WO2014170090A1

WO2014170090A1 - Large diesel internal combustion engine

Info

Publication number: WO2014170090A1
Application number: PCT/EP2014/055813
Authority: WO
Inventors: Thomas Cartus
Original assignee: Avl List Gmbh
Priority date: 2013-04-18
Filing date: 2014-03-24
Publication date: 2014-10-23
Also published as: AT513133A4; DE112014001180A5; AT513133B1

Abstract

The invention relates to a large diesel internal combustion engine (1) which can be operated in a first operating mode with a first fuel of relatively low quality and in a second operating mode with a second fuel of relatively high quality, having, in the exhaust tract (2), at least one exhaust-gas aftertreatment device (3) which can be bypassed by way of a bypass line (4), wherein at least one first shut-off element (5) is arranged at least upstream of the exhaust-gas aftertreatment device (3). To prevent damage to the exhaust-gas aftertreatment device in as simple a manner as possible, it is provided that at least one second shut-off element (6) is arranged downstream of the exhaust-gas aftertreatment device (3), wherein, when the first and second shut-off elements (5, 6) are in a first position assigned to the first operating mode, the exhaust tract part (2a) that has the exhaust-gas aftertreatment device (3) is separated from the rest of the exhaust tract (2), and, when the first and second shut-off elements (5, 6) are in a second position assigned to the second operating mode, the exhaust tract part (2a) that has the exhaust-gas aftertreatment device (3) is connected in terms of flow to the rest of the exhaust tract (2), that the first and/or second shut-off element (5, 6) is designed so as to exhibit leakage, and that at least one first sealing-air line (14a, 14b) issues into the exhaust tract part (2a) that has the exhaust-gas aftertreatment device (3).

Description

Large diesel engine

The invention relates to a large diesel internal combustion engine which is operable in a first operating mode with a first low quality fuel and in a second operating mode with a second higher quality fuel, with at least one exhaust aftertreatment device bypassable via a bypass line in the exhaust line, at least upstream of the exhaust aftertreatment device at least a blocking member is arranged. Furthermore, the invention relates to a method for operating a large diesel engine, which is operated in a first operating mode with a first low-quality fuel and in a second operating mode with a higher-quality fuel, the exhaust passed in the first operating mode past at least one exhaust gas treatment device and is passed through the exhaust aftertreatment device in the second operating mode.

Due to increasingly stringent emissions legislation exhaust gas quality measures, such as exhaust aftertreatment and / or external exhaust gas recirculation, are required for large diesel engines. As a result, predetermined exhaust emission limit values can be met. Typically, large engines, especially for marine use, are now poorly fueled, e.g. Heavy fuel oil (HFO) operated with sulfur contents of up to 3.5 to 4 percent by weight and high sediment fractions (eg vanadium). Exhaust gases resulting from the combustion of such bad fuels would damage or even destroy the additional emission reduction measures, e.g. through poisoning, corrosion and blocking. Therefore, exhaust gas measures are only operated with fuels of sufficiently good quality, especially in marine applications within the Emission Control Areas (ECA) defined by the legislator. When operating with bad fuel, especially in marine applications outside the emission controlled areas, exhaust aftertreatment devices and exhaust gas recirculation devices are separated from the exhaust gas flow by exhaust flaps. In the case of exhaust aftertreatment, the exhaust gas flow is passed through a bypass line. This bypass line is also a constructive necessity by a so-called "Failsave" function.

These exhaust valves must be airtight, since even the smallest amounts of exhaust gas from the combustion of bad fuels in the exhaust aftertreatment devices cause damage. High-density flaps in sufficiently reliable design, however, are expensive, heavy and require high restoring forces. From EP 2 332 826 A, an exhaust gas purification system for a watercraft is known, which can be operated with a lower quality fuel and a higher quality fuel, wherein in the operating mode with low quality fuel, the exhaust gas is passed over a bypass line to an exhaust aftertreatment device.

