Patent Application
20150233276
The present disclosure relates to a modular assembly, and more particularly to the modular assembly for an aftertreatment system associated with an engine.
An aftertreatment system is associated with an engine system. The aftertreatment system is configured to treat and reduce oxides of nitrogen (NOx) present in an exhaust gas flow, prior to the exhaust gas flow exiting into the atmosphere. In order to reduce NOx, the aftertreatment system may include a reductant delivery module, a reductant injector, and a Selective Catalytic Reduction (SCR) module.
The aftertreatment system may additionally include a muffler assembly having a sound suppression element. The sound suppression element performs sound attenuation function and suppresses noise of high pressure created by the exhaust gas. Generally, the muffler assembly is provided as a separate module downstream of the SCR module. In some examples, the SCR module and the sound suppression element are integrated into a single muffler assembly. However, the SCR module includes square cross-sectioned SCR units. Such shape of the SCR units may lead to an increase in stresses caused due to pressure pulsations. Further, stresses are also induced across weld joints thereby affecting a mounting of the SCR units within the muffler assembly. In some situations, such a design of the SCR units causes increase in hoop stresses.
U.S. Pat. No. 5,578,277 hereinafter referred to as '277 patent, describes a modular catalytic converter and muffler used to purify exhaust from a relatively large diesel engine. The modular catalytic converter and muffler includes a plurality of catalytic converter sub-cans mounted within a housing of the modular catalytic converter and muffler. The modular catalytic converter and muffler also includes a flow distributor mounted within the housing upstream of the catalytic converter sub-cans. Further, a muffler structure is mounted within the housing between the catalytic converter sub-cans and an outlet in order to attenuate noise in the exhaust. However, the modular catalytic converter and muffler of the '277 patent has a bulky structure.
In one aspect of the present disclosure, a modular assembly for an exhaust aftertreatment system is provided. The modular assembly includes an inlet portion defined by a housing of the modular assembly. The inlet portion is configured to connect to an exhaust conduit. The modular assembly also includes a mixing element positioned within the inlet portion and downstream of a reductant injector with respect to an exhaust gas flow direction. The modular assembly further includes a first frusto-conical region diverging from the inlet portion. The modular assembly also includes a selective catalytic reduction assembly provided within a central portion of the housing. The selective catalytic reduction assembly includes a bank of catalysts positioned in a vertical arrangement with respect to each other. A central axis of each of the bank of catalysts is parallel to a central axis of the exhaust conduit. The modular assembly further includes a sound suppression element provided within the central portion of the housing and positioned downstream of the selective catalytic reduction assembly. The modular assembly includes a baffle arrangement provided within the central portion of the housing. The baffle arrangement includes a first baffle provided upstream of the selective catalytic reduction assembly and a second baffle provided downstream of the sound suppression element. Further, the central portion of the housing containing the baffle arrangement, the selective catalytic reduction assembly, and the sound suppression element has an oblong cross section. The modular assembly also includes a second frusto-conical region converging from the central portion of the housing. The modular assembly further includes an outlet portion connected to the second frusto-conical region.
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 engine 102 may include other components (not shown), such as, a fuel system, an intake system, a drivetrain including a transmission system, and so on. The engine 102 may be used to provide power to a machine (not shown) including, but not limited to, an on-highway truck, an off-highway truck, an earth moving machine, an electric generator, and so on. Accordingly, the engine system 100 may be associated with an industry including, but not limited to, transportation, construction, agriculture, forestry, power generation, and material handling.
The engine system 100 includes an exhaust aftertreatment system 104, hereinafter interchangeably referred to as the aftertreatment system 104 fluidly connected to an exhaust manifold (not shown) of the engine 102. The aftertreatment system 104 may treat an exhaust gas flow exiting the exhaust manifold of the engine 102. The exhaust gas flow contains emission compounds that may include oxides of nitrogen (NOx), unburned hydrocarbons, particulate matter, and/or other combustion products known in the art. The aftertreatment system 104 may trap or convert NOx, unburned hydrocarbons, particulate matter, combinations thereof, or other combustion products present in the exhaust gas flow, before exiting the engine system 100.
