JP6266730B2 - Two-stroke internal combustion engine having an SCR reactor provided downstream of an exhaust gas receiver - Google Patents

Description

  The present invention is a two-stroke internal combustion engine comprising a plurality of cylinders having combustion chambers and an exhaust gas system, the exhaust gas system comprising: an exhaust gas receiver for receiving exhaust gas from the plurality of cylinders; With one turbocharger and at least one SCR reactor located downstream of the exhaust gas receiver, each cylinder having a cylinder wall with a scavenging port and an exhaust duct extending to the exhaust gas receiver in the exhaust gas system And a regeneration flow path that relates to a two-stroke internal combustion engine that can be connected to the SCR reactor to regenerate the catalyst material in the SCR reactor.

  Two-stroke internal combustion engines are used as propulsion engines in ships such as container ships, bulk carriers, tankers and gas carriers. The two-stroke internal combustion engine is also used as a prime mover in a fixed power plant where an internal combustion engine drives a generator that supplies power to a power supply network. Environmental issues relate to both propulsion engines and fixed prime movers. The two-stroke internal combustion engine of the present invention is typically a large in-line engine having an output of at least 400 kW per cylinder. These two-stroke engines are typically of the crosshead type, which are high efficiency (low fuel) with low quality fuel oils, such as heavy oil and heavy oil containing sulfur, or with fuel gas and pilot oil. Consumption rate). Here, the pilot oil is a fuel oil containing sulfur.

The SCR reactor (SCR is selective catalytic reduction) is an exhaust that can reduce NO _x produced during the combustion process in the cylinder to a low level before the exhaust gas leaves the chimney and is released to the environment. Standard components used for gas processing. In the SCR reactor, NO _x is catalytically reduced to nitrogen and water by adding ammonia as a reducing agent. Further details in this regard, the document "Emission Project ^{Guide", 2 nd Edition, March 2014,} MAN Diesel & Turbo, are described in Denmark.

  The operating temperature of the SCR reactor is affected by the temperature of the exhaust gas flowing to the SCR reactor to be cleaned, the pressure of the exhaust gas in the SCR reactor, and the fuel sulfur content. If the exhaust gas temperature is too low (for example, less than 320 ° C. at 2.5 bara and 3% sulfur component), the sulfuric acid is neutralized by ammonia and is a sticky byproduct, ammonium bisulfate called ABS And ammonium bisulfate may be deposited on the catalyst material in the SCR reactor. If the exhaust gas temperature exceeds a maximum temperature, such as 550 ° C., the catalyst material can begin to sinter. If the temperature exceeds 350 ° C., the deposited ABS may dissolve and thus the catalyst material will regenerate.

  EP2216523A1 discloses an SCR reactor for cleaning exhaust gas from a large marine diesel engine when the temperature of the exhaust gas is 300 ° C. or less. To regenerate the catalyst material, the output producing an auxiliary diesel engine, which is a four-stroke engine different from the internal combustion engine, is used to provide exhaust at a higher temperature of about 350 ° C., which is Directed to the selected section of the SCR reactor to regenerate the catalyst material in this section.

  Japanese Patent Laid-Open No. 5-285343 discloses a two-stroke operation with exhaust gas temperatures ranging from 230 ° C. to 280 ° C., operating with fuel containing 2% to 5% sulfur, and the sulfur component increasing the formation of ABS. An internal combustion engine is disclosed. The SCR reactor is provided downstream of the turbocharger. The SCR reactor is divided into sections, and in each section, a gate valve capable of blocking the inflow of exhaust gas from the turbocharger and an exhaust passage between the exhaust gas receiver and the turbocharger, that is, the turbocharger And a control valve that opens for hot gas taken from the upstream of the turbocharger, which has a higher exhaust gas temperature than downstream.

