U.S. patent application number 16/083326 was filed with the patent office on 2019-04-04 for a control system and a method for controlling the exhaust gas flow in an exhaust line of a combustion engine.
This patent application is currently assigned to SCANIA CV AB. The applicant listed for this patent is SCANIA CV AB. Invention is credited to Torbjorn ELLIASSEN, Johan LINDERYD, Thomas TIMREN, Matthias USSNER.
Application Number | 20190101038 16/083326 |
Document ID | / |
Family ID | 59852037 |
Filed Date | 2019-04-04 |
United States Patent
Application |
20190101038 |
Kind Code |
A1 |
LINDERYD; Johan ; et
al. |
April 4, 2019 |
A CONTROL SYSTEM AND A METHOD FOR CONTROLLING THE EXHAUST GAS FLOW
IN AN EXHAUST LINE OF A COMBUSTION ENGINE
Abstract
The present invention relates a control system and a method for
controlling exhaust flow in an exhaust line of a combustion engine
comprising at least one exhaust treatment component and an
evaporator of a waste heat recovery system. The control system
comprises a valve arrangement in the exhaust line control unit, a
temperature sensor to sense a temperature of the exhaust treatment
component and a control unit configured to position the valve
arrangement in a first position, when the exhaust treatment
component has a lower temperature than a specific temperature of
exhaust gases directed flow through to the exhaust treatment
component before being directed to flow through the evaporator, and
in a second position, when the exhaust treatment component has a
higher temperature than said specific temperature of exhaust gases
that are directed to flow through the evaporator before being
directed to flow through the exhaust treatment component.
Inventors: |
LINDERYD; Johan; (Ronninge,
SE) ; USSNER; Matthias; (Sodertalje, SE) ;
ELLIASSEN; Torbjorn; (Nykvarn, SE) ; TIMREN;
Thomas; (Trosa, SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SCANIA CV AB |
Sodertalje |
|
SE |
|
|
Assignee: |
SCANIA CV AB
Sodertalje
SE
|
Family ID: |
59852037 |
Appl. No.: |
16/083326 |
Filed: |
March 15, 2017 |
PCT Filed: |
March 15, 2017 |
PCT NO: |
PCT/SE2017/050249 |
371 Date: |
September 7, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y02T 10/12 20130101;
F01N 5/02 20130101; Y02A 50/20 20180101; F01N 3/28 20130101; Y02T
10/20 20130101; Y02A 50/2325 20180101; F01N 3/0205 20130101; Y02T
10/16 20130101; F01N 3/2006 20130101; F01N 2240/02 20130101; F01N
3/2093 20130101 |
International
Class: |
F01N 5/02 20060101
F01N005/02; F01N 3/02 20060101 F01N003/02; F01N 3/20 20060101
F01N003/20 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 15, 2016 |
SE |
1650345-0 |
Claims
1. A control system for controlling exhaust flow in an exhaust line
of a combustion engine, wherein the exhaust line comprises at least
one exhaust treatment component and an evaporator of a waste heat
recovery system, and wherein the control system comprises: a valve
arrangement in the exhaust line; a temperature sensor configured to
sense a temperature related to a temperature of the exhaust
treatment component; and a control unit configured to position the
valve arrangement in a first position, when the exhaust treatment
component has a lower temperature than a specific temperature of
exhaust gases that are directed to flow through the exhaust
treatment component before being directed to flow through the
evaporator, and to position the valve arrangement in a second
position, when the exhaust treatment component has a higher
temperature than a specific temperature of the exhaust gases that
are directed to flow through the evaporator before being directed
to flow through the exhaust treatment component, wherein the valve
arrangement comprises a valve member or a valve part configured to
change flow direction of a working medium in the evaporator, such
that the working medium and the exhaust gases always flow in
opposite directions through the evaporator.
2. A control system according to claim 1, wherein the valve
arrangement comprises a valve member configured to alternatively
direct the exhaust gases from an upstream exhaust line section to
either the exhaust treatment component or to the evaporator.
3. A control system according to claim 1, wherein the exhaust line
comprises: at least one intermediate exhaust line configured to
direct exhaust gases between the exhaust treatment component and
the evaporator; and a valve member configured to control exhaust
gas flow through the intermediate exhaust line.
