US20140013728A1

US20140013728A1 - Fluid cooled injector and exhaust aftertreatment system, vehicle, and method using a fluid cooled injector

Info

Publication number: US20140013728A1
Application number: US14/003,805
Authority: US
Inventors: Sten Shao; Philip Meier
Original assignee: Mack Trucks Inc
Current assignee: Mack Trucks Inc
Priority date: 2011-04-04
Filing date: 2011-09-16
Publication date: 2014-01-16
Also published as: CN103649479A; JP2014514493A; WO2012138373A1; RU2013148822A; WO2012138373A8; EP2694784A1; BR112013025571A2; EP2694784A4

Abstract

A fluid cooled injector includes an injector body comprising an injector tip and a cooling channel, the injector tip comprising an injector orifice, and a heat conducting shield, the heat conducting shield comprising a heat conducting shield orifice arranged coaxially with the injector orifice, the heat conducting shield being in direct contact with at least one of the injector body and the injector tip. An exhaust after treatment system and a vehicle including such an injector, and a method involving the use of such an injector, are also disclosed.

Description

BACKGROUND AND SUMMARY

The present invention relates generally to fluid cooled injectors and, more particularly, to such injectors including heat shields to facilitate heat transfer from the injector tip.
In exhaust aftertreatment systems for diesel engines, it is typical to use a so-called seventh injector to inject fuel into an exhaust stream to raise the temperature of the exhaust stream, usually for purposes of regenerating a diesel particulate filter in the exhaust aftertreatment system, although there are other circumstances when the seventh injector is used to raise the temperature of the exhaust gas. In diesel engines used in over-the-road trucks, these injectors tend to clog every 20-40000 miles. Clogging of these injectors is problematic and in the past, clogging has typically been addressed by conducting an air purge, which wastes time and fuel.
The inventors have discovered what they understand to be the mechanism behind the clogging problem and have devised a simple solution to address the problem. The inventors realized that, when diesel fuel is heated to around 180-230° C., the fuel tends to become sticky and can adhere to surfaces. Further investigation revealed that the mixture of soot and fuel can bind strongly on a metal surface at this temperature range. Above the temperature range, the bonded mixture becomes loosed and will ordinarily easily come off the surface and, below the temperature range, the mixture of soot and fuel will not ordinarily adhere to the surface.
The inventors observed that temperatures around the seventh injector tip in vehicles can vary from about 100-280° C. depending upon engine application and running conditions. They believe that this explains why clogging tends to occur for some vehicles, but not for others, because the temperature at the seventh injector tip varies. For certain vehicles and conditions, the temperature around the seventh injector tip can be in the range of around 180-230° C. at which the fuel tends to become sticky and adheres to surfaces, thus tending to clog the seventh injectors in these vehicles.
It is desirable to provide a solution to the problem of seventh injector clogging. It is also desirable to provide a solution that involves little or no extra use of fuel to overcome clogging problems, that is inexpensive to implement, and that is adapted to be retrofit on existing vehicles.
According to an aspect of the present invention, a fluid cooled injector comprises an injector body comprising an injector tip and a cooling channel, the injector tip comprising an injector orifice, and a heat conducting shield, the heat conducting shield comprising a heat conducting shield orifice arranged coaxially with the injector orifice, the heat conducting shield being in direct contact with at least one of the injector body and the injector tip to transfer heat from the injector tip to the cooled injector body.
According to another aspect of the present invention, a heat conducting shield for a fluid cooled injector is provided, the fluid cooled injector comprising an injector body comprising an injector tip and a cooling channel, the injector tip comprising an injector orifice. The heat conducting shield comprises a first portion having a heat conducting shield orifice adapted to be arranged coaxially with the injector orifice and a second portion, separate from the first pot at least one of the first portion and the second portion being adapted to be in direct contact with the injector body.
According to yet another aspect of the present invention, a method of regenerating a diesel particulate filter (DPF) in an exhaust aftertreatment system is provided and includes injecting fuel into or upstream of the DPF through an injector orifice in an injector tip of an injector, cooling a main body of the injector from which the injector tip extends by circulating a coolant through channels in the injector, and transferring heat from the injector tip via a heat conducting shield in direct contact with at least one of the injector tip the main body around the injector tip, and comprising a heat conducting Shield orifice arranged coaxially with the injector orifice.
According to another aspect of the invention, the beat conducting shield may include a coating of a material to prevent fuel and exhaust matter from adhering to the shield. A suitable material may be Teflon® or another non-stick coating. Preferably, the coating material is applied to a surface of the heat conducting shield exposed to the exhaust gas flow.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the present invention are well understood by reading, the following detailed description in conjunction with the drawings in which like numerals indicate similar elements and in which:

