KR20220145268A - Large turbocharged two-stroke internal combustion engine with egr system - Google Patents

Abstract

The present invention provides a large turbocharged multi-cylinder two-stroke internal combustion engine (100) of a uniflow type with an EGR system for transferring the flow of exhaust gas from an exhaust system to an intake system, which is less complex, stable, and inexpensive. The EGR system comprises an EGR blower (29) and an electronically adjustable EGR throttling valve (32, 43). An AC electric drive motor (33) is coupled to the EGR blower (29) to drive the EGR blower (29). The AC electric drive motor (33) is configured to operate at a predetermined constant speed. A sensor (27) provides a signal representing the oxygen concentration in a scavenge gas receiver (2), and a controller (50) receiving the signal is coupled to the electronically adjustable EGR throttling valve (32). The controller (50) is configured to adjust the flow of exhaust gas through the EGR system by adjusting the position of the electronically adjustable EGR throttling valve (32, 43) as a function of a first signal as a primary means.

Description

LARGE TURBOCHARGED TWO-STROKE INTERNAL COMBUSTION ENGINE WITH EGR SYSTEM

The present invention relates to a large turbocharged two-stroke internal combustion engine and method having an exhaust gas recirculation (EGR) system, and more particularly to operation control of the EGR system.

Large turbocharged two-stroke internal combustion engines are commonly used as propulsion systems (as marine engines) on large ships or as prime movers in power plants. Their enormous size, weight and power output make these engines completely different from regular combustion engines, and the large two-stroke turbocharged compression internal combustion engine is itself a class. The height of these engines is usually not critical, so they are constructed with a crosshead to avoid lateral loads on the pistons. Typically, these engines are dual fuel engines configured to run on either fuel oil and natural gas, petroleum gas, methanol or ethane.

Emissions from marine diesel engines are limited by awareness of the environmental impact of emissions. In 2016, as suggested by the International Maritime Organization, Tier III limits were introduced in some regions to limit NOx emissions from marine diesel engines. Meeting these emission limits requires the use of technologies to reduce NOx emissions. One such technology is exhaust gas recirculation (EGR), which has been applied to four-stroke engines in the automotive industry for decades.

The principle of EGR is to recirculate a portion of the exhaust gas back to the engine's scavenging manifold. This reduces the level of scavenging oxygen in the scavenging gas and in turn reduces the formation of NOx gas during combustion. Unfortunately, lowering the oxygen content of the scavenging gas also affects the combustion efficiency. At excessively low scavenging oxygen levels, the engine produces undesirable visible smoke.

In a four-stroke automobile engine, there is a positive pressure difference between the exhaust gas side and the intake side. That is, the exhaust gas is recirculated and flows to the intake side without the need for a blower or the like due to the positive pressure difference. However, in a large turbocharged two-stroke internal combustion engine, there is a negative pressure difference between the exhaust gas side and the intake side, and if a simple conduit is installed between the intake side and the exhaust side as in a four-stroke automobile engine, the supercharged air will flow to the exhaust side. Thus, the EGR system of a two-stroke turbocharged internal combustion engine requires a blower or pump to force a portion of the exhaust gas into the charge air. That is, in a large turbocharged two-stroke diesel engine, the exhaust gas is recirculated by the blower to overcome the pressure difference between the exhaust system and the intake system.

Thus, large turbocharged two-stroke internal combustion engines require a blower or compressor to force the exhaust gas to be recirculated from the exhaust system to the intake system. These huge engines need very large blowers to do this job, and these very large blowers need large drive motors to do the job of forcing exhaust gases from the exhaust system to the intake system.

To meet emission requirements for both NOx and soot, a scavenging gas receiver is required because soot formation will exceed acceptable limits if the oxygen concentration is too low and NOx emissions will exceed acceptable limits if the oxygen concentration is too high. I need to control my oxygen concentration accurately.

Known large turbocharged two-stroke internal combustion engines equipped with EGR rely on a controllable variable speed EGR blower to regulate EGR flow to reach an oxygen concentration setpoint.

Patent Document 1: Korean Patent Registration Publication No. 10-1959852

It is an object of the present invention to provide a large turbocharged two-stroke internal combustion engine of the uniflow type which overcomes or at least reduces the above-mentioned problems.

The above and other objects are achieved by the features of the independent claims. Further implementation forms are apparent upon examination of the dependent claims, the detailed description and the drawings.