4. A control system according to claim 1, wherein the valve
arrangement comprises a valve member configured to alternatively
direct exhaust gases from either the exhaust treatment component or
the evaporator to a downstream exhaust line section.
5. A control system according to claim 1, wherein the valve
arrangement comprises a valve member which, in said first position,
is configured to direct exhaust gases from an upstream exhaust line
section to the exhaust treatment component and exhaust gases from
the evaporator to a downstream exhaust line section.
6. A control system according to claim 5, wherein said valve member
is, in said second position, configured to direct exhaust gases
from the upstream exhaust line section to the evaporator and
exhaust gases from the exhaust treatment component to the
downstream exhaust line section.
7. A control system according to claim 1, wherein the valve
arrangement comprises a valve member which, in said first position,
is configured to direct exhaust gases from an upstream exhaust line
section to the exhaust treatment component and exhaust gases from
the exhaust treatment component to the evaporator.
8. A control system according to claim 7, wherein said valve member
is, in said second position, configured to direct exhaust gases
from the evaporator to the exhaust treatment component and exhaust
gases from the exhaust treatment component to a downstream exhaust
line section.
9. A control system according to claim 1, further comprising a
temperature sensor configured to sense the temperature of the
exhaust gases in an upstream exhaust line section.
10. A control system according to claim 1, further comprising a
sensor configured to sense a pressure or a the temperature of the
working medium in the waste heat recovery system.
11. A control system according to claim 1, wherein the exhaust
treatment component is a selective catalytic reduction
catalyst.
12. A vehicle comprising a control system for controlling exhaust
flow in an exhaust line of a combustion engine, wherein the exhaust
line comprises at least one exhaust treatment component and an
evaporator of a waste heat recovery system, and wherein the control
system comprises: a valve arrangement in the exhaust line; a
temperature sensor configured to sense a temperature related to a
temperature of the exhaust treatment component; and a control unit
configured to position the valve arrangement in a first position,
when the exhaust treatment component has a lower temperature than a
specific temperature of exhaust gases that are directed to flow
through the exhaust treatment component before being directed to
flow through the evaporator, and to position the valve arrangement
in a second position, when the exhaust treatment component has a
higher temperature than a specific temperature of the exhaust gases
that are directed to flow through the evaporator before being
directed to flow through the exhaust treatment component, wherein
the valve arrangement comprises a valve member or a valve part
configured to change flow direction of a working medium in the
evaporator, such that the working medium and the exhaust gases
always flow in opposite directions through the evaporator.
13. A method for controlling the exhaust flow in an exhaust line of
a combustion engine in a vehicle, wherein the exhaust line
comprises at least one exhaust treatment component and an
evaporator of a waste heat recovery, a valve arrangement, wherein
said method comprises: directing exhaust gases in the exhaust line
to flow through the exhaust treatment component before being
directed to flow through the evaporator, when the exhaust treatment
component has a lower temperature than a specific temperature;
directing the exhaust gases to flow through the evaporator before
being directed to flow through the exhaust treatment component,
when the exhaust treatment component has a higher temperature than
said specific temperature; and changing flow direction of a the
working medium in the evaporator, such that the working medium and
the exhaust gases always flow in opposite directions through the
evaporator.
14. A vehicle according to claim 12, wherein the valve arrangement
comprises a valve member configured to alternatively direct the
exhaust gases from an upstream exhaust line section to either the
exhaust treatment component or to the evaporator.
15. A vehicle according to claim 12, wherein the exhaust line
comprises: at least one intermediate exhaust line configured to
direct exhaust gases between the exhaust treatment component and
the evaporator; and a valve member configured to control exhaust
gas flow through the intermediate exhaust line.
16. A vehicle according to claim 12, wherein the valve arrangement
comprises a valve member configured to alternatively direct exhaust
gases from either the exhaust treatment component or the evaporator
to a downstream exhaust line section.
17. A method according to claim 13 further comprising alternatively
directing the exhaust gases from an upstream exhaust line section
to either the exhaust treatment component or to the evaporator.
