Exhaust gas aftertreatment method and system

Abstract

When the exhaust gas aftertreatment system with a specific catalyst reduction (SCR) system operates in regeneration mode, the DEF metering rate (70a) decreases to the regeneration test metering rate (70b). NO levels from sensors upstream and downstream of the SCR system are analyzed. x Horizontal data to determine the actual NO achieved x Reduction (72). This is compared with the desired NO achievable at the regeneration test metrology rate (74). x The reduction was compared. The NO was higher than expected. x High reduction rate of actual NO x The reduction rate indicates that regeneration is not yet complete. At the expected NO... x Actual NO within the tolerance range of reduction rate x The reduction rate indicates that regeneration is complete and the regeneration mode can be terminated. Protection is required for the exhaust gas aftertreatment system configured to implement the method.

Description

[0001] Cross-reference to related applications

[0002] not applicable. Technical Field

[0003] Embodiments of the present invention generally relate to an exhaust gas aftertreatment system, and also to a method for removing reducing agent deposits in the exhaust gas aftertreatment system. Background Technology

[0004] The demand for cleaner, more efficient internal combustion engines, especially diesel engines, continues to grow. In response to these demands, new standards continue to be introduced to reduce exhaust emissions, particularly particulate matter and nitrogen oxides (NOx). x )emission.

[0005] Exhaust gas aftertreatment systems (EATS) for engine exhaust systems have been developed to meet these standards. Known EATS include those for NO... x A selective catalytic reduction (SCR) system. The SCR system includes a metering module upstream of the SCR catalyst for introducing a reductant into the exhaust gas stream. The reductant reacts with the SCR catalyst to reduce NO in the exhaust gas. x Level. Commonly used reducing agents include anhydrous ammonia (NH3) and ammonia water (NH4OH).

[0006] It is also known to use urea (CO(NH2)2) solution as a reducing agent. Urea solution is commonly referred to as diesel exhaust fluid (DEF). When added to a hot exhaust gas stream, the urea volatilizes and decomposes to produce ammonia (NH3) and carbon dioxide (CO2). NH3 reacts with the SCR catalyst to produce NO. x The NH3 is converted into nitrogen (N2) and water vapor (H2O). The SCR system may also include an ammonia leakage catalyst (ASC) to remove excess levels of NH3 from the exhaust gas that were not fully utilized during the SCR process. The ASC is conveniently integrated into the SCR unit located downstream of the SCR catalyst.

[0007] In known SCR systems, a reducing agent (this term includes DEF) can form a liquid film on the wall surface within the exhaust gas pipeline. If the temperature is not high enough and / or the exhaust gas flow rate is low, the reducing agent may crystallize, leading to the accumulation of deposits in the exhaust gas system. This creates an obstruction to the flow of exhaust gas. Reducing agent deposits in the exhaust gas system can be removed by a process called regeneration, in which the exhaust gas temperature is increased to melt the deposits. A regeneration method for removing reducing agent deposits is disclosed in U.S. Patent Application Publication No. 2012 / 0216510 A1 (published August 30, 2012, by Xu et al.). Regeneration can be a relatively slow process, and to comply with exhaust emission regulations, regeneration needs to be maintained for as short a period as possible. Therefore, it is desirable to be able to monitor the regeneration process to determine when the reducing agent deposits have been sufficiently removed, allowing the regeneration procedure to be terminated. Summary of the Invention

[0008] In one aspect of the invention, a computer-executed method is provided for determining when a regeneration process for removing reducing agent deposits in an exhaust aftertreatment system for treating exhaust gases received from an internal combustion engine (ICE) is sufficiently completed to terminate the regeneration process, as described in claim 1. Further optional features are given in the claims dependent on claim 1.

[0009] The method may include terminating the regeneration mode after a predetermined time limit if the criteria for terminating the regeneration mode under step iii) are met before the predetermined time limit expires. The predetermined time limit may be in the range of 1 to 3 hours, and may be approximately 2 hours.

[0010] In another aspect of the invention, an exhaust aftertreatment system for treating exhaust gases received by an internal combustion engine (ICE), as described in claim 11, is provided. Further optional features are given in the claims dependent on claim 11.

[0011] The control system can be configured to terminate the regeneration mode after a predetermined time limit if the criteria for terminating the regeneration mode under step iii) are met before the predetermined time limit expires. The predetermined time limit can be in the range of 1 to 3 hours, and can be approximately 2 hours.

[0012] Within the scope of this application, it should be understood that the aspects, embodiments, examples, and alternatives set forth herein, as well as their individual features, may be used independently or in any possible and compatible combination. Features described with respect to a single aspect or embodiment should be understood to apply to all aspects and embodiments, unless otherwise stated or such features are incompatible. Attached Figure Description

[0013] One or more embodiments disclosed will now be described by way of example only with reference to the accompanying drawings, wherein:

[0014] Figure 1 This is a schematic illustration of an agricultural vehicle in the form of a tractor, which includes an exhaust aftertreatment system.

[0015] Figure 2 Schematic illustration of the use of Figure 1 Implementation plan for the vehicle's exhaust aftertreatment system;

[0016] Figure 3 The graph illustrates the DEF metering rate strategy used to determine when regeneration is satisfactorily completed; and

[0017] Figure 4 The graph illustrates an alternative DEF metering rate strategy for determining when regeneration is satisfactorily completed. Detailed Implementation

[0018] The invention will be described with reference to the accompanying drawings.

[0019] It should be understood that the detailed description and specific examples, while illustrating exemplary embodiments of the described apparatus, systems, and methods, are for illustrative purposes only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems, and methods described herein will be better understood from the following description, the appended claims, and the accompanying drawings. It should be understood that the drawings are merely schematic and not drawn to scale. It should also be understood that the same reference numerals denote the same or similar parts in all the drawings.

