GScholz more ont turbo props:

[rshubert]

Originally posted by Tilt
Turbo fan or piston engine there is somewhere a spinning shaft that is geared up/down to a rotor.................

Given the same rotor and the same footlbs at its tip then the opposing force applied to the mounting system is the same.

ahh, but remember, it depends on WHICH rotating member is actually imparting the torque to the mount.  The prime mover does it, not the output device.  An important point, but one that is getting lost in the discussions of propellor torque.  Drop the concept that it is the prop that transfers the torque, and you, too will see the light.

[hitech]

rshubert:

In your prat & witney example, the torque you calculated would be between the crank shaft and the gear box housing. There would be aprox.  a 2 - 1 reduction in prop speed. Hence to the motor mount and air frame, it would be (3889 * 2) ft/lbs.

Except for the stator vane example: I havn't seen enyone describe how a hi bypass engine transmits torque to the mounts.


The problem I trying to solve in my head, and it is a close example to a turbo fan, is a very simple pinwheel childs toy.

Hold said pinwheel and blow on it. Asumption no torque is transmited to the handle (excpet for minor friction)

My assumption the air down wind of the pin wheel will be rotating in 2 directions.

They way I see what is happening to balance things out is that the slip stream behind the pin wheel would be rotating the oposit
the direction of the pin wheel. (air stricking angled blade goes one way pin wheel other) Once the pin wheel has reached a steady Vel the blades are also pushing air out do to drag rotating in the oposit direction of the slip stream.

Hence no torque on handle but we we have 2 masses of air rotation different directions.

HiTech

[GScholz]

Originally posted by Holden McGroin
How does it work w/o connection? same way a cylinder head pushes a piston down with force but with no mechanical connection. Expanding gasses shove against a static cylinder head, and a moving piston.

Nonsense. In a piston engine the pistons operate 90 degrees on the shaft and are literarily cranking the shaft. That's a rather substantial mechanical connection between shaft and engine frame. In a turbine engine the only mechanical connection would be in the bearings (with the noted exception of reduction gearing being used).

 

Originally posted by Holden McGroin
The airfoils which are the stators in the turbine have a fluid dynamic differential pressure associated with the hot gas flowing past them.

One side it high pressure due to Newtonian ram effect, the other side is low pressure due to Bernolli's equation.

This differential pressure on the stator ring is connected to the turbine casing. The casing then has a force (torque) that needs to be countered in the aircraft structure.

This torque would then be produced by all jet engines of similar construction, and as such has nothing to do with torque specific of turboprops. If all jet engines produce torque then naturally all machinery powered by a jet engine will also have torque (unless otherwise countered).

Originally posted by Holden McGroin
In your water turbine, you will put into the engine a certian amount of thrust, associated with the impulse of the tap water nozzle against the turbine.  You will get the same amount of thrust minus the mechanical inefficiency of the prop, turbine, and bearings.  You still need to absorb the impulse of the water jet in the structure of the boat, so your action has a reaction.  

If the turbine you use is a pelton wheel which would be appropriate, the nozzles would be pushing 90 degrees to the shaft at the pelton wheels radius, and the force of the water impulse at a radius is torque.

No, the water nozzles are (just like in a turboprop) vectored aft and literally blowing on a windmilling fan. This fan is directly connected to a prop via a shaft that runs parallel to the direction of water thrust.

The source of power is the water hose. The nozzles themselves create linear forward force by ejecting water aft. The water hits the fan and creates two new forces. 1: an aft linear force, which counteracts some of the force created by the nozzles, and 2: a rotational force on the fan. The fan turns the propeller via a direct mechanical connection.



Voilà! Propeller driven propulsion without applied torque on me! (not going to go very fast though )

[Tails]

With the exception of torque forces created by friction losses in the bearings, and a -rearward- force on the whole thing from those nifty water jets. Now, add a gear-box with changes in direction of rotation or ratio, and you get torque on that thing.

And if that example of yours had stator vanes attached, those would cause torque forces too.

(And lucky for you guys, I go back to work in a half hour, so I wont be able to argue again until I get back )

[Casca]

This is an interesting discussion.  While reading it I'm starting to feel like Brian Fellows on SNL.

Of course a propeller powered by a turbine produces a torque.  The source of power does not matter, it can be reciprocating, turbine, rubber band, or sitting in the wing in a rubber space suit shooting a pelton wheel with a firehose.  The propeller and whatever its source of motive power is affixed to the airframe.

I stated above and I will restate here that torque is one of the primary power indicating instruments on smaller PT-6 engines (the other being ITT).  It senses the actual torque that is being imparted to the airframe by the prop.  

To run the rough numbers:

Torque =  hp * 5252 / rpm

For a -27 flat rated to 680 shp that would be:

Torque = 680 * 5252 / 33,000 = 108.2 pounds feet.

The prop spins at 2200 rpm at takeoff so assuming a 10% loss though the gearbox (just a guess) the prop produces:

Torque = 612 * 5252 / 2200 = 1451 pounds feet of torque.

