Mixer and diesel engine aftertreatment system

Abstract

The invention relates to a mixer and a diesel engine aftertreatment system. The mixer comprises a shell, a nozzle assembly and a multi-stage mixing pipe, the shell is in a hollow barrel shape, the nozzle assembly is installed on the side wall of the shell, and the shell is provided with an air inlet part and an air outlet part; the multiple stages of mixing pipes are arranged in the air inlet part in the axial direction of the shell, at least one mixing pipe in the multiple stages of mixing pipes is provided with a plurality of rotational flow blades rotationally arranged around the axis of the mixing pipe, and in the direction from the air inlet part to the air outlet part, the circulation sectional area of the multiple stages of mixing pipes is in the trend of decreasing. According to the mixer and the diesel engine aftertreatment system, the mixing uniformity of the urea solution and the tail gas can be improved, and urea crystallization is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of diesel engine exhaust treatment equipment, and in particular to a mixer and a diesel engine after-treatment system. Background Art

[0002] With the implementation of the National VI Emissions Regulations for diesel engines, higher requirements are placed on the post-treatment system for reducing nitrogen oxides (NOx). The urea selective catalytic reduction (Urea-SCR) system is considered to be an effective nitrogen oxide (NOx) post-treatment technology. Urea-SCR (urea selective catalytic reduction) is a technology used to control diesel engine emissions, with the main purpose of reducing the emission of nitrogen oxides (NOx) in exhaust gas. This technology injects urea aqueous solution into the diesel engine exhaust system, and the urea aqueous solution evaporates and pyrolyzes to produce ammonia (NH3), which reduces nitrogen oxides (NOx) in the exhaust gas to N2 in the catalyst.

[0003] The mixer is used to mix the urea aqueous solution and the exhaust gas. If the mixing effect of the urea aqueous solution and the exhaust gas is poor, serious urea crystals will form in the exhaust pipe, and the exhaust channel will be blocked, thus affecting the performance of the engine. In the related art, the mixer uses a perforated tube, a perforated plate or a fiber unit to break up the urea particles and accelerate the decomposition of urea. However, the structures such as the perforated tube and the perforated plate are prone to cause urea accumulation; and the fiber unit structure can increase the urea breaking effect, but it may bring higher exhaust back pressure. Summary of the invention

[0004] Based on this, it is necessary to provide a mixer that can improve the mixing uniformity of urea solution and tail gas and reduce urea crystallization.

[0005] A mixer comprises a shell, a nozzle assembly and a multi-stage mixing tube. The shell is in a hollow cylindrical shape. The nozzle assembly is installed on the side wall of the shell. The inner cavity of the shell has an air inlet and an air outlet located on both sides of the nozzle assembly. The multi-stage mixing tube is arranged along the axial direction of the shell in the air inlet. At least one of the multi-stage mixing tubes is provided with a plurality of swirl blades arranged and rotating around the axis of the mixing tube. In addition, the flow cross-sectional area of ​​the multi-stage mixing tube tends to decrease along the direction from the air inlet to the air outlet. The nozzle assembly is used to spray urea into the shell. The exhaust gas flows from the air inlet through the plurality of mixing tubes in sequence and rotates and circulates under the disturbance of the corresponding swirl blades. The rotating exhaust gas mixes with the urea and flows to the air outlet.

[0006] In one embodiment, the mixer further comprises a swirl plate, which is arranged on the outer periphery of the mixing tube, and the swirl plate is provided with a plurality of window fins arranged and rotating around its own axis.

[0007] In one embodiment, the mixing tube is configured in two stages. Along the direction from the air inlet to the air outlet, the mixer includes a first mixing tube and a second mixing tube. Along the axial direction of the shell, the second mixing tube is arranged close to the nozzle assembly relative to the first mixing tube, and the swirl plate is sleeved on the outer periphery of the second mixing tube, and the inner diameter of the first mixing tube is larger than the outer diameter of the swirl plate; wherein, a part of the exhaust gas flowing out of the first mixing tube flows to the swirl plate, and the other part flows to the second mixing tube.

[0008] In one embodiment, the first mixing tube is provided with a plurality of first swirl blades, and the second mixing tube is provided with a plurality of second swirl blades; the rotation arrangement direction of the plurality of first swirl blades is the same as the rotation arrangement direction of the plurality of second swirl blades, and the rotation arrangement direction of the plurality of first swirl blades is opposite to the rotation arrangement direction of the plurality of window fins.

