water into efi system before injectors.

[Greg Hermann]

>At 08:20 PM 13/3/2000 -0700, you wrote:
>
>>No papers I know of, but have done the math/thermo. Comes out to about 75
>>or 80% of mass flow rate of stoich fuel mix fuel flow in water will get you
>>saturated vapor conditions at TDC when it's time for the spark. Any more
>>than this, and you lose power.
>
>mmm Can you clarify - for say 100ml of fuel flow per minute you want
>75 to 85 ml water flow ?

!00 GRAMS of fuel flow would equate to 75 or 85 GRAMS of fuel flow--the
water is denser than the fuel, though.
>
>>Same old saw--gotta have the H2O atomized, but not vaporized until the
>>intake closes, or you lose because water vapor (molecular weight = 18)
>>displaces a lot of air (avg. molecular weight =29), thus losing you power.
>
>Probably due to heat difference between liquid water and gaseous water
>at 100deg C transition, ie Latent heat of vaporisation - can swallow
>large amount of heat...

Precisely. What is going on is the compression stroke begins to act a lot
more like an isothermal process than an adiabatic one. Consequently, much
less power goes into the compression stroke. Temperature at TDC (ignition
event) is MUCH lower--on the order of 235 to 250 degrees F, instead of 900
degrees or so.

Lower peak temp after burn means less power available on the expansion
(power) stroke, but this is more than completely balanced by the lower
negative power on the compression stroke. (About 1.5% net gain.)

Lower peak cycle temp means significantly lower losses to water jackets,
though, so net gain becomes still greater.

Durability is of course significantly improved with the lower temps.

Lower temps and lower partial air and fuel vapor pressures at TDC help
avoid detonation, and there is also the detonation resistance added by the
highly polar chemical nature of the water molecules themselves  and that
effect on the free radical detonation precursor molecules during the
combustion process itself.


>
>>Ideal amount of water increases with increasing effective compression ratio.

Basically this means that with higher compression ratio, there is more work
available to provide latent heat with which to evaporate the water.

Lots of folks don't realize that engines running straight methanol fuel
have _NOT_ evaporated all of the fuel at TDC!! Not enough work available to
provide the needed latent heat! The first part of the burn provides heat to
finish evaporating the fuel.
>
>Has anyone published any actual curves, water flow vs power vs CR vs Fuel
>or anything even similar ?

Never seen any, Riccardo published as much as I have seen.

Greg
>
>Rgds
>
>:) mike
>
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