U.S. patent application number 16/087715 was filed with the patent office on 2019-02-14 for waste heat recovery system.
The applicant listed for this patent is Robert Bosch GmbH. Invention is credited to Frank Scholz, Peter Schwaderer, Benjamin Schweizer.
Application Number | 20190048749 16/087715 |
Document ID | / |
Family ID | 61656381 |
Filed Date | 2019-02-14 |
United States Patent
Application |
20190048749 |
Kind Code |
A1 |
Scholz; Frank ; et
al. |
February 14, 2019 |
WASTE HEAT RECOVERY SYSTEM
Abstract
The invention relates to a waste heat recovery system (1)
comprising a working fluid circuit (18), having a heat exchanger
which is connected in an exhaust gas line (4) of an internal
combustion engine (2). The heat exchanger is part of the working
fluid circuit (18) together with an expansion machine (20) which
has at least one working fluid bypass (21) that is controlled by a
valve. According to the invention, a waste heat recovery system (1)
is provided with improved functionality. This is achieved in that
the valve is a directional valve which connects a fluid inlet (36)
to an expansion machine fluid outlet (37) and/or a bypass fluid
outlet (38), in particular a 3/2-way valve (22), and the connection
of the fluid inlet (36) to the expansion machine fluid outlet (37)
is leakage-free relative to the bypass fluid outlet (38), whereas
the connection of the fluid inlet (36) to the bypass fluid outlet
(38) exhibits leakages with respect to the expansion machine fluid
outlet (37).
Inventors: |
Scholz; Frank;
(Stuttgart-Feuerbach, DE) ; Schweizer; Benjamin;
(Horb, DE) ; Schwaderer; Peter; (Wildberg,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Robert Bosch GmbH |
Stuttgart |
|
DE |
|
|
Family ID: |
61656381 |
Appl. No.: |
16/087715 |
Filed: |
November 17, 2016 |
PCT Filed: |
November 17, 2016 |
PCT NO: |
PCT/EP2016/077992 |
371 Date: |
September 24, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F05D 2220/40 20130101;
Y02T 10/16 20130101; Y02T 10/12 20130101; F01N 5/02 20130101; F16K
3/267 20130101; F01N 2410/00 20130101; F01K 23/065 20130101; F02G
5/02 20130101; F16K 31/061 20130101; F16K 31/0624 20130101 |
International
Class: |
F01K 23/06 20060101
F01K023/06 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 24, 2016 |
DE |
10 2016 205 041.9 |
Claims
1. A waste-heat recovery system (1) with a working fluid circuit
(18) having a heat exchanger connected into an exhaust-gas line (4)
of the internal combustion engine (2), wherein the heat exchanger
is part of the working fluid circuit (18) with at least one
expansion machine (20) which has a working fluid bypass (21)
controlled by a valve, wherein the valve is a directional valve
(22) which connects a fluid inlet (36) to an expansion machine
fluid outlet (37) and/or to a bypass fluid outlet (38), and wherein
a connection made between the fluid inlet (36) and the expansion
machine fluid outlet (37) exhibits no leakage to the bypass fluid
outlet (38).
2. The waste-heat recovery system (1) as claimed in claim 1,
characterized in that a connection made between fluid inlet (36)
and the bypass fluid outlet (38) exhibits leakage, with a leakage
quantity (46a, 46b), to the expansion machine fluid outlet
(37).
3. The waste-heat recovery system (1) as claimed in claim 2,
characterized in that the leakage quantity (46a, 46b) is less than
10% of the maximum volume flow of the working fluid.
4. The waste-heat recovery system (1) as claimed in claim 2,
characterized in that the directional valve (22) has a slide (31)
with two opposite switching positions that can be assumed by the
slide (31).
5. The waste-heat recovery system (1) as claimed in claim 2,
characterized in that the directional valve (22) has a slide
housing (30) and a slide (31) which is displaceable in said slide
housing axially counter to the force of a spring (32), which slide
has a permanent flow connection to the fluid inlet (36) and can be
adjusted in each case into a flow connection with the bypass fluid
outlet (38) and with the expansion machine fluid outlet (37).
6. The waste-heat recovery system (1) as claimed in claim 2,
characterized in that the directional valve (22) has a bypass fluid
outlet seat (40) configured to have an end-side slide seat (41) of
the slide (31) engaged therein with sealing action.
7. The waste-heat recovery system (1) as claimed in claim 2,
characterized in that the slide housing (30) has an expansion
machine fluid outlet seat (43) configured to have a slide edge (44)
of the slide (31) engaged therein with sealing action.
