Urban Air Pollution / Mobile Sources
Urban Air Pollution: Motor Vehicle Emissions
3/30/2011
Urban Air Quality • One to two centuries ago in developed cities – Industrial sources – Domestic heating (coal and some wood) – London Fog
Petros Koutrakis, Ph.D. Professor of Environmental Sciences Harvard School of Public Health Copyright © 2000 Petros E. Koutrakis, Ph.D. This presentation may not be reproduced, in whole or in part, without the express written permission of the author.
London December 1952
Urban Air Quality • Modern cities – Less industry and domestic heating – More vehicular emissions
4000 persons died as an atmospheric ‘inversion’ trapped a cloud of toxic smog in the city. city Emissions from the burning of coal fuel, used in home heating, produced particulates and other pollutants in air and enabled them to penetrate into the lungs.
Harvard University / ENVR E-102 / Koutrakis
• Photochemical smog – Experiments by Professor Haagen-Smit
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Urban Air Pollution / Mobile Sources
Most Vehicles Are In Cities
Major Cities Around The World Are Increasingly Polluted
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Los Angeles Over the Last 60 years
One Result: Serious Health Concerns • According to WHO: 800,000 Premature Deaths Each Year From Urban PM • Ozone, NO2, Various Toxics Also Serious Health Concerns
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Urban Air Pollution / Mobile Sources
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Billions of Vehicle Miles per Day in US
Millions of Barrels of Gasoline per Day in US
Energy Demand in the Transport Sector:
Petroleum Consumption by Sector
Annual Average Growth Rate (%) by Region 2004 - 2030
6 5 Growth (%) G
4 3 2 1 0
Source: IEA WEO 2006
Harvard University / ENVR E-102 / Koutrakis
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Urban Air Pollution / Mobile Sources
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Vehicle Miles vs. Population 1975-1995 Population Growth rose only 27%
Carbon Dioxide is Not The Whole Story!
1975-1995 V hi l miles Vehicle il ddriven i iin the h United States increased by 125% to 2.5 trillion miles/year
While cars are 95% cleaner today than in 1975, overall atmospheric pollution has increased.
World Motor Vehicle Population
Fleet Average Emission Trends
Millions 1200 1000 800 600
Motorcycles Commercial Vehicles Cars
400 200 0 1930
1940
1950
1960
1970
1980
1990
2000
Calendar Year
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Urban Air Pollution / Mobile Sources
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EU and US Passenger Car Exhaust Emissions Standards
Internal Combustion Engine
NOx Emissions Standards Grams/Kilometer 5
4
3
US Gasoline
EU Gasoline
US Diesel
EU Diesel
2
1
0 1973 1976 1979 1982 1985 1988 1991 1994 1997 2000 2003 2006 2009
Internal Combustion Engines
Burning of a Hydrocarbon Fuel +
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Urban Air Pollution / Mobile Sources
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The Otto Cycle Spark-ignition Engine
An 1876 Version of Otto’s Engine
N. A.Otto (1831 - 1891), from Germany, d l d the developed h ffour-stroke k cycle l engine i in i a series i of experiments dating from 1862. He founded the first engine company - "N.A.Otto & Cie". In 1867 he won a gold medal at the Paris Exposition. Nicolaus August Otto
http://techni.tachemie.uni-leipzig.de/otto/otto_g0_eng.html#takte http://techni.tachemie.uni-leipzig.de/otto/otto_g0_eng.html#takte
Parts of the Spark-ignition Engine
The Otto Cycle - intake stroke
IV = intake valve SP = spark plug EV = exhaust valve PR = piston ring P = piston CR = connecting rod CS = crank shaft
http://techni.tachemie.uni-leipzig.de/otto/otto_g0_eng.html#takte
Harvard University / ENVR E-102 / Koutrakis
http://techni.tachemie.uni-leipzig.de/otto/otto_g0_eng.html#takte
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Urban Air Pollution / Mobile Sources
The Otto Cycle - compression stroke
http://techni.tachemie.uni-leipzig.de/otto/otto_g0_eng.html#takte
The Otto Cycle - power stroke
http://techni.tachemie.uni-leipzig.de/otto/otto_g0_eng.html#takte
Harvard University / ENVR E-102 / Koutrakis
3/30/2011
The Otto Cycle - ignition
http://techni.tachemie.uni-leipzig.de/otto/otto_g0_eng.html#takte
The Otto Cycle - exhaust stroke
http://techni.tachemie.uni-leipzig.de/otto/otto_g0_eng.html#takte
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Urban Air Pollution / Mobile Sources
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Four Stroke Gasoline Engine
Vehicular Emissions • Hydrocarbons – Engine exhaust – Crankcase emissions – Evaporative losses
• Nitrogen oxides, Carbon monoxide – Engine exhaust
• Sulfur dioxide and particles – Engine exhaust Source: How Stuff Works (www.howstuffworks.com)
Sources of Automobile Pollutants Volatile Organics Fuel Evaporation
20%
Engine Exhaust
Percentage estimates prior to application of emissions controls
U.S. Federal Motor Vehicle Exhaust Emission Standards (g mi-1)
CO HC NOx as NO2
Autos A t 3.4 0.4 1.0
Trucks T k 17 0.9 2.0
Crankcase Vapors
60%
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20%
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Urban Air Pollution / Mobile Sources
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EPA Emission Standards
Pollutant Emissions from the Internal Combustion Engine • Exhaust emissions: – – – – – –
Air fuel ration Ignition timing Compression ratio Combustion chamber geometry Engine speed Type of fuel
Source: Ecopoint, Inc.
