Air Pollution, the Automobile, and Public Health (1988) / Chapter Skim
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Automotive Emissions
Automotive Emissions
Pages 39-76
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From page 39... ...
JOHNSON Michigan Technological University Pollution from Automobiles Problems and Solutions / 40 Emissions Standards and Control Approaches / 40 Fuel Economy / 40 In-Use Passenger Car Emissions / 41 Emissions Regulations / 42 Emission Test Procedures / 43 Emission Standards / 45 U.S. Fuel Economy Standards / 46 Vehicle and Emission Control System Technology / 46 Spark-Ignition Gasoline-Powered Vehicles / 47 Diesel-Powered Passenger Cars: Particulate Control / 48 Diesel-Powered Heavy-Duty Vehicles / 49 In-Use Vehicle and Engine Characteristics / 50 Gasoline-Powered Passenger Cars and Trucks / 50 Diesel-Powered Passenger Cars / 52 Diesel-Powered Trucks / 52 Models for Predicting Future Emissions / 53 Fuels and Fuel Additives / 54 Trends in Gasoline Fuel Properties / 54 Fuel Usage Trends / 56 Methanol-Fueled Vehicles / 56 Trends in Diesel Fuel Properties / 59 Refueling Emissions / 59 Additives / 60 Methods for Measuring the Unregulated Pollutants / 61 Sampling / 62 Analytical Methods / 63 Current Regulated and Unregulated Emissions / 64 Regulated Emissions / 64 Unregulated Emissions / 64 Summary of Research Recommendations / 70 Air Pollution, the Automobile, and Public Health.
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From page 40... ...
This paper reviews our current knowledge of automotive emi~cion~ in~l',rlin~ standards, control technology, fuel economy, fuels and additives, in-use emissions, measurement methods for unregulated pollutants, and models for predicting future automotive emissions. Fuel economy is included because achieving high fuel economy and low emissions together makes the engineering effort more difficult.
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From page 41... ...
Further emission reduction with simultaneous fuel economy improvement continues through application of new technology, especially computer engine control. In-Use Passenger Car Emissions The in-use emissions from passenger cars exceed the new car standards mandated by law.
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The 1970 Clean Air Act further imposed stringent HC, CO, and NOX reductions for 1975 and 1976. These reductions were subsequently delayed and changed by the 1974 Energy 40r ~ 35 O 30 8 J 25 LL Lu 20 LL 11 ~ 15 Automotive Emissions Maximum power IStoichiometric mixture Maximum fuel economy Lean burn area 400C 300C Q x 200C o 1 OOC o - 800 .
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(Adapted from Greco 1985.) Emission Test Procedures Passenger Cars.
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(g/mi) NOr Passenger Cars Pre control 10.60C 84.0 4.1 47 10.60' 84.0 4.1 47 1966 6.30 51.0 (6.0)
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Emission Standards United States. Emissions standards and test procedures in the United States have changed significantly since the first automobile emission standards were imposed in California in 1966 (see table 1)
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Vehicle and Emission Control System Technology The technology used for emission control in cars changed rapidly in the 1970s as the automotive industry spent considerable research and development funds to meet the stringent emission standards originally set by the 1970 amend 1977 Clean Air Act Amendments. This technology is now being optimized to reduce the product cost associated with emission controls while improving the in-use durability of the emission control systems.
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From page 47... ...
increased fuel economy and improved emission control through exploitation of the high HC and CO removal efficiency of the oxidizing catalytic converter, so that the engine calibration could be optimized for efficiency. Progress was made by decreasing the cold-start engine-out HC and CO emissions, by achieving faster converter light-off, by reducing heat loss from the exhaust system, and by reducing the deterioration of catalyst performance with cumulative driving distance (Amann 1985~.
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This alternate emission control approach achieves good fuel economy (potential 10-15 percent improvement) and also meets the emission standards by operating beyond 22:1 A/F where NOX emission is low enough to meet the 1-g/mi standard.
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From page 49... ...
Diesel engines are designed for a commercial market and hence durability, reliability, and fuel economy drive their development. The approaches enforced to date to meet the standards for particulates, HCs, and NOX have involved improved turbochargers, intercooling, improved fuel systems and nozzles, and electronic fuel injection control.
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EPA standards have emphasized particulate control rather than NOx control. There is the feeling that the 1988 standards will result in some loss of fuel economy.
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The difference in prevalence of catalytic converter tampering is particularly striking nearly three times as prevalent in light-duty trucks as in passenger cars (14 percent versus 5 percent) (Greco 1985~.
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Diesel-Powered Trucks There are limited data on diesel engines in operational use although there are some recent laboratory data obtained by the various manufacturers in an EPA/Engine Manufacturers Association (EMA) in-use emission factor test program for heavyduty diesels.
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From page 53... ...
There is a need for continued research on particulate control technology, including the regeneration systems, to reduce the cost and complexity of these systems and the associated fuel economy penalties. Work needs to continue with various additives, substrate materials, regeneration systems, and controls to develop optimum systems that are able to decrease the diesel particulate emissions to the levels of 0.1 g/bhp-hr for heavy-duty diesels and 0.08 g/mi for light-duty vehicles required in California.
