Patent Application
20130145820
The present disclosure relates to an exhaust system, and more particularly, to an aftertreatment module and sensor mount.
Internal combustion engines, including diesel engines, gasoline engines, gaseous-fuel powered engines, and other engines known in the art generate a complex mixture of exhaust gases and particulates. Components of the exhaust gases may include, among other things, oxides of nitrogen (NOx). Exhaust emission standards have become more stringent, and the amount of NOx emitted to the atmosphere by an engine may be regulated depending on the type, size and/or class of engine.
In order to comply with the regulation of NOx, some engine manufacturers have implemented a strategy called selective catalytic reduction (SCR). SCR is an exhaust aftertreatment process where a reductant, most commonly urea ((NH2)2CO) or a water and urea solution, is selectively injected into the exhaust gas stream of an engine and adsorbed onto a downstream substrate. The injected urea solution decomposes into ammonia (NH3), which reacts with NOx in the exhaust gas to form water (H2O) and diatomic nitrogen (N2).
Temperatures associated with SCR implementation may approach or exceed 200° C. In particular, high temperature exhaust gases and heat generated by exothermic reactions within aftertreatment components may heat the packaging of the SCR system. Removal of heat from the SCR system is especially problematic in stationary applications where airflow over the system may not be sufficient to readily cool the system. This high temperature environment presents particular problems for locating sensors and associated electronics required for ensuring emissions compliance.
U.S. Pat. No. 7,192,463 discloses an arrangement for disposing sensor electronics on a diesel particulate filter.
This disclosure provides an arrangement for mounting at least one electrical component to a portion of an aftertreatment module, the arrangement including; at least one standoff member coupled between the electrical component and the portion of the aftertreatment module, and an enclosure substantially surrounding at least three sides of the electrical component.
Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings.
Multiple separate sub-systems may be included within power system 10 to promote power production. For example, power system 10 may include among other things, an air induction system 18 and an exhaust system 20. Air induction system 18 may be configured to direct air or an air/fuel mixture into the combustion chamber(s) of power system 10 for subsequent combustion. Exhaust system 20 may treat and discharge byproducts of the combustion process to the atmosphere. Air induction and exhaust systems 18, 20 may be mechanically coupled to each other by way of one or more turbochargers 21.
Exhaust system 20 may include components that condition exhaust from the cylinders of engine 14 and direct it to the atmosphere. For example, exhaust system 20 may include one or more exhaust passages 22 fluidly connected to the cylinders of engine 14, one or more turbines of the turbochargers 21 driven by exhaust flowing through exhaust passages 22, and an aftertreatment module 24 connected to receive and treat exhaust from exhaust passages 22. As the hot exhaust gases exiting the cylinders of engine 14 move through the one or more turbines and expand against vanes (not shown) thereof, the one or more turbines may rotate and drive one or more compressors of the turbochargers 21 of the air induction system 18 to pressurize inlet air. Aftertreatment module 24 may treat, condition, and/or otherwise reduce constituents of the exhaust generated by engine 14 before the exhaust is discharged to the atmosphere.
As shown in
Aftertreatment module 24 may house a plurality of exhaust treatment devices. For example,
The DOCs 44 may each include a porous ceramic honeycomb structure, a metal mesh, a metal or ceramic foam, or another suitable substrate coated with or otherwise containing a catalyzing material, for example a precious metal, that catalyzes a chemical reaction to alter a composition of exhaust passing through DOCs 44. In one embodiment, DOCs 44 may include palladium, platinum, vanadium, or a mixture thereof that facilitates a conversion of NO to NO2. In another embodiment, DOCs 44 may alternatively or additionally perform particulate trapping functions (i.e., DOCs 44 may be a catalyzed particulate trap), hydro-carbon reduction functions, carbon-monoxide reduction functions, and/or other functions known in the art.
