JP5681742B2 - Large low-speed turbocharged two-cycle internal combustion engine having a crosshead and an exhaust gas (combustion gas) recirculation system - Google Patents

Description

  The present invention relates to a large low-speed turbocharged two-cycle internal combustion engine having a crosshead and an exhaust gas (combustion gas) recirculation system. The present invention further relates to a method of operating a large low speed turbocharged internal combustion engine having a crosshead and an exhaust gas (combustion gas) recirculation system.

Background of the Invention

  A large low-speed turbocharged two-cycle internal combustion engine having a crosshead is an engine (engine) having at least one cylinder and a reciprocating piston received therein. These engines have a crosshead disposed between the piston and the crankshaft. The combustion chamber is defined by a piston, a cylinder inner wall, and a cylinder cover at one end of the cylinder. The cylinder cover includes an exhaust valve. The exhaust valve can be controllably and intermittently opened to discharge combustion debris from the combustion chamber to the exhaust duct system. These engines also have means for intermittently establishing an opening near the second end of the cylinder prior to combustion therein. Then, scavenging is performed toward the first end by introducing a pressurized scavenging gas containing oxygen through the opening. These engines also include means for injecting fuel into the pressurized scavenging gas to generate combustion in the combustion chamber.

  Engines according to the above definition are often referred to as “crosshead uniflow large turbocharged two-cycle diesel engines” or simply “large two-cycle engines”. However, these terms are not completely correct. Also, these engines are often implemented with a plurality of upright cylinders arranged in series, with these pistons operating on a single crankshaft. These engines can have a pure two-cycle operating sequence. Also, these engines are usually large in cylinder diameter and physical size of piston stroke and are often as high as a house. These engines are capable of producing several megawatts of power at relatively low rotational speeds to drive generators in power plants, for marine vessel propulsion, or to meet power requirements in the range of more than MW. Occur.

Currently, there are many options for reducing NOx generation in large, low speed turbocharged internal combustion engines. These options should be applied to the engine process. Specifically, there are the following.
Exhaust gas or combustion gas recirculation (EGR)
・ Use of water emulsion fuel ・ Humidification of fresh air, that is, Scavenge Air Moisterization (SAM)

  In this specification, the term “exhaust gas recirculation or combustion gas recirculation” is referred to as EGR.

  So far, the most effective way to reduce NOx generation is EGR. DE19809618 discloses a large two-cycle turbocharged diesel engine with an exhaust gas recirculation system. This type of EGR is also referred to as Combustion Gas Recirculation (CGR) because in the engine of this document the gas is taken directly from the cylinder. Where the term “exhaust gas recirculation” is used in this document, it covers both the recirculation of gas taken from exhaust gas and the recirculation of gas taken directly from each combustion cylinder.

In exhaust gas recirculation, the exhaust gas is mixed with uncleaned scavenging, so that the oxygen content of the gas mixture at the start of combustion is reduced. This achieves a reduction in the possibility of NO _x generation during the combustion process.

  Beginning in 2011, marine diesel engines installed on new vessels must meet the IMO Tier II NOx emission requirements. In the case of a large low-speed turbocharged internal combustion engine, the limit is 14.4 g / kWh. This can be achieved by improvements of conventional engines, but these lead to increased fuel consumption.

  When sailing into a specific Emission Control Area (ECA), institutions installed on ships constructed after 1 January 2016 must meet the much lower limit Tier III In the case of a low speed engine, it is 3.4 g / kWh. This limitation cannot be achieved by improvements to conventional engines, and other methods for reducing emissions, such as EGR, must be used.

  The exhaust gas system may be provided with a SOx scrubber or other device on the low pressure side of the turbine of one or more turbochargers of the engine. The SOx scrubber is a bulky device because it must be able to handle the mass flow of exhaust gases that are produced when the engine delivers power at maximum continuous rating (MCR).

DE19809618

  In view of this background, the object of the present application is to provide an engine that meets various emission regulations and that can make it economically possible from the perspective of both manufacturing and operating costs. That is.

