I eccentric haenergy criteriaIgive the upor, respectivesubjected toal value of tvould be in beim value of thon of the nod

rial damping ojicentric point toorkee, India, 1991

mbers in structu

160,1969.

istic (McGraw-

3 (Sept., 1975) N

;larcel Dekker I

IndianJournal of Engineering & Materials SciencesVol.II, April 2004, pp. 85-92

Investigation of the flow field in the various regions of intake manifoldof a S.1. engine

s C Kale & V GanesanInternal Combustion Engines Laboratory, Department of Mechanical Engineering, Indian Institute of Technology,

Chennai 600 036, India

Received 4 February 2003; accepted 1 March 2004

The main objective of the present worlds to make a computational study of steady flow through intake manifold, port,valve and valve seat of a S.1. engine for various valve lifts. Three-dimensional flow within the manifold, port and valve hasbeen simulated using the computational fluid dynamics (CFD) using the code STAR-CD. Flow field details in the identifiedregions in the manifold for the various valve lifts have been predicted. Analysis has been carried out for runners 1 and 3 atthree different valve lifts for various speeds at wide-open throttle condition. A trimmed cell (adjust and cut process based onan underlying structured grid) has been adopted for meshing the geometries. Flow has been simulated by solving governingequations, viz., conservation of mass and momentum using the SIMPLE-algorithm. Turbulence has been modeled by highReynolds number version of k-t: model. Mass flow rate measurements have been made for validating the numerical predic-tion. A reasonably good agreement has been obtained between predicted and the experimental results. Also, it is seen thatvalve lift has a predominant effect on flow structure and it is found that with increase in valve lift there is a tendency forflow separation near the valve seat region.

gions. In the present work, the influence of valve lifton the steady flow in the port and valve has beenstudied through the use of the CFD code STAR-CD.Velocity fields in the inlet manifold, port and valvehave been predicted.

Many authors have studied intake region flows inthe past. Taylor et al. I predicted that the eliminationof the valve recess leads to large reductions in totalpressure loss at low lifts. With the advent of recentcomputational methodologies, the authors were of theview that such CFD-based tools could be quite valu-able in the geometry-specific problems of an indus-trial design setting.

Peters and Gosman/ have presented a numericalsimulation method for the calculation of an unsteady,one-dimensional flow and heat transfer in the branchintake manifolds of multi-cylinder engines. Themethod operates on the one-dimensional differentialconservation equation. The equations are solved by atime-marching finite volume method, on a computa-tional mesh in which velocities are located betweenthe nodes of pressures, which drive them. Using theabove method, flow calculations have been carriedout in the intake in order to obtain the time-varyingvelocity and overall efficiency of the engine for a

IPC Code: Int. ci.' F 02B 29/02; F 15D 1100

Design methods based on CFD have the potential tobecometruly predictive design tool capable of as-sessingimportant parameters, such as total pressurelossesin engine intake regions before a prototype isbuilt.Such a predictive capability represents a cost-effectivestep away from the current "build and..test"designapproach. By significantly lowering the needforcostly and time-consuming tests, CFD has the po-tential in reducing the overall engine design cycletime.

The prediction of flow field in the intake region isveryimportant in engine design. A well-designed in-takesystem will reduce flow resistance and allow theengine to "breathe better". More air can thus bepackedinto the combustion chamber, resulting in in-creasedpower output with improved volumetric effi-ciency. Key parameters controlling emission levels,includingturbulence intensity, swirl and tumble in thecombustioncylinder are also influenced by events intheintake region directly upstream of the combustionchamber.Clearly, it is in the intake region that theflowconditioning is accomplished. Therefore, it is ofcritical importance for internal combustion enginedesignerto have more advanced, and validated meth-odology to predict complex flows in the intake re-

86 INDIAN J. ENG. MATER. set, APRIL 2004

range of speeds. Also, redesign of the upstream sideof valve region seems to produce considerable effecton flow field structure.

Dent and Chan3 investigated the computationalstudy of flow through a curved inlet port. The authorssimulated the three-dimensional flow within the port'and cylinder for the intake process and predicted thedetails of flow structure affected by the valve lift andport shape. The numerical prediction showed an ap-preciable pressure recovery for a favourable flow pas-sage between valve seat and the valve head.