In the depicted embodiment, two separate banks of DOCs 44 are disclosed as being arranged to receive exhaust in parallel from a pair of inlets 34. Each bank of DOCs 44 may include two or more substrates disposed in series and configured to receive exhaust from one inlet 34 and one associated diffuser 50. In the depicted embodiment, diffuser 50 is configured as a cone or multiple concentric cones, although any diffuser geometry known in the art may be utilized. In the arrangement of
The mixing duct 51 has an upstream open end 52 in fluid communication with the output of the DOCs 44 and a downstream end 53 in fluid communication with the one or more banks of SCR catalysts 48. A reductant injector 54 may be located at or near upstream open end 52 and configured to inject a reductant into the exhaust flowing through mixing duct 51. A gaseous or liquid reductant, most commonly a water/urea solution, ammonia gas, liquefied anhydrous ammonia, ammonium carbonate, an amine salt, or a hydrocarbon such as diesel fuel, may be sprayed or otherwise advanced into the exhaust passing through mixing duct 51.
Reductant injector 54 may be located a distance upstream of SCR catalysts 48 and at an inlet portion of mixing duct 51 to allow the injected reductant sufficient time to mix with exhaust from power system 10 and to sufficiently decompose before entering SCR catalysts 48. That is, an even distribution of sufficiently decomposed reductant within the exhaust passing through SCR catalysts 48 may enhance NOx reduction therein. The distance between reductant injector 54 and SCR catalysts 48 may enhance NOx reduction therein. The distance between reductant injector 54 and SCR catalysts 48 (i.e., the length of mixing duct 51) may be based on a flow rate of exhaust exiting power system 10 and/or on a cross-sectional area of mixing duct 51. In the example depicted in
Each SCR catalyst 48 may be substantially identical in shape, size and composition. In particular, each SCR catalyst 48 may include a generally cylindrical substrate fabricated from or otherwise coated with a ceramic material such as titanium oxide; a base metal oxide such as vanadium and tungsten; zeolites; and/or a precious metal. With this composition, decomposed reductant entrained within the exhaust flowing through mixing duct 51 may be adsorbed onto the surface and/or adsorbed within each SCR catalyst 48, where the reductant may react with NOx (either NO, NO2 or both) in the exhaust gas to form water (H2O) and diatomic nitrogen (N2).
In order to monitor the operation of aftertreatment module 24 and/or satisfy certain requirements established by various emissions regulations, various sensors and associated electronics may be disposed throughout the aftertreatment module 24. In particular,
As illustrated in
The first sensor ECU 71 and the second sensor ECU 81 receive input signals from the inlet NOx sensor 73 and the outlet NOx sensor 83, respectively. The first sensor ECU 71 and the second sensor ECU 81 process the received input signals and transmit the processed signals to an aftertreatment control ECU (not shown) via a wiring harness 90. The aftertreatment control ECU may interpret the processed signals from the ECUs 71 and 81 to control engine operating characteristics and/or reductant dosing characteristics in order to maintain the desired performance of aftertreatment module 24. Embodiments include configurations wherein the aftertreatment control ECU may be a separate component, the aftertreatment control may be integrated into a main ECU used for all engine controls, or various other similar configurations.
Referring now to
The first sensor thermal isolating arrangement 72 includes two standoff members 100. The two standoff members 100 may be made from a thermally insulating material relative to the mounting bracket 33 to which they are coupled. While the illustrated embodiment includes two standoff members 100, alternative embodiments may include additional standoff members (not shown) or fewer standoff members (not shown); in general a smaller number of standoff members decreases a flow path for heat conduction between the portion of the aftertreatment module 24 it contacts and the first sensor ECU 71, however, the number of standoff members must also be adequate to provide positional rigidity to the first sensor thermal isolating arrangement 72. In the present embodiment, the two standoff members 100 each have a height “H1”.
The two standoff members 100 are coupled to a first pair of thermally insulating spacers 101. In one embodiment, the first pair of thermally insulating spacers 101 may be made from a thermally insulating material such as mica or other materials with similar characteristics. The first pair of thermally insulating spacers 101 contact an enclosure 102 including a bottom plate 103 and a top plate 104. The enclosure 102 substantially surrounds the first sensor ECU 71 except on sides leading to the inlet NOx sensor 73 and the port 74. In the embodiment illustrated in
The first sensor ECU 71 is coupled to the enclosure 102 with a second pair of thermally insulating spacers 105 disposed therebetween. The second pair of thermally insulating spacers 105 may have substantially the same characteristics as the first pair of thermally insulating spacers 101.
