Hooters ain't necessarily hooters!

[gaunty]

Knew that would get your attention John :)

Whilst listening to the Australian ABC Science show this am, an Australian Prof based in San Diego was taking about the problem they are investigating called "hooting" in large jet engines using lean fuel techniques for low NOx emmision control.

Yup, a combustion instability that causes a combustion flame front oscillation that sounds like a hoot or hum and other organ like notes.

Good ol Google took me here for a fascinating look at the physics.

Hooting (http://www.memagazine.org/mepower02/thathum/thathum.html)

I wonder if it is the same unstable combustion mechanism that causes that hooting sound during most gas turbine start ups.??

We learn something useful every day.:cool: :ok:

edited to fix fumble fingered incoherence.:uhoh:

[john_tullamarine]

Gaunty ... you know me too well, mate.

Absolutely fascinating stuff ...

Is this phenomenon, by any chance, related in any way to that which I observed (as a young hoon .. weren't we all ?) in my then vehicular pride and joy, a Morris 1000. Coasting downhill, I observed that, by turning the ignition to "off", singing a brief refrain of "God Save the Queen", and then selecting the ignition to "on", a loud report was heard to occur at the rear of the vehicle (music to a young hoon's ear .. other young hoons who could afford decent cars would, no doubt, find alternative measures of automotive delight).

Quite sadly, after a pleasing number of repetitions, I found that I couldn't hear the desirable loud report above the ambient exhaust note as effectively as before ... after 99.99% of the exhaust system disengaged itself from the vehicle during one such repetition ....

[gaunty]

Ahhh the venerable Moggie, there are still a few around my parts going as strong as ever. A fine example of simple and effective design.

My first one was an Austin A55 "Cambridge" with extra string, no less, with that stump puller 1st Gear, the injudicious use of which could start a driver induced rapidly divergent feedback loop of kangaroo hops.:rolleyes:

Yes indeeed a very efficient way of dismantling an exhaust system.

Whilst converting a young tyro to a C421C I was once not quick enough to stop the chappie from turning the mags back on after he somehow turned all four of them off with that gang bar thingy whilst he was supposed to be checking them one by one.

Deafening silence followed by frantic lunge and "NO leave them off now", too late, dual Kabooms, satisfyingly large sheet of flame followed by clanking noises as various parts of the exhaust system are distributed randomly beneath the aircraft.:rolleyes: :{

[ramsrc]

Wonderful vehicle the Moggie Minor. My Father had a Traveller, and what a vehicle it was. Simple to maintain, cheap to run and you have a feeling of really being "in touch with he road". Take one up to 60mph on the motorway and you'll know what I mean :p


I observed that, by turning the ignition to "off", singing a brief refrain of "God Save the Queen", and then selecting the ignition to "on", a loud report was heard to occur at the rear of the vehicle

My Grandfather told a story similar to this. During part of his time with the REME he drove a Scammell heavy breakdown. At some point the horn stopped working, but he found that the aforementioned method was far more effective. He didn't mention the effect that it had on the exhaust system, but apparantly it was quite good at warning people that he was there :E

[Shore Guy]

On the west side of the pond, I did this in ’50 Chevy Coupe. I stopped after replacing three mufflers…..

The other attention getter……I used to fire rockets off the front of my car. The solid rocket motor type. Had an arming switch and the “fire control” was a doorbell button.
The launch pad was a welding rod stuck into one of the cooling fins of the radiator with a coffee can lid as a blast pad.


:E :E :E

For the engineering types…On takeoff/climb in moderate/heavy rain, if in an “EPR” airplane, my assumption is that takeoff/climb thrust will be as indicated. On an N1 airplane, will takeoff/climb at a computed N1 result in a higher net thrust due to the “mass flow” phenomenon?

For the engineering types…On takeoff/climb in moderate/heavy rain, if in an “EPR” airplane, my assumption is that takeoff/climb thrust will be as indicated. On an N1 airplane, will takeoff/climb at a computed N1 result in a higher net thrust due to the “mass flow” phenomenon?

Whoops....below the smiles were my question for another thread...(still don\'t know how I did that). If a moderator can erase, that would be fine.