Thermochemistry study of internal combustion engine

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1 Avalable onlne a Energy Proceda 18 (2012 ) Conference Tle Thermochemsry sudy of nernal combuson engne Feh BOURAS*, Azeddne SOUDANI and Mohamed SI AMEUR a Unversy of HL-Bana, BATNA- Algera. Absrac The majory of aerospace engnes such as urboreacor and rocke engnes work due o he process of combuson, whch s also responsble for he formaon of harmful and polluans chemcal speces n he envronmen. The progress n engne echnology asks consrucors o respec he envronmenal regulaons; hs s requred o develop ecologcal and cleaner engnes. Our nvesgaon was based on a confguraon of cylndrcal combuson chamber smlar o he urboreacor, usng he njecon of mehane and ar wh dfferen nle velocy, n order o calculae he emperaure feld and esmae he mass fracon of carbon monode (CO) a dfferen regon of he burner, usng he soluon of aerohermochemsry equaons. The valdaon s based on epermenal daa of C.P. Davd (Sanford-USA. 2001). * Correspondng auhor. Tel.: ; fa: E-mal address: f.bouras@homal.fr Publshed by Elsever by Elsever Ld. Selecon Ld. Selecon and/or peer and/or revew peer-revew under responsbly under of responsbly The TerraGreen of Socey. [name organzer] Open access under CC BY-NC-ND lcense. Keywords Combuson; Turbulence; Large eddy smulaon (LES); Probably densy funcon (PDF). Nomenclaure Roman Symbols C n p P( ) r progress varable Boundary-normal coordnae Pressure Probably densy funcon Radal coordnae Tme Publshed by Elsever Ld. Selecon and/or peer revew under responsbly of The TerraGreen Socey. Open access under CC BY-NC-ND lcense. do: /j.egypro

2 Feh Bouras e al. / Energy Proceda 18 ( 2012 ) T u y Z Temperaure Velocy componen Spaal coordnae Mass fracon of speces Mure fracon Greek Symbols Kronecker dela Thermal conducvy Molecular vscosy; Dsrbuon mean Knemacs vscosy Mass densy Vscous sress ensor Abbrevaon LES PDF WALE Large eddy smulaon Probably Densy Funcon Wall Adapng Local Eddy Vscosy. Inroducon Advancemen of scence has helped o develop many doman of lfe, whch helped o creae he condons of human comfor. Ths shows clearly ha he machne replaced human n agrculure and ndusry. The man resul of hs advancemen s an abundan producon wh less effor n less me. As well as he means of ransporaon helped o ranspor for ndvduals and goods n a less me n erms of comfor and away from danger. Wh all hese advanages for he humany, can ha assure a clean envronmen? The polluon has begun snce cenures; he developmen of amalgamaon process no ndusral operaon n 1551 smulaed he massve producon of slver n he New World bu lef behnd an unprecedened quany of mercury polluon. The annual loss of mercury n he slver mnes of Spansh Amerca averaged 612 onnes/year beween 1580 and Appromaely 90% of he mercury consumed o he envronmen due o he producon of precous meals n he Amercas oaled onnes. Appromaely 60-65% of he mercury los s beleved o have been released o he amosphere, suggesng ha gold and slver mnes were a domnan source of amospherc mercury polluon. Because of s hgh volaly, any deposed mercury can readly be re-emed o he amosphere [1]. The polluon doesn' only ouch he envronmen where humans lve, bu can arrve o he sea and ocean. J.G.B. Derrak dscussed he polluon of he marne envronmen and also some of he ways o mgae he problem. The deleerous effecs of plasc and meal debrs on he marne envronmen were revewed by brngng ogeher mos of he leraure publshed so far on he opc. A

