US20100205949A1 - Combustion Air and Exhaust Gas Arrangement of an Internal Combustion Engine - Google Patents

Abstract

The invention relates to an arrangement for supplying an internal combustion engine (1), particularly of a motor vehicle, with a stream of combustion air (2) and for removing a stream of exhaust gas (3) from the internal combustion engine (1). The arrangement comprises a fresh air channel (4) for conveying the stream of combustion air (2), an exhaust channel (5) for conveying the stream of exhaust gas (3), an exhaust gas turbocharger (6) comprising a condenser (7) disposed in the fresh air channel (4) and comprising a turbine (8) disposed in the exhaust gas channel (5), a swirl generator (9) connected directly upstream of the condenser (7) for the stream of combustion air (2) arriving in the condenser (7), and a low-pressure exhaust gas return (10) comprising a return channel (11) emptying into the fresh air channel (4) upstream of the condenser (7) for conveying an exhaust gas return stream (12). The swirl generator (9) is designed as a centrifugal separator (13) for condensate forming in the exhaust gas return stream (12).

Description

TECHNICAL FIELD
• The invention concerns an arrangement for supplying an internal combustion engine, in particular of a motor vehicle, with a combustion air stream and for discharging an exhaust gas stream from the internal combustion engine in accordance with the features of the preamble of claim1.
PRIOR ART
• Performance, running behavior, and exhaust gas emission of internal combustion engines, in particular of motor vehicles, are affected in many respects not only by the motor itself but also by its arrangement for supply of combustion air and discharge of the exhaust gas stream. For improving performance, exhaust gas turbochargers are widely used that comprise a compressor arranged in the fresh air passage and a turbine arranged in the exhaust gas passage. At medium and high power output of the internal combustion engine such an exhaust gas turbocharger provides in the desired way a charge pressure increase of the combustion air stream and, based thereon, an increased power yield.
• Under partial load, it can be advantageous to generate intake with a defined swirl at the compressor of the exhaust gas turbocharger. For this purpose, the swirl generator is arranged upstream of the compressor of the exhaust gas turbocharger and induces a swirl in the incoming combustion air stream. In this way, the operating properties of the exhaust gas turbocharger under partial load are improved.
• Independent of the aforementioned problem, the prior art provides various measures in order to improve exhaust gas emissions. A known measure resides in providing a low-pressure exhaust gas return with which the exhaust gas return stream is introduced into the combustion air stream during partial load. This serves primarily for reducing pollutants, in particular for reducing the NOX emission.
• Across the length of the exhaust gas return the exhaust gas return stream will cool down. This can lead to condensate formation, in particular to generation of water droplets that can damage the compressor when impinging on the compressor vanes of the exhaust gas turbocharger that rotate at high speed. For avoiding this undesirable effect condensate separators are used that at least partially remove the condensate formed in the exhaust gas stream. Constructive expenditure and cost expenditure are high. This separator is located in known configuration at a certain spacing relative to the compressor inlet so that, as the exhaust gas return stream and the combustion air stream mix with one another, an after-condensation with repeated droplet formation may begin.
• It is an object of the present invention to further develop a combustion air and exhaust gas arrangement of an internal combustion engine such that the operating safety of the exhaust gas turbocharger is improved.
• This object is solved by an arrangement with the features of claim1.
SUMMARY OF THE INVENTION
• An arrangement for supplying an internal combustion engine with a combustion air stream and for discharging an exhaust gas stream is proposed in which the swirl generator provided for improved partial load operation is configured as a centrifugal separator for condensate that is formed in the exhaust gas return stream.
• By utilizing the centrifugal force and mass inertia forces that occur in the swirl generator and that act on the formed condensate, it is possible without any additional measures to provide an effective separation. The expenditure for an additional centrifugal separator is no longer required. With respect to the system requirements, the swirl generator is arranged for its function under partial load immediately at the compressor inlet so that a long mixing travel and thus the risk of repeated droplet formation is eliminated. Since the additional separator is not required, only a reduced mounting space is needed. The internal combustion engine including its attachment parts may be designed more compact.
• It can be expedient to mix the exhaust gas return stream upstream of the swirl generator with the combustion air stream wherein the swirl generation and simultaneous condensate separation happen only once the downstream swirl generator is reached. In an advantageous further embodiment, an introduction of the exhaust gas return stream is substantially tangential in the rotational direction of the air stream in the swirl generator. In this way, the stream velocity of the exhaust gas return stream in the mixed or unmixed state is transformed directly into a swirl with simultaneously initiated separation effect. An additional energy introduction for swirl generation is not required. Expediently, in addition or as an alternative, an introduction of the exhaust gas return stream into the swirl generator is provided with an axial directional component, i.e., at an acute angle to the main flow direction of the swirl generator. The axial intake velocity of the compressor is thus improved.
