JP2013160224A - Turbo supercharging type large-sized two-stroke diesel engine with exhaust gas emission control function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a uniform mixture by mixing ammonia into exhaust gas and to minimize countermeasure cost for a pressure loss, on the other hand, in a turbo supercharger in which an SCR reactor is installed at a high pressure side of a turbine.SOLUTION: A cross head type large-sized turbo supercharging type two-cycle diesel engine includes: a plurality of cylinders disposed in series; a turbo supercharger; and an SCR reactor at an upstream side of the turbo supercharger and a downstream side of an exhaust gas receiver 3. The exhaust gas receiver 3 is connected to the respective cylinders, introduces exhaust gas in a tangential direction and generates an eddy current in the exhaust gas on the inside of the exhaust gas receiver 3. A reductant is introduced to a flow within a center duct 47. A plurality of vanes are included around the center duct 47, and the vanes cause the exhaust gas to dissipate the eddy current and cause pressure to be acquired. The acquired pressure causes a part of the exhaust gas in an outlet section 49 to reversely flow through the center duct 47 to a mixing section 48.

Description

  The present invention relates to a crosshead turbocharged large two-stroke internal combustion piston engine, which is preferably a diesel engine having an exhaust gas purification system, and in particular, an SCR (Selective Catalytic Reduction) for purifying NOx of exhaust gas. The present invention relates to a crosshead large two-stroke diesel engine having a reactor.

  A crosshead type large two-stroke engine is typically used as a propulsion system for a large ship or a main engine of a power plant. Regulations on emissions, particularly on nitrogen oxide (NOx) levels, have been stricter and are expected to become increasingly strict.

  Public interest in environmental issues is growing rapidly. The International Maritime Organization (IMO) is also discussing emission regulations regarding air pollution in the ocean. The authorities are doing the same in various places around the world. For example, the US Environmental Protection Agency (EPA) proposes to institutionalize what is currently being discussed.

  NOx in the exhaust gas can be reduced by a primary reduction device and / or a secondary reduction device. As a primary method, there is a method that directly affects the combustion process of the engine. How much can actually be reduced depends on the type of engine and the reduction technique, but varies from about 10% to over 80%. The secondary method is a method that uses a device that is not a part of the engine itself, and is a means of reducing the emission level without changing the engine performance due to the optimized fuel setting. is there. The most successful secondary method to date is the SCR (Selective Catalytic Reduction) method, which is a method for reducing NOx. This method is a method of adding ammonia or urea to the exhaust gas before entering the exhaust gas into the catalytic converter, and can reduce the NOx level by 95% or more.

  The SCR reactor comprises multiple layers of catalyst. The volume of the catalyst, and consequently the size of the reactor, varies depending on the activity of the catalyst and the required NOx reduction. The catalyst usually has a monolithic structure, which means that it is composed of a compartment of the catalyst having a large number of parallel channels with catalytic activity on the wall.

  The exhaust gas must have a temperature of at least 280-350 ° C., depending on the sulfur content. That is, in order to efficiently convert NOx into nitrogen and water, the temperature of the exhaust gas at the inlet of the SCR reactor must be high when the sulfur content is high, and the temperature when the sulfur content is low. May be lower.

  The temperature of the exhaust gas on the high pressure side of the turbocharger turbine is approximately 350-450 ° C. Oh, the temperature of the exhaust gas on the turbine low pressure side of the turbocharger is usually approximately 250-300 ° C.

  For this reason, it is preferable to install an SCR reactor on the high pressure side of the turbine of the turbocharger. However, the SCR reactor has a very large number of pipes and containers inside, but when installed on the high pressure side of the turbine, these pipes and containers must be able to withstand a pressure of approximately 4 atmospheres, Moreover, it will be exposed to temperature changes from 20 ° C to 400 ° C. For this reason, there are many complicated problems in the configuration in which the SCR reactor is installed on the high pressure side of the turbine. The expansion and contraction due to temperature causes a big design problem.

  Usually, the reducing agent is injected and atomized upstream of the SCR reactor in the exhaust gas system. The present invention addresses the problem of mixing ammonia into the exhaust gas to obtain uniform mixing while minimizing costs (in terms of pressure drop). Usually, the reducing agent is ammonia, which is obtained when the injected urea evaporates and decomposes. This process takes time, and in order to avoid deposits, contact with the walls of the exhaust system must be avoided during evaporation. It is very important to correctly add a reducing agent such as ammonia or urea, as contact between the liquid reducing agent and the exhaust system wall can cause unwanted deposits on the inner wall of the exhaust system.

  Because of this background, it has been proposed to employ a sophisticated but expensive spraying system for the SCR system. This spraying system can uniformly spray ammonia and urea in the flow of exhaust gas. Further, the existing SCR system uses a dedicated unit called a mixing unit so that sufficient mixing is performed on the downstream side. This is usually quite large. This mixing unit results in an overall head loss (pressure loss) of the exhaust system, which is equivalent to reducing the efficiency of the turbocharger. Such a loss of efficiency of the turbocharger is unacceptable from the viewpoint of fuel efficiency. Furthermore, pressure loss also limits the availability of power turbines driven by bypassed exhaust gas flows (for waste heat utilization).

