INTERNALCOMBUSTION ENGINES

(IncludingAir Compressors and Gas T\rbinesand Jct Propulsion)

By

R.K. RAIPUTM.E. (Heat Power Engg.).lons.-Gold Medallist ;Gtad' (Mech' Eryg' & Elect' Erqg')

M.l.E. (Indb) ; M'S.E.S.I. ; M.I.S.T.E. ; C.E. (Ib)Princlpal (Formcrlfl,

Puaiob College of Infonnotion TeehtplqlPATIAIA (Puajob)

rN(Ml PUBLICATIONS (P) tTDBANGALORE. CHENNAIJALANDHAR O KOLKATA

o GOCHIN oo LUCKNOW o

NEW DELHI

GUWAHATI o HYDERABADMUMBAI o RANCHI

..

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PREFACE TO THE SECOND EDITIONI am pleased to presen the Second edition ofthis book. The warm reception, which theprevious edition ofttre book has enjoyed all over India, has been

" -att"r orgt"t ;atisfaction tome.

The book has been thoroug_ hly rwised, besides adding a new chapter (No. 22) on..shortAnswer Quections'to enable the itudents to prepare more effectively forpro ctical Viua-ueE xamhtatia ns and I nter v iew s.Any suggestions for improvement of this bbok will be thankfully acknowledged andincorporated in the next edion.

r.qlo{r -ii',#f,8rrtb er rro1lB, Golden House, Daryasani.New Delhi_il000i -

phonc :011_4A bg 25 00.Far : 011-4t 5g 2E 28

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@ Nl rights rewrud, utth tlu pubtishrs. No part of this publilxrtfunm.ay be rcprodued,, sbed in a.retrizu! "lrteii, t*i*^rr.d io oo,fotm or by aryr means,

"t""t*"., ;;h";;;;*;;;,*, rca.it*or otherwise without the pnor urrtten penni,ssion of the publishen

-Author

Price:fu. S98.fi) Ozly.s eayt Editia n, r*r, liiJ^Ylrtt,,Zffi

OFI.TCES@ Bangalore@ Cochi@ Hyderabad@ Kolkata@ Mumbat

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EIC.O65O.395.INTERNAI COMBUSTION ENGINESIlpeeet at : Goswami Associatee, Delhi. c_t74ilosto4

Printed at: ljitfuintars, Delhi.

{ i..

PREFACE TO THE FIRST EDITIONThis treahise on olnternal Combustion Engineco (Induditg gos turbnes) contains

comprehensive treatment of-e suject matter in a_simple, lucid and direct language' It eirvelopsa large number of solved p*ff"-J n""nerly graited including typical worked examples fromexamination point of view.

Thebookcomprises2lchapters.Allchaptersaesaturatedwithmuchneededtext,"upport"J

y ,i.pf"."rr *fi"*pi"".tow-figurs-.At the end of eactr chapter-Highlights'r:.ti"" ivp.'qo."u"i", it .i.ti {uestiors and unsolved Eximples have beenadded ; besides tfris a "queJion Bank' containing "Adtional Objective Tlrye Questions(with Answer"

"oa Sofii""-Comments)",'Theoretical Questions withAnswers" and

..Addiional Typical p*"ipl"" (Includ,ing lniuersities and Competitiue ExominationA;;J;;;; t

"r," L""o io"to"Tto rnake the bok a comprehensive and a complete unit in all

respects.The book will prove to be a boon to the students preparing for engineering undergradu-

ut", e..i.O., post graduate, U'P'S'C' and other competitive examinations'Theaut,hor,sthanksaredueohiswifeRameshRajputforextendingallcotiperation

during preparation ofthe manuscript and proofreading'In the end t;.e author wishes o express his gratude o Shri R.K. Gupta, Chairman,

sh. saurabh Gupta, Managi"g Di;.**, l,axmi puucauons hrt. Ltd., New Delhi for taking alot of pains in bringrng out"th; book with very good presentation in a short span oftime'

Althougheverycarehasbeentakentomakehebookfreeoferrorsbothintextasrvellasir solved examples, v.t trr" u"irro, shall feel obliged if any enors present are brought to ltis,roti.". Corr"trrr.tive criticism of the book will be warmly received'

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CONTENTSChapter

I. BASIC CONCEPTS OF TEERMODYNAMICS1.1. Deffnition of ThermodYuamics1.2. Thermoclynamic SYstems

1.2.1. System, bobndary and surroundings1.2.2. Closed sYstem1.2.3. OPen sYstemL.2.4. Isolated sYetemL.2.5. Adiabatic sYstemL.2.6. Homogeneous sYstemL.2.7. Hetemgeneous sYstem

1.3. Pure Subgtance1.4. Thermodynanic Equilibrium1.5. Properties of SYstems1.6. State1.7. Process1.8. Cycle1.9. Point Function1.10. Path Function1.11. TemPerature!.12. 7'erclh Law of Thermodynamics1.13, PresEure

1.13.1. Definition of Pressure1.13.2. Unit of Pressure1.13.3. \rpes of pressure meaaurement devices

1.14. Rversible and Irreversible Processs1.15. EnergY, Work and Heat

1.15.1. EnergY1.15.2. Work and heat

1.16. First Law of Thermodnamics1.17. The Perfect Gas

1.17.1. The characterietic equation of state1.17.2. SPecific heats1.17.3. Joule'e law1.17,4. Rlationship between two specific heats1.17.5. EnthalPY i1.1?.6. Ratio of sPecific heats

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(vni)Chapter

1.18. Steady Flow Eaergr Equation (S.F.E.E.)1.lg.l. Enerry relatios for flow process1.19. Limitations of First f., of fn"._-Jyotio1.20. performance of Heat Eagine and n"r1,""" lleat Engine1.21. Statement of.Seconil f-* of fn"._Jilaurics1.21.1. Clausius statement1.21.2. Kelvin-planck statementL.22. Entropy1.22.1. IntroductionL.22.2. Tempetature.euhopy diagram1.22.8. Characteristics of entrop|1.28. The Third Law ofThermodynariics

1.24. Available and Unavailabt" irr""gy-HightightsObjectiue fupe euestionsThoretical euestions

2. IMRODUCTION I1O TNIEnNAL CoMBUsfioN ENGINES2.I. Heat Engines?.2. Developmeat of I.C. Engines2.3. Claseification of I.C. Engines2.4. Appcation of I.C. Eagil-es?.5. Engine Cycte-Eou"gy B"l*""2.6. Basic ldea of t.C. Engineg2.7. Different parts of I.C. EnginesZ.B. Terms Connected with I.C: Oi6ne"2.9. Working Cycles2.10. Indicator Diagra-2-.Il Four Stroke Cycle Engines? 12 TVo Srroke Cycle Engines2.I3. Intake for Compression Igaition Engines2.L4. Comparison of Four Strokl ."a f*iit-t" Cycle Engines2.15. Comparison of Spark lgntion fs.i.l anJoirop."".ioo Ignition (C.I.)2.16. Comparison between a petml Engine and a Diesel Engine2.L7. Hott to Tell a T$o Shoke Cy"l" ;;;'-f; a Four StrokeCycle Engine !

Highl,ightaO bje ct iv e Ilpe e ue stiansTheoretical euestions

3. AIR STANDARD CYCI,ES3.1. Denition of a Cycle3.2. Air Standard Efficiencv3.3. The Carnot Cycle3.4. Constant Volume or Otto Cycle

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Chapter

3.5. Constant Pressure or Dieeel Cycle3.6. Dual Combustion Cycle3.7. Cornparison of Otto, Diesel and Dual Combustion GrclesA.1.L. Efficiency versus compression ratio3.7.2. For the sane coopression ratio anil e same heat input3.7,5, For congtant maximum pressue anil heat suppliedS.8. Atkinson Cycle3,9. Ericsson Cycl3.10. Brayton Cycle3.11. Stirling Cycle3.12. Mille" Cycle3.13. Lenoir Cycle

Highlights iO bj ectiu e Type Q ues tionsTheoreticol QuestinnsUnsolued Enmples

FT,'EI-AIR AND ACTUAL CYCI,ES4.L. Fuel-air Cycles

4.I.7. Introduction4.1.2. Factorg considered for fuel-air cycle calculations4.1.3. Aesumptions oade for fuel-air cycle analysis4.7.4. Importance of fuel_air cycle4.1.5. Variable specific heats4.1.6. Effect ofvariation of epesific heats4.1.7. Dissociation4.1.8. Thermal efficiencr and fiel consumption4.1.9. Efect of @rmon engine variables4.1.10. Charactristics of costant volume fuel-air cvcle4.1.11. Combustion charts4.1.12. Gas tables

4.2. Actual Cycles4.2.L. Introduction4.2.2. Causes of deriation of actual cycles hom fuel-air cycles4.2.3. Real fuel-air engine cycles4.2,4. Difference between real cycle and fuel-air cycle4.2.5. Comparison of operations and working media for ,air cycle,,_-.

- -. _fuel-air cycle' and ,actual cycle' of S.I.-engrnes

Highli.ghtsObjectiue Type euestiansTheoretical QuestionsUnsolved Exarnples

COMBUSTION IN S.T. ENGINES5.1. Introduction

5.1.1. Definition of combustion5.7.2. Ignition limits

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()Chapter

5.2. Combustion phenomenon5.2.L. Normal combustion5,2.2. Abnormal conbustion

I 3 Effect of Engine Variables on Ignition Lag5.4. Spark Advance and Factors Afiecting lgni-tion Timing5.5. Pre-ignition5.6. Detonation

5.6.1. Introduction5.6.2. Process of detonation or knockiug5.6.3. Theories of detonation5.6.4. Efects of detonation6,6.5. Factors affecting detonation/kocksPerformance Nuober (pN)Higheat Usefi:l Compression Ratio (HUCR)99Tbuslion Ch-ber Desigrr-'S.I. Engines5.9.1. Induction swirl5.9.2. Squish and tumble5.9.3. Quench area5.9,4. Turbulence5.9.5. Flarne propagation5.9.6. Swirl ratio5.9.7. Surface-to-volume ratio6.9.8. Stroke-to-bore ratio5.9.9. Compression ratio (C.R.)

5.10. Some Tlpes of Combustion Chambee5.10.1. Divided combustion chambersHighlightsObjective Type euestiansTheoretical euestbns

COMBUSTION IN C.I. ENGINES6.1. Introduction6.2. Combustion phenomenon in C.I. Engines6.3. Fundamentale of the Conbustion pr-ocegs in Diesel Engines9^_ Delay period (or Ignition Lag) in C.I. Engines6.5. Diesel Knock6.6. C.I. Engine Combustion Chambers

6.6.f . Pimay considemtions in the desiga of combustionchambers for C.I. engines

6.6.2. Basic methods of generating air swirl in C.I. enginescombu.stion chambers

6.6.3. Types of combustion chambers6.7. Cold Starting of C.I. EnginesHighlightsObjective Type euestonsTheoretical euestons

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AIR CAPACIT OF IIOT'R SIROI{B ENGINES7.t. Introduction7.2. Ideal Air Capacity7.3. Volumetric EfEciengy7,4. Effect of Various Factors o Volu.metric EfEciency7.5. Inlet Valve Mach Index

HighlightsObjectiue Type QuestionsTheoretial Questionsunsolued Emmples )

TWO SIROIiE:EF{GINES8.1. General Aspects

8.1.1. Construstion and working8.f.2. Comparison between two-stmke cycle and four-stroke

cycle engine8.1.3. Disadvantagee oftwo-stroke S.I. engine comtared to

twoshlke C.I. engine8.1.4. Rason8 for use oftwo-eroke C.L engines for marine

propulsion8.1.5. Reasons for the use of two-stroke S.I. engines for low horse

power two wheelersIntake for Two stroke Cycle EnginesScavenging hocesScavenging ParmeteruScavenging SystemsCrankcase ScavengingScavenging Pumps and BlowersHishliAhtsObjective Type QrestbnsTheoretical Questiorc

CI{N}trCAL TIIERMODYNAMICS AND FTJELS(CONIENTIONAL AND ALTERNATIVE)9.1. Chemical Thermodynmics

