A compact natural gas engine aftertreatment system based on aerodynamic rectification and control method

Abstract

The application discloses a compact natural gas engine aftertreatment system based on aerodynamic rectification and a control method thereof, comprising a compact aerodynamic rectification coupled aftertreatment device, an intelligent urea injection control system, a multi-parameter monitoring system and an exhaust gas circulation system. The aftertreatment device integrates an oxidation catalyst, an aerodynamic rectification structure and an SCR / ASC integrated catalyst, and is packaged in a shared shell; the aerodynamic rectification structure adopts a converging-diverging flow channel, a gradient-pore porous medium rectification layer and static guide vanes to realize uniform distribution of exhaust flow and deep evaporation mixing of urea; the intelligent urea injection control system adopts a self-adaptive UKF-MPC composite control system to precisely adjust the urea injection amount; the multi-parameter monitoring system constructs a sensor network to realize feedback control; and the exhaust gas circulation system adjusts the exhaust gas exceeding the standard through an electric three-way valve to realize recycling treatment. x The application improves the system integration, methane purification efficiency and NOx conversion rate through the functional synergy of multi-stage catalytic units and aerodynamic rectification optimization.

Description

Technical Field

[0001] This invention relates to the field of internal combustion engine exhaust gas purification technology, and more particularly to a compact natural gas engine aftertreatment system and control method based on pneumatic rectification. Background Technology

[0002] Natural gas engines are considered clean power sources due to their low carbon emissions, but their exhaust still contains unburned methane (CH4) and nitrogen oxides (NOx). x Pollutants include nitrogen oxides (NOx) and carbon monoxide (CO). Methane, in particular, is a potent greenhouse gas with a global warming potential (GWP) 25-30 times that of carbon dioxide, and its stable molecular structure makes it difficult to remove effectively through conventional oxidation methods. x This will lead to photochemical smog and acid rain, posing a serious threat to the environment and human health.

[0003] Currently, most aftertreatment systems employ a configuration of multiple independently packaged catalytic units connected in series. For example, Chinese patent CN114856780A discloses a natural gas vehicle exhaust treatment system that uses a pre-coupled tightly coupled oxidation catalyst (DOC) and reduction catalyst (SCR) structure. However, this system still suffers from drawbacks such as large system size, complex connecting pipelines, low thermal management efficiency, and high methane and NO emissions during cold starts. x Problems such as poor conversion efficiency exist. In particular, the traditional spatially separated layout of the selective catalytic reduction (SCR) unit and the ammonia escape catalysis (ASC) unit easily leads to poor uniformity of the NH3 reducing agent distribution, and the limited temperature window for ASC activity results in high NO conversion efficiency. x Effective synergistic optimization between conversion efficiency and NH3 slip control is difficult to achieve. Furthermore, existing technologies lack systematic solutions to problems such as the difficulty in oxidizing methane and uneven urea mixing in natural gas engine exhaust.

[0004] In addition, existing urea mixing units mostly adopt a single static mixer structure. Under conditions of small displacement and low exhaust flow rate, the urea droplets evaporate insufficiently and the NH3 distribution is not uniform, which can easily cause uneven reaction at the SCR carrier end face. At the same time, there is a risk of urea crystallization and blockage. Traditional PID injection control strategies are not adaptable to dynamic changes in operating conditions and cannot achieve the dual goals of high NOx conversion efficiency and low ammonia escape.

[0005] Therefore, in view of the shortcomings of existing after-treatment technologies for pollutants from natural gas engines, there is an urgent need for a highly integrated after-treatment system with significant synergistic effects to achieve synergistic and efficient purification of multiple pollutants. Summary of the Invention

[0006] To address the aforementioned technical problems, a compact natural gas engine aftertreatment system and control method based on pneumatic rectification are provided. This system addresses the shortcomings of existing natural gas engine aftertreatment systems, such as low integration, poor urea mixing uniformity, insufficient low-temperature purification efficiency, and low ammonia escape control accuracy. It employs a modular, compact, coupled structure, combining multi-stage pneumatic rectification design with adaptive unscented Kalman filter-model predictive control (UKF-MPC) composite control to achieve synergy between high-efficiency purification, precise control, and system miniaturization.

[0007] The technical means employed in this invention are as follows: A compact natural gas engine aftertreatment system based on pneumatic rectification, comprising: A compact pneumatic rectification coupled aftertreatment device includes an air inlet, an oxidation catalyst, a pneumatic rectification structure, and an integrated SCR / ASC catalyst connected in sequence; the oxidation catalyst is externally equipped with a housing; The intelligent urea injection control system includes a urea injection valve, a mixer, a urea tank, a urea pump, and an adaptive UKF-MPC composite control system. The urea tank is connected to the inlet of the urea pump via a liquid pipeline, and the outlet of the urea pump is connected to the urea injection valve via a liquid pipeline. The urea injection valve is installed in the throat channel and located upstream of the mixer. The adaptive UKF-MPC composite control system is electrically connected to both the urea pump and the urea injection valve to control the urea injection pressure and injection volume. A multi-parameter monitoring system, including temperature sensors, pressure sensors, exhaust mass flow sensors, and NO sensors. x The system includes a sensor, an NH3 sensor, and the adaptive UKF-MPC composite control system; the adaptive UKF-MPC composite control system is electrically connected to each sensor. The exhaust gas recirculation system includes a first exhaust port, a second exhaust port, a third exhaust port, an electrically operated three-way regulating valve, a gas delivery pipeline, a one-way valve, a PLC, and the adaptive UKF-MPC composite control system. The electrically operated three-way regulating valve is connected to the first, second, and third exhaust ports. The second exhaust port is located at the end of the SCR / ASC integrated catalytic converter and is directly connected to one port of the electrically operated three-way regulating valve. The third exhaust port is connected to the gas delivery pipeline. The one-way valve is located at the top of the gas delivery pipeline where it connects to the intake pipeline. The PLC is electrically connected to the electrically operated three-way regulating valve and the adaptive UKF-MPC composite control system.

