Fuel injection device, piston engine, acoustic resonator and method of operating piston engine

Abstract

A fuel injection device for a piston engine comprises a fuel injector (1) configured to inject liquid fuel into an inlet passage (5) of the engine and a component (2) for generating and applying an acoustic field to the fuel injected into the inlet passage (5) to atomize the injected fuel outside the fuel injector (1).

Description

Technical Field

[0001] This invention relates to a fuel injection device for a piston engine according to claim 1. The invention also relates to a piston engine, an acoustic resonator to be retrofitted to a piston engine, and a method of operating the piston engine. Background Technology

[0002] Large piston engines, such as those used in marine and power plants, typically operate using liquid fossil-based hydrocarbon fuels, such as conventional light or heavy fuel oils. Over time, the use of natural gas and other gaseous fuels has increased. Conventional liquid hydrocarbon fuels are usually injected directly into the cylinder. Gaseous fuels can be introduced directly into the main combustion chamber or via a pre-combustion chamber into the intake manifold or cylinder. In particular, dual-fuel engines that can operate with two different fuels can have different injection strategies for the two fuels. This can be applied to the main fuel and, possibly, a pilot fuel. The use of a pilot fuel improves the ignition of the main fuel, which typically occurs via compression ignition. Depending on the fuel and combustion phase, the combustion modes can range from premixed combustion to diffusion combustion.

[0003] There is a growing demand for engines that can utilize alternative fuels (such as hydrogen, ammonia, and methanol) as a portion of their fuel mix, and preferably as the main component. Due to the different properties of various fuels, new solutions for fuel injection are also needed, which typically have a major impact on ignition and combustion phasing.

[0004] Especially in smaller, high-speed engines, such as those in motor vehicles and machinery, spark ignition and pure Otto mode can be used. In larger, medium-speed engines, diesel combustion mode and direct injection into the cylinders can be used. It should be noted that larger engines, such as those used in marine and power plants, typically have significantly longer lifespans than engines used in automobiles, for example. Therefore, it is important to find solutions that can be improved for these larger engines, utilizing their major, expensive components while still improving their efficiency and emissions performance. This may result in solutions where, for example, direct injection engines need to be retrofitted later to utilize port fuel injection as part of their fuel injection strategy.

[0005] Among emerging bio-based fuels, methanol is known to be suitable for compression or spark ignition. However, achieving maximum efficiency and minimum emissions with methanol, especially when used as a primary fuel, is challenging. Methanol's characteristics include a high heat of vaporization and low saturation pressure. When targeting premixed combustion, methanol intake manifold injection involves the risk of wall wetting due to the high heat of vaporization; wall wetting refers to fuel condensation on the inlet port, the inner surface of the cylinder liner, or the surface of the intake valve. This leads to variations between different combustion cycles and also creates problems when optimizing engine operation under varying loads and / or speeds. All these effects reflect the engine's overall fuel efficiency and emissions.

[0006] Large piston engines operating at nominal power levels typically operate using fairly high boost pressures generated by turbochargers. When combined with port fuel injection, the high pressure and high air velocity affect fuel delivery in the inlet manifold and can increase the risk of wall wetting, making optimized and well-controlled port injection more challenging.

[0007] Wall wetting can lead to incomplete combustion, and fuel condensation on the cylinder liners can also wash away and / or contaminate the lubricating oil. Fuel interacting with the cylinder liners can cause residual buildup on the liner surfaces, clogging the cross-grooving formed by honing, resulting in increased fuel consumption. These can lead to premature wear of related engine components and / or more frequent oil changes and other servicing needs. To avoid wall wetting or the other problems mentioned above, effective atomization of methanol and other fuels with similar behavior is therefore important for optimizing engine performance and avoiding unnecessary servicing. Summary of the Invention

[0008] The object of this invention is to provide an improved fuel injection device for a piston engine. Another object of this invention is to provide an improved piston engine and an acoustic resonator to be retrofitted to a piston engine. Yet another object of this invention is to provide an improved method of operating a piston engine.

[0009] The fuel injection device according to the invention includes a fuel injector configured to inject liquid fuel into an inlet passage of an engine, and a component for generating a sound field and applying the sound field to the fuel injected into the inlet passage to atomize the fuel injected outside the fuel injector.

[0010] The piston engine according to the invention includes the fuel injection device defined above.

[0011] The acoustic resonator according to the invention is configured to be adapted to a piston engine to generate a sound field and apply the sound field to fuel injected into the engine inlet passage by means of a fuel injector, so as to atomize the fuel outside the fuel injector.

[0012] According to the present invention, a method for operating a piston engine includes the following steps: injecting liquid fuel into the engine inlet passage by means of a fuel injector, and applying a sound field to the fuel jet injected by the fuel injector to atomize the injected fuel outside the fuel injector.

[0013] By applying an acoustic field to the fuel jet injected into the inlet channel, the liquid jet surface can be disturbed by sound waves to influence the atomization process and promote the formation of small droplets. This is particularly beneficial when using fuels with high heat of vaporization, such as methanol. Effective fuel atomization helps avoid wall wetting and the adverse effects caused by it.

