Exhaust gas sample collector and mixer for aftertreatment system

An exhaust gas treatment system includes an exhaust gas pathway configured to receive exhaust gas from an internal combustion engine. The exhaust gas treatment system further includes a treatment element configured to reduce an emissions component of the exhaust gas, and a sample collector positioned within the exhaust gas pathway downstream of the treatment element. The sample collector includes a plurality of inlet openings spaced about a periphery of the exhaust gas pathway and configured to receive a sample of exhaust gas from the exhaust gas pathway, and an outlet in fluid communication with the plurality of inlet openings. A sensor located at the outlet of the sample collector is configured to measure a characteristic of the sample.

BACKGROUND

The present disclosure relates to exhaust gas treatment systems, and more particularly, to exhaust gas treatment systems including one or more sensors for measuring aspects of the exhaust gas.

Diesel exhaust is typically subject to emissions regulations covering a variety of emission components, including particulate matter and nitrogen oxides (NOx). A variety of exhaust treatment devices have been developed to reduce these emission components. For example, a diesel particulate filter (DPF) can be used to trap diesel particulate matter and oxidize soot, and a selective catalytic reduction (SCR) element can be used to convert the NOxpresent in exhaust gas into other compounds, such as nitrogen, water, and carbon dioxide. Typically, diesel exhaust fluid (DEF) is injected upstream of the SCR element to provide ammonia, which acts as a reducing agent and reacts with the NOxin the presence of the SCR catalyst. A selective catalytic reduction on filter (SCR+F) element combines SCR and DPF functionality such that NOxreduction and particulate matter filtration and oxidation can occur in a single element. One or more treatment devices may provided downstream of the engine to form an exhaust gas treatment system, also known as an aftertreatment system.

SUMMARY

The present disclosure provides, in one aspect, an exhaust gas treatment system including an exhaust gas pathway configured to receive exhaust gas from an internal combustion engine. The exhaust gas treatment system further includes a treatment element configured to reduce an emissions component of the exhaust gas, and a sample collector positioned within the exhaust gas pathway downstream of the treatment element. The sample collector includes a plurality of inlet openings spaced about a periphery of the exhaust gas pathway and configured to receive a sample of exhaust gas from the exhaust gas pathway, and an outlet in fluid communication with the plurality of inlet openings. A sensor located at the outlet of the sample collector is configured to measure a characteristic of the sample.

In some embodiments, the exhaust gas treatment system includes a treatment device having a housing enclosing the treatment element. The housing includes an inlet passage upstream of the treatment element and an outlet passage downstream of the treatment element, and the sample collector is positioned within the outlet passage.

In some embodiments, the sample collector includes a body, a first flange extending from the body, a second flange extending from the body opposite the first flange, and a rib positioned between the first flange and the second flange.

In some embodiments, the first flange, the second flange, and the rib engage an interior wall of the outlet passage such that a first chamber is defined between the first flange and the rib, and a second chamber is defined between the second flange and the rib.

In some embodiments, the rib includes a gap, and the first chamber is in fluid communication with the second chamber through the gap.

In some embodiments, the plurality of inlet openings is formed in the first flange.

In some embodiments, the sample of exhaust gas flows from the plurality of inlet openings into the first chamber, and then into the second chamber through the gap before flowing through the outlet.

In some embodiments, the sample collector includes a torturous flow path from the plurality of inlet openings to the outlet.

In some embodiments, the sensor is a NOx concentration sensor.

In some embodiments, the exhaust gas treatment system further includes a reductant injector configured to inject reductant into the exhaust gas pathway upstream of the treatment element.

In some embodiments, the sample collector includes a tubular collar.

