Exhaust gas treatment system for controlling hydrocarbon adsorption / desorption in a hydrocarbon trap

Abstract

Exhaust gas treatment system (200) comprising: an internal combustion engine (201) comprising an exhaust outlet (203); a first three-way catalyst (205) downstream of the exhaust outlet (203), the first three-way catalyst (205) receiving an exhaust gas discharged from the exhaust outlet (203); a hydrocarbon trap (209) downstream of the first three-way catalyst (205), the hydrocarbon trap (209) receiving an exhaust gas output from the first three-way catalyst (205); an exhaust gas heating unit (213) downstream of the hydrocarbon trap (209), the exhaust gas heating unit (213) receiving an exhaust gas discharged from the hydrocarbon trap (209); and a second three-way catalyst (215) downstream of the exhaust gas heating unit (213), the second three-way catalyst (215) receiving an exhaust gas output from the heating unit (213), wherein an air injection opening (211) is configured to selectively supply an air flow upstream of the hydrocarbon trap (209) and downstream of the first three-way catalyst (205), and wherein the exhaust gas treatment system (200) further comprises a control unit (217) configured to supply the air stream upstream of the hydrocarbon trap (209) after the hydrocarbon trap (209) has stopped absorbing hydrocarbons and before the hydrocarbon trap (209) begins to desorb the hydrocarbons.

Description

INTRODUCTION

[0001] The present disclosure relates to exhaust emission control systems for internal combustion engines and, more particularly, to minimizing hydrocarbon emissions during cold starting of engines.

[0002] Exhaust gas emitted by an internal combustion engine is a heterogeneous mixture containing gaseous emissions such as carbon monoxide (“CO”), unburned hydrocarbons (“HC”) and nitrogen oxides (“NO x Many of these emission components are highly regulated. In engine exhaust systems, catalyst components, typically disposed on catalyst supports or substrates, are provided as part of an aftertreatment system to convert some or all of these exhaust components into unregulated compounds.

[0003] An exhaust treatment system typically includes one or more catalyst-based treatment devices, such as a three-way catalyst (TWC). The function of a TWC is to convert primary emissions from the engine into carbon dioxide, water, and nitrogen. For the TWC to function as an effective catalyst for hydrocarbon oxidation, it is necessary to achieve a high operating temperature, which can be difficult during cold-start operations. Thus, hydrocarbon traps (HCTs) are commonly used to store hydrocarbons during cold start and release the hydrocarbons when the TWC has reached a sufficient temperature.However, the HCT may reach a temperature at which it releases hydrocarbons before the TWC has reached a sufficient temperature for catalytic oxidation of the hydrocarbon species, resulting in inefficient and / or insufficient hydrocarbon oxidation.

[0004] Accordingly, it is desirable to ensure sufficient time for the TWC to reach operating temperature before the majority of hydrocarbon contaminants enter the catalyst system.

[0005] JP 2021-183829 A describes an exhaust gas treatment system for an internal combustion engine having an exhaust outlet connected to a first three-way catalyst, a hydrocarbon trap, an exhaust gas heating unit, and a second three-way catalyst. The exhaust gas treatment system further includes an air injection opening between the first three-way catalyst and the hydrocarbon trap.

[0006] A similar exhaust gas treatment system with two unspecified catalysts is described in US 6 029 441 A.

[0007] KR 10 2 383 213 B1 also describes a similar exhaust gas treatment system, but in which a warm-up catalyst is provided instead of the first three-way catalyst.

[0008] US 9 931 596 B2 also describes a similar exhaust gas treatment system, but in which no exhaust gas heating unit is provided in front of a second catalyst.

[0009] US 6 112 520 A also describes a similar exhaust gas treatment system, but in which no air injection opening is provided above a hydrocarbon trap.

[0010] US 10 753 291 B1 also describes a similar exhaust gas treatment system without an air injection opening above a hydrocarbon trap. SUMMARY

[0011] One aspect provides an exhaust treatment system. The exhaust treatment system includes an internal combustion engine having an exhaust outlet. A first three-way catalyst is downstream of the exhaust outlet, the first three-way catalyst receiving exhaust gas discharged from the exhaust outlet. A hydrocarbon trap is downstream of the first three-way catalyst, the hydrocarbon trap receiving exhaust gas discharged from the first three-way catalyst. An exhaust heating unit is downstream of the hydrocarbon trap, the exhaust heating unit receiving exhaust gas discharged from the hydrocarbon trap. A second three-way catalyst is downstream of the exhaust heating unit, the second three-way catalyst receiving exhaust gas discharged from the heating unit, wherein an air injection port is configured to selectively supply an airflow upstream of the hydrocarbon trap and downstream of the first three-way catalyst.

[0012] According to one embodiment, the air flow is combined with the exhaust gas emitted by the first three-way catalyst.

