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`Page 1 of 237
`Page 1 of 237
`
`
`
`INTERNAL
`
`C01VIBUSTION
`
`ENGINE
`
`
`
`FUNDAMENTALS
`
`John B. Heywood
`
`Professor of Mechanical Engineering
`
`Director, Sloan Automotive Laboratory
`Massachusetts Institute of Technology
`
`McGraw—Hill, Inc.
`New York St. Louis San Francisco Auckland Bogoté
`Caracas Lisbon London Madrid Mexico City Milan
`' Montreal New Delhi San Juan Singapore
`Sydney Tokyo Toronto
`FORD 1109
`FORD 1109
`FMC 1011
`
`Page 1 of 237
`
`

`

`INTERNAL COMBUSTION ENGINE FUNDANIENTALS
`
`This book was set in Times Roman.
`
`The editors were Anne Duffy and John M. Morriss; the designer
`was Joan E. O‘Connor; the production supervisor was
`Denise L. Puryear. New drawings were done by ANCO.
`Project Supervision was done by Santype International Ltd.
`R. R. Donnelley & Sons Company was printer and binder.
`
`See acknowledgements on page and.
`
`Copyright ('9) 1988 by MeGraw-Hill, Inc. All rights reserved.
`Printed in the United States of America. Except as permitted under the
`United States Copyright Act of1976, no part of this publication may be
`reproduced or distributed in any Form or by any means, or stored in a data
`base or retrieval system, without the prior written permission
`of the publisher.
`
`25262728DOC/D()C1098765432l
`
`ISBN: 978-0-07-028637-5
`MHID: 0-07-028637~X
`
`Library of Congress Cataloging-in-Puhlicnfion Data
`
`Heywood, John B.
`Internal combustion engine fundamentals.
`
`(MeGraw-I—Iill series in mechanical engineering)
`BibliOgraphy: p.
`Includes index.
`1. Internal combustion engines.
`TJ'iSSJHS 1933
`621.43
`
`I. Title.
`87-15251
`
`II. Series.
`
`This book is printed on acid-free paper.
`
`!
`
`
`
`
`
`Page 2 of 237
`;e 2 of 237
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`Page 2 of 237
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`FORD 1109
`FORD 1109
`FMC 1011
`
`

`

`
`
`
`
`CONTENTS
`
`Preface
`
`Commonly Used Symbols, Subscripts, and
`Abbreviations
`
`Chapter 1 Engine Types and Their Operation
`
`1.1
`1.2
`1.3
`1.4
`1.5
`1.6
`1.?
`1.8
`1.9
`
`Introduction and Historical Perspective
`Engine ClassificatiOns
`Engine Operating Cycles
`Engine Components
`Spark-Ignition Engine Operation
`Examples of Spark-Ignition Engines
`CompreSsion-Ignition Engine Operation
`Examples of Diesel Engines
`Stratified~Charge Engines
`
`'
`
`_
`
`Chapter 2 Engine Design and Operating Parameters
`
`15,
`
`2.]
`2.2
`2.3
`2.4
`2.5
`2.6
`2.7
`
`2.8
`2.9
`
`Important Engine Characteristics
`Geometrical Preperties of Reciprocating Engines
`Brake Torque and Power
`Indicated Work Per Cycle
`Mechanical Efficiency
`Road-Load Power
`Mean Effective Pressure
`
`Specific Fuel Consumption and Efficiency
`Air/Fuel and Fuel/Air Ratios
`
`page 3 of 237
`Page 3 of 237
`
`Page 3 of 237
`
`xvii
`
`xxiii
`
`1
`
`I
`7
`9
`12
`15
`19
`25
`31
`37
`
`42
`
`42
`43
`45-
`46
`48
`49‘
`50
`
`51
`53
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`FORD 1109
`FMC 1011
`
`

`

`X
`
`CONTENTS
`
`2.10 Volumetric Efficiency
`
`2.11
`2.12
`2.13
`2.14
`2.15
`
`Engine Specific Weight and Specific Volume
`Correction Factors for Power and Volumetric Efficiency
`Specific Emissions and Emissions Index
`Relationships between Performance Parameters
`Engine Design and Performance Data
`
`'
`
`Chapter 3 Thermochemistry of Fuel-Air Mixtures
`
`3.1
`3.2
`3.3
`3.4
`3.5
`
`3.6
`
`3.7
`
`Characterization of Flames
`Ideal Gas Model
`Composition of Air and Fuels
`Combustion Stoichiometry
`The First Law ”of Thermodynamics and Combustion.