9.1.1. General aspects9.1.2. Baic chemitry9.1.3. Fuels9.1.4. Combuetion equations9.1.5. Theoretical air and excess air9.1.6. Stoichiometric air-fuel (A/F) ratio9.1.7. Air-fuel ratio from analysis of products9.1.8. Analysis of exhaust and flue gas9.1.9. Internal energy and enthalpy of reaction9.1.10. Enthalpy of formation (AlI.)9.1.11. Heating values of fuels

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I (xii)Chapter

9.1.12. Adiabatic flame tenpeatur9.1.13. Chemical equilibriui9.1.14. Actual combuetion

_""i"9.2. Conventional Iuels (For lClffi""--9.2.L Introduction9.2.2. Desirable-propertiee of good I.C.cngioes fuels9.2.9. Gaseous fuels9.2.4. Liquid fuels9.2.8. Structure ofpetrolen9.2.6, petrolelo aod coinpoeition of crude oil9.2.7. Fuels for

"p""f_ig"iUoo ""gi""l-9.2.9. Knors 2 s,,Jil:ffi"jj*;H;",T:*ne

tue,s9.2.10. Dieeet fuel9.A. Alternative Fuels for I.C, Engines9.4.1. General aspectol.i:i. ifl:i:i.*"" and dieadvanrases of using alrerative fuele9.9.4. Alcohol-gasoline fuel bleds9.8.5. Hydrogen9.8.6. Natural gas (Eethae)9.9.2. LpG and LNG9.8.8. BiogasHisht@hbObjective Type euestionsTheoretical euestionsUnsolued Examples

ro. F.UEr./ArR MrxTuRE REQUIREMEIYTS10.1. Introduction10.2. FueUAir Mixture Bequirements for Steady Runningl0'S Optimum FueUAir RaUo" ' - --' vwqqr I10.4. Idling and Low Load10.5. Normal power Range or Cruise Ranse10.6. Maximum power RLge -- -'v '.*Es10.7. Transient Mixture Requirements

10.?.1. Starting and warming up hitu.e requirements10.2.2. Mixture "eqrrire-ent fol ;;;n""10.8. Effects of operarine variables ;; j;;;"-t"quiremenk10.9. Mixture Requirements f"" Di"""l-;;;;;; ..Highlights --- -'6ee

Objectiue Type euestionsTheoretical euestinns

rT. CARBT.IRETION AID CANBURTTORS11,1. Introduction11.2. Induction System

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11.3. Factors Influencing Cabrretion11.4. Mixture Requirenents11.5. Distribution11.6. Transient Mixtue Requirenentsf1.7. A Sinple or Elementary Caburettor11.8. Complete Carburettor11.9. Carburettors

11.9.1. Eseential featues o,fgood commercial carburettor forautomotive engines11.9.2. $pes of carburettors

- _ _ ^

11.9.3. Description of some important maLes of carburettors11.10. Petrol Injection11.10.1. Drawbacks of modern carbuettors11.10.2. Introduction to fuel iqiection11. 10.3. Direct injection11. 10.4. Indirect injectionI l. 10.S. Injection considerations11'10'6' comparison ofpetror idection and carburetted fuelsupply systeme11. 10.2. Electrouic fuel injecti,on

11.11. Theory of Simple CarburetorHighlightsObjectue Type etnstiowTheoretical euestionsUnsolued, Eramples

12. FUEL INJECIION SYSTEMS FOR C.I. ENGINESIntroductionFunctional Requiremeats of an $ection SystemFuntions of a Fuel Injection SrstemFuel Injection Systens12.4.1. Air injection12.4.2. Solid or ailess injectionl^ue_l

Pumn and Fuel Injector (Atomiser)12.5.1. Fuel pump12.5.2. Fuel atomiser or injector12.5.3. Faults, causes and remediee of injectorsT}pes of Nozzles d Fuel Spray pattems12.6.-1. Main reqrris6sts of an injector nozzle12.6-2. Classification and description of nozzlesEngine Starting SystemsFuel,Injection Computation in C.I. EnginesHighlightsO bje c t iu e Type eue stiansTheoretical QuestionsUnsolued Etamples

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Chapter

13. IGMTTON SYSTEMS (S.r. ENGINES)13.1. Introduction13.2. Requirements of an Ignition System13.3. Basic Igaition Systems13.4. Battery (or Coil) Ignition System13.5. Magneto Ignition System13.6. Firing Order13.7. Ignition Timing13.8. Spark Plugs13.9. Limitations of Cbnvetional Ignition13.10. Electronic Ignition Systems

Hightights' Objectiue Type Questions

Theoretical euestbns

14. ENGINE FB,ICTTON ND LI]BRICATION14.1. Introduction14.2. Total Engine Friction14.3. Effect of Engine Parameters on Engine Friction14.4. Determination of Engine Friction14.5. Lubrication

14.5.1. Definition and objects14.5.2. Behaviour of a journal in its bearing14.5.3. Properties of lubricantg14.5.4. Types of lubricants

14.6. Lubcation Systems14.6.1. Introduction14.6.2. Wet sump lubrication srstem14.6.3. Dry sump lubrication systen14.6.4. Mist lubrication system14.6.5. Lubrication of different engine parts14.6.6. Lubrication of ball and roller bearings

. L4.6.7. Oil filters

14.7. Crankcase VentilationHishlightsObjectiue Type Questions?heoretical Questians

15. ENGINE COOLING15.1. Necessity of Engine Cooling15.2. Areas of Heat Flow in Engines15.3. Gas Temperature Variation15.4. Heat Transfer,'Temperature Distribution and Temperature profiles

15.4.1. Heat transfer15.4.2. Temperature distribution15.4.3. Temperature profiles

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. (p)Chapter

15.5. Effects of Operang Vriables on Engiue Heat Tlansfer15.6. Cooling Air and Water Requirements15.7. Cooling Systeqs

15.7.1. Ai-cooling system15.?.2. Wateriquid cooling system

15.8. Components of Iater Cooling SystemHishlightsObjectiue Type QuestionsTheoretical Questions

16. SUPERCEARGING OF I,C. ENGINES16.1. Purpose of Superchaiging16.2. Supercharging of S.I. Engines

16.2.1. Natually aspirated cycle of operation16.2.2. Supercharged cycle of operation16.2.3. Comparison of actual natwally aspirated and supercharged

engine pressure_volume diagrams16.2.4. Boost pressure and pressure ratio16.2.5. The effect of presaure ratio on air charge rmperature16.2.6. Thermodynanic cycle and superchargiag power16.2.7. Supercharging limits of S.I. enginee

16.3. Supercharging of C.I. Engines16.3.1. Supercharging limits of C.I. enginesModification of an Engine for SuperchargingSupercbargersSupercharging ArrangementsTurbochargers16.7.1. Introduction16.7.2. Altitude compensation16.?.3. Turbocharging-Buchi system16.7.4. Methods of turbcharging16.7.5. Limitations of turbochargingHighlightsO bj ec tiu e Typ e Quc stionsTheoretical QuestinnsUnsolued Etamples

TESTING AND PER'ORIITANCE OF I.C. ENGINES

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(s')Chapter

Objective Type euestinsTheoretical euestionsUnsolved, Emmples

18. AIR, POLLUIION TB'O LC. ENGINES AYD ITS CONTR,OL18.1. Introduction18.2. Pollutants

18.2.1. pollution deriyed from combustion pmducts18.2.2. Mixtue

-rlegth and oombustion product characteristics18.3. Spark Ignition (S.I.) Bngine Emissioml8.B.l. Crantcaee euision18.8.2. Evaporative eoission18.3.3. Exhaus! siion

18.4. S.I. Engine Emission C,onhol18.4.1. Modificatioa in the engine deeign and operating parameers18,4.2. Exhaust gas cidation18.4.3. Exhawt ghicion control by fuel variation18.4.4. BIow-.by conkrd18,4.5. Evaporation iaion control device (EECD)18.4.6. .Control of oddcs of nit,ogen (NO )18.4.?. Total siaim mtol paclageg .

18.5. Diesel Engine Enieciru18.6. Diesel Smoke and Conkol

18,6.1. Exhaust smole18.6.2, Causes ofsnoe18.6.3. Measuremmt of smke18.6.4. Control of smo[e18.6.5. Diesel odow ad contol18.7. Comparison of Gasoline and Diesel Emissions18.8. Zero Emission

18.9. Air Pollution from Gs Turbines and its Controlf8.10. Effects of Engine Emissions oo ffo-uo U""ltlHighlights@jectiue Ilpe euestimsThoreticol euestions

19. MTSCELII{N]EOUS EIVGINES19.1. Duel-fuel and Multi_fid Engines

19.1. 1. . Duel-fuel engines

19. 1.2. Multi-fuel engines19.2. Sratified Charge Engiu

19.2.1. Intrcduction19.2.2. ClassificatioD19.2.8, Advantages ad disadvantages of stratified charge engines19.3. Stirling Engine19.3.1. Stirling cycle19.3.2. Working princide of stirling engine

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19.3.3. Difrerences between camot and stirling engines19.3.4. Engine geomstry and driving mechanism

19.4. The Wankel Rotary Combution (RC) Engine19.4.1. Introduction19.4.2. Construction and working19.4.3. Features19.4.4. Constructional and other details of Wankel engine19.4.5. Perfomance of Wankel engine19.4.6. Advantages and applications of rotary combustion engincs19.4.7. Why Wankel rotary engine could not become successful ?

19.5. Variable Compression Ratio (VCR) Engines19.5.1. Introductionf9.5.2. Methods to obtain variable compression ratio19.5.3. Analysis of VCR engine19.5.4. Performance of VCR engine

19.6. Free-Piston Engine PlantHighlightsO bjective Type QuestionsTheoretical Questians

20. AIR COMPRESSORS20.1. General Aspec'ts20.2. Classification of Air Compressors20.3. Reciprocating Compressors

20.3.1, Construstion and working of a reciprocating compressor. (eingle-stage)

' 20.3.2. Single-stage oompressor : equation for work(neglecting clearance)

20.3.3. Equation for work (with clearance volume)20.3.4. Volumetric efciency/ 20.3.5. Actual pV (indicatr) diagram for single-stage compressor20.3.6. Multi-stage compression20.3.7. Effisiency of, compressorI 20.3.8. How to increase isothermal ef,Eciency 'l20.3.9. Clearance in conpressors20.3.10. Etrect of cleaance volume20.3.1l. Free air delivered (F.A.D.) and displacement20,a. f l Compressor perfomance

. 20,3.f. Etrect of atmospheric conditions on the output of a compressoi20.y,f4. Conttol of compressors2O/3.Lf. Anangeq.rgnt of 'reciprocating conpressors20.3.f6. Intercoolef

' 20.3.17. Compreesed-hir motors20.3.18. Reciprocating air notor20.3.19. Rotary trpe a nctor

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20.4. 1. - Classification

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20.4.2. Displacement compreesors20.4.3. Steady-flow compressorgComparison betreen Reciprocating and Centrifugal CompresorsComparison betreen Rcciprocahn! and notr"y . C-o"_i1""""r"C_omparisou between C""t"in ga-a"a eri"i f"i^C""loi""**Hishlishts

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786787787795796798800

Objective Tlpe (fustionsTheoretical QuaionsUnsolved Era.mfu"s

GAS TURBINES AND iIET PROPUISION21.1. Gas ?urbines-Cieaeral Aspects21.2. Classification of Ga Tubines21.3. Merits of Gas Ttnbiaes21.4. Const&rt Pressuro Combustion Turbines

21.4.1. Open cfde Sas turbinee21.4.2. Methods for impmvement of thermal efficiency of open cyclegas urtine plalt

Bosia Coneepts of Thermadynannics1.1. Denition of thermodynamics. 1.2. Tternodynamic aystems-System, boundaryand surroundings+Closed system--Open oystem-Isolated eystem-Adiabatic system-Homogeneous systen-Hetarogenoous Bystem" 1.3. Pure substane. l.4.lheruiodylamicequilibrium. 1.5. hopertieo of syBtems. 1.6. Stt. 1.7. Process. 1.8. Cyde. 1.9. Pointfunction. 1.10. Path fungtion. 1.11. Temperature. 1.12. Zeroth law ofthermodynanics.1.13. hessure-Definition ofpressure-Unit forpressure-$pes ofpressure meaerementdevices. 1. 14. Rversible aad irreversible procesrs. 1. 15. Energr, work and heat

-Enerry-Work and heat. 1.16. Firgtlaw ofthermodynamies. 1.17. lbe perfect gae-Ibe characteristicequation of state-Specific heats-Ioule'e lsw-Rlationship between two specifi c heat*Enthalpy-Ratio of specifrc heats. 1.18. Steady flow energy equation (S.F.E.E.)-Energyelations for flow procees. 1.19. Limitations of first law of thermodynamics.1.20. Perfornance ofheatengine and reverged heat engie. 1.21. Statemente ofsecond lawofthermodynamics-Clausius statement Kelvin-Planck statement. 1.22. Entropy-Introduction-Temperatre etropydiagram-Characterietics ofenhopy. 1.23. The thirdlaw of thermodynamics. 1.'1. Available antl unavailable energy-Highghte-ObjectiveType Questions-Theoretical Questions.

