Patent Application
20120216515
The subject matter disclosed herein relates to exhaust gas systems for an engine, and other embodiments relate to devices and methods for controlling an exhaust gas flow.
During operation, internal combustion engines generate various combustion by-products that are emitted from the engine in an exhaust stream. As such, an exhaust gas treatment system is included in an exhaust system of the engine in order to reduce regulated emissions, for example. In some examples, the exhaust gas treatment system includes a flow-through device, such as a catalyst, through which the exhaust stream flows. In such an example, a pressure drop may be induced on the system dependent on parameters such as the flow rate, density, and viscosity of the exhaust stream, and the geometry of the flow-through device. The pressure drop may result in parasitic losses, for example, thereby reducing the efficiency of the engine.
In one embodiment, an exhaust gas treatment device for an exhaust gas treatment system includes a primary flow passage through which exhaust gas flows to the exhaust gas treatment device. The exhaust gas treatment device further includes a first sub-catalyst partially disposed in the primary flow passage splitting the exhaust gas into a first gas flow and a bypass flow, and a second sub-catalyst disposed downstream of the first sub-catalyst in the bypass flow forming a second gas flow, where the second gas flow is different from the first gas flow.
By including at least two sub-catalysts in the exhaust gas treatment device, each sub-catalyst with a separate flow path, a cross-sectional area through which the exhaust gas flows may be increased. Further, when a cross-sectional area of the catalysts is increased, a length of the catalyst can be decreased without reducing the efficiency of the exhaust gas treatment device. In this manner, a pressure drop on the system may be reduced, for example, as the drop in pressure decreases with a decrease in length.
It should be understood that the brief description above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.
The present invention will be better understood from reading the following description of non-limiting embodiments, with reference to the attached drawings, wherein below:
The following description relates to various embodiments of an exhaust gas treatment device which includes a plurality of sub-catalysts which form separate flow paths through the exhaust gas treatment device. In some embodiments, the exhaust gas treatment device includes a primary flow passage through which exhaust gas flows to the exhaust gas treatment device. The exhaust gas treatment device further includes a first sub-catalyst partially disposed in the primary flow passage splitting the exhaust gas into a first gas flow and a bypass flow, and a second sub-catalyst disposed in the bypass flow forming a second gas flow, where the second gas flow is different from the first gas flow. In other embodiments, the exhaust gas treatment device includes more than two sub-catalysts disposed therein.
In some embodiments, the exhaust gas treatment device is configured for an exhaust gas treatment system in a vehicle, such as a rail vehicle. For example,
The engine 104 receives intake air for combustion from an intake conduit 114. The intake conduit 114 receives ambient air from an air filter (not shown) that filters air from outside of the rail vehicle 106. Exhaust gas resulting from combustion in the engine 104 is supplied to an exhaust passage 116. Exhaust gas flows through the exhaust passage 116, and out of an exhaust stack of the rail vehicle 106. In one example, the engine 104 is a diesel engine that combusts air and diesel fuel through compression ignition. In other non-limiting embodiments, the engine 104 may combust fuel including gasoline, kerosene, biodiesel, or other petroleum distillates of similar density through compression ignition (and/or spark ignition).
The vehicle system 100 includes a turbocharger 120 that is arranged between the intake conduit 114 and the exhaust passage 116. The turbocharger 120 increases air charge of ambient air drawn into the intake conduit 114 in order to provide greater charge density during combustion to increase power output and/or engine-operating efficiency. The turbocharger 120 may include a compressor (not shown in
The vehicle system 100 further includes an exhaust gas treatment system 108 coupled in the exhaust passage downstream of the turbocharger 120. The exhaust gas treatment system 108 includes an exhaust gas treatment device 124. The exhaust gas treatment device may be a catalyst, for example, such as a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), a selective catalytic reduction (SCR) catalyst, etc. As further elaborated with reference to
The rail vehicle 106 further includes a controller 148 to control various components related to the vehicle system 100. In one example, the controller 148 includes a computer control system. The controller 148 further includes computer readable storage media (not shown) including code for enabling on-board monitoring and control of rail vehicle operation. The controller 148, while overseeing control and management of the vehicle system 100, may be configured to receive signals from a variety of engine sensors 150, as further elaborated herein, in order to determine operating parameters and operating conditions, and correspondingly adjust various engine actuators 152 to control operation of the rail vehicle 106. For example, the controller 148 may receive signals from various engine sensors 150 including, but not limited to, engine speed, engine load, boost pressure, exhaust pressure, ambient pressure, exhaust temperature, etc. Correspondingly, the controller 148 may control the vehicle system 100 by sending commands to various components such as traction motors, alternator, cylinder valves, throttle, etc.
