Russian jet exhaust question

This is kind of a random post. I have always wondered why is the exhaust smoke of Russian jets so dirty? If you look at pictures and video of russian jets (commercial and military) from any generation they seem to be pumping out almost black/gray smoke all the time.

American/UK/French jets dont seem to do this.

Is there a difference in fuel and or in the engines construction?

Do licensed copies from the chinese do the same thing?

reply to post by drock905

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When it comes to Military-Jets it;s just the MiG-29's not the Su's, anyways I've heard the black smoke is recently in the last 15 years because of fuels shortages, the Russians have been adding kerosien and something else to the fuels.

Alot of it can be traced back to Engine quality and how well oil and fuel was burned or kept out of the system. To generalize this issue to just the russians is unfair and incorrect as the B-52 and KC-135 have been notorious for the "clouds" of black smoke left behind them. Here take a look.




Watch this F-86 video, 1:00-1:20, you'll see how the older jets smoked at MIL too.
www.youtube.com...

Even older commercial engines smoke. (Unlike modern High-Bypass Ratio engines)
www.youtube.com...

Now you want smoke? Watch this one!
www.youtube.com...

Also of note any sort of water injection which was common to B-52s have a smoking effect as it makes the mixture to the engine that much richer. I almost forgot the Phantom as well was well known for it rich burning engine (read more tax dollars for fuel).

Let's not forget the F-4's damningly huge smoke trail. The MiG pilots in Vietnam used it against them - like big black arrows pointing to the plane.

reply to post by drock905

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Hi there - I asked the resident AE (my retired Dad who worked designing jet engines for P&W) and he said this:

Efficiency & engine design. Basically how well (thoroughly?) the engine burns it's fuel. I may well have missed something in translation so, take it with a grain of salt =)

reply to post by SlightlyAbovePar

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While true that engine efficiency is the over arching issue when talking about "smoke" it is also worth keeping in mind that as engine throttle/power reaches its higher limits say above 85% power it starts to produce the "smoke" in a visible way. The type of engine and how the mixture is achieved all impact "smoke". When a afterburner is engaged on a plane like the F-4 (not available on the B-52) it burns off this smoke which is basically carbon and oil/fuel mixture that is expelled at high power settings.