AERODYNAMIC REGULATION OF AIRSCREW, FAN AND WIND TURBINE BLADES WITH BORES AND/OR CUTTING AND/OR NOTCHING

REGULATION AERODYNAMIQUE DE PALES D'HELICE, DE SOUFFLANTE ET D'EOLIENNE AVEC DES ALESAGES ET/OU UNE COUPE ET/OU UN CRANTAGE

English Abstract

Axial airplane airscrew, fan, and wind turbine blade of low loading characterised by the aspect ratio of the blades is low; near to the wide blade ends, but in an appropriate distance a notch is formed in the tip of each blade, which extends between a pressure side and a suction side, and a channel leading to the notch formed through the body of the blade between said sides. The distance between the notch and the tip of the blade changes in the diameter of the blades from 1.2 % to 1.67 % along the length of the notch. When being operated, the air flowing through this aperture eliminates the turbulence formed at the end of the blades. Resonant vibrations occurring on the blades and the turbines are also reduced, which extends the lifetime of the blades.

French Abstract

Une pale dhélice, une soufflante et une éolienne davion axial de faible charge caractérisées par le rapport daspect des pales faible; à proximité de lensemble des extrémités de pale, mais dans une distance appropriée, sont formées dans la pointe de chaque pale, qui sétend entre un côté pression et un côté aspiration, et un canal menant à lencoche formée à travers le corps de la pale entre les côtés. La distance entre lencoche et la pointe de la pale modifie le diamètre des pales de 1,2 % à 1,67 %, le long de la longueur de lencoche. Pendant lexploitation, lair sécoulant à travers cette ouverture élimine la turbulence formée à lextrémité des pales. Les vibrations en résonance survenant sur les pales et les éoliennes sont également réduites, ce qui étend la durée de vie des pales.

Claims

Patent claims:
1. Blades for an airscrew, fan, or wind turbine having wide blade tips for
use in an axial
flow rotor stage, having a body with pressure and suction surfaces on opposite
sides of each
blade, a span extending between a root and a tip and a chord extending between
a leading edge
and a trailing edge, wherein there is a notch formed in the tip of each blade,
which extends
between the pressure and suction side, and a channel leading to the notch, on
the pressure side,
formed through the body of the blade between said pressure and suction
surfaces, and wherein
the distance between the notch and the tip of the blade changes from 1.2 % to
1.67 % of the
blade's diameter along the length of the notch.
2. Blades as claimed in claim 1 wherein the notch, for ensuring strength,
is divided into
sections with small interruptions.
3. Blades as claimed in claim 1 or 2 wherein the length of the notch is
approximately 60% of
the length of the tip of the blade.
4. Blades as claimed in any one of claims 1 to 3 wherein the width of the
notch is 3.53 % of
the length of the notch.
5. Blades as claimed in any one of claims 1 to 4 wherein a root of the
notch is formed near the
trailing edge.
4
Date Reçue/Received Date 2020-07-14

Description

Title:
Aerodynamic Regulation of Airscrew, Fan and Wind Turbine Blades with Bores
and/or Cutting and/or Notching
The subject of the invention
The pressure distribution of airscrew, fan, and wind turbine blades, and by
this the
determination of flow characteristics are solved by means of linking the areas
of different
pressure (low and high) on the blades with bores and/or cutting and/or
notching.
The original pressure characteristics are changed due to the flow resulting
from the pressure
difference in the bores, cuts or notches. These changes are of such nature
that on the blades (from
a physical and technical point of view) the emergence of unfavourable
turbulences is reduced or
eliminated. The solution can be used on tools of any desired size.
One way for realisation is when close to the end of the blade, but on a point
which is in an
appropriate distance from it, a cut of appropriate width and almost parallel
to the end of the blade
can be shaped. The air flowing through this aperture eliminates the air
turbulence otherwise
occurring on the end of the blades.
Summary of the invention
Axial airplane airscrew, fan, and wind turbine blade of low loading
characterised by the
fact that the aspect ratio of the airscrew, fan and wind turbine blades is
low; near to the
wide blade ends, but in an appropriate distance an aperture of appropriate
length and width
almost parallel to the side of the blade end is formed, which connects the
surfaces of lower
and higher pressure. When being operated, the air flowing through this
aperture eliminates
the turbulence formed at the end of the blades.
With regards to diameter, the choice of the distribution of strings on the
airscrew blade (its blade
width) caused problems in case of adapting a huge performance, as well as
there was a need to
form wide blade ends. The losses resulting from the circular flow of the blade
ends were,
however, increased dramatically.
In case of adapting wide blade ends, the invention uses the phenomenon known
from
physics as interference, more precisely whirl interference to reduce or
eliminate the loss
of potential resulting from the circular flow of the blade ends tips on the
airscrew.
A whirl of contrary direction and of equal angular momentum (or impulse
momentum) is induced
at the ends of the airscrew blades, which by this eliminates or significantly
reduces the whirls
appearing at the end of wide blades and causing losses.
As a result of this, a tractive force evolves on the airscrews and the range
of action of the aircraft
as well as the time spent on flying can be increased.
1
Date Recue/Date Received 2020-06-19

