U.S. patent application number 15/820389 was filed with the patent office on 2018-05-24 for internal combustion engine aftertreatment heating loop.
This patent application is currently assigned to Clean Train Propulsion. The applicant listed for this patent is Clean Train Propulsion. Invention is credited to David Cook.
Application Number | 20180142595 15/820389 |
Document ID | / |
Family ID | 69528055 |
Filed Date | 2018-05-24 |
United States Patent
Application |
20180142595 |
Kind Code |
A1 |
Cook; David |
May 24, 2018 |
Internal Combustion Engine Aftertreatment Heating Loop
Abstract
An engine with an SCR catalyst aftertreatment system includes a
turbocharger exhaust duct in fluid communication with the
turbocharger outlet and a heating loop segment including an inlet
and an outlet. The inlet and the outlet are in fluid communication
with the exhaust duct, and the inlet extracts a portion of exhaust
gases from the exhaust duct. The engine further includes an exhaust
pressure driven air amplifier, an electric preheater, a fuel
injector, an oxidation catalyst, a urea injector, and a temperature
sensor on the heating loop segment.
Inventors: |
Cook; David; (Fullerton,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Clean Train Propulsion |
Fullerton |
CA |
US |
|
|
Assignee: |
Clean Train Propulsion
|
Family ID: |
69528055 |
Appl. No.: |
15/820389 |
Filed: |
November 21, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62424914 |
Nov 21, 2016 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60L 7/10 20130101; F01N
3/2033 20130101; G06Q 30/0645 20130101; F01N 11/002 20130101; G01R
31/367 20190101; F01N 3/2066 20130101; F01N 3/106 20130101; Y02T
10/12 20130101; F01N 2560/06 20130101; F01N 2610/02 20130101; F01N
2610/1453 20130101; Y02A 50/20 20180101; F01N 3/2013 20130101; G01R
31/3842 20190101; B60L 2200/26 20130101; B60M 7/003 20130101; Y02T
90/16 20130101; Y02T 10/40 20130101 |
International
Class: |
F01N 3/20 20060101
F01N003/20; F01N 3/10 20060101 F01N003/10; F01N 11/00 20060101
F01N011/00 |
Claims
1. An engine with an SCR catalyst aftertreatment system comprising:
a turbocharger exhaust duct in fluid communication with the
turbocharger outlet; a heating loop segment including an inlet and
an outlet, wherein the inlet and the outlet are in fluid
communication with the exhaust duct, wherein the inlet extracts a
portion of exhaust gases from the exhaust duct; an exhaust pressure
driven air amplifier on the heating loop segment; an electric
preheater on the heating loop segment; a fuel injector on the
heating loop segment; an oxidation catalyst on the heating loop
segment; a urea injector on the heating loop segment; and a
temperature sensor on the heating loop segment.
2. The engine of claim 1, further comprising a compressed air
amplifier on the heatling loop segment.
3. An engine with an oxidation catalyst aftertreatment system
comprising: an exhaust duct in fluid communication with the engine
outlet; a heating loop segment including an inlet and an outlet,
wherein the inlet and the outlet are in fluid communication with
the exhaust duct, wherein the inlet extracts a portion of exhaust
gases from the exhaust duct; a compressed air amplifier on the
heating loop segment; a fuel injector on the heating loop segment;
an oxidation catalyst on the heating loop segment; and a
temperature sensor on the heating loop segment.
4. The engine of claim 3, further comprising a burner system on the
heating loop segment.
5. The engine of claim 4, further comprising an electric preheater
on the heating loop segment.
6. The engine of claim 3, further comprising electric preheater on
the heating loop segment.
7. The engine of claim 3, wherein the engine is a natural gas
engine.
8. The engine of claim 3, wherein the fuel injector comprises an
air amplifier.
9. An engine with an oxidation catalyst aftertreatment system
comprising: an exhaust duct in fluid communication with the engine
outlet; a heating loop segment including an inlet and an outlet,
wherein the inlet and the outlet are in fluid communication with
the exhaust duct, wherein the inlet extracts a portion of exhaust
gases from the exhaust duct; a compressed air amplifier on the
heating loop segment; a fuel injector on the heating loop segment;
an oxidation catalyst on the heating loop segment; a urea injector
on the heating loop segment; and a temperature sensor on the
heating loop segment.
