ezflyr

My Feedback: (32)

Red B.,

A little bit off topic, but would you by any chance know what a "festering gobutit" is ?

John

Wayne22

My Feedback: (2)

I think we established that the tip speed of the compressor wheel is well over mach 1. The air that is being compressed is traveling at right angles relative to the compressor wheel, and is a totally different situation from what the original question asked...

turnnburn

My Feedback: (49)

make that a double HUH for me !!!!!!!!!!!!!!

BMT

Nony, you spotted the difference! Yes tip speed has something to do with the speed of the air but there are several other factors that determine the actual air speed. The air leaves the tip at a different tangent under different conditions. The ideal swept back high compression ratio compressor would have the lowest possible gas speed for the highest pressure. This also eases the diffusor design. Also the air exiting the channel of the compressor in a centrifugal compressor is a dual contra rotating vortex and by no means is the flow simple. It takes CFD software on a cray days to predict airflow like this.
Andre

Shaun Evans

Wow. I sure feel dumb. Let's talk about Shakespeare's plays and sonnets.......

Red B.

Sure, I know my Monty Python!
Question is, should I consider your posting from "the bright side of life"* or is it simply a "heap of parrot droppings"**?

/Red B?

In case the moderator reads this:
* from "Life of Brian" by Monty Python
** from the "The Argument Clinic" by Monty Python

Rupurt

So in simple terms, due to the conditions experienced in the turbine, the compressor and turbine wheels mach# will always be below 1 even tough the velocities are greater than required to break the sound barrier at STP.

Miniflyer

Rupurt, you just put in 2 lines what i was trying to express in many long sentences *lol*.

Now while we are at theoretical discussions: will the fuel ignite in the evaporizer tubes, or only after exiting into the chamber? Had many long and interesting talks about that one.....lets hear some opinions

TREADSTONE.

One hundred and sixteen inch fan diameter... take Your N1 Value as 3000rpm...i just rounded this up to make life easy

.. The rest is simple

Rupurt

Only after exiting into the chamber gets my vote. The small positive pressure created by the fuel being pumped in and then vaporizing on the hot walls, should keep oxygen out of the sticks.

TREADSTONE.

... The tip speed of the HP turbine in a T900 is Faster than the Fan tip speed[:-]

Gazzer

Finally it all came out in the wash and I understood.


I have had my models go supersonic, judging by the "bang" it made when it hit the ground.

Instead of saying "sod it" it should have been "sonic"

So to prove my theory of supersonic flight

= theorem of S (speed) x H (height) x I (integer for mach number follwing variables as discussed) x T (thrust in use to give acceleration)

So if I here another sonic bang, when the model hits the grounds I should shout the out the shortened theory S H I T.[>:]

Am I off topic?

So how can we now explain afterburning theories and why aren't there many if any out there?

Gazzer

Graeme Marion

Thanks.

That all made sense.....I think

Gordon Mc

My Feedback: (11)

To beat mach 1, or not to beat mach 1? That is the question. Whether 'tis nobler on the jets forum to suffer the ignomity and confusion of outrageous discussions, or to take arms against a sea of theories, and by opposing end them? To have your engine die; to sleep; no more (must be a RAM); and, by a sleep to say we end the confusion and the thousand natural shocks that the compressor is heir to, 'tis a consummation devoutly to be wished. To die, to sleep; To sleep: perchance to dream of flying; aye, there's the rub. For in that sleep of death what dreams may come when we have shuffled off this mortal Rossi R-8 glo-plug coil

or something like that. I learned the original about 25 years ago, and still can't get the damned thing out of my head. Kinda like the downwind-check-list that's so ingrained in my head that it will probably be the last thing ever to go through my noggin....

unknown

Is there any web site with SPECS on turbo charge compressor??. BMT question isn't both blades on the compressor for sub sonic and super sonic speed ???.

ps2727

Don't know the math but it seems like lots of thought goes into inlet designs for supersonic airplanes in order to slow the flow to subsonic before it gets to the engine. That's why there is such interest in the scram jet technology- the first successful supersonic flow engine.

UK Flier

"When all aloud the wind doth blow"

Love labour's Lost - Act 5 scene 2 William Shakespeare 1595

JimBrown

My Feedback: (2)

"Life's but a walking shadow, a poor player
That struts and frets his hour upon the stage
And then is heard no more: it is a tale
Told by an idiot, full of sound and fury,
Signifying nothing."

The Tragedy of Macbeth, Act 5, Scene 5.



...jim

Terry Holston

My Feedback: (1)

SHOW OFF

Graeme Marion

This is the best example of a practical use being made of "Einstein's Theory of Relativity" that I have ever heard.

Randy M.

My Feedback: (38)

All I know is my AT180 pushes my Hot Spot through the air and sounds really cool when it goes by!!!
ssshhhheeeeewwwwwwwwwwwwwww

EddieWeeks

Einstein's Theory would say only say that time slows down for the faster moving air and compressor..

Newton still rules here..

Miniflyer

"Thy shall not argue".... Hank, act:now, without a scene :P

No more people getting into the argument about where the fuel begins to burn?
Rupurt, i personally believe the fire starts within the stick, at about 2/3 length, going from the walls towards the center as the stick is coming to the end.
Reason as follows: you have a whole lot of air moving through the stick (thats the big reason why fuel injectors always point at a stick wall, never down the center...the drops would get ripped through the stick without evaporating). Fuel coming down the glowing hot stick, evaporating on the wall and forming a burnable mixture with the air. As you pass along the stick temperature rises....somewhere near 2/3 you should be getting over 700-some degrees C, and bang, auto-ignition of the kerosene....
Just a theory....

Gazzer

To be or not to be, right about this is a question!!!!

I have to say my interest now focus's on beyond the combustion tube and into the exhaust. The idea of an afterburner, I understand to be dumping fuel at a critical poin in the exhaust eflux, and whey hey, more expanding gas, greater velocity and Zoooooooooooooooooooommmmmmmmmmmmmmmmmmm

However, if the gas now doing X mph in velocity out of the back of the engine, has already been expanded and presumably de oxygenised, than no flame without O2, dumping fuel into the exhaust stream would not create an "afterburn".

IS the science of this a reason for not doing it in models, or is it the curious mix of temperatures, and high fuel usage the issue..................

And that my come back to where the fuel burns in the motor itself!

Looking forward to the next lesson,
For it will be a great session,
Learning about the rules of gas
Making sure its not a pain in the XXXXX[8D]

Shakespeare turns in his grave......

Oh well, I tried, this is heavy stuff!!

Gazzzzzzeeeeerrrrrrrrr

Rupurt

There should still be about 3/4 of the oxygen left in the exhaust gas, so it will work, just got to get it right. It has been done!

Miniflyer,
I think i will have to agree, provided the pressure at the back of the sticks is higher than that in the combustion chamber. You obviously have to believe it is so I will take your word for it