Flame detection device and method for detecting a flame using a flame detection device

Abstract

A flame detection device that uses a breakdown voltage across a pair of electrodes located in a flame region to detect the presence or absence of a flame. The flame detection device can be used with a burner that is part of a furnace in a home or building's central heating system. Unlike conventional flame detection devices that measure an ionization current in a flame, the flame detection device detects a flame by determining a voltage (also referred to as a breakdown voltage) required for a spark event across a spark gap located in a flame region, and evaluating the breakdown voltage and / or various characteristics thereof to detect the presence or absence of a flame. According to one example, the flame detection device includes a power source, an ignition unit, an output line, an insulator, and electrodes.

Description

[0001] Related Applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 289,355, filed December 14, 2021, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present invention relates generally to sensors and detection devices, and in particular to flame detection devices that can be used with furnaces, boilers, and other equipment that use a flame to burn gaseous and / or liquid fuels. BACKGROUND

[0004] Some conventional flame detection devices, particularly those used in applications that burn natural gas, butane, and / or propane, detect the presence or absence of a flame by measuring an ionization current in the flame. However, for applications that burn hydrogen, particularly those that operate on 100% hydrogen or near 100% hydrogen, detecting a flame by measuring an ionization current is generally not feasible. Other flame detection techniques have been developed, such as those that use ultraviolet radiation sensors or thermocouples. However, these solutions can be cost prohibitive and can suffer from drawbacks such as time response delays and reduced durability.

[0005] Accordingly, there is a need for a flame detection device that can operate with different fuels, including those that burn on 100% hydrogen or near 100% hydrogen, in a variety of settings, but that is still cost effective, performs well, and is durable. SUMMARY

[0006] According to one aspect, there is provided a flame detection device comprising: a sparking unit for providing a high-voltage electrical pulse; one or more output lines for transmitting the high-voltage electrical pulse and coupled to the sparking unit; and one or more electrodes for establishing a spark gap at least partially located in a flame zone and coupled to the output lines, wherein the high-voltage electrical pulse is provided to cause a spark event across the spark gap, and the flame detection device is configured to determine a breakdown voltage associated with the spark event and determine the presence or absence of a flame in the flame zone based on the breakdown voltage.

[0007] According to various embodiments, the flame detection device can further include any one or a portion or all of the following features in any technically feasible combination:

[0008] - the flame detection device is configured to be used with a burner that is part of a furnace, a boiler, or a blast furnace;

[0009] - the flame detection device is configured to be used with at least one gaseous fuel selected from the group consisting of: hydrogen (H2), natural gas (CH4), butane (C4H10), propane (C3H8), and mixtures thereof; C4 H10 propane (C3H8) and / or mixtures thereof;

[0010] - the ignition unit is coupled at the input side to a power supply, at the output side to the output line, and the power supply provides electrical energy for the flame detection unit;

[0011] - the ignition unit comprises a step-up transformer having a primary side winding and a secondary side winding, and the step-up transformer is arranged to step up the power voltage from the primary side power supply to a secondary side voltage in the range of 0.5 kV - 30 kV;

[0012] - the flame detection device further comprises a logic circuit having a combination of sensing and / or processing means for determining the voltage, and the logic circuit is arranged to determine the breakdown voltage across the electrode;

[0013] - the logic circuit comprises at least one sensing means selected from the following sensing means: a voltmeter, a resistive voltage divider, a capacitive voltage divider, a high voltage probe, or a field strength sensor;

[0014] - the output line is coupled at the input side to the ignition unit, at the output side to the electrode, and the output line transmits a high voltage electrical pulse from the ignition unit to the electrode;

[0015] - the electrode is coupled at the input side to the output line and arranged to be positioned in the vicinity of the burner such that the spark gap is located in a flame zone where a flame is expected to be present;

[0016] - the spark gap is in the range of 2 mm - 8 mm, inclusive; and

[0017] - the flame detection device is further configured to act as an ignition electrode such that the flame detection device can both sense when a flame is extinguished and ignite an air / fuel mixture when required.

