U.S. patent application number 15/761214 was filed with the patent office on 2018-09-13 for exhaust-gas energy recovery system and method for exhaust-gas energy recovery.
The applicant listed for this patent is Fuelsave GmbH. Invention is credited to Dirk Hoffmann.
Application Number | 20180258818 15/761214 |
Document ID | / |
Family ID | 54196815 |
Filed Date | 2018-09-13 |
United States Patent
Application |
20180258818 |
Kind Code |
A1 |
Hoffmann; Dirk |
September 13, 2018 |
EXHAUST-GAS ENERGY RECOVERY SYSTEM AND METHOD FOR EXHAUST-GAS
ENERGY RECOVERY
Abstract
The invention relates to an exhaust-gas energy recovery system,
comprising an exhaust-gas line system (111) for conducting exhaust
gases of an internal combustion engine and comprising a
motor-generator device (101), which can be driven by means of
exhaust-gas energy in order to produce electric current. The
exhaust-gas line system (111) comprises a first line arm (124) to
the motor-generator device (101) for conducting exhaust gases into
the motor-generator device (101). The motor-generator device
comprises a motor (100), which is arranged in such a way that the
motor can be driven by a pressure of exhaust gas flowing through
the motor. The invention further relates to a corresponding method
for exhaust-gas energy recovery.
Inventors: |
Hoffmann; Dirk; (Buchholz
i.d.N., DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Fuelsave GmbH |
Walldorf |
|
DE |
|
|
Family ID: |
54196815 |
Appl. No.: |
15/761214 |
Filed: |
September 14, 2016 |
PCT Filed: |
September 14, 2016 |
PCT NO: |
PCT/EP2016/071725 |
371 Date: |
March 19, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F02B 41/10 20130101;
F01N 3/00 20130101; F01C 11/008 20130101; F01C 1/123 20130101; F01N
5/02 20130101; Y02T 10/166 20130101; Y02T 10/17 20130101; F01C
21/008 20130101; Y02T 10/12 20130101; Y02T 10/16 20130101; F01C
19/025 20130101; F01N 5/00 20130101; F02G 5/04 20130101; F01N 5/04
20130101; Y02T 10/163 20130101 |
International
Class: |
F01N 5/04 20060101
F01N005/04; F01C 1/12 20060101 F01C001/12; F01C 19/02 20060101
F01C019/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 21, 2015 |
EP |
15186105.1 |
Claims
1. An exhaust gas energy recovery system comprising: an exhaust
line system (111) for guiding exhaust gases from a combustion
engine, a motor/generator unit configured to be driven by exhaust
energy to generate electrical energy, wherein the exhaust line
system comprises a first line arm to the motor/generator unit for
guiding exhaust gases to the motor/generator unit, wherein the
motor/generator unit comprises a motor which is arranged to be
driven by a pressure of passing exhaust gases, and wherein the
motor is a rotary engine comprising: a housing defining an inner
room, at least two rotary pistons arranged in the inner room, an
inlet opening which is connected with the exhaust line system for
introducing the exhaust gases into the inner room, and an outlet
opening for the exhaust gas defined at the inner room at a side
opposite to the inlet opening, wherein each rotary piston comprises
a gear rim at its outer circumference, and the rotary pistons are
arranged such that their gear rims mesh.
2. The exhaust gas energy recovery system as defined in claim 1,
further comprising: a combustion engine and an exhaust gas
treatment system for cleaning exhaust gases, wherein the exhaust
line system is configured for guiding at least a part of the
exhaust gases of the combustion engine first through the motor of
the motor/generator unit and then to the exhaust gas treatment
system.
3. The exhaust gas energy recovery system as defined in claim 1,
wherein the exhaust line system comprises a fork from which a first
line arm runs via the motor in the direction of the exhaust gas
treatment system and a second line arm bypasses the motor; and runs
in the direction of the exhaust gas treatment system, and wherein
the exhaust gas energy recovery system further comprises a control
device at the fork configured to set proportions in which the
exhaust gas in divided to the first and second line arms.
4. The exhaust gas energy recovery system as defined in claim 1,
wherein the control device comprises a rotatable shutter, and
wherein a rotation position of the rotatable shutter determines in
which parts the exhaust gas in guided into the first line arm and
the second line arm.
5. The exhaust gas energy recovery system as defined in claim 1,
further comprising: two rotary pistons, wherein each rotary piston
comprises at least two sealing strips; and at least two recesses at
its outer circumference, the shapes of the recesses; and the
sealing strips are chosen for sealing engagement of the sealing
strips of each one of the rotary pistons with the recesses of the
respective other rotary piston, wherein the sealing strips are
sized to sealingly contact a housing inner surface in a radial
direction.
6. The exhaust gas energy recovery system as defined in claim 5,
wherein the sealing strips comprise a deformable material such that
the sealing strips can be pressed against the housing inner surface
by incoming exhaust gases.
