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
  • F23D14/46—Details
  • F23D14/72—Safety devices, e.g. operative in case of failure of gas supply
  • F23D14/82—Preventing flashback or blowback
• • A—HUMAN NECESSITIES
  • A62—LIFE-SAVING; FIRE-FIGHTING
  • A62C—FIRE-FIGHTING
  • A62C4/00—Flame traps allowing passage of gas but not of flame or explosion wave
  • A62C4/02—Flame traps allowing passage of gas but not of flame or explosion wave in gas-pipes
• • 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
  • F23D14/18—Radiant burners using catalysis for flameless combustion

Definitions

• the present invention relates to gas heaters, and more specifically to gas heaters comprising flame arresters for preventing flashback of flames.
• Gas heaters are typically used for space heating purposes in various settings, including vehicles. These heaters feature a fuel supply system designed to deliver a fuel to a burner, which converts the energy stored in the fuel to heat through a combustion process.
• gas heater may be equipped with a flame arrester, which is a device aimed at preventing flames from flashing back into the fuel supply system.
• This arrester is typically composed of a series of parallel metallic plates permitting the passage of combustible gas to the burner while effectively quenching flames attempting to propagate back towards the fuel supply.
• a gas heater comprising a burner for producing heat from a gaseous fuel, a fuel supply system for providing the fuel from a fuel source to the burner, and a flame arrester arranged between the fuel supply and the burner.
• the flame arrester comprises a plurality of plates arranged in a stack, wherein each plate of said plurality of plates comprises integrally formed shoulders abutting against corresponding shoulders of an adjacent plate within the stack to provide a spacing between each plate of the stack.
• the shoulders and the spacings define inter-plate channels for guiding the fuel to the burner and quenching flames propagating away from the burner. For each inter-plate channel, a width of the inter-plate channel is determined by a lateral separation between adjacent shoulders of a plate and a height of the inter-plate channel is determined by the spacing between adjacent plates of the stack.
• the integral shoulders make it possible to obtain consistent spacing between the plates without separate spacers or fixtures.
• the plates may naturally establish and define the inter-plate channels through their shape. This allows for an improved assembly efficiency and reduces the need for precise spacer placement and attachment.
• the plates can self-align within the stack, thereby reducing the need for dedicated aligning structures or jigs.
• the shoulders may act as reinforcement structures, enhancing the robustness and structural integrity of individual plates, making handling of the plates easier and improving the robustness of the flame arrester.
• the shoulders may be arranged to divide a contour of the plate into depressed areas and elevated areas, each forming a wall of corresponding inter-plate channel.
• the shoulders may run along a length of the inter-plate channel, aligning with the direction of flow that the channel guides. Consequently, the depressed and elevated areas respectively act as the floor or ceiling of the inter-plate channels.
• the fuel may flow through channels formed by the vertically aligned sections of neighbouring plates - namely, the elevated or depressed areas - separated by the shoulders.
• the shoulders may hence be configured to define alternating depressed and elevated regions, which are interconnected through the shoulders.
• a shoulder may feature both a convex and a concave segment forming a smooth transition between elevated and depressed regions.
• the elevated region may transition into the convex segment, the convex segment into the concave segment, and the concave segment transition into the depressed region, as seen in a direction orthogonal to the length direction of the inter-plate channel.
• the concave segments of one plate may be aligned to rest against the corresponding convex segment of an adjacent plate.
• the convex and concave segments may also be understood as positive and negative radii of curvature provided by the forming of the elevated and depressed regions. In some examples, the radii of curvature are determined by the press forming tool used.
• the inter-plate channels may be substantially uniform across the entire stack, or at least across a major part of the stack.
• a cross-sectional shape and area of the inter-plate channels may be substantially uniform in at least a part of the stack, enhancing the uniformity of fuel flow to the burner.
• at least one of the depressed areas and at least one of the elevated areas may share substantially the same width, contributing to this uniformity.
• at least a subset of the plates may be arranged in a substantially equidistant manner in the stack, further promoting consistent spacing.
• the stack could include one or more plates with a distinct shape, potentially placed at locations such as the top, bottom, or other parts of the stack.
• maintaining a majority of the plates with substantially identical shapes may be preferable to ensure uniform inter-plate channel formation, facilitating consistent gas flow characteristics.
• the shoulders may be configured to provide an elasticity of the stack in the stacking direction.
• the elasticity allows for the stack to be compressed in the stacking direction and press fitted into a supporting frame.
• the shoulders can abut each other at a specific angle relative to the stacking direction.
• the angled contact point (or contact line, considering that the shoulders may abut each other along their entire length), may be designed to redistribute compressive forces applied along the stack's vertical axis into lateral forces. As a result, these lateral forces may induce a slight bending in the plates or shoulders, enabling a "springy" characteristic of the stack.