[0013] According to another embodiment, the air stream is added to the hydrocarbon trap.

[0014] According to the invention, the exhaust gas treatment system further includes a control unit configured to supply the air flow upstream of the hydrocarbon trap after the hydrocarbon trap has stopped absorbing hydrocarbons and before the hydrocarbon trap begins to desorb the hydrocarbons.

[0015] According to another embodiment, the control unit is further configured to supply the air stream upstream of the hydrocarbon trap while the hydrocarbon trap desorbs the hydrocarbons.

[0016] According to another embodiment, the control unit is further configured to stop supplying the air flow upstream of the hydrocarbon trap after the hydrocarbon trap has stopped desorbing the hydrocarbons.

[0017] According to another embodiment, the exhaust treatment system further includes a second sensor disposed downstream of the hydrocarbon trap and upstream of the exhaust heating unit, wherein a storage state of the hydrocarbon trap is determined using measurements from the second sensor.

[0018] According to another embodiment, the air flow is supplied at an air mass flow of 1 to 30 liters per second.

[0019] Another aspect provides a method for treating an exhaust gas using the exhaust treatment system, the method including operating the internal combustion engine to provide an exhaust fluid at the exhaust outlet. The exhaust fluid is passed through the exhaust treatment system. The air stream is selectively supplied upstream of the hydrocarbon trap and downstream of the first three-way catalyst.

[0020] According to one embodiment of the method, the air flow is combined with the exhaust gas emitted by the three-way catalyst.

[0021] According to another embodiment of the method, the air stream is added to the hydrocarbon trap.

[0022] According to the invention, the method further includes supplying the air stream after the hydrocarbon trap has stopped absorbing hydrocarbons and before the hydrocarbon trap begins to desorb the hydrocarbons.

[0023] According to another embodiment, the method further includes supplying the air stream after the hydrocarbon trap has stopped absorbing hydrocarbons and while the hydrocarbon trap is desorbing the hydrocarbons.

[0024] According to another embodiment, the method further includes stopping the supply of the air flow after the hydrocarbon trap stops desorbing the hydrocarbons.

[0025] According to another embodiment, the method further includes measuring a temperature, a gas concentration, a pressure, or a combination thereof using a first sensor located upstream of the hydrocarbon trap and downstream of the first three-way catalyst. The air flow is selectively supplied based on the measurement of the first sensor, wherein the air flow is supplied after the hydrocarbon trap has stopped absorbing hydrocarbons and before the hydrocarbon trap begins to desorb the hydrocarbons.

[0026] According to another embodiment, the method further includes selectively supplying the airflow based on the timing of an engine event, wherein the airflow is supplied after the hydrocarbon trap stops absorbing hydrocarbons and before the hydrocarbon trap begins to desorb the hydrocarbons.

[0027] According to another embodiment, the method further includes supplying the air stream while the hydrocarbon trap desorbs the hydrocarbons.

[0028] According to another embodiment, the method further includes measuring a temperature, a gas concentration, a pressure, or a combination thereof using a second sensor located downstream of the hydrocarbon trap and upstream of the exhaust gas heating unit. The air flow is selectively supplied based on the measurement of the second sensor, wherein the air flow is supplied after the hydrocarbon trap has stopped absorbing hydrocarbons and before the hydrocarbon trap begins to desorb the hydrocarbons.

[0029] According to another embodiment, the method further includes supplying the air stream while the hydrocarbon trap desorbs the hydrocarbons.

[0030] The above features and advantages and other features and advantages of the disclosure will be readily apparent from the following detailed description when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Further features, advantages and details appear only as examples in the following detailed description, which refers to the drawings; they show: Fig. 1 a motor vehicle including an internal combustion engine and an emissions control system according to one or more embodiments; Fig. 2 is a schematic plan view of an exhaust gas treatment system according to one or more embodiments; Fig. 3 is a flowchart of an illustrative method according to one or more embodiments; and Fig. 4 is a graph of hydrocarbon (HC) concentration (parts per million, ppm) versus time (seconds, s) as measured at the inlet of a hydrocarbon trap and at the outlet of a hydrocarbon trap according to one or more embodiments. DETAILED DESCRIPTION

[0032] The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application, or uses.

[0033] For cold-start hydrocarbon control (CTC), hydrocarbon traps (HCTs), such as those using zeolites as hydrocarbon capture components, are being investigated. In these systems, the molecular sieve zeolite component adsorbs and stores hydrocarbons during the cold-start period and rapidly releases the stored hydrocarbons when the exhaust temperature is high enough to desorb hydrocarbons. The desorbed hydrocarbons are subsequently converted by a three-way catalyst (TWC) component downstream of the HCT. However, during a cold start, HCTs may reach the hydrocarbon desorption temperature (HCT) before the TWC has reached a suitable temperature for HC oxidation, even when an exhaust heater (EH) is used to heat the TWC.As disclosed herein, injecting air downstream of a first three-way catalyst and upstream of a hydrocarbon trap according to a specific schedule creates a cooling effect at the HCT to delay the release of hydrocarbons from the HCT, allowing additional time for the EH to heat the TWC to a suitable operating temperature for hydrocarbon oxidation. Furthermore, the cooling effect of injecting air upstream of the HCT can serve to maximize a temperature differential between the HCT and the TWC, thereby improving hydrocarbon oxidation efficiency.

