Behold the CityCAT air car, powered by compressed air.

"jim beam" > wrote in message
t...
>
> as i understand it, common rail/electronic injection control makes diesels
> /much/ quieter though. you can get up to 5 injection events per ignition
> cycle - one to start the flame, and subsequent events to keep the process
> going. since the fuel is not all exploding at once, and burning fuel is
> much quieter than igniting fuel, there's subsequently much reduced diesel
> "knock".
>
Sort of an analog of progressive air bags, eh? Interesting. Do you have any
links for more info?

Michael Pardee wrote:
> "jim beam" > wrote in message
> t...
>> as i understand it, common rail/electronic injection control makes diesels
>> /much/ quieter though. you can get up to 5 injection events per ignition
>> cycle - one to start the flame, and subsequent events to keep the process
>> going. since the fuel is not all exploding at once, and burning fuel is
>> much quieter than igniting fuel, there's subsequently much reduced diesel
>> "knock".
>>
> Sort of an analog of progressive air bags, eh? Interesting. Do you have any
> links for more info?
>
>
>
there's plenty of online resources on the basics like:
http://www.exploroz.com/Vehicle/Tech...I_Systems.aspx

this is better tho:
http://www.amazon.com/BOSCH-Automoti...0802731&sr=8-1

The topic recently came up in the Yahoo! Toyota_Prius forum. One of the
Dutch engineers there had visited their factory in Carros, France, around
1999.

He says there are some conceptual problems that are unavoidable and several
that they failed to avoid. In particular, when air is compressed part of the
recoverable energy is stored as heat. (The loss due to the ratio of specific
heats is unrecoverable, lost to that pesky second law of thermodynamics.)
When the heat dissipates that energy is lost. The flip side is that as air
is drawn from the tanks the remaining air cools and the pressure drops. He
says, "the only way to retrieve most energy from compressed air is to
decompress it in small steps, not in one big step. This means a series of
cylinders, each next one larger than the previous, can retrieve most of the
energy. One decompression step will be very wasteful. To overcome the
problem with thermal energy loss, the
multi-cylinder engine can feed the decompressed air through a heat exchanger
in between each cylinder, so it will recoup a (large) portion of its
original -heat- energy and can become quite efficient again. As you can see
when you look at the engine, they did not implement many decompression
steps, nor used heat exchangers, which would have made it efficient."

As a consequence of the temperature drop, he says "there is a big problem
with the engine freezing up." Use of a single stage engine also means the
engine has to be designed for a particular pressure (as opposed to bypassing
stages as the pressure drops) and efficiency over the range of pressure of
the tanks is poor.

He says, "I used to be a big fan of the air car - that is why I visited
them. After I saw that the physics did not work out, I stopped maintaining
my website about the Air car ... and stopped promoting their invention,
because it is not an improvement in the way it was implemented."

Jeremy wrote:

> > Eeyore wrote:
> >
> > How the heck do you think the air gets compressed in the first place ?
> > Just because it has no tailpipe emissions doesn't make a car 'green'.
>
> I never said that no tailpipe emissions makes a car green. But It's likely
> far 'greener', at least in this case.

No. A pure EV is easily twice as good in terms of energy usage and this does
normally means CO2 emissions somewhere at the end of the day.

Graham

On Jun 4, 12:33 am, Eeyore >
wrote:
> Jeremy wrote:
> > > Eeyore wrote:
>
> > > How the heck do you think the air gets compressed in the first place ?
> > > Just because it has no tailpipe emissions doesn't make a car 'green'.
>
> > I never said that no tailpipe emissions makes a car green. But It's likely
> > far 'greener', at least in this case.
>
> No. A pure EV is easily twice as good in terms of energy usage and this does
> normally means CO2 emissions somewhere at the end of the day.


A "pure" EV presumably means that there is no on board energy
production. I'm presuming you're gonna consider "remote" energy
generation, even from the charging point. If so, you're gonna have
to consider the transmission losses, and those might eat up your
efficiency gains, including CO2 production.