As further elaborated with reference to
In one example embodiment, the vehicle system is a locomotive system which includes an engine cab defined by a roof assembly and side walls. The locomotive system further comprises an engine positioned in the engine cab such that a longitudinal axis of the engine is aligned in parallel with a length of the cab. Further, an exhaust gas treatment system is included, and is mounted on the engine within a space defined by a top surface of an exhaust manifold of the engine, the roof assembly, and the side walls of the engine cab such that a longitudinal axis of the exhaust gas treatment system is aligned in parallel with the longitudinal axis of the engine. The exhaust gas treatment system includes an exhaust gas treatment device with a primary flow passage and a plurality of sub-catalysts. Each of the sub-catalysts forms a corresponding flow path configured to receive a different portion of an exhaust gas flow from the exhaust manifold of the engine. Detailed examples of such an embodiment are described below.
Turning to
In the example of
In the example embodiment of
As mentioned above, the engine system 200 includes a turbocharger 204 positioned at a front end 210 of the engine 202. In the example of
In the example embodiment shown in
The exhaust gas treatment system 208 is defined by the exhaust passage aligned in parallel with the longitudinal axis of the engine. In the example embodiment shown in
Further, the exhaust flow passage 218 includes an inlet through which the exhaust gas stream enters the exhaust gas treatment system 208.
In another embodiment, the exhaust gas treatment system 208 may include a plurality of distinct flow passages aligned in a common direction (e.g., along the longitudinal axis of the engine). In such an embodiment, each of the plurality of flow passages may include one or more exhaust gas treatment devices which may each include a plurality of sub-catalysts.
By positioning the exhaust gas treatment system on top of the engine such that the exhaust passage is aligned in parallel with the longitudinal axis of the engine, as described above, a compact configuration can be enabled. In this manner, the engine and exhaust gas treatment system can be disposed in a space, such as an engine cab as described above, where the packaging space may be limited.
In a vehicle system, such as the locomotive system described above, in which packaging space is limited, a cross-sectional area of the exhaust gas treatment device perpendicular to the direction of exhaust gas flow may be reduced such that the device fits within the space between the engine and the roof assembly of the engine cab. For example, a diameter of the exhaust gas treatment device is reduced. Further, in such a configuration, the device may be elongated so that exhaust gas is exposed to the catalyst for a desired duration, for example.
In some examples, the catalyst may have a honeycomb-like structure formed of a plurality of channels through which the exhaust gas flows. In such an embodiment, a pressure drop induced by the exhaust gas treatment device may be increased when a length of the device is increased according to the Hagen-Poiseuille equation for pressure drop through a tube (e.g., a channel):
where μ is the viscosity of the fluid flowing through the tube, L is the length of the tube, Q is the volumetric flow rate, and r is the radius of the tube. If a pressure drop on the system is increased, parasitic losses on the system may be increased thereby decreasing the efficiency of the engine. As can be further deduced from the Hagen-Poiseuille equation (1), the pressure drop can be reduced by increasing the cross-sectional area and/or decreasing the length of the tube.
When the length of the exhaust gas treatment device 402 is increased, a pressure drop on the system is increased, as described above, which may lead to a decrease in engine efficiency. Thus,
In an example embodiment, an exhaust gas treatment device for an exhaust gas treatment system includes a primary flow passage through which exhaust gas flows to the exhaust gas treatment device. The device further includes a first sub-catalyst partially disposed in the primary flow passage splitting the exhaust gas into a first gas flow and a bypass flow, and a second sub-catalyst disposed downstream of the first sub-catalyst in the bypass flow forming a second gas flow, where the first gas flow is different from the second gas flow.
In another example embodiment, an exhaust gas treatment device includes a flow passage and a first sub-catalyst disposed in the flow passage and located at a first location along the flow passage. The first sub-catalyst partially but not entirely fills a radial extent of the flow passage at the first location. Further, a portion of the radial extent at the first location that is not filled by the first sub-catalyst is unoccupied, such that exhaust gas can flow unfettered around the first sub-catalyst. The exhaust gas treatment device further includes a second sub-catalyst disposed in the flow passage and located at a downstream, second location along the flow passage. The second sub-catalyst partially but not entirely fills a radial extent of the flow passage at the second location. Further, a portion of the radial extent at the second location that is not filled by the second sub-catalyst is unoccupied, such that exhaust gas can flow unfettered around the second sub-catalyst.