EP2216523A1 JP-A-5-285343

"Emission Project Guide", 2nd Edition, March 2014, MAN Diesel & Turbo, Denmark

  The object of the present invention is to improve the possibility of regeneration of the catalyst material in the SCR reactor, for example when a two-stroke internal combustion engine is operating below full engine load.

  For this purpose, the first-described two-stroke internal combustion engine according to the present invention has a first exhaust gas whose temperature is higher than the temperature of the exhaust gas in the exhaust gas receiver. Characterized in that it is adapted to supply a flow of

  The entire two-stroke internal combustion engine operates at the engine load set by the engine governor, and the engine power supplied at this engine load is the result of the sum of the power produced by the individual cylinders. If all cylinders on the engine supply the regeneration flow path, for example by diverting the first hottest portion of the exhaust gas to the regeneration flow path, the engine governor will automatically compensate for this. If at least one of the cylinders supplies higher temperature exhaust gas to the regeneration flow path, this may affect the power supplied by this cylinder or these cylinders, Other cylinders of the cylinder compensate for this. This is because the engine governor maintains the set engine load. When at least one cylinder supplies exhaust gas at a temperature higher than the exhaust gas from the other cylinders, it is possible to provide exhaust gas having a temperature higher than the average temperature of the exhaust gas in the exhaust gas receiver to the regeneration path. It is. High temperature exhaust gas supply can also occur when a two-stroke internal combustion engine operates at a partial load, such as 50% engine load (MCR being 100% engine load, ie 50% of maximum continuous rating). . This possibility of obtaining sufficiently hot exhaust gas from at least one cylinder is very advantageous when the two-stroke internal combustion engine is a propulsion engine in a ship. Because ships typically navigate at a reduced speed and therefore at low engine loads when the ship is near a harbor, in these waters the emission requirements are strict and the SCR This is because the reactor should operate. It is also possible to operate a two-stroke internal combustion engine with a partial load, such as 75% of the MCR, for long periods of use. This is because the regeneration of the SCR reactor is possible due to the high temperature exhaust gas supplied by the single cylinder.

  In normal prior art operation of a two-stroke internal combustion engine, all cylinders have the same operating cycle. This is also possible for the two-stroke internal combustion engine according to the invention, in which case only the hottest part of the exhaust gas from the single cylinder is directed to the regeneration flow path. However, in one embodiment of the invention, a plurality of cylinders are divided into a first group comprising the at least one cylinder and a second group comprising the remaining cylinders, which are within the first group. The operating cycle of the at least one cylinder of the second group may be different from the operating cycle of the one or more cylinders in the second group. If regeneration is required, at least one cylinder in the first group is set to a modified operating cycle, resulting in a higher exhaust gas temperature. When regeneration is complete, at least one cylinder returns to its normal operating cycle, so that all cylinders have the same operating cycle until the next regeneration process. Of course, it is possible for at least one cylinder to permanently have a different operating cycle than the other cylinders, but this is not preferred. This is because the fuel consumption rate, or SFOC, of a two-stroke internal combustion engine is typically lower when all cylinders have the same operating cycle.

  The exhaust gas receiver has a diameter that is larger than the diameter of the individual exhaust pipes from the cylinder, e.g. at least twice the diameter of the individual exhaust pipes, or at least three times the diameter of the individual exhaust pipes, It is an elongated pressure vessel. The exhaust gas receiver has an equalizing effect on pressure fluctuations caused by individual exhaust pulsations from the cylinder. The exhaust gas receiver ensures that the pulsation energy from the exhaust pulsation is largely dissipated so that the exhaust gas flows stably to the turbocharger rather than intermittently and at a constant pressure at the turbine inlet of the turbocharger. to enable. Thus, the turbocharger is provided with an equalized pressure exhaust gas. The two-stroke internal combustion engine according to the invention is therefore provided with so-called constant pressure system turbocharging due to the presence of the exhaust gas receiver. This is in contrast to, for example, a turbocharger in a road vehicle where exhaust gas from a cylinder is passed through a manifold system consisting of tubes of approximately uniform diameter. As a result, the turbocharger is pulsed. It has a lower efficiency than a turbocharger that receives a constant pressure at the turbine inlet.

