> Also, Hydrogen could be usable to suppress the
knock onset somewhat.
> H/Air mixture burns 5 times as fast as fuel/air
mixture, thus speeding
> up the whole combustion event - so there's less
time for yet-burned
> mixture ahead the flame front to "think about
behaving badly". This is a
> "might", since free hydrogen is a known factor on
knock onset. If H can
> be combined to mostly H2 before injection, it
might help.
> > If H2-assist could be tested together with 16X
-type direct chamber
> injection, we might be able to reach low .40's SFC
on rotaries. Might,
> could, perhaps :)

More notes regarding combustion event and knock:

Some sources state that Formula 1 engines don't
knock above 12 000 rpm.
Things are happening so fast above that point that
there's simply no
time left for knock. That also explains those 5 bar
boost levels on past
1.5 liter F1 turbo engines with 1200 hp peak powers.

12000 rpm is 200 Hz crank frequency, or 5 us per
revolution. If we say
that combustion event is 40 deg or 1/9 of revolution
( -20 - +20 TDC )
then the whole event lasts 0.55 us on 12000 rpm.

6000 rpm is double that, or 1.1 us. So, if this
event can be made 2x
faster by eg. H2 injection (1.5x on 7500 rpm, and
1.35x on 9000 rpm),
we're on realm of 12000 rpm combustion - and
hopefully killed the knock
altogether.

H2 injection could be done by simply installing a
bottle on airplane,
and putting injector on manifold. just like on N20
injection system.
Practical, non-racing or long cruise applications
might need a water
electrolysis unit instead. Gas bottles are not
necessarily light.

Then, how much water is 5% H2 of gasoline flow on 1h
of flight? Let's
take mistral G-360. cruise sfc abt. 0.44 on 65%, so
fuel flow is 103
lb/hr. 5% of this is ~5 lb. And 2x600 hp, 8 hours is
480 lbs.

How much H2 is on one unit of water?
O atomic mass: 16, H atomic mass: 1 =2/18=11%.
Then, for G-360 we would need 45.5 lbs of water per
hour, and 12% less
intake air for combustion, if O2 is injected to
manifold.

40 lbs water for every 100 lbs of avgas? to get 10%
benefit on sfc?

Of course not.
H2 is not cheap, neither are light composite tanks
to keep extra weight
down, so tank H2 injection seems to be limited to
racing - provided it
works at first place.
And electrolysis H2 seems to be limited to marine
and stationary
applications.

But then,
all the time when flying, we are leaving behind a
trail of H2O, CO2 and
NOx. How about a partially closed loop to extract
the water on exhaust
gas, ie. condensing heat exchanger on exhaust
combined with 6-stroke cycle?
Now, Napier Nomad starts to look like a
garden-variety appliance...


Then one semi-unrelated tidbit:

Maximum motor octane number (MON) possible is 124.
This is achieved with
pure toluene with atrocious amounts of TEL - almost
twice what 115/145
AVGAS had. Research octane number for that is about
134, so US pump gas
AKI (R+M/2) for that lead soup would be 129 :)
Aviation PN (performance number) could be something
like 125/170.

So, VP fuels 120 MON air racing brand seems to be as
good as gasoline
ever gets.

Cheers,

Petri

Excellent work Petri. Thanks. You are a very clear
thinker and writer.
You do your homework. You see the big picture.

BTW I added some pictures of the Napier Nomad for
the new people.
-- 
Paul Lamar ...No rotor no motor.

Whoa, back up the math bus a ways. The period of 1
crank rev at 200 R/S would be 5 milli sec not 5 u sec.
Robert



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