Particulate Emissions from Vehicles By

Peter Eastwood

Ford Motor Company, Ltd.

John Wiley &. Sons, Ltd

Contents

Preface xi

Acronyms and Abbreviations xiii

About the Author xvii

1 Introduction 1 1.1 AirTraffic 4 1.2 Motor Vehicles 4 1.3 The Legislative Framework 6

2 Fundamentals 9 2.1 Introduction 9 2.2 Properties of Aerosol Particles 9

2.2.1 Diameter and Shape 10 2.2.2 Size Distribution 12 2.2.3 Transport and Deposition 14 2.2.4 Transformation and Mutation 18

2.3 Particles in the Atmosphere 22 2.3.1 Character and Behaviour 23 2.3.2 Aerosols in Nature 27 2.3.3 Anthropogenic Aerosols 30 2.3.4 Environmental Implications 37

2.4 Motor Vehicle Particulate 42 2.4.1 Some Typical Particles Dissected 42 2.4.2 What Happens Within the Engine 48 2.4.3 What Happens Within the Exhaust 51 2.4.4 Number Versus Mass 53

2.5 Closure 55 2.5.1 Properties of Aerosol Particles 55 2.5.2 Particles in the Atmosphere 57 2.5.3 Motor Vehicle Particulate 58

vi Particulate Emissions from Vehicles

3 Formation I: Composition 61 3.1 Introduction 61 3.2 Carbonaceous Fraction: I. Classical Models 62

3.2.1 Empiricisms 65 3.2.2 Inception 68 3.2.3 Surface Growth 73 3.2.4 Agglomeration 75 3.2.5 Oxidation 79

3.3 Carbonaceous Fraction: II. The Combusting Plume 84 3.3.1 Historical Overview 85 3.3.2 Premixed Burn 86 3.3.3 Mixing-controlled Burn 88 3.3.4 Late Burn 90

3.4 Carbonaceous Fraction: III. Wall Interactions 91 3.4.1 Theoretical 92 3.4.2 Experimental 93

3.5 Ash Fraction 95 3.5.1 Chemical Reactions 96 3.5.2 Gas-to-Particle Conversion 100

3.6 Organic Fraction 104 3.6.1 Preparatory Chemical Reactions 104 3.6.2 Chemical Reactions in the Exhaust 109 3.6.3 Gas-to-Particle Conversion: Models 112 3.6.4 Gas-to-Particle Conversion: Measurements 117 3.6.5 White Smoke 119

3.7 Sulphate Fraction 122 3.7.1 Chemical Reactions 122 3.7.2 Gas-to-Particle Conversion 125

3.8 Closure 129 3.8.1 Carbonaceous Fraction I. Classical Models 129 3.8.2 Carbonaceous Fraction II. The Combusting

Plume 131 3.8.3 Carbonaceous Fraction III. Wall Interactions 132 3.8.4 Ash Fraction 132 3.8.5 Organic Fraction 133 3.8.6 Sulphate Fraction 134

4 Formation II: Location 135 4.1 Introduction 135 4.2 Within the Exhaust System 136

4.2.1 Storage and Release 137 4.2.2 Deposition Within Catalysts 139

4.3 Within the Exhaust Plume 141 4.3.1 Long-term Ageing in the Atmosphere 145

4.4 Within the Transfer Line 145 4.5 Within the Dilution Tunnel 147 4.6 On the Filter 150 4.7 Closure 152

Contents

4.7.1 Within the Exhaust System 152 4.7.2 Within the Exhaust Plume 153 4.7.3 Within the Transfer Line 153 4.7.4 Within the Dilution Tunnel 153 4.7.5 On the Filter 154 4.7.6 General Remarks 154

5 Measurement 157 5.1 Introduction 157 5.2 Particulate Measured Conventionally 158

5.2.1 Drawing a Sample of Exhaust Gas 158 5.2.2 Diluting the Exhaust 160 5.2.3 Collection onto a Filter 165 5.2.4 Fractionation by Gasification 168 5.2.5 Fractionation by Dissolution 171 5.2.6 Chemically Assaying the Organic Fraction 175 5.2.7 Biologically Assaying the Organic Fraction 179

5.3 Particulate Measured Individually 182 5.3.1 Inertial Mobility 183 5.3.2 Electrica! Mobility 185 5.3.3 Laser-induced Incandescence 186 5.3.4 Light Scattering 189

5.4 Particulate Measured Collectively 191 5.4.7 Photoacousticity 191 5.4.2 Photoelectric and Diffusion Charging 193 5.4.3 Electrica! Charge 195 5.4.4 Flame Ionisation 197 5.4.5 Mass 198 5.4.6 Smoke 200

5.5 Closure 204 5.5.7 Particulate Measured Conventionally 204 5.5.2 Particulate Measured Individually 206 5.5.3 Particulate Measured Collectively 207 5.5.4 Further Remarks 209

