S.V.C.E.T S.V.C.E.T ME Dept.
Thermal Engineering Lab
ASSEMB LY AND DISASSEM ASSEMBL DI SASSEMBLY BLY DISASS D ISASSEMBLY EMBLY OF IC ENGINES
__________________________________________________________________ ______________________________________ ____________________________
S.V.C.E.T ME Dept Engineering Lab
Thermal
Aim: To study the diferent types o I.C engines, arious parts o I.C engines, !y!les o operation et!., Introduction: "ny type o engine, #hi!h deries heat energy rom the !ombustion o uel and !onerts this energy into me!hani!al #or$, is termed as a heat engine. These are !lassi%ed as &. E'ternal Combustion engines (E.C) *. Internal Combustion engines (I.C) I the !ombustion o uel ta$es pla!e outside the #or$ing !ylinder then the engine is !alled E'ternal Combustion Engine. I the !ombustion ta$es pla!e inside the #or$ing !ylinder the engine is !alled Internal Combustion Engine. The most !ommon e'amples o E.C engines are steam engines and steam turbines. I.C engines are used in s!ooters, !ars, lo!omoties, agri!ulture and earth moing ma!hinery, po#er generation and in many industrial appli!ations. The adantages o I.C engines oer E.C engines are high e+!ien!y, simpli!ity, !ompa!tness, light #eight, easy starting and lo# !ost.
Classifcation o I.C Engines: I.C Engines are !lassi%ed as ollo#s &. "!!ording to the uel used -etrol engine, Diesel engine and as engine. *. "!!ording to !y!le o operations */stro$e engine and 0/stro$e engine 1. "!!ording to the method o ignition Spar$ ignition (S.I) engine, Compression Ignition (C.I) engine. 0. "!!ording to the number o !ylinders single !ylinder engine, multi !ylinder engine. 2. "!!ording to the method o !ooling the !ylinder "ir/!ooled engine and 3ater/ !ooled engine. 4. "!!ording to the arrangement o !ylinder 5ori6ontal engine, Verti!al engine and 7adial engine.
I.C Engine Parts and their Function: "n I.C engine !onsists o many diferent parts, ho#eer the main !omponents are des!ribed belo#.
1.Cylinder: The heart o the engine is the !ylinder and its primary un!tion is to !ontain the #or$ing uel under pressure and the se!ondary un!tion is to guide the piston. To aoid the #ear o the !ylinder blo!$ !ylinder liners are proided. The !ylinder is made o ray Cast Iron.
8Type te't9
S.V.C.E.T ME Dept Engineering Lab
Thermal
2.Cylinder Head: :ne end o the !ylinder is !losed by means o a remoable !ylinder head, #hi!h usually !ontains the inlet ale or admitting uel and e'haust ale or dis!harging produ!ts o !ombustion. The ales are operated by means o !ams geared to the engine shat. The !ylinder head is usually made o !ast iron or alloy !ast iron !ontaining ;i!$el, Chromium and Molybdenum.
3.Piston: The piston used in I.C engines is usually o trun$ type and are open at one end. The main un!tion o the piston is to re!eie the impulse rom the e'panding gas and transmit the energy to the !ran$shat through the !onne!ting rod. "t the same time the piston must also disperse a large amount o heat rom the !ombustion !hamber to the !ylinder #alls. -istons are made o !ast iron or "luminum alloys or lightness. . Piston !ings: These are !ir!ular rings and made o spe!ial steel alloys, #hi!h retain elasti! properties een at high temperatures. The piston rings are housed in the !ir!umerential grooes proided on the outer sura!e o the piston. enerally there are t#o sets o rings mounted on the piston. The un!tion o the upper rings is to proide air tight seal to preent lea$age o the burnt gases into the lo#er portion. Similarly the un!tion o the lo#er rings is to proide efe!tie seal to preent lea$age o the oil into the engine !ylinder. ".Connecting !od: :ne end o the !onne!ting rod is !onne!ted to the piston through piston pin and the other end is !onne!ted to the !ran$ through the !ran$ pin. The usual !ross se!tion o !onne!ting rod is I/se!tion or 5/se!tion and these are made o !arbon steel or alloy steel. The main un!tion is to transmit or!e rom the piston to the !ran$shat. Moreoer, it !onerts re!ipro!ating motion o the piston into the !ir!ular motion o the !ran$ shat in the #or$ing stro$e. #.Cran$ shat: !ran$ shat !onsists o the shat part #hi!h reole in the main bearing. The big end o the !onne!ting rod is !onne!ted to the !ran$ pin. The !ran$ #eb !onne!ts to the !ran$ pin and shat part. The un!tion o the !ran$shat is to transorm re!ipro!ating motion into rotary motion. Cran$shats are made o !arbon steel. %.Cam shat: It is drien rom the !ran$ shat by timing gears on a !hain. It operates the inta$e ale and the e'haust ale through the !ams and ollo#ers, push rods and ro!$er arms. &.Fly 'heel It is a big #heel mounted on the !ran$ shat #hose un!tion is to redu!e the ibrational
8Type te't9
S.V.C.E.T ME Dept Engineering Lab
Thermal
stro$e !y!le engine and t#o stro$e !y!le engine. " our/stro$e !y!le engine re=uires our stro$es o piston or t#o reolutions o the !ran$shat to !omplete one !y!le. In a t#o/stro$e engine there are t#o stro$es o the piston or one reolution o the !ran$shat to !omplete one !y!le. The our stro$e and t#o stro$e engines are urther diided into petrol and diesel engines a!!ording to the type o uel used.
