Exhaust system with pressure sensing system having a clog relief conduit forming a normally open leak path

Abstract

An exhaust system includes an exhaust pressure sensing system having a sensor conduit configured to be fluidly connected to an exhaust pipe in the exhaust system and to feed exhaust gas to a differential pressure sensor. The differential pressure sensor generates a pressure signal indicative of a pressure drop across an exhaust aftertreatment element, such as an exhaust filter. A clog mitigation conduit provides a normally open leak path for conveying condensate in a leaked exhaust stream between the sensor conduit to prevent the formation of deposits that can affect pressure sensing accuracy.

Description

Technical Field

[0001] The present invention generally relates to exhaust pressure sensing in an exhaust system for an internal combustion engine, and more specifically to preventing sensor pipes from being blocked by deposits that affect the accuracy of exhaust pressure signals. Background Technology

[0002] Monitoring, evaluating, and controlling all aspects of the exhaust system's operation and condition in an internal combustion engine is crucial for optimizing performance. In recent years, various regulatory requirements have been implemented, limiting the relative amounts of certain exhaust components that can be emitted into the atmosphere. Of particular concern are emissions of nitrogen oxides (NOx) and particulate matter. Over the years, various monitoring systems and technologies have been developed to monitor factors such as temperature, absolute pressure, pressure differential, mass flow rate, and other characteristics of engine exhaust for a wide range of purposes.

[0003] In one example pressure-sensing implementation, the pressure drop across the particulate filter in the exhaust system is monitored so that the controller can determine the relative state of the particulate filter's filling with particulate matter. During engine operation, particulate matter (especially soot) is trapped in the exhaust filter to prevent it from being released into the atmosphere. However, as the particulate filter fills, the accumulated material may begin to restrict the exhaust flow through the filter, creating back pressure that, if left unchecked, can interfere with engine operation.

[0004] Various techniques have been proposed for regenerating particulate filters, typically by utilizing a catalyst residing on the particulate filter to promote the oxidation of soot, or by passively regenerating the particulate filter through various means. So-called active regeneration can utilize manipulation of engine operation to generate increased exhaust temperatures that facilitate the oxidation of trapped particulate matter, fuel delivery into the exhaust stream to aid regeneration, electric resistance heaters, or other techniques. Because active regeneration requires energy and alters the current engine operating mode, there is usually an efficiency loss associated with regeneration. For this reason, various control systems and sensing strategies are known to attempt to determine with relative precision when regeneration is needed, or when favorable conditions for regeneration exist. In most active regeneration strategies, it is typically necessary to monitor exhaust pressure at one or more locations in the exhaust system. U.S. Patent No. 8,968,443, granted to Brinkmeyer et al., discloses an example closed-loop pressure management system for an exhaust regeneration system. Brinkmeyer et al. have presented a wide variety of applications; however, there is always room for improvement and development of alternative strategies. Summary of the Invention

[0005] In one aspect, the exhaust system includes an exhaust conduit extending between an upstream exhaust inlet and a downstream exhaust outlet. The exhaust system also includes an exhaust aftertreatment device, fluidly positioned within the exhaust conduit and configured to treat the exhaust gas delivered from the upstream exhaust inlet to the downstream exhaust outlet. The exhaust system also includes an exhaust pressure sensor, and a sensor conduit fluidly connected to the exhaust conduit and extending to the exhaust pressure sensor to expose the sensor to the fluid pressure of the exhaust gas. The exhaust system also includes a clogging relief conduit that forms a normally open leakage path from the sensor conduit.

[0006] On the other hand, the exhaust pressure sensing system includes an upstream sensor conduit having a first inlet end configured to be fluidly connected to an exhaust pipe at an upstream location and a first sensing end opposite to the first inlet end. The exhaust pressure sensing system also includes a downstream sensor conduit having a second inlet end configured to be fluidly connected to an exhaust pipe at a downstream location and a second sensing end opposite to the second inlet end. The exhaust pressure sensing system also includes a differential pressure sensor and a blockage relief conduit. The differential pressure sensor has at least one sensing element exposed at respective first and second sensing ends to the fluid pressure of the upstream sensor conduit and the fluid pressure of the downstream sensor conduit. The blockage relief conduit is fluidly connected to the upstream and downstream sensor conduits and includes a flow-restriction that allows fluid flow between the upstream and downstream sensor conduits and forms a normally open leakage path to transport condensate in the leaked exhaust flow from the upstream sensor conduit to the downstream sensor conduit.

