Flashback-proof gas burner

Abstract

The present invention relates to a flashback-proof gas burner adapted to be coupled to an aperture of a combustion chamber. The gas burner is characterized by a specific configuration of a probe and its location for sensing the temperature. The probe has a fast response to changes in temperature, in particular when the flame is extinguished, allowing a fast response to close a valve for supplying gas to the inlet port, thereby preventing any explosion.

Description

FIELD OF THE INVENTION

[0001] The present invention relates to a flashback-proof gas burner adapted to be coupled to an aperture of a combustion chamber. The gas burner is characterized by a specific configuration of a probe and its location for sensing the temperature. The probe has a fast response to changes in temperature, in particular when the flame is extinguished, allowing a fast response to close a valve for supplying gas to the inlet port, thereby preventing any explosion.PRIOR ART

[0002] One of the technical fields with a more intensive development is any area related to the combustion of hydrocarbons, mainly because of its impact on the emission of greenhouse gases, gases with some type of toxicity such as NOx and, above all, because the combustion of hydrocarbons requires very demanding safety requirements.

[0003] The combustion of hydrocarbons formed by mixtures of various gases such as natural gas, has conditions that differ from the combustion of gases such as hydrogen, methane or propane. Each of the gases has different chemical kinetics with very different reaction velocities and combustion temperatures.

[0004] A different velocity of reaction means that the flame position in a burner tends to be closer to the nozzles or further away, so the burner designs must be suitable for stable and safe flame anchoring.

[0005] Burners based on the premixing of the fuel gas and the combustion gas, usually air, are well known. Premix burners are easy to manufacture since the mixing and injection stages in the combustion chamber are different, making the burners easy to manufacture since each component only has to perform one function.

[0006] However, premix burners have several problems related to safety. The most obvious one is that once the fuel is mixed with the comburent the reaction can start any time an ignition energy is reached and this condition could happen before reaching the introduction of the mixture into the combustion chamber. If this happens an explosion occurs with the danger of such an accident.

[0007] Another problem that exists in premix burners is that the parts that form the conduits of the mixture from the place where the mixture is formed to the burner have joints that must be very carefully sealed against leaks since the diffusion of a mixture of gas and comburent outside the device generates risk in the vicinity of the device.

[0008] In any case, the accumulation of fuel and comburent without the fuel being burned is a source of explosion risk. This condition occurs mainly when the burner is operating and for any reason there is a flame extinction. The fuel or fuel and comburent mixture continues to be entering into the combustion chamber without combustion that exhausts the fuel so very high storage volumes of fuel and comburent can be reached which can explode causing serious damage.

[0009] In addition, when there is a flame extinction after the burner has been operating, there are areas of the burner at high temperature that could be a source of ignition since the combustion fuel mixture could reach an ignition energy level.

[0010] To avoid fuel accumulation, it is necessary to operate a valve that shuts off the fuel supply as quickly as possible. According to the regulations, this shut-off should take place in less than one second.

[0011] Very fast acting sensors based on flame radiation measurements are known, so that an abrupt drop in radiation, such as that which occurs when the flame is extinguished, has an almost instantaneous response. The problem with this type of system is its technical complexity and high cost, especially when, in addition to its complexity, it is necessary to install more than one for measurement redundancy for safety reasons.

[0012] The problems described and known in the state of the art are solved in a very effective and inexpensive way according to the invention described below.DESCRIPTION OF THE INVENTION

[0013] A first aspect of the invention is a flashback-proof gas burner. The flashback-proof gas burner is adapted to be coupled to an aperture of a combustion chamber such that the combination of the burner and the combustion chamber is a heat generating system.

[0014] The first aspect of the invention is a burner that allows a rapid response to flame extinction. The first aspect of the invention is suitable and, more specifically, adapted to be installed in an opening of a combustion chamber, allowing it to serve, for example, as a part of a replacement kit for other burners installed on the opening of the combustion chamber, replacing different combustion mechanisms or burners adapted to burn different gases. In this configuration it is not necessary to make any changes to the combustion chamber.

[0015] The gas burner is suitable for the combustion of a fuel gas comprising hydrogen, more specifically adapted for the combustion of hydrogen.

[0016] The gas burner is a flashback-proof gas burner, where the junction between fuel and comburent occurs just a short time before combustion takes place. This configuration is very safe since the fuel does not have the ability to react until it is already introduced into the combustion chamber.

[0017] Therefore, the fuel is fed through one set of conduits and the comburent is fed separately through a different set of conduits than the fuel.

[0018] The burner comprises: an air inlet port; a fuel gas inlet port; a fuel gas manifold in fluid communication with the fuel gas inlet port by means of a fuel gas conduct, the fuel gas manifold comprising at least one fuel gas nozzle arranged for injecting fuel gas into the combustion chamber when the burner is operatively coupled to the combustion chamber; an air manifold in fluid communication with the air inlet port by means of an air conduct, the air manifold comprising at least an air outlet configured to supply air at the proximity of the gas nozzle for causing, in operative manner, the junction of the air and the fuel gas in the combustion chamber and out of the flashback-proof gas burner.

