black smoke

[minipilot100]

hi all

on most of the A/C that have russian made engines like TU 154 ,...most of time these type of engines have black smoke in all power setting in comparison with other type enginges.so I`d like to know what is the main reason of this?

best regards

minipilot:)

[On-MarkBob]

The Exhaust of all internal combustion engines burning hydro-carbon fuels are a guage of how efficient and indeed how well the engines are. White Smoke with a blue 'tinge' indicates oil and might point at an oil seal problem. Black smoke relates to incomplete combustion and points at high levels of hydrocarbons left over in the exhaust. Basically the old Russian engines are less efficient, old or are in need of attention, or all three. Modern engines are required to be much more efficient and thus more economical, ensuring that all of the fuel is properly burned. Fuel is money after all and it is false economy to throw it away down the tailpipe! So the exhaust in a modern engine is therefore much cleaner and this of course is far less harmfull to our environment than something that is producing clouds of black smoke, obviously.

[flyboyike]

I see a lot of DC-9s coming out of MSP trailing a little black smoke behind them.

[barit1]

You haven't seen smoky engines till you've seen CJ805's on a CV880 or 990!

[flyboyike]

You haven't seen smoky engines till you've seen CJ805's on a CV880 or 990!


That's before my time.

[CV880]

I am not sure if On-Mark Bob is quite correct. I think the main cause of black smoke in jet engines is the way the air and fuel was mixed and burnt in the primary combustrion zone where an over rich mixture was easier to light off and sustain (less chance of flameouts) but resulted in the formation of particulates (soot) like a diesel under load. The JT8D in the DC9, 737 and 727 was originally a filthy smoker, but to meet the anti pollution requirements P & W came up with a smokeless burner can which greatly reduced the amount of smoke to what you see today. Back in the 70's it was quite common to see aircraft flying with what appeared engines inoperative when in reality they were fitted with a mix of modified (smokeless) and original burner cans JT8D's. I don't think there was any measureable efficiency gain with smokeless burner cans.
Hey barit 1, you are right about the Convair 880. After a full power run up there was a layer of soot all over the ramp behind each engine in which noticeable footprints were left if anyone walked over it. GE did come up with a smokeless can for the CJ805 but they fell apart with thermal distress in a fairly short time during in service trials so the operator I was involved with abandoned them.

[matkat]

You haven't seen smoky engines till you've seen CJ805's on a CV880 or 990!
Or DC8-63S

[lomapaseo]

I agree with CV880

Unlike internal combustion engines, black smoke in gas turbines does not necessarily indicate an inefciency in the engine cycle (fuelburn vs payload/cycle) it only indicates a variation in fuel/air ratio far below stoichrometric (in order to keep the tubine from melting)

The jet engine designers tinkered with all those little air holes in the combustion cans back in the 50-60's to get rid of the visible smoke for two reasons

1. It was easier to track fighter aircraft by eye whith those old type anti-aircraft

2. Folks on the ground around commercial airports associated black smoke with polution.

Bingo they got rid of the visible polution and now you don't know what you're breathing :)