Diesels are going to have the same thing, just it has to be hotter at the end of the day pressure and temperature are independent. Modern engines may already recirculate exhaust into order to help catalytic converters which don’t like oxygen.
Probably its just easier to sate my rather limited knowledge, im a mech eng student undergrad (its different in the uk im master level in comparison to the USA) and one of my courses happens to be in SI (otto is the word I use not sterling, I take sterling to refer to sterling engines which are heat pumps in a way). This course is taken by a doc who designs engines or some part for Honda and what he does for an hour each week is tell us how to design engines well. I’ve also read John Lumneys book and introduction to engines twice (nice book). The course notes wer originally written by a guy called Prof Langford who is apparently a god of engine design., he may (if ive not got him confused with some one) invented modern superchargers. Next term I get a doc who runs probably the top turbocharging testing rig in the world teaching me about turbochargers (he apparently doesn’t like dumpvalves so we might make some funny noises).
Based on what my lecturer syas most of the stuff from the 80s in terms of fluid dynamics is completely wrong CFD analysis showed that other things were going wrong although the correlations are obviously still right as they are based on hard data.
I’m not convinced (and indeed the doc likes banging on about it, including how crap people are at designing a good water pump, which uses up some of his hard fought for hp) if you move to adiabatic that everything goes out the window if a spark or pressure (I use pressure to emphasize that compression and gas temperature are dependent). And even if It could theoretically be done practical issues still dominate i.e. you cant make it.
I think multiple flame fronts still exist in some engines Lumley has an example of one with a single top spark plugs and 3 around the edge. I think given current turbulence advances they are not needed in comparison to the problems that they create. I accept flame speed I think it is about 1.2m/s for your average engine but I think recently its going up.
Squish = tumble which I didn’t mention besides you cant have swirl without tumble Lumley says that tumble is 16 x more effective than swirl, this is one of the things CFD proved I believe.
A lot of old engine design was guesswork with no real science some old engine designs from the 1910s would not look out of place to some engines now (DOHC penta head, 4 valve) if they were tuned a bit. The old preference to longer strokes was ultimately a fallacy as shorter ones are better but I believe that some fiats one with a long stroke engine and everyone followed that for 20 years. IF it wasn’t for piston rign requirements we would all probably be running f1 or higher bore to stroke ratios as these are thermodynamically better.
The chain in increasing speed was probably a result of increasing power requirements a lot of countries brought taxes in based on engine volume and related characteristics. As I mentioned above high bore/stroke is better for thermodynamic reasons. The reasons for this were based on hard science I believe.
Other types are always on the go one of my docs has suggest a gas turbine I imagine it would be quite easy to do if we move to hydrogen or LPG. Gearing losses are still there but gas turbine tech is getting better. The problem is NOx is bad from a gas turbines (hippies who fly around are far worse than boy racers for air pollution). External combustion is one way as you point out but you have to accept big efficiency problems. Ultimately these days hitting the performance is easy, hitting the pollution controls is not. The doc who’s currently teaching us engines is really against fuel cells and hybrids from good arguments, one of the others teaching the course is actively working on developing them.
The new power plant designs is one of my other docs things. Basically for 25% more energy costs you can get CO2 free electrical power from fossil fuels the extra cost comes from the fact that the plant is less efficient (37-40% vs 55% for a modern coal plant vs 80% for ultra modern combined cycle gas plant) and they cost twice as much as a standard coal plant. There are already working plants and it is proven technology. If there was political will and it was implemented you could meet Kyoto fairly easily. The reason this tech is being developed part from lack of good renewables and public dislike of nuclear is china has a lot of coal and we need a source of hydrogen if we move to a hydrogen economy.
im guessing my speeling and grammer is going to be wrong in this so sorry in advance.
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