U.S. patent application number 11/607182 was filed with the patent office on 2008-06-05 for particulate filter cleaning methods and apparatus.
This patent application is currently assigned to United Technologies Corporation. Invention is credited to Raymond N. Henderson.
Application Number | 20080127637 11/607182 |
Document ID | / |
Family ID | 39468210 |
Filed Date | 2008-06-05 |
United States Patent
Application |
20080127637 |
Kind Code |
A1 |
Henderson; Raymond N. |
June 5, 2008 |
Particulate filter cleaning methods and apparatus
Abstract
An internal combustion engine is run to emit an exhaust flow
containing particulate. The exhaust flow passes through a filter
element to remove at least a portion of the particulate from the
exhaust flow. The removed particulate accumulates on the filter
element. The filter element is cleaned. The cleaning includes
detonating a fuel-oxidizer combination in a conduit and impacting
the filter element with a wave from the detonation.
Inventors: |
Henderson; Raymond N.;
(Renton, WA) |
Correspondence
Address: |
BACHMAN & LAPOINTE, P.C. (P&W)
900 CHAPEL STREET, SUITE 1201
NEW HAVEN
CT
06510-2802
US
|
Assignee: |
United Technologies
Corporation
|
Family ID: |
39468210 |
Appl. No.: |
11/607182 |
Filed: |
December 1, 2006 |
Current U.S.
Class: |
60/295 ;
60/274 |
Current CPC
Class: |
F01N 3/0226 20130101;
F01N 3/025 20130101; F01N 3/0233 20130101 |
Class at
Publication: |
60/295 ;
60/274 |
International
Class: |
F01N 3/023 20060101
F01N003/023; F01N 3/025 20060101 F01N003/025 |
Claims
1. A method comprising: operating an internal combustion engine in
a first mode comprising: running the engine to emit an exhaust flow
containing particulate from the engine; passing the exhaust flow
through a filter element to remove at least a portion of the
particulate from the exhaust flow, the removed particulate
accumulating on the filter element; cleaning the filter element,
the cleaning comprising: detonating a fuel-oxidizer combination in
a conduit; and impacting the filter element with a wave from the
detonation.
2. The method of claim 1 wherein: the removed particulate
accumulates as soot; and the impacting and an associated blowdown
jet incinerate the soot to form ash.
3. The method of claim 2 wherein the cleaning further comprises:
collecting the ash in a trap.
4. The method of claim 3 wherein the cleaning comprises: a
plurality of said detonations and impacts.
5. The method of claim 4 further comprising: removing collected ash
from the trap after a plurality of the cleanings.
6. The method of claim 1 wherein: the cleaning comprises: measuring
a pressure difference across the filter element; responsive to the
pressure difference reaching a first predetermined value,
initiating said detonating; and repeating the detonating until the
measured pressure difference decreases to a second predetermined
value, lower than the first predetermined value.
7. The method of claim 1 wherein: the cleaning occurs while the
internal combustion engine is running.
8. The method of claim 1 wherein: the cleaning occurs while the
internal combustion engine is not running.
9. The method of claim 1 wherein: the cleaning comprises:
introducing the fuel as at least one of propane and MAPP gas; and
introducing the oxidizer as essentially oxygen.
10. The method of claim 1 wherein: the running comprises running as
a compression ignition engine.
11. The method of claim 1 wherein: heat is transferred from the
exhaust flow to the fuel-oxidizer combination in the conduit.
12. An apparatus comprising: an internal combustion engine; and an
exhaust system coupled to the internal combustion engine and
including: an exhaust flowpath; a particulate filter element along
the exhaust flowpath; a conduit having a first end and a second
end, the second end being an outlet facing the filter element
downstream of the filter element along the exhaust flowpath; a
source of fuel and oxidizer coupled to the conduit to deliver the
fuel and oxidizer; and an ignitor coupled to the conduit to ignite
the fuel and oxidizer in the conduit.
13. The apparatus of claim 12 wherein: the exhaust system further
comprises: a first pressure sensor positioned to measure a pressure
upstream of the filter element; a second pressure sensor positioned
to measure a pressure downstream of the filter element; and a
controller coupled to the first pressure sensor, second pressure
sensor, source, and ignitor, and configured to operate the conduit
responsive to outputs of the first and second pressure sensors to
discharge waves from the conduit to impact the filter element.
14. The apparatus of claim 12 wherein: the fuel consists
essentially of at least one of propane and MAPP gas; and the
oxidizer consists essentially of pure oxygen.
15. The apparatus of claim 12 wherein: the fuel consists
essentially of diesel fuel; and the oxidizer consists essentially
of pure oxygen.
16. The apparatus of claim 12 wherein: the filter element does not
have a separate heater; and there is no separate second filter
element positioned for blowback filtering of ash from said filter
element.