FIG. 1A is a schematic, cross-sectional view of an injector according to an aspect of the Present invention;

FIG. 1B is a schematic, cross-sectional view of a portion of an injector according to an aspect of the present invention;

FIG. 2 is as cross-sectional view of a heat conducting shield according to an aspect of the present invention; and

FIG. 3 schematically shows an engine and a portion of an exhaust aftertreatment system according to an aspect of the present invention.

DETAILED DESCRIPTION

FIG. 1A shows a fluid cooled injector 21 according to an aspect of the present invention. The injector 21 comprises an injector body 23 comprising an injector tip 25 and a cooling channel 27 through which a coolant (not shown) is circulated. The cooling channel 27 is ordinarily ring shaped and surrounds a central passage 28 leading to an injector orifice 29 in the injector tip.
The injector 21 further comprises a heat conducting shield 31 to facilitate heat transfer away from the injector tip 25 and more particularly, the portion 33 of the injector tip surrounding the outlet of the injector orifice 29, to the cooled injector body 23 in order to maintain the temperature of the portion surrounding the outlet of the injector orifice below the critical temperature, i.e., usually below about 180° C. The heat conducting shield comprises a heat conducting shield orifice 35 arranged coaxially with the injector orifice 29. The heat conducting shield 31 is in direct contact with at least one of the injector body 23 and the injector tip 25 (shown in contact with both in FIGS. 1A and 1B). The heat conducting shield 31 is shown in cross-section in FIGS. 1B and 2. The heat conducting shield 31 is ordinarily made of a material that is at least as conductive as the material from which the injector tip 25 is made. A presently preferred material for the heat conducting shield 31 is copper, although other materials are also suitable.
The injector 21 can be a seventh injector of the type commonly used in diesel engine exhaust systems such as that shown in FIG. 3. The exhaust system may be of the type used in a vehicle 100 as shown schematically in phantom. The injector 21 can he arranged downstream of a diesel engine 37 and in or upstream of an exhaust aftertreatment component such as a diesel particulate filter 39 (DPF). The injector 21 can be arranged to inject fuel into the exhaust gas stream in order to e.g., raise the temperature in the DPF 37 to regenerate the DPF. The injector 21 may be used for purposes other than raising the temperature of a DPF during regeneration, however, that is a typical application of such an injector.
The injector body 23 comprises a main body portion 41 and the injector tip 25 comprises a cylindrical portion 43 that extends from the main body portion. The cylindrical portion 43 can be generally circularly cylindrical or a series of stepped, circularly cylindrical portions as shown in FIGS. 1A-1B, which shapes can facilitate manufacturing or it can be other shapes. To facilitate heat transfer from the cylindrical portion 43 and, more particularly, from the portion of the injector tip 25 surrounding the injector orifice 29, it is typically desirable that the cylindrical portion is less massive than the Main body portion 41.
The heat conducting shield 31 can be in direct contact with at least part of the cylindrical portion 41, ordinarily at least the portion 33 of the injector tip 25 surrounding the outlet of the injector orifice 29, which is typically the top surface of the cylindrical portion surrounding the injector orifice. The heat conducting shield 31 may be spaced from at least part of the cylindrical portion 41 as seen in, e.g., FIG. 1B so that the heat conducting shield may only contact the cylindrical portion at the portion 33 surrounding the outlet of the injector orifice 29, however, the heat conducting shield may contact the entire exterior surface of the injector tip 25. The heat conducting shield 31 can also or alternatively be in direct heat conducting contact with the main body portion 41. To facilitate heat transfer between the heat conducting shield 31 and the injector, in particular, the cooled body portion 41 and the injector tip 25, a heat sink paste may be applied between the heat conducting shield and the body portion and tip.