[0014] In the context of this application, the phrase "exterior of the fuel injector" should be understood to refer to the arrangement of the fuel spray after it has been initially sprayed through the injector's nozzle. The injector has one or more orifices through which pressurized liquid is propelled to form one or more fuel jets ejected from the injector. The design of the injector, particularly the design of the orifice openings, defines the characteristics and stages of the initial atomization of the fuel as it leaves the injector.

[0015] The operation of a fuel injector can be broadly divided into the following stages: injection initiation when the injector needle opens, steady-state injection when the needle opens, and injection termination when the injector needle closes. During injection initiation and termination, the atomization of fuel exiting the injector nozzle may not be perfect because the liquid jet needs to break up, potentially resulting in filamentous flow and larger fuel droplets. This invention helps mitigate these effects because the acoustic field following the injector helps further atomize the droplets, providing a more uniform fuel delivery into the inlet channel. Furthermore, smaller droplet sizes reduce the Stokes number, which characterizes the behavior of particles or droplets in the fluid flow. A low Stokes number means the droplets closely follow the fluid streamlines. In the inlet channel, this reduces the contact between the fuel and the inlet channel walls.

[0016] According to an embodiment of the invention, the component for generating a sound field includes at least one acoustic resonator at least partially disposed in the entrance channel. The at least one acoustic resonator may protrude fully or partially into the entrance channel.

[0017] According to an embodiment of the invention, the acoustic resonator is configured to operate by introducing pressurized gas into the acoustic resonator.

[0018] According to an embodiment of the invention, the fuel injection device is configured to introduce exhaust gas into the acoustic resonator to operate the resonator. By using the exhaust gas, the heat from the exhaust gas can be used to further reduce the risk of wall wetting through improved further atomization of the fuel. However, pressurized air can also be used to operate the acoustic resonator.

[0019] According to an embodiment of the invention, the acoustic resonator is provided with an opening for discharging at least a portion of the pressurized gas introduced into the acoustic resonator, such that the discharged pressurized gas can influence the flow direction of the fuel jet injected by the fuel injector. Therefore, by improving fuel atomization and by reducing the contact between the fuel and the wall of the inlet channel, the acoustic resonator can have the dual function of reducing wall wetting.

[0020] According to an embodiment of the invention, the acoustic resonator is configured such that the pressurized gas discharged from the acoustic resonator counteracts the effect of the airflow in the inlet channel causing the fuel jet to deviate from the longitudinal axis of the fuel injector. If the fuel injection direction is not parallel to the airflow direction in the inlet channel, the airflow can deviate from the fuel jet. The acoustic resonator can be arranged to counteract this effect.

[0021] According to an embodiment of the invention, the acoustic resonator includes a cavity having a closed end and an open end, and a component for introducing pressurized gas into the cavity via the open end of the cavity. Therefore, the acoustic resonator is a Hartmann whistle or a variant of a Hartmann whistle.

[0022] According to an embodiment of the invention, the length of the cavity is adjustable to allow for adjustment of the fundamental frequency of the acoustic resonator. An adjustable fundamental frequency contributes to effective fuel atomization.

[0023] According to an embodiment of the invention, the length of the cavity is 10-30 mm. This length range corresponds to a fundamental frequency of approximately 2830-8500 Hz.

[0024] According to an embodiment of the present invention, the angle between the fuel injection direction and the longitudinal direction of the cavity is 0-45 degrees. The atomization and flow direction of the fuel injected by the fuel injector can be influenced by the appropriate orientation of the acoustic resonator.

[0025] According to an embodiment of the present invention, the cavity has an opening on one side of the cavity, the opening facing the fuel injected by the fuel injector. The opening on the side guides the pressurized gas flow towards the fuel jet, thereby guiding the fuel jet.

[0026] According to an embodiment of the invention, the fuel injector and the acoustic resonator are configured such that at least a portion of the fuel is injected toward an opening in the cavity. By injecting fuel toward the opening, the fuel is effectively atomized.

[0027] According to an embodiment of the invention, the acoustic resonator is arranged to protrude into the inlet channel through the wall of the inlet channel, such that the open end of the cavity is closer to the wall than the closed end of the cavity. This allows pressurized gas to be introduced into the acoustic resonator from the direction of the wall.

[0028] According to an embodiment of the invention, the fuel injection device includes a valve for controlling the timing of supplying pressurized gas to the cavity of the acoustic resonator. By means of the valve, the operating period of the acoustic resonator can be limited to a period closer to the operating period of the fuel injector, thereby avoiding unnecessary supply of pressurized gas.

[0029] According to an embodiment of the present invention, the fuel injection device includes a pressure regulating component for controlling the pressure of pressurized gas introduced into the cavity of the acoustic resonator. By controlling the pressure of the pressurized gas, the acoustic resonator can be arranged to generate the overtone of the fundamental frequency of the acoustic resonator.

