Patent Grant
11808282
The present invention relates generally to propeller fan assemblies and, more particularly, but not by way of limitation, to axial propeller fan assemblies for heating, ventilation and air conditioning units. The present invention further relates to methods of using axial propeller fan assemblies.
The present invention is directed to a propeller fan for a heating, ventilation and air conditioning HVAC unit, the propeller fan comprising a plurality of blades arranged in a concentric configuration, each of the plurality of blades comprising a leading edge, trailing edge, a suction side and a discharge side; a plurality of protrusions P configured on the suction side proximate the leading edge of at least one of the plurality of blades; wherein the plurality of protrusions lowers sound pressure levels generated during operation of the propeller fan.
The present invention further is directed to a method of lowering sound pressure generation during operation of a heating, ventilation, and air conditioning system comprising a propeller fan having blades, the method comprising the steps of reducing dipole source strength as air passes over the blades during operation of the fan by providing a plurality of protrusions at a leading edge of a suction side of at least one of the blades.
A propeller fan for heating, ventilation, and air conditioning system unit, the propeller fan comprising a plurality of blades arranged in a concentric configuration around a central hub wherein the central hub comprises at least two circumferential layers and at least one connecting rib between the two circumferential layers.
The present invention is further directed to a method of a method of reducing deflection of blades of a propeller fan having a plurality of blades, the method comprising the steps of configuring the plurality of blades in a concentric configuration around a central hub wherein the central hub comprises at least two circumferential layers by providing a plurality of protrusions at a leading edge of a suction side of at least one of the blades.
The present invention is further directed to a modular mounting assembly for attaching different motor types and sizes to a propeller fan, the modular mounting assembly comprising: a sidewall; an inner ring forming a central annulus; a plurality of spokes extending between the sidewall and the inner ring; a motor connection forming a central aperture and positioned atop the inner ring; and a plate positioned above the motor connection, the plate forming a central aperture; wherein, when in assembled configuration, the central aperture of the plate aligns with the central aperture of the motor connection for receiving a motor.
The present invention further is directed to a heating, ventilation and air conditioning (HVAC) unit comprising: a propeller fan, comprising: a plurality of blades arranged in a concentric configuration, each of the plurality of blades comprising a leading edge, trailing edge, a suction side and a discharge side; and a plurality of protrusions P configured on the suction side proximate the leading edge of at least one of the plurality of blades; wherein the plurality of protrusions lowers sound pressure levels generated during operation of the propeller fan.
A refrigeration system relies on a cyclical process to remove heat from the area or from the equipment that is being cooled and rejects the heat to the ambient surroundings, away from the cooled area. In many rooftop heating, ventilation and air conditioning (“HVAC”) units, a condenser section has a heat exchanger coil containing the refrigerant that has been discharged from the compressor. To summarize the basic refrigeration cycle, heat is absorbed by refrigerant in an evaporator coil via warm air that flows through the coil and becomes cold in the process. From the evaporator, the refrigerant flows into the compressor as a low pressure vapor. The compressor adds pressure and temperature to the refrigerant (“heat of compression”). The refrigerant then flows into the condenser as a high pressure vapor. As the refrigerant, at this point, has a higher temperature and enthalpy than its surroundings, the condenser fan induces surrounding airflow to flow through the condenser coil, which transfers energy from the refrigerant to this airflow. Consequently, the refrigerant “dumps” heat to the surroundings while lowering its own enthalpy. The refrigerant then flows to an expansion valve as a high pressure liquid. The expansion valve is a pressure-reducing device and the high pressure liquid becomes a low pressure liquid. From here, the refrigerant flows into the evaporator coil, and the cycle repeats itself.
The cooling requirements for large retail, commercial and industrial scale processes sometimes separate the various components of the system for efficiency. In order for the refrigerant and the air to interact and exchange heat, an axial fan is commonly used in a refrigeration condensing section to force air to flow through the condenser coil. An axial fan is an air-moving device that causes a fluid to flow through the fan in a direction parallel to the axis of the fan rotation. Air passing through the condenser coil exchanges heat with the refrigerant that is flowing inside the condenser coil. The air gains enthalpy and becomes warmer, and the refrigerant loses this enthalpy after this air-refrigerant heat exchange. The refrigerant in the condenser coil thereby changes from a high pressure gas to a high pressure liquid after it flows through the condenser coil.