According to a first aspect, there is provided a single flow type large turbocharged two-stroke internal combustion engine, the engine comprising: a plurality of cylinders having a scavenging port at a lower end thereof and an exhaust valve at an upper end thereof, and an intake system in which scavenging gas is introduced into the cylinder As an intake system comprising a scavenging gas receiver connected to a cylinder through a scavenging port, an exhaust system through which exhaust gas generated in the cylinder is exhausted, comprising an exhaust gas receiver connected to the cylinder through an exhaust valve, and a turbine to the exhaust system An exhaust system having at least one turbocharger having at least one turbocharger driving a compressor in an intake system, a fuel system for delivering fuel to cylinders, an EGR system for delivering exhaust gas flow from the exhaust system to an intake system, comprising: an EGR blower and electronically regulated An EGR system comprising an EGR throttling valve capable of, an AC electric drive motor coupled to the EGR blower for driving the EGR blower, the AC electric drive motor coupled directly to the AC grid by an electrical switch, the electrical drive wherein the motor comprises an AC electric drive motor configured to operate at a constant speed determined by the AC frequency, a sensor providing a signal indicative of oxygen concentration in the scavenging gas receiver, and a controller receiving the signal and coupled to an electronically adjustable EGR throttling valve; The controller comprises a controller configured to regulate the flow of exhaust gas through the EGR system by adjusting the position of an electronically adjustable EGR throttling valve as a function of a signal as a primary means for regulating the flow of exhaust gas through the EGR system. do.

An EGR blower driven directly by an AC electric drive motor connected directly to the grid and comprising a controller configured to regulate EGR flow by adjusting the position of an electrically adjustable EGR valve by primary means without changing the speed of the EGR blower. By providing a large turbocharged two-stroke internal combustion engine, variable speed EGR blowers (e.g. AC electric), such as variable frequency electric drives, where EGR blowers power a variable mechanical or electric drive and/or AC electric drive motor without expensive equipment. a variable speed mechanical transmission between the drive motor and the EGR blower) may be enabled to be a variable speed EGR blower. As a result, these engines are less complex, more reliable and cheaper.

The load dependent scavenging oxygen concentration set point is predefined. The actual oxygen concentration is measured or estimated by means of feedback and/or feedforward control of this measurement by adjusting the electrically adjustable EGR throttling valve and reaching a set point.

In a possible implementation form of the first aspect, the controller moves the electronically adjustable EGR throttling valve in a closing direction to decrease the flow of exhaust gas through the EGR system and electronically to increase the flow of exhaust gas through the EGR system. configured to move the adjustable EGR throttling valve in an open direction.

In a possible implementation form of the first aspect, the controller is disposed in a bypass conduit connecting to the intake system downstream of the compressor and upstream of the exhaust system of the turbine as a primary or secondary measure for regulating the flow of exhaust gas through the EGR system. The electronically controlled cylinder bypass throttling valve or orifice is configured to adjust an opening degree to regulate the flow of exhaust gas through the EGR system.

In a possible implementation form of the first aspect, the controller moves the electronically controlled cylinder bypass throttling valve or orifice in the closing direction to increase the flow of exhaust gas through the EGR system and decrease the exhaust gas flow through the EGR system. configured to move an electronically controlled cylinder bypass throttling valve or orifice in an open direction to

In a possible implementation form of the first aspect, the controller is configured to control the flow of exhaust gas through the EGR system to keep the oxygen concentration in the scavenging gas receiver close to the oxygen concentration set point.

In a possible implementation form of the first aspect, the controller is configured to maintain an oxygen concentration in the scavenging gas receiver close to a scavenging oxygen concentration setpoint using the signal from the first sensor in the feedback/feedforward control, wherein the scavenging oxygen concentration setpoint is It is preferably adapted to the engine load.

In a possible implementation form of the first aspect, the AC electric drive motor is an asynchronous electric motor.

In a possible implementation form of the first aspect, the AC electric drive motor is a synchronous electric motor.

In a possible implementation form of the first aspect, the AC electric drive motor is coupled directly to the drive shaft of the EGR blower.

In a possible implementation form of the first aspect, an electronically adjustable EGR throttling valve is arranged downstream of the EGR blower.

In a possible implementation form of the first aspect, an electronically adjustable EGR throttling valve is arranged downstream of the EGR blower.

