Rotor Blade Tip Temperature 1

• Jun 23, 2004

1
• #2

Sparweb

Aerospace

May 21, 2003

5,187

CA

You can look up the isentropic flow equations in any fluid mechanics or aerodynamics textbook.
At Mach=1, T_o/T₁=1.2

Starting at 300 Kelvin, the temperature would rise to 360 K.

This effect is not very significant until much higher Mach numbers.

An interesting college exercise I remember was to start with the melting point of aluminum and feed that backward through the equation to find the aircraft's top speed, then to compare the result to the Concorde.


Steven Fahey, CET
"Simplicate, and add more lightness" - Bill Stout

 

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• Jun 23, 2004

• #3

Intermesher

New member

Jun 6, 2001

179

CA

I have never read or heard anything about aerodynamic heating of blade tips. Perhaps this is because the tip is only operating at a high airspeed during a small portion of its rotation; i.e. When it is on the advancing side.

 

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• Jun 23, 2004

• #4

GraviMan

Automotive

Feb 4, 2003

214

US

OT (sorry).

"An interesting college exercise I remember was to start with the melting point of aluminum and feed that backward through the equation to find the aircraft's top speed, then to compare the result to the Concorde."

That is an interesting excercise. What was the result? I gather the russians are sticking to Mach 1.8 for precisely that reason.

Mart

 

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• Jun 23, 2004

• Thread starter
• #5

LloydofDSS

Electrical

Jun 14, 2004

3

US

In a hover, the blade tips are at a constant speed and it is generally 150-200 kts below Mach 1 (Sea level). At max Vne the tips going forward come pretty close to Mach 1, but as they go aft they drop below their hover speed by the forward velocity of the aircraft. At least that is how I understand it.

Thanks for the info, that was very helpful.

 

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• Jun 24, 2004

• #6

Sparweb

Aerospace

May 21, 2003

5,187

CA

Lloyd,
Yes, I didn't state explicitly that I was using Mach 1 for a maximum tip speed, even though they are almost always less than that.

Graviman,
The exact resulting Mach number escapes me, but the point of the exercise demonstrated that above a certain speed, aluminum cannot be used for a leading edge, and titanium must be substituted (for extra cost). For higher and higher speeds, increasingly resistant materials are required, until you reach the ludicrous point of gluing millions of brittle 12 inch thick tiles all over your shuttle.

Sorry Lloyd, I've totally sidetracked your thread now.


Steven Fahey, CET
"Simplicate, and add more lightness" - Bill Stout

 

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