8. The waste-heat recovery system (1) as claimed in claim 6,
characterized in that the slide seat (41) is arranged on a slide
base wall of the slide (31) of piston-like form, and in that the
slide base wall has passage openings (45) for an unhindered
throughflow of the working fluid.
9. The waste-heat recovery system (1) as claimed in claim 4,
characterized in that the slide (31) interacts with an actuator
(33).
10. The waste-heat recovery system (1) as claimed in claim 2,
characterized in that the leakage quantity (46a, 46b) is less than
1% of the maximum volume flow of the working fluid,
Description
BACKGROUND OF THE INVENTION
[0001] The invention relates to a waste-heat recovery system with a
working fluid circuit having a heat exchanger connected into an
exhaust-gas line of the internal combustion engine, wherein the
heat exchanger is part of the working fluid circuit with at least
one expansion machine which has a bypass controlled by a valve.
[0002] A waste-heat recovery system of said type is known from DE
10 2013 021 251 A1. Said waste-heat recovery system has a working
fluid circuit which has the conventional components. These are,
substantially, an evaporator connected into an exhaust-gas line of
an internal combustion engine, and expansion machine with the
bypass control by a valve, a condenser, and a working fluid pump.
By means of the bypass control by the valve, the expansion machine
can be switched into a torque-free state. Here, the bypass and the
valve are arranged within or integrated into the expansion
machine.
SUMMARY OF THE INVENTION
[0003] The invention is based on the object of providing a
waste-heat recovery system which is improved with regard to its
function.
[0004] Said object is achieved in that the valve is a directional
valve, in particular 3/2 directional valve, which connects a fluid
inlet to an expansion machine fluid outlet and/or to a bypass fluid
outlet, and in that a connection made between fluid inlet and
expansion machine fluid outlet exhibits no leakage to the bypass
fluid outlet. Said 3/2 directional valve can conduct the working
fluid flowing and the working fluid circuit either via the
expansion machine or, pass the expansion machine, directly to a
condenser provided in the working fluid circuit downstream of the
expansion machine. It is a first object of said 3/2 directional
valve, for example in the case of a mechanical connection of the
expansion machine to a crankshaft of the internal combustion
engine, and in the presence of a torque demand of "zero", to
conduct the working fluid directly to the condenser, such that the
expansion machine is not driven by the working fluid and therefore
outputs no torque to the crankshaft. It is a second object of the
3/2 directional valve to protect the expansion machine if the
working fluid is in a wet steam range. During expander operation,
in which the expansion machine is flowed through in the intended
manner by the working fluid, leakage in the direction of the
bypass, which would constitute an impairment of the efficiency of
the expansion machine, is prevented according to the invention. By
means of this embodiment, the function of the waste-heat recovery
system is improved.
[0005] In a refinement of the invention, a connection made between
fluid inlet and bypass fluid outlet exhibits leakage, with a
leakage quantity, to the expansion machine fluid outlet. Here, in a
further embodiment of the invention, the leakage quantity to the
expansion machine fluid outlet is less than 10% of the maximum
volume flow of the working fluid through the working fluid circuit,
preferably less than 1% of the maximum volume flow. Such a minimum
leakage quantity is expedient because, in this way, the expansion
machine is for example heated during a commencement of operation of
the waste-heat recovery system, or in the event of temporary
bypassing the expansion machine, cooling of the expansion machine
is prevented. "Permanent lubrication" of the expansion machine is
also ensured. This embodiment also sustainably improves the
function of the waste-heat recovery system.
[0006] In a refinement of the invention, the 3/2 directional valve
has a slide (in the form of a piston) with two opposite switching
positions that can be assumed by the slide. Here, the switching
positions of the slide can be defined or occupied by a slide seat
on the bypass fluid outlet and an expansion machine outlet seat at
the expansion machine fluid outlet. This is one possible
embodiment, in which a short stroke of the slide can be realized,
whereby, in turn, a simple, inexpensive design of an actuating
element for the adjustment of the slide can be realized.
[0007] In a second embodiment, the switching positions of the slide
may be defined by a slide seat on the bypass fluid outlet and, as a
substitute for the single expansion machine outlet seat at the
expansion machine fluid outlet, by an overlap gap assumed by the
slide relative to a slide housing. This embodiment is basically
similar in terms of function to the first embodiment, wherein here,
the required stroke of the slide is longer owing to the overlap
that is to be realized.