In a possible implementation form of the first aspect, the engine comprises an electronically adjustable EGR throttling valve downstream of the EGR blower and an electronically adjustable EGR throttling valve upstream of the EGR blower.

In a possible implementation form of the first aspect, the AC electric drive motor is coupled to the AC grid without including equipment for changing the frequency and/or voltage.

In a possible implementation form of the first aspect, the EGR blower layout is required to achieve the relevant oxygen setpoint in the scavenging air receiver, and is covered by the fixed speed of the EGR blower, a predefined exhaust gas bypass valve and a cylinder bypass valve. In accordance with the operating point with the lowest pressure ratio and volumetric flow rate at the position, the controller is configured to control the EGR flow as a function of the oxygen setpoint for all other operating points by opening the controlled exhaust gas bypass valve.

In a possible implementation form of the first aspect, the EGR blower layout is an auxiliary blower or blower, covered by the fixed speed of the EGR blower, which is required to achieve the relevant oxygen setpoint in the scavenging air receiver to the extent that the auxiliary blower is normally operating. In the off state, the operating point with the lowest pressure ratio and volumetric flow rate is followed, and the controller controls this and other operating points for this and other operating points by switching off and/or throttling the flow of one or more of the auxiliary blowers. and control the EGR flow as a function of an oxygen set point.

These and other aspects of the present invention will become apparent from the following examples.

As described above, according to the present invention, a variable speed EGR blower such as a variable frequency electric drive in which the EGR blower supplies power to a variable mechanical or electric drive and/or an AC electric drive motor without expensive equipment is a variable speed EGR blower. It has the advantage of making the engine less complex, more reliable and cheaper.

In the following detailed part of the present disclosure, the present invention will be described in more detail with reference to exemplary embodiments shown in the drawings.
1 is an elevated front view of a large two-stroke internal combustion engine according to an exemplary embodiment;
Fig. 2 is an elevated side view of the large two-stroke internal combustion engine of Fig. 1;
3 is a schematic diagram of a large two-stroke internal combustion engine according to FIG. 1 ;
4 is a schematic diagram of an embodiment of a large two-stroke internal combustion engine equipped with an EGR system;
5 is a schematic diagram of another embodiment of a large two-stroke internal combustion engine equipped with an EGR system;
6 is a schematic diagram of another embodiment of a large two-stroke internal combustion engine equipped with an EGR system;

1 , 2 and 3 show a large low speed turbocharged two-stroke compression ignition engine equipped with a crankshaft 8 and a crosshead 9 . 3 shows a schematic diagram of a large low-speed turbocharged two-stroke diesel engine with intake and exhaust systems; In this exemplary embodiment, the engine is equipped with six cylinders 1 in a row. A large low speed turbocharged two-stroke diesel engine is typically supported by a cylinder frame 23 supported by an engine frame 11 and has 4 to 14 cylinders 1 in a row. This engine can be used, for example, as a stationary engine to run the main engine of a ship or the generator of a power plant. The total power of this engine may range, for example, from 1,000 to 110,000 kW.

This engine, in this exemplary embodiment, is a compression ignition engine of the two-stroke single flow type equipped with a scavenging port 18 in the region below each cylinder liner 1 and a central exhaust valve 4 at the top of the cylinder liner 1 . . However, it is understood that this engine need not be compression ignited and may instead be spark ignited. Thus, in this embodiment, the compression pressure of the engine will be moderately high for compression ignition, but it is understood that the engine will operate at a lower compression pressure and may be ignited by a spark or similar means.

The intake system of the engine comprises a scavenging air receiver (2). The scavenging air passes from the scavenging receiver 2 to the scavenging port 18 of the individual cylinder 1 . The piston 10 reciprocating between the bottom dead center (BDC) and the top dead center (TDC) in the cylinder liner 1 compresses the scavenging air. Fuel is injected through the fuel valves 55 disposed on the cylinder cover 22 . Then, combustion proceeds and exhaust gas is produced.

The exhaust valve 4 is disposed in the center of the cylinder cover 22 and a plurality of fuel valves 55 are distributed around the central exhaust valve 4 (two or three fuels per cylinder for each fuel type used). valve 55 is preferred). The exhaust valve 4 is actuated by an electrohydraulic exhaust valve actuation system (not shown) controlled by the controller 50 . Controller 50 is, in one embodiment, an electronic control unit, such as an electronic computer, including one or more microprocessors, memory, and other hardware necessary for the operation of such control unit. The controller 50 is connected to various sensors and various devices that affect the operation of the engine 100 . The connections between the controller 50 and these sensors and devices may be in the form of signal lines or wireless connections not shown in the figures for simplicity. The controller 50 may be formed by a combination of various control units or may be a single control unit.

