`
`INTERNAL
`
`COMBUSTION
`
`
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`ENGINE
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`FUNDAMENTALS
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`John B. Heywood
`
`Professor ofMechanico! Engineering
`
`Director, Sloan Automotive Laboratory
`
`Mosmchusea'zs Institute of Technology
`
`Mchw-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
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`Page 1 of 237
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`
`
`
`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
`1.7
`1.8
`L9
`
`Introduction and Historical Perspective
`Engine Classificatims
`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
`
`2.1
`2.2
`2.3
`2.4
`
`2.5
`2.6
`
`2.7
`
`2.8
`2.9
`
`Important Engine Characteristics
`Geometrical Properties of Reciprocating Engines
`Brake Torque and Power
`Indicated Work P'er Cycle
`
`Mechanical Efficiency
`Road-Load Power
`
`Mean Effective Pressure
`
`Specific Fuel Consumption and Eificiency
`Air/Fuel and Fuel/Air Ratios
`
`xvii
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`xxiii
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`1
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`I
`7
`9
`12
`15
`19
`25
`31
`37
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`42
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`42
`43
`45
`46
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`43
`49
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`50
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`51
`53
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`CON-rem
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`2.10 Volumetric Efficiency
`2.1]
`Engine Specific Weight and Specific Volume
`2.12
`Correction Factors for Power and Volumetric Efficiency
`2.13
`Specific Emissions and Emissions Index
`2.14 Relationships between Performance Parameters
`2.15
`Engine Design and Performance Data
`
`.
`
`Chapter 3 Thennochemistry of Fuel-Air Mixtures
`3.1
`Characterization of Flames
`3.2
`Ideal Gas Model
`3.3
`Composition of Air and Fuels
`3.4
`Combustion Stoichiomctry
`3.5
`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 Elficiency 01' 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
`
`3.6
`
`3.7
`
`Engine and Efficiency
`Chemically Reacting Gas Mixtures
`3.7.1 Chemical Equilibrium
`3.7.2 Chemical Reaction Rates
`
`Chapter 4 Properties of Working Fluids
`4.1
`Introduction
`
`4.2
`4.3
`4.4
`4.5
`
`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
`
`.
`
`-
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`4.5.3 Relation between Unbumecl and Burned
`Mixture Charts
`
`4.6
`4.7
`
`Tables of Properties and Composition
`Computer Routines for Property and Composition Calculations
`4.7.1 Unburned Mixtures
`
`4.7.2 Burned Mixtures
`
`' 4.8
`4.9
`
`Transport Properties
`Exhaust Gas Composition
`4.9.1
`Species Concentration Data
`4.9.2 Equivalence Ratio Determination from Exhaust
`Gas Caustituents
`
`4.9.3 Effects of Fuel/Air Ratio Nonuniformity
`4.9.4 Combustion Inelliciency
`
`53
`54
`54
`56
`$6
`57
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`62
`62
`54
`64
`68
`72
`72
`76
`73
`30
`3]
`83
`83
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`83
`85
`86
`92
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`100
`100
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`102
`107
`109
`112
`112
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`116
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`123
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`127
`130
`130
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`135
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`141
`145
`145
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`143
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`152
`154
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`comsms
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`xi
`
`Chapter 5
`5.1
`5,2
`5. 3
`5.4
`
`Ideal Models of Engine Cycles
`Introduction
`Ideal Models of Engine Processes
`Thermodynamic Relations for Engine Processes
`Cycle Analysis with Ideal Gas Working Fluid with c” and c,
`Constant
`‘
`
`5.4.1 Constant~Volume Cycle
`5.4.2 Limited- and Constant-Pressure Cycles
`5.4.3 Cycle Comparison
`Fuel~Air Cycle Analysis
`5.5.1
`31 Engine Cycle Simulation
`5.5.2 CI Engine Cycle Simulation
`5.5.3 Results of Cycle Calculations
`Overexpanded Engine Cycles
`Availability Analysis 01' 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
`
`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 Effects
`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
`
`6.4
`
`6.3
`
`6.5
`6.6
`
`6.7
`6.8
`
`Exhaust Gas Flow Rate and Temperature Variation
`Scavengjng in Two—Stroke Cycle Engines
`6.6.1
`Two—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
`6.8.4 Turbines
`
`6.8.5 Wave-Compression Devices
`
`Chapter 7
`
`5] Engine Fuel Metering and Manifold
`Phenomena
`
`7.1
`7.2
`
`Spark-Ignition Engine Mixture Requirements
`Carburetors
`
`161
`161
`162
`164
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`169
`
`169
`172
`173
`177
`178
`180
`181
`133
`186
`135
`188
`189
`192
`193
`
`205
`206
`209
`209
`212
`216
`220
`220
`225
`230
`
`231
`235
`235
`23?
