finite element and mbd analysis of piston to predict · pdf filefinite element and mbd...

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Int. J. Mech. Eng. & Rob. Res. 2013 Vijaykumar N Chalwa et al.s, 2013

FINITE ELEMENT AND MBD ANALYSIS OFPISTON TO PREDICT THE ENGINE NOISE

S N Kurbet1, Vinay V Kuppast1 and Vijaykumar N Chalwa2*

*Corresponding Author: Vijaykumar N Chalwa,[email protected]

The engine vibration is considered as the major source of engine noise which deteriorates theengine performance and increases the pollution. The noise from the engine comprises ofmechanical and combustion noise. Combustion noise is primarily due to rapid pressurefluctuations in the combustion chamber. The mechanical noise is due to mechanical impactforces during both motions of piston viz. primary and secondary motions.In this study the effectof the piston secondary motion is taken for the analysis considering combustion pressurecontributing to the dynamics of the piston. The Kirloskar Diesel Engine is considered for thepresent study. The geometrical modeling of the engine is done using CATIA V-5 modeling tool.The finite element meshing is done using Hypermesh 9.0 meshing tool. This work analysis iscarried out in ANSYS 10 commercial finite element analysis software. To understand the complexbehavior of the piston in motion relative to the other engine parts, viz., connecting rod, crankshaft,a Multi Body Dynamic (MBD) analysis is carried out. This analysis showed the occurrence ofpiston tilt near TDC and BDC. The stress and displacement results are viewed and analyzedusing Hyperview. The analysis results can effectively be used to optimize piston geometry andhence lateral forces are minimized to obtain minimum tilt of the piston. The minimization of thepiston tilt eventually leads to the reduction of engine noise.

Keywords: Piston, Vibration, Finite element analysis, piston secondary motion, Hypermesh,Multibody dynamics

INTRODUCTIONThe present work is study the engine parts vizpiston considered as the main source orvibration and noise. The emphasis on theengine vibration and noise given rise to widescope for the methods of predicting and

ISSN 2278 – 0149 www.ijmerr.comVol. 2, No. 1, January 2013

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Int. J. Mech. Eng. & Rob. Res. 2013

1 Department of Mechnanical Engineering, Basaveshwar Engineering College Bagalkot 587102, Karnataka, India.2 SMS Mohite Patil Institute of Technology and Research, Akluj, MH, India.

controlling the engine noise and vibration. Thenoise and vibration in the IC engine isemphasis the combustion and mechanicalmovement of engine part. The Combustionnoise is primarily due to rapid pressurefluctuations in the combustion chamber. The

Research Paper

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Int. J. Mech. Eng. & Rob. Res. 2013 Vijaykumar N Chalwa et al., 2013

Mechanical noise is produced by the primaryand secondary motion of the engine part.Primary motion of engine part is due tocombustion pressure in the combustionchamber which makes piston to move fromTDC to BDC but this motion is linear in nature,Secondary motion of engine part is due toimpact load of the combustion, and it istransverse motion of engine part while pistonmoving from TDC to BDC vice versa.

The most common two internal combustionengines are petrol and diesel engines.Presently the IC diesel engines are replacingthe more expensive petrol engines. The dieselengine are mostly being used as commercialengines due to high break power and high fueleconomy, but it produces bad noise. The pistonslap which is the result of piston side thrust onthe cylinder liner as it moves TDC to BDC(Vinay and Kurbet, 2008).

The objectives of the present work is, todevelop 3-Dimentional Finite Element (FE)model of piston for the piston motionconsidering regions; piston, piston beforeTDC, at TDC and after TDC, and to studystress distribution and deformation of pistonin different regions.

An overview is given based on a literaturesurvey of general theory for IC engine. Thesystem is modeled using CATIA5 software tocreate needed geometry and finite elementsoftware to implement physics and carry outsimulations. The problem is described in asingle finite element model. 3-D models of thesystem are analyzed. The next would be a forceanalysis of the piston slap followed by thesimulation aspects of the Finite elementMethod. Using commercial software ANSYS 10and then meshing with software Hypermesh-9.

The Objectives of the paper is

• To develop 3-Dimentional Finite ElementModel of piston liner assembly for pistonmotion considering regions:

– Piston at TDC.

– Piston after TDC.

– Piston before TDC.

• To study stress distribution and deformationin liner assembly in region of objective 1.

• To study the mechanical impact loading onthe piston for deformation of slap in theregion of objective 1.

