DK177631B1

DK177631B1 - Large two-stroke diesel engine with exhaust gas purification system

Info

Publication number: DK177631B1
Application number: DK201000409A
Authority: DK
Inventors: Peter Skjoldager
Original assignee: Man Diesel & Turbo Deutschland
Priority date: 2010-05-10
Filing date: 2010-05-10
Publication date: 2014-01-06
Also published as: CN103216298B; JP5581259B2; CN102242670A; JP2011236892A; KR101400832B1; CN103216298A; CN102242670B; JP5860923B2; DK201000409A; JP2014196745A; KR20110124133A

Abstract

The invention relates to a large turbocharged two-stroke diesel engine of the crosshead type comprising a plurality of cylinders that are each connected to an exhaust gas receiver. A selective catalytic reduction reactor is arranged downstream of the exhaust gas receiver. An exhaust conduit connects the outlet of the selective catalytic reduction reactor to a turbine of a turbocharger. The turbine drives a compressor of the turbocharger that delivers scavenge air via a scavenge air path to a scavenge air receiver. The scavenge air receiver is connected to the plurality of cylinders. An auxiliary blower in the scavenge air path assists the compressor at low load conditions. A controllable by pass line extends from the scavenge air receiver to the exhaust conduit. At low engine load a controlled flow of scavenge air is directed from the scavenge air receiver to the exhaust conduit at a position downstream of the selective catalytic reduction reactor and upstream of the turbine of the turbocharger. This measure increases the temperature of the exhaust gases entering the selective catalytic reduction reactor. Further, a cooler in the scavenge air path can be controlled so as to the cooling effect partially or completely. Alternatively, the cooler can be controlled to become a heater or a heater is installed in the scavenge air path.

Description

i DK 177631 B1

LARGE TWQ-STROKE DIESEL ENGINE WITH AN EXHAUST GAS PURIFICATION SYSTEM

5 The present invention relates to a large turbocharged two-stroke internal combustion piston engine of crosshead type, preferably a diesel engine with an exhaust gas purification system, in particularly to a large two-stroke diesel engine of the crosshead type with a 10 selective catalytic reduction reactor.

BACKGROUND ART

Large two-stroke engines of the crosshead type are 15 typically used in propulsion systems of large ships or as prime mover in power plants. Emission requirements have been and will be increasingly difficult to meet, in particular with respect to mono-nitrogen oxides (NOx) levels.

20

Using a selective catalytic reduction (SCR) reactor is a measure that is known to assist in diesel engines to reduce NOx emissions. A minimum temperature of approximately 300 to 350 °C for the exhaust gases 25 entering the SCR converter is required for proper functioning of the SCR reactor.

However, due to the characteristics of the two-stroke turbocharged engine the exhaust gas temperature at low 30 engine load, e.g. lower than 40% of the maximum continuous rating of the engine concerned are relatively low, i.e. too low for the exhaust gases to be converted in the SCR reactor.

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At the above mentioned low load conditions it is difficult to maintain sufficient scavenge pressure in a large turbocharged two stroke diesel engine. Therefore, an auxiliary blower is used in at these low load 5 conditions to maintain the scavenge air pressure. Thus, any measures that, are taken to increase the temperature of the exhaust gases at the inlet of the SCR reactor should not have a negative effect on the scavenge air pressure.

10

Thus, there is a need for turbocharged two-stroke diesel engine that overcomes or at least reduces the above mentioned drawbacks.

15 DISCLOSURE OF THE INVENTION

On this background, it is an object of the present invention to provide a large turbocharged two-stroke diesel engine that can operate with an SCR reactor at a 20 wide range of engine load conditions.

