Mixer and corresponding exhaust aftertreatment system

Abstract

The utility model relates to a mixer which comprises an outer shell, a sealing plate and a mixing pipe, a mixing cavity is defined by the outer shell and the sealing plate, the mixing cavity is provided with a baffle, the baffle is provided with at least one valve assembly, and the at least one valve assembly is arranged to be in a closed state when exhaust pressure is smaller than preset pressure. When the exhaust pressure exceeds the preset pressure, the bypass valve is in an open state, so that a bypass channel is formed between the upper cavity and the lower cavity; when at least one valve assembly is in an open state, part of exhausted gas enters the upper cavity through the gas inlet, enters the mixing pipe through the inlet, is mixed with the reducing agent in the mixing pipe, enters the lower cavity through the outlet and is exhausted through the gas outlet. And the other part of exhausted gas enters the lower cavity through a bypass channel formed after the valve assembly is opened and is exhausted through the gas outlet. The utility model further relates to a corresponding exhaust aftertreatment system. The purposes of controlling the overall back pressure, effectively reducing or eliminating urea crystals and effectively improving the uniformity index of exhaust gas and ammonia gas before SCR can be achieved at the same time.

Description

Technical Field

[0001] The utility model relates to the technical field of tail gas treatment, in particular to a mixer and a corresponding exhaust aftertreatment system. Background Art

[0002] With the continuous upgrading of domestic diesel vehicle emission regulations, more stringent requirements are put forward for the automotive exhaust aftertreatment system and its core component mixer. As a key component in the aftertreatment system, the performance of the mixer directly affects the emission of NOx.

[0003] The mixer needs to ensure the full mixing of exhaust gas and reducing agent (such as aqueous urea solution) to improve the conversion efficiency of the SCR system. The mixer also needs to have good heat transfer performance to ensure that the aqueous urea solution vaporizes rapidly during injection and is fully mixed with the exhaust gas, which helps to improve the conversion efficiency of the SCR system and reduce urea consumption.

[0004] Due to the more stringent emission limits under low-temperature and low-load conditions in the "National VI" standard and the increased injection volume, the crystallization risk of the mixer increases. The generation of a large amount of crystallization will block the aftertreatment channel, resulting in an increase in the back pressure of the aftertreatment system and insufficient vehicle power, and at the same time, there is a risk of emissions exceeding the regulatory limits.

[0005] Generally speaking, the main technical problems existing in the current exhaust aftertreatment system are as follows:

[0006] 1) The back pressure of the aftertreatment system is high, resulting in poor fuel economy of the engine;

[0007] 2) Urea crystallization in the mixer;

[0008] 3) Low mixing efficiency of urea and exhaust gas, and low De-NOx conversion efficiency.

[0009] Therefore, it is hoped to improve the existing exhaust aftertreatment system to solve the above main technical problems simultaneously. Summary of the Utility Model

[0010] In view of the deficiencies of the existing technology, the utility model provides a mixer and a corresponding exhaust aftertreatment system that can control the overall back pressure, effectively reduce or eliminate urea crystallization, and effectively improve the uniformity index of exhaust gas and ammonia before SCR.

[0011] To achieve the above object, the first aspect of the present utility model provides a mixer, which has the following technical solutions: The mixer includes a housing, a sealing plate, and a mixing pipe. The housing and the sealing plate enclose a mixing chamber. A baffle is provided in the mixing chamber. The baffle divides the mixing chamber into an upper chamber and a lower chamber. The sealing plate is provided with an air inlet corresponding to the upper chamber and an air outlet corresponding to the lower chamber. The mixing pipe extends downward from the upper chamber and passes through the baffle to the lower chamber. An inlet is provided in the upper section of the mixing pipe, and an outlet is provided in the lower section of the mixing pipe. At least one valve assembly is provided on the baffle, and the at least one valve assembly is configured to be in a closed state when the exhaust gas is less than a preset pressure, and in an open state when the exhaust gas exceeds the preset pressure to form a bypass channel between the upper chamber and the lower chamber;

[0012] When the at least one valve assembly is in the closed state, all the exhaust gas enters the upper chamber through the air inlet, enters the mixing pipe through the inlet, is mixed with the reducing agent in the mixing pipe, and then is discharged through the outlet into the lower chamber and out through the air outlet;

[0013] When the at least one valve assembly is in the open state, part of the exhaust gas enters the upper chamber through the air inlet, enters the mixing pipe through the inlet, is mixed with the reducing agent in the mixing pipe, and then is discharged through the outlet into the lower chamber and out through the air outlet; another part of the exhaust gas enters the lower chamber through the bypass channel formed after the valve assembly is opened and is discharged through the air outlet.

