Exhaust gas heating device for combustion engines, in particular for marine engines

Abstract

The invention relates to an exhaust gas heating device (10), in particular for the exhaust gas aftertreatment of the exhaust gas from ship engines, comprising an inner tube (16) having an exhaust gas inlet (14) and a transfer opening (24), between which a heating channel (26) is formed, a burner (20) associated with the heating channel (26), and an outer tube (12) surrounding the inner tube (16), such that a flow channel (30) is formed from the transfer opening (24) of the inner tube (16) to an outlet (18). The invention further relates to an exhaust gas aftertreatment system with a diesel particulate filter and a corresponding exhaust gas heating device (10).

Description

[0001] The invention relates to an exhaust gas heating device, in particular for the exhaust gas aftertreatment of the exhaust gas of ship engines, comprising an inner tube having an exhaust gas inlet and an overflow opening, between which a heating channel is formed, a burner associated with the heating channel, and an outer tube surrounding the inner tube.

[0002] Such an exhaust gas heating device can be used to heat the exhaust gas of an internal combustion engine, thereby bringing a downstream exhaust gas aftertreatment device to operating temperature in a comparatively short time during a cold engine start. If the exhaust gas aftertreatment device is a particulate filter, the exhaust gas heating device can be used to trigger regeneration of the particulate filter by raising the temperature of the exhaust gas flowing through the particulate filter to the ignition temperature of the deposited particles.

[0003] Exhaust gas heating devices are known in which the exhaust gas is heated with a burner. A burner tube extends into a straight exhaust line. The exhaust gas and the hot burner gases are swirled together using a continuous mixer. To prevent the burner tube from overheating, the cold exhaust gas is directed to the burner tube before it is heated to cool it. The disadvantage of such exhaust gas heating devices is that they require a relatively large amount of space for the mixing process and have limited installation flexibility, as different components are required for different mounting positions.

[0004] EP 2 713 022 A1 discloses a heating device with a burner, which is used in an exhaust gas purification system. The burner has a tubular flame stabilizer and a recirculation unit.

[0005] Another system is known from JP 2007 146700 A.

[0006] It is the object of the invention to provide an exhaust gas heating device which has a compact design and a high degree of installation flexibility.

[0007] The problem is solved by an exhaust gas heating device having an inner tube having an exhaust gas inlet and an overflow opening, between which a heating channel is formed, a burner assigned to the heating channel, and an outer tube surrounding the inner tube so that a flow channel is formed from the overflow opening of the inner tube to an outlet arranged on the outer tube. The exhaust gas inlet, the overflow opening, and the outlet are arranged such that the flow direction of the exhaust gas of an internal combustion engine from the exhaust gas inlet to the overflow opening runs, at least in sections, opposite to the flow direction from the overflow opening to the outlet. This nested arrangement achieves a number of advantages: The design is technically simple, but the deflection between the inner and outer tubes alone results in good turbulence and thus good mixing of fuel gas and exhaust gas.The exhaust outlet can be arranged in different positions with little effort, without compromising its operating principle and without requiring numerous component modifications. The use of the inner tube ensures that the outer tube does not come into contact with the burner flame. Therefore, the outer tube does not need to be made of a high-temperature-resistant material, and lower insulation requirements can be imposed. Finally, it ensures that the inner tube does not overheat, as exhaust gas flows around it on the outside and is thus cooled.

[0008] In one embodiment of the invention, the burner is designed so that the flame it generates is shorter than the distance from the burner to the overflow opening. This ensures that only the inner tube can come into contact with the burner flame; the outer tube behind it cannot have direct contact with the burner flame.

[0009] The inner tube can be provided with a pre-combustion chamber located at a greater distance from the overflow opening than the exhaust gas inlet, with the burner being arranged at the pre-combustion chamber. This places the flame root of the burner flame outside of the turbulent flow area at the exhaust gas inlet. Additionally, the flame root is protected by the pre-combustion chamber. This results in a stable, undisturbed, and easily controllable burner flame.

