Outlet passage for aftertreatment sensor

An outlet assembly for an aftertreatment system comprises an outlet conduit configured to receive an exhaust gas from the aftertreatment system. The outlet conduit defines a first aperture through a sidewall thereof. An outlet passage is disposed within the outlet conduit. The outlet passage comprises a first end facing an upstream side of the outlet conduit and a second end located downstream from the first end. The second end is fluidly coupled to the first aperture. A hole is defined through an outlet passage sidewall at a radial location that is proximate to the sidewall of the outlet conduit. The hole is configured to allow a sensor to be inserted therethrough into a flow path defined by the outlet passage. The outlet passage is configured to receive a portion of the exhaust gas from the outlet conduit such that the sensor is exposed to the portion of the exhaust gas.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a National Stage of PCT Application No. PCT/US2019/060258, filed Nov. 7, 2019 and the contents of which are incorporated by herein reference in their entirety.

TECHNICAL FIELD

The present application relates generally to the field of sensors for exhaust aftertreatment systems.

BACKGROUND

Exhaust aftertreatment systems are used to receive and treat exhaust gas generated by internal combustion engines. Generally, exhaust gas aftertreatment systems include any of several different components to reduce the levels of harmful exhaust emissions present in the exhaust gas. For example, certain exhaust gas aftertreatment systems for diesel-powered internal combustion engines include a selective catalytic reduction (SCR) system including a catalyst formulated to convert NOx (NO and NO2in some fraction) into harmless nitrogen gas (N2) and water vapor (H2O) in the presence of ammonia (NH3). Generally, in such aftertreatment systems, an exhaust reductant, (e.g., a diesel exhaust fluid such as urea) is injected into the SCR system to provide a source of ammonia, and mixed with the exhaust gas to partially reduce the NOx gases. The reduction byproducts of the exhaust gas are then fluidly communicated to the catalyst included in the SCR system to decompose substantially all of the NOx gases into relatively harmless byproducts which are expelled out of the aftertreatment system. The exhaust gas also includes particulate matter (PM) such as soot, ash, dust, debris or inorganic PM entrained therein. Generally, filters are used in aftertreatment systems to filter the PM, and PM sensors are used downstream of the filter to measure an amount of PM that remains in the exhaust gas downstream of the filter that can be used to determine a filtering efficiency of the filter. Other sensors may also be disposed downstream of the filter and/or SCR system to determine various operational parameters of the exhaust gas.

SUMMARY

Embodiments described herein relate generally to systems and methods for enhancing performance of a sensor for an aftertreatment system and in particular, to an outlet assembly that includes an outlet passage disposed within the outlet conduit and configured to receive a portion of the exhaust gas flowing through the outlet passage. A sensing tip of a sensor is disposed through the outlet passage such that the sensor is exposed to the portion of the exhaust gas.

In some embodiments, an outlet assembly for an aftertreatment system comprises: an outlet conduit configured to receive an exhaust gas flow of an exhaust gas flowing through the aftertreatment system, the outlet conduit defining a first aperture through a sidewall thereof; and an outlet passage disposed within the outlet conduit, the outlet passage comprising: a first end facing an upstream side of the outlet conduit, a second end located downstream from the first end, the second end fluidly coupled to the first aperture, and a hole defined through an outlet passage sidewall at a radial location that is proximate to the sidewall of the outlet conduit, the hole configured to allow a sensor to be inserted therethrough into a flow path defined by the outlet passage, wherein the outlet passage is configured to receive a portion of the exhaust gas from the outlet conduit such that the sensor is exposed to the portion of the exhaust gas.

In some embodiments, an aftertreatment system comprises: an exhaust conduit defining an internal volume within which at least one aftertreatment component configured to treat constituents of an exhaust gas flowing through the aftertreatment system is disposed; an outlet assembly is fluidly coupled to the exhaust conduit and configured to receive the exhaust gas from the exhaust conduit, the outlet assembly comprises: an outlet conduit coupled to the exhaust conduit, the outlet conduit defining a first aperture through a sidewall thereof, and an outlet passage disposed within the outlet conduit, the outlet passage comprising: a first end facing an upstream side of the outlet conduit, a second end located downstream from the first end, the second end fluidly coupled to the first aperture, and a hole defined through an outlet passage sidewall at a radial location that is proximate to the sidewall of the outlet conduit. A sensor is disposed through the hole into the flow path defined by the outlet passage, wherein the outlet passage is configured to receive a portion of the exhaust gas from the outlet conduit such that the sensor is exposed to the portion of the exhaust gas.

