In the final formula for Thrust, shouldn't the sin(phi0) be multiplied by the coefficient of drag and not epsilon? I think the epsilon should have been cancelled when Cl was multiplied into the brackets? time: 14:26 Thanks,
Can I use these equations with a propeller inside a circular chimney which is placed vertically to conclude the the optimum blade section that generate the maximum power output ?
Hello. Thank you for the videos on the propeller. However how would I do the calculation to maintain power in different velocities by changing pitch angle?
I suppose we need to integrate those formulas from 0 to R w.r.t dr in order to calculate the total lift, thrust, etc. However, in the formulas expressed in the video there is also the chord length c, which varies from section to section. So whats the way to calculate the overall blade forces?
Hello again, basically i am carrying out a project on Variable Pitch Propellers and i assume the propeller analysis is the same as the one explained in the video. However, i am going to calculate the blade pitching moment about an offset axis of rotation (pivot) and i want to test it at 2 different cases; take off (high RPM) and cruising (low RPM). For start, i am going to use conventional symmetric constant airfoils throughout the blade and the propeller will be tested on a stationary position. So my question is how i am gonna analyze the propeller with only knowing the RPM (wr) and the geometry of the blade? what about the forward velocity (airspeed)? will it be zero duw to the stationary position of the propeller?? thanks
geoklavaris I don't think you should use an airspeed of zero as the angle of attack will probably work out to be too high. How about looking up the take-off speed for an aircraft with that propeller and using that for the fine pitch condition, then use the cruise speed for the coarse pitch.
Sir, Can this be used for propellers which have a curved surfaced like surfaces on boat propellers? For e.g. For Radio Controlled models (quadcopters) I see propellers which don't have any thickness but still provide lift. I think they are called slowfly propellers.
The principles are the same. The lift is proportional to the airspeed over the blade, the area of the blade and the angle of attack. This video was demonstrating the effect of airspeed and angle of attack for a given area S.
I have a quick question , as far as i know with increase in forward velocity thrust must decrease, however using this method with change in forward velocity thrust is also increasing . Can you tell where i might be wrong. I am working on a project and will be grateful if you can reply ASAP.
You're right. As velocity increases the thrust reduces because Thrust=Mass*(final-velocity - initial-velocity). However, you need thrust to give you velocity in the first place. It's a bit like a ball having potential energy on top of a hill, but having no kinetic energy. As the ball falls off the hill the kinetic energy increases and the potential energy decreases. Similarly, on the runway when the pilot is standing on the brakes and has the throttle fully foward, the propeller is producing a lot of thrust. But when he releases the brakes the aircraft moves (velocity increases) and hence the thrust reduces. However, without that initial thrust the aircraft wouldn't have moved at all. Hope that helps.
In the final formula for Thrust, shouldn't the sin(phi0) be multiplied by the coefficient of drag and not epsilon? I think the epsilon should have been cancelled when Cl was multiplied into the brackets? time: 14:26
Thanks,
You're correct. Thanks for that.
great video, How can we reduce noise generate by propeller ?
great video. Just one question, if you have a twisted blade, how can you calculate beta? since blade angle is changing through the blade span
I have ploted the T using m code, but the results I get are negtive, can you help me to understand whats im wrong?
Angelo Garibaldi Rodriguez can you post your code or post a video explaining your code. If I get a chance I’ll look at it.
Can I use these equations with a propeller inside a circular chimney which is placed vertically to conclude the the optimum blade section that generate the maximum power output ?
Yes.
Thank you so much. would you mind explaining about airfoil on your way please?
Very helpful video. Question, where can i find more information on the effect of the number of blades on thrust?
I'll get back to you.
one correction at time 6:03 min is that you had used '+' intead of '-' in equating the two velocities
Hello. Thank you for the videos on the propeller. However how would I do the calculation to maintain power in different velocities by changing pitch angle?
Gabriel Joiner good question. Let me think
I suppose we need to integrate those formulas from 0 to R w.r.t dr in order to calculate the total lift, thrust, etc. However, in the formulas expressed in the video there is also the chord length c, which varies from section to section. So whats the way to calculate the overall blade forces?
geoklavaris the chord length c is the mean aerodynamic chord.
thanks
Hello again, basically i am carrying out a project on Variable Pitch Propellers and i assume the propeller analysis is the same as the one explained in the video. However, i am going to calculate the blade pitching moment about an offset axis of rotation (pivot) and i want to test it at 2 different cases; take off (high RPM) and cruising (low RPM). For start, i am going to use conventional symmetric constant airfoils throughout the blade and the propeller will be tested on a stationary position. So my question is how i am gonna analyze the propeller with only knowing the RPM (wr) and the geometry of the blade? what about the forward velocity (airspeed)? will it be zero duw to the stationary position of the propeller?? thanks
geoklavaris I don't think you should use an airspeed of zero as the angle of attack will probably work out to be too high. How about looking up the take-off speed for an aircraft with that propeller and using that for the fine pitch condition, then use the cruise speed for the coarse pitch.
I will check it out...Appreciate the response, thanks!
Great video, thanks for such a good explanation of this complicated method.
Thank you. I'm glad that at least one person got something from it.
thank you very much :) ... i have a question the thrust in this situation is produced from lift and drag ..isn't?
Yes. But the drag is acting in the opposite direction.
Sir, Can this be used for propellers which have a curved surfaced like surfaces on boat propellers? For e.g. For Radio Controlled models (quadcopters) I see propellers which don't have any thickness but still provide lift. I think they are called slowfly propellers.
The principles are the same. The lift is proportional to the airspeed over the blade, the area of the blade and the angle of attack. This video was demonstrating the effect of airspeed and angle of attack for a given area S.
I have a quick question , as far as i know with increase in forward velocity thrust must decrease, however using this method with change in forward velocity thrust is also increasing . Can you tell where i might be wrong. I am working on a project and will be grateful if you can reply ASAP.
You're right. As velocity increases the thrust reduces because Thrust=Mass*(final-velocity - initial-velocity). However, you need thrust to give you velocity in the first place. It's a bit like a ball having potential energy on top of a hill, but having no kinetic energy. As the ball falls off the hill the kinetic energy increases and the potential energy decreases. Similarly, on the runway when the pilot is standing on the brakes and has the throttle fully foward, the propeller is producing a lot of thrust. But when he releases the brakes the aircraft moves (velocity increases) and hence the thrust reduces. However, without that initial thrust the aircraft wouldn't have moved at all. Hope that helps.
I have a question..where can we get the value of cl? Is it take from NACA formulation?
The coefficient of lift can be obtained from NACA Airfoil data. en.wikipedia.org/wiki/NACA_airfoil
Thank you kind sir
Part 1 and part 2 ; excellent !
part 3 : not very clear.
Thank you for your videos.
0:30 you mention a forward velocity, but don't do much to explain it. This breaks the early immersion :)
Vr0 can never be Vr*cos theta, because it should be larger than Vr
cool