The object of the invention is to avoid damage to the exhaust aftertreatment device by operating with lower quality fuel with the least possible effort in a large diesel engine of the type mentioned.

According to the invention, this is achieved by arranging at least one second blocking element downstream of the exhaust gas aftertreatment device, wherein in a first position of the first and second blocking element assigned to the first operating mode, the exhaust line aftertreatment section having the exhaust aftertreatment device is separated from the remaining exhaust line and in a second position of the second position assigned to the second operating mode first and second obturator of the exhaust aftertreatment device having exhaust tract part is fluidly connected to the rest of the exhaust system, that the first and / or second locking member is designed to leak and that in the exhaust aftertreatment device having exhaust line part at least a first barrier air line opens.

According to one variant of the invention, at least one internal first blocking air line starts from a charge air line of the intake branch of the internal combustion engine downstream of at least one compressor. According to a further variant of the invention, at least one external first blocking air line starts from an external blocking air source, wherein preferably the external blocking air source is formed by an external compressor and / or a blocking air store.

It can be provided that between the exhaust line and the intake line at least one exhaust gas recirculation line for recirculation of exhaust gas is arranged, wherein in the region of an initial portion of the Abgasrückführstrangs a third locking member and in the region of an end portion of the Abgasrückführstrangs fourth obturator is arranged, and wherein in a first operating mode associated with the first position of the third and fourth blocking member of the exhaust gas recirculation line between the third and fourth locking member separated from the exhaust line and the intake manifold and in a second operating mode associated second position of the third and fourth blocking member of the exhaust gas recirculation line with the exhaust line and the inlet line is flow-connected. The third and / or fourth blocking element may also be leaking, in particular if between the third and the fourth Barrier at least a second barrier air line opens into the exhaust gas recirculation line.

In one variant of the invention, at least one internal second blocking air line starts from a charge air line of the internal combustion engine downstream of at least one compressor, preferably an exhaust gas turbocharger. In a further variant, at least one external second blocking air line originates from an external blocking air source, wherein preferably the external blocking air source is formed by an external compressor and / or a blocking air accumulator.

In a further embodiment of the invention it can be provided that the bypass line is separable from the exhaust line via bypass valves, wherein preferably at least a third internal or external barrier air line opens into the bypass line between a first and a second bypass valve. The internal third blocking air line can emanate again from the charge air line of the internal combustion engine downstream of at least the compressor. The external third blocking air line can start from the external blocking air source.

The introduction of the sealing air through the first and second barrier air line reliably prevents the ingress of exhaust gas from the combustion of the bad fuel in the field of exhaust aftertreatment and / or exhaust gas recirculation and allows the use of inexpensive leaking simple shut-off valves as shut-off devices. The use of high-density expensive flaps is therefore not required.

By means of the sealing air introduced into the bypass line via the third blocking air line, it is prevented that unpurified exhaust gas can flow past the exhaust aftertreatment device via the leakage of the first bypass obstruction formed, for example, by a flap, which would have a detrimental effect on the emission values. Nevertheless, simple and cost-effective leak-tight shut-off valves can also be used for the bypass.

The blocking air can come from internal and / or external compressed air sources. As already described, a simple embodiment of the invention provides that at least one first and / or second and / or third internal blocking air line originate from a charge air line of the internal combustion engine downstream of at least one compressor.

Alternatively or additionally, it can also be provided that at least one first and / or second and / or third external blocking air line from an external Blocking air source emanates, wherein preferably the external compressed air source is formed by an external compressor and / or a blocking air reservoir.

The blocking air supply from internal compressed air sources, such as an exhaust gas turbocharger or a mechanical supercharger, is particularly advantageous in full load operation of the internal combustion engine, in which sealing air can be provided with sufficiently high pressure and in sufficient quantities by the loader. In part-load operation of the internal combustion engine, however, the internal compressed air source may prove to be insufficient. Thus, it is advantageous to supply the blocking air from an external compressed air source, for example an external compressor, during partial load operation of the internal combustion engine.