Cui et al. 4 studied the physical mechanisms respon-sible for cylinder-to-cylinder variation of flow be-tween different cylinders. A validated comprehensivecomputational methodology was used to generate gridindependent and fully convergent results. Three-dimensional viscous, turbulent flow simulations, in-volving finite volume cells and the complete form ofthe time-averaged Navier-Strokes equations, weresolved to study the mechanisms responsible for totalpressure losses in the entire intake system.

Bicen et al.' indicated that the flow pattern in theintake region is insensitive to flow unsteadiness andvalve operation, and thus could be predicted throughsteady flow tests and computational simulations withreasonable accuracy. The validity of the quasi-steadyassumption was examined here by comparing LDAmeasurements of the velocity field at the intake valveexit plane under both steady and unsteady conditions.The obtained results provide detailed information onthe flow through the intake valve to minimize the un-certainties with the lack of boundary conditions forcalculation methods and quantify earlier findingsabout the influence of the geometric and flow pa-rameters on the valve performance. Thus, it is seenthat there is tremendous potential to study the intakeexhaust flow in a multi-cylinder four-stroke engineespecially using CFD techniques for understandingthe open period process of the engine.

The main objective of the present work is to ana-lyze the flow through the various regions of port andvalve at different valve lift, prediction of mass 'flowrate and to compare it. with experimental data for afour-cylinder S.1. engine at wide open throttle. This isaimed at revealing the performance of the intakemanifold.

Theoretical

Geometry under considerationFig. 1 provides details of the geometry considered.

The geometry has been generated using the solidmodel software ProEngineer. The geometry consistsof a plenum chamber to reduce the fluctuations offlow in the runners. The steady flow analysis has beencarried out for various runners. The inlet valves ofother three cylinders are assumed to be closed whenthe flow analysis is carried out. The sectional view ofa runner (runner 1) is given in Fig. 2. As can be seen,the manifold is divided into 5 important regions,which are assumed to be critical. Region 1 is a placewhere injector is located. Region 2 is the place wherevalve is located. Region 3 is the entrance section tothe cylinder. Region 4 is close to the section wherevalve and port interaction takes place. Region 5 is theflow region where the flow has minimum interfer-ence. All these regions are very critical for importantfrom the design point of view.

Governing equationsThe continuity and Navier Strokes momentum con-

servation equations for incompressible and com-pressible fluid flows in .any coordinate system in-cluding moving coordinates, viz. in tensor notationcan be expressed as:

Inlet pipe

KALE&I

Intake port

Fuel injector ---"''''-':'1,..location

A: Runner 1c . Runner 3

B: Runner 2D: Runner 4

Continuity equatio

1 a 0--(Dp)+-(D at OXj

Momentum equati

Fig. 1 - Geometry under consideration

Fig. 2 - Sectional view of a runner

1 a 0--(Dpu)+-D at I oxwhere t represe(i=1,2,3), Uj thedifferent directi

between fluidmoves with velcp (piezometric I

=Ps+ Pogll/xlI/

!where Ps is statigill is gravitati:coordinate frorr

Using p (de

Sm (mass SOurCID (determinardependent COOlfor Cartesian I

scripts denotenents, 7:ij, for a .

where the U'ifsemble averageensemble aver,sents the additmotions. It mu.gation the stemoving coordii

Turbulence mod.

Several turlprovide excelhused properly.the discretisatispace is fine ernot appropriateto the intensivstress models,

re solidconsiststions ofras beenuves of:d whenview ofbe seen,regions,a place

e wherection to1 where5 is theinterfer-nportant

urn con-d com-item in-notation

take port

No.3

KALE & GANES AN : FLOW FIELD IN THE VARIOUS REGIONS OF INTAKE MANIFOLD OF A S.l. ENGINE 87

Continuity equation,

I a a_Dat(DP) +a;(Puj) = Sill

J

Momentum equation,

I a a _ opD at (Dpui) +a;(Pujui -Tij) =- ax. +SiJ I

where t represents time, Xi the Cartesian coordinate(i=l,2,3), Ui the absolute fluid velocity component indifferentdirection, uj (Ui - Ucj), the relative velocity

between fluid and local coordinate frame whichmoveswith velocity. In this work Ucj=O.

p (piezometric pressure)

=Ps+ PoglllxlII,

'wherePs is static pressure, Po is reference density, thegill is gravitational field component and xm refers tocoordinatefrom a datum where Po is defined.

