Item 0864
OTHER:
Miscellaneous - Thoughtless Idea - StarFire5-blade tip jet rotor with no coning angle, near ideal taper and twist.
Drawing:
Notes:
General note:
The tip jet configuration eliminates the need for an anti-torque device, such as tail rotor.
5-blade configuration with near ideal taper plus twist:
The rotor is comprised of five blades. This, combined with the taper and twist brings the center of lift on the blades closer to the blade roots. This results in a shorter moment arm of lift and gives a more even lift distribution. It also provides a larger blade cross section inboard for greater strength with minimal increase in weight.
Hub:
The hub has large diameter slewing ring bearings, which are mounted on a rigid mast.
No conning angle or rigid coning angle:
The large inboard section combined with five blades and shorter moment arms of lift reduces significantly the vertical bending moment on the arms and therefore allows for the elimination or the rigidity of the conning angle.
Burp Tip:
The burp tip allows allow for a larger radius for the flow of hot gases. The gases make a smoother transition from flowing out the blade to straight back. The trailing edge of the burp tip is cut off and this slot is the exhaust port for the gasses.
Pitch change:
The inboard portion of the blade and the root of the blades have independant pitch control. The tip pitch change is similar to the Kaman helicopters except that an internal torque tube is used instead of the external tabs.
Blade construction:
The spar consists of unidirectional carbon fiber. The outer portion of the shin consists of flexible cross-ply glass cloth. This allows for the tip of the blade to rotate about the feathering axis while maintaining total rigidity about the flapping and drag axes.
Pitch spar & Exhaust gas tube:
In the location of a conventional spar is located a large diameter tube. The tube is constructed of braided carbon composite. At the root this spar is attached to the pitch linkage and is attached to the blade at the tip only. The inside of this tube is lined with a ceramic composite cloth, so that the hot gasses can be transmitted to the tip.
Autorotation:
During autorotation, the tips of the blades have a slightly negative pitch. As opposed to the conventional rotor, in this rotor the outer portion of the rotor disk drives the inner portion.
Tip Jets:
The fact that there is five tip jets should/may provide enough rotational force.
Dissymitry of lift:
Cyclic is used to overcome dissymitry of lift in stead of flapping. A device must be included that reads the forward velocity and applies the appropriate amount of cyclic.
Yaw:
Yaw control during hover could be achieved by directing some of the air volume to the far end of the boom and vectoring it. During forward flight, a rudder could control yaw and all air flow would go the rotor.
Possible Problems:
Noise.
The tip end of the exhaust gas tubes, that are located in the blades, may not be large enough.
Possible Solution:
Notes re Fast Forward Flight:
General:
Consider locating the pitch change at the root end only (variable twist) and providing a means of horizontal thrust. The root end of the blades would be given negative pitch when the blade is on the retreating side. This will provide additional lift. The amount of the span in negative pitch will vary with the μ [mu] of the rotor. For additional information on this see OTHER: Aerodynamics - Rotor L/D - Negative Pitch
Noise:
The thrust from the tip jets will be considerably reduced in forward flight. Their thrust is only needed to provide some lift and minimal rotor rotation. It should be noted that the reverse airflow over the retreating blade will have high profile drag and this will assist with rotor rotation.
Propulsion:
Early train were powered by coal fired steam engines. Behind the engine was a coal-car that carried the fuel and the water. How about applying the same idea to a tip jet helicopter?
A high-tech boiler in the fuselage is interrelated to a combustion engine. It brings the water up to a temperature just below boiling. This water passes up to the rotor hub and down the blade to the tip.
The combustion engine drives an electrical generator. The electrical power passes up to the rotor hub and down the blade to the tip. At the tips, the hot water is converted to steam and the steam provides relatively silent rotation.
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Last Revised: October 9, 2004