[0008] Furthermore, the oxidation catalyst is connected to the pneumatic rectification structure via a flange, and the pneumatic rectification structure is connected to the integrated SCR / ASC catalyst via a V-shaped ring.

[0009] Furthermore, the aerodynamic rectification structure includes a converging flow channel, a throat flow channel, a diverging flow channel, a gradient porous medium rectification layer, and static guide vanes; the gradient porous medium rectification layer is disposed at the connection between the throat flow channel and the diverging flow channel; the static guide vanes are disposed on the inner wall of the diverging flow channel behind the gradient porous medium rectification layer.

[0010] Furthermore, the gradient porous medium rectifying layer is a three-layer gradient structure, including an upstream layer, an intermediate layer, and a downstream layer; the upstream layer is a high porosity and ultra-large pore size structure, the intermediate layer is a medium pore size and porosity structure, and the downstream layer is a minimum pore size and minimum porosity structure.

[0011] Furthermore, the SCR / ASC integrated catalyst is coated in sections on the same support. The front end of the support is a selective catalytic reduction unit coated with SCR catalyst, and the rear end of the support is an ammonia escape catalytic unit coated with ASC catalyst. The connection between the SCR unit and the ASC unit adopts a textured coating pattern.

[0012] Furthermore, in the multi-parameter monitoring system, the NO x The sensor includes an upstream NO sensor installed before the oxidation catalyst. x Sensors and downstream NO installed after the SCR / ASC integrated catalyst x Sensors; there are four temperature sensors, which are respectively located before the oxidation catalyst, after the oxidation catalyst, before the SCR / ASC integrated catalyst, and after the SCR / ASC integrated catalyst; there are three pressure sensors, which are respectively located before the oxidation catalyst and before and after the SCR / ASC integrated catalyst; the NH3 sensor is installed after the SCR / ASC integrated catalyst.

[0013] Furthermore, the first end of the electric three-way regulating valve is connected to the bottom of the compact pneumatic rectification coupling aftertreatment device through the second exhaust port, the second end is connected to the air through the first exhaust port, and the third end is connected to the gas transmission pipeline through the third exhaust port; the adaptive UKF-MPC composite control system is electrically connected to the PLC, and the PLC controls the opening and closing of the port of the electric three-way regulating valve to send the non-compliant exhaust gas back to the air inlet for reprocessing through the gas transmission pipeline and the one-way valve; the opening pressure of the one-way valve matches the exhaust back pressure to prevent the airflow from the air inlet from flowing back into the gas transmission pipeline.

[0014] The present invention also discloses an exhaust gas aftertreatment method using the above-described system, comprising the following steps: Step 1: Start the multi-parameter monitoring system to collect real-time data on exhaust mass flow rate, temperature at each monitoring point, and NO. xThe concentration, flow resistance after rectification, and NH3 escape concentration are recorded and transmitted to the adaptive UKF-MPC composite control system. Step 2: The exhaust gas flows sequentially through the oxidation catalyst, the aerodynamic rectification structure, and the integrated SCR / ASC catalyst. In the aerodynamic rectification structure, the adaptive UKF-MPC composite control system calculates the optimal urea injection rate based on sensor signals and the internal NH3 load model, controlling the urea injection valve to inject urea into the throat channel. The urea undergoes evaporation, pyrolysis, and hydrolysis to generate NH3, which mixes with the exhaust gas in the mixer. Then, it passes through a gradient porous media rectification layer and static guide vanes to form a uniform airflow before entering the integrated SCR / ASC catalyst for NO removal. x Reduction and ammonia escape catalysis; Step 3: The adaptive UKF-MPC composite control system is compared with the final NO. x The concentration and target value are used to dynamically fine-tune the urea injection rate; simultaneously, based on downstream NO... x The monitoring results of the sensor and the NH3 sensor, if NO x Both the concentration of NH3 and the concentration of NH3 meet the emission standards. The PLC controls the electric three-way regulating valve to open the first exhaust port to discharge the exhaust gas. If the standard is not met, the third exhaust port is opened so that the exhaust gas re-enters the air inlet through the gas pipeline and the one-way valve for further treatment.

[0015] Compared with the prior art, the present invention has the following advantages: 1. This invention integrates three units—DOC, pneumatic rectification structure, and SCR / ASC integrated catalyst—into a continuous configuration, connected by flanges and V-rings. This reduces the need for traditional separate flange connections, piping, and independent encapsulation, thereby lowering system volume, weight, heat loss, and manufacturing costs. Simultaneously, the pneumatic rectification structure enables deep evaporation and component mixing of urea, optimizing airflow distribution.

