Method and large two-stroke uniflow scavenged internal combustion engine configured to operate with high jacket water temperature

Abstract

To provide a method and a large two-stroke uniflow scavenged internal combustion engine configured to operate with high jacket water temperature.SOLUTION: An orifice is provided at each of fluid connections between a pressure vessel or expansion tank (77) and a water-cooling circuit (70) in order to limit a water flow from the water-cooling circuit (70) to the pressure vessel or expansion tank (77) in an accidental event where stagnation in the water-cooling circuit (70) causes water in a cooling jacket, cylinder cover or exhaust valve to boil.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to large two-stroke internal combustion engines, and in particular to a large crosshead type, fuel (gas fuel or liquid fuel) operated, two-stroke, uniflow scavenged internal combustion engine configured to operate at high jacket water temperatures, and a method of operating such an engine at high jacket water temperatures.

[0002] Large two-stroke uniflow scavenging internal combustion engines with crosshead are used, for example, in the propulsion systems of large ships and as prime movers in power plants. These large two-stroke diesel engines are huge in size. Not only because of their huge size, they have a different structure than other internal combustion engines. For example, the exhaust valves can weigh up to 400 kg and the pistons can have diameters of up to 100 cm. The maximum pressure in the combustion chamber during operation is typically several hundred bar. The forces resulting from such high pressure levels and piston sizes are enormous.

[0003] Large two-stroke turbo internal combustion engines can run on liquid fuels (e.g. fuel oil, marine diesel, heavy fuel oil, ethanol, dimethyl ether (DME)) or gas fuels (e.g. ammonia, methane, natural gas (LNG), petroleum gas (LPG), methanol or ethane).

[0004] An engine that runs on gaseous fuel may operate according to the Otto cycle, in which gaseous fuel is admitted through a fuel valve located near the longitudinal centre of the cylinder liner or in the cylinder cover. In this type of engine, the gaseous fuel is admitted into the cylinder during the piston's upward stroke (from bottom dead centre to top dead centre), well before the exhaust valve closes. The engine compresses a mixture of gaseous fuel and scavenging air in the combustion chamber and ignites the compressed mixture at or near top dead centre (TDC) by a timed ignition means (such as liquid fuel injection).

[0005] Liquid fuelled engines and high pressure injected gas fuelled engines inject gas or liquid fuel when the piston is close to TDC, i.e. when the compression pressure in the combustion chamber is at or near maximum, i.e. these engines operate on the Diesel cycle, i.e. compression ignition.

[0006] The fuel efficiency of a two-stroke turbocharged internal combustion engine is limited by Carnot's theorem (https: / / en.wikipedia.org / wiki / Carnot%27s_theorem_(thermodynamics)). And, operating at higher absolute temperatures improves fuel economy. In known two-stroke turbocharged internal combustion engines, the cylinder liner, cylinder cover and exhaust valves are cooled by jacket water, which is kept at about 80-90 °C. This limits the temperature of the cylinder liner, cylinder cover and exhaust valves, and indirectly the maximum absolute temperature in the combustion chamber. It is not possible to simply increase the temperature of the jacket water in known engines, because known jacket water cooling systems are not constructed to handle such high temperatures and there is a risk of the jacket water boiling. If the jacket water boils and is rapidly pushed out of the jacket water system, the engine will be left without any forced cooling capacity if the jacket water cooling system runs out of jacket water.

[0007] JP 2015132191 A discloses a large two-stroke internal combustion engine according to the preamble of claim 1.

[0008] It is an object to provide an engine and method which overcomes or at least mitigates the above mentioned problems.

[0009] These and other objects are achieved by the features of the independent claims. Further detailed implementations will become apparent from the dependent claims, the description and the drawings.

[0010] According to the first aspect, there is provided a crosshead type large two-stroke turbocharged uniflow scavenging internal combustion engine as follows. This engine has: a plurality of combustion chambers each defined by a cylinder liner, a piston configured to reciprocate within the cylinder liner, and a cylinder cover; a scavenging port for introducing scavenging gas into the combustion chamber, the scavenging port being disposed in the cylinder liner; at least one cooling passage within the cylinder cover; an annular cooling chamber surrounding a portion of the cylinder; exhaust outlets disposed in the cylinder cover, each of the exhaust outlets being controlled by an exhaust valve; The plurality of combustion chambers are connected to a scavenging air receiver through the scavenging ports and to an exhaust air receiver through the exhaust outlet, and the engine further comprises: an exhaust system having a turbine driven by the exhaust flow, the turbine being a turbocharging system; an air intake system having a compressor of the turbocharging system configured to supply pressurized scavenging air to the scavenging receiver; a primary cooling circuit having at least one primary circulation pump configured to circulate water within the primary cooling circuit, the at least one cooling path and preferably the annular cooling chamber being part of the primary cooling circuit; a pressure vessel or expansion tank connected by a fluid connection to the primary cooling circuit for regulating the pressure of water in the primary cooling circuit and for allowing expansion and contraction of water in the primary cooling circuit; wherein the fluid connection is formed by one or more conduits, each of the plurality of conduits having an orifice for throttling the flow of water from the primary cooling circuit to the pressure vessel or the expansion tank.

[0011] By providing an orifice in the fluid connection between the pressure vessel or expansion tank and the primary cooling circuit, the flow of water from the primary cooling circuit to the pressure vessel or expansion tank is throttled in the event of a water blockage in the primary cooling circuit causing unintentional boiling of the water in the cooling chamber. This throttle effect slows the drainage of water from the primary cooling circuit to the pressure vessel or expansion tank sufficiently for the temperature in the cooling chamber to drop by passive cooling (assuming the engine load is reduced or the engine is shut down in the event of an unintentional blockage of water in the primary cooling circuit). Thus, the primary cooling circuit is prevented from running dry, allowing normal engine operation to be resumed quickly when the circulating capacity of the primary cooling circuit is re-established.

[0012] In one example implementation of the first approach, the orifice reduces a cross-sectional area through which fluid can flow for one or more of the conduits forming the fluid connection by at least 50 times, preferably at least 100 times, and most preferably at least 150 times.

[0013] In one example implementation of the first approach, the orifice reduces a cross-sectional area through which fluid can flow by a factor of 75-250.

[0014] In one example implementation of the first approach, the one or more conduits have a substantially constant inner diameter, the inner diameter being between 35 mm and 80 mm, and the at least one orifice has a minimum diameter between 3 mm and 5 mm.

[0015] In one example of an implementation of the first approach, the engine includes a first check valve in the fluid connection, preferably in a supply pipe fluidly connecting a pressure vessel or expansion tank to a degassing device, the first check valve being arranged in parallel with one of the at least one orifice and preferably allowing water to flow from the pressure vessel or expansion tank to the primary cooling circuit when water in the cooling circuit contracts.

[0016] In one implementation of the first aspect, the engine is provided with a pressure setting valve in the fluid connection to allow flow of water from the primary cooling circuit to the pressure vessel or expansion tank when pressure of the water in the primary cooling circuit rises above a threshold (preferably due to expansion of the water in the primary cooling circuit), the pressure setting valve being preferably disposed in parallel with one of the at least one orifice in a supply pipe fluidly connecting the pressure vessel or expansion tank to the degasser.

