Device for controlling a fuel-oxidizer mixture for premix gas burners

Abstract

Described is a device for controlling a fuel-oxidizer mixture for a premix gas burner, comprising an intake duct, which defines a cross section for the passage of a fluid inside the duct and includes an inlet, a mixing zone and an outlet, an injection duct, connected to the intake duct in the mixing zone, a monitoring device, configured for generating a control signal, representing a combustion state in the burner, a gas regulating valve, positioned along the injection duct, a fan, positioned in the intake duct for generating therein an operating flow in an inflow direction, a control unit, configured to control the rotation speed of the fan, a regulator, coupled with the intake duct for varying the cross section. The control unit is configured for controlling the gas regulating valve in real time.

Claims

1. A device for controlling a fuel-oxidizer mixture for a premix gas burner, comprising: an intake duct, which defines a cross section for the admission of a fluid into the duct and includes an inlet for receiving the oxidizer, a mixing zone for receiving the fuel and allowing it to be mixed with the oxidizer, and an outlet for delivering the mixture to the burner; an injection duct, connected to the intake duct in the mixing zone to supply the fuel; a monitoring device that generates a control signal representing a state of combustion in the burner; a gas regulating valve, located along the injection duct; a fan, rotating at a variable speed of rotation and located in the intake duct to generate therein a workflow in a direction of inflow oriented from the inlet to the delivery outlet; a control unit that controls the speed of rotation of the fan; a regulator coupled to the intake duct to vary its cross section as a function of the speed of rotation of the fan, the regulator comprising a ball and a tapered duct whose cross section increases in size in the direction of inflow, and wherein the ball is movable in the tapered duct along a sliding direction, perpendicular to the cross section of the intake duct and parallel to the direction of the weight force, wherien the control unit receives the control signal and generates a drive signal representing a fuel flow rate as a function of the control signal to drive the gas regulating valve in real time.

2. The device according to claim 1, wherein the regulator varies the cross section of the intake duct steplessly from a first limit cross section to a second limit cross section.

3. The device according to claim 1, wherein the regulator is a mechanically controlled regulator, including a shutter and a housing, and wherein the shutter is movable relative to the housing to vary the cross section of the intake duct.

4. The device according to claim 3, wherein the shutter is movable between a first limit position, corresponding to a first limit cross section, different from zero, and a second limit position, corresponding to a second limit cross section and wherein the first limit cross section is smaller than the second limit cross section.

5. The device according to claim 3, wherein the shutter moves relative to the housing by effect of a pressure variation produced by the fan in the intake duct downstream of the shutter.

6. The device according to claim 3, wherein the fan produces on the shutter a cut-out pressure (P.sub.cut-out) at a corresponding cut-out speed (v.sub.cut-out) and wherein the shutter is subject to a hold pressure which is less than, and directed in the direction opposite to, the cut-out pressure (P.sub.cut-out).

7. The device according to claim 6, wherein the hold pressure and the cut-out speed (v.sub.cut-out) depend on the weight of the shutter.

8. The device according to claim 1, wherein the regulator and the cross section of the intake duct are located upstream of the mixing zone in the direction of inflow.

9. The device according to claim 1, wherein the regulator includes a flowmeter.

10. A premix burner comprising: a device for controlling a fuel-oxidizer mixture according to claim 1; a combustion head connected to the device through the delivery outlet; and an ignition device that starts combustion in the combustion head.

11. A method for controlling the fuel-oxidizer mixture in a premix gas burner, the method comprising: admitting oxidizer into an intake duct through an inlet; delivering fuel-oxidizer mixture through a delivery outlet; mixing oxidizer and fuel in a mixing zone; feeding fuel to the mixing zone through an injection duct connected to the intake duct; monitoring the combustion in the burner and generating control signals through a monitoring device; generating a drive signal through a control unit as a function of the control signals; varying a fuel flow rate through a gas regulating valve located along the injection duct; operating a fan at a variable speed of rotation and generating a flow in the intake duct in a direction of inflow oriented from the inlet to the delivery outlet; varying a cross section which admits a fluid into the intake duct as a function of the speed of rotation of the fan through a regulator coupled to the intake duct, the regulator comprising a ball and a tapered duct whose cross section increases in size in the direction of inflow, and wherein the ball is movable in the tapered duct along a sliding direction, perpendicular to the cross section of the intake duct and parallel to the direction of the weight force, wherein varying the fuel flow rate comprises: with the control unit, receiving the control signal and generating the drive signal representing a fuel flow rate as a function of the control signal to drive the gas regulating valve in real time.

12. The method according to claim 11, wherein varying the cross section of the intake duct comprises steplessly varying the cross section between a first limit cross section and a second limit cross section.

13. The method according to claim 11, wherein varying the cross section of the intake duct comprises: moving a shutter of the regulator by varying a pressure in the intake duct as a result of a respective variation of the speed of rotation of the fan.