[0030] According to an embodiment of the invention, the acoustic resonator is arranged in a ring around the fuel injector. The ring acoustic resonator can effectively and uniformly atomize the fuel.

[0031] According to an embodiment of the invention, the acoustic resonator is arranged separately from the fuel injector. This allows the use of a standard fuel injector as a component of the fuel injection device.

[0032] According to an embodiment of the invention, the distance between the acoustic resonator and the fuel injector is at least 50 mm. Alternatively, the distance may be at least 100 mm or at least 150 mm. By arranging the acoustic resonator and the fuel injector at a distance from each other, the fuel injector can be arranged further away from the cylinder head inlet opening to reduce heat-related problems. Arranging the acoustic resonator closer to the inlet opening allows for effective fuel atomization before fuel enters the main combustion chamber and effective control of the fuel jet direction.

[0033] According to embodiments of the invention, a fuel injector is configured to inject a fuel jet with a cone angle of less than 10 degrees, and an acoustic resonator is arranged at a distance from the fuel injector and configured to disperse the fuel jet. In the case of a narrow fuel jet, the injector can be positioned further away from the cylinder inlet opening. The injected fuel can have a relatively large droplet size, which can be characterized by a Sauter mean diameter. The acoustic resonator can atomize and diffuse the fuel jet. The acoustic resonator can be positioned close to the inlet opening.

[0034] According to an embodiment of the invention, the fuel injection device includes a tube disposed between a fuel injector and an acoustic resonator, and the fuel injector is configured to inject fuel into the tube. Using the tube, the fuel injector can even be located outside the inlet channel, which protects the fuel injector from heat. The tube helps guide the fuel jet. The tube also facilitates the installation and maintenance of the fuel injection device.

[0035] According to an embodiment of the invention, an outer tube is arranged around the tube such that pressurized gas can be delivered to the acoustic resonator in the space formed between the tube and the outer tube. The outer tube contributes to forming a robust and modular construction for the fuel injection device.

[0036] According to an embodiment of the invention, the acoustic resonator is ring-shaped. The fuel jet can be guided through the ring-shaped acoustic resonator for effective fuel atomization.

[0037] According to embodiments of the invention, the components for generating the sound field include at least two acoustic resonators protruding into the inlet channel. By having two or more acoustic resonators, fuel atomization can be improved, and the acoustic resonators can also be used to guide the fuel jet.

[0038] According to an embodiment of the invention, the number of acoustic resonators is equal to or greater than the number of nozzle openings of the fuel injector. This allows the fuel jet to be guided close to the acoustic resonators to achieve effective fuel atomization.

[0039] According to an embodiment of the invention, the acoustic resonator is arranged symmetrically with respect to the fuel injector.

[0040] According to embodiments of the invention, the fuel injector is configured to inject methanol or ethanol. While the invention can also be used in combination with other fuels, it offers particular benefits when using methanol or ethanol. The invention also benefits from utilizing other alcohol-based fuels, as these fuels readily absorb energy during vaporization and are effective solvents that can cause lubrication problems if the fuel is not effectively atomized. Even ammonia, despite its tendency to vaporize better after injection, can benefit from the invention because condensed ammonia, which interacts with surfaces, is known to cause undesirable chemical reactions with engine materials and structures.

[0041] According to an embodiment of the present invention, the fuel injection device is configured to inject fuel at a pressure 1-50 bar higher than the pressure of the boosted air in the inlet channel.

[0042] According to an embodiment of the invention, the component for generating a sound field is configured to reduce the soter mean diameter of the fuel injected by the fuel injector by at least 50%. After the component for generating the sound field, the soter mean diameter of the fuel is therefore at least 50% smaller than when the fuel injector is used alone. According to an embodiment of the invention, the fuel injection device is configured such that when the fuel enters the main combustion chamber of the engine, the soter mean diameter of the fuel is less than 100 μm.

[0043] According to an embodiment of the invention, the fuel injector is configured to produce a fuel jet with a soter average diameter of at least 200 μm. The larger droplet size increases the Stokes number. This helps to keep the fuel jet focused and guided toward the acoustic resonator, where the fuel is further atomized. This allows the fuel injector to be placed further away from the cylinder inlet opening.

[0044] According to an embodiment of the method of the invention, an acoustic field is applied to the fuel jet by at least one acoustic resonator arranged at least partially in the inlet channel.

[0045] According to an embodiment of the present invention, the fundamental frequency of the at least one acoustic resonator is 2800-8500 Hz.

[0046] According to an embodiment of the present invention, the acoustic resonator includes a cavity having a closed end and an open end, and pressurized gas is introduced into the cavity through the open end of the cavity.

[0047] According to an embodiment of the present invention, pressurized gas is introduced into the cavity at a pressure 0.1-10.0 bar higher than the pressurized air pressure in the inlet channel.

[0048] According to an embodiment of the present invention, the pressurized gas is exhaust gas.

