Patent Application
20140360159
The present disclosure relates to an apparatus for an exhaust system. More specifically, the present disclosure relates to an apparatus comprising a precipitation cover for the exhaust system.
All engines—diesel, gasoline, propane, and natural gas—produce exhaust gas containing carbon monoxide, hydrocarbons, and nitrogen oxides. These emissions are the result of incomplete combustion. Diesel engines also produce particulate matter. As more government focus is being placed on health and environmental issues, agencies around the world are enacting more stringent emission's laws.
Because so many diesel engines are used in trucks, the U.S. Environmental Protection Agency and its counterparts in Europe and Japan first focused on setting emissions regulations for the on-road market. While the worldwide regulation of nonroad diesel engines came later, the pace of cleanup and rate of improvement has been more aggressive for nonroad engines than for on-road engines.
Manufacturers of nonroad diesel engines are expected to meet set emissions regulations. For example, Tier 3 emissions regulations required an approximate 65 percent reduction in particulate matter (PM) and a 60 percent reduction in NOx from 1996 levels. As a further example, Interim Tier 4 regulations required a 90 percent reduction in PM along with a 50 percent drop in NOx. Still further, Final Tier 4 regulations, which will be fully implemented by 2015, will take PM and NOx emissions to near-zero levels.
To meet such emissions levels, at least a portion of the exhaust gas being emitted from many engines must pass through an aftertreatment system. The aftertreatment system is configured to remove various chemical compounds and particulate emissions, such as PM and NOx. The aftertreatment system may comprise a NOx sensor, which is configured to produce a NOx signal indicative of a NOx content of exhaust gas flowing thereby. An ECU may use the NOx signal to control, for example, a combustion temperature of the engine and/or to control the amount of a reductant injected into the exhaust gas, so as to minimize the level of NOx entering the atmosphere.
However, a problem associated with NOx sensors is that, if they come into contact with precipitation—such as rain, melted snow, or melted ice—they may be prone to sending inaccurate NOx signals, and they may even be prone to complete failure. Complete failure may occur if precipitation contacts a sensor element of the NOx sensor, causing the sensor element to crack, especially if the exhaust gas superheats the precipitation (e.g., 800° C. and above). Such failures may lead to the engine being derated, customer dissatisfaction, and expensive repairs.
Therefore, what is needed in the art is an apparatus for minimizing the amount of precipitation that comes into contact with the NOx sensor, while at the same time, minimizing the effect on the normal exhaust function (i.e., minimizing any back pressure). And what is additionally needed in the art is an apparatus that is cost effective, easy to implement, does not require moving parts, and is visually appealing.
Disclosed is an apparatus for an exhaust system, the apparatus comprising a precipitation cover adapted to be positioned at least partially downstream of a tailpipe relative to a direction of an exhaust gas flow. The precipitation cover comprises a first cover end and a second cover end. The first cover end is configured as a precipitation outlet, and the second cover end is configured as an exhaust gas outlet and a precipitation inlet. When the first cover end and the tailpipe are coupled together, the first cover end and the tailpipe cooperate so as to form a precipitation exit opening.
The disclosed apparatus minimizes the amount of precipitation that enters the tailpipe and, thus, the amount that comes into contact with the NOx sensor. At the same time, the disclosed apparatus only minimally interferes with the normal exhaust function of the engine (i.e., it minimizes any back pressure). And, further yet, it is cost effective, easy to implement, does not require moving parts, and is visually appealing.
The detailed description of the drawings refers to the accompanying figures in which:
Referring to
The power system 100 may be used for providing power to a variety of machines, including on-highway trucks, construction vehicles, marine vessels, stationary generators, automobiles, agricultural vehicles, and recreation vehicles.
The engine 106 may be any kind of engine 106 that produces an exhaust gas, the exhaust gas being indicated by directional arrow 192. For example, engine 106 may be an internal combustion engine, such as a gasoline engine, a diesel engine, a gaseous fuel burning engine (e.g., natural gas) or any other exhaust gas producing engine. The engine 106 may be of any size, with any number cylinders (not shown), and in any configuration (e.g., “V,” inline, and radial). Although not shown, the engine 106 may include various sensors, such as temperature sensors, pressure sensors, and mass flow sensors.
The power system 100 may comprise an intake system 107. The intake system 107 may comprise components configured to introduce a fresh intake gas, indicated by directional arrow 189, into the engine 106. For example, the intake system 107 may comprise an intake manifold (not shown) in communication with the cylinders, a compressor 112, a charge air cooler 116, and an air throttle actuator 126.
