DEVICE AND METHOD FOR CONTROLLING A FUEL-OXIDIZER MIXTURE IN A PREMIX GAS BURNER

Abstract

A method for controlling a fuel-oxidizer mixture in a premix gas burner includes: receiving a flame signal representing the presence of a flame deriving from the combustion of a fuel of a first predetermined type or a second predetermined type inside a combustion cell; accessing fuel data representing the fact that the gas fuel belongs to the first type or the second type; generating drive signals to control a gas flow regulating valve that supplies gas to the burner and to control a rotation speed of a fan configured to take in oxidative air; sending the drive signals to the gas flow regulating valve and to a motor connected to the fan. A memory unit contains first regulation data and second regulation data and is programmed to generate the drive signals based on the first regulation data or on the second regulation data, depending on the fuel data.

Claims

1. A method for controlling a fuel-oxidizer mixture in a premix gas burner comprising the following steps performed by a processor: receiving a flame signal, representing the presence of a flame deriving from the combustion of a fuel belonging to a first predetermined type or a second predetermined type inside a combustion cell of the burner accessing fuel data, representing the fact that the gas fuel belongs to the first type or the second type; generating drive signals, to control a gas flow regulating valve that supplies gas to the burner and to control a rotation speed of a fan configured to take in oxidative air; and sending the drive signals to the gas flow regulating valve and to a motor connected to the fan; wherein the processor has access to a memory unit containing first regulation data and second regulation data different from the first regulation data and is programmed to generate the drive signals based on the first regulation data or, alternatively, on the second regulation data depending on the fuel data.

2. The method according to claim 1, wherein the step of receiving the flame signal comprises the following steps: receiving a first flame signal, representing the presence of a flame deriving from the combustion of a fuel of the first type; and receiving a second flame signal, representing the presence of a flame deriving from the combustion of a fuel of the second type; wherein the processor generates the drive signals based on the first flame signal and/or on the second flame signal.

3. The method according to claim 2, wherein the method comprises a step of processing the first flame signal and the second flame signal to derive the fuel data representing a presence of fuel of the first type and/or a presence of fuel of the second type.

4. The method according to claim 3, wherein the fuel data represent a quantity of fuel of the first type and/or a quantity of fuel of the second type.

5. The method according to claim 4, wherein, if the quantity of the first fuel is greater than a first value, the processor performs the following steps: deriving a quantitative ratio between the fuel and the oxidizer based on the first flame signal; and comparing the derived quantitative ratio with an ideal quantitative ratio, and wherein the processor generates the drive signals based on the comparison between the derived quantitative ratio and the ideal quantitative ratio.

6. The method according to claim 5, comprising a step of receiving at least one temperature signal representing a temperature inside a combustion cell of the burner and wherein the processor derives the quantitative ratio between the fuel and the oxidizer based also on the temperature signal.

7. The method according to claim 2, wherein the processor calculates, for the first and/or the second flame signal a first and/or a second value of signal intensity, and wherein the processor compares the first and/or the second intensity value with reference data that represent: an association between the first intensity value and the quantity of fuel of the first type; and/or an association between the second intensity value and the quantity of fuel of the second type.

8. The method according to claim 2, comprising the following steps: receiving a flow rate signal, identifying a gas flow rate detected by a gas flow sensor; determining a gas flow rate as a function of the flow rate signal; comparing the quantity of fuel of the first type and/or the quantity of fuel of the second type, calculated on the basis of the first and the second flame signal with the gas flow rate calculated on the basis of the flow rate signal; and performing a diagnostic test on the gas flow sensor based on the comparison.

9. The method according to claim 2, wherein the fuel of the first type comprises hydrogen and wherein the first flame signal represents: an electromagnetic wave in the ultraviolet field or at least one temperature in the combustion cell; and wherein the fuel of the second type comprises methane and/or LPG and the second flame signal representative of a direct current due to ionization of an electrode or of the flame impedance.