`3.5.1 Energy and Enthalpy Balances
`3.5.2 Enthalpies of Formation
`3.5.3 Heating Values
`3.5.4 Adiabatic Combustion Processes
`3.5.5 Combustion Efficiency of an Internal Combustion Engine
`The Second Law of Thermodynamics Applied to Combustion
`
`3.6.1 Entropy
`3.6.2 Maximum Work from an Internal Combustion
`
`Engine and Efiiciency
`Chemically Reacting Gas Mixtures
`3.7.1 Chemical Equilibrium
`3.7.2 Chemical Reaction Rates
`
`Chapter 4 Properties of Working Fluids
`4.1
`Introduction
`
`
`
`
`
`Page 4 of 237
`
`4.2
`4.3
`4.4
`4.5
`
`4.6
`4.7
`
`' 4.8
`4.9
`
`53
`
`54
`54
`56
`56
`57
`
`62
`
`62
`64
`64
`68
`'72
`72
`76
`78
`30
`81
`83
`
`83
`
`83
`85
`86
`92
`
`100
`100
`
`102
`107
`109
`112
`112
`
`116
`
`123
`
`127
`130
`130
`135
`
`141
`145
`145
`
`143
`
`Unburned Mixture Composition
`Gas PrOperty Relationships
`A Simple Analytic Ideal Gas Model
`Thermodynamic Charts
`4.5.1 Unburned Mixture Charts
`
`4.5.2 Burned Mixture Charts
`
`_
`
`-
`
`4.5.3 Relation between Unburned and Burned
`Mixture Charts
`
`Tables of Properties and Composition
`Computer Routines for Property and Composition Calculations
`4.7.1 Unburned Mixtures
`4.7.2 Burned Mixtures
`
`Transport Properties
`Exhaust Gas Composition
`4.9.1
`Species Concentration Data
`4.9.2 Equivalence Ratio Determination from Exhaust
`Gas Constituents
`
`4.9.3 Effects of Fuel/Air Ratio Nonunil'ormity
`4.9.4 Combustion Inefliciency
`
`Page 4 of 237
`
`152
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`15
`
`11
`
`15
`
`15
`
`13
`
`14
`
`Chapter 7 SI Engine Fuel Metering and Manifold
`Phenomena
`Sparkwlgnition Engine Mixture Requirements
`Carburetors
`
`7.1
`7.2
`
`:--
`I
`Page 5 of 237
`Page 5 of 237
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`Page 5 of 237
`
`CONTENTS
`
`xi
`
`Chapter 5
`5.1
`
`Ideal Models of Engine Cycles
`Introduction
`
`5,2
`5,3
`5.4
`
`Ideal Models of Engine Processes
`Thermodynamic Relations for Engine Processes
`Cycle Analysis with Ideal Gas Working Fluid With Cu and e,
`Constant
`'
`
`5.4.1 ConstantuVolunle Cycle
`5.4.2 Limited- and Constant-Pressure Cycles
`5.4.3 Cycle Comparison
`Fuel—Air Cycle Analysis
`5.5.1
`SI Engine Cycle Simulation
`5.5.2
`(:1 Engine Cycle Simulation
`5.5.3 Results of Cycle Calculations
`Overexpanded Engine Cycles
`Availability Analysis of Engine Processes
`5.7.1 Availability Relationships
`5.7.2 Entropy Changes in Ideal Cycles
`5.7.3 Availability Analysis of Ideal Cycles
`5.7.4 Effect of Equivalence Ratio
`Comparison with Real Engine Cycles
`
`5.5
`
`5.6
`5.?
`
`5.8
`
`6.3
`
`6.4
`6.5
`6.6
`
`Chapter 6 Gas Exchange Processes
`6.1
`Inlet and Exhaust Processes in the Four-Stroke Cycle
`6.2
`Volumetric Efficiency
`6.2.1 Quasi-Static Effects
`6.2.2 Combined Quasi-Static and Dynamic Efl'ects
`6.2.3 Variation with Speed, and Valve Area, Lift, and Timing
`Flow Through Valves
`6.3.1. Poppet Valve Geometry and Timing
`6.3.2 - Flow Rate and Discharge Coefficients
`Residual Gas Fraction
`Exhaust Gas Flow Rate and Temperature Variation
`Scavenging in TwoLStroke Cycle Engines
`6.6.1 Twc~Stroke Engine Configurations
`6.6.2 Scavenging Parameters and Models
`6.6.3 Actual Scavenging Processes
`Flow Through Ports
`Supercharging and Turbocharging
`6.8.1 MEthods of Power Boosting
`6.8.2 Basic Relationships
`6.8.3 Compressors
`5.3.4 Turbines
`6.8.5 Wave-Compression Devices
`
`6.7
`6.3
`
`161
`151
`
`162
`164
`
`169
`
`169
`172
`173
`177
`173
`130
`181
`183
`186
`136
`133
`189
`192
`193
`
`205
`206
`209
`209
`212
`216
`220
`220
`225
`230
`231
`235
`235
`237
`240
`245
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`248
`249
`255
`363
`2‘70
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`Page 6 of 237
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`CONTENTS
`
`7.3
`
`7.4
`7.5
`7.6
`
`7.2.1 Carburetor Fundamentals
`
`7.2.2 Modern Carburetor Design
`Fuel-Injection Systems
`7.3.1 Multipoint Port Injection
`7.3.2 Single-Point Throttle-Body Injection
