WO2010000286A1

WO2010000286A1 - Exhaust gas energy recovery using an absorption-type refrigerating machine

Info

Publication number: WO2010000286A1
Application number: PCT/EP2008/005434
Authority: WO
Inventors: Knut Habermann
Original assignee: Fev Motorentechnik Gmbh
Priority date: 2008-07-03
Filing date: 2008-07-03
Publication date: 2010-01-07
Also published as: DE112008003887A5

Abstract

The invention relates to a method for operating an internal combustion engine (11) utilizing thermal exhaust gas energy, wherein heat from the exhaust gas of the internal combustion engine (11) is transmitted to the solution of an absorption-type refrigerating machine while driving the refrigerant out of the solvent.

Description

Exhaust gas energy utilization by means of an absorption chiller

description

The invention relates to a method for operating an internal combustion engine, is additionally used in the thermal energy of the exhaust stream, and an internal combustion engine with system components for the application of the method.

In an internal combustion engine, only a relatively small proportion of the chemically bound energy in the fuel used is converted into mechanical power, while a comparatively large proportion of the exhaust gas heat flows and the cooling water heat flows of the internal combustion engine are discharged unused into the environment. As far as internal combustion engines are considered for use in vehicles, the proportion of the mechanical energy used for the vehicle drive in relation to the applied chemically bound energy of the fuel is even lower, although the radiant heat losses, engine friction losses and transmission losses are relatively low.

With the increasing scarcity and increase in the price of fossil fuels, increasing the overall efficiency of internal combustion engines, including the use of exhaust gas energy, is becoming increasingly important.

In the publication "Waste heat recovery options for motor vehicles", Michael Hoetger, Jörg Collisi; 11th session "The working process of the internal combustion engine" 20/21. September 2007, describes how the exhaust heat of an internal combustion engine can be used by means of a closed quay process, wherein in an exhaust gas steam heat exchanger, which is located in the exhaust gas sträng is arranged behind the turbine of an exhaust gas turbocharger, the gas of the 2-substance mixture of the quay process is overheated and the gas energy is converted into mechanical energy in an expander.

The system described here uses the available exhaust heat by means of a complex mechanism. It is therefore an object of the present invention to provide a method for utilizing the exhaust gas energy of an internal combustion engine and an internal combustion engine of the type mentioned above, which permit additional use of the exhaust gas heat with simplified means.

The solution to this consists in a method for operating an internal combustion engine using thermal exhaust energy, in which heat from the exhaust gas stream of the internal combustion engine is transferred to the solution of a Absorptionskäl- temaschine while expelling the refrigerant from the solvent. An absorption chiller is a chiller in which, in contrast to the compression chiller, the compression takes place by means of a temperature-influenced solution of the refrigerant. This is also referred to as a thermal compressor. The refrigerant is absorbed in a solvent cycle at low temperature in a second material and desorbed at higher temperatures. The process uses the temperature dependence of the physical solubility of two substances. Prerequisite for the process is that the two substances in the temperature interval used in each ratio are soluble in each other. In a preferred embodiment, it is provided that the heat is expelled for expelling the refrigerant from the solvent to the exhaust gas before entering into facilities for exhaust aftertreatment.

In order to be able to work at a high temperature level, the exhaust gas flow should be deprived of the heat to expel the refrigerant before the facilities for exhaust aftertreatment, in particular in front of the turbine of an exhaust gas turbocharger, ie the expeller or the separator of the absorption refrigeration machine must be very close to the engine, for example in the Exhaust manifold can be arranged integrated. This has the advantage that at full load cooling the exhaust stream and thus a component protection of the facilities for exhaust aftertreatment (catalysts) and optionally the turbine of the exhaust gas turbocharger of the internal combustion engine takes place. However, in the case of acceleration from partial load or in similar operating states, at low load, during idling and during coasting, heat extraction from the exhaust gas is not permissible, so that the drive and the acceleration of the exhaust gas turbocharger is not impaired. That is, the flow of the solution through the expeller must be interrupted in phases. Appropriate control means are provided in the solution cycle of the absorption chiller. This leaves sufficient energy for the drive of the exhaust gas turbocharger and thus for the undisturbed operation of the internal combustion engine available in case of need.

