Control method of nitrogen oxide emission

Abstract

The invention relates to a control method for nitrogen oxide emission in the technical field of tail gas treatment, which comprises the following steps: S1, starting an engine, judging whether the engine meets an enabling condition or not, if the enabling condition is met, executing a step S2, and if not, continuing to execute the step S1; s2, two-dimensional temperature gradient intervention: obtaining a first-level parameter based on the temperature of the tail gas after-treatment system and the environment temperature; s3, selecting secondary parameters according to the primary parameters, wherein the secondary parameters are selected from one or more of a main injection advance angle correction parameter, a main injection fuel quantity correction parameter, a throttle valve correction parameter and a pre-injection and post-injection related correction parameter; and S4, based on the combination of the second-level parameters, regulation and control over engine combustion are executed. According to the control method for nitrogen oxide emission, emission of nitrogen oxide can be effectively reduced, and the control capacity for nitrogen oxide emission is improved.

Description

Technical Field

[0001] This application relates to the field of exhaust gas treatment technology, and in particular to a method for controlling nitrogen oxide emissions. Background Technology

[0002] Currently, bench tests have revealed that the WHTC / SC test is affected by a combination of factors, including ambient temperature, the initial temperature upstream of the SCR system, and the interruption of post-injection, leading to excessive exhaust emissions and poor emission consistency in actual applications. Currently, the common practice is to trigger urea injection after the upstream temperature sensor of the SCR system detects a temperature threshold, with post-injection used as an auxiliary measure. However, this is subject to other controls and has limited ability to control nitrogen oxides. Heating the SCR system involves separately adding fuel injection and combustion heating via DPM (hydrocarbon injection system), significantly increasing costs. The current exhaust emission control performance is heavily dependent on ambient temperature and the upstream temperature of the SCR system; control is slower at low temperatures and faster at high temperatures, resulting in poor adaptability. Especially during the start-up phase, nitrogen oxide (NOx) emissions severely exceed standards, making it difficult to meet the local testing requirements in some areas. Summary of the Invention

[0003] The main objective of this invention is to provide a method for controlling nitrogen oxide emissions, aiming to solve at least one of the above-mentioned technical problems.

[0004] To achieve the above objectives, this invention proposes a method for controlling nitrogen oxide emissions, comprising: S1, starting the engine and determining whether the engine meets the enabling conditions; if the enabling conditions are met, proceeding to step S2; otherwise, continuing to proceed to step S1; S2, two-dimensional temperature gradient intervention: obtaining primary parameters based on the exhaust aftertreatment system temperature and ambient temperature; S3, selecting secondary parameters based on the primary parameters, wherein the secondary parameters are selected from one or more of the following: main injection advance angle correction parameters, main injection quantity correction parameters, throttle correction parameters, and pre-injection and post-injection related correction parameters; S4, performing engine combustion regulation based on the combination of secondary parameters.

[0005] In some embodiments of the present invention, the enabling condition is selected from one or a combination of enabling condition one and enabling condition two; enabling condition one is: the cumulative amount of nitrogen oxides downstream of the SCR system is greater than the nitrogen oxide emission exceeding warning value within a certain period of time or the numerical range of nitrogen oxide accumulation per unit time is within a set range; enabling condition two is: the engine start time is greater than a set time, the set time is the first time point after the engine starts with an additional first duration, and the engine start time is the second time point after the engine starts with an additional second duration.

[0006] In some embodiments of the present invention, the engine start time and set time are determined by laboratory calibration or set to meet road exhaust emission testing requirements.

[0007] In some embodiments of the present invention, the first time point is selected from the time node after the engine starts and the vehicle enters or leaves a certain region or country, or enters or leaves a certain altitude or altitude range, and the second time point is the time node required for the engine to compliantly emit exhaust gas from the start of the engine to reach its target position after entering or leaving the target position under normal circumstances.

[0008] In some embodiments of the present invention, the cumulative amount of nitrogen oxides is obtained by integrating the nitrogen oxide detection results over a set time domain.