17. The apparatus of claim 12 wherein: the apparatus is a wheeled
vehicle.
18. An apparatus comprising: an internal combustion engine; and an
exhaust system coupled to the internal combustion engine to pass an
exhaust flow from the internal combustion engine and comprising: a
filter element positioned to filter particulate from the exhaust
flow; and detonative cleaning means for cleaning the filter
element.
19. The apparatus of claim 18 wherein: the internal combustion
engine is a diesel engine; the detonative cleaning means comprises:
a conduit having a first end and a second end, the second end being
an outlet facing the filter element; a source of fuel and oxidizer
coupled to the conduit to deliver the fuel and oxidizer; and an
ignitor coupled to the conduit to ignite the fuel and oxidizer in
the conduit; the exhaust system further comprises: a controller
coupled to the source and ignitor and configured to discharge waves
from the conduit responsive to a measured pressure difference
across the filter element.
20. A method for retrofitting a pollution source or reengineering a
configuration of the pollution source, the pollution source having
an internal combustion engine, the method comprising: adding a
filter element in an exhaust gas flowpath from the internal
combustion engine; adding a detonative cleaning apparatus
positioned to discharge a wave to impact the filter element.
21. The method of claim 20 wherein: the filter replaces a larger
baseline filter.
22. The method of claim 20 wherein: the detonative cleaning
apparatus comprises: a conduit having a first end and a second end,
the second end being an outlet facing the filter element; a source
of fuel and oxidizer coupled to the conduit to deliver the fuel and
oxidizer; and an ignitor coupled to the conduit to ignite the fuel
and oxidizer in the conduit.
23. The method of claim 1 wherein: the cleaning comprises
momentarily reversing flow through the filter element.
24. The method of claim 2 wherein: the blowdown jet passes through
the filter element in a reverse direction from the exhaust
flow.
25. The apparatus of claim 12 wherein: the particulate filter
element has, along the exhaust flowpath, an upstream surface and a
downstream surface; and the second end faces the downstream
surface.
26. The method of claim 11 wherein: the heat is transferred from an
exhaust pipe to the fuel-oxidizer combination in a space within the
conduit surrounding the exhaust pipe.
Description
BACKGROUND OF THE INVENTION
[0001] The invention relates to particulate filtering. Particular
examples relate to the filtering of particulate from diesel engine
exhaust.
[0002] The US Environmental Protection Agency (EPA) is implementing
New Source Performance Standards for mobile and stationary diesel
engines. The new rules limit the amount of diesel particulate
matter or soot and ash that can be emitted to the atmosphere.
Exemplary diesel engines are used in trucks, locomotives, school
buses, generators, tractors, and other off-road construction
equipment. The California Air Resources Board (CARB) has dictated
that the soot and ash limits be 0.1 gram per brake horsepower per
hour. This will require 85-90% of the particulate to be eliminated
from exemplary exhaust. Engine modifications alone may not be
practical to achieve the required reduction. Thus, particulate
filters have been developed for future equipment and for retrofit
installations on existing diesel engines.
[0003] Trapped particulates would quickly buildup and clog a
filter, blocking exhaust flow and shutting down the engine if the
particulates were not removed. Removing the trapped particulate is
called regeneration. Filter regeneration can be accomplished by
burning the trapped soot by various processes. U.S. Pat. No.
5,566,545 discloses a filter cleaned by reverse flow from an air
feeder. When air is supplied to the filter in a reverse flow
direction, the air may remove captured particulates from the
filter. A second filter may capture the reversed flow of
particulates.
[0004] Some filters use a metal mesh filter as an electric
resistance heating element to burn the soot. Extra fuel can also be
allowed to pass through the engine to burn the soot in the exhaust
system particulate filter. A recent example of an added fuel system
is found in US Pregrant Publication 20060254262A1. Such thermal
regeneration processes turn the larger soot particles into a fine
ash on the filter. This fine ash may be periodically washed off,
vacuumed off or blown off with high-pressure air during a shop
maintenance cycle. Yet other regeneration processes exist.
SUMMARY OF THE INVENTION
[0005] One aspect of the invention involves running an internal
combustion engine to emit an exhaust flow containing particulate.
The exhaust flow passes through a filter element to remove at least
a portion of the particulate from the exhaust flow. The removed
particulate accumulates on the filter element. The filter element
is cleaned. The cleaning includes detonating-a fuel-oxidizer
combination in a conduit and impacting the filter element with a
wave from the detonation.
[0006] Another aspect involves an apparatus having an internal
combustion engine. An exhaust system is coupled to the internal
combustion engine. A particulate filter element along is along an
exhaust flowpath. A conduit has a first end and a second end, the
second end being an outlet facing the filter element. A source of
fuel and oxidizer is coupled to the conduit to deliver the fuel and
oxidizer. An ignitor is coupled to the conduit to ignite the fuel
and oxidizer in the conduit. The ignition may produce a wave
impacting the filter element to clean the filter element.
