Flashback detection sensor, burner control system and method for controlling a burner control system

Abstract

A flashback detection sensor configured to be arranged in a gas burning system, the system comprising: - a gas burner arranged in a combustion area; and - one or more than one fluid inlet line(s) arranged in between a fluid source and the combustion area, for guiding the fluid in a transport direction towards the combustion area, wherein the flashback detection sensor in use is arranged in at least one of the one or more than one fluid inlet line(s), at a position upstream of the combustion area when seen in the transport direction, the flashback detection sensor configured for monitoring a physical property of the fluid in the fluid inlet line and detecting the occurrence of a flashback event in the fluid inlet line based on changes in the physical property of the fluid present in said fluid line.

Description

[0001] Title: Flashback detection sensor, burner control system and method for controlling a burner control system.

[0002] Description:

[0003] The present disclosure relates to a burner control system and sensors used therein, as for example applied in a central heating system, a domestic water heater system or a pool water heater system. Such burner control systems and sensors are typically comprised by a hot water appliance in which fluid (generally water) is heated before being fed back into the heating system or drafted for use. The present disclosure moreover relates to a method for controlling such a burner control system.

[0004] The purpose of prior burner control systems is primarily twofold. Firstly, burner control systems perform flame supervision by continuously monitoring the presence of a flame. In the event that the flame unexpectedly disappears, combustible gas may accumulate within a combustion chamber of the burner control system or the component in which it is housed (e.g. a hot water appliance, such as a gas boiler), which may violently explode when brought to ignition. Upon the flame unexpectedly disappearing, the burner control system may initiate a safety procedure to prevent a potentially dangerous accumulation of combustible gas from occurring.

[0005] Secondly, a burner control system controls the sequence of actions that are performed for initiating combustion of combustible gas.

[0006] Prior art burner control systems typically utilise natural gas, or other hydrocarbon-fuels such as propane, as fuel for heating fluid of the heating system to which they are connected. Recently, there has been an increased interest in utilising hydrogen gas for such systems instead of natural gas - in part due to the fact that when burning hydrogen gas less CO2 is emitted than when burning natural gas, as well as due to the assumption that hydrogen gas can be harvested I produced in a more sustainable way than natural gas.

[0007] However, the prior art burner control systems have been found inadequate for heating systems based on hydrogen gas. In particular, safety aspects that are more-or-less ignored for natural gas burner systems become apparent in hydrogen gas burner systems. This mainly results from the fact that hydrogen-based explosions are more powerful than natural gas-based explosions. As such, when hydrogen gas ignites this may lead to an audible bang or, in more extreme cases, an explosion powerful enough to impose a safety hazard. Such problems are not recognized for natural gas-based burner systems.

[0008] The burner control system according to the present disclosure is mainly aimed at detecting flashback events, i.e. events where the flame moves in the direction of the fluid source and may or may not disappear from the combustion area. This may mainly occur during initial combustion or during seemingly stable operation of the burner. During a flashback event, especially when hydrogen gas is used as a fuel for the heating system, a loud bang may be heard, which might not be acceptable for the vast majority of users of such systems because it might simply scare them (even though the system may be designed to withstand the pressures associated with such bangs). This may be unacceptable and be a cause for the non-usage I non-adaptation of hydrogen-based burners. As such, to help the global energy transition it is desirable when such flashback events can be controlled I prevented, so that a hydrogen burner system is accepted by the market.

[0009] Notwithstanding the above, the herein disclosed embodiments may also be applied in non-hydrogen gas based systems, such as biogas-based systems, to achieve at least some of the advantages of the present disclosure that will be elucidated further in the below.

[0010] As such, it is an objective of the present disclosure to provide a burner control system with which at least some of the above-described limitations of known burner control systems are obviated or abated.

