EP4226995A1

EP4226995A1 - An air-gas mixing unit with an air-gas mixer

Info

Publication number: EP4226995A1
Application number: EP23151042.1A
Authority: EP
Inventors: Tom Collins; Patrick Hemmen
Original assignee: Bosch Thermotechnology Ltd
Current assignee: Bosch Thermotechnology Ltd
Priority date: 2022-01-27
Filing date: 2023-01-11
Publication date: 2023-08-16
Also published as: GB2615105A; GB202201086D0

Abstract

An air-gas mixing unit (500) comprising an air-gas mixer (600) and a bluff body plate (505), wherein the air-gas mixer comprises a main flow passage (410) with an inlet end (120) for inlet of a first fluid and at least one lateral inlet opening for inlet of a second fluid, and wherein the bluff body plate (505) comprises at least one first bluff body arrangement (510) with at least one first bluff body (151), and at least one second bluff body arrangement (520) with at least one second bluff body (551), the at least one first bluff body (151) being adapted to enable creation of low pressure with a first degree of turbulence of the first fluid, and the at least one second bluff body (551) being adapted to enable creation of low pressure with a second degree of turbulence of the first fluid.

Description

Background of the Invention

The present invention relates to an air-gas mixing unit with an air-gas mixer which comprises a main flow passage for mixing a first fluid with a second fluid into a mixed fluid, the main flow passage comprising an inlet end for inlet of the first fluid, at least one lateral inlet opening for inlet of the second fluid, and an outlet end for outlet of the mixed fluid.
From the state of the art, an air-gas mixing unit with an air-gas mixer which comprises a main flow passage for mixing a first fluid with a second fluid into a mixed fluid is known. The main flow passage comprises an inlet end for inlet of the first fluid, at least one lateral inlet opening for inlet of the second fluid, and an outlet end for outlet of the mixed fluid. The air-gas mixer may e.g. be a Venturi-type mixing nozzle that mixes air that forms the first fluid, with gas, such as hydrocarbon gas or hydrogen gas, that forms the second fluid, into a combustible air-gas mixture that forms the mixed fluid, with a desired concentration or ratio.
The document EP 3 919 815 A1 describes such a Venturi-type mixing nozzle that is intended for mixing of air and hydrogen gas. This Venturi-type mixing nozzle further comprises at least one bluff body that is arranged in the main flow passage such that its wake shields the at least one lateral inlet opening.