The object of the invention is also achieved by a method described above, wherein in the first operating mode, the exhaust gas treatment device exhibiting Abgasstrangteil is separated by a first and a second obturator from the rest of the exhaust system and in this exhaust line part sealing air is introduced, preferably a defined leakage flow in the first operating mode flows past the closed first and / or second obturator.

According to a variant of the invention, in the first operating mode, an exhaust gas recirculation loop between exhaust line and intake line is separated from the intake line by a third obturator and a fourth obturator and blocking air is introduced into the exhaust gas recirculation line, and in the second operating mode, exhaust gas from the exhaust line through an exhaust gas recirculation line to the intake line passed, wherein preferably a defined leakage flow flows past the closed third and / or fourth obturator in the first operating mode.

Conveniently, in the second operating mode, a bypass line bypassing the exhaust gas aftertreatment device is separated from the remainder of the exhaust line by bypass shut-off devices, and blocking air is introduced into the separate bypass line. Again, by the bypass valves a defined leakage of the sealing air can be allowed.

Thus, in shut-off strand parts in each case as much sealing air is supplied, as flows through leaks in the shut-off valves.

The inventions will be explained in more detail below with reference to FIGS. They show schematically:

1 shows a large diesel engine according to the invention in a first embodiment; and Fig. 2 shows a large diesel engine according to the invention in a second embodiment.

Functionally identical parts are provided in the embodiment variants with the same reference numerals.

Fig. 1 shows an internal combustion engine with low-pressure exhaust gas recirculation and Fig. 2 shows an internal combustion engine with high-pressure exhaust gas recirculation.

In both variants, the large diesel engine 1 has an exhaust line 2, in which an exhaust gas aftertreatment device 3 is arranged, which can be bypassed by means of a bypass line 4. Upstream and downstream of the exhaust gas aftertreatment device 3, a first Abgasabsperrorgan 5 and second obturator 6 are arranged. The bypass line 4 branches off the exhaust gas line 2 upstream of the first Abgasabsperrorgans 5 and flows into the exhaust line downstream of the second locking member 6 a. The bypass line 4 can be separated from the remaining exhaust line 2 via further first and second bypass valves 7, 8.

Furthermore, the internal combustion engine 1 an intake manifold 9, and an exhaust gas recirculation train 10 between the exhaust line 2 and the intake manifold 9. In the exhaust gas recirculation train 10 may optionally be arranged another exhaust aftertreatment device and / or an exhaust gas cooler.

In the exhaust gas recirculation train 10, after the branching off of the exhaust gas line 2 in the region of an initial section 10a of the exhaust gas recirculation line 10 or before the connection to the intake branch 9 in the region of an end section 10b of the exhaust gas recirculation line 10, a third blocking element 11 or fourth blocking element 12 is arranged. Furthermore, the internal combustion engine 1 has an exhaust gas turbocharger 13 with an exhaust gas turbine 13a and a compressor or supercharger 13b.

The blocking members, in particular the first 5, the second 6, the third 11 and fourth locking member 12, but also the bypass valves 7, 8, can be designed as simple and inexpensive leak-proof exhaust control valves. In the exhaust tract section 2a in the area around the exhaust gas aftertreatment device 3, at least one first sealing air line 14a, 14b opens between the first and the second exhaust gas element 5, 6. Analogously, at least one second barrier air line 15a, 15b opens into the area of the exhaust gas recirculation line 10 between the third and fourth blocking elements 11, 12, the internal first 14a and second barrier air lines 15a having an internal blocking air source of an internal blocking air system and the external first 14b and second barrier air lines 15b with an external blocking air source 16 of an external Sperrluftsys- tems are connected. The internal barrier air source is formed by the inlet branch 9, in particular by the charge air line 9 a of the inlet strand 9.