• This elasticity allows the stack to absorb and dissipate forces and thermal expansion, thereby enhancing its mechanical resilience and contributing to the stability of the assembly.
• the elasticity, or compressibility may be employed when fitting the stack into a frame structure. By slightly compressing the stack as it is being inserted into the open space of the frame structure, a tight interference fit may be achieved.
• all or a majority of the plates comprises opposing flank portions that run along the inter-plate channels. These flank portion may be formed by folding the edges of the plate back onto themselves. Viewed in the stacking direction, a thickness of such a folded flank portion may be less than a centre-to-centre spacing between adjacent plates of the stack. Consequently, the flank portions may serve as compression stops, establishing a maximum compression limit of the stack. When the stack is compressed to a specific degree, these flank portions come into contact with one another, effectively preventing any further compression of the stack. This may be advantageous from an assembly perspective, as it may reduce the risk of plastic deformation of the plates that could occur due to the inadvertent application of excessive compressive forces.
• the gas heater may be of a catalytic type, in which the burner comprises a catalyst plate for combusting the fuel.
• the catalytic burner typically combusts the fuel at lower temperatures than burners which rely on an open flame. Further, the catalytic combustion tends to be more efficient and produces fewer emissions of harmful substances.
• the catalytic reaction may occur when gaseous fuel passes over a catalyst-coated surface, which typically is referred to as a catalytic plate.
• the catalyst facilitates the oxidation of the gas, releasing heat.
• the flame arrester may be arranged at the catalyst plate, at the side facing the fuel supply, at a predetermined distance sufficient to prevent direct contact between the flame arrester and the catalyst plate. Direct contact may be undesirable, as this can lead to undesirable cooling of the catalyst plate, reducing the temperature below the temperature optimal for catalytic efficiency.
• ⁇ flame arrester' commonly describes a device designed to inhibit flame propagation within the gas heater.
• Alternative terms, such as ⁇ flame trap', ⁇ flame stop', and ⁇ flashback arrestor' may also be used to denote similar functionalities.
• shoulders being 'integral' or ⁇ integrally formed' is typically meant that the shoulders are formed as a unified part of the plate rather than being a separate piece that is attached or added later.
• the shoulders may hence be formed from the same piece of material as the plate itself, preferably through a process such as stamping or press forming.
• the fuel may in some examples comprise a gas such as natural gas, propane, biogas, or hydrogen.
• the fuel may as well be formed of an aerosolised liquid, such as gasoline, diesel, or ethanol.
• FIG. 1 is a schematic cross-sectional view of a gas heater 100 in accordance with an embodiment of the present disclosure.
• the gas heater 100 may, for example, be configured for space heating purposes in various settings, including vehicles.
• the gas heater 100 comprises a fuel supply system 120 designed to deliver gaseous fuel to a burner 110, which converts the energy stored in the fuel to heat through a combustion process.
• the heat produced during the combustion process within the burner 110 may be harnessed by a heat exchanger assembly 130 arranged downstream of the burner 110.
• a flame arrester 200 may be arranged between the fuel supply 120 and the burner 110 for guiding the fuel to the burner 110 and quenching flames propagating away from the burner 110.
• the flame arrester 200 comprises a plurality of plates 210, or lamellae, arranged in a stack permitting the passage of gas through inter-plate channels while effectively quenching flames attempting to propagate back towards the fuel supply 120. Exemplary flame arrester designs are discussed below with reference to figures 2-5c .
• the burner 110 may be of a catalytic type, comprising a catalyst plate 112 for combusting the fuel.
• the flame arrester 200 may be arranged at the catalyst plate 112, at the side facing the fuel supply.
• the flame arrester 200 may be arranged at a predetermined distance from the catalyst plate 112, sufficient to prevent direct contact between the flame arrester 200 and the catalyst plate 112.
• the spacing between the flame arrester 200 and the catalyst plate 112 is provided to avoid undesired cooling of the catalyst plate 112, as lower temperatures might negatively impact the combustion process and lead to inefficient combustion of the fuel.
• the fuel supply system 120 typically includes a fuel tank or a connection to such a tank.
• the fuel supply system 120 may deliver a mixture of fuel and air (or oxygen) to the burner 110, where the fuel is combusted to release heat.
• the fuel may in some examples comprise a gas such as natural gas, propane, biogas, or hydrogen. However, the fuel may as well be formed of an aerosolised liquid, such as gasoline, diesel, or ethanol.
• the fuel may be mixed with air by the fuel supply system 120 and guided in a gaseous flow to the burner 110 through the inter-plate channels of the flame arrester 200.