[0019] The fuel inlet port allows fuel to enter the combustion chamber, e.g., from a pressure pump or from a tank containing the fuel at a pressure above the pressure at which the combustion chamber is in operation, preferably about the ambient pressure.

[0020] The fuel gas manifold receives the fuel coming from the inlet port and serves as a space where the fluidic conditions of the fuel are homogenized, for example the pressure, so that it is the same at any location and, in particular where the at least one fuel gas nozzle is located. If according to an embodiment the fuel gas manifold comprises a plurality of fuel gas nozzles, each nozzle operates approximately at the same conditions.

[0021] The air inlet port allows air to enter the combustion chamber, e.g. from an air impeller, thereby providing control of the flow, in particular the air / fuel rate when the flow of the fuel gas is also under control as it is in our case. According to preferred embodiments, the air / fuel rate is in an operative manner with respect to the air / fuel rate at stochiometric conditions in the range [1.05, 2.1], and more preferably in the range [1.0, 1.8], and more preferably in the range [1.1, 1.7], and more preferably in the range [1.2, 1.6], and more preferably in the range [1.3. 1.5], and more preferably about 1.4, in all cases operating with excess of oxygen, measurements in volume.

[0022] For clarification, we use as notation the standard mathematical format where (a,b) denotes an open interval between a value and b value and, [a,b] denotes a closed interval between a value and b value. The open interval does not contain the extreme values and the closed interval contains the extreme values. An interval can be open at one end and closed at the other end.

[0023] According to an example of realization, the system formed by the combustion chamber and the burner includes an exhaust probe at the exhaust gas outlet to measure at least one component concentration of exhaust gas. This probe is part, preferably, of a closed loop control system to ensure the air / fuel ratio as a setpoint value.

[0024] According to a preferred embodiment, the air / fuel ratio is constant for any air intake flow rate.

[0025] Air enters an air manifold from an air inlet port, the air manifold housing the fuel gas manifold. The air manifold comprises at least one air outlet wherein the at least one fuel gas nozzle injects fuel into the combustion chamber passing through the air outlet. The fuel gas exits the gas nozzle passing through the air outlet allowing a flow of air to impinge on the injected fuel gas causing the two flows to meet in the combustion chamber.

[0026] According to a preferred embodiment, the fuel gas manifold comprises a plurality of fuel gas nozzles injecting fuel gas through the at least one air outlet of the air manifold.

[0027] According to another embodiment, which may be according to any of the embodiments disclosed below, the air manifold comprises a plurality of air outlets and each fuel gas nozzle is adapted to inject fuel gas through an air outlet of the air manifold.

[0028] Additionally: the burner comprises a probe adapted for sensing temperature, the probe comprising a connecting portion and a thermal measurement region; the connecting portion of the probe being housed in the air manifold, and the thermal measurement region being located in, or proximal to, a region where the flame is located when the gas burner is in operative mode.

[0029] The probe is the element responsible for carrying out a thermal measurement of a thermal condition where this probe comprises at least two distinct parts, a region where a parameter representative of a thermal condition is measured and, a connecting portion that establishes a link between the region where the measurement is carried out and the connections that provide the signal with the measurement allowing to act for example at the moment when a flame extinction is detected.

[0030] The connecting portion is a structural part although it may have other functions such as that of transporting the signal obtained in the measurement region. The connecting portion is interpreted as a part of the probe other than the measurement area. An example of a connecting portion is the body of the probe with wires or communication elements for carrying the measurement signal. Another example of connecting portion is a part of the head body, wherein the head comprises the measurement region and a distinct part which is cooled according to the invention and is different from the measurement region. In order for the probe to respond quickly, the connecting portion does not have to be a complete part or piece, but only a portion that, in operative manner, is under different temperature conditions than the measurement region of the probe.

[0031] The measurement region is located in, or close to, a region where the flame is operationally located during combustion. This allows the flame temperature, an estimate of the flame temperature, or a parameter representative of a thermal condition to be measured. An example of a parameter representative of a thermal condition is a probe that provides an electrical potential difference in response to a temperature or a temperature variation. Any physical element of the probe that supports the measurement region will also be at an elevated temperature. This causes a thermal inertia which means that sudden temperature changes such as that caused by flame extinction are not detected in the signal provided by the temperature measurement region instantaneously but require a period of time which may be too long for safety requirements. A very slow response of the signal with the temperature value of the measuring region prevents the fuel feed valve from being closed in time.

[0032] However, according to the first aspect of the invention, the connecting portion of the probe is housed in the air manifold. The interior of the air manifold contains fresh air since it has not yet been met even with the fuel. The flow of fresh air, in this configuration, is in direct contact with the connecting portion of the probe by convention, a very effective form of heat transport, which allows its temperature to tend to drop as rapidly as possible.

[0033] As a result, upon flame extinction, the temperature measurement region, being attached to the cooled connecting portion, reduces its temperature by conduction, giving a response in the probe output signal that shows the actual temperature drop with a much faster response time.

[0034] It has been seen experimentally that this configuration allows a response time well below one second, the maximum time imposed by the regulations for the device to be safe.

