EXHAUST ENGINE TREATMENT SYSTEM FOR USE WITH AN INTERNAL COMBUSTION ENGINE

Abstract

An exhaust aftertreatment system comprises a selective catalytic reduction (SCR) device that stores a reducing agent which reacts with the NOx emissions, and a reducing agent supply system that injects the reducing agent according to a reducing agent loading model. At least one temperature sensor or model generates a temperature signal indicating the SCR device temperature. The exhaust aftertreatment system also includes a control module in electrical communication with the reducing agent supply system. The control module is configured to determine the amount of reducing agent exiting the SCR device based on the at least one temperature signal and the rate of change of the SCR temperature. The control module further determines a correction factor based on the amount of reducing agent exited to modify the reducing agent loading model.

Description

[0001] The present invention relates to exhaust gas treatment systems and in particular to an exhaust gas treatment system comprising a system for selective catalytic reduction and ammonia injection.

[0002] The exhaust gas emitted by an internal combustion engine (IC engine) is a heterogeneous mixture that can contain gaseous emissions such as carbon monoxide (CO), unburned hydrocarbons (HCs), and nitrogen oxides (NOx), as well as materials in the condensed phase (liquids and solids) that form particulate matter. An engine exhaust system typically incorporates catalyst compositions arranged on catalyst carriers or substrates to convert some or all of these exhaust gas components into unregulated exhaust gases.

[0003] Exhaust aftertreatment systems typically incorporate selective catalytic reduction (SCR) devices to reduce the amount of NOx in the exhaust gas. A typical exhaust aftertreatment system also includes a reducing agent injection system that injects a reducing agent, such as ammonia (NH3). The SCR devices utilize NH3 to reduce the NOx. For example, if the correct amount of NH3 is supplied to the SCR device under the correct conditions, the NH3 reacts with the NOx in the presence of the SCR device to reduce NOx emissions. However, if the reduction reaction rate is too slow, or if there is excess NH3 in the exhaust gas, NH3 can escape from the SCR device and be released into the environment.

[0004] DE 102 28 660 A1 discloses a method for reducing the nitrogen oxide content in the exhaust gas of an internal combustion engine, which has an exhaust gas purification system with an exhaust gas line in which a nitrogen oxide reduction catalyst with reducing agent storage capability is arranged, by adding a reducing agent upstream of the nitrogen oxide reduction catalyst. A target value for the reducing agent loading of the nitrogen oxide storage catalyst is specified, wherein the target value is determined from a reducing agent loading capacity of the nitrogen oxide reduction catalyst that is given as a function of at least one temperature of the exhaust gas and / or the nitrogen oxide reduction catalyst and the exhaust gas mass flow rate. Subsequently, the current reducing agent loading of the nitrogen oxide reduction catalyst is determined, and the reducing agent is added depending on the target value for the reducing agent loading and the current reducing agent loading of the nitrogen oxide reduction catalyst.The target value for the reducing agent loading of the nitrogen oxide reduction catalyst is corrected depending on the rate of change of the exhaust gas temperature, the nitrogen oxide reduction catalyst temperature, and / or the rate of change of the exhaust gas mass flow. Internal combustion engine operation is controlled based on this correction of the target value for the reducing agent loading of the nitrogen oxide reduction catalyst.

[0005] Further state of the art is described in DE 43 15 278 A1.

[0006] The object of the invention is to create an exhaust gas treatment system for use with an internal combustion engine that enables a precise determination of the loading of an SCR device with reducing agent, adapted to the operating conditions of the internal combustion engine.

[0007] The problem is solved by the subject matter of claim 1. An advantageous embodiment of the invention is described in the dependent claim.

[0008] Other features and details are only made clear by way of example in the following detailed description of embodiments, the detailed description referring to the drawings in which: Fig. 1 a schematic diagram of an exhaust gas treatment system with a reducing agent supply system according to exemplary embodiments; Fig. 2 is a block diagram showing a control module that generates a correction factor of a reducing agent loading model of a reducing agent supply system according to an exemplary embodiment; and Fig. 3 is a flowchart showing a method for generating a correction factor of a reducing agent loading model according to exemplary embodiments.

