CH716568A2 - Method for operating a slow-running large engine and slow-running large engine. - Google Patents

Abstract

The invention relates to a method for operating a slow-running large engine (1), in particular for operating a longitudinally flushed, slow-running cross-head large engine, comprising a cylinder liner (2) with a combustion chamber (3) which is surrounded by a cylinder cover (4), the cylinder liner ( 2) and a piston (5) that moves back and forth in the cylinder liner (2) between a bottom dead center (BDC) and a top dead center (TDC), as well as an exhaust valve (6) assigned to the combustion chamber (3) for discharging Combustion gases from the combustion chamber (3). Air (7) compressed by a charging unit is introduced into the cylinder liner (2) via a scavenging air opening (8) as charge air, and a gas-air mixture compressed in the combustion chamber (3) is introduced into the gas-air mixture by means of an ignition nozzle (9) injected ignition fluid ignited. According to the invention, gas (101) is introduced under low pressure into the combustion chamber (3) via a gas inlet opening (10) in a lower area of the cylinder liner (2), and in addition, via a water inlet opening (11) in a lower area of the cylinder liner (2) Water (111) introduced into the combustion chamber (3) under low pressure. The invention also relates to a large engine that can be operated using a method according to the invention.

Description

description

The invention relates to a method for operating a slow running large engine, in particular for operating a longitudinally flushed slow running cross head large engine, and a large engine, in particular longitudinally flushed slow running cross head large engine according to the preamble of the independent claims.

Slow-running large engines, in particular longitudinally flushed large engines of the crosshead type according to the present invention, are preferably used in shipbuilding or in stationary systems, for example for generating electrical energy, for many decades in a large number of different variants in detail.

Such large engines in many cases include three large housing segments that form the frame of the engine. A so-called stand is arranged on a base plate, which has transverse support elements in addition to a bearing saddle with a crankshaft main bearing for receiving the crankshaft, separated by a base plate. According to the number of cylinder liners of the large diesel engine, the known uprights comprise several oppositely arranged support bodies, each of which has a perpendicular sliding surface for guiding two adjacent crossheads which are connected to the crankshaft via push rods. A cylinder section, often also called a cylinder jacket, which is suitable for receiving one or more cylinder liners, is then arranged above the stand. The base plate, the stand and the cylinder section are connected to one another by tie rods, which generally extend within the support body in the region of the stand, by screwing the tie rods into or on the base plate with considerable pretension.

To increase the performance of reciprocating internal combustion engines, not only but in particular also for those of the type described above, fresh air is introduced under increased pressure into the combustion chamber of a cylinder liner after a combustion cycle by means of a charging group, which usually comprises at least one exhaust gas turbocharger. As a result, part of the thermal energy of the exhaust gases can be used in a manner well known to the person skilled in the art. For this purpose, the hot exhaust gases are fed from the combustion chamber of the cylinder liner to the charging group by opening an exhaust valve provided in a cylinder cover of the cylinder liner. The supercharging group essentially consists of a turbine that is driven by the heated exhaust gases entering the supercharging group under pressure. The turbine in turn drives a compressor, which draws in fresh air and compresses it. Finally, the compressed fresh air, also referred to as charge air or scavenging air, is fed into the individual combustion chambers of the cylinder liner of the large engine via so-called scavenging slots in the lower area of the cylinder liner. By using such a charging group, the supply of fresh air can be increased and the efficiency of the combustion process in the combustion chamber of the cylinder can be increased.

A large number of different methods are now known in the prior art with which large engines of the type described can be operated. Depending on the type of operating process, the corresponding motors can be equipped with special features.

[0006] Slow-running two-stroke large diesel engines that are operated with heavy fuel oil or diesel oil mostly as compression-ignition, that is, according to a diesel process, were widespread for many decades. Such engines and operating methods have the disadvantage that they emit considerable quantities of pollutants into the environment via the exhaust gases. In particular, nitrogen oxides, which are primarily formed at higher combustion temperatures, are increasingly becoming a problem due to ever stricter exhaust gas limit values.

In order to reduce nitrogen oxides in the exhaust gas in particular, it has therefore long been known to add water to the fuel-air mixture in the combustion chamber of the cylinder. Such a self-igniting large engine and a corresponding operating method is shown, for example, in EP 0 781 907 A1, in which the large engine is operated with an emulsion consisting of water and fuel.

