DK202101100A1

DK202101100A1 - Fuel supply system for large two-stroke turbo-charged uniflow-scavenged crosshead internal combustion engine

Info

Publication number: DK202101100A1
Application number: DKPA202101100A
Authority: DK
Inventors: Kourtidis Nikolaos
Original assignee: Man Energy Solutions Filial Af Man Energy Solutions Se Tyskland
Priority date: 2021-11-22
Filing date: 2021-11-22
Publication date: 2022-09-08

Abstract

Described is a fuel supply system (5) for a large two-stroke turbo-charged uniflow-scavenged crosshead internal combustion engine comprising a gaseous fuel supply line for supplying a gaseous fuel (25) from a fuel supply to the internal combustion engine, said gaseous fuel supply line comprises a double walled piping system comprising a first pipe (7) configured to guide the gaseous fuel (25) to the internal combustion engine and a second pipe (8) circumferenting the first pipe (7) defining a space (9) between the first pipe (7) and the second pipe (8) for preventing gaseous fuel leaking from the gaseous fuel supply line, wherein said space (9) comprises a fluid (10). The fuel supply system (5) is peculiar in that it comprises a heating unit (30) to provide heat to the fluid (10) in said space (9). Hence, it will be possible to obtain an effective supply of gaseous fuel (25) to the internal combustion engine without any risk of condensation of the gaseous fuel in the first pipe (7) configured to guide the gaseous fuel (25) to the internal combustion engine. This is due to the fact that the heating unit (30) may keep the fluid (10) in the space (9) between the first pipe (7) and the second pipe (8) at a required temperature to prevent heat loss and thus condensation of the gaseous fuel (25).

Description

DK 2021 01100 A1 1 FUEL SUPPLY SYSTEM FOR LARGE TWO-STROKE TURBO-CHARGED UNIFLOW-SCAVENGED CROSSHEAD INTERNAL COMBUSTION ENGINE

TECHNICAL FIELD The present invention relates to a fuel supply system for a large two-stroke turbo-charged uniflow-scavenged crosshead internal combustion engine comprising a gaseous fuel supply line for supplying a gaseous fuel from a fuel supply to the internal combustion engine, said gaseous fuel supply line comprises a double walled piping system comprising a first pipe configured to guide the gaseous fuel to the internal combustion engine and a second pipe circumferenting the first pipe defining a space between the first pipe and the second pipe for preventing gaseous fuel leaking from the gaseous fuel supply line, wherein said space comprises a fluid.

BACKGROUND Large two-stroke turbo-charged uniflow-scavenged crosshead engines are typically used in propulsion systems of marine vessels or as the prime mover in power plants. Typically, these engines are operated with heavy fuel oll marine diesel, an/or with gaseous fuel, for example, gaseous methanol, LPG, LNG, ethane, gaseous ammonia, methanol and/or other similar fuels.. In designing vessels, e.g. container ships and tankers, the main focus is safety on board and to prevent environmental damage. In order to protect the environment, vessels may be required to run on other types of fuel, such as the gaseous fuels mentioned above. Such requirements give rise to challenges since such gaseous fuels are low-flashpoint fuels and may more easily ignite inducing a higher risk in the engine room on board the vessel. Therefore, regulations require that the fuel supply line for supplying gaseous fuel to the engine to be double-walled in order to reduce the leak risk and thus reduce unintended ignition of such leaking gaseous fuel. The fluid in

DK 2021 01100 A1 2 the double walled piping system is ventilated or circulated. The natural convection created by the ventilation or circulation of the fluid in the double walled piping system may result in heat losses and thus condensation of the gaseous fuel, such as gaseous ammonia, in the first pipe configured to guide the gaseous fuel. Consequently, the engine performance will be negatively affected by liquid flowing in the first pipe, which is designed and intended for gaseous fuel. At the same time, after operation the risk of residual fuel in the pipes can be eliminated.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fuel supply system of the kind mentioned in the introduction having a double walled piping system, where the above mentioned challenges relating to condensation of the gaseous fuel are at least significantly reduced. The foregoing and other objects are achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description, and the figures.

