There are two types of reciprocating engines: 1) Spark ignition Otto cycle 2) Compression Diesel cycle

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1 Intodtion to heodynais, Lete 5-6 of. G. Ciaelli (0) Gas owe Cyles Deal with systes that pode powe whih the wog flid eas a gas thoghot the yle, i.e., no hange phase. Intenal Cobstion (IC) Enge hee ae two types of eipoatg enges: ) Spa ignition Otto yle ) Copession Diesel yle eology: Soe URL: Saylo URL: Ciaelli/eens Uniesity ( Saylo.og Used by peission. age of

2 Enge displaeent = (# of yldes) x (stoe length) x (boe aea) (DC) (sally gien o lites) (BDC) Copession atio = ylde ole (BDC) ylde ole (DC) Can shaft stoe = ½ eoltion of the an shaft Soe URL: Saylo URL: Ciaelli/eens Uniesity ( Saylo.og Used by peission. age of

3 Fo stoe Spa Ignition Enge: Cyle onsists of fo distt stoes (poesses) A I R FUEL Inta e ale open Fel/Ai Mixte Ignition Exhast ale opens Cobstio n odts Intae Sto Copession Stoe owe Sto Exhast Sto A oplete yle ( stoes) eqies e two eoltions e of the an shaft x Ignition at Soe URL: Saylo URL: Ciaelli/eens Uniesity ( Saylo.og Used by peission. age of

4 A opehensie stdy of IC enges eqies onsideation of the details of the ai tae, obstion, and exhast poesses (MECH 5 th yea eletie) heodynai Ai-Standad Analysis Used to pefo eleentay analyses of IC enges. Siplifiations to the eal yle lde: ) Fixed aont of ai (ideal gas) fo wog flid ) Cobstion poess eplaed by onstant ole heat addition with piston at DC ) Intae and exhast not onsideed, yle opleted with onstant ole heat eoal with piston at BDC ) All poesses onsideed tenally eesible Ai-Standad Otto yle oess oess oess oess Isentopi opession Constant ole heat addition Isentopi expansion Constant ole heat eoal Soe URL: Saylo URL: Ciaelli/eens Uniesity ( Saylo.og Used by peission. age of

5 ot DC BDC ()() ()() ()() ()() ot DC B D BD C opession atio se fixed ass Soe URL: Saylo URL: Ciaelli/eens Uniesity ( Saylo.og Used by peission. age 5 of

6 W Apply Fist Law ( ) to eah poess: Isentopi Copession ( ) W ( ) W ( ) R Constant ole Heat Addition W ( ) ( ) ( ) R R Soe URL: Saylo URL: Ciaelli/eens Uniesity ( Saylo.og Used by peission. age 6 of

7 Isentopi Expansion ( ) W ( ot ) W ot ( ) Constant ole Heat Reoal ot W ( ) ( ) o ot ( ) R R Soe URL: Saylo URL: Ciaelli/eens Uniesity ( Saylo.og Used by peission. age 7 of

8 Soe URL: Saylo URL: Ciaelli/eens Uniesity ( Saylo.og Used by peission. age 8 of Otto yle theal effiieny is W W W ot yle yle yle otto Cold Ai-Standad Analysis he speifi heats ae assed to be onstant at thei abient tepeate ales. Fo the two isentopi poesses the yle, assg onstant speifi heat yields: : and : and whee =. fo ai at abient tepeate.

9 Soe URL: Saylo URL: Ciaelli/eens Uniesity ( Saylo.og Used by peission. age 9 of Ftheoe, fo onstant speifi heats so yle otto bt so onst otto Fo high theal effiieny want a high opession atio Cent spa ICE 7 < < 0

10 Spa ignition enge opession atio liited de to a phenoenon nown as no Kno efes to the noise poded when obstion os explosiely daagg to enge. In ode to ede no between 90 and 975 tetaethyl lead added to gasole = possible Also, lage highe highe oe eissions sh as NOx and Sox Soe URL: Saylo URL: Ciaelli/eens Uniesity ( Saylo.og Used by peission. age 0 of

11 Enge owe W ( hose powe ) wo tie wo yle yles se wo yle yles an es an es se Fo a stoe enge, an shaft es pe yle W W yle N whee N an shaft speed (e/s) Inease powe by easg the enge speed N Anothe way to ease powe is to ease the net wo otpt pe yle Wyle by eithe: (i) Ineasg the opession atio, o (ii) Inease (ease the enge displaeent). (ii) W yle (i) Soe URL: Saylo URL: Ciaelli/eens Uniesity ( Saylo.og Used by peission. age of

