Turbocharged internal combustion engines and methods for determining the NOx reduction rate of engines.

Abstract

A large two-stroke single-flow scavenging turbocharged multi-cylinder internal combustion engine and a method for controlling the NOx reduction rate in the engine, the engine having an SCR reactor (28) supplied with a reducing agent flow and a controller (50) configured to calculate the NOx reduction rate of the SCR reactor (28) and accordingly control the magnitude of the reducing agent flow.

Description

Technical Field

[0001] This invention relates to a large, crosshead-type turbocharged, two-stroke, single-flow internal combustion piston engine, and more specifically to a large, crosshead-type turbocharged, two-stroke, single-flow internal combustion piston engine with an SCR (Selective Catalytic Reduction) reactor, the SCR reactor being used to remove NO from the exhaust gas. x The process involves reduction to purify the exhaust gases produced by the engine. Background Technology

[0002] Large, two-stroke, single-flow, scavenging, turbocharged, crosshead compression-ignition internal combustion engines are typically used in the propulsion systems of large ships or as prime movers in power plants. Their enormous size, weight, and power output make them entirely different from ordinary internal combustion engines, establishing the large, two-stroke, turbocharged compression-ignition internal combustion engine as a distinct category.

[0003] The emission requirements for these engines are becoming increasingly difficult to meet, and will become increasingly difficult to meet, especially regarding nitrogen oxides (NOx). x This is especially true at the maritime level. Public awareness of environmental issues is rapidly increasing. There are currently emission limits for forms of air pollution at sea within the IMO (International Maritime Organization). Authorities around the world are taking similar measures. One example is the proposed EPA (U.S. Environmental Protection Agency).

[0004] NO in emissions x Reduction can be achieved through primary and / or secondary reduction methods. Primary methods directly affect the engine's combustion process. The actual reduction level depends on the engine type and the reduction method, but varies from 10% to over 80%. Secondary methods are measures to reduce emissions without altering engine performance from its fuel-optimized settings; these methods use equipment that is not part of the engine itself. The most successful secondary method to date is the removal of NO. x The SCR (Selective Catalytic Reduction) method. This method removes NO by adding a reducing agent, such as ammonia or urea, to the exhaust gas before it enters the catalytic converter. x The level is reduced by more than 95%. Typically, the reducing agent is located upstream of the SCR reactor in the exhaust gas system or injected and atomized within the SCR reactor. The SCR reactor contains multiple layers of catalyst. The catalyst volume, and therefore the reactor size, depends on the catalyst activity and the required NO. x Degree of reduction. Catalysts typically have an integrated structure, meaning that a catalyst comprises a catalyst block with numerous parallel channels whose walls are catalytically active.

[0005] For example, when urea is added as a reducing agent to an SCR reactor, it acts as a reducing agent to reduce nitrogen oxide (NOx) emissions into nitrogen (N2) and water vapor (H2O), both of which are harmless byproducts. The process proceeds in multiple steps:

[0006] 1. Urea Injection: Urea (CO(NH2)2) is injected into the exhaust stream before it enters the SCR catalytic chamber. Urea is typically dissolved in water to form a urea solution (UWS), which is then sprayed into the exhaust gas.

[0007] 2. Thermal decomposition: When the urea aqueous solution enters the hot exhaust stream, the urea aqueous solution evaporates and decomposes into ammonia (NH3) and isocyanate (HNCO) through thermal decomposition. This reaction occurs while the exhaust gas is still very hot, usually above 200°C.

[0008] 3. Hydrolysis: Isocyanate is further hydrolyzed to form additional ammonia and carbon dioxide (CO2). This step ensures that most of the urea is converted into ammonia, which is the actual reducing agent in the SCR process.

[0009] 4. Catalytic Reaction: Ammonia then reacts with nitrogen oxides present in the exhaust gases in the presence of a catalyst. The catalyst is typically made of materials such as vanadium, titanium dioxide, zeolite, or various base metals, which promote the reaction but are not consumed in the process. SCR catalysts promote the selective reduction of NOx to nitrogen and water vapor in the presence of oxygen—which is present in diesel engine emissions.

[0010] This process effectively reduces NOx levels in the exhaust gases. The efficiency of an SCR system depends on a variety of factors, including the temperature of the exhaust gases, the concentration of NOx, the amount and distribution of the injected urea solution, and the design and materials of the SCR catalyst.

