Method for detecting presence of flame in a premix hydrogen burner

Abstract

The object of the present invention is a control method for certifying the presence of a flame in the combustion chamber (41) of a premix gas burner (1) which burns a mixture of air and a gas mainly and / or substantially containing hydrogen H2. The method is based on the use of at least one temperature sensor (6) whose values are sent to a control device (8) which uses these values to calculate the derivative of the temperature T with respect to time T' which is compared with suitable feedback thresholds (Tau1, Tau2; Tau3, Tau4) to determine the occurrence of ignition, the failure of ignition or the extinction of the flame.

Description

Technical Field

[0001] The following describes a method for controlling the flame presence in a premixed gas burner, particularly a premixed gas burner with adjustable power and an adjustable excess air coefficient λ.

[0002] A premixed gas burner, particularly a premixed gas burner with adjustable power and an adjustable excess air coefficient λ, is also described, equipped with a device for controlling the presence of the flame.

[0003] The control method described below is suitable for verifying the presence of a flame in the premixed gas burner during both the ignition and steady-state operation phases.

[0004] The control method is particularly suitable for premixed burners fed with pure hydrogen or high-hydrogen-content fuel gas (e.g., hydrogen volume content equal to or greater than 98%).

[0005] The briefly described method and burner are specifically designed for condensing boilers fed with hydrogen (H2) and intended for the production of domestic hot water. Background Technology

[0006] As is well known, the approach involves premixing the fuel gas with the combustion air to suppress the emission of nitrogen oxides (NOx) and supplying an air volume greater than the stoichiometric amount, i.e., operating with an excess air coefficient λ.

[0007] It is also well known that by changing the excess air coefficient λ according to the burner's operating power, a more stable flame can be achieved (reducing the risk of backfire at low power or flame separation at high power).

[0008] It is also well known that increasing the excess air coefficient λ during the ignition step reduces the risk of backfire and the risk of explosion due to delayed ignition. Compared to the combustion of gaseous hydrocarbons, the combustion of hydrogen has certain characteristics that should be considered in the design and operation management of burners.

[0009] For example, the risk of backfire in hydrogen combustion is greater than that encountered in the combustion of conventional gaseous hydrocarbons (such as methane, butane, ethane, and propane). This risk of backfire, which is more likely to occur when the burner is ignited or at low heat power, can be avoided, for example, by increasing the excess air coefficient λ.

[0010] Furthermore, the flame of hydrogen is not an ionized flame if it is not at the highest power level: in the case of hydrogen combustion, it is therefore impossible to detect the presence of the flame by resorting to conventional ionization sensors (as is usually the case with conventional methane or other light hydrocarbon burners), and other solutions must be used to detect the presence of the flame.

[0011] In addition, air and hydrogen mixtures are particularly prone to explosion; therefore, the accumulation of the mixture in the combustion chamber should be avoided when there is no combustion (especially during the burner ignition process and during the accidental extinction process).

[0012] Therefore, when the premixed burner is fed with hydrogen, special attention should be paid to minimizing the flame ignition time and the time between accidental flame extinction and burner restart or shutdown.

[0013] Clearly, flame detection systems should have sufficiently short response times to minimize these transients.

[0014] Several solutions are known to monitor the presence of flame during hydrogen combustion in premixed burners.

[0015] One known technique is to monitor the presence of a flame produced by hydrogen combustion using an optical device that monitors ultraviolet emission (e.g., within a frequency range corresponding to the presence of hydroxyl radicals OH).

[0016] When the burner operates at low power or with a high air / fuel ratio (which occurs during both the ignition and low-power operation phases), the time constant of the ultraviolet sensor is very low, but its sensitivity is low.

[0017] In other words, when the intensity of ultraviolet emission from a flame is very low, the reliability of the ultraviolet sensor is poor.

[0018] Therefore, proper management of the burner is very complex, whether it is operating at low power or at a high air / gas ratio, as this may happen, for example, when operating at low power or during the burner's ignition phase.

[0019] Furthermore, the use of optical sensors also brings further problems: for example, specific glass is required to achieve optical connection with the combustion chamber, which increases the risk of fogging of the glass during the instantaneous operation of the burner, thus leading to erroneous sensor readings.