[0018] According to another aspect, there is provided a method of detecting a flame using a flame detection device, the flame detection device comprising an ignition unit, one or more output lines, and one or more electrodes, and the method comprising the steps of: initiating a spark event; determining a breakdown voltage associated with the spark event; and using the breakdown voltage to judge whether a flame is present in a flame zone.

[0019] According to various embodiments, the method of detecting a flame using a flame detection device can further comprise any one or a part or all of any technically feasible combination of the following features:

[0020] - the ignition unit is coupled to an electrical power source at an input side and to an output line at an output side, and comprises a step-up transformer; and the initiating step further comprises initiating the spark event by causing the step-up transformer to step up a voltage of the electrical power from the electrical power source to a voltage in a range of 0.5 kV - 30 kV, providing the stepped-up voltage to the output line and the electrode in the form of a high-voltage electrical pulse, and causing the high-voltage electrical pulse to generate a spark over a spark gap established by the electrode, wherein the spark gap is at least partially located in the flame zone;

[0021] - the initiating step further comprises periodically initiating the spark event every 20 ms to 500 ms;

[0022] - the determining step further comprises determining the breakdown voltage by measuring a voltage representative of a voltage across the electrode with a sensing device, identifying a highest voltage measured by the sensing device, and setting the breakdown voltage to the highest voltage measured;

[0023] - the using step further comprises using the breakdown voltage to determine whether a flame is present by comparing the breakdown voltage to one or more predefined threshold values, and determining that a flame is present when the breakdown voltage is within an expected voltage range established by the predefined threshold values, and determining that a flame is not present when the breakdown voltage is outside the expected voltage range;

[0024] - the predefined threshold values are based on an expected type of medium in the spark gap when a flame is present and at least one additional factor selected from the following: a known size of the spark gap, an expected temperature of the electrode when a flame is present, or an expected pressure of the medium in the spark gap when a flame is present;

[0025] - the using step further comprises using the breakdown voltage to determine whether a flame is present by monitoring the breakdown voltage, determining a rate at which the breakdown voltage decreases or increases over time, comparing the rate at which the breakdown voltage decreases or increases to one or more predefined threshold rates, and determining that a flame is present when the rate at which the breakdown voltage decreases exceeds the predefined threshold rate, and determining that a flame is not present when the rate at which the breakdown voltage increases exceeds the predefined threshold rate;

[0026] - the using step further comprises using the breakdown voltage to determine whether a flame is present by observing the breakdown voltage over a period of time, detecting a trend or pattern in the breakdown voltage, and determining whether a flame is present based on the detected trend or pattern;

[0027] - further comprising the step of taking remedial action to shut off the fuel supply or re-ignite the flame when it is determined that a flame is not present in the flame zone. BRIEF DESCRIPTION OF DRAWINGS

[0028] Preferred embodiments will be described hereinafter with reference to the drawings, wherein like reference numerals denote like elements, and wherein:

[0029] Figure 1 is a schematic diagram of an example of a domestic heating system;

[0030] Figure 2 is a schematic diagram of a flame detection device that can be used with Figure 1 a domestic heating system of the type shown in

[0031] Figure 3 is a flowchart of a method for detecting a flame that can be used with Figure 2 a flame detection device of the type shown in DETAILED DESCRIPTION

[0032] The flame detection device disclosed herein uses the breakdown voltage on both sides of a pair of electrodes located in a flame zone to detect the presence or absence of a flame, and it can be used with a wide variety of furnaces, boilers, and / or other types of domestic and industrial equipment. According to one example, the flame detection device is used with a burner that is part of a furnace in a central heating system for a home or building. In such a system, the burner ignites or burns a gaseous or liquid fuel, thereby converting the fuel to heat energy that in turn is used to heat air or water that can be circulated throughout the home or building. Some non-limiting examples of suitable gaseous fuels include hydrogen (H2), natural gas (CH4), butane (C4H 10 ), propane (C3H8), and / or mixtures thereof; non-limiting examples of suitable liquid fuels include ethanol, fuel oil, and / or other types of oil. A simple furnace or boiler can include a single burner that burns a single type of fuel, while more complex equipment can have multiple burners that inject flames into a common combustion chamber where different fuels are simultaneously burned. Regardless of the system employed, it is often important to monitor the status of the flame so that certain remedial measures can be taken by the system in the event that the flame goes out, such as shutting off the gas.

