RU2262041C2 - Updated mixer for air and gas - Google Patents

Abstract

FIELD: air or gas mixers.

SUBSTANCE: proposed air and gas mixer is used in gas burners at forced ventilation; mixer includes mixing chamber for forming combustible mixture fed to burner; first flow of primary air and gas and second flow of secondary air are fed to chamber through first and second passages, respectively. Mixer is provided with units for throttling the first and/or second passage for selective throttling of mixture of primary air and gas and/or secondary air fed to tubular chamber; mixer has tubular housing; cross section of first passage reduces in way of air-and-gas mixture flow; it is coaxial with second passage; first passage is located inside tubular housing and second passage is formed by tubular housing and first passage.

EFFECT: reduction of acoustic waves emitted by flame fronts; increased range of modulation of air-and-gas mixture; reduction of CO and No_x emissions.

29 cl, 6 dwg

Description

Field of Invention

The invention relates to an improved mixer device for air and gas in accordance with the preamble of the main claim.

BACKGROUND OF THE INVENTION

As is well known, devices of this type are used in boilers and similar devices mainly for home use, containing gas burners, in particular with forced ventilation.

A device is known for a mixer for air and gas, in particular for gas burners with forced ventilation, comprising a mixing chamber for air and gas for the production of a combustible mixture supplied to the burner, in which a first stream of a mixture of primary air and gas and a second stream of secondary air are fed into the chamber through the first and second channels, respectively (EP No. 0896191).

In the known device, the dosage of the combustible mixture supplied by introducing gas into the air stream is controlled depending on the pressure loss determined at the point of narrowing of the channel through which the air and gas flows in the mixture are admitted. Moreover, the uniformity of the mixture of air and gas is mainly improved by a fan located downstream after the specified channel.

The main limitations that may occur in known devices are associated with inaccurate dosing of the incoming gas, as well as with a relatively narrow effective range of modulation of the supplied flow rate.

Another limitation that may occur in known devices is related to the resonance phenomenon, which is initiated by the flame front in the burner. The noise resulting from the propagation of sound waves from the apparatus in which the device is installed can be extremely annoying for the user.

Description of the invention

An object of the present invention is to provide an improved device for a mixer for air and gas, which is designed structurally and functionally in order to prevent all the problems that are indicated above with reference to the prior art.

This problem is solved by means of a mixer for air and gas, in particular for gas burners with forced ventilation, containing a mixing chamber for air and gas to produce a combustible mixture supplied to the burner, the first stream of a mixture of primary air and gas and a second the secondary air flow through the first channel and the second channel, respectively, which according to the invention contains means for throttling the first channel and / or second channel so as to selectively throttle the amount of the mixture of primary air and gas and / or secondary air supplied to the mixing chamber and containing a tubular body, the first channel having a cross section that decreases in the direction of flow of the mixture of air and gas, and is coaxial with the second channel, the first the channel is placed inside the tubular body, and the second channel is formed by the tubular body and the first channel.

The second channel contains at least one through hole for the inlet of a stream of secondary air, and the hole is adapted for throttling the first throttling means. In addition, the second channel contains a first plurality of through holes that can be throttled selectively.

In the mixer device according to the invention, the throttling is adjustable.

A first plurality of holes are provided in the tubular body. These holes of the first set are located on the same line around the circumference and are divided at equal intervals in the tubular body.

The first throttling means comprises a first closing means that can be moved between a first working position in which the first plurality of openings is completely closed and a second working position in which it is fully open. The first closing means also comprises a first sleeve aligned coaxially with the tubular body and acting on the holes.

Moreover, the first sleeve has a second set of holes located on a line along the periphery in positions corresponding to the positions of the first set of holes, when the first closing means is fitted to the tubular body so that the first set of holes can be throttled by the parts of the first sleeve formed between the respective adjacent holes of the second set .

The first closure means is rotatable about an axis common to the tubular body and the first closure means, so that the second plurality of holes can constantly move between the first completely closed working position and the second fully open working position, in which the first plurality and the second plurality of holes overlap to a friend.