10. The engine of claim 9, further comprising a burner system on
the heating loop segment.
11. The engine of claim 10, further comprising an electric
preheater on the heating loop segment.
12. The engine of claim 9, further comprising electric preheater on
the heating loop segment.
13. The engine of claim 9, wherein the engine is a natural gas
engine.
14. The engine of claim 9, wherein the fuel injector comprises an
air amplifier.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of benefit of priority
to U.S. Provisional Application No. 62/424,914 filed on Nov. 21,
2016, the disclosure of which is incorporated by reference
herein.
BACKGROUND OF THE INVENTION
[0002] The first portion of the background relates to the
challenges of engine aftertreatment system operation at low exhaust
temperatures. One of the findings from the blended aftertreatment
system (BATS) program in North Carolina was that exhaust gas
temperatures where the Urea is injected and vaporized needs to be
220.degree. C. for early stage dissociation, but the overall SCR
system and bulk exhaust gas temps could be cooler in the
165.degree. C. range and the SCR system still had good NOx
reduction efficiency at low loads and air flows.
[0003] While the BATS solution was good for passenger locomotives
that had both a large prime mover and a smaller generator that ran
at higher loads and exhaust temperatures, it did not offer a
solution to the majority of locomotives that only had a single
large prime mover. These large medium speed engines were very
efficient and spent considerable times at idle and low loads, where
exhaust temperatures would be below the 220.degree. C. needed to
vaporize and process a mixture of UREA liquid and exhaust gas.
[0004] For locomotive engines operating with natural gas as the
primary fuel, this low temperature operation also hinders the use
of an oxidizing catalyst (OC) which is needed to reduce carbon
monoxide (CO) emissions and help reduce non-methane hydrocarbon
(NMHC) emissions, two of the EPA-mandated criteria emissions that
are generated in higher quantities when a diesel engine is
converted to natural gas. The temperature range for making an OC
efficiently reduce CO and start reducing NMHC is the same 200+
Celsius that is needed for effective SCR operation.
[0005] A similar problem but at a different range of temperatures
is becoming apparent with the introduction of heavy duty natural
gas engines that operate at very lean air fuel ratios in order to
both increase thermal efficiency and lower NOx emissions. In the
emissions regulations for on-road applications, there is not an
exception for methane emissions and therefor total hydrocarbons
(HC) need to be reduced. Methane has a very high ignition
temperature over 500.degree. C. and therefore an OC needs to be at
a temperature greater than 400.degree. C. before it is effectively
oxidizing methane, which makes up a majority of the challenging HC
emissions from a high efficiency lean burn engine.
[0006] What would help solve the above problems is an effective
solution to increase engine out exhaust temperatures on these
engines with a minimal penalty in extra fuel consumption and
complexity.
BRIEF SUMMARY OF THE INVENTION
[0007] Instead of second engine operating at a higher exhaust
temperature to make up for the low main engine exhaust temperature
as in the first BATS system, there could be a separate exhaust gas
heating loop where urea is mixed with a portion of the main engine
exhaust. In this loop, the urea is vaporized if needed and the
dissociation process is started. If the hot exhaust gasses in this
loop are not hot enough at some operating conditions, they could be
locally heated with the injection of fuel that is burned across a
small oxidizing catalyst. Typical aftertreatment systems on heavy
duty engines dose all of the exhaust gases with raw fuel and or
UREA. What is novel in this case is that a portion of the total
exhaust gas flow is removed and locally heated to the appropriate
temperature before dosing with fuel or UREA. This separate external
exhaust gas loop will be called the heating loop.
[0008] This system is not specific to just SCR systems that require
UREA dosing. It would work for any exhaust aftertreatment system
that is challenged to reduce emissions at low exhaust temperatures,
including an OC by itself or in series with an SCR.
