Method for controlling nitrogen oxide emissions

Abstract

The application relates to a nitrogen oxide emission control method in the tail gas treatment technical field, which comprises the following steps: S1, engine starting, judging whether the engine satisfies an enabling condition, if the enabling condition is satisfied, executing step S2, otherwise, continuing to execute step S1; S2, two-dimensional temperature gradient intervention: obtaining a primary parameter based on tail gas aftertreatment system temperature and environment temperature; S3, selecting a secondary parameter according to the primary parameter, the secondary parameter is selected from one or more of a main injection advance angle correction parameter, a main injection oil quantity correction parameter, a throttle correction parameter and a pre-injection post-injection related correction parameter; S4, based on the combination of the secondary parameter, executing regulation and control on engine combustion. The nitrogen oxide emission control method can effectively reduce nitrogen oxide emission and improve the control ability of nitrogen oxide emission.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of tail gas treatment, in particular to a control method for nitrogen oxide emission. BACKGROUND

[0002] At present, during the bench test process, it is found that the WHTC / SC experiment is affected by the environmental temperature, the initial temperature of the upstream of the SCR and the interruption of the post-injection, so that the tail gas emission result exceeds the standard in the actual application, and the emission consistency is poor; at present, the temperature sensor on the upstream of the SCR system is usually used to detect the temperature to trigger the urea injection after the threshold value is reached, the post-injection is used as an auxiliary, and the control ability of the nitrogen oxide is limited by other regulations, the heating of the SCR system is to separately increase the DPM (hydrocarbon injection system) oil injection combustion heating, and the cost is obviously increased; the current tail gas control effect is highly dependent on the environmental temperature and the temperature on the upstream of the SCR, the control is slow when the external temperature is low, the control is fast when the external temperature is high, the adaptability is poor, and in particular, during the starting stage, the nitrogen oxide (NOx) emission seriously exceeds the standard, and it is difficult to meet the local detection requirements. SUMMARY

[0003] The main purpose of the application is to provide a control method for nitrogen oxide emission, which aims to solve at least one of the above technical problems.

[0004] In order to achieve the above-mentioned purpose, the application provides a control method for nitrogen oxide emission, comprising: S1, starting the engine, judging whether the engine meets the enabling condition, if the enabling condition is met, executing step S2, otherwise continuing to execute step S1; S2, two-dimensional temperature gradient intervention: obtaining a first parameter based on the temperature of the tail gas aftertreatment system and the environmental temperature; S3, selecting a second parameter according to the first parameter, the second parameter is selected from one or more of the main injection advance angle correction parameter, the main injection oil quantity correction parameter, the throttle correction parameter and the pre-injection post-injection related correction parameter; S4, based on the combination of the second parameter, executing the regulation of the engine combustion.

[0005] In some embodiments of the application, the enabling condition is selected from one or a combination of the enabling condition one and the enabling condition two; the enabling condition one is that the accumulated amount of nitrogen oxide downstream of the SCR system in a certain time period is greater than the emission over-standard early warning value of nitrogen oxide or the numerical interval of the accumulated amount of nitrogen oxide per unit time is between the set range; the enabling condition two is that the engine starting time is greater than the set time, the set time is a first time point after the engine starting time is increased by a first time length, and the engine starting time is a second time point after the engine starting time is increased by a second time length.

[0006] In some embodiments of the application, the engine starting time and the set time are set by laboratory calibration or by meeting the requirements of road tail gas detection.

[0007] In some embodiments of the present application, the first time point is selected from a time point when the vehicle enters or exits a certain region or country, enters or exits a certain altitude or altitude range after the engine is started, and the second time point is a time point when the engine normally needs to reach a compliant exhaust emission after starting and reaching a target position.

[0008] In some embodiments of the present application, the nitrogen oxide accumulation amount is obtained by integrating the nitrogen oxide detection results in a set time domain.

[0009] In some embodiments of the present application, any time period after the engine is started is set as a 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, and the nitrogen oxide accumulation amount is obtained by integrating the nitrogen oxide values in the time domain L.

[0010] In some embodiments of the present application, when the nitrogen oxide accumulation amount is greater than the emission over-limit early warning value, the nitrogen oxide emission over-limit early warning is triggered.

