Design method of exhaust aftertreatment device of old special vehicle

Abstract

The application discloses a design method of an old special vehicle tail gas aftertreatment device, and belongs to the technical field of diesel engine tail gas aftertreatment, and comprises the following steps: S1, obtaining the installation structure and size parameters of an original muffler installed on an old special vehicle; S2, setting a through-wall flow nanometer catalytic purification silencer system with a purification and silencing integrated structure aiming at noise suppression, pollution elimination and continuous regeneration; S3, the through-wall flow nanometer catalytic purification silencer system is divided into three parts, namely, a nanometer catalyst continuous regeneration system design, a catalytic silencer structure design and an interface design; and S4, an old special vehicle tail gas aftertreatment device capable of replacing the original muffler in situ is designed. The application designs a tail gas aftertreatment device which can be used in a compact and closed power cabin, is used for replacing an old muffler in situ, reduces the discharge of harmful tail gas of the old special vehicle, reduces environmental pollution and improves the riding comfort in the vehicle.

Description

Technical Field

[0001] The invention relates to the technical field of diesel engine exhaust treatment, in particular to a design method of an exhaust post-treatment device for old-style special vehicles. Background Art

[0002] Due to the technical limitations of the production era, the diesel engines of old special vehicles do not have special harmful gas filtering devices and are only equipped with mufflers to eliminate noise.

[0003] Older special vehicles meet the National I emission standard. Diesel engine exhaust is discharged directly through the muffler and exhaust pipe, producing high levels of harmful gases and causing considerable noise. However, current common exhaust treatment equipment is cylindrical in shape. Exhaust treatment equipment that meets performance requirements is larger than the original muffler, making it difficult to install in the compact, cramped engine compartments of special vehicles. Exhaust treatment equipment with a smaller diameter also fails to meet the performance requirements of special vehicles, making it impossible to replace them in situ.

[0004] In view of this shortcoming, it is urgent to develop a special vehicle exhaust after-treatment equipment to solve the above problems. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a design method for an exhaust gas after-treatment device of an old special vehicle. Without affecting the engine output power and the appearance of the whole vehicle, the old muffler of the old special vehicle is replaced with the exhaust gas after-treatment device in situ, that is, the original vehicle exhaust muffler is removed and directly replaced with the exhaust gas after-treatment device in situ. Its installation structure and dimensional parameters are completely consistent with the exhaust muffler of the old special equipment vehicle, without causing major changes to the structure and appearance of the whole vehicle, and has good interchangeability.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A design method for an exhaust gas after-treatment device for an old-style special vehicle comprises the following steps:

[0008] S1, obtaining the installation structure and size parameters of the original muffler installed on the old special vehicle;

[0009] S2, a through-wall flow nanocatalytic purification and silencing system with an integrated structure of purification and silencing is set up with the goal of "noise suppression + pollution elimination + continuous regeneration";

[0010] S3, the through-wall nanocatalytic purification and silencer system is divided into three parts: nanocatalyst continuous regeneration system design, catalytic silencer structure design and interface design;

[0011] S4 is an exhaust gas after-treatment device for old special vehicles that can replace the original muffler in situ.

[0012] A further improvement of the technical solution of the present invention is that S3 specifically includes:

[0013] S31, the nanocatalyst continuous regeneration system uses an oxidation unit + a capture unit + a muffler unit to oxidize and decompose harmful substances in diesel exhaust and physically capture particulate matter, achieving continuous regeneration through catalytic combustion to achieve the goal of smoke elimination;

[0014] S32, in the structural design of catalytic muffler, the exhaust gas flow field and acoustics of the exhaust gas after-treatment device structure are simulated and optimized;

[0015] The S33 adopts the same interface design as the original muffler, so it can be replaced in situ on old special vehicles.