`240
`245
`248
`248
`249
`
`255
`263
`
`270
`
`279
`
`279
`282
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`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
`7.6.3 Fuel-Flow Phenomena
`
`Chapter 8 Charge Motion within the Cylinder
`3.1
`Intake Jet Flow
`3.2
`Mean Velocity and Turbulence Characteristics
`8.2.] Definitions
`8.2.2 Application to Engine Velocity Data
`Swirl
`Swirl Measurement
`8.3.1
`8.3.2 Swirl Generation during Induction
`8.3.3
`Swirl Modification within the Cylinder
`Squish
`Preehamber Engine Flows
`Crevice Flows and Blowbjr
`Flows Generated by Piston—Cylinder Wall Interaction
`
`8.3
`
`8.4
`3.5
`3.6
`8.7
`
`.
`
`9.3
`
`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 Analysis of Cylinder Pressure Data
`9.2.3 Combustion Process Characterization
`Elaine 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 System
`9.5.3 Alternative Ignition Approaches
`Abnormal Combustion: Knock and Surface Ignition
`9.6.1 Description of Phenomena
`
`9.4
`
`9.5
`
`9.6
`
`1
`
`282
`285
`294
`294
`299
`301
`304
`308
`308
`309
`314
`
`326
`326
`330
`330
`336
`342
`343
`345
`349
`353
`357
`360
`365
`
`371
`371
`376
`376
`383
`389
`390
`390
`395
`402
`4.05
`413
`413
`
`419
`424
`427
`427
`437
`443
`450
`450
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`age 6 of 237
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`CONTENTS
`
`xiii
`
`457
`470
`
`491
`491
`
`493
`493
`494
`495
`
`497
`
`497
`503
`506
`508
`509
`509
`5 14
`517
`517
`522
`525
`
`529
`532
`535
`539
`539
`
`541
`542
`546
`550
`553
`555
`555
`555
`558
`
`567
`
`567
`
`572
`572
`
`577
`578
`586
`592
`
`596
`596
`599
`
`i1
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`. 1 E
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`i;
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`Chapter 10
`10.1
`10.2
`
` i
`
`i
`E.
