Description:FORM 2
THE PATENTS ACT, 1970
[39 of 1970]
&
THE PATENTS RULES, 2003

COMPLETE SPECIFICATION
[See Section 10 and Rule 13]

TITLE: “A ZERO DEFLECTION BLADE ”

Name and Address of the Applicant:
TATA STEEL LIMITED, Jamshedpur, Jharkhand, India 831001.

Nationality: INDIAN

The following specification particularly describes the nature of the invention and the manner in which it is to be performed.
TECHNICAL FIELD

Present disclosure in general relates to a blade connected to a rotor. Particularly, but not exclusively, the present disclosure relates to the blade which undergoes zero deflection during operation.

BACKGROUND OF THE DISCLOSURE

Generally, a number of blades are connected to a rotor depending on requirement. During operation, the blades are subjected to external forces such as gravity due to blade weight, centrifugal force caused due to rotational speed along with mass of the blade, and aerodynamic pressure caused due to rotation of the blade. These external forces act in sequence, where gravity and centrifugal forces deflect the blade in one direction, while the aerodynamic pressure deflects the blade in other direction. Due to difference in magnitude of the forces acting on the blade in opposite directions, the external forces remain unbalanced, thereby developing a resultant force causing the blade to deflect from its desired position. Such deviation of the blade affects the performance and causes damage to the blades, which is undesired.

Considering the above, several techniques have been evolved to reduce deflection of the blade during its operation. One such technique includes incorporation of additional stiffening mechanisms and weights on to the blade in order to balance the external forces and reduce deflection of the blade. However, adding additional stiffening mechanisms and weight onto the blade increases weight of the blade. Increasing weight of the blade results in increased power consumption and also reduces life of the blade, which is again undesired.

The present disclosure is directed to overcome one or more limitations stated above or any other limitation associated with the prior arts.

SUMMARY OF THE DISCLOSURE

One or more shortcomings of the prior art are overcome by configuration of a blade as disclosed and additional advantages are provided through the blade as described in the present disclosure.

Additional features and advantages are realized through the technique of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed disclosure.

In one non-limiting embodiment, there is provided a zero deflection blade. The blade includes a body. The body is defined with a leading edge and a trailing edge, a first surface extending between the leading edge and the trailing edge. Further, the body is defined with a second surface extending between the leading edge and the trailing edge, on an opposite side of the body relative to the first surface. Furthermore, the body is defined with a tip end and a tail end. The tip end of at least one of the first surface and the second surface is defined with a thickness t_1 and the tail end of at least one of the first surface and the second surface is defined with a thickness t_2, where the thickness t_1 is variable to the thickness t_2 along a length L_1 between the tip end and the tail end. The configuration of the blade aids in reducing weight of the blade and aids in shifting centre of gravity of the blade towards a hub of a rotor. This aids in lowering the bending forces generated by gravity and centrifugal forces, thereby minimizing or achieving zero deflection of the blade, during operation of the blade.
In an embodiment, the thickness along the length L1 varies continuously from the thickness t_1 to the thickness t_2.
In an embodiment, the thickness t_2 is greater than the thickness? t?_1.
In an embodiment, ratio of the thickness t_2 and the thickness t_1 ranges between 1:2 for metallic materials. The metallic materials are aluminium, steel.
In an embodiment, ratio of the thickness t_2 and the thickness t_1 ranges between 1:3 for thermoplastic materials. The thermoplastic materials are Acrylonitrile butadiene styrene (ABS) and polypropylene.
In an embodiment, L1 ranges between 400 mm to 500 mm.
In an embodiment, the tail end comprises a mounting stub. The mounting stub is configured to couple the blade with a hub of a rotor.
It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined together to form a further embodiment of the disclosure.
The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES

The novel features and characteristics of the disclosure are set forth in the appended description. The disclosure itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying figures. One or more embodiments are now described, by way of example only, with reference to the accompanying figures wherein like reference numerals represent like elements and in which:

Figure. 1 illustrates a bottom view of a blade, in accordance with an embodiment of the present disclosure.

