Air-gas mixer for mixing an air stream with a gas stream

Abstract

In an air-gas mixer (220) for mixing an air stream (111) with a gas stream (119) to produce a combustible air-gas mixture (130), wherein the air-gas mixer (220) has a tubular mixer body (224) extending along a longitudinal axis (222) from an inlet end (226) for the air stream (111) to flow into the tubular mixer body (224) to an outlet end (228) for the combustible air-gas mixture (130) to flow out of the tubular mixer body (224), and wherein a gas inlet opening (319) is provided for admitting the gas stream (119), a thermally deformable adjusting element (350) is provided to control the flow rate of the gas stream (119) through the gas inlet opening (319) into the to adjust the tubular mixer body (224) depending on the thermal expansion of the thermally deformable adjusting element (350).

Description

State of the art

[0001] The present invention relates to an air-gas mixer for mixing an air stream with a gas stream to produce a combustible air-gas mixture.

[0002] An air-gas mixer for mixing an air stream with a gas stream to produce a combustible air-gas mixture is known from the prior art. The air-gas mixer has an air inlet opening for admitting the air stream and a gas inlet opening or a gas guide gap for admitting the gas stream.

[0003] Such an air-gas mixer can be used in an air-gas mixing unit of an air-gas mixture combustion plant, which has a combustion unit for burning the combustible air-gas mixture. During combustion, the occurrence of an unwanted flame flashback must be prevented in order to effectively avoid potential damage to the air-gas mixing unit or the air-gas mixer. Disclosure of the invention

[0004] The present invention relates to an air-gas mixer for mixing an air stream with a gas stream to produce a combustible air-gas mixture. The air-gas mixer has an air inlet opening for admitting the air stream and a gas inlet opening or gas guide gap for admitting the gas stream. According to the invention, a thermally deformable adjusting element is provided to adjust the respective flow rate of the gas stream through the gas inlet opening or the gas guide gap as a function of the thermal expansion of the thermally deformable adjusting element.

[0005] By adjusting the respective flow rate of the gas through the gas inlet or gas guide gap depending on the thermal expansion of the thermoformable adjusting element, a reduction in the respective flow rate of the gas can be achieved, for example, when the thermoformable adjusting element heats up. In this case, the thermoformable adjusting element can, for instance, expand thermally when heated to such an extent that the gas inlet or gas guide gap is covered or closed proportionally to the temperature increase.

[0006] This reduces the amount of gas in the combustible air-gas mixture, resulting in cleaner combustion with longer flames and reduced burner load, which in turn lowers the burner temperature. This advantageously prevents unwanted flame flashback, at least to a significant degree, by reducing the gas flow rate.

[0007] Preferably, the thermally deformable adjusting element is heated in response to the burner temperature of a combustion unit associated with the air-gas mixer, thereby increasing the pressure drop at the gas inlet opening. This is achieved without the need for active temperature measurement and / or flow rate reduction via an actuator. This is particularly advantageous when using hydrogen as the gas to be mixed.

[0008] According to a first embodiment, an air-gas mixer for mixing an air stream with a gas stream to produce a combustible air-gas mixture comprises a tubular mixer body extending along a longitudinal axis from an inlet end for the air stream to flow into the tubular mixer body to an outlet end for the combustible air-gas mixture to flow out of the tubular mixer body, wherein a gas inlet opening is provided for admitting the gas stream. A thermally deformable adjusting element is provided to adjust the respective flow rate of the gas stream through the gas inlet opening into the tubular mixer body as a function of the thermal expansion of the thermally deformable adjusting element.

[0009] Thus, an air-gas mixer with a stable and robust tubular mixer body can be provided, in which a suitable thermally deformable adjusting element can be easily arranged.

[0010] Preferably, the tubular mixer body forms a Venturi nozzle and has a constriction along the longitudinal axis between the inlet end and the outlet end, with the gas inlet opening being located at the constriction.

[0011] This allows for the provision of a simple and efficient mixer body.