  This object is achieved by providing a large low speed multi-cylinder turbocharged internal combustion engine having a crosshead and having a defined maximum continuous rating. The engine includes an exhaust gas system, a scavenging system, a turbocharger having a compressor in the scavenging system, a turbine in the exhaust gas system, an EGR system connected to the exhaust system and the scavenging system, and a controller With. This controller distributes the total mass flow rate of exhaust gas coming from the cylinder between the EGR mass flow rate entering the EGR system and the exhaust gas mass flow rate flowing through the exhaust gas system towards the turbine Configured as follows. The controller has a selected EGR rate that is a ratio of the EGR mass flow rate to the total mass flow rate of the exhaust gas, and an EGR rate that can be selected in a range from zero to a predetermined maximum rate. The exhaust gas system has a specified maximum continuous capacity to handle the exhaust gas mass flow rate, which is less than the total exhaust gas mass flow rate coming from the cylinder at the maximum continuous rating. The controller delivers excess mass flow rate into the EGR system when the actual total exhaust gas mass flow rate coming from the cylinder exceeds the specified maximum capacity of the exhaust gas system, regardless of the selected EGR rate. Configured as follows.

  Thus, the maximum mass flow of exhaust gas flowing through the exhaust gas system towards the turbocharger turbine can be significantly reduced, providing considerable cost savings both in terms of engine operation and configuration.

  Therefore, the controller will distribute the total mass flow rate of exhaust gas coming from the cylinder between the EGR mass flow rate entering the EGR system and the exhaust gas flow rate flowing through the exhaust gas system towards the turbine. Configured. However, the distribution is configured based on a selected EGR rate of the EGR mass flow rate relative to the total mass flow rate.

  In one embodiment, the specified maximum capacity is in the range of 50% to 90% of the total exhaust gas mass flow rate coming from the cylinder with maximum continuous rating.

  In one embodiment, the exhaust gas system comprises at least an exhaust gas treatment element.

  In one embodiment, the scavenging system has a specified maximum capability for handling a scavenging mass flow rate, and a specified maximum that is less than the charge gas mass flow rate of the total scavenging gas flowing to the scavenging gas receiver at the maximum continuous rating. Have the ability. Accordingly, the components of the scavenging system can be reduced in size, thereby saving manufacturing and operating costs.

  In one embodiment, the scavenging system comprises at least a scavenging cooler.

  In one embodiment, the controller is configured to operate in at least two modes:

  One is a low emission mode in which the engine depends on the load of the engine and the selected EGR rate is selected to just meet the exhaust requirements in the absence of excess mass flow rate.

  The other is to avoid that the mass flow rate of the engine depending on the load of the engine and flowing through the exhaust gas system to the turbine of the turbocharger exceeds the specified maximum continuous capacity. Except when an EGR rate higher than zero is required, the selected EGR rate is an emission reduction mode that is selected to be zero.

  The above object is also achieved by providing a method for operating a large, low speed, multi-cylinder turbocharged internal combustion engine having a crosshead and having a defined maximum continuous rating. The engine includes an exhaust gas system, a scavenging system, a turbocharger having a compressor in the scavenging system, a turbine in the exhaust gas system, an EGR system connected to the exhaust system and the scavenging system, and a controller With. The method distributes the total mass flow rate of exhaust gas coming from the cylinder between the EGR mass flow rate entering the EGR system and the exhaust gas mass flow rate flowing through the exhaust gas system towards the turbine. And selecting an EGR rate in the range from zero to a predetermined maximum rate according to the selected EGR rate, which is the ratio of the EGR mass flow rate to the total mass flow rate of the exhaust gas. The exhaust gas system has a specified maximum continuous capacity with respect to handling exhaust gas mass flow rate, which is less than the total exhaust gas mass flow rate coming from the cylinder with a maximum continuous rating, Regardless of the selected EGR rate, when the actual total exhaust gas mass flow rate coming from the cylinder exceeds the specified maximum capacity of the exhaust gas system, the excess mass flow rate is sent to the EGR system.

  Thus, the maximum mass flow of exhaust gas flowing through the exhaust gas system toward the turbocharger turbine can be significantly reduced, providing considerable cost savings in both engine manufacture and configuration.

  In certain embodiments, the method includes determining an actual total mass flow rate coming from a cylinder; determining a difference between the actual mass flow rate and a specified capability; Applying a desired EGR rate selected from zero to a predetermined maximum rate when less than the specified capacity; and through the exhaust gas system when the actual mass flow rate is greater than the specified capacity Applying an EGR rate that is large enough to ensure that the mass flow flowing to the turbocharger turbine does not exceed a specified capacity.

  In one embodiment, the method comprises a low emission mode, wherein the engine is dependent on the load of the engine and operates at an EGR rate required to meet a low emission requirement when there is no excess mass flow rate; The minimum required to avoid that the engine depends on the load of the engine and the mass flow rate flowing through the exhaust gas system to the turbine of the turbocharger exceeds the specified maximum continuous capacity And further operating the engine in one of at least two modes: an exhaust reduction mode that operates at an EGR rate of:

  In one embodiment of the method, the operating mode is selected manually by an operator or automatically by an electronic controller unit.