Air/Fuel Ratio
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Three-Way Catalyst Control
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The Three-way Catalytic Converter
Tailpipe Emissions Control
Layered washcoat architectures andd support materials i l with i h hi high h thermal stability Integrated HC adsorption functions Mounting materials with improved p durabilityy High cell density ceramic or metallic substrates Insulation schemes for heat management
Light Duty MV Emissions Test
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MV Emissions Test Graph
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Urban Air Pollution / Mobile Sources
Pollutant Emissions from the Internal Combustion Engine
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Crankcase Emissions Control
• C Crankcase a case emissions e ss o s – Definition – Depend on engine airflow – Controlled since 1963
Pollutant Emissions from the Internal Combustion Engine
Evaporative Emissions Control
• Evaporative emissions – D Definition fi iti (from (f tank t k andd engine) i ) – Depend on temperature and fuel volatility
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Urban Air Pollution / Mobile Sources
Evaporation Canister
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Diesel Engine Cycle
Source: How Stuff Works (www.howstuffworks.com)
Some Diesel Facts • Diesel’s market share in Europe rose from 7% to 33% in i the h two decades d d 1980 - 2001 • Only 3% of US passenger vehicles are diesel • A diesel engine uses 65% of fuel that is required by a spark ignition engine doing comparable work
Harvard University / ENVR E-102 / Koutrakis
Diesel fuel has a higher energy density than gasoline. On average a gallon of Diesel fuel average, contains approximately 155x106 joules (147,000 BTUs), while a gallon of gasoline contains 132x106 joules (125,000 BTUs). This, combined with the improved efficiency of Diesel engines, explains why Diesel engines get better mileage than equivalent gasoline engines.
Diesel versus Gasoline The Energy Advantage Diesel fuel has a higher energy density than gasoline. On average, a gallon of Diesel fuel contains approximately 155x106 J (147,000 BTU ) while BTUs), hil a gallon ll off gasoline li contains i 132x10 132 106 J (125 (125,000 000 BTUs). This, combined with the improved efficiency of Diesel engines, explains why Diesel engines get better mileage than equivalent gasoline engines.
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Urban Air Pollution / Mobile Sources
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Typical Diesel Truck Emissions
Diesel Generated Air Pollution • • • • •
Catalyst-based Particulate Filter (A Johnson-Matthey proprietary design)
CO2: 935 g/km CO: 1.76 g/km NOx: 7.69 g/km fine PM: 0.185 g/km Semi volatile organic gases: 54 mg/km PM phase organic compounds: 41 mg/km Fine p particles consist of 19.7% organic g C,, 30.8% elemental C, remainder being all inorganic material
How The Trap Functions
NO is oxidized to NO2, which reacts to burn soot, CO and VOC
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Urban Air Pollution / Mobile Sources
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Diesel Particulate Filters
Emissions control system for Euro VI
Reductions:
Trapped PM
•-80 to 95% PM
Cell Plugs •-80-100% HC, CO •-80%+ toxins
Exhaust (CO2, H2O) Out
Exhaust (PM CO, (PM, CO HC) Enter
Ceramic Honeycomb Wall
Oxidation catalyst (DOC), catalyst-based particulate fil andd urea-SCR filter SCR with i h ammonia i slip li catalyst l (ASC) (ASC). NOx sensor
(optional) NOx sensor
DOC
Mixer
SCR + ASC
Issues to balance: •sulfate formation •regeneration and back pressure •Fuel Economy
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National Fuel Consumption
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Environmental Impact of Cars
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Urban Air Pollution / Mobile Sources
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Light-Duty Automotive Technology and Fuel Economy Trends