[0020] The terms “comprising,” “including,” “containing,” “characterized in,” and their grammatical equivalents used in this document are inclusive or open-ended terms that do not exclude additional unmentioned elements or methodological steps, and also include the more restrictive terms “consisting of” and “substantially consisting of” and their grammatical equivalents.

[0021] As used herein, the term “may” refers to the behavior of materials, structures, features, or methods in relation to embodiments used to carry out the invention, and such a term is preferred over the more restrictive term “is” in order to avoid any implication that other compatible materials, structures, features, and methods that may be used in combination with it should or must be excluded.

[0022] As used herein, the term “configuration” refers to the size, shape, material composition, and arrangement of one or more of at least one structure and at least one device in a predetermined manner that facilitates the operation of one or more of the structure and device.

[0023] The singular form following the article used in this article is also used to include the plural form, unless the context explicitly indicates otherwise.

[0024] The term “and / or” as used in this document includes any and all combinations of one or more of the listed items.

[0025] Spatial relation terms used in this document, such as “below,” “under,” “lower,” “bottom,” “above,” “upper,” “top,” “front,” “rear,” “left,” “right,” etc., are used to conveniently describe the relationship between one element or feature and another element or feature as shown in the figure. Unless otherwise stated, spatial relation terms are used to cover different orientations of materials, except for those shown in the figure.

[0026] As used herein, the term "substantially" when referring to a given parameter, property, or condition means and includes, as would be understood by one of ordinary skill in the art, the degree to which a given parameter, property, or condition conforms to a certain variation, such as within acceptable manufacturing tolerances. By way of example, depending on the specific parameter, property, or condition that substantially conforms, it may conform to at least 90.0%, at least 95.0%, at least 99.0%, or even at least 99.9%.

[0027] As used in this document, the term “about” refers to a given parameter that includes the value and has a meaning determined by the context (e.g., it includes the degree of error associated with the measurement of the given parameter).

[0028] Figure 1 The diagram schematically illustrates a vehicle 10, particularly in the form of an agricultural tractor. Tractor 10 includes a chassis 12, an operator's cab 14, a front axle 16, and a rear axle 18. Tractor 10 has an engine compartment 20 housing an internal combustion engine (schematically shown at 22), which selectively drives the front and / or rear axles 16, 18 via a transmission. In this example, the internal combustion engine 22 is specifically a diesel engine that burns diesel fuel and atmospheric air, producing power and exhaust gases. These exhaust gases are generally referred to as exhaust gases and are rich in particulate matter and nitrogen oxides NO and NO2 (collectively referred to as NO). x The exhaust system, typically indicated at location 24, receives exhaust gases from engine 22 and includes an exhaust aftertreatment system (typically located at...). Figure 2 (26 indications in the document), the exhaust gas aftertreatment system operates to remove at least some NO from the exhaust gas before it is released into the atmosphere. x .like Figure 1 As shown, the exhaust gas aftertreatment system can be enclosed by the housing 27.

[0029] Figure 2A portion of the exhaust system 24 of the tractor 10 is illustrated, which includes an example of an exhaust aftertreatment system 26 for treating exhaust gases from the combustion engine, and is configured to operate a regeneration method according to one aspect of the invention to remove reducing agent deposits.

[0030] The exhaust aftertreatment system 26 defines a gas flow path 28 through which exhaust gases from the engine 22 flow in the direction of arrow X, which indicates the flow direction of the gas from the upstream inlet 28a to the downstream outlet 28b. The outlet 28b may be in fluid communication with an exhaust tailpipe, which in one embodiment may include a vertical exhaust pipe 30 through which exhaust gases are released into the atmosphere.

[0031] The exhaust aftertreatment system 26 may include a diesel oxidation catalyst (DOC) 32 and a diesel particulate filter (DPF) 34 to reduce particulate mass and quantity emissions. The DPF may be a catalytic soot filter (CSF), wherein the DPF has a catalyst coating, typically made of a precious metal.

[0032] The exhaust gas aftertreatment system 26 includes a selective catalytic reduction (SCR) system configured to reduce nitrogen oxides (NOx) in the exhaust gas. x (Level). When present, the SCR system can be located downstream of DOC 32 and DPF 34.

[0033] The SCR system includes a metering module 36 for introducing a reducing agent (DEF) into the exhaust gas stream, a mixer 38 for mixing the DEF with the exhaust gas, and an SCR catalyst 40 in an SCR unit 42 located downstream of the mixer. The DEF is vaporized in the hot exhaust gas, decomposing to produce ammonia (NH3) and carbon dioxide (CO2). The ammonia produced from this decomposition can then be reacted with NO in the catalyst brick 40. x The reaction will convert NO x It is converted into nitrogen gas and water vapor.

[0034] SCR catalyst 40 may include any suitable catalyst, provided that the catalyst is capable of catalyzing the above-mentioned NO in the presence of a nitrogen oxide reducing agent. x It is converted into nitrogen and water. For example, the catalyst may include one or more base metal oxides, such as vanadium, molybdenum and / or tungsten oxides, supported on a porous ceramic material such as titanium dioxide.

[0035] As is known in the art, the SCR system may also include an NH3 leak catalyst (ASC) 44 for oxidizing NH3 to remove excess levels of NH3 from the exhaust gas that are not fully utilized in the SCR process (referred to as NH3 leak). The ASC can be conveniently incorporated into the SCR unit 42 located downstream of the SCR catalyst 40, but many other arrangements are possible. The ammonia leak catalyst is configured to minimize or prevent unreacted ammonia from flowing downstream, in other words, "leaking." To this end, the ammonia leak catalyst catalyzes the conversion of ammonia to nitrogen and water.