Using p (density), Tij (stress tensor components),

Sill (mass source), S; (momentum source components),D (determinant of metric tensor used in time-dependent coordinate transformation and becomes 1for Cartesian coordinate system and repeated sub-scriptsdenote summation), the stress tensor compo-nents,Tij, for a turbulent flow can be expressed as:

2 aUk ~ _-,-,f;j = 2J,lS;j - 3Ji aX

kUij - pU;U j

wherethe u/ is the fluctuating component of the en-sembleaverage velocity and the over-bar denotes theensembleaverage process. The rightmost term repre-sentsthe additional Reynolds stress due to turbulentmotions.It must be noted that in the present investi-gation the steady flow only is considered and nomovingcoordinate system is employed.

Turbulence modeling

Several turbulence models are available, whichprovide excellent engineering design solutions' whenusedproperly. Direct numerical simulation, wherebythe discretisation of the equations in both time andspaceis fine enough to capture all turbulent models, isnotappropriate for large-scale complex problems dueto'the intensive computer power required. Reynoldsstress models, which are additional transport equa-

tions to solve for the Reynolds stresses are also com-putationally intensive for 3-d complex flows.

Currently, the most preferred turbulence model thatcan be used in practical setting is the two equation k-£model. This model employs two additional transportequations: one for turbulence kinetic energy (k) andanother one for the dissipation rate of the turbulencekinetic energy (£). The standard k-E model is the mostrobust and reliable model available for complex tur-bulent flows. The high Reynolds number k-E model isa variant of standard k-t: model.

Turbulence energy

~~(DPk)+~[P/ii-(Ji+~J~lD at aXj a, aXj

( ) 2( au. Jau.=Jit P+PB -p£-- Jit-' +pk -' + JitPNL. 3 ax; ax;au. g. 1 ap

where, P = 2s;j -' , PB = --' -- andaXj ah,t pax;

PNL

= -.E./i;Uj au; - [p - ~(au. + pk J au; 1u, aXj 3 ax; u, aXj

PNL =0 for linear models and O'kis an empirical coef-ficient. The first term on the right-hand side of turbu-lence energy equation represents turbulent generationby shear and normal stress and buoyancy forces, thesecond viscous dissipation, and the third amplificationor attenuation due to compressibility effects. The lastterm accounts for the non-linear contributions.

Turbulence dissipation rate

1 a (D ) a [- ( Jit J a£ 1-'-- p£ +- puj£- Ji+- --D~ ~ ~ ~

e [ 2( au. Jau.]= CEIk JitP - 3 Jit ax; + pk ax;

£ . £2 . a~ £+CE3 - JitPB - CE2P- +ce4P£-a + CEI - JitPNL

k k x; k

where O'E,CEI.CE2' CE3and CE4are empirical coeffi-cients whose values are given in Table 1. The right-hand side terms represent analogous effects to thosedescribed above for the k equation. The turbulentviscosity Ilt' appearing in the above, is obtained viaequation:

88 INDIAN J. ENG. MATER. SCL, APRIL 2004

Table I - Values assigned to standard k-E turbulence model. coefficients

0.09 1.0 1.22 0.9 0.9 1.44 1.92 0.0 or -0.331.44*

*C,3 =1.44 for ?B>O and is zero otherwise

where CJ1 is an empirical coefficient usually taken asconstant, and fJ1 is another coefficient, to be definedwhen the individual model variant are presented.

Computational methodology

In CFD simulations, consistently accurate resultscan be obtained by applying a complete computa-tional methodology to the problem at hand. The com-putational methodology applied here consists of fourtasks: (i) Computational modeling, (ii) Geometry andgrid generation, (iii) discretization of the governingfluid flow equations, and (iv) turbulence modeling.The details are:

Computational Domain - The solid model ge-ometry under consideration for the current study isshown in Fig. 1. It consists of the inlet duct, plenum,various runners (A to D), port and valve. This domainrepresents the intake regions of a four-cylinder en-gine. The upstream effects on the flow entering theports are to be captured, which can lead to realisticin-port flow structure prediction.

