DE102013207170A1 - Waste heat recovery system for an internal combustion engine - Google Patents

Abstract

The invention relates to a waste heat recovery system for an internal combustion engine 3, comprising a heat exchanger 1a, 1b connected to an exhaust pipe 5 of internal combustion engine 3, which is part of a working fluid circuit 8 with at least one expansion machine 9, a condenser 10 and a fluid pump 13. According to the invention, a possibility of using the power available from a waste heat recovery system to drive a high-pressure pump 23, in particular a common rail injection system, is shown. This is achieved in that the expansion machine 9 is directly or indirectly and a shaft 34 of the internal combustion engine 3 is controllably connected to a high pressure pump shaft of a high pressure pump 23 of a common rail injection system via a clutch system and / or a transmission system.

Description

The present invention relates to a waste heat recovery system for an internal combustion engine, comprising a switched on in an exhaust line of the internal combustion engine heat exchanger, which is part of a working fluid circuit with at least one expansion machine, a condenser and a fluid pump. Furthermore, the invention relates to a method for operating such a waste heat recovery system for an internal combustion engine.

State of the art

Such a waste heat recovery system is from the DE 10 2011 007 386 A1 known. The expansion machine is part of a waste heat recovery system on an engine system for a ship. In this case, the ship has two internal combustion engines whose exhaust systems are each connected to the system for waste heat recovery. These two systems have a common expansion machine in the form of a turbine designed as an expansion machine, which is traversed by a transferred through a heat exchanger of the respective exhaust pipe in the vapor phase fluid. The expansion machine or an output shaft of the expansion machine is rotationally connected to generate energy via a gear with a generator.

The invention is based on the object to provide a waste heat recovery system for an internal combustion engine, the deliverable power is useful usable.

Disclosure of the invention

Advantages of the invention

This object is achieved in that the expansion machine is connected directly or indirectly and / or a shaft of the internal combustion engine via a clutch system and / or a transmission system controllably connected to a high pressure pump shaft of a high pressure pump, in particular a common rail injection system. The corresponding method for operating the waste heat recovery system is characterized in that an expansion machine directly or indirectly and a shaft of the internal combustion engine via a clutch system and / or a transmission system controllably connected to a high pressure pump shaft of a high pressure pump, in particular a common rail injection system is connectable. This refinement or this method is based, first of all, on the knowledge that the recovered energy is converted into electrical energy by known waste heat recovery systems, which energy is then fed, for example, into the vehicle electrical system of a vehicle into which the internal combustion engine is installed. The overall efficiency of the system depends very much on whether this additional electrical energy is used at all, i. either stored in a battery or used directly by various electrical consumers in the vehicle. In addition, it should be taken into account that storage in, for example, a battery is associated with losses. These disadvantages are avoided by the embodiment according to the invention and the method according to the invention by the power provided by the waste heat recovery system is used to drive a high pressure pump, in particular a common rail injection system. It should be noted that in a conventional common rail injection system, the speed of the high-pressure pump is coupled with a fixed ratio to the speed of the internal combustion engine. The power required to drive the high-pressure pump increases proportionally to the set pressure in a high-pressure accumulator (rail) of the common-rail injection system and to the speed of the high-pressure pump (flow rate). An improvement of the energy efficiency is possible by a fuel inlet side (suction side) flow control of the high-pressure pump. In this case, the fuel flowing into the (possibly several) pump elements of the high-pressure pump is metered through a continuously variable solenoid valve, which is normally a metering unit (ZME). This solenoid valve adjusts the amount of fuel delivered to the high-pressure accumulator according to the system requirements. For example, such a high-pressure pump in a 2-liter 4-cylinder diesel engine with about 105kw requires a necessary mechanical drive power of 2kw to about 3kw at 300Nm (at maximum high-pressure accumulator pressure and maximum speed). Such power may be achieved by the exhaust heat recovery system at least at a vehicle speed above about 70km / km / h in vehicle applications.