Summary of the Invention

The present invention relates to an air-gas mixing unit comprising an air-gas mixer and a bluff body plate, wherein the air-gas mixer comprises a main flow passage for mixing a first fluid with a second fluid into a mixed fluid. The main flow passage comprises an inlet end for inlet of the first fluid, at least one lateral inlet opening for inlet of the second fluid, and an outlet end for outlet of the mixed fluid. The bluff body plate comprises at least one first bluff body arrangement with at least one first bluff body, and at least one second bluff body arrangement with at least one second bluff body, the at least one first bluff body being adapted to enable creation of low pressure with a first degree of turbulence of the first fluid in the main flow passage around the at least one lateral inlet opening, and the at least one second bluff body being adapted to enable creation of low pressure with a second degree of turbulence of the first fluid in the main flow passage around the at least one lateral inlet opening.
Advantageously, the at least one first or second bluff body is positioned in the main flow passage upstream of the at least one lateral inlet opening such that its wake shields the at least one lateral inlet opening. The pressure in the shielded region of the at least one lateral inlet opening may, thus, be reduced compared to the pressure in circumjacent unshielded regions of the passage constriction, such that pressure loss at the at least one lateral inlet opening is significantly reduced. As a result, injection of the second fluid into the main flow passage and, thus, mixing of the first and second fluids is improved and performed over a significantly reduced longitudinal length inside of the air-gas mixer. Moreover, a required supply pressure for the second fluid may advantageously be reduced.
Furthermore, provision of the bluff body plate with the at least one first bluff body arrangement and the at least one second bluff body arrangement allows to convert the inventive air-gas mixing unit easily, quickly and reliably from use with a first type of gas, such as a hydrocarbon gas, e.g. methane, to a second type of gas, such as hydrogen gas. More specifically, this may advantageously be achieved by merely switching the air-gas mixing unit and, more particularly, the air-gas mixer from use of the at least one first bluff body arrangement to use of the at least one second bluff body arrangement.
According to one aspect, the bluff body plate is exchangeable to enable provision of different bluff body arrangements which are configured for use with different types of gases, wherein the different bluff body arrangements comprise different properties of optimizing mixing and pressure losses.
Thus, different bluff body arrangements may be provided for a given type of gas to optimize mixing and pressure losses in the air-gas mixer.
According to one aspect, the bluff body plate is re-orientable relative to the air-gas mixer to enable positioning of the at least one first bluff body arrangement or the at least one second bluff body arrangement at the inlet end of the air-gas mixer.
Thus, the inventive air-gas mixing unit may easily, quickly and reliably be switched from use with a first type of gas, such as a hydrocarbon gas, e.g. methane, to a second type of gas, such as hydrogen gas, by merely re-orienting the bluff body plate relative to the air-gas mixer.
Preferably, the bluff body plate is rotatable or flippable between a first position and a second position relative to the air-gas mixer, wherein the at least one first bluff body arrangement is positioned at the inlet end of the air-gas mixer in the first position, and wherein the at least one second bluff body arrangement is positioned at the inlet end of the air-gas mixer in the second position.
Thus, a required re-orientation of the bluff body plate relative to the air-gas mixer may easily and reliably be achieved.
According to one aspect, at least one of the at least one first bluff body arrangement and the at least one second bluff body arrangement defines a throat of the air-gas mixer at the inlet end.
Thus, a required throat of the air-gas mixer may advantageously be embodied by means of the at least one first bluff body arrangement or the at least one second bluff body arrangement.
According to one aspect, the air-gas mixer comprises a plurality of lateral inlet openings, wherein at least one of the at least one first bluff body arrangement and the at least one second bluff body arrangement is configured to impede at least one of the plurality of lateral inlet openings.
Accordingly, a required air-gas ratio may securely and reliably be adjusted.
Preferably, the at least one of the at least one first bluff body arrangement and the at least one second bluff body arrangement that is configured to impede the at least one of the plurality of lateral inlet openings is embodied to enable a high velocity flow of the first fluid at the at least one of the at least one first bluff body arrangement and the at least one second bluff body arrangement.
By enabling a high velocity flow of the first fluid at the at least one of the at least one first bluff body arrangement and the at least one second bluff body arrangement, the at least one of the plurality of lateral inlet openings may easily be impeded.
According to one aspect, the at least one first bluff body of the at least one first bluff body arrangement and the at least one second bluff body of the at least one second bluff body arrangement are attached to, or integrally formed with, the bluff body plate.
Accordingly, a robust and solid bluff body plate may be provided.
According to one aspect, the at least one first bluff body arrangement comprises a plurality of first bluff bodies with differing shapes.
Thus, creation of a low pressure with a first degree of turbulence of the first fluid in the main flow passage around the at least one lateral inlet opening may easily be improved, thereby further improving mixing of the first and second fluids.
According to one aspect, the air-gas mixer is a Venturi-type mixing nozzle with a nozzle body that forms the main flow passage.
Thus, a well-known type of mixing nozzle may advantageously be used to embody the air-gas mixer.

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 perspective view of a Venturi-type mixing nozzle with bluff bodies,
Fig. 2: shows a sectional view of the Venturi-type mixing nozzle of Fig. 1,
Fig. 3: shows a schematic view of exemplary flows of first and second fluids in the Venturi-type mixing nozzle of Fig. 1 and Fig. 2,
Fig. 4: shows a perspective view of a Venturi-type mixing nozzle with bluff bodies according to a variant, for an air-gas mixing unit according to the present invention,
Fig. 5: shows a top view of an air-gas mixing unit according to a first embodiment,
Fig. 6: shows a top view of an air-gas mixing unit according to a second embodiment,
Fig. 7 to Fig. 9: show sectional views of alternative air-gas mixing units, and
Fig. 10: shows a schematic view of an air-gas mixer with an alternative bluff body arrangement.