12 Anothe aaete sed to diate enge pefoane is the ean effetie pesse (ep) the theoetial onstant pesse that, if it ated on the piston dg the powe stoe, wold pode the sae net wo as atally deeloped one yle, i.e., ep net wo pe yle displaeent ole W yle Fo two enges with sae displaeent ole, the one with a highe ep podes oe net wo, and at the sae enge speed wold pode oe powe. Soe URL: Saylo URL: Ciaelli/eens Uniesity ( Saylo.og Used by peission. age of

13 Fo stoe Copession Enge No spa plg fo ignition, ely on atoignition at high tepeate fo itiatg obstion A I R Inta e ale open Fel Injeto Exhast ale opens Ai Cobstio n odts Intae Sto Copession Stoe owe Sto e When piston appoahes DC when ai is nea its axi tepeate fel jetion is stated obstion itiated. Exhast Sto e Conte to jet fel as the piston is og down (ixte ole is easg) at the sae tie liqid fel eapoates and eats as it passes thogh the standg flae obstion os at oghly onstant pesse Soe URL: Saylo URL: Ciaelli/eens Uniesity ( Saylo.og Used by peission. age of

14 Ai-Standad Diesel yle oess oess oess oess Isentopi opession Constant pesse heat addition Isentopi expansion Constant ole heat eoal ot DC BDC ()() ()() ()() ()() ot D BD Soe URL: Saylo URL: Ciaelli/eens Uniesity ( Saylo.og Used by peission. age of

15 Reall opession atio Defe the t-off atio W Apply Fist Law ( ) to eah poess: Isentopi Copession ( ) W ( ) W ( ) R Soe URL: Saylo URL: Ciaelli/eens Uniesity ( Saylo.og Used by peission. age 5 of

16 Soe URL: Saylo URL: Ciaelli/eens Uniesity ( Saylo.og Used by peission. age 6 of Constant esse Heat Addition ) ( ) ( ) ( ) ( ( ) h h R R Isentopi Expansion ) ( ( ) W ot ( ) W ot note = and

17 Constant ole Heat Reoal ot W ( ) ( ) o ot ( ) R R Diesel yle theal effiieny is yle W yle W ot W ot Diesel yle ot h h Soe URL: Saylo URL: Ciaelli/eens Uniesity ( Saylo.og Used by peission. age 7 of

18 Soe URL: Saylo URL: Ciaelli/eens Uniesity ( Saylo.og Used by peission. age 8 of Cold Ai-Standad Analysis he speifi heats ae assed to be onstant at thei abient tepeate ales. Fo the two isentopi poesses the yle, assg onstant speifi heat yields: : and : and whee =. fo ai at abient tepeate. Fo onstant speifi heats and h so h h yle Diesel

19 Soe URL: Saylo URL: Ciaelli/eens Uniesity ( Saylo.og Used by peission. age 9 of eall: sbstittg yields onst Diesel Fo gien highe theal effiieny is obtaed ia highe opession atio Fo a gien highe theal effiieny is obtaed ia lowe t-off atio

20 Howee a salle yields less net wo pe yle, so to ahiee the sae powe need highe enge speeds Soe URL: Saylo URL: Ciaelli/eens Uniesity ( Saylo.og Used by peission. age 0 of

21 Copae Effiieny of Otto and Diesel Cyles Otto onst Diesel onst Cent Diesel ICE < < Note: fo a gien opession atio the diesel enge is less effiient than the spa ignition enge Otto onst Diesel onst Soe URL: Saylo URL: Ciaelli/eens Uniesity ( Saylo.og Used by peission. age of

22 Copae the Otto yle (--O-O) and the Diesel yle (--D-D) fo: - the sae opession atio, Otto Diesel D O - the sae heat pt, ds ds (sae aea nde the e - fo both yles) = = O O = Soe URL: Saylo URL: Ciaelli/eens Uniesity ( Saylo.og Used by peission. age of

23 he heat ejeted by the Otto yle ot is less than that fo the Diesel yle: D Ods ds Se Wyle = ot the net yle wo fo the Otto yle is geate than that fo the Diesel se ot is salle fo the Otto yle Wyle Se yle Otto yle Diesel yle Howee, se one an se a highe opession atio fo the Diesel one an ahiee obta a highe yle effiieny! Soe URL: Saylo URL: Ciaelli/eens Uniesity ( Saylo.og Used by peission. age of