EP3974720A1

EP3974720A1 - An air-gas mixture burning appliance with a gas governor

Info

Publication number: EP3974720A1
Application number: EP21193437.7A
Authority: EP
Inventors: Tom Collins
Original assignee: Bosch Thermotechnology Ltd
Current assignee: Bosch Thermotechnology Ltd
Priority date: 2020-09-23
Filing date: 2021-08-27
Publication date: 2022-03-30
Anticipated expiration: 2041-08-27
Also published as: EP3974720B1; GB2599629A; GB202015055D0

Abstract

In an air-gas mixture burning appliance (100) that comprises an air-gas mixing unit (110) with a plurality of air-gas mixers (118), an air supply (112) that is connected to the air-gas mixing unit and comprises a common air way (412) for supply of air to the plurality of air-gas mixers, and a gas governor (410) that is adapted to control supply of gas to the plurality of air-gas mixers dependant on an air pressure signal (430) that is indicative of a static air pressure in the common air way (412), the plurality of air-gas mixers (118) is at least partially surrounded by a slot (210) which encompasses at least partially the common air way (412), and the slot (210) is connected to the gas governor (410) via an air pressure signal port (230) which is configured to provide the air pressure signal (430) from the slot to the gas governor.

Description

Background of the Invention

The present invention relates to an air-gas mixture burning appliance that comprises an air-gas mixing unit with a plurality of air-gas mixers for mixing of air and gas to form a combustible air-gas mixture, an air supply that is connected to the air-gas mixing unit and comprises a common air way for supply of air to the plurality of air-gas mixers, and a gas governor that is adapted to control supply of gas to the plurality of air-gas mixers dependant on an air pressure signal that is indicative of a static air pressure in the common airway. Furthermore, the present invention relates to a Venturi plate that forms a manifold which interconnects inlet sides of a plurality of Venturi-type mixing nozzles.
From the state of the art an air-gas mixture burning appliance with an air-gas mixing unit, a burning unit, and a gas governor is known, wherein e.g. hydrogen may be used as gas and mixed with air to form a combustible air-gas mixture. Such an air-gas mixture burning appliance usually performs "just in time" mixing of air and gas directly before the burning unit to minimise a respective volume of combustible air-gas mixture available in the event of a flashback. Thus, a predefined point of mixing for the air and gas may be located near an associated combustion space directly downstream of the burning unit.
In such an air-gas mixture burning appliance, the gas governor may be used to accomplish a suitable pneumatic air-gas ratio control by regulating gas supply pressure in relation to an aspiration air pressure signal, i.e. by controlling supply of gas to the air-gas mixing unit. In order to provide stable control of the gas supply pressure, the gas governor must, nevertheless, be provided with a stable measurement of air pressure, i.e. with a stable air pressure signal, which indicates a respective unaccelerated static pressure of the air in the air-gas mixing unit.
From the state of the art the measurement of air pressure is well-known for air-gas mixture burning appliances having an air-gas mixing unit that is respectively only provided with a single air-gas mixer. In this case, if a given single air-gas mixer is e.g. embodied as a Venturi-type mixing nozzle, a stable measurement of a suitable air pressure signal that indicates the unaccelerated static pressure of the air may be performed by sampling this pressure via an annular slot of the Venturi-type mixing nozzle that encircles an air inlet of the Venturi-type mixing nozzle and that faces into a respective air flow.