[0020] The second known technique uses a temperature sensor that measures the temperature inside the combustion chamber to monitor the presence of a flame produced by the combustion of hydrogen.

[0021] This existing technology compares the detected temperature with a lower consensus threshold to identify extinguishing, and compares the detected temperature with an upper consensus threshold to identify ignition.

[0022] However, the response time of the temperature sensors currently known to detect ignition or extinguishing is too long, thus posing a high risk of excessively high concentrations of air / hydrogen mixture in the combustion chamber, which in turn poses an explosion risk. Patent application EP3933267 is an example of the prior art mentioned above, describing a method for controlling the presence of flame in a premixed burner for hydrogen feed during the flame ignition step and stable operation, wherein a measured temperature value is compared with a expected value, i.e., with a previously stored reference value.

[0023] Comparing the measured value with the expected value can reveal whether ignition occurred correctly and whether a flame is present.

[0024] However, for the reasons mentioned above, the solution described in EP3933267 is unreliable.

[0025] In fact, it takes too long to detect the presence of a flame when the burner is ignited; similarly, it takes a long time to reach a reference value representing the absence of a flame when the burner is accidentally extinguished, which is incompatible with the risk of excessive buildup of the air / hydrogen mixture in the combustion chamber.

[0026] Application DE19903305 describes an alternative solution similar to that described in EP3933267; however, this application relates to a device and related method for controlling combustion initiation in a vehicle engine.

[0027] Patent application DE102021102740 discloses another prior art, which relates to a method for monitoring the presence of flame in a premixed burner, wherein the burner body is made of two different metallic materials forming a thermocouple.

[0028] By monitoring the thermoelectric voltage generated by the thermocouple and comparing it with a reference value, the DE102021102740 can identify whether a flame has ignited.

[0029] Therefore, the prior art DE102021102740 overcomes some of the problems of the prior art; however, it requires the use of a burner body with two different metal materials; in addition, in the case of external interference of electromagnetic nature, the voltage signal generated by the thermocouple may lead to reading errors. Summary of the Invention

[0030] The object of this invention is to at least partially solve the problems of the prior art, particularly the problems mentioned above.

[0031] In particular, the object of the present invention is to provide a reliable solution for monitoring the presence of flame in hydrogen-fed premixed gas burners, especially power-adjustable and excess air coefficient λ-adjustable premixed gas burners.

[0032] Another object of the present invention is to provide a solution for monitoring the flame of a premixed burner for burning hydrogen, particularly under low thermal power conditions and / or high air / fuel ratio values. Attached Figure Description

[0033] The following describes some possible embodiments of a flame control method and related apparatus using the same method with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the control and regulation device for a hydrogen-feed premixed burner; Figure 2.A It is a qualitative diagram showing the temperature trend in the space where the burner flame forms during the ignition step of the burner; Figure 2.B It is a qualitative graph showing the trend of the temperature derivative over time in the space where the burner flame forms during the ignition step of the burner; Figure 3 yes Figure 2.B The detailed diagram shown depicts the trend of the temperature derivative over time when the burner flame is correctly ignited; Figure 4 It is a qualitative graph showing the trend of the temperature derivative over time in the space where the burner flame forms during the ignition step of the burner in the event of an error signal or subsequent flameout; Figure 5.A It is a qualitative diagram showing the temperature trend in the space where the burner flame forms during the stable operating phase of the burner in the case of flame extinguishing; Figure 5.B It is a qualitative graph showing the trend of the temperature derivative over time in the space where the burner flame is formed during the stable operation of the burner in the case of flame extinguishing; Figure 6 It is a qualitative graph showing the trend of the temperature derivative over time in the space where the burner flame is formed during the stable operating phase of the burner, under the condition that the flame is actually extinguished; Figure 7 It is a qualitative graph showing the trend of the temperature derivative over time in the space where the burner flame forms in the case of an erroneous flame extinction signal during the stable operation phase of the burner; Figure 8 The summary is illustrated schematically. Figure 3 and Figure 4 The diagram shows a block diagram of the steps of a method for controlling the presence of a flame during the ignition step of a burner. Figure 9 The summary is illustrated schematically. Figure 6 and Figure 7 The diagram shows the steps of a method for controlling the presence of flame during the stable operation phase of a burner.

