Ford Taurus, Руководство пользователя

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trapped, so are the pollutants, causing a severe smog condition. Should this
stagnant air mass extend to a few thousand feet high, enough air movement with
the inversion takes place to allow the smog layer to rise above ground level but
the pollutants still cannot dissipate. This inversion can remain for days over an
area, with only the smog level rising or lowering from ground level to a few
hundred feet high. Meanwhile, the pollutant levels increases, causing eye
irritation, respirator problems, reduced visibility, plant damage and in some
cases, cancer type diseases.
This inversion phenomenon was first noted in the Los Angeles, California area.
The city lies in a basin type of terrain and during certain weather conditions, a
cold air mass is held in the basin while a warmer air mass covers it like a lid.
Because this type of condition was first documented as prevalent in the Los
Angeles area, this type of smog was named Los Angeles Smog, although it occurs
in other areas where a large concentration of automobiles are used and the air
remains stagnant for any length of time.
Internal Combustion Engine Pollutants
Consider the internal combustion engine as a machine in which raw materials
must be placed so a finished product comes out. As in any machine operation, a
certain amount of wasted material is formed. When we relate this to the internal
combustion engine, we find that by putting in air and fuel, we obtain power from
this mixture during the combustion process to drive the vehicle. The by-product
or waste of this power is, in part, heat and exhaust gases with which we must
concern ourselves.
Heat Transfer
The heat from the combustion process can rise to over 4000°F (2204°C). The
dissipation of this heat is controlled by a ram air effect, the use of cooling fans to
cause air flow and having a liquid coolant solution surrounding the combustion
area and transferring the heat of combustion through the cylinder walls and into
the coolant. The coolant is then directed to a thin-finned, multi-tubed radiator,
from which the excess heat is transferred to the outside air by 1 or all of the 3
heat transfer methods, conduction, convection or radiation.
The cooling of the combustion area is an important part in the control of exhaust
emissions. To understand the behavior of the combustion and transfer of its heat,
consider the air/fuel charge. It is ignited and the flame front burns progressively
across the combustion chamber until the burning charge reaches the cylinder
walls. Some of the fuel in contact with the walls is not hot enough to burn,
thereby snuffing out or quenching the combustion process. This leaves unburned
fuel in the combustion chamber. This unburned fuel is then forced out of the
cylinder along with the exhaust gases and into the exhaust system.
Many attempts have been made to minimize the amount of unburned fuel in the
combustion chambers due to the snuffing out or quenching, by increasing the
coolant temperature and lessening the contact area of the coolant around the
combustion area. Design limitations within the combustion chambers prevent the
complete burning of the air/fuel charge, so a certain amount of the unburned fuel
is still expelled into the exhaust system, regardless of modifications to the engine.
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18.11.2005 http://www.chiltondiy.com/content/8687/8687_4_1.html