1.1. DEFINMON OF ISERIUODTNAIfiCSThermodynamics may be defined ae follows :Therrrndynatnics s o axiomotic science which d.eals with the relatons arnong hcat, work

and. properties of system whih are in equilibrium. It d.escribes stote ond. changes in state ofphyecal systems.

OrThermodynamics is [e science of the r4ularities governing processes of energy conver-

sion.Or

Thermodynarnics is l scince tnat deats with the interacton between energy and mate-rial systems,

Thermodynamics, basically entails four laws or axiomg known as Zeroth, First, Second andThird law of thermodynanics.

-

the Firs I throws ght on concept of internal energy.

-

tbe Zeroth Joar deals with thrmol equilibrium and establishes a concept of temperd,ture.

-

tbe Second I@ indicaes the limit of converting heot into work and introduces theprinciple of increase of entropX.

-

thid law defines the absolute zero of entropy,These laws are based on experimental observations and have o mathematical proof. Like

all physical laws, these laws ae based on logcoJ reasoning.I

2t.

:1 1q lgect of ryerating variables on thermal efficiency?1 1 1 9]*4 sde gas rurbine (con-sran;";;';;je cycle)21.4.5. Merits d demerfts of closed

"y"i"';"_;;b;J-ou.. op"r,cycle gre turbineConstqnt Vsluhe eo[ustioa TubinesUses ofGas I\rbinesGas Turbine FuelsJet Propulsion21.8.1. Turbo-jet21.8.2. Turbo-prop21.8.3. Ram-jet21.8.4. Pulse-jet eagine21.8.5. Rocket enginesHighlightsObjectiue Ilpe QustionsT he o ret ical Q ue.ationeUnsolued Eramplcs

22. SHORTANSWER QUESTIONSQUESTIONS BAK-With Answers(Including Universities and Competitive Examinations, euestions)PART.T. ADDITIONAL O&rEcTfvE TrpE QrrEsTroNsA. Choose the Correct Answer

B. Match List I nith List II

PART-rr TEEORETTCAL QUESTToNS TVTTIT ANSWERSPART.III ADDITIONAL TTPICAL WORreD EXAMPT.ESAPPENDD(INDEX

C. Competitive Exalrinations euesions (With Soluions_Comments)D. Fill in the Blanks50

t-221---3

r.2. THERMODYNAMIC SYSTBMS1.2.L. System, Boundarr and Sunoundingssystem. A system is a finite quantity of matter or a prescribed. regbn o/space (Refer Fig. 1.1)Boundary. T\e actual or hypothetical enuerope enclosing the system is the boundary ofthe system The boundary ma{ be qrcd or it may ,nou",

". and when a system containing a gas iscompressed or expanded. rhe boundary maybe rear or imaginary. It is not difticult to envisage areal boundary but an exampre llinacinag bo'ntrary *oold b" ne drawn

""ooo .

"yst"- .o.r-sisting of i'i'o trosh mixture about to enter L cynder f a I.c. engine togethei*tr, trr" ""-^.ruot"of the last cylinder charge after the exhaust p"o"""" G"f". fig. f]Zl.

Surroundings

/,--...ttBoundary/\\ system /\l

'b""h#Fig. 1.1. The systen.

fNTERNAL COMBUSTTON ENCINES

System

Fig. 1.2. The real and imaginary bounilaries.

Fig. 1.4. Open system.

BASIC CONCEPTS OF THERMODYNAMICS 11.2.4. Isolated SystenAn isolated system is that system which erchanges neither energ r.or matter with any

other s)tstem or with enuironment,13.6. Adiabatic SyetemAn adiabatic systen is one which is thermcilly nsulated, from its surround,ings. It can,

however, erchonge worh wh its sutoundngs. Ifit does not, it becomes an isolated system.Phase. A phase is a quantity of matter which is homogeneous throughout in chemical

composition and physical structure.1J.6. Homogeneous SyetemA Bystem which consists of a single phase is termed as homogenaus sysfen. Examples :

Mixture of air and water vapour, water plus nitric acid and octane plus heptane.1.2.7.' Heterogeneous SystenA system which consists of two or more phases is called a heterogena us syslznz. Examples :

Water plus stearn, ice plus water and water plus oil.

1.3. P[]N SI'BSTANCEA pure substance is one that has a homogeneous and invariable chemical composition even

though there is a change of phase. In other words, it is a system which is (c) homogeneous incomposition, () homogeneous in chemical aggregation. Examples : quid, water, mixture of liquidwater and steam, mixture of ice and water. the mixture of liquid air and gaseous air is not a presubstance.

1.4. TIIERMODYNAMIC EQI,'ITIBRITMA system is in tlumd.lnamic equilibrum if the temperature and pressure at all points

are same ; there should be no velocity gradient ; the chemical equilibrium is also necessary.Systems under temperature and pressure equilibrium but not under chemical equilibrium aresometimes said to be in metastable equilibrium contions. It is only undcr thermodynamb equi-librium cond,itons that tlrc properti.es of o system can be fi,rcd.

firus for attaining a stsrta of thermdlrwmic equiJibrir the following three types of equ!libium states must be aieved :

1. Thermal eQuibrirm. The temperature of the systern does not change with time andhas same value at all points of tho system,

2. Mechsnical equilibrirrn. llere are no unbalanced forces within the system or betweenthe suroudings. The pressure in the system is same at all points and does not change withrespect to time,

3. Chemical eqiribriun. No chenical reaction takes place in the system and the chemi-cal'composition rvhich is sarne throughout the system does not vary with time.

1.5. PROPERTIES OF SYSTEMSA property ofa system is a characteristic ofthe system which.depends upon its state, but

not upon how the state is reached. There are two sork ofprbperty :1. Intensive properties. These properties d.o not d.epend on the mass of the system.

Examples : Temperature and pressure.

1.2.2. Closed SystemRefr Fig' l'3' Ifthe boundary ofthe system is impervious to the flow ofmatter, it is calleda clos.ed sqste-'. An example of this system is mass oi g^" o, vapour contained in an enginecylinder, the boundary ofwhich is drawn by the cylinder walrs, the cylinder head and pistoncrown. Hee the bound,ary s continuous on no

^ft", tnd! enter or leaue,

Fig. 1.3. Closed system.1.2.S. Open SystenRefer Fig. 1.4. An open system is one in which matter flous into or out of theof the engineering systems are open.

Convenientimaginary

Mass remains conslantregardless vadation of

boundar'es

System

qysern, Most

rI\ I E^!AL LUMI'USI'ION ENGINES

2. Extensive properties. These properties depend on the nass ofthe qstem. Exampre :volume' Extensive propertis ae often divided by mass associated with thern to obtain the inten-sive properties. For exanprg if the volume of a system of mass.r is v, then the specifi.y6lu6 6matter within the system i" # = " which is an intensive properry.1.6. STATE

state is the contin of the system ot an instant of time as describeit or measured fur itsproperties. Or each unique ond,itan of a system is called a state.rt follows from the definition of state hat each property has a singre value at each state.stated differently, all properties ate state or point funciions. r\ercfore, all-pmperties ae identicalfor identical states.on the basis of the above scussion, we can

J,it

INTERNAL COMBUSTION ENC I N\ESo fnstruments a" fl.::l_t"S{lnary temperatures ae known as,thermometers,, andthose for neasuring high temperatres are known as _pyrometers,,r It has been found.that a gas will not occupy any volume at a certain temperature. Thistemperature is kown as absorute zero tu|iperature. The temperatures measured withabsolute zero as basis are calred ;;;fu;;'t:;;"r"rures. Absolute temperature is stated

;:,*1f;H:jiff*;Tt'"pi"t or "'oi,'tf,^p"""tu"e is found to occur at 273.15"cThen : Absolute temperature

= Tbermometer reading in .C + 2?3.15.Absolute temperature in degree centigrade is kno; as degrees kelvin, denoted by K (SI unit).r.12. ZENOTH LAW OF THERMODYNAMICS

o 'zeroth 'aw

of thermodynamics' states that if two s,,stems are each equal intemperature to a third, they are "q"d;;;;;;"rature to euh other.fi,Tlll;l1ff:ir *:J*i l^try*,:t Ji. *",,.ore"s encrosed in a rigid vesser

:"'i::J1lf ,';,:::i,f lf,:,'lli"::'t.'i:*1i'"iJ":#ffi:f ffi 1i""X'1,ilT$,i:'"Tiil:;1i#il1'iT-:;i',l::i'":"::::l*ri'1";ffi;";,1';ffiTJ:'.T::ll?l#,,i;:i"'trT:,#li*:::::i1:t;{:|iffifi :T#ffi ;,;,:ffi'":"S'.:#::i;::l"J:fl,;1;:"i._l:yllt*:,.:::1T_tf .-*j#ffiH,l"fff ii""':',",:ffii;""ifl:;ffi

"*"'ff '""?"ffi ;;i:'""-'::-:::*:'.-:;;il#":;ffi'r:i:il;:f :ffi:ilT:*'"7

:::i,iH* *act with each other ;J;;iiJT' #fi:5;HH:":::;Tj"T'"TTT:equilibrium.

OOFig. 1.6. Z,eroth law ofthermodynamics.

r This law was enunciated by R.H._Fowler in the year 1981. However, since the rst andsecond laws already.exist ut trt"t ii-",'if.." designated as zerothlor so that itpreced,es the first and second l"*" toii)ii o toguot sequcnce.r.T3. PRESSURE

1.13.1. Definition of pressurePresture is defined as, a

.forcd per unit aiia. pressures ae exerted by gases, vapours andliquids' The instruments that we ;;;;';;; n=iurr"., record pressure s the difference

BAsIc coNcEPTs oF THERMoDYNAMCS .Ibetween two prssures. Thus, it is the dffirence between thz pressure eerted by a ftuid. of nter-est and the ambient atrnospheric pressure. Such devices indicate the pressure either above orbelow that ofthe atmosphere. when it is oouc the atmospheric pressure, it is termed gczgepressur and is posifiue, when it is below atmospheric, it is ncgaue and is kown aa udcuum.Vacuum readings are given in millimetres of mercury or millimetes of waer below the atmos-phere.

It is necessary to establish an absolute pressure scale which is independent ofthe changesin atmospheric pressure. A pressure of absolute zero can exist only iu complete vacuum. nypressure measured. aboue the absolute zero of pressure is trmed an,absolute pressure'.A schematic diagram showing tbe gauge pressure, udcuum pnessr and the absolute pres-

sure is given in Fig. 1.7.Mathematically :(i) Absolute pressure

= Atmospheric prssure + Gauge pressrrepb,

=patu *pc"ug",(i) Vacuum pressure = Atmospherit pressure

-

Absolute pressure.Vucuum is defined as the obsene of pressure, A perfect uacrn is obtained when absolute

pressure is zero, at this instant rnolecular mamentum is zero.Atnospheric pressure is measured with the help of barometer.

