Mixer of liquid ammonia post-processing system of diesel engine

Abstract

The invention relates to the field of diesel engine post-treatment systems, and particularly discloses a diesel engine liquid ammonia post-treatment system mixer which comprises a shell, a gas mixing pipe fitting, a rotational flow plate, a baffle and an ammonia gas nozzle, the gas mixing pipe fitting, the rotational flow plate, the baffle and the ammonia gas nozzle are arranged on the shell, and a cavity is formed in the shell and provided with a waste gas inlet and a waste gas outlet which are communicated with the cavity; the gas mixing pipe fitting comprises a premixing pipeline, a rotational flow pipeline, a partition plate and a flow guide pipeline; the rotational flow plate is fixedly mounted below the flow guide pipeline and is arranged in a W shape, and a plurality of first vent holes are formed in the surface of the rotational flow plate; the baffle is fixedly mounted at the waste gas outlet, and a plurality of second vent holes are formed in the surface; one end of the ammonia gas nozzle is communicated with an external ammonia gas supply pipeline, and the other end extends into the premixing pipeline. The mixer of the liquid ammonia post-processing system of the diesel engine has the advantages of low back pressure and high flow field uniformity.

Description

Technical Field

[0001] The present invention relates to the field of diesel engine after-treatment systems, and particularly to a mixer for a diesel engine liquid ammonia after-treatment system. Background Art

[0002] In the prior art, an aqueous urea solution mixer is usually used to mix urea droplets and harmful exhaust gas, and then the mixture is introduced into an SCR carrier to complete reduction. However, the aqueous urea solution mixer for vehicles has a large volume, a long mixing distance, and a complex structure, and there is a risk of urea crystallization under certain working conditions, resulting in poor mixing effect and affecting the final purification effect. For this reason, the utility model patent with the publication number CN 213775494 U discloses an ammonia mixer and an after-treatment device, which mix ammonia with exhaust gas to avoid the problem of urea crystallization, and at the same time can realize the full mixing of ammonia and exhaust gas, improving the purification effect. However, in this patent, the exhaust gas flow rate is relatively fast, the mixing effect of the exhaust gas and NH3 is limited, and the back pressure inside the pipe body assembly is relatively large, which is not conducive to the full entry of fresh air into the cylinder, reducing the charging efficiency, resulting in insufficient combustion, and thus reducing the power performance and fuel economy of the diesel engine. Summary of the Invention

[0003] The present invention aims to solve at least one of the above-mentioned technical problems, and provides a mixer for a diesel engine liquid ammonia after-treatment system, which has the advantages of low back pressure and high flow field uniformity.

[0004] To achieve the above object, the technical solution adopted by the present invention is: a mixer for a diesel engine liquid ammonia after-treatment system, comprising:

[0005] A housing, which has a cavity inside, and has an exhaust gas inlet and an exhaust gas outlet communicating with the cavity;

[0006] A mixing pipe member, which is arranged inside the housing, and comprises a premixing pipeline, a swirling pipeline, a partition plate and a guiding pipeline. The side wall of the premixing pipeline is provided with a first air inlet hole and an air outlet hole. The upper end of the swirling pipeline is fixedly connected to the premixing pipeline and is closed. The lower end of the swirling pipeline is fixedly connected to the partition plate. The side wall of the swirling pipeline is provided with a plurality of second air inlet holes, and swirling guide vanes are arranged at the edges of the second air inlet holes. The upper end of the guiding pipeline is fixedly connected to the partition plate. The partition plate is fixedly connected to the inner wall of the cavity, and divides the cavity inside the housing into an independent intake cavity and an exhaust cavity. A through hole communicating the swirling pipeline and the guiding pipeline is arranged in the middle of the partition plate. The inner diameters of the swirling pipeline, the guiding pipeline and the aperture of the through hole are the same;

[0007] A swirling plate, which is arranged inside the housing, is fixedly installed below the guiding pipeline, and is arranged in a W shape, and a plurality of first ventilation holes are arranged on its surface;

[0008] A baffle plate, which is fixedly installed at the exhaust gas outlet and has a plurality of second ventilation holes on its surface;

[0009] An ammonia nozzle, which is arranged on the shell, one end of which is communicated with an external ammonia supply pipeline, and the other end extends into the premixing pipeline.

[0010] Preferably, the shell is U-shaped, and the exhaust gas inlet and the exhaust gas outlet are respectively arranged at both ends of the shell.