[0033] While the flame detection device is described below in connection with a single burner that is part of a furnace in a central heating system for a home or building, it should be understood that the flame detection device can be used in any number of different applications and is not limited to the examples disclosed herein. For example, the flame detection device can be used with hydrogen (H2) combustion systems as well as with other gaseous and / or liquid fuels (e.g., natural gas (CH4), butane (C4H 10It can be used with systems that use hydrogen (H2), methane (C¾), propane (C3H8), and / or mixtures thereof; it can be used with single burner systems as well as complex multi-burner systems; it can be used with furnaces in homes or other buildings, as well as boilers, blast furnaces, and other types of domestic and / or industrial equipment; it can be used with low pressure systems as well as high pressure systems such as those in jet or rocket engines (for such systems, certain logic can need to be reversed because high voltage sometimes indicates high pressure as well as the presence of a flame); and it can be used with continuous combustion systems as well as intermittent combustion systems - for example, internal combustion engines and pulsejet engines (certain logic can need to be modified for such systems) - to name a few possibilities. The flame detection device can also be used in conjunction with thermocouples, pyrometers, optical sensors, infrared sensors, ultraviolet sensors, and other sensors and devices.

[0034] Turning now to Figure 1 , an example of a central heating system 10 is shown that relies on hydrogen (H2) for operation and has a furnace 12 with a burner 14 and a flame detection system 20. Unlike conventional flame detection devices that measure the ionization current in a flame, the flame detection device 20 detects a flame F by determining the voltage (also referred to as the breakdown voltage) required to initiate a spark event S across a spark gap G (formed) located in a flame zone Z, and evaluating the breakdown voltage and / or various characteristics thereof. According to the example in Figure 2 , the flame detection device 20 includes a power source 30, an ignition unit 32, an output line 34, an insulator 36, and an electrode 38.

[0035] The power source 30 provides the flame detection device 20 with the electrical power needed to operate the device. Depending on the particular application, the power source 30 can supply the flame detection device 20 with alternating current and / or direct current electrical power at any level from relatively low voltage levels (e.g., 5-40 VDC) to more moderate voltage levels (e.g., 110 VAC) and even higher voltage levels (e.g., 230 VAC). The power source 30 can be configured to provide power according to any number of suitable current types, current magnitudes, voltage levels, etc., and is not limited to the examples referenced above. According to one example, the power source 30 is coupled to an electrical utility or power provider at an input side 50 and to the ignition unit 32 at an output side 52.