The external blocking air source 16 is required for the provision of the sealing air, in particular in the partial load range of the internal combustion engine 1. In the nominal load range, an external blocking air source 16 is not necessarily required, but charge air can be taken from the intake branch 9 downstream of the supercharger 13b and introduced into the exhaust tract section 2a around the exhaust aftertreatment device 3 or into the exhaust gas recirculation line 10. This allows for better efficiency. Only when operating in the partial load range, the supply of the sealing air from an external compressed air source 16 via the external blocking air lines 14b and 15b is necessary. The external compressed air source 16 may be, for example, an external barrier air compressor. Furthermore, the external compressed air source 16 can also be formed by a blocking air accumulator, which can be filled in the nominal load range of the internal combustion engine 1 by the loader 13b (not shown).

The supply of the sealing air makes it possible to use as locking members 5, 6, 11, 12 leaking, inexpensive flaps. In addition to the cost advantage, this has the advantage that sticking or blocking, as is often the case with high-density flaps after a long closure period, can be avoided.

In the first operating mode with a first fuel of inferior quality - for example, heavy oil - the blocking elements 5, 6, 11 and 12 are thus closed and introduced in the entire first operating mode blocking air in the foreclosed areas of the exhaust line part 2a to the exhaust aftertreatment device 3 and the exhaust gas recirculation line 10. As a result, an influx of dirt-laden exhaust gas into the aftertreatment device 3 and into the exhaust gas recirculation line 10 can be reliably avoided, since there is always a slight overpressure around the after-treatment device 3 and in the exhaust gas recirculation line 10.

When the ship reaches an emission controlled area (ECA), it switches to the second operating mode in which a second higher quality fuel is burned. In this second operating mode, the shut-off elements 5, 6, 11, 12 can be opened, the flow connection between the exhaust line part 2a and the remaining exhaust line 2 on the one hand, and between the exhaust gas recirculation line 10 and the remaining exhaust line 2 on the other hand, and the blocking air supply via the sealing air line 14a, 14b, 15a, 15b, for example, by closing not shown blocking air valves in the blocking air lines 14a, 14b, 15a, 15b - be terminated. The exhaust gases originating from the combustion of the higher quality fuel flow through. Thus, the exhaust aftertreatment device 3 and are partly recycled by the exhaust gas recirculation train 10 again.

During operation with exhaust gas purification, the bypass line 4 can be pressurized with sealing air via a third sealing air line 17a or 17b according to one embodiment. This prevents untreated exhaust gas from flowing past the leakage of the bypass valve 7 formed by a flap, for example, past the exhaust gas aftertreatment device 3. This exhaust gas leakage would necessitate a correspondingly higher purification efficiency for the exhaust gas which passes through the exhaust aftertreatment device 3, which is only possible to a limited extent, especially with regard to the future expected low legal limit values.

The sealing air for the bypass 4 is generated according to the procedure previously described either externally or internally (engine charging).

Claims

PATENT APPLICATIONS

1. Large diesel internal combustion engine (1), which in a first operating mode with a first low-quality fuel and in a second operating mode with a second fuel of higher quality is operable, with at least one via a bypass line (4) bypassable exhaust aftertreatment device (3) in the exhaust line (2), wherein at least upstream of the exhaust gas aftertreatment device (3) at least a first obturator (5) is arranged, characterized in that at least one second obturator (6) downstream of the exhaust aftertreatment device (3) is arranged, wherein in a first operating mode associated with the first Position of the first and second blocking member (5, 6) of the exhaust aftertreatment device (3) having exhaust line part (2a) separated from the remaining exhaust line (2) and in a second operating mode associated second position of the first and second blocking member (5, 6) of the Exhaust aftertreatment device (3) having exhaust gas is connected flow-connected with the rest of the exhaust line (2), that the first and / or second blocking member (5, 6) is carried out leaking and that in the exhaust aftertreatment device (3) having exhaust line part (2a) at least a first barrier air line (14a, 14b) opens.

Second internal combustion engine (1) according to claim 1, characterized in that at least one internal first barrier air line (14a) of a charge air line (9a) of the intake branch (9) of the internal combustion engine (1) downstream of at least one compressor (13b) emanates

3. Internal combustion engine (1) according to claim 1 or 2, characterized in that at least one external first barrier air line (14b) emanating from an external blocking air source (16), wherein preferably the external blocking air source (16) by an external compressor and / or a blocking air reservoir is formed.