[0034] The internal combustion engine generally represents any device capable of producing an exhaust stream containing gaseous (e.g. NO x , CO x, O2) species and / or particulate species, and the present disclosure should accordingly be interpreted as applicable to all such devices. As used herein, "exhaust gas" refers to any chemical species or mixture of chemical species that may require treatment, and includes gaseous, liquid, and / or solid species. For example, an exhaust gas stream may be a mixture of one or more NO x -species, one or more liquid hydrocarbon (HC) species, carbon dioxide, and / or carbon monoxide. Furthermore, it should be understood that the embodiments disclosed herein may be applicable to the treatment of exhaust streams that do not include hydrocarbon and / or particulate species. Exhaust particulates generally include carbon soot and other solid and / or liquid carbonaceous species.

[0035] According to an exemplary embodiment, an exhaust treatment system for a motor vehicle is provided. In Fig. 1, a motor vehicle 10 is shown in the form of a delivery truck with an open bed. It should be understood that the motor vehicle 10 may take various forms, including passenger cars, commercial vehicles, watercraft, or the like. The motor vehicle 10 includes a body 12 with an engine compartment 14 and optionally a passenger compartment 15 and / or a cargo bed 17. The engine compartment 14 houses an internal combustion engine 24. The internal combustion engine 24 includes an exhaust system 30 fluidly connected to an exhaust treatment system 34. The internal combustion engine 24 may also be connected to other engine components 26. The exhaust gas produced by the internal combustion engine 24 passes through the exhaust treatment system 34 to reduce and / or convert emissions that may exit through an exhaust outlet pipe 36 into the surrounding atmosphere.

[0036] Although in Fig. 1, the internal combustion engine 24 is shown as a single primary power source of the vehicle 10, it may also represent a second primary engine source used in conjunction with another primary power source, such as an electric motor in a hybrid.

[0037] According to one aspect and as in Fig. 2, an exhaust treatment system 200 is provided that includes an internal combustion engine 201 having an exhaust outlet 203, wherein the internal combustion engine 201 supplies an exhaust gas stream via the exhaust outlet 203. The internal combustion engine 201 may include one or more exhaust outlets 203. For example, Fig. 2 a pair of exhaust outlets 203 which conduct combustion gases from the internal combustion engine 201.

[0038] A first three-way catalyst (TWC) 205 is provided downstream of the exhaust outlet 203. The first TWC 205 is in fluid communication with the exhaust outlet 203 to receive an exhaust gas output (an exhaust gas stream) from the exhaust outlet 203 of the internal combustion engine 201.

[0039] The first TWC 205 may be one of various flow-through catalyst devices capable of oxidizing CO and HCs as well as NO xto reduce. According to some embodiments, the first TWC 205 may include a flow-through metal or flow-through ceramic monolith substrate. The substrate may be packaged in a stainless steel housing or metal container having an inlet in fluid communication with the exhaust outlet 203 and an outlet in fluid communication with an exhaust conduit 207. The substrate may include a catalyst compound disposed thereon. The catalyst compound may be applied as a washcoat and may include platinum group metals such as platinum (Pt), palladium (Pd), rhodium (Rh), or other suitable oxidizing catalysts, or a combination thereof. A washcoat layer includes a differently composed layer of material disposed on the surface of the monolithic substrate or on an underlying washcoat layer.A catalyst may contain one or more washcoat layers, and each washcoat layer may have unique chemical catalytic functions. In the first TWC 205, the catalyst compositions for the oxidation and reduction functions may be located in discrete washcoat layers on the substrate, or alternatively, the compositions for the oxidation and reduction functions may be located in discrete longitudinal zones on the substrate.

[0040] The exhaust treatment system 200 includes a hydrocarbon trap (HCT) 209 located downstream of the first TWC 205. The HCT 209 is in fluid communication with the first TWC 205 and receives an exhaust output therefrom.

[0041] As mentioned above, the first TWC 205 may be in fluid communication with the HCT 209, for example, via a portion of the exhaust conduit 207.