Instead of supplying an emulsion of fuel and water to the combustion chamber, EP 0 967 371 A1 also discloses the injection of water into the combustion chamber via special water nozzles. In EP 0 967 371 A1, the water injection nozzles are arranged in the cylinder cover. This is also the case with the four-stroke diesel engine from EP 1 099 846 A1, in which the fuel injection nozzles are designed as tandem nozzles and thus simultaneously serve to inject fuel and water into the combustion chamber.

Another advantageous measure to avoid harmful exhaust gases is the use of alternative fuels. Here, gas-powered engines or so-called dual-fuel engines, which can be operated both with gas and with classic fuels such as heavy oil or diesel oil, are becoming more and more popular.

Engines are known in which the fuel gas is introduced into the combustion chamber under very high pressure, for example of more than 400 bar, more than 500 bar or at an even higher pressure. Such motors or methods for operating such motors are disclosed, for example, in DK 2016 70287 A1, which relates to a longitudinally flushed, slow-running, large cross-head motor that is operated with gas under high pressure. Since undesired nitrogen oxides can also arise in gas operation of the engine in accordance with DK 2016 70287 A1 or the engines often tend to "knock", water is also introduced into the cylinder here. This lowers the temperature of the hot, compressed gas-air mixture somewhat, so that A premature ignition of the mixture is prevented. At the same time, less harmful nitrogen oxides are produced. A decisive disadvantage of an engine according to DK 2016 70287 A1, however, is

that the gas has to be brought to the very high pressure of 400 bar and also significantly more, so that suitable pressure increasing means must also be provided.

It is known to operate the engines either according to a diesel process, that is to say as a compression ignition, or according to an Otto process in which the mixture can be spark-ignited in a targeted manner with a suitable ignition source at a suitable crank angle. In large engines in particular, shortly before the piston has reached top dead center, a short jet of mostly liquid fuel such as diesel oil is often injected under very high pressure into the highly compressed gas-air mixture in the combustion chamber as the ignition source, which then triggers the ignition of the mixture.

Such a motor operated by means of spark ignition is described, for example, in DE 10 2011 003 909 B4 or US 5,035,2016. The engines described there are operated with gas that is introduced into the combustion chamber at relatively low pressure, which is usually equal to or only slightly above the charge air pressure of approx. 3-4 bar. Typical pressure ranges for introducing the gas into the combustion chamber in a low-pressure process, for example, are between 3 bar and 50 bar, preferably between 5 bar and 30 bar, or between 10 bar and 20 bar.

The engines according to DE 10 2011 003 909 B4 or US Pat. No. 5,035,2016 have the advantage that they are operated externally ignited according to an Otto process, so that, unlike the compression ignition engine, the ignition timing can be set much more precisely. However, these engines still tend to knock, since the compression process of the fuel-air mixture can lead to such high temperatures, especially locally, that an ignition is initiated prematurely locally, which of course leads to a loss of power, too uneven running of the engine and others, according to the expert known disadvantages during operation. In addition, the high combustion temperatures in the combustion chamber can lead to the formation of harmful nitrogen oxides.

The object of the invention is therefore to provide a low pressure gas engine of the large type and a corresponding method for operating such an engine available, so that harmful knocking is avoided, an optimal combustion process of high energy efficiency is guaranteed, thus the fuel consumption and the Amount of exhaust gases can be optimized and at the same time the formation of nitrogen oxides is reduced below the limit values required by law.

The objects of the invention that achieve these objects are characterized by the features of the independent claims.

The dependent claims relate to particularly advantageous embodiments of the invention.

The invention thus relates to a method for operating a slow-running large engine, in particular for operating a longitudinally flushed slow-running cross-head large engine, comprising a cylinder liner with a combustion chamber, which is through a cylinder cover, the cylinder liner and a cylinder liner between a bottom dead center UT and a top dead center OT reciprocating piston is limited. Furthermore, an outlet valve assigned to the combustion chamber is provided for discharging combustion gases from the combustion chamber, with air compressed by means of a charging unit being introduced into the cylinder liner via a scavenging air opening as charge air. A gas-air mixture compressed in the combustion chamber is ignited by means of an ignition fluid injected into the gas-air mixture via an ignition nozzle. According to the invention, gas is introduced into the combustion chamber under low pressure via a gas inlet opening in a lower area of the cylinder liner, with water being additionally introduced into the combustion chamber under low pressure via a water inlet opening in a lower area of the cylinder liner.

