U.S. patent application number 12/511117 was filed with the patent office on 2011-02-03 for heating exhaust gas for diesel particulate filter regeneration.
This patent application is currently assigned to International Engine Intellectual Property Company, LLC. Invention is credited to Brad J. Adelman, Paul L. Berke.
Application Number | 20110023469 12/511117 |
Document ID | / |
Family ID | 43032884 |
Filed Date | 2011-02-03 |
United States Patent
Application |
20110023469 |
Kind Code |
A1 |
Berke; Paul L. ; et
al. |
February 3, 2011 |
HEATING EXHAUST GAS FOR DIESEL PARTICULATE FILTER REGENERATION
Abstract
An electrically heated element within the exhaust system of a
diesel engine raises the exhaust temperature sufficiently at idle
or similar low exhaust flow/low exhaust temperature conditions to
the point where the DOC is activated to burn fuel. As soon as the
catalyst within the DOC housing is active, the DPF regeneration can
be initiated. The electrically heated element can be provided
within the exhaust pipe between the turbine outlet of turbocharged
diesel engines and the DOC housing inlet. The electrically heated
element can be powered from the engine alternator and activated
when needed by the engine electronic control module.
Inventors: |
Berke; Paul L.; (Chicago,
IL) ; Adelman; Brad J.; (Chicago, IL) |
Correspondence
Address: |
INTERNATIONAL ENGINE INTELLECTUAL PROPERTY COMPANY
4201 WINFIELD ROAD, P.O. BOX 1488
WARRENVILLE
IL
60555
US
|
Assignee: |
International Engine Intellectual
Property Company, LLC
Warrenville
IL
|
Family ID: |
43032884 |
Appl. No.: |
12/511117 |
Filed: |
July 29, 2009 |
Current U.S.
Class: |
60/295 ; 60/297;
60/303 |
Current CPC
Class: |
Y02T 10/47 20130101;
F01N 13/009 20140601; F01N 3/035 20130101; Y02T 10/26 20130101;
F01N 3/2013 20130101; Y02T 10/40 20130101; F02B 37/00 20130101;
F01N 3/106 20130101; F01N 9/002 20130101; F01N 2560/06 20130101;
Y02T 10/144 20130101; Y02T 10/12 20130101 |
Class at
Publication: |
60/295 ; 60/297;
60/303 |
International
Class: |
F01N 3/023 20060101
F01N003/023; F01N 3/035 20060101 F01N003/035; F01N 3/10 20060101
F01N003/10 |
Claims
1. An exhaust system for a diesel engine, the diesel engine
generating exhaust from the combustion of fuel, comprising: an
exhaust path receiving exhaust from the diesel engine; a diesel
oxidation catalyst (DOC) housing within the exhaust path; a diesel
particulate filter (DPF) within the exhaust path downstream of the
DOC housing; and an electric heating element within the exhaust
path upstream of the DOC housing, the electric heating element
configured to raise the temperature of exhaust gas entering the DOC
housing.
2. The exhaust system according to claim 1, comprising an engine
control and a relay having a signal side that is signal-connected
to the engine control and a power side connected between engine
electric power and the electric heating element, the engine control
triggering the relay to provide electric power to the electric
heating element when exhaust temperature must be raised for
sufficient DOC activation for effective DPF regeneration.
3. The exhaust system according to claim 2, wherein the exhaust
path comprises a turbine upstream of the DOC housing and the
electric heating element is arranged between the turbine and the
DOC housing.
4. The exhaust system according to claim 3, wherein the electric
heating element is arranged at the inlet of the DOC housing.
5. The exhaust system according to claim 1, wherein the electric
heating element is sized to heat exhaust gas to about 250.degree.
C.
6. In a vehicle powered by a diesel engine, the diesel engine
providing mechanical power to drive an electrical power generator,
the diesel engine having a turbocharger that includes a compressor
and an exhaust-driven turbine, the turbine having an exhaust outlet
that is flow connected to a diesel oxidation catalyst (DOC) housing
that is flow-connected to a diesel particulate filter (DPF), and an
engine electronic control unit that receives engine sensor signals
and sends engine control signals to change engine controllable
parameters to control engine emissions, the improvement comprising:
an electric heating element arranged in a flow path between the
turbine and the DOC housing, the electric heating element being
signal-connected to the engine electronic control unit and powered
by the electrical power generator when the engine electronic
control unit requests a higher exhaust gas temperature into the DOC
housing.
