JP2014224524A - Combustion engine and method of supplying gas fuel to such engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently cool boil-off gas using a heat exchanger.SOLUTION: A combustion engine comprises: a fuel supply system that includes at least one second fuel storage 4 for liquefied gas fuel and a gas fuel pump 25 for supplying gas at a pressure of at least 200 bars; and an injection system for injecting gas fuel. In a first heating medium flow passage, an outlet line from the second fuel storage 4 for boil-off gas is coupled to a heat exchange 27 via a compressor device. The first heating medium flow passage includes an outlet coupled to an inlet line on the heat exchanger 27, and the inlet line extends downward to at least one expansion nozzle device located in the at least one second fuel storage 4 via an upper portion of the second fuel storage 4.

Description

  The present invention relates to an internal combustion engine, the internal combustion engine comprising at least a first fuel reservoir for pilot fuel, at least a second fuel reservoir for liquefied gas fuel, a pilot fuel pump, and A fuel supply system comprising a gas fuel pump for supplying gas at a pressure of at least 200 bar; and an injection system for injecting pilot fuel and for injecting gaseous gas fuel, the gas fuel pump comprising: , At least partially positioned in the at least one second fuel reservoir and connected to the injection system through a high pressure gas conduit, the high pressure gas conduit at least for evaporating the liquefied gas fuel into the gaseous gas fuel Has one heat exchanger.

  Danish patent application 200900434 discloses such an internal combustion engine, in which a gas fuel pump delivers liquefied gas fuel, a heat exchanger is supplied with a heating medium in the form of ambient air, and the heat exchanger Downstream, the cooled air is delivered to the turbocharger compressor inlet above the engine. As an alternative embodiment, it has been proposed that the heating medium is removed from the air outlet of the compressor, where the air is warmer due to compression.

  European Patent No. 1990272 describes a fuel gas supply system to an internal combustion engine in an LNG carrier vessel having an LNG storage tank. A first pump is installed in or just outside the LNG storage tank and performs an initial compression of LNG to a pressure of about 27 bar at the pump outlet. The LNG then passes through the heat exchanger, and at its outlet, the LNG has a temperature of about -100 ° C and a pressure of about 27 bar. Downstream of the heat exchanger, LNG is pressurized in a second pump to a pressure of about 250 bar and passed through the second heat exchanger as liquid LNG to the engine's injection system. The first heat exchanger is supplied with boil-off gas that is removed from the upper portion of the second fuel reservoir and returned through one side in the lower portion of the second fuel reservoir. A compressor and cooler are positioned in the boil-off gas line upstream of the heat exchanger. Downstream of the heat exchanger, the boil-off gas is a liquid. A pressure control valve in the line expands the pressure in the line to add the pressure head of the LNG liquid column in the reservoir to correspond to the pressure in the second fuel reservoir.

  An object of the present invention is to improve the energy utilization of an internal combustion engine during operation.

  To this end, the internal combustion engine according to the invention has an outlet line for boil-off gas from the second fuel reservoir in the first heating medium flow path through the compressor device. The first heating medium flow path has an outlet portion connected to the inlet line on the heat exchanger, the inlet line being an upper portion of the second fuel storage section And extending downward to at least one expansion nozzle device positioned in the at least one second fuel reservoir.

  The high pressure gas conduit delivers liquid LNG to the heat exchanger at a pressure above 200 bar and the boil-off gas is used as the first heating medium to warm the gaseous fuel. By warming the gas fuel, the boil-off gas itself is cooled, and the boil-off gas is compressed upstream of the heat exchanger, so it expands the boil-off gas and thus allows the boil-off gas to be further cooled. . The boil-off gas exiting the heat exchanger is delivered to the second fuel reservoir via the inlet line, and expansion to gas pressure in the second fuel reservoir is caused by the second fuel reservoir. Causes cooling of the boil-off gas inside.

  In some embodiments, the at least one heat exchanger is a fluid circuit in an air conditioning system in a ship, a water cooler in a ship, a cooling fluid circuit in a refrigerator, or an oil cooler of an internal combustion engine or At least a second heating medium flow path connected to a liquid supply, such as an inlet air cooler. The liquid source delivers heat to the gas fuel while the liquid source itself is cooled, thus otherwise avoiding cooling by other means that typically consume electricity.