18. A method according to claim 13 further comprising alternatively
directing exhaust gases from either the exhaust treatment component
or the evaporator to a downstream exhaust line section.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application is a national stage application (filed
under 35 .sctn. U.S.C. 371) of PCT/SE2017/050249, filed Mar. 15,
2017 of the same title, which, in turn claims priority to Swedish
Application No. 1650345-0, filed Mar. 15, 2016 of the same title;
the contents of each of which are hereby incorporated by
reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a control system and a
method for controlling the exhaust gas flow in an exhaust line of a
combustion engine.
BACKGROUND OF THE INVENTION
[0003] Exhaust lines of internal combustion engines such as diesel
engines may comprise a plurality of exhaust treatment components
such as, for example, a SCR catalyst (Selective Catalytic
Reduction). In order to clean the exhaust gases from nitrogen
oxides, a urea solution is sprayed into the exhaust line in a
position upstream of the SCR catalyst. The urea solution is
vaporized by the hot exhaust gases so that ammonia is formed. The
ammonia and nitrogen oxides in the exhaust gases react with each
other in the SCR catalyst so that nitrogen gas and water vapor are
formed. The efficiency of a SCR catalyst depends on its
temperature. The ability of the SCR catalyst to reduce nitrogen
oxides is optimal within a temperature range which may be about
300-450.degree. C. At lower and higher exhaust gas temperatures the
capacity of the SCR catalyst to reduce nitrogen oxides is
reduced.
[0004] WHR system (Waste Heat Recovery System) can be used for
recovering waste thermal energy and convert it to mechanical energy
or electric energy. A WHR system includes a pump which pressurizes
and circulates a working medium in a closed circuit. The circuit
comprises an evaporator where the working medium is heated and
evaporated by a heat source such as, for example, exhaust gases.
The pressurized and heated gaseous working medium expands in an
expander. The expander generates mechanical energy which can be
used to support the engine and/or apparatuses in a vehicle.
Alternatively, the expander is connected to a generator generating
electric energy. The working medium leaving the expander is
directed to a condenser. The working medium is cooled down in the
condenser to a temperature at which it condenses. The fuel
consumption of a combustion engine can be reduced by means of a
WHR-system.
[0005] The exhaust gases are cooled down in an evaporator of a WHR
system. In view of this fact, the evaporator is arranged in a
downstream position of the exhaust treatment components. In this
position, the existence of the evaporator does not influence on the
operation of the exhaust treatment components. However, in case
when the combustion engine is high loaded during a longer period of
time, there is a risk that the exhaust gases heat the exhaust
treatment components to a too high temperature. In this cases, the
exhaust treatment components do not provide an optimal treatment of
the exhaust gases and might be permanently damaged.
SUMMARY OF THE INVENTION
[0006] The object of the present invention is to control the
exhaust gas flow in an exhaust line comprising at least one exhaust
treatment component and an evaporator of a WHR system in a manner
such that the exhaust treatment component provides a substantially
optimal treatment of the exhaust gases also during operating
conditions when the exhaust gases have a high temperature.
[0007] The above mentioned object is achieved by the control system
according to the claims. During operating conditions when an
exhaust treatment component has a lower temperature than a specific
temperature, the control unit initiates a movement of a valve
arrangement to a first position in which it directs the exhaust
gases to the exhaust treatment component before the exhaust gas
flow is directed to the evaporator. The specific temperature may be
an upper temperature of a temperature range at which the exhaust
treatment component provides a substantially optimal treatment of
the exhaust gases. The specific temperature may be a constant
temperature or a temperature varying with other operating
parameters. When the valve arrangement is in the first position,
the relatively hot exhaust gases may increase or maintain the
temperature the exhaust treatment component before they are cooled
down in the evaporator. During operating conditions when the
exhaust treatment component has a higher temperature than the
specific temperature, the control unit initiates a movement of the
valve arrangement to a second position in which the exhaust gases
are directed to the evaporator before they are directed to the
exhaust treatment component. In this case, the exhaust gases are
cooled down in the evaporator before they enter the exhaust
treatment component. In this case, the exhaust gases entering the
exhaust treatment component mostly have a lower temperature than
the exhaust treatment component. As a consequence, the exhaust
gases cool down the exhaust treatment component. As soon as the
exhaust treatment component has been cooled to a temperature below
the specific temperature, the control systems initiates a movement
of the valve arrangement back to the first position. The control
system makes it possible to avoid heating of the exhaust treatment
component to a too high temperature. As a consequence, it is
possible to maintain a substantially optimal treatment of the
exhaust gases even when the exhaust gases have a very high
temperature. Furthermore, the exhaust gases may receive a lower
temperature when they have passed through the exhaust treatment
component. As a consequence, the working medium in the evaporator
may be heated to a higher temperature when the valve arrangement is
in the second position which increases the efficiency of the WHR
system.