In some embodiments, a method for enhancing a functionality of a sensor of an aftertreatment system comprises: providing an exhaust conduit configured to house an aftertreatment component of the aftertreatment system; coupling an outlet assembly to the exhaust conduit, the outlet assembly comprising: an outlet conduit defining a first aperture through a sidewall thereof, and an outlet passage disposed within the outlet conduit, the outlet passage comprising: a first end facing an upstream side of the outlet conduit, a second end located downstream from the first end, the second end fluidly coupled to the first aperture, and a hole defined through an outlet passage sidewall at a radial location that is proximate to the sidewall of the outlet conduit, wherein the outlet conduit is coupled to the exhaust conduit; and inserting a sensor through the hole into a flow path defined by the outlet passage, wherein the outlet passage is configured to receive a portion of the exhaust gas from the exhaust conduit such that the sensor is exposed to the portion of the exhaust gas.

DETAILED DESCRIPTION

Embodiments described herein relate generally to systems and methods for enhancing performance of a sensor for an aftertreatment system and in particular, to an outlet assembly that includes an outlet passage disposed within the outlet conduit and configured to receive a portion of the exhaust gas flowing through the outlet passage. A sensing tip of a sensor is disposed through the outlet passage such that the sensor is exposed to the portion of the exhaust gas.

Aftertreatment systems include various sensors disposed in an outlet passage or a tail pipe of the aftertreatment system, that are configured to measure various operational parameters, e.g., NOx concentration, oxygen concentration, carbon monoxide concentration, or particulate matter (PM) concentration, in the exhaust gas being expelled into the environment after passing through the aftertreatment system. The functionality, for example, sensitivity of PM sensors may be dependent on the flow velocity of the exhaust gas at a sensing tip of the sensor and/or a sampling volume of the exhaust gas at the sensing tip of the sensor. In conventional aftertreatment systems, the flow velocity of the exhaust gas and sampling volume of the exhaust gas that the sensing tip of the sensor is exposed to are defined by the operational parameters of the engine and/or the aftertreatment system and do not have any structures to alter the flow velocity and/or sampling volume at the outlet of such aftertreatment systems that can enhance the functionality of the sensors disposed proximate to the outlet of the aftertreatment system.

Also, water (e.g., rain water) may sometimes enter into the aftertreatment system through an outlet of the aftertreatment system. If the water entering the aftertreatment system contacts one or more of the sensors disposed in the outlet passage, the water may damage the sensors disposed in the outlet leading to sensor replacement and increased maintenance costs.

Various embodiments of the outlet conduit assemblies described herein may provide one or more benefits including, for example: (1) enhancing functionality of sensors, particularly PM sensors, by providing an outlet passage disposed within an outlet conduit that receives a sensing tip of the sensor and enhances functionality of the sensor by increasing a flow velocity and sampling volume within the outlet passage; (2) protecting a sensing tip of the sensor from water damage; and (3) increasing sensor life, thereby reducing maintenance costs.

FIG.1is a schematic illustration of an aftertreatment system100, according to an embodiment. The aftertreatment system100is configured to receive an exhaust gas (e.g., a diesel exhaust gas) from an engine10and decompose constituents of the exhaust gas such as, for example, NOx gases, CO, etc. The aftertreatment system100includes a reductant storage tank110, a reductant insertion assembly112, a reductant injector120, an exhaust conduit101within which a SCR system150is disposed, and an outlet assembly104coupled to the exhaust conduit101, and may also include a filter140disposed upstream of the SCR system150within the exhaust conduit101.

The engine10may be an internal combustion engine, for example a diesel engine, a gasoline engine, a natural gas engine, a biodiesel engine, a dual fuel engine, an alcohol engine, an E85 or any other suitable internal combustion engine.

The reductant storage tank110contains a reductant formulated to facilitate reduction of the constituents of the exhaust gas (e.g., NOx gases) by a catalyst154included in the SCR system150. In embodiments in which the exhaust gas is a diesel exhaust gas, the reductant may include a diesel exhaust fluid (DEF) which provides a source of ammonia. Suitable DEFs can include urea, aqueous solution of urea or any other DEF (e.g., the DEF available under the tradename ADBLUE®). In particular embodiments, the reductant includes an aqueous urea solution containing 32.5% urea and 67.5% de-ionized water. In other embodiments, the reductant includes aqueous urea solution containing 40% urea and 60% de-ionized water.

