smartt1982
Topic Author
Posts: 226
Joined: Sat Nov 24, 2007 11:17 pm

Purpose Of Spinner Cone On The Front Of Fan Jet

Tue Oct 19, 2010 9:55 pm

Hello,

Probably most obvious but can someone remind me the exact reason/reasons for the spinner cone at the centre of the fan blade on turbo fan engines?

Many Thanks
 
474218
Posts: 4510
Joined: Mon Oct 10, 2005 12:27 pm

RE: Purpose Of Spinner Cone On The Front Of Fan Jet

Tue Oct 19, 2010 10:37 pm

Quoting smartt1982 (Thread starter):
reason/reasons for the spinner cone at the centre of the fan blade

You have to attach the blades to something?
 
User avatar
Starlionblue
Posts: 17055
Joined: Fri Feb 27, 2004 9:54 pm

RE: Purpose Of Spinner Cone On The Front Of Fan Jet

Tue Oct 19, 2010 10:55 pm

Aerodynamic fairing for the shaft?
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
SEPilot
Posts: 4916
Joined: Sat Dec 30, 2006 10:21 pm

RE: Purpose Of Spinner Cone On The Front Of Fan Jet

Tue Oct 19, 2010 11:20 pm

Quoting Starlionblue (Reply 2):
Aerodynamic fairing for the shaft?

I believe this is the function, much like the spinner on the hub of a prop plane. The blade attachment to the shaft takes a fairly large diameter, and to have just a flat plate would create a lot of drag. Older prop planes used to not have spinners, but they flew much slower and spinners were added to just about all of them that continued in production because it reduces drag. On a jet engine it is far more important.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
User avatar
lightsaber
Crew
Posts: 11739
Joined: Wed Jan 19, 2005 10:55 pm

RE: Purpose Of Spinner Cone On The Front Of Fan Jet

Wed Oct 20, 2010 1:33 am

Quoting SEPilot (Reply 3):
The blade attachment to the shaft takes a fairly large diameter, and to have just a flat plate would create a lot of drag.

It also helps correct the velocity profile into the core. Having no 'spinner' would result in poor air feed to the core which would impact hot/high performance,


The main purpose is aerodynamic as part of the nacelle cowling diffuser into the fan. The ideal is a plug flow velocity into the fan.

It also helps control vibration. A flat plat at the hub would be a Karman pump. It would be inherently unstable for vortex shedding.

Lightsaber
"They did not know it was impossible, so they did it!" - Mark Twain
 
User avatar
Stitch
Posts: 22947
Joined: Wed Jul 06, 2005 4:26 am

RE: Purpose Of Spinner Cone On The Front Of Fan Jet

Wed Oct 20, 2010 3:31 am

And in the off chance you are referring to the white "blob" on said cone, smartt1982, as I understand it, it is designed to scare birds and keep them out of the fan.
 
b78710
Posts: 311
Joined: Fri Mar 24, 2006 4:21 am

RE: Purpose Of Spinner Cone On The Front Of Fan Jet

Wed Oct 20, 2010 9:21 am

aerodynamics, fairs the attatchment of the fan blades to the hub and allows a good no turbulent flow through into the core.

the tip on our trents is a small rubber cone. designed to oscillate and shed any ice that may build up on it.
 
smartt1982
Topic Author
Posts: 226
Joined: Sat Nov 24, 2007 11:17 pm

RE: Purpose Of Spinner Cone On The Front Of Fan Jet

Wed Oct 20, 2010 9:49 am

Quoting lightsaber (Reply 4):
It also helps correct the velocity profile into the core. Having no 'spinner' would result in poor air feed to the core which would impact hot/high performance,


The main purpose is aerodynamic as part of the nacelle cowling diffuser into the fan. The ideal is a plug flow velocity into the fan.

It also helps control vibration. A flat plat at the hub would be a Karman pump. It would be inherently unstable for vortex shedding

lighsaber, can you just elaborate on this. I will be the first to admit my knowledge of this is is poor so would be very interested to hear how that works if you would be so kind. What is a Kaman pump and how does the spinner help or what is a plug type flow?

I have read a bit about jet engines, any suggestions on a book that would describe this also?

Quoting Stitch (Reply 5):
And in the off chance you are referring to the white "blob" on said cone, smartt1982, as I understand it, it is designed to scare birds and keep them out of the fan.

I have heard that before aswell, has it ever been confirmed?
 
26point2
Posts: 809
Joined: Wed Mar 03, 2010 6:01 am

RE: Purpose Of Spinner Cone On The Front Of Fan Jet

Wed Oct 20, 2010 12:56 pm

I thought the "blob" as well as the "swirl" was a safety design for ramp workers. Easy to see if the fan is rotating on a noisy ramp in low visibility.

I've only ever seen this done on underwing mounted engines.
 
User avatar
Stitch
Posts: 22947
Joined: Wed Jul 06, 2005 4:26 am

RE: Purpose Of Spinner Cone On The Front Of Fan Jet

Wed Oct 20, 2010 4:13 pm

Quoting 26point2 (Reply 8):
I thought the "blob" as well as the "swirl" was a safety design for ramp workers. Easy to see if the fan is rotating on a noisy ramp in low visibility.