• In an expedient embodiment, a circumferential section of the swirl generator is provided with a radially outwardly positioned discharge groove for the separated condensate. The condensate droplets that as a result of the swirl effect are forced radially outwardly collect at the inner side of the circumferential section and enter the discharge groove under the effect of the swirl-caused centrifugal force, assisted by the carrying effect of the gas stream. The collection in the discharge groove reduces reintroduction of the separated condensate into the gas stream and allows also a controlled discharge from the centrifugal separator.
• The discharge groove extends advantageously in the circumferential direction of the swirl generator about at least 180 degrees and in particular about approximately 270 degrees. In this way, it is ensured that the separated condensate can be substantially completely collected and discharged.
• The cross-section of the discharge groove increases advantageously in the rotational direction of the swirl generator. In particular, a condensate discharge passage exits from the discharge groove at a terminal area of the discharge groove with respect to the rotational direction of the swirl generator. The condensate quantity that increases in the rotational direction can be reliably and completely received by the discharge groove and, by utilizing its kinetic energy that exists in the rotational direction of the swirl generator, can be discharged through the condensate discharge passage.
• In an expedient further embodiment, on at least one longitudinal edge of the discharge groove a sealing lip is provided that is in particular slanted in a radial outward direction. The arrangement of the discharge groove and sealing lip acts as a trap for the separated condensate that can penetrate easily into the discharge groove but cannot leave it to return into the gas stream.
• In an advantageous further embodiment the swirl generator has a central substantially straight main air passage and a swirl air passage that opens with a tangential directional component into the main air passage, wherein the return passage extends into the swirl air passage. By means of suitable control devices an auxiliary air stream that is introduced through the swirl air passage and also the exhaust gas return stream can be matched to the respective operating states of the internal combustion engine. For example, in full load operation an exhaust gas return is not used wherein the introduction of the auxiliary air stream for swirl generation can be reduced or even switched off. By means of the auxiliary air stream provided for partial load operation the exhaust gas return stream is introduced at high kinetic energy and a swirl is imparted so that, without additional measures, significant mass forces and thus an excellent separating effect will occur.
• Upstream of the swirl generator there is expediently a heat exchanger arranged in the return passage that cools the exhaust gas return stream. The exhaust gas turbocharger and the internal combustion engine are supplied with cool combustion air that is enriched with returned exhaust gas so that the internal combustion engine can be operated at high power yield with reduced pollutant emissions. In connection with the increased tendency of condensate formation as a result of the cooling action of the heat exchanger, the advantages of the inventive arrangement become particularly apparent. The effective separation immediately at the inlet of the compressor ensures that a substantially condensate-free gas stream enters the compressor so that the latter has an increased operational safety.
BRIEF DESCRIPTION OF THE DRAWINGS
• One embodiment of the invention will be explained in the following with the aid of drawing in more detail. It is shown in:
• FIG. 1 as a schematic block diagram an internal combustion engine with an exhaust gas turbocharger, with a low-pressure exhaust gas return and with a swirl generator embodied as a centrifugal separator for improved partial load operation of the engine;
• FIG. 2 a side view of a section of the fresh air passage with a swirl generator according toFIG. 1;
• FIG. 3 an enlarged perspective illustration of the swirl generator with integrated centrifugal separator according toFIG. 2;
• FIG. 4 a perspective longitudinal section illustration of the swirl generator according toFIG. 3 with details of the stream guiding action and its effect on the separation and condensate discharge in a discharge groove;
• FIG. 5 a schematically enlarged cross-section illustration of the discharge groove according toFIG. 4 with sealing lips arranged at the longitudinal edges.
EMBODIMENT(S) OF THE INVENTION
• FIG. 1 shows as a schematic block diagram an internal combustion engine1 that can be a diesel engine, a gasoline engine or the like. In the illustrated embodiment the internal combustion engine1 is provided for driving a motor vehicle. A stationary engine or the like may also be expedient. The internal combustion engine1 is provided with an arrangement according to the invention for supplying acombustion air stream2 and for discharging anexhaust gas stream3. The arrangement comprises a fresh air passage4, anexhaust gas passage5, an exhaust gas turbocharger6 as well as a low-pressure exhaust gas return10 with areturn passage11.