[0036] In the illustrated embodiment, SCR catalyst 40 and ASC 44 can be housed in a single catalyst brick comprising a monolithic support coated with a nitrogen oxide reduction catalyst, and a downstream portion thereof coated with an ammonia leakage catalyst. However, in an alternative embodiment, the SCR unit can have two catalyst bricks, a first brick coated with a nitrogen oxide reduction catalyst and a second brick coated with an ammonia leakage catalyst. In another embodiment, the second brick can be a monolithic support coated with a nitrogen oxide reduction catalyst, and a downstream portion thereof coated with an ammonia leakage catalyst.

[0037] The exhaust gas aftertreatment system 26 includes an electronic control system 46, which has a controller that... Figure 2 The schematic representation is 48, which can be in the form of one or more electronic control units (ECUs). ECU 48 includes a programmable processing unit (e.g., a microcontroller CPU) and memory, and is configured and programmed to control and manage the operation of the exhaust aftertreatment system according to operating conditions in a predetermined program. Electronic control system 46 is typically part of engine management system and can be part of vehicle management system that controls various other functions of the vehicle (e.g., transmission). The function of ECU 48 can be implemented by a single ECU or by multiple separate ECUs interconnected as part of a network, such as a CAN bus system (e.g., ISOBUS).

[0038] The electronic control system 46 also includes sensors for monitoring various operating parameters of the exhaust gas aftertreatment system 26. These sensors include those for detecting NO in the exhaust gas upstream of DOC 32. x upstream NO concentration level x Sensor 50 and used for detecting NO in the exhaust gas downstream of SCR unit 42 x Downstream NO concentration levels x Sensor 52. In this context, with NO x The term "upstream" related to sensor 50 refers to NO located upstream of the SCR system. x Sensors, and NO x The term "downstream" related to sensor 52 refers to NO located downstream of the SCR system.x Sensors. Compare the relative NO detected by these two sensors. x Concentration levels can be determined by the SCR system for NO. x The degree of decline.

[0039] The electronic control system may also include the following sensors:

[0040] The first temperature sensor 54 is used to detect the exhaust gas temperature (EGT) upstream of DOC 32;

[0041] The first pressure sensor 56 is used to detect the exhaust back pressure upstream of DOC 32;

[0042] Differential pressure sensor 58 is used to measure the exhaust pressure difference across DOC 32 and DPF 34 (alternatively, the differential pressure sensor can be configured to measure only the exhaust pressure difference across DPF 34);

[0043] The second temperature sensor 60 is used to detect the EGT downstream of the DPF 34;

[0044] A third temperature sensor 62 is used to detect the EGT near the inlet of the SCR unit 42; and

[0045] The fourth temperature sensor 64 is used to detect the EGT downstream of the SCR unit 42.

[0046] Sensors provide inputs to the ECU 48 for managing the operation of the exhaust aftertreatment system under various operating conditions. Control of the exhaust aftertreatment system 26 can be implemented using a combination of mathematical modeling to predict operating conditions and parameters at various locations within the system and closed-loop feedback control, both utilizing inputs from the various sensors. Inputs from other sensors associated with the engine 22 and / or the exhaust system upstream of the exhaust aftertreatment system can also be used. These can provide data related to engine status, speed, load, and temperature, for example, as inputs to the exhaust aftertreatment control system. It should be understood that the above-described sensor system is merely an exemplary embodiment, and the invention is not limited to use with EATS having such a sensor system.

[0047] DEF metering is controlled by ECU 48 and can be controlled using a model-based DEF metering control strategy. DEF metering is only permitted when the engine is running, and the DEF metering strategy is adjusted according to the specific operating conditions of the engine and exhaust aftertreatment system.

[0048] Typically, when the engine is running and the exhaust gas is at a suitable temperature, exhaust gas aftertreatment 26 uses NO. x Restore mode operation. In NO... x In recovery mode, ECU 48 utilizes power from two NO...x Data from sensors 50 and 52 determines the NO in the exhaust gas introduced by metering module 36 for DEF. x Restore metering rate. NO x The reduction metering rate is typically selected to achieve the desired tailpipe NO while minimizing NH3 leakage and overuse of DEF. x Emissions. NO x The choice of reduction metering rate can at least partially depend on the upstream NO x NO detected by sensor 50 x The level, and its selection may also take into account other operating conditions of the engine and / or exhaust aftertreatment. NO can be set according to a predetermined metering chart or lookup table. x The restored measurement rate, the graph or lookup table, can be generated using data obtained from testing. In an alternative embodiment, NO can be determined based on a predetermined procedure established using data obtained from testing. x Restoring the metering rate. In one implementation, NO can be determined through mathematical modeling. x Restore metering rate.

[0049] ECU 48 generates one or more control signals, which are sent to metering module 36 to cause metering module 36 to output NO. x The metering rate is restored to DEF. ECU 48 can compare the NO from upstream. x Sensor 50 and downstream NO x Data from sensor 52 is used to determine the achieved NO. x The restoration level is then compared with the selected NO under the current operating conditions. x Expected NO reduction rate x The restoration level is compared, and the latter can also be obtained from a lookup table or graph. This provides control feedback, and ECU 48 can be configured to respond to the detected actual NO. x Restore the expected NO x Reduction or by downstream NO x NO detected by the sensor x When the concentration exceeds acceptable levels, change NO x Reduction of metering rate. In an alternative implementation, the predicted NO... x The restored value can be determined by one or more controllers based on a predetermined procedure. In one implementation, the predicted NO can be determined through mathematical modeling. x Restoration. In one implementation, the predicted NO can be determined by the following formula. x Reduction rate:

[0050] Predicted NO x Reduction rate = (Measured upstream NO)x -Forecasted downstream NO x ) / Measurement of upstream NO x —Equation 1.