[0011] This objective is achieved with a flashback detection sensor according to claim 1. In accordance with the present disclosure, the flashback detection sensor monitors physical properties such a pressure, density, emitted radiation and / or temperature of the fluid in the fluid inlet line - in particular in the burner gas supply line and / or in the gas mixture inlet line. As is deemed known to one skilled in the art, in normal operating mode - whether it be start up phase, ignition phase, idle phase or burning phase - the physical properties of the fluid in the fluid inlet line are well-known I can be predicted with great accuracy. However, due to all kinds of reasons at a given time a flashback event may occur. For example this flashback event may occur in the fluid line itself, but in principle it can occur at any place in the system, the effect being usually noticeable in the physical properties of the fluid in the fluid inlet line. This will have a significant effect on the physical properties of the fluid in the fluid inlet line. In particular, when the flame moves from the combustion area into the fluid inlet line, towards the fluid source, pressure in the fluid inlet line will initially increase, followed by a rapid decrease. Also, the temperature of the gas will rapidly increase during a flashback event. Also the (UV) radiation emitted by the fluid will rapidly change during a flashback event. The same holds for the gas density during a flashback event; with other physical properties likely to be affected as well. By monitoring for such sudden changes of the fluid property in the fluid inlet line, in particular changes generally corresponding to a pre-established pattern and / or beyond predetermined thresholds, a potential flashback event can be recognized from monitoring physical properties in the fluid inlet line. In response to a flashback event being registered, a safety protocol may e.g. be initiated by the system, in which the fluid inlet line is closed, the burner is shut off and safety issues are prevented. Possibly the burner system may be reignited a certain period after closing the fluid inlet line, or the visit of a mechanic may be required to restart the burner.

[0012] Advantageously, although the system may be designed to withstand the forces associated with a flashback event, the system may function suboptimally, e.g. due to wear and tear and / or due to production errors. It may for that reason be beneficial to recognize flashback events, perform system checks after the detection, and decide whether or not the system can be restarted I further operated. The flashback detection sensor may in that sense be regarded a fail-safe I redundancy measure.

[0013] Depending on the type of gas that is supplied to the burner, a different radiation pattern may be observed. When hydrogen gas is burned mainly, the radiation emitted is in the UV range. As such, for such applications in particular the radiation change detectable by the flashback detection sensor may be in the ultraviolet spectrum, having a wavelength of in between 100 nm - 400 nm. When natural or biogas is burned mainly, the radiation emitted may partly be in the UV spectrum as well as partly be in the visible light spectrum. As such, for these application in particular the radiation change detectable by the flashback sensor may have a wavelength of in between 100 - 620 nm. A person skilled in the art, having gained an understanding of the inventive concept as disclosed herein, will be well suited to determine the normal and expected radiation pattern of a gas mixture burned in a particular system, and select a suitable optical sensor accordingly.

[0014] In an embodiment of the present disclosure, the fluid inlet line with which the flashback detection sensor is associated may be a burner gas supply line, in particular a hydrogen gas supply line, a natural gas supply line or a biogas supply line. Typically the system comprises a burner gas supply line and an air supply line. These may be mixed in the combustion area, or they may be pre-mixed so that there is a third fluid inlet line being the mixed gas supply line. Regardless of whether the gas is pre-mixed or not, the flow volume through the burner gas supply line may be lower than through the air supply line. As such, physical fluid property changes during a flashback event may be aggravated more significantly in the burner gas supply line compared to the air supply line.

[0015] In an alternative embodiment of the present disclosure, the fluid inlet line with which the flashback detection sensor is associated, may be an air supply line. Although the changes in the physical properties of the fluid through the air supply line may be less significant than in the burner gas supply line, they may still be large enough to detect change patterns associated with flashback events.

[0016] In an embodiment of the present disclosure, where the system is of the pre-mixed type, the fluid inlet line with which the flashback detection sensor is associated may be configured to supply a mixture of a burner gas and air, the burner gas in particular being hydrogen, natural gas or biogas.

[0017] In a further embodiment of the present disclosure, the system comprises a burner gas supply line as well as an air supply line, a flashback detection sensor being associated with each of the lines. It may be assumed that in case of a flashback event, the same pattern of changes in the physical property of the fluid occurs in both the burner gas supply line and the air supply line, albeit that the magnitude of the change may differ between the lines. Hence, in certain embodiments the occurrence of a flashback event may be double-checked I verified based on the occurrence of changes in both lines, where it may e.g. be assumed that the occurrence of physical property changes in only one of the lines may be the result of a “false positive” registration. It may not be needed to take action - such as shutting off the system - after false positive registrations. In a particularly preferred embodiment of the present disclosure, the sensor is a pressure sensor configured for detecting pressure changes in the incoming fluid stream. Especially the change in pressure signal during a flashback event may be well-suited to spot and recognize such an event. In particular, during a flashback event the pressure in the fluid inlet line will initially sharply increase, due to the flashback causing a shockwave and compressing the fluid in the line. This may then be followed by a rapid decrease in the pressure. The negative pressure peak may be less stark I pronounced than the positive pressure peak. When the negative pressure peak and / or the positive pressure peak exceeds a certain threshold, this may lead to the deemed identification of a flashback event.