Steady-State Flow Assumption - The flow patternin the intake region is insensitive to flow unsteadinessand valve operation and thus can be predicted throughsteady flow test and computational simulation withreasonable accuracy': 3, 7-9.

Experimental measurements have been carried outfor providing the necessary boundary conditions tothe prediction: At inlet of the plenum chamber is amanifold pressure and at the exit of valve, cylinderpressure is given corresponding to the valve lift. Inthe absence of any measured data, it is the practice toassume a turbulence intensity of 5%, and a lengthscale of 10 per cent of the port diameter at the inletplane. Hence, these values are specified to estimatethe inlet boundary condition on turbulent kinetic en-ergy, k and its dissipation rate, E. .

Fig. 3 - Grid arrangement

Geometry and Grid Generation - The geometryhas been generated in PRO-ENGINEER 2001 soft-ware and imported to the CATIA for the surface meshgeneration and then it has been transferred to pro-amfor volume mesh generation. A multi-block, trimmedcell has been generated. The original mesh size wasbetween 450,000 and 480,000 cells, varying slightlybetween the low, medium and high lift. Fig. 3 showsthe grid arrangement for a medium lift position. Cellswere refined in the critical region of valve and port(Region No.3 in Fig. 2) in anticipation of the highvelocity and pressure gradient. Grid independent testswere conducted to ascertain the adequacy of the grid.Initially, 300,000 and later 600,000 grid nodes weretried. The velocity variation between 450,000 and600,000 grids were less than 1%. Therefore,it wasdecided that the grid distribution, viz., 450,000 usedare quite adequate.

Differencing Scheme - The choice of differencingscheme will affect the convergence rate and accuracyof the final computational solution. Lower orderschemes tend to be more stable but introduce numeri·cal viscosity into the solution, while higher orderschemes are more accurate but requires more corn-.puter time to solve and are less stable. Present studymakes use of first order scheme, which is stated to befar more robust and stable.

Currently, the most advanced turbulence model,which can be used in a practical setting, is the two-equation, k-t: model. This model employs two addi-tional transport equations: one for turbulence kineticenergy (k) and another one for the dissipation rate (El.Near wall treatment is handled through generalizedwall functions. High Reynolds number k-e model hasbeen used. This model is well established and also the

KALE

, most widelythe details ofprevious secti

Results and]As already

of the intakeseen, there isto die downthis section, ,the five critiidentified in F

Flow FieldFigs 1 and 2,very importan4a-4c show thcorrespondingrespectively. Iis the indicaticonstrued as tl

It is clearlystructure. As cgiven in the wrecirculation 0

tial because itrecirculating ebe noted is tha

Projection ro1----lIUector location .~-(rerer Fig.!) - ~

, ~ '! ~

f;; -'.-~~

ProjecHon forInj«tor lontfon(reruFtI.I)

Fig.4-

eometryn soft-:e meshpro-am-rimmedize wasslightly\ showsn. Cellsnd porthe highmt testshe grid.es were100 and,it was)0 used

:rencingccuracyr ordernumeri-:r order~e com-lt studyed to be

model,he two-10 addi-•kineticrate (E).eralizedxlel hasalso the

KALE & GANESAN: FLOW FIELD IN THE VARIOUS REGIONS OF INTAKE MANIFOLD OF A S.I, ENGINE 89

most widely validated turbulence model as on date,the details of which have already been explained inprevious section.

Results and DiscussionAs already mentioned, Fig. 1 gives the solid model

of the intake system under consideration. As can beseen, there is a plenum which makes the oscillationsto die down before the flow enters the manifold. Inthis section, we will discuss the flow field details inthe five critical regions which have already beenidentified in Fig. 2.