14. The method according to claim 11, wherein varying the cross section of the intake duct comprises: moving a shutter of the second regulator from a first limit position, corresponding to a first limit cross section, different from zero, to a second limit position, corresponding to a second limit cross section, and wherein the first limit cross section is smaller than the second limit cross section.

15. The method according to claim 14, wherein the shutter is held at the first limit position by a hold pressure and wherein varying the cross section of the intake duct comprises: performing a cut out during which the fan produces on the shutter a cut-out pressure (p.sub.cut-out), corresponding to a respective cut-out speed (v.sub.cut-out) and which is greater than and directed in the direction opposite to, the hold pressure, thereby moving the shutter away from the first limit position.

16. The method according to claim 15, wherein the shutter moves along a direction parallel to the direction of the weight force and wherein the hold pressure is produced by the weight of the shutter.

17. A device for controlling a fuel-oxidizer mixture for a premix gas burner, comprising: an intake duct, which defines a cross section for the admission of a fluid into the duct and includes an inlet for receiving the oxidizer, a mixing zone for receiving the fuel and allowing it to be mixed with the oxidizer, and an outlet for delivering the mixture to the burner; an injection duct, connected to the intake duct in the mixing zone to supply the fuel; a monitoring device that generates a control signal representing a state of combustion in the burner; a gas regulating valve, located along the injection duct; a fan, rotating at a variable speed of rotation and located in the intake duct to generate therein a workflow in a direction of inflow oriented from the inlet to the delivery outlet; a control unit that controls the speed of rotation of the fan; a regulator coupled to the intake duct to vary its cross section as a function of the speed of rotation of the fan, wherien the control unit receives the control signal and generates a drive signal representing a fuel flow rate as a function of the control signal to drive the gas regulating valve in real time, wherein the regulator is a mechanically controlled regulator, including a shutter and a housing, and wherein the shutter is movable relative to the housing to vary the cross section of the intake duct, wherein the regulator and the cross section of the intake duct are located upstream of the mixing zone in the direction of inflow.

18. A device for controlling a fuel-oxidizer mixture for a premix gas burner, comprising: an intake duct, which defines a cross section for the admission of a fluid into the duct and includes an inlet for receiving the oxidizer, a mixing zone for receiving the fuel and allowing it to be mixed with the oxidizer, and an outlet for delivering the mixture to the burner; an injection duct, connected to the intake duct in the mixing zone to supply the fuel; a monitoring device that generates a control signal representing a state of combustion in the burner; a gas regulating valve, located along the injection duct; a fan, rotating at a variable speed of rotation and located in the intake duct to generate therein a workflow in a direction of inflow oriented from the inlet to the delivery outlet; a control unit that controls the speed of rotation of the fan; a regulator coupled to the intake duct to vary its cross section as a function of the speed of rotation of the fan, wherien the control unit receives the control signal and generates a drive signal representing a fuel flow rate as a function of the control signal to drive the gas regulating valve in real time, wherein the regulator is a mechanically controlled regulator, including a shutter and a housing, and wherein the shutter is movable relative to the housing to vary the cross section of the intake duct, wherein the shutter is movable between a first limit position, corresponding to a first limit cross section, different from zero, and a second limit position, corresponding to a second limit cross section and wherein the first limit cross section is smaller than the second limit cross section, wherein the shutter is in contact with the housing solely in the first limit position.

19. The device according to claim 18, wherein the shutter moves by translation along the direction of inflow oriented from the inlet to the delivery outlet.

Description

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWING

(1) This and other features will become more apparent from the following description of a preferred embodiment of the invention, illustrated by way of non-limiting example in the accompanying tables of drawings, in which:

(2) FIGS. 1A, 1B, 1C and 1D schematically illustrate four embodiments of a device for controlling the mixture, respectively;

(3) FIGS. 2A and 2B illustrate two embodiments of a second regulator of the device of FIG. 1A;

(4) FIGS. 3A, 3B, 3C and 3D schematically illustrate four embodiments of the second regulator of FIG. 2A;

(5) FIG. 4A, 4B, 4C schematically illustrate a first limit position, an intermediate position and a second limit position of a shutter of the second regulator relative to a housing of the second regulator, respectively;

(6) FIG. 5 illustrates the diagram of an operating pressure as a function of the rotation speed of a fan of the device of FIG. 1A;

(7) FIGS. 6A and 6B illustrate the diagram of the operating pressure as a function of the flow rate of mixture in the ideal case and in the real case, respectively; and

(8) FIG. 7 is a plot showing a graphical comparison of Pressure vs. Power for an embodiment of the present technology relative to an existing technology.

DETAILED DESCRIPTION OF THE INVENTION

(9) In particular, the accompanying drawings denote with the reference numeral 1 in FIGS. 1A, 1B, 1C and 1D, a device for controlling the fuel-oxidizer mixture in premix gas burners. The term air will be used below when referring to the oxidizer without wishing to limit the scope of protection to this type of oxidizer.