[0012] The thermally deformable adjusting element is preferably tongue-shaped and extends from the gas inlet opening towards the outlet end.

[0013] By extending the thermally deformable adjusting element downstream of the gas inlet opening in the tubular mixer body, it is possible to position the element relatively close to the combustion unit in an air-gas mixture combustion system. This allows the thermally deformable adjusting element to heat up and expand accordingly during operation of the air-gas mixture combustion system, thus directly regulating the gas flow rate in relation to the combustion unit's operating temperature.

[0014] Preferably, the thermally deformable adjusting element is designed to expand when heated and to close the gas inlet opening proportionally to the heating, in order to reduce the respective flow rate of the gas stream through the gas inlet opening into the tubular mixer body when heated.

[0015] This allows for a simple and efficient adjustment of the respective flow rate of the gas stream through the gas inlet opening into the tubular mixer body.

[0016] Preferably, the thermally deformable adjusting element is bi-metallic and has a cover section for closing the gas inlet opening.

[0017] This allows for the provision of a simple and reliable, thermally deformable adjustment element.

[0018] According to a second embodiment, an air-gas mixer for mixing an air stream with a gas stream to produce a combustible air-gas mixture comprises an air guide element and an air-gas mixture guide element, wherein the air guide element extends along a longitudinal axis of the air-gas mixer from an inlet end for the air stream to flow into the air guide element to an outlet end for the air stream to flow out, wherein the air-gas mixture guide element extends along the longitudinal axis from an inlet end for the gas stream to flow into the air-gas mixture guide element to an outlet end for the air-gas mixture to flow out, and wherein the outlet end of the air guide element engages at least sectionally with the air-gas mixture guide element at the inlet end of the air-gas mixture guide element to form a gas guide gap with the air-gas mixture guide element.A thermally deformable adjusting element is provided to adjust the respective flow rate of the gas stream through the gas guide gap depending on a thermal expansion of the thermally deformable adjusting element.

[0019] Thus, a compact and space-saving air-gas mixer with an air guide element and an air-gas mixture guide element can be provided, in which a suitable thermally deformable adjustment element can be easily arranged.

[0020] Preferably, the thermally deformable adjusting element is arranged at the outlet end of the air guide element.

[0021] Thus, the thermally deformable adjusting element can be easily arranged in the air-gas mixer.

[0022] Preferably, the gas guide gap is annular in shape.

[0023] This allows a uniform gas flow to enter the air-gas mixture guide element.

[0024] Preferably, the thermally deformable adjusting element is designed in a ring shape.

[0025] Such a ring-shaped design of the thermally deformable adjusting element enables precise adaptation of the thermally deformable adjusting element to the ring-shaped gas guide gap.

[0026] Preferably, the thermally deformable adjusting element is designed to expand more when heated than the air guide element and / or the air-gas mixture guide element in order to narrow the gas guide gap proportionally to the heating.

[0027] Thus, an efficient adjustment of the respective flow rate of the gas stream through the gas guide gap can be achieved in a simple manner, depending on the thermal expansion of the thermally deformable adjusting element.

[0028] Preferably, the air-gas mixture guide element is made of stainless steel and the thermally deformable adjusting element is made of aluminum.

[0029] Thus, both a robust and stable air-gas mixture guide element and a robust and stable, thermally deformable adjustment element can be provided.

[0030] Alternatively, the air guide element and the air-gas mixture guide element can be made of metal, and the thermally deformable adjustment element can be made of plastic and / or rubber.