[0014] Preferably, a reducing agent nozzle is provided at the top end of the housing for spraying the reducing agent towards the top end of the mixing pipe.

[0015] Preferably, the mixing pipe includes a mixing inner pipe. A swirl pipe and a mixing outer pipe are sleeved outside the mixing inner pipe. The swirl pipe is located above the mixing outer pipe. The swirl pipe forms the inlet of the mixing pipe. Several openings are provided on the lower section of the pipe wall of the mixing outer pipe. The bottom end pipe orifice of the mixing inner pipe, the bottom end pipe orifice of the mixing outer pipe, and the openings on the lower section of the pipe wall of the mixing outer pipe form the outlet of the mixing pipe.

[0016] Preferably, an arc plate is provided at the bottom end of the mixing pipe. At least one side of the arc plate has a concave channel, so that the mixed gas flowing out from the bottom end pipe orifice of the mixing inner pipe and the bottom end pipe orifice of the mixing outer pipe enters the lower chamber through the concave channel and is discharged through the air outlet.

[0017] Preferably, several vane windows are arranged on the periphery of the cyclone tube, and the vane openings form a preset angle with the tangential direction, so that the gas forms a rotating pattern when entering the mixing tube through the vane openings.

[0018] Preferably, several vanes facing inwards or outwards are provided on the inner mixing tube.

[0019] Preferably, the baffle is provided with an installation hole, and the valve assembly includes a valve cover plate, a valve seat with a through hole, and an elastic member. The through hole of the valve seat is aligned with the installation hole for installation. The valve cover plate is connected to the valve seat in an openable and closable manner through the elastic member. The opening and closing degree of the valve cover plate under different exhaust pressures is controlled by the elastic force of the elastic member, and the opening and closing of the valve cover plate controls the opening and closing of the valve assembly.

[0020] Preferably, the elastic member is a torsion spring. The torsion spring is sleeved on a shaft rod, and the shaft rod is installed on the valve seat. One end of the torsion spring abuts against the valve cover plate, and the other end of the torsion spring abuts against the valve seat.

[0021] A second aspect of the present invention provides an exhaust aftertreatment system, and its main feature is that it includes the mixer.

[0022] Preferably, the system includes a DOC and an intake sub-assembly, a DPF sub-assembly, an SCR and an outlet sub-assembly. The DOC and the intake sub-assembly, the DPF sub-assembly are communicated with the intake port of the mixer. The DPF sub-assembly is located between the DOC and the intake sub-assembly and the intake port of the mixer. The SCR and the outlet sub-assembly are communicated with the outlet port of the mixer.

[0023] For the mixer and the corresponding exhaust aftertreatment system of the present invention, at a preset pressure, the valve assembly opens to directly bypass part of the high-temperature gas, achieving the effect of controlling the overall back pressure; at a preset high load, the valve assembly opens, and the high-temperature exhaust gas wraps around the outside of the mixing tube to heat the mixing tube, which can effectively reduce and eliminate crystallization; the opening and closing of the valve assembly can effectively reduce the generation of crystallization and can generate more ammonia for reduction reaction with nitrogen oxides; through the opening degree control of the valve assembly, the airflow and ammonia distribution at the outlet can be adjusted, which can effectively improve the uniformity index of the gas and ammonia before the SCR, and further improve the reduction reaction ability with nitrogen oxides. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] For a clearer description of the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required to be used in the embodiments.

[0025] Figure 1 It is a schematic structural diagram of the exhaust aftertreatment system of the present invention.

[0026] Figure 2 This is a simplified schematic diagram of the principle of the exhaust aftertreatment system of the present utility model.