[0017] In one example of an implementation form of the first aspect, the engine is provided with a first control valve in the fluid connection portion, the first control valve being preferably arranged in parallel with one of the at least one orifice in a supply pipe fluidly connecting a pressure vessel or expansion tank to the degassing device, and preferably provided for initially filling the cooling circuit with water.

[0018] In one example of an implementation of the first approach, the institution: · Engine cooling water inlet and engine cooling water outlet; a circulation line connecting the engine cooling water outlet to the engine cooling water inlet; a degasser disposed in the circulation line and connected to the pressure vessel or the expansion tank by a supply line having an orifice and a first vent line having an orifice; and preferably a second vent pipe connecting the engine water outlet to the pressure vessel or the expansion tank, the second vent pipe having an orifice.

[0019] In one example of an implementation of the first approach, an orifice is provided in the circulation pipeline at a position upstream of the degassing device, and a second control valve is arranged in parallel with the orifice.

[0020] In one example implementation of the first aspect, the at least one primary circulation pump is disposed upstream of the degasser.

[0021] In one example of an implementation form of the first approach, the engine is provided with a cooler for cooling water in the primary cooling circuit, the cooler preferably arranged in parallel with a cooling restriction disposed in the circulation line, the cooler preferably connected to the circulation circuit by a third control valve, the third control valve preferably controlled by a control device.

[0022] In one example implementation of the first approach, the engine includes a control device that receives a first signal representative of the temperature of the water in the cooling circuit (preferably the temperature at a location close to where the water leaves the engine and enters a circulation line), and the control device is configured to control the temperature of the water in the primary cooling circuit to at least 100°C, preferably 120-130°C.

[0023] In one example of an implementation form of the first approach, the engine is equipped with a cooler, the cooler being controlled by the control device and configured to apply a selective amount of cooling to water in the primary cooling circuit under control of the control device and to control the temperature of water in the primary cooling circuit to a temperature of at least 100°C, preferably between 120 and 130°C, by adjusting the amount of cooling applied to the water in the primary cooling circuit.

[0024] In one example of an implementation of the first approach, the engine is configured to operate in an engine load range between a minimum engine load and a maximum engine load, and the control device is configured to control the temperature of the water in the primary cooling circuit, preferably at a location near where the water leaves the engine and enters the circulation line, to a temperature greater than 100°C for at least the maximum engine load, and preferably for the entire engine load range between the minimum engine load and the maximum engine load.

[0025] In one example implementation of the first aspect, the engine is configured to operate at a pressure in the primary cooling circuit of at least 3 barg.

[0026] In one example of an implementation form of the first aspect, the secondary cooling circuit is connected to the pressure vessel or the expansion tank to adjust the pressure of the water in the primary cooling circuit and to allow expansion and contraction of the water in the primary cooling circuit.

[0027] In one example of an implementation form of the first approach, the primary cooling circuit has a first portion inside the engine and a second portion outside the engine, the first portion having an area from the engine inlet to the engine outlet, the first portion having a cooling chamber, and the first portion preferably having at least one flow passage within the cylinder cover and preferably at least one flow passage and / or chamber within a housing of the exhaust valve.

[0028] In one example of an implementation form of the first approach, the second portion has a circulation line having at least one primary circulation pump and a degassing device upstream of the at least one primary circulation pump, and preferably a cooling device upstream of the degassing device.

[0029] In one example implementation of the first aspect, the engine includes an annular water jacket surrounding at least a portion of the cylinder liner and defining an annular cooling chamber with a radially outer portion of the cylinder liner.

[0030] According to the second aspect, there is provided a crosshead type large two-stroke turbocharged uniflow scavenging internal combustion engine as follows. This engine has: a plurality of combustion chambers each defined by a cylinder liner, a piston configured to reciprocate within the cylinder liner, and a cylinder cover; at least one cooling passage within the cylinder cover; a scavenging port disposed in each of the cylinder liners for introducing scavenging gas into the at least one combustion chamber; an annular cooling chamber surrounding a portion of the cylinder; exhaust outlets disposed in the cylinder cover, each of the exhaust outlets being controlled by an exhaust valve; The plurality of combustion chambers are connected to a scavenging air receiver through the scavenging ports and to an exhaust air receiver through the exhaust outlet, and the engine further comprises: an exhaust system having a turbine driven by the exhaust flow, the turbine being a turbocharging system; an air intake system having a compressor of the turbocharging system configured to supply pressurized scavenging air to the scavenging receiver; a secondary cooling circuit having a secondary circulation pump configured to circulate water within the secondary cooling circuit, the at least one cooling path and preferably the annular cooling chamber being part of the secondary cooling circuit; Equipped with the secondary cooling circuit is fluidly connected to the primary cooling circuit by a valve system for mixing water from the primary cooling circuit with water of the secondary cooling circuit; the primary cooling circuit having at least one primary circulation pump for circulating water in the primary cooling circuit; The apparatus further includes a controller receiving a first signal representative of a temperature of the water in the secondary cooling circuit and a second signal representative of a temperature of the water in the primary cooling circuit; The control device is configured to control the temperature of the water of the primary cooling circuit to a temperature below 95°C and to control the temperature of the water of the secondary cooling circuit to a temperature above 100°C, preferably between 120°C and 140°C, said controlling being preferably performed by regulating the amount of water of the primary cooling circuit mixed with the water of the secondary cooling circuit by controlling the valve system.

[0031] By providing a secondary cooling system including an annular cooling chamber for said cylinder and operating said secondary cooling system at temperatures above 100°C, the fuel efficiency of the engine can be increased as explained above with reference to Carnot's theorem, while the primary cooling system can be constructed in the same or similar manner as prior art primary cooling systems which typically operate at temperatures between 80 and 90°C. Thus, only the secondary cooling system and associated components need to be suitable for operation at higher temperatures.

[0032] In one example embodiment of the second aspect, the engine is configured to operate over an engine load range between a minimum engine load and a maximum engine load;

[0033] The control device is configured to control the temperature of the water in the secondary cooling circuit to a temperature above 100°C, at least for maximum engine load, preferably for engine loads between medium engine load and maximum engine load, and more preferably for engine loads between minimum engine load and maximum engine load.

[0034] In one example embodiment of the second aspect, the valve system includes a fourth control valve, preferably a three-way control valve controlled by a control device, the fourth control valve being disposed in the primary cooling circuit and fluidly connected to the secondary cooling circuit via a return line, and the fourth control valve being configured to divert a controllable amount of water flow from the secondary cooling circuit via the return line.

[0035] In one example of an embodiment of the second aspect, the engine comprises a supply pipe connecting the secondary cooling circuit to the primary cooling circuit, preferably upstream of the fourth control valve.

[0036] In one example embodiment of the second approach, the valve system includes a second check valve disposed in the secondary cooling circuit, preferably between the position where the return line connects to the secondary cooling circuit and the position where the supply pipe connects to the secondary cooling circuit.

[0037] In one example of an embodiment of the second aspect, the engine includes a cooler for cooling water in the secondary cooling circuit.