[0018] In an alternative embodiment of the present disclosure, a similar monitoring may be applied to the radiation profile emitted by the fluid in the fluid inlet line, so that the sensor may be an optical sensor configured for detecting emitted radiation changes in the incoming fluid stream - where it is noted that the radiation may only change in one direction during a flashback; in particular more towards the UV end of the light spectrum, characterised by wavelengths up to 620nm. Possibly the optical radiation during a flashback event could even extend into the infrared range, having wavelength longer than 620 nm.

[0019] Further alternatively, or additionally, radio-frequency radiations may be observed during a flashback event, so that the flashback detection sensor may alternatively be a sensor configured for detecting changes in radio-frequency radiation associated with the combustion area and / or the incoming fluid stream. In additional or alternatively there may be an additional sensor, such as a second flashback detection sensor, configured for detecting radio-frequency radiation associated with the combustion area and / or the incoming fluid stream.

[0020] In a yet further alternative embodiment of the present disclosure, a similar monitoring may be applied to a signal of the heat emitted by the fluid in the fluid inlet line, so that the sensor may be a temperature sensor configured for detecting temperature changes in the incoming fluid stream - where it is noted that the temperature may only change in one direction during a flashback; and in particular increase.

[0021] It should go without saying that, of course, more than one sensor, e.g. more than one type of sensor, may be present in the fluid inlet line. In particular, in such embodiments, the readings of the different sensors may be compared to each other to verify that a “positive” flashback identification by one of the sensors is not a “false positive” identification. For example, when the pressure changes in the way that is expected for a flashback event but the temperature of the fluid remains the same, as is unexpected during a flashback event, the pressure sensor may give off a false positive signal (or the temperature sensor may not function).

[0022] In a particularly preferred embodiment of the present disclosure the sensor is configured for measuring (semi-)continuously. A flashback event may happen over the course of less than 10 ms, so that any sensor must be able to have a measurement frequency of preferably continuously and otherwise in intervals of e.g. 1-2 ms or less. It should be obvious to one skilled in the art that the precise duration of and change in physical fluid properties during a flashback event will depend on many variables - including the precise layout of the system, the gas that is burned, the ratio with which the air and the gas are mixed, the location where the flashback event occurs and other variables.

[0023] In a particularly preferred embodiment of the present disclosure the fluid line comprises a valve, e.g. near the inlet of the line, and the flashback detection sensor is arranged on or near said valve. Providing a valve in the fluid line would allow the closing of the valve after a flashback event has been detected, to stop the supply of fluid and kill the flame. In such cases, the valve is preferably associated with the gas supply line, so that no gas is built up in the system while it is switched off.

[0024] A second aspect of the present disclosure relates to a burner control system comprising a gas burner arranged in a combustion area, a fluid inlet line arranged in between a fluid source and the combustion area, for guiding the fluid in a transport direction towards the combustion area, a valve associated with the fluid inlet line and configured for opening and closing an inlet of said line, the flashback detection sensor as described in the above, and a controller arranged in communication with the flashback detection sensor and the valve, the controller configured for closing the valve in response to a flashback event being detected by the sensor.

[0025] Advantages obtainable with the sensor according to the first aspect of the present disclosure may likewise be obtained with the system according to the second aspect of the present disclosure, the system essentially integrating said sensor therein. It goes without saying that embodiments and options described in relation to the sensor of the first aspect are likewise applicable to and advantageous for the system of the second aspect.

[0026] In a particularly preferred embodiment the controller is further configured for counting the number of flashback events. For example it may be useful to know the number of flashback events occurring in a certain time period and / or to schedule a maintenance event after a certain number of flashback events.

[0027] In a particularly preferred embodiment the flashback detection sensor is a pressure sensor that is configured for detecting pressure changes in the incoming fluid stream, wherein the controller is further configured for registering a maximum and / or minimum pressure having occurred in the fluid inlet line. Based on the profile of the pressure in the fluid line over time, it may be determined whether or not a flashback has occurred. The pressure signal is particularly suited for this monitoring, as it will typically have both a positive and a negative peak during a flashback event.