[0027] Figure 3 This is a schematic structural diagram of the mixer of the present utility model.

[0028] Figure 4 This is an exploded schematic diagram of the mixer of the present utility model.

[0029] Figure 5 This is a schematic diagram for explaining the working principle of the mixer of the present utility model.

[0030] Figure 6 This is a schematic structural diagram of the valve assembly in the mixer of the present utility model.

[0031] Figures 7A and 7B are schematic structural diagrams of the mixing tube in the mixer of the present utility model.

[0032] Reference numerals

[0033] 1 DOC and intake subassembly; 2 DPF subassembly; 3 mixer; 4 clamp; 5 SCR and outlet subassembly; 6 strap bracket; 7 reductant nozzle; 8 valve assembly; 801 valve cover plate; 802 valve seat; 803 torsion spring; 804 shaft rod; 9 mixing tube; 901 swirl tube; 902 mixing outer tube; 903 mixing inner tube; 10 heat shield; 11 heat insulation cotton; 12 outer shell; 13 baffle; 14 arc plate; 15 sealing plate; 151 intake port; 152 outlet port; 16 nozzle mounting seat. Detailed implementation manners

[0034] In order to be able to more clearly describe the technical content of the present utility model, the following will be further described in conjunction with specific embodiments.

[0035] Such as Figures 1 to 2As shown, it is a specific embodiment of the exhaust aftertreatment system of the present utility model. Among them, the exhaust aftertreatment system includes the mixer 3, the DOC and intake subassembly 1, the DPF subassembly 2, the SCR and outlet subassembly 5. DOC (Diesel Oxidation Catalyst) is a diesel oxidation catalyst, DPF (Diesel Particulate Filter) is a diesel particulate filter, and SCR (Selective Catalytic Reduction) is a selective catalytic reducer. The DOC, DPF, and SCR subassemblies all contain catalyst carriers. The DOC and intake subassembly 1 and the DPF subassembly 2 are connected to the intake port of the mixer 3. The DPF subassembly 2 is located between the DOC and intake subassembly 1 and the intake port of the mixer 3. The SCR and outlet subassembly 5 is connected to the outlet port of the mixer 3. The DOC and intake subassembly 1, the DPF subassembly 2, the mixer 3, the SCR and outlet subassembly 5 can be connected and fixed by means of flanges, clamps or welding, etc.

[0036] In this embodiment, two clamps 4 are used. One clamp 4 is used to fixedly connect the mixer and the DPF subassembly, and the other clamp is used to fixedly connect the mixer and the SCR and outlet subassembly 5 to achieve the functions of connection and fixation and maintain sealing.

[0037] In this embodiment, a strap bracket 6 is used to install and fix the aftertreatment system to the vehicle. On the one hand, it is fixed to the outer surface of the aftertreatment system by straps, and on the other hand, it is connected to the vehicle installation position through the installation holes on the strap bracket.

[0038] As Figure 2 shown, based on the connection relationship of the components of the exhaust aftertreatment system of the present utility model, the high-temperature exhaust gas (exhaust gas) of the engine passes through the internal cavity formed by the DOC and intake subassembly 1, the DPF subassembly 2, the mixer 3, and the SCR and outlet subassembly 5 in sequence. The high-temperature exhaust gas of the engine is mixed with the reducing agent inside the mixer 3, and after a catalytic reduction reaction in the subsequent SCR and outlet subassembly 5, the qualified exhaust gas is discharged.

[0039] As Figures 3 to 5 shown, it is an embodiment of the mixer 3 of the present utility model. Among them, the mixer 3 includes a housing 12, a sealing plate 15, and a mixing tube 9. The housing 12 and the sealing plate 15 enclose a mixing chamber. In this embodiment, a heat-insulating cotton 11 and a heat-insulating cover 10 are sequentially arranged on the outside of the housing 12.

