U.S. patent application number 15/319767 was filed with the patent office on 2017-05-11 for system for a heat energy recovery.
This patent application is currently assigned to VOLVO TRUCK CORPORATION. The applicant listed for this patent is VOLVO TRUCK CORPORATION. Invention is credited to Arne ANDERSSON, Lennart ANDERSSON, Peter M RDBERG.
Application Number | 20170130612 15/319767 |
Document ID | / |
Family ID | 51177019 |
Filed Date | 2017-05-11 |
United States Patent
Application |
20170130612 |
Kind Code |
A1 |
ANDERSSON; Lennart ; et
al. |
May 11, 2017 |
SYSTEM FOR A HEAT ENERGY RECOVERY
Abstract
A system is provided for heat energy recovery in a vehicle
including an internal combustion engine, such as a diesel engine,
and a corresponding method is provided for operating such a
system.
Inventors: |
ANDERSSON; Lennart;
(Varberg, SE) ; ANDERSSON; Arne; (Molnlycke,
SE) ; M RDBERG; Peter; (Vastra Frolunda, SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
VOLVO TRUCK CORPORATION |
S-405 08 Goteborg |
|
SE |
|
|
Assignee: |
VOLVO TRUCK CORPORATION
S-405 08 Goteborg
SE
|
Family ID: |
51177019 |
Appl. No.: |
15/319767 |
Filed: |
June 26, 2014 |
PCT Filed: |
June 26, 2014 |
PCT NO: |
PCT/EP2014/001749 |
371 Date: |
December 17, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01N 3/2066 20130101;
F01K 23/101 20130101; F01K 25/06 20130101; F01K 23/065
20130101 |
International
Class: |
F01K 23/06 20060101
F01K023/06; F01N 3/20 20060101 F01N003/20; F01K 23/10 20060101
F01K023/10 |
Claims
1. An exhaust gas system for a vehicle, comprising: an arrangement
for conveying an exhaust gas stream; a thermodynamic engine
comprising a heat exchanger positioned in the exhaust gas stream
for recovery of heat from the exhaust gas stream, the thermodynamic
engine comprising a working fluid circulation circuit holding a
working fluid, the working fluid comprising a first base component
mixed with a first additional component at a selected
concentration, and a first container for storing an amount of at
least the first additional component of the working fluid, the
first container fluidly connected to the working fluid circulation
circuit, wherein the first container is connected downstream of the
heat exchanger at a gaseous phase of the working fluid circulation
circuit, and that the exhaust gas system is further configured to
allow adjustment of a pressure of the working fluid at the gaseous
phase of the working fluid circulation circuit to conform with one
of a plurality of predetermined conditions, wherein the plurality
of predetermined conditions are dependent on different operational
conditions for the vehicle.
2. The exhaust gas system according to claim 1, further comprising
a pressure detector arranged downstream of the heat exchanger at
the gaseous phase of the working fluid circulation circuit, wherein
the adjustment of the pressure of the working fluid at the gaseous
phase of the working fluid circulation circuit is dependent on a
pressure detected by the pressure detector.
3. The exhaust gas system according to claim 1, wherein the
pressure of the working fluid at the gaseous phase of the working
fluid circulation circuit is adjusted by adjusting the selected
concentration of the first additional component in relation to the
first base component.
4. The exhaust gas system according to claim 1, wherein the
selected concentration of the first additional component in
relation to the first base component is adjusted based on an
ambient temperature detected by a temperature sensor.
5. The exhaust gas system according to claim 1, further comprising
a second container fluidly connected to the working fluid
circulation circuit at the gaseous phase of the working fluid
circulation circuit, wherein the first container is configured for
allowing an increase of the pressure at one of the predetermined
conditions, and the second container is configured for reducing the
pressure at another one of the predetermined conditions.
6. The exhaust gas system according to claim 1, further comprising
a working fluid release means and an exhaust gas treatment unit,
wherein the working fluid release means is configured to provide a
fluid connection between the working fluid circulation circuit and
the exhaust gas treatment unit, and the first container is
configured for allowing an increase of the pressure at one of the
predetermined conditions, and the exhaust gas treatment unit in
combination with the working fluid release means is configured for
reducing the pressure at another one of the predetermined
conditions.
7. The exhaust gas system according to claim 6, wherein in the
exhaust gas treatment unit is formed by a selective catalytic
reduction unit (SCR).
8. The exhaust gas system according to claim 6, wherein the working
fluid release means is connected downstream of the beat exchanger
at the gaseous phase of the working fluid circulation circuit.
9. The exhaust gas system according to claim 1, wherein the first
additional component is at least one of ammonia and alcohol.
10. The exhaust gas system according to claim 5, wherein at least
one of the first and the second container is configured to stare
liquid ammonia and/or an ammonia adsorbing material.
