Axial fan blades and fan assembly

Abstract

Embodiments of the present invention pertain to the design and assembly of high-efficiency industrial axial fan blades (1) achieved through rigorous Computational Fluid Dynamics (CFD) analysis The focus is on selecting airfoil profiles and blade dimensions to maximize energy efficiency, with considerations for uniform velocity distribution, twist angles, and other aerodynamic factors. The invention also involves various analyses such as Finite Element Analysis, Fatigue Analysis, Critical Speed Analysis, and Model Testing to ensure optimal performance. The disclosed invention is applicable particularly to axial fans used in low-pressure, high-volume applications like cooling towers, air-cooled condensers, and wind tunnels.

Description

[0001] AXIAL FAN BLADES AND FAN ASSEMBLY

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] Embodiments of the present invention relate to axial fan blade profile and dimensional range tailored for achieving high efficiency in fan assemblies. The blade profile is based on extensive CFD analysis and simulation of the Fan Performance Curve, ensuring superior energy efficiency and savings.

[0004] BACKGROUND OF THE INVENTION

[0005] Industrial axial fan assemblies have been integral components in various applications across diverse industries. Typically, these assemblies consist of a central hub and two or more blades, with variations in design based on specific requirements. The design criteria for these fans often center around factors such as efficiency and noise reduction to enhance energy savings and improve overall system operation. In the context of industrial axial fan blades, achieving optimal efficiency is a paramount concern. The conventional approach involves giving these blades an airfoil shape, where the cross-section exhibits camber and twist. This design principle is rooted in the understanding that an airfoil shape, with camber and twist, generates more lift than flat blades of the same area. It is a well-established fact that a flat blade is less efficient than a fully shaped blade with the necessary camber, curve, and twist.

[0006] The conventional fans are typically crafted from extruded aluminium or molded fiberglass blades, both inheriting a uniform chord width. Extruded aluminium blades are constrained by their inherent uniformity, while molded fiberglass blades may exhibit irregular shapes. However, the conventional approach faces significant drawbacks, particularly in the challenge of ensuring uniform airflow over the entire fan plane and they also face challenges in achieving the required twist. Mechanical yielding is employed to induce twist to a prescribed degree. However, this approach is limited by the elasticity of the material, resulting in constraints on the extent of twist that can be achieved.

[0007] The inefficiency of the conventional fan blades stems from the aerodynamic principles governing blade design. The work done along the blade radius is intricately tied to blade width, angle of attack, and the tangential velocity squared. The "angle of attack" dictates the necessary blade twist, especially as the point on the blade moves from tip to hub. Here, the tangential velocity decreases sharply, necessitating an increase in both blade width and twist for uniform airflow. Limitations arise when the blade chord cannot widen, forcing an increase in twist, a challenge more pronounced in extruded blades due to constraints in mechanical yielding.

[0008] The conventional axial fans, while foundational, face limitations in achieving optimal efficiency, primarily stemming from challenges in maintaining uniform airflow and addressing the constraints associated with extruded blade designs.

[0009] These challenges highlight the need for an innovative approach, a need that the present invention addresses. The invention recognizes the limitations of conventional designs and emphasizes the importance of variability in blade profiles during fan selection. It particularly underscores the inefficiencies associated with extruded aluminium blades and their constrained twist capabilities. In contrast, the invention's focus on innovative axial fan seeks to create an 'ideal' blade shape that minimizes problems of non-uniform airflow and inefficiency.

[0010] SUMMARY OF THE INVENTION

[0011] Accordingly, it is the primary aim of the present invention to provide a solution to the challenges faced by conventional axial fan blades, targeting enhanced efficiency, reduced noise, and improved fluid-moving capabilities

[0012] It is yet another objective of the present invention to introduce a novel fan blade shapes crafted through comprehensive Computational Fluid Dynamics (CFD) analysis.

[0013] It is yet another objective of the present invention to offer a versatile approach to manufacturing these fan blades, allowing for processes such as extrusion, molding, casting, or other suitable methods. This flexibility in manufacturing methods ensures adaptability to various industrial settings and applications.