[0007] In another aspect, a method for sensing exhaust pressure in an exhaust system includes: fluidly connecting a sensor conduit to an exhaust pipe in the exhaust system; and fluidly connecting a blockage relief conduit to the sensor conduit to form a leakage path from the sensor conduit. The method further includes feeding exhaust gas from the exhaust pipe into the sensor conduit such that the fluid pressure of the exhaust gas impinges on an exhaust pressure sensor, and leaking the exhaust gas from the sensor conduit through the exhaust leakage path. The method also includes: discharging the leaked exhaust gas along with condensate from the sensor conduit; returning the leaked exhaust gas and the discharged condensate to the exhaust pipe; and generating an exhaust pressure signal using the exhaust pressure sensor based on the fluid pressure of the exhaust gas. Attached Figure Description

[0008] Figure 1 This is a schematic view of an engine system according to one embodiment;

[0009] Figure 2 yes Figure 1 A diagrammatic view of a part of the engine system;

[0010] Figure 3 This is a schematic view of a service package including an exhaust pressure sensing system according to one embodiment; and

[0011] Figure 4 This is a schematic view of replacing a used exhaust pressure sensing system in an exhaust system with a replacement exhaust pressure sensing system according to one embodiment. Detailed Implementation

[0012] Reference Figure 1 The diagram illustrates an internal combustion engine system 10 according to one embodiment. The internal combustion engine system 10 includes an internal combustion engine 12 having an engine housing 14 in which a plurality of cylinders 16 are formed in a conventional manner. The internal combustion engine system 10 (hereinafter referred to as "engine system 10") may include a direct-injection compression ignition diesel engine 12 configured, for example, to operate with diesel distillate fuel; however, the invention is not limited thereto. The cylinders 16 may include any number of cylinders in any suitable arrangement. The engine system 10 may also include a turbocharger 18 having a compressor 20 and a turbine 22. Air is fed to the compressor 20 through an intake port 24 and supplied to the cylinders 16 through an aftercooler 26 for fuel combustion therein.

[0013] Exhaust from cylinder 16 is fed into exhaust system 30 via turbine 22. Exhaust system 30 includes exhaust duct 32 extending between upstream exhaust inlet 34 and downstream exhaust outlet 36.

[0014] Exhaust aftertreatment device 38 is fluidly positioned within exhaust duct 32 and configured to treat exhaust gas delivered from upstream exhaust inlet 34 to downstream exhaust outlet 36. As used herein, the term "upstream" refers to the direction in exhaust system 30 toward internal combustion engine 12, while "downstream" refers to the opposite direction. Exhaust aftertreatment device 38 may include filter media of exhaust particulate filter assembly 39 having housing 42. Housing 42 forms part of exhaust duct 32 and is configured to deliver exhaust gas from internal combustion engine 12 through exhaust aftertreatment device 38, thereby capturing particulate matter therein, such as soot and ash. Housing 42 may include housing inlet 44 and housing outlet 46, with exhaust aftertreatment device 38 fluidly positioned between housing inlet 44 and housing outlet 46. In many embodiments, additional exhaust aftertreatment devices and components may be positioned between upstream exhaust inlet 34 and downstream exhaust outlet 36, such as diesel engine oxidation catalyst or DOC, and selective catalytic reduction or SCR devices, sulfate traps, or combinations and alternatives to these.

[0015] The exhaust system 30 also includes an exhaust pressure sensing system 50, which is configured, for example, to monitor the pressure drop across the device 38 to determine the timing or suitability of the regeneration device 38, monitor or modify the operation of the internal combustion engine 12, or for other purposes, as will be discussed further herein. The exhaust system 30 also includes a regeneration control system 70, which includes an electronic control unit 72 coupled to the fuel injector 74. Fuel, for example, diesel distillate fuel, can be supplied from the fuel tank 78 to the fuel injector 74 via a pump 76. The electronic control unit 72 may include a central processing unit, such as a microprocessor, microcontroller, or any other suitable computerized device. The regeneration control system 70 may be configured to controllably regenerate the exhaust aftertreatment device 38 based on one or more of the absolute exhaust pressure or exhaust pressure differential measured at one or more sensing locations, as will be discussed further herein.

