CN112733294A

CN112733294A - Design method of engine cylinder gasket

Info

Publication number: CN112733294A
Application number: CN202110032194.3A
Authority: CN
Inventors: 徐熹; 赵洁; 贾正锋; 曾庆强
Original assignee: Chongqing Changan Automobile Co Ltd
Current assignee: Chongqing Changan Automobile Co Ltd
Priority date: 2021-01-11
Filing date: 2021-01-11
Publication date: 2021-04-30
Anticipated expiration: 2041-01-11
Also published as: CN112733294B

Abstract

The scheme relates to a design method of an engine cylinder gasket, which comprises the following steps: establishing a geometric model of a cylinder cover, a cylinder body, a cylinder gasket and a bolt; grid division; and (3) boundary condition processing: applying bolt pretightening force, applying assembly interference magnitude between a valve seat ring of a cylinder body and a cylinder cover, applying assembly interference magnitude between a valve guide pipe of the cylinder body and the cylinder cover, mapping CFD temperature field results corresponding to three reliability bench tests of an engine, applying gas explosion pressure in a combustion chamber of the cylinder body, and enabling the applied gas explosion pressure and the temperature field to form sequential heat-force coupling; carrying out finite element analysis calculation; obtaining respective sealing pressure and dynamic separation clearance of the cylinder gasket under the working condition of gas explosion pressure and the working condition of a temperature field; judging whether the sealing pressure is within a preset standard sealing pressure range and the dynamic separation gap is within a preset standard dynamic separation gap range; and when the requirements are met, determining that the cylinder gasket meets the design requirements.

Description

Design method of engine cylinder gasket

Technical Field

The invention relates to the technical field of Computer Aided Engineering (CAE), in particular to a design method of an engine cylinder gasket.

Background

In the field of current automobile engineering, CAE (computer aided engineering) has been widely applied to product design, and becomes an effective tool for finding problems, solving problems and supporting product development in the automobile development process. The finite element method can achieve higher precision in the aspects of analyzing structural stress, strain, deformation, vibration, temperature, fatigue and the like, and can solve various problems in the engineering development process. The method predicts the weak sealing area of the cylinder gasket under the actual working condition of the bench by means of a finite element analysis tool, and provides a design method of the cylinder gasket of the automobile engine.

When the finite element method is used, a continuous structure is required to be dispersed into a plurality of units, and the units are connected into a whole through the nodes of the units. A certain quantity of nodes is used as an unknown quantity, the unknown quantity to be solved is expressed by an approximation function of an assumption unit, an equation set of the unknown quantity is obtained by a variational principle, and then a solution is obtained by a numerical method. The discrete effect and boundary condition of the continuous structure (finite element analysis model) are important factors influencing the accuracy of the approximate solution.

The cylinder gasket of the automobile engine is used as a key part of the engine, mainly used for sealing gas, cooling liquid and engine oil among cylinder bodies of a cylinder cover of the engine, simultaneously bearing the explosion pressure of the gas, the temperature of the gas, the pressure of the cooling liquid and the pressure of the engine oil, and having an abnormally complex working environment, and the analysis of the sealing performance of the cylinder gasket is an important work in the development of the engine. The temperature field used in the finite element analysis of the cylinder gasket at present is based on CFD simulation data of a full-speed full-load bench test of an engine, and cannot cover three reliability bench tests of the engine, particularly working conditions with rapid temperature changes of the cold and hot impact bench test of the engine and the alternating load bench test of the engine, which are also test items of key attention to the sealing performance of the cylinder gasket. As shown in fig. 1a and 1b, it can be seen that the temperature difference between the full speed full load bench test and the cold and hot impact bench test of the engine is very large, and the corresponding cylinder gasket sealing performance is also very large. Compared with a full-speed full-load bench test and a cold-hot impact bench test, the temperature cloud graph and the corresponding cylinder gasket sealing pressure cloud graph are used as examples, the engine temperature difference is very large, and the corresponding cylinder gasket sealing performance is also very different.

Disclosure of Invention

The invention aims to simulate various severe working environments of an engine cylinder head gasket through finite element analysis of three reliability bench tests of an engine, improve the sealing robustness of the cylinder head gasket, better guide the design and development of the cylinder head gasket, and provide a design method of the engine cylinder head gasket to meet the product development requirements.