[0042] Suitable HCT storage materials for hydrocarbons contain microporous solids, so-called molecular sieves, with zeolite material representing a suitable microporous solid for HC capture. Storage materials such as zeolite materials (or zeotype materials) have a suitable porosity for storing or capturing hydrocarbons, at least until a desired desorption temperature is reached. This means that the hydrocarbons are adsorbed while the exhaust gas is cold (e.g., during a cold start) and desorbed when a higher exhaust gas temperature is reached. Zeolites are microporous crystalline aluminosilicate materials characterized by well-ordered 3D structures with uniform pore / channel / cage structures, e.g.,from 3 to 12 Å or 3 to 10 Å (depending on the framework type), and are characterized by the ability to undergo ion exchange to allow the incorporation of catalytically active cations throughout the structure. Zeotypes are structural isotypes / isomorphs of zeolites, whereby, instead of a framework structure derived from coupled silica and alumina tetrahedra, zeotypes are based, for example, on alumina phosphate (ALPO), silica-alumina-phosphate (SAPO), metal-alumina-phosphate (M-ALPO), or metal-silica-alumina-phosphate (M-APSO). Exemplary zeolite materials include, for example, mordenite (MOR), Y-zeolites (FAU), ZSM-5 (MFI), β-zeolites (BEA), or combinations thereof. These are preferably used in H form or in NH4 form exchanged with transition metals.

[0043] The exhaust treatment system 200 includes an exhaust heating unit 213 located downstream of the HCT 209. The exhaust heating unit 213 is in fluid communication with the HCT 209 and receives exhaust gas output therefrom. As noted above, the exhaust heating unit 213 may be in fluid communication with the HCT 209, for example, via a portion of the exhaust conduit 207. Any suitable exhaust heating unit 213 may be used. The exhaust heating unit 213 may be, for example, an electric heater. If the vehicle is a conventional vehicle powered only by the internal combustion engine 201, the exhaust heating unit 213 is powered by the engine 201 after cranking (i.e., post-crank heating after the engine 201 has been started).If the engine is a hybrid vehicle powered by either the internal combustion engine 201 and / or a separate ICE / electric motor combination (not shown), the exhaust heating unit 213 may be powered by either the engine 201 or the ICE / electric motor combination.

[0044] The exhaust treatment system 200 includes a second three-way catalyst (second TWC) 215 located downstream of the exhaust heating unit 213. The second TWC 215 is in fluid communication with the exhaust heating unit 213 and receives exhaust gas output therefrom. As noted above, the second TWC 215 may be in fluid communication with the exhaust heating unit 213, for example, via a portion of the exhaust conduit 207. The second TWC 215 may be one of various flow-through catalyst devices capable of oxidizing CO and HCs, as well as NO xto reduce, using any suitable three-way catalyst such as those described above for the first TWC 205.

[0045] The exhaust treatment system 200 includes an air inlet opening 211 configured to selectively supply an airflow upstream of the HCT 209 and downstream of the first TWC 205. The location of the air inlet opening 211 is not particularly limited. According to some embodiments, the airflow may be combined with the exhaust gas discharged from the first TWC 205 at a location proximate the outlet of the first TWC 205. According to other embodiments, the air inlet opening 211 may be located proximate the inlet of the HCT 209.

[0046] The air injection source may be provided by an auxiliary pump or may be branched off the engine compressor with a valve and / or throttle. For vehicles with a turbocharger, boost pressure and turbocharged air may be used as the source. According to other embodiments, the air source may come from the crankcase, using the energy generated therein to provide the air injection. According to some embodiments, the air source may be a turbocharger compressor or another air pumping device included with the engine.

[0047] The exhaust treatment system 200 further includes a control unit 217 configured to deliver the airflow upstream of the HCT 209 after the HCT 209 has ceased to absorb or capture hydrocarbons and before the HCT 209 begins to desorb or release the hydrocarbons. According to some embodiments, the control unit 217 may be further configured to deliver the airflow upstream of the HCT 209 while the HCT 209 is desorbing the hydrocarbons. For example, according to one or more embodiments, the control unit 217 may be configured to deliver the airflow upstream of the HCT 209 after the HCT 209 has ceased to absorb hydrocarbons and while the HCT 209 is desorbing the hydrocarbons.

[0048] According to some embodiments, the control unit 217 may be operatively connected to a number of sensors for monitoring the exhaust treatment system 200. The control unit may include a control module (not shown). As used herein, the term module refers to an application-specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory executing one or more software or firmware programs, combinational logic circuitry, and / or other suitable components that provide the described functionality. Example sensors include hydrocarbon sensors, oxygen sensors, temperature sensors, pressure sensors, or the like, or a combination thereof.The signal generated by a sensor may be sent to the control unit 217 and may be interpreted by the control unit 217 as needed for operation of the exhaust treatment system 200.