11. The exhaust gas system according to claim 2, further comprising
a control unit (110) being electrically connected to the pressure
detector and configured to adjust, using at least one controllable
valve (42) operatively connected to the control unit (110), the
pressure of the working fluid at the gaseous phase of the working
fluid circulation circuit.
12. A method for controlling an exhaust gas system for a vehicle,
the exhaust gas system comprising an arrangement for conveying an
exhaust gas stream, a thermodynamic engine comprising a heat
exchanger positioned in the exhaust gas stream for recovery of heat
from the exhaust gas stream, the thermodynamic engine comprising a
working fluid circulation circuit holding a working fluid, the
working fluid comprising a first base component mixed with a first
additional component at a concentration, and a first container for
storing an amount of at least a first additional component of the
working fluid, wherein the first container is fluidly connected
downstream of the heat exchanger at a gaseous phase of the working
fluid circulation circuit, comprising: detecting a pressure of the
working fluid at a gaseous phase of the working fluid circulation
circuit; and adjusting the pressure to conform to one of a
plurality of predetermined conditions, wherein the plurality of
predetermined conditions are dependent on different operational
conditions for the vehicle.
13. The method according to claim 12, further comprising the step
of: fluidly connecting a working fluid release means between the
working fluid circulation circuit and an exhaust gas treatment unit
provided with the vehicle, wherein the first container is
configured for allowing an increase of the pressure at one of the
predetermined conditions, and the exhaust gas treatment unit in
combination with the working fluid release means is configured for
reducing the pressure at another one of the predetermined
conditions.
14. The method according to claim 12, further comprising the steps
of: determining a current operational condition for the vehicle,
and controlling a least one controllable valve dependent on the
determined current operational condition for the vehicle for
adjusting the pressure of the working fluid at the gaseous phase of
the working fluid circulation circuit.
15. Computer program product comprising a non-transitory computer
readable medium having stored thereon a computer program for
controlling an exhaust gas system for a vehicle according to claim
12.
Description
BACKGROUND AND SUMMARY
[0001] The present invention generally relates to a system for heat
energy recovery in a vehicle comprising an internal combustion
engine, such as a diesel engine. The invention also relates to a
corresponding method for operating such a system.
[0002] Recent advances in efficient operation of internal
combustion engines include the use of thermodynamic engines,
panicularly Rankine cycle engines, for recuperation of waste heat.
As commonly known, a Rankine cycle engine is an engine that
converts heat into work. The heat is applied externally to a
preferably closed working fluid circuit which may use water or
other suitable liquids as working fluids. A pump is used to
pressurize the liquid working fluid received from a condenser which
is then heated and thereby convened into its gaseous phase.
Subsequently, the gaseous working fluid is transported to a steam
engine, where the thermal energy is converted to kinetic energy. In
a further step the gaseous working fluid is converted back to its
liquid phase in the condenser.
[0003] A common working fluid is water as it is easy to supply,
already present on a vehicle and harmless to the environment. Even
if water has some attractive properties, it also has some
drawbacks. For example, if the steam is mixed with air, the
functionality of the steam engine drops. Additionally, small
amounts of air in the steam can be rather aggressive to the
construction material. For avoiding air accumulating in the steam
it has been suggested to keep the pressure in the working fluid
above ambient air pressure. Disadvantageously, this results in a
constraint in the efficiency, since the condensing temperature
needs to be relatively high (particularly above 100 degree
Celsius). However, during a longer standstill (night, weekend,
etc.) it is difficult to avoid a pressure drop below ambient
pressure in the system, which in turn results in air leaking into
the system. Further, in some designs it is even preferred to have
lower pressure than ambient pressure its some parts of the Rankine
cycle for a good efficiency.
[0004] There exists further problems water as the working fluid,
for example as water freezes at 0.degree. C. US2010212304 tries to
solve the freezing problem by mixing the water with small amounts
of ammonia or alcohol, so that the freezing point is lowered.
Additionally, ammonia or alcohol also lowers the dew-point so that
the condensing can, be performed at lower temperatures.
[0005] Disadvantageously, ammonia is both caustic and hazardous.
Therefore, ammonia has to be handled with great care and should not
be released to the environment. However, such a release is
necessary for instance in case of an accident involving the
thermodynamic engine or a vehicle comprising such an engine (e.g. a
collision of the vehicle with another vehicle) or during
maintenance of the thermodynamic engine and/or of the vehicle. Up
to now, a bypass of the expander device is used for releasing the
pressure in the working fluid and providing safe maintenance
possibilities. Disadvantageously, this procedure is very time
consuming so that stand-still periods of the vehicle in a workshop
are unnecessarily prolonged and/or waiting times for safe access to
a vehicle, for e.g. a rescue team, are unacceptable long.
[0006] Further attention is drawn to US 2013/327041A1 relating to a
waste heat utilization device for an internal combustion engine, in
particular of a motor vehicle having a waste heat utilization
circuit. A working medium is circulated in waste heat utilization
circuit by means of a pumping device provided for pressurizing the
working medium. The waste heat utilisation circuit is in
communication with a pressure store capable of maintaining a
pressure for setting and ensuring a predetermined adjustable
minimum pressure of the working medium in tile waste heat
utilization circuit.