[0009] The first challenge of a heating loop would be to induce the
correct portion of the total exhaust gas mass to go through the
separate loop. The simplest technique would be to use the main
exhaust gasses kinetic energy to drive the portion of exhaust gas
through the loop. In the main exhaust pipe, an inlet could be
facing into the exhaust flow using ram air pressure to drive
exhaust into the loop. Where the heated loop gasses are
reintroduced back into the main exhaust flow, the outlet could be
directed in the direction of the main exhaust gas flow causing a
low pressure region at the loop exit and further increasing the
flow of exhaust gases drawn into and through the heating loop.
[0010] In a preferred embodiment, the ram inlet and lower exit
pressure would generate all of the heating loop flow that is
required. Any additional flow that is not moved by these pressure
differences that is needed could be generated in a simple fashion
using an air amplifier similar to that disclosed in U.S. Pat. No.
4,046,492. Compressed air is a readily available source to drive an
air amplifier. Trucks, locomotives, busses and many other
heavy-duty engine applications typically have compressed air
supplies to operate the air brakes on the vehicle. Air amplifiers
(a type of jet pump) are simple and low maintenance. The only
moving part would be an air flow control mechanism, typically a
solenoid that is controlling reasonably low pressure (likely
100-150 psi) and near ambient temperature air. Further, the
pressurized air flow to the air amplifier can be manipulated by
using more than one solenoid to control the pressurized air flow or
pulsing one or more solenoids at varying duty cycles to vary the
amount of additional exhaust gases that the air amplifier draws
into the heating loop.
[0011] On turbo engines, the exhaust back pressure upstream of the
turbine can be used as a source of pressurized air to drive the air
amplifier operating at the near ambient pressure that the exhaust
gasses going through the aftertreatment are operating at. As most
turbochargers operate with a wastegate slightly open at higher
loads, bypassing the turbine with some exhaust gas to drive a air
amplifier in the heating loop should have no or very little effect
on engine efficiency. Compressed air from the turbine would be at a
lower pressure than typical compressed air from and air brake
compressor so it will operate at a lower mass amplification ratio.
Also turbine back pressure varies with engine load and is
negligible at idle. The turbo pressure variation with engine load
will vary in the same direction as the requirement for the air
amplifier to induce exhaust gas flow. Like the airbrake compressed
air supply system, the preturbine pressurized exhaust gas supply
flow or pressure could be manipulated with a valve that controls
flow rate. Because valves that operate at these high temperatures
can be problematic, in a preferred embodiment the pressurized
exhaust gas supply would be controlled by a fixed orifice with no
moving parts.
[0012] If there is a benefit to having the orifice larger at lower
exhaust temperatures, one variation could be an orifice that varies
with temperature using the premise of thermal expansion. This could
be with a bimetallic spring that when heated moves into position to
restrict the orifice. While technically a moving part, a bimetallic
spring system could be designed that had no rubbing parts such as a
bearing that over time would wear and change its characteristics.
The preferred embodiment would have the flow control orifice be the
actual jet nozzle where the compressed exhaust gas is mixed with
the heating loop exhaust gases.
[0013] In some air amplifiers, the fixed orifice is actually a
continuous radial gap between two radial faces of almost touching
parts. In the case of the Nex Flow Air Products Corp part number
30003TS this gap is set to 0.004 inch and is adjustable by turning
the threaded body parts in relation to each other. These two parts
could be designed in such a way that this gap was closed up at
higher temperatures that would correspond to higher engine loads
and higher turbine boost pressure. If one part was made from
stainless steel and one from carbon steel, the stainless part would
grow in length 1.5 times that of the steel part thereby changing
the gap distance.
[0014] In a natural gas fueled engine using a heating loop, if
natural gas fuel is being injected into the heating loop to add
temperature, the natural gas injector could also be used to drive
an air amplifier. This would have the secondary benefit of also
helping to evenly mix the air and fuel if the air amplifier has a
continuous radial gap for an orifice like the Nex Flow PN
30003TS.
[0015] A natural gas-powered air amplifier would both improve
mixing and get the benefit of recycling the energy used to compress
the natural gas, it likely will still need an additional compressed
air powered air amplifier to both increase and control the amount
of exhaust gas flowing through the heating loop.