That makes sense, as well.
 
doug_or
Posts: 3118
Joined: Sat Mar 18, 2000 9:55 am

RE: Purpose Of Spinner Cone On The Front Of Fan Jet

Thu Oct 21, 2010 2:03 am

Quoting 26point2 (Reply 8):
I thought the "blob" as well as the "swirl" was a safety design for ramp workers. Easy to see if the fan is rotating on a noisy ramp in low visibility.

yes, makes a running engine much more distinguishable from a non-running engine.

Not sure what it would do for birds. At any thrust setting it will just be a blur. The thing that scares birds will not be the spinning little painted bit. The thing that scares birds will be the 100 ton chunk of metal moving at 150+ mph while emitting 90+ decibels.
When in doubt, one B pump off
 
Stealthz
Posts: 5546
Joined: Wed Feb 02, 2005 11:43 am

RE: Purpose Of Spinner Cone On The Front Of Fan Jet

Thu Oct 21, 2010 9:51 am

Quoting doug_Or (Reply 10):
At any thrust setting it will just be a blur.

Actually it isn't, many birds(if not all) have a far higher flicker fusion rate than humans so the swirly thing may just look like the scary eye of a huge predator!
If your camera sends text messages, that could explain why your photos are rubbish!
 
User avatar
Faro
Posts: 1491
Joined: Sun Aug 12, 2007 1:08 am

RE: Purpose Of Spinner Cone On The Front Of Fan Jet

Thu Oct 21, 2010 10:10 am

Quoting 26point2 (Reply 8):
I thought the "blob" as well as the "swirl" was a safety design for ramp workers. Easy to see if the fan is rotating on a noisy ramp in low visibility.

Great idea; why not extend it and paint the blobs on the fan blades themselves too so that the a running engine is even easier to spot for ramp agents?

Faro
The chalice not my son
 
User avatar
bikerthai
Posts: 2152
Joined: Wed Apr 28, 2010 1:45 pm

RE: Purpose Of Spinner Cone On The Front Of Fan Jet

Thu Oct 21, 2010 6:43 pm

Has the "cone" shape spinner become the preferred configuration over the paraboloid shape?
What is the +/- of each design?

bikerthai
Intelligent seeks knowledge. Enlightened seeks wisdom.
 
b78710
Posts: 311
Joined: Fri Mar 24, 2006 4:21 am

RE: Purpose Of Spinner Cone On The Front Of Fan Jet

Thu Oct 21, 2010 10:34 pm

Quoting faro (Reply 12):
Great idea; why not extend it and paint the blobs on the fan blades themselves too so that the a running engine is even easier to spot for ramp agents?

i usually find the huge jet blast coming out the back, the high pitched screaming noise and the vibrations running through my chest enough to be honest!

if you have any business out on the ramp and you miss all of that you probably deserve to go through the engine
 
26point2
Posts: 809
Joined: Wed Mar 03, 2010 6:01 am

RE: Purpose Of Spinner Cone On The Front Of Fan Jet

Fri Oct 22, 2010 12:17 am

Quoting b78710 (Reply 14):
f you have any business out on the ramp and you miss all of that you probably deserve to go through the engine

You would be surprised how disorienting it can be in a very noisy environment. Then imagine it's night or windy or raining or all of that.

Remember, on a ramp there are often several operating aircraft nearby.

Try it. You will see.
 
b78710
Posts: 311
Joined: Fri Mar 24, 2006 4:21 am

RE: Purpose Of Spinner Cone On The Front Of Fan Jet

Fri Oct 22, 2010 8:26 am

Quoting 26point2 (Reply 15):
You would be surprised how disorienting it can be in a very noisy environment. Then imagine it's night or windy or raining or all of that.

Remember, on a ramp there are often several operating aircraft nearby.

Try it. You will see.

I've been doing it for the last 6 years, in exactly the conditions you've mentioned.
 
UAL Bagsmasher
Posts: 1839
Joined: Wed Sep 08, 1999 12:52 pm

RE: Purpose Of Spinner Cone On The Front Of Fan Jet

Tue Nov 02, 2010 12:04 pm

Painting the fan blades would alter the precision balancing that they require to keep fan vibration low. Since they are also changed in matched sets, you'd have pairing issues to deal with as well.
 