  In certain embodiments, the at least one heat exchanger has at least a third heating medium flow path coupled to a gas supply, such as an inlet air flow path to the internal combustion engine. The third medium channel can be applied without any second medium channel. The gas source delivers heat to the gas fuel and at the same time the gas source itself is cooled, thus acquiring the state of the cooler, and advantageously using the specific fuel consumption of the engine (per kWh produced). Reducing the fuel mass) or otherwise just avoiding cooling by other means that are usually consuming electricity.

  In an embodiment combining the advantages of the two previous embodiments, at least one heat exchanger is at least a second heating medium flow path connected to the liquid source and at least connected to the gas source. A third heating medium flow path.

  In an embodiment, a gas fuel pump positioned in the second fuel gas reservoir has two stages, the first stage is a primer pump delivery stage, and the second stage is Centrifugal pump pressure stage. The advantage of the piston pumping stage allows the centrifugal pump to be mounted at a predetermined distance from the inner wall of the second fuel gas reservoir and further pumps virtually all liquid LNG from the reservoir. Because the piston pump feed stage can draw LNG from the bottom of the reservoir via a suction line with an inlet opening near the bottom of the reservoir. is there.

  In another aspect, the invention relates to a method of supplying an internal combustion engine with gaseous gas fuel at a pressure of at least 200 bar in an injection system, wherein the internal combustion engine is at least a first fuel reservoir for pilot fuel. And at least one second fuel reservoir for liquefied gas fuel, the injection system injects pilot fuel, injects gaseous gas fuel, and the gas fuel pump has at least one second fuel reservoir. Located at least partially within the fuel reservoir and connected to the injection system through a high pressure gas conduit, the high pressure gas conduit having at least one heat exchanger for evaporating the liquefied gas fuel into the gaseous gas fuel .

  According to the invention, the boil-off gas in the first heating medium flow path from the second fuel reservoir is compressed to a set pressure in the compressor device and heats the gas fuel. The at least one expansion nozzle device delivered to the at least one second fuel reservoir is supplied with boil-off gas from the heat exchanger, and this boil-off gas is passed to the second fuel reservoir. Inflate into the boil-off gas in the upper part. Using boil-off gas to heat the gaseous fuel saves energy and separate energy consumption to liquefy the boil-off gas. The cooled boil-off gas expands into the gas in the upper portion of the second fuel reservoir, resulting in efficient further cooling of the boil-off gas.

  The set pressure of the boil-off gas is set as an example in the range of 2 bar to 5 bar, about 3 bar, etc., so that the boil-off gas is brought to a temperature approximately between −153 ° C. and −138 ° C. When expanded to a pressure of 1 bar, it is then possible to cool to a temperature of -163 ° C. It is also possible to increase the set pressure, but since compression consumes energy, this pressure should not be greater than needed.

  In some cases, the flow control valve in the bypass line bypasses the boil-off gas from the inlet line to the outlet line when the temperature of the boil-off gas in the inlet line is higher than the set temperature. Can be advantageous. If the gas fuel consumption is low, it may be advantageous to bypass the second fuel reservoir and circulate boil-off gas from the inlet line to the outlet line, which can be controlled by a flow control valve.

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

The figure which shows the LNG carrier provided with the internal combustion engine by this invention. FIG. 2 is an external end view of the engine of FIG. 1. The figure which shows the fuel supply and injection system of the engine of FIG. FIG. 4 shows the system of FIG. 3 in more detail, looking at a single cylinder on the engine. Graph showing Reynolds for methane. The figure which shows the 2nd fuel storage part and heat exchanger of the internal combustion engine of FIG.

  The LNG carrier of FIG. 1 has a main propulsion engine in an engine room 1 positioned below the superstructure 2. The engine drives the propeller 3 to propel the ship. The LNG carrier has a plurality (four in the illustrated embodiment) LNG storage tanks, each being a second fuel storage 4 for liquefied gas fuel to the internal combustion engine. Although the purpose of the LNG carrier is to transport LNG from the production site to the site of use for LNG, the LNG storage tank also serves as a fuel storage for the internal combustion engine during transport.

  The vessel need not be an LNG carrier, but can be any other type of vessel, and the second fuel reservoir 4 serves merely as a fuel reservoir, from the cargo area of the vessel. be independent. Examples of such other types of ships are RoRo ships, container ships, tankers, car carriers, bulk carriers, product tankers, shuttle carriers, and the like.

