U.S. patent application number 16/380671 was filed with the patent office on 2019-08-01 for assemblies and methods for reducing particulate matter, hydrocarbons, and gaseous oxides from internal combustion engine exhaust.
The applicant listed for this patent is Tecogen, Inc.. Invention is credited to Joseph Gehret, Ahmed F. Ghoniem, Jean Roy.
Application Number | 20190234284 16/380671 |
Document ID | / |
Family ID | 63104491 |
Filed Date | 2019-08-01 |
![](/patent/app/20190234284/US20190234284A1-20190801-D00000.png)
![](/patent/app/20190234284/US20190234284A1-20190801-D00001.png)
![](/patent/app/20190234284/US20190234284A1-20190801-D00002.png)
![](/patent/app/20190234284/US20190234284A1-20190801-D00003.png)
![](/patent/app/20190234284/US20190234284A1-20190801-D00004.png)
![](/patent/app/20190234284/US20190234284A1-20190801-D00005.png)
![](/patent/app/20190234284/US20190234284A1-20190801-D00006.png)
![](/patent/app/20190234284/US20190234284A1-20190801-D00007.png)
United States Patent
Application |
20190234284 |
Kind Code |
A1 |
Ghoniem; Ahmed F. ; et
al. |
August 1, 2019 |
ASSEMBLIES AND METHODS FOR REDUCING PARTICULATE MATTER,
HYDROCARBONS, AND GASEOUS OXIDES FROM INTERNAL COMBUSTION ENGINE
EXHAUST
Abstract
Exhaust generated from an internal combustion engine includes
particulates and gas-phase volatile hydrocarbon condensables. The
exhaust is cooled in an exhaust gas cooler from a first temperature
to a second temperature such that a first portion of the gas-phase
volatile hydrocarbon condensables in the exhaust condense to the
liquid phase and a second portion of the gas-phase volatile
hydrocarbon condensables in the exhaust condense on black carbon
particles to form semivolatile brown carbon particulates. Some or
all of the liquid-phase volatile hydrocarbon condensables and the
semivolatile brown carbon particulates are trapped in a gasoline
particulate filter or a catalyzed gasoline particulate filter
located downstream of the exhaust gas cooler.
Inventors: |
Ghoniem; Ahmed F.;
(Winchester, MA) ; Roy; Jean; (Middleton, MA)
; Gehret; Joseph; (North Reading, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Tecogen, Inc. |
Waltham |
MA |
US |
|
|
Family ID: |
63104491 |
Appl. No.: |
16/380671 |
Filed: |
April 10, 2019 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
15892599 |
Feb 9, 2018 |
|
|
|
16380671 |
|
|
|
|
62457846 |
Feb 11, 2017 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01N 3/32 20130101; F01N
2900/1404 20130101; F01N 2900/10 20130101; B01D 53/9454 20130101;
B01D 53/96 20130101; F01N 3/0821 20130101; B01D 53/9477 20130101;
B01D 2255/915 20130101; Y02T 10/12 20130101; B01D 2255/904
20130101; F01N 3/0835 20130101; F01N 9/002 20130101; B01D 53/9445
20130101; F01N 11/007 20130101; Y02A 50/20 20180101; Y02T 10/40
20130101; F01N 3/0205 20130101; F01N 3/035 20130101; F01N 3/10
20130101; F01N 13/009 20140601; F01N 9/00 20130101; F01N 13/08
20130101; F01N 2900/0418 20130101; B01D 53/9418 20130101; B01D
2255/102 20130101; B01D 53/9495 20130101; F01N 2900/08 20130101;
F01N 3/021 20130101 |
International
Class: |
F01N 13/00 20060101
F01N013/00; B01D 53/94 20060101 B01D053/94; F01N 3/02 20060101
F01N003/02; F01N 13/08 20060101 F01N013/08; F01N 3/10 20060101
F01N003/10; F01N 3/035 20060101 F01N003/035; F01N 9/00 20060101
F01N009/00; F01N 11/00 20060101 F01N011/00; B01D 53/96 20060101
B01D053/96; F01N 3/021 20060101 F01N003/021; F01N 3/08 20060101
F01N003/08; F01N 3/32 20060101 F01N003/32 |
Claims
1. A method of reducing emissions in exhaust generated by an
engine, said exhaust comprising particulates and volatile
hydrocarbon condensables, the method comprising: cooling said
exhaust from a first temperature to a second temperature, said
cooling causing a first portion of said volatile hydrocarbon
condensables in said exhaust to condense into liquid-phase volatile
hydrocarbon condensables; passing said exhaust, including said
liquid-phase volatile hydrocarbon condensables and said
particulates, through a gas particulate filter (GPF); and trapping,
in said GPF, at least some of said liquid-phase volatile
hydrocarbon condensables and at least some of said
particulates.
2. The method of claim 1, wherein said first temperature is at
least about 650.degree. F.
3. The method of claim 1, wherein the second temperature is about
350.degree. F. to about 450.degree. F.
4. The method of claim 1, wherein said cooling comprises: passing a
first stream of said exhaust through a cooled exhaust path; passing
a second stream of said exhaust through a bypass exhaust path; and
combining said first and second streams of said exhaust to form a
combined exhaust stream, said combined exhaust stream having said
second temperature.
5. The method of claim 4, further comprising passing said first
stream of said exhaust through a heat exchanger.
6. The method of claim 4, further comprising controlling a ratio of
exhaust in said first stream and said second stream to adjust said
second temperature.