• To develop 3-Dimentional Finite ElementMulti body dynamics Model of complete ICengine of real Kirlosker engine and applyingReal boundary condition and working gaspressure curve of Kirlosker engine taken at1500 rpm on piston head and observe theoutput.

• To study stress distribution and piston-slapof MBD analysis of Kirlosker engine.

INTERNAL COMBUSTIONENGINESEngine Parts

The essential parts of automobile engine areas follows: cylinder block, cylinder head, crankcase, piston, piston rings, piston pin,connecting rod, crank shaft, fly wheel, valvesand mechanism.

Piston

Piston is considered to be one of the mostimportant parts in a reciprocating engine inwhich it helps to convert the chemical energyobtained by the combustion of fuel into usefulmechanical power. The purpose of the piston

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is to provide a means of conveying theexpansion of the gasses to the crankshaft, viathe connecting rod, without loss of gas fromabove or oil from below. Piston is essentiallycylindrical plug that moves up and down in thecylinder. It is equipped with piston rings toprovide a good seal between the cylindricalwall and piston. Although the piston appearsto be a simple part, it actually quite complexfrom the design point of view. The efficiencyand economy of the engine primarily dependson the working of piston. it must operate in thecylinder with minimum of friction and shouldbe able to with stand the high explosive forcedeveloped in the cylinder and also the very hightemperature ranging from 2000 °C to over2800 °C during operation. The piston shouldbe as strong as possible, however its weightshould be minimized as for as possible inorder to reduce the inertia due to itsreciprocating mass (Nagaraj et al., 2005).

Functions of Piston

• To receive the thrust force generated byexplosion of the gas in the cylinder andtransmits it to the connecting rod.

• To reciprocate in the cylinder as a gas tightplug causing suction, compression,expansion and exhaust stroke.

• To form a guide and bearing to the smallend of the connecting rod and to take theside thrust due to the obliquity of the rod.

The top of the piston is called head ringgrooves are located at the top circumferenceportion of the piston. Portion below the ringgrooves is called skirt. The portion of the pistonthat separates the grooves iscalled the lands.Some pistons have a groove in the top landcalled a heat dam which reduces heat

transferred to the rings. The piston bosses arethose reinforced section of the piston designedto hold the piston pin.

Piston Materials

The material used for pistons is mainlyaluminium alloy. Aluminium pistons can beeither cast or forged. Cast iron is also usedfor pistons. In early years cast iron was almostuniversal material for pistons because itposses excellent wearing qualities, coefficientof expansion and general suitability inmanufacture. But due to the reduction of weightin reciprocating parts, the use of aluminium forpiston was essential. To obtain equal strengtha greater thickness of metal is necessary. Butsome of the advantage of the light metal is lost.Aluminium is inferior to cast iron in strengthand wearing qualities, and its greatercoefficient of expansion necessitates greaterclearance in the cylinder to avoid the risk ofseizure. the heat conductivity of aluminium isabout thrice that of cast iron and this combinedwith the greater thickness necessary forstrength, enables and aluminium alloy pistonto run at much lower temperature than a castiron one (200 °C to 250 °C as compared with400 °C to 450 °C) as a result carbonized oildoesn’t form on the underside of the piston,and the crank case therefore keeps cleaner.This cool running property of aluminium is nowrecognized as being quite as valuable as itslightness. Indeed; pistons are sometimesmade thicker than necessary for strength inorder to give improved cooling.

DESCRIPTION OF I.C.ENGINE MODELS FORFINITE ELEMENT STUDYThe Table 1 shows engine details:

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GEOMETRIC MODELINGImportant steps in Geometric modeling are:

• Creating part (solid) modeling of each part;

• Assembling;

• Converting solid model into IGES format.

Drawing and dimension used in this studywere retrieved from kirlosker engine by CMMcoordinate measuring machine (Toshiyakiet al., 2007) (Figures 1 and 2).

Finite Element Modeling

Finite element modeling and analysis is oneof the most popular mechanical Enggapplications offered by existing cad /camsystems. This is attributed to the fact that theFEM is perhaps the most popular numericaltechnique for solving Engg problems. Themethod is general enough to handle anycomplex shape or geometry, any materialproperties, any boundary conditions, and anyloading conditions .the generality of the FEMfits the analysis requirements of the complexEngg systems and designs, where closed formsolutions of governing equilibrium equationsare usually not available. In addition it is anefficient design tool by which designers canperform parametric design studies byconsidering various design cases, analyzingthem and choosing the optimum design(Kurbet and Krishnakumar, 2004).

