Exhaust system with nox sampling device and exhaust conduit assembly

Abstract

An exhaust system for an internal combustion engine includes an exhaust conduit and a NOx sampling device arranged to sample exhaust gas flow fed through the exhaust conduit to an exhaust outlet. The NOx sampling device is to be coupled with a NOx sensor having a sensor probe fluidly connected to a mixing chamber in the NOx sampling device. A plurality of sampling slots each form an exhaust feed passage to sample exhaust gas at a location that provides improved sensor reading accuracy.

Description

Technical Field

[0001] This disclosure relates generally to exhaust systems, and more specifically to NOx sampling devices in exhaust systems having sampling slots for improving the accuracy of sensor readings. Background Technology

[0002] Internal combustion engines are widely known around the world and are used in virtually countless applications, including vehicle propulsion and the operation of pumps, compressors, and generators. The general process of burning fuel and air to drive a piston to rotate under load is familiar to many. The combustion of any fuel produces exhaust gases, and depending on the fuel type and operating environment, these exhaust gases contain a variety of emissions that are expected to be reduced.

[0003] For example, the combustion of liquid hydrocarbon fuels results in emissions of particulate matter, carbon monoxide, carbon dioxide, and various nitrogen oxides (collectively known as "NOx"). For decades, engineers have been experimenting with various so-called aftertreatment systems to reduce the amount of some of these emissions that would otherwise be released into the environment in other ways.

[0004] A well-known aftertreatment system for reducing NOx emissions utilizes a process known as Selective Catalytic Reduction, or "SCR". SCR systems reduce NOx to nitrogen and water, both considered less hazardous emissions. Most modern SCR systems utilize an onboard reducing agent, selectively delivered to the exhaust system, and is commonly referred to as diesel exhaust fluid or "DEF". DEF is a fluid carried on the engine system or associated machinery. For optimal SCR operation and cost considerations, it is generally desirable to limit the overuse and / or underuse of DEF.

[0005] To deliver DEF optimally for SCR operation, it is beneficial to know relatively accurately how much NOx is actually in the exhaust gas (potentially both before and after the exhaust passes through the SCR). Various strategies for monitoring NOx have been proposed over the years. U.S. Patent No. 10,066,535B2 discloses an example exhaust aftertreatment system utilizing a NOx sensor. Ample opportunities exist in the art for improving and / or developing alternative strategies. Summary of the Invention

[0006] In one aspect, an exhaust system includes: an exhaust duct extending to an exhaust outlet; and a NOx sampling device arranged to sample an exhaust stream fed through the exhaust duct to the exhaust outlet. The NOx sampling device forms a mixing chamber and includes a plurality of sampling slots, each of the plurality of sampling slots forming an exhaust feed passage extending from at least one corresponding exhaust inlet to the mixing chamber.

[0007] In another aspect, a NOx sampling device includes a device body extending circumferentially about a central axis and including an inner surface and an outer surface, the inner surface forming an exhaust duct section for feeding exhaust gas to an exhaust outlet. The device body also forms a mixing chamber radially disposed between the inner and outer surfaces. The NOx sampling device further includes a plurality of sampling slots positioned to be exposed to exhaust gas feeding through the exhaust duct section, and each forming an exhaust gas feeding passage extending from at least one corresponding exhaust gas inlet to the mixing chamber.

[0008] In another aspect, an exhaust duct assembly includes a NOx sampling device having a device body extending circumferentially about a central axis and including an inner surface and an outer surface, the inner surface forming an exhaust duct segment. The device body further forms a mixing chamber and includes a plurality of sampling slots arranged to feed exhaust gas from the exhaust duct segment into the mixing chamber. The exhaust duct assembly also includes a NOx sensor coupled to the device body and including a sensor probe fluidly connected to the mixing chamber. Attached Figure Description

[0009] Figure 1 This is a schematic view of an internal combustion engine system according to one embodiment;

[0010] Figure 2 This is a view of a NOx sampling device according to one embodiment;

[0011] Figure 3 This is a schematic view of a NOx sensor assembly according to one embodiment;

[0012] Figure 4 Is it like this? Figure 3 A partial cross-sectional view of the NOx sensor assembly in the diagram;

[0013] Figure 5 This is another cross-sectional view of the NOx sensor assembly;

[0014] Figure 6 This is a cross-sectional side view of the NOx sensor assembly; and

