AFTERTREATMENT SYSTEM
An aftertreatment system of an engine is disclosed. The aftertreatment system includes a housing. The aftertreatment system also includes a Selective Catalytic Reduction (SCR) catalyst provided within the housing. The aftertreatment system further includes an exhaust duct associated with the SCR catalyst. The aftertreatment system includes a sampling flute provided within the exhaust duct. The aftertreatment system also includes a NOx sensor at least partly enclosed by a first end of the sampling flute. The aftertreatment system further includes a spring member. The spring member is joined to the sampling flute and the exhaust duct.
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The present disclosure relates to an aftertreatment system, and more specifically to a mounting arrangement for a sampling flute of the aftertreatment system.
BACKGROUNDEngines generate exhaust gas as a byproduct of combustion. The exhaust gas includes nitrogen oxides (NOx) among other components. An aftertreatment system is used to treat an exhaust gas flow. Some aftertreatment systems may include a Selective Catalytic Reduction (SCR) catalyst. Typically in such systems, a reductant is injected into the exhaust gas flow upstream of the SCR catalyst. Thereafter, the NOx is reduced to diatomic nitrogen (N2) and water with the help of the SCR catalyst.
One or more nitrogen oxide sensors (NOx sensor) may be positioned at various locations in an engine system in order to measure a concentration of nitrogen oxides in the exhaust gas flow. For example, the NOx sensors may be present upstream and/or downstream of the SCR catalyst with respect to a direction of the exhaust gas flow. The NOx sensors located upstream and downstream of the SCR catalyst may be provided within respective ducts. A reading provided by each of the NOx sensors is based on a portion of the exhaust gas flowing thereover. However, in some situations, each of the NOx sensors may contact with a relatively small portion of the exhaust gas flow due to its position within the duct of the exhaust system. Known designs include providing a sampling flute within the duct in order to direct a portion of the exhaust gas flow over the NOx sensor.
In such known designs, the sampling flute is attached to the duct. The duct typically has a large diameter compared to the sampling flute. Therefore, heat capacities of the duct and the sampling flute are different due to the differences in thermal mass. Also contributing to potentially differential thermal characteristics, the material of the sampling flute may also differ from a material of the duct. Both the duct and the sampling flute get heated and undergo thermal expansion due to exposure to heated exhaust gas. However, a differential thermal expansion may be caused by different temperatures of the sampling flute and the duct due to different heat transfer rates to the sampling flute and the duct, and/or the different heat capacities. This may lead to a high thermal stress in a joint between the sampling flute and the duct.
SUMMARY OF THE DISCLOSUREIn one aspect of the present disclosure, an aftertreatment system of an engine is disclosed. The aftertreatment system includes a housing configured to receive an exhaust gas flow from the engine. The aftertreatment system also includes a Selective Catalytic Reduction (SCR) catalyst provided within the housing. The aftertreatment system further includes an exhaust duct associated with the SCR catalyst. The exhaust duct is configured to discharge the exhaust gas flow out of the housing. The aftertreatment system includes a sampling flute provided within the exhaust duct. The sampling flute includes a plurality of holes configured to allow passage of the exhaust gas flow therethrough. Further, a first end of the sampling flute is coupled to the exhaust duct. The aftertreatment system also includes a NOx sensor at least partly enclosed by the first end of the sampling flute. The aftertreatment system further includes a spring member. The spring member is joined to the sampling flute and the exhaust duct.
Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings.
Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or the like parts. Referring to
The aftertreatment system 100 may include a number of components therein. An inlet duct (not shown) of the aftertreatment system 100 may be fluidly coupled to an exhaust manifold (not shown) of the engine. The inlet duct may be configured to receive the exhaust gas flow from the engine. Further, the housing 102 may be configured to receive the exhaust gas flow from the inlet duct of the aftertreatment system 100.
The aftertreatment system 100 further includes an exhaust duct 104 in fluid communication with an outlet of the SCR catalyst. In an embodiment, an Ammonia Oxidation (AMOX) catalyst (not shown) may be provided between the exhaust duct 104 and the outlet of the SCR catalyst. The exhaust duct 104 is provided downstream of the SCR catalyst and is configured to discharge the exhaust flow out of the housing 102 via an outlet 106. In one embodiment, the exhaust duct 104 may be fluidly coupled to an exhaust stack (not shown). The exhaust stack may be open to atmosphere. In another embodiment, the exhaust duct 104 may be further fluidly coupled to another module (not shown) of the aftertreatment system 100. The exhaust duct 104 illustrated in the accompanying figures has a hollow cylindrical configuration defining a longitudinal axis X-X′. The exhaust duct 104, as shown in
The exhaust duct 104 may include a NOx sensor 108 disposed therein. In the illustrated embodiment, the NOx sensor 108 is located on a surface of the exhaust duct 104 to extend substantially perpendicularly thereto. However, alternative exemplary embodiments include configurations wherein the NOx sensor 108 may be disposed in a manner such that the NOx sensor 108 protrudes into the exhaust duct 104 at an angle relative to the longitudinal axis X-X′. In such various alternative embodiments, the angle between the NOx sensor 108 and the longitudinal axis X-X′ may be up to about 10 degrees. The NOx sensor 108 may be affixed to the exhaust duct 104 by any fastening method known in the art including, but not limited to, bolting, welding, adhesion, and the like. The NOx sensor 108 may be configured to measure a concentration of NOx in the exhaust gas flow. Further, the NOx sensor 108 may be connected to an engine control module (not shown) via one or more electrical connections (not shown).
