Yo what’s up Lou Mellon?
We are starting a blobg that we may never use again or we may start using for a week and then stop using or that we may use forever, if you can blog in the after life – fingers crossed.
Today I am interested in PROPELLERS. A propeller is essentially a type of fan which transmits power by converting rotational motion into thrust for propulsion of a vehicle such as an aircraft. That’s a duh.
But did you know that the forces of lift and drag on the blade, dA, where force normal to the surface is dL:
![\mbox{d}L = \frac {1}{2}\rho V_1^2 C_L dA = \frac {1}{2}\rho C_L[V_a^2(1+a)^2+4\pi^2r^2(1-a')^2]b\mbox{d}r](http://upload.wikimedia.org/math/7/2/5/7253f9578b848a4ab4d6f175a709b04b.png)
where:
![\mbox{d}D = \frac {1}{2}\rho V_1^2C_D\mbox{d}A = \frac {1}{2}\rho C_D[V_a^2(1+a)^2+4\pi^2r^2(1-a')^2]b\mbox{d}r](http://upload.wikimedia.org/math/6/f/6/6f6fecc590ec7f60f03c5cbea876091f.png)
These forces contribute to thrust, T, on the blade:
where tanβ = dD / dL = CD / CL
As 
,
From this total thrust can be obtained by integrating this expression along the blade. The transverse force is found in a similar manner:
Substituting for V1 and multiplying by r, gives torque as:
which can be integrated as before.
The total thrust power of the propeller is proportional to TVa and the shaft power to 2πNQ. So efficiency is TVa / 2πNQ. The blade efficiency is in the ratio between thrust and torque:
That’s it for now. Ti’ll then don’t thrust your torque too often! ! ! !
See ya tomorrow or never again 
phil
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