Exemplarily, the compressor 112 may be a fixed geometry compressor, a variable geometry compressor, or any other type of compressor configured to receive the fresh intake gas, from upstream of the compressor 112. The compressor 112 compress the fresh intake gas to an elevated pressure level. As shown, the charge air cooler 116 is positioned downstream of the compressor 112, and it is configured to cool the fresh intake gas. The air throttle actuator 126 may be positioned downstream of the charge air cooler 116, and it may be, for example, a flap type valve controlled by an electronic control unit (ECU) 115 to regulate the air-fuel ratio.
Further, the power system 100 may comprise an exhaust system 140. The exhaust system 140 may comprise components configured to direct exhaust gas from the engine 106 to the atmosphere. Specifically, the exhaust system 140 may comprise an exhaust manifold (not shown) in fluid communication with the cylinders. During an exhaust stroke, at least one exhaust valve (not shown) opens, allowing the exhaust gas to flow through the exhaust manifold and a turbine 111. The pressure and volume of the exhaust gas drives the turbine 111, allowing it to drive the compressor 112 via a shaft (not shown). The combination of the compressor 112, the shaft, and the turbine 111 is known as a turbocharger 108.
The power system 100 may also comprise, for example, a second turbocharger 109 that cooperates with the turbocharger 108 (i.e., series turbocharging). The second turbocharger 109 comprises a second compressor 114, a second shaft (not shown), and a second turbine 113. Exemplarily, the second compressor 114 may be a fixed geometry compressor, a variable geometry compressor, or any other type of compressor configured to receive the fresh intake flow, from upstream of the second compressor 114, and compress the fresh intake flow to an elevated pressure level before it enters the engine 106.
The power system 100 may also comprises an exhaust gas recirculation (EGR) system 132 that is configured to receive a recirculated portion of the exhaust gas, as indicated by directional arrow 194. The intake gas is indicated by directional arrow 190, and it is a combination of the fresh intake gas and the recirculated portion of the exhaust gas. The EGR system 132 comprises an EGR valve 122, an EGR cooler 118, and an EGR mixer (not shown).
The EGR valve 122 may be a vacuum controlled valve, allowing a specific amount of the recirculated portion of the exhaust gas back into the intake manifold. The EGR cooler 118 is configured to cool the recirculated portion of the exhaust gas flowing therethrough. Although the EGR valve 122 is illustrated as being downstream of the EGR cooler 118, it could also be positioned upstream from the EGR cooler 118. The EGR mixer is configured to mix the recirculated portion of the exhaust gas and the fresh intake gas into, as noted above, the intake gas.
As further shown, the exhaust system 140 may comprise an aftertreatment system 120, and at least a portion of the exhaust gas passes therethrough. The aftertreatment system 120 is configured to remove various chemical compounds and particulate emissions present in the exhaust gas received from the engine 106. After being treated by the aftertreatment system 120, the exhaust gas is expelled into the atmosphere via a tailpipe 178. The apparatus 102 comprises a precipitation cover 129 adapted to be positioned at least partially downstream of a tailpipe 124 relative to a direction of the exhaust gas flow (see directional arrow 192).
The aftertreatment system 120 may comprise a NOx sensor 119, the NOx sensor 119 being configured to produce and transmit a NOx signal to the ECU 115 that is indicative of a NOx content of exhaust gas flowing thereby. The NOx sensor 119 may, for example, rely upon an electrochemical or catalytic reaction that generates a current, the magnitude of which is indicative of the NOx concentration of the exhaust gas.
The ECU 115 may have four primary functions: (1) converting analog sensor inputs to digital outputs, (2) performing mathematical computations for all fuel and other systems, (3) performing self diagnostics, and (4) storing information. Exemplarily, the ECU 115 may, in response to the NOx signal, control a combustion temperature of the engine 106 and/or the amount of a reductant injected into the exhaust gas, so as to minimize the level of NOx entering the atmosphere.
Referring back to
In other words, in the embodiment shown, the DPF 164 is positioned downstream of the DOC 163, the SCR catalyst 170 downstream of the DPF 164, and the AOC 174 downstream of the SCR catalyst 170. The DOC 163, the DPF 164, the SCR catalyst 170, and the AOC 174 may be coupled together. Exhaust gas treated, in the aftertreatment system 120, and released into the atmosphere contains significantly fewer pollutants—such as diesel particulate matter, NO2, and hydrocarbons—than an untreated exhaust gas.
