[Gasification] engine

[Daniel Chisholm]

On Tue, 2007-06-02 at 07:18 -0800, Toby Seiler wrote:
> Jim and Doug Williams and list;
>    
>   Is the compressability of the gas affected by the amount of nitrogen
> in it?  If the gas had higher hydrogen content and lower nitrogen,
> would you expect it to precombust more or less?  How would compression
> ratio be affected? 

By "compressability" I assume you mean, how much can you compress the
gas:air mixture before you get detonation problems?

In an engine you start with combustion, which might (you hope not!)
transition into a detonation.  The combustion might be intentional
(spark plug firing, or diesel fuel spray), or unintentional (a hot spot
pre-ignites the mixture).

The transition to detonation is favoured by an increase in density, an
increase in temperature, a reduction in the inert fraction (i.e. N2),
and the fuel characteristics (different fuels have different detonation
thresholds).

So, a lower nitrogen content (let's say you use syngas) would result in
a more-easily-detonated gas:air mixture, which you would have to
compensate for by using a lower compression ratio in order to avoid
detonation.

>   Jim, how about putting another stage in your setup?  Setup a chamber
> that feeds wet fuel  into a hot zone created by the hot gas of stage
> one, under very precise manual control.  Flare it off and compare.  I
> think the higher water content can be made into an advantage in
> reducing nitrogen and increasing hydrogen for your engine feed gas.

Adding water won't make more hydrogen, unless you have energy available
(temperature) to make the reaction happen.  If you want a higher
calorific fuel, you have to increase the thermal efficiency of your
gasifier - insulate it, make sure that you are not too far from
equilibrium (don't want excess air), make use of hot gas stream's heat
(e.g. preheat your air or fuel).


-- 
- Daniel
Fredericton, NB  Canada