Flow Field Analysis in Region No.1 - ComparingFigs 1 and 2, it can be noticed that Region No. 1 isveryimportant since the injector is located here. Figs4a-4c show the enlarged view of the Region 1 and thecorresponding flow field structure for 3, 6 and 9 mmrespectively. It may be noted that the velocity vectoris the indicative of the magnitude and should not beconstrued as the flow crossing the solid boundary.

It is clearly seen that the valve lift affects the flowstructure. As can be noticed, the deliberate projectiongivenin the wall of the manifold (Fig. 1) helps in therecirculation of air. In this zone recirculation is essen-tial because it is here the fuel is injected. Hence, therecirculating eddies will cause better mixing. Also tobe noted is that with increase in valve lift from 3 mm

VELOCITY MAGNITUDEMIS

3Z.SJ30.44zaaa211.272.192210200217.';'15.8513.16 ,"(11.66,.S,S1.50'95."l43339

-~, '''-- ;-~...•.-: .. '\ .•

~~~~~--(a) 3 nun valve lift

VElOCllY MAGNITUDEMIS

ZCW]190.2

--_ l1S.11_ 1613:.:..:: 141U1

132.4111.9,."89.001•. 5360.0745.8131.15

_'6.58- l.UO

ProJectionror~J«torlocatlon(rtftTFlg.1)

~!S'_"""""'"

(b) 6 nun valve liftVELOCllY MAGNITUDEIliVS

139.5129.7119.91,0.1100.390.1\800.68

.--.. 70.130,__ -"--61,08__ " 51.Z8;;;:;;; 41.46.••••••••. 31,68

21.8812.08Z.283

(c) 9 nun valve lift

Fig. 4 - Flow Field details in Region No.1

to 6 mm, the amount of fuel injection will also in-crease. This is because of the characteristics of theinjector. Hence, when more fuel is getting injected therecirculation also should become large and intense.Further, when the valve lift is increased from 6 to 9mm, the velocity in the Region 1 decreases. This is tobe expected because the air will find the path of theleast resistance to flow into the cylinder because ofthe maximum valve lift and the amount of fuel in-jected will also decrease. It is gratifying to note thatwhat is expected to happen is happening in this regionindicating that location of the injector is at the appro-priate place.

Flow Field Analysis in Region No. 2 - Referringto Fig, 2, it can be seen that in Region No.2 there isvalve interference. The flow entering into the mani-fold from plenum starts moving towards the inlet portin the cylinder because of the pressure differential. Asit moves towards the inlet port it encounters the valvestem and feels the resistance and also the flow areagetting reduced. As can be observed from Figs Sa-So,the flow is thrown towards the wall and can be seen toaccelerate. In order to make the flow to movesmoothly, a good wall contour is an important design

VELOCity MAGNITUDEMIS

~ 61.1157.5453.3749.20AS.OJ40.6638.8932.S?28.;)6Z4.1920.0215.6511.667.5093,339

.:.~

---"""'"'~eeeee--

(a) 3 mm valve lift

VELOCllY MAGNITUDEMIS·--~

74.536'3.3564.20SS.0353.87~1).7043.540".3733.Z1ae 042Z.8817,71lZ.SS7.385Z.ZZO

....--.......,...............,~

(b) 6 mm valve lift

VELOCITY MAGNITUDEMIS

~ '3~.5'Z~.l_"9.9110.1100.;39D.4860.66708861.08ar.ze41,46as.ee21.8812.0e2.Z63

~~..•••...--eeeee-(c) 9 mm valve lift

Fig. 5 - Flow Field details in Region No.2

90 INDIAN J. ENG. MATER. scr., APRIL 2004

criterion. If the walls are not contoured properly therewill be losses. From the figures, it is observed that forall the valve openings the flow seems to move quitesmoothly.