A pair of fasteners 106 couples a third pair of thermally insulating spacers 107, the first sensor ECU 71, the second pair of thermally insulating spacers 105, the enclosure 102, the first pair of thermally insulating spacers 101 and the two standoff members 100 to the appropriate portion of the aftertreatment module 24 (e.g., the mounting bracket 33). In the present embodiment, each fastener of the pair of fasteners 106 includes a bolt 108 and a washer 109. When the first sensor thermal isolating arrangement 72 is assembled, a bolt 108 of the pair of fasteners 106 passes through the washer 109, a spacer of the third pair of thermally insulating spacers 107, a through-hole in the first sensor ECU 71, a spacer of the second pair of thermally insulating spacers 105, through-holes in the enclosure 102, a spacer of the first pair of thermally insulating spacers 101 and one of the two standoff members 100. A distal end of the bolt 108 (e.g., a head of the bolt 108) contacts the spacer of the third pair of thermally insulating spacers 107. In one embodiment, the fasteners 106 may extend to be inserted into the mounting bracket 33.
The two standoff members 100 and the first and second pair of thermally insulating spacers 101 and 105 may create an air gap between the components to which they are immediately adjacent. For instance, the two standoff members 100 and the first pair of thermally insulating spacers 101 may create an air gap between the mounting bracket 33 and the enclosure 102 while the second pair of thermally insulating spacers 105 may create an air gap between the enclosure 102 and the first sensor ECU 71. These air gaps reduce paths for conduction of thermal energy from the portion of aftertreatment module 24 to which the mounting arrangement 70 is coupled to the first sensor ECU 71. The air in such gaps acts as an insulator when air currents are not flowing, and acts as a heat sink when air currents are flowing through the gaps. The benefits of such an arrangement will be discussed in more detail below with respect to the industrial applicability of the disclosure.
Referring now to
The second sensor thermal isolating arrangement 82 includes two standoff members 200. The two standoff members 200 may be made from a thermally insulating material relative to the housing 32 to which they are coupled. While the illustrated embodiment includes two standoff members 200, alternative embodiments may include additional standoff members (not shown) or fewer standoff members (not shown); in general a smaller number of standoff members decreases a flow path for heat conduction between the portion of aftertreatment module 24 it contacts and the second sensor ECU 81, however, the number of standoff members must also be adequate to provide positional rigidity to the second sensor thermal isolating arrangement 82. In the present embodiment, the two standoff members 200 each have a height “H2”. The height H2 is different from the height H1 of the two standoff members 100; the height of the standoff members 100 and 200 are predetermined to produce desired temperatures at the respective first sensor ECU 71 and second sensor ECU 81.
The two standoff members 200 are coupled to a first pair of thermally insulating spacers 201. In one embodiment, the first pair of thermally insulating spacers 201 may be made from a thermally insulating material such as mica or other materials with similar characteristics. The first pair of thermally insulating spacers 201 contact an enclosure 202 including a bottom plate 203 and a top plate 204. The enclosure 202 substantially surrounds the second sensor ECU 81 except on sides leading to the outlet NOx sensor 83 and the port 84. In the embodiment illustrated in
The second sensor ECU 81 is coupled to the enclosure 202 with a second pair of thermally insulating spacers 205 disposed therebetween. The second pair of thermally insulating spacers 205 may have substantially the same characteristics as the first pair of thermally insulating spacers 201.
A pair of fasteners 206 couples a third pair of thermally insulating spacers 207, the second sensor ECU 81, the second pair of thermally insulating spacers 205, the enclosure 202, the first pair of thermally insulating spacers 201 and the two standoff members 200 to the appropriate portion of the aftertreatment module 24. In the present embodiment, each fastener of the pair of fasteners 206 includes a bolt 208 and a washer 209. When the second sensor thermal isolating arrangement 82 is assembled, a bolt 108 of the pair of fasteners 206 passes through the washer 209, a spacer of the third pair of thermally insulating spacers 207, a through-hole in the second sensor ECU 81, a spacer of the second pair of thermally insulating spacers 205, through-holes in the enclosure 202, a spacer of the first pair of thermally insulating spacers 201 and one of the two standoff members 200. A distal end of the bolt 208 (e.g., a head of the bolt 208) contacts the spacer of the third pair of thermally insulating spacers 207. In one embodiment, the fasteners 206 may extend to be inserted into the housing 32.
