As i said: Power = Torque * angular velocity, No torque - no power, so obviously you want torque, you need torque or the plane will not move.
But from an aerodynamic point of view you want to use the engine to accelerate air, and you want to accelerate it straight bakcward. Any other direction, including spinning of that air is lost power (except vectoring thrust where you want to divert the thrust). A turbojet and turbofan does this with exellence, a propeller does not.
Newton said that force equal opposite force, this is the truth, and there really is no way of fooling it (although many have tried
). If you manage to accelerate the air straight back, you will have thrust straight forward. If for some reason you set the air into spin, you will also have an opposing force rotating the plane in opposite direction. What you want is to convert all the torque on the engine shaft into thrust, straight clean thrust with no spin because this will give maximum efficiency, maximum thrust. In a fan or propeller the torque on the shaft is a result of the drag on the blades. The drag on the blades is a direct result of the lift on the blades (thrust) - more thrust = more drag = more torque. The air see this thrust (lift) as linear acceleration straight back while it see the drag as angular acceleration (spinning).
In a fan this spinning is stopped by stationary vanes. The result of this is that the fan sets the air into spin. You need torque to do this from the shaft. The stationary vanes stop the spinning of the air which require an equal amount of torque in the opposite direction. The engine see two torques - one from the shaft and one from the stationary vanes and since they are opposite in direction and roughfly equal in size they cansel each other out. The air comes in straight and linear and leaves straight and linear, thus no net spin is put on the air and therefore no net torque is put on the plane (Newton's law). The torque on the shaft however, is large but so are the torque on the stationary vanes. (The stationary vanes can also be in front of the fan setting the air in spinning motion and any combination, it doesnt matter just as long as the air comes in straight and leaves straight).
On a propeller there really is no way of balancing the torque properly, unless you use contrarotating props which is complicated and expensive, and does not work as good in real life as in theory. On a propeller airplane you therefore allways will have an amount of unbalanced torque that will rotate the plane in roll and create swirling propeller slipstream.
Another general principle is that it is more efficient to accelerate large amounts of air a little than it is to accelerate a small amount of air alot (Thrust = mass of air * acceleration of air). This means that although a propeller is not as efficient in terms of lost torque, it can nevertheless have a better overall efficiency due to the large amount of air that is accelerated just a little.
Gyroscopic forces and other transient forces (slamming the throttle for instance) really has nothing to do with aerodynamics at all. They all produce torque in some way, but not continously. Ever done a lomcevak by the way?
About the vertical stab, just think about it, force = opposite force ALLWAYS. The slipstream hits the vertical fin and creates a force on it - you adjust the rudder to compensate. What you really are doing is to set an effective aoa on the vertical fin so that the rotating slipstream do not create any force either way. The effective aoa on the vertical fin = angle on slipstream. The only way to have the plane not to yaw is to have zero resulting torque about the yaw axis (Newton again) and there is NO other way.
Originally posted by Straiga
Bod,
I total cannot understand what you are talking about. First of all Jet turbines do have torge its measured on takeoff on the N1 and N2 gauges or torge gauge in someplanes or EPR gauge. Increase power on a turbine can torge an airplane. A single Eng Jet figher needs to on takeoff, counter torge and gyro precession.(a Rotating Mass) depending on what type of turbine is in its belly.
The N1 stage off a jet engine has as many as 13 stages of stator vanes, these are for diverting and decreasing pressure of the air before it enters the burner canisters, fuel is introduced into fine mist not touching anypart of the canisters, then the ignitors light the fuel. Then the exploding gas exits onto the N2 stage of the
of the turbine which has a shaft that turns the N1 compressure. this is an axil flow type turbine. Some N1 and N2 sections turn opposite of each other. No torge just gyro precession.
Counter rotating or not you will still have prop slip stream! Thats just the way its is.
About the vertical Stab zeroing out. ???????????????????????????