[0028] In an embodiment the controller is further configured for comparing a pressure in the fluid inlet line to a predetermined threshold pressure, wherein the valve is only closed upon the pressure in the fluid inlet line, as measured by the flashback detection sensor, exceeding the threshold pressure. It should be understood that the threshold may vary from machine to machine and from day to day instead of being a pre-programmed one. Depending on all kinds of circumstances, flow of fluid through the supply line(s) may vary in different set-ups and time instances, due to which the absolute physical properties of the fluids in the supply lines may be non-constant. For example, a time-constant value for the control property may be determined from time to time, the threshold e.g. being defined as X times the control value. It should go without saying that X may be either positive or negative.

[0029] In a particularly preferred embodiment of the present disclosure the system further comprises a flame detector in the combustion area, the flame detector arranged in communication with the controller and configured for detecting gas burner flame out events, wherein the controller is configured for comparing a timestamp of a flashback event as detected by the flashback detection sensor to a timestamp of a gas burner flame out event as detected by the flame detector. As such, an additional validation step may be performed regarding the true existence of a flashback event I a positive flagging of the flashback detection sensor. It may namely be assumed that during a flashback event the flame has disappeared from the combustion area. Hence, when a flame is registered by the flame detector at the same time as a flashback event by the flashback detection sensor, this may be indicative of one of the two sensors reading a false signal - leading to the need of more investigation. Of course, optimal calibration between the two sensors should be performed in such an embodiment.

[0030] For example, the controller is configured for evaluating measurement signals generated by the flame detector and the flashback detection sensor simultaneously, in particular using a logical AND-port.

[0031] In this embodiment, for example the flame detector as described in the (presently pending and not-yet-published) patent application PCT / NL2023 / 020056 in the name of the same applicant may be used. However many more flame detectors are known to one skilled in the art and / or may be developed in the future. For example, flame detectors based on temperature in the combustion area are known, as well as systems based on ionisation protection and other radiation-based detectors.

[0032] A third embodiment of the present disclosure relates to a method for controlling a burner control system of or for a heating system, the method comprising:

[0033] - obtaining a measurement signal of a fluid property monitoring sensor arranged in a fluid inlet line of the heating system;

[0034] - determining an operational state of a burner, from a group of use states comprising at least a flashback state, based on the obtained measurement signal corresponding to said use state, wherein the burner is connectable to a combustible gas supply and comprised by the burner control system; and

[0035] - selectively controlling a controllable valve of the fluid inlet line in dependency of said use state of the burner.

[0036] Advantages obtainable with the sensor according to the first aspect of the present disclosure and / or with the system according to the second aspect of the present disclosure may likewise be obtained with the method according to the third aspect of the present disclosure. It goes without saying that embodiments and options described in relation to the sensor of the first aspect and / or the system according to the second aspect are likewise applicable to and advantageous for the method of the third aspect.

[0037] The various aspects and features described and shown in the specification can be applied, individually, wherever possible. These individual aspects, and in particular the aspects and features described in the attached dependent claims and clauses, may be an invention in its own right that is related to a different problem relative to the prior art.

[0038] This holds, in particular, for a burner control system comprising: a gas burner arranged in a combustion area; one or more than one fluid inlet line(s) arranged in between a fluid source and the combustion area, for guiding the fluid in a transport direction towards the combustion area; a valve associated with the fluid inlet line and configured for opening and closing an inlet of said line; a flashback detection sensor arranged in at least one of the one or more than one fluid inlet line(s), at a position upstream of the combustion area when seen in the transport direction, the flashback detection sensor configured for monitoring a physical property of the fluid in the fluid inlet line and detecting the occurrence of a flashback event based on changes in the physical property of the fluid present in said fluid line; a controller arranged in communication with the flashback detection sensor and the valve, the controller configured for closing the valve in response to a flashback event being detected by the sensor; and a flame detector in the combustion area, the flame detector arranged in communication with the controller and configured for detecting gas burner flame out events, wherein the controller is configured for comparing a timestamp of a flashback event as detected by the flashback detection sensor to a timestamp of a gas burner flame out event as detected by the flame detector These and other aspects of the present disclosure will now be elucidated further in the below, with reference to the figures, in which:

[0039] Fig. 1 schematically illustrates an exemplary embodiment of a burner control system including a flashback detection sensor according to the present disclosure, and

[0040] Fig. 2 schematically illustrates an exemplary fluid flow through a fluid supply line of the burner control system of Fig. 1 over time.