7. The method of claim 6, further comprising adjusting an operating
position of a valve to control said ratio, said valve fluidly
coupled to said first stream and said second streams.
8. The method of claim 1, further comprising temporarily stopping
said cooling to regenerate said GPF.
9. The method of claim 8, further comprising regenerating said GPF
on a periodic basis.
10. The method of claim 8, further comprising: determining whether
said engine is in an idling state or a coasting state; and
regenerating said GPF only when said engine is in said idling state
or said coasting state.
11. The method of claim 10, wherein said idling state and said
coasting state is determined based on one of or a combination of
(a) a rotational speed of said engine and (b) a fuel intake of said
engine.
12. The method of claim 10, further comprising regenerating said
GPF for a predetermined time period.
13. The method of claim 12, further comprising stopping said
regenerating when said engine is in a drive state.
14. The method of claim 1, wherein at least some of said
liquid-phase volatile hydrocarbon condensables are condensed on a
first group of black carbon particles to form brown carbon
particles.
15. The method of claim 14, further comprising trapping at least
some of a second group of black carbon particles and at least some
of said brown carbon particles in said GPF.
16. The method of claim 1, further comprising passing said cooled
exhaust over one or more catalytic elements that promote chemical
reactions that remove at least some carbon monoxide and at least
some unburned hydrocarbons from said exhaust.
17. The method of claim 16, wherein said one or more catalytic
elements are disposed in said GPF.
18. The method of claim 16, wherein said one or more catalytic
elements are disposed in a second stage catalytic converter, said
second stage catalytic converter disposed downstream of said
GPF.
19. The method of claim 16, further comprising injecting air into
said cooled exhaust before passing said exhaust through said GPF,
said air increasing an oxygen content of said exhaust.
20. The method of claim 1, further comprising, prior to said
cooling, passing said exhaust over one or more catalytic elements
that promote chemical reactions that remove at least some NO.sub.x
compounds from said exhaust.
Description
RELATED APPLICATIONS
[0001] The present application is a divisional of and claims the
priority of U.S. Application Ser. No. 15/892,599, entitled
"Assemblies and Methods for Reducing Particulate Matter,
Hydrocarbons, and Gaseous Oxides from Internal Combustion Engine
Exhaust," filed on Feb. 9, 2018, which claims priority to, and
benefit of Provisional Application No. 62/457,846, filed on Feb.
11, 2017. The foregoing applications are hereby incorporated by
reference.
TECHNICAL FIELD
[0002] The present application relates generally to emissions
control systems for internal-combustion engines.
BACKGROUND
[0003] Vehicle emissions are highly regulated to minimize the
output of environmentally-harmful exhaust emissions. The major
regulated pollutants include carbon monoxide (CO), nitrogen oxide
compounds (NO.sub.x), and unburned hydrocarbons (C.sub.xH.sub.y).
If the vehicle exhaust is left untreated, the levels of pollutants
would far exceed the emissions standards set by, for example, the
U.S. Environmental Protection Agency, the states, or another
country.
[0004] To meet these standards, vehicles include exhaust treatment
systems that include catalytic converters, such as three-way
catalytic (TWC) converters, to convert gaseous CO, NO.sub.x, and
C.sub.xH.sub.y into less harmful compounds through oxidation and
reduction reactions. An example of such an exhaust treatment system
is illustrated in FIG. 1, which is a block diagram of an underbody
of a vehicle 10. The vehicle 10 includes engine 100, first
catalytic converter 110, second catalytic converter 120, and
muffler 130, which are in fluid communication with one another
through pipe or conduit 140. In operation, the engine 100 generates
exhaust, which travels through conduit 140 to first catalytic
converter 110, second catalytic converter 120, muffler 130, and
then into the environment through tail pipe 150.
[0005] Recently, emissions regulators have become increasingly
concerned about particulate emissions and setting limits on their
levels in engine exhausts both in terms of their total mass (PM)
and number (PN). These particulates are generated in internal
combustion engines in three basic forms: (1) condensables (also
referred to as PM2.5 when their size is less than 2.5 microns), (2)
pure solids, generally referred to as "black carbon," and (3)
carbon particles saturated with volatile hydrocarbon condensables,
generally referred to as semivolatile particles or "brown carbon."
At the high temperatures typical inside a standard exhaust
treatment system (e.g., about 650.degree. F. to about 1250.degree.
F.), such as that illustrated in FIG. 1, some particulates form
before the exhaust gases reach the tailpipe, while some of the
volatile hydrocarbon condensables remain in their gaseous phase.
After exiting the tailpipe, volatile hydrocarbon condensables cool
and return to the liquid phase, appearing as an aerosol. The final
state of the condensables depends on the temperature, degree of
dilution, other particulates in the atmosphere, etc.
[0006] Gasoline particulate filters (GPFs) and catalyzed gasoline
particulate filters (cGPFs), coupled in some form to a catalytic
converter, have been proposed for removing particulates from hot
exhaust gases before they exit the tailpipe. However, GPFs and
cGPFs cannot remove volatile hydrocarbon condensables in their
gaseous form. In addition to exiting the exhaust system as a liquid
(e.g., as an aerosol), gaseous volatile hydrocarbon condensables
can form additional particulates downstream of the GPF/cGPF, for
example in the muffler or as they exit the tail pipe.
[0007] It would be desirable to overcome one or more of the
foregoing problems.