[0031] This allows, in particular, the provision of a cost-effective, thermally deformable adjustment element. Brief description of the drawings

[0032] The invention is explained in more detail below with reference to exemplary embodiments illustrated in the drawings. The drawings show: Fig. 1 a schematic view of an air-gas mixture combustion plant with an air-gas mixing unit, Fig. 2 a schematic view of the air-gas mixture combustion plant of Fig. 1 with the air-gas mixing unit of Fig. 1, which has an air-gas mixer according to a first embodiment, Fig. 3 an enlarged section of the air-gas mixer of Fig. 2, Fig. 4 the air-gas mixer rotated by 90° from Fig. 3, Fig. 5 a perspective view of the air-gas mixer of Fig. 3 and Fig. 4, and Fig. 6 a sectional view of an air-gas mixer according to a second embodiment. Description of the exemplary implementations

[0033] In the figures, elements with the same or comparable function are given identical reference symbols and described in detail only once.

[0034] Fig. Figure 1 shows an exemplary air-gas mixture combustion plant 100 for burning a combustible air-gas mixture 130. The air-gas mixture combustion plant 100 can be used, for example, in any application that requires a heat exchanger. For instance, the air-gas mixture combustion plant 100 can be used in a building heating system or a water heater.

[0035] For illustrative purposes, the air-gas mixture combustion plant 100 has an airtight casing 102 or a so-called air box for room air-independent operation of the air-gas mixture combustion plant 100. Alternatively, however, the airtight casing 102 can be omitted to enable room air-dependent operation of the air-gas mixture combustion plant 100.

[0036] As in Fig. As shown in Figure 1, the air-gas mixture combustion plant 100, illustratively the airtight casing 102, can comprise an external air inlet 105 for supplying air 111, an external gas inlet 107 for supplying gas 119, and an exhaust outlet 150 for discharging exhaust gas 152. The gas 119 is supplied to the air-gas mixing unit 110 for mixing with air and can be any gas, such as hydrogen, propane, butane, methane, liquefied petroleum gas, etc., particularly preferably hydrogen. Furthermore, the air-gas mixture combustion plant 100 can include an air-gas mixing unit 110 for mixing air with gas, a combustion unit 120, and a heat exchanger 140, all of which can be arranged in the airtight casing 102.

[0037] The air-gas mixing unit 110 is preferably designed to mix the air 111 with the gas 119 to produce the flammable air-gas mixture 130. Preferably, the flammable air-gas mixture 130 is a homogeneous mixture of the air 111 and the gas 119. Preferably, the air-gas mixing unit 110 is designed as a single-stage air-gas mixing unit 110, as shown in Fig. 2 shown.

[0038] The air-gas mixing unit 110 includes, for illustrative purposes, an air inlet 113, which, by way of example, receives air 111 from the outer air inlet 105 of the air-gas mixture combustion plant 100 and supplies it to the air-gas mixing unit 110 as an airflow. For the sake of simplicity, the airflow will also be referred to as 111 below. Furthermore, the air-gas mixing unit 110 includes a gas inlet 117, which receives gas 119 from the outer gas inlet 107 and supplies it to the air-gas mixing unit 110 as a gasflow. For the sake of simplicity, the gasflow will also be referred to as 119 below.

[0039] For illustrative purposes, the flammable air-gas mixture 130 is formed in the single-stage air-gas mixing unit 110 from the air flow 111 supplied by the air inlet 113 and the gas flow 119 supplied by the gas inlet 117. According to the invention, the flammable air-gas mixture 130 is mixed by an air-gas mixer (220 in Fig. 3 to Fig. 5, or 600 in Fig. 6) generated, as in Fig. 3 to Fig. 6 described. The combustible air-gas mixture 130 is supplied to the combustion unit 120 via an air-gas outlet 132.

[0040] For example, the combustion unit 120 is provided with a burner surface 124, which is preferably arranged downstream of the air-gas mixing unit 110 such that the combustible air-gas mixture 130, which is formed in the single-stage air-gas mixing unit 110, flows towards the burner surface 124. If desired, a fan can drive the combustible air-gas mixture 130 towards the burner surface 124.

[0041] The combustible air-gas mixture 130 is combusted by the combustion unit 120 and, in particular, at the burner surface 124. The heat exchanger 140 can transfer the heat generated by the combustion at the burner surface 124 to another medium. For example, the heat exchanger 140 can transfer the heat generated at the burner surface 124 to water in a water circuit. The exhaust outlet 150 can evacuate the exhaust gas 152 from the air-gas mixture combustion unit 100.

