X-Mozilla-Keys:                                                                                 
Jeff Spitzer wrote:

At 11:14 PM 7/1/99 -0700, you wrote:

Oh good another data point. Let's see 300 HP with 800 pounds of thrust.
4.8% efficient at 10 feet per second. Do you have a curve
showing the thrust as a function of aircraft velocity or
did Paul Moller consider that amount of thrust constant with speed?

Of course you realize that you're number of 4.8% or whatever has
practically no meaning.  It's amazing how jets manage to fly given that
they have zero propulsive efficiency when they release the brakes.  There
is a proper way to calculate static efficiency.  I don't recall the proper
formula right now but maybe one of the other fan experts on here can
provide it.

Jeff Spitzer

Of course I know that Jeff. It is just the start of the curve.
We need the thrust as a function of aircraft speed. Do you have it?

This way of calculating duct and fan  eff. is very valid indeed.
If thrust is constant with speed than the method is quite
simple and very valid.

The same method is used for calculating the eff. of props.

They all have zero eff. at static so no thrust HP is being generated.
Work and HP are being done but they are merely heating the air.
The static thrust number is useful however for calculating
the initial accelleration.
 
Paul Lamar
 
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