Water injection (was: Re: fuel cooling intake air)

[Axel Rietschin]

----- Original Message -----
From: "Bruce Plecan" <nacelp at bright.net>

>  I tried explaining it to you and you don't get it,  If you want to call
my
> explaination is in error in your opinion fine

I do. By the way, do you have a turbine speed measurement setup? (I have a
turbine speed input in my ECU, but I currently don't know what kind of
sensor to use).

> > Modern ECUs just happens to be "clever and precise" and last time I
> checked,
> > reliability was not such a problem, so why not apply the same concept
for
> > WI, too?
>
> The term KISS seems to apply here.  Ricardo explains the ratios of water
to
> fuel, and they need not be anywhere as exacting as fuel does.

While it is true that water is cheap, I'm trying to spend the least of it.
This may not be a concern to you given the short running times you have to
make.

> > > as you approach max torgue, and continues to max HP
> > What's the difference? same amount of work, different rate.
>
> You asked when, I answered, and then you restate the obvious, what's your
> point?

Sorry, I misread you.

>
> > >  Does this speed fall in the diesel engines operating
> > > > range? Below that speed, what the water is useful for, beside as an
> > > > in-cylinder coolant and detonation retardant?
> > > Define diesel's operating range..
> > Low rpm. Now please answer the question: what's the 'magic' speed?
>
> OK, now what's your definition of speed?

It is my general perception that diesel engines runs slower than SI engine.

Also, it seems that the benefits of water on combustion are realized at high
rpm "It is important to note that these improvements came at the upper end
of the power range where sufficient fuel and air was available to have an
excess of energy that could not be converted to usable pressure in a timely
manner." said Mr. Harris.

So I'm interested in knowing the approximate speed referred to as "the upper
end of the power range". If we are talking F1 engines, it may well be around
18000 rpm or more.

It is my understanding that the combustion should take at most 40-50 crank
degrees or so, thus there must be a speed above which this cannot be
realized, the crank turning too fast, and power is wasted.

Water, speeding up the combustion as I've just learned, should help release
the energy quick enough.

Also, IMHO, the maximum torque speed (as in your statement above) is
certainly not a speed where any "excess of energy" cannot be "converted in a
timely manner" - or it would not be the "maximum torque" speed, indeed.

Then, given that, as noted by Mr. Colon, "the total energy is of course the
same" and that you need "sufficient fuel and air" so I still fail to see how
you can _gain_ anything by making your engine swallow its air already
saturated with water vapor. I argue that you _recover_ a lot of power that
would otherwise be lost due to abnormal combustion, and I pretend that you'd
probably recover more by injecting the water as late as possible. This claim
in backed up by information posted on the ERL web site (see Mr. Dennis Doza
II's post) where someone saw a power increase of 5-20%, IIRC, by injecting
water directly inside the combustion chamber. They claim the gain comes from
vapor pressure, so no complex thermochemistry here, according to them.
Please note that I mentioned the potential gain due to vapor pressure,
thanks to in-cylinder evaporation, in my original post.

Reports and testimonies I've read so far in this thread (and related ones
recently posted) supports more the "detonation retardant" due to
"in-cylinder cooling" aspect of things, allowing to safely reach MBT by
proper spark advance setting,  than the "combustion stimulator" side, so I
come to suspect that this benefit, while apparently tangible and real, is
only seen at very high engine speed, probably well above a typical diesel
operating range, running lean of top of that ( "20 percent (or more) lean of
stoichiometric" [at maximum engine power] - Heywood 10.1, p492) so there is
not that much "excess of energy" to be released anyway. Also, what Saab is
able to achieve in a research lab may not be easy to reproduce at home. For
example, I know they use a variable compression engine in their quest for
maximum efficiency.

The speed issue may explain why I saw nothing on my own engine, which only
runs up to 8000 rpm, speed at which gasoline seems to burn fast enough (too
fast, indeed, as I'm facing detonation when I insist with spark advance).

Axel


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