Internal combustion engine

Abstract

To provide an internal combustion engine and a method of operating the internal combustion engine with better performance than in the prior art.SOLUTION: Provided is an internal combustion engine (20), namely a large vessel engine or a stationary engine, comprising at least one cylinder (21) having an inner diameter (22) of at least 200 mm. The internal combustion engine (20) comprises a system (1) for exhaust gas recirculation with an EGR path (13) arranged between an exhaust outlet (2) and an air inlet (3), and the internal combustion engine (20) comprises a turbocharger (5). The system (1) for exhaust gas recirculation comprises at least one first sensor (12) providing a signal representative of the NOx content of exhaust gas leaving the cylinder, and a control unit (11) configured to control the amount of exhaust gas recirculated to the air inlet (3) on the basis of the signal from the first sensor (12).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an internal combustion engine equipped with an exhaust gas recirculation system and a method for operating the internal combustion engine.

[0002] The present invention preferably relates to an internal combustion engine such as a large ship, a marine engine or a stationary engine, in which the cylinder has an inner diameter of at least 200 mm. The engine is preferably a two-stroke engine or a two-stroke crosshead engine. The engine can be a diesel or gas engine, a dual-fuel or multi-fuel engine. In such an engine, not only self-ignition or forced ignition but also combustion of liquid fuel and / or gaseous fuel is possible.

Background Art

[0003] The engine has at least one cylinder having a piston inside. The piston is connected to a crankshaft. During the operation of the engine, the piston reciprocates between the top dead center (TDC) and the bottom dead center (BDC). The cylinder usually has at least one air passage opening for intake, particularly an air inlet disposed in the liner of the cylinder, and at least one air passage opening for exhaust, particularly an exhaust outlet disposed in the cover of the cylinder.

[0004] The internal combustion engine can be a two-stroke engine with a flat longitudinal surface.

[0005] The term internal combustion engine also refers to large engines that can operate not only in the diesel mode characterized by self-ignition of fuel but also in the Otto mode characterized by reliable ignition of fuel, or a mixture of the two. Further, the term internal combustion engine particularly includes dual-fuel engines and large engines in which self-ignition of fuel is used for reliable ignition of another fuel.

[0006] The engine speed is preferably less than 800 RPM (four-stroke), more preferably less than 200 RPM (two-stroke), indicating that it is a low-speed engine.

[0007] The fuel can be diesel oil or marine diesel oil, or heavy oil, or emulsion, or slurry, or methanol or ethanol, and gases such as liquefied natural gas (LNG), liquefied petroleum gas (LPG), etc.

[0008] Additional possible fuels that can be added according to requirements are LBG (liquefied biogas), biofuels (e.g., algae fuel or seaweed oil), hydrogen, and synthetic fuels from CO2 (e.g., made by Power-To-Gas or Power-To-Liquid).

[0009] Large ships, especially those for transporting goods, are usually powered by internal combustion engines, especially diesel and / or gas engines, mainly two-stroke crosshead engines. In the case of liquid fuels such as heavy oil, marine diesel oil, diesel, or other liquids, and in the case of gaseous fuels such as LNG, LPG, etc. burned by the engine, the exhaust from this combustion process needs to be purified to comply with existing pollutant regulations such as IMO Tier III rules.

[0010] Generally, IMO emission standards, commonly referred to as Tier I - Tier III standards, define, among other things, NO x emission standards for existing and new marine engines.

[0011] In the case of large ships, especially regarding nitrogen oxide emissions, the emission requirements are increasing. Therefore, it is necessary to regulate the amount of nitrogen oxides (NO x ) in the exhaust gas discharged by the internal combustion engines of these ships.

[0012] Selective catalytic reduction (SCR) and exhaust gas recirculation (EGR) are the main technologies for diesel engines to reduce NO x and achieve Tier III limits. SCR reduces NO x after combustion, while EGR reduces the generation of NO x .

[0013] If the EGR rate is too low, NO x If emissions become too high and the EGR rate is too high, combustion will no longer occur. As a result, soot contamination will occur, which is dangerous for the engine.

[0014] Patent Document 1 describes a system for controlling emissions. The control device changes the amount of EGR to control particulate matter and NO x Keep it within range, and then NO x The system may be configured to respond to one or more of the intake manifold air temperature, intake airflow rate, or detected or estimated intake oxygen fraction by adjusting the EGR amount based on sensor feedback. [Prior art documents] [Patent Documents]

[0015] [Patent Document 1] U.S. Patent No. 10508606 [Overview of the project] [Problems that the invention aims to solve]

[0016] The object of the present invention is to avoid the drawbacks of the prior art, and in particular to provide an internal combustion engine and a method for operating an internal combustion engine that have better performance than the engines of the prior art. [Means for solving the problem]

[0017] This objective is achieved by the internal combustion engine and method for operating the internal combustion engine as described in the independent claim.

[0018] The internal combustion engine comprises at least one cylinder having a bore of at least 200 mm. The internal combustion engine can be a large marine engine or a stationary engine.