[0016] A further improvement of the technical solution of the present invention is that: S31 specifically includes:

[0017] The oxidation unit uses a DOC carrier with an asymmetric cross-section and a nano-palladium-based catalyst coated on the surface of the DOC carrier to convert CO and HC compounds into harmless H2O and CO2, and convert NO into NO2;

[0018] The capture unit uses a POC copper-based molecular sieve carrier with a split-flow structure, and a catalyst is coated on the surface of the POC copper-based molecular sieve carrier to achieve continuous catalytic regeneration of particulate matter;

[0019] The silencer unit optimizes the internal flow field results through the design of resistive silencer + resistant sound-absorbing material, reduces the turbulence caused by the structure of the after-treatment device, and combines the dynamic flow field synergistic optimization when the engine changes working conditions to reduce the exhaust flow rate, change the noise fluctuation frequency characteristics, and achieve the impedance silencer goal.

[0020] A further improvement of the technical solution of the present invention is that the capture unit is divided into an oxidation section and a capture section, a nano-platinum-based catalyst is coated on the POC copper-based molecular sieve carrier of the oxidation section, and a nano-platinum-based particle regeneration catalyst is coated on the POC copper-based molecular sieve carrier of the capture section.

[0021] A further improvement of the technical solution of the present invention is that: S32 specifically includes:

[0022] A first cavity as a pre-cavity is provided behind the air intake pipe connected to the exhaust pipe of the old special vehicle to slow down the flow of the exhaust gas and reduce the intensity of turbulent changes;

[0023] A second chamber is provided after the first chamber as an oxidation unit to reduce harmful substances such as CO, HC, and VOF;

[0024] A third chamber is set up behind the second chamber as a capture unit to accurately identify and capture the amount of carbon deposits and intelligently implement active regeneration;

[0025] A fourth cavity is provided behind the third cavity as a muffler unit, and an impedance muffler reduces exhaust noise;

[0026] An exhaust pipe is arranged behind the fourth cavity.

[0027] Further improvements to the technical solution of the present invention are that: the cross-sectional sizes of the first cavity, the second cavity, the third cavity and the fourth cavity are consistent; a front end cover is provided at the connection between the intake pipe and the first cavity; a rear end cover is provided at the connection between the fourth cavity and the exhaust pipe; the cross-sectional area of ​​the first cavity is larger than the cross-sectional area of ​​the intake pipe; and the cross-sectional area of ​​the fourth cavity is larger than the cross-sectional area of ​​the exhaust pipe.

[0028] A further improvement of the technical solution of the present invention is that the first cavity and the second cavity, the second cavity and the third cavity, and the third cavity and the fourth cavity are all connected via cavity connecting flanges.

[0029] A further improvement of the technical solution of the present invention is that: a first pressure sensor interface is provided at the upper end of the connection between the second cavity and the third cavity; a second pressure sensor interface is provided at the upper end of the connection between the third cavity and the fourth cavity; the first pressure sensor interface and the second pressure sensor interface are respectively installed with a first pressure sensor and a second pressure sensor, which are linked to the vehicle EUC, and the usage status of the exhaust gas after-treatment device is displayed on the instrument panel.

[0030] A further improvement of the technical solution of the present invention is that: a first temperature sensor interface is provided at the bottom end of the connection between the intake pipe and the first cavity; a second temperature sensor interface is provided at the bottom end of the connection between the second cavity and the third cavity; a third temperature sensor interface is provided at the bottom end of the connection between the third cavity and the fourth cavity; the first temperature sensor interface, the second temperature sensor interface and the third temperature sensor interface are respectively installed with a first temperature sensor, a second temperature sensor and a third temperature sensor, which are linked to the vehicle EUC, and the usage status of the exhaust gas after-treatment device is displayed on the instrument panel.

[0031] A further improvement of the technical solution of the present invention is that the cross-sections of the first cavity, the second cavity, the third cavity and the fourth cavity are all in the shape of an upper semicircle + a rectangular parallelepiped + a lower semicircle, and the cross-sections of the intake pipe and the exhaust pipe are both circular.