The closure means comprises a drive motor and drive means located between the engine and the closure means, the first closure means being rotated by the electric motor by means of the drive. The electric motor may be a stepper motor. The electric motor is operatively controlled by an electronic control punch card and is driven depending on the signals correlating the parameters determined by the sensors and sent to the electronic control punch card.

The mixer device also includes a fan located downstream after the first channel and the second channel with respect to the direction of flow of primary and secondary air. The fan is enclosed by a box-type housing, and a mixing chamber is formed inside the box-type housing. The case type of the box contains a cover made as a unit with the first channel and the second channel. The cap can be made by injection molding.

The device of the mixer according to the invention contains a set of stator blades inside the first channel for transmitting the rotational component to the flow of primary air and the gas mixture entering the first channel. The device contains a set of stator blades inside the second channel for transmitting the rotational component to the secondary air stream entering the second channel.

The mixer device contains a third channel for admitting gas into the mixing chamber. The third channel is formed coaxially with the first channel and inside it.

The mixer device also comprises second throttling means for throttling the third channel in order to selectively and in a controlled manner throttle the amount of gas supplied to the mixing chamber. The third channel comprises a shutter base at the free end, with at least one through hole provided at the end portion. The third channel contains a third set of holes that can be throttled selectively.

The second throttling means comprises a second closing means that can be moved between the first working position in which the third plurality of holes are completely closed and the second working position in which it is fully open. The second closing means is operatively connected to the first closing means so that the throttling of the first plurality of holes correlates with the throttling of the third plurality of holes as a result of the angular movement of the first closing means between the first and second operating positions. The second closing means comprises a second sleeve fitted to the third channel, the second sleeve being rigidly connected to the first sleeve.

The mixer device comprises at least one connecting lever extending radially between the first and second bushings in order to secure the second closing means for rotation together with the first closing means.

A fourth plurality of holes in the second sleeve are provided in the mixer device, the holes being located on a peripheral line in positions corresponding to the positions of the third plurality of holes when the second sleeve is fitted to the third channel so that the third plurality of holes can be closed by portions of the second sleeve formed between corresponding nearby holes of the fourth set.

Brief Description of the Drawings

The features and advantages of the invention will become clearer from a detailed description of its three preferred designs, described below by way of non-limiting example with reference to the accompanying drawings, in which:

Figure 1 is a partial sectional view of a side elevational view of an apparatus equipped with an air and gas mixer device formed in accordance with the present invention.

Figure 2 is a perspective view showing in detail a detail of the device of the mixer for air and gas in accordance with the invention in an enlarged scale.

Figure 3 is a perspective view of a variant of the details of the device of the mixer for air and gas in figure 2.

Figure 4 is a partial sectional view of a side elevational view of an apparatus equipped with a second embodiment of a mixer for air and gas in figure 1.

Figure 5 is a perspective view showing a detail of the device of the mixer for air and gas in figure 4 on an enlarged scale.

Fig.6 is a partial sectional perspective view of an additional part of the device of the mixer for air and gas of Fig.5.

The best example embodiment of the invention

First, reference is made to FIG. 1, in which the device of the mixer for air and gas formed in accordance with the invention, in particular for supplying a forced-air burner 2, is generally designated 1.

The device 1 comprises a tubular cylindrical body 3 with an X axis, having a cylindrical wall 4 and opposite ends 3a and 3b in the direction of the axis. Inside the tubular element 3 and coaxially there is a first converging channel 5, which extends from the end 3a of the housing 3 to the opposite end 3b and by means of which the tubular housing 3 is divided into the first converging channel 5 and the second channel 6, the latter being limited by a cylindrical wall 4 and the outer side surface 7 of the first converging channel 5.

The third channel 13 for admitting gas into the converging channel 5 is formed coaxially with the converging channel 5 and inside it. Channel 13 is mounted in channel 5 by means of a plurality of radial connecting elements 14 of jumpers (FIG. 2).

Gas is supplied to the third channel 13 by means of a valve unit 17 connected to external trunk pipelines for supplying gas at a constant pressure equal to atmospheric pressure. The direction of the incoming gas flow supplied by the valve unit 17 is shown by arrow G in FIG.