The exhaust duct 104 further includes a sampling flute 110 provided in cooperation with the NOx sensor 108. In the illustrated embodiment, the sampling flute 110 is disposed within the exhaust duct 104 substantially perpendicular to the longitudinal axis X-X′ of the exhaust duct 104. Alternative exemplary embodiments include configurations wherein the sampling flute 110 may be inclined at an angle relative to the longitudinal axis X-X′. The sampling flute 110 may extend across at least a portion of a width of the exhaust duct 104. In the illustrated embodiment, the sampling flute 110 is provided extending diametrically within the exhaust duct 104. The sampling flute 110 may be configured to sample the exhaust gas flow by channeling a portion of the exhaust gas flow towards the NOx sensor 108. The sampling flute 110 may also be configured for increasing fills per measurement of the sampled exhaust gas flow. The fills per measurement may refer to a volume of the exhaust gas flow which is in contact with the NOx sensor 108 for providing a value indicative of the NOx concentration. Therefore, any increase in the fills per measurement may be regarded as an increase in the amount of exhaust gas flow sampled by the NOx sensor 108. Additionally, the sampling flute 110 may also homogenize the exhaust gas flowing towards the NOx sensor 108. Further, another set of the NOx sensor 108 and the sampling flute 110, as described above, may be provided upstream of the of the SCR catalyst. This set of the NOx sensor 108 and the sampling flute 110 may measure a concentration of NOx present in the exhaust gas flow before being treated by the SCR catalyst.
Further, as shown in
The various dimensions, as expressed above, are purely exemplary in nature, and the dimensions the spring member 212 may vary as per system design and requirements. The material of the spring member 212 may also vary according to design. The spring member 212 be made of any metal or metal alloy, for example, but not limited to, spring steel, aluminum/aluminum alloy, and the like. The shape of the spring member 212 may also vary. For example, the third portion 218 may be inclined obliquely relative to the first portion 214. One or more of the first, second and third portions 214, 216 and 218 may have a curvilinear shape. Moreover, a width and/or thickness of each of the first, second and third portions 214, 216, 218 may vary. Further, in alternative embodiments (not shown), the spring member 212 have an overall planar or curvilinear shape without any inclined portion.
An aftertreatment system may be used to treat an exhaust gas flow of an engine. An aftertreatment system may include an SCR catalyst which aids a reductant, injected into the exhaust gas flow, to reduce nitrogen oxides in the exhaust gas flow to diatomic nitrogen (N2) and water. A NOx sensor may be provided upstream and/or downstream of the SCR catalyst in an exhaust duct of the aftertreatment system. A sampling flute may be attached to the exhaust duct in order to direct a portion of the exhaust gas flow over the NOx sensor. The exhaust duct may have a large diameter compared to the sampling flute. Therefore, heat capacities of the exhaust duct and the sampling flute are different due to the size difference. A material of the sampling flute may also differ from a material of the exhaust duct. Both the exhaust duct and the sampling flute may get heated and undergo thermal expansion due to a high temperature of the exhaust gas. However, a differential thermal expansion may be caused by different temperatures of the sampling flute and the exhaust duct due to different heat transfer rates to the sampling flute and the exhaust duct and/or the different heat capacities. The differential thermal expansion may also result due to a difference in material thermal expansion coefficient between the exhaust duct and the sampling flute. This may lead to a high thermal stress in a joint between the sampling flute and the exhaust duct.
Referring to
During operation of the engine, the exhaust flow may result in a thermal expansion of the sampling flute 110 and the exhaust duct 104 due to a high temperature. However, due to a size difference between the sampling flute 110 and the exhaust duct 104, the sampling flute 110 may undergo higher thermal expansion as compared to the exhaust duct 104. The thermally expanded state of the sampling flute 110 is shown by dashed lines in
As shown in
The various parameters of the spring member 212, including the lengths 402, 404, and 406 of the first, second and third portions 214, 216 218, respectively; the angle 220 between the first and second portions 214, 216; the thickness 408 and the width 410 of the spring member 212; the thicknesses of the welds 304, 306; and the diameter 412 of the aperture 302 may be varied as per requirements of the aftertreatment system 100. For example, an overall length and/or the thickness 408 of the spring member 212 may be increased in order to cater to a larger size of the exhaust duct 104, and hence higher differential thermal expansion and thermal stress.
Though the operation of the spring member 212 is described above, it may be apparent that the spring members 502, 602 and 702 may also deform and permit an expansion of the second end 204 of the sampling flute 110. Therefore, the spring members 502, 602 and 702 may accommodate differential thermal expansion between the sampling flute 110 and the exhaust duct 104. The spring member 702 may also provide support to the sampling flute 110 at any desired region between the first and second ends 202, 204.
While aspects of the present disclosure have been particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by the modification of the disclosed machines, systems and methods without departing from the spirit and scope of what is disclosed. Such embodiments should be understood to fall within the scope of the present disclosure as determined based upon the claims and any equivalents thereof.
Claims
1. An aftertreatment system of an engine, the aftertreatment system comprising:
- a housing configured to receive an exhaust gas flow from the engine;
- a Selective Catalytic Reduction (SCR) catalyst provided within the housing;
- an exhaust duct associated with the SCR catalyst;
- a sampling flute provided within the exhaust duct, wherein the sampling flute comprises a plurality of holes configured to allow passage of the exhaust gas flow therethrough, and wherein a first end of the sampling flute is coupled to the exhaust duct;
- a NOx sensor at least partly enclosed by the first end of the sampling flute; and
- a spring member joined to the sampling flute and the exhaust duct.
Type: Application
Filed: Mar 28, 2014
Publication Date: Jul 31, 2014
Applicant: Caterpillar Inc. (Peoria, IL)
Inventors: Andrew M. Denis (Peoria, IL), James D. Peltier (Santa Fe, NM), Kevin J. Weiss (Peoria, IL)
Application Number: 14/228,674
International Classification: F01N 3/20 (20060101);