Patent Application
20070107399
The invention relates to fibrous media coalescers, and more particularly to coalescers having variable properties.
Fibrous media coalescers are known in the prior art for coalescing and separating a medium having two immiscible phases, namely a continuous phase and a dispersed phase. For example: in engine crankcase ventilation systems, and other air-oil separation systems, the continuous phase is air, and the dispersed phase is oil; in fuel-water separation systems, such as fuel filters, fuel is the continuous phase, and water is the dispersed phase; in water-oil separation systems, water is the continuous phase, and oil is the dispersed phase. The invention is particularly well suited for engine crankcase ventilation applications, but may be used in other separation systems having immiscible fluids, e.g. air-oil, fuel-water, water-oil, etc.
The present invention arose during continuing development efforts directed toward coalescers and methods of making same.
In the preferred embodiment, the present system uses melt blowing techniques for making a coalescer in accordance with the invention. Melt blowing techniques for particulate filters are known in the prior art, for example U.S. Pat. No. 6,860,917, 3,755,527, incorporated herein by reference. Referring to
In one aspect, the present application provides a method for producing essentially continuous, long fibers of polymer with varying diameter by a melt blown process. The fibers are wound into a form of defined shape to produce the coalescer element with graded fiber diameter and porosity characteristics. The coalescer coalesces a medium having two immiscible phases, namely a continuous phase and a dispersed phase. The continuous phase flows from upstream to downstream. The coalescer element is provided by fibrous media capturing droplets of the dispersed phase, coaslescingly growing the droplets into larger drops which further coalesce and grow to form pools that drain. In one preferred embodiment, it is desirable for the coalescer media properties to vary as a function of depth. In coalescer applications such as crankcase ventilation coalescers, mist removal filters, fuel water coalescers, and oil water separators, it is desirable in one preferred embodiment for porosity and/or fiber diameter to decrease with increasing distance into the media, reaching a minimum at mid depth, i.e. somewhere between the upstream and downstream ends, and then for the porosity and/or fiber diameter to increase and become more open with further increasing distance into the media from mid depth to downstream, approaching the downstream face. This U-shaped profile is further described hereinafter, e.g.
A variety of methods have been used to vary coalescer media properties as a function of depth. For example, different media layers can be stacked to obtain such effect. Coalescing filters, for example, are constructed of an inner, high efficiency coalescing layer, and an outer, coarser drainage layer. In some applications, multiple layers, e.g. perhaps as many as seven distinct layers, are used to achieve the noted benefits. Typically, this may be done by rolling or pleating different media sheets together in layers or by melt blowing, including melt spinning, different layers on top of one another. Each layer may consist of a different material to be obtained and handled in production. Each layer may require a different step and/or piece of equipment for handling and production. Transitions between layers tend to be abrupt or exhibit a step function change, which can result in corresponding discontinuities in fluid flow and may result in increased restriction and reduced life and capacity.
In one aspect of the present application, a method is provided for producing coalescer elements, including for crankcase ventilation and mist removal coalescers, and for other types of coalescers using fibrous coalescer media in which it may be desirable to vary fiber diameter and/or porosity as a function of depth into the coalescer. Fibers are created of essentially continuous length by melt blowing from a suitable thermoplastic polymer, for example those noted above. The fibers are collected onto a turning/spinning/rotating mandrel or other suitable collector of suitable cross-sectional shape, e.g. circular, oval, elliptical, racetrack, triangular, rectangular, diamond, trapezoidal, star-shaped and so on. In one aspect, the diameter of the individual fibers is varied as they are produced to create long fibers that have different diameters at different points along their length. In a further aspect, the diameter of the fibers is controlled as they are produced relative to the thickness of the coalescer media being formed on the mandrel in order to create a coalescer element with coalescer media properties, e.g. fiber diameter and/or porosity that vary as a function of depth. In another aspect, the collector, or mandrel, and the melt blowing die are moved relative to one another in a one, two or three dimensional manner.
Porosity can also be controlled by applying pressure to the media.