[0051] The exhaust aftertreatment system 26 operates periodically in a regeneration mode (or alternatively, a reductant deposit removal mode), wherein the exhaust gas temperature is raised sufficiently to melt the reductant (DEF) deposits in the exhaust system. In one embodiment, during regeneration, the exhaust gas can be raised to a temperature in the range of 350°C to 650°C. Exhaust gas temperatures in the range of 450°C to 550°C have been found to be particularly effective in removing reductant deposits while simultaneously maintaining the surface temperature of the exhaust system within acceptable limits. However, depending on vehicle and exhaust system requirements, the exhaust gas temperature required for effective regeneration may be higher or lower than the ranges described above. Entry into the regeneration mode can be triggered periodically. In one embodiment, the ECU can be programmed to enter the regeneration mode after a set number of operating hours, which in this embodiment can be any value between 20 and 100 or more operating hours. Alternatively, entry into the regeneration mode can be triggered in response to an input from the ECU 48 indicating the need to remove reductant deposits to maintain the effectiveness of the EAT system within acceptable limits. In the implementation scheme, ECU 48 can be programmed to respond to an input indication and / or NO in response to high exhaust back pressure (e.g., above a predetermined limit). x The conversion rate is lower than the expected NO for DEF metering rate over a period of time. x The conversion rate input indicates the start of regeneration mode. The required regeneration frequency depends on various factors, including vehicle operating conditions, exhaust pipeline design, and environmental conditions. Therefore, the required frequency for removing reducing agent deposits can vary considerably.

[0052] Typically, reducing agent deposits are found in areas of the exhaust gas aftertreatment system near metering module 16, including mixer 38 and at least upstream of SCR unit 42. As the DEF deposits melt, NH3 is released from the deposits into the exhaust gas stream passing through SCR unit 42. The NH3 released as the DEF deposits melt increases the level of NH3 in the exhaust gas that interacts with SCR catalyst 40, and thus affects NO. x Conversion / reduction level.

[0053] According to one aspect of the invention, when the exhaust gas aftertreatment system 26 operates in regeneration mode, the electronic control system 46 implements a method for determining when the reducing agent deposits have been sufficiently removed so that the regeneration mode can be terminated. This method uses NO from upstream and downstream... x Data acquired by sensors 50 and 52. As part of this method, during at least a portion of the time when operating in regeneration mode, the reducing agent metering rate is set lower than if the system uses NO.x When operating in restore mode, select NO. x Reduction metering rate. This reduced reducing agent metering rate will be referred to as the "regeneration test metering rate". When setting the regeneration test metering rate, the control system 46 can determine a suitable NO for the operating conditions. x The metering rate is restored, and then reduced to determine the regeneration test metering rate. This reduction can be a percentage reduction, such as at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, or at least 90%. In one embodiment, the regeneration test metering rate can be a sufficiently low fixed value such that it is always less than the appropriate NO0. x Restore metering rate. In this case, ECU 48 can simply apply a fixed regeneration test metering rate without determining the appropriate NO. x Regeneration metering rate. In one implementation, the regeneration test metering rate is zero. In this case, ECU 48 may not be able to determine the appropriate NO. x Instead of adjusting the reductant metering rate, the reductant metering can be simply stopped. The selection of the regeneration test metering rate can take into account the need to ensure that NO is discharged from the exhaust gas system during regeneration. x The level does not exceed the permissible limit. Therefore, in some applications, a zero regeneration test metering rate may be unsuitable, and a higher regeneration test metering rate should be used. The electronic control system 46 generates one or more appropriate control signals, which are transmitted to the metering module 36 to cause the metering module to deliver the reducing agent into the exhaust gas stream at the regeneration test metering rate.

[0054] When DEF is introduced at a reduced regeneration test metering rate, the control system 46 will draw NO from the upstream and downstream x NO received by sensors 50 and 52 x Horizontal data are compared to determine the actual NO achieved. x Restore. The control system 46 will realize the actual NO x The expected NO reduction and SCR system can achieve at the DEF regeneration test metering rate under the current engine and exhaust aftertreatment system operating conditions. x The reduction levels were compared. Regarding the expected NO... x The restoration level data can be stored in a lookup table or graph accessible to the ECU48, and this data can be obtained through testing. In an alternative implementation, the predicted NO... x The restored value can be determined by one or more controllers based on a predetermined program, which can be established using data obtained from testing. In one implementation, the predicted NO... xThe reduction can be determined by mathematical modeling and can be achieved using Equation 1 as described above.

[0055] If the actual NO is achieved x The reduction level of NO was higher than expected. x A reduced level indicates that DEF deposits in the exhaust system are melting, releasing NH3 into the exhaust gas, which in turn helps reduce NO in SCR unit 42. x The reduction. This indicates that regeneration is not yet fully complete. However, if the achieved NO x If the reduction level is essentially the same as expected at the regeneration test metering rate, this indicates that there is no further melting of DEF deposits and release of additional NH3 into the exhaust gas. This indicates that regeneration is complete and the regeneration mode can be terminated.