[0034] In all the qualitative graphs above, the derivative T' of temperature T (or, if otherwise stated, temperature T) lies on the vertical axis, while time t lies on the horizontal axis. Detailed Implementation refer to Figure 1 Reference numeral 1 in the figure represents a premixed gas burner including combustion control and regulation device 8.

[0035] The burner 1 includes a first pipe 11 (or a combustion air flow pipe), a second pipe 12 (or a gaseous fuel flow pipe, specifically mainly and / or substantially composed of hydrogen H2), and a variable speed fan 2 having an intake port 21 and a delivery port 22 connected to the first pipe 11.

[0036] The speed of fan 2 can be varied according to the required thermal power and the required excess air coefficient λ.

[0037] The mixing of air from the first pipe 11 and gas from the second pipe 12 can be achieved through a venturi tube 3, which may be located, for example, upstream of the fan 2.

[0038] The second pipe 12 connects to the narrow section of the venturi pipe 3, thereby drawing in combustion gas.

[0039] An electric valve 7 is provided to regulate the flow rate of the gas through the second pipe 12.

[0040] The first conduit 13 or the outlet conduit for the mixture of air and gaseous fuel is located downstream of the Venturi tube 3 that supplies air to the burner body 4.

[0041] The burner body 4 can be a conventional burner body with a perforated surface and is inserted into the combustion chamber 41.

[0042] An ignition device 5 is provided to ignite the air and gaseous fuel mixture that escapes from the venturi tube 3 and reaches the burner body 4.

[0043] The flame ignition device 5 can be of the discharge type.

[0044] The combustion chamber 41 contains at least one temperature sensor 6, which is suitable for detecting the presence of a flame.

[0045] For the sake of simplicity, in the following description, reference will be made to a variation of the invention with a single temperature sensor 6, which does not disadvantage the possibility of a second temperature sensor, which may be used as a redundant sensor to determine the correct operation of the first temperature sensor.

[0046] In the illustrated embodiment, the temperature sensor 6 is not in contact with the burner body 4, but is positioned so that it can be struck by the flame escaping from the opening in the burner body 4.

[0047] Temperature sensor 6 must be able to withstand the temperature generated inside combustion chamber 41.

[0048] In this regard, it should be noted that in the case of hydrogen combustion, the flame temperature may vary from approximately 800°C to approximately 1200°C, depending on the value of the excess air coefficient λ and the operating power of burner 1.

[0049] In a possible embodiment, the temperature sensor 6 may be a thermocouple type.

[0050] In another embodiment, the temperature sensor 6 may be a thermistor, particularly a positive temperature coefficient thermistor (so-called PTC).

[0051] In the embodiment, the temperature sensor 6 includes an outer coating of ceramic material (e.g., SiC or Si3N4) to protect the sensor from the strong oxidizing atmosphere generated in the combustion chamber 41 during the combustion process.

[0052] The electronic control and regulation device 8 receives an input signal ST from the temperature sensor 6 and a control signal SC indicating the required thermal power (e.g., from a user interface not shown in the figure).

[0053] Then, the device 8 provides the ignition device 5 with an ignition output signal SA, a signal SV for adjusting the speed of the fan 2, and a signal SG for adjusting the opening of the electric valve 7. According to the present invention, the device 8 can use the signal ST received from the temperature sensor 6 to check whether there is a flame in the combustion chamber 41.

[0054] In particular, the device 8 can verify whether the ignition step of the burner 1 is performed regularly, and whether there is any unexpected flame extinction during the stable operation phase.

[0055] Therefore, as described below, the device 8 uses the signal ST received from the temperature sensor 6 to calculate the derivative of temperature with respect to time and compares it with an appropriate feedback threshold to determine whether ignition has occurred, ignition has failed, or the flame has been extinguished.

[0056] In this specification, the term "derivative" refers to the absolute value of the instantaneous change of the temperature T of a flame over time, and also includes the discrete derivative obtained by sampling the temperature signal T with a sufficiently small sampling step size (e.g., every 0.1 seconds).