The converging channel 5 is an inlet for the primary air flow directed axially through the channel 5 in the direction shown by the arrow F in FIG. 1, from the end of Za towards the opposite end 3b of the tubular body 3. This primary air flow is mixed at the exit section of the first channel 5 with a gas stream exiting from the third channel 13.

The radial fan, designated 8, driven by the drive means 8b, is provided downstream of the tubular body 3 in the direction of flow of air and / or gas, and is positioned so that its inlet is facing an end 3b for discharging air and gas mixture.

The fan 8, by which the flow of primary air and gas is sucked in, is closed by a box-type housing 9, the cover 10 of which is integral with the tubular housing 3. Preferably, the cover 10 is integral with the tubular housing 3, converging channel 5 and third channel 13 and made by injection molding.

Into the mixing chamber 12, which is formed inside the box type casing 9, between the fan 8 and the tubular casing 3, is fed through the first converging channel 5 and the second channel 6, as described in more detail below.

In accordance with the principal distinguishing feature of the invention, in the cylindrical wall 4 of the tubular body 3 there is a first plurality of through holes 18 which are arranged at a predetermined angular distance from each other and through which the stream of secondary air drawn in by the fan 8 in the direction of arrow F ₂ in FIG. 1, is introduced into the second channel 6. Into the mixing chamber 12, a secondary air stream is thus supplied in the same way as the aforementioned stream of a mixture of gas and primary air.

The holes 18, the number of which in the described embodiment is three, are preferably arranged in a single line on the periphery and are separated by gaps at regular intervals.

The mixer device 1 also includes first means for throttling the holes 18, which includes first closing means 19. The throttling performed in this way is adjustable, as described in detail below.

The first closing means 19 comprises a first sleeve 20 aligned coaxially with the tubular body 3 and having opposite ends 20a, 20b in the axis direction. The first protrusion 21, by means of which the first closing means 19 abuts the second protrusion 23 formed on the cylindrical wall 4 of the tubular body 3, extends from the end 20b. An annular inlet 28 is also formed in the protrusion 23, in particular in its surface, which is in contact with the protrusion 21 of the first closing means 19 and the seal 29, for example, of the type of an O-ring, is placed in it.

The first sleeve 20 has a second plurality of through holes 22, preferably of a similar shape and size, with holes 18 in the cylindrical wall 4 that extend into positions corresponding to the positions of the holes 18 when the closure 19 is fitted onto the tubular body 3.

The first throttling means is driven by an electric motor 25, preferably a stepper motor, by means of which the closing means 19 is rotated around the X axis by means of the first means 26 for transmitting movement, for example a ratchet wheel and a gear type connection. This rotation is facilitated by lubricants placed between the contacting surfaces of the cylindrical wall 4 of the tubular body 3 and the first sleeve 20.

The relative angular distances between the openings 18, and therefore between the respective openings 22, are such that the openings 22 for the secondary air flow into the mixing chamber can be continuously moved by turning the closing means 19 between the first, fully closed working position, in which the openings 18 are closed by parts the first sleeve 20, located on the periphery between the holes 22, and the second, fully open working position, that is, the position in which the holes 18 and 22 overlap each other and other. The flow rate of the secondary air passing through the second channel 6, and therefore into the mixing chamber 12, can thus be modulated between a minimum value substantially equal to zero and a maximum value.

A variant of the invention, which is not shown, also provides that the aforementioned throttling is set in advance, which means that the first closing means 19 must be fixed relative to the tubular body 3 in a predetermined angular position, without any operational drive being provided. In this case, the openings 18 are throttled in a manner that is determined in advance at the calibration stage to ensure a pre-selected flow rate of the secondary air in the channel 6 depending on the type of burner 2 to which it is suitable.

In an additional embodiment, which is not shown, the throttling is also set in advance, and the closing means is fixed in a predetermined angular position relative to the tubular body 3, a set of closing means 19 is provided, each closing means 19 containing corresponding calibrated holes 22 of a predetermined cross-section, preferably smaller than the cross-section of the holes 18. The corresponding closure means 19 from the kit can thus be mounted in a tubular orpuse 3 alternatively, in dependence on the secondary air flow to be fed into the mixing chamber.