Positivegauge pfessufb

Negative gaug6Ariospheric

pressufeorvaqum

1I

eoqpo-

Zro absolut pressute

Fig. 1.7. Schematic diagram showing gauge, vacuum and abeolute pnessures.

1.13.2. Unit for PressureThe fundamental SI unit of pressure is N/m2 (sometimes called pascot, pa) or bar. 1 bar

= 106 N/m2 = 105 Pa. Standard atmsphdd pressure = 1.01825 bar - 9.76 -

ir.Low pressures are often expressed in terms of mm ofwater or mm of rnercury. This is an

abbreviated way of saying that the pressure is such that which will support a liquid column ofstated height.. 1.13.3. $pes of Pressure Measuremen Devices

The pressure may be measured by neans of indicating gauges or recorders. These instru-rnents may be mechanical, slecf6msqhnical, electrical o"

"t""t-. in operation.1. Mechgnical instnment& These instruments may be classified into following two groups :-

Tbe first group includes those instruments in which thb pressure measurement is madeby baloncing an unhnown force wth a known force'.--

TheseI,otld.groupincludesthoseemployinggzantitatiaedeformationofanelast.cnemberfor pressure neg,surement,

ffiI

i

8 TNTBRNAL coMBusrloN ENctNEs2, Electro-mcchanicel instrumens. These inshunents usually employ a mchanical

meons for d'etectittg thc pressure and. electrical neans for v/rirzclting or record.ing tlt d,tectedpressure,3. Electronic ingtrunents. Electronic pessuro measuriiig instruents normally de-pend on some phpical change that can be detected ad.idicated or recorded electronicallv.

1.14. BEVERSIBI,E AND IRNSVERSIBLE PBOCETIES

BASIC CONCEPTS OF THERMODYNAMICS 9

1.15. ENERGY, rvonr AND IIEATl.16.l. EnergaBnrgy is a geoeral term embracing energl in transitbn and, stored energr. The stored

energr of a substance may be in the forms of mecion ical energr ard intennl nr8C, (other formsofetored energy rnay be chemicd energr and electrical energy). Part ofthe stored energy nay takethe form of either potential energr (which is the gravitational energy due to height above a chosendatun line) or kinetic energy due to velocity. The balance part of the energy is knolrn as nterrlolervr&t.lla tnn-flow process usually there is no change ofpotential or kinetic enerry and hencechange ofmeclranical energy will not enter the calculations. ln a flow process, however, there maybe clanges in both potential and lcinetic energy and these must be taken into account whileconsidering the changes of etored energy. Heat utd uorh an the forms of energt in transition.Thes ae the only forms io which energr can cross the boudaries of a system. Nether heat tnrworh an ezist as stored energy,

1.152, Work and EeatlYorkWork is said to be done when a force moues through a distance. If a part of the boundary of

a srstem undergoes a displacement under the action of a pressure, the work done I{ is the productofthe force (pressure x area), and the distance it moves in the diection ofthe force. Fig. 1.10 (o)illustat,s tis with the conventional pieton and cylinder arrangement, the heavy line defining theboundary of the eystem. Fig. 1.10 () illustrates another way in which work might be applied to asystem. A force is exerted by the paddle as it changes the momenturn ofthe fluid, and since thisforce moves dwing rotation of the paddle room work is done.

Revereible pncesr. A reaersible process (also sclzldrincshwwn a,s quasi-stat process) is one whh can be $opfi d atqrstage and, reversed so that the qtstem and turround,irqt are a,-actly restored, to thir nial staEs.

This process has the following charateristias1. It must pass rough the eane states on th reversed path

aa were initially sited on the forward path.2. This process when undone will leave no history ofeveots in

the surroundings.3. It must pass through a continuous eeries of equibri-n

staes.

llri

No real proes is truely reversble but ame prwsct naXt approach reversibity, to closeapprorimation.

Exomplea. fu etamples of rcarly reversible pnGarrn ae :(j) Frictionless relative motion.() Expaneion and curnpreasiou of spring.

(iii) Frictionless adiabatic expansioo or compression off,uid.(iu) Polytropic erpansion or comprression of fluid,(u) Isothermal expansion or compression.

(ui) Electrolysis.

-_ .

Irreversible proceaa. An irreversible p.ocess is oc in which heat is transferred, througha finite temperature.

Fig. 1,8. Reversible process.

Examplee:(i) Relative motion with friction

(i) Diffusion(u) Throttling

(uii) Heat transfer

(a) Combustion(iu) Free erpansion(ui) Electricity flow through a resistance

(ui) Plastic deformation.

BoundaryBoundary

(a) (b)Fig. 1.10

'Worh' is a tansent quontit! which only apped.rs at thc bound'ary whIe a change of stateis tohing place within a slsteim. "Worh is'something' which appears at the boundary when aqrstem changes its state d.ue to the mouement of a part of the boundary und.er the acton of aforce.

Sign convertion :Ifthe work is done Qy the system on the surroundings, e.g. wheu a fluid expands pushinga piston outwards, the work is said to be posiiue.

Worh output of the sXstem = + WIfthe work is done o the system y the surroundings, e,g, when a foe is applied to arotating handle, or to a piston to compress a fluid, the work is said tnbe rcgatiue.

Worh input to system = - W

Sr

An irreuersible process is usually representeil by a dathl (ordiscontinuous) line fuining the end, stctes to ittdiate that tlv intr-mediate stotes are indterminate (FiA. 1,9).

Irreversibilities are of two grpes:1. External ineversibilitie& These are associated withds-

spating effects outside the worhing flui.d.Examplc. Meclunbal friction ucurring d,uring a praess dve

to gone extental source.2. Internal ireversibllities. lhese are associated with dis-

sipatng effects within tlc worhing flud,,v

Fig. 1.9. Irreversible proces.

i.e.,

i,e.,

1I\ _..zNonEquilibrium

'{ / srares'.f

-"-----2

E .mple. Uwestricted erpansbn of gas, vscosity td inertia of the gas.

lo TNTERNAL coMBusrtoN ENGINESHeatHeat (denoted by tbe symbol e), may be, defined in 6 lsgoua way to work as follows :is'nnething'whbh appeers at the boundary wrvn a u,so,m changes its std'e d,ue toa d,ffirerue in tempemture between the system ond its cur"rrlwdlittgs,,

.

Heat, like wor\ is a transient quantity whichonry appears at the boundary while a changeis taking place within the system.It is apparent that neittre 6ll or 6e are exact difrerenots ad therefore any itegration ofthe elemental quantitiee ofwork or heat which appear during a chge from state tio

"tat" z mostbe rvritten as (' I 6W = 17,-, or ,W, (or llr), and

2

srgn convenro" ,'

* = Q;2or rQ2 (or Q

rftle heat flows in o a system from the surrounngr, the quardty is said to be postiueand, converselv, if heat frows ?om the system to tbe surroundings ii is sa tn lre ,neotr".In other words :Het receiied by the systetn

= + etrIeat rejected or given up by the tystern = _ e.Comparison of \tork and lleatSimilarities :(i) Both are path functions and. inerat dffirentizts.() Both are boundary phenomenon i.e., both are recognized at the boundaries ofthe systemas they cross them.

(tti) Both are assosiated with a process, not a state. unke properties, work or heat has nomeaning at a state.(iu) gys"-. possess energy, but not work or heat.Dissimilorities :(i) In heat transfer temperature difference is required,() In a stable system there cannot be work hansier, however, there is no restriction fo thetransfer ofheat.

(iii) The sole effect external to the system could be reduced to rise ofa weight but in the caseof a heat transfe other effects are also observed.r.T6. FIRST III1V OF TIIERMODYNAJVIICS

It is observed that rvhen a sJstem is made to undergo a comprete cycle then net work is doneon or by the systern, consider a cycle in which n"t ",o"t i.'ao." uy the system. since energy cannorbe created, this mechanical en:rry

.r.nu:t har" ."n ,rpplU fr "._;;;;;;;;;; Now thesystem has been retuned to its-initiar state: rteee,'it" ior"* energy is unchanged, andhence the mechnicar enerry has Dot been p"";idJ;;;" system itself. The only other energyinvolved in the cvcle is theLat which was

"rppriJ",etectd in various processes. Hence, bythe law ofconsenation ofenergy, tbe net work ii"" y ii" ryrt.. is equar to the net heat - :r..,:r.c

,:: BAsIc CoNCBPTS OF THERMODYNAMCS 1Ito the system. The First Law of thermodynanics can, therefore, be stated as follows :

. {hen a eystem underaoee a tlernodynarnic cycle then the net heat eupplied tothe syetem from the eurroundlngs le equal to nct work done by tbe system on lteeurroundingsor $e=6dwt't

where f rpresents the sum for a complete cycle.

The frst law of Thermodyomics canrct be proued, analytically, but erperimental eui.dsrcehas repeatey confirmed, its valt!, and gince no phenomenon has been shown to contradict it,the firet law is accepted as a ldw of nature It may be remarked that no restrictiou was inpooedwhich limited the application ofst law to reversible energr transformation. Hence th? firgt lawapplies to reversible ae well as irrcverible transformations : For non+yclic prooess, a-rnoe gen-eral formulaon of rst law of tfermodyn-cs is required, A new concept which involves a termcalbd internal energy fulfi'lla this need.

-

the First Law of thermodynamics may also be stated as follows :Ileat and work are mutually convertible but since energ:f esn neither bo cre-

ated nor destroyed, the total onergr associated with an energy converlon emainscoDstant'.

Or-

fio machine can produce energy without correrpondlng expenditure of en-ergy, i.e., it is lnpoeeible to construct a perpetud noion macbine of firstkind".

1.17. TEE PER'ECT GAS1.17.1. The Characteristic Equion of State-

At temperatures that are considerably in excess ofcritical temperature ofa fluid, andalso at very low presBure, the vapour of fluid tends to obey the equation

ff=constant=EIn practice, no gas oben this law rigidly, but many gases tend towards it.An imaginary ideal gas which obeys this law is called a prfect go,s, and the equation

ff = n, is catled the chdrateristic equatian of o state of a perfect gas. The constant I is calledthe ga.s consaut. Each perfect gas has a diferent gas constant.

Units of ,R are Nmftg K or hllkg K.Usually, the characteristic equation is written as

pu=RTor for n kg, occupying V mg

pV= mRT

...(1.1)

...(r.2)-

The characteristic equation in another form, can be derived by using kilogram-mole asa unit.

'I\6 kitogmm-mole is defined as a quantity of a gas equivalent to M kg of the gas, where Mis the molecula weight of the gas (.1. since the rnolecular weight of orygen is 32, then 1 kg moleof oxygen is equivalent to 32 kg of oxygen).

r.i

INTERNAL COMBUSTON ENCINBt

As per denition of the kilogram-mole, for m Lg of a gas, we have.m=nM

where n = Number of moles.

Note. Sine the gtndard of mas is the kg, hilogram-mole will be written simply ae nole.. Substituting for m from Eqn. (1.8) iu Eqn. (1.2) Cives

pV = ntrIRT

or *r= #,

Acgoldinq tn Auogadro's hypottusis the vorume of 1 more of any gas is the sam as thevolunre of I mole bf ny other gas, when the gses aE at the ame t;;"J";; ;d pressue.Therefore, f is the same for all gases at the same value ofp and ?. rhat is the quantitr ff i" ^conatd,nt for all gases. This constant is called uiueroot gaa cor.stant, and is given the symbol, Bo,

We havedQ = m cp dT For a eversibte noa-Oow poce8s at constant Pressurc "'(1'6)

and dQ = m , itT For a reversible non-flow process at constant aolume "'(1'7)The values of co and c,, for a perfect gas, are constant for any one gas at all pressures and

tomperatures. Hencc,-integrting Eqns. (1.6) and (1.?), we hveFlow of heat in a reversrole constant pressure pmcese

= mcp (Tz- T)

Flow ofheat in a reversible constant volume process=

mcu (T"- T1)In case of recl gases, c, aid cu uory with tunprdtwe, but a suitable auerage value may be

used for most practical Purposes. \1.17.3. Joule's LawJoule's law states as folows :"The intenwl

"n"rg oi o perfect gas is a furctbn of tlw a'bsolute temperature only"'i.e., u=flT)To evaluate this function let 1 kg of a Peect gas be heated at constant volume'According to non-flow energ equation,

dQ=d,u+dWd.W = O, eince volune remains constant

:. dQ= duAt constnt volume for a perfect gas, from Eqn. (1.7)' for 1 kg

dQ = codTdQ=d,u=cpT

u = co T + If, f being conetant.Accorng to Joule's law = ?), rhich mesns that internal energy varies nealy with

absolute temperature. Intemal energy can be made zero at any arbitrary reference temperature.For a perfect gas it can be assumed that r = O when ? = 0, hence constant K is zero.

