Re: Propeller Blade Temperature

From:         dave lawson <dave.lawson@alliedsignal.com>
Organization: Dave Lawson
Date:         Fri, 27 Dec 1996 06:42:41 GMT
References:   1
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Thundercraft wrote:
> 
> In article <rddE1LLut.576@netcom.com>, don@tsc.com says...
> >
> >
> >We are simulating the infrared signature of a turboprop aircraft.
> >Does anyone know what propeller blade temperatures might typically be,
> >in flight?
> >
> I remember that the DC-3 had an anti-icing system for the propellers.  Also,
> the de Havilland dash8 has sheilding on the fuselage to protect it from ice
> being thrown from the props.  I believe that the dash 8 uses an anti-icing
> system.
> 
> With these two thoughts in mind, I would say that the blade temperature would
> be pretty low.  Probably ambient temperature.  Remember, the bigger the prop,
> the slower they turn.  No heating up the surfaces from friction heating.

The props on the Dash 8 use a de-icing system rather than an anti-icing 
system.  The difference being that a de-icer removes a build-up of ice
and an anti-icing system prevents the ice build-up in the first place. 
Normally, however, you are correct.  The blades are not heated during
normal flight.  There will be some aerothermal heating on the outer,
say, 20 to 40 percent of the span due to high mach values.  It is not
unreasonable to expect several degrees above ambient, depending on local
mach number.  Some props get tip speeds up to M0.8 or so.  Remember,
both the rotational speed and forward velocity must be vector summed in
this calculation.

As an aside, many helicopters accret little ice on the outboard half of
rotor span due to the combination of heating, flexure and centrifugal
forces.

Dave