[0049] According to embodiments of the present invention, the flow rate and / or pressure of the pressurized gas are adjusted based on the engine speed and / or load. The engine speed and load affect the intake flow rate and pressure in the intake passage, and by adjusting the pressurized gas flow rate, the operation of the acoustic resonator can be optimized for the conditions in the intake passage.

[0050] According to an embodiment of the present invention, fuel is injected into the inlet channel at a pressure 1-50 bar higher than the pressure of the pressurized air in the inlet channel.

[0051] According to an embodiment of the invention, the sound field includes one or more peaks in the frequency range of 2-100 kHz. Attached Figure Description

[0052] Embodiments of the present invention will now be described in more detail with reference to the accompanying drawings, wherein...

[0053] Figure 1 A cross-sectional view of a portion of the cylinder head of a piston engine with a fuel injection device according to an embodiment of the present invention is shown. Figure 2 It shows Figure 1 An enlarged view of the fuel injector and acoustic resonator in the fuel injection arrangement. Figure 3 It shows Figure 2 Cross-sectional diagrams of the fuel injector and acoustic resonator. Figure 4 A fuel injector and an acoustic resonator according to another embodiment of the present invention are shown, as well as Figure 5 It shows Figure 4 Cross-sectional view of the fuel injector and acoustic resonator. Detailed Implementation

[0054] This invention relates to a fuel injection device for a piston engine, a piston engine, and a method of operating a piston engine. The engine is a large piston engine, such as a main or auxiliary engine of a ship or a power plant engine. The engine cylinder diameter is at least 150 mm. The engine can include any reasonable number of cylinders, which can be arranged in a straight or V-shaped configuration. Each cylinder of the engine has its own cylinder head 6. The engine is a four-stroke engine. The engine can be a medium-speed engine configured to operate at speeds of 250-1300 RPM. The engine can be operated using at least one fuel injected in the liquid phase. The expression "injected in the liquid phase" here means that the fuel is liquid before being discharged from the fuel injector. The fuel can be a liquid fuel, here referring to a fuel that is liquid at a temperature of 20°C and atmospheric pressure. The liquid fuel can be, for example, methanol or ethanol. However, the fuel injected in the liquid phase can also be a gaseous fuel, which here refers to a fuel that is gaseous at a temperature of 20°C and atmospheric pressure, but can be injected in the liquid phase using sufficiently high pressures and / or sufficiently low temperatures. Thus, the fuel can be, for example, ammonia injected as a liquid but vaporized after injection. The engine can be additionally configured to operate using one or more gaseous fuels introduced into the engine in the gas phase. The engine can be configured to operate using two or more different fuels. Therefore, the engine can be a dual-fuel or multi-fuel engine.

[0055] The engine can be configured to operate with a lean air-fuel mixture. The air-fuel equivalence ratio λ can, for example, exceed 2.0. Lean air-fuel mixtures may present combustibility issues, therefore effective fuel atomization is important. The engine can be turbocharged. The engine can be configured to operate at a boost air pressure of at least 2 bar.

[0056] The fuel injection device according to the invention includes a fuel injector 1. The fuel injector 1 is configured to inject liquid fuel into an inlet passage 5 of the engine. The term "inlet passage" here refers to all passages that deliver intake air to the engine. Thus, the inlet passage 5 includes a boost air receiver configured to receive pressurized intake air from a turbocharger, an inlet port that is an integral part of a cylinder head 6, and an inlet pipe connecting the inlet port of the cylinder head 6 to the boost air receiver.

[0057] In the embodiment shown in the accompanying drawings, the fuel injector 1 is arranged to inject fuel into an inlet port within the cylinder head 6. However, the fuel injector 1 can also be arranged to inject fuel into an inlet pipe attached to the cylinder head 6. Each cylinder of the engine is provided with a fuel injector 1. The fuel injector 1 can be a conventional fuel injector. The fuel injector 1 may include one or more nozzle openings configured to form a desired injection pattern. Fuel injection timing can be controlled by a valve needle. The opening and closing of the valve needle can be electrically controlled. Each cylinder of the engine is provided with one or more, preferably two or three, intake valves 8. The intake valves 8 open and close fluid communication with the main combustion chamber of the cylinder through the inlet opening. The fuel injector 1 produces a fuel jet 7 directed toward the inlet opening.

[0058] The engine may also include additional fuel injectors. For example, each cylinder of the engine may include an ignition fuel injector configured to inject liquid ignition fuel directly into the main combustion chamber. Fuel introduced into the inlet passage 5 and further into the main combustion chamber by means of fuel injector 1 can be ignited by the combustion of the ignition fuel. The ignition fuel may be a different fuel from the fuel introduced into the inlet passage 5. For example, if methanol or ethanol is introduced into the inlet passage 5, the ignition fuel may be a light fuel oil.