[0036] The ignition unit 32 generates a high voltage electrical pulse (e.g., 0.5 kV - 30 kV) that meets or exceeds the breakdown voltage at the spark gap G, which extends between the electrodes 38 and is located in the flame zone Z. The breakdown voltage is primarily dependent on four factors: the size of the spark gap G, the temperature of the electrodes 38, the pressure of the medium in the spark gap G, and the composition of the medium in the spark gap G. If the first three factors can generally be held constant (i.e., the size of the spark gap, the temperature of the electrodes, and the pressure of the medium), the flame detection device 20 is able to use the fourth factor (the composition of the medium) to detect the presence or absence of a flame, as will be explained. In Figure 2 In the example shown, the ignition unit 32 is coupled to the power source 30 at an input side 60, to the output line 34 at an output side 62, and further includes a step-up transformer 64 and a logic circuit 66. The step-up transformer 64 can include any suitable structure and arrangement known in the art, and includes windings on a primary side 68 and a secondary side 70, and is preferably arranged such that it can step up the voltage from the power source 30 to a voltage in the range of 0.5 kV - 30 kV. The logic circuit 66 can include any combination of suitable sensing and / or processing devices for determining and / or evaluating the breakdown voltage. For example, the logic circuit 66 can include a voltmeter, a voltage divider (resistive or capacitive), a high voltage probe, a field intensity sensor, and / or other sensing devices for determining the breakdown voltage at the electrodes 38. The logic circuit 66 can also include a microcontroller, a microprocessor, a central processing unit (CPU), an analog-to-digital converter (ADC) and / or other type of converter, an embedded processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), and / or other processing devices for evaluating, analyzing, and / or determining sensor readings, such as readings related to the breakdown voltage. In one example, the logic circuit 66 includes a voltmeter or voltage divider 72 connected to the secondary side 70 of the step-up transformer 64, such that it can measure the voltage across the electrodes 38, which corresponds to the breakdown voltage, and it includes electronic processing devices for evaluating and / or analyzing the breakdown voltage to determine whether a flame is present. Other components and / or techniques for monitoring, measuring, and / or evaluating the breakdown voltage are of course possible. It should be understood that the logic circuit 66 can be integrated within the ignition unit 32, it can be a separate standalone unit that is functionally connected to the ignition unit 32, or it can be provided as a hybrid type of unit that is partially integrated and partially separate (for the purposes of this application, all of these embodiments are considered to be examples of an ignition unit that includes a logic circuit).

[0037] The output lines 34 and the insulator 36 serve to safely connect the output of the ignition unit 32 to the electrodes 38, and can be provided according to any embodiment known in the art. In one non-limiting example, the output lines 34 comprise a pair of standard ignition wires capable of transmitting high-voltage electrical pulses (e.g., 0.5 kV - 30 kV). As the name implies, the insulator 36 electrically insulates or isolates the output lines 34 so that they do not short-circuit during operation. In addition to electrical insulation, the insulator 36 can also provide a degree of thermal insulation. According to the non-limiting example of FIG. 1, the output lines 34 are coupled to the ignition unit 32 at an input side 80, and to the electrodes 38 at an output side 82. Figure 2

[0038] The electrodes 38 are located in a flame zone Z where the flame F is expected to be present, and they define a spark gap G. One of the electrodes 38 is positive, while the other electrode is negative or grounded, and the electrodes act as the ignition elements between which an electrical spark is formed. The "breakdown voltage" is the voltage or potential across the electrodes 38 that is required to cause an electrical spark to arc or jump from one electrode to the other. In most cases, the breakdown voltage corresponds to the maximum or peak voltage between the electrodes 38 during a spark event, and is the primary parameter that is monitored in terms of flame detection. A "spark event" can occur during a time period before, during, and / or after a spark discharge. The breakdown voltage is primarily dependent on four factors: the size of the spark gap G, the temperature of the electrodes 38, the pressure of the medium in the spark gap G, and the composition of the medium in the spark gap G. The size of the spark gap G can vary from application to application, but is typically in the range of 2 mm to 8 mm, inclusive, and more preferably in the range of 3 mm to 5 mm, inclusive. The shape, orientation, and / or arrangement of the electrodes 38 are also factors that can vary from application to application; for example, the electrodes 38 can have tips that are bent parallel, oriented tip-to-tip or edge-to-edge, or arranged so that one electrode sparks directly to a grounded object such as a grounded pin or electrode in the furnace 12. In the last example, where one of the electrodes 38 sparks directly to a grounded object in the furnace 12 such as a grounded pin or electrode, in the context of the present application the grounded object should be considered an electrode 38, and the spark gap G is the gap between the one electrode and the grounded object. During operation, the temperature of the electrodes 38 can become quite hot (e.g., up to 1,300 °C), which has an effect on the breakdown voltage. As described below, the flame detection device 20 can employ techniques for addressing high electrode temperatures. In the example of FIG. 1, the electrodes 38 are coupled to the output lines at an input side 90, and are positioned in the vicinity of the burner 14 so that they are located in the expected flame zone Z. In examples where one of the electrodes 38 is a grounded object, it can be necessary to provide a Figure 2 Figure 2 ​​The wiring scheme of the middle output line 34 is subject to some modifications, such as the omission of one of the lines; such modifications will be known and understood by those skilled in the art. The electrodes 38 should be positioned so that the respective spark gap G is at least partially located in the flame F itself when the flame F is present.