(10) Moreover, the term fluid will be used to refer without distinction to air or to the air-gas mixture.

(11) The device 1 comprises an intake duct 2. The intake duct 2 comprises an inlet 201. The intake duct 2 comprises an outlet 203. The intake duct 2 comprises a mixing zone 202.

(12) The inlet 201 is in contact with the outside environment to allow the entry of air into the intake duct 2 at ambient pressure Pa.

(13) The delivery outlet 203 opens onto a combustion head TC in which the air/gas mixture is burnt.

(14) The mixing zone 202 is between the inlet 201 and the outlet 203 and is configured to allow an adequate mixing between the gas and air.

(15) The intake duct 2 is passed through by a work flow in a direction of flow D and in a direction of inflow V, oriented from the inlet 201 to the outlet 203.

(16) The intake duct 2 may have a variable cross section along a direction of flow D.

(17) The device 1 comprises an injection duct 3. The injection duct 3 is connected with the intake duct 2. In particular, the injection duct 3 is connected with the intake duct 2 at the mixing zone 202. The injection duct 3 comprises an injection nozzle 301, located at a first end of the intake duct 3. The injection duct is in communication with the mixing zone 202 through the injection nozzle 301.

(18) A second end of the injection duct 3, which is opposite the injection nozzle 301, is, on the other hand, connected to gas supplier, for example, the gas mains.

(19) According to an embodiment, the device 1 comprises a monitoring display 4. The monitoring device is configured to detect control signals 401 inside the combustion head TC. The control signals 401 represent the state of combustion inside the combustion head TC. The monitoring device 4 may be a flame detector or any other system, known to an expert in the trade, which is able to detect significant information representative of the combustion.

(20) According to an embodiment, the device 1 comprises a control unit 5. According to an embodiment, the device 1 comprises a user interface 6. The control unit 5 is connected with the monitoring device 4 and with the user interface 6. The control unit 5 is programmed for receiving the control signals 401 from the monitoring device 4. The control unit 5 is programmed to receive input signals 601 from the user interface 6.

(21) The control unit 5 is programmed for processing the control signals 401. According to an embodiment, the control unit 5 is programmed to process the input signals 601.

(22) The control unit 5 is programmed to generate drive signals 501, as a function of the control signals 401.

(23) According to an embodiment, the control unit 5 is programmed to generate drive signals 501, as a function of the input signals 601.

(24) According to an embodiment, the device 1 comprises a first regulator 7. The first regulator 7 is positioned on the injection duct 3 in such a way as to intercept the flow of gas in the injection duct 3. The first regulator 7 is connected to the control unit 5.

(25) According to an embodiment, the control unit 5 is programmed to send the drive signals 501 to the first regulator 7.

(26) According to an embodiment, the first regulator 7 is controlled by the control unit 5 by means of the control signals.

(27) The first regulator 7 comprises a movable element. The movable element of the first regulator 7 is configured to vary a relative position as a function of the drive signals 501. In particular, the position of the movable element of the first regulator 7 influences the flow of gas which is adopted in the mixing zone 202. According to an embodiment, the first regulator 7 is a gas valve equipped with motor-driven actuators, controlled by the control unit 5 by means of the drive signals 501. According to another embodiment, the first regulator 7 is a gas valve equipped with solenoid-type actuators, controlled by the control unit 5 by means of the drive signals 501. According to another embodiment, the first regulator 7 is a gas valve equipped with actuators the action of which is subject to pneumatic (delta P) and electric (motor or solenoid) quantities, controlled by the control unit 5 by means of the drive signals 501.

(28) According to an aspect of the invention, the gas flow rate is independent of the air pressure in a position upstream of the mixing zone 202, but depends only on the control signals 401, representing the state of combustion.

(29) According to an embodiment, the device 1 comprises a fan 8.

(30) The fan 8 is configured to rotate at a variable rotation speed. The speed of rotation of the fan is included in a range delimited by a first limit rotation speed and a second limit rotation speed, greater than the first limit speed of rotation.

(31) The device 1 is configured for operating within a range of mixture flow rates between a first limit flow rate Q.sub.min and a second limit flow rate Q.sub.max, greater than the first limit flow rate Q.sub.min, as represented in FIGS. 6A and 6B, for example.

(32) It should be noted that the fan 8 is configured to rotate at the first limit rotation speed for the first limit flow rate Q.sub.min and to rotate at the second limit speed for the second limit flow rate Q.sub.max.

(33) The fan 8 is positioned in the intake duct 2. The axis of rotation of the fan 8 is parallel to the direction of flow D. The fan 8 is configured to generate the operating flow inside the intake duct.

(34) According to an embodiment, the fan 8 is connected to the control unit 5. According to an embodiment, the fan 8 is controlled by the control unit 5 by means of the drive signals 501.

