Report Phase1

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Contents1– Introduction.................................................................................................................................4

1.1 Introduction to Intake manifold.....................................................................................4

1.1.1 Working principle of Intake manifold.......................................................................5

1.2 Design of Intake Manifold............................................................................................6

1.2.1 Design Parameters for Intake Manifold..........................................................................7

1. !ngine Intake s"stem...................................................................................................12

1.4#ompression Ignition !ngines..............................................................................................1

1.4.1#omponents of #I !ngine.............................................................................................1

1.5#om$ustion in #I !ngines....................................................................................................15

1.6%our&stroke # I engine 'al'e timing(....................................................................................17

1.4.P&) Diagram of a diesel engine(..........................................................................................1*

2– +iterature ,ur'e" and -e'ie..................................................................................................1/

2.1 -e'ie of tec0nical Papers..............................................................................................1/

2.2 ,ummar" of t0e literature re'ie....................................................................................2

– Pro$lem ,tatement....................................................................................................................24

.1 im of t0e proect................................................................................................................24

.2 Proect o$ecti'es............................................................................................................24

. Met0ods and met0odolog" to meet t0e o$ecti'es..........................................................24

4. #%D nal"sis of I# !ngine Intake Manifold............................................................................26

4.1 Introduction to #%D.............................................................................................................26

4.2 3o'erning !uations in #%D..............................................................................................27

4.2.1 #ontinuit" !uation......................................................................................................27

4. Introduction to %+!.....................................................................................................2/

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4..1 #apa$ilit" of %+! ,ol'er......................................................................................8

4..2 %+! pro'ides t0ree different sol'er formulations................................................1

4.. )iscous %los...............................................................................................................2

4..4 ,teps in'ol'ed in sol'ing pro$lem...............................................................................6

4.4 0e d'antages of #%D......................................................................................................6

4.6 pplications of #%D............................................................................................................7

4.7 +imitations of #%D..............................................................................................................7

4.* 9"perMes0..........................................................................................................................*

4./. Procedure #omputational Met0od......................................................................................48

5. #ase description.........................................................................................................................41

5.1 3eometric Model #reation..................................................................................................41

5.2 3eometr" Decomposition&Mes0 generation........................................................................4

5. :oundar" conditions............................................................................................................4*

5.4 Discreti;ation.......................................................................................................................55

5.5 #on'ergence #riteria...........................................................................................................56

5.5.1 :oundar" and Initial #onditions...................................................................................56

5.5.2 spects of Modelling....................................................................................................57

5.5. #omputational Procedure.............................................................................................57

6. -!,+, D DI,#,,I<,..............................................................................................5/

7.#om$ustion nal"sis..................................................................................................................71

7.1 0e !ffect of Performance and !mission #0aracteristics on !ngine sing :io&diesel

:lends......................................................................................................................................11*

-!%!-!#!,............................................................................................................................125

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1– Introduction

1 Introduction to Intake manifold

0e engine c"cle of t"pical internal com$ustion engines consist of four consecuti'e processes as intake= compression= e>pansion ?including com$ustion@ and e>0aust. <f t0ese four

processes= t0e intake and compression stroke is one of t0e most important processes 0ic0

influences t0e pattern of air flo structure coming inside c"linder during intake stroke and

generates t0e condition needed for t0e fuel inection during t0e compression stroke. s a result of

t0e 0ig0 'elocit" inside t0e internal com$ustion engine ?I#!@ during operation= all in c"linder

flos are t"picall" tur$ulent. 0e e>ception to t0is is t0e flos in t0e corners and small cre'ices

of t0e com$ustion c0am$er 0ere t0e close distance of t0e alls diminis0ed out tur$ulence. 9eat

transfer= e'aporation= mi>ing and com$ustion rates all increase as engine speed increases. 0is

increases t0e time rate of fuel e'aporation= t0e mi>ing of t0e fuel 'apor and air as ell as

com$ustion process.

In toda"As orld= maor o$ecti'es of engine designers are to ac0ie'e t0e tin goals of

$est performance and loest possi$le emission le'els. o ma>imise t0e mass of air inducted into

t0e c"linder during t0e suction stroke= t0e intake manifold design= 0ic0 pla"s an important role=

0as to $e optimised. 0e design $ecomes more comple> in case of a multic"linder engine as air

0as to $e distri$uted euall" in all t0e c"linders. 9ence= configuration of manifold geometr"

$ecomes an important criterion for t0e engine design. c0ie'ing t0is $" means of e>perimental

met0ods ould cost time and mone". 0ere is a need for #%D met0od ?numerical met0od@=

0ic0 could estimate t0e 'olumetric efficienc" of t0e engine during t0e design stage itself=

it0out undergoing an" time consuming e>periments. lso mapping t0e total pressure

distri$ution at t0e manifold= port and 'al'e is an effecti'e met0od for anal";ing computational

prediction of t0e flo separation process in t0e region upstream of t0e 'al'e stem and in t0e

'icinit" of t0e 'al'e seat= $ecause t0e total pressure is influenced $" t0e mean. t"pical diesel

engine it0 intake manifold as s0on in %ig.1.1

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Figure.1. 1 Diesel engine with intake manifold

B,ource(& 0ttp(CCgossna$.comC164dieselengines.0tmE

1 Working principle of Intake manifold

0e intake manifold distri$utes air to eac0 c"linder. Intake runners connect eac0 intake port

to t0e manifold. Piston action creates a 'acuum in t0e manifold= 0ic0 dras outside air t0roug0

t0e t0rottle $od" and into t0e manifold. 0e 'acuum ill increase 0en t0e t0rottle 'al'e closes

?air flo is restricted@ and ill decrease 0en t0e t0rottle 'al'e opens ?air flo is less restricted.@

Diesel engines do not 0a'e a t0rottle 'al'eF t0erefore t0e 'acuum in t0e manifold is eaker t0an

a gasoline engine. 1.2 s0os t0e orking principle of intake manifold.

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Figure.1. 2 Typical intake manifold with engine flow

2 Design of Intake Manifold

0e internal com$ustion engine is a 0eat engine t0at con'erts c0emical energ" in a fuel

into mec0anical energ"= usuall" made a'aila$le on a rotating output s0aft. 0e ide range of

internal com$ustion engines is classified and t0e" 0a'e its on ad'antages and disad'antages.

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ccording to t0e t"pe of t0e fuel used t0e engine is classified as follos( Petrol !ngine= Diesel

!ngine and 3as engine.

1.2.1 Design arameters for Intake Manifold

o design an optimal intake manifold= folloing parameters s0ould $e taken into

consideration(

1. niform distri$ution of air to all c"linders.

2. Minimum possi$le resistance in IM runners.

. Proper designs of IM profile 0elps to reduce t0e sudden raise in pressure a'es 0ic0

impro'e induction process and also eliminate t0e unnecessar" tur$ulence and eddies

inside t0e intake manifold.

1.2.2. Tur!ulence

ur$ulence is generated 0ene'er air flos uickl" past a stationar" surface= $ut rapidl"

deca"s aa" t0roug0 'iscosit" once t0e $ulk air speed reduces. ,o modern t0inking is to use

careful design of t0e engineGs inlet ports. :" aiming t0e intake flo correctl"= rapid air motion is

set up during t0e induction stroke. 0is rapid motion $reaks don into tur$ulence as t0e piston

rises on t0e compression stroke= and if t0e engine is correctl" designed= 0its ust t0e rig0t le'el at

t0e point of ignition. 0is HsirlH tec0nolog" 0as $een standard on engines for decades and is

ell understood.

0e sirl strengt0 and mass flo rate are main factors to impro'e t0e com$ustionefficienc". 0e sirl 0as a role to impro'e t0e mi>ing effect of fuel and air in t0e c"linder

c0am$er. um$le motion as measure on t0e 'ertical s"mmetric plane of t0e com$ustion

c0am$er. ,irl motion as measured on a plane parallel to t0e piston cron it0 one of t0e

intake ports $locked. um$le 'orte> is produced in t0e earl" stage of t0e compression stroke and

distorted in t0e late stage of t0e stroke. B1E

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Figure.1. " #ow swirl engine$ Inlet port designed for high flow% no strong direction to air

&et. 'ery little air motion in the cylinder at the point of ignition

Figure.1. ( )igh swirl engine$ Inlet port designed to produce *ery directional air &et. +trong

swirling motion set up in the cylinder

%rom t0e figure 1.5 s0os circulating flo pattern in a diesel engine designated as sirl

motion= it0 t0e c"linder a>is as t0e a>is of rotation. 0e flo enters tangentiall" t0roug0 t0e

intake ports. %rom t0e figure 1.6 s0os transient tum$le motions in a gas engine. 0e a>is of

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motion mo'es as t0e c"linder e>pands and sta"s 0alfa" $eteen t0e top c"linder all and t0e

piston 0ead at t0e $ottom.

0e amount of tur$ulence an engine s0ould 0a'e is a compromise. 0e num$er sirl ratio

is used to c0aracterise t0e le'el of sirl= 0ere 8. ould represent uite lo sirl and 1.5 prett"

0ig0= for a petrol engine. ,ince generating more sirl reuires more restricti'e inlet ports= 'alues

around 8.5 to 1.8 are usuall" found in production engines. dding more sirl speeds up t0e $urn=

less sirl slos it don.

Most Hfuel sa'ing de'icesH t0at claim to speed up t0e $urn sa"s t0at t0is impro'es fuel

econom". 'er" slo $urn gi'es $ad econom" $ecause t0e fuel is still $urning 0en t0e e>0aust

'al'e opens 0eoreticall" t0e $est efficienc" ould $e o$tained $" an instantaneous $urn= $ut

t0is ould produce an e>tremel" 0ig0 in&c"linder temperature and so t0e 0eat loss to t0e c"linder

alls ould $e muc0 0ig0er. 0e o'erall effect is as s0on in %ig1.7.

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Figure.1. , The *isuali-ation of swirl flow on a slice through the com!ustion cham!er of a

diesel engine1/

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Figure.1. 0 The *isuali-ation of tum!le flow on a slice through the com!ustion cham!er of a

diesel engine1/

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Figure.1. Fuel consumption 's +wirl ratio

0e optimum is t"picall" around 1.5 to 2.8= $ut t0e fuel econom" loss from dropping to

around 8.5 is 'er" small and gi'es muc0 $etter H$reat0ingH= so impro'ing poer. 0is is t0e kind

of sirl le'el t0at most modern engines operate it0. In general t0e sirl ratio could $e altered

0ile t0e engine as running ?0ig0 at part load= lo at full load@= $ut in t0e end t0e 0ig0er

tur$ulence le'els simpl" did not gi'e enoug0 $enefit to ustif" t0e cost andCor reduced

performance.

,ome engines do emplo" 'aria$le&sirl tec0nolog"= suc0 as )au>0all ?<pel@Gs ne in

port engine= and some %ords. Partl" t0is is $ecause t0ere is a slig0t econom" $enefit= $ut mainl"

$ecause it allos use of 0ig0 le'els of 'al'e o'erlap or e>0aust gas recirculation 0ile still

gi'ing a sta$le $urn. ormall" 0ig0 o'erlap or !3- leads to roug0 engine runningF adding

tur$ulence increases t0e engineGs tolerance to o'erlap or !3-= 0ic0 $ring t0eir on $enefits

" ngine Intake system

0e $asic function of engine intake s"stems is to pro'ide t0e engine it0 a fres0 air&fuel

mi>ture e'er" c"cle for com$ustion to take place. Different engine operation reuirements

demand indi'idualised intake s"stems suc0 as t0e racing engines and passenger cars ?!'er"da"&

use 'e0icles@. %or racing cars reuire ma>imum 'olumetric efficienc" for increased poer and

torue= $ut t0is is not desira$le as far as econom" is concerned and for passenger cars 0ardl"

reuires top end poer= t0us econom" and dri'ea$ilit" at loer speeds are more important in t0is

instance. It is t0erefore important t0at intake s"stems are designed to suit t0e purpose for 0ic0

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t0e engine is intended. 0erefore potential to stud" t0e intake flo in a multic"linder four&stroke

engine especiall" using #%D tec0niues for getting more insig0t a$out t0e flo field= t0ere$"

impro'e t0e intake manifold configuration= to o$tain $etter performance from t0e engine

1.(3ompression Ignition ngines

diesel engine ?also knon as a compression4ignition engine@ is an internal com$ustion

engine t0at uses t0e 0eat of compression to initiate ignition to $urn t0e fuel t0at 0as $een inected

into t0e com$ustion c0am$er . 0is is in contrast to spark&ignition engines suc0 as a petrol engine

?gasoline engine@ or gas engine ?using a gaseous fuel as opposed to gasoline@= 0ic0 uses a spark

plug to ignite an air&fuel mi>ture. 0e engine as de'eloped $" 3erman in'entor -udolf

Diesel in 1*/.