[0009] In some embodiments of the present invention, an arbitrary time period after engine start-up is set as time domain L. The nitrogen oxide content in the time domain L is detected in real time by a nitrogen oxide sensor downstream of the SCR system to obtain a set of nitrogen oxide values. The cumulative amount of nitrogen oxides is obtained by integrating the nitrogen oxide values ​​in time domain L.

[0010] In some embodiments of the present invention, a nitrogen oxide emission exceeding warning value is triggered when the cumulative amount of nitrogen oxides exceeds the emission exceeding warning value.

[0011] In some embodiments of the present invention, the primary parameter is obtained by looking up the MAP table from the exhaust aftertreatment system temperature and the ambient temperature; the exhaust aftertreatment system temperature is selected from one or more of the upstream temperature of the SCR system, the downstream temperature of the DPF, the exhaust temperature in the middle of the exhaust pipe, and the exhaust temperature at the tail of the exhaust pipe; the ambient temperature is selected from one or more of the engine water temperature, the engine coolant temperature, the air temperature before the intercooler, and the air temperature after the intercooler.

[0012] In some embodiments of the present invention, the combination of the secondary parameters is based on the selection of the influence factors of each secondary parameter; using the secondary parameters, the corresponding injection can be completely shut off, up to the point of shutting off the overall injection of a cylinder.

[0013] In some embodiments of the present invention, after step S4 is completed, step S1 is executed to determine whether the engine still meets the enabling conditions. If the enabling conditions are met, step S2 is executed; otherwise, step S1 is executed.

[0014] This application provides a method for controlling nitrogen oxide emissions. This method sets enabling conditions and combines the dual-trigger approach of integrating the downstream nitrogen oxide value of the SCR system and the engine start-up time to solve two problems. At the same time, it limits the scope of influence to avoid excessive functions. While effectively reducing nitrogen oxide emissions, it ensures the power and economy of the product. Furthermore, it adopts a comprehensive influence analysis method of exhaust after-treatment system temperature and ambient temperature to reduce the instability of single-factor control and improve the stable control of nitrogen oxide emissions. With the help of influence shadow and control priority, it further improves the control accuracy and greatly meets the requirements for reducing nitrogen oxide emissions during vehicle start-up, especially in cold start and even winter start-up scenarios. Attached Figure Description

[0015] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. In the drawings:

[0016] Figure 1 This is a logic flowchart of the nitrogen oxide emission control method of the present invention;

[0017] Figure 2 This is a detailed flowchart of the nitrogen oxide emission control method of the present invention. Detailed Implementation

[0018] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0019] The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of methods consistent with some aspects of this application as detailed in the appended claims. In the description of this application, it should be understood that the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances. Furthermore, in the description of this application, unless otherwise stated, "multiple" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, and B alone. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship.

[0020] This application discloses a method for controlling nitrogen oxide emissions, such as... Figure 1 and Figure 2 As shown, the control method includes the following steps:

[0021] S1, the engine starts. It is determined whether the engine meets the enabling conditions. If the enabling conditions are met, step S2 is executed; otherwise, step S1 is executed.

[0022] In some embodiments of the present invention, the enabling condition includes enabling condition one, which is: the cumulative amount of nitrogen oxides downstream of the SCR system within a certain time period or the cumulative amount of nitrogen oxides per unit time. If the cumulative amount of nitrogen oxides is greater than the warning value for excessive nitrogen oxide emissions or the numerical range of the cumulative amount of nitrogen oxides per unit time is within a set range, then it is determined that the engine meets the enabling condition and step S2 will be executed.

[0023] In some embodiments of the present invention, when the cumulative amount of nitrogen oxides exceeds the emission exceedance warning value, a nitrogen oxide emission exceedance warning can be triggered to issue a warning and reminder; furthermore, the emission exceedance warning includes, but is not limited to, warnings based on sound, light, vibration, or a combination thereof.

