Online prediction method for N2O emission of diesel engine aftertreatment system

Abstract

The invention relates to an online prediction method for N2O emission of a diesel engine aftertreatment system. A thermodynamic model and a chemical reaction kinetic model are established for each catalytic unit. The engine rear fuel injection quantity, the DOC inlet exhaust temperature and the like serve as input, and the DOC outlet NO2 concentration is output through a DOC model; the DPF outlet NO2 concentration is output through a DPF model by combining the input of the DPF inlet exhaust temperature and the like; then, the SCR inlet exhaust temperature and the like serve as input, and the concentration of N2O and NH3 at an SCR outlet is output through an SCR model; and finally, outputting the N2O concentration of the tail pipe through an ASC model according to the input such as the exhaust temperature of an ASC inlet, so as to realize the accurate online prediction of the N2O emission of the diesel engine post-processing system. Compared with the prior art, the N2O emission condition of the whole aftertreatment system can be accurately predicted based on the chemical reaction kinetic model and the thermodynamic model, and a scientific basis is provided for cooperative control of the aftertreatment unit.

Description

Technical Field

[0001] The present invention relates to the technical field of motor vehicle emission control, and in particular to an online prediction method for N2O emissions from a diesel engine after-treatment system. Background Art

[0002] In recent years, with global warming and environmental pollution becoming increasingly pressing, governments around the world have introduced stricter emissions regulations to limit greenhouse gas and pollutant emissions. Among them, nitrous oxide (N2O), a potent greenhouse gas, has a per-molecule warming potential 298 times greater than that of carbon dioxide and persists in the atmosphere for 100-120 years. Furthermore, N2O depletes the ozone layer, contributing to ozone holes and increasing ultraviolet radiation, posing serious risks to human health and ecosystems. Therefore, controlling N2O emissions has become a global concern.

[0003] Diesel engines, as an important power source in the transportation sector, produce exhaust emissions containing a certain amount of N2O. While diesel engine aftertreatment systems have achieved significant success in reducing pollutants such as nitrogen oxides (NOx) and particulate matter (PM), they remain deficient in controlling N2O emissions. Existing aftertreatment systems primarily reduce pollutant emissions through the synergistic effects of units such as the diesel oxidation catalyst (DOC), particulate filter (DPF), selective catalytic reduction (SCR), and ammonia oxidation catalyst (ASC). However, each catalytic unit may generate N2O during operation, and existing systems lack the means to accurately predict and control N2O generation and emissions.

[0004] Some existing technical solutions, such as patent CN116646015A, propose a hierarchical prediction method for diesel engine exhaust concentration. This method primarily focuses on the hierarchical prediction of NO2 concentration. While this method can provide some support for SCR low-temperature conversion efficiency and DPF passive regeneration performance, it has limitations in predicting N2O emissions. This method does not fully consider the impact of each catalytic unit on N2O generation in the entire aftertreatment system, lacking a comprehensive prediction and control strategy for N2O emissions from the entire system.

[0005] Another patent, CN118088296A, describes an active control method for N2O emissions from a diesel engine aftertreatment system. This method primarily focuses on controlling N2O emissions from the SCR unit by establishing a prediction model and adjusting the urea injection rate. However, this method, which focuses solely on the SCR unit, lacks comprehensive N2O emission prediction and control capabilities for the entire aftertreatment system.

[0006] In summary, the existing technologies for N2O emission prediction and control in diesel engine aftertreatment systems have the following major problems:

[0007] The lack of a comprehensive prediction model for N2O emissions from each catalytic unit in the entire aftertreatment system makes it impossible to accurately assess the contribution of each unit to N2O emissions. The prediction accuracy of N2O emissions is insufficient to meet the requirements of ultra-low emission regulations. Existing technologies primarily focus on controlling NOx and particulate matter, with insufficient consideration of coordinated control of N2O emissions, making it difficult to achieve comprehensive reductions in multiple pollutants. Summary of the Invention

[0008] The purpose of the present invention is to overcome the above-mentioned shortcomings of the existing technology and provide an online prediction method for N2O emissions from a diesel engine aftertreatment system. Based on chemical reaction kinetics and thermodynamic models, this method can accurately predict N2O emissions from the entire aftertreatment system, provide a scientific basis for the coordinated control of aftertreatment units, effectively reduce N2O emissions, and meet increasingly stringent emission regulations.

[0009] The purpose of the present invention can be achieved by the following technical solutions:

[0010] The present invention provides an online prediction method for N2O emissions from a diesel engine aftertreatment system, comprising the following steps:

[0011] S1. Establishing a thermodynamic model and a chemical reaction kinetic model for each catalytic unit of the target diesel engine after-treatment system;

[0012] The thermodynamic model of each catalytic unit includes mathematical descriptions of convection heat transfer, heat conduction, and heat radiation processes.

[0013] The chemical reaction kinetics model is defined according to the catalytic unit type;

[0014] S2. Based on catalyst sample test data, identify the thermodynamic parameters and chemical reaction kinetic parameters of each catalytic unit;

[0015] S3, using the engine post-injection amount, DOC inlet exhaust temperature, exhaust mass flow, DOC inlet NOx concentration, and DOC inlet O2 concentration as input, outputs the DOC outlet NO2 concentration through the DOC thermodynamic model and the DOC chemical reaction kinetic model;

[0016] S4, using the DOC outlet NO2 concentration output by S3 and the DPF inlet exhaust temperature, exhaust mass flow rate, and DPF carbon load as input, outputs the DPF outlet NO2 concentration through the DPF thermodynamic model and CRT reaction kinetic model;

[0017] S5, using the DPF outlet NO2 concentration output by S4 and the SCR inlet exhaust temperature, exhaust mass flow rate, and urea injection amount as input, outputs the SCR outlet N2O concentration and SCR outlet NH3 concentration through the SCR thermodynamic model and chemical reaction kinetic model;

[0018] S6, using the SCR outlet NH3 concentration output by S5 and the ASC inlet exhaust temperature and exhaust mass flow as input, outputs the tail pipe N2O concentration through the ASC thermodynamic model and chemical reaction kinetic model.

[0019] Furthermore, in S1 , the catalytic units of the diesel engine aftertreatment system include a DOC unit, a DPF unit, an SCR unit, and an ASC unit, and the diesel engine exhaust flows through each unit in sequence.