  Under such background, it is an object of the present invention to provide an engine having an SCR reactor, which overcomes or at least reduces the above-mentioned problems.

  This object is achieved by providing a turbocharged large two-stroke uniflow diesel engine having a crosshead as follows. The engine includes a plurality of cylinders arranged in series; a turbocharger having a turbine driven by exhaust gas and a compressor driven by the turbine, and supplying air to the cylinders; Each of the cylinders is connected to each other via its own exhaust duct, and is a long cylindrical exhaust gas receiver extending along the row of the plurality of cylinders, wherein the exhaust duct is the cylindrical exhaust gas A cylindrical exhaust gas receiver that directs exhaust gas from the cylinder into the cylindrical exhaust gas receiver in a tangential direction to produce a vortex in the exhaust gas in the receiver; A unit comprising a plurality of vanes around the periphery of the exhaust gas duct; and the unit is installed downstream of the exhaust gas duct in the exhaust gas receiver; Split in the longitudinal direction into a mixing section where the exhaust gas duct is present on the longitudinal side and an outlet section on the other side of the longitudinal direction of the unit; the outlet section is a selective catalyst present outside the exhaust gas receiver An outlet connected to an inlet of the reduction reactor; an outlet of the selective catalytic reduction reactor is connected to an inlet of the turbine of the turbocharger; the unit is between the mixing section and the outlet section , Arranged such that a swirl of exhaust gas flows along the vane; the unit further dissipates the swirl in the exhaust gas passing along the vane from the mixing region to the outlet region; Configured to acquire pressure, wherein the acquired pressure passes a portion of the exhaust gas that has passed along the vane to the outlet region via the axial duct. From the outlet region to the external selective catalytic reduction reactor via the outlet, whereby the other portion of the exhaust gas that has passed along the vane is configured to flow back to the mixing region. The engine further comprises a supply of reducing agent added to the exhaust gas at a reducing agent introduction point, wherein the reducing agent mixes with the part of the exhaust gas flowing back from the outlet section to the mixing section; The reducing agent introduction point is provided in the axial duct so that it can be made.

  By injecting the reducing agent into a central duct that is isolated from the vortex in the exhaust gas receiver, the reducing agent evaporates before it can contact the wall of the exhaust gas receiver.

  According to an embodiment, the exhaust gas flowing backward through the axial duct and added with a reducing agent can be mixed with the vortex mixed gas in the mixing section.

  According to another embodiment, the axial duct extends axially into the mixing section.

  According to another embodiment, the axial duct is part of a concentric tube extending into the mixing section, and the exhaust gas forms a vortex around the concentric tube.

  Preferably, the tube has a length sufficient for the reducing agent to evaporate before exiting the tube.

  According to another embodiment, the flow of exhaust gas in the concentric tube is not a vortex.

  According to another embodiment, the vane extends radially from the duct towards the inner wall of the exhaust gas receiver.

  According to another embodiment, the vane has a bent section upstream and an unbent section downstream.

  According to another embodiment, the blade is configured to cause the vortex exhaust gas flowing past the blade to lose its vortex and gain pressure.

  According to another embodiment, the engine comprises two or more exhaust gas receivers arranged in series.

  The exhaust gas receiver includes a bypass outlet that connects the mixing section to a bypass conduit that connects to a turbine of the turbocharger.

  This object is also achieved by providing the following exhaust gas receiver for a turbocharged large two-stroke uniflow diesel engine with a crosshead. The exhaust gas receiver is a long cylindrical exhaust gas receiver housing that receives exhaust gas tangentially from the cylinder of the engine, thereby creating a vortex in the exhaust gas inside the exhaust gas receiver An exhaust gas receiving housing, wherein a plurality of openings are individually disposed along a longitudinal portion of the length of the exhaust gas receiver; and a plurality of vanes around the central axial duct A unit comprising: a unit that is installed downstream of the exhaust opening in the exhaust gas receiver; and the unit is a mixing section in which the exhaust gas duct exists on a longitudinal side of the unit; A longitudinally divided outlet section on the other longitudinal side of the unit; the outlet section including an outlet to the outside of the exhaust gas receiver; the unit comprising the mixing section From the mixing zone to the outlet zone; the unit is further adapted to the exhaust gas passing along the vane from the mixing zone to the outlet zone. The vortex flow disappears and is configured to acquire pressure, the acquired pressure passing a portion of the exhaust gas that has passed along the vane from the outlet region via the axial duct. Backflow to the mixing zone, whereby the other part of the exhaust gas that has passed along the vane is configured to exit the outlet zone via the outlet; The reducing agent introduction point provided in the axial duct is provided so that the exhaust gas flowing backward from the outlet section to the mixing section can be mixed with the reducing agent. That.