BASIC CONCEPTS OF THERMODYNAMICS

and integrating

l3

L.,or

Since 8 = fto then

MR=Ro= #pV= nRoT

...(1.3)

...(1.4)

,..(1.8)

...( 1.9)

...(1.10)

...(1.11)

n= #' ...(r.5)^ - ^ .

It has been found erperimentally that the volume of I nore of any prefect gas at 1 bar and0'C is approximately 22.71 ns,Therefore from Eqn. (1.4),

p _

pV _Lxlo5x22.7l

-.- nT - _r;?sls= 8314.3 Nm/mote K

Using Eqn. (r.5)' the gas constant for any gas can be found when the molecula weight isknown.Example. For oxygen which has a molecular weight of 82, the gas constant

*=#==

259.8 Nm,/kg K.1.17.2. Specific lfeak-

The specifrc heat of a solid or liquid is usuay dened as the heat requred. to raise unitlzzass through one d.egree tenperoture rise,-

Fo small quantities, we havedQ = mcdT

where n = Massc = Specic heat

d? = Temperature rise.For a gas there are an infrnite uumber ofways in which heat may be added between any twotemperatures, nd hence a gas courd, have an infite nutnber of specificeos. However, onry twospecific heats for gaseq are dened.

Specifrc heat at constant voiutne, cuand Specifrc heat ot constclnt pretsure, co.

i.e. Internal eners, t = c,,T for a perfect gasor For mass m, of a prefect gas

Internalenergy, U=tncoTFor a perfect gas, in any process between states I aod 2, we have from Eqn. (1.11)Gain in internal energl,

12- ur= mc, (T"- Trl ...(1.12)Eqn. (1.12) gives the gains ofinteroal energ/ for a perfect gas between two states pr any

process, reuerslble or irreuersble.

L17.4. R.elationship Beween Two Specific HeatConsider a perfect gas being heated at constant pe$ue from ?r to ?r.According to non-flow equation,

Q=(Uz-Ur\+WAlso for a perfect gas,

U2- U,= mcu (T,- T,\Q = mcu (Tr- Tr) + W

8|14-v

t4

In a constant preasure process, te wod< done o" *" o*nt**Al coMBusrtoN

w =

p(Vz_yt)f': ptl.r=vftfi, I

=mXTz-T) I *W=,nr; II Pr = Pz= p i +J'is cse]On eubstituting A =_y: \rr- Tr) + mR (Tr- f = m(co + R) (Tz_ T)Bu for a coDst^nt pregguro p(rcsss, t' - "'vo - t|t \t z- t t)_

e = mc, (T2_ T1)By equating the two expressions, r" 1"""

m(cu + R)(Tz- Tr) =

nur(T"_ Tr)

BASC CONCEPTS OF THERMODYNAMICSl5

1.U.6. Ratlo of Specific Eeatslhe ratio of specific heat at coDs+ant preseure to the specic heat at constant volume isgiven by the symbol y (gamma).

i.e., "

=9p-. ' c" .'.(1.15)since c,

= cu + R, it is cler that c, must be

'reaer trran co for any pe;fect gar. rt follows,

therefore, that the ratio, a = 7 s ahrnls grater tlan unitXr.

In general, the apprfomaUi valuer of Tare is follows :Ft monoatomrc garee such O org,or, lulium = 1.6,Fq d.itomi gases such * abon ttnwid, niir"n", nitrogen *a oryg"n ) Ll.For triatomic gases such 3s wbodiifu arrd, iulpiur df""*ti = t,For some hydro.carbons the value of y is quie low.

cr+ R= c"cr- cv= n

Dividing both sides b c,, we get

r.o, IIFPRNAL. COMBUFTTEN,.Br{CiAgES

1.18. STEADY F,OW EI\TERGY TEUATION (S.r.N.E.)In many practical problems, tbe ratc at rhich te ftuiil flows thmugh a rnachioe or piece ofappalatus is constant. This type of flow is called *eX fuw.A,csumptione :The following assumptbru aie nade i te s,stcn anbnie (i) The mass flow through the rysten r@ains oostanlt(tD Fluid is uniform in compoeitioa.

(dij) The ouly interactioa betwesn tho syge. ad surroradFgg ae wqk and. beat.(iu) The state of fluid at any point remin octa*t wit time.(u) trn the analrsis oqly potcctFl, ftinatl] d &ow eneqgis ae coneidb,ed.Fig. 1 , 1 1 shows schematic flow proccss r s oFco ayrtm. .dn open srstem is one illlich lolh mass and ener,F Day croes the bo?qr*is. *i" i.tr.""d ;

"rr""s, *"y t*tupl'ace wifhin aa pen systen' It the sy8th be a rnrtootic eugioe rith the inlet DaniftIil at thfirst state poiqt aF4 eebat$t nine as tbg secqsd ga1 lbee wqrd be ea iutercharye of chemicatenetgr in the fuel' kinetie euerlgr of notriag patidcr, iate.rnd energr of gas ar t*ar*t r"aand shaft work within the system' rbra Fr!. r,11it is obvious that if there is no variatios of flowof mass or energr with time aerosg the bourdaries dtbe system tb stedy llow will prevail. Thecontions may-pass through te cydie r,r non-cyelb I+angas sirhi tbe systeo. As a ressh tbe

,nass entering the syaeo equals tbg mass leaviag, aho enerqy entering the ystsm equals energrleaVing.

Boandary

ffil Bnsrc coNc'prs oF r'aRn{ciDy*^McsThe steady flow equation can be expressed as follow :

ut * * * to+Prur+ Q = uz+ 4',

"r, + pur+ w

(ur+ prvr) * # * z,F * e = @r+ prv") * 4 * Z"s + whr*+ +Zg+e=hz+ $ *zrg+w

If Z, and, Z"are neElcted, we g

hr* 4 +e=hz*$ *wiyhere e = Heat supplied (r emteriag the bordary) per kg of fluitl ;W

= Yltork done by (or wcrk coming out of the boundary) 1 kg of fluid,C = Velocity of flud;Z =Height aborre {afuiri;.p

= Pressue ofthe fluid;z = Iutemal enerry per kg orf fluid ;

pu = Energr required for I kg of fluid

.

Tliis-equation io applrcabre to anymedium in any eeady frow. It ie appcable no'ly torotary rnachines such as centrifugal fans, punrps and cumpreeao* but arso to reciprocatipg ma-chiner euch as sterm engines.Io a steedy flow the rat" ol masg flow of ftuid a any secion is the same aa at a'y othrsection' Consider any secion of_c'oc-sectioal erea r{, where thc fluid velocity is c, tbe rat ofvolune flow past tbe section is cr{. Also, since mass flJ is volum flow divided by specic volune,

Mass 0ow t".be,;=+(wherc u = epecifrc uolwe at tte section)

Thir equation is known as the conntity of maer equa6on.With reference to Fig. 1.U.

=crA, =44u1 021.18,1. Energy Relaflone for Flow proeecThe energr equation (m fu offluid) for a steady flow systern is given ae follows :

^ (o.4. *-4 ., = ^ F *$ * r* * o*) * oe = ^ b -,,) + (z* - 4E) +(+ - +). r*r- a,rr] . we = ^lr-^)+se,-;a+(q#)*@*- w)l *w

I!

IIII'|

-^-

I

It

T7

,..(1.16)

t... h=u+Pvl

,..[1.16 (c)l

...(1.17)

...[1.17 (c)l

t.?.,

l.e. r

Fig. r.ll

,i. ,

l8

i.e.,

= LU + LPE + LKE +A (pu) + ItrLU=m(ur-u)

L PE = mg (22- Zr)(c,'-c'\LKE = m l_-J

Lpu = m(p"vr-p1u1)'

INTERNAL COMBUSTTON ENGTNES

...(1.18)

...(1.19)

...(1.21)

BASIC CONCEPTS OF THERMODYNAMTCS

' Co-efficient of performanoe, (C.O.p.)nrp,,,re =

where Q, = IIea transfer to ,t rcenoirW = Net work transfer to the heat pump.

(a)(c) Heat engine

Arw

t9

,..(L.22)

For non-flow process,

Q-tU=l^PE+ KE + ^(pu)+ WI2Q=AU+W=LU+ Lpdv

e- w= [inav1.19. LIMITATIONS OF FIRST II\W OF TUERJT,TODYNAMICS

It has been observed thal eturgr can flow from a system in tbe form of heat or worh- TJnefirst law of thermodynamics sets no mit to e amount of the total energr of a syetem which canbe caused to flow out as work. A limit is impos"d, however, as a result of the principle euunciatedin the second law of thermodynamics which states that heat will flow uaturally from oue energrresevoir to anothe at a iower tenperature, but not in opposite diection without assistance. Thisis very important because a heat engine operates between rwo eDerg'y reservoirs at different tem-peratures.

Further the frst law of thermodyn amiq estoblishes equvalence betw,een the quatttty ofheat used and' the mechanial worhbut dbes wt specify the conditions under whbh conversian ofheat into work is possible, neitltr tlp dirttion in which heat transfer can taheplace. This gaphas been bri.d.ged by the second law of thermrodynamics.1.20. PENtr'ORMANCE OF EEAT ENGINE AND RBYERSED HEAT ENGINE.

Refer Fig. 1.12 (a). A heat etqine is used to produce the maximum work ransfer fron agiven positive heat transfer. The measure ofsuccess is called ttre thermal efficiena ofthe engineand is defined by the ratio :

Thermal efciency, , WLu = e, ...(1.20)where f{ = Net work transfer from the engine, and

Qr = Heat transfer to engine.For a reversed. hzat engine^[fig. l.l2 () acing as a refrigerator when the purpose is to

achieve the maximum heat transfer from the cold resJnoir, tle easue of r,r."r" is called theco-efficient of performance (C.O.P.). It is dened by the ratio :

Co-eflicient of performance , (C,O.P,)-f. = 92where Q, = Heat.trasfer ftorn cold eseruoir

W = The net work transfer to the refrigerator.For a revereed heat engine [Fig. 1.12 ()l acting as a hcat pump,the measure ofsuccessis again called the co-efficicnt of perfqrnance. It is defined ty the ratio :

Fig. r.l2In all the above three cases application of the first law gives the relation e, _ e2= W, andthis can be used to rewrire the exprtsions ror tr,"r-ai"m"i;;;J";;;;ritJp""ror."r,.u

solely in terms of the heat trasfers.

qo =q:g(c.o.P.)rcf =#6

(c'o'P')'wtP P=d3" .,(tz6)uoir, .lt ^ t

be seen that 'n is alwals less thn 'itv o'd (c'o'P.) ; pup is always greater than

11. STATEMENTI OF SECOND I.AW OF IHERMODYNAT}ICSThe second law of ther:arodyramics has been euunciated meticulously by Clausius, Kelvinand Planck in slightly different words although both statenents are basically identical. Eachetatment is based on an i*euersiblz process.l\e first considers tf"irrrtli-if heat betweentwo thermal reseruoirs while the second, considrs the transfonnation of heat intL work.1.21.1. Claueiue Statcnent'It is impossibre for.a serf acting machine worhing in a cycric process unaided. by anyexternal agency, to conuey hear from a body at a lower tenperature to a boily ot a hgher tem_perature".rn other words, heat of, itsel{, cannot flow from a colder to a hotter body.