In order to ensure the proper functioning of the facilities for exhaust aftertreatment (catalysts), can generally be provided that the exhaust gas is withdrawn heat only at an exhaust gas temperature of about 800 ⁰ C and transferred to the solution of the absorption chiller, while the absorption cooling process exposed below this exhaust gas temperature or is interrupted. At higher exhaust gas temperatures is due to the removal of heat from the exhaust gas already mentioned component protection for the facilities for exhaust aftertreatment and optionally for the turbine of the exhaust gas turbocharger.

In an internal combustion engine with exhaust gas recirculation can in favorable process management additionally exhaust heat in a heat exchanger in the exhaust gas recirculation, which is upstream of the expeller in the solution cycle, be used in addition to the preheating of the solution.

According to a further special process control is provided that the exhaust gas flow of the engine additionally heat in a further heat exchanger behind the facilities for exhaust aftertreatment and optionally behind the turbine of an exhaust gas turbocharger of the engine removed and fed to the solution circuit for preheating the solution. The latter two process supplements can be used individually or both together in combination to preheat the solution before the phase separation in near-motor expeller.

According to a preferred embodiment, if a solution is used from which different refrigerants can be expelled at different temperatures, said further heat exchangers can also be used as further expulsions for the different refrigerants.

On the other hand, by means of suitable control means and bypass lines, depending on the exhaust gas temperature, in each case one of the expeller can be selectively acted on or bypassed. With this, even in the case of a solution with only one refrigerant, the operation of the refrigerating machine can be ensured in a further temperature range of the exhaust gas of the internal combustion engine in which the location of the phase separation relative to the exhaust gas line of the internal combustion engine is changed when the exhaust gas temperature behind the internal combustion engine changes.

The expeller (s) is followed by a condenser in the refrigerant branch of the absorption chiller, which may be e.g. can be externally cooled with cooling air. For cooling the condenser, the cooling water of the internal combustion engine can also be used. This is followed by a throttle and an evaporator, in which the refrigerant absorbs heat again. In a preferred embodiment, it may be provided to integrate the evaporator of the absorption chiller in the air intake line of the internal combustion engine as an additional intercooler. After the evaporator, the refrigerant branch and the solution circuit are combined again in an absorber to dissolve the refrigerant in the solvent.

The solution pump of the absorption process can be driven electrically or mechanically directly from the internal combustion engine. The invention, which has been described above from the point of view of process management, includes an internal combustion engine with means for utilizing thermal exhaust energy, in which the exhaust line of the internal combustion engine, a primary expeller is used, which is part of an absorption chiller, the one before the expeller lying solution pump, downstream of the expeller capacitor, a downstream of the condenser and a downstream evaporator, from which the refrigerant finally reaches the absorber, in which the refrigerant branch is returned to the solution cycle.

Particular embodiments of this internal combustion engine with absorption chiller, which are in particular in the arrangement of different heat exchangers in the line strands of the internal combustion engine and in the solvent circuit of the refrigerator, are described in subclaims, to which reference is made here.

Preferred embodiments of an internal combustion engine according to the invention with integrated absorption refrigeration system are shown in the drawing.

Figure 1 shows a system diagram in the basic structure with a front of the facilities for exhaust aftertreatment before the turbine of an exhaust gas turbocharger of the internal combustion engine arranged expeller of the integrated absorption chiller.

Figure 2 shows a system scheme similar to Figure 1 with three arranged in the exhaust system of the internal combustion engine expeller of the integrated absorption chiller and additional control means.

FIG. 1 shows a system diagram which reveals a four-cylinder internal combustion engine 11 with an air intake line 12 and an exhaust line 13. It is a supercharged internal combustion engine with an exhaust gas turbocharger 14, the compressor 15 in the air intake line 12 of the combustion engine. engine 11 is located and the turbine 16 is located in the exhaust line 13 of the engine. Compressor 15 and turbine 16 of the exhaust gas turbocharger 14 are mechanically coupled to each other via a shaft 18.