[0016] 2. This invention significantly improves the low-temperature methane oxidation and NO production. x In terms of conversion efficiency, DOC raises the overall system temperature through a strongly exothermic reaction, partially oxidizing methane above 400℃, thus solving the problem of difficult methane removal. Simultaneously, DOC regulates the NO / NO2 ratio, providing rapid SCR reaction conditions for downstream SCR and significantly improving NO conversion efficiency in the low-temperature region. x Conversion efficiency. The integrated SCR / ASC structure, through its concave-convex coating, allows escaped NH3 to be immediately captured by the ASC, avoiding the uneven distribution of NH3 caused by connecting pipe sections in the separate design. This greatly improves the dynamic response speed and accuracy of ammonia escape control and effectively suppresses secondary pollution.

[0017] 3. The three-stage rectification structure of the present invention, consisting of a gradually narrowing-expanding flow channel, a gradient porous medium rectifying layer, and static guide vanes, utilizes the Venturi effect to accelerate and stabilize the flow. The three-layer gradient porous medium achieves deep evaporation of urea and NH3 / NO3. x The microscopic uniform mixing and the static guide vanes further precisely distribute the airflow, ensuring a highly uniform temperature, velocity, and concentration distribution in the flow field before the SCR reaction, thereby improving the overall purification efficiency.

[0018] 4. The multi-parameter sensor network based on the adaptive UKF-MPC composite control system monitors and dynamically optimizes the urea injection quantity in real time to compensate for performance degradation such as catalyst aging; the exhaust gas recirculation system sends non-compliant exhaust gas back to the intake port for reprocessing through an electric three-way regulating valve to ensure that emissions always meet environmental protection requirements. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a connection diagram of a compact natural gas engine aftertreatment system based on pneumatic rectification according to the present invention; Figure 2 This is a schematic diagram of the compact pneumatic rectification coupling post-processing device in this invention; Figure 3 This is a schematic diagram of the integrated SCR / ASC catalyst structure in the compact pneumatic rectification coupled aftertreatment device of the present invention; Figure 4 This is a schematic diagram of the gradient pore porous medium rectifying layer structure in the pneumatic rectification structure of the compact pneumatic rectification coupling post-processing device of the present invention; The components include: 1. Inlet; 2. Oxidation Catalyst (DOC); 3. Pneumatic Rectification Structure; 4. Integrated SCR / ASC Catalyst; 5. First Exhaust Port; 6. Electric Three-Way Control Valve; 7. Gas Delivery Pipeline; 8. Check Valve; 9. Housing; 10. Flange; 11. V-Ring; 12. Exhaust Mass Flow Sensor; 13. NO xSensors; 14. Temperature sensor; 15. Pressure sensor; 16. NH3 sensor; 17. Gradient pore porous media rectifying layer; 18. Urea injection valve; 19. Mixer; 20. Selective catalytic reduction (SCR) unit; 21. Ammonia escape catalysis (ASC) unit; 22. Static guide vane; 23. Gradient converging flow channel; 24. Throat flow channel; 25. Gradient expanding flow channel; 26. Urea tank; 27. Urea pump; 28. PLC; 29. ​​Adaptive UKF-MPC composite control system; 30. Second exhaust port; 31. Third exhaust port; 32. Upstream layer; 33. Intermediate layer; 34. Downstream layer. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0024] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0025] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0026] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0027] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0028] like Figures 1-4As shown, this embodiment of the invention discloses a compact natural gas engine aftertreatment system based on pneumatic rectification, comprising: A compact pneumatic rectification coupled aftertreatment device includes an air inlet 1, an oxidation catalyst (DOC) 2, a pneumatic rectification structure 3, and an integrated SCR / ASC catalyst 4 connected in sequence; the oxidation catalyst 2 is externally provided with a housing 9; optionally, the compact pneumatic rectification coupled aftertreatment device encapsulates the oxidation catalyst (DOC), the pneumatic rectification structure, and the integrated SCR / ASC catalyst into a continuous shared housing.

[0029] The intelligent urea injection control system includes a urea injection valve 18, a mixer 19, a urea tank 26, a urea pump 27, and an adaptive UKF-MPC composite control system 29. The urea tank 26 stores urea solution and is connected to the urea pump 27. The urea tank 26 is connected to the inlet of the urea pump 27 via a liquid pipeline, and the outlet of the urea pump 27 is connected to the urea injection valve 18 via a liquid pipeline. The urea injection valve 18 is installed in the throat channel 24 and is located upstream of the mixer 19. The adaptive UKF-MPC composite control system 29 is electrically connected to both the urea pump 27 and the urea injection valve 18, and is used to control the urea injection pressure and injection volume. The multi-parameter monitoring system includes a temperature sensor 14, a pressure sensor 15, an exhaust gas mass flow sensor 12, and a NO sensor. x Sensor 13, NH3 sensor 16, and the adaptive UKF-MPC composite control system 29; the adaptive UKF-MPC composite control system 29 is electrically connected to each sensor; the system constructs a multi-parameter sensor network with the adaptive UKF-MPC composite control system as the core to realize feedback control and closed-loop correction; The exhaust gas recirculation system includes a first exhaust port 5, a second exhaust port 30, a third exhaust port 31, an electrically operated three-way regulating valve 6, a gas supply pipeline 7, a one-way valve 8, a PLC 28, and the adaptive UKF-MPC composite control system 29. The electrically operated three-way regulating valve 6 is connected to the first exhaust port 5, the second exhaust port 30, and the third exhaust port 31. The second exhaust port 30 is located at the end of the SCR / ASC integrated catalytic converter 4 and is directly connected to one port of the electrically operated three-way regulating valve 6. The third exhaust port 31 is connected to the gas supply pipeline 7. The one-way valve 8 is located at the top of the gas supply pipeline 7 where it connects to the inlet 1 pipeline. The PLC 28 is electrically connected to the electrically operated three-way regulating valve 6 and the adaptive UKF-MPC composite control system 29. The PLC controls the opening and closing of the two ports of the electrically operated three-way regulating valve to ensure that exhaust gas emissions always meet requirements, thereby controlling pollutants.