3 1088 Feh Bouras e al. / Energy Proceda 18 ( 2012 ) large number of marne speces s known o be harmed and/or klled by plasc and meal debrs [2, 3], whch could jeopardze her survval, especally snce many are already endangered by oher forms of anhropogenc acves. Marne anmals are mosly affeced hrough enanglemen n and ngeson of plasc ler. Oher less known hreas nclude he use of plasc and meal debrs by nvader speces and he absorpon of polychlornaed bphenyls from ngesed plascs. Less conspcuous forms, such as plasc pelles and scrubbers are also hazardous. S.E Aknson and D.H Lews (1974) have nvesgaed n he lnear programmng models purpor o mnmze he coss of emsson conrol o acheve amben ar qualy sandards. Many of he smulaons ncorporae he smplfyng assumpon ha mprovemens n amben ar qualy are proporonal o reducons n regonal emssons [4]. Ths approach mnmzes he cos of mass emsson reducon, bu no he cos o acheve a prescrbed amben ar qualy. The coss of hs emssons leas-cos sraegy are compared o an amben leas-cos sraegy whch does acheve prescrbed amben ar qualy a mnmum cos. The cos savng acheved by hs sraegy relave o he emssons leas-cos sraegy s as much as 50%. In addon, boh are compared o sraegy ypcal of hose currenly used by he saes, whch found o be as much as en mes as epensve as he amben leas-cos sraegy. Progress n engne echnology provdes powerful engnes bu wh emsson of harmful speces (CO, N2O and NO). In he 80s M. Kavanaugh neresed on he emssons of CO, N 2 O and NO from combuson and were esmaed usng a common se of demographc, economc and regulaory assumpons [4,5]. The esmaes represen a sum of emssons from s large geographcal regons n whch energy usage was predced usng an economc forecasng model. Analyss was performed for 1960, 1975, 2000 and Fuure global CO emssons from combuson are lkely o decrease because of regulaon n he developed naons and fuel-swchng n he developng naons. Fuure global N 2 O and NO combuson emssons are lkely o ncrease unless here s new regulaon [5-7]. A. Abu-Jra e al. (2007) deal wh he reducon of NO and parculae maer emssons whle mananng effcen combuson performance s one of he man drvers for nernal combuson engne research. Modern desel and premed charge compresson gnon engnes have mproved engne fuel economy and sgnfcanly reduced NO and emssons acheved by advances n boh combuson and ehaus afer reamen echnologes [8]. To dae, has been shown ha vehcle emssons can be furher mproved by several caalyc sysems ncludng fuel reformers (.e. paral odaon, auohermal, and ehaus gas reformng) and afer reamen sysems, such as he selecve caalyc reducon of NO under oygen-rch condons. Among he mos promsng on-board reformng echnologes s he ehaus-gas reformng, whch allows he fuel/ar feed o he engne o be enrched wh reformae conanng H 2 and CO. Ths mehod s a combnaon of reformng and ehaus-gas recrculaon [4-8]. In 2002, he European research projec called MOLECULES (MOdellng of Low Emssons Combusors Usng Large Eddy Smulaons) was launched. The man objecve of hs projec s he conrol of combuson ar and fuel whch has a val capacy n he developmen of new

4 Feh Bouras e al. / Energy Proceda 18 ( 2012 ) propulson sysems and he susanably of s busness [9, 10]. One of he challenges facng oday's avaon ndusry o suppor he developmen of ar ranspor s o reduce he mpac of polluan speces on he envronmen and hs, boh n erms of nose polluon n areas arpor han o he release of chemcal speces pollung frs and foremos found nrogen odes (NO) and gases nvolved n global warmng, such as carbon odes CO and CO2. Emsson reducon of polluan speces from 50 o 25 % and forcng moorss o offer ever more nnovave soluons, snce he only reducon n specfc fuel consumpon due o he connuous mprovemen of curren sysems s nsuffcen o acheve he objecves. Among he new echnologes ha are already n operaon nclude he combuson chamber wh wo heads (Double Annular Combusor DAC) (A320 CFM56-5B and CFM56-7B B737) proposed snce 1995 by CFMInernaonal (CFMI) and ha can lead reducons n NO emssons up o 40% n some confguraons. One of he grea dffcules encounered n he developmen of hese sysems s o acheve he desred reducons n polluon regardless of he curren engne speed and hus o acheve precse conrol a all engne speeds. Ths nvolves n parcular by mprovng njecon sysems (e.g. Twn-Annular Pre-Swrl by CFMI) o opmze he spray and he vaporzaon of kerosene and s mure wh ar, o burn as much as possble n Lean Premed Prevaporzed (LPP), whch s one of he conceps used for he developmen of fuure combuson chambers called LPP [9, 10]. C. D. Perce (2002) focused hs work n he developmen of a large eddy smulaon based predcon mehodology for urbulen reacng flows wh prncpal applcaon o gas urbne combusors. I s n he gas urbne ndusry where accurae, hgh fdely predcon mehods for urbulen combuson are desperaely needed for he desgn of ne generaon, low emssons combusors. Curren pracce n he ndusry reles heavly on mehod calculaons, backed up by epensve physcal esng. The rend n he ndusry and n engneerng n general, s owards shorer desgn cycles hrough ncreased relance on numercal predcon. Mahemac models for urbulen combuson do no appear capable of meeng he needs of ndusry n hs regard, and he ndusry s begnnng o look owards more sophscaed predcon ools ha can ake advanage of new compuaonal capables. In hs fac, he advance of compuer echnology ha s he drvng force behnd ncreasng epecaons for compuaonal flud dynamcs and he man movaon for hs sudy [11,12]. Combuson s a very comple phenomenon and used wdely n our lves and n he ndusry, bu s he source of he polluan speces. The dffcul o measure he characersc parameers n all regons of he burner and gven he lmaon n he epermenal measuremen, we choose he smulaon usng new couplng models LES/PDF o esmae he felds of emperaure and mass fracon of carbon monode (CO). Followng of he work of F. Bouras e al.[12] we connue he hermochemsry par n hs paper, usng a confguraon smlar o a combuson chamber of a gas urbne, njec CH 4 /Ar n cylndrcal burner, he resuls wll be valdaed by epermenal resuls [11].