[0049] According to some embodiments, the exhaust treatment system 200 may include a first sensor 221 located upstream of the HCT 209 and downstream of the first TWC 205. The first sensor 221 may, for example, be used to measure a concentration of one or more gases (e.g., oxygen, carbon dioxide, hydrocarbons, or the like, or a combination thereof) present in the exhaust conduit 207. The first sensor 221 may, for example, be used to measure a temperature and / or pressure present in the exhaust conduit 207. For example, the first sensor 221 may be located near the inlet of the HCT 209 to determine a concentration of gases, a temperature, and / or a pressure at the inlet of the HCT 209.

[0050] According to some embodiments, the exhaust treatment system 200 may include a second sensor 223 located downstream of the HCT 209 and upstream of the exhaust heating unit 213. The second sensor 223 may, for example, be used to measure a concentration of one or more gases (e.g., oxygen, carbon dioxide, hydrocarbons, or the like, or a combination thereof) present in the exhaust conduit 207. The second sensor 223 may, for example, be used to measure a temperature and / or pressure present in the exhaust conduit 207. The second sensor 223 may, for example, be located near the outlet of the HCT 209 to determine a concentration of gases, a temperature, and / or a pressure at the outlet of the HCT 209.

[0051] The control unit 217 may be used to evaluate or determine a storage state of the HCT 209 based on the parameters being measured (e.g., the concentrations of gases, temperature, and / or pressure), where the storage state is defined as herein. For example, according to some embodiments, the storage state may be determined by comparing the concentrations of gases, temperature, and / or pressure at the inlet of the HCT 209 with the concentrations of gases, temperature, and / or pressure at the outlet of the HCT 209. According to some embodiments, the storage state of the HCT 209 may be determined based on the timing of an engine event, such as the time elapsed since a cold start of an engine, or the like.

[0052] The control unit 217 may be used to evaluate or determine a storage state of the HCT 209 based on the data measured by the first sensor 221 and / or the second sensor 223. According to some embodiments, the control unit 217 may be used to evaluate or determine the storage state of the HCT 209 based on the timing of an engine event, such as the time elapsed since a cold start of an engine or the like. As used herein, the term "storage state" refers to the state of the hydrocarbon trap and may be an active state, an inactive state, or a release state. The term "active state" indicates that hydrocarbons are stored (e.g.,adsorbed), the term "release state" indicates that hydrocarbons are released from the HCT 209, and the term "inactive state" indicates that the hydrocarbons are neither stored nor released at the HCT 209. For example, the active state may be indicated when it is determined that the concentration of hydrocarbons at the inlet of the HCT 209 is greater than a concentration of hydrocarbons at an outlet of the HCT 209, the release state may be indicated when it is determined that the concentration of hydrocarbons at the outlet of the HCT 209 is greater than the concentration of hydrocarbons at the inlet of the HCT 209, and the inactive state may be indicated when it is determined that the concentration of hydrocarbons at the inlet of the HCT 209 is substantially the same as the concentration of hydrocarbons at the outlet of the HCT 209.The storage state may be determined using any number of parameters, such as gas concentrations, time, pressure, and / or temperature. However, embodiments are not limited thereto, and the storage state of the HCT 209 may be assessed using one or more of the sensors described herein or by other methods.

[0053] Additionally, one or more sensors may also be located in the various components of the exhaust treatment system 200. According to some embodiments, the one or more sensors may include one or more temperature sensors 225, 227, 229 in contact with the components of the exhaust treatment system 200. For example, the exhaust treatment system 200 may include a first temperature sensor 225 configured to measure the temperature of the HCT 209, a second temperature sensor 227 configured to measure the temperature of the exhaust heating unit 213, and / or a third temperature sensor 229 configured to measure the temperature of the second TWC 215. According to some embodiments, a temperature signal generated by a temperature sensor may be sent to the control unit 217 and may be interpreted by the control unit 217 as needed for operation of the exhaust treatment system 200.The temperature sensors may be in fluid communication with the exhaust gas in the respective components and / or may be a measurement of component temperatures.

[0054] As noted above, the exhaust treatment system 200 may include an exhaust conduit 207, which may include multiple sections, for transporting the exhaust gas from the internal combustion engine 201 to the various exhaust treatment devices of the exhaust treatment system 200. As shown in Fig. For example, as shown in Figure 2, the exhaust treatment system 200 includes portions of an exhaust conduit 207 that fluidly connects the first TWC 205, the HCT 209, the exhaust heating unit 213, and the second TWC 215. The outlet of the second TWC 215 may include an exhaust pipe that vents the treated exhaust to the surrounding atmosphere.

[0055] Another aspect provides a method for treating an exhaust gas using the exhaust treatment system 200. The method includes operating the internal combustion engine 201 to provide an exhaust fluid (e.g., an exhaust stream) at the exhaust outlet 203. The exhaust fluid is directed or transported through the exhaust treatment system 200 and through the first TWC 205, the HCT 209, the exhaust heating unit 213, and the second TWC 215. The air stream is selectively supplied upstream of the HCT 209 and downstream of the first TWC 205.

