CN101673416B

CN101673416B - Method for dividing hexahedral mesh of piston of internal-combustion engine

Info

Publication number: CN101673416B
Application number: CN2009101910588A
Authority: CN
Inventors: 司庆九; 詹樟松; 闵龙; 徐勇
Original assignee: Chongqing Changan Automobile Co Ltd
Current assignee: Chongqing Changan Automobile Co Ltd
Priority date: 2009-09-30
Filing date: 2009-09-30
Publication date: 2012-06-13
Anticipated expiration: 2029-09-30
Also published as: CN101673416A

Abstract

The invention relates to a method for dividing hexahedral mesh of a piston of an internal-combustion engine, comprising the following steps: (1) a three-dimensional geometric model is built; (2) a piston ring land is removed: (3) initial topology is carried out to the piston which removes the piston ring land, and the volume of the hexahedral mesh after initial topology is carried out is more than the volume of the three-dimensional geometric model; (4) the piston which removes the piston ring land is divided into a two-dimensional closed surface mesh; (5) topology computation is carried out to an initial finite element model and the two-dimensional closed surface mesh, so as to obtain the finite element model; (6) a piston ring land mesh is artificially added. By adopting the method to build and divide the hexahedral mesh of the piston, the piston ring land is removed, and finally the ring land is built, so as to conveniently process irregular parts in the piston and improve the working efficiency of division of the whole hexahedral unit of the piston.

Description

A kind of method of dividing hexahedral mesh of piston of internal-combustion engine

Technical field

The invention belongs to the Computer Image Processing field, be specifically related to a kind of method of dividing hexahedral mesh of piston of internal-combustion engine.

Background technology

In the IC Engine Design process in modern times, for the reliability that improves design to save time and to reduce the failure of an experiment rate, often use CAD (computer-aided design (CAD)) and CAE (computer-aided engineering) technology.CAD software has CATIA, PRO/E, and UG etc., CAE software has NASTRAN, ABAQUS etc.Set up the digital three-dimensional geometric model through utilization CAD software, the pre-processing software through CAE carries out discretize to 3-D geometric model then, sets up finite element model.

In the utilization process, because piston structure is complicated,, will exist the tetrahedron element node many if adopt tetrahedron element, matrix is big, calculates big and the relatively poor defective of computational accuracy, adopts the second order tetrahedron element, and then calculated amount is bigger, and height assesses the cost.Adopt hexahedral element just to become very desirable solution.

Number of patent application is that the patent documentation that CN200510121431, name are called " a kind of method that generates three-dimensional finite element mesh " discloses a kind of method that generates three-dimensional finite element mesh; Specifically may further comprise the steps: the two-dimensional surface grid dividing is carried out on the surface at object entity three-dimensional model; Produce the entity basic grid that surrounds three-dimensional model through the entity basic grid of setting up by contour projection; The two-dimensional surface grid is inserted into after the entity basic grid; Remove the entity grid outside the object entity veil lattice, obtain the entity 3D grid of ultimate demand.Adopt the method to divide the piston hexahedral element; Because the piston ring groove gauge is very little, have only 1～2mm usually, and number of patent application is that the minimum dimension discerned in the method for CN200510121431 is also more than 2mm; Therefore; If adopting number of patent application is the method for CN200510121431, for the miniature gasoline engine piston, thus the not enough mesh quality that influences of its accuracy of identification.And then influence the division of whole piston hexahedral element.

Summary of the invention

For solving the problems referred to above that exist in the prior art, the present invention adopts a kind of effective method to handle piston land, so that divide the piston hexahedral element fast, efficiently, in high quality.

The technical scheme that the present invention adopts is:

A kind of method of dividing hexahedral mesh of piston of internal-combustion engine may further comprise the steps:

1.1 set up the 3-D geometric model of piston;

1.2 removal piston land;

1.3 the piston initial topology to through 1.2 step process obtains initial finite element model, and makes initial hexahedral mesh volume greater than three-dimensional model;

1.4 to divide two-dimensional closed veil lattice through the piston of 1.2 step process;

1.5, obtain finite element model to carrying out topology calculating through resulting initial finite element model of 1.3 steps and two-dimensional closed veil lattice;

1.6 the artificial piston land grid that adds.

Adopt said method to go to make up and divide hexahedral mesh of piston, the ring bank is removed in advance, making up the ring bank, handled irregular position in the piston easily at last, improved the work efficiency of the division of whole piston hexahedral element.

Description of drawings.

The three-dimensional model diagram of the piston that the first step obtains in the method that Fig. 1 the present invention adopts;

The three-dimensional model diagram of the piston that second step obtained in the method that Fig. 2 the present invention adopts;

Design sketch after the piston topology that the 3rd step obtained in the method that Fig. 3 the present invention adopts;

Piston topology process synoptic diagram in the method that Fig. 4 the present invention adopts;

The two-dimensional closed veil trrellis diagram of piston that the 4th step obtained in the method that Fig. 5 the present invention adopts;

Piston finite element model after the topology that the 5th step obtained in the method that Fig. 6 the present invention adopts;

The complete hexahedral mesh piston that the 6th step obtained in the method that Fig. 7 the present invention adopts.

Embodiment

Below in conjunction with accompanying drawing, carry out bright specifically to the method for division hexahedral mesh of piston of internal-combustion engine disclosed by the invention.