[0019] An internal combustion engine is equipped with an exhaust gas recirculation system that has an EGR path. The EGR path of the exhaust gas recirculation system runs from the exhaust outlet of a cylinder to the air inlet of a cylinder.

[0020] The internal combustion engine further comprises at least one turbocharger having a turbine and a compressor.

[0021] The exhaust gas recirculation system can be a low-pressure system, in which the exhaust gas can be guided through the turbine of a turbocharger, and at least a portion of the exhaust gas can then be guided through the compressor of the turbocharger to the air inlet of the cylinder.

[0022] In a low-pressure EGR system, the turbocharger is positioned within the EGR path so that the recirculated exhaust gas contributes to driving the turbocharger.

[0023] The EGR path, which runs from the exhaust outlet of one cylinder to the air inlet of the other, includes the turbocharger's turbine and the turbocharger's compressor.

[0024] Typically, exhaust gases can be directed by a turbocharger to the air inlet of the cylinder, where they are mixed with fresh air. The turbocharger's compressor then draws in the recirculated exhaust gases and fresh air.

[0025] Typically, the EGR path includes a junction preferably located downstream of the turbocharger turbine, from which exhaust gases may be directed toward the cylinder air inlet, preferably toward the turbocharger compressor, or toward the exhaust gas funnel.

[0026] Alternatively, the exhaust gas recirculation system can be a high-pressure system, in which the exhaust gas is directed to the cylinder air inlet without passing through the compressor, preferably without passing through the turbocharger turbine.

[0027] The exhaust gas recirculation system recycles NO from the exhaust gases leaving the cylinders.x It includes at least one first sensor that provides a signal representing the content. NO x The term "content" NO x refers to the absolute amount, for example, the amount of exhaust gas, NO x the concentration, or for example, the ratio related to the engine load. NO x can be represented.

[0028] Preferably, the sensor is configured to provide a signal related to the amount of NO in ppm units. x

[0029] The first sensor can be arranged within the EGR path, preferably downstream of the turbine of the turbocharger and adjacent to it, because the exhaust gas is still hot at this point. The cooled exhaust gas may contain more humidity that can cause damage to the sensor.

[0030] NO x The NO content can be determined using UV spectrometry (for example, using a DANFOSS IXA MES 1001 sensor), an electrochemical method (for example, using a TESTO 340 or TESTO 350 sensor), or NDIR (for example, using a SICK MARSIC 300 sensor). Alternatively, lambda measurement, IR absorption, or chemiluminescence can also be used.

[0031] The first sensor can be configured to provide periodic measurements and / or continuous measurements.

[0032] The exhaust gas recirculation system further includes a control unit configured to control the amount of exhaust gas recirculated to the air inlet based on the signal from the first sensor. The first sensor can be configured to send a signal to the control unit.

[0033] The control unit is particularly configured to set the exhaust gas pressure and / or the exhaust gas flow rate within the EGR path.

[0034] ​ By setting the exhaust gas pressure and / or exhaust gas flow rate, the amount of exhaust gas discharged at the exhaust outlet and branched off to follow the EGR path, and thus the amount of exhaust gas recirculated into the cylinder, is determined.

[0035] The amount of exhaust gas recirculated to the air inlet, particularly the exhaust gas pressure and / or exhaust gas flow rate, can be set by operating at least one valve and / or blower.

[0036] Operating a valve means increasing or decreasing the valve's opening. Operating a blower means increasing or decreasing the blower's output.

[0037] The amount of exhaust gas recirculated to the air inlet, particularly the exhaust gas pressure and / or EGR flow rate, depends on the specific NO content in the exhaust gas. x The level can be achieved and adjustments can be made to avoid system damage.

[0038] The control unit measures NO x If the NO level is considered too low, reduce the amount of exhaust gas that is recirculated and measure the NO x If the value is considered too high, the system can be configured to increase the amount of exhaust gas that is recirculated.

[0039] NO x Direct feedback allows for the highest level of accuracy and flexibility regarding unexpected impacts.

[0040] The air inlet of the cylinder can be a scavenging receiver. Before entering the scavenging receiver, the gas may be guided through a scavenging cooler.

[0041] The exhaust outlet of a cylinder may lead to, for example, an exhaust gas receiver that collects exhaust gases from multiple cylinders.

[0042] The EGR path may be equipped with an exhaust gas cooler and a demister.

[0043] Preferably, the control unit is NO x The content is configured to be maintained within a predetermined range and / or below a predetermined value. The control unit can be configured to operate in closed-loop control, where the amount of exhaust gas recirculated to the air inlet, e.g., exhaust gas pressure and / or exhaust gas flow rate, is controlled by NO x Unless the content is outside the specified range and / or below the specified value, or if it is, it will be adjusted immediately.

[0044] The specified range and / or specified value can be selected according to the experience of factory testing.

[0045] A specified range and / or a value below a specified value can be set to comply with the limits given by the pollutant regulations.

[0046] Restrictions due to pollutant regulations are NO x While sometimes defined as a percentage, the signal provided by the first sensor may relate to an absolute quantity. For example, NO x It may be necessary to maintain the level below 5.1 g / kWh.

[0047] Further parameters can be taken into consideration to determine key limits based on pollutant regulations, which are compared with the signal provided by the first sensor.