[0010] In one embodiment of the invention, a swirl body is provided to swirl and redirect the exhaust gas in the flow channel. This swirl effect improves the mixing of the exhaust gas with the hot burner gases, thereby achieving a uniform temperature profile at the outlet. Furthermore, the swirl body improves the flow guidance of the exhaust gas.

[0011] Preferably, the swirl body is provided immediately after the overflow opening, with the swirl body being attached to an end region of the outer tube facing away from the burner. In this way, the swirl body helps deflect the flow and also protects the end of the outer tube from direct contact with hot burner gases.

[0012] A further aspect of the invention provides for additional mixing elements to be provided in the flow channel. This further improves the mixing of the gases.

[0013] Preferably, the mixing elements are mounted on one side of the inner tube and the other side of the outer tube. In addition to improving the turbulence of the burner gases and exhaust gases, the mixing elements serve as spacers between the inner and outer tubes, increasing mechanical stability.

[0014] In one embodiment of the invention, the swirl body and the mixing elements are designed to introduce a swirl in the same direction into the flow. This achieves a particularly advantageous mixing of the gases.

[0015] Preferably, the flow is deflected by substantially 90° after the exhaust inlet and by substantially 180° after the overflow opening. This allows for a particularly simple and compact design with a flow path that is particularly long compared to the external dimensions.

[0016] In one embodiment of the invention, the inner tube is made, at least in sections, of high-temperature stainless steel. This protects this component from overheating despite direct contact with the burner flame.

[0017] Another aspect of the invention provides for the outer tube to be made of conventional steel, stainless steel, or boiler plate. This allows for the use of a cost-effective material.

[0018] In a further embodiment of the invention, a flame guide element can be provided within the inner tube. The flame guide element can further guide and protect the burner flame.

[0019] Preferably, the flame guide element extends from the pre-combustion chamber to the exhaust inlet area to protect the burner flame from the turbulent inlet flow. This creates a very stable flame that can be easily controlled.

[0020] In another embodiment of the invention, the flame guide element is a perforated flame guide tube. This provides particularly good protection against turbulence in the flow and also guides the burner flame on all sides, resulting in a particularly stable flame.

[0021] The object is also achieved according to the invention by an exhaust gas aftertreatment system with a diesel particulate filter and an exhaust gas heating device as described above, which is fluidly connected to the diesel particulate filter. The exhaust gas heating device has an inner tube having an exhaust gas inlet and an overflow opening, between which a heating channel is formed, a burner, and an outer tube surrounding the inner tube, so that a flow channel is formed from the overflow opening of the inner tube to an outlet, the flow direction in the heating channel running, at least in sections, opposite to the flow direction in the flow channel. The advantages discussed for the exhaust gas heating device naturally also apply to the exhaust gas aftertreatment system.

[0022] Further features and advantages of the invention will become apparent from the following description and the accompanying drawings, to which reference is made. In the drawings: Fig. 1 a perspective view of the exhaust gas heating device; Fig. 2 a longitudinal section through the exhaust gas heating device Fig. 1 ; Fig. 3 a longitudinal section through the exhaust gas heating device Fig. 1 with burner flame and indicated exhaust gas flow; Fig. 4 a longitudinal section through a second embodiment of the exhaust gas heating device with flame guide element and Fig. 5 a longitudinal section through a third embodiment of the exhaust gas heating device with flame guide tube.

[0023] The Figure 1 and 2show a first embodiment of an exhaust gas heating device 10 with an outer tube 12 serving as a housing. An exhaust gas inlet 14 protrudes through an opening from the outer tube 12 and is associated with an inner tube 16.

[0024] On the side opposite the exhaust gas inlet 14, the outer tube 12 has an outlet 18.

[0025] However, it is conceivable that the outlet 18 can be offset within a range of 180°, i.e. 90° forwards or 90° backwards, on the outer tube 12, as shown by arrows in Figure 1 is clarified.

[0026] Furthermore, a pre-combustion chamber 22, which is attached to the inner tube 16, protrudes from the outer tube 12. A burner 20 is attached to the pre-combustion chamber 22, wherein the burner 20 is designed here as a swirl burner.

