[Digestion] Diesels with pilot fuel injection

[F. Marc de Piolenc]

This is very encouraging. I have NACA reports from the 30s reporting 
successful use of hydrogen in diesels with pilot injection, but when 
I mention it to contemporary "experts" I get blank looks, and solemn 
assurance that it is not practical to replace more than 70% of the 
diesel fuel with gas. Here in the Philippines the main application is 
pollution reduction in big cities, and fleet vehicles - buses and 
delivery trucks - are the main target. But being able to use biogas 
in a diesel vehicle should be a strong incentive to implement 
small-scale anaerobic digestion - in piggeries especially - so this 
technique could have a further environmental benefit.

Can you direct me to manufacturers of engines or conversion kits, or 
any (preferably online) information that supports my contention that 
diesels can be run on a high percentage of gas fuel without adding 
spark ignition?

The NACA reports are "old," you see - and as everybody knows, the 
laws of physics and chemistry are completely different these days!

Marc de Piolenc
http://www.archivale.com/catalog/

"Zietsman, Rex" <Rex at Process.co.za> wrote:

Realistically, you can get down to about 70% to 80% replacement but with
a whole lot of challenges. With bleeding into the air intake, you can
safely replace 50% of the diesel with low risk of mechanical problems -
over fueling, etc. If you are running at a nice steady load, you can
increase the replacement but, to get to the really high replacement
values, you need to control both the gas and the diesel. This is less
straight forward than simply bleeding in the biogas.

For your information, there are engines out there that have pilot diesel
injectors in addition to the main injectors. They start with diesel on
the main injectors, introduce gas cutting back on the diesel until only
the pilot injectors are running. This cuts back the diesel to as low as
1%, just enough to fire the gas mixture. So, when answering your
question, it is a bit of "how long is a piece of string?".


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