KR100845686B1 - Large two stroke dual fuel diesel engine - Google Patents

Abstract

A high-pressure fuel gas valve for a large two-stroke diesel engine is provided to allow the engine to maintain high pressure in a fuel gas injection system, when the large two-stroke diesel engine having the high-pressure fuel gas injection system and a high-pressure fuel oil injection system is not operated with fuel gas. A high-pressure fuel gas valve for a large two-stroke diesel engine includes a high-pressure sealing oil system(100) and an oil control system. The high-pressure sealing oil system functions to prevent the leakage of fuel gas from the high-pressure fuel gas valve. The oil control system opens a gas spindle so that high-pressure fuel gas flows to a fuel gas nozzle. Fuel gas pressure and an elastic member force the gas spindle to be closed.

Description

LARGE TWO STROKE DUAL FUEL DIESEL ENGINE}

The present invention relates to high pressure fuel gas valves for gaseous fuel and dual fuel (oil as well as gas) two-stroke diesel engines that directly inject fuel at high pressure into the combustion chamber (s).

Large two-stroke diesel engines can operate at the same high efficiency using gas as they would with conventional fuel oil.

Gas fuel engines can easily access to the natural gas probably local or sulfur dioxide that can be achieved with a very difficult low-cost disposal of natural gas (SO ₂₎ reduction and nitrogen oxide emissions (NO _X) for the reduction of emissions The high potential of the off-gas after-treatment makes it particularly suitable for generating electricity in areas that favor the use of gaseous fuels due to environmental considerations. For such plants, gas is generally available whenever the engine is started. Dual fuel engines are particularly used in the field of propulsion of natural gas carriers. These engines are capable of full load operation on oil fuel. This may be advantageous, for example, if the natural boil-off of the gas in the tanks is not sufficient to fuel the engine.

Gaseous fuels, for example natural gas, can be injected into the combustion chamber of turbocharged two-stroke diesel engines at a pressure that must be somewhat higher than the maximum combustion pressure of the engine. After ignition, the gas serves as a very suitable fuel for combustion. Ignition is obtained by the injection of a predetermined amount of liquid fuel oil, which has a much better self-ignite capability than natural gas at the end of the compression stroke under pressure and temperature conditions in the diesel combustion chamber. Has

Both gaseous fuel and dual fuel large two-stroke diesel engines (the latter do not yet exist) require a fuel oil injection system for ignition as well as a system for high pressure gas injection. One of the differences between gaseous fuel and dual fuel large two-stroke diesel engines is that the gaseous fuel engine has a fuel oil system that only has the capacity for the injection of pilot oil for ignition, The dual fuel engine is provided with a fuel oil system capable of injecting fuel oil for full load operation without any gas injection.

A common feature of gaseous fuel and dual fuel engines is that they can be operated without gas injection for some period of time. During this time period, the supply of pressurized gas is stopped. Conventional practice has been to purify the gas system with inert gas (preferably N ₂ ) at low pressure, when no supply of high pressure gas is required. This is done to reduce the risk of accumulation of an explosive mixture of air and gas.

Two disadvantages relate to the purification sequence.

1) If gas fuel injection valves leak to the combustion chamber, combustion gases will enter and contaminate the gas system.

2) Leak detection is virtually impossible if the system is filled with low pressure inert gas.

Against this background, the object of the present invention is to overcome the problems described above For providing a high pressure fuel gas valve of a large two-stroke diesel engine with at least a reduction, for large two-stroke diesel engines with reduced risk of intake of exhaust gases during non-fuel gas operation of large two-stroke diesel engines with fuel gas valves disposed therein It is to provide a high pressure fuel gas valve.

Another object of the present invention is to provide a high-pressure fuel gas injection system and a large turbocharged two-stroke diesel engine with a high pressure fuel oil injection system configured to maintain high pressure in the fuel gas injection system when the diesel engine is not operated with fuel gas. It is.