[0057] Figure 3 The method according to the invention is shown during the ignition step of burner 1. The ignition process begins by introducing air and combustion gas into the burner body 4 and generating an electrical discharge in the combustion chamber 41 for a first time interval Δt1.

[0058] For this purpose, fan 2 must be started and electric valve 7 must be opened to ensure that the air and gas mixture flows into the burner body 4 and out through the openings on the burner surface.

[0059] During the first time interval Δt1, sensor 6 detects the temperature T of point P in combustion chamber 41 located near the outer surface of burner body 4.

[0060] Electronic device 8 receives the temperature value detected by sensor 6 and calculates the derivative T' of temperature T at point P in combustion chamber 41 with respect to time during the first time interval Δt1.

[0061] If the derivative T' never exceeds the first threshold Tau1 during the first time interval Δt1, it is reasonable to assume that the ignition of the flame does not occur or occurs irregularly under any circumstances.

[0062] In this case, at the end of the first time interval Δt1, the device 8 interrupts the ignition cycle by driving the ignition device 5 to stop and the electric valve 7 to close, so as to avoid unwanted gas accumulation in the combustion chamber 41.

[0063] Preferably, the fan 2 is kept running for a period of time to allow for a complete cleaning of the combustion chamber 41, thereby removing any buildup of hydrogen therein: this extended operation of the fan 2 can be defined as a post-ventilation step, a term that will be used in the description below.

[0064] This can prevent any explosions during the next ignition attempt of burner 1.

[0065] Conversely, if the derivative T' of the temperature T at the midpoint P of the first time interval Δt1 exceeds the first preset threshold Tau1, the flame can be considered to have been ignited, and the air and gas flow can be maintained for the next step of flame stabilization cycle.

[0066] In this situation, device 8 drives ignition device 5 to stop, immediately stopping the discharge: it should be noted that the first time interval Δt1 is very short only to avoid excessive accumulation of the air and hydrogen mixture in combustion chamber 41, thereby avoiding the risk of a loud and dangerous explosion in the event of delayed flame ignition, i.e., ignition at the last moment, for the integrity of burner 1.

[0067] However, it is impossible to rule out the possibility that reaching the first preset threshold Tau1 is not a false positive, such as a false positive caused by temporary external interference of electromagnetic properties. Furthermore, although the flame was ignited during the first time interval Δt1, it is impossible to rule out the possibility that the flame was unstable for any reason.

[0068] To ensure that the flame is indeed ignited and remains ignited, the inventors proposed a method to continue calculating the derivative T' of temperature T in the second time interval Δt2 (after Δt1), where Δt2 > Δt1.

[0069] If, within the second time interval Δt2, the derivative T' remains consistently above the second preset threshold Tau2, wherein Tau2<Tau1 in absolute value, it is confirmed that the flame remains ignited (see again Figure 3 ).

[0070] It can be inferred that the ignition step of the burner 1 is successful and the flame is stable: therefore, the supply of the mixture of air and fuel gas to the burner main body 4 can be continued for transitioning to the steady operation step of the burner 1.

[0071] Otherwise, that is, in the case where the derivative T' drops below the second threshold Tau2 within the second time interval Δt2, the device 8 closes the electric valve 7 and keeps the fan 2 running for a period of time, so as to completely purge the combustion chamber 41 through a post-ventilation step.

[0072] Figure 4 shows the situation where the flame is extinguished during the ignition cycle of the burner 1, wherein the figure shows that the derivative T' of the temperature T decreases instantaneously within the second time interval Δt2 and drops below the threshold Tau2.

[0073] In the case of combustion of hydrogen or fuel gas with high hydrogen content, the first threshold Tau1 may be between about 20°C / s and 70°C / s, while the second threshold Tau2 may be between about 5°C / s and 30°C / s, it is understood that Tau2<Tau1 in absolute value in general.

[0074] Both the two thresholds Tau1 and Tau2 are values preset and stored in the device 8, defined by experiments or similar empirical methods in a laboratory.

