WO2007132484A1 - Dispositif de mesure de l'intensité de la flamme - Google Patents

Dispositif de mesure de l'intensité de la flamme Download PDF

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Publication number
WO2007132484A1
WO2007132484A1 PCT/IT2006/000352 IT2006000352W WO2007132484A1 WO 2007132484 A1 WO2007132484 A1 WO 2007132484A1 IT 2006000352 W IT2006000352 W IT 2006000352W WO 2007132484 A1 WO2007132484 A1 WO 2007132484A1
Authority
WO
WIPO (PCT)
Prior art keywords
transistor
flame intensity
duty cycle
signal
measuring
Prior art date
Application number
PCT/IT2006/000352
Other languages
English (en)
Inventor
Franco Giacon
Original Assignee
Sit La Precisa S.P.A.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sit La Precisa S.P.A. filed Critical Sit La Precisa S.P.A.
Priority to PCT/IT2006/000352 priority Critical patent/WO2007132484A1/fr
Priority to EP06756288.4A priority patent/EP2016336B1/fr
Publication of WO2007132484A1 publication Critical patent/WO2007132484A1/fr

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N5/00—Systems for controlling combustion
    • F23N5/02—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium
    • F23N5/12—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using ionisation-sensitive elements, i.e. flame rods
    • F23N5/123—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using ionisation-sensitive elements, i.e. flame rods using electronic means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2223/00—Signal processing; Details thereof
    • F23N2223/08—Microprocessor; Microcomputer