[0020] Furthermore, in S1, the chemical reaction kinetic model includes a NO oxidation reaction model of the DOC unit, a continuous passive regeneration reaction model of the DPF unit, a selective catalytic reduction reaction model of the SCR unit, and an oxidation catalytic reaction model of the ASC unit;

[0021] The chemical equations corresponding to each reaction kinetic model include:

[0022] NO oxidation reaction of DOC unit: 2NO+O2→2NO2,

[0023] Continuous passive regeneration reaction of DPF unit: C+2NO2→CO2+2NO,

[0024] The SCR unit includes low-temperature N2O generation reactions: 2NH3+2NO2→NH4NO3+N2+H2O and NH4NO3→N2O+2H2O.

[0025] The ASC unit contains the high-temperature N2O generation reaction: 2NH3+2O2→2N2O+3H2O.

[0026] Furthermore, in S2, the thermodynamic parameters include: convection heat transfer coefficient, thermal conductivity, specific heat capacity, heat radiation area, and heat exchange area;

[0027] The chemical reaction kinetic parameters include: chemical reaction activation energy, chemical reaction pre-exponential factor, and chemical reaction rate correction factor.

[0028] Furthermore, in S2, the catalyst sample test includes:

[0029] For DOC unit: introduce different concentrations of O2 and NO, and measure the NO2 generation rate under temperature gradient;

[0030] For DPF unit: different NO2 concentrations and carbon loadings are introduced to measure the CRT reaction rate;

[0031] For the SCR unit: adjust the ratio of NH3 to NOx and measure the N2O formation window temperature range.

[0032] Furthermore, in S3, the DOC thermodynamic model includes an HC oxidation heat release correction sub-model, which uses the engine post-injection amount, engine speed, exhaust mass flow rate, and DOC inlet exhaust temperature as inputs to calculate the HC oxidation reaction heat release rate in real time;

[0033] The calculated heat release rate is input as a heat source into the DOC thermodynamic model. Combined with the convection heat transfer equation and the thermal radiation equation, the DOC carrier temperature is output. The DOC carrier temperature is used as an input parameter of the DOC chemical reaction kinetic model to participate in the calculation of the NO oxidation reaction rate.

[0034] Furthermore, in S4, the DPF carbon load is calculated in real time based on the functional relationship between the DPF differential pressure sensor signal and the exhaust mass flow rate;

[0035] The DPF thermodynamic model outputs the DPF substrate temperature based on the DPF inlet and outlet exhaust temperatures and the catalyst internal heat conduction equation;

[0036] The carrier temperature and DPF carbon load are input into the continuous passive regeneration reaction model, and the NO2 consumption is dynamically corrected through the reaction rate equation.

[0037] Furthermore, in S5, the SCR chemical reaction kinetics model includes an inlet NH3 concentration calculation module, which uses the urea injection mass flow rate, hydrolysis efficiency and exhaust volume flow rate as inputs to calculate the SCR inlet NH3 concentration in real time;

[0038] The SCR chemical reaction kinetics model also includes an ammonia storage calculation module, which uses the carrier temperature, ammonia coverage, and NO2 concentration output by the SCR thermodynamic model as input and predicts the amount of N2O generated using the low-temperature N2O generation reaction rate equation.

[0039] Furthermore, in S6, the ASC chemical reaction kinetics model includes an inlet NH3 concentration input interface, and the inlet NH3 concentration input interface receives the SCR outlet NH3 concentration output by the SCR chemical reaction kinetics model in S5;

[0040] The ASC chemical reaction kinetics model also includes a high-temperature N2O generation reaction submodule, which uses the carrier temperature and inlet O2 concentration calculated by the ASC thermodynamic model as input and corrects the tailpipe N2O concentration through the reaction rate equation.

[0041] Furthermore, the SCR unit selective catalytic reduction reaction model includes an ammonia oxidation inhibition submodule, which activates the ammonia oxidation reaction when the SCR carrier temperature exceeds a set threshold;

[0042] The ammonia oxidation inhibition submodule calculates the NH3 consumption through the ammonia oxidation reaction rate equation, which is used to correct the predicted value of NH3 concentration at the SCR outlet.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] This invention provides an online prediction method for N2O emissions from diesel engine aftertreatment systems based on chemical reaction kinetic and thermodynamic models. This method establishes corresponding chemical reaction kinetic models based on the dynamic characteristics of N2O-related reactions occurring in various aftertreatment units, addressing the difficulty of accurately predicting N2O emissions under different exhaust conditions in existing technologies. Given the current lack of N2O concentration sensors in complete vehicles, this N2O concentration prediction method provides a robust foundation for coordinated control of aftertreatment units, helping to more accurately achieve comprehensive control targets for NOx, NH3, and N2O emissions, thereby enabling the engine-aftertreatment system to meet ultra-low emission regulations. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 A schematic diagram of the hardware environment corresponding to the preferred embodiment of the present invention;

[0046] Figure 2 This is a schematic diagram of the implementation process of the online prediction method for N2O emissions;

[0047] Figure 3 Schematic diagram of the thermodynamic model and chemical reaction kinetic model required to optimize the post-treatment system;

[0048] Figure 4 Schematic diagram of the thermodynamic parameters and chemical reaction kinetic parameters that need to be identified;

[0049] Figure 5 Schematic diagram of the method for predicting gas component concentration and state parameters at the DOC outlet;

[0050] Figure 6 Schematic diagram of the method for predicting gas component concentration and state parameters at the DPF outlet;

[0051] Figure 7 Schematic diagram of the method for predicting gas component concentration and state parameters at the SCR outlet;

[0052] Figure 8 Schematic diagram of the method for predicting gas component concentration and state parameters at the ASC outlet. DETAILED DESCRIPTION

[0053] In general, the online prediction method for N2O emissions from a diesel engine aftertreatment system of the present invention comprises the following steps.

[0054] Step (1) first confirms the composition of the catalytic unit of the target after-treatment system and establishes a corresponding thermodynamic model and chemical reaction kinetic model for the target catalytic unit. The thermodynamic model mainly includes the mathematical description of the three main processes of convection heat transfer, heat conduction and heat radiation. The chemical reaction kinetic model is specifically confirmed based on the catalytic unit of the target after-treatment system. In the preferred after-treatment system solution of the present invention, it includes the NO oxidation reaction model on the DOC, the continuous passive regeneration (CRT) reaction model on the DPF, the selective catalytic reduction reaction model on the SCR, and the oxidation catalytic reaction model on the ASC.