  By injecting the reducing agent into the central duct isolated from the turbulent flow in the exhaust gas receiver, the reducing agent evaporates before it can contact the wall of the exhaust gas receiver.

  Another object of the present invention is to provide an exhaust gas receiver capable of suppressing energy loss in the flow of exhaust gas through the exhaust gas receiver.

  This object is achieved by providing a turbocharged large two-stroke uniflow diesel engine having a crosshead as follows. The engine includes a plurality of cylinders arranged in series; a turbocharger having a turbine driven by exhaust gas and a compressor driven by the turbine, and supplying air to the cylinders; Each of the cylinders is connected to each other through its own exhaust duct, and is a long cylindrical exhaust gas receiver that extends along the row of the plurality of cylinders, and the inside of the cylindrical exhaust gas receiver includes: The exhaust duct is configured to be free of any obstruction to the flow inside the exhaust gas receiver, and each of the exhaust ducts is adapted to create a vortex in the exhaust gas in the exhaust gas receiver. A cylindrical exhaust receiver configured to direct exhaust gas tangentially into the cylindrical exhaust receiver; and connected to a conduit leading to the turbine of the turbocharger Is, an outlet directed tangentially; comprises.

  By providing a tangential inlet to the exhaust gas receiver that allows the exhaust gas to perform vortex motion towards the outlet, and by arranging the outlet tangentially, the exhaust gas flow has minimal energy loss. Can pass through the exhaust gas receiver.

  In an embodiment, the tangentially directed outlet is arranged and configured to allow the vortex exhaust gas to exit the exhaust gas receiver with minimal change in flow direction.

  Further problems, features, advantages, and properties of the engine and exhaust gas receiver according to the present disclosure will become apparent from the detailed description that follows.

1 is a front view of a large two-stroke diesel engine according to an exemplary embodiment. FIG. 2 is a side view of the large two-stroke engine of FIG. 1. 2 is a diagrammatic representation of the large two-stroke engine of FIG. It is sectional drawing of the exhaust-gas receiver of the large sized 2-stroke engine of FIG. FIG. 5 is a cross-sectional view taken along line VV ′ of FIG. 4. FIG. 5 is an elevation view and a perspective view of the exhaust gas receiver of FIG. 4. FIG. 6 is a cross-sectional view of an exhaust gas receiver according to another exemplary embodiment. It is sectional drawing of another embodiment of the exhaust-gas receiver of a large sized 2 stroke engine. FIG. 9 is a sectional view taken along line IX-IX ′ in FIG. 8. It is sectional drawing of another embodiment of the exhaust-gas receiver of a large sized 2 stroke engine. It is sectional drawing along line XI-XI 'of FIG.

Detailed Description of the Preferred Embodiment

  In the following detailed description section of the specification, the present invention will be described in more detail with reference to exemplary embodiments depicted in the accompanying drawings.

  In the following detailed description, a large two-stroke engine will be described using an exemplary embodiment. FIG. 1-3 shows a turbocharged large-sized low-speed two-stroke diesel engine. This engine includes a crankshaft 52 and a crosshead 43. FIG. 3 is a diagram representation of a turbocharged large low speed two-stroke diesel engine, in which an intake system and an exhaust system are drawn. In this exemplary embodiment, the engine comprises six cylinders 1 in series. A turbocharged large two-stroke diesel engine typically has 5 to 16 cylinders arranged in series. These are supported by the engine frame 45. Such an engine is used, for example, as a main engine of an ocean vessel. It is also used as a fixed engine for turning a generator at a power plant. The total output of such an engine ranges, for example, from 5,000 kW to 110,000 kW.

  This type of engine is a two-stroke uniflow type, has a scavenging port in the lower region of the cylinder 1, and has an exhaust valve 4 in the upper portion of the cylinder 1. The air supply is guided from the air supply receiver 2 to a scavenging port (not shown) of each cylinder 1. When the piston 51 of the cylinder 1 compresses the supply air, fuel is injected, combustion occurs, and exhaust gas is generated. When the exhaust valve 4 is opened, the exhaust gas flows into the exhaust receiver 3 through the exhaust duct 35 corresponding to the cylinder 1, and further passes through the first exhaust pipe 18 including the SCR reactor to the turbine 6 of the turbocharger 5. Further, the exhaust gas flows out through the second exhaust pipe 7 from there. The turbine 6 rotates a compressor 9 provided via an intake port 10 via a shaft 8. The compressor 9 supplies the compressed air supply to the air supply pipe 11 that continues to the air supply receiver 2.

  The air supply to the tube 11 is passed through the intercooler 12 for cooling. As a result, the supply air temperature, which was about 200 ° C. when the compressor is discharged, is lowered to 36-80 ° C.

  The cooled intake air is guided to an auxiliary blower 16 driven by an electric motor. The auxiliary blower 16 compresses the intake air guided to the air supply receiver 2 in a low load condition or a partial load condition. When the turbocharger is under high load, the compressor 9 can supply sufficient scavenging, so that the auxiliary blower 16 is bypassed by the check valve 15.