`Feedback Systems
`Flow Past Throttle Plate
`Flow in Intake Manifolds
`7.6.1 Design Requirements
`7.6.2 Air-Flow Phenomena
`7.5.3 Fuel-Flow Phenomena
`
`Chapter 8 Charge Motion within the Cylinder
`3.1
`Intake Jet Flow
`
`8.2
`
`8.3
`
`8.4
`8.5
`8.6
`8.7
`
`Mean Velocity and Turbulence Characteristics
`8.2.1 Definitions
`
`8.2.2 Application to Engine Velocity Data
`Swirl
`
`8.3.1
`
`Swirl Measurement
`
`8.3.2 Swirl Generation during Induction
`8.3.3
`Swirl Modification within the Cylinder
`Squish
`Prechamber Engine Flows
`I
`Crevice Flows and Blowby
`Flows Generated by Piston—Cylinder Wall Interaction
`
`Chapter 9 Combustion in Spark-Ignition Engines
`9.1
`Essential Features of Process
`
`9.2
`
`Thermodynamic Analysis of SI Engine Combustion
`9.2.1 Burned and Unburned Mixture States
`
`9.2.2 Anaiysis of Cylinder Pressure Data
`9.2.3 Combustion Process Characterization
`
`9.3
`
`9.4
`
`9.5
`
`9.6
`
`Flame Structure and Speed
`9.3.]. Experimental Observations
`9.3.2 Flame Structure
`
`9.3.3 Laminar Burning Speeds
`9.3.4 Flame Propagation Relations
`Cyclic Variations in Combustion, Partial Burning, and Misfire
`9.4.1 Observations and Definitions '
`
`9.4.2 Causes of Cycle-by-Cycle and Cylinder-to—Cylinder
`Variations
`
`9.4.3 Partial Burning, Misfire, and Engine Stability
`
`Spark Ignition
`9.5.1
`Ignition Fundamentals
`9.5.2 Conventional Ignition Systems
`9.5.3 Alternative Ignition Approaches
`Abnormal Combustion: Knock and Surface Ignition
`9.6.1 Description of Phenomena
`
`Page 6 of 237
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`285
`294
`294
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`301
`304
`308
`303
`309
`314
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`326
`326
`
`330
`330
`
`336
`342
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`343
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`345
`349
`353
`357
`360
`365
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`371
`371
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`376
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`390
`390
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`FMC 1011
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`'Warrm'ew1“(weewe-'enmars-cwm~rmwmfim>aWursnwmvwrnemswwwarm...
`
`
`
`9.6.2 Knock Fundamentals
`9.6.3 Fuel Factors
`
`CONTENTS
`
`xiii
`
`457
`I 470
`
`Chapter 10
`10.1
`10.2
`
`10.3
`
`10.4
`
`10.5
`
`10.6
`
`10.7
`
`Combustion in Compression-Ignition Engines
`Essential Features of Process
`Types of Diesel Combustion Systems
`10.2.1 Direct-Injection Systems
`10.2.2
`Indirecthnjeetion Systems
`10.2.3 Comparison of Different Combustion Systems
`Phenomenological Model of Compression-Ignition Engine
`Combustion
`10.3.1 Photographic Studies of Engine Combustion
`10.3.2 Combustion in Direct-Injection, Multispray Systems
`10.3.3 Application of Model to Other Combustion Systems
`Analysis of Cylinder Pressure Data
`10.4.1 Combustion Efficiency
`10.4.2 Direct~Injection Engines
`10.4.3
`Indirect-Injection Engines
`Fuel Spray Behavior
`10.5.1
`Fuel Injection
`
`10.5.2 Overall Spray Structure
`10.5.3 Atomization
`10.5.4 Spray Penetration
`10.5.5 Droplet Size Distribution
`10.5.6 Spray Evaporation
`Ignition Delay
`10.6.] Definition and Discussion
`
`10.6.2 Fuel Ignition Quality
`10.6.3 Autoignition Fundamentals
`10.6.4 Physical Factors Affecting Delay
`10.6.5 Effect of Fuel Properties
`10.6.6 Correlations for Ignition Delay in Engines
`Mixing-Controlled Combustion
`10.7.1 Background
`10.7.2 Spray and Flame Structure
`10.7.3 Fuel-Air Mixing and Burning Rates
`
`Chapter 11
`11.1
`11.2
`
`Pollutant Formation and Control
`
`Nature and Extent of Problem
`
`Nitrogen Oxides
`11.2.1 Kinetics of NO Formation
`
`491
`491
`493
`493
`494
`495
`
`497
`497
`503
`506
`508
`509
`509
`514
`517
`517
`
`522
`525
`529
`532
`535
`539
`539
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`541
`542
`546
`550
`553
`555
`555
`555
`558
`
`567
`