  In one embodiment, the operating cycle of the at least one cylinder is adapted by injecting additional fuel. The additional fuel increases the combustion gas temperature in the at least one cylinder so that the exhaust gas from the at least one cylinder has an increased temperature. If at least one cylinder provides more power, as a result, the engine governor regulates the other cylinders to provide less power by reducing the amount of fuel injected into the other cylinders. To do.

  In a further development, the operating cycle of the at least one cylinder is adapted by opening the exhaust valve earlier in the engine cycle than opening the exhaust valve in the cylinders in the second group. Normally, the exhaust valve is opened near the end of the working stroke, and in the second half of the working stroke, both the pressure and temperature of the combustion chamber are reduced. Thus, the early opening of the exhaust valve in the at least one cylinder results in the exhaust gas from the at least one cylinder having a higher pressure and a higher temperature. Another effect is that at least one cylinder provides a smaller output, so that the engine governor regulates the other cylinders to provide a greater output.

  In another further development, the operating cycle of the at least one cylinder is adapted by closing the exhaust valve earlier in the engine cycle than closing the exhaust valve in the cylinders in the second group. Early valve closing can cause incomplete scavenging and consequently higher temperatures, as not all combustion gases have been replaced by cold scavenging.

  In one embodiment, the control device in the at least one cylinder is adapted to separate the exhaust gas into a first part consisting of pure combustion gas and a second part consisting of combustion gas and scavenging, The first part is a first flow of exhaust gas supplied to the regeneration flow path. The pure combustion gas flowing out of the cylinder has a high temperature when the exhaust valve opens. The exhaust gas has a lower temperature when scavenging reaches the exhaust valve, and immediately before scavenging is terminated, the exhaust gas is mostly scavenged, resulting in a relatively cool exhaust gas. A mixture of combustion gas and scavenging gas. In the exhaust gas receiver, all exhaust gases are mixed, and the average temperature of the exhaust gas in the exhaust gas receiver is lower than the temperature of the pure combustion gas in the first flow of exhaust gas. As an example, when operating at an engine load of 25%, the temperature of the exhaust gas at the exhaust gas receiver can be 280 ° C., whereas the pure combustion gas in the first flow of exhaust gas is at a temperature of 700 ° C. Can have. A single cylinder may have the same or different operating cycle as the other cylinders as described above.

  In one embodiment, the control device controls an adjustable gate in the single-cylinder exhaust duct that opens to an exhaust position where exhaust gas is directed into the regeneration flow path and exhaust gas is directed to the exhaust gas receiver. And a closed position. In this embodiment, an adjustable gate may be disposed in the exhaust passage downstream of the exhaust valve, the cylinder cover on at least one cylinder in the first group and the cylinder on the other cylinder in the second group. It has the advantage that it can be the same design as the cover. In an alternative embodiment, the control device controls an additional exhaust valve in at least one cylinder, which additional exhaust valve is located at the end of the regeneration flow path. However, this alternative embodiment requires deformation of the cylinder cover.

  In another embodiment, the at least one cylinder is provided at the end of a two-stroke internal combustion engine, the exhaust duct from the at least one cylinder extends to the end region of the exhaust gas receiver, and the regeneration flow path is exhausted Connected to the end region of the gas receiver. Exhaust gas is supplied to the regeneration channel from at least one cylinder via an end region of the exhaust gas receiver. The exhaust gas receiver is provided with an inner plate provided between an outlet opening for an exhaust duct from at least one cylinder and an outlet opening for an exhaust duct from a cylinder adjacent to the at least one cylinder. obtain. The inner plate creates a barrier between the exhaust gas from the adjacent cylinder and the exhaust gas from the at least one cylinder such that the exhaust gas is supplied to the regeneration flow path from the at least one cylinder.