[0048] The control unit can be configured to set predetermined ranges and / or predetermined values, preferably in compliance with pollutant regulations, depending on ambient conditions, scavenging pressure, scavenging temperature, scavenging humidity, compression pressure, engine load, ignition pressure, and / or turbocharger operating parameters.

[0049] Ambient conditions include ambient temperature, ambient pressure, and / or ambient humidity.

[0050] Turbocharger operating parameters include the pressure upstream of the turbine, the pressure downstream of the turbine, the temperature upstream of the turbine, the temperature downstream of the turbine, the pressure upstream of the compressor, the pressure downstream of the compressor, the temperature upstream of the compressor, the temperature downstream of the compressor, the turbine nozzle area, the turbine speed, the turbine bypass rate, the status of additional blowers, and the turbine flow characteristics.

[0051] Furthermore, the temperature of the exhaust gas downstream of the exhaust gas cooler, the pressure drop along the exhaust gas cooler, and / or the location of the valves may also be taken into consideration.

[0052] The engine may be equipped with at least one second sensor that provides signals representing ambient conditions, scavenging pressure, scavenging temperature, scavenging humidity, compression pressure, engine load, ignition pressure, and / or turbocharger operating parameters.

[0053] The second sensor can also provide signals representing the temperature of the exhaust gas downstream of the exhaust gas cooler, the pressure drop along the exhaust gas cooler, and / or the position of the valve.

[0054] The control unit is preferably configured to receive signals provided by a second sensor.

[0055] The control unit uses the signal from the second sensor to determine NO x It can be configured to determine the limit range and / or limit value of the content.

[0056] In one advantageous embodiment of the internal combustion engine, the control unit is further configured to control the amount of exhaust gas recirculated to the air inlet based solely on ambient conditions, scavenging pressure, scavenging temperature, scavenging humidity, compression pressure, engine load, pressure drop in the EGR path, ignition pressure, and / or turbocharger operating parameters. The temperature of the exhaust gas downstream of the exhaust gas cooler, the pressure drop along the exhaust gas cooler, and / or the location of the valves may also be taken into consideration.

[0057] The control unit can be configured to control the amount of exhaust gas recirculated to the air inlet based solely on the above parameters in feedback control and / or predictive control.

[0058] NO x If no measurement can be obtained, the control unit will NO based on the parameters described above. x Predict the content and the predicted NO x The exhaust gas pressure and / or exhaust gas flow rate can be set based on the content. The control unit predicts NO x The content can be configured to be kept within a predetermined range and / or below a predetermined value.

[0059] The control unit may be configured to receive signals from at least one second sensor that provides signals representing ambient conditions, scavenging pressure, scavenging temperature, compression pressure, engine load, ignition pressure, and / or turbocharger operating parameters. The control unit may be configured to keep the signals or combinations of signals within a predetermined range and / or below a predetermined value.

[0060] The control unit can be configured to use a model developed during factory testing. The control unit may include a memory device where the model is stored and accessible during engine operation.

[0061] The model uses ambient conditions, scavenging pressure, scavenging temperature, compression pressure, engine load, ignition pressure, turbocharger operating parameters, exhaust gas temperature downstream of the exhaust gas cooler, pressure drop along the exhaust gas cooler, and / or valve position values ​​to predict NO x It can be saved as a template or map associated with a value or a predetermined range or limit.

[0062] The control unit can preferably be configured to automatically switch between a first mode in which the exhaust gas flow through the exhaust gas recirculation system is controlled based on a signal from a first sensor, and a second mode in which the exhaust gas flow through the exhaust gas recirculation system is controlled based only on ambient conditions, scavenging pressure, compression pressure, engine load, pressure drop in the EGR path, ignition pressure, and / or turbocharger operating parameters. In the second mode, the exhaust gas flow through the exhaust gas recirculation system is not controlled based on a signal from the first sensor. Therefore, the control unit can control the NO of the exhaust gas exiting the cylinder in the second mode. x The content is not used directly.

[0063] NO x If the measurement is unavailable or fails, or NO x If the closed-loop control based on measurement becomes unstable, the control unit will NO x It can be switched to a second mode that does not require measurement.

[0064] The control unit is NO x It can be configured to detect situations where content-based control is impossible or undesirable, and to automatically change modes.

[0065] The control unit can be configured, for example, to turn off the second mode and / or switch back to the first mode depending on detected parameters, user input, and / or a predetermined period of time.

[0066] The control unit can be configured to switch to Tire II mode, in which the engine operates without exhaust gas recirculation.

[0067] For example, in transient conditions, the second mode can enable safe load changes using only a predictive model.

[0068] NO xFeedback control and predictive control without measurement are NO x It is less accurate than control based on measurement. It cannot respond to unexpected changes that could not be detected in factory testing.

[0069] Therefore, the control unit should be configured to switch to the first mode whenever possible. For example, as soon as a stable load can be achieved, the first mode should be reactivated.

[0070] An internal combustion engine may be equipped with an exhaust gas back pressure device, particularly an exhaust gas back pressure valve, positioned between the EGR path and the exhaust gas funnel, which provides adaptable back pressure within the EGR path.

