阅读说明：本技术 用于包括在后处理系统中的催化器的脱硫的系统和方法 (System and method for desulfurization of a catalyst included in an aftertreatment system ) 是由 迈克尔·J·坎宁安 阿力克斯·叶泽列茨 李军辉 詹姆士·A·克拉默 于 2020-03-30 设计创作，主要内容包括：用于减少具有硫含量的废气的成分的后处理系统包括氧化催化器。过滤器被设置在氧化催化器的下游。后处理系统还包括控制器,该控制器被配置成：响应于确定过滤器将被再生并且氧化催化器标准被满足,升高氧化催化器的温度,响应于确定过滤器将被再生升高到大于或等于400摄氏度且小于550摄氏度的第一再生温度。控制器使氧化催化器保持在第一再生温度持续预先确定的时间段。控制器被配置成随后使氧化催化器的温度升高到等于或大于550摄氏度的第二再生温度。(An aftertreatment system for reducing a constituent of an exhaust gas having a sulfur content includes an oxidation catalyst. The filter is disposed downstream of the oxidation catalyst. The aftertreatment system also includes a controller configured to: the temperature of the oxidation catalyst is increased in response to determining that the filter is to be regenerated and that the oxidation catalyst criteria are met, and the temperature is increased to a first regeneration temperature that is greater than or equal to 400 degrees Celsius and less than 550 degrees Celsius in response to determining that the filter is to be regenerated. The controller maintains the oxidation catalyst at a first regeneration temperature for a predetermined period of time. The controller is configured to subsequently increase the temperature of the oxidation catalyst to a second regeneration temperature equal to or greater than 550 degrees celsius.)

1. An aftertreatment system for reducing a constituent of an exhaust gas having a sulfur content, the aftertreatment system comprising:

an oxidation catalyst;

a filter disposed downstream of the oxidation catalyst; and

a controller configured to, in response to determining that the filter is to be regenerated and that an oxidation catalyst criterion is met:

increasing the temperature of the oxidation catalyst to a first regeneration temperature that is greater than or equal to 400 degrees Celsius and less than 550 degrees Celsius;

maintaining the temperature of the oxidation catalyst at the first regeneration temperature for a first period of time; and is

After the first period of time, increasing the temperature of the oxidation catalyst to a second regeneration temperature equal to or greater than 550 degrees Celsius.

2. The aftertreatment system of claim 1, wherein the oxidation catalyst criteria includes a desulfation condition of the oxidation catalyst, and wherein the oxidation catalyst criteria being met includes the desulfation condition being met.

3. The aftertreatment system of claim 2, wherein the desulfation condition includes a concentration of sulfur in a fuel combusted to produce the exhaust gas, and wherein the desulfation condition being satisfied includes the concentration of the sulfur in the fuel being equal to or greater than a predetermined sulfur concentration threshold.

4. The aftertreatment system of claim 2, wherein the controller is configured to, in response to determining that the filter is to be regenerated and the desulfation condition is not satisfied:

increasing the temperature of the oxidation catalyst to the second regeneration temperature without maintaining the oxidation catalyst at the first regeneration temperature for the first period of time; and is

Introducing hydrocarbons into the oxidation catalyst.

5. The aftertreatment system of claim 2, wherein the desulfation condition includes a measured exotherm across the oxidation catalyst, and wherein the desulfation condition is satisfied including the measured exotherm being outside a predetermined range based on a reference exotherm.

6. The aftertreatment system of claim 1, further comprising:

an oxidation catalyst heater coupled to the oxidation catalyst and configured to be controlled by the controller to increase and maintain a temperature of the oxidation catalyst.

7. An aftertreatment system for reducing a constituent of an exhaust gas having a sulfur content, comprising:

a selective catalytic reduction catalyst; and

a controller configured to:

determining NO of the selective catalytic reduction catalyst_XThe conversion efficiency;

in response to said NO_XRaising the temperature of the selective-catalytic-reduction catalyst to a first regeneration temperature that is greater than or equal to 400 degrees celsius and less than 550 degrees celsius when the conversion efficiency is less than a predetermined threshold; and is

Maintaining the temperature of the selective catalytic reduction catalyst at the first regeneration temperature for a first period of time.

8. The aftertreatment system of claim 7, wherein the controller is further configured to:

after the first period of time, increasing the temperature of the selective catalytic reduction catalyst to a second regeneration temperature that is greater than the first regeneration temperature and less than 550 degrees Celsius; and is

Maintaining the temperature of the selective catalytic reduction catalyst at the second regeneration temperature for a second period of time.

9. The aftertreatment system of claim 7, wherein the controller is further configured to:

in response to a time interval between regeneration events not satisfying a time interval threshold, increasing the temperature of the selective catalytic reduction catalyst to a third regeneration temperature in a subsequent regeneration event, the third regeneration temperature being greater than the first regeneration temperature and less than 550 degrees Celsius; and is

Maintaining the temperature of the selective catalytic reduction catalyst at the third regeneration temperature for a predetermined third period of time.

10. The aftertreatment system of claim 9, wherein the time interval threshold is in a range of 10 hours to 12 hours.

11. The aftertreatment system of claim 9, wherein the controller is further configured to:

in response to the time interval between regeneration events not satisfying a threshold time interval, increasing the temperature of the selective catalytic reduction catalyst to a fourth regeneration temperature in a subsequent regeneration event, the fourth regeneration temperature being equal to or greater than 550 degrees Celsius.

12. The aftertreatment system of claim 11, wherein the critical time interval is 1 hour.

13. The aftertreatment system of claim 11, wherein the controller is further configured to:

generating a fault code in response to the time interval between regeneration events continuing to not satisfy the critical time interval after the subsequent regeneration event.

14. The aftertreatment system of claim 7, wherein ammonia produced by a reductant introduced into the exhaust gas is associated with NO contained in the exhaust gas flowing through the aftertreatment system_XThe ratio of the amount of gas is greater than 1.0.

15. The aftertreatment system of claim 7, further comprising:

an oxidation catalyst disposed upstream of the selective catalytic reduction catalyst; and

a hydrocarbon introduction assembly configured to introduce hydrocarbons into the oxidation catalyst,

wherein the controller is configured to increase the temperature of the selective catalytic reduction catalyst by instructing the hydrocarbon introduction assembly to introduce hydrocarbons into the oxidation catalyst.

16. The aftertreatment system of claim 7, further comprising:

a selective catalytic reduction catalyst heater operatively coupled to the selective catalytic reduction catalyst,

wherein the controller is configured to instruct the selective catalytic reduction heater to increase and maintain a temperature of the selective catalytic reduction catalyst.

17. The aftertreatment system of claim 7, wherein the predetermined threshold comprises the NO_XThe conversion efficiency was 90%.

18. An aftertreatment system for reducing a constituent of an exhaust gas having a sulfur content, comprising:

a selective catalytic reduction catalyst; and

a controller configured to:

determining NO of the selective catalytic reduction catalyst_XThe conversion efficiency;

in response to said NO_XRaising the temperature of the selective-catalytic-reduction catalyst to a first regeneration temperature greater than or equal to 400 degrees celsius and less than 550 degrees celsius when the conversion efficiency is less than a first predetermined threshold;

maintaining the temperature of the selective catalytic reduction catalyst at the first regeneration temperature for a first period of time;

in response to said NO_XRaising the temperature of the selective catalytic reduction catalyst to a second regeneration temperature equal to or greater than 550 degrees celsius when the conversion efficiency is less than a second predetermined threshold lower than the first predetermined threshold or a time interval between subsequent regeneration events at the first temperature is less than a time interval threshold;

maintaining the temperature of the selective catalytic reduction catalyst at the second regeneration temperature for a second period of time; and is

In response to said NO_XThe conversion efficiency is less than a third predetermined threshold lower than the second predetermined threshold or the time interval between subsequent regeneration events at the second temperature is less than a time interval threshold, generating a fault code.

19. The aftertreatment system of claim 18, wherein the first predetermined threshold corresponds to 90% NO_XConversion efficiency, said second predetermined threshold corresponding to 80% NO_XConversion efficiency and said third predetermined threshold corresponds to 70% NO_XThe conversion efficiency.

20. The aftertreatment system of claim 18, wherein the controller is further configured to:

increasing the temperature of the selective catalytic reduction catalyst to the first regeneration temperature in response to a fuel tank associated with an engine that produces the exhaust gas being refilled or a predetermined amount of fuel having been consumed.

Technical Field

The present disclosure relates generally to aftertreatment systems for use with Internal Combustion (IC) engines.

Background

An exhaust aftertreatment system is used to receive and treat exhaust gas produced by the IC engine. Typically, exhaust aftertreatment systems include any of several different components that reduce the level of harmful exhaust emissions present in the exhaust gas. For example, certain exhaust aftertreatment systems for diesel-powered IC engines include provisions for oxygenAn oxidation catalyst (oxidation catalyst) that oxidizes carbon monoxide (CO) or unburned hydrocarbons, and may also be used to raise the temperature of the exhaust gas for regenerating a filter (regeneration) disposed downstream of the oxidation catalyst. The aftertreatment system may also include a Selective Catalytic Reduction (SCR) system for decomposing constituents of the exhaust gas, such as Nitrogen Oxides (NO) contained in the exhaust gas_X) A gas. The fuel burned by some IC engines may contain high sulfur content, which may degrade the oxidation catalyst and/or the SCR catalyst.

SUMMARY

Embodiments described herein relate generally to systems and methods for desulfation, i.e., removal of sulfur accumulated on an oxidation catalyst or SCR catalyst included in an aftertreatment system. In particular, the systems and methods described herein include heating an oxidation catalyst or an SCR catalyst to a regeneration temperature that is lower than conventional regeneration temperatures in order to desulfate the oxidation catalyst or the SCR catalyst while reducing hydrothermal aging.

In some embodiments, an aftertreatment system for reducing a constituent of an exhaust gas having a sulfur content comprises: an oxidation catalyst; a filter disposed downstream of the oxidation catalyst; and a controller configured to, in response to determining that the filter is to be regenerated and that the oxidation catalyst criteria are met: increasing the temperature of the oxidation catalyst to a first regeneration temperature that is greater than or equal to 400 degrees Celsius and less than 550 degrees Celsius; maintaining the temperature of the oxidation catalyst at a first regeneration temperature for a first period of time; after the first period of time, the temperature of the oxidation catalyst is increased to a second regeneration temperature equal to or greater than 550 degrees Celsius.

In some embodiments, the oxidation catalyst criteria includes a desulfation condition of the oxidation catalyst, and wherein the oxidation catalyst criteria being met includes the desulfation condition being met.

In some embodiments, the desulfurization conditions include a concentration of sulfur in a fuel from which the exhaust gas is produced by combustion, and wherein the desulfurization conditions are satisfied including the concentration of sulfur in the fuel being equal to or greater than a predetermined sulfur concentration threshold.

In some embodiments, in response to determining that the filter is to be regenerated and that the desulfation conditions are not met, the controller is configured to: increasing the temperature of the oxidation catalyst to a second regeneration temperature without maintaining the oxidation catalyst at the first regeneration temperature for a first period of time; and introducing hydrocarbons into the oxidation catalyst.

In some embodiments, the desulfation conditions include a measured exotherm across the oxidation catalyst, and wherein the desulfation conditions are satisfied including the measured exotherm being outside of a predetermined range based on the reference exotherm.

In some embodiments, the aftertreatment system further comprises: an oxidation catalyst heater coupled to the oxidation catalyst and configured to be controlled by the controller to raise and maintain a temperature of the oxidation catalyst.

In some embodiments, an aftertreatment system for reducing a constituent of an exhaust gas having a sulfur content comprises: an SCR catalyst; and a controller configured to: determining NO of SCR catalyst_XThe conversion efficiency; in response to NO_XThe conversion efficiency is less than a predetermined threshold value, and the temperature of the SCR catalyst is increased to a first regeneration temperature which is greater than or equal to 400 ℃ and less than 550 ℃; and maintaining the temperature of the SCR catalyst at the first regeneration temperature for a predetermined first period of time.

In some embodiments, the controller is further configured to: after the first period of time, increasing the temperature of the SCR catalyst to a second regeneration temperature that is greater than the first regeneration temperature and less than 550 degrees Celsius; and maintaining the temperature of the SCR catalyst at the second regeneration temperature for a second period of time.

In some embodiments, the controller is further configured to: in response to the time interval between regeneration events not satisfying the time interval threshold, increasing the temperature of the SCR catalyst to a third regeneration temperature in a subsequent regeneration event, the third regeneration temperature being greater than the first regeneration temperature and less than 550 degrees celsius; and maintaining the temperature of the SCR catalyst at the third regeneration temperature for a predetermined third period of time.

In some embodiments, the time interval threshold is in a range of 10 hours to 12 hours.

In some embodiments, the controller is further configured to: in response to the time interval between regeneration events not satisfying the threshold time interval, the temperature of the SCR catalyst is increased to a fourth regeneration temperature in a subsequent regeneration event, the fourth regeneration temperature being equal to or greater than 550 degrees Celsius.

In some embodiments, the critical time interval is 1 hour.

In some embodiments, the controller is further configured to: a fault code is generated in response to the time interval between regeneration events continuing to not satisfy the critical time interval after a subsequent regeneration event.

In some embodiments, ammonia produced by the reductant introduced into the exhaust gas and NO contained in the exhaust gas flowing through the aftertreatment system_XThe ratio of the amount of gas is greater than 1.0.

In some embodiments, the aftertreatment system further comprises: an oxidation catalyst disposed upstream of the SCR catalyst; and a hydrocarbon introduction assembly configured to introduce hydrocarbons into the oxidation catalyst, wherein the controller is configured to increase the temperature of the SCR catalyst by instructing the hydrocarbon introduction assembly to introduce hydrocarbons into the oxidation catalyst.

In some embodiments, the aftertreatment system further comprises: an SCR catalyst heater operably coupled to the SCR catalyst, wherein the controller is configured to instruct the selective catalytic reduction heater to increase and maintain a temperature of the SCR catalyst.

In some embodiments, the predetermined threshold comprises NO_XThe conversion efficiency was 90%.

In some embodiments, an aftertreatment system for reducing a constituent of an exhaust gas having a sulfur content comprises: an SCR catalyst; and a controller configured to: determining NO of SCR catalyst_XThe conversion efficiency; in response to NO_XThe conversion efficiency is less than a first predetermined threshold, raising the temperature of the SCR catalyst to a first regeneration temperature greater than or equal to 400 degrees celsius and less than 550 degrees celsius; maintaining the temperature of the SCR catalyst at a first regeneration temperature for a first period of time; in response to NO_XIncreasing the temperature of the SCR catalyst to a second regeneration temperature equal to or greater than 550 degrees Celsius when the conversion efficiency is less than a second predetermined threshold that is lower than the first predetermined threshold or a time interval between subsequent regeneration events at the first temperature is less than a time interval threshold; maintaining the temperature of the SCR catalyst at a second regeneration temperature for a second period of time; and in response to NO_XThe conversion efficiency is less than a third predetermined threshold that is lower than the second predetermined threshold or the time interval between subsequent regeneration events at the second temperature is less than the time interval threshold, generating a fault code.

In some embodiments, the first predetermined threshold corresponds to 90% NO_XConversion efficiency, the second predetermined threshold corresponding to 80% NO_XConversion efficiency and a third predetermined threshold corresponds to 70% NO_XThe conversion efficiency.

In some embodiments, the controller is further configured to: the temperature of the SCR catalyst is increased to a first regeneration temperature in response to a fuel tank associated with the engine that produces exhaust gas being refilled or a predetermined amount of fuel having been consumed.

It should be understood that all combinations of the foregoing concepts and additional concepts discussed in greater detail below (assuming such concepts are not mutually inconsistent) are contemplated as being part of the subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the subject matter disclosed herein.

Brief Description of Drawings

The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only several embodiments in accordance with the disclosure and are, therefore, not to be considered limiting of its scope, the disclosure will be described with additional specificity and detail through use of the accompanying drawings.

Fig. 1 is a schematic diagram of an aftertreatment system, according to an embodiment.

Fig. 2 is a schematic block diagram of a control circuit that may be used as a controller of the aftertreatment system of fig. 1, according to an embodiment.

FIG. 3 shows a graph of hydrothermal aging factor for an SCR catalyst at various regeneration temperatures.

FIG. 4 shows a graph of exothermic efficiency across an oxidation catalyst for a plurality of cumulative sulfur exposure levels in exhaust gas flowing therethrough at a plurality of bed temperatures of the oxidation catalyst, and highlights a light-off temperature transition of the oxidation catalyst.

FIG. 5 illustrates an exothermic efficiency curve for an oxidation catalyst exposed to a plurality of cumulative sulfur exposure levels, highlighting the recovery of a lower light-off temperature of the oxidation catalyst after desulfation.

6A-6D illustrate SCR catalyst time versus NO based on measured sulfur release data_XSimulated plots of conversion efficiency showing satisfaction of target NO under different temperature and time sulfur removal strategies assuming operation with 50ppm sulfur fuel in an exemplary duty cycle_XFrequency of regeneration at the conversion level.

FIG. 7 shows multiple NOs_XExemplary plot of conversion efficiency threshold, plurality of NO_XThe conversion efficiency threshold is used to trigger low or high temperature regeneration of the SCR catalyst or to generate a fault code indicating that the fuel has a critical high sulfur concentration or that the SCR has a deactivation unrelated to high sulfur fuels.

FIG. 8 is a schematic flow diagram of a method for desulfating an oxidation catalyst for regeneration of the oxidation catalyst, according to an embodiment.

Fig. 9A-9B are schematic flow diagrams of methods for desulfating an SCR catalyst for regeneration of the SCR catalyst, according to embodiments.

Reference is made to the accompanying drawings throughout the following detailed description. In the drawings, like numerals generally identify like components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure.

Detailed Description

Embodiments described herein relate generally to systems and methods for desulfation, i.e., removal of sulfur accumulated on an oxidation catalyst or SCR catalyst included in an aftertreatment system. In particular, the systems and methods described herein include heating an oxidation catalyst or an SCR catalyst to a regeneration temperature that is lower than conventional regeneration temperatures in order to desulfate the oxidation catalyst or the SCR catalyst while reducing hydrothermal aging.

The aftertreatment system may include an oxidation catalyst for decomposing CO or hydrocarbons contained in the exhaust gas flowing therethrough. The aftertreatment system may further comprise means for decomposing NO contained in the exhaust gas_XSCR catalyst of gas. Conventional aftertreatment systems are designed and certified in anticipation that they will operate with fuels having low sulfur concentrations, e.g., 15ppm or less sulfur concentrations (e.g., diesel fuel). However, it is possible that diesel fuels with higher concentrations of sulfur can be used, and this may lead to reversible deterioration of the function of the oxidation catalyst and the SCR catalyst, in particular due to the accumulation of sulfur on the oxidation catalyst and the SCR catalyst.

The sulfur regeneration of the oxidation catalyst and/or the SCR catalyst is typically carried out by heating the oxidation catalyst or the SCR catalyst to a temperature equal to or greater than a high regeneration temperature, for example equal to or greater than 550 degrees celsius. Further, regeneration of the filter disposed downstream of the oxidation catalyst (i.e., removal of accumulated soot or ash from the filter by burnout) may be performed by raising the temperature of the exhaust gas to a high regeneration temperature (e.g., about 550 degrees celsius or higher). Such high regeneration temperatures are generally achieved by introducing hydrocarbons into or over the oxidation catalyst, which are combusted in the oxidation catalyst, causing the temperature of the exhaust gas to increase. The hot exhaust gas oxidizes soot that accumulates on the downstream filter and thereby regenerates the filter.

Since both sulfur and soot regeneration are effective at such high regeneration temperatures, they are typically performed with the same type of regeneration event. However, heating the oxidation catalyst or the SCR catalyst to high regeneration temperatures for sulfur regeneration creates several problems. High frequency thermal regeneration at high regeneration temperatures may result in rapid hydrothermal aging of the oxidation catalyst components or the SCR catalyst components. As shown in fig. 3, the aging factor is an exponential function of the temperature for sulfur removal for the SCR catalyst. Hydrothermal aging can be further accelerated by the presence of sulfur on the SCR catalyst. Thus, the combination of sulfur and high temperature may result in NO for the SCR catalyst_XThe conversion efficiency is irreversibly deteriorated more quickly.

Another challenge of sulfur exposure is that the light-off temperature of the oxidation catalyst, i.e., the temperature at which hydrocarbons introduced into the oxidation catalyst ignite, may shift to a higher temperature. For example, FIG. 4 illustrates an exothermic efficiency curve across an oxidation catalyst and an increase in light-off temperature of the oxidation catalyst when exposed to exhaust gas (including increased cumulative exposure of sulfur). This may be a problem from the filter during filter soot regeneration events, where fuel is injected into the oxidation catalyst to raise the filter inlet temperature to the target regeneration temperature. If the inlet temperature of the oxidation catalyst is below the light-off temperature, unburned fuel may enter the filter, which may result in thermal damage to the filter. Removing sulfur from the oxidation catalyst prior to a filter regeneration event may help alleviate this problem. While oxidation catalysts and SCR catalysts may be made larger such that they require longer to be affected by exhaust gases including high sulfur content, this increases the cost of the aftertreatment system and may also increase the complexity of the packaging.

In contrast, various embodiments of the systems and methods for desulfating an oxidation catalyst and/or an SCR catalyst described herein may provide one or more benefits, including, for example: (1) desulfating the oxidation catalyst and/or the SCR catalyst by heating to a temperature below the high regeneration temperature (i.e., less than 550 degrees celsius) in order to limit aging of the respective catalyst; (2) preventing an increase in the light-off temperature of the oxidation catalyst, thereby protecting the downstream filter from exposure to unburned hydrocarbons; (3) avoiding over-design of the oxidation catalyst or the SCR catalyst, and simultaneously preventing thermal aging; (4) allows operation of the aftertreatment system in situations where the engine consumes high sulfur content fuels (e.g., up to 50ppm sulfur); and (5) increased catalyst life, thereby reducing maintenance and warranty costs.

Fig. 1 is a schematic diagram of an aftertreatment system 100, according to an embodiment. Aftertreatment system 100 is configured to receive exhaust from engine 10 (e.g., a diesel engine, a gasoline engine, a natural gas engine, a dual fuel engine, a biodiesel engine, an E-85 engine, or any other suitable engine) and reduce a component of the exhaust, such as, for example, NO_XGas, CO, hydrocarbons, etc. In some embodiments, the fuel consumed by engine 10 may include a fuel having a high sulfur concentration (e.g., greater than 15ppm) (e.g., a high sulfur diesel fuel). Aftertreatment system 100 may include a reductant storage tank 110, a reductant introduction assembly 120, a housing 101, an oxidation catalyst 130, a filter 140, an SCR catalyst 150, and a controller 170. In some embodiments, the aftertreatment system 100 may also include a hydrocarbon introduction assembly 132 and an ammonia oxidation (AMOx) catalyst 160.

The housing 101 defines an interior volume, an oxidation catalyst 130, a filter 140, an SCR catalyst 150, and AMO_XA catalyst 160 is disposed within the interior volume. The housing 101 may be formed from a rigid, heat and corrosion resistant material, such as stainless steel, iron, aluminum, metal, ceramic, or any other suitable material. The housing 101 may have any suitable cross-section, such as circular, square, rectangular, oval, elliptical, polygonal, or any other suitable shape.

An inlet conduit 102 is fluidly coupled to the inlet of the housing 101 andand is configured to receive exhaust gas from engine 10 and communicate the exhaust gas to the interior volume defined by housing 101. Further, an outlet conduit 104 may be coupled to an outlet of the housing 101 and configured to discharge the treated exhaust gas into the environment (e.g., treated by a filter 140 to remove particulate matter such as soot and/or reduce constituents of the exhaust gas, such as NO contained in the exhaust gas)_XGas, CO, unburned hydrocarbons, etc.).

A first sensor 103 may be positioned in the inlet duct 102. The first sensor 103 may include a sensor configured to measure NO contained in exhaust gas flowing into the SCR catalyst 150_XAmount of gas NO_XSensors, and may include physical sensors or virtual sensors. In various embodiments, a temperature sensor, a pressure sensor, an oxygen sensor, or any other sensor may also be positioned in the inlet conduit 102 to determine one or more operating parameters of the exhaust gas flowing through the aftertreatment system 100.

A second sensor 105 may be positioned in the outlet conduit 104. The second sensor 105 may include a second NO_XSensor of the second NO_XThe sensor is configured to determine NO emitted to the environment after passing through the SCR catalyst 150_XThe amount of gas. In other embodiments, the second sensor 105 may include a particulate matter sensor configured to determine an amount of particulate matter in the exhaust gas emitted to the environment (e.g., soot contained in the exhaust gas exiting the filter 140). In still other embodiments, the second sensor 105 may include an ammonia sensor configured to measure an amount of ammonia in the exhaust gas flowing out of the SCR catalyst 150, i.e., determine an ammonia slip (slip). This can be used as a measure of: determining the catalytic efficiency of the SCR catalyst 150, adjusting the amount of reductant to be introduced into the SCR catalyst 150, and/or adjusting the temperature of the SCR catalyst 150 in order to allow the SCR catalyst 150 to effectively use ammonia for catalytically decomposing NO contained in exhaust gas flowing therethrough_XA gas. Ammonia oxide (AMO)_X) Catalyst 160 may be positioned downstream of SCR catalyst 150 to decompose exhaust downstream of SCR catalyst 150Any unreacted ammonia in the gas.

An oxidation catalyst 130 is positioned downstream of and fluidly coupled to inlet duct 102 to receive exhaust gas therefrom. The oxidation catalyst 130 may be configured to decompose unburned hydrocarbons and/or CO contained in the exhaust gas. In particular embodiments, oxidation catalyst 130 comprises a diesel oxidation catalyst. An oxidation catalyst inlet temperature sensor 133 may be positioned upstream of the oxidation catalyst 130 and configured to determine an inlet temperature of exhaust gas entering the oxidation catalyst 130. An oxidation catalyst outlet temperature sensor 135 may be positioned downstream of the oxidation catalyst 130 and configured to determine an outlet temperature of the exhaust gas exiting the oxidation catalyst 130. The oxidation catalyst heater 134 may be coupled to the oxidation catalyst 130 and configured to selectively heat the oxidation catalyst 130 to a predetermined temperature, such as a low regeneration temperature (e.g., greater than or equal to 400 degrees celsius and less than 550 degrees celsius) or a high regeneration temperature (e.g., equal to or greater than 550 degrees celsius).

The filter 140 is disposed downstream of the oxidation catalyst 130 and is configured to remove particulate matter (e.g., soot, debris, inorganic particulates, etc.) from the exhaust gas. In various embodiments, the filter 140 may comprise a ceramic filter. In some embodiments, the filter 140 may comprise a cordierite filter, which may be, for example, an asymmetric filter. In yet other embodiments, filter 140 may be catalyzed.

Further, a hydrocarbon introduction assembly 132 may be coupled to the housing 101 and configured to selectively introduce hydrocarbons onto the oxidation catalyst 130. The oxidation catalyst 130 is configured to catalyze the ignition of hydrocarbons when the inlet temperature 133 of the oxidation catalyst 130 is heated above the light-off temperature (> 275-300 degrees celsius) of the hydrocarbons introduced into the oxidation catalyst 130 to raise the outlet temperature of the exhaust gas to a high temperature (e.g., 550 degrees celsius) sufficient to burn off soot accumulated on the filter 140 to regenerate the filter 140, or to a low oxidation catalyst outlet temperature (400-550 degrees celsius) to regenerate sulfur to the SCR catalyst.

SCR catalyst 150 is formulated to decompose constituents of the exhaust gas flowing therethrough in the presence of a reductant, as described herein. In some embodiments, filter 140 may be removed and SCR catalyst 150 may include a Selective Catalytic Reduction Filter (SCRF). Any suitable SCR catalyst 150 may be used, such as, for example, a platinum, palladium, rhodium, cerium, iron, manganese, copper, vanadium based catalyst, any other suitable catalyst, or a combination thereof. The SCR catalyst 150 may be disposed on a suitable substrate such as, for example, a ceramic (e.g., cordierite) or metal (e.g., kanal-cobalt refractory steel) monolithic core, which may, for example, define a honeycomb structure. Washcoat (washcoat) may also be used as a support material for the SCR catalyst 150. Such washcoat materials may include, for example, alumina, titania, silica, any other suitable washcoat material, or combinations thereof.

Exhaust gas (e.g., diesel exhaust gas) may flow over the SCR catalyst 150 and/or around the SCR catalyst 150 such that any NO contained in the exhaust gas_XThe gas is further reduced to produce a substantially NO-free gas_XThe off-gas of the gas. SCR catalyst temperature sensor 153 may be positioned near SCR catalyst 150 (e.g., upstream of SCR catalyst 150) and configured to determine a temperature of exhaust gas entering SCR catalyst 150. The second SCR catalyst temperature sensor 155 may be located at the SCR catalyst 150 or AMO_XDownstream of the catalyst 160, and is configured to determine the SCR catalyst 150 temperature, e.g., the temperature of the exhaust gas downstream of the SCR catalyst 155. When referring to the SCR catalyst 150 temperature, the SCR catalyst 150 temperature may be determined via the first SCR catalyst temperature sensor 153, the second SCR catalyst temperature sensor 155, or a virtual representation calculated from one or both sensors. The SCR catalyst heater 154 may be coupled to the SCR catalyst 150 and configured to selectively heat the SCR catalyst 150 to a predetermined temperature (e.g., greater than or equal to 400 degrees celsius and less than 550 degrees celsius) or a high regeneration temperature (e.g., equal to or greater than 550 degrees celsius).

Although FIG. 1 only shows the statorAn oxidation catalyst 130, a filter 140, an SCR catalyst 150, and AMO positioned within an interior volume defined by the housing 101_XCatalyst 160, but in other embodiments, in addition to oxidation catalyst 130, filter 140, SCR catalyst 150, and AMO_XBeyond the catalyst 160, more than one aftertreatment component may be positioned within the interior volume defined by the housing 101. Such aftertreatment components may include, for example, mixers, baffles, secondary filters (e.g., secondary flow splitters or catalytic filters), or any other suitable aftertreatment component.

The reductant port 156 may be positioned on a sidewall of the housing 101 and configured to allow reductant to be introduced therethrough into an interior volume defined by the housing 101. The reductant port 156 may be positioned upstream of the SCR catalyst 150 (e.g., to allow reductant to be introduced into the exhaust gas upstream of the SCR catalyst 150) or positioned on the SCR catalyst 150 (e.g., to allow reductant to be introduced directly onto the SCR catalyst 150). In other embodiments, the reductant port 156 may be disposed on the inlet conduit 102 and configured to introduce reductant into the inlet conduit 102 upstream of the SCR catalyst 150. In such embodiments, a mixer, baffle, vane, or other structure may be positioned in inlet duct 102 to facilitate mixing of the reductant with the exhaust gas.

The reductant storage tank 110 is configured to store reductant. The reducing agent is formulated to promote a component of the exhaust gas (e.g., NO contained in the exhaust gas)_XGas) decomposition. Any suitable reducing agent may be used. In some embodiments, the exhaust gas comprises diesel exhaust gas and the reductant comprises diesel exhaust fluid (diesel exhaust fluid). For example, the diesel exhaust fluid may include urea, an aqueous solution of urea, or any other diesel exhaust fluid known in the art (e.g., by name)Diesel exhaust fluid sold). For example, the reductant may include an aqueous urea solution having a particular ratio of urea to water. In particular instancesIn embodiments, the reducing agent may include an aqueous urea solution comprising 32.5% urea by volume and 67.5% deionized water by volume, 40% urea by volume and 60% deionized water by volume, or any other suitable ratio of urea to deionized water.

The reductant introduction assembly 120 is fluidly coupled to the reductant storage tank 110. The reductant introduction assembly 120 is configured to selectively introduce reductant into the SCR catalyst 150 or upstream of the SCR catalyst 150 (e.g., into the inlet conduit 102) or into a mixer (not shown) positioned upstream of the SCR catalyst 150. The reductant introduction assembly 120 may include a variety of structures to facilitate receiving reductant from the reductant storage tank 110 and delivering the reductant to the SCR catalyst 150, such as pumps, valves, screens, filters, and the like.

The aftertreatment system 100 may also include a reductant injector fluidly coupled to the reductant introduction assembly 120 and configured to introduce a reductant (e.g., a combined flow of reductant and compressed air) into the SCR catalyst 150. In various embodiments, the reductant injector may include a nozzle having a predetermined diameter. In various embodiments, a reductant injector may be positioned in the reductant port 156 and configured to deliver a stream or jet of reductant into the interior volume of the housing 101 for delivery of the reductant to the SCR catalyst 150.

The controller 170 may be communicatively coupled to the first sensor 103 and may be configured to receive a first sensor signal from the first sensor 103, e.g., to determine NO contained in exhaust gas entering the aftertreatment system_XThe amount of gas. Controller 170 may also be communicatively coupled to second sensor 105 and may be configured to determine NO contained in exhaust emitted into the environment_XGas or ammonia concentration. Controller 170 may also be coupled to, and configured to receive temperature signals from, oxidation catalyst temperature sensors 133 and 135 and SCR catalyst temperature sensors 153 and 155 to determine exhaust gas entering and exiting oxidation catalyst 130 or SCR catalyst 150, respectivelyThe temperature of (2). The controller 170 may also be coupled to the oxidation catalyst heater 134 and the SCR catalyst heater 154, and configured to selectively activate either heater 134 or 154 to heat the oxidation catalyst 130 and the SCR catalyst 150, respectively, to a predetermined temperature. Controller 170 may be operatively coupled to the various components of aftertreatment system 100 using any type and any number of wired or wireless connections. For example, the wired connection may include a serial cable, a fiber optic cable, a CAT5 cable, or any other form of wired connection. The wireless connection may include the internet, Wi-Fi, cellular, radio, bluetooth, ZigBee, and the like. In one embodiment, a Controller Area Network (CAN) bus provides for the exchange of signals, information, and/or data. The CAN bus includes any number of wired and wireless connections.

In some embodiments, the controller 170 may be configured to determine whether the filter 140 is to be regenerated and whether the oxidation catalyst criteria are met. For example, the controller 170 may be configured to receive a signal from the filter 140, such as a pressure signal from a differential pressure sensor 142 positioned across the filter 140, and estimate the amount of soot loading within the filter 140. For example, controller 170 may determine that filter 140 should be regenerated in response to the pressure differential across filter 140 exceeding a predetermined pressure threshold corresponding to a soot loading within filter 140 exceeding a soot loading threshold.

In response to determining that filter 140 is to be regenerated and that the oxidation catalyst criteria are met, controller 170 is configured to increase the outlet temperature of oxidation catalyst 130 to a low regeneration temperature or a first regeneration temperature, for example, greater than or equal to 400 degrees celsius and less than 550 degrees celsius, including 400 degrees celsius and 550 degrees celsius. For example, the controller 170 may inject hydrocarbons into the oxidation catalyst 130 via the hydrocarbon introduction assembly 132 to increase the exhaust gas temperature. In another embodiment, the controller 170 may be configured to command the hydrocarbon introduction assembly 132 to introduce hydrocarbons into the engine 10 to increase the temperature of the exhaust gas and, thus, the temperature of the oxidation catalyst 130. In yet another embodiment, the controller 170 may activate the oxidation catalyst heater 134 such that the oxidation catalyst heater 134 raises the temperature of the oxidation catalyst 130 to a low regeneration temperature. The controller 170 is configured to maintain the temperature of the oxidation catalyst 130 at the low regeneration temperature for a predetermined period of time, such as 15 minutes, 20 minutes, 25 minutes, or 30 minutes, including all ranges and values therebetween. The low regeneration temperature and the predetermined period of time are sufficient to desulfate the oxidation catalyst 130, i.e., remove the sulfur that has accumulated on the surfaces of the oxidation catalyst 130.

The removal of sulfur from the oxidation catalyst 130 shifts the light-off temperature of the hydrocarbons of the oxidation catalyst 130 (i.e., the temperature at which the hydrocarbons introduced into the oxidation catalyst 130 ignite) to the light-off temperature of a non-sulfated oxidation catalyst (e.g., a fresh oxidation catalyst that is not exposed to sulfur). For example, fig. 5 shows a heat release efficiency curve across a non-sulfating reference oxidation catalyst after being heated to a different low regeneration temperature compared to a heat release efficiency curve across a sulfating oxidation catalyst that has been exposed to a variety of cumulative sulfur levels. Regenerating the oxidation catalyst shifts the exotherm efficiency curve of the sulfated oxidation catalyst to a non-sulfated reference.

After the first period of time, the controller 170 is further configured to increase the outlet temperature of the oxidation catalyst 130 to a high or second regeneration temperature, for example equal to or greater than 550 degrees celsius, by instructing the hydrocarbon introduction assembly 132 to increase the amount of hydrocarbons introduced into the oxidation catalyst 130 until a target is reached. The hydrocarbons ignite or light-off on the regenerated oxidation catalyst 130 and raise the temperature of the exhaust gas sufficient to oxidize the particulate matter accumulated on the downstream filter 140, thereby regenerating the filter 140.

In some embodiments, the oxidation catalyst criteria may include desulfation conditions. For example, the controller 170 may be configured to determine whether the desulfation condition is met, and configured to increase the temperature of the oxidation catalyst 130 to a low regeneration temperature in response to the desulfation condition being met. In some embodiments, the desulfation conditions include a concentration of sulfur in a fuel combusted in engine 10 to produce exhaust gas, and the desulfation conditions are satisfied to include the concentration of sulfur in the exhaust gas being equal to or greater than a predetermined threshold concentration of sulfur, for example 15ppm of sulfur in the fuel. For example, the controller 170 may be coupled to a sulfur sensor 12, the sulfur sensor 12 being coupled to the engine 10 or a fuel tank of the engine 10 and configured to determine a concentration of sulfur in the fuel.

In other embodiments, the first sensor 103 may be configured to detect SO in the exhaust gas corresponding to the concentration of sulfur in the fuel_XThe concentration of the gas, and the controller 170 may be configured to determine the concentration of sulfur in the fuel based on the signal received from the first sensor 103. In still other embodiments, the signal may be received from a virtual sensor (e.g., a signal received from a central controller of a system including engine 10 that determines the concentration of sulfur in the fuel based on an operating parameter of engine 10 or exhaust system 101). As previously described herein, a high sulfur content in the fuel or exhaust gas causes the oxidation catalyst 130 to be sulfated, and thus, desulfation, i.e., removal of sulfur accumulated on the oxidation catalyst 130, would be beneficial to prevent a shift in the light-off temperature of the oxidation catalyst 130.

Thus, after controller 170 determines that a high sulfur fuel (e.g., having a sulfur concentration greater than 15ppm) is used in engine 10 (e.g., based on the fuel being filled into a fuel tank associated with engine 10 in the last tank fill), controller 170 initiates a low temperature regeneration cycle of oxidation catalyst 130. Conversely, if the desulfation conditions are not met, for example, low sulfur fuel is used, controller 170 may determine that oxidation catalyst regeneration is not desired. In such embodiments, when controller 170 detects a desired soot filter regeneration, controller 170 may be configured to increase the temperature of oxidation catalyst 130 to a high regeneration temperature without maintaining the oxidation catalyst at a low regeneration temperature, and introduce hydrocarbons into oxidation catalyst 130 to regenerate filter 140, as previously described herein.

In some embodiments, the sulfur saturation of the oxidation catalyst 130 may be evaluated via an exothermic efficiency curve across the oxidation catalyst 130. The reference exotherm efficiency curve indicates an expected temperature rise profile across the oxidation catalyst 130 for a given reductant injection amount for the non-sulfating oxidation catalyst. The reference heat release efficiency curve may be stored in the memory of the controller 170 in the form of a look-up table, algorithm, or equation. In some embodiments, the desulfurization conditions being met may include the measured exotherm being outside a predetermined range. For example, if the oxidation catalyst 130 is sulfated, its measured heat release may be less than the heat release efficiency curve of a non-sulfated oxidation catalyst because the light-off temperature of the oxidation catalyst 130 is increased due to the sulfur accumulation thereon. In response to the measured exotherm being outside of the predetermined range, controller 170 may initiate a low temperature regeneration cycle of oxidation catalyst 130 for a predetermined period of time before initiating the high temperature regeneration cycle. Otherwise, the controller 170 may initiate a high temperature regeneration cycle.

In some embodiments, the controller 170 may also be configured to selectively cause regeneration of the SCR catalyst 150. The high sulfur fuel content may also cause sulfur to accumulate on the SCR catalyst 150, causing NO to the SCR catalyst 150_XA reduction in conversion efficiency. As previously described herein, the SCR catalyst 150 may be regenerated at a high regeneration temperature, for example, about 550 degrees celsius. However, high temperature regeneration may thermally age the SCR catalyst 150 and reduce its life, as previously described herein. To prevent thermal aging of the SCR catalyst 150, the controller 170 may be configured to cause regeneration of the SCR catalyst 150 using a low regeneration temperature regeneration in which the injected ammonia is greater than or equal to the incoming NO, rather than a high temperature regeneration cycle_XOr ammonia to NO_XRatio of (ANR)>1.0。

For example, FIGS. 6A-6D show simulated graphs demonstrating sulfur removal regeneration events versus NO for a sulfur catalyst at different regeneration temperatures and different regeneration times_XThe effect of regeneration of conversion efficiency. If ammonia is present with NO_XIs greater than 1.0, then some sulfur may be removed with an SCR catalyst 150 inlet temperature of 400 degrees celsius (fig. 6A-6B). Ammonia and NO_XMay be determined by a ratio based on the presence of NO in the exhaust gas_XQuantity control device for gasThe amount of reducing agent introduced into the exhaust gas is controlled. During a conventional regeneration event, the SCR catalyst is heated at a high regeneration temperature for a predetermined period of time (e.g., 30 minutes to 60 minutes) to desulfate the SCR catalyst. In contrast, the regeneration events shown in fig. 6A-6B are performed at low regeneration temperatures, and therefore less sulfur is removed during the same time period. For example, in FIG. 6A, regeneration is performed at 400 degrees Celsius for 30 minutes, which removes enough sulfur from the SCR catalyst to convert the catalyst's NO to_XThe conversion efficiency is improved to about 94%. SCR catalyst begins sulfation again and NO_XConversion efficiency reaches a threshold (e.g., 90% NO)_XConversion efficiency), the 400 degree celsius regeneration event is again continued for 30 minutes, and so on. Fig. 6B is similar to fig. 6A, the only difference being that the low temperature regeneration event is performed at 400 degrees celsius for 60 minutes. At 450 degrees celsius (fig. 6C), additional sulfur may be removed, and at 500 degrees celsius (fig. 6D), even more sulfur may be removed, resulting in a further reduction in regeneration frequency.

The controller 170 is configured to determine NO of the SCR catalyst 150_XThe conversion efficiency. For example, the controller 170 may be configured to receive NO from the first sensor 103 and the second sensor 105_XSignal and thereby determine NO of the SCR catalyst 150_XThe conversion efficiency. NO responsive to SCR catalyst 150_XThe conversion efficiency is less than a predetermined threshold, the controller 170 is configured to increase the temperature of the SCR catalyst 150 to a first regeneration temperature that is greater than or equal to 400 degrees celsius and less than 550 degrees celsius, and to maintain the SCR catalyst 150 at the first regeneration temperature for a predetermined period of time.

For example, the predetermined threshold may correspond to the SCR catalyst 150 being at 90% NO_XThe conversion efficiency proceeds. This may indicate to controller 170 that SCR catalyst 150 is to be regenerated. The controller 170 may instruct the hydrocarbon introduction assembly 132 to inject hydrocarbons into the oxidation catalyst 130 to increase the outlet temperature of the oxidation catalyst 130 and thereby increase the SCR inlet exhaust gas temperature to the first regeneration temperature, or heat the SCR catalyst 150 to the first regeneration temperature using the SCR catalyst heater 154For example, greater than or equal to 400 degrees celsius and less than 550 degrees celsius (which is lower than a conventional high regeneration temperature of, for example, 550 degrees celsius or higher), and the SCR catalyst 150 is maintained at the first regeneration temperature for a predetermined period of time (e.g., about 30 minutes to 60 minutes). This will reduce the effect of hydrothermal aging on the SCR catalyst 150. The first regeneration temperature may cause at least partial regeneration of the SCR catalyst 150, resulting in NO of the SCR catalyst 150_XThe conversion efficiency increases above a predetermined threshold. For example, as shown in fig. 6A and 6B, regeneration at 30 minutes at 400 degrees celsius causes NO to the SCR catalyst_XThe conversion efficiency is increased to about 94%, and the regeneration at 60 minutes at 400 degrees celsius causes NO to the SCR catalyst_XConversion efficiency increased to about 95% in the exemplary duty cycle.

In some embodiments, NO in response to SCR catalyst 150_XThe conversion efficiency is less than a predetermined threshold, the controller 170 is configured to increase the temperature of the SCR catalyst 150 to a first regeneration temperature (e.g., in the range of 400-450 degrees celsius) for a predetermined first period of time, and then increase the temperature of the SCR catalyst 150 to a second regeneration temperature (e.g., in the range of 450 to less than 550 degrees celsius) that is greater than the first regeneration temperature and less than 550 degrees celsius (e.g., in the range of 450 to less than 550 degrees celsius). Controller 170 maintains SCR catalyst 150 at the second regeneration temperature for a predetermined second period of time. For example, as shown in fig. 6C and 6D, the controller 170 may be configured to heat the SCR catalyst to 400 degrees celsius for a predetermined first period of time (30 minutes or 60 minutes as shown in fig. 6A and 6B, respectively), and then warm to 450 degrees celsius (fig. 6C) or 500 degrees celsius (fig. 6D) for a short period of time (e.g., 10 minutes-15 minutes) to cause NO for the SCR catalyst 150_XHigher increase in conversion efficiency.

In some embodiments, in response to the time interval between regeneration events not satisfying the minimum time interval threshold, the controller 170 is configured to increase the temperature of the SCR catalyst 150 to a third regeneration temperature in a subsequent regeneration event. Third regeneration temperatureGreater than the first regeneration temperature and less than 550 degrees celsius, and in some embodiments, the third regeneration temperature may be equal to the second regeneration temperature. Controller 170 maintains the temperature of SCR catalyst 150 at the third regeneration temperature for a predetermined third period of time. For example, if NO of SCR catalyst 150_XThe conversion efficiency falls below a predetermined threshold within less than a time interval threshold (e.g., about 10 hours to about 12 hours), then the controller 170 may determine that NO is present_XRegeneration at a first regeneration temperature (e.g., 400 degrees Celsius) is insufficient to recover NO from the SCR catalyst 150 for at least a time interval threshold (e.g., 10 hours-12 hours) before the conversion efficiency falls below the threshold_XThe conversion efficiency. Accordingly, the controller 170 may cause the SCR catalyst 150 to be heated to a third regeneration temperature (e.g., 500 degrees celsius) and maintain the SCR catalyst 150 at the third regeneration temperature for a predetermined third period of time, e.g., 500 degrees celsius for 30 minutes, as shown in fig. 6D. Heating the SCR catalyst 150 to a third, higher regeneration temperature may recover more NO_XConversion efficiency, and thus, reduced NO for the SCR catalyst 150_XThe probability that the conversion efficiency falls below a predetermined threshold within a time interval threshold.

In some embodiments, in response to the time interval between regeneration events not satisfying the threshold time interval, the controller 170 may be configured to increase the temperature of the SCR catalyst 150 to a fourth regeneration temperature (e.g., equal to or greater than 550 degrees celsius) in a subsequent regeneration event. The critical time interval is shorter than the time interval threshold. In some embodiments, the critical time interval is about 1 hour. For example, where the fuel has a sulfur concentration equal to or greater than a threshold sulfur level threshold (e.g., a sulfur concentration equal to or greater than 500pm), low temperature regeneration events for desulfating the SCR catalyst 150 may begin to occur very frequently such that NO is recovered due to high sulfur concentrations in the fuel_XConversion efficiency occurs at a slower rate than sulfur accumulation. Thus, when the accumulation of sulfur on the SCR catalyst 150 is as fast as the removal of sulfur from the SCR catalyst 150, the NO of the SCR catalyst 150_XThe conversion efficiency drops very quickly.

Controller 170 may be configured such that if a regeneration event begins to occur between a time interval equal to or less than the threshold time interval, controller 170 initiates a standard desulfation event at a fourth regeneration temperature (e.g., 550 degrees celsius or greater). In some embodiments, in response to the time interval between regeneration events continuing to not meet the critical time interval after a subsequent regeneration event, the controller 170 generates a fault code and/or illuminates a fault indicator light (MIL) to indicate to a user that the fuel has a very high sulfur content. In such embodiments, controller 170 may be configured to stop attempting low or high temperature regeneration of SCR catalyst 150 until controller 170 receives a signal that a fuel tank associated with engine 10 has been refilled, or a signal that an amount of fuel corresponding to a volume of the fuel tank has been consumed.

In some embodiments, the controller 170 may be configured to respond to NO of the SCR catalyst 150_XThe conversion efficiency is equal to or less than a predetermined threshold, and low temperature regeneration of the SCR catalyst 150 is initiated, as previously described herein. In other embodiments, the controller 170 may be configured to initiate low temperature regeneration of the SCR catalyst 150 in response to a sulfur signal received from the sulfur sensor 12 (e.g., a physical sensor or a virtual sensor) corresponding to a sulfur concentration in the fuel that is greater than a high sulfur concentration (e.g., greater than 15ppm) but less than a threshold sulfur level threshold (e.g., 500 ppm). If the sulfur concentration is greater than the threshold sulfur level threshold, controller 170 generates a fault code and/or lights the MIL until the fuel in the fuel tank is consumed or the fuel tank is refilled.

In still other embodiments, the controller 170 may be configured to detect NO of the SCR catalyst 150 based on the detected NO_XConversion efficiency to initiate a low temperature event or a high temperature event. For example, FIG. 7 illustrates multiple NO's for triggering different temperatures of SCR catalyst 150 regeneration events_XA threshold level of conversion efficiency. These NO's of the SCR catalyst 150_XThe conversion efficiency will be determined at the specific conditions of flow and temperature of the exhaust gas and may be a time-averaged signal. As shown in fig. 7, NO if the SCR catalyst 150_XThe conversion efficiency drops to a first predetermined threshold (e.g., a low temperature threshold), e.g., 90% NO_XConversion efficiency, then controller 170 may be configured to initiate a low temperature regeneration event (e.g., greater than or equal to 400 degrees celsius and less than 550 degrees celsius). In response to NO_XThe conversion efficiency drops to a second predetermined threshold (e.g., a high temperature threshold), e.g., 80% NO, less than the first predetermined threshold_XConversion efficiency (e.g., after a predetermined time interval), controller 170 may be configured to initiate a high temperature regeneration event (e.g., at 550 degrees celsius or higher). Furthermore, if NO_XConversion efficiency continues to drop to a third predetermined threshold (e.g., a fault threshold) less than the second predetermined threshold, e.g., 70% NO_XConversion efficiency, then the controller 170 may be configured to generate a fault code and/or light the MIL and the additional regeneration event is stopped until the fuel tank is refilled or a predetermined amount of fuel has been consumed. A low temperature regeneration event may then be performed to observe NO of the SCR catalyst 150_XWhether the conversion efficiency has improved. If this is the case, low temperature regeneration is resumed.

In particular embodiments, controller 170 may be included in a control module. For example, fig. 2 is a schematic block diagram of a control module 171 that includes a controller 170, according to an embodiment. Controller 170 includes a processor 172, a memory 174 or any other computer-readable medium, and a communication interface 176. In addition, the controller 170 includes a pressure determination module 174a, a sulfur concentration determination module 174b, a temperature determination module 174c, a temperature control module 174d, NO_XA conversion efficiency determination module 174e, a hydrocarbon introduction module 174f, and a fault code generation module 174 g. It should be understood that any other controller capable of performing the operations described herein may be used.

Processor 172 may include a microprocessor, a Programmable Logic Controller (PLC) chip, an ASIC chip, or any other suitable processor. The processor 172 is in communication with the memory 174 and is configured to execute instructions, algorithms, commands, or other programs stored in the memory 174.

Memory 174 includes any of the memory and/or storage components discussed herein. For example, memory 174 may include RAM and/or cache memory of processor 172. The memory 174 may also include one or more storage devices (e.g., hard disk drives, flash drives, computer-readable media, etc.) local or remote to the controller 170. The memory 174 is configured to store a look-up table, algorithm, or instructions.

In one configuration, the pressure determination module 174a, the sulfur concentration determination module 174b, the temperature determination module 174c, the temperature control module 174d, NO_XThe conversion efficiency determination module 174e, the hydrocarbon introduction module 174f, and the fault code generation module 174g are embodied as a machine-readable medium or computer-readable medium (e.g., stored in the memory 174) executable by a processor, such as the processor 172. As described herein, a machine-readable medium (e.g., memory 174) facilitates the performance of certain operations to enable the receipt and transmission of data. For example, a machine-readable medium may provide instructions (e.g., commands, etc.) to, for example, collect data. In this regard, the machine-readable medium may include programmable logic that defines a frequency of data acquisition (or data transmission). Thus, the computer-readable medium may include code that may be written in any programming language, including but not limited to Java or a similar programming language, and any conventional procedural programming languages, such as the "C" programming language or a similar programming language. The computer readable program code may be executed on one processor or on multiple remote processors. In the latter case, the remote processors may be connected to each other through any type of network (e.g., CAN bus, etc.).

In another configuration, the pressure determination module 174a, the sulfur concentration determination module 174b, the temperature determination module 174c, the temperature control module 174d, NO_XThe conversion efficiency determination module 174e, the hydrocarbon introduction module 174f, and the fault code generation module 174g are embodied as hardware units, such as electronic control units. Thus, the pressure determination module 174a, the sulfur concentration determination module 174b, the temperature determination module 174c, the temperature control module 174d, NO_XA conversion efficiency determination module 174e,The hydrocarbon introduction module 174f and the fault code generation module 174g may be embodied as one or more circuit components including, but not limited to, processing circuitry, network interfaces, peripherals, input devices, output devices, sensors, and the like.

In some embodiments, the pressure determination module 174a, the sulfur concentration determination module 174b, the temperature determination module 174c, the temperature control module 174d, NO_XThe conversion efficiency determination module 174e, the hydrocarbon introduction module 174f, and the fault code generation module 174g may take the form of one or more analog circuits, electronic circuits (e.g., Integrated Circuits (ICs), discrete circuits, system on a chip (SOC) circuits, microcontrollers, etc.), telecommunications circuits, hybrid circuits, and any other type of "circuit". In this regard, the pressure determination module 174a, the sulfur concentration determination module 174b, the temperature determination module 174c, the temperature control module 174d, NO_XThe conversion efficiency determination module 174e, the hydrocarbon introduction module 174f, and the fault code generation module 174g may include any type of components for accomplishing or facilitating the implementation of the operations described herein. For example, a circuit as described herein may include one OR more transistors, logic gates (e.g., NAND, AND, NOR, OR, XOR, NOT, XNOR, etc.), resistors, multiplexers, registers, capacitors, inductors, diodes, wiring, AND so forth.

Thus, the pressure determination module 174a, the sulfur concentration determination module 174b, the temperature determination module 174c, the temperature control module 174d, NO_XThe conversion efficiency determination module 174e, the hydrocarbon introduction module 174f, and the fault code generation module 174g may also include programmable hardware devices, such as field programmable gate arrays, programmable array logic, programmable logic devices, or the like. In this regard, the pressure determination module 174a, the sulfur concentration determination module 174b, the temperature determination module 174c, the temperature control module 174d, NO_XThe conversion efficiency determination module 174e, the hydrocarbon introduction module 174f, and the fault code generation module 174g may include one or more memory devices for storing the temperature information determined by the pressure determination module 174a, the sulfur concentration determination module 174b, and the temperature determination module174c, temperature control module 174d, NO_XThe processor-executable instructions of the conversion efficiency determination module 174e, the hydrocarbon introduction module 174f, and the fault code generation module 174 g. The one or more memory devices and the processor may have the same definitions as provided below with respect to the memory 174 and the processor 172.

In the illustrated example, the controller 170 includes a processor 172 and a memory 174. The processor 172 and memory 174 may be configured or arranged to execute or implement the methods described herein with respect to the pressure determination module 174a, the sulfur concentration determination module 174b, the temperature determination module 174c, the temperature control module 174d, NO_XThe conversion efficiency determination module 174e, the hydrocarbon introduction module 174f, and the fault code generation module 174g describe the instructions, commands, and/or control processes. Thus, the depicted configuration represents the arrangement mentioned above, the pressure determination module 174a, the sulfur concentration determination module 174b, the temperature determination module 174c, the temperature control module 174d, NO_XThe conversion efficiency determination module 174e, the hydrocarbon introduction module 174f, and the fault code generation module 174g are embodied as machine-readable or computer-readable media. However, as mentioned above, this illustration is not meant to be limiting as the present disclosure contemplates other embodiments such as those mentioned above, wherein the pressure determination module 174a, the sulfur concentration determination module 174b, the temperature determination module 174c, the temperature control module 174d, NO_XThe conversion efficiency determination module 174e, the hydrocarbon introduction module 174f, and the fault code generation module 174g, or the pressure determination module 174a, the sulfur concentration determination module 174b, the temperature determination module 174c, the temperature control module 174d, NO_XAt least one circuit of the conversion efficiency determination module 174e, the hydrocarbon introduction module 174f, and the fault code generation module 174g is configured as a hardware unit. All such combinations and variations are intended to fall within the scope of the present disclosure.

Processor 172 may be implemented as one or more general processors, Application Specific Integrated Circuits (ASICs), one or more Field Programmable Gate Arrays (FPGAs), Digital Signal Processors (DSPs), a set of processing elements, or other suitable electronic processing elements. At one endIn some embodiments, one or more processors may be shared by multiple circuits (e.g., pressure determination module 174a, sulfur concentration determination module 174b, temperature determination module 174c, temperature control module 174d, NO)_XThe conversion efficiency determination module 174e, the hydrocarbon introduction module 174f, and the fault code generation module 174g may include or otherwise share the same processor, which in some example embodiments may execute instructions stored or otherwise accessed via different regions of memory). Alternatively or additionally, one or more processors may be configured to perform or otherwise perform certain operations independently of one or more coprocessors. In other exemplary embodiments, two or more processors may be coupled via a bus to enable independent, parallel, pipelined, or multithreaded instruction execution. All such variations are intended to fall within the scope of the present disclosure. Memory 174 (e.g., RAM, ROM, flash memory, hard disk memory, etc.) may store data and/or computer code for facilitating the various processes described herein. Memory 174 may be communicatively connected to processor 172 to provide computer code or instructions to processor 172 for performing at least some of the processes described herein. Further, the memory 174 may be or include tangible, non-transitory volatile memory or non-volatile memory. Thus, memory 174 may include database components, object code components, script components, or any other type of information structure for supporting the various activities and information structures described herein.

Communication interface 176 may include a wireless interface (e.g., jack, antenna, transmitter, receiver, communication interface, wired terminal, etc.) for communicating data with various systems, devices, or networks. For example, the communication interface 176 may include an ethernet card and port for sending and receiving data via an ethernet-based communication network and/or a Wi-Fi communication interface for communicating with the first sensor 103, the second sensor 105, the engine 10, the temperature sensors 133 and 153, the pressure sensor 142, or the heaters 134 and 154. Communication interface 176 may be configured to communicate via a local or wide area network (e.g., the internet, etc.) and may use a variety of communication protocols (e.g., IP, LON, bluetooth, ZigBee, radio, cellular, near field communication, etc.).

The pressure determination module 174a is configured to receive the pressure signal from the differential pressure sensor 142 and determine the pressure across the filter 140 therefrom. The pressure determination module 174a may determine whether the filter 140 is loaded with soot in comparison to a soot loading threshold level based on the pressure differential across the filter 140 exceeding a pressure differential threshold at which the filter 140 should be regenerated. The pressure signal may be used to initiate a regeneration event to regenerate the filter 140.

The sulfur concentration determination module 174b is configured to receive a sulfur concentration signal, for example, from the sulfur sensor 12 or the first sensor 103, and determine the concentration of sulfur in the fuel or the exhaust gas from the fuel, respectively. The temperature determination module 174c is configured to receive temperature signals from the oxidation catalyst temperature sensor 133 and the SCR catalyst temperature sensor 153 and determine the temperature of the oxidation catalyst 130 and the SCR catalyst 150, respectively, therefrom.

The temperature control module 174d is configured to generate the oxidation catalyst temperature control signal. The control signal may be a command to the engine 10 to control the actuators to increase the exhaust gas temperature at the inlet of the aftertreatment assembly 100 or target the oxidation catalyst outlet temperature (e.g., as measured by the oxidation catalyst outlet temperature sensor 135) if the temperature is above a target level for the hydrocarbon introduction assembly 132. Alternatively, the temperature control module 174d may be in selective communication with the oxidation catalyst heater 134 and configured to cause the oxidation catalyst heater 134 to heat the oxidation catalyst 130 to a low regeneration temperature or a high regeneration temperature. Further, the temperature control module 174d is configured to generate the SCR catalyst temperature control signal, which may be achieved via the methods set forth to meet the target oxidation catalyst outlet temperature, and to target reductant injection control to maintain ANR above 1.0. Optionally, 174d may be in selective communication with the SCR catalyst heater 154 and configured to cause the SCR catalyst heater 154 to heat the SCR catalyst 150 to a low regeneration temperature or a high regeneration temperature, as previously described herein.

NO_XThe conversion efficiency determination module 174e is configured to determine NO for the SCR catalyst 150_XThe conversion efficiency. For example, NO_XThe conversion efficiency determination module 174e may receive NO from the first sensor 103 and the second sensor 105_XSignal and thereby determine NO of the SCR catalyst 150_XThe conversion efficiency.

The hydrocarbon introduction module 174f is configured to generate a hydrocarbon introduction signal configured to cause the hydrocarbon introduction assembly 132 to selectively introduce a predetermined amount of hydrocarbons into the oxidation catalyst 130 to regenerate the filter 140 or the SCR catalyst 150, as previously described herein. The fault code generation module 174g is configured to generate the fault code signal, for example, in response to the concentration of sulfur in the fuel being equal to or greater than a threshold sulfur threshold or the SCR catalyst 150 regeneration event occurring within a threshold time interval threshold.

In some embodiments, the controller 170 may also include a reductant introduction control module 174 h. The reductant introduction control module 174h is configured to receive, for example, inlet NO from the first sensor 103_XSignals, and determines inlet NO into the SCR system 150_XAmount or NO_XThe level of the gas. The reductant introduction control circuit 174h is configured to determine ammonia and NO_XFor the amount of inlet NO_XThe amount was converted to nitrogen. The reductant introduction control circuit 174h may generate a reductant introduction signal configured to cause the reductant introduction assembly 120 to introduce an appropriate amount of reductant into the exhaust gas for achieving the requisite ammonia and NO_XThe ratio of (a) to (b). For example, during a low-temperature SCR catalyst 150 desulfation event, the reductant introduction control component 174h may be configured to introduce an appropriate amount of reductant into the exhaust gas such that ammonia and NO_XRatio of (A) to (B)>1.0。

FIG. 8 is a schematic flow diagram of an exemplary method 200 for desulfating an oxidation catalyst (e.g., oxidation catalyst 130) for regenerating the oxidation catalyst, according to an embodiment. The oxidation catalyst may be included in an aftertreatment system (e.g., aftertreatment system 100) that also includes a filter (e.g., filter 140) disposed downstream of the oxidation catalyst 130 and configured to decompose components of the exhaust gas flowing therethrough. Although the method 200 is described herein as being implemented with the controller 170, it should be understood that the operations of the method 200 may be implemented in any controller included in any aftertreatment system.

Method 200 includes determining, at 202, that a filter is to be regenerated. For example, the pressure determination module 174a may receive a signal from the differential pressure sensor 142 and thereby determine whether the filter 140 is loaded with soot above a predetermined soot loading threshold. The pressure determination module 174a determines that the filter 140 is to be regenerated in response to the filter 140 being loaded with soot above a threshold level corresponding to a pressure differential that exceeds a pressure differential threshold.

In some embodiments, the method 200 includes determining whether desulfation conditions are met at 204. In some embodiments, the desulfurization conditions include a concentration of sulfur in the fuel from which the exhaust gas is combusted, and the desulfurization conditions are satisfied include the concentration of sulfur in the exhaust gas from the combustion being equal to or greater than a predetermined threshold concentration of sulfur. For example, the sulfur concentration determination module 174b may receive the signal from the sulfur sensor 12 and determine whether the concentration of sulfur in the fuel provided to the engine 10 is equal to or greater than a sulfur concentration threshold (e.g., approximately 15 ppm).

In other embodiments, the desulfation conditions include comparing the measured exotherm across the oxidation catalyst 130 to a reference exotherm efficiency curve. In such embodiments, the desulfation conditions are satisfied including the measured exotherm being outside a predetermined range. For example, the temperature determination module 174c may receive the temperature signal from the oxidation catalyst temperature sensor 133 to determine an exothermic temperature of the exhaust gas flowing across the oxidation catalyst 130 and the filter 140 due to combustion of hydrocarbons introduced into the oxidation catalyst 130, which heats the exhaust gas in an exothermic reaction.

At 206, in response to determining that the desulfation condition is not met (204: no), the temperature of the oxidation catalyst is increased to a second or high regeneration temperature and hydrocarbons are introduced into the oxidation catalyst. For example, in response to the sulfur concentration determination module 174b determining that the concentration of sulfur in the fuel consumed by the engine 10 is less than a sulfur concentration threshold (e.g., less than 15ppm), or the temperature determination module 174c determining that the measured exotherm across the oxidation catalyst 130 is within a predetermined range, the temperature control module 174d commands the hydrocarbon introduction assembly 132 or the oxidation catalyst heater 134 to increase the temperature of the oxidation catalyst 130 to a high regeneration temperature (e.g., equal to or greater than 550 degrees celsius).

At 208, in response to the desulfation condition being met (204: YES), the temperature of the oxidation catalyst is increased to a first regeneration temperature or a low regeneration temperature. For example, in response to the sulfur concentration determination module 174b determining that the concentration of sulfur in the fuel consumed by the engine 10 is equal to or greater than a sulfur concentration threshold (e.g., 15ppm), or the temperature determination module 174c determining that the measured exotherm across the oxidation catalyst 130 is outside of a predetermined range, the temperature control module 174d commands the oxidation catalyst heater 134 to increase the temperature of the oxidation catalyst 130 to a low regeneration temperature (e.g., greater than or equal to 400 degrees celsius and less than 550 degrees celsius).

At 210, the temperature of the oxidation catalyst is maintained at the low regeneration temperature for a predetermined period of time. For example, the temperature control module 174d is configured to maintain the temperature at the low regeneration temperature for a predetermined period of time (e.g., 15 minutes to 30 minutes) to remove the sulfur accumulated on the oxidation catalyst 130. The method 200 may then proceed to operation 206.

Fig. 9A-9B are schematic flow diagrams of a method 300 for desulfating an SCR catalyst (e.g., SCR catalyst 150) for regeneration of the SCR catalyst, according to an embodiment. The SCR catalyst may be included in an aftertreatment system (e.g., aftertreatment system 100) configured to decompose constituents of exhaust gas produced by an engine (e.g., engine 10). Although the method 300 is described herein as being implemented with the controller 170, it should be understood that the operations of the method 300 may be implemented in any controller included in any aftertreatment system.

Method 300 includes determining NO of SCR catalyst at 302_XThe conversion efficiency. For example, NO_XThe conversion efficiency determination module 174e may receive signals from the first and/or second sensors 103 and 105 and determine NO of the SCR catalyst 150 therefrom_XThe conversion efficiency.

At 304, method 300 includes determining NO for the SCR catalyst_XWhether the conversion efficiency is less than a predetermined threshold. For example, NO_XThe conversion efficiency determination module 174e may determine NO_XWhether the conversion efficiency is less than a predetermined threshold (e.g., 90% NO) due to sulfur accumulation on the SCR catalyst 150_XConversion efficiency). The NO is_XThe conversion efficiency may be an instantaneous or time averaged value over a particular operating condition and time interval.

NO responsive to SCR catalyst_XThe conversion efficiency is greater than the predetermined threshold (304: no), and the method 300 returns to operation 302. NO determination for SCR catalysts_XThe conversion efficiency is less than the predetermined threshold (304: yes), method 300 includes, at 306, increasing the temperature of the SCR catalyst to a first regeneration temperature, and targeting the SCR reductant dosing to maintain ANR>1.0, and maintaining the temperature of the SCR catalyst at the first regeneration temperature for a predetermined first period of time. For example, the temperature control module 174d may command the hydrocarbon introduction assembly 132 to dose hydrocarbons into the oxidation catalyst 130 to increase the outlet temperature, or command the SCR catalyst heater 154 to heat the SCR catalyst 150 to a predetermined first regeneration temperature (e.g., greater than or equal to 400 degrees celsius and less than 550 degrees celsius, including 400 degrees celsius and 550 degrees celsius), and maintain the SCR catalyst at the first regeneration temperature for a first period of time (e.g., approximately 30 minutes-60 minutes). In some embodiments, the low temperature regeneration operation may be initiated in response to a sulfur concentration in the fuel combusting the produced exhaust gas being greater than a predetermined sulfur concentration threshold (e.g., greater than 15ppm) but less than a critical sulfur concentration threshold (e.g., 500 ppm).

In some embodiments, method 300 further includes increasing the temperature of the SCR catalyst to a predetermined second regeneration temperature that is higher than the first regeneration temperature but lower than the high regeneration temperature (e.g., less than 550 degrees celsius), and maintaining the SCR catalyst at the second regeneration temperature for a predetermined second period of time, at 308. For example, the temperature control module 174d may be configured to increase or warm the temperature of the SCR catalyst 150 from a first regeneration temperature (e.g., 400 degrees celsius or 450 degrees celsius) to a second regeneration temperature (e.g., 500 degrees celsius) that is less than the high regeneration temperature (e.g., 550 degrees celsius), and maintain the SCR catalyst 150 at the second regeneration temperature for a second predetermined period of time (e.g., approximately 15 minutes-30 minutes).

At 310, method 300 includes determining whether a time interval between regeneration events satisfies a time interval threshold. For example, the controller 170 may determine whether the time interval between subsequent regeneration events for regenerating the SCR catalyst 150 is equal to or greater than a predetermined time interval threshold, such as 12 hours. In response to the time interval satisfying the time interval threshold (310: yes), e.g., the time interval is equal to or greater than the time interval threshold (e.g., 12 hours), the method 300 returns to operation 302.

In response to the time interval not satisfying the time interval threshold (310: no), e.g., the time interval between regeneration events is less than 12 hours, method 300 includes, at 312, heating the SCR catalyst to a third regeneration temperature (e.g., less than 550 degrees celsius) that is greater than the first regeneration temperature but less than the high regeneration temperature, and maintaining the SCR catalyst 150 at the third, lower regeneration temperature. For example, the temperature control module 174d may command the SCR catalyst heater 154 to heat the SCR catalyst 150 to a third regeneration temperature (e.g., 500 degrees celsius) for a third period of time (e.g., 30 minutes-60 minutes).

In some embodiments, the method 300 includes determining whether a time interval between regeneration events satisfies a critical time interval at 314. In response to the time interval satisfying the critical time interval threshold (314: yes), e.g., the time interval is greater than the critical time interval (e.g., 12 hours), the method 300 returns to operation 302. In response to the time interval not satisfying the threshold time interval (314: no), e.g., less than the threshold time interval, method 300 includes increasing the temperature of the SCR catalyst 150 to a fourth regeneration temperature (e.g., 550 degrees Celsius or greater) in a subsequent regeneration event at 316. For example, the temperature control module 174d may increase the temperature of the SCR catalyst 150 to a high regeneration temperature during a subsequent regeneration event.

At 318, method 300 includes again determining whether the time interval satisfies the critical time interval. If the critical time interval is met (318: Yes), the method 300 returns to operation 302. At 320, a fault code is generated in response to the critical time interval still not being satisfied (318: NO). For example, the fault code generation module 174g may generate a fault code and may also be configured to illuminate the MIL. In some embodiments, the method 300 may further include generating a fault code in response to the concentration of sulfur in the fuel being equal to or greater than a threshold sulfur level threshold (e.g., 500 ppm).

At 322, method 300 may include determining whether a fuel condition is satisfied. For example, the controller 170 may determine whether all of the fuel including a sulfur concentration greater than a threshold sulfur concentration is consumed, or whether the fuel tank is refilled. If the fuel condition is satisfied (322: Yes), the method 300 returns to operation 302. If the fuel condition is not met (322: NO), the method returns to operation 320 and a fault code is generated.

It should be noted that the term "exemplary" as used herein to describe various embodiments is intended to indicate that such embodiments are possible examples, representations, and/or illustrations of possible embodiments (and such terms are not intended to imply that such embodiments must be specific or best examples).

As used herein, the term "about" generally means plus or minus 10% of the stated value. For example, about 0.5 would include 0.45 and 0.55, about 10 would include 9 to 11, and about 1000 would include 900 to 1100.

The term "coupled" and similar terms as used herein mean that two members are directly or indirectly connected to each other. Such a connection may be fixed (e.g., permanent) or movable (e.g., removable or releasable). Such connection may be made with the two members or the two members and any additional intermediate member being integrally formed with each other as a single unitary body or with the two members or the two members and any additional intermediate member being attached to each other.

It is important to note that the construction and arrangement of the various exemplary embodiments are illustrative only. Although only a few embodiments have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described herein. Furthermore, it should be understood that features from one embodiment disclosed herein may be combined with features of other embodiments disclosed herein, as would be understood by one of ordinary skill in the art. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the embodiments herein.

While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any embodiments or of what may be claimed, but rather as descriptions of features specific to particular implementations of particular embodiments. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.