[0042] Fig. Figure 2 shows the air-gas mixture combustion plant 100 for burning the combustible air-gas mixture 130. Fig. 1. As with Fig. As described in Figure 1, the air-gas mixture combustion plant 100 includes, for example, the airtight casing 102, in which, for illustrative purposes, the combustion unit 120 and the single-stage air-gas mixing unit 110 are located. Fig. 1 for mixing air with gas to produce the combustible air-gas mixture 130. The single-stage air-gas mixing unit 110 comprises according to Fig. 1 the air inlet 113 for supplying the airflow 111, the gas inlet 117 for supplying the gasflow 119, and the air-gas outlet 132 for supplying the combustible air-gas mixture 130 to the combustion unit 120. For illustrative purposes, the air-gas outlet 132 includes an air-gas mixture guide element 290, which connects the air-gas mixing unit 110 to the combustion unit 120 and can be an integral part of the combustion unit 120.

[0043] Airflow 111 is supplied to an air-gas mixer 220, to which gasflow 119 is also supplied via a gas valve 210. For illustrative purposes, the gas valve 210 is arranged downstream of the gas inlet 117 to regulate the gasflow 119. The gas valve 210 optionally has a reference air pressure port 212. Based on a reference airflow supplied to the reference air pressure port 212, which is preferably branched off from airflow 111 and is therefore also designated with the reference numeral 111 for simplicity, the gas valve 210 regulates the gasflow 119 supplied by the gas inlet 117 and supplies it to the air-gas mixer 220 via a gas supply channel 227. The air-gas mixer 220 mixes the air flow 111 with the gas flow 119 regulated by the gas valve 210 to produce the combustible air-gas mixture 130.

[0044] The gas valve 210 can, for example, be a pneumatic gas valve that regulates the gas flow 119 based on the pressure of the reference air flow 111 applied to the reference air pressure port 212. The gas valve 210 can be configured to adjust the outlet pressure of the gas flow 119 to the pressure of the reference air flow 111 applied to the reference air pressure port 212.

[0045] For illustrative purposes, a fan 270 is arranged upstream of the air-gas mixer 220. The fan 270 preferably serves to draw in the airflow 111 and to supply the drawn-in airflow 111 to the air-gas mixer 220. By using the fan 270, the airflow 111 can be supplied to the air-gas mixer 220 in a simple, relatively homogeneous manner and at a predetermined intensity. Alternatively, instead of arranging the fan 270 upstream of the air-gas mixer 220, it can also be arranged downstream of the air-gas mixer 220.

[0046] Fig. Figure 3 shows a section of the air-gas mixer 220 of the single-stage air-gas mixing unit 110. Fig. 2, which are in Fig. 2 is connected to the combustion unit 120 via the air-gas mixture guide element 290. The airflow 111 is supplied to the air-gas mixer 220, which for illustrative purposes has a longitudinal axis 222. Furthermore, the air-gas mixer 220 is designed according to Fig. 2 with the gas supply channel 227 for supplying the gas flow 119, in particular the gas flow from the gas valve 210 Fig. 2 regulated gas flow 119, connected. The gas supply channel 227 may have a flow restrictor or a throttle 327.

[0047] The air-gas mixer 220 is designed to mix the air stream 111 with the gas stream 119 to produce the combustible air-gas mixture 130. Fig. 2 a tubular mixer body 224, which is in Fig. Figure 3 is slightly simplified. A gas inlet opening 319 is provided for admitting the gas flow 119.

[0048] For illustrative purposes, the tubular mixer body 224 extends along the longitudinal axis 222 from an inlet end 226 for the airflow 111 into the tubular mixer body 224 to an outlet end 228 for the flammable air-gas mixture 130 to flow out of the tubular mixer body 224. Preferably, the tubular mixer body 224 forms a Venturi nozzle. Here, the tubular mixer body 224 preferably has a constriction 240 between the inlet end 226 and the outlet end 228 along the longitudinal axis 222, at which the tubular mixer body 224 has, for illustrative purposes, a minimum inner diameter.