The DOC 163 may be configured in a variety of ways and contain catalyst materials useful in collecting, absorbing, adsorbing, and/or converting hydrocarbons, carbon monoxide, and/or oxides of nitrogen contained in the exhaust gas. Such catalyst materials may include, for example, aluminum, platinum, palladium, rhodium, barium, cerium, and/or alkali metals, alkaline-earth metals, rare-earth metals, or combinations thereof. The DOC 163 may include, for example, a ceramic substrate, a metallic mesh, foam, or any other porous material known in the art, and the catalyst materials may be located on, for example, a substrate of the DOC 163. The DOC(s) may also be configured to oxidize NO contained in the exhaust gas, thereby converting it to NO2. Or, stated slightly differently, the DOC 163 may assist in achieving a desired ratio of NO to NO2 upstream of the SCR catalyst 170.
The DPF 164 may be any of various particulate filters known in the art configured to reduce particulate matter concentrations, e.g., soot and ash, in the exhaust gas to meet requisite emission standards. Any structure capable of removing particulate matter from the exhaust gas of the engine 106 may be used. For example, the DPF 164 may include a wall-flow ceramic substrate having a honeycomb cross-section constructed of cordierite, silicon carbide, or other suitable material to remove the particulate matter. The DPF 164 may be electrically coupled to a controller, such as the ECU 115, that controls various characteristics of the DPF 164.
If the DPF 164 were used alone, it would initially help in meeting the emission requirements, but would quickly fill up with soot and need to be replaced. Therefore, the DPF 164 is combined with the DOC 163, which helps extend the life of the DPF 164 through the process of regeneration. The ECU 115 may be configured to measure the PM build up, also known as filter loading, in the DPF 164, using a combination of algorithms and sensors. When filter loading occurs, the ECU 115 manages the initiation and duration of the regeneration process.
Moreover, the reductant delivery system 135 may comprise a reductant tank 148 configured to store the reductant. One example of a reductant is a solution having 32.5% high purity urea and 67.5% deionized water (e.g., DEF), which decomposes as it travels through a decomposition tube 160 to produce ammonia. Such a reductant may begin to freeze at approximately 12 deg F. (−11deg C.). If the reductant freezes when a machine is shut down, then the reductant may need to be thawed before the SCR system 152 can function.
The reductant delivery system 135 may comprise a reductant header 136 mounted to the reductant tank 148, the reductant header 136 further comprising, in some embodiments, a level sensor 150 configured to measure a quantity of the reductant in the reductant tank 148. The level sensor 150 may comprise a float configured to float at a liquid/air surface interface of reductant included within the reductant tank 148. Other implementations of the level sensor 150 are possible, and may include, exemplarily, one or more of the following: (a) using one or more ultrasonic sensors; (b) using one or more optical liquid-surface measurement sensors; (c) using one or more pressure sensors disposed within the reductant tank 148; and (d) using one or more capacitance sensors.
In the illustrated embodiment, the reductant header 136 comprises a tank heating element 130 that is configured to receive coolant from the engine 106, and the power system 100 may comprise a cooling system 133 that comprises a coolant supply passage 180 and a coolant return passage 181. A first segment 196 of the coolant supply passage 180 is positioned fluidly between the engine 106 and the tank heating element 130 and is configured to supply coolant to the tank heating element 130. The coolant circulates, through the tank heating element 130, so as to warm the reductant in the reductant tank 148, therefore reducing the risk that the reductant freezes therein. In an alternative embodiment, the tank heating element 130 may, instead, be an electrically resistive heating element.
A second segment 197 of the coolant supply passage 180 is positioned fluidly between the tank heating element 130 and a reductant delivery mechanism 158 and is configured to supply coolant thereto. The coolant heats the reductant delivery mechanism 158, reducing the risk that reductant freezes therein.
A first segment 198 of the coolant return passage 181 is positioned between the reductant delivery mechanism 158 and the tank heating element 130, and a second segment 199 of the coolant return passage 181 is positioned between the engine 106 and the tank heating element 130. The first segment 198 and the second segment 199 are configured to return the coolant to the engine 106.
The decomposition tube 160 may be positioned downstream of the reductant delivery mechanism 158 but upstream of the SCR catalyst 170. The reductant delivery mechanism 158 may be, for example, an injector that is selectively controllable to inject reductant directly into the exhaust gas. As shown, the SCR system 152 may comprise a reductant mixer 166 that is positioned upstream of the SCR catalyst 170 and downstream of the reductant delivery mechanism 158.
The reductant delivery system 135 may additionally comprise a reductant pressure source (not shown) and a reductant extraction passage 184. The reductant extraction passage 184 may be coupled fluidly to the reductant tank 148 and the reductant pressure source therebetween. Exemplarily, the reductant extraction passage 184 is shown extending into the reductant tank 148, though in other embodiments the reductant extraction passage 184 may be coupled to an extraction tube via the reductant header 136. The reductant delivery system 135 may further comprise a reductant supply module 168, and it may comprise the reductant pressure source. Exemplarily, the reductant supply module 168 may be, or be similar to, a Bosch reductant supply module, such as the one found in the “Bosch Denoxtronic 2.2—Urea Dosing System for SCR Systems.”