[0007] According to an aspect of the invention, the above is at
least partly alleviated by an exhaust gas system for a vehicle,
comprising an arrangement for conveying an exhaust gas stream, a
thermodynamic engine comprising a heat exchanger positioned in the
exhaust gas stream for recovery of heat from the exhaust gas
stream, the thermodynamic engine comprising a working fluid
circulation circuit holding a working fluid, the working fluid
comprising a first base component mixed with a first additional
component at a selected concentration, and a first container for
storing an amount of at least the first additional component of the
working fluid, the first container fluidly connected to the working
fluid circulation circuit, wherein the first container is connected
downstream of the heat exchanger at a gaseous phase of the working
fluid circulation circuit, and that the exhaust gas system is
further configured to allow adjustment of a pressure of the working
fluid at the gaseous phase of the working fluid circulation circuit
to conform with one of a plurality of predetermined conditions,
wherein the plurality of predetermined conditions are dependent on
different operational conditions for the vehicle.
[0008] The general use of the exhaust gas system according to the
invention is for achieving useful recovery of waste heat from an
internal combustion engine typically provided with the vehicle. By
the advantageous introduction of the first container fluidly
connected at the gaseous phase of the working fluid circulation
circuit it will be possible to allow for a swift alternation of
the, typically, gaseous pressure in case of a deviation from one of
a predetermined condition. As such, it may be possible to fine tune
the working fluid to be optimized towards an operational state of
the vehicle, possibly including conditions within the surrounding
of the vehicle, for example in relation to a temperature within the
surrounding of the vehicle.
[0009] The pressure detector may in one exemplary embodiment be
comprised with the exhaust gas system and arranged at the gaseous
phase of the working fluid circulation circuit. However, it may as
an alternative be possible to acquire the detected pressure using
an alternatively arranged pressure detector, possibly not
explicitly provided for use with the exhaust gas system, but rather
as an element of a complete vehicle system.
[0010] The first container may preferably be configured to provide
for both an increase and, a decrease of the pressure within the
gaseous phase of the working fluid circulation circuit for example
using a thereto connected pump. As such, the first container may be
provided with a bi-directional and valve control connection the
working fluid circulation circuit. However, in a preferred
embodiment of the invention the exhaust gas system further
comprises a second container connected to the working fluid
circulation circuit at the gaseous phase of the working fluid
circulation circuit, wherein the second container in some stages of
operation of the system is configured to be used for decreasing the
gaseous pressure within the working fluid circulation circuit,
again e.g. using a pump. Accordingly, the first container will in
such an embodiment essentially be used for increasing the gaseous
pressure (e.g. introduction of an "excess amount" of working fluid)
within the working fluid circulation circuit. As such, the first
and the second container will work together for optimizing the
gaseous pressure within the working fluid circulation circuit to
correspond to at least one of the above mentioned predetermined
conditions.
[0011] Such predetermined conditions may further to the above
general introduction relate to a safety condition concerning the
vehicle. For example, in case of servicing of the vehicle or of the
exhaust gas system it may be desirable to reduce the pressure
within the working fluid circulation circuit, thus making the
exhaust gas system easier to service.
[0012] Similarly, in case of an emergency or accident such a
pressure reduction may also be desirable for the purpose of
reducing any risks for response personnel involved with handling
the following procedure of the emergency/accident.
[0013] Furthermore, the introduction of an excess amount of working
fluid within the gaseous phase of the working fluid circulation
circuit may at some conditions allow for a reduction of air
accumulation tendency of the thermodynamic engine due to ambient
air leaking into the system. Such conditions typically arise when
the vehicle is in a stand-still mode (shutdown), for example during
nights and weekends when the vehicle is not used. Preferably this
supply takes place if a pressure below ambient pressure is detected
at the high pressure side of the circuit so that the additional
amount of working fluid may compensate the pressure drop.
[0014] Within the context of the invention it is possible to adjust
the pressure either by introducing a further amount of the working
fluid to the working fluid circulation circuit or by adjusting the
selected concentration of the first additional component in
relation to the first base component. A typical scenario when this
is possible is when the first base component of the working fluid
is water and the first additional component of the working fluid is
ammonia.
[0015] In a preferred embodiment of the invention, the exhaust gas
system further comprises a working fluid release means and an
exhaust gas treatment unit, such as a selective catalytic reduction
unit (SCR). Accordingly, also the SCR may be used fin storage of a
temporary excess of working fluid for reducing the pressure within
the working fluid circulation circuit. This is specifically
advantageous in a case where the working fluid comprises a
combination or water and ammonia. Specifically, using a selective
catalytic reduction unit, which uses ammonia for reducing emissions
of nitrogen oxides (NOx), allows for the possibility to make good
use of the "released" temporarily excessive working fluid as a
catalyst component of the SCR may temporarily store the ammonia and
then use it in the NOx reduction process, i.e. not being directly
released into the atmosphere.