[0055] The preferred post-treatment system solution of the present invention is the current mainstream DOC+DPF+SCR+ASC technology route;

[0056] Step (2) is to complete the parameter identification of the thermodynamic model and the chemical reaction kinetic model through catalyst sample testing, and confirm the thermodynamic parameters such as the convection heat transfer coefficient, thermal conductivity, specific heat capacity, heat radiation area and heat transfer area of various catalysts and the reaction kinetic parameters such as the chemical reaction activation energy, chemical reaction pre-exponential factor, and chemical reaction rate correction factor;

[0057] Step (3) uses the engine post-injection amount, DOC inlet exhaust temperature, DOC outlet exhaust temperature, exhaust mass flow rate, DOC inlet NOx concentration, DOC inlet O2 concentration, etc. as inputs of the DOC thermodynamic model and chemical reaction kinetic model to complete the prediction of DOC outlet NO2 concentration, NOx concentration and O2 concentration;

[0058] Step (4) uses the DPF inlet exhaust temperature, DPF outlet exhaust temperature, exhaust mass flow rate, DPF inlet NOx concentration, DPF inlet O2 concentration and inlet NO2 concentration as inputs to the DPF thermodynamic model and the CRT reaction kinetic model to complete the prediction of the NO2 concentration, NOx concentration and O2 concentration at the DPF outlet;

[0059] Step (5) uses the SCR inlet exhaust temperature, SCR outlet exhaust temperature, exhaust mass flow rate, SCR inlet NOx concentration, SCR inlet O2 concentration, and SCR inlet NO2 concentration as inputs to the SCR thermodynamic model and the SCR internal chemical reaction kinetic model to complete the prediction of the SCR outlet N2O concentration, NH3 concentration, NO2 concentration, NOx concentration, and O2 concentration;

[0060] Step (6) uses the exhaust temperature at the ASC inlet, the exhaust mass flow rate, the NOx concentration at the ASC inlet, the NO2 concentration at the ASC inlet, the NH3 concentration at the ASC inlet, and the O2 concentration at the ASC inlet as inputs to the ASC chemical reaction kinetics model to complete the prediction of the N2O concentration, NH3 concentration, NO2 concentration, NOx concentration, and O2 concentration at the ASC outlet, thereby achieving the goal of online prediction of tailpipe N2O emissions;

[0061] According to the preferred DOC+DPF+SCR+ASC system layout of the present invention, the engine exhaust will flow through the DOC, DPF, SCR and ASC in sequence, so steps (3) to (6) will be described in this order. This description order is only for the convenience of explaining the patent implementation steps and does not constitute a limitation on the application of this patent. The exhaust component concentration calculation modules of each post-processing unit of this patent can work independently, and can be combined in any order to achieve online prediction of tail pipe N2O concentration;

[0062] The present invention provides an online prediction method for N2O emissions from diesel engine aftertreatment systems based on chemical reaction kinetic and thermodynamic models. This method establishes corresponding chemical reaction kinetic models based on the dynamic characteristics of N2O-related reactions occurring in various aftertreatment units, addressing the difficulty of accurately predicting N2O emissions under different exhaust conditions in existing technologies. Given the current lack of N2O concentration sensors in complete vehicles, this N2O concentration prediction method provides a robust foundation for coordinated control of aftertreatment units, helping to more accurately achieve the combined control targets for NOx, NH3, and N2O emissions, thereby enabling the engine-aftertreatment system to meet ultra-low emission regulations.

[0063] The above description is merely a preferred embodiment of the present invention. It should be noted that when a different combination of post-treatment units than the typical one described above is selected, the prediction of N2O is also based on the primary chemical reaction kinetics in step (1). For example, the SDPF post-treatment unit is essentially a combination of an SCR unit and a DPF unit. It will be apparent to those skilled in the art that, without departing from the principles of the present invention, various additions, subtractions, and combinations of the mathematical equations describing the physical and chemical processes of the model may be made to improve and embellish the model. Such improvements and embellishments are also within the scope of protection of the present invention.

[0064] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Component models, material names, connection structures, control methods, algorithms, and other features not explicitly described in this technical solution are considered common technical features disclosed in the prior art.

[0065] Example 1

[0066] Figure 1 This is a schematic diagram of the hardware environment corresponding to the preferred implementation of this embodiment.

[0067] The post-treatment system corresponding to the preferred embodiment of this embodiment is a DOC+DPF+SCR+ASC scheme. When the exhaust passes through the DOC, its oxidation catalysis oxidizes the reducing gases such as HC and CO in the exhaust. At the same time, NO can also further react with O2 on the DOC to produce NO2, resulting in NO2 / NO in the exhaust. x When the temperature is right, NO2 will react with PM captured in DPF to produce CRT reaction, resulting in NO2 / NO in the exhaust gas after the reaction. x The ratio decreases. When the SCR substrate temperature exceeds the critical urea injection temperature, the urea nozzle begins injecting urea. The injected urea undergoes thermal and hydrolysis reactions under the influence of exhaust gas, primarily producing NH3. However, at temperatures between 200 and 250°C, a high NO2 content can also easily lead to the formation of NH4NO3. NH3 reacts rapidly with NOx on the SCR catalyst, producing N2 and H2O. The presence of NO2 facilitates a rapid SCR reaction, while NH4NO3 further decomposes to produce N2O at low temperatures. If the urea injection rate upstream of the SCR is insufficient, excess NOx will be discharged through the tailpipe. If the urea injection rate is excessive, excess NH3 will flow downstream and continue to react with the ASC. Reactions on the ASC primarily produce N2, but at high temperatures, ASC selectivity begins to decline, making side reactions that lead to the formation of N2O more likely.

[0068] The reductant supply system of the entire post-treatment system uses a urea aqueous solution with a mass concentration of 32.5% as the reductant. The ECU and DCU can be independent hardware structures or combined into a complete control unit. The ECU and DCU collect engine speed, engine fuel injection amount, intake air temperature, intake air pressure, intake air mass flow, EGR valve opening, cooling water temperature, DOC catalyst upstream temperature, DPF upstream temperature, SCR catalyst upstream temperature, SCR catalyst downstream temperature, DOC catalyst upstream NO x concentration, NOx downstream of SCR catalyst x The corresponding control function modules calculate the signals such as concentration and urea liquid level to complete the coordinated distribution of reducing agent in the urea injection system and achieve the emission control target.