SUMMARY
[0008] Example embodiments described herein have innovative
features, no single one of which is indispensable or solely
responsible for their desirable attributes. The following
description and drawings set forth certain illustrative
implementations of the disclosure in detail, which are indicative
of several exemplary ways in which the various principles of the
disclosure may be carried out. The illustrative examples, however,
are not exhaustive of the many possible embodiments of the
disclosure. Without limiting the scope of the claims, some of the
advantageous features will now be summarized. Other objects,
advantages and novel features of the disclosure will be set forth
in the following detailed description of the disclosure when
considered in conjunction with the drawings, which are intended to
illustrate, not limit, the invention.
[0009] An aspect of the invention is directed to a system for
reducing emissions in exhaust generated by an engine, said exhaust
comprising particulates and volatile hydrocarbon condensables, the
system comprising: a heat exchanger having an inlet that receives
said exhaust at a first temperature and an outlet that outputs said
exhaust at a second temperature, the second temperature lower than
the first temperature, wherein said heat exchanger causes at least
some of said volatile hydrocarbon condensables to condense; and a
gasoline particulate filter (GPF) having an inlet in fluid
communication with the outlet of said heat exchanger to receive
said exhaust at said second temperature, said GPF having an outlet
to output said exhaust, said GPF trapping at least some
liquid-phase volatile hydrocarbon condensables and at least some of
said particulates, thereby reducing said emissions from said
engine.
[0010] In one or more embodiments, the first temperature is at
least about 650.degree. F. In one or more embodiments, the second
temperature is about 350.degree. F. to about 450.degree. F. In one
or more embodiments, said heat exchanger includes a valve in fluid
communication with a cooled exhaust path and a bypass exhaust path,
said exhaust in said cooled exhaust path being cooled by said heat
exchanger, said exhaust in said bypass exhaust path bypassing said
heat exchanger.
[0011] In one or more embodiments, the system further comprises a
controller in electrical communication with said valve to adjust a
ratio of exhaust that passes through said cooled exhaust path and
said bypass exhaust path. In one or more embodiments, said
controller is in electrical communication with first and second
thermocouples, said first thermocouple disposed proximal to said
inlet of said heat exchanger, said second thermocouple disposed in
an exhaust conduit that extends from said heat exchanger to said
GPF. In one or more embodiments, said controller is configured to
regenerate said GPF by adjusting an operating position of said
valve such that all exhaust passes through said bypass exhaust
path.
[0012] In one or more embodiments, said controller is configured to
regenerate said GPF on a periodic basis. In one or more
embodiments, said controller is configured to regenerate said GPF
only when said engine is in an idling state or a coasting state. In
one or more embodiments, said controller determines whether said
engine is in said idling state or said coasting state based on one
of or a combination of (a) a rotational speed of said engine and
(b) a fuel intake of said engine. In one or more embodiments, said
controller is configured to regenerate said GPF for a predetermined
time period. In one or more embodiments, said controller is
configured to stop regenerating said GPF during said predetermined
time period when said engine is in a drive state.
[0013] In one or more embodiments, said particulates includes black
carbon particles and brown carbon particles, said brown carbon
particles including said liquid-phase volatile hydrocarbon
condensables. In one or more embodiments, said GPF includes a
coating that traps said at least some of said liquid-phase volatile
hydrocarbon condensables and said at least some of said
particulates. In one or more embodiments, said GPF includes one or
more catalytic elements that promote chemical reactions that remove
at least some carbon monoxide and at least some unburned
hydrocarbons from said exhaust.
[0014] In one or more embodiments, the system further comprises an
exhaust conduit that extends from said heat exchanger to said GPF,
said exhaust conduit including an air inlet to receive a stream of
injected air. In one or more embodiments, the system further
comprises an assembly comprising said GPF and a second stage
catalytic converter. In one or more embodiments, said second stage
catalytic converter includes one or more catalytic elements that
promote chemical reactions that remove at least some carbon
monoxide and at least some unburned hydrocarbons from said
exhaust.
[0015] In one or more embodiments, the system further comprises an
exhaust conduit that extends from said heat exchanger to said GPF,
said exhaust conduit including an air inlet to receive a stream of
injected air. In one or more embodiments, the system further
comprises a first stage catalytic converter disposed between said
engine and said heat exchanger, said first stage catalytic
converter including one or more catalytic elements that promote
chemical reactions that remove at least some NO.sub.x compounds
from said exhaust.
[0016] Another aspect of the invention is directed to a method of
reducing emissions in exhaust generated by an engine, said exhaust
comprising particulates and volatile hydrocarbon condensables, the
method comprising: cooling said exhaust from a first temperature to
a second temperature, said cooling causing a first portion of said
volatile hydrocarbon condensables in said exhaust to condense into
liquid-phase volatile hydrocarbon condensables; passing said
exhaust, including said liquid-phase volatile hydrocarbon
condensables and said particulates, through a gas particulate
filter (GPF); and trapping, in said GPF, at least some of said
liquid-phase volatile hydrocarbon condensables and at least some of
said particulates.
[0017] In one or more embodiments, said first temperature is at
least about 650.degree. F. In one or more embodiments, the second
temperature is about 350.degree. F. to about 450.degree. F. In one
or more embodiments, said cooling comprises: passing a first stream
of said exhaust through a cooled exhaust path; passing a second
stream of said exhaust through a bypass exhaust path; and combining
said first and second streams of said exhaust to form a combined
exhaust stream, said combined exhaust stream having said second
temperature. In one or more embodiments, the method further
comprises passing said first stream of said exhaust through a heat
exchanger. In one or more embodiments, the method further comprises
controlling a ratio of exhaust in said first stream and said second
stream to adjust said second temperature. In one or more
embodiments, the method further comprises adjusting an operating
position of a valve to control said ratio, said valve fluidly
coupled to said first stream and said second streams.