[0008] In a further configuration of the invention, the 3/2
directional valve has a slide housing and a slide which is
displaceable in said slide housing axially counter to the force of
a spring, which slide has a permanent flow connection to the fluid
inlet and can be adjusted in each case into a flow connection with
the bypass fluid outlet and with the expansion machine fluid
outlet. This is an embodiment of the 3/2 directional valve realized
in all conceivable configurations.
[0009] In a refinement of the invention, the bypass fluid outlet
has a bypass fluid outlet seat into which an end-side slide seat of
the slide can be engaged with sealing action. In this way, in a
corresponding switching position of the slide, the absence of
leakage of the fluid inlet to the bypass fluid outlet is
ensured.
[0010] In a refinement of the invention, the slide seat is arranged
on a slide base wall of the slide of piston-like form (opposite the
side of the connection of an actuator switching rod), and wherein
the slide base wall has at least one passage opening which permits
a throttling-free throughflow of the working fluid.
[0011] The desired leakage of the working fluid to the expansion
machine outlet may be produced or set by means of corresponding
play between the slide and the slide housing. Alternatively, the
leakage may however also be produced by means of a leakage throttle
bore in the slide.
[0012] In a further configuration of the invention, the slide
interacts with an actuator. The actuator may be designed as an
electromagnet or else may be configured or actuated in pneumatic,
hydraulic or electromagnetic or some other form.
[0013] In summary, the waste-heat recovery system configured in
this way offers the following advantages: [0014] in turbine
operation, in which the working fluid is to be conducted entirely
through the expansion machine, it is ensured that no leakage occurs
in the direction of the bypass fluid outlet, [0015] by contrast, in
bypass operation, when the working fluid is conducted through the
bypass, a minimal leakage in the direction of the expansion machine
fluid outlet is set in order, for example, to heat the expansion
machine, [0016] only low actuator forces are necessary, because the
slide is pressure-balanced. The actuator consequently has to
overcome only spring forces and flow forces, [0017] in expander
operation, it is likewise the case that only low actuator forces
are necessary, because, in this switching state, the slide is not
force-balanced, and the acting force acts with a closing action
toward the bypass fluid outlet, [0018] a robust design with low
acting seat forces can be implemented, and [0019] the 3/2
directional valve can be implemented inexpensively.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Further advantageous configurations of the invention emerge
from the description of the drawings, which gives a description of
exemplary embodiments illustrated in the figures.
[0021] In the figures:
[0022] FIG. 1 shows a schematic circuit diagram of a waste-heat
recovery system which has an expansion machine and a working fluid
circuit, wherein the waste-heat recovery system is installed on an
internal combustion engine,
[0023] FIG. 2a shows a first exemplary embodiment of a bypass,
controlled by a valve, of the working fluid circuit past an
expansion machine in a first switching position,
[0024] FIG. 2b shows a first exemplary embodiment of a bypass,
controlled by a valve, of the working fluid circuit past an
expansion machine in a second switching position,
[0025] FIG. 3a shows a second exemplary embodiment of a bypass,
controlled by a valve, of the working fluid circuit past an
expansion machine in a first switching position,
[0026] FIG. 3b shows a second exemplary embodiment of a bypass,
controlled by a valve, of the working fluid circuit past an
expansion machine in a second switching position.
DETAILED DESCRIPTION
[0027] FIG. 1 shows a waste-heat recovery system 1, which is
installed on an internal combustion engine 2 which has a cooling
system (not illustrated in any more detail). The internal
combustion engine 2 furthermore has a fresh-gas line 3 and an
exhaust-gas line 4. Via the fresh-gas line 3, the internal
combustion engine 2 is supplied with combustion air which, in the
exemplary embodiment, is compressed by a compressor 5 of an
exhaust-gas turbocharger 6, which in turn is driven by a turbine 7
incorporated into the exhaust-gas line 4. A charge-air cooler 8 and
a throttle flap 9 are connected downstream of the compressor 6.
[0028] The fresh gas supplied to individual combustion chambers of
the internal combustion engine 2 with a simultaneous supply of
fuel, for example diesel fuel, burns in the combustion chambers of
the internal combustion engine 2, generating working power, which
is output, for example via an output shaft 10 which is connected to
the crankshaft of the internal combustion engine 2 via a
transmission, to a drive axle 11, by means of which an arbitrary
vehicle in which the internal combustion engine 2 is installed is
driven. Via the exhaust-gas line 4, the mixture of fuel and fresh
gas burned in the combustion chambers of the internal combustion
engine 2 is ultimately discharged as hot gas into the surroundings.