4. internal combustion engine (1) according to one of claims 1 to 3, characterized in that between the exhaust line (2) and the intake manifold (9) at least one exhaust gas recirculation line (10) is arranged for the return of exhaust gas, wherein in the region of an initial portion (10a ) of the Abgasrückführstranges (10) a third locking member (11) and in the region of an end portion (10b) of the exhaust gas recirculation line (10) a fourth obturator (12) is arranged, and wherein in a first operating mode associated with the first position of the third and fourth Blocking organ (11, 12) the exhaust gas recirculation line (10) between the third and the fourth blocking member (11, 12) from the exhaust line (2) and the intake manifold (9) separated and in a second operating mode associated second position of the third and fourth blocking member (11, 12) of the exhaust gas recirculation train (10) is fluidly connected to the exhaust line (2) and the inlet line (9).

5. Internal combustion engine (1) according to claim 4, characterized in that the third and / or fourth blocking member (11, 12) is designed to be leaking.

6. Internal combustion engine (1) according to claim 4 or 5, characterized in that between the third and the fourth blocking member (11, 12) at least a second barrier air line (15a, 15b) opens into the exhaust gas recirculation line (10).

7. Internal combustion engine (1) according to one of claims 4 to 6, characterized in that at least one internal second barrier air line (15a) of a charge air line (9a) of the internal combustion engine (1) downstream of at least one compressor (13b) - preferably an exhaust gas turbocharger (13 ) - goes out

8. Internal combustion engine (1) according to one of claims 4 to 7, characterized in that at least one external second barrier air line (15b) emanating from an external blocking air source (16), wherein preferably the external blocking air source (16) by an external compressor and / or a barrier air storage is formed.

9. internal combustion engine (1) according to one of claims 1 to 7, characterized in that the bypass line (4) via bypass valves (7, 8) from the exhaust line (2) is separable, preferably between a first and a second bypass gate (7, 8) at least a third barrier air line (17a, 17b) opens into the bypass line (4).

10. Internal combustion engine (1) according to claim 9, characterized in that at least one internal third blocking air line (17a) from a charge air line (9a) of the internal combustion engine (1) downstream of at least one compressor (13b) - preferably an exhaust gas turbocharger (9) - goes out

11. Internal combustion engine (1) according to claim 9 or 10, characterized in that at least one external third blocking air line (17b) emanating from an external blocking air source (16), wherein preferably the external blocking air source (16) is formed by an external compressor and / or a barrier air storage.

12. A method for operating a large diesel engine (1) which is operated in a first operating mode with a first low-quality fuel and in a second operating mode with a higher-quality fuel, wherein the exhaust gas in the first operating mode at least one exhaust aftertreatment device (3) passed and in the second operating mode by the exhaust aftertreatment device (3) is passed, characterized in that in the first operating mode, the exhaust gas aftertreatment device (3) exhibiting Abgasstrangteil (2a) by a first and a second obturator (5, 6) from the remaining exhaust line (2 ) is separated and in this exhaust line part (2 a) sealing air is introduced, wherein preferably a defined leakage flow in the first operating mode on the closed first and / or second obturator (5, 6) flows past.

13. The method according to claim 12, characterized in that in the first operating mode between the exhaust line (2) and inlet line (9) guided exhaust gas recirculation train (10) by a third obturator (11) from the exhaust line (2) and a fourth obturator (12) from In the second operating mode, exhaust gas from the exhaust line (2) through an exhaust gas recirculation line (10) to the inlet line (9) is passed, preferably a defined leakage flow in the first operating mode on closed third and / or fourth obturator (11, 12) flows past.

14. The method of claim 12 or 13, characterized in that in the second operating mode, the exhaust aftertreatment device (3) bypassing the bypass line (4) is separated from the remaining exhaust line (2) and in the separate bypass line (4) sealing air is introduced.