Thermal Engineering - 1

774 Pages·015.462 MB·English

by  Ramachandran S

THERMAL
ENGINEERING - I
(For B.E./B.Tech., Mechanical Engineering Students)
(As per New Syllabus of Leading Universities)

Dr. S.Ramachandran, M.E., Ph.D.,
Professor and Research Head
Dr. A. Anderson, M.E., Ph.D.,
Asst. Professor
Faculty of Mechanical Engineering
Sathyabama University
Jeppiaar Nagar
Chennai - 600 119
AIR WALK PUBLICATIONS
(Near All India Radio)
80, Karneeshwarar Koil Street
Mylapore, Chennai - 600 004.
Ph.: 2466 1909, 94440 81904
Email: [email protected],
[email protected]
www.airwalkpublications.com
First Edition: 2nd Feb 2016
ISBN :978-93-84893-66-8
SYLLABUS
Thermal Engineering - I
Chapter 1: I.C. ENGINES
Four & Two stroke engine - SI & CI engines - Valve and Port
Timing Diagrams - Fuel injection Systems for SI engines - Fuel
injection systems for CI engines- Ignition - Cooling and Lubrication
system - Fuel properties and Combustion Stoichiometry.
Chapter 2: Combustion in SI and CI Engine
Combustion in SI and CI Engine: Normal combustion and
abnormal combustion in SI Engine - Importance of flame speed and
effect of engine variables - Abnormal combustion - Pre Ignition and
Knocking in SI Engine - Fuel requirement and fuel rating - anti
knock additives - combustion chamber - Requirement - types of SI
Engine - Four stages of combustion in CI Engine - Delay period and
its Importance - Effect of engine variables - Diesel knock - Need for
air movement, suction, compression and combustion induced
turbulence in Diesel engine - Open and divided combustion chambers
and fuel Injection - Diesel fuel requirements and fuel rating.
Chapter 3: Testing and Performance of Engines
Indicator diagram and properties - Pressure Transducer- Brake
power measurements. Dynamometers - Performance calculations
-Morse test - Air consumption - Fuel consumption Exhaust gas
compositon - Heat balance sheet.
Chapter 4: Air Compressors
Classification of Compressors - Fans, blowers and compressors
- Positive displacement and dynamic types - Reciprocating and rotary
types
Rotary, Dynamic and Axial Flow (Positive Displacement type):
Roots Blower, Vane sealed compressor, Lysholm compressor -
mechanical details and principle of working - efficiency considerations.
Centrifugal compressors: Mechanical details and principle of
operation - Velocity and pressure variation. Energy transfer - impeller
blade shape - losses - slip factor, power input factor, pressure
coefficient and adiabatic coefficient - velocity diagrams - power.
Axial flow compressors: Mechanical details and principle of
operation - velocity triangles and energy transfer per stage, degree
of reaction, work done factor - Isentropic efficiency - pressure rise
calculation - polytropic efficiency.
Chapter 5: Refrigeration
Mechanical Refrigeration and types - Units - Air refrigeration
system, Details, Principle of operations application - Vapour
compression refrigeration - Calculation of COP - Effect of super
heating and sub cooling - Desired properties of refrigerants and
Common refrigerants - Vapour absorption system - Mechanical
Details, Working and Principle - Use of p-h chart for calculation.
Chapter 6: Actual Cycles and their Analysis
Introduction, Comparison of air standard and actual cycles,
Time loss factor, Heat loss factor, Exhaust Blowdown - Loss due to
Gas exchange processes, Volumetric efficiency. Loss due to Rubbing
friction, Actual and fuel - air cycles of CI engine.