[0071] The control unit can be configured to control the amount of exhaust gas recirculated to the air inlet by setting the exhaust gas pressure by setting the exhaust gas back pressure device.

[0072] The exhaust gas back pressure device can be power-operated, electrically operated, or spring-operated. Preferably, the valve is operated by pneumatic or hydraulic pressure.

[0073] The exhaust gas flow limiting device can be placed between the joint and the exhaust gas funnel.

[0074] The greater the opening of the exhaust back pressure valve, the higher the probability that gas will flow towards the exhaust gas funnel. The more the exhaust back pressure valve is closed, the higher the exhaust pressure in the EGR path and the greater the flow rate into the EGR path.

[0075] An exhaust gas treatment device can be placed between the exhaust gas flow limiting device (e.g., an exhaust back pressure valve) and the funnel.

[0076] Additionally or alternatively, the internal combustion engine may be equipped with a blower, particularly located within the EGR path, that provides an adaptable pressure within the EGR path. The control unit may be configured to control the amount of exhaust gas recirculated to the air inlet by setting the exhaust gas pressure and exhaust gas flow rate by setting the blower.

[0077] An internal combustion engine may be equipped with a flow control device (in particular, an exhaust gas recirculation valve) located within the EGR path (preferably downstream of the exhaust gas cooling device).

[0078] The control unit can be configured to control the amount of exhaust gas recirculated to the air inlet by setting the exhaust gas flow rate through the setting of the flow control device.

[0079] Measured NO x If the pressure is too high, for example, exceeding a predetermined range, the amount of exhaust gas recirculated to the air inlet can be increased by closing the exhaust back pressure valve upstream of the exhaust funnel and / or by opening the exhaust gas recirculation valve in the EGR path.

[0080] Measured NO x If the value is too low, for example, below a predetermined range or above a predetermined value, the amount of exhaust gas recirculated to the air inlet can be reduced by opening the exhaust back pressure valve and / or closing the exhaust gas recirculation valve.

[0081] The amount of exhaust gas recirculated to the air inlet corresponds to the EGR rate, which can be determined according to the CO2 content.

number

[0082] Exhaust gas recirculation valves can be used at low EGR rates, while back pressure valves can be used at high EGR rates. The object of the present invention can also be achieved by the method of operating the internal combustion engine as described above.

[0083] This method involves the steps of recirculating at least a portion of the exhaust gas to the air inlet and the NO of the exhaust gas leaving the cylinder. x The steps include providing a signal representing the content and controlling the amount of exhaust gas recirculated to the air inlet based on the signal by setting the exhaust gas pressure and / or exhaust gas flow rate.

[0084] Preferably, an exhaust gas back pressure device located between the EGR path and the exhaust gas funnel and / or a flow control device located within the EGR path are configured, preferably via a control unit.

[0085] The exhaust gas back pressure device can be an exhaust back pressure valve positioned between the EGR path and the funnel.

[0086] The flow control device is preferably an exhaust gas recirculation valve, and is preferably located downstream of the exhaust gas cooling device and immediately upstream of the turbocharger's compressor.

[0087] NO x The signal representing the content can be compared to a predetermined range and / or a predetermined value, and the amount of exhaust gas that passes through the exhaust gas recirculation system and thus reaches the air inlet can be changed if the signal is not within the predetermined range and / or exceeds a predetermined value.

[0088] The range and / or value exceeding a predetermined range can be selected depending on ambient conditions, scavenging pressure, scavenging temperature, compression pressure, engine load, pressure drop in the EGR path, ignition pressure, turbocharger operating parameters, exhaust gas temperature downstream of the exhaust gas cooler, pressure drop along the exhaust gas cooler, and / or valve position.

[0089] Furthermore, the flow of exhaust gas recirculated to the air inlet can be controlled based on ambient conditions, scavenging pressure, scavenging temperature, compression pressure, engine load, pressure drop in the EGR path, ignition pressure, turbocharger operating parameters, exhaust gas temperature downstream of the exhaust gas cooler, pressure drop along the exhaust gas cooler, and / or valve position.

[0090] This method may preferably include a step of automatically switching between a first mode and a second mode.

[0091] In the first mode, the flow of exhaust gas through the exhaust gas recirculation system is controlled based on a signal from a first sensor.

[0092] In the second mode, the flow of exhaust gas recirculated to the air inlet can be controlled based on ambient conditions, scavenging pressure, scavenging temperature, scavenging humidity, compression pressure, engine load, pressure drop in the EGR path, ignition pressure, turbocharger operating parameters, exhaust gas temperature downstream of the exhaust gas cooler, pressure drop along the exhaust gas cooler, and / or valve position.

[0093] In the second mode, the flow of exhaust gases recirculated to the air inlet can be controlled based on at least one signal from at least two sensors, which provide signals representing ambient conditions, scavenging pressure, scavenging temperature, scavenging humidity, compression pressure, engine load, pressure drop in the EGR path, ignition pressure, turbocharger operating parameters, exhaust gas temperature downstream of the exhaust gas cooler, pressure drop along the exhaust gas cooler, and / or valve position.