  In FIG. 2, the main propulsion engine is shown in more detail as an internal combustion engine. The internal combustion engine is a piston engine, preferably a two-stroke crosshead internal combustion engine, generally indicated at 5. The engine can have 4 to 15 cylinders. The engine can be, for example, type ME or MC from MAN Diesel & Turbo, manufactured by Wartsila, or manufactured by Mitsubishi. The cylinder can have holes in the range of, for example, 25 cm to 120 cm, preferably in the range of 60 cm to 120 cm. Two-stroke crosshead internal combustion engines used as main propulsion engines typically have a speed indicated as rpm in the range of 60 rpm to 200 rpm. These engines are named low speed engines. Low speed is required to transmit propulsive thrust force through the propeller to the water that follows the vessel. In order to transmit the thrust force to the water, the propeller needs to have a large area and therefore a large diameter. Since cavitation in the propeller is undesirable, it is necessary to limit the speed of the propulsion engine to a low speed range such as 60 rpm to 200 rpm.

  The engine 5 has a plurality of cylinders, each having a reciprocating piston in the cylinder. In a two-stroke crosshead internal combustion engine, the cylinder is typically of the uniflow scavenging type, the exhaust valve 6 is positioned at the top of the cylinder, and the scavenging air port (not shown) is below the cylinder. Located on the side edge. Exhaust gas from the cylinder is passed through the exhaust gas receiver 7 and the turbine portion of the turbocharger 8, and the compressor portion of the turbocharger 8 supplies the compressed inlet air to the inlet air chamber 9. From this chamber, the inlet air can pass through the inlet air cooler 10 and travel to the area surrounding the scavenging air port in the cylinder.

  The engine has an injection system for injecting pilot fuel and for injecting gas fuel, and for safety reasons, the system for injecting gas fuel includes an air intake system and an inert gas System. An air intake system is provided in the pipe 15 surrounding the gas fuel pipe 16, and the annular space between the two pipes makes it possible to monitor gas leaks from the inner pipe. The air inlet is at 11 and the air outlet is at 12 when the system is operating normally. A pair of hydrocarbon detectors 13 are installed downstream of the engine in a conduit leading to the air outlet 12. A source of pressurized inert gas 14 is connected to the gas fuel pipe 16 so that when the engine is shut down, the inert gas is fed into the gas fuel pipe to purge the gas fuel pipe with gas. Supplied.

  A first fuel reservoir 17 supplies pilot fuel to a fuel injector 18 on each cylinder 19 of the internal combustion engine. The pilot fuel is supplied at a pressure of, for example, 300 bar and is used to initiate each fuel injection sequence in the cylinder. The pilot fuel can be fuel oil and can self-ignite in the combustion chamber at the compression pressure available in the combustion chamber at the end of the combustion stroke. When the required pilot oil pressure is detected, the gas injectors 20 on each cylinder 19 are provided with control oil from the pumps 21 and are controlled in the gas injectors 20 to inject gas. Oil pressure is required. The control oil ensures that the gas is not injected into the cylinder if the pilot oil cannot be injected. The gas injector 20 is also supplied with pressurized sealing oil via a sealing oil line 22. Sealing oil prevents leakage of gas from the gas injector other than through the injection nozzle.

  Gas from the second fuel reservoir 4 is supplied to the gas fuel pipe 16 and flows to the accumulator 23 where the control valve 24 opens for gas to the injector 20 when gas injection occurs. There can be a common rail pipe between the gas fuel pipe 16 and the injector 20, in which case the accumulator 23 can be eliminated.

  The gas fuel pump 25 in the second fuel storage unit 4 (FIG. 6) is attached through the upper part of the storage unit. The pump can be a single stage pump, but preferably it has at least two stages, the first stage is a primer pump, such as a piston pump, and the second stage is a centrifugal pump It is. Centrifugal pumps can have multiple pump stages. The pump is a cryopump, an example is a model TC-34 manufactured by Cryogen Industries, CA, USA, and a high pressure centrifugal LNG pump as disclosed in Hydrocarbon Processing, July 2011, pages 37-41. It is. The gas fuel pump 25 delivers liquid LNG gas fuel to the high pressure gas conduit 26 at a pressure in the range of 200 bar to 500 bar, preferably at least 200 bar, such as about 300 bar.