(b)() Heat p.-F or refrigerator.

...(1.23)

,..(L.24)

.i

rj

r.21.2. tervrn-planck statement INTBTNAL covBusrul BcHBs

"ftn "::;,tf'::;:i #:ff;l?i*ifT;"!"!fo::!*.*"":ti,ts in a cycb prcdrut to other"0"*.,t1',n,"Jili:*,:*ff "ffi,H#i{:z#:i,:#i"#ffiIL{,1ft ;r.22. ElvrR,opy

vt e'wr $atunrcnt implies violatian of ittw'

1.22.1. fnrodueionIn heat en''ine theory, ,h: l":- :ntropy plays a vitel role aud leads to importan reeulswhich by other rnethods can be obtained

_u.h Joi,.iuuo.ioorr".It mav be notecr that.alr l^":1* l" lrdly **"le for.converting into wor* Ireat tbt is;::i:l:ii'"",f:ffil:I'Ifilf"T:trJfj'1Tt"" po.,i'*y orconvereion inr,owc* than

,*u"fi,T"l,#0."#::H"";x:H'ly#r:::"showethepossibitttof uu*nbnofa3d is.sreater when tat add,ition

" "r"ii "'2:f:-!*: i8 addpd' at a hish t"^p*"ht;

'f:;':,::;:';;W;iy::!::,,:;#i;;;,ffi";:n#fr ::#ffi ffi",,"r*"i:n::{"it#l'-'f*e}Hn;f ;i_T::ystT.relchesarabreequibriumthermodynami" p-U"tilitv. aximum dieoder and i one of

--;-uui1.22.2. Tempereture-Entropy DiegreinIfentropy is proted horizonta,y rrrd .dote ternpe:ature. vertica'y, the diagram so obtainedis ealled temperatire entropy (T+),"g."_. rtI'iil*a_ is showriu ne. i.rJ. rf rorhing

&AS,TCCONCETTS OF TmnMqDyNAHTCS 2lfluid receives a emalr smo',rt of Led de in an elementar-y portion o of an ope,ration B whentemperatur is r, and if de is rwreeecm t tb; ;;-;:ffffi"; d";ir" ff; ordiaare; rhewidth of the figure mrrrt be# . lais is cslled 'bwrenzent of entropy, and is denoted by ds, thei"J:13:#ffffi"ffifr be siven bv the area uder the cu*"e B and (s, - so) wr

From absve we coclde tbat :Entropy chaugt, g= -- SeatChange(Q)

.Aboeflute temperature (Z) '"Entopy mey oleo fu defincd as th,e thermar property of a subeta.nce which remainsconstant wrun suhswe t e$t

.atcd or compressed, oint""uy' n "-li""b.Notet d stDdrfoi secic eotrcpy wfreees .S,meaas total entroID, (., ,g = n$). )

1.22.8, Chorctt$Ice of Eofi:ppy\\e cllrlrorlteri&ics of ttopy in nnmarised form ae given below :.

o" oot,1' rt ioceases FL.o hed b cupplied irespective of the fact whether temperature changes

2' It deceases cen heat i8 reuo'ed whether temperature changeo or not.L It remais unchagd in all adiabatic frictionlesE pr,ocesses.oro""J'

rt irasei f tmperature ofheat is lswered wito* work being done s in a thottling

I

I

I3. IITD THIRD I./TW OF TEaNMODYNAMICSThe third law of therrnodynamics is stated as follows :"The entropx of atl perfect crystalrne sorids is zero at absorute zero temperature,,.

Table 1.2. Sunnery of FornuleChonge oferopf @er hg)

Contstvolube

C@setFersorB

IsotheDDI

Adibeti:

Polytneic

G) culos"fr **r*,f (intcmofTandu)(ii) c,lo4 ff *",tog,f, nrrmsoflanau)Gi) cotos, 7 - *r*,f 0n terms of ranaet

",",c,+-72cp1o8, E

*r*,tZero

".(#),,"7Fig. t. 13. Temperature_euhopy diagram.

+ i..

Z' INTBRNAL COMBUSTION ENGINBSThe third law of thermodynarnics, often referred to as Nerrrat law, provides the basis forthe calculations of absolute entropies of substances.According to this law, if the entropy is zero at T

= 0, the absolute entropy 9o,. of a substanceat any temperature ? and pressur p is expressed by the expression L Tlernd'ynamis is a! axiomrtic science whidl desls rrith the relation amogbea! wort and propertiesofqrstems whidr are in equilibriunr" It basically mtails four laws or arioms hqD ashrcth, First, Secondand fIrird law ofthemodynamics.

Z A syctem is a finite quantity ofmatter or a preecribed region ofspace.A syeten may be aclovd,, open or isolced system.

& Apce is a qumtity of matter which is homogeneous thmughout in chemiol compoeition antl physiel8tructure"

4 A,lonryenazssysem is onewhichcosists of a singleptuse,I Alctcrogenaus sysfzrn is one whic cosi.sts of ftro or more phavzt,(L ltpttrc subctme is one that has a homogeou md invriable chernical compcitim evln though there

is a change ofphase.7. Asysterrisinthznd'yrumicquilibriumtempratureanilpreesumatallpointsaresame;thereshould

be w velor;if gndiznt.& Aprcperllofasystmisacharactristicofresystemwhichdependsuponitsdate,brutnotuponhowe

gtatis readred.Intznsive prcprter do not depend on the mass of the system.Extzrciw prcpertics depeud on the mass of the eysterng. 'Sae is the condition of the system at an ingtant of time as descibed or measured by ite properties. Or eachmique condition of a system is called a etate.

1O. Aprooess oceurs when the system tndergoes a ange in state or an energy banrfertales placs t a steadystta.

11. Any pmce.ss or series ofproceesee whose end states are identical is termed ac)cr.12 Theprussn of a system is the force exerted by the syrtem on rit area ofbouilrie. Vactrum is defitred

as the absence ofpresilne.13. A rcwrsiblz process is one which can be etopped at a-ny stage ad revesd so tlat the system atrd

surroundings are exactly restored to tleir iitial state.Aomve''ible ptwss is one in whidr het is transferred tlrough a finite temperature.

14' Zcroth law oftermodynamics stat8 that iftwo systems are each equal in taqerature to a third, they areequal in temperature to ead other.

lS. rnfinite slmees is the draracteristic feature of a quasi-static pmess. A quari

'il

d

1& I'here ca be no maine whi wuld continuoucly eupply nedradcal wort without soe fom of enagydisappearing simultaneouly. su a ctuou ncrrine is cana a perpctuI mtior mschi'e of the firstkind, or in brief, PMMI. A pMMf itue impossible.19. Ttre eDergr of an ieolated ryateu ie elwar constaa20 Incaseof

(i) Reverible conetalt votroc proceae (u =

sonstaD

(ii)Reversibrec.o"*"r*ji";[[:"1;l.*f "Qz-r)(i)Bcversibr,e*-*'"tJ':1';:li:#'"-K=8j13"r,r,

where =

s)rpansr"" ",

..fl]5;efttoa a a=r(iu) Beverlble adiaboti,c pmr(pu?= couetat)

t&= r w= &4__4) ,*=0,+=(#l ,=(*)+(u) Polytroplo reversible proccee (pu

= contat)

*e ffi':,;'':;;..2L Steady llow equation can be e4reeced as followe :

ur* # + zg + pror+ e =u"* 4 +zrg + pr, + Vnr*$ re=n"*$

BASIC CONCEFTS OF THBRMODYNAMICS 25'When a sntenr performs a revenible qrcle, then

s r!9)ffi\r t =o,but who the cycle

"

*, *TT*)L lT ) .0."Cr.lc '

24 Etropt' i! a frraction of e quaotity ofheat whidr shws tle poeeibility of mveraioa of tat hat intowort ltireaeineobopyiremallwhenheatiaddedetahightaopcabeaodiagreaterwheuheatatldition is mds at lower tmperature. llg fe qlrimrr cntropy, tiie i! r nniru availabity forconvenin ito work and for miium entropy there is nn 'r avilabili$for coaveion into work.2 Thethtdlwof termodynanlcistatedasfollorg: ' )The enEopy of all perfect crystalline ode iE zero at absolrdc rero temperture'.

OBJESITVE TTPE QTJESf,ONSChooe tbc corcct anrer :

L A dofite are or 4lace wbere some therrnodynamic pmcesc tatee placa is Lnown as

where Q = Hea eupplied pBr Lg offtu ;C

= Velocity of fluid;

p =

Preagure ofthe f,rid ;pu

= Energr required per kg offluid.

+l7,neglelngZrald!2" ...(tt)

If =

Wck ilone by I tgd0uid;Z

= Height aboveiltuo;

z =

Jatml eoe4t per lg of f,uid ;

(a) thcmodynaoic ryatem(c) ttcrodyo:rricproess

(c) erteocivo heat il trasfered(c) extroeive eneqg i utilied

(o) Vohme(c) lf

(c) hcs!r(c) Tempcehrre

() themodynamic sycle(d) themo4ynaniclaw.

() ertensive wori( is done@) allofeabove

() Tenperature(d) Energt

An open syrtacrir one i whidr(o) het ad work croaa tbe boundary ofthe syrtem, but the mrrs ofe wutiag substancs does not() narr of wo'*ing ubgtace croe the boundary of tba ryrtcrn but te beat ad rork ilo not(c) both the heat asd wort a well a mass of the workiag eubctaacc croee tbe boundary of the rystem(d) neitb e het and *ork uor the mass of the worting sub3ts 6osr e bouudary of the system.Al iaolatcdeyutem(c) ir e rpcdfed region whee tranfer of eaergr aaor marr taLe place() lr r rrgio of cortt .re rtrd otdy euergr ie allowed to ooes t boundrig(c) c!d trrnrfrr citber energr or maas to or from the currmndingr(d) ir me iwhic,buaas withintlre rystenir not neceerarilycstrnt() none ofthe above,In an edeosivc pronrty ofa themodynarnic sysem

This equatioor is applicableto anynedium in anysteady f,ow.Clauius tetement:Tt is impossible for a serf-acting maLine working in a cyclic proeer, rmaidetl by e ent'lal agency, roconvey heat from a body at a lower tomperatur" to . t*iy

"t a ltr, tcopemtua.;

Kelvi-Planck tatement :tt is impoesible to coastruct au eogine, which wlile operating in a cycle producec no other e&ct exept toextract heet from a siagle resenroir and do equivalen:t amorit of woL.Although above statements ofecond-Iaw ofthermodynanics aprear to be difieeut, tley are rea'yequivalent in the sense tat violation of eitler stater*jt impliee violation of orer.Clausius inequality is givea by,

() one ofte above.Wbich ofthe followingir aointearive pmpertyof a themodmamicryrtam ?

Y r!e')k\r)

^a'

k*-*r-

26INTERNAL COMBUSTTON ENGINES

The tempenture t whic the volume of a gm becomes zero ie eed(c) absoldclcaleoftenperatue () absolutezemtempeatrre(c) absolulctoperature (d) none ofthe above.lhe value ofmo ba ( SI units) is equal to

BASIC CONCEPTS OF THERMODYNAMCS

21. Itre main cause ofthe irreversibity ie(a) mechmiol aod fl uid friction () urestricted erPani@(c) heat trafer wi a finite temperatue ilifrerence

'(d)alloftheaborre (c) noeofeabove.2a Acmrdingtokineceory ofheat

(d) tempentuo should rise drring boiling () tempenture should fa during freezing(c) at low temperatue all bodies are i sod state(d) at beolute *rc there is absolutely no vibration ofmoleol() none oftlre bove.

2& Asystm @mprising asinglephrue is called a(c) closedslBtm () opensystem (c) isoltdEstzm(d) homogeneous system (e) heterogeneoue sntern

2L If all thevariables of a stream are independent of time it is seid to be i(c) rniform flow

aa

L

10.

() lO0llrf(d) I x 1grqot

(d) -273'C(c) 237"C

l2 Which of thcfollordngis correct ?