#ompression ignition engines differ from spark ignition engines in a 'ariet"of a"s $ut t0e most

o$'ious one $eing t0e a" in 0ic0 t0e air and fuelMi>ture is ignited. s stated a$o'e a spark

plug is used to create a spark int0e com$ustion c0am$er 0ic0 ignites t0e mi>ture. In a

compression ignitionengine t0ere is no spark to create t0e flame $ut rat0er 0ig0 temperatures

andpressures in t0e com$ustion c0am$er cause a flame to initiate at different sitesof t0e

com$ustion c0am$er. #om$ustion increases it0 increasing pressureand temperature.

#ompression ignition engines are di'ided into direct andindirect ignition engines. Diesel engines

reuire fuel inection s"stems toinect fuel into t0e com$ustion c0am$er.

1.(.13omponents of 3I ngine

#"linder 0ead( 0e space at t0e com$ustion c0am$er top is formed and sealed $" a c"linder

0ead. 0e c"linder 0ead of a four&stroke engine 0ouses intake and e>0aust 'al'es= t0e fuel

inection 'al'e= air starting 'ale= safet" 'al'e?t0e to&stroke engine lacks t0e intake 'al'e@.

Fig.1. 13ylinder head

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http://en.wikipedia.org/wiki/Diesel_fuel

http://en.wikipedia.org/wiki/Combustion_chamber


http://en.wikipedia.org/wiki/Petrol_engine

http://en.wikipedia.org/wiki/Gasoline

http://en.wikipedia.org/wiki/Spark_plug


http://en.wikipedia.org/wiki/Diesel_fuel


http://en.wikipedia.org/wiki/Petrol_engine

http://en.wikipedia.org/wiki/Gasoline






Piston( It is one of t0e maor mo'ing parts of an engine.It must $e designed to it0stand e>treme

0eat and com$ustion pressure.It is made of cast iron or aluminium ?to reduce eig0t@.

Fig.1. 2iston

Pistonrod( It connects t0e piston it0 t0e cross0ead.

#ross0ead( 0e cross0ead pin connects t0e piston rod to t0e connecting rod.#ross0ead slippers

are mounted on eit0er side of t0e cross0ead pin. 0e slippers run up and don in t0e cross0ead

guides and pre'ent t0e connecting rod from mo'ing sidea"s as t0e piston and rod reciprocate.

#onnecting( It is fitted $eteen t0e cross0ead and t0e cranks0aft. It transmits t0e firing force=

and toget0er it0 t0e cranks0aft con'erts t0e reciprocating motion to a rotar" motion.

Fig.1. " connecting rod

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1.,3om!ustion in 3I ngines

0e main difference $eteen com$ustion in #I and ,I engines is t0e a" in0ic0 com$ustion

occurs. In ,I engines t0e com$ustion process occurs$" igniting a 0omogeneous mi>ture using a

spark plug. 0e main differencearises 0en t0e flame is initiated and t0e flame tra'els at acertain direction=dictated $" t0e flame propagation= 0ereas com$ustion in #I engines t0ereis no

flame propagation it0 a direction. #om$ustion in a #I engine is anonstead" process 0ere a

non0omogeneous mi>ture is controlled t0roug0fuel inection. 0e mi>ture is non0omogeneous

since air is t0e onl" su$stance$eing compressed until late in t0e compression stroke. Inection of

t0e fueloccurs at a$out 15 $D# and ends at a$out 5 aD#. %olloing are t0esteps t0at t0e

fuel goes t0roug0= after inection= in order to cause t0e propercom$ustion.

1. tomi;ation( t0e fuel droplets $reak into smaller droplets.

2. )apori;ation( t0e small droplets of fuel 'apori;e in t0e c0am$er due to0ig0 temperatures.

$out J/8K of t0e fuel inected into t0e c"linder 0as $een 'apori;ed it0in 8.881 second after

inection.

. Mi>ing( after 'apori;ation of t0e fuel= t0e fuel mi>es it0 t0e air toform a com$usti$le air&fuel

mi>ture.

4. ,elf&ignition( self&ignition usuall" starts around * $D#= 6&*= aftert0e start of inection. t

t0is point some of t0e mi>tureill ignite. 0ese small reactions are caused $" 0ig0 temperature

it0int0e c0am$er. 0e" are e>ot0ermic and furt0er raise t0e temperature of t0ecom$ustion

c0am$er.

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Fig.1. (3om!sution cham!er and process

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1.0Four4stroke 3 I engine *al*e timing$

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Fig.1. , 'al*e timing diagram

1.(.4' Diagram of a diesel engine$

Fig.1. 0 4' Diagram

P&) Diagram for t0e Ideal Diesel c"cle. 0e c"cle follos t0e num$ers 1&4 in clockise

direction. In t0e diesel c"cle t0e com$ustion occurs at almost constant pressure and t0e e>0aust

occurs at constant 'olume. <n t0is diagram t0e ork t0at is generated for eac0 c"cle corresponds

to t0e area it0in t0e loop.

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2– #iterature +ur*ey and 5e*iew

2.1 5e*iew of technical apers

Man" researc0ers 0ad $een studied on Intake manifold distri$ution of diesel engineaspects t0at constitute a premise to t0e modelling and simulation of intake manifold it0 !3-

and intake port alone at different 'al'e lift in t0e past. 0is c0apter re'ies t0e pre'ious

pu$lis0ed literatures= 0ic0 la"s t0e foundation and $asis for furt0er ork in t0is proect. 0is

0elps to gi'e a $etter understanding a$out t0e topic and also acts as a guideline for t0is t0esis.

-o$ert et.al B1E in'estigated to important= common fluid flo patterns from

computational fluid d"namics ?#%D@ simulations= namel"= sirl and tum$le motion t"pical of

automoti'e engines and studied to 'isuali;e sirl and tum$le flo using t0ree different flo

'isuali;ation tec0niues( direct= geometric= and te>ture&$ased. W0en illustrating t0ese met0ods

side&$"&side= e descri$e t0e relati'e strengt0s and eaknesses of eac0 approac0 it0in a

specific spatial dimension and across multiple spatial dimensions t"pical of an engineerAs

anal"sis. 0is stud" is focused on stead"&state flo. :ased on t0is in'estigation e offer

perspecti'es on 0ere and 0en t0ese tec0niues are $est applied in order to 'isuali;e t0e

$e0a'iour o sirl and tum$le motion.

#0en et.al B2E com$ined e>perimental and computational stud" of t0e stead" flo

t0roug0 an internal com$ustion engine inlet port. 0e port as of generic design it0 a straig0t

centreline. 0e t0ree&dimensional 'elocit" and tur$ulence fields in t0e port and c"linder ere

simulated using a computational fluid d"namics programme. +aser s0eet flo 'isuali;ation and

laser Doppler anemometr" ere also emplo"ed to in'estigate t0e flos and assess t0e

predictions. 0e results s0o t0at a large&scale flo structure is created in t0e c"linder $" t0e

inlet et and its interaction it0 t0e 'al'e and c"linder alls. :ot0 predictions and measurements

s0o t0at t0e flo is strongl" dependent on t0e 'al'e lift $ut is not affected $" t0e flo rate.

#omparisons of t0e numerical predictions it0 t0e e>perimental data indicated t0at t0e mean

flo features are accuratel" predicted in man" parts of t0e flo fieldF some discrepancies are

e'ident and stem primaril" from t0e failure of t0e simulation to predict a small recirculation

region in t0e port 0ic0 affects t0e traector" of t0e annular et entering t0e c"linder.

#alculations ere also made it0out modelling t0e port s0ape $" using simplified inlet

conditions upstream of t0e 'al'e seat. It as found t0at t0is appro>imation can pro'ide a

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reasona$le= al$eit less accurate= description of t0e flo= $ut modelling of t0e port s0ape is

necessar" for accurate flo predictions.

:enn" and 3anesan BE studied on t0e effect of 0elical= spiral= and 0elical&spiral

com$ination manifold configuration on air motion and tur$ulence inside t0e c"linder of a Direct

Inection ?DI@ diesel engine motored at 888 rpm. 0ree&dimensional model of t0e manifolds and

t0e c"linder is created and mes0ed using t0e pre&processor 9LP!-M!,9. 0e flo

c0aracteristics of t0ese engine manifolds are e>amined under transient conditions using

#omputational %luid D"namics ?#%D@ code ,-&#D. 0e predicted #%D results of mean sirl

'elocit" of t0e engine at different locations inside t0e com$ustion c0am$er at t0e end of

compression stroke are compared it0 e>perimental results a'aila$le in t0e literature. We also

compared t0e 'olumetric efficienc" of t0e modeled 0elical manifold. 0e results o$tained

s0oed reasona$l" good agreement it0 t0e measured data gi'en in t0e literature. %urt0er= t0is

paper discusses t0e predicted flo structure= sirl 'elocit" and 'ariation of tur$ulent energ"

inside t0e c"linder it0 different manifold. #omparisons of 'olumetric efficienc" it0 different

manifold configuration at 888 rpm speed are also presented. 0e tur$ulence is modeled using

-3 k& model. It is o$ser'ed t0at 0elical&spiral manifold gi'es t0e ma>imum sirl ratio inside

t0e c"linder t0an 0elical manifold. :ut 'olumetric efficienc" o$ser'ed is less for 0elical&spiral

manifold engine. ,irl inside t0e engine is important for diesel engine. 9ence= for $etter

performance a 0elical&spiral inlet manifold configuration is recommended.Nurniaan.et.alB4E in'estigated t0e effect of t0e piston cron inside t0e com$ustion

c0am$er of a 4&stroke direct inection automoti'e engine under t0e motoring condition is

presented. 0e anal"ses are dedicated to in'estigate t0e outcome of t0e piston s0ape differences

to t0e fluid flo= 0eat transfer and tur$ulence c0aracteristics for air&fuel mi>ture preparation in

t0e terms of sirl and tum$le ratio= tur$ulence kinetic energ"= tur$ulence dissipation rate=

tur$ulence 'iscosit" and transient 0eat flu> along t0e crank angle degrees occurred inside engine

model. 0e first t0ree parameters represents t0e fluid flo c0aracteristics occurred inside

c"linder 0ic0 influences muc0 to t0e com$ustion c0am$er 0ere t0e air flos to t0e c"linder

during t0e intake stroke and en0ances greatl" t0e mi>ing of air and fuel to gi'e a $etter mi>ing

for t0e com$ustion process. W0ile= t0e tur$ulence kinetic energ" and its dissipation rate

c0aracterise t0e k& tur$ulence model emplo"ed in t0is stud" it0 its 'iscosit" to represent t0e

small scale motion. <n t0e ot0er 0and= t0e 0eat flu> correspond to t0e all 0eat transfer arises

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during engine c"cle. 0e numerical calculations ere performed in a single c"linder of 1.6 litre

of a 4&stroke direct inection engine running at ide open t0rottle $" using t0e #%D code to

o$tain t0e $etter piston cron used for suc0 engine. 0e to different piston $ols for different

engine speeds ere compared to e'aluate t0ose mentioned parameters produced during intake

and compression stroke. 0e results o$tained from t0e numerical anal"sis can $e emplo"ed to

e>amine t0e 0omogeneit" of air&fuel mi>ture structure for $etter com$ustion process and engine

performance.

Prasad.et.al B5E studied t0e effect of air sirl generated $" directing t0e air flo in intake

manifold on engine performance. 0e tur$ulence as ac0ie'ed in t0e inlet manifold $" groo'ing

t0e inlet manifold it0 a 0elical groo'e of si;e of 1mm idt0 and 2mm dept0 of different pitc0es

to direct t0e air flo. 0e tests are carried it0 different configurations $" 'ar"ing t0e pitc0 of

t0e 0elical groo'e from 2 mm to 18 mm in steps of 2 mm inside t0e intake manifold. 0e

measurements as done at constant speed of 1588 rpm . 0e results are compared it0 normal

engine ?it0out 0elical groo'e@. 0e results of test s0o an increase in air flo= increases t0e

$rake t0ermal efficienc"= mec0anical efficienc" and decrease in 9# and #< emissions. <n t0e

ot0er 0and t0e 'olumetric efficienc" is dropped $" a$out 5K.