[0016] The exhaust pressure sensing system 50 (hereinafter referred to as "sensing system 50") includes an upstream sensor conduit 52 having a first inlet end 54 configured to be fluidly connected to an exhaust conduit 32 at an upstream location, and a first sensing end 56 opposite to the first inlet end 54. The sensing system 50 also includes a downstream sensor conduit 58 having a second inlet end 60 configured to be fluidly connected to the exhaust conduit 32 at a downstream location, and a second sensing end 62 opposite to the second inlet end 60. The sensing system 50 also includes an exhaust pressure sensor 64, such as a differential pressure sensor, which includes at least one sensing element 66 exposed to the fluid pressure of the exhaust gas in the sensor conduit, including the fluid pressure of the exhaust gas in the upstream sensor conduit 52 at the respective first sensing end 56 and the fluid pressure of the exhaust gas in the downstream sensor conduit 58 at the respective second sensing end 62.

[0017] At least one sensing element 66 may include a diaphragm and one or more strain gauges 68 operatively coupled to the sensing element 66, the diaphragm being exposed to fluid pressure in the upstream sensor conduit 52 and fluid pressure in the downstream sensor conduit 58. The one or more strain gauges 68 may be electrically connected to an electronic control unit 72, such that the electronic control unit 72 can calculate, observe, infer, or otherwise determine a value indicating the exhaust pressure in the exhaust system 30. As described above, the exhaust pressure may include a differential pressure, and a differential pressure sensor 64 may generate an exhaust differential pressure signal output to the electronic control unit 72.

[0018] Those skilled in the art will understand that differential pressure can be calculated based on absolute pressure signals from different pressure sensing locations, for example, using multiple diaphragms, multiple strain gauges, or various other sensing devices. It should be understood that the invention is applicable to, but not limited to, the sensing of exhaust pressure, regardless of the specific sensor hardware configuration or system used. It should also be understood that although this specification focuses on sensing differential pressure, the teachings herein can be applied to sensing absolute pressure to determine filter regeneration timing, filter status, exhaust back pressure magnitude, or various other pressure parameters that may be of interest in the operation and control of an internal combustion engine system. It should also be understood that other regeneration techniques, such as active regeneration with an electric heater, passive regeneration, or a combination of passive and active regeneration, may be appropriately applied in this context, and the illustrative description of the regeneration control system 70 is for illustrative purposes only.

[0019] In some exhaust pressure sensing systems, sensor reading errors, calibration deviations, inaccuracies, fault code logging, or pressure sensor malfunctions have been observed, with deposits accumulating in the fluid lines that feed exhaust to the sensor. It is believed that, under certain conditions, condensation generated in the sensor lines in the presence of raw engine exhaust can lead to deposit formation, which may protect the sensing element from pressure or pressure changes, or interfere with the normal operation of the pressure sensor. For example, when the engine starts, the relatively hot exhaust carrying water vapor encounters the relatively cool surfaces of equipment in the exhaust system, including the sensor lines, causing water in the exhaust to condense. Over time, condensation is repeatedly generated, mixing with other materials carried in the exhaust to form solid deposits, which can trigger fault codes in the relevant control systems, leading to inaccurate sensor readings or other problems. These challenges are sometimes further complicated by packaging limitations, such as the need for the sensor lines to be placed in a relatively horizontal orientation, which promotes condensation buildup.

[0020] According to the present invention, providing a controlled positive exhaust pressure within and through the sensor conduit limits or eliminates the accumulation of condensate that causes the aforementioned problems. To this end, the sensing system 50 may include a blockage relief conduit 80 fluidly connected to an upstream sensor conduit 52 and a downstream sensor conduit 58, and has a flow restrictor 82 between the upstream and downstream sensor conduits 52. The blockage relief conduit 80 forms a normally open leakage path to transport condensate in the leaked exhaust flow from the upstream sensor conduit 50 to the downstream sensor conduit 58. Normally open means that the leakage path is not opened, closed, or restricted by a movable valve or the like, but rather provides a continuous, unobstructed flow path.

