High-performance fabric for water / diesel separation filter

Abstract

A fabric for a filter for separating water from a water / diesel emulsion, said fabric having a rectangular mesh (11) whose sides (12, 13) are formed by respective threads (26, 27). Compared to conventional water / diesel filter fabrics, the fabric of the present invention offers the advantage of having a high separation efficiency, thereby allowing separation of diesel with a low residual water content downstream of the filter.

Description

Technical Field

[0001] (Background Art) The present invention relates to a high-performance fabric that can be used for a diesel fuel filter that exhibits a function of separating water from a water / diesel emulsion.

Background Art

[0002] For example, diesel such as diesel fuel for automobiles contains water in the emulsion, which is known to be harmful to the life of the injection system and engine efficiency. Therefore, it is necessary to separate the aqueous fraction from the diesel entering the injection system.

[0003] For this purpose, it is known to use a filter including a square mesh fabric sized to stop water droplets. The filter is typically formed from two or three filtration media having different functions, and the fabric which is the subject of the present invention occupies the last filtration stage. The first filtration media is typically a non-woven fabric or paper which performs the function of filtering solid particles. The second filtration media is also made of a similar material, appropriately surface-treated or manufactured in such a way as to obtain a coalescence effect of water droplets dispersed in diesel in order to facilitate the continued blocking of droplets. In either case, inexpensive materials manufactured with randomly distributed fibrous materials and randomly distributed pores are usually used. After the coalescence stage, large droplets precipitate to the bottom of the filter and are discharged there due to the weight difference, while small droplets continue to flow. In order to prevent these droplets from coming into contact with the delicate parts of the vehicle's hydraulic machine circuit, they are blocked by the means of the fabric which is the subject of the present invention representing the third filtration stage. In this case, unlike the previous two stages, in order to reasonably ensure that all droplets larger than the characteristic size of the mesh openings (all identical to each other) are blocked, the use of a precision filtration media with a uniform pore (mesh) size in space and time is preferred. For this reason, a synthetic precision fabric formed of a suitable polymer, appropriately treated and provided with a square mesh is an ideal media for this type of application.

[0004] The problem of separating water from diesel fuel is becoming increasingly important for the following two reasons: 1. The use of substances stabilizing the emulsion in biodiesel, 2. The use of pumps which crush water droplets and reduce their size in order to achieve increasingly high engine performance, as a result of which it becomes more difficult to block them.

[0005] For the purpose of increasing the separation efficiency of a filter, defined as the percentage of water stopped by the fabric relative to the total amount of water present in the water / diesel emulsion reaching the filter, it is known to shorten the length of the side of the square mesh of the fabric used, resulting in a fabric with an ever smaller mesh. Said practice must clearly be adjusted according to the size of the water droplets entering the filtration medium of the fabric.

[0006] There are two ways to reduce the mesh size. The first is to increase the number of threads inserted in the fabric while maintaining the same diameter. The second is to use threads of a larger diameter while using the same number of threads. In both cases, it is clear that the empty to full ratio decreases. Therefore, in order to reduce the mesh size while keeping the empty to full ratio constant, it is considered that the only solution is to increase the number of threads and at the same time decrease the diameter of the threads. However, this seemingly ideal third method has the following two limitations: - Due to technical limitations in the thread processing stage, monofilaments cannot be extruded or woven below a certain diameter; - Due to technical limitations in the weaving stage, the number of threads / cm cannot be increased beyond a certain reference value: if the thread diameter is made smaller, a very small mesh size cannot be obtained. Therefore, beyond a certain reference value, a reduction in the free (empty / full) surface is inevitable.

[0007] The cited conventional practice, i.e., the method of reducing the mesh size based on the above description, has the drawback that the free surface of the mesh also shrinks. In fact, if the square mesh of the prior art is too small or too narrow, the mesh surface is blocked by the body or footprint of the retained droplets, increasing the fluid pressure upstream of the filter or the diesel supply. This type of pressure increase in the diesel supply area can deform the water droplets, push them until they can pass through the mesh, and potentially reduce the separation efficiency of the filter.

[0008] The presence of a narrow mesh further has the drawback of reducing the flow rate of the filtered diesel to the engine and thus reducing its efficiency.

[0009] Therefore, in some cases, the advantages of reducing the mesh size may be nullified by the parallel reduction of the free surface. SUMMARY OF THE INVENTION MEANS FOR SOLVING THE PROBLEM

[0010] The main object of the present invention is to provide a high-performance fabric for a water / diesel separation filter that, unlike known fabrics, has better water / diesel separation efficiency.