The SCR system150is configured to receive and treat the exhaust gas (e.g., a diesel exhaust gas) flowing through the SCR system150in the presence of ammonia. The exhaust conduit101defines an exhaust flow path within which the SCR system150is disposed. In some embodiments, the exhaust conduit101includes an inlet tube102positioned upstream of the SCR system150and configured to receive exhaust gas from the engine10and communicate the exhaust gas to the SCR system150. The outlet assembly104is coupled to the exhaust conduit101and is configured to receive the exhaust gas from the exhaust conduit101.

An upstream sensor103may be positioned in the inlet tube102. The upstream sensor103may include, for example a NOx sensor (e.g., a physical or virtual NOx sensor), an oxygen sensor, a particulate matter sensor, a carbon monoxide sensor, a temperature sensor, a pressure sensor, any other sensor or a combination thereof configured to measure one or more operational parameters of the exhaust gas. Such operating parameters may include, for example, an amount of NOx gases in the exhaust gas, a temperature of the exhaust gas, a flow rate and/or pressure of the exhaust gas.

The SCR system150includes at least one catalyst154positioned within an internal volume defined by the exhaust conduit101. In some embodiments, the SCR system150may comprise a selective catalytic reduction filter (SCRF), or any other aftertreatment component configured to decompose constituents of the exhaust gas (e.g., NOx gases such as such nitrous oxide, nitric oxide, nitrogen dioxide, etc.), flowing through the exhaust conduit101in the presence of a reductant, as described herein. Any suitable catalyst154can be used such as, for example, platinum, palladium, rhodium, cerium, iron, manganese, copper, vanadium based catalysts (including combinations thereof).

The catalyst154can be disposed on a suitable substrate such as, for example, a ceramic (e.g., cordierite) or metallic (e.g., kanthal) monolith core which can, for example, define a honeycomb structure. A washcoat can also be used as a carrier material for the catalyst154. Such washcoat materials can include, for example, aluminum oxide, titanium dioxide, silicon dioxide, any other suitable washcoat material, or a combination thereof. The exhaust gas can flow over and about the catalyst154such that NOx gases included in the exhaust gas are further reduced to yield an exhaust gas which is substantially free of carbon monoxide and NOx gases.

In some embodiments, a filter140(e.g., a diesel particulate filter) may be disposed within the exhaust conduit101upstream of the SCR system150. The filter140is configured to filter particulate matter such as soot or ash entrained in the exhaust gas flowing through the aftertreatment system100. In various embodiments, the aftertreatment system100may also include other aftertreatment components such as, for example, an oxidation catalyst (e.g., a diesel oxidation catalyst), ammonia oxidation catalysts, mixers, baffle plates, or any other suitable aftertreatment component. Such aftertreatment components may be positioned upstream or downstream of the SCR system150within the exhaust conduit101.

The reductant insertion assembly112is fluidly coupled to the reductant storage tank110and is configured to provide the reductant to the reductant injector120positioned upstream of the SCR system150. The reductant insertion assembly112may comprise various structures to facilitate receipt of the reductant from the reductant storage tank110and delivery to the reductant injector120, as described in detail herein.

In various embodiments, the reductant insertion assembly112may include one or more pumps (e.g., a diaphragm pump, a positive displacement pump, a centrifugal pump, a vacuum pump, etc.) for delivering the reductant to the reductant injector120at an operating pressure and/or flow rate. The reductant insertion assembly112may also include filters and/or screens (e.g., to prevent solid particles of the reductant or contaminants from flowing into the one or pumps) and/or valves (e.g., check valves) configured to draw reductant from the reductant storage tank110. Screens, check valves, pulsation dampers, or other structures may also be positioned downstream of the one or more pumps of the reductant insertion assembly112and configured to remove contaminants and/or facilitate delivery of the reductant to the reductant injector120.

In various embodiments, the reductant insertion assembly112may also include a bypass line structured to provide a return path of the reductant from the one or more pumps to the reductant storage tank110. A valve (e.g., an orifice valve) may be provided in the bypass line to allow selective returning of the reductant to the reductant storage tank110(e.g., when the engine10is turned OFF or during a purge operation of the reductant insertion assembly112).

The outlet assembly104is coupled to the exhaust conduit101. The outlet assembly104includes an outlet conduit106configured to receive the exhaust gas from the aftertreatment system100. The outlet conduit106defines a first aperture109through a sidewall107of the outlet conduit106.