[0056] The air flow is injected via the air injection port 211, as described herein. For example, the air flow may be combined with the exhaust gas discharged from the first TWC 205 at a location proximate the outlet of the first TWC 205. According to other embodiments, the air injection port 211 may be located proximate the inlet of the HCT 209.

[0057] The method includes supplying the air stream after the HCT 209 has stopped absorbing hydrocarbons and before the HCT 209 begins to desorb hydrocarbons. According to some embodiments, the method may include supplying the air stream after the HCT 209 has stopped absorbing hydrocarbons and while the HCT 209 is desorbing the hydrocarbons. According to some aspects, the method may further include stopping supplying the air stream after the HCT 209 has stopped desorbing the hydrocarbons.

[0058] The method may include measuring a temperature, a gas concentration, a pressure, or a combination thereof using a first sensor 221 located upstream of the HCT 209 and downstream of the first TWC 205, and selectively delivering the air flow based on the measurement of the first sensor 221, as described herein. The air flow may be selectively delivered after the HCT 209 has stopped absorbing hydrocarbons and before the HCT 209 begins to desorb the hydrocarbons. In some aspects, the air flow may further be selectively delivered while the hydrocarbons are being released from the HCT 209.

[0059] According to some embodiments, the method may further include selectively supplying the airflow based on the timing of an engine event, wherein the airflow is supplied after the hydrocarbon trap has stopped absorbing hydrocarbons and before the hydrocarbon trap begins to desorb the hydrocarbons. The engine event may be measured, for example, from the cold start of an engine.

[0060] According to some embodiments, the method may further include measuring a temperature, a gas concentration, a pressure, or a combination thereof using a second sensor 223 located downstream of the HCT 209 and upstream of the exhaust heating unit (HER) 213; and selectively supplying the air flow based on the measurement of the second sensor 223, wherein the air flow may be selectively supplied after the HCT 209 has stopped absorbing hydrocarbons and before the HCT 209 begins to desorb hydrocarbons. In some aspects, the air flow may further be selectively supplied while the hydrocarbons are being released from the HCT 209.

[0061] According to some embodiments, the air stream may be supplied at any suitable air mass flow rate. For example, the air stream may be supplied at an air mass flow rate sufficient to provide a suitable temperature differential between a hydrocarbon release temperature at the HCT 209 and a hydrocarbon oxidation temperature at the TWC 219. As used herein, the term "hydrocarbon release temperature" refers to a temperature at which hydrocarbons are released (e.g., desorbed) from the HCT 209. As used herein, the term "hydrocarbon oxidation temperature" refers to a temperature at which hydrocarbons are oxidized at the TWC 215.

[0062] According to one or more embodiments, the airflow may be supplied at an air mass flow rate of 1 to 30 liters per second (l / s). For example, the airflow may be supplied at an air mass flow rate of 2.5 to 30 l / s or 5 to 25 l / s, but embodiments are not limited thereto. According to some embodiments, the airflow is supplied at an air mass flow rate sufficient to provide a suitable temperature difference, wherein the temperature difference is a difference between a temperature of the HCT 209 and a temperature of the second TWC 215. According to some embodiments, the airflow is supplied at an air mass flow rate sufficient to provide a suitable temperature difference, wherein the temperature difference is a difference between a temperature of the HCT 209 and a temperature of the exhaust heating unit 213.According to some embodiments, a method for selecting the HCT material and selecting the TWC material to maximize the temperature difference is provided.

[0063] According to some embodiments, the air stream may be supplied at an air mass flow rate sufficient to provide a temperature difference of at least 10°C, at least 25°C, at least 50°C, at least 100°C, at least 150°C, at least 180°C, or at least 200°C, wherein the temperature difference is a difference between a temperature of the HCT 209 and a temperature of the second TWC 215. According to some embodiments, the air stream may be supplied at an air mass flow rate sufficient to provide a temperature difference of at least 10°C, at least 25°C, at least 50°C, at least 100°C, at least 150°C, at least 180°C, or at least 200°C, wherein the temperature difference is a difference between a temperature of the HCT 209 and a temperature of the exhaust heating unit 213.

[0064] Fig. 3 shows a flowchart 300 illustrating a method for treating exhaust gas from an internal combustion engine according to one or more embodiments. The flowchart begins at block 301, which leads to block 303, where the amount of hydrocarbon absorption is estimated. As shown at block 305, a determination is made as to whether hydrocarbons are being absorbed. If the hydrocarbons are being absorbed, flow proceeds to block 307, where air injection is stopped. If the hydrocarbons are not being absorbed, flow proceeds to block 309, while air injection is stopped.As described herein, the assessment of whether hydrocarbons are absorbed may be determined based on one or more parameters such as time, gas concentrations, temperature, and / or pressure as measured upstream and / or downstream of the hydrocarbon trap (or at other locations) using one or more sensors.