[0069] The online prediction method for N2O emissions in this embodiment is as follows: Figure 2As shown, first, the composition of the catalytic unit of the target after-treatment system is confirmed and a corresponding thermodynamic model and chemical reaction kinetic model are established for the target catalytic unit. The thermodynamic model mainly includes the mathematical description of the three main processes of convection heat transfer, heat conduction and heat radiation. The chemical reaction kinetic model is specifically determined based on the catalytic unit of the target after-treatment system. In the preferred embodiment of this embodiment, it includes the NO oxidation reaction model on the DOC, the continuous passive regeneration (CRT) reaction model on the DPF, the selective catalytic reduction reaction model on the SCR, and the ammonia oxidation catalytic reaction model on the ASC.

[0070] The effective flow volume, cross-sectional area, porosity, mesh size, wall thickness, specific surface area and other dimensional parameters of different catalyst units were determined. The parameters of the thermodynamic model and chemical reaction kinetic model were identified through catalyst sample testing. These parameters mainly included thermodynamic parameters such as convective heat transfer coefficient, thermal conductivity, specific heat capacity, thermal radiation area and heat transfer area, and reaction kinetic parameters such as chemical reaction activation energy, chemical reaction pre-exponential factor, and chemical reaction rate correction factor.

[0071] The NO2 concentration prediction at the DOC outlet uses the engine post-injection amount, DOC inlet exhaust temperature, DOC outlet exhaust temperature, exhaust mass flow, DOC inlet NOx concentration, DOC inlet O2 concentration, etc. as inputs to the DOC thermodynamic model and chemical reaction kinetic model to complete the NO2 concentration prediction at the DOC outlet. The O2 concentration at the DOC outlet is predicted based on the engine post-injection amount, DOC inlet exhaust temperature, and DOC inlet O2 concentration, mainly considering the impact of further oxidation of HC and CO on the O2 concentration. After passing through the DOC, only the reaction of NO converting to NO2 occurs, so the outlet NOx concentration is considered to be consistent with the inlet.

[0072] The changes in NO2 and O2 concentrations at the DPF outlet are mainly affected by the CRT reaction. O2 and NO2 will be consumed by the accumulated PM. Therefore, the DPF inlet exhaust temperature, DPF outlet exhaust temperature, exhaust mass flow rate, DPF inlet NOx concentration, DPF inlet O2 concentration, inlet NO2 concentration, and DPF carbon load are used as inputs to the DPF thermodynamic model and CRT reaction kinetic model to complete the prediction of NO2 and O2 concentrations at the DPF outlet. When NO2 passes through the DPF, if the CRT reaction occurs, NO is generated. Therefore, it is assumed that the NOx concentration at the DPF outlet is consistent with that at the inlet.

[0073] The NO2 concentration and NO concentration at the SCR outlet are mainly affected by the SCR reaction. Therefore, the urea injection amount, SCR inlet exhaust temperature, SCR outlet exhaust temperature, exhaust mass flow, SCR inlet NOx concentration, SCR inlet O2 concentration and SCR inlet NO2 concentration are used as the input of the SCR thermodynamic model and SCR reaction kinetic model to complete the NO concentration at the SCR outlet. x The NH3 concentration at the SCR outlet is mainly affected by the carrier adsorption and desorption reaction rate and the SCR reaction rate. Under high temperature conditions, direct NH3 oxidation reaction will also occur. Therefore, it is necessary to add ammonia storage calculation to the above SCR reaction-related parameters to obtain the NH3 desorption concentration and the proportion of NH3 oxidized, and finally calculate the NH3 concentration downstream of the SCR. N2O at the SCR outlet mainly occurs in the temperature range of 200-250℃. Under this condition, the NH3 coverage and NO2 of the SCR carrier will have a positive impact on the generation of NH4NO3. Therefore, the prediction of N2O at this stage requires the carrier temperature, NH3 coverage and NO2 concentration as the main inputs.

[0074] The NO2 concentration and NO concentration at the ASC outlet are mainly affected by the upstream SCR reaction. If there is residual NO2 and NO from the upstream reaction, the original concentration will be maintained and discharged through the ASC into the environment. The NH3 concentration flowing through the ASC will change due to the catalytic oxidation reaction. Therefore, the NH3 concentration at the ASC outlet is mainly affected by the inlet NH3 concentration, the inlet O2 concentration and the reaction conditions. The ammonia oxidation reaction kinetic model of the ASC is used to complete the prediction of the NH3 concentration at the ASC outlet; the N2O at the ASC outlet comes from the side reaction of the NH3 selective catalytic oxidation reaction of the ASC under high temperature conditions. The non-selective catalytic oxidation of NH3 at high temperature will lead to the generation of N2O. At this time, O2, NO+O2 or NO2 can act as oxidants. The stronger the oxidizing power of the oxidant, the more N2O. Therefore, the exhaust temperature at the ASC inlet, the exhaust mass flow rate, the NOx concentration at the ASC inlet, the O2 concentration at the ASC inlet and the NO2 concentration at the ASC inlet are used as inputs to the ASC internal chemical reaction kinetic model to complete the prediction of the N2O concentration at the ASC outlet;

[0075] Figure 3 Thermodynamic model and chemical reaction kinetic model required for optimizing post-processing system. Figure 3 As shown, the DOC+DPF+SCR+ASC post-treatment system is taken as the preferred embodiment of this embodiment to illustrate the thermodynamic model establishment process and chemical reaction kinetic model establishment process of each catalytic unit.

[0076] First, the thermodynamic processes of the DOC+DPF+SCR+ASC after-treatment system were modeled. The carrier temperature estimation models for SDPF and SCR mainly model the following thermodynamic processes: 1) convective heat transfer between the exhaust and the catalyst; 2) heat conduction within the catalyst; and 3) radiation heat transfer from the catalyst housing to the atmosphere. In addition to the thermodynamic part, the DOC carrier temperature estimation model also considers the further oxidation heat release of hydrocarbons (HC) on the DOC and establishes a corresponding HC oxidation heat release correction model.

