posted on Nov, 17 2013 @ 05:04 PM
Global Skywatch has published something that I am sure they think is the definitive Truth about Contrails
, but the truth about this is
that it serves only as an illustration of how many "facts" can someone get wrong in a short bit of writing!
Every Condition is Wrong for Contrail Formation
The formation of condensation trails requires high vacuum,
there is no such thing as "high vacuum" - perhaps he means "low pressure"? And of course that is wrong- contrails will form at sea level if the
humidity and temperature are suitable - hence "ice fog" in Alaska!
cold temperatures, and high humidity, however, the output side of a jet engine contains mostly outside air that has been pushed through the
engine by the large ducted fan (The ducted fan is the set of spinning blades that you see when you look at the front of the engine). This
high-pressure at the output of the engine is contrary for the formation of condensation trails because pressurized air has the ability to hold much
more water in suspension, without condensation.
Actually this is more-or-less correct - albeit in a pidgin-technical manner - denser air such as that compressed by a turbo fan will hold more
moisture. As long as it remains denser of course....which isn't very long once it leaves the engine!
A fraction of the air that enters the engine is taken in by the turbine engine. This air is mixed with jet fuel (essentially kerosene), combusted,
and then exits the engine under very high pressure and high temperature. Condensation formation requires a decrease in ambient air pressure to form,
but the output of the turbine is under very high pressure which prohibits the formation of condensation trails.
Physics also tells us that condensation forms when air is cooled, but since the exhaust of the turbine engine within a jet is very hot, condensation
formation is - once again - prohibited.
lol - and that is why the contrails do not form at the output of the turbine, and why they form some distance behind - when the pressure is rapidly
reducing - thus also rapidly reducing the temperature!
Furthermore, the ratio of air-to-fuel used in turbofan engines is as high as possible (lots of air but relatively little fuel) so as to keep
engines efficient and cost-effective, and this lack of fuel in this ratio results in a lack of water vapor; yet another reason jet turbofans cannot
produce condensation trails.
There is no lack of fuel "in this ratio" - all jet engines seek a "perfect" mixture, which IIRC is about 14:1 air to fuel - some get closer than
others, but there is always fuel!!
In short, the more efficient the engine, the less fuel it uses per unit of air moved, and this renders turbofans incapable of producing
condensation trails, unless they use water injection (see section below).
Using less fuel does not render them "incapable" even by his own reasoning - it should render them less LIKELY by simplistic reasoning - however
other considerations actually make it MORE likely- put simply the higher the efficiency of the engine, the higher the temperature at which contrails
can form, and so the more likely they are to do so - the math is in the link if you want to examine it closely.
Simply said, every condition necessary for contrail formation is absent in a high-bypass turbofan engine.
simply said this guy is ignorant, or a liar - ignorant if he actually believes this rubbish and has not been told otherwise, or a liar if he has.
WATER VAPOR IS INVISIBLE - YOU NEVER SEE IT!!
If you go to an airport and watch jets take off, you will see that they emit a faint trail of black soot, which is typical of burnt jet fuel
(kerosene), but you will not see water vapor.
Sorry for shouting, but the level of ignorance or disinfo in just this short piece is appalling!