[0011] A further object of the present invention is to provide a fabric of the aforementioned type that, while having high separation efficiency, does not pose an obstacle to the desired passage of diesel through the fabric and thus avoids unduly reducing the fuel flow rate or significantly increasing the pressure drop.

[0012] These and other objects are achieved by Subject of claim 1. Preferred embodiments of the invention are disclosed in the remaining claims.

[0013] Compared with the fabric used in conventional water / diesel filters, the fabric of the present invention offers the advantage of having higher separation efficiency and thus enables the separation of diesel with a lower residual moisture content downstream of the filter.

[0014] A further advantage of the fabric of the present invention is that it exhibits high separation efficiency without unduly reducing the diesel flow rate and thus does not impair engine efficiency.

[0015] (BRIEF DESCRIPTION OF THE DRAWINGS) The description of the preferred embodiments of the fabric of the present invention, shown by way of non-limiting illustration in the figures of the accompanying drawings, shows these and other objects, advantages and features.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figures 3-4

Figure 5

Figures 6-7

Figure 8

Figure 9

Figures 10-11

Figure 12

Modes for Carrying Out the Invention

[0017] In the illustration shown in Figure 1, a water / diesel separation filter 1 is illustrated, which has a main body with a filtration fabric 2 accommodated therein.

[0018] As shown in Figure 2, in the operation of the filter, a diesel flow (arrow F1) is carried in the direction of the fabric 2, a diesel flow F2 is obtained on the downstream side, and water droplets 3 present in the upstream flow F1 are filtered.

[0019] In the prior art illustrated in FIGS. 3, 4a, and 4b, the mesh 4 of the fabric 2 is square and is composed of threads 5 that form each side 6 of the square mesh 4.

[0020] The free surface of the prior art mesh 4 illustrated in FIGS. 4a and 4b is calculated as the percentage ratio of the surface of the smaller square 7 formed between the profiles or inner edges of the threads 5 that form the sides 6 of the mesh 4 and the surface of the larger square 8 measured within the range of the center line of the thickness of the threads 5.

[0021] When the prior art mesh 4 receives water droplets 3 having a diameter comparable to the length of the side 6 of the square mesh from the diesel flow F1 to be filtered, the latter's openings are blocked, and only a small portion 10 of the surface of the smaller square 7 of the mesh 4 becomes free for the passage of the diesel flow (FIG. 5).

[0022] As a result of the described phenomenon, there is a possibility of an increase in the fluid pressure in the upstream portion of the fabric 2 (arrow F1 in FIG. 2), which can deform the water droplets 3 and allow them to pass through the mesh 4. In this way, the separation efficiency of the fabric, calculated as the percentage of water blocked by the fabric relative to the total amount of water present in the diesel supplied to the filter, decreases compared to the design value of the filter.

[0023] Furthermore, the blockage of the prior art square mesh 4 increases the pressure drop across the filter fabric, and as a result, the energy required to maintain the same flow rate to the engine increases.

[0024] To overcome these drawbacks, the fabric 25 of the present invention has a rectangular mesh 11 with a long side 12 and a short side 13 (Figure 6). The free surface of the mesh 11 is smaller than the surface of a rectangle 14 measured between the profiles or inner edges of the threads 26, 27 that face the inside of the mesh 11 and form the respective sides 12, 13, and is calculated as a percentage ratio of the surface of a larger rectangle 15 measured within the range of the center lines of the thicknesses of the threads 26, 27. The sides of the rectangular mesh of the fabric of the present invention have a ratio of short side to long side of 0.38 to 1.

[0025] The fabric of the present invention is preferably obtained by weaving threads 26, 27 made of synthetic monofilaments or multifilaments with a diameter of 10 to 90 μm, and the short side of the mesh of the fabric preferably has a length that varies between 5 and 150 μm.

[0026] In the present invention, the threads 26, 27 are formed of synthetic technopolymers belonging to the family of polyester, polyamide, polyaryletherketone, polyphenylene sulfide, polypropylene, perfluorocarbon, polyurethane, or polyvinyl chloride. Alternatively, the threads are made of artificial polymers belonging to the cellulose or viscose family. The fabric of the present invention can also be formed from metal threads.

