Air Pollution & Vehicle Emissions

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    AIR POLLUTION &

    EVAPORATIVE EMISSIONS

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    Hydrocarbons

    Unburned fuel vapors

    When exposed to sunlight, chemical

    reaction occurs that producesground-level ozone O3.

    Harmful to all living things

    Vehicle emissions create 50% of thisozone

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    Carbon Monoxide

    Colorless, odorless, toxic gas

    Product of incomplete combustion

    Displaces oxygen which reducesoxygen in bloodstream

    Vehicles produce 2/3s of co in

    atmosphere

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    Carbon Dioxide

    Product of proper combustion

    Does not directly impair human

    health Greenhouse gas

    Traps heat

    Helping to increase global warming

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    Just What is Ozone?

    Ozone is a form of oxygen with adifferent chemical property

    Ozone differs from oxygen: Has a distinctive odor Contains 3 oxygen atoms

    Absorbs damaging ultraviolet (UV)

    radiation

    In large concentrations ozone ishazardous

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    Earths Atmosphere

    Troposphere start on the

    surface and extends 59

    miles

    Air most dense

    All weather occurs is

    this region

    Stratosphereextends for31 miles

    Contains the Ozone layer

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    Good Ozone

    Blocks or absorbs most of the

    suns ultraviolet rays

    Approx. 3,000 million tons of

    ozone in atmosphere

    If concentrated at sea level,

    would measure only 3 mm thick

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    Bad Ozone (Smog)

    Brown haze seen on hot summer days Result from burning fossil fuelschemical

    reaction from heat & sun light

    Health problems

    Aggravates heart, lung ailments Can lower immune system

    Eye & nose irritations

    Environmental problems Inhibits plant growth, weakens plants

    Reduce yields

    Deteriorates man-made materials

    Acid rain

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    Evaporative EmissionsHydrocarbons escaping through fuel evaporation.

    Diurnalgas evaporation as daytime

    temps increase

    Running Lossvaporization fromhot engine & exhaust parts

    Hot Soakhot engines (off),

    vaporization can continue RefuelingVapors forced out of tank

    as liquid fuel enters

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    Evap. Emission Control

    Systems Sealed fuel tankdomed to allow for vaporexpansion

    Liquid-vapor separatorwhen tank is full

    fuel can enter vent lines Vent linesroutes vapor to canister &

    engine

    Activated charcoal canisterabsorbs fuelvapors, releases vapors with fresh air

    Non venting gas cappressure/vacuumrelief valve

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    Carbon Canister

    Holds vapors when engine not running Engine fully warm & off idle, canister

    is purged allowing fresh air in, fuel

    vapors routed to engine & burned

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    Canister Operation

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    Purge Valve

    Normally closed

    Vacuum or electric solenoid

    Engine off or idling valve is closed Engine running valve opens allowing

    purge of canister

    Solenoids either on/off or PWM

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    Basic Purge Operation

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    Thermostatic Vacuum

    Switch (TVS)

    Installed in intake manifold coolantpassage

    Valve opens @ 115 F, allows vacuum to

    flow

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    Canister Venting

    Open bottomWhen purging fresh

    air enters from bottom of canister

    Closed bottomfresh air enters forclean side of air filter

    Electric vent solenoidPCM

    controlled, allows fresh air in whencommanded, seals system when

    closed.