  In one embodiment of the method, the controller determines an operating mode based on information regarding the geographic location of the institution.

  Further objects, features, advantages and characteristics of the engine and the method for operating the engine according to the present disclosure will become apparent from the following detailed description.

The following detailed description portion of the specification describes the invention in more detail with reference to the exemplary embodiments shown in the drawings.
FIG. 2 is a schematic diagram of an engine according to an exemplary embodiment. 2 is a schematic diagram of an engine according to another exemplary embodiment. FIG. 2 is a flowchart illustrating an exemplary embodiment of a method for operating an engine.

Detailed Description of the Preferred Embodiment

  FIG. 1 shows a schematic view of an engine having the form of a crosshead type large-scale low-speed turbocharged two-cycle internal combustion engine 1. In the exemplary embodiment, the engine 1 has six cylinders 4 (indicated by dashed circles) arranged in series. Large turbocharged two-stroke diesel engines typically have 5 to 16 cylinders in series, which are supported by the engine frame 2.

  The engine 1 is a two-cycle uniflow type having a scavenging port in the lower region of the cylinder 4 and an exhaust valve at the top of the cylinder 4. The general operating principle of such engines is well known and will not be described in detail here.

  The engine 1 has an air supply system. The air supply system has an inlet 5, which may be equipped with a silencer or a filter unit, which are provided upstream of the compressor 7 of the turbocharger 6. The turbocharger 6 is also provided with a turbine 8 that is part of an exhaust gas system that will be described in detail later. Although only one turbocharger 6 is shown in the figure, a plurality of turbochargers can be installed in the engine and operated. The compressed hot scavenging gas leaves the compressor 7 through a pipe 9 leading to a scavenging gas receiver 16. Before arriving at the scavenging gas receiver 16, the scavenging gas first passes through the first cooler 11, then passes through the second air cooler 12, and then passes through the inversion chamber / water mist collector 14. pass.

  In the first cooler 11, the scavenging air is humidified and slightly cooled. In the air cooler 12, the scavenging air is typically cooled from a range of about 190 degrees Celsius to about 40 degrees Celsius.

  At the mixing point 10, the recirculated exhaust gas flow is added to the scavenging airflow. The amount of recirculated exhaust gas added to the scavenging air varies between zero and a predetermined maximum mass flow ratio, depending on the operating mode and engine load / operating conditions.

  In FIG. 1, the components of the air supply system that are upstream of the mixing point 10 are shown included within a dashed line 42.

  The inversion chamber / water mist collector 14 ensures that any water droplets in the gaseous scavenging medium are collected and removed to avoid eventually going to the combustion chamber.

  Except at low engine loads (typically less than about 40% of the MCR), the scavenging gas proceeds directly from the reversing chamber / water mist collector 14 to the scavenging gas receiver 16. When the engine load is low, the scavenging pressure generated by the turbine 7 is usually insufficient, so the scavenging pressure may be increased by the auxiliary blower 15 when switched to function at low engine load conditions. .

  The scavenging gas enters the combustion chamber in the cylinder 4 from the scavenging gas receiver 16 through the above-described scavenging port according to a predetermined operation sequence of the cylinder 4.

  After combustion, the exhaust gas leaves the combustion chamber in the cylinder 4 through the exhaust valve and reaches the exhaust gas receiver 17. The exhaust gas receiver 17 is often a large cylindrical container extending along the longitudinal direction of the engine 1. The exhaust gas receiver 17 has a large volume in order to sufficiently weaken the pressure fluctuation of the exhaust gas coming from each cylinder 4. The exhaust gas receiver 17 may be divided into separate parts, and each part may contain various elements to assist the overall function of the engine. They may be, for example, for collecting useful heat from exhaust gases or for adding various substances to improve the overall function of the engine.

  The engine 1 has a mass flow rate of exhaust gas that leaves the cylinder 4 and enters the exhaust gas receiver 17 at the maximum continuous rating.

  The exhaust gas exits the exhaust gas receiver 17 through the pipe 18. At split point 20, a portion (percentage) of the total exhaust gas mass flow coming from cylinder 4 is directed to the EGR system, while the remaining exhaust gas total mass flow coming from the cylinder is split in the exhaust gas system. Directed downstream of point 20.