[0021] exist Figure 1In one embodiment, the flow restrictor 82 includes an orifice plate as shown, wherein reduced-sized orifices or ports allow fluid to be positioned in a relatively large flow path between the upstream sensor conduit 52 and the downstream sensor conduit 58. In other embodiments, as further discussed herein, the size of the clogging relief conduit 80 itself can provide the required flow restriction. It should be understood that the leak path formed by the clogging relief conduit 80 can provide a relatively small continuous flow of leaked exhaust gas, which flows continuously between the upstream sensor conduit 52 and the downstream sensor conduit 58. In other embodiments, for example, an additional positive pressure source can be provided to increase the fluid flow through the clogging relief conduit 80 by connecting a supply line separate from the upstream conduit 52 to another location in the exhaust system 30, or a supply line from the compressor 20, or another arrangement.

[0022] Still referencing Figure 2 and Figure 3 Additional features of the sensing system 50 are shown, including Figure 2 The example installation configuration is shown in the figure. The sensing system 50 may be at least partially included in the sensor assembly 51, which is mounted on the housing 42 and arranged such that the upstream sensor conduit 52 and the downstream sensor conduit 58 are substantially horizontally oriented. In the sensor assembly 51, a blockage relief conduit 180 is also used to provide flow restriction only due to its size. Figure 2 The diagram depicts a general exhaust flow pattern from an upstream exhaust system component 40 through the housing 42. The upstream exhaust system component 40 may include another aftertreatment device or be positioned, for example, as a pipe to deliver exhaust gas into the housing inlet 44. Figure 3 It can also be seen that the sensing system 50 can be provided as a service package 84, wherein the sensor assembly 51 is assembled for service, or provided in a disassembled state in a container 86 (such as a box, padded envelope, etc.).

[0023] As described above, the upstream sensor conduit 52 includes a first inlet end 54 and a first sensing end 56. The first inlet end 54 may be equipped with a fitting 55, and the first sensing end 56 is equipped with another fitting 69. The downstream sensor conduit 58 may include a second inlet end 60 and a second sensing end 62. The second inlet end 60 may be equipped with a fitting 61, and the second sensing end 62 is equipped with a fitting 71. The pressure sensor 64 includes a sensor body 83, which is fluidly connected to the first sensing end 56 and the second sensing end 62 via fittings 87 and 89. Sensing elements and strain gauges similar to the aforementioned sensing elements may be housed within or coupled to the sensor body 83. Electrical connectors are located in... Figure 3 It is shown as 85 in the middle and can be configured to connect with electrical plug 65, such as Figure 2As shown in the diagram. The sensor assembly 51 also includes a mounting bracket 67 with a plurality of fasteners 81, configured to attach the fastener assembly 51 to the housing 42. It should also be recalled that the conduit size of the blockage relief conduit 180 provides the necessary flow restriction. Figure 3 In this configuration, each of the upstream sensor conduit 52 and the downstream sensor conduit 58 has a larger pipe size, as shown in 88, while the blockage relief conduit 180 has a smaller pipe size, as shown in 91, which creates a flow restriction. The ratio of the larger pipe size 88 to the smaller pipe size 91 can be at least 5:1, and in some cases can be approximately 6:1. Pipe size refers to the outer diameter dimensional size, and it should be understood that the inner diameter dimensional size forming the internal flow region of the various pipes will substantially correspond to the outer diameter dimensional pipe size. In other words, in some embodiments, the cross-sections of the internal flow regions of the upstream sensor conduit 52, the downstream sensor conduit 58, and the blockage relief conduit 180 may have the aforementioned ratio. In some cases, it may be desirable to connect the blockage relief conduit 180 as close as possible to the sensor body 83 where feasible. In the illustrated case, the blockage relief conduit 180 is fluidly connected at a first connection location to the upstream sensor conduit 52, which is closer to the first sensing end 56 than the first inlet end 54, and at a second connection location to the downstream sensor conduit 58, which is closer to the second sensing end 62 than the second inlet end 60.

