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.

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 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

[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 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 (i.e., an angle of 180 about the rotation axes 21). Also the two recesses 27, 28 are separated from each other by an azimuth angle of 180, and by an azimuth angle of 90 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, as shown in FIG. 2, and may for example be between 185 and 240. 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 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.