The present disclosure provides, in another aspect, an exhaust gas treatment system including an exhaust gas pathway configured to receive exhaust gas from an internal combustion engine. The exhaust gas treatment system further includes a treatment device with a housing having an inlet passage and an outlet passage, and a collar positioned within the outlet passage such that the collar engages an interior wall of the outlet passage. The collar includes an inlet configured to receive a sample of the exhaust gas and an outlet downstream from the inlet. The collar defines a tortuous pathway from the inlet to the outlet, between the collar and the interior wall. The exhaust gas treatment system further includes a sensor located at the outlet of the collar to measure a characteristic of the sample.

In some embodiments, the sensor is a NOx concentration sensor.

In some embodiments, the tortuous pathway includes a first chamber and a second chamber separated by a rib.

In some embodiments, the rib includes a gap providing fluid communication between the first chamber and the second chamber.

In some embodiments, the sample changes direction at least three times when flowing along the tortuous pathway.

In some embodiments, the inlet is one of a plurality of circumferentially spaced inlets.

In some embodiments, each of the plurality of inlets is in fluid communication with the outlet.

The present disclosure provides, in another aspect, an exhaust gas treatment system including an exhaust gas pathway configured to receive exhaust gas from an internal combustion engine. The exhaust gas treatment system includes a reductant injector configured to inject a reductant into the exhaust gas pathway, a treatment device including an SCR element positioned downstream of the reductant injector, the SCR element configured to reduce NOx from the exhaust gas, and a sample collector positioned within the exhaust gas pathway. The sample collector includes a plurality of inlet openings spaced about a periphery of the exhaust gas pathway and configured to receive a sample of exhaust gas from the exhaust gas pathway, an outlet in fluid communication with the plurality of inlet openings, and a tortuous flow path extending from the plurality of inlet openings to the outlet. A NOx concentration sensor is located at the outlet of the sample collector to measure a NOx concentration of the sample, and a controller is in communication with the NOx concentration sensor and the reductant injector. The controller is configured to control operation of the reductant injector based on feedback from the NOx concentration sensor.

In some embodiments, the sample collector is positioned within an outlet passage of the treatment device.

Before any embodiments of the disclosure are explained in detail, it is to be understood that the disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the accompanying drawings. The disclosure is capable of supporting other embodiments and of being practiced or of being carried out in various ways.

DETAILED DESCRIPTION

FIG.1illustrates an exhaust gas treatment system100according to an embodiment of the present disclosure, for treating exhaust gas emitted by a diesel-powered internal combustion engine10. The illustrated exhaust gas treatment system100may be used in a wide variety of applications. For example, the exhaust gas treatment system100may be incorporated into an agricultural machine, construction machine, passenger vehicle, or any other equipment powered by a diesel engine (e.g., generators, compressors, pumps, and the like).

With continued reference toFIG.1, the exhaust gas treatment system100includes an exhaust pathway104(e.g., an exhaust pipe) having an inlet or upstream side108and an outlet or downstream side112. In some embodiments, a turbocharger116is disposed in the exhaust pathway104proximate the inlet108, but in alternative embodiments, the turbocharger116may be omitted. A treatment device120is located along the exhaust pathway104, between the inlet108and the outlet112.

In the illustrated embodiment, the treatment device120includes a first treatment element122and a second treatment element124. The second treatment element124is located downstream of the first treatment element122in the illustrated embodiment; however, the numeric designations “first,” “second,” etc. are used herein for convenience and should not be regarded as defining order, quantity, or relative position.

The first treatment element122may include a diesel particulate filter (DPF) or a combined selective catalytic reduction and diesel particulate filter (SCR+F) element having a catalytic washcoat and a porous filter substrate. In such embodiments, the washcoat of the SCR+F element may include one or more metal catalysts, such as a copper-based catalyst, an iron-based catalyst, or a vanadium-based catalyst. Alternatively, other washcoats (e.g., zeolite-based) may be used. The first treatment element122preferably captures particulate matter, oxidizes soot, and, in some embodiments, reduces NOxfrom exhaust gas passing through the first treatment element122.

