Note: Descriptions are shown in the official language in which they were submitted.
1
DEVICE AND METHOD FOR CONTROLLING A FUEL-OXIDIZER
MIXTURE IN A PREMIX GAS BURNER
This invention relates to a method and a device for controlling a fuel-
oxidizer mixture in a premix gas burner.
Known in the field of these control devices are devices that comprise a
control unit configured to send drive signals to the different components of
the burner to regulate its operation. More specifically, the burner
comprises an intake duct in which an air suction fan is installed. The intake
duct comprises a mixing zone into which a gas injection duct leads and the
gas injection duct is operated on by a gas regulating valve to regulate the
gas flow injected into the mixing zone. The control unit sends drive signals
to the fan and to the gas regulating valve to regulate the flow of mixture
and the fuel-oxidizer ratio to regulate the operation of the burner based on
specific regulation data. Prior art devices comprise a flame sensor,
configured for detecting the state of the flame. Thus, the control unit
regulates the fan and the valve based on the regulation curves and on the
signal received from the flame sensor, representing a state of combustion
in the burner.
Devices of the type just described are disclosed, for example, in the
following documents: FR2301775A1, W02004053900A2 and
W02009110015A1. Other solutions known in the prior art are described in
documents EP3663648A1 and US2015077009A1.
In these documents, however, the flame sensor is chosen on the basis of
the fuel which the burner is programmed to run on. Thus, if the device
were to change, the flame sensor would no longer be able to reliably
detect the state of the combustion that is taking place. Moreover, in the
devices described above, the control unit includes a regulation curve
which is linked to the type of fuel the boiler is designed to work with. These
devices, therefore, are not suitable for working with different fuels and are
thus relatively inflexible.
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There is an ever increasing need for greater flexibility with regard to the
fuel used, which is increasingly varied in nature or is constituted by
mixtures of different fuels or, for the purposes of ecological development,
even by pure hydrogen (>98%).
This invention has for an aim to provide a method and a device for
controlling a fuel-oxidizer mixture in a premix gas burner to overcome the
above mentioned disadvantages of the prior art.
This aim is fully achieved by the method and device of this disclosure as
characterized in the appended claims.
According to an aspect of it, this disclosure provides a method for
controlling the fuel-oxidizer mixture in a premix gas burner. Preferably, the
steps described below are performed by the processor; some of them
may, however, also regard the components of a device which the
processor is part of.
The method comprises a step of 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.
The method comprises a step of accessing fuel data, representing the fact
that the gas fuel belongs to the first type or the second type.
It is noted that the expression "type of fuel" is not intended as being
limited
to a fuel comprising a single compound (for example, methane and/or
LPG) but also to those types (that is, families) of fuels which are mixtures
of compounds but which, in terms of current legislation, also constitute a
specific family of fuels.
In any case, in general terms, the first type and the second type are
distinguished not so much in the compounds they are composed of as in
the physical parameter involved in their combustion and the measurement
of which allows deriving information regarding the specific fuel, as clarified
below.
The method comprises a step of generating drive signals to control a gas
flow regulating valve that supplies gas to the burner and/or to control a
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rotation speed of a fan configured to take in oxidative air.
The method comprises a step of sending the drive signals to the gas flow
regulating valve and/or to a motor connected to the fan.
Preferably, the processor has access to a memory unit containing first
regulation data and second regulation data, different from the first
regulation data. In other words, the first and second regulation data
represent regulation curves which allow deriving drive signals from input
data such as the flame signal and/or flow rate data, if any, representing a
flow of mixture fed into the combustion cell.
The processor 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.
In other words, the first regulation data allow generating the drive signals
(at least) from the flame signal in the case where the fuel is of the first
type, whilst the second regulation data allow generating the drive signals
(at least) from the flame signal in the case where the fuel is of the second
type. Thus, the processor derives the type of fuel from the fuel data and,
based on the type of fuel, selects the first or the second regulation data.