Another object of the present invention is to provide a method for operating a large two-stroke diesel engine having a high pressure fuel gas injection system and a high pressure fuel oil injection system.

The present invention for achieving the above object is a high-pressure fuel gas valve for a large two-stroke diesel engine,

A high pressure sealing oil system for preventing leakage of fuel gas from the high pressure fuel gas valve, and

A control oil system for opening the gas spindle to allow high pressure fuel gas to flow into the fuel gas nozzle,

The gas spindle is characterized by being forced to be closed by the fuel gas pressure and the elastic member.

In addition, the present invention provides a large two-stroke diesel in which the gas spindle is forced to be opened by the force caused by the control oil pressure against the force caused by the fuel gas pressure and the force caused by the elastic member. It features a high pressure fuel gas valve of the engine.

The gas pressure will be maintained during non-fuel gas operation, and since the pressure of the gas is generally higher than the combustion pressure, the risk of combustion gas leakage into the fuel gas valve is minimized.

The gas spindle may be pressurized to be in an open position by a force caused by a control oil pressure against a force caused by the fuel gas pressure and a force caused by the elastic member.

The large two-stroke diesel engine according to the present invention pressurizes the gas system up to the normal operating pressure (higher than the combustion chamber maximum pressure), so that when the engine is operated only with fuel oil, the inlet of combustion gases into the gas system is eliminated.

Moreover, permanent pressurization is a gas fuel valve in that gas pressure acting on the region of the valve spindle can be arranged to assist a mechanical spring or other device in keeping the valve tightly closed at all times when no injections occur. It may be used in the design of. In this way, the dimensions of the valve may be reduced.

The engine may be configured to maintain high pressure in the fuel gas injection system whenever the engine is operating.

When the engine is not operated with fuel gas, the fuel gas injection system may be filled with a mixture of inert gases or a mixture of non-combustible gases or with inert gases and non-combustible gases.

By pressurizing the gas system with a substantially inflammable gas or gas mixture instead of the combustion gas, the gas system will be completely safe from flames or explosions.

The substantially non-flammable gas may be nitrogen gas, and the substantially non-flammable gas mixture may contain nitrogen gas. However, since about 80% of the atmosphere is nitrogen, leaks of nitrogen into the atmosphere are very difficult to detect.

The substantially inert or non-combustible gas or mixture of inert gases and non-combustible gases may contain a gas suitable for leak detection. Such gas or tracer gas suitable for leak detection can be mixed with nitrogen gas. For this purpose, it is important that the tracer gas has some properties that are significantly different from the corresponding properties of the atmosphere.

Helium may be used as the tracer gas. Helium has a different thermal conductivity than nitrogen, and thus can be easily detected. However, a small amount of flammable fuel gas may be used instead of helium. Methane (CH ₄ ) is the main component of natural gas. At concentrations below 5% in the atmosphere, methane is not flammable. If 5 weight percent methane is mixed with 95 weight percent nitrogen (N2), leakage of the mixture into the atmosphere will not be a flammable mixture and therefore will be safe. Moreover, such leaks can be easily detected with common hydrocarbon (HC) sensors that detect methane content as low as 50 ppm.

The engine may include one or more fuel gas valves associated with one or more cylinders thereof, wherein the engine operates the fuel gas valves regularly during fuel oil operation and thus fuel gas that is substantially inert. It may also be configured to inject into a cylinder or cylinders for actuating the valves. Pressurization with (almost) inert gas allows monitoring of operation of gas fuel valves and gas fuel valve movement and function during fuel oil operation. Without the operation of the gas fuel valves, the fuel gas valves will be at risk of sticking or other malfunction after the fuel oil operation period. This will only be recognized at the time of conversion to gaseous fuel. Injection of the inert gas may also serve to cool the nozzles of the gas fuel valve heated by oil combustion.

When the engine is not operated with fuel gas, the high pressure in the fuel gas system can be used to help keep the fuel gas valves tightly closed. In this way, the dimensions of the valve can be reduced.