`
`9.15.2 Knock Fundamentals
`9.6.3
`Fuel Factors
`
`Combustion in Compression-Ignition Engines
`Essential Features of Process
`
`Types of Diesel Combustion Systems
`10.2.1 Direct-Injection Systems
`10.2.2
`IndirectvInjection Systems
`10.2.3 CompariSOn of Different Combustion Systems
`Phenomenological Model of Compression-Ignition Engine
`Combustion
`
`Photographic Studies 01 Engine Combustion
`10.3.1
`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 Behavim
`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
`10.6.1 Definition and Discussion
`
`10.6.2 Fuel Ignition Quality
`10.6.3 Autoignition Fundamentals
`10.6.4 Physical Factors Affecting Delay
`10.6.5
`Efi‘eet 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
`
`10.3
`
`10.4
`
`10.5
`
`10.15
`
`10.7
`
`Chapter 1]
`11.1
`11.2
`
`Pollutant Formation and Control
`
`Nature and Extent of Problem
`
`Nitrogen Oxides
`11.2.1 Kinetics of NO Formation
`
`11.3
`
`11.4
`
`11.2.2 Formation of N01
`11.2.3 NO Formation in Spark-Ignition Engines
`11.2.4 NO, Formation in Compression-Ignition Engines
`Carbon Monoxide
`
`Unbutned Hydrocarbon Emissions
`11.4.1 Background
`11.4.2 Flame Quenching and Oxidation Fundamentais
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`11.5
`
`11.6
`
`11.4.3 HC Emissions from Spark-Ignition Engines
`11.4.4 Hydrocarbon Emission Mechanisms in Diesel Enginm
`Particulate Emissions
`11.5.1 Spark-Ignition Engine Particulates
`11.5.2 Characteristics of Diesel Particulates
`11.5.3 Particulate Distribution within the Cylinder
`11.5.4 Soot Formation Fundamentals
`11.5.5 Soot Oxidation
`11.5.6 Adsorption and Condensation
`Exhaust Gas Treatment
`11.6.1 Available Options
`11.6.2 Catalytic Converters
`11.6.3 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
`122.3 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 Time—Averaged Heat Flux
`12.4.3 Correlations for Instantaneous Spatial
`Average Coeilicients
`12.4.4 Correlations for Instantaneous Local Coeflieients
`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 Spark-Ignition 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 Effect of Engine Variables
`
`12.3
`12.4
`
`12.5
`
`12.?
`
`‘
`
`Chapter 13 Engine Friction and Lubrication
`13.1
`Background
`13.2
`Definitions
`13.3
`Friction Fundamentals
`
`601
`620
`626
`626
`626
`631
`635
`642
`646
`648
`648
`649
`657
`659
`
`668
`668
`670
`670
`670
`671
`671
`673
`676
`676
`677
`
`678
`681
`682
`683
`683
`684
`688
`689
`689
`690
`692
`694
`697
`698
`698
`701
`
`712
`712
`'1‘ 14
`71.5
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`13.3.1 Lubricated Friction
`
`13.3.2 Turbulent Dissipation
`13.3.3 Total Friction
`
`Measurement Methods
`
`' Engine Friction Data
`13.5.1
`51 Engines
`
`1.3.5.2 Diesel Engines
`Engine Friction Components
`13.6.1 Motored Engine Breakdowo Tests
`13.6.2 Pumping Friction
`13.6.3 Piston Assembly Friction
`13.6.4 Crankshaft Bearing Friction
`13.6.5 Valve Train Friction
`Accessory Power Requirements
`Lubrication
`
`13.3.1 Lubrication System
`13.8.2 Lubricant Requirements
`
`13.4
`13.5
`
`13.6
`
`13.7
`
`13.3
`
`CONTENTS
`
`X1?
`
`715
`
`' 719
`
`719
`719
`722
`722
`
`724
`
`725
`725
`726
`
`729
`
`734
`737
`
`739
`740
`
`740
`
`741
`
`Chapter 14
`
`Modeling Real Engine Flow and Combustion
`Processes
`
`748
`
`14.1
`14.2
`
`14.3
`
`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
`
`{14.4
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`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 Multicylinder 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 Methodology
`14.5.4 Flow Field Predictions
`
`14.5.5 Fuel Spray Modeling
`14.5.6 Combustion Modeling
`
`14.5
`
`Chapter 15
`15.1
`15.2
`
`Engine Operating Characteristics
`
`Engine Performance Parameters
`Indicated and Brake Power and MEP
`
`748
`
`750
`750
`
`751
`753
`
`753
`753
`
`754
`756
`762
`762
`766
`
`778
`784
`789
`792
`
`797
`797
`
`300
`
`803
`
`807
`313
`
`816
`
`823
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`823
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`comm-rs
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`15.3
`.