[0008] According to an embodiment of the invention, the valve
arrangement comprises a valve member which alternatively directs
exhaust gases from an upstream exhaust line section to the exhaust
treatment component or to the evaporator. By means of such a valve
member, it is easy to alternatively direct the exhaust gas flow
initially to the exhaust treatment component or the evaporator. The
exhaust line may comprise at least one intermediate exhaust line
directing exhaust gases between the exhaust treatment component and
the evaporator and a valve member configured to control the exhaust
gas flow through the intermediate exhaust line. When the valve
arrangement is in the first position, such an intermediate exhaust
line directs the exhaust gases from the exhaust treatment component
to the evaporator. When the valve arrangement is in the second
position, such an intermediate exhaust line directs the exhaust
gases from the evaporator to the exhaust treatment component. The
exhaust gas flow through the intermediate exhaust line may be
controlled by a valve member. Furthermore, the valve arrangement
may comprise a valve member which alternatively directs the exhaust
gases from the exhaust treatment component or the evaporator to a
downstream exhaust line section. By means of such a valve member,
it is easy to alternatively direct the exhaust gas flow from the
exhaust treatment component or the evaporator to a downstream
located part of the exhaust line. The valve member may be of
arbitrary kind. The valve member may, for example, be a butterfly
valve.
[0009] According to an embodiment of the invention, the valve
arrangement comprises a valve member which, in said first position,
is configured to direct exhaust gases from an upstream exhaust line
section to the exhaust treatment component and from the evaporator
to a downstream exhaust line section. Such a valve member may, in
said second position, be configured to direct exhaust gases from
the upstream exhaust line section to the evaporator and from the
exhaust treatment component to the downstream exhaust line section.
Such a valve member has several tasks. Thus, a valve arrangement
including such a valve member may include few further valve
members.
[0010] According to an embodiment of the invention, the valve
arrangement may comprise a valve member which, in said first
position, is configured to direct exhaust gases from an upstream
exhaust line section to the exhaust treatment component and from
the exhaust treatment component to the evaporator. Such a valve
member may, in said second position, be configured to direct
exhaust gases from the evaporator to the exhaust treatment
component and from the exhaust treatment component to a downstream
exhaust line section. Such a valve member also has several tasks.
As a consequence, a valve arrangement including this valves member
may include few further valve members.
[0011] According to an embodiment of the invention, the control
system comprises a temperature sensor configured to sense the
temperature of the exhaust gases in an upstream exhaust line
section. In this case, the control unit receives information about
the temperature of the exhaust gases which are led towards the
exhaust treatment component and the evaporator. In view of this
information, it is possible to adjust said specific temperature.
Alternatively or in combination, the control system may comprise a
sensor configured to sense the pressure or the temperature of the
working medium in the WHR system. In order to provide an efficient
operation of the WHR system, it is, for example, important to
control the cooling of the working medium in a condenser of the WHR
system. The cooling demand of the working medium is related to the
absorption of heat in the evaporator.
[0012] According to an embodiment of the invention, the exhaust
treatment component is a SCR catalyst. The ability of a SCR
catalyst to reduce nitrogen oxides decreases above a temperature of
about 450.degree. C. Thus, it is suitable to use the control system
for controlling the temperature of a SCR catalyst. Alternatively or
in combination, the exhaust treatment component may include an
oxidation catalytic converter DOC, a particulate filter DPF, or an
ammonia slip catalytic converter ASC.
[0013] According to an embodiment of the invention, the valve
arrangement comprises a valve member or valve part configured to
change flow direction of the working medium in the evaporator. In
certain cases, the exhaust gas flow may be directed through the
evaporator in an opposite directions when the valve arrangement is
in the first position or in the second position. In this case, it
is also favorable to change the direction of the working medium
flow through the evaporator in order to favor the heat transfer in
the evaporator. This valve member may be a part of a valve member
controlling the exhaust gas flow.