[0007] The details of one or more embodiments of the invention are
set forth in the accompanying drawings and the description below.
Other features, objects, and advantages of the invention will be
apparent from the description and drawings, and from the
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a schematic view of a first pollutant source in a
normal mode of operation.
[0009] FIG. 2 is a schematic view of the source of FIG. 1 during a
filter cleaning mode of operation.
[0010] FIG. 3 is a schematic view of an alternate source during a
filter cleaning mode of operation.
[0011] Like reference numbers and designations in the various
drawings indicate like elements.
DETAILED DESCRIPTION
[0012] FIG. 1 shows a pollutant source 20 having a powertrain 22
including an engine 24. Exemplary sources are fixed (e.g.,
stationary power generators, tools, and the like) or mobile (e.g.,
vehicular, mobile generators, and the like). Exemplary engines are
internal combustion engines, more particularly, multi-cylinder
compression ignition or diesel engines. The engine receives diesel
fuel from a fuel source (e.g., tank) 26.
[0013] An exhaust system 30 extends in a primary downstream
direction 500 from the engine 24 to an outlet 32 to define a
primary exhaust flowpath 502. At an upstream end of the flowpath
502, the exhaust system 30 includes an exhaust manifold 34. A
filter system 40 is downstream of the manifold. The exemplary
filter system includes a filter element 42 within a filter housing
44 and extending across the flowpath 502. In a normal operational
mode, the exhaust flow 504 passes through an upstream exhaust inlet
port 46 of the housing, then through the filter element 42, and
then through an exhaust outlet port 48 of the housing. An exhaust
pipe 50 extends downstream from the outlet port 48 to the outlet
32.
[0014] Other exhaust system components (e.g., sound mufflers,
catalytic emissions control devices, exhaust gas recirculation
devices, and the like) may be present but are not shown for ease of
illustration.
[0015] The filter exemplary element has first and second surfaces
or boundaries 60 and 62. In the normal operational mode, the
surfaces 60 and 62 are respectively upstream and downstream along
the flowpath 502. Thus, particulate (e.g., soot) 64 will accumulate
on the surface 60 and/or within the filter element, forming an
accumulation 66. The accumulation increases the flow restriction
presented by the filter element. Increased restriction, causes
increased backpressure (the pressure difference between a higher
pressure location or space 70 upstream of the filter and a lower
pressure location or space 72 downstream of the filter). The
pressures at these two locations may be measured by pressure
sensors 74 and 76 coupled to a controller 78. The exemplary
controller is shown as a dedicated controller of the system 40.
However, the controller may be integrated with an overall
controller of the source 20, or otherwise. Various,
microcontrollers, computers, or lesser control systems are
appropriate for use as the controller 78. The controller 78 may be
configured by one or both of software and hardware configuration to
operate as discussed further below.
[0016] In exemplary implementation, upon reaching a predetermined
differential pressure across the filter element the controller 78
will initiate a clearing of the accumulation from the filter
element. An exemplary clearing involves directing a shock wave 100
(FIG. 2) through the space 72 (e.g., the portion of the housing
interior downstream of the filter element). The exemplary wave 100
impacts the surface 62. The wave 100 and associated combustion gas
(discussed further below) may incinerate the accumulation 66. The
incineration may form ash 104 which dislodges and may fall from the
surface 60. The falling ash may be directed to a trap 106, forming
an ash accumulation 108 in the trap.
[0017] The exemplary ash accumulation 108 is held in bulk (i.e.,
not in a separate filter that must be disposed of or cleaned),
although other trap configurations are possible. The ash
accumulation 108 may be removed in bulk (e.g., via a door 110) when
the trap 106 is full (or earlier) as part of manual maintenance.
The required interval for clearing the accumulation 108 may be
substantially longer than the typical filter cleaning interval
(e.g., ten times or more). To facilitate the falling, the exemplary
filter element 42 is oriented so that the surface 60 is partially
downward-facing.
[0018] An exemplary wave generator system 120 for generating the
wave 100 includes a detonation conduit 122 having a first end 124
and a second end 126. The exemplary second end 126 is an outlet end
positioned in the space 72 and aimed at the surface 62. An
exemplary fuel and oxidizer source 128 comprises a fuel source 130
and an oxidizer source 132. An exemplary fuel is propane or MAPP
gas. Small replaceable and/or refillable oxygen cylinders of these
gases are readily commercially available (e.g., for welding
applications). Alternatives include, hydrogen, ethylene, diesel
fuel, kerosene, and gasoline. Diesel fuel has the advantage of
being available from the fuel source 26. Gasoline is, at least,
readily available where the diesel fuel for the source 26 is
obtained.