Fiber diameter is also a function of the types of thermoplastic polymer introduced into the hopper. This can be used to advantage to create higher performance coalescer elements. For example, by mixing pellets of two or more different types of compatible polymers, for example two polyesters with different melting points, in the hopper, and melt blowing the resultant mixture, fibers of two or more different diameters, chemical and physical characteristics can be simultaneously melt blown and laid down at the same location with respect to depth in the element. If for example, the two polymers have different melting points, one will cool faster than the other, and the one with the lowest melting point will bond strongly to the other type and increase the overall strength and structural integrity of the media, while creating a bi-modal fiber diameter distribution, with the fiber diameter of each mode varied during fiber production. Similarly, restriction and removal, for example, can be optimized by blending a small percentage of a polymer that yields large diameter fibers with a higher percentage of a polymer that yields finer fibers. Alternatively, the structural integrity of the element, for example, can be increased by blending a small percentage of a polymer that yields large diameter strong fibers with a higher percentage of a polymer that yields finer fibers better suited to capture fine contaminants but lacking in structural integrity. Drainage of coalesced liquid from a coalescer and reduced restriction may be obtained by blending a relatively highly wetting polymer with a relatively non-wetting polymer. To further optimize coalescer media structure, one could vary the relative amounts of the different types of fibers as a function of depth by controlling the relative amounts of the different polymers in the hopper or being pumped to the die. The combinations produce elements particularly well suited for coalescer applications, including crankcase ventilation filters, mist removal filters, fuel water coalescers, and oil water separators. Such elements coalesce and remove contaminant droplets from the fluid stream. They achieve high removal efficiency, to facilitate drainage of coalesced liquid contaminant, to have high contaminant holding capacity and long service life.
As an example, in a first coalescer embodiment, fibers having at least a bi-modal fiber diameter distribution are wound in a roll as a single sheet but effectively providing multiple layers in an element roll 15 achieving a porosity which varies as a function of depth. The average diameter for the smaller fibers in the fiber distribution is in the range of 0.05 to 10 μm, depending on the efficiency requirements. The function of these fibers is to remove fine contaminant with high efficiency. The coarser fibers have diameters from 20 to 100 μm to facilitate drainage. These elements are made as depth type elements with a minimum thickness of 10 mm. In order to make the elements physically robust and simultaneously generate fibers of two different diameters, two different types of polymers are used, e.g. 95% PBT (polybutyleneterphthalate) polymer and 5% PET (polyethyleneterephthalate) polymer is used. The average fiber density is 1.38 grams per cubic meter, and the average element porosity is greater than 80%. The use in combination of fine and coarse fibers, i.e. an individual fiber with differing diameters at different points along its length, results in high efficiency, good drainage properties, and low droplet re-entrainment. The removal efficiency for a new element is greater than 90% for ultra fine oil mist and soot while testing on a diesel engine in application to crankcase ventilation. The droplet size of oil mist ranges from less than 0.03 μm to 10 μm, while an average diameter is in the range of 0.4 to 1.0 μm. An efficiency of greater than 80% is obtained, even for the oil saturated stage of the coalescing process.
In a second coalescer embodiment example, the same polymer mixture is used to achieve a bi-modal distribution, however the distance between the die and collector mandrel is decreased at the beginning of coalescer element production (e.g. near the center 15a of an annular element 15 adjacent the mandrel), then gradually increased near the middle of element production, e.g. mid depth 15b for the media, and then decreased again near the end of the element production, e.g. at the outer portion 15c of the annular element. This is achieved by moving the die 3 and mandrel 9 relative to one another in the X direction. Simultaneously, the die 3 and mandrel 9 may be moved relative to one another in the Z direction to achieve a desired fiber orientation. This results in an element structure with coarser fibers of both types near filter face 15a to facilitate removal of coarser contaminants, but not finer contaminants, at the upstream side of the element when used in an inside-out flow geometry. Fiber diameter is at a maximum at regions 15a and 15c, and is at a minimum at region 15b. Fiber diameter decreases from region 15a to 15b, and then increases from region 15b to region 15c. Porosity is at a maximum at regions 15a and 15c, and is at a minimum at region 15b. Porosity decreases from region 15a to region 15b, and then increases from region 15b to region 15c. Fiber diameter and porosity vary as a function of distance outwardly from mandrel 9, i.e. vary as a function of filter depth from region 15a to region 15b and from region 15b to region 15c. This is illustrated in
The noted U-shaped profile 23,
The above examples note annular element rolls having a closed loop shape, e.g. circular, oval, elliptical racetrack, triangular, rectangular, diamond, trapezoidal, star-shaped, and so on. In some applications, packaging or other reasons may dictate other shapes or open shapes, such as flat panel configurations. These may be made from the noted closed loop annular shape by cutting or splitting the resultant element axially along a plane parallel to the axis of the annulus to provide a panel element or the like or otherwise obtain a desired cross-section.