It is also an integrated therein absorption chiller 21, the working medium is a solution (2-substance mixture) and comprising a solvent circuit 30 and a refrigerant branch 25. The solvent circuit 30 of a solution pump 22 via a tertiary heat exchanger 26, which is located in the exhaust line 13 of the internal combustion engine 11 behind the turbine 16 of the exhaust turbocharger 14, via a secondary heat exchanger 27 which is in the Abgasrück- strand 20 from the exhaust line 13 to the air intake line 12, to an expeller / separator 28, which is traversed by the exhaust line 13 and in which refrigerant, which is continued in a refrigerant branch, is expelled from the solvent, which is continued in a solvent circuit 30. While the expeller 28 is a necessary component of the absorption refrigeration system, the secondary heat exchanger 27 and the tertiary heat exchanger 26 are to be understood as supplementary options that can be used individually or in combination.

The expeller 28 is followed in the solvent circuit 25 by a condenser 23, to which a throttle 31 follows. The condensed refrigerant is vaporized in an evaporator 24, which is located in the exhaust line 12 of the internal combustion engine 11 and has the function of another charge air cooler behind the first intercooler 17. The re-evaporated refrigerant eventually flows to the absorber 29, where the refrigerant branch 25 is reunited with the solvent circuit 30. The section of the solvent circuit 30 between the expeller 28 and the absorber 29 likewise contains a throttle 32. The absorber 29 is followed by the already mentioned solution pump 22 in the solvent circuit 30.

FIG. 2 shows a system diagram which largely corresponds to that shown in FIG. 1 and comprises all assemblies and components shown there. Like parts are given the same reference numerals, so that reference can be made to the preceding description. In addition to the expeller 28 in the region of the exhaust manifold of the internal combustion engine 11 is another expeller 27 ', which is instead of a pure heat exchanger in the exhaust gas recirculation train 20 from the exhaust line 13 to the air intake 12, provided. This can be connected in the solution circuit via a line 34 to the input of the Au-driver 28 and via a bypass 35, bypassing the expeller 28 with the solution circuit 25. The switching between these two guides (34, 35) by means of a 2/2-way valve 36. The expeller 27 'is further connected with respect to the refrigerant phase via a branch line 37 with the refrigerant branch 30, wherein a check valve 38 is arranged in the stub line. This can be closed when the expeller 27 'serves only as a heat exchanger in preheat function for the solution.

The expeller 27 'is provided for a refrigerant phase that outgass at a lower temperature level than the refrigerant phase that is to outgas in the expeller 28 or for sole operation in an exhaust temperature range of the internal combustion engine where the temperature level in the expeller 28 is too high. A return line 44 from the expeller 28 to the solution circuit 30 can be shut off by means of a check valve 45.

In a further supplement to the expeller 27 'in the exhaust gas recirculation train 20 of the internal combustion engine 11 is another expeller 26', which is instead of a pure heat exchanger in the exhaust line 13 behind the devices 19 exhaust aftertreatment provided. This is in the solution circuit via a line 39 to the input of the expeller 27 'and via a bypass 40, bypassing the expeller 27', 28 connected to the solution circuit 25. The reversal between these two guides (39, 40) by means of a 2/2-way valve 41. The expeller 26 'is further connected with respect to the refrigerant phase via a branch line 42 with the refrigerant branch 30, wherein a check valve 43 is disposed in the stub line. This can be closed when the expeller 26 'serves only as a heat exchanger in preheat function for the solution.

The expeller 26 'is provided for a refrigerant phase that outgases at a low temperature level than the refrigerant phase that is to outgas in the expeller 27', or for sole operation in an exhaust gas temperature range of the internal combustion engine, in which the temperature level in the expulsions 28 and 27 'is too high.

The operation with three expellers at the same time requires a solution that has three outgassing at different temperatures refrigerant.

LIST OF REFERENCE NUMBERS

11 internal combustion engine

12 air intake line

13 exhaust system

14 exhaust gas turbocharger

15 compressors

16 turbine

17 intercooler

18 wave

19 Catalytic converter 0 Exhaust gas recirculation line 1 Absorption chiller 2 Solution pump 3 Condenser 4 Evaporator 5 Solution circuit 6 Exchangers / heat exchangers tertiary 7 Exchangers / Heat exchangers secondary 8 Exhausters 9 Absorber 0 Refrigerant branch 1 Throttle 2 Throttle 3 Shut-off valve 4 Line 5 Bypass 6 Directional valve 7 Stub line check valve

management

bypass

way valve

stub

check valve

management

shutoff valve

Claims

Exhaust gas energy utilization by means of an absorption chiller

1. A method for operating an internal combustion engine (11) using thermal exhaust energy,

characterized,

that heat from the exhaust gas of the internal combustion engine (11) is transferred to the solution of an absorption chiller while expelling the refrigerant from the solvent.

