ANALYSIS OF THE ENGINE THERMAL BALANCE. DETERMINATION OF ENERGY QUANTITY NECESSARY FOR COOLING A NAVAL ENGINE

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1 Th 4th Intrntionl Confrnc Computtionl Mchnics nd Virtul Enginring COMEC OCTOBER 2011, Brsov, Romni ANALYSIS OF THE ENGINE THERMAL BALANCE DETERMINATION OF ENERGY UANTITY NECESSARY FOR COOLING A NAVAL ENGINE Florin VASILE 1, Dumitru CATANĂ 2, Ion ŞERBĂNESCU 3, Cătălin Ptrişor MIREA 4, Dorl Dumitru VELCEA 5 1 Militry Tchnicl Acdmy, Bucurşti, ROMÂNIA, tm@mtro 2 Militry Tchnicl Acdmy, Bucurşti, ROMÂNIA, tm@mtro 3 Militry Tchnicl Acdmy, Bucurşti, ROMÂNIA, tm@mtro 4 Militry Tchnicl Acdmy, Bucurşti, ROMÂNIA, tm@mtro 5 Militry Tchnicl Acdmy, Bucurşti, ROMÂNIA, tm@mtro Abstrct: Th cooling procss hs grt influnc on th dynmic, conomic nd durbility prformnc of n ngin In th prsnt ppr r prsntd in th first prt som thorticl spcts linkd by th cooling instlltion of th ngin nd th thrml blnc; this r prcdd in th scond prt by n clculus xmpl for th dtrmintion of nrgy quntity ncssry for cooling nvl ngin chousd rbitrry, using his tchnicl documnttion Kywords: thrml blnc, nrgy quntity, cooling 1 THERMAL BALANCE COOLING SYSTEM Enrgy flow producd by combustion bcoms prtilly ffctiv powr nd th rst is dischrd through vrious wys out s loss of ht flows Th distribution of ths losss dpnds on ngin typ, motor cycl, oprting conditions nd powr output Thrml blnc xprsss th qulity btwn th nrgy flow introducd into th ngin by burning ful in th cylindrs nd th vrious nrgy flows tht occur btwn ngin, consumr nd nvironmnt Th nrgy blnc rprsnts th distribution of vilbl nrgy flow, diffrnt loss Ht blnc qution is: rc rz, btwn ffctiv powr nd If lubriction oil cooling is chivd with swtr, in opn circuit cooling, in th nrgy blnc qutions ppr n dditionl trm, rc uli, corrsponding to th swtr nrgy flow tkn from lub oil On th othr sid, whn r usd svrl closd cooling circuits, th trm componnts of ch circuit In such css th nrgy blnc qutions bcoms: Whr: rc rc rc rc uli rz rc (1) will b dividd in corrsponding (2) = vilbl nrgy flow introducd into th ngin by combustion; = ffctiv powr; = nrgy flow xhust with combustion gss; 45

2 rc = nrgy flow vcutd by cooling; rz = rsidul nrgy flow (vcutd by rdition); Figur 1: Ht blnc digrm In prcnt th nrgy blnc qution bcoms: q q qrc qrc uli qrz 100 % Whr: Tbl 1: q 100[%] q = ; q qrc r 100[%] 100[%] q = ; q r = ; u q 100[%] q u = 3 7 ; rc uli qrz rz C 100[%] h P 1 i c i q rz = 1 5 ; (3) Engin cooling is rquird to provid crtin tmprturs for mobil nd fixd prts, nd thus, to crt bttr conditions for lubriction, to mintin norml clrnc btwn on nd cylindr, spindls nd brings Mrin ngin cooling systm rprsnts ll ggrgts nd dvics tht provid forcd vcution through wlls for quntity of ht dvlopd in th ngin cylindrs, during combustion From thrml blnc digrm nlysis, it follows tht th incrs of th ctul fficincy is possibl by rducing th losss or by rcovring som nrgy flows For closd circuit cooling systm, th cooling wtr tmprtur is loctd btwn C, this fct hs fvorbl influnc in th ngin cylindr trnsformtion procss nd dtrmins th incrsing of rltiv ht flow tht cn b rcovrd Th closd cooling circuit wtr cn b usd for th following purposs: For swtr dslintion plnt, s sourc of ht; 46