[0024] Industrial applicability

[0025] Exhaust pressure sensing in an exhaust system according to the invention includes fluidly connecting a sensor conduit, for example, an upstream sensor conduit 52, to an exhaust conduit in the exhaust system. Exhaust pressure sensing also includes fluidly connecting a blockage relief conduit, as described herein, to the sensor conduit to form a leak path. When the exhaust system is operated, exhaust gas is fed from the exhaust conduit into the sensor conduit such that the fluid pressure of the exhaust gas impinges on the exhaust pressure sensor. Feeding exhaust gas in this manner will cause exhaust gas to leak from the sensor conduit through the exhaust leak path. Condensate (including water and other materials condensed from the original exhaust gas) will readily drain from the sensor conduit along with the leaking exhaust gas. As further discussed herein, in some embodiments, the leaking exhaust gas and the drained condensate are returned to the exhaust conduit. The exhaust pressure sensor 64 can be operated to generate an exhaust pressure signal based on the fluid pressure of the exhaust gas impinging on the sensing element 66. As discussed herein, the invention is contemplated for application to both absolute pressure sensors and differential pressure sensors.

[0026] Still referencing Figure 4As can be seen, sensor assembly 51 is assembled for service and positioned to replace used sensor assembly 151. It can also be noted that the used sensor assembly 151, including one or more used sensor conduits and a used exhaust pressure sensor, has been decoupled from housing 42. First port 90 and second port 92 are formed in housing 42 and configured to mate with fitting 55 and fitting 61, respectively. Fastener opening 94 is also formed in housing 42 and configured to receive fastener 81 attached to bracket 67 of sensor assembly 5. In this general manner, used sensor assemblies can be replaced with new fastener assemblies 51 at predetermined service intervals or at another time, wherein sensor assembly 51 has suitable dimensions, fittings, and configurations for use as an embedded replacement system. It should be understood that in other cases, a smaller number of parts may be provided in the service package, including, for example, only suitable fittings and blockage relief conduits, such as… Figure 3 The accessories 69 and 71 shown, as well as the blockage relief conduit 180, are installed for use with existing upstream sensor conduits, downstream sensor conduits, exhaust pressure sensors, and mounting hardware.

[0027] This description is for illustrative purposes only and should not be construed as limiting the scope of the invention in any way. Therefore, those skilled in the art will understand that various modifications can be made to the currently disclosed embodiments without departing from the full and proper scope and spirit of the invention. Other aspects, features, and advantages will become apparent upon examination of the accompanying drawings and claims. As used herein, the articles “a” and “an” should include one or more items and may be used interchangeably with “one or more.” The word “an” or similar language is used where only one item is intended to be used. Additionally, as used herein, the words “has,” “have,” “having,” etc., should be open-ended terms. Furthermore, unless explicitly stated otherwise, the phrase “based on” should mean “at least partially based on.”

Claims

1. An exhaust system comprising: an exhaust conduit extending between an upstream exhaust inlet and a downstream exhaust outlet; an exhaust aftertreatment device fluidly positioned within the exhaust conduit and configured to treat exhaust gas conveyed from the upstream exhaust inlet to the downstream exhaust outlet; an exhaust pressure sensor; an upstream sensor conduit and a downstream sensor conduit fluidly connected to the exhaust conduit and extending to the exhaust pressure sensor to expose the exhaust pressure sensor to fluid pressure of the exhaust gas; and a blockage mitigation conduit fluidly connected to the upstream sensor conduit and the downstream sensor conduit, the blockage mitigation conduit including a flow restriction and forming a normally open leak path to convey condensate in a leaked exhaust flow from the upstream sensor conduit to the downstream sensor conduit, the flow restriction fluidly connected between the upstream sensor conduit and the downstream sensor conduit.

2. The exhaust system of claim 1, wherein: the upstream sensor conduit is fluidly connected to the exhaust conduit at a location upstream of the exhaust aftertreatment device; the exhaust aftertreatment device includes filter media in a particulate filter assembly; the normally open leak path is connected to the exhaust conduit at a location downstream of the exhaust aftertreatment device.