[0041] Figure 1 shows a flame 101 in a combustion area 100 of a burner system 200. The flame 101 is ignited and fed by a mixture of air and gas, each of the air and the gas supplied via a respective supply line 12, 13. It is assumed that one skilled in the art is generally familiar with igniting and feeding a flame 101 I operating a gas burner. In particular the gas may be a hydrogen gas, or alternatively e.g. natural gas or another combustible gas such as biogas. Gas is supplied from a reservoir, here illustrated as gas tank 102 but in reality typically a regional / national maze of pipes, whereas air may be taken directly from the environment. Gas is supplied through gas supply line 12 from the gas tank 102 towards the flame 101 ; air is supplied through air supply line 13. A transport direction is defined from the left to the right in figure 1 : towards the flame 101. In the present embodiment the two gasses are pre-mixed before they enter the combustion area 101 , in mixture supply line 11. The skilled person is deemed aware of the advantages and disadvantages of pre-mixing the gas / air mixture compared to directly supplying the gasses in the combustion area.

[0042] In the normal situation, during operation of the burner system 200, the gas / air mixture is burned in the combustion area 100, where the flame 101 is present. However, due to a variety of reasons, the flame 101 may in certain circumstances move out of the combustion area 100 and into the supply line(s) 11 , 12, 13. Although this may more frequently occur in pre-mixed systems, as there is a burnable mixture of gas and air in the air / gas mixture supply line 11 , this may also occur in direct supply systems where the pure gas may be burned. When the flame 101 moves inside the fluid supply line 11 , a relative large volume of fluid may be burned at the same time, which may lead to a powerful explosion and a loud bang. This is especially true when the supplied gas is hydrogen. Apart from this powerful explosion being harmful to the physical components of the system 200, the associated bang may be frightening and at the very least unpleasant to users of the gas burner system 200.

[0043] It has now been realized by the inventors that, although a single flashback event may not be prevented, at least a series of flashback events - and the associated series of bangs - may be prevented by shutting off the system in one way or another after a flashback has been registered. As such, the present disclosure is aimed at how to reliably register a flashback event - preferably with as little “false positive” registrations as possible as - to give one illustrating example - shutting off the gas burner system 200 in a sub-optimally isolated house when it is freezing outside is to be prevented as much. As will be discussed in more detail with reference to Figure 2, it has been realized by the inventors that the fluid properties in the fluid supply line change when a flashback event takes place. And that they tend to do so according to a predictable pattern. As such, when a sensor 1 can be installed in the fluid supply line 11 , 12, 13 that consistently monitors the fluid property to spot the occurrence of this predictable pattern, in this way a flashback event may be registered automatically.

[0044] As such, in the embodiment shown in Figure 1 the flashback detection sensor 1 is installed in the gas supply line 12. The flashback detection sensor 1 is here of the pressure monitoring type, that compares a pressure in the gas supply line 12 to a pressure in the outside environment - where it is assumed that the pressure in the outside environment is constant at 1 atm. As gas is typically supplied by applying an underpressure in the gas supply line 12, in normal operating conditions the pressure differential between the pressure of the outside environment and the pressure inside the gas supply line 12 may be negative. The measurement values obtained by the sensor 1 are sent to a controller 31 , which registers a time plot of the pressures I pressure differentials, to detect if and when a flashback event occurs. If a flashback event would occur, a valve 21 in the fluid supply line 12 may be closed, to kill the supply of gas towards the gas supply line 12, the air / gas mixture supply line 11 and the combustion area 100, so that the flame 101 extinguishes.

[0045] In the embodiment shown in Figure 1 , the monitored fluid property is gas pressure. In the graph shown as Figure 2, it is shown how the differential gas pressure fluctuates during a flashback event. However, one can image that other fluid properties such as radiation emitted by the fluid, fluid temperature, fluid density and many other fluid properties will also be affected by a flashback event taking place in the fluid supply line 11 , 12, 13. As long as the change pattern registered for the respective fluid property may be predicted, the change pattern is unique to a flashback and the property may be monitored semi-continuously, in principle any fluid property alternative to the pressure may be used to detect the occurrence of a flashback event.

[0046] In the embodiment shown in Figure 1 , the flashback detection sensor 1 is mounted in the burner gas supply line 12. In the alternative, the flashback detection sensor 1 may instead by mounted in the air supply line 13 or, when present, the air / gas mixture supply line 11. Of course, the system 200 may comprise more than one flashback detection sensor 1 , e.g. two or more associated with the same fluid supply line 11 , 12, 13 or two or more each associated with a different fluid supply line 11 , 12, 13.