The electric motor 25 is electrically connected to the electronic control card 27 of the burner control 2, and thereby operatively controlled.

Signals correlated with parameters determined by a plurality of sensors, for example, a combustion sensor 30 or a temperature sensor 31, are sent to a control punch card 27. The electronic control of the motor 8b of the fan 8 is also carried out by means of a punched card 27.

In the second preferred embodiment shown in FIG. 3, in which parts similar to those of the previous embodiment are denoted by the same reference numbers, a set of stator vanes 15 is provided in the annular space between the third channel 13 and the first channel 5. The set of vanes 15 contains a plurality the blades 16 with a pre-selected twisting, extending radially from the channel 13 and attached at their opposite ends to the wall 7 of the first channel 5. The blades 16 also perform the function of structural connection channel 5 with channel 13.

The blades 16 are stationary and have such a curvature of their twisting profiles in order to transfer the rotational component to the flow of primary air entering the first converging channel 5.

In an embodiment that is not shown, on the other hand, there is a set of stator blades similar to the set of blades 15, exclusively in the second channel 6, in which case the blades are attached to the wall 7 of the converging channel 5 at one end thereof and to the cylindrical wall 4 of the tubular body 3 at the other end.

In a further embodiment, also not shown, sets of stator vanes are provided in both the first channel 5 and the second channel 6.

In the described second embodiment and its variants, the fan is arranged so that it has the same direction of rotation as the rotation transmitted by the set of stator vanes 15. In this case, given the fact that the direction of rotation of the fan is the same as the rotational component transmitted to the gas-air mixture stream and / or the secondary air stream, the above mixture and / or secondary air are introduced into the fan 8 at very low pressure losses .

In a third preferred embodiment shown in FIG. from 4 to 6, in which parts similar to those of the previous embodiment are indicated by the same reference numbers, the device of the air and gas mixer according to the invention is generally indicated as 100. In this device, the third channel 13 for admitting gas into the mixing chamber 12 contains on one at the end 13b, a shutter base 13a and a cylindrical wall 13d in which a third plurality of through holes 32 are made at the end 13b. These holes 32, the number of which in the design shown in Fig.6 is equal to two, are located on the same line around the periphery and are placed at equal intervals in the cylindrical wall 13d.

The device 100 also comprises a second throttling means including a second closing means 33 of the same construction as the first closing means 19 described above for throttling the third plurality of holes 32 in an adjustable manner.

The second closing means 33 comprises a second sleeve 34 aligned coaxially with the third channel 13. A fourth set of radial through holes 35 is also formed in the second sleeve 34 and arranged to throttle the third set of holes 32 by angular rotation in the same manner as the first set of holes 18 throttled by sleeve 20.

Gas is introduced into the mixing chamber 12 through openings 35 in a substantially radial direction about the X axis.

The connecting lever 36 extends from the second closure means 33 and is connected at one of its ends 36a to the first sleeve 20 in order to secure the second closure means 33 for rotation together with the first closure means 19. Joint fastening of the two closure means creates a throttling relationship between the holes 18 and openings 32, whereby the relationship between the flow rate of the secondary air and the flow rate of gas introduced into the mixing chamber 12 is fixed. The device according to the invention operates as follows. During operation, the fan 8 draws in primary air and secondary air into the first converging channel 5 and into the second channel 6, respectively.

The primary air stream passes through the converging channel 5 and mixes with the gas that leaves the third channel 13 and the dosage of which depends on the pressure signal that is present in the narrowed part of the first channel 5 and on any rotation transmitted to the primary air stream. The resulting mixture is then introduced into the mixing chamber 12.

The throttling of the holes 18 can be further modified, if required, in accordance with the power required from the burner 2, or depending on the signals sent by the sensors 30, 31 of combustion and / or temperature to the electronic control card. In this case, the start signal of the electric motor 25 is generated by the punched card 27. The closing means 19 is thus rotated by the means 26 for driving into the angular position corresponding to the pre-selected throttling of the holes 18 and, therefore, the required amount of secondary air flow in the channel 6.