The fuel valve 55 is part of the fuel supply system. If the engine is a dual or multi-fuel engine, there is a multi-fuel system. In one embodiment, the controller 50 is also configured to control the operation of the fuel valve 55 .

When the exhaust valve 4 is opened, the exhaust gas flows into the exhaust gas receiver 3 through an exhaust system comprising an exhaust duct coupled with the cylinder 1 and continues through the first exhaust conduit 19 to the turbocharger system. It flows into the turbine 8 of (5) (the turbocharging system 5 may include one or more turbochargers), from which exhaust gases are discharged via the economizer 20 to the outlet 21 and to the atmosphere. 2 Flow through the exhaust conduit.

Via a shaft, the turbine 8 of the turbocharging system 5 drives a compressor 7 , which is supplied with fresh air through an air inlet 12 . This compressor (7) delivers pressurized scavenging air to the scavenging air conduit (13) leading to the scavenging air receiver (2). The scavenging air in this scavenging air conduit 13 passes through the intercooler 14 for cooling of the scavenging air.

If the compressor 7 of the turbocharger 5 does not deliver sufficient pressure to the scavenging air receiver 2 , ie at low or partial load conditions of the engine, the cooled scavenging air pressurizes the scavenging air flow. It passes through an auxiliary blower 16 driven by At higher engine loads, the turbocharger compressor ( 7 ) delivers fully pressurized scavenging air, and then a stopped auxiliary blower ( 16 ) is passed through a non-return valve ( 15 ).

Scavenging gas is introduced into the cylinder 1 via an intake system, which includes a scavenging gas receiver 2 connected to the cylinder 1 via a scavenging port 18 .

The exhaust gas generated in the cylinder is exhausted through an exhaust system, which includes an exhaust gas receiver 3 connected to the cylinder 1 through an exhaust valve 4 .

4 , the engine has an exhaust gas recirculation path extending from the exhaust system from a location upstream of the turbine 8 of the turbocharger 5 to the intake system at a location downstream of the compressor 7 of the turbocharger 5 . and an exhaust gas recirculation system comprising (60). The exhaust gas that has to be recirculated can thus flow from the exhaust system to the intake system. In this embodiment, structures and features that are the same as or similar to the corresponding structures and features previously described or shown herein are, for simplicity, denoted by the same reference numerals as previously used.

The exhaust gas recirculation system includes an exhaust gas recirculation unit 61 configured to treat the recirculated exhaust gas. Exhaust gas to be recirculated generally needs to be purified before entering the intake system in order to prevent damage to the engine 100 . Here, the exhaust gas recirculation unit 61 will typically comprise an aqueous wet scrubber, the inflow and outflow of water illustrated by horizontal arrows in FIG. 4 . A water mist catch 63 removes water used in the wet scrubber. Accordingly, relatively clean water is supplied to the exhaust gas recirculation unit 61 , and relatively polluted water is removed from the exhaust gas recirculation unit 61 .

An EGR blower 29 is provided to force the recirculated exhaust gas from the exhaust system to the intake system. The EGR blower 29 is necessary because the pressure in the exhaust system of a large two-stroke internal combustion engine is generally lower than the charging pressure in the intake system.

The EGR blower 29 is driven by an AC electric drive motor 33 . An AC electric drive motor 33 is coupled directly to the EGR blower 29 for driving the EGR blower 29 in the embodiment. The AC electric drive motor 33 is connected to the AC grid (eg, the AC power grid of a ship in which the large two-stroke internal combustion engine 100 is installed, or a building or other facility in which the large two-stroke internal combustion engine 100 is installed by means of an electric switch 35 ). connected directly to the AC power grid).

The AC electric drive motor 33 is configured to operate at a constant speed determined by the AC frequency when powered by the AC power of the power grid. Since the EGR blower 29 is directly mechanically coupled to the AC electric drive motor 33, the EGR blower 29 is also configured to operate at a predetermined constant speed.