Detailed Description

Fig. 1 shows an illustrative Venturi-type mixing nozzle 100 with a nozzle body 105 that forms a main flow passage 110. The Venturi-type mixing nozzle 100 as such is shown as one example of an air-gas mixer that may be used in an air-gas mixing unit according to the present invention. More specifically, the Venturi-type mixing nozzle 100 may used for mixing of a combustible gas, e.g. hydrogen gas or a hydrocarbon gas, such as methane, with air at a desired concentration or ratio in an associated air-gas mixing unit that embodies a combustion device. Such a combustion device may e.g. be used in building heating systems.
The main flow passage 110 has an inlet end 120 with a throat 199, and an outlet end 130 and is illustratively formed along the longitudinal direction of the nozzle body 105. More specifically, the main flow passage 110 in the nozzle body 105 is generally formed as a tubular channel with a smooth inner surface.
Illustratively, the main flow passage 110 has a passage constriction 140 that is arranged between the inlet end 120 and the outlet end 130. The passage constriction 140 represents the region with the smallest diameter of the throat 199.
By way of example, the main flow passage 110 is funnel-shaped between the inlet end 120 and the passage constriction 140 and, thus, having a converging inflow section. Between the passage constriction 140 and the outlet end 130, the main flow passage 110 is illustratively conical and, thus, having a diverging outflow section.
By way of example, at least one bluff body is arranged in the main flow passage 110 between the inlet end 120 and the passage constriction 140, i.e. in the converging inflow section. Illustratively, a plurality of bluff bodies 150 is provided but, however, only a single bluff body is separately labelled with the reference sign 151, for simplicity and clarity of the drawing. In the following description, reference is generally made to the bluff body 151, representative for all respectively provided bluff bodies of the plurality of bluff bodies 150.
The bluff body 151 protrudes preferably from the smooth inner surface of the main flow passage 110 and is - in the illustrated example - attached to, or integrally formed with, the nozzle body 105. In other words, the bluff body 151 is formed as a bump or dent on the otherwise smooth inner surface inside of the main flow passage 110 and, thereby, forms an additional constriction of the main flow passage 110.
However, it should be noted that the bluff body 151 is only illustratively attached to, or integrally formed with the nozzle body 105 to simplify description of an illustrative operation of the Venturi-type mixing nozzle 100 with the bluff body 151 at Fig. 2 and Fig. 3 below. Nevertheless, according to the present invention the bluff body 151 is preferably embodied separate from the nozzle body 105, as described by way of example at Fig. 4 below, and preferentially integrated into a bluff body plate (505 or 605 in Fig. 5 to Fig. 9), as described by way of example at Fig. 5 to Fig. 9 below.
Fig. 2 shows the Venturi-type mixing nozzle 100 of Fig. 1 with the nozzle body 105 that forms exemplarily along its nozzle body central axis 290 the main flow passage 110 having the inlet end 120, the outlet end 130, and the passage constriction 140. Illustratively, the nozzle body central axis 290 is a plane of symmetry.
The passage constriction 140 is arranged between the inlet end 120 and the outlet end 130 for creation of a negative pressure region 125 in the main flow passage 110 during operation of the Venturi-type mixing nozzle 100. The negative pressure region 125 is only by way of example and for illustration purposes delimited by means of two dashed lines.
Preferably, the passage constriction 140 comprises at least one lateral inlet opening. By way of example, a plurality of lateral inlet openings is provided but, however, only two lateral inlet openings are illustrated and separately labelled with the reference signs 220, 221, for simplicity and clarity of the drawing. In the following description, reference is generally made to one or both of the lateral inlet openings 220, 221, representative for all respectively provided lateral inlet openings.
As described above at Fig. 1, the bluff body 151 is preferably arranged in the main flow passage 110 between the inlet end 120 and the passage constriction 140. More specifically, the bluff body 151 is preferably arranged in the main flow passage 110 between the inlet end 120 and the lateral inlet opening 221.
By way of example, one bluff body is provided for each lateral inlet opening. However, at least one bluff body may alternatively also be provided for two or more lateral inlet openings. In other words, it is possible to provide even only a single bluff body for all lateral inlet openings.