Definitions

  • the present invention relates to a device for measuring flame intensity having the characteristic features set out in the preamble of the main claim.
  • the invention is applied in particular, but not exclusively, in the sector of systems for the control of the gas supply to burners of appliances for heating in general, whose flame is adapted to heat the environment or an intermediate fluid circulating in a boiler plant.
  • a typical application is in systems controlling the gas supply to burners of boilers for domestic heating and/or heating of domestic hot water.
  • a main object of the present invention is to provide a device for measuring flame intensity which is structurally and functionally adapted to satisfy the above-mentioned requirements and at the same time to remedy the drawbacks described with reference to the cited prior art.
  • Fig. 1 is a circuit diagram of a preferred embodiment of a device for measuring flame intensity of the present invention
  • Fig. 2 shows the duty cycle variation (in %) of the voltage V as a function of the ionisation current (in ⁇ A) of five different examples of a flame sensor at predetermined temperature, in accordance with the diagram of Fig. 1;
  • Fig. 3 shows the temperature dispersion (in 0 C) of the magnitudes shown in Fig. 2;
  • Fig. 4 shows a preferred embodiment of the input/output signal to various components of the device of Fig. 1;
  • Fig. 5 diagrammatically shows a preferred embodiment of a control system of the invention comprising the device of Fig. 1.
  • the device for measuring flame intensity 1 comprises a flame sensor
  • the sensor Ul is preferably produced using conventional techniques in the sector and comprises, for instance, two electrodes.
  • the operation of the flame sensor may be compared with that of a current generator connected to a one-way member, for instance a diode in series with a resistor (see diode D2 and resistor RlO in Fig 1) : the current generated by the sensor as a result of the presence of the flame in practice flows in only one direction. This is in particular due to the fact that the burner is often connected to earth in boilers embodied according to the prior art, with the result that when current is flowing in the sensor Ul as a result of the presence of a flame, this current "drains" towards earth.
  • the currents generated by flame sensors coupled to known burners in the sector are of the order of microamperes.
  • the ionisation current generated in the sensor Ul preferably varies within a range of 0.8 ⁇ A to 7.5 ⁇ A.
  • the device of the invention may nevertheless also be used in the case of ionisation currents having different orders of magnitude.
  • flame intensity has the following meaning in the preferred embodiment described below: a "low” flame is a flame which licks the sensor partially from a volumetric point of view and a "high” flame is when the sensor is completely surrounded by the flame. Various flame levels from low to high therefore correspond to a flame which licks an increasingly greater portion of the sensor until it is completely surrounded.
  • the device for measuring flame intensity 1 is supplied not just with the current signal from the flame sensor Ul but also with an alternating voltage signal Vl having a first predetermined duty cycle, for instance a voltage having a zero-centred duty cycle of 50%.
  • the voltage V may for instance be the mains voltage from which the direct component is eliminated by means of a capacitor Cl (see Fig. 1, in which a resistor Rl, the capacitor Cl and two further resistors R2 and R4 are disposed in series, this being one of the possible embodiments of the invention) in order to obtain a sinusoidal signal having a first duty cycle of 50% and substantially centred on 0 (i.e. having a mean value which is substantially zero).
  • the voltage Vl may also be supplied by an alternating signal generator or by batteries (not shown).
  • the device for measuring flame intensity 1 further comprises means 2 for varying the first predetermined duty cycle of the signal Vl whose input is supplied with both the ionisation current generated by the sensor Ul downstream of a resistor R6 and the alternating voltage signal Vl.
  • These means 2 generate as output an alternating voltage signal V having a second duty cycle which is a function of the first duty cycle (which is known and set when the device 1 is installed) and the ionisation current Ul, as will be explained below.
  • the second duty cycle of the output signal V increases as the ionisation current increases.
  • the variation means 2 comprise a switch member, preferably a transistor Ql, whose base is supplied by the signal Vl and by the ionisation current.
  • a positive supply voltage shown in Fig. 1 as a direct voltage Vcc, is supplied to the collector of the transistor Ql.
  • the collector resistor is also shown by R5 in Fig. 1.
  • the potential difference between the base and emitter of the transistor Ql is determined by the base input signal (the emitter is preferably connected to earth).
  • the values of the various components of the device 1, the values of the ionisation current and the value of the alternating current signal Vl having a first duty cycle are such that the input signal of the base of the transistor Ql has a value which oscillates between saturation values (when the input signal of the base of the transistor is maximum) and cut-off values for the transistor Ql, causing the latter to operate substantially as a "switch".
  • the transistor Ql is substantially invariable with respect to temperature variations, which would not be the case if the transistor were operating in the linear zone.
  • the transistor gain is not a relevant parameter, extremely economic transistors may be used in the device of the invention.
  • the measuring device 1 further comprises optional filter means 3 by means of which the alternating voltage signal Vl and the current signal from the flame sensor (if a flame is present) are advantageously filtered and then supplied as input to the base of the transistor Ql.
  • the optional filter means 3 preferably comprise a low-pass filter 3 which is more preferably formed by two low-pass filters in parallel, a first low-pass filter 4, for instance in series with a resistor R8' and a capacitor C3, and a second low-pass filter 5, for instance in series with a resistor R9 and a capacitor C2.
  • a low-pass filter 3 which is more preferably formed by two low-pass filters in parallel, a first low-pass filter 4, for instance in series with a resistor R8' and a capacitor C3, and a second low-pass filter 5, for instance in series with a resistor R9 and a capacitor C2.
  • One terminal of both the capacitor C3 and the capacitor C2 is preferably connected to earth.
  • a low-pass filter 3 comprising the two low-pass filters 4 and 5 in parallel is preferred in order to make it possible to lower the overall signal cut-off frequency by using commercially available, economic and reliable components. Disposing two low-pass filters in parallel in practice makes it possible to use resistors and capacitors of a lower value than in the case of a single low-pass filter. For the same reason, i.e. for cost savings and ease of location of components, the resistor R8' preferably comprises two resistors R7 and R8 in series. It will be appreciated that the input signal to the low-pass filter 3 has a negative offset with respect to the signal Vl, which offset depends on the value of the ionisation current through the flame sensor Ul to earth.
  • the signal supplied as input to the filter 3 and therefore to the base of the transistor Ql has a duty cycle lower than that of the signal Vl as a result of the ionisation current which, when present, entails a negative offset of the signal Vl, i.e. its "translation" by a particular value, determined by the intensity of the ionisation current, to negative voltage values.
  • the low-pass filter 3 is electrically connected as output to the base of the transistor Ql by regulation means 6 of the base voltage of the transistor Ql.