Da'id -at0nara and Mic0ael . Numar B6E studied OVariable Swirl Intake System for DI

Diesel Engine Using CFD. 0e" undertook a researc0 stud" on sirl of a 0elical intake portdesign for different operating conditions. 0e 'aria$le sirl plate set up of t0e W86DI!2

engine is used to e>perimentall" stud" t0e sirl 'ariation for different openings of t0e 'al'e. 0e

sliding of t0e plate results in t0e 'ariation of t0e area of inlet port entr". 0erefore in t0is stud" a

strong sirl optimi;ed com$ustion s"stem 'ar"ing according to t0e operating conditions $" a

'aria$le sirl plate mec0anism is studied e>perimentall" and compared it0 t0e computational

fluid d"namics ?#%D@ predictions. In t0is stud" t0e fluent #%D code 0as $een used to e'aluate

t0e flo in t0e port –'al'e – c"linder s"stem of a DI diesel engine in a stead" flo.

MuraliNris0an and Mallikaruna B7E ,tudied OCharacteristics of flow through the intake

valve of a single cylinder engine using practical image velocimetry! 0e" in'estigated t0e flo

pattern in&c"linder around t0e intake 'al'e of a single&c"linder at different intake air flo rates.

0e intake air flo rates are corresponding to t0e t0ree engine speeds of 1888= 2888 and 888

re'Cmin.= at all t0e static intake 'al'e opening conditions. In t0is stud"= in&c"linder flo structure

[Type text] Page 21




is c0aracteri;ed $" t0e tum$le ratio and ma>imum tur$ulent kinetic energ" of t0e flo fields. In

addition= at to specified lines of t0e com$ustion c0am$er= t0e radial and a>ial 'elocit" profiles

0a'e $een plotted. %rom t0e results= it is found t0at t0e o'erall airflo direction at t0e e>it of t0e

intake 'al'e does not c0ange significantl" it0 t0e air flo rate and intake 'al'e opening

conditions. 0e tum$le ratio increases it0 increase in intake 'al'e opening and not muc0

affected $" t0e c0ange in t0e air flo rates. It is also found t0at= t0e 'ariations of t0e 'elocit"

profiles at t0e to specified lines are smoot0 at full intake 'al'e opening irrespecti'e of t0e air

flo rate. lso= t0eir magnitudes increase it0 increase in t0e intake 'al'e openings at all t0e air

flo rates.

Nale , # and 3anes0an B*E studied OSteady flow through a SI engine intake system using CFD .

0e" carried out a stud" of stead" flo t0roug0 intake manifold= port= 'al'e and 'al'e seat for

'arious 'al'e lifts. 0ree&dimensional flo it0in t0e manifold= port and 'al'e as simulated

using computational fluid d"namics ?#%D@ and t0e code ,-&#D. %lo structures for t0e

'arious 'al'e lifts ere predicted. 0e total pressure map from computation pro'ided

compre0ensi'e information on t0e intake region flo. nal"sis as carried out for runner 1 at

t0ree different 'al'e lifts for 'arious speeds at ide&open t0rottle condition. trimmed cell as

adopted for mes0ing t0e geometries created in P-<&!3I!!- softare. %lo as simulated

$" sol'ing go'erning euations= namel"= conser'ation of mass and momentum using t0e,IMP+!&algorit0m. ur$ulence as modelled $" 0ig0 -e"nolds num$er 'ersion of k epsilon

model. !>perimental measurements ere made for 'alidating t0e numerical prediction. 3ood

agreement as o$ser'ed $eteen predicted result and t0e e>perimental dataF t0at 'al'e lift 0ad

significant effect on flo fieldF and t0at as t0e 'al'e lift increased flo separation occurred near

t0e 'al'e seat region.

,oonseong 9ong et al . B/E studied O"ptimi#ation of Intake $anifold . 0is paper presents

t0e implementation of t0e D%,, met0od to optimi;e an engine intake manifold it0 port de&

acti'e s"stem. 0e focus of optimi;ation is to ma>imi;e t0e sirl strengt0 and mass flo rate in

t0e c"linder c0am$er. 0ere are so man" factors t0at affect t0e sirl strengt0 and mass flo rate

in intake manifold s"stem= $ut onl" si> main control factors suc0 as plenum s0ape= primar" and

secondar" lengt0= port diameterF primar" pipe section s0ape= etc are adopted.

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,eminet al . B18E studied OComputation Visuali#ation and Simulation of Diesel Engines

Valve %ift &erformance Using CFD. 0e" simulated t0e intake and e>0aust 'al'e lift in t0e

single&c"linder four&stroke direct inection diesel engine. 0e 'isuali;ation and simulation 0ad

s0on t0e diesel engine $ased on t0e crank angle intake and e>0aust 'al'e lift and mo'ing

parameters. 0e result of t0is 'isuali;ation and simulation s0os t0e intake and e>0aust 'al'e lift

and air fluid flo as simulated.

2.2 +ummary of the literature re*iew

Man" researc0 carried stud" on t0e anal"sis of intake manifold= c"linder 0ead= com$ustion

c0am$er= 'al'e etc.= t0e folloing are t0e summar" of t0e literature re'ie(

•

0e literature re'eals t0e need for impro'ed flo&field anal"sis in Impro'ing t0e design of intake manifold and port design.

• 0e flo&field anal"sis in integrating t0e intake manifold to t0e intake port it0 different

t"pes of manifolds is limited so far to e>perimental met0ods. 0e limitations of t0e

e>periments lies in t0e fact t0at o$taining intricate flo features is rat0er comple>= and if so

desired reuires e>0austi'e instrumentation.

• 0e tum$le ratio increases it0 increase in intake 'al'e opening and not muc0 affected $"

t0e c0ange in t0e air flo rates.

• #omputational met0ods are an alternati'e to understand t0e finer details it0in t0e flo&

field.

0us t0e e>perimental studies and #%D simulations reported in t0e literatures act as $ase

guidelines for understanding t0e flo $e0a'iour and distri$ution of an engine. 0e de'elopments

reported in t0e literature 0a'e $een taken into consideration in t0e current proect.

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"– ro!lem +tatement

%uel econom" demands and pollution t0reats 0a'e posed serious c0allenges to t0e design

and de'elopment of ne generation diesel engines. 0e performances of t0e diesel engines are

en0anced $" proper design of inlet and e>0aust manifolds. In t0is= inlet manifold is mainl"

responsi$le for inducting appropriate amount of air into t0e c"linder. It s0ould $e t0e endea'or of

t0e designer to see t0at ma>imum 'olumetric efficienc" is o$tained. t t0e same time= t0e design

s0ould $e in suc0 a a" t0at it creates larger tur$ulence and sirl.

".1 6im of the pro&ect

o stud" t0e computational fluid d"namics in'estigation on in&c"linder flo for non&reacting

flo in a DI diesel engine using different t"pes of inlet manifolds.

2 ro&ect o!&ecti*es

• ,imulation of t0e engine it0 inlet 'al'e and intake manifold

• !ffect of inlet manifold configurations on t0e in&c"linder flo&?<nl" intake and

compression stroke@

• ur$ulence in a diesel engine under non&firing conditions

• !ffect of straig0t inlet manifold configurations on 'olumetric efficienc"= tur$ulence= and

sirl in t0e engine.

" Methods and methodology to meet the o!&ecti*es

:ased on t0e literature re'ie= t0e geometric model of t0e c"linder= intake port it0

different intake ill $e created $" using t0e cad softare as #I.

0e geometr" as mes0ed using t0e preprocessor tool as 9LP!-M!,9.

%lo $e0a'ior of t0e $aseline model as done in %+!.

,imulation of flo t0roug0 an ,tationar" !ngine Inlet )al'e it0 straig0t Manifold using

,L, %luent and 'alidation of results it0 !>perimental results. ,imulation of flo t0roug0 an ,tationar" !ngine Inlet )al'e it0 straig0t and 0elical=

using ,L, %luent and #omparison of results

,tud" t0e effect of inlet manifold configurations on t0e in&c"linder flo&?<nl" intake and

compression stroke@ using d"namic mes0 option using ,L, %luent and Preprocessing

is done in 9M /.8

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#ompare t0e !ffect of different ?straig0t and 0elical@ inlet manifold configurations on

'olumetric efficienc"= tur$ulence= and sirl in t0e engine.

#om$ustion anal"sis of I# engine

[Type text] Page 25




(. 3FD 6nalysis of I3 ngine Intake Manifold

(.1 Introduction to 3FD

%luid d"namics deals it0 t0e d"namic $e0a'ior of fluids and its mat0ematical

interpretation is called as #omputational %luid D"namics. %luid d"namics is go'erned $" sets of

partial differential euations= 0ic0 in most cases are difficult or rat0er impossi$le to o$tain

anal"tical solution. #%D is a computational tec0nolog" t0at ena$les t0e stud" of d"namicsof

t0ings t0at flo.

0e P0"sical aspects of an" fluid flo are go'erned $" t0ree fundamental principles(

Mass is conser'edF etonGs second la and !nerg" is conser'ed. 0ese fundamental principles

can $e e>pressed in terms of mat0ematical euations= 0ic0 in t0eir most general form areusuall" partial differential euations. #omputational %luid D"namics ?#%D@ is t0e science of

determining a numerical solution to t0e go'erning euations of fluid flo 0ilst ad'ancing t0e

solution t0roug0 space or time to o$tain a numerical description of t0e complete flo field of

interest.

#omputational %luid D"namics ?#%D@ t0us pro'ides a ualitati'e ?and sometimes e'en

uantitati'e@ prediction of fluid flos $" means of Mat0ematical modeling ?partial differential

euations@ umerical met0ods ?discretisation and solution tec0niues@

,oftare tools ?sol'ers= pre& and post processing utilities@ #%D ena$les scientists and engineers

to perform Qnumerical e>perimentsA ?i.e. #omputer simulations@ in a Q'irtual flo la$orator"A real

e>periment #%D simulation.

0e procedure for t0e #%D anal"sis in %+! follos t0e simple steps $elo(

i 0e model used for t0e anal"sis is dran= mes0ed and t0e $oundar" la"ers are

determined. 0is is done using t0e 9LP!-M!,9 softare= 0ic0 is t0e compati$le

modelling softare for %+!. ll t0e files for t0e geometr" and mes0ing of t0e model

are sa'ed as mes0 or grid file.

ii e>t= in %+!= t0e sa'ed mes0 or grid file of t0e model is read= c0ecked and scaled

for t0e reuired orking unit.

iii 0e model is defined for t0e t"pe of sol'er and $oundar" conditions to $e used. 0e

model is defined according to t0e t"pe of anal"sis reuired in t0e researc0 proect.

[Type text] Page 26




i' 0e model is sol'ed $" setting t0e reuired parameters in t0e solution panel and t0en

iterated for con'ergence.

' -esults can $e o$tained from t0e grap0ic displa" and report in %+!. -esults can $e

displa"ed in terms of contour= 'elocit" 'ector= and particle track and pat0 line. n"

calculation reuired can $e performed in %+! also.

'i %inall"= t0e results and all t0e data can $e sa'ed for future references $" riting t0e files.

e>t= t0e folloing section ill discuss on t0e go'erning euations used in %+! 0en

computing and anal";ing t0e fluid flo $e0a'iour. ll t0e euations ill gi'e t0e details on 0o

t0e #%D orks in order to simulate t0e result for certain pro$lems.

(.2 7o*erning 8uations in 3FD

0ere are mainl" t0ree euations e sol'e in computational fluid d"namics pro$lem.

0e" are #ontinuit" euation= Momentum euation ?a'ier ,tokes euation@ and !nerg"

euation. 0e flo of most fluids ma" $e anal";ed mat0ematicall" $" t0e use of to euations.

0e first= often referred to as t0e #ontinuit" !uation= reuires t0at t0e mass of fluid entering a

fi>ed control 'olume eit0er lea'es t0at 'olume or accumulates it0in it. It is t0us a Hmass

$alanceH reuirement posed in mat0ematical form= and is a scalar euation. 0e ot0er go'erning

euation is t0e Momentum !uation= or a'ier&,tokes !uation= and ma" $e t0oug0t of as a

Hmomentum $alanceH.