[0077] The method for establishing a DOC carrier temperature prediction model that includes an HC oxidation heat release model and a thermodynamic process model is as follows: When the DOC catalytic performance is determined, the inlet temperature and exhaust mass flow rate determine the degree of occurrence of the HC oxidation reaction, and the post-injection amount determines the total heat that can be released when the HC oxidation reaction is completely completed. Therefore, the HC oxidation heat release correction model established in this embodiment uses the engine post-injection amount, engine speed, exhaust mass flow rate, and DOC inlet temperature as inputs to calculate the heat release rate of the HC oxidation reaction in real time. The calculated heat release rate of the HC oxidation reaction is input as the energy source of the exhaust gas into the thermodynamic process model to achieve accurate prediction of the DOC carrier temperature; wherein the engine post-injection amount, engine speed, and DOC inlet temperature are respectively obtained by the engine control unit (ECU) by calculating the injection pulse width signal, the speed sensor signal, and the exhaust temperature sensor signal at the DOC inlet, and the exhaust mass flow rate is calculated by the ECU's intake mass flow sensor signal and the injection amount signal;

[0078] The three thermodynamic process models can be described by the following mathematical equations:

[0079] 1) Convective heat transfer between exhaust and catalyst per unit time Φ P-C It can be calculated by the following formula

[0080] Φ P-C =hA H-T (T P -T C )

[0081] Where: h is the heat transfer coefficient of exhaust gas and catalyst convection heat transfer, W / (m 2 ·K); T P is the exhaust temperature, K; T C is the catalyst temperature, K; A H-T The total surface area of the catalyst that can contact the exhaust gas. ε represents the porosity of the catalyst (i.e., the volume ratio of the exhaust gas that can flow per unit volume of the catalyst, %). cat Indicates the internal surface area of the catalyst per unit volume of gas that can flow through the catalyst, m 2 / m 3 Among them AH-T It can be expressed as:

[0082]

[0083] Where: r C is the catalyst cross-sectional radius, m; L C is the length of the catalyst, m; That is, the total volume of the catalyst V C ; That is, the total cross-sectional area A of the catalyst f ; The area of exhaust blocked by the catalyst is very small and can be ignored, so the above formula can be expressed as

[0084]

[0085] 2) The heat conduction inside the catalyst can be deduced from Fourier's theorem. The heat conducted by the catalyst per unit time is:

[0086]

[0087] 3) The radiation heat transfer from the catalyst housing to the atmosphere can be calculated based on the Stefan-Boltzmann law:

[0088]

[0089] Among them: A Rad is the radiation area between the catalyst and the outside world, m 2 ; ε Rad is the radiation blackness; σ SB is the gas radiation constant, W / m 2 K 4 ;T amb is the ambient temperature, K;

[0090] Then, for the DOC, DPF, SCR and ASC catalytic units in the target after-treatment system, the corresponding chemical reaction kinetic process model is established to describe the concentration changes of gas components such as NO, NO2, N2O, NH3, O2 inside the catalytic unit.

[0091] For DOC, the main NO2-related chemical reaction occurring on it is the NO oxidation reaction, and its chemical reaction equation is: 2NO+O2→2NO2, and the corresponding reaction rate equation is:

[0092]

[0093] For DPF, the main NO2-related chemical reaction occurring on it is the continuous passive regeneration (CRT) reaction, and its chemical reaction equation is: C+2NO2→CO2+2NO, and the corresponding reaction rate equation is:

[0094]

[0095] For SCR, the main chemical reactions occurring therein are fast SCR reaction, standard SCR reaction and slow SCR reaction, and their chemical reaction equations are:

[0096] 4NH3+2NO+2NO2→4N2+6H2O (fast)

[0097] 4NO+4NH3(S)+O2→4N2+6H2O(standard)

[0098] 8NH3+6NO2→7N2+12H2O (slow)

[0099] Combining the above equations, the corresponding reaction rate equation can be obtained:

[0100]

[0101] Under high temperature conditions, direct oxidation of ammonia occurs in the SCR, and the chemical reaction equation is:

[0102] 4NH3(S)+3O2→2N2+6H2O

[0103]

[0104] Under low temperature conditions, ammonium nitrate, an intermediate product of the rapid SCR reaction, is prone to accumulation, which may then cause a side reaction to produce N2O under low temperature conditions. The chemical reaction equation is:

[0105] 2NH3+2NO2→NH4NO3+N2+H2O

[0106] NH4NO3→N2O+2H2O

[0107] The corresponding reaction rate equation is:

[0108]

[0109] The reaction temperature of the above reaction is determined by the carrier temperature of the post-processing unit.

[0110] For ASC, the main chemical reaction occurring thereon is NH3 oxidation reaction, and its chemical reaction equation is:

[0111] 4NH3+3O2→2N2+6H2O

[0112] The corresponding reaction rate equation is:

[0113]

[0114] Under certain conditions, the selectivity of ASC for NH3 oxidation decreases, and the following side reactions will occur to produce N2O:

[0115] 2NH3+2O2→2N2O+3H2O

[0116] The corresponding reaction rate equation is:

[0117]

[0118] Figure 4 This is a schematic diagram of the thermodynamic parameters and chemical reaction kinetic parameters required to be identified in this example.

[0119] This example first conducts small-scale tests on various types of after-treatment catalysts to identify the model's thermodynamic parameters. This identification is primarily accomplished through a step-by-step temperature rise test, with the same test protocol for DOC, DPF, SCR, and ASC units. Standard exhaust gas is introduced at temperatures of 200°C, 250°C, 300°C, 350°C, 400°C, 500°C, and 600°C, with the exhaust temperature remaining constant until thermal equilibrium is reached. The catalyst carrier temperature at various locations is recorded over time, along with the carrier's radiant heat release rate.

[0120] The identification of chemical reaction kinetic parameters of catalyst samples is mainly achieved by conducting gas reaction tests under different conditions. However, the test methods for DOC, DPF, SCR and ASC are different due to the different factors affecting their related chemical reactions. The details are as follows:

[0121] Parameter acquisition test for NO oxidation reaction: Using N2 as the balance gas, different concentrations of O2 and NO were introduced, and the concentration changes of NO, NO2, O2 and other components at the outlet of the DOC catalyst sample were measured at different temperatures and space velocities. The O2 concentration range was 2.5% to 21%, and the NO concentration range was 100ppm to 2000ppm.

[0122] CRT reaction parameter acquisition test: using N2 as the balance gas, different concentrations of NH3, O2, NO2 and NO were introduced, and the concentration changes of NH3, O2, NO, NO2 and other components at the outlet of the DPF carrier sample and the changes in carbon load were measured in real time under different temperatures, carbon loads and air speeds. x The ratio range is 10%, 25%, 50%, 60%, 80%, NH3 / NO xThe ratio range is 0, 0.3, 0.5, 0.7, and 1.0; the carbon loading range is 0.5g / L, 1.0g / L, 2g / L, and 4g / L.

[0123] Parameter acquisition test for fast SCR reaction, standard SCR reaction and slow SCR reaction: using N2 as the balance gas, different concentrations of NH3, NO2 and NO were introduced, and the concentration changes of NH3, NO, NO2 and other components at the outlet of the SCR catalyst sample at different temperatures and space velocities were measured in real time, among which NO2 / NO x The ratio range is 10%, 25%, 50%, 60%, 80%, NH3 / NO x The ratio changes range is 0.3, 0.5, 0.7, 0.9, and 1.1.