10. The method according to claim 1, comprising a step of receiving a flow rate signal identifying a gas flow rate detected by a gas flow or pressure sensor and wherein the processor derives the fuel data also on the basis of the flow rate signal.

11. The method according to claim 1, comprising a step of receiving at least one temperature signal representing a temperature inside a combustion cell of the burner and wherein the processor is able to confirm that the burner is on based on the flame signal and on the temperature signal.

12. The method according to claim 1, wherein the fuel data are received by the processor through manual entry by a user from a user interface.

13. A method for controlling a fuel-oxidizer mixture in a premix gas burner comprising the following steps performed by a processor: receiving a flame signal representing the presence of a flame deriving from the combustion of a fuel belonging to a first predetermined type or a second predetermined type inside a combustion cell of the burner; accessing fuel data representing the fact that the gas fuel belongs to the first type or the second type; generating drive signals to control a gas flow regulating valve that supplies gas to the burner and to control a rotation speed of a fan configured to take in oxidative air; sending the drive signals to the gas flow regulating valve and to a motor connected to the fan; and receiving a flow rate signal identifying a gas flow rate detected by a gas flow or pressure sensor; wherein the processor derives the fuel data also on the basis of the flow rate signal.

14. A method for controlling a fuel-oxidizer mixture in a premix gas burner comprising the following steps performed by a processor: receiving a flame signal representing the presence of a flame deriving from the combustion of a fuel belonging to a first predetermined type or a second predetermined type inside a combustion cell of the burner; accessing fuel data representing the fact that the gas fuel belongs to the first type or the second type; generating drive signals to control a gas flow regulating valve that supplies gas to the burner and to control a rotation speed of a fan configured to take in oxidative air; sending the drive signals to the gas flow regulating valve and to a motor connected to the fan; and receiving at least one temperature signal representing a temperature inside a combustion cell of the burner; wherein the processor is configured to confirm that the burner is on based on the flame signal and on the temperature signal.

15. A device for controlling a fuel-oxidizer mixture for a premix gas burner, comprising: an intake duct which defines a section for the admission of a fluid into the duct and includes an inlet for receiving the oxidizer, a mixing zone for receiving the fuel and allowing it to be mixed with the oxidizer, and an outlet for delivering the mixture to the burner; an injection duct connected to the intake duct in the mixing zone to supply the fuel; a gas regulating valve located along the injection duct; a fan configured and adapted to rotate at a variable rotation speed and located in the intake duct to generate therein a flow of oxidizer in a direction of inflow oriented from the inlet to the delivery outlet; a first flame sensor configured to detect a first flame signal representing the presence of a flame deriving from the combustion of a fuel of a first type inside a combustion cell of the burner; a control unit including a processor programmed to receive a flame signal and to generate drive signals representing a position of the gas regulating valve and the rotation speed of the suction fan based on the flame signal; and a second flame sensor configured to detect a second flame signal representing the presence of a flame deriving from the combustion of a fuel of a second type inside a combustion cell of the burner; wherein the processor is programmed to receive fuel data representing the fact that the fuel is of the first type or of the second type; and wherein the flame signal is defined by the signal of the first flame sensor and/or of the second flame sensor depending on the fuel data.

16. The device according to claim 15, wherein the processor is configured to derive the fuel data, representing a quantity of fuel of the first type and/or a quantity of fuel of the second type, based on the first flame signal and on the second flame signal.

17. The device according to claim 16, wherein the processor is programmed for: accessing a memory unit containing first regulation data and second regulation data, different from the first regulation data; selecting one between the first regulation data and the second regulation data, based on the fuel data; and generating the drive signals based on the regulation data selected.

18. The device according to claim 15, comprising a user interface connected to the control unit and configured to allow a user to enter the fuel data manually.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0064] These and other features will become more apparent from the following description of a preferred embodiment, illustrated by way of non-limiting example in the accompanying drawings, in which:

[0065] FIGS. 1A and 1B illustrate, respectively, a first embodiment and a second embodiment of a device for controlling fuel-oxidizer mixture in a premix gas burner according to this disclosure;

[0066] FIG. 2 is a block diagram schematically representing a method for controlling a fuel-oxidizer mixture in a premix gas burner according to this disclosure.

