REINFORCED MEMBRANE SYSTEMS

A fiber de-gassing membrane includes a plurality of membrane fibers. At least one of the membrane fibers has a first stiffness. The membrane includes reinforcing fibers. The reinforcing fibers are positioned adjacent to at least one of the membrane fibers. The reinforcing fibers have a second stiffness. The second stiffness is greater than the first stiffness.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to fiber membranes and more particularly to fiber membrane cartridges used in fuel deoxygenation systems.

2. Description of Related Art

For purposes of fuel deoxygenation, devises based on membrane fibers are commonly applied in industry. The deoxygenation function is largely performed by cartridges consisting of interwoven membrane fibers. These membrane fibers usually consist of a polymeric thick hollow fiber with coated membrane. The coating allows penetration of O2via solution-diffusion and subsequent transport through pores and the hole in the fiber. In spite of efficiency of this deoxygenation implementation, there are risks of fuel leakage through the membrane, especially when the membrane fibers are subject to more aggressive load and thermal conditions or/and during longer service. Due to load (e.g., internal pressure) and thermal (e.g., temperature variation and associated thermal expansion) conditions, the membrane fibers are subjected to local loads, mainly axial local loads, which increase risk of local damage in individual membrane fibers. Increased number and sizes of these micro-damages can increase risk and severity of fuel leakage. If there are local micro-damages in either coating or polymeric fibers, applied axial load can accelerate growth of such micro-damages or initiation of new ones, ultimately increasing the risk of fuel leakage.

The conventional techniques have been considered satisfactory for their intended purpose. However, there is an ever-present need for improved membrane cartridges, i.e., reduction of risk of fuel leakage. This disclosure provides a solution for this need.

SUMMARY

A fiber de-gassing membrane system includes a plurality of membrane fibers each defining a longitudinal membrane fiber axis. At least one of the membrane fibers has a first stiffness in a longitudinal membrane fiber axis direction. Reinforcing fibers positioned adjacent to at least one of the plurality of membrane fibers. The reinforcement fibers each define a longitudinal reinforcing fiber axis. At least one of the reinforcing fibers has a second stiffness in a longitudinal reinforcing fiber axis direction. The second stiffness is greater than the first stiffness.

In some embodiments, the reinforcing fibers include a carbon, glass, and/or organic fiber. The reinforcing fibers can include an impregnated polymeric matrix, e.g., a first polymeric matrix. The membrane fibers can be impregnated with a second polymeric matrix. The second polymeric matrix can be the same as the polymeric matrix used for impregnation of reinforcing fibers. At least one of the reinforcing fibers can be positioned adjacent to and/or abutting at least one of the plurality of membrane fibers. At least one of the reinforcing fibers can be parallel with at least one of the plurality of membrane fibers. The at least one reinforcing fiber can be configured and adapted to provide re-distribution of local axial stresses in the at least one membrane fiber arranged parallel to the at least one reinforcing fiber.

At least one of the reinforcing fibers can be positioned parallel to a longitudinal axis of the membrane system. At least one of the reinforcing fibers can be positioned at an angle α relative to a longitudinal axis of the membrane system. The angle can be an absolute angle 80 degrees or more relative to the longitudinal axis or −80 degrees or less relative to the longitudinal axis of the membrane. At least one of the reinforcing fibers can be positioned parallel to a longitudinal axis of the membrane system, radially outward from the plurality of membrane fibers. At least one of the reinforcing fibers can be positioned parallel to a longitudinal axis of the membrane system, radially inward from the plurality of membrane fibers. At least one of the reinforcing fibers can be spirally wrapped radially outward from the plurality of membrane fibers. At least one of the reinforcing fibers can be spirally wrapped radially inward from the plurality of membrane fibers.

The angle can be an absolute angle 15 degrees or less relative to the longitudinal axis of the membrane system, or −15 degrees or more relative to the longitudinal axis of the membrane system. The angle between the reinforcing fibers and the longitudinal axis of the membrane system can be greater than 20 degrees and less than 75 degrees. Similarly, the angle between the reinforcing fibers and the longitudinal axis of the membrane system can be less than −20 degrees and greater than −75 degrees.