[0056] Typically, ECU 48 will apply a time delay after the DEF metering rate decreases to the regeneration test metering rate before determining the actual NO achieved. x Reduce and combine with the expected NO x The reduction is compared. This allows the system to reach steady-state operation at a reduced regeneration test metering rate. The required time delay length depends on several factors, such as the SCR catalyst temperature (response time) and the ammonia loading level of the SCR catalyst at that temperature. Typically, a suitable time delay can be in the range of 20 seconds to 5 minutes. Furthermore, ECU 48 can be configured to determine regeneration completion as soon as the actual NO... x The reduction rate is within the expected NO x The reduction rate should be within a predetermined threshold to allow for a margin of error. For example, even if the actual NO x The reduction rate was higher than expected for NO. x If the reduction rate does not exceed a predetermined amount, ECU 48 can also be configured to determine that regeneration is complete. The predetermined amount can be set at any suitable level, but is within the expected NO range in the implementation scheme. x The reduction rate is within the range of 5% to 20% or 10% to 15%. However, predetermined amounts higher or lower than the above ranges can be appropriately used for any given system and current operating conditions. In an implementation, the ECU can be programmed to only use the amount determined when it determines the actual NO. x The regeneration mode stops only after the reduction has reached an appropriate level for a predetermined time period. This is to ensure the exhaust gas pipeline is as clean as possible so that no small amount of sediment remains that could serve as "seeds" for further sediment buildup. The appropriate time period can be in the range of 3 to 5 minutes, but can be longer or shorter. Therefore, in an implementation, the system can apply criteria to determine when regeneration is complete and can be terminated, which requires actual NO... x The reduction rate has decreased to the expected NO xWithin a given time period, the predetermined threshold for the reduction rate.

[0057] Used with the expected NO x The actual NO reduction rate was compared. x The reduction rate can be determined substantially continuously or periodically during the testing phase. In one implementation, the actual NO... x The reduction rate was determined on a substantially continuous basis, with the results averaged over a period of time, and said average was used to compare with the expected NO. x The reduction rates were compared. For example, the determined actual NO... x The reduction rate can be averaged over a period of time ranging from 10 to 30 seconds.

[0058] Once the ECU 48 determines that the criteria for terminating regeneration have been met (i.e., regeneration is complete and there is little or no DEF deposit melting), it operates in stop regeneration mode, and then, if this is appropriate for the operating conditions of the engine and / or exhaust aftertreatment, it can resume normal NO regeneration. x The exhaust gas aftertreatment system operates in reduction mode 26. A method for determining when regeneration is essentially complete, involving the removal of reducing agent deposits, ensures that the regeneration mode is kept as short as possible while guaranteeing the effectiveness of the regeneration process.

[0059] The control system 46 can be configured to implement a method for determining when the regeneration mode is complete only after the exhaust gas aftertreatment system 26 has been operating in regeneration mode for a period of time. The control system can select an appropriate time period based on an estimate of the time required for successful regeneration. When the control system determines the actual NO... x If the reduction has not yet reached an appropriate level to stop regeneration, it can be configured to continue operating the exhaust gas aftertreatment system in regeneration mode, and the test method can be repeated subsequently if necessary until the actual NO level is determined. x The reduction has been reduced to the point where the criteria for terminating the regeneration mode are met, and the regeneration mode is terminated.

[0060] In one implementation, the control system 46 maintains the DEF metering rate at the regeneration test metering rate in regeneration mode and analyzes NO from upstream and downstream sources. x NO of sensors 50 and 52 x Horizontal data is used until it determines that the criteria for terminating the regeneration mode have been met. This is in Figure 3 The graph shown in the figure gives the DEF measurement rate and the actual NO time relative to the X-axis. x Reduction rate. The DEF metering rate is represented by line 70, and the typical actual NO expected for the DEF metering rate. x The reduction rate is represented by line 72. When the system enters regeneration mode, or at least when the system is in regeneration mode, the DEF metering rate 70 changes from NO.x The reduction metering rate 70a is reduced to the regeneration test metering rate 70b and maintained at this level until the regeneration mode terminates. As shown in line 72, when the DEF metering rate decreases, the actual NO... x The reduction rate typically begins to decrease. As mentioned above, the actual NO... x Reduction rate and expected NO x The reduction rate (represented by line 74) is compared until it is determined that it has dropped to the expected NO for the DEF regeneration test metering rate. x Until the reduction rate is reached. Once the system determines the actual NO... x The reduction rate has dropped to the expected NO x The recovery rate is 74%, and the criteria for terminating regeneration mode have been met; therefore, regeneration mode is terminated. System 26 typically returns to NO. x Reduction mode, and the DEF metering rate increases to NO. x The reduction rate is 70%. As shown in the figure, system 26 can achieve a reduction rate of 70% in actual NO. x The reduction rate dropped from 72% to the expected NO level. x A delay time is applied after the reduction rate reaches 74%, and then the regeneration mode ends. As the DEF metering rate increases by 70, the actual NO... x The reduction rate increased from 72% to NO. x The normal operating level is achieved at the DEF metering rate 70a. In the described example, the regeneration test metering rate 70b is greater than zero to help maintain NO levels during regeneration. x NO emissions kept within acceptable limits x Reduction rate. However, in other implementations, the regeneration test metering rate can be lower and may even be zero.