According to a first aspect, there is provided a fuel supply system for a large two-stroke turbo-charged uniflow-scavenged crosshead internal combustion engine comprising a gaseous fuel supply line for supplying a gaseous fuel from a fuel supply to the internal combustion engine, said gaseous fuel supply line comprises a double walled piping system comprising a first pipe configured to guide the gaseous fuel to the internal combustion engine and a second pipe circumferenting the first pipe defining a space between the first pipe and the second pipe for preventing gaseous fuel leaking from the gaseous fuel supply line, wherein said space comprises a fluid, and being characterized in that it comprises a heating unit to provide heat to the fluid in said space. Hence, it will be possible to obtain an effective supply of gaseous fuel to the internal combustion engine without any risk of condensation of the gaseous

DK 2021 01100 A1 3 fuel in the first pipe configured to guide the gaseous fuel to the internal combustion engine. This is due to the fact that the heating unit may keep the fluid in the space between the first pipe and the second pipe at a required temperature to prevent heat loss and thus condensation of the gaseous fuel. The heat transfer from the fluid in the space to the main fuel line, i.e. the first pipe, will enable a faster evaporation of the gaseous fuel in said first pipe, thus reducing the total amount of purging volume needed when the operation of the engine is stopped. If the whole piping system is warmer, it is easier to purge it so a side effect by heating the fluid in the space is that less nitrogen (purging media) is consumed to clean the pipes after operation. The heating unit may be constituted of any heating unit capable of providing heat to the fluid in the space between the first pipe and the second pipe. Thus the heating unit may as examples be an electrical heater or a heat exchanger.

The heating unit may advantageously be installed close to an inlet to introduce fluid into the space between the first pipe and the second pipe, so as to minimize the installation The internal combustion engine may be a dual-fuel engine capable of operating in a liquid fuel mode, in which the main fuel is diesel or heavy fuel oil, and a gaseous fuel mode, in which the main fuel is a gaseous fuel. In the gaseous fuel mode, the internal combustion engine operates as a Otto cycle engine and the gaseous fuel is ignited by a pilot liquid fuel or a spark plug. The gaseous fuel may comprise gaseous methanol, LPG, LNG, gaseous ethane and/or gaseous ammonia. Additionally, the gaseous fuel pressure may be above 300 bar. The mentioned gaseous fuels are so-called low flash point fuels, which are fuels having a flash point under 60 °C at 1 atm. The fluid in the space between the first pipe and the second pipe may be a liquid, such as water, ion liquids, silicone liquids or a combination thereof, or a

DK 2021 01100 A1 4 gas, preferably an inert gas. Also, the fluid may have a higher heat capacity than that of the gaseous fuel. Moreover, the liquid may have a compressibility of less than 9-109 Pa"! at 25 °C and a bulk modulus over 1.1 GPa. In addition, the liquid may be non-corrosive, non-toxic, and/or not inflammable.

In case the fluid is a liquid, the fuel supply system according to invention may further comprise a pump, such as a variable displacement pump, which may be an axial piston pump with an adjustable swashplate. The pump may provide a predetermined flow rate of the liquid in the space and have a capacity of less than 100 cm%/minute. The heating unit may be positioned on either side of the pump as seen in the direction of flow of the liquid.

In case the fluid is a gas, the fuel supply system according to invention may further comprise a fan, such as a variable displacement fan. The engine size may vary from small engines where the volume of the space between the first and second pipe is about 100 liters to large engines where the space is about 500 liters. As the gas according to the regulations has to be changed 30 times per hour, the fan should have a capacity of between 3.000 and 15.000 I/h. The pressure of the gas leaving the fan is a little above atmospheric pressure and provides a simple gas flow.