The two standoff members 200 and the first and second pair of thermally insulating spacers 201 and 205 may create an air gap between the components to which they are immediately adjacent. For instance, the two standoff members 200 and the first pair of thermally insulating spacers 201 may create an air gap between the housing 32 and the enclosure 202 while the second pair of thermally insulating spacers 205 may create an air gap between the enclosure 202 and the second sensor ECU 81. These air gaps reduce paths for conduction of thermal energy from the portion of the aftertreatment module 24 to which the second mounting arrangement 80 is coupled to the second sensor ECU 81. The air in such gaps acts as an insulator when air currents are not flowing, and acts as a heat sink when air currents are flowing through the gaps. The benefits of such an arrangement will be discussed in more detail below with respect to the industrial applicability of the disclosure.
The aftertreatment module 24 of the present disclosure may be applicable to any power system 10 configuration where exhaust gas conditioning is desired. The sensor system 60 including both first mounting arrangement 70 and second mounting arrangement 80 may be used in such an aftertreatment module 24 to prevent premature failure of associated electronic components.
The aftertreatment module 24 may operate at temperatures exceeding 200° C. The first and second sensor ECUs 71 and 81 may have a failure threshold temperature significantly lower than a temperature of the aftertreatment module 24, e.g., the first and second sensor ECUs 71 and 81 may fail at temperatures exceeding 85° C. The first mounting arrangement 70, including the first sensor thermal isolating arrangement 72, maintains the temperature of the first ECU 71 below the failure threshold temperature through one or more mechanisms. First, the two standoff members 100 raise the first sensor ECU 71 away from a surface of the aftertreatment module 24, thereby limiting conductive heat transfer therebetween. Second, the first sensor ECU 71 is substantially surrounded on at least three sides by the enclosure 102, wherein the enclosure 102 reflects thermal radiation away from the first sensor ECU 71, e.g., the enclosure 102 may be reflective in at least the infrared wavelength of the electromagnetic spectrum. Third, the first sensor ECU 71 is thermally isolated from the standoff members 100 and the enclosure 102 by pairs of thermally insulating spacers 101, 105 and 107. In addition, the thermally insulating spacers 101, 105 and 107 create and/or enlarge air gaps between first sensor ECU 71 and the enclosure 102 and the enclosure 102 and the aftertreatment module 24. These air gaps may function as insulation between the first sensor ECU 71 and adjacent components, and may allow additional surfaces of the first mounting arrangement 70 to function as heat exchangers when air currents move therebetween as compared to configurations wherein the air gaps are not present.
Similarly, the second mounting arrangement 80, including the second sensor thermal isolating arrangement 82, maintains the temperature of the second sensor ECU 81 below the failure threshold temperature through one or more similar mechanisms. First, the two standoff members 200 raise the second sensor ECU 81 away from a surface of the aftertreatment module 24, thereby limiting conductive heat transfer therebetween. Second, the second sensor ECU 81 is substantially surrounded on at least three sides by the enclosure 202, wherein the enclosure 202 reflects thermal radiation away from the second sensor ECU 81, e.g., the enclosure 202 may be reflective in at least the infrared wavelength of the electromagnetic spectrum. Third, the second sensor ECU 81 is thermally isolated from the standoff members 200 and the enclosure 202 by pairs of thermally insulating spacers 201, 205 and 207. In addition, the thermally insulating spacers 201, 205 and 207 create and/or enlarge air gaps between second sensor ECU 81 and the enclosure 202 and the enclosure 202 and the aftertreatment module 24. These air gaps may function as insulation between the second sensor ECU 81 and adjacent components, and may allow additional surfaces of the second mounting arrangement 80 to function as heat exchangers when air currents move therebetween as compared to configurations wherein the air gaps are not present.
Essentially, the present disclosure discloses a method for mounting at least one electrical component, such as a first sensor ECU 71, within the aftertreatment module 24, the method including providing a first sensor ECU 71, thermally isolating the first sensor ECU 71 from a surface of the aftertreatment module 24 and reflecting thermal energy away from the first sensor ECU 71.
It will be apparent to those skilled in the art that various modifications and variations can be made to the exhaust system 20 and aftertreatment module 24 of the present disclosure without departing from the scope of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the system and module disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalent.