[0016] Now that there is an adequate and controlled amount of
exhaust gas flowing through the heating loop, a system needs to be
implemented to raise its temperature. This additional heat will
typically be provided by combusting injected fuel and excess oxygen
in the exhaust gases across an OC mounted inside the dosing loop
flow path. Compared to an open flame burner, combusting the fuel
across a catalyst will minimize the amount of criteria emissions
added to the total exhaust flow when this extra fuel combusted.
[0017] If or when the exhaust temperature entering the dosing loop
is not hot enough to ignite the injected fuel when it reaches the
dosing loop OC, an additional system will be needed to temporarily
provide extra heat to the exhaust gas flow until the OC is at a
high enough temperature to light off and insure continuous
catalytic combustion of the injected fuel. A simple way of doing
this is with an electric exhaust heater similar to a Watlow ECO
Heat unit. This electric heater could be used for both diesel
injection or natural gas injection. The electric heater is more
likely to be effective with diesel fuel injection because of diesel
fuels much lower light off temperature at the OC.
[0018] Instead of an electric heater when using natural gas, a
conventional burner with a flame holder and ignition system could
be used to drive the OC temperature up to that needed for light off
and continuous catalytic combustion. The supply pressure of natural
gas to the natural gas injector could be manipulated to control the
heat rate of both the preheater and the catalytic combustion
system. The flame holder system should only need an ignition source
to start combustions. One method to switch from combustion at the
flame holder to combustion at the catalyst system is to temporarily
turn off the natural gas supply to the heating loop and keep it off
long enough to extinguish the flame at the flame holder but then
turn the natural gas fuel back on soon enough that the OC is still
hot enough to light off and maintain continuous catalytic
combustion.
[0019] Various embodiments of the above described system will be
effective for engines that only need an OC. For systems that will
use an SCR the system is the same up to the OC that combusts the
added fuel for heating up the exhaust gases. After the OC is where
the UREA would be injected and then there would need to be a length
of straight and well insulated ducting to give the UREA time to mix
with the hot exhaust gases and start decomposing into ammonia
before the mixture of ammonia and exhaust gas from the heating loop
mixes with the bulk of the exhaust gases in the main exhaust system
on its way to the SCR unit.
[0020] For an aftertreatment system that only has an OC, the
heating loop system should not need to increase flow capacity at
higher loads as the main engine exhaust temperature should become
high enough to keep the after treatment operating, in this case the
air amplifiers and fuel injection for the heating loop can be
turned off.
[0021] On the other hand, for an SCR system, the systems exhaust
gas mass flow and heating capacity will need to increase as the
required amount of UREA increases. This makes the turbocharged
engine slightly easier for an SCR application as the exhaust back
pressure being used to drive an air amplifier requires less energy
than suppling compressed air from an engine driven compressor to
drive the increasing amounts of exhaust gas through the heating
loop.
[0022] Exhaust gas heating can also be used in the main exhaust
system. As high efficiency engines are able to operate at lower and
lower exhaust temperatures, two problems are becoming apparent.
First the exhaust temperatures are getting so low that at moderate
loads it is not high enough to oxidize any of the methane that
isn't burned in the main chamber. Also these lower temperatures
make it a challenge to drive the turbo charger. Putting an OC
upstream of the turbocharger has been investigated in prior art but
at the time found not practical. What would be an improvement over
a heating loop as proposed above could be a pre-turbine and after
treatment system. The preferred embodiment would be a natural gas
engine with a pre turbine after treatment system that has both OC
substrates and SCR substrates. This could have a heating system in
front of the first OC substrate, then a UREA injection system, then
a second heater, then a final OC before the exhaust gases reach the
turbocharger. In this case the extra fuel needed to increase the
exhaust temperature enough to burn off the methane and the oxidized
methane that originally left the engine cylinder without being
burned would now provide energy to the turbo charger turbine. The
reason that a heater after the SCR is needed is that the light off
temperature for methane in the final OC is higher than the
temperature that the SCR should be operating at.
[0023] To add further benefit to this system, the turbocharger
could be electrified. This will greatly accelerate engine response
and increase engine efficiency by eliminating the need for a waste
gate and capturing as much energy as possible with the exhaust
turbine. For more efficiency a second electrically driven
compressor can be used in series with the turbocharger.
