REDUCTION OF FOULING IN AFTER TREATMENT COMPONENTS

Abstract

A device and method for influencing exhaust gas flow downstream of a turbocharger turbine and upstream of after treatment components prevents doser tip fouling by using a passive exhaust flow control surface comprising ridges protruding into the exhaust gas flow conduit. The ridges are disposed parallel to each other, and perpendicular to the direction of gas flow. In one embodiment, a funnel is disposed in the conduit, downstream of the ridges, to further direct the exhaust gas flow more precisely towards a HC doser tip.

Description

FIELD OF THE INVENTION

This invention relates to internal combustion engines and more particularly to diesel engines that have exhaust gas treatment devices for treating exhaust gases passing through their exhaust systems.

BACKGROUND OF THE INVENTION

Most modern diesel engines, particularly diesel engines for large tractor-trailer trucks, have a diesel oxidation catalyst associated with diesel particulate filters (DPF) incorporated in the exhaust system to filter carbon and other diesel particulate matters (DPM) from the exhaust gas stream, thereby preventing significant amounts of pollutants such as hydrocarbons, carbon monoxide, soot, soluble organic fraction (SOF), and ash from entering the atmosphere.

When enough particulate material has accumulated on the filter element, the DPF begins to become plugged and needs to be regenerated. Regeneration is a process whereby deposits on the filter element of the DPF are induced to combust, typically by raising the engine exhaust temperature if necessary by appropriate engine operations.

Two particular types of regeneration are recognized by those familiar with the regeneration technology as presently being applied to motor vehicle engines. “Passive regeneration” is generally understood to mean regeneration that can occur anytime that the engine is operating under conditions that burn off DPM without initiating a specific regeneration strategy embodied by algorithms in an engine control system. “Active regeneration” is generally understood to mean regeneration that is initiated intentionally, either by the engine control system on its own initiative or by the driver causing the engine control system to initiate a programmed regeneration strategy, with the goal of elevating temperature of exhaust gases entering the DPF to a range suitable for initiating and maintaining burning of trapped particulates.

Active regeneration may be initiated even before a DPF becomes loaded with DPM to an extent where regeneration would be mandated by the engine control system on its own. When DPM loading beyond that extent is indicated to the engine control system, the control system forces active regeneration, and that is sometimes referred to simply as a forced regeneration.

The creation of conditions for initiating and continuing active regeneration, whether forced or not, generally involves elevating the temperature of exhaust gas entering the DPF to a suitably high temperature.

In many cases, to reach the high temperatures needed for regeneration, a hydrocarbon, typically diesel fuel in the case of diesel engines, is dosed into the exhaust stream and allowed to mix with the exhaust gases and evaporate from its dosed liquid form. The hydrocarbon is then oxidized on an oxidation catalyst, releasing heat which raises the exhaust temperature to the level required for filter regeneration.

The combustion event of a DPF regeneration harmlessly cleans the filter element of the DPF deposits. The regeneration process repeats as often as necessary to maintain smooth and reliable engine operation.

When a hydrocarbon (HC) is dosed into the exhaust stream, the HC doser might experience deterioration such as fouling due to soot accumulation in and around the doser tip. Fouling occurs when certain conditions are present, such as when the walls of the exhaust pipes are cold, and when the exhaust gas flows at low velocity. Fouling of the HC doser leads to blockage which can affect various parameters within the after treatment system, including the precision of the amount of HC delivered into the exhaust stream, and the flow of HC into the exhaust stream. Such deterioration of the doser is a frequent mode of failure in after treatment systems.

The present inventors have recognized the need for an after treatment system that increases the exhaust flow around the doser tip to minimize fouling.

The present inventors have recognized the need for an after treatment system that minimizes fouling at the doser tip and requires minimal modification to an exhaust system.

SUMMARY OF THE INVENTION

An exemplary embodiment of the invention provides a device and method of reducing fouling of the HC doser tip by incorporating in the exhaust gas conduit upstream of the doser, a conduit design comprising passive exhaust flow control surfaces.

The passive exhaust flow control surfaces comprise at least one ridge within the exhaust gas conduit upstream of the doser. According to an exemplary embodiment of the present invention, an after treatment system comprises an exhaust gas conduit with a plurality of ridges situated upstream of a doser tip. The ridges are disposed perpendicular to the direction of exhaust gas flow, and are aligned parallel to each other. A funnel is disposed in the conduit to further focus the exhaust gas stream at the doser tip.

Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a turbocharged engine system that includes an after treatment device.

FIG. 2 is a schematic diagram of an exhaust system that includes an after treatment device and passive exhaust flow control surfaces in accordance with an exemplary embodiment of the invention.

FIG. 3 is an enlarged side view of the passive exhaust flow control surfaces within an exhaust gas conduit with portions removed to view underlying components.

FIG. 4 is an enlarged side view of another exemplary embodiment of the passive exhaust flow control surfaces within an exhaust conduit with portions removed to view underlying components.

FIG. 5 is a perspective longitudinal cross section view of the passive exhaust flow control surfaces of FIG. 4.

FIG. 6 is a perspective longitudinal cross section view of the passive exhaust flow control surfaces of FIG. 4, illustrating an alternative embodiment of the passive exhaust flow control surfaces.

FIG. 7 is a cross section view of the passive exhaust flow control surfaces along line 7-7′of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

While this invention is susceptible of embodiment in many different forms, there are shown in the drawings, and will be described herein in detail, specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated.

An engine 100 is shown schematically in FIG. 1. The engine 100 has a block 101 that includes a plurality of cylinders. The cylinders in the block 101 are fluidly connected to an intake system 103 and to an exhaust system 105. The exhaust system includes a first pipe 105a from cylinders 1, 2 and 3 of one bank of cylinders and a second pipe 105b from cylinders 4, 5 and 6. Although an inline arrangement of six cylinders is illustrated, inline or V-arrangements or other arrangements of plural cylinders of any number of cylinders are also encompassed by the invention.

A turbocharger 107 includes a turbine 109. The turbine 109 shown has a single turbine inlet port 113 connected to the exhaust system 105. The turbocharger 107 includes a compressor 111 connected to the intake system 103 through an inlet air passage 115.

During operation of the engine 100, air may enter the compressor 111 through an air inlet 117. Compressed air may exit the compressor 111 through a discharge nozzle 207, pass through the inlet air passage 115, and pass through an optional charge air cooler 119 and an optional inlet throttle 120 before entering an intake air mixer 121 and an intake air manifold 122 of the intake system 103. The compressed air enters the engine cylinders 1-6.

A stream of exhaust gas from the exhaust system 105 may be routed through an EGR passage or conduit 124, through an exhaust gas recirculation (EGR) valve 125, through an exhaust gas recirculation (EGR) cooler 126 and pass through a further EGR conduit 127 before meeting and mixing with air from the inlet throttle 120 at the mixer 121.

At times when the EGR valve 125 is at least partially open, exhaust gas flows through pipes 105a, 105b, through the conduit 124, through the EGR valve 125, through the EGR cooler 126, through the further conduit 127 and into the mixer 121 where it mixes with air from the inlet throttle 120. An amount of exhaust gas being re-circulated through the EGR valve 125 may depend on a controlled opening percentage of the EGR valve 125.

The inlet port 113 of the turbine 109 may be connected to the exhaust pipes 105a, 105b in a manner that forms a divided exhaust manifold 129. Exhaust gas passing through the turbine 109 may exit the engine 100 through an exhaust gas conduit 132 which passes the exhaust gas through after treatment components 133 to reduce emissions before the exhaust gas goes into the tailpipe 134 to be released to atmosphere. The exhaust gas 132 conduit is typically curved for better reception of the angular momentum of the exhaust gas exiting the turbine 109.

As illustrated in FIG. 2, after treatment components includes a diesel oxidation catalyst (DOC) housing 136 and a diesel particulate filter (DPF) 137 for treating exhaust gas before it passes into the atmosphere. Although the DOC housing 136 and the DPF 137 are shown as separate components, it is also possible that the DOC housing 136 and DPF 137 share a common housing.

The DPF 137 physically traps a high percentage of diesel particulate matter (DPM) in the exhaust gas, preventing the trapped DPR from otherwise passing into atmosphere. Oxidation catalyst within the DOC housing 136 oxidizes hydrocarbons (HC) in the incoming exhaust gas to CO₂ and H₂O and converts NO to NO₂. The NO₂ is then used to reduce the carbon particulates trapped in the DPF. With regard to passive and active regeneration as mentioned above, U.S. Pat. No. 6,829,890; and U.S. Published Patent Applications 2008/0184696 and 2008/0093153 describe systems and methods for undertaking regeneration. These patents and publications are herein incorporated by reference.

