[opendtv] Re: Off topic: Iris engine
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: "opendtv@xxxxxxxxxxxxx" <opendtv@xxxxxxxxxxxxx>
- Date: Wed, 9 Jun 2010 14:43:41 -0500
Tom McMahon wrote:
> When I was at Symbolics back in Cambridge MA in the 80's there was
> this MIT guy from across the street working on an electrical engine
> where you had big edge-wound voice coils around the cylinders (much
> like high power pro speakers). He absolutely believed and talked
> about regenerative braking etc. Never heard where that ended up but
> he was fun to talk to.
Most of these ideas can be disproved with simple physics.
I can see that coils around the cyclinders could be used to generate
electricity, e.g. if the pistons are magnetized. But of course if you generate
any amount of electricity from them, you are also going to create resistance to
the (magnetized) piston's motion, which requires more fuel to keep the pistons
moving.
Used only for engine braking, to charge the battery while slowing down, is a
thought. Hybrid cars do the same thing, but they use the equivalent of the
starter motor, running "backwards" as a generator, to trap that energy.
If you read the Iris engine explanations, although it's never stated completely
clearly, the IMPLICATION is certainly made that a greater "working area" by
itself creates a more efficient engine. But that's plainly false. It's quite
straightforward to prove that the efficiency of an internal combustion engine
is related to the volume into which the hot gases can expand, compared to the
volume at the beginning of combustion. In other words, COMPRESSION RATIO. Not
area. It is this compression ratio that makes the exhaust as cool as possible.
Cool exhaust, as well as high combustion temperatures of course, are THE key to
high efficiency in the Carnot cycle. Find me anyhing about "working area" that
is a factor in Carnot efficiency.
Is the comnpression ratio achievable with the Iris engine higher than that
achieved with a piston engine? That's the right question to be asking. I think
the sealing surfaces of the Iris engine are the weakest link in all of this.
Bert
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