[0024] For gaseous fuels the heaters in this system could use a
burner at first until the OC substrates reach light off temperature
and then turn off the gas supply momentarily to extinguish the
burner flame so that the combustion then starts up again and
continues in the OC downstream of that burner.
DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is a side view of a turbocharged engine with an
aftertreatment system including a heating loop.
[0026] FIG. 2 is a side view of a normally aspirated engine with an
aftertreatment system including a heating loop.
[0027] FIG. 3 is a preferred embodiment for a turbocharged diesel
engine with an SCR aftertreatment system.
[0028] FIG. 4 is a block diagram of a control system with its
sensors and valves.
DETAILED DESCRIPTION
[0029] To facilitate an understanding of the present disclosure, a
number of terms and phrases are defined below:
[0030] Blended Aftertreatment System (BATS): As described in U.S.
Pat. No. 9,752,481, incorporated herein by reference, a BATS system
reduces the NOx emissions from the mixed exhaust of two engines in
a single larger SCR assembly using only one UREA injection point
into the exhaust of the smaller engine.
[0031] Gaseous Fuel: The predominant gaseous fuel used in internal
combustion engines is natural gas consisting mostly of methane, but
with minor modifications these engines could consume any gaseous
fuel including but not limited to propane, natural gas and
hydrogen. In this document the term natural gas and gaseous fuel
are used interchangeably.
[0032] Hydrocarbon (HC): Emissions resulting from incomplete
combustion of fuel and engine lube oil.
[0033] Main Charge: The air fuel mixture in the main combustion
chamber space between the piston top and the cylinder head. If an
opposed piston engine, this would be the space between the opposed
piston faces.
[0034] Particulate Matter (PM): Particulate matter is a criteria
pollution emitted from many sources. In this document we will
commonly refer to it simply as PM. It could include both diesel
soot PM that is considered toxic in California or the type of PM
created by the consumption and combustion of lube oil from an
engine. While still considered PM as a criteria emission, the PM
from lube oil consumption is considered less toxic than diesel
soot.
[0035] Reductant: In active NOx reductions systems like a Selective
Catalytic Reduction (SCR) system, a reductant is mixed with the hot
exhaust gases and is chemically processed by the catalyst system
along with the exhaust gasses to reduce NOx emissions to N2 and
water. Diesel Exhaust Fluid (DEF) is currently the most common
reductant for SCR systems in mobile applications. DEF is actually a
mixture of 32.5% UREA and 67.5% water. Once injected into the
engine the DEF is first vaporized, and then the UREA crystals are
decomposed into ammonia and CO2 molecules. It is the ammonia
particles that the SCR catalyst uses to reduce NOx into N2 and
water. SCR systems can be used on heat engines burning any kind of
fuel so the DEF term can be misleading, in Germany DEF falls under
the trademark AdBlue. DEF is also frequently called UREA for short.
In some instances ammonia gas is extracted from some other system
and injected directly into the exhaust flow as a gas before the
exhaust and ammonia mixture reaches the SCR catalysts. Throughout
this document the reductant injected into any aftertreatment device
that actively reduces NOx will typically be referred to as UREA. In
addition the term SCR will be used to identify any active NOx
reduction system that uses a reductant.
[0036] FIG. 1 is a side view of a turbocharged medium speed engine
with a heating loop. Exhaust Manifold 3 is on top of engine 1 and
routes pressurized exhaust gases into turbocharger 2. Main exhaust
duct 4 routes the exhaust gases from turbocharger 2 into
aftertreatement 5. After the exhaust gases are treated in
aftertreatment 5 they exit the engine system through main exhaust
outlet 20. Aftertreatment 5 may contain OC substrates, SCR
substrates or a combination of both. If an aftertreatment 5 system
contains both types of substrates it is controlled in the same
manner as a system with only SCR substrates.