(35) The fan 8 is configured to provide to the air (or to the mixture) an operating pressure which allows the fluid to reach the combustion head TC.

(36) According to an embodiment, the device 1 comprises a second regulator 9. The second regulator 9 is configured for varying a cross section S (e.g., FIG. 4B) of the intake duct 2.

(37) According to an embodiment, the second regulator 9 is positioned upstream of the fan 8 in the inflow direction V. According to another embodiment, the second regulator 9 may be located downstream of the fan 8 in the inflow direction V.

(38) The difference between these two embodiments lies in the different trend of the pressures of the air and then of the mixture along the intake duct 2. In particular, if the fan 8 is located downstream of the second regulator 9 in the inflow direction V, the fan will have suction pressure less than the ambient pressure. If, on the other hand, the fan 8 is positioned upstream of the second regulator 9 in the inflow direction V, then the suction pressure of the fan suction 8 will be equal to the ambient pressure. The position of the fan 8 does not, however, change the aim of the invention. For sake of brevity, the description below will refer to the embodiment wherein the second regulator 9 is located downstream of the fan 8, without this wishing to limit the scope of the invention to this single solution.

(39) According to an embodiment, the second regulator 9 is located upstream of the mixing zone 202 in the inflow direction V. The second regulator 9 is subjected to a first pressure, applied by the fluid in a first position 91 (FIG. 2A) of the intake duct 2 upstream of the second regulator 9. The second regulator 9 is subjected to a second pressure, applied by the fluid in a second position 92 of the intake duct 2 downstream of the second regulator 9. The second regulator 9 is subjected to a differential pressure, resulting from the difference between the first pressure and the second pressure.

(40) According to a preferred embodiment, the second regulator 9 is a mechanical control regulator. This definition means a regulator which responds to stimuli of a mechanical or fluid-dynamic nature and not to electrical pulses. However, this does not mean excluding the solution in which the second regulator 9 can be controlled by the control unit 5, by further drive signals 501.

(41) According to an embodiment, the second regulator 9 is a direct control regulator. This definition describes a solution in which the regulator is configured to detect itself a variation of a parameter which determines a corresponding variation in its operating condition. What is expressed in this paragraph will be described in more detail below, when the forces to which the second regulator 9 is subjected are described. In this case, too, the intention is not to exclude an indirect regulator from the scope of protection, that is to say, which needs a controller to vary the relative operating condition.

(42) In fact, according to an embodiment, the control unit 5 can be connected to the second regulator 9.

(43) According to an embodiment, the second regulator 9 comprises a shutter 901. The shutter 901, according to an embodiment, is a ball 901A. According to other embodiments, the shutter 901 may be a floating plate 901B or a gate valve 901C.

(44) According to other embodiments, which can be equally implemented, the shutter 901 may be a vane hinged to the housing 902, configured to rotate about a hinge and to vary the cross section S of the intake duct 2. According to an embodiment, the shutter 901 may be a float with a guide rod.

(45) According to an embodiment, the shutter 901 comprises a passage hole 901.

(46) According to an embodiment, the shutter 901 has a relative weight P.

(47) Reference will be made hereafter to the shutter 901 in its preferred embodiments in which it is a ball 901A, without any limitations to the scope of protection.

(48) According to an embodiment, the second regulator comprises a housing 902. The housing 902 is configured for containing the ball 901A. According to an embodiment, the housing 902 is a duct with a variable cross section along the direction of flow D. According to another embodiment, the housing 902 is a duct with a constant cross section along the direction of flow D. The housing 902 is fixed to the intake duct 2.

(49) According to an embodiment, the ball 901A is movable inside the housing 902. The ball 901A is movable between a first limit position, 903 and a second limit position 904, for varying in a continuous fashion the cross section S. The first limit position of the ball 901A corresponds to a first limit cross section S1 (e.g., FIGS. 3A-3D and 4A). The second limit position of the ball 901A corresponds to a second limit cross section S2 (e.g., FIGS. 3A, 3C, 3D and 4C). According to an embodiment, the first limit cross section S1 is different from zero. In other words, the ball 901A is configured to allow the passage of fluid even when it is in the first limit position 903.

(50) According to an embodiment, the second regulator comprises a transit channel, configured to allow a passage of mixture from the first position 91 (upstream of the shutter) to the second position 92.

(51) According to an embodiment, the ball 901A comprises a passage hole 901A.

(52) According to an embodiment, the first limit cross section S1 is defined by the area, along a plane perpendicular to the sliding direction D, of the passage hole 901A.

(53) According to an embodiment, the passage hole 901A is not on the ball but is located between the ball 901A and the housing 902.

(54) According to an embodiment, the passage hole 901A is a bypass hole 901A and the ball 901A rests on the housing 902 and is configured to prevent a passage of mixture through the housing 902, in this way forcing the mixture to flow towards the bypass branch.