[0011] In some embodiments of the present application, the primary parameter is obtained by looking up a MAP table with 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; and 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 application, the combination of the secondary parameters is selected based on the influence factors of each secondary parameter; and using the secondary parameters can completely close the corresponding injection until the overall injection of a certain cylinder is closed.

[0013] In some embodiments of the present application, after the step S4 is executed, the step S1 is continued to be executed to determine whether the engine still meets the enabling condition, if the enabling condition is met, the step S2 is continued to be executed, otherwise the step S1 is continued to be executed.

[0014] The embodiment of the application provides a control method of nitrogen oxide emission, which sets an enabling condition, combines and solves two problems in a dual-trigger mode of integrating nitrogen oxide value integration downstream of an SCR system and a starting time point of an engine, limits an influence range to avoid excessive functions, ensures product power and economy while effectively reducing nitrogen oxide emission, adopts a comprehensive influence analysis mode of exhaust gas aftertreatment system temperature and ambient temperature to reduce instability of single factor control, improves stable control of nitrogen oxide emission, and further improves control precision by using control ideas such as influence shadow and control priority, greatly meets the requirement of reducing nitrogen oxide emission of a vehicle in a starting stage, especially in a cold start and even in a winter start application scenario. BRIEF DESCRIPTION OF DRAWINGS

[0015] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The accompanying drawings are included to provide a description of the preferred embodiments and are not intended to limit the scope of the present application. In the drawings:

[0016] Figure 1 is a logic flow chart of the control method of nitrogen oxide emission of the application;

[0017] Figure 2 is a detailed flow chart of the control method of nitrogen oxide emission of the application. DETAILED DESCRIPTION

[0018] It should be clear that the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

[0019] The embodiments described in the following exemplary embodiments do not represent all the embodiments consistent with the present application. Instead, they are only examples of methods consistent with some aspects of the present application as detailed in the appended claims. In the description of the present application, it should be understood that the terms "first", "second", etc. are only for the purpose of description, and cannot be understood as indicating or implying relative importance. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances. In addition, in the description of the present application, "multiple" means two or more, unless otherwise specified. "And / or", which describes the relationship between the associated objects, means that there can be three relationships, for example, A and / or B can mean that there are three cases of A alone, A and B together, and B alone. The character " / " generally represents that the associated objects before and after are in an "or" relationship.

[0020] The application discloses a control method for nitrogen oxide emission, as shown in Figure 1 and Figure 2 The control method comprises the following steps:

[0021] S1, judging whether the engine meets an enabling condition, if yes, executing step S2, otherwise, continuing to execute step S1.

[0022] In some embodiments of the application, the enabling condition comprises an enabling condition one, which is that the nitrogen oxide accumulation amount downstream of the SCR system within a certain time period or the nitrogen oxide accumulation amount per unit time, if the nitrogen oxide accumulation amount is greater than the nitrogen oxide emission over-limit early warning value or the nitrogen oxide accumulation amount per unit time is in a value interval between the set range, it is judged that the engine meets the enabling condition, and step S2 is executed.

[0023] In some embodiments of the application, when the nitrogen oxide accumulation amount is greater than the emission over-limit early warning value, the nitrogen oxide emission over-limit early warning can be triggered to issue a warning to remind.

[0024] In some embodiments of the application, any time period after the engine starts can be set as a 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, the nitrogen oxide value set can be obtained, the nitrogen oxide accumulation amount is obtained by integrating the nitrogen oxide value in the time domain L, the emission over-limit early warning value is set as B, and the size of the integral result of the nitrogen oxide value in the time domain L and B is compared, so as to judge whether the engine meets the enabling condition one.

[0025] In some embodiments of the application, the enabling condition can also comprise an enabling condition two, which is that the engine starting time, if the engine starting time is greater than the set time, it is judged that the engine meets the enabling condition, and step S2 is executed.

[0026] In the application, the set time is a first time point after the engine starts and increases by a first time length, and the engine starting time is a second time point after the engine starts and increases by a second time length, wherein the first time point is a time node selected according to actual needs, and the second time point is a node required for the engine to reach the compliant emission exhaust gas from starting under normal circumstances.

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

[0028] In some embodiments of the present application, the engine start time and the set time include, but are not limited to, being set by laboratory calibration or meeting road exhaust detection requirements.

