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#31
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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? |
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#32
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Behold the CityCAT air car, powered by compressed air.
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 |
#33
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Behold the CityCAT air car, powered by compressed air.
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." |
#34
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Behold the CityCAT air car, powered by compressed air.
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 |
#35
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Behold the CityCAT air car, powered by compressed air.
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. |
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