Talk-Polywell.org

The volcano in Iceland is reported to be a very small one but it is causing all sorts of disruptions in air travel with significant economic impact. People are stranded in Europe trying to get home, and Europeans are stranded all over the world trying to get back to Europe.

http://apnews.excite.com/article/201004 ... 4DIO0.html

It has been 5 days now and stranded travelers are running out of money. What would happen if there was a big eruption? Could the European economy stand a one month or six month shutdown of air travel? Is there any location in the world where a small volcanic eruption could have more impact on world wide air travel than the location in Iceland?

What would it take for an aircraft to be able to fly with this stuff in the atmosphere? Rocket powered craft could fly but the windshields would fog over, recip engines could run but would need heavy air filtering. We are lucky that there are no Genghis Khan type armies in the region because once air power is removed from the battle field, everything changes.

For military purposes, this is not an issue. You can fly at most altitudes in most places in Europe with very minimal risk. Civilian airflight requires a much lower level of risk taking to fly than miltary aviation. Particularly in war time.

Disruptions in air travel was mainly due to to the point that no responsible was willing even to take the slightest chance of a problem happening.
This was done against the recomendations of most of the pilots and airlines that was suggesting to limit the flight denial area to a specific area of the flight space surrounding the dust cloud.

Many commercial planes (without passengers) have made several trips on Sunday just to prove that there was no safety concern.
A re-opening of the flight space in most of Europe was issued Sunday effective Monday morning.

The damage to the flight Industry has been in the range of hundreds of million Euro.

This whole story is a perfect example of idiotic bureocracy and people in responsible position who have no knowledge of what they are responsible for.

Photos show ash impact on engines -

http://www.msnbc.msn.com/id/36649628/ns ... nvironment

Interesting wear and tear. Evidently it doesn't take much. Does anyone know how much air a jet engine breaths during a trip through an ash cloud? Is one particle the same as the next? That is, does flying for one hour through air with parts per trillion contamination by ash equate to ten hours of flying in air with parts per 10 trillion?

My guess is that shorter time at higher concentration is worse, because the likelihood of particles gumming up the turbine blade cooling passages goes up as more particles pass through at the same time. The pdf linked in the article, http://www.alpa.org/portals/alpa/volcan ... Damage.pdf , says that some of the DC-8's turbine blades may have had only ~100 hr of life left at time of landing. It also said the ash particles were covered with ice, so no scouring of windscreen, paint, or fan blades was found, yet the turbine damage occurred. The airlines are hoping that engine overhaul costs will be less than losses due to the shutdown.

Aero wrote:Photos show ash impact on engines -

http://www.msnbc.msn.com/id/36649628/ns ... nvironment

Interesting wear and tear. Evidently it doesn't take much. Does anyone know how much air a jet engine breaths during a trip through an ash cloud? Is one particle the same as the next? That is, does flying for one hour through air with parts per trillion contamination by ash equate to ten hours of flying in air with parts per 10 trillion?

Depends from engine to engine, but to give you a rough idea, the engines of the DC-8 of that PDF have a total mass flow of around 130 Kg/sec, while the latest GE90 has a total mass flow rate of about 1300 Kg/sec of air.

As for direct damage to the blades, low time/high concentration or long time/low concentration is mostly the same. In the end it gets down to total kinetic energy absorbed by the turbine blades, with damages generally increasing toward the external of the blades due to greater peripherical speed (and hence more energetic impacts).

In reality it gets much more complicated than the above, but this is just to give a quick answer.

It seems that volcanic ash and aircraft interaction is a subject that has not been studied very much.

http://apnews.excite.com/article/201004 ... OCIO0.html

Experts aren't sure what amount of volcanic ash - made up of sand and tiny abrasive glasslike particles - is dangerous to jet engines and what density is safe. And for that matter, they can't say how much of the ash is floating in any one spot along the air traffic routes or where it is specifically going next.

Lets design a project to answer some of these questions.

The first question can be answered on an engine test stand. Feed some ash into the engine and measure the damage. Then document it and distribute it to the airlines.

The second question could be answered by using a hepa filter on some of the outside air, perhaps air taken in to pressurize the cabin. The filter could be quite small because it would not be necessary to filter very much air to discover the ppm of volcanic ash. Of course it would be nice if the filter device could record the ppm ash as a function of location, but not necessary. Just clean or replace the filter before takeoff, and check it upon landing, determine the average ppm ash, then check it against the damage documented on the test stand. And of course, tell air traffic control so that other airline flights could benefit from the knowledge gained.

Yes, it would be some extra work but it seems to me to be less expensive than leaving the plane sitting on the ground if it is not necessary. Maybe the ash measuring filter could be automated to report expected damage automatically.

Giorgio wrote:As for direct damage to the blades, low time/high concentration or long time/low concentration is mostly the same. In the end it gets down to total kinetic energy absorbed by the turbine blades, with damages generally increasing toward the external of the blades due to greater peripherical speed (and hence more energetic impacts).

In reality it gets much more complicated than the above, but this is just to give a quick answer.

It's not just the kinetic energy of the particles. It's also how hot the blade is when it gets hit by a particle. A properly cooled turbine blade will suffer far less damage from particle impact than a blade that has become soft because its cooling passages are clogged. Hence my contention that low time/high concentration is worse because clogging is more likely, and it takes very little time for a clogged blade to overheat.

DeltaV wrote:

Giorgio wrote:As for direct damage to the blades, low time/high concentration or long time/low concentration is mostly the same. In the end it gets down to total kinetic energy absorbed by the turbine blades, with damages generally increasing toward the external of the blades due to greater peripherical speed (and hence more energetic impacts).

In reality it gets much more complicated than the above, but this is just to give a quick answer.

It's not just the kinetic energy of the particles. It's also how hot the blade is when it gets hit by a particle. A properly cooled turbine blade will suffer far less damage from particle impact than a blade that has become soft because its cooling passages are clogged. Hence my contention that low time/high concentration is worse because clogging is more likely, and it takes very little time for a clogged blade to overheat.

I agree, that's why I say it is more complicated than what you can disgress in a post.
If we want to do a more precise study we should first of all define particle average size distribution, composition/structure and concentration of the particles . But than the mathematics becomes a little bit too much messy to be discussed in few lines.