Gas burners and a burner matrix with at least three gas burners

Abstract

Gas burner, suitable for heat stress tests for components in general and for flame testing of lithium-ion batteries according to standard ECE R100 Rev.3, comprising a burner nozzle assembly with at least one nozzle for a fuel gas outlet (1), a homogenizing tube (2) into which the burner nozzle assembly opens concentrically, and a flame tube (4) into which the homogenizing tube opens, wherein the flame tube (4) is open at both ends and has a larger inner diameter than the outer diameter of the homogenizing tube (2), a flowable structure (3) with through-openings (6) is provided between the homogenizing tube and the flame tube, spanning the entire inner diameter of the flame tube (4), and the flowable structure (3) forms a gas inlet for the ambient atmosphere away from the homogenizing tube (2).

Description

The invention relates to a gas burner and a burner matrix, suitable for heat stress tests for components in general and for flame treatment of lithium ion batteries according to the standard ECE R100 Rev.3 (standard for homologation of lithium batteries for electric vehicles) in particular, according to the first claim or ninth claim. Lithium-ion batteries, like nickel-metal hydride batteries (such as those based on nickel-manganese-cobalt), have recently become increasingly popular as traction batteries, i.e., energy storage devices for powering vehicles, or in photovoltaic systems. The charging and discharging of the battery alone generates heat. If irregularities occur during this process or if the battery is subjected to external mechanical and thermal influences, it can quickly overheat. In extreme cases, particularly with flammable electrolyte liquids, this, combined with high energy density, can lead to a significant fire hazard. Due to the encapsulated design of these batteries, conventional fire suppression methods involving cooling with large quantities of water are unsuitable; furthermore, toxic emissions of harmful combustion products are to be expected. Traction batteries require approval from a national authority. Flame tests for the systematic assessment of fire resistance in accumulator or battery systems are regularly conducted over an open flame, using conventional methods with gasoline as fuel. Such flame tests are specified in the ECE R100 standard and are a condition of approval for accumulator systems intended for use in vehicle propulsion systems. ECE R100 Rev.3, paragraph 9E, which has been in effect since June 2021, regulates the testing of fire resistance, i.e., the verification of a lithium-ion battery's resistance to fire outside the vehicle, caused, for example, by fuel leakage from a vehicle (either the vehicle itself or a nearby vehicle). The test aims to ensure that the systems are designed in such a way that the driver and passengers have sufficient time to evacuate the vehicle without endangering themselves. The test requires that, after a warm-up period (Phase A), the battery (test specimen) is directly exposed to flames of a free-burning fuel (fire tray) from below for 70 seconds (Phase B). This is followed by indirect temperature control for a further 60 seconds in a throttled flame (Phase C), followed by the end of the test (Phase D).This current version of the standard incorporates a key element of the Korean standard KMVSS by including flame testing with LPG gas burners as an alternative to conventional gasoline baths. This alternative promises ease of use and virtually no soot buildup compared to conventional fuels. Defined requirements for flame height and temperature are specified for the use of gas burners. Common burner designs are primarily used for heating molten metals and glass, as well as for heat treatment in industrial applications using heat exchangers and steam generators. The focus here is on improving the premixing of fuel gas with atmospheric oxygen and flame stability under varying operating conditions, achieved, among other things, through baffles. Furthermore, the flexible adjustability of burner output and flame length, mainly achieved through adjustable air channels, represents a particularly valuable burner characteristic. Almost all burner designs are based on conventional two-fluid nozzles (i.e., fuel gas and atmospheric oxygen are supplied in defined quantities) and are used in closed furnaces. German patent DE 74 04 685 U1 discloses, by way of example, a manually operated burner for propane and similar fuels for drying surfaces or welding bitumen sheets. It consists of a handle with an operating valve on an angled tube shaft serving as the gas supply to a burner head. The burner head itself has a cup-shaped flame tube with circumferentially arranged slotted openings for combustion air supply. The operating valve regulates the gas supply through the tube shaft to the burner head and, consequently, the flame, particularly between the working flame and pilot flame modes. This burner represents a basic design. Furthermore, DE 79 16 802 U1 describes a gas-operated safety burner for construction