• Theexhaust gas stream3 of the internal combustion engine1 is collected by means of anexhaust gas manifold31 and is discharged through theexhaust gas passage5. Thecombustion air stream2 for combustion of fuel in the internal combustion engine1 is supplied by fresh air passage4 to the internal combustion engine1. In this connection, it passes at the inlet side throughair filter28 arranged in the fresh air passage4 and is supplied by means of anintake manifold30 to the individual cylinders of the internal combustion engine1.
• The exhaust gas turbocharger6 has acompressor7 arranged in the fresh air passage4 as well as aturbine8 arranged in theexhaust gas passage5 wherein theturbine8 that is driven by thecombustion air stream2 guided in theexhaust gas passage5 drives in turn thecompressor7. Thecompressor7 increases the charge pressure of thecombustion air stream2 passing through theair filter28. For reducing the temperature increase of thecombustion air stream2 that is caused thereby, acharge air cooler29 is arranged between thecompressor7 and theintake manifold30.
• By means of thereturn passage11 of the low-pressureexhaust gas return10 at certain operating states of the internal combustion engine1, in particular at partial load, an exhaustgas return stream12 is branched off theexhaust gas stream3 and is admixed to thecombustion air stream2 upstream of the exhaust gas turbocharger6.
• Under comparable operating conditions, and in particular for improving the operating behavior of the exhaust gas turbocharger at minimal engine load and low engine speed, the combustion engine1 is operated with swirl-loaded compressor intake. For this purpose, in the fresh air passage4 aswirl generator9 is arranged that is arranged upstream of thecompressor7 immediately at the inlet. Theswirl generator9 impresses a swirl on thecombustion air stream2 entering thecompressor7 in a way disclosed in the following in more detail. Theswirl generator9 is moreover embodied in a way described also in more detail in the following as acentrifugal separator13 for the condensate that is formed in the exhaustgas return stream12. The condensate is separated in thecentrifugal separator13 and in accordance witharrow43 is discharged from theswirl generator9 and can be collected, treated further, or returned into the engine.
• It can be expedient to connect a simple fresh air passage4 without further branches coaxially and centrally to thecompressor7. In this connection, the incomingcombustion air stream2, for example, by means of aerodynamic vanes or the like, is impressed with a swirl so that the response behavior of the exhaust gas turbocharger6 is improved. This swirl acts also on the exhaustgas return stream12 that is admixed upstream so that the separating effect described in the following is generated. In the illustrated embodiment, the fresh air passage4 between theair filter28 and thecompressor7 has abranch32 so that downstream of the branch32 amain air passage21 and aswirl air passage22 are fluidically connected in parallel. In themain air passage21 and in theswirl air passage22 optionally acontrol device26,27 is arranged, respectively, by means of which amain air stream24 in themain air passage21 as well as anauxiliary air stream25 in theswirl air passage22 can be controlled or governed with regard to their quantity. Theswirl air passage22 opens into theswirl generator9 where theauxiliary air stream25 and themain air stream24 are joined with one another immediately upstream of thecompressor7. By means of the auxiliary gas stream25 a swirl is generated in a way to be described in the following in more detail that acts not only proportionally on theauxiliary air stream25 but also on themain air stream24 so that the exhaust gas turbocharger6 operates with swirl enhancement. In this way, the operating properties of the exhaust gas turbocharger under partial load and at low engine speed are improved. For certain operating states it can be expedient to reduce or even shut off the swirl-generatingauxiliary air stream25 by means of thecontrol device27. In this state, the exhaust gas turbocharger6 is supplied primarily with the substantially swirl-free combustion air of themain air stream24 that in turn can be controlled or governed by means ofcontrol device26.
• Thereturn passage11 opens into theswirl air passage22 downstream of the correlatedcontrol device27 and upstream of theswirl generator9. Upstream of the swirl generator9 aheat exchanger23 that cools the exhaustgas return stream12 is arranged in thereturn passage11. Depending on the position of thecontrol device27 more or less combustion air in the form of theauxiliary air stream25 is admixed to theexhaust gas stream12. The mixture of theauxiliary air stream25 and the exhaustgas return stream12, optionally also the exhaustgas return stream12 alone, is imparted with a swirl in theswirl generator9. Condensate in the exhaustgas return stream12 which is formed in particular downstream of theheat exchanger23 as a result of its cooling action is separated in thecentrifugal separator13, integrated in theswirl generator9, immediately upstream of thecompressor7 and is discharged in accordance with thearrow43. As a result of this, substantially condensate-free mixture of combustion air and returned exhaust gas is supplied to thecompressor7.
