Fan Impeller with Turbulance-Reducing Blades

Laptop cooling fans are important components in the thermal management of high-performance notebook computers. As laptops continue to evolve, their cooling requirements have become increasingly demanding due to rising power consumption and more restrictive design constraints. Modern laptops consume more power at both the system-on-chip (SoC) and overall system levels, driven by the need to enhance user experience through improved performance and functionality.

At the same time, users expect laptops to be thinner, quieter, and cooler. Meeting these expectations requires fan systems capable of delivering improved pressure-flow (P-Q) characteristics while maintaining low acoustic noise and fitting within increasingly slim form factors. In conventional radial blowers, air entering the impeller is directed toward the backplate, with a substantial portion of the airflow exiting near the lower section adjacent to the backplate. This localized outflow contributes to increased turbulence and elevated noise levels in that region.

Historically, blower blade tips have been designed with surfaces oriented perpendicular to adjoining structures to maximize the airflow sweep area. In some instances, small flanges have been added to the upper and lower surfaces of the blade tips to reduce noise. These features have occasionally been implemented using metal blades; however, blower fans with metal components are not widely adopted due to higher manufacturing costs, lower production yields, and marginal performance benefits, especially in light of recent advancements in thin plastic molding technologies, which now allow for sub-0.1 mm features with comparable or improved aerodynamic performance.

This disclosure is directed to an impeller that reduces noise generation in the bottom section of a fan assembly and at the trailing edges of its blades, thereby minimizing overall acoustic noise. The aerodynamic characteristics of the impeller design allow the fan assembly to operate at higher rotational speeds without a corresponding increase in noise, resulting in enhanced performance, specifically, higher pressure-flow (P-Q) output, while maintaining the same noise level.

illustrates an electronic devicewith a conventional fan assembly. The fan assemblyincludes an impellerand a cover. The impelleris configured to rotate within the fan assembly, generating airflow for cooling purposes. The coverencloses the impellerand directs the airflow generated by the impellertoward specific components of the electronic devicethat require cooling.

The fan assembly, in this example, is part of a dual-fan cooling system within the electronic device. Each fan assemblyis positioned to optimize airflow distribution across the internal components of the electronic device, such as processors, memory modules, and other heat-generating elements.

The electronic devicemay be a laptop, notebook, or other computing device that requires efficient thermal management in a compact form factor. The fan assemblyis configured to operate within the constraints of such devices, providing enhanced cooling performance without increasing noise levels or requiring additional space.

illustrates a detailed view of a conventional fan assembly. The fan assemblyincludes the impellersurrounded by a volute housing. The impellercomprises a plurality of bladesthat are radially arranged around a central axis. The bladesare connected to an annular structureand are positioned above a backplatewithin a volute housing. The backplateis a surface within the fan assembly housing that serves as a structural boundary and influences airflow dynamics during fan operation. The volute housingis the enclosure that surrounds the impeller, directing the airflow generated by the impellertoward specific components that require cooling. It includes features such as a cutwaterto guide airflow efficiently. The cutwater, which is not shown in this figure, is a feature within the volute housingthat directs airflow generated by the impeller, typically positioned to optimize the distribution of air exiting the impeller.

Airflow through the impelleris directed radially outward, moving from the inner region near the hub to the outer region near the annular structure. Air is drawn into the impellerfrom the top due to the negative pressure created at the center when the impeller rotates, typically in a counterclockwise direction. As the impellerrotates, centrifugal force pushes the air outward through the channels formed between the blades. This radial airflow pattern ensures efficient air movement, with the negative pressure at the center facilitating continuous intake and the centrifugal force driving the air outward for effective cooling or ventilation.

The disclosed impeller design enables the fan assembly to deliver improved pressure-flow (P-Q) characteristics while reducing noise, all while maintaining compatibility with existing manufacturing processes and cost constraints. The blades of the impeller include an inclination angle relative to the backplate. This inclination angle reduces turbulence and noise generation by directing airflow more smoothly toward the backplateand increasing the air gap between the impeller and the volute housing. Each blade may additionally or alternatively include a slot that is configured to interrupt turbulent boundary layer growth, reduce tip vortices, and promote flow reattachment, thereby further reducing noise.