Figures. 2a and 2b illustrates perspective views of a portion of the blade, in accordance with an embodiment of the present disclosure.

Figure. 3 illustrates a schematic view of forces acting on a conventional blade during its operation, in accordance with an embodiment of the present disclosure.

Figure. 4 illustrates a schematic view of variation of moments acting on a conventional blade and resultant moment, in accordance with an embodiment of the present disclosure.
Figures. 5a and 5b are graphical representations of variation of function F(r)·A(r) along radial distance from axis of rotation (r/L) and variation of the cross-sectional area (A(r)/A_0 ) along radial distance from axis of rotation (r/L) of the blade of present disclosure, respectively in accordance with an embodiment of the present disclosure.
Figure. 6 illustrates a schematic view of variation of moments acting on the blade of the present disclosure and resultant moment, in accordance with an embodiment of the present disclosure.
The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAILED DESCRIPTION

The foregoing has broadly outlined the features and technical advantages of the present disclosure in order that the detailed description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter which form the subject of the description of the disclosure. It should also be realized by those skilled in the art that such equivalent configuration of the blade do not depart from the scope of the disclosure. The novel features which are believed to be characteristic of the disclosure, as to a zero deflection blade, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure.

In the present document, the word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or implementation of the present subject matter described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

While the disclosure is susceptible to various modifications and alternative forms, specific embodiment thereof has been shown by way of example in the drawings and will be described in detail below. It should be understood, however that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the spirit and the scope of the disclosure.

The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a method that comprises a list of acts does not include only those acts but may include other acts not expressly listed or inherent to such method. In other words, one or more acts in a method proceeded by “comprises… a” does not, without more constraints, preclude the existence of other acts or additional acts in the method.
In order to overcome the limitations stated in the background, the present disclosure provides the following paragraphs which describe the present disclosure with reference to Figures. 1 to 6. In the figures, the same element or elements which have same functions are indicated by the same reference signs. One skilled in the art would appreciate that the blade as disclosed in the present disclosure can be connected to a rotor of such as but not limiting to a fan, a turbine and the like.