[0016] In some embodiment the SCR will also be feed with a further
source of ammonia, that it, not only though the release of
water/ammonia from the working fluid circulation circuit through
the working fluid release means. The synergistic effects provided
thereby allow for a system which provides a release of working
fluid without problems as well as a recuperation of waste energy of
the internal combustion engine.
[0017] However, in some conditions it may be possible to make use
of the water/ammonia from the working fluid circulation circuit
rather than acquiring the ammonia from the further source (e.g. an
externally arranged tank provided with the vehicle). Such
conditions may for example relate to cold start of the vehicle,
where a warm provision of ammonia may be released from the working
fluid circulation circuit as compared to what may be achieved in
release from the further source.
[0018] It should be noted that it according to the invention may be
possible to "refill" e.g. the first and/or the second container
with ammonia from the further source, e.g. from the externally
arranged tank provided with the vehicle. There may be a direct
connection between the external tank and the first and/or the
second container, alternatively a chemical process may be
introduced in an intermediate step for "reconstructing" the e.g.
urea stored in the take to make it suitable for use in relation to
the working fluid circulation circuit.
[0019] In addition, the use of ammonia as a first additional
component of the working fluid will minimize the risk of problems
when operating the vehicle in cold, e.g. winter, conditions as the
ammonia will act as an antifreeze component. It may of course be
possible to use another (or further in combination) type or
antifreeze component, such as alcohol. Preferably, the
concentration of ammonia and/or alcohol can be adapted on a daily,
weekly and/or a monthly basis depending on the expected temperature
variations, for example measured using a temperature sensor
surveying the ambient temperature surrounding the vehicle. Of
course it is also possible to adapt the concentration on a shorter
time scale or an even longer time scale.
[0020] In case ammonia is used as the first additional component of
the working fluid, the first container may be adapted to be heated
to a temperature where the ammonia in the first container has a
pressure above ambient air pressure and/or above the pressure in
the working fluid circuit at the connection of the first container.
This has the advantage that no additional pump (as mentioned above)
is necessary for propelling flow of ammonia from the ammonia
reservoir/tank to the working fluid circuit. The ammonia is
preferably provided in form of urea.
[0021] According to a further preferred embodiment, the second
container is adapted to store liquid ammonia and/or an ammonia
adsorbing material, preferably CaCl2 and/or MgCl2 and/or SRCl2 an
ammonia compound preferably urea, ammonium carbamate and/or
ammonium carbonate. Preferably, ammonia adsorbing materials or
ammonia compounds are used since working with liquid ammonia calls
for additional safety precautions.
[0022] In a preferred embodiment of the invention the exhaust gas
system further comprising a control unit being electrically
connected to the pressure detector and configured to adjust, using
at least one controllable valve operatively connected to the
control unit, the pressure of the working fluid at the gaseous
phase of the working fluid circulation circuit. As such, the
control unit is typically electrically connected to the pressure
detector for acquiring a current pressure within the working fluid
circulation circuit, and use this measure and an input for
controlling valves relating to the first and the second container
as well as the working fluid release means providing a controllable
connection between the working fluid circulation circuit and the
SCR. The control unit typically comprises processing means for
regulating the pressure within the working fluid circulation
circuit to correspond to at least one of the above discussed
plurality of predetermined vehicle conditions. In addition, the
control unit typically controls the concentration of the antifreeze
component within the working fluid circulation circuit.
[0023] According to another aspect of the present invention there
is provided a method for controlling an exhaust gas system for a
vehicle, the exhaust gas system comprising an arrangement for
conveying an exhaust gas stream, a thermodynamic engine comprising
a heat exchanger positioned in the exhaust gas stream for recovery
of heat from the exhaust gas stream, the thermodynamic engine
comprising a working fluid circulation circuit holding a working
fluid, the working fluid comprising a first base component mixed
with a first additional component at a concentration, and a first
container for storing an amount of at least a first additional
component of the working fluid, the first container fluidly
connected to the working fluid circulation circuit, the method
comprising the steps of detecting a pressure of the working fluid
at a gaseous phase of the working fluid circulation circuit, and
adjusting the pressure to conform with one of a plurality of
predetermined conditions, wherein the plurality of predetermined
conditions are dependent on different operational conditions for
the vehicle. This aspect of the invention provides similar
advantages as discussed above in relation to the previous aspect of
the invention.
[0024] In an embodiment, the method farther comprises the step of
arranging a pressure detector downstream of the heat exchanger at
the gaseous phase of the working fluid circulation circuit, wherein
the step of adjusting the pressure is dependent on a pressure
detected by the pressure detector.
[0025] In another embodiment, the step of adjusting the pressure is
dependent on an ambient temperature detected by a temperature
sensor. The pressure may be adjusted by adjusting the selected
concentration of the first additional component in relation to the
first base component.