• the fuel/air mixture is passed over surfaces of the catalytic plate 112 covered by a catalyst, such as platinum, palladium, or rhodium, which lowers the activation energy required for combustion and allows the fuel to oxidise and release heat without the use of an open flame.
• the heated gaseous flow comprising the combustion by-products, may then be guided to the heat exchanger arrangement 130 for transferring the heat to a secondary medium, such as air, water, or another fluid, for further transport to the space that is to be heated.
• FIG. 2 is a perspective view of flame arrester 200, which may be designed for integration into a gas heater 100 similar to the one depicted in figure 1 .
• This flame arrester 200 features a stack of plates or sheets 210 that are arranged substantially parallel to each other and with spacings forming inter-plate channels 230 facilitating the passage of a gaseous flow through the arrester 200.
• figure 2 illustrates a configuration of 30 substantially identical and parallel plates 210 stacked atop one another. It is important to note that this configuration servers as an example; the actual number of plates 210 in the flame arrester 200 can vary, with possibilities including fewer or greater than 30 plates.
• the flame arrester 200 may comprise several hundreds of plates 210, such as 300 or more. Additionally, the flame arrester 200 may include other plates with different configurations not depicted here. Therefore, references to ⁇ plates', ⁇ set of plates', or ⁇ plurality of plates' should be understood to not exclude additional plates.
• the plates 210 may be formed of a metal sheet, with a thickness often less than 1 mm, and in some cases even less than 0.5 mm. In the particular example shown in figure 2 , the plates 210 may be formed of a metal sheet having an average thickness of about 0.3 mm.
• the plates 210 may be formed through a press forming, or stamping process, in which a press tool applies force to the sheet material against a die. This pressure causes the sheet to deform and assume the shape of the die cavity. Consequently, this process provides the plates 210 with a specific contour in which shoulders 220 divide each plate 210 into depressed areas 242 and elevated areas 244. These shoulders 220 may extend along the inter-plate channels 230, aligning with the direction of flow guided by the channels 230.
• the depressed areas 242 and the elevated areas 242 may hence act as the floor or ceiling of the inter-plate channels 230.
• the surfaces of the inter-plate channels 230 i.e., the depressed and elevated areas 242, 244 may dissipate heat from the gases to reduce the temperature below the ignition temperature and prevent flames from propagating through the flame arrester 200.
• the shoulders 220 and the alternation between depressed and elevated areas 242, 244 may aid in the alignment of the plates 210 within the stack.
• this configuration helps the depressed areas 242 of one plate 210 to be fitted in the corresponding depressed areas 242 of the plate 210 directly beneath it in the stack.
• Each plate 210 in the depicted stack further comprises opposing flank portions 250, or edge portions, that run along the inter-plate channels 230.
• These flank portions 250 may be formed by folding the edges of the plate 210 back onto themselves, as shown in further detail in figure 3 .
• Figure 3 is an enlarged side view of the flank portions 250 of a subset of the plates 210 shown in figure 2 .
• the spacing, or centre-to-centre spacing d between the plates 210 in the stack is determined by the shoulders 220.
• the shoulders 220 of one plate 210 directly abut the corresponding shoulders of the adjacent plates 210, creating contact lines 262 extending along the shoulders 220.
• the shoulders 220 may be designed so that the spacing between the plates 210 exceeds the thickness of the flank portions 250, i.e., the combined thickness of the edges of a plate 210 when folded back onto themselves.
• This design choice allows for adjacent flank portions 250 to be separated by a gap 264, introducing a degree of compressibility of the stack. During compression of the stack, this gap 264 may be reduced until the flank portions 250 abut against each other.
• the flank portions 250 may hence serve as compression stops, establishing the maximum level of compression of the stack.
• the shoulders 210 typically abut each other along the contact lines 262 at a specific angle in relation to the stack's vertical axis (i.e., the stacking direction). This allows compressive forces applied along the vertical axis to be redistributed into lateral components, orthogonal to the vertical axis. As a result, these lateral forces may induce a slight bending in the plates or shoulders, enabling a certain elasticity of the stack that can accommodate compressible forces and thermal expansion of the plates.
• the geometry of the inter-plate channels 230 may be defined by their width w and height h, as well as their length (not shown).
• the width w is determined by the lateral separation between adjacent shoulders 230 of a plate, i.e., as seen in a direction orthogonal to the length direction of the inter-plate channels 230, whereas the height h is determined by the spacing d between adjacent plates 210 of the stack and the thickness of the plates 210.
• the width w of a channel may be determined by the width of the depressed and elevated areas 242, 244, respectively.
• the channel width w may in some examples be 10 mm or more, such as 20 mm or more, such as 40 mm or more.