The embodiment of the invention provides a design method of an engine cylinder gasket, which comprises the following steps:

step 1, establishing a geometric model of a cylinder cover, a cylinder body, a cylinder gasket and a bolt, and performing pretreatment;

step 2, carrying out mesh division on the pre-processed geometric model;

and step 3, boundary condition processing: applying bolt pretightening force, applying assembly interference magnitude between a valve seat ring of a cylinder body and a cylinder cover, applying assembly interference magnitude between a valve guide pipe of the cylinder body and the cylinder cover, mapping CFD temperature field results corresponding to three reliability bench tests of an engine, applying gas explosion pressure in a combustion chamber of the cylinder body, and enabling the applied gas explosion pressure and the temperature field to form sequential heat-force coupling;

step 4, finite element analysis and calculation are carried out;

step 5, obtaining respective sealing pressure and dynamic separation clearance of the cylinder gasket under the working condition of gas explosion pressure and the working condition of a temperature field;

and step 6, judging whether the following conditions are met: the respective sealing pressure of the cylinder gasket under the working condition of gas explosion pressure and the working condition of a temperature field is within a preset standard sealing pressure range, and the respective dynamic separation gap of the cylinder gasket under the working condition of gas explosion pressure and the working condition of the temperature field is within a preset standard dynamic separation gap range;

and 7, if so, determining that the cylinder gasket meets the design requirements.

Preferably, in step 5, the dynamic separation gap of the cylinder head gasket is specifically a difference value of a normal deformation amount of the cylinder head gasket under a gas explosion pressure working condition and a temperature field working condition.

The invention has the beneficial effects that:

by means of a finite element method, three reliability bench tests of the engine are completely considered, various severe working environments of the engine cylinder head gasket can be covered, the problem that complete finite element analysis cannot be carried out on the engine cylinder head gasket is avoided, the sealing robustness of the cylinder head gasket is improved, and design and development of the cylinder head gasket are guided better.

Drawings

FIG. 1a is a temperature cloud and a corresponding cylinder head gasket seal pressure cloud of a prior art engine under a full speed, full load bench test;

FIG. 1b is a temperature cloud and a corresponding cylinder head gasket sealing pressure cloud of a prior art engine under a cold and thermal shock bench test;

FIG. 2 is a flow chart of the method.

Detailed Description

The invention is further illustrated below with reference to fig. 2:

referring to fig. 2, the design method of the cylinder gasket of the automobile engine according to the present invention comprises the following steps:

1. carrying out three-dimensional geometric model establishment and pretreatment

First, a three-dimensional geometric model (three-dimensional CAD model) of parts such as a cylinder head, a cylinder block, a cylinder head gasket, a bolt, etc. is built in commercial software such as ProE/solid/UG/Catia/Autocad, etc. And then introducing the established three-dimensional geometric model into finite element preprocessing software (the finite element preprocessing software comprises Abaqus CAE/Patran/Hypermesh/ANSA and the like) to perform relevant geometric cleaning. For example, the established three-dimensional geometric model is processed as necessary by using a quick edge panel of HyperMesh software, and meshing is prepared for the finite element software in advance. The necessary processing steps specifically include: projecting the sealing line profile of the established three-dimensional geometric model of the cylinder gasket onto the sealing surface of the established three-dimensional geometric model of the cylinder cover and the cylinder body; projecting the outer contour of the flange surface of the established bolt model onto a cylinder cover mounting surface; and remove non-critical chamfers, fillets and other fine features.

2. Meshing by using finite element preprocessing software

Then, the Automesh subpanel, the drag subpanel and the tetramesh subpanel of the Hypermesh software are used for dividing the finite element mesh. The gasketed cylinder gasket is meshed with the cylinder gasket by using a gasketed unit, a valve guide pipe and a bolt of a cylinder body are meshed with the cylinder gasket by using a non-coordinated first-order hexahedral unit, and the rest other parts are meshed with the cylinder gasket by using a modified second-order tetrahedron unit. In addition, grid encryption is carried out on the position of the sealing rib of the cylinder gasket; the contact parts of the cylinder cover and the cylinder body with the sealing ribs of the cylinder gasket respectively ensure that the grid nodes correspond to each other; meanwhile, positions of a combustion chamber, a water jacket, an oil duct and the like of the cylinder body also need to be subjected to grid encryption, and particularly, more than four layers of grids are distributed at key round corners and chamfer positions so as to ensure that characteristic profiles at the key positions are clear and no serious distortion occurs.

3. Establishing finite element analysis boundary conditions

Then, according to the working environment of the cylinder gasket, reasonable boundary conditions are applied in finite element preprocessing software (such as Hypermesh software or Abaqus software). When the boundary condition is applied, the displacement boundary condition, the contact boundary condition and the load boundary condition are applied according to the actual situation. Wherein the applying of the load boundary condition specifically comprises:

1) applying bolt pretightening force on the bolt, wherein the pretightening force of the bolt is obtained by theoretical calculation of pretightening torque in advance;

2) and applying a pre-designed value of interference at the contact part of the valve seat ring and the valve guide pipe of the cylinder body and the cylinder cover.

3) And mapping CFD temperature field results on the established integral finite element model, wherein the mapped CFD temperature field results comprise CFD temperature field results under the full-speed full-load operation condition of the engine, CFD temperature field results under the cold-hot shock operation condition and CFD temperature field results under the alternating load operation condition (step 5 in fig. 2).

4) Applying gas explosion pressure to the combustion chamber of the engine and forming a sequential thermal-force coupling with the temperature field in the previous step 3) (step 4 in fig. 2).

6. And finally, carrying out finite element analysis calculation, submitting an analysis model, and solving through a solver of Abaqus software.

7. Seal pressure and dynamic clearance acquisition

And obtaining the sealing pressure and the dynamic separation clearance of the cylinder gasket under different working conditions according to the calculation result.

Specifically, a finite element solver is used for solving and calculating the integral model to obtain the sealing pressure and the normal deformation of the cylinder gasket under the working condition of gas explosion pressure and the sealing summer profit and the normal deformation of the cylinder gasket under the working condition of a temperature field, and further obtain the dynamic separation gap of the cylinder gasket (the dynamic separation gap is the difference value of the normal deformation of the cylinder gasket under the working condition of the gas explosion pressure and the working condition of the temperature field).

8. Making result judgment

And comparing the sealing pressure and the dynamic separation clearance of the cylinder gasket under different working conditions with a standard sealing pressure range and a standard dynamic separation clearance range obtained based on experience, and then evaluating the obtained result.

If the sealing pressures of the cylinder gasket under different working conditions are all within the range of the standard sealing pressure, and the dynamic separation gaps of the cylinder gasket under different working conditions are all within the range of the standard dynamic separation gaps, the currently designed cylinder gasket is considered to meet the design requirements; if the above condition is not satisfied, the design requirement is not satisfied.

9. Design optimization

If one of the results does not meet the requirements of the corresponding standard range, the main influencing factors causing the result need to be analyzed, and corresponding optimization measures need to be taken until the sealing performance of the cylinder gasket meets the requirements. When the optimization is carried out, optimization measures such as locally increasing the rigidity of a cylinder body of a cylinder cover, optimizing sealing ribs of the cylinder gasket, locally increasing limiting ribs and increasing the pre-tightening axial force of cylinder bolts can be carried out based on the sealing condition of the cylinder gasket.

10. Completion of the analysis

If the results in step 8 are all evaluated as meeting the requirements, the analysis is completed.

In the step of mapping the CFD temperature field result of the integral finite element model, it should be noted that the temperature field of the full-speed full-load operation condition of the engine is steady state, and the temperature fields of the cold and hot shock operation condition and the alternating load operation condition of the engine are transient. Therefore, according to the simulation result of the CFD, a temperature field at a suitable transient time point needs to be reasonably selected, and temperature field result mapping is performed. Therefore, the test bench can cover three reliability test benches of the engine, in particular to the working conditions of the engine cold and hot impact bench test and the engine alternating load bench test with the rapid temperature change. In the engine bench test, under the condition of abrupt temperature change, the engine cylinder gasket is more prone to sealing problems, so that the design of the engine cylinder gasket must be considered.

Claims

1. A method of designing an engine cylinder head gasket, comprising:

step 2, carrying out mesh division on the pre-processed geometric model;

step 4, finite element analysis and calculation are carried out;

2. The method according to claim 1, wherein in step 5, the dynamic clearance of the head gasket is defined as a difference between a normal deformation of the head gasket under a gas explosion pressure condition and a temperature field condition.