[0011] Emissions regulations (IMO regulations) for engines operating on marine vessels require that the NOx reduction rate at each test point differ from the reduction rate specified in the NOx technical document (established on a test bench for the relevant engine type) by no more than 5%. However, establishing and monitoring NOx reduction rates during engine operation is challenging because when commercially available NOx sensors are placed downstream of the SCR reactor, the PPM levels they provide do not correspond to either the NOx mass flow rate or the specific NOx level in g / kWh upon which the emissions regulations are based. Furthermore, to determine the reduction rate, the NOx mass flow rate or the specific NOx level in g / kWh of the exhaust gas upstream of the SCR reactor must be known. However, because measurements are performed at high pressure, determining the NOx mass flow rate or the specific NOx level in g / kWh of the exhaust gas upstream of the SCR reactor, for example, using the aforementioned commercially available NOx sensors located upstream of the SCR reactor, is also challenging.

[0012] DK177462 discloses a large turbocharged two-stroke diesel engine with a crosshead, comprising multiple cylinders, a turbocharger, and an SCR reactor located upstream of the turbocharger and downstream of the exhaust gas receiver. A reducing agent for the SCR reactor is introduced into the exhaust gas upstream of the SCR reactor.

[0013] DK180561 discloses a large turbocharged two-stroke internal combustion engine. Summary of the Invention

[0014] The objective is to provide a large two-stroke single-flow scavenging turbocharged internal combustion engine that overcomes or at least reduces the aforementioned problems.

[0015] According to a first aspect, a large two-stroke single-flow scavenging turbocharged internal combustion engine is provided, the engine comprising:

[0016] Multiple cylinders that produce a stream of NOx-containing exhaust gases during engine operation.

[0017] A turbocharger system comprising a compressor and an exhaust gas-driven turbine located in the exhaust gas system, and a compressor located in the scavenging air system for supplying scavenging air to the cylinders of the engine.

[0018] A selective catalytic reduction reactor, located in the exhaust gas system.

[0019] A reducing agent source, configured to add a given metered stream of reducing agent to the exhaust gas duct for reaction with NOx in the SCR reactor.

[0020] An O2 sensor generates a signal representing the O2 ppm in the exhaust gas downstream of both the SCR reactor and the turbine.

[0021] The NOx sensor generates a signal representing the NOx ppm in the exhaust gas downstream of both the SCR reactor and the turbine.

[0022] The controller, which is informed of the engine load, is configured to:

[0023] The NOx mass flow rate in the exhaust gas downstream of the SCR reactor is calculated based on the following:

[0024] The signal from the O2 sensor,

[0025] NOx sensor signal

[0026] Engine thermal efficiency.

[0027] Engine load, and

[0028] Adjustment coefficient,

[0029] The NOx mass flow rate in the exhaust gas upstream of the SCR reactor is calculated based on the magnitude of the reducing agent flow.

[0030] The NOx reduction rate of the SCR reactor is calculated based on the NOx mass flow rates in the exhaust gas upstream and downstream of the SCR reactor.

[0031] The magnitude of the reducing agent flow is adjusted by comparing the calculated NOx reduction rate with the desired NOx reduction rate.

[0032] By placing O2 and NOx sensors downstream of the SCR reactor on the low-pressure side of the turbocharger, and by calculating the NOx mass flow rates before and after the SCR reactor (e.g., in [g / s] or [kg / h]), the actual accurate NOx reduction rate can be determined. This actual accurate NOx reduction rate can then be used as a signal in the feedback loop by comparing it with the required minimum reduction rate. Accordingly, the magnitude of the reductant flow to the SCR reactor can be accurately controlled to achieve the legally required NOx reduction rate.

[0033] According to the possible implementation of the first aspect, the adjustment coefficient is an adjustment coefficient related to the engine load.

[0034] According to the possible implementation of the first aspect, the adjustment coefficient is a function of the engine's thermal efficiency and the fuel adjustment coefficient, with the fuel adjustment coefficient preferably being Thornton's constant.

[0035] Based on the possible implementations of the first aspect, the adjustment coefficient is SFOC, Thornton's constant, and for NOx... u gas A function of LHV of fuel.

[0036] According to a possible implementation of the first aspect, the controller is configured to take into account the ambient O2 concentration when calculating the NOx mass flow rate in the exhaust gas downstream of the SCR reactor, preferably, the ambient O2 concentration is assumed to be 20.95%.