It is therefore essential for the invention that gas is introduced under low pressure into the combustion chamber via a gas inlet opening in a lower region of the cylinder liner, and via a water inlet opening, also in a lower region of the cylinder liner, additional water under low or medium low pressure is introduced into the combustion chamber.

Thus, in a two-stroke low-pressure gas process according to the invention, a gas-air mixture is compressed during a purging stroke in the compression stroke. In this case, gas is introduced into the combustion chamber of the cylinder liner under low pressure, preferably just above the scavenging slots. Water is introduced into the combustion chamber under low or medium low pressure, preferably simultaneously with the gas, with the water inlet openings, preferably designed as nozzles, particularly advantageously at the same height as the gas inlet openings, also preferably designed as nozzles, or just above the gas inlet openings are provided on the cylinder liner. The water inlet openings and / or the gas inlet openings are particularly preferably aligned in the direction of the cylinder cover, so that the properties of the rotating upwardly directed gas vortex or corresponding turbulence that already prevails in the cylinder can be used to achieve optimal mixing with the water additionally introduced into the combustion chamber . By mixing the gas-air mixture with water, part of the heat present in the compressed gas-air mixture is absorbed by the evaporation of the water, and the gas-air mixture burns correspondingly more slowly. As a result, the uncontrolled combustion before the actual ignition of the mixture by the ignition fluid is practically completely prevented and the combustion pressure is reduced. This ultimately prevents harmful knocking, the formation of nitrogen oxides is significantly minimized, and the efficiency of the large engine is further improved and fuel consumption is reduced as a result.

According to the invention, the gas is introduced into the combustion chamber of the cylinder liner through the gas inlet opening at a pressure between 2bar and 200bar, preferably between 3bar and 10Obar, particularly preferably between 5bar and 50bar, in particular under a pressure of approx. 10bar to 20bar. The pressure is therefore preferably in the range or slightly above the pressure with which the charging group feeds the freshness into the cylinder liner via the flushing slots.

Correspondingly, the water is also introduced into the combustion chamber of the cylinder liner through the water inlet opening at a pressure between 2bar and 200bar, preferably between 3bar and WObar, particularly preferably between 5bar and 50bar, in particular under a pressure of approx. 10bar to 20bar. The gas inlet opening and / or the water inlet opening are advantageously provided in the area of the purge air openings.

In a large engine according to the invention, the bottom dead center UT of the piston is by definition at a crank angle of 180 ° and the top dead center OT of the piston at a crank angle of 360 ° and the gas inlet opening and / or the water inlet opening are arranged in the cylinder liner in such a way that the Gas and / or the water are introduced in a crank angle range between 190 ° and 330 °, especially in a crank angle range between 200 ° and 300 °, preferably in a crank angle range between 210 ° and 260 °, particularly preferably at a crank angle of approx. 230 ° becomes.

The invention further relates to a slow-running large engine for performing a method according to the present invention and is in particular a longitudinally flushed slow-running cross-head large engine which can be operated according to an Otto method, i.e. externally ignited. The large engine according to the invention comprises a cylinder liner with a combustion chamber which is delimited by a cylinder cover, the cylinder liner and a piston that can be moved back and forth in the cylinder liner between a bottom dead center UT and a top dead center OT. Furthermore, an outlet valve assigned to the combustion chamber is provided for discharging combustion gases from the combustion chamber and, in the operating state, compressed air can be introduced into the cylinder liner as charge air by means of a charging unit via a scavenging air opening. For external ignition of a gas-air mixture compressed in the combustion chamber, an ignition nozzle for introducing an ignition fluid is provided, particularly preferably in the cylinder cover. Optionally, an ignition pre-chamber can also be provided in the cylinder liner for igniting the gas-air mixture, preferably in the upper region of the cylinder liner, into which the ignition fluid for igniting the gas-air mixture is introduced, specifically injected. According to the invention, a gas inlet opening for introducing gas under low pressure into the combustion chamber is provided in a lower area of the cylinder liner, and a water inlet opening for introducing water into the combustion chamber is also provided in the lower area of the cylinder liner.

The gas inlet opening and / or the water inlet opening are preferably provided in the area of the purge air openings. Expressed somewhat more precisely, the gas inlet opening and / or the water inlet opening is in a crank angle range between 190 ° and 330 °, in particular in a crank angle range between 200 ° and 300 °, preferably in a crank angle range between 210 ° and 260 °, particularly preferably at a crank angle of approx. 230 ° is provided, whereby by definition the bottom dead center UT of the piston is at a crank angle of 180 ° and the top dead center OT of the piston is at a crank angle of 360 °.

