EP0784190B1 - Device for optimizing the efficiency of a gas-fired heat generator - Google Patents
Device for optimizing the efficiency of a gas-fired heat generator Download PDFInfo
- Publication number
- EP0784190B1 EP0784190B1 EP96110211A EP96110211A EP0784190B1 EP 0784190 B1 EP0784190 B1 EP 0784190B1 EP 96110211 A EP96110211 A EP 96110211A EP 96110211 A EP96110211 A EP 96110211A EP 0784190 B1 EP0784190 B1 EP 0784190B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- signal
- gas
- fan
- mains
- burner
- Prior art date
- Legal status (The legal status 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 status listed.)
- Expired - Lifetime
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Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N3/00—Regulating air supply or draught
- F23N3/08—Regulating air supply or draught by power-assisted systems
- F23N3/082—Regulating air supply or draught by power-assisted systems using electronic means
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N1/00—Regulating fuel supply
- F23N1/06—Regulating fuel supply conjointly with draught
- F23N1/062—Regulating fuel supply conjointly with draught using electronic means
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N2227/00—Ignition or checking
- F23N2227/04—Prepurge
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N2233/00—Ventilators
- F23N2233/02—Ventilators in stacks
- F23N2233/04—Ventilators in stacks with variable speed
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N2235/00—Valves, nozzles or pumps
- F23N2235/12—Fuel valves
- F23N2235/16—Fuel valves variable flow or proportional valves
Definitions
- This invention relates to a device in accordance with the introduction to claim 1.
- a modern gas-fired heat generator or boiler is known to comprise a fan used both as the device for evacuating burnt gases from the combustion chamber and as the combustion air feed member.
- the heat output of the adjustable heat generator is regulated by the action of its control unit on the pressure regulator of the gas valve, but the rotational speed of the fan is left unaltered to give a constant volumetric throughput (optimized for maximum heat output).
- combustion takes place with optimum combustion air throughput only for maximum heat output, the air throughput being excessive and increasing as the heat output decreases.
- the thermal efficiency with respect to the water decreases in relation to the air excess.
- JP-A-62169929 relates to a device according to the preamble of the main claim.
- a control of the rotational speed of an intake and exhaust fan corresponding to the opening of a proportional control valve which represents the amount of combustion of a burner In order to obtain said control, there are provided rotational speed setting means which sets in a plurality of stages the fan speed corresponding to the openineg of the control valve, and drive data output means which outputs to a rotation drive means data for driving the intake and exhaust fan.
- the data of the drive data output means are renewed by the result of a comparison of the output of a rotational speed detection circuit, obtained by detection means, with the output of the rotational speed setting means; as a consequence of this comparison, when the fan speed drops, it is corrected, and when said speed rises, it is not corrected, and an amount of blast close to a set amount can be secured.
- An object of the present invention is therefore to provide an improved device for optimizing the efficiency of a gas-fired boiler.
- a particular object of the invention is to provide a device of the stated type allowing the combustion air throughput to be substantially and instantaneously regulated for all operating ranges (ie for every possible required heat output) of the heat generator.
- a further object is to provide a device of the stated type which, even if the mains voltage varies (rises or falls), enables optimum combustion air throughput to be maintained for any gas flow to the burner, in particular enabling a minimum air throughput corresponding to minimum heat output to be maintained even following a drop in mains voltage.
- FIG. 1 shows the device 1 of the invention, comprising means 2 for controlling a motor 3 of a usual fan (not shown) positioned within the combustion chamber of a gas-fired heat generator (not shown).
- the means 2 measure the voltage across a usual electrically operated flow regulator (not shown), and on the basis of this (ie on the basis of the gas flow rate to the burner) they act on the fan motor 3 to modify the fan speed and hence modify the combustion air flow rate.
- a voltage V REF is withdrawn from across the modulator of a gas valve (not shown) defining the said gas flow regulator.
- This voltage is fed to an amplifier 5 which amplifies the V REF signal and constitutes a stage with a high impedance input. From the amplifier there leaves a signal V C which is fed to a comparator 6 which compares this signal with a voltage signal V R originating from a block 7 which measures the voltage of the electricity mains powering the heat generator.
- the block 7 in particular comprises a ramp generator 8 connected to a zero sensor 9 from which it receives a signal V Z . This latter is formed from a sequence of pulses generated each time the mains voltage passes through zero.
- the block 7 is connected to the mains voltage V A (symbolize by the block 10) via a voltage reducer 12.