[0037] According to a possible implementation of the first aspect, the controller receives a humidity sensor configured to sense ambient humidity, and wherein the controller is configured to take into account the ambient humidity sensed by the humidity sensor when calculating the NOx mass flow rate in the exhaust gas downstream of the SCR reactor.

[0038] According to a possible implementation of the first aspect, the controller is configured to take into account the ambient O2 concentration when calculating the NOx mass flow rate in the exhaust gas downstream of the SCR reactor, preferably by using a stored fixed value for the ambient O2 concentration.

[0039] Based on the possible implementation of the first aspect, the controller is configured as follows:

[0040] Calculate specific NOx downstream of the SCR reactor as the NOx mass per unit of energy produced by the engine, and

[0041] The NOx mass flow rate upstream of the SCR reactor is calculated based on the magnitude of the reducing agent flow, and is taken as the NOx mass per unit of energy generated by the engine.

[0042] According to the possible implementation of the first aspect, for each engine cycle, a given amount of fuel is injected into the cylinder.

[0043] According to a possible implementation of the first aspect, the controller is configured to calculate the engine load based on a given metering of engine speed and fuel, preferably, assuming that SFOC is constant.

[0044] According to a possible implementation of the first aspect, the engine is equipped with a tachometer for sensing the rotational speed of the engine crankshaft.

[0045] According to a possible implementation of the first aspect, the controller is configured to use a closed loop to regulate the magnitude of the reducing agent flow.

[0046] According to a possible implementation of the first aspect, the cylinder includes a cylinder liner, a reciprocating piston located in the cylinder liner, and a cylinder head covering the cylinder, wherein a combustion chamber is formed inside the cylinder and between the reciprocating piston and the cylinder head.

[0047] According to the possible implementation of the first aspect, the compressor is driven directly or indirectly by the turbine.

[0048] According to a second aspect, a method is provided for determining the NOx reduction rate of a large two-stroke, single-flow scavenging, turbocharged, multi-cylinder internal combustion engine, the engine comprising:

[0049] Multiple cylinders that produce a stream of NOx-containing exhaust gases during engine operation.

[0050] A turbocharger system comprising a compressor and an exhaust gas-driven turbine located in the exhaust gas system, and a compressor located in the scavenging air system for supplying scavenging air to the cylinders of the engine.

[0051] A selective catalytic reduction reactor, located in the exhaust gas system.

[0052] A reducing agent source, configured to add a given metered stream of reducing agent to the exhaust gas duct for reaction with NOx in the SCR reactor.

[0053] An O2 sensor generates a signal representing the O2 ppm in the exhaust gas downstream of both the SCR reactor and the turbine.

[0054] The NOx sensor generates a signal representing the NOx ppm in the exhaust gas downstream of both the SCR reactor and the turbine.

[0055] The method includes:

[0056] The NOx mass flow rate in the exhaust gas downstream of the SCR reactor is calculated based on the following:

[0057] The signal from the O2 sensor,

[0058] NOx sensor signal

[0059] Engine thermal efficiency.

[0060] Engine load, and

[0061] Adjustment coefficient,

[0062] The NOx mass flow rate in the exhaust gas upstream of the SCR reactor is calculated based on the magnitude of the reducing agent flow.

[0063] The NOx reduction rate of the SCR reactor is calculated based on the NOx mass flow rates in the exhaust gas upstream and downstream of the SCR reactor.

[0064] The magnitude of the reducing agent flow is adjusted by comparing the calculated NOx reduction rate with the desired NOx reduction rate.

[0065] These and other aspects will become apparent through the following implementation methods. Attached Figure Description

[0066] In the following detailed description of this disclosure, various aspects, implementations, and forms will be described in more detail with reference to exemplary embodiments illustrated in the accompanying drawings, in which:

[0067] Figure 1 This is an elevation view of a large two-stroke diesel engine according to an embodiment.

[0068] Figure 2 yes Figure 1 A side view of a large two-stroke engine.

[0069] Figure 3 It is based on Figure 1 A schematic diagram of an implementation method for a large two-stroke engine.

[0070] Figure 4 It is based on Figure 1 A schematic diagram of another embodiment of a large two-stroke engine.

