Filed under: Etc., Tech, Videos
VIDEO: So that's what it looks like! -- Slo-Mo combustion closeup
We all learn the theory of what happens inside an internal combustion engine; a mixture of fuel and air is ignited by a short electric spark. Some people describe the ensuing event as an explosion, but the ideal is a controlled burn, but it's still so fast that it could be confused for an uncontrolled explosion. An engine is a practical application of thermodynamics, when it comes right down to it. The piston moves by the pressure exerted by the burning fuel mixture, and as the piston moves down the bore, pressure reduces, and work is extracted from the fuel.Of course, there's a lot more to it, but that's the basics. We're sure you had a little animated diagram dancing around in your head the first time you really tried to understand the common Otto cycle. My mental flash player still fires up when I'm trying to figure out different cycles like the Atkinson. Wouldn't it be great to actually see inside the cylinder during combustion events? No, we didn't videotape our lawnmower with a Colortune plug -- this technique is far fancier.
Video and technique info after the jump
[Source: Hemmings]
The imaging technique is known as Schlieren photography. Traditionally achieved with optics, this method is used to display variations in fluid density. When supersonic aircraft were under development, Schlieren photography was instrumental to solving the puzzle of flying faster than sound. This particular video uses modern digital techniques, rather than optics, no matter, it's still a really interesting peek inside the cylinder at the moment of combustion.
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Reader Comments (Page 1 of 1)
Ricky 7:31PM (4/27/2007)
That's a little bit of cool and a whole lotta awesome. Although, I kind of wanted to see the down stroke...
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Dave 7:37PM (4/27/2007)
Why is the fire happening on the upswing? Its supposed to explode from the spark plug out and push the piston up? Or the video is backwards actually?
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Talis 7:40PM (4/27/2007)
I agree with #1, where's the power stroke? #2, spark happens a split second before full compression, otherwise you might blow your valve train through the hood. It's called valve timing, you might want to look it up before you rebuild your engine.
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Perry 7:50PM (4/27/2007)
#3, are you high? The method films fluid density. As the A/F mixture (fluid) is compressing, it shows the compression and eventual quench. The spark nearly always happens before the piston reaches TDC, hence spark is referenced usually as Before Top Dead Center (BTDC). What you see is the partial mixture at the chamber starting to ignite while the piston is coming up to TDC, you also see the quench, then the eventual flame front and pressure build up from the full mixture igniting.
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Amber 8:36PM (4/27/2007)
#1 to #4
If this video continued for a full cycle rather than half of one cycle all our questions would have been answered. Can Autoblog post the whole video please? Is there a clip of a full cycle for one piston?
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Will 10:11AM (4/28/2007)
A little more info here:
http://blog.hemmings.com/index.php/2007/04/18/inside-your-engine-combustion-at-10000-fps/
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cuneyt 12:58PM (4/28/2007)
I didn't understand anything.
Is it me?
I believe they were just showing a little part of it.
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MikeW 7:49PM (4/28/2007)
Adiabatic compression anyone.
It would be nice to see BMW's N53 or N54 engine. See those piezo injectors in action.
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NSFW 3:30PM (4/29/2007)
Actually if you want to understand why the spark happens when it does, it would be more helpful to look up ignition timing. Valve timing is a whole other subject.
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