This object is achieved by providing a large turbocharged two-stroke combustion engine of the crosshead type comprising a plurality of cylinders that are each . 25 connected to an exhaust gas receiver, a selective catalytic reduction reactor with an inlet connected to the outlet of the exhaust gas receiver, an exhaust conduit connecting an outlet of the selective catalytic reduction reactor to a turbine of a turbocharger, a 30 compressor of the turbocharger driven by the turbine, the compressor delivers scavenge air via a scavenge air path that includes a scavenge air cooler to a scavenge air receiver, an auxiliary blower in the scavenge air path for assisting the compressor at low load conditions, the

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3 DK 177631 B1 scavenge air receiver is connected to each of the plurality of cylinders, a controllable by pass line extending from a position in the scavenge air path downstream the auxiliary, blower or from the scavenge air 5 receiver to a position in the exhaust conduit between the outlet of the selective catalytic reduction reactor and the inlet of the turbine, an electronic control unit operably connected to the bypass line, the electronic control unit being configured to allow a flow of scavenge 10 air from the scavenge air receiver through the controllable by pass line to the exhaust conduit when the engine load is below a predetermined threshold or when the temperature of the exhaust gases entering the selective catalytic reduction reactor is lower than a 15 given threshold.

At low engine load a controlled flow of scavenge air is directed from the scavenge air receiver to the exhaust conduit at a position downstream of the selective 20 catalytic reduction reactor and upstream of the turbine of the turbocharger. This measure increases the temperature of the exhaust gases entering the selective catalytic reduction reactor, without affecting the scavenge air pressure negatively.

25

The exhaust conduit may include a three port mixing point for mixing the by-passed scavenge air with the exhaust gas.

30 The by-pass line may include a valve for controlling the flow of scavenge air through the by-pass line.

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The valve can be an electronically controlled valve of the on-off type that is controlled in an open loop by the electronic control unit 33.

5 Alternatively, the valve can be an electronically controlled valve of the proportional type that is controlled in a closed loop by the electronic control unit.

10 The engine may further comprise a temperature sensor near the inlet of the selective catalytic reduction reactor.

The engine may be configured such that the scavenge air cooler can be deactivated by the electronic control unit.

15

The electronic control unit can be configured to open up for the bypass line as first measure, and to deactivate the scavenge air cooler as a second measure.

20 The engine can be configured so that the scavenge air cooler can be turned into a heater by the electronic control unit).

The engine can be configured so that the electronic 25 control unit is configured to turn the scavenge air cooler into a heater as a third measure.

The object is also achieved by providing a large turbocharged two-stroke combustion engine of the 30 crosshead type comprising a plurality of cylinders that are each connected to an exhaust gas receiver, a selective catalytic reduction reactor with an inlet connected to the outlet of the exhaust gas receiver, an exhaust conduit connecting an outlet of the selective

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5 DK 177631 B1 catalytic reduction reactor to a turbine of a turbocharger, a compressor of the turbocharger driven by the turbine, the compressor delivers scavenge air via a scavenge air path that includes a scavenge air cooler to 5 a scavenge air receiver, an auxiliary blower in the scavenge air path for assisting the compressor at low load conditions, the scavenge air receiver is connected to each of the plurality of cylinders, an electronic control unit configured to reduce or deactivate the 10 cooling function of the scavenge air cooler when the engine load is below a given threshold or when the temperature of the exhaust gases entering the selective catalytic reduction reactor is lower than a given threshold.

15

The engine may further comprise a scavenge air bypass conduit for bypassing the scavenge air cooler.

The engine may further comprise a one or more 20 electronically controlled valves under command of the electronic control unit for controlling the flow of scavenge air through the scavenge air bypass conduit.

The engine may further comprise a cooling medium supply 25 conduit with an electronically controlled separation valve, a cooling medium return conduit and a cooling medium bypass circuit including an electronically controlled bypass valve. The engine may further comprise a recirculation conduit and a recirculation pump. The 30 engine may further comprise a heat exchanger in the recirculation conduit for heating the medium flowing through the recirculation conduit.

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DK 177631 B1 6

The engine may further comprise a second scavenge air cooler, wherein the electronic control unit is configured to control the cooling capacity of at least one of the scavenge air coolers.

5

The engine may further comprise a steam injection conduit connected, to the scavenge air path, the steam injection conduit including an electronically controlled steam injection control valve under command of the electronic 10 control unit.