Furthermore, the pump or fan may be operatibly connected with a control unit for controlling the fluid pressure in the space.

The fuel supply system according to invention may further comprise a check valve fluidly connected to an outlet of the pump or fan for letting liquid or gas into the space but preventing the liquid or gas from returning.

Additionally, the control unit may comprise an adjustable regulation means connected to the pump or fan for adjusting an output pressure of the pump or fan.

DK 2021 01100 A1 Moreover, in case the fluid is a liquid, the fuel supply system may further comprise a throttle for leaking part of the liquid from the space to a liquid tank. Furthermore, the pump or fan may be operatibly connected to the control unit 5 for controlling the fluid pressure PI to maintain a substantially constant pressure in the space. In addition, the pump or fan may circulate the fluid in the space to obtain optimum regulation the temperature of the gaseous fuel in the first pipe.

Moreover, the fuel supply system may further comprise a system control unit for operating a system valve to close the supply of gaseous fuel from the gaseous fuel supply line when a leakage is detected, the system control unit comprising a sensor for measuring pressure and/or temperature of the fluid in the space for detection of leakage in the gaseous fuel supply line. Additionally, the system control unit may be configured to open a second fuel supply line supplying another gaseous fuel, conventional fuel, marine diesel, or "heavy fuel” to the internal combustion engine when closing the system valve.

Further, the system control unit may comprise a sensor for measuring pressure and/or temperature of the gaseous fuel in the first pipe. The required temperature of the gaseous fuel depends on the gaseous fuel used and the pressure of the gaseous fuel in the first pipe. The temperature of the gaseous fuel in the first pipe should preferably be about 5 °C above the condensation temperature of the gaseous fuel at the given pressure. Also, the fluid may comprise a tracer for detection of a position of a leak in the first pipe, the tracer may be a colourant or a chemical. In case the fluid is a liquid, it may comprise an emulsified oil. Moreover, the first pipe and/or the second pipe may have a circular cross- section, a rectangular cross-section, or a triangular cross-section.

DK 2021 01100 A1 6

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be explained in more details with reference to the example embodiment shown in the drawings, in which: Fig. 1 shows a diagram of part of a first embodiment of a fuel supply system according to the invention, and Fig. 2 shows a diagram of part of a second embodiment of a fuel supply system according to the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS In Fig. 1 shows a diagram of part of a first embodiment of a fuel supply system 5 for supplying gaseous fuel 25 from a gaseous fuel supply, not shown. The gaseous fuel supply line of the fuel supply system 5 comprises a first pipe 7 configured to guide gaseous fuel 25 at a predetermined fuel pressure Pg to the internal combustion engine 2. At least along the part of the first pipe 7 which is arranged in the engine room of a vessel, the gaseous fuel supply line comprises a second pipe 8 circumferenting the first pipe 7 defining a space 9 between the first pipe 7 and the second pipe 8 for preventing gaseous fuel leaking from the gaseous fuel supply line into the engine room. In the embodiment shown in Fig. 1 the space 9 comprises a liquid 10 having a liquid pressure PI that is higher than the fuel pressure Pg of the gaseous fuel 25 in the first pipe 7. As shown in Fig. 1, the gaseous fuel supply system 5 further comprises a pump 11, such as a variable displacement pump. The pump 11 is driven by a motor 24, such as an asynchronous electric motor, which is connected with a pump control unit 12, for controlling the liquid pressure (Pl) in order to maintain a substantially constant pressure in the space 9. The fuel supply system 5 further comprises a check valve 16 fluidly connected to an outlet 17 of the pump 11 for letting liquid 10 into the space 9 but preventing the liquid 10 from returning.