3. The exhaust system of claim 1 or 2, wherein: the exhaust pressure sensor includes a differential pressure sensor, the downstream sensor conduit fluidly connected to the exhaust conduit at a location downstream of the exhaust aftertreatment device and extending to the exhaust pressure sensor.

4. An exhaust pressure sensing system comprising: an upstream sensor conduit including a first inlet end configured to fluidly connect to an exhaust conduit at an upstream location and a first sensing end opposite the first inlet end; a downstream sensor conduit including a second inlet end configured to fluidly connect to the exhaust conduit at a downstream location and a second sensing end opposite the second inlet end; a differential pressure sensor including at least one sensing element exposed to fluid pressure of the upstream sensor conduit and the downstream sensor conduit at respective first and second sensing ends; and a blockage mitigation conduit fluidly connected to the upstream sensor conduit and the downstream sensor conduit, the blockage mitigation conduit including a flow restriction and forming a normally open leak path to convey condensate in a leaked exhaust flow from the upstream sensor conduit to the downstream sensor conduit, the flow restriction fluidly connected between the upstream sensor conduit and the downstream sensor conduit.

5. The system of claim 4, wherein: the at least one sensing element includes a diaphragm exposed to fluid pressure of the upstream sensor conduit and the downstream sensor conduit and a strain gauge operably coupled to the diaphragm; and The blockage mitigation conduit is fluidly connected to the upstream sensor conduit at a first connection location that is closer to the first sensing end than the first inlet end, and fluidly connected to the downstream sensor conduit at a second connection location that is closer to the second sensing end than the second inlet end.

6. The system of claim 4 or 5, further comprising a service pack containing the upstream sensor conduit, the downstream sensor conduit, the differential pressure sensor, and the blockage mitigation conduit.

7. The system of claim 4 or 5, wherein: each of the upstream sensor conduit and the downstream sensor conduit has a larger conduit size, while the blockage mitigation conduit has a smaller conduit size that forms a flow restriction; the blockage mitigation conduit includes an orifice that forms the flow restriction; and the ratio of the larger conduit size to the smaller conduit size is at least 5:

1.

8. A method of exhaust pressure sensing in an exhaust system, comprising the steps of: fluidly connecting an upstream sensor conduit and a downstream sensor conduit to an exhaust conduit in the exhaust system; fluidly connecting a blockage mitigation conduit to the upstream sensor conduit and the downstream sensor conduit to form a normally open leak path to transport condensate in a leaked exhaust stream from the upstream sensor conduit to the downstream sensor conduit, the blockage mitigation conduit including a flow restriction fluidly connected between the upstream sensor conduit and the downstream sensor conduit; feeding exhaust from the exhaust conduit into the upstream sensor conduit and the downstream sensor conduit such that a fluid pressure of the exhaust impinges on an exhaust pressure sensor; leaking exhaust from the upstream sensor conduit through the normally open leak path; draining condensate from the downstream sensor conduit with the leaked exhaust; returning the leaked exhaust and drained condensate to the exhaust conduit; and generating an exhaust pressure signal with the exhaust pressure sensor based on the fluid pressure of the exhaust.

9. The method of claim 8, wherein: the fluid connection of the upstream sensor conduit includes fluidly connecting the upstream sensor conduit to the exhaust conduit at a location upstream of an exhaust aftertreatment device in the exhaust system; the fluid connection of the downstream sensor conduit includes fluidly connecting the downstream sensor conduit to the exhaust conduit at a location downstream of the exhaust aftertreatment device; the generation of an exhaust pressure signal further includes generating an exhaust pressure signal indicative of an exhaust pressure drop across the exhaust aftertreatment device; the fluid connection of the blockage mitigation conduit includes fluidly connecting the blockage mitigation conduit to the downstream sensor conduit.

10. The method of claim 8 or 9, further comprising the step of: replacing, in the exhaust system, an assembly of a used sensor conduit and a used exhaust pressure sensor with an assembly including the upstream sensor conduit, the downstream sensor conduit, the exhaust pressure sensor, and the blockage mitigation conduit.

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