Fan selection and design are critically important for adequate delivery of the air and efficiency of the process. Airflow is important for many refrigeration systems as it is a medium for heat exchange, which is a critical process for an overall refrigeration system. The pattern of the air leaving the axial fan is impacted by multiple factors, including the position of the fan, the mounting orifice, the operating point, and the design features of the fan. The fan must have favorable acoustics and meet demands for reduction in noise pollution. As consumer demands heighten over time, lowering sound production from the fan is a key improvement. The fan must fit into the unit design constraints, and it must not have any kind of interference or collision with the surrounding parts during assembly and/or operation.
An axial fan may be designed to be HVLS (High Volume Low Static), meaning that the more important purpose of the axial condenser fan is to move a higher volume of airflow than to move air against a higher pressure. An axial fan assembly achieves at least two desirable characteristics, namely, it should be acoustically favorable, meaning the fan generates relatively less noise during operation, and it should not create interference issues during assembly or operation. The present invention achieves these goals and generates lesser sound pressure levels while operating at a desired favorable operating point, with respect to the air volumetric flow rate and static pressure.
The present invention achieves these goals at least in part through the provision of protrusions, or silencer seeds, strategically arrayed, shaped and sized, on the suction side proximate the leading edge of at least one blade of the fan. The location, arrangement, shape, sizes and surface area of these protrusions, or silencer seeds, on the suction side of the blades lowers sound generation. The evidence from the studies and tests is that these protrusions reduce sound pressure levels by as much as 3 dB, which is a significant difference, without altering the performance of the fan in terms of the volumetric flow rate of air at a particular static pressure. The invention has application in HVAC units, including space cooling, data center cooling, and industrial, commercial and residential cooling. The invention also presents a mounting mechanism for mounting the fan to the motor that enables the use and interchange of a variety of sizes and types of motors with the invention.
Further, the present invention minimizes blade deflection and preserves the performance of the blade as it was intended. Through advanced finite element-based computer simulations and physical verifications of models, it was found that a plastic fan that has two circumferential layers provided significant additional support to the blades during operation and minimizes blade deflection.
Turning now to the drawings, and to
Turning now to
The mounting orifice 38 of the propeller fan 14 may range in diameter from about 5 inches (12.7 cm) to about 50 inches (127 cm). For efficiency, the diameter of the mounting orifice 38 is usually only minutely wider than the blades 40, which are mounted within the mounting orifice in a manner yet to be described, although it will be appreciated that greater clearances may be required for some applications. Therefore, the diameter of the frame 30 of the propeller fan 14 ranges from about 5.01 inches (12.73 cm) to about 50.01 inches (127.02 cm). In one embodiment of the invention, the propeller fan 14 is about 30 inches. References herein to diameters are to inside diameters, unless specifically stated to reference an outer diameter. It will be appreciated, however, that the fan 14 and the mounting orifice 38 may be any diameter, or length, width, or other dimension, suited for the application and the conditions at the site where in use.
The frame 30 may made be of any material suitable for use in refrigeration units, including steel, chrome, steel chrome-plated, steel with nickel/silicon carbide composite coating, brass, brass-chrome plated, brass with nickel/silicon carbide composite, stainless steel, stainless chrome-plated, stainless with nickel/silicon carbide composite coating, carbonitrided steel, nickel carbide plated steel, tempered steel, polyvinylchloride, and plastics, including polypropylene, and talc-filled polypropylene. It will be appreciated that the frame 30 may be produced from other materials suited to the particular temperatures, pressures, fluids and other conditions for the application and the site where the unit 10 is installed. In one embodiment of the invention, the frame is made with a talc-filled propylene plastic.
In one embodiment of the invention, the motor 34 is rated to output a certain horsepower, and the fan 14 is designed so that it will not pull any more power than the motor is designed to provide. The fan 14 must be able to move the desired airflow against a static pressure for which the unit 10 is designed. The motor 34 comprises a motor shaft 43 that, when in assembled configuration, penetrates an annulus 47 formed in the mounting assembly 36. The motor 34 is secured in place within the mounting assembly 36 via one or more setscrews (not shown), tightened onto the shaft.