[0014] It is yet another objective of the present invention to provide axial fan blades designed to optimize performance. These dimensions encompass a front side, rear side, inner attachment portion, outer edge, curved leading edge, and curved trailing edge. Such a detailed and tailored design ensures not only improved efficiency and significant energy saving, but also addresses challenges related to noise reduction and fluid dynamics.

[0015] It is yet another objective of the present invention to extend its adaptability to fan assembly diameters of varying sizes, adding versatility to its application across diverse industrial contexts. The invention's adaptability to different fan assembly diameters further positions it as a versatile and scalable solution for industries seeking improvements in energy efficiency and overall fan performance.

[0016] Additional objects of the invention will become apparent with an understanding of the following detailed description of the invention or upon employment of the invention in actual practice.

[0017] According to the preferred embodiment of the present invention the following is provided: An axial fan blade for industrial applications, comprising: a hollow fan body comprising a front surface, a rear surface, a first side, a second side, a tip, and a root; at least a neck attached to the root for connection to the rotor or hub of a fan assembly; an airfoil portion; characterized in that said airfoil portion is defined by a gradual width widening and thickness increasing of the fan body from the tip to the root; wherein the body width widens on at least one side, forming an outer edge at the root, with the widening being either substantially straight or slanted; wherein the body thickness increases gradually from the tip toward a position proximal to the root and subsequently tapers gradually to the root; wherein, when the first side and second side are widened, the widening of the body width is executed differentially on one side compared to the other; wherein either the first side experiences a deliberate but smaller widening compared to the second side, or vice versa; and the widening of both sides being either substantially straight or slanted, or combination thereof; the widening of the fan body concludes with two outer edges at the root, comprising a less widened edge and a most widened edge; further characterized in that the airfoil portion is twisted, with at least one side continuously twisted upwards or downwards from the root to a position before the tip.

[0018] BRIEF DESCRIPTION OF THE DRAWINGS Other aspect of the present invention and their advantages will be discerned after studying the Detailed Description in conjunction with the accompanying drawings in which:

[0019] FIG. 1-A, 1-B, 1-C and 1-D illustrates an exemplary axial fan blade according to the preferred embodiment of the present invention. FIG. 2-A, 2-B and 2-C illustrate an exemplary assembly of axial fan blades according to the preferred embodiment of the present invention.

[0020] FIG. 3 showcases an exemplary fan blade in accordance with the preferred embodiment of the present invention, accompanied by dimension references. TABLE 1 presents diverse dimensions for a fan assembly in alignment with the embodiments of the present invention, wherein reference is made to the dimension references both in TABLE 1 and FIG. 3 for a comprehensive understanding and reading. FIG. 4 illustrates an exemplary fan blade of 3960mm fan assembly according to the preferred embodiment of the present invention.

[0021] FIG. 5-A illustrates an exemplary performance result of a conventional fan assembly with flat fan blades.

[0022] FIG. 5-B illustrates an exemplary performance result of an axial fan blade assembly according to the preferred embodiment of the present invention.

[0023] DETAILED DESCRIPTION OF THE DRAWINGS

[0024] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by the person having ordinary skill in the art that the invention may be practised without these specific details. In other instances, well known methods, procedures and / or components have not been described in detail so as not to obscure the invention. The invention will be more clearly understood from the following description of the embodiments thereof, given by way of example only with reference to the accompanying drawings, which are not drawn to scale.

[0025] As used in this disclosure and the appended claims herein, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates or denotes otherwise.

[0026] Throughout the disclosure and claims of this specification, the word "comprise" and variations of the word, such as "comprising" and "comprises," means "including but not limited to," and is not intended to exclude, for example, other components, integers or steps. "Exemplary" means "an example of" and is not intended to convey an indication of a preferred or ideal embodiment, "such as" is not used in a restrictive sense, but for explanatory purposes.