[0049] Preferably, the gas inlet opening 319 for introducing the gas flow 119 is arranged at or in the region of the constriction 240. By way of example, the gas inlet opening 319 is formed by the gas supply channel 227, which is connected to the tubular mixer body 224 at or in the region of the constriction 240.

[0050] According to the invention, a thermally deformable adjusting element 350 is provided to adjust the flow rate of the gas stream 119 through the gas inlet opening 319 into the tubular mixer body 224 as a function of the thermal expansion of the thermally deformable adjusting element 350. For illustrative purposes, the thermally deformable adjusting element 350 is tongue-shaped and extends from the gas inlet opening 319 towards the outlet end 228.

[0051] Preferably, the thermally deformable adjusting element 350 is designed to expand when heated and to close the gas inlet opening 319 proportionally to the temperature increase, in order to reduce the respective flow rate of the gas stream 119 through the gas inlet opening 319 into the tubular mixer body 224 when heated. The thermally deformable adjusting element 350 can, for example, be bimetallic and have a cover section 450 for closing the gas inlet opening 319. The cover section 450 can, for example, move towards the gas inlet opening 319 when the thermally deformable adjusting element 350 is heated, as indicated by arrow 360, in order to at least partially cover or close it and thus reduce the respective flow rate of the gas stream 119 through the gas inlet opening 319 into the tubular mixer body 224.Alternatively or additionally, the cover section 450 can preferably also move in the direction of the longitudinal axis 222 above the gas inlet opening 319 in order to cover or close it in order to reduce the respective flow rate of the gas stream 119 through the gas inlet opening 319 into the tubular mixer body 224.

[0052] Preferably, the thermally deformable adjusting element 350 is used as a component of the air-gas mixer 220 of the single-stage air-gas mixing unit 110. Fig. 2 at least in certain areas and relatively close to the combustion unit 120 of Fig. 2 of the air-gas mixture combustion plant 100 of Fig. 2 arranged. Thus, it is advantageous to be able to heat the thermally deformable adjusting element 350 in response to heating or depending on a respective temperature of the combustion unit 120. Fig. 2, so that a flow rate of the gas stream 119 set by the thermally deformable adjusting element 350 through the gas inlet opening 319 into the tubular mixer body 224 is determined by the respective temperature of the combustion unit 120. Fig. 2 depends on or is proportional to it.

[0053] Fig. Figure 4 shows the 220 air-gas mixer from Fig. 3, which compared to Fig. Figure 3 illustrates that the gas inlet opening 319 formed by the gas supply channel 227 on the tubular mixer body 224 is rotated by 90°. Furthermore, it illustrates Fig. 4 also the exemplary tongue-shaped, thermally deformable adjusting element 350 with the cover section 450, which essentially covers or closes the gas inlet opening 319 for illustrative purposes.

[0054] Fig. Figure 5 shows the 220 air-gas mixer from Fig. Figure 3 shows a partially transparent perspective view to further illustrate the gas inlet opening 319 formed by the gas supply channel 227, which is at least substantially covered or closed by the exemplary tongue-shaped, thermally deformable adjusting element 350 with the cover section 450. Here, the respective covering, as described above, preferably depends on a momentary heating of the thermally deformable adjusting element 350, with the gas inlet opening 319 preferably being covered or closed more completely the warmer the thermally deformable adjusting element 350 is.

[0055] Fig. Figure 6 shows a section of an air-gas mixer 600, which replaces the air-gas mixer 220. Fig. 2 to Fig. 5 in the single-stage air-gas mixing unit 110 of Fig. 2, which are in Fig. 2, which is connected to the combustion unit 120 via the air-gas mixture guide element 290, can be used. Accordingly, the air flow 111 and the gas flow 119 are also supplied to the air-gas mixer 600, which for illustrative purposes has a longitudinal axis 622.