Four stro$e (etrol ) *iesel engine: The our stro$e engine utili6es our stro$es namely su!tion stro$e, !ompression stro$e, po#er stro$e, and e'haust stro$e or !ompletion o a !y!le and it has t#o ales, one or the inust beore the end o the !ompression stro$e o the piston ignition o!!urs due to a spar$ in !ase o petrol engines or a spray o oil in?e!ted into the !ylinder in !ase o diesel engines. In either !ase, the thermal energy released ma$es the !ompressed gas e'pand rapidly and dries the piston out#ards. The resulting stro$e is !alled the po#er stro$e. "s the piston !ompletes the po#er stro$e and returns T.D.C, the e'haust ale opens and the burnt e'haust gases in the !ylinder are drien out. "t the instant the, piston rea!hes the TDC position, the e'haust ale !loses and the inlet ale #ill be ready to open, starting a ne# !y!le o operation again. +'o stro$e ,.I ) C.I engines: The t#o stro$e engines utili6e only t#o stro$es (Compression stro$e and po#er stro$e) or the !ompletion o a !y!le. In t#o/stro$e engine there are t#o ports. :ne in the inlet and one in the outlet or gasses. The opening and !losing o the ports depends on the position o the piston in the !ylinder. The piston is at T.D.C both outlet and transer ports are !losed #hen the !ompressed air uel mi'ture or air in the !ylinder is about to be ignited by either a spar$ing dei!e or uel in?e!tion. 3hen piston traels ba!$ during the po#er stro$e, it un!oers the e'haust port %rst and a moment later the transer port. The opening o the transer port puts the !ylinder in !onta!t #ith the !ran$!ase !ontaining a slightly !ompressed air uel mi'ture or air. The in!oming resh !harge helps in driing out the burnt gases through the e'haust port. The head o the piston being shaped to assist this s!aenging a!tion. "s the piston returns into the !ylinder, it !oers both the transer and e'hausts ports and !ompresses the trapped gas until it rea!hes the T.D.C position. "t the same time a resh !harge is dra#n into the !ran$!ase through the inlet port. " !y!le is thus !ompleted #ith one po#er stro$e in eery t#o/piston stro$es.
8Type te't9
S.V.C.E.T ME Dept Engineering Lab
Thermal
In a t#o stro$e engine a small amount o burnt gas al#ays remains in the !ylinder along #ith the resh !harge #hen the piston !oers the ports and starts !ompressing the gases trapped inside. Moreoer, sin!e both transer port and e'haust ports are simultaneously open during part o the piston stro$e, some o the in!oming resh !harge es!apes #ith the burnt gases. "s a result the e+!ien!y o a t#o stro$e engine is lo#er, urther t#o stro$e engines !onsume large amounts o lubri!ating oil !ompared #ith our stro$e engines and are li$ely to be noisier be!ause o the sudden opening o the e'haust ports.
-ale +iming *iagram:
The ale timing diagram sho#s the position o the !ran$ #hen the arious operations, i.e. su!tion, !ompression, e'pansion and e'haust begin and end. The ale timing is the regulation o the positions in the !y!le at #hi!h the ales are set to open and !lose. Sin!e the ales re=uires a %nite period o time to open or !lose #ithout a rupture, a slight @leadA time is ne!essary or the proper operation. The design o ale operating !an proide or smooth transition rom one position to the other, #hile !am setting determines the timing o the ale. Theoreti!ally it may be assumed that the ales open and !lose and spar$ (or in?e!tion o uel) o!!urs at the engine dead !enters. 5o#eer, in a!tual operation the ales do not operate at it !enter positions but operate some degrees a#ay on either side o the dead !enters. The opening o!!urs earlier and the e'haust !ontinues een at later !ran$ angles. The ignition is also timed to o!!ur earlier. The in?e!tion o uel in the !ase o diesel engine is also timed to o!!ur in adan!e o the !ompletion o !ompression stro$e. The timing o these eents reerred in terms o !ran$ angles rom dead !enter positions, is presented on a ale/timing diagram. The !orre!t timings are o undamental importan!e or the e+!ient and su!!essul running o the I.C engine.
8Type te't9
S.V.C.E.T ME Dept Engineering Lab
8Type te't9
Thermal