In the mixing chamber 12, the secondary air is mixed with the mixture of gas and air, and the resulting combustible mixture is then supplied to the burner 2.

If the closing means 19 is fixed relative to the tubular body 3 in accordance with the aforementioned embodiment, the throttling of the holes 18 is predetermined in the installation and calibration stages depending on the type of boiler installed and the characteristics of the fan so that the secondary air flow is optimal. Alternatively, in a further embodiment, optimal throttling of the holes is achieved by installing closure means in which the cross section of the holes is suitable for achieving a predetermined secondary air flow rate.

In a third embodiment, the rotation of the first closing means 19 by a predetermined angle made by the electric motor 25 causes a corresponding rotation of the second closing means 33 by the same angle by means of the connecting lever 36, so that both the secondary air flow and the gas flow that are introduced into the mixing chamber 12 is throttled in the same motion. The costs of the two flows thus change, while their ratio is kept constant.

The invention thus solves the tasks, providing many advantages over the prior art.

The first advantage, which has become clear from the tests performed by the applicant, is that the geometric characteristics of the installation, as well as the inlet of a secondary air stream of the described type, which is separated from the primary air-gas mixture stream, into the mixer device clearly contribute to the attenuation of sound waves emitted by flame fronts, which are usually created in known devices of this type and which can be heard outside the boiler.

The second advantage is that the joint control of the flow rates of the secondary air flow and the gas flow, which can be achieved in the mixer device in accordance with the invention, leads to a significant increase in the effective range of modulation of the flow rate of the mixture of air and gas supplied by the device.

Continuously controlled throttling of the secondary air flow allows the fan to operate continuously under conditions close to operating conditions with maximum efficiency, which correspond to a predetermined value of CO ₂ and a minimum value of CO and MOx emissions for each pre-selected flow rate, even with changes in power depending on the burner .

It is also important that, by optimally controlling the stoichiometric ratio of air and gas in the mixture, the pollutant emissions from the burner to which the feed is provided by the mixer of the invention are particularly low.

Claims (29)

