US20140140892A1

US20140140892A1 - Exhaust after-treatment system

Info

Publication number: US20140140892A1
Application number: US14/164,485
Authority: US
Inventors: Jason W. Hudgens; Allen B. Chu
Original assignee: Caterpillar Inc
Current assignee: Caterpillar Inc
Priority date: 2014-01-27
Filing date: 2014-01-27
Publication date: 2014-05-22
Also published as: CN204419324U

Abstract

An exhaust after-treatment system for heating a sensor system attached to a diesel particulate filter for determining the condition of the diesel particulate filter is provided. The exhaust after-treatment system includes a diesel particulate filter, a sensor system, and a heating mechanism. The sensor system is configured to monitor pressure at an input end and an output end of the diesel particulate filter. The heating mechanism is in thermal contact with the sensor system. The heating mechanism is disposed downstream of an engine cooling system and enables a flow of engine coolant around the sensor system, preventing condensation and freezing of the sensor system.

Description

TECHNICAL FIELD

The present disclosure generally relates to an exhaust system used in vehicles and, more particularly, to an exhaust after-treatment system for preventing condensation or freezing of a sensor system mounted on the exhaust after-treatment system.

BACKGROUND

Vehicles, such as trucks, buses, and other similar automobiles, are equipped with an exhaust after-treatment system to meet the new emission regulation requirements. The exhaust after-treatment system includes multiple components; one such component may be a diesel particulate filter. The diesel particulate filter is designed to remove diesel particulate matter (or soot) from exhaust gas of a diesel engine of such a vehicle. The diesel particulate filter accumulates the diesel particulate matter (or soot) as an ash when the exhaust gas passes through the diesel particulate filter. Such an accumulation of the ash may fill up the diesel particulate filter over time. Beyond a pre-specified threshold, the accumulation of the ash may increase a back pressure on the diesel engine, elevate the temperature of exhaust gases and/or produce high amount of nitrogen oxide.
The diesel particulate filter may be subjected to cleaning and/or regular maintenance to avoid the above mentioned situation. There are various known methods in the art for cleaning and/or regular maintenance of the diesel particulate filter. Such known methods may include active methods or passive methods. The active methods may be based on direct interaction with the diesel particulate filter, such as flame shooter or increasing exhaust gas temperature. The passive methods may be based on indirect interaction with the diesel particulate filter such as use of a catalyst. Such cleaning and/or regular maintenance methods are also known as ‘filter regeneration’ and will be referred by the same term further in the document. The filter regeneration is a periodic process and must be done carefully to avoid damage of the diesel particulate filter. Thus, there may be a need to determine a condition of the diesel particulate filter that whether the filter regeneration is required or not.
There are various methods and processes known in the art to determine the condition of the diesel particulate filter. One such method is measuring a pressure difference across both ends of the diesel particulate filter. A sensor system can be mounted on the diesel particulate filter to determine the condition of the diesel particulate filter. The sensor system may sense the condition of the diesel particulate filter by determining the pressure difference across the diesel particulate filter. Based on the condition of diesel particulate filter, it may be determined if the filter regeneration is required. However, in cold weather condition, water vapors in the exhaust gas may condense or freeze and the sensor system may malfunction. The condensed water vapors may lead to blocking of exhaust gas passage to the sensor system. The blocked passages may lead to false reading or no reading. While various solutions have been developed to provide arrangements that can solve the problem cited above, there is still a room for development.

SUMMARY

In an embodiment, an exhaust after-treatment system is provided. The exhaust after-treatment system includes a diesel particulate filter. The diesel particulate filter has an input end and an output end. Further, the exhaust after-treatment system includes a sensor system. The sensor system is mounted on the diesel particulate filter. The sensor system includes a pressure sensor, a first pilot line and a second pilot line. The first pilot line transfers exhaust gases from the input end of the diesel particulate filter to the pressure sensor. The second pilot line transfers exhaust gases from the output end of the diesel particulate filter to the pressure sensor. The exhaust after-treatment system further includes a heating mechanism in thermal contact with the sensor system. The heating mechanism enables a flow of fluid around the sensor system.
Other features and advantages of the disclosure will become apparent to those skilled in the art, upon review of the following detailed description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a perspective view of an exhaust after-treatment system, in accordance with an embodiment of the present disclosure; and

FIG. 2 and FIG. 3 illustrates a sectional view of a sensor system for an exhaust after-treatment system, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