[0027] The embodiments disclosed in the present invention focus on an axial fan blade (1) and its assembly (2), with a primary goal of enhancing fan blade (1) performance through increased efficiency, reduced noise, improved fluid-moving capability, and energy consumption reduction. The fan blade (1) is tailored for industrial use, including common applications in cooling towers, air-cooled condensers, wind tunnels, and is also adaptable for household usage. Referring to FIG. 1-A, 1-B, and 1-C, the fan blade (1) in the preferred embodiment is a hollow and monolithic structure or body (3) crafted from fiberglass and epoxy resin, or alternatively cast, molded, or produced using other desired methods.

[0028] It comprising a front or upper surface (5), a rear or lower surface (7), a first side (9), a second side (11), a tip portion (13) with a trailing edge, an airfoil portion (15) with a leading edge which defines the root (17) of the fan body (3). The blade's geometry evolves from the tip (13) towards the root (17), where it attaches to the hub (27), as further shown in FIG. 2-A, 2-B, and 2-C. Notably, the tip (13) of the fan blade (1) is intentionally slanted, introducing an additional aerodynamic feature for enhanced performance.

[0029] A noteworthy feature is the gradual widening of the blade body (3) or the airfoil portion (15) width on both first and second sides (9, 11), creating a nuanced asymmetry. The tip portion (13) gradually widens the fan body (3) width until the root (17) of the airfoil portion (15). This gradual widening plays a pivotal role in enhancing aerodynamic efficiency.

[0030] Starting from the tip (13), the blade body (3) exhibits a gradual expansion in width, a characteristic that imparts unique aerodynamic properties. This widening of the body width is executed differentially on one side compared to the other, introducing a deliberate asymmetry to enhance airflow dynamics. Specifically, either the first side (9) experiences a deliberate but smaller widening compared to the second side (11), or vice versa. In one embodiment, both sides (9, 11) undergo a widening process that is either straight or slanted. Alternatively, a combination can be implemented where the first side (9) undergoes a straight widening, and the second side (11) experiences a slanted widening, or vice versa. Another embodiment entails widening on only one side, executed in either a straight or slanted manner, while the opposite side remains unaltered.

[0031] The asymmetric widening is strategically implemented to address specific aerodynamic principles. This design choice contributes to improved lift, reduced drag, and enhanced overall efficiency. The intricate balance of widening dimensions on either side ensures uniform airflow over the entire blade surface, a critical factor in achieving optimal fan performance.

[0032] The expansion of the fan body (3) width culminates at the root (17) of the blade (3), delineating two distinct outer edges, i.e, the less widened edge (19) and the most widened edge (21). This root portion (17) connects to a substantially cylindrical neck (23), and subsequently links to a collar (25) intended for attachment to a hub (27) within a fan assembly (2). It is contemplated that the cylindrical neck (23) may directly attach to the hub (27) without the collar (25).

[0033] In addition to the expansion in width, the thickness of the fan blades (3) assumes a crucial role. The thickness of the airfoil portion (15) gradually increases from the tip (13) until a portion before the root (17), after which it decreases or tapers towards the root (17). As depicted in FIG. 1-C, the thickness of the fan blade (3) is categorized into three segments: a thin airfoil portion at the tip area, a medium airfoil portion in the middle area, and a thick airfoil at the middle to root area. This represents an enhancement compared to conventional fan blades that exhibit a uniform thickness increment from tip to root.

[0034] The airfoil portion (13) features a twisted profile, where the most widened edge (21) may exhibit an upward or downward twist, and the following less widened edge (19) follows suit in the same direction. Alternatively, the twist direction of the less widened edge (19) may oppose that of the most widened edge (21). In another scenario, only one of the edges undergoes twisting, leaving the other unaltered. In cases where both edges (19, 21) adopt a twisting profile, the twisting persists continuously throughout the entire airfoil portion (15), concluding before the tip (13) of the fan blade (3). Alternatively, when only one edge embraces a twisting profile, the twist is consistent for the complete airfoil portion (15), concluding before the blade's tip (13).

