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(Please, scroll down for free eBook with description of both concept and mathematical support.)
Teflon (TM) & Kevlar (TM) & Carbon fiber
Emerging new materials in subsonic aviation offer great new challenge.
Replacing old and inefficient blade pitch control with advanced blade twist control of rotors and propellers has never been more technically feasible.
Benefits and Beneficiaries are the following.
Environment:
• Fuel efficiency UP
• Noise DOWN
•
Passengers:
• Noise DOWN >> Comfort UP
• Flight Cost / Km DOWN
•
Companies:
• New long-term business UP
•
Pilots:
• Aircraft flight envelope UP
• Top cruising speed UP
• Low speed / hover stability UP
• Thrust controllability UP
(E.g. immediate effect on thrust.)
•
Helicopter expert Daniel Newman, Chief Technical Officer of Honeywell’s Advanced Air Mobility Division, on the potential
Blade Twist Control
of the rotors:
… As far as benefit, it could be substantial. As the airfoil sections of rotor blades experience such a wide variety of flow conditions – over a long timescale between flight conditions (e.g., hover vs. cruise), and over a shorter timescale during each rotation in edgewise flight (advancing vs. retreating blades) – they are perhaps the ideal component for geometry variation to maximize performance across all conditions.
Variation (also reconfiguration, morphing and adaptation) by its very nature is the ideal means to improve capability under varying conditions, as it avoids the compromise of balancing the performance between conditions and allows optimizing for each.
The ability to parse requirements in time, and solve them in series as opposed to simultaneously, is an incredibly powerful approach to design…
You write that twist control has immediate effect on thrust, as opposed to the delayed effect of RPM control. This presumes a means of changing twist very rapidly, far more rapidly than proposed approaches such as shape memory alloys and circulation control. This benefit is only available if a means of twist change is proven with a sufficiently high bandwidth (rate). And note that if such a high rate capability were available, it might enable cyclic rotor control as well.
•
•
BLADE TWIST CONTROL OF THE PROPELLERS
All the stiff bladed rotors and propellers of today’s aircraft are held hostage by the phantom of DESIGN SPEED. A single speed value, or – for the variable pitch propellers – a narrow speed range where (and only there!) operation without heavy blade stall is possible.
In reality, when you fly speed must change. That is why most rotors and propellers work with significant blade stall, and turn much of the precious engine power into losses.
For most people aviation is a synonym of loud and costly business, where you must pay dearly for the privilege of flying.
A new technology may change all this by eliminating much of the blade stall, and promising some great improvements in rotor/propeller efficiency.
Maybe it is just
TIME TO FLY STALLFREE !!
Even the finest variable pitch propellers tend to become noisy at low speed, and lose thrust at high speed.
Watch the GIF to see why and how this happens :
… or download better quality:
https://onedrive.live.com/?cid=C06DC4A61754F5C0&id=C06DC4A61754F5C0%219926&parId=root&o=OneUp
Scanning the axial speed range of a traditional propeller – download GIF scenario here:
https://stallfreepropellers.com/wp-content/uploads/2021/08/GIF-Scenario__FN_Flight_XXXIV__-1.docx
Conclusion:
In order to keep full alignment between the resulting wind and blade sections along the whole propeller radius, for all (!) values of the cruising speed, blade surface must twist (not rotate), geometrically following the same function that the vector field follows.
Such twisting means a controlled deformation that widespread blades are not capable of.
Only special morphing blades are suitable.
Those manufactured using the Stallfree Technology.
New Propeller Concept Can Yield Also High Profits. Prototyping Needed.
Here is a new concept for prototyping :
— unmatched efficiency, speed-range & silent operation are part of the promise ;
— simple math of blade motion & geometry both reduces risk of failure and strengthens chances of success.
Documentation is available for download below.
Get the eBook here :
For high quality graphics there are two more options to download the eBook in PPT format. Choose the one more suitable for your computer (The end result in both cases is the same zipped bundle.) :
Standard ZIP file
https://1drv.ms/u/s!AsD1VBemxG3AzTc_E9kRmYLl2vRj?e=9MN8fV
Self-extacting ZIP file
https://1drv.ms/u/s!AsD1VBemxG3AzThCI4S5rO8MwNpW
There are 21 PowerPoint files packed in the bundle. Unzip them into the same library. To start the eBook you shall pick and open the file named “StallFreeProp_Front Page.pptx”. It has an active Contents list consisting of the links pointing to the respective chapters. Use this list to go through the eBook.
(Please contact if any problems occur during download. There should not any.)
. . .
Variable blade twist of rotors and propellers – implementation of an old wish for propulsion in subsonic aviation.
Download better quality:
https://1drv.ms/i/s!AsD1VBemxG3AziogijkzyUx98oqO?e=kg7dKb
HOW EXACTLY THE BLADES OF A PROPELLER SHALL TWIST?