[0024] In some embodiments of the present invention, any time period after engine start-up can be set as time domain L. The nitrogen oxide content in the time domain L interval is detected in real time by the nitrogen oxide sensor downstream of the SCR system, and a set of nitrogen oxide values ​​can be obtained. By integrating the nitrogen oxide values ​​in time domain L, the cumulative amount of nitrogen oxides is obtained. The emission exceedance warning value is set to B. By comparing the integral result of the nitrogen oxide value in time domain L with the value of B, it can be determined whether the engine meets the first enabling condition.

[0025] In some embodiments of the present invention, the enabling condition may further include enabling condition two, which is: engine start time. If the engine start time is greater than a set time, it is determined that the engine meets the enabling condition, and step S2 will be executed.

[0026] In this invention, the set time is the first time point after the engine starts and the first duration is added, and the engine start time is the second time point after the engine starts and the second duration is added. The first time point is a time node selected according to actual needs, and the second time point is the node required for the engine to reach compliant exhaust emission under normal circumstances from start-up.

[0027] It should be understood that when the selected first time point is before the second time point, that is, the engine start time is greater than the set time, it means that the engine cannot reach the state of compliant exhaust emission when it reaches the first time point, and step S2 needs to be executed; when the selected first time point is after the second time point, that is, the engine start time is less than the set time, it means that the engine can reach the state of compliant exhaust emission before it reaches the first time point, and step S2 does not need to be executed.

[0028] In some embodiments of the present invention, the engine start time and the set time include, but are not limited to, those calibrated in a laboratory or those set to meet road exhaust emission testing requirements.

[0029] The first time point can be selected from the time when the vehicle enters or leaves a certain region or country after the engine starts, or enters or leaves a certain altitude or altitude range, etc. The second time point is the time required for the engine to compliantly emit exhaust gases from the time it starts until it reaches the target location after entering or leaving the target location under normal circumstances.

[0030] For example, on roads, there are remote sensing or real-time monitoring points to detect exhaust emissions. In this case, the estimated travel time from the vehicle start-up to the landmark detection location can be set as the set time A, and the time from engine start-up to reaching compliant exhaust emission standards under normal operating conditions can be set as the engine start-up time.

[0031] It should be understood that when the vehicle is close to the landmark inspection that is about to be carried out, that is, the engine start time is longer than the set time A, step S2 can be executed. Through subsequent adjustments, the exhaust emissions can be brought up to the standard in advance, so as to pass the landmark inspection smoothly and reduce the possibility of misjudgment.

[0032] When the vehicle is far from the upcoming landmark inspection, i.e., the engine start time is less than the set time A, it means that relying on the normal exhaust gas treatment performance of the SCR system, the exhaust gas treatment level can be made within the regulatory requirements before entering the landmark inspection. In other words, there is no need to determine whether to execute step S2 according to the enabling condition two. Thus, the exhaust gas treatment procedure is entered according to the normal start-up process of the SCR system, which effectively avoids increased energy consumption, reduces the impact on the engine system, and reduces costs.

[0033] In some embodiments of the present invention, step S2 can be executed when the engine satisfies enabling condition one, enabling condition two, or both enabling condition one and enabling condition two.

[0034] This invention combines the downstream nitrogen oxide value integration of the SCR system and the engine start-up time point as dual triggers to solve two problems in one step, while limiting the scope of influence to avoid excessive functions affecting the product's power and economy.

[0035] S2, Two-dimensional temperature gradient intervention: First-level parameters are obtained based on the temperature of the exhaust gas aftertreatment system and the ambient temperature.

[0036] In this invention, the primary parameter is obtained by looking up the MAP table based on the exhaust aftertreatment system temperature and the ambient temperature, and is set as the gradient total parameter X. In this invention, the two-dimensional temperature refers to the exhaust aftertreatment system temperature and the ambient temperature. The MAP table is a pulse spectrum of nitrogen oxide content downstream of the SCR system based on the exhaust aftertreatment system temperature and the ambient temperature. That is, the gradient total parameter X is obtained by looking up the MAP table based on the gradient intervention of the exhaust aftertreatment system temperature and the ambient temperature. It should be understood that after the gradient total parameter X is adjusted, the engine meets the normal exhaust emission requirements.