The bluff body 151 preferably extends at least partly from the nozzle body 105 and, more particularly, from the smooth inner surface of the main flow passage 110 towards the nozzle body central axis 290, preferentially in radial direction 107 of the main flow passage 110, for creation of an associated low pressure zone during operation of the Venturi-type mixing nozzle 100. A respective low pressure zone that is associated with the bluff body 151 is illustratively labelled with the reference sign 241 and another low pressure zone is illustratively labelled with the reference sign 240. Each one of the low pressure zones 240, 241 preferably extends from its associated lateral inlet opening 220, 221 along the respectively associated bluff body, preferentially in the radial direction 107 of the main flow passage 110.
In an illustrative operation of the Venturi-type mixing nozzle 100, a first fluid 210 enters the main flow passage 110 via the inlet end 120 and a second fluid 230 enters the main flow passage 110 via the lateral inlet openings 220, 221 for being mixed with the first fluid 210 in the main flow passage 110 into a mixed fluid 235. By way of example, the first fluid 210 is air and the second fluid 230 is a combustible gas, e.g. hydrogen gas or a hydrocarbon gas, such as methane. More specifically, the first fluid 210 that enters the main flow passage 110 via the inlet end 120 backs up in the converging section between the inlet end 120 and the passage constriction 140 such that the negative pressure region 125 is created due to an acceleration of the first fluid 210 by means of the nozzle effect. Since the lateral inlet openings 220, 221 open into the passage constriction 140, the second fluid 230 is drawn into the main flow passage 110, where the second fluid 230 is mixed with the first fluid 210 into the mixed fluid 235. Illustratively, the second fluid 230 is guided to the lateral inlet openings 220, 221 via associated support channels 227, 229, which are illustratively arranged at an angle of 90° relative to the nozzle body central axis 290.
By way of example, the bluff body 151 is provided for creation of the low pressure zone 241 in the negative pressure region 125 such that the first fluid 210 has a flow velocity in the low pressure zone 241 that is at least reduced compared to a flow velocity that is otherwise attributed to the first fluid 210 in the negative pressure region 125. More particularly, the bluff body 151 is preferably adapted to ensure that the second fluid 230 is fully surrounded by the first fluid 210 after having entered the main flow passage 110 through the lateral inlet opening 221.
Fig. 3 shows a section of the main flow passage 110 with the throat 199 that is formed by the nozzle body 105 of the Venturi-type mixing nozzle 100 of Fig. 1 and Fig. 2. Illustratively, the bluff body 151 protrudes from the smooth inner surface of the main flow passage 110 at a predetermined position upstream of the lateral inlet opening 220. The bluff body 151 is preferably attached to, or integrally formed with, the nozzle body 105.
Illustratively, the bluff body 151 creates at least partly turbulences of the first fluid 210 flowing around the bluff body 151 and, more particularly, a low pressure with a first degree of turbulences 310 of the first fluid 210. Preferably, the low pressure with the first degree of turbulences 310 of the first fluid 210 is at least created in the negative pressure region 125.
In an illustrative operation of the Venturi-type mixing nozzle 100, the second fluid 230 is drawn through the lateral inlet opening 220 along the bluff body 151 into the main flow passage 110 such that the first fluid 210 flows along the throat 199 and directly surrounds the second fluid 230 downstream of the lateral inlet opening 220. By creating the low pressure with the first degree of turbulences 310 of the first fluid 210 around the second fluid 230, mixing of the first and second fluids 210, 230 is improved.
Fig. 4 shows a Venturi-type mixing nozzle 400 with a nozzle body 405 that forms a main flow passage 410 having an inlet end 420 and a passage constriction 440 that is illustratively provided with a plurality of lateral inlet openings 421. The Venturi-type mixing nozzle 400 as such is shown as one example of an air-gas mixer that may be used in an air-gas mixing unit according to the present invention. For simplicity, the Venturi-type mixing nozzle 400 as such is embodied similar to the Venturi-type mixing nozzle 100 of Fig. 1 to Fig. 3 so that a detailed description of the Venturi-type mixing nozzle 400 may be omitted for brevity and conciseness.
The Venturi-type mixing nozzle 400 is illustratively provided with the plurality of bluff bodies 150 according to Fig. 1. However, for simplicity and clarity of the drawing only the bluff body 151 is separately labelled. Nevertheless, in contrast to the Venturi-type mixing nozzle 100 of Fig. 1 to Fig. 3, the plurality of bluff bodies 150 of the Venturi-type mixing nozzle 400 is neither attached to, nor integrally formed with, the nozzle body 405. Instead, the plurality of bluff bodies 150 is now attached to, or integrally formed with, a bluff body support 450 that is adapted to be mounted to the nozzle body 405. By way of example, the bluff body support 450 is ring-shaped and at least partly funnel-shaped.