[0040] A baffle 13 is provided in the mixing chamber. The baffle 13 can be fixed on the inner surface of the outer housing 12. The baffle 13 divides the mixing chamber into upper and lower cavities. The upper part is the upper cavity, and the lower part is the lower cavity. The sealing plate 15 is provided with an air inlet 151 corresponding to the upper cavity and an air outlet 152 corresponding to the lower cavity. The mixing pipe 9 extends downward from the upper cavity and passes through the baffle 13 to the lower cavity, that is, the upper cavity and the lower cavity are penetrated by the mixing pipe 9. An inlet is provided in the upper section of the mixing pipe 9, and an outlet is provided in the lower section of the mixing pipe 9. A pair of valve assemblies 8 are provided on the baffle 13. The pair of valve assemblies 8 are symmetrically arranged on both sides of the mixing pipe 9.

[0041] The valve assembly 8 is set to be in a closed state when the exhaust gas is less than a preset pressure, and in an open state when the exhaust gas exceeds the preset pressure to form a bypass channel between the upper cavity and the lower cavity.

[0042] Specifically, when the pressure value at which the valve assembly 8 is located is less than the preset opening pressure of the valve assembly 8, the valve assembly 8 is in a closed state. All gases enter the interior of the mixing pipe 9 through the inlet in the upper section of the mixing pipe 9, are mixed with the reducing agent sprayed out by the reducing agent nozzle 7 inside the mixing pipe 9, and the mixed gases flow out from the internal channel of the mixing pipe 9 through the outlet, enter the SCR and the air outlet subassembly and are discharged.

[0043] When the pressure value at which the valve assembly 8 is located is greater than or equal to the preset opening pressure of the valve assembly 8, the valve assembly 8 is in an open state. Part of the gases enter the interior of the mixing pipe 9 through the inlet in the upper section of the mixing pipe 9, are mixed with the reducing agent sprayed out by the reducing agent nozzle 7 inside the mixing pipe 9, and the mixed gases flow out from the internal channel of the mixing pipe 9 through the outlet and enter the SCR and the air outlet subassembly and are discharged; another part of the gases form a bypass channel after passing through the opened valve assembly 8 and directly enter the air outlet 152 of the lower cavity of the mixing chamber, enter the SCR and the air outlet subassembly and are discharged.

[0044] In the mixer embodiment of the present invention, the valve assembly is located outside the mixing pipe, and the high-temperature exhaust gas can be directly bypassed. That is, most of the high-temperature exhaust gas is still mixed with the reducing agent inside the mixing pipe, and a small part of the high-temperature exhaust gas is not mixed inside the mixing pipe and is directly bypassed to the air outlet of the mixer. Through the bypass control of the valve assembly, the back pressure of the mixer system can be adjusted; bypassing the high-temperature gas can directly heat the outer wall of the mixing pipe, reduce and eliminate the risk of urea crystallization; bypassing the high-temperature gas can directly heat the outer wall of the mixing pipe, improve the urea evaporation rate, and further improve the nitrogen oxide removal efficiency; through the opening degree control of the valve assembly, the surface air flow and ammonia uniformity index of the SCR can be adjusted.

[0045] The number of the valve assemblies 8 can also be one or more, and the valve diameter of the valve assemblies 8 can also vary. The present invention does not limit this.

[0046] At the top of the outer housing 12, a reductant nozzle 7 is provided for injecting a reductant, such as an aqueous urea solution, into the top of the mixing tube 9. The reductant nozzle 7 is fixedly installed on the nozzle mounting seat 16, and the reductant nozzle 7 injects the reductant into the inner cavity of the mixing tube 9.

[0047] Such as Figure 3 As shown in FIGS. 7A to 7B, the mixing tube 9 includes a mixing inner tube 903, and a swirl tube 901 and a mixing outer tube 902 are sleeved outside the mixing inner tube 903. The swirl tube 901 is located above the mixing outer tube 902. That is, the swirl tube 901 is connected to the mixing outer tube 902 to form a gas and reductant mixing cavity, and the mixing inner tube 903 is located inside the mixing cavity formed by the mixing outer tube and the swirl tube.