site use, which, in contrast to the aforementioned basic design, features a main burner and a separate pilot flame burner. To counteract the risk of malfunctions, particularly due to clogging of the burner nozzles, especially the pilot flame, a filter arrangement is proposed. This arrangement includes a main filter near the hose connection and a finer-mesh secondary filter upstream of the pilot flame nozzle, for example, designed as a sieve, sintered bronze filter, or granular filter element, through which only the fuel flows. DD 1 48 670 A1 discloses a gas burner with a burner nozzle arrangement having a nozzle for a fuel gas outlet, a homogenizing tube into which the burner nozzle arrangement opens concentrically, and a guide tube open at both ends with a diverging interior into which the homogenizing tube opens and between this and the homogenizing tube a flowable structure with secondary air openings is provided, which spans the entire inner diameter of the homogenizing tube outside the guide tube and the flowable structure away from the homogenizing tube forms a gas inlet for the ambient atmosphere. DD 12 357 A1 further describes a low-pressure gas burner in which a burner nozzle opens concentrically into a mixing tube, which in turn is surrounded by a jacket whose inner diameter is larger than the outer diameter of the mixing tube. A flow-through structure is also provided between the jacket and the mixing tube, spanning the entire inner diameter of the homogenizing tube outside the guide tube, and this flow-through structure forms a gas inlet for the ambient atmosphere away from the homogenizing tube. DE 8 523 177 U1 represents a liquid burner, as is generally known from the construction industry for heating floor surfaces, roof surfaces and sealing materials. Currently, no gas burner design is known that demonstrably meets the requirements of ECE R100 Rev. 3 (UN Regulation No. 100 - Uniform provisions concerning the approval of vehicles with regard to specific requirements for electric propulsion [2021 / 2190]. In: Official Journal of the European Union L: Legislation, Vol. 64, 2021, No. 449, pp. 1-90. - ISSN 1977-0642. URL: https: / / eur-lex.europa.eu / legal-content / DE / TXT / PDF / ?uri=CELEX:42021X2190=DE [accessed on 2022-03-22]), in particular Annex 9E - Fire resistance. To comply with the new standard, the resulting free flame length of the gas burner from bottom to top of the test specimen must be increased to at least 60 cm (Annex 9E, Section 3.4.2). The underside of the test specimen must be directly and completely exposed to the uniform flame produced by the combustion of the fuel.The flame of the LPG burner must extend at least 20 cm above the horizontal projection of the test specimen (Annex 9E, Section 3.4.5). The average temperature must be continuously monitored throughout the entire flame exposure period (Annex 9E, Sections 3.4.3 and 3.4.4). An average temperature of 800 °C must be reached within 30 seconds and a temperature of 800 °C to 1100 °C must be maintained (Annex 9E, Section 3.4.6). Firstly, compliance with the aforementioned standard ECE R100 Rev.3 depends on the fuel mass flow rate at the nozzle head for effective air intake. Secondly, defined distances between the gas burners must be maintained to ensure a uniform temperature distribution, as required. This is preferably achieved using a burner matrix. Conventional systems, particularly those with a flat, open design, do not achieve the required flame height and temperature distribution values ​​as specified in the standard. Based on this, one object of the invention is to propose a gas burner and a burner matrix suitable for testing the fire resistance of accumulators in accordance with ECE R100 Rev.3 (UN Regulation No. 100 - Uniform provisions for the approval of vehicles with regard to specific requirements for electric propulsion [2021 / 2190]. In: Official Journal of the European Union L: Legislation, Vol. 64, 2021, No. 449, pp. 1-90. - ISSN 1977-0642. URL: https: / / eur-lex.europa.eu / legal-content / DE / TXT / PDF / ?uri=CELEX:42021X2190=DE [accessed on 2022-03-22]). The problem is solved by a gas burner and a burner matrix having the features of claim 1 and 9, respectively. Dependent claims relating thereto describe advantageous embodiments. To solve the problem, a gas burner is proposed comprising the following components: a) a burner nozzle assembly with at least one nozzle for a fuel gas outlet. The fuel gas exits through the burner outlets of the burner nozzle assembly, preferably controlled by the volume flow via corresponding control valves in the gas supply line or in the outlets themselves, wherein, in the case of multiple outlets, the volume flow can be controlled by individually closing one of them as a whole. b) a homogenizing tube into which the burner nozzle assembly preferably opens concentrically as a single outlet or as an outlet configuration. The volume flow from the burner outlets enters this homogenizing tube, whereby, due to the enlarged flow cross-section in the homogenizing tube, the flow velocity is reduced