Fig. 5 shows in parts (A) and (B) an air-gas mixing unit 500 comprising an air-gas mixer 600. The air-gas mixing unit 500 may embody a combustion device which may e.g. be used in building heating systems. The air-gas mixer 600 may be embodied similar to the Venturi-type mixing nozzle 400 of Figure 4 and, thus, illustratively comprises the nozzle body 405 that forms the main flow passage 410, as well as the plurality of bluff bodies 150 having the bluff body 151, which is neither attached to, nor integrally formed with, the nozzle body 405.
Preferably, the plurality of bluff bodies 150 is now attached to, or integrally formed with, a bluff body plate 505. Illustratively, the bluff body plate 505 is arranged on, and fixed to, an inlet end side 590 of the nozzle body 405.
By way of example, the plurality of bluff bodies 150 with the bluff body 151 forms a first bluff body arrangement 510. For instance, the bluff body 151 is adapted to enable creation of low pressure with a first degree of turbulence of a selected fluid, such as air, in the main flow passage 410. This first bluff body arrangement 510 is illustratively arranged in a first - in Fig. 5, part (A) upper and in Fig. 5, part (B) lower- section 502 of the bluff body plate 505.
Furthermore, the bluff body plate 505 illustratively comprises at least one other plurality of bluff bodies 550 that forms at least one second bluff body arrangement 520. For simplicity and clarity of the drawing, only a single bluff body of the other plurality of bluff bodies 550 is separately labelled with the reference sign 551. For instance, the bluff body 551 is adapted to enable creation of low pressure with a second degree of turbulence of the selected fluid, such as air, in the main flow passage 410. The second bluff body arrangement 520 is illustratively arranged in a second - in Fig. 5, part (A) lower and in Fig. 5, part (B) upper- section 504 of the bluff body plate 505.
By way of example, the first bluff body arrangement 510 is configured for use with a first type of gas, and the second bluff body arrangement 520 is configured for use with a second type of gas. For instance, the first type of gas may be a hydrogen gas, and the second type of gas may be a hydrocarbon gas, such as e.g. methane.
Preferably, the bluff body plate 505 is exchangeable to enable provision of the first bluff body arrangement 510 and/or the second bluff body arrangement 520 with the air-gas mixer 600. Preferentially, the bluff body plate 505 is re-orientable relative to the air-gas mixer 600 to enable positioning of the first bluff body arrangement 510 or the second bluff body arrangement 520 on the inlet end side 590 of the air-gas mixer 600.
According to one aspect, the bluff body plate 505 may at least be flippable between a first position and a second position relative to the air-gas mixer 600. Thus, the first bluff body arrangement 510 may be positioned on the inlet end side 590 of the air-gas mixer 600 in the first position, and the second bluff body arrangement 520 may be positioned on the inlet end side 590 of the air-gas mixer 600 in the second position.
Illustratively, the first bluff body arrangement 510 is positioned on the inlet end side 590 of the air-gas mixer 600 in a position 580 of the bluff body plate 505, as illustrated in Fig. 5, part (A). The bluff body plate 505 may then be flipped as illustrated with an arrow 570 such that the second bluff body arrangement 520 is positioned on the inlet end side 590 of the air-gas mixer 600 in a position 588 of the bluff body plate 505, as illustrated in Fig. 5, part (B).
In the example of Fig. 5, the air-gas mixing unit 500 is shown with a single air-gas mixer, i.e. the air-gas mixer 600, as well as only two different bluff body arrangements, i.e. the bluff body arrangements 510, 520. Thus, the bluff body plate 505 is merely shown with a rectangular shape, by way of example. However, other shapes and overall configurations are likewise contemplated, as described below at Fig 6.
Fig. 6 shows in parts (A) and (B) the air-gas mixing unit 500 of Fig. 5. However, in contrast to Fig. 5 the air-gas mixing unit 500 now illustratively comprises two air-gas mixers 600 and a circular bluff body plate 605 with two first bluff body arrangements 510 and two second bluff body arrangements 520.
According to one aspect, the circular bluff body plate 605 is rotatable between a first position and a second position relative to the two air-gas mixers 600. Thus, the two first bluff body arrangements 510 may be positioned on the two air-gas mixers 600 in the first position, and the two second bluff body arrangements 520 may be positioned on the two air-gas mixers 600 in the second position.
Illustratively, the two first bluff body arrangements 510 are positioned on the two air-gas mixers 600 in a position 680 of the circular bluff body plate 605, as illustrated in Fig. 6, part (A). The circular bluff body plate 605 may then be rotated as illustrated with an arrow 610 around an associated rotation axis 620 such that the two second bluff body arrangements 520 are positioned on the two air-gas mixers 600 in a position 688 of the circular bluff body plate 505, as illustrated in Fig. 6, part (B).
