Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
  • F23D14/12—Radiant burners
  • F23D14/14—Radiant burners using screens or perforated plates
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/002—Manufacture of articles essentially made from metallic fibres
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
  • F23D14/12—Radiant burners
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D2203/00—Gaseous fuel burners
  • F23D2203/10—Flame diffusing means
  • F23D2203/102—Flame diffusing means using perforated plates
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D2203/00—Gaseous fuel burners
  • F23D2203/10—Flame diffusing means
  • F23D2203/105—Porous plates
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D2211/00—Thermal dilatation prevention or compensation
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D2212/00—Burner material specifications
  • F23D2212/20—Burner material specifications metallic
  • F23D2212/201—Fibres

Definitions

• the invention relates to a porous metal fiber membrane for gas burners. 5
• a porous metal fiber plate which contains a regular pattern of holes, all together com ⁇ prising between 5 X and 35 X of the total surface area of the 15 plate.
• the advantages of this embodiment include a more uniform flow of gas transversely through the plate over its entire surface.
• It is an object of the invention is to prevent this uncontrollable deforming tendency.
• a metal fiber burner membrane for gas burners comprising a sintered metal fiber web with a pattern of a number of consecutive quadrangular porous zones with each a length L and a width D and with intermediate densified, solidified or sealed boundary areas or rows in the form of a grid.
• the surface of each porous zone should be at least 100 cm2 and any distance D or L between each two adjacent rows of the grid is at least 40 mm, while the width B of each sealed area is between 5 mm and 20 mm.
• the grid should preferably be regular. This means that the porous zones should preferably all have the same shape and surface.
• the width B must be a minimum of 5 mm in order to obtain sufficient rigidity in the intermediate sealed or solidified areas. If the width B is greater than 20 mm, however, then too much of the effective surface area of the membrane may be lost. Likewise, when the surface area of each porous zone or of a majority of them is smaller than 100 cm2, then again the effective burning surface decreases too much.
• the porous zones can have the shape of a rectangle or of a square.
• the boundary grid lines of solidified or densified areas between the consecutive porous zones can be produced by locally compacting the metal fiber skeleton along these lines. Otherwise they can be produced by filling up the pores of the metal fiber skeleton of the membrane within these lines (or strips) at least in part • for example over at least half the thickness of the membrane - with heat resistant (e.g. ceramic) material, such that the membrane in these zones is sealed. This means that in the areas covered by the grid lines the membrane must become impermeable to the stream of gas sent transversely through the membrane.
• the terms "densified”, “solidified” or “sealed” are always to be understood as meaning that the material has been treated in order to obtain substantial impermeability to a stream of gas.
• the solidified zones can also be obtained by keeping the metal fiber skeleton of the membrane fixed to a metal strip or bar on one side or pressed locally between parallel metal strips. These strips can be attached to the membrane either 15 with a ceramic glue that is to be hardened, or by welding, by binding or with nuts and bolts or otherwise.
• porous zones can be provided with non- cylindrically curved subzones with concave and convex sur-
• porous zones 20 faces lying opposite one another as described in Belgian patent application No. 09301056 filed by the applicants.
• the porous zones can be provided with cylindrically curved subzones with concave and convex surfaces lying opposite one another.
• 25 holes can also be provided in the porous zones, such that all together these holes comprise between 5 X and 35 X of the porous membrane surface area, with each hole having a surface area of between 0.03 mm 2 and 10 mm 2 , as is known from WO 93/18342 of present applicants.
• the invention also relates to a gas burner apparatus comprising a housing with inlet means for the gas mixture to 35 be burned, possibly a distribution device and a membrane as described above. Details will now be explained on the basis of a number of embodiments with reference to the accompanying drawings.