7. The exhaust gas energy recovery system as defined in claim 5,
wherein each of the sealing strips comprises an exhaust gas contact
surface facing inflowing exhaust gas when the respective rotary
piston is at a rotation angle position at which said sealing strip
contacts the housing inner surface (12), and wherein the exhaust
gas contact surface has a concave shape.
8. The exhaust gas energy recovery system as defined in claim 7,
wherein each of the sealing strips has a rear side which is
opposite the exhaust gas contact surface and which does not face
inflowing exhaust gas when the respective rotary piston is at a
rotation angle position in which said sealing strip contacts the
housing inner surface, and wherein the rear side has a convex
shape.
9. The exhaust gas energy recovery system as defined in claim 5,
wherein the rotary pistons comprise at their respective outer
circumference slots for receiving and securing the sealing strips,
and wherein the sealing strips are formed as slot nuts for securely
coupling with the slots of the respective rotary piston.
10. The exhaust gas energy recovery system as defined in claim 9,
wherein the slots are formed as T-slots and each slot nut comprises
a laterally protruding shroud for engaging with one of the
T-slots.
11. The exhaust gas energy recovery system as defined in claim 5,
wherein each rotary piston comprises exactly two sealing strips at
opposite angle positions at its outer circumference, and wherein
each rotary piston comprises exactly two recesses arranged at the
outer circumference at angle positions which are each offset by
90.degree. relative to the angle positions of the two sealing
strips.
12. The exhaust gas energy recovery system as defined in claim 1,
wherein the sealing strips protrude from their respective rotary
piston further outwards in a radial direction than the respective
gear rim.
13. A method for exhaust gas energy recovery, the method comprising
generating electrical energy from exhaust energy with a
motor/generator unit, by: guiding exhaust gases to the
motor/generator unit via a first line arm of an exhaust line system
(111), wherein the motor/generator unit comprises a motor which is
driven by a pressure of passing exhaust gases, wherein the motor is
a rotary engine comprising: a housing defining an inner room, at
least two rotary pistons arranged in the inner room, an inlet
opening through which exhaust gases are transported from the
exhaust line system into the inner room, and an outlet opening for
the exhaust gas defined at the inner room at a side opposite to the
inlet opening, each rotary piston comprises a gear rim at its outer
circumference, and the rotary pistons are arranged such that their
gear rims mesh.
Description
[0001] The present invention relates to an exhaust gas energy
recovery system according to the preamble to claim 1, and to a
method for exhaust gas energy recovery according to the preamble to
claim 13.
[0002] For the goal of efficient operation of combustion engines,
in particular in vehicles, efforts are made to improve
characteristics of the combustion process. On the other hand, the
total efficiency can also be increased by further use of the energy
of exhaust gases produced by the combustion process.
[0003] To this end, a generic exhaust gas energy recovery system
comprises an exhaust line system for guiding exhaust gases of a
combustion engine, and a motor/generator unit which can be driven
by exhaust energy to generate electrical energy.
[0004] Similarly, in a generic method for exhaust gas energy
recovery, electrical energy is generated by a motor/generator unit
using exhaust gas energy.
[0005] Conventional exhaust gas energy recovery systems use exhaust
waste heat to generate electrical energy. To this end, heat of the
exhaust gas is transferred to another working fluid. The working
fluid is usually arranged in a closed circuit and passes the motor.
A line system of the working fluid comprises further components,
for example a pump, a condenser, facultatively further heaters and
a recuperator. The selection of these components depends on the
instant thermodynamic cycle. In particular, Rankine cycles are
used, which are also referred to as ORC or Organic Rankine
Cycles.
[0006] Conventional exhaust gas energy recovery systems may be able
to make use of a substantial part of the exhaust gas energy.
However, the subsequently emitted exhaust gas still has much energy
that remains unused.
[0007] It may be regarded an object of the invention to provide an
exhaust gas energy recovery system and a method for exhaust gas
energy recovery which use exhaust gas energy particularly
efficiently.
[0008] This object is solved with the exhaust energy recovery
system comprising the features of claim 1, and the method
comprising the features of claim 13.
[0009] Preferred variants of the exhaust energy recovery system of
the invention of the method of the invention are subject-matter of
the dependent claims and are also illustrated in the following
description.
[0010] In the exhaust gas energy recovery system of the
above-referenced kind, according to the invention the exhaust line
system comprises a line (which is referred to in the following as a
first line arm) to the motor/generator unit for guiding exhaust
gases into the motor/generator unit, and the motor/generator unit
comprises a motor which is arranged to be driven by a pressure of
passing exhaust gases.
[0011] Similarly, according to the invention the method of the
above-referenced kind comprises: guiding exhaust gases through a
line of an exhaust line system into the motor/generator unit which
comprises a motor that is driven by a pressure of exhaust gases
flowing through the motor.
[0012] As an important idea of the invention, the pressure of the
exhaust gases is used to generate electrical energy. Whereas
hitherto only the heat of the exhaust gases has been used for
generating electrical energy, the invention allows to additionally
or alternatively use the exhaust gas pressure. Thus, kinetic energy
of the exhaust gases, which has hitherto not been used, is at least
partially converted into electrical energy.
