DE102010047518A1 - Device for energy recovery from exhaust stream of internal combustion engine in vehicle, has working medium that is guided in closed joule-cyclic process in waste heat recovery device - Google Patents

Abstract

The device (1) has a working medium (AM) that is guided in a closed joule-cyclic process in a waste heat recovery device (3). An electric machine (15) is mechanically coupled with an internal combustion engine (2). The electric machine and the internal combustion engine occur in interaction such that the electric machine acts as a starter or as a generator on the internal combustion engine.

Description

The invention relates to a device for energy recovery from an exhaust gas stream of an internal combustion engine according to the preamble of claim 1.

Modern internal combustion engines have efficiencies in the range of 30% to 40%. As a result, a large part of the chemical energy supplied to the internal combustion engine in the form of waste heat is preferably delivered to a vehicle environment via a coolant and an exhaust gas heat.

Known techniques for energy recovery from the exhaust stream of an internal combustion engine are the exhaust gas turbocharger and the heating systems for motor vehicles. In the exhaust gas turbocharger, the exhaust gas flow drives a turbine. The energy that the turbine supplies uses a compressor to compress the air supplied to the engine. The compression of the air improves a cylinder filling of the internal combustion engine and thus leads to an increase in performance of the internal combustion engine.

Alternatively, the internal combustion engine is followed by a cycle in which the hot exhaust gas flow and partly the coolant of an internal combustion engine is used as a heat source for operating a second, downstream machine in the cycle. The cyclic process is usually a so-called Clausius-Rankine process, in which a liquid medium absorbs heat, which is predominantly evaporated with the supply of heat and then expanded in an expansion machine with release of mechanical energy to an output shaft. As a working medium come here organic agents, a mixture of such organic agents, alcohol mixtures or water-alcohol mixtures, water with certain additives into consideration. Of course, a Joule process, in particular a closed Joule process is conceivable in which a gas is conveyed via a compressor to a correspondingly high pressure level and is transmitted in an exhaust gas heat exchanger, exhaust heat of the engine to the working gas located in the Joule cycle. This compressed and heated working gas is then expanded to release mechanical work in an expansion machine and recooled in a cooler before being fed back to the compressor.

Furthermore, the waste heat recovery units known from the general state of the art are in part relatively complex and expensive in their construction, which leads to a high space requirement and a high complexity associated with high costs.

An electric machine in the form of a conventional alternator or generator is present on any conventional internal combustion engine to provide electrical energy for control of the internal combustion engine and / or other electrical consumers in a vehicle.

The invention has for its object to provide a device for recovering energy from the exhaust stream and at least partially from the coolant of an internal combustion engine, in which the energy recovery is increased as compact as possible space of the device.

With regard to the device, the object is achieved by the features specified in claim 1.

Advantageous developments of the invention are the subject of the dependent claims.

In the apparatus for recovering energy from an exhaust gas stream of an internal combustion engine in a vehicle in a waste heat recovery device, a working medium is guided in a closed Joule cycle and the closed Joule cycle is followed by a Rankine cycle, wherein a arranged in the Joule cycle turbine and an expansion machine arranged in the Clausius-Rankine cycle can be mechanically coupled to a flywheel of the internal combustion engine.

According to the invention, at least one electric machine can be mechanically coupled to the internal combustion engine, the electric machine and the internal combustion engine interacting in such a way that the electric machine acts as a starter or as a generator on the internal combustion engine.

Thus, the electric machine is integrated into the waste heat recovery device and the internal combustion engine such that a high overall efficiency of the device is possible while minimizing the space, weight and cost.

Particularly advantageously, conventional devices and functionalities, such as, for example, a starter, an alternator and an on-board power supply, are combined in the electric machine. As a result, these devices and functionalities as an electric machine are in the waste heat recovery device and the internal combustion engine can be integrated, whereby the overall efficiency of the device is improved.

The energy recovery from the exhaust gas flow of internal combustion engines is improved by the exhaust side of the internal combustion engine, a waste heat recovery device is switched. In particular, the exhaust gas flow leaving the exhaust gas heat exchanger of the exhaust heat recovery device has such thermal energy, which advantageously enables the operation of the waste heat recovery device. An energy recovery carried out in this way has a higher efficiency compared to conventional internal combustion engines. In addition, fuel savings are achieved and the costs are significantly reduced due to the compact design.

Embodiments of the invention are explained in more detail below with reference to drawings.