[0009] In one embodiment, one end of the first swirl blade is connected to the circumferential edge of the first mixing tube, and the other end is twisted and extended toward the axial direction close to the first mixing tube and is set at an angle relative to the circumferential edge of the first mixing tube; one end of the second swirl blade is connected to the circumferential edge of the second mixing tube, and the other end is twisted and extended toward the axial direction close to the second mixing tube and is set at an angle relative to the circumferential edge of the second mixing tube.

[0010] In one embodiment, the angle between the first swirl blade and the circumferential edge of the first mixing tube is α, the angle between the second swirl blade and the circumferential edge of the second mixing tube is β, α=β; and / or, the extension length of the first swirl blade is l1, the extension length of the second swirl blade is l2, and l1<l2.

[0011] In one embodiment, the diameter of the first mixing tube is d1, the extension length of the first swirl blade is l1, and 10% d1≤l1≤15% d1; the angle between the edge of the first swirl blade along its own width direction and the circumferential edge of the first mixing tube is α, and 105°≤α≤125°; and / or, the diameter of the second mixing tube is d2, the extension length of the second swirl blade is l2, and 40% d2≤l2≤50% d2; the angle between the edge of the second swirl blade along its own width direction and the circumferential edge of the second mixing tube is β, and 105°≤α≤125°.

[0012] In one embodiment, an angle γ is formed between the window fin and the plane where the swirl plate is located, and 40°≤γ≤50°.

[0013] In one of the embodiments, the shell includes an outer cylinder, an inner cylinder and a baffle located inside the outer cylinder, one end of the inner cylinder is provided with a flange extending toward the outer cylinder, and is fixed to the outer cylinder through the flange, and the other end is fixedly connected to the outer cylinder through the baffle; a first mounting hole is opened on the side wall of the outer cylinder, and a second mounting hole is opened on the side wall of the inner cylinder, the first mounting hole and the second mounting hole are correspondingly arranged along the radial direction of the outer cylinder and are used to install the nozzle assembly, and the air inlet and the air outlet are located on both sides of the nozzle assembly along the axial direction of the shell.

[0014] In one embodiment, the first mixing tube is connected and fixed to the inner wall of the outer cylinder, and the second mixing tube is connected and fixed to the inner wall of the inner cylinder via a swirl plate.

[0015] In one embodiment, the mixer further comprises a mixing blade, and the mixing blade is installed at the air outlet portion.

[0016] In one of the embodiments, a heat insulation cover is provided outside the shell, and a thermal insulation layer is provided between the shell and the heat insulation cover.

[0017] The present application also provides a diesel engine aftertreatment system, which includes the mixer described in any one of the above embodiments.

[0018] Compared with the prior art, the mixer and diesel engine aftertreatment system provided by the present application enable the exhaust gas to rotate and circulate by arranging swirl blades on the mixing tube. The rotating exhaust gas can break up the urea, and since the flow cross-sectional area of ​​the exhaust gas tends to decrease along the direction from the air inlet to the air outlet, the flow velocity of the exhaust gas increases step by step as it flows through the multi-stage mixing tubes in sequence. The high-speed rotating exhaust gas can further accelerate the crushing and decomposition of urea, and fully mix with the ammonia generated by the decomposition of urea, thereby reducing urea crystallization. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 An axonometric view of a mixer in one of the embodiments provided in this application;

[0021] Figure 2 An exploded schematic diagram of a mixer in one of the embodiments provided in this application;

[0022] Figure 3 A cross-sectional view of a mixer along its own axial direction in one of the embodiments provided in the present application;

[0023] Figure 4 This is a schematic diagram of the assembly of the first mixing tube, the second mixing tube and the swirl plate in one of the embodiments provided in this application;

[0024] Figure 5 This is a side view of a second mixing tube in one of the embodiments provided in the present application.