In accordance with another aspect, a method of assembling a fiber de-gassing membrane system includes winding a plurality of membrane fibers. Each membrane fiber defines a longitudinal membrane fiber axis. At least one of the membrane fibers has a first stiffness in a longitudinal membrane fiber axis direction. The method includes adding reinforcing fibers adjacent to at least one of the plurality of membrane fibers. Each reinforcing fiber defines a longitudinal reinforcing fiber axis. The reinforcing fibers have a second stiffness in a longitudinal reinforcing fiber axis direction. The second stiffness is greater than the first stiffness.

In some embodiments, the method includes winding the reinforcing fibers adjacent to the membrane fibers concurrently with winding the membrane fibers. Adding the reinforcing fibers can include winding at least one of the reinforcing fibers adjacent to at least one of the plurality of membrane fibers concurrently with winding the plurality of membrane fibers. Winding at least one of the reinforcing fibers can include winding the reinforcing fibers parallel to at least one of plurality of membrane fibers. Adding reinforcing fibers can include positioning at least one of the reinforcing fibers in at least one of a circumferential direction or an axial direction in a reinforcing layer at least one of radially inward or radially outward from the plurality of membrane fibers.

DETAILED DESCRIPTION

Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, a schematic view of an exemplary embodiment of the fiber de-gassing membrane system with reinforcing fibers positioned within a fuel deoxygenation systems is shown inFIG.1and is designated generally by reference character100. Other embodiments of the fiber de-gassing membrane system in accordance with the disclosure, or aspects thereof, are provided inFIGS.2A-5as will be described. The systems and methods described herein can be used to provide stress reduction in the fiber axial direction the absorbent interwoven membrane fibers in their axial directions, of a membrane in a fuel de-oxygenation system. Non-membrane reinforcement fibers are introduced to a membrane and help to relieve the load in the absorbent membrane fibers. By subjecting the absorbent membrane fibers to less stress, fuel leakage through the membrane is minimized.

As shown inFIGS.1-2B, a fuel deoxygenation system10includes a fiber de-gassing membrane system100. Fiber de-gassing membrane system100includes a combination of membrane fibers104. The membrane system100includes reinforcing fibers106. Reinforcing fibers106are positioned adjacent to the membrane fibers104. Reinforcing fibers106are interwoven with the membrane fibers104parallel to membrane fibers104. Each membrane fiber104defines a longitudinal membrane fiber axis M. Each membrane fiber104has a first stiffness in a direction aligned with its longitudinal membrane fiber axis. Each reinforcing fiber106defines a longitudinal reinforcing fiber axis R. The reinforcing fibers106have a second stiffness in a direction aligned with its longitudinal reinforcing fiber axis. The second stiffness is greater than the first stiffness. The reinforcing fibers106are configured and adapted to provide re-distribution of local stresses in the direction of respective longitudinal membrane fiber axes between parallelly-arranged membrane fibers104. This re-distribution is aimed to reduce local stresses in membrane fibers in the membrane fiber axial direction, i.e., reduce risk of their damage and associated probability of fuel leakage. Reinforcing fibers106are generally impermeable and therefore do not perform membrane functions but help to relieve axial load in membrane fibers104.

With continued reference toFIGS.1-2B, it is contemplated that reinforcing fibers106include a carbon fiber, a glass fiber, an organic fiber (e.g., Kevlar) material, and/or any other suitable material in a variety of combinations. In some embodiments, the reinforcing fibers106include an impregnated polymeric matrix (e.g., thermoplastics, thermosets, elastomers, etc.). The membrane fibers104can include a polymeric matrix with hollow fiber body111with covered with coating109. The polymeric matrix can be the same as the impregnated polymeric matrix in reinforcing fibers106or different.

The addition of reinforcing fibers106offers a low-cost option to enhance durability of membrane fibers104by reducing membrane micro-damage to coating109, thereby and improving leakage resistance. Those skilled in the art will readily appreciate that interweaving non-membrane “parasitic” tension elements with high stiffness with membrane fibers104, results in a significant re-distribution of local stresses between parallelly-arranged membrane and non-membrane fibers,104and106respectively. In this case, membrane fibers are much less loaded, i.e., have significantly lower risk of micro-damage.