  • the regulation means 6 of the base voltage of the transistor Ql for instance comprise a diode D4 in parallel with the base, i.e. joining the base and emitter of the transistor Ql, in order to limit the base voltage below a maximum limit authorised for the transistor Ql, so as to prevent damage to this transistor. It is preferable for the diode D4 to be disposed in parallel with the base (although this diode D4 may also be disposed in series with the base of the transistor) as this arrangement enables better temperature behaviour of the device 1.
  • the diode D4 is further connected in parallel with a resistor RIl which is adapted to connect the base to earth.
  • the transistor Ql further preferably comprises a collector resistor R5 and has a collector voltage V which represents the output signal from the measuring device 1 : the output signal V substantially comprises a two-level voltage (for simplicity, known in short as “high” and “low") with a second duty cycle depending on the alternation of saturation (to which a "low” voltage V corresponds) and cut-off (to which a "high” voltage V corresponds) in the transistor Ql.
  • the value of the duty cycle of the signal V depends, as the value of the first duty cycle of Vl is set and remains set, on the negative offset proportional to the ionisation current generated by the flame sensor Ul of the signal supplying the base of the transistor Ql.
  • the resistors Rl-RIl are of the type which do not vary with variations in temperature, for instance resistors of the SMD (Surface Mounting Device) type, in order to ensure, together with the use of the transistor Ql outside the linear zone, that the performance of the device 1 is reproducible in a predetermined temperature range equivalent to the range of use of the burner, for instance in the range between -4O 0 C and 8O 0 C.
  • the alternating signal voltage Vl depends, however, on the type of mains supply to which the device is connected, i.e. a signal of 50 Hz in Italy. If the voltage varies, i.e. a mains voltage of 60 Hz, all that is needed is a software modification as the device may be used with any mains voltage.
  • a control system 7 of the invention shown in Fig. 5, comprises the device for measuring flame intensity 1 and means 8 for comparing the second duty cycle of the output signal from the device 1 with a plurality of predetermined levels so as to assign a flame intensity to a specific value of the second duty cycle.
  • a control function therefore assigns a predetermined level to specific values of the second duty cycle.
  • the ionisation current generated in the sensor Ul may vary in a range of 0.8 ⁇ A to 7.5 ⁇ A which leads to a substantially linear variation of the second duty cycle (minimal when there is no flame and then increasing as the ionisation current increases).
  • the comparison means 8 preferably comprise a microprocessor ⁇ P having as input the collector voltage V sampled at high frequency, typically every 64 ⁇ s, which value may nevertheless be varied and depends, inter alia, on the frequency of the alternating signal Vl and on the ionisation current.
  • control system 7 further comprises, if the device 1 is supplied directly from the electrical mains, an isolation transformer 9 adapted to make the alternating signal Vl independent from the mains supply.
  • the isolation transformer 9 has a supplementary winding on the secondary (not shown), isolating the "high voltage" part of the variation circuit 2 making it unnecessary to use photocouplers for the interface with the microprocessor.
  • the device 1 of the present invention operates as follows.
  • the flame sensor Ul In the absence of a flame, the flame sensor Ul has no ionisation current flowing through it and therefore the input and output signals of the filter means 3, which attenuate solely the amplitude of the signal but do not change its duty cycle, are the alternating voltage signals Vl having a predetermined duty cycle, for instance that of the mains.
  • the first duty cycle is 50%.
  • the potential difference between the base and emitter of the transistor Ql therefore alternates between cut-off and saturation values during time intervals depending on the signal Vl and the second duty cycle of the collector voltage V is proportional and "inverted" with respect to the first reference duty cycle.
  • the signal V when there is a positive input signal at the base of the transistor Ql, the signal V is negative, and when there is a negative signal at the base, the signal V is positive.
  • the signal V does not have a duty cycle coinciding with the duty cycle Vl because of the presence of the resistor R3 (of 2.2 M ⁇ in the preferred embodiment) in order to ensure more accurate detection of the signal V.
  • the duty cycle of the signal V at zero flame is set to be equal to 20%, although the duty cycle of the signal V at zero flame can be set as desired.
  • the ionisation current in the flame sensor Ul is responsible for a negative offset with respect to the alternating signal Vl at the input of the low-pass filter 3 proportional to the intensity of this current: the greater the current, the greater will be the negative offset, i.e. the "translation" of the signal Vl to negative voltage values, and therefore the duty cycle of the signal supplied to the base of the transistor Ql will be proportionally reduced.
  • Fig. 4 shows an example of the signal present as input/output at various points (in particular points A, B, C, D in the presence and absence of a flame) of the device 1.
  • the embodiment illustrated shows a sinusoidal signal Vl with a duty cycle of 50%, it will be appreciated that the signal Vl may be any alternating signal having a predetermined set duty cycle.
  • the signal Vl is sinusoidal with a duty cycle of 50%.
  • the signal Vl is a triangular signal with a duty cycle of 50%.
  • a triangular wave generator is in particular preferred in cases in which it is necessary to use an alternating current generator (for instance in cases in which connection to the electrical mains is impossible and it is therefore necessary to use, for instance, an appropriate battery).
  • the potential difference between the base and emitter of the transmitter Ql is such as to cut off the transistor Ql for a time interval greater than the saturation interval as the signal supplying the base of the transistor is in negative voltage for a period longer than the period in which the base is supplied with positive voltage.
  • the output signal V of the device 1 is therefore "high” for a longer period than when it is “low” with the result that its duty cycle increases (see the signals of Fig. 4). Consequently, the more the duty cycle of the input signal of the base of the transistor Ql decreases, the more the duty cycle of the collector signal (i.e. the voltage V) increases.
  • the second duty cycle of the collector voltage V is therefore proportional to the flame intensity detected, as shown in Fig. 2: the abscissa shows the ionisation current (proportional to the flame intensity) and the ordinate shows the resulting duty cycle of the signal V.
  • the various curves shown in Fig. 2 refer to a plurality of different devices 1, in particular including different sensors Ul, in order to verify that their behaviour is analogous.
  • the device 1 is appropriately dimensioned so that the saturation value is reached for the maximum flame levels generally encountered in the burners in which it is applied.
  • the Applicants have been able to ascertain that there are maximum variations of 2% of the duty cycle of the signal V for temperature variations from -40 to +80, making the device 1 substantially invariable with respect to temperature in the normal temperature range of use.
  • Fig. 3 shows a graph similar to that of Fig. 2 obtained for three different operating temperatures of the device 1 equal to -20 0 C, 25 0 C and 7O 0 C (in this case as well, simulations of different devices 1 including different sensors are given for each temperature).
  • the collector voltage V is sampled at high frequency and the sample values are compared by the microprocessor with the predetermined levels of the control function.
  • the invention thus achieves the proposed objects and provides the above-described advantages with respect to known solutions.
  • the device for measuring flame intensity is invariable with respect to temperature variations, dispersions of the characteristics of components and variations of the supply voltage.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
  • Photometry And Measurement Of Optical Pulse Characteristics (AREA)