The method for operating a large two-stroke diesel engine according to the invention comprises pressurizing a fuel gas injection system at high pressure when the engine is not operated with fuel gas.

The method includes filling the high pressure fuel gas injection system with a substantially inert gas or a substantially combustible gas when the engine is not operated with fuel gas.

The gas, which is substantially flammable, may include a small fraction of fuel gas or other tracer to facilitate leak detection.

The high pressure fuel gas injection system includes fuel gas valves, and the method includes operating the fuel gas valves by regularly or intermittently opening the fuel valves when the engine is not operated with fuel gas. .

Further objects, features, advantages and inherent properties of the high pressure fuel gas valve of the large two-stroke engine according to the present invention will become apparent from the detailed description.

The present invention has many advantages. Various embodiments or implementations bring one or more of the following advantages. Note that this is not an exhaustive list and that there may be other advantages not described here. One advantage of the present invention is that it is possible to reduce the risk of inlet exhaust gas into the fuel gas injection system while operating with non fuel gas. Another advantage of the present invention is that it is possible to operate the exhaust gas valves during non fuel gas operation. Another advantage of the present invention is that it can improve outflow detection during non fuel gas operation. Another advantage of the present invention is that the fuel gas valve closes more reliably during non fuel gas operation.

Although singular in the claims, this does not exclude a plurality.

Although we have endeavored to derive these features of the invention which are considered to be of particular importance in the foregoing specification, the Applicant, whether specifically emphasized or not, is concerned with any and all patentable features or combinations of the features mentioned above and / or shown in the figures. It should be understood as claiming protection of rights with respect to. Moreover, in view of the specification of the present invention, it should be understood that one of ordinary skill in the art may modify and / or improve the apparatus of the specification. However, such changes and / or improvements will fall within the scope of the technical and spirit as suggested in the appended claims.

1 and 2 show the engine 1 according to a preferred embodiment of the present invention, respectively, in cross section and in longitudinal section (for one cylinder). The engine 1 is a uniflow low-speed two-stroke crosshead diesel engine of the crosshead type and may be a prime mover of a propulsion system of a ship or a power plant. Such engines generally have 3 to up to 14 cylinders per line. The engine 1 is mounted on a bedplate 2 with main bearings for the crankshaft 3.

The crankshaft 3 is composed of a semi-built type. The semi-built type is made from forged or cast steel throws that are connected to the main journals by shrink fit connections.

The bedplate 2 may be formed integrally or divided into parts of suitable size depending on the production equipment. The bedplate consists of welded cross girders with sidewalls and bearing supports. The cross girders are also called "transverse girders" in the technical field to which the invention belongs. An oil pan 58 is welded to the base of the bedplate 2 and collects oil returning from the forced lubrication and cooling oil system.

The connecting rods 8 connect the crankshaft 3 with the crosshead bearings 22. Crosshead bearings are guided between vertical guide planes 23.

A welded A-shaped frame box 4 is mounted on the bedplate 2. The frame box 4 is a welded design. On the exhaust side, the frame box 4 is equipped with relief valves for each cylinder, while on the crankshaft side the frame box 4 is fitted with a hinged large door for each cylinder. Doing. The crosshead guide planes 23 are integrally formed in the frame box 4.

The cylinder frame 5 is mounted on the upper surface of the frame box 4. Staybolts 29 connect the bedplate 2, frame box 4 and cylinder frame 5 to hold the structure together. Stay bolts 29 are tightened using hydraulic jacks.

The cylinder frame 5 has a camshaft housing 25 that is cast into one or more parts and ultimately formed integrally, or the cylinder frame 5 is a welded design. According to a variant of this embodiment (not shown), the exhaust valve actuation is electronically controlled, without the camshaft 28 and the camshaft housing 25 but instead of the electronically controlled hydraulic system. hydraulic system).