  FIG. 3 shows the layout of the SCR system. This system comprises an SCR (Selective Catalytic Reduction) reactor 19. A reducing agent such as ammonia or urea is added to the exhaust gas before entering the SCR reactor 19. The exhaust gas must be mixed with a reducing agent such as ammonia before passing through the SCR reactor 19. In order to promote the chemical reaction in the SCR reactor 19, the temperature level must be between 200 ° C. and 400 ° C., depending on the sulfur content in the exhaust gas. In this embodiment, the ammonia source is a water-based urea solution.

  In the embodiment depicted in FIG. 3, the tank 26 stores an aqueous solution of urea. A pipe 25 connects the tank 26 to the inlet of the pump 24. Pump 24 is configured to provide a substantially constant pressure. The outlet of the pump 24 is connected to the supply pipe 22, and the supply pipe 22 carries the pressurized component aqueous solution to the injection valve 21 via the electronic control valve 23 (see FIG. 4). The electronic control valve 23 in the present embodiment is an on / off type, but a proportional valve can also be used. The electronic control valve 23 is controlled by a signal from an electronic control unit (processing computer) 50. The electronic control valve may be a hydraulic valve, a pneumatic valve, or may be a valve that operates purely electrically. The injection valve 21 is installed inside the exhaust receiver 3. The injection valve 21 is provided with a nozzle having a nozzle hole. By this nozzle hole, the urea aqueous solution injected to the exhaust gas receiver 3 is atomized. The injection valve 21 is configured to perform injection only when the pressure exceeds a threshold value. This is because the injection is performed only when there is sufficient pressure to make the urea aqueous solution mist. A NOx and oxygen analyzer is connected to the second exhaust pipe 7, and the analysis result is transmitted to the electronic control unit 50. The sensor 32 may measure the NOx content of the exhaust gas in the pipe 18 upstream or downstream of the SCR reactor 19 and upstream of the turbocharger 6.

  The amount of reducing agent injected into the exhaust gas is controlled by the electronic control unit 50, which is performed based on the amount of NOx produced under actual operating conditions (load conditions). The relationship of the NOx generation amount with respect to the operation condition (load condition) is derived from the measurement of the NOx generation amount under various operation conditions (load conditions) measured during the test operation of the engine. The amount of reducing agent injected into the exhaust gas is also controlled based on signals from NOx and oxygen analyzers, or based on experimentally determined signals from tables and sensors 32, and all of these. In some cases. The timing for injecting the reducing agent is performed without considering the actual position of the crankshaft 52 of the engine. This is because it is not necessary. Exhaust gas to be mixed with the reducing agent always flows out from the exhaust duct 35, and the exhaust gas always exists in the path from the reducing agent injection point to the outlet 33.

  With reference to FIGS. 4, 5, and 6, the configuration of the cylindrically long exhaust gas receiver 3 and the reducing agent injection system will be described in more detail using an exemplary embodiment. The exhaust gas receiver 3 has a fairly long cylindrical shape and has a large cross-sectional area. For example, the exhaust gas receiver may be as long as 10 m while the diameter may be 1-2 m.

  The exhaust gas receiver 3 is provided along the row of cylinders 1 and is provided relatively close to the upper part of the cylinder 1 where the exhaust valve 4 and the exhaust duct 35 are provided. Each exhaust duct 35 opens to the exhaust gas receiver 3. In many engines, the exhaust valve 3 extends so as to straddle all the cylinders 1 arranged in series in the engine. However, the exhaust gas receiver 3 is often divided into two or more sections in the longitudinal direction. For example, in the case of a very large engine having many cylinders, the exhaust gas receiver 3 Such a configuration may be employed so that the size does not exceed the size compatible with the manufacturing facility. Another reason for dividing the exhaust gas receiver 3 into a plurality in the length direction is when there are a plurality of turbochargers 5. In this case, one divided section of the exhaust gas receiver 3 is assigned to each turbocharger 5.

  Usually, the cross-sectional area of the exhaust gas receiver 3 is equal to or larger than the cross-sectional area of the piston 51 of the engine. As a result, the exhaust gas receiver 3 has a large volume. When the exhaust valve 4 of the cylinder 1 is opened, an exhaust gas jet flows into the exhaust gas receiver 3 through the exhaust duct 35, and the jet may generate pressure fluctuations. The large volume of the exhaust gas receiver 3 makes it possible to mitigate this pressure fluctuation.

  The long exhaust gas receiver 3 is provided with an outlet 33. The outlet 33 is connected to the tube 18 and is therefore connected to the SCR reactor 19. For this reason, the exhaust gas collected in the exhaust gas receiver 3 flows to the turbine of the turbocharger 5 through the SCR reactor 19. In this embodiment, the outlet 33 is located at one end in the longitudinal direction of the exhaust gas receiver 3. Therefore, the main flow inside the exhaust gas receiver 3 is unidirectional and directed toward the outlet 33.