Electric Vehicles Zero Emissions Electric Vehicles (EV) generate no pollutants
Source: Ford Motor Company
Electric Motor
70 Miles Per Gallon Commutator (switch) reverses current to electromagnet each half cycle.
Honda Click Here for
360o Exterior View
Gasoline Electric Hybrid
Cli k Here Click H for f
360o Interior View
The future of transportation: Ecologically--minded and fuelEcologically fuel-efficient Source: How Stuff Works (www.howstuffworks.com)
Harvard University / ENVR E-102 / Koutrakis
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Urban Air Pollution / Mobile Sources
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Hybrid Vehicles
Hybrid ‘Parallel Configuration’
"Parallel" or "Power Assist" Hybrid Vehicle Configuration
A hybrid differs from an all-Electric V hi l in Vehicle i that th t it uses an internal i t l combustion engine to generate electricity for its electric motor. As a result, hybrid vehicles can be designed to never need recharging from an external source of electricity. Their need for batteries can also be reduced to little more than needed for a typical gasoline vehicle.
Benefits of a parallel configuration versus a series configuration: The vehicle has more power because both the engine and the motor supply power simultaneously
Cmb - Miles per gallon (combined), based on 55% city and 45% highway miles
Plug In Hybrids Are Emerging
Vision For 2015 • Every New Diesel Has PM Filter & Low NOx • Gasoline Vehicles Approaching pp g ZERO Emissions • Hybrid Technologies (Including Plug In Hybrids) Are Mature, Widespread Technology • Small Battery Electric Vehicles (City) Vehicles Widely Used • Fuel Cell Vehicle Numbers Increasing
Harvard University / ENVR E-102 / Koutrakis
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Urban Air Pollution / Mobile Sources
Future Fuels • • • •
Fuel cells (clean but rely on a fuel) Hydrogen (clean but rely on a fuel) Bio-fuels (limited supplies) Electricity (potentially for countries with sufficient electric supplies) • ???
Bio-diesel • Alkyl esters produced from fats/oils and alcohols (ethanol or methanol) • Domestic bio-production capacity • CO2 emissions are fully offset in nature • Infrastructure is not dramatically different • Adaptation of existing engine design is relatively straightforward
Harvard University / ENVR E-102 / Koutrakis
3/30/2011
Future Cars • Large size cars (diesel with controls) • Medium size cars (hybrid) – Powered electrically
• Small size cars (more efficient)
What are the regulatory tools to minimize mobile source emissions? • Vehicle emission standards • Fuel economy standards (CAFÉ—Corporate Average Fuel Economy) • Fuel formulation specifications • Inspection p and maintenance p programs g • Adoption of alternative technologies • Traffic control strategies
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Urban Air Pollution / Mobile Sources
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The Diesel Cycle Compression-ignition Engine After studying the internal combustion engines developed by Nikolaus Otto, Diesel conceived of an engine that would approach the thermodynamic limit established by Sadi Carnot in 1824. If the fuel in a cylinder could be expanded at constant pressure, it could get closer D R d lf Diesel Dr.Rudolf Di l to Carnot's limit. He patented the b 1858 Paris,. Educated at concept in 1892, while working at the Munich Polytechnic Inst.. d1913, English Channel firm of Carl von Linde in Berlin. http://world.std.com/~jlr/doom/diesel.htm
Diesel Cycle Air Intake Process
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Diesel Cycle Compression Process
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Urban Air Pollution / Mobile Sources
Diesel Cycle Combustion Process
Diesel Cycle Release Process
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Diesel Cycle Expansion Process
Diesel Cycle Exhaust Process
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Standardized Comparison of International Fuel Economy and GHG Standa MILES PER GALLO ON (A All countries converted to CA AFE test
55 50 45
UNITED STATES EUROPE JAPAN AUSTRALIA CANADA CHINA CALIFORNIA S. KOREA Dotted line: Proposed or contested Solid lines: Enacted
EUROPEAN UNION JAPAN
40 CHINA
35
AUSTRALIA CANADA
UNITED STATES
CALIFORNIA + 16 STATES
S. KORE
30 25 20 2002
2004
2006
2008
2010
2012
2014
2016
2018
2020
2022
Source: Passenger Vehicle Greenhouse Gas and Fuel Economy Standards: A Global Update, International Council on Clean Transportation, 2007
Slide 77
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