The second treatment element124may include a selective catalytic reduction (SCR) element and/or an ammonia oxidation catalyst (AOC). The SCR element may include, for example, a catalytic washcoat on a monolithic support material, such as ceramic. The washcoat may include one or more metal catalysts, such as a copper-based catalyst, an iron-based catalyst, or a vanadium-based catalyst. Alternatively, other washcoats (e.g., zeolite-based) may be used. The SCR element reduces NOxfrom exhaust gas passing through it. The AOC converts excess ammonia leaving the SCR element to nitrogen and water. In embodiments in which the second treatment element124includes both an SCR element and an AOC, the SCR element and the AOC are preferably positioned in series, with the AOC located downstream of the SCR element. In some embodiments, the AOC may be provided as a separate treatment element positioned downstream of the second treatment element124. In some embodiments, the exhaust gas treatment system100may include one or more additional treatment elements, such as a diesel oxidation catalyst (DOC), NOxstorage catalyst, passive NOxadsorber (PNA), or the like.

With continued reference toFIG.1, the exhaust gas treatment system100further includes a reductant supply136and a reductant injector140in fluid communication with the reductant supply136via a distributor144. The reductant supply136includes a reservoir for storing a reductant, such as diesel exhaust fluid (DEF) or ammonia. The distributor144includes one or more pumps, valves, or the like to selectively control the flow of reductant from the reductant supply136to the injector140. The reductant injector140is positioned to introduce reductant into the treatment device120upstream of the first treatment element122. In some embodiments, one or more flow affecting features (e.g., fins, vanes etc.) may be provided downstream of the reductant injector140to enhance mixing.

An electronic control unit (ECU148) actively controls various aspects of the operation of the exhaust gas treatment system100. The ECU148preferably includes, among other things, an electronic processor, non-transitory, machine-readable memory, and an input/output interface. The electronic processor is communicatively coupled to the memory and configured to retrieve from memory and execute, among other things, instructions related to the control processes and methods described herein.

A first sensor152, which is a temperature sensor in the illustrated embodiment, is disposed upstream of the first treatment element122. The temperature sensor152may be a thermistor, thermocouple, resistance temperature detector, infrared sensor, or any other sensor suitable for measuring the temperature of exhaust gas. All or a portion of the temperature sensor152may extend into the exhaust pathway104so as to be directly exposed to exhaust gas. Alternatively, the temperature sensor152may be located outside the exhaust pathway104and measure the temperature of the exhaust gas indirectly (e.g., by measuring the temperature of the exhaust pipe). A second sensor154, which is a NOxconcentration sensor in the illustrated embodiment, is disposed downstream of the second treatment element124. The second sensor154may additionally or alternatively be configured to measure another characteristic of the exhaust gas, such as ammonia concentration, hydrocarbon concentration, or the like.

The sensors152,154are communicatively coupled to the ECU148to provide feedback to the ECU148. The ECU148is communicatively coupled to the distributor144to control reductant dosing through the injector140in response to feedback from one or both sensors152,154. The ECU148may also be configured to communicate with external systems including, for example, engine controls and/or vehicle controls.

FIGS.2and3illustrate an embodiment of the treatment device120. The treatment device120includes a cylindrical housing200having an inlet passage204and an outlet passage208coupled to the exhaust gas pathway104. An injector port212, a first sensor port216, and a second sensor port220provide mounting locations and access to the interior of the housing200for the reductant injector140, the temperature sensor152, and the NOxconcentration sensor154, respectively.

With reference toFIGS.4-6, the treatment device120includes a sample collector in the form of a collar224fixed within the outlet passage208proximate the second sensor port220(FIG.4). The collar224includes a tubular body228, a first flange232defining an upstream end236of the collar224, and a second flange240opposite the first flange232and defining a downstream end244of the collar224(FIGS.5-6). A rib248extends in a circumferential direction around the body228at a position between the first flange232and the second flange240.