In many cases, to reach the high temperatures needed for regeneration, a hydrocarbon, typically diesel fuel in the case of diesel engines, is delivered into the exhaust stream by a doser 135 (FIG. 2). The doser 135 typically injects diesel fuel into the exhaust stream upstream of the DOC. The doser 135 is in fluid communication with a fuel line 153 coupled to the same, or a different fuel source used to supply fuel to the engine 100 (FIG. 3). The doser 135 is connected to an engine control unit (ECU) 155 which signals the doser to inject fuel into the exhaust conduit 132 when the ECU 155 senses that regeneration is needed. The doser 135 is connected to the exhaust stream by a mount 151, such as a threaded, weld-on fitting.

To prevent fouling, or accumulation of soot and other particles around the doser tip 152, passive exhaust flow control surfaces (PEFCS) 150 are used upstream of the doser 135 to increase the velocity of the exhaust gas passing the doser tip 152. Without wishing to be bound by any particular theory, it is believed that an increased velocity prolongs the separation of the particles, as well as moves the stagnant, exhaust gas re-circulation zone away from the HC doser tip. The increased velocity also assists in removing particles that may have accumulated on the doser tip 152.

The PEFCS comprise a flow conditioning portion 160. The flow conditioning portion 160 contains at least one protrusion or ridge 162 protruding into the exhaust gas conduit 132, along the inner circumference of the exhaust gas conduit 132. The flow conditioning portion 160 may comprise several ridges, such as 3 ridges, but may contain 5, or up to 10 ridges. The ridges can circumscribe a portion of about 10 mm to about 80 mm in length “L” along the inner circumference of the exhaust gas conduit 232, as illustrated in FIG. 7. The depth “D” of the ridges can be between 5 mm to 10 mm. The ridges within an exhaust gas conduit may be the same or different size. In one embodiment, as illustrated in FIGS. 3 and 4, the ridges are aligned parallel to each other, and perpendicular to the direction of exhaust gas flow.

In one embodiment, as illustrated in FIGS. 2 and 3, the flow conditioning portion 160 is disposed along a curved portion 161 of the exhaust gas conduit 132. The doser 135 is longitudinally aligned along an outside surface of the exhaust gas conduit 132 of the flow conditioning portion 160. In another embodiment, as illustrated in FIG. 4, the doser 235 is positioned along the side of the exhaust gas conduit 232.

One skilled in the art would recognize that the number, depth, position, and degree of circumscription required of the ridges along the inner circumference of the exhaust gas conduit to reach a desired exhaust velocity is dependent on various parameters, including the packaging of the exhaust conduit, and the angular velocity of the exhaust gas as it exits the turbine. Correct positioning of the HC doser relative to the ridges can also be determined by testing and analysis of fluid dynamics by one skilled in the art. By adjusting parameters including width, depth, length, and alignment of the ridges, it is possible to generate a desired exhaust gas velocity at the HC doser tip, for example, between 3.45 m/s to 22.41 m/s.

In an alternative embodiment, as illustrated in FIG. 4, the PEFCS can further comprise a gas flow directing surface, such as a funnel 270, downstream of the flow conditioning portion 260. The end 285 of the funnel is positioned such that the flow of exhaust gas is aimed at the doser tip 252 to further enhance the velocity of the exhaust gas flow passing the tip of the doser 252.

The mouth 271 of the funnel 270 is disposed such that the mouth 271 of the funnel is within a plane perpendicular to the direction of exhaust gas flow as show in FIG. 4, or alternatively is disposed such that the mouth 271 of the funnel obliquely aligned with respect to the direction of exhaust gas flow (not shown). In alternative embodiments (not shown), the gas flow directing mechanism be a curved surface, for example, such as in the case of using half of a funnel shaped gas flow directing surface, to direct gas flow towards a desired direction, such as towards the doser tip.

FIGS. 5 and 6 illustrate alternate embodiments of ridges. FIG. 5 illustrates ridges 262a which protrude into the inner region 265 of the exhaust gas conduit 232 as a result of forming indentations 281 on the surface 280 of the exhaust gas conduit 232. FIG. 6 illustrates ridges 262b which extend from the inner surface 275 of the exhaust gas conduit 232.