The engine may further comprise an exhaust gas injection conduit connected to the scavenge air path, the exhaust gas injection conduit including an electronically 15 controlled exhaust gas injection control valve under command of the electronic control unit.

The engine may further comprise a heater unit in the scavenge air path. The heater unit can be operated with 20 hot air as a heating medium.

The engine may further comprise a heat exchanger in the cooling medium supply conduit for supplying heat to the medium flowing through the cooling medium supply conduit.

25

Further objects, features, advantages and properties of the large two-stroke internal combustion engine according to the invention will become apparent from the detailed description.

30

BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed portion of the present description, the invention will be explained in more

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7 DK 177631 B1 detail with reference to the exemplary embodiments shown in the drawings, in which:

Fig. 1 is a diagrammatic view of an engine according to a 5 first embodiment of the present invention,

Fig. 2 shows a diagrammatic view of a second embodiment of the invention,

Figs. 3 to 7 show further embodiments using reduced cooling of the scavenge air, and 10 Figs. 8 to 12 show further embodiments using active heating of the scavenge air.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

15 In the following detailed description of the large turbocharged two-stroke diesel engine of the crosshead type and the method for operating a large turbocharged two-stroke diesel engine of the crosshead type according to the invention will be described by the exemplary 20 embodiments.

The construction and operation of large turbocharged diesel engines of the cross-head type is as such well-known and should not require further explanation in the 25 present context. Further details regarding the operation of the exhaust gas purification system are provided below.

Fig. 1 shows a first exemplary embodiment of a large two-30 stroke diesel engine 1 according to the invention. The engine 1 may e.g. be used as the main engine in an ocean going vessel or as a stationary engine for operating a generator in a power station. The total output of the engine may, for example, range from 5,000 to 110,000 kW.

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The engine 1 is provided with a plurality of cylinders arranged besides one another in line. Each cylinder is provided, with an exhaust valve associated with their 5 cylinder cover. The exhaust channels can be opened and closed by the exhaust valve. A cross-head of the engine connects the piston rod to a big end of the crankshaft.

Exhaust bends connect to an exhaust gas receiver 6. The exhaust gas receiver 6 is disposed in parallel to the row 10 of cylinders. The exhaust gas receiver 6 is a large container with dimensions that are specifically adapted to the characteristics of the engine for optimal gas flow, counter pressure and acoustical considerations. Typically, the exhaust gas receiver 6 is a large hollow 15 cylindrical body made of steel plates. Due to its large size and weight the exhaust gas receiver is suspended from the engine construction with the aim of handling vibration aspects.

20 From outlet of the exhaust gas receiver 6 the exhaust gas stream is guided towards a turbine 12 of a turbocharger via an selective catalytic reactor 8 (SCR reactor) and exhaust conduit 10. Thus, the outlet of the exhaust gas receiver 6 is connected to the inlet of the SCR reactor 25 8. The exhaust gases flow through the SCR reactor 8 and NOx in the exhaust gases is removed or the amount is at least substantially reduced converting NOx to nitrogen and oxygen. The outlet of the SCR reactor is connected to the exhaust conduit 10 that leads the hot and pressurized 30 exhaust gases to the turbine 12. The exhaust gases are disposed into the atmosphere downstream of the turbine 12.

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The turbocharger also includes a compressor 14 driven by the turbine 12. The compressor 14 is connected to an air intake. The compressor 14 delivers pressurized scavenge air to a scavenge air receiver 22 via a scavenge air flow 5 path 16 that includes a scavenge air cooler 18 and an auxiliary blower 20.

The scavenge air cooler 18 is operated with water as a cooling medium. The scavenge air cooler 18 can be of 10 various types. One possibility is a plate cooler in which the cooling medium is not in direct physical contact with the scavenge air. Another possibly is a scrubber, in which the cooling medium is in direct contact with the scavenge air.

15

The auxiliary blower 20 is typically driven by an electric motor (could also be driven by a hydraulic motor) and kicks in at low load conditions (typically below 40% of the maximum continuous rating) to assist the 20 compressor 14 in maintaining sufficient scavenging pressure. When the auxiliary blower is not used it is bypassed via a not shown bypass.