[0035] The incorporation of a hollow body (3) in the construction further enhances the aerodynamic profile of the blade (1), simultaneously reducing weight while upholding structural integrity. This lightweight design not only enhances overall efficiency but also minimizes inertia, allowing for quicker response to changing operational conditions. The synergy of these features marks a significant advancement in the design of fan blades (1).

[0036] FIG. 1-D illustrates the hollow construction of said fan blade.

[0037] Illustrated in FIG. 2- A, 2-B, 2-C is a fan assembly (2) aligned with the principles of the present invention, showcasing two or more fan blades (1) securely attached to a central hub (27), forming a cohesive and efficient fan assembly (2).

[0038] In certain embodiments, the outer edge of the fan blade (1) is configured to delineate an arc spanning from a forward position to a rearward position. In these embodiments, the leading edge extends outward to intersect the arc of the outer edge at the forward position, while the trailing edge extends outward to the rearward position.

[0039] In determining the sizes of the fan blades (1) in the current invention, the careful selection of an airfoil (15) and blade profile for industrial axial fans (1) plays a pivotal role in achieving optimal energy efficiency. The primary goal is to attain the Best Efficiency Point of the Axial Fan through comprehensive Computational Fluid Dynamics (CFD) analysis. There is no one-size-fits-all solution, as the ideal airfoil (15) is contingent upon factors such as the fan's operating conditions, speed, volume flow rate, and pressure requirements. However, specific airfoil (15) characteristics are generally linked to heightened efficiency. Essential considerations for maximizing the energy efficiency of the axial fan (1) include ensuring a uniform velocity across the entire blade area (1). Achieving uniform velocity necessitates a fan blade design that transitions from a thin tip (13) to a thick cambered root (17). This variation in blade dimensions is crucial for maintaining consistent airflow. Each point along the blade (1) requires a proper balance of chord and angle, inducing the necessary twist in the blade to enhance aerodynamic efficiency.

[0040] The comprehensive approach to optimizing fan blade sizes involves various analyses, including CFD Analysis, Finite Element Analysis, Fatigue Analysis, Critical Speed Analysis, and Model Testing. These analyses collectively contribute to the meticulous design process, ensuring that the selected fan blade sizes align with the desired energy-efficient characteristics for industrial axial fans.

[0041] The configurations of the blades (1) in various embodiments of the current invention can be delineated, at least partially, by one or more angles or lengths, encompassing the radius of the fan assembly at distinct locations on the blade. Blades falling within the scope of this invention may be defined, in part, by the magnitude of one or more of these blade parameters.

[0042] Concerning the chamber-to-chord ratios of cross-sections of the blade (1) at diverse radial distances from its rotational axis, certain embodiments maintain a camber-to-chord ratio within the range of 2.0% and 7.5%. This ratio may remain constant or vary with the increasing distance from the rotational axis of the fan assembly (2). Regarding the angle of the outer radial portion of the blade (1) concerning a plane passing perpendicularly through the rotational axis of the blade (1), this angle falls within different ranges in various embodiments: between 4 and 15 degrees, 6 and 13 degrees, or 8 and 11 degrees.

[0043] FIG. 3 showcases an exemplary fan blade (1) in accordance with the preferred embodiment, accompanied by dimension references. These dimension references are intended to be interpreted in conjunction with Table 1, presenting diverse blade profiles and dimensions. The dimensions are subject to variation within a range of + / - 30%, contingent upon the operational conditions of the fan system application. Each dimension is specifically determined to accommodate diverse applications.

[0044] FIG. 4 illustrates a fan blade (1) of 3960mm fan assembly (2). The dimension and the profile of the blade (1) is a result of enormous trial and error during CFD analysis of various shapes and dimensions simulated for best efficiency point in fan performance curve of highest efficiency fan design selection.