Summary of the Invention

The present invention relates to an air-gas mixture burning appliance that comprises an air-gas mixing unit with a plurality of air-gas mixers for mixing of air and gas to form a combustible air-gas mixture, an air supply that is connected to the air-gas mixing unit and comprises a common air way for supply of air to the plurality of air-gas mixers, and a gas governor that is adapted to control supply of gas to the plurality of air-gas mixers dependant on an air pressure signal that is indicative of a static air pressure in the common air way. The plurality of air-gas mixers is at least partially surrounded by a slot which encompasses at least partially the common air way, and the slot is connected to the gas governor via an air pressure signal port which is configured to provide the air pressure signal from the slot to the gas governor.
The gas governor may be embodied to perform a pneumatic air-gas ratio control. The gas used by the inventive air-gas mixture burning appliance may be hydrogen.
Advantageously, provision of the slot that surrounds at least partially the plurality of air-gas mixers of the air-gas mixing unit in the inventive air-gas mixture burning appliance allows stable and undisturbed measurement of static air pressure in the air-gas mixing unit of the inventive air-gas mixture burning appliance. Thus, an improved air pressure signal representing the mean static air pressure experienced by all air-gas mixers of the plurality of air-gas mixers can be provided to the gas governor of the inventive air-gas mixture burning appliance such that control of supply of gas to the plurality of air-gas mixers by means of the gas governor may be improved significantly.
According to one aspect, the slot is connected to the air pressure signal port via an associated plenum chamber.
Thus, the air pressure signal that is provided from the slot via the air pressure signal port to the gas governor may further be stabilised.
Preferably, the plenum chamber is connected to the slot via a first plenum opening, the plenum chamber is connected to the air pressure signal port via a second plenum opening, and the second plenum opening is arranged closer to the common airway than the first plenum opening.
This configuration is advantageous by providing an enhanced stability and accuracy in reading of the air pressure signal, thus, allowing the air pressure signal to be more representative of the true average static air pressure in the common air way, i.e. of all air-gas mixers of the plurality of air-gas mixers.
Preferably, the slot faces into an air flow which is directed via the common air way toward the plurality of air-gas mixers.
Thus, the air flow may directly enter the slot via the common airway.
The plurality of air-gas mixers is preferably arranged inside a housing, and the slot is formed inside, and at least partly along the housing.
Accordingly, the slot may easily be formed and provided in the inventive air-gas mixture burning appliance.
According to one aspect, each one of the plurality of air-gas mixers is connected at a respective inlet side to a manifold, and the slot is formed in the manifold. Each one of the plurality of air-gas mixers may be embodied as a Venturi-type mixing nozzle.
Thus, the plurality of air-gas mixers may securely and reliably be interconnected mechanically to form a single air-gas mixing unit in the inventive air-gas mixture burning appliance.
According to one aspect, each one of the plurality of air-gas mixers is configured to restrict a gas flow supplied from the gas governor upstream of an associated point of mixing where the gas flow is combined with an air flow which is directed via the common air way toward the plurality of air-gas mixers.
Accordingly, the mixing of air and gas to form the combustible air-gas mixture may easily be improved.
According to one aspect, the slot extends relative to a flow direction of the combustible air-gas mixture to such an extent that the air pressure signal port is located entirely downstream of the associated point of mixing.
This configuration is also advantageous by providing an enhanced stability and accuracy in reading of the air pressure signal, thus, allowing the air pressure signal to be more representative of the true average static air pressure in the common air way, i.e. of all air-gas mixers of the plurality of air-gas mixers.
Preferably, the slot has a width that ranges between 1mm and 9mm.
By providing the slot with a width that ranges between 1mm and 9mm, an adequate reading of the air pressure signal may be guaranteed. In fact, if the slot width is greater than 9mm, then the pressure reading is no longer representative of the true average static air pressure due to the flow of air not being restricted sufficiently. However, if the slot width is less than 1mm, then a respective response time in reading of the air pressure signal will be too great and affect performance and efficiency of the gas governor and, hence, performance and efficiency of the air-gas mixture burning appliance as such, as the gas governor may lag changes in air flow rate.
Furthermore, the present invention relates to a Venturi plate that forms a manifold which interconnects inlet sides of a plurality of Venturi-type mixing nozzles, comprising a slot which is connected to an associated plenum chamber and surrounds all inlet sides at least partially.
Thus, a manifold-type plate that interconnects inlet sides of a plurality of Venturi-type mixing nozzles and that enables stable and undisturbed measurement of static air pressure in an associated air-gas mixing unit that uses the inventive Venturi plate may be provided.

Brief Description of the Drawings

Exemplary embodiments of the present invention are described in detail hereinafter with reference to the attached drawings. In these attached drawings, identical or identically functioning components and elements are labelled with identical reference signs and they are generally only described once in the following description.

Fig. 1: shows a schematic view of an air-gas mixture burning appliance with an air-gas mixing unit according to the present invention,
Fig. 2: shows a schematic cross-sectional view of the air-gas mixing unit of Fig. 1 according to a first embodiment,
Fig. 3: shows a top view of the air-gas mixing unit of Fig. 2,
Fig. 4: shows a functional representation of the air-gas mixture burning appliance of Fig. 1 to Fig. 4,
Fig. 5: shows a schematic cross-sectional view of the air-gas mixing unit of Fig. 1 according to a second embodiment, and
Fig. 6: shows a schematic cross-sectional view of the air-gas mixing unit of Fig. 1 according to a third embodiment.