[0038] In one example of an embodiment of the second aspect, the engine is provided with a deaerator arranged in the primary cooling circuit piping and connected to the pressure vessel or the expansion tank, the deaerator adjusting the water pressure in the primary cooling circuit and the secondary cooling circuit and enabling expansion and contraction of water in the primary cooling circuit and the secondary cooling circuit.

[0039] The pressure vessel or expansion tank is preferably configured to maintain sufficient pressure to prevent water boiling in the secondary cooling circuit up to a water temperature of 140°C, preferably up to 130°C.

[0040] According to a third aspect, there is provided a method of operating a large crosshead type two-stroke turbocharged uniflow scavenged internal combustion engine, said engine comprising: a plurality of combustion chambers each defined by a cylinder liner, a piston configured to reciprocate within the cylinder liner, and a cylinder cover; at least one cooling passage within the cylinder cover; a scavenging port disposed in each of the cylinder liners for introducing scavenging gas into the at least one combustion chamber; an annular cooling chamber surrounding a portion of the cylinder; exhaust outlets disposed in the cylinder cover, each of the exhaust outlets being controlled by an exhaust valve; The plurality of combustion chambers are connected to a scavenging air receiver through the scavenging ports and to an exhaust air receiver through the exhaust outlet, and the engine further comprises: an exhaust system having a turbine driven by the exhaust flow, the turbine being a turbocharging system; an air intake system having a compressor of the turbocharging system configured to supply pressurized scavenging air to the scavenging receiver; a secondary cooling circuit having a secondary circulation pump configured to circulate water within the secondary cooling circuit, the at least one cooling path and preferably the annular cooling chamber being part of the secondary cooling circuit; Equipped with the secondary cooling circuit is fluidly connected to the primary cooling circuit by a valve system for mixing water from the primary cooling circuit with water of the secondary cooling circuit; The primary cooling circuit has at least one primary circulation pump for circulating cooling water within the primary cooling circuit. And the method further comprises: measuring a temperature of water in the secondary cooling circuit; measuring a temperature of water in the primary cooling circuit; controlling the temperature of the water in the primary cooling circuit to less than 95°C; controlling the temperature of the water in the secondary cooling circuit to be higher than 100°C, preferably 120-140°C; Includes.

[0041] In one example implementation of the third aspect, the engine is configured to operate in an engine load range between a minimum engine load and a maximum engine load;

[0042] The method includes controlling the temperature of water in the secondary cooling circuit to a temperature above 100°C for at least maximum engine load, preferably for engine loads between medium and maximum engine loads, and more preferably for engine loads between minimum and maximum engine loads.

[0043] In one example of an implementation form of the third approach, controlling the temperature of the water in the secondary cooling circuit includes adjusting the amount of water from the primary cooling circuit that is mixed with the water in the secondary cooling circuit by controlling a valve system.

[0044] In one example implementation of the third aspect, the method includes maintaining a pressure in the primary cooling circuit and the secondary cooling circuit at at least 5 barg.

[0045] These and other aspects will be apparent from the examples described below. [Brief description of the drawings]

[0046] Various aspects, embodiments, and implementations will be described in detail below with reference to exemplary embodiments illustrated in the drawings. [Figure 1] This is an overview of a large two-stroke diesel engine. [Diagram 2] This is an overview of the large two-stroke engine in Figure 1, seen from a different angle. [Diagram 3] FIG. 3 is a schematic representation of the large two-stroke engine of FIGS. 1 and 2. [Figure 4] 4 is a diagrammatic representation of a first embodiment of the engine of FIGS. 1 to 3; [Diagram 5] 4 is a schematic representation of a second embodiment of the engine of FIGS. 1 to 3; [Figure 6] 4 is a schematic representation of a third embodiment of the engine of FIGS. 1 to 3; Detailed explanation

[0047] In the following detailed description, the internal combustion engine will be described with reference to an example crosshead type large low speed two-stroke turbocharged internal combustion engine. Figures 1-3 depict an example of a turbocharged large low speed two-stroke diesel engine. The engine has a crankshaft 8 and a crosshead 9. Figures 1 and 2 are schematic views from different angles. Figure 3 is a schematic representation of the turbocharged large low speed two-stroke diesel engine of Figures 1 and 2 according to an embodiment, together with its intake and exhaust systems. In this example, the engine has six cylinders in series. A turbocharged large low speed two-stroke internal combustion engine may have from 4 to 14 cylinders arranged in series. The cylinders have cylinder liners carried by an engine frame 11. Such an engine may also be used, for example, as the main engine of a ship or as a stationary engine for driving a generator in a power plant. The total power output of the engine may be, for example, in the range of 1,000 to 110,000 kW.

[0048] The engine in this embodiment is a two-stroke uniflow scavenging engine, and scavenging ports 18 are provided in the lower region of the cylinder liner 1. A central exhaust valve 4 is provided in a cylinder cover 22 on the upper part of the cylinder liner 1. Scavenging gas is led from the scavenging receiver 2 to the scavenging ports 18 of each cylinder liner 1 when the piston is below the scavenging ports 18.

[0049] When the engine is operated as a premixed engine (engine based on the Otto principle), gaseous fuel (e.g. methanol, petroleum gas or LPG, methane, natural gas (LNG), ethane) is introduced through the gas inlet valve 50' under the control of the electronic control unit 100. This occurs during the upward stroke of the piston 10 (from BDC to TDC) before it passes the fuel valve (gas inlet valve) 50'. The gaseous or liquid fuel (e.g. fuel oil) is injected into the combustion chamber through the fuel valve 50 at high pressure (preferably 300 bar or more) when the piston 10 is at or near TDC. The gaseous fuel is supplied by the gaseous fuel supply system 30' and is introduced into the combustion chamber at a relatively low pressure. This pressure is less than 30 bar, preferably 25 bar, more preferably less than 20 bar. The fuel-containing flow for injection through the fuel valve 50 is supplied by the fuel system 30. The high pressure for injection through the fuel valve 50 can be generated in the fuel system 30 (common rail) or in the fuel valve 50. The fuel introduction valves 50' are preferably arranged so as to be equally spaced around the circumference of the cylinder liner. Also, preferably, they are arranged near the center of the cylinder liner in the longitudinal direction. The introduction of gas fuel is performed when the compression pressure is relatively low. In other words, the introduction is performed when the compression pressure is much lower than the compression pressure when the piston reaches TDC, so that it is possible to introduce the gas fuel at a relatively low pressure.

[0050] When the engine is operated as a compression ignition engine (diesel principle), there is no gas inlet valve 50' and fuel (gaseous or liquid) is injected at high pressure through the fuel valve 50 when the piston 10 is at or near TDC.

[0051] A piston 10 within the cylinder liner 1 compresses a mixture of gaseous fuel and scavenging gas (or scavenging gas in the case of operation with only fuel injection at TDC) and ignition is induced at or near TDC by injection of high pressure fuel from a fuel valve 50, preferably located in the cylinder cover 22. In the case of only liquid fuel injection at or near TDC, ignition is induced by compression. Combustion occurs and exhaust gases are produced.