[0035] Even if in an embodiment two probes are included under these conditions, the manufacturing costs are very low for a solution based on a temperature sensor that is not based on the flame radiation index.

[0036] In an embodiment according to any of the previous disclosed embodiments, the probe is a thermocouple.

[0037] A thermocouple is a device that makes use of two dissimilar metals in such a way that depending on the temperature in one and the other metal a potential difference is established. In an example of a thermocouple the dissimilar metals are close together so that the potential difference occurs at the junction. This is not the only configuration but the metals can be at different points under different thermal conditions.

[0038] In the context of the invention two types of thermocouples will be differentiated, a first type of thermocouple where the measurement occurs in a measurement region located at the tip of the probe and where the response in the form of potential difference is representative of the absolute temperature at which the tip is located.

[0039] A second type of thermocouple, of lower cost, has a first metal in the region of measurement, in the tip of the probe, and a second metal in a reference point that we will call cold point, distant from the region of measurement and, that is located in the connecting portion.

[0040] In this second, although the measured value does not establish the absolute temperature measurement value, it provides a signal representative of the thermal conditions near the flame that depends, among other factors, on the temperature difference between the measurement region and the cold point.

[0041] Then, in an embodiment according to any of the previous disclosed embodiments, the probe is a thermocouple, the temperature measurement region of the probe being at the bimetallic joint of the thermocouple and, the connecting portion of the probe being at least a part of metallic connections connecting the bimetallic joint of the thermocouple.

[0042] This embodiment is according to the first type of thermocouple.

[0043] As said before, thermocouple according to this first type, is a probe comprising a bimetallic joint adapted to provide a signal responsive to the temperature.

[0044] The signal is a potential difference of greater or lesser magnitude depending on the temperature of the bimetallic joint. The signal is transmitted to a connection through electrically conductive elements. These electrically conductive elements are also good heat conducting elements and are part of the connecting portion so that in operating mode it is subjected to the burner supply air flow.

[0045] As a result, the bimetallic joint is at a temperature close to the flame temperature when the burner is in operating mode. When the flame is extinguished, the burner feed air is cold and in contact with the connecting portion which is also cold, closer to ambient temperature than the measurement region, so that as soon as flame extinction occurs the temperature of the connecting portion causes rapid cooling of the bimetallic joint through the conductive elements that keep the bimetallic joint and the connecting portion connected.

[0046] An embodiment according to any of the disclosed embodiments and using the second type of thermocouple as probe. In this embodiment the probe is a thermocouple comprising two dissimilar metal parts, and wherein the measurement region of the probe comprises one dissimilar metal and, the other dissimilar metal is at a reference cold point located in the connecting portion of the probe wherein the probe is adapted to provide a signal amplitude at least responsive to the temperature difference between the temperature of the two dissimilar metals.

[0047] According to this thermocouple structure, the signal amplitude is responsive to the temperature difference between two parts of the probe, the measurement region, which is operatively located near or in the flame, and the cold point, which is operatively located in the connecting portion and is cooled by the fresh air flowing inside the air manifold.

[0048] In this embodiment, when the flame is extinguished, the temperature of the measurement region is cooled down and the temperature of the cold point is also cooled down. Since the cold point is refrigerated by the fresh air flowing within the air manifold where it is located, the temperature difference is increased at a first stage and tends to be zero as time goes on.

[0049] Flame extinction can be detected in several ways. According to a first criterion, because the variation of the signal being proportional to the temperature difference, in absolute value, exceeds a predetermined threshold.

[0050] Threshold values are positive values and are lower the smaller the variation allowed. The values are positive because variation relative to a reference is measured using the absolute value function, which is always positive.

[0051] However, the same criterion can be transformed into one that uses absolute (or real) values instead of values relative to a given reference. In this case, the comparison is not with a threshold value, but with values that are either above or below the reference value. However, this alternative form of expression is considered equivalent in all cases.

[0052] According to a second criterion, because the derivative with respect to time of the signal being proportional to the temperature difference, or an estimate of such a derivative, varies in absolute value beyond a predetermined threshold.

[0053] A third criterion in which the first criterion and the second criterion are evaluated on the signal being proportional to the temperature difference, and the criterion which first identifies a change that establishes the need to act on a commanded valve to shut off the fuel gas.

[0054] In an embodiment according to any of the previous disclosed embodiments, the probe has an elongated shape, the temperature measurement region being located at one end of the probe.

[0055] The elongated configuration of the probe allows the installation of the probe positioned in two different orientations: perpendicular to the wall of the air manifold and the measurement region under the influence of the flow entering through an air outlet of the air manifold for entering air within the combustion chamber, or, inclined to the wall of the air manifold locating the measurement region out of the influence of the flow entering through an air outlet of the air manifold for entering air within the combustion chamber.

[0056] These two options can be used for any of the disclosed embodiments, in particular to the first type of thermocouple and to the second type of thermocouple.