(55) In particular, according to an embodiment, the housing 902 comprises a first tubular element 902C on which rests the ball 901A. According to this embodiment, the device 1 comprises an additional passage hole 901A to form a plurality of passage holes 901A. The plurality of passage holes 901A is located on the first tubular element 902B (e.g., FIG. 2B) and is configured to place in communication the first position 91, located upstream of the ball 901A in the sliding direction D, with the second position 92, located downstream of the ball 901A in the sliding direction D.

(56) According to an embodiment, the housing 902 comprises a fixing flange 906, configured to allow the assembly of the second regulator 9 in the device 1.

(57) According to the embodiment in which the passage hole 901A is a bypass hole 901A, the bypass hole is executed on the fixing flange 906. The bypass hole 901A is in communication with the first position 91, located upstream of the ball 901A in the sliding direction D, and with the second position 92, located downstream of the ball 901A in the sliding direction D.

(58) The first tubular element 902C comprises a shoulder 902B (e.g., FIGS. 2A and 2B). The shoulder 902B is located at the first end 902B of the housing 902 and is configured for supporting the ball 901A in its first limit position 903.

(59) According to an embodiment, the ball 901A is movable along a sliding direction D parallel to the direction of flow D. According to another embodiment, the sliding direction D is, on the other hand, perpendicular to the direction of flow D.

(60) According to an embodiment, the sliding direction D is perpendicular to the direction of the weight force. According to another embodiment, the sliding direction D is parallel to the direction of the weight force.

(61) According to an embodiment, the ball 901A is in contact with the housing only in the first limit position 903 whilst in the other intermediate positions and in the second limit position 904 it is spaced from the walls 902A of the housing 902.

(62) In the first limit position 903 the ball 901A rests on the housing 902 at a relative first end 902B. The housing 902 comprises a shoulder 902B, at its first end 902B, configured for supporting the ball 901A in its first limit position 903.

(63) According to an embodiment, the ball 901A is configured to move under the effect of a pressure variation generated by the fan 8 in the intake duct 2 downstream of the second regulator 9, that is to say, downstream of the ball 901A. In other words the ball 901A is configured to move under the effect of a variation of the second pressure.

(64) In particular, the differential pressure applied to the ball 901A is a function of the operating flow rate Q, which passes through the cross section S, and of the cross section S itself. It should be noted that whilst the first pressure depends on the elements located upstream of the second regulator 9 (such as, for example, the fan 8 or the outside environment at an ambient pressure), the second pressure is, on the other hand, a function of the operating flow rate Q, which passes through the cross section S, and the cross section S itself.

(65) According to an embodiment, the ball is subjected to a hold pressure. The hold pressure is a pressure configured to hold the ball 901A resting on the shoulder 902B of the housing 902. The drawings show two types of hold pressure. According to an embodiment, the hold pressure is determined by the relative weight of the ball 901A. According to another embodiment, the hold pressure is determined by an elastic force generated by a return spring 905. According to other embodiments, suitable friction forces between the side walls 902A of the housing and the ball 901A might be worthwhile, which are able to hold, by static friction, the ball 901A in its first limit position 903.

(66) The embodiments of the hold pressure described may obviously be coupled and redundant.

(67) The description below will therefore consider the hold pressure to be dependent on the weight of the ball 901A without wishing to limit in any way the scope of protection.

(68) According to an embodiment, the fan 8 is configured to rotate at a cut-out speed. The cut-out speed is between the first limit rotation speed and the second limit rotation speed.

(69) The cut-out speed corresponds to a corresponding cut-out flow rate. According to an embodiment, the fan 8 is configured for generating a cut-out pressure p.sub.cut-out. The cut-out pressure p.sub.cut-out is the second pressure exerted on the ball 901A with the rotation speed of the fan 8 equal to the cut-out speed.

(70) According to an embodiment, the cut-out pressure p.sub.cut-out is greater than the hold pressure.

(71) According to an embodiment, the cut-out pressure p.sub.cut-out is a function of the weight of the ball 901A. According to other embodiments, the cut-out pressure p.sub.cut-out is a function of the elastic force of the return spring 905 or, if necessary, a friction force.

(72) According to an embodiment, the ball 901A is configured to start to move in the sliding direction D with the fan 8 in rotation at the cut-out speed.

(73) According to an embodiment, the second regulator is configured to perform a regulation with a constant cross section. According to an embodiment, the second regulator is configured to perform regulation with variable cross section.

(74) The second regulator comprises two operating configurations: a first operating configuration, with a cross section S constant over time, corresponding to a first range of rotation speeds of the fan 8 and a second operating configuration, with a cross section S variable over time, corresponding to a second range of rotation speeds of the fan 8. The first range of rotation speed of the fan 8 is between the first limit rotation speed and the cut-out speed. The second range of the rotation speed of the fan 8 is between the cut-out speed and the second limit rotation speed.

(75) According to an embodiment, in the first operating configuration, the ball 901A is configured to remain resting on the shoulder 902B of the housing 902.