[0013] As another central idea, exhaust gases are guided directly
through the motor of the motor/generator unit. This is relevant for
harvesting a particularly large share of the energy present in the
pressure. Preferred designs of the motor for providing a
particularly high efficiency also at rather low pressures, will be
described later in more detail.
[0014] A motor/generator unit may generally indicate a device
comprising a motor (engine) and being configured to convert motion
energy into electrical energy. The necessary components may form a
local unit or may be distributed at different spatial locations and
being functionally connected. In particular, a generator may be
provided which may in general be any device with which the
(rotational) energy provided by the motor can be converted into
electrical energy.
[0015] Also a combustion engine and an exhaust gas treatment system
for cleaning exhaust gases may be regarded as part of the exhaust
gas energy recovery system of the invention. The exhaust line
system may be configured to guide at least a part of the exhaust
gases of the combustion engine first through the motor of the
motor/generator unit and then to the exhaust gas aftertreatment
system. By arranging the motor/generator unit in the direction of
flow upstream of the exhaust gas aftertreatment system, the energy
present in the pressure may be used before the pressure through the
exhaust gas aftertreatment system drops. If a turbocharger is
provided, the motor/generator unit is preferably in the direction
of flow downstream of the turbocharger. This facilitates in
particular retrofitting conventional systems because the components
up to the turbocharger, which components interact with each other,
may remain unchanged.
[0016] The exhaust line system may comprise a fork/diversion from
which a first line arm runs via the motor in the direction of the
exhaust gas treatment system, and a second line arm bypasses the
motor and runs in the direction of the exhaust gas treatment
system. A control device may be provided at the fork and may be
configured to set proportions in which the exhaust gas is divided
to the first and second line arms. Advantageously, this control may
in particular set a desired minimal pressure of the exhaust gas
downstream of the engine/motor. Furthermore, a maximum amount of
exhaust gases to the motor may be set to comply with limits of
suitable operating conditions for the engine. Furthermore, this
control adjusts the amount of generated electrical energy. For
example, the amount of exhaust gases to the motor may be reduced if
less electrical energy is required and/or if a storage for
electrical energy is completely charged.
[0017] The control device may preferably comprise a rotatable flap
or shutter. A rotation position of the flap/shutter defines the
shares in which exhaust gas is guided into an entrance opening of
the first line arm and into an entrance opening of the second line
arm. In this way, a control can be effected reliably with simple
means.
[0018] In principle, the motor of the motor/generator unit may be
of any kind. However, it has to be considered that many motors only
have a sufficient efficiency at rather high pressures. Furthermore,
many motors impose narrow criteria for the passing medium, for
example with regard to its temperature or viscosity. For a
particularly high efficiency, the medium that flows through the
motor should be the exhaust gas itself. In the following, preferred
features of the motor are described for using the exhaust pressure
particularly efficiently.
[0019] The engine is preferably a rotary engine in which at least
one rotary plunger is rotated by passing exhaust gas and thus a
drive shaft is rotated which drives the generator.
[0020] The rotary engine may comprise a housing which forms an
inner room. At least one, preferably at least two or exactly two,
rotary pistons may be arranged in the inner room. Furthermore, an
inlet opening is provided for introducing exhaust gas into the
inner room. The inlet opening is connected with the exhaust line
system, in particular with the first line arm. The rotary engine
further comprises an outlet opening for the exhaust gas, the outlet
opening being arranged at the inner room at a side opposite to the
inlet opening. The exhaust gas thus flow through the inner room and
thus make the rotary pistons rotate. Each rotary piston preferably
comprises at its outer circumference at least two sealing strips
and at least two recesses, wherein the shapes of the recesses and
of the sealing strips are chosen for engaging, in particular
sealingly engaging, of the sealing strips of one rotary piston with
the recesses of the other rotary piston, respectively. Furthermore,
the sealing strips are radially sized for sealingly contacting a
housing inner surface. A radial direction refers to the radius of
the corresponding rotary piston, and thus the radial direction is
transverse or perpendicular to the rotary direction of the
respective rotary piston. The exhaust gas coming from the inlet
opening pushes against (at least) some of the sealing strips, thus
pushing these sealing strips against the housing inner surface. In
particular, depending on a rotary position, at least one (or
exactly one) of the sealing strips of each rotary piston may be
exposed to incoming exhaust gas and may thus be pushed against the
housing inner surface.
[0021] It may be regarded as an important characteristic of the
invention to provide for a sealing of a rotary engine by means of
sealing strips which are attached to or inserted at the rotary
pistons. An exhaust gas pressure acts on the sealing strips and
pushes these against the inner surface of the housing, which
produces a particularly good sealing. The exhaust gas pressure thus
leads to a certain deformation of the sealing strips which is
important for an efficient sealing.
[0022] Such a deformation would not or hardly be possible if the
whole outer circumference of a rotary piston were formed rigidly,
in particular from the same material.