[0094] Unless otherwise defined, valves include exhaust back pressure valves located between the EGR path and the exhaust gas funnel, exhaust gas recirculation valves located within the EGR path (preferably downstream of the exhaust gas cooling device), shut-off valves located within the EGR path (preferably upstream of the exhaust gas cooling device), and exhaust wastegates located within the turbine bypass circuit.

[0095] The relationship between the set valve position of the exhaust back pressure valve and the EGR rate, and the relationship between the exhaust gas recirculation valve and the EGR rate, have a linear range over a wide range of valve positions. Therefore, measurement of the EGR rate is not necessary.

[0096] To increase the EGR rate, you can first open the exhaust gas recirculation valve while fully opening the back pressure valve. As soon as the exhaust gas recirculation valve is fully open, you can close the back pressure valve and further increase the EGR rate until the back pressure valve is fully closed.

[0097] If the exhaust gas recirculation valve and back pressure valve are operated sequentially, and the back pressure valve begins to close after the exhaust gas recirculation valve is fully open, the dependence of the EGR rate on the valve setting includes a range of lower gradients.

[0098] A range of different (i.e., lower) gradients occurs while the exhaust gas recirculation valve is nearly fully open and the back pressure valve is still open, until the exhaust gas recirculation valve is fully open and the back pressure valve begins to close. For example, a range of lower gradients occurs when the exhaust gas recirculation valve is more than 50% open and before the back pressure valve is closed to 50%.

[0099] Preferably, the exhaust gas recirculation valve and back pressure valve are operated in a region having a similar linear relationship across the entire valve setting regime, preferably in a region with a large gradient, so that the EGR rate can be controlled more robustly and therefore more precisely.

[0100] To avoid varying gradients, the valves are operated such that the back pressure valve is already closed before the exhaust gas recirculation valve is fully open.

[0101] Preferably, to increase the EGR rate, the control unit provides to open the exhaust gas recirculation valve and close the back pressure valve, the closing of which is initiated after the exhaust gas recirculation valve has been opened to 50% to 100% (preferably 50% to 70%, more preferably 60%).

[0102] The reduction in the EGR rate is achieved in the opposite way, with the exhaust gas recirculation valve beginning to close before the back pressure valve is fully open.

[0103] Preferably, in order to reduce the EGR rate, the control unit provides to open the back pressure valve and close the exhaust gas recirculation valve, and closing the exhaust gas recirculation valve is initiated after the back pressure valve has been opened to 50% to 100% (preferably 50% to 70%, more preferably 60%).

[0104] Preferably, when both valves are operated simultaneously, both valves are operated in the same manner so that the percentage of their opening and closing changes by the same amount at the same time. This means, for example, that a 10% increase in the full opening of the exhaust gas recirculation valve is achieved while the opening of the back pressure valve decreases by 10% from its full opening, and vice versa.

[0105] In the following, the present invention will be further described by embodiments using the figures. The same reference numerals indicate functionally corresponding components. [Brief explanation of the drawing]

[0106] [Figure 1] A schematic diagram of the first example of a combustion engine is shown. [Figure 2] A schematic diagram of a second example of a combustion engine is shown. [Figure 3] A schematic diagram of a third example of a combustion engine is shown. [Figure 4] A schematic diagram of a fourth example of a combustion engine is shown. [Figure 5] A schematic diagram of the fifth example of a combustion engine is shown. [Figure 6] A schematic diagram of the sixth example of a combustion engine is shown. [Figure 7] The EGR rate according to the valve settings is roughly shown. [Modes for carrying out the invention]

[0107] Figure 1 shows a first example of an internal combustion engine 20 having a cylinder 21 having a reciprocating piston 23 having a bore diameter 22 of at least 200 mm. The internal combustion engine 20 includes an exhaust gas recirculation system 1 having an EGR path 13 located between the exhaust outlet 2 and the air inlet 3 of the cylinder 21. The internal combustion engine 20 also includes a turbocharger 5 having a turbine 4 and a compressor 10.

[0108] The exhaust gas recirculation system 1 is a low-pressure system, and the recirculated exhaust gas can be guided to the air inlet 3 of the cylinder 21 via the compressor 10 of the turbocharger 5, where the exhaust gas is mixed with fresh air 6, and at least a portion of the recirculated exhaust gas can be guided through the turbine 4 of the turbocharger 5.

[0109] Another portion of the exhaust gas may bypass the turbocharger 5 and be guided through the turbine bypass 31 when the exhaust wastegate valve 27 is open.

[0110] The internal combustion engine 20 may be a dual-fuel engine and may be equipped with a gas inlet valve 24.

[0111] The exhaust gas recirculation system 1 recirculates NO from the exhaust gas coming out of cylinder 21. x It includes a first sensor 12 that provides a signal indicating the content. The sensor is located downstream of the turbine 4.

[0112] The exhaust gas recirculation system 1 includes a control unit 11 configured to control the amount of exhaust gas recirculated to the air inlet 3 based on a signal from a first sensor 12. The control unit 11 is configured to set the exhaust gas pressure and / or exhaust gas flow rate.