[0014] The above mentioned object is also achieved by the claimed
method.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] In the following preferred embodiments of the invention are
described, as examples, with reference to the attached drawings, in
which:
[0016] FIG. 1 shows a control system with a valve arrangement
according to a first embodiment of the invention where the valve
arrangement is in a first position,
[0017] FIG. 2 shows the valve arrangement in FIG. 1 in a second
position.
[0018] FIG. 3 shows an alternative embodiment of the valve
arrangement in a first position,
[0019] FIG. 4 shows the valve arrangement in FIG. 3 in a second
position,
[0020] FIG. 5 shows a further alternative embodiment of the valve
arrangement in a first position, and
[0021] FIG. 6 shows the valve arrangement in FIG. 5 in a second
position.
DETAILED DESCRIPTION OF THE INVENTION
[0022] FIG. 1 shows a schematically disclosed vehicle 1 powered by
a supercharged combustion engine 2. The combustion engine 2 may be
a diesel engine. The vehicle 1 may be a heavy vehicle. The vehicle
1 comprises an exhaust line 3 receiving exhaust gases from the
combustion engine 2. The exhaust line 3 comprises a turbine 4 of a
turbo aggregate. The exhaust gases in the exhaust line 3 receive a
reduced pressure and a reduced temperature when they expand through
the turbine 4a of a turbo charger 4. A number of schematically
disclosed exhaust treatment components 5 are arranged in the
exhaust line 3 in a position downstream of the turbine 4a. The
exhaust treatment components 5 may, for example, include one or
several of the following exhaust treatment components namely an
oxidation catalytic converter DOC, a particulate filter DPF, a SCR
catalytic converter and an ammonia slip catalytic converter ASC.
The efficiency of each exhaust treatment component 5 depends on its
temperature. An efficient operating temperature of such exhaust
treatment components are usually above 200.degree. C. The ability
of the SCR catalyst 6 to reduce nitrogen oxides may be optimal
within the temperature range 300-450.degree. C. At higher and lower
temperatures the capacity of the SCR catalyst to reduce nitrogen
oxides is reduced.
[0023] A temperature sensor 6 senses the temperature of the exhaust
gases in an exhaust line section 3a located upstream of the exhaust
treatment components 5 and an evaporator 7 of a WHR system. The
upstream exhaust line section 3a comprises a first valve member 8
and a second valve 9. A control unit 10 controls the first valve
member 8 and a second valve 9. A temperature sensor 11 senses the
temperature of the at least one of the exhaust treatment components
5. The exhaust line 3 has an intermediate exhaust line 3b arranged
between the exhaust treatment component 5 and the evaporator 7. An
exhaust line section 3c is located downstream of the exhaust
treatment component 5 and the evaporator 7. The turbine 4a drives a
compressor 4b of the turbo charger 4. The compressor 4b compresses
air which is led, via a charged air line 12 to the combustion
engine 2. The charged air line 12 comprises a charge air cooler 13
arranged at a front portion of the vehicle 1.
[0024] The combustion engine 2 is cooled by a cooling system with a
circulating coolant. The cooling system comprises an engine inlet
line 14 provided with a coolant pump 15 circulating the coolant in
the cooling system. An engine outlet line 16 receives the coolant
leaving the combustion engine 2. A thermostat 17 is arranged at an
end of the engine outlet line 16. In case the coolant has a lower
temperature than the regulating temperature of the thermostat 17,
the coolant is directed back to the coolant pump 15 via a bypass
line 18. In case the coolant has a higher temperature than the
regulating temperature of the thermostat 17, the coolant is
directed to a radiator 19 arranged at a front portion of the
vehicle 1 in a position behind the charge air cooler 13. The
radiator fan 20 and ram air provide a cooling air flow through the
charge air cooler 13 and the radiator 19. The coolant that has
circulated through the radiator 19, it is directed, via a radiator
outlet line 21, back to the engine inlet line 14 and the coolant
pump 15. The cooling system comprises a loop. The loop comprises a
coolant inlet line 22 receiving coolant from the bypass line 18 or
the radiator outlet line 21 depending on the position of the
thermostat 17. The inlet line 22 leads coolant to a condenser 23.
The loop comprises an outlet line 24 leading the coolant from the
condenser 23 to the engine inlet line 14 and the coolant pump
15.