Abstract

La présente invention concerne un dispositif (1) servant à mesurer l'intensité de la flamme dans un brûleur, ce dispositif (1) recevant un premier signal alterné (VI) ayant un premier cycle de travail prédéterminé. Le dispositif comprend un détecteur de flamme (UI) qui génère un courant d'ionisation proportionnel à l'intensité de la flamme présente dans le brûleur et un moyen (2) qui fait varier le cycle de travail en fonction du courant d'ionisation, ce moyen de variation étant envoyé en tant qu'entrée en même temps que le premier signal alterné (VI) et que le courant d'ionisation et générant en sortie un signal alterné (V) ayant un deuxième cycle de travail qui est établi en fonction du courant d'ionisation.
PCT/IT2006/000352 2006-05-11 2006-05-11 Dispositif de mesure de l'intensité de la flamme WO2007132484A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
PCT/IT2006/000352 WO2007132484A1 (fr) 2006-05-11 2006-05-11 Dispositif de mesure de l'intensité de la flamme
EP06756288.4A EP2016336B1 (fr) 2006-05-11 2006-05-11 Dispositif de mesure de l'intensité de la flamme

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/IT2006/000352 WO2007132484A1 (fr) 2006-05-11 2006-05-11 Dispositif de mesure de l'intensité de la flamme

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WO2007132484A1 true WO2007132484A1 (fr) 2007-11-22

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009110015A1 (fr) * 2008-03-07 2009-09-11 Bertelli & Partners S.R.L. Procédé et dispositif perfectionnés pour détecter la flamme dans un brûleur fonctionnant avec un combustible solide, liquide ou gazeux
KR20200097792A (ko) * 2017-12-21 2020-08-19 지오다노 컨트롤즈 에스.피.에이. 가스 버너의 화염을 검출하고 제어하는 장치 및 방법

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3627458A (en) * 1968-08-27 1971-12-14 United Gas Industries Ltd Flame detection system
US20020004186A1 (en) * 2000-05-12 2002-01-10 Siemens Building Technologies Ag Measuring device for a flame
GB2367172A (en) * 2000-04-26 2002-03-27 Pektron Group Ltd Flame detection apparatus

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3627458A (en) * 1968-08-27 1971-12-14 United Gas Industries Ltd Flame detection system
GB2367172A (en) * 2000-04-26 2002-03-27 Pektron Group Ltd Flame detection apparatus
US20020004186A1 (en) * 2000-05-12 2002-01-10 Siemens Building Technologies Ag Measuring device for a flame

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009110015A1 (fr) * 2008-03-07 2009-09-11 Bertelli & Partners S.R.L. Procédé et dispositif perfectionnés pour détecter la flamme dans un brûleur fonctionnant avec un combustible solide, liquide ou gazeux
US8773137B2 (en) 2008-03-07 2014-07-08 Bertelli & Partners, S.R.L. Method and device to detect the flame in a burner operating on a solid, liquid or gaseous combustible
KR20200097792A (ko) * 2017-12-21 2020-08-19 지오다노 컨트롤즈 에스.피.에이. 가스 버너의 화염을 검출하고 제어하는 장치 및 방법
EP3728950B1 (fr) * 2017-12-21 2022-06-08 Giordano Controls S.p.A. Dispositif et procédé de régulation et de détection de flamme de brûleur à gaz
KR102422728B1 (ko) 2017-12-21 2022-07-19 지오다노 컨트롤즈 에스.피.에이. 가스 버너의 화염을 검출하고 제어하는 장치 및 방법

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Publication number Publication date
EP2016336B1 (fr) 2014-07-09
EP2016336A1 (fr) 2009-01-21

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