(76) According to an embodiment, in the first operating configuration, the hold pressure is greater than the differential pressure.

(77) According to an embodiment, in the second operating configuration, the ball 901A is configured to rise when the operating flow rate Q increases.

(78) According to an embodiment, in the second operating configuration, the ball 901A is configured to lower when the operating flow rate Q decreases.

(79) According to an embodiment, in the first operating configuration, the hold pressure is less than the differential pressure.

(80) In the first operating configuration, the second regulator 9 is configured to increase the head losses through the second regulator 9 (that is to say, increase the differential pressure applied to the ball 901A). In the second operating configuration, the second regulator 9 is configured to ideally maintain constant the head losses through the second regulator 9 (that is to say, to keep constant the differential pressure applied to the ball 901A).

(81) According to an embodiment, the second regulator 9 is configured for regulating the flow rate of fluid (air or mixture) using the physical principle of the Asameter . According to an embodiment, the second regulator 9 is an Asameter .

(82) According to an aspect of this invention, the invention intends to protect a premix gas burner 100 comprising the device 1 according to any one of the features described above. The burner 100 comprises the combustion head TC. The combustion head TC is connected to the device 1 through the outlet 203. The combustion TC head is configured to allow the combustion of the oxidizer-gas mixture (air/gas). The burner comprises an ignition device 101. The ignition device 101 is configured to start the combustion in the combustion head TC.

(83) According to an aspect of the invention, the invention also provides a method for controlling the fuel-oxidizer mixture in premix gas burners.

(84) According to an embodiment, the method comprises a step of preparing a device 1 for controlling the fuel-oxidizer mixture in premix gas burners. The term air will be used below when referring to the oxidizer without wishing to limit the scope of protection to this type of oxidizer. Moreover, the term fluid will be used to refer without distinction to air or to the air-gas mixture. The method comprises a step of preparing one or more of the following elements: an intake duct 2, including an inlet 201, an outlet 203 and a mixing zone 202.

(85) The method comprises a receiving step, wherein the air flows through the inlet 201, in contact with the outside environment, and reaches the intake duct 2 at the ambient pressure Pa.

(86) The method comprises a delivery step, wherein the air-gas mixture is delivered to a combustion head TC through the outlet 203.

(87) The method comprises a mixing step, wherein the air and the gas are mixed in the mixing zone 202, between the inlet 201 and the outlet 203, to allow an adequate mixing between the gas and the air.

(88) According to an embodiment, an operating flow (which may be only air or an air-gas mixture, as a function of the position along the intake duct 2) passes through the intake duct in a direction of flow D and in an inflow direction V, oriented from the inlet 201 to the outlet 203.

(89) According to an embodiment, the method comprises an injection step. In the initiation step, an injection duct 3, connected with the intake duct 2, injects gas in the intake duct 2. According to an embodiment, the gas is injected into the mixing zone 202. According to an embodiment, the gas is injected by an injection nozzle 301, facing the mixing zone and located at a first end of the injection duct 3.

(90) The method comprises a supplying step, wherein a second end of the injection duct 3, opposite the injection nozzle 301 receives gas from a gas supplier, for example the gas network.

(91) The method comprises a monitoring step, wherein a monitoring device 4 detects control signals 401 inside the combustion head TC, for determining the state of combustion inside the combustion head TC.

(92) According to an embodiment, the method comprises a control step, wherein a control unit 5 controls the device 1 by regulating the air-gas mixture.

(93) The control unit 5 receives the control signals 401 from the monitoring device 4. The control unit 5 receives input signals 601 from the user interface 6.

(94) In the control step, the control unit 5 processes the control signals 401.

(95) According to an embodiment, the control unit 5 processes the input signals 601.

(96) The controlling step comprises a step of generating commands, wherein the control unit 5 generates drive signals 501, as a function of the control signals 401. According to an embodiment, the control unit 5 generates drive signals 501, as a function of input signals 601.

(97) According to an embodiment, the method comprises a first regulation step, wherein the control unit 5 sends the drive signals 501 to a first regulator 7, positioned on the injection duct 3 and intercepting the flow of the gas in the injection duct 3.

(98) The first regulation step comprises a step of varying the gas flow rate. In this step of varying the gas flow rate, a mobile element of the first regulator 7 varies its position as a function of the drive signals 501. In particular, the position of the movable element of the first regulator 7 varies the gas flow rate which flows into the mixing zone 202. This occurs because, with the variation of the position of the movable element, the head loss which a flow of gas in the injection duct 3 must overcome varies and with the increase of the head losses the flow of gas injected reduces.

(99) In the first regulation step, the gas flow rate is independent of the air pressure in a position upstream of the mixing zone 202, but depends only on the control signals 401, representing the state of combustion.

(100) According to an embodiment, the method comprises an actuation step, wherein a fan 8, located in the intake duct 2, rotates at a speed of rotation variable in a range delimited by a first limit rotation speed v.sub.min and a second limit rotation speed v.sub.max, greater than the first limit rotation speed v.sub.min.