• Figure 1 shows a perspective view of a flat metal fiber 5 membrane according to the invention.
• Figure 2 shows a cross-section of a gas burner apparatus with a cross-section of the membrane along the line I • I in Figure 1.
• Figure 3 is a top plan view of a second embodiment of the invention.
• Figure 4 is a cross section along line IV-IV of thebumer according to figure 3 showing other fixingmeans 15 of the membrane in its sealed areas.
• the piate-shaped metal fiber burner membrane 1 shown in Figure 1 comprises in essence a porous sintered metal fiber web with a thickness of between 0.8 mm and 4 mm.
• the consecutive porous zones or areas 2 have a porosity of between 60 X and 95 X, and preferably between 78 X and 88 X.
• the metal fibers are of course resistant to high temperatures (over 1000°C) and to thermal shocks. For this purpose they
• the fibers can be produced using a
• the fibers can be processed into a non woven web and further into a sintered web membrane as described in U.S. patents 3,469,297 and 3,505,038,
• the grid 3 between the porous zones 2 is produced with a ceramic material 4 filling up the metal fiber skeleton of the membrane, the amount of this material (thickness and width B of the strip 4) and the distances D and L together 5 determine the reinforcement and resistance to bending.
• the ceramic material 4 can be covered, for example, with strips of adhesive ceramic paper 15, either on the gas inlet side (as shown in Figure 2) or on both sides of 10 the membrane 1.
• parallel metal supporting elements such as strips 5 and 6 can also be used, with the membrane held between them.
• the strips can be attached to one
• the attachment can also be achieved by introducing a ceramic glue 4 between the strips.
• the strips 5 on the gas inlet side can be equipped with upright edges 14, which then function as cooling fins; they also increase the bending strength of the
• the metal strip 6 can be composed of AISI 430 steel , and the U-profile 5 of 18/8 chrome-nickel steel. If so desired, the grid can be discontinuous or interrupted at the crossing points 7 of the strips.
• a supporting layer of expanded metal 17 can be attached to the gas inlet side of the membrane 1.
• This layer has a thickness, for example, of at most 1 mm and has consecutive diamond- shaped mesh openings with axial dimensions of 2 mm and-4 mm
• the mem ⁇ brane in the porous zones 2, either in the flat or the sphe ⁇ rical shell form, can be provided with a regular pattern of
• the holes 9 can, for example, be circular or rectangular.
• the surface area of the holes per opening will usually be selected to be lower than 3 mm 2 and, by preference, between
• the consecutive circular holes are situated by prefe ⁇ rence at the corner points of adjoining equilateral triangles. The length of the triangle sides is then selected such that the total free passageway in the porous zones
• 25 amounts to between 5 X and 25 X of their surface area, and by preference between 8 X and 16 X, as for example 10 X, 12 X or 15 X.
• the gas burner apparatus comprises 30 a housing 11 with an inlet duct 12 for the gas mixture to be burned.
• a gas distribution means 13, such as for example a per-forated plate, can be provided upstream from the membrane 1.
• a compression spring 10 can be installed on the gas inlet side of the porous zones 2. This spring 10 can 35 thereby force a controlled expansion movement perpendicular to the membrane surface.
• the springs 10 can be placed between - 7 -
• the height of the open spring is then approximately equal to the height of the bulge in the membrane.
• a rectangular metal fiber membrane of 90 cm by 30 cm was assembled as follows.
• the porous membrane 1 was constructed from a sintered web of FeCr-alloy fibers (containing at least O.IH and produced by bundled drawing).
• the equivalent fiber diameter was 22 ⁇ m.
• the porosity of the membrane was 80 X and its thickness was 2 mm. It had a pattern of holes 9 as described in WO 93/18342.
• the round holes had a diameter of 0.8 mm.
• the pitch, or distance between the holes was 2 mm, which resulted in a free passageway surface area of nearly 15 *.
• a preformed deformation 8 in the shape of a spherical shell with a height of 5 mm and a shell diameter S of 12 cm was pressed into each zone.
• a steel strip 5 (12 mm x 3 mm) was placed over the entire length along the center line of the gas inlet side of the membrane 1 and fastened to this membrane 1 by means of a ceramic glue (Aremco) 4.
• Strip segments (12 mm x 3 mm) were placed parallel to one another across this longitudinal strip every 14 cm and fastened with Aremco glue to form the edges or boundaries of the square porous zones.