The mounting assembly 36 comprises a plurality of spokes 39 that are integral with aerodynamically shaped sidewalls 41. The spokes 39 extend from the sidewalls 41 and conjoin at an inner wall 46 forming the annulus 47. These components may all be made of the same plastic material as the mounting assembly 36. The spokes 39 provide structural integrity, strength and stability to the mounting assembly 36 and the overall fan 14. The number of spokes 39 will vary with the size of the fan 14 and the application; however, in one embodiment of the invention, the mounting assembly 36 comprises eight spokes 39.
With continuing reference to
Returning now to
A fan, by virtue of its rotational motion, creates a pressure differential that causes airflow to move from an area of high pressure to low pressure. To that end, the fan 14 comprises a top, or discharge side, 50 and a bottom, or suction side, 52. The fan 14 may be installed in any configuration within the refrigeration unit 10 although, in one embodiment of the invention, the fan 14 is installed in a rooftop refrigeration unit 10 in an orientation wherein the discharge side 50 faces the sky.
Turning now to
The dimensions of the blades 40 vary according to application and the requirements at the site where the unit 10 is in use. In one embodiment of the invention, the largest circumscribed circle formed by the assembled blades 40 has a diameter of about 30 inches (761 mm), although it will be appreciated that this measurement will vary and may be smaller or larger.
The number of blades 40 comprising the plurality of blades will vary depending on the application and will be optimized for the application and the size of the unit 10. Increasing the number of in the plurality of blades 40 has potential to move more air but will also increase manufacturing costs and may consume more power. Additionally, if air is moved through a smaller diameter fan, the fan must be rotated at higher velocity to achieve the same flow. Therefore, the number of blades comprising the plurality of blades 40 will be optimized for the particular application, blade size, blade material, blade pitch, desired airflow, power consumption and the size of the unit 10. Having fewer blades or smaller blades may reduce drag but may also generate lesser airflow. Increasing blade size or the number of blades may not necessarily generate more airflow because of the larger drag. The increased drag requires a more powerful, energy-hungry and noisier motor. Additionally, having more blades adds weight to the fan and a more powerful motor may be needed to overcome the higher moment of inertia. Although it will be appreciated that the number of blades comprising the plurality blades 40 may be any number adapted for the particular application and size of the unit, in one embodiment of the invention, the number of blades comprising the plurality of blades 40 ranges is between two and six, and, in another embodiment of the invention, the number of blades equals four.
Each of the plurality of blades 40 may comprise any shape adapted for the particular application and for the size of the unit 10. Conventional condenser fans may comprise a stamped metal blade, which may be of a relatively simple blade shape. One such geometry is illustrated in
In one embodiment of the invention, the blades comprising the plurality of blades 40 have a complicated swept blade geometry, as shown by way of example, but without limitation, in
With continuing reference to
As previously mentioned, the fan 14 of the present invention achieves the dual goals of generating less noise during operation, or acoustic favorability, while minimizing or eliminating instances of interference during assembly and operation. Through CFD simulations, an axial fan has been designed that generates lower sound pressures while operating at favorable operating points, with respect to volumetric flow rate and static pressure. This CFD-based study has been physically validated in experimental test data.
Turning now to
Each of the silencer seeds 70 has a shape, and in one embodiment of the invention, the shape of the silencer seeds is uniform for each of the silencer seeds in the array 72, although it will be appreciated that the shape of the silencer seeds 70 may vary and differentiate for each of the plurality of silencer seeds. For example, the shape of each of the plurality of silencer seeds 70 may comprise a segmented cylinder, a horizontal segmented cylinder, a hemisphere, or other segmented geometry. In one embodiment of the invention, each of the plurality of silencer seeds 70 comprises a horizontal segmented cylinder.
Each of the plurality of silencer seeds 70 in the array 72 has a surface area, and each of the silencer seeds in each successive row R1 through RT of the array increases progressively in surface area from one row to the next from the leading edge 60 to the central hub 54. Thus, the array 72 essentially forms a pyramid or an array of ascending height as the rows RT of the array extend from the leading edge 60 toward the central hub 54, with the surface area of the silencer seeds increasing with each row. It will be appreciated that the respective surface areas of the silencer seeds 70 within each row RT of the array 72 may differ, although the surface area of each of the plurality of silencer seeds 70 may be substantially equal within each row RT of the array 72.