Thus, it is not necessary to provide different types of sensors to detect
different parameters because the control unit automatically adapts by
selecting the correct regulation data based on the type of fuel.
This gives flexibility to the control method, which is capable of controlling
the burner with different types of fuels without having to change the control
logic which is essentially self-adaptive based on the fuel data.
Advantageously, the step of receiving the flame signal comprises a step of
receiving a first flame signal representing the presence of a flame deriving
from the combustion of a fuel of the first type. Further, the step of
receiving
the flame signal comprises a step of receiving a second flame signal
representing the presence of a flame deriving from the combustion of a
fuel of the second type.
The processor generates the drive signals based on the first flame signal
and/or on the second flame signal. In other words, based on the fuel data,
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the processor determines which between the first and the second flame
signal defines the flame signal that will be used to generate the drive
signals.
This makes the measurement more precise in that the processor receives
the more significant flame signal based on the fuel used (that is the signal
captured with the technology most sensitive to the specific fuel).
Preferably, 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. In other words, by the combined analysis (processing) of the first
flame signal and of the second flame signal according to the method, it is
possible to determine the qualitative composition of the fuel, that is to say,
whether it contains only fuel of the first type, only fuel of the second type
or a mixture of the two types of fuel.
This allows the control method to automatically detect the fuel data, that is,
the type of fuel used, by analysing and processing the first and the second
flame signal.
Advantageously, in some example embodiments, the fuel data represent a
presence or a quantity of fuel of the first type and/or a presence or a
quantity of fuel of the second type. Thus, by processing the first and the
second flame signal, the processor derives a fuel composition in terms of
the presence of the first and/or the second type of fuel or in terms of
relative quantities of the first and/or the second type of fuel.
In an embodiment, if the quantity of the first fuel is greater than a first
value, the processor performs a step of checking the ratio between the
fuel and the oxidizer.
The step of checking the ratio between the fuel and the oxidizer comprises
a step of deriving a quantitative ratio between the fuel and the oxidizer
based on the first flame signal.
The step of checking the ratio between the fuel and the oxidizer comprises
a step of comparing the derived quantitative ratio with an ideal quantitative
ratio. The ideal quantitative ratio is stored in a memory unit which the
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processor has access to.
The processor generates the drive signals based on the comparison
between the derived quantitative ratio and the ideal quantitative ratio. This
allows the method to operate on the fan and on the valve to bring the real
quantitative ratio as close as possible to the ideal ratio, thus improving the
efficiency of the burner.
Preferably, the step of checking the ratio between the fuel and the oxidizer
also comprises a step of receiving a temperature signal, representing a
temperature inside a combustion cell of the burner. This temperature may,
for example, be measured both in contact with, or in proximity to, the
inside surface of the burner (not on the side where the flame is formed) or
on the outside, in the combustion chamber, (on the side where the flame
is) with a similar result. In this embodiment, the processor derives the
quantitative ratio between the fuel and the oxidizer also on the basis of the
temperature signal.
For example, if the first type of fuel is hydrogen, the first flame signal
represents a detection of UV radiation. In such a case, the processor
calculates the ratio between the fuel and the oxidizer based on the UV
signal and on the temperature of the combustion cell.
In calculating the quantities of fuel of the first and second type, the
processor finds, for the first and/or the second flame signal, a
corresponding first and/or second value of signal intensity. The processor
compares the first and/or the second intensity value with reference data.
The reference data represent an association between the first intensity
value and the quantity of fuel of the first type. In addition, or
alternatively,
the reference data represent an association between the second intensity
value and the quantity of fuel of the second type.
In an example embodiment, the method comprises a step of receiving flow
rate data, identifying a gas flow detected by a gas flow sensor.
The method comprises a step of calculating a gas flow rate as a function
of the flow rate data. The method comprises a step of comparing the
quantity of fuel of the first type and/or the quantity of fuel of the second
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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 data.