Accordingly, the water inlet opening is provided in particular between the top dead center and the gas inlet opening, the water inlet opening in particular in a crank angle range of 5 ° to 30 °, preferably in a crank angle range between 10 ° and 20 ° from the gas inlet opening spaced between the Gas inlet opening and top dead center (TDC) is provided, the water inlet opening and / or the gas inlet opening preferably being designed in the form of a nozzle

A slow-running large engine according to the invention can be a pure gas engine or a dual-fuel engine or another variant of a corresponding large engine.

The invention is explained in more detail below with reference to the drawing. It shows in a schematic representation:

1 schematically shows a large, slow-running engine of the present invention in the operating state.

1, a slow-running large engine 1 according to the present invention is shown schematically in the operating state, which in the present special embodiment is designed as a longitudinally flushed, slow-running cross-head large engine. The engine according to FIG. 1 comprises a cylinder liner 2 with a combustion chamber 3, which is delimited by a cylinder cover 4, the cylinder liner 2 and a piston 5 which can be moved back and forth in the cylinder liner 2 between a bottom dead center UT and an upper dead center OT. In a manner known per se, an outlet valve 6 for discharging combustion gases from the combustion chamber 3 is assigned to the combustion chamber 3. In the operating state, compressed air 7 is introduced into the cylinder liner 2 via a scavenging air opening 8 as charge air by means of a charging unit (not explicitly shown in FIG. 1). Furthermore, an ignition nozzle 9 for introducing an ignition fluid is provided for the external ignition of a gas / air mixture compressed in the combustion chamber 3, so that the large engine according to the invention can be operated according to an Otto process. According to the invention, a gas inlet opening 10 for introducing gas 101 under low pressure into combustion chamber 3 is provided in a lower area of cylinder liner 2, and a water inlet opening 11 for introducing water 111 into combustion chamber 3 is also provided in the lower area of cylinder liner 2.

Claims (10)