Showing:

1 1 schematically shows an embodiment of an apparatus for recovering energy from an exhaust gas stream of an internal combustion engine, wherein the electric machine is arranged in the force flow between the expansion engine and the flywheel of the internal combustion engine,

2 2 schematically shows an alternative embodiment of a device for recovering energy from an exhaust gas stream of an internal combustion engine, wherein the electric machine is arranged in the force flow between turbine and flywheel of the internal combustion engine,

3 1 schematically shows a further alternative embodiment of a device for energy recovery from an exhaust gas stream of an internal combustion engine, wherein the electric machine is coupled directly to the flywheel of the internal combustion engine,

4 1 schematically shows a further alternative embodiment of a device for energy recovery from an exhaust gas stream of an internal combustion engine, which is part of a serial hybrid drive device, wherein a first electric machine is coupled directly to the flywheel of the internal combustion engine and a second electric machine is arranged in the force flow between expansion engine and flywheel of the internal combustion engine,

5 1 schematically shows a further alternative embodiment of a device for energy recovery from an exhaust gas stream of an internal combustion engine, wherein the electric machine is coupled directly to the flywheel of the internal combustion engine,

6 schematically another alternative embodiment of an apparatus for energy recovery from an exhaust stream of an internal combustion engine, which is part of a serial hybrid drive device, wherein a first electric machine is coupled directly to a drive shaft of the internal combustion engine and a second electric machine is arranged in the power flow between the expansion engine and flywheel of the internal combustion engine and

7 schematically another alternative embodiment of a device for energy recovery from an exhaust stream of an internal combustion engine, wherein the electric machine is directly coupled to the flywheel of the drive shaft of the internal combustion engine.

Corresponding parts are provided in all figures with the same reference numerals.

1 shows a device 1 for energy recovery from the exhaust gas flow AG of an internal combustion engine 2 , In the internal combustion engine 2 it may be a conventional diesel or gasoline engine or another combustion engine, for. B. a vehicle, in particular a motor vehicle or commercial vehicle act. 1 shows a 4-cylinder internal combustion engine.

Exhaust side of the internal combustion engine 2 is a waste heat recovery device 3 downstream. The waste heat recovery device 3 is preferably formed as a closed Joule cycle JK.

The Joule cycle JK is a thermodynamic cycle, according to physicist James Prescott Joule. The closed Joule cycle JK includes an exhaust gas heat exchanger 4 , The primary side is flowed through by the exhaust stream AG and the secondary side is flowed through by a working medium AM of the Joule cycle JK.

On the primary side, an exhaust pipe opens 5 in the exhaust gas heat exchanger 4 and starts from this again.

Secondary side is the exhaust gas heat exchanger 4 in the Joule cycle JK on the input side a compressor 6 upstream. On the output side is the exhaust gas heat exchanger 4 in Joule cycle JK a turbine 7 downstream. Between the turbine 7 and the compressor 6 is closed Joule cycle JK a cooler 8th , in particular a recooler or gas cooler arranged. The compressor 6 and the turbine 7 are on a common wave 9 arranged.

Instead of the turbine 7 can also another expansion machine, z. B. a piston expansion machine can be used.

The hot exhaust gas flow AG of the internal combustion engine 2 is used to heat the Joule cycle JK downstream (especially the closed gas turbine process). This is particularly advantageous because especially the hot exhaust gases from an energetic and thermodynamic point of view have a temperature level that is capable of working and thus can lead to a relatively high overall efficiency. This is also advantageous from the point of view of construction costs with less space requirement, lower costs, lower weight, since the expense for the downstream Joule cycle JK is indeed present, but by using the high and thus thermodynamically working temperature levels to a relatively high efficiency gain in comparison for non-use of the temperature level of the exhaust stream AG leads.

At the wave 9 is a clutch 10 arranged, by means of which the shaft 9 and as a result the turbine 7 with a gear 11 can be coupled mechanically separable. The gear 11 stands with a flywheel 12 the internal combustion engine 2 engaged.

The recooling of the working medium AM of the Joule cycle JK takes place in the cooler 8th by means of the Joule cycle JK downstream Clausius-Rankine cycle CK. The Clausius-Rankine cycle CK and the Joule cycle JK are by means of the cooler 8th thermally coupled. Due to the heat transfer from the Joule cycle JK (recooling) to the Clausius-Rankine cycle CK (evaporation), a working medium AT in the cooler, which is guided in the Clausius-Rankine cycle CK 8th evaporates and overheats or at least evaporates. The cooler 8th For this purpose, it is designed as a recooler / evaporator, which is arranged on the primary side in the Joule cycle JK and on the secondary side in the Clausius-Rankine cycle CK. The overheated or vaporized working fluid AT then becomes the Clausius-Rankine cycle CK of an expansion machine 13 fed, in which the working fluid AT is expanded and thereby cooled.