[0011] Preferably, a first air inlet hole and a plurality of air outlet holes are arranged on the side wall of the premixing pipeline, and the plurality of air outlet holes are evenly distributed along the circumferential direction of the premixing pipeline.

[0012] Preferably, the premixing pipeline and the swirling pipeline adopt the same pipe body and are closed and blocked by a sealing plate.

[0013] Preferably, the second air inlet hole is strip-shaped and extends along the axial direction of the swirling pipeline, and a plurality of second air inlet holes are evenly distributed along the circumferential direction of the side wall of the swirling pipeline.

[0014] Preferably, the included angle between the extending direction of the swirling guide vane and the tangent line of the swirling pipeline at this place is 25° to 35°.

[0015] Preferably, the diversion pipeline is arranged in a cylindrical shape.

[0016] Preferably, one side of the swirling plate is fixedly connected to the inner wall of the shell, and the other side is inclined downward towards the baffle plate.

[0017] Preferably, the inner diameter of the swirling pipeline, the inner diameter of the diversion pipeline and the aperture of the through hole are the same.

[0018] Compared with the prior art, a mixer of a diesel engine liquid ammonia post-treatment system of the present invention has the following beneficial effects:

[0019] 1. Ammonia flows out of the nozzle and enters the premixing pipeline. At the same time, after the tail gas flows into the intake cavity through the exhaust gas inlet, a part of it flows into the premixing pipeline through the first air inlet hole to be mixed with ammonia to form a primary mixed gas, and then flows out from the air outlet hole. The flowing primary mixed gas is mixed with the exhaust gas in the intake cavity to form a secondary mixed gas, and then enters the swirling pipeline through the second air inlet hole to form a swirling motion, and is mixed with the tail gas again to form a tertiary mixed gas. Through the mixing of the three gases, the mixing process of the exhaust gas and NH3 is prolonged, the internal space of the shell is fully utilized, and it is beneficial to achieve the performance index of high flow field uniformity of the mixer;

[0020] 2. The swirl pipeline and the diversion pipeline are directly connected through a through-hole, and the inner diameters of the swirl pipeline, the diversion pipeline, and the aperture of the through-hole are the same, so that the inner diameters of the swirl pipeline and the diversion pipeline are fully utilized. Moreover, the larger the cross-sectional area of the pipeline, the smaller the back pressure of the pipeline. Therefore, the back pressure in the swirl pipeline and the diversion pipeline can be fully reduced.

[0021] 3. By arranging a W-shaped swirl plate, the exhaust gas flowing out from the guide pipe will generate vortices when passing through its surface, thereby further enhancing the mixing of ammonia and the exhaust gas. At the same time, the surface of the swirl plate is perforated, which can effectively avoid the formation of negative pressure. Meanwhile, the swirl plate is inclined towards the baffle, which can play a guiding role, enabling the exhaust gas flowing out from the guide pipe to flow towards the baffle after passing through the swirl plate.

[0022] 4. The surface of the baffle is perforated, and a certain height of block is formed at the exhaust gas outlet, which can avoid the formation of negative pressure at the exhaust gas outlet. At the same time, it can reduce the uniformity coefficient of the NH3 concentration at the inlet of the SCR carrier, and can control a part of the mixed gas to flow downstream through the holes on the surface of the porous baffle. Description of the Drawings

[0023] The following further elaborates on the specific embodiments of the present invention in conjunction with the accompanying drawings, where:

[0024] Figure 1 is a schematic structural diagram of a mixer for a diesel engine liquid ammonia post-treatment system of the present invention;

[0025] Figure 2 is a disassembled schematic diagram of a mixer for a diesel engine liquid ammonia post-treatment system of the present invention;

[0026] Figure 3 is a cross-sectional view of a mixer for a diesel engine liquid ammonia post-treatment system of the present invention. Detailed Description of the Embodiment

[0027] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0028] It should be noted that when a component is referred to as "fixed to" another component, it can be directly on the other component or there may be an intermediate component. When a component is considered to be "connected to" another component, it can be directly connected to the other component or there may be an intermediate component at the same time. When a component is considered to be "disposed on" another component, it can be directly disposed on the other component or there may be an intermediate component at the same time. When a part is referred to as "disposed in the middle", it is not only disposed at the exact middle position, as long as it is not disposed at the two ends, it belongs to the range defined by the middle. The terms "vertical", "horizontal", "left", "right" and similar expressions used in this article are only for the purpose of illustration.