The primary flow passage is an entry flow passage where the exhaust gas flow converges into the exhaust gas treatment device, for example, before the flow is split by the sub-catalysts. As used herein, the term “split” implies the exhaust gas flow is divided into two or more separate portions of gas flow (e.g., first gas flow, bypass flow, and the like). Further, “partially disposed in” implies the sub-catalyst extends partially across the diameter of the exhaust gas treatment device such that at least some exhaust gas can bypass the sub-catalyst. In particular, a portion of a radial extent of the flow passage at a location of the sub-catalyst is unoccupied such that exhaust gas can flow unfettered around the sub-catalyst. The gas flow is the operational flow through the sub-catalyst. For example, the first gas flow is the operational flow through the first sub-catalyst. Further, “bypass” implies the exhaust flow does not flow through the sub-catalyst. For example, the bypass flow does not pass through the first sub-catalyst. Instead, the bypass flow flows around the first sub-catalyst where it becomes the second gas flow upon passing through the second sub-catalyst. In other examples, as described below, the bypass flow may be further divided into two or more gas flows.
The example embodiment depicted in
In the example embodiment of
As an example, as shown in
In some embodiments, the first sub-catalyst 506 and the second sub-catalyst 508 are substantially the same. For example, the sub-catalysts may be formed of the same type of material (e.g., substrate, catalyst, washcoat, or the like) and have the same size and structure (e.g., channel diameter and spacing). In other embodiments, the first sub-catalyst 506 and the second sub-catalyst 508 may be different. For example, the sub-catalysts may have different sizes. In one embodiment, the sub-catalysts may have different substrates and/or coatings such that one of the sub-catalysts is more effective at a relatively high temperature and the other sub-catalyst is more effective at a relatively low temperature, for example. In such an embodiment, the exhaust gas treatment system 500 may include a valve 514 that can be closed so that exhaust gas flow to one of the sub-catalysts is substantially reduced, as will be described in greater detail below with reference to
As shown in the example of
Thus, an exhaust gas treatment device may include two sub-catalysts which divide the exhaust flow through the exhaust gas treatment device into two flow paths. In this way, a catalyst surface area through which exhaust gas flows may be increased and a length along which each portion of exhaust gas flow may be decreased, thereby reducing a pressure drop on the system.
As shown in
In some embodiments, the first sub-catalyst 606, the second sub-catalyst 608, and the third sub-catalyst 610 are substantially the same. For example, the sub-catalysts may be formed of the same material (e.g., substrate, catalyst, washcoat, or the like) and have the same size and structure (e.g., channel diameter and spacing). In other embodiments, each of the sub-catalysts may be different. In one example, each of the sub-catalysts may have a different shape and cross-sectional area. Alternatively or additionally, the sub-catalysts may have different substrates and/or coatings such that at least one of the sub-catalysts is more effective at a relatively high temperature and the other sub-catalysts are more effective at a relatively low temperature, for example. In still other embodiments, two of the sub-catalysts may be the same while the other sub-catalyst is different.