  Downstream of the dividing point 20, the exhaust gas travels through the pipe 31 to the turbine 8 of the turbocharger 6. In this embodiment, the exhaust gas travels downstream of turbine 8 through pipe 32 via exhaust heat recovery unit 33 and then through SOx scrubber 34. Thereafter, the exhaust gas is directed to the environment, ie the ambient air. The exhaust heat recovery unit 33 and particularly the SOx scrubber 34 are devices having a very large volume. For example, in a ship where an engine is used as a propulsion unit, it is difficult to find a space for mounting. Various additional or alternative recovery or processing devices may be provided in the middle of the exhaust ducts 31 and 32 downstream of the dividing point 20. As the mass flow rate of exhaust gas increases, the trend of increasing the physical volume of the associated equipment is common, and is generally true for all of the above recovery and treatment equipment.

  For ease of understanding, the components of the exhaust gas system downstream of the dividing point 20 are shown in FIG.

  From the dividing point 20, the recirculated exhaust gas passes through the pipe 28 via the electronic control valve 21, the press scrubber 22, the mixture cooler 23, the wet scrubber 24, the water mist collector 25, and the EGR blower 26. Proceed to mixing point 10 where the recirculated exhaust gas is added to the scavenging air.

  A controller in the form of an electronic control unit 50 sends control signals to the electronic control valve 21, EGR blower 26, auxiliary blower 15 and also to water pumps (not numbered) associated with the cooling units 11, 12, 23. Send a control signal. This electronic control unit can also be used to control other functions of the engine, such as, for example, fuel injection systems, engine cooling systems, engine lubrication systems, exhaust valve actuation systems, and the like.

  The electronic control unit 50 determines the recirculated exhaust gas ratio through signals to the electronic valve 21 and the EGR blower 26.

  The electronic control unit 50 determines the required EGR rate based on the engine operating conditions such as the selected operation mode and engine load. The engine 1 and the electronic control unit 50 are configured to be able to operate in at least two different modes. One mode is Low Emission Mode (LEM) that provides low NOx emission values. Another mode is a reduced exhaust mode (REM). This mode provides better fuel efficiency at engine loads below the maximum continuous rating, but has the tradeoff of higher NOx emission levels at engine loads below the maximum continuous rating.

  These modes of operation can be selected automatically based on the geographic location of the engine 1 or can be selected through input by an operator of the engine 1. Alternatively, it can be selected automatically by combining a GPS unit with the control.

  According to the engine 1 according to the present exemplary embodiment, in the LEM, the NOx emission value can be suppressed to less than the strict upper limit value of ECA Tier III without any problem. REM also has good fuel efficiency and NOx emission levels are much lower than required in non-ECA waters.

  In order to meet the most stringent emission regulations applicable to ECA under Tier III, the engine is operated at a relatively high EGR rate in low emission mode (LEM). This relatively high EGR rate is often kept constant regardless of engine load. Typically, the EGR rate in the low emission mode is between about 32% and about 44%. In the example given in Table 1 below, the low emission mode (LEM) EGR rate is 38%. Also, in emission reduction mode (REM), the EGR rate may vary in relation to the engine load to compensate for the effects of the specific behavior of the engine in specific partial load conditions.

Table 1 below shows engine load as a percentage of maximum continuous rating and EGR rate at different engine loads, ie, 25% MCR, 50% MCR, 75% MCR, and 100% MCR, and NO _x The emission level (g / kWh) is listed. NO _x value for use in IMO NO _x cycles, and NO _x values are also shown combined in accordance with IMO cycle. Table 1 also shows the exhaust gas passing through the downstream portion of the split point 20 in the exhaust gas system as a percentage of the mass flow rate of exhaust gas coming from all cylinders of the engine when the engine is operating at a maximum continuous rating of 100%. The mass flow rate is listed.

  The size of the part downstream of the dividing point 20 in the exhaust gas system (enclosed by the broken line 44) is determined by the exhaust gas throughput, which is the maximum and the engine 1 operates at the maximum continuous rating. Exhaust that must pass through the EGR system at maximum continuous rating (to comply with IMO Tier III ECA limits for the engine in question) from the mass flow rate corresponding to the total mass flow rate of exhaust gas coming from cylinder 4 when It is good also as the quantity which subtracted the value of the mass flow rate of gas.

  This prescribed capacity C for the mass flow rate of the exhaust gas system downstream of the split point 20 is determined by the “size” or capacity of the component in the region enclosed by the dashed line 44 in the exhaust gas system (ie, Restricted).

