Very interesting.
I have a water injection system on a early Chevy Camaro and I used it to survive
the lousy fuel available in the early 80's while running 11.5:1 compression. It
worked well. Actually it is quite amazing the amount of water a gas engine can
pass without slowing significantly. Running 16 oz through a Chevy V8 (about 5.7
liters) in a couple minutes is not unrealistic.
Dave
>>>>>>>>>>>>>>>>
Richard Notton wrote:
> ----- Original Message -----
> From: "DaveCole" <davidcole@tk7.net>
> To: "Military Vehicles Mailing List" <mil-veh@mil-veh.org>
> Sent: Monday, April 02, 2001 7:48 PM
> Subject: Re: [MV] runaways
>
> > This may sound a bit extreme, but I can't imagine how less extreme a
> runaway
> > diesel might be, but what if someone was to dump some water (hopefully in
> a
> > controlled manner into a diesel engine that was running away. Has that
> ever been
> > done??
> >
> Very tricky indeed.
>
> > It is common (at least to me) to run a small amount of water into a
> running gas
> > engine to clean out carbon deposits. It actually works quite well. The
> trick is
> > to dump it in slowly so the engine can pass the water through it, however
> if you
> > dump it in too fast, the effect is that the engine will slow down
> substantially
> > until it stalls. The water cools off the charge sufficiently to shut down
> the
> > engine. Obviously sticking a running water hose into the air intake would
> > probably blow the engine, but I'm not talking about doing that. Having a
> can of
> > water near the engine upon startup might be a lot more available than a
> C02
> > extinguisher or something that can effectively be used to cut off the
> airflow.
> >
> Firstly remember there is a very fundamental difference between the petrol
> (gas) engine and a CI diesel.
>
> At idle the spark ignition petrol (gas) engine is taking in very little gas
> charge as the throttle butterfly is barely cracked open by a few thou and so
> it is running at a CR of very much less than 1, its often overlooked but the
> spark ignited engine does not realise its CR until full open and then it is
> less than the calculated static figure owing to imperfect cylinder filling.
>
> The diesel has its intake wide open at all times and is controlled by the
> quantity of fuel injected into an always "full" cylinder of compressed air.
>
> The amount of water needed to stop a spark ignited engine at idle or a bit
> above is quite small and in any case virtually sticking a water hose in the
> intake will only take on a minimal amount of water that can get past the few
> thou of the butterfly especially as water is a lot thicker than air, very
> little will kill the engine purely by removing the air supply and pose
> little or no danger of a hydraulic lock.
>
> To stop the diesel, even at idle (where you don't need to anyway), you would
> have to replace most of the wide open inlet air charge with water and this
> quantity would invariably cause a hydraulic lock with disastrous
> consequences. An inert gas like CO2 would be effective and safe but I
> wonder if the average extinguisher bottle actually has sufficient with the
> inevitable wastage to inhibit firing whilst the engine runs down and stops.
>
> Sure, you can clean a spark engine with a drop of water, preferably gingerly
> sprayed into the carb mouth with a fine mist hand sprayer, the effect is
> like a partial steam clean as the already finely atomised water flashes into
> steam when the cylinder fires. It has long been known that water injection
> to petrol SI engines keeps them clean and realises some extra power by
> keeping the inlet charge cool, any drag racer will be able to recite rhyme
> and verse about water injection.
>
> Where the inlet charge has excess unwanted heat entrained in it thus
> reducing volumetric efficiency and leading to detonation, controlled water
> injection is an old technique to alleviate the effect, many WWII military
> aircraft used in PR duties were fitted with almost "drag" engines
> (Mosquitoes especially) and had facilities to allow higher boost
> (supercharge) pressures with methanol and auto water injection to cool the
> mixture owing to the effect of supercharger compression. (Some even had
> nitrous-oxide. . . . .)
>
> I just happen to have a manual for the P&W R4360, a 4 bank radial of 7
> cylinders per bank displacing some 70 litres, there are many references to
> the water injection which is actually a 50/50 mix of water and methanol,
> broadly, it activates automatically at some 50 to 54 inches of mercury
> (that'd be about 25/28psi I guess) inlet boost pressure to cool the now
> compressed and heated inlet charge.
>
> Richard
> Southampton - England
>
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This archive was generated by hypermail 2b29 : Tue May 01 2001 - 07:42:39 PDT