[0113] To do so, the control unit 11 can control the exhaust gas recirculation valve 7 located in the EGR path 13 downstream of the exhaust gas cooling device 8. The control unit 11 can further control the exhaust back pressure valve 9 located between the EGR path 13 and the exhaust gas funnel 14.

[0114] Engine 1 may be equipped with a second sensor 32 for measuring ambient conditions such as ambient temperature, ambient pressure, and ambient humidity.

[0115] Figure 2 shows a second example of an internal combustion engine similar to the first example.

[0116] The exhaust gases are collected in the exhaust gas receiver 17. The EGR path 13 includes a cooling device 8 and a demister 29. The recirculated exhaust gas and fresh air pass through the scavenging cooler 19 and are led to the scavenging receiver 18.

[0117] The exhaust gas recirculation system 1 includes a second sensor 32 for measuring signals related to scavenging pressure and / or scavenging temperature. These signals can be received by the control unit 11.

[0118] The first sensor 12 is located behind the turbine 4 and detects NO in the exhaust gas. x The content is measured in ppm units. The difference between the measured value and a predetermined target value for a specific load can be used for closed-loop control of the EGR rate.

[0119] Measured NO x If the value is too high, increase the EGR rate or the measured NO x If the value is too low, the EGR rate can be reduced.

[0120] The EGR rate can be adjusted using two valves 7 and 9. The exhaust gas recirculation valve 7 is located just upstream of the compressor 10, at the outlet of the cooler 8 or demister 29. When the exhaust gas recirculation valve 7 is closed, the EGR rate is 0. There is no exhaust gas flow through the cooler 8 and demister 29. The exhaust gas recirculation valve 7 can be opened, increasing the EGR rate. As soon as the exhaust gas recirculation valve 7 is fully open, the pressure loss across the cooler 8 and demister 29 defines the maximum EGR rate in this case.

[0121] Typically, the EGR rate is between 20% and 30%.

[0122] To further increase the EGR rate, an exhaust back pressure valve 9 between the EGR path 13 and the funnel 14 can be used to increase the back pressure after the turbine 4, thereby increasing the flow through the cooler 8 and demister 29.

[0123] The exhaust back pressure valve 9 is normally fully open. The exhaust back pressure valve 9 begins to close as soon as the exhaust gas recirculation valve 7 opens to at least 50%, preferably 60%. The maximum EGR rate can be achieved when the exhaust gas recirculation valve 7 is fully open and the exhaust back pressure valve 9 is fully closed.

[0124] Normally, the first sensor 12 detects NO in the exhaust gas after the turbine 4. x The content is measured in ppm units. IMO NO x Regulations are specific NO x Emissions are limited in units of g / kWh.

[0125] NO x The limit calculation includes corrections for humidity [g / kg], ambient temperature [K], and scavenging temperature [°C] compared to baseline values. The flow rate through the engine is also considered, proportional to measured values ​​such as scavenging pressure [bar] and the position [%] of the exhaust wastegate valve 27. Engine output is also taken into account in the calculation.

[0126] In accordance with MEPC 58 / 23 / Add.1 Annex 14, Chapter 5, if emissions are not measured on a wet basis, the measured concentration c d is, formula c w =k w ×c d According to the wetness standard c w It is assumed that it will be converted to the coefficient k. w This may depend on the absolute humidity of the intake air, the intake air mass flow rate, the fuel mass flow rate, the CO2 concentration, the CO concentration, and the H, N, and O content of the fuel. The absolute humidity of the intake air can be determined based on the ambient temperature and atmospheric pressure.

[0127] Instead of measuring fuel mass flow rate and CO2 and CO concentration, turbine energy balance may be used.

[0128] Additional information, such as pressure loss across the cooling unit 8 and demister 29, may be provided by a further second sensor 32 (not explicitly shown) to determine whether the system behaves as expected and the measured NO x It may be used to estimate whether a value is plausible.

[0129] The pressure loss across the cooling device 8 and the demister 29 can be measured by measuring the differential pressure across the cooling device 8 and the demister 29.

[0130] Measurements can also be taken across the shut-off valve 26 to the exhaust gas recirculation valve 7, or across specific elements of the EGR path 13 that are characteristic of the flow.

[0131] If the deviation of the measured pressure loss from the target pressure loss at a particular load exceeds a predetermined value, it may be necessary to adjust the valve position to bring it into line.

[0132] The pressure loss measurement was too low. x If the measured value is too high, or if the measured value of pressure loss is too high, NO x If the measurement is too low, you need to check if the pressure measurement is correct and / or if the valve is set up correctly.

[0133] The measured pressure loss is within the specified range, NO x If the deviation of the measurement exceeds a certain limit, NO x The measured values ​​need to be checked.

[0134] If further adjustments clearly lead in the wrong direction, damage may occur, therefore NO x Signals will not be used.

[0135] In this case, for example, the operator may be prompted to switch to the first mode or to switch back to the Tier II regime or gas mode.

[0136] NO x If the deviation is small (below a predetermined limit), the control unit 11 can be operated in the first mode, and the EGR rate is NO x It can be adjusted based on the measured values.