[0056] Similar to the 220 air-gas mixer from Fig. 2 to Fig. 5 The air-gas mixer 600 serves to mix the air stream 111 with the gas stream 119 to produce the combustible air-gas mixture 130 of Fig. 2 to Fig. 5. For this purpose, the air-gas mixer 600 has an air guide element 610 and the air-gas mixture guide element 290. Fig. 2 up.

[0057] The air guide element 610 extends along the longitudinal axis 622 of the air-gas mixer 600 from an inlet end 612 for the airflow 111 to flow into the air guide element 610 to an outlet end 615 for the airflow 111 to flow out. The air guide element 610 is preferably funnel-shaped, at least in some areas.

[0058] The air-gas mixture guide element 290 extends along the longitudinal axis 622 from an inlet end 692 for the inflow of the gas stream 119 into the air-gas mixture guide element 290 to an outlet end 695 for the outlet of the air-gas mixture 130. The outlet end 615 of the air guide element 610 engages at least partially with the air-gas mixture guide element 290 at the inlet end 692 in order to form a gas guide gap 620 with the air-gas mixture guide element 290 through which the gas stream 119 can flow into the air-gas mixture guide element 290.

[0059] According to the invention, a thermally deformable adjusting element 650 is provided to adjust the respective flow rate of the gas stream 119 through the gas guide gap 620 as a function of the thermal expansion of the thermally deformable adjusting element 650. Preferably, the thermally deformable adjusting element 650 is arranged at the outlet end 615 of the air guide element 610, but alternatively, it can also be arranged at another suitable location in the gas guide gap 620.

[0060] Preferably, the gas guide gap 620 is annular. To enable this, preferably at least the outer circumference of the air guide element 610 and the inner circumference of the air-gas mixture guide element 290 in the region of the gas guide gap 620 are annular. In such a configuration, the thermally deformable adjusting element 650 can also be annular.

[0061] For illustrative purposes, the thermo-deformable adjusting element 650 is designed to expand more when heated than the air guide element 610 and / or the air-gas mixture guide element 290, in order to narrow the gas guide gap 620 proportionally to the heating. To enable this, the air-gas mixture guide element 290 can be made of stainless steel, whereas the thermo-deformable adjusting element 650 is made of aluminum. Alternatively, the air guide element 610 and the air-gas mixture guide element 290 can be made of metal, whereas the thermo-deformable adjusting element 650 is made of plastic and / or rubber.

[0062] A narrowing of the gas guide gap 620 can be achieved, in the case of an annular design of the thermally deformable adjusting element 650, by a radially outward expansion of the thermally deformable adjusting element 650. This is illustrated by an arrow 690.

[0063] The thermally deformable adjusting element 650 is preferably used as a component of the air-gas mixer 600 when used with the single-stage air-gas mixing unit 110. Fig. 2 at least in certain areas and relatively close to the combustion unit 120 of Fig. 2 of the air-gas mixture combustion plant 100 of Fig. 2 arranged. Thus, it is advantageous to be able to heat the thermally deformable adjusting element 650 in response to heating or depending on a respective temperature of the combustion unit 120. Fig. 2, so that a flow rate of the gas stream 119 set by the thermally deformable adjusting element 650 through the gas guide gap 620 depends on the respective temperature of the combustion unit 120. Fig. 2 depends.

[0064] It should be noted at this point that the Fig. 3 to Fig. The embodiments of the thermally deformable adjusting elements 350, 650 described in Section 6 are merely exemplary and are not to be understood as limiting the invention. Rather, the invention relates generally to an application of thermally deformable adjusting elements for regulating the flow rate of a supplied gas stream. For example, in the embodiment according to Section 6, the following can be used: Fig. 6 instead of the thermally deformable adjusting element 650, the material selection for the air guide element 610 and the air-gas mixture guide element 290 shall be such that the air guide element 610 expands more when heated than the air-gas mixture guide element 290, so that a required narrowing of the gas guide gap 620 can be achieved, etc.