[0009] With reference to Fig. Figure 1 is an exemplary embodiment of an exhaust gas treatment system 10 for reducing regulated exhaust gas components of an internal combustion engine (IC engine, short for "internal combustion engine") 12. The exhaust gas treatment system 10 described here can be implemented in various engine systems. Such engine systems can include, for example, but are not limited to, diesel engine systems, gasoline engine systems with direct injection, and engine systems with homogeneous compression ignition.

[0010] The exhaust gas treatment system 10 generally comprises one or more exhaust pipes 14 and one or more exhaust gas treatment devices. The exhaust gas treatment devices include, but are not limited to, an oxidation catalyst (OC) device 18 and a two-way selective catalytic reduction (SCR) and particulate filter (PF) device 20 (i.e., SCR device 20). As noted, the exhaust gas treatment system 10 of the present disclosure may include various combinations of one or more of the devices described therein. Fig. The exhaust gas treatment devices shown in 1 and / or other exhaust gas treatment devices (not shown) are included and is not limited to the present example.

[0011] In Fig. 1. The exhaust pipe 14, which may comprise several segments, transports exhaust gas 15 from the engine 12 to the various exhaust treatment devices of the exhaust treatment system 10. As noted, the OC 18 can consist of various flow-through devices with an oxidation catalyst known in the art. In various embodiments, the OC 18 can have a flow-through substrate made of a metal or ceramic monolith, which is wrapped in an intumescent mat or other suitable support that expands upon heating, thereby securing and insulating the substrate. The substrate can be packed in a stainless steel tray or canister with an inlet and an outlet in fluid communication with the exhaust pipe 14. The substrate can have an oxidation catalyst compound arranged thereon.The oxidation catalyst compound can be applied as a washcoat and may contain platinum group metals such as platinum (Pt), palladium (Pd), rhodium (Rh), or other suitable oxidizing catalysts or combinations thereof. OC 18 is suitable for the treatment of unburned gaseous and non-volatile hydrocarbons and CO, which are oxidized to form carbon dioxide and water.

[0012] The SCR device 20 can be arranged downstream of the OC 18 and is configured to filter the exhaust gas 15 of carbon and other particles, as well as to reduce the NOx components in the exhaust gas. As noted, the SCR device 20 can be made of various materials known in the art. In various embodiments, the SCR device 20 can, for example, be constructed using a wall-flow monolithic filter or other devices, such as wound or packed fiber filters, open-cell foams, sintered metal fibers, etc. In various embodiments, the SCR device 20 has a catalyst composition applied to the filter. The SCR device 20 can use a reducing agent, such as ammonia (NH3), to reduce the NOx.More specifically, the catalyst composition of the SCR device can contain a zeolite as well as one or more base metal components, such as iron (Fe), cobalt (Co), copper (Cu), or vanadium (V), which can efficiently convert NOx components in the exhaust gas 15 in the presence of NH3. The reducing agent used by the SCR device 20 can be in the form of a gas, a liquid, or an aqueous urea solution and can be mixed with air to aid the dispersion of the injected spray.

[0013] In at least one exemplary embodiment, which is described in Fig. As shown in Figure 1, an NH3 reducing agent can be supplied by a reducing agent supply system 22. The reducing agent supply system 22 comprises a reducing agent supply source 24, an injection device 26, and a control module 28. The reducing agent supply source 24 stores a reducing agent 25 and is in fluid communication with the injection device 26. The reducing agent 25 can, but is not limited to, NH3 and urea. Accordingly, the injection device 26 can inject a selectable amount of reducing agent 25 into the exhaust gas line 14, so that the reducing agent 25 is introduced into the exhaust gas 15 at a point upstream of the SCR device 20.