  Each cylinder 1 of the engine burns individually according to a predetermined combustion sequence. Accordingly, the corresponding exhaust valves 4 are also opened in the same sequence, and high-speed exhaust gas jets also flow into the exhaust gas receiver 3 through the exhaust duct 35 in the same sequence. The speed of the exhaust gas jet is initially higher than 100 m / s, and becomes slower after the exhaust valve opening phase.

  The exhaust duct 35 is directed in a tangential direction with respect to the cylindrical exhaust gas receiver, whereby the exhaust gas (pulse) from the cylinder 1 enters the exhaust gas receiver 3 from the tangential direction, and the exhaust gas receiver 3 Causes exhaust gas swirl or swirl motion in it. While the exhaust gas moves toward the outlet 33, a vortex is also generated. The vortex is shown by arrows in FIG.

  A unit 42 is provided downstream of the exhaust gas duct 35 in the exhaust gas receiver 3. The unit 42 divides the exhaust gas receiver 3 in the longitudinal direction into a mixing section 48 on the upstream side of the unit 42 and an outlet section 49 on the downstream side (that is, the opposite side) of the unit 42. An exhaust gas duct 35 is located in the mixing section 48. The unit has an overall shape like a thick disk or ring, and its diameter corresponds to the inner diameter of the exhaust gas receiver 3. The unit 42 includes a plurality of vanes (blades) 43. This vane is arranged around the central and axial duct 47 of the unit 42. The vanes extend radially from the duct to the inner wall of the exhaust gas receiver 3 in the outer region of the unit 42. For this reason, an area outside the unit in the radial direction forms an exhaust gas passage in which many vanes are present. The vane or blade 43 has an upstream section that is bent and a downstream section that is not bent. The bent upstream section is at the end of the vane 43 closest to the mixing section 48, receives the swirl exhaust gas, and converts the swirl component of the exhaust gas into a pressure gain. The uncurved downstream section extends from the bent upstream section to the end of the vane 43 closest to the exit section 49. The unbent section stabilizes the direction of the exhaust gas flow into the outlet section 49, resulting in a straight and unvortexed flow. Any vane or blade, as long as the shape and arrangement of the vane or blade, etc. is configured to dissipate the vortex from the exhaust gas vortex flowing through the radially outer section of the unit 42 and gain pressure. A shape or arrangement such as these may be used.

  The inner surface of the unit is formed by a duct 47. In this embodiment, the duct 47 is formed by the tube 40. The reducing agent introduction point has the form of an injection nozzle 21 and is arranged in the duct 47 or in the pipe 40 slightly below. An axial duct 47 extends axially into the mixing section and exists over most of the length of the mixing section 48. The axial duct is the part of the concentric tube 40 that extends into the mixing section 48, and the exhaust gas forms a vortex around the concentric tube 40. The proximal end of the tube 40 is formed by a duct 47 in the unit 42 and constitutes the inlet of the tube 40. The distal end of the tube 40 is open and spaced from the longitudinal end of the exhaust gas receiver 3 and constitutes the outlet of the tube 40.

  The outlet section 49 of the exhaust gas receiver 3 includes an outlet 33. The outlet 33 is connected to the inlet of the selective catalytic reduction reactor 19 via the conduit 18.

  During operation, the exhaust gas from the cylinder 1 entering through the individual exhaust ducts 35 performs a vortex motion around the pipe 40 and travels toward the unit 42. The unit 42 is arranged so that the vortex exhaust gas flows along the vane 43 in the radially outer section of the unit in the middle from the mixing section 48 to the outlet section 49. In this process, the exhaust gas loses its vortex and the exhaust gas gains pressure. That is, the vortex component of the exhaust gas is converted into the pressure gain of the exhaust gas. The pressure of the exhaust gas exiting from the radially outer section of the unit 42 is higher than the pressure of the exhaust gas entering the radially outer section of the unit 42. Accordingly, similarly, the pressure of the exhaust gas near the outlet of the tube 40 is lower than the pressure of the exhaust gas exiting from the radially outer section of the unit 42. As a result, the pressure at the inlet of the tube 40 is higher than the pressure at the outlet of the tube, and this pressure difference causes an exhaust gas flow from the mixing section 48 through the duct 47 and the tube 40 to the mixing section.

  The mixing unit and exhaust gas receiver are configured so that the flow returning to the mixing section 48 through the tube 40 is a relatively slow non-vortex. Furthermore, the mixing unit and the exhaust gas receiver are configured such that only a small part, preferably only a small part, of all exhaust gas exiting the radially outer section of the unit 42 is carried back into the mixing section 48; Most of the exhaust gas leaving the radially outer section of the unit 42 is configured to flow through the outlet 33 to the catalytic reduction reactor 19.

  Due to the addition of the unit 42 and the outlet chamber 49, the total length of the exhaust gas receiver 3 becomes longer than that of the conventional exhaust gas receiver.