5 1090 Feh Bouras e al. / Energy Proceda 18 ( 2012 ) I. Epermenal confguraon and compuaonal doman The epermenal reference case used for he valdaon of he resuls of he presen smulaon s depced n Fg.1. The coaal je combusor confguraon was he focus of numerous epermenal nvesgaons because of boh s relavely smple geomery and s represenavely o he gas urbne burner. The combuson s a cylndrcal of ray R4= and L=1m n lengh. The burner s suppled by wo coaal jes. The cenral one havng he nernal ray R1= m and eernal R2= m, njecs he mehane wh velocy and emperaure respecvely V1=0.985 m/s and T1= 300 K. The annular one havng nernal ray R3= m, njecs he ar, wh hgher velocy V2=20.63 m/s and preheaed a emperaure T2=750K. The combuson chamber s pressurzed o 3.8 am and has consan emperaure wall of T wall =500K [11,12]. Fg 1. Schemac of he coaal je combusor epermen. II. Governng equaon Our sudy, concerns he behavour of a non-premed urbulen mehane flame n hree dmensons usng numercal smulaon. The equaons governng gaseous combuson are summarzed below. The flered governng equaons n LES for compressble flow can be wren n Caresan coordnaes for a mure of deal gases as [10-12]: Connuy: ( u~ ) 0 Momenum: u~ ( u~ u~ ) j [ ( u u j u~ u~ )] Mure fracon ) ~ Z ( u Z ~ ) ( D j ~ Z p j (1) (2) (3)

6 Feh Bouras e al. / Energy Proceda 18 ( 2012 ) Progress varable Thermodynamc sae c~ ( u~ c~ ) Where: =1, 2, 3 and j=1, 2, 3 p ~ RmT c.( D c~ ) c (4) (5) The majory of he subgrd models are based on he assumpon of Boussnesq whch presen he ensor of he unsolved consrans o he ensor velocy of deformaon S ~ by he nermedary of a urbulen vscosy. The small scales nfluence he large scales va he subgrd-scale sress [10-12]: ~ 1 2 S kll (6) 3 Where k ll s he subgrd knec energy. The flered sran rae ensor s defned by [10-12]: u~ ~ 1 u~ j 1 S u~ ll (7) 2 3 j We seleced he WALE (Wall-Adapng Local Eddy-Vscosy) eddy vscosy model from Ncoud and Ducros [10,12] o represen he eddy vscosy erm n Eq8. The man dea of hs model s o recover he proper behavor of he eddy vscosy near he wall n case of wall-bounded flows, whle preservng neresng properes such as he capacy o provde no eddy-vscosy n case of vanshng urbulence (propery requred for he ranson from lamnar o urbulen saes). The major neres of hs model frs reles on he fac ha needs no nformaon abou he drecon and dsance from he wall (avodng he use of any dampng funcon) hus beng really suable for unsrucured grds, where evaluang a dsance o he wall s precarous. The resdual sress ensor of he WALE eddy vscosy model can be found as [10,12]: And Where s ( s s ) C (8) d d 3 / / 2 5 / 4 ( ~ ( w ) ~ d d s s ) ( s s ) d ( g ~ g~ j ) g~ kk 1 2 g~ Cw: WALE model consan (Cw =0.49). The s he spaal fler wdh, whch s generally relaed o he grd sze of he resolved feld. When Favre flerng s used for he scalar varables, s more approprae o evaluae flered quanes usng he jon Favre PDF of he subgrd scalar flucuaons. Favre-flered quanes would be evaluaed usng [11,12], ~ 1 ~ (11) y Z 0 u~ y( Z) P( Z) dz j 3 (9) (10)