[0071] Figure 5 This is a schematic diagram illustrating the implementation of the NOx control system for an engine, and

[0072] Figure 6 This is a schematic diagram of another implementation of the NOx control system for an engine. Detailed Implementation

[0073] In the following detailed description, the internal combustion engine will be described with reference to the crosshead-type large two-stroke low-speed single-flow scavenging turbocharged internal combustion engine in the embodiment. The large two-stroke low-speed single-flow scavenging turbocharged internal combustion engine can be of the following (high-pressure) type: in this engine, fuel is injected at or near the top dead center of the piston, i.e., compression ignition; or the large two-stroke low-speed single-flow scavenging turbocharged internal combustion engine can be of the following (low-pressure) type: in this engine, fuel is mixed with scavenging air before or during compression, i.e., spark ignition. In the case of the low-pressure type, there is typically a "pilot" ignition via an ignition fluid, such as fuel, to ensure reliable ignition.

[0074] Figure 1 , Figure 2 , Figure 3 and Figure 4 A large, low-speed turbocharged two-stroke diesel engine with a crankshaft 8 and a crosshead 9 is shown. Figure 3 and Figure 4 Schematic diagrams of a large, low-speed turbocharged two-stroke diesel engine and its intake and exhaust systems are shown in two embodiments. In these embodiments, the engine has six inline cylinders. Large, low-speed turbocharged two-stroke diesel engines typically have between four and fourteen inline cylinders supported by a cylinder block 23, which is supported by an engine frame 11. The engine can be used, for example, as a main engine in marine vessels or as a stationary engine in power plants to operate generators. The total output of the engine can, for example, be in the range of 1,000 kW to 110,000 kW.

[0075] In these embodiments, the engine is a two-stroke, single-flow compression-ignition engine with scavenging ports 18 in the lower region of the cylinder liner 1 and a central exhaust valve 4 at the top of each cylinder liner 1. The engine can operate using different fuels, such as marine fuel oil, ethanol, methanol, natural gas, petroleum gas, or ammonia. The engine can also be a dual-fuel engine capable of switching between two different fuels, allowing the engine to have an operating mode associated with a first fuel and another operating mode associated with a second fuel.

[0076] During operation, scavenging air is delivered from the scavenging air receiver 2 to the scavenging ports 18 of each cylinder 1. The piston 10, reciprocating between bottom dead center (BDC) and top dead center (TDC) within the cylinder liner 1, compresses the scavenging air. Fuel is injected into the combustion chamber within the cylinder liner 1 at or near the TDC via (high-pressure) fuel valves 49 arranged in the cylinder head 22. Combustion then occurs, producing exhaust gases. Each cylinder head 22 is provided with two or more fuel valves 49. The fuel valves 49 are arranged in the cylinder head 22 around the central exhaust valve 4 and receive fuel from the fuel supply system 30.

[0077] In this embodiment, the fuel valve 49' (indicated by the dashed line) is arranged along the cylinder liner 1 and allows fuel to enter the cylinder liner before the piston 10 passes through the fuel valve 49' on its journey from the BDC to the TDC. Therefore, the piston 10 compresses the mixture of scavenging air and fuel. Timing ignition at or near the TDC is triggered by spark, laser, ignition fluid injection, etc. In the embodiment with the fuel valve 49', the pressure at which fuel is allowed to enter is significantly lower than the pressure at which fuel is injected in the embodiment where the fuel valve 49 is located in the cylinder head 22. Therefore, the pressure required for the fuel supply system 30' to deliver fuel can be significantly lower, and / or the turbocharger commonly used in the fuel valve 49 located in the cylinder head can be avoided, which is particularly advantageous for gaseous fuels.

[0078] When exhaust valve 4 is opened, exhaust gases flow through exhaust pipes associated with each cylinder to exhaust gas receiver 3, and then through first exhaust pipe 19 via selective catalytic reduction (SCR) reactor 28 to turbine 6 of turbocharger 5. From turbine 6, exhaust gases exit through second exhaust pipe via outlet 21 and into the atmosphere. SCR reactor 28 reduces emissions, particularly NOx emissions. Figure 3 In this embodiment, the SCR reactor 28 is arranged upstream of the turbine 6 of the turbocharger 5, that is, on the high-pressure side of the turbocharger 5, while Figure 4 In this embodiment, the SCR reactor 28 is arranged downstream of the turbine 6 of the turbocharger 5, that is, on the low-pressure side of the turbocharger 5.

[0079] The turbine 6 drives the compressor 7 via a shaft, and the compressor 7 is supplied with fresh air through the air inlet 12. The compressor 7 delivers the pressurized scavenging air to the scavenging air duct 13 leading to the scavenging air receiver 2. The scavenging air in the scavenging air duct 13 passes through the intercooler 14 to cool it.

