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 Post subject: Engine Combustion
PostPosted: Sun Apr 17, 2016 8:18 am 
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Interesting article in Motor Sport Magazine:

http://www.motorsportmagazine.com/f1/f1s-power-secret/


Seems most F1 engines use a combination of compression ignition - like diesels - and conventional spark plug ignition. Was anyone else aware of this? Some diagrams to go with the article would have helped visualise how the system works.


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 Post subject: Re: Engine Combustion
PostPosted: Sun Apr 17, 2016 9:50 am 
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Yeah there were articles last year about it and about Ferrari's big change over the winter. There were also rumours that Honda were going to use it last Feburary in a Japanese presser but until Kravitz said last race Honda were already running it I hadn't read anything but now Hughes seems to confirm it. They must be way behind on fuel though.

Mercedes system is an absolute gem and plays a key role in their dominant thermal efficiency over the field. Apparently they're working on not just the auto combustion itself but with extending the actual combustion phase which is where their extra qualy pace comes from. Bigger longer bang for your buck and all that.

I'll try to find some of the articles and post them.

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 Post subject: Re: Engine Combustion
PostPosted: Wed Apr 20, 2016 3:17 pm 
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The Holy Grail for any combustion engineer is to burn the fuel so it delivers the maximum efficiency for the given scenario, and that every molecule is burned. That applies from jet engines to ship diesels, to gasoline burning spark ignited internal combustion engines.

It is important to realize that Formula One did not invent it, nor did they develop or refine it, the heavy lifting was done in auto manufacturer's labs and test facilities.

In the HCCI (homogeneous charge compression ignition) engine, the end game is to produce a well-mixed gas and air product within the combustion chamber, and then ignite it so it produces maximum power and is efficient. This next picture is interesting, a comparison.

Image
http://www.nissan-global.com/JP/TECHNOLOGY/FILES/2010/07/f4c4d72533563e.jpg

The middle frame in both examples is very interesting. In the normal sparkignition engine, the flame front is still growing and travelling, which means there is still a lot of combustion waiting to happen. The problem is that the piston is already traveling down, and this is lost power. In the HCCI example, combustion is basically everywhere, and the fuel is being burned very quickly and efficiently.

For this to happen a few things are required. There must be a thorough understanding of the gas flow inside the combustion chamber, courtesy of massive computing power. The amount of fuel injected per cycle must be very precise, courtesy of injector technology. The engine must be stout enough to withstand such forces, and great precision in dimensions is also required. Lastly, a high compression pressure is required, and a turbo does make that a reality.

Image
http://image.slidesharecdn.com/homogeneouschargecompressionignitionhcciengines-150611051721-lva1-app6891/95/homogeneous-charge-compression-ignition-hcci-engines-9-638.jpg?cb=1433999967

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 Post subject: Re: Engine Combustion
PostPosted: Wed Apr 20, 2016 4:21 pm 
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There was a lot of work done on this when the laws to remove led from petrol was introduced. Dont have any links or references for it as it was more than 20 years ago, but I think porsh tried it out in conjunction with Gulf. (in competition that is).

There was one engine (NSU?) that actually had what was in fact an extra valve that had no port, but on opening rises the compression in that part of the chamber by displacing. I will have a scan back through some of my old books and see what I can find.

It is all to do with the speed and direction of the flame front. It has to all burn, before any self detonates. This of course changes with RPM, temperature, injection pressure, timing, and even throttle opening.


Anyone interested in that would probably be interested in this too

http://www.autoevolution.com/news/how-porsche-plans-to-revolutionise-turbo-engines-with-variable-compression-ratio-95062.html


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 Post subject: Re: Engine Combustion
PostPosted: Wed Apr 20, 2016 10:15 pm 
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Isn't this something that used to be considered a fault in normal road cars if the combustion chamber and/or the gases inside it became too hot before the ignition spark and the fuel combusted prematurely? Are they just allowing this to happen and harnessing the power of it rather than it causing damage?


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 Post subject: Re: Engine Combustion
PostPosted: Thu Apr 21, 2016 12:58 am 
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flyboy10 wrote:
Isn't this something that used to be considered a fault in normal road cars if the combustion chamber and/or the gases inside it became too hot before the ignition spark and the fuel combusted prematurely? Are they just allowing this to happen and harnessing the power of it rather than it causing damage?


If it's not controlled and results in unexpected levels of heat or stress, then it is definitely a major problem. The goal in this new burn technology is to get a very controlled burn where there are no unplanned spikes in pressure.


You can easily burn up the piston, it's rings and cylinder walls. The bearings can be crushed into being completely useless. The block can be distorted, heat can burn off oil and get past a ring, fouling the oil in seconds, it can be a big bang or a nice fire coming out of the air intake.

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 Post subject: Re: Engine Combustion
PostPosted: Thu Apr 21, 2016 9:42 am 
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flyboy10 wrote:
Isn't this something that used to be considered a fault in normal road cars if the combustion chamber and/or the gases inside it became too hot before the ignition spark and the fuel combusted prematurely? Are they just allowing this to happen and harnessing the power of it rather than it causing damage?


When it happens in a road car, if you will excuse the simple words, it happens in one spot, and usually when the piston is still going up, rather than the whole charge in one go and with the piston in the right place. I have in my garage a piston with a hole in it due to this happing. It makes a good pen holder :D


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 Post subject: Re: Engine Combustion
PostPosted: Mon Apr 25, 2016 10:44 pm 
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New developments here

http://www.f1technical.net/news/20316?sid=3511408ebb618dc0c0f04f949c4bdef5

It has recently emerged that Turbulet Jet Ignition (TJI), and not HCCI, is one of the key technologies that Scuderia Ferrari is using in Formula One engines to push the power unit's efficiency further forward.

Looks like the future.


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 Post subject: Re: Engine Combustion
PostPosted: Tue Apr 26, 2016 6:14 pm 
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I love this stuff.

Yea, Moby, I just read about Mahle's idea, and I contemplate the amount of competition between different German companies. The end goal is always the same, to achieve a complete fuel burn in a controlled manner to deliver the expected results. The TJI seems to be one where a blast of burning gas is injected into the combustion chamber to get a good burn.

Getting the fuel to burn in the manner you wish is not that easy, it can get very complicated. In the 60's while Honda was just beginning their adventure into racing, they came up with a high revving series of motorcycles. The problem was that at such high revs, the fuel didn't have enough time to complete the burn before the exhaust valve opened and dumped everything into the exhaust pipes. Leaded fuel was the norm back then because it slowed combustion, to avoid pre-combustion (knocking). So Honda had to revert to unleaded gasoline to get the fuel to burn fast enough for those high revving engines.

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