  During operation, the reducing agent is injected into the laminar flow in the duct 47 / pipe 40 via the injection valve 21 with the nozzle so that the reducing agent mixes with the exhaust gas returning from the outlet section 49 to the mixing section 48. It becomes possible to do. Since it is not a vortex, the reducing agent can be prevented from contacting the inner wall of the tube 40. It also allows a reducing agent such as urea to have sufficient time to evaporate and decompose before it can come into contact with the exhaust gas receiving wall. Accordingly, the risk of reducing agent deposition is reduced. When the reducing agent is urea, the high temperature of the exhaust gas in the pipe 40 hydrolyzes (thermally decomposes) urea into ammonia gas, and the aqueous portion of the injected aqueous urea solution evaporates.

  To further ensure that the flow in the duct 47 / tube 40 is non-vortex, a guide vane can be provided near the location where the reducing agent is injected. Preferably, the guide vanes are straight and extend axially in the tube 40. In one embodiment, the axial length of the guide vane is approximately equal to the diameter of the tube 40.

  In this embodiment, the reducing agent introduction point is the injection valve 21 located in the duct 47. The aqueous urea solution is injected into the duct 47 from the nozzle hole of the injection valve 21 in the form of a spray or jet. The evaporated aqueous urea solution enters the exhaust gas receiver 3 at the beginning of the pipe 48. From this point, the evaporated aqueous urea solution is carried in the main direction of the laminar flow in the tube 48.

  When the exhaust gas with the added reducing agent exits the tube 40, it can be mixed with the vortex exhaust gas in the mixing section 48. Thus, the reducing agent is present in the vortex exhaust gas, and most of the exhaust gas properly mixed with the reducing agent flows from the outlet section 49 through the outlet 33 to the inlet of the SCR reactor 19. The exhaust gas appropriately mixed with the reducing agent flows through the SCR reactor 19 to the outlet of the SCR reactor 19. In this process, NOx is reduced to N2 and water with the aid of a reducing agent. The exhaust gas in which the amount of NOx is reduced flows from the outlet of the SCR reactor 19 to the inlet of the turbine 6 of the turbocharger 5 and from there to the second exhaust conduit 7. The second exhaust conduit 7 guides exhaust gas from the outlet of the turbine 6 to the inlet of the silencer 28. The third exhaust conduit 29 guides exhaust gas from the outlet of the silencer 28 to the outside air.

  The reducing agent (urea aqueous solution) may be injected as a constant flow. Further, the reducing agent may be intermittently injected. This is because there is sufficient time and opportunity for the injected reducing agent to be mixed and dispersed in the exhaust gas receiver 3 with the exhaust gas. Therefore, the timing of reducing agent injection is not so important. This enables the use of a timing-based medicine injection system in which the electronic control unit 50 controls the opening timing of the electronic control valve 23. Since timing control is an accurate process over a wide range of input rates, a relatively simple, accurate and reliable input system is provided. The single point of introduction of the reducing agent helps to simplify the system.

  Being able to control the injection of the reducing agent according to the timing is to maintain a practically constant pressure for the injection event, and to construct a system that can correctly atomize the reducing agent at each injection event. make it easier.

  In some embodiments, the reducing agent input system employs a steady flow using control performed by adjusting the injection pressure, or selectively activates a predetermined number of nozzles. You may adopt that.

  The diameter of the duct 47 and the length of the tube 40 can be varied appropriately according to the needs and circumstances. In some embodiments, the tube can be very short or completely omitted so that the duct extends axially only slightly beyond the thickness of the unit 42. The effect of vortex flow in the mixing section 48 results in a relatively concentric region of flow with a relatively low pressure in the middle of the mixing section 48, providing a mild environment away from the wall for the reducing agent to evaporate and hydrolyze. .

  Instead of using one injection valve 21 / nozzle, multiple valves and / or nozzles can be used.

  FIG. 7 illustrates another exemplary embodiment. This embodiment is essentially the same as the embodiment of FIG. However, in this embodiment, the exhaust gas receiver 3 is provided with two outlets 33, one at each longitudinal end. Thus, the exhaust gas receiver has two outlet chambers 49 at opposite longitudinal ends of the exhaust gas receiver, with one mixing chamber 48 and two units 42 between them. Otherwise, the operation and structure are the same as the embodiment of FIG. The embodiment of FIG. 7 has a plurality of turbochargers 5 such that there are many (eg more than 5) cylinders in series and a turbocharger is provided for each of the outlets 33, for example. It is particularly useful for engines that have. Such an engine may also have two SCR units 19, one between each outlet 33 and the turbocharger 5.