The section of the exhaust gas conduit containing the PEFCS can be cast or otherwise formed to substitute only the portion of the exhaust gas conduit upstream of the doser, or cast or otherwise formed as a continuous piece with a doser cavity 255. Because only the piping of the exhaust gas conduit 132 upstream of the HC doser needs to be modified, the PEFCS provides a low-cost option to increase the magnitude of the exhaust gas velocity at the HC doser tip. As the PEFCS is cast or otherwise formed in its shape, it is also possible to cast or otherwise form the PEFCS with a funnel as illustrated in FIG. 4 and as discussed above, with minimal additional cost.

PARTS LIST

100 engine

101 block

103 intake system

105 exhaust system

105a first exhaust pipe

105b second exhaust pipe

107 turbocharger

109 turbine

111 compressor

115 inlet air passage

119 optional charge air cooler

120 optional inlet throttle

121 inlet air mixer

122 intake manifold

124 EGR conduit

125 EGR valve

126 cooler

127 further conduit

129 divided exhaust manifold

132 exhaust gas conduit

133 after treatment components

134 tailpipe

135 doser

136 DOC housing

137 DPF

151 doser mount

152 doser tip

153 fuel line

150 passive exhaust flow control surface

155 engine control unit

160 flow conditioning portion

161 curved portion of exhaust gas conduit

162 ridge

232 exhaust gas conduit

235 doser

252 doser tip

255 doser cavity

260 flow conditioning portion

265 inner region of exhaust gas conduit

270 funnel

271 mouth of funnel

275 inner surface of the exhaust gas conduit

280 surface of the exhaust gas conduit

281 indentations

285 end of funnel

Although the present invention is described above with respect to a HC doser disposed upstream of the DOC, it is possible to utilize the passive exhaust gas controlling surface with other types of dosers positioned elsewhere along the exhaust gas stream other than upstream of the DOC. It is also possible to use the passive exhaust gas controlling surface with other conduits for transporting exhaust gas flow.

From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred.

Claims

1. An active regeneration arrangement for a diesel particulate filter (dpf) comprising:

a conduit upstream of the dpf;

a doser mounted to the conduit for injecting hydrocarbon fuel into the conduit; and

at least one protrusion for influencing the flow of exhaust gas in the conduit to decrease fouling of the doser, the protrusion located upstream of the doser in an exhaust gas flow direction and extending into the conduit, the protrusion being disposed along an inner circumferential surface of the conduit such that the protrusion is in contact with the flow of exhaust gas.

2. The arrangement of claim 1, wherein the protrusion is a ridge.

3. The arrangement of claim 1, wherein the at least one protrusion comprises a plurality of protrusions that are aligned in parallel.

4. The arrangement of claim 3, wherein the protrusions of the plurality are evenly spaced apart.

5. The arrangement of claim 1, wherein the at least one protrusion comprises a plurality of protrusions that are aligned perpendicular to the net direction of gas flow along the conduit.

6. The arrangement of clam 1, further comprising a gas flow directing surface disposed downstream of the at least one protrusion.

7. The arrangement of claim 6, wherein the gas flow directing surface extends from a portion of an inner surface of the conduit.

8. The arrangement of claim 6, wherein the gas flow directing surface is a funnel.

9. The arrangement of claim 8, wherein the mouth of the funnel is disposed within a plane perpendicular to the direction of gas flow.

10. The arrangement of claim 8, wherein the mouth of the funnel is disposed within a plane oblique to the direction of gas flow.

11. The arrangement of claim 8, wherein the stem of the funnel is oriented to direct gas flow toward a tip of the doser disposed within the conduit.

12. The arrangement of claim 6, wherein the gas flow directing surface is oriented to direct gas flow toward a tip of the doser disposed within the conduit.

13. The arrangement of claim 1, wherein the at least one protrusion comprises a plurality of protrusions wherein the protrusions circumscribe an inner surface of the conduit with consistent depth.

14. A method for increasing the velocity of gas in a conduit past a doser in a diesel particulate filter active regeneration arrangement, comprising:

providing a flow of gas past at least one protrusion disposed within an inner surface of a conduit upstream of the doser.

15. The method of claim 14, further comprising the step of providing a flow of gas past a gas flow directing surface.

16. The method of claim 14, further comprising the step of channeling the flow of gas around a curved portion in the conduit, wherein the protrusion is located on an inside of the curved portion.

17. The method of claim 15, wherein the steps of providing a flow of gas past at least one protrusion and providing a flow of gas past a gas flow directing surface allows for a predetermined gas velocity into a predetermined region of the conduit.