(101) The device 1 operates within a range of mixture flow rates between a first limit flow rate Q.sub.min and a second limit flow rate Q.sub.max, greater than the first limit flow rate Q.sub.min.

(102) The actuation step comprises a first limit actuation step, wherein the fan 8 rotates at the first limit rotation speed v.sub.min and the device 1 operates at the first limit flow rate Q.sub.min. The actuation step comprises a second limit actuation step, wherein the fan 8 rotates at the second limit rotation speed v.sub.max and the device 1 operates at the second limit flow rate Q.sub.max.

(103) In the actuation step, the fan 8 rotates about an axis of rotation parallel to the direction of flow D. In the actuation step, the fan 8 generates the operating flow inside the intake duct.

(104) In the actuation step, the control unit 5 actuates the fan 8.

(105) In the actuation step, the control unit 5 actuates the fan 8, as a function of the drive signals 501.

(106) The fan 8 is configured to provide to the air (or to the mixture) an operating pressure which allows the fluid to reach the combustion head TC.

(107) According to an embodiment, the method comprises a second regulation step, wherein a second regulator 9 of the device 1 varies a cross section S of the intake duct 2. According to an embodiment, the second regulation step may occur with the second regulator 9 positioned upstream of the fan 8 in the inflow direction V. According to another embodiment, the second regulation step may occur with the second regulator 9 located downstream of the fan 8 in the inflow direction V.

(108) According to an embodiment, the second regulation step may occur with the second regulator 9 located upstream of the mixing zone 202 in the inflow direction V.

(109) In the second regulation step, the second regulator 9 receives a thrust of a first pressure, applied by the fluid in a first position 91 of the intake duct 2 upstream of the second regulator 9. In the second regulation step, the second regulator 9 receives a thrust of a second pressure, applied by the fluid in a second position 92 of the intake duct 2 downstream of the second regulator 9. In the second regulation step, the second regulator 9 receives a thrust of a differential pressure, resulting from the difference between the first pressure and the second pressure.

(110) According to a preferred embodiment, in the second regulation step a mechanical control regulator is used, which defines the second regulator 9. This definition means a regulator which responds to stimuli of a mechanical or fluid-dynamic nature and not to electrical pulses. However, this does not mean excluding the solution in which the second regulator 9 can be controlled by the control unit 5, by further drive signals 501.

(111) According to an embodiment, in the second regulation step the second regulator 9 is controlled directly. In other words, the second regulator varies a relative operating configuration with the variation of a physical parameter, as a function of which the second regulator 9 is able to automatically vary its operating configuration. This definition describes a solution in which the regulator is configured to detect itself a variation of the physical parameter which determines a corresponding variation of its operating condition. What is expressed in this paragraph will be described in more detail below, when the forces to which the second regulator 9 is subjected are described. In this case, too, the intention is not to exclude an indirect regulator from the scope of protection, that is to say, which needs a controller to vary the relative operating condition. In fact, according to an embodiment, the control unit 5 controls the second regulator 9, as a function of the drive signals 501.

(112) According to an embodiment, the second regulation step comprises a cross section variation step, wherein a shutter 901 of the second regulator 9 moves in a housing 902 of the second regulator and varies (produces a variation) the cross section S of the intake duct 2.

(113) According to an embodiment, the cross section variation step is carried out by means of a housing 902 (preferably with a variable cross section along the direction of flow D) which contains a ball 901A, defining the shutter. According to an embodiment, in the second variation step, the housing 902 of the second regulator 9 executes a seal with the intake duct, in such a way as to avoid any flow leakages.

(114) According to an embodiment, in the cross section variation step, the ball 901A moves inside the housing 902, between a first limit position 903 and a second limit position 904, for steplessly varying the cross section S. In the cross section variation step, when the ball 901A is in the first limit position the cross section S is equal to a first limit cross section S1, defined by a passage hole 901A formed on the ball 901A. In other words, the ball 901A also allows the passage of fluid when it is in the first limit position 903, since the area of the passage hole 901A is different from zero.

(115) In the cross section variation step, when the ball 901A is in the second limit position the cross section S is equal to a second limit cross section S2.

(116) According to an embodiment, in the cross section variation step, the ball 901A moves along a sliding direction D parallel to the direction of flow D. In the cross section variation step, the ball 901A moves along the sliding direction D, which, on the other hand, is perpendicular to the direction of flow D.

(117) According to an embodiment, the sliding direction D is perpendicular to the direction of the weight force. According to another embodiment, the sliding direction D is parallel to the direction of the weight force.

(118) According to an embodiment, in the cross section variation step (of second regulation) the ball 901A touches the housing only in the first limit position 903 whilst in the other intermediate positions and in the second limit position 904 it is spaced from the walls 902A of the housing 902.