The expansion machine 13 is in particular designed as a steam turbine or another steam expansion machine and by means of a further coupling 14 separable with an electric machine 15 coupled. The electric machine 15 is by means of another coupling 16 with a gear 17 coupled with the flywheel 12 the internal combustion engine 2 engaged. Thus, the means of the expansion machine 13 generated mechanical energy for vehicle drive and for generating electrical energy by means of the electric machine 15 available.

The electric machine 15 is electric with a conventional electric energy storage 18 , For example, a battery, a vehicle battery, a lithium-ion battery or a supercap (double-layer capacitor) connected.

That from the expansion machine 13 escaping agent AT is in a condenser 19 condensed and then again in liquid form by means of a feed pump 20 the radiator 8th fed.

That from the condenser 19 escaping, liquid working fluid AT is before entering the cooler 8th by means of the feed pump 20 increased to a corresponding pressure level. The working medium AT of the Rankine cycle CK is a liquid, in particular organic and / or inorganic, in particular hydrocarbon-containing working medium, such as. As methanol, ethanol, ammonia, ethers, other liquids and / or solutions of these. That is, it does not necessarily water to be used, but for example, a freezer-compatible hydrocarbon-containing working fluid, which is typically up to about 400 ° C resistant.

The in the expansion machine 13 generated mechanical energy is by means of the electric machine 15 converted into electrical energy and / or the flywheel 12 the internal combustion engine 2 fed.

The feed pump 20 can, as shown, be engine operated. For this purpose, for example, an electric motor 21 provided that the feed pump 20 driving.

The closed Joule cycle JK and this downstream Clausius-Rankine cycle CK are interconnected so that this is as simple and compact and allows use of the thermal energy of the exhaust stream AG on a very wide range of existing temperature levels, resulting in a high overall efficiency of the entire drivetrain or the overall aggregate leads.

All couplings 10 . 14 and 16 are designed as conventional, switchable couplings.

In operation of the device 1 is by means of the turbine 7 in the closed Joule cycle JK of the waste heat recovery device 3 from at least a subset of the thermal energy of the exhaust stream AG of the internal combustion engine 2 generates mechanical energy. The generated mechanical energy is generated by means of the coupling 10 and the gear 11 on the flywheel 12 the internal combustion engine 2 transferred and is available there for the vehicle drive. By means of the expansion machine 13 mechanical energy generated in the Rankine cycle cycle CK is generated by means of the electric machine 15 converted into electrical energy. Excess, from the expansion machine 13 generated mechanical energy, which is not by means of the electric machine 15 is converted into electrical energy, by means of the coupling 16 and the gear 17 on the flywheel 12 the internal combustion engine 2 transferred and is available there for the vehicle drive.

If no sufficiently hot exhaust gas flow AG is present, for example, directly after the start of the internal combustion engine 2 To operate the closed Joule cycle JK, the clutch becomes 10 at the start of the internal combustion engine 2 open until the working medium AM in the closed Joule cycle JK through the exhaust stream AG of the internal combustion engine 2 is sufficiently heated. Since the Joule cycle JK is not self-starting, the clutch becomes 10 closed at sufficiently heated working medium AM, so that the internal combustion engine 2 or the flywheel 12 the internal combustion engine 2 the wave 9 the turbine 7 and also on the wave 9 arranged compressor 6 drives briefly, so that the Joule cycle JK starts and is able to work. In the further course, the at the turbine 7 delivered mechanical energy supporting the internal combustion engine 2 fed. An otherwise conventional starter or a starter unit for starting the closed Joule cycle JK deleted advantageously, resulting in reduced costs, weight and space.

The means of the expansion machine 13 mechanical energy generated in the Rankine cycle cycle CK can be generated via the switchable clutch 14 the electric machine 15 be supplied. The electric machine 15 is for example designed as a motor-generator unit which converts mechanical energy into electrical energy. This engine-generator unit can serve to take over the on-board power supply of the vehicle in the operating states when the working means AT of the Rankine cycle CK, immediately after the start of the internal combustion engine 2 , not yet sufficiently heated to the expansion machine 13 drive. In this operating state is then the clutch 14 opened and there is no mechanical connection between the expansion machine 13 and the electric machine 15 , At the same time is the clutch 16 closed. Thus, the internal combustion engine takes over 2 which about flywheel 12 , Gear 17 and the closed clutch 16 in mechanical connection with the electric machine 15 stands and acts on these, the drive of the electric machine 15 , Thus, the on-board power supply or the provision of electrical energy is also possible if Joule cycle JK and Clausius-Rankine cycle CK are not yet able to work.