Detailed Description

Fig. 1 shows an exemplary air-gas mixture burning appliance 100 with an air-gas mixing unit 110, an air supply 112, a gas supply 116, and a burning unit 120. By way of example, the air-gas mixture burning appliance 100 may be used in a boiler or, more generally, in a building heating system. Preferably, the gas used is hydrogen such that the air-gas mixture burning appliance 100 forms an air-hydrogen mixture burning appliance.
The air-gas mixing unit 110 is preferably adapted for mixing of air and gas to form a combustible air-gas mixture 130. Preferentially, the combustible air-gas mixture 130 is a homogenous mixture of the air and the gas.
The air is preferably drawn into the air-gas mixing unit 110 via the air supply 112, which is illustratively connected to the air-gas mixing unit 110, and the gas is preferably supplied to the air-gas mixing unit 110 via the gas supply 116. Illustratively, the air supply 112 includes a fan 114 that may be operated with an adaptable fan speed and/or within predetermined ranges of fan speeds to draw air into the air-gas mixing unit 110.
According to one aspect, the air supply 112 and the gas supply 116 are interconnected via a plurality of air-gas mixers 118 of the air-gas mixing unit 110. Each one of the plurality of air-gas mixers 118 forms preferably an associated discrete point of mixing 119. Preferably, the combustible air-gas mixture 130 is formed at all such discrete points of mixing 119 from a respective air flow 140 supplied via the air supply 112 and a respective gas flow 150 supplied via the gas supply 116. The combustible air-gas mixture 130 is then guided via the plurality of air-gas mixers 118 to the burning unit 120.
Illustratively, the burning unit 120 is provided with a burner surface 124 that is arranged downstream of the air-gas mixing unit 110 such that the combustible air-gas mixture 130 that is formed at the points of mixing 119 flows towards the burner surface 124. The combustible air-gas mixture 130 is burned by the burning unit 120 and, more specifically, at the burner surface 124.
By way of example, the burner surface 124 is illustrated with a comparatively small flame 122 which occurs e.g. at a low firing rate of the air-gas mixing unit 110, i.e. at a comparatively low rate at which feed of the combustible air-gas mixture 130 from the air-gas mixing unit 110 to the burning unit 120 occurs, in terms of volume, heat units, or weight per unit time. Such a low firing rate may e.g. be applied to the air-gas mixing unit 110 during an ignition phase of the air-gas mixture burning appliance 100.
Fig. 2 shows the air-gas mixing unit 110 of Fig. 1 with the plurality of air-gas mixers 118. The plurality of air-gas mixers 118 is provided for mixing of air supplied by means of the airflow 140 and gas supplied by means of the gas flow 150 via the gas supply 116 at respective points of mixing 119 in order to form the combustible air-gas mixture 130.
Illustratively, the plurality of air-gas mixers 118 is arranged inside a housing 205. Preferably, each one of the plurality of air-gas mixers 118 is embodied as a Venturi-type mixing nozzle.
For simplicity and clarity of the drawing, only a single air-gas mixer of the plurality of air-gas mixers 118 is individually labelled in Fig. 2 with the reference sign 218. This single air-gas mixer 218 is hereinafter described representative for all air-gas mixers of the plurality of air-gas mixers 118, which are preferably embodied identically, at least within predetermined manufacturing tolerances and with respect to an underlying functioning. Thus, a detailed description of each one of the plurality of air-gas mixers 118 may be omitted for brevity and conciseness.
Illustratively, the air-gas mixer 218 and, thus, each one of the plurality of air-gas mixers 118 has an air inlet 240 and a combustible air-gas mixture outlet 250. Furthermore, the air-gas mixer 218 and, thus, each one of the plurality of air-gas mixers 118 is preferably connected to the gas supply 116 such that the gas flow 150 may be guided from the gas supply 116 to the point of mixing 119 that is associated with the air-gas mixer 218. Preferably, the air-gas mixer 218 and, thus, each one of the plurality of air-gas mixers 118 is preferentially connected at its inlet side, illustratively at the air inlet 240, to a manifold 202. If each one of the plurality of air-gas mixers 118 is embodied as a Venturi-type mixing nozzle, then the manifold 202 may be embodied as a so-called "Venturi-plate".
According to one aspect, the plurality of air-gas mixers 118 is at least partially surrounded by a slot 210. Preferably, the slot 210 is formed inside, and at least partly along the housing 205, i.e. close to a respective housing wall. By way of example, the slot 210 is formed in the manifold 202. Illustratively, the slot 210 faces the air flow 140.
Preferably, the slot 210 is connected to an associated plenum chamber 220. The plenum chamber 220 is preferably connected to an air pressure signal port 230.
However, it should be noted that provision of the plenum chamber 220 is not mandatory and may also be omitted. A corresponding embodiment of the air-gas mixing unit 110 without the plenum chamber 220 is described below at Figure 6. Furthermore, it should be noted that also a particular location of the plenum chamber 220 may vary, as e.g. described below at Fig. 5.
Fig. 3 shows the air-gas mixing unit 110 of Fig. 1 with the plurality of air-gas mixers 118. According to Fig. 2, the plurality of air-gas mixers 118 is arranged inside the housing 205 and connected to the manifold 202.
In Fig. 3, the slot 210 of the air-gas mixing unit 110 is further illustrated. According to one aspect, the slot 210 completely surrounds the plurality of air-gas mixers 118. By way of example, the slot 210 is formed in the manifold 202 and arranged inside, and at least partly along the housing 205.