[0015] Figure 7 This is an example of a NOx sampling device for displaying the NOx mass fraction in an exhaust system, according to one embodiment. Detailed Implementation

[0016] refer to Figure 1The image illustrates an internal combustion engine system 10 according to one embodiment. The engine system 10 includes an internal combustion engine 12, wherein a plurality of cylinders 13 are formed. The engine 12 may include a compression ignition engine operating using a suitable compression ignition liquid fuel, such as a diesel fraction. In other cases, the engine 12 may operate using a suitable spark ignition liquid or gaseous fuel for spark ignition, pre-combustion chamber ignition, or through various other strategies. The engine 12 may also be a dual-fuel engine operating using both liquid and gaseous fuels, or possibly a dual-fuel engine operating using two liquid fuels, such as diesel and methanol. The engine 12 can be used in any known application, such as operating a transmission system in a land vehicle or vessel, or powering a pump, compressor, or generator, to name just a few.

[0017] The operation of engine 12 produces exhaust gas, generally indicated by reference numeral 8. As discussed above, the exhaust stream from the internal combustion engine can include various exhaust components for which emission reduction is desired. For this purpose, engine system 10 can be equipped with an exhaust system 16 having various aftertreatment components. In the illustrated embodiment, exhaust system 16 includes an upstream aftertreatment module 18, a downstream aftertreatment module 20, and connectors 22 and 24 fluidly connecting the respective aftertreatment modules 18 and 20. Unless otherwise discussed herein, this disclosure is not limited to any particular order or characteristics of the aftertreatment components. For example, exhaust system 16 may include a diesel oxidation catalyst (DOC) and a diesel specific filter (DPF) located upstream, such as within or coupled to the upstream aftertreatment module 18. Exhaust system 16 may also include selective catalytic reduction, or “SCR,” which includes components housed in the downstream aftertreatment module or SCR module 20. SCR module 20 operates according to well-known principles. The ammonia oxidation catalyst (AMOX) can also be positioned in or coupled to the SCR module 20 to reduce so-called ammonia slip from the SCR, which is also done in a well-known manner.

[0018] Exhaust system 16 also includes a diesel emission stream or “DEF” system 26, which includes a DEF supply device 28, a DEF pump 30, and a DEF injector 32 electrically actuated and injecting DEF into or upstream of the SCR module 20. Exhaust system 16 may also include a first or upstream NOx sensor 34 fluidly positioned between the upstream aftertreatment module 18 and the SCR module 20, and a second or downstream NOx sensor 36 positioned downstream of or within the SCR module 20. Exhaust system 16 also includes a control system 38 comprising any one or more suitable computer control units and calculating how much DEF to inject based on NOx sensor readings from NOx sensor 34, then checking its calculation using NOx sensor 36. In this general manner, control system 38 may increase or decrease the DEF dosage as needed, or possibly decrease it, based on readings from NOx sensor 36.

[0019] For reasons readily apparent to those skilled in the art of exhaust systems, accurate NOx readings are generally desired, as close as possible to the actual amount of NOx in the exhaust stream. To this end, the NOx sensor 36 is associated with a unique design to improve the accuracy of sensor readings during use. For this purpose, the exhaust system 16 includes a NOx sampling device 44 coupled to the SCR module 20 and arranged to sample the exhaust stream fed through an exhaust duct 40 extending to an exhaust outlet 42. In a practical implementation, the NOx sampling device 44 is fluidly located between the SCR module 20 and the exhaust outlet 42, and may form part of, or be part of, an end flange of the exhaust system 16 and the SCR module 20 that delivers the exhaust to, for example, an exhaust pipe or exhaust stack. In other words, the NOx sampling device 44 may be the last device involved in engine exhaust aftertreatment before the engine exhaust is discharged to its final outlet to the atmosphere.

[0020] Now refer to another source Figures 2 to 6 The NOx sampling device 44 may include a device body 46 extending circumferentially around a central axis 48. The device body 46 includes an inner surface 50 forming an exhaust duct section 52, which is understood as a segment of an exhaust duct 40 for feeding exhaust gas to an exhaust outlet 42. The device body 46 also includes an outer surface 54. The device body 46 further forms a mixing chamber 56 radially arranged between the inner surface 50 and the outer surface 54. The NOx sampling device 34 also includes a plurality of sampling slots 58, 60, and 62 positioned to be exposed to the exhaust gas feed through the exhaust duct section 52. Each of the sampling slots 58, 60, and 62 forms an exhaust gas feed passage 64, 66, 68 extending from at least one corresponding exhaust gas inlet 70 to the mixing chamber 56.