[0052] When the exhaust valve 4 is opened, the combustion gas (exhaust gas) flows through a combustion gas duct associated with the cylinder 1 into the combustion gas receiver 3 and flows out into the first exhaust pipe 19. The first exhaust pipe 19 is provided with a selective catalytic reactor 33 for reducing nitrous oxide (NOx) in the exhaust gas.

[0053] The turbine 6 drives the compressor 7 via a shaft. The compressor 9 is supplied with outside air through an air intake 12. The compressor 7 sends compressed scavenging air to a scavenging pipe 13 connected to the scavenging air receiver 2. The scavenging air in the scavenging pipe 13 passes through an intercooler 14 for cooling the scavenging air.

[0054] Either upstream (as shown) or downstream (not shown) of the intercooler 14, the exhaust gas recirculation pipe 35 is connected to the scavenge pipe 13. At this point the recirculated exhaust gas is mixed with the scavenge air to form the scavenge gas. The scavenge gas flows to the scavenge air receiver 2. As will be explained in more detail below, the control unit 100 (electronic control unit) is configured to adjust the ratio of scavenge air to exhaust gas in the scavenge gas.

[0055] The cooled scavenging air or gas passes through an auxiliary blower 16 driven by an electric motor 17. The auxiliary blower 16 compresses the scavenging flow when the compressor 7 of the turbocharger 5 cannot provide sufficient pressure for the scavenging receiver 2, i.e. when the engine is at low or partial load. At high engine loads, the turbocharger compressor 7 can provide sufficiently compressed scavenging air and the auxiliary blower 16 is bypassed by a check valve 15. An engine may comprise several turbochargers 5 forming a turbocharging system.

[0056] The control unit 100 (electronic control unit) may be composed of a number of interconnected electronic units, each of which may comprise a processor and other hardware for performing the functions of the control unit. The control unit 40 generally controls the operation of the engine, for example controlling gas fuel introduction (amount and timing), liquid fuel injection (amount and timing), exhaust valve 4 opening and closing (timing and lift amount), exhaust gas recirculation ratio, and also controls the operation of various coolers, pumps, and other equipment. The control unit 100 receives various signals from sensors indicating the operating conditions of the engine. These signals may include signals representing the engine load, engine speed, blower speed, scavenging air temperature, exhaust gas temperature at various locations, and exhaust gas temperature at various locations. They may also include signals representing the pressure of the scavenging system, the pressure in the combustion chamber, the pressure in the exhaust system, and the pressure in the exhaust gas recirculation system (if present). The engine is preferably equipped with a variable timing exhaust valve actuation system, which allows individual control of exhaust valve timing for each combustion chamber. The control unit 100 is connected to the fuel valve 50, the liquid fuel inlet valve 50', the exhaust valve actuator, the angular position sensor, and the pressure sensor via signal lines or wireless connections. The angular position sensor detects the angle of the crankshaft and generates a signal representative of the position of the crankshaft. The pressure sensor is preferably located in the cylinder cover 22, or alternatively in the cylinder liner 1, and generates a signal representative of the pressure in the combustion chamber.

[0057] Depending on the size of the engine, the cylinder liner 1 is made in a variety of sizes, with typical sizes having a cylinder bore diameter of 250 mm to 1000 mm and a corresponding overall length of 1000 mm to 4500 mm.

[0058] The cylinder liner 1 is placed on the cylinder frame 23, and a cylinder cover 22 is placed on the cylinder liner 1. The cylinder liner 1 and the cylinder cover 22 are arranged so that gas does not leak between them. At least one cooling passage is provided in the cylinder cover 22 to cool the cylinder cover 22. At least one cooling passage of each cylinder cover 22 is fluidly connected to a water cooling system 60, 70, which will be described in detail below. The piston 10 is configured to reciprocate between a bottom dead center (BDC) and a top dead center (TDC). These two dead center positions of the piston 10 are separated by 180 degrees in terms of the rotation angle of the crankshaft 8. The cylinder liner 1 is provided with a number of cylinder lubrication holes distributed in the circumferential direction. These cylinder lubrication holes are connected to a cylinder lubrication line. The cylinder lubrication line supplies cylinder lubrication oil when the piston 10 passes through the cylinder lubrication hole 25. A piston ring (not shown) of the piston 10 then distributes the cylinder lubrication oil over the entire running surface (inner surface) of the cylinder liner. Although not shown, a jacket is provided on the cylinder liner, and jacket cooling water circulates in the space between the jacket and the cylinder liner.

[0059] A plurality of liquid fuel valves 50, preferably three or four per cylinder, are attached to the cylinder cover 22 and connected to a pressurized fuel supply source (not shown). The liquid fuel valves 50 are preferably arranged at equal intervals in the circumferential direction around the exhaust valve 4, particularly around the central outlet (opening) of the cylinder cover 22. The outer shape of the central portion is controlled by the exhaust valve 4. The injection timing and injection amount of fuel are controlled by the control unit 100. The fuel valve 50 is used only to inject a small amount of ignition liquid (pilot) when the engine is operated in a premixed mode. When the engine is operated in a compression ignition mode, the liquid fuel valve 50 injects an amount of liquid fuel necessary to operate the engine at the engine load actually used. The cylinder cover 22 may be provided with a prechamber (not shown). In addition, the tip of the liquid fuel valve 50, typically a tip provided with a nozzle having one or more nozzle holes, is arranged so that pilot oil (ignition liquid) is injected into the prechamber and atomized. The anteroom aids in reliable ignition.

[0060] The fuel inlet valve 50' is installed in the cylinder liner 1 (or the cylinder cover 22) with its nozzle substantially flush with the inner surface of the cylinder liner 1 and the rear end of the fuel valve 50' protruding from the outer wall of the cylinder liner 1. Typically, one or two, but at most three or four, fuel valves 50' are provided in each cylinder liner 1. They are arranged (preferably equidistantly) in the circumferential area of ​​the cylinder liner 1. In this embodiment, the fuel inlet valve 50' is arranged exactly in the longitudinal center of the cylinder liner 1. The fuel inlet valve 50' is connected to a pressurized supply 30' of gaseous fuel (e.g., methanol, LPG, LNG, ethane or ammonia). That is, the fuel is in gaseous phase when it is supplied to the fuel inlet valve 50'. Since the gaseous fuel is introduced during the stroke from BDC to TDC of the piston 10, the pressure of the gaseous fuel supply source only needs to be higher than the pressure existing in the cylinder liner 1. Typically a pressure of less than 20 bar is sufficient for the gas fuel delivered to the fuel inlet valve 50'. The fuel inlet valve 50' is connected to a control unit 100. The control unit 40 determines the opening and closing timing and the opening time of the fuel inlet valve 50'.

[0061] In some embodiments, the liquid fuel for ignition is heavy fuel oil, marine diesel, heavy fuel oil, ethanol, or dimethyl ether (DME).