Fig. 4 shows the air-gas mixture burning appliance 100 of Fig. 1 with the air-gas mixing unit 110, the air supply 112, and the gas supply 116 for further illustrating the functionality of the air-gas mixture burning appliance 100. However, for simplicity and clarity of the drawing, illustration of the burning unit 120 is omitted.
The air-gas mixing unit 110 is embodied as described above at Fig. 2 and Fig. 3 and comprises the plurality of air-gas mixers 118 that is arranged inside the housing 205 and connected to the manifold 202 having the slot 210. Illustratively, the housing 205 connects the air-gas mixing unit 110 to the air supply 112 and forms a common air way 412 for the air flow 140 toward the manifold 202, for supply of air to the plurality of air-gas mixers 118.
By means of the common air way 412, the air flow 140 is also supplied to the slot 210, which preferably encompasses at least partially the common airway 412. More specifically, the slot 210 faces into the air flow 140 which is directed via the common air way 412 toward the plurality of air-gas mixers 118.
According to one aspect, the slot 210 is connected to a gas governor 410 via the air pressure signal port 230 which is configured to provide an air pressure signal 430 from the slot 210 to the gas governor 410. Illustratively, the air pressure signal 430 is provided from the slot 210 via the plenum chamber 220 to the gas governor 410. The plenum chamber 220 is preferably provided to allow stable and undisturbed measurement of static air pressure in the air-gas mixing unit 110 such that the air pressure signal 430 represents at least essentially the mean static air pressure experienced by all air-gas mixers of the plurality of air-gas mixers 118.
According to one aspect, the gas governor 410 is adapted to control supply of gas to the plurality of air-gas mixers 118 dependant on the air pressure signal 430 that is indicative of the static air pressure in the common air way 412 and, thus, in the air-gas mixing unit 110. Illustratively, the gas governor 410 controls an incoming gas flow 420 on the basis of the air pressure signal 430 to generate the gas flow 150.
In other words, the gas governor 410 is preferably embodied to perform a pneumatic air-gas ratio control. However, it should be noted that functioning of a gas governor to perform a pneumatic air-gas ratio control as such is well-known to the person skilled in the art. Thus, a more detailed description of the functioning of the gas governor 410 may be omitted for brevity and conciseness. Nevertheless, independent of a particular realisation of the gas governor 410, each one of the plurality of air-gas mixers 118 is preferably configured to restrict the gas flow 150 supplied from the gas governor 410 upstream of the point of mixing 119 where the gas flow 150 is combined with the air flow 140 which is directed via the common air way 412 toward the plurality of air-gas mixers 118.
Fig. 5 shows the air-gas mixing unit 110 of Fig. 1 with the plurality of air-gas mixers 118 that are provided for mixing of air supplied by means of the air flow 140 and gas supplied by means of the gas flow 150 via the gas supply 116 at respective points of mixing 119 in order to form the combustible air-gas mixture 130. As described above at Fig. 2 and Fig. 3, the plurality of air-gas mixers 118 is illustratively arranged inside the housing 205 and connected to the manifold 202 having the slot 210 and the plenum chamber 220, which is connected to the air pressure signal port 230. The housing 205 forms the common air way 412 of Fig. 4 for the air flow 140 toward the manifold 202 for supply of air to the plurality of air-gas mixers 118.
However, in contrast to Fig. 2 the plenum chamber 220 is now connected to the slot 210 via a first plenum opening 510 and to the air pressure signal port 230 via a second plenum opening 520, wherein the second plenum opening 520 is arranged closer to the common airway 412 than the first plenum opening 510. In other words, the second plenum opening 520 is illustratively above the first plenum opening 510 in order to provide an enhanced stability and accuracy in reading of the air pressure signal (430 in Fig. 4), thus, allowing the air pressure signal (430 in Fig. 4) to be more representative of the true average static air pressure in the common air way 412, i.e. of all air-gas mixers of the plurality of air-gas mixers 118.
Fig. 6 shows the air-gas mixing unit 110 of Fig. 1 with the plurality of air-gas mixers 118 that are provided for mixing of air supplied by means of the air flow 140 and gas supplied by means of the gas flow 150 via the gas supply 116 at respective points of mixing 119 in order to form the combustible air-gas mixture 130. As described above at Fig. 2 and Fig. 3, the plurality of air-gas mixers 118 is arranged inside the housing 205 and connected to the manifold 202 having the slot 210 and the air pressure signal port 230.
However, in contrast to Fig. 2 the slot 210 is now directly connected to the air pressure signal port 230. In other words, provision of the plenum chamber 220 is omitted. Nevertheless, according to one aspect the slot 210 now extends relative to a flow direction of the combustible air-gas mixture 130 to such an extent that the air pressure signal port 230 is located entirely downstream of, i.e. illustratively below the respective points of mixing 119.
Fig. 6 further illustrates an exemplary width 610 of the slot 210. According to one aspect, the width 610 ranges between 1mm and 9mm. However, it should be noted that although the width 610 is only shown in Fig. 6, it preferably applies to all embodiments described above at Fig. 1 to Fig. 6.