[0061] Figure 4 Alternative strategies for adjusting the DEF metering rate when the system is operating in regeneration mode are described. Figure 4 The graph relative to the X-axis time gives the DEF measurement rate and the actual NO. x Reduction rate. The DEF measurement rate is represented by line 70', and the actual NO detected. x The reduction rate is represented by line 78. When the system enters regeneration mode, the DEF metering rate changes from NO. x The reduction mode 70'a is reduced to a regeneration metering rate 70'b. This is lower than NO. x The metering rate was 70'a, but not low enough to be used as a metering rate for regeneration testing. A DEF regeneration metering rate of 70'b was chosen to maintain NO levels during regeneration, taking into account the level of NH3 released into the exhaust gas when crystallized ammonia deposits melt during regeneration. xThe reduction is kept at an acceptable level. Periodically, the DEF metering rate 70' is reduced to the regeneration test metering rate 70'c, and the actual NO is calculated. x The reduction rate of 78 and line 74 represent the expected NO at the DEF metering rate in the regeneration test. x The reduction rates are compared. If system 26 determines the actual NO... x If the reduction rate 78 has not sufficiently decreased to meet the criteria for terminating regeneration after a period of time, the DEF metering rate 70' is increased back to the regeneration metering rate 70'b for a period of time, and then the test method is repeated. The test method is repeated periodically until system 26 determines that the criteria for terminating regeneration have been met and the regeneration mode is terminated. Typically, the system will return to NO. x Restore mode, and the DEF metering rate returns to NO. x The reduction metering rate is 70'a. Figure 4 Two test cycles are described, in which the DEF metering rate 70' is reduced to the regeneration test metering rate 70'c. However, the system can undergo more than two test cycles, and the necessary number of test cycles can be implemented until the criteria for terminating the regeneration mode are determined to be met. Figure 4 As shown, system 26 can actually NO x The reduction rate of 78% has been reduced to the expected NO at a regeneration test metering rate of 70°C. x After the reduction rate reaches 74%, a delay time is applied before ending the regeneration mode and increasing the DEF metering rate back to NO. x Regeneration metering rate 70'a. In a further alternative, the system may not apply regeneration DEF metering rate 70'b, but instead simply maintain NO during the regeneration process. x The metering rate is reduced to 70'a, and the DEF metering rate is periodically reduced to the regeneration test metering rate 70'c. A test method is implemented according to one aspect of the invention to determine when regeneration is satisfactorily completed and the regeneration mode can be terminated.

[0062] The system can be configured to operate in regeneration mode only for a maximum predetermined time period. For example, a time limit of one to three hours can be set. In one implementation, a two-hour time limit is set. If the criteria for terminating regeneration mode are not met within the stated time limit, regeneration mode is stopped, and the system can return to NO. x Restore mode. In this mode, the system may generate an error message indicating that regeneration was unsuccessful. The error message can be displayed to the driver or otherwise made known to the driver, such as as an error message on a display screen (which can be a code or an icon). Alternatively or additionally, the error message or signal can be sent to a system remote from the vehicle. This could be, for example, the vehicle's central monitoring system.

[0063] ECU 48 may communicate with one or more sensors and / or devices associated with internal combustion engine 22 and may be equipped with a data carrier. ECU 48 may receive input signals from the sensors, which are configured to generate signals proportional to the physical parameters associated with internal combustion engine 22. Note that dashed lines are used to indicate the communication between ECU 48 and the various sensors and devices, but some have been omitted for clarity.

[0064] ECU 48 may include at least one digital central processing unit (CPU) connected to a storage system and an interface bus. The CPU may be configured to execute instructions stored as a program in the storage system and to send and receive signals from the interface bus. The storage system may include various storage types, including optical storage, magnetic storage, solid-state storage, and other non-volatile storage. The interface bus may be configured to send modulated analog and / or digital signals to and receive modulated analog and / or digital signals from various sensors and control devices, such as metering module 36. The program may embody the methods disclosed herein, allowing the CPU to implement the steps of the methods and control the exhaust aftertreatment system 26 and possibly also the internal combustion engine 22.

[0065] It should be understood that the method described above can be implemented on any exhaust gas aftertreatment system 26 with an SCR system, said SCR system including a reducing agent metering module and an SCR catalyst, and NO upstream and downstream of the SCR system. x Sensors and a suitable control system 46. This is true regardless of the presence of other components (such as DOC, DPF, or ASC) or the specific configuration of the exhaust aftertreatment system. Similarly, it should be understood that, in addition to the need for upstream and downstream NO... x In addition to sensors 50 and 52, the method can be applied to and used by a variety of exhaust gas aftertreatment systems with different sensor configurations.

[0066] Although embodiments of the exhaust aftertreatment system and method of the present invention have been described with reference to an agricultural vehicle 10 (in the form of a tractor), it should be understood that the disclosed exhaust aftertreatment system and method can be applied to a variety of vehicles and machines (whether stationary or mobile) using internal combustion engines (especially diesel engines). This includes, but is not limited to, tracked vehicles, combine harvesters, industrial and construction vehicles, and generators. Furthermore, although the invention has been described with reference to exhaust aftertreatment configured to receive diesel engine exhaust, the principles can be applied in cases where the exhaust aftertreatment system is used for engines burning alternative fuels such as hydrogen. In this case, the exhaust aftertreatment may have an oxidation catalyst (OC) upstream and adjacent to the particulate filter (PF) (these are used to replace the type of fuel burned by DOC and DPF). Typically, the OC and PF will be constructed and function in a similar manner to DOC and DPF, but will be configured for a specific fuel. Similarly, the DEF can simply be referred to as exhaust gas fluid (EF) or reducing agent, where the engine is not a diesel engine. The principle of the method for determining when the regeneration of reducing agent deposits is complete can be applied to exhaust gas aftertreatment systems that use any type of reducing agent to reduce pollutants in exhaust gas, where the reducing agent forms deposits in the system, and where regeneration to remove the reducing agent deposits releases the catalyst into the gas stream, thereby affecting the amount of pollutants removed by the SCR catalyst.

[0067] Other embodiments involve a computer-readable storage medium (e.g., a non-transitory computer-readable storage medium) having processor-executable instructions configured to implement one or more of the techniques presented herein.

[0068] This invention is not limited to the embodiments or examples described herein, and can be adjusted or adapted without departing from the scope of this invention.

[0069] All references cited in this paper are incorporated herein in their entirety. In the event of any conflict between the definitions in this paper and those in the incorporated references, the definitions in this paper shall prevail.