`
`15.4
`
`15.5
`
`15.6
`
`15.7
`
`Operating Variables That Affect SI Engine Performance,
`Elficiency, 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 Cl Engine Performance, Efficiency, and
`Emissions
`15.5.] 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 FounStroke 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
`El
`Ideal Gas Law
`3.2 The Mole
`3.3 Thermodynamic Properties
`13.4 Mixtures of Ideal Gases
`Equations for Fluid Flow through a Restriction
`C.l Liquid Flow
`C-2 Gas Flow
`D Data on Working Fluids
`Index
`
`C
`
`‘
`
`32'?
`82'?
`829
`339
`841
`844
`844
`846
`850
`352
`857
`
`853
`858
`863
`866
`869
`869
`874
`881
`883
`386
`
`899
`902
`902
`903
`903
`905
`906
`907
`907
`911
`91'}
`
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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 combustion
`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 engines? Because of
`their simplicity, ruggedness and high powerfweight 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»
`
`TThe gas turbine is also, by this definition, an “internal combustion engine.“ Conventionally,
`hewaver, 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
`this book.
`
`l
`
`FORD 1109
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`
`1
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`[i
`:
`
`2 INTERNAL consumers enema 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 reality.1' 2 The early engines developed for commercial
`use burned coal-gas air mixtures at atmospheric pressure—there was no com-
`pression before combustion. J. J. F...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 186';r
`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 stratified-charge 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 1862 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 de Rochas also out-
`lined the conditions under which maximum efficiency in an internal combustion
`engine could be achieved. These were:
`
`I. The largest possible cylinder volume with the minimum boundary surface
`
`2. The greatest possible working speed
`
`I
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`
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`TABLE 1.!
`
`ENGINE TYPES AND THEIR OPERATION
`Comparison of lOtto four-stroke cycle and Otto—Longer:
`engines“l
`
`3
`
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`acter-
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`f cen-
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`tlSan-
`ustion
`-
`tercral
`com—
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`1g the
`k,
`the
`
`troke.
`
`to six
`
`I 1867
`, pres~
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`piston
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`cies of
`e, and
`
`3; and
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`power
`:troke.
`gh this
`876. A
`r indie
`engine
`inter-
`:3 had
`
`can do
`stroke
`:nt for
`0 out—
`ustion
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`Otto four-stroke
`Otto and Langen
`___’__————————~—
`2
`p55
`4000
`~
`4900
`310
`28
`30
`90
`160
`ss
`34
`l1
`l4
`
`Brake horsepower
`Weight. lb. approx-
`Fusion displaccmflnl. in3
`Power strokes per min
`Shaft speed. rev/min
`Mechanical efficiency, %
`Overall efficiency, “/0
`
`3. The greatest possible expansion ratio
`4. The greatest possible pressure at the beginning of expansion
`
`two conditions hold heat losses from the charge to a minimum. The
`The first
`third condition recognizes that the greater the expansion of the postcombustion
`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 Roehas’ 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 [8805 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
`developments were required, and occurred, before high-speed gasoline engines
`suitable for automobiles became available in the late 18305. Stationary engine
`progress also continued. By the late 1890s, large single-cylinder engines of 1.3-rn
`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-Aekroyd engine became the most
`
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`4
`
`INTERNAL COMBUSTION ENGIN F. FUNDAMEN'I'ALS
`
`popular oil engine in Britain, and was also built in large numbers in the United
`States.2
`In 1892, the German engineer Rudolf Diesel (1858-4913) 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 possible. However,
`even with the efforts of Diesel and the resources of MAN. in Ausburg combined,
`it took fiv: 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?"4 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 Wankel." 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 1 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 antiknoclc
`properties to be produced in large quantities; thus engine compression ratios
`steadily increased, improving power and efficiency.
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`
`enema Types AND men: oreasnou
`
`5
`
`During the past three decades, new factors for change have become impor-
`tant 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,
`second,
`the need to achieve significant improvements in automotive fuel con-
`gumption.
`The automotive air-pollution problem became apparent in the 19405 in the
`Los Angeles basin. In 1952, it was demonstrated by Prof. A. J. Haagen-‘lmit that
`the smog problem there resulted from reactions between oxides of nitrogen and
`hydrocarbon compounds in the presence of sunlight.8 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-
`tides, 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 antiltnoclt 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-
`tialiy reduced. 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 19705.