[0062] The gas mode of operation may be one of several operating modes of the engine. Other modes may include a liquid fuel mode of operation in which all of the fuel required for the operation of the engine is supplied in liquid form through the liquid fuel valve 50. In the gas fuel mode of operation, the engine is primarily fueled by gas fuel, which is introduced at relatively low pressure during the piston stroke from BDC to TDC. That is, the major portion of the energy supplied to the engine is provided by such gas fuel. On the other hand, in comparison to the gas fuel, liquid fuel is used in smaller amounts and contributes relatively little to the amount of energy supplied to the engine. The purpose of the liquid fuel is to ignite at a predetermined time. That is, the liquid fuel acts as an ignition fluid.

[0063] In this manner, the engine of the present embodiment can be a dual fuel engine having a mode in which it operates solely on liquid fuel and a mode in which it operates almost exclusively on gas fuel.

[0064] In this embodiment, the engine is shown as a premixed engine operating according to the Otto principle, but there are also embodiments in which the engine is a compression ignition engine (operating according to the Diesel principle), in which case fuel (gaseous or liquid) is injected at high pressure when the piston 10 is at or near TDC.

[0065] The engine is operated by supplying fuel (liquid and / or gaseous fuel) to a combustion chamber and combusting the fuel therein, thereby generating an exhaust gas stream. In certain embodiments not shown, a first portion of the exhaust gas (or combustion gas, in embodiments where the recirculated gas is taken directly from the combustion chamber) stream is recirculated and another (second) portion of the exhaust gas stream is exhausted as exhaust gas.

[0066] Downstream of the turbine 6 of the turbocharger 5, the exhaust gases enter a second exhaust pipe 28, which leads the exhaust gases to a boiler 20 (also called an economizer). The boiler 20 is typically arranged to generate steam. This steam is used for various purposes, for example in the ship on which the engine is installed. Downstream of the boiler 20, a second exhaust line 28 follows, which opens to the atmosphere.

[0067] The cylinder liner 1 includes a jacket 21 that defines an annular cooling chamber 23. The annular cooling chamber 23 is preferably located at the top of the cylinder liner 1, which is the most thermally loaded area of ​​the cylinder liner 1. The annular cooling chamber 23 is fluidly connected to a water cooling system 60, 70, which is described in more detail below. Typically, the cylinder cover 22 and the housing of the exhaust valve 4 are provided with passages and chambers for receiving cooling water from the water cooling system.

[0068] FIG. 4 is a diagram of a first embodiment of an engine with a water-cooling system. In this embodiment, the water-cooling system comprises a primary cooling circuit 70 and a secondary cooling circuit 60. The primary cooling circuit 70 comprises a primary circulation line 73 that is filled with water during engine operation. The primary circulation line 73 has a primary circulation pump 72, which serves to circulate the water in the primary circulation line 73. For redundancy, two or more primary circulation pumps 72 are provided. Downstream of each primary circulation pump 72, a check valve is provided. Upstream of the check valve, a first temperature sensor 75 is provided. Upstream of the primary circulation pump 72, a deaerator (deaerator vessel) 78 is arranged to remove air, gas or steam trapped in the water and to remove trapped air bubbles. The deaerator 78 is connected to a pressure vessel 74 or an expansion tank 77 via a supply line and a vent line. The function of pressure vessel 74 or expansion tank 77 is to store water, provide pressure to the water cooling system, and allow for the expansion and contraction of the water within the water cooling system as the water temperature changes.

[0069] Typically, a cooling system is provided upstream of the deaerator 78. The cooling system comprises a cooler 79, which may be a heat exchanger with seawater, for example if the engine is installed on a ship. The cooler 79 may be a heat exchanger with another cooling medium. The cooler 79 is fluidly connected to the primary circulation line 73 by a third control valve 71, for example a three-way control valve. The cooler 79 is also arranged in parallel with an orifice, which is not depicted in FIG. 4 but is depicted as orifice 83 in FIGS. 5 and 6. The orifice restricts the flow approximately equal to the flow restriction by the cooler 79. This is so that a change in the amount of the water flow that passes through the cooler 79 relative to the amount that bypasses the cooler 79 does not substantially affect the flow conditions, i.e. does not substantially affect the resistance experienced by the primary circulation pump 72. The third control valve 71 is under the control of the controller 100 and adjusts the ratio of water passing through the cooler 79 to water bypassing the cooler 79, and thereby the cooling capacity to control the temperature of the water in the primary cooling circuit 70. The controller 100 receives a signal indicative of the temperature of the cooling water from the first temperature sensor 75 and is configured to adjust the temperature of the water in the primary cooling circuit 70 to a temperature of, for example, 80-90°C, preferably below 95°C, with the target temperature being 85°C. The primary circulation line 73 is coupled to the engine (for example by means of a flange) by an engine water inlet 41 and an engine water outlet 42.

[0070] A fourth control valve 56 is arranged in the primary circulation line 73 downstream of the primary circulation pump 72 and its associated check valve. The fourth control valve 56 is, for example, a three-way valve. The fourth control valve 56 is preferably arranged in the primary circulation line 73 between the engine inlet 41 and the engine outlet 42. The fourth control valve 56 is connected to a return line 82 which is connected to the secondary circulation line 63 of the secondary circulation circuit 60. The secondary circulation line 63 has a secondary check valve 57. The return line 82 is connected to the secondary circulation line 60 upstream of the secondary check valve 57. A supply line 81 is connected to the primary circulation line 73 upstream of the fourth control valve 56 and to the secondary circulation line 63 downstream of the secondary check valve 57.

[0071] The pressure vessel 74 / expansion tank 77 together with the primary circulation pump 72 are configured to maintain a pressure sufficient to prevent boiling of the water in the primary and secondary cooling circuits 60, 70 up to a temperature of 140°C, preferably 130°C, i.e. to maintain a pressure of the water in the primary cooling circuit of at least 3 barg, preferably at least 4 barg, most preferably at least 5 barg.

[0072] The fourth control valve 56 is under the control of the control device 100 and adjusts the ratio between the water passing through it that is fed to the secondary circulation line 63 and the water that bypasses the secondary circulation line 63, and thus adjusts the amount of water in the primary circulation line 73 that is mixed with the water in the secondary circulation line 63 due to the water temperature in the secondary cooling circuit 60. The control device 100 receives a signal from the second temperature sensor 65 that is representative of the temperature of the cooling water in the secondary circulation line 63, and the control device 100 is configured to adjust the temperature of the water in the secondary cooling circuit 60, for example to a temperature above 100°C, preferably between 120 and 140°C. The secondary circulation pump 62 allows water to circulate in the secondary circulation line 63. Provisions are provided for bypassing the secondary circulation pump 62 so that the secondary circulation pump 62 can be bypassed when necessary.

[0073] The fourth control valve 56 is preferably a three-way control valve controlled by the controller 100. The fourth control valve 56 is disposed in the primary cooling circuit 70 and is fluidly connected to the secondary cooling circuit 60 via a supply line 82. The fourth control valve 56 is also configured to divert a controllable amount of water flow through the supply line 82 to the secondary cooling circuit 60, thereby diverting a same amount of water flow from the secondary cooling circuit 60 to the primary cooling circuit 70.