It can be desirable to limit contact of the heat conducting shield 31 to direct contact with the portion 33 of the injector tip 25 surrounding the injector orifice 29 and with the cooled main body portion 41, and minimizing contact of the heat conducting shield at other portions of the injector tip, to better ensure that there is heat transfer away from the portion around the injector orifice to better ensure that that part of the injector tip is cooled to below the critical temperature. Thus, as seen in FIG. 1B, an empty space 45 may be provided between exterior wall surfaces 47, 49, and 51 of the injector tip 25 and interior wall surfaces 53, 55, and 57 of the heat conducting shield 31.
A surface of an outer side of the heat conducting shield 31, the surface opposite the side facing the injector 21 in FIG. 1 b, is intended to be exposed to exhaust gas and unburned hydrocarbon (fuel). To avoid exhaust gas matter and fuel horn adhering to the heat conducting shield, the exposed, outer surface of the heat conducting shield may be coated with a non-stick coating, such as Teflon® or another suitable coating material.
The heat conducting shield 31 may be secured to the injector 21 in any suitable fashion. FIG. 1B shows the heat conducting shield 31 secured to the injector 21 by means of an interference fit between an interior surface 59 of the heat conducting shield 31 and an exterior surface 61 of the injector tip 25. Instead of an interference fit, the injector tip 25 and the heat conducting shield 31 may have a threaded connection, or the heat conducting shield may be secured to the main body portion 41, such as by welding, brazing, by some suitable fasteners, or by an adhesive such as epoxy.
The heat conducting shield 31 can be a variety of shapes, however, a presently preferred shape includes a first portion 63 having the heat conducting, shield orifice 35, with the heat conducting shield orifice and the injector orifice being arranged coaxially. The first portion 63 can be adapted to contact the injector tip 25 by the portion 33 of the injector tip around the injector orifice 29. A second portion 65 of the heat conducting shield 31 is separate from the first portion 63 and can be adapted to be in direct contact with the injector body 23 and the injector tip. The heat conducting shield 31 comprises a generally cylindrical wall 67 including interior surfaces 53, 55, 57, and 59 defining an opening for receiving the injector tip 25. The second portion 65 of the heat conducting shield 31 can comprise a flange 69 disposed annularly around the first portion 63.
In a method according to an aspect of the present invention, a DPF 39 of an exhaust aftertreatment system as shown in FIG. 3 is regenerated by injecting fuel into or upstream of the DPF through an injector orifice (29. FIGS. 1A-2) in an injector tip (25. FIGS. 1A-2) of an injector 21. A main body (41 FIGS. 1A-1B) of the injector 21 from which the injector tip extends is cooled b circulating a coolant through a channel (27 FIG. 1A) in the injector 21, Heat from the injector tip is transferred via the heat conducting shield (31, FIGS. 1A-2) in direct contact with at least one of the injector tip and the main body around the injector tip. The temperature of the portion 33 of the injector tip 25 around the injector orifice 29 is kept at a temperature below a critical, temperature of about 180° C. above which diesel fuel tends to become sticky and adhere to the injector tip, thereby reducing the possibility of clogging. Coolant flow can be controlled to adjust the temperature of the portion 33 of the injector tip 25 in response to different conditions.
Aspects of the present invention over a solution to the problem of seventh injector clogging by preventing temperatures at the seventh injector tip from being within the range of temperatures at which diesel fuel tends to become sticky and adhere to metal. The use of a simple heat conducting shield on conventional seventh injectors provides a solution that involves little or no extra use of fuel to overcome clogging problems, that is inexpensive to implement, and that is adapted to be retrofit on existing vehicles.
In the present application, the use of terms such as “including” is open-ended and is intended to have the same meaning as terms such as “comprising” and not preclude the presence of other structure, material, or acts. Similarly, though the use of terms such as “can” or “may ” is intended to be open-ended and to reflect that structure, material, or acts are not necessary, the failure to use such terms is not intended to reflect that structure, material, or acts are essential. To the extent that structure, material, or acts are presently considered to be essential, they are identified as such.
While this invention has been illustrated and described in accordance with a preferred embodiment, it is recognized that variations and changes ma be made therein without departing from the invention as set forth in the claims.