Flow Field Analysis in Region No.3 - Referring toFig. 2, it can be seen in Region No.3 is continuationof Region No.2. In this region the valve seat is lo-cated. As can be seen from Figs 6a-6c that along theconcave portion the flow gets detached and comes outthrough the space between the port and the valve headas a jet. For a 3 mm opening, the jet that is corning outwill have a higher velocity [Fig. 6a] compared to 6mm or 9 mm opening [Figs 6b and 6c]. This is to beexpected since with increase in valve opening, theflow area increases with corresponding decrease inthe velocity. In these figures, it should be noted thatthe vectors show only the magnitude and directionand should not be construed as flow crossing the solidboundary.

Flow Field Analysis in Region No.-4 - Region No.4 is in the left side of the valve seat (refer to Fig. 1)with properly curved convex portion and the solidvalve stem on the right side. Figs 7a-7c give details ofthe flow field structure in this region. For a 3 mm

VELOCITY MAGNITUDEMIS

ZOl.619l.D178.3

- 163.15- '.',9- !3412

11'.S10'.15SO.Hi

-'5.40-8tl.79-.e.l1- 31.42-11>.7.- Z.0S3

(a) ~ nun valve lift

VELOCITY MAGNITUDEMIS

Z04.7193.3HIIZ.O170.8159.2147.9lJ6.5125,2113.8102.491,0&79.7080.3456.9745.151

(b) 6 nun valve lift

VELOCI"TYMAGNITUDEMIS

139.!:j129.7,'9.91101100.390."~IIO.R!70.M81.08st.ze41,4831.6821,$812.08Z.Z83

( C) 9 inm valve lift

Fig. 6 - Flow Field details in Region No.3

opening [Fig. 7a], the flow is more or less attached tothe convex wall of the inlet manifold. As the valve liftstarts increasing, there is a tendency for the flow toget separated from the wall. However, as could beseen that the manifold contour nicely guides the flowinto the cylinder and the tendency for flow separationnear valve seat should be addressed by contouring thisregion appropriately.

. Flow Field Analysis in Region No.5 - Figs 8a-8cdepict flow field for Region No. 5 for 3, 6, 9 rnmvalve lift. This is the region that helps to develop andguide the flow to various other regions. As could benoted the flow seems to be smooth and reasonablyguided. This shows that this region in the intake sys-tem is reasonably well configured. Further the velo-city profiles upstream of the stem and the port bend asindicated, as Region 5 are found to be independent ofthe valve lift because of a favourable pressure gradi-ent and hence the flow accelerates. The accelerationseems to be maximum for a 6 mm lift [Fig. 8b].

In order to validate the prediction, experimentshave been conducted using the flow bench setup de-scribed in detail in reference 10. The airflow has been

VELOCITY MAGNITUDEMIS

134.2124.B115.3 -10S.996.4487.0017.5768.1358.69049.2539.8130.3720.9311.49Z.053

KAL

(a) 3 mm valve lift

VELOCITY MAGNITUDEMIS

lQ.4.7190.2175.8'81.~146.6132.4111.9103.589.0074.5360.0145.81'31.151&.88H20

measured by(i) When allis open; andlap in the op

The measwith the prer

ValidationFig: 9 ilh

~--........- •• -"0~~- ..• - ... '"••• Ii 4 .••_••••••••• 4i:4ii ••••••••••••• oiI.oI7oi1ls oil" oilS••••••• I Iii •••• iE ••••• ii ••••••••••• elJ

••• :ii: ••• .,. ••••• oil.••• :1 .

.•.• ct •••••••• -

.411"" •.••••• 5••••• d t d

~:.~

(b) 6 nun valve lift

VELOCITY MAGNITUDEMIS

139.S.132.51Z5.S118.5'1'.5104.597.4890.4803.4818.48&9.488Z.48$::5.4848.4641 ..&8

-- -- ~._- .. --.--..-------- ::---..--.... -- ~:.::::::::•...

(c) 9 mm valve lift

Fig. 7 - Flow Field details in Region No.4

Fi:

75.!l

i' \60.1I

~ 45.0::!e~ 3D.a

~ill

~ 15.0'e00

F

ched tolive liftflow tomld bere flowiarationing this

:s Se-Se9 mm

lop andould besonablyike sys-ievelo-bend asident of~ gradi-leration

riments.tup de-as been

~AGNITUOE

vlAGNITUDE

MAGNITUDE

.'KALE & GANES AN : FLOW FIELD IN THE VARIOUS REGIONS OF INTAKE MANIFOLD OF A S.l. ENGINE 91

measuredby an orifice flow meter for two conditions:(i) When all other valves are closed and valve 1 aloneisopen; and (ii) When valve 1 and 3 has a little over-lapin the opening.

The measured flow rate has been used to comparewiththe predicted values.