[0057] According to a preferred example that applies to all described examples, the air manifold houses the fuel gas manifold wherein, the air manifold has a flat or convex wall. It is this flat or convex wall where the air openings are located through which the fuel gas is introduced by the use of the nozzles or injectors (both terms will be used). The fuel gas manifold, housed inside the air manifold, locates the nozzles close to the internal area of the flat or convex wall of the air manifold. In a preferred example this fuel gas manifold is formed by at least two pieces, preferably in stamped sheet metal, which are joined together. These two pieces extend along a main reference surface which is either flat or convex. The fuel gas manifold, according to one example, has openings and does not cover the entire main reference surface. The probe preferably passes through one of these openings and the perpendicular or inclined direction is with respect to this main reference surface.

[0058] The first option is optimal for the first type of thermocouple wherein the measurement region is under the influence of the air flow, and the second option is optimal for the second type of thermocouple, where the measurement region is out of the influence of the air flow.

[0059] These two positions means that the elongated configuration allows three probe locations to be differentiated in a small space: the temperature measurement region located on the side of the combustion chamber, in operative manner, inside or close to the region where the flame is anchored; the connecting portion located inside the air manifold; and the connection end for obtaining the measured signal, which is located outside the air manifold and is accessible for connection to the control means.

[0060] In an embodiment according to any of the previous disclosed embodiments, the fuel gas manifold is housed within the air manifold.

[0061] A configuration in which the fuel gas manifold is housed inside the air manifold is a very effective configuration for locating the at least one fuel gas nozzle or injector on a side of the wall of the air manifold defining a boundary between its interior and the combustion chamber.

[0062] When the fuel gas manifold comprises a plurality of injectors or nozzles, these are distributed on a surface of the fuel gas manifold close to the inner surface of the wall of the air manifold. Thus, it is possible to inject the fuel gas into the interior of the combustion chamber through the openings of the air manifold and, at the same time, to allow the injection of an air stream which is met with the fuel gas just before it enters the combustion chamber. The resulting burner is therefore a flashback-proof burner.

[0063] In an embodiment according to the previously disclosed embodiment, the at least one fuel gas nozzle injects the fuel gas through the at least one air outlet, and wherein there is a clearance between the fuel gas nozzle and the air outlet to allow the passage of the air.

[0064] According to this embodiment, the air outlet through which the fuel gas is injected by means of a nozzle or injector has a clearance between the outlet and the nozzle. According to a preferred embodiment, the clearance is shown according to the radial direction taking the axis of the nozzle as a reference.

[0065] According to an example, when the embodiment includes a plurality of air outlets and also a plurality of nozzles, air ducts are provided between an inner wall of the air manifold wall and the fuel gas manifold wall. These ducts promote air distribution near each nozzle. These air ducts are also reinforcing ribs for the surface of the air manifold located facing the combustion chamber.

[0066] This clearance allows air to enter the combustion chamber but causes it to flow against the fuel gas flow, preferably in a direction transverse to the gas flow, which promotes junction between the two.

[0067] In an embodiment according to any of the previous disclosed embodiments, the fuel gas manifold comprises at least two plates joined configuring either a flat collector or a collector that extends along a convex surface.

[0068] A very efficient combustion mode is one in which the flame has a flat configuration or at least extends along a surface. The joining process of the air and fuel gas takes place on one side of the surface feeding the flame and after combustion the hot gases carry the heat to the rest of the combustion chamber where there are exchange means to transport the heat to the final application site.

[0069] It has been shown that an easily constructed configuration is based on the joining of two plates, preferably die-cut and stamped, which together give rise to a flat manifold or a manifold extending along a convex surface. A special case of a convex surface is a spherical surface portion.

[0070] In an embodiment according to any of the previous disclosed embodiments, the air manifold comprises a wall with the air outlets being either a flat wall or a wall that extends along a convex surface.

[0071] The wall of the air manifold with the air outlets defines, among other parameters, the shape and anchorage of the flame. A flat wall or a wall extending along a convex surface allows to optimize the available surface of the burner when installed in the opening of the combustion chamber. In a specific embodiment, the flat wall or a wall extending along a convex surface is hosted within an area surrounded by the seat adapted to close the aperture of the combustion chamber when in operative manner the burner is installed in the combustion chamber.

[0072] In an embodiment according to any of the previous disclosed embodiments, the probe passes through at least the wall of the air manifold comprising the air outlets.

[0073] The probe is partially located in the interior of the air manifold and the end with the region for temperature measurement is located in the space of the combustion chamber. According to this embodiment, the probe passes through at least the wall of the air manifold that contains the air outlets.

[0074] This arrangement has the advantage of giving rise to a very compact and reactive device and is particularly useful when the configuration of the area where the nozzles are distributed has a configuration extending according to a plane or according to a convex surface since a position perpendicular or close to perpendicular to this surface allows a very fast cooling effect.

[0075] In an embodiment according to the previous disclosed embodiment, the probe passes through the fuel manifold.

