saviour stivala wrote: ↑
Thu Nov 08, 2018 12:48 pm
henry wrote: ↑
Thu Nov 08, 2018 9:53 am
godlameroso wrote: ↑
Thu Nov 08, 2018 12:26 am
None, our descriptions are in agreement in how flame jet ignition, and combustion in general work. It's more than just spark flame, heat. There's thousands of steps involving radicals formed at the spark gap, which create further radicals, and as these radicals interact with the hydrocarbons, new bonds are formed, which release heat, and some are broken which absorbs heat. During the combustion process, partially unburned hydrocarbons further release free radicals which again create and break bonds in the A/F mixture. Understanding and modeling these radicals are key to making improvements to both fuel and the combustion process itself.
Elemental nitrogen is a radical by the way, and the fact that these engines have high combustion temperatures and they produce plenty of NOx, perhaps the process makes use of elemental nitrogen to some extent.
No doubt the actual combustion processes are very complex. But surely in a discussion of TJI that’s not the key issue.
In a TJI solution there is a small chamber in which combustion is initiated by a spark and then the combustion products are ejected in a controlled manner into a larger chamber where those combustion products cause ignition. The process is spark, burn, eject, burn.
In your post above you seem to agree with this characterisation and show a shrouded plug, with a small chamber and ejection holes.
Whilst it is obviously important that the actual chemistry supports this, and there are almost certainly some specifics that are beneficial to the differing fuel-air ratios in the two chambers, as far as I can see the chief difference for a TJI concept is how the spark chamber is formed and how the air movements and injection patterns form the two environments in which the combustion processes operate.
The alternative to TJI is that the differing fuel-air ratios are generated within the space of the combustion chamber by some form of stratification. It seems unlikely that at the extreme air-fuel ratios used reliable ignition could happen in a homogenous charge.
Possibilities that "differing fuel-air ratios are generated within the space of the combustion chamber" I personally believe that there is very little possibility if any of therec being 'differing fuel-air ratios' inside a formula 1 engine cylinder when as i belive the fuel is being injected at a pressure of 500bar and at least 60 degrees BTDC and before being fully compressed.
So you think that there is a homogenous fuel-air mixture in the combustion chamber and it is ignited by a single spark plug, and runs at 45% BTE.
With TJI the differing fuel-air ratios are in two physically separate parts of the combustion chamber. One is very much smaller than the other. Obviously getting these right with a single injector is tricky. However:
There is nothing in the regulations that requires a single injection event. Peak pressure before combustion is, I guess, less than 100 bar. So an injector at 500 bar would be able to inject at any point in the compression cycle, and multiple points to help generate differing fuel-air mixtures.
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