Mortimer wrote:
> "z" <gzuckier@[EMAIL PROTECTED]
> wrote in message
>
news:e7a73155-1e9e-4bd6-8955-464cab4a30b8@[EMAIL PROTECTED]
> On May 8, 1:50 pm, N8N <njna...@[EMAIL PROTECTED]
> wrote:
>>>> 2: Unthrottled operation. In the Diesel cycle load is controlled by
>>>> fuel
>>>> alone. This reduces gas pumping losses incurred during the
>>>> intake/exhaust strokes. In future Diesels this may fade somewhat as
>>>> throttling is being used to facilitate achieving the EGR levels
needed
>>>> to meet oxides of nitrogen regulations.
>
> So having an excess of air, compared with the minimum needed to fully
burn
> the fuel, is actually a bad thing for a diesel, is it, as regards the
> production of NOx?
>
Yes. Even though the overall A/F is lean, the nature of the Diesel
combustion process is that of a stratified charge process. This, to
simplify, means that overall while there is just air in the cylinder, as
the fuel is injected, the charge is locally closer to stoichiometry
(which burns pretty hot). So, when you have high temperatures and plenty
of excess O2, you get high NOx production.
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