DK 2021 01100 A1 7 The gaseous fuel supply system 5 comprises an inlet 29 to introduce liquid 10 into the space 9 between the first pipe 7 and the second pipe 8. The pump control unit 12 comprises an adjustable valve 18 fluidly connected to the outlet 17 of the pump 11, and pump control unit 12 comprises a cylinder 21, where the cylinder 21 is connected to the pump 11 for adjusting an output pressure of the pump 11. Thus, the pump control unit 12 is operationally connected to the pump 11 for regulating an output pressure of the pump 11. The pump 11 circulates the liquid 10 in the space 9 The fuel supply system 5 further comprises a throttle 19 for leaking part of the liquid 10 from the space 9 to a liquid tank 20, so as to maintain a small circulation in the space 9 and thus a slight activation of the pump 11. According to the invention, the fuel supply system further comprises a heating unit 30 for supplying heat to liquid 10 before it enters the space 9. In this way it is possible to control the temperature of and thus avoid condensation of the gaseous fuel 25, e.g. if, because of cold weather lowering the temperature of the second pipe 8 and thus the liquid 10, a risk is present for the gaseous fuel 25 to be cooled down somewhere in the gaseous fuel supply system 5. In such a situation the liquid 10 is heated before entering the space 9. The temperature of the gaseous fuel in the first pipe 7 is about 5 °C above the condensation temperature of the gaseous fuel at the given pressure. Fig. 2 shows a diagram of part of a second embodiment of a fuel supply system

5. The main difference between the system shown in Fig. 1 and 2 is that in Fig. 2 the fluid in the space 9 between the first pipe 7 and the second pipe 8 is a gas, preferably an inert gas. The gas is vented to the space 9 by means of a fan 31 from a not shown gas reservoir.

Claims

DK 2021 01100 A1 1 Claims

1. A fuel supply system (5) for a large two-stroke turbo-charged uniflow- scavenged crosshead internal combustion engine comprising a gaseous fuel supply line for supplying a gaseous fuel (25) from a fuel supply to the internal combustion engine, said gaseous fuel supply line comprises a double walled piping system comprising a first pipe (7) configured to guide the gaseous fuel (25) to the internal combustion engine and a second pipe (8) circumferenting the first pipe (7) defining a space (9) between the first pipe (7) and the second pipe (8) for preventing gaseous fuel leaking from the gaseous fuel supply line, wherein said space (9) comprises a fluid (10), characterized in that it comprises a heating unit (30) to provide heat to the fluid (10) in said space (9).

2. A fuel supply system (5) according to claim 1, characterized in that the heating unit (30) is an electrical heater or a heat exchanger.

3. A fuel supply system (5) according to claim 1 or 2, characterized in that the heating unit (30) is installed close to an inlet (29) to introduce fluid into the space (9) between the first pipe (7) and the second pipe (8).

4. A fuel supply system (5) according to claim 1, 2 or 3, characterized in that the temperature of the gaseous fuel in the first pipe (7) is about 5 °C above the condensation temperature of the gaseous fuel at the given pressure.

5. Afuel supply system (5) according to any of claims 1 to 4, characterized in that the internal combustion engine is a dual-fuel engine capable of operating in a liquid fuel mode, in which the main fuel is diesel or heavy fuel oil, and a gaseous fuel mode, in which the main fuel is a gaseous fuel.

6. Afuel supply system (5) according to any of claims 1 to 5, characterized in that in the gaseous fuel mode, the internal combustion engine operates as a Otto cycle engine and the gaseous fuel is ignited by a pilot liquid fuel or a spark plug.

DK 2021 01100 A1 2

7. A fuel supply system (5) according to any of the proceeding claims, characterized in that the gaseous fuel comprises gaseous methanol, LPG, LNG, gaseous ethane and/or gaseous ammonia.

8. A fuel supply system (5) according to any of the proceeding claims, characterized in that the fluid (10) in the space (9) between the first pipe (7) and the second pipe (8) may be a liquid, such as water, ion liquids, silicone liquids or a combination thereof, or a gas, preferably an inert gas.

9. A vessel comprising a fuel supply system (5) according any of claims 1 to 8.