[0074] Since the cooling circuit 60 passes through the annular cooling chambers 23 of all cylinder liners 1, the cylinder covers 22, and in some embodiments, the housings of the exhaust valves 4, all cylinder liners 1, the cylinder covers 22, and in some embodiments, the housings of the exhaust valves 4 are operated at high temperatures. In other words, they are operated at higher temperatures than known large two-stroke internal combustion engines that operate with cooling water at a temperature of 80 to 90°C in the cooling chambers. This improves fuel efficiency.

[0075] The dashed rectangle in FIG. 4 indicates all components that are considered part of the actual engine, the remaining components can be considered as part of the water cooling system, i.e. auxiliary systems.

[0076] Figure 5 shows a second embodiment of the engine. In this embodiment, features and functions similar to those already described or illustrated are numbered with the same reference numerals as previously used. The engine and its operation in this embodiment is substantially similar to the previous embodiment, and therefore only the differences from the previous embodiment will be described in detail.

[0077] This embodiment has a primary cooling circuit 70 which is connected to the engine by an engine water inlet 41 and an engine water outlet 42. Part of the primary cooling circuit passes through the engine, in particular through the cooling chamber 23 and in some embodiments through the cylinder cover 22 and the housing of the exhaust valve 4 to cool these elements. In this embodiment, an expansion tank 77 serves to provide static pressure and form a reservoir to allow for expansion and contraction of the water in the primary cooling circuit 70 due to temperature fluctuations.

[0078] The expansion tank 77 together with the primary circulation pump 72 is arranged to maintain a pressure sufficient to prevent boiling of the water in the primary cooling circuit 70 up to a temperature of 140°C, preferably 130°C, i.e. arranged to maintain a pressure of the water in the primary cooling circuit of at least 3 barg, preferably at least 4 barg and most preferably at least 5 barg.

[0079] A supply pipe 89 is connected to the expansion tank 77 for refilling with water. The expansion tank 77 is also provided with a vent 90 to allow air above the water level in the expansion tank 77 to communicate with the atmosphere, thereby maintaining a constant pressure in the expansion tank. In some embodiments, a level sensor is provided to monitor the water level in the expansion tank 77. Thus, during normal operation, the expansion tank 77 is always partially filled with water.

[0080] Upstream of the degasser is a third control valve 71 and an orifice 83 associated with the cooler 79. The third control valve 71 operates under the control of the controller 100.

[0081] It should be understood that the primary cooling circuit may operate with more than one circulation pump to provide a sufficient level of redundancy. In this embodiment, three primary circulation pumps 72 are shown. A degassing vessel 78 is connected to the expansion tank 77 by a first vent pipe 85. The degassing vessel 78 allows air, gas, or vapor removed from the water in the primary cooling circuit 72 to escape to the atmosphere. The degassing vessel 78 is also connected to the expansion tank 77 by a supply pipe 84. The supply pipe 84 forms the main fluid connection between the primary circulation line 73 and the expansion tank 77 for conveying water pressure and exchanging a volume of water. A second vent pipe 87 connects the engine water outlet 42 directly to the expansion tank 77. Thus, in this embodiment, there are three lines 84, 85, 87 connecting the expansion tank 77 to the primary circulation line 73. Each of these three lines 84, 85, 87 is provided with an orifice 87, 88, 93 for adjusting the flow of water from the primary circulation line 73 to the expansion tank 77. If the water in the primary circulation line 73 stagnates, the water may boil in the part of the circulation line 73 inside the engine (particularly the part inside the cooling chamber 23 and the part passing through the cylinder cover 22). In particular, when the engine is operated at high load or maximum load and the cylinder liner 1 and the cylinder cover 22 are relatively hot, the orifices 87, 88, 93 can throttle the amount of water from the primary circulation line 73 to the expansion tank 77. In such a situation, it is advantageous for the boiling water not to drain all the water from the primary circulation line 73 to the expansion tank 77 (or from the expansion tank 77 to the atmosphere). This is achieved by the throttling effect of the orifices 87, 88, 93. The orifices 87, 88, 93 slow the flow of water towards the expansion tank 77, thereby allowing sufficient time for the cylinder liner 1 (and cylinder cover 22 and housing of the exhaust valve 4) to cool passively, so that most or all of the water in the primary circulation line 73 is retained within the primary circulation line 73. The piping forming the supply pipe 84, the first vent pipe 85 and the second vent pipe 87 will usually have a substantially constant internal diameter, typically between 35 and 80 mm. The orifices preferably have a minimum diameter between 3 and 5 mm.Preferably, orifices 87,88,93 reduce the cross-sectional area through which fluid can flow relative to piping 84,85,87 by at least a factor of 50, preferably at least a factor of 100, and most preferably at least a factor of 150.

[0082] In some embodiments, a first check valve 91 is disposed in parallel with an orifice 93 in the supply line 84 to ensure rapid filling of the circulation line 73 with water from the expansion tank 77 upon contraction of the water.

[0083] In some embodiments, a pressure setting valve 92 is disposed in the supply line 84 in parallel with the orifice 93. It allows water to flow from the primary cooling line 73 to the pressure vessel 74 or expansion tank 77 when the pressure of the water in the primary cooling circuit 70 rises above a threshold value (preferably due to expansion of the water in the primary cooling circuit 70). This threshold value is a pressure threshold set by the opening pressure of the pressure setting valve.

[0084] In some embodiments, a first control valve 94 is disposed in the supply pipe 84 in parallel with the orifice 93 for initial charging of the cooling circuit 70 with water.

[0085] In some embodiments, the controller is adapted to receive a first signal representative of the temperature of the water in the cooling circuit, preferably near where the water leaves the engine and enters the primary circulation line. The controller 100 is then configured to control the temperature of the water in the primary cooling circuit 70 to a temperature of at least 100°C, preferably between 120-130°C. The cooler 79 is controlled by the controller 100 and applies a selective amount of cooling to the water in the primary cooling circuit 70 under the control of the controller 100. The cooler 79 is configured to control the temperature of the water in the primary cooling circuit 70 to a temperature of at least 100°C, preferably between 120-130°C by adjusting the amount of cooling applied to the water in the primary cooling circuit 70.

[0086] The engine is configured to operate over a load range between a minimum engine load and a maximum engine load (maximum continuous rating). The controller 100 is configured to control the temperature of the water at a location in the primary cooling circuit 70 proximate to where the water leaves the engine and enters the primary circulation line 73 to a temperature greater than 100° C. for at least the maximum engine load, and preferably for the entire engine load range between the minimum and maximum engine loads.

[0087] Although the embodiment of FIG. 5 is disclosed using an expansion tank 77, this embodiment would work equally well using a pressure vessel 74. Although the embodiment of FIG. 5 is disclosed using a single cooling circuit 70 (primary cooling circuit 60), this embodiment would work equally well using a combination of a primary cooling circuit 70 and a secondary cooling circuit 60, as disclosed with reference to FIG.

[0088] Figure 6 shows a third embodiment of the engine. In this embodiment, features and functions similar to those already described or illustrated are numbered with the same reference numerals as previously used. The engine and its operation in this embodiment is substantially similar to the previous embodiments, and therefore only the differences from the previous embodiments will be described in detail.