The scavenge air receiver 22 is an elongated hollow 25 cylindrical body extending along the cylinders of the engine. The scavenge air is passed from the scavenge air receiver 22 to the scavenge air ports of the individual cylinders .

30 A controllable by-pass line 2 6 is branched off from the scavenge air receiver 22. The other end of the controllable by-pass line 26 is connected to the exhaust conduit 10 at a three port mixing point 30. The mixing

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10 DK 177631 B1 point 30 is located downstream of the outlet of the SCR reactor 8 and upstream of the inlet of the turbine 12.

Alternatively, the start.of the controllable by-pass line 5 2 6 could be located in the scavenge air conduit 16 at a position downstream of the auxiliary blower 20.

An electronically controlled valve 28 regulates the flow of scavenge air from the scavenge air flow path 16 to the 10 exhaust conduit 10 under command of an electronic control unit 33. In one embodiment the valve 28 is an on/off type valve that is controlled by the electronic control unit 33 in an open loop. In this embodiment the electronic control unit 33 is configured to open the valve 28 when 15 the engine load drops below a predetermined threshold and closes the valve 28 when the engine load rises above a predetermined threshold. These two thresholds need not be the same and can be defined as a percentage of the maximum continuous rating of the engine.

20

In another embodiment the electronically controlled valve 28 is a proportional valve that is controlled by the electronic control unit 33 in a closed loop. Hereto, the controller receives information about the temperature of 25 the exhaust gas at the inlet of the SCR reactor 8 from a temperature sensor 35 and the electronic control unit 33 is configured to control the degree of opening of the valve 28 in response to the measured temperature of the exhaust gas entering the SCR reactor 8. Thus, the 30 electronic control unit 33 will increase the opening degree of the electronically controlled valve 28 to increase the temperature of the exhaust gases when the measured temperature is below a minimum desired temperature.

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The thresholds can also be controlled by the mixing temperature at turbine inlet, i.e. higher temperature than required for the SCR reactor 8, the by-pass line 2 6 5 closes and at nearly too low temperature than required by the SCR reactor 8, the by-pass line 26 opens.

The on/off by-pass will be controlled after pre-set mixing temperatures at turbine inlet, in a way similar to 10 described for load control.

Fig. 2 shows a second exemplary embodiment of a large two-stroke diesel engine 1 according to the invention.

The same reference numbers refer to the same parts as in 15 Fig. 1. The embodiment according to Fig. 2 is largely identical to the embodiment of Fig. 1 except for the following aspects of the scavenge air cooler 18 in the scavenge air path 16.

20 A supply conduit 40 delivers cool water to the scavenge air cooler 18 and a return conduit 42 transports warm water away from the scavenge air cooler 18. In the second embodiment an electronically controlled bypass valve 44 in a cooling medium bypass circuit 43 and an 25 electronically controlled separation valve 46 under command of the controller 33 allow the supply of cool water in the supply conduit 40 to be deviated to the return conduit 42 without passing through the scavenge air cooler 18. A recirculation conduit 48 including a 30 pump 50 and a heater (or heat exchanger) 52 ensure that water flows through the scavenge air cooler 18 that is now changed into a heater and functions effectively as a heat exchanger. The heater 52 is provided with a warm heating medium, such a as warm water form the engine

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12 DK 177631 B1 cooling system and heats the medium circulating through the scavenge air cooler 18.

In the second embodiment the electronic control unit 33 5 can deactivate the cooler 18 via valves 44 and 46 by bypassing the cooling medium. At the same time the controller 33 will activate the pump 50 to ensure that a medium is circulating in the scavenge air cooler 18. . Further, the control unit 33 can activate the heater 52 10 by delivering a heating medium to heater 52 and thereby change the scavenge air cooler 18 into a heater. The electronic control unit 33 is configured to take various measures to increase the temperature of the scavenge air in relation to the need for increasing the temperature of 15 the exhaust gases entering the SCR reactor 8.

