Patent Application
20210046433
The present disclosure relates to fluid agitation. More particularly, the present disclosure relates to devices and methods for agitating liquids. Still more particularly, the present disclosure relates to devices and methods for gas dispersion within a liquid. Still more particularly, the present disclosure relates to a particular impeller geometry for gas dispersion in a liquid.
The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Gas dispersion may involve introducing gas into a liquid below an impeller and relying on the impeller to disperse the gas into the liquid as the gas rises to the level of the impeller. For purposes of discussion, the impeller may be assumed to be arranged in a substantially horizontal rotation plane above a gas entry point and the impeller's driving shaft may be assumed to be arranged along a vertical axis. In contrast to axial flow impellers, the goal of the gas dispersion impeller may be to disperse the incoming gas rather than merely pump it in an axial direction. Accordingly, and historically, a disc-type impeller was often used to control the flow of gas and arrest its upward motion. The disc-type impeller included perpendicularly arranged plate-shaped blades for forcing the gas in a radial direction with the goal of dispersing it within the liquid. Later developments substituted semi-circular cup-shaped blades for forcing the gas in a radial direction. Still later developments substituted parabolic cup-shaped blades for forcing the gas in a radial direction.
The presently known systems for gas dispersion require relatively sophisticated fabrication techniques to create the semi-circular and/or parabolic cups and to attach those cups to a circular plate. Moreover, once fabricated, the angle of attack of the upper and lower portions of the cups relative to one another are defined and variations from that relationship are generally not available.
In one or more embodiments, a gas dispersion system may be provided. The gas dispersion system may include a drive shaft having a proximal end operably coupled to the drive mechanism, extending to a distal end, and configured to transfer rotational motion and torque. The gas dispersion system may also include a mixing element arranged at or near the distal end of the drive shaft. The mixing element may include a hub and a plurality of blade pairs. The blade pairs may include an upper blade and a lower blade secured to the hub and the blades may cantilever freely and generally radially away from the hub.
In one or more embodiments, a mixing element for gas dispersion operations may be provided. The mixing element may include a hub and a plurality of blade pairs. The blade pairs may include an upper blade and a lower blade secured to the hub and the blades may cantilever freely and generally radially away from the hub.
In one or more embodiments including the above described system or the above described mixing element, several additional features may be provided. For example, the upper blade and the lower blade of the plurality of blade pairs may extend along substantially parallel lines. In another example, the upper blade and the lower blade of each of the plurality of blade pairs may be arranged at substantially the same circumferential position on the hub. In still another example, each blade of the plurality of blade pairs may have a leading edge and a trailing edge and the distance between the leading edges of the blades of a pair of blades may be greater than the distance between the trailing edges of the blades of a pair of blades. The blades may also have a stiffness sufficient to avoid deflective contact during dispersing operations. The blades may have a decreased angle of attack at the leading edge as compared to the trailing edge. The blades may also include a blade pitch and the amount of pitch may be established by a blade stub arranged on the hub. The pitch of the blades may be equal and opposite between the upper blade and the lower blade and may range from +45 degrees to −45 degrees or from +30 degrees to −30 degrees. The blade shape of the upper blade may be a mirror image of the lower blade. In one or more embodiments, the blades may be tapered so as to have a first width at an outer edge and a second narrower width at an inner edge. In addition, the leading edge may have an arcuate shape and the outer edge may also have an arcuate shape. In one or more embodiments, the blades may extend substantially radially away from the hub or, alternatively, may extend radially away and in a swept back fashion. In one or more embodiments, the system may include a tank configured for arrangement of the mixing element therein and may also include a gas supply for introducing gas into the tank.
