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JP-7855511-B2 - Internal combustion engine

JP7855511B2JP 7855511 B2JP7855511 B2JP 7855511B2JP-7855511-B2

Inventors

  • ツォン、シェンフイ
  • パン、カル・ムン
  • ボードイン、エリック

Assignees

  • マン・エナジー・ソリューションズ、フィリアル・エフ・マン・エナジー・ソリューションズ・エスイー、ティスクランド

Dates

Publication Date
20260508
Application Date
20201207
Priority Date
20191206

Claims (10)

  1. A two-stroke uniflow scavenging crosshead internal combustion engine comprising at least one cylinder, a cylinder cover, a piston, a fuel gas supply system, and a scavenging air system, wherein the cylinder has a cylinder wall, the cylinder cover is positioned on the top of the cylinder and has an exhaust valve, the piston is positioned to be movable within the cylinder between bottom dead center and top dead center, the scavenging air system has a scavenging air inlet positioned at the bottom of the cylinder, and the two-stroke uniflow scavenging crosshead internal combustion engine is configured to inject fuel gas into the at least one cylinder via the fuel gas supply system, and the fuel gas The fuel supply system comprises one or more fuel gas valves for at least one cylinder, each at least partially positioned in the cylinder wall and configured to inject fuel gas into the cylinder during a compression stroke, allowing the fuel gas to mix with scavenging air, and allowing the mixture of scavenging air and fuel gas to be compressed before ignition, wherein the fuel gas supply system is configured to inject fuel gas into the at least one cylinder during a single compression stroke in at least a first fuel gas injection event and a second fuel gas injection event following the first fuel gas injection event, under an engine load of 50% or more of the maximum engine load. The first fuel gas valve among the one or more fuel gas valves is configured to inject fuel gas into the cylinder during both the first fuel gas injection event and the second fuel gas injection event, the maximum flow rate of the fuel gas through the first fuel gas valve is higher during both the first and second fuel gas injection events than the flow rate between the first and second fuel gas injection events, the injected fuel gas is non-autoignitable under the conditions present in the cylinder, and the internal combustion engine is configured to inject a small amount of autoigniting pilot fuel to ignite a mixture of fuel gas and scavenging air. A two-stroke uniflow scavenging crosshead internal combustion engine is provided with a configured dedicated ignition system, the fuel gas supply system comprising a control unit operably connected to the first fuel gas valve, the control unit configured to modify the first fuel gas injection event and/or the second fuel gas injection event in accordance with the engine load, and the control unit configured to change the number of injection events in which fuel gas is injected during the compression stroke in accordance with the engine load, such that there are more injection events at low engine loads where the length of each injection event is relatively short than at high engine loads where the length of each injection event is relatively long .
  2. The two-stroke uniflow scavenging crosshead internal combustion engine according to claim 1, wherein the fuel gas supply system is configured to completely close the first fuel gas valve between the first fuel gas injection event and the second fuel gas injection event.
  3. The two-stroke uniflow scavenging crosshead internal combustion engine according to claim 2, wherein the fuel gas supply system is configured to keep the first fuel gas valve closed between the first fuel gas injection event and the second fuel gas injection event during the idle period.
  4. A two-stroke uniflow scavenging crosshead internal combustion engine according to any one of claims 1 to 3, wherein the one or more fuel gas valves further comprises a second fuel gas valve, the second fuel gas valve being configured to inject fuel gas into the cylinder during at least two fuel gas injection events.
  5. The two-stroke uniflow scavenging crosshead internal combustion engine according to claim 4 , wherein the first fuel gas valve and the second fuel gas valve are at least partially positioned in the cylinder wall at substantially the same height.
  6. The timing of the first fuel gas valve and the second fuel gas valve is asynchronous to produce a more homogeneous mixture of scavenging air and fuel gas, as described in claim 5 , for the two-stroke uniflow scavenging crosshead internal combustion engine.
  7. The two-stroke uniflow scavenging crosshead internal combustion engine according to any one of claims 1 to 6, wherein the fuel gas supply system is configured to further inject fuel gas into the at least one cylinder during the compression stroke in a third fuel gas injection event following the second fuel gas injection event.
  8. A two-stroke uniflow scavenging crosshead internal combustion engine according to any one of claims 1 to 7, wherein a first amount of fuel gas is introduced into the cylinder through one or more fuel gas valves, and the first fuel gas injection event and the second fuel gas injection event are designed to produce a more homogeneous mixture of fuel gas and scavenging air compared to a situation in which the first amount of fuel gas is introduced into the cylinder during a single fuel gas injection event.
  9. A two-stroke uniflow scavenging crosshead internal combustion engine according to any one of claims 1 to 8, wherein the fuel gas supply system is capable of injecting fuel gas into the cylinder through one or more fuel gas valves during the injection period of the compression stroke, and the fuel gas supply system is oversized so that the fuel gas supply system can deliver at least 120% of the fuel gas required when the two-stroke uniflow scavenging crosshead internal combustion engine is operating at maximum engine load, thereby allowing multiple fuel gas injection events to be used even when the two -stroke uniflow scavenging crosshead internal combustion engine is operating at maximum engine load.
  10. A non-temporary computer-readable medium for storing computer-readable code, the computer-readable code being executable by a control unit of a two-stroke uniflow scavenging crosshead internal combustion engine, the two-stroke uniflow scavenging crosshead internal combustion engine comprising at least one cylinder, a cylinder cover, a piston, a fuel gas supply system, and a scavenging air system, wherein the cylinder has a cylinder wall, the cylinder cover is positioned on the top of the cylinder and has an exhaust valve, the piston is positioned to be movable within the cylinder between bottom dead center and top dead center, the scavenging air system has a scavenging air inlet positioned at the bottom of the cylinder, the two-stroke uniflow scavenging crosshead internal combustion engine is configured to inject fuel gas into the at least one cylinder via the fuel gas supply system, the fuel gas supply system is positioned at least partially within the cylinder wall and, under an engine load of 50% or more of the maximum engine load, injects fuel gas into the cylinder during the compression stroke to allow the fuel gas to mix with scavenging air and to allow the mixture of scavenging air and fuel gas to be compressed before ignition. A non-transient computer-readable medium comprising one or more fuel gas valves configured to enable for at least one cylinder, the injected fuel gas being non-autoignitable under conditions present in the cylinder, the internal combustion engine being provided with a dedicated ignition system configured to inject a small amount of autoigniting pilot fuel to ignite a mixture of fuel gas and scavenging air, the control unit being operably connected to a first fuel gas valve of the one or more fuel gas valves, the computer-readable code being configured to control the control unit to control the first fuel gas valve to inject fuel gas into the at least one cylinder during a single compression stroke in at least a first fuel gas injection event and a second fuel gas injection event following the first fuel gas injection event , and the computer-readable code being further configured to control the control unit to change the number of injection events in which the fuel gas is injected during a compression stroke in accordance with the engine load, such that there are more injection events at low engine loads where the length of individual injection events is relatively short than at high engine loads where the length of individual injection events is relatively long.