As shown inFIG.3, another embodiment of a fiber de-gassing membrane system200includes a plurality of membrane fibers204. In the embodiment ofFIG.3, membrane fibers204form at least one layer202that can be interwoven with other layers. Membrane system200includes reinforcing fibers206. Orientation of reinforcing fibers206with respect to the longitudinal orientation of the membrane system is defined by angle +α (or −α in the anti-symmetric direction). Membrane system200is similar to membrane system100, except that instead of showing reinforcing fibers206with membrane fibers204in a common layer, or interwoven with membrane fibers204, they make up their own layer201. It is also contemplated that the interwoven layers of membrane system100could be combined with the individual layers201of reinforcing fibers206of membrane system200into the same membrane. In the reinforcing layer201, the reinforcing fibers206are arranged at an angle α relative to longitudinal axis A of the membrane system200. Angle α between the reinforcing fibers206and the longitudinal axis is greater than 20 degrees and less than 75 degrees. Similarly, this angle α between the reinforcing fibers206and the longitudinal axis A can be less than −20 degrees and greater than −75 degrees.

With reference now toFIG.4, membrane system200is the same as membrane system200ofFIG.3. In the embodiment ofFIG.4, reinforcing fibers206are arranged in an axial direction, extending from one end of the membrane system200to the other. Fibers206are shown grouped into a layer203of reinforcing fibers206, however those skilled in the art will readily appreciate that reinforcing fibers206can be interwoven with membrane fibers204as well. In all of the embodiments forFIGS.3-5, the membrane fibers204have a first stiffness in a membrane fiber axis direction and the reinforcing fibers206have a second stiffness in a reinforcing fiber axis direction. The second stiffness is greater than the first stiffness. The reinforcing fibers206can be radially inward or radially outward from membrane fibers204. In the embodiment ofFIG.4, the angle α is an absolute angle 15 degrees or less relative to the longitudinal axis. Similarly, this angle α can be an absolute angle −15 degrees or greater relative to the longitudinal axis.

As shown inFIG.5, membrane system200is the same as membrane system100ofFIG.3, except that reinforcing fibers206are arranged at an angle α relative to longitudinal axis A of the membrane that is in the hoop direction, e.g., substantially circumferential. InFIG.5, the reinforcing fibers206are shown grouped together in a reinforcing layer205. InFIG.5, the angle α is an absolute angle 80 degrees or more relative to the longitudinal axis. Similarly, angle α is an absolute angle −80 degrees or less relative to the longitudinal axis. Similar to above, the membrane fibers204have a first stiffness in their longitudinal membrane fiber axis direction and reinforcing fibers206have a second stiffness in their longitudinal reinforcing fiber axis direction. The second stiffness is greater than the first stiffness.

With continued reference toFIG.5, it is also contemplated that axially arranged reinforcing fibers206, like those ofFIG.4, can be used in the same membrane system200as reinforcing fibers206arranged in the hoop direction, like those ofFIG.5, and/or reinforcing fibers206of layer202ofFIG.3. In conventional membrane layups, the membrane fibers are mainly two-directional, i.e., as +α and −α, where a is typically close to 45 deg. In the case of non-ideal implementations or conditions (imperfections, misalignments, statistical variation, non-uniformity through thickness, etc.) two-directional layups can be associated with considerable local overload due to limited ability of individual fibers to handle stresses other than axial ones. By adding reinforcing fibers206in the hoop direction, axial direction, parallel to existing membrane layers, or in some combination, in addition to [+α/−α] layers102ofFIGS.1-2B, local overload can be reduced.

A method of assembling a fiber de-gassing membrane, e.g., membrane system100or200, includes winding a plurality of membrane fibers, e.g., membrane fibers104or204, around a spool20. Each membrane fiber defines a longitudinal membrane fiber axis. At least one of the membrane fibers has a first stiffness in a direction aligned with its longitudinal membrane fiber axis. The method includes adding reinforcing fibers, e.g., reinforcing fibers106or206, adjacent to at least one of the plurality of membrane fibers. The reinforcing fibers have a second stiffness in a direction aligned with its longitudinal reinforcing fiber axis. The second stiffness is greater than the first stiffness. Adding the reinforcing fibers includes winding the reinforcing fibers in the membrane fibers concurrently with winding the membrane fibers. Winding the reinforcing fibers can include winding the reinforcing fibers parallel with the membrane fibers. Adding reinforcing fibers can include positioning the reinforcing fibers in at least one of a circumferential, axial or oblique direction at least one of radially inward or radially outward from the plurality of membrane fibers.

The methods and systems of the present disclosure, as described above and shown in the drawings, provide for low-cost systems and methods for reducing stress on membrane fibers, thereby reducing fuel leakage, with superior properties including improved reliability and product quality. While the apparatus and methods of the subject disclosure have been shown and described with reference to preferred embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the scope of the subject disclosure.