[0021] In a practical implementation strategy, the multiple sampling slots 58, 60, and 62 extend completely across the exhaust flow area defined by the exhaust duct section 52. As can be seen from the figures, the device body 46 may also include a plurality of sampling slot seats 72 formed on the inner surface 50 and receiving the multiple sampling slots 58, 60, and 62. In the illustrated embodiment, each corresponding at least one exhaust inlet 70 includes a plurality of exhaust inlet holes longitudinally distributed in the corresponding sampling slots 58, 60, and 62.

[0022] Similarly, in practical implementations, the inner diameter of slots 58, 60, and 62 can be approximately 10.9 mm, and their outer diameter can be approximately 12 mm. The diameter of the exhaust inlet 70 can be approximately 3 mm. In this context, "approximately" means within the range of measurement error, or other general or approximate measurements that can be understood by one of ordinary skill in the art. The number of exhaust inlets 70 in each of the respective slots 58, 60, and 62 can be one or more (such as, for example, two, three, four, or five). In other implementations, configurations different from the illustrated circular orifice can be used, such as slits, slits with non-uniform opening diameters, or some other arrangement. The size of the exhaust inlet 70 can also vary within the respective sampling slots 58, 60, and 62.

[0023] It can also be understood that slots 58, 60, and 62 can be elongated, as illustrated. Similarly, in practical implementations, sampling slots 58, 60, and 62 extend from the mixing chamber 56 in a mutually divergent arrangement. In some embodiments, the plurality of sampling slots 58, 60, and 62 may include a total of three sampling slots. Focus Figure 2 It should be understood that the inner surface 50 can be understood as defining a circle around a central axis 48, and typically centered on that central axis. The three sampling slots, as illustrated, may include sampling slot 58 arranged along and / or on the diameter of the subject circle, and two sampling slots 60 and 62 arranged along or on a corresponding chord of the subject circle. The exhaust inlet 70 may open in an upstream direction away from the exhaust outlet 42.

[0024] Now focus Figure 5 and Figure 6 It is understood that the NOx sampling device 44 and the NOx sensor 36 can together form a NOx sensor assembly. In some cases, when the device body 46 forms the duct section 52, the NOx sampling device 44 and the NOx sensor 36 can form an exhaust duct assembly 74. (As from...) Figure 5 As is most clearly seen, the device body 46 may include an end flange 80 extending circumferentially around the exhaust outlet 42. Figure 6The sensor cavity 82 of the NOx sampling device 44 is shown extending radially through the device body 46 to the mixing chamber 56. The sensor cavity 82 receives the NOx sensor 36. The NOx sensor 36 includes a sensor probe 78 fluidly connected to the mixing chamber 56.

[0025] Industrial applicability

[0026] Still refer to the attached diagram as a whole, but now also refer to... Figure 7 Example 100 of a NOx sampling device 44 is shown, which may be present in the exhaust stream from an engine. Figure 7 Section 102 shows an example region where NOx provides a relatively low exhaust gas mass fraction. Section 104 shows NOx at a moderate level of exhaust gas mass fraction. Section 106 shows NOx at a higher mass fraction of the exhaust gas. It is evident that the relative concentration of NOx is not uniform at all; in the specific example illustrated, most of the NOx distribution is biased towards one side of the exhaust duct.

[0027] Some known NOx sampling devices recommend placing a single sampling tube across or partially across the exhaust duct. Given... Figure 7 It should be understood that a single sampling tube or similar device can collect exhaust gas samples with relatively high or relatively low concentrations, and therefore cannot accurately reflect the actual amount of NOx in the exhaust stream. In contrast, this disclosure provides a more robust exhaust stream sampling method. Figure 7 This is a snapshot of the NOx mass fraction distribution at a certain point in time. During engine operation, various factors can cause the NOx distribution to change. Therefore, this disclosure is more robust to changes in the NOx distribution in the exhaust stream.

[0028] This specification is for illustrative purposes only and should not be construed as limiting the breadth of this disclosure in any way. Therefore, those skilled in the art will understand that various modifications can be made to the embodiments currently disclosed without departing from the full and reasonable scope and spirit of the invention. Other aspects, features, and advantages will become apparent from a study of the accompanying drawings and appended claims. As used herein, the articles “a” and “an” are intended to include one or more items and may be used interchangeably with “one or more.” The term “an” or similar language is used where only one item is desired. Furthermore, as used herein, the terms “has,” “have,” “having,” etc., are intended to be open-ended terms. Further, the phrase “based on” is intended to mean “at least partially based on,” unless otherwise explicitly stated.