(119) In the first limit position 903 the ball 901A rests on the housing 902, at its first end 902B. In this first limit position 903, a shoulder 902B of the housing 902 supports the ball 901A in its first limit position 903.

(120) According to an embodiment, in the cross section variation step, the ball 901A moves from a relative position in the housing by effect of a pressure variation which the fan 8 generates in the intake duct 2 downstream of the second regulator 9, that is to say, downstream of the ball 901A. The pressure variation which the fan 8 generates is due to a variation in the speed of rotation of the fan. In other words, the ball 901A moves due to the effect of a variation of the second pressure.

(121) According to an embodiment, the method also comprises a hold step, wherein the ball undergoes the thrust of a hold pressure.

(122) The hold pressure holds the ball 901A resting on the shoulder 902B of the housing 902. The drawings show two types of hold pressure. According to an embodiment, the hold pressure is defined by the relative weight of the ball 901A, which keeps the ball 901A on the housing 902B. According to another embodiment, the hold pressure is defined by an elastic force generated by a return spring 905, which pushes the ball towards the housing 902B. The embodiments of the hold pressure described may obviously be coupled and redundant.

(123) The description below will therefore consider the hold pressure to be dependent on the weight of the ball 901A without wishing to limit in any way the scope of protection.

(124) According to an embodiment, the fan 8 rotates at a cut-out speed v.sub.cut-out, between the first limit rotation speed v.sub.min and the second limit rotation speed v.sub.max, as represented in FIG. 5, for example.

(125) When the fan 8 rotates at the cut-out speed v.sub.cut-out, the device 1 operates at a corresponding cut-out flow rate Q.sub.cut-out, as shown in FIGS. 6A and 6B. According to an embodiment, the fan 8 generates a cut-out pressure p.sub.cut-out. More precisely, the fan 8 generates a variation of the second pressure, up to a value equal to the cut-out pressure p.sub.cut-out.

(126) When the rotation speed of the fan 8 is equal to the cut-out speed v.sub.cut-out the second pressure exerted on the ball 901A is equal to the cut-out pressure.

(127) The cut-out pressure p.sub.cut-out exceeds the hold pressure. In other words, the cut-out pressure p.sub.cut-out is the pressure immediately higher than the hold pressure, which, being in the opposite direction to the hold pressure, causes the detachment of the ball 901A from its housing 902.

(128) According to an embodiment, the cut-out pressure p.sub.cut-out depends on the weight of the ball 901A. According to other embodiments, the cut-out pressure p.sub.cut-out depends on the elastic force of the return spring 905 or, if necessary, a friction force.

(129) According to an embodiment, the ball 901A starts to move in the sliding direction D when the fan 8 rotates at the cut-out speed v.sub.cut-out.

(130) According to an embodiment, the second regulation step is a variable cross section regulation. According to an embodiment, the second regulation step is a constant cross section regulation.

(131) In the second regulation step, the second regulator may be in a first operating configuration, with a cross section S constant over time, when the rotation speed of the fan is included in a first range of rotation speeds of the fan 8 between the first limit rotation speed v.sub.min and the cut-out speed v.sub.cut-out.

(132) In the second regulation step, the second regulator may be in a second operating configuration, with a cross section S variable over time, when the rotation speed of the fan is included in a second range of rotation speeds of the fan 8 between the cut-out speed v.sub.cut-out and the first limit rotation speed v.sub.min.

(133) According to an embodiment, in the first operating configuration, the ball 901A remains resting on the shoulder 902B of the housing 902. According to an embodiment, in the first operating configuration, the hold pressure exceeds the differential pressure.

(134) According to an embodiment, in the second operating configuration, the ball 901A rises when the operating flow rate Q rises, increasing consequently the cross section S. According to an embodiment, in the second operating configuration, the ball 901A lowers the flow rate Q, reducing consequently the cross section S.

(135) According to an embodiment, in the first operating configuration, the differential pressure exceeds the hold pressure.

(136) In the first operating configuration, the second regulator 9 increases the head losses through the second regulator 9 with the increase in the flow rate Q (increasing the differential pressure applied to the ball 901A). In the second operating configuration, the second regulator 9 ideally keeps constant the head losses through the second regulator 9 (keeping the differential pressure applied to the ball 901A constant). The term ideally refers to the fact that due to the complexity of the problem it is very unlikely that the head losses remain constant. There is, however, a very low rate of increase, which is approximately constant.

(137) According to an embodiment, the second regulator 9 regulates the flow rate of fluid (air or mixture) using the physical principle of the Asameter .

(138) According to an aspect of the invention, the invention also intends to protect a method for regulating a premix gas burner 100 comprising one or more of the steps of the method described in the invention. The method comprises a combustion step, wherein the combustion head TC maintains the conditions for a combustion of the oxidizer-gas mixture (air/gas). The method comprises an ignition step, wherein an ignition device 101 starts the combustion inside the combustion head TC.