[0023] The sealing exhaust gas pressure may already be reached at a
comparably low pressure. Furthermore, the viscosity of the exhaust
gas only plays a minor role. The rotary engine of the invention may
thus be deployed for many different exhaust gas compositions and
under very different pressures. As a further advantage, lubricants
or lubricating oils are not required with the rotary engine of the
invention.
[0024] A particularly good sealing may be achieved if the sealing
strips comprise a deformable or elastic material so that the
sealing strips may be pushed/deformed by the exhaust gas against
the housing inner surface. The material of the sealing strips is
easier deformable or more elastic than a material of the rotary
piston surrounding the sealing strips, in particular easier
deformable or more elastic than the material in which the slots for
receiving the sealing strips are formed, which slots are described
in more detail further below.
[0025] The rotary pistons are sized and positions in the inner room
such that the exhaust gas can only flow from the inlet opening to
the outlet opening if the rotary pistons are thereby rotated. In
other words, the two rotary pistons provide for a sealing at
standstill such that no exhaust gas can flow through the inner room
without rotation. For this sealing, a contact of the two rotary
pistons is necessary. This contact provides that little or no
exhaust gas may pass through the two rotary pistons. On the other
hand, also a contact of the two rotary pistons to the housing inner
surface is necessary for said sealing. This contact is provided for
at least at a side facing outwards of the respective rotary piston,
which is opposite the contact area between the rotary pistons. For
example, by means of its sealing strips, each rotary piston may
provide for a sealing contact with a neighbouring housing inner
surface through an angle range of at least 150.degree., preferably
at least 180.degree. and particularly preferably more than
180.degree..
[0026] The sealing strips may extend in a longitudinal direction
which is substantially parallel to the rotation axes of the two
rotary pistons. In particular, an angle between the longitudinal
direction and the rotation axes may be smaller than 20.degree.,
preferably smaller than 10.degree..
[0027] The two rotation axes of the two rotary pistons may be
parallel to each other or at an angle which is not more than
40.degree. or preferably not more than 20.degree.. Furthermore, the
two rotary pistons may be formed identically. If asymmetric sealing
strips are used, as described further below, the rotary pistons may
be identical to each other except for a mirror-inverted design or
shape.
[0028] A rotary piston may be understood as a component that is
rotatably mounted and rotates a driveshaft when it rotates. The
rotation of the driveshaft may then be used to rotate other
components, for example, and/or to drive a generator for generating
electrical energy.
[0029] For attaching the sealing strips at the rotary pistons, the
sealing strips may be accommodated in slots, i.e., grooves or
similar recesses, formed at the respective outer circumference of
the rotary pistons. In particular, the slots may be formed in the
gear rims of the rotary pistons which are described in more detail
further below. The sealing strips may be attached in the slots in
basically any manner. The sealing strips may thus be exchangeable,
thus allowing easy replacement of the sealing strips when necessary
because of wear due to the sealing contact; without the necessity
to replace further components of the rotary engine.
[0030] In a preferred variant, the sealing strips are formed as
slot nuts for securely engaging with the slots in the rotary
piston. This may be understood such that the sealing strips
comprise a widening or a collar at their respective inner end which
is received in the corresponding rotary piston. The slots which
receive the sealing strips are formed such that said widening or
collar securely engages with the slot.
[0031] In particular, the slots may be formed as T-slots and each
of the slot nuts may comprise a laterally protruding collar for
engagement with one of the T-slots. In a cross-section traverse or
perpendicular to the rotation axis of the corresponding rotary
piston, the slots may have the shape of a T. An end of the slot
nuts facing the inner side of the rotary piston also has a T-shape
such that the slot nuts are secured in the T-slot. In principle,
threaded fasteners or adhesive attachments may also be provided for
securing the sealing strips in the slots.
[0032] More generally but in particular in the above examples, the
sealing strips and the corresponding slots may be formed such that
the sealing strips are secured, i.e., cannot be moved, in a radial
direction of the corresponding rotary piston. In contrast, in a
perpendicular direction hereto, for example, in particular in the
direction of the rotation axis of the rotary piston, a movement
(and thus insertion and replacement) of the sealing strips may be
possible. It is thus easily possible to replace worn or used
sealing strips.
[0033] The sealing effect between the sealing strips and the
housing inner surface depends on the deformation of the sealing
strips. It may be preferable if the exhaust gas pressure causes a
deformation of the sealing strips towards the housing inner surface
and not a deformation of the sealing strips away from the housing
inner surface. Each of the sealing strips has a surface which faces
incoming exhaust gas, for a rotation angle position of the rotary
piston at which the sealing strip contacts the housing inner
surface. In the following, this surface is referred to as the
exhaust gas contact surface or as the surface facing incoming
exhaust gases. For providing a deformation for sealingly contacting
the housing inner surface, the exhaust gas contact surface may
preferably not have a convex shape or at least may not have a
convex shape at its end facing the housing inner surface. It may be
preferable that the exhaust gas contact surface may rather have a
concave shape or at least may have a concave shape at its end
facing the housing inner surface. Alternatively, also a
substantially plane extension of the exhaust gas contact surface
may provide a sufficient deformation, depending on the
circumstances.