[0076] The configuration described for the fuel manifold is either flat or convex. This does not mean that the entire manifold covers an area of either flat or convex configuration but rather that it positions the nozzles according to either a flat or convex spatial distribution. That is, according to an embodiment the fuel manifold is formed by conduits for example radially distributed covering the area where the nozzles are positioned. With this configuration, the characteristic that the probe "passes through" the fuel manifold admits two interpretations, either that it passes from one side to the other taking advantage for example of the gaps or openings left by the radial ducts, or that it actually passes through the walls of the fuel gas where, in this case, it would be necessary to seal the inlet and outlet openings in the fuel manifold and to thermally insulate the section of the probe housed inside the fuel manifold. The first case is the preferred one.

[0077] According to this embodiment, the probe passes through the fuel manifold, preferably passing through openings, and also through at least one wall of the air manifold, preferably through an opening.

[0078] According to the specific examples to be described below, not only the elements involved in combustion extend close to a surface that is either flat or convex but the entire burner essentially adopts this shape making the sensor easily accessible from the outside while keeping the two most relevant parts inside, the connecting portion and the temperature measurement region, at a different temperature.

[0079] In an embodiment according to any of the previous disclosed embodiments, the burner further comprises a processor, the processor being in communication with the probe and in communication with a commanded valve for feeding the fuel gas manifold, the commanded valve adapted to shut off the flow of the fuel gas when commanded, and wherein the processor is further adapted to receive a signal from the probe providing a measurement responsive to the temperature and is adapted to send a signal to the commanded valve to shut off the flow fuel gas inlet if the variation of: a) the absolute value measured signal value, or b) the absolute value of the first derivative respect to time, or c) any of the two former options, a) or b), exceeds a threshold value.

[0080] These three options applies to any kind of probe.

[0081] Option a) is preferably used when the probe is a thermocouple of the first type when the measurement responsive to the temperature is the temperature value at the measurement region of the probe and, option b) is preferably used when the probe is a thermocouple of the second type when the measurement responsive to the temperature is a measurement of the temperature difference between the measurement region and the cold region of the probe.

[0082] According to this embodiment, the burner is provided with safety means that allow to react to a dangerous situation, such as the extinction of the flame. The signal generated by the probe is transmitted to a processor which compares the value of the signal, which is representative of the temperature in the temperature measurement region, with a threshold value. If the signal representative of the temperature falls below this threshold, the processor sends a signal that commands the closure of a fuel supply valve to the burner.

[0083] The closing time is not instantaneous, but the configuration according to one of the examples described allows a very fast response when causing a signal generation, the signal indicating the temperature changes due to the low thermal inertia. The processor responds to this change in the input signal by closing the valve in a very short time, demonstrably less than the second required by the regulations.

[0084] In an embodiment according to the previous disclosed embodiment, the processor is further adapted to send a signal to the commended valve to shut off the flow fuel gas inlet if the signal that is representative of temperature is higher than a second threshold value.

[0085] According to this embodiment, the processor is adapted to react by closing the fuel gas flow inlet when it detects a flame extinction and also when there are combustion conditions that result in a very high temperature that exceeds a predetermined condition. This is also a dangerous condition that must be controlled and, according to this embodiment, the processor also responds by closing the commanded valve.

[0086] A second aspect of the invention is a burner system comprising a burner according to any of the previously disclosed embodiments and, further comprising a combustion chamber, the burner installed and adapted to be coupled to an aperture of a combustion chamber.

[0087] The burner, according to any of previous embodiments, may further comprise two probes to have a redundant measure, being possible to have both thermocouples of one type, both of the second type or a first probe of one type and the second probe of the second type.

[0088] It is also a system burner embodiment, a system as the previous one, wherein it further comprises a exhaust probe adapted to measure at least one component concentration of exhaust gas, and wherein the processor is further adapted to control the burner, preferably under a closed loop, such that the air / fuel rate, in an operative manner, with respect to the air / fuel rate at stochiometric conditions, is in the range [1.05, 2.1], and more preferably in the range [1.0, 1.8], and more preferably in the range [1.1, 1.7], and more preferably in the range [1.2, 1.6], and more preferably in the range [1.3. 1.5], and more preferably about 1.4, measurements in volume, in all cases operating with excess of oxygen, preferably the air / fuel ratio being constant for any air intake flow rate.DESCRIPTION OF THE DRAWINGS

[0089] These and other features and advantages of the invention will be seen more clearly from the following detailed description of a preferred embodiment provided only by way of illustrative and non-limiting example in reference to the attached drawings. Figure 1This figure shows in perspective a first embodiment of the burner including the air impulsion means and the fuel gas feed management valve. The burner is installed in an aperture of the combustion chamber. Figure 2This figure shows in perspective the same embodiment as in the previous figure where the burner, the fuel gas valve and the drive means are separated from the combustion chamber to allow visual access to both the combustion chamber aperture and the rest of the elements. Figure 3This figure shows in perspective the same embodiment as in the previous figures, with the valve and pipe for fuel gas supply and the air impulsion means removed, allowing an enlarged view of the burner. Figure 4This figure shows in perspective the same burner removing the combustion chamber. Figure 5This figure shows the same burner as in the previous figure in perspective from the opposite side, allowing visual access to the air outlets and fuel gas nozzle outlets. Figure 6This figure shows a sectional view of the previous figure allowing the visual access to the inner part of the air manifold and the inner part of the fuel gas manifold. Figure 7This figure shows a sectional view of the previous figure using a different perspective, moving the probe out of the burner providing visual access to all parts of the probe. Figure 8This figure shows an enlargement of figure 7 but with the probe located in its final position. Figure 9This figure shows the same elements than those shown in figure 7 and the same sectional view but the probe is located in its final position. DETAILED DESCRIPTION OF THE INVENTION

[0090] As will be appreciated by one skilled in the art, aspects of the present invention may be embodied a burner flashback-proof gas burner adapted to be coupled to an aperture.