[0045] In FIG. 5-A, the performance outcomes of a traditional axial fan equipped with a flat fan blade are depicted, whereas in FIG. 5-B, the results showcase the prototype fan assembly (2) of the present invention with a diameter of 3960mm. Remarkably, a significant energy-saving of more than 43% has been achieved, concurrently delivering equivalent or superior airflow compared to the conventional fan assembly in a cooling tower. This substantiates that the specific fan blade profile design introduced by this invention has the capability to generate a High-Efficiency Industrial Axial

[0046] Fan. It is essential to note that the blade dimensions and profiles for fans of varying diameters may fluctuate within a range of + / - 30%, contingent upon the specific operating conditions during the fan selection for the cooling system.

[0047] The current invention demonstrates a remarkable increase in energy efficiency, ranging from 80% to 95%, when compared to the efficiency of conventional fans, which typically fall within the range of 60% to 70% based on existing designs. This enhanced efficiency is attributed to several factors, including the utilization of an optimized airfoil shape, the creation of a superior blade profile, careful adjustment of blade width and twist along the blade's length, and the selection of an appropriate blade pitch angle to achieve the desired airflow at the lowest possible energy consumption. Additionally, the efficiency is influenced by the optimal determination of the number of blades (1) in the fan assembly (2) based on the fan shaft speed.

[0048] In crafting an efficient design for an industrial axial fan blade (1), the selection of airfoil (15) along the blade (1) stands out as a pivotal aspect, directly impacting the fan's aerodynamic performance. The following key considerations and procedural steps delineate the process of forming airfoil along the blade:

[0049] A. Design Point Considerations: Understand Design Conditions: Identify crucial design conditions such as desired airflow rate, pressure head, and rotational speed, collectively known as the "design point," providing the foundation for airfoil selection.

[0050] B. Performance Requirements: Efficiency Goals: Determine the desired efficiency, aiming to strike a balance between airfoil that offer optimal efficiency and other relevant factors.

[0051] Operating Range: Consider the expected fan operating range, ensuring selected airfoil perform well not only at the design point but also across varied operating conditions. C. Specific Speed (Ns):

[0052] Calculate specific speed: a vital parameter classifying fans into distinct categories.

[0053] D. Airfoil Characteristics:

[0054] Lift and Drag Characteristics: Scrutinize lift and drag characteristics of potential airfoil, aiming for sufficient lift and minimized drag to enhance overall performance.

[0055] Angle of Attack Range: Assess the airfoil's angle of attack range, crucial for determining the twist angle along the blade. E. Twist Angle Design:

[0056] Optimize Twist Angle: Based on airfoil aerodynamic characteristics, determine the twist angle along the blade, contributing to consistent angle of attack and uniform airflow. F. Manufacturability:

[0057] Consider Practical Constraints: Evaluate practical aspects of manufacturing, ensuring selected airfoils can be manufactured using feasible and cost- effective processes.

[0058] G. Computational Fluid Dynamics (CFD): Simulation Studies: Employ CFD simulations to analyze airflow around blades with different airfoils, optimizing airfoil selection and blade design.

[0059] H. Iterative Design Process:

[0060] Refinement Based on Testing: If feasible, build prototypes with selected airfoils, conducting testing to validate performance. The design process may involve iterations based on testing results.

[0061] I. Historical Experience:

[0062] Learn from Past Designs: Draw insights from past fan designs or industry standards, leveraging historical experience to inform airfoil choices. J. Compliance with Standards:

[0063] Ensure Compliance: Ensure selected airfoils and the overall fan design adhere to industry standards and safety requirements such as ISO 5801, DIN 24163 and AMCA 210.07. In crafting a fan blade design, engineers leverage theoretical analysis, simulations, and practical testing, striving to choose airfoils that collectively contribute to the desired performance characteristics of the industrial axial fan.

[0064] Continuing with the design considerations for industrial axial fan blades, determining the dimensions involves a holistic approach combining engineering principles, aerodynamics, and application-specific requirements. The following key factors are critical in deciding blade dimensions:

[0065] 1. Airflow Requirements: Volume Flow Rate: Specify the required volume flow rate in cubic meters per second (m3 / s) or cubic feet per minute (CFM).