DETAILED DESCRIPTION

[0067] With reference to the accompanying drawings, the numeral 1 denotes a device for controlling the fuel-oxidizer mixture in premix gas burners 100.

[0068] The device comprises an intake duct 2 which defines a section S through which a fluid is admitted into the duct. The intake duct 2 may be circular or rectangular in section. The intake duct 2 extends from (includes) an inlet 201, configured to receive the oxidizer, to (and) a delivery outlet 203, configured to supply the mixture to the burner 100. The intake duct 2 comprises a mixing zone 202 for receiving the fuel and allowing it to be mixed with the oxidizer.

[0069] The device 1 comprises an injection duct 3. The injection duct 3 is connected, at a first end of it 301, to the intake duct 2 in the mixing zone 202, to supply the fuel. The injection duct 3 is connected, at a second end of it, to a gas supply such as, for example, a gas cylinder or the national gas grid.

[0070] The device 1 comprises a gas regulating valve 7. The gas regulating valve 7 is located along the injection duct 3. In an embodiment, the gas regulating valve 7 is electronically controlled. The gas regulating valve 7 comprises a solenoid valve. The gas regulating valve 7 is configured to vary a section of the injection duct 3 as a function of drive signals 501 sent by a control unit 5.

[0071] The device 1 comprises a fan 9. The fan 9 rotates at a variable rotation speed v. The fan 9 is located in the intake duct 2 to generate therein a flow of oxidizer in a direction of inflow V oriented from the inlet 201 to the delivery outlet 203.

[0072] In an embodiment, the device 1 comprises a regulator 8. In an embodiment, the regulator 8 is configured to vary the flow rate of oxidizer flowing through the intake duct 2. In an embodiment, the regulator 8 is configured to prevent fluid from flowing in a return direction, opposite of the direction of inflow V.

[0073] In an embodiment, the regulator comprises at least one partializing valve (and/or a non-return valve). By partializing valve is meant a valve capable of varying its operating configuration as a function of the rotation speed of the fan 9, that is, of the flow rate of oxidizer. By non-return valve is meant a valve configured to allow a fluid to flow in one direction only and to prevent the fluid from flowing back in the opposite direction in the event of counterpressure.

[0074] In an embodiment, the regulator comprises at least two partializing valves. In an embodiment, one partializing valve is configured to vary its position in a working range different from that of the other partializing valve.

[0075] The device 1 comprises a control unit 5. The control unit 5 is configured to control the speed of rotation v of the fan 9 between a first rotation speed, corresponding to a minimum flow rate of oxidizer, and a second rotation speed, corresponding to a maximum flow rate of oxidizer.

[0076] The control unit 5 is configured to generate F6 drive signals 501 used to control the fan 9 and the gas regulating valve 7. The drive signals 501 represent a rotation speed of the fan 9.

[0077] In an embodiment, the control unit 5 is configured to control opening of the gas regulating valve 7. Thus, in an example embodiment, the drive signals 501 represent opening the gas regulating valve 7, hence a flow of gas delivered to the mixing zone.

[0078] In an embodiment, the device 1 comprises a user interface 50, configured to allow a user to enter configuration data. The configuration data comprise data that represent working parameters of the device 1 such as, for example, temperature of the fluid heated by the burner, pressure of the fluid in the burner, flow rate.

[0079] In an embodiment, the control unit 5 is configured to receive configuration signals 500′, representing the configuration data, and to generate the drive signal 501 as a function of the configuration signals 500′.