Fig. 7 shows in parts (A) and (B) the air-gas mixing unit 500 of Fig. 5 with the air-gas mixer 600 having the nozzle body 405 that forms the main flow passage 410, as well as with the rectangular bluff body plate 505. The nozzle body 405 is illustratively shown with a supply 710, e.g. a gas supply. The main flow passage 410 is funnel-shaped between the inlet end 420 and the passage constriction 440, as described above at Fig. 4, and, thus, comprises a converging inflow section.
In Fig. 7, part (A), the first bluff body arrangement 510 of the rectangular bluff body plate 505 is arranged at the inlet end 420 of the nozzle body 405. Illustratively, the rectangular bluff body plate 505 is adapted at the first bluff body arrangement 510 to the inlet end 420 of the nozzle body 405 and, thus, comprises a funnel-shaped section 720 that is embodied to comply with the inlet end 420. However, the rectangular bluff body 505 according to Fig. 7, part (A), preferably does not form a throat 810 in the converging inflow section of the main flow passage 410 between the inlet end 420 and the passage constriction 440. Instead, the throat 810 is formed by the nozzle body 405.
In Fig. 7, part (B), the second bluff body arrangement 520 of the rectangular bluff body plate 505 is arranged at the inlet end 420 of the nozzle body 405. However, in contrast to part (A) the rectangular bluff body plate 505 is not adapted at the second bluff body arrangement 520 to the inlet end 420 of the nozzle body 405 and, thus, does not comprise a funnel-shaped section, but merely comprises a flat section 730. Nevertheless, similar to part (A) the rectangular bluff body 505 according to Fig. 7, part (B), preferably does not form the throat 810 in the converging inflow section of the main flow passage 410 between the inlet end 420 and the passage constriction 440, as the throat 810 is formed by the nozzle body 405.
Fig. 8 shows in parts (A) to (C) the air-gas mixing unit 500 of Fig. 7 with the air-gas mixer 600 having the nozzle body 405 that forms the main flow passage 410, as well as with the rectangular bluff body plate 505. The nozzle body 405 is shown with the supply 710. The main flow passage 410 comprises the inlet end 420. However, in contrast to Fig. 7, the main flow passage 410 does not comprise the passage constriction 440 and, thus, does not comprise a converging inflow section.
In Fig. 8, part (A), the rectangular bluff body plate 505 is provided at the first bluff body arrangement 510 with the funnel-shaped section 720 according to Fig. 7, part (A). Preferably, the rectangular bluff body plate 505 with the funnel-shaped section 720 forms the throat 810 at the inlet end 420.
In Fig. 8, part (B), the rectangular bluff body plate 505 is provided at the second bluff body arrangement 520 with the flat section 730 according to Fig. 7, part (B). Preferably, the rectangular bluff body plate 505 with the flat section 730 forms the throat 810 at the inlet end 420.
In Fig. 8, part (C), the rectangular bluff body plate 505 is again provided at the second bluff body arrangement 520 with the flat section 730 according to Fig. 7, part (B). Preferably, the rectangular bluff body plate 505 with the flat section 730 forms a throat 820 at the inlet end 420, which is illustratively less constricting than the throat 810 of Fig. 8, part (B).
Fig. 9 shows the air-gas mixing unit 500 of Fig. 8, part (B), with the air-gas mixer 600 having the nozzle body 405 that forms the main flow passage 410, as well as with the rectangular bluff body plate 505. The nozzle body 405 is shown with the supply 710 and the plurality of lateral inlet openings comprising, by way of example, the lateral inlet openings 220 of Fig. 2 and 421 of Fig. 4. The main flow passage 410 comprises the inlet end 420.
However, in contrast to Fig. 8, part (B), the rectangular bluff body plate 505 is provided with a bluff body arrangement 910 that is preferably configured to impede at least one of the plurality of lateral inlet openings. By way of example, the bluff body arrangement 910 is configured to impede the lateral inlet opening 220 by enabling a high velocity flow of the fluid, e. g. the air, that enters the main flow passage 410 via the rectangular bluff body plate 505. However, the bluff body arrangement 910 is preferably further adapted to enable creation of low pressure with a first degree of turbulence of the fluid in the main flow passage 410 around the lateral inlet opening 421 in a low pressure zone 920.
Fig. 10 shows the air-gas mixer 600 of Fig. 5 and Fig. 6 with the bluff body arrangement 510. However, in contrast to Fig. 5 and Fig. 6 the bluff body arrangement 510 comprises a plurality of bluff bodies 1050 with differing shapes. For instance, four different bluff bodies 1010, 1020, 1030, 1040 are shown, which may comprise different sizes and inclination angles.
Preferably, the shape of the bluff bodies 1010, 1020, 1030, 1040 is optimized to control size of a respective low pressure and low velocity zone of a respective fluid flow, e.g. air flow, and a respective degree of turbulence induced in the fluid flow. The optimization improves fluid mixing and reduces pressure loss across the air-gas mixer 600 dependent on the characteristics of the gas.