[0032] Due to the adoption of the above technical solution, the technical advancements achieved by the present invention are:

[0033] 1. The present invention is to design an exhaust after-treatment device for old special vehicles to purify the exhaust containing harmful substances such as HC, CO, and VOF emitted by old special vehicles. The device can be replaced in situ in old special vehicles with small and compact power compartments to reduce the emission of harmful exhaust gases from existing old special vehicles, reduce environmental pollution, and improve vehicle riding comfort.

[0034] 2. After the muffler of the old special vehicle in the present invention was replaced in situ with the exhaust after-treatment device designed in this application, the subsequent sports car test showed that the vehicle's power did not decrease, the exhaust emissions were significantly reduced, and the noise was significantly reduced, effectively reducing the pollution to the environment caused by the existing old special vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. Those skilled in the art can derive other drawings based on these drawings without inventive effort.

[0036] Figure 1 This is a schematic diagram of the integrated purification and silencing design of the exhaust after-treatment device for special vehicles provided by the present invention;

[0037] Figure 2 This is a schematic structural diagram of the exhaust gas after-treatment device for special vehicles provided by the present invention;

[0038] Figure 3 This is a schematic diagram of the installation of the exhaust gas after-treatment device for special vehicles provided by the present invention on an old special vehicle;

[0039] Figure 4 2 is a schematic cross-sectional view of the oxidation unit carrier in the present invention;

[0040] Figure 5 Schematic diagram of the capture unit carrier structure in the present invention;

[0041] Figure 6 is a transmission loss curve obtained by simulation in the present invention;

[0042] Figure 7 This is a back pressure simulation result diagram in the present invention;

[0043] Among them, 1. Intake pipe; 2. First cavity; 3. Second cavity; 4. Third cavity; 5. Fourth cavity; 6. Exhaust pipe; 7. Front end cover; 8. Cavity connecting flange; 9. Rear end cover; P1, First pressure sensor interface; P2, Second pressure sensor interface; T1, First temperature sensor interface; T2, Second temperature sensor interface; T3, Third temperature sensor interface; 10, Exhaust pipe; 11, Vehicle side panel. DETAILED DESCRIPTION

[0044] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0045] The terms "first," "second," and the like in the specification and claims of the present invention and in the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a particular order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having," as well as any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to these processes, methods, products, or apparatus.

[0046] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments:

[0047] like Figure 1-3 As shown, a design method for an exhaust gas after-treatment device for an old-style special vehicle includes the following steps:

[0048] S1, obtaining the installation structure and size parameters of the original muffler installed on the old special vehicle;

[0049] S2, a through-wall flow nanocatalytic purification and silencing system with an integrated structure of purification and silencing is set up with the goal of "noise suppression + pollution elimination + continuous regeneration";

[0050] S3, the through-wall nano-catalytic purification and silencer system is divided into three parts: nano-catalyst continuous regeneration system design, catalytic silencer structure design and interface design; specifically including:

[0051] S31, the nanocatalyst continuous regeneration system uses an oxidation unit + a capture unit + a muffler unit to oxidize and decompose harmful substances in diesel exhaust and physically capture particulate matter, achieving continuous regeneration through catalytic combustion to achieve the goal of smoke elimination;

[0052] Specifically, such as Figure 4 、 5 As shown, the oxidation unit uses a DOC carrier with an asymmetric cross-section, and a nano-palladium-based catalyst is coated on the surface of the DOC carrier to convert CO and HC compounds into harmless H2O and CO2, and convert NO into NO2;

[0053] The capture unit uses a POC copper-based molecular sieve carrier with a split-flow structure, and a catalyst is coated on the surface of the POC copper-based molecular sieve carrier to achieve continuous catalytic regeneration of particulate matter;

[0054] Furthermore, the capture unit is divided into an oxidation section and a capture section. A nano-platinum-based catalyst is coated on the POC copper-based molecular sieve carrier in the oxidation section, and a nano-platinum-based particle regeneration catalyst is coated on the POC copper-based molecular sieve carrier in the capture section.