In one embodiment of invention, the silencer seeds comprise a horizontal segmented cylinder configured in a triangular shaped array 70 having three rows of silencer seeds. The first row, R1, comprises a single silencer seed 70 having a surface area of 0.0062 in2 (0.003999992 mm2) and a perimeter of 0.3229 in (8.20166 mm), wherein the total number of protrusions P equals 1. The second row, R2, comprises two silencer seeds 70, each having a surface area of 0.0078 in2 (0.005032248 mm2) and a perimeter of 0.3614 in (9.1796 mm), wherein the total number of protrusions P equals 2. The third row, R3, comprises three silencer seeds 70, each having a surface area of 0.0093 in2 (0.02332 mm2) and a perimeter of 0.3958 in2 (10.0533 mm), wherein the total number of protrusions P equals 3. The increasing surface area of the silencer seeds 70 comprising each row RT in the array 72 provides a shape of ascending height as the array progresses from the leading edge 60 of the blade 50 toward the central hub 54.
The distances between each of the plurality of silencer seeds 70 in the array 72 may be identical, or the distances may vary. For example, the distance between the each of the plurality of silencer seeds 70 within the same row R1 may be identical (a) with respect to each other in the same row R1 and (b) with respect to the silencer seeds 70 within the subsequent row R2. Alternatively, the distance between the silencer seeds 70 within the same row R1 may differ from the distance between the plurality of silencer seeds 70 in row R2. In one embodiment of the invention, the distance between the silencer seeds 70 in rows R1 and R2 is smaller than the distance between the silencer seeds 70 in rows R2 and R3. In another embodiment of the invention, the silencer seeds 70 are uniformly spaced within the array 72 a substantially uniform distance with respect to each of the silencer seeds 70 within each row R and with respect to each of the silencer seeds 70 within each successive row R1+N. In one embodiment of the invention, the distance between each of the silencer seeds 70 within the array 72 is approximately 0.6250 in (15.875 mm).
The effectiveness of the silencer seeds 70 is demonstrated by the monopole source contour illustrated in
As shown in
Fan manufacturers unanimously attempt to lower sound pressure levels generated by their fans during operation. However, it is seen in the industry that many of the features added to the axial blade design end up also lowering the performance of the fan; in other words, the volumetric flow rate moved by the fan at a particular static pressure is lowered. Thus, the capability of the fan “shrinks” in order to lower the sound pressures generated by the fan blades. Designs that alter the outer contour of the blade, especially those that deviate from a smooth contour in order to lower sound generation, tend also to significantly affect the fan performance negatively. The subject invention is able to lower sound pressure levels without dramatically altering the blade and fan performance.
The fan 14 of the present invention rotates at up to speeds of 1200 RPM, which, without support, may cause the plurality of blades 40 to mechanically undergo forces that potentially deform the shape of the blade and, consequently, alter the performance of the blade from its intended design. If the deformation of the blade 40 during operation of the fan 14 is drastic, the performance of the blade will be impacted and suffer in comparison to the intended design.
Blade deflection is a function of the modulus of elasticity of the material comprising the blade 40 along with the rotational speed. Plastic has a significantly lower modulus of elasticity than that of most metals. Thus, a plastic design will deflect significantly more than an identically shaped metal design at the same speed. Consequently, it is critical to design the plastic fan with features that lower blade deflection during operation to ensure the blade performs as intended.
As shown in
Tests conducted using finite element-based computer simulations and physical verifications of models show that a plastic fan with two concentric, circumferential layers 80 and 82 provides significant additional support to the plurality of blades 40 during operation of the fan 14 and preserve the performance of the blades 40. As shown in
Through advanced finite element-based computer simulations and physical verifications of models, it was found that a plastic fan that has two circumferential layers provided significant additional support to the blades during operation. This allowed to minimize blade deflection and preserve the performance of the blade as it was intended. By conducting finite element analyses on the blade design, the overall blade deflection during operation was quantifiable. Without the dual layered hub, the maximum deflection was approximately 10 mm. With this feature, this value is reduced by 70% as seen below. The greyed-out portion overlapping is the undeflected blade shape.