[0080] When the compressor 7 of the turbocharger 5 cannot deliver sufficient pressure to the scavenging air receiver 2, i.e., under low or partial engine load conditions, cooled scavenging air is delivered via an auxiliary blower 16 driven by an electric motor 17, which pressurizes the scavenging air stream. At higher engine loads, the turbocharger compressor 7 delivers sufficient compressed scavenging air, and the auxiliary blower 16 is bypassed via a check valve 15, and the electric motor 17 is deactivated.

[0081] For each engine cycle, a precisely metered amount of fuel is injected into cylinder 1 through fuel valves 49, 49', and in this embodiment, controller 50 is configured to calculate engine load based on the given amount of fuel.

[0082] In one embodiment, the engine is equipped with a tachometer (not shown) for sensing the rotational speed of the crankshaft 8, and in this embodiment, the controller 50 can be configured to determine the power output of the engine based on the product of the rotational speed and the engine load.

[0083] An engine has a Specific Fuel Oil Consumption (SFOC) rating, which describes the mass of fuel consumed per unit of energy supplied at the engine's output. The unit of SFOC is kilograms per kilowatt-hour (kg / kWh).

[0084] The exhaust gases produced in cylinder liner 1 contain excessively high concentrations of NOx, which cannot be directly released into the atmosphere. Therefore, an SCR reactor 28 is required to reduce the NOx in the exhaust gases. In an embodiment where the SCR reactor 28 is arranged on the high-pressure side of the turbocharger 5, the SCR reactor 28 can be smaller due to the higher pressure and temperature. In an embodiment where the SCR reactor 28 is arranged on the low-pressure side of the turbocharger 5, the temperature and pressure will be lower, and the SCR reactor will need to be correspondingly larger to achieve the same effect.

[0085] exist Figure 3 and Figure 4In the illustrated embodiment, tank 26 contains an aqueous urea solution. A reducing agent conduit 25 connects tank 26 to the inlet of pump 24. Pump 24 is configured to provide substantially adjustment factor pressure. The outlet of pump 24 is connected to feed conduit 22, which delivers pressurized reducing agent, such as an aqueous urea solution, via electronically controlled valve 23 to injection module 20 for mixing with exhaust gas. In this embodiment, electronically controlled valve 23 is an on / off type, but a proportional valve may also be used. Electronically controlled valve 23 is controlled by signals from an electronic control unit including processor (controller) 50. Electronically controlled valve 23 may be a hydraulically or pneumatically actuated valve or a valve actuated only electrically. Injection module 20 is installed in or upstream of the SCR reactor, and injection module 20 may be arranged inside exhaust gas receiver 3, and injection module 20 is preferably provided with nozzles having nozzle orifices for atomizing the reducing agent solution when it is injected into the exhaust gas stream. The controller 50 is configured to control the magnitude of the reducing agent flow leading to the injection module 20, for example by controlling the speed of the pump 24.

[0086] Figure 3 Implementation methods and Figure 4 The only difference in the implementation method is that the SCR reactor 28 and the reducing agent injection module 20 are arranged on the low-pressure side of the turbocharger 5.

[0087] Emissions regulations (IMO regulations) for engines operating on marine vessels require that the NOx reduction rate at each test point must not differ by more than 5% from the value specified in the NOx technical document (established on a test bench for the relevant engine type). Test points typically correspond to: 100% engine load, weighted at 0.2; 75% engine load, weighted at 0.5; 50% engine load, weighted at 0.15; and 25% engine load, weighted at 0.1. In the regulations, the NOx level in the exhaust gas is expressed as a specific NOx level in g / kWh, and the NOx reduction rate of the SCR reactor 28 during engine operation must be better than or equal to the value specified in the technical document. Therefore, the controller 50 is configured to ensure that the NOx reduction rate is equal to or higher than the value specified in the technical document for each operating point.

[0088] Figure 5The controller 50 and the engine components associated with it are shown. The O2 sensor 27 sends a signal to the controller 50 indicating the molar PPM of O2 in the exhaust gas at a location downstream of the turbine 6 of the turbocharger 5 and downstream of the SCR reactor 28. Similarly, the NOx sensor 29 sends a signal to the controller 50 indicating the molar PPM of NOx in the exhaust gas at a location downstream of the turbine 6 of the turbocharger 5 and downstream of the SCR reactor 28.