In the following detailed description, embodiments of the disclosure are explained with reference of accompanying figures that form a part hereof, and in which are shown by way of illustration specific embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present disclosure. The following description is, therefore, not to be taken in a limiting sense.
Figures. 1, 2a-2b are exemplary embodiments of the present disclosure, illustrating a bottom view and perspective views of a zero deflection blade (100) [hereinafter referred as blade (100)], respectively. As an example, the blade (100) may be adapted to be coupled with a rotor (not shown in Figures) which may be a part of but not limiting to a fan, a turbine and the like. The blade (100) may be configured to rotate along with rotation of the rotor. As apparent from Figures. 1, 2a-2b, the blade (100) may broadly include a body (101) and a mounting stub (107) extending from one end of the body (101). In an embodiment, the mounting stub (107) may be structured to couple with the rotor through a mechanical joining such as but not limiting to fasteners, for coupling the blade (100) with the rotor.
Further, referring to Figures. 2a-2b, the body (101) may be defined with a leading edge (102) and a trailing edge (103), where the trailing edge (103) is opposite to the leading edge (102). Further, the body (101) may be defined with a first surface (104) which may extend between the leading edge (102) and the trailing edge (103). Furthermore, the body (101) may be defined with a second surface, which may extend between the leading edge (102) and the trailing edge (103). The second surface may extend on an opposite side of the body (101) relative to the first surface (104). Additionally, the body (101) may be defined with a tip end (105) and a tail end (106). The tip end (105) of at least one of the first surface (104) and the second surface is defined with a thickness t_1 and the tail end (106) of at least one of the first surface (104) and the second surface is defined with a thickness t_2. The thickness t_1 at the tip end (105) is variable to the thickness t_2 along a length L_1, between the tip end (105) and the tail end (106). In an embodiment, length L_1 may range from 400 mm to 500 mm. In another embodiment, thickness along the length L_1 may vary continuously from the thickness t_1 to the thickness t_2. Further, the thickness t_2 may be greater than the thickness t_1. The configuration of the blade (100) aids in shifting centre of gravity of the blade (100) towards the hub of the rotor and also reduces mass of the blade (100). This aids in lowering the bending forces generated by gravity and centrifugal forces, thereby reducing deflection of the blade (100), during operation of the blade (100).
In an embodiment, the blade (100) may be made of metallic materials. As an example, the metallic materials may be but not limiting to aluminium. Ratio of the thickness t_2 and the thickness t_1 is 1: 2 for the blade (100) made of metallic materials. Further, the blade (100) may also be made of thermoplastic materials. As an example, thermoplastic materials may be but not limiting to Acrylonitrile butadiene styrene (ABS), polypropylene and the like. The ratio of the thickness t_2 and the thickness t_1 is 1: 3 for the blade (100) made of thermoplastic materials.
Turning now to Figure. 3, depicts schematic view of a conventional blade (100) with a lift angle ?, during its operation. As seen in Figure. 3, during operation of the blade (100), three types of loads (gravity, centrifugal force and the air pressure) act on the blade (100). The loads due to air pressure act in the opposite direction than that of forces due to gravity and centrifugal force. The deflection of the blade (100) is caused by the resultant moment generated by these individual forces. If the resultant moment is minimized, the deflection can also be reduced and a zero deflection can be achieved when the resultant moment is zero. The resultant moment on the conventional blade (100) is given by:
M_R (r)=M_b (r)-M_a (r), where
M_b (r)=M_A-R_x^A·r·tan?-R_y^A·r+?_0^(r_0)¦?g(r_0-r) dV+?_0^(r_0)¦??r(r_0-r)?^2 tan?? dV,
is the moment along the length of the blade (100) due to gravity and centrifugal load and M_a is the moment generated due to air pressure. In the above
M_A=?_0^l¦?(?gr+??^2 r^2 tan?) dV ,?
R_x^A=?_0^l¦???^2 r dV,?
R_y^A=?_0^l¦??g dV?
are the reaction moment, horizontal and the vertical reaction forces respectively at the fixed end. Here ? is the density of the fan blade (100) material, g is the acceleration due to gravity, ? is the rotational speed of the fan and ? is the lift angle as shown in Figure. 3.
Turning now to Figure. 4, which depicts variation of moments acting on the conventional blade (100). From Figure. 4 it is evident that, the resultant moment is non-zero leading to non-zero deflection.
In order obtain zero deflection, the resultant moment M_R˜0, which leads to M_b (r)=M_a (r) and indicates that the moment generated by air pressure must be balanced exactly by the moment generated due to gravity and centrifugal forces along the length of the blade (100). The moment due to air pressure (M_a) primarily depends on the rotational speed of the fan, whereas the moment M_b additionally depends on the fan blade (100) geometry. It is clear from the above, when M_b>M_a, the moment M_b should be reduced and it would be vice versa. For a given operating speed, if there is a deflection of the fan blade (100), it indicates that there is an imbalance of the moments and to achieve zero deflection M_b must be rectified by appropriate geometry modification. As the moment on the free end is always zero, and as it increases monotonically towards the fixed end, M_b can be optimized by modifying the value M_A at the fixed end. If the density ? of the material is assumed to be constant along the length of the blade (100), then
M_A=??_0^l¦(gr+r^2 ?^2 tan?) dV=??_0^l¦?F(r)·A(r) ? dr,
where A(r) is the cross-sectional area of the fan blade (100) at a radial location r from the axis of rotation and dV=A(r)dr. To understand the effect of fan blade (100) design on the reaction moment M_A, the function F(r)·A(r) is plotted in Error! Reference source not found.over the radial distance r for various choices of A(r). The moment can be calculated from the area under these curves. It can be seen when A(r)=A_0 is assumed to be constant along the length of the blade (100), the plot corresponds to the function F(r) only. To reduce the moment M_A on the fan blade (100), the area under the curve must be reduced by designing appropriate cross section A(r) because F(r) is determined only by the speed, gravity and the lift angle and is independent of the fan blade (100) geometry. Clearly the function F(r) increases monotonically with increasing r. Hence, to reduce the moment (or the area under the curve), two approaches can be adopted. In a first approach, the area of the blade (100) section A(r) can uniformly be reduced throughout the length of the blade (100) which leads to reduced mass of the blade (100) and hence the reduced moment. In a second approach to reduce the moment, if the mass needs to remain unchanged, the cross-sectional area A(r) must follow an opposite trend of the function F(r) to compensate for the higher values of F(r) as the distance from the axis increases. This indicates that the blade (100) should have more area (or mass) towards the axis of rotation and the area A(r) should decrease as the distance from axis increases. To demonstrate this, the function F(r)·A(r) is plotted in Error! Reference source not found. for two different profiles of A(r) which are shown in Figure. 5b. The cross-sectional profile for the first one remains constant over the length of the blade (100), while the other has linearly varying cross-section with higher area towards the axis. Total volume of the fan blade (100) is same for both cross-sectional profiles. Clearly the moment reduced when the strategy mentioned above is adopted as can be seen from Figure. 5a. The different components of the moment for this case are shown in Figure. 6 where the resultant moment M_R is very close to zero. By adopting combination of the both the approaches mentioned above, a blade design which has zero deflection is achieved.
EQUIVALENTS