`567
`
`572
`572
`
`11.3
`11.4
`
`11.2.2 Formation of N02
`11.2.3 NO Formation in Spark-Ignition Engines
`11.2.4 NO: Formation in Compressiomlgnitiqn Engines
`Carbon Monoxide
`Unburned Hydrocarbon Emissions
`1 1.4.1 Background
`11.4.2 Flame Quenching and Oxidation Fundamentals
`
`Page 7 of 237
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`586
`592
`596
`596
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`7 of 237
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`AUGWQHHH‘O
`
`

`

`xiv
`
`CONTENTS
`
`11.5
`
`11.6
`
`11.4.3 HC Emissions from Spark-Ignition Engines
`11.4.4 Hydrocarbon Emission Mechanisms in Diesel Engines
`Particulate Emissions
`11.5.1 Spark-Ignition Engine Particulates
`11.5.2 Characteristics of Diesel Particulates
`1 1.5.3 Particulate Distribution within the Cylinder
`11.5.4 Soot Formation Fundamentals
`11.5. 5 Scot Oxidation
`11.5.6 Adsorption and Condensation
`Exhaust Gas Treatment
`11.6.1 Available Options
`11.6.2 Catalytic Converters
`1 1.6.3 Thermal Reactors
`11.6.4 Particulate Traps
`
`Chapter 12 Engine Heat Transfer
`12.1
`Importance of Heat Transfer
`12.2
`Modes of Heat Transfer
`12.2.1 Conduction
`12.2.2 Convection
`12.2.3 Radiation
`12.2.4 Overall Heat-Transfer Process
`Heat Transfer and Engine Energy Balance
`Convective Heat Transfer
`12.4.1 Dimensional Analysis
`12.4.2 Correlations for TimenAveraged Heat Flux
`12.4.3 Correlations for Instantaneous Spatial
`Average Coelficients
`12.4.4 Correlations for Instantaneous Local Coefficients
`12.4.5
`Intake and Exhaust System Heat Transfer
`Radiative Heat Transfer
`12.5.1 Radiation from Gases
`12.5.2 Flame Radiation
`12.5.3 Prediction Formulas
`12.6 Measurements of Instantaneous Heat—Transfer Rates
`12.6.1 Measurement Methods
`12.6.2 Sparkmlgnition Engine Measurements
`12.6.3 Diesel Engine Measurements
`12.6.4 Evaluation of Heat-Transfer Correlations
`12.6.5 Boundary-Layer Behavior
`Thermal Loading and Component Temperatures
`12.7.1 Component Temperature Distributions
`12.7.2 Efi‘ect of Engine Variables
`
`'
`
`12.3
`12.4
`
`12.5
`
`12.7
`
`
`
`
`
`
`
`Chapter 13 Engine Friction and Lubrication
`13.1
`Background
`13.2
`Definitions
`13.3
`Friction Fundamentals
`
`'
`
`Page 8 of 237
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`626
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`648
`648
`649
`657
`659
`
`668
`668
`670
`670
`670
`671
`671
`673
`676
`676
`677
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`678
`681
`682
`683
`683
`684
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`689
`689
`690
`692
`694
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`698
`698
`701
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`712
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`FMC 1011
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`'1.13
`1:7
`‘11
`
`13.4
`13.5
`
`13.6
`
`13.3.1 Lubricated Friction
`
`13.3.2 Turbulent Dissipation
`13.3.3 Total Friction
`Measurement Methods
`
`' Engine Friction Data
`13.5.1
`SI Engines
`
`1.3.5.2 Diesel Engines
`Engine Friction Components
`13.6.1 Motorod Engine Breakdown Tests
`13.6.2 Pumping Friction
`
`‘
`
`13.6.3 Piston Assembly Friction
`13.6.4 Crankshaft Bearing Friction
`13.6.5 Valve Train Friction
`
`3.3.13.7
`13.8
`
`Accessory Power Requirements
`Lubrication
`
`13.3.1 Lubrication System
`13.8.2 Lubricant Requirements
`
`'
`
`.
`
`Chapter 14
`
`Modeling Real Engine Flow and Combustion
`Processes
`
`14.1
`14.2
`
`14.3
`
`14.4
`
`14.5
`
`Purpose and Classification of Models
`Governing Equations for Open Thermodynamic System
`14.2.1 Conservation of Mass
`
`14.2.2 Conservation of Energy
`Intake and Exhaust Flow Models
`
`1.4.3.1 Background
`
`14.3.2 Quasi-Steady Flow Models
`14.3.3 Filling and Emptying Methods
`14.3.4 Gas Dynamic Models
`Thermodynamic-Based In-Cylinder Models
`
`14.4.1 Background and Overall Model Structure
`14.4.2 Spark-Ignition Engine Models
`14.4.3 Direct-Injection Engine Models
`.