0e a'ier&,tokes euations are 'ector euations= meaning t0at t0ere is a separate

euation for eac0 of t0e coordinate directions ?usuall" t0ree@.

(.2.1 3ontinuity 8uation

0e euation of continuit" e>presses t0e conser'ation of matter&&if matter flos aa"

from a point= t0ere must $e a decrease in t0e uantit" remaining. :" definition= t0e continuit"

euation s0ould $e recogni;ed as a statement of mass conser'ation. 0e #ontinuit" !uation

relates t0e speed of a fluid mo'ing t0roug0 a pipe to t0e cross sectional area of t0e pipe.

It defines t0at as a radius of t0e pipe decreases t0e speed of fluid flo must increase and

'ice&'ersa. continuit" euation e>presses a conser'ation la $" 'E(uating a net flu> o'er a

surface it0 a loss or gain of material it0in t0e surface. #ontinuit" euations often can $e

e>pressed in eit0er integral or differential form as s0on $elo.

[Type text] Page 27




8=∂

∂+ ∫ ∫

cvcs

d)t

d)V ρ ρ

RRRRRRRRR.. ?4.1@

0is is a statement of t0e principle of mass conser'ation for a stead"= one&dimensional flo=

it0 one inlet and one outlet.

( ) 8=∂

∂+∇

t V

ρ ρ

RRRRRRRRRRRR ?4.2@

W0ere=

SSS

k #

* y

i + ∂

∂+

∂

∂+

∂

∂=∇

RRR

RRR. ?4.@

4.2.2 Momentum (Navier Stokes) Equations

0e momentum euation is a statement of etonGs ,econd +a and relates t0e sum of

t0e forces acting on an element of fluid to its acceleration or rate of c0ange of momentum. 0e etonAs second la of motion % T ma forms t0e $asis of t0e momentum euation. In fluid

mec0anics it is not clear 0at mass of mo'ing fluid e s0ould use so e use a different form of

t0e euation. 0e a'ier&,tokes euations are t0e fundamental partial differentials euations t0at

descri$e t0e flo of incompressi$le fluids. In fluid d"namics= t0e a'ier&,tokes euations are a

set of nonlinear partial differential euations t0at descri$e t0e flo of fluids suc0 as liuids and

gases. 0e euations are a set of coupled differential euations and could= in t0eor"= $e sol'ed for

a gi'en flo pro$lem $" using met0ods from calculus.

0e a'ier&,tokes euations consist of a time&dependent continuit" euation for

conser'ation of mass= t0ree time&dependent conser'ation of momentum euations and a time&

dependent conser'ation of energ" euation. 0e a'ier&,tokes !uations ?,!@ are regarded as

t0e ultimate anser to fluid d"namic pro$lems. 0ese euations ma" as ell $e t0e most idel"

studied euations in applied p0"sics. 0e range of 'alidit" of t0e a'ier&,tokes is onl" limited

[Type text] Page 28




$" t0e model used for t0e 'iscous stresses. 0ere are t0us t0ree different momentum euations

t0at toget0er comprise t0e a'ier&,tokes !uations.

RRRRRRRR. ?4.4@

4.2.3 Energy Equation

RRRRRRR.. ?4.5@

0e energ" euation is a scalar euation= meaning t0at it 0as no particular direction

associated it0 it. 0is euation demonstrates t0at= per unit 'olume= t0e c0ange in energ" of t0e

fluid mo'ing t0roug0 a control 'olume is eual to t0e rate of 0eat transferred into t0e control

[Type text] Page 29




'olume plus t0e rate of ork done $" surface forces plus t0e rate of ork done $" gra'it". 0is

e>pression of t0e energ" euation is 'alid for most applications. Mat0ematicall"= t0e energ" is

e>pressed as follos=

(." Introduction to F#9:T

0e term #omputational %luid D"namics ?#%D@ 0as come into use to co'er all aspects of

computational tec0niues t0at can $e applied to t0e solution of pro$lems in'ol'ing %luids and

3ases. #%D studies are $" no means limited to t0e area of !ngineering ,tudies and co'er fields

suc0 as eat0er forecasting= geological and geograp0ical studies= medical applications so on. In

t0e area of !ngineering ,tudies= from 0ic0 e ill $e draing our e>amples= #%D is primaril"

used as a design aid for predicting t0e performance c0aracteristics of euipment in'ol'ing

%luidC3as flo and 0eat transfer.

0e a$ilit" to simulate 0eat transfer and fluid flo pro$lems numericall" $efore a

protot"pe is $uilt cuts t0e cost and time of de'elopment $" orders of magnitude. <f course= #%D

must $e continuousl" $acked up $" e>perimentation in order to ensure t0at t0e numerical

predictions are relia$le. 0us a c"cle is formed in'ol'ing t0eoretical predictions= #%D and

e>perimentation. )alidit" of ne mat0ematical models can $e tested it0in t0e conte>t of t0is

relations0ip= it0 resulting impro'ements in t0e accurac" of #%D anal"sis.

%luent uses finite 'olume numerical procedures to sol'e t0e go'erning euations for fluid

'elocities= mass flo= pressure= temperature= species concentration and tur$ulence parameters

and fluid properties. umerical tec0niues in'ol'e t0e su$&di'ision of t0e domain into a finite

set of neig0$oring cells knon as Hcontrol 'olumesH and appl"ing t0e discretised go'erning

partial differential euations o'er eac0 cell. 0is "ields a large set of simultaneous alge$raic

euations= 0ic0 are 0ig0l" non&linear. 0ese euations are in turn sol'ed $" iterati'e means

until a con'erged solution is ac0ie'ed.

0e criteria of con'ergence can $e c0anged $" t0e user= and is generall" applied to t0e

c0anges in t0e 'alues of all t0e field 'aria$les from one iteration to t0e ne>t. W0en all t0e

euations are satisfied on all t0e discretisation points t0ere ill $e no c0ange from one iteration

to t0e ne>t. 0is t0eoretical con'ergence is not normall" ac0ie'a$le in a finite num$er of steps.

9ence t0e selection of suita$le criteria to detect near con'ergence $ecomes important.

[Type text] Page 30




(.".1 3apa!ility of F#9:T +ol*er

0is softare 0as 'arious modelling capa$ilities t0at can $e used in numerous kinds of

anal"sis and application. mong its capa$ilities are listed $elo ?%+! Manual –Program

#apa$ilities 2884@(

%los in 2D or D geometries are using unstructured solution&adapti'e

triangularCtetra0edral= uadrilateralC0e>a0edral= or mi>ed ?0"$rid@ grids t0at include

prisms ?edges@ or p"ramids.

Incompressi$le or compressi$le flos

,tead"&state or transient anal"sis

In 'iscid= laminar= and tur$ulent flos

etonian or non&etonian flo

#on'ecti'e 0eat transfer= including natural or forced con'ection

#oupled conductionCcon'ecti'e 0eat transfer

-adiation 0eat transfer

Inertial ?stationar"@ or non&inertial ?rotating@ reference frame models

Multiple mo'ing reference frames= including sliding mes0 interfaces and mi>ing planes

for rotorCstator interaction modelling.

#0emical species mi>ing and reaction= including com$ustion su$&models and surface

deposition reaction models

r$itrar" 'olumetric sources of 0eat= mass= momentum= tur$ulence= and c0emical species

+agrangian traector" calculations for a dispersed p0ase of particlesCdropletsC$u$$les=

including coupling it0 t0e continuous p0ase

%lo t0roug0 porous media.

<ne&dimensional fanC0eat&e>c0anger performance models

o&p0ase flos= including ca'itation

%ree&surface flos it0 comple> surface s0apes.

ll t0e capa$ilities mentioned a$o'e are useful in pro'iding a $etter approac0 for t0e anal"sis

in applications suc0 as process euipment= aerospace and tur$o mac0iner"= automo$ile= 0eat

e>c0anger poer generation in oilCgas industr" and material processing. 0erefore= it0 t0e

[Type text] Page 31




a'aila$ilit" of suc0 capa$ilities= t0e anal"sis for t0e purpose of t0is researc0 proect can $e

carried out in a more accurate and user friendl" a".

(.".2 F#9:T pro*ides three different sol*er formulations

• ,egregated

• #oupled implicit

• #oupled e>plicit

ll t0ree sol'er formulations ill pro'ide accurate results for a $road range of flos= $ut

in some cases one formulation ma" perform $etter ?i.e.= "ield a solution more uickl"@ t0an t0e

ot0ers. 0e segregated and coupled approac0es differ in t0e a" t0at t0e continuit"= momentum=

and ?0ere appropriate@ energ" and species euations are sol'ed( t0e segregated sol'er sol'es

t0ese euations seuentiall" ?i.e.= segregated from one anot0er@= 0ile t0e coupled sol'er sol'es

t0em simultaneousl" ?i.e.= coupled toget0er@. :ot0 formulations sol'e t0e euations for

additional scalars ?e.g.= tur$ulence or radiation uantities@ seuentiall". 0e implicit and e>plicit

coupled sol'ers differ in t0e a" t0at t0e" lineari;e t0e coupled euations.

Fig.(. 1 shows +egregated +olution #oop

[Type text] Page 32




0e segregated s0on in fig 4.1 sol'er is c0osen as t0e most appropriate sol'er for t0is

proect $ecause it operates $" sol'ing t0e go'erning euation seuentiall" until t0e solution

con'erged. 0e sol'er ill iterate t0e solution loop according to t0e user specification of t0e

num$er of iterations to $e performed in order to get t0e final solution= 0ic0 ill con'erge at t0e

end of t0e iteration. 0e steps on t0e solution loop are illustrated.

?%+! Manual – ,egregated ,olution Met0od 2884@

(."." 'iscous Flows

W0en talking a$out fluids= to different states of flos e>ist and t0e" are easil"

identified( laminar flo and tur$ulent flo. +aminar flos are t0e ones t0at smoot0l" 'ar" t0eir

'elocit" fields in space and time in 0ic0 indi'idual Os0eets of fluid mo'e past eac0 ot0er

it0out generating cross currents. 0is t"pe of flos appear 0en t0e fluid 'iscosit" force is $ig=

in comparison it0 t0e inertial forces= and t0e" damp out pertur$ations t0at ma" 0appen $ecause

of imperfections and irregularities. 0ese flos occur at lo 'alues of t0e -e"nolds num$er(

:eing + a c0aracteristic lengt0.

0e ot0er 0and= tur$ulent flos are c0aracteri;ed $" $ig fluctuations in 'elocit" and pressure

in space and time= sometimes nearl" at random. 0ese flos 0a'e fluctuating 'elocit" fields. 0e

fluctuations turn up from insta$ilities t0at gro until some interactions make t0e fluctuations

split into smaller and smaller 0irlinds t0at dissipate in t0e end ?generall" $" 0eat formation@

due to t0e action of 'iscosit". 0ese flos take place at 0ig0 -e"nolds num$ers. 0e fluctuations

can $e of small si;e and 0ig0 freuenc"= so it is 'er" cost effecti'e to make simulations of t0em

directl" in practical engineering cases. W0at it is done is t0at t0e euations of $e0a'ing can $e

ensem$le&a'eraged= time a'eraged= or small scales can $e remo'ed. 0e euations after t0ese

modifications are easier to sol'eF ne'ert0eless= t0e modifications add ot0er incognita and

different tur$ulence models appear to determine t0ese unknon 'aria$les. %+! 0a'e t0e

folloing tur$ulence models(

,palart&llmaras model

N&epsilon models ?k&

,tandard k& model

[Type text] Page 33




-enormali;ation&group ?-3@ k& model

-eali;a$le k& model

k&omega models ?k&U@

,tandard k&Umodel

,0ear&stress transport ?,,@ k&Umodel

v2 & f model

Ta!le (.1 Tur!ulence models in F#9:T

+palart46llmaras

!conomical for large mes0es. Performs poorl" for D flos=

free s0ear flos= flos it0 strong separation. ,uita$le for

mildl" comple> ?uasi&2D@ e>ternalCinternal flos and

$oundar" la"er flos under pressure gradient ?e.g. airfoils=

ings= airplane fuselage= missiles= s0ip 0ulls@.