[0047] For the embodiment shown in Figure 1 , the system 200 may be shut down by closing a valve 21 in the gas supply line 12. In the alternative, a valve associated with another one of the fluid supply lines 11 , 13 may be closed. Further alternatively, any other component of the system 200 that helps in allowing one of the burning gas mixture to enter the combustion area 100 / supply line 11 , 12, 13 may be closed in response to a flashback being detected - in particular a pump for pumping the fluid.

[0048] When a flame detector 103 is additionally present in the combustion area 100, a true / false check regarding the correctness of the determination of a flashback event may be performed. Using the flame detector 103 it may, in other words, become possible to verify, at the controller 31 , the existence of a flashback event with the (near-)simultaneous existence of a flame-out event. As a flashback event is principally defined by the flame 101 moving inside the supply line, at such times the flame 101 will have disappeared from the combustion area 100. When a flame 101 is registered at the combustion area 100 simultaneously with a deemed flashback event, it cannot be guaranteed that the sensor readings are correct and / or the change in fluid characteristics may be the result of another anomaly in the gas burner system.

[0049] Turning now to Figure 2, several operational conditions of the burner system 200 of Figure 1 are shown in terms of fluid pressure of the fluid flowing through the gas supply line 12. At tO, the system is at rest. There is no transportation of gas, nor is there transportation of air. The differential pressure reading, the pressure difference between the fluid in the supply line and the outside environment, is zero.

[0050] Moving from tO to t1 , the pump that initiates a transport of the fluid through the gas supply line 12 is turned on. Typically, the valve between the gas source and the gas supply line is closed, so that only a small volume of air can move through the gas supply line. As a pressure (only) sensor cannot distinguish between the movement of burner gas or air, the sensor will give a negative reading as pressure decreases when air moves in the line. It should go without saying that when there is no gas in the system, the spark plug that is to ignite the flame may be off, and that there is no flame.

[0051] At t1 , target speed of the pump is reached, and the pressure in the gas supply line has reached an a prior known negative value. The system may operate in this condition for a certain period of time, here schematically indicated as the time that lapses between t1 and t2.

[0052] At t2, the gas valve is opened and the spark plug is turned on. Initially the flow of gas through the gas supply line may be relatively high, leading to a relatively low pressure reading. This flow is typically decreased over time, leading in this example to a higher (but still negative) pressure reading at t3 where the flame 101 has ignited. Once the flame 101 is ignited, relatively less gas may be needed to keep it burning; as the flame 101 is being ignited with the spark plug on built-up of gas in the combustion chamber may be undesired hence the gradual decrease of the gas flow in between t2 and t3. It should however be noted that, depending on the type of sensor, the type of measurement carried out therewith and the type of system 200 that is operated, a positive pressure may be attained at t3 as well.

[0053] In between t3 and t4 the system is in a rather constant operating mode. This will, in reality, of course be the case for the majority of the time so that it is immediately clear to one skilled in the art that the figure is not to scale. During this time, gas flow is predictable and constant - at least during the idle stage.

[0054] It is between t4 and t5 where it can - retroactively - be said that a flashback event has occurred. Initially, due to the flame bursting into the line and pushing the gas present in the lines of the system against the transportation direction, the pressure reading becomes significantly positive. It should be noted that not every positive reading, as stated in the above, will lead to a sure flashback event, so that preferably a threshold is set for determining the flashback event. The pressure in the supply line becoming positive and increasing beyond the threshold is a first indicator for the existence of a flashback event. This is typically followed, within the matter of a few milliseconds, by a sharp negative pressure in the gas supply line. This sharp increase in pressure rapidly followed by a decrease in pressure is a second indicator of the occurrence of a flashback event. As stated in the above, these first and second indicators may be sufficient to call out a flashback event. However, to verify the existence of a flashback event, these pressure readings may be combined with readings of sensors in other lines and / or with a flame sensor present in the combustion area. As stated in the above, high-frequency and preferably constant measurement signals are needed to allow a flashback event to be recognized - it all taking place in the matter of a mere few milliseconds. Once the flashback event is recognized and registered, the system may be shut down, leading the pressure reading finally to zero again at t6.