[0014] The control module 28 can control the engine 12 and the reducing agent supply system 22 based on acquired and / or modeled data. In various embodiments, the control module 28 further diagnoses one or more subsystems and / or devices of the exhaust aftertreatment system 10 based on one or more acquired and / or modeled inputs based on the diagnostic methods and systems of this disclosure. In one example, the control module 28 is in electrical communication with a first temperature sensor 30, which is arranged at the outlet of the OC 18, a second temperature sensor 32, which is arranged upstream of the SCR device 20, and a third temperature sensor 34, which is arranged downstream of the SCR device 20. The first temperature sensor 30 acquires a temperature of exhaust gas 15 at the outlet of the OC 18 and generates a first temperature signal based on this.The second temperature sensor 32 detects the temperature of exhaust gas 15 at the inlet of the SCR device 20 and generates a second temperature signal based on this. A third temperature sensor 34 detects the temperature of exhaust gas 15 at the outlet of the SCR device 20 and generates a third temperature signal based on this. Although the exemplary embodiment shown in . Fig. Figure 1, which shows three sensors, should be noted that fewer or more sensors may be included. Furthermore, the invention is not limited to the arrangement of the sensors described above.

[0015] The control module 28 determines the absolute temperature of the SCR device 20 (i.e., the SCR absolute temperature) and the temperature gradient of the SCR device 20 (i.e., the SCR temperature gradient). The SCR temperature can be determined according to various measurements, algorithms, and / or models known to those skilled in the art. The temperature gradient is the rate of change of the SCR temperature. This means the SCR temperature gradient is the change in the SCR temperature over time. The SCR temperature can be measured in units of Kelvin (K) per second (s) (i.e., K / s).

[0016] In general, the control module 28 receives one or more temperature signals from one or more temperature modules and controls the operation of the injection device 26 according to a reductant storage model. The temperature modules can include temperature sensors 30, 32, 34, as shown in Fig. Figure 1 shows the following features. In another exemplary embodiment, the temperature module can include control modules that store one or more temperature models. The temperature sensors 30, 32, 34 and / or the temperature models can provide a specific temperature for a particular component and / or thermal range. For example, the temperature sensors 30, 32, 34 and / or a temperature model can determine a temperature that indicates an SCR temperature of the SCR device 20. Additionally, the control module 28 can determine a correction coefficient corresponding to the reducing agent storage model based on the temperature gradient of the SCR device 20 and can more accurately control the amount of injected reducing agent 25 supplied by the injection device 26, as described in more detail below. Accordingly, the supply of reducing agent 25 can be used more efficiently.

[0017] Now, referring to Fig. Figure 2 shows a block diagram of a control module 28 that determines a correction coefficient corresponding to a reducing agent storage model in order to more accurately control the amount of injected reducing agent 25 supplied by the reducing agent supply system 22. Various embodiments of the exhaust gas treatment system 10 of Fig. 1 according to the present disclosure can have any number of submodules embedded in the control module 28. As noted, the in Fig. The two submodules shown can be combined in the same way or further partitioned.

[0018] As in Fig. As shown in Figure 2, the control module 28, according to at least one embodiment, comprises a memory 102, a reducing agent module 104, an inlet condition module 106, and a module 108 for correcting reducing agent leakage. Each of the modules 104 to 108 is coupled to the memory 102 via an interface and communicates electrically with it to retrieve and update stored values ​​as needed.

[0019] In one embodiment, the memory 102 stores one or more threshold values, time periods over which temperatures were measured, a number of configurable limits, characteristic maps, data values, variables, and system models used to control the reducing agent supply system 22. In at least one exemplary embodiment, the memory 102 stores a reducing agent loading model that determines the amount of reducing agent contained in the SCR device 20. The reducing agent loading model uses various operating parameters provided by at least one model and / or vehicle sensors to determine the stored reducing agent, including, but not limited to, exhaust gas flow and reducing agent injection rate.

[0020] Memory 102 can also store one or more temperature thresholds and / or temperature threshold ranges corresponding to a respective soot combustion temperature. Additionally, memory 102 stores one or more temperature SCR device models. The at least one temperature SCR device model comprises an absolute temperature model and a temperature gradient model. The absolute temperature model uses the temperature signal generated by the first temperature sensor 30, located at the outlet of the OC 18, the distance between the OC 18 and the SCR device 20, and the ambient temperature of the SCR device 20 to determine the absolute temperature, as discussed above. The temperature gradient model determines a temperature change of the SCR device 20 based on the change in temperature at the outlet of the SCR device 20 over a selected time period.