[0075] In the case of combustion of hydrogen or fuel gas with high hydrogen content, the first time interval Δt1 is suitably less than or equal to about 2 seconds, while the second time interval Δt2 is generally less than or equal to about 4 seconds.

[0076] As expected, the above-mentioned burner 1 is also capable of monitoring the presence of flame after the ignition step, thereby confirming any accidental extinguishment phenomenon during the steady operation step.

[0077] For this purpose, the temperature T at the point P of the combustion chamber 41 is monitored, and the derivative T' of the temperature T with respect to time within the first time interval Δt3 is continuously calculated.

[0078] Since during the steady operation step of a hydrogen burner, the temperature T of the flame is indicatively between 800°C and 1200°C, in the event of accidental extinguishment, the derivative T' of the temperature T tends to decrease instantaneously, which can be immediately confirmed by comparing its value with a preset feedback threshold Tau3.

[0079] If the derivative T' of the temperature T does not drop below the first preset threshold Tau3 within the first time interval Δt3 (which has a very short duration, preferably equal to the minimum sampling step, for example 0.1 seconds, this is achieved by continuously monitoring the change of the derivative over time), it can be assumed that the flame has been ignited and the stable operation of the burner 1 can be correctly continued.

[0080] Conversely, if the derivative T' of the temperature T drops below said first preset threshold Tau3 during the first time interval Δt3, it can be reasonably assumed that an unexpected flame extinction has actually occurred.

[0081] In order to confirm that the flame is actually extinguished and that the derivative T' of the temperature T reaching the first threshold Tau3 is not a false positive caused by a temporary external disturbance, for example of an electromagnetic nature, the proposed method continues to calculate the derivative T' of the temperature T during a second time interval Δt4 immediately following Δt3, wherein Δt4>Δt3.

[0082] During the second time interval Δt4, the air and fuel gas flows remain in operation.

[0083] If during the second time interval Δt4, the derivative T' continues to remain consistently below said second preset threshold Tau4 (wherein in absolute value Tau4<Tau3), it is confirmed that the flame is actually extinguished.

[0084] At this point, the device 8 interrupts the fuel gas flow by acting on the electric valve 7, and performs a post-ventilation step to clean the combustion chamber 41, thereby preparing the burner for a new ignition step.

[0085] Figure 6 There is shown the situation where the flame is extinguished during the operation cycle of the burner 1, wherein it is shown that the derivative T' of the temperature T suddenly drops below the threshold Tau3 and subsequently fails to reach the second threshold Tau4 in the second time interval Δt4, which proves that the flame is actually extinguished.

[0086] Conversely, if the flame is actually still ignited during the second time interval Δt4 (the derivative T' reaching the threshold Tau3 during the first time interval Δt3 is configured as a false positive), the trend of the derivative T' will reverse instantaneously and exceed the second preset threshold Tau4: in this case, the device 8 continues to supply the mixture of air and fuel gas to the burner body 4 for continuing the normal and stable operation step of said burner 1.

[0087] Figure 7 There is depicted the situation of false flame extinction during the operation cycle of the burner 1, wherein it can be seen that the derivative T' of the temperature T exceeds the threshold Tau4 within the second time interval Δt4, which proves that the flame is actually ignited or reignited during the second time interval Δt4.

[0088] Like thresholds Tau1 and Tau2, thresholds Tau3 and Tau4 are preset values ​​stored in device 8, defined in the laboratory through experiments or similar empirical methods.

[0089] In the case of combustion of hydrogen or fuel gas with a high hydrogen content, the first threshold Tau3 may be between approximately 20 °C / s and 70 °C / s, while the second threshold Tau4 may be between approximately 5 °C / s and 30 °C / s. This is understood to be generally expressed in absolute terms as Tau4. <Tau3。

[0090] As mentioned above, the duration of the first time interval Δt3 is very short, for example, 0.1 seconds, because the control of the derivative over time must be carried out continuously during the stable operation phase of burner 1.

[0091] Conversely, the second time interval Δt4 is typically less than or equal to about 4 seconds to avoid the risk of a loud and dangerous explosion due to excessive buildup of the air-hydrogen mixture in the combustion chamber 41 and the resulting delay in ignition discharge, for the integrity of the burner 1, especially in the event that the flame is actually extinguished within the second time interval Δt4.