[0080] The device 1 comprises a first monitoring device 41 (that is, a first flame sensor 41). The first flame sensor 41 is configured to generate a first control signal 401 (or first flame signal 401). In an embodiment, the first flame signal 401 represents a state of combustion in the burner 100 due to the combustion of a first type of fuel. In an embodiment, detecting or not detecting the first flame signal 401 represents a state of combustion in the burner 100 due to the combustion of a first type of fuel. Preferably, the first type of fuel is hydrogen. The first flame sensor 41 is located in a combustion head TC of the burner 100.

[0081] Specifying that detecting or not detecting the first flame signal 401 represents a state of combustion in the burner 100 due to the combustion of a first type of fuel indicates the following embodiments (depending on the type of detection performed): [0082] the presence of the first flame signal indicates the presence of the first type of fuel (for example, because only combustion of the first type of fuel allows detecting the first flame signal 401), or [0083] the presence of the first flame signal indicates the possible presence of the first type of fuel (for example, because combustion of the first type of fuel is not the only one that allows detecting the first flame signal 401); [0084] non-detection of the first flame signal 401 indicates the absence of the first type of fuel.

[0085] The first flame signal 401 is a signal representing a physical parameter which the respective sensor is configured to detect in order to assess combustion. For example, in the case of hydrogen, the first flame signal 401 is preferably a signal representing the detection of invisible radiation (for example, ultraviolet—UV—rays).

[0086] For example, in the case of UV rays, the first flame signal indicates the possible presence of hydrogen but not the certainty of its presence, since other fuels (for example, fuels of the second type) which, when burnt, are detectable by UV detection.

[0087] In an embodiment, the first flame signal 401 might also be a signal that identifies the temperature of the combustion cell TC which, combined with the signal representing the electrical ionization current, would make it possible to determine the type or mixture of types the fuel is composed of.

[0088] In a particularly advantageous embodiment, the device 1 comprises a second monitoring device 42 (that is, a second flame sensor 42). The second flame sensor 42 is configured to generate a second control signal 402 (or second flame signal 402). In an embodiment, the second flame signal 402 represents a state of combustion in the burner 100 due to the combustion of a second type of fuel. In an embodiment, detecting or not detecting the second flame signal 402 represents a state of combustion in the burner 100 due to the combustion of a second type of fuel. Preferably, the second type of fuel comprises methane, LPG or, more in general, a mixture of hydrocarbons. The second flame sensor 42 is located in a combustion head TC of the burner 100.

[0089] Specifying that detecting or not detecting the second flame signal 402 represents a state of combustion in the burner 100 due to the combustion of a second type of fuel indicates the following embodiments (depending on the type of detection performed): [0090] the presence of the second flame signal 402 indicates with certainty the presence of the second type of fuel (for example, because only combustion of the second type of fuel allows detecting the second flame signal 402), or [0091] the presence of the second flame signal 402 indicates the possible presence of the second type of fuel (for example, because combustion of the second type of fuel is not the only one that allows detecting the second flame signal 402); [0092] non-detection of the second flame signal 402 indicates the absence of the second type of fuel.

[0093] The second flame signal 402 is a signal representing a physical parameter which the respective sensor is configured to detect in order to assess combustion of the second type of fuel. For example, in the case of the hydrocarbons, the second flame signal 402 is preferably a signal representing the entity of a current due to the ionization of an electrode.

[0094] Therefore, purely by way of example, if the first type of fuel is hydrogen and the second type of fuel includes hydrocarbons, the first UV signal is due to the presence either of the fuel of the first type or of the fuel of the second type, since fuel including hydrocarbons also causes UV emission. The second flame signal, on the other hand, is due only to the presence of the second type of fuel, since the combustion of hydrogen does not produce current due to the ionization of an electrode. Thus, by crossing these pieces of information, it is possible to determine the qualitative composition of the mixture being burnt, based on the detection or non-detection of the first and the second flame signal. For example, if only the UV signal is detected, the control unit deduces that only hydrogen is present. If both the signals are detected, on the other hand (non-visible—UV and ionization current), the control unit deduces that only fuel of the second type (with hydrocarbons) or a mixture of the first and second type of fuel might be present. At this point, based also on the features of the first and the second flame signal, the control unit discriminates between the presence and absence of hydrogen in the burnt mixture.