[0039] The flame detection device 20 can also serve as an ignition electrode, such that it can both sense when the flame is extinguished and ignite the air / fuel mixture when needed. In this case, for example, the flame detection device 20 can be installed in the combustion chamber of a furnace or boiler that is part of a home heating system. This arrangement would make an additional flame detection unit (such as those that measure ionization current) unnecessary, as the system already requires a safety ignition electrode. Other features, embodiments, examples, etc. are possible, as the foregoing description is merely meant to illustrate some possibilities.

[0040] In operation, the flame detection method 100 uses the breakdown voltage across the spark gap G to determine whether the flame F is present. This is a different approach than many conventional flame detection devices, which use ionization current to determine whether a flame is present. As described above, the breakdown voltage is primarily dependent on four factors: the size of the spark gap G, the temperature of the electrodes 38, the pressure of the medium in the spark gap G, and the composition of the medium in the spark gap G. Generally speaking, the first three factors remain relatively constant and / or are compensated for (the size of the spark gap G does not change, the temperature of the electrodes 38 can vary but is compensated for, and the pressure of the medium does not change significantly). This leaves the fourth factor (i.e., the composition of the medium), which is the primary factor that can cause the breakdown voltage to vary significantly. Thus, the breakdown voltage is somewhat a function of the medium present in the region between the electrodes 38. The medium in the spark gap G, in turn, is heavily influenced by the presence or absence of a flame (e.g., when there is no flame, there is no combustion, so the medium is essentially an air / fuel mixture; when there is a flame, there is combustion, so the medium is a byproduct of the combustion process). Thus, the breakdown voltage is somewhat a function of the presence of a flame in the region between the electrodes 38. The flame detection device 20 uses this functional or relationship between the breakdown voltage across the spark gap G and the presence or absence of a flame in the same region to determine the state of the flame (i.e., whether the flame is lit or has been extinguished).

[0041] The breakdown voltage is lower when a flame F is present between the two electrodes 38 than when a flame F is not present between the electrodes. While not wishing to be bound by any particular scientific theory, one possible explanation is that the presence of a flame in the spark gap G means that the region will have byproducts of the combustion process present. For example, in the case of hydrogen gas (H2) combustion, the byproduct is typically water vapor (H2O); in the case of natural gas (CH4), propane (C3H8), and butane (C4H 10In the case of combustion, the byproducts are primarily carbon dioxide (CO2) and water vapor (H2O). In each of these cases, the byproducts of the combustion process that contain water vapor (H2O) can be more susceptible to electrical breakdown than the original fuel itself. This means that when a flame is present between the electrodes 38 (whether the flame is between the two electrodes or between one electrode and a grounded object), the medium in the spark gap G can be more susceptible to electrical breakdown, making the voltage required to jump from one electrode to the other (i.e., the breakdown voltage) lower. As described below, the flame detection device 20 and the methods described herein are capable of monitoring, measuring, and / or assessing the breakdown voltage. As noted above, the present application is not bound or limited by the above potential explanation. Factors other than “susceptibility to electrical breakdown” (e.g., factors associated with combustion byproducts, gas temperature, free ions or electrons, etc.) can affect the breakdown voltage at the spark gap G and should be considered part of or incorporated into the present application.