[0018] In one or more embodiments, the method further comprises
temporarily stopping said cooling to regenerate said GPF. In one or
more embodiments, the method further comprises regenerating said
GPF on a periodic basis. In one or more embodiments, the method
further comprises determining whether said engine is in an idling
state or a coasting state; and regenerating said GPF only when said
engine is in said idling state or said coasting state. In one or
more embodiments, said idling state and said coasting state is
determined based on one of or a combination of (a) a rotational
speed of said engine and (b) a fuel intake of said engine. In one
or more embodiments, the method further comprises regenerating said
GPF for a predetermined time period. In one or more embodiments,
the method further comprises stopping said regenerating when said
engine is in a drive state.
[0019] In one or more embodiments, at least some of said
liquid-phase volatile hydrocarbon condensables are condensed on a
first group of black carbon particles to form brown carbon
particles. In one or more embodiments, the method further comprises
trapping at least some of a second group of black carbon particles
and at least some of said brown carbon particles in said GPF.
[0020] In one or more embodiments, the method further comprises
passing said cooled exhaust over one or more catalytic elements
that promote chemical reactions that remove at least some carbon
monoxide and at least some unburned hydrocarbons from said exhaust.
In one or more embodiments, said one or more catalytic elements are
disposed in said GPF. In one or more embodiments, said one or more
catalytic elements are disposed in a second stage catalytic
converter, said second stage catalytic converter disposed
downstream of said GPF. In one or more embodiments, the method
further comprises injecting air into said cooled exhaust before
passing said exhaust through said GPF, said air increasing an
oxygen content of said exhaust. In one or more embodiments, the
method further comprises, prior to said cooling, passing said
exhaust over one or more catalytic elements that promote chemical
reactions that remove at least some NO.sub.x compounds from said
exhaust.
IN THE DRAWINGS
[0021] For a fuller understanding of the nature and advantages of
the present invention, reference is made to the following detailed
description of preferred embodiments and in connection with the
accompanying drawings, in which:
[0022] FIG. 1 is a block diagram of an underbody of a vehicle
according to the prior art;
[0023] FIG. 2 is a block diagram of an exhaust treatment system
according to one or more embodiments of the invention;
[0024] FIG. 3 is a block diagram of an exhaust treatment system
according to one or more embodiments of the invention;
[0025] FIG. 4 is a flow chart of a method for reducing particulate
matter, hydrocarbons, nitrogen oxides, and carbon monoxide from
exhausts of internal combustion engines;
[0026] FIG. 5 is a flow chart of a method for operating and
regenerating a GPF/cGPF in an exhaust treatment system;
[0027] FIG. 6 is a block diagram of an exhaust treatment system for
reducing emissions of volatile hydrocarbon condensables according
to one or more embodiments of the invention; and
[0028] FIG. 7 is a flow chart of a method for reducing volatile
hydrocarbon condensables from exhausts of internal combustion
engines.
DETAILED DESCRIPTION
[0029] Aspects of the invention are directed to reducing
particulate and volatile hydrocarbon emissions from the exhaust of
an internal combustion engine. The exhaust gas is cooled from a
first temperature to a second temperature in an exhaust gas cooler
(e.g., a heat exchanger) such that a first portion of the volatile
hydrocarbon condensables in the exhaust condense to the liquid
phase and a second portion of the volatile hydrocarbon condensables
in the exhaust condense on black carbon particles to form
semivolatile brown carbon particulates. Some or all of the
liquid-phase volatile hydrocarbon condensables and the semivolatile
brown carbon particulates are trapped in a GPF or cGPF located
downstream of the exhaust gas cooler.
[0030] FIG. 2 is a block diagram of an exhaust treatment system 20
according to one or more embodiments of the invention. The system
20 includes a first stage catalytic converter 210, an exhaust heat
exchanger 220, an air pump 230, a second stage catalytic
converter/cGPF 240, a muffler and tailpipe 250, and a controller
260. Exhaust from an internal combustion engine 200 enters the
first stage catalytic converter 210 through a conduit, which can be
connected to each cylinder of the engine 200 via a manifold. The
exhaust enters the first stage catalytic converter 200 at or near
the operating temperature of the engine. At steady state (i.e.,
after the engine has warmed up from a cold start), engine 200
generally operates in the range of about 650.degree. F. to about
1250.degree. F. As used herein, "about" means plus or minus 10% of
the relevant value. Engine 200 can be a spark-ignited internal
combustion engine or a diesel engine. In addition, engine 200 can
be in a vehicle or it can be stationary, for example to drive a
combined heat and power (CHP) system.
[0031] The engine 200 can operate with an air-fuel ratio (AFR) in
the rich burn regime (i.e., less than or equal to a stoichiometric
AFR). In some embodiments, the stoichiometric AFR is 14.64:1 (by
mass) for gasoline. The stoichiometric AFR can vary depending on
the type of fuel. For example, the stoichiometric AFR can be lower
if the fuel includes ethanol. As an example, E85 fuel (85% ethanol,
15% gasoline) can have a stoichiometric AFR of about 9.8:1. When
the engine 200 operates in the rich burn regime, the exhaust
contains a minimal or a substantially zero oxygen content. For
example, the oxygen content can be less than or equal to about 0.1%
by volume, less than or equal to about 0.05% by volume, and/or less
than or equal to about 0.025% by volume.