In a development of the invention, the high-pressure pump shaft is connected via an initial coupling of the coupling system to the expansion machine. Furthermore, in an advantageous embodiment of the invention, the high-pressure pump shaft is connected via a second clutch of the clutch system with a shaft of the internal combustion engine. It can then be switched between the two clutches controlled or it can also be connected to the high-pressure pump shaft both with the expansion machine and with the shaft of the internal combustion engine. This variant will be chosen in particular when the power provided by the expander machine is not or not completely sufficient to drive the high pressure pump with the necessary power. In In this case, additional power is then removed from a shaft of the internal combustion engine and used to drive the high-pressure pump.

In a development of the invention, the coupling system has at least one proportional coupling. A proportional clutch has been particularly suitable for use in the clutch system according to the invention. In principle, however, any type of coupling system can be used in the subject matter of the invention.

In a further embodiment of the invention, the transmission system has at least one continuously variable transmission. The transmission system has, in a further embodiment, at least one planetary gear with a planetary gear bearing planetary gear, a ring gear and a sun gear. Such a planetary gear is tried and constructed structurally relatively simple. In this case, such a planetary gear with respect to the translation or einzuleitender drive power and different inputs in a simple manner controllable. As a result, the drive speed of the high-pressure pump can be set particularly advantageously independently of the speed of the internal combustion engine.

In a development of the invention, a shaft, in particular a crankshaft, of the internal combustion engine with the planet carrier, the expansion engine with the sun gear and the high-pressure pump shaft with the ring gear shaft are coupled. This connection of the planetary gear to the individual components has proven to be particularly suitable.

Again, in a further development of the invention, the shaft, in particular the crankshaft, the internal combustion engine coupled via the continuously variable transmission with the planet carrier. This integration of the continuously variable transmission (CVT transmission) is particularly suitable for making the portion of the power provided by the internal combustion engine for driving the high-pressure pump variable within wide limits with respect to the drive torque and / or the drive speed.

The control of the clutch system or the control of the planetary gear and the continuously variable transmission via actuators, which are controlled by a control unit. In this case, for example, in the planetary gear an individual support of the planet gears of the planetary gear set. In the clutch system, the necessary power of the high-pressure pump can be calculated from a high-pressure accumulator pressure to be calculated and the injection quantities injected by the fuel injectors into assigned combustion chambers of the internal combustion engine. The power available from the waste heat recovery system can be determined from the exhaust gas energy of the engine (via an exhaust gas mass flow and an engine operating point) and the efficiency of the waste heat recovery system. If the performance of the waste heat recovery system is sufficient, the expansion machine can be coupled with the high-pressure pump and the engine disengaged via the couplings. About the proportional couplings or differently designed couplings can be a jerk-free switching enable. The changing torque requirement of the internal combustion engine is taken into account via the moment coordination and then finally via the fuel injection. The reduced injection quantity when the waste heat recovery system is active corresponds basically to the saving due to the recuperation of exhaust gas energy.

In the transmission system with a planetary gear and a continuously variable transmission is a connection of the individual components as described above. The calculation of the performance shares is carried out as previously described.

A further advantageous embodiment is also the combination of an expansion engine, an internal combustion engine and another drive system, for example a hybrid drive (for example, electrically, pneumatically or hydraulically or any combination thereof). Such a system offers the advantage, with regard to the switching process, that this takes place smoothly can, because when engaging and / or disengaging the expansion engine and / or the internal combustion engine to the high-pressure pump of the hybrid drive briefly generate or recuperate corresponding mechanical power.

Further advantageous embodiments of the invention are described in the drawings, are described in more detail in the embodiments illustrated in the figures of the invention.