Detailed embodiments of the present disclosure are described herein with reference to FIG. 1. The specific structural and functional details disclosed herein are intended to be exemplary and should not be interpreted as limiting the disclosure.
FIG. 1 illustrates a perspective view of an exhaust after-treatment system 100 for an exhaust system, in accordance with an embodiment of the present disclosure. The exhaust after-treatment system 100 includes a diesel particulate filter 102, a sensor system 104 and a heating mechanism 106.
The diesel particulate filter 102 is a flow-through device having two ends. The two ends of the diesel particulate filter 102 may include an input end 108 and an output end 110. The diesel particulate filter 102 can be a part of the exhaust after-treatment system 100 and may be disposed downstream to an engine exhaust system (not shown in the FIG. 1) on an exhaust conduit (not shown in the FIG. 1). The diesel particulate filter 102 can be configured to absorb diesel particulate matter (or soot) from exhaust gases coming from the engine exhaust system (not shown in the FIG. 1). The diesel particulate filter 102 can be configured to absorb the diesel particulate matter (or soot) from the exhaust gases as ash. Thus, the diesel particulate filter 102 helps an engine (not shown in the FIG. 1) to meet emission regulation requirements and may reduce particulate matter in exhaust. A continuous accumulation of the ash, over a period of time, may block or clog the diesel particulate filter 102. The blocked diesel particulate filter 102 may lead to back pressure in the engine (not shown in the FIG. 1), an elevated temperature of exhaust gases and/or a high amount of nitrogen oxide. Thus, cleaning and/or maintenance of the diesel particulate filter 102 is required at a regular interval. The cleaning and/or maintenance of the diesel particulate filter 102 is commonly known as ‘filter regeneration’ and will be referred by the same term further in the document. The filter regeneration is a periodic process and must be performed carefully to avoid damage of the diesel particulate filter 102. Condition of the diesel particulate filter 102 needs to be determined before performing the filter regeneration. The condition of the diesel particulate filter 102 can be determined using the sensor system 104.
The sensor system 104 includes a first pilot line 112, a second pilot line 114, and a pressure sensor 116. The first pilot line 112 can have a first end 118 and a second end 120. Similarly, the second pilot line 114 can have a first end 122 and a second end 124. The first end 118 and the first end 122 can be in fluid connection with the input end 108 and the output end 110 of the diesel particulate filter 102, respectively. Further the pressure sensor 116 is disposed between the second end 120 and the second end 124 of the first pilot line 112 and the second pilot line 114, respectively. In other words, the pressure sensor 116 is disposed between the first pilot line 112 and the second pilot line 114. The first pilot line 112 and the second pilot line 114 provide a fluid connection between the pressure sensor 116 and the input end 108 and the output end 110. It can be contemplated that the exhaust gases passing through the diesel particulate filter 102 may also enter the first pilot line 112 and the second pilot line 114. In other words, the pressure sensor 116 is exposed to pressure of the exhaust gas at the input end 108 and the output end 110. Hence, the pressure sensor 116 determines a pressure at the input end 108 and the output end 110 to pressure difference across the diesel particulate filter 102. In one embodiment, the pressure sensor 116 may include a pair of diaphragms. Each diaphragm of the pair of the diaphragms may be sensitive to the pressure of the exhaust gas at the input end 108 and the output end 110. The pair of diaphragms may flex or move based on the pressure at the input end 108 and the output end 110. Hence, a difference in pressure can be sensed by the pressure sensor 116. It can be contemplated that the difference in the pressure between the first end 108 and the second end 110 may indicate that the filter may be clogged and may require regeneration. It is to be noted that present disclosure can be independent of the type of pressure sensor 116 described herein.
The heating mechanism 106 may be of several configurations. In one embodiment, the heating mechanism 106 may consist of a length of conduit which wraps around and maintains thermal contact with the first pilot line 112, second pilot line 114 and the pressure sensor 116 as shown in FIGS. 1 and 2. Alternative embodiments include configurations wherein the heating mechanism consists of a coolant jacket envelope substantially surrounding at least a portion of the sensor system 104 wherein engine coolant makes direct contact with the first pilot line 112, second pilot line 114 and the pressure sensor 116. In other words, the heating mechanism 106 can be heat exchanger in thermal contact with the sensor system 104. The heating mechanism 106 is further described in subsequent figures.
FIG. 2 and FIG. 3 illustrates a sectional view 200 of the sensor system 104 with the heating mechanism 106, for the exhaust after-treatment system 100, in accordance with an embodiment of the present disclosure. The sensor system 104 as described in FIG. 1 includes the first pilot line 112, the second pilot line 114, and a pressure sensor 116. The heating mechanism 106 is configured to include a fluid line 202. The fluid line 202 may be a pipe or flexible hose configured to withstand high temperature. In other words, the heating mechanism 106 may include a tube-like structure, for example, a steel tube. However, it is evident to a person with ordinary skills in the art, that the mentioned example nowhere limits the disclosure to a specified structure, shape or material for the fluid line 202. In one embodiment, as shown in FIG. 2, the heating mechanism 106 may be a hollow cylinder 204 and may envelop the sensor system 104 such that the sensor system 104 is disposed inside the hollow cylinder 204. Further, fluid such as engine coolant, flows through the hollow cylinder 204 via the fluid line 202. Specifically, the sensor system 104 is immersed in the fluid. In one embodiment, the fluid can be engine oil, hydraulic oil or any other suitable fluid.
In one alternative embodiment, as shown in FIG. 3, the fluid line 202 may be wrapped or wound around the sensor system 104 to form a coil shaped structure 302. In this embodiment, the fluid line 202 can swathe the first pilot line 112, the second pilot line 114 and the pressure sensor 116 to envelop the sensor system 104. Hence the heating mechanism 106 can be in thermal contact with the sensor system 104. Further, the fluid line 202 is connected to a source of fluid, for example, the fluid line 202 can be downstream of a cooling system of an engine (not shown in FIG. 3). In other words, coolant fluid flows through the fluid line 202. The coolant fluid from the engine cooling system (not shown in the FIG. 3.) may be coming out of the engine (not shown in the FIG. 3.), and thus, is hot in nature. When the hot coolant flows around the sensor system 104 the heat of the hot fluid is transferred to the sensor system 104. The transferred heat raises the temperature of the sensor system 104, thereby preventing the condensation (or freezing) of the sensor system 104.
Thus, the condensation and freezing of the first pilot line 112, the second pilot line 114, and the pressure sensor 116 can be prevented. Heat exchange from the fluid line 202 may avoid partial blockage and/or complete blockage of the first pilot line 112 and the second pilot line 114. Thus, the fluid line 202 reduces the downtime of sensor system 104.