[0091] Figure 1 shows an embodiment of the flashback-proof gas burner (B) including a combustion chamber (5). The combustion chamber (5) is a chamber where the combustion reaction takes place in the form of a flame. In this combustion reaction heat is generated which is transferred for example via a heat exchanger to the destination of this energy depending on the end application.

[0092] In this embodiment the combustion chamber (5) has an aperture (5.1) over which the burner (B) is coupled and fixed. This configuration allows not only the maintenance of both the burner(B) and also of the elements accessible from inside the combustion chamber (5) but also allows for example the replacement of the complete burner (B). This replacement may be justified by the need to use a burner (B) configured for a different type of fuel.

[0093] The burner (B) according to this embodiment is configured to burn a gas fuel comprising hydrogen and more specifically only hydrogen.

[0094] The burner(B) of this embodiment is a flashback-proof gas burner and therefore has an air inlet port (1), the comburent, and a gas fuel inlet port (2). Figure 1 shows at the lower part of the figure air impulsion means (4) for to draw air from the atmosphere into the combustion chamber (5) imposing an overpressure above atmospheric pressure. The air leaving the impulsion means (4) is conducted through an air conduct (6.1) to the interior of an air manifold (6).

[0095] A commanded valve (8) is also shown in the lower part of figure 1, which controls the flow of fuel gas. The fuel gas comes either from a source under pressure or by means of an impulsion of the fuel gas. This source of the fuel gas is not shown in the figure in the sake of clarity.

[0096] Figure 2 is a perspective view of the same embodiment where the burner (B) is held together with the commanded valve (8) and the air impulsion means (4) and, in turn, this group of elements is separated from the combustion chamber (5) to allow observing the aperture (5.1) of the combustion chamber (5) on which the burner (B) is engaged.

[0097] The flame formation in the burner (B) occurs just behind the circular plate that engages over the aperture (5.1) of the combustion chamber (5) also of circular configuration according to this specific embodiment. Also according to this embodiment, the flame has a configuration also mainly flat and projects the heat into the combustion chamber (5) which in this embodiment comprises a heat exchanger (5.2) shown through the aperture (5.1) as a ring stack.

[0098] In Figure 3 both the commanded valve (8) and the air impulsion means (4) have been eliminated to allow to observe in an enlarged view the burner (B) installed over the combustion chamber (5).

[0099] Figure 4 shows the same burner (B) after having removed the combustion chamber (5).

[0100] Figures 1 to 4 also show the outer part of two probes (7), mainly the end allowing the connection that receives the signal measured by the probe (7) and that allows to determine a measurement of the flame temperature or of a zone close to the flame. The use of two probes (7) is a safety measure for redundancy in the measurement of the same parameter.

[0101] It is at this end that they engage the connections that carry the signal to a processor, not shown, in charge of processing the signal and responding to the measured values and in particular to its changes.

[0102] The commanded valve (8) allows the burner (B) to be shut off, for example, because it receives a signal from the processor in response to flame extinction event.

[0103] The fuel gas is led from the commanded valve (8) to a fuel gas manifold (3) by means of a fuel gas conduct (3.1).

[0104] The burner (B) is a flashback-proof gas burner so that the fuel gas and the comburent are meet just at the moment of entering into the combustion chamber (5) and also in cross flow. To achieve this condition the fuel gas manifold (3) is housed inside the air manifold (6) and both (3, 6) have a similar configuration. In this embodiment the fuel gas manifold (3) has a flat configuration, at least of the surface on which there is distributed a plurality of fuel gas nozzles (3.2) for providing the injection of fuel gas jets inside the combustion chamber (5).

[0105] Figure 5 shows a perspective view of the burner (B) with the point of view located on the other side of the burner with respect to the point of view used in figures 1 to 4. This view shows a heat insulator (10) which located within the aperture (5.1) of the combustion chamber (5) ensuring a thermally protected closure.

[0106] This figure also shows the electrode (9) that cause the flame ignition, placing their end in a position close to the region where, in an operative way, the flame is anchored to the burner.

[0107] In the inner zone of the heat insulator (10) several outlets are shown which correspond to the outlet openings of the plurality of fuel gas nozzles (3.2) destined to introduce the fuel gas inside the combustion chamber (5). These outlets are air outlets (6.2), i.e., they are the outlets through which the air exits since the ends of the fuel gas nozzles (3.2) do not completely close the surrounding air outlets (6.2). The air outlets (6.2) are outlets located at a wall of the air manifold (6). Thus, in this embodiment, the fuel gas manifold (3) and the air manifold (6) have a flat configuration because the location of the fuel gas nozzles (3.2) must be close to and inside in the air outlets (6.2) located in a wall of the air manifold (6).