• the height h of the channels may be less than 1 mm, such as 0.6 mm or less. In this particular example, the height h of the channels may be about 0.4 mm.
• Figure 4 shows a plate 210 in which the width w 1 of the depressed areas 242 and the width w 2 of the elevated areas 244 are substantially the same, resulting in the flame arrester 200 having substantially uniform inter-plate channels 230 over the full width.
• Figures 4b and c show examples where the channels 230 formed by the elevated areas 244 are wider than the channels 230 formed by the depressed areas 422. This may be achieved by arranging the shoulders 220 defining the depressed areas at a closer distance w 1 than the distance w 2 between the shoulders 220 defining the elevated areas 244.
• Figure 4c also shows an example of a plate 210 without any folded flank portions 250.
• the inter-late channels 230 have a width-to height ratio that is relatively large, ensuring the gaseous flow encounters an extensive surface area. This extensive exposure helps cooling the gas to temperatures below its ignition point. In specific examples, this ratio exceeds 10, and may reach values of 50 or more.
• the shoulders 220 may comprise a convex segment 222 and a concave segment 224 extending along the inter-plate channels 230.
• These segments 222, 224 may also be understood as positive and negative radii of curvature of the surface of the plate, forming the respective shoulders 220.
• these radii of curvature may be formed by the by the press forming tool used to define the alternate lowered and raised areas 242, 244 of the plates 210. Moving from left to right in the figures, the elevated area 244 transitions into the convex segment 222 (as seen from above; from below, it may be considered concave), which in turn transitions into the concave segment 224.
• the concave segment 224 then transitions into the depressed area 242.
• the concave segment 224 of one of the plates is aligned with, and rests against, the convex segment 222 of an adjacent one of the plates 210 to form the contact lines 262 illustrated in figure 3 .
• Figures 5a-c show various examples of the stack arranged in a support structure facilitating mounting of the flame arrester 200 into a gas heater 100, such as the one shown in figure 1 .
• the support structure which also may be referred to as a frame assembly or housing, typically comprises a pair of top/bottom panels or plates 272, between which the stack is fitted.
• the stack may be press fitted between the top/bottom panels 272, which in turn may be connected by side elements, or lateral supports/walls 274, which may extend along the stack to complete an enclosed frame structure.
• Two examples of such lateral supports 274 are indicated in figures 5a and c.
• Figure 5a shows rod-shaped lateral support elements 274 slotted into recesses formed into the flank portions 250 of the flame arrester plates 210.
• the recesses may be designed to snugly accommodate the full width of the lateral supports 274, ensuring they do not extend beyond the stack's sides.
• the lateral support 274 may facilitate alignment of the plates 210 within the stack and improve the structural integrity of the stack.
• the top and bottom panels 272 may be equipped with corresponding recesses to seat the lateral supports 274.
• the lateral supports 274 may be attached to the top and bottom panels 272 by means of press fitting or welding.
• the end portions of the lateral supports 274 may be deformed after insertion into the respective top and bottom panels 272 to form a joint with the same. This design facilitates the integration of the entire assembly within an external frame structure 274, as depicted in figure 5b .
• the lateral supports 274 are formed as brackets connecting the top and bottom panels 272.
• the lateral supports 274 in figure 5c are formed of sheet-like structures that can be arranged to span the distance between the top and bottom panels 272.
• the end portions of these lateral supports 274 may engage in an interlocking mechanism 275 with the corresponding end portions of the top and bottom panels 272, exemplified by a tongue and groove joint or a hook engaging a groove, as indicated in figure 5c .
• the stack may be slightly compressed in the stacking direction, enabling the lateral supports 274 to securely snap into the receiving structure of the top and bottom panels 272 for the interlocking mechanism 275.
• the stack of flame arrester plates 220 may be press fitted into the support structure 272, 274, 276.
• This technique commonly relies on the precision manufacturing of both elements, i.e., the stack and the support structure, to ensure a snug fit, where the dimensions of the stack are slightly larger than the receiving space within the frame to create a tight interference fit upon insertion.
• the flame arrester 200 can more easily accommodate minor variations in manufacturing tolerances, ensuring a snug fit within the frame structure even when there are slight discrepancies in dimensions.
• a stack with inherent compressibility can better accommodate thermal expansions and contractions, maintaining a consistent fit and performance across a range of operating temperatures.
• the flame arrester 200 may comprise two of more distinct sets of plates, wherein each set may have a uniform design among its plates. However, the design may vary from one set to another, allowing for tailored functionality and performance across different sections of the arrester.

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Citations (3)

• 2024
  • 2024-03-11 EP EP24162565.6A patent/EP4617563A1/de active Pending
• 2025
  • 2025-02-21 WO PCT/EP2025/054797 patent/WO2025190635A1/en active Pending

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