INDUSTRIAL APPLICABILITY

The present disclosure provides an exhaust after-treatment system, with a sensor system 104 mounted on a diesel particulate filter 102 used in vehicles. The present disclosure finds specific applicability in preventing condensation and freezing in the sensor system 104 in cold weather conditions.
The sensor system 104 is required to measure a pressure difference across the diesel particulate filter 102. The pressure difference helps in sensing the condition of the diesel particulate filter. Based on the sensed condition, the need for filter regeneration can be determined. In cold climatic conditions, water vapor in the exhaust gas can freeze inside the first pilot line and/or the second pilot line, thereby blocking block flow of exhaust gas to the pressure sensor 116. This may lead to an error in sensing or no reading by the sensor system 104. The disclosed idea is used to prevent the condensation and freezing of the different components of the sensor system 104. The exhaust after-treatment system includes a heating mechanism 106 enveloped around the sensor system 104. The heating mechanism 106 can be configured to include a fluid line 202. Hot fluid from the engine cooling system flows through the fluid line 202. The hot fluid may be at higher temperature as compared to ambient temperature. Hence, the heat from the hot fluid is exchanged with the sensor system 104 and avoid condensation or freezing of water vapors or melt the frozen water vapors in the first pilot line 112 and the second pilot line 114.
It should be understood that the above description is intended for illustrative purposes only and is not intended to limit the scope of the present disclosure in any way. Thus, those skilled in the art will appreciate that other aspects of the disclosure can be obtained from a study of the drawings, the disclosure, and the appended claim.

Claims

What is claimed is:

1. An exhaust after-treatment system, comprising:

a diesel particulate filter coupled to an exhaust conduit, wherein the diesel particulate filter comprises an input end and an output end;

a sensor system mounted on the diesel particulate filter, comprising:

a pressure sensor;

a first pilot line configured to transfer exhaust gases from the input end to the pressure sensor;

a second pilot line configured to transfer exhaust gases from the output end to the pressure sensor; and

a heating mechanism, in thermal contact with the sensor system, configured to enable a flow of fluid around the sensor system.