[0025] Figure numerals: 100, mixer; 10, shell; 101, outer cylinder; 101a, first mounting hole; 102, inner cylinder; 102a, flange; 102b, second mounting hole; 103, baffle; 11, air inlet; 12, air outlet; 20, nozzle nut seat; 30, mixing tube; 31, swirl blade; 311, first swirl blade; 312, second swirl blade; 32, first mixing tube; 33, second mixing tube; 40, swirl plate; 42, window fin; 50, mixing blade; 51, blade; 60, heat shield; 70, insulation layer. DETAILED DESCRIPTION

[0026] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0027] It should be noted that when a component is referred to as being "fixed to" or "disposed on" another component, it may be directly on the other component or there may also be a central component. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may be a central component at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used in the specification of this application are for illustrative purposes only and do not represent the only implementation method.

[0028] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0029] In the present application, unless otherwise clearly specified and limited, a first feature being “above” or “below” a second feature may mean that the first feature is directly in contact with the second feature, or the first feature and the second feature are indirectly in contact through an intermediate medium. Moreover, a first feature being “above”, “above” or “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “below”, “below” or “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0030] Unless otherwise defined, all technical and scientific terms used in the specification of this application have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used in the specification of this application includes any and all combinations of one or more related listed items.

[0031] See also Figure 1 to Figure 2 The present application provides a mixer 100, which includes a shell 10, a nozzle assembly and a multi-stage mixing tube 30. The shell 10 is in a hollow cylindrical shape, and the nozzle assembly is installed on the side wall of the shell 10. The inner cavity of the shell 10 has an air inlet 11 and an air outlet 12. The multi-stage mixing tube 30 is arranged along the axial direction of the shell 10 in the air inlet 11. At least one mixing tube 30 in the multi-stage mixing tube 30 is provided with a plurality of swirl blades 31 arranged and rotated around the axis of the mixing tube 30, and the flow cross-sectional area of ​​the multi-stage mixing tube 30 tends to decrease along the direction from the air inlet 11 to the air outlet 12; wherein the nozzle assembly is used to spray urea toward the shell 10, and the exhaust gas flows through the plurality of mixing tubes 30 in sequence from the air inlet 11, and rotates and circulates under the disturbance of the corresponding swirl blades 31, and the rotating exhaust gas is mixed with urea and flows to the air outlet 12.

[0032] It can be understood that by providing the swirl blades 31, the exhaust gas is allowed to rotate and circulate, and the rotating exhaust gas can break up the urea. In addition, since the flow cross-sectional area of ​​the exhaust gas tends to decrease along the direction from the air inlet 11 to the air outlet 12, the flow velocity of the exhaust gas increases step by step as it flows through the multi-stage mixing tube 30 in sequence. The high-speed rotating exhaust gas can further accelerate the crushing and decomposition of urea, and fully mix with the ammonia produced by the decomposition of urea, thereby reducing urea crystallization.

[0033] In one embodiment, each stage of the mixing tube 30 is provided with a plurality of swirl blades 31 rotatably arranged around the axis of the mixing tube 30. Of course, in other embodiments, only some of the mixing tubes 30 may be provided with a plurality of swirl blades 31 rotatably arranged around the axis of the mixing tube 30.

[0034] Furthermore, if Figure 4 As shown, a plurality of swirl blades 31 are evenly spaced apart and arranged around the axis of the mixing tube 30 .

[0035] The mixer 100 also includes a swirl plate 40, which is arranged on the periphery of the mixing tube 30. The swirl plate 40 is provided with a plurality of window fins 42 arranged and rotated around its own axis. In this way, the exhaust gas flowing through the swirl plate 40 can also rotate and circulate under the disturbance of the window fins 42, thereby enhancing the disturbance of the exhaust gas by the mixer 100. In addition, the window fins 42 are formed by integrally processing the swirl plate 40, and the molding process is simple and the connection is more stable. In other embodiments, the window fins 42 can also be processed separately and then welded and fixed to the swirl plate 40.

[0036] Furthermore, a plurality of window fins 42 are evenly spaced and arranged around the axis of the swirl plate 40 .

[0037] In one embodiment, if Figure 3 As shown, the angle γ is formed between the window fin 42 and the plane where the swirl plate 40 is located, and 40°≤γ≤50°. It can be understood that if γ is too small, the window fin 42 will produce a large resistance to the exhaust gas flowing through the swirl plate 40, and if γ is too large, it is difficult to produce a disturbance effect on the exhaust gas. Therefore, by setting 40°≤γ≤50°, it is beneficial to avoid excessive resistance to the exhaust gas while ensuring the disturbance effect on the exhaust gas.