7. The improvement according to claim 6, comprising a relay having
a signal side connected to the engine electronic control module and
a power side connected between the electrical power generator and
the electrical heating element.
8. The improvement according to claim 7, wherein the electrical
heating element is located within an exhaust pipe between a turbine
outlet and a DOC housing inlet.
9. The improvement according to claim 8, comprising a temperature
sensor arranged between the DOC housing and the electric heating
element.
10. A method of initiating diesel particulate filter (DPF)
regeneration for a diesel engine having an exhaust path that
includes a diesel oxidation catalyst (DOC) upstream of a DPF
comprising the steps of: determining if regeneration is required;
and heating the exhaust gas in communication with the DOC using an
electric heating element in heat transfer communication with the
exhaust gas.
11. The method according to claim 10, wherein the step of heating
the exhaust gas is further defined by the steps of: sensing the
temperature of the exhaust gas in communication with the DOC; and
only if the temperature of the exhaust gas is below a required DOC
activation temperature, undertaking the heating of the exhaust
gas.
12. The method according to claim 11 wherein the step of heating
the exhaust gas is further defined by the step of: generating the
electric power required for the electric heating element by
converting engine mechanical power to electrical power.
Description
FIELD OF THE INVENTION
[0001] This invention relates generally to motor vehicles, such as
trucks, that are powered by internal combustion engines,
particularly diesel engines that have exhaust gas treatment devices
for treating exhaust gases passing through their exhaust
systems.
BACKGROUND OF THE INVENTION
[0002] A known system for treating exhaust gas passing through an
exhaust system of a diesel engine comprises a diesel oxidation
catalyst (DOC) that oxidizes hydrocarbons (HC) to CO.sub.2 and H2O
and converts NO to NO.sub.2, and a diesel particulate filter (DPF)
that traps diesel particulate matter (DPM). DPM includes soot or
carbon, the soluble organic fraction (SOF), and ash (i.e. lube oil
additives etc.). The DPF is located downstream of the DOC in the
exhaust gas flow. The combination of these two exhaust gas
treatment devices prevents significant amounts of pollutants such
as hydrocarbons, carbon monoxide, soot, SOF, and ash, from entering
the atmosphere. The trapping of DPM by the DPF prevents black smoke
from being emitted from a vehicle's exhaust pipe.
[0003] The DOC oxidizes hydrocarbons (HC) and converts NO to
NO.sub.2. The organic constituents of trapped DPM within the DPF,
i.e., carbon and SOF, are oxidized within the DPF, using the
NO.sub.2 generated by the DOC, to form CO.sub.2 and H.sub.2O, which
can then exit the exhaust pipe to atmosphere.
[0004] The rate at which trapped carbon is oxidized to CO.sub.2 is
controlled not only by the concentration of NO.sub.2 or O.sub.2 but
also by temperature. Specifically, there are three important
temperature parameters for a DPF.
[0005] The first temperature parameter is the oxidation catalyst's
"light off" temperature, below which catalyst activity is too low
to oxidize HC. Light off temperature is typically around
250.degree. C.
[0006] The second temperature parameter controls the conversion of
NO to NO.sub.2. This NO conversion temperature spans a range of
temperatures having both a lower bound and an upper bound, which
are defined as the minimum temperature and the maximum temperature
at which 40% or greater NO conversion is achieved. The conversion
temperature window defined by those two bounds extends from
approximately 250.degree. C. to approximately 450.degree. C.
[0007] The third temperature parameter is related to the rate at
which carbon is oxidized in the filter. Reference sources in
relevant literature call that temperature the "Balance Point
Temperature" (or BPT). It is the temperature at which the rate of
oxidation of particulate, also sometimes referred to as the rate of
DPF regeneration, is equal to the rate of accumulation of
particulate. The BPT is one of the parameters that determines the
ability of a DPF to enable a diesel engine to meet expected
tailpipe emissions laws and/or regulations.
[0008] Typically, a diesel engine runs relatively lean and
relatively cool compared to a gasoline engine. That factor makes
natural achievement of BPT problematic.