[0089] Controller 50 is configured to calculate the NOx mass flow rate in the exhaust gas downstream of SCR reactor 28 based on the following:

[0090] The signal from O2 sensor 27,

[0091] The signal from NOx sensor 29

[0092] Engine load,

[0093] Engine thermal efficiency, and

[0094] Adjustment coefficient.

[0095] The controller includes a first module 51, which executes an algorithm to calculate the mass concentration of NOx in the exhaust gas at the outlet of the SCR reactor 28. This algorithm receives signals from the O2 sensor 27 and the NOx sensor 29, determines the engine load, the engine's thermal efficiency, and the adjustment coefficient.

[0096] The adjustment factor can be an adjustment factor related to engine load or an adjustment factor unrelated to engine load.

[0097] In this embodiment, the adjustment coefficient is a function of the engine's thermal efficiency and the fuel adjustment coefficient, and the fuel adjustment coefficient is preferably the Thornton constant.

[0098] Measuring the heat release rate in fire testing is highly complex and was previously impossible to measure with high precision until the development of oxygen consumption calorimetry in the late 1970s. Oxygen consumption calorimetry is based on Thornton's observation that the net heat released per unit mass of oxygen consumed for complete combustion is almost a moderating factor and independent of the fuel. In most fire experiments, the common value for the Thornton constant is 13.1 kJ / gO₂.

[0099] W.M. Thornton first mentioned this in his 1917 article, "The Relation of Oxygen to the Heat of Combustion of Organic Compounds." He explained how the heat (energy) released by the combustion of hydrocarbons depends on the amount of oxygen available for combustion, and that each unit of oxygen releases almost the same amount of energy, regardless of the hydrocarbons being burned.

[0100] Furthermore, the controller 50 is configured to calculate the mass concentration of NOx in the exhaust gas upstream of the SCR reactor 28 based on the magnitude of the reducing agent flow. To this end, the controller 50 includes a second module 52 equipped with an algorithm for calculating the mass concentration of NOx at the inlet of the SCR reactor 28 based on the magnitude of the reducing agent flow. The second module may be configured with an adjustment coefficient that provides the relationship between the magnitude of the reducing agent flow and the mass of NOx generated.

[0101] The controller 50 is configured in a third module 53 to calculate the NOx reduction rate of the SCR reactor 28 based on the NOx mass flow rate in the exhaust gas upstream of the SCR reactor 28 and the NOx mass flow rate in the exhaust gas downstream of the SCR reactor 28. The third module 53 receives the NOx mass flow rate in the exhaust gas downstream of the SCR reactor 28 from the first module and the NOx mass flow rate in the exhaust gas upstream of the SCR reactor 28 from the second module.

[0102] The controller 50 is configured to adjust the magnitude of the reductant flow by comparing a calculated NOx reduction rate with a desired NOx reduction rate. The result of this comparison is sent to a fourth module 54, which acts as a dispensing unit and provides a signal to the dispensing pump 24 to adjust the magnitude of the reductant flow injected into the exhaust gas stream. Therefore, the magnitude of the reductant flow injected into the exhaust gas stream is controlled in a closed-loop manner to ensure that the NOx reduction rate is equal to or higher than the desired level.

[0103] Since the mass flow rate of the exhaust gas through the exhaust gas system is basically the same on both sides of the SCR reactor 28, the controller 50 does not absolutely need to calculate the mass concentration in the exhaust gas. Instead, the controller 50 only needs to determine the NOx reduction rate of the SCR reactor 28 by determining the NOx mass flow rate in the exhaust gas before and after the SCR reactor 28.

[0104] In an implementation, the controller 50 may be configured to take into account the ambient O2 concentration when calculating the NOx mass flow rate in the exhaust gas downstream of the SCR reactor 28, preferably assuming the ambient O2 concentration to be 20.95%.

[0105] In one embodiment, the controller 50 receives a humidity sensor configured to sense ambient humidity, and in this embodiment, the controller 50 is configured to take into account the ambient humidity sensed by the humidity sensor when calculating the NOx mass flow rate in the exhaust gas downstream of the SCR reactor 28.

[0106] In this embodiment, the controller 50 is configured to take into account the ambient O2 concentration when calculating the NOx mass flow rate in the exhaust gas downstream of the SCR reactor 28, preferably by using a stored fixed value for the ambient O2 concentration. This fixed value can be selected as 20.95%.

[0107] In one implementation, the controller 50 is configured to: calculate a specific NOx downstream of the SCR reactor 28 as the NOx mass per unit of energy generated by the engine, for example in g / kWh; and calculate the NOx mass flow rate upstream of the SCR reactor 28 based on the magnitude of the reducing agent flow, as the NOx mass per unit of energy generated by the engine, for example in g / kWh.