[0032] The first stage and second stage catalytic converters 210,
240 can include a catalyst comprising one or more platinum-group
metals (PGMs), such as Pt, Pd, and/or Rh. In some embodiments, one
or both of the first and second stage catalytic converters 210, 240
include a TWC. The first stage catalytic converter 210 promotes
chemical reactions (e.g., reduction reactions) that remove at least
some NO.sub.x compounds from the exhaust stream (e.g., by reducing
NO.sub.x to form N.sub.2 and O.sub.2).
[0033] After passing through the first stage catalytic converter
210, the exhaust flows into the exhaust heat exchanger 220 (e.g.,
into an inlet of heat exchanger 220) which lowers the temperature
of the exhaust from a first temperature to a second temperature,
the second temperature lower than the first temperature. The first
temperature can be at or near the steady-state operating
temperature of the engine 200 (e.g., at least about 650.degree. F.
such as about 650.degree. F. to about 1250.degree. F.). The second
temperature can be about 400.degree. F., such about 350.degree. F.
to about 450.degree. F., including about 375.degree. F., about
400.degree. F., about 425.degree. F., about 450.degree. F., or any
value or range between any two of the foregoing values. The heat
exchanger 220 includes a cooled path in which heat exchanger 220
cools the exhaust and an optional bypass path that is not cooled by
the heat exchanger 220. The cooled and optional bypass paths of the
heat exchanger 220 converge at the downstream end of the heat
exchanger 220, where the paths mix and have a temperature
T.sub.mix. The exhaust that flows through the cooled path can be
cooled to a temperature of about 250.degree. F. to about
350.degree. F., including about 275.degree. F., about 300.degree.
F., about 325.degree. F., or any value or range between any two of
the foregoing values. The heat exchanger 220 cools the exhaust with
a cooling fluid, such as radiator fluid or coolant, which is in
thermal communication with the exhaust that flows through the
cooled path. For example, the cooling fluid can be received from
the vehicle's radiator and pass through a coil that provides a
surface area for thermal communication between the cooling fluid
and the exhaust flowing through the cooled path.
[0034] The temperature T.sub.mix can be adjusted by varying the
flow rates (e.g., volumetric and/or mass flow rates) or the ratio
of flow rates (e.g., volumetric and/or mass flow rates) of the
exhaust in each path. For example, the heat exchanger 220 can
include a bypass valve 270, in fluid communication (and/or fluidly
coupled) with the cooled and bypass paths, that can be adjusted to
vary the flow rate of the exhaust in the bypass path. When the
bypass valve 270 is fully closed, all of the exhaust flows through
the cooled path. When the bypass valve 270 is fully open, the
exhaust flows through both the cooled and bypass paths without
restriction. The bypass valve can also be partially opened or
closed to limit the flow rate of exhaust through the bypass path.
In an alternative embodiment, fully closing the bypass valve 270
causes all of the exhaust to flow through the cooled path, fully
opening the bypass valve 270 causes all of the exhaust to flow
through the bypass path, and partially opening the bypass valve 270
causes some exhaust to flow through the cooled and bypass paths,
the respective amount/ratio depending on the operating position of
the bypass valve 270.
[0035] In some embodiments, the heat exchanger 220 can also include
a cooled path valve to open or close the cooled path. For example,
during cold start the cooled path valve can be fully closed while
the bypass valve 270 is fully open so the exhaust is at a maximum
temperature when it passes through the second stage catalytic
converter 240 to promote the chemical reactions at the second stage
catalytic converter 240. Alternatively, the heat exchanger 220 can
include a valve at its upstream side to direct the exhaust to
either the cooled or bypass path, or to both the cooled and bypass
paths. Any of the foregoing valves can be adjusted by controller
260, which receives as inputs a first temperature of the exhaust
before it enters the heat exchanger 220, measured by thermocouple
225 (e.g., located proximal to the inlet of heat exchanger 220),
and a second temperature of the exhaust after it exits the heat
exchanger 220, measured by thermocouple 235 (e.g., located in the
exhaust conduit that extends from the outlet of heat exchanger 220
to the inlet of second stage catalytic converter/cGPF 240). The
controller 260 adjusts the valve(s) (e.g., valve 270) so that the
second temperature is at a set point temperature of about
400.degree. F., such as about 350.degree. F. to about 450.degree.
F., as discussed above.
[0036] When the exhaust gas is cooled by the heat exchanger 220 to
about 400.degree. F., at least some or most of the gaseous
condensables (e.g., volatile unburned hydrocarbons) undergo a phase
change and condense as a liquid. Thus, the reduction in temperature
of the exhaust stream causes a higher fraction of the condensables
to reach their liquid phase while still contained in the exhaust
gas stream. The reduction in temperature has the added benefit of
forming more brown carbon when some of the gaseous condensables
condense on the black carbon particles that act as nucleation sites
during the phase change process.
[0037] After the exhaust gas exits the heat exchanger 220, it
passes through a conduit that receives a volume of air injected by
air pump 230. The injected air increases the oxygen concentration
of the exhaust before it passes through the second stage catalytic
converter 240. The increased oxygen concentration promotes
oxidation reactions in the second stage catalytic converter that
remove carbon monoxide and unburned hydrocarbons from the exhaust.