[0029] The first time point can be selected from the time node when the vehicle enters or exits a certain region or country or enters or exits a certain altitude or altitude range after the engine starts, and the second time point is the node of the time required for the engine to reach compliant exhaust emission after starting from the normal condition to enter or exit a certain target position.

[0030] For example, on the road, there are remote sensing detection or real-time monitoring points for exhaust detection, at this time, the expected driving time of the vehicle from starting to the landmark detection position can be set as the set time A, and the time required for the engine to reach compliant exhaust emission under normal working conditions after starting can be set as the engine start time.

[0031] It should be understood that when the vehicle is close to the landmark detection to be performed, i.e., the engine start time is greater than the set time A, at this time, step S2 can be performed, and the exhaust emission is made to reach the standard in advance through subsequent regulation, so as to smoothly pass the landmark detection and reduce the possibility of misjudgment.

[0032] When the vehicle is far away from the landmark detection to be performed, i.e., the engine start time is less than the set time A, it indicates that at this time, the exhaust treatment performance of the SCR system is relied on, i.e., the exhaust treatment degree can reach the range required by the regulations before entering the landmark detection, i.e., it is not necessary to judge whether to perform step S2 according to the enabling condition two, so as to enter the exhaust treatment program according to the normal start flow of the SCR system, effectively avoid increasing energy consumption, reducing the influence on the engine system, and reducing the cost.

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

[0034] The present application can solve the two problems by fusing the downstream nitrogen oxide value integration of the SCR system and the start time point of the engine, limit the influence range, and avoid excessive function affecting the product power and economy.

[0035] S2, two-dimensional temperature gradient intervention: obtaining a primary parameter based on the tail gas aftertreatment system temperature and the ambient temperature.

[0036] The primary parameter in the present application is obtained by looking up a MAP table based on the tail gas aftertreatment system temperature and the ambient temperature, and is set as a gradient total parameter X; in the present application, the two-dimensional temperature refers to the tail gas aftertreatment system temperature and the ambient temperature, and the MAP table is a SCR system downstream nitrogen oxide content map based on the tail gas 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 tail gas aftertreatment system temperature and the ambient temperature in a gradient, and it should be understood that after the regulation of the gradient total parameter X is completed, the engine meets the normal tail gas emission.

[0037] In the present application, the tail gas aftertreatment system temperature includes but is not limited to the SCR system upstream temperature, the DPF downstream temperature, the exhaust pipe middle exhaust temperature or the exhaust pipe tail exhaust temperature, etc.; 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, etc.

[0038] The present application adopts a comprehensive influence analysis mode of the tail gas aftertreatment system temperature such as the SCR system upstream temperature and the ambient temperature, thereby reducing the instability of single factor control.

[0039] S3, selecting a secondary parameter according to the primary parameter.

[0040] In the present application, the secondary parameter includes but is 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 parameter, etc., and each secondary parameter is selected and combined based on the gradient total parameter X.

[0041] Among them, the main injection advance angle correction can increase the afterburning ratio; the main injection quantity correction is the main injection quantity compensation, which can compensate for the power loss caused by increasing the afterburning; the throttle correction can be the throttle opening correction, which can affect the air-fuel ratio and adjust the combustion rate; the pre-injection and post-injection related correction can be the control of affecting the pre-injection and post-injection decision, that is, the pre-injection and post-injection priority decision, for example, some selective abandonment for the demand that may cut off the pre-injection and post-injection, so as to enter the post-injection quantity and enable and pre-injection enable after meeting the enabling condition.

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

[0043] For example, using the secondary parameters can completely close the corresponding injection until closing the overall injection of a certain cylinder, which can increase the load rate of the working cylinder, make the fuel burn more fully in the combustion chamber, reduce fuel waste, and reduce the emission of pollutants such as carbon monoxide and hydrocarbons generated by incomplete combustion, so as to achieve the balance of emissions.

[0044] Further, when some cylinders are closed, the intake volume, fuel injection volume and other parameters of the working cylinder can be more optimally adjusted. For example, the fuel injection time and fuel injection pressure can be accurately controlled according to the actual working condition, so that the mixing ratio of fuel and air is closer to the ideal state, the combustion efficiency is improved, and the generation of pollutants such as nitrogen oxides is reduced.