[0108] The specific NOx downstream of SCR reactor 28 can be calculated, for example, as follows:

[0109] NOx molar PPM / (engine thermal efficiency x engine O2 molar consumption [%] x fuel coefficient).

[0110] The fuel coefficient is referred to as the aforementioned Thornton constant and is expressed in [kWh / g].

[0111] Figure 6 Another embodiment of the controller 50 is shown. In this embodiment, for simplicity, structures and features that are the same as or similar to those previously described or shown herein are indicated by the same reference numerals as previously used. This embodiment is similar to... Figure 5 The implementation methods are basically the same, except that the first module 51 receives a signal corresponding to the engine load, is informed of SFOC, and is informed of the NOx situation. u gas And informed of the fuel's LHV, and the adjustment factor being SFOC, Thornton constant, and for NOx... u gas A function of LHV of fuel.

[0112] u gas In IMO NTC2008 (NOx Technical Code), it is defined as the standard density ratio between the emission gas and NOx (or CO, HC, CO2, O2).

[0113] The low calorific value of fuel (also known as net calorific value, net CV, or LHV) is defined as the amount of heat released when a specific amount of fuel (initially at 25°C or other reference conditions) is burned and the temperature of the combustion products is restored to 150°C.

[0114] In this embodiment, the adjustment coefficient can be an adjustment coefficient related to engine load or an adjustment coefficient unrelated to engine load.

[0115] This document describes various aspects and implementations in conjunction with different embodiments. However, those skilled in the art, upon studying the accompanying drawings, disclosure, and appended claims, can understand and implement other variations of the disclosed embodiments in practicing the claimed subject matter. In the claims, the term "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude multiple. Other units of a single processor or controller can perform the functions of multiple items listed in the claims. The fact that certain measures are listed only in mutually different dependent claims does not mean that combinations of these measures cannot be used advantageously.

[0116] The reference numerals used in the claims should not be construed as limiting the scope. Unless otherwise stated, the drawings are intended to be read in conjunction with the specification (e.g., section lines, arrangement of components, scale, extent, etc.) and should be considered as part of the entire written description of this disclosure.

Claims

1. A large two-stroke single-flow scavenging turbocharged internal combustion engine, the engine comprising: Multiple cylinders (1) that generate a NOx-containing exhaust gas stream during engine operation. A turbocharger system (5) includes a compressor (7) and an exhaust gas driven turbine (6), the turbine (6) being located in the exhaust gas system and the compressor (7) being located in the scavenging air system for supplying scavenging air to the cylinders (1) of the engine. A selective catalytic reduction reactor (28) is located in the exhaust gas system. A reducing agent source (26) is configured to: add a given dose of reducing agent stream to an exhaust gas duct for reaction with NOx in the selective catalytic reduction reactor (28). O2 sensor (27), which generates a signal representing the O2 ppm in the exhaust gas downstream of both the selective catalytic reduction reactor (28) and the turbine (6), NOx sensor (29), which generates a signal representing the NOx ppm in the exhaust gas downstream of both the selective catalytic reduction reactor (28) and the turbine (6), Controller (50), which is informed of engine load, is characterized in that the controller (50) is configured to: - The NOx mass flow rate in the exhaust gas downstream of the selective catalytic reduction reactor (28) is calculated based on the following: -The signal from the O2 sensor (27), -The signal from the NOx sensor (29), - The thermal efficiency of the engine. -The engine load, and -Adjustment coefficient, -The NOx mass flow rate in the exhaust gas upstream of the selective catalytic reduction reactor (28) is calculated based on the magnitude of the reducing agent flow. -Based on the NOx mass flow rate in the exhaust gas upstream of the selective catalytic reduction reactor (28) and the NOx mass flow rate in the exhaust gas downstream of the selective catalytic reduction reactor (28), the NOx reduction rate of the selective catalytic reduction reactor (28) is calculated, and - The magnitude of the reducing agent flow is adjusted by comparing the calculated NOx reduction rate with the desired NOx reduction rate.

2. The engine according to claim 1, wherein, The adjustment coefficient is an adjustment coefficient related to engine load.

3. The engine according to claim 1, wherein, The adjustment coefficient is a function of the fuel constant and the thermal efficiency of the engine.

