Talk: Internal combustion engine
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Hi, Not sure if I'm using the 'talk' feature correctly, but I saw this in the page:
P = Tω where P is the engine's power in kilowatts, T is the engine's torque in Newton metres and ω is the speed of the engine in radians per second.
It says P is in kilowatts, but isn't the SI unit for power just Watts? P should be Newton * meters * radians / seconds , I'm too lazy to look up what that comes out to, but is it a possible mistake?
What's so special about 1911? -- stewacide 04:47, 8 Sep 2003 (UTC)
- Hmm, doesn't make a lot of sense. Wonder whether it refers to something later elided? It would seem that it was talking about the invention of the modern spark plug EXCEPT that way preceded 1911. --Morven 04:55, 8 Sep 2003 (UTC)
- It was the year that the edition of the Encycopedia Britannica which is cited in wikipedia was published. Maybe?
- Ah! Then it's definitely something to remove, given we're not publishing in 1911! --Morven 07:43, 8 Sep 2003 (UTC)
Actually it was the date of the book "Gas, Gasoline, and Oil-Engines including Producer-Gas Plants" by Gardner D. Hiscox, M.E., that I got the information from, not the Encycopedia Britannica. I wanted some sense of when each went obsolete, and that was all I had. The replacement is fine, although it would be nice to know when the mechanical system was abandoned (the book seemed to indicate that some older equipment still in use at the time might use it, but was unclear except that nothing being made at the time of publication did). -- RTC 22:26, 29 Sep 2003 (UTC)
Renamed
Renamed to 'Internal combustion engine' to follow standard usage in English. It is MUCH rarer to find the dash. Google isn't an easy help with this since dashes are a space character in Google searches, but it's notable that of the top 40 or so results for such a search, the only ones with dashes are Wikipedia and its mirrors. —Morven 19:40, Jun 21, 2004 (UTC)
graph colours
Hi,
could the colours on the graph at the bottom of the page be changed? it's rather hard to distinguish the lines.
Efficiency
I had a little trouble with the following statement and I removed it (Sep. 9 2004). I'm not sure of its accuracy. Heat, energy (kinetic, potential, chemical), efficiency an work are all tricky, so I may just misunderstand the statement.
"An ideal, 100% efficient engine would run and remain at ambient temperature and convert all the energy in the fuel to kinetic energy - not into heat."
The statement which preceded it (heat in the cooling system is waste) is accurate and sufficient (if not comprehesive).
Mechanical efficiency in an engine is defined as the indicated mean effective pressure over the mean brake effective pressure. The lack of efficiency comes from friction.
- That's not correct. *A* source of inefficiency is friction- but the combustion creates heat, and that heat cannot be converted 100% into work- the Carnot efficiency cannot be improved upon. The Carnot efficiency depends on the highest combustion temperature reached and the temperature the exhaust/radiator reach. It cannot be improved upon; otherwise a perpetual motion machine can be made.
Describing efficiency from checmical to work is difficult and the assumptions need to be clear. For a example, the statement that I removed does not say anything about the temperature of the gas coming out of the engine. It could be cooler than ambient.
- No, it can't. Well, not unless you are heating the air through a radiator- the heat has to go somewhere.
Thus, the engine could be tranfering heat from the gas to the engine block during combustion, but expansion cools the gas below ambient.
- That would *take* energy. Where are you going to get the energy to do that?
The work could be the same as the claimed 'ideal' engine, but, there would be some energy transfered to heat. Or, you could be more than 100% efficient.
- No, that's a perpetual motion machine! That's not physically possible! Many, many, many, many... people have tried. All have failed.
Also, kinetic energy of a gas is sensible as temperature. See the "Heat as kinetic energy" section of the kinetic energy entry. So, to which kinetic energy does the statement refer, gas, shaft, car?
The reactant gases have both chemical and sensible energy - since a chemical conversion occurs during combustion, the same sensible energy of the products may occur at a different temperature than the reactants.
See also carnot cycle and fuel efficiency.