The gauge that I'm looking at redlines at 1500 pounds feet so we know we're in the ballpark.  

If you use a propeller to power an airplane it will produce a torque on the airframe.  The exception: contra rotating props, like the Tupolev T-95 Bear Bomber.

[Straiga]

Nonsense. In a piston engine the pistons operate 90 degrees on the shaft and are literarily cranking the shaft. That's a rather substantial mechanical connection between shaft and engine frame. In a turbine engine the only mechanical connection would be in the bearings (with the noted exception of reduction gearing being used).

The same goes for the turbine and stator blades they are also 90 degrees and connected to the turbine shaft. So whats the difference. The mechanical connection in a piston engine is the same as a turbine they both have bearings.

Tails, Rshubert, Milo Morai and Holden Mcgroin have it correct.

In a helicopter you have a turbine engine turning a hydralic pump to a transmission then to the rotors. The only mechanical connection in this instance is the hydralic fluid in the pump. So why do you still need a tail rotor on a helicopter. It the same as a turbo prop. Blade drag torque.

High bypass fan jet have a rotational airflow from the bypass section and this rotational airflow creates a rotational torque.

A high bypass stage fan is a hughe 70 blade ducted propeller turning at a great RPM and produces about 70 percent of the total thrust of the engine. As this fan turns and blows air around the turbine case the air flow rotates as its exited the nacell. This creates a torque from the airflow.

When you power up an electric drill the torque is felt from the increase in rotation. The only mechanical connection is the motor with magnets around it but it still porduces a torque. The drill case that holds all the motor and magnets and drill shaft and while being held in your hand, can be the same as the engine case connected to the motor mount. This is the same a turbine as its increasing its rotation and torquing on an airframe.

A prop moves a large mass of air and accelerates it in a small amount, a jet engines moves a relative small mass or air and accelerates it in a large amount, a high bypass turbine moves a large mass of air and accelerates it in a large amount.

Straiga

[minus]

wel cant resist ,  remember time HT send me to hel cose i told there is no torque , btw abotu discusion , some 1 in RL  teling me  until u not get ride  of all transmision element , example even  liqid or air viscosity  or even in vacum   there is a theoretical  distance barier where even a  2 mases close to each other can be create or react on action reaction ,   and stop whinign about my  typing   HT do not type beter like me  ( who care abotu spel check ? )

[GScholz]

Originally posted by Casca
Of course a propeller powered by a turbine produces a torque.  The source of power does not matter, it can be reciprocating, turbine, rubber band, or sitting in the wing in a rubber space suit shooting a pelton wheel with a firehose.  The propeller and whatever its source of motive power is affixed to the airframe.

...

 If you use a propeller to power an airplane it will produce a torque on the airframe.

This is a fallacy. The propeller never create or impart torque to the airframe. Whether or not torque is applied ALWAYS depend on where the power is created and where and how the forces are directed. If you mechanically separate the power source and the airframe no torque is transferred.



This helicopter's rotor does not transfer any torque to the airframe, because its power source (rotor-tip jets) is not mechanically connected to the airframe. You will however notice that the rotor is in fact still connected to the airframe.

Originally posted by Straiga
The same goes for the turbine and stator blades they are also 90 degrees and connected to the turbine shaft. So whats the difference. The mechanical connection in a piston engine is the same as a turbine they both have bearings.

I'm sorry, this is completely false. If you can't see the difference between ...

... this ...




... and this ...




... then I don't think you will ever understand.

Originally posted by Straiga
When you power up an electric drill the torque is felt from the increase in rotation. The only mechanical connection is the motor with magnets around it but it still porduces a torque. The drill case that holds all the motor and magnets and drill shaft and while being held in your hand, can be the same as the engine case connected to the motor mount. This is the same a turbine as its increasing its rotation and torquing on an airframe.

A jet-turbine is nothing like an electrical motor. Do you have any idea of what you are talking about? I don't think so.

[Straiga]

then I don't think you will ever understand.

I understand so much that I actually fly jets, turbo props, and helicopters. Also I instruct people how to fly them too.

Keep reading from people who know, like jet engine mechanics, pilots. I think you will understand eventually.

What you have to look at is that there is a power source turning a prop in one way and a force acting in another. Meaning that if you had an any engine (recip, turbine, electric) in the airframe turning a rotor, the oposite reation would be the airframe turning oposite the rotor.
This is just like your wrench, its is a torque leverage. The pin wheel on the other hand has no torque leverage associated with it at all like your little jet tip rotor.

Your little jet tip rotor is not the same princyple except for the jets tips, for every action there is an oposite and equal reaction, because of jet thrust.

This helicopter's rotor does not transfer any torque to the airframe, because its power source (rotor-tip jets) is not mechanically connected to the airframe. You will however notice that the rotor is in fact still connected to the airframe.

How can a rotor that rotates and that is attached to the helicopter, not be mechanicaly connected to the airframe. UUHHHH!