The outlet assembly104also includes an outlet passage160disposed within the outlet conduit106. The outlet passage160includes a first end161facing an upstream side of the outlet conduit106, and a second end165located downstream from the first end161. The second end165is fluidly coupled to the first aperture109. A hole is defined through an outlet passage sidewall of the outlet passage160at a radial location that is proximate to the sidewall107of the outlet conduit106where the first aperture109is defined.

The hole is configured to allow a sensor105to be inserted therethrough into a flow path defined by the outlet passage160. In some embodiments, the sensor105may be a PM sensor. In other embodiments, the sensor105may be a NOx sensor, an oxygen sensor, an ammonia sensor, a temperature sensor, or any other suitable sensor or combination of sensors. The outlet conduit106may define a second aperture at a location proximate to the hole upstream of the first aperture109, and configured to allow the sensor105to be inserted therethrough into the outlet passage160via the hole. The second aperture may be defined through the sidewall107of the outlet conduit106upstream of the first aperture109, and the sensor105may be inserted such that a sensing tip of the sensor105is inserted through the hole defined in the outlet passage160and disposed in a flow path defined by the outlet passage160.

The outlet passage160is configured to receive a portion of the exhaust gas flow from the outlet conduit106such that the sensor105is exposed to the portion of the exhaust gas. As shown inFIG.1, the outlet passage160has a smaller cross-sectional width than the outlet conduit106but is sufficiently large for incorporating at least a tip of the sensor105. The cross-sectional width of the outlet passage160determines a sampling volume of the portion of the exhaust gas. The faster velocity of the portion of the exhaust gas enhances the functionality (e.g., increases sensitivity) of the sensor105.

Expanding further, atmospheric pressure of the environment surrounding the aftertreatment system100is substantially less than the pressure inside the outlet conduit106. If an alternate path is provided for the exhaust gases to escape, the flow and velocity of the exhaust gas can be beneficially manipulated. Providing the outlet passage160that is coupled to the first aperture109, provides an alternate outlet for the portion of the exhaust gas, and creates a large pressure difference. As flow occurs from a higher pressure area to a lower pressure area, the exhaust gas naturally tries to escape via the outlet passage160as it provides a quicker and shorter escape route relative to the outlet conduit106.

Because of this created pressure difference, the exhaust gas flow and velocity through the outlet passage160increases. The location of the outlet passage160is selected to be radially inwards of a location at which the sensor105is inserted into the outlet conduit106, thus allowing the sensing tip of the sensor105to be inserted through the hole into the flow path defined by the outlet passage160. The increase in flow volume and velocity of the portion of the exhaust gas and thereby, on the sensing tip of the sensor105relative to bulk of the exhaust gas flowing through the outlet conduit106enhances the functionality of the sensor105.

As shown inFIG.1, the outlet passage may include a first portion162, and a second portion164located downstream of the first portion162. The first portion162is substantially aligned with a gas axis of the outlet conduit and defines a first portion inlet located at the first end161that is configured to receive the portion of the exhaust gas. As used herein, the term “substantially aligned” implies that an axis of the first portion162is within ±5 degrees of the axis of the outlet conduit106. The second portion164is inclined at angle with respect to the first portion162, and defines a second portion outlet located at the second end165configured to expel the portion of the exhaust gas into the environment via the first aperture109. In some embodiments, the angle is in a range of 30 degrees to 90 degrees.

In some embodiments, a tail pipe (e.g., tail pipe208shown inFIG.2) may be coupled to the outlet conduit106downstream of the outlet passage160. In addition to enhancing the functionality of the sensor105, the outlet passage160also protects the sensing tip of the sensor105from coming in contact with any water that makes its way inside the outlet conduit106. In some embodiments, the outlet assembly104may also include a step (e.g., step370shown inFIG.4) disposed on an outer surface of the sidewall107of the outlet conduit106around at least a portion of a periphery of the first aperture109. The step may be configured to prevent water from entering the outlet passage160via the first aperture109. For example, the aftertreatment system100may be mounted vertically on a mounting structure. In such embodiments, the step prevents water (e.g., rain water) from flowing into the outlet passage160thereby offering further protection to the sensing tip of the sensor105.