  As used herein, the phrase “sized” refers to the capability (mass flow rate) of the exhaust gas system and its components downstream of the dividing point 20 that are required without substantially being overcapacity. It means that it is designed and constructed so that it can cope with, i.e., not larger than necessary.

  The amount of exhaust gas flow rate from cylinder 4 that exceeds this specified capacity C and that needs to be passed to the EGR system is referred to in this specification as “Excess Mass Flow Rate”. Rate) ".

  For example, in a 6-cylinder engine with a bore of 98 cm and a stroke of about 2.4 m, such as MAN B & W 6K98ME-C7, which provides about 36 MW of torque at about 100 revolutions, all exhaust gases coming from cylinder 4 with maximum continuous rating The mass flow rate is about 300,000 kg / h. In the case of this engine, if the EGR rate shown in Table 1 below is adopted, the size of the downstream part of the dividing point 20 in the exhaust gas system is determined so that only 62%, that is, 186,000 kg / h can be processed. It is done. Therefore, the excess mass flow rate at the maximum continuous rating passed through the EGR system is 114 metric tons / h.

100％の最大連続定格時にシリンダ4からやってくる排気ガスの全質量流量率より低い質量流量率の排気ガスに対応できるように大きさが決定された（すなわちそのような処理能力を有する）、排気システムにおける分割点20の下流部分と、機関負荷に応じて最低限のEGR率を適用するREM運転モードとの組み合わせは、製造および運転の両方の観点において、総合的に経済的な機関のコンセプトを提供する。 When the engine 1 is operated in the emission reduction mode (REM), the EGR rate is not kept constant with respect to fluctuations in engine load. Instead, the EGR rate is kept as low as possible while not exceeding the specified capacity of the downstream part of the split point 20 in the exhaust gas system. As shown in Table 1, the electronic control unit 50 maintains the EGR rate at zero in all regions where the engine load is 62% or less of the maximum continuous rating. When the engine load exceeds 62% of the maximum continuous rating, the electronic control unit 50 adjusts the EGR rate so that the mass flow rate through the downstream part of the dividing point 20 in the exhaust gas system is a rate corresponding to the specified capacity. Apply. That is, an EGR rate is applied such that the mass flow rate is 62% of the mass flow rate of exhaust gas sent from the cylinder when the maximum continuous rating is 100%. Therefore, in emission reduction mode, engine 1 will be used when the engine load is between 62% and 100% unless there is another reason that it is desirable to further recirculate some exhaust gas through the EGR system. It operates at an EGR rate that varies between zero and 38%, and at an engine load of less than 62%, it operates at an EGR rate of zero.

An exhaust system that is sized (ie, has such processing capability) to accommodate exhaust gas with a mass flow rate lower than the total mass flow rate of exhaust gas coming from cylinder 4 at 100% maximum continuous rating The combination of the downstream part of the divide point 20 and the REM operating mode that applies the minimum EGR rate according to engine load provides a comprehensive economic engine concept from both a manufacturing and operating point of view. To do.

  The numbers in Table 1 above are exemplary. Other values of EGR rate that can be applied in TIRE III mode are also possible. Of the total mass flow rate of the exhaust gas coming from the cylinder, the proportion of the mass flow rate used for the EGR flow is in the range of 10% to 50%, preferably in the range of 20% to 45%, more preferably 36. % To 40%.

  Therefore, the magnitude of the exhaust gas mass flow rate, determined so that the downstream part of the split point 20 in the exhaust gas system can be processed, is the mass flow rate of the total exhaust gas flow coming from the cylinder at the maximum continuous rating It can be in the range of 50% to 90% of the rate, preferably in the range of 55% to 80%, more preferably between 60% and 64%.

  FIG. 2 shows another exemplary embodiment of the engine 1. This embodiment is basically the same as the embodiment shown in FIG. 1, except that the EGR system is connected to the exhaust system at the exhaust gas receiver 17 so that the exhaust gas receiver 17 has a clear dividing point or position. The difference is that the EGR system is connected to the scavenging system at the scavenging gas receiver 16 and thus a mixing point is formed. In this embodiment, the water mist collector 14 and the auxiliary blower 15 are provided upstream of the mixing point in the scavenging system. Therefore, these components can be designed to be small in size. Otherwise, the operation and control of the engine according to FIG. 2 is the same as that of the engine according to FIG.