Claims

An air-gas mixing unit (500) comprising an air-gas mixer (600) and a bluff body plate (505), wherein the air-gas mixer (600) comprises a main flow passage (410) for mixing a first fluid (210) with a second fluid (230) into a mixed fluid (235), the main flow passage (410) comprising an inlet end (120) for inlet of the first fluid (210), at least one lateral inlet opening (220, 221) for inlet of the second fluid (230), and an outlet end (130) for outlet of the mixed fluid (235), and wherein the bluff body plate (505) comprises at least one first bluff body arrangement (510) with at least one first bluff body (151), and at least one second bluff body arrangement (520) with at least one second bluff body (551), the at least one first bluff body (151) being adapted to enable creation of low pressure with a first degree of turbulence (310) of the first fluid (210) in the main flow passage (410) around the at least one lateral inlet opening (220, 221), and the at least one second bluff body (551) being adapted to enable creation of low pressure with a second degree of turbulence of the first fluid (210) in the main flow passage (410) around the at least one lateral inlet opening (220, 221).
The air-gas mixing unit of claim 1, wherein the bluff body plate (505) is exchangeable to enable provision of different bluff body arrangements which are configured for use with different types of gases, wherein the different bluff body arrangements comprise different properties of optimizing mixing and pressure losses.
The air-gas mixing unit of claim 1 or 2, wherein the bluff body plate (505) is re-orientable relative to the air-gas mixer (600) to enable positioning of the at least one first bluff body arrangement (510) or the at least one second bluff body arrangement (520) at the inlet end (120) of the air-gas mixer (600).
The air-gas mixing unit of claim 3, wherein the bluff body plate (505) is rotatable or flippable between a first position (580) and a second position (588) relative to the air-gas mixer (600), wherein the at least one first bluff body arrangement (510) is positioned at the inlet end (120) of the air-gas mixer (600) in the first position (580), and wherein the at least one second bluff body arrangement (520) is positioned at the inlet end (120) of the air-gas mixer (600) in the second position (588).
The air-gas mixing unit of any one of the preceding claims, wherein at least one of the at least one first bluff body arrangement (510) and the at least one second bluff body arrangement (520) defines a throat (810) of the air-gas mixer (600) at the inlet end (120).
The air-gas mixing unit of any one of the preceding claims, wherein the air-gas mixer (600) comprises a plurality of lateral inlet openings (220, 221), and wherein at least one of the at least one first bluff body arrangement (910) and the at least one second bluff body arrangement (520) is configured to impede at least one of the plurality of lateral inlet openings (220, 221).
The air-gas mixing unit of claim 6, wherein the at least one of the at least one first bluff body arrangement (910) and the at least one second bluff body arrangement (520) that is configured to impede the at least one of the plurality of lateral inlet openings (220, 221) is embodied to enable a high velocity flow of the first fluid (210) at the at least one of the at least one first bluff body arrangement (910) and the at least one second bluff body arrangement (520).
The air-gas mixing unit of any one of the preceding claims, wherein the at least one first bluff body (151) of the at least one first bluff body arrangement (510) and the at least one second bluff body (551) of the at least one second bluff body arrangement (520) are attached to, or integrally formed with, the bluff body plate (500).
The air-gas mixing unit of any one of the preceding claims, wherein the at least one first bluff body arrangement (510) comprises a plurality of first bluff bodies (1050) with differing shapes.
The air-gas mixing unit of any one of the preceding claims, wherein the air-gas mixer (600) is a Venturi-type mixing nozzle with a nozzle body (405) that forms the main flow passage (410).