+tandard

ε − ,

-o$ust. Widel" used despite t0e knon limitations of t0e

model. Performs poorl" for comple> flos in'ol'ing se'ere

p∇= separation= strong streamline cur'ature. ,uita$le for

initial iterations= initial screening of alternati'e designs= and

parametric studies.

5:7ε − ,

,uita$le for comple> s0ear flos in'ol'ing rapid strain=

moderate sirl= 'ortices= and locall" transitional flos ?e.g.=

$oundar" la"er separation= massi'e separation and 'orte>&

s0edding $e0ind $luff $odies= stall in ide&angle diffusers=

room 'entilation@

5eali-a!le ε − ,

<ffers largel" t0e same $enefits and 0as similar applications

as -3. na$le to use it0 multiple rotating reference

frames. Possi$l" more accurate and easier to con'erge t0an

-3.

[Type text] Page 34




+tandardω − ,

,uperior performance for all&$ounded $oundar" la"er= free

s0ear= and lo -e flos. ,uita$le for comple> $oundar"

la"er flos under ad'erse pressure gradient and separation

?e>ternal aerod"namics and tur$o mac0iner"@. #an $e used

for transitional flos ?t0oug0 tends to predict earl"

transition@. ,eparation is t"picall" predicted to $e e>cessi'e

and earl".

++Tω − ,

,imilar $enefits as ,N<. Dependenc" on all distance

makes t0is less suita$le for free s0ear flos.

-k. is t0e tur$ulence kinetic energ" and is defined as t0e 'ariance of t0e fluctuations in

'elocit". It 0as dimensions of ?+2&2@= e.g. m2Cs2.ε is t0e tur$ulence edd" dissipation ?t0e

rate at 0ic0 t0e 'elocit" fluctuations dissipate@ and 0as dimensions of k per unit time ?+2&@=

e.g. m2Cs.

0e tur$ulent kinetic energ" euation as modeled0as a num$er of simplifications from t0e

rigorous euation.

@7.......?........................................

22

@6.....?..........C

GG

= i*i*t *ii*t

*

k t

* *

iti*

*

*

k S uu

+k

+ +u

+k u

t k

δ υ τ

σ υ ν ε τ

−=−=

∂∂+∂∂+−∂

∂=∂∂+∂∂

0e first term on t0e -9, is t0e production of Q k. = t0e second term ?ε

/ is t0e specific

dissipation per unit mass. 0e last terms descri$e t0e transport of Qk. $" molecular and tur$ulent

diffusion.

[Type text] Page 35




@*........?..........C2C l k C d =ε @/..?....................C2 ε υ k C d t =

)irtuall" all one and to

euation tur$ulence models sol'e t0is euation. o close t0e Qk. euation calculation ofε

is

reuired and also edd" 'iscosit"QtA is to $ecalculate %rom dimensional considerations(.

( )[ ] @18....?..............................82G

=∂

∂

∂

∂i

* *

i u 0 + +

uυ

n e>act transport euation for Qε

can $e deri'ed $" taking t0e folloing moment a$out t0e a'ier& ,tokes euations. ?0e

procedure is $asicall" t0e same as t0e deri'ation of rigorous -e"nolds ,tress ransport euation

& see Wilco> p12@.

@1......?..........................................................................................C

@12..?....................C

@11.........?..............................C

2

2

21

ε υ

ε σ υ ν

ε τ

ε ε ε

σ υ ν ε τ

µ

ε ε ε

k C

+ +k C

+

u

k C

+u

t

+

k

+ +

u

+

k u

t

k

t

*

t

* *

i

ti*

*

*

*

k t

* *

i

ti*

*

*

=

∂

∂+

∂

∂+−

∂

∂=

∂

∂+

∂

∂

∂

∂+

∂

∂+−

∂

∂=

∂

∂+

∂

∂

0e

standard k&

ε

model is t0e default tur$ulence model in %luent. -at0er t0an sol'ing for a lengt0

scale it sol'es a second transport euation for t0e dissipation rate.

0is model as deri'ed and tuned for %los it0 0ig0 -e"nolds num$ers. 0is implies

t0at it is suited for flos 0ere t0e tur$ulence is nearl" iso&tropic and is suited to flos 0ere

t0e energ" cascade proceeds in local euili$rium it0 respect to generation. %luent also 0as t0e

-3 and -eali;a$le k&ε

models.

(.".( +teps in*ol*ed in sol*ing pro!lem

%irst create t0e grid of appropriate dimensions and it0 appropriate step lengt0 to

specif" t0e pro$lem domain in )yper mesh.

[Type text] Page 36




#reate geometries like 'ertices at appropriate grid points.

#reate lines oining to 'ertices.

#reate 6reas selecting all t0e lines.

#reate ;oundary Mesh around t0e c"linder.

#reate Face Mesh to rest of t0e model.

3i'e t0e ;oundary 3onditions for entire domain.

,a'e it and e>port it to mes0 file.

-ead t0e file in %+! and c0eck t0e mes0 and scale t0e model.

!nter 'alues for $oundar" conditions= operating conditions etc.

,electing t0e appropriate sol'er to sol'e t0e pro$lem.

,ol'e t0e pro$lem $" initiali;ing from 'elocit" inlet and specif"ing t0e num$er of

iterations.

,ol'e t0e pro$lem and note don t0e results.

(.( The 6d*antages of 3FD

:asicall"= t0e compelling reasons to use #%D are t0ese t0ree(

Insight( 0ere are man" de'ices and s"stems t0at are 'er" difficult to protot"pe. <ften=

#%D anal"sis s0os parts of t0e s"stem or p0enomena 0appening it0in t0e s"stem t0at ould

not ot0erise $e 'isi$le t0roug0 an" ot0er means. #%D gi'es a means of 'isuali;ing and

en0anced understanding of "our designs.

Foresight$ :ecause #%D is a tool for predicting 0at ill 0appen under a gi'en set of

circumstances= it can anser man" Q0at ifVA uestions 'er" uickl". Pro'ided t0e 'aria$les it

gi'es "ou outcomes. In a s0ort time= #%D can predict design performance= and 0ence num$er of

'ariants can $e tested until optimal result is found. ll of t0is is done $efore p0"sical protot"ping

and testing. 0is foresig0t made a'aila$le from #%D 0elps engineers and designers to design

$etter and faster.

fficiency$ :etter and faster design or anal"sis leads to s0orter design c"cles. ime and

mone" are sa'ed. Products get to market faster. !uipment impro'ements are $uilt and installed

it0 minimal dontime. #%D is a tool for compressing t0e design and de'elopment c"cle.

[Type text] Page 37




(.0 6pplications of 3FD

#%D can predict 0at ill 0appen= uantitati'el"= 0en fluids flo= often it0 t0e

complications of(

•

,imultaneous flo of 0eat=

• Mass transfer ?eg perspiration= dissolution@=

• P0ase c0ange ?eg melting= free;ing= $oiling@=

• #0emical reaction ?eg com$ustion= rusting@=

• Mec0anical mo'ement ?eg of pistons= fans= rudders@

• ,tresses in and displacement of immersed or surrounding solids.

Nnoing 0o fluids ill flo= and 0at ill $e t0eir uantitati'e effects on t0e solids it0

0ic0 t0e" are in contact= assists(

1 :uilding&ser'ices engineers and arc0itects to pro'ide comforta$le and safe 0uman

en'ironments

2 Poer&plant designers to attain ma>imum efficienc"= and reduce release of pollutants

#0emical engineers to ma>imi;e t0e "ields from t0eir reactors and processing euipment

(. #imitations of 3FD

#%D&$ased predictions are ne'er 188K& relia$le $ecause of t0e folloing reason(

1 0e input data ma" in'ol'e too muc0 guess ork or imprecision

2 0e a'aila$le computer poer ma" $e too small for 0ig0 numerical accurac" ?in terms of

t0e memor" spaces and capa$ilities@

0e scientific knoledge $ase ma" $e inadeuate

4 In terms of t0e relia$ilit"= #%D softare differentiates itself it0 t0e folloing aspects(

%or laminar flos rat0er t0an tur$ulent ones

%or single&p0ase flos rat0er t0an multi&p0ase flos

%or c0emicall"&inert rat0er t0an c0emicall"&reacti'e materials

%or single c0emical reactions rat0er t0an multiple ones

%or simple fluids rat0er t0an t0ose of comple> composition

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(.< )yperMesh

9"perMes0 /.8 is a 0ig0&performance pre&processor for computational fluid d"namics

?#%D@ and inection molding simulations. 9"per Mes0 ena$les users to generate ualit" grids

and mes0es in a 0ig0l" interacti'e and 'isual en'ironment. 9"per Mes0 supports most #Dgeometr" formats and e>ports #%D mes0es in nati'e formats= including %+!= ,-&#D=

#%D and Mold %lo. 9"per Mes0As state&of&t0e&art mes0ing tec0nolog" allos users to

de'elop 0ig0&ualit" mes0es to guarantee fast con'ergence rates. utomated mi>ed&t"pe mes0

generation minimi;es mes0ing time= 0ile $atc0 mes0ing ena$les large&scale mes0ing o$s it0

no model clean&up and minimal user input. 9"per Morp0= a module of 9"per Mes0= ena$les

users to define geometrical c0anges or morp0ing s0apes to stud" t0e sensiti'it" of #%D models

to c0anges in t0e flo domain= as ell as to perform manual or automatic #%D optimi;ations.

9"per Mes0 *.8&,-1 incorporates a 'ariet" of tools for seamless integration into an" e>isting

engineering process= it0 a streamlined mes0ing process t0at leads to s0orter turnaround times.

Fig.(. 2$ )e=ahedral Mesh with +tructured ;oundary4#ayer Mesh.

0e most commonl" used approac0 includes importing #D data from a 'ariet" of #D

formatsF performing a com$ination of manual and automatic geometr" clean&up it0 automatic

or user&defined criteriaF and surface mes0ing it0 default or user&defined element t"pes= si;es=

$iasing= ualit"&inde>= etc.

not0er approac0 includes full" automatic= D #%D mes0ing it0 $oundar"&la"er

mes0es consisting of 0e>a0edral andCor edge elements= an ar$itrar" num$er of la"ers=

t0icknesses or grot0 rates= and a tetra0edral core&'olume mes0ing algorit0m. 0is tetra0edral

algorit0m 0as se'eral mes0ing options= including si;e= grot0 rate and element&ualit" criteria.

9"per Mes0As #%D mes0ing capa$ilities span a 'er" ide range of target applications= including

internal and e>ternal flos= conugate 0eat transfer= species and c0emical reactions= com$ustion=

etc. 'er" large class of #%D applications can $enefit from t0e 0ig0&ualit" simulation mes0es

generated $" ltair 9"perMes0.

[Type text] Page 39




%+! uses an unstructured algorit0m for mes0 generation in order to simplif" t0e

geometr" and mes0 generation process= model more comple> geometries and adapt t0e mes0 to

resol'e t0e flo&field features. %+! can also use $od"&fitted= $lock structured mes0es. 0e

softare is capa$le of 0andling triangular and uadrilateral elements in 2D= and tetra0edral=

0e>a0edral= p"ramid= and edge elements ?or a com$ination of t0ese@ in D. 0e initial mes0 is

first generated using 9M= and t0en it can $e adapted in %+! in order to resol'e large

gradients in t0e flo field.

o model flos 0ere t0e s0ape of t0e domain is c0anging it0 time due to motion in t0e

domain $oundaries= d"namic mes0 model can $e used in %+!. 0e motion can $e a

prescri$ed motion or unprescri$ed motion 0ere t0e su$seuent motion is determined $ased on

t0e solution at t0e current time.

:ased on t0e ne position of t0e $oundaries at eac0 time step t0e update of t0e 'olume

mes0 is 0andled automaticall" $" %+!. 0e motion can $e descri$ed using eit0er $oundar"

profiles or user defined functions ?D%@ in %+!.

In %+! to update t0e 'olume mes0 in t0e deforming region su$ected to t0e motion

defined at t0e $oundaries= t0ree mes0 motion met0ods are a'aila$le.

1. ,pring $ased smoot0ing

2. D"namic la"ering and. +ocal remes0ing

.

(.>. rocedure 3omputational Method

0e steps to o$tain a proper solution for t0e flo of a fluid in %+! are(

[Type text] Page 40




• Pre Processing( #onsisting in t0e construction of geometr"= t0e generation of t0e mes0 on

t0e surfaces or 'olumes. 0is stage is done it0 t0e softare 9"perMes0= linked to

%+!. 0e geometr" can $e also imported from ot0er #D softareAs like #I.

