research on coupling simulation between dynamics of multi-body and

8/6/2019 Research on Coupling Simulation Between Dynamics of Multi-Body And

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Research on Coupling Simulation Between Dynamics of Multi-body and

Hydrodynamic Lubrication of Piston-Cylinder Sleeve System

Cheng Ying, Song Xiao, Wang Dong-jieSchool of Mechanical and Vehicular Engineering

Beijing Institute of Technology， BIT

Beijing, China

[email protected]

Abstract —For the purpose of establish a more accurate

dynamic model of internal combustion engine (I.C.E) piston-

cylinder system, the model coupling between hydrodynamic

lubrication and dynamics of multi-body system of piston-

cylinder system was built by linking ADAMS and FORTRAN

subroutine. The coupling simulation analysis was conducted.

The simulation results demonstrated that because of the

coupling effect of oil film lubrication between piston and

cylinder sleeve the maximum force on the cylinder sleeve

decreases and the minimum force increases so that the change

of the force on the cylinder sleeve becomes smooth. At the same

time the influence on the piston lubricating characteristics of

clearance of piston-sleeve and piston skirt length were

analyzed, while the analysis provides basis for the selection and

design of piston parameters.

Keywords- multi-body system dynamics; piston; coupling

simulation; hydrodynamic lubrication; cylinder

I. I NTRODUCTION

In the working process of I.C.E, the piston skirt has thefunctions of bearing, guiding and lubrication. With thereciprocating cyclic motion of a piston in a cylinder, thelubricating oil film comes into being between piston skirtand cylinder wall, so the impact of piston on cylinder sleeveand the wear of piston is alleviated. On dissimilar parts of piston there have different kinds of time-varying forcesincluding combustion gas pressure, pressure of lubricatingoil film between piston and cylinder sleeve, friction, forcestransferred by connecting rod. The lubrication between piston and cylinder sleeve affects the motion of piston, and atthe same time the motion of piston system not only affectsthe forces on the cylinder sleeve from piston, but alsochanges the thickness of lubricating oil film betweencylinder sleeve and piston. So the motion of piston affectsthe lubrication, friction and wear between cylinder sleeveand piston.[1]

A 12-cylinde diesel engine was as research object, themulti-body system dynamic model of I.C.E piston-cylinder sleeve system was established based on ADAMS and thecoupling model on lubrication and dynamics of piston-cylinder sleeve system was established by linking ADAMSsolver and the FROTRAN subroutine. On these bases, thecoupling simulation analysis was conducted and a series of correlative conclusions were achieved.

II. ESTABLISHMENT OF THE COUPLING MODEL

The establishment of piston-cylinder sleeve couplingmodel is the course of solving the system dynamics equation[2] and the average Reynolds equation[3] simultaneouslyusing ADAMS solver and FORTRAN subroutine. The

numerical solutions can only be gained when solving the twoequations. Considering the mutual effects of the twoequations, the reiteration of variable must be carried out between different programs solving the two differentequations to solve the coupling equations of the wholesystem.

Fig 1 shows the I.C.E piston-cylinder sleeve system. Onthe plane which is vertical to the piston pin the force and thetorque on the piston make the piston translate and rotateslightly in the cylinder sleeve. This paper assumes that thedisplacements the top and the bottom of the piston skirt

deviate from the centerline of the cylinder sleeve are t e and

be respectively.

On the premise that the speed of the engine is fixed,choosing the time in which the crankshaft rotate 2 degrees as

a step size to disperse the time of a cycle, using signs 0t e ,

0be , 0t e , 0be as the initial values of the displacement and

speed of the top and the bottom of the piston skirt deviatingthe cylinder sleeve centerline, the oil film thickness

),( yhT θ between cylinder sleeve and piston skirt and its

derivative /T h t ∂ ∂ can be calculated through (1) and (2).

),,(),,(),(

cos)]()([cos)(

t yd t yd y f

L

yt et et eC h

v

t bt T

θ θ θ

θ θ

+++

−++= (1)

C is the radial clearance between piston skirt and cylinder

sleeve; L is the length of piston skirt; ),( y f θ is the

function of lateral outline and radial outline of piston skirt;

),,( t yd θ is the radial clearance variation value between

piston skirt and cylinder sleeve caused by the thermal

deformation; ),,( t yd v θ is the radial clearance variation

value caused by the cylinder structure vibration.