[0025] The vehicle is provided with a WHR-system (Waste Heat
Recovery system). The WHR system comprises a pump 25 which
pressurizes and circulates a working medium. The working medium may
be ethanol, R245fa or other kind of working medium. The pump 25
pressurizes and circulates the working medium, via an evaporator
inlet line 26, to the evaporator 7. The working medium is heated in
the evaporator 7 by exhaust gases to a temperature at which it
evaporates. The working medium is directed from the evaporator 7,
via an expander inlet line 27, to an expander 28. A third valve
member 37 is arranged in contact with the evaporator inlet line 26
and the evaporator outlet line 27. The third valve member 37 is
settable in a first position in which it directs the working medium
in one direction through the evaporator 7 and in a second position
in which it directs the working medium in an opposite direction
through the evaporator 7. The pressurized and heated working medium
expands in the expander 28. The expander 28 generates a rotary
motion which may be transmitted, via a suitable mechanical
transmission, to a shaft of the drive train of the vehicle 1.
Alternatively, the expander 28 may be connected to a generator
transforming mechanical energy into electrical energy. The
electrical energy may be stored in e.g. a battery. After the
working medium has passed through the expander 28, it is directed,
via an expander outlet line 29 to the condenser 23. The working
medium is cooled in the condenser 23 by the coolant in the loop 22,
24 of the cooling system. The working medium is directed from the
condenser 23, via a condenser outlet line 30, to a receiver 31.
Working medium sucks, via an inlet line 32 from the receiver 31, to
the pump 25.
[0026] During operation of the combustion engine 2, the control
unit 10 receives substantially continuously information from the
sensor 11 about the temperature of the exhaust treatment component
5. The control unit 6 may also receive information from the sensor
6 about the exhaust gas temperature in the upstream exhaust line
section 3a and information from the sensor 33 about the temperature
or the pressure of the working medium in the WHR system. The
control unit 10 verifies if the temperature of the exhaust
treatment component 5 is higher than a specific temperature. The
specific temperature may be an upper temperature of a temperature
range at which the exhaust treatment component 5 provides a
substantially optimal treatment of the exhaust gases. The specific
temperature may be a constant temperature or a temperature varying
with other operating parameters such as the temperature of the
exhaust gases in the upstream exhaust line section 3a or the
temperature/pressure of the working medium in the WHR system.
[0027] During operating conditions when the exhaust treatment
component 5 has a lower temperature than a predetermined operating
temperature, the control unit 10 initiate a movement of the first
valve member 8, the second valve member 9 and the third valve
member 37 to a first position which is shown in FIG. 1. In this
case, the first valve member 8 and the second valve member 9 direct
the exhaust gases from the upstream exhaust line section 3a to the
treatment component 5. In this case, the exhaust gases may heat the
treatment component 5. The exhaust gases leave the exhaust
treatment component 5 and enter the intermediate exhaust line 3b.
The second valve member 9 directs the exhaust gases from the
intermediate exhaust line 3b of the exhaust line 3 to the
evaporator 7. The exhaust gases heat the working medium in the
evaporator 7 which flows in an opposite direction through the
evaporator 7. The exhaust gases leaving the evaporator 7 are
directed to the downstream exhaust line section 3c by the first
valve member 8. Consequently, the first valve member 8 and the
second valve member 9 direct the exhaust gases to the exhaust
treatment component 5 before they are directed to the evaporator 7
when they are in the first position.
[0028] During operating conditions when the treatment component 5
have a higher temperature than the predetermined operating
temperature, the control unit 10 initiates a movement of the first
valve member 8 and the second valve member to a second position
which is seen in FIG. 2. In this case, the first valve member 8 and
the second valve member 9 direct the exhaust gases from the
upstream exhaust line section 3a to the evaporator 7. The exhaust
gases are cooled down in the evaporator 7 by the working medium
which also in this case flows in an opposite direction through the
evaporator 7. The exhaust gases leaving the evaporator 7 are
directed to the exhaust treatment component 5 by the second valve
member 9. In this case, the exhaust gases have a lower temperature
than the temperature of the exhaust treatment component 5.
Consequently, the exhaust gases cool the exhaust treatment
component 5. The exhaust gases leaving the exhaust treatment
component 5 are directed to the downstream exhaust line section 3c
by means of the second valve member 9 and the first valve member 8.