Claims

What is claimed is:

1. A fluid cooled injector, comprising:

an injector body comprising an injector tip and a cooling channel, the injector tip comprising an injector orifice; and

a heat conducting shield, the heat conducting shield comprising a heat conducting shield orifice arranged coaxially with the injector orifice, the heat conducting shield being in direct heat conducting contact with at least one of the injector body and the injector tip.

2. The fluid cooled injector as set forth in claim 1, wherein the injector body comprises a main body portion and the injector tip comprises a cylindrical portion that extends from the main body portion.

3. The fluid cooled injector as set forth in claim 2, wherein the heat conducting shield is in direct contact with at least part of the cylindrical portion.

4. The fluid cooled injector as set forth in claim 2, wherein the heat conducting shield is in direct contact with a top surface of the cylindrical portion surrounding the injector orifice.

5. The fluid cooled injector as set forth in claim 2, wherein the heat conducting shield is spaced from at least part of the cylindrical portion.

6. The fluid cooled injector as set forth in claim 2, wherein the heat conducting, shield is in direct contact with the main body portion and the cylindrical portion.

7. The fluid cooled injector as set forth in claim 1, wherein the heat conducting shield is made of a material that is at least as conductive as the injector tip.

8. The fluid cooled injector as set forth in claim 1, wherein the cooling channel is ring-shaped and surrounds a central passage leading to the injector orifice.

9. The fluid cooled injector as set forth in claim 1, wherein the heat conducting shield includes a non-stick material coating on an outer surface.

10. An exhaust system for an engine comprising a diesel particulate filter and a fluid cooled injector according to claim 1 upstream of the diesel particulate filter.

11. A vehicle comprising an engine and an exhaust system according to claim 10.

12. A heat conducting shield for a fluid cooled injector, the fluid cooled injector comprising an injector body comprising an injector tip and a cooling channel, the injector tip comprising an injector orifice, the heat conducting shield comprising a first portion having a heat conducting shield orifice adapted to be arranged coaxially with the injector orifice and a second portion, separate from the first portion, at least one of the first portion and the second portion being adapted to he in direct contact with the injector body.

13. The beat conducting shield as set forth in claim 12, wherein the heat conducting shield comprises a generally cylindrical wall defining an opening for receiving the injector tip.

14. The heat conducting shield as set forth in claim 12, wherein the second portion of the heat conducting shield comprises a flange extending from and annularly around the first portion.

15. The heat conducting shield as set forth in claim 12, wherein the beat conducting shield is made of copper.

16. The beat conducting shield as set forth in claim 12, wherein the beat conducting shield includes a non-stick material coating on an outer surface.

17. A method of regenerating a diesel particulate filter (DPF) in an exhaust aftertreatment System, comprising:

injecting fuel into or upstream of the DPF through an injector orifice in an injector tip of an injector;

cooling a main body of the injector from which the injector tip extends by circulating a coolant through channels in the injector; and

transferring heat from the injector tip via a heat conducting shield in direct contact with at least on of the injector tip the main body around the injector tip, and comprising a heat conducting shield orifice arranged coaxially with the injector orifice.