In one embodiment, the drive shaft of the AC electric drive motor 33 is directly coupled to the drive shaft of the EGR blower 29 . The AC electric drive motor 33 is configured to operate at a predetermined constant speed, that is, when electric power AC having a constant frequency is supplied.

The rotational speed of the AC electric drive motor 33 is determined by the frequency of the AC power delivered to the AC electric drive motor 33 . In one embodiment, the AC power of the grid has a constant frequency so that the operating speed of the AC electric drive motor 33 is constant.

In one embodiment, the AC electric drive motor 33 is an asynchronous motor in which the rotation of the output shaft in steady state is slightly less than the integer number of AC cycles of the supplied current.

In one embodiment, the AC electric drive motor 33 is a synchronous motor whose rotation of the shaft is synchronized with the frequency of the supply current in steady state. The rotation period is exactly equal to an integer number of AC cycles.

Thus, a variable mechanical or electrically variable drive, such as a variable speed mechanical transmission between the AC electric drive motor 33 and the EGR blower 29 and/or a variable frequency drive (VFD) of the power supply system for the AC electric drive motor 33 . there is no No equipment is required to change the frequency and/or voltage of the current supplied from the grid to the AC electric drive motor 33 .

In one embodiment, the AC power for the AC electric drive motor 33 is generated by a generator driven by the engine 100 where the generator supplies power to the grid. In another embodiment, AC power is generated by an auxiliary engine, ie, a generator set, that powers the grid (not shown). In another embodiment, the AC power is provided by another source connected to the grid.

In the embodiment of FIG. 4 , the EGR blower 29 is shown downstream of the EGR unit 61 , but it should be understood that the EGR blower 29 may also be located upstream of the EGR unit 61 .

An electronically adjustable EGR throttling valve 32 is disposed in the EGR path 60 downstream of the EGR blower 29 . The adjustable EGR throttling valve 32 is preferably motorized to open the valve and connected to the controller 50 so that the controller can control the position of the EGR throttling valve 32 via a command signal. 32 instructs to control the degree of throttling applied to the flow of recirculated exhaust gas through the EGR path 60 . Accordingly, the controller 50 may increase or decrease the throttling effect of the EGR throttling valve 32 through the control signal.

The controller 50 is connected to various sensors to inform the operating state of the engine 100 (eg, engine load, engine speed, ambient temperature, scavenging air pressure, etc.). The controller 50 receives a signal from the sensor 27 , which provides a signal indicative of the oxygen concentration of the scavenging gas receiver 2 .

The controller 50 regulates the flow of exhaust gas through the EGR system by adjusting the position of the electronically adjustable EGR throttling valve 32 as a function of a signal, which is a main means for regulating the flow of exhaust gas through the EGR system. configured to do

The controller 50 is preferably configured to control the flow of exhaust gas through the EGR system for the purpose of maintaining the oxygen concentration in the scavenging gas receiver 2 close to a given oxygen concentration set point. In one embodiment, the oxygen concentration setpoint is a function of engine load or other operating conditions such as temperature, humidity, scavenging air pressure in the scavenging receiver, cylinder pressure and average effective pressure, and emission requirements applied to the geographic location in which the engine operates.

The controller 50 is configured to maintain the oxygen concentration in the scavenging gas receiver 2 close to a scavenging oxygen concentration setpoint using the signal from the sensor 27 in feedback control optionally combined with a feedforward control.

The controller 50 moves the electronically adjustable EGR throttling valve 32 in a closing direction (increasing throttling) to decrease the flow of exhaust gas through the EGR system and increase the flow of exhaust gas through the EGR system. to move the electronically adjustable EGR throttling valve 32 in an opening direction (reducing throttling) to

In one embodiment, engine 100 includes a cylinder bypass 47 connected to an intake system downstream of compressor 7 and an exhaust system upstream of turbine 8 . The cylinder bypass conduit 47 includes an electronically adjustable cylinder bypass throttling valve 42 and/or an electronically adjustable orifice 49 . The controller 50 regulates the opening of an electronically controlled cylinder bypass throttling valve 42 or orifice 49 as the primary means for regulating the flow of exhaust gas through the EGR system. It can be configured to regulate the flow of throttling losses, particularly by reducing EGR fluctuations.