3 For ir hting or ir conditioning plnt usd for ship cbins nd comprtmnts; For rcovry boilrs to prht wtr; To produc wtr for so nd domstic fitis To incrs wtr tmprtur in closd cooling circuit, somtims th instlltion prssuriztion is usd (4 5 br), so tht, t th output of th ngin w will hv wtr tmprtur btwn o C In this cs, th cycl fficincy is rising Also, th nrgy flow tht cn b rcovrd from th cooling wtr is incrsing, which lds to n incrsd ovrll fficincy of th ngin cooling instlltion 2 DETERMINATION OF ENERGY UANTITY NECESSARY FOR COOLING A NAVAL ENGINE W chos for xmplifiction th following ngins:, şi Strting from th following chrctristics nd msurd vlus: P = kw - ffctiv powr ngin; n = 100 rot/min - ngin spd; c = 0,170 kg/kwh - spcific ful consumption; ṁ m = 274 m 3 /h - swtr pump flow; ṁ = 82 m 3 /h - rquird lubricting oil cooling wtr flow; cu m rc p d = 115 m 3 /h - pump wtr flow rt of rcovry boilrs; m = 197 m 3 /h - frshwtr flow pump(closd circuit); ṁ u = 155 m 3 /h - circultion pump lubricting oil flow; W cn dtrmin th mount of nrgy introducd into th ngin through combustion, P c i [KW] (4) Whr th ful low clorific powr is: i = [kj/kg] (5) Prforming clcultion, rsult: [KW] (6) In figur 4 is shown schmticlly th lubricting oil systm with th lmnts tht ffct th ngin nrgy blnc Th cylindrs cooling dgr, nd th rtionl orgniztion of th cooling procss hs grt influnc of th dynmic, conomic nd durbility prformnc for intrnl combustion ngin Frsh fluid contct with hot wlls of th cylindr rducs th dgr of filling, instd, cylindr wlls too low tmprtur incrss ht loss nd dgrss th indictd fficincy Also, th ngin prts tmprtur hs n influnc on th mchnicl losss If th cooling fluid circuit is not rtionlly orgnizd, locl tmprtur incrss my occur; this lds to crcks in th cylindr hd, in th ngin block or on nd vlvs burning Both high tmprtur nd low tmprtur, oil film loss its consistncy; in th first cs by rducing th viscosity, nd in th scond cs bcus of oil dilution with hvy ful frctions, condnsd on th cylindr mirror In both css, th prts wr is incrsing du to friction nd th ngin durbility is rducd Insufficint cooling or misus orgniztion of th cooling fluid circuit cn ld to locl tmprtur incrss which will produc locl burns, crcks, dformtions or xcssiv wr rts Also, th xcssiv cooling hs som dvrs ffcts s: ngtiv influncs on th nrgy blnc; incrsd wr (du to dgrdtion of lubricting oil qulitis, sply); induction of thrmomcnicl strss, tht nrts crcks, in xcssivly coold prts It is thrfor ncssry to dtrmin n optimum tmprtur, for ch prticulr ngin Trnds rgrding th thrml rgim, r diffrnt W cn mntion th xprimnts on th us of ht-rsistnt mtrils (crmics); rducing th prcnt of nrgy dischrd by th cooling fluid For smll nd mdium powr mrin ngins r usd cooling systms consisting of on closd circuit tht provid ngin cooling nd n opn circuit which provid th cooling of th clos circuit wtr For slow ngins, with high powr, bsids th opn circuit, mor closd circuits r usd 47

4 Enrgy flow vcutd by cooling wtr is: rc m m c m T m Figur 4: Schm nd functionl prmtrs for cooling systm whr wtr spcific ht is: c m = 4,186 [kj/kg 0 C] (8) rsult: 6372 (9) rc Knowing tht th nrgy flow vcutd by lubricting oil is tkn by cooling wtr, w cn vrify if th clculus rsults for th nrgy flow vcutd by cooling wtr corrsponds with th prcnts of nrgy blnc qution W know tht: q r = ; [%] (10) q u = 3 7 ; [%] (11) nd rc 100% 28,9% W cn s tht th clcultd vlu is btwn th limits Enrgy flows r influncd by ngin lod nd nvironmnt conditions For xmplifiction, th quntitis of nrgy rlsd by ngin cooling, lubriction nd rcovry boilr wr clcultd; rsult r prsntd grphiclly in th following figur (7) (12) 48

5 Figur 6 Th nrgy loss by ngin cooling, lubriction nd rcovry boilr for th ngin Th nrgy flow vlus vcutd with cooling wtr r prsntd furthr: Ht flow introducd into th ngin: C h i [KJ/h] (13) Ch i [KW] (14) , ,2 Ht flow vcutd with cylindrs cooling wtr: rc m m c T (15) - pump wtr flow rt [kg/s] (16) c = 4,186 - wtr spcific ht [kj/kg 0 C ] (17) T = 15 0 C tmprtur diffrnc [ 0 C ] (18) V p [m 3 /h] m [kg/s] rc ,7 76,39 15, , Ht flow vcutd with ons cooling wtr: rc m m c T (19) - Pump wtr flow rt [kg/s] (20) c = 4,186 - wtr spcific ht [kj/kg 0 C] 49

6 T = 10 0 C - tmprtur diffrnc [ 0 C ] (21) V p [m 3 /h] m [kg/s] rc * 200 * * 55,55 * * 2325 * * - on cooling is md by lubriction oil rc m Ht flow vcutd with ction nozzls cooling wtr: c T (22) 1 m V [kg/s] (23) c = 4,186- wtr spcific ht [kj/kg grd] u = 1000 [kg/m 3 ] (24) T = 15 0 C - tmprtur diffrnc [ 0 C] (25) V [m 3 /h] m [kg/s] rc - 313,95-3 CONCLUSION Engin cooling provids crtin tmprturs of moving prts, which r md conditions for n optiml lubriction, mintin norml clrncs btwn on nd cylindr, nd protct som prts whos tmprturs cn rch vlus tht ffct th ngin prts mtril Rtionl orgniztion of th cooling procss hs significntly influnc to dynmic, conomic nd durbility prformnc of th ngin To prvnt insufficint or xcssiv cooling hving disstrous impct on ngin oprtion grt importnc is ttchs for cooling systm dsign nd clcultion REFERENCES [1] A Pruiu : Instlţii nrtic nvl Editur Muntni & Editur Ld, Constnţ, 2000 [2] A Drglin: Motor cu rdr intrnă Vol 1, 2, 3, Editur Acdmii Nvl Mirc cl Bătrân, Constnţ, 2003 [3] DWoodyrd, Elsvir-Buttrworth Hinmnn: Poundr s Mrin Disl Engins nd Gs Turbins, Woburn, 2004 [4] wwwdislngin motorcom Sulzr Disl Engins 50