  A high pressure gas conduit 26 for gas fuel is connected to the heat exchanger 27 and the second heat exchanger 28 and continues to the gas fuel pipe 16. The heat exchanger 27 has a first heating medium flow path including an outlet line 29 for boil-off gas from the second fuel storage unit 4. An outlet line 29 extends from the upper portion of the second fuel reservoir to the compressor 30 and from the compressor to the heat exchanger 27. The outlet line 29 is connected to the heat exchanger so that the boil-off gas is counterflowed with the gaseous fuel in the high pressure gas conduit 26. From the outlet of the heat exchanger 27, the first heating medium flow path has an inlet line 31 that extends downwardly through the upper portion of the second fuel reservoir 4 to the expansion nozzle 32. The expansion nozzle 32 is usually positioned at the uppermost part of the second fuel reservoir 4 in the region filled with boil-off gas.

  The first heating medium flow path also includes a bypass line 33 including a flow control valve 34, and the flow control valve 34 is normally closed. In order to recirculate the boil-off gas from the outlet line 29 to the inlet line 31 when the boil-off gas is reusable to heat the gaseous fuel because the flow of gas fuel through the heat exchanger 27 is low, The control valve 34 can be opened.

  The second heat exchanger has a second heating medium flow path 35 connected to a liquid supply source 36, such as a coolant fluid circuit in an air conditioning unit in the ship. The second heat exchanger has a third heating medium flow path 37 connected to a gas supply source 38, such as an inlet air flow path to the internal combustion engine. Thus, the gas supply can be part of the inlet air cooler 10. When the gas fuel flows out of the heat exchanger 28, it is heated to a gaseous state and to a temperature in the range of 30 ° C to 60 ° C, preferably 45 ° C.

  An example process is illustrated in the Reynolds chart in FIG. The chart shows the methane pressure (bar) and enthalpy (kJ / kg) on a logarithmic scale, showing the temperature curve. The inverted U-curve shows a region where methane is partly gaseous and partly liquid. The temperature in the second fuel reservoir 4 is about −163 ° C. and the pressure is about 1 bar. Depending on where the second fuel reservoir 4 is positioned relative to the compressor 30 in the vessel, the outlet line 29 may have a substantial length, such as a few meters to 400 meters. Is possible. If the outlet line 29 has a substantial length, as may be the case when the compressor is located close to the engine room and the second fuel reservoir is in the forward end of the ship, The boil-off gas may be somewhat warm when it reaches the compressor. In FIG. 5, the boil-off gas is assumed to have a temperature of −100 ° C. at the compressor inlet, which is shown at point 40. The compressor increases the pressure of the boil off gas to a pressure such as 3 bar, which is shown at point 41. In the heat exchanger 27, the boil-off gas is cooled, which is indicated by a horizontal line at a pressure of 3 bar. If cooling does not liquefy the boil-off gas and is expanded to a pressure of 1 bar, the boil-off gas can have a temperature of −163 ° C., as shown at point 42. If the cooling completely liquefies the boil-off gas and is expanded to a pressure of 1 bar, the boil-off gas can have a temperature of −163 ° C., as shown at point 43. If cooling proceeds to a temperature of about −150 ° C. and the boil-off gas is expanded to a pressure of 1 bar, the boil-off gas has a temperature of −163 ° C., as shown at point 44. Is possible. The gas fuel pump 25 pressurizes the liquid gas fuel from a pressure of 1 bar, -163 ° C. (shown at point 45), for example, to a pressure of 300 bar and a temperature of about −150 ° C. (shown at point 46). In the heat exchanger 27, the gas fuel can be heated to, for example, a temperature of −50 ° C. (shown at point 47), and in the second heat exchanger 28, the gas fuel can be heated to, for example, a temperature of 45 ° C. Can be heated to point 48).