The controller 50 moves the electronically controlled cylinder bypass throttling valve 42 or orifice 49 in a closed direction to increase the flow of exhaust gas through the EGR system and decrease the exhaust gas flow through the EGR system. The electronically controlled cylinder bypass throttling valve 42 or orifice 49 is configured to move in the open direction to

In a possible implementation of this embodiment, the engine comprises an exhaust bypass comprising an electronically adjustable exhaust gas bypass throttling valve 41 controlled by the controller 50 .

Engine 100 and controller 50 may be configured to control EGR flow according to the following scenario.

- the EGR blower layout is an open electronically adjustable EGR throttling valve 32, which is required to achieve the relevant oxygen setpoint in the scavenging air receiver 2 and is covered by the EGR blower 29 at a predefined operating speed ) depends on the operating point where the pressure ratio and volumetric flow are highest. The EGR flow closes the electronically adjustable EGR throttling valve 32 and operates the EGR blower 29 at the correct pressure ratio to achieve the correct flow in the EGR flow path 60 of the oxygen set point for all other engine operating points. The function is controlled by the controller 50 .

In this scenario the controller 50 is configured to operate with the following optimization strategy. The electronically controlled cylinder bypass throttling valve 42 or orifice 49 is opened to the allowable range depending on engine performance to reduce the operating point at peak pressure ratio and volumetric flow rate, thereby reducing EGR fluctuations and thus reducing throttle losses.

- the EGR blower layout is an open electronically adjustable EGR throttling valve (32), which is required to achieve the relevant oxygen setpoint in the scavenging air receiver (2) and is covered with the EGR blower (29) at a predefined operating speed In accordance with the operating point where the pressure ratio and volumetric flow rate are lowest, the electronically controlled cylinder bypass throttling valve 42 or orifice 49 is closed. The EGR flow is directed to all other engine operating points by opening the electronically adjustable EGR throttling valve 49 or orifice 32 and operating the EGR blower 29 at the correct pressure ratio to achieve the correct flow in the EGR flow path 60. is controlled by the controller 50 as a function of the oxygen set point for In this scenario the controller 50 is configured to operate with the following optimization strategy.

Control the oxygen level by opening the electronically controlled cylinder bypass throttling valve (42) or orifice (49) to an acceptable range depending on engine performance, and closing the EGR throttling valve (32) when the allowable range of cylinder bypass is exceeded. use.

Fig. 5 shows another embodiment of an engine similar to the embodiment of Fig. 4; In this embodiment, structures and features that are the same as or similar to the corresponding structures and features previously described or shown herein are, for simplicity, denoted by the same reference numerals as previously used. However, in this embodiment, the valve for throttling the EGR flow in the EGR flow path 60 is disposed upstream of the EGR blower 29 , and the sensor 27 is disposed upstream of the scavenging air receiver 2 , but is recirculated. It is arranged downstream of the intake system location where the exhaust gas mixes with the air exiting the turbine 7 .

In this embodiment, engine 100 and controller 50 may be configured to control EGR flow according to the following scenario.

- the EGR blower layout is an open electronically adjustable EGR throttling valve 43, which is required to achieve the relevant oxygen setpoint in the scavenging air receiver 2 and is covered by the EGR blower 29 at a predefined operating speed ) depends on the operating point where the pressure ratio and volumetric flow are highest. The EGR flow closes the electronically adjustable EGR throttling valve 43 and operates the EGR blower 29 at the correct pressure ratio to achieve the correct flow in the EGR flow path 60 to achieve the oxygen set point for all other engine operating points. is controlled by the controller 50 as a function of

In this scenario the controller 50 is configured to operate with the following optimization strategy. By opening the electronically controlled cylinder bypass throttling valve 42 or orifice 49 to the allowable range depending on engine performance, the operating point at peak pressure ratio and volumetric flow rate is reduced, thereby reducing EGR fluctuations and thus reducing throttle losses.

In one embodiment, the EGR blower layout is a predefined exhaust gas bypass valve 41 required to achieve the relevant oxygen setpoint in the scavenging air receiver 2 and covered by the fixed speed of the EGR blower 29 . ) and the operating point with the lowest pressure ratio and volumetric flow rate at the cylinder bypass valve 42 position. The controller 50 opens the controlled exhaust gas bypass valve 41 and thereby operates the EGR blower 29 at the correct pressure ratio to achieve the correct flow of EGR as a function of the oxygen set point for all other operating points. is configured to control the EGR flow. The EGR flow path 60 is provided with a non-return valve (not shown) for closing the EGR flow path 60 in an emergency. The controller 50 is configured to open the cylinder bypass valve 42 as a function of engine performance and deploy other measures to reduce the applicable EGR fluctuations within the IMO NOx cycle acceptable limits.