The cylinder frame 5 is equipped with access covers for cleaning the scavenge air space and for inspecting scavenge ports and piston rings from the camshaft side. The cylinder frame 5 together with the cylinder liner 6 forms a scavenging chamber. The scavenge air receiver 9 has its opening side bolted to the cylinder frame 5. At the base of the cylinder frame 5 is a piston rod stuffing box, which is equipped with sealing rings for scavenging, and also an exhaust product. It is fitted with oil scraper rings that prevent penetration into the space of the frame box 4 and the bedplate 2 and thus protect all bearings present in this space.

The piston 13 includes a piston crown and a piston skirt. The piston crown is made of heat-resistant steel and has four ring grooves, all of which are hard chromium plated.

The piston rod 14 is connected to the crosshead 22 with four screws. The piston rod 14 has two coaxial bores (not shown in the drawing) that form an inlet and outlet for the cooling oil for the piston 13 in relation to the cooling oil pipe. ).

The cylinder liners 6 are carried by the cylinder frame 5. The cylinder liners 6 are made of alloyed cast iron and are inserted into the cylinder frame by a lowly positioned flange. The top of the cylinder liner is surrounded by a cast iron cooling jacket. The cylinder liners 6 have drilled holes (not shown) for cylinder lubrication.

The cylinders are of uniflow type and comprise scavenge air ports 7 located in the air box and are pressurized by the turbocharger 10 (see FIG. 1). ) Is supplied from the organelle 9 (see FIG. 1).

The engine is fitted with one or more turbochargers 10 arranged at its rear end for 4 to 9 cylinder engines and on the exhaust side for 10 or more cylinder engines.

Air intake into the turbocharger 10 takes place directly from the engine room via the intake silencer of the turbocharger. Air is led from the turbocharger 10 to the scavenging ports 7 of the cylinder liners 6 via a charging air pipe (not shown), an air cooler (not shown), and an elementary pipe 9. .

The engine is equipped with electrically-driven scavenge air blowers (not shown). The suction side of the blowers is connected to the scavenging chamber via an air cooler. Non-return valves (not shown) are installed between the air cooler and the scavenge receiver to automatically close when the auxiliary blowers supply air. Auxiliary blowers assist the turbocharger compressor at low and medium load conditions.

Fuel oil valves 50 and fuel gas valves 51 (shown in greater detail in the back FIG. 2A) are mounted in cylinder cover 12. In pure fuel oil operation, fuel oil injection valves 50 inject fuel at high pressure through the injection nozzles of the valves in the form of fine mist into the combustion chamber 15 at the end of the compression stroke. In fuel gas operation, the fuel oil valves 50 inject a small amount of fuel oil at high pressure through the injection nozzles of the valves in the form of fine spray into the combustion chamber 15 at the end of the compression stroke, while fuel gas injection The valves 51 inject a large amount of fuel gas at high pressure through the injection nozzles of the valves into the combustion chamber 15 at the end of the compression stroke. In fuel gas operation, about 10% of the fuel is fuel oil and about 90% of the fuel is fuel gas so that the fuel oil is used to ensure ignition. The exhaust valve 11 is mounted at the upper center of the cylinder in the cylinder cover 12. At the end of the expansion stroke, the exhaust valve is opened before the engine piston 13 passes under the scavenging ports 7 so that combustion gas in the piston upper combustion chamber 15 is discharged through the opening of the exhaust passage 16 to the exhaust receiver 17. The pressure in the combustion chamber 15 is reduced. The exhaust valve 11 is closed again while the piston 13 is raised. The exhaust valve 11 is operated hydraulically.

3 is a plan view illustrating a dual fuel injection system with one of the engine cylinders. The dual fuel injection system includes a conventional or common rail high pressure fuel oil injection system that can be mechanically and / or electrically controlled. The high pressure fuel oil injection system is suitable for operation with heavy fuel oil and has the necessary equipment therein such as piping and valves or valve blocks and tracking / heating devices for fuel oil circulation systems. Include. In another embodiment, the fuel oil injection system is suitable for marine diesel or similar clean diesel oil. As shown in FIG. 3, the fuel oil injection system is connected to the fuel oil injection valves 50 (two fuel oil valves per cylinder, or three per cylinder although not shown in the embodiment) via the common rail 55. Or a high pressure fuel oil pump station 53 connected to four fuel oil valves). Opening of the fuel valves 50 is electronically controlled in one embodiment by control valves not shown and mechanically controlled in another embodiment.