[0124] For DOC, the chemical reaction kinetic parameters that need to be confirmed are: the activation energy E of the NO oxidation reaction NO Oxi , pre-exponential factor K of NO oxidation reaction NO_Oxi ; The thermodynamic parameters that need to be confirmed are: effective flow volume V DOC , effective cross-sectional area of the carrier A fr_DOC , convective heat transfer coefficient h DOC , thermal conductivity λ DOC , effective heat exchange area A H-T_DOC , heat radiation area A Rad_DOC , carrier specific heat capacity c p,C(DOC) .

[0125] For DPF, the chemical reaction kinetic parameters that need to be confirmed are: the activation energy E of the CRT reaction CRT , pre-exponential factor K of CRT reaction CRT ; The thermodynamic parameters that need to be confirmed are: effective flow volume V DPF , effective cross-sectional area of the carrier A fr_DPF , convective heat transfer coefficient h DPF , thermal conductivity λ DPF Effective heat exchange area A H-T_DPF , heat radiation area A Rad_DPF , carrier specific heat capacity c p,C(DPF) .

[0126] For SCR, the chemical reaction kinetic parameters that need to be confirmed are: the activation energy E of the fast SCR reaction SCR_F , Pre-exponential factor K of fast SCR reaction SCR_F , activation energy E of standard SCR reaction SCR_St , the pre-exponential factor K of the standard SCR reaction SCR_St , activation energy E of slow SCR reaction SCR_S , pre-exponential factor K of slow SCR reactionSCR_S ; Activation energy E of ammoxidation reaction oxi , pre-exponential factor K of ammonia oxidation reaction oxi Activation energy E of low-temperature N2O formation reaction Lo_N2O , pre-exponential factor K of low-temperature N2O formation reaction Lo_N2O The thermodynamic parameters that need to be confirmed are: effective flow volume V of the carrier SCR , effective cross-sectional area of the carrier A fr_SCR , convective heat transfer coefficient h SCR , thermal conductivity λ SCR , effective heat exchange area A H-T_SCR , heat radiation area A Rad_SCR , carrier specific heat capacity c p,C(SCR) .

[0127] For ASC, the chemical reaction kinetic parameters that need to be confirmed are: the activation energy E of the ammoxidation reaction oxi , pre-exponential factor K of ammonia oxidation reaction oxi Activation energy E of high temperature N2O formation reaction Hi_N2O , pre-exponential factor K of high temperature N2O formation reaction Hi_N2O The thermodynamic parameters that need to be confirmed are: effective flow volume V of the carrier ASC , effective cross-sectional area of the carrier A fr_ASC , convective heat transfer coefficient h ASC , thermal conductivity λ ASC , effective heat exchange area A H-T_ASC , heat radiation area A Rad_ASC , carrier specific heat capacity c p,C(ASC) .

[0128] This embodiment completes the prediction of gas component concentration and state parameters at the DOC outlet by establishing a NO oxidation reaction kinetic model of DOC. The specific prediction method is as follows: Figure 5 shown.

[0129] The established kinetic model of NO oxidation reaction of DOC is based on the NO x The concentration, inlet O2 concentration, inlet NO2 / NOx ratio, DOC carrier temperature and exhaust mass flow are input to calculate the NO oxidation reaction rate occurring on the DOC and output the outlet NO in real time. x concentration signal, outlet O2 concentration signal and outlet NO2 concentration signal.

[0130] The DOC inlet NO x The concentration is obtained from the NOx sensor signal arranged at the DOC inlet or the engine NOx emission model.

[0131] The O2 concentration at the DOC inlet is obtained through an engine combustion model or an oxygen sensor or a NOx sensor at the DOC inlet.

[0132] The DOC inlet NO2 / NOx ratio is obtained by looking up the engine outlet NO2 / NOx ratio MAP table based on the engine fuel injection amount, speed and EGR rate, and then adding corrections for the cooling water temperature, intake air temperature and intake air pressure.

[0133] The engine outlet NO2 / NOx ratio MAP is obtained by experimentally determining the relationship between the engine outlet NO2 / NOx ratio and the engine fuel injection amount, speed and EGR rate.

[0134] The DOC carrier temperature is derived from the output of a DOC carrier temperature prediction model.

[0135] The DOC carrier temperature prediction model consists of two parts: an HC oxidation heat release model and a thermodynamic process model. The HC oxidation heat release model uses engine post-injection fuel quantity, engine speed, exhaust mass flow rate, and DOC inlet temperature as inputs to calculate the heat release rate of the HC oxidation reaction in real time. The calculated HC oxidation heat release rate is input into the thermodynamic process model as the exhaust energy source to estimate the DOC carrier temperature.

[0136] This embodiment completes the prediction of gas component concentration and state parameters at the DPF outlet by establishing a DPF reaction kinetic model. The specific prediction method is as follows: Figure 6 shown.

[0137] The CRT reaction within the DPF operates within a specific temperature window. At lower temperatures, the CRT reaction is less likely to occur, while at higher temperatures, both NO2 and O2 react with PM. Therefore, the DPF substrate temperature also needs to be calculated. Furthermore, given that the CRT reaction rate of PM is directly related to carbon loading, a DPF carbon loading model is required to calculate carbon loading in real time. The specific implementation process for predicting the chemical reaction process within the DPF is as follows: The DPF NO2 concentration calculation module consists of three components: a DPF thermodynamic model, a DPF carbon loading model, and a DPF chemical reaction kinetics model. The DPF thermodynamic model first obtains exhaust temperature signals from the DPF inlet and outlet temperature sensors. It then obtains an exhaust mass flow rate signal from the intake mass flow sensor and the injection amount. This signal is used as input to calculate the thermodynamic processes within the DPF and output the DPF substrate temperature. The DPF carbon loading model then estimates the current carbon loading of the DPF substrate using the exhaust mass flow rate and the differential pressure measured by the DPF differential pressure sensor. Subsequently, the DPF chemical reaction kinetics model calculates the CRT reaction rate by taking the outlet NO2 concentration output by the previous NO2 prediction model as the DPF inlet NO2 concentration signal, the DOC outlet O2 concentration output by the previous NO2 prediction model as the DPF inlet O2 concentration signal, the DPF carrier temperature output by the DPF thermodynamic model, and the carbon load signal obtained by the DPF carbon load model, and then combines the exhaust mass flow signal to calculate the CRT reaction rate, and outputs the outlet NO in real time. x Concentration signal, outlet O2 concentration signal, outlet NO2 concentration signal and PM consumption rate are used to complete the prediction of gas component concentration and state parameters at the DPF outlet.