Its application is also recommended on wind turbine rotor blades.
If applied, it reduces the resonant vibrations occurring on the blades and the
turbines, and
thus extending their lifetime significantly. Using aerodynamic braking the
forming of the
pivoting tip is more effective and less vibrating. The blade edges are working
as slotted
flaps.
According to an aspect of the invention, there is provided blades for an
airscrew, fan, or wind
turbine having wide blade tips for use in an axial flow rotor stage, having a
body with pressure
and suction surfaces on opposite sides of the blade, a span extending between
a root and a tip
3 and a chord extending between a leading edge 1 and a trailing edge 2,
wherein there is a
notch 4 formed in the tip of the blade, which extends between the pressure and
suction sides,
and a channel leading to the notch on the pressure side formed through the
body of the blade
between said pressure and suction surfaces, and wherein the distance between
the notch and
the tip of the blade changes from 1.2 % to 1.67 % of the blade's diameter
along the length of
the notch.
In one embodiment, the notch for ensuring strength is divided into sections
with small
interruptions.
In another embodiment, the notch 4 is approximately 60% of the length of the
tip of the blade.
In yet another embodiment, the width of the notch is 3.53 % of the length of
the notch.
In a further embodiment, the root of the notch is formed near the trailing
edge.
Brief Description of the Drawings
The embodiments of the invention are described having regard to the drawings
in which:
Figure 1 is a top perspective view of blades according to one embodiment, in
which feature A is
shown in an enlarged view;
Figure 2 is a top plan view of the blades of Figure 1, in which features A and
B are shown in
enlarged views;
Figure 3 is a bottom perspective view of the blades of Figure 1, in which
feature A is shown in an
enlarged view; and
Figure 4 is a bottom plan view of the blades of Figure 1, in which a cross-
sectional view taken
along lines A-A is shown.
2
Date Recue/Date Received 2020-06-19

The development state of the technology
The elaborator of the most modern theory on airscrews so far is Sydney
Goldstein, who took into
consideration the circulation on the airscrew blades serving the ascensional
force, as well as by
assuming a constant circulation the effect of whirling strings of spiral shape
leaving the end tips
of the airscrew blades.
[Goldstein, Sydney. (1929). On the Vortex Theory of Screw Propeller.
Proceedings of The Royal
Society A: Mathematical, Physical and Engineering Sciences. 123. 440-465.
10.1098/rspa.1929.0078.11.
Goldstein solved the task of potential theory defining the velocity
distribution by a lightly loaded
airscrew of two, three and four blades.
From a practical point of view, the result of the theory appears in a
corrective factor, which
mainly phrases the loss of potential resulting from the circular flow of the
blade end tips 3 on the
airscrew.
With regards to diameter, the choice of the distribution of strings on the
airscrew blade (its blade
width) caused problems in case of adapting a huge performance, as well as
there was a need to
form wide blade ends. The losses resulting from the circular flow of the blade
ends were,
however, increased dramatically.
In case of adapting wide blade ends, the invention uses the phenomenon known
from physics as
interference, more precisely whirl interference to reduce or eliminate the
loss of potential
resulting from the circular flow of the blade ends tips 3 on the airscrew.
A whirl of contrary direction and of equal angular momentum (or impulse
momentum) is induced
at the ends of the airscrew blades, which by this eliminates or significantly
reduces the whirls
appearing at the end of wide blades and causing losses.
As a result of this, a tractive force evolves on the airscrews and the range
of action of the aircraft
as well as the time spent on flying can be increased.
Its application is also recommended on wind turbine rotor blades.
If applied, it reduces the resonant vibrations occurring on the blades and the
turbines, and thus
extending their lifetime significantly. Using aerodynamic braking the forming
of the pivoting tip
is more effective and less vibrating. The blade edges 1, 2 are working as
slotted flaps.
3
Date Recue/Date Received 2020-06-19

Representative Drawing