The reductant delivery system 135 may also comprise a reductant dosing passage 186 and a reductant return passage 188. The reductant return passage 188 is shown extending into the reductant tank 148, though in some embodiments of the power system 100, the reductant return passage 188 may be coupled to a return tube via the reductant header 136.
The reductant delivery system 135 may comprise—among other things—valves, orifices, sensors, and pumps positioned in the reductant extraction passage 184, reductant dosing passage 186, and reductant return passage 188.
As mentioned above, one example of a reductant is a solution having 32.5% high purity urea and 67.5% deionized water (e.g., DEF), which decomposes as it travels through the decomposition tube 160 to produce ammonia. The ammonia reacts with NOx in the presence of the SCR catalyst 170, and it reduces the NOx to less harmful emissions, such as N2 and H2O. The SCR catalyst 170 may be any of various catalysts known in the art. For example, in some embodiments, the SCR catalyst 170 may be a vanadium-based catalyst. But in other embodiments, the SCR catalyst 170 may be a zeolite-based catalyst, such as a Cu-zeolite or a Fe-zeolite.
The AOC 174 may be any of various flowthrough catalysts configured to react with ammonia to produce mainly nitrogen. Generally, the AOC 174 is utilized to remove ammonia that has slipped through or exited the SCR catalyst 170. As shown, the AOC 174 and the SCR catalyst 170 may be positioned within the same housing. But in other embodiments, they may be separate from one another.
The precipitation cover 129 comprises a first cover end 110 and a second cover end 117. The first cover end 110 is configured as a precipitation outlet, and the second cover end 117 is configured as an exhaust gas outlet and a precipitation inlet. As shown, for example, in
At least a portion of the first cover end 110 may be positioned radially outside of an end 147 of the tailpipe 124. For example, as illustrated, the precipitation cover 129 and the tailpipe 124 may both be tubularly shaped, wherein an inner diameter 154 of the precipitation cover 129 may be larger than an outer diameter 159 of the tailpipe 124. In other embodiments, the precipitation cover 129 and/or the tailpipe 124 may take other shapes, such as an extended square shapes, extended oblong shapes, and so forth.
Further, the precipitation cover 129 may comprise a hood 162 extending axially away from the second cover end 117. The hood 162 may be angularly aligned with a spacer 125 relative to the imaginary cover axis 153. The hood 162 may minimize the amount of precipitation 165 that enters the precipitation cover 129 and tailpipe 124, particularly if the precipitation 165 is falling in the direction shown in
The tailpipe 124 may further comprise a first tailpipe section 128 and a second tailpipe section 139. The second tailpipe section 139 may be substantially elbow shaped and may be positioned downstream of the first tailpipe section 128, relative to the direction of the exhaust gas flow. The first tailpipe section 128 may define an imaginary tailpipe axis 142, and the precipitation cover 129 may define an imaginary cover axis 153. And as shown in
The precipitation cover 129 may be made of, for example, aluminized steel or stainless steel. Aluminized steel provides a surface that paints stick to, even when the aluminized steel is very hot, and the aluminized steel does not rust, even if the paint is scratched off thereof. Likewise, the first tailpipe section 128, the second tailpipe section 139, and the spacer 125 may also be made of, for example, either aluminized steel or stainless steel.
As shown, in
The apparatus 102 may further comprise a spacer 125 mounted to the tailpipe 124, and the precipitation cover 129 may be mounted to the spacer 125. Or, more specifically, the spacer 125 may be mounted to an outer surface 157 of the tailpipe 124, and the precipitation cover 129 may be mounted to an outer surface 157 of the spacer 125. As illustrated in, for example,
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Finally, in the embodiment illustrated in
Further, the spacer 325 may be “horseshoe shaped” and may partially extend around the outer surface 157 of the tailpipe 124. For example, the spacer 325 may extend around approximately 270° of the tailpipe 124 (see angle 393), though the spacer 325 may extend around a smaller or a larger angle. In other embodiments, the spacer 325 may comprise multiple pieces and take a number of different shapes, and it may comprise holes, slots, and the like.
While the disclosure has been illustrated and described in detail in the drawings and foregoing description, such illustration and description is to be considered as exemplary and not restrictive in character, it being understood that illustrative embodiments have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected. It will be noted that alternative embodiments of the present disclosure may not include all of the features described yet still benefit from at least some of the advantages of such features. Those of ordinary skill in the art may readily devise their own implementations that incorporate one or more of the features of the present disclosure and fall within the spirit and scope of the present invention as defined by the appended claims.