Thus, if it is sufficient to let some scavenge air pass through the controllable by-pass line 26 to the exhaust conduit 10, the electronic control unit 33 will not take 20 any further measures. However, if this first measure is not sufficient, the electronic control unit 33 will deactivate the cooling function of the scavenge air cooler 18. If this second measure is not sufficient, the electronic control unit 33 will as a third measure turn 25 the scavenge air cooler 18 into a heater to actively heat the scavenge air.

Fig. 2 shows an example of the temperatures of the scavenge air and of the exhaust gas at various positions 30 in the system. The examples are for low engine load conditions, e.g. under 40% of the maximum continuous rating of the engine concerned. The figures without brackets are the temperatures with scavenge air being passed through the bypass line 26 and with heat being

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13 DK 177631 B1 added to the scavenge air at the scavenge air cooler 18.

The figures in brackets are the temperatures when the engine is conventionally operated without scavenge air passing through the by-pass line 26 and with the scavenge 5 air cooler 18 cooling the scavenge air. With the new measures the temperature of the exhaust gas entering the SCR reactor 8 is 325 deg. C and the exhaust gas is sufficiently hot for being converted in the SCR reactor 8. Without the new measures the temperature of the 10 exhaust gas entering the SCR reactor 8 is 220 deg. C and the exhaust gas is not sufficiently hot for being converted in the SCR reactor 8.

t

Fig. 3 shows the supply and return of cooling medium to 15 the scavenge air cooler 18 via a cooling medium supply conduit 40 and a cooling medium return conduit 42.

Figs. 4 to 7 show various embodiments for controlled reduction of the cooling capacity of the scavenge air 20 cooler 18.

In Fig, 4 the engine is provided with a scavenge air bypass conduit 17 for bypassing the scavenge air cooler 18. The scavenge air bypass conduit 17 includes an 25 electronically controlled valve 23 for opening and closing the scavenge air bypass conduit 17 under command of the electronic control unit 33. The scavenge air path 16 includes another electronically controlled valve 21 for opening and closing the scavenge air path 16 under 30 command of the electronic control unit 33. Thus, the electronic control unit 33 can control the flow of scavenge air through said scavenge air bypass conduit 17 in ’ accordance with the need to increase the temperature

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14 DK 177631 B1 of the scavenge air and thereby increase the temperature of the exhaust gas entering the SCR reactor 8.

In Fig. 5 the cooling medium supply conduit 40 is 5 provided with an electronically controlled separation valve 4 6 and a cooling medium bypass circuit 43 that includes an electronically controlled bypass valve 44 and connecting the cooling medium supply conduit 40 directly to the cooling medium return conduit 42. The electronic 10 control unit 33 commands the electronic valves 44 and 46 and can thereby control the extent to which the cooling medium passes through the scavenge air cooler 18 (could be on/off or proportional control).

15 In Fig. 6 a recirculation conduit 48 including a recirculation pump 50 (under control of the electronic control unit 33) is added to the embodiment shown in Fig.

5 for enabling the cooling medium to circulate in the scavenge air cooler 18.

20

In Fig. 7 the engine is provided with an additional (second) scavenge air cooler 19. The electronic control unit 33 is configured to control the cooling capacity of at least one of the scavenge air coolers 18,19 as 25 explained above.

Figs. 8 to 12 show various embodiments for controlled adding of heat to the scavenge air.

30 In Fig. 8 the engine is provided with a steam injection conduit 50 connected to the scavenge air path 16. The steam injection conduit 90 includes an electronically controlled steam injection control valve 92 under command of the electronic control unit 33. Thus, the temperature

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15 DK 177631 B1 of the scavenge air and thereby the. temperature of the exhaust gas entering the SCR reactor 8 can be increased as desired by controllably injecting steam without a drop in scavenge air pressure.

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In Fig. 9 the engine is provided with an exhaust gas injection conduit 60 connected to the scavenge air path 16. The said exhaust gas injection conduit 60 includes an electronically controlled exhaust gas injection control 10 valve 62 under command of the electronic control unit 33.

Thus, the temperature of the scavenge air and thereby the temperature of the exhaust gas entering the SCR reactor 8 can be increased as desired by controllably injecting exhaust gas without a drop in scavenge air pressure.