[0021] The reducing agent module 104 can process a reducing agent storage model signal 114, which specifies a reducing agent storage model stored in the memory 102 to control the operation of the reducing agent supply system 22. According to the invention, the reducing agent storage model specifies the amount of reducing agent that should be stored (i.e., contained) in the SCR device 20 during various driving conditions 110. By detecting the driving conditions 110 using sensors for temperature, pressure, and NOx content, the reducing agent module 104 determines an amount of reducing agent 25 for injection and generates an injection device control signal 115 to control the injection device 26 accordingly.

[0022] In at least one embodiment, the reducing agent module 104 can control the injection device 26 to inject the reducing agent 25 in response to the receipt of one or more inlet conditions 112 provided by the inlet condition module 106. The inlet conditions 112 may, for example, include an excessive increase in exhaust gas temperature, which causes an excessive temperature change in the SCR device 20. The excessive increase in exhaust gas temperature can be detected by comparing a change in exhaust gas temperature with a predetermined threshold. If the change in exhaust gas temperature exceeds the temperature threshold, the inlet condition 112 (i.e., the excessive temperature change) can be determined. However, if the SCR device 20 is subjected to excessive temperature changes, reducing agent may escape from the SCR device 20.Consequently, the amount of reducing agent stored at the SCR device 20 is reduced.

[0023] The reducing agent leakage correction module 108 can determine the amount of reducing agent leaking from the SCR device 20 and can generate a correction signal 116 that specifies a correction factor to compensate for the leaked reducing agent. The amount of reducing agent leakage can be determined when one or more inlet conditions 112, provided by the inlet condition module 106, occur, such as an excessive temperature change. The memory 102 can store a reducing agent leakage model that determines the amount of reducing agent that has leaked from the SCR device 20 based on the SCR absolute temperature, the SCR temperature gradient, and an actual stored amount (i.e., the amount of reducing agent currently stored) at the SCR device 20. In at least one embodiment, which is described in Fig. As shown in Figure 2, the reducing agent leakage correction module 108 can determine the SCR absolute temperature and the SCR temperature gradient based on a first, second, and third temperature signal 118, 120, 122, respectively, provided by the first, second, and third temperature sensors 30, 32, 34. In another exemplary embodiment, the reducing agent leakage correction module 108 can determine the SCR absolute temperature and the SCR temperature gradient based on a heat loss model signal, which specifies a heat loss model stored in memory 102, and the first temperature signal 118 provided by the first temperature sensor, which measures the inlet and / or outlet temperature of the OC 18.

[0024] The amount of reducing agent stored in the SCR device 20 can be determined according to signal 126 of the reducing agent loading model, which specifies the reducing agent loading model stored in the memory 102, as discussed above. According to the invention, the age of the SCR device 20 is used to determine the amount of reducing agent stored in the SCR device 20. For example, as the age (e.g., the amount of use over time) of the SCR device 20 increases, its ability to retain the reduced agent decreases. According to the invention, an aging factor corresponding to a new SCR device 20 is initially stored in the memory 102. Over time, the reducing agent module 104 updates the aging factor based on a temperature provided by the SCR device 20 over a period of time.The aging factor is supplied to the module 108 for the correction of reducing agent leakage via an aging factor signal 128 and applied to the predetermined amount of reducing agent specified by the reducing agent loading model in order to determine more accurately the amount of reducing agent stored at the SCR device 20.

[0025] Module 108 for reducing agent leakage correction can generate a correction value based on the difference between the amount of reducing agent contained in SCR device 20 and the amount of reducing agent that has leaked from SCR device 20. For example, if the amount of reducing agent contained in SCR device 20 is determined to be 2.0 grams (g) and the amount of reducing agent that has leaked from SCR device 20 is 0.2 g, then Module 108 for reducing agent leakage correction determines a correction value of 0.2 g, meaning that an additional 0.2 g of reducing agent 25 is required. Based on the correction value, an additional amount of reducing agent 25 (e.g., 0.2 g of additional reducing agent 25) should be injected to compensate for the reducing agent that leaked from SCR device 20.