[0137] The EGR rate can be adjusted in stages. For example, the valve position of the exhaust gas recirculation valve 7 can be set to NO x Change it to a quantity proportional to the deviation. NO x The measurement is repeated after a while, for example, a few minutes later. x If the target value has not yet been achieved, the valve position will be readjusted.

[0138] When the load changes, the control unit 11 switches to the second mode, and as soon as the load stabilizes again, it switches to the closed-loop NO x The control can switch back to the first mode in which it is used. NO only when a stable load is achieved. x It may not be necessary to measure it continuously.

[0139] NO x Measurements are provided at defined intervals, for example, every 15 minutes, after final adjustments under a stable load.

[0140] NO x The sensor only needs to be active, and the control unit 11 can be operated only in the first mode while in diesel mode.

[0141] In transient conditions, closed loop NO x Control may be disabled. A second mode can be activated, allowing temporary use of feedforward values ​​to avoid smoke.

[0142] Figure 3 shows a schematic diagram of a third example of a combustion engine 21 similar to the second example. Instead of the exhaust back pressure valve 9 (see Figure 2), a blower 28 is located in the EGR path 13.

[0143] The blower 28 is operated similarly to the back pressure valve 9. Instead of closing the back pressure valve 9 to increase the EGR rate, the output of the blower 28 is increased.

[0144] Figure 4 shows a schematic diagram of a fourth example of a combustion engine 21 in which the exhaust gas recirculation system 1 is a high-pressure system. The EGR path 13 branches off upstream of the turbine bypass 31 and does not include a turbocharger.

[0145] The exhaust gas is mixed with fresh air downstream of the scavenging cooler 19.

[0146] The exhaust back pressure valve 9 is located upstream of the turbine bypass circuit 31.

[0147] Figure 5 shows a schematic diagram of a fifth example of a combustion engine 21 similar to the fourth example.

[0148] The EGR path 13 branches off upstream of turbine 4.

[0149] The exhaust back pressure valve 9 is located downstream of the turbine bypass circuit 31 and upstream of the turbine 4.

[0150] Figure 6 shows a schematic diagram of a sixth example of a combustion engine 21 similar to the fourth and fifth examples. Instead of the exhaust back pressure valve 9 (see Figures 4 and 5), a blower 28 is located in the EGR path 13.

[0151] Figure 7 schematically shows the EGR rate depending on the valve setting.

[0152] To increase the EGR rate, you can first close the exhaust gas recirculation valve 7 (see previous diagram), and then close the back pressure valve 9 (see previous diagram).

[0153] If the back pressure valve begins to close after the exhaust gas recirculation valve has fully opened, the relationship between the EGR rate and the valve setpoint (shown by the white circle) has a flat region.

[0154] When the exhaust gas recirculation valve opens to 70% and the back pressure valve begins to close, the flat region in the relationship between the EGR rate and the valve setpoint (shown by the black circles) becomes smaller.

[0155] When the exhaust gas recirculation valve is opened to 60% (indicated by a white square) or even further to 50% (indicated by a black square), and the back pressure valve begins to close, the relationship between the EGR rate and the valve setting becomes nearly linear across the entire setting range, starting with the exhaust gas recirculation valve fully closed (FRV, 0%) and the back pressure valve fully open (BPV, 100%), and ending with the exhaust gas recirculation valve fully open (FRV, 100%) and the back pressure valve fully closed (BPV, 0%).

[0156] When the valve settings for the exhaust gas recirculation valve and the back pressure valve overlap, the EGR rate is equally sensitive to the valve settings across the entire setting range. This makes the control concept robust and therefore allows for very precise setting of the EGR rate. [Explanation of symbols]

[0157] 1. Exhaust gas recirculation system 2 Exhaust outlet 3. Air Inlet 4 Turbines 5 Turbocharger 6. Fresh air 7 Flow control device 8 Cooling device 9. Exhaust gas back pressure device 10 Compressor 11 Control Unit 12 First Sensor 13 EGR Route 14 Exhaust gas funnel 17. Exhaust gas receiver 18. Scavenging Receiver 19. Scavenging condenser 20 Internal Combustion Engines 21 cylinders 22 Inner diameter 23 pistons 24 Gas inlet valve 26 Shut-off valve 27 Exhaust Wastegate 28 Blower 29, 30 Demister 31 Turbine Bypass 32. Scavenging pressure sensor