The first valve member 8 and the second valve member 9 direct the
exhaust gases to the evaporator 7 before they are directed to the
exhaust treatment component 5. In this case, it is possible to cool
the exhaust treatment component 5 to a lower temperature at which
they are able to provide a substantially optimal treatment of the
exhaust gases. Furthermore, the exhaust gases entering the
evaporator 7 may have a higher temperature which improves the
efficiency of the WHR system.
[0029] FIGS. 3 and 4 shows an alternative embodiment of the valve
arrangement. The embodiment corresponds to the embodiment show in
FIGS. 1 and 2 except the existence of an additional valve portion
9a of the second valve member 9. When the valve members 8, 9 are in
the first position in the embodiment in FIG. 1, the exhaust gases
flow and the working medium in the WHR system are directed in the
same direction through the evaporator 7. In this case, the
evaporator 7 works as a parallel flow heat exchanger. When the
valve members 8, 9 are in the second position in the embodiment in
FIG. 2, the exhaust gas flow and the working medium flow are
directed in opposite directions through the evaporator 7. The
evaporator 7 works as a counter flow heat exchanger. A counter flow
heat exchanger has usually a higher efficiency than a parallel heat
exchanger. In order to remedy the drawback with a parallel heat
exchanger, the second valve member 9 is provided with the above
mentioned valve portion 9a which makes it possible to change flow
direction of the working medium in the evaporator 7. FIG. 3 shows
the valve portion 9 in the first position in which it changes
direction of the working medium flow through the evaporator 7. FIG.
4 shows the valve portion 9 in the second position in which it does
not change the direction of the working medium flow through the
evaporator 7.
[0030] FIGS. 5 and 6 show a further embodiment of the valve
arrangement. In this case, a third valve member 34 is configured to
alternatively direct the exhaust gas flow from the upstream exhaust
line section 3a to the exhaust treatment component 5 or the
evaporator 7. A first intermediate exhaust line 3b.sub.1 is able to
direct exhaust gases from an outlet of the exhaust treatment
component 5 to an inlet line of the evaporator 7. A second
intermediate exhaust line 3b.sub.2 is able to direct exhaust gases
from an outlet line of the evaporator 7 to an inlet line of the
exhaust treatment component 5. A fourth valve member 35 is
configured to allow exhaust gas flow in one of the intermediate
exhaust lines 3b.sub.1, 3b.sub.2 at the same time as it blocks the
exhaust gas flow in the other intermediate exhaust line 3b.sub.1,
3b.sub.2. A fifth valve member 36 is configured to alternatively
direct exhaust gases from the exhaust treatment component 5 or the
evaporator 7 to the downstream exhaust line section 3c.
[0031] In case the exhaust treatment component 5 has a lower
temperature than the specific temperature, the control unit 10
initiates a movement of the valve members 34, 35, 36 to a first
position which is shown in FIG. 5. In this case, the third valve
member 34 directs the exhaust gas flow from the upstream exhaust
line section 3a to the exhaust treatment component 5. The exhaust
gas flow leaving the exhaust treatment component 5 is directed by
the fourth valve member 35 to the evaporator 7. The exhaust gas
flow leaving the evaporator 7 is directed by the fifth valve member
36 to the downstream exhaust line section 3c. In case the exhaust
treatment component 5 has a higher temperature than the specific
temperature, the control unit 10 initiate a movement of the valve
members 34, 35, 36 to a second position which is shown in FIG. 6.
In this case, the third valve member 34 directs the exhaust gas
flow from the upstream exhaust line section 3a to the evaporator 7.
The above mentioned design of the exhaust gas flow results in that
the exhaust gases always flows in the same direction trough the
evaporator 7. In this embodiment, it is not necessary change the
flow direction of the working medium through the evaporator 7 in
order to provide an exhaust flow and a working medium flow in
opposite directions through the evaporator 7. The exhaust gas flow
leaving the evaporator 7 is directed by the fourth valve member 35
to the exhaust treatment component 5. The exhaust gas flow leaving
the exhaust treatment component 5 is directed by the fifth valve
member 36 to the downstream exhaust line section 3c.
[0032] The invention is not restricted to the described embodiment
but may be varied freely within the scope of the claims.
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