[0089] The third embodiment is essentially the same as the second embodiment, except that a pressure vessel 74 is used to accommodate pressure and accommodate the expansion and contraction of water in the primary circulation line 73. Furthermore, the supply pipe 84 is not provided with an orifice 93, but instead an orifice 98 is arranged in the primary circulation line 73 downstream of the engine water outlet 42. The return valve between the primary circulation pump 72 and the engine water inlet 41 prevents water from flowing from the engine inlet towards the primary circulation pump 72 in a situation where there is water stagnation, for example, when the circulation pump 72 fails or the electric motor driving the circulation pump 72 is not powered. Thus, in such a situation where there is water stagnation in the primary circulation line 73, for example, the water in the annular cooling chamber 23 can only flow out through the engine water outlet 42. However, the orifice 98 throttles the flow from the annular cooling chamber 23 and the cylinder cover 22 to the pressure vessel 74. However, during normal operation, the orifice 98 should not restrict the circulation of water in the primary circulation line 73. As such, in some embodiments, a second control valve 97 is disposed in parallel with the orifice 98. The second control valve 97 is normally open and automatically closes, for example, when water stagnates in the primary circulation line 73. In some embodiments, the second control valve can be configured to automatically close by a hydraulic or hydromechanical device in response to a lack of flow in the primary circulation line 73. In some embodiments, the second control valve can be configured to automatically close by an electronic device in response to a signal, for example, a signal indicating that the primary circulation pump 72 is not operating or another signal indicative of stagnation of water in the primary circulation line.

[0090] Although the embodiment of Figure 6 is disclosed using a pressure vessel 74, it will be understood that this embodiment will function equally well using an expansion tank 77. Although the embodiment of Figure 6 is disclosed using a single cooling circuit 70 (primary cooling circuit 60), this embodiment will function equally well using a combination of a primary cooling circuit 70 and a secondary cooling circuit 60, as disclosed with reference to Figure 4.

[0091] Various ways of understanding and implementation of the invention have been described with several examples. The above embodiments can be combined in various ways. In addition, by studying the specification, drawings, and claims of this application, a person skilled in the art will understand and be able to embody many variations in addition to the described examples in carrying out the invention described in the claims. The words "comprise", "have", and "include" in the claims do not exclude the presence of elements or steps not described. Even if the number of elements described in the claims is not explicitly stated as being multiple, the presence of multiple elements is not excluded. The functions of several elements described in the claims may be performed by a single processor, controller, or other unit. The fact that several items are described in separate dependent claims does not exclude them from being combined and may be advantageously combined. The signs used in the claims should not be interpreted as limiting the scope of the invention.

Claims

1. A crosshead type large two-stroke turbocharged uniflow scavenging internal combustion engine, a plurality of combustion chambers each defined by a cylinder liner, a piston configured to reciprocate within the cylinder liner, and a cylinder cover; a scavenging port for introducing scavenging gas into the combustion chamber, the scavenging port being disposed in the cylinder liner; At least one cooling passage within the cylinder cover; an annular cooling chamber surrounding a portion of the cylinder liner; exhaust outlets disposed in the cylinder cover, each of the exhaust outlets being controlled by an exhaust valve; The plurality of combustion chambers are connected to a scavenging air receiver through the scavenging ports and to an exhaust air receiver through the exhaust outlet, and the engine further comprises: an exhaust system having a turbine driven by the exhaust flow, the turbine being a turbocharging system; an air intake system having a compressor of the turbocharging system configured to supply pressurized scavenging air to the scavenging receiver; a primary cooling pathway having at least one primary circulation pump configured to circulate water through the primary cooling pathway, the at least one cooling pathway being a portion of the primary cooling pathway; and a pressure vessel or expansion tank connected by a fluid connection to said primary cooling path to allow expansion and contraction of water in said primary cooling path, said fluid connection being formed by one or more conduits, each of said plurality of conduits having an orifice for throttling the flow of water from said primary cooling path to said pressure vessel or expansion tank.

2. 2. The engine of claim 1, wherein the orifice reduces a cross-sectional area through which fluid can flow for one or more of the conduits forming the fluid connection by at least 50 times, or at least 100 times, or at least 150 times.

3. the one or more conduits have a substantially constant inner diameter, the inner diameter being between 35 mm and 80 mm; The at least one orifice has a minimum diameter of between 3 mm and 5 mm.

3. The engine of claim 2.

4. 4. An engine according to claim 1, further comprising a first check valve in said fluid connection.

5. An engine as described in claim 4, wherein the first check valve is arranged in parallel with one of the at least one orifice in a supply pipe fluidly connecting the pressure vessel or expansion tank to the degassing device and allows water to flow from the pressure vessel or expansion tank to the primary cooling path when water in the cooling path contracts.

6. 4. An engine as claimed in any one of claims 1 to 3, wherein a pressure setting valve is provided in the fluid connection to allow water to flow from the primary cooling path to the pressure vessel or the expansion tank when the pressure of the water in the primary cooling path rises above a threshold value due to expansion of the water in the primary cooling path, the pressure setting valve being disposed in parallel with one of the at least one orifice in a supply pipe fluidly connecting the pressure vessel or the expansion tank to a degassing device.

7. An engine according to any one of claims 1 to 3, wherein the engine comprises a first control valve in the fluid connection.

8. the first control valve is disposed in parallel with one of the at least one orifice in a supply line fluidly connecting the pressure vessel or the expansion tank to a degasser; The first control valve is provided for initially filling the cooling path with water; 8. The engine of claim 7.

9. - an engine cooling water inlet and an engine cooling water outlet; a primary circulation line connecting the engine cooling water outlet to the engine cooling water inlet; a degasser disposed in the primary circulation line and connected to the pressure vessel or the expansion tank by a supply line having an orifice and a first vent line having an orifice; 4. An engine according to claim 1 , comprising:

10. An engine as described in claim 1, further comprising a second vent pipe connecting an engine water outlet to the pressure vessel or the expansion tank, the second vent pipe having an orifice.

11. 10. The engine of claim 9, further comprising an orifice in the primary circulation line upstream of the degasser and a second control valve disposed in parallel with the orifice.

12. The engine of claim 9 , wherein the at least one primary circulation pump is disposed upstream of the degasser.

13. 10. The engine of claim 9, further comprising a cooler for cooling water in the primary cooling path, the cooler being disposed in parallel with a cooling restriction disposed in the primary circulation line.

14. The engine of claim 13, wherein the cooler is connected to the primary circulation line by a third control valve.

15. a controller that receives a first signal representative of a temperature of water in the cooling path; The control device is configured to control the temperature of the water in the primary cooling path to at least 100°C or 120-130°C; An engine according to any one of claims 1 to 3.

16. 16. The engine of claim 15, further comprising a cooler, the cooler being controlled by the controller and configured to apply selective amounts of cooling to water in the primary cooling path under control of the controller to control a temperature of water in the primary cooling path to at least 100°C or between 120-130°C by adjusting the amount of cooling applied to water in the primary cooling path.

17. The engine configured to operate over an engine load range between a minimum engine load and a maximum engine load; The control device is configured to control the temperature of the water in the primary cooling path to a temperature greater than 100° C. for at least maximum engine load.