[0030] The oxidation catalyst (DOC) achieves deep oxidation of hydrocarbons (HC) and carbon monoxide (CO) through a strongly exothermic reaction. The released heat of reaction effectively increases the overall system temperature. Simultaneously, the DOC oxidizes NO emitted from the engine to NO2. Furthermore, the NO / NO2 ratio output by the DOC provides conditions for rapid SCR reaction downstream (NO + NO2 + 2NH3 → 2N2 + 3H2O), thereby significantly increasing NO levels in the low-temperature region. x Conversion efficiency. The pneumatic rectification structure improves system compactness through a highly integrated multi-stage rectification design, achieving uniform exhaust flow distribution and creating ideal reaction conditions for downstream SCR, ensuring the efficient conversion of urea decomposition products NH3 and NO. x Sufficient contact is achieved. The integrated SCR / ASC catalyst integrates two units onto the same carrier using a partitioned coating technology. NH3 escaping from the SCR reaction zone immediately enters the ASC reaction zone and can be efficiently captured, solving the problem of uneven NH3 distribution caused by connecting pipe sections in separate designs.

[0031] Furthermore, the oxidation catalyst 2 is connected to the pneumatic rectification structure 3 via a flange 10, and the pneumatic rectification structure 3 is connected to the SCR / ASC integrated catalyst 4 via a V-shaped clamp 11. The V-shaped clamp 11 includes a V-shaped clamp body, bolt fasteners, and a sealing ring; a first flange is provided at the rear end of the pneumatic rectification structure 3, and a second flange is provided at the front end of the SCR / ASC integrated catalyst 4. The outer edges of both the first and second flanges are provided with tapered inclined surfaces, and the two tapered inclined surfaces are arranged opposite each other to form a V-shaped groove. The cross-section of the V-shaped clamp body is V-shaped and matches the shape of the V-shaped groove. The first and second flanges are pressed and fixed by bolt fasteners.

[0032] Furthermore, the aerodynamic rectification structure 3 includes a converging flow channel 23, a throat flow channel 24, a expanding flow channel 25, a gradient porous media rectification layer 17, and static guide vanes 22. The gradient porous media rectification layer 17 is disposed at the connection between the throat flow channel 24 and the expanding flow channel 25. The static guide vanes 22 are disposed on the inner wall of the expanding flow channel 25 behind the gradient porous media rectification layer 17. The converging-expanding flow channel design, based on the Venturi effect, initially stabilizes and accelerates the turbulent airflow from DOC, thereby optimizing the airflow distribution. The gradient porous media rectification layer is located at the connection between the throat flow channel and the expanding flow channel, and the material of the gradient porous media rectification layer can be selected according to the actual situation. It causes the airflow to pass through countless tiny pores, converting macroscopic kinetic energy into microscopic, uniform flow for deep evaporation. Static guide vanes are positioned behind the gradient porous media rectifying layer, on the inner wall of the gradually expanding flow channel, to achieve micro-mixing of the airflow. The urea injection valve 18 and mixer 19 are located within the throat flow channel 24 of the pneumatic rectifying structure 3 in the compact pneumatic rectifying coupled post-treatment device. Based on the synergistic effect of the gradient porous media rectifying layer 17 and the gradually expanding flow channel 25, the necessary path for urea droplet evaporation is effectively compressed, thereby achieving optimization and compact design of the system structure dimensions.

[0033] Optionally, the outer edge of the gradient pore porous medium rectifying layer 17 is provided with an annular metal skeleton, the outer diameter of which is adapted to the inner diameter of the gradually expanding channel 25. The annular metal skeleton is embedded in an annular mounting groove provided on the inner wall of the gradually expanding channel 25, and a wave spring washer is provided in the annular mounting groove. The annular metal skeleton and the inner wall of the gradually expanding channel 25 are fixed by laser welding, and the weld points are evenly distributed along the circumference of the annular metal skeleton. The upstream layer 32, the intermediate layer 33, and the downstream layer 34 are connected into a whole by sintering or diffusion welding, and the contact surfaces between the layers are provided with a positioning structure with concave and convex fits.

[0034] Furthermore, the gradient porous media rectifying layer 17 has a three-layer gradient structure, including an upstream layer 32, an intermediate layer 33, and a downstream layer 34. The upstream layer 32 has a high porosity and ultra-large pore size structure, the intermediate layer 33 has a medium pore size and porosity structure, and the downstream layer 34 has a minimum pore size and lowest porosity structure. The upstream layer, with its high porosity and ultra-large pore size structure, can further break up large droplets that are not completely broken in the urea mist, and evenly distribute the broken droplets and airflow to the downstream fine structure, preventing liquid flow concentration. The intermediate layer, with its medium pore size and porosity structure, is a key area for urea droplet evaporation and hydrolysis. Its more complex pore structure than the upstream layer enhances airflow turbulence and promotes the initial mixing of gaseous products (NH3) and the exhaust gas. The downstream layer, with its minimum pore size and lowest porosity structure, creates a very strong microscopic mixing environment through its extremely small pores, ensuring that NH3 molecules mix with NO. x Molecules achieve thorough mixing at the molecular level before entering the SCR process.

