Date: Thu, 12 Dec 1996 17:06:27 -0800 (PST)
From: Mike West <mwest@cdsnet.net>
Subject: Smog, what, why and how

 the old saying goes, 
"The less a man knows,the more he suspects" 

 Well, we suspect government and that's healthy, but reguardless, we
all know the smog laws keep the air relatively clean for our part
and we also know they are getting closer to home on all of us.

 So I thought we should at least find out what they're talking about.

 There's no humour in here, bummer! It's too long as is.

 I'm not an enviromentalist but then again I like breathing.

 These are not my views but more an outline of what, why and how
of the Smog stuff.

 Once we know what we are fighting, we'll know how.

 Probably something from Sun Tzu.   (real old guy)



 smog: "The Big Three"

Identifying the enemy is the first priority, and in the fight for 
clean air the main "perps" are hydrocarbons (HC),carbon monoxide (CO), 
and oxides of nitrogen (NOx).

 HC is simply unburned fuel and lubricating oil, and may be 
found in the crankcase as blow-by, evaporating from the gas tank
and escaping from the tailpipe.

 It is a fact of life that all piston engines must produce some HC 
because the flame front is quenched every time it gets going good, 
which leaves a small amount of fuel unburned.
 Even the cylinder walls in a hot engine are relatively cold.
 
Misfiring and cold engines don't help matters.

 CO is the product of incomplete combustion. If everything were
burned up, you'd get harmless CO2 instead of its deadly cousin.

A mixture that's too rich in fuel or too poor in oxygen will 
cause CO levels to rise. Too cold is in there too.

 Some combustion must occur for CO to form.

 The catalytic converter allows the burning to go on in the exhaust 
system and further reduces HC and CO.

 Adding an air pump or air aspirator assist the catalytic converter
in the burn by bringing in fresh oxygen.

 NOx is a convenient abbreviation for what's actually a group 
of gases, all of which create nasty photochemical smog in the 
presence of sunlight.

 Here's the kicker, some 80% of the atmosphere we breath is Nitrogen.

 These products of combustion are produced during the highest
temperature periods of the Otto cycle.

 There's big problems balancing these bad guys. 

 A lot of what was done to cut the levels of HC and CO raised 
combustion temperatures, and that increased the output of NOx, 
which just shows how contrary nature can be about new laws she 
wasn't consulted on.

 But our engineers kept at it until they found the key: 

 It seems that only the peak temperatures of combustion caused 
nitrogen and oxygen to create NOx, not the long, hot burn that 
reduced HC and CO.

 Diluting the mixture with a relatively inert gas (exhaust) 
through valve overlap and EGR knocked the top off the 
temperature curve and brought NOx production down to acceptable 
levels.

 Other garbage:

 Engines pump other pollutants too, such as particulates (carbonsoot).

 This is what you see as smoke from the tailpipe of a diesel engine, 
and is one reason that type of powerplant has trouble meeting current 
laws in spite of its being relatively clean-running otherwise.

 They're working on it.

 Gas engines don't produce much in the way of this pollutant,
by comparison.

 There's also sulphur which causes acid rain but that will have to 
be removed from the fuel by the manufacturers.

 There is always more 

 west