With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.

It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should typically be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to "at least one of A, B, and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to "at least one of A, B, or C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Referral Numerals:

Referral Numerals Description
100 Blade
101 Body
102 Leading edge
103 Trailing edge
104 First surface
105 Tip end
106 Tail end
107 Mounting stub
, Claims:We Claim:

A zero deflection blade (100), the blade (100) comprising:
a body (101) defined with,
a leading edge (102) and a trailing edge (103);
a first surface (104) extending between the leading edge (102) and the trailing edge (103);
a second surface extending between the leading edge (102) and the trailing edge (103), on an opposite side of the body (101) relative to the first surface (104); and
a tip end (105) and a tail end (106), the tip end (105) of at least one of the first surface (104) and the second surface is defined with a thickness t_1 and the tail end (106) of at least one of the first surface (104) and the second surface is defined with a thickness t_2, wherein the thickness t_1 is variable to the thickness t_2 along a length L_1 between the tip end (105) and the tail end (106).

The blade (100) as claimed in claim 1, wherein the thickness along the length L1 varies continuously from the thickness t_1 to the thickness t_2.

The blade (100) as claimed in claim 1, wherein the thickness t_2 is greater than the thickness? t?_1.

The blade (100) as claimed in claim 1, wherein ratio of the thickness t_2 and the thickness t_1 is 1:2 for metallic materials.

The blade (100) as claimed in claim 4, wherein the metallic materials include aluminium, steel.

The blade (100) as claimed in claim 1, wherein ratio of the thickness t_2 and the thickness t_1 is 1:3 for thermoplastic materials.

The blade (100) as claimed in claim 6, wherein thermoplastic materials include Acrylonitrile butadiene styrene (ABS), polypropylene..

The blade (100) as claimed in claim 1, wherein L1 ranges between 400 – 500 mm.

The blade (100) as claimed in claim 1, wherein the tail end (106) comprises a mounting stub (107), the mounting stub (107) is configured to couple the blade (100) with a hub of a rotor.

Dated this 01st day of September 2022

Gopinath Arenur Shankararaj
IN/PA-1852
of K&S Partners
Agent for the Applicant