[0042] Beginning with step 110, the method periodically initiates a spark event so that the flame detection device 20 can assess the measured breakdown voltage. Some preliminary testing has shown that the typical reaction time of the breakdown voltage after a change in state of the flame F (i.e., the flame is extinguished or the flame is ignited) is less than 60 ms. Thus, the present method can initiate a spark event, and thus a new cycle or iteration of the method is performed every 20 ms to 500 ms. It should be understood that any suitable spark event period can be used as the present method is not limited to the above example.

[0043] Next, the method determines the breakdown voltage, which corresponds to the voltage across the electrodes 38 when an electrical spark arcs or jumps from one electrode to the other (step 120). Since the breakdown voltage corresponds to the highest or peak voltage between the electrodes 38 during a spark event, step 120 can monitor the voltage on the secondary side 70 (which is the same as the voltage at the electrodes 38) with the voltage sensor 66 and simply record the highest voltage measured during the time period in question; such a voltage will correspond to the breakdown voltage. In a different example, step 120 can monitor the voltage on the secondary side 70 and record the history of the voltage over a period of time; this enables the method to assess the breakdown voltage not only in terms of absolute value, but also in terms of how the breakdown voltage changes over time (i.e., assess the breakdown voltage pattern, level, history, etc.). Any number of different voltage determination or collection techniques can be used as the present method is not limited to any particular method.

[0044] In step 130, the method evaluates the breakdown voltage to determine whether a flame is present. This step can be performed in a number of different ways. In a first example, step 130 can compare the previously determined breakdown voltage to one or more predetermined thresholds. If the breakdown voltage is within an expected voltage range established by the predefined thresholds, the method can conclude that a flame is present; if the breakdown voltage is outside the expected voltage range, the method can determine that the flame has been extinguished and the method can take some type of remedial step to shut off the fuel or re-ignite the flame. For example, if the previously determined breakdown voltage is less than a predefined threshold - which can be based on details of the particular application (i.e., the threshold can be based on known dimensions of the spark gap G, expected temperatures of the electrodes when a flame is present, and expected pressures and types of media that should be present when a flame is present - step 130 can determine that a flame F is present. If the breakdown voltage is equal to or greater than the predetermined threshold, step 130 can conclude that the flame F has been extinguished. While the predefined threshold can be a static value stored in an electronic storage component of the flame detection device 10, the predefined threshold advantageously is a dynamic value that is periodically updated or adjusted (e.g., based on closed loop feedback, machine learning techniques, etc.). To name a few possibilities, some factors that can be considered in updating or adjusting the dynamic threshold include the condition of the burner 14, parameters sensed by other sensors in the system, or changes in the breakdown voltage itself.

[0045] In a second example, step 130 evaluates the breakdown voltage to determine whether a flame F is present by looking at how the breakdown voltage changes over time. If the breakdown voltage decreases at a rate that is greater than a predefined threshold rate, step 130 can conclude that the flame F has just been ignited. Conversely, if the breakdown voltage increases at a significant rate that exceeds some threshold rate, step 130 can determine that the flame has just been extinguished. Minor changes in the breakdown voltage, e.g., changes that do not exceed the upper and / or lower threshold rate boundaries, are to be expected and will typically cause step 130 to conclude that the flame F is still in the same state (e.g., the flame is still ignited). Of course, the present method can use a combination of techniques - e.g., a combination of the first and second examples described above - to evaluate the breakdown voltage and determine whether a flame is present. In some cases, the method can make such determinations based on a single cycle of the method (i.e., based on a single spark event and a single determined breakdown voltage), while in other cases the method can average the breakdown voltages over a cycle period and use the average in the evaluation.

