Sorry, but this line of discussion has got me on my soapbox.
I think it is somewhat inaccurate to say "diesel engines make more NOx."
Historically, the goal of engine development has been to make an engine as
efficient as possible. From a thermodynamic standpoint, efficiency is achieved
by raising the "input temperature" and lowering the exhaust temperature. This
is what the Carnot efficiency formula tells you. The way you get the high
input temperature is by increasing cylinder compression. (Basic thermo, has
nothing to do with the kind of engine or the fuel.) The great success of the
diesel engine is its undoing:
1) diesel engines are more efficient because they use higher compression
ratios
2) diesel engines are capable of running well on really crappy fuel.
3) diesels have superior combustion efficiency because they can run very
lean.
(This is all explained in an excellent book, Engineering Fundamentals of the
Internal Combusion Engine by W. Pulkrabek, 2nd Ed. 2004. Everyone should read
it.)
If you built a gasoline (spark ignition) engine with the efficiency of a
diesel, it would also have high NOx production.
So, the correct statement might be "very efficient engines make more NOx."
There are four solutions to this problem:
1) Use less efficient engines (e.g., gasoline engines)
2) Develop the catalyst sytem that will work with diesels
3) Forget about NOx, it isn't really a pollutant anyway. The real
pollutants are particulates, HCs (or VOCs) and CO. The problem comes when
these
react with NOx or ozone. Eliminating these removes the problem.
4) Develop a new kind of engine that gets around NOx formation. (A
little harder.)
Ernie Rogers
In a message dated 8/20/2004 7:58:14 AM Mountain Standard Time,
biofuel@yahoogroups.com writes:
Date: Fri, 20 Aug 2004 00:54:59 +0100 (BST)
From: Donald Allwright <[EMAIL PROTECTED]>
Subject: RE: NOX and catalytic converter use
--- Robert Del Bueno <[EMAIL PROTECTED]> wrote:
> So does a 2 way catalytic converter have any effect on NOx,
> specifically
> with biodiesel usage?
> I am sure you see what I am getting at.
> NOx emissions combined with high ambient VOCs are very problematic
> for
> urban areas (specifically Atlanta, GA).
> In order to be able to really push biodiesel usage, the NOx rise must
> be
> addressed.
No, it will have no effect. Therefore, this rise must be combatted at
source, by improving the combustion process. This is one of the
downsides of Diesel engines over petrol engines.
[Non-text portions of this message have been removed]
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