The method comprises a step of performing a diagnostic test on the gas
flow sensor based on the comparison.
These steps of the method, therefore, also make it possible to make an
accurate diagnosis of the flow sensors of the control device by verifying
the flow rate identified on the basis of the flame signals.
It should be noted that, preferably, the first flame signal represents an
electromagnetic wave in the ultraviolet field and the fuel of the first type
comprises hydrogen.
Preferably, also, the second flame signal represents a direct current signal
or a measurement of impedance (resistance) of the flame, measured by
an electrode immersed in the flame itself and made possible by ionization,
and the fuel of the second type comprises methane and/or LPG and/or
any other fossil fuel. More generally speaking, the second type of fuel is a
fuel that allows the passage of ions in the presence of a flame, so that the
passage of the ions can be detected by measuring an electrical signal,
such as current, for example, (or a value of impedance obtained
therefrom) which passes through an electrode supplied with voltage.
This electrode may be distinct from the electrode that produces the spark
or arc to ignite the mixture or, more advantageously, it may be the same
electrode.
In an advantageous embodiment, the processor derives the fuel data also
on the basis of the flow rate data. In other words, to derive the quantity of
each fuel, the processor also uses the information it receives from the flow
sensor regarding the flow rate of the mixture.
According to an aspect of the method, the processor, based on the flame
signal and/or on the temperature signal, generates a burner ignited
confirmation signal.
In addition, or alternatively to automatic calculation of the fuel data, the
fuel data for use by the processor can be entered manually by a user
through a user interface of the control device.
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According to an aspect of this disclosure, the method comprises a step of
performing a diagnostic test on the flame sensors. In the step of
performing a diagnostic test on the flame sensors, a thermal output
sensor, located in the water outlet pipes of the exchanger, detects the
temperature of the water flowing out of the exchanger. The thermal output
sensor sends a signal to the control unit, representing the temperature of
the water flowing out of the burner. Upon ignition of the burner, the control
unit ascertains whether flame is present based on the first and/or the
second flame signal. Based on the signal received from the thermal output
sensor, the control unit ascertains an increase in water temperature within
a time frame defined by experimental values representing the water
flowing out of the exchanger. Responsive to the detection of the flame in
the burner, the control unit verifies that the temperature of the water
flowing out of the burner is increasing. Should the control unit detect that
the temperature has remained unchanged despite the flame having been
detected in the combustion head, the control unit sends a notice of fault to
the first flame sensor and/or to the second flame sensor.
According to an aspect of it, this disclosure provides a device for
controlling a fuel-oxidizer mixture for a premix gas burner.
The device comprises an intake duct which defines a section through
which a fluid is admitted into the duct. The intake duct includes an inlet for
receiving the oxidizer. The intake duct comprises a mixing zone for
receiving the fuel and allowing it to be mixed with the oxidizer. The intake
duct comprises a delivery outlet for delivering the mixture to the burner.
The device comprises an injection duct, connected to the intake duct in a
mixing zone, to supply the fuel.
The device comprises a gas regulating valve, located along the injection
duct.
The device comprises a fan, rotating 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.
In an embodiment, the mixing zone is located downstream of the fan,
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along the intake duct in the direction of inflow.
In an embodiment, the mixing zone is located upstream of the fan, along
the intake duct in the direction of inflow.
The device comprises a first flame sensor, configured to detect a first
flame signal, representing the presence of a flame deriving from the
combustion of a first type of fuel inside a combustion cell of the burner.
The device comprises a control unit, including a processor programmed to
receive a flame signal. The processor is programmed to generate drive
signals, representing a position of the gas regulating valve and/or the
rotation speed of the suction fan, based on the flame signal.
Advantageously, the device comprises a second flame sensor, configured
to detect a second flame signal, representing the presence of a flame
deriving from the combustion of a second type of fuel inside a combustion
cell of the burner.