• FIG. 2 shows in a side view a section of the fresh air passage4 according toFIG. 1 in the area of themain air passage21, theswirl air passage22, and theswirl generator9. Theswirl generator9 is flange-connected immediately at the intake side of the schematically indicatedcompressor7 at its end face. Themain air passage21 with themain air stream24 opens substantially straight into thecompressor7. In addition to themain air passage21 theswirl air passage22 is part of the fresh air passage4 and branches off theauxiliary air stream25 at thebranch32 from thecombustion air stream2. The schematically indicatedreturn passage11 opens upstream of theswirl generator9 into theswirl air passage22 where the exhaustgas return stream12 is mixed with theauxiliary air stream25. This mixture is substantially introduced tangentially with an axial directional component into theswirl generator9 and is subjected thereby to a swirl with a rotational direction that is indicated byarrow33. This swirl is also imparted to the centralmain air stream24. By entraining the exhaustgas return stream12 with theauxiliary air stream25 the introduction of the exhaustgas return stream12 is realized with the same rotational direction as the air stream in the swirl generator.
• Further details of the swirl generation with integrated condensate separation result from the perspective illustration according toFIG. 3 in which theswirl generator9 according toFIG. 2 is shown as an individual part. Same features are identified with same reference numerals. Theswirl generator9 comprises a central approximatelycylindrical pipe section34 with alongitudinal axis38. When looking also atFIG. 2, it can be seen that the substantiallystraight pipe section34 is part of the centralmain air passage21 through which themain air stream24 is guided straight and axis-parallel to thelongitudinal axis38 in accordance witharrow37. Theswirl air passage22 opens tangentially as well as at a slant toward thelongitudinal axis38 into theswirl generator9 wherein theswirl air passage22 extends with an tangential and with an axial directional component into themain air passage21. This introduction is realized by means of aspiral section35 that extends externally about thepipe section34 in which the gas stream of theswirl air passage22 that enters in accordance with arrow36 with tangential and axial directional component is subjected to a swirl effect. Within theswirl generator9 the various gas streams are mixed in accordance witharrows36,37,39 to a total gas stream with swirl and axial directional component in accordance witharrow40.
• For forming thecentrifugal separator13, theswirl generator9 in the area of itsspiral section35 has acircumferential section15 in the form of a circumferential wall in which, at the radial outer circumference, an inwardlyopen discharge groove16 for separated condensate is formed integrally. Relative to the intake of the gas in accordance with arrow36 thedischarge groove16 extends in the circumferential direction of theswirl generator9 about at least 180 degrees. In the illustrated embodiment it extends in accordance witharrow39 about approximately 270 degrees about thelongitudinal axis38. Relative to the rotational direction of the air stream in theswirl generator9, as indicated byarrow40, thedischarge groove16 has aterminal area20 in therotational direction40. Acondensate discharge passage19 is provided that extends from thisterminal area20 away from thedischarge groove16 and, in accordance with the illustration ofFIG. 1, discharges the separated condensate in accordance with the illustratedarrow43.
• FIG. 4 shows a longitudinal section illustration of theswirl generator9 according toFIG. 3. Thecircumferential section15 of thespiral section35 provided for forming thecentrifugal separator13 surrounds a cylindricalinner wall41 of thepipe section34 that projects partially in the longitudinal direction wherein, in accordance witharrow42, a fluidic connection between thespiral section35 and thepipe section34 exists however. Relative to the flow direction in thespiral section35, indicated by thearrow42, its cross-section in the axial direction of theswirl generator9 becomes more narrow so that along the circumferential path an increasing proportion of gas stream introduced in accordance witharrow42 is mixed into the main air stream24 (FIG. 2) in thepipe section34. The main air stream24 (FIG. 2) has amain flow direction14 in accordance with the illustration ofFIG. 4. As a result of the slant of theswirl air passage22 relative to thelongitudinal axis38 of themain air passage21 that deviates from 90 degrees and is illustrated inFIG. 3 and the narrowing cross-sectional shape of thespiral section35, an introduction of the exhaustgas return stream12 together with the auxiliary air stream25 (FIG. 2) into theswirl generator9 is realized not only substantially tangential but also with an axial directional component parallel to themain flow direction14 of theswirl generator9 in accordance with arrow42 (FIG. 3).
• The illustration according toFIG. 4 shows that the cross-section of thedischarge groove16 in the rotational direction of theswirl generator9 is enlarged in accordance witharrow42. In the embodiment illustrated inFIG. 4 the cross-section of thedischarge groove16 increases in the width direction as well as in the depth direction.
• Further details for configuring thedischarge groove16 can be seen in the schematic cross-sectional illustration ofFIG. 5. Thedischarge groove16 integrally formed in thecircumferential section15 is limited relative to its open side bylongitudinal edges17. At bothlongitudinal edges17 schematically indicated sealinglips18 are arranged that in the illustrated cross-sectional illustration beginning at thelongitudinal edges17 converge and, in doing so, are slanted slightly radially outwardly, i.e., in the direction of the bottom of thedischarge groove16. In this way, the condensate that has been separated can enter thedischarge groove16 but cannot return or return only with difficulty into the spiral section35 (FIG. 4).