- the ramp generator 8 is connected to a timer member 15 which receives mains voltage downstream of the voltage reducer and is connected in parallel with the zero sensor 9.
- the purpose of the member 15 is to enable the fan motor 3 to be powered to achieve maximum rotational speed (and hence maximum combustion air flow) for a predetermined time period each time the heat generator is started, independently of the value of V REF , so as to prepurge the combustion chamber.
- the comparator 6 compares the signals V C and V R , and generates an output signal V U which is fed to an adder node 17 which also receives a signal V K from a filter member 18 of compensator-limiter type which receives the mains voltage downstream of the reducer 12.
- the member 18 compensates for mains voltage variations which would otherwise influence the feed voltage of the motor 3. In particular, the member 18 ensures that the motor feed voltage never falls below a predetermined minimum value so as to set a minimum rotational speed of the motor 3 at which the air flow rate corresponds to the minimum heat output of the boiler.
- a signal V X leaves the adder node 17 to reach the control means 2.
- These latter can be an actual microprocessor unit (so as for example to allow automatic memorized control of the motor 3 on the basis of each value of V REF measured or of the signal V X ) or a simple comparator member or other known control means.
- the unit 2 is connected to a galvanic separator 20 which ensures adequate electrical isolation between the mains voltage and the very low safety voltage present in the circuit.
- the signal from the unit 2 hence controls the closure and opening of a static switch (for example a TRIAC) 22 through which the mains power reaches the motor 3.
- a static switch for example a TRIAC
- the control means or unit 2 measure the voltage V REF corresponding to the state of gas flow to the burner, and hence by means of this signal measure the gas flow rate to said burner.
- This signal is compared with the signal V R representative of the instantaneous mains voltage powering the motor 3. If this comparison shows that there is a preset difference between these two signals, the signal V U is generated and, suitably treated with the signal V K , reaches the means 2.
- the means 2 operate to modify the duty cycle of the static switch, to hence vary the speed of the motor 3 and of the fan.
- the device of the invention is reliable, is simple to construct and can be mounted in boilers already provided with an electrically controlled gas flow regulator, even after their installation.
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Regulation And Control Of Combustion (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
- Led Devices (AREA)
- Filling Or Discharging Of Gas Storage Vessels (AREA)
- Sorption Type Refrigeration Machines (AREA)
Abstract
Description
- This invention relates to a device in accordance with the introduction to claim 1.
- A modern gas-fired heat generator or boiler is known to comprise a fan used both as the device for evacuating burnt gases from the combustion chamber and as the combustion air feed member.
- In a boiler of known type, as the required heat output varies, the heat output of the adjustable heat generator is regulated by the action of its control unit on the pressure regulator of the gas valve, but the rotational speed of the fan is left unaltered to give a constant volumetric throughput (optimized for maximum heat output). Hence in such a generator, combustion takes place with optimum combustion air throughput only for maximum heat output, the air throughput being excessive and increasing as the heat output decreases. As a result the thermal efficiency with respect to the water decreases in relation to the air excess.
- To obviate this drawback it is known to control the fan speed and hence the combustion air throughput as a function of the fuel gas flow. This is achieved by providing in the feed pipe a pressure sensor connected to the control unit. By means of this sensor the unit measures the variation in gas throughput in the feed pipe and consequently acts on the fan to modify its rotational speed. Although this solution enables the air flow to be varied as a function of the fuel gas flow, it is very complicated to arrange and cannot be used on already operating boilers without modifying the gas feed pipe, with obvious drawbacks. In addition, the known solution does not enable an adequate combustion air throughput to be maintained (by maintaining a suitable fan rotational speed) if the electricity supply mains voltage falls.
- JP-A-62169929 relates to a device according to the preamble of the main claim. In this prior art, it is disclosed a control of the rotational speed of an intake and exhaust fan corresponding to the opening of a proportional control valve which represents the amount of combustion of a burner. In order to obtain said control, there are provided rotational speed setting means which sets in a plurality of stages the fan speed corresponding to the openineg of the control valve, and drive data output means which outputs to a rotation drive means data for driving the intake and exhaust fan. The data of the drive data output means are renewed by the result of a comparison of the output of a rotational speed detection circuit, obtained by detection means, with the output of the rotational speed setting means; as a consequence of this comparison, when the fan speed drops, it is corrected, and when said speed rises, it is not corrected, and an amount of blast close to a set amount can be secured.