  In one embodiment, the at least one cylinder is a single cylinder. In this embodiment, the first group includes one cylinder, the second group includes the remaining cylinders, and these numbers are obtained by subtracting a single cylinder from the number of cylinders in the plurality of cylinders. is there.

  In one embodiment, the SCR reactor is provided upstream of the turbocharger, which provides the advantage of higher temperature levels since the exhaust gas has not yet expanded in the turbocharger turbine.

  In one embodiment, the SCR reactor has an outlet connected to a control valve, which is a pressure control valve. In normal operation of the engine, the control valve is in a fully open position. When regeneration is to be performed, the control valve can be set to a partially open position with a small opening area, so that a pressure drop occurs at the control valve and at the same time the pressure increases in the SCR reactor, This results in a higher temperature in the SCR reactor. This is because the temperature of the exhaust gas decreases when the exhaust gas expands at a lower pressure.

  Examples of embodiments of the invention are described in more detail below with reference to a very schematic drawing.

The figure which illustrates 1st Embodiment which concerns on this invention. The figure which illustrates 2nd Embodiment which concerns on this invention. The figure which illustrates 3rd Embodiment which concerns on this invention. The figure which illustrates how exhaust gas temperature changes with engine load.

  The two-stroke internal combustion engine 1 has a plurality of cylinders 2 such as 4 to 15 cylinders. In the illustrated embodiment, the engine has six cylinders 2. The engine may be, for example, a type ME or MC manufactured by MAN Diesel & Turbo, or manufactured by Waertsilae, or manufactured by Mitsubishi. The cylinder can have a bore in the range of, for example, 25 cm to 120 cm, preferably 35 cm to 98 cm. A two-stroke internal combustion engine used as the main propulsion engine is of the crosshead type and typically has a speed indicated by rpm in the range of 20 rpm to 260 rpm, typically 55 rpm to 195 rpm. These engines are termed low speed engines. Low speed is required to transmit propulsive thrust with high efficiency through the propeller to the water just behind the ship.

  Each cylinder 2 has a reciprocating piston in the cylinder. The cylinder is typically a uniflow scavenging type in which a scavenging port is provided in the lower end region of the cylinder and the exhaust valve 3 is mounted on the cylinder cover 4 and provided at the upper end of the cylinder. The exhaust valve opens and closes the exhaust duct 5 that extends to the exhaust gas receiver 6. The turbocharger 7 has a compressor portion that supplies pressurized intake air to the scavenging receiver 8. The scavenging receiver 8 is connected to an intake chamber provided at the lower end of each cylinder so that scavenging and intake are provided to a scavenging port on the cylinder wall. Exhaust gas is provided to the turbine portion of the turbocharger, and after expanding the exhaust gas in the turbine portion, the exhaust gas flows forward in the exhaust system and terminates at the chimney, where the exhaust gas is moved to the arrow 10. Released as indicated by.

  When a two-stroke internal combustion engine is operated with heavy oil, especially when operated with heavy oil containing sulfur, or with fuel oil as fuel gas and pilot oil, or with any other fuel containing sulfur. It may be desirable to clean the exhaust gas in the SCR reactor 11.

  In different embodiments, the same reference signs are used for the same type and functional details. In the embodiment of FIGS. 1 and 3, the SCR reactor is incorporated into an exhaust gas system downstream of the turbocharger, and in the embodiment of FIG. 2, the SCR reactor is incorporated into an exhaust gas system upstream of the turbocharger. ing. Since the exhaust gas is expanded in the turbine section, the exhaust gas has a higher temperature upstream of the turbocharger than downstream of the turbocharger.

  The first control valve 13 can be opened for the exhaust gas flow to the SCR reactor when the exhaust gas is to be cleaned, and the urea supply unit 14 can pass urea to the exhaust gas upstream of the SCR reactor. Added. The first control valve can be closed and the second control valve 15 in the bypass line 12 can be opened so that no exhaust gas is allowed to pass through the SCR reactor. The third control valve 16 is provided between the SCR reactor and the bypass line 12 on the downstream side of the SCR reactor.

