Friday 2010-12-10 Dev. video update and Discussion

[Spinnetti]

So, some may know already, but "proper" color of flame is not just what you like, but depends on many factors including Fuel type and Mixture, and mixture varies by type and amount of boost. Actual flame color is relative to combustion temperature and oxygen concentration. Generally speaking, the leaner the mixture, the "bluer" the flame, and the richer, the more yellow it is. At full boost, you tend to run richer to avoid burning a piston, and it should be more yellow. At cruise, it should be leaner, and thus bluer. For game purposes, I would probably have a couple settings - yellower for start up and full power, and bluer for all other settings - Important to note, but generally the only time you see any flame at all is on a missfire. If the engine is running in tune, there should be little missfires, and thus not much flame (although even a 2% missfire rate is still about 11 missfires/sec on a 16 cyl at 2000 rpm if I did the math right). The flame occurs when the unburned mixture hits the hot exhaust and combusts in the exhaust stack.... This is the general truth, but I'm sure experts could refine the exact details.

let's not forget that the flaming alternation of different exhausts is more visible at low revs/idle. When the engine is on cruise the blue flames are more constant from all the exhausts, as the engine is working at higer revs.

[Sutts]

Originally Posted by Spinnetti

So, some may know already, but "proper" color of flame is not just what you like, but depends on many factors including Fuel type and Mixture, and mixture varies by type and amount of boost. Actual flame color is relative to combustion temperature and oxygen concentration. Generally speaking, the leaner the mixture, the "bluer" the flame, and the richer, the more yellow it is. At full boost, you tend to run richer to avoid burning a piston, and it should be more yellow. At cruise, it should be leaner, and thus bluer. For game purposes, I would probably have a couple settings - yellower for start up and full power, and bluer for all other settings - Important to note, but generally the only time you see any flame at all is on a missfire. If the engine is running in tune, there should be little missfires, and thus not much flame (although even a 2% missfire rate is still about 11 missfires/sec on a 16 cyl at 2000 rpm if I did the math right). The flame occurs when the unburned mixture hits the hot exhaust and combusts in the exhaust stack.... This is the general truth, but I'm sure experts could refine the exact details.

That sounds all very good but please show us a video where these yellow flames are being ejected by a running engine or point to the entry in the WWII exhaust flame colour chart where yellow flames are referred to. That chart covers everything from weak to rich mixtures and a whole lot of other scenarios including engine damage. Strange how yellow flames don't even get a mention - orange on a damaged engine but everything else is red and blue. I know it's for an Allison engine but I can't believe it differs much from any other inline carburated aero engine.

The only yellow flames I've ever seen are from raw fuel burning in the stacks of a flooded engine and an initial burst of yellow/orange flame when the engine first fires up.

I'd be happy to be proved wrong as I like the pretty yellow flames but the overwhelming evidence so far is against yellow flames from a running engine.

[major_setback]

The big question is this: Will be be able to over-prime the engine in the game?

[Richie]

That's a very good question. I think because of the fuel injection of the German fighters the Allied aeroplanes will have more fun with the flames.

Originally Posted by Richie

That's a very good question. I think because of the fuel injection of the German fighters the Allied aeroplanes will have more fun with the flames.

...what do you mean exactly?

[T}{OR]

Originally Posted by Sternjaeger

...what do you mean exactly?

When burning fuel in the cylinder, if we're talking about an ideal process - you need exactly the same amount of fuel and air in your mixture. Since space in cylinder is limited, there is only so much air and fuel you can put in there (if we're not talking about turbo or supercharging). And certain amount of fuel requires exactly certain amount of air (I forgot the exact ratio but I can dig it up if you want, I have it one of my books).

The biggest downside of carburetors is that they can produce such ideal mixture only on certain RPMs, or RPM ranges. While direct fuel injection is much more flexible and can provide the engine with better mixture on all RPM ranges.

I am talking theory here, but I believe this is what Richie meant with:

That's a very good question. I think because of the fuel injection of the German fighters the Allied aeroplanes will have more fun with the flames.

[SlipBall]

Originally Posted by Richie

That's a very good question. I think because of the fuel injection of the German fighters the Allied aeroplanes will have more fun with the flames.

Damm, I think I flooded her!...

Now you know the real reason, why I fought so hard for realistic start up's .. Flames

[Chill31]

Oleg,

If you havent already recieved enough info at this point, I want you to know that the flame color coming out of the exhaust of a running engine like that would be more blue! than red or yellow. The flame is burning hot and mostly clean, so it comes out with a nice blue flame at night. In the day, you wont see it.

On engine start, the only time you will get the yellow/orange flame out the exhaust is if the engine is too rich and it spits out unburnt fuel that burns exiting the exhaust stack. In that case you will get a lot of orange/yellow fire coming out for a short time. I was on the wing of a P-51 when that happened and it does get warm...

Note: its easiest to over prime with the electric fuel pumps found on P-51s and the like.

*edit The short stacks in most of the videos lets you see a lot of blue flame...more than if the full length stack was in place. If you leave the exhaust as is with no blue, you really will be misrepresenting the way exhaust looks coming out of the stacks at night...

http://www.youtube.com/watch?v=g2gef...eature=related

This video (previously posted) shows what I would expect to see coming from the exhaust at high power settings at night...see it at 0:30 video time

http://www.youtube.com/watch?v=UDZmq2VrcNQ

This video shows over priming at about 5:30. His first couple of attempts to start were underprimed and he didnt keep it running with additional priming.

Also, when you go from high power to low power rapidly, you will get some light popping and orange flame as the rpm comes down.

Good luck with your great project!
Chill31

*edit, looking back at all of the posts, it looks well covered!