[0037] In this invention, the exhaust aftertreatment system temperature includes, but is not limited to, the upstream temperature of the SCR system, the downstream temperature of the DPF, the exhaust temperature in the middle of the exhaust pipe, or the exhaust temperature at the tail of the exhaust pipe; the ambient temperature includes, but is not limited to, the engine water temperature, the engine coolant temperature, the air temperature before the intercooler, or the air temperature after the intercooler.

[0038] This invention employs a comprehensive analysis method that considers the combined effects of exhaust gas aftertreatment system temperature, such as the upstream temperature of the SCR system and the ambient temperature, thereby reducing the instability of single-factor control.

[0039] S3, select the secondary parameter based on the primary parameter.

[0040] In this invention, the secondary parameters include, but are not limited to, the main injection advance angle correction parameter, the main injection quantity correction parameter, the throttle correction parameter, and the pre-injection and post-injection related correction parameters, etc., and each secondary parameter is selected and combined based on the total gradient parameter X.

[0041] Among them, the main injection advance angle correction can increase the proportion of afterburning; the main injection quantity correction is the main injection quantity compensation, which can compensate for the power loss caused by the increase in afterburning; the throttle valve correction can specifically be the throttle valve opening correction, which can affect the air-fuel ratio and adjust the combustion rate; the pre-injection and post-injection related correction can specifically be the control of the pre-injection and post-injection decisions, that is, the pre-injection and post-injection priority decision, such as selectively abandoning certain needs that may cut off pre-injection and post-injection, so that the post-injection quantity and pre-injection enablement can be entered after the enablement conditions are met.

[0042] In some embodiments of the present invention, the main injection advance angle correction parameter, main injection quantity correction parameter, throttle correction parameter, and pre-injection and post-injection related correction parameter can be selected according to the influence factors of each secondary parameter to obtain a combination of secondary parameters. That is, one or more of the main injection advance angle correction, main injection quantity correction, throttle correction, and pre-injection and post-injection related correction can be selected for regulation to achieve the purpose of reducing nitrogen oxide content.

[0043] For example, using secondary parameters can completely shut down the corresponding injection or even shut down the overall injection of a certain cylinder, which can increase the load rate of the working cylinder, allow the fuel to burn more completely in the combustion chamber, reduce fuel waste, and thus reduce emissions of pollutants such as carbon monoxide and hydrocarbons caused by incomplete combustion, thereby achieving emission balance.

[0044] Furthermore, by shutting down some cylinders, parameters such as the intake air volume and fuel injection volume of the working cylinders can be further optimized. For example, the injection timing and injection pressure can be precisely controlled according to actual operating conditions, making the fuel-air mixture ratio closer to the ideal state, improving combustion efficiency, and reducing the generation of pollutants such as nitrogen oxides.

[0045] This invention improves control precision through a gradient control method, effectively controlling the types and degrees of intervention of multiple factors such as main injection, pre-injection, post-injection and air intake.

[0046] Secondly, the control approach that prioritizes post-spray and pre-spray can effectively balance the impact of other functional control requirements on the interruption of post-spray and pre-spray.

[0047] In addition, the newly added main injection and throttle control in this invention help to increase the control capability under special working conditions and increase product adaptability, such as cold start or even winter start-up.

[0048] Moreover, compared to reducing nitrogen oxide content with only post-spray control, introducing main spray and pre-spray control increases the overall control capability, thereby making the post-treatment temperature increase capability more powerful.

[0049] S4, based on a combination of secondary parameters, regulates engine combustion, improves the ability to treat nitrogen oxides, thereby reducing nitrogen oxide emissions, thus reducing emission risks and environmental pollution.

[0050] In this invention, after step S4 is completed, step S1 can be continued to determine whether the engine still meets the set enabling conditions. If the enabling conditions are met, steps S2, S3, etc. can be continued until the nitrogen oxide treatment capacity meets the regulatory requirements or the predetermined usage conditions are met. If the enabling conditions are not met, it means that the nitrogen oxide treatment capacity has met the regulatory requirements or the predetermined usage conditions are met.