15

In Fig. 10 the engine is provided with a heater unit 27 in the scavenge air path 16. The heater unit 27 is supplied with a heating medium (such as hot water or hot air) via a heating medium supply conduit 70 and the 20 return heating medium is transported away by a heating medium return conduit 72. The heating medium supply conduit 70 and the heating medium return conduit 72 are provided with electronically controlled valves that are under the command of the electronic control unit 33.

25 Thus, the temperature of the scavenge air and thereby the temperature of the exhaust gas entering the SCR reactor 8 can be increased as desired without a drop in scavenge air pressure.

30 The embodiment of Fig. 11 is essentially identical to the embodiment of Fig. 6, but further including a heat exchanger 52 for adding heat to the medium circulating through he scavenge air cooler 18.

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In the embodiment of Fig. 12 the engine is provided with a heat exchanger 80 in the a cooling medium supply conduit 40 for supplying heat to the medium flowing through the cooling medium supply conduit 40.

5

Although the teaching of this application has been described in. detail for purpose of illustration, it is understood that such detail is solely for that purpose, and variations can be made therein by those skilled in 10 the art without departing from the scope of the teaching of this application.

The embodiments described above may be combined in every possible way to improve the function of the engine.

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It should also be noted that there are many alternative ways of implementing the apparatuses of the teaching of this invention.

20 The term "comprising" as used in the claims does not exclude other elements or steps. The term "a" or "an" as used in the claims does not exclude a plurality. The single processor or other unit may fulfill the functions of several means recited in the claims.

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Claims

A large, cross-head turbocharged two-stroke internal combustion engine (1), comprising: a plurality of cylinders each connected to an exhaust gas receiver (6), a selective catalytic reduction reactor (8) having an input which is connected to the outlet of the exhaust gas receiver (6), an exhaust gas duct (10) connecting an output of the selective catalytic reduction reactor (8) to a turbocharger turbine (12), a compressor (14) to the turbocharger operated by the turbine (12), the compressor (14) supplies rinsing air via a rinsing air path (16) including a rinsing air cooler (18) for a receiver (22) to 25 rinsing air, an auxiliary blower (20) in the rinsing air path (16 ) to assist the compressor (14) at low load conditions, the rinsing air receiver (22) is connected to each of the plurality of cylinders, a controllable bypass line (26) extending from a downstream rinsing air path (16) the side of 00863-DK-P c * DK 177631 B1 2 the auxiliary blower or from the receiver (22) to the rinsing air to a position in the exhaust duct (10) between the output of the selective catalytic reduction reactor (8) and the input of the turbine (12), 5 an electronic control unit (33) operatively connected to the bypass line (26), said electronic control unit (33) configured to allow a flow of flushing air from the receiver (22) to flushing air through the controllable bypass line (26) to the exhaust duct ( 10) when the engine load is below a predetermined threshold or when the temperature of the exhaust gases entering the selective catalytic reactor (8) is below that of a given threshold. 15

A large, two-stroke, turbocharged two-head turbocharged internal combustion engine according to claim 1, wherein the exhaust duct (10) includes a three-port mixing point (30) for mixing the diverted flushing air with the exhaust gas. 20

A large, cross-head turbocharged two-stroke internal combustion engine according to claim 1, wherein the bypass line (26) includes a valve (28) for controlling the flow of flushing air through the bypass line (26). 25

A large, cross-head turbocharged two-stroke internal combustion engine according to claim 3, wherein the valve (28) is an on-off type electronically controlled valve controlled in an open loop by the electronic control unit 30 (33).

A large, two-stroke turbocharged two-stroke internal combustion engine according to claim 3, wherein the valve (28) is an electronically controlled valve of the proportional type that is controlled in a closed loop by the electronic control unit. (33).

5 PATENT REQUIREMENTS:

A large, 5-head type turbocharged two-stroke internal combustion engine according to claim 6, further comprising a temperature sensor (35) in the vicinity of the input of the selective catalytic reduction reactor (8).