Claims

1. A computer-executed method for determining when a regeneration process for removing reducing agent deposits in an exhaust aftertreatment system for treating internal combustion engine (ICE) exhaust gases is sufficiently completed to terminate the regeneration process, the method being used in an exhaust aftertreatment system comprising: a. An exhaust gas flow path for receiving exhaust gas from an internal combustion engine (ICE) and allowing it to flow from upstream to downstream; b. A component in the exhaust gas flow path used to reduce NO in the exhaust gas. x A horizontal specific catalyst reduction (SCR) system, the SCR system including a metering module for introducing a reducing agent into the exhaust gas stream and an SCR catalyst downstream of the metering module; c. The upstream NO located upstream of the metering module x Sensor and downstream NO located downstream of the SCR catalyst x sensor; d. A control system, comprising one or more controllers, said controllers being configured to receive inputs from upstream and downstream NO. x Each of the sensors receives NO x Horizontal data, and analysis of NO from upstream and downstream x NO received by the sensor x Horizontal data to determine NO in upstream and downstream x NO in exhaust gas between sensors x In addition to the horizontal change, the control system is also configured to generate and output one or more control signals for controlling the operation of the metering module; e. The exhaust gas aftertreatment system can selectively operate in NO2 / NO ... x In either reduction mode or regeneration mode, wherein a regeneration procedure is performed in regeneration mode to remove reducing agent deposits from the exhaust gas system; f. The control system is configured to, when the exhaust gas aftertreatment system is based on the upstream NO... x NO detected by the sensor x Horizontal operation in NO x In restoration mode, the metering module is adjusted to adjust the NO... x The reducing agent is introduced into the exhaust gas at a reduction metering rate; g. When the exhaust gas aftertreatment system is operating in regeneration mode, the method includes: i. The control system adjusts the metering module to maintain a level below the suitable upstream NO. x NO detected at the sensor x NO levels x The regeneration test at the reduction metering rate involves introducing the reducing agent into the exhaust gas at the metering rate. ii. When the reducing agent is introduced at the regeneration test metering rate, the control system analyzes the NO from upstream and downstream. x NO received by the sensor x Horizontal data to determine NO in upstream and downstream x Actual NO between sensors x Restoration level; iii. The control system will determine the actual NO x Reduction and prediction of NO at reduced regeneration test metering rates x Reduction and comparison; and:

1. If the actual NO x Reduction ratio prediction NO x If the reduction exceeds the threshold amount, continue operating the exhaust gas aftertreatment in regeneration mode; or 2. If the actual NO x Restoration is not as good as prediction. x If the amount of regeneration exceeds the threshold, the regeneration mode is terminated.

2. The method according to claim 1, wherein, In determining the actual NO x Reduction ratio prediction NO x After restoring at least the threshold amount, the method is repeated periodically until the determined actual NO is reached. x Restoration is no longer better than prediction. x Restore the amount to at least the threshold and terminate the regeneration mode.

3. The method according to claim 2, wherein, In determining the actual NO x Reduction ratio prediction NO x After reducing to at least a threshold amount, the method includes maintaining the reducing agent metering rate at the regeneration test metering rate and periodically repeating steps ii) and iii) until the determined actual NO x Restoration is not as good as prediction. x Restore the amount to at least the threshold and terminate the regeneration mode.

4. The method according to claim 2, wherein, The method includes reducing the DEF metering rate to below NO when the exhaust gas aftertreatment system is operating in regeneration mode. x The regeneration metering rate is reduced to a rate higher than the regeneration test metering rate, and steps i) to iii) are performed periodically until the determined actual NO is obtained. x Restoration is not as good as prediction. x The regeneration mode is terminated after restoring the amount of NO to at least the threshold, wherein the actual NO is determined each time in step iii). x Reduction ratio prediction NO x After reducing the amount above the threshold, the DEF metering rate increases back to the regeneration metering rate to continue operating the exhaust gas aftertreatment in regeneration mode.

5. The method according to claim 2, wherein, In determining the actual NO x Reduction ratio prediction NO x After reducing to at least a threshold amount, the method includes increasing the reducing agent metering rate to NO. x Restore the metering rate for a period of time, then repeat steps i) to iii) until the determined actual NO is obtained. x Restoration is not as good as prediction. x Restore the amount to at least the threshold and terminate the regeneration mode.

6. The method according to any one of claims 1 to 5, wherein, The control system is configured to apply a time delay after setting the reducing agent metering rate to the regeneration test metering rate, and then determine the actual NO in step ii). x reduction.

7. The method according to any one of claims 1 to 6, wherein, Compare the determined actual NO x Reduction and prediction of NO for regeneration test metering rate x The restoration process includes determining the actual NO x Restore the predicted NO in a lookup table or graph accessible to one or more controllers. x The restored value or the predicted NO calculated by one or more controllers based on a predetermined program x The restored values ​​are compared.

8. The method according to any one of claims 1 to 6, wherein, The method is only started after the exhaust gas aftertreatment system has been operating in regeneration mode for a predetermined time.

9. The method according to any one of claims 1 to 8, wherein, The reducing agent is diesel exhaust gas, which may be ammonia, urea, or an aqueous solution of urea.

10. The method according to any one of claims 1 to 9, wherein, Regeneration test metering rate ratio NO x The reduction metering rate is at least 20%, or at least 30%, or at least 40%, or at least 50%, or at least 60%, or at least 70%, or at least 80%, or at least 90%, or the regeneration test metering rate is zero.