and, in particular, turbulent flow components are reduced in favor of laminar flow.c) A flame tube into which the homogenization tube opens concentrically. The flame tube is open at both ends and has a larger inner diameter than the outer diameter of the homogenization tube. Only upon entering the flame tube from the homogenization tube does the fuel gas come into contact with the ambient atmosphere, mix, and form a flame emerging downstream from the flame tube. Due to the preceding homogenization, the mixing of the fuel gas and ambient atmosphere volume flows occurs with low, preferably laminar, flow. This results in a generally more constant flame propagation compared to mixing with higher and more turbulent flow velocities, which is advantageously suited to the standard-compliant control of flames in accumulators. A key feature of the gas burner is a flow-through structure with openings, positioned between the homogenizing tube and the flame tube. This structure spans the entire inner diameter of the flame tube and thus also the flow outlet of the homogenizing tube. The flow-through structure therefore forms a gas inlet for the ambient atmosphere, separate from the homogenizing tube. The flow-through structure with openings is preferably selected from the group consisting of a grid structure, a lamellar structure, a helical structure, an open-pore structure, or structures with serrated outlet edges. It is preferably installed flat and perpendicular to the flow direction of the fuel gas in the gas burner and preferably has a constant flow cross-section across its entire extent. The flow-through structure with openings is formed by a perforated sheet, which mechanically connects the flame tube to the homogenization tube and also holds it in place. This structure thus creates a flow resistance that, on the one hand, increases the volume flow of the combustion gas in the homogenization tube and, on the other hand, reduces and evens out the inflow of both combustion gas and ambient air into the flame tube, promoting consistent flame propagation. The flow-through structure with through-openings preferably has a homogeneous flow resistance over its (lateral) extent, whereby the entry of fuel gas and ambient atmosphere into the flame tube occurs parallel and uniformly over the lateral extent of the structure, thus reducing the risk of additional turbulence in the flame tube generated by possible compensating cross currents. The achievable flame length depends significantly on the design of the gas burner. For the proposed gas burner with a diffusion flame (fuel gas and atmospheric oxygen are separate), it increases considerably compared to premixed flames (fuel gas and atmospheric oxygen are already mixed) due to the additional mixing time required for the fuel gas and atmospheric oxygen. In the laminar case, the exit velocity of the fuel gas from the burner nozzle, its nozzle diameter, and the diffusion coefficient of the fuel gas all influence the resulting flame length. Above a critical exit velocity, the laminar flow transitions into turbulent flow, and the flame length then depends solely on the nozzle diameter, which in turn determines the fuel gas flow rate. Therefore, achieving the maximum flame length for a burner system with the lowest possible fuel gas flow rate requires a delay in the mixing time.This delay time is achieved primarily, as proposed, by shifting the mixture of fuel gases into and beyond the flame tube. The proposed gas burner is based on the concept of a laminarized, partially premixed diffusion flame. Compared to conventional burner heads, the mixing of fuel and air is not directed immediately around the burner nozzle assembly, but rather shifted downstream into the flame tube. At the downstream open end of the homogenization tube, an additional flow resistance induces laminarization (reduction of turbulence) of the exiting fuel stream, thus producing a fundamentally calmer flame that ideally approximates a stationary (constantly extended) flame. This results in a mixing delay at the burner nozzle assembly, whereby the resulting extended laminar diffusion flame advantageously not only lengthens but also homogenizes the flame. This leads to improved, more uniform flame formation, particularly when used in a burner matrix with planar burners. As a gaseous fuel, in particular and in accordance with ECE R100 Rev.3, LPG gas (LPG = Liquefied Petroleum Gas) is proposed, which is particularly common for operating motor vehicle combustion engines with liquefied gas as autogas and contains a mixture in particular of butane and propane. The proposed gas burner enables the generation of a consistently free flame length of at least 60 cm. A homogeneous flame zone is formed, reliably maintaining an average temperature of at least 800°C. Unlike conventional burner heads, the fuel-air mixture is not mixed directly at the burner nozzle assembly, but rather downstream of the homogenization tube into the flame tube. At the outlet, laminarization of the fuel flow is achieved through a flow-through structure, such as a perforated