[0027] When the mesh 11 of the fabric 25 of the present invention receives water droplets 3 having a diameter comparable to the length of the short side 13 of the rectangular mesh 11 from the diesel flow F1 to be filtered, the latter opening is not completely blocked as in the case of the conventional square mesh 4, and when the diesel flow passes through, most of the free surface 16 of the mesh 11 remains unblocked (Figure 8).

[0028] In this way, a dual purpose of allowing the diesel flow to pass through the free portion 16 while retaining the water droplets 3 on the mesh 11 is achieved. This can avoid the pressure increase in the water / diesel emulsion flow F1 where the liquid droplets 3 can be pushed beyond the square mesh 4 when using the prior art fabric 2.

[0029] To provide a higher separation efficiency, the fabric of the present invention can be used as is, or can be subjected to a fluorocarbon or silicone water repellent, and / or a water / oil repellent treatment.

[0030] The yarns 26, 27 forming the fabric of the present invention have a diameter of 10 to 90 μm in one or both of the warp and weft directions. The fabric of the present invention can further be manufactured with a fiber structure that requires a number of yarns per centimeter varying from 23 to 350.

[0031] The fabric can use various textile structures and can be formed using various types or various diameters of yarns for the weft and warp. The mesh openings of the fabric of the present invention can have a short side in the range of 5 to 150 μm.

[0032] According to the present invention, it is further possible to form a rectangular mesh 11 having a short side 13 shorter than the side 6 of the square mesh 4 of the prior art fabric 2, and thus the separation efficiency of the fabric 25 of the present invention can be further increased. The minimum size of the rectangular mesh must be such that a clearly deformed droplet cannot pass through. Similarly, the size of the long side of the rectangle cannot be made infinite. This is clearly because when the droplet is deformed, it tends to pass through the long side of the rectangular mesh. Therefore, the ratio 0.38 to 1 between the size of the short side 13 and the size of the long side 12 of the rectangle 11 is defined within the aforementioned range as a function of the operating parameters of the filter.

[0033] From the description of the present invention, it can be seen that by adjusting the ratio of the long side to the short side of the rectangular mesh within the above range, the following can be obtained: - By making the size of the side of the square and the size of the short side of the rectangle the same, a larger free surface can be obtained compared to the square mesh; for example, when the diameter of the thread is fixed at 24 μm and the side of the square is 18 μm, the free surface is 18%, but when the sides of the rectangle are 18×20 μm, the free surface is 20%. - When the free surface is the same, the short side of the rectangle can be made shorter compared to the size of the side of the square; specifically, when the diameter of the thread is fixed at 24 μm, one side of the square with a free surface of 18% is 18 μm, but the sides of the rectangle with a free surface of 18% are 16×20 μm; - The size of the short side of the rectangle is smaller than the side of the square, and the free surface becomes even larger; specifically, when the diameter of the thread is fixed at 24 μm, one side of the square with a free surface of 18% is 18 μm, but the rectangle with a free surface of 19% has sides of 16×22 μm.

[0034] According to the above, the separation efficiency is inversely proportional to the mesh size and directly proportional to the free surface. According to this, by adjusting the ratio of the long side to the short side of the rectangular mesh to 0.38 - 1, the separation efficiency of the filter can be optimized. For example, a rectangular mesh of 23×25 μm (therefore, the ratio is 0.92) has a separation efficiency of 35% when tested at a specific flux of 3.33 l / h / cm 2 and a droplet size of 20 μm. On the other hand, a rectangular mesh of 15×21 μm (therefore, the ratio is 0.7) has a separation efficiency of 48% when tested at a specific flux of 3.33 l / h / cm 2 and a droplet size of 20 μm.

[0035] Figure 9 shows a diagram of a test bench for measuring the separation efficiency of the prior art fabric 2 and the fabric 25 of the present invention. The separation efficiency is calculated as the percentage ratio of the volume of water blocked from flowing out by the filter fabric to the total volume of water present in the water / diesel emulsion supplied to the fabric.

[0036] The test is carried out in accordance with the ISO16332 standard and requires passing emulsions 17 of water 3 and diesel 9 through filter fabrics 2, 25. The water 18 separated at the upstream stage 19 of the fabric is collected in a suitable measuring device 20.

[0037] The graph shown in Figure 10 shows the results of tests carried out on a prior art fabric 2 with a square mesh and a fabric 25 of the present invention with a rectangular mesh.

[0038] In particular: - The prior art fabric 2 is formed from a square mesh having a size of 18×18 μm and a free surface of the mesh of 18%; - The fabric 25 of the present invention is formed from a rectangular mesh having a size of 15×20 μm and a free surface of the mesh of 22%.