Straiga

[Golfer]

I'm dumbfounded.  I post in another thread about moving engines off-axis of the CG and talk about how the left turning tendency of torque is reduced.  I thought I made a good point saying I never touch the rudder trim once the ball is centered up no matter what phase of flight or power setting.  That degenerated into talk about Vmc which has nothing to do with anything when you've got 2 working engines.






THERE IS TORQUE its effect on a multi engine airplane is just not seen significantly during flight.

Ok, now that that is out of the way.


There is torque because you've got something spinning.  Whatever force is causing that to spin, there must be something reacting against it and that causes an opposite direction spinning motion.  

In a helicopter (Please correct me if I am wrong Straiga, using a Bell 206 Jetranger as an example)

The blades rotate clockwise when looking DOWN from above at the helicopter.  Because of this, there is a significant torque effect causing the helicopter want to torque to the right.

The tail rotor is mounted on the left side of the tail boom, producing left yaw movement to counter the right yaw movement created by the torque of the main rotor blades.

If there were no torque, no need for a tail rotor.  (Or the notar system, which simply blows air to the left, still producing a left yaw movement when viewed from the cockpit)

[Straiga]

If your looking down its counter clockwise or from the right side pilots seat the rotation is from right to left. With left anti-torque pedal. Your close! LOL

Straiga

[Holden McGroin]

Originally posted by GScholz
Nonsense. In a piston engine the pistons operate 90 degrees on the shaft and are literarily cranking the shaft. That's a rather substantial mechanical connection between shaft and engine frame. In a turbine engine the only mechanical connection would be in the bearings (with the noted exception of reduction gearing being used).

I am referring to the cylinder head and the top of the piston.  What shoves a piston down is expanding gas.  What shoves the turbine rotor around is expanding gas.  Same principal... expanding hot gas is indeed a mechanical connection.

This torque would then be produced by all jet engines of similar construction, and as such has nothing to do with torque specific of turboprops. If all jet engines produce torque then naturally all machinery powered by a jet engine will also have torque (unless otherwise countered).

Correct to a point. A turbojet puts its main force to the atmosphere by the expansion of hot exhaust gas.  The compressor and turbine are there just to support combustion.  Torques are present on the rotor shaft and the casing, but turbine and compressor torques wrap aroung the engine in opposite directions, cancelling each other within the engine system.

No, the water nozzles are (just like in a turboprop) vectored aft and literally blowing on a windmilling fan. This fan is directly connected to a prop via a shaft that runs parallel to the direction of water thrust.

The source of power is the water hose. The nozzles themselves create linear forward force by ejecting water aft. The water hits the fan and creates two new forces. 1: an aft linear force, which counteracts some of the force created by the nozzles, and 2: a rotational force on the fan. The fan turns the propeller via a direct mechanical connection.

(Image removed from quote.)

Voilà! Propeller driven propulsion without applied torque on me! (not going to go very fast though ) [/B]

But you will have less thrust than if you just squirted the water nozzle out the back in the first place.  Your turbine is just mechanical loss and wasted money, and can do no work.  

The fact that horsepower is being put to the atmosphere through a rotating fan or prop necessarily requires that rpm and torque exist.  The torque is absorbed by the engine mounting though fluid dynamic related differential pressures in the turbine section, which is a mechanical system, just like pneumatics and hydraulics.   Newton's equal and opposite law applies to rotational motion.

[Tails]

Originally posted by Holden McGroin
Correct to a point. A turbojet puts its main force to the atmosphere by the expansion of hot exhaust gas.  The compressor and turbine are there just to support combustion.  Torques are present on the rotor shaft and the casing, but turbine and compressor torques wrap aroung the engine in opposite directions, cancelling each other within the engine system..

False statement on torque. Yes, while the torques created in the compressor and turbine sections of a jet engine are opposed, the turbine section creates a considerable ammount more torque in comparison to what the compressor creates. The same holds true for turbines with seperate high and low pressure compressor setups that rotate complementory.

A turbojet or bypassing fan engine with N1 and N2 spinning the same way will make torque, and most of it originates from the hot section.

EDIT: And after thinking a couple minutes, you proved yourself wrong. A turbojet does work on priciple of compressed hot air expanding in the comparitivly cooler ambient air. HOWEVER, if all the energy produced by the combustion section was absorbed by the turbine section (in the form of torque imparted on the compressor/turbine shaft from the turbine wheels) to offset the power loss (torque loading, opposed to torque created by power source) from driving the compressor, you would have hot, but uncompressed, air squirting out the back of your turbojet, with little available thrust due to all the energy losses internally.

End result: A really expensive hair dryer

[Golfer]

End result: A really expensive hair dryer

More like a Toaster.

Or one of those boot dryers I use, Same thing as a toaster but you put your boots on them and they come out nice, dry and toasty the next morning.

[Tails]

Open-air convection oven, maybe?

Now that I think about it, there is one example of a turbine engine that DOES use all its energy driving the turbines, with little if any jet thrust...

Turboshafts, turboprops, they use all that energy driving the power turbine (or the main turbine section, in the case of direct drive turboshaft, as opposed to free-turbine), that the poundage of leftover jet thrust is in the double digits.