The air pump 230 can inject unheated air taken from outside of the
vehicle, which can have a temperature in the range of about
32.degree. F. (or lower in the winter) to about 90.degree. F. (or
higher in the summer), depending on the climate in which the
vehicle is located. The unheated air can cause the temperature of
the exhaust to decrease. In other embodiments, the injected air is
preheated in which case it has little effect on the exhaust
temperature. To control for the temperature change caused by the
injected air, thermocouple 235 is preferably located downstream of
the injected air inlet to provide the appropriate feedback
temperature to controller 260. Likewise, the injected air inlet is
preferably located upstream of thermocouple 235 and downstream of
heat exchanger 220. In some embodiments, the air pump 230 is also
in electrical communication with the controller 260, for example to
adjust the oxygen concentration based on feedback from an oxygen
sensor disposed downstream of the injected air inlet.
[0038] After receiving the injected air from air pump 230, the
exhaust passes into the second stage catalytic converter 240. As
discussed above, the second stage catalytic converter 240 promotes
chemical reactions (e.g., oxidation reactions) that remove at least
some carbon monoxide and at least some unburned hydrocarbons from
the exhaust stream. At the reduced temperature that the exhaust
enters the second stage catalytic converter 240 (i.e., about
400.degree. F., such as about 350.degree. F. to about 450.degree.
F.), the oxidation reactions occur without reforming nitrogen oxide
compounds, which are controlled by emissions regulators. In some
embodiment, the second stage catalytic converter 240 can also
reduce the concentration of any remaining NO.sub.x in the
exhaust.
[0039] The second stage catalytic converter 240 also includes a
GPF. The GPF can be a separate unit (e.g., a modular portion of an
assembly that includes a second stage catalytic converter) of the
second stage catalytic converter 240 or it can be integrated into
the second stage catalytic converter 240. In some embodiments, the
second stage catalytic converter is a cGPF, which can include some
or all catalytic elements that are also disposed in the second
stage catalytic converter 240. For example, the cGPF can include
one or more of the above-described platinum-group metals and/or it
can include the catalysts that are typically included in a TWC. In
some embodiments, the second stage catalytic converter 240 and/or
cGPF is integrated into a single unit that also includes the
muffler 250. In an alternative embodiment, a GPF is disposed
between the second stage catalytic converter 240 and the injected
air inlet for air pump 230.
[0040] The GPF or cGPF (in general, GPF) includes a coating 245
that traps particulate emissions, such as black and brown carbon,
in the exhaust. The coating 245 can be a coating as known in the
art. A three-way catalyst washcoat containing one or more PGMs
and/or other metals with oxygen-storage capability may be added or
included in coating 245. The coating 245 also collects the
additional brown carbon and the liquid-phase condensables formed as
a result of the lower exhaust temperature. Therefore, the reduction
in temperature allows the GPF to trap more volatile hydrocarbon
condensables, as liquid and as brown carbon, than it could when the
exhaust is at a higher temperature (e.g., higher than about
400.degree. F.) where the liquid phase change does not occur. This
reduction in the concentration of hydrocarbon condensables reduces
the overall hydrocarbon emissions and reduces the chance of
condensables forming particulates as the exhaust exits the
tailpipe.
[0041] Aspects of the invention described herein can provide one or
more of the following advantages:
[0042] (1) Cooling the exhaust gases in an exhaust gas cooler
(e.g., heat exchanger 220) after the first stage catalytic
converter (e.g., first stage catalytic converter 210) condenses a
larger fraction of gaseous hydrocarbons into their liquid phase
while they are still in the exhaust system (e.g., exhaust treatment
system 20). These can be captured by the GPF/cGPF, making it more
effective in removing a larger fraction of the condensables in
liquid form and as solid particulates (e.g., brown carbon) that
carry the liquefied condensables.
[0043] (2) Cooling the exhaust gases in an exhaust gas cooler
(e.g., heat exchanger 220) after the first stage catalytic
converter (e.g., first stage catalytic converter 210) results in
the formation of particles containing large fractions of
semivolatiles (e.g., brown carbon) that can be more easily captured
in the GPF due to their larger size. Because a higher fraction of
the particles forming after the exhaust gas cooler has larger
sizes, it helps the GPF filtration system to remove more
particulate mass and particulate numbers leaving the exhaust stream
(e.g., exhaust treatment system 20) with a much smaller fraction of
condensable hydrocarbons.
[0044] (3) Employing a catalyzed GPF (cGPF) can have the added
benefit of reducing/replacing the second stage catalytic converter.
Thus, the exhaust system (e.g., exhaust treatment system 20) can
have approximately the same footprint and take up approximately the
same amount of space as existing exhaust systems.
[0045] (4) Employing other forms of exhaust gas cooling systems
(i.e., different than heat exchanger 220) that cool down the entire
exhaust stream or fractions of it before treatment in the GPF/cGPF
is also possible and will lead to similar benefits
[0046] (5) The systems and processes described herein can be used
in internal combustion engine designs that utilize exhaust gas
recirculation to reduce NO formation in the engine and/or to
improve the engine efficiency.
