 (10)

1. A simulation analysis method for simulating residual exhaust gas of a two-stroke engine is characterized by comprising the following steps:

obtaining size parameters of an engine, constructing an engine entity model according to the size parameters, and performing meshing on the engine entity model to output a mesh model file;

building an engine one-dimensional performance simulation model according to the conditions and control parameters of the engine, and resolving through the engine one-dimensional performance simulation model to obtain boundary conditions required by the grid model;

reading the grid model file, setting the initialization condition of numerical simulation on the boundary condition, carrying out numerical simulation calculation, and analyzing the result of the numerical simulation calculation to obtain the simulation result image data in the engine cylinder;

and carrying out multiple times of numerical simulation calculation based on the simulation result image data to obtain the residual change value of the exhaust gas in the engine cylinder.

2. The method of claim 1, wherein the dimensional parameters comprise: the engine may include a plurality of engine bore sizes, scavenge passage sizes and locations, exhaust passage sizes and locations, piston sizes and locations, scavenge port sizes, and exhaust port sizes.

3. The method of claim 1, wherein the condition and control parameters comprise: the sizes and the arrangement modes of the air inlet passage and the air outlet passage, the compression ratio, the ignition advance angle and the air-fuel ratio.

4. The method of claim 1, after reading the mesh model file, further comprising:

setting a mathematical model, a dynamic grid model and a grid interaction surface of the engine solid model; wherein the mathematical model comprises an energy transfer model, a turbulence model, and a component transport model; the grid interaction surface comprises an interaction surface of the piston and the exhaust passage and an interaction surface of the piston and the scavenging passage.

5. The method of claim 4, wherein the boundary condition comprises: scavenge port pressure and exhaust port pressure.

6. The method of claim 1, wherein the initialization condition setting of the numerical simulation comprises: and dividing the pressure, the temperature and the initial component mass fraction of the scavenging passage, the combustion chamber and the exhaust pipe.

7. The method of claim 5, wherein after said performing a plurality of said numerical simulation calculations, further comprising:

adjusting the position and size of a scavenging passage, the shape of a combustion chamber and the position and size of an exhaust passage of the engine according to parameters; and the number of the first and second groups,

and adjusting parameters of the dynamic grid model and the scavenging port pressure of the boundary condition.

8. A simulation analyzer for simulating residual exhaust gas of a two-stroke engine, comprising:

the model division module is used for obtaining size parameters of the engine, constructing an engine entity model according to the size parameters, and performing meshing on the engine entity model to output a mesh model file;

the condition calculation module is used for building an engine one-dimensional performance simulation model according to the conditions and the control parameters of the engine, and calculating the boundary conditions required by the engine entity model through the engine one-dimensional performance simulation model;

the data analysis module is used for reading the grid model file, setting the initialization condition of numerical simulation on the boundary condition, carrying out numerical simulation calculation, and analyzing the result of the numerical simulation calculation to obtain the simulation result image data in the engine cylinder;

and the calculation output module is used for carrying out multiple times of numerical simulation calculation on the basis of the simulation result image data to obtain the residual change value of the exhaust gas in the engine cylinder.

9. The apparatus of claim 7, further comprising, after the data analysis module:

the model setting module is used for setting a mathematical model, a dynamic grid model and a grid interaction surface of the engine solid model; wherein the mathematical model comprises an energy transfer model, a turbulence model, and a component transport model;

the grid interaction surface comprises an interaction surface of the piston and the exhaust passage and an interaction surface of the piston and the scavenging passage.

10. The apparatus of claim 8, wherein the computing output module comprises:

the first parameter adjusting module is used for adjusting the position and the size of a scavenging passage, the shape of a combustion chamber and the position and the size of an exhaust passage of the engine; and the number of the first and second groups,

and the second parameter adjusting module is used for carrying out parameter adjustment on the dynamic grid model and the scavenging port pressure of the boundary condition.

Images