  The first fuel reservoir, the pilot fuel pump, and the injection system for injecting the pilot fuel serve to start combustion in the combustion chamber, and when the injected gas fuel is injected It is supposed to burn. The pilot fuel has a function of becoming an ignition assist device for the gas fuel. According to an aspect of the present invention, it is possible to replace the first fuel storage unit, the pilot fuel pump, and the injection system for injecting the pilot fuel with another ignition auxiliary device such as discharge ignition. Yes, discharge ignition is supplied by a power source and controlled by a control unit and an electrical switching device. In this case, the internal combustion engine comprises at least one second fuel reservoir for liquefied gas fuel, a fuel supply system comprising a gas fuel pump for supplying gas at a pressure of at least 200 bar, gaseous gas An injection system for injecting fuel and a gas ignition auxiliary device are included. A gas fuel pump is positioned at least partially within the at least one second fuel reservoir and is coupled to the injection system through a high pressure gas conduit. The high pressure gas conduit has at least one heat exchanger for evaporating the liquefied gas fuel into the gaseous gas fuel. In the first heating medium channel, an outlet line for boil-off gas from the second fuel storage unit is connected to the heat exchanger via the compressor device, and the first heating medium channel On the heat exchanger has an outlet connected to the inlet line, the inlet line passing through the upper part of the second fuel reservoir and into the at least one second fuel reservoir. Extends down to the positioned at least one expansion nozzle device.

  The details of the various described embodiments can be combined into further embodiments within the scope of the claims. The heat exchangers 27 and 28 can be combined into a single heat exchanger, for example, or the heat exchanger 28 can be subdivided into several heat exchangers.

Claims (10)

  At least a first fuel reservoir for pilot fuel, at least one second fuel reservoir for liquefied gas fuel, a gas fuel for providing gas at a pilot fuel pump and a pressure of at least 200 bar An internal combustion engine having a fuel supply system comprising a pump and an injection system for injecting pilot fuel and for injecting gaseous gas fuel, wherein the gas fuel pump is the at least one second fuel At least partially positioned in a reservoir and connected to the injection system through a high pressure gas conduit, the high pressure gas conduit being at least one heat exchanger for evaporating the liquefied gas fuel to a gaseous gas fuel In the internal combustion engine, the second fuel storage unit is disposed in the first heating medium flow path. The boil-off gas outlet line is connected to the heat exchanger via a compressor device, and the first heating medium flow path is connected to the inlet line above the heat exchanger And the inlet line passes through an upper portion of the second fuel reservoir and down to at least one expansion nozzle device positioned in the at least one second fuel reservoir. An internal combustion engine, characterized in that   The at least one heat exchanger has at least a second heating medium flow path connected to a liquid source, such as a fluid circuit in an air conditioning system in a ship. 2. The internal combustion engine according to 1.   The at least one heat exchanger has at least a third heating medium flow path connected to a gas supply, such as an inlet air flow path to the internal combustion engine. The internal combustion engine described.   The at least one heat exchanger includes at least a second heating medium flow path connected to a liquid source, such as a fluid circuit in an air conditioning system in a ship, and an inlet air flow to the internal combustion engine The internal combustion engine according to claim 1, comprising at least a third heating medium flow path connected to a gas supply source, such as a path.   5. The gas fuel pump has two stages, the first stage is a primer pump feed stage, and the second stage is a centrifugal pump pressure stage. The internal combustion engine according to any one of the above.   The internal combustion engine according to any one of claims 1 to 5, wherein the internal combustion engine is a two-stroke crosshead type piston engine.   7. The internal combustion engine according to claim 1, wherein a bypass line extends from the inlet line to the outlet line, and the bypass line is provided with a flow control valve. engine.   A method of supplying an internal combustion engine with gaseous gas fuel at a pressure of at least 200 bar in an injection system, the internal combustion engine comprising at least a first fuel reservoir for pilot fuel, and a liquefied gas fuel And at least one second fuel reservoir, wherein the injection system injects pilot fuel, injects gaseous gas fuel, and the gas fuel pump has the at least one second fuel reservoir. And is connected to the injection system through a high pressure gas conduit, the high pressure gas conduit having at least one heat exchanger for evaporating the liquefied gas fuel into a gaseous gas fuel The boil-off gas in the first heating medium flow path from the second fuel reservoir is at a set pressure in the compressor device. And is delivered to the heat exchanger for heating the gaseous fuel and positioned in the at least one second fuel reservoir, the at least one expansion nozzle device from the heat exchanger A boil-off gas is supplied and the boil-off gas is expanded into the boil-off gas in the upper part of the second fuel reservoir.   9. A method according to claim 8, characterized in that the set pressure is in the range of 2 bar to 5 bar.   When the temperature of the boil-off gas in the inlet line is higher than a set temperature, the flow control valve in the bypass line opens to divert the boil-off gas from the inlet line to the outlet line. The method according to claim 8 or 9.

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