[0039] The test was carried out at a specific water / diesel emulsion flow rate of 30 l / h on samples of the filter fabric with a surface of 9 cm 2 (specific flow rate of 3.33 l / h / cm 2 while varying the droplet size distribution.

[0040] Reference numeral 21 indicates the separation efficiency value achieved by the prior art square mesh fabric 2, and 22 indicates the separation efficiency value of the rectangular mesh fabric 25 of the present invention.

[0041] The tests carried out show the following: - For the droplet distribution at a droplet diameter of 20 μm, the separation efficiency is 45% for the prior art fabric 2 and 51% for the fabric 25 of the present invention; - For the droplet distribution at a droplet diameter of 30 μm, the separation efficiency is 59% for the prior art fabric 2 and 66% for the fabric 25 of the present invention; - For the droplet distribution at a droplet diameter of 45 μm, the separation efficiency is 78% for the prior art fabric 2 and 82% for the fabric 25 of the present invention.

[0042] The graph of FIG. 11 shows the results of tests conducted on a prior art square mesh fabric and a rectangular mesh fabric of the present invention of the type already described with reference to the test of FIG. 10. This time, the size distribution of the water droplets was kept constant at a value of 30 μm, and instead, the specific flow rate of the water / diesel emulsion was varied for the test. Reference numeral 23 indicates the separation efficiency curve of the square mesh fabric 2, while 24 indicates the separation efficiency curve obtained using the rectangular mesh fabric 25 of the present invention.

[0043] The tests show the following: - For a specific flow rate of -1.7 l / h / cm 2 the separation efficiency is 68% for the prior art fabric 2 and 74% for the fabric 25 of the present invention; - For a specific flow rate of -6.7 l / h / cm 2 the separation efficiency is 50% for the prior art fabric 2 and 57% for the fabric 25 of the present invention.

[0044] When the water / diesel emulsion entering the filter has the same specific flow rate, the pressure drop of the fabric of the present invention is smaller than that of the prior art fabric. In particular: - For a specific flow rate of -0.07 l / min cm 2 the pressure drop of the fabric of the present invention is 1.70 kPa, while the pressure drop of the prior art fabric is 1.98 kPa; - For a specific flow rate of -0.21 l / min cm 2 the pressure drop of the fabric of the present invention is 3.92 kPa, while the pressure drop of the prior art fabric is 4.89 kPa.

[0045] Figure 12 shows the tendency of the specific discharge / pressure curve for, respectively, (I) the rectangular mesh fabric of the present invention and (PA) the square mesh fabric of the prior art.

Claims

1. Use of a filter fabric for separating water from a water / diesel emulsion in an automotive diesel fuel filtration system, wherein the fabric has a rectangular mesh (11) whose sides (12, 13) are formed by respective threads (26, 27), wherein the rectangular mesh (11) allows diesel flow to pass through an unrestricted portion (16) in the vicinity of water droplets (3) while retaining the water droplets (3), wherein the size ratio of the short side to the long side of the rectangular mesh (11) is in the range of 0.38 to 0.92, wherein when the rectangular mesh (11) receives water droplets (3) having a diameter comparable to the length of the short side (13) of the rectangular mesh (11) from the diesel flow to be filtered, the water droplets (3) are retained by the rectangular mesh (11) and the portion (16) of the rectangular opening is formed to allow diesel flow to pass through, characterized in the use of the fabric.

2. Use of the fabric according to claim 1, characterized in that the short side of the rectangular mesh is in the range of 5 to 150 μm.

3. Use of the fabric according to claim 1, characterized in that the threads (26, 27) are synthetic monofilaments or multifilaments with a diameter of 10 to 90 μm.

4. Use of the fabric according to claim 1, characterized in that the number of threads per centimeter is in the range of 23 to 350.

5. Use of the fabric according to claim 1, characterized in that the material of the threads (26, 27) is a synthetic technopolymer belonging to the family of polyester, polyamide, polyaryl ether ketone, polyphenylene sulfide, polypropylene, perfluorocarbon, polyurethane, or polyvinyl chloride.

6. Use of the fabric according to claim 1, characterized in that the threads (26, 27) are made of an artificial polymer belonging to the cellulose or viscose family or consist of metal threads.

7. Use of the fabric according to claim 1, characterized in that the threads (26, 27) have a water-repellent coating.

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