[0009] Therefore, a DPF requires regeneration from time to time in
order to maintain particulate trapping efficiency. Regeneration
involves the presence of conditions that will burn off trapped
particulates whose unchecked accumulation would otherwise impair
DPF effectiveness. While "regeneration" refers to the general
process of burning off DPM, two particular types of regeneration
are recognized by those familiar with the regeneration technology
as presently being applied to motor vehicle engines.
[0010] "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.
[0011] 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.
[0012] 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.
[0013] There are several methods for initiating a forced
regeneration of a DPF such as retarding the start of main fuel
injections or post-injection of diesel fuel to elevate exhaust gas
temperatures entering the DPF while still leaving excess oxygen for
burning the trapped particulate matter. Post-injection may be used
in conjunction with other procedures and/or devices for elevating
exhaust gas temperature to the relatively high temperatures needed
for active DPF regeneration.
[0014] These methods are able to increase the exhaust gas
temperature sufficiently to elevate the catalyst's temperature
above catalyst "light off" temperature and provide excess HC that
can be oxidized by the catalyst. Such HC oxidation provides the
necessary heat to raise the temperature in the DPF above the
BPT.
[0015] Low load/low flow drive cycles such as garbage trucks,
utility trucks, and airport re-fueling trucks have difficulty
attaining the necessary temperatures to initiate DPF regeneration.
Typically, the exhaust gas temperature at engine idle is
150.degree. C. while DOC activation is not achieved until about
250.degree. C. Engine based modifications can be made to overcome
this drawback but not without a fuel and performance penalty. Some
auxiliary options can compensate for this drawback such as
fuel-burners or a syn-gas reformer system.
[0016] The present inventors have recognized that drive cycles
exist today where active DPF regeneration is not achievable because
exhaust gas temperatures and diesel oxidation catalyst (DOC)
temperature are insufficient to oxidize fuel which generates the
desired exotherm.
SUMMARY
[0017] The disclosed embodiments of the invention provide a heater
that raises the exhaust gas temperature at low flow rates, such as
at engine idle, to the point where the catalyst within the DOC
housing is activated to burn fuel. As soon as the catalyst within
the DOC housing is active, the DPF regeneration can be initiated.
The heater system will raise the exhaust temperature sufficiently
at the idle point or similar low flow/low temperature point.
Accordingly, DPF regeneration is no longer dependent upon vehicle
drive cycle.
[0018] An electrically heated element can be provided within the
exhaust pipe between the turbine outlet and the DOC housing inlet,
preferably located just in front of the DOC housing to minimize
temperature losses. The heater can be powered through a relay from
the vehicle alternator. A control signal to the relay will turn on
when the engine control system requests DPF regeneration but cannot
achieve the desired exhaust gas temperature to the DOC housing.
[0019] The disclosed embodiment provides an exhaust system for a
diesel engine. The diesel engine includes an exhaust path that
receives exhaust from combustion of fuel within the diesel engine.
A DOC housing is arranged within the exhaust path. A DPF is
arranged within the exhaust path downstream of the DOC housing. An
electric heating element is arranged within the exhaust path
upstream of the DOC housing. The electric heating element is
configured to raise the temperature of exhaust gas entering the DOC
housing. The electric heating element can be sized to heat exhaust
gas to about 250.degree. C.
[0020] An engine control receives engine operating signals and
controls engine parameters to control emissions and optimizes
engine performance. The engine control is in signal-communication
with an electronic relay. The relay has a signal side that is
signal-connected to the engine control and a power side connected
between engine electric power and the electric heating element. The
engine control triggers the relay to provide electric power to the
electric heating element when exhaust temperature must be raised
for sufficient DOC activation for effective DPF regeneration. In
this regard, a temperature sensor can be arranged between the DOC
housing and the electric heating element, the sensor being
signal-connected to the engine control.
[0021] The exhaust path can include a turbine upstream of the DOC
housing. The electric heating element can be arranged between the
turbine and the DOC housing, or at the inlet to the DOC
housing.
[0022] The invention provides a method of initiating diesel
particulate filter regeneration that includes the steps of:
[0023] determining if regeneration is required; and
[0024] heating the exhaust gas in communication with the DOC using
an electric heating element in heat transfer communication with the
exhaust gas.