Contents C.1
Contents
1. I.C. ENGINES
1.1 Introduction...................................................................... 1.1
1.2 Basic Terms Connected With I.C. Engines................. 1.1
1.3 Four Stroke SI (Petrol) Engine..................................... 1.4
1.4 Four Stroke CI Engine................................................... 1.6
1.5 Working of Two Stroke Cycle Engine.......................... 1.9
1.6 Working of Two Stroke Petrol Engine......................... 1.10
1.7 Classification of IC Engines........................................... 1.12
1.8 IC Engine Components – Functions And Materials.. 1.13
1.9 Valve Timing And Port Timing Diagrams................... 1.24
1.9.1 Valve Timing Diagram for a 4-Stroke Cycle
Petrol Engine.................................................................. 1.26
1.9.2 Valve Timing Diagram of 4-Stroke Diesel
Engine............................................................................ 1.29
1.9.3 Port Timing Diagram of Two Stroke Cycle
Petrol Engine.................................................................. 1.29
1.9.4 Port timing Diagram for Two Stroke Cycle
Diesel Engine................................................................. 1.32
1.10 Fuel Supply System...................................................... 1.34
1.10.1 Fuel injection Systems for S.I. Engines.......... 1.34
1.10.2 Different types of Fuel Systems....................... 1.35
1.10.3 Fuel Injection System In SI Engines.............. 1.36
1.10.4 Fuel Pump (for S.I. Engine)............................ 1.36
1.11 Carburetor...................................................................... 1.37
1.12 Air Fuel Ratio ............................................................... 1.40
1.13 Various Compensation In Carburetors....................... 1.40
1.14 Types of Carburetors..................................................... 1.43
1.15 Fuel Injection Systems For C.I Engines.................... 1.53
1.15.1 Fuel Pump (C.I. Engine).................................. 1.53
1.16 Fuel Injection System................................................... 1.55
C.2 Thermal Engineering - I
1.16.1 Fuel Injector....................................................... 1.56
1.17 Ignition Systems............................................................ 1.57
1.17.1 Spark Plug......................................................... 1.57
1.17.2 Types of Electronic ignition systems:.............. 1.65
1.18 Lubrication System........................................................ 1.69
1.18.1 Purpose of Lubrication...................................... 1.69
1.18.2 Systems of Lubrication...................................... 1.70
1.19 Cooling System............................................................... 1.73
1.19.1 Purpose of Cooling............................................. 1.73
1.19.2 Methods of Cooling IC Engine......................... 1.74
1.20 Fuels And Combustion.................................................. 1.77
1.20.1 Introduction........................................................ 1.77
1.20.2 Classification of fuels:....................................... 1.78
1.21 Solid Fuels ..................................................................... 1.79
1.22 Gaseous Fuels: ............................................................... 1.80
1.23 Fuel Properties............................................................... 1.81
1.23.1 Determination of Calorific value of fuel by
Bomb Calorimeter.......................................................... 1.83
1.23.2 Determination of Higher Calorific value of
Gaseous fuel................................................................... 1.85
1.24 Combustion Stoichiometry............................................ 1.88
1.25 Excess Air And Air Fuel Ratio Calculation.............. 1.95
2. Combustion in SI and CI Engine
2.1 Normal Combustion......................................................... 2.1
2.1.1 Factors affecting normal combustion in S.I
Engines........................................................................... 2.3
2.1.2 Flame Front Propagation.................................... 2.4
2.3 Importance of Flame Speed And Effect of Engine
Variables................................................................................. 2.5
2.3.1 Factors affecting flame speed............................. 2.5
2.2 Abnormal Combustion..................................................... 2.8
2.2.1 Pre-ignition...........................................................
Contents C.3
2.8
2.2.2 Knocking (or) Detonation (or) Pinking.............. 2.9
2.2.3 The phenomenon of knock in SI Engine.......... 2.10
2.2.4 Effects of knocking in SI Engine...................... 2.13
2.2.5 Effect of engine variables on knock.................. 2.14
2.3 Fuel Requirement And Fuel Rating............................. 2.18
2.3.1 Important properties of fuel in SI Engine....... 2.18
2.3.2 Important characteristics of SI Engine fuel..... 2.18
2.3.5 Octane Number (ON).......................................... 2.21
2.4 Anti-Knock Additives....................................................... 2.23
2.4.1 Anti-knock Agents................................................ 2.23
2.4.2 Effects of Anti knock additives.......................... 2.24
2.4.3 Factors affecting Detonation and Remedies..... 2.25
2.5 Types of Combustion Chamber In SI Engine............. 2.26
1. Overhead valve (or) I - Head combustion
chamber.......................................................................... 2.26
2. T-Head combustion chamber................................... 2.27
3. L-head combustion chamber.................................... 2.27
4. F-head combustion chamber.................................... 2.28
2.6 Combustion in CI Engines............................................. 2.28
1. Ignition Delay period............................................... 2.29
2. Period of Rapid Combustion (or) Uncontrolled
Combustion..................................................................... 2.32
2.7 Factors That Affect Delay Period In Diesel Engine.. 2.32
2.7.1 Effect of variables on the Delay period............ 2.34
2.8 Knocking (or) Diesel Knock............................................ 2.35
2.8.1 The phenomenon of knock in CI engine........... 2.36
2.8.2 Comparison of knock on SI and CI Engines.. 2.38
2.8.3 Characteristics Tending to Reduce Detonation 2.40
2.9 Need For Air Movement In Diesel Engine.................. 2.40
2.10 Combustion Chamber Design For Compression
Ignition Engine...................................................................... 2.42
C.4 Thermal Engineering - I
1. Open combustion chamber....................................... 2.42