[0038] Optionally, in one embodiment, if Figures 2 to 5 As shown, the mixing tube 30 is configured in two stages. Along the direction from the air inlet 11 to the air outlet 12, the mixer 100 includes a first mixing tube 32 and a second mixing tube 33. Along the axial direction of the shell 10, the second mixing tube 33 is arranged close to the nozzle assembly relative to the first mixing tube 32, and the swirl plate 40 is sleeved on the outer periphery of the second mixing tube 33. The inner diameter of the first mixing tube 32 is larger than the outer diameter of the swirl plate 40. In this way, a part of the exhaust gas flowing out of the first mixing tube 32 flows to the swirl plate 40, where it is accelerated and circulated after being disturbed by the window fins 42; the other part flows to the second mixing tube 33, where it is accelerated and circulated after being disturbed by the swirl blades 31 on the second mixing tube 33.

[0039] Furthermore, the first mixing tube 32 is provided with a plurality of first swirl blades 311 arranged in rotation around its own axis, and the second mixing tube 33 is provided with a plurality of second swirl blades 312 arranged in rotation around its own axis; the rotation arrangement direction of the plurality of first swirl blades 311 is the same as the rotation arrangement direction of the plurality of second swirl blades 312, and the rotation arrangement direction of the plurality of first swirl blades 311 is opposite to the rotation arrangement direction of the plurality of window fins 42. In this way, the exhaust gas flowing out of the first mixing tube 32 is divided into two parts, one part of the exhaust gas changes its rotation direction and accelerates forward flow under the disturbance of the window fins 42 after flowing through the swirl plate 40, and the other part of the exhaust gas further increases the flow rate and flows forward along the original rotation direction after the second mixing tube 33. The two parts of the exhaust gas have opposite rotation directions and different flow rates, so that the collision effect on urea can be enhanced, which is conducive to further accelerating the crushing and decomposition of urea, and fully mixing with the ammonia generated by the decomposition of urea, thereby reducing urea crystallization.

[0040] Specifically, the plurality of first swirl blades 311 and the plurality of second swirl blades 312 may be arranged in a clockwise rotation, and the plurality of window fins 42 may be arranged in a counterclockwise rotation; or, the plurality of first swirl blades 311 and the plurality of second swirl blades 312 may be arranged in a counterclockwise rotation, and the plurality of window fins 42 may be arranged in a clockwise rotation. For example, in one embodiment, the first mixing tube 32 is provided with a plurality of first swirl blades 311 arranged in a clockwise rotation, the second mixing tube 33 is provided with a plurality of second swirl blades 312 arranged in a clockwise rotation, and the swirl plate 40 is provided with a plurality of window fins 42 arranged in a counterclockwise rotation.

[0041] However, it is not limited thereto. In other embodiments, the rotation arrangement direction of the plurality of first swirl blades 311 , the rotation arrangement direction of the plurality of second swirl blades 312 , and the rotation arrangement direction of the plurality of first swirl blades 311 may all be the same.

[0042] Along the flow direction of the exhaust gas, the first swirl blade 311 is arranged at the end of the first mixing tube 32, one end of the first swirl blade 311 is connected to the circumferential edge of the first mixing tube 32, and the other end is twisted and extended toward the axial direction close to the first mixing tube 32 and is set at an angle relative to the circumferential edge of the first mixing tube 32. The connection position of the first swirl blade 311 and the first mixing tube 32 is smoothly twisted and transitioned. One end of the second swirl blade 312 is connected to the circumferential edge of the second mixing tube 33, and the other end is twisted and extended toward the axial direction close to the second mixing tube 33 and is set at an angle relative to the circumferential edge of the second mixing tube 33. The connection between the second swirl blade 312 and the second mixing tube 33 is smoothly twisted and transitioned.

[0043] The included angle of the edge of the first swirl blade 311 along its width direction relative to the circumferential edge of the first mixing tube 32 is α, and the extension length of the first swirl blade 311 is l1. The included angle of the second swirl blade 312 along its width direction relative to the circumferential edge of the second mixing tube 33 is β, and the extension length of the second swirl blade 312 is l2.

[0044] In one embodiment, 105°≤α≤125°.