• This membrane thus reinforced with solidified zones 3, was installed in a burner with the flame pointing downwards (gas flowing from top to bottom).
• the membrane was -suitably clamped onto the bottom of a horizontal metal frame 11, which functioned as the housing, and the gas inlet 12 was connected at the top side of the frame 11.
• the frame itself was composed oftubular profiled sections through which a coolant was able to circulate. This construction prevents the membrane from deforming in an irregular manner, even after long-term use and with a cyclical burning schedule at varying intensities.
• a rectangular metal fiber membrane of 200 cm by 30 cm is assembled as follows.
• the porous membrane 1 is produced from a sintered web, provided with holes 9, as described in example 1.
• the width D will preferably be choosen below 20 cm when L>20 cm.
• the membrane 30 D will preferably be choosen smaller than 15 cm, and often even smaller than 10 cm.
• the membrane is sealed by applying a ceramic strip coating 4 (Aremco glue) to the back side of the membrane.
• membrane is mounted at the upper peripheral edge of a housing 11 on top of a metallic rectangular grate 20 of 200 cm by 30 cm.
• This grate 20 is built up of an outer frame 24 to which tubular elements 21 are fixed and which support the membrane.
• the elements 21 can also consist of bars or rods in stead of tubes and with other cross sectional shapes than round. Each element 21 faces thereby a sealed area 4. It may however suffice to have an element 21 facing only each second sealed area 4.
• the elements 21 are fixed to the outer frame 24 of the grate 20 at one end 25. At the other end 26 of said frame 24, pins 27 can be fixed onto which the tube ends 28 can slide in an axial direction.
• This sliding arrangement is useful in view of allowing thermal expansion of the elements 21 during the heating up before a burning cycle, respectively their retraction during the cooling down after a burning cycle. It may even be useful to subdivide the elements 21 in consecutive longitudinal sections linked to each other by means of a sliding pin arrangement 29.
• the membrane is then fixed at regular distances A eg. with binding wires 23 to the elements 21.
• the fixing or binding spots (23) are preferably distributed in an even pattern (at regular distances) over the surface of the membrane as shown in figure 3.
• the wires 23 may be covered on the burning side of the membrane with a local sealing spot 30 of ceramic glue. Suitable distances A are situated between 2 cm and 20 cm.
• the porous zones may bulge outwardly to form cylindrical shells 8 whereby the shell dimension S should remain below half its radius of curvature R.
• the housing 11 When the burner is to be used in an open environment, the housing 11 may be composed of steel . However, when the burner is to be used in a closed hot environment, its temperature may rise to a very high level during operation. Therefore its housing will then have to be composed preponderantly of ceramic parts. These parts of ceramic material have a much lower coefficient of thermal expansion than metallic parts. So the difference of expansion between the membrane and the housing may become quite important when using a ceramic - 10 -
• the design of supporting the metallic porous membrane according to the invention is thus a breakthrough solution, in particular for making burners having large burning surfaces and which have to operate in closed 5 environments.
• the densified grid lines 3 in the membrane can then consist of compressed narrow strips therein facing these generatrices. These lines 3 then can favour an easy bending of the membrane along these
• the adjacent porous sections between these grid lines can then bulge outwardly to allow for thermal expansion.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• General Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Gas Burners (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=3888086

Family Applications (1)

Country Status (6)

Cited By (1)

Families Citing this family (13)

Family Cites Families (4)

• 1994
  • 1994-04-07 BE BE9400362A patent/BE1008483A3/nl not_active IP Right Cessation
• 1995
  • 1995-04-04 KR KR1019950705465A patent/KR960702898A/ko not_active Application Discontinuation
  • 1995-04-04 CA CA002164101A patent/CA2164101A1/en not_active Abandoned
  • 1995-04-04 JP JP7525983A patent/JPH08511616A/ja active Pending
  • 1995-04-04 WO PCT/BE1995/000031 patent/WO1995027871A1/en not_active Application Discontinuation
  • 1995-04-04 EP EP95915706A patent/EP0702770A1/de not_active Ceased

Non-Patent Citations (1)

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