Claims (16)

1. Arrangement for supplying an internal combustion engine (1), in particular a motor vehicle, with a combustion air stream (2) and for discharging an exhaust gas stream (3) from the internal combustion engine (1), comprising

a fresh air passage (4) for guiding the combustion air stream (2),

an exhaust gas passage (5) for guiding the exhaust gas stream (3),

an exhaust gas turbocharger (6) with a compressor (7) arranged in the fresh air passage (4) and with a turbine (8) arranged in the exhaust gas passage (5),

a swirl generator (9) arranged immediately upstream of the compressor (7) for the combustion air stream entering the compressor (7),

as well as a low-pressure exhaust gas return (10) with a return passage (11) opening upstream of the compressor (7) into the fresh air passage (4) for guiding an exhaust gas return stream (12),

characterized in that the swirl generator (9) is embodied as a centrifugal separator (15) for condensate forming in the exhaust gas return stream (12) or for particles.

2. Arrangement according toclaim 1, characterized in that an introduction of the exhaust gas return stream (12) into the swirl generator (9) is provided substantially tangentially in the rotational direction of the swirl generator (9).

3. Arrangement according toclaim 1, characterized in that an introduction of the exhaust gas return stream (12) into the swirl generator (9) is provided with an axial directional component at an acute angle to the main flow direction (14) of the swirl generator (9).

4. Arrangement according toclaim 1, characterized in that a circumferential section (15) of the swirl generator (9) is provided with a radial outwardly positioned discharge groove (16) for separated condensate.

5. Arrangement according toclaim 4, characterized in that the discharge groove (16) in the circumferential direction of the swirl generator (9) extends about at least 180 degrees.

6. Arrangement according toclaim 4, characterized in that the cross-section of the discharge groove (16) increases in the rotational direction of the swirl generator (9).

7. Arrangement according toclaim 4, characterized in that a condensate discharge passage (19) relative to the rotational direction of the swirl generator (9) extends away from the discharge groove in a terminal area (20) of the discharge groove (16).

8. Arrangement according toclaim 4, characterized in that on at least one longitudinal edge (17) of the discharge groove (16) a particularly radial outwardly slanted sealing lip (18) is arranged.

9. Arrangement according toclaim 1, characterized in that the swirl generator (9) has a central, substantially straight extending main air passage (21) and a swirl air passage (22) that opens with a tangential directional component into the main air passage (21), wherein the return passage (11) is guided into the swirl air passage (22).

10. Arrangement according toclaim 1, characterized in that upstream of the swirl generator (9) a heat exchanger (23) that cools the exhaust gas return stream (12) is arranged in the return passage (11).

11. Arrangement according toclaim 5, wherein the discharge groove (16) in the circumferential direction of the swirl generator (9) extends approximately 270 degrees.

12. Arrangement according toclaim 2, wherein

an introduction of the exhaust gas return stream (12) into the swirl generator (9) is provided with an axial directional component-at an acute angle to the main flow direction (14) of the swirl generator (9);

wherein a circumferential section (15) of the swirl generator (9) is provided with a radial outwardly positioned discharge groove (16) for separated condensate; and

wherein the discharge groove (16) in the circumferential direction of the swirl generator (9) extends about at least 180 degrees.

13. Arrangement according toclaim 12, wherein the discharge groove (16) in the circumferential direction of the swirl generator (9) extends approximately 270 degrees.

14. Arrangement according toclaim 12, wherein

the cross-section of the discharge groove (16) increases in the rotational direction of the swirl generator (9);

wherein a condensate discharge passage (19) relative to the rotational direction of the swirl generator (9) extends away from the discharge groove in a terminal area (20) of the discharge groove (16); and

wherein on at least one longitudinal edge (17) of the discharge groove (16) a particularly radial outwardly slanted sealing lip (18) is arranged.

15. Arrangement according toclaim 14, wherein

the swirl generator (9) has a central, substantially straight extending main air passage (21) and a swirl air passage (22) that opens with a tangential directional component into the main air passage (21); and

wherein the return passage (11) is guided into the swirl air passage (22).

16. Arrangement according toclaim 15, wherein upstream of the swirl generator (9) a heat exchanger (23) that cools the exhaust gas return stream (12) is arranged in the return passage (11).

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