[0034] Each sealing strip has a rear side opposite the exhaust gas
contact surface. This rear side does not face incoming exhaust gas
when a rotation angle position of the rotary piston is such that
the sealing strip contacts the housing inner surface or is next to
the housing inner surface. The shape of the rear side also has
consequences on the deformation and thus sealing effect. It may be
preferable that the rear side is not concave or at least not
concave at an end facing the housing inner surface. It may be
preferable that the rear side is convex or has a convex end facing
the housing inner surface. A sufficient sealing effect may also be
possible with a linear or plane shape of the rear side.
[0035] The sealing strips may comprise an edge at which a sealing
contact to the housing inner surface is achieved. An edge may
result from a cross-section that is not rounded, in particular when
the exhaust gas contact surface is concave or the rear side is
convex.
[0036] It may be preferable that each rotary piston comprises (in
particular exactly) two sealing strips at opposite angle positions
at its respective outer circumference. In particular, the two angle
positions may be offset to each other by a rotation angle of
180.degree. about the rotation axis of the corresponding rotary
piston. Furthermore, each rotary piston may comprise two recesses
which are located at the outer circumference at angle positions
that are also offset to each other by 180.degree., and are
preferably offset to the angle positions of the two sealing strips
by 90.degree.. This has the effect that incoming exhaust gas always
pushes against one of the sealing strips at each rotary piston and
thus causes rotation of the rotary piston. Furthermore this design
has the effect that a sealing of the two rotary pistons to the
housing inner surface is provided independently from a current
rotation position of the rotary piston.
[0037] The sealing strips may be sized and a housing inner surface
may be formed such that the sealing strips sealingly contact the
housing inner surface within a rotation angle range of the rotary
piston. This rotation angle range may be opposite to a contact area
between the two rotary pistons. Depending on the rotary position of
the rotary piston, at least one of the sealing strips thus contacts
the housing inner surface. It may be preferable that the shape of
the housing inner surface is such that two sealing strips instead
of just one sealing strip contact the housing inner surface over a
rotary angle range, which may be between 5.degree. and 20.degree.,
for example. Such an overlap ensures for all rotary positions that
no exhaust gas may pass the rotary pistons without rotating the
rotary pistons.
[0038] Each rotary piston may comprise a gear rim at its outer
circumference. The rotary pistons may be arranged such that its
gear rims intermesh. This substantially prevents exhaust gas from
passing between the two rotary pistons. The exhaust gas is rather
guided at the edge/perimeter between the rotary pistons and the
housing inner surface.
[0039] The gear rims may be interrupted or broken by the recesses
and the sealing strips, and otherwise may extend over the whole
circumference of the two rotary pistons. A gear rim may be
understood such that an outer circumferential surface of the
corresponding rotary piston comprises radially protruding teeth. It
may be preferable that each tooth extends over the whole height of
the rotary pistons along their rotary axes.
[0040] In particular temperature variations may slightly change the
relative position between the two rotary pistons. The
intermeshing/engagement of the gear rims may, however, provide a
sealing effect also with such positional variations. In contrast,
the gear rims would be unsuited to provide a sealing towards the
housing inner surface. Here no intermeshing teeth are provided and
thus positional variations would lead to leakage currents. To avoid
this, a sealing to the housing inner surface is not provided with
the gear rims but with the sealing strips.
[0041] Depending on a rotary position of the two rotary pistons, a
substantially sealing contact between the rotary pistons is
provided either by the intermeshing gear rims or by one of the
sealing strips of one rotary piston which protrudes into one of the
recesses of the other rotary piston.
[0042] In a radial direction, the sealing strips may protrude
further outwards from the respective rotary piston than the
respective gear rim. The gear rim is thus always spaced apart from
the housing inner surface. A free space is thus formed in between,
through which exhaust gas is passed in the direction of the outlet
opening. The free space is limited in the circumferential direction
of the rotary pistons by the sealing strips.
[0043] The sealing strips protrude over the respective gear rim
preferably by a radial distance which is between 5% and 30%, in
particular between 10% and 25%, of a radius of the gear rim. This
radius may be defined starting at the center point of the rotary
piston to the outer circumference of the respective gear rim. The
protruding radial distance affects the amount of a deformation of
the sealing strip and thus affects sealing properties. Furthermore,
the protruding radial distance is decisive for the amount of
exhaust gas that is led along/past the corresponding rotary piston.
It has become evident that with the above-mentioned values a good
sealing effect can be achieved und a high efficiency can be
achieved over a comparably large span of flow rate amounts.
[0044] A radial size of teeth of the gear rim is preferably not
more than 15%, preferably not more than 10%, of a radius of the
gear rim. In this way a exhaust gas flow between the two gear rims
is sufficiently reduced. Larger teeth may have, depending on the
exhaust gas, negative impacts of the exhaust gas flow. The radius
of the gear rim may be defined by the distance from its center
point to its outer circumference, i.e., to the outermost end of the
teeth.