[0092] The aforementioned flame presence control method is particularly effective in the management of premixed burners that burn hydrogen, thereby eliminating the problems caused by the use of temperature sensors to monitor the flame in the prior art.

[0093] Relative to the corresponding consensus thresholds Ta and Tau representing the ignition of a flame, Figure 2.A and 2.B Qualitative plots compare the temperature trends of the burner during the ignition phase of the burner. Figure 2.A ) and the trend of the derivative of temperature with respect to time ( Figure 2.B ).

[0094] The comparison clearly shows that, compared to methods known to date that use temperature sensors to monitor flames, the main advantage of the control method described above lies in its ability to detect the consensus threshold for flame ignition much faster: in fact, compared to methods that must be verified to reach the threshold... Figure 2.A Compared to the feedback threshold Ta at medium temperature T, Figure 2.B The definition of the feedback threshold Tau for the derivative T' of the intermediate temperature T allows for an almost instantaneous or significantly shorter time to reach.

[0095] When considering the feedback threshold of temperature T in the flame extinguishing step (according to known methods) and the derivative T' of temperature T (according to the method proposed in this invention), the exact same situation occurs, as follows: Figure 5.A and 5.BAs shown: Using the value of the derivative T' can confirm the absence of flame in a significantly shorter time, which is beneficial to the safety of burner 1, in terms of reducing the risk of loud and dangerous explosions for the integrity of the burner.

[0096] The above control method can be applied to the burner's ignition phase and subsequent stable operation phase, respectively. Figure 8 and Figure 9 The block diagram illustrates this.

[0097] As mentioned above, also in Figure 3 and Figure 4 With the assistance of [unclear], the steps of the method in the ignition step of the burner are as follows: a1) The air and fuel mixture is introduced into the burner body 4 and discharged by the ignition device 5 for a first time interval Δt1; b) Measure the temperature T at point P in the combustion chamber 41; c) Calculate the derivative T' of temperature T during the first time interval Δt1; d) Compare the derivative T' with the first preset threshold Tau1; If the derivative T' never exceeds the first preset threshold Tau1 during the first time interval Δt1, then: e1) Determine that the flame has not ignited, and further: e11) Stop the ignition device 5. e12) Close the gas valve 7 to interrupt the airflow into the burner body 4. e13) Preferably, after ventilation is carried out, the fan 2 is kept running for a period of time to allow air to flow into the burner body (4). Otherwise, if the derivative T' exceeds the first preset threshold Tau1 during the first time interval Δt1, then: f1) Determine that the flame is ignited, and further: f11) Stop the ignition device 5. f12) Maintain the flow of the air and fuel mixture into the burner body 4; g) Calculate the derivative T' of temperature T in the second time interval Δt2, and compare it with a second preset threshold Tau2, wherein the second time interval Δt2 is greater than the first time interval Δt1, and the second threshold Tau2 is lower than the first threshold Tau1 in absolute value. If the derivative T' in the second time interval Δt2 does not exceed the second threshold Tau2, then: h1) Determine that the flame is either not ignited or has been extinguished, and further: h11) Close the gas valve 7 to interrupt the airflow into the burner body 4. h12) Keep the fan 2 running for a period of time to allow airflow into the burner body 4 for a post-ventilation step; Otherwise, if the derivative T' in the second time interval Δt2 exceeds the second threshold Tau2, then: i1) Confirm that the flame is ignited, and further: i11) Maintain the flow of the air and gas mixture into the burner body 4 to switch to the stable operation step of the burner 1.