[0138] This embodiment predicts the concentration and state parameters of the gas components at the SCR outlet by establishing an SCR internal chemical reaction kinetic model including a fast SCR reaction, a standard SCR reaction, a slow SCR reaction, an ammonia oxidation reaction, and a low-temperature N2O generation reaction. The specific prediction method is as follows: Figure 7 shown.

[0139] Since the heat released by the reaction on the SCR is very low and can be ignored, the temperature estimation of the SCR only needs to consider its thermodynamic reaction part. Therefore, the SCR gas component concentration calculation module only includes two parts: the SCR thermodynamic model and the SCR chemical reaction kinetic model. The specific implementation process is as follows: the SCR thermodynamic model first obtains the exhaust temperature signal through the temperature sensors at the SCR inlet and outlet. Then, it calculates the exhaust mass flow signal based on the measurement value of the intake mass flow sensor and the injection amount. This signal is used as input to calculate the thermodynamic process inside the SCR and output the SCR substrate temperature.

[0140] Subsequently, the SCR chemical reaction kinetics model uses the outlet NO2 concentration output by the previous level NO2 prediction model as the SCR inlet NO2 concentration signal, the DOC inlet NOx concentration as the SCR inlet NOx concentration signal, the SCR carrier temperature signal output by the SCR thermodynamic model, and the inlet NH3 concentration signal calculated by the exhaust mass flow rate and urea injection amount. The SCR reaction rate, ammonia oxidation reaction rate, and low-temperature N2O generation reaction rate are then calculated in combination with the exhaust mass flow rate signal, and the outlet NH3 concentration signal and outlet NO are output in real time. x Concentration signal, outlet NO2 concentration signal, outlet N2O concentration signal, outlet O2 concentration signal, complete the prediction of gas component concentration and state parameters at the SCR outlet.

[0141] This example predicts the concentration and state parameters of the ASC outlet gas components by establishing an ASC internal chemical reaction kinetics model including the ammonia oxidation reaction rate and the high-temperature N2O generation reaction. The specific prediction method is as follows: Figure 8 shown.

[0142] Because the heat released by the reactions occurring on the ASC is negligible, the ASC temperature estimation only needs to consider its thermodynamic reaction component. Therefore, the ASC gas component concentration calculation module only includes two parts: the ASC thermodynamic model and the ASC chemical reaction kinetics model. The specific implementation process is as follows: The ASC thermodynamic model first obtains exhaust temperature signals from the temperature sensors at the ASC inlet and outlet. It then calculates the exhaust mass flow rate signal using the intake mass flow sensor measurement and the injection amount. This signal is used as input to calculate the thermodynamic processes within the ASC and output the ASC carrier temperature.

[0143] Subsequently, the ASC chemical reaction kinetics model uses the outlet NH3 concentration and O2 concentration output by the previous model as the NH3 concentration and O2 concentration signals at the ASC inlet, the DOC inlet NOx concentration as the SCR inlet NOx concentration signal, and the ASC carrier temperature signal output by the ASC thermodynamic model, and then combines the exhaust mass flow signal to calculate the ammonia oxidation reaction rate and the high-temperature N2O generation reaction rate, and outputs the outlet NH3 concentration signal and outlet NOx concentration signal in real time. x Concentration signal, outlet NO2 concentration signal, outlet N2O concentration signal, outlet O2 concentration signal, complete the prediction of gas component concentration and state parameters at the ASC outlet.

[0144] The present invention achieves accurate prediction of N2O emissions from the entire after-treatment system. By establishing a thermodynamic model and a chemical reaction kinetic model for each catalytic unit, the impact of each component in the after-treatment system on N2O emissions can be fully considered. It not only covers key catalytic units such as DOC, DPF, SCR and ASC, but also describes in detail the physical and chemical processes within each unit, including convective heat transfer, heat conduction, thermal radiation and various chemical reactions. Compared with the existing technology, the prediction model of the present invention is more comprehensive and accurate, and can effectively solve the problem that the existing technology is difficult to fully predict N2O emissions from the entire after-treatment system. It enables engine manufacturers and after-treatment system developers to accurately understand the generation and emission of N2O under different operating conditions, thereby providing strong data support for optimizing the design and operation of the after-treatment system. This not only helps to meet increasingly stringent emission regulations, but also makes a positive contribution to environmental protection.

[0145] The present invention has good system integration and collaborative control capabilities. By connecting the models of each catalytic unit in series and using the output of the previous step as the input of the next step, a complete prediction process is formed. This method can reflect the dynamic changes of N2O in the entire after-treatment system in real time, and provides a solid foundation for the collaborative control of the after-treatment units. For example, by predicting the NO2 concentration at the DOC outlet, the NO2 concentration at the DPF outlet, the N2O and NH3 concentrations at the SCR outlet, and the final N2O concentration at the tail pipe, the operator can fully understand the operating status of the after-treatment system, adjust the operating parameters of each unit in time, and achieve comprehensive emission reduction of multiple pollutants. This system integration and collaborative control capability is difficult to achieve with existing technologies. The present invention fills this technical gap by establishing a complete prediction chain.

[0146] The present invention has high economy and practicality. On the one hand, by accurately predicting N2O emissions, the design and operation of the after-treatment system can be optimized, and unnecessary equipment investment and operating costs can be reduced. For example, the urea injection amount can be reasonably controlled to avoid NH3 slippage and N2O generation caused by excessive injection, thereby reducing urea consumption and maintenance costs of related equipment. On the other hand, the prediction method of the present invention is based on the existing after-treatment system architecture and sensor configuration, and does not require the addition of a large amount of additional hardware equipment, and has good economy and operability. In addition, the online prediction method of the present invention can respond to changes in operating conditions in a timely manner, provide real-time emission data, provide strong support for the coordinated control of the engine and the after-treatment system, and help to improve the overall performance and reliability of the system. This makes the present invention have broad application prospects and economic value in practical applications.

[0147] In summary, the present invention demonstrates significant benefits in terms of accurate prediction, system integration, optimized control, and economic efficiency. It not only effectively addresses the shortcomings of existing technologies in N2O emission prediction and control, but also provides a scientific basis for the optimized design and operational management of diesel engine aftertreatment systems, promoting the development of diesel engine emission control technology and contributing to the goal of low-carbon, environmentally friendly transportation.