The aftertreatment system 104 includes a modular assembly 200. The modular assembly 200 is provided in fluid communication with an exhaust conduit 106. Referring to
The housing 202 of the modular assembly 200 defines an inlet portion 204. The inlet portion 204 may include a circular cross section. Alternatively, the inlet portion 204 may include an oblong, square, or rectangular cross section. The inlet portion 204 of the housing 202 receives the exhaust gas flow from the exhaust manifold via the exhaust conduit 106 (see
Referring now to
The reductant supply system 108 includes a reductant tank 112. The reductant is contained within the reductant tank 112. Parameters related to the reductant tank 112 such as size, shape, location, and material used may vary according to system design and requirements. Further, the reductant injector 110 may be communicably coupled to a controller (not shown). Based on control signals received from the controller, the reductant from the reductant tank 112 is provided to the reductant injector 110 by a pump assembly 114. The amount of the reductant that may be injected into the inlet portion 204 may be appropriately metered based on engine operating conditions. In one example, a NOx sensor (not shown) may be mounted in the inlet portion 204. The NOx sensor may measure an amount of NOx present in the exhaust gases entering the inlet portion 204. The NOx sensor may send a signal indicative of the NOx in the exhaust gases to the controller or an ECM (not shown) present on board the machine. The NOx sensor 260 may include any known sensor capable of measuring NOx present in the exhaust gases, without limiting the scope of the present disclosure.
Referring to
The inlet portion 204 is connected to a first frusto-conical region 216. The first frusto-conical region 216 diverges from the inlet portion 204. More particularly, the first frusto-conical region 216 includes a diverging profile along the exhaust gas flow direction “F”. In some examples, a surface 218 of the first frusto-conical region 216 may make an angle of approximately 45° with an axis X-X′ (see
The housing 202 includes a central portion 220. The central portion 220 is provided downstream of the first frusto-conical region 216 with respect to the exhaust gas flow direction “F”. The central portion 220 has an oblong cross section, having a pair of curved sections at a top portion and a bottom portion respectively. The curved sections of the central portion 220 respectively define an upper interior wall 222 and a lower interior wall 224.
Referring to
The first and second baffles 228, 230 have a similar design. The design of the first baffle 228 will now be explained in detail. Referring to
A face 236 of the first baffle 228 is defined between the curved profiles of the first baffle 228. The face 236 of the first baffle 228 includes a planar profile. The face 236 of the first baffle 228 includes a number of central bores 238. In one embodiment, the first baffle 228 includes three central bores 238. Further, a number of openings 240 are provided on the face 236 such that the openings 240 surround each of the central bore 238. In one example, six openings 240 may be provided on the face 236 of the first baffle 228. However, the number of openings 240 may vary as per system requirements. The central bore 238 and the openings 240 allow uniform mixing and distribution of the exhaust gas flow with the reductant.
Referring to
As shown in
The SCR assembly 246 includes a bank of catalysts 248 positioned in a vertical arrangement with respect to each other, such that a central axis Y-Y′ (see
The modular assembly 200 includes the sound suppression element 252 provided within the housing 202. The sound suppression element 252 is positioned downstream of the SCR assembly 246 with respect to the exhaust gas flow direction “F”. The sound suppression element 252 is embodied as an acoustic sound-proofing element that performs sound attenuation or noise absorbing function. More particularly, the sound suppression element 252 reduces the amount of noise of sound pressure created by the exhaust gas flow exiting the engine 102.
The sound suppression element 252 includes a mesh like structure and may be made of any known sound absorbing material known in the art that exhibits high heat resistance and high noise absorbing efficiency. In one example, the sound suppression element 252 may include a lattice structure, and may be made of steel wool, mineral wool, glass wool, or any permeable membrane like structure. The sound suppression element 252 may include an oblong cross section corresponding to the cross section of the central portion 220. Further, the sound suppression element 252 may have variable width. More particularly, the width of the sound suppression element 252 may be varied as per the sound attenuation requirements.
The modular assembly 200 also includes a second frusto-conical region 254. The second frusto-conical region 254 converges from the central portion 220 of the housing 202. The second frusto-conical region 254 is positioned downstream of the sound suppression element 252 with respect to the exhaust gas flow direction “F’. The second frusto-conical region 254 may deflect and direct the exhaust gases towards an outlet portion 256. The outlet portion 256 is connected to, and provided downstream of the second frusto-conical region 254 with respect to the exhaust gas flow direction “F”. In some examples, a surface 258 of the second frusto-conical region 254 may make an angle of approximately 45° with the axis X-X′. In one example, the outlet portion 256 may be provided inline with the inlet portion 204 to reduce back-pressure within the modular assembly 200.