  Other locations of the mixing “point” are possible, ie 10 locations. A group of embodiments as defined in the claims includes adding recirculated exhaust gas at a location upstream of the compressor 7. Thereby, for example, the requirement that the output from the EGR system is pressurized is substantially reduced. However, capacity must be increased for some of the components in the scavenging gas inlet system 42 to handle the total mass flow rate of the feed gas at maximum continuous rating. Furthermore, embodiments in which the exhaust gas is introduced directly into the respective cylinders for recirculation before or after closing the cylinder openings for scavenging are also included in the scope of the claims. For such embodiments, the EGR system must be adapted, especially with respect to valves for distribution to the cylinder and the required pressure level.

  FIG. 3 is a simple flowchart showing an example of an operation method of the engine. The method includes determining the geographical location of the vessel / engine 1 through navigation signals such as GPS to the electronic control unit 50. The electronic control unit 50 determines whether the determined geographical location is within the ECA area based on the information stored therein. If the determined geographical location is within the ECA, the electronic control unit 50 selects a low emission mode (LEM) operating method with a fixed predetermined EGR rate. If the determined geographical location is outside the ECA, the electronic control unit 50 selects the emission reduction mode (REM) and operates with a minimum EGR rate. The electronic control unit 50 confirms the geographical location at specific intervals and automatically selects the operating mode depending on the conclusion that it is located inside or outside the ECA. Basically, the engine operator can always manually discard the mode of operation selection, for example when an emergency needs to do so.

  In order to determine the minimum EGR rate when operating in the emission reduction mode (REM), the electronic control unit 50 determines the actual mass flow rate flowing from the cylinder. In certain embodiments, this is enabled by using a look-up table stored in the electronic control unit 50. This table contains the mass flow rate coming from the cylinder with respect to the engine load as a percentage of the maximum continuous rating. The electronic control unit 50 then determines the difference between the determined actual mass flow rate and the defined capacity of the downstream portion of the split “point” 20 in the exhaust gas system. When the determined actual mass flow rate is equal to or less than the specified capacity, the electronic control unit 50 applies zero as the EGR rate. When the determined actual mass flow rate is larger than the specified capacity of the exhaust system paths 31 and 32 downstream from the dividing point, the electronic control unit 50 opens the EGR valve 21 and determines the mass of the determined difference. The flow rate is separated and guided downstream of the EGR valve 21. This establishes an EGR rate equal to the separated mass flow rate divided by the actual mass flow rate from the cylinder. As an example, when the mass flow rate coming from the cylinder is 100 kg / s and the specified capacity is 80 kg / s, 20 kg / s is led through the EGR valve 21, so the established EGR rate is ( 100-80) /100=0.2, that is, 20%.

  Also, keeping the limit on the maximum mass flow rate through the exhaust system low is inevitably necessary when the engine is operated to produce more combustion gases than the allowable limit of the exhaust system according to the present invention. Note that the separation gas that is led to the positive contribution to the total mass flow rate of the scavenging gas supplied to the cylinder. Also, the mass flow rate capacity required at the inlet / upstream (5-7-9-11-14) of the scavenging system is reduced.

  Thus, the present invention also offers the possibility of a useful combination of reducing the size of both intake and exhaust system elements to the extent allowed by the EGR rate. The above elements here include, for example, turbochargers, scavenging “treatment devices”, engine room ventilation, SOx scrubber systems, Waste Heat Recovery (WHR) systems, and other applications. included. The reduction in size greatly reduces the hardware and installation costs of these elements, and can be expected to gain significant engine room space when installing SOx scrubbers and WHRs.

  Waste heat recovery unit 33 also benefits from the reduced maximum mass flow rate. The reason for this is that there is a relatively large (~ maximum amount) of hot exhaust gas flow rate over a fairly wide range of operating range and operating time of the engine, and since it is stably saturated, the heat transfer efficiency It is because it becomes favorable. In contrast, conventional engines rarely reach the maximum continuous rating and can rarely beneficially “saturate” their WHR units.

  Further, by suppressing the maximum intake amount of the engine, the ventilation of the engine room is reduced, resulting in further savings. In particular, the costs for the silencer and the engine room blower can be reduced.

  The emission reduction mode (REM) is a dedicated operation mode for marine diesel engines to which EGR is applied. REM includes the control of the EGR rate in order to maintain a permanently low or reduced maximum mass flow rate downstream of the split point or location of the exhaust gas (to the environment) and thereby Means providing an opportunity to reduce the size and cost of components in the exhaust system.

  When navigating outside the Emission Control Areas (ECA), the EGR rate is significantly higher than the ratio required to comply with NOx standards outside the ECA. At 100% MCR, the EGR rate is equal to the ratio required to comply with NOx standards in the ECA. When the load is low, the EGR rate can be reduced while keeping the NOx level below the on-site NOx standard.