The exhaust-gas line 4 is connected to the fresh-gas line 3 via an
exhaust-gas recirculation line 12 with, incorporated therein, an
exhaust-gas recirculation cooler 13 and an exhaust-gas
recirculation valve 14. Via the exhaust-gas recirculation line 12,
exhaust gas is recirculated in controlled fashion into the
fresh-gas line 3, in particular in order to reduce the harmful
exhaust-gas emissions. Downstream of the turbine 7, an exhaust-gas
aftertreatment device 15 is likewise provided for reducing the
harmful exhaust-gas emissions. Further downstream, a heat exchanger
in the form of a superheater 16 of the waste-heat recovery system 1
is incorporated into the exhaust-gas line 4, which heat exchanger
can be bypassed in controlled fashion via an exhaust-gas line
bypass 17. The superheater 16 is incorporated into a working fluid
circuit 18 of the waste-heat recovery system 1--as will be
discussed in more detail below.
[0029] The internal combustion engine 2 has the abovementioned
cooling system with a coolant circuit, which is however of no
further importance of the subject matter of the invention and is
therefore not illustrated. The cooling system serves for the
cooling of the internal combustion engine 2 and has a coolant
cooler incorporated into the cooling circuit and a coolant pump.
The coolant pump conveys the coolant through cooling chambers of
the internal combustion engine 2 into the coolant cooler, which is
connected at the outlet side to the suction side of the coolant
pump. Also suitably incorporated into said coolant circuit are, for
example, a lubricating oil heat exchanger, a retarder heat
exchanger, the charge-air cooler 8 and the exhaust-gas
recirculation cooler 13.
[0030] Returning to the waste-heat recovery system 1, the latter
has the working fluid circuit 18 with the superheater 16
incorporated into the exhaust-gas line 4. Also incorporated into
the working fluid circuit 18 is an expansion machine 20 which is
driven by the working fluid changed into the gaseous state in the
superheater 16, with expansion of said fluid, and which outputs
working power to the internal combustion engine 2 or to some other
machine, for example a generator. Here, the expansion machine 20
can be bypassed via a working fluid bypass 21, which is controlled
by a directional valve 22 formed preferably as a 3/2 directional
valve. Furthermore, a condenser 23 is incorporated into the working
fluid circuit 18 downstream of the expansion machine 20, in which
condenser the working fluid is normally cooled down into the liquid
state and is subsequently supplied to a working fluid pump 24. The
working fluid pump 24 is for example electrically driven by a motor
19 and conveys the cooled-down working fluid back to the
superheater 16. Here, at the outlet side of the working fluid pump
24, a pressure compensation tank 25 is incorporated into the
working fluid circuit 18.
[0031] The abovementioned condenser 23 is in turn a constituent
part of a working fluid cooling circuit 26, which furthermore has a
cooler 27. The cooler 27 is for example arranged upstream or
downstream of the coolant cooler and is flowed through by a cooling
air flow which is conveyed for example by a fan 28, which is driven
directly or indirectly by the internal combustion engine 2.
Finally, an electric or electronic control device 29 is provided,
which controls the waste-heat recovery system 1 including possibly
the entire internal combustion engine 2. Said control device 29
also serves for controlling the 3/2 directional valve 22 of the
waste-heat recovery system 1, which valve will be discussed in more
detail with regard to its design and function in the following
figures.
[0032] FIG. 2a shows the directly controlled 2/3 directional valve
22, which is pressure-balanced at least in one switching position,
in a first embodiment, and shows a switching position in which the
working fluid of the working fluid circuit 18 is conducted to the
expansion machine 20. By contrast, in the switching position of the
3/2 directional valve 22 illustrated in FIG. 2b, the working fluid
is conducted to the working fluid bypass 21 and thus so as to
bypass the expansion machine 20. The 3/2 directional valve 22 has a
cylindrical tubular slide housing 30 in which a slide 31 of
piston-like form is adjustable axially counter to the force of a
spring 32. Said adjustment movement is effected by an actuator 33
which is fixedly connected by means of an actuator holding device
34 to the slide housing 30 and which has an actuator switching rod
35, which in turn is connected to the slide 31 for the direct axial
adjustment of the slide 31. For example, the actuator 33 is formed
as an electromagnet and, when electrically energized, moves the
actuator switching rod 35 with the slide 31 into the position
illustrated in FIG. 2a, whereas, when electrically deenergized, the
position of the slide 31 illustrated in FIG. 2b is set by means of
the restoring force of the spring 32. The actuator 33 may however
also for example be of pneumatic, hydraulic or electromagnetic form
in other embodiments.