- An object of the present invention is therefore to provide an improved device for optimizing the efficiency of a gas-fired boiler.
- A particular object of the invention is to provide a device of the stated type allowing the combustion air throughput to be substantially and instantaneously regulated for all operating ranges (ie for every possible required heat output) of the heat generator.
- A further object is to provide a device of the stated type which, even if the mains voltage varies (rises or falls), enables optimum combustion air throughput to be maintained for any gas flow to the burner, in particular enabling a minimum air throughput corresponding to minimum heat output to be maintained even following a drop in mains voltage.
- These and further objects which will be apparent to the expert of the art are attained by a device in accordance with the accompanying claims.
- The present invention will be more apparent from the accompanying drawing, which is provided by way of non-limiting example and in which the only figure represents a block diagram of the invention.
- Said figure shows the device 1 of the invention, comprising means 2 for controlling a motor 3 of a usual fan (not shown) positioned within the combustion chamber of a gas-fired heat generator (not shown). The means 2 measure the voltage across a usual electrically operated flow regulator (not shown), and on the basis of this (ie on the basis of the gas flow rate to the burner) they act on the fan motor 3 to modify the fan speed and hence modify the combustion air flow rate.
- More specifically, a voltage VREF is withdrawn from across the modulator of a gas valve (not shown) defining the said gas flow regulator. This voltage is fed to an
amplifier 5 which amplifies the VREF signal and constitutes a stage with a high impedance input. From the amplifier there leaves a signal VC which is fed to a comparator 6 which compares this signal with a voltage signal VR originating from a block 7 which measures the voltage of the electricity mains powering the heat generator. The block 7 in particular comprises a ramp generator 8 connected to a zero sensor 9 from which it receives a signal VZ. This latter is formed from a sequence of pulses generated each time the mains voltage passes through zero. The block 7 is connected to the mains voltage VA (symbolize by the block 10) via avoltage reducer 12. - The ramp generator 8 is connected to a
timer member 15 which receives mains voltage downstream of the voltage reducer and is connected in parallel with the zero sensor 9. The purpose of themember 15 is to enable the fan motor 3 to be powered to achieve maximum rotational speed (and hence maximum combustion air flow) for a predetermined time period each time the heat generator is started, independently of the value of VREF, so as to prepurge the combustion chamber. - The comparator 6 compares the signals VC and VR, and generates an output signal VU which is fed to an adder node 17 which also receives a signal VK from a
filter member 18 of compensator-limiter type which receives the mains voltage downstream of thereducer 12. Themember 18 compensates for mains voltage variations which would otherwise influence the feed voltage of the motor 3. In particular, themember 18 ensures that the motor feed voltage never falls below a predetermined minimum value so as to set a minimum rotational speed of the motor 3 at which the air flow rate corresponds to the minimum heat output of the boiler. - A signal VX leaves the adder node 17 to reach the control means 2. These latter can be an actual microprocessor unit (so as for example to allow automatic memorized control of the motor 3 on the basis of each value of VREF measured or of the signal VX) or a simple comparator member or other known control means. The unit 2 is connected to a
galvanic separator 20 which ensures adequate electrical isolation between the mains voltage and the very low safety voltage present in the circuit. The signal from the unit 2 hence controls the closure and opening of a static switch (for example a TRIAC) 22 through which the mains power reaches the motor 3. - The use of the device is clear from the aforesaid description. During this use the control means or unit 2 measure the voltage VREF corresponding to the state of gas flow to the burner, and hence by means of this signal measure the gas flow rate to said burner. This signal is compared with the signal VR representative of the instantaneous mains voltage powering the motor 3. If this comparison shows that there is a preset difference between these two signals, the signal VU is generated and, suitably treated with the signal VK, reaches the means 2. Depending on said signal VU representative of unbalance between the combustion air flow (measured by the signal powering the motor) and the gas flow to the burner, the means 2 operate to modify the duty cycle of the static switch, to hence vary the speed of the motor 3 and of the fan.
- The device of the invention is reliable, is simple to construct and can be mounted in boilers already provided with an electrically controlled gas flow regulator, even after their installation.
- With the device of the invention it is possible to optimize the efficency of a heat generator of the above cited kind because the combustion air throughput is regulated according to the gas flow to the burner.