Referring toFIG.4, the first flange232, second flange240, and rib248each project radially outwardly with respect to the body228of the collar224and engage an interior surface252of the outlet passage208. As such, the body228is spaced radially-inwardly from the interior surface252of the outlet passage208. Thus, the collar224and outlet passage208define a first chamber256extending axially between the first flange232and the rib248, and radially between the body228and the interior surface252. The collar224and outlet passage208further define a second chamber260extending axially between the rib248and the second flange240, and radially between the body228and the interior surface252.

Referring toFIG.6, the rib248includes a first end248aand a second end248bspaced from the first end248ain the circumferential direction of the collar224to define a gap G therebetween. The gap G provides fluid communication between the first chamber256and the second chamber260(FIG.4). The first flange232includes a plurality of cut-outs264, spaced about the circumference of the first flange232, which act as inlets into the first chamber256. The second flange240includes an indentation268, which acts as an outlet opening from the second chamber260. As described in greater detail below, exhaust gas flowing through the outlet passage208of the treatment device120may enter the first chamber256through the cut-outs264, flow into the second chamber260through the gap G, and finally flow out of the second chamber260through the indentation268. The second sensor port220is aligned with the indentation268such that the NOx concentration sensor154(FIG.1) extends into the indentation268to sample gas exiting the second chamber260.

Referring toFIG.1, in operation, untreated exhaust from the internal combustion engine10is directed into the exhaust pathway104at the inlet108. The exhaust then flows through the turbocharger116, which turns a compressor to feed compressed air back to the engine10. After flowing through the turbocharger116, the exhaust gas flows into the treatment device120through the inlet passage204. The ECU148monitors the temperature sensor152, and then commands the distributor144to supply reductant to the injector140once the temperature sensor152indicates that the treatment device120is sufficiently warm to allow for SCR reactions. The mixture of reductant and exhaust then enters the first treatment element122. The reductant reacts with NOxin the presence of the catalyst of the SCR+F element to form nitrogen and water, while soot is captured on the porous filter substrate. The partially treated exhaust then enters the second treatment element124, where the reductant reacts with any remaining NOxin the SCR element, and any unreacted reductant is subsequently oxidized by the AOC. Of course, in other embodiments in which the first treatment element122and second treatment element124have other configurations, the treatment process for the exhaust gas may vary. The treated exhaust exits the treatment device120through the outlet passage208.

The ECU148may receive feedback from the NOxconcentration sensor154and modulate the distributor144accordingly in order to maintain a target level of NOxand/or reductant (e.g., ammonia) downstream of the second treatment element124. However, reductant injection may lead to non-uniform variations in the composition of the exhaust gas at different locations in the exhaust stream. In order to obtain an accurate measurement of NOxconcentration, or other measured characteristics of the exhaust gas determined by the sensor154, it is advantageous for the sensor154to measure a uniformly mixed sample of exhaust gas.

The collar224improves the accuracy of the NOxconcentration sensor154by collecting samples of exhaust gas from multiple points around the inner periphery of the outlet passage208, and then mixing the multiple incoming sample streams and directing the mixed sample to the sensor154. More specifically, as shown inFIG.5, exhaust gas enters the first chamber256in an axial direction, through each of the circumferentially spaced cut-outs264. The exhaust then changes direction and flows in a circumferential direction toward the gap G in the rib248(FIG.6). The exhaust again changes direction to flow axially through the gap G. Because the gap G is misaligned with the indentation268, the exhaust changes direction for a third time to flow in a circumferential direction toward the indentation. The multiple changes in direction form a tortuous flow path that mixes the incoming exhaust sample before it reaches the indentation268where the sensor154is located.

The collar224may be inexpensively formed from a single piece of sheet material suitable for withstanding a high temperature exhaust environment (e.g., stainless steel sheet). In addition, unlike mixing plates, which may project inwardly into the exhaust gas pathway to create turbulence, the collar224adds minimal flow resistance and back pressure to the exhaust gas treatment system100, thereby improving efficiency.