The trained as a motor-generator unit electric machine 15 is designed so that it can not only be operated as a generator, but also as an electric motor. This means that the motor-generator unit not only allows the generation of electrical energy, but also the start of the internal combustion engine 2 , The motor-generator unit thus assumes several functions and can both by the internal combustion engine 2 as well as from the downstream waste heat recovery device 3 be used. This integration of several functions in the electric machine 15 allows a lower total weight, reduced installation space and reduced costs for the entire device 1 , where the full functionality and maximum flexibility of the operation of the internal combustion engine 2 and the waste heat recovery device 3 are possible.

If more mechanical energy is generated in the Clausius-Rankine cycle CK than in or on the electric machine 15 consumed or converted, the two clutches can 14 and 16 be closed at the same time, so that in addition to the generation of electrical energy propulsion support of the internal combustion engine 2 is possible.

2 shows one to 1 very similar construction of the device 1 but with the difference that the electric machine 15 and the associated clutch 16 in the power flow between turbine 7 and flywheel 12 the internal combustion engine 2 are arranged. As a result, act in this embodiment, the internal combustion engine 2 and / or the turbine 7 of the Joule cycle JK on the electric machine 15 one.

Thus, the electric machine 15 not in the power flow between expansion machine 13 and flywheel 12 arranged. Between expansion machine 13 and gear 17 is the clutch 14 arranged.

In operation of this embodiment of the invention, the internal combustion engine 2 by means of the electric machine 15 started. These are the clutches 10 and 14 open, ie neither the Clausius-Rankine cycle CK nor the closed Joule cycle JK of the waste heat recovery device 3 can deliver mechanical energy at this time because the waste heat recovery device 3 , in particular the working means AT and the working media AM of the waste heat recovery device 3 , not enough heat energy from the exhaust stream AG of the internal combustion engine 2 have recorded. The coupling 16 is closed, ie there is a mechanical connection between the electric machine 15 and the internal combustion engine 2 , The electrical energy for the operation of the electric machine 15 as a starter is in this case from the electrical energy storage 18 made available. Have the individual components and the working fluid AT and the working media AM of the waste heat recovery device 3 heated enough, the clutch will 10 closed, leaving a mechanical connection between the shaft 9 on which the turbine 7 and the compressor 6 are arranged, and the electric machine 15 consists. Will the clutch 10 closed, the actual closed Joule cycle JK is started, which is then itself operable. For the period in which the Joule cycle JK can not deliver any mechanical energy, and thus the electric machine 15 can not drive in generator mode, the clutch remains 16 closed, allowing the drive of the electric machine 15 through the internal combustion engine 2 he follows. Thus, the on-board power supply is secured at virtually any time. Is the closed Joule cycle JK capable of sufficient mechanical energy to drive the electric machine 15 The Joule cycle JK can be the sole drive of the electric machine 15 take. That is, the clutch 16 is opened while the clutch 10 remains closed. Thus, the internal combustion engine 2 relieved, resulting in fuel savings and thus to increase the overall efficiency of the entire device 1 leads. The coupling 14 remains open until the Joule cycle JK in the cooler 8th has given sufficient heat to the working fluid AT the Clausius-Rankine cycle CK, so that it evaporates in sufficient quantity and the expansion machine 13 can give off mechanical energy. If the expansion machine 13 releases mechanical energy, the clutch becomes 14 closed and there is a mechanical connection between the expansion machine 13 and the flywheel 12 the internal combustion engine 2 , resulting in a further relief of the internal combustion engine 2 and a fuel saving result.

Produces the turbine 7 in the Joule cycle JK a greater amount of mechanical energy, as by the electric machine 15 is consumed, the clutch can 16 be closed, so that turbine 7 on the flywheel 12 and thus supportive of the internal combustion engine 2 acts.

Depending on the operating state and / or operating strategy of the waste heat recovery device 3 and the internal combustion engine 2 can the couplings 10 . 14 and 16 be switched so that the operation in an optimized manner to the requirement of the internal combustion engine 2 and / or the entire device 1 be adjusted.

3 schematically shows a further alternative embodiment of the device 1 for energy recovery from the exhaust stream AG of the internal combustion engine 2 , where the electric machine 15 directly with the flywheel 12 the internal combustion engine 2 is coupled.

In this embodiment, both the cycle of the Joule cycle JK and the cycle of the Rankine cycle CK of the waste heat recovery device 3 be very simple. The couplings 10 and 14 are used to generate the mechanical energy from the turbine 7 Joule cycle process JK and expansion machine 13 the Rankine cycle cycle CK only to drive support the internal combustion engine 2 to turn on when turbine 7 and / or expansion machine 13 give off mechanical energy and not unnecessarily from the internal combustion engine 2 must be driven with.