(a) Shallow depth chamber.......................................... 2.43
(b) Hemispherical chamber........................................... 2.43
(c) Cylindrical chamber................................................ 2.43
(d) Toroidal chamber.................................................... 2.43
2. Divided combustion chamber type.......................... 2.45
(a) Turbulent combustion chamber............................. 2.45
(b) Pre combustion chamber......................................... 2.46
(c) Energy-cell chamber................................................. 2.47
2.11 Diesel Fuel Requirement : For Compression
Ignition Engines ..................................................................... 2.50
1. Knocking characteristics........................................... 2.50
2. Volatility of the fuel................................................. 2.51
3. Starting characteristics of the fuel......................... 2.51
4. Smoke produced by fuel and its odour................. 2.51
5. Viscosity of fuel......................................................... 2.51
6. Corrosion and wear.................................................. 2.51
7. Easy to handle.......................................................... 2.51
2.11.1 Cetane Number (CN)......................................... 2.52
2.11.2 Fuel Rating for CI Engine............................... 2.52
3. Testing and Performance of Engines
3.1 Performance Calculations (or) Performance Test On
I.C. Engines............................................................................ 3.1
1. Indicator Diagram.................................................... 3.1
2. Indicated Power (IP)................................................ 3.2
3. Mean Effective Pressure Pm.................................. 3.2
5. Brake Power (BP)..................................................... 3.6
6. Different Arrangements used to find Brake
Power.............................................................................. 3.6
7. Friction Power (FP).................................................. 3.9
8. Specific Fuel Consumption (S.F.C)......................... 3.9
9. Mechanical Efficiency mech.................................. 3.10
Contents C.5
10. Thermal Efficiency.................................................. 3.10
11. Indicated Thermal Efficiency indicated.............. 3.10
12. Brake Thermal Efficiency Brake........................ 3.11
12. Relative Efficiency or Efficiency Ratio................. 3.11
14. Volumetric Efficiency volumetric........................ 3.11
3.2 Dynamometer................................................................... 3.12
3.2.1 Hydraulic Dynamometer..................................... 3.13
3.2.2 Eddy Current Dynamometer............................... 3.15
3.3 Measurement of Indicated Power of Multicylinder
Engine Morse Test................................................................ 3.21
3.4 Measurement of Air Consumption................................ 3.31
3.5 Fuel Consumption ........................................................... 3.34
3.5.1 Volumetric type.................................................... 3.35
3.5.1.1 Burette method.................................................. 3.35
3.5.1.2 Automatic volumetric flow meter.................... 3.37
.........................................................................................
3.5.2 Gravimetric fuel flow measurement................... 3.38
Construction.................................................................... 3.39
3.5.3 Measurement of Heat Carried Away by
Cooling Water................................................................. 3.40
3.6 Exhaust Gas Composition............................................... 3.41
3.6.1 Oxides of Nitrogen............................................... 3.41
3.6.2 Carbon monoxide (CO)........................................ 3.43
3.6.3 Unburnt hydrocarbons......................................... 3.45
3.6.4 Aldehydes.............................................................. 3.47
3.7 Visible Emissions............................................................ 3.47
3.7.1 Smoke.................................................................... 3.47
3.7.1.1 Comparison method.......................................... 3.47
3.7.1.2 Obscuration method.......................................... 3.48
3.7.2 Measurement of Heat Carried Away by
Exhaust Gas................................................................... 3.52
3.8 Heat Balance Sheet......................................................... 3.52
C.6 Thermal Engineering - I
Solved Problems........................................................3....5..3-3.96
4. Air Compressors
4.1 Introduction...................................................................... 4.1
4.2 Classification of Air Compressors.................................. 4.2
4.3 Single Acting Reciprocating Air Compressor............... 4.3
4.4 Double Acting Air Compressor...................................... 4.4
4.5 Single Stage Compressor................................................ 4.4
4.6 Multi Stage Compressor................................................. 4.5
4.7 Working Principle of Reciprocating Air Compressors 4.5
4.7.1 Workdone during isothermal compression
PV  c without clearance volume............................... 4.7
4.7.2 Workdone during polytropic compression
[ PVn  constant ] without clearance volume.............. 4.8
4.7.3 Workdone During Isentropic Compression
PV  constant Without Clearance Volume............... 4.10
4.8 Minimum Workdone........................................................ 4.11
4.9 Power Required To Run The Compressor................... 4.11
Solved Problems........................................................4....1..2-4.15
4.9.1 Clearance Volume................................................ 4.16
4.10 Workdone By Reciprocating Air Compressor With
Clearance Volume.................................................................. 4.16
4.11 Isothermal Efficiency of A Reciprocating Air
Compressor.............................................................................. 4.18
4.12 Volumetric Efficiency in A Reciprocating Air
Compressor.............................................................................. 4.18
4.12.1 Factors affecting volumetric efficiencies.......... 4.20
4.13 Important Technical Terms.......................................... 4.20
1. Volumetric Efficiency vol........................................ 4.20
2. Clearance Ratio ‘k’.................................................... 4.21
3. Volume and Volume Rate........................................ 4.21
4. Indicated Power (I.P) and Brake Power (B.P)..... 4.22