[0026] In an embodiment, the method further comprises the step of
fluidly connecting a second container to the working fluid
circulation circuit at the gaseous phase of the working fluid
circulation circuit, wherein the first container is configured for
allowing an increase of the pressure at one of the predetermined
conditions, and the second container is configured for reducing the
pressure at another one of the predetermined conditions.
[0027] According to a still further aspect of the invention there
is provided a computer program product comprising a computer
readable medium having stored thereon computer program means for
controlling an exhaust gas system for a vehicle, wherein the
computer program product comprises code for performing the steps as
discussed above in relation to the previous aspect of the
invention. Also this aspect provides similar advantages as
discussed in relation to the previous aspects of the invention.
[0028] The computer program product is typically executed using a
control unit, preferably including a micro processor or any other
type of computing device. Similarly, a software executed by the
control unit for operating the inventive exhaust gas system may be
stored on a computer readable medium, being any type of memory
device, including one of a removable nonvolatile random access
memory, a hard disk drive, a floppy disk, a CD-ROM, a DVD-ROM, a
USE memory, an SD memory card, or a similar computer readable
medium known in the art. The present invention may be thus
implemented using a combination of software and hardware
elements.
[0029] Further features of; and advantages with, the present
invention will become apparent when studying the appended claims
and the following description. The skilled addressee realize that
different features of the present invention may be combined to
create embodiments other than those described in the following,
without departing from the scope of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] The various aspects of the invention, including its
particular features and advantages, will be readily understood from
the following detailed description and the accompanying drawings,
in which:
[0031] FIG. 1 illustrates a vehicle equipped with an exhaust gas
system according to a currently preferred embodiment of the
invention;
[0032] FIG. 2 shows an example of a prior art exhaust gas system,
and
[0033] FIGS. 3-6 provide schematic drawings of currently preferred
embodiments of the exhaust gas system according to the
invention.
DETAILED DESCRIPTION
[0034] The present invention will now be described more fully
hereinafter with reference to the accompanying drawings, in which
currently preferred embodiments of the invention are shown. This
invention may, however, be embodied in many different forms and
should, not be construed as limited to the embodiments set forth
herein; rather, these embodiments are provided for thoroughness and
completeness, and fully convey the scope of the invention to the
skilled addressee. Like reference characters refer to like elements
throughout.
[0035] Referring now to the drawings and to FIG. 1 in particular,
there is depicted an exemplary vehicle, here illustrated as a truck
500. The truck 500 is provided with a source of motive power 12 for
propelling the truck via a driveline connecting the power source to
the wheels. The power source 12 is constituted by an internal
combust on engine in the for of a diesel engine. It will in the
following for ease of presentation be referred to as an internal
combustion engine 12. The vehicle 500 is provided with a tank for
storage 502 holding an amount of urea to be used in an emission
reduction process as discussed above.
[0036] FIG. 2 shows an example of a prior art exhaust gas system
100 preferably for being used in conjunction with the internal
combustion engine 12, adapted for a recuperation of waste energy of
the internal combustion engine 12, and for allow a reduction of
emission of nitrogen oxides (NOx) by means of an exhaust gas
treatment unit 20. The exhaust gas treatment unit 20 is formed by
using a selective catalytic reduction unit (SCR) using ammonia for
reducing a NOx amount of the exhaust gas. The ammonia, typically in
the form of urea, is stored in the externally arranged storage tank
502.
[0037] The exhaust gas system 100 comprises an arrangement 17 for
conveying an exhaust gas stream 80 to the exhaust gas treatment
unit 20 comprised with the arrangement 17. The exhaust gas system
100 further comprises a thermodynamic engine 1, operating in
parallel with the exhaust gas treatment unit 20, connected to the
exhaust gas stream conveying arrangement 17 for recovery of heat
from the exhaust gas stream 80. The thermodynamic engine 1
comprises a working fluid circulation circuit 11. The thermodynamic
engine 1 may for example operate in accordance with a Rankine
cycle. In the embodiment illustrated in FIG. 2 the working fluid
circulation circuit 11 is closed.
[0038] The exhaust gas conveying arrangement 17 is arranged such
that it receives exhaust gases from the internal combustion engine
12. Further, the waste heat of the internal combustion engine 12 is
used as heat source for the thermodynamic engine 1, wherein the
thermodynamic engine forms at least part of a waste heat recovery
system for the internal combustion engine.
[0039] The thermodynamic engine 1 further comprises a pump device 2
for circulating the working fluid, a heating device 4 for heating
the working fluid and thereby converting a liquid working fluid to
the gaseous phase working fluid, an expander device 8 for
converting thermal energy of the gaseous phase working fluid into
kinetic energy and a condensation device 10, which are
interconnected by the working fluid circuit 11. The heating device
4 is formed by a first heat exchanger, which is positioned in the
exhaust gas stream 80 from the internal combustion engine 12. In
other words, the first heat exchanger 4 is in heat exchanging
connection to an exhaust gas side of the internal combustion engine
12.