plate. A preferred embodiment of the gas burner features a cylindrical or at least rotationally symmetrical design of the homogenizing tube and / or the flame tube, preferably extending concentrically around a preferably symmetrical axis. Deviating from a preferably rotationally symmetrical design undesirably increases the probability of flame instabilities or an inhomogeneous temperature distribution above the burner matrix. Furthermore, cylindrical designs are potentially more cost-effective to manufacture and operate, as well as being mechanically more robust in operation and construction. Another preferred embodiment of the gas burner provides that the burner nozzle arrangement has only one nozzle, but thereby not only allows for finer control of the flow directly at the nozzle outlet, but also enables a symmetrical outlet of the fuel gas around an axis of symmetry, for example of the subsequent homogenizing tube. Another preferred embodiment of the gas burner provides that the burner nozzle arrangement has a nozzle arrangement for only one gas. This means that, for example, gaseous fuels composed of several components, which are then subsequently mixed with the ambient atmosphere, are preferably premixed upstream (relative to the volume flow of the fuel gas) of the burner nozzle arrangement and fed as a mixture into the homogenization tube. For example, the preferred LPG gas as fuel comprises a variable gas mixture, preferably a mixture of propane and propene. Another preferred embodiment of the gas burner provides that the burner nozzle assembly completely encloses and seals the inner diameter of the homogenizing tube. This means that the burner nozzle assembly represents the only gas inlet at one end of the homogenizing tube, while the other end is completely spanned by the flow-through structure and represents the sole gas outlet for the homogenized fuel gas into the flame tube. The outer surface of the homogenizing tube is preferably gas-tight, as is the outer surface of the flame tube. Another preferred embodiment of the gas burner provides that the area of ​​the gas inlet to the ambient atmosphere exceeds the cross-sectional area of ​​the inner diameter of the homogenizing tube. The proposed designs represent structurally simple and therefore cost-effective options. To solve the problem, a burner matrix, i.e., an arrangement of at least three of the aforementioned gas burners, is further proposed. In light of the requirements of ECE R100 Rev. 3, a planar arrangement of the individual gas burners is proposed, wherein their orientation is unidirectionally orthogonal to the planar arrangement. Preferably, the gas burners are also arranged at a constant distance from one another, for example, in a uniform pattern distributed across the burner matrix, with the flames generated by adjacent gas burners preferably overlapping to achieve a homogeneous temperature load across the entire surface of the test specimen.In particular, for optimal design, a distance between the burner nozzles in a burner matrix is ​​proposed which lies between two to five times, preferably between 2.5 and three times, more preferably 2.7 times the diameter of the burner nozzles (inner diameter). The invention is explained in more detail with reference to exemplary embodiments, the following figures, and descriptions. All illustrated features and their combinations are not limited to these exemplary embodiments and their configurations. Rather, they are intended to be considered representative of further possible configurations that are not explicitly shown as exemplary embodiments. Fig. 1 shows a perspective view of a burner with burner nozzle arrangement, homogenization tube, flame tube, and flow-through structure in the form of a perforated sheet; Fig. 2 shows a longitudinal section of the exemplary embodiment shown in Fig. 1; Fig. 3 shows a top view of the flow-through structure of the exemplary embodiment shown in Fig. 1 and Fig. 2 (view AA in Fig. 2); and Fig.4a and b show a top view and a lateral partial section view of an exemplary burner matrix on a support profile and connected to gas supply lines via a network. As illustrated in the exemplary embodiment shown in Figures 1 and 2, a gas burner comprises as essential components a gas nozzle 1 as a burner nozzle assembly, screwed into a pipe fitting 2 as a homogenizing tube, onto which a perforated plate 3 is mounted as a flow-through structure, and through which the homogenizing tube opens into a flame tube 4. The internal volumes of these components are preferably rotationally symmetrical, preferably cylindrical, and arranged concentrically to one another. Preferably, the homogenizing tube and the flame tube are connected to the perforated plate by means of a welded connection (e.g., by arc welding). The inner diameter of the flame tube exceeds the outer diameter of the homogenizing tube, so that a bypass flow can be drawn in through the perforated plate parallel to the fuel gas inlet from the homogenizing tube through the perforated plate.In contrast, the gas nozzle is preferably a brass