Yes Carsten, I intuitively know their is a limit to what an internal combustion engine can tolerate in atmospheric positive pressure extremes but, I can not explain it. Your explanation appears right on track. Go the other way, negative pressure, and it stops breathing.
Joe
From: Carsten Standfuss <Merlinsub@t-online.de>
Reply-To: personal_submersibles@psubs.org
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Speaking of 1ATM construction...
Date: Sun, 22 Jan 2006 10:35:40 +0100
>The backpressure in a dry ambient is for the motor maye not the
>problem.. but..
>
>Imagine you motor compress the air with a ratio of 1:20.
>
>On the surface:
>Inlet 1 atm , cylinder head compressed say to 20 atm, outlet 1atm
>That means inside the engine 20 bar wants to lift the cylinder head
>against 1 bar on top of it - 19 atm difference right ?
>
>In a dray ambient in 20 meter deep (60foot)
>Inlet 2 atm, clyinder compress that to 2 x 20 = 40 bar, outlet 2atm.
>40 bar inside the cylinder against 2 bar on top of the head = 38 atm
>difference on the head - right ?
>
>I think the cylinderhead will fly away..
>But I am not an engine man and maybe I am wrong..
>
>regards Carsten
>
>
>Nomdae Plume schrieb:
> >
> > Thanks Joe. Backpressure was something I thought about after I sent
> > the email, but I presumed that since the engine is only having to work
> > against the differential pressure to force out the exhaust, then it
> > should be able to run underwater. However, that's my own guess.
> >
> > Heck, you could even set up a mechanical linkage between an airvalve
> > and the throttle to dump extra air into the engine bay if
> > it's running. Add a solonoid that automatically activates it when the
> > snorkel is closed, and your engine bay gets a shot of air when the
> > boat dips just below snorkel depth.
> >
> > Let us know what Yanmar has to say. Inquiring minds want to know. ;-)
> >
> > NP
> >
> > ------------------------------------------------------------
> > From: "Joseph Perkel" <joeperkel@hotmail.com>
> > Reply-To: personal_submersibles@psubs.org
> > To: personal_submersibles@psubs.org
> > Subject: RE: [PSUBS-MAILIST] Speaking of 1ATM
> > construction...
> > Date: Sun, 22 Jan 2006 00:09:12 +0000
> >
> > NP
> >
> > Carsten mentioned something recently regarding Spurdog
> > starting the diesel at depth to blow ballast with the
> > exhaust but, as you noted, this is in a 1 atm boat. (Same as
> > sea level). Too much negative pressure is not a good thing
> > either.
> >
> > In my ambient, I am anticipating exhaust backpressure issues
> > to be resolved, partly by routing the exhaust up high in the
> > sail. This is a potential deal killer for the 14 hp engine
> > and I have yet to receive an answer from Yanmar on the
> > subject.
> >
> > Joe
> >
> > --------------------------------------------------
> > From: "Nomdae Plume" <nomdae@hotmail.com>
> > Reply-To: personal_submersibles@psubs.org
> > To: personal_submersibles@psubs.org
> > Subject: [PSUBS-MAILIST] Speaking of 1ATM
> > construction...
> > Date: Sat, 21 Jan 2006 23:35:21 +0000
> >
> > Will a diesel engine run in a pressurized
> > environment? For example: If I had a 1ATM boat,
> > and for some reason needed to run it at depth,
> > (aside from the obvious huge consumption of air)
> > would the engine run at all?
> >
> > NP
> >
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