[0059] Fuel injector 1 can be used to inject the main fuel. Therefore, the fuel delivered through fuel injector 1 can correspond to more than 50% of the energy content of the fuel delivered to the cylinder in a single combustion cycle, preferably up to 90% or even 100%. The fuel share delivered by fuel injector 1 can vary depending on the engine's operating mode. For example, the fuel share delivered by fuel injector 1 can differ under stable and dynamic (rpm and / or load changes) conditions. The remaining fuel can be delivered as liquid or gaseous fuel via the inlet port or pre-combustion chamber or directly to the main combustion chamber. The remaining fuel may consist of a small amount of ignition fuel used to ignite the main fuel. Alternatively, the remaining fuel may contain additional fuel or support fuel or fuel additives that affect the combustion process.

[0060] The fuel injection device also includes a component 2 for generating a sound field and applying it to the fuel injected into the inlet channel 5 to atomize the injected fuel. The term "sound field" here refers to a sound field within the audible and ultrasonic range. The sound field can involve sounds with different frequencies. The component 2 for generating the sound field is configured to atomize the injected fuel outside the fuel injector 1. The fuel thus exits the fuel injector 1, and the sound field is applied to the injected fuel outside the fuel injector 1.

[0061] The components used to generate the sound field may include one or more acoustic resonators 2, at least partially arranged in the entrance channel 5. The acoustic resonators 2 may protrude completely or partially into the entrance channel 5, as shown in... Figures 1 to 3 In the embodiments. In Figures 1 to 3 In one embodiment, the fuel injection device includes two acoustic resonators 2 for each cylinder of the engine. Figures 1 to 3 In one embodiment, the acoustic resonators 2 are symmetrically arranged on opposite sides of the fuel injector 1. However, the fuel injection device may include only one, three, or more acoustic resonators 2. The acoustic resonators may be arranged in a ring around the fuel injector 1.

[0062] In the embodiment shown in the accompanying drawings, the acoustic resonator 2 operates essentially on the principle of a Hartmann whistle. The acoustic resonator 2 includes a cavity 3. The cavity 3 has a closed end 3A and an open end 3B. Pressurized gas (e.g., air) can be introduced into the cavity 3 through the open end 3B. The open end 3B has an opening 3C on its side surface.

[0063] When pressurized gas is introduced into the cavity 3 of the acoustic resonator 2 through the open end 3B, a standing wave is formed within the cavity 3. The wave is reflected from the closed end 3A of the cavity 3 with a phase shift of 180 degrees. A node is formed at the closed end 3A of the cavity 3. An antinode is formed at the open end 3B of the cavity 3. The fundamental frequency of the acoustic resonator 2 is the frequency corresponding to four times the wavelength of the cavity 3. Therefore, the fundamental frequency f1 of the acoustic resonator 2 can be expressed by the following equation:

[0064] Where c is the speed of sound in the cavity, λ1 is the wavelength corresponding to the fundamental frequency f1, and L is the length of cavity 3.

[0065] In addition to generating sound at the fundamental frequency of acoustic resonator 2, acoustic resonator 2 can also generate overtones at the fundamental frequency.

[0066] Since there is always a node at the closed end 3A of cavity 3 and always an antinode at the open end 3B of cavity 3, acoustic resonator 2 only generates odd harmonics of the fundamental frequency. th The frequency f of the overtone n It can be expressed by the following equation:

[0067] Where f1 is the fundamental frequency.

[0068] If the length L of cavity 3 is 18mm and the sound speed is assumed to be 340m / s, the fundamental frequency of acoustic resonator 2 can be calculated as 4722 Hz using formula (1).

[0069] If pressurized gas is introduced into cavity 3 at a higher pressure, a higher frequency is generated. Using equation (2), the second overtone (fifth harmonic) has a frequency of 23610 Hz, which is within the ultrasonic range. The fifth overtone (eleventh harmonic) has a frequency of 51942 Hz.

[0070] The acoustic resonator 2 may be equipped with a component for adjusting the length L of the cavity 3. This component may be, for example, a bolt positioned at the closed end 3A of the cavity 3. By adjusting the length of the cavity 3, the fundamental frequency of the acoustic resonator 2 can be changed. Changing the fundamental frequency also changes the frequency of the overtones.

[0071] The length L of cavity 3 can be, for example, in the range of 10mm-30mm, corresponding to a fundamental frequency of 2833-8500 Hz.

[0072] exist Figures 1 to 3 In this embodiment, the longitudinal direction of each acoustic resonator 2 is parallel to the direction of the fuel jet 7. However, the longitudinal direction of the cavity 3 of the acoustic resonator 2 does not need to be parallel to the fuel injection direction, but the angle between the fuel injection direction and the longitudinal direction of the cavity 3 can be, for example, 0-45 degrees. The free end of the acoustic resonator 2 can be guided toward or away from the fuel jet 7.

[0073] In the embodiment shown in the accompanying drawings, the acoustic resonator 2 is separate from the fuel injector 1. This provides the advantage of using a standard fuel injector. However, one or more acoustic resonators can be integrated with the fuel injector 1. For example, a ring-shaped acoustic resonator can be arranged around the fuel injector 1.