[0095] In an embodiment, the processor receives F3″ fuel data 403, representing the fact that the fuel used belongs to the first type, to the second type or is a mixture of the first and the second type.

[0096] In an example, the fuel data 403 are sent via the user interface 50, for example, as part of the configuration data entered manually by the user.

[0097] In a preferred embodiment, the first and the second flame signal 401, 402 are sent to (are received in F1, F2) the processor. In other embodiments, the processor receives only one between the first and the second flame signal 401, 402, based on the fuel that is being used, that is to say, based on the fuel data 403.

[0098] In an embodiment, the device comprises a memory unit containing first regulation data R1 representing regulation data of the burner in the presence of fuel of the first type, and second regulation data R2 representing regulation data of the burner in the presence of fuel of the second type. More generally speaking, the memory unit includes a plurality of regulation data groups R, each of which is associated with a respective type (composition) of the fuel being used.

[0099] The processor is programmed to select F5 the first or the second regulation data R1, R2 based on the fuel data 403.

[0100] The processor is programmed to generate the drive signals 501 based on the regulation data selected and based on the first and/or the second flame signal 401, 402.

[0101] In the embodiment in which the processor receives both the first and the second flame signal 401, 402, the processor is programmed to automatically receive F3′ the fuel data 403.

[0102] More specifically, in an embodiment, the intensity of the first flame signal (that is, the intensity of the UV signal) is associated with the quantity of hydrogen used in the combustion head TC. Further, the intensity of the second flame signal (that is, the intensity of the continuous ionization or flame impedance signal) is associated with the quantity of fossil fuels used in the combustion head TC.

[0103] This allows distinguishing the type of fuel used so that the burner can be monitored, run and maintained more safely and efficiently.

[0104] The processor, therefore, is programmed to derive a presence of the first and/or the second type of fuel (to define the fuel data 403) based on the intensity of the first and/or the second flame signal 401, 402. Preferably, the processor is programmed to derive a quantity of the first type of fuel and/or a quantity of the second type of fuel (to define the fuel data 403) based on the intensity of the first and/or the second flame signal 401, 402.

[0105] Based on the first and/or the second flame signal 401, 402, the processor may also determine a flow rate (a quantity) of fuel of the first type and/or of the second type in the combustion head.

[0106] In an embodiment, the monitoring device 4 comprises a flow sensor 43. The flow sensor 43 is located on the intake duct 2 or on the injection duct 3 and is configured to detect a flow rate signal 431 representing a flow of fuel-oxidizer mixture delivered to the combustion head TC or a flow of fuel injected into the mixing zone. In an embodiment, there may be more than one flow sensor 43 to form a plurality of flow sensors 43. The flow sensors 43 may be pressure sensors or flow meters. In an embodiment, one flow sensor 43′ is located in the gas injection duct 3 and another flow sensor 43″ is located on the intake duct 2.

[0107] The processor receives F4 the flow rate signal 431 from the flow sensor 43.

[0108] In an embodiment, the flow sensor 43 is configurable on the basis of the fuel data 403. More specifically, the flow sensor 43 is configurable in such a way as to select a working curve that is more suitable for the fuel to be measured.

[0109] The flow sensor 43, or the flow sensor 43″ located on the intake duct, may be mounted in different configurations, for example, but not limited to the following: upstream of the fan 9, downstream of the fan 9, upstream of the mixing zone 202 or downstream of the mixing zone 202.

[0110] The processor is programmed to compare the flow rate calculated with the flow sensor 43 with the flow rate calculated from the first and/or the second flame signal 401, 402. Based on this comparison, the processor calculates a real (measured) ratio between fuel and oxidizer. The processor compares the real (measured) ratio between fuel and oxidizer with an ideal ratio and accordingly generates an adjustment signal. The processor processes the adjustment signal and generates the drive signals 501 based also on the adjustment signal to set the real (measured) ratio between fuel and oxidizer as close as possible to the ideal ratio again.