Claims

1. An internal combustion engine (20) having at least one cylinder (21) with an inner diameter (22) of at least 200 mm, i.e., a large ship engine or a stationary engine, The internal combustion engine (20) is equipped with an exhaust gas recirculation system (1) having an EGR path (13) located between an exhaust outlet (2) and an air inlet (3). In the internal combustion engine (20) equipped with a turbocharger (5), The exhaust gas recirculation system (1) is, NO in the exhaust gas coming out of the aforementioned cylinder ｘ At least one first sensor (12) that provides a signal indicating the content, A control unit (11) is configured to control the amount of exhaust gas recirculated to the air inlet (3) based on the signal from the first sensor (12). Equipped with, The control unit (11) is configured to set an exhaust back pressure valve (9) positioned between the EGR path (13) and the exhaust gas funnel to provide an exhaust gas pressure adaptable to the EGR path (13), and to set an exhaust gas recirculation valve positioned in the EGR path (13). The control unit (11) is configured to open the exhaust gas recirculation valve and close the exhaust back pressure valve (9) in order to increase the EGR rate, and the closing of the exhaust back pressure valve (9) is initiated after the exhaust gas recirculation valve is opened to 50% to 100%. The control unit (11) is configured to open the exhaust back pressure valve (9) and close the exhaust gas recirculation valve in order to reduce the EGR rate, and the closing of the exhaust gas recirculation valve is initiated after the exhaust back pressure valve (9) is opened to 50% to 100%, characterized in that it is an internal combustion engine (20).

2. The internal combustion engine (20) according to claim 1, wherein the exhaust gas recirculation system (1) is a low-pressure system, and the recirculated exhaust gas can be guided through the compressor (10) of the turbocharger (5) to the air inlet (3) of the cylinder (21), and at least a portion of the recirculated exhaust gas can be guided through the turbine (4) of the turbocharger (5).

3. The control unit (11) is the NO ｘ An internal combustion engine (20) according to claim 1 or 2, configured to maintain the content within a predetermined range and / or below a predetermined value.

4. The internal combustion engine (20) according to claim 3, wherein the control unit (11) is configured to set the predetermined range and / or the predetermined value in accordance with at least one of the ambient conditions, namely ambient temperature, ambient pressure, ambient humidity, scavenging pressure, scavenging temperature, scavenging humidity, compression pressure, engine load, ignition pressure, and the operating parameters of the turbocharger.

5. The internal combustion engine (20) according to claim 1, comprising at least one second sensor (32) that provides at least one signal representing at least one ambient condition, namely ambient temperature, ambient pressure, ambient humidity, scavenging pressure, scavenging temperature, scavenging humidity, compression pressure, engine load, ignition pressure, and operating parameters of the turbocharger, wherein the control unit (11) is configured to receive the signal provided by the second sensor.

6. The control unit (11) is configured to change the flow of exhaust gas through the exhaust gas recirculation system (1) between a first mode controlled based on a signal from the first sensor (12) and a second mode in which the flow of exhaust gas through the exhaust gas recirculation system (1) is controlled based on at least one of at least one ambient condition, namely ambient temperature, ambient pressure, ambient humidity, scavenging pressure, scavenging humidity, compression pressure, engine load, pressure drop in the EGR path (13), ignition pressure, and the operating parameters of the turbocharger, according to claim 1, the internal combustion engine (20).

7. The internal combustion engine (20) according to claim 1, comprising a blower (28) located in the EGR path (13) that provides an adaptable pressure within the EGR path (13), and the control unit (11) is configured to control the amount of exhaust gas recirculated to the air inlet (3) by setting the exhaust gas pressure by setting the blower (28).

8. A method for operating an internal combustion engine (20) according to claim 1, The steps include: recirculating at least a portion of the exhaust gas to the air inlet (3); NO of the exhaust gas coming out of the cylinder ｘ A step of providing a signal representing the content, A step of controlling the amount of exhaust gas recirculated to the air inlet (3) based on the signal, by setting an exhaust back pressure valve (9) positioned between the EGR path (13) and the exhaust gas funnel to provide an exhaust gas pressure adaptable to the EGR path (13), and by setting an exhaust gas recirculation valve positioned in the EGR path (13). The control unit (11) opens the exhaust gas recirculation valve and closes the exhaust back pressure valve (9) in order to increase the EGR rate, and after the exhaust gas recirculation valve is opened to 50% to 100%, the closing of the exhaust back pressure valve (9) is initiated. The control unit (11) controls the amount of exhaust gas, such that the exhaust back pressure valve (9) is opened and the exhaust gas recirculation valve is closed in order to reduce the EGR rate, and the closing of the exhaust gas recirculation valve is started after the exhaust back pressure valve (9) is opened to 50% to 100%. A method that includes this.

9. The method according to claim 8, comprising the step of comparing the signal with a predetermined range and / or a predetermined value, and if the signal is not within the predetermined range and / or exceeds the predetermined value, changing the amount of exhaust gas recirculated to the air inlet (3) via the exhaust gas recirculation system (1).

10. The method according to claim 9, comprising the step of controlling the flow of exhaust gas to be recirculated to the air inlet (3) based on ambient conditions, scavenging pressure, scavenging temperature, scavenging humidity, compression pressure, engine load, pressure drop in the EGR path (13), ignition pressure, and operating parameters of the turbocharger (5).

11. The method according to claim 9, comprising the step of changing the flow of exhaust gas through the exhaust gas recirculation system (1) between a first mode controlled based on a signal from the first sensor (12) and a second mode in which the flow of exhaust gas through the exhaust gas recirculation system (1) is controlled based on at least one of ambient conditions, scavenging pressure, scavenging temperature, scavenging humidity, compression pressure, engine load, pressure drop in the EGR path (13), ignition pressure, and the operating parameters of the turbocharger.

Images