Description

This invention relates to a two-stroke internal combustion engine and a non-temporary computer-readable medium. Two-stroke internal combustion engines are used as propulsion systems in vessels such as container ships, bulk carriers, and tankers. Reducing undesirable exhaust emissions from internal combustion engines is becoming increasingly important. An effective method for reducing the amount of undesirable exhaust gases is to switch from fuel oil, such as heavy fuel oil (HFO), to fuel gas. Fuel gas can be injected into the cylinder at the end of the compression stroke, where it can be ignited either by the high temperature reached when the gas in the cylinder is compressed, or by the ignition of pilot fuel. However, injecting fuel gas into the cylinder at the end of the compression stroke requires a large gas compressor to compress the fuel gas before injection in order to overcome the high pressure in the cylinder. Large gas compressors, however, are expensive and complex to manufacture and maintain. One way to avoid the need for a large compressor is to have a fuel gas valve configured to inject fuel gas at the beginning of the compression stroke when the pressure in the cylinder is significantly lower. EP3015679 discloses such a fuel gas valve. However, ensuring rapid and efficient mixing of scavenging air and fuel gas in the cylinder can be difficult. An imbalanced mixture of fuel gas and scavenging air can lead to insufficient combustion of the fuel gas, premature ignition, or knocking. One possible solution is to inject the fuel gas very early in the compression stroke, allowing the gases to mix over a longer period of time. However, if the fuel gas is injected into the cylinder before the exhaust valve closes, undesirable fuel gas leakage may occur. Therefore, improving the mixing of fuel gas and scavenging air in the cylinder remains a challenge. According to a first aspect, the present invention relates to a two-stroke uniflow scavenging crosshead internal combustion engine comprising at least one cylinder, a cylinder cover, a piston, a fuel gas supply system, and a scavenging air system, wherein the cylinder has a cylinder wall, the cylinder cover is located on the top of the cylinder and has an exhaust valve, the piston is positioned to be movable within the cylinder between bottom dead center and top dead center, the scavenging air system has a scavenging air inlet located at the bottom of the cylinder, and the two-stroke uniflow scavenging crosshead internal combustion engine is configured to inject fuel gas into at least one cylinder via the fuel gas supply system, the fuel gas supply system is located at least partially within the cylinder wall and injects fuel gas into the cylinder during the compression stroke to allow the fuel gas to mix with scavenging air and fuel The fuel gas supply system is configured to inject fuel gas into at least one cylinder during the compression stroke of at least a first fuel gas injection event and a second fuel gas injection event following the first fuel gas injection event, under an engine load of at least 50% of the maximum engine load, with the first fuel gas valve of the one or more fuel gas valves configured to inject fuel gas into the cylinder during both the first and second fuel gas injection events, and the maximum flow rate of fuel gas through the first fuel gas valve is higher during both the first and second fuel gas injection events than between the first and second fuel gas injection events. By injecting fuel gas during multiple injection events, the impact of the injected fuel gas against the portion of the inner cylinder wall opposite the fuel gas valve can be reduced. This can result in better mixing of the scavenging air and fuel gas. In addition, the reduced degree of impact can decrease the velocity component of the injected fuel gas along the longitudinal axis of the cylinder, thereby reducing the risk of undesirable fuel gas leakage through the exhaust valve. The internal combustion engine is preferably configured to use multiple injections during normal operation, for example, when a container ship is at cruising speed. Thus, the engine may be configured to use multiple injections under engine loads of at least 50%, 70%, 90%, or 100% of the maximum engine load. The internal combustion engine is preferably a large, low-speed, two-stroke crosshead internal combustion engine with uniflow scavenging and a turbocharger, for propelling a vessel with an output of at least 400 kW per cylinder. The internal combustion engine may include a turbocharger configured to be driven by the exhaust gases produced by the engine and to compress the scavenging air. The internal combustion engine may be a dual-fuel engine having an Otto cycle mode when operating on fuel gas and a diesel cycle mode when operating on an alternative fuel, such as heavy fuel oil or marine diesel fuel. Such a dual-fuel engine has its own dedicated fuel supply system for inje