[0047] (5) In a standard emissions system without intermediate
exhaust cooling, the GPF/cGPF is regenerated by temporarily running
the engine's AFR under fuel lean conditions to provide extra oxygen
at the high temperatures necessary to oxidize the particulate
matter caught in the filter. This may greatly increase the
formation and/or reformation of nitrogen oxides, for example in the
second catalytic converter. Because the above system 20 includes
additional air for oxidation (i.e., air injected by air pump 230),
regeneration of the GPF can be accomplished by temporarily
increasing the temperature at the second stage catalytic converter
240 (e.g., by closing the cooled path valve) without changing the
engine's AFR. While this may induce a slight increase in nitrogen
oxides due to reformation, the overall tailpipe levels are much
lower than would be produced by leaning the AFR. Nitrogen oxide
reformation can be further reduced by increasing the temperature at
a time when minimal fuel is consumed by the engine, such as when
coasting down a hill or idling. Such regeneration can occur on a
periodic basis, for example once a day, once a week, once every
1,000 miles, or other interval or periodic basis.
[0048] FIG. 3 is a block diagram of an exhaust treatment system 30
according to one or more embodiments of the invention. System 30 is
the same or similar to system 20 except as described below. In
place of the combined second stage catalytic converter/cGPF 240 in
system 20, system 30 includes a GPF 380 disposed between the inlet
for the air injected by air pump 230 and the inlet to second stage
catalytic converter 340. In an alternative embodiment, the GPF 380
can be disposed between the outlet of heat exchanger 220 and the
inlet for the air injected by air pump 230. The second stage
catalytic converter 340 is otherwise the same or similar to second
stage catalytic converter 240. For example, second stage catalytic
converter 340 can include one or more platinum-group metals and/or
it can include a TWC in some embodiments.
[0049] GPF 380 is the same or similar to the GPF described above
with respect to second stage catalytic converter/cGPF 240. For
example, GPF 380 includes a coating 345 which is the same or
similar to coating 245. Thus, coating 345 can trap black carbon,
brown carbon, and condensables in liquid form. It is noted that if
additional GPFs are desired in system 30, the second stage
catalytic converter 340 can include a second GPF or, alternatively,
it can include or can be a cGPF, as described above.
[0050] In an alternative embodiment, the air pump 230 and/or the
second stage catalytic converter 340 are not included in system 30.
When the air pump 230 and/or second stage catalytic converter 340
are removed from system 30, the GPF 345 still functions to trap
black carbon, brown carbon, and condensables in liquid form, as
discussed above.
[0051] FIG. 4 is a flow chart 40 of a method for reducing
particulate matter, hydrocarbons, nitrogen oxides, and carbon
monoxide from exhausts of internal combustion engines. The method
according to flow chart 40 can be performed on system 20 and/or 30,
described above. In step 400, the exhaust is passed through a first
stage catalytic converter. The first stage catalytic converter
includes one or more active catalytic elements (e.g., a
platinum-group metal and/or a TWC) that catalyzes a chemical
reaction to reduce the concentration of nitrogen oxide compounds in
the exhaust. The exhaust is generated by an internal combustion
engine which can run at a stoichiometric or a rich AFR, as
described above. In step 410, the exhaust is cooled to about
400.degree. F., such as about 350.degree. F. to about 450.degree.
F. The exhaust can be cooled by passing some or all of it through a
heat exchanger or by using another cooling unit. As discussed
above, a portion of the exhaust can bypass the cooling unit and the
flow rate and/or ratio of cooled and bypassed exhaust can be
controlled (e.g., by valves in communication with a controller) to
provide the desired temperature.
[0052] In step 420, the lower temperature causes at least a portion
or most of the volatile hydrocarbon condensables to undergo a phase
change into a liquid. The liquid-phase condensables can remain as
liquid and/or they can condense on the black carbon particles, that
act as nucleation sites during the phase change process, to form
semivolatile brown carbon, as discussed above. In step 430, the
oxygen concentration of the cooled exhaust is increased to at least
about 0.25%, such as at least about 0.5%, at least about 0.75%, at
least about 1%, or a higher concentration. The oxygen concentration
can be increased by injecting air into the cooled exhaust stream.
In step 440, the exhaust is passed through a GPF that includes a
coating to trap the liquid-phase condensables and semivolatile
particles formed in step 420 in addition to other particulates in
the exhaust such as black carbon. In step 440, the exhaust is
passed through a second stage catalytic converter. The second stage
catalytic converter includes one or more active catalytic elements
(e.g., a platinum-group metal and/or a TWC) that catalyzes chemical
reactions to reduce the concentration of unburned hydrocarbons and
carbon monoxide in the exhaust. The second stage catalytic
converter can also reduce the concentration of nitrogen oxide
compounds in some embodiments.
[0053] FIG. 5 is a flow chart 50 of a method for operating and
regenerating a GPF/cGPF (in general, GPF) in an exhaust treatment
system. The method according to flow chart 50 can be performed on
system 20 and/or 30, described above. In step 500, the GPF collects
or traps particulates, such as black and brown carbon, and
liquid-phase condensables from the exhaust stream. After a first
predetermined period or interval (e.g., once a day or every 100
miles), a controller in the exhaust treatment system at step 510
determines whether the regeneration period for the GPF has been
exceeded. The regeneration period can be based on time (e.g., once
a day, once a week, once a month, or other time period), based on
mileage (e.g., every 500 miles, every 1,000 miles, or other mileage
interval), based on a combination of time or mileage (e.g., once a
week or once every 300 miles, whichever occurs first), or other
factors. The regeneration period can occur on a periodic or a
non-periodic basis. If the controller determines that the
regeneration period has not been exceeded, the flow chart returns
to step 500 and the GPF continues to collect particulates (e.g.,
black and/or brown carbon particulates) and liquid-phase
condensables from the exhaust. If the controller determines that
the regeneration period has been exceeded, the controller then
determines at step 520 whether the engine is in an idling or
coasting state (and/or that the engine is not in a drive state),
for example based on the engine's rotational speed (e.g., RPMs)
and/or the fuel intake of the engine. If the engine is not in an
idling or coasting state (and/or if the engine is in a drive
state), the flow chart 50 returns to step 500 and the GPF continues
to collect particulates and liquid-phase condensables from the
exhaust for a second predetermined period, or interval which can be
the same or less than the first predetermined period or interval.