() Joule ((c) Tttatt(W)Onewattircqual(c) lN/(d) 100Nn/bOe joule (is equl to(a) lNm(c) r0Nn/s

(c)lx10rN/m2

(b) 273C(d)

-373.C.

() Joule metre (Jn)(d) Jouldmete (Jt).

(c) l0N/s

() kNm(d) r0kNm/s.

() therrrodraanic cycte(d) thermodynamiclaw.() ineversiblecycle(d) none ofthe above.

() no loss ofheat(d) no gain ofheat

(a) steadYflow(d) dcedflow

25. Aconholvolumsrefrsto() afiedngioninspace(c) mioltedsystem(e) adedsyrten.

() aspecifiednass(d) a reversible pocess only

() temperature, specic heats and enthalpy(d) temperature onlY.

() the entropy remairo constilt(d) the intemal enersf remains coDstant

(b) rwesible and isothemal(d) revenible and adiabac

() newton's law ofviscosity be satisfied

() 1000N/m() I x 106N/mr.

lt.

T?re absolulG rero presure will be() whe mdecular monetum ofthe system becomes zero() atselenst(d) undervaomon'itios []1ff"Hffi1il:";fr*Absolute rceotempenture is taken ag

(c) Absoha preasure = 9r96 pressure + atmospheric pressue(b) Gaugr Fsue = absolute pressure + atmcpheric preesue(c) Atno4:ric peseun

= absolut prcssue + gauge pessue(d) Abaolo peasurs

= gpugs pessure _ atmospheric pessure.1& Theunitofcaergrinsluitsis

() unsteadylow() eonstatflow.

14

l

te

(c) thermodpamic tlrgtn(c) thenno{aamic proceee

(o) re*rsiblccycle(c) thennoQnamic crcle

19. fire conditionforthe wersibty of a cycle is

(a) loss ofhert(c) gain ofheat

The amouat of heat rquired t raise the temperatun of l kg of water trr,mgh r.c is carlod(o) specic beat at cooitant volure () epecifc heat at corstat prssure(c) kilo caluicfire heaingmd expandingof agaa is called

26, Internal energr ofa perfect gaa depeuds on(a) teryerature, specic heats and pressure(c) tenpeatue, spcifcheats.inalntroPy

Zr. Inrwersiblspolytopicprocese(a) trueheat hasfer ocsurs(c) t,he enthalpy remains comtant(e) thetmporaturereminr costant,

2& Anisenbopicprocecsiealwayr(a) iresersiblo nd adiabac(c) frictioless andineversible .() none ofthe above.

29. The net wort doae per kg ofgas in a polytropic process ie equal to

() f N/Din() lffiNrr/n

17.

l& t"lorl*-al\ v2)lT::If:.rn,whichtakeplaceinacertainord*"orot ""t"rO_"rO_*knowaas

(a)Prurb& fr@rry

30. Steady flow ocore when(o) conditius do s chnge with time at anypoint

' () cmalitimg are e sane at adjaceot poins at any instDt(c) onilition chage steadily with the time

fau\(d) I:J isconstaL81. A reversible process requires tlat

(c) there be o heat transfer

() pt (u1-u)

@)u#(c) t'he prcerure 'd temperature of the working substance Dust lot differ, apprciably, fiom those of thesumundiogr at aay stagein tlre process() alt e poceases, taking place in the cycle of operation, must be extremely slow(c) tlre wotbgparts of the engine nust be friction free(d) there shoold ba no lms ofenergy during the cycle ofoperation(e) allofthebove

a). Inairrwsibleproceas,thereisa (fl uoneoftheabove'

(c) tcnperature ofarsten and surmundings be equal(d) therc be no viscous or coloumb fiction in the system(e) heat transfer ocos from surrourdings to system only.

NTERNAL COMBUSTTON ENGINES3Z the first law of thermorlynamica for eteadyforr(o) accouts for all cnergrentering:andlcavingacontrol volune() is an eoergy balance for a :pecied ,.- iu(c) is an orpreaeion of the conevtio. of linea momeotum(d) is primaily concemed vith heat bafer.() i.restricted iD its applicatio to pede grs.s.u rne characteristic equatio of gasespV

= zrffl ho$s good for(o) monoatomicgases () rthtolricgs (c) nalgaaes(d) idealgaes (e) ni:tunofgsatl4 Agas which obeys kinetictlreoryp""f*tIyf"f"* ""

(c) monoatomicgas fal aatlcg - - (c) realgas(d) puegas (e) perfecg;85' Wok done in a free eryansiouproceer le(a) zero () -il*- (c) _"*m_o(d) positive (e) regrve.36. Whidr ofthefollowingis not apoprty oftGsrrtem ?(alremperatue () precurr

(d) Heat82. In-che polytropic procese equa;Ul"*.*r,

-" *:X::"fiiffin1!""*" ()coeh*pre

-'' (c)cm8t&rrodperahlrBB' Inthe polykopi" n"oor. *o"oJl*ffia ifn ir fufiaitely hrge, the process i8 ttr'd as(c) corutautvotrme d) otst ; (c) cortanttemperatura(d) aabatic () iotcol89; ?herocesses or aystens that do ot itvohc het re called(a)isotlernalpocesses ()qrdfoi;-; (c)rermalproceeses(d) steadyprocesses (a) adiabaticgooesses.4{L In a reverible adiabatic proceee tLe ntio ("rllr) eq".f t"

Y-l(") frl t /,.. \.-

\p2 ) () 11! | 1\rz )

BASTC CONCEPTS OF THERMODYNAMICS

d5. thsgtetgsfaeubetalcewhose wapontioofromitsquidetateiscompleta,islcnown as

tt6. I SI Eait, ths value oftle miwrsal Sas cotrstnt is(c) OtlSl4JbolelK(c) 83.1,1Jnole/K(e) 8314J/nollK

Wheo te gas i,o heated at constantpreraure,tbs heat nrrpedh) increases the iaterual eneqy dtbe gac () iiraeaes the temperature ofthe gas(c) ds sne *tmal work drring erpauim (d) both () and (c)(e) otr ofthe above-

48, The garconetot(.R)iseqdtoet(c) sum of two specifi c he(e) poduct of two spedfic list

d9 the hoat absorbed or rejected riag a polytropic procees ie

61. For reversible adiabatie prrceea, the ge h empy ir

() perfectgas(d) stan-

() E,314J/tole/K(d) 8illJ/noldl(

)() feence oftwo specifcheats(d) ntiroof tro specic hears.

(c) enthalpy

(q) ntmtn

(c) negtive

(c) negative

(o) valnur(c) h

() hat(d) entropy

(a) z*o(d) ifinito

(c) ero(d) neitive

() zero(d) inita

() worL(c) intrnaleer$.

() niinum(e) wity.

(b) rlaity(e) ifinite.

(b) pcitivs(e) uity.

fv -'\C) |.i:1J x work done ()

("-o\w", lijj x wortdone

(d)6lL Secoud lrr of thermodynamice rh6nes

[t+)'xworkdone(t:!r-J

'worldooe.

6A For aly reversible process, the ag in entropy ofthe system aad surroundingp is

6E For any inevmible prrcss the net ltmpy change i8

v-I(c) lula)fi.41. Inisothermalprocess

(o) adiabaticproess(d) frictionless process

1a [d'.\ut.i

() volume emains coDstent(d) enthalpy ctralg is marimum

() preesure doeo mt chaag?(d) eothalpy does not change

() tempeature inaeares gradually(c) presoure remaine costant(e) dange ia otenal enery is zero.

During throttling process(c) ioternal energr doee not chaage(c) entropy-doee ot change() volume chage ie negtigible.

when agas isto be stored, the type'ofcorpresaion tlat would be idear i() isotheimal () adiabac -(d) constnt voiums (e) noe of thc bove. (c) polytqic

Ift*::".S+ be.rroped at any stag aad rwersed so rhat trestord to teir inu"r-"Lt"i, iii, too*o ""

ly8t and surrouadirya are eractly

the rocesses of a Cauot cycle re(a) two adiabatic ad two mmtat volune() cre costent volume and one coDstast prrssswe and two iseotropics(c) two aabatics ad two isothemab (d) two costart volumes md two isothemals() two isotermals ad two isentrooics.

6& Isentropicf,owis(c) iraersible adiabatic flow (D) iileal f,uid flow (c) perfect gas flow(d) frictioless reversible llow (e) reversible adiabaticflow,

6d In a Carnot engine, when the working eubetane give heat to tle eik(c) tlre temperature of the sit inceasa (b) the temperature of the sink remains the same(c) the temperature of the or:ee decneacs(d) the temperaturea of both tbe giDt and the source decree(e) chaagns depend on the operating coaditions.irl i**,"rtn"tp"o""""

() energyless pocess.(c) idealprocess

I

:

't. .

30

67, If the temperatur of the source(a) decreaees(c) does not angu(e) depends on otler factore.

is iroeased the eficiency "

j:::" """'"usnoN

ENGINES

() inqeaca(d) rill be equal to the eficiency ofa practical engine

() conservation ofheat (c) cunervation ofmas(e) convesion ofwork into heat.

BASIC CONCEPTS OF THERMODYNAMICS

66. T.l:e entropynay be expresed s a fuction of(c) pressure and temperature(c) heat and work() noe ofthe above.

47. The mge of entropy, wheu heat is absorbed by the gas is(o) positive () negative (c) positive or negative,

60'

Which of the foowing statemeats i a comct ?() Tle icraase in entropy is obtained from a given quanty ofheat at a low tempeiature() The ange i etropy may be regarded as a measure of e rate of re availabilitr of heat for

transformation into wort(c) The enkopr represents the maximm amout of work obtainable per degree op in temperature(d) All ofthe above.The conon for the revenibtr of a cycle is() the pressure and tenperaturo ofworkin! substance mu6t not tlifrer, appreciably fmm tlose ofthe

surroundingr at any atage in the process() alltheproceset"lo.gplaceithecycleofoperaon,roustbeextremelyelow(c) the wortig parts of the engine must be friction fre(d) there should be no loss denergr during the cycle ofoperatioa(e) all ofthe above,I an irrwecible process ere ia a(a) loes ofhet(c) gain ofheat

The mai cauge for the irr,cversibilityir(o) mechical ad fluid frfutim(c) heat traDcfer with a fiite temperature diffeence(d) allofeabove.fire efcieosy of e Carnot rycle maybe iacreased by

5&

69.

The efficiency of a ideal Carnot engine dependa on(c) working substace ,.r_ ..- ^__(c) on the lemperature of the sint only

() on e temprature of the source onry(d) on the tenperahrres of bo e sorru and tle eint() o the constructio of engine.The effrciency ofa Carnot engine using an ideal gu aa the working eubetance is

6&

(a) increasige higheettgmperature(c) increasing the lowest tenxrature

() temperature and volune(d) all ofthe above

() no loss ofwork(d) no gai ofheat.

() unreshicted erpansion

() decreasiog the highest temperahre(d) decreaeing tlre lowest tsmprtur

b) rrlr,'1

@w *,ffi.()

(d) 0'K

TrTt-Tz

"rffi60. I. a reveraible cycle, the entropy

"f thj.;;(c) increases

(c) does not change

(c) equal to its input temporaturc ;

() leceae(d) first inaeares and ther decreueg

^_ . (e) depends on the pmrertiea ofworking eubstance61. A-frictionless heat engine can Ue fOO* emae* mly ifits erhaust temperature is 70.

(c) 0'Cd lGlvin-plac,elawtlealswitt

(c) conservation of energr(d) conversion ofheat into work

() leas lhn its input tempraho()

-100"C.

o H*f*efollowingstatementsiscorrectaccordingtoctawiusstatementofsecod"J;;L*,(c) rt is impossible to trasferhet from a body at a lmer teinperature to a body at a higher temperaturet"

*iilTf:*.1rfiT** m: * "i",.** "mperature to a body ar a higher remperarurc,"' ffifl:t*:*m"h""*,' abodvatalowertemperature toa bodyatahigherremperarureby(d) None of tle above.