In the present system, the diameter of individual fibers of the coalescer is controlled and varied along the length of the fiber. Fiber diameter, pore size and/or porosity are varied as a function of depth in the coalescer element and is accomplished using the same media and same media sheet, i.e. the same media and media sheet is used to obtain a wide range of properties. Fiber diameter, pore size and/or porosity may be varied continuously and gradually, eliminating the noted step-changes in media properties as a function of depth and avoiding the corresponding discontinuities in fluid flow velocity and pressure drop characteristics within the element, resulting in longer lasting elements. The noted gradual continuous changes may be achieved by varying and controlling the melt blown production parameters, including for example the distance between the die and mandrel/collector, the relative position of the die and mandrel to one another, polymer throughput, air pressure, flow rate, mandrel/collector speed, and temperature. Media properties as a function of depth may be varied and controlled by moving the die and collector relative to one another in the X, Y and/or Z directions. The system combines concepts to produce coalescers wherein fiber diameter, pore size and/or porosity vary as a function of depth giving performance advantages. There is no need to produce separate multiple layers in serial fashion, whether each layer is produced independently by different melt blowing machines and the unfinished element is transferred from machine to machine, or whether layering is accomplished by aligning multiple dies in serial fashion along the Z direction and continuously producing tubular elements that grow or progress in the same Z direction, with the finished element cut to length after the last die, with each die in the series producing a different layer with its own properties.
The present system provides a method of making a coalescer element 15 by melt blowing a plurality of polymer fibers 7 onto a collector 8, and during the melt blowing, varying the diameter of individual fibers along their length such that an individual fiber has differing diameters at different points along its length. Fibers 7 are melt blown from die 3 ejecting melted polymer through spinnerets 6 to produce the fibers. Fiber diameter is varied along the length of the fiber during fiber production. Collector 8 is spaced from die 3, and in one embodiment fiber diameter along the length of the fiber is varied during fiber production by varying the spacing between collector 8 and die 3. When collector 8 is a rotating mandrel 9 in such embodiment, fiber diameter is varied along the length of the fiber during fiber production by varying the relative position of die 3 and mandrel 9 relative to one another along at least one of the X and Y axes. In another embodiment, fiber diameter is varied along the length of the fiber during fiber production by varying polymeric throughput through spinnerets 6. Polymer is ejected through spinnerets 6 into a pressurized gas stream, as noted above, to produce fibers 7. In another embodiment, fiber diameter is varied along the length of the fiber during fiber production by varying at least one of the gas pressure and gas flow rate. In another embodiment when collector 8 is a rotating mandrel 9, fiber diameter is varied along the length of the fiber during fiber production by varying the speed of rotation of mandrel 9. In another embodiment, fiber diameter is varied along the length of the fiber during fiber production by varying the temperature of the melted polymer. In another embodiment, two polymers are used simultaneously in the die to produce a bi-modal fiber distribution, with fiber diameter of each mode being varied as above described. In one embodiment, the two polymers have different melting points. In the preferred embodiment of the noted methods, fiber diameter is varied along the length of the fiber during fiber production while the fibers are being melt blown from die 3.
When collector 8 is a rotating mandrel 9, the rotating mandrel collects and rolls fibers 7 into an annular element roll 15 having an inner region 15a at the mandrel, and having an outer region 15c spaced radially outwardly of inner region 15a by the radial thickness of the element roll. Element roll 15 has a depth dimension along such radial thickness. Fiber diameter is varied along the length of the fiber during fiber production such that fiber diameter varies as a function of element depth. In one embodiment, as noted, fiber diameter is varied along the length of the fiber during fiber production to provide a first annular region such as 15a of a first fiber diameter, and a second annular region such as 15b and/or 15c of a second fiber diameter different than the first fiber diameter and of the same individual melt blown fiber. An individual fiber is melt blown from die 3. Such individual fiber is rolled on mandrel 9 to form the noted first annular region. The same such given individual fiber is rolled on the first annular region to form a second annular region such as 15b, and the same such given individual fiber is further rolled on second annular region 15b to form a third annular region such as 15c, and so on as desired. The given individual fiber is rolled at the noted first diameter in first annular region 15a, then the fiber diameter of the same such given individual fiber is gradually varied to a second diameter, and then the same such given individual fiber is rolled at such second fiber diameter in second annular region 15b, and so on. The given individual fiber may be rolled in other annular regions in sequential steps but still rolling the same such given individual fiber, thus providing the noted continuity and gradual changes and avoiding the above noted step-change discontinuities. The change in diameter of the given individual fiber occurs gradually during melt blowing, and the change from region to region across the radial thickness and depth of the element is gradual.