%or creating t0e mes0 t0ere are different options t0at 9"perMes0 pro'ides. %or D t0ere

are structured mes0es of uadrilateral faces and ot0er faces easier to de'elop like t0e

triangles. ransporting t0e pro$lem to D= 0e>a0edral and p"ramidal ?tetra0edral@

'olumes can $e carried out.

• Definition of $oundar" conditions and ot0er parameters= initial conditions= $efore starting

a simulation in %+!= t0e mes0 0as to $e c0ecked and scaled and modified if

necessar". 0e p0"sical models 0a'e to $e tackled. 0is includes t0e c0oice of

compressi$ilit"= 'iscosit"= 0eat transfer considerations= laminar or tur$ulent flo= stead"

or time dependant flo. 0e $oundar" conditions 0a'e to $e clear $ecause t0e" specif"

t0e information of t0e state of t0e flo in t0e determined ;ones( alls= s"mmetries= inlet

air= outlet air= etc.

• -esolution of t0e pro$lem= 0ic0 is done t0roug0 iteration until t0e con'ergence of t0e

'aria$les is o$tained. %irst of all= t0e 'aria$les of t0e flo 0a'e to $e initiali;ed and set to

$e computed from a certain part specified $" t0e user. In t0is stage t0e euations of t0e

flo are sol'ed. 0e 'alues of t0e pressures are constantl" updated and corrected t0roug0

iterations. 0e con'ergence is c0ecked until it reac0es t0e criterion 'alue set $" t0e user.

Post Processing or anal"sis of t0e results computed. 0ere are lots of c0oices( #ontours=

X&L plots= 'elocit" 'ectors= pat0 lines. In t0em= se'eral 'aria$les can $e anal";ed( 'elocit"=

pressure= tur$ulence= forces= densit" and ot0ers.

[Type text] Page 41




,. 3ase description

,.1 7eometric Model 3reation

3eometries can $e created top&don or $ottom&up.op&don refers to an approac0 0ere

t0e computational domain is created $" performing logical operations on primiti'e s0apes suc0

as c"linders= $ricks= and sp0eres.:ottom&up refers to an approac0 0ere one first creates 'ertices

?points@= connects t0ose to form edges ?lines@= connects t0e edges to create faces= and com$ines

t0e faces to create 'olumes.3eometries can $e created using t0e same pre&processor softare t0at

is used to create t0e grid= or created using ot0er programs ?e.g. #D= grap0ics@. 3eometr" files

are imported into 9M to create computational domain. 0e !>tracted fluid domain of I# engine

as s0on in %ig.5.1= 0e geometr" of t0e different com$ustion c0am$ers is s0on in fig.5..

Ta!le ,.1$

!ngine model #ummins #&4/5&3

um$er of c"linders 4

Displacement 'olume*878 cm

3

:ore

,troke

#onnecting rod lengt0 8*mm

!ngine speed 1588rpm

#rank radius 76mm

#ompression ratio

Intake 'al'e opening 12$D#

Intake 'al'e closing 2/a:D#

!>0aust 'al'e opening /$:D#

!>0aust 'al'e closing 4aD#

Ma>imum intake 'al'e lift /.6mmMa>imum e>0aust 'al'e lift /.2mm

[Type text] Page 42



!elical


Fig.,. 1 7eometry of the com!ustion cham!er

Fig.,. 2 geometric model of I3 ngine manifold

[Type text] Page 43



!elical


Fig.,. " 3FD Model of I3 ngine iston at TD3

,.2 7eometry Decomposition4Mesh generation

o approac0es are emplo"ed in %luent 12.8 to sol'e in&c"linder pro$lems= namel"=

0"$rid approac0 and la"ering approac0. W0ile t0e 0"$rid approac0 is used for engines it0

canted 'al'es like most ,I engines= t0e la"ering approac0 is t"picall" used for engines it0

'ertical 'al'es like most diesel engines.

[Type text] Page 44




Fig.,. (7eometry decomposition of I3 engine

%or eit0er approac0 mentioned a$o'e= in&c"linder pro$lems sol'ed in %luent consist of

t0ree stages. 0e first stage is to decompose t0e geometr" into different ;ones and mes0 t0em

properl". :" $reaking up t0e model into different ;ones= it is possi$le to appl" different mes0

motion strategies to different regions in a single simulation. 0e second stage is to set up t0e

engine case inside %luent it0 t0e 0elp of a setup ournal. 0e t0ird stage is to perform a

transient in&c"linder simulation.

0e decomposition process is s0on in %ig. 5.4.

0"$rid mes0 is generated using 9"per Mes0 preprocessor.

Y Man" different cellCelement and grid t"pes are a'aila$le. #0oice depends on t0e pro$lem

and t0e sol'er capa$ilities.

Y #ell or element t"pes(

[Type text] Page 45




%irst= t0e surface is mes0ed it0 triangular element. In order to resol'e t0e tur$ulent

$oundar" la"er on t0e solid surfaces= it is $est to 0a'e groing prismatic cells from t0e )al'e

surfaces. %inall" t0e remaining region in t0e domain is filled it0 tetra0edral cells. o of elements is used for all t0e strokes appro>imatel" 8.25 millions. %or t0e mes0 generation special

care 0as $een taken to t0e ;ones close to t0e alls. In t0e pro>imit" of t0e crest t0e mes0 is finer

t0an an" ot0er part of t0e domain. 0e domain 0as $een su$di'ided into groing $o>es to make

it easier to generate t0e grid. 0e c0oice for t0e elements 0as $een $ot0 tetra0edral and

0e>a0edral mes0 'olumes.

-epresentations of t0e different mes0es t0at take part in t0e stud" are depicted in t0e

folloing detailed figures.

[Type text] Page 46




otal o of elementsT 8.25 millions

etra0edral elementsT 8.1 millions

9e>a0edral elementsT 8.15 millions

Fig.,. , Meshing Methodology

[Type text] Page 47




Fig.,. 0Mesh ;oundary and 3ell ?one :omenclature

"# in many nume$ical #imulation u#ing comme$cial #o%t&a$e' #ucce##

o% the analy#i# (y )*+,-T la$gely depend# on me#h .uality o% the model/ Th$ee #ucce##%ul model# hae (een c$eated th$ough nume$ou# t$ial# and

e$$o$#/ ome o% the pe$tinent in%o$mation' techni.ue# and #ill# deeloped

du$ing the modelling a$e #umma$ied a# %ollo&#

• The geomet$y o% the uid domain i# made #imple #uch that it i#

#uita(le %o$ the coope$ me#h techni.ue due to it# uni.ue adantage

o% haing a #imple algo$ithm %o$ dynamic me#hing/

•

The length o% inlet and outlet uid pa##age i# u#t #ucient to#imulate the actual inletoutlet condition# &ith $ea#ona(ly accu$acy/

• o$e laye$# o% element# a$e accommodated in :ne gap# en#u$ing

cone$gence o% the #olution/ The num(e$ o% laye$ o% element# i#

[Type text] Page 48



Pi#ton ;n T<=-o o% element# 0/25 million#

Pi#ton ;n ><=-o o% element# goe# up to 1/6 million#


limited to 3 due to #mall gap #ie and limitation# o% dynamic

me#hing/

• The #e&ne## o% the me#h i# cont$olled (y diiding the uid domain

in di?e$ent %ace# and me#hing it #epa$ately &ith inte$%ace (et&een

t&o %ace#/

• The den#ity o% me#h i# cont$olled (y a #iing %unction in pa$ticula$

$egion# o% the uid domain &he$e the g$adient o% a$ia(le# #uch a#

p$e##u$e and elocity i# high@ the pu$po#e i# to mae the me#h

den#e$ in tho#e a$ea#@ e#pecially &ithin na$$o& gap# and nea$ &all#/

• The #e&ne## o% the 2A< me#h i# cont$olled (elo& 0/6 in o$de$ to

p$eent p$ematu$e collap#e o% cell#/

[Type text] Page 49




Fig.,. Meshing details of Ic engine with Manifold

,." ;oundary conditions

)ollo&ing a$e the a##umption# incu$$ed on the p$e#ent analy#i#

%lo is ur$ulent

%lo is ransient and incompressi$le

,egregated sol'er

0e decomposition and ;one name matc0ing e>plained in %ig.5.* and %ig. 5./contains a

sketc0 of t0e decomposition and t0e corresponding ;one names. t t0e inlet= pressure $oundar"

condition is applied. 0e engines alls are defined as stationar" no slip alls.

Fig.,. < shows ;oundary -one names

[Type text] Page 50




Fig.,. > Fluid -one names and mesh re8uirement

[Type text] Page 51




Fig.,. 1@ Dynamic Meshing #ayering

[Type text] Page 52




Fig.,. 11 3ylinder Mesh Motion setup panel Angine arameters Ta!B

[Type text] Page 53




Fig.,. 12 +wirl tum!le input a=is and method

[Type text] Page 54




Fig.,. 1" 3ylinder Mesh -one setup panel for piston and !owl

[Type text] Page 55




Fig.,. 1( In cylinder -one setup panel for in*al*e

,.( Discreti-ation0e transient -, simulations are conducted on t0e geometr" using %luent. ,egregated

sol'er is used for t0e computations 0ic0 emplo"s a cell&centered finite 'olume met0od.

second&order upind discreti;ation is used for t0e momentum euation and a first order upind

discreti;ation is used for tur$ulent kinetic energ" and specific dissipation rate16. 0e sol'er

settings applied in %luent for t0e simulations are ta$ulated in a$le 5.2.

Ta!le ,.2$ +ol*er settings.

,ol'er ,egregated

%ormulation Implicit

Pressure discreti;ation ,tandard

Momentum discreti;ation ,econd order upind

[Type text] Page 56




ur$ulent kinetic energ" %irst order upind

,pecific dissipation rate ?omega@ %irst order upind

Pressure&)elocit" coupling ,IMP+!

,., 3on*ergence 3riteria

0e iterati'e process is repeated until t0e c0ange in t0e 'aria$le from one iteration to t0e ne>t

$ecomes so small t0at t0e solution can $e considered con'erged.

Y t con'ergence(

– ll discrete conser'ation euations ?momentum= energ"= etc.@ are o$e"ed in all

cells to a specified tolerance.

– 0e solution no longer c0anges it0 additional iterations.

– Mass= momentum= energ" and scalar $alances are o$tained.

-esiduals measure im$alance ?or error@ in conser'ation euations0e con'ergence of t0e

simulations is said to $e ac0ie'ed 0en all t0e residuals reac0 t0e reuired con'ergence criteria.

0ese con'ergence criteria are found $" monitoring. 0e con'ergence criterion for t0e continuit"

euation is 1!&4 and it is set to 1!& for t0e momentum= k and U euations.

,.,.1 ;oundary and Initial 3onditions

0e flo domain considered for simulation is donstream of t0e engine intake manifold.

0erefore= flo t0roug0 intake manifold is not modelled. 9oe'er= t0e transient flo condition

in t0e intake manifold is accounted $" introducing time&'ar"ing $oundar" condition ?pressure@ at

t0e intake 'al'e. 0e engine operating at rated speed ?1588 re'[email protected] and e>0aust 'al'e

mo'ement is simulated using t0e actual 'al'e lift profile of t0e engine.

0e computations commence it0 t0e induction process in 0ic0 a set of initial

conditions is assumed for t0e first c"cle. 0e initial conditions correspond to a pressure of /28

kpa ?corresponding to atmosp0eric pressure at :angalore@ and a temperature of 88 N for t0e

orking fluid. 9oe'er suita$le assumptions are made of t0e remaining 'aria$les. 0e t0ree

components of 'elocit" are taken as 8.881 mCsF similarl"= initial lo 'alues for tur$ulence kinetic

energ" and dissipation rate are assumed at 8.881 m2Cs2 and 8.881 m2Cs respecti'el". 0e orking

fluid is treated as a premi>ed gas since com$ustion is considered. 0ese computations are one

complete c"cles.

[Type text] Page 57




#onstant pressure $oundar" conditions ere assigned at $ot0 inlets= so t0e d"namic

effects ere neglected. emperature $oundar" conditions ere assigned separatel" for t0e 0ead=

t0e c"linder all and t0e piston cron t0at form t0e alls of t0e com$ustion c0am$er.