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From page 54... ...
Fuels and Fuel Additives Trends in Gasoline Fuel Properties The EPA limited the use of Pb in gasoline to 0.5 g/gal after July 1, 1985, and to 0.1 g/gal after January 1, 1986. This has increased refineries' interest in the use of alternative low-cost octane boosters, particularly light alkanes and methanol and/or ethanol alcohols blended with gasoline.
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The EPA estimates that the difference in volatility between the certification fuel and commercial gasoline is responsible for about half of the evaporative emissions from late-model light-duty vehicles and that this trend will continue, as shown in figure 13, if no action is taken to change it (Schwarz 1985~. The Coordinating Research Council-Air Pollution Research Advisory Committee (CRC-APRAC)
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Department of Trans portation establishes the post-1988 fuel economy standards at 26 mpg. Total diesel highway fuel demand will continue to grow over the next two decades primarily because of increased use of diesel engines in heavy-duty vehicles.
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Spark-Ignition Engines for Passenger Cars. The technology for methanol-fueled vehicles exists and demonstration fleets have been tested.
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Second, the particulate and odor emissions are less than those of the diesel engines it would replace. Third, the use of methanol should improve the reactivity of the exhaust, although the methanol and formaldehyde emissions could be a problem if control systems are not properly developed and maintained.
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From page 59... ...
Trends in Diesel Fuel Properties Recent trends in diesel fuel properties have an adverse effect on particulate emissions. They make it harder to meet stringent particulate emission standards for cars and trucks (0.2 g/mi in 1987 for cars and 0.6 g/bhp-hr in 1988, 0.25 g/bhp-hr in 1991 for trucks)
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How additives may affect control technologies needs additional research. Knowledge of the size distribution of particles from diesel particulate traps and the metal species they contain.
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Diesel Fuel Additives. Data should be obtained about the size distribution of particles in diesel exhaust and about the metal species they contain, with and without a particulate trap, with a diesel fuel containing a typical additive under consideration for production use.
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The effects of artifact formation can be minimized by reducing the length of time a filter is exposed to the exhaust stream to the minimum required to collect Deposit modifiers Automotive Emissions Table 6. Chemicals Typically Used as Diesel Additives Additive Type Chemicals Detergents Polymeric dispersants Combustion modifiers Cetane improvers Same as for gasoline (table 5)
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Diesel engines produce higher levels of particulates, NOx, sulfur oxides (SON and certain HCs, all of which can interfere with one or more of the analyses that are commonly used on spark-ignition engine emissions. Some real-time monitoring techniques based on the absorption of light fail when applied to diesel exhaust analysis, either because of scatter -- =- -r -- ~ ~ ~r ~ ing of light by suspended particulates or absorption of light by aromatic HCs present in the gaseous phase.
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Emissions Measurement Methods. Studies should begin immediately with an evaluation of the best available emissions data on engines operating with and without emission control devices, to determine which of the unregulated pollutants really pose a potential threat to human health.
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From page 65... ...
Unregulated Gaseous Hydrocarbons Emitted from Vehicles All n-alkanes from e-butane through n-hexacosane Four methyl-substituted butanes Ten methyl- and ethyl-substituted pentanes and 11 cyclopentanes Eleven methyl- and ethyl-substituted hexanes and 35 cyclohexanes Fifteen methyl- and ethyl-substituted heptanes Five methyl-substituted octanes One methyl-substituted nonane One methyl-substituted decane One methyl-substituted undecane Decalin and two methyl-substituted decalins Two Can alkanes Eleven Cal alkanes Nine Cal alkanes Thirteen C~3 alkanes Eleven C~4 alkanes Eight C's alkanes Eight C'6 alkanes Five C~7 alkanes Three C,~ alkanes Seven methyl-substituted butenes and two methyl butadienes Eighteen pentenes and pentadiene Fourteen hexenes Six heptenes Four octenes Decene and dodecene through heneicosene Seven cyclic olefins Seventy-one alkyl-substituted benzenes Eight styrenes and the three xylenes Fourteen indans and three indenes Twenty-eight alkyl-substituted naphthalenes Three alkylthiophenes and two benzothiophenes Two alkylsulfides and one alkylamine Six nonaromatic alcohols and eight aromatic alcohols Eighteen aliphatic and aromatic aldehydes Six furans, 17 ketones, and six organic acids SOURCE: Adapted with permission from the National Research Council 1983b. zones, and derivatives of the polycyclic aromatic hydrocarbons (PAM)
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From page 66... ...