One of the inner and outer regions 15a and 15c is at an upstream surface, and the other of the inner and outer regions 15a and 15c is at a downstream surface. The direction of flow is from upstream to downstream. For example, in an inside-out flow geometry, region 15a is at the upstream surface, and region 15c is at the downstream surface. In an outside-in flow geometry, outer region 15c is at the upstream surface, and inner region 15a is at the downstream surface. In one embodiment, as above noted, fiber diameter is varied along the length of the fiber during fiber production to vary fiber diameter as a function of element depth such that fiber diameter decreases with increasing depth into the element along the flow direction. Further in such embodiment, the fibers are rolled such that porosity also decreases with increasing depth into the element along the flow direction. In another embodiment, fiber diameter along the length of the fiber is varied during fiber production to vary fiber diameter as a function of element depth such that fiber diameter increases with increasing depth into the element along the flow direction. Further in such embodiment, the fibers are rolled such that porosity also increases with increasing depth into the element along the flow direction. In another embodiment, fiber diameter along the length of the fiber is varied during fiber production to vary fiber diameter as a function of element depth such that fiber diameter decreases with increasing depth into the element along the flow direction from upstream to mid depth 15b, and then increases with increasing depth into the element along the flow direction from mid depth 15b to downstream. These characteristics are shown in
The system further provides a method of making a coalescer by melt blowing a plurality of polymer fibers onto a collector, and during the melt blowing, controllably varying the porosity of the coalescer formed by the fibers, e.g. by varying fiber diameter as above described and/or by the noted rolling. In one embodiment, porosity decreases with increasing depth into the coalescer. In another embodiment, porosity increases with increasing depth into the coalescer. In another embodiment, porosity decreases with increasing depth into the coalescer from upstream to mid depth 15b, and then increases with increasing depth into the coalescer from mid depth 15b to downstream,
The present system and method provides a coalescer having a plurality of melt blown fibers wherein the diameter of an individual fiber varies along the length of the fiber such that an individual fiber has differing diameters at different points along its length. Fiber diameter is varied along the length of the fiber to provide an individual fiber having differing diameters at different points along its length such that fiber diameter of such individual fiber varies as a function of coalescer depth. The coalescer has a first region such as 15a of a first fiber diameter, a second region such as 15b of a second fiber diameter different than the first fiber diameter and of the same individual melt blown fiber, and so on. As above noted, the change in fiber diameter is gradual to avoid the noted discontinuities and step-changes and the noted disadvantages inherent therein. In one embodiment, fiber diameter varies along the length of the individual fiber to vary fiber diameter as a function of element depth such that fiber diameter along the individual fiber decreases with increasing depth into the element. Further in such embodiment, porosity also preferably decreases with increasing depth into the element. In another embodiment, fiber diameter varies along the length of the individual fiber to vary fiber diameter as a function of element depth such that fiber diameter along the individual fiber increases with increasing depth into the element. In such embodiment, porosity also preferably increases with increasing depth into the element. In another embodiment, fiber diameter varies along the length of the individual fiber to vary fiber diameter as a function of element depth such that fiber diameter along the individual fiber decreases with increasing depth into the element from upstream to mid depth 15b, and then increases with increasing depth into the element from mid depth 15b to downstream,
The system and method also provides a coalescer having a plurality of melt blown fibers, with the coalescer having an upstream surface spaced from a downstream surface by a depth dimension therebetween, with the coalescer having a first depth region of a first porosity, and a second depth region downstream of the first depth region and of a second porosity different than the first porosity and of the same individual melt blown fiber of the first region. As above noted, the change is gradual to avoid the noted disadvantages of discontinuities or step-changes. In one embodiment, porosity decreases with increasing depth into the coalescer element. In another embodiment, porosity increases with increasing depth into the element. In another embodiment, porosity decreases with increasing depth into the element from upstream to mid depth 15b, and then increases with increasing depth into the element from mid depth 15b to downstream,
It is expected that numerous of the above techniques may also be applied to particulate filters. For example, in a solids filter embodiment, the same polymer mixture may be used to achieve a bi-modal distribution, and the distance between the die 3 and mandrel 9 is increased at the beginning of element production at region 15a, then gradually decreased as the diameter of the element and the thickness of the media increases from region 15a to region 15b and 15c. As in the above example, this is accomplished by moving die 3 and mandrel 9 relative to one another in X and Z directions. This results in an element structure with finer fibers of both types in region 15a to facilitate the removal of fine particles at the downstream side of the element for outside-in flow geometry, and coarse particle and sludge removal by coarse fibers at the upstream side 15c in such outside-in flow geometry. Fiber diameter is at a minimum at region 15a and gradually increases to an increased fiber diameter at region 15b and continues to increase to a maximum fiber diameter at region 15c. Porosity is at a minimum at region 15a and increases to a higher porosity at region 15b and continues to increase to a maximum porosity at region 15c. Fiber diameter and porosity thus change as a function of distance from mandrel 9, i.e. as a function of radial thickness and filter depth dimension. This results in a net lowering of the total restriction across the filter element because restriction and efficiency gradually increase as the fluid penetrates further into the element. The gradual change in both fiber diameter and porosity avoids the flow and contaminant build-up discontinuities inherent in multi-media filters of multiple layers or sheets of different filter media of different fiber diameter and/or porosity. The noted gradual change eliminates step-change discontinuities and reduces restriction and increases service life.
It is recognized that various equivalents, alternatives and modifications are possible within the scope of the appended claims.