[0108] That is, between the fuel gas nozzles (3.2) and the air outlets (6.2) through which the fuel gas nozzles (3.2) are inside, there is a clearance that determines a distance through which the air or comburent enters into the surroundings of the jet of fuel gas injected by the fuel gas nozzles (3.2). Under these conditions the air inlet occurs in the radial direction which is mainly transverse to the fuel gas inlet direction. This condition causes the flows to be crossed and generates a combining process in a very small space.

[0109] We will return to figure 8 to see what this configuration looks like according to a sectional view.

[0110] Figure 6 shows a sectional view of the example shown in figure 5 where the flat configuration of the fuel gas manifold (3) is observed and how it is housed inside the air manifold (6) where one of its walls is approximately flat, the wall where the air outlets (6.2) are located. However, the wall of the air manifold (6.2) that is close and parallel to a wall of the fuel gas manifold (3) has reinforcing ribs that also generate channels that facilitate the entry of air into the area surrounding the air outlets (6.2) to reduce pressure drop.

[0111] Figure 7 shows another sectional view where the probe (7) is shown in an exploded perspective. This same view is seen in Figure 9 where the probe (7) is now in its final position. The sectioned view has removed half of the burner (B) where a second probe (7) is located.

[0112] Figure 8 is an enlargement of Figure 9 and shows how the probe (7) is positioned in relation to each of the internal spaces of the burner (B), in particular the air manifold (6) and the fuel gas manifold (3).

[0113] For extracting the measured signal, the probe (7) has, one connection located at the measurement region (7.2) and a second connection, the cold point, at the connecting region. The signal is responsive to the potential difference between the two points. In this embodiment, the probe (7) is a second type thermocouple in which the signal is generated in the form of a potential difference in response to a certain temperature conditions at the measurement region (7.2) and at the cold point.

[0114] Between the two ends is shown in elongated configuration a sleeve-shaped section that allows the threading on the rear wall of the air manifold (6) establishing a sealed joint and, also an elongated section, which in this embodiment is metallic, where the signal is transmitted. This extension which in this embodiment is metallic comprises good conductors for heat and, the parts that conduct the signal are also good signal conductors. It is to be interpreted as connecting portion (7.1) to any intermediate section between the two ends of the probe (7) having thermal conduction ability with the temperature measuring region (7.2). In this embodiment, the connecting portion (7.1) also has the cold point of the thermocouple.

[0115] Referring to Figure 8, the connecting portion (7.1) is located inside the space formed by the air manifold (6) so that this connecting portion (7.1) will be subjected to heat transfer phenomena by convection upon interaction with the air circulating inside the air manifold (6). As a result, the temperature of the connecting portion (7.1) is close to the ambient temperature except for the changes that may be produced by the pressure rise of the air impulsion means (4).

[0116] In turn, the temperature measuring region (7.2) is at one end wherein the probe (7) passes through at least the wall of the air manifold (6), and then the temperature measuring region (7.2) is in direct contact with the interior of the combustion chamber (5). To reach this position inside the combustion chamber (5) the probe (7) also overcomes the position of the fuel gas manifold (3) either by passing through it or, more safely, by passing between channels or ribs that carry the fuel gas leaving free spaces or openings between such channels or ribs such as the one that allows the passage of the probe (7). This form of passage without passing through the interior of the fuel gas manifold (3) makes it possible not to transmit high temperature to the interior of a space which in operational form contains the fuel gas reducing risks.

[0117] As shown in the above disclosed figures 5 and 6, the temperature measuring region (7.2) emerges from the surface formed by the wall of the air manifold (6) which is in direct contact with the interior of the combustion chamber (5) and projects a distance that allows the temperature measuring region (7.2) to be at least close to the flame.

[0118] The measurement of the temperature measurement region (7.2) will be either the flame temperature or a temperature close to it.

[0119] Upon flame extinction, the temperature of the temperature measuring region (7.2) drops because heat of this regions is transferred both to the surroundings and along the probe (7) and in particular through the connecting portion (7.1). The cold point located at the connecting portion is cooled down faster because is under the influence of the air flow within the air manifold so the difference of temperature increases in a first period of time and then tend to decrease. This fast variation at the very first period of time is detected and generating a signal with very short response time, sufficient to respond by cutting off the fuel gas supply.

[0120] In this embodiment, the signal representative of the difference of temperature, and proportional to it, and in particular this rapid evolution due to flame extinction, is processed by the processor in such a way that, upon comparing it with a threshold value, assessing the absolute value of the comparison, and verifying that it has exceeded said threshold value, it transmits a signal that commands the closing of the commanded valve (8) and, therefore, cuts off the fuel gas supply.

[0121] This rapid response prevents the accumulation of fuel gas inside the combustion chamber (5) that could lead to an explosion.