[0055] This application uses nano-scale palladium-based, platinum-based and platinum-based particle regeneration catalysts with smaller diameters than traditional precious metal oxides as catalysts, which increases the contact area between the catalyst and the particulate matter, thereby improving the catalytic activity and ignition characteristics of the catalyst and widening the regeneration temperature window.

[0056] DOC stands for diesel oxidation catalyst. DOCs typically use metal or ceramic as a catalyst carrier, with the primary active ingredients in the coating being precious and rare metals such as platinum and palladium. When diesel exhaust passes through the catalyst, hydrocarbons (HC) and carbon monoxide (CO) react rapidly with the oxygen in the exhaust at relatively low temperatures, producing pollution-free H2O and CO2. The DOC purifies the HC and CO in the exhaust.

[0057] POC stands for particle oxidation catalyst. It works by capturing particulate matter and burning it at high exhaust temperatures (250-500°C) to reduce PM.

[0058] The muffler unit optimizes the internal flow field through the design of resistive muffler + resistant sound absorbing material, reduces the turbulence caused by the post-processing device structure, and combines the dynamic flow field optimization under the engine's variable working conditions to reduce the exhaust flow rate, change the noise fluctuation frequency characteristics, and achieve the impedance muffler goal. The carrier of the oxidation unit and the capture unit also has a muffler effect

[0059] S32, in the structural design of catalytic muffler, the exhaust gas flow field and acoustics of the exhaust gas after-treatment device structure are simulated and optimized;

[0060] (1) Simulation calculation:

[0061] (1) Sound field

[0062] The muffler unit is designed with a perforated tube expansion cavity structure and a foam ceramic carrier matrix structure. The influence of fillets and flange structures on the analysis results is not considered in the acoustic simulation calculation. The wall boundary is assumed to be a rigid wall surface and the sound absorption of the wall surface is not considered. By setting reasonable sound field boundary conditions and simulation, the transmission loss curves of the unit with and without a purification matrix are obtained, as shown in the figure below. Figure 6 shown.

[0063] The simulation results show that the transmission loss curve Figure I In the region, the transmission loss of the exhaust gas treatment device with a purification matrix is ​​significantly improved compared to that without a purification matrix, and the rules are basically the same. Figure II In the region, the transmission loss band of the exhaust gas treatment device with purification matrix is ​​significantly wider than that without purification matrix, and the anechoic trough disappears. Figure III In this region, the transmission loss of exhaust gas treatment devices with a purification matrix significantly increased compared to those without, but the curve pattern was not clear. Without a purification unit, the average transmission loss of the resistant exhaust gas treatment device was 14.7dB. With the purification unit, the average transmission loss increased to 37.6dB, meeting the design requirement for noise reduction (above 15dB).

[0064] (2) Flow field

[0065] Since the exhaust treatment device has a relatively complex resistant silencer structure, it is easy to cause a sudden change in the cross-section of the exhaust gas flowing in its pipeline, thereby causing turbulence, so an appropriate turbulence calculation formula should be selected to calculate it. In the simulation calculation, the porosity, flow resistivity, permeability of the carrier material and the inlet velocity of the exhaust gas are adjusted to optimize the parameters. The optimal calculation result is determined: the increase in the original exhaust system does not exceed 5 kPa, which meets the design requirements. Figure 7 shown.

[0066] Experiment: Through preliminary fluid analysis and post-treatment matching, three post-treatment systems with different technical routes were initially determined, including the application and matching of different post-treatment equipment such as DPF, DOC, and POC, as well as the selection and coating of catalysts. After simulation and bench test verification, and after two rounds of tests, the DOC+POC structure was finally determined as the final post-treatment system. The appearance was designed according to the appearance and interface dimensions of the special vehicle muffler. By developing a special carrier to adapt to the existing structural dimensions, the optimal treatment system was achieved. Through experimental verification, under the premise of meeting the power requirements, the free acceleration method tested the light absorption coefficient between 1.3 and 1.6, which met the design requirements.