Nonpolar fractions Phenanthrenes and anthracene Methylphenanthrenes and methylanthracenes Dimethylphenanthrenes and dimethylanthracenes Pyrene Fluoranthene Methylpyrenes and methylfluoranthenes Chrysene Cyclopenta|cdlpyrene Benzotghi] fluoranthene Benz~ajanthracene Benzota~pyrene Other PAHs, heterocyclics HCs and alkylbenzenes Total nonpolar fractions Moderately polar fractions PAH ketones Fluorenones Methylfluorenones Dimethylfluorenones Anthrones and phenanthrones Methylanthrones and methylphenanthrones D imeth ylan thrones and dim eth ylp hen anthro nes Fluoranthones and pyrones Benzanthrones Xanthones Methylxanthones Thioxanthones Methylthioxanthones Total PAH carboxaldehydes Fluorene carboxaldehydes Methyl fluorene carboxaldehydes Phenanthrene and anthracene carboxaldehydes Methylanthracene and methylphenanthrene carboxaldehydes Dimethylanthracene and dimethylphenanthrene carboxaldehydes Benz~ajanthracene, chrysene, and triphenylene carboxaldehydes Naphthalene dicarboxaldehydes Dimethylnaphthalene carboxaldehydes Trimethyluaphthalene carboxaldehydes Pyrene and fluoranthene carboxaldehydes Xanthene carboxaldehydes Dibenzofuran carboxaldehydes Total PAH acid anhydrides Naphthalene dicarboxylic acid anhydrides Methylnaphthalene dicarboxylic acid anhydrides Dimethylnaphthalene dicarboxylic acid anhydrides Anthracene and phenanthrene dicarboxylic acid anhydrides Total (Table continued next page.)
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From page 67... ...
Continued Compound Approximate Concentration in Oldsmobile Extract (ppm) Hydroxy PAHs Hydroxyfluorene Methylhydroxyfluorene Dimethylhydroxyfluorene Hydroxyanthracenes and hydroxyphenanthrenes Hydroxymethylanthracenes and hydroxymethylphenanthrenes Hydroxydimethylanthracenes and hydroxydimethylphenanthrenes Hydroxyfluorenone Hydroxyxanthone Hydroxyxanthene Total PAH quinones Fluorene quinones Methylfluorene quinones Dimethylfluorene quinones Anthracene and phenanthrene quinones Methylanthracene and methylphenanthrene quinones Fluoranthene and pyrene quinones Naphthot1,8-cdlpyrene 1,3-dione Total Nitro-PAHs Nitrofluorenes Nitroanthracenes and nitrophenanthrenes Nitrofluoranthenes Nitropyrenes Methylnitropyrenes and methylnitrofluoranthenes Total Other oxygenated PAHs PAH carryover from nonpolar fraction Phthalates, HC contaminants Total, moderately polar fractions 1,400 400 1,500 600 900 1,300 2,000 1,300 1,000 10,400 700 600 500 1,900 2,000 200 600 6,500 30 70 10 150 20 280 8,000 6,000 30,000 91,000 SOURCE: Adapted with permission from the National Research Council 1983b.
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anthracene Nitro (C3-alkyl) phenanthrene Nitrochrysene Nitrobenzoanthracene Nitronaphthacene Nitrotriphenylene Nitromethylnaphthacene or nitromethylchrysene Nitromethylbenzanthracene Nitromethyltriphenylene Nitrobenzopyrene Nitroperylene Nitrobenzofluoranthene Automotive Emissions Polynitroarenes Dinitromethylnaphthalene Dinitrofluorene Dinitromethylbiphenyl Dinitrophenanthrene Dinitropyrene Trinitropyrene Trinitro (C5-alkyl)
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From page 69... ...
Measurement of particulate emissions from heavy-duty diesel engines using the EPA test procedures with dilution tunnels is inadequate. The current reneatabilitv of measurements is poor.
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From page 70... ...
of diesel engines. Flow reactor studies with the basic species NO, NO2, CO, CON, N2, 02, S02, HCs present in the exhaust, along with detailed engine studies that include the effects of the particles in the reactions, could help resolve this issue.
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From page 71... ...
Recommendation 7 Data should be obtained about the size distribution of particles in Diesel Fuel diesel exhaust and about the metal species they contain with and Additives without a particulate trap, with a diesel fuel containing a typical additive under consideration for production use. Data on the HCs bound to the particles and the vapor-phase HCs should also be obtained.
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From page 72... ...
Recommendation 9 There is a need for a program of comparative measurements of PAH measurements PAHs in partial-exhaust sampling systems and in full-flow dilution tunnel systems, with measurements made in the atmosphere down wind from the plume, for the purpose of determining how well laboratory data reflect the true composition of emissions into the atmosphere. Recommendation 13 There is a need to investigate and develop analytical methods that Diesel Odor quantify diesel odor.
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From page 73... ...
1985. The trap oxidizers an emission control technology for diesel engines, Society of Automotive Engineers Paper 850015, Warrendale, Pa.
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From page 74... ...
1985. Diesel particulate trap regeneration using ceramic wall flow traps, fuel additives, and supplemental electrical igniters, Society of Automotive Engineers Paper 850016, Warrendale, Pa.
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From page 75... ...
1984. Current and future light duty diesel engines and their fuels, Society of Automotive Engineers Paper 840105, Warrendale, Pa.
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