`14.4.4 Prechamber Engine Models
`14.4.5 Multieylinder and Complex Engine System Models
`14.4.6 Second Law Analysis of Engine Processes
`Fluid-Mechanic—Based Multidimensional Models
`
`14.5.1 Basic Approach and Governing Equations
`14.5.2 Turbulence Models
`
`14.5.3 Numerical MethodOIogy
`14.5.4 Flow Field Predictions
`
`14.5.5 Fuel Spray Modeling
`14.5.6 Combustion Modeling
`
`1
`
`15'
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`{1
`.1
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`13
`
`1'
`
`1 1 1
`
`::11
`
`CONTENTS
`
`XV
`
`715
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`' 719
`719
`719
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`722
`722
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`724
`725
`725
`726
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`729
`734
`737
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`739
`740
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`740
`741
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`748
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`748
`750
`750
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`751
`753
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`753
`
`753
`754
`756
`762
`
`762
`766
`778
`784
`789
`792
`797
`
`797
`800
`
`803
`807
`
`813
`816
`
`GO
`
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`
`06
`
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`
`Engine Operating Characteristics
`
`Engine Performance Parameters
`Indicated and Brake Power and ME]?
`
`Page 9 of 237
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`Chapter 15
`.
`115.1
`.1
`.
`15.2
`
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`CONTENTS
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`15.3
`
`15.4
`
`15.5
`
`15.6
`
`15.7
`
`.
`
`Operating Variables That Affect SI Engine Performance,
`Efficiency, and Emissions
`15.3.1 Spark Timing
`15.3.2 Mixture Composition
`15.3.3 Load and Speed
`15.3.4 Compression Ratio
`SI Engine Combustion Chamber Design
`15.4.1 Design Objectives and Options
`15.4.2 Factors That Control Combustion
`15.4.3 Factors That Control Performance
`15.4.4 Chamber Octane Requirement
`15.4.5 Chamber Optimization Strategy
`Variables That Affect CI Engine Performance, Efficiency, and
`Emissions
`15.5.1 Load and Speed
`15.5.2 Fuel-Injection Parameters
`15.5.3 Air Swirl and Bowl-in-Piston Design
`Supercharged and Turbocharged Engine Performance
`15.6.1 Four-Stroke Cycle SI Engines
`15.6.2
`Four—Stroke Cycle CI Engines
`15.6.3 Two-Stroke Cycle SI Engines
`15.6.4 Two-Stroke Cycle CI Engines
`Engine Performance Summary
`
`Appendixes
`
`A Unit Conversion Factors
`B
`Ideal Gas Relationships
`3.1
`Ideal Gas Law
`11.2 The Mole
`3.3 Thermodynamic Properties
`R4 Mixtures of Ideal Gases
`Equations for Fluid Flow through a Restriction
`C.1 Liquid Flow
`(3.2 Gas Flow
`D Data on Working Fluids
`Index
`
`C
`
`'
`
`827
`827
`829
`339
`341
`844
`344
`846
`850
`852
`857
`
`353
`853
`863
`366
`869
`869
`8'74
`381
`883
`886
`
`899
`902
`902
`903
`903
`905
`906
`90‘?
`907
`911
`917
`
`1;
`)1
`9
`
`3
`1
`11
`3:
`'
`1
`.
`i
`1 1.
`1
`5
`
`.
`
`1
`1 1;
`1
`:
`7
`11
`
`11
`
`11
`‘
`1
`
`,1!
`1
`1
`1'
`
`1
`:1
`1
`
`
`
`Page 10 of 237
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`CHAPTER
`
`-
`
`_
`
`ENGINE
`TYPES
`AND THEIR
`OPERATION
`
`1.1
`
`INTRODUCTION AND HISTORICAL
`
`PERSPECTIVE
`
`The purpose of internal combustion engines is the production of mechanical
`power from the chemical energy contained in the fuel. In internal cornbustion
`engines, as distinct from external combustion engines, this energy is released by
`burning or oxidizing the fuel inside the engine; The fuel-air mixture before com-
`bustion and the burned products after combustion are the actual working fluids.
`The work transfers which provide the desired power output occur directly
`between these working fluids and the mechanical components of the engine. The
`internal combustion engines which are the subject of this book are spark-ignition
`engines (sometimes called Otto engines, or gasoline or petrol engines,
`though
`other fuels can be used) and compression-ignition or diesel enginesrr Because of
`their simplicity, ruggedness and high power/weight ratio,
`these two types of
`engine have found wide application in transportation (land, sea, and air) and
`power generation. It is the fact that combustion takes place inside the work-
`
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`
`TThe gas turbine is also, by this definition, an “ internal combustion engine.“ Conventionally,
`howaver, the term is used for spark—ignition and compression-ignition engines. The operating prin-
`ciples of gas turbines are fundamentally different, and they are not discussed as separate engines in
`:va.
`this book.
`Page 11 of 237
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`ti?
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`2
`
`INTERNAL COMBUSTION ENGINE FUNDAMENTALS
`
`producing part of these engines that makes their design and operating character—
`istics fundamentally different from those of other types of engine.