[0067] DPF is the abbreviation of Diesel Particulate Filter. It is installed in the exhaust system. DPF can filter and capture PM (particulate matter) in the exhaust gas, which can reduce PM (particulate matter) in the exhaust gas. Usually the filtering effect can reach 70%-90%.

[0068] (2) Optimization design

[0069] like Figure 2 As shown in FIG, the exhaust gas after-treatment device for old special vehicles specifically includes:

[0070] A first cavity 2 serving as a pre-cavity is provided behind an air intake pipe 1 connected to an exhaust pipe of an old-fashioned special vehicle to slow down the flow of exhaust gas and reduce the intensity of turbulent changes;

[0071] A second chamber 3 is provided after the first chamber 2 as an oxidation unit to reduce harmful substances such as CO, HC, and VOF (soluble organic matter, sometimes also called volatile organic matter).

[0072] A third chamber 4 is provided behind the second chamber 3 as a capture unit to accurately identify and capture the amount of carbon deposits and intelligently implement active regeneration;

[0073] A fourth cavity 5 is provided behind the third cavity 4 as a muffler unit, and the impedance muffler reduces exhaust noise;

[0074] An exhaust pipe 6 is provided behind the fourth cavity 5 .

[0075] Furthermore, the cross-sectional sizes of the first cavity 2, the second cavity 3, the third cavity 4 and the fourth cavity 5 are the same; a front end cover 7 is provided at the connection between the intake pipe 1 and the first cavity 2; a rear end cover 9 is provided at the connection between the fourth cavity 5 and the exhaust pipe 6; the cross-sectional area of ​​the first cavity 2 is larger than the cross-sectional area of ​​the intake pipe 1; the cross-sectional area of ​​the fourth cavity 5 is larger than the cross-sectional area of ​​the exhaust pipe 6.

[0076] Furthermore, the first cavity 2 and the second cavity 3 , the second cavity 3 and the third cavity 4 , and the third cavity 4 and the fourth cavity 5 are all connected via cavity connecting flanges 8 .

[0077] Furthermore, a first pressure sensor interface P1 is provided at the upper end of the connection between the second cavity 3 and the third cavity 4; a second pressure sensor interface P2 is provided at the upper end of the connection between the third cavity 4 and the fourth cavity 5; the first pressure sensor interface P1 and the second pressure sensor interface P2 are respectively installed with a first pressure sensor and a second pressure sensor, which are linked to the vehicle EUC and display the usage status of the exhaust after-treatment device on the instrument panel.

[0078] Furthermore, a first temperature sensor interface T1 is provided at the bottom end of the connection between the intake pipe 1 and the first cavity 2; a second temperature sensor interface T2 is provided at the bottom end of the connection between the second cavity 3 and the third cavity 4; a third temperature sensor interface T3 is provided at the bottom end of the connection between the third cavity 4 and the fourth cavity 5; the first temperature sensor interface T1, the second temperature sensor interface T2 and the third temperature sensor interface T3 are respectively installed with the first temperature sensor, the second temperature sensor and the third temperature sensor, which are linked to the vehicle EUC to display the usage status of the exhaust after-treatment device on the instrument panel.

[0079] Furthermore, the cross sections of the first cavity 2 , the second cavity 3 , the third cavity 4 and the fourth cavity 5 are all in the shape of an upper semicircle + a rectangular parallelepiped + a lower semicircle, and the cross sections of the air intake pipe 1 and the exhaust pipe 6 are both circular.

[0080] The S33 adopts the same interface design as the original muffler, so it can be replaced in situ on old special vehicles;

[0081] S4 is an exhaust gas after-treatment device for old special vehicles that can replace the original muffler in situ.