III. Impeller with Blades Including Inclination Angles

illustrates an impellerA with blades, each including an inclination angledesigned to reduce turbulence and noise during operation, in accordance with aspects of the disclosure. The impellerA includes a hubat its center, an annular structurepositioned radially outward of the hub, and a plurality of bladesextending radially between the huband the annular structure. The annular structuredefines a peripheral surface that lies in a first plane, while the main surface of each bladelies in a second plane that is substantially perpendicular to the first plane.

Each bladeincludes an edge region proximate the annular structure, the edge region being tapered to define an inclination anglebetween the blade's top and bottom edges. Unlike conventional impellers in which the edge region is vertical, forming a 90-degree angle with the backplate or annular structure, this tapered configuration forms an acute angle (less than 90 degrees) relative to the horizontal reference plane. The inclination anglereduces the normal component of air velocity (V=impeller tip radius×fan speed) near the bottom of the blade, thereby decreasing the relative air exit velocity in that region. This reduction in relative velocity minimizes turbulence and, consequently, lowers noise levels during operation. The inclined geometry not only enhances acoustic performance but also improves the overall aerodynamic efficiency of the impeller.

The inclination anglealso increases the air gap between the impellerA and the volute housing in the region near the backplate. This increased air gap reduces the interaction between the airflow exiting the impeller and the volute housing, further decreasing turbulence and broadband noise. The edge region of each bladeterminates at the peripheral surface of the annular structure, ensuring structural integrity and smooth airflow distribution.

provides a close-up view of the inclined edge region of the bladesin the impellerB. The figure highlights the tapering of the edge region, which defines the inclination angle. This inclination angleis acute and preferably ranges from approximately 45 to 85 degrees. The inclination angleof the edge region is designed to optimize airflow dynamics by reducing turbulence at the blade tips, a common source of noise in conventional impellers. The annular structureis shown in greater detail, demonstrating its role in supporting the bladesand maintaining the overall stability of the impellerB during operation.

The inclination angleof the edge region also disrupts the formation of eddies and local recirculation at the blade tips, which are significant contributors to turbulence and noise in conventional fan designs. By replacing the vertical 90-degree edge with an inclined edge, the impellerachieves smoother airflow and reduced noise levels, reducing the need for additional components or modifications to the manufacturing process.

illustrate an impellerincorporating blades defining slotsconfigured to reduce turbulence and noise during fan operation. The slotsare formed through the main surface of each blade. A support structure, such as a support ring, maintains the mechanical stability of the impeller. The slotsand support structurework together to disrupt turbulent boundary layer growth near the trailing edge of the blades, thereby improving aerodynamic performance and reducing broadband noise.

is an isometric view of the impellerA, showing the overall configuration of the blades, the annular structure, and the slots. Each bladedefines a slotformed through its main surface, positioned near the trailing edge of the blade. The slotsare configured to interrupt turbulent boundary layer growth as air flows along the blade surface. By disrupting the boundary layer, the slotsreduce turbulence and promote flow reattachment near the trailing edge, thereby minimizing noise and improving aerodynamic efficiency. The annular structureprovides structural support for the bladesand ensures uniform airflow distribution.

provides a detailed view of the impellerB, highlighting the slotted blade profile and the support ring. The slotsare shown as openings formed through the main surface of each blade, positioned proximate to the support ring. The support ringis positioned between the huband the annular structureand is coupled to the blades. The support ringis configured to maintain the structural continuity of the blades, ensuring that the slotted blade profile does not compromise the mechanical stability of the impeller during high-speed operation. The slots, in conjunction with the support ring, allow for effective disruption of boundary layer growth while maintaining the overall integrity of the impeller.

provides a close-up view of the slotted blade profile in the impellerC. The figure shows the slotsin greater detail, demonstrating how they are formed through the main surface of each blade. The slotsare positioned near the trailing edge of the bladesand are configured to reduce turbulence by interrupting the low-velocity boundary layer that forms during operation. This configuration ensures that the slotsare integrated into the overall structure of the impellerC, providing both aerodynamic benefits and mechanical stability. The width of each slotmay be designed to fall within a range of approximately 0.4 millimeters to 0.7 millimeters, ensuring optimal disruption of the boundary layer without compromising the structural integrity of the blades.

provides a back view of the impellerD, showing the arrangement of the blades, the annular structure, and the support ring. Again, the support ringprovides additional stability to the slotted blade profile.