`Practical heat engines have served mankind for over two and a half cen-
`turies. For the first 150 years, water, raised to steam, was interposed between the
`combustion gases produced by burning the fuel and the work-producing piston-
`in-cylinder expander. It was not until the 1860s that the internal combustion
`engine became a practical realityl' 1 The early engines developed for commercial
`use burned coal-gas air mixtures at atmospheric pressure-“there was no com-
`pression before combustion. J. J. E..Lenoir (1822—1900) developed the first mar-
`ketable engine of this type. Gas and air were drawn into the cylinder during the
`first half of the piston stroke. The charge was then ignited with a spark, the
`pressure increased, and the burned gases then delivered power to the piston for
`the second half of the stroke. The cycle was completed with an exhaust stroke.
`Some 5000 of these engines were built between 1860 and 1865 in sizes up to six
`horsepower. Efficiency was at best about 5 percent.
`A more successful development—an atmospheric engine introduced in 1867
`by Nicolaus A. Otto (1832—1891) and Eugen Langen (1833—1895}—used the pres-
`sure rise resulting from combustion of the fuel-air charge early in the outward
`stroke to accelerate a free piston and rack assembly so its momentum would
`generate a vacuum in the cylinder. Atmospheric preSSure then pushed the piston
`inward, with the rack engaged through a roller clutch to the output shaft. Pro-
`duction engines, of which about 5000 were built, obtained thermal efficiencies of
`up to 11 percent. A slide valve controlled intake, ignition by a gas flame, and
`exhaust.
`To overcome this engine’s shortcomings of low thermal efficiency and
`excessive weight, Otto proposed an engine cycle with four piston strokes: an
`intake stroke, then a compression stroke before ignition, an expansion or power
`stroke where work was delivered to the crankshaft, and finally an exhaust stroke.
`He also proposed incorporating a stratifiedrcharge induction system, though this
`was not achieved in practice. His prototype four-stroke engine first ran in 1876. A
`comparison between the Otto engine and its atmospheric-type predecessor indi-
`cates the reason for its success (see Table 1.1): the enormous reduction in engine
`weight and volume. This was the breakthrough that effectively founded the inter-
`nal combustion engine industry. By 1890, almost 50,000 of these engines had
`been sold in Europe and the United States.
`In 1884, an unpublished French patent issued in 1362 to Alphonse Beau de
`Rochas (1815—1893) was found which described the principles of the four-stroke
`cycle. This chance discovery cast doubt on the validity of Otto’s own patent for
`this concept, and in Germany it was declared invalid. Beau dc Rochas also out-
`lined the conditions under which maximum efficiency in an internal combustion
`
`engine could be achieved. These were:
`
`1. The largest possible cylinder volume with the minimum boundary surface
`2. The greatest possible working speed
`
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`
`ENGINE TYPES AND THEIR OPERATION
`
`3
`
`"
`
`2-
`
`i
`ii
`7;
`_;
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`7;
`
`'acter-
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`f cen-
`3:11 the’
`llStDnr
`ustion
`mom
`com-
`'. mar-
`."lg the
`kI
`the:
`on for
`troke.
`
`to six
`
`1 1867
`, pres-
`.tward
`
`TABLE 1.1
`Comparison of Otto four-stroke cycle and Otto—Langen
`engines2
`
`Otto four-stroke
`Otto and Langen
`__r_.___.————#—-————————————
`Brake horsepower
`4000
`125(3)
`:flthiifiiflhfii, in3
`4900
`310
`Power strokes per min
`80
`Shaft speed, rev/min
`.150
`Mechanical efficiency, %
`84
`Overall eificienclf, %
`14
`Expansion ratio
`2.5
`
`3. The greatest possible expansion ratio
`4. The greatest poserble pressure at the beginning of expansion
`
`would
`piston
`. Pro-
`sies of
`e, and
`
`51 and
`es: an
`power
`stroke.
`5h this
`876, A
`r indie
`engine
`inter-
`;3 had
`
`gau de
`stroke
`int for
`0 out
`rustic,“
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`e
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`i
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`
`The first two conditions hold heat losses from the charge to a minimum. The
`third condition recognizes that the greaterthe expansion of the postcornbustion
`gases, the greater the work extracted. The fourth condition recognizes that higher
`initial pressures make greater expansion possible, and give higher pressures
`throughout the process, both resulting in greater work transfer. Although Beau
`de Rochas’ unpublished writings predate Otto’s developments, he never reduced
`these ideas to practice. Thus Otto, in the broader sense, was the inventor of the
`modern internal combustion engine as we know it today.
`Further developments followed fast once the full impact of what Otto had
`achieved became apparent. By the 18805 several engineers (e.g., Dugald Clerk,
`1854—1913, and James Robson, 1833—1913, in England and Karl Benz, 1844—
`1929, in Germany) had successfully developed two-stroke internal combustion
`engines where the exhaust and intake processes occur during the end of the
`power stroke and the beginning of the compression stroke. James Atkinson
`(1346—1914) in England made an engine with a longer expansion than compres-
`sion stroke, which had a high efficiency for the times but mechanical weaknesses.
