Re: [Amc-list] Interesting Water Injection for DIY

[adh@xxxxxxxxxxxxxxxxx (Sandwich Maker)]

" From: Tom Jennings <tomj@xxxxxxx>
" 
" On Thursday 02 August 2007 07:49:40 Don Johnson wrote:
" > Tom, I think you're off a little in your explanation of the use of water
" > injection. Water injection is used in aircraft to slow the onset of
" > detonation at high boost and power settings. Steam will not increase
" > cylinder pressures over what is obtained by burning gasoline, especially at
" > high boosts.
" 
" I don't recall my source so I'll defer to you here. Somewhere though I recall 
" a discussion of handling wasted heat -- since producing heat to increase gas 
" pressure of course is all the burning gasoline is good for! -- but I could 
" have the scale of things off, for starters, or just be plain old wrong (nahh, 
" that never happens :-)
" 
" Was W.I. used WITH turbo/supercharging then?

it was, on the merlins used in spits and mustangs.

" > Water injection slows the burning and avoids detonation which 
" > allows more power to be derived from the engines during emergency
" > conditions. I believe water injection was either selected or came in
" > automatically at boost above a certain number of inches of manifold
" > pressure. 
" 
" For suppressing detonation the amount and timing would be pretty critical. I 
" bet all that aircraft stuff is well-documented somewhere, especially the old 
" stuff. Would be some interesting reading. 

there's a book by sir harry ricardo, from the mid-late '60s, a virtual
encyclopedia of internal engine development over the 4 decades since
the '20s - and not just engines his firm worked on.  there's also a
lot of technical analysis and discussion iirc about various
technologies, most of which you've never heard of, with examples.
sleeve valves?  double sleeve valves?  several kinds of rotary valves.
opposed pistons of course.  etc.

iirc as he describes it, the rr water/alcohol [antifreeze] injection
was into the eye of the centrifugal compressor where it worked a bit
of synergy: the heat of compression vaporized the water, distributing
it evenly, and the vaporizing water cooled the compressed air, making
the compressor more efficient.  one penalty: water droplets impacting
the fast-turning compressor tended to erode the blades.

it engaged automatically at high boost.  the compressor had multiple
speeds - up to 3 - aneroid comtrolled, so that your boost increased
automatically as you climbed.  the engine would not tolerate maximum
boost even with w.i. at low altitudes.

also iirc he says something about w.i. increasing engine efficiency,
but at a mechanical and operational complexity that's scarcely worth
it for that alone.  maybe today, with electronics...  but the biggest
problem the olds turbo 215 had was owners neglecting to refill the
water injection tank.

and for those of you who don't know it, ricardo's is the world's
largest independent internal combustion r&d company, and he pioneered
the field.
________________________________________________________________________
Andrew Hay                                  the genius nature
internet rambler                            is to see what all have seen
adh@xxxxxxxxxxxxxxxxx                       and think what none thought
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