[0027] The inner tube 16 and the outer tube 12 are arranged substantially concentrically to one another and extend along a central axis A. The exhaust gas inlet 14 is formed by a lateral nozzle, which here runs orthogonal to the central axis A. The outlet 18 is also designed as a lateral nozzle in this exemplary embodiment, which runs orthogonal to the central axis A.

[0028] The outer tube 12 surrounds the inner tube 16. This forms a flow channel 30 between the inner tube 16 and the outer tube 12, which is fluidly connected to the outlet 18 (see Fig. 2 ).

[0029] The inner tube 16 has a round cross-section here. Together with the exhaust gas inlet 14 and a pre-combustion chamber 22 (explained later), a substantially T-shaped structure is formed.

[0030] In the illustrated embodiment, the center axes of the pre-combustion chamber 22 and the inner tube 16 are arranged concentrically. The center axis of the exhaust gas inlet 14 extends at an angle of 90° to the center axis of the pre-combustion chamber 22 or the inner tube 16.

[0031] It is also possible that the central axis may deviate from the orientation shown by a range of ± 15°.

[0032] At the end facing away from the burner 20, the inner tube 16 has an overflow opening 24 so that a heating channel 26 is formed between the exhaust gas inlet 14 and the overflow opening 24, wherein the heating channel 26 is fluidly connected to the flow channel 30.

[0033] This results in a defined flow path, which initially runs through the exhaust gas inlet 14 into the inner tube 16 and then away from the burner 20 to the overflow opening 24. There, the flow path is redirected and runs parallel back in the flow channel 30, then ends at the outlet 18.

[0034] Additional elements can be attached or preferably incorporated into the overflow opening 24. For example, it is conceivable that the inner tube 16 in the area of the overflow opening 24 has slopes directed outward or inward.

[0035] The pre-combustion chamber 22 is attached to the left part of the inner tube 16, with the burner 20 being attached to the pre-combustion chamber 22. The pre-combustion chamber 22 protrudes from an opening in the outer tube 12. Thus, the burner 20 is easily accessible from the outside and can be easily replaced.

[0036] The pre-combustion chamber 22 is thus located, as viewed from the overflow opening 24, at a greater distance from the overflow opening 24 than the exhaust gas inlet 14, since the pre-combustion chamber 22 is mounted on the left part of the inner tube 16.

[0037] In the embodiment shown, the pre-combustion chamber 22 has a round cross-section, with an opening for the burner 20 being provided on a side facing away from the overflow opening 24.

[0038] A swirl body 28 is attached to the outer tube 12, on the side facing away from the burner 20. The swirl body is arranged directly after the overflow opening 24. In the embodiment shown, the swirl body 28 is mounted concentrically to the overflow opening 24. However, it is also conceivable for the swirl body 28 to be mounted radially offset.

[0039] The swirl body 28 here has a conical base body with several curved blades that extend from the center of the swirl body 28 to the projected diameter of the overflow opening 24.

[0040] Additional mixing elements 32 are arranged in the flow channel 30. These are attached to the outer tube 12 on the one hand and to the inner tube 16 on the other, thus forming, among other things, a spacer between the outer tube 12 and the inner tube 16. The mixing elements 32 can be designed as straight or curved metal sheets.

[0041] In the following, the Figure 3 the function of the exhaust gas heating device 10 is described.

[0042] The exhaust gas, e.g., the exhaust gas from a diesel engine, flows through the exhaust inlet 14 and is then deflected by 90° upon entering the heating channel 26. In the heating channel 26, the exhaust gas encounters the burner flame 34 generated by the burner 20. The exhaust gas is heated and mixed by the burner flame 34 and the hot burner gases, creating a gas mixture.

[0043] The gas mixture then flows further through the heating channel 26 toward the overflow opening 24, where the heating channel 26 ends. After the overflow opening 24, the gas mixture encounters the swirl body 28, which redirects the gas mixture by 180° into the flow channel 30 and swirls it to improve the mixing of the gases. The 180° reversal of the flow direction further aids the mixing of the gases.

[0044] In addition, the burner 20 is designed as a swirl burner in order to introduce a swirl into the flow from the burner 20.

[0045] It may also be provided that elements not shown here are incorporated into the overflow opening 24 to improve the mixing. These may, for example, be bevels on the overflow opening 24 that are directed inward or outward to introduce additional swirl into the flow.