[0033] The slide housing 30 has a tubular and flange-mounted fluid
inlet 36, which is connected to the working fluid circuit 18 at the
outlet side of the superheater 16. Furthermore, the slide housing
30 has a likewise tubular expansion machine fluid outlet 37, which
is connected directly or indirectly to the flow inlet into the
expansion machine 20. The expansion machine fluid outlet 37 may,
like the fluid inlet 36, be configured as a metallic pipe
connection piece, which is welded to the slide housing 30, the
latter likewise being manufactured from a metallic material.
Furthermore, the 3/2 directional valve 22 has a bypass fluid outlet
38, which is connected to the working fluid bypass 21. The bypass
fluid outlet 38 is arranged on a closure plate 39, opposite the
actuator holding device 34, on the slide housing 30, or is a
constituent part of the closure plate 39 and formed for example as
a bypass fluid outlet pipe with a throttling action set by means of
the pipe diameter.
[0034] The bypass fluid outlet 38 or the bypass fluid outlet pipe
has a bypass fluid outlet seat 40, in which an end-side facing
slide seat 41 of the slide 31 can be engaged with sealing action
and thus in leakage-free fashion. The slide seat 41 is arranged on,
or formed in one piece with, a slide base wall of the slide 31 of
piston-like form, wherein the slide base wall has passage openings
45 for an unhindered throughflow of the working fluid.
[0035] The corresponding switching position is illustrated in FIG.
2a. In this switching position, the working fluid flowing into the
3/2 directional valve 22 or the slide housing 30 via the fluid
inlet 36 flows in leakage-free fashion into the expansion machine
fluid outlet 37 in accordance with the illustrated flow arrows. In
the region of the expansion machine fluid outlet 37, an encircling
ring-shaped groove 42 is recessed into the slide housing 30, which
ring-shaped groove promotes an unhindered flow through the 3/2
directional valve 22 and, at the same time, in the direction of the
actuator holding device 34, transitions into an expansion machine
fluid outlet seat 43 adjacent to the fluid inlet 36.
[0036] The slide 31 is displaceable with an encircling slide edge
44 into the expansion machine fluid outlet seat 43, which is formed
for example by a cylindrical pipe diameter reduction of the slide
housing 30. The corresponding switching position is, as stated
above, illustrated in FIG. 2b. In this switching position, the
direct passage from the fluid inlet 36 via the expansion machine
outlet seat 43 and the ring-shaped groove 42 into the expansion
machine outlet 37 is blocked. At the same time, it is however the
case that the working fluid flows, in accordance with the
illustrated flow arrows, through the slide 31 of piston-like form,
and passes via the passage openings 45 directly into the bypass
fluid outlet 38, because, in this switching position, the slide
seat 41 has been moved out of the bypass fluid outlet seat 40 and
opens up a flow connection.
[0037] At the same time, in this switching position, a small
leakage of the maximum volume flow of the working fluid from the
fluid inlet 36 to the expansion machine fluid outlet 37 is set,
which is set by means of the play with which the slide 31 is guided
in the slide housing 30. Here, the defined leakage quantity 46a of
the working fluid passes from the slide seat 41 back to the
expansion machine fluid outlet 37. Alternatively (in the case of
play-free guidance of the slide 31 in the slide housing 30) or in
addition, it is also possible for at least one leakage throttle
bore 47a, illustrated only in FIG. 2b, to be provided in the slide
31 in the region of the ring-shaped groove 42. The leakage quantity
46a of the working fluid is less than 10% of the maximum volume
flow, preferably less than 1% of the maximum volume flow.
[0038] The exemplary embodiment as per FIGS. 3a, 3b differs from
that of FIGS. 2a, 2b in that, here, no expansion machine fluid
outlet seat 43 is provided into which a slide edge 44 could engage
in the switching position as per FIG. 3b. In this exemplary
embodiment, the slide housing 30 is formed with a shoulder-free
internal diameter. Thus, it is also the case in the switching
position as per FIG. 3b (the switching position is identical to
that of FIG. 2a at least in terms of function) that a leakage
quantity 46b flows from said side from the fluid inlet 36 into the
expansion machine fluid outlet 37. In this embodiment, too, the
entire leakage quantity 46a, 46b of the working fluid is less than
10% of the maximum volume flow, preferably less than 1% of the
maximum volume flow. Furthermore, in this embodiment, the switching
travel to be covered by the actuator 33 is longer than in the
exemplary embodiment as per FIGS. 2a, 2b.
[0039] It is finally pointed out that any design details
illustrated in the figures may be combined with one another within
the scope of the invention.
* * * * *