The high pressure fuel gas injection system is provided with a gas accumulator 63 by means of a conduit 64 including various shut off valves 67 and gas vents 68. And a gas supply system 60 having a gas compressor 62 connected thereto. The inlet of the high pressure fuel gas compressor 62 is connected with a reservoir (not shown) of fuel gas, which can be natural gas. Gas compressor 62 pressurizes fuel gas, such as natural gas, to a pressure well above the combustion pressure of the engine. In general, the combustion pressure can be up to 180 bar and the fuel gas pressure is maintained at about 200 bar and generally above 200 bar. Gas accumulator 63 (which may be more than one) is connected to each gas fuel valve 51 via valves 69, which may be part of the valve block.

A suction pan 81 connected to each valve block area via a suction channel 82 and a ventilation inlet connected to each valve block 65 area via a ventilation channel 87 The valve block 65 or blocks are ventilated with fresh atmospheric air by a ventilation system 80 including a venting air intake. Ventilation system 80 includes hydrocarbon sensors for detecting leakage of fuel gas.

The gas supply system also includes an inert gas supply system 70 that provides an inert or at least substantially inert or substantially combustible gas. The inert gas supply device includes a high pressure inert gas compressor 72 capable of pressurizing a substantially inert gas to a pressure approximately equal to the pressure provided by the high pressure fuel gas compressor 62. The outlet of the high pressure inert gas compressor 72 is connected to the high pressure gas fuel injection system through a valve 73 which controls the flow of substantially inert gas into the high pressure fuel gas injection system. In one embodiment, the valve 73 is electronically controlled. The inlet of the high pressure inert gas compressor 72 is connected with a tank (not shown) of a substantially inert gas, such as nitrogen or a mixture of nitrogen and tracer gas, which is used at a concentration of up to about 5% of the total inert gas. It may be natural gas.

During non-gas fuel operation of the engine, for example, when the engine is operated with fuel oil, the high pressure fuel gas injection system is purged with substantially inert gas from the inert gas supply system 70 and then Is pressurized.

The high pressure fuel gas injection system further includes a sealing oil system 100 that provides the pressurized sealing oil to the fuel gas valves 51 at high pressure. The pressure of the sealing oil is higher than the pressure of the fuel oil, and as will be explained in more detail below with reference to FIG. 4, the sealing oil is used to prevent gas leakage from the fuel gas valves 51. The sealing oil system 100 includes a high pressure pump device 102. The high pressure pump device 102 has an inlet port of the high pressure pump device 102 connected with the sealing oil tank and a discharge port of the high pressure pump device 102 connected with the pipe 104 for guiding the high pressure sealing oil to the fuel gas valves 51. Include.

4 shows a fuel gas valve according to an embodiment of the present invention. In general, a fuel gas valve 51 having two to three valves mounted to each cylinder of the engine 1 includes a housing 90 having a central bore in which a spindle guide 91 is accommodated. Include. Spindle guide 91 cooperates with gas spindle 92. The spindle guide 91 has a slim portion which is received in the bore in the gas spindle 92 to form the fuel gas pressure chamber 96. The pressure in the fuel gas chamber 96 causes the gas spindle to be in the closed position. An elastic spring disposed between the spindle guide 91 and the gas spindle 92 also causes the gas spindle 92 to be in the closed state. Upon pressurization, the control oil pressure chamber 95 connected with the control oil conduit 97 causes the gas spindle 92 to be in the open state. In addition to gaskets not shown, the fuel gas valve 51 is provided with a sealing oil device comprising a sealing oil tube 93 pressurized to a level above the fuel gas pressure. The sealing oil tube 93 distributes the sealing oil to various unshown ring chambers forming barriers for preventing the leakage of fuel gas from the fuel gas valve 51.