While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter that is regarded as forming the various embodiments of the present disclosure, it is believed that the invention will be better understood from the following description taken in conjunction with the accompanying Figures, in which:
The present application, in one or more embodiments, relates to a particular design of a gas dispersion impeller. The impeller may include a hub with substantially radially extending blade pairs. The blade pairs may include upper and lower blades that are attached to the huh that extend relatively or substantially parallel to one another away from the hub and may avoid connection or contact with each other. In one or more embodiments, the blade pairs may mimic the arrangement or shape of a cupped or parabolic gas dispersion blade, but individually, the blades may be more akin to blades of axial flow impellers. The design of the disclosed impellers may reflect a significant simplification in design and may provide for more flexibility in design due to not being tied to a particular cupped or parabolic shape. That is, the separate blades may be arranged relative to one another to create a wider array of blade pair shapes while using a single blade design.
As shown in
A gas supply system 104 may be provided for introducing gas into the tank 102 and into the fluid within the tank or container 102. The gas supply system 104 may include a pressurized gas source (not shown) such as a compressed gas tank or cylinder and/or a compressor or blower, for example. The gas supply 104 may also include a feed line 108 for conveying the gas from the source to a location within the tank 102. The feed line 108 may extend to a bubbler, diffuser, or other gas introduction or addition mechanism 110 within the tank 102. In one or more embodiments, the gas introduction mechanism 110 may be arranged at or near the bottom of the tank 102 so as to introduce the gas below the gas dispersion system 106. Alternatively or additionally, the gas introduction mechanism 110 may be arranged at another position in the tank 102 and multiple gas introduction mechanisms 110 may be provided. In one or more embodiments, the gas introduction mechanism 110 may include a tubular member having gas introduction orifices in a surface thereof. In one or more embodiments, the tubular member may be annularly shaped or another shape may be provided. Alternatively or additionally, the gas introduction mechanism 110 may include a pressurized plenum or space having a perforated plate arranged on a top side thereof. A selected pattern of perforations may be provided in the plenum to introduce gas in a desired pattern, for example. In one or more embodiments, the pressure in the gas introduction mechanism 110 may exceed that of the fluid in the tank or container 102 to avoid flow of fluid into the gas introduction mechanism 110.
The mixing or dispersing system 106 may be arranged on and/or in the tank or container 102 and may be configured for dispersing the gas introduced by the gas supply system 104. The mixing or dispersing system 106 may include a drive portion 112, a drive shaft 114, and a mixing element 116.
The drive portion 112 may include a motor such as an electric motor, a gas powered motor, or another motor for providing rotational power. In one or more embodiments, a direct drive motor, an offset drive motor, a gear reducing motor, a belt driven motor, or other motors may be provided. The drive portion 112 may be connected to a drive shaft 114 and may operate to rotate the drive shaft 114 at relatively high angular velocities. The drive shaft 114 may extend from the drive portion 112 to a distal end where an impeller or other mixing element 116 may be secured or mounted. The drive shaft 114 may include a cylindrical rod, rectangular rod, a tube, or other relatively stiff and torsionally resistive element such that rotation and torque from the drive portion 112 may be transferred to the mixing element 116. The drive shaft 114 may have a length selected to suitably position the mixing element 116 in the tank or container 102 and at a distance from the drive portion 112.
The mixing element 116 may be arranged on the drive shaft 114 and may be secured to the drive shaft 114 so as to rotate with the drive shaft 114. The mixing element 116 may be configured for rotating within a liquid to stir or mix the liquid in a container or tank 102. More particularly, the mixing element 116 may be configured to disperse gas within a liquid.
As show in
The plurality of blades 120 or blade pairs 122 may be arranged on the hub 118 and may extend radially away from the hub 118. The blades 120 or blade pairs 122 may be configured to interact with the liquid or slurry in a mixing fashion and, in particular, to create flow within the liquid or slurry. The blades 120 may include an inner end 124 and an outer end 126. The blades 120 may be secured to the hub 118 at their inner end 124 and may extend radially outward to an outer end 126. In one or more embodiments as shown in
The above-described crease or bend may create a reduced angle of attack at the leading edge as compared to the trailing edge. A crease or relatively focused bend may be one approach to decreasing the angle of attack at the leading edge. However, other approaches may include a more arcuate blade shape where the bend is less focused and extends over a larger portion of the blade surface. Still other approaches may be used where the crease, focused bend, or more broadly spread bend or arc is positioned closer to or further from the leading edge such that the transition between a decreased angle of attack and a sharper angle attack is closer to the leading edge or further from the leading edge. Still other approaches may include an increased angle of attack at the leading edge instead of a reduced angle of attack.