[0045] The exhaust gas energy recovery system of the invention may
in general also be configured to use the heat energy of the exhaust
gas in addition to the pressure of the exhaust gas to generate
electrical energy. For using the heat energy it may be preferred to
use an additional rotary engine which is designed as described
herein or to use the same rotary engine which is also used for the
exhaust gas pressure. If another rotary plunger (engine) is
provided, it can be arranged in a working fluid circuit in which a
working medium different from the exhaust gas circulates. Heat can
be transferred from the exhaust gas to the working fluid in the
working fluid circuit through a heat exchanger. The working fluid
may in principle be of any kind. The working fluid circuit is
designed as a thermodynamic cycle and comprises means for
converting heat energy of the exhaust gas into motion energy. For
example, the working fluid circuit may be designed as an organic
Rankine cycle (ORC) and may comprise the components required for
this. The rotary engine according to the invention is provided as
the engine of the thermodynamic cycle (or: as the turbine that is
used instead in such cycles). The passing-through exhaust gas is
relaxed in that engine and rotation of the rotary pistons is thus
caused. Instead of an ORC process, also other thermodynamic cycles
may be used, in which cycles an engine is driven by heat energy.
The thermodynamic cycle may for example comprise a feed pump, a
heater or the heat exchanger, the rotary engine of the invention
and a condenser as well as optionally a recuperator. The invention
also relates to a vehicle, for example a passenger car or a truck
comprising an internal combustion engine, wherein the vehicle
comprises the exhaust gas energy recovery system according to the
invention.
[0046] The rotary engine is described with two rotary pistons. In
general, however, also further rotary pistons may be provided in
the same inner room or in another inner room. Furthermore, the
number of sealing strips and corresponding recesses may deviate
from the numbers indicated with respect to the different
embodiments.
[0047] The characteristics of the invention described as additional
device features shall also be understood as variants of the method
of the invention, and vice versa.
[0048] Further features and advantages of the invention are
described below with reference to the attached schematic figures in
which:
[0049] FIG. 1 is a schematic view of an embodiment of an exhaust
gas energy recovery system of the invention;
[0050] FIG. 1 is a cross-section of a rotary engine of the exhaust
gas energy recovery system of FIG. 1; and
[0051] FIG. 3 is an enlarged detail of FIG. 2.
[0052] Similar components and components with similar effects are
generally indicated with the same reference signs throughout the
figures.
[0053] FIG. 1 shows a schematic view of an embodiment of an exhaust
gas energy recovery system 200 according to the invention. The
system serves for generating electrical energy from energy from the
exhaust gases emitted by a combustion machine (not depicted). The
combustion machine may in particular be an internal combustion
engine of a vehicle, however the invention is not limited to
this.
[0054] The exhaust gas energy recovery system 200 comprises as
important components a motor/generator unit 101 and an exhaust line
system 111 which is configured to guide exhaust gases through an
engine 100 of the motor/generator unit 101 and to drive the engine
100 in this way. The exhaust gas pressure is thus used to drive the
engine 100. Advantageously, the exhaust energy provided by the
pressure can be used for electricity generation.
[0055] The exhaust line system 111 comprises a line 110 which
transports exhaust gases from a combustion engine which is not
shown here. Further components, in particular a turbocharger, may
be arranged between the combustion engine and the depicted
line.
[0056] The line 110 leads to a fork at which the exhaust gas
flowing through line 110 are guided into a first line arm 124
and/or a second line arm 122. This is controlled by a control
device arranged at the fork, e.g., by a valve or shutter. The
shutter is rotatably mounted wherein its rotation position defines
in which proportions the exhaust gases are guided into the two line
arms 122 and 124. While line arm 124 guides exhaust gas through the
engine 100, the other line arm 122 bypasses the engine 100.
Subsequently both lines 122 and 124 are united. The exhaust gas may
then be further transported and processed in generally known ways.
For example, it may be transported through an exhaust gas
processing system 130 which serves for cleaning or filtering the
exhaust gases.
[0057] The engine/generator unit 105 comprises, in addition to the
engine 100, also a generator 105 which generates electrical energy
by means of the rotational energy provided by the engine 100. To
this end, the generator 105 may in particular be arranged on the
shaft of the engine 100.
[0058] The electrical current output by the generator 105 may, for
example, be transported to the battery of any consumers. If the
exhaust gas energy recovery system is part of a vehicle, the
consumers may be any components of the vehicle. Furthermore, a
storage (not depicted in FIG. 1) may be provided in addition to the
vehicle battery and loaded by the electrical current. This storage
may for example be a Lithium ion battery or a (super)
capacitor.
[0059] The engine 100 may be of any kind, however, it must be
suitable for being driven by exhaust gases. Furthermore, it should
have a particularly high efficiency at rather low exhaust gas
pressures. This is achieved with an engine 100 which is described
below with reference to FIGS. 2 and 3.
[0060] FIG. 2 shows schematically a cross-section of an embodiment
of an engine 100 which is formed as a rotary engine 100. An
enlarged detail thereof is shown in FIG. 3.