As is further illustrated in the example of
The example embodiment depicted in
Thus, an exhaust gas treatment device may include three sub-catalysts which divide the exhaust flow through the exhaust gas treatment device into three flow paths. In this way, a catalyst surface area through which exhaust gas flows may be increased and a length along which each portion of exhaust gas flow may be decreased, thereby reducing a pressure drop on the system
In the example embodiment of
In some embodiments, the first sub-catalyst 706, the second sub-catalyst 708, and the third sub-catalyst 710 are substantially the same. For example, the sub-catalysts may be formed of the same material (e.g., substrate, catalyst, washcoat, or the like) and have the same size and structure (e.g., channel diameter and spacing). In other embodiments, each of the sub-catalysts may be different. In one example, one or more of the sub-catalysts may have a different shape and/or cross-sectional area, as shown in
As is further shown in the example of
In some examples, the first sub-catalyst 706 and the third sub-catalyst 710 may be the same sub-catalyst which form a first flow path (e.g., flow paths 712 and 716 are part of the same flow path). For example, the sub-catalyst may have a ring-shape which appears as two sub-catalysts when viewed through a cross-section, such as in
Thus, an exhaust gas treatment device may include two or three sub-catalysts which divide the exhaust flow through the exhaust gas treatment device into two or three flow paths, respectively. In this way, a catalyst surface area through which exhaust gas flows may be increased and a length along which each portion of exhaust gas flow may be decreased, thereby reducing a pressure drop on the system
Another example embodiment of an exhaust gas treatment system 800 with an exhaust gas treatment device 802 with a divided flow path is shown in
In the example embodiment of
In some embodiments, the first sub-catalyst 806, the second sub-catalyst 808, the third sub-catalyst 810, the fourth sub-catalyst 812, and the fifth sub-catalyst 814 are substantially the same. For example, the sub-catalysts may be formed of the same material (e.g., substrate, catalyst, washcoat, or the like) and have the same size and structure (e.g., channel diameter and spacing). In other embodiments, each of the sub-catalysts may be different. In one example, one or more of the sub-catalysts may have a different shape and/or cross-sectional area, as shown in
As is further shown in the example of
The exhaust gas treatment device 802 further includes a plurality of flow dividers 826. For example, one divider 826 is coupled between the first sub-catalyst 806 and the second sub-catalyst 808 such that exhaust gas that exits sub-catalyst 806 does not enter any of the other sub-catalysts. Another divider 826 is coupled between the second sub-catalyst 808 and the third sub-catalyst 810 such that exhaust gas that exits sub-catalyst 808 does not enter sub-catalyst 810. Another divider 826 is coupled between the fourth sub-catalyst 812 and the fifth sub-catalyst 814 such at that exhaust gas that exits sub-catalyst 812 foes not enter the other sub-catalysts. Another divider 826 is coupled between the fifth sub-catalyst 814 and the third sub-catalyst 810 such that exhaust gas that exits sub-catalyst 814 does not enter the third sub-catalyst 810. The dividers 826 may be formed of any suitable material such as stainless steel, for example. In some embodiments, one or both sides of one or more of the dividers 826 may be coated with a catalytic material to further facilitate emissions reduction. The dividers 826 may be attached or otherwise secured in any suitable manner.
In some examples, the first sub-catalyst 806 and the fourth sub-catalyst 812 may be the same sub-catalyst which form a first flow path (e.g., flow paths 816 and 822 are part of the same flow path). For example, the sub-catalyst may have a ring-shape which appears as two sub-catalysts when viewed through a cross-section, such as in
Similarly, the second sub-catalyst 808 and the fifth sub-catalyst 814 may be the same ring-shaped sub-catalyst which forms a second flow path (e.g., flow path 818 and 824 are part of the same flow path). In this manner, the exhaust gas treatment device 802 may include two ring-shaped sub-catalysts forming two separate flow paths, and a third cylindrical sub-catalyst forming a third flow path which is different from the other two flow paths.
Thus, an exhaust gas treatment device may include three, four, or five sub-catalysts which divide the exhaust flow through the exhaust gas treatment device into three, four, or five flow paths, respectively. In this way, a catalyst surface area through which exhaust gas flows may be increased and a length along which each portion of exhaust gas flow may be decreased, thereby reducing a pressure drop on the system
In the example embodiment of
In some embodiments, each of the sub-catalysts 906 is substantially the same. For example, the sub-catalysts 906 may be formed of the same material (e.g., substrate, catalyst, washcoat, or the like) and have the same size and structure (e.g., channel diameter and spacing), such as shown in
As is further shown in the example of
In some examples, two of the sub-catalysts 906 disposed along the line 912 may form a ring-shaped sub-catalyst. For example, the exhaust gas treatment device 902 may include one or two ring-shaped sub-catalysts disposed along the line 912. The exhaust gas treatment device may further include a ring-shaped catalyst disposed along line 914. In this manner, the exhaust gas treatment device 902 shown in
Thus, an exhaust gas treatment device may include four, five, six, or seven sub-catalysts which divide the exhaust flow through the exhaust gas treatment device into four, five, six, or seven flow paths, respectively. In this way, a catalyst surface area through which exhaust gas flows may be increased and a length along which each portion of exhaust gas flow may be decreased, thereby reducing a pressure drop on the system
In the example embodiment of
In some embodiments, each of the sub-catalysts 1006 is substantially the same. For example, the sub-catalysts 1006 may be formed of the same material (e.g., substrate, catalyst, washcoat, or the like) and have the same size and structure (e.g., channel diameter and spacing). In other embodiments, each of the sub-catalysts may be different. In one example, one or more of the sub-catalysts may have a different shape and/or cross-sectional area. In the example of
Further,
In some examples, two of the sub-catalysts 1006 disposed along the line 1012 may form a ring-shaped sub-catalyst. For example, the exhaust gas treatment device 902 may include one, two, or three ring-shaped sub-catalysts disposed along the line 1012. The exhaust gas treatment device may further include one or two ring-shaped catalysts disposed along line 1014. In this manner, the exhaust gas treatment device 1002 depicted in
Thus, an exhaust gas treatment device may include six, seven, eight, nine, ten, or eleven sub-catalysts which divide the exhaust flow through the exhaust gas treatment device into six, seven, eight, nine, ten, or eleven flow paths, respectively. In this way, a catalyst surface area through which exhaust gas flows may be increased and a length along which each portion of exhaust gas flow may be decreased, thereby reducing a pressure drop on the system
The illustrated embodiments in
At 1102 of method 1100, operating conditions of the engine and/or exhaust gas treatment system are determined. The operating conditions may include exhaust gas temperature, engine load, sub-catalyst temperature, etc.