[0082] like Figure 3 As shown in the schematic diagram of installing the exhaust gas after-treatment device of a special vehicle on an old special vehicle, the exhaust muffler originally installed on the side panel 11 of the old special vehicle is removed without affecting the engine output power and the appearance of the whole vehicle, and the exhaust gas after-treatment device designed in this application is directly replaced in situ on the exhaust pipe 10. Its installation structure and dimensional parameters are completely consistent with the exhaust muffler of the old special equipment vehicle, without causing major changes to the structure and appearance of the whole vehicle, and has good interchangeability;

[0083] The specific usage process is as follows:

[0084] (1) After the diesel engine exhaust enters the intake pipe 1 from the exhaust pipe 10, it flows through the first cavity 2, reduces the exhaust gas flow rate, and then enters the second cavity 3. In the process of the exhaust gas passing through the various channels in the catalytic oxidant carrier, under the action of the catalyst, CO and HC are oxidized into CO2 and H2O, and NO is converted into NO2, which increases the NO2 concentration. Since NO2 has a stronger oxidizing property than O2 under lower temperature conditions, it is conducive to the oxidation and combustion of carbon soot particles within the normal exhaust temperature range of the diesel engine. At the same time, the oxidation and combustion of CO and HC increase the exhaust temperature, ensuring the continuous regeneration of the particles captured by the capture unit within the normal operating range of the diesel engine.

[0085] (2) If the engine is in a low-load operation for a long time, which is a specific harsh working condition, resulting in a significantly low exhaust temperature, it is difficult to continuously regenerate the particles in the POC copper-based molecular sieve carrier of the capture unit. The ECU uses the first and second pressure sensors to detect the exhaust pressure at the inlet and outlet of the device in real time. When the exhaust back pressure value reaches the set value based on the detection data, an alarm is issued to intelligently remind the driver to perform maintenance operations: the first method is to increase the diesel engine workload to increase the exhaust temperature and promote the oxidation and combustion of particles; the second method is to use compressed air to blow back toward the exhaust treatment device. This avoids clogging of the exhaust treatment device and further monitors the use status of the exhaust treatment device.