`During the 19705 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 fer 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-
`oline 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
`nonwpetroleum—based 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-
`sibilitics.
`It might be thought that after over a century of development, the internal
`
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`
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`6
`
`INTERNAL COMBUSTION ENGINE FUNDAMENTALS
`
`TABLE 1.2
`
`The automotive urban air-pollution problem
`
`Automobile emissions
`
`Truclt emissions“
`
`Mobile
`
`source
`emissions Uncontrolled
`
`Reduction
`in new
`
`51
`
`as % of
`vehicles,
`vehicles,
`engines,
`Diesel,
`
`Pollutant
`Impact
`totalT
`giltrni
`”A: T
`gfkm
`giltm
`
`Oxides of
`
`Reactant in
`
`40—60
`
`2.5
`
`nitrogen
`(NO and N01)
`
`Car hon
`monoxide
`
`(CO)
`Unburncd
`
`hydrocarbons
`(HC, many
`hydrocarbon
`compounds)
`Particulates
`(5001 and
`absorbed
`
`photochemical
`smog; N02 is
`toxic
`Toxic
`
`Reaetant in
`
`photochemical
`smog
`
`Reduces
`visibility;
`some of HC
`
`75
`
`95
`
`90
`
`7
`
`150
`
`1711
`
`12
`
`I?
`
`3
`
`90
`
`-
`30—50
`
`6 5
`
`10
`
`50
`
`0.5§
`
`40§
`
`n
`
`0.5
`
`
`
`compounds
`hydrocarbon
`
`compounds) mutagem’e
`
`f Depends on type ofurbnn area and room: mitt.
`
`test procedure
`1 Average values for pre-I‘JGB automobiles which had no emission controls, determined by US.
`which simulates typical urban and highway driving. Exhaust emissions. except t‘or HC where 55 percent an: exhaust
`missions, 20 percent nre evaporative emissions from fuel
`tank and carburetor. and 25 percent are crankme
`blowby gases.
`
`5; Diesel engine automobiles only. Parliculatc emissions from spark-ignition engines are negligible.
`
`1| Compares emissions from new spark-ignition engine automobiles with uncontrolled automobile levels in prcVious
`column. Varies from country to counlry. The United States,-Canada, Western Europe, and Japan have standards
`with dil’t'erent degrees of severity. The United States. Europe, and Japan have difierent test procedures. Standards
`are strictest in the United States and Japan.
`
`11' Represcntativa. average emission levels for trucks.
`
`11 With 95 percent exhaust emissions and 5 percent evaporatiye emissions.
`
`n = negligible.
`
`combustion engine has reached its peak and little potential for further improve-
`ment remains. Such is not
`the case. Conventional spark-ignition and diesel
`engines continue to show substantial
`improvements in efficiency, power, and
`degree of emission control. New materials now becoming available offer the pos-
`sibilities of reduced engine weight, cost, and heat lossw, and of different and more
`efficient internal combustion engine systems. Alternative types of internal com-
`bostion engines, such as the stratified—charge (which combines characteristics nor-
`mally associated with either the spark-ignition or diesel) with its wider fuel
`tolerance, may become sufficiently attractive to reach large~scale production. The
`engine development opportunities of the future are substantial. While they
`
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`ENGINE TYPES AND THEIR OPERATlON
`
`7
`
`
`
` lonst’r
`
`Mel,
`’1‘”
`1?.
`
`17
`
`3
`
`0.5
`
`need urn
`exhaust
`ankcase
`
`_
`WBVIOUS
`Wards
`lndardg
`
`Egg;
`, and
`:pos-
`more
`com—
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`
`r fuel
`I. The
`they
`
`*trlN‘rwfilrfl-‘Im!—'\:w'wwam3mmamm.
`
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`4Wow-TMs-Wfit
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`*1
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`present a formidable challenge t