The method and operation of the invention will now be explained. The foregoing description of the invention is incorporated herein. The invention comprises a method of lowering sound pressure generation during operation of a heating ventilation and air conditioning refrigeration system comprising a propeller fan having blades, the method comprising the step of reducing dipole source strength as air passes over the blades during operation of the fan. The method further comprises the step of reducing dipole source strength further comprises the step of providing a plurality of protrusions at a leading edge of a suction side of at least one of the blades. The method further comprising the step of arranging the plurality of protrusions in an array comprising a plurality of rows. The method further comprises the step of increasing the surface area of the plurality of protrusions in each successive row comprising the plurality of rows. The method further comprises the step of arranging the plurality of protrusions in a pyramidal array.
The invention comprises a method of reducing deflection of blades of a propeller fan having a plurality of blades, the method comprising the step of configuring the plurality of blades in a concentric configuration around a central hub wherein the central hub comprises at least two circumferential layers. The method may further comprise the step of providing a connecting rib between the two circumferential layers. The method may further comprise the step of providing circumferential layers of the central hub in a concentric arrangement.
The present invention allows modularity of the fan components and offers benefits related thereto. The type and size of the motor for use with the propeller fan assembly of the present invention can be altered according to the application, to meet changing conditions and requirements or for convenience during maintenance. An illustrative example of a method for assembling the propeller fan 14 is provided. To assemble a one HP condenser fan, with annual usage of approximately 28000 hours across rooftop unit products, the following components or equivalents are may be used:
The mounting plate 104 comes with four push pins to hold the motor connection component 100 together. These pins should not be removed at any point. The mounting plate 104 has been created to accommodate these pins. Place the motor connection component 100 such that the four push pins align with and go through the four slots 108 on the mounting plate 104. On the outer holes of the motor connection component, use a drill to fasten screws with a minimum torque of 61 in-lbs. Ensure that the screws have gone all the way and there is a tight fit between the motor mount component 100 and mounting plate 104. Place the motor 34 under the motor mount component 100 and have the four motor throughbolts go through four slots 108 in the mounting plate 104. Add four washers to the motor throughbolts now. Add four nuts on top of the washers (one nut per washer) and tighten the nuts to a maximum torque of 9 in-lb2. Ensure there is a tight fit between the nuts and the mounting plate 104. Using a tool as a set-handle, rotate the motor shaft 43 until the flat part of the motor shaft is in line with the fan setscrew hole. Once the fan setscrew hole and the motor flat are in line, drop the blades 40 on the motor shaft 43 and let them slide down as far as it will go, until the motor shaft head stops the fan. Ensure the fan setscrew hole is in line with the motor shaft flat. Add the setscrew to the fan insert, ensuring that it is setting on the motor shaft flat and tighten the setscrew until it reaches 65 in-lbs. Give the fan a quick spin by hand and visually ensure the fan is rotating with the motor shaft. Place the grill 32 on top of this assembly. The horizontal rods must be under the spiral rods. Using four plastic-special screws, tighten all four holes to a torque of 20 in-lb. Ensure the grill 32 has a tight fit with the orifice. The invention employs a unique assembly method that allows for wide flexibility and permits use of motors 40 of different types and sizes seamlessly with this propeller fan assembly 36.
It now will be appreciated that the present invention reduces sound generation, without limiting fan performance, through the provision of silencer seeds, strategically arrayed, shaped and sized, on the suction side proximate the leading edge of at least one blade of the fan. The invention also presents a mounting assembly for mounting the fan blades to the motor, which enables the use and interchange of a variety of sizes and types of motors with the invention. Further, the present invention minimizes blade deflection and preserves the performance of the blade as it was intended. Circumferential, concentric layers at a central hub provide significant additional support to the blades during operation and minimize blade deflection.
The invention has been described above both generically and with regard to specific embodiments. Although the invention has been set forth in what has been believed to be preferred embodiments, a wide variety of alternatives known to those of skill in the art can be selected with a generic disclosure. Changes may be made in the combination and arrangement of the various parts, elements, steps and procedures described herein without departing from the spirit and scope of the invention as defined in the following claims.
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