[0045] In one embodiment, 10% d1≤l1≤15% d1. It is understandable that the longer l1 is, the greater the disturbance of the exhaust gas by the first swirl blade 311, which makes it easier for the exhaust gas to rotate and circulate, while also increasing the resistance to the exhaust gas. Therefore, by setting 10% d1≤l1≤15% d1, it is possible to ensure that the first swirl blade 311 has a disturbing effect on the exhaust gas, and it is also helpful to avoid the first swirl blade 311 from generating greater resistance to the exhaust gas. For example, the value of l1 can be 10% d1, 11% d1, 12% d1, 12.5% ​​d1, 15% d1, etc. It can be set specifically according to actual needs, as long as it is within the above range.

[0046] In one embodiment, the angle between the edge of the second swirl blade 312 along its width direction and the circumferential edge of the second mixing tube 33 is β, and 105°≤β≤125°.

[0047] In one embodiment, 40% d2≤l2≤50% d2. It is understandable that the longer l2 is, the greater the disturbance of the second swirl blade 312 to the exhaust gas, which makes it easier for the exhaust gas to rotate and circulate, while also increasing the resistance to the exhaust gas. Therefore, by setting 40% d2≤l2≤50% d2, it can not only ensure the disturbance effect of the second swirl blade 312 on the exhaust gas, but also help to avoid the first swirl blade 311 from generating greater resistance to the exhaust gas. For example. The value of l2 can be 40% d2, 41% d2, 42% d2, 45.5% d2, 50% d2, etc., which can be set according to actual needs, as long as it is within the above range.

[0048] Optionally, in one embodiment, α=β. Manufacturing errors are allowed.

[0049] Optionally, in one embodiment, the extension length of the first swirl blade 311 is l1, the extension length of the second swirl blade 312 is l2, and l1<l2. Since the two-stage mixing tube 30 is respectively the first mixing tube 32 and the second mixing tube 33 along the direction from the air inlet 11 to the air outlet 12, that is, the second mixing tube 33 is arranged closer to the nozzle assembly than the first mixing tube 32 along the axial direction of the housing 10, therefore, by setting the extension length of the second swirl blade 312 longer, it is beneficial for the urea sprayed from the nozzle assembly to hit the second swirl blade 312, thereby promoting the decomposition of urea.

[0050] like Figure 2 and Figure 3 As shown, the shell 10 includes an outer cylinder 101 and an inner cylinder 102 and a baffle 103 respectively located inside the outer cylinder 101. One end of the inner cylinder 102 is provided with a flange 102a extending toward the outer cylinder 101, and is connected and fixed to the outer cylinder 101 through the flange 102a. Specifically, the flange 102a extends outward from the end of the inner cylinder 102 along the radial direction of the inner cylinder 102, so that the connection structure between the inner cylinder 102 and the outer cylinder 101 is simple and easy to install. Among them, the flange 102a and the inner cylinder 102 are an integral structure formed by bending. Of course, a connecting piece can also be set between the inner cylinder 102 and the outer cylinder 101, and the connecting piece is fixedly connected to the inner cylinder 102 and the outer cylinder 101 respectively, and the inner cylinder and the outer cylinder are connected and fixed together through the connecting piece.

[0051] The other end of the inner cylinder 102 is fixedly connected to the outer cylinder 101 through a baffle 103 .

[0052] The baffle 103 is annular and fixedly connected to the outer wall of the inner cylinder 102 , and the outer ring of the baffle 103 is fixedly connected to the inner wall of the outer cylinder 101 .

[0053] The side wall of the outer cylinder 101 is provided with a first mounting hole 101a, and the side wall of the inner cylinder 102 is provided with a second mounting hole 102b. The first mounting hole 101a and the second mounting hole 102b are correspondingly arranged along the radial direction of the outer cylinder 101 and are used to install the nozzle assembly. The air inlet 11 and the air outlet 12 are located on both sides of the nozzle assembly along the axial direction of the shell 10. The mixer 100 also includes a nozzle nut seat 20, the nozzle nut seat 20 has a first mounting hole 101a, and the nozzle assembly is fixed to the outer cylinder 101 through the nozzle nut seat 20.