2009 Second International Conference on Information and Computing Science

978-0-7695-3634-7/09 $25.00 © 2009 IEEE

DOI 10.1109/ICIC.2009.386

300



cos 1

cos 1

vT t b

t b

d h y y d e e

t L L t t

y ye e

L L

θ

θ

∂∂ ⎡ ⎤ ∂⎛ ⎞= − + + +⎜ ⎟⎢ ⎥

∂ ∂ ∂⎝ ⎠⎣ ⎦

⎡ ⎤⎛ ⎞= − +⎜ ⎟⎢ ⎥

⎝ ⎠⎣ ⎦

(2)

Based on ),( yhT θ and /T h t ∂ ∂ of current time, the

average flow factor and shear press factor can be confirmed.

And then, oil film pressure ),( y P h θ can be gained through

solving the average Reynolds equation using finite differencemethod and successive over-relaxation method. The lateral

resultant force h F on the piston of lubricating oil film

pressure, the torque hM on the piston pin of lubricating oil

film pressure, resultant force of friction force fh F and the

friction torque fhM on the piston pin of friction force can

be taken out further. The force and the torque solved above

are substituted into the system dynamics equationreciprocally until the result is convergent and the value is theresult of considering the coupling effect between oil filmlubrication and system dynamics. Fig. 2 shows the flow chart.

Figure 1. PISTON-CYLINDER SLEEVE system

Figure 2. Flowchart

III. COUPLING SIMULATION ANALYSIS

A. Simulation Result of PISTON-CYLINDER SLEEVE

System Ignoring Lubrication

The I.C.E parameters which have been known are shownin table 1.

Table 1. SYSTEM PARAMETERS WHICH HAVE BEEN KNOWN

Piston stroke 160mm piston rotary inertia9.257E-3

N.m2

Piston mass 4.545 kg piston young modulus 75 GPa

Piston diameter 75 mmcylinder sleeve young

modulus200 GPa

Cylinder sleeve bore150.05

mmPoisson ratio 0.3

Clearance of piston-

sleeve

0.025

mm

lubricating oil kinetic

viscosity

0.008

Pa.s

Piston skirt length83.6

mm

surface roughness root

mean square value of

piston skirt,σ1

1.515E-6

um

Degree of bearing

region35°

surface roughness root

mean square value of

cylinder sleeve

1.715E-6

um

The lateral distance

between piston centroid

and piston pin

0 mmviscosity-temperature

coefficient)0.03/

Longitude distance

between piston centroid

and piston pin

5.12

mm

viscosity-pressure

coefficient

2.2×108

m2/N

Distance between piston

pin and the top of piston

skirt

33.6

mmspeed of crankshaft

2200

r/min

Piston pin mass 1.03 kg

The dynamics simulation result of changing the pistonthrust on the major thrust surface and the minor face of cylinder sleeve ignoring lubrication was shown in Figure 3.

1-major thrust surface ; 2-minor thrust surface

Figure 3. Piston Thrust on the major thrust surface and minor face of

cylinder sleeve

B. Coupling Simulation of PISTON-CYLINDER SLEEVE

It is assumed that piston-cylinder sleeve is in condition of perfect fluid lubrication and micro convex body contact

301



between cylinder sleeve and piston is not considered. Basedon the method mentioned above, through invokingFORTRAN lubrication subroutine in ADAMS the couplingmodel between piston-cylinder sleeve lubrication and pistondynamics is established and the coupling analysis isconducted using sequential coupling-field method.

Fig.4 shows the curves of dimensionless lateral

displacement (displacement/radial clearance) of the top andthe bottom of piston skirt which are changing as the changeof the crankshaft angle. That the piston has secondary motionin a cycle is shown in Fig.4.

Real line-displacement of the top;Broken line-displacement of the bottom

Figure 4. Lateral displacement of the top and the bottom of the piston

skirt

Fig.5 shows the friction curves on the major thrustsurface and on the minor thrust surface. The friction on themajor thrust surface is greater than that on the minor thrustsurface. Fig.6 shows the change curves of the minimum oilfilm thickness on the major surface and on the minor surfaceof the piston skirt in an circulation. Since the minimum oilfilm thickness on the major surface is less than that on theminor surface, the piston is tilted to the side of major thrust

surface when the piston moves reciprocally and there is a bigger possibility that the impact on the cylinder happens onthe side of major thrust surface.

Fig.7 shows the piston thrust curves on the cylinder sleeve under the frictionless condition and the perfect fluidlubrication condition. With the coupling effect between theoil film lubrication of piston-cylinder sleeve system and the piston dynamics, the maximum value of the force on thecylinder sleeve drops by 1217.73N and the minimum valueincreases. This demonstrates that the coupling effect makesthe force curve on the cylinder sleeve much smoother.