While a particular blade shape has been described, several blade shapes may be used. For example, in one or more embodiments, a blade 720 may be provided having a substantially rectilinear crease 772 extending along a longitudinal length thereof. That is, as shown in
The leading portion may include a second bend or crease 774 that may be generally linear and extend from a point along the leading edge between the root and tip to a point on the tip that is spaced from the point at which the first crease intersects the tip. The crease may form a bend line for the tip portion, which may be a part of the leading portion and may be generally flat.
Thus, as shown, the leading portion may be substantially flat and may include a tip portion which itself is substantially flat and angled relative to the remainder of the leading portion. As shown, the leading portion may form a camber with the trailing portion at an angle that may be approximately 155°. The tip portion may be angled at an angle of approximately 165° relative to the trailing portion. Put another way, the tip portion may form an angle along a second crease of approximately 13.5 degrees with the remainder of the leading portion.
The plurality of blades 120 and blade pairs 122 may be generally arranged in a rotational plane, or planes, that is substantially perpendicular to the drive shaft 114. In one or more embodiments, the blades 120 of a given pair may include mirror images of one another. The blades 120 of each pair 122 may be secured to the hub 118 at their respective inner ends 124 and both blades 120 may extend radially from the hub 118 generally parallel to one another establishing a plane of rotation passing between the blades 120. The blades 120 may cantilever freely from the hub 118 in a radial direction and, as such, may not be connected to the other blade 120 of the blade pair 121
The blades 120 of each pair 122 may have a blade pitch defined by the blades angular orientation 136 relative to the plane of rotation. The blade pitch may be selected giving consideration to a desired power number, a desired gassed power number, a desired mass transfer rate, and/or other factors. In one or more embodiments, the blade pitch may range from approximately 45 degrees to approximately −45 degrees. In other embodiments, the blade pitch may range from approximately 20 degrees to approximately −20 degrees. In still other embodiments, the blade pitch may range from approximately 10 degrees to approximately −10 degrees. It is to be appreciated that while an equal and opposite blade pitch may be provided for the upper and lower blades, other combinations may be provided where the blade pitch may be opposite, but not equal, for example. In one or more embodiments, an upper blade may have a blade pitch of 20 degrees and a lower blade may have a blade pitch of −10 degrees. Still other ranges of blade pitch may be provided within and/or outside the ranges mentioned and with varying blade pitches on the top or bottom. Most any particular combination of blade pitches may be selected based on the performance desired.
W hen measured as shown in
In contrast to the substantially rectangular blade shape shown in
Other than the differences mentioned, the mixing elements 216, 316 of
In one or more embodiments, the blade pairs may be arranged in a swept back direction. That is, for example, the embodiments shown in
Referring now to
As used herein, the terms “substantially” or “generally” refer to the complete or nearly complete extent or degree of an action, characteristic, property, state, structure, item, or result. For example, an object that is “substantially” or “generally” enclosed would mean that the object is either completely enclosed or nearly completely enclosed. The exact allowable degree of deviation from absolute completeness may in some cases depend on the specific context. However, generally speaking, the nearness of completion will be so as to have generally the same overall result as if absolute and total completion were obtained. The use of “substantially” or “generally” is equally applicable when used in a negative connotation to refer to the complete or near complete lack of an action, characteristic, property, state, structure, item, or result. For example, an element, combination, embodiment, or composition that is “substantially free of” or “generally free of” an element may still actually contain such element as long as there is generally no significant effect thereof.
In the foregoing description various embodiments of the present disclosure have been presented for the purpose of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The various embodiments were chosen and described to provide the best illustration of the principals of the disclosure and their practical application, and to enable one of ordinary skill in the art to utilize the various embodiments with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the present disclosure as determined by the appended claims when interpreted in accordance with the breadth they are fairly, legally, and equitably entitled.