  8 and 9 show another exemplary embodiment. See in combination with the dashed line in FIG. This exemplary embodiment is essentially the same as the embodiment of FIGS. 4-6 except that a bypass outlet 39 is provided and an SCR bypass valve 37 is added in the bypass outlet 39. ing. The bypass outlet 39 is connected to the mixing section 48 and directly connects to the turbine 6 inlet of the turbocharger 5 via a bypass conduit 38 to bypass the SCR 19. A bypass outlet 39, a bypass valve 37 under the control of the electronic control unit 50, and a bypass conduit 38 allow the exhaust gas to bypass the SCR unit. The bypass valve 37 is closed when the SCR 19 is in use. SCRs are usually used only to the extent required by law. When the SCR 19 is not in use, it is beneficial to direct the exhaust gas directly to the turbocharger 5 in terms of reducing pressure loss and improving fuel consumption. When using the SCR 19, it is necessary to slowly warm the SCR 19 by slowly closing the bypass valve 37 (over about 1 hour). The bypass pipe acts as a tangentially directed outlet and is arranged and configured to allow vortex exhaust gas to exit the exhaust gas receiver 3 with minimal change in flow direction. When the SCR is not used, the combination of the exhaust gas entering the exhaust gas receiver 3 from the tangential direction and the exhaust gas leaving the exhaust gas receiver 3 from the tangential direction is the combination of the exhaust gas and the exhaust gas. Reduce energy loss when passing through the receiver. For this reason, the amount of energy available in the turbocharger turbine may be greater than in conventional exhaust gas receivers.

  10 and 11 show another exemplary embodiment of an exhaust gas receiver for a large two-cycle diesel engine. This embodiment may include some form of mixing system, but differs from the embodiment described above in that no means for mixing the reducing agent is provided in the exhaust gas receiver 3. In this embodiment, the exhaust gas receiver 3 is placed along the cylinder 1 of a large turbocharged two-cycle diesel engine as in the above embodiment, and is connected to the cylinder 1 via individual exhaust ducts 35. The The individual exhaust ducts 35 are arranged so that the exhaust gas from the cylinder 1 enters the cylindrical exhaust gas receiver 3 in a tangential direction in order to generate a vortex in the exhaust gas in the exhaust gas receiver 3. . In particular, the exhaust gas receiver 3 minimizes energy loss and is free from any obstruction to the flow in the exhaust gas receiver 3, in particular tangential flow or tangential and axial flow, ie spiral. Optimized to be free of any obstructions that block or obstruct the flow. Thus, as shown in FIG. 11, there may be a cylindrical tube 40 disposed axially inside the exhaust gas receiver, but any object that impedes tangential and / or axial flow is avoided. Should be. Furthermore, the outlet 36 is oriented tangentially so that the vortex exhaust gas can exit the exhaust gas receiver with minimal energy loss in a spiral flow pattern. The outlet 36 is connected to a conduit that leads to the turbine 6 of the turbocharger 5. Since the entire flow pattern from the exhaust gas duct to the outlet 36 is basically a spiral, the outlet 36 directed in the tangential direction is such that the vortex exhaust gas generated by the tangential exhaust gas duct minimizes the change in the flow direction. And / or arranged and configured to allow exit from the exhaust gas receiver 3 to be as gentle as possible. Therefore, the energy of the exhaust gas exiting from the exhaust gas receiver is high, and more energy can be delivered to the turbine of the turbocharger of the engine in which the exhaust gas receiver is used.

  In the claims, the expressions “comprising” and “having” do not exclude further including (having) other elements and processes. In the claims, a single element does not exclude a configuration having a plurality of elements. The single processing means or unit described in the claims may be a plurality of means having the same function.

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

  Although the present invention has been described in detail for purposes of illustration, these details are presented purely for this purpose and various modifications may be made by those skilled in the art without departing from the scope of the invention. Please understand that. For example, the present invention can be implemented in a large two-stroke engine using exhaust gas recirculation.

Claims (13)