  FIG. 4 illustrates how the average exhaust gas temperature at the exhaust gas receiver varies with engine load. At full engine load (100% of MCR), the exhaust gas temperature is high, but when a two-stroke internal combustion engine is operated at a partial load, such as a load in the range of 25% to 80% of the MCR, , Get lower. Curves a, b and c in FIG. 4 illustrate different layouts of a two-stroke internal combustion engine, with the same trend, i.e., the exhaust gas temperature will be lower when the engine load is lower. I understand. When the SCR reactor is cleaning exhaust gas having a temperature below 320 ° C., ammonium bisulfate accumulates on the catalyst material in the SCR reactor, reducing the catalyst cleaning effect on the reactor. As ABS accumulates on the surface of the catalyst material, the pressure drop in the SCR reactor increases. It is therefore possible to measure this pressure drop and if the predetermined limit value is exceeded, the regeneration process is started. Instead of monitoring the pressure drop, it is also possible to perform the regeneration process at regular intervals.

  The regeneration process may be performed on the entire SCR reactor or the SCR reactor has an internal separation that divides the SCR reactor into two or more sections, so that one section is the other section May be performed on a section of the SCR reactor if it can be regenerated during the operation of cleaning the exhaust gas. If the SCR reactor has sections, each section has a valve, such as a first control valve 13, to stop providing exhaust gas and a control valve that opens for flow leading to the regeneration flow path 17. It is also possible to incorporate several SCR reactors in parallel and regenerate one of the SCR reactors while another SCR reactor is operating.

  The regeneration channel 17 has a fourth control valve 18 that can be opened and closed for flow in the regeneration channel. In the embodiment of FIG. 1, the regeneration channel is connected to an exhaust duct 5 downstream of the exhaust valve and upstream of the exhaust gas receiver. This embodiment may be supplemented with a control device for a single cylinder that supplies a first flow of exhaust gas at an elevated temperature. In FIG. 1, the single cylinder is a cylinder at the left-hand side end of the engine, but the regeneration flow path can be attached to any of the cylinders. The control device separates the exhaust gas into a first part consisting of pure combustion gas directed to the regeneration flow path 17 and a second part consisting of combustion gas and scavenging directed to the exhaust gas receiver 6. . This can be done by operating an adjustable gate in the exhaust duct. Alternatively, the single cylinder may have an additional exhaust valve that is first opened and then closed before or when the exhaust valve 3 is opened. An additional valve is connected to the regeneration channel.

  In the embodiment of FIG. 3, the regeneration channel 17 is connected to an end region of the exhaust gas receiver, and an internal plate 19 is provided inside the exhaust gas receiver. The internal plate 19 ensures that the main exhaust gas from the single cylinder at the end of the engine is provided to the regeneration channel 17.

  The first flow of higher temperature exhaust gas can also be obtained by changing the operating cycle of the single cylinder. This preferably involves additional fuel injection into the single cylinder at the end of the fuel injection process, or the single cylinder exhaust valve opens before the exhaust valves in the other cylinders, or otherwise This may involve a change in the timing of the exhaust valve, such as closing before the exhaust valve in the cylinder. Fuel injection and exhaust valve operation are preferably electronically controlled so that the open and close signals to the exhaust valve actuator are easily adjusted to different timings in the engine cycle. When additional fuel is to be injected, the engine governor controls the single cylinder injection system to inject additional amounts of fuel.

  By way of example, the first stream of higher temperature exhaust gas may have a temperature in the range of 680 ° C. to 750 ° C. when entering the regeneration flow path 17 and the exhaust gas pressure is about 1 bar abs. When expanding to pressure, the temperature will be in the range of 450 ° C. to 470 ° C., high enough to perform regeneration.