part, preferably screwed into the pipe fitting via a thread. Fig. 2 shows the same embodiment in a sectional view. The gas nozzle 1 essentially consists of a turned part with only one nozzle opening 5, which extends concentrically into the interior of the pipe fitting 2, serving as the fuel gas outlet. In this example, the nozzle opening before the outlet, as well as the interior of the pipe fitting and the flame tube, are preferably cylindrical. The gas flow propagating from the nozzle opening through the pipe fitting, as well as the bypass flow from the ambient atmosphere entering the flame tube through the perforated plate, are indicated by dashed lines. Furthermore, Fig. 2 shows preferred dimensions of the gas burner. Starting with the inner diameter D0 of the flame tube 4 as the initial parameter, a preferred inner diameter DR = 0.4 x D0 and a preferred length LR = D0 of the pipe fitting 2 are specified. For an optimal length LF of the flame tube 4, a value of LF = 1.5 x D0 is proposed. Fig. 3 shows a top view of the perforated sheet 3 as a flow-through structure of the embodiment illustrated in Fig. 1 and Fig. 2 (view AA in Fig. 2). In this embodiment, the perforated sheet 3 has uniformly sized openings 6 along its lateral extent, serving as gas passages for the ambient atmosphere into the flame tube. The perforated sheet is laterally bounded by the flame tube 4 and connected to it by means of a weld. The position of the pipe fitting 2, which is only schematically indicated and preferably welded to the perforated sheet, is shown concentrically to the flame tube on the perforated sheet. Figures 4a and 4b show a top view and a partial sectional side view AA of a burner matrix 7 (detail showing nine gas burners 8) on a support profile 9. The individual gas burners are connected via a network of gas supply lines 10, each via a connection fitting 11, to a gas supply (not shown), which in this example also allows the gas burners to be positioned and aligned relative to each other within the burner matrix. The burner matrix 7 thus comprises the network of gas supply lines, the connection fittings, and the gas burners. In this example, it is attached to the support profile 9 via the gas supply line 10 using clamps 12. The arrangement of the gas burners (8) in the burner matrix shown in this example follows a preferred planar arrangement and is preferably also equidistant from each other, with the gas burners being oriented unidirectionally orthogonal to the planar arrangement. Reference symbol list: 1 Gas nozzle 2 Pipe fitting 3 Perforated plate 4 Flame tube 5 Nozzle opening 6 Openings 7 Burner matrix 8 Gas burner 9 Support profile 10 Gas supply line 11 Connection fitting 12 Clamp

Claims

Gas burner comprising a) a burner nozzle assembly with at least one nozzle for a fuel gas outlet (1), b) a homogenizing tube (2) into which the burner nozzle assembly opens concentrically, and c) a flame tube (4) into which the homogenizing tube opens, wherein d) the flame tube (4) is open at both ends and has a larger inner diameter than the outer diameter of the homogenizing tube (2), e) a flowable structure (3) with through-openings (6) is provided between the homogenizing tube and the flame tube, and f) the flowable structure (3) forms a gas inlet for the ambient atmosphere away from the homogenizing tube (2), characterized in that g) the flowable structure (3) with through-openings is formed by a perforated sheet and spans the entire inner diameter of the flame tube (4). Gas burner according to claim 1, characterized in that the flowable structure (3) with through-openings (6) is selected from the group consisting of a grid structure, a lamellar structure, a screw structure, an open-pore structure or structures with serrated exit edges. Gas burner according to one of the aforementioned claims, characterized in that the flowable structure (3) with through-openings has a homogeneous flow resistance over its extent. Gas burner according to one of the aforementioned claims, characterized in that the homogenizing tube (2) and / or the flame tube (4) are cylindrical. Gas burner according to one of the aforementioned claims, characterized in that the burner nozzle arrangement has only one nozzle. Gas burner according to one of the preceding claims, characterized in that the burner nozzle arrangement (1) has a nozzle arrangement for only one gas. Gas burner according to one of the aforementioned claims, characterized in that the burner nozzle arrangement (1) completely surrounds and closes off the inner diameter of the homogenizing tube (2). Gas burner according to one of the aforementioned claims, characterized in that the area of ​​the gas inlet for the ambient atmosphere exceeds the cross-sectional area of ​​the inner diameter of the homogenizing tube. burner matrix (7) comprising an arrangement of at least three gas burners (8) according to one of the preceding claims in a planar arrangement, wherein the orientation of the gas burners is unidirectionally orthogonal to the planar arrangement.

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