[0086] That is, the special vehicle exhaust after-treatment device designed in this application can be used as exhaust after-treatment equipment in a compact and sealed power compartment, and can be used to replace old mufflers in situ to reduce the emission of harmful exhaust gases from old special vehicles, reduce environmental pollution, and improve vehicle riding comfort.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A design method for an exhaust gas after-treatment device for old-style special vehicles, characterized in that: The following steps are involved: S1, obtaining the installation structure and size parameters of the original muffler installed on the old special vehicle; S2, a through-wall nano-catalytic purification and silencing system with an integrated structure of purification and silencing is set up with the goal of "noise suppression + pollution elimination + continuous regeneration"; S3, the through-wall nano-catalytic purification and silencer system is divided into three parts: nano-catalyst continuous regeneration system design, catalytic silencer structure design and interface design; specifically including: S31, the nanocatalyst continuous regeneration system uses an oxidation unit + a capture unit + a muffler unit to oxidize and decompose harmful substances in diesel exhaust and physically capture particulate matter, achieving continuous regeneration through catalytic combustion to achieve the goal of smoke elimination; S32, in the structural design of the catalytic muffler, simulate and optimize the exhaust gas flow field and acoustics of the exhaust gas after-treatment device structure; specifically including: A first cavity (2) serving as a pre-cavity is provided behind an air intake pipe (1) connected to an exhaust pipe of an old-style special vehicle to slow down the flow of exhaust gas and reduce the intensity of turbulent changes; A second chamber (3) serving as an oxidation unit is provided after the first chamber (2) to reduce harmful substances such as CO, HC, and VOF; A third cavity (4) is provided behind the second cavity (3) as a capture unit to accurately identify and capture the amount of carbon deposits and intelligently implement active regeneration; A fourth cavity (5) serving as a muffler unit is provided behind the third cavity (4), and the impedance muffler reduces exhaust noise; An exhaust pipe (6) is provided behind the fourth cavity (5); The cross-sections of the first cavity (2), the second cavity (3), the third cavity (4), and the fourth cavity (5) are of the same size; a front end cover (7) is provided at the connection between the intake pipe (1) and the first cavity (2); a rear end cover (9) is provided at the connection between the fourth cavity (5) and the exhaust pipe (6); the cross-section of the first cavity (2) is larger than the cross-section of the intake pipe (1); the cross-section of the fourth cavity (5) is larger than the cross-section of the exhaust pipe (6); A first pressure sensor interface (P1) is provided at the upper end of the connection between the second cavity (3) and the third cavity (4); a second pressure sensor interface (P2) is provided at the upper end of the connection between the third cavity (4) and the fourth cavity (5); a first pressure sensor and a second pressure sensor are respectively installed on the first pressure sensor interface (P1) and the second pressure sensor interface (P2), and are linked to the vehicle EUC to display the use status of the exhaust gas post-treatment device on the instrument panel; A first temperature sensor interface (T1) is provided at the bottom end of the connection between the intake pipe (1) and the first cavity (2); a second temperature sensor interface (T2) is provided at the bottom end of the connection between the second cavity (3) and the third cavity (4); and a third temperature sensor interface (T3) is provided at the bottom end of the connection between the third cavity (4) and the fourth cavity (5); the first temperature sensor interface (T1), the second temperature sensor interface (T2) and the third temperature sensor interface (T3) are respectively installed with a first temperature sensor, a second temperature sensor and a third temperature sensor, which are linked to the vehicle EUC and display the use status of the exhaust gas post-treatment device on the instrument panel; The S33 adopts the same interface design as the original muffler, so it can be replaced in situ on old special vehicles; S4 is an exhaust gas after-treatment device for old special vehicles that can replace the original muffler in situ.

2. The design method of an exhaust gas post-treatment device for old-style special vehicles according to claim 1, characterized in that: S31 specifically includes: The oxidation unit uses a DOC carrier with an asymmetric cross-section and a nano-palladium-based catalyst coated on the surface of the DOC carrier to convert CO and HC compounds into harmless H2O and CO2, and convert NO into NO2; The capture unit uses a POC copper-based molecular sieve carrier with a split-flow structure, and a catalyst is coated on the surface of the POC copper-based molecular sieve carrier to achieve continuous catalytic regeneration of particulate matter; The silencer unit optimizes the internal flow field results through the design of resistive silencer + resistant sound-absorbing material, reduces the turbulence caused by the structure of the after-treatment device, and combines the dynamic flow field synergistic optimization when the engine changes working conditions to reduce the exhaust flow rate, change the noise fluctuation frequency characteristics, and achieve the impedance silencer goal.

3. The design method of an exhaust gas post-treatment device for old-style special vehicles according to claim 2, characterized in that: The capture unit is divided into an oxidation section and a capture section. A nano-platinum-based catalyst is coated on the POC copper-based molecular sieve carrier in the oxidation section, and a nano-platinum-based particle regeneration catalyst is coated on the POC copper-based molecular sieve carrier in the capture section.

4. The design method of an exhaust gas post-treatment device for old-style special vehicles according to claim 1, characterized in that: The first cavity (2) and the second cavity (3), the second cavity (3) and the third cavity (4), and the third cavity (4) and the fourth cavity (5) are all connected via cavity connecting flanges (8).

5. The design method of an exhaust gas post-treatment device for old-style special vehicles according to claim 1, characterized in that: The cross sections of the first cavity (2), the second cavity (3), the third cavity (4) and the fourth cavity (5) are all in the shape of an upper semicircle + a rectangular parallelepiped + a lower semicircle, and the cross sections of the air intake pipe (1) and the exhaust pipe (6) are both circular.

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