[0074] exist Figures 1 to 3 In this embodiment, the acoustic resonator 2 is arranged to protrude into the inlet channel 5 through the wall of the inlet channel 5, such that the open end 3B of the cavity 3 is closer to the wall than the closed end 3A of the cavity 3. Therefore, pressurized gas can be easily introduced into the cavity 3 through the wall of the inlet channel 5.

[0075] The fuel injection arrangement can be configured such that the opening 3C on the side of the cavity 3 of the acoustic resonator 2 faces the fuel injected by the fuel injector 1. This allows the sound field to be effectively aimed at the fuel jet. At least a portion of the fuel can be injected toward the opening 3C of the cavity 3.

[0076] The number of acoustic resonators 2 can be configured to be equal to or greater than the number of nozzle openings of the fuel injector 1. This allows for effective atomization of the entire fuel jet 7 injected by the fuel injector 1.

[0077] Fuel injector 1 can be configured to inject methanol. The fuel injection pressure can be, for example, in the range of 5-50 bar or 1-50 bar higher than the boost air pressure in inlet channel 5.

[0078] The fuel injection device may include a valve for controlling the timing of the supply of pressurized gas to the cavity 3 of the acoustic resonator 2. By means of the valve, the operating period of the acoustic resonator 2 can be limited to approximately the same period as the operating period of the fuel injector 1, thereby preventing unnecessary supply of pressurized gas to the acoustic resonator 2. The valve may be, for example, a magnetic valve. The valve may open shortly before fuel injection begins and close shortly before fuel injection ends.

[0079] The fuel injection device may also include a pressure regulating component for controlling the pressure of the pressurized gas introduced into the cavity 3 of the acoustic resonator 2. By controlling the pressure of the pressurized gas, the acoustic resonator 2 can be arranged to produce the overtone of the fundamental frequency of the acoustic resonator 2.

[0080] The pressurized gas can be air. Alternatively, the pressurized gas can be exhaust gas.

[0081] The purpose of fuel atomization is to reduce the size of fuel droplets. The Sauter mean diameter (SMD) can be used as a measure of the average droplet size. The acoustic resonator 2 can be configured to reduce the SMD of the fuel injected by the fuel injector 1 by at least 50%. The goal of atomization is to ensure that the SMD of the fuel is less than 100 μm when it enters the engine's main combustion chamber.

[0082] By using fully atomized fuel, problems caused by wall wetting can be reduced, and more uniform combustion can be achieved.

[0083] While it is beneficial for fuel to enter the main combustion chamber with small droplet sizes, in some cases, injecting fuel with larger droplet sizes may be advantageous. Larger droplet sizes increase the Stokes number of droplets in the airflow. With a higher Stokes number, the droplets do not closely follow the fluid streamlines. This allows the fuel jet to be aimed at a target regardless of the behavior of the airflow in the inlet passage 5. Therefore, the fuel injector 1 can be arranged further away from the cylinder inlet opening, while the acoustic resonator 2 can be arranged closer to the inlet opening. As an example, the fuel injector 1 can be configured to produce a fuel jet with a soter mean diameter of at least 200 μm. The fuel jet can be aimed at the acoustic resonator 2 positioned close to the inlet opening. The acoustic resonator 2 can atomize the injected fuel, reducing the soter mean diameter to below 100 μm before the fuel enters the main combustion chamber. By arranging the fuel injector 1 further away from the cylinder inlet opening, problems caused by heat can be reduced.

[0084] Figure 4 and Figure 5 A fuel injector 1 and an acoustic resonator 2 of a fuel injection device according to another embodiment of the present invention are shown. Figure 4 and Figure 5In this embodiment, the fuel injector 1 is configured to generate a fuel jet 7 with a small cone angle. The cone angle can be configured, for example, less than 10 degrees. This results in a substantially straight fuel jet 7. The fuel injector 7 can have a relatively large droplet size. Therefore, the main portion of fuel atomization can be performed by the acoustic resonator 2. Figure 4 and Figure 5 In one embodiment, pipe 9 is arranged between fuel injector 1 and acoustic resonator 2. Fuel injector 1 is configured to inject fuel into pipe 9, which guides the fuel jet 7 toward acoustic resonator 2. Acoustic resonator 2 both atomizes the fuel and diffuses the fuel jet 7. Figure 4 and Figure 5 In this embodiment, the acoustic resonator 2 is annular, and the fuel jet 7 is guided through the acoustic resonator 2. The distance between the fuel injector 1 and the acoustic resonator 2 can be, for example, at least 50 mm, or at least 100 mm, or at least 150 mm. The tube 9 allows the fuel injector 1 to be located even outside the inlet channel 5 to protect the fuel injector 1 from heat.