[0029] Unless otherwise defined, all technical and scientific terms used in this article have the same meaning as those commonly understood by those skilled in the technical field to which this invention belongs. The terms used in the specification of this invention are only for the purpose of describing specific embodiments and are not intended to limit this invention. The term "and / or" used in this article includes any and all combinations of one or more of the related listed items.

[0030] As Figures 1 to 3 shown, the present application discloses a mixer for a diesel engine ammonia post-treatment system, including a housing 1, a mixing pipe component, a swirl plate 14, a baffle 16 and an ammonia nozzle 18. Specifically:

[0031] A cavity is provided inside the housing 1, which has an exhaust gas inlet 2 and an exhaust gas outlet 3 communicating with the cavity. Preferably, the housing 1 of the present application can be in a U shape, and the exhaust gas inlet 2 and the exhaust gas outlet 3 are respectively arranged at both ends of the housing 1, so as to make full use of the internal space of the housing 1, making the overall structure of the mixer very simple and compact;

[0032] The mixing pipe component is arranged inside the housing 1, and it includes a premixing pipeline 4, a swirl pipeline 5, a partition plate 6 and a diversion pipeline 7. The side wall of the premixing pipeline 4 is provided with a first air inlet 8 and an air outlet 13. The upper end of the swirl pipeline 5 is fixedly connected to the premixing pipeline 4 and is closed. The lower end of the swirl pipeline 5 is fixedly connected to the upper surface of the partition plate 6. The side wall of the swirl pipeline 5 is provided with a plurality of second air inlets 9, and swirl guide vanes 10 are arranged at the edges of the second air inlets 9. The upper end of the diversion pipeline 7 is fixedly connected to the lower surface of the partition plate 6. Preferably, the diversion pipeline 7 can be arranged in a cylindrical shape, and it has openings only at both ends and no openings on the side wall. The diversion pipe plays a role in guiding the gas. The partition plate 6 is fixedly connected to the inner wall of the cavity and divides the internal cavity of the housing 1 into independent intake cavities 11 and outlet cavities 12. A through hole communicating the swirl pipeline 5 and the diversion pipeline 7 is provided in the middle of the partition plate 6. The inner diameters of the swirl pipeline 5, the diversion pipeline 7 and the through hole are the same;

[0033] The swirl plate 14 is arranged inside the housing 1, fixedly installed below the diversion pipeline 7, and is arranged in a W shape. A plurality of first ventilation holes 15 are arranged on its surface;

[0034] The baffle 16 is fixedly installed at the exhaust gas outlet 3, and a plurality of second ventilation holes 17 are arranged on its surface. In this application, the height of the baffle 16 directly affects the direction of the mixed gas flowing downstream. Therefore, the height of the baffle 16 needs to be appropriate. The determination of the height of the baffle 16 and the shape and size of the second ventilation holes on the baffle requires two steps: the first step is to design the original model according to existing usage experience, and the second step is to optimize through CFD verification to ensure that its performance meets the target requirements;

[0035] The ammonia nozzle 18 is arranged on the housing 1. One end of it is connected to the external ammonia supply pipeline, and the other end extends into the premixing pipeline 4.

[0036] In one preferred embodiment of this application, a first intake hole 8 and a plurality of air outlet holes 13 are arranged on the side wall of the premixing pipeline 4. Preferably, there are five air outlet holes 13, and the five air outlet holes 13 are evenly distributed along the circumferential direction of the premixing pipeline 4. The first intake hole 8 and the air outlet holes 13 can be in an elongated waist shape and extend along the circumferential direction of the premixing pipeline 4. By arranging a plurality of elongated waist-shaped air outlet holes 13, it is more conducive to enhancing the mixing of ammonia and exhaust gas. In this application, the mixing of exhaust gas and NH3 occurs inside the premixing pipeline 4. The purpose of evenly arranging the air outlet holes on the side wall surface of the premixing pipeline 4 is that the primary mixed gas flows out of the premixing pipeline 4 and can be more uniform after entering the intake cavity 11. Of course, the cross-sectional area of the air outlet hole 13 will affect the outflow of the primary mixed gas from the premixing pipeline 4. If the cross-sectional area of the air outlet hole 13 is too large, the primary mixed gas cannot be fully mixed; if the cross-sectional area of the air outlet hole 13 is too small, the primary mixed gas cannot flow out smoothly, which is not conducive to controlling the injection amount of NH3.