[0048] The swirl tube 901 forms the inlet of the mixing tube 9, and the gas enters the mixing outer tube 902 and the mixing inner tube 903 through the swirl tube 901 and is fully mixed with the reductant injected by the reductant nozzle 7. A plurality of openings are provided on the lower section of the pipe wall of the mixing outer tube 902. The bottom pipe orifice of the mixing inner tube 903, the bottom pipe orifice of the mixing outer tube 902, and the openings on the lower section of the pipe wall of the mixing outer tube 902 form the outlet of the mixing tube. That is to say, the openings of the mixing outer tube 902 within the range of the lower cavity are used as a part of the outlet, and the bottom pipe orifice of the mixing tube 9 (the bottom pipe orifice of the mixing inner tube 903 and the bottom pipe orifice of the mixing outer tube 902) is used as another part of the outlet. That is, the mixed gas will flow out through the openings and the bottom channel.

[0049] An arc plate 14 is provided at the bottom end of the mixing tube. Both sides of the arc plate have concave channels, so that the mixed gas flowing out from the bottom pipe orifice of the mixing inner tube and the bottom pipe orifice of the mixing outer tube enters the lower cavity through the concave channels and is discharged through the air outlet. The gas mixed in the mixing tube 9 flows out through the arc plate 14. In addition to the function of fixing and supporting the mixing tube 9, the arc plate 14 can effectively prevent crystal deposition, and at the same time can adjust the air flow direction and improve the uniformity index of the exhaust gas and ammonia before SCR.

[0050] A plurality of blade windows are provided on the periphery of the swirl tube 901, and the blade openings form a preset angle with the tangential direction, so that the gas forms a rotating shape when entering the mixing tube through the blade openings.

[0051] As shown in FIG. 7A, the mixing inner tube 903 is provided with a plurality of blades facing inwards or outwards to enhance the swirl effect; at the same time, a plurality of small holes are provided on the mixing inner tube 903 for adjusting the air flow and the back pressure.

[0052] Such as Figure 5 AndFigure 6 As shown, the baffle 13 is provided with mounting holes. The valve assembly 8 includes a valve cover plate 801, a valve seat 802 having a through hole, and an elastic member 803. The through hole of the valve seat 802 is aligned with the mounting holes for installation. The valve cover plate 801 is connected to the valve seat 802 in an openable and closable manner through the elastic member 803. The opening and closing degree of the valve cover plate 801 under different exhaust pressures is controlled by the elastic force of the elastic member 803, and the opening and closing of the valve assembly 8 is controlled by the opening and closing of the valve cover plate 801. The opening angle of the valve cover plate 801 is related to the pressure difference between the upper and lower sides of the valve cover plate 801. The larger the opening angle, the greater the elastic force of the elastic member.

[0053] The valve assembly 8 can be directly and independently fixed on the baffle 13, or the structure of the baffle itself can be used as the valve seat, and the elastic member and the valve cover plate are directly placed on the baffle, that is, the entire baffle serves as a bypass valve mechanism.

[0054] In this embodiment, the elastic member 803 is a torsion spring. The torsion spring is sleeved on a shaft rod 804. The shaft rod 804 is installed on the valve seat 802. One end of the torsion spring abuts against the valve cover plate 801, and the other end of the torsion spring abuts against the valve seat 802. The valve cover plate 801 rotates around the shaft rod 804 and is opened and closed by the elastic force of the torsion spring.

[0055] For the mixer and the corresponding exhaust after-treatment system of the present invention, under a preset pressure, the valve assembly opens to directly bypass part of the high-temperature gas, achieving the effect of controlling the overall back pressure; under a preset high load, the valve assembly opens, and the high-temperature exhaust gas wraps around the outside of the mixing pipe to heat the mixing pipe, which can effectively reduce and eliminate crystallization; the opening and closing of the valve assembly can effectively reduce the generation of crystallization and can generate more ammonia for reduction reaction with nitrogen oxides; through the control of the opening degree of the valve assembly, the airflow and ammonia distribution at the outlet can be adjusted, which can effectively improve the uniformity index of the gas and ammonia before SCR, and further improve the reduction reaction ability with nitrogen oxides.

[0056] In this specification, the present invention has been described with reference to its specific embodiments. However, it is obvious that various modifications and transformations can still be made without departing from the spirit and scope of the present invention. Therefore, the specification and drawings should be regarded as illustrative rather than restrictive.