[0040] A turbocharger 13 is arranged for charging an incoming air
to the internal combustion engine 12. The turbocharger 13 comprises
a turbine 14 positioned in the exhaust gas stream 80 from the
internal combustion engine 12 and a compressor 15 positioned in an
inlet air stream to the internal combustion engine 12. The turbine
14 and compressor 15 are rotationally rigidly interconnected via a
shaft in a known way. The exhaust gas stream 80 is conveyed via an
exhaust gas duct 18. Further, the internal combustion engine 12
comprises a gas intake side, where fuel and air are mixed in the
known way and fed to the internal combustion engine 12.
[0041] Even if the exhaust gas treatment unit 20 is depicted as
single unit in the figures it is clear for a person skilled in the
art that an exhaust after treatment system may comprise a plurality
of units. Preferably, the exhaust gas after treatment system
comprises at least a particulate filter for removing particulates
from the exhaust gas stream 80 entering the atmosphere, the filter
arranged following the selective catalytic reduction unit in a
direction of the gas stream 80. The exhaust gas after treatment
unit 20 and the heat exchanger 4 may be integrated into a single
device. In the case of a single heat exchanger 4 in the exhaust gas
stream 80, which is arranged downstream of the exhaust gas after
treatment system 20, the exhaust gas of the combustion engine 12 is
not cooled before it reaches the exhaust gas after treatment system
20.
[0042] The thermodynamic engine 1 has at least four stages. In the
first stage I, upstream of pump device 2, the working fluid of the
thermodynamic engine 1 is in its liquid phase and has a pressure
around ambient air pressure. In a second stage IL downstream of the
pump device 2, the working fluid is still in its liquid phase but
pressurized to a predetermined pressure by pump device 2. In the
subsequent stage III downstream of the heat exchanger 4, the
working fluid has been transferred into its gaseous phase and is
pressurized to a predetermined pressure above ambient air pressure.
In its fourth stage IV downstream of expander device 8, the working
fluid is still in its gaseous phase, but has a pressure around
ambient air pressure.
[0043] Therefore, the cycle can be divided in different sides (see
also table 1); [0044] A low pressure side which is downstream of
expander device 8 and upstream of the pump device 2 (stages II and
III) and a high pressure side which is downstream of the pump
device 2 and upstream of expander device 8 (stages I and IV); or
[0045] A cold side which is downstream of the condenser device 10
and upstream of the heat exchanger 4 (stages I and II), and a hot
side which is downstream of the heat exchanger 4 and upstream of
the condenser device 10 (stages III and IV).
TABLE-US-00001 [0045] TABLE 1 Stage I Stage II Cold, Liquid phase
Cold, Liquid phase Low pressure High pressure Stage IV Stage III
Hot, Gaseous phase Hot, Gaseous phase Low pressure High
pressure
[0046] In the following the working principle of the thermodynamic
engine 1 will be explained, in the first stage I the cool liquid
working fluid streams to the pump device 2, where the cool liquid
working fluid is pressurized to a predetermined pressure above
ambient air pressure. Then the pressurized liquid working fluid is
transported to the heat exchanger 4 where it is heated and
converted from its liquid phase to its gaseous phase. Due to the
conversion into the gaseous phase the pressure may be increased
once more. The pressurized gaseous phase working fluid then streams
to the expander device 8, where the thermal energy is converted to
mechanical or electrical energy. Mechanical energy can be generated
by e.g. a displacement engine (not shown), such as a piston engine,
where the pressurized working fluid operates a piston, or may be
generated by a turbine (not shown). Alternatively, the expander
device 6 may operate a generator (not shown) for generating
electrical energy. The pressure of the working fluid is used to
displace e.g. the piston or to operate the turbine or the
generator. Consequently, the pressure of the working fluid drops so
that in the fourth stage IV, the working fluid has low pressure,
even if it is still in its gaseous phase. The low pressure gaseous
phase working fluid is subsequently transported to the condenser
device 10, where the hot working fluid is cooled below its dew
point and thereby convened hack into its liquid phase.
[0047] The working fluid for such a thermodynamic engine 1 can be a
pure liquid e.g. water or a mixture of water and for example a
first additional component, such as e.g. ammonia or ethanol. In
case the further component is the thermodynamic phase transition
points of the working fluid, as is the case e.g., with the
ammonia-water mixture and/or the ethanol-water mixture, the first
additional component may advantageously be adapted to lower the
freezing point of e.g. water so that it serves as anti-freeze
protection for the working fluid.
[0048] As discussed above, it is advantageous to be able to adjust
the concentration of the anti-freeze component as well as to be
able to adjust the gaseous pressure within the gaseous phase of the
thermodynamic engine 1, typically within stage III of the
thermodynamic engine 1.