[0085] An outer pipe 10 is arranged around a pipe 9. Pressurized gas can be delivered to the acoustic resonator 2 within the space 4 formed between the pipe 9 and the outer pipe 10. The pipe 9, outer pipe 10, acoustic resonator 2, and fuel injector 1 can form a module that can be easily installed and removed for maintenance. This module can also be used in retrofit solutions.

[0086] Figure 4 and Figure 5 The working principle of acoustic resonator 2 and Figures 1 to 3 The same as in the embodiments. Tube 9 can be used with... Figures 1 to 3 In the embodiment, the acoustic resonator 2 protrudes into the inlet channel 5 in a similar manner.

[0087] The method according to the invention can be implemented using the fuel injection device shown above and / or in the accompanying drawings. However, the method can also be implemented using different fuel injection arrangements.

[0088] In the method according to the invention, liquid fuel is injected into the engine inlet passage 5 through a fuel injector 1. A sound field is applied to the fuel jet 7 injected by the fuel injector to atomize the injected fuel outside the fuel injector 1.

[0089] The sound field can be applied to the fuel injector 7 by means of one or more acoustic resonators 2 protruding into the inlet channel 5. The fundamental frequency of the one or more acoustic resonators 2 can be 2800-8500 Hz. If two or more acoustic resonators 2 are used, the acoustic resonators 2 can have the same or different fundamental frequencies. The sound field can include one or more peaks in the frequency range of 2-100kHz.

[0090] The acoustic resonator 2 can be Figures 1 to 3 or Figure 4 and Figure 5 The type shown is described. Therefore, the acoustic resonator 2 may include a cavity 3 having a closed end 3A and an open end 3B. A sound field can be generated by introducing pressurized gas into the cavity 3 via the open end 3B of the cavity 3.

[0091] Pressurized gas can be introduced into cavity 3 at a pressure 0.1 to 10 bar higher than the boost air pressure in inlet channel 5. If two or more acoustic resonators 2 are used, pressurized gas can be introduced into different acoustic resonators 2 at different pressures to generate a sound field with several peaks at different frequencies. The required mass flow rate of pressurized gas depends on several factors, such as boost air pressure and fuel injection quantity, but can be in the range of, for example, 3-30 g / s for each fuel injector 1. The flow rate and pressure of pressurized gas can be adjusted based on engine speed and / or load.

[0092] Fuel can be injected into inlet passage 5 at a pressure 1-50 bar higher than the pressurized air pressure in inlet passage 5. The fuel can be, for example, methanol or ethanol. By injecting liquid ignition fuel into the main combustion chamber, the fuel injected into inlet passage 5 can be ignited in the main combustion chamber. The liquid ignition fuel can be, for example, light fuel oil.

[0093] The engine can be operated using a lean air-fuel mixture. The air-fuel equivalence ratio λ can be, for example, at least 2.0.

[0094] The aforementioned acoustic resonator 2 can be configured for retrofitting into piston engines. This allows existing engines to be converted to use new fuels. Alternatively, the improved resonator 2 can be used to improve the atomization of fuels already used in the engine.

Claims

1. A fuel injection device for a piston engine, the fuel injection device comprising a fuel injector (1) and a component (2), the fuel injector being configured to inject liquid fuel into an inlet passage (5) of the engine, the component being configured to generate a sound field and apply the sound field to the fuel injected into the inlet passage (5) to atomize the fuel injected outside the fuel injector (1).

2. The fuel injection device according to claim 1, wherein, The component used to generate the sound field includes at least one acoustic resonator (2) arranged at least partially in the inlet channel (5).

3. The fuel injection device according to claim 2, wherein, The acoustic resonator (2) is configured to operate by introducing pressurized gas into the acoustic resonator (2).

4. The fuel injection device according to claim 3, wherein, The fuel injection device is configured to introduce exhaust gas into the acoustic resonator (2) to operate the acoustic resonator (2).

5. The fuel injection device according to claim 3 or 4, wherein, The acoustic resonator (2) is provided with an opening (3C) for discharging at least a portion of the pressurized gas introduced into the acoustic resonator (2), such that the discharging pressurized gas can influence the flow direction of the fuel jet injected by the fuel injector (1).

6. The fuel injection device according to claim 5, wherein, The acoustic resonator (2) is configured such that the pressurized gas discharged from the acoustic resonator (2) counteracts the effect of the airflow in the inlet channel (5) causing the fuel jet to deviate from the longitudinal axis of the fuel injector (1).

7. The fuel injection device according to any one of claims 2 to 6, wherein, The acoustic resonator (2) includes a cavity (3) having a closed end (3A) and an open end (3B) and a component (4) for introducing pressurized gas into the cavity (3) via the open end (3B) of the cavity (3).

8. The fuel injection device according to claim 7, wherein, The length of the cavity (3) is adjustable to allow adjustment of the fundamental frequency of the acoustic resonator (2).

9. The fuel injection device according to claim 7 or 8, wherein, The length of the cavity is 10mm-30mm.

10. The fuel injection device according to any one of claims 7 to 9, wherein, The angle between the fuel injection direction and the longitudinal direction of the cavity (3) is 0-45 degrees.