4 shows one to 1 very similar construction of the device 1 but with the difference that an additional generator 22 on the flywheel 12 the internal combustion engine 2 is arranged.

The generator 22 converts the entire mechanical energy of the internal combustion engine 2 into electrical energy, for example in a vehicle with a serial hybrid drive. The generator 22 Here, typically supplies high-voltage electrical energy for the traction motors of the hybrid vehicle, while the electric machine 15 as a starter for the internal combustion engine 2 and as a generator produces a voltage at the level of conventional vehicle electrical systems.

5 shows one to 3 very similar construction of the device 1 , but with the difference that in place of the electric machine 15 a generator 22 on the flywheel 12 the internal combustion engine 2 is arranged.

In this embodiment, the internal combustion engine 2 from the generator 22 started. For the on-board power supply of the vehicle is that of the generator 22 generated high voltage by means of a corresponding, not shown electrical transformer to the vehicle electrical system voltage of the vehicle transformed.

6 shows one to 4 very similar construction of the device 1 but with the difference that the generator 22 not on the flywheel 12 the internal combustion engine 2 is arranged. The generator 22 is on the opposite side of the internal combustion engine 2 on an output shaft 23 the internal combustion engine 2 arranged.

7 shows one to 5 very similar construction of the device 1 but with the difference that the generator 22 not on the flywheel 12 the internal combustion engine 2 is arranged. The generator 22 is at the flywheel 12 opposite side of the internal combustion engine 2 on the output shaft 23 the internal combustion engine 2 arranged.

In an advantageous, not shown embodiment, a regenerative preheating and / or a reheat can be arranged to increase the efficiency in Clausius Rankine cycle CK.

In a further advantageous embodiment, not shown, a so-called recuperator can be integrated in the Joule cycle JK.

In a particularly advantageous, not shown embodiment is a use of the waste heat of a coolant of the internal combustion engine 2 in the waste heat recovery device 3 allows.

Alternative to the gears 11 and 17 Conventional transmissions of different types can be used, for example, belt transmissions, chain transmissions, external gear or internal gear transmissions.

LIST OF REFERENCE NUMBERS

1

contraption

2

Internal combustion engine

3

Waste heat recovery device

4

Exhaust gas heat exchanger

5

exhaust pipe

6

compressor

7

turbine

8th

cooler

9

wave

10

clutch

11

gear

12

flywheel

13

expander

14

clutch

15

electric machine

16

clutch

17

gear

18

energy storage

19

capacitor

20

feed pump

21

engine

22

generator

23

output shaft

AT

work equipment

AT THE

working medium

AG

exhaust gas flow

CK

Rankine Cycle

JK

Brayton cycle

Claims (5)

Contraption ( 1 ) for energy recovery from an exhaust gas stream (AG) of an internal combustion engine ( 2 ) in a vehicle, wherein in a waste heat recovery device ( 3 ) a working medium (AM) is guided in a closed Joule cycle (JK) and the closed Joule cycle (JK) is followed by a Clausius-Rankine cycle (CK), whereby a turbine arranged in the Joule cycle (JK) (JK) 7 ) and an expansion machine arranged in the Clausius-Rankine cycle (CK) ( 13 ) mechanically with a flywheel ( 12 ) of the internal combustion engine ( 2 ) can be coupled, characterized in that at least one electric machine ( 15 ) with the internal combustion engine ( 2 ) is mechanically coupled, wherein electric machine ( 15 ) and internal combustion engine ( 2 ) in such a way that the electric machine ( 15 ) as a starter or as a generator on the internal combustion engine ( 2 ) acts. Contraption ( 1 ) according to claim 1, characterized in that the electric machine ( 15 ) directly or with the interposition of a coupling ( 16 ) with the internal combustion engine ( 2 ) is coupled to an output shaft ( 23 ) of the internal combustion engine ( 2 ) acts. Contraption ( 1 ) according to claim 1, characterized in that the electric machine ( 15 ) directly or with the interposition of a coupling ( 16 ) and a gear ( 11 . 17 ) with the Flywheel ( 12 ) of the internal combustion engine ( 2 ) is coupled. Contraption ( 1 ) according to claim 1 or 3, characterized in that the electric machine ( 15 ) in the power flow between expansion machine ( 13 ) and flywheel ( 12 ) of the internal combustion engine ( 2 ) is arranged. Contraption ( 1 ) according to claim 1 or 3, characterized in that the electric machine ( 15 ) in the power flow between turbine ( 7 ) and flywheel ( 12 ) of the internal combustion engine ( 2 ) is arranged.

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