[0019] An exemplary oxidizer is essentially pure oxygen. Small
replaceable and/or refillable oxygen cylinders are readily
commercially available (e.g., for welding applications).
Alternatively, nitrous oxide may similarly be used. Air may be used
and may be compressed on board for delivering enhanced quantities.
One or more inlet valves 140 controlled by the controller 78 may
admit the fuel and oxidizer near the conduit inlet end. After the
conduit 122 is filled with a desired volume of fuel and oxidizer,
an ignitor 142 (e.g., a spark plug) is triggered by the controller
to initiate combustion of the fuel-oxidizer mixture.
[0020] Initially, combustion near the ignitor is via deflagration.
The wave 100 is initially formed as a deflagration pressure wave
that passes toward the conduit second end (outlet) 126. During
travel of the wave, the deflagration transitions into a detonation.
The detonation wave travels down the remainder of the conduit at a
supersonic velocity and is discharged from the outlet 126.
[0021] As the detonation wave exits the outlet 126, it forms a
quickly decaying, high pressure blast wave. The blast wave is
followed by a blowdown jet of relatively high pressure/temperature
combustion products exiting the conduit. Depending on the fuel and
oxidizer utilized the exit pressure (at the outlet 126) can be on
the order of 150 psi and the temperature can be in the
400&-4900.degree. F. range. The pressure pulse duration is very
short on the order of a few milliseconds.
[0022] The shock and high temperature nature of the blast wave 100
and trailing blowdown jet may be used to regenerate the filter. The
very quick pressure pulse created by the blast wave and blowdown
jet may remove the soot and ash from the filter by momentarily
reversing the flow through the filter. The resulting ash may fall
into the particle trap 106 as discussed above. The relatively short
duration of the blast wave 100 and trailing blowdown jet may
advantageously incinerate the soot particles but not affect the
filter element. An exemplary filter element is a metal mesh filter
element having a much larger thermal mass than the soot
accumulation 66 so as to survive the heating by the blowdown jet.
Alternative filter elements made from sintered metal material may
be the easiest to use because they may be readily fabricated in a
desired shape.
[0023] The conduit may be sized and fueled so that a single firing
is unlikely to provide the necessary cleaning. For example, to
produce a single firing of sufficient magnitude may take a large,
impractical system. A single firing of sufficient magnitude might
also damage system components or create so much back pressure as to
interfere with engine operation. Thus, an exemplary system is
configured to typically require multiple firings for a full
cleaning. For example, a closed loop control may initiate a first
firing upon backpressure reaching a first predetermined level or
threshold value. After the first firing, the backpressure is
remeasured, and firings repeated until the backpressure has
decreased to a second predetermined level (e.g., a baseline level
associated with a nominally clean filter element), less than the
first backpressure level.
[0024] FIG. 3 shows an alternate combustion conduit 200 otherwise
similar to the conduit 122, but concentrically surrounding an
upstream portion of the exhaust pipe. Combustion thus occurs in an
annular space 202 surrounding the exhaust pipe. This configuration
may allow greater exposure of the filter element to the wave 100.
The FIG. 3 configuration may also provide enhanced heat transfer
from the exhaust pipe to the conduit 200 and its fuel/air charges.
This would allow the heat from the exhaust assist in vaporizing the
fuel used in the detonation process. This would be particularly
useful for less volatile liquid fuels such as diesel fuel and
kerosene. Such heating might eliminate the need for a high pressure
injector to achieve fuel vaporization.
[0025] In other alternative embodiments, the orientation of the
conduit could vary from the illustrated horizontal orientation
(e.g. a downwardly directed vertical orientation). A non-straight
conduit having one or more turns to accommodate to existing
structure is also possible as the deflagration/detonation wave can
travel around corners and still be effective.
[0026] In other control variations, instead of using a closed loop
feedback system based on differential pressures, the control system
could activate the cleaner periodically (e.g., based on the engine
hour meter or other interval calculated by an engine computer based
upon use history). The system could activate after a predetermined
engine run time for a set cleaning period (e.g., number of firings)
and then shut off. Another option would be to include a manual mode
(e.g., to allow a mechanic to activate the system in the shop
during scheduled or other maintenance).
[0027] One or more embodiments of the present invention have been
described. Nevertheless, it will be understood that various
modifications may be made without departing from the spirit and
scope of the invention. For example, when implemented in the
reengineering of an existing source configuration or the retrofit
of an existing source, details of the existing configuration/source
may influence details of the particular implementation. In a
reengineering or retrofit of a system having an existing filter,
the reengineering or retrofit may achieve one or more of: reduced
filter size, lengthened maintenance interval; or increased
filtration. Accordingly, other embodiments are within the scope of
the following claims.
* * * * *