`It was recognized that efficiency was a direct function of expansion ratio, yet
`compression ratios were limited to less than four if serious knock problems were
`to be avoided with the available fuels. Substantial carburetor and ignition system
`deveIOpments were required, and occurred, before high-speed gasoline engines
`suitable for automobiles became available in the late 1880s. Stationary engine
`progress also continued. By the late 18903, large single-cylinder engines of 1.3-m
`bore fueled by low-energy blast furnace gas produced 600 bhp at 90 rev/min. In
`Britain, legal restrictions on volatile fuels turned their engine builders toward
`kerosene. Low compression ratio “oil ” engines with heated external fuel vapor-
`izers and electric ignition were developed with efficiencies comparable to those of
`gas engines (14 to 18 percent). The Hornsby~Ackroyd engine became the most
`Page 13 of 237
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`lage 14 of 237
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`4
`
`INTERNAL COMBUSTION ENGINE FUNDAMENTALS
`
`popular oil engine in Britain, and was also built in large numbers in the United
`States.2
`'
`'
`In 1892, the German engineer Rudolf Diesel (1858—1913) outlined in his
`patent a new form of internal combustion engine. His concept of initiating com-
`bustion by injecting a liquid fuel into air heated solely by compression permitted
`a doubling of efficiency over other internal combustion engines. Much greater
`expansion ratios, without detonation or knock, were now pessible. However,
`even with the efforts of Diesel and the resources of MAN. in Ausburg combined,
`it took fiVc years to develop a practical engine.
`Engine developments, perhaps less fundamental but nonetheless important
`to the steadily widening internal combustion engine markets, have continued ever
`since?” One more recent major development has been the rotary internal com-
`bustion engine. Although a wide variety of experimental rotary engines have been
`proposed over the years,5 the first practical rotary internal combustion engine,
`the Wankel, was not successfully tested until 1957. That engine, which evolved
`through many years of research and development, was based on the designs of
`the German inventor Felix Wankelfi- 7
`
`Fuels have also had a major impact on engine development. The earliest
`engines used for generating mechanical power burned gas. Gasoline, and lighter
`fractions of crude oil, became available in the late 18005 and various types of
`carburetors were developed to vaporize the fuel and mix it with air. Before 1905
`there were few problems with gasoline; though compression ratios were low (4 or
`less) to avoid knock, the highly volatile fuel made starting easy and gave good
`cold weather performance. However, a serious crude oil shortage developed, and
`to meet the fivefold increase in gasoline demand between 1907 and 1915, the yield
`from crude had to be raised. Through the work of William Burton (1865—1954)
`and his associates of Standard Oil of Indiana, a thermal cracking process was
`developed whereby heavier oils were heated under pressure and decomposed into
`less complex more volatile compounds. These thermally cracked gasolines satis-
`fied demand, but their higher boiling point range created cold weather starting
`problems. Fortunately, electrically driven starters,
`introduced in 1912, came
`along just in time.
`On the farm, kerosene was the logical fuel for internal combustion engines
`since it Was used for heat and light. Many early farm engines had heated carbu-
`retors or vaporizers to enable them to operate with such a fuel.
`The period following World War I saw a tremendous advance in our
`understanding of how fuels affect combustion, and especially the problem of
`knock. The antiknock effect of tetraethyl
`lead Was discovered at General
`Motors,4 and it became commercially available as a gasoline additive in the
`United States in 1923. In the late 19305, Eugene Houdry found that vaporized
`oils passed over an activated catalyst at 450 to 480°C were converted to high«
`quality gasoline in much higher yields than was possible with thermal cracking.
`These advances, and others, permitted fuels with better and better antiknock
`properties to be produced in large quantities; thus engine compression ratios
`steadily increased, improving power and efficiency.
`
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`ENGINE rvras AND THEIR opsaarrou
`
`5
`
`During the past three decades, new factors for change have become impor-
`rant and now significantly afl‘ect engine design and operation. These factors are,
`first, the need to control the automotive contribution to urban air pollution and,
`secrmd, the need to achieve significant improvements in automotive fuel con-
`SumptiOI‘l.