The finite element model of the piston isdeveloped using ANSYS 11 modeling tool(Figure 4). The meshing the model was donewith axisymmetric PLANE 42 elements. The

1. Engine Kirlosker Engine

2. Bore 80 mm

3. Stroke 110 mm

4. Engine rpm taken for study 1500 rpm

5. Compression ratio 16.5:1

6. Maximum torque 66 Nm

7. Test condition/Type Water cooled directinjection dieselsingle cylinderengine

8. Max pressure at study rpm 54 bars

Table 1: Description of IC Engine

S.No.

Description Specification

Figure 1: 2D Drawing of Piston

Figure 2: Piston Solid Model

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material models is created using the Kirloskarengine data and are shown in the Table 2.

three dimensional form by using hexahedralelements, Tetrahedral and Pentamesh. All themeshed components are tested for the quality ofthe mesh. After proving the quality of the mesh,the components are assembled to represent theIC engine system. The quality setting inHypermesh-9 preprocessor for quality check ofthe mesh was shown in Figure 5:

Each components were meshedindependently and were shown in Figures 6and 7:

1 Piston Al alloy 2630 72.4 72400 0.31

Table 2: Material Propertiesof the Kirloskar Diesel Engine

S.No.

PartName

MaterialName

DensityYoung’sModulus Poison

RatioIn Kg/m3

InGPA

InN/mm2

For defining boundary conditions, thepressure curve of the Kirloskar engine atrunning speed of 1500 rpm is considered. Thevariation of the pressure with a different crankangle is shown in the Figure 3. The bottom skirtof the piston is constrained in all degrees offreedom. It is solved for different pressurevalues corresponding to the crank angle.

Figure 3: The Variation of the Pressurewith Different Crank Angles

GENERATION OF FINITEELEMENT MESH FOR MBDANALYSISThe required geometric information for the meshgeneration is collected by importing the IGES fileof the model in Hypermesh-9. The finite elementmesh is generated for each of the assemblycomponents by using standard command in the

Figure 4: Model Generated in ANSYS

Figure 5: Meshed Model of Piston

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Piston

Piston is critical to mesh with hexahedral henceit is meshed with tetrahedral mesh.

RESULTS AND DISCUSSIONThe analysis is carried out for different casesconsidered. The result data have beentabulated to plot the respective graph. Thestress and displacement graphs have beenconsidered to study the effect of gas pressureon the piston at different crank angle position.

The displacement curves are plotted tostudy the piston slap (displacement in x-direction). From the finite element analysis, thevarious stress and displacement values havebeen found out corresponding to the gaspressure taken from the actual engine readingsand are tabulated in the Table 3. The 3600crank angle corresponds to the TDC of thepiston position in the cylinder. From Figure 3,the pressure v/s crank angle graph, it is evidentthat the maximum pressure of 56 bar isobserved near TDC. Hence the structuralanalysis of the piston is taken from TDC toBDC travel during power stroke, i.e., aftercombustion of fuel in the chamber.

Figure 6: Boundary Conditions Appliedin ANSYS

MULTI BODY DYNAMICSIMULATION OF PISTONMOTIONThe MBD analysis is carried out to understandthe complex behavior of the engine partsduring operating conditions. The pressurecurve of the Kirloskar engine as consideredfor the structural analysis is considered for thisanalysis. The combustion pressure on thepiston causes the piston to reciprocatebetween TDC and BDC. This in turn carriedto the connecting rod and then to thecrankshaft. Hence the engine componentsexperience the gas force exerted on the piston.Here it is obvious to study the stress regionsand displacements in different engine parts topredict the behavior of the parts. This willreveal the lateral motion of the piston fordifferent crank angle positions and is used topredict the piston slap or tilt (Kurbet andMalagi, 2009).

Figure 7: Assembled Meshed Modelin Hypermesh with Quality Check

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The stress developed in the piston fordifferent crank angle position and the lateraldisplacements of the piston in x-axis aretabulated in the Table 3 shown in below (Malagiand Kurbet, 2009).

the gap between piston and cylinder reducescompared to the other region (Figure 9). Thisphenomenon causes the piston to tilt about thegudgeon pin axis and causes the piston to slap(Cho et al., 2005).

The graph of x-displacement v/s crankangle shown in the Figure 10 which clearlyindicates the change in the gap betweencylinder and piston travel from TDC to BDC.This behavior of the piston tilt repeats forregular interval of the crank angle between 00to 7200 of the complete cycle.