In one embodiment, the EGR blower layout is required to achieve the relevant oxygen setpoint in the scavenging air receiver 2 and is covered by the fixed speed of the EGR blower 29, an auxiliary blower or blowers 16 being In the off state, it follows the operating point with the lowest pressure ratio and volumetric flow rate. The controller 50 switches off the auxiliary blower(s) 16 and throttles the flow of the auxiliary blower 16 to operate the EGR blower 29 close to the correct pressure ratio to achieve the correct flow in the EGR flow path. configured to control the controlled EGR flow as a function of the oxygen set point relative to the operating point. The controller 50 provides additional control means for accurately operating the EGR blower 29 at the correct pressure ratio, particularly in a load range without the auxiliary blower 16 , which does not need to run to maintain the scavenging pressure. is configured to develop.

In one embodiment, (not shown) engine 100 includes an electronically adjustable EGR throttling valve 32 downstream of the EGR blower 29 and an electronically adjustable EGR throttling valve 43 upstream of the EGR blower. includes

Fig. 6 shows another embodiment of an engine similar to the embodiment of Fig. 4; In this embodiment, structures and features that are the same as or similar to the corresponding structures and features previously described or shown herein are, for simplicity, denoted by the same reference numerals as previously used. However, in this embodiment, the exhaust gas to be recirculated is taken from the low pressure side of the turbine 8 of the turbocharging system 5, and the recirculated exhaust gas is fed to the intake system of the turbocharging system 5 compressor 7 low pressure side. is added Thus, this embodiment operates with exhaust gas recirculation on the low pressure side of the turbocharging system 5 , while the embodiments of FIGS. 4 and 5 operate with exhaust gas recirculation on the high pressure side of the turbocharging system 5 .

Various methods and engines have been described in connection with various embodiments herein. However, other modifications to the disclosed embodiments may be understood and effected by those skilled in the art when practicing the claimed invention upon study of the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude pluralities. A single controller, processor or other unit may refer to multiple units recited in the claims. It does not indicate that these combinations cannot be used to advantage, as measured by the mere fact that certain measures are recited in different dependent claims. Reference signs used in the claims are intended to limit the scope. should not be interpreted.

1: Cylinder
2: Small gas receiver
3: exhaust gas receiver
4: exhaust valve
5: Turbocharger
7: Compressor
8: turbine
18: scavenging port
29: EGR blower
33: AC electric drive motor
50: controller

Claims (14)