The slotted blade profile, as shown in, is particularly advantageous for use in compact fan assemblies, such as those found in laptops or other portable electronic devices. By incorporating the slots, the support ring, and the extended annular structure, the impellerA-D achieves improved pressure-flow characteristics, reduced turbulence, and lower noise levels, enabling higher fan speeds and better cooling performance while maintaining compatibility with existing manufacturing techniques.

illustrates a detailed perspective view of an impellerincorporating a slotted blade profile with an extended annular structure, in accordance with aspects of the disclosure. The impellerincludes a plurality of bladesextending radially outward from the hub, and an annular structurepositioned radially outward of the blades. Each bladedefines a slotformed through its main surface, positioned near the trailing edge of the blade. The slotsare configured to interrupt turbulent boundary layer growth along the blade surface, thereby reducing turbulence, tip vortices, and broadband noise during operation.

A distinctive aspect is the extension of the annular structure, that is, the extended annular structure, into the slots. The extended annular structurepartially bounds the slots, providing additional structural support and ensuring the slotsare securely integrated into the impeller design. This configuration enhances the mechanical stability of the bladeswhile maintaining the aerodynamic benefits of the slotted blade profile. By extending into the slots, the extended annular structurealso helps guide airflow through the impeller, further improving pressure-flow characteristics and reducing noise.

The slotsare designed with a width optimized to balance aerodynamic performance and structural integrity. Specifically, the width of each slotmay range from approximately 0.4 millimeters to 0.7 millimeters. This range is sufficient to effectively disrupt the boundary layer while ensuring that the bladesremain structurally robust during high-speed operation.

The slot design illustrated in, and/or the slot design illustrated in, operates independently of the inclination angle described with respect to, providing a distinct aerodynamic improvement that does not rely on the inclined blade edge. In the slot design, the primary mechanism for reducing turbulence and noise is the interruption of turbulent boundary layer growth near the trailing edge of the blades through the incorporation of slots formed through the main surface of each blade. These slots disrupt the low-velocity boundary layer, reduce tip vortices, and promote flow reattachment, thereby minimizing turbulence and broadband noise. The aerodynamic benefits of the slot design are achieved solely through the placement and configuration of the slots/, as well as the structural support provided by the support ringor the extended annular structure, along with the annular structure. Unlike the inclination angle, which modifies the blade geometry to reduce turbulence near the backplate, the slot design focuses on managing airflow along the blade surface itself. As such, the slot design can be implemented independently of the inclination angle, allowing for flexibility in impeller configurations while still achieving significant noise reduction.

illustrate simulation and performance results of a fan arrangement incorporating aspects of the disclosure. These figures demonstrate the acoustics and acoustic benefits of the inclination angle and slot features, both individually and in combination, as well as their impact on fan noise reduction.

shows a comparisonA of the ⅓rd octave band Fast Fourier Transform (FFT) results at a fan speed of 4500 rpm, with and without the inclination angleof. The aeroacoustic simulations indicate that the inclusion of the inclination angleresults in up to a 9 dBA reduction in individual frequency bands, leading to an overall reduction of 5.1 dBA in the Overall Sound Pressure Level (OSPL). This significant reduction in broadband noise validates the hypothesis that the inclination anglereduces turbulence near the backplate by decreasing the relative air exit velocity and increasing the air gap between the impeller and the volute housing. The results confirm that the inclination angleis highly effective in minimizing noise.

illustrates a comparisonB of the ⅓rd Octave Band FFT results at 4500 rpm for a fan arrangement incorporating both an impeller with the inclination angleof, in addition to the slotsofor the slotsof. The aeroacoustic simulations show that the addition of the slot feature further reduces noise, with up to a 6 dBA reduction in individual frequency bands and an overall reduction of 2.9 dBA in the OSPL. The slot feature disrupts turbulent boundary layer growth near the trailing edge of the blades, reducing tip vortices and promoting flow reattachment. The combined effect of the inclination angle and the slot feature results in a significant reduction in broadband noise, demonstrating the complementary nature of these two features in improving fan acoustic performance.

shows test dataC comparing the ⅓rd octave band FFT results at 3300 rpm for a conventional impeller and the disclosed impellerwith inclination anglearrangement. The disclosed impellerachieves a significant reduction in broadband noise, with a lower overall sound pressure level (OSPL) across a wide range of operating conditions. This improvement results from the combined effects of the inclination angle, which reduces turbulence near the backplate.