[0049] This is according to the invention achieved, with further
reference to FIG. 3, by fluidly connecting a first container,
illustrated as a working fluid storage tank 40, holding an amount
of the working fluid (e.g. being a mixture of the first base
component and the first additional component), or only an amount of
the first additional component, e.g. ethanol, or ammonia. As
mentioned above, the working fluid storage tank 40 is fluidly
connected to the high pressure side, i.e. stage III, of the working
fluid circuit 11. More specifically, the working fluid storage tank
40 is connected to the working fluid circuit 11 downstream of the
heating device 4 and upstream of the expander device 8. The exhaust
gas system 100 comprises a working fluid storage tank valve 42
configured to control working fluid flow between the working fluid
storage tank 40 and the working fluid circuit 11. The exhaust gas
system 100 further comprises a working fluid storage tank conduit
44, which fluidly connects the working fluid storage tank 40 with
the working fluid circuit 11. The working fluid storage tank valve
42 is positioned in the conduit 44.
[0050] The working fluid storage tank 40 may be pressurized to a
pressure above the pressure present at the high pressure side III
or, alternatively, the ammonia may be, transported to the working
fluid circuit by means of a pump (not shown).
[0051] As mentioned above, the leaking in of air is, besides the
freezing, one of the main disadvantages of the known thermodynamic
engines. Particularly during standstill, the high pressure side III
may cool down to such a degree that the pressure drops below
ambient air pressure. This results in air leaking into the working
fluid circuit 11 which in turn compromises the efficiency of the
thermodynamic engine 1. Additionally, air, particularly in the form
of bubbles or cavities can be rather aggressive to the construction
materials of the thermodynamic engine parts.
[0052] Since the problem of air leaking in arises only during cool
down and when the pressure drops below ambient press re, the valve
42 arranged in the connection duct 44 between the working fluid
storage tank 40 and the working fluid circuit 11 can be opened in
dependence of a detected pressure drop or engine operation status
so that additional ammonia may stream into the working fluid
circuit 11. Thereby, as discussed above, the pressure in the
working fluid circuit 11 can be increased to a level around ambient
air pressure, which prevents air from leaking in.
[0053] Besides the above discussed possibility to flood the working
fluid circuit 11 with working fluid during cool down and thereby
preventing air from leaking in, the provision of the working fluid
storage tank 40 enables an adaptation of the ammonia concentration
in the working fluid to the local climate and/or a sensed ambient
temperature. Advantageously, at cold temperatures a high ammonia
concentration can be used as antifreeze protection so that an
increased ammonia amount during cold temperatures, i.e. during
wintertime, is provided, wherein at higher temperatures a lower
ammonia concentration is provided so that the condenser can operate
at higher temperatures.
[0054] Preferably, the ammonia concentration can be adapted on a
daily, weekly and/or a monthly basis depending on the expected
temperature variations. Of course it is also possible to adapt the
ammonia concentration on a shorter time scale or an even longer
time scale.
[0055] The working fluid storage tank. 40 may also be used e.g. in
a case where the pressure in the working fluid circuit 11 exceeds a
predetermined pressure threshold, and thus be configured to receive
any surplus amount of the working fluid within the working fluid
circuit 11. Such an operational condition of the truck 500 may for
example include startup of the thermodynamic engine 1, where the
surplus of working fluid can again be received by the working fluid
storage tank 40. For achieving such functionality it may be
possible to use the above discussed pump (not shown) in a backward
manner, i.e. for transporting working fluid from the working fluid
circuit 11 to the working fluid storage tank 40. It may also be
possible to adjust a temperature surrounding the working fluid
storage tank 40, i.e. to cool down the working fluid storage tank
40 such that the pump only will be an optional component of the
system 100.
[0056] Further operational conditions for the truck 500 exists
where it may be desirable to lower the pressure within the working
fluid circuit 11, e.g. in case of a collision or for maintenance
purposes of the thermodynamic engine 1 and/or the truck 500.
[0057] Turning now to FIG. 4, which shows a further development of
the embodiment example of FIG. 3. The exhaust gas system 100
comprises the first and an additional second container, implemented
as the working fluid storage tank 40 and as an additional working
fluid storage tank 50, which are fluidly connected to the high
pressure side, i.e. stage III, of the working fluid circulation
circuit 11. The additional working fluid storage tank 50 forms in
this embodiment a collector, thus the release of e.g. ammonia from
the working fluid circuit 11 to the working fluid storage tank 50
works the same way but in contrast to the general functionality of
the working fluid storage tank 40. A controllable valve 52 is
arranged at a connection duct 54 between the working fluid storage
tank 50 and the working fluid circuit 11. As such, the working
fluid storage tank 40 will be used for increasing the pressure
within the working fluid circuit 11 and the working fluid storage
tank 50 will be used for decreasing the pressure within the working
fluid circuit 11. It may be possible to include a further pump (not
shown) together with the working fluid storage tank 50. However,
the working fluid storage tank 50 may also be cooled or kept cool
so that also a pressure difference between the working fluid
circuit 11 and the working fluid storage tank 50 is provided, i.e.
making the pump optional.