[0046] Step 130 can require compensation for temperature changes in the electrode. As mentioned above, one of the four main factors affecting the breakdown voltage is the temperature of the electrode 38, which, given that the electrode is at least partially located within the flame F, can become quite hot (up to about 1300 °C) during operation. The higher the temperature of the electrode 38, the lower the breakdown voltage. In certain abnormal situations, the electrode temperature can even become so high that its effect as a factor determining the breakdown voltage is comparable to that of the medium between the electrodes, i.e. the presence of the flame. In such cases, additional precautions can help to mitigate or reduce the effect or influence of the electrode temperature as a factor determining the breakdown voltage. One example of such a precaution is to increase the size of the spark gap G, which has the effect of increasing the weight of the presence of the flame as a factor. If the spark gap G is increased sufficiently, the influence of the presence of the flame on the breakdown voltage will be considerably higher than that of the electrode temperature. Another example of a precaution that can be used to address extreme electrode temperatures is to continuously observe the breakdown voltage over a period of time and / or cycle, rather than just checking the breakdown voltage on a per-cycle basis. This technique is similar to the second example above, in which the method observes the breakdown voltage over a period of time in order to see voltage trends or patterns that indicate when the flame is lit or extinguished. Another possibility is a detailed analysis of the voltage demand over a period of time, which is coarse-tuned / levelled / integrated. Not only does the breakdown voltage change when the flame is present, but so does the corresponding current. Analyzing one or both of the breakdown voltage and / or the current and their levelling over time can also help to detect flame extinguishment, even when the electrode is at a high temperature.

[0047] If the flame is present, step 140 returns the method to step 110 to continue monitoring. If the flame is not present, step 140 directs the method to step 150, so that one or more remedial measures can be taken. If the flame is extinguished unexpectedly, step 150 can perform a gas shut-off or attempt to relight the flame, assuming that the appropriate safety procedures have been followed. Other remedial actions such as sending an alert are of course also possible.

[0048] It should be understood that the foregoing description is directed to one or more preferred exemplary embodiments of the application. The application is not limited to the particular embodiment disclosed, but is only defined by the claims that follow. Furthermore, statements herein that recite "one embodiment," "an embodiment," or the like mean that a particular feature, structure, or characteristic being described is included in at least one embodiment, and multiple embodiments can exist that include the particular feature, structure, or characteristic. Furthermore, the foregoing description is not intended to be exhaustive, or to limit the application to the precise forms disclosed. Modifications and alterations are always possible. Accordingly, the scope of the application is defined only by the claims that follow.

[0049] As used in this specification and claims, the terms "for example," "for instance," "such as," and "like," and the verbs "comprising," "having," "including," and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that that the listing is not to be considered as excluding other, additional components or items. Other terms are to be construed using their broadest reasonable meaning consistent with the context, unless otherwise indicated.

Claims

1. A flame detection device, comprising: a firing unit for providing a high voltage electrical pulse; one or more output lines for transmitting the high voltage electrical pulse and coupled to the firing unit; and one or more electrodes for establishing a spark gap at least partially located in a flame zone and coupled to the output lines, wherein the high voltage electrical pulse is provided to initiate a spark event across the spark gap and the flame detection device is configured to determine a breakdown voltage associated with the spark event and compare the breakdown voltage to one or more predefined thresholds, wherein the predefined thresholds are based on an expected type of medium in the spark gap when a flame is present and at least one of the following additional factors: a known size of the spark gap, an expected temperature of the electrodes when a flame is present, an expected pressure of the medium in the spark gap when a flame is present; wherein the flame detection device determines that a flame is present in the flame zone when the breakdown voltage falls within an expected voltage range established by the predefined thresholds and determines that a flame is not present in the flame zone when the breakdown voltage falls outside the expected voltage range. The flame detection device is configured for use with a burner that is part of a furnace, boiler or blast furnace.

2. The flame detection apparatus of claim 1, wherein, The firing unit comprises a step-up transformer having a primary side winding and a secondary side winding and the step-up transformer is arranged to step up a power voltage from a primary side power source to a secondary side voltage in the range of 0.5 kV - 30 kV.

3. The flame detection apparatus of claim 1, wherein, The flame detection device is configured for use with at least one gaseous fuel selected from the group consisting of: hydrogen H2, natural gas CH4, butane C4H 10 10, propane C3H8 and / or mixtures thereof.