By definition, the bottom dead center UT of the piston 5 is at a crank angle of 180 ° and the top dead center OT of the piston 5 is at a crank angle of 360 °. In the present special embodiment, the gas inlet opening 10 and the water inlet opening 11 are provided in a crank angle range between 210 ° and 260 °, here approximately preferably at a crank angle of approximately 230 °. The water inlet opening 11 is provided between the top dead center and the gas inlet opening 10, the water inlet opening 11 in the present special embodiment of FIG. 1 being spaced between the gas inlet opening 10 in a crank angle range between approx. 10 ° and 20 ° from the gas inlet opening 10 and the top dead center OT is provided. The water inlet opening 11 and the gas inlet opening 10 are designed in the form of a nozzle. The water inlet openings 11 and the gas inlet openings 10 are aligned in the present embodiment in the direction of the cylinder cover 4, so that the properties of the already prevailing in the cylinder liner 2 rotating upward gas vortex 12 or corresponding turbulence 12 can be used to optimally mix with the water 111 additionally introduced into the combustion chamber 3. By mixing the gas-air mixture with water 111, part of the heat present in the compressed gas-air mixture is absorbed by the evaporation of the water 111, and the gas-air mixture burns correspondingly more slowly, which also eliminates the uncontrolled combustion before the actual ignition of the mixture practically completely prevented by the ignition fluid and the combustion pressure is reduced. This ultimately prevents harmful knocking, the formation of nitrogen oxides is significantly minimized, and the efficiency of the large engine is further improved and fuel consumption is reduced as a result. In the present special embodiment, the large engine 1 is a pure gas engine, which can be seen in particular from the fact that no additional injection nozzle for a liquid fuel such as diesel or heavy oil is provided in the cylinder cover. In another exemplary embodiment it is of course possible for the large engine according to the invention to be a dual-fuel engine that can be operated both with gas and with another fuel, such as diesel oil or heavy oil. The person skilled in the art understands that the invention is not limited to the exemplary embodiments discussed explicitly, but that corresponding developments are also covered by the invention. In particular, of course, the invention relates to all suitable combinations of the specific embodiments discussed. Claims 1. A method for operating a slow-running large engine (1), in particular for operating a longitudinally flushed, slow-running cross-head large engine, comprising a cylinder liner (2) with a combustion chamber (3), which is formed by a cylinder cover (4), the cylinder liner (2) and a piston (5) moving back and forth in the cylinder liner (2) between bottom dead center (UT) and top dead center (OT), as well as an exhaust valve (6) assigned to the combustion chamber (3) for discharging combustion gases from the Combustion chamber (3), with air (7) compressed by means of a charging unit being introduced into the cylinder liner (2) via a scavenging air opening (8) as charge air, and a gas-air mixture compressed in the combustion chamber (3) by means of an ignition nozzle (9) Ignition fluid injected into the gas-air mixture is ignited, characterized in that gas (101) under low pressure enters the combustion chamber (3) via a gas inlet opening (10) in a lower region of the cylinder liner (2) is introduced, and that in addition, water (111) is introduced into the combustion chamber (3) under low pressure via a water inlet opening (11) in a lower region of the cylinder liner (2). 2. The method according to claim 1, wherein the gas (101) through the gas inlet opening (10) with a pressure between 2bar and 200bar, preferably between 3bar and 10Obar, particularly preferably between 5bar and 50bar, in particular under a pressure of about 10bar 20bar is introduced into the combustion chamber (3) of the cylinder liner (2). 3. The method according to any one of claims 1 or 2, wherein the water (111) through the water inlet opening (11) with a pressure between 2bar and 200bar, preferably between 3bar and 100bar, particularly preferably between 5bar and 50bar, in particular under a pressure of approx. 10 bar to 20 bar is introduced into the combustion chamber (3) of the cylinder liner (2). 4. The method according to any one of the preceding claims, wherein the gas inlet opening (10) and / or the water inlet opening (11) is provided in the region of the scavenging air opening (8). 5. The method according to any one of the preceding claims, wherein the bottom dead center (UT) of the piston (5) is at a crank angle of 180 ° and the top dead center (OT) of the piston (5) is at a crank angle of 360 ° and the gas inlet opening (10) and / or the water inlet opening (11) are arranged in the cylinder liner (2) in such a way that the gas (101) and / or the water (111) in a crank angle range between 190 ° and 330 °, in particular in a crank angle range between 200 ° and 300 °, preferably in a crank angle range between 210 ° and 260 °, particularly preferably at a crank angle of approximately 230 °. 6. Slow running large engine (1) for performing a method according to one of the preceding claims, in particular longitudinally flushed slow running cross head large engine, comprising a cylinder liner (2) with egg a combustion chamber (3) which is delimited by a cylinder cover (4), the cylinder liner (2) and a piston (5) that can be moved back and forth in the cylinder liner (2) between a bottom dead center (BDC) and an upper dead center (TDC) , as well as an outlet valve (6) assigned to the combustion chamber (3) for discharging combustion gases from the combustion chamber (3), whereby in the operating state compressed air (7) can be introduced into the cylinder liner (2) via a scavenging air opening (8) as charge air by means of a charging unit and an ignition nozzle (9) for introducing an ignition fluid is provided for external ignition of a gas-air mixture compressed in the combustion chamber (3), characterized in that a gas inlet opening (10) for introducing gas (101 ) is provided under low pressure in the combustion chamber (3), and a water inlet opening (11) for introducing water (111) into the combustion chamber (3) is also provided in the lower region of the cylinder liner (2). 7. Slow running large engine (1) according to claim 6, wherein the gas inlet opening (10) and / or the water inlet opening (11) is provided in the region of the scavenging air openings (8). 8. Slow running large engine (1) according to one of claims 6 or 7, wherein the bottom dead center (UT) of the piston (5) is at a crank angle of 180 ° and the top dead center (OT) of the piston (5) at a crank angle of 360 °, and the gas inlet opening (10) and / or the water inlet opening (11) in a crank angle range between 190 ° and 330 °, especially in a crank angle range between 200 ° and 300 °, preferably in a crank angle range between 210 ° and 260 ° °, is particularly preferably provided at a crank angle of approximately 230 °. 9. Slow running large engine (1) according to one of claims 6 to 8, wherein the water inlet opening (11) is provided between the top dead center and the gas inlet opening (10), the water inlet opening (11) in particular in a crank angle range of 5 ° to 30 °, preferably in a crank angle range between 10 ° and 20 ° from the gas inlet opening (10), spaced between the gas inlet opening (10) and top dead center (OT), the water inlet opening (11) and / or the gas inlet opening (10) is preferably designed in the form of a nozzle 10. Slow-running large engine (1) according to one of claims 6 to 9, wherein the large engine (1) is a pure gas engine or a dual-fuel engine, and / or wherein an ignition pre-chamber in the cylinder liner (2 ) is provided.