[0046] Further mixing elements 32 are provided in the flow channel 30 to further improve the mixing of the gases so that a uniform temperature profile is present in the gas mixture at the outlet 18.

[0047] Preferably, the mixing elements 32 and the swirl body are designed such that they introduce a swirl in the same direction into the flow, since it has been found that a particularly advantageous mixing of the gases can be achieved in this way.

[0048] In the flow channel 30, the already heated gas mixture flows over the hot outer wall of the inner tube 16. As a result, the gas mixture is further heated and the inner tube 16 is cooled accordingly.

[0049] Up to outlet 18, where the flow is again deflected by 90°, the gas mixture is heated to a temperature that exceeds the reaction temperature of the particles that have accumulated in a downstream diesel particulate filter (not shown). These particles can thus be burned out of the diesel particulate filter, thereby regenerating it.

[0050] To protect the flame root 36 from flow turbulence in a turbulence zone 38 at the exhaust gas inlet 14, the pre-combustion chamber 22 is located at a greater distance from the overflow opening 24 than the exhaust gas inlet 14, as viewed from the overflow opening 24. The flame root 36 is additionally protected by the pre-combustion chamber 22 itself. This enables a particularly stable and easily controllable burner flame 34.

[0051] The burner 20 is designed such that the burner flame 34 it generates is shorter than the distance from the burner 20 to the overflow opening 24. This can be adjusted, for example, via the ratio of fuel to ambient air drawn into the burner. The speed of the exhaust gas flowing through the inner tube 16 also has an influence. In other words, the inner tube 16 is longer than the burner flame 34, which prevents the swirl body 28 and the end of the outer tube 12 located behind it from having direct flame contact.

[0052] Due to the direct flame contact and the high temperatures of up to 1500°C in the heating channel 26, the inner tube 16 is made, at least in sections, of high-temperature stainless steel to prevent damage from overheating. The swirl body 28 can also be made of such a material to provide additional protection for the outer tube 12 located behind it. However, the inner tube 16 can also be made entirely of high-temperature stainless steel.

[0053] The inner tube 16 and the swirl body 28 protect the outer tube 12 from direct flame contact. Therefore, the outer tube 12 can be made of a material that has lower heat resistance requirements than the material of the inner tube 16. Therefore, the outer tube 12 can be made of, for example, boiler plate or conventional stainless steel, such as V2A or V4A. Additionally, external hot spots that could lead to insulation problems are avoided.

[0054] The flow reversal by essentially 180°, combined with the nested arrangement of outer tube 12 and inner tube 16, provides a particularly compact exhaust gas heating device 10 with excellent mixing characteristics. Furthermore, the exhaust gas heating device 10 features a particularly advantageous cooling principle for the inner tube 16 due to the flow reversal, with the inner tube being cooled by the already heated gas mixture. Furthermore, the exhaust gas heating device 10 is particularly easy to install and flexible in design due to the flexible position of the outlet 18.

[0055] In Figure 4 A second embodiment of the exhaust gas heating device 10 is shown. The same reference numerals are used for the components known from the first embodiment, and reference is made to the above explanations.

[0056] The basic principle of the exhaust gas heating device according to the second embodiment is the same as that of the first embodiment. Therefore, only the differences will be explained below.

[0057] In the second embodiment, a flame guide element 40 is provided on the inner tube 16. The flame guide element 40 is designed here as a simple sheet metal and extends into the heating channel 26, into the area of the exhaust gas inlet 14.

[0058] The flame guide element 40 protects the burner flame 34 from flow turbulence and partially shields the burner flame 34 from the inlet flow.

[0059] In Figure 5 A third embodiment of the exhaust gas heating device is shown. The same reference numerals are used for the components known from the previous embodiments, and reference is made to the above explanations.

[0060] In the exhaust gas heating device 10 according to the third embodiment, the inner tube 16 and the exhaust gas inlet 14 together form a substantially L-shaped tube. On the side opposite the overflow opening 24, the inner tube 16 has an opening through which the flame guide element 40 protrudes into the heating channel 26.