[0054] Furthermore, the first mixing tube 32 is connected and fixed to the inner wall of the outer cylinder 101, and the second mixing tube 33 is connected and fixed to the inner wall of the inner cylinder 102 through the swirl plate 40. In this way, the internal space of the outer cylinder 101 and the inner cylinder 102 can be fully utilized, so that the structure of the mixer 100 is more compact. Among them, the swirl plate 40 is annular, and the inner ring of the swirl plate 40 is welded or clamped to the outer wall of the second mixing tube 33; the outer ring of the swirl plate 40 is welded or clamped to the inner wall of the inner cylinder 102. Specifically, the flange 102a is arranged toward the first swirl blade 311, and the second mixing tube 33 and the swirl plate 40 are arranged at one end of the inner cylinder 102 close to the flange 102a.

[0055] The mixer 100 further includes a mixing blade 50, which is installed at the gas outlet 12. Specifically, the mixing blade 50 includes a plurality of blades 51, which are arranged around the axis of the housing 10, and two adjacent blades 51 are arranged at an angle and spaced to form a flow gap. After the exhaust gas and urea are mixed, they pass through the flow gap and are discharged from the housing 10. In this way, after the exhaust gas and the decomposed urea are mixed, they can be further fully mixed by the disturbance of the mixing blade 50 when flowing through the gas outlet 12.

[0056] Furthermore, the inner diameter of the inner cylinder 102 is reduced at one end away from the flange 102a to form a contraction section, and the mixing blade 50 is installed in the contraction section. In this way, the exhaust gas flows through the mixing blade 50 to further increase the flow rate, which is conducive to preventing urea from crystallizing in the mixing blade 50.

[0057] The shell 10 is provided with a heat insulation cover 60, and a heat insulation layer 70 is provided between the shell 10 and the heat insulation cover 60. The heat insulation layer 70 between the heat insulation cover 60 plays a heat insulation role, which is conducive to the decomposition of urea in the mixer 100 and reduces the risk of urea crystallization. The heat insulation layer 70 is configured as heat insulation cotton.

[0058] Optionally, in one embodiment, the outer cylinder 101, the inner cylinder 102, the first mixing tube 30, the second mixing tube 33, the swirl plate 40 and the mixing blade 50 are coaxially arranged.

[0059] In the mixer 100 provided by the present application, urea enters the inner cylinder 102 radially from the nozzle assembly along the inner cylinder 102, and the tail gas enters the outer cylinder 101 and flows through the first mixing tube 32. The tail gas rotates and circulates under the disturbance of the first swirl blade. Then, the rotating tail gas is divided into two parts, one part is accelerated and circulated in the reverse rotation at the swirl plate 40, and the other part is accelerated and circulated in the second mixing tube 33 while maintaining the original rotation direction. Then, the tail gas is fully mixed with the urea sprayed by the nozzle assembly in the inner cylinder 102 and flows to the mixing blade 50. The mixed gas flow is accelerated again at the mixing blade 50 and then discharged from the outer cylinder 101.

[0060] The present application also provides a diesel engine aftertreatment system, which includes the mixer 100 described in any one of the above embodiments.

[0061] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0062] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the scope of patent protection of the present application shall be subject to the attached claims.

Claims

1. A mixer, characterized in that: The mixer (100) comprises a shell (10), a nozzle assembly and a multi-stage mixing tube (30); the shell (10) is in the shape of a hollow cylinder; the nozzle assembly is mounted on the side wall of the shell (10); and the inner cavity of the shell (10) comprises an air inlet (11) and an air outlet (12); The multiple stages of mixing tubes (30) are arranged in the air inlet (11) along the axial direction of the shell (10), at least one of the multiple stages of mixing tubes (30) is provided with a plurality of swirl blades (31) arranged and rotating around the axis of the mixing tube (30), and the flow cross-sectional area of ​​the multiple stages of mixing tubes (30) tends to decrease along the direction from the air inlet (11) to the air outlet (12); The nozzle assembly is used to spray urea into the housing (10), and the exhaust gas flows from the air inlet (11) through the plurality of mixing tubes (30) in sequence and circulates in rotation under the disturbance of the corresponding swirl blades (31). The circulated exhaust gas mixes with urea and flows toward the air outlet (12).

2. The mixer according to claim 1, characterized in that The mixer (100) further comprises a swirl plate (40), wherein the swirl plate (40) is arranged on the outer periphery of the mixing tube (30), and the swirl plate (40) is provided with a plurality of window fins (42) arranged and rotating around its own axis.