When the control oil pressure chamber 95 is pressurized, the valve spindle 92 is raised from its seat so that the high pressure fuel gas can flow from the annular chamber 98 into the dispersion nozzle 99. If the control oil pressure chamber 95 is not pressurized or only pressurized to a low pressure, the fuel gas pressure and the spring 94 inside the pressure chamber 96 keep the valve spindle in place. The fuel gas reaches the annular ring chamber 98 through ports and tubes not shown. The fuel gas reaches the fuel gas pressure chamber 96 from the annular chamber 98 through a tube that is only partially visible within the valve spindle 92.

5 shows an embodiment of a dual fuel injection system. This embodiment is essentially the same as the embodiment shown in FIG. 3 except that the control oil system 107 is shown symbolically in this embodiment.

In fuel gas operation, fuel gas compressor 62 provides high pressure fuel gas to fuel valves 51. Accumulator 66 compensates for pressure and / or flow rate variations. Suitable operating pressures for fuel gas are in one embodiment at least 200 bar, preferably about 250 bar. Gas fuel valves 51 are opened by applying control oil pressure from control oil system 107. Control oil system 107 is mechanically controlled in one embodiment and electronically controlled in another embodiment.

During non-fuel gas operation, the fuel gas compressor 62 does not operate, and the inert gas compressor 72 purifies the fuel gas injection system having substantially inert gas or substantially non-combustible gas, and substantially reduces the pressure used for the fuel gas. Pressurizes the fuel gas system to the same pressure. Substantially inert or substantially non-combustible gas is nitrogen gas in one embodiment, and in other embodiments, substantially inert or substantially non-combustible gas is a nitrogen mixture comprising a tracer gas that is easily detectable. In one embodiment, the tracer gas is natural gas, methane or other hydrocarbon gas that is easily detectable. The concentrations of natural gas, methane or other hydrocarbon gases are so low that a substantial mixture of non-combustible gas and atmosphere is non-combustible. Hydrocarbon sensors in the ventilation system 80 can detect leaks of nitrogen and methane mixtures or other hydrocarbon gases such that gas leak detection is also possible when the gaseous fuel injection system is filled with substantially inert or non-combustible gas. .

The present invention has shown dual fuel embodiments. However, it is also clear that the present invention can also be used in engines which are primarily gas operated and whose emergency operation is possible only with a reduced capacity fuel oil system.

The invention will be described in more detail with reference to exemplary embodiments shown in the accompanying drawings, in which:

1 is a cross-sectional view of an engine according to the present invention,

FIG. 2 is a longitudinal sectional view of one cylinder portion in the engine shown in FIG. 1; FIG.

2A is a symbolic cross sectional view of the cylinder illustrated in FIG. 2, FIG.

3 is a symbolic representation of a dual fuel injection system according to an embodiment of the present invention, and FIGS. 3A to 3C are enlarged views of different portions of FIG.

4 is a cross-sectional view of one embodiment of a fuel gas injector according to the present invention, and

      5 is a schematic representation of a dual fuel injection system in accordance with one embodiment of the present invention.

Claims (2)

High pressure fuel gas valve for large two-stroke diesel engines, A high pressure sealing oil system for preventing leakage of fuel gas from the high pressure fuel gas valve, and A control oil system for opening the gas spindle to allow high pressure fuel gas to flow into the fuel gas nozzle, The gas spindle is a high pressure fuel gas valve of a large two-stroke diesel engine, characterized in that the force is forced to be closed by the fuel gas pressure and the elastic member. The method of claim 1,       The gas spindle is forced to be opened by the force caused by the control oil pressure against the force caused by the fuel gas pressure and the force caused by the elastic member. High pressure fuel gas valve on the engine.

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