I'm probably missing something obvious here, but this is bugging me: are turbofan blades heated or something?
I mean the fan stage at the front; it's ahead of any heat being generated, it's got thin leading edges moving fast. Prop blades are deiced.
Fan blades are not heated, just the intake lip and I believe on some types the spinner to protect the fan disc from damage from shedding ice. Props spin at a much lower RPM than turbine spools in flight. On the ground though fan blades can ice up and every type I've flown requires a run up after 30 minutes to ensure the blades haven't collected any ice. Ice fog is particularly bad for a fan blades on the ground.
The higher speed of the fan vs. the speed of a propeller is such that centrifugal forces prevent ice buildup.
As Rockie already said, the inlet lip and some spinners are deiced, as well as the compressor inlet struts in some engines.
Inlet icing has to be on prior to entering icing or the building up of ice, as shedding an accumulation of ice from the inlet lip into the engine would be undesirable for obvious reasons.
If recall the Brazilian jungle jet, when selecting anti-ice all for takeoff, only the engine inlet is heated, and not until 40 knots wheel speed is the leading edges heated. Not really what you asked, but never the less. (CF34-8E)
Now for the other turbine I fly (GE 701D), there is two systems: engine bleed air, just like the fancy jet some of us fly. (the biggest concern with this, is that it takes away 20% from your max torque available).
The other is a more intricate system where engine oil is ducted through the first stage inlet vanes. It's two fold: heats incoming air, and cools the oil. This is preferable, since it doesn't penalize performance. However it's not nearly as effective as flipping the anti-ice switch.
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What about Air Temperature rise with the incoming air impacting the spinning Fan Blades.... Does that happen and would it be enough to keep ice from forming as well ???
Fan ice (N1) can occur at low power settings and felt as vibration through the airframe. This is especially true during prolonged taxi for takeoff in conditions such as ice fog etc,
To eliminate fan ice, you simply increase the fan rpm and the ice will shed off the blades and pass harmlessly out the bypass duct.
Hard for ice to stay on a blade that is turning in excess of 7600 rpm, and in essence this is the ice protection system for the N1 blades.....rpm/centrifugal force.
On the JT15 engines installed on the Citation, after the bleed air passes through the inlet it is exhausted toward the fan blades. If you look inside the inlet you can see the ring of holes approximately 2 inches apart and 1/4 inch in diameter just in front of the fan blades. The engine nose cone is continuously heated by bleed air anytime the engine is running.
Should posting the below link break a rule of this board, I apologize to the mods. I could not find the posting rules.
An excellent site for technical information on how things work on most any aircraft from a Caravan on up is http://www.smartcockpit.com/
There you may consult the actual aircraft manual and learn how each system works.
The site also contains an extensive library of technical, pilot technique and safety articles.
The information on the site may not apply to your type of flying, however I believe that all information is good information.
I know you didn't ask, and everything told so far is correct, but . . .
Ice buildup during flight on fan blades is not an issue due to their high RPM. However, icing in the jet core itself (in the low-pressure compressor section) is believed to have caused a number of engine failures. This section is unprotected from ice and can occur at temperatures where icing conditions would not be expected (extreme cold). Boeing calls this "ice crystal icing."