[0037] Heating loop inlet 6 extracts a portion of exhaust gases
from main exhaust duct 4 and directs it through heater loop 7. Once
the portion of exhaust gases have been processed through all the
devices along heater loop piping 7 they are then injected back into
the main exhaust duct 4 through heater loop exit 8. Air amplifier
EP 10 will be fed pressurized exhaust gas sourced from exhaust
manifold 3 to assist drawing more exhaust gas into heater loop
piping 7. Air Amplifier CA 11 is driven by compressed air from an
external source somewhere in the vehicle. This could be supplied by
an engine driven air compressor that supplies air to the air brake
system. If the vehicle doesn't already have an air compressor is
could be supplied by the compressor in turbo 3, although this would
be less efficient as turbo 3 boost pressure is likely 1/4 that of
the air brake system and will require 4 times as much air mass to
be as effective and all of this air will need to be heated by
adding more heat energy into the heating loop 7. Electric preheater
12 is used to increase the temperature of the portion of exhaust
gases to a point that the OC 15 will light off and burn the fuel
and lean exhaust gas mixture. Electric preheater 12 would typically
only be used with a fuel other than methane that has a lower
ignition temperature, diesel fuel would be the most appropriate
fuel for use with electric preheater 12. Fuel injector 13 is used
to inject fuel into the heating loop 7. This is most likely the
same fuel used to power engine 1, it could be a liquid hydrocarbon
fuel such as diesel or any gaseous fuel. In the case of pressurized
gaseous fuels, fuel injector 13 may also act as an air amplifier
that is powered by the pressurized gaseous fuel. Fuel burner 14 is
used typically for gaseous fuels like methane that have very high
ignition temperatures that are not reasonable for use of an
electric preheater 12. Fuel burner 14 will likely incorporate a
flame holder and ignition system to start combustion. OC 15 is
where flameless combustion will occur once the heating loop 7 is at
operating temperature. Temperature sensor 16 is the parameter that
a control system will monitor to determine the system status and
determine when to inject fuel, how much fuel to inject and when to
transition from fuel burner 14 to OC 15 to catalytically burn the
injected fuel at the highest efficiency at lowest emissions.
Gaseous fuel can be injected at any time, but diesel fuel should
only be injected after the portion of exhaust gas flow has been
preheated by electric preheater 12 to a threshold temperature that
will cause light off of OC 15. After light off, the temperature
sensor 16 will monitor the exit temperature of OC 15 and that
temperature will be used to determine if more or less fuel should
be injected by fuel injector 13 to achieve the target temperature
in the heating loop 7.
[0038] For an aftertreatment 5 unit that only has an OC substrate,
the temperature sensor 16 will be the last device that heating loop
7 is equipped with and the now heated portion of exhaust gases
would be then injected through heating loop exit 8 back into the
main exhaust duct 4.
[0039] For an aftertreatment 5 unit that does have an SCR
substrate, additional components will be added to heating loop 7.
UREA injector 17 is used to inject UREA into heating loop 7.
Temperature sensor 19 will be used to measure the temperature of
the portion of exhaust gas that was first heated and then cooled by
injecting UREA into it. With an SCR function temperature sensor 19
becomes the parameter that is used to determine fuel flow through
fuel injector 13 to maintain a target temperature at the exit of
heating loop 7. In some embodiments, if a temperature sensor 19 is
installed, the temperature sensor 16 after OC 15 can be
eliminated.
[0040] Recent research has indicated that decomposition of UREA is
assisted by being passed through a catalyst at high temperature. In
a conventional SCR system, when the air and UREA mixture gets to
the SCR substrates, the UREA is typically only 50% of the way
through the decomposition process and the remaining decomposition
to ammonia occurs as the exhaust gas and decomposing UREA move
along the flow length of the substrate. This lowers the overall
effectiveness of the substrate. If all of the UREA had been
decomposed to ammonia before the exhaust gases started passing
through the SCR substrate, it would have a higher NOx reduction
efficiency and would be able to operate at lower temperatures. OC
18 is used to increase the amount of decomposition of the mixture
of UREA and heated exhaust gases before they exit the heating loop
7 on their way to the SCR substrates inside of aftertreatment
5.