Brief description of the drawings

Show it:

1 a circuit diagram of a fluid circuit having waste heat recovery system from an exhaust stream of an internal combustion engine, wherein an expansion machine of the system and a shaft of the internal combustion engine is connected via a clutch system with a high pressure pump of a common rail injection system and

2 a circuit diagram of a fluid circuit having waste heat recovery system from an exhaust stream of an internal combustion engine, wherein an expansion machine of the system and a shaft of the internal combustion engine is connected via a transmission system with a high pressure pump of a common rail injection system.

Embodiments of the invention

This in 1 schematically represented waste heat recovery system has a heat exchanger 1a on top of one in an exhaust pipe 5 guided and the waste heat stream forming exhaust stream 2 an internal combustion engine 3 is flowed through. Additionally or alternatively to the heat exchanger 1a can be a heat exchanger 1b be provided in an exhaust gas recirculation line 4 is used. About the exhaust gas recirculation line 4 becomes the exhaust gas flow 2 taken a subset of exhaust gas and controlled the intake system of the internal combustion engine, not shown 3 fed. The two heat exchangers 1a . 1b may optionally be bypassed via bypass lines, for example, in certain operating conditions of the internal combustion engine or a vehicle in which the internal combustion engine is installed

The internal combustion engine 3 During operation, fuel and combustion air are supplied, which in combustion chambers produce hot gas to produce work, the continuous operation of the internal combustion engine 3 the exhaust gas flow 2 makes, burn. This is the exhaust gas flow 2 through the exhaust pipe 5 , from which also the exhaust gas recirculation line 4 branches off, being in the exhaust pipe 5 before and / or behind the heat exchanger 1a exhaust silencer 6 as well as facilities 7 for after-treatment of the exhaust gas may be incorporated in the form of, for example, a catalyst and / or a filter, ultimately discharged into the environment. The internal combustion engine 3 is in particular a self-igniting internal combustion engine, which is operated by diesel power. In this case, the diesel fuel is injected into the combustion chambers, for example by means of a common-rail injection system. The internal combustion engine can also be a spark-ignited gasoline-fueled internal combustion engine, which also has a common-rail injection system.

The heat exchanger 1a and the heat exchanger 1b are in turn part of a system for energy recovery from the exhaust stream 2 or the recirculated exhaust gas amount, a working fluid circuit 8th having. The working fluid circuit 8th points next to the heat exchangers 1a . 1b an expansion machine 9 , a capacitor 10 , if necessary, a condensate pump 11 , a compensation and storage tank 12 , a fluid pump 13 and a distribution valve 14 on. With the distribution valve 14 becomes the heat exchangers 1a . 1b supplied amount of the fluid adjusted. In addition to the designated components, for example, the output side of the heat exchanger 1a . 1b Temperature sensors, on the output side of the expansion machine 9 a temperature and a pressure sensor and the output side of the fluid pump 13 another pressure sensor is provided.

The expansion machine 9 may be a piston engine or a turbine. In the case of a turbine, a reduction gear is normally connected downstream in order to reduce the high turbine speeds and to the speeds of a high-pressure pump 23 preferably to adapt to a common rail injection system. The output of the piston engine or the output of the reduction gear are via an output shaft 18 mechanical energy for driving the aforementioned high-pressure pump 23 from. In the case of using a reduction gear on the expansion machine, a gearbox on the internal combustion engine can be omitted (or vice versa). The high pressure pump 23 must then be designed or constructed accordingly.

When operating the system for waste heat recovery is provided by the fluid pump 13 a fluid suitable for a Rankine process is brought to a high pressure and the heat exchangers 1a . 1b fed. The fluid is in the heat exchangers 1a . 1b heated and transferred under high pressure in the vapor state. The steam produced in this way becomes the expansion machine 9 fed and drives this. The expansion machine 9 is preferably a turbomachine, for example in the form of a turbine. To the working fluid circuit 8th at the expansion machine 9 can lead past, a bypass line 19 with a bypass valve 20 be provided on the the expansion machine 9 is bypassable. The expansion machine 9 but may - as previously stated - optionally be a piston engine and then directly to the output shaft 18 be connected.

