Fw: Holden Commodore, Aerodynamics. AND NOW: WATER INJECTION...

[Chris Conlon]

Hi yall, it's good to be back.

Actually I really wanted to ask if anyone had any info about
injecting hydrogen peroxide, downstream of a turbo or SC. I'd like
to think with the right strength (30%?) you could get some of the
water-injection intercooling effect, but also some extra O2 from
the H2O2 breaking down. Hopefully it would all break down before
hitting the fuel, if not that'd probably be "bad", so it seems
like it's best suited to a low-efficiency SC and would only be
turned on above some temperature.

(Don't worry, I wouldn't do this any more than I'd do nitromethane
injection, I just wondered what people had to say about it.)

But while I'm here I can't resist this tidbit:

Wayne Strasser wrote:

> By injecting more water, the
> normally-wasted heat energy is utilized to induce a phase change in the
> water from liquid to vapor, which obviously raises combustion chamber
> pressures since water (at STP) expands by a factor of ~ 1400 when
> evaporated.  Obviously, there is some optimum point here, since the
> existence of water molecules in the chamber impedes radical electron
> transfer processes and drops temperatures (hence the impact on
> detonation).
> not sure where that optimum is....comments from all?

The problems are the high heat capacity of water and the high latent
heat of vaporization. You only get some number of kJ from burning
your cylinderfull of gas+air, and the water takes a great amount
of that heat to heat up and evaporate. Yes, it expands tremendously
when it does evaporate, and that's the only way you might come
out ahead, because otherwise that heat of evaporation will kill
you. It might help to have the water almost at boiling when you
inject it, but even so, compare water to some other hypothetical
fluid with a very low latent heat of vaporization. This other
fluid will use up much less energy evaporating, leaving much more
to heat & pressurize the just-evaporated gas.

(As an aside, does anyone have the actual figures for latent heat
of v. for water, the the heat capacity of air? I think the former
was something like 500cal/g but I'm really not sure. I'd love to
make some actual calculations of some of this stuff.)

OTOH it's exactly this high latent heat of v. that makes water
injection so great for intercooling.

Probably the optimum is somewhere near the point at which the
water is heated almost to evaporation just before entering the
cylinder. You get maximum usable intercooling (without diluting
your charge with a tremendous volume of water vapor), but during
combustion the water *does* vaporize, giving you the phase
transition, but for a minimum of required heat. Now if someone
can manage the perfect droplet size profile to achieve this...

(The above theoretical b.s. aside, yeah, it's a research project.)

   Chris C.

p.s. got a cone shaped hat on order just in case I flubbed this one.