,.,.2 6spects of Modelling

0e #%D code sol'es t0e &D= ensem$le&a'eraged a'ier&,tokes and energ" euations

go'erning tur$ulent and compressi$le gas flo along it0 0eat transfer for t0e geometr"

descri$ed a$o'e. o simulate com$ustion #&com$ustion euation is used as t0e model 0as

performed 'er" satisfactor"= ualitati'e features of t0e reacting flos 0a'e $een ell reproduced=

and t0e model is computationall" ro$ust and 'er" efficient. 0e orking fluid is treated as a

premi>ed mi>ture since com$ustion is simulated. 0e program is $ased on t0e pressure&

correction met0od and uses t0e PI,< algorit0m. 0e second order upind differencing sc0eme is

used for t0e momentum= energ" and tur$ulence euations. 0e go'erning euation set includes

t0e continuit" euation= t0ree momentum euations= t0e ent0alp" euation= to tur$ulence

euations and # com$ustion euation.

,.,." 3omputational rocedure

#omputations 0a'e $een made for an operational speed of 1588 re'Cmin= it0 time step

of t0e order of 8.25Z # ?25 micro seconds@. 0e calculations commence it0 t0e piston at D#=

it0 t0e intake 'al'e and e>0aust port closed. sing t0e initial and $oundar" conditions as

mentioned earlier= t0e computation proceeds it0 t0e piston descending donards and t0eintake 'al'e $eginning to open so as to allo fluid to enter t0e flo domain i.e. c"linder. 0e

d"namic mes0 and in c"linder setting is done. 0e #%D codes 0ic0 are ritten in #&program

are knon as ser Defined %unctions ?D%As@. 0ese functions are used to define man"

parameters in %luent. 9ere t0ree D%As are used first one is to initiali;e t0e domain= second one

is to define fuel= to calculate un$urnt gas temperature and laminar flame speed for premi>ed

com$ustion since laminar flame speed is a strong function of temperature and eui'alence ratio

t0is D% is used to modif" t0at to $e more realistic 'alue. 0e t0ird D% as used to calculate

t0e Indicated ork= output pressure= output 'olume= output $urned fuel mass fraction as a

function of crank angle. 0ese t0ree D%As are compiled and 0ooked to t0e fluent.

0e closure of t0e intake 'al'e takes place in accordance it0 t0e actual 'al'e timing of

t0e engine. 0e intake 'al'e closes at 2/Z a:D# ?after :ottom Dead #entre@= at 0ic0 time t0e

$oundar" condition at t0e intake 'al'e is c0anged from QpressureA to QallA to pre'ent fluid

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escaping from t0e c"linder. 0e 'al'e closure is 0alted it0 a cell si;e of less t0an 8.25 mm to

pre'ent collapse of t0e grid. In t0is transitional period a loer time&step of t0e order of 8.1Z #

?18 micro second@ is adopted to so as to pre'ent di'ergence in t0e solution. %urt0er upard

mo'ement of t0e piston results in compression of t0e fluid till t0e piston reac0es D#= $e"ond

0ic0 fluid e>pansion occurs. 0e e>0aust port opens at /Z ::# ?:efore :ottom #entre@ $"

introducing a pressure $oundar" condition at t0e e>0aust port. 0e e>0aust process continues till

t0e piston reac0es #= 0ic0 completes one c"cle of operation.

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0. 5+9#T+ 6:D DI+39++IC:+

0e in&c"linder fluid d"namics in engines 0as $een s0on to pla" an important role

during t0e com$ustion process. In particular= in&c"linder fluid flos contri$ute to fuel air mi>ing

0ic0 is important to t0e fuel&$urning rate. ur$ulence generated in an I.#. engine is anisotropic.

During t0e Intake process= t0e flo passing t0e 'al'e separates and results in a 0ig0l" unstead"

motion. 0is flo contains $ot0 large&scale and small&scale tur$ulence. ,ince tur$ulence 0as a

maor effect on com$ustion= flo&mi>ing and on 0eat&transfer in an engine= to model t0e flo

inside an engine a proper tur$ulence model s0ould $e used. In t0is anal"sis -3 k epsilon model

is used.

0e intake manifold and piston $ol design is one of t0e most important factors t0at

affect t0e airCfuel mi>ing and t0e su$seuent com$ustion and pollutant formation processes in a

direct inection diesel engine. 0e $ol geometr" and dimensions= suc0 as t0e pip region= t0e

$ol lip area and t0e torus radius= are all knon to 0a'e an effect on t0e in&c"linder mi>ing and

com$ustion process. In order to understand $etter t0e effect of t0e pip region= t0ree piston $ols

it0 different pip designs $ut it0 t0e same lip area and torus radius ere designed and

in'estigated using computational fluid d"namics ?#%D@ engine modelling. commercial #%D

as used to model t0e in&c"linder flos and it0out com$ustion process.

In t0is c0apter= t0e results from t0e modelling and #%D simulation using %+!

softare are s0on and discussed. -esults are s0on in term of grap0s for t0e simulation results

for pressure distri$ution= temperature distri$ution and )elocit".

0e mo'ing mes0 is generated $" DLMI# M!,9 -<I!= a mo'ing mes0

module in %+!. In engine operation= 'al'es and t0e piston mo'e= so t0e mes0 s0ould mo'e

according to t0e real engine in order to simulate t0e c0arge of 'al'e and piston position it0

crank angle. Piston and piston $ol mo'ement are decided $" t0e stroke= connecting rod and

crank angle. #alculation starts at 68o # and ends at 18*8o #.

cold flo anal"sis is performed for t0is purpose. #old flo simulations for I# engines

can pro'ide 'alua$le design information to engineers. 0ese simulations allo for t0e effect on

'olume efficienc" andCor sirl and tum$le c0aracteristics to $e predicted $ased on c0anges in

port and com$ustion c0am$er design= 'al'e lift timing= or ot0er parameters.

,.1 3old Flow +imulation

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#old flo simulation is t0e simulation in 0ic0 engine c"cle it0 mo'ing geometr"= air

flo= no fuel inection nor ignition and no reactions. In t0is section= a 'elocit" 'ector plot= across

t0e different cross sectional plane is presented= for different crank angle= and also t0e P&[ are

illustrated. 0e c0aracteristics of in&c"linder flo are discussed in t0e folloing paragrap0s at

t0e a>ial planes. 0e interaction of t0e 0ig0 'elocit" intake et flo it0 t0e c"linder alls

toget0er it0 mo'ing piston= produce large scale rotating patterns it0in t0e c"linder. s a result

of t0is= t0e flo $e0a'ior ould $e tur$ulent in 0ic0 t0e rate of mi>ing as ell as t0e rate of

0eat transfer are se'eral times greater t0an t0e rates due to molecular diffusion. 0e flo during

t0e compression and e>0aust stroke is o$ser'ed to $e transient= 0ig0l" tur$ulent and fluctuating.

Fig.0. 1ressure 's crank angle

0e grap0s for pressure distri$ution= temperature distri$ution are plotted against t0e time

step for 'arious cases. ote t0at eac0 increment of a time step is euals to an increment of 8.25Z

of crank angle. Piston starts from D# a$out 8 degrees and t0e ma>imum pressure reac0es at

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68 degree. t t0e start of com$ustion after t0e ignition dela" t0ere is a sudden c0ange of slope

of t0e p&[ cur'e. 0e pressure rises rapidl" for a fe crank angle degrees= and t0en mo'es slol"

toards a peak 'alue.

Fig.0. 2Temperature 's crank angle

Inlet 'al'e is kept open during suction strokeF t0e 'ariation in pressure is s0on in t0e fig 6.1

and it is found t0at t0e 'acuum pressure e>ists at t0e suction stroke. <ne of important

o$ser'ation in t0is figure is t0e 'elocit" is ma>imum at t0e cur'ature of port and 'al'e seat.

W0en a piston is at :D#= t0e inlet 'al'e is closed. )ariations in pressure a$o'e t0e piston are

studied. Pressure increases rapidl" 0en piston is at t0e middle of t0e compression stroke. 0e

pressure at corners ?i.e.= $elo t0e 'al'e and a$o'e t0e piston rig0t side@ is more compare to t0e

centre of t0e com$ustion c0am$er.

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Fig.0. " ressure contours at different crank angle

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Fig.0. (ressure contours at different crank angle

s t0e piston mo'e toards D# t0ere ill $e a rise in pressure and reac0es ma>imum of 54

$ars. 3raduall" pressure decreases during e>pansion stroke e can o$ser'e t0e 'ariations in t0e

domain since t0e pressure decreases $elo atmosp0eric pressure flo regime ill $ecome

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supersonic 0ence supersonic condition is used at outlet to e'acuate t0e fluid from t0e c"linder

and pressure inside is almost same.

Fig.0. ,Temperature contours at different crank angle

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Fig.0. 0Temperature contours at different crank angle

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Fig.0. 'elocity contours at different crank angle

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Fig.0. <'elocity contours at different crank angle

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Fig.0. >'elocity +treamlines at different crank angle

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Fig.0. 1@'elocity +treamlines at different crank angle

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Fig.0. 11'elocity +treamlines at different crank angle

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.3om!ustion 6nalysis

Internal com$ustion engineF more specificall"= it is a compression ignition engine= in

0ic0 t0e fuel is ignited solel" $" t0e 0ig0 temperature created $" compression of t0e air&fuel

mi>ture= rat0er t0an $" a separate source of ignition= suc0 as a spark plug= as is t0e case in t0e

gasoline engine. 0e engine operates using t0e diesel c"cle. In 'er" cold eat0er= diesel fuel

t0ickens and increases in 'iscosit" and forms a> cr"stals or a gel. 0is can make it difficult for

t0e fuel inector to get fuel into t0e c"linder in an effecti'e manner= making cold eat0er starts

difficult at times= t0oug0 recent ad'ances in diesel fuel tec0nolog" 0a'e made t0ese difficulties

rare. commonl" applied ad'ance is to electricall" 0eat t0e fuel filter and fuel lines. <t0er

engines utili;e small electric 0eaters called glo plugs inside t0e c"linder to arm t0e c"linders

prior to starting. small num$er use resisti'e grid 0eaters in t0e intake manifold to arm t0e

inlet air until t0e engine reac0es operating temperature. !ngine $lock 0eaters ?electric resisti'e

0eaters in t0e engine $lock@ plugged into t0e utilit" grid are often used 0en an engine is s0ut

don for e>tended periods ?more t0an an 0our@ in cold eat0er to reduce startup time and engine

ear.

3ompression In&ection Ignition

'ital component of older diesel engine s"stems as t0e go'ernor= 0ic0 limited t0e

speed of t0e engine $" controlling t0e rate of fuel deli'er". nlike a petrol ?gasoline@ engine= t0e

incoming air is not t0rottled= so t0e engine ould o'er&speed if t0is as not done. <lder inection

s"stems ere dri'en $" a gear s"stem from t0e engine ?and t0us supplied fuel onl" linearl" it0

engine speed@

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In diesel engines= onl" air is send into t0e com$ustion c0am$er during induction. 0is air

is compressed during t0e compression stroke and toards t0e end of compression stroke= fuel is

inected $" t0e fuelinection s"stem into t0e c"linder & ust $efore t0e desired start of com$ustion.

+iuid fuel is inected at 0ig0 'elocities as one or more ets t0roug0 small orifices or no;;les in

t0e inector tip. 0e fuel atomi;es into small droplets and penetrates into t0e com$ustion

c0am$er & t0e droplets 'apori;e and mi> it0 it0 0ig0&temperature and 0ig0pressure c"linder

air.,ince t0e air temperature and pressure are a$o'e t0e fuelAs ignition point= spontaneous

ignition of portions of alread" mi>ed fuel and air occurs after a dela" period of a fe crank angle

degrees.0e c"linder pressure increases as com$ustion of fuel&air mi>ture occurs.

0e pro$lem to $e sol'ed in t0is tutorial is s0on in %igure 1. 68 degree simplified sector

model of a4&stroke diesel engine 0ic0 corresponds to one fuel inector 0ole is modeled. ,ince

t0e o$ecti'e is to model compression and com$ustion stroke= t0e actual simulation starts at 2

# ?i.e. I)#@. ,ince t0e mes0ed model corresponds to D# condition= initial part of t0e tutorial

descri$es 0o to setup d"namic mes0 model and perform mes0 motion to get mes0 at 2 #.