[0037] The premixing pipeline 4 and the swirl pipeline 5 adopt the same pipe body and are blocked by a sealing plate 19. Specifically, the sealing plate 19 can be fixed by welding, and the lower end of the premixing pipeline 4 is not connected to the upper end of the swirl pipeline 5. By adopting the premixing pipeline 4 and the swirl pipeline 5 composed of the same pipe body, the structure is simpler and more compact.

[0038] In another preferred embodiment of this application, the second intake hole 9 is in a long strip shape and extends along the axial direction of the swirl pipeline 5. A plurality of second intake holes 9 are evenly distributed along the circumferential direction of the side wall of the swirl pipeline 5, and the included angle between the extending direction of the swirl guide vane 10 and the tangent line of the swirl pipeline 5 at this place is 25° to 35°, which can improve the mixing effect of exhaust gas and NH3.

[0039] In one specific embodiment of the present application, one side of the swirl plate 14 is fixedly connected to the inner wall of the housing 1, and the other side is inclined downward towards the baffle 16, thereby being able to play a guiding role, so that the waste gas flowing out of the guiding pipe flows through the swirl plate 14 and then towards the baffle 16.

[0040] Verified by CFD, the mixer of the diesel engine liquid ammonia after-treatment system of the present application has the following performance advantages:

[0041] 1. Low back pressure: When the exhaust gas flow rate at the inlet of the after-treatment system is 2040 kg / h and the exhaust gas temperature is 560 °C, the back pressure of the U-shaped mixing section pipeline is only 4 kPa. The small back pressure makes the exhaust more smooth. During the intake process, the pressure in the cylinder is relatively low, which is beneficial for fresh air to enter the cylinder more fully, thereby improving the charging efficiency, making the combustion more complete, and enhancing the power performance and fuel economy of the diesel engine. The improvement of the charging efficiency and more complete combustion help to reduce the emissions of pollutants such as carbon monoxide, hydrocarbons, and particulate matter in the diesel engine exhaust gas, improve the emission performance of the diesel engine, and better meet the environmental protection requirements.

[0042] 2. High flow field uniformity: Under the uniform working condition, the velocity uniformity coefficient of the SCR selective catalytic reduction carrier inlet section reaches 0.975, and the NH3 concentration uniformity coefficient of the SCR carrier inlet section reaches 0.965. The high NH3 concentration uniformity coefficient at the SCR carrier inlet enables relatively uniform NH3 concentration to be contacted at each part of the SCR catalyst surface. When reacting with nitrogen oxides NOx in the exhaust gas, the reaction rates at each part are relatively consistent, so that the active sites of the catalyst can be fully utilized, the overall denitrification efficiency is improved, the conversion rate of NOx is higher, and nitrogen oxide emissions are reduced more effectively.

[0043] In summary, a mixer of a diesel engine liquid ammonia after-treatment system of the present invention has the following beneficial effects:

[0044] 1. Ammonia flows out of the nozzle and enters the premixing pipeline 4. At the same time, after the tail gas flows into the intake cavity 11 through the exhaust gas inlet 2, a part of it flows into the premixing pipeline 4 through the first intake hole 8 and mixes with ammonia to form a primary mixed gas, and then flows out through the air outlet hole 13. The flowing out primary mixed gas mixes with the exhaust gas in the intake cavity 11 to form a secondary mixed gas, and then enters the swirl pipeline 5 through the second intake hole 9 to form a swirling motion inside, and mixes with the tail gas again to form a tertiary mixed gas. Through the mixing of the three gases, the mixing process of the exhaust gas and NH3 is extended, the internal space of the housing 1 is fully utilized, and it is beneficial to achieve the performance index of high flow field uniformity of the mixer;

[0045] 2. The swirling pipeline 5 and the diversion pipeline 7 are directly connected through a through-hole, and the inner diameters of the swirling pipeline 5, the diversion pipeline 7, and the aperture of the through-hole are the same, so that the inner diameters of the swirling pipeline 5 and the diversion pipeline 7 are fully utilized. Moreover, the larger the cross-sectional area of the pipeline, the smaller the back pressure of the pipeline. Therefore, the back pressure in the swirling pipeline 5 and the diversion pipeline 7 can be fully reduced;