[0098] The methods for stable operation of burners (also referenced above) Figure 6 and Figure 7 (described) Figure 9 The block diagram in the image illustrates the following steps: a2) Maintain the flow of the air and fuel mixture into the burner body 4 to sustain flame ignition; b) Measure the temperature T at point P in the combustion chamber 41; c) Calculate the derivative T' of temperature T during the first time interval Δt3; d) Compare the derivative T' with the first preset threshold Tau3; If the derivative T' never exceeds the first preset threshold Tau3 during the first time interval Δt3, then: e2) Determine that the flame continues to ignite, and further: e21) Maintain the flow of the air and fuel mixture into the burner body 4 to continue the stable operation of the burner 1; Otherwise, if the derivative T' exceeds the first preset threshold Tau3 during the first time interval Δt3, then: f2) Determine that the flame has been extinguished, and further: f21) The air and fuel mixture is kept flowing into the burner body 4 for a second time interval Δt4; g) Calculate the derivative T' of temperature T in the second time interval Δt4 and compare it with a second preset threshold Tau4, wherein the second time interval Δt4 immediately following the first time interval Δt3 is greater than the first time interval Δt3, and the second threshold Tau4 is less than the first threshold Tau3 in absolute value. If the derivative T' during the second time interval Δt4 does not exceed the second threshold Tau4, then: h2) Confirms that the flame has been extinguished, and further: h21) Close the gas valve 7 to interrupt the gas flow into the burner body 4. h22) Keep fan 2 running for a period of time to allow airflow into the burner body 4 for a post-ventilation step; If the derivative T' in the second time interval Δt4 exceeds the second threshold Tau4, then: i2) Determine that the flame is ignited, and further: i21) Maintain the flow of the air and fuel mixture into the burner body 4 to continue the stable operation of the burner 1.

Claims

1. A method for controlling the presence of flame in the combustion chamber (41) of a premixed gas burner (1) fed primarily and / or substantially hydrogen-containing air and fuel gas mixture, The burner (1) includes a burner body (4) inserted into the combustion chamber (41). The presence of the flame is controlled by at least one temperature sensor (6), which sends a signal (ST) representing the temperature T measured at point (P) in the combustion chamber (41) to a control device (8). The control device (8) uses the signal to perform at least the following steps during the ignition and stable operation of the burner (1): a1) In the ignition step, the air and gas mixture is introduced into the burner body (4) and an discharge is generated by the ignition device (5); a2) During the stable operation phase, the air and fuel mixture is kept flowing into the burner body (4) to keep the flame ignited; b) Measure the temperature T at point (P) in the combustion chamber (41); c) Calculate the derivative T' of temperature T in the first time interval (Δt1) or the third time interval (Δt3); d) Compare the derivative T' with either the first preset threshold (Tau1) or the third preset threshold (Tau3); If the derivative T' never exceeds the first preset threshold (Tau1) or the third preset threshold (Tau3) during the first time interval (Δt1) or the third time interval (Δt3), then: e1) During the ignition step, it is determined that the flame has not ignited. e2) During the stable operation step, it is determined that the flame continues to ignite; Otherwise, if the derivative T' exceeds the first preset threshold (Tau1) or the third preset threshold (Tau3) in the first time interval (Δt1) or the third time interval (Δt3), then: f1) In the ignition step, it is determined that the flame is ignited. f2) During the stable operation step, it is determined that the flame is extinguished; g) Calculate the derivative T' of temperature T in the second time interval (Δt2) or the fourth time interval (Δt4) to compare it with the second preset threshold (Tau2) or the fourth preset threshold (Tau4); If the derivative T' in the second time interval (Δt2) or the fourth time interval (Δt4) does not exceed the second preset threshold (Tau2) or the fourth preset threshold (Tau4), then: h1) During the ignition step, determine whether the flame has not ignited or extinguished. h2) During the stable operation step, it is confirmed that the flame is extinguished; Otherwise, if the derivative T' exceeds the second preset threshold (Tau2) or the fourth preset threshold (Tau4) in the second time interval (Δt2) or the fourth time interval (Δt4), then: i1) In the ignition step, confirm that the flame is ignited. i2) In the stable operation step, the flame is determined to be ignited.

2. The control method according to claim 1, Its features are, The ignition step of the burner (1) includes the following steps: If the derivative T' never exceeds the first preset threshold (Tau1) during the first time interval (Δt1), then after step e1), the method further includes the following steps: e11) Stop the ignition device (5). e12) Close the gas valve (7) to interrupt the airflow into the burner body (4); Otherwise, if the derivative T' exceeds the first preset threshold (Tau1) during the first time interval (Δt1), then after step f1), the method further includes the following steps: f11) Stop the ignition device (5). f12) Maintain the flow of the air and fuel mixture into the burner body (4); And execute step g), wherein the second time interval (Δt2) is greater than the first time interval (Δt1), and the second preset threshold (Tau2) is lower than the first preset threshold (Tau1) in absolute value.