[0035] In this embodiment, the tapered channel 23 has a cone angle of 30°, the tapered channel 25 has a cone angle of 15°, the gradient porous medium rectifying layer 17 is made of FeCrAl metal foam material, the upstream layer 32 has a pore diameter of 1.5mm and a porosity of 0.9, the middle layer 33 has a pore diameter of 1.0mm and a porosity of 0.85, the downstream layer 34 has a pore diameter of 0.5mm and a porosity of 0.75, and the entire unit has undergone superhydrophobic surface modification treatment. The static guide vane 22 adopts a spiral design with an installation angle of 30°.

[0036] The compact coupled structure design effectively improves system integration and reduces heat loss. The oxidation catalyst (DOC) 2 achieves deep oxidation of hydrocarbons (HC) and carbon monoxide (CO) through a strongly exothermic reaction. The released heat of reaction effectively increases the overall system temperature. Simultaneously, the DOC oxidizes NO emitted from the engine to NO2, providing key reactants for the rapid SCR reaction within the SCR unit. The aerodynamic rectification structure 3 enhances system compactness through a highly integrated multi-stage rectification design, achieving uniform exhaust flow distribution and creating ideal reaction conditions for downstream SCR, ensuring the efficient reaction of urea decomposition products NH3 and NO. x Sufficient contact is achieved. The SCR / ASC integrated catalyst 4 integrates two units onto the same carrier using a partitioned coating technology. NH3 escaping from the SCR reaction zone immediately enters the ASC reaction zone and can be efficiently captured, solving the problem of uneven NH3 distribution caused by connecting pipe sections in separate designs. The stepped reaction process inside the device achieves effective control of CH4, CO, and NO. xComprehensive and efficient purification. In this example, DOC2 is coated with a noble metal catalyst (Pt / Pd), the SCR unit (front section of the support) 20 in the SCR / ASC integrated catalyst 4 is coated with a Cu-based molecular sieve catalyst, and the ASC unit (back section of the support) 21 is coated with a Pt-based catalyst.

[0037] Furthermore, the integrated SCR / ASC catalyst 4 is coated in sections on the same carrier. The front end of the carrier is a selective catalytic reduction unit 20 coated with SCR catalyst, and the rear end of the carrier is an ammonia escape catalytic unit 21 coated with ASC catalyst. The connection between the SCR unit and the ASC unit adopts a textured coating pattern. Specifically, the rear end of the coating layer of the SCR unit is an axially interlocking end face with alternating concave and convex shapes, and the front end of the coating layer of the ASC unit is a mating end face that matches the shape of the interlocking end face. The two are interlocked along the axial direction of the carrier without any gap transition.

[0038] Furthermore, in the multi-parameter monitoring system, the NO x Sensor 13 includes an upstream NO sensor installed before the oxidation catalyst 2. x Sensors and downstream NO installed after the SCR / ASC integrated catalyst 4 x Sensors; there are four temperature sensors 14, which are respectively located before the oxidation catalyst 2, after the oxidation catalyst 2, before the SCR / ASC integrated catalyst 4, and after the oxidation catalyst 2; there are three pressure sensors 15, which are respectively located before the oxidation catalyst 2 and before and after the SCR / ASC integrated catalyst 4; the NH3 sensor 16 is installed after the SCR / ASC integrated catalyst 4.

[0039] Furthermore, the first end of the electric three-way regulating valve 6 is connected to the bottom of the compact pneumatic rectification coupling aftertreatment device through the second exhaust port 30, the second end is connected to the air through the first exhaust port 5, and the third end is connected to the gas transmission pipeline 7 through the third exhaust port 31; the adaptive UKF-MPC composite control system 29 controls the opening and closing of the port of the electric three-way regulating valve 6 through the PLC 28 according to the monitoring signal of the multi-parameter monitoring system, so as to send the non-compliant exhaust gas back to the air inlet 1 for reprocessing through the gas transmission pipeline 7 and the one-way valve 8.

[0040] The present invention also discloses a method for exhaust gas aftertreatment of the above system, comprising the following steps: Step 1: Start the multi-parameter monitoring system to collect real-time data on exhaust mass flow rate, temperature at each monitoring point, and NO. x The concentration, flow resistance after rectification, and NH3 escape concentration are recorded and transmitted to the adaptive UKF-MPC composite control system 29. Step 2: The exhaust gas flows sequentially through the oxidation catalyst 2, the aerodynamic rectification structure 3, and the SCR / ASC integrated catalyst 4. In the aerodynamic rectification structure 3, the adaptive UKF-MPC composite control system 29 calculates the optimal urea injection quantity by integrating sensor signals and the internal NH3 load model, and controls the urea injection valve 18 to inject urea into the throat channel 24. The urea is evaporated, pyrolyzed, and hydrolyzed to generate NH3, which mixes with the exhaust gas in the mixer 19, and then passes through the gradient pore porous media rectification layer 17 and the static guide vanes 22 to form a uniform airflow before entering the SCR / ASC integrated catalyst 4 for NO removal. x Reduction and ammonia escape catalysis; Step 3: The adaptive UKF-MPC composite control system 29 is compared with the final NO. x The concentration and target value are dynamically adjusted to finely control the urea injection volume. At the same time, based on the exhaust gas composition monitoring results, if the standard is met, the PLC28 controls the electric three-way regulating valve 6 to open the first exhaust port 5 to discharge the exhaust gas. If the standard is not met, the third exhaust port 31 is opened so that the exhaust gas re-enters the intake port 1 through the gas transmission pipeline 7 and the one-way valve 8 for further treatment.

