View Full Version : Jet Engines To Clear Delhi's Smog?

13th Dec 2016, 14:51
The BBC is reporting that there are plans afoot to clear Delhi's terrible smog by mounting retired jet (tim-ex?) engines vertically by power station chimneys and using them to blast the fumes through the inversion and into the cleaner air above.
Can jet engines clean up Delhi's foul air? - BBC News (http://www.bbc.co.uk/news/world-asia-india-38285567)

Would/could this work?
Jet efflux seldom reaches more than a hundred meters or two (?) beyond an aeroplane - would this be enough to break through an inversion?
How deep is the inversion in Delhi?
If you did break through would the smog you lifted just sink back down, or could it be heated enough to mix in above the inversion?

Help pollution by burning many hundreds if nor thousands of tons of jet fuel per day?

I guess they wouldn't be using the J58s they have blithely drawn in the graphics, but this hardly seems a practical idea even with a big fan.

Any Engineering based opinions on the viability of such a plan?

13th Dec 2016, 19:39
Saw this via another news source.

That story contained critiques similar to those you raise - just not enough punch to do any good in a layer multi-hundreds of meters deep.

In extremely rough outline, somewhat reminds me of the FIDO experiments in WW2 (Fog, Induced Dispersion Of, or some such title). That at least worked, using both heat and the lift of rising heated air - but was not economical (roughly, the fuel burn rate of five A380s running at once).

However, that does raise the points that HOT jet exhaust will:

1. add its own lifting power (hot-air-balloon-style) to the mechanical jet blast
2. will heat the cooler trapped air beneath the inversion, lessening the intensity of the inversion

and targeting the flow at the pollution source means one is not trying to lift the whole trapped air mass over the city, simply the pollutants where they exit the stacks.

Seems to me if the general principle can work at all, it makes more sense to put the "reheat" engines directly into the top of the smokestacks (with side inlets so the jets are not soley breathing the coal fire's own CO2 output and particulates). That also adds ~100 meters to the effective height.

14th Dec 2016, 14:03
Personally, I would be very surprised if it worked.
I say this because power station chimneys are designed to have a quite high velocity, designed to get the output, both gaseous and particulate, above the surface wind and into the geostrophic wind.
This is the reason why flight over a large coal fired power stations is often restricted.
Whether the heat output can make a difference, I can't even guess.

14th Dec 2016, 16:24
If the powerstation is particularly dirty, might passing the smoke through the jet combust some of particulate material in the power station smoke?

14th Dec 2016, 16:53
If the powerstation is particularly dirty, might passing the smoke through the jet combust some of particulate material in the power station smoke?

Dirty in = dirty out

14th Dec 2016, 18:19
Maybe Im completely off here, but let me consult Wikipedia (https://en.wikipedia.org/wiki/Stack_effect).

A natural draft smokestacks throughput can be calculated by this formula:

Q(m/s)=cA sqrt(2g h ((Ti-To)/To)).

Assuming an area (A) of 4m, c of 0,65 (Wikipedia claims this to be realistic), g of 9,81m/s, an internal temperature of the smokestack of 100C= 376 K (Ti), an outside air temperature of 25C = 301 K and a height of 100m (h), there will be a mass flow of 81m/s, divided by the area, this means a velocity of 20m/s. And with an air density of 1,293 kg/m, this is 105kg/s. For simplification, I assume pure air here, which is of course daring for a smokestack.

Now let us add a jet engine to the top of the smokestack, drawing external air for its combustion and discharging via some kind of mixer nozzle right at the top of the smokestack.

A RR Avon as used in the Comet for example is said to put out 104kg/s at 360m/s.

p = m v.

Therefore, 104kg/s times 360m/s = 37440 (for the Avon), and 105kg/s times 81m/s = 8505 (for the smokestack).

Summed up, this leaves us with a total impulse of 45945 kgm/s, divided by the total mass flow of 209 kg/s, this will give a velocity of the exhaust of 220 m/s.

Compared to the original 49m/s before the addition of the Avon, this is quite a difference, I think. However, how high the exhaust plume will rise before this additional velocity has been eaten up by assorted eddies is beyond my humble means of calculation.

14th Dec 2016, 19:22
The term simply shifting the :mad: elsewhere comes to mind, adding more pollution does nothing to address the problem, simply adds to it.

Peter H
14th Dec 2016, 21:37
Several decades ago there were serious suggestions for smoke-ring blowing power stations in the UK.
The aim being to punch the smoke though a temperature inversion layer. I suspect that the idea would
have worked, but the clean-air act reduced/removed the need for it.

The idea seems to be being re-investigated.
Video shows trail for BIG's smoke-ring-blowing chimney (

The idea of using vortex rings to gain height also seems to work very well at a much smaller scale, and is
the basis of the sphagnum mosses spore dispersion mechanism.
Exploding Moss Reproduces with a Bang (http://www.livescience.com/6732-exploding-moss-reproduces-bang.html)

Piltdown Man
15th Dec 2016, 00:45
So your activities are creating an unhealthy environment. So bad it's affecting local weather and killing your people. And your solution is export the sh!t you pump out every day and spread it over everyone else? Assuming this scheme works, what do you in the future when your now increased sh!t production results in this scheme being insufficient, what do you do then? Wouldn't it be a better idea to start reducing emissions now? If you don't, you will be shooting yourself (and the rest of us) in the foot.