Claims

[1] Air-gas mixer (220) for mixing an air stream (111) with a gas stream (119) to produce a combustible air-gas mixture (130), comprising a tubular mixer body (224) extending along a longitudinal axis (222) from an inlet end (226) for the air stream (111) to flow into the tubular mixer body (224) to an outlet end (228) for the combustible air-gas mixture (130) to flow out of the tubular mixer body (224), wherein a gas inlet opening (319) is provided for letting in the gas stream (119), characterized by , that a thermally deformable adjusting element (350) is provided to adjust a respective flow rate of the gas stream (119) through the gas inlet opening (319) into the tubular mixer body (224) depending on a thermal expansion of the thermally deformable adjusting element (350). [2] Air-gas mixer according to claim 1, wherein the tubular mixer body (224) forms a Venturi nozzle and has a constriction (240) along the longitudinal axis (222) between the inlet end (226) and the outlet end (228), and wherein the gas inlet opening (319) is arranged at the constriction (240). [3] Air-gas mixer according to claim 1 or 2, wherein the thermally deformable adjusting element (350) is tongue-shaped and extends from the gas inlet opening (319) towards the outlet end (228). [4] Air-gas mixer according to one of the preceding claims, wherein the thermally deformable adjusting element (350) is designed to expand when heated and to close the gas inlet opening (319) proportionally to the heating in order to reduce the respective flow rate of the gas stream (119) through the gas inlet opening (319) into the tubular mixer body (224) when heated. [5] Air-gas mixer according to claim 4, wherein the thermally deformable adjusting element (350) is bi-metallic and has a cover section (450) for closing the gas inlet opening (319). [6] Air-gas mixer (600) for mixing an air stream (111) with a gas stream (119) to produce a combustible air-gas mixture (130), comprising an air guide element (610) and an air-gas mixture guide element (290), wherein the air guide element (610) extends along a longitudinal axis (622) of the air-gas mixer (600) from an inlet end (612) for the air stream (111) to flow into the air guide element (610) to an outlet end (615) for the air stream (111) to flow out, wherein the air-gas mixture guide element (290) extends along the longitudinal axis (622) from an inlet end (692) for the gas stream (119) to flow into the air-gas mixture guide element (290) to an outflow end (695) extends to the outflow of the air-gas mixture (130), and wherein the outflow end (615) of the air guide element (610) engages at least sectionally in the air-gas mixture guide element (290) at the inflow end (692) of the air-gas mixture guide element (290),to form a gas guiding gap (620) with the air-gas mixture guiding element (290), , characterized by , that a thermally deformable adjusting element (650) is provided to adjust a respective flow rate of the gas stream (119) through the gas guide gap (620) depending on a thermal expansion of the thermally deformable adjusting element (650). [7] Air-gas mixer according to claim 6, wherein the thermally deformable adjusting element (650) is arranged at the outflow end (615) of the air guide element (610). [8] Air-gas mixer according to claim 6 or 7, wherein the gas guide gap (620) is annular. [9] Air-gas mixer according to one of claims 6 to 8, wherein the thermally deformable adjusting element (650) is ring-shaped. [10] Air-gas mixer according to one of claims 6 to 9, wherein the thermally deformable adjusting element (650) is designed to expand more when heated than the air guide element (610) and / or the air-gas mixture guide element (290) in order to narrow the gas guide gap (620) proportionally to the heating. [11] Air-gas mixer according to any one of claims 6 to 10, wherein the air-gas mixture guide element (290) is made of stainless steel, and wherein the thermally deformable adjusting element (650) is made of aluminium. [12] Air-gas mixer according to any one of claims 6 to 10, wherein the air guide element (610) and the air-gas mixture guide element (290) are made of metal, and wherein the thermally deformable adjusting element (650) is made of plastic and / or rubber.

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