[0066] Pressure Head: Consider the necessary pressure head to overcome resistance in ducts or the system.

[0067] 2. Fan Performance Curve: Design Point: Identify the design point on the fan performance curve, representing the primary combination of airflow and pressure conditions.

[0068] Operating Range: Ensure selected blade dimensions offer satisfactory performance across varying operating conditions. 3. Specific Speed:

[0069] Calculate Specific Speed (Ns): Use this dimensionless parameter to characterize fan geometry and performance.

[0070] 4. Aerodynamic Design:

[0071] Airfoil Selection: Choose an airfoil shape suitable for desired performance characteristics based on aerodynamic considerations.

[0072] Twist Angle: Optimize the twist angle along the blade length to achieve the best angle of attack at different sections.

[0073] 5. Material and Manufacturing Considerations:

[0074] Material Strength: Assess blade material strength to withstand mechanical loads during operation.

[0075] Manufacturability: Ensure the chosen blade design is practical for manufacturing processes. 6. Tip Speed Limitations:

[0076] Avoid Cavitation: Prevent cavitation by ensuring the tip speed of the blades does not exceed critical values.

[0077] 7. Efficiency and Noise Considerations: Efficiency Goals: Strike a balance between high efficiency and other performance requirements.

[0078] Noise Levels: Optimize blade design to minimize noise if low noise levels are a priority.

[0079] 8. Computational Fluid Dynamics (CFD): Simulation Studies: Utilize CFD simulations to analyze airflow around the blades, optimizing design for performance and efficiency.

[0080] 9. Prototyping and Testing:

[0081] Prototype Construction: Build prototypes based on calculated dimensions for real-world testing. Iterative Process: Embrace an iterative design process, making adjustments based on testing results. Additionally, the main parameters influencing fan performance include the meridional profile of the blade, beta, theta angle distribution through the leading edge to the trailing edge, number of blades, and profile thickness. These parameters collectively contribute to achieving the desired efficiency and performance of the industrial axial fan.

[0082] While the present invention has been shown and described herein in what are considered to be the preferred embodiments thereof, illustrating the results and advantages over the prior art obtained through the present invention, the invention is not limited to those specific embodiments. Thus, the forms of the invention shown and described herein are to be taken as illustrative only and other embodiments may be selected without departing from the scope of the present invention, as set forth in the claims appended hereto. The scope of the invention encompasses numerous alternatives, modifications and the equivalents. Of necessity, there are many alternative ways of configuring and implementing the invention to suit particular installations and environments while providing biological outcomes of differing design.

Claims

WHAT IS CLAIMED IS:

1. An axial fan blade (1) for industrial applications, comprising: a hollow fan body (3) comprising a front surface (5), a rear surface (7), a first side (9), a second side (11), a tip (13), and a root (17); at least a neck (23) attached to the root for connection to the rotor or hub (27) of a fan assembly (2); an airfoil portion (15); characterized in that said airfoil portion (15) is defined by a gradual width widening and thickness increasing of the fan body (3) from the tip (13) to the root(17); wherein the body width widens on at least one side, forming an outer edge at the root (17), with the widening being either substantially straight or slanted; wherein the body thickness increases gradually from the tip (13) toward a position proximal to or before the root (17) and subsequently tapers gradually to the root (17);wherein, when the first side (9) and second side (11) are widened, the widening of the body width is executed differentially on one side compared to the other; wherein either the first side (9) experiences a deliberate but smaller widening compared to the second side (11), or vice versa; and the widening of both sides (9, 11) being either substantially straight or slanted, or combination thereof; the widening of the fan body (1) concludes with two outer edges at the root (17), comprising a less widened edge (19) and a most widened edge (21); further characterized in that the airfoil portion (15) is twisted, with at least one side continuously twisted upwards or downwards from the root (17) to a position before the tip (13).

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