6 Characterisation 211 6.1 Introduction 211 6.2 Physical Characterisation 212

6.2.7 Microstructure 212 6.2.2 Morphology 215 6.2.3 Density 219 6.2.4 Surface Area 222 6.2.5 Electrica! Charge 224

6.3 Chemical Characterisation 228 6.3.1 Carbonaceous Fraction 228 6.3.2 Ash Fraction 230 6.3.3 Organic Fraction 233 6.3.4 Sulphate Fraction 237

viii Particulate Emissions from Vehicles

6.4 Biological Characterisation 238 6.5 Demographic Characterisation 240 6.6 Closure 244

6.6.1 Physical Characterisation 244 6.6.2 Chemical Characterisation 246 6.6.3 Biological Characterisation 246 6.6.4 Demographic Characterisation 247

249 249 250 252 254 256 261

262 265 265 266 269 271 275 275 277 279 279 285 291 293 294 300 306 306 308 309 309 310 310 311

Gasoline Engines 313 8.1 Introduction 313 8.2 A Historical Perspective 314

8.2.1 Organometallic Fuel Additives and Ash 314 8.2.2 Oxidation Catalysts and Sulphates 317

8.3 Port-injection Engines 318 8.3.1 Formation 319

7.1 7.2

7.3

7.4 7.5

7.6

7.7 7.8

7.9

Introduction Fuel Formulation 7.2.7 Sulphur 7.2.2 Hydrocarbons 7.2.3 Oxygenates 7.2.4 Additives 7.2.5 Volatility, Cetane Number and

Density Fuel Injection 7.3.1 The Injector Nozzle 7.3.2 Injection Pressure 7.3.3 Injection Scheduling Exhaust Gas Recirculation Induction 7.5.1 Externa! to the Engine 7.5.2 Internal to the Engine Lubrication 7.6.1 Oil in Particulate 7.6.2 Particulate in Oil Alternative Combustion Systems Aftertreatment 7.8.1 Catalytic Converters 7.8.2 Particulate Filters Closure 7.9.1 Fuel Formulation 7.9.2 Fuel Injection 7.9.3 Exhaust Gas Recirculation (EGR) 7.9.4 Induction 7.9.5 Lubrication 7.9.6 Alternative Combustion Systems 7.9.7 Aftertreatment

Contents ix

8.3.2 Characterisation 322 8.3.3 Abatement 325

8.4 Direct-injection Engines 326 8.4.1 Formation 327 8.4.2 Characterisation 330 8.4.3 Abatement 333

8.5 Two-stroke Engines 334 8.6 Closure 338

8.6.1 Port-injection Engines 338 8.6.2 Direct-injection Engines 339 8.6.3 Two-stroke Engines 340

9 Disintegration 341 9.1 Introduction 341 9.2 Roads 342 9.3 Brakes 344 9.4 Tyres 346 9.5 Exhausts 348 9.6 Catalysts 349 9.7 Closure 352

9.7.1 Roads 352 9.7.2 Brakes 352 9.7.3 Tyres 353 9.7.4 Exhausts 353 9.7.5 Catalysts 353

10 Toxicology 355 10.1 Introduction 355 10.2 Public Exposure 356

10.2.1 Nanoparticles 360 10.3 Public Health 362 10.4 Pathogenesis 364

10.4.1 Particle Deposition and Clearance 364 10.4.2 The Chemistry and Biochemistry of Particle-induced

Reactions 367 10.4.3 Particle-induced Diseases 369

10.5 Epidemiology 371 10.6 In Vitro 375 10.7 In Vivo 311 10.8 Humans 381 10.9 Closure 382

10.9.1 Public Exposure 382 10.9.2 Public Health 382 10.9.3 Pathogenesis 382 10.9.4 Epidemiology 383 10.9.5 In Vitro 383 10.9.6 In Vivo 384 70.9.7 Humans 384

X Particulate Emissions from Vehicles

10.9.8 Which Particulate Fraction? 384 10.9.9 Healthy Antioxidant Diet 385

10.10 Glossary of Biomedical Terms 385

11 Closure 387 11.1 Recommendations for Research 387

11.1.1 Signal-to-noise Ratios 387 11.1.2 Statutory Test Cycles and Real Emission Rates 388 11.1.3 Inspection and Maintenance 388 11.1.4 The Soot Sensor in Engine and Aftertreatment Management 388 11.1.5 Surface Area Distribution 389 11.1.6 Instrumentation for Number-based Legislation 389 11.1.7 Nanoparticles in Real Exhaust Plumes (and the Ambient) 389 11.1.8 How Should Primary and Secondary Particles Be Demarcated? 390 11.1.9 Will Gas-particle Partitioning in the Wider Environment Be Affected? 390 11.1.10 The Chemical Compositions oflndividual Particles 390 11.1.11 Toxicity as a Function of Particle Size 390

11.2 Smaller Particles in Larger Numbers; or Larger Particles in Smaller Numbers 391 11.3 Smaller and Smaller and Smaller 395 11.4 Broader Questions of Policy 396

Further Reading 399

Literature Cited (Cross-referenced Against the Text) 401

Index 485