[0041] Specifically, step one: activate the multi-parameter monitoring system to monitor the exhaust gas velocity in real time using an exhaust mass flow sensor; monitor the exhaust temperatures at the DOC inlet, DOC outlet, and the inlet and outlet of the SCR / ASC integrated catalytic converter in real time using a temperature sensor; and monitor the exhaust temperatures upstream of the DOC converter using an upstream NO3-O4 sensor. x Sensors measure the engine's raw NO x Concentration, via the downstream NO located after the SCR / ASC integrated catalyst x Sensor measures final NO x Concentration; real-time monitoring of flow resistance after rectification via a pressure sensor bridging the DOC and the pneumatic rectifier structure; real-time monitoring of NH3 escape concentration via an NH3 sensor; all monitored data are transmitted to the adaptive UKF-MPC composite control system as input variables for control decisions; Step Two: The exhaust gas enters the DOC unit of the compact pneumatic rectification coupled aftertreatment device through the inlet. The noble metal catalyst (Pt / Pd) in the DOC promotes the oxidation reaction of carbon monoxide (CO) and non-methane hydrocarbons (NMHC) in the exhaust gas, generating CO2 and H2O. The reaction process is continuously exothermic. When the temperature is higher than 400℃, the DOC partially oxidizes unburned methane (CH4), further releasing heat. Some of the nitric oxide (NO) in the exhaust gas is catalytically oxidized to nitrogen dioxide (NO2), providing key reactants for the rapid SCR reaction in the SCR unit. The exhaust gas treated by the DOC enters the pneumatic rectification structure unit, where acceleration and initial flow stabilization are achieved in the converging section. Subsequently, the adaptive UKF-MPC composite control system integrates multi-parameter sensor signals and internal storage. The NH3 loading model is used to calculate the optimal injection rate of urea solution and instruct the urea injection valve to inject precisely. The urea solution evaporates, pyrolyzes, and hydrolyzes in the high-temperature exhaust gas to generate NH3, the reducing agent required for the SCR reaction. At the throat, peak kinetic energy is used to achieve ultra-fine atomization of the urea, which is then fully mixed with the exhaust gas in the mixer. The uniformly mixed airflow enters the gradient pore porous media rectifying layer, where forced flow homogenization is achieved, along with deep evaporation and micro-mixing of components. Upon entering the diffuser section, the airflow decelerates and pressure is restored, while macro-mixing occurs. Precise distribution by static guide vanes creates an ideal airflow with highly uniform temperature, velocity, and concentration distribution. The mixed exhaust gas enters the SCR unit (front section of the support) in the integrated SCR / ASC catalyst. Under the action of the Cu-based molecular sieve catalyst, NH3 and NO... x A selective catalytic reduction reaction (NO + NO2 + 2NH3 → 2N2 + 3H2O) occurs, efficiently generating nitrogen and water. Unreacted NH3 escapes into the ASC unit (back section of the support) with the gas flow, where it is selectively catalytically oxidized on a low-load Pt-based catalyst (4NH3 + 3O2 → 2N2 + 6H2O), maximally suppressing side reactions and preventing NH3 leakage from causing secondary pollution. Among them, the adaptive UKF-MPC composite control system transforms the NH3 load and emission status, which cannot be directly measured, into controllable variables through UKF. Then, MPC achieves the optimal injection decision under constraints. Furthermore, it can incorporate aging factor estimation and fault diagnosis into the control process to enhance the robustness, fault tolerance and long-term stability of the system.

[0042] The specific control process of the adaptive UKF-MPC composite control system includes the following steps: (1) Data collection steps: Obtain engine operating conditions, exhaust temperature, NO x Concentration, flow rate, oxygen concentration, and injection feedback signals; (2) Preprocessing steps: Complete filtering, amplitude limiting and cross-sensitivity compensation; (3) State estimation steps: Adaptive UKF is used to estimate NH3 coverage, ammonia storage, input NH3 and tail gas NO. x The state is reconstructed; the state variables of the adaptive UKF include NO. x The system uses a low-order control-guided SCR model as the object model for NH3 concentration, NH3 coverage, and state prediction and measurement updates. It adopts an unscented Kalman filter recursive formula and updates the noise covariance matrix online. (4) Aging factor estimation and fault diagnosis steps: used to identify catalyst aging, sensor deviation and actuator abnormality, and update model parameters or trigger fault-tolerant reconstruction accordingly; (5) MPC optimization steps: using NO x The optimal urea injection rate for the current cycle is solved by using the cost function with error, NH3slip, and injection fluctuation as objectives, under the constraints of injection upper limit, NH3slip upper limit, and actuator dynamics. (6) Execution feedback step: convert the optimal injection quantity into nozzle control command and continue iterating in the next sampling cycle.

[0043] The system is constructed using a low-order control-oriented SCR model as the object model to take into account both NH3 storage and NO. x The transformation and dynamic description capabilities of NH3slip, as well as its real-time feasibility; subsequently, the state variable is defined as NO. x Internal states that can be controlled, such as concentration, NH3 concentration, NH3 coverage, ammonia storage, or input NH3, are then used to establish an observer via adaptive UKF to correct for sensor noise, NH3 cross-sensitivity, time-varying operating conditions, and aging disturbances online. During operation, sensor data is first acquired and filtered, limited, and anomaly removed. Then, adaptive UKF is used to recursively estimate the internal states of NH3 that cannot be directly measured. Next, this estimated state is used as the initial value for MPC, and a system is constructed in the prediction time domain with NO... x The cost function is set as the objective of error, NH3 slip, and injection fluctuation, and the optimal control quantity is solved. Finally, only the urea injection command at the current moment is executed, and the new measurement value after execution is fed back to the estimator and optimizer, forming a continuously iterative rolling closed loop.