[0065] As shown in block 309, estimates of the hydrocarbon inventory and desorption rate are determined. In block 311, a determination is made as to whether hydrocarbon desorption has ended. If hydrocarbon absorption has ended, flow proceeds to block 313, where air sparging is stopped. If hydrocarbon desorption has not ended, flow proceeds to block 315, while air sparging is kept on. As described herein, the assessment that hydrocarbons are being desorbed may be determined based on one or more parameters such as time, gas concentrations, temperature, and / or pressure, as measured using one or more sensors upstream and / or downstream of the hydrocarbon trap (or at other locations).Similarly, the hydrocarbon inventory assessment may be determined based on one or more parameters such as time, gas concentrations, temperature, and / or pressure as measured using one or more sensors upstream and / or downstream of the hydrocarbon trap (or at other locations).

[0066] Now based on Fig. Figure 4 is a graph illustrating the hydrocarbon concentrations measured at the inlet of an HCT 401 and at the outlet of an HCT 402 based on time since engine start. During the time period from 0 seconds (s) to approximately 30 s, referred to as the "HCT storage period" (A), hydrocarbons are stored in the HCT unit while air injection would remain off. At a time of approximately 30 s, hydrocarbon storage by the HCT unit was completed, and air injection may begin upstream of the HCT unit and downstream of the first TWC, referred to as the "inactive period - no HC storage or HC release" (B). Near 70 s, the HCT unit may reach a temperature at which the hydrocarbons begin to desorb and be released from the HCT outlet, referred to as the "HCT release period" (C).Subsequently, at approximately 220 s, the hydrocarbons have been released from the HCT unit, and the air injection can be stopped. Fig. 4, the start of air injection is designated as 404 (“on”) and the cessation of air injection is designated as 406 (“off”).

[0067] The technical methods described herein enable improvements to emission control systems used in internal combustion engines, such as those used in vehicles. The technical features described herein improve the conventional emission control system by providing a control scheme based on the capture and release of hydrocarbons by the hydrocarbon trap. Advantageously, the control scheme reduces emissions during cold starts.

[0068] In terms of hardware architecture, the emissions control system may be implemented in part using a computing device that may include a processor, memory, and one or more input and / or output device (I / O) interfaces communicatively coupled via a local interface. The local interface may include, for example, but is not limited to, one or more buses and / or other wired or wireless connections. The local interface may include additional elements, omitted for simplicity, such as controllers, buffers (caches), drivers, repeaters, and receivers to enable communications. Further, the local interface may include address, control, and / or data connections to enable appropriate communications between the aforementioned components.

[0069] When the computing device is operating, the processor may be configured to execute software stored in the memory to transfer data to and from the memory and generally control operations of the computing device according to the software. Software in the memory is read in whole or in part by the processor, possibly buffered within the processor, and then executed. The processor may be a hardware device for executing software, particularly software stored in the memory. The processor may be a custom or commercially available processor, a central processing unit (CPU), an auxiliary processor among a plurality of processors associated with the computing device, a semiconductor-based microprocessor (in the form of a microchip or chipset), or generally any device for executing software.

[0070] The memory may include any one or a combination of volatile memory elements (e.g., random access memory (RAM such as DRAM, SRAM, SDRAM, VRAM, etc.)) and / or non-volatile memory elements (e.g., ROM, hard disk drive, CD-ROM, etc.). In addition, the memory may include electronic, magnetic, optical, and / or other types of storage media. It is noted that the memory may also have a distributed architecture in which various components are remote from each other but accessible by the processor.

[0071] The software in memory may contain one or more separate programs, each containing an ordered list of executable instructions for implementing logical functions. A system component embodied as software may also be embodied as a source program, an executable program (object code), a script, or any other entity comprising a set of instructions to be executed. If the program is embodied as a source program, it is compiled via a compiler, an assembler, an interpreter, or the like, which may or may not be included in memory.

[0072] It is noted that Fig.3 illustrates an architecture, functionality, and / or operating scheme that may be partially implemented using software. In this regard, one or more of the blocks may be interpreted to represent a module, segment, or section of code comprising one or more executable instructions for implementing the one or more specified logical functions. It is noted that, according to some alternative implementations, the functions mentioned in the blocks may occur out of order and / or not at all. For example, depending on the functionality involved, two consecutively shown blocks may in fact execute substantially concurrently, or the blocks may occasionally execute in the reverse order.

[0073] It is noted that any functionality described herein may be embodied in any computer-readable medium for use with or in connection with an instruction execution system, device, or apparatus, such as a computer-based system, a system including a processor, or any other system that can retrieve the instructions from the instruction execution system, device, or apparatus and execute the instructions. In the context of this document, a "computer-readable medium" contains, stores, transmits, propagates, and / or transports the program for use by or in connection with the instruction execution system, device, or apparatus. The computer-readable medium may, for example,An electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor device, or an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor apparatus. More specific examples (a non-exhaustive list) of a computer-readable medium include a portable computer diskette (magnetic), random access memory (RAM) (electronic), read-only memory (ROM) (electronic), erasable programmable read-only memory (EPROM or Flash memory) (electronic), and a portable compact disc read-only memory (CD-ROM) (optical).

[0074] The terms "a" and "an" do not imply a limitation on the quantity, but rather denote the presence of at least one of the mentioned objects. Unless the context clearly indicates otherwise, the term "or" means "and / or." Reference throughout the specification to "an aspect" means that a particular element described in connection with the aspect (e.g., feature, structure, step, or property) is included in at least one aspect described herein and may or may not be included in other aspects. It is also understood that the described elements according to the various aspects may be combined in any suitable manner.

[0075] When an element, such as a layer, film, region, or substrate, is described as being "on" another element, it may be directly on top of the other element or there may also be intervening elements. In contrast, when an element is described as being "directly on" another element, no intervening elements are present.

[0076] Unless otherwise specified herein, all examination standards are the most recent examination standards in effect as of the filing date of this application or the filing date of the earliest priority application in which the examination standard appears, if priority is claimed.

[0077] Unless otherwise defined, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0078] Although the above disclosure has been described with reference to exemplary embodiments, those skilled in the art will understand that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope thereof. Furthermore, many changes may be made to adapt a particular situation or material to the teachings of the disclosure without departing from its essential scope. Thus, the present disclosure is not intended to be limited to the particular embodiments disclosed, but is intended to include all embodiments falling within its scope.

Claims

[1] Exhaust gas treatment system (200) comprising: an internal combustion engine (201) comprising an exhaust outlet (203); a first three-way catalyst (205) downstream of the exhaust outlet (203), the first three-way catalyst (205) receiving an exhaust gas discharged from the exhaust outlet (203); a hydrocarbon trap (209) downstream of the first three-way catalyst (205), the hydrocarbon trap (209) receiving an exhaust gas output from the first three-way catalyst (205); an exhaust gas heating unit (213) downstream of the hydrocarbon trap (209), the exhaust gas heating unit (213) receiving an exhaust gas discharged from the hydrocarbon trap (209); and a second three-way catalyst (215) downstream of the exhaust gas heating unit (213), the second three-way catalyst (215) receiving an exhaust gas output from the heating unit (213), wherein an air injection opening (211) is configured to selectively supply an air flow upstream of the hydrocarbon trap (209) and downstream of the first three-way catalyst (205), and wherein the exhaust gas treatment system (200) further comprises a control unit (217) configured to supply the air stream upstream of the hydrocarbon trap (209) after the hydrocarbon trap (209) has stopped absorbing hydrocarbons and before the hydrocarbon trap (209) begins to desorb the hydrocarbons. [2] The exhaust treatment system (200) of claim 1, wherein the air stream is combined with the exhaust gas output from the first three-way catalyst (205), the air stream being added to the hydrocarbon trap (209), or a combination thereof. [3] The exhaust gas treatment system (200) of claim 1, wherein the control unit (217) is further configured to stop supplying the air flow upstream of the hydrocarbon trap (209) after the hydrocarbon trap (209) has stopped desorbing the hydrocarbons. [4] A method of treating an exhaust gas using the exhaust gas treatment system (200) of claim 1, the method comprising: Operating the internal combustion engine (201) to provide an exhaust fluid at the exhaust outlet (203); Passing the exhaust fluid through the exhaust treatment system (200); selectively supplying the air flow upstream of the hydrocarbon trap (209) and downstream of the first three-way catalyst (205) and Supplying the air stream after the hydrocarbon trap (209) has stopped absorbing hydrocarbons and before the hydrocarbon trap (209) begins to desorb the hydrocarbons. [5] The method of claim 4, wherein the air stream is combined with the exhaust gas output from the first three-way catalyst (205), the air stream being added to the hydrocarbon trap (209), or a combination thereof. [6] The method of claim 4, comprising supplying the air stream after the hydrocarbon trap (209) has stopped absorbing hydrocarbons and while the hydrocarbon trap (209) is desorbing the hydrocarbons. [7] The method of claim 4, further comprising stopping the supply of the air stream after the hydrocarbon trap (209) has stopped desorbing the hydrocarbons. [8] The method of claim 4, further comprising: Measuring a temperature, a gas concentration, a pressure, or a combination thereof using a first sensor (221) arranged upstream of the hydrocarbon trap (209) and downstream of the first three-way catalyst (205); and selectively supplying the air flow based on the measurement of the first sensor (221). [9] The method of claim 4, further comprising: selectively delivering airflow based on the timing of an engine event.

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