`The automotive air—pollution problem became apparent in the 1940s in the
`L05 Angeles basin. In 1952, it was demonstrated by Prof. A. J. HaagemSmit that
`the smog problem there resulted from reactions between oxides of nitrogen and
`hydrocarbon compounds in the presence of sunlight.“ In due course it became
`clear that the automobile was a major contributor to hydrocarbon and oxides of
`nitrogen emissions, as well as the prime cause of high carbon monoxide levels in
`urban areas. Diesel engines are a significant source of small soot or smoke par-
`tieles, as well as hydrocarbons and oxides of nitrogen. Table 1.2 outlines the
`dimensions of the problem. As a result of these developments, emission standards
`for automobiles were introduced first ,in California,
`then nationwide in the
`United States, starting in the early 1960s.. Emislion standards in Japan and
`Europe, and for other engine applications, have followed. Substantial reductions
`in emissions from spark-ignition and diesel engines have been achieved. Both the
`use of catalysts in spark-ignition engine exhaust systems for emissions control
`and concern over the toxicity of lead antiknock additives have resulted in the
`reappearance of unleaded gasoline as a major part of the automotive fuels
`market. Also, the maximum lead content in leaded gasoline has been substan-
`tially reduoed. The emission-control requirements and these fuel developments
`have produced significant changes in the way internal combustion engines are
`designed and operated.
`Internal combustion engines are also an important source of noise. There
`are several sources of engine noise: the exhaust system, the intake system, the fan
`used for cooling, and the engine block surface. The noise may be generated by
`aerodynamic effects, may be due to forces that result from the combustion
`process, or may result from mechanical excitation by rotating or reciprocating
`engine components. Vehicle noise legislation to reduce emissions
`to the
`environment was first introduced in the early 1970s.
`During the 1970s the price of crude petroleum rose rapidly to several times
`its cost (in real terms) in 1970, and concern built up regarding the longer-term
`availability of petroleum. Pressures for substantial
`improvements in internal
`combustion engine efficiency (in all its many applications) have become very sub-
`stantial indeed. Yet emission-control requirements have made improving engine
`fuel consumption more difficult, and the removal and reduction of lead in gas-
`Ohm: has forced spark-ignition engine compression ratios to be reduced. Much
`Work is being done on the use of alternative fuels to gasoline and diesel. Of the
`non~petroleumubased fuels, natural gas, and methanol and ethanol (methyl and
`ethyl alcohols) are receiving the greatest attention, while synthetic gaSoline and
`diesel made from shale oil or coal, and hydrogen could be longer-term pos-
`sibilities.
`
`Jnited
`.
`in his
`:com-
`mitted
`greater
`wever,
`bined,
`
`ortant
`d ever
`l com-
`e been
`:ngine,
`rolved
`gns of
`
`arliest
`lighter
`pes of
`31905
`v (4 or
`good
`d, and
`3 yield
`4954)
`;s was
`:d into
`satisu
`‘arting
`came
`
`ngines
`:arbu-
`
`11 our
`em of
`enera]
`in the
`orized
`high-
`.cking.
`knock
`ratios
`
`3"
`'i
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`5
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`
`
`it might be thought that after over a century of development, the internal
`
`Page 15 of 237
`Page 5 of 237
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`
`6
`
`INTERNAL COMBUSTION ENGINE FUNDAMENTALS
`
`TABLE 1.2
`
`The automotive urban air-pollution problem
`
`Automobile emissions
`Truck emissions'l'i'
`
`
`Pollutant
`Impact
`
`Mobile
`source
`emissions Uncontrolled
`
`as "/c. of
`total1'
`
`vehicles,
`g/kmi
`
`Reduction
`in new
`
`vehicles,
`”Va
`‘11
`
`Oxides of
`
`Reactant in
`
`40—60
`
`2.5
`
`engines, Diesel,
`gfkm
`glkm
`
`7
`
`12
`
`150
`
`1711
`
`17
`
`3
`
`75
`
`95
`
`90
`
`photochemical
`smog; ND2 is
`toxic
`Toxic
`
`Reaetant in
`
`photochemical
`smog
`
`90
`
`-
`30—50
`
`65
`
`10
`
`nitrogen
`(NC) and N01)
`
`Carbon
`monoxide
`
`(CO)
`Unborncd
`
`hydrocarbons
`(HC, many
`hydrocarbon
`compounds)
`Particulates
`
`Reduces
`
`50
`
`0.5§
`
`40§
`
`n
`
`0.5
`
`(soot and
`absorbed
`
`visibility;
`some of HC
`
`compounds
`hydrocarbon
`
`compounds) mutagenie
`
`1' Depends on type of urban area and source mix.
`
`iAverage values for pro—1963 automobiles which had no emission commie. determined by U-S- “351 Procedurc
`which simulates typical urban and highway driving. Exhaust emissions, except for BC where 55 percent are exhaust
`emissions, 20 percent are cvaporativc emissions from fuel
`tank and carburetor, and 25 percent are crankcase
`blowby gases.
`
`1} Diesel engine automobiles only. Particulate emissions from spark—ignition engines are negligible.
`
`{I Compares emissions from new sparknignition engine automobiles with uncontrolled automobile levels in previous
`column. Varies from country to country. The United States, Canada, Western Europe, and Japan have standards
`with different degrees of severity. The United States, Europe, and Japan have different test procedures. Standards
`are strictest in the United States and Japan.
`
`1'1' Representative. average emission levels for trucits.
`
`It With 95 percent exhaust emissions and 5 percent evaporative emissions.
`n = negligible.
`
`co