  In the embodiment described above, at least one cylinder is embodied as a single cylinder, but two or more cylinders are designed as a single cylinder and form part of a first group of cylinders. Also good. In this case, if there are remaining cylinders, they form part of the second group. In the second group, the cylinders are not designed to have the potential to supply higher temperature exhaust gases to the regeneration flow path.

  The details of the various described embodiments can be combined into further embodiments within the scope of the claims.

Claims (14)

  A two-stroke internal combustion engine comprising a plurality of cylinders having combustion chambers and an exhaust gas system, the exhaust gas system including an exhaust gas receiver for receiving exhaust gas from the plurality of cylinders, and at least one turbo A charger and at least one SCR reactor provided downstream of the exhaust gas receiver, each cylinder having a cylinder wall having a scavenging port and an exhaust duct extending to the exhaust gas receiver in the exhaust gas system A two-stroke internal combustion engine, wherein the regeneration flow path is connectable to the SCR reactor to regenerate the catalyst material in the SCR reactor. At least one cylinder is connected to the exhaust gas receiver Characterized in that it is adapted to kick first flow of the exhaust gas temperature higher than the temperature of the exhaust gas so as to supply to the reproduction channel, two-stroke internal combustion engines.   The two-stroke internal combustion engine of claim 1, wherein the plurality of cylinders are divided into a first group comprising the at least one cylinder and a second group comprising the remaining cylinders.   The two-stroke internal combustion engine of claim 2, wherein the operating cycle of the at least one cylinder is adapted to be different from the operating cycle of the cylinders in the second group. The two-stroke internal combustion engine of claim 3 , wherein the operating cycle of the at least one cylinder is adapted by injecting additional fuel. Wherein said operating cycle of the at least one cylinder is adapted by opening the fast the exhaust valve in the engine cycle than the opening of the exhaust valve in the cylinder in the second group, according to claim 3 or 4 2 stroke internal combustion engine. Wherein said operating cycle of the at least one cylinder is adapted by closing the exhaust valve earlier in the engine cycle than the closing of the exhaust valve in the cylinder in the second group, according to claim 3 or 4 2 stroke internal combustion engine.   A control device in the at least one cylinder is adapted to separate the exhaust gas into a first part consisting of pure combustion gas and a second part consisting of combustion gas and scavenging; The two-stroke internal combustion engine according to any one of claims 1 to 6, wherein the portion becomes a first flow of the exhaust gas supplied to the regeneration flow path.   The control device controls an adjustable gate in the exhaust duct of the at least one cylinder, the gate being in an open position where exhaust gas is directed into the regeneration flow path, and exhaust gas to the exhaust gas receiver. The two-stroke internal combustion engine of claim 7, having a closed position directed.   9. The two-stroke internal combustion engine of claim 8, wherein the control device controls an additional exhaust valve in the at least one cylinder, the additional exhaust valve being disposed at an end of the regeneration flow path. .   The at least one cylinder is provided at an end of the two-stroke internal combustion engine, the exhaust duct from the at least one cylinder extends to an end region of the exhaust gas receiver, and the regeneration channel is The two-stroke internal combustion engine according to any one of claims 2 to 6, which is connected to the end region of the exhaust gas receiver.   The exhaust gas receiver is provided between an outlet opening for the exhaust duct from the at least one cylinder and an outlet opening for the exhaust duct from the cylinder adjacent to the at least one cylinder. The two-stroke internal combustion engine of claim 10, wherein an internal plate is provided.   The two-stroke internal combustion engine according to any one of claims 1 to 11, wherein the at least one cylinder is a single cylinder.   The two-stroke internal combustion engine according to any one of claims 1 to 12, wherein the at least one SCR reactor is provided upstream of the turbocharger.   The two-stroke internal combustion engine according to any one of claims 1 to 13, wherein the SCR reactor has an outlet connected to a third control valve, and the third control valve is a pressure control valve. .

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