4. The flame detection apparatus of claim 1, wherein The flame detection device further comprises a logic circuit having a combination of sensing and / or processing means for determining the voltage and the logic circuit is arranged to determine the breakdown voltage across the electrodes and determine from the breakdown voltage whether a flame is present in the flame zone.

5. The flame detection apparatus of claim 1, wherein, The logic circuit comprises at least one sensing means selected from the following sensing means: a voltmeter, a resistive voltage divider, a capacitive voltage divider, a high voltage probe or a field strength sensor.

6. The flame detection apparatus of claim 5, wherein, The spark gap is in the range of 2 mm - 8 mm, inclusive.

7. The flame detection apparatus of claim 1, wherein The flame detection device is further configured to act as a firing electrode such that the flame detection device can both sense when a flame is extinguished and ignite an air / fuel mixture when required.

8. The flame detection apparatus of claim 1, wherein, 9. A method of detecting a flame using a flame detection device comprising a firing unit, one or more output lines and one or more electrodes and the method comprising the steps of: initiating a spark event; determining a breakdown voltage associated with the spark event; and determining from the breakdown voltage whether a flame is present in a flame zone by comparing the breakdown voltage to one or more predefined thresholds, determining that a flame is present when the breakdown voltage falls within an expected voltage range established by the predefined thresholds and determining that a flame is not present when the breakdown voltage falls outside the expected voltage range. ​ ​ wherein the predefined threshold is based on an expected type of medium in the spark gap in the presence of a flame and at least one of the following additional factors: a known size of the spark gap, an expected temperature of the electrodes in the presence of a flame, an expected pressure of the medium in the spark gap in the presence of a flame.

10. The method of claim 9, wherein, The ignition unit is coupled to a power source on an input side, coupled to the output line on an output side, and comprises a step-up transformer; and characterized in that the step of initiating a spark event further comprises initiating the spark event by causing the step-up transformer to step up a voltage of the power from the power source to a voltage in a range of 0.5 kV - 30 kV, providing the stepped-up voltage to the output line and the electrodes in the form of high voltage electrical pulses, and causing the high voltage electrical pulses to create a spark across a spark gap established by the electrodes, wherein the spark gap is at least partially located in the flame zone.

11. The method of claim 9, wherein, The determining step determines the breakdown voltage by measuring a voltage representative of the voltage across the electrodes with a sensing device, identifying a highest voltage measured by the sensing device, and setting the breakdown voltage to the highest voltage measured.

12. The method of claim 9, further comprising the steps of: when it is determined that there is no flame in the flame zone, taking remedial action to shut off a fuel supply or re-ignite the flame.

13. A method of detecting a flame using a flame detection apparatus comprising an ignition unit, one or more output lines, and one or more electrodes, and the method comprising the steps of: initiating a spark event; determining a breakdown voltage associated with the spark event; and using the breakdown voltage to determine whether there is a flame in a flame zone by monitoring the breakdown voltage, determining a rate at which the breakdown voltage decreases or increases over time, comparing the rate at which the breakdown voltage decreases or increases to one or more predefined threshold rates, and determining that there is a flame when the rate at which the breakdown voltage decreases exceeds the predefined threshold rate and determining that there is no flame when the rate at which the breakdown voltage increases exceeds the predefined threshold rate.

14. The method of claim 13, further comprising the steps of: when it is determined that there is no flame in the flame zone, taking remedial action to shut off a fuel supply or re-ignite the flame.

15. A method of detecting a flame using a flame detection apparatus comprising an ignition unit, one or more output lines, and one or more electrodes, and the method comprising the steps of: initiating a spark event; determining a breakdown voltage associated with the spark event; and using the breakdown voltage to determine whether there is a flame in a flame zone by observing the breakdown voltage over a period of time, detecting a trend or pattern in the breakdown voltage, and determining whether there is a flame based on the detected trend or pattern.

16. The method of claim 15, further comprising the steps of: when it is determined that there is no flame in the flame zone, taking remedial action to shut off a fuel supply or re-ignite the flame.

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