Claims

1. A flashback-proof gas burner (B) adapted to be coupled to an aperture (5.1) of a combustion chamber (5), suitable for the combustion of a fuel gas comprising hydrogen, the burner (B) comprising: - an air inlet port (1); - a fuel gas inlet port (2); - a fuel gas manifold (3) in fluid communication with the fuel gas inlet port (2) by means of a fuel gas conduct (3.1), the fuel gas manifold (3) comprising at least one fuel gas nozzle (3.2) arranged for injecting fuel gas into the combustion chamber (5) when the burner (B) is operatively coupled to the combustion chamber (5); - an air manifold (6) in fluid communication with the air inlet port (1) by means of an air conduct (6.1), the air manifold (6) comprising at least one air outlet (6.2) configured to supply air at the proximity of the gas nozzle (3.2) for causing, in operative manner, the junction of the air and the fuel gas in the combustion chamber (5) and out of the flashback-proof gas burner (B); wherein - the burner (B) comprises a probe (7) adapted for sensing temperature, the probe (7) comprising a connecting portion (7.1) and a temperature measurement region (7.2); - the connecting portion (7.1) of the probe (7) being housed in the air manifold (6), and the temperature measurement region (7.2) being located in, or proximal to, a region where the flame is located when the gas burner (B) is in operative mode.

2. A burner according to claim 1, wherein the probe (7) is a thermocouple, the temperature measurement region (7.2) of the probe (7) being the bimetallic joint of the thermocouple and, the connecting portion (7.1) of the probe (7) being at least a part of metallic connections connecting the bimetallic joint of the thermocouple.

3. A burner according to claim 1, wherein the probe (7) is a thermocouple comprising two dissimilar metal parts, and wherein the measurement region (7.2) of the probe (7) comprises one dissimilar metal and, the other dissimilar metal is at a reference cold point located in the connecting portion (7.1) of the probe (7) wherein the probe (7) is adapted to provide a signal amplitude at least responsive to the temperature difference between the temperature of the two dissimilar metals.

4. A burner according to any of previous claims, wherein the probe (7) has an elongated shape, the temperature measurement region (7.2) being located at one end of the probe (7).

5. A burner according to any of previous claims, wherein the fuel gas manifold (3) is housed within the air manifold (6).

6. A burner according to claim 4, wherein the at least one fuel gas nozzle (3.2) inject the fuel gas through the at least one air outlet (6.2), and wherein there is a clearance between the fuel gas nozzle (3.2) and the air outlet (6.2) to allow the passage of the air.

7. A burner according to any of previous claims, wherein the fuel gas manifold (3) comprises at least two plates joined configuring either a flat collector or a collector that extends along a convex surface.

8. A burner according to any of previous claims, wherein the air manifold comprises a wall with the air outlets (6.2) being either a flat wall or a wall that extends along a convex surface.

9. A burner according to any of claims 2,3, 4 and according to claim 8, wherein the probe (7) is positioned perpendicular to the wall of the air manifold (6) and the measurement region (7.2) under the influence of the flow entering through an air outlet (6.2) of the air manifold (6) for entering air within the combustion chamber.

10. A burner according to any of claims 2,3, 4 and according to claim 8, wherein the probe (7) is positioned inclined to the wall of the air manifold (6) locating the measurement region (7.2) out of the influence of the flow entering through an air outlet (6.2) of the air manifold (6) for entering air within the combustion chamber.

11. A burner according to any of previous claims, wherein the probe (7) passes through at least the wall of the air manifold (6) comprising the air outlets (6.2).

12. A burner according to the previous claim, wherein the probe (7) passes through the fuel manifold (3).

13. A burner according to any of previous claims, wherein it further comprises a processor, - the processor being in communication with the probe (7) and in communication with a commanded valve (8) for feeding the fuel gas manifold (3), the commanded valve (8) adapted to shut off the flow of the fuel gas when commanded, and - wherein the processor is further adapted to receive a signal from the probe (7) providing a measurement responsive to the temperature and is adapted to send a signal to the commanded valve (8) to shut off the flow fuel gas inlet if the variation of: a) the absolute value measured signal value, or b) the absolute value of the first derivative respect to time, or c) any of the two former options, a) or b), exceeds a threshold value and, - optionally, the processor is further adapted to send a signal to the commended valve (8) to shut off the flow fuel gas inlet if the signal that is representative of the temperature is higher than a second threshold value.

14. A burner system, comprising a burner according to claim 13 and, further comprising a combustion chamber (5), the burner installed and adapted to be coupled to an aperture (5.1) of a combustion chamber (5).

15. A burner system according to claim 14, wherein it further comprises a exhaust probe adapted to measure the at least one component of the exhaust gas, and wherein the processor is further adapted to control the burner, preferably under a closed loop, such that the air / fuel rate, in an operative manner, with respect to the air / fuel rate at stochiometric conditions, is in the range [1.05, 2.1], and more preferably in the range [1.0, 1.8], and more preferably in the range [1.1, 1.7], and more preferably in the range [1.2, 1.6], and more preferably in the range [1.

3. 1.5], and more preferably about 1.4, measurements in volume, in all cases operating with excess of oxygen, preferably the air / fuel ratio being constant for any air intake flow rate.

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