[0061] The flame guide element 40 extends into the heating channel 26 as far as the exhaust gas inlet 14 and is designed as a flame guide tube. The flame guide tube may also be perforated.

[0062] The flame guide element 40 also serves as additional protection for the burner flame 34 and shields it from flow turbulence in the area of the exhaust gas inlet 14.

[0063] The perforation of the flame guide tube achieves a good compromise between the protection of the burner flame 34, heating of the exhaust gas and oxygen introduction into the flame.

Claims

1. An exhaust gas heating device, in particular for the exhaust gas aftertreatment of exhaust gas of marine engines, comprising an inner pipe (16) which includes an exhaust gas inlet (14) and an overflow opening (24), between which a heating channel (26) is formed, a burner (20) which is associated with the heating channel (26), an outer pipe (12) surrounding the inner pipe (16) so that a flow duct (30) is formed from the overflow opening (24) of the inner pipe (16) to an outlet (18) that is arranged on the outer pipe (12), wherein the exhaust gas inlet (14), the overflow opening (24) and the outlet (18) are arranged such that the flow direction of the exhaust gas of an internal combustion engine from the exhaust gas inlet (14) to the overflow opening is at least in sections opposite to the flow direction from the overflow opening (24) to the outlet (18).

2. The exhaust gas heating device according to claim 1, characterized in that the burner (20) is designed such that the flame produced by it is shorter than the distance from the burner (20) to the overflow opening (24).

3. The exhaust gas heating device according to either of the preceding claims, characterized in that the inner pipe (16) includes a precombustion chamber (22) which, as viewed from the overflow opening (24), is located at a greater distance from the overflow opening (24) than the exhaust gas inlet (14), the burner being arranged at the precombustion chamber (22).

4. The exhaust gas heating device according to any of the preceding claims, characterized in that a swirl body (28) is provided for swirling and redirecting the exhaust gas in the flow duct (30).

5. The exhaust gas heating device according to claim 4, characterized in that the swirl body (28) is provided immediately downstream of the overflow opening (24), the swirl body (28) being fastened to an end portion of the outer pipe (12) facing away from the burner (20).

6. The exhaust gas heating device according to any of the preceding claims, characterized in that additional mixing elements (32) are provided in the flow duct (30), which are attached, on the one hand, to the inner pipe (16) and, on the other hand, to the outer pipe (12).

7. The exhaust gas heating device according to any of the preceding claims, characterized in that the swirl body (28) and the mixing elements (32) are configured such that they introduce a swirl in the same direction into the flow.

8. The exhaust gas heating device according to any of the preceding claims, characterized in that the flow is deflected by substantially 90 degrees downstream of the exhaust gas inlet (14) and by substantially 180 degrees downstream of the overflow opening (24).

9. The exhaust gas heating device according to any of the preceding claims, characterized in that the inner pipe (16) is made at least in sections of high-temperature-resistant stainless steel.

10. The exhaust gas heating device according to any of the preceding claims, characterized in that the outer pipe (12) is made of conventional steel, stainless steel or boiler plate.

11. The exhaust gas heating device according to any of the preceding claims, characterized in that a flame directing element (40) is provided inside the inner pipe (16).

12. The exhaust gas heating device according to claim 11, characterized in that the flame directing element (40) extends from the precombustion chamber (22) up to the area of the exhaust gas inlet (14) in order to protect the flame from the turbulent inlet flow.

13. The exhaust gas heating device according to claim 11 or 12, characterized in that the flame directing element (40) is a perforated flame directing pipe.

14. An exhaust gas aftertreatment system comprising a diesel particulate filter and an exhaust gas heating device (10) according to any of the preceding claims, which is in fluid communication with the diesel particulate filter, wherein the exhaust gas heating device (10) includes an inner pipe (16) which includes an exhaust gas inlet (14) and an overflow opening (24) between which a heating channel (26) is formed, a burner (20), and an outer pipe (12) which surrounds the inner pipe (16) so that a flow duct (30) is formed from the overflow opening (24) of the inner pipe (16) to an outlet (18), wherein the flow direction in the heating channel (26) is at least in sections opposite to the flow direction in the flow duct (30).

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