ValidationFig: 9 illustrates mass flow rate variation with re-

--..~ VELOCITY MAGNITUDEMIS-......---~....-..-..•.---~ .•.- ..- .,.~~~ .. --.---."J _ ...~-.. __..... -J. Ii......... .. •.• 75.46

70.2464.~959.7554.5D49.2644.01'36.7733.5226.2623.0317.7912.~47 2~62.053

(a) 3 mm valve lift

VELOCITY MAGNITUDEMIS

161.31530144.8136.5126.2120.01l1.7103.5951966.3378.S670.4062.14538145.61

~.~~ " ~

(b) 6 mm valve lift

VELOCITY MAGNITUDEMIS

90.486416718871.S865.26589652.68-=6.38 ~t

400833.7827.46211814.888.5832263

(c) 9 mm valve liftFig. 8 - Flow Field details in Region No.5

75m ,-,-------------------,- Flow through only Runner 1

~. 80m 1-Flow through Runner 1 and 3~ •• Measuredflowl.> 4500e~ 30.D);:lII>

~ 15mS

000 I " ,Io 1000'2000 3000 4000 5000 6000

Engine speed (!p!II)

Fig. 9 --,--:M~ss flow rate vs. engine speed<

spect to engine speed. The mass flow rate predictedby the CFD and the measured rate are comparable.The variation in the measured and the predicted massflow rate is within 4-10%. The CFD values for Run-ner No.1 are less than measured because the analysishas been carried out for only one manifold whereasthe measured value takes into account all four mani-folds. So, there may be some interference due to othermanifolds, which is giving higher mass flow rate forthe measured value. While the analysis of RunnerNo.1 in addition to the Runner No.3 shows that CFDpredicted values are more than measured ones be-cause in this analysis flow through the third runnerhas also been taken into account. Also, we can ob-serve the increase in the mass flow rate with increasein speed because of the increased pressure differentialbetween the cylinder and the runner.

Conclusions

From the present study, it is seen that CFD contrib-utes significantly in understanding the three"dimensional flow in the intake system- and also pro-vides detailed information, about the flow structurewhere measurements are difficult to make. The mainconclusions from the present investigations are:

(i) Multi-dimensional modeling of the air intakeregion including the inlet manifold, plenum, portand valve are very important in predicting pres-sure loss.

(ii) The flow which is highly three-dimensional, isstrongly dependent on the valve lift except up-stream of the port bend.

(iii) Losses in the valve clearance are higher. Athigher valve lift flow separation is found to oc-cur and should be addressed carefully.

(iv) Predicted mass flow rates compare favourablywith experimentally measured values.

ReferencesWilliam Taylor III, James H Leylek, Randall G Sommer &Sunil K Jain, SAE Paper, No. 981026 (1998).

2 Peters B & Gosman A D, SAE Paper, No. 930609 (1993).3 Dent J C & Chen A, SAE Paper, No. 940522 (1994).4 Yingjin Cui, Wenyu Pan, James H Leylek, Randall G Som-

mer & Sunil K Jain, SAE Paper, No. 981025 (1998).5 Bicen A F, Vafidis C & Whitelaw J H, J Fluid Eng, 107,

(1985).6 Masaaki Takizawa, Tatsuo Uno, Toshiaki Oue & Tadayoshi

Yura, SAE Paper, No. 820410 (1982).

92 INDIAN J. ENG. MATER. SCI., APRIL 2004

7 Desmond E Winterbone & Richard J Pearson, Design tech-niques for engine manifolds wave action methods for I. C. en-gines (Professional Engineering Publishing, UK), 2000.0

8 Heywood J B, internal combustion engine fundamentals(McGraw-Hili, London), 1988.

9 STAR-CD Manuals Version 3.05, 1998.10 Suresh Kumar J, Flow analysis of air intake system using

computational flow dynamics, M.Tech.Thesis, Department ofMechanical Engineering, Indian Institute of Technology, Ma-dras, Chennai, India, 2003.

Indian Journal (Vol. 11, April 2

Fl~

~ternal

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