3. The mixer according to claim 2, characterized in that The mixing tube (30) is configured in two stages, and the mixer comprises a first mixing tube (32) and a second mixing tube (33). Along the axial direction of the shell (10), the second mixing tube (33) is arranged close to the nozzle assembly relative to the first mixing tube (32), and the swirl plate (40) is sleeved on the outer circumference of the second mixing tube (33), and the inner diameter of the first mixing tube (32) is greater than the outer diameter of the swirl plate (40); Part of the exhaust gas flowing out of the first mixing tube (32) flows toward the swirl plate (40), and the other part flows toward the second mixing tube (33).

4. The mixer according to claim 3, characterized in that The first mixing tube (32) is provided with a plurality of first swirl blades (311), and the second mixing tube (33) is provided with a plurality of second swirl blades (312); The rotational arrangement direction of the plurality of first swirl blades (311) is the same as the rotational arrangement direction of the plurality of second swirl blades (312), and the rotational arrangement direction of the plurality of first swirl blades (311) is opposite to the rotational arrangement direction of the plurality of window fins (42).

5. The mixer according to claim 4, characterized in that One end of the first swirl blade (311) is connected to the circumferential edge of the first mixing tube (32), and the other end is twisted and extended toward the axial direction close to the first mixing tube (32) and is arranged at an angle relative to the circumferential edge of the first mixing tube (32); One end of the second swirl blade (312) is connected to the circumferential edge of the second mixing tube (33), and the other end is twisted and extended toward the axial direction close to the second mixing tube (33) and is arranged at an angle relative to the circumferential edge of the second mixing tube (33).

6. The mixer according to claim 5, characterized in that The included angle between the edge of the first swirl blade (311) along its width direction and the circumferential edge of the first mixing tube (32) is α, and the included angle between the edge of the second swirl blade (312) along its width direction and the circumferential edge of the second mixing tube (33) is β, α=β; And / or, the extension length of the first swirl blade (311) is l1, the extension length of the second swirl blade (312) is l2, and l1<l2.

7. The mixer according to claim 5, characterized in that The diameter of the first mixing tube (32) is d1, the extension length of the first swirl blade (311) is l1, and 10% d1≤l1≤15% d1; the angle between the edge of the first swirl blade (311) along its width direction and the circumferential edge of the first mixing tube (32) is α, and 105°≤α≤125°; And / or, the diameter of the second mixing tube (33) is d2, the extension length of the second swirl blade (312) is l2, and 40% d2 ≤ l2 ≤ 50% d2; the angle between the edge of the second swirl blade (312) along its own width direction and the circumferential edge of the second mixing tube (33) is β, and 105° ≤ β ≤ 125°.

8. The mixer according to any one of claims 2 to 7, characterized in that: An angle γ is formed between the window opening fin (42) and the plane where the swirl plate (40) is located, and 40°≤γ≤50°.

9. The mixer according to claim 3, characterized in that The shell (10) comprises an outer cylinder (101), an inner cylinder (102) and a baffle (103) located inside the outer cylinder (101); one end of the inner cylinder (102) is provided with a flange (102a) extending toward the outer cylinder (101), and is connected and fixed to the outer cylinder (101) via the flange (102a); the other end of the inner cylinder (102) is fixedly connected to the outer cylinder (101) via the baffle (103); The side wall of the outer cylinder (101) is provided with a first mounting hole (101a), and the side wall of the inner cylinder (102) is provided with a second mounting hole (102b); the first mounting hole (101a) and the second mounting hole (102b) are arranged correspondingly along the radial direction of the outer cylinder (101) and are used to mount the nozzle assembly; the air inlet (11) and the air outlet (12) are located on both sides of the nozzle assembly along the axial direction of the shell (10).

10. The mixer according to claim 9, characterized in that The first mixing tube (32) is connected and fixed to the inner wall of the outer cylinder (101), and the second mixing tube (33) is connected and fixed to the inner wall of the inner cylinder (102) via the swirl plate (40).

11. The mixer according to claim 1, characterized in that The mixer further comprises a mixing blade (50), wherein the mixing blade (50) is installed at the air outlet portion (12).

12. The mixer according to claim 1, characterized in that The shell (10) is externally covered with a heat insulation cover (60), and a heat insulation layer (70) is provided between the shell (10) and the heat insulation cover (60).

13. A diesel engine aftertreatment system, characterized in that: The diesel engine aftertreatment system comprises the mixer according to any one of claims 1 to 12.

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