4. The engine according to claim 1, wherein, The adjustment coefficient is the fuel consumption rate, the Thornton constant, and the NOx ratio. u gas The function of the lower calorific value of fuel, where, for NOx, u gas In the International Maritime Organization's Technical Code on Nitrogen Oxides 2008, it is defined as the standard density ratio between the emitted gas and NOx.

5. The engine according to claim 1, wherein, The controller (50) is configured to take into account the ambient O2 concentration when calculating the NOx mass flow rate in the exhaust gas downstream of the selective catalytic reduction reactor (28).

6. The engine according to claim 5, wherein, The ambient O2 concentration was assumed to be 20.95%.

7. The engine according to claim 1, wherein, The controller (50) receives a signal from a humidity sensor configured to sense ambient humidity, and wherein the controller (50) is configured to take into account the ambient humidity sensed by the humidity sensor when calculating the NOx mass flow rate in the exhaust gas downstream of the selective catalytic reduction reactor (28).

8. The engine according to claim 1, wherein, The controller (50) is configured to take into account the ambient O2 concentration when calculating the NOx mass flow rate in the exhaust gas downstream of the selective catalytic reduction reactor (28).

9. The engine according to claim 1, wherein, The controller (50) is configured to: - Calculate the specific NOx downstream of the selective catalytic reduction reactor (28) as the NOx mass per unit of energy produced by the engine, and -Calculate the NOx mass flow rate upstream of the selective catalytic reduction reactor (28) based on the magnitude of the reducing agent flow, as the NOx mass per unit of energy generated by the engine.

10. The engine according to claim 1, wherein, For each engine cycle, a given dose of fuel is injected into the cylinder (1).

11. The engine according to claim 10, wherein, The controller (50) is configured to calculate the engine load based on the engine speed and a given dose of fuel.

12. The engine according to claim 11, wherein, The controller (50) is configured to calculate the engine load based on the engine speed and a given dose of fuel, assuming that the fuel consumption rate is constant.

13. The engine according to claim 1, wherein, The engine is equipped with a tachometer for sensing the rotational speed of the engine's crankshaft.

14. The engine according to claim 1, wherein, The controller (50) is configured to use a closed loop to regulate the magnitude of the reducing agent flow.

15. The engine according to claim 1, wherein, The cylinder (1) includes a cylinder liner, a reciprocating piston (10) located in the cylinder liner, and a cylinder head (22) covering the cylinder liner, wherein a combustion chamber is formed inside the cylinder liner, between the reciprocating piston (10) and the cylinder head (22).

16. The engine according to claim 1, wherein, The compressor (7) is driven directly or indirectly by the turbine (6).

17. A method for determining the NOx reduction rate of a large two-stroke, single-flow scavenging, turbocharged, multi-cylinder internal combustion engine, the engine comprising: Multiple cylinders (1) that generate a NOx-containing exhaust gas stream during engine operation. A turbocharger system (5) includes a compressor (7) and an exhaust gas driven turbine (6), the turbine (6) being located in the exhaust gas system and the compressor (7) being located in the scavenging air system for supplying scavenging air to the cylinders (1) of the engine. A selective catalytic reduction reactor (28) is located in the exhaust gas system. A reducing agent source (26) is configured to: add a given dose of reducing agent stream to an exhaust gas duct for reaction with NOx in the selective catalytic reduction reactor (28). O2 sensor (27), which generates a signal representing the O2 ppm in the exhaust gas downstream of both the selective catalytic reduction reactor (28) and the turbine (6), NOx sensor (29), which generates a signal representing the NOx ppm in the exhaust gas downstream of both the selective catalytic reduction reactor (28) and the turbine (6), The method includes: - The NOx mass flow rate in the exhaust gas downstream of the selective catalytic reduction reactor (28) is calculated based on the following: -The signal from the O2 sensor (27), -The signal from the NOx sensor (29), - The thermal efficiency of the engine. - Engine load, and -Adjustment coefficient, -The NOx mass flow rate in the exhaust gas upstream of the selective catalytic reduction reactor (28) is calculated based on the magnitude of the reducing agent flow. -Based on the NOx mass flow rate in the exhaust gas upstream of the selective catalytic reduction reactor (28) and the NOx mass flow rate in the exhaust gas downstream of the selective catalytic reduction reactor (28), the NOx reduction rate of the selective catalytic reduction reactor (28) is calculated, and - The magnitude of the reducing agent flow is adjusted by comparing the calculated NOx reduction rate with the desired NOx reduction rate.

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