  In particular, reducing the size of the SOx scrubber has a significant economic impact for several reasons. The SOx scrubber installed on the low pressure side of the turbocharger is part of a device that is very bulky, costly, and takes up space, so any size reduction will reduce the cost of other devices Provide space for. In addition, SOx scrubbers are usually operated using a large amount of seawater as a cleaning medium, and pumping this seawater consumes energy. In addition, chemicals such as NaOH must be added to the seawater, which can increase the amount of exhaust gas (mass flow rate) to be treated, further increasing costs. Therefore, reducing the maximum mass flow rate of exhaust gas that needs to pass through the part downstream of the split point in the exhaust system, thereby reducing the maximum mass flow rate of exhaust gas that needs to pass through the SOx scrubber, Provides considerable economic benefits.

  Of course, the engine may also be operated in a mode that falls between the LEM mode to operate within the ECA and the REM mode. That is, the EGR rate may be greater than the ratio required to maintain the exhaust system mass flow rate downstream of the split point. The EGR rate may be greater than the exhaust system mass flow rate downstream of the split point. It means that it is larger than the ratio required in order not to impair the rate. However, for fuel economy reasons, it may operate at a minimum EGR rate.

  From the above description, in the engine according to the invention, the advantages in terms of any of size, spatial requirements and costs are from the elements of the scavenging intake, from the elements of the group involved in “treatment or regulation”, and It will also be clearly understood that it can be obtained from the elements upstream of the inlet that takes the recirculated exhaust gas into the scavenging / feeding gas.

  For many marine vessels that have been operated with less stringent NOx emission standards, instead of replacing existing engines or dismantling the ships to meet more stringent future NOx emission standards. There may be some interest in adapting existing institutions to new standards. possible. Existing institutions that are modified in accordance with the concepts of the present invention are also within the scope of the appended claims.

  The number and type of engine components used for such refurbishment are significantly different from the parts used in the engine in its original state, and may vary from engine to engine and even for new engines. Electronically readable / writable tags, preferably remotely readable, to quickly identify new institutions or institutions that have been modified to become inventions, and to notify them of revision history, etc. It would be beneficial to incorporate an RFID type into the institution of the present invention.

  The term “comprising”, when used in the claims, does not exclude the inclusion of other elements or steps. The singular terms in the claims do not exclude a plurality. A single processor, apparatus, or other unit may fulfill the functions of several means recited in the claims.

  Any reference signs used in the claims shall not be construed as limiting the scope.

  Although the present invention has been described in detail for purposes of illustration, such detailed description is intended solely for that purpose and modifications may be made by those skilled in the art without departing from the scope of the invention. Please understand that you may.

Claims (13)