[0026] According to the invention, the reducing agent correction module 108 determines a corrected amount of injected reducing agent 25 to achieve a desired load of the SCR device 20 under certain driving conditions. For example, the reducing agent module 104 can determine a desired reducing agent load of the SCR device 20, for example 3.0 g of reducing agent, based on one or more driving conditions of the vehicle. The reducing agent model can then determine the amount of reducing agent currently stored at the SCR device 20, taking into account any reducing agent that has leaked from the SCR device 20, as discussed above.For example, if the amount of reducing agent stored in the SCR device 20 is determined to be 2.0 g and the amount of reducing agent that has leaked from the SCR device 20 is 0.2 g, then the reducing agent leakage correction module 108 determines that the SCR device 20 currently contains 1.8 g. Therefore, the reducing agent leakage correction module 108 determines that a total of 1.2 g of reducing agent must be injected to achieve the desired reducing agent loading of 3.0 g.

[0027] Now, referring to Fig.Figure 3 shows a flowchart illustrating a procedure for determining a correction factor based on a reducing agent loading model according to an exemplary embodiment. The procedure begins at operating step 300 and proceeds to operating step 302 to determine the quantity of reducing agent stored in the SCR device (i.e., the reducing agent loading of the SCR device). The quantity of stored reducing agent can be based, for example, on a reducing agent loading model stored in a storage unit and the age of the SCR device. At operating step 304, the absolute temperature of an SCR device included in an exhaust gas treatment system is determined. The absolute temperature of the SCR device is determined based on temperature measurements provided by one or more temperature sensors and models. At operating step 306, the temperature gradient of the SCR device is determined.The temperature gradient can be determined, for example, based on a change in the temperature of the SCR device over a selected time period. In operating step 308, the amount of reducing agent that has leaked from the SCR device is determined based on the absolute temperature and the temperature gradient. A correction factor is generated in operating step 310 based on the amount of reducing agent leaked, and the procedure ends in operating step 312. The correction factor can be used to determine the amount of additional reducing agent that should be injected to compensate for the reducing agent that has leaked from the SCR device. Accordingly, a more accurate reducing agent loading model can be generated, which increases the overall efficiency of a reducing agent supply system.

Claims

[1] An exhaust gas treatment system (10) for use with an internal combustion engine (12) to treat exhaust gas (15) containing NOx emissions, the exhaust gas treatment system (10) comprising: an oxidation catalyst device (18); a selective catalytic reduction (SCR) device (20) arranged downstream of the oxidation catalyst device (18) and storing a reducing agent (25) that reacts with the NOx emissions; a reductant supply system (22) configured to inject the reductant (25) according to a reductant loading model; at least one temperature module configured to generate at least one temperature signal indicative of an SCR temperature of the SCR device (20), wherein the at least one temperature module comprises a temperature sensor (34) that measures the SCR temperature and a temperature model that estimates the SCR temperature; and a control module (28) in electrical communication with the reductant delivery system (22) and the at least one temperature module, wherein the control module (28) is configured to determine an amount of reductant (25) exiting the SCR device (20) based on an absolute temperature of the SCR device (20) indicative of the SCR temperature and a temperature gradient of the SCR device (20) indicative of the rate of change of the SCR temperature, and to determine a correction factor based on the amount of exited reductant (25) to modify the reductant loading model; wherein the control module (28) adjusts the amount of reductant (25) injected in response to modifying the reductant loading model with the correction factor; wherein the correction factor is based on an amount of leaked reductant (25) and an actual amount of reductant (25) stored at the SCR device (20), wherein the actual amount of reductant (25) stored at the SCR device (20) is based on the reductant loading model stored in a storage unit and an age of the SCR device (20), wherein the reductant loading model indicates an amount of reductant (25) to be injected in response to one or more driving conditions (110), wherein the driving conditions (110) are detected by sensors for temperature, pressure and NOx; wherein the absolute temperature is determined based on a temperature signal generated by a temperature sensor (30) at the outlet of the oxidation catalyst device (18), a distance between the oxidation catalyst device (18) and the SCR device (20), and an ambient temperature of the SCR device (20). [2] The exhaust treatment system (10) of claim 1, wherein the control module (28) determines the correction factor in response to a temperature change of the SCR device (20) exceeding a threshold.

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