The processor is programmed to receive fuel data, representing the fact
that the gas fuel belongs to the first type or the second type.
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.
Thus, the processor processes the first or the second flame signal based
on the fuel data.
Advantageously, the processor is programmed 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.
In an example embodiment, the processor is programmed to access a
memory unit containing first regulation data and second regulation data,
different from the first regulation data. The processor is also programmed
to generate the drive signals based on the first regulation data or,
alternatively, on the second regulation data, depending on the fuel data.
Preferably, the device comprises a user interface, connected to the control
unit. The user interface is configured to allow a user to enter the fuel data
manually.
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According to an aspect of this disclosure, the device comprises a thermal
output sensor, configured to detect the temperature of the water flowing
out of the exchanger. The thermal output sensor sends a signal to the
control unit, representing the temperature of the water flowing out of the
exchanger. Upon ignition of the burner, the control unit is programmed to
ascertain whether flame is present based on the first and/or the second
flame signal. Based on the signal received from the thermal output sensor,
the control unit is programmed to ascertains an increase in the
temperature of the water flowing out of the exchanger. Responsive to the
detection of the flame in the burner, the control unit is programmed to
verify, within a predetermined time frame, that the temperature of the
water flowing out of the burner is increasing. Should the control unit detect
that the temperature has remained unchanged despite the flame having
been detected in the combustion head, the control unit is programmed to
send a notice of fault to the first flame sensor and/or to the second flame
sensor.
According to an aspect of it, this disclosure provides a computer program,
including instructions for executing any of the steps of the method
described in this disclosure.
It should be noted that the term "burner" is used to denote the set of
features described herein, including, amongst others, the combustion
head and the control device according to one or more of the features
described herein with reference to the control device. According to an
aspect of it, therefore, this disclosure provides a premix gas burner
including a combustion head into which the premixed gas is delivered for
combustion, and a control device according to one or more of the features
described herein with reference to the control device.
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:
- Figures 1A and 1B illustrate, respectively, a first embodiment and a
second embodiment of a device for controlling fuel-oxidizer mixture in a
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premix gas burner according to this disclosure;
- Figure 2 is a block diagram schematically representing a method for
controlling a fuel-oxidizer mixture in a premix gas burner according to this
disclosure.
With reference to the accompanying drawings, the numeral 1 denotes a
device for controlling the fuel-oxidizer mixture in premix gas burners 100.
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.
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.
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.
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.
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
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the direction of inflow V.
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.
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.
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.
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.
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.
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.
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'.
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
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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 TO of the burner 100.
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):
- 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
- 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);
- non-detection of the first flame signal 401 indicates the absence of the
first type of fuel.
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).
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.
In an embodiment, the first flame signal 401 might also be a signal that
identifies the temperature of the combustion cell TO 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.
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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.
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):
- 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
- 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);
- non-detection of the second flame signal 402 indicates the absence of
the second type of fuel.
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.
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
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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.
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.
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.
In a preferred embodiment, the first and the second flame signal 401, 402
are sent to (are received in Fl, 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.
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.
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The processor is programmed to select F5 the first or the second
regulation data R1, R2 based on the fuel data 403.
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.
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.
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 TO.
This allows distinguishing the type of fuel used so that the burner can be
monitored, run and maintained more safely and efficiently.
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.
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.
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 TO 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
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sensor 43' is located in the gas injection duct 3 and another flow sensor
43" is located on the intake duct 2.
The processor receives F4 the flow rate signal 431 from the flow sensor
43.
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.
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.
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.
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.
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
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be more than one temperature sensor 44 to form a plurality of temperature
sensors 44.
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.
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).
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.
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.
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).
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.
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
Date recue/Date received 2023-03-06
18
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.
Another drawback overcome by this invention regards cases of low gas
supply pressure.
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.
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.
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.
Date recue/Date received 2023-03-06