A turbocharged large two-stroke uniflow diesel engine with a crosshead (53) comprising:
A plurality of cylinders (1) arranged in series;
A turbocharger (5) having a turbine (6) driven by exhaust gas and a compressor (9) driven by the turbine (6) and supplying air to the cylinder (1);
Each of the plurality of cylinders (1) is connected to each other via its own exhaust duct (35), and is a long cylindrical exhaust gas receiver (that extends along the row of the plurality of cylinders (1)). 3) in which the exhaust duct (35) causes the exhaust gas from the cylinder (1) to flow in the cylindrical exhaust in order to generate a vortex in the exhaust gas in the cylindrical exhaust gas receiver (3). A cylindrical exhaust gas receiver (3), directed tangentially into the gas receiver (3);
A unit (42) comprising a plurality of vanes (43) around a central axial duct (47);
Having
The unit (42) is installed in the exhaust gas receiver (3) downstream of the exhaust gas duct (35);
The unit (42) includes a mixing section (48) in which the exhaust gas duct (35) is present on the longitudinal side of the unit (42) and an outlet section (49 on the other side in the longitudinal direction of the unit (42). ) In the longitudinal direction;
The outlet section (49) includes an outlet (33) connected to an inlet of a selective catalytic reduction reactor (19) existing outside the exhaust gas receiver;
The outlet of the selective catalytic reduction reactor is connected to the inlet of the turbine (6) of the turbocharger (5);
The unit (42) is arranged such that a swirl of exhaust gas flows along the vane (43) between the mixing section (48) and the outlet section (49);
The unit (42) is further configured to cause the exhaust gas passing along the vane (43) from the mixing region to the outlet region to lose its vortex and acquire pressure, The pressure applied causes a portion of the exhaust gas that has passed along the vane (43) to flow back from the outlet region to the mixing region (48) via the axial duct (47), thereby Another portion of the exhaust gas that has passed along the vane (43) flows from the outlet region to the external selective catalytic reduction reactor (19) via the outlet (33);
The engine further comprises a reducing agent supply source (26) added to the exhaust gas at a reducing agent introduction point, wherein the exhaust gas flowing back from the outlet section (49) to the mixing section (48) is provided. The reducing agent introduction point is provided in the axial duct (47) so that a part and the reducing agent can be mixed;
engine.   The exhaust gas backflowed through the axial duct (47) and added with a reducing agent can be mixed with the vortex mixed gas in the mixing section (48). The listed engine.   The engine according to claim 1, wherein the axial duct (47) extends axially in the mixing section.   The axial duct is part of a concentric tube (40) extending into the mixing section (48), and the exhaust gas forms a vortex around the concentric tube (40). Engine described in.   Engine according to claim 3, wherein the flow of exhaust gas in the concentric tube (40) is not a vortex.   The engine according to claim 1, wherein the vane (43) extends radially from the duct (47) to an inner wall of the exhaust gas receiver (3).   The engine of claim 6, wherein the vane has a bent upstream section and an uncurved downstream section.   The engine of claim 1, wherein the blade (43) is configured to cause the vortex exhaust gas flowing past the blade (43) to lose its vortex and gain pressure.   Engine according to claim 1, comprising two or more exhaust gas receivers (3) in series.   The exhaust gas receiver (3) comprises a bypass outlet (36) connecting the mixing section (48) to a bypass conduit (38) connecting to a turbine (6) of the turbocharger (5). The engine according to 1. An exhaust gas receiver (3) for a turbocharged large two-stroke uniflow diesel engine with a crosshead (53) comprising:
A long cylindrical exhaust gas receiving housing (3) for receiving exhaust gas tangentially from the cylinder (1) of the engine, thereby vortexing the exhaust gas inside the exhaust gas receiver (3) An exhaust gas receiving housing (3), in which a plurality of openings for producing the exhaust gas are individually arranged along a part of the length of the exhaust gas receiver (3);
A unit (42) comprising a plurality of vanes (43) around a central axial duct (47);
Having
The unit (42) is installed in the exhaust gas receiver (3) downstream of the exhaust opening;
The unit (42) includes a mixing section (48) in which the exhaust gas duct (35) is present on the longitudinal side of the unit (42) and an outlet section (49 on the other side in the longitudinal direction of the unit (42). ) In the longitudinal direction;
The outlet section (49) includes an outlet (33) to the outside of the exhaust gas receiver (3);
The unit (42) is arranged such that a swirl of exhaust gas flows along the vane (43) between the mixing section (48) and the outlet section (49);
The unit (42) is further configured to cause the exhaust gas passing along the vane (43) from the mixing region to the outlet region to lose its vortex and acquire pressure, The pressure applied causes a portion of the exhaust gas that has passed along the vane (43) to flow back from the outlet region to the mixing region (48) via the axial duct (47), thereby Another portion of the exhaust gas that has passed along the vane (43) exits the outlet region via the outlet (33);
The engine is further provided in the axial duct (47) so that the exhaust gas flowing back from the outlet section (49) to the mixing section (48) and the reducing agent can be mixed. Said reducing agent introduction point being provided;
engine. A turbocharged large two-stroke uniflow diesel engine with a crosshead (53) comprising:
A plurality of cylinders (1) arranged in series;
A turbocharger (5) having a turbine (6) driven by exhaust gas and a compressor (9) driven by the turbine (6) and supplying air to the cylinder (1);
Each of the plurality of cylinders (1) is connected to each of the plurality of cylinders (1) through its own exhaust duct (35) and extends along a row of the plurality of cylinders (1). 3) The inside of the cylindrical exhaust gas receiver (3) is configured to be free from any obstruction to the flow inside the exhaust gas receiver (3), and the exhaust duct (35) Each directs the exhaust gas from the cylinder (1) into the cylindrical exhaust gas receiver (3) in a tangential direction in order to create a vortex in the exhaust gas in the exhaust gas receiver (3). A cylindrical exhaust receiver (3) configured to be attached;
A tangentially directed outlet (36) connected to a conduit leading to the turbine (6) of the turbocharger (5);
With an engine.   13. The tangentially directed outlet is arranged and configured to allow the vortex exhaust gas to exit the exhaust gas receiver (3) with minimal change in flow direction. Engine described in.

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