[0055] As a final note it is mentioned that the scope of protection for the present disclosure is exclusively determined based on the limitations mentioned in the appended independent claims, but that it may, in some jurisdictions, even encompass obvious alternatives for features in the independent claims. Other variations for specifically described elements, components and functions may also be embodied withing the scope of the appended claims of the present disclosure, have been at least hinted at in the above embodiment description or the skilled person may be considered to be able to contemplate there variations within the range of this skilled person’s general knowledge. This exemplary reference to alternative embodiments substantiates that any limitation to any specific claim, that is not defined as a limitation in the independent claims, is unwarranted.

[0056] CLAUSES

[0057] 1. A flashback detection sensor configured to be arranged in a gas burning system, the system comprising: a gas burner arranged in a combustion area; and one or more than one fluid inlet line(s) arranged in between a fluid source and the combustion area, for guiding the fluid in a transport direction towards the combustion area, wherein the flashback detection sensor in use is arranged in at least one of the one or more than one fluid inlet line(s), at a position upstream of the combustion area when seen in the transport direction, the flashback detection sensor configured for monitoring a physical property of the fluid in the fluid inlet line and detecting the occurrence of a flashback event based on changes in the physical property of the fluid present in said fluid line.

[0058] 2. The flashback detection sensor according to clause 1 , wherein the physical property monitored by the sensor is selected from a group comprising at least: pressure, radiation profile, temperature and density.

[0059] 3. The flashback detection sensor according to clause 1 or 2, wherein the fluid inlet line is a burner gas supply line, in particular a hydrogen gas supply line or a natural gas supply line.

[0060] 4. The flashback detection sensor according to clause 1 or 2, wherein the fluid inlet line is an air supply line.

[0061] 5. The flashback detection sensor according to clause 1 or 2, wherein the fluid inlet line is configured to supply a mixture of a burner gas and air, the burner gas in particular being hydrogen or natural gas.

[0062] 6. The flashback detection sensor according to any one of the preceding clauses, wherein the system comprises a burner gas supply line and an air supply line, a flashback detection sensor being associated with each of the lines.

[0063] 7. The flashback detection sensor according to any one of the preceding clauses, wherein the sensor is a pressure sensor configured for detecting pressure changes in the incoming fluid stream.

[0064] 8. The flashback detection sensor according to any one of the clauses 1 - 6, wherein the sensor is an optical sensor configured for detecting radiation changes in the incoming fluid stream.

[0065] 9. The flashback detection sensor according to clauses 7 or 8, wherein the sensor is configured for measuring (semi-)continuously.

[0066] 10. The flashback detection sensor according to any one of the preceding clauses, wherein the fluid line comprises a valve and wherein the flashback detection sensor is arranged on or near said valve.

[0067] 11. A burner control system comprising: a gas burner arranged in a combustion area; one or more than one fluid inlet line(s) arranged in between a fluid source and the combustion area, for guiding the fluid in a transport direction towards the combustion area; a valve associated with the fluid inlet line and configured for opening and closing an inlet of said line; the flashback detection sensor according to any one of the clauses 1 - 10; and a controller arranged in communication with the flashback detection sensor and the valve, the controller configured for closing the valve in response to a flashback event being detected by the sensor.

[0068] 12. The burner control system according to clause 11 , wherein the controller is further configured for counting and registering the number of flashback events.

[0069] 13. The burner control system according to clause 11 or 12, wherein the flashback detection sensor is a pressure sensor configured for detecting pressure changes in the incoming fluid stream and wherein the controller is further configured for registering a maximum and / or minimum pressure having occurred in the fluid inlet line.

[0070] 14. The burner control system according to any one of the clause 11 - 13, wherein the controller is further configured for comparing a pressure in the fluid inlet line to a predetermined threshold pressure, wherein the valve is only closed upon the a pressure in the fluid inlet line, as measured by the flashback detection sensor, exceeding the threshold pressure.

[0071] 15. The burner control system according to any one of the clauses 11 - 14, further comprising a flame detector in the combustion area, the flame detector arranged in communication with the controller and configured for detecting gas burner flame out events, wherein the controller is configured for comparing a timestamp of a flashback event as detected by the flashback detection sensor to a timestamp of a gas burner flame out event as detected by the flame detector.

[0072] 16. A method for controlling a burner control system of or for a heating system, the method comprising:

[0073] - obtaining a measurement signal of a fluid property monitoring sensor arranged in a fluid inlet line of the heating system; - determining an operational state of a burner, from a group of use states comprising at least a flashback state, based on the obtained measurement signal corresponding to said use state, wherein the burner is connectable to a combustible gas supply and comprised by the burner control system; and - selectively controlling a controllable valve of the fluid inlet line in dependency of said use state of the burner.