[0045] The present application can improve the control accuracy by gradient control, and effectively control the intervention type and intervention degree of multiple factors such as main injection, pre-injection, post-injection and intake.

[0046] Secondly, the control idea of the priority of post-injection and pre-injection control can effectively balance the influence of other functional control requirements on the interruption of post-injection and pre-injection.

[0047] In addition, the newly added main injection and throttle control of the present application is beneficial to increase the control ability under special working conditions and increase the product adaptability, such as cold start and even winter start.

[0048] Moreover, compared with reducing the content of nitrogen oxides by only post-injection control, the introduction of main injection and pre-injection control increases the overall control ability, and further makes the post-processing temperature improvement ability more powerful.

[0049] S4, based on the combination of secondary parameters, the control of engine combustion is performed to improve the ability to treat nitrogen oxides, thereby reducing the emission of nitrogen oxides and further reducing the risk of emission and pollution to the environment.

[0050] In the present application, after step S4 is performed, step S1 can be continuously performed to determine whether the engine still meets the set enabling condition. If the enabling condition is met, steps S2, S3 and the like can be continuously performed until the treatment ability of nitrogen oxides reaches the regulatory requirements or meets the predetermined use condition. If the enabling condition is not met, it means that the treatment ability of nitrogen oxides has reached the regulatory requirements or meets the predetermined use condition.

[0051] The present application can help to control the cost without adding new equipment, and can effectively control the emission of nitrogen oxides to meet the emission requirements and detection requirements of regulations on nitrogen oxides.

[0052] The above merely describes preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any changes or replacements within the technical scope disclosed by the present application, which can be easily thought by those skilled in the art, should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method of controlling nitrogen oxide emissions, characterized by, Comprise: S1, engine start, determine whether the engine meets the enabling condition, if the enabling condition is met, step S2 is executed, otherwise step S1 is continued; The enabling condition includes enabling condition two, the enabling condition two is that the engine start time is greater than the set time, the set time is the first time point after increasing the first time length after the engine starts, and the engine start time is the second time point after increasing the second time length after the engine starts; The engine start time and the set time are set by the laboratory calibration or by meeting the requirements of road exhaust detection, the first time point is selected from the time node of the vehicle entering or leaving a certain area or entering or leaving a certain altitude after the engine starts, and the second time point is the node of the time required for the engine to start to meet the emission exhaust under normal circumstances; S2, two-dimensional temperature gradient intervention: based on the temperature of the exhaust aftertreatment system and the ambient temperature, the first level parameter is obtained; S3, selecting the second level parameter according to the first level parameter, the second level parameter is selected from one or more of the main injection advance angle correction parameter, the main injection quantity correction parameter, the throttle correction parameter and the pre-injection related correction parameter; S4, based on the combination of the second level parameter, the regulation of engine combustion is executed.

2. The method of controlling nitrogen oxide emissions according to claim 1, wherein, The enabling condition also includes enabling condition one; The enabling condition one is that the nitrogen oxide accumulation amount downstream of the SCR system in a certain time period is greater than the emission over-standard early warning value of nitrogen oxide.

3. The method of controlling nitrogen oxide emissions according to claim 2, wherein, The nitrogen oxide accumulation amount is obtained by integrating the nitrogen oxide detection results in the specified time domain.

4. The method of controlling nitrogen oxide emissions according to claim 3, wherein, Set any time period after the engine starts as the 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, the nitrogen oxide value set is obtained, and the nitrogen oxide accumulation amount is obtained by integrating the nitrogen oxide value of the time domain L.

5. The method of controlling nitrogen oxide emissions of claim 2, wherein, When the nitrogen oxide accumulation amount is greater than the emission over-standard early warning value, the nitrogen oxide emission over-limit early warning is triggered.

6. The method of controlling nitrogen oxide emissions of claim 1, wherein, The combination of the second level parameter is selected based on the influence factor of each second level parameter; Using the second level parameter can completely close the corresponding injection until closing the overall injection of a certain cylinder.

7. The method of controlling nitrogen oxide emissions of claim 1, wherein, After the step S4 is executed, step S1 is continued, and it is determined whether the engine still meets the enabling condition, if the enabling condition is met, step S2 is continued, otherwise step S1 is continued.

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