[0061] The rotary engine 100 comprises as important components two
rotary pistons 20 and 30 which are arranged in an inner room 11
which is limited by a housing inner surface 12 of a housing 10.
[0062] An inlet opening 13 which is not shown in more detail allows
exhaust gas to enter the inner room 11. The inlet opening 13 is
connected with the first line arm of FIG. 1. An outlet opening 15
is furthermore provided at the inner room 11. If the exhaust gas
flows from the inlet opening 13 through the inner room 11 to the
outlet opening 15, it must pass both rotary pistons 20, 30, and has
to rotate these. The reference signs 21 and 31 mark the rotation
axes of the two rotary pistons 20 and 30. The rotation axes 21, 31
extend into the drawing plane.
[0063] The design of the rotary pistons 20, 30 is decisive for an
efficient functioning. The rotary pistons shall provide a sealing
to each other and a sealing to the surrounding housing inner
surface 12 so that the exhaust gas cannot reach the outlet opening
15 if the rotary pistons 20, 30 do not move.
[0064] Simultaneously, the rotary pistons 20, 30 should be easily
rotated by the exhaust gas, i.e., the rotary pistons 20, 30 should
already rotate at low pressure.
[0065] To this end, the two rotary pistons 20 and 30 comprise
sealing strips 25, 26, 35, 36 at their respective outer surfaces.
The outer surfaces may be regarded as the shell surfaces of
substantially cylindrical rotary pistons 20, 30. The sealing strips
25, 26, 35, 36 extend preferably over the whole height of the inner
room 11, wherein the height may refer to a direction of the
rotation axes 21, 31.
[0066] The rotary piston 20 comprises at least two, preferably
exactly two, sealing strips 25, 26. Similarly, the rotary piston 30
comprises at least two, preferably exactly two, sealing strips 35,
36. The sealing strips 25, 26, 35, 36 extend radially beyond the
remaining outer circumference of the respective rotary piston 20,
30. The sealing strips 25, 26, 35, 36 are preferably received in
slots at the respective rotary piston 20, 30, and may preferably
consist of a material different to the part of the rotary piston
20, 30 in which the slots are formed. The sealing strips 25, 26,
35, 36 may consist, in particular, of a deformable material, which
may be, for example, rubber, resin or a plastic material. In this
way the sealing strips 25, 26, 35, 36 may be slightly deformed by
exhaust gas flowing against it, and may thus be pressed against the
housing inner surface 12. In this way a particularly good sealing
to the housing inner surface 12 is achieved. In principle, the
sealing strips 25, 26, 35, 36 may also consist of a rigid material,
for example a metal. Alternatively or additionally the sealing
strips 25, 26, 35, 36 may be received with some leeway in their
respective slots, and thus the exhaust gas pressure can slightly
tilt the sealing strips 25, 26, 35, 36. In this way the sealing
strips 25, 26, 35, 36 may in principle also be pressed against the
housing inner surface 12.
[0067] The two rotary pistons 20, 30 are arranged in the inner room
11 such that they contact each other. In this way, a exhaust gas
flow between the rotary pistons is substantially ruled out. The
rotation axes 21 and 31 may be parallel to each other. However,
also a tilt between the rotation axes 21, 31 is possible as long as
a substantially sealing contact between the rotary pistons 20, 30
is ensured.
[0068] To this end, the rotary pistons 20, 30 also each comprise a
gear rim 23, 33 at the respective outer circumference, which gear
rim is rigidly connected with the remainder of the corresponding
rotary piston 20, 30. The two gear rims 23, 33 are sized and
arranged to intermesh. Thereby the two gear rims 23, 33 rotate
jointly and form hardly any free spaces between each other. It is
thus hardly possible for exhaust gas to flow between the two gear
rims 23, 33.
[0069] Furthermore, the rotary pistons 20 and 30 comprise recesses
27, 28 and 37, 38, respectively, at their respective outer
circumference. The number of recesses 27, 28 of the first rotary
piston 20 is equal to the number of sealing strips 35, 36 of the
second rotary piston 30. Similarly, the number of recesses 37, 38
of the second rotary piston 30 is equal to the number of sealing
strips 25, 26 of the first rotary piston 20. Furthermore the
recesses 27, 28, 37, 38 and the sealing strips 25, 26, 35, 36 are
arranged at the two rotary pistons 20, 30 such that the sealing
strips 25, 26 of the first rotary piston 20 mate with the recesses
37, 38 of the second rotary piston 30 when the two rotary pistons
20 and 30 rotate. Similarly the sealing strips 35, 36 of the second
rotary piston 30 mate with the recesses 27, 28 of the first rotary
piston 20. To this end, a recess and a sealing strip may alternate
in 90.degree. separations at the outer circumference of each rotary
piston 20, 30, for example. In other words, the two sealing strips
25, 26 are distanced from each other by an azimuth angle of
180.degree. (i.e., an angle of 180.degree. about the rotation axes
21). Also the two recesses 27, 28 are separated from each other by
an azimuth angle of 180.degree., and by an azimuth angle of
90.degree. relative to the sealing strips 25, 26. This is
analogously valid for the sealing strips 35, 36 and recesses 37, 38
of the other rotary piston 30. In general, also other angles are
possible. Other azimuth angles result in particular if there are
more than two sealing strips and two recesses per rotary piston 20,
30. Size and shape of the recesses are thus chosen such that the
sealing strips may be received therein, in particular in a sealing
manner.