[0044] The system uses engine speed, load, exhaust temperature, flow rate, and NO to measure data. x Concentration, oxygen concentration, and injection feedback signals are used as external inputs, and combined with internal variables such as the internal NH3 load model, NH3 storage, NH3 coverage, catalyst capacity, and aging factor, the adaptive UKF first adjusts the NH3 coverage, ammonia storage, input NH3, and exhaust NO. xThe state is reconstructed online, and the estimation results are then input into the MPC. Under the constraints of the injection upper limit, NH3slip upper limit, and actuator dynamics, the optimal urea injection quantity for the current cycle is solved in a rolling manner. Finally, the nozzle pulse width, injection rate, or injection time is output, and the value is further corrected in the next sampling cycle based on the newly acquired signal, thus forming a closed-loop calculation process of "sensor signal input - state reconstruction - constraint optimization - injection execution - feedback update".

[0045] The control program comprises six steps: data acquisition, preprocessing, state estimation, aging factor estimation and fault diagnosis, MPC optimization, and execution feedback. The data acquisition step obtains engine operating conditions, exhaust temperature, and NO... x Concentration, flow rate, oxygen concentration, and injection feedback signals; the preprocessing step completes filtering, amplitude limiting, and cross-sensitivity compensation; the state estimation step uses adaptive UKF to measure NH3 coverage, ammonia storage, input NH3, and exhaust NO. x The state is reconstructed; the aging factor estimation and fault diagnosis steps are used to identify catalyst aging, sensor deviation and actuator abnormality, and update model parameters or trigger fault-tolerant reconstruction accordingly; the MPC optimization step solves for the optimal urea injection quantity in the current cycle under the injection limit, NH3slip limit and actuator constraints; the execution feedback step converts the optimal injection quantity into nozzle control commands and continues to iterate in the next sampling cycle, thereby forming closed-loop control.

[0046] Step 3: The adaptive UKF-MPC composite control system continuously monitors temperature and pressure data at various points to diagnose the system's thermal management status; and compares the final NO... x The concentration and target value are dynamically adjusted to fine-tune the urea injection rate to compensate for performance degradation caused by catalyst aging, sulfur poisoning, and other factors; the exhaust gas composition is monitored, specifically based on downstream NO... x The monitoring results of the sensor and the NH3 sensor, if NO x Both the concentration of NH3 and the concentration of PM2.5 meet the emission standards. If the PLC receives a signal that it meets the air pollution prevention and control standards in the "Law of the People's Republic of China on the Prevention and Control of Atmospheric Pollution", the PLC controls the electric three-way regulating valve to connect the exhaust port 1 connected to the air, and the exhaust gas is discharged. If the PLC does not receive a signal that it meets the air pollution prevention and control standards in the "Law of the People's Republic of China on the Prevention and Control of Atmospheric Pollution", the PLC controls the electric three-way regulating valve to connect the exhaust port 3 connected to the gas pipeline. The exhaust gas is then re-entered into the compact pneumatic rectification coupling post-treatment device through the gas pipeline via a one-way valve for filtration again until it meets the standards. Only then can it be discharged from the exhaust port 1 connected to the air by the electric three-way regulating valve, so as to ensure that the emissions always meet the standards.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions 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 compact aftertreatment system for a natural gas engine based on pneumatic rectification, characterized in that, include: A compact pneumatic rectification coupled aftertreatment device includes an air inlet (1), an oxidation catalyst (2), a pneumatic rectification structure (3), and an integrated SCR / ASC catalyst (4) connected in sequence; the oxidation catalyst (2) is provided with a housing (9) on its exterior. The intelligent urea injection control system includes a urea injection valve (18), a mixer (19), a urea tank (26), a urea pump (27), and an adaptive UKF-MPC composite control system (29). The urea tank (26) is connected to the inlet of the urea pump (27) via a liquid pipeline, and the outlet of the urea pump (27) is connected to the urea injection valve (18) via a liquid pipeline. The urea injection valve (18) is installed in the throat flow channel (24) and is located upstream of the mixer (19). The adaptive UKF-MPC composite control system (29) is electrically connected to the urea pump (27) and the urea injection valve (18) respectively, and is used to control the urea injection pressure and injection volume. The multi-parameter monitoring system includes a temperature sensor (14), a pressure sensor (15), an exhaust mass flow sensor (12), and a NO sensor. x Sensor (13), NH3 sensor (16), and the adaptive UKF-MPC composite control system (29); the adaptive UKF-MPC composite control system (29) is electrically connected to each sensor; The exhaust gas recirculation system includes a first exhaust port (5), a second exhaust port (30), a third exhaust port (31), an electric three-way regulating valve (6), a gas transmission pipeline (7), a one-way valve (8), a PLC (28), and the adaptive UKF-MPC composite control system (29). The electric three-way regulating valve (6) is connected to the first exhaust port (5), the second exhaust port (30), and the third exhaust port (31). The second exhaust port (30) is located at the end of the SCR / ASC integrated catalyst (4) and is directly connected to one port of the electric three-way regulating valve (6). The third exhaust port (31) is connected to the gas transmission pipeline (7). The one-way valve (8) is located at the top of the gas transmission pipeline (7) where it connects to the gas inlet (1). The PLC (28) is electrically connected to the electric three-way regulating valve (6) and the adaptive UKF-MPC composite control system (29).