Claims

An air-gas mixture burning appliance (100), comprising:
an air-gas mixing unit (110) with a plurality of air-gas mixers (118) for mixing of air and gas to form a combustible air-gas mixture (130),

an air supply (112) that is connected to the air-gas mixing unit (110) and comprises a common air way (412) for supply of air to the plurality of air-gas mixers (118), and

a gas governor (410) that is adapted to control supply of gas to the plurality of air-gas mixers (118) dependant on an air pressure signal (430) that is indicative of a static air pressure in the common air way (412),

wherein the plurality of air-gas mixers (118) is at least partially surrounded by a slot (210) which encompasses at least partially the common airway (412), and

wherein the slot (210) is connected to the gas governor (410) via an air pressure signal port (230) which is configured to provide the air pressure signal (430) from the slot to the gas governor (410).
The air-gas mixture burning appliance of claim 1, wherein the slot (210) is connected to the air pressure signal port (230) via an associated plenum chamber (220).
The air-gas mixture burning appliance of claim 2, wherein the plenum chamber (220) is connected to the slot (210) via a first plenum opening (510), wherein the plenum chamber (220) is connected to the air pressure signal port (230) via a second plenum opening (520), and wherein the second plenum opening (520) is arranged closer to the common airway (412) than the first plenum opening (510).
The air-gas mixture burning appliance of any one of the preceding claims, wherein the slot (210) faces into an air flow (140) which is directed via the common air way (412) toward the plurality of air-gas mixers (118).
The air-gas mixture burning appliance of any one of the preceding claims, wherein the plurality of air-gas mixers (118) is arranged inside a housing (205), and wherein the slot (210) is formed inside, and at least partly along the housing (205).
The air-gas mixture burning appliance of any one of the preceding claims, wherein each one of the plurality of air-gas mixers (118) is connected at a respective inlet side (240) to a manifold (202), and wherein the slot (210) is formed in the manifold (202).
The air-gas mixture burning appliance of any one of the preceding claims, wherein each one of the plurality of air-gas mixers (118) is configured to restrict a gas flow (150) supplied from the gas governor (410) upstream of an associated point of mixing (119) where the gas flow (150) is combined with an air flow (140) which is directed via the common air way (412) toward the plurality of air-gas mixers (118).
The air-gas mixture burning appliance of claim 7, wherein the slot (210) extends relative to a flow direction of the combustible air-gas mixture (130) to such an extent that the air pressure signal port (230) is located entirely downstream of the associated point of mixing (119).
The air-gas mixture burning appliance of any one of the preceding claims, wherein the slot (210) has a width (610) that ranges between 1mm and 9mm.
A Venturi plate (202) that forms a manifold which interconnects inlet sides (240) of a plurality of Venturi-type mixing nozzles (118), comprising a slot (210) which is connected to an associated plenum chamber (220) and surrounds all inlet sides (240) at least partially.