[0046] 3. By providing the W-shaped swirling plate 14, vortices will be generated when the exhaust gas flowing out from the guiding pipe passes through its surface, thereby further enhancing the mixing of ammonia and the exhaust gas. Moreover, the openings on the surface of the swirling plate 14 can effectively prevent the formation of negative pressure. At the same time, the swirling plate 14 is arranged obliquely towards the baffle 16, which can play a guiding role, so that the exhaust gas flowing out from the guiding pipe flows towards the baffle 16 after passing through the swirling plate 14;

[0047] 4. The surface of the baffle 16 is provided with openings and forms a certain height of blockage at the exhaust gas outlet 3, which can prevent the formation of negative pressure at the exhaust gas outlet 3. At the same time, the uniformity coefficient of the NH3 concentration at the inlet of the SCR carrier is reduced, and a part of the mixed gas can be controlled to flow downstream through the holes on the surface of the porous baffle 16.

[0048] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention shall be covered by the technical solutions of the present invention.

Claims

1. A mixer for a diesel engine liquid ammonia post-treatment system, characterized in that, Comprising: A housing (1) with a cavity inside, having an exhaust gas inlet (2) and an exhaust gas outlet (3) communicating with the cavity; A mixing pipe component disposed inside the housing (1), which includes a premixing pipeline (4), a swirling pipeline (5), a partition plate (6) and a guiding pipeline (7). The side wall of the premixing pipeline (4) is provided with a first air inlet (8) and an air outlet (13). The upper end of the swirling pipeline (5) is fixedly connected to the premixing pipeline (4) and is closed. The lower end of the swirling pipeline (5) is fixedly connected to the partition plate (6). The side wall of the swirling pipeline (5) is provided with a plurality of second air inlets (9), and swirling guide vanes (10) are arranged at the edges of the second air inlets (9). The upper end of the guiding pipeline (7) is fixedly connected to the partition plate (6), and the partition plate (6) is fixedly connected to the inner wall of the cavity, and divides the inner cavity of the housing (1) into an independent air inlet cavity (11) and an air outlet cavity (12). A through hole communicating the swirling pipeline (5) and the guiding pipeline (7) is provided in the middle of the partition plate (6). The inner diameter of the swirling pipeline (5), the inner diameter of the guiding pipeline (7) and the aperture of the through hole are the same; A swirling plate (14) disposed inside the housing (1), fixedly installed below the guiding pipeline (7) and arranged in a W shape, and having a plurality of first ventilation holes (15) on its surface; A baffle plate (16) fixedly installed at the exhaust gas outlet (3) and having a plurality of second ventilation holes (17) on its surface; An ammonia nozzle (18) is disposed on the housing (1), one end of which communicates with an external ammonia supply pipeline, and the other end extends into the premixing pipeline (4).

2. The mixer of a diesel engine liquid ammonia post-treatment system according to claim 1, characterized in that The housing (1) is U-shaped, and the exhaust gas inlet (2) and the exhaust gas outlet (3) are respectively arranged at both ends of the housing (1).

3. The mixer of a diesel engine liquid ammonia post-treatment system according to claim 1, characterized in that, The side wall of the premixing pipeline (4) is provided with one first air inlet (8) and a plurality of air outlets (13), and the plurality of air outlets (13) are evenly distributed along the circumferential direction of the premixing pipeline (4).

4. The mixer of a diesel engine liquid ammonia post-treatment system according to claim 1, characterized in that, The premixing pipeline (4) and the swirling pipeline (5) adopt the same pipe body and are sealed and blocked by a sealing plate (19).

5. A mixer of a diesel engine liquid ammonia post-treatment system according to claim 1, characterized in that, The second air inlet (9) is strip-shaped and extends along the axial direction of the swirling pipeline (5), and a plurality of second air inlets (9) are evenly distributed along the circumferential direction of the side wall of the swirling pipeline (5).

6. The mixer of a diesel engine liquid ammonia post-treatment system according to claim 1, wherein, The included angle between the extending direction of the swirling guide vane (10) and the tangent of the swirling pipeline (5) at this position is 25° to 35°.

7. The mixer of a diesel engine liquid ammonia post-treatment system according to claim 1, characterized in that The guiding pipeline (7) is arranged in a cylindrical shape.

8. The mixer of a diesel engine liquid ammonia post-treatment system according to claim 1, wherein, One side of the swirling plate (14) is fixedly connected to the inner wall of the housing (1), and the other side is inclined downward towards the baffle plate (16).

Images