3. The method according to claim 2, in, If the derivative T' exceeds the first preset threshold (Tau1) during the first time interval (Δt1), then after step i1), the method further includes the following steps: i11) Maintaining the flow of the air and gas mixture into the burner body (4) to transition to the stable operation of the burner (1); Otherwise, after step h1), the method further includes the following steps: h11) Close the gas valve (7) to interrupt the airflow into the burner body (4), h12) Keep the fan (2) running for a period of time to allow airflow into the burner body (4) for the post-ventilation step.

4. The method according to claim 2, in, Following step e1), the method further includes the following steps: e13) Keep the fan (2) running for a period of time to allow airflow into the burner body (4) for the post-ventilation step.

5. The method according to any one of claims 2 to 4, The first time interval (Δt1) is less than or equal to 2 seconds.

6. The method according to any one of claims 2 to 4, The second time interval (Δt2) is greater than the first time interval (Δt1) and less than or equal to 4 seconds.

7. The method according to any one of claims 2 to 4, The first preset threshold (Tau1) is between 20°C / second and 70°C / second, and the second preset threshold (Tau2) is lower than the first preset threshold (Tau1) and is between 5°C / second and 30°C / second in absolute value.

8. The control method according to claim 1, Its features are, The stable operation of the burner (1) includes the following steps: If the derivative T' never exceeds the third preset threshold (Tau3) during the third time interval (Δt3), then after step e2), the method further includes the following steps: e21) Maintain the flow of the air and fuel mixture into the burner body (4) to continue the stable operation of the burner (1); Otherwise, if the derivative T' exceeds the third preset threshold (Tau3) during the third time interval (Δt3), then after step f2), the method further includes the following steps: f21) Maintain the flow of the air and fuel mixture into the burner body (4); And execute step g), wherein the fourth time interval (Δt4) is greater than the third time interval (Δt3), and the fourth preset threshold (Tau4) is lower than the third preset threshold (Tau3) in absolute value.

9. The method according to claim 8, in, If the derivative T' exceeds the fourth preset threshold (Tau4) in the fourth time interval (Δt4), then after step i2), the method further includes the following steps: i21) Maintain the flow of the air and fuel mixture into the burner body (4) to continue the stable operation of the burner (1); Otherwise, after step h2), the method further includes the following steps: h21) Close the gas valve (7) to interrupt the airflow into the burner body (4), h22) Keep the fan (2) running for a period of time to allow airflow into the burner body (4) for a post-ventilation step.

10. The method according to claim 8 or 9, The third time interval (Δt3) is approximately 0.1 seconds.

11. The method according to claim 8 or 9, The fourth time interval (Δt4) is greater than the third time interval (Δt3) and less than or equal to 4 seconds.

12. The method according to claim 8 or 9, The third preset threshold (Tau3) is between 20°C / second and 70°C / second, and the fourth preset threshold (Tau4) is lower than the third preset threshold (Tau3) and is between 5°C / second and 30°C / second in absolute terms.

13. The control method according to claim 1, The first preset threshold (Tau1), the third preset threshold (Tau3), the second preset threshold (Tau2), and the fourth preset threshold (Tau4) are preset values ​​stored in the control device (8).

14. A premixed gas burner (1), primarily and / or substantially fed with hydrogen (H2), comprising at least: - The burner body (4) is inserted into the combustion chamber (41) and connected to the outlet pipe (13) for the air and fuel mixture. - Ignition device (5) for igniting the air and gas mixture. - At least one temperature sensor (6) adapted to measure the temperature value T at point (P) in the combustion chamber (41), Its features are: It also includes a combustion control and regulation device (8) adapted to receive an input signal (ST) from the at least one temperature sensor (6) to implement the method according to any one of claims 1 to 13.

15. The burner (1) according to claim 14. Its features are, The at least one temperature sensor (6) is a thermocouple or a thermistor.

Images