16. The engine of claim 15.

18. The engine of claim 17, wherein the control device is configured to control the temperature at a location within the primary cooling path near where water leaves the engine and enters a primary circulation line.

19. 4. An engine as claimed in any preceding claim, wherein the primary cooling path is connected to the pressure vessel or expansion tank to allow expansion and contraction of water within the primary cooling path.

20. 4. An engine as claimed in any one of claims 1 to 3, wherein the primary cooling path has a first portion inside the engine and a second portion outside the engine, the first portion having an area from an engine inlet to an engine outlet, the first portion having a cooling chamber.

21. The engine of claim 20, wherein the first portion has at least one flow passage within the cylinder cover.

22. The engine of claim 20, wherein the first portion has at least one passage or chamber within a housing of the exhaust valve.

23. 21. The engine of claim 20, wherein the second portion includes a primary circulation line having at least one primary circulation pump and a degasser upstream of the at least one primary circulation pump.

24. The engine of claim 23, wherein the second portion has a cooling device upstream of the degassing device.

25. 4. An engine according to claim 1, further comprising an annular water jacket surrounding at least a portion of the cylinder liner and defining, together with a radially outer portion of the cylinder liner, the annular cooling chamber.

26. An engine as described in any of claims 1 to 3, wherein the annular cooling chamber is part of the primary cooling path.

27. A crosshead type large two-stroke turbocharged uniflow scavenging internal combustion engine, a plurality of combustion chambers each defined by a cylinder liner, a piston configured to reciprocate within the cylinder liner, and a cylinder cover; at least one cooling passage in the cylinder cover; and a scavenging port for introducing scavenging gas into the at least one combustion chamber, the scavenging port being disposed in each of the cylinder liners; an annular cooling chamber surrounding a portion of the cylinder liner; exhaust outlets disposed in the cylinder cover, each of the exhaust outlets being controlled by an exhaust valve; The plurality of combustion chambers are connected to a scavenging air receiver through the scavenging ports and to an exhaust air receiver through the exhaust outlet, and the engine further comprises: an exhaust system having a turbine driven by the exhaust flow, the turbine being a turbocharging system; an air intake system having a compressor of the turbocharging system configured to supply pressurized scavenging air to the scavenging receiver; a secondary cooling pathway having a secondary circulation pump configured to circulate water through the secondary cooling pathway, the at least one cooling pathway being a portion of the secondary cooling pathway; Equipped with the secondary cooling pathway is fluidly connected to the primary cooling pathway by a valve system for mixing water from the primary cooling pathway with water in the secondary cooling pathway; the primary cooling path includes at least one primary circulation pump for circulating water within the primary cooling path; the engine further comprising a controller receiving a first signal representative of a temperature of the water in the secondary cooling path and a second signal representative of a temperature of the water in the primary cooling path; The control device is configured to control the temperature of the water in the primary cooling path to a temperature less than 95° C. and to control the temperature of the water in the secondary cooling path to a temperature equal to or greater than 100° C. or between 120° C. and 140° C.; institution.

28. The engine described in claim 27, wherein the control device controls the temperature of the primary cooling path by controlling the valve system to adjust the amount of water from the primary cooling path that is mixed with water in the secondary cooling path.

29. The engine control system according to claim 28, wherein the engine control system is configured to operate over an engine load range between a minimum engine load and a maximum engine load; The control device is configured to control the temperature of the water in the secondary cooling path to a temperature greater than 100° C., at least for maximum engine load.

28. The engine of claim 27.

30. 30. The engine of claim 27 or 29, wherein the valve system includes a fourth control valve disposed in the primary cooling path and fluidly connected to the secondary cooling path via a return line, the fourth control valve configured to divert a controllable amount of water flow from the secondary cooling path via the return line.

31. The engine of claim 30, wherein the fourth control valve is a three-way control valve controlled by the control device.

32. 32. The engine of claim 31, further comprising a supply line upstream of the fourth control valve connecting the secondary cooling path to the primary cooling path.

33. 33. The engine of claim 32, wherein the valve system includes a second check valve disposed in the secondary cooling path, the second check valve being disposed between a location where the return line connects to the secondary cooling path and a location where the supply line connects to the secondary cooling path.

34. 30. An engine as claimed in any one of claims 27 to 29, comprising a cooler for cooling water in the secondary cooling path.

35. A deaerator is provided in the primary cooling path and connected to a pressure vessel or an expansion tank, The degassing device adjusts water pressure in the primary cooling path and the secondary cooling path to allow expansion and contraction of water in the primary cooling path and the secondary cooling path.

30. An engine according to any one of claims 27 to 29.

36. An engine as described in claim 35, wherein the pressure vessel or expansion tank is configured to maintain sufficient pressure to prevent water from boiling in the secondary cooling path up to a water temperature of 140°C or 130°C.

37. An engine as described in any of claims 27 to 29, wherein the annular cooling chamber is part of the secondary cooling path.

38. 1. A method of operating a large crosshead type two-stroke turbocharged uniflow scavenged internal combustion engine, comprising: a plurality of combustion chambers each defined by a cylinder liner, a piston configured to reciprocate within the cylinder liner, and a cylinder cover; At least one cooling passage within the cylinder cover; a scavenging port disposed in each of the cylinder liners for introducing scavenging gas into the at least one combustion chamber; an annular cooling chamber surrounding a portion of the cylinder liner; exhaust outlets disposed in the cylinder cover, each of the exhaust outlets being controlled by an exhaust valve; The plurality of combustion chambers are connected to a scavenging air receiver through the scavenging ports and to an exhaust air receiver through the exhaust outlet, and the engine further comprises: an exhaust system having a turbine driven by the exhaust flow, the turbine being a turbocharging system; an air intake system having a compressor of the turbocharging system configured to supply pressurized scavenging air to the scavenging receiver; a secondary cooling pathway having a secondary circulation pump configured to circulate water through the secondary cooling pathway, the at least one cooling pathway being a portion of the secondary cooling pathway; Equipped with the secondary cooling pathway is fluidly connected to the primary cooling pathway by a valve system for mixing water from the primary cooling pathway with water in the secondary cooling pathway; the primary cooling path has at least one primary circulation pump for circulating cooling water within the primary cooling path; And the method further comprises: measuring a temperature of the water in the secondary cooling path; measuring a temperature of the water in the primary cooling path; Controlling the temperature of the water in the primary cooling path to less than 95°C; Controlling the temperature of the water in the secondary cooling path to above 100°C, or between 120°C and 140°C; A method comprising:

39. The method of claim 38, wherein the annular cooling chamber is part of the secondary cooling path.

40. the engine is configured to operate over an engine load range between a minimum engine load and a maximum engine load; The method includes controlling the temperature of water in the secondary cooling path to a temperature above 100°C or between 120°C and 140°C, at least for maximum engine load.

39. The method of claim 38.

41. 41. The method of claim 38 or 40, wherein controlling the temperature of the secondary cooling path water comprises regulating the amount of water from the primary cooling path that is mixed with the secondary cooling path water by controlling a valve system.

42. 41. A method according to any of claims 38 to 40, comprising maintaining a pressure in the primary and secondary cooling paths at at least 5 barg.

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