A NOx sensor 260 may be mounted in the outlet portion 256. The NOx sensor 260 may measure an amount of NOx present in the exhaust gases flowing through the outlet portion 256. The NOx sensor 260 may send a signal indicative of the NOx in the exhaust gases to the controller or an ECM (not shown) present on board the machine. The NOx sensor 260 may include any known sensor capable of measuring NOx present in the exhaust gases, without limiting the scope of the present disclosure.
The exhaust gas flow enters the inlet portion 204 of the modular assembly 200 from the exhaust conduit 106. As the exhaust gases flow through the inlet portion 204, the reductant is injected therein. As the exhaust gas flows through the inlet portion 204, the mixing element 208 enhances mixing of the reductant with the exhaust gas flow entering into the first frusto-conical region 216. The exhaust gases are then deflected by the first frusto-conical region 216, and flow through each of the baffles 228, 230, the SCR assembly 246, and the sound suppression element 252. The treated exhaust gases are then deflected from their path towards the outlet portion 256. In one embodiment, the exhaust gases are let out into the atmosphere from the outlet portion 256.
The housing 202 of the modular assembly 200 may be cast as a unitary component. Alternatively, the components of the housing 202 such as the inlet portion 204, the first frusto-conical region 216, the central portion 220, the second frusto-conical region 254, and the outlet portion 256 may be manufactured as separate units and assembled later on to form the housing 202. The components of the housing 202 may be connected to each other using any conventional joining process known in the art. In some situations, welding may be used to join the components of the housing 202. For example, overlapped welded joints may be used to join the components together. Further, the modular assembly 200 may be supported and secured to the machine externally via a band type or strap type wrap-around clamp (not shown) that allow unconstrained thermal expansion of the modular assembly 200 during operation.
The aftertreatment system 104 disclosed herein is provided as a non-limiting example. It will be appreciated that the aftertreatment system 104 may be disposed in various arrangements and/or combinations relative to the exhaust manifold. These and other variations in aftertreatment system design are possible without deviating from the scope of the disclosure. For example, the aftertreatment system 104 may include components (not shown), such as, a Diesel Oxidation Catalyst (DOC) unit, a Diesel Particulate Filter (DPF) unit, and/or an Ammonia Oxidation Catalyst (AMOX) without limiting the scope of the disclosure.
The present disclosure describes providing the sound suppression element 252 and the SCR assembly 246 within the single modular assembly 200. The housing 202 of the modular assembly 200 has an oblong shape with overlapped welded joints. As the housing 202 has a compact shape, the modular assembly 200 can be accommodated and mounted in a compact mounting space. This design of the housing 202 leads to the reduction in stresses induced due to pressure pulsations. The design of the housing 202 further allows for a smooth flow of the exhaust gases within the housing 202. The modular assembly 200 includes the baffle arrangement 226 provided upstream of the SCR assembly 246 with respect to the exhaust gas flow direction “F”. The baffle arrangement 226 functions to uniformly distribute the exhaust gas flow across a face of the SCR assembly 246. The first and second baffles 228, 230 are mounted diametrically opposite to each other within the housing 202 using overlapping weld or fillet weld. Such welding joints help in the reduction in pressure pulsations and stresses induced by the pressure pulsations.
The SCR assembly 246 includes a curved profile, as against conventional square profile. This leads to reduction in the stresses caused due to pressure pulsations. Hence, hoop or circumferential stresses induced in the SCR assemblies of earlier designs may be avoided. The SCR assembly 246 includes the catalysts 248. The catalysts 248 are removably provided within the housing 202, such that they may be conveniently removed for servicing or replacement as per system requirements. Further, the complete SCR assembly 246 is removably mounted within the housing 202 by the holding plates.
The modular assembly 200 may be supported and secured to the machine externally via band/strap type wrap-around clamps. This type of mounting arrangement allow unconstrained thermal expansion of the modular assembly 200 during operation, thereby reducing stresses in the modular assembly 200 and its mounting materials. Also, the modular assembly 200 of the present disclosure helps in reducing backpressure developed in the system. In some examples, the back pressure in the system may reduce from an existing 12 kPa to 4-6 kPa. The modular assembly 200 includes fewer components and is less bulky.
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.