Claims (6)
- A device (1) for optimizing the efficiency of a gas-fired heat generator comprising a burner positioned within a combustion chamber provided with a fan for evacuating burnt gases, the gas reaching said burner via a feed pipe in which there is positioned an electrically powered pressure regulator, said regulator being controlled to vary the gas-flow rate to the burner by electrical signals generated by a heat generator control unit, said device comprising command and control means (2) for the fan motor (3) which are arranged to modify the speed of said motor (3) and hence the rate of flow of combustion air to the combustion chamber, characterised in that the control means (2) are connected to control switch means (22) connected between a feeding line supplying mains power (10) and the fan motor (3) in order to feed mains power to the fan motor, a signal (VREF) from the pressure regulator corresponding to the state of gas-flow to the burner being continuosly measured by said control means (2), the latter modifying the speed of the fan motor (3) according to a continous comparison between a signal (VR) representing the voltage of the mains powering the motor and said measured signal (VREF).
- A device as claimed in claim 1, characterised by comprising comparison means (6) arranged to compare the measured signal (VREF) of the pressure regulator with the mains signal (VR) representative of the mains voltage powering said motor, said comparison means (6) generating an output signal (VU) which is fed to the command and control means (2) for controlling the fan motor (3).
- A device as claimed in claim 1, characterised by comprising timer means (15) enabling the fan motor (3) to be electrically powered so that, each time the heat generator is started, the fan generates maximum combustion-air flow through the combustion chamber for a predetermined time.
- A device as claimed in claim 3, characterised in that the timer means (15) are connected to means generating the mains signal (VR) representative of the mains voltage.
- A device as claimed in claim 1, characterised by comprising means (18) for compensating mains voltage variations and for limiting the minimum-feed voltage to the fan motor (3) so that the minimum combustion air-flow rate corresponds to the minimum fuel-gas flow rate.
- A device as claimed in claim 5, characterised in that the compensator and limiter means (18) generate an output signal (VK) fed to an adder node (17) to which the output signal (VU) of the comparator means (6) is also fed, said node (17) generating an output signal (VX) fed to the command and control means.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
IT96MI000044A IT1281658B1 (en) | 1996-01-12 | 1996-01-12 | DEVICE FOR OPTIMIZING THE PERFORMANCE OF A GASEOUS FUEL HEAT GENERATOR |
ITMI960044 | 1996-01-12 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0784190A1 EP0784190A1 (en) | 1997-07-16 |
EP0784190B1 true EP0784190B1 (en) | 2000-03-15 |
Family
ID=11372893
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP96110211A Expired - Lifetime EP0784190B1 (en) | 1996-01-12 | 1996-06-25 | Device for optimizing the efficiency of a gas-fired heat generator |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0784190B1 (en) |
AT (1) | ATE190711T1 (en) |
DE (1) | DE69607129T2 (en) |
IT (1) | IT1281658B1 (en) |
Family Cites Families (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS60169014A (en) * | 1984-02-14 | 1985-09-02 | Rinnai Corp | Burning safety device |
JPS61202011A (en) * | 1985-03-01 | 1986-09-06 | Sanyo Electric Co Ltd | Combustion apparatus of forced feed and discharge type |
JPH0637975B2 (en) * | 1986-01-20 | 1994-05-18 | 三洋電機株式会社 | Combustion control device |
JPS62280516A (en) * | 1986-05-27 | 1987-12-05 | Rinnai Corp | Combution device |
DE3928114C2 (en) * | 1989-08-25 | 1994-02-10 | Webasto Ag Fahrzeugtechnik | Method for controlling a combustion air blower driven by a motor for a heater |
JP2594363B2 (en) * | 1989-09-29 | 1997-03-26 | 株式会社ハーマン | Air supply for combustion equipment |
-
1996
- 1996-01-12 IT IT96MI000044A patent/IT1281658B1/en active IP Right Grant
- 1996-06-25 DE DE69607129T patent/DE69607129T2/en not_active Expired - Fee Related
- 1996-06-25 EP EP96110211A patent/EP0784190B1/en not_active Expired - Lifetime
- 1996-06-25 AT AT96110211T patent/ATE190711T1/en not_active IP Right Cessation
Also Published As
Publication number | Publication date |
---|---|
ATE190711T1 (en) | 2000-04-15 |
IT1281658B1 (en) | 1998-02-26 |
EP0784190A1 (en) | 1997-07-16 |
DE69607129D1 (en) | 2000-04-20 |
DE69607129T2 (en) | 2000-07-13 |
ITMI960044A0 (en) | 1996-01-12 |
ITMI960044A1 (en) | 1997-07-12 |
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