6if, According to Kelvin-planclCs satement ofsecond law ofthermodynamicst'll,:,Hff;?:tocmshuctaneogirc'*"';;;";"*';;;i."or"o"r"eitoonverrhear*'

lt":rffi$"frco8buct an engie working on a cyc proceas, whoee sole purpose ia to covert the(c) It is impossible to constluct a device which while working in a cyclic process prod.uces no effect otherrhan the trasfe orruat run a coieiuy t"i-Irllii u""(d) whe two dissimilar metale ar-e heted at one end ad cooled at the other, the e,m.f. ateveloped isproportional to the diference ofteir tqrp;;;;the two erd"(e) None ofthe above.

*

3::"1iTTi*T,:"H:#bstaDce which iDcresres or decreases ar the heat is supped or removed i a

71.

72.

78.

L ()& ()

1&'(a)z. (d)n.kD88. (d)tl3. (c)EO (d)67. ()64 (e)7t. kL

2. (c)s (d)

tA (c)13. (d)Sl, ()87. ()it1, (c)6L (n)6& (d)6 (c)7z (d)

& (c)lo ()r7. ()!( ()EL (d)8& (c)aB.()6& ()S, (a)S. (s)?il. (c).

tL (e)ln. (o)1& (c)%.(a)8 (d)8& (){A (e)6& ()dt (c)87. (a)

()l& (o)lg. (e)n@)8& (c){ft, (o)4fl, @'L (a)8r. (d)8A (d)

6. ()18. (o)tL ()tl. (alSd ()L (e)ae (D)65. ()@"(d)69. ()

't, \@t14 (o)2t (d)a.@)86. (c)a^@){O ()6A ()0s. (b)7o' (o)

(e) keepinge lowest temrnture constanLTfhich of tbe following ie teorac statement ?(a) All tlre evereible engine have the same efficienc:/() AII the sersible and irrwewible eugines have re eame effcienry(c) Inwersible engines hqve n-im'n eficieary(d) Atl ergines are desigled as rcersitle in order to obtei. m-imrm.effisienoy.

(o) enthalpy(c) entropy () internal energy(d) erternal energr.

TNTERNAL COMBUSTION BhCINES

THEOR^ETICAL QI'ESTIONSDefine a thermodynanic syrten Difiereatiate between open srstr\ clced system nd a ieol,td sys-tem.How does a homogeneou rrrtendiffer fron a heterogeneous system ?What do you mean by a pure substonce ?Explin the following terms :( State, (it)Poces,and

l.

z,&tL

6.'1.

&9.

1(I

11.

tz13.t4

Erplain briefly zegth taw ofthernodyaaaies.Whatisaquasi-it[iprocei?" : -rI:.', ilWat do you tr byteveigttciotr ? " .."

' (i) Ceatrirgal water pump(iii) Steamnozzle

(i;i) 6!de.. :,' il:,i,.! n-i. t t ;-; l:,i1, :',: i.: ;. r t...

(tii) Recipmcating aircomprreeeor(iu) Steamtubine

Introduetion to Internal Cornbugton Engines

16.t7.1&19.

m.21,

a,B,?A2E%.yt.n

Defnelnternalenerg/an{p.rwetlatitisp-lprqgfatSlFtFr$i.:,,"i:.ri. ,,,!:; .;..,Explain the'FirstLaw ofllbegrodyaanics aereferr{-to_elosgil rrste.ns unttergoi{i ry .dit""g"

state the First Iw of fiermodynamics and prcve'tlat fora ob-flow process,.it leads to the onergrequationQ =AU+W.Wtat is the me.hanical equivalernt ofheat ? Write downits valuewhen heatis epresedinkl anilworkis expressed in N-m.What do you mean by ?erpeturl motion macline of first ldad.pMM l, ?Why only in mrotmt pressure n*.liw process, the athalpy ange is equal to heat ba*fa ?hove that the rate of drange ofheat interclarg peruit chaage of volume when gas ie conpressed orexpandedisgiven W#"#wri-te down thegeneralenerrgraqumforsteadyfloweystenandsinplifywh*.fitiat*"ton*iogsystems:

2.1. Heat eugines. 2.2. DEvelpiiidt,r;f tC.,erginasr 2.3, Classification of I.C. ")rro"".2.4. Appnci'ii?,IiG; iinbs.'2,5. Engine iycle-Energy balmce. 2.6. Basic idea of I.g.

engin6. 2.7:'Dlfiertrt'parti'bf I:C. engines.' 23. Terms connected with I.C. engis..2.9. Wortingcycles. 2.10. Incator diagram. 2.11. Four-troke cycle engines. 2.12. TWo stroke cycle engines.2.13. IntakE fdfompression'iga,ition engines. 2.14. Cornparison offour stoke aud two strokecycle eughe. 2.16. Cooparieol of epuk ignition (S.I.) mil conpression ign:ition (O.I.) enginea.2.16. Compuison between a petrol engiue and a dieeel elgine. 2.1?. How to tell wo strokecycle engine &om a fou atmke cycle engine ? Highlights--Objective tlpe Questious-theoretical Questione.

2.1. IIEAT ENGINESAny type of engine or machne which deriues heat energt from tle combuctian offuel or

any otlrcr source and. converts this energy ihto mechanal worh is termed. as a lrrltit engine.Het engines may be classifizd into two main classes as followe :1. Erternal Conbuson Engines.2. Intemal Combustion Egires,1. External combudlon

nglns (E.C. enginer)In thie case, combustion of fuel takee place outsi& tlu cylndcr as in cas of stedm engines

where the heat of combugtion is enrployed to generate eteam which is used to move a pieton in acylinder. Other examples of erteriial combustion engines are hot oir engines, steam turbine andelnsed cyck gas turbine. lheee engines are generally u6ed for driving locomotives, ships, genera-tion of electric porer tc,

2. Intnol combugtion englnes (I.C. enginee)In this case, combuston of th fuel with orygen of the ar occurs within the eylind,er of lhe

engine. the internal combustion eugines group includes enginea employing nixtures of combusti-ble gases aDd air, known as gas ergirrs, tho* uing lighter l4uid. fueJ or apirit known as pefroJengines and' thooe using heavier liquid fuels, known as oiL cornpressDn ignitian ot disel errgines.

(u) Gastwbine.Explain clearly the dilferencc between a non-flow and a steady flowprocesa.State the limitations of rst law of temodynamics,TVhat is the diftereoce betweeu a heat engine and a rtt8sd h.Ht bgiDe ?Enmerate the contiom whicl mut be fuIfied by a rerrerrible process. Givo soms.'qFros of idealrwersible procesees.What is an irrevenible proes ? Give some emple of,ineversible pmceasas.Give the following statemets of se6nd law of tlerodmamiee.(i) Clauiwstatemat(iD lGlvin-Planck statemnlDefne heat engine, rfrigrator and heat pump.What is the perpetual motion madine of the second kind ?What do you mean by'Ttrermodynamic temrrature'?

.

'What do you mean by'Claueiue inequality' ?Describe tlre working ofa Caot cycle. 1Derive an erpressioa for the e6eienry oftle rversible heat eagine.What do you mean by the term'htropy' ?

l. i..

INTERNAL COMBUSTION ENCINES

The detailed classifcation ofheat engines is given in Fig. 2.1.

NTRODUCTION TO INTERNAL COMBUSTTON ENGINES 35

1. Starting torque is generally high'2. Because of externaicombustion of fuel, cheaper fuels

can be used. Even solid fuels can be

used advantageouslY'3. Due to externat combustion of fuel it is possible to have flexibility

in arrangement'

4.Theseunitsareself.etartingwiththeworkingfluiilwhereasincaseofinternalcombus.tion engines, *_;;;i;;"'J equipment o. d--".ri"" is used for starting the

engines.

2.2. DEVELOPMENT OF I.C' ENGINES

Brief early bistory of dweloprneot of I'C' engines is as follows :

a Many clifferent styles ofinternal combustion engines were built and tested during the

seond half of the 19th century'o The frst fairly practical engine was invented bv J'J'E' Lenoir which

apeared on the

scene about 1g60. During the next ilecade, r"i"J.iu""a*d ofthese engines were built

with power "p".J;5 tw

t" mechanical efEciencv upto 6%'

eTlreotto.LangenenSinewith.efficiencyimprovedtoaboutll%wasfistinroducedin186? antl eeveral thousands ofthese wee pto""" during

the next decade' This was a

typeofatmosple;;;st""withthepowrstrokepropelledbyatmosphericpressureacing against a vacuum'Although nrany people were working on four-stroke cycle design'

Otto was given credit

;-h"; hj; prototvpe engine was built in 1876'In the 1880s, the internal combustion engioee frrst apoeared

in automobiles' Also in

this decade the twostroke;;;"; ;"""t" ptttiiol and was manufactured in

Porcr FodwingI Ootstrityh.atngir)I r----I Air RotrlgEntoBI onPresr lptpumpg

lntemel @mbGli$ Ar rnoloc ExlsrBl combGti$

ReiprocEtngtype Ryltpc Ffrip|utingtlPelllI G&tB R*ip|wtng slam onglno

r-------t-----rspa;kigniim Compsskiiffie smpl compound Uniflou/--i-i"""""1rt(

Petrol (and GaE srriEk@no) trgire an9m3 -l

, wh. Nr Ytor

Rolary t}!

St3cmn dim

tlFaifdfril AJdal

coolod @ddl*_I- | .l,I

z-stbt

@(i) Single cylinder

INTERNAL COMBUSTTON ENGINES(iii) Dual-combustion or semi-Dieser cycle engine (combustion partry at conetant vorumeand partly at constant pressure).3. According to rirangement of cylinder : Refer Fig. 2.2.

INTRODUCTION TO INTERNAL COMBUSTION ENqINTJS

(du) OPPoeed qYlinder "gio"o Two banls of rylin

INTERNAL COMBUSTION ENGTNES10. According to number of cylindere :(i) Singleeylider engiae (ij) Multi_cylinder engine.11. Accordilg to eir intake pocess :(i) Natumlly espirdd. No intake air pressure boost system.

..rro"f']rf't-arged' IntLe air pressure increased with the compnessor driven off the engine

""rr"J':']#ilur#:n Inake air pressure increased wirh the rurbine-compressor driven by rhe

.

(iu) crankw --p3ar: stroke-cycrg engine which uses the crakcase as he intakear compressor' Limited dev.elopment work has alsoten done on the design and construction offour-stroke cycle engines utb L"rr.."""-;"il#;J

12. According to fuel employed :0) Oil egine () petrol engine(iii) Gas cngrne (du) Kerosene engine(u) LPG engiue (ui) Alcohol_ethyl, methyl engine(uii) Duel fuel eogine (ui) ess6.1 (90% gasoline and LY%alcohol).

18, Method or st input for S.L engines :( Carbuettcd,( Multtptint ptt fwl i4iection one or more iqiectors at each cyliniter intake.(iii) l7s. bdy ftul i4j*tior" Iqiectors

"n"" in itake nnifold.2.4. APPLICATION OF I.C. ENCII\ES

The LC. engines are generally used for :(i) Road vicles (e, scooter, rnotorcycle, buses etc.)(ii) Aircraft(jdi) Ioconotives(du) c*r**oo in civil engineering equipmont such as bull-doze, scraper, power shwels(u) Pumping sets

(ui) Cinemas(ud) Hospital

(udi) $everal industrial applications.T\e applintbns of varbus englws separately are listed below :L. SmdI ro-gtroke petrol engines :t

f;;:mTr##T:::t* vthre simpticity and. the tsw cost of the prime ,,over aret

ff :3 :i ##: develops maximum braie power (8.p. or t.o kw at 5000 r.p.m. ando The 10o c'c' engine developing maximun brake power ofabout 3 kw a b000 r.p.rr. isused' n xooters' The 150 c.c.-e"ct"; J;;;;;'m"*imo- brake power of about 6 kwat 5000 r.p.m.o The 250 c'c' engine developing a maximum brake power of about g kw at 4500 r.p.m.is genera\r used in motor cycles,

INTRoDUCTION To INTERNAL coMBUsToN ENGINES 39o These engines also find applications in very small electric generating sets, pumping

setg etc.

2. Smsll