[0070] Similar to the gear rims 23, 33, also the sealing strips 25,
26 35, 36 provide together with the recesses 27, 28, 37, 38 that
exhaust gas can hardly pass between the two rotary pistons.
[0071] Independent from a current rotary position, always one of
the sealing strips 25, 26 35, 36 of each rotary piston 20, 30 shall
provide a sealing to the housing inner surface 12. To this end a
rotation angle is relevant over which one and the same sealing
strip 25, 26 35, 36 causes a sealing to the housing inner surface
12. This rotation angle may be larger than 180.degree., as shown in
FIG. 2, and may for example be between 185.degree. and 240.degree..
To this end, the housing wall 12 may have the shape of a segment of
a circle at each rotary piston, wherein this shape forms a segment
of a circle which is larger than 180.degree. and thus forms more
than a semi-circle.
[0072] FIG. 3 shows in greater detail the reception of the sealing
strips 25, 26 35, 36 in their corresponding slots. The sealing
strip 35 is shown in its cross-section as an example for all
sealing strips 25, 26 35, 36. The sealing strip 35 may have the
shape of a profile, i.e., it may have the same cross-section
throughout its length (in particular in the direction of the
rotation axis 31). As shown, the cross-sectional shape forms a slot
nut. Towards the inner end of the sealing strip, a collar 35C is
formed, which engages with a T-shaped recess/slot. This inhibits
that the slot nut may inadvertently come loose out of the slot of
the rotary piston in a radial direction. Inserting and removing the
slot nut 35 is possible in the longitudinal direction, i.e., in the
direction of the rotation axis 31. By forming slot nuts, the
sealing strips can be easily secured. Furthermore, also replacement
is facilitated. This is relevant as gradual abrasion of the sealing
strips 25, 26, 35, 36 may occur and may thus make a replacement
necessary due to the sealing contact with the housing inner surface
12.
[0073] As shown in FIG. 2, the exhaust gas in the inner room 11
pushes against the rotary pistons 20, 30 and those sealing strips
25, 35 that face the inlet opening 13 in the momentary rotary
position of the rotary pistons 20, 30. This pressure causes
rotation of the rotary pistons 20, 30 in the direction of the
arrows shown in FIG. 2.
[0074] For the rotation and in particular for the sealing effect of
the sealing strips 25, 35, the shape of the sealing strips is
important. This is explained in more detail with respect to FIG. 3,
which shows a sealing strip 35 which protrudes radially from the
gear rim 33. The sealing strip 35 has a point of maximal radial
extension or an edge which extends into the paper plane (or in the
direction of the rotation axis 31). Starting from this edge, the
sealing strip 35 has a surface 35A or exhaust gas contact surface
35A facing the incoming exhaust gas (this is valid for rotation
positions in which the sealing strip 35 contacts the housing inner
surface 12). On the opposite side of said edge, the sealing strip
35 comprises another surface 35B which is referred to as a rear
side 35B. The rear side 35B does not face the incoming exhaust gas
when the sealing strip 35 contacts the housing inner surface
12.
[0075] The exhaust gas contact surface 35A comprises a recess or a
concave shape, whereas the rear side 35B has an outwardly curved or
convex shape. In this way, the outer end of the sealing strip 35,
i.e., the radially furthest extending part, is deformed
transversely or approximately perpendicularly to the radial
direction by the exhaust gas flowing against it. The sealing strip
35 is thus pressed against the housing inner surface 12. In FIG. 3,
the lower end of the sealing strip 35 is deformed approximately to
the left and thus against the housing inner surface 12.
[0076] Advantageously, in this way a particularly good sealing is
provided, without however causing unduly high friction between the
sealing strips and the housing inner surface. Advantageously,
already at a comparably low exhaust gas pressure, the rotary
pistons may thus be set in rotation. Also exhaust gases at low
pressure may thus be employed for energy usage.
[0077] The sealing strips may have other shapes than the described
shapes. For example, it may thus suffice if the exhaust gas contact
surface or the rear side is formed as described. The other side
may, for example, be flat or shaped like the other side. It is also
possible that the described shapes of the exhaust gas contact
surface and the rear side are only formed at an end portion of the
sealing strips and not across the whole part that radially
protrudes beyond the corresponding gear rim. It may generally
suffice for sufficient sealing properties if the sealing strips are
deformable or movable relative to the gear rim and are, in
particular, not formed integrally with the gear rim. As a central
idea the exhaust gas pressure produced by a combustion engine can
be used to generate electrical energy. This is possible with an
engine which is preferably formed by the described rotary
engine.
* * * * *