2. The compact natural gas engine aftertreatment system based on pneumatic rectification according to claim 1, characterized in that, The oxidation catalyst (2) is connected to the pneumatic rectification structure (3) via a flange (10), and the pneumatic rectification structure (3) is connected to the SCR / ASC integrated catalyst (4) via a V-shaped ring (11).

3. The compact natural gas engine aftertreatment system based on pneumatic rectification according to claim 1, characterized in that, The aerodynamic rectification structure (3) includes a tapered flow channel (23), a throat flow channel (24), a gradually expanding flow channel (25), a gradient porous medium rectification layer (17), and a static guide vane (22); the gradient porous medium rectification layer (17) is disposed at the connection between the throat flow channel (24) and the gradually expanding flow channel (25); the static guide vane (22) is disposed on the inner wall of the gradually expanding flow channel (25) behind the gradient porous medium rectification layer (17).

4. The compact natural gas engine aftertreatment system based on pneumatic rectification according to claim 3, characterized in that, The gradient porous medium rectifying layer (17) is a three-layer gradient structure, including an upstream layer (32), an intermediate layer (33) and a downstream layer (34); the upstream layer (32) is a high porosity and ultra-large pore size structure, the intermediate layer (33) is a medium pore size and porosity structure, and the downstream layer (34) is a minimum pore size and minimum porosity structure.

5. The compact natural gas engine aftertreatment system based on pneumatic rectification according to claim 1, characterized in that, The SCR / ASC integrated catalyst (4) is coated in sections on the same support. The front end of the support is a selective catalytic reduction unit (20) coated with SCR catalyst, and the rear end of the support is an ammonia escape catalytic unit (21) coated with ASC catalyst. The connection between the SCR unit and the ASC unit adopts a coating form with concave and convex joints.

6. The compact natural gas engine aftertreatment system based on pneumatic rectification according to claim 1, characterized in that, In the multi-parameter monitoring system, the NO x The sensor (13) includes an upstream NO sensor installed before the oxidation catalyst (2). x Sensors and downstream NO installed after the SCR / ASC integrated catalyst (4) x Sensors; there are four temperature sensors (14), which are respectively located in front of the oxidation catalyst (2), behind the oxidation catalyst (2), in front of the SCR / ASC integrated catalyst (4), and behind the oxidation catalyst (2); there are three pressure sensors (15), which are respectively located in front of the oxidation catalyst (2) and in front of and behind the SCR / ASC integrated catalyst (4); the NH3 sensor (16) is installed behind the SCR / ASC integrated catalyst (4).

7. The compact natural gas engine aftertreatment system based on pneumatic rectification according to claim 1, characterized in that, The first end of the electric three-way regulating valve (6) is connected to the bottom of the compact pneumatic rectification coupling aftertreatment device through the second exhaust port (30), the second end is connected to the air through the first exhaust port (5), and the third end is connected to the gas transmission pipeline (7) through the third exhaust port (31). The adaptive UKF-MPC composite control system (29) is electrically connected to the PLC (28). The PLC (28) controls the opening and closing of the port of the electric three-way regulating valve (6) to send the substandard exhaust gas back to the air inlet (1) for reprocessing through the gas transmission pipeline (7) and the one-way valve (8). The opening pressure of the one-way valve (8) matches the exhaust back pressure to prevent the airflow from the air inlet from flowing back into the gas transmission pipeline.

8. A method for exhaust gas aftertreatment using the system described in any one of claims 1 to 7, characterized in that, Includes the following steps: Step 1: Start the multi-parameter monitoring system to collect real-time data on exhaust mass flow rate, temperature at each monitoring point, and NO. x The concentration, flow resistance after rectification and NH3 escape concentration are recorded and transmitted to the adaptive UKF-MPC composite control system (29). Step 2: The exhaust gas flows sequentially through the oxidation catalyst (2), the aerodynamic rectification structure (3), and the SCR / ASC integrated catalyst (4). In the aerodynamic rectification structure (3), the adaptive UKF-MPC composite control system (29) calculates the optimal urea injection quantity by integrating sensor signals and the internal NH3 load model, and controls the urea injection valve (18) to inject urea in the throat channel (24). The urea is evaporated, pyrolyzed, and hydrolyzed to generate NH3, which is mixed with the exhaust gas in the mixer (19). Then, it passes through the gradient pore porous medium rectification layer (17) and the static guide vanes (22) to form a uniform airflow, which enters the SCR / ASC integrated catalyst (4) for NO removal. x Reduction and ammonia escape catalysis; Step 3: The adaptive UKF-MPC composite control system (29) is compared with the final NO x The concentration and target value are used to dynamically fine-tune the urea injection rate; simultaneously, based on downstream NO... x The monitoring results of sensor (13) and NH3 sensor (16) show that if NO x If the concentrations of NH3 and NH3 both meet the emission standards, the PLC (28) controls the electric three-way regulating valve (6) to connect the first exhaust port (5) to discharge the exhaust gas. If the standard is not met, the third exhaust port (31) is connected so that the exhaust gas re-enters the air inlet (1) through the gas pipeline (7) and the one-way valve (8) for further treatment.

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