0e simulation is performed onl" upto 488 # alt0oug0 t0e e>0aust 'al'e closes muc0 later after

t0is point.

0e engine specification and ot0er inputs are pro'ided as follos(

Y I)# T 2 #

Y I)#T 484.4/1 N

Y PI)# T 422648 PaY c"linder T 567 N

Y 0ead T 682 N

Y pistonT 645 N Y ,irl -atio I)# T 1.26

0e detailed material properties of liuid fuel are pro'ided later in t0e tutorial. 0e inection is

'aria$le in nature and follos t0e folloing cur'e

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360 365 370 375 380 385 390

0

100

200

300

400

500

600

Injection Velocity Profle

;nection Belocity

P$o:le

<t0er inection specific inputs are as follos(

Y Disc0arge #oefficient T 8.7

Y otal Mass ,pra"ed T 8.2 gY ,<I T 62.1 # ?2 deg after D#@ and 66

Y Inection Duration T 25 degree

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Fig.. 1 Transient Temperature 3ontours

%ig&7.1 s0o t0e 'ariation of temperature in t0e domain during different crank angle or four

strokes 0as $een discussed. In suction stroke as t0e fuel and air mi>tures enter into t0e c"linder=

during t0is stroke t0e fuel 0as temperature of 88./ N In t0e compression stroke as t0e piston

mo'es from t0e :D# to D# t0e mi>tures get compressed= 0ence temperature of t0e fuel air mi>ture graduall" increase. 0e colour difference in t0e figure s0os= 0o t0e temperature

c0anges 0ile piston in mo'ing. t t0e # of 788 degree as t0e diesel inected and causes t0e

mi>tures to ignite as a result of ignition t0e temperature inside t0e c"linder increases and

ma>imum temperature attained inside t0e c"linder is 2444 N. 0en t0e piston is at D# almost

constant temperature is attained. s t0e piston mo'e toards :D# e can o$ser'e t0at t0e

constant fall in temperature.

















































Fig.. 2 ;io4diesel articles colored !y temperature

















































Fig.. " articles colored !y 'elocity Magnitude





















































Fig.. ( 'elocity Magnitude





.1 The ffect of erformance and mission 3haracteristics on ngine 9sing

;io4diesel ;lends.

0 10 20 30 40 50 60 70 80 90 1000

5

10

15

20

25

30

;56 T)5M6# FFI3I:3E*s #C6D

<;,,*

>10

>20

>40

>60

>80

>100

#C6D AGB

;T AGB

Fig.. , 'ariation of ;T *s #oad

;rake Thermal fficiency( %rom t0e fig t0e :! of :48 is ?27.*K@ for petro diesel :! is

?26.*K@. :! of :48 is 0ig0er t0an diesel and $lends of $io&diesel. 0e :! for :18= :28=

:68= :*8= and :188 is 26.16= 25.8/= 24.26= 24.75= and 24.2 respecti'el". Wit0 increase in load

t0e $rake t0ermal efficienc" impro'es. 0is is due to t0e spra" form during t0e inection and

impro'ed atomi;ation and t0is ma" due to reduction in 0eat losses at 0ig0er load. s t0e $rake

poer increases t0e 0eat generated in t0e c"linder increases= and 0ence= t0e t0ermal efficienc"

increases. -eduction in :! it0 t0e increase in $iodiesel percentage in t0e fuel $lends due to

t0e decrease in calorific 'alue of fuel $lend.





0 10 20 30 40 50 60 70 80 90 1000

0/5

1

1/5

2

2/5

;56 CW5 *s #C6D

<;,,*>10

>20

>40

>60

>80

>100

#C6D AGB

; AkwB

Fig.. 0 'ariation of ; *s #oad

;rake ower$ %rom t0e fig t0e :P of :48 is ?1./75NW@ for petro diesel :P is ?1./85NW@. 0e

:P of :48 is 0ig0er t0an diesel and $lends of $io&diesel. 0e :P for :18= :28= :68= :*8= and

:188 is 1.*51= 1./55= 1.*/= 1./2* and 1.*/5 respecti'el". 0is is due to t0e torue de'eloped at

full load is 0ig0er for :48 t0an diesel and $lends of $io&diesel. 0e loer poer output it0

ot0er $iodiesel $lends ?:18= :28= :68= :*8 and :188@ is due to t0e 0ig0er 'iscosit" and loer

0eating 'alue of t0e $lends as compared to petro diesel. :rake poer decreases slig0tl" 0en

$lends are used $ecause of loer 0eating 'alue of $iodiesel.





0 10 20 30 40 50 60 70 80 90 1000

2

4

6

8

10

12

14

;+F3 *s #C6D

<;,,*

>10

>20

>40

>60

>80

>100

#C6D AGB

;+F3Akgkw4hB

Fig.. 'ariation of ;+F3 *s #oad

;rake +pecific Fuel 3onsumption$ %rom t0e fig t0e :,%# of :48 is ?8.42kgCk&0@ for petro

diesel :,%# is ?8.84kgCk&0@. 0e :,%# for :18= :28= :68= :*8= and :188 is 8.27= 8.75=

8.4/8= 8.422 and 8.4* respecti'el". 0e $rake specific fuel consumption ?:,%#@ as found

to $e loest for diesel and tend to increase a little it0 t0e $lends. 0e :,%# is more it0 0ig0er

$lends of $iodiesel. 0is is $ecause of loer 0eating 'alue and 0ig0er 'iscosit" of t0e $lends ascompared to petro diesel.





0 10 20 30 40 50 60 70 80 90 1000

0/5

1

1/5

2

2/5

3C2 *s #C6D

<;,,*

>10

>20

>40

>60

>80

>100

#C6D AGB

3C2 AGB

Fig.. < 'ariation of 3C2 *s #oad

3ar!on dio=ide$ 0e car$on dio>ide emission from t0e diesel engine it0 different $lends is

s0on in t0e figure. 0e #<2 for Diesel= :18= :28= :48= :68= :*8= and :188 is 1./= 1.2= 1.7=

1.5= 1.= 1.4 and 2 respecti'el". Its uantit" increases it0 increase in t0e load conditions for

diesel and also for t0e $lends= $lend :18 emits lo emissions compared to diesel. 0is is due to

t0e fact t0at $iodiesel in general is a lo car$on fuel and as loer elemental car$on to 0"drogen

ratio t0an diesel.





0 10 20 30 40 50 60 70 80 90 1000

0/01

0/01

0/02

0/02

0/03

0/03

0/04

3C *s #C6D

<;,,*

>10

>20

>40

>60

>80

>100

#C6D AGB

3C AGB

Fig.. > 'ariation of 3C *s #oad

3ar!on mono=ide$ 0e #< for Diesel= :18= :28= :48= :68= :*8= and :188 is 8.82= 8.81= 8.82=

8.82= 8.81= 8.82 and 8.82 respecti'el". It is seen t0at t0e #< concentration is loer compared to

diesel for t0e $lend :18. 0e #< emission as constant it0 increasing load. 9ig0er t0e load=

ric0er t0e air&fuel mi>ture and t0us less a'aila$ilit" of o>"gen due to less air. t loer loads= #<

emissions are minimi;ed and are close to t0at of diesel.

0 10 20 30 40 50 60 70 80 90 1000

5

10

15

20

25

30

)3 *s #C6D

<;,,*

>10

>20

>40

>60>80

>100

#C6D AGB

)3 AppmB





Fig.. 1@ 'ariation of )3 *s #oad

)ydrocar!on$ %igure indicates 0"drocar$on emission trends for diesel and $lends at different

load. 0e 9# for Diesel= :18= :28= :48= :68= :*8= and :188 is 24= 18= 25= 16= /= 11 and 1/respecti'el". s t0e cetane num$er of ester $ased fuel is 0ig0er t0an diesel= it e>0i$its s0orter

dela" period and results in $etter com$ustion. 0erefore= o>"gen content and cetane num$er of

t0e $lends leads to loer 0"dro car$on emissions as compare to diesel. ItAs least for t0e $lend

:18.

0 10 20 30 40 50 60 70 80 90 1000

50

100

150

200

250

:C= *s #C6D

<;,,*

>10

>20

>40

>60

>80

>100

#C6D AGB

:C= AppmB

Fig.. 11 'ariation of :C= *s #oad

:itrogen o=ide$ 0e <> for Diesel= :18= :28= :48= :68= :*8= and :188 is 284= 145= 1/6= 1*8=

14*= 1*6 and 282 respecti'el". It can $e seen t0at t0e decreasing proportion of $iodiesel in t0e

$lends as found to decrease <> ?itrogen o>ide@ emissions= 0en compared it0 t0at of pure

diesel. 0is could $e attri$uted to t0e increased e>0aust gas temperatures and t0e fact t0at

$iodiesel 0ad some o>"gen content in it 0ic0 facilitated <> ?itrogen o>ide@ formation. In

general= t0e itrogen o>ide concentration 'aries linearl" it0 t0e load of t0e engine. s t0e load

increases= t0e o'erall





fuel&air ratio increases resulting in an increase in t0e a'erage gas temperature in t0e com$ustion

c0am$er and 0ence <> ?itrogen o>ide@ formation= 0ic0 is sensiti'e to temperature increase.

.2 3omparison of erformance and mission arameters

Ta!le ,.(.1 3omparison of erformance and mission arameters of 'arious ;lends at

Full #oad.

;lends

erformance mission

;

AkwB

;T

G

;+F3

kgkw4h

3C2

G

3C

G

)3

ppm

:C=

ppm

Diesel 1.>@, 20.<>, @."@(( 1.> @.@2 2( 2@(

;1@ 1.<,"1 20.102 @."2" 1.2 @.@1 1@ 1(,

;2@ 1.>,,2 2,.@>( @."", 1. @.@2 2, 1>0

;(@ 1.>, 2.<2( @."1(> 1., @.@2 10 1<@

;0@ 1.<>@< 2(.20 @."(>@ 1." @.@1 > 1(<

;<@ 1.>2<, 2(.,1 @."(22 1.( @.@2 11 1<0

;1@@ 1.<>, 2(."2< @."(< 2 @.@2 1> 2@2





5F5:3+

1. L.akenaka= M.La$e= L. o"agi and . ,0io;aki ?1//8@ 0as studied O0ree dimensional

computation of In&c"linder %lo it0 intake port in DI Diesel !ngine.

2. ,emin= -osli $u :akar and $dul -a0im Ismail ?288*@ 0as studied #omputational)isuali;ation and ,imulation of Diesel !ngines )al'e +ift Performance sing #%D.

. \. :enaes.B1//8E Oumerical solution of flo and com$ustion in an a> s"mmetric

internal com$ustion engine.

4. 3osman and 9ar'e" 0as studied Oumerical solution of flo and com$ustion in an a>

s"mmetric internal com$ustion engine.5. :enn" Paul1 %lo field de'elopment in a direct inection diesel engine it0 different

manifolds. International ournal of engineering= science and tec0nolog"=)ol.2.o.1=2818.

6. %. Pa"ri= \. :enaes= X. Margot= . 3il= O#%D modeling of t0e in c"linder flo in direct&

inection diesel engines= Computers 1 Fluids= 'ol. = pp. //5&1821= 2884.7. ippelmann 3. ne met0od of in'estigation of sirl ports. ,! 778484= 1/77.

*. ;kan = :orgnakke #= Morel . #0aracteri;ation of flo produced $" a 0ig0&sirl inlet

port. ,! Paper *8266= 1/*.

/. )ersteeg 9N= Malalasekera W. n introduction to computational fluid d"namics. 0e

finite 'olume met0od. +ongMan ,cientific ] ec0nicalF 1//5.

18. Wakisaka = ,0imamoto L= Issi0iki L. 0ree&dimensional numerical anal"sis of in&

c"linder flos in reciprocating engines. ,! *68464= 1/*6.11. Wit;e P<. Measurements of t0e spatial distri$ution and engine speed dependence of

tur$ulent air motion in an I# engine. ,! 778228= 1/77.12. Wosc0ni 3. uni'ersall" applica$le euation for t0e instantaneous 0eat transfer

coefficient in t0e internal com$ustion engine. ,! 678/1= 1/67.

1. Lun \&!. e e'aluation indices for $ulk motion of in&c"linder flo troug0 intake port

s"stem in c"linder 0ead. Proc IMec0!= Part D( \ utomo$ile !ng 2882F216(51–21.




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