[0111] It should be noted that in an embodiment, comparing the flow rate calculated with the flow sensor 43 with the fuel flow rate calculated from the first and/or the second flame signal 401, 402 makes it possible to derive information regarding the correct operation of the flow sensor 43, which is an essential condition for the safety measurements of the control device.

[0112] In an embodiment, the monitoring device 4 comprises a temperature sensor 44. The temperature sensor 44 is located in the combustion head TC and is configured to detect a temperature signal 441, representing a temperature inside the combustion head TC. In an embodiment, there may be more than one temperature sensor 44 to form a plurality of temperature sensors 44.

[0113] It is noted that in calculating the real (measured) ratio between fuel and oxidizer, the processor receives the temperature signal and calculates the flow rate (the quantity) of the fuel of the first type and/or of the second type in the combustion head (that is, the real ratio between fuel and oxidizer) based on the temperature signal 441.

[0114] In an embodiment, the temperature sensor 44 is located on an inside surface of the combustion head or of a distributor (that is of the delivery outlet 203) of the combustion head TC. The inside surface faces towards a side of the combustion head TC from which the mixture flows in (that is, it faces towards the delivery outlet 203). Alternatively, the inside surface faces towards the side where combustion effectively occurs (on the actual surface or spaced from it to measure the temperature of the flame).

[0115] In an embodiment, the device comprises a gas detection sensor, configured to measure the presence and/or the quantity of gas (preferably hydrogen) present inside the burner or in an outside space adjacent thereto.

[0116] In an embodiment, the processor has access to experimental data including, amongst other things, the ignition flow rate ranges for the first type of fuel and the second type of fuel (or a mixture thereof) and, for each ignition flow rate range, a respective expected flame signal (first flame signal 401 or second flame signal 402) and expected fuel flow rate.

[0117] In the step of igniting the burner, the method comprises supplying a progressive flow of fuel and interrupting the progression once the presence of the flame is detected (via the first flame signal 401 or the second flame signal 402).

[0118] Once ignition has been ascertained, the method comprises determining the type of gas being supplied, based on the level of the ionization signal and/or on the intensity of the UV radiation and/or on the fuel flow.

[0119] When the type of gas being supplied has been identified, the flow sensor 43 can be reconfigured in such a way as to select a working curve more suitable for the fluid to be measured (typically, in this specific case, for the oxidizer), hence keeping accuracy and resolution at the maximum allowed by the instrument, for improved adjustment quality and working/modulation range (defined as the ratio between the maximum and the minimum flow rate of the appliance). The configurability of the flow sensor 43 might not be automatic (via a self-learning boiler control) but determined by factory setting or set during installation.

[0120] Another drawback overcome by this invention regards cases of low gas supply pressure.

[0121] In the prior art, for example, in systems comprising only flow/pressure sensors or even mixture composition sensors, the management of low pressure is not safe. In effect, if the sensor does not detect the necessary quantity of fuel flow, the control systems might adjust the mixture by reducing the quantity of air but without direct feedback from combustion (in the case of a faulty sensor or a reading corrupted for some other reason), with possible dangerous consequences such as, for example, an increased risk of flashback or explosion.

[0122] Detecting the first flame signal 401 (that is, the intensity of UV radiation) allows confirming whether the presumed reduction in the availability of fuel is real and thus allows the quantity of air to be reduced and the appliance to operate correctly in complete safety, albeit with a reduced range.

[0123] Another function useful for safety is, at the ignition stage, checking whether the presence of the flame is detected via the first and/or the second flame signal 401, 402 even in the cases where the detected gas flow rate is not within a range considered minimal for ignition. In effect, in such a case, it is more than likely that the problem lies in a fault or malfunction of the flow sensor 43.