User avatar
DocLightning
Posts: 19616
Joined: Wed Nov 16, 2005 8:51 am

RE: Purpose Of Spinner Cone On The Front Of Fan Jet

Wed Nov 03, 2010 12:34 am

Quoting b78710 (Reply 14):

if you have any business out on the ramp and you miss all of that you probably deserve to go through the engine

Be that as it may, the airline also has an interest in not having your ground-up corpse destroy their multimillion dollar engine. Not to mention lawsuits and payouts from your untimely demise.
-Doc Lightning-

"The sky calls to us. If we do not destroy ourselves, we will one day venture to the stars."
-Carl Sagan
 
spencer
Posts: 1518
Joined: Sun Apr 25, 2004 8:30 pm

RE: Purpose Of Spinner Cone On The Front Of Fan Jet

Wed Nov 03, 2010 11:22 am

I may well be thinking of inlet cones, primarily on supersonic ac, but does the spinner not generate a shock wave favourable to the air entering the engine?
Spencer.
EOS1D4, 7D, 30D, 100-400/4.5-5.6 L IS USM, 70-200/2.8 L IS2 USM, 17-40 f4 L USM, 24-105 f4 L IS USM, 85 f1.8 USM
 
tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

RE: Purpose Of Spinner Cone On The Front Of Fan Jet

Wed Nov 03, 2010 1:39 pm

Quoting spencer (Reply 19):
does the spinner not generate a shock wave favourable to the air entering the engine?

Not on a commercial turbofan...the air entering the inlet is subsonic, so it can't form a shockwave.

Tom.
 
spencer
Posts: 1518
Joined: Sun Apr 25, 2004 8:30 pm

RE: Purpose Of Spinner Cone On The Front Of Fan Jet

Wed Nov 03, 2010 10:10 pm

Thanks Tom, obviously I was half way there thinking of the inlet cone.
Spence.
EOS1D4, 7D, 30D, 100-400/4.5-5.6 L IS USM, 70-200/2.8 L IS2 USM, 17-40 f4 L USM, 24-105 f4 L IS USM, 85 f1.8 USM
 
musang
Posts: 788
Joined: Sun Apr 08, 2001 4:11 am

RE: Purpose Of Spinner Cone On The Front Of Fan Jet

Wed Nov 03, 2010 11:23 pm

The other reason for the precise contouring of the spinner is to deflect foreign objects past the core intake. Stones, volcanic ash, bird wreckage etc. will do much less damage through the fan/bypass duct than if they go through the core. However I don't know why some are cone shaped and some domed.

I always thought the "blob" or "teardrop" shape painted on a spinner was intended for ground staff, as they'd only ever be near it when the engine was at or near idle speed, when such a design would be visible. The spiral stripe was intended for birds, as its still visible (i.e. not a blur) even when the engine is at take-off rpm.

Quoting 474218 (Reply 1):
You have to attach the blades to something?

Close! That "something" is the hub, behind the spinner.

Regards - musang
 
User avatar
bikerthai
Posts: 2152
Joined: Wed Apr 28, 2010 1:45 pm

RE: Purpose Of Spinner Cone On The Front Of Fan Jet

Thu Nov 04, 2010 4:55 pm

Quoting musang (Reply 22):
However I don't know why some are cone shaped and some domed.

Could it be that the cone is better at deflect object than a dome?

Quoting musang (Reply 22):
The other reason for the precise contouring of the spinner is to deflect foreign objects past the core intake.

You would think the dome would provide a better flow profile of the air going into the compressor. But in the case of foreign object deflection you don't want that better flow?

As good an argument as any . . . .

bikerthai
Intelligent seeks knowledge. Enlightened seeks wisdom.
 
User avatar
lightsaber
Crew
Posts: 11739
Joined: Wed Jan 19, 2005 10:55 pm

RE: Purpose Of Spinner Cone On The Front Of Fan Jet

Sun Nov 21, 2010 10:36 pm

Quoting smartt1982 (Reply 7):
What is a Kaman pump and how does the spinner help or what is a plug type flow?

Sorry for the late response...

Ok, we've already discussed that the spinner covers where the fan blades attach. Well... for optimum fan performance, it is best to have a 'reasonably high' mach number on the fan blades. There is no thrust (or more precisely pressure) generated at the hub of a fan anyway...

Now if there was no aerodynamic shape over the hub, it would be a flat circle. A spinning flat circle is a very primitive pump called a Karman pump. (Complex fluids). So the shape of the hub cover is based on:
1. aerodynamics (minimum pressure drop into the engine as that would be lost thrust)
2. Minimizing vortex shedding into the fan (noise oscillations that are both annoying to NIMBYS as well as likely to do high cycle fatigue wear on the engine).

"Plug flow" is idealized flow where everything is at the same velocity. In a jet engine 'plug flow' isn't quite the ideal... (I over-simplified.) One wants the bulk of the mass flow about 2/3rds of the radius out from the hub. But the engine has air coming in at the hub that needs to be moved outward to where the fan blades can do work on it, but not too much as the air still needs to flow into the core.

Quoting bikerthai (Reply 13):
Has the "cone" shape spinner become the preferred configuration over the paraboloid shape?
What is the +/- of each design?

The cone is cheaper to make. Since the inlet part of the nacelle is becoming longer, the differences in shapes matters less than many would note. The inlet of the nacelle is shaped with the spinner. Most of the cost/work is on the nacelle... So the hubs have become more of an engine makers trademark than critical. Oh, there needs to be a spinner, but the exact are not as critical as the engineers designing them think they are.

Lightsaber
"They did not know it was impossible, so they did it!" - Mark Twain

Who is online

Users browsing this forum: No registered users and 14 guests