I have a doubt is possible have a propeller with a variable RPM, I mean the change the maximum speed at tip of propeller ( always less than mach 1 ) but changing this not only with a variable pitch angle but directly from the engine . Because in this way at low speed of fly I can use a lower...
this is an example of 4 blade propeller with a diameter of 4 meter.
For my application the advance ratio is between zero and 0.35 if i consider the maximum speed at tip with mach 0.75.
how you can see the thrust is good but the efficiency don't reach the 60% .
I can increase it with a three...
I know the speed , i know the drag of airship , so i know the thrust .
I can calculate all the characteristic curve of propeller but there isn't a mathematical method to select the best solution or it is Just look at graphs and see Which One look the best .
The same to select the best airfoil...
the aircraft is a solar airship with electric motor.
the velocity is less of 30 m/s and at this velocity the advance ratio is low and this mean very low efficiency and if i do the blade smaller I don't have enough thrust.
It's a lop where I don't found a solution for this I am doing some...
Considering the ideal case that I can have always the best engine appropriate for the propeller and a variable pitch angle.
The advance ratio J=V/(nD) is function of speed but also the diameter.
if i change the diameter the best propeller is always the same ?
for the second problem I use...
Two problem to solve.
1) I have 4 propellers built with different airfoils. I have the graphs of coefficient of thrust and efficiency in function of advance ratio. There is a mathematical method to select which one is the best or the only way is just look at graphs
2)I know the maximum thrust...