[0058] Turning now to FIG. 5, which shows a still further
development of the embodiment example of FIGS. 3 and 4. As an
alternative to using the working fluid storage tank 50 for
decreasing the amount of working fluid within the working fluid
circuit 11, it may instead be possible to branch off the working
fluid circuit 11 using a working fluid release means 24 comprising
a controllable valve 26 arranged at the high pressure side III of
the working fluid circuit 11. As such, the working fluid, e.g.
ammonia can be released from the working fluid 11 to the catalytic
treatment unit 20 in the exhaust gas after treatment system for a
catalytic treatment of the released working fluid. Accordingly, the
working fluid release means 24 may serve as safety release or
generally as release possibility for the working fluid in a similar
manner as discussed above. However, it should be noted that it may
be possible, as is indicated in FIG. 5, to include both the working
fluid storage tank 50 and the working fluid release means 24 with
the system 100 (i.e. further to the first working fluid storage
tank 40). That is, the working fluid storage tank 50 and the
working fluid release means 24 may be controlled individually, for
example dependent on different operational conditions of the truck
500. In any case, it will be possible to make good use of the
released working fluid, without releasing it to the atmosphere.
[0059] It should be stressed that the catalyst component of the SCR
may temporarily store a fair amount the ammonia and then use it in
the NOx reduction process, i.e. not being directly released into
the atmosphere. Generally, the SCR will be feed with a further
source of ammonia, such as from the tank 502.
[0060] It is advantageous to branch off the working fluid release
means 24 upstream of the expander device 8 and downstream of the
heat exchanger 4, where the highest pressure is to be expected.
Since the pressure at the high pressure side is usually higher than
the pressure in the exhaust gas duct 18, further means for
propelling flow of the working fluid to the exhaust gas duet 18 is
not necessary.
[0061] The released working fluid or the released part of the
working fluid is subsequently catalytically treated in the exhaust
gas after treatment unit 20 and thereby converted into, harmless
compounds which can be released to the atmosphere. Thereby it
should be noted that the location where the part of the working
fluid is released into the exhaust gas after-treatment system
depends on the type of working fluid. E.g. when ammonia is used, it
is preferred to introduce the released working fluid into the
exhaust gas after treatment system upstream of the selective
catalytic reduction unit. If alcohol is comprised in the working
fluid, it is advantageous to release the working fluid into the
exhaust gas after treatment system upstream of the oxidation
catalyst.
[0062] Branching off working fluid release means 24 at the high
temperature and high pressure side of the working fluid circuit 11
has the additional advantage that the exhaust gas streaming through
the exhaust gas duct 18 is not excessively cooled down so that
operation of the exhaust gas after treatment system is not
compromised. Typically, the operation temperature for the exhaust
gas after treatment system is above 250.degree. Celsius.
[0063] Turning finally to FIG. 6 which shows an additional further
embodiment example of FIGS. 3-5. The exhaust gas system 100
comprises a control unit 110 for implementing the control method as
discussed above and which is operatively connected to the
controllable valves 42, 52 and 26 for opening and/or closing the
valves 42, 52 and 26. The exhaust gas system 100 comprises at least
one pressure detector 102 arranged in the working fluid circuit 11.
Further, the control unit 110 is operatively connected to the
pressure detector 102 for controlling the opening and/or closing of
the valves 42, 52 and 26 in dependence on a detected pressure. More
specifically, the pressure detector 102 is arranged in the high
pressure side, i.e. stage III, of the working fluid circuit 11. The
control unit 110 is configured to control the valves 42, 52 and 26
in dependence on different operational conditions of the truck 500
in a manner as discussed above. Further, the exhaust gas system 100
comprises a manually operable means 106, which is connected to the
control unit 100 for manually controlling opening and/or closing of
the valves 42, 52 and 26.
[0064] Although the figures may show a specific order of method
steps, the order of the steps may differ from what is depicted.
Also two or more steps may be performed concurrently or with
partial concurrence. Such variation will depend on the software and
hardware systems chosen and on designer choice. All such variations
are within the scope of the disclosure. Likewise, software
implementations could be accomplished with standard programming
techniques with rule based logic and other logic to accomplish the
various connection steps, processing steps, comparison steps and
decision steps. Additionally, even though the invention has been
described with reference to specific exemplifying embodiments
thereof, many different alterations, modifications and the like
will become apparent for those skilled in the art.
[0065] Variations to the disclosed embodiments can be understood
and effected by the skilled addressee in practicing the claimed
invention, from a study of the drawings, the disclosure, and the
appended claims. Furthermore, in the claims, the word "comprising"
does not exclude other elements or steps, and the indefinite
article "a" or "an" does not exclude a plurality.
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