Claims

1. An exhaust system, the exhaust system comprising: An exhaust duct that extends to an exhaust outlet; NOx sampling device, the NOx sampling device being arranged to sample the exhaust flow fed to the exhaust outlet through the exhaust duct; and The NOx sampling device forms a mixing chamber and includes a plurality of sampling slots, each of which forms an exhaust feed channel extending from at least one corresponding exhaust inlet into the mixing chamber.

2. The exhaust system according to claim 1, further comprising: A selective catalytic reduction (SCR) module is arranged to treat exhaust gas fed through the exhaust duct, and a NOx sampling device is fluidly arranged between the SCR module and the exhaust outlet in the exhaust system. and An upstream aftertreatment module and an upstream NOx sensor, wherein the upstream NOx sensor is fluidly disposed between the upstream aftertreatment module and the SCR module in the exhaust system.

3. The exhaust system according to claim 1 or 2, further comprising: The NOx sensor assembly includes the NOx sampling device and a NOx sensor having a sensor probe fluidly connected to the mixing chamber.

4. The exhaust system according to any one of claims 1 to 3, wherein the NOx sampling device comprises a device body extending circumferentially around a central axis and a sensor cavity extending radially through the device body to the mixing chamber.

5. The exhaust system according to claim 4, wherein the device body forms a duct segment of the exhaust duct.

6. The exhaust system according to any one of claims 1 to 5, wherein each of the plurality of sampling slots extends across the exhaust duct, and each respective at least one exhaust inlet includes a plurality of exhaust inlet holes longitudinally distributed in the respective sampling slot and opening in an upstream direction away from the exhaust outlet.

7. The exhaust system according to any one of claims 1 to 6, wherein the plurality of sampling slots comprises a total of three sampling slots, and the plurality of sampling slots extend from the mixing chamber in a mutually divergent arrangement.

8. A NOx sampling device, the NOx sampling device comprising: The device body extends circumferentially around a central axis and includes an inner surface and an outer surface, the inner surface forming an exhaust duct section for feeding exhaust gas to an exhaust outlet; The main body of the device further forms a mixing chamber radially arranged between the inner surface and the outer surface; and Multiple sampling slots are positioned to be exposed to exhaust feed through the exhaust duct section and each forms a feed channel extending from at least one corresponding exhaust inlet to the mixing chamber.

9. The NOx sampling device of claim 8, wherein the plurality of sampling slots extend completely across the exhaust flow region defined by the exhaust duct section, and the device body includes a plurality of sampling slot seats formed on the inner surface and receiving the plurality of sampling slots.

10. The NOx sampling apparatus of claim 8 or 9, wherein each corresponding at least one exhaust inlet includes a plurality of exhaust inlets longitudinally distributed in the corresponding sampling slot, and wherein the plurality of sampling slots extend from the mixing chamber in a mutually divergent arrangement.

11. The NOx sampling apparatus according to any one of claims 8 to 10, wherein the plurality of sampling slots comprises a total of three sampling slots.

12. The NOx sampling device of claim 11, wherein the inner surface defines a circle around the central axis, and the three sampling slots include a central slot arranged along the diameter of the circle and two slots arranged along corresponding chords of the circle.

13. An exhaust duct assembly, the exhaust duct assembly comprising: The NOx sampling device includes a device body that extends circumferentially around a central axis and has an inner surface and an outer surface, the inner surface forming an exhaust duct section; The main body of the device further forms a mixing chamber and includes a plurality of sampling slots arranged to feed exhaust gas from the exhaust duct section into the mixing chamber; and A NOx sensor is coupled to the device body and includes a sensor probe fluidly connected to the mixing chamber.

14. The exhaust duct assembly of claim 13, wherein the exhaust duct segment includes an end flange extending circumferentially around an exhaust outlet.

15. The exhaust duct assembly according to claim 13 or 14, wherein: Each of the plurality of sampling slots includes a plurality of exhaust inlet holes longitudinally distributed in the respective sampling slot and opening in an upstream direction away from the exhaust outlet. The inner surface defines a circle around the central axis, and the plurality of sampling slots include a central slot arranged along the diameter of the circle and two slots arranged along the corresponding chords of the circle.

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