In a uniflow type large turbocharged two-stroke internal combustion engine 100,
a plurality of cylinders (1) having a scavenging port (18) at its lower end and an exhaust valve (4) at its upper end,
an intake system through which scavenging gas is introduced into the cylinder (1), the intake system comprising a scavenging gas receiver (2) connected to the cylinder (1) through the scavenging port (18);
an exhaust system from which exhaust gas generated in the cylinder is exhausted, the exhaust system comprising an exhaust gas receiver (3) connected to the cylinder (1) through the exhaust valve (4);
at least one turbocharger (5) with a turbine (8) of the exhaust system for driving the compressor (7) of the intake system;
a fuel system for delivering fuel to the cylinder (1);
an EGR system for delivering a flow of exhaust gas from the exhaust system to the intake system, the EGR system comprising an EGR blower (29) and an electronically adjustable EGR throttling valve (32,43);
an AC electric drive motor (33) coupled to the EGR blower (29) for driving the EGR blower (29), wherein the AC electric drive motor (33) is directly coupled to the AC grid by an electrical switch (35) and , an AC electric drive motor 33 configured to operate at a predetermined constant speed determined by the AC frequency;
a sensor (27) for providing a signal indicative of an oxygen concentration in said scavenging gas receiver (2), and
a controller (50) receiving said signal and coupled to said electronically adjustable EGR throttling valve (32);
The controller 50 controls the EGR system by adjusting the position of the electronically adjustable EGR throttling valves 32 , 43 as a function of the signal which is the primary means for regulating the flow of exhaust gas through the EGR system. A large turbocharged two-stroke internal combustion engine (100) of a single flow type, configured to regulate the flow of exhaust gas through the engine (100). According to claim 1,
The controller 50 moves the electronically adjustable EGR throttling valves 32 , 43 in a closed direction to decrease the flow of exhaust gas through the EGR system and increase the flow of exhaust gas through the EGR system. and move the electronically adjustable EGR throttling valves (32, 43) in an open direction to 3. The method of claim 1 or 2,
The controller 50 is a bypass connected to an intake system downstream of the compressor 7 and an exhaust system upstream of the turbine 8 as a primary or secondary means for regulating the flow of exhaust gas through the EGR system. of the single flow type, configured to regulate the flow of exhaust gas through the EGR system by adjusting the degree of opening of an electronically controlled cylinder bypass throttling valve (42) or orifice (49) disposed in a conduit (47) A large turbocharged two-stroke internal combustion engine (100). 4. The method of claim 3,
The controller 50 moves the electronically controlled cylinder bypass throttling valve 42 or orifice 49 in a closed direction to increase the flow of exhaust gas through the EGR system and exhaust through the EGR system. A large turbocharged two-stroke internal combustion engine (100) of a single flow type, configured to move the electronically controlled cylinder bypass throttling valve (42) or orifice (49) in an open direction to reduce the flow of gas. 5. The method according to any one of claims 1 to 4,
The controller (50) controls the flow of exhaust gas through the EGR system to maintain the oxygen concentration in the scavenging gas receiver (2) close to an oxygen concentration setpoint, the scavenging oxygen concentration setpoint being preferably an engine A large turbocharged two-stroke internal combustion engine (100) of a single flow type, configured to be adapted to a load. 6. The method according to any one of claims 1 to 5,
the controller is configured to maintain the oxygen concentration in the scavenging gas receiver (2) close to a scavenging oxygen concentration set point using the signal from the first sensor (27) in feedback and/or feedforward control, the scavenging oxygen concentration A large turbocharged two-stroke internal combustion engine 100 of single flow type, the setpoint preferably being adjusted to the engine load. 7. The method according to any one of claims 1 to 6,
The AC electric drive motor (33) is a single flow type large turbocharged two-stroke internal combustion engine (100), which is a synchronous electric drive motor or an asynchronous electric drive motor. 8. The method of claim 7,
A single flow type large turbocharged two-stroke internal combustion engine (100), wherein the drive shaft of the AC electric drive motor (33) is directly coupled to the drive shaft of the EGR blower (29). 9. The method according to any one of claims 1 to 8,
and the electronically adjustable EGR throttling valve (32) is disposed downstream of the EGR blower (29). 9. The method according to any one of claims 1 to 8,
and the electronically adjustable EGR throttling valve (43) is disposed upstream of the EGR blower (29). 9. The method according to any one of claims 1 to 8,
Large turbo of single flow type, comprising an electronically adjustable EGR throttling valve (32) downstream of the EGR blower (29) and an electronically adjustable EGR throttling valve (43) upstream of the EGR blower (29) A charging two-stroke internal combustion engine (100). 12. The method according to any one of claims 1 to 11,
and the AC electric drive motor (33) is coupled to the AC grid without equipment for changing frequency and/or voltage. 13. The method according to any one of claims 1 to 12,
The EGR blower layout is a predefined exhaust gas bypass valve (41) and cylinder required to achieve the relevant oxygen setpoint in the scavenging air receiver (2) and covered by the fixed speed of the EGR blower (29). In accordance with the operating point having the lowest pressure ratio and volumetric flow rate at the bypass valve 42 position, the controller 50 opens the controlled exhaust gas bypass valve 41, thereby reducing the oxygen setpoint for all other operating points. A large turbocharged two-stroke internal combustion engine (100) of a single flow type, configured to control the EGR flow as a function. 13. The method according to any one of claims 1 to 12,
The EGR blower layout is required to achieve the relevant oxygen set point in the scavenging air receiver (2) to the extent in which the auxiliary blower normally operates, and is covered by the fixed speed of the EGR blower (29). In accordance with the operating point with the lowest pressure ratio and volumetric flow rate with 16 turned off, the controller 50 switches off and/or off one or more of the auxiliary blowers 16 of the auxiliary blower or blowers 16. A large turbocharged two-stroke internal combustion engine (100) of a single flow type, configured to control the EGR flow as a function of an oxygen setpoint for this and other operating points by throttling the flow.

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