360 3.600 60.835 0.277

396 5.280 89.227 0.406

432 1.560 26.361 1.200

468 0.480 08.109 0.369

504 0.240 04.055 0.185

540 0.180 03.039 0.138

576 0.144 02.431 0.111

612 0.120 02.027 0.923

684 0.180 03.042 0.189

720 0.240 04.055 0.185

Table 3: The Gas Pressure, Von MisesStress and x-Displacement of Piston

CrankAngle

GasPressurein N/mm2

Von MisesStress in

N/mm2

x-Displacement

in mm

Figure 8: Variation of Von Mises Stressfor Different Crank Angles

From the Figure 8, it was observed that thestress in the piston ismaximum near the90 N/mm2 pressure regions and causes thepiston to deform more at this region. Hence

Figure 9: VonMises Stress

Figure 10: Variation of Piston-CylinderGap for Differentcrank Angles

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Figure 11: Displacement

Figure 12: Deformation Zonein Piston at TDC

Figure 13: Distribution of Stressesin Piston-Cylinder Assembly at TDC

Figure 14: Piston Deformation AlongX-Axis

Figure 15: Piston Deformation AlongY-Axis

MBD ANALYSISThe results obtained from the MultibodyDynamic analysis (MBD) are discussed asfollows.

The stress distribution in the enginecomponents is shown in the Figure 13. It wasobserved from the MBD analysis that thecombined effect of the various forces acting onthe engine components viz, connecting rod,crankshaft, piston, is inducing stress in eachcomponent. The maximum stress level in thepiston is observed as 3.584 102 N/mm2. Themaximum displacement observed as 1.710 mm.

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Table 4 shows the difference between theMBD analysis and structural analysis for stressand displacement.

position of the piston in the cylinder movingbetween TDC to BDC have been studied andthe following conclusions are made.

• The piston experiences maximum stress inthe region where the combustion of the fueltakes place, i.e., at the piston head andskirt.

• This high stress region in the piston deformsmore than the other region of thepiston.

• The maximum x-displacement of the pistonfor structural analysis resembles themaximum displacement of the piston inMBD analysis. Hence the pistonexperiences maximum displacement in thisregion.

• The deformation in the piston causes it todisplace more in this region and this cyclerepeats even for the reduction incombustion pressure.

• The MBD analysis confirms the relativemotion between the parts and reveals thatthe engine noise is associated with thestress developed in the engine parts.

FUTURE SCOPEMBD Analysis is proposed, to incorporate theforces in motion for prediction of piston tilt andoptimization of the geometry of the piston toreduce engine noise and vibration (NVH).

REFERENCES1. Cho S H, Ahn S I and Kim Y H (2005), “A

Simple Model to Estimate the ImpactForces Induced by Piston Slap”, KoreaAdvanced Institute of Science and Tech.,Daejon, Korea.

2. Kurbet S N and Krishnakumar R (2004),“A Finite Element Study of Piston Tilt

Figure 16: Von Mises Stress Distributionof MBD Analysis of Engine

(Radioss Analysis)

Figure 17: Displacement of MBD Analysisof Engine (Radioss Analysis)

MBD Analysis Structural Analysis

Displacementalong X-axes 1.741 1.710in mm

Stress in N/mm2 159 157

Table 4: Comparision Between MBD ANSStructural Analysis

CONCLUSIONThe structural analysis of the piston for thevarious pressure on the piston for different

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Effects on Piston Ring Dynamics in ICEngines”, Proc. Instn. Mech. Engrs.(IMECHE), Part K, pp. 107-117.

3. Kurbet S N and Malagi R R (2009), “AComprehensive Model to Study DynamicMotion of Piston and Friction andLubrication in IC Engines”, Journal ofTribology Trans., ASME Tribo-081024.

4. Malagi R R and Kurbet S N (2009), “StressAnalysis of Piston Ring-FE Approach”, 2nd

International Conference on RecentAdvances in Manufacturing Held atKovilpetti TN from February 25-27.

5. Nagaraj Nayak, Reddy P V, YogeshAghav, Navtej Singh Sohi and Dani A D

(2005), “Study of Engine Vibration Due toPiston Slap on Single Cylinder, HighPowered Engine”, SAE Iternational,2005-26-046.

6. Toshiyaki Kobayashi, Yukitaka Takahashiand David J Bell (2007), “How to Predictthe Piston Slap-Noise Using 3D PistonMotion Simulation”, SAE International,2007-01-1245.

7. Vinay V Kuppast and S N Kurbet (2008),“Review of Finite Element Analysis of theIC Engine Noise and its ExperimentalValidation”, International Conference onTotal Engineering Analysis , IISC,Bangalore.

finite element and mbd analysis of piston to predict · pdf filefinite element and mbd...

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