[0025] The step of heating the exhaust gas can be further defined
by the steps of:
[0026] sensing the temperature of the exhaust gas in communication
with the DOC; and
[0027] only if the temperature of the exhaust gas is below a
required DOC activation temperature, undertaking the heating of the
exhaust gas.
[0028] Numerous other advantages and features of the present
invention will be 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
[0029] FIG. 1 is a schematic illustration of a representative
diesel engine and control with exhaust after-treatment devices.
DETAILED DESCRIPTION
[0030] 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.
[0031] FIG. 1 shows a schematic diagram of an exemplary diesel
engine 20 for powering a motor vehicle. Engine 20 has a
processor-based engine control 22, such as an engine electronic
control unit or module, that processes data from various sources to
develop various control data for controlling various aspects of
engine operation. The data processed by control 22 may originate at
external sources, such as sensors, and/or be generated
internally.
[0032] Control 22 includes an injector driver module 24 for
controlling the operation of electric-actuated fuel injectors 26
that inject fuel into combustion chambers in the engine cylinder
block 28. A respective fuel injector 26 is associated with each
cylinder and comprises a body that is mounted on the engine and has
a nozzle through which fuel is injected into the corresponding
engine cylinder. A processor of engine control system 22 can
process data sufficiently fast to calculate, in real time, the
timing and duration of injector actuation to set both the timing
and the amount of fueling.
[0033] Engine 20 further comprises an intake system having an
intake manifold 30 mounted on block 28. An intercooler 32 and a
compressor 34 of a turbocharger 36 are upstream of manifold 30.
Compressor 34 draws air through intercooler 32 to create charge air
that enters each engine cylinder from manifold 30 via a
corresponding intake valve that opens and closes at proper times
during engine cycles.
[0034] Engine 20 also comprises an exhaust system 37 through which
exhaust gases created by combustion within the engine cylinders can
pass from the engine to atmosphere. The exhaust system comprises an
exhaust manifold 38 mounted on block 28. Exhaust gases pass from
each cylinder into manifold 38 via a respective exhaust valve that
opens and closes at proper times during engine cycles.
[0035] Turbocharging of engine 20 is accomplished by turbocharger
36 that further comprises a turbine 40 associated with the exhaust
system and coupled via a shaft to compressor 34. Hot exhaust gases
acting on turbine 40 cause the turbine to operate compressor 34 to
develop the charge air that provides boost for engine 20.
[0036] The exhaust system further comprises a DOC housing 44 and a
DPF 48 downstream of turbine 40 for treating exhaust gas before it
passes into the atmosphere through an exhaust pipe 49. Although the
DOC housing 44 and the DPF 48 are shown as separate components, it
is also possible that the DOC housing 44 and the DPF 48 share a
common housing.
[0037] DPF 48 physically traps a high percentage of DPM in exhaust
gas passing through it, preventing the trapped DPM from passing
into the atmosphere. Oxidation catalyst within the DOC housing 44
oxidizes hydrocarbons (HC) in the incoming exhaust gas to CO.sub.2
and H.sub.2O and converts NO to NO.sub.2. The NO.sub.2 is then used
to reduce the carbon particulates trapped in DPF 48.
[0038] 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.
[0039] According to the disclosed exemplary embodiment of the
invention, an electric heating element, such as an electric
resistance coil 52 is arranged within the exhaust system between
the turbine 40 and the DOC housing 44. The coil 52 is powered
through a relay 56 that is energized by vehicle power, such as from
an engine alternator 60 that is driven conventionally by the engine
20 through a belt driven pulley, or the like. The alternator 60
also recharges the vehicle batteries 64 as known. A temperature
sensor 70, such as a thermocouple, is arranged upstream of the DOC
housing 44 or on the DOC housing 44. The temperature sensor 70
communicates an exhaust gas temperature corresponding to the
exhaust gas temperature within the DOC housing 44 to the engine
22.
[0040] During engine idle or other low exhaust gas flow conditions,
if the temperature falls below the required temperature for
regeneration, and the control 22 demands regeneration, the engine
control 22 energizes the relay 56 to pass electric current to the
coil 52 to heat the exhaust gas flowing into the DOC housing 44.
Once the temperature sensed by the sensor 70 exceeds the exhaust
gas temperature needed for regeneration, the control 22
de-energizes the relay and current is cut off from the coil 52.
[0041] 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.
* * * * *