Claims

1. A mixer, characterized in that: The mixer comprises an outer shell, a sealing plate, and a mixing tube. The outer shell and the sealing plate surround a mixing chamber. The mixing chamber is provided with a baffle. The baffle separates the mixing chamber into an upper chamber and a lower chamber. The sealing plate is provided with an air inlet corresponding to the upper chamber and an air outlet corresponding to the lower chamber. The mixing tube extends downward from the upper chamber and passes through the baffle to the lower chamber. The upper section of the mixing tube is provided with an inlet, and the lower section of the mixing tube is provided with an outlet. The baffle is provided with at least one valve assembly, and the at least one valve assembly is configured to be in a closed state when the exhaust gas is less than a preset pressure, and to be in an open state when the exhaust gas exceeds the preset pressure to form a bypass channel between the upper chamber and the lower chamber. When at least one of the valve components is in a closed state, all exhaust gas enters the upper cavity through the air inlet, enters the mixing tube through the inlet, mixes with the reducing agent in the mixing tube, enters the lower cavity through the outlet, and is discharged through the air outlet; When at least one of the valve components is in an open state, part of the exhaust gas enters the upper cavity through the air inlet and enters the mixing tube through the inlet, mixes with the reducing agent in the mixing tube, enters the lower cavity through the outlet, and is discharged through the air outlet; another part of the exhaust gas enters the lower cavity through the bypass channel formed after the valve component is opened, and is discharged through the air outlet.

2. The mixer according to claim 1, characterized in that A reducing agent nozzle is arranged at the top of the outer shell for spraying the reducing agent toward the top of the mixing tube.

3. The mixer according to claim 1, characterized in that The mixing tube comprises an inner mixing tube, the outer tube of which is provided with a swirl tube and an outer mixing tube, the swirl tube is located above the outer mixing tube, the swirl tube forms the inlet of the mixing tube, the lower tube wall of the outer mixing tube is provided with a plurality of openings, the bottom tube opening of the inner mixing tube, the bottom tube opening of the outer mixing tube, and the openings on the lower tube wall of the outer mixing tube form the outlet of the mixing tube.

4. The mixer according to claim 3, characterized in that An arc plate is arranged at the bottom end of the mixing tube, and at least one side of the arc plate has a concave channel, so that the mixed gas flowing out from the bottom end pipe opening of the mixing inner tube and the bottom end pipe opening of the mixing outer tube enters the lower cavity through the concave channel and is discharged through the gas outlet.

5. The mixer according to claim 3, characterized in that A plurality of blade windows are arranged on the periphery of the swirl tube, and the blade windows form a preset angle with the tangent direction, so that the gas forms a rotating shape when passing through the blade windows and entering the mixing tube.

6. The mixer according to claim 3, characterized in that The inner mixing tube is provided with a plurality of blades facing inwards or outwards.

7. The mixer according to claim 1, characterized in that The baffle is provided with a mounting hole, and the valve assembly includes a valve cover plate, a valve seat with a through hole, and an elastic member. The through hole of the valve seat is aligned with the mounting hole and installed, and the valve cover plate is connected to the valve seat in an openable and closable manner through the elastic member. The opening and closing degree of the valve cover plate under different exhaust pressures is controlled by the elastic force of the elastic member, and the opening and closing of the valve assembly is controlled by the opening and closing of the valve cover plate.

8. The mixer according to claim 7, characterized in that The elastic member is a torsion spring, which is passed through a shaft rod, which is mounted on the valve seat, one end of the torsion spring abuts against the valve cover plate, and the other end of the torsion spring abuts against the valve seat.

9. An exhaust gas aftertreatment system, characterized in that: A mixer comprising the mixer according to any one of claims 1 to 8.

10. The exhaust gas aftertreatment system according to claim 9, characterized in that: The system includes a DOC and an air intake subassembly, a DPF subassembly, an SCR and an air outlet subassembly. The DOC and the air intake subassembly, the DPF subassembly and the air inlet of the mixer are connected. The DPF subassembly is located between the DOC and the air intake subassembly and the air inlet of the mixer. The SCR and the air outlet subassembly are connected to the air outlet of the mixer.

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