[0041] FIG. 2 is a side view of a normally aspirated medium speed
engine with a heating loop. FIG. 2 has all the same components and
functionality as FIG. 1 except that turbo main exhaust duct 4'
connects exhaust manifold 3 directly to aftertreatment 5 and turbo
3 and the exhaust pressure driven air amplifier EP 10 have been
deleted. Because air amplifier EP 10 has been deleted, the
compressed air driven air amplifier CA 11 may have to provide more
motive force to induce enough exhaust gas flow through heating loop
7
[0042] FIG. 3 is the preferred embodiment of a medium speed
turbocharged diesel engine with and SCR aftertreatment system and
simplified heating loop. Exhaust Manifold 3 is on top of engine 1
and routes pressurized exhaust gases into turbocharger 2. Main
exhaust duct 4 routes the exhaust gases from turbocharger 2 into
aftertreatement 5. After the exhaust gases are treated in
aftertreatment 5 they exit the engine system through main exhaust
outlet 20.
[0043] Heating loop inlet 6 extracts a portion of exhaust gases
from main exhaust duct 4 and directs it through heater loop 7. Once
the portion of exhaust gases have been processed through all the
devices along heater loop piping 7 they are then injected back into
the main exhaust duct 4 through heater loop exit 8. Air amplifier
EP 10 will be fed pressurized exhaust gas sourced from exhaust
manifold 3 to assist drawing more exhaust gas into heater loop
piping 7. Electric preheater 12 is used to increase the temperature
of the portion of exhaust gases to a point that the OC 15 will
light off and burn the diesel fuel and lean exhaust gas mixture.
Fuel injector 13 is used to inject diesel fuel into the heating
loop 7. OC 15 is where flameless combustion will occur once the
heating loop 7 is at operating temperature. Temperature sensor 19
is the parameter that a control system will monitor to determine
the system status and determine when to inject fuel and how much
fuel to inject. Diesel fuel should only be injected after the
portion of exhaust gas flow has been preheated by electric
preheater 12 to a threshold temperature that will cause light off
of OC 15. After light off temperature sensor 19 will monitor the
exit temperature of OC 15 and that temperature will be used to
determine if more or less fuel should be injected by fuel injector
13 to achieve the target temperature in the heating loop 7. Once OC
15 is at temperature and catalytically combusting the injected
fuel, electric preheater 12 can be turned down or off.
[0044] After temperature sensor 19 has determined that the heating
loop 7 temperature is hot enough, UREA injector 17 is used to
inject UREA into heating loop 7. As more UREA is injected through
injector 17, temperature sensor 19 will detect a dropping
temperature in heating loop 7 and the control system will command
more fuel be injected through injector 13 to bring the heating loop
exhaust gas exit temperature back up to its target temperature.
[0045] FIG. 4 is a bock diagram of a simplified control system for
a heating loop 7. Controller unit 30 is electrically connected to
various sensors and control valves. Temp sensor 31 will read the
exhaust exit temperature from heating loop 7 and depending on its
control mode with control the amount of fuel flowing through
injector 3. This fuel flow can be controlled by valve 32 which
could be an on or off solenoid valve that is modulated to control
the flow rate of fuel to injector 13 or this control valve 32 could
be an integral part of injector 13. Control solenoide 33 will
control the flow of electricity to electric preheater 12 if the
system is so equipped. This electric current flow could be
controlled by several different electrical devices ranging from a
simple switch to a PWM controlled transistor module.
[0046] Control valve 34 regulates the supply of compressed air to
an air amplifier CA 11 if the system is so equipped. It may be a
simple on off valve with one setting, it can also be PWM controlled
to linearly regulate flow.
[0047] Control valve 35 will control UREA flow to UREA injector 17.
This could be a solenoid valve that modulates flow or a pumping
system of some sort that provides a metered amount of UREA.
[0048] Controller 30 may have its own table of engine operating
parameters, but it most likely will be in communication with a
master controller that will send it engine load information and
updated operating parameters such as heating loop 7 target exhaust
temperature. Any of these control valves or solenoids could be
physically integrated into control 30 without changing its
functionality. Controller unit 30 itself could be integrated into
another controller that controls other devices and even the entire
engine system or vehicle.
[0049] It should be noted that various changes and modifications to
the presently preferred embodiments described herein will be
apparent to those skilled in the art. Such changes and
modifications may be made without departing from the spirit and
scope of the present invention and without diminishing its
attendant advantages.
* * * * *