7 1092 Feh Bouras e al. / Energy Proceda 18 ( 2012 ) In hs work, he probably densy funcon (PDF) mehodology s employed as a subgrd scale (SGS) closure n LES of urbulen non-premed Mehane/Ar flames. The jon probably densy funcon of he SGS scalars s deermned va he soluon of s modelled ranspor equaon. III. Resuls and dscusson Smulaon s performed under he same epermenal condons, usng he couplng models LES/ PDF. The parameers ha are used o valdae he smulaon are he emperaure and mass fracon of carbon monode, were compared wh epermenal daa, consderng R R 3. III.1. Temperaure Dsrbuon of he emperaure feld s shown n Fg.2. Comparson of predced emperaure profles wh epermenal daa s shown n Fg. 3. Temperaure s a quany ha s derved from he mure fracon and progress varable by assumng sohermal walls and neglecng hermal radaon. Where hese assumpons are vald, he emperaure can be epeced o behave very smlarly o produc mass fracon, bu where he assumpons breakdown, an overpredcon of emperaure s epeced. Therefore, f produc mass fracon predcons are n good agreemen wh epermenal daa, dscrepances beween predced and measured emperaure profles mus be due o he breakdown of hese assumpons or o epermenal error, whch owng o dfferences n measuremen echnque beween speces concenraons and emperaure can be sgnfcan. One of he nvesgaors nvolved wh he epermen has saed ha he emperaure daa have been measured usng a raher large, nvasve, and dynamcally unresponsve hermocouple probe, are n fac subjec o consderable epermenal uncerany, especally n regons wh large emperaure flucuaons [11]. I could also be he case n whch hermal radaon s nonneglgble n some regons of he flow, parcularly n fuelrch, slow movng regons where soo formaon s lkely and resdence mes are long enough for radave effecs o accumulae. I s also mporan o noe ha he aal measuremen saons used for emperaure are dfferen from hose used for speces concenraons. Snce he epermen had sohermal, waer-cooled walls a roughly 500K, hermal boundary layers would be epeced o develop, affecng he emperaure close o he wall (Fg. 3). The annular ar sream (a 750K) ends o creae an nsulang sheah beween he ho combuson producs and he wall, alhough appears ha he flame n Fg. 2 does occasonally brush up agans he wall. These facors should accoun for he good agreemen of he seleced model.

8 Feh Bouras e al. / Energy Proceda 18 ( 2012 ) Fg.2 Dsrbuon of he emperaure n he burner /R=4,52 /R=5, T(K) 1200 LES/PDF EXP T(k) 1200 LES/PDF EXP ,0 0,2 0,4 0,6 0,8 1,0 1,2 r/r 0,0 0,2 0,4 0,6 0,8 1,0 1,2 r/r Fg. 3 Radal profles of emperaure. III.2. Carbon Monode The mprovemen s o consder ow new varable (he mure fracon and he progress varable) whou need o use Arrhenus equaon, n order o esmae producon or consumpon of each speces consdered n he reacon. Fg. 4 presens he CO mass fracon dsrbuon n he burner, and shows ha CO s more found n he cener of he burner a he fuel-rch regon (he njecor of CH 4 ). In addon Fg.5 shows he resuls of he smulaon compared o he epermenally predc values of CO mass fracon. The resuls obaned of he smulaon clearly show good agreemen wh epermen daa n ow saons (Fg.5). Carbon monode s a sgnfcan speces n he fuel-rch neror regon of he flame, because dsspaon raes are low n hs regon, whch have low emperaures and hgh concenraons of CO n fuel-rch mures (Fg.5). Ths par s mapped by he presen smulaon, so ha such hgh CO chemcal saes can be accessed relavely, regardng prevous sudy usng he same confguraon, for more deal see [11].