The techniques described in this disclosure may also be illustrated in the following examples.

Example 1. A fan impeller, comprising: a hub; an annular structure positioned radially outward of the hub and defining a peripheral surface lying in a first plane; and a plurality of blades extending radially between the hub and the annular structure, each blade having a main surface lying in a second plane that is perpendicular to the first plane, wherein each of the plurality of blades includes an edge region proximate the annular structure, the edge region tapering to define an inclination angle between a top edge and a bottom edge of the blade, the inclination angle being configured to reduce turbulence during operation.

Example 2. The fan impeller of example 1, wherein the edge region terminates at the peripheral surface of the annular structure.

Example 3. The fan impeller of any one or more of examples 1-2, wherein the inclination angle is acute.

Example 4. The fan impeller of any one or more of examples 1-3, wherein the inclination angle is in a range from approximately 45 to 85 degrees.

Example 5. The fan impeller of any one or more of examples 1-4, wherein each of the plurality of blades defines a slot formed through the main surface of the blade, the slot being configured to interrupt turbulent boundary layer growth towards a trailing edge of the respective blade.

Example 6. The fan impeller of example 5, further comprising: a support ring extending between the hub and the annular structure and coupled to the plurality of blades, wherein the slots are formed proximate the support ring, and the support ring is configured to maintain structural continuity of the blades.

Example 7. The fan impeller of example 5, wherein the annular structure extends into the slots such that the slots are at least partially bounded by the annular structure.

Example 8. The fan impeller of example 5, wherein each of the slots has a width in a range from approximately 0.4 millimeters to 0.7 millimeters.

Example 9. The fan impeller of any one or more of examples 1-8, wherein the annular structure comprises a peripheral ring and is configured to connect of the plurality of blades.

Example 10. A fan, comprising: a volute housing including a backplate; and the fan impeller of any one or more of examples 1-9 rotatably mounted within the volute housing, wherein the inclination angle is configured to reduce turbulence near a backplate during rotation of the fan impeller.

Example 11. An electronic device comprising the fan of example 10.

Example 12. A fan impeller, comprising: a hub; an annular structure positioned radially outward of the hub and defining a peripheral surface lying in a first plane; and a plurality of blades extending radially between the hub and the annular structure, each blade having a main surface lying in a second plane that is perpendicular to the first plane, wherein each of the plurality of blades defines a slot formed through the main surface of the blade, the slot being configured to interrupt turbulent boundary layer growth towards a trailing edge of the respective blade.

Example 13. The fan impeller of example 12, further comprising: a support structure positioned between the hub and the annular structure and coupled to the plurality of blades, wherein the slots are formed proximate the support structure, and the support structure is configured to maintain structural continuity of the blades.

Example 14. The fan impeller of example 13, wherein the support structure comprises a ring.

Example 15. The fan impeller of any one or more of examples 12-14, wherein the annular structure extends into the slots and the slots are at least partially bounded by the annular structure.

Example 16. The fan impeller of any one or more of examples 12-15, wherein each of the slots has a width in a range from approximately 0.4 millimeters to 0.7 millimeters.

Example 17. A fan assembly, comprising: a volute housing including a backplate; and the fan impeller of example 12 rotatably mounted within the volute housing.

Example 18. An electronic device comprising the fan assembly of example 17.

While the foregoing has been described in conjunction with exemplary aspects, it is understood that the term “exemplary” is merely meant as an example, rather than the best or optimal. Accordingly, the disclosure is intended to cover alternatives, modifications, and equivalents, which may be included within the scope of the disclosure.