FIGS.2-3show various views of an outlet assembly204, according to another embodiment. The outlet assembly204is configured to be coupled to an exhaust conduit, for example, the exhaust conduit101. The outlet assembly204includes an outlet conduit206configured to receive an exhaust gas211from an aftertreatment system (e.g., the aftertreatment system100). A tail pipe208may be coupled to an end of the outlet conduit206that is located distal from the exhaust conduit. The outlet conduit206defines a first aperture209through a sidewall207of the outlet conduit206. The outlet assembly204also includes an outlet passage260disposed within the outlet conduit206. The outlet passage260includes a first end261facing an upstream side of the outlet conduit206, and a second end265located downstream from the first end261. The second end265is fluidly coupled to the first aperture209.

A hole268is defined through an outlet passage sidewall of the outlet passage260at a radial location that is proximate to the sidewall207of the outlet conduit206where the first aperture209is defined. The hole268is configured to allow a sensor205(e.g., a PM sensor) to be inserted therethrough into a flow path defined by the outlet passage260. The outlet conduit206may define a second aperture215at a location proximate to the hole268upstream of the first aperture209, and configured to allow the sensor205to be inserted therethrough such that a sensing tip219of the sensor205can be inserted into the outlet passage260via the hole268. The second aperture215may be defined through the sidewall207of the outlet conduit206upstream of the first aperture209. A sealing member217(e.g., a gasket) may be disposed between a body of the sensor205and the second aperture215to fluidly seal the second aperture215once the sensor205is inserted therethrough.

The outlet passage260is configured to receive a portion213of the exhaust gas211from the outlet conduit206such that the sensor205is exposed to the portion213of the exhaust gas. As shown inFIG.2, the outlet passage260has a smaller cross-sectional width (e.g., diameter) than the outlet conduit206. The cross-sectional width of the outlet passage260determines a sampling volume of the portion of the exhaust gas flowing therethrough. The faster velocity of the portion213of the exhaust gas enhances the functionality (e.g., increases sensitivity) of the sensor205, as previously described herein. Furthermore, the outlet passage260also protects the sensing tip219of the sensor205from water damage.

As shown inFIG.2, the outlet passage260may include a first portion262, and a second portion264located downstream of the first portion262. The first portion262is substantially aligned with an axis ALof the outlet conduit206and defines a first portion inlet located at the first end261configured to receive the portion213of the exhaust gas211. The second portion264is inclined at angle α with respect to the first portion262, and defines a second portion outlet located at the second end265configured to expel the portion213of the exhaust gas into the environment via the first aperture209. In some embodiments, the angle α is in a range of 30 degrees to 90 degrees.

FIG.4is a side view of an outlet assembly304for an aftertreatment system (e.g., the aftertreatment system100), according to another embodiment. The outlet assembly304includes the outlet conduit206having the outlet passage260disposed within a flow path defined by the outlet conduit206. The outlet assembly304also includes a step370disposed on an outer surface of the sidewall207of the outlet conduit206around at least a portion of a periphery of the first aperture209. The step370serves as water shield to prevent water, for example, rain water flowing into the first aperture209along an outer surface of the outlet conduit206from entering the outlet passage260via the first aperture209.

FIG.5is a schematic flow diagram of an example method400for enhancing functionality of a sensor of an aftertreatment system (e.g., the aftertreatment system100), according to an embodiment. The method400includes providing an exhaust conduit (e.g., the exhaust conduit101) configured to house an aftertreatment component (e.g., the SCR system150and/or the filter140) of the aftertreatment system (e.g., the aftertreatment system100), at402.

At404, an outlet assembly (e.g., the outlet assembly104,204,304) is coupled to the exhaust conduit. The outlet assembly includes an outlet conduit (e.g., the outlet conduit106,206) that is coupled to the exhaust conduit. The outlet conduit defines a first aperture (e.g., the first aperture109,209) through a sidewall of the outlet conduit. An outlet passage (e.g., the outlet passage160,260) disposed within the outlet conduit. The outlet passage includes a first end facing an upstream side of the outlet conduit, and a second end located downstream from the first end. The second end is fluidly coupled to the first aperture. A hole is defined through an outlet passage sidewall at a radial location that is proximate to the sidewall of the outlet conduit.

At406, a sensor (e.g., the sensor105,205) is inserted through the hole into a flow path defined by the outlet passage. The outlet passage is configured to receive a portion of the exhaust gas from the exhaust conduit such that the sensor is exposed to the portion of the exhaust gas. In some embodiments, a tail pipe may also be coupled to the outlet conduit, at408.

It should be noted that the term “example” 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 term is not intended to connote that such embodiments are necessarily extraordinary or superlative examples).