Claims

CLAIMS1. A flashback detection sensor configured to be arranged in a gas burning system, the system comprising: a gas burner arranged in a combustion area; and one or more than one fluid inlet line(s) arranged in between a fluid source and the combustion area, for guiding the fluid in a transport direction towards the combustion area, wherein the flashback detection sensor is configured to be arranged, in use, in at least one of the one or more than one fluid inlet line(s), at a position upstream of the combustion area when seen in the transport direction, the flashback detection sensor configured for monitoring a physical property of the fluid in the fluid inlet line and detecting the occurrence of a flashback event based on changes in the physical property of the fluid present in said fluid line, wherein the flashback detection sensor is an optical sensor configured for detecting radiation changes in the incoming fluid stream.

2. The flashback detection sensor according to claim 1 , wherein the radiation change detectable by the flashback detection sensor is in the ultraviolet spectrum, having a wavelength of in between 100 nm - 400 nm.

3. The flashback detection sensor according to claim 1 or 3, wherein the radiation change detectable by the flashback sensor has a wavelength of in between 400 - 620 nm.

4. The flashback detection sensor according to any one of the preceding claims, wherein the fluid inlet line is a burner gas supply line, in particular a hydrogen gas supply line, a natural gas supply line or a biogas supply line.

5. The flashback detection sensor according to claim 1 , 2 or 3, wherein the fluid inlet line is an air supply line.

6. The flashback detection sensor according to claim 1 , 2 or 3, wherein the fluid inlet line is configured to supply a mixture of a burner gas and air, the burner gas in particular being hydrogen, natural gas or biogas.

7. The flashback detection sensor according to any one of the preceding claims, wherein the system comprises a burner gas supply line and an air supply line, a flashback detection sensor being associated with each of the lines.

8. The flashback detection sensor according to any one of the preceding claims, further comprising a pressure sensor configured for detecting pressure changes in the incoming fluid stream.

9. The flashback detection sensor according to any one of the preceding claims, wherein the sensor is configured for measuring (semi-)continuously.

10. The flashback detection sensor according to any one of the preceding claims, wherein the fluid line comprises a valve and wherein the flashback detection sensor is arranged on or near said valve.

11. A burner control system comprising: a gas burner arranged in a combustion area; one or more than one fluid inlet line(s) arranged in between a fluid source and the combustion area, for guiding the fluid in a transport direction towards the combustion area; a valve associated with the fluid inlet line and configured for opening and closing an inlet of said line; the flashback detection sensor according to any one of the claims 1- 10; and a controller arranged in communication with the flashback detection sensor and the valve, the controller configured for closing the valve in response to a flashback event being detected by the sensor.

12. The burner control system according to claim 11 , further comprising a flame detector in the combustion area, the flame detector arranged in communication with the controller and configured for detecting gas burner flame out events, wherein the controller is configured for comparing a timestamp of a flashback event as detected by the flashback detection sensor to a timestamp of a gas burner flame out event as detected by the flame detector.

13. The burner control system according to claim 12, wherein the controller is configured for evaluating measurement signals generated by the flame detector and the flashback detection sensor simultaneously.

14. The burner control system according to any one of the claims 11 - 13, wherein the controller is further configured for counting and registering the number of flashback events.

15. The burner control system according to any one of the claims 11 - 14, wherein the is the system further comprises a pressure sensor configured for detecting pressure changes in the incoming fluid stream and wherein the controller is further configured for registering a maximum and / or minimum pressure having occurred in the fluid inlet line.

16. The burner control system according to any one of the claims 11 - 15, wherein the controller is further configured for comparing a pressure in the fluid inlet line to a predetermined threshold pressure, wherein the valve is only closed upon the a pressure in the fluid inlet line, as measured by the pressure sensor, exceeding the threshold pressure.

17. A method for controlling a burner control system of or for a heating system, the method comprising:- obtaining a measurement signal of an optical fluid property monitoring sensor arranged in a fluid inlet line of the heating system, the optical fluid property monitoring sensor configured for detecting radiation changes in the incoming fluid stream;- determining an operational state of a burner, from a group of use states comprising at least a flashback state, based on the obtained measurement signal corresponding to said use state, wherein the burner is connectable to a combustible gas supply and comprised by the burner control system; and - selectively controlling a controllable valve of the fluid inlet line in dependency of said use state of the burner.

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