A large-sized low-speed multi-cylinder turbocharged internal combustion engine (1) having a crosshead and having a predetermined maximum rating,
An exhaust gas system (44), a scavenging system (42), a turbocharger (6) having a compressor (7) in the scavenging system (42), and a turbine in the exhaust gas system (44) (8) and
An EGR system connected to the exhaust system (44) and the scavenging system (42);
A controller (50);
The controller (50) includes a total exhaust gas mass flow rate coming from the cylinder (4), an EGR mass flow rate entering the EGR system, and an exhaust gas system (44) toward the turbine (8). And the controller has a selected EGR rate that is a ratio of the EGR mass flow rate to the total exhaust gas mass flow rate and is zero. And an EGR rate that is selectable in a range from a predetermined maximum value, the institution further:
The exhaust gas system (44) has a specified maximum capacity (C) for handling exhaust gas mass flow, wherein the specified maximum capacity (C) is the total capacity directly coming from the cylinder at the maximum rating. Less than the exhaust gas mass flow rate,
The controller (50) causes the actual total exhaust gas mass flow rate of exhaust gas coming from the cylinder to exceed the specified maximum capacity (C) of the exhaust gas system (44) regardless of the selected EGR rate. Sometimes configured to deliver excess mass flow into the EGR system;
An engine (1) characterized by   The specified maximum capacity (C) of the exhaust gas system (44) downstream of the split is in the range of 50% to 90% of the total exhaust gas mass flow coming from the cylinder at the maximum rating, or 55% The engine (1) according to claim 1, which is in the range of -80% or in the range of 60% -64%.   The engine (1) according to claim 1 or 2, wherein the exhaust gas system (44) comprises at least an exhaust gas treatment element (33, 34).   The scavenging system (2) has a prescribed maximum capacity for handling the scavenging mass flow rate (A) and is less than the scavenging mass flow rate of the total scavenging gas (B) flowing to the scavenging gas receiver (14) at the maximum rating. 4. The engine (1) according to any of claims 1 to 3, having a defined maximum capacity.   The engine (1) according to any of the preceding claims, wherein the scavenging system (42) comprises at least a scavenging cooler (12). The controller (50) has at least two modes:
A low emission mode in which the engine depends on the load of the engine and the selected EGR rate is selected to just meet the exhaust requirements in the absence of excess mass flow;
To avoid that the engine depends on the load of the engine and that the exhaust gas mass flow through the exhaust gas system (44) towards the turbine (8) exceeds the specified maximum capacity (C). Exhaust reduction mode, wherein the selected EGR rate is selected to be zero, except when an EGR rate higher than zero is required for
An engine (1) according to any of the preceding claims, configured to be operable with A method of operating a large, low speed, multi-cylinder turbocharged internal combustion engine (1) having a crosshead and having a defined maximum rating, the engine comprising an exhaust gas system (44); and a scavenging system A turbocharger (6) having a compressor (7) in the scavenging system (42); a turbine (8) in the exhaust gas system (44); and the exhaust system (44) And an EGR system connected to the scavenging system (42); and a controller (50), the method comprising:
The total exhaust gas mass flow rate coming from the cylinder (4) is defined as the EGR mass flow rate entering the EGR system and the exhaust gas mass flow rate flowing through the exhaust gas system (44) toward the turbine (8). Distributing between;
Selecting an EGR rate in a range from zero to a predetermined maximum rate according to a selected EGR rate, which is the ratio of the EGR mass flow rate to the total exhaust gas mass flow rate;
Including
The exhaust gas system (44) has a specified maximum capacity (C) for handling exhaust gas mass flow, wherein the specified maximum capacity (C) is the total capacity directly coming from the cylinder at the maximum rating. Less than the exhaust gas mass flow rate,
Regardless of the selected EGR rate, excess mass flow to the EGR system when the actual total exhaust gas mass flow coming from the cylinder exceeds the specified maximum capacity (C) of the exhaust gas system (44). And sending
A method characterized by. Determining the actual total exhaust gas mass flow rate coming from the cylinder (4);
Determining a difference between the actual total exhaust gas mass flow rate and the specified maximum capacity (C);
Applying a desired EGR rate selected in a range from zero to a predetermined maximum rate when the actual total exhaust gas mass flow rate is less than or equal to the specified maximum capacity (C) ;
When the actual total exhaust gas mass flow rate is greater than the specified maximum capacity (C) , the exhaust gas mass flow rate flowing through the exhaust gas system (44) toward the turbine (8) is Applying an EGR rate large enough to ensure that the specified maximum capacity (C) is not exceeded;
The method of claim 7, further comprising: Depending the engine load of the engine, operates the EGR rate required to meet the low emissions requirements when there is no excess mass flow rate, low emission mode and the engine depends on the load of said engine, said Operates at the minimum EGR rate required to avoid the exhaust gas mass flow through the exhaust gas system (44) toward the turbine (8) exceeding the specified maximum capacity (C) The exhaust reduction mode,
Further comprising operating the engine (1) in one of at least two modes of:
The method of claim 7 .   10. The method according to claim 9, wherein operating the engine (1) means that the operation mode is manually selected by an operator or the operation mode is automatically selected by an electronic controller unit. Including.   The method of claim 10, wherein the controller determines the mode of operation based on information regarding a geographic location of the institution. Any minimum EGR rate that may prevent the exhaust gas mass flow through the exhaust gas system (44) toward the turbine (8) from exceeding the specified maximum capacity (C), either The method of operating an engine according to claim 7 , further comprising applying in a mode of operation. And to determine the actual total exhaust gas mass flow coming from the cylinder (4),
Determining a difference between the actual total exhaust gas mass flow rate and the specified maximum capacity (C) ;
If the actual total exhaust gas mass flow rate is less than or equal to the specified maximum capacity (C) , applying an EGR rate of zero;
If the actual total exhaust gas mass flow rate is greater than the maximum capacity (C) of the prescribed, the difference obtained by subtracting the maximum capacity (C) of the specified from the actual total exhaust gas mass flow rate, the actual total exhaust Applying an EGR rate equal to that divided by the gas mass flow rate;
The method of claim 7 , further comprising:

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