11. The fuel injection device according to any one of claims 7 to 10, wherein, The opening end (3B) of the cavity (3) is provided with an opening (3C) on one side of the cavity (3), and the opening (3C) faces the fuel injected by the fuel injector (1).

12. The fuel injection device according to claim 11, wherein, The fuel injector (1) and the acoustic resonator (2) are configured such that at least a portion of the fuel is injected toward the opening (3C) of the cavity (3).

13. The fuel injection device according to any one of claims 7 to 12, wherein, The acoustic resonator (2) is arranged to protrude into the entrance channel (5) through the wall of the entrance channel (5) such that the open end (3B) of the cavity (3) is closer to the wall than the closed end (3A) of the cavity (3).

14. The fuel injection device according to any one of claims 7 to 13, wherein, The fuel injection device includes a valve for controlling the timing of supplying pressurized gas to the cavity (3) of the acoustic resonator (2).

15. The fuel injection device according to any one of claims 7 to 14, wherein, The fuel injection device includes a pressure regulating component for controlling the pressure of the pressurized gas introduced into the cavity (3) of the acoustic resonator (2).

16. The fuel injection device according to any one of claims 2 to 15, wherein, The acoustic resonator (2) is arranged in a ring around the fuel injector (1).

17. The fuel injection device according to any one of claims 2 to 15, wherein, The acoustic resonator (2) is arranged separately from the fuel injector (1).

18. The fuel injection device according to claim 17, wherein, The distance between the acoustic resonator (2) and the fuel injector (1) is at least 50 mm.

19. The fuel injection device according to any one of claims 2 to 18, wherein, The fuel injector (1) is configured to inject a fuel jet (7) with a cone angle of less than 10 degrees, and the acoustic resonator (2) is arranged at a distance from the fuel injector (1) and configured to diffuse the fuel jet (7).

20. The fuel injection device according to any one of claims 2 to 19, wherein, The fuel injection device includes a pipe (9) disposed between the fuel injector (1) and the acoustic resonator (2), and the fuel injector (1) is configured to inject the fuel into the pipe (9).

21. The fuel injection device according to claim 20, wherein, The outer tube (10) is arranged around the tube (9) so that pressurized gas can be delivered to the acoustic resonator (2) in the space (4) formed between the tube (9) and the outer tube (10).

22. The fuel injection device according to any one of claims 19 to 21, wherein, The acoustic resonator (2) is ring-shaped.

23. The fuel injection device according to any one of claims 2 to 22, wherein, The components used to generate the sound field include at least two acoustic resonators (2) protruding into the inlet channel (5).

24. The fuel injection device according to claim 23, wherein, The number of acoustic resonators (2) is equal to or greater than the number of nozzle openings of the fuel injector (1).

25. The fuel injection device according to claim 23 or 24, wherein, The acoustic resonator (2) is arranged symmetrically about the fuel injector (1).

26. The fuel injection device according to any one of the preceding claims, wherein, The fuel injector (1) is configured to inject methanol or ethanol.

27. The fuel injection device according to any one of the preceding claims, wherein, The fuel injection device is configured to inject fuel at a pressure 1-50 bar higher than the pressure of the pressurized air in the inlet channel (5).

28. The fuel injection device according to any one of the preceding claims, wherein, The component (2) used to generate the sound field is configured to reduce the average diameter of the fuel injected by the fuel injector (1) by at least 50%.

29. The fuel injection device according to any one of the preceding claims, wherein, The fuel injection device is configured such that when the fuel enters the main combustion chamber of the engine, the soter average diameter of the fuel is less than 100 μm.

30. The fuel injection device according to any one of the preceding claims, wherein, The fuel injector (1) is configured to generate a fuel jet (7) with a soter average diameter of at least 200 μm.

31. A piston engine comprising a fuel injection device according to any one of the preceding claims.

32. An acoustic resonator (2) configured to be adapted to a piston engine for generating a sound field and for applying the sound field to fuel injected into the engine's inlet passage (5) via a fuel injector (1) to atomize the fuel outside the fuel injector (1).

33. A method of operating a piston engine, the method comprising the following steps: - Liquid fuel is injected into the engine inlet passage (5) via a fuel injector (1), and - Apply an acoustic field to the fuel jet (7) injected by the fuel injector (1) to atomize the injected fuel outside the fuel injector (1).

34. The method according to claim 33, wherein, The sound field is applied to the fuel jet (7) by at least one acoustic resonator (2) arranged at least partially in the inlet channel (5).

35. The method according to claim 34, wherein, The fundamental frequency of the at least one acoustic resonator (2) is 2800-8500Hz.

36. The method according to claim 34 or 35, wherein, The acoustic resonator (2) includes a cavity (3) having a closed end (3A) and an open end (3B), and pressurized gas is introduced into the cavity (3) via the open end (3B) of the cavity (3).

37. The method of claim 36, wherein, The pressurized gas is introduced into the cavity (3) at a pressