Apparatus, system, and method for exhaust aftertreatment efficiency enhancement

An apparatus, system, and method are disclosed for enhancing the efficiency of an exhaust aftertreatment application. The method may include determining the current operating conditions of the application, the optimal operating conditions of a target component, and the performance criteria of a conditioning component relative to the optimal operating conditions. The method may include determining an optimal fraction of an exhaust flow to pass through the conditioning component to achieve the optimal operating conditions of the target component. The method may further include manipulating a bypass valve position based on the optimal fraction of exhaust flow to pass through the conditioning component. The target component may be a selective catalyst reduction (SCR) component that operates optimally at a designed NO2/NOx mole ratio. The conditioning component may be a diesel oxidation catalyst (DOC) that affects the NO2/NOx mole ratio. A method is thereby provided to operate an exhaust aftertreatment application more efficiently relative to an application without the invention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the efficient operation of engine aftertreatment systems, and more particularly relates to aftertreatment systems comprising a diesel particulate filter or a selective catalytic reduction system.

2. Description of the Related Art

Diesel emissions regulations are driving many modern diesel engine systems to utilize aftertreatment devices to clean up exhaust emissions downstream of the engine. These devices typically have the property that they cannot be reconfigured in real time, and therefore must be designed such that the engine system can meet emissions regulations at all operating points. In practical terms, this typically means that the aftertreatment devices are configured to treat the full engine exhaust at rated operation, or maximum load on the engine system.

While this method makes an emissions compliant engine, it produces an over-designed system that operates at a low efficiency in many operating conditions for many applications. Some examples are in selective catalytic reduction (SCR) systems, and diesel particulate filters (DPFs).

SCR systems are utilized to reduce NOxin the exhaust gas to nitrogen. The SCR system operates optimally when the engine out NOxcomprises equal parts NO and NO2. The NOxcoming out of a diesel engine is typically mostly NO, and a component configured active to NOx, specifically to convert NO to NO2, is often installed upstream of the SCR component. This upstream component may be a diesel oxidation catalyst (DOC). The DOC typically contains a platinum-based catalyst, and is usually designed to convert enough NO to NO2that the SCR system can convert enough NOxat rated engine operation to meet emissions regulations. The result of this is that at many operating conditions, the DOC converts too much NO to NO2, resulting in excessive use of the SCR reagent (usually urea or ammonia) as the SCR system operates at non-optimal efficiency with the excess NO2.

Another inefficiency in SCR systems is that an SCR catalyst may require a certain temperature to convert sufficient NOx for the engine system to meet emissions constraints. However, in a cold start environment, there may be several components upstream of the SCR catalyst that must be heated up before the exhaust stream will reach the SCR catalyst at a temperature sufficient to heat the SCR catalyst up. While those emissions components may be important for meeting overall emissions, the engine system may be designed such that they only need to be utilized intermittently to achieve the emissions targets. In one example, a DPF may be upstream of the SCR catalyst. The DPF may be 95% efficient at trapping particulates, but the engine system may only need 80% trapping to meet the emissions targets.

Some DPF systems utilize a DOC to convert NO to NO2, and enhance oxidation of soot in the DPF during normal operation between oxygen-based regeneration events. In these systems, the DOC may be sized for a high flow rate of exhaust flow, and there may be excessive NO to NO2conversion during lower flow rates. Excessive NO2can exceed design limitations—for example a limitation on the amount of NO2out of the tailpipe to control brown smoke. Further, as a DPF becomes loaded with soot, it may begin exerting excessive backpressure on the engine.

From the foregoing discussion, it should be apparent that a need exists for an apparatus, system, and method that provides for enhancing efficiency in an exhaust aftertreatment system. Beneficially, such an apparatus, system, and method would manage an exhaust stream to help an SCR system perform optimally, to assist a DPF in performing optimally, and/or minimize the time and fuel consumed in getting an SCR system up to operating temperatures.

SUMMARY OF THE INVENTION

The present invention has been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available particulate filter systems. Accordingly, the present invention has been developed to provide an apparatus, system, and method for enhancing the efficiency of an aftertreatment system that overcome many or all of the above-discussed shortcomings in the art.

An apparatus is provided to enhance the efficiency of an aftertreatment system. The apparatus may have an intake module configured to receive a fluid stream. The apparatus may further include a bypass valve configured to direct a first fraction of the fluid stream to a first flowpath, and a second fraction of the fluid stream to a second flowpath. One or both flowpaths may comprise at least one conditioning component configured to change some characteristic of the fluid stream relevant to a downstream target component. The apparatus may further include a controller provided with a plurality of modules configured to functionally execute some aspects of the invention.

The controller may comprise a sensing module, a target selection module, a conditioning performance module, a fraction determination module, and a valve position module. The controller may further comprise an emissions module.

The sensing module may be configured to interpret a plurality of operating conditions which may include temperatures, flow rates, and other parameters of the conditioning component(s), the target component(s), and the fluid stream. The target selection module may be configured to interpret the operating criteria of the target component(s). The operating criteria of the target component(s) may indicate the optimal and/or preferred operating parameters for the target component.

The conditioning performance module may be configured to interpret the performance criteria for the conditioning component(s). The performance criteria may indicate the performance of the conditioning component(s) relative to the operating criteria of the target component(s). The fraction determination module may utilize the interpreted operating criteria, the interpreted performance criteria, and the interpreted operating conditions to determine an optimal value for the first fraction, or that portion of the fluid stream that the bypass valve will direct to the first flowpath.

The emissions module may interpret an emissions scheme to determine a minimum first fraction value that will meet the current emissions considerations for the current operating point of the system. The fraction determination module may be further configured to combine the minimum first fraction value with the optimal first fraction value to determine a first fraction target. The valve position module may be configured to manipulate the bypass valve based on the first fraction target.

The target component may comprise a selective catalytic reduction (SCR) component which operates well at an optimal NO2/NOxmole ratio, and at a minimum temperature. The target component may comprise a diesel particulate filter (DPF) configured to collect soot, and that may operate well at certain NO2flow rates through the filter.

The first flowpath may comprise a diesel oxidation catalyst (DOC) as a conditioning component. The first flowpath may further include a DPF as a conditioning component. The second flowpath may comprise a fluid conduit configured to bypass flow around the conditioning component(s) of the first flowpath. The second flowpath may further comprise one or more conditioning components.

A method is presented including the operations to enhance the efficiency of an exhaust aftertreatment system. The method may be operated on a computer programming product. The method may include interpreting a plurality of operating conditions, interpreting operating criteria for each target component, and interpreting performance criteria for each conditioning component. The method may further include interpreting an emissions compliance scheme to determine a minimum first fraction value. The method may include determining a first fraction target based on the minimum first fraction value, the operating criteria, the performance criteria, and the operating conditions. The method may include manipulating a bypass valve position based on the first fraction target.

In one embodiment, a method is presented for modifying an exhaust aftertreatment system to enhance the efficiency of the exhaust aftertreatment system. The method may include installing a bypass valve and a second flowpath on an exhaust aftertreatment system. The method may further include installing a controller on the existing exhaust aftertreatment system. The controller may comprise a sensing module, a target selection module, a conditioning performance module, a fraction determination module, and a valve position module. The controller may further comprise an emissions module.

A system for enhancing the efficiency of an exhaust aftertreatment application is presented. The system may include an internal combustion engine providing an exhaust stream. The system may further include a bypass valve configured to direct a first fraction of the fluid stream to a first flowpath, and a second fraction of the fluid stream to a second flowpath. The first flowpath may comprise a DOC, and the second flowpath may comprise a fluid conduit. The system may further include a mixing component to mix the flow from the first and second flowpaths. The system may include a reagent injector, which may be configured to inject a reducing agent into the exhaust stream. The system may further include a target component which may be an SCR component.

The system may further include a controller provided with a plurality of modules configured to functionally execute some aspects of the invention. The controller may comprise a sensing module, a target selection module, a conditioning performance module, a fraction determination module, and a valve position module. The controller may further comprise an emissions module.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is a schematic block diagram depicting one embodiment of a system100for enhancing exhaust aftertreatment efficiency in accordance with the present invention. The system100may include an internal combustion engine102producing an exhaust stream104. The exhaust stream104may be a fluid stream of combustion byproducts containing particulate matter and nitrogen oxides (NOx). The system100may further include an aftertreatment system103configured to reduce one or more emissions of the exhaust stream104.

The aftertreatment system103may comprise a bypass valve106configured to direct a first fraction108of the exhaust stream104to a conditioning component110, which may be a diesel oxidation catalyst (DOC). The bypass valve106may be further configured to direct a second fraction of the exhaust stream to a fluid conduit114. The sum of the first fraction108and the second fraction112may equal 100 percent of the exhaust stream104. For example, if the first fraction108is 40% of the exhaust stream104, the second fraction112may be 60% of the exhaust stream104.

The aftertreatment system103may further include a mixing component116configured to combine the flow from the DOC110and the fluid conduit114. In the embodiment ofFIG. 1, the bypass valve106is thereby configured to direct none, some, or all of the exhaust stream104to the DOC110, and to bypass the DOC110with the remainder of the flow.

The aftertreatment system103may further include a reagent injector118configured to add a reducing reagent to the flow from the mixing component116. Without limitation, the reducing reagent may be a chemical such as ammonia or urea. The aftertreatment system103may further include a target component120which may be a selective catalytic reduction (SCR) component. The SCR component120may be configured to reduce NOxto N2within the flow from the mixing component116.

The aftertreatment system103may further include a controller124which may comprise an electronic control module (ECM). The controller124may be configured to interpret various operating conditions within the system100, and to control the bypass valve106. Without limitation, the controller124may interpret operating conditions by communication over a datalink with other controllers (not shown), and/or by communication with one or more sensors within the system100. The controller124may control the bypass valve106by electronic commands over a datalink, electronic control of the valve, pneumatic control of the valve, or by other methods known in the art.

FIG. 2is a schematic block diagram depicting one embodiment of a controller124in accordance with the present invention. The controller124may comprise a sensing module202configured to interpret a plurality of operating conditions204. Without limitation, the sensing module202may interpret the plurality of operating conditions204through electronic communication with sensors, through communication over a datalink to other electronic control modules, and/or through virtual sensors which may comprise calculated values of certain operating conditions based on other measured parameters. The plurality of operating conditions204may comprise one or more of an exhaust stream104flow rate, a NOxfraction in the exhaust stream104, an NO2/NOxmole ratio in the exhaust stream104, a temperature in the DOC110, and various other temperatures, pressures, compositions, flow rates, and other operating parameters within the system100.

The controller124may further comprise a target selection module206configured to interpret operating criteria208for the SCR component120. The operating criteria208may comprise a NOxto N2conversion based on an NO2/NOxmole ratio into the SCR component120from the mixing component116. The operating criteria208may comprise NOxto N2conversion values at a given exhaust stream104flow rate and NOxfraction in the exhaust stream104. The operating criteria208may further comprise several sets of NOxto N2conversions based on an NO2/NOxmole ratio for several different exhaust stream104flow rates and NOxfractions in the exhaust stream104. Without limitation, interpreting the operating criteria208may comprise reading the criteria from a datalink, reading the criteria from a data memory location, measuring the criteria electronically, or calculating the criteria from other parameters according to a defined function or algorithm.

The controller124may further comprise a conditioning performance module210configured to interpret performance criteria212for the conditioning component110. In one embodiment, the performance criteria212may comprise an NO2/NOxmole ratio out of the DOC110based on a flow rate108through the DOC110. In one embodiment, the performance criteria208may comprise several sets of NO2/NOxmole ratios out of the DOC110based on the NOxfraction in the exhaust stream104, and/or based on the temperature of the DOC110. Without limitation, interpreting the performance criteria212may comprise reading the criteria from a datalink, reading the criteria from a data memory location, measuring the criteria electronically, or calculating the criteria from other parameters according to a defined function or algorithm.

The controller124may further comprise a fraction determination module214configured to determine a first fraction108target based on the plurality of operating conditions204, the operating criteria208, and the performance criteria212. In one embodiment, the fraction determination module214may determine a first fraction target216such that if the first fraction108achieves the first fraction target216, an optimal NO2/NOxmole ratio is achieved at the mixing component116.

For example, the optimal NO2/NOxmole ratio at the mixing component116may be 0.5, a current NO2/NOxmole ratio in the exhaust stream104may be 0.1, the exhaust stream104may be flowing at 20 lbm/min, the DOC110temperature may be 300 deg C., and the performance criteria for the DOC110may indicate an NO2/NOxmole ratio out of the DOC110of 0.83 at 5 lbm/min flow through the DOC110, 0.65 at 20 lbm/min flow through the DOC110, with a linear interpolation of NO2/NOxmole ratio between the defined flow rates. For the example, the fraction determination module214may determine that a first fraction108of 0.623, or 12.45 lbm/min through the DOC110and 7.55 lbm/min through the fluid conduit114, would yield a NO2/NOxmole ratio of approximately 0.5 at the mixing component116. In the example, the fraction determination module214sets the first fraction target216to 0.623.

The controller124may further comprise an emissions module210configured to determine a minimum first fraction value220based on an emissions compliance scheme222. For example, the conditioning component110may comprise a diesel particulate filter (DPF), the emissions compliance scheme222may indicate a maximum particulate emissions level of 0.01 grams/hp-hour, the operating conditions204may indicate that the engine is emitting 0.03 grams/hp-hour of particulates, and the performance criteria212may indicate that the DPF is removing 95% of the engine102out particulates. In the example, the emissions module210may determine that the minimum first fraction value220must be 0.103 for the system100to meet the emissions requirements.

In an alternate example, the emissions compliance scheme222may indicate that the bypass valve106may not bypass more than 30% of the exhaust flow104past the conditioning component110, and only for fifteen minutes out of each hour of engine102operation. In the example, the emissions module210determines whether bypass time is available under the emissions scheme222. If bypass time is available, the emissions module210may set the first fraction value220to 70%, and if bypass time is not available, the emissions module210may set the first fraction value220to 100%.

The fraction determination module214may be further configured to determine the first fraction target216based on the first fraction value220. For example, the fraction determination module214may determine the ideal first fraction108for the target component120, and set the first fraction target216to the greater of the first fraction value220and the ideal first fraction108for the target component120. The fraction determination module214may utilize other relevant considerations in determining the first fraction target216. For example, the fraction determination module214may override the first fraction value220in a condition where a failure has occurred in the system100.

The controller124may further comprise a valve position module218. The valve position module218may be configured to manipulate the bypass valve106position based on the first fraction target216. For example, the first fraction target216may be 0.60, the bypass valve position106required to meet the first fraction target216may be 0.83, and the current bypass valve position106may be 0.40. In the example, the valve position module218may operate a proportional-integral-derivative (PID) controller to command the valve106to the position 0.83. The control of the valve may comprise a command on a datalink, an electronic signal, and the like. The valve position module218may override the first fraction target216in certain circumstances, for example where a failure has occurred in the system100.

FIG. 3is a schematic block diagram depicting one embodiment of an apparatus300for enhancing the efficiency of an exhaust aftertreatment system103in accordance with the present invention. The apparatus300may comprise an intake module302which may comprise a fluid conduit configured to receive a fluid stream104. The apparatus may further comprise a bypass valve106configured to direct a first fraction108of the fluid stream104to a first flowpath304, wherein the first fraction108comprises an amount between zero and one hundred percent inclusive of the fluid stream104. The first flowpath304may comprise one or more conditioning components which may comprise aftertreatment components such as a DOC and/or a DPF.

The bypass valve106may be further configured to direct a second fraction112of the fluid stream104to a second flowpath306, wherein the second fraction112comprises an amount such that the first fraction108added to the second fraction112comprise one hundred percent of the fluid stream104. The second flowpath may comprise one or more aftertreatment components, and/or a fluid conduit configured to convey the second fraction112of the fluid stream104. The apparatus300may further comprise a controller124which may comprise a sensing module202, a target selection module206, a conditioning performance module210, and a fraction determination module214.

FIG. 4is a schematic block diagram depicting an alternate embodiment of an apparatus400for enhancing the efficiency of an exhaust aftertreatment system103in accordance with the present invention. In addition to the embodiment described inFIG. 3, the apparatus400may further comprise a mixing component116configured to combine the flow from the first flowpath304with the flow from the second flowpath306. The apparatus400may further comprise a target component120which may be an SCR component configured to receive the combined flow from the mixing component, and further configured to reduce NOxwithin the exhaust stream104to N2. In the embodiment ofFIG. 4, the controller124may manipulate the bypass valve106to enhance the efficiency of the SCR component120.

FIG. 5is a schematic block diagram depicting an alternate embodiment of an apparatus500for enhancing the efficiency of an exhaust aftertreatment system103in accordance with the present invention. In addition to the description inFIG. 4, the apparatus500may further comprise a first flowpath304comprising a conditioning component which may be a DOC, and a second flowpath306comprising a fluid conduit. The DOC304may be configured to convert a portion of the NO in the exhaust stream104to NO2, and the fluid conduit306may be configured to deliver the second fraction112of the exhaust stream104to the mixing component116.

The operating conditions204may comprise a fluid stream104mass flow rate, a NOxfraction in the fluid stream104, an NO2/NOxmole ratio in the fluid stream104, and a temperature of the DOC304. The performance criteria212may comprise an NO2/NOxmole ratio out of the DOC304based on a flow rate through the DOC304, and a temperature of the DOC304. The operating criteria208may comprise a NOxto N2conversion based on an NO2/NOxmole ratio into the SCR component120.

In the embodiment ofFIG. 5, the controller124may manipulate the bypass valve106to enhance the efficiency of the SCR component120. In one embodiment, the apparatus500may be configured such that the fluid conduit306comprises a lower thermal capacitance than the DOC304, and the controller124may be configured to bypass some or all of the exhaust flow104past the DOC304at some operating conditions where the SCR component120should be heated as quickly as possible. In the example embodiment, the apparatus500enhances the efficiency of the aftertreatment system103by reducing the time and fuel cost for the SCR component120to begin operating effectively after a cooldown.

FIG. 6is a schematic block diagram depicting an alternate embodiment of an apparatus600for enhancing the efficiency of an exhaust aftertreatment system103in accordance with the present invention. In addition to the description inFIG. 5, the apparatus600, the first flowpath304may comprise two conditioning components, a DOC110and a DPF602. The DOC110may be configured to convert a portion of the NO in the exhaust stream104to NO2, and the fluid conduit306may be configured to deliver the second fraction112of the exhaust stream104to the mixing component116. The DPF602may be configured to filter particulate matter from the first fraction108, to convert some NO to NO2via catalytic oxidation, and/or to convert some NO2to NO when oxidizing soot via an NO2based mechanism.

In the embodiment ofFIG. 6, the controller124may manipulate the bypass valve106to enhance the efficiency of the SCR component120. The operating condition204may further include the temperature of the SCR component120. In one embodiment, the apparatus600may be configured such that the fluid conduit306comprises a lower thermal capacitance than the first flowpath304, and the controller124may be configured to bypass some or all of the first flowpath304at some operating conditions where the SCR component120should be heated as quickly as possible. In the example embodiment, the apparatus600enhances the efficiency of the aftertreatment system103by reducing the time and fuel cost for the SCR component120to begin operating effectively after a cooldown.

In one embodiment, the apparatus600is configured to enhance the efficiency of the exhaust aftertreatment system103by bypassing a portion of the first flowpath304to reduce backpressure on the engine from the DPF602, and/or to generate temperature quickly within the first flowpath304to provide more rapid and fuel efficient oxygen-based regeneration of the DPF602.

FIG. 7is a schematic block diagram depicting an alternate embodiment of an apparatus700for enhancing the efficiency of an exhaust aftertreatment system103in accordance with the present invention. In addition to the description inFIG. 5, the apparatus700may include second target component which may be a DPF602.

In the embodiment ofFIG. 7, the controller124may manipulate the bypass valve106to enhance the efficiency of the SCR component120and/or the DPF602. The DOC304may be configured to convert NO to NO2. The controller124may be configured to manipulate the bypass valve106to achieve an optimal NO2/NOxmole ratio at the mixing component116for the SCR component120, and/or to achieve a sufficient NO2level at the mixing component116to support oxidation of soot within the DPF602while meeting constraints on maximum NO2levels due to emissions, sociability, and other concerns.

The operating criteria208may thereby comprise an NO2 flow rate into the DPF602, and standard prioritization algorithms may be utilized to select between meeting the NO2levels optimal for the DPF602and the NO2levels optimal for the SCR component120. For example, the DPF602component may be presumed, in one embodiment, to never request an NO2 flow rate unless a soot regeneration is required, therefore in the example the DPF602request always wins if present, while the SCR component120request is met whenever a DPF602request is not present.

FIG. 8is a schematic block diagram depicting an alternate embodiment of an apparatus800for enhancing the efficiency of an exhaust aftertreatment system103in accordance with the present invention. In addition to the description inFIG. 5, the apparatus800may include a second conditioning component306, which may be a second DOC, in the second flowpath. In one embodiment, the second DOC306may be configured to convert a portion of the NO in the second fraction112to NO2. The operating conditions204may further comprise a temperature of the second DOC306. In one embodiment, the performance criteria may further comprise a second NO2/NOxmole ratio out of the second DOC based on a flow rate through the second DOC.

One potential advantage of an embodiment corresponding toFIG. 8is that all of the fluid stream104is treated with a catalyst, rather than some of the fluid stream104completely bypassing all catalysts. For example, the first DOC304may be configured with the NO to NO2 conversion capacity that may be required at a low engine load like idle. The second DOC306may be configured with the additional NO to NO2conversion capacity that would be required at full engine load. Rather than bypassing flow through a fluid conduit that would not clean up unburned hydrocarbons, all of the flow passes through a DOC and hydrocarbons are cleaned up, while at the same time the NO to NO2conversion capacity can be optimized. The embodiment ofFIG. 8may be more expensive than a single DOC embodiment, and therefore both embodiments are useful and the economics, or other appropriate decision criteria, of a particular application should be used to determine an appropriate implementation for each application.

FIG. 9is a schematic block diagram depicting an alternate embodiment of an apparatus900for enhancing the efficiency of an exhaust aftertreatment system103in accordance with the present invention. In addition to the description inFIG. 8, the apparatus900may include a second target component602which may be a DPF. The DPF602may be configured to receive the combined flow from the mixing component116. The operating criteria208for the DPF may comprise a soot oxidation rate based on an NO2flow rate into the DPF.

FIG. 10is a schematic block diagram depicting an alternate embodiment of an apparatus1000for enhancing the efficiency of an exhaust aftertreatment system103in accordance with the present invention. In addition to the description inFIG. 8, the apparatus1000may comprise a first and second conditioning component602in the first flowpath304. The first conditioning component110may be a first DOC, and the second conditioning component602may be a DPF.

FIG. 11is a schematic block diagram depicting an alternate embodiment of an apparatus1100for enhancing the efficiency of an exhaust aftertreatment system103in accordance with the present invention. In addition to the description ofFIG. 3, the first flowpath304may comprise a DOC, and the second flowpath306may comprise a fluid conduit. The apparatus1100may further comprise a mixing component116.

The apparatus1100may further comprise at least one target component which may be a DPF1102. The performance criteria212for the DOC304may comprise an NO2/NOxmole ratio out of the DOC304based on a flow rate through the DOC304. The operating criteria208for the DPF306may comprise a soot oxidation rate based on an NO2flow rate into the DPF306. The at least one operating condition204may comprise a mass flow rate of the fluid stream, a NOx concentration of the fluid stream104, a temperature of the DOC, and a temperature of the DPF.

One embodiment ofFIG. 11may be useful where the DPF306utilizes an NO2based regeneration as a primary mechanism for oxidizing soot from the DPF306. The DOC304can be configured to convert most of the available NOxfrom the fluid stream104to NO2. During many operating conditions, generating such a quantity of NO2may create excessive brown smoke or other issues. Therefore, when large quantities of NO2are unnecessary, the controller124can bypass much of the fluid stream104around the DOC304to prevent these issues.

FIG. 12is a schematic block diagram depicting an alternate embodiment of an apparatus1200for enhancing the efficiency of an exhaust aftertreatment system103in accordance with the present invention. In addition to the description ofFIG. 11, one embodiment ofFIG. 12may comprise a second DOC306in the second flowpath. Similar to the embodiment ofFIG. 8, this may increase the costs of the apparatus1200, but provides capabilities that bypassing through fluid conduit will not provide.

FIG. 13is an illustration of one embodiment of performance criteria212for a conditioning component304,306in accordance with the present invention. In one embodiment, the performance criteria212may comprise an NO2/NOx mole ratio1302out of a DOC110based on a flowrate through the DOC110. In one embodiment, the performance criteria212is dependent upon the temperature of the DOC110, and therefore multiple curves1306,1308based on temperature may be provided. In a further embodiment, the performance criteria212is dependent upon the NO2/NOxmole ratio entering the DOC, and multiple curves (not shown) based on NO2/NOxmole ratio entering the DOC may be provided.

The curves shown inFIG. 13comprise discrete data points with linear interpolation between data points. However, functions, model equations, table lookups, non-linear interpolation, extrapolation, and other data storage and retrieval techniques are contemplated within the scope of the invention for the performance criteria212.

FIG. 14is an illustration of one embodiment of operating criteria208for a target component120in accordance with the present invention. The operating criteria208may comprise a NOxto N2conversion1402based on an NO2/NOxmole ratio1404into the SCR component. A single curve1406is illustrated inFIG. 14, although multiple curves may be developed based on the SCR120temperature, a total NOx flow rate into the SCR120, and other parameters which may affect the final NOxto N2conversion.

FIG. 15is an illustration of one embodiment of performance criteria212for a second conditioning component306in accordance with the present invention. The performance criteria212for the second conditioning component306may comprise a different set of performance curves than the performance criteria for the first conditioning component304. The curves ofFIG. 15are consistent with a second DOC306with lower capacity than a first DOC304with performance curves shown inFIG. 13.

FIG. 16is a schematic flow chart illustrating one embodiment of a method1600for enhancing the efficiency of an exhaust aftertreatment system103in accordance with the present invention. The method1600may comprise a computer program product comprising program code on a computer readable medium.

The method1600may include a sensing module202interpreting1602a plurality of operating conditions204. A target selection module206may interpret1604operating criteria208for each of one or more target components. The target component may comprise an SCR component120, and the operating criteria208may comprise a NOxto N2conversion based on an NO2/NOxmole ratio into the SCR component120. A conditioning performance module210may interpret1606performance criteria212for each of one or more conditioning components. An emissions module218may interpret an emissions compliance scheme222to determine a minimum first fraction value220for a first fraction108of a split fluid stream104.

A fraction determination module214may determine1612a first fraction target216from the operating conditions204, the operating criteria208, the performance criteria212, and the first fraction value220. A valve position module218may manipulate1614a bypass valve106position based on the first fraction value220.

FIG. 17is a schematic flow chart illustrating one embodiment of a method1700to modify an exhaust aftertreatment application103in accordance with the present invention. A practitioner may install1702a bypass valve106and a second flowpath114on an existing exhaust aftertreatment system103. The practitioner may further install1704a controller124on the existing exhaust aftertreatment system103.

A sensing module202may interpret1602a plurality of operating conditions204. A target selection module206may interpret1604operating criteria208for each of one or more target components. The target component may comprise an SCR component120, and the operating criteria208may comprise a NOxto N2conversion based on an NO2/NOxmole ratio into the SCR component120. A conditioning performance module210may interpret1606performance criteria212for each of one or more conditioning components.

A fraction determination module214may determine1612a first fraction target216from the operating conditions204, the operating criteria208, the performance criteria212, and the first fraction value220. A valve position module218may manipulate1614a bypass valve106position based on the first fraction value220.

From the foregoing discussion, it is clear that the invention provides a system, method, and apparatus for enhancing the efficiency of an exhaust aftertreatment system. The invention overcomes previous limitations in the art by allowing a designer to optimally size aftertreatment components rather than over-designing them to cover the intended range of operation, and the invention allows the aftertreatment system to achieve operational temperatures quickly with a minimal energy input and efficiency loss.