2. The method of claim 1 for operating an internal combustion engine (11) nit means (19) for the exhaust aftertreatment,

characterized,

that heat is expelled to expel the refrigerant from the solvent from the exhaust gas prior to entering the exhaust after-treatment means (19).

3. The method according to any one of claims 1 or 2 for operating an internal combustion engine (11) with means for exhaust gas recirculation,

characterized,

that heat is removed from the exhaust gas in the region of the exhaust gas recirculation (20) and in particular is transferred to the solution of the absorption chiller for preheating.

4. The method according to any one of claims 1 to 3,

characterized,

that heat is withdrawn from the exhaust gas behind the devices (19) for exhaust aftertreatment and in particular is transferred to the solution of the absorption chiller for preheating.

5. The method according to any one of claims 1 to 4,

characterized,

that the operation of the absorption chiller after a start of the internal combustion engine (11) is initially suspended or interrupted until reaching a sufficient operating temperature of the internal combustion engine (11).

6. The method according to any one of claims 1 to 5, for operating a supercharged internal combustion engine (11) with an exhaust gas turbocharger (14),

characterized,

that the heat for removing the refrigerant from the solution in front of the turbine (16) of the exhaust gas turbocharger (14) is removed from the exhaust gas.

7. The method according to any one of claims 1 to 6,

characterized,

that the cooling capacity of the absorption chiller is used at least partially for cooling the charge air of the internal combustion engine (11).

8. The method according to any one of claims 6 to 7,

characterized,

that the exhaust gas only temporarily heat is removed from the turbine of the exhaust gas turbocharger (14), especially only at high load and full load operation of the internal combustion engine (11).

9. The method according to any one of claims 6 to 8,

characterized,

that the exhaust gas behind the turbine (16) of the exhaust gas turbocharger (14) is constantly withdrawn heat.

10. The method according to any one of claims 1 to 9,

characterized,

a solution is used from which different refrigerants can be expelled at different temperatures.

11. The method according to any one of claims 1 to 10,

characterized,

that for the expulsion of the refrigerant or the heat transfer takes place at different points of the exhaust system.

12. Internal combustion engine with means for utilizing thermal exhaust energy,

characterized,

that in the exhaust line (13) of the internal combustion engine (11) is an expeller (28) of an absorption chiller (21) is used, the one before the expeller (28) lying solution pump (22), the expeller (28) downstream capacitor (23) comprising an evaporator (24) downstream of the condenser and an absorber (29) arranged downstream of the evaporator,

13. Internal combustion engine according to claim 12 with means (19) for the exhaust aftertreatment,

characterized,

that the expeller (28) in the exhaust line (13) in front of the means (19) arranged for exhaust aftertreatment.

14. Internal combustion engine according to one of claims 12 or 13 with an exhaust gas recirculation line (20) from the exhaust gas line (13) to the air intake line (12),

characterized,

that an expeller (27 ') or heat exchanger (27), which is optionally upstream of the expeller (28) in the solution circuit (25), in the exhaust gas recirculation line (20) is arranged.

15. Internal combustion engine according to one of claims 12 to 14,

characterized,

that an expeller (26 ') or further heat exchanger (26), if necessary the expeller (28) and optionally the expeller (27 ') or heat exchanger (27) in the solution circuit (25) is connected upstream, is arranged in the exhaust line (13) behind the means (19) for exhaust aftertreatment.

16. Internal combustion engine according to one of claims 12 to 15 with an exhaust gas turbocharger,

characterized,

that the expeller (28) in front of the turbine (16) of the exhaust gas turbocharger (14) in the exhaust line (13) is arranged.

17. Internal combustion engine according to any one of claims 12 to 16,

characterized,

that the evaporator (24) is arranged as a charge air cooler in the air intake line (12) of the internal combustion engine (11).

18. Internal combustion engine according to claim 17,

characterized,

in that a further intercooler (17) is arranged in the air intake line in front of the evaporator (24).