1. The device (1, 100) of the mixer for air and gas, in particular for gas burners (2) with forced ventilation, containing a mixing chamber (12) for air and gas for the production of a combustible mixture supplied to the burner, and in the chamber (12 ) a first stream of a mixture of primary air and gas and a second stream of secondary air are supplied through the first channel (5) and the second channel (6), respectively, characterized in that it contains means for throttling the first channel (5) and / or the second channel (6) in order to selectively throttle the amount of the mixture of primary air and gas and / or secondary air supplied to the mixing chamber (12) and the tubular body (3), while the first channel (5) has a cross section that decreases in the direction of flow of the mixture of air and gas and is coaxial with the second channel (6), and the first channel (5) is placed inside the tubular body (3), and the second channel (6) is formed by the tubular body (3) and the first channel (5). 2. The mixer device according to claim 1, characterized in that the second channel (6) contains at least one through hole (18) for the inlet of the secondary air flow, the hole being adapted for throttling with the first throttling means. 3. The mixer device according to claim 2, characterized in that the second channel (6) contains a first set of through holes (18) that can be throttled selectively. 4. The mixer device according to any one of claims 1 to 3, characterized in that the throttling is adjustable. 5. The device of the mixer according to claim 2, characterized in that the first plurality of holes (18) is provided in the tubular body (3). 6. The mixer device according to claim 5, characterized in that the holes (18) of the first set are located on the same line around the circumference and are divided at equal intervals in the tubular body (3). 7. The mixer device according to any one of claims 3 to 6, characterized in that the first throttling means comprises a first closing means (19) that can move between the first working position, in which the first set of holes (18) is completely closed, and the second working position in which it is completely open. 8. The device of the mixer according to claim 7, characterized in that the first closing means (19) comprises a first sleeve (20) aligned coaxially with the tubular body (3) and acting on the holes (18). 9. The mixer device of claim 8, characterized in that the first sleeve (20) has a second plurality of holes (22) arranged in a line along the periphery in positions corresponding to the positions of the first plurality of holes (18) when the first closure means (19) is fitted onto the tubular body (3) so that the first plurality of holes (18) can be throttled by portions of the first sleeve (20) formed between respective adjacent holes (22) of the second plurality. 10. The device of the mixer according to claim 9, characterized in that the first closing means (19) is rotatable around an axis common to the tubular body (3) and the first closing means (19), so that the second plurality of holes (22) can constantly move between the first fully closed working position and a second fully open operating position in which the first plurality (18) and the second plurality (22) of holes are superimposed on each other. 11. A mixer device according to any one of claims 7 to 10, characterized in that the closing means comprises a drive motor (25) and means for a drive (26) located between the engine (25) and the closing means (19), the first closing means (19) is rotated by an electric motor (25) by means of a drive (26). 12. The mixer according to claim 11, characterized in that the electric motor (25) is a stepper motor. 13. The device of the mixer according to claim 11 or 12, characterized in that the electric motor (25) is operatively controlled by an electronic control punch card (27) and is driven depending on the signals correlating the parameters determined by the sensors (30, 31) and sent to the electronic control punch card (27). 14. The mixer device according to any one of claims 1 to 13, characterized in that it comprises a fan (8) located downstream after the first channel (5) and the second channel (6) with respect to the direction of primary and secondary air flows. 15. The device of the mixer according to 14, characterized in that the fan (8) is enclosed by a box type case (9), and a mixing chamber (12) is formed inside the box type case (9). 16. The mixer device according to clause 15, characterized in that the box-type housing (9) comprises a cover (10) made integrally with the first channel (5) and the second channel (6). 17. The mixer device according to clause 16, characterized in that the cover (10) is made by injection molding. 18. The mixer device according to any one of claims 1 to 17, characterized in that it contains a set of stator vanes (15) inside the first channel (5) for transmitting the rotational component to the flow of primary air and gas mixture entering the first channel (5). 19. The mixer device according to any one of claims 1 to 18, characterized in that it comprises a set of stator vanes (15) inside the second channel (6) for transmitting the rotational component to the secondary air stream entering the second channel. 20. The mixer device according to any one of claims 1 to 19, characterized in that it comprises a third channel (13) for admitting gas into the mixing chamber (12). 21. The mixer device according to claim 20, characterized in that the third channel (13) is formed coaxially with the first channel (5) and inside it. 22. The mixer device according to claim 20 or 21, characterized in that it comprises a second throttling means for throttling the third channel (13) in order to selectively and in a controlled way throttle the amount of gas supplied to the mixing chamber (12). 23. A mixer device according to any one of claims 20 to 22, characterized in that the third channel (13) comprises a shutter base (13a) at the free end (13b), with at least one through hole (32) provided end portion (13b). 24. The mixer device according to any one of paragraphs.20-23, characterized in that the third channel (13) contains a third set of holes (32) that can be throttled selectively. 25. The device of the mixer according to item 23 or 24, characterized in that the second throttling means comprises a second closing means (33) that can move between the first working position in which the third set of holes (32) is completely closed and the second working position in which it is fully open. 26. The device of the mixer according A.25, characterized in that the second closing means (33) is operatively connected to the first closing means (19) so that the throttling of the first plurality of holes (18) correlates with the throttling of the third plurality of holes (32) as a result of the angular movement of the first closing means (19) between the first and second working provisions. 27. The mixer device according to claim 25 or 26, characterized in that the second closing means (33) comprises a second sleeve (34) fitted to the third channel (13), the second sleeve (34) being rigidly connected to the first sleeve (20). 28. A mixer device according to claim 27, characterized in that it comprises at least one connecting lever (36) extending radially between the first and second bushings (20, 34) in order to secure the second closing means (33) for rotation together with the first closing means (19). 29. The mixer device according to item 27 or 28, characterized in that a fourth plurality of holes (35) are provided in the second sleeve (34), the holes (35) being peripherally aligned in positions corresponding to the positions of the third set of holes (32) when the second sleeve (34) is fitted to the third channel (13) so that the third set of holes (32) can be closed by parts of the second sleeve (34) formed between the corresponding nearby holes of the fourth set (35).

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