The expansion machine 9 supplied fluid relaxes in this under the provision of mechanical shaft work, via the output shaft 15 (or directly through the output shaft 18 ) is discharged. Thereafter, the "cold" steam in the condenser 10 condenses and finally the fluid pump again 13 fed.

The output shaft 18 is in the embodiment according to 1 over a first clutch 21 a coupling system with a high pressure pump shaft 22 a high pressure pump 23 in particular a common rail injection system connected. In principle, however, the injection system can also be a different type of injection system. In the example of the common rail injection system promotes the high pressure pump 23 from a tank 24 from a low-pressure pump via a filter 25 supplied fuel controlled by a metering unit integrated in the high-pressure pump by a High pressure line in a high pressure accumulator 26 , The high-pressure accumulator 26 has a pressure relief valve 27 on, that via a fuel return line 28 with the tank 24 connected is. Also to the fuel return line 28 connected to the metering unit, the fuel pumped by the low pressure pump, which is not forwarded by the metering unit for delivery in the high-pressure accumulator, back into the fuel return line 28 absteuert. The high-pressure accumulator 26 has a number of high-pressure connections, which via injection lines 29 with fuel injectors 30 are connected. For clarity, in the figure, only one injection line 29 and a fuel injector 30 shown. By means of the fuel injectors is from the high-pressure accumulator 26 removed fuel controlled in associated combustion chambers of the internal combustion engine 3 injected. Leakage fuel of the fuel injectors 30 is via a leakage line 31 back to the low pressure line in front of the filter 25 derived.

The high pressure pump shaft 22 the high pressure pump 23 is via a second clutch 32 directly or via a continuously variable transmission 33 with a wave 34 , which is in particular the crankshaft, the internal combustion engine 3 , which is shown in fragmentary detail in the corresponding section of the figure connected. The first clutch 21 and the second clutch 32 For example, they are designed as proportional couplings as an embodiment and enable a smooth switching of the drive of the high-pressure pump shaft 22 from the expansion machine 9 to the wave 34 the internal combustion engine 3 , With sufficient performance through the expansion machine 9 becomes the high pressure pump shaft 22 from the expansion machine 9 driven. For the case, for example, at partial load operation or idling operation of the internal combustion engine 3 that the expansion machine 9 does not deliver sufficient power, the high pressure pump shaft 22 directly from the internal combustion engine 3 driven. If necessary, it is also conceivable that the internal combustion engine 3 supporting the drive of the high pressure pump shaft 22 is used. In this case, the first clutch must 21 and the second clutch 32 be designed so that such a dual drive is possible. The operation of the entire system is controlled by a control unit, which may be the advanced engine control unit: The control unit determines from the necessary power of the high-pressure pump 23 and the power available from the waste heat recovery system, in particular, the circuit of the first clutch 21 and the second clutch 32 ,

In the embodiment according to 2 is in contrast to the embodiment according to 1 the clutch system replaced by a transmission system. The waste heat recovery system and the injection system are analogous to the 1 built up. Accordingly, reference is made in this regard to the previous description. The transmission system has a planetary gear 35 with a planet wheels 36 bearing planet carrier, a ring gear 37 and a sun wheel 38 on. The output shaft 18 is with the sun wheel 38 , the planet carrier is direct or via the continuously variable transmission 33 with the wave 34 the internal combustion engine 3 and the ring gear 37 is with the high pressure pump shaft 22 connected. In this embodiment, always from the output shaft 18 introduced power in the planetary gear 35 introduced and to the high pressure pump shaft 22 forwarded. In addition, if required, required power from the internal combustion engine 3 in the planetary gear 35 initiated. In this case, the proportion of the internal combustion engine 3 to be provided power via the continuously variable transmission 33 be set. In the case of using a reduction gear on the expansion machine 9 can the continuously variable transmission 33 account for the internal combustion engine. When using a low-speed piston expansion machine and appropriate design of the planetary gear 35 can the reduction gear on the expansion machine 9 and the continuously variable transmission 33 omitted. Also controlled in this embodiment, the operation of the entire system of a control unit, which may be the advanced engine control unit: The controller determines from the necessary power of the high-pressure pump 23 and the power available from the waste heat recovery system, particularly the control of the planetary gear 35 and the continuously variable transmission 33 ,

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102011007386 A1 [0002]

Claims (11)

Waste heat recovery system for an internal combustion engine ( 3 ), having one in an exhaust pipe ( 5 ) of the internal combustion engine ( 3 ) switched-on heat exchanger ( 1a . 1b ), the part of a working fluid circuit ( 8th ) with an expansion machine ( 9 ), a capacitor ( 10 ) and a fluid pump ( 13 ), characterized in that the expansion machine ( 9 ) directly or indirectly and / or a wave ( 34 ) of the internal combustion engine ( 3 ) via a clutch system and / or a transmission system controllable with a high-pressure pump shaft ( 22 ) a high pressure pump ( 23 ) is connected in particular a common rail injection system. Waste heat recovery system according to claim 1, characterized in that the high-pressure pump shaft ( 22 ) via a first clutch ( 21 ) of the coupling system with expansion machine ( 9 ) connected is. Waste heat recovery system according to claim 1 or 2, characterized in that the high-pressure pump shaft ( 22 ) via a second clutch ( 32 ) of the coupling system with a shaft ( 34 ) of the internal combustion engine ( 3 ) connected is. Waste heat recovery system according to one of the preceding claims, characterized in that the coupling system has at least one proportional coupling. Waste heat recovery system according to one of the preceding claims, characterized in that the transmission system at least one continuously variable transmission ( 33 ) having. Waste heat recovery system according to one of the preceding claims, characterized in that the transmission system at least one planetary gear ( 35 ) with a planetary gear ( 36 ) bearing planet carrier, a ring gear ( 37 ) and a sun wheel ( 38 ) having. Waste heat recovery system according to claim 6, characterized in that the shaft ( 34 ), in particular the crankshaft of the internal combustion engine ( 3 ) directly or indirectly with the planet carrier, the expansion machine ( 9 ) with the sun wheel ( 38 ) and the high pressure pump shaft ( 22 ) with the ring gear ( 37 ) are coupled. Waste heat recovery system according to claim 7, characterized in that the shaft ( 34 ) of the internal combustion engine ( 3 ) via the continuously variable transmission ( 33 ) is coupled to the planet carrier. Waste heat recovery system according to one of the preceding claims, characterized in that a further drive system, for example a hybrid drive is present, the a jerk-free switching operation of the expansion machine ( 9 ) and / or the internal combustion engine ( 3 ) on the high pressure pump ( 23 ). Method for operating a waste heat recovery system for an internal combustion engine ( 3 ), having one in an exhaust pipe ( 5 ) of the internal combustion engine ( 3 ) switched-on heat exchanger ( 1a . 1b ), the part of a working fluid circuit ( 8th ) with at least one expansion machine ( 9 ), a capacitor ( 10 ) and a fluid pump ( 13 ), characterized in that the expansion machine ( 9 ) directly or indirectly and a wave ( 34 ) of the internal combustion engine ( 3 ) via a clutch system and / or a transmission system controllable with a high-pressure pump shaft ( 22 ) a high pressure pump ( 23 ) in particular a common rail injection system is connectable. Method for operating a waste heat recovery system according to claim 10, characterized in that a necessary power of the high-pressure pump ( 23 ) is calculated from an accumulator pressure to be achieved and an injection quantity to be achieved, that a power available from the exhaust heat recovery system from an exhaust gas energy of the internal combustion engine ( 3 ), and that, depending on the necessary power of the deliverable power, the drive control of the high-pressure pump ( 23 ) he follows.

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