Once the operating conditions are determined, method 1100 proceeds to 1104 where it is determined if the exhaust gas temperature is greater than a threshold temperature. For example, exhaust gas temperature may be measured by an exhaust gas temperature sensor positioned in the exhaust passage. The threshold temperature may be based on a warm-up condition of the engine or based on engine load, for example. As an example, under low engine loads, the exhaust gas may have relatively low temperature as compared to the exhaust gas temperature under high loads.
If it is determined that the exhaust gas temperature is less than the threshold temperature, method 1100 continues to 1106 where the valve, such as valve 514 described above with reference to
At 1108 of method 1100, it is determined if the exhaust gas temperature is above a threshold temperature. In some examples, the threshold temperature may be the same threshold temperature as described above at 1104 of method 1100. In other examples, the threshold temperature may be a different threshold temperature than that described above at 1104 of method 1100.
If it is determined that the threshold temperature is not greater than the threshold temperature, method 1100 returns to 1108 and the valve remains in the closed position. On the other hand, if it is determined that the exhaust gas temperature is greater than the threshold temperature at 1108 or if it determined that the exhaust gas temperature is greater than the threshold temperature at 1104, method 1100 moves to 1110.
At 1100 of method 1100, the valve is opened such that a first portion of the exhaust gas flow along the primary exhaust passage is directed along a first flow path through the first sub-catalyst and a second portion of the exhaust gas flow is directed along the second flow path through the second sub-catalyst such that it bypasses the first sub-catalyst.
In other embodiments, control of the valve may be based on engine load. For example, during low load conditions, the valve may be closed such that flow through the first sub-catalyst is substantially reduced and a substantial portion of the exhaust gas flowing through the primary flow passage flows along the second flow path and through the second sub-catalyst. In this manner, the exhaust gas treatment device may operate with a higher efficiency, for example. Further, by using a valve to control flow through the exhaust gas treatment device, degradation of the exhaust gas treatment device may be reduced.
In another embodiment, control of the valve may be based on sub-catalyst temperature. For example, a threshold temperature may be a light-off temperature of the first sub-catalyst or the second sub-catalyst. When a temperature of the first sub-catalyst is less than the threshold temperature, the valve may be closed to substantially reduce flow through the first sub-catalyst. In this way, light-off time of one or both of the sub-catalysts may be reduced, for example.
Thus, a valve positioned upstream of an exhaust gas treatment device with a plurality of sub-catalysts may be adjusted to control exhaust gas flow along flow paths corresponding to each of the sub-catalysts. As such, efficiency of the exhaust gas treatment device may be increased and degradation may be reduced.
The method 1100 is described for an example embodiment in which the exhaust gas treatment system includes an exhaust gas treatment device which has two sub-catalysts, such as the example embodiment depicted in
As explained above, the terms “high temperature” and “low temperature” are relative, meaning that “high” temperature is a pressure higher than a “low” temperature. Conversely, a “low” temperature is a pressure lower than a “high” temperature.
As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural of said elements or steps, unless such exclusion is explicitly stated. Furthermore, references to “one embodiment” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments “comprising,” “including,” or “having” an element or a plurality of elements having a particular property may include additional such elements not having that property. The terms “including” and “in which” are used as the plain-language equivalents of the respective terms “comprising” and “wherein.” Moreover, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements or a particular positional order on their objects.
This written description uses examples to disclose the invention, including the best mode, and also to enable a person of ordinary skill in the relevant art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those of ordinary skill in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