Real line-friction force on the major thrust surfaceBroken line- friction force on the minor thrust surface

Figure 5. Friction force on the major thrust surface and minor thrust

surface

1-Minimum oil film thickness on the major thrust surface2-Minimum oil film thickness on the minor thrust surface

Figure 6. Minimum oil film thickness on the major thrust surface andminor thrust surface

1-Ignoring lubrication case 2- Fluid lubrication case

Figure 7. the thrust curve on the cylinder sleeve

1- Clearance of piston-sleeve is 0.01mm； 2－Clearance of piston-

sleeve is 0.025mm；3－Clearance of piston-sleeve is 0.04mm；

Figure 8. The influence on the friction of clearance of piston-sleeve

1-Clearance of piston-sleeve is 0.01mm； 2－Clearance of piston-


Figure 9. The influence on the lateral displacement of clearance of piston-

sleeve

302



1-Clearance of piston-sleeve is 0.01mm； 2－Clearance of piston-


Figure 10. Bearing force contrast of the different systems

IV. THE INFLUENCES ON THE LUBRICATION

CHARACTERISTICS OF THE DIFFERENT FACTORS

A. Influence of the Clearance of piston-sleeve

The initial clearance of piston-sleeve of the piston-

cylinder sleeve system researched in the paper is 0.025mm.On the condition that other parameters are not changed, thevariations of secondary motion and friction force of pistonare measured respectively when the clearance of piston-sleeve is 0.04mm and 0.01mm. And then compared with thesituation that the initial clearance of piston-sleeve is0.025mm, the influence on lubrication characteristics of clearance of piston-sleeve is elicited.

Fig.8 shows the friction force variation curves under thecondition of three different clearance of piston-sleeve. Theclearance of piston-sleeve has obvious influence on thefriction force of piston skirt. As the clearance of piston-sleeve of piston skirt increases, the friction force of skirtdecreases. When the clearance decreases to 0.01mm from

0.04mm, the friction force raises about 5 times.Fig.9 shows the change curves of lateral displacements

which are changing as the variation of the crankshaft anglewhen the clearance of piston-sleeve is 0.01mm, 0.025mmand 0.04mm respectively. The clearance of piston-sleeveinfluences the lateral motion of the top of piston skirtobviously. When the clearance of piston-sleeve decreases,the lateral motion of piston skirt also decreases quickly andthe lateral displacement of the top of piston skirt approacheszero as the clearance of piston-sleeve is 0.01mm.

Fig.10 shows three bearing capacity curves of oil film inthree different systems. The system1 and system3 have thesame bearing capacity of oil film while the load of system2is the smallest one.

In summary, the two factors above-mentioned should beconsidered in a comprehensive way when the suitableclearance of piston-sleeve of engine is chose.

B. Influence of Piston Skirt Length

The piston skirt initial length is 83.6mm. Fig.11 showsthe friction power loss curve when the piston skirt length is

reduced to 78mm compared with that of the initial length.The friction power loss has the tendency of descent as the piston skirt length reduces. This is consistent with thetendency of reducing the I.C.E piston skirt length at present.

Real line-skirt length is 78mm;Broken line-skirt length is 83.6mm

Figure 11. The influence of piston skirt length on the friction power loss

The design parameters above-mentioned are the factorswhich affect the lubrication characteristics of the piston skirtand the purpose of the designer is to choose a set of suitable

parameters so that the secondary motion and the friction power loss of piston achieve the ideal result.[4]

The

clearance of piston-sleeve has obvious effects on thesecondary motion and friction power loss of the piston, sowe should confirm the clearance firstly. The longitude profile of piston should be considered when the clearance of piston-sleeve is being confirmed, because the different profile causes the different clearance distributing between piston skirt and cylinder sleeve so as to have an effect on thelubrication characteristics of piston skirt. On the other handthe piston skirt length should be chose combining the profileof piston skirt.

V. CONCLUSION

Because of the coupling effect of oil film lubrication between piston and cylinder sleeve the maximum force onthe cylinder sleeve decreases and the minimal force mountsup. So the changing tendency of the force on the cylinder sleeve becomes smooth.

The analysis of influence on the piston lubricatingcharacteristics of clearance of piston-sleeve and piston skirtlength provides basis for the selection and design of piston parameters.

R EFERENCES

[1] Kevin L. Hoag, “Vehicular Engine Design”, SAE International

[2] Lu Youfang, “Dynamics of Flexible Multibody Systems”, HighEducation Press, Sep. 1996

[3] Wen Shizhu, Huang Ping, “Tribology Theory”,Tsinghua UniversityPress, Nov. 2003

[4] Yang Junwei，Yu Xu, Reserch on piston parametrics based onLubrication Analysis. Lubrication Engineering. May.2002：5～8

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