11. An exhaust aftertreatment system for treating exhaust gases from an internal combustion engine (ICE), comprising: a. An exhaust gas flow path for receiving exhaust gas from an internal combustion engine (ICE) and allowing it to flow from upstream to downstream; b. A component in the exhaust gas flow path used to reduce NO in the exhaust gas. x A horizontal specific catalyst reduction (SCR) system, the SCR system including a metering module for introducing a reducing agent into the exhaust gas stream and an SCR catalyst downstream of the metering module; c. The upstream NO located upstream of the metering module x Sensor and downstream NO located downstream of the SCR catalyst x sensor; d. A control system, comprising one or more controllers, said controllers being configured to receive inputs from upstream and downstream NO. x Each of the sensors receives NO x Horizontal data, and analysis of NO from upstream and downstream x NO received by the sensor x Horizontal data to determine NO in upstream and downstream x NO in exhaust gas between sensors x In addition to the horizontal change, the control system is also configured to generate and output one or more control signals for controlling the operation of the metering module; e. The exhaust gas aftertreatment system can selectively operate in NO2 / NO ... x In either the reduction mode or the regeneration mode, wherein a regeneration process is performed in the regeneration mode to remove reducing agent deposits from the exhaust gas system; f. The control system is configured to, when the exhaust gas aftertreatment system is based on the upstream NO... x NO detected by the sensor x Horizontal operation in NO x In restoration mode, the metering module is adjusted to adjust the NO... x The reducing agent is introduced into the exhaust gas at a reduction metering rate; g. The control system is configured to determine when the regeneration process for removing reducing agent deposits is fully completed to terminate the regeneration process when the SCR system is operating in regeneration mode, by: i. Adjust the metering module to a level lower than suitable for upstream NO x NO detected at the sensor x NO levels x The regeneration test of the reduction metering rate introduces the reducing agent into the exhaust gas; ii. Receive and analyze NO from upstream and downstream x sensor NO x Horizontal data were used to determine the upstream and downstream NO levels at the regeneration test reducing agent metering rate. x Actual NO between sensors x reduction; iii. The determined actual NO x Reduction and prediction of NO for reduced regeneration test metering rate x Reduction and comparison; and 1. If the actual NO x Reduction ratio prediction NO x If the amount of waste gas reduced is higher than the threshold, the exhaust gas aftertreatment will continue to operate in regeneration mode; or 2. If the actual NO x Restoration is not as good as prediction. x If the amount of regeneration exceeds the threshold, the regeneration mode is terminated.

12. The waste gas after-treatment system according to claim 11, wherein, In determining the actual NO x Reduction ratio prediction NO x After reducing the amount to at least the threshold level, the control system is configured to periodically measure the actual NO at the determined regeneration test metering rate of the reducing agent. x Reduction and prediction of NO for reduced regeneration test metering rate x The reduction comparison continues until the actual NO is determined. x Restoration is not as good as prediction. x The maximum amount of data restored is at least the threshold, and the regeneration mode is terminated.

13. The waste gas aftertreatment system according to claim 12, wherein, In determining the actual NO x Reduction ratio prediction NO x After reducing the amount to at least the threshold, the control system is configured to maintain the reducing agent metering rate at the regeneration test metering rate, and periodically adjust the actual NO content achieved at the determined regeneration test metering rate of the reducing agent. x Reduction and prediction of NO for reduced regeneration test metering rate x The reduction comparison continues until the actual NO is determined. x Restoration is not as good as prediction. x The maximum amount of data restored is at least the threshold, and the regeneration mode is terminated.

14. The waste gas aftertreatment system according to claim 12, wherein, When the exhaust gas aftertreatment system operates in regeneration mode, the control system is configured to reduce the DEF metering rate to below NO. x The regeneration metering rate is restored but higher than the regeneration test metering rate, and steps i) to iii) are performed periodically. The control system is configured to determine the actual NO each time in step iii). x Reduction ratio prediction NO x After restoring to at least the threshold amount, the DEF metering rate is increased back to the regeneration metering rate.

15. The waste gas aftertreatment system according to claim 12, wherein, In determining the actual NO x Reduction ratio prediction NO x After reducing the amount to at least the threshold, the control system is configured to increase the reducing agent metering rate to NO. x The reduction metering rate was maintained for a period of time, then the reducing agent metering rate was reduced to the regeneration test metering rate, and the actual NO achieved at the determined regeneration test metering rate was again measured. x Reduction and prediction of NO for reduced regeneration test metering rate x The reduction comparison is performed, and the control system is configured to periodically cycle through this procedure until the actual NO at the determined regeneration test metering rate is reached. x Restoration is not as good as prediction. x The maximum amount of data restored is at least the threshold, and the regeneration mode is terminated.

16. The exhaust gas aftertreatment system according to any one of claims 11 to 15, wherein, The control system is configured to apply a time delay after setting the reducing agent metering rate to the regeneration test metering rate, and then determine the actual NO for the regeneration test metering rate. x reduction.

17. The exhaust gas aftertreatment system according to any one of claims 11 to 16, wherein, The determined actual NO x Reduction and prediction of NO for reduced regeneration test metering rate x The steps of the reduction comparison include determining the actual NO x Restore the predicted NO in a lookup table or graph accessible to one or more controllers. x The restored value or the predicted NO calculated by one or more controllers based on a predetermined program x The restored values ​​are compared.

18. The exhaust gas aftertreatment system according to any one of claims 11 to 17, wherein, The control system is configured to determine when the regeneration process for removing reducing agent deposits is fully completed and terminate the regeneration process only after the exhaust gas aftertreatment system has been operating in regeneration mode for a predetermined period of time.

19. The exhaust gas aftertreatment system according to any one of claims 11 to 18, wherein, The reducing agent is a diesel exhaust fluid, which can be ammonia or urea, or an aqueous solution of urea.

20. The exhaust gas aftertreatment system according to any one of claims 11 to 19, wherein, Regeneration test metering rate ratio NO x The reduction metering rate is at least 20%, or at least 30%, or at least 40%, or at least 50%, or at least 60%, or at least 70%, or at least 80%, or at least 90%, or the regeneration test metering rate is zero.

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