[0148] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. An online prediction method for N2O emissions from a diesel engine aftertreatment system, characterized in that: The following steps are involved: S1. Establishing a thermodynamic model and a chemical reaction kinetic model for each catalytic unit of the target diesel engine after-treatment system; The thermodynamic model of each catalytic unit includes mathematical descriptions of convection heat transfer, heat conduction, and heat radiation processes. The chemical reaction kinetics model is defined according to the catalytic unit type; S2. Based on catalyst sample test data, identify the thermodynamic parameters and chemical reaction kinetic parameters of each catalytic unit; S3, using the engine post-injection amount, DOC inlet exhaust temperature, exhaust mass flow, DOC inlet NOx concentration, and DOC inlet O2 concentration as input, outputs the DOC outlet NO2 concentration through the DOC thermodynamic model and the DOC chemical reaction kinetic model; S4, using the DOC outlet NO2 concentration output by S3 and the DPF inlet exhaust temperature, exhaust mass flow rate, and DPF carbon load as input, outputs the DPF outlet NO2 concentration through the DPF thermodynamic model and CRT reaction kinetic model; S5, using the DPF outlet NO2 concentration output by S4 and the SCR inlet exhaust temperature, exhaust mass flow rate, and urea injection amount as input, outputs the SCR outlet N2O concentration and SCR outlet NH3 concentration through the SCR thermodynamic model and chemical reaction kinetic model; S6, using the SCR outlet NH3 concentration output by S5 and the ASC inlet exhaust temperature and exhaust mass flow as input, outputs the tail pipe N2O concentration through the ASC thermodynamic model and chemical reaction kinetic model.

2. The online prediction method for N2O emissions from a diesel engine aftertreatment system according to claim 1, characterized in that: In S1 , the catalytic units of the diesel engine aftertreatment system include a DOC unit, a DPF unit, an SCR unit, and an ASC unit, and the diesel engine exhaust flows through each unit in sequence.

3. The online prediction method for N2O emissions from a diesel engine aftertreatment system according to claim 1, characterized in that: In S1, the chemical reaction kinetic model includes the NO oxidation reaction model of the DOC unit, the continuous passive regeneration reaction model of the DPF unit, the selective catalytic reduction reaction model of the SCR unit, and the oxidation catalytic reaction model of the ASC unit; The chemical equations corresponding to each reaction kinetic model include: NO oxidation reaction of DOC unit: 2NO+O2→2NO2, Continuous passive regeneration reaction of DPF unit: C+2NO2→CO2+2NO, The SCR unit includes the low-temperature N2O generation reaction: 2NH3+2NO2→NH4NO2+N2+H2O and NH4NO3→N2O+2H2O. The ASC unit contains the high-temperature N2O generation reaction: 2NH3+2O2→2N2O+3H2O.

4. The online prediction method for N2O emissions from a diesel engine aftertreatment system according to claim 1, characterized in that: In S2, the thermodynamic parameters include: convection heat transfer coefficient, thermal conductivity, specific heat capacity, heat radiation area, and heat exchange area; The chemical reaction kinetic parameters include: chemical reaction activation energy, chemical reaction pre-exponential factor, and chemical reaction rate correction factor.

5. The online prediction method for N2O emissions from a diesel engine aftertreatment system according to claim 1, characterized in that: In S2, the catalyst sample test includes: For DOC unit: introduce different concentrations of O2 and NO, and measure the NO2 generation rate under temperature gradient; For DPF unit: different NO2 concentrations and carbon loadings are introduced to measure the CRT reaction rate; For the SCR unit: adjust the ratio of NH3 to NOx and measure the N2O formation window temperature range.

6. The online prediction method for N2O emissions from a diesel engine aftertreatment system according to claim 1, characterized in that: In S3, the DOC thermodynamic model includes an HC oxidation heat release correction sub-model, which uses the engine post-injection amount, engine speed, exhaust mass flow rate, and DOC inlet exhaust temperature as inputs to calculate the HC oxidation reaction heat release rate in real time; The calculated heat release rate is input as a heat source into the DOC thermodynamic model. Combined with the convection heat transfer equation and the thermal radiation equation, the DOC carrier temperature is output. The DOC carrier temperature is used as an input parameter of the DOC chemical reaction kinetic model to participate in the calculation of the NO oxidation reaction rate.

7. The online prediction method for N2O emissions from a diesel engine aftertreatment system according to claim 1, characterized in that: In S4, the DPF carbon load is calculated in real time based on the functional relationship between the DPF differential pressure sensor signal and the exhaust mass flow rate; The DPF thermodynamic model outputs the DPF substrate temperature based on the DPF inlet and outlet exhaust temperatures and the catalyst internal heat conduction equation; The carrier temperature and DPF carbon load are input into the continuous passive regeneration reaction model, and the NO2 consumption is dynamically corrected through the reaction rate equation.

8. The online prediction method for N2O emissions from a diesel engine aftertreatment system according to claim 1, characterized in that: In S5, the SCR chemical reaction kinetics model includes an inlet NH3 concentration calculation module, which uses the urea injection mass flow rate, hydrolysis efficiency and exhaust volume flow rate as input to calculate the SCR inlet NH3 concentration in real time; The SCR chemical reaction kinetics model also includes an ammonia storage calculation module, which uses the carrier temperature, ammonia coverage, and NO2 concentration output by the SCR thermodynamic model as input and predicts the amount of N2O generated using the low-temperature N2O generation reaction rate equation.

9. The online prediction method for N2O emissions from a diesel engine aftertreatment system according to claim 1, characterized in that: In S6, the ASC chemical reaction kinetics model includes an inlet NH3 concentration input interface, which receives the SCR outlet NH3 concentration output by the SCR chemical reaction kinetics model in S5; The ASC chemical reaction kinetics model also includes a high-temperature N2O generation reaction submodule, which uses the carrier temperature and inlet O2 concentration calculated by the ASC thermodynamic model as input and corrects the tailpipe N2O concentration through the reaction rate equation.

10. The online prediction method for N2O emissions from a diesel engine aftertreatment system according to claim 1, characterized in that: The SCR unit selective catalytic reduction reaction model includes an ammonia oxidation inhibition submodule, which activates the ammonia oxidation reaction when the SCR carrier temperature exceeds a set threshold; The ammonia oxidation inhibition submodule calculates the NH3 consumption through the ammonia oxidation reaction rate equation, which is used to correct the predicted value of NH3 concentration at the SCR outlet.

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