9 1094 Feh Bouras e al. / Energy Proceda 18 ( 2012 ) Fg.4 Dsrbuon of he carbon monode n he burner. 0,5 0,5 y CO 0,4 0,3 0,2 LES/PDF EXP /R=3,16 y CO 0,4 0,3 0,2 LES/PDF EXP /R=3,84 0,1 0,1 0,0 0,0 0,2 0,4 0,6 0,8 1,0 1,2 r/r 0,0 0,0 0,2 0,4 0,6 0,8 1,0 1,2 r/r Fg. 5 Radal profles of CO mass fracon. IV. Concluson The relaonshp beween ndusral polluon and economc developmen creaed he challenges facng he ndusry oday on supporng he developmen of moor ranspor s o reduce he mpac of harmful gases and producs on he envronmen and hs, boh n erms of nose polluon n arpor zones o ha of rejecon of chemcal speces pollung frs and foremos found nrogen odes (NO) and gases nvolved n global warmng, such as carbon odes CO and CO2. Emsson reducons of polluan speces from 25 o 50% and he agenda and forcng moorss o offer ever more nnovave soluons, snce he only reducon n specfc fuel consumpon due o he connuous mprovemen of curren sysems s nsuffcen o acheve he objecves. In hs paper, we have used new models n order o esmae he dsrbuon of he emperaure feld and Carbone monode (CO) n combuson chamber, usng he flered governng equaons for gaseous combuson, basng on he epermenal daa for he valdaon. Fnally, he followng concluson may be drawn from our nvesgaon:

10 Feh Bouras e al. / Energy Proceda 18 ( 2012 ) LES/PDF s a modelng echnque ha offers much poenal for sudes where he resoluons of flow deals are mporan lke deecon of he morphology of flow (flame holder, recalculang regon), The predced of coupled models LES/PDF resul shows a good agreemen wh he epermenal daa, and also gave resuls of somewha quanavely and qualavely sasfacory and hey may gve some nformaon for dfferen physcal parameers (velocy, pressure...) and oher chemcal speces (CO2, OH, H2O, C(s) ) for he mean aal velocy, he poson of peak velocy and urbulen nensy. The advanage of he ulzaon of PDF s o evaluae he mean of scalar parameers and o negrae he mure fracon n order o predc dfferen speces mass fracon whou usng Arrhenus s law. Resuls obaned n hs work allow us o eplo hem drecly n oher domans: Eergy analyss, envronmen. References [1] Nragu, J.: Mercury polluon from he pas mnng ogf gold and slver n he Amercas. The scence of he oal envronmen. 149, (1994). [2] Derrak, J.G.B.: The polluon of he marne envronmen by plasc debrs: a revew. Marne Polluon Bullen. 44, (2002). [3] Rubo, B., Nombela M. A. and Vlas F.: Geochemsry of Major and Trace Elemens n Sedmens of he Ra de Vgo (NW Span): an Assessmen of Meal Polluon. Marne Polluon Bullen. 40, (2000). [4] Aknson, S.E. and Lews, D.H.: A Cos-Effecveness Analyss of Alernave Ar Qualy Conrol Sraeges. Journal of envronmenal economcs and managemen. 1, (1974). [5] Kavanaugh, M.: Esmaes of fuure co, N 2 O and NO emssons from energy combuson. Amospherc envronmen. 21, (1987). [6] Wang, L., Haworh, D.C., Turns, S.R. and Modes, M.F.: Ineracons among soo, hermal radaon, and NO emssons n oygen-enrched urbulen nonpremed flames: a compuaonal flud dynamcs modelng sudy. Combuson and Flame. 141, (2005). [7] Guo, H. and Smallwood, G. J.: The neracon beween soo and NO formaon n a lamnar asymmerc coflow ehylene/ar dffuson flame. Combuson and Flame. 149, (2007). [8] Abu-Jra,A and Tsolaks., A.: The nfluence of H 2 and CO on desel engne combuson characerscs, ehaus gas emssons, and afer reamen selecve caalyc NO reducon. Inernaonal Journal of Hydrogen Energy.32, (2007). [9] Nguyen, P.D., Bruel, P. and Rechsad, S.: An Epermenal Daabase for Benchmarkng Smulaons of Turbulen Premed Reacng Flows: Lean Encon Lms and Velocy Feld Measuremens n a Dump Combusor. Flow, Turbulence and Combuson. 82, (2009). [10] Bouras, F and Soudan, A.: Impac of he equvalence rao and he mass flow rae on urbulen lean premed prevaporzed combuson. Energy Proceda. 6, (2011). [11] Perce, C. D. and Mon, P.: Progress-varable approach for large-eddy smulaon of non-premed urbulen combuson. Journal of Flud Mechancs. 504, (2004). [12] Bouras, F., Soudan,A. and S Ameur, M.: Bea-pdf approach for large-eddy smulaon of nonpremed urbulen combuson. Inernaonal Revew of Mechancal Engneerng. 4, (2010).