THEORETICALLY. TO ACHIEVE BEST (*) THRUST AT ANY SPEED.
Imagine a working propeller. Observation point is rotating in synchronism with the blades.
One blade is selected. Theoretical blade surface is represented by a set of red bars, all of which are hinged at the axis of rotation of the propeller. This particular arrangement allows all the necessary deformations the blade surface has to be subjected to in order the sections remain aligned with the direction of the resulting wind, while the axial speed keeps changing vigorously. Maintaining this alignment will provide the best (*) thrust at any axial speed.
To avoid clutter AoA is not shown in the chart. (Optimal AoA is a relatively small value (= (4° ±Δ) ), therefore it is possible to graphically neglect it without losing basic correctness of the chart.)
(*) “Best thrust” means the greatest possible thrust with the lowest drag. Blade sections must work at their maximum Lift to Drag Ratio point. Thus, the propeller itself will work at its maximum efficiency level.
Application text available here:
https://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/20220402594
Variable Blade Twist is Next Level Sophistication in Propeller Technology!
Variable Twist is a Morphing Blade Propeller Technology. It helps to
(1.) increase top speed of the aircraft;
(2.) maintain improved propeller efficiency both at low and at high speed;
(3.) expand range of electric aircraft;
(4.) make operation less noisy.
Domestic patent secured…
USPTO application published
https://patentcenter.uspto.gov/applications/17771825
Subsonic Aviation Industry Can’t Afford Not Having Variable Twist Propellers
See a new FB post here:
https://www.facebook.com/Stallfree-Propellers-100452335016157
Morphing Blade Propeller Concept
Technology to Improve Efficiency of Aviation Rotors / Fans / Propellers
Works by Reducing Turbulence Caused by the Propeller In the Airflow (Slipstream)
Morphing Blade Propellers
Stage 1. design
Compatible (can be integrated in present day constant-speed units)
Concept ready for prototyping (Description exists, complete with drawings and mathematical support)
Public (presented at the www.stallfreepropellers.com website; commercial use tied to license)
Stage 2. design
Further increases flight efficiency (fuel economy & silent operation)
RPM reduction even more significant
Thrust vectoring support improved / enhanced
Electric drive preferred
Requires modification of the airframe
Not compatible (cannot be integrated in present day constant-speed units)
Concept unfinished (main features are identified, mathematical support and machine design incomplete)
Not public
A Game-Changer
. . .
FB https://www.facebook.com/Stallfree-Propellers-100452335016157/
Morphing cycle of the blades :
Proven & Supported Mathematically
Ready for Prototyping / Implementation
Applicable to
– traditional propeller propulsion systems ,
– turboprops ,
– turbofans .
In contrast to the monolithic blades of recent propellers application of TORSIONAL or MORPHING blades is proposed.
Displacements of all parts involved in the blades’ morphing process are performed
a) during the undisturbed rotation of the propeller,
b) in accordance with functional necessity and/or the pilot’s will. (It is understood the actuator mechanism is controlled by the pilot and/or by an optional automated control system.)
The full morphing cycle of the blades, going through all possible phases of the process, is shown in the below GIF:
Blades have a skeleton and a skin. Skeleton is a set of masts – massive cylindrical or tapered rods made of carbon fibre.
https://1drv.ms/b/s!AsD1VBemxG3AzVAR7g1DPMF80nUX?e=4effCk
These propeller/fan blades twist – not just rotate :
End-product is a kind of wide-range variable pitch propeller.
Given the power and strength of the aircraft with Stallfree propulsion
the whole subsonic speed range can be flown
with the same propeller,
having both a good climb rate and top speed of about 0.8 Mach.
All this at a propeller-efficiency close to its maximum value.
Reasons why the Morphing Blade Propeller / Rotor Family is
Optimal for Tiltrotor Application
Stage 1. design
1./ Reduced RPM propeller
Noise and vibration down.
2./ No VRS
No Vortex Ring State happens to morphing blade propellers, as also hover (zero axial speed) is part of the normal speed range of such rotors.
For VRS to form, stall at the base of the blades (in the middle of the rotor disk) is required. These props are free of blade-stall along the whole radius, at any speed below 0,8 Mach.
Stage 2. design
1./ RPM reduction even more significant
2./ No VRS
(Same as at Stage 1. design.)
3./ No Retreating Blade Stall
Stage 2. design of the morphing blade propeller, physically eliminates the option to form Retreating Blade Stall.
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Stallfree Technology – Definition Stallfree Technology Definition – stallfreepropellers.com
Turbo-Fans & Props TURBO-FANS & -PROPS – stallfreepropellers.com
VTOL & eVTOL Issues Alleviated VTOL – eVTOL Issues Alleviated – stallfreepropellers.com
Superior Flight Envelope Superior flight envelope – stallfreepropellers.com
Sophistication Level of Propellers Improved Make traditional propeller propulsion “smart” – stallfreepropellers.com