For example, the second predetermined period can be less than an
hour, such as 15 minutes, or less than 10 miles in some
embodiments.
[0054] After the controller determines at step 520 that the engine
is in an idling or coasting state (and/or not in a drive state),
the controller at step 530 causes the temperature of the exhaust
exiting the cooling unit to increase (e.g., by adjusting the bypass
valve and/or cooling valve). The temperature of the exhaust exiting
the cooling unit can raised to about 500.degree. F. to about
1,000.degree. F., such as about 600.degree. F., about 700.degree.
F., about 800.degree. F., about 900.degree. F., or any value or
range between any two of the foregoing values. In step 540, the GPF
regenerates using the high temperature exhaust.
[0055] On a periodic basis or interval, the controller checks
whether the regeneration is complete in step 550, which can be
based on a predetermined time period. If the regeneration is
complete, the flow chart 50 proceeds to step 570 where the
controller causes the cooling unit to lower the temperature of the
exhaust exiting the cooling unit to an operating temperature of
about 400.degree. F., as discussed above. After the exhaust
temperature is decreased in step 570, the flow chart 50 returns to
step 500 where the GPF collects particulates and liquid-phase
condensables from the exhaust. The controller also resets the first
predetermined time period and the regeneration period.
[0056] If the regeneration is not complete in step 550, the flow
chart proceeds to step 560 where the controller determines whether
the engine continues to be in an idling or coasting state (and/or
that the engine is not in a drive state). If the engine is in an
idling or coasting state, the flow chart 50 returns to step 540 to
continue to regenerate the GPF using the high temperature exhaust.
If the engine is not in an idling or coasting state (and/or if the
engine is in a drive state), the flow chart 50 proceeds to step 570
to decrease the exhaust temperature, as discussed above. After the
exhaust temperature is decreased in step 570, the flow chart 50
returns to step 500 where the GPF collects particulates and
liquid-phase condensables from the exhaust. The controller can
reset the first predetermined period and/or the regeneration period
to a secondary, lower period so that the controller attempts to
complete the regeneration sooner than it normally would.
Alternatively, the controller can set the first predetermined
period and/or the regeneration period to zero, in which case flow
chart 50 passes immediately to steps 510 and 520 in an attempt to
complete the GPF regeneration process.
[0057] FIG. 6 is a block diagram of an exhaust treatment system 60
for reducing emissions of volatile hydrocarbon condensables
according to one or more embodiments of the invention. Exhaust
treatment system 60 includes an exhaust heat exchanger 620, a
controller 660, and a GPF 680. Heat exchanger 620, controller 670,
and GPF 680 can be the same as or substantially the same as heat
exchanger 220, controller 260, and GPF 380, respectively.
Accordingly, exhaust treatment system 60 operates in the same or
substantially the same way as exhaust treatment system 30 with
respect to heat exchanger 220, controller 260, and GPF 380.
[0058] In operation, exhaust from an engine passes through an
exhaust conduit and into an inlet of heat exchanger 620 at a
temperature at or near the operating temperature of the engine
(e.g., about 650.degree. F. to about 1250.degree. F.). Upstream of
the heat exchanger 620, the exhaust can optionally pass through a
first stage catalytic converter, as discussed above. The controller
660 adjusts the operating position of one or more valves (e.g.,
bypass valve 670) in the heat exchanger 620, based on feedback from
thermocouples 625, 635) to adjust the flow rate and/or ratio of
exhaust that passes through a cooled path and a bypass path such
that the temperature of the exhaust exiting the heat exchanger 620
is about 400.degree. F. (e.g., about 350.degree. F. to about
450.degree. F.), as discussed above. The reduction in temperature
causes a portion or most of the volatile hydrocarbon condensables
in the exhaust to undergo a phase change into a liquid, which are
trapped or collected by GPF 680 as liquid and as brown carbon, as
discussed above. GPF 680 can also collect black carbon particles in
the exhaust.
[0059] In some embodiments, GPF 680 can be a cGPF as discussed
above. In addition or in the alternative, a second stage catalytic
converter can be disposed downstream of the GPF 680, as discussed
above.
[0060] FIG. 7 is a flow chart 70 of a method for reducing volatile
hydrocarbon condensables from exhausts of internal combustion
engines. The method according to flow chart 40 can be performed on
system 20, 30, and/or 40, described above. Steps 700, 710, and 720
can be the same as or substantially the same as steps 410, 420, and
440, respectively. It is noted that in step 720 the exhaust can
pass through either a GPF or a cGPF. In step 730, the liquid-phase
condensables and particulates (e.g., black carbon and/or
semivolatile brown carbon particles) are trapped in the
GPF/cGPF.
[0061] In the foregoing specification, the invention has been
described with reference to specific embodiments. However, one of
ordinary skill in the art appreciates that various modifications
and changes can be made without departing from the scope of the
disclosure and technology described herein. Accordingly, the
specification and figures are to be regarded in an illustrative
rather than a restrictive sense, and all such modifications are
intended to be included within the scope of the claims and this
disclosure.
* * * * *