[0051] This invention helps control costs without adding new equipment and enables effective control of nitrogen oxide emissions, meeting regulatory requirements for nitrogen oxide emissions and detection.

[0052] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for controlling nitrogen oxide emissions, characterized in that: include: S1, the engine is started, and it is determined whether the engine meets the enabling conditions. If the enabling conditions are met, step S2 is executed, otherwise, step S1 is continued; S2, two-dimensional temperature gradient intervention: obtain primary parameters based on the exhaust gas aftertreatment system temperature and ambient temperature; S3, selecting a secondary parameter according to the primary parameter, wherein the secondary parameter is selected from one or more of a main injection advance angle correction parameter, a main injection amount correction parameter, a throttle correction parameter, and a pre-injection and post-injection related correction parameter; S4. Based on the combination of the secondary parameters, control the engine combustion.

2. The method for controlling nitrogen oxide emissions according to claim 1, characterized in that: The enabling condition is selected from one or a combination of two of enabling condition 1 and enabling condition 2; The enabling condition 1 is: the accumulated amount of nitrogen oxides downstream of the SCR system within a certain period of time is greater than the warning value of excessive nitrogen oxide emissions or the numerical range of the accumulated amount of nitrogen oxides per unit time is within a set range; The second enabling condition is: the engine start time is greater than the set time, the set time is a first time point after the engine starts and a first time length is added, and the engine start time is a second time point after the engine starts and a second time length is added.

3. The method for controlling nitrogen oxide emissions according to claim 2, characterized in that: The engine start time and set time are calibrated by the laboratory or set to meet the road exhaust gas detection requirements.

4. The method for controlling nitrogen oxide emissions according to claim 3, characterized in that: The first time point is selected from the time node when the vehicle enters or exits a certain area or country or enters or exits a certain altitude or altitude range after the engine is started, and the second time point is the time node required for the engine to discharge exhaust gas in compliance with regulations from the time it is started to the time it reaches a target position or enters or exits a certain target position under normal circumstances.

5. The method for controlling nitrogen oxide emissions according to claim 2, characterized in that: The nitrogen oxide accumulation amount is obtained by integrating the nitrogen oxide detection results within a set time domain.

6. The method for controlling nitrogen oxide emissions according to claim 5, characterized in that: Any time period after the engine is started is set as time domain L. The nitrogen oxide content in the time domain L is detected in real time by the nitrogen oxide sensor downstream of the SCR system to obtain a set of nitrogen oxide values. The nitrogen oxide accumulated amount is obtained by integrating the nitrogen oxide values ​​in time domain L.

7. The method for controlling nitrogen oxide emissions according to claim 2, characterized in that: When the accumulated amount of nitrogen oxides is greater than the excessive emission warning value, the nitrogen oxide emission excessive warning is triggered.

8. The method for controlling nitrogen oxide emissions according to claim 1, characterized in that: The primary parameters are obtained by looking up the MAP table based on the exhaust gas after-treatment system temperature and the ambient temperature; The exhaust gas aftertreatment system temperature is selected from one or more of the SCR system upstream temperature, the DPF downstream temperature, the exhaust gas temperature in the middle of the exhaust pipe and the exhaust gas temperature at the tail end of the exhaust pipe; The ambient temperature is selected from one or more of an engine water temperature, an engine coolant temperature, an air temperature before an intercooler, and an air temperature after an intercooler.

9. The method for controlling nitrogen oxide emissions according to claim 1, characterized in that: The combination of the secondary parameters is selected based on the influencing factors of the secondary parameters; Using the secondary parameters, the corresponding injection can be completely shut down until the entire injection of a cylinder is shut down.

10. The method for controlling nitrogen oxide emissions according to claim 1, characterized in that: After step S4 is completed, step S1 is continued to be executed to determine whether the engine still meets the enabling condition. If the enabling condition is met, step S2 is continued to be executed, otherwise, step S1 is continued to be executed.

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