3350 Exhaust Flames

[punkalouver]

I know……the mods don’t really like Instagram links.

But maybe they will forgive me after watching this one…..https://www.instagram.com/p/CKcGA6SFYZH/?igshid=pscjrswcq5r5

[Pypard]

It's an old post from YouTube (IIRC posted here at that time?), so maybe that link would be OK? Lovely bit of film either way.

[washoutt]

As a 10 year old boy I remember the flight to our parents in S-America in the KLM Super Constellation, and during the night I used to stare at the exhaust of the engines, the pipe glowing light red, and inside the pipe a light blue flame was visible. Both the colours and the engine drone was very reassuring during the 8 hour flight over the second half of the atlantic (Sal Island to Paramaribo).

[India Four Two]

Here's a different but equally spectacular Connie video:

https://www.youtube.com/watch?v=taU6qu5pXBo

[washoutt]

I would expect, that with turbo compound engines, the exhaust flames would have been doused after passage through the turbines with the subsequent temperature drop. Apparantly not. Is there still considerable energie left in these hot gasses, that they still are visible as flames ? As I said earlier, during cruise the exhaust was nothing more than a faint blue light inside the exhaust pipe.

[Self loading bear]

Were these full flow turbocharged engines or did they have a bypass?

[mustafagander]

washoutt,
You miss the point. The engines were operated spectacularly rich for fuel cooling of the cylinders. This rich mixture was still burning when it exited the cylinder and passed into the exhaust pipes. If the cylinders weren't so much over rich they would likely have simply melted stuff.
The Wright DA TC engines were pushed way, way over sensible limits to make the power.

[chevvron]

Yellow or possibly red flames would indicate a 'rich' mixture for takeoff/climb whereas blue or even white flames would indicate a 'lean' mixture for cruise.
In the days of carburreted cars, I used to own a 'Colortune' spark plug which allowed you to look into the combustion chamber and view the colour of the flame and adjust your mixture accordingly.