A large, two-stroke turbocharged two-stroke internal combustion engine according to claim 1, wherein the purge air cooler (18) can be deactivated by means of the electronic control unit (33).

A large, cross-head turbocharged two-stroke internal combustion engine according to claim 7, wherein the electronic control unit (33) is configured to open the bypass line (26) as a first measure and to deactivate the purge air cooler (18) as a second measure.

A large, two-stroke turbocharged two-stroke internal combustion engine of claim 7, wherein the purge air cooler (18) can be changed to a heating device by the electronic control unit (33).

A large, cross-head turbocharged two-stroke internal combustion engine according to claim 8, wherein the electronic control unit (33) is configured to change the purge air cooler (18) to a heating device as a third measure.

A large, two-stroke turbocharged two-stroke internal combustion engine (1), comprising: 00863-DK-P 4 DK 177631 B1 a plurality of cylinders each connected to an exhaust gas receiver (6), a selective catalytic reduction reactor (8) having an input connected to the outlet of the exhaust gas receiver (6), an exhaust gas duct (10) connecting an output of the selective catalytic reduction reactor (8) to a 10 turbocharger turbine (12) a compressor (14) for the turbocharger operated by the turbine (12), the compressor (14) supplies flushing air via a flushing air path (16) including a flushing air cooler (18) to a flushing air receiver (22), an auxiliary blower (20) in the rinsing air path (16) to assist the compressor (14) at low load conditions, the rinsing air receiver (22) is connected to each of the plurality of cylinders, an electronic control unit (33) configured to provide reduce or they activate the cooling function of the purge air cooler (18) when the engine load is below a given threshold or when the temperature of the exhaust gases entering the selective catalytic reactor (8) is below that of a given threshold.

A large, two-stroke, turbocharged two-head turbocharged internal combustion engine according to claim 11, further comprising an internal circulation line (17) for flushing air for diverting the flushing air cooler (18).

A large, turbocharged two-stroke turbocharged type 5 combustion engine according to claim 12, further comprising one or more electronically controlled valves (23, 21) controlled by the electronic control unit (33) for controlling the purge air flow through the purge air circulation line ( 17). 10

A large, cross-head turbocharged two-stroke internal combustion engine according to claim 11, further comprising a channel (40) for supplying refrigerant with an electronically controlled separation valve 15 (46), a channel (42) for returning refrigerant and a circuit ( 43) for diverting refrigerant including an electronically controlled bypass valve (44).

A large, cross-head turbocharged two-stroke internal combustion engine 20 of claim 14, further comprising a recirculation duct (48) and a recirculation pump (50).

A large, cross-head turbocharged two-stroke internal combustion engine 25 of claim 15, further comprising a heat exchanger (52) in the recirculation duct for heating the agent flowing through the recirculation duct (48).

A large, cross-head turbocharged two-stroke internal combustion engine according to claim 14, further comprising a second purge air cooler (19), wherein the electronic control unit (33) is configured to control the cooling capacity of at least one of the purge air coolers (18, 19).

A large, cross-head turbocharged two-stroke type 5 combustion engine according to claim 11, further comprising a vapor injection channel (90) connected to the purge air path (16) including a vapor injection channel (50) controlled control valve (92) for injecting steam controlled 10 by the electronic control unit (33).

A large, cross-head turbocharged two-stroke internal combustion engine according to claim 11, further comprising an exhaust gas duct (60) connected to the purge air web (16), said exhaust gas duct (60) including an electronic controlled control valve (62) for injection of exhaust gas controlled by the electronic control unit (33). 20

A large, cross-head turbocharged two-stroke internal combustion engine according to claim 11, further comprising a heating unit (27) in the rinsing air path.

A large, two-stroke turbocharged two-stroke internal combustion engine according to claim 20, wherein the heating unit (27) is operated with hot air as a heating medium.

A large, cross-head turbocharged 2-stroke internal combustion engine of claim 14, further comprising a heat exchanger (80) in the duct (40) for supplying refrigerant for supplying heat to the agent flowing through the duct (40) refrigerant. 00863-EN-P