The first step, as shown in Figure 1, at first set up the 3-D geometric model of piston.The foundation of this model can be adopted commercial three-dimensional software commonly used, for example Pro/E, CATIA, UG.

Second step, as shown in Figure 2, remove piston land.This step can realize through three-dimensional software mentioned in the first step.Because model is different, the piston land number is also different.No matter which kind of model is all removed all the ring banks between top land and last annular groove.What remove in the present embodiment is the second ring bank and the 3rd ring bank.

The 3rd step; As shown in Figure 3; To removing the piston initial topology of ring bank; Said initial topology is exactly to adopt maximum envelope principle to make hexahedral mesh volume after the topology greater than by topology objects, and makes initial hexahedral mesh volume greater than the piston 3-D geometric model of removing in second step behind the piston land.This step can be passed through the finite element pre-processing software, and like FAME, MENTAT realizes.This step is preferred but be not limited to following operation in the present embodiment:

3.1 as shown in Figure 4, judge the part 1 that can 1. be stretched to the piston skirt end beyond the key seat along direction from piston crown, comprise the above part 2 and the following part 4 of key seat of part 3, key seat of inside and outside key seat;

3.2 confirm the piston ring groove degree of depth (the said annular groove degree of depth can be confirmed according to 2D or 3D figure), as shown in Figure 4, confirm annular groove position C cell position (the C position is the annular groove depth location), the piston ring groove of the present embodiment in the diagram has three-layer unit;

3.3 key seat is projected on the central plane, the manifold unit, 3. copy face unit projects on the face of cylinder (being the outside piston face) along direction, carries out the entity grid that topology obtains comprising the part 3 of inside and outside key seat.

When topology, can be in two steps: the C unit inside be done a face of cylinder in Fig. 4, and topology remains the topology of (promptly) again behind this face of cylinder.

3.4 will comprise the upper surface and the lower surface topology of the part 3 of inside and outside key seat.Wherein comprise inside and outside key seat part 3 upper surface upwards, promptly obtain the above part 2 of key seat along 2. direction topology, the lower surface of part 3 that comprises inside and outside key seat is downward, promptly along the part 4 below 4. the direction topology obtains key seat.

3.5 after the seamed edge in piston-top surface and skirt section projected to end face, guarantee the unit of annular groove after, obtain blue face unit, top, 1. stretch along direction, obtain being stretched to the hexahedral mesh of the part 1 of piston skirt end from piston crown.

3.6 whole hexahedral mesh model with the piston of 1/4 model (is 1/4 model like Fig. 4 demonstration) mirror after encircling bank for removal.

The 4th step, as shown in Figure 5, the piston 3-D geometric model after diameter the 3rd step handles, be that initial hexahedral mesh is divided two-dimensional closed veil lattice.

The 5th step, as shown in Figure 6, to initial finite element model, promptly the 3rd initial hexahedral mesh that obtain of step and two-dimensional closed veil lattice carry out topology calculating, obtain the finite element model after the topology.Initial hexahedral mesh of three-dimensional and two-dimensional surface grid are merged; And calculate to judge all nodes outside two-dimensional closed veil lattice the unit and remove them, will have part of nodes to project on two-dimensional closed at this part node of the unit outside two-dimensional closed.

In the 6th step, as shown in Figure 7, the artificial piston land grid that adds is accomplished the piston grid dividing, forms final piston finite element grid.In this example, interpolation is the second ring bank and the 3rd ring bank.

Owing to adopted advanced disposal route, the piston hexahedral element that obtains at last is of high quality and required time reduces greatly.

Claims

1. a method of dividing hexahedral mesh of piston of internal-combustion engine is characterized in that, said method comprising the steps of:

(1) sets up the 3-D geometric model of piston;

(2) remove piston land;

(3) to the piston initial topology behind the removal piston land, and the piston 3-D geometric model after making initial hexahedral mesh volume greater than removal piston land in (2) step; Step (3) realizes through following operation:

(3.1) in 1/4 model, confirm that key seat is stretched to the part (1) of piston skirt end in addition from piston crown, comprise the above part (2) and the following part (4) of key seat of part (3), key seat of inside and outside key seat;

(3.2) in 1/4 model, confirm the piston ring groove degree of depth;

(3.3) in 1/4 model, the entity grid of the part (3) of key seat inside and outside topology obtains comprising;

(3.4) in 1/4 model, will comprise the upper surface and the lower surface topology of the part (3) of inside and outside key seat;

(3.5) in 1/4 model, the seamed edge in piston-top surface and skirt section is projected to piston-top surface, guarantee the unit of annular groove after, obtain being stretched to the part (1) of piston skirt end from piston crown;

(3.6) with 1/4 model mirror to whole hexahedral mesh model for the piston after removing the ring bank;

(4) to the piston 3-D geometric model after handling through (3) step, be that initial hexahedral mesh is divided two-dimensional closed veil lattice;

(5) to initial finite element model, promptly (3) the initial hexahedral mesh that obtains of step and two-dimensional closed veil lattice carry out topology calculating, obtain finite element model;

(6) the artificial piston land grid that adds.

2. according to the method for the described division hexahedral mesh of piston of internal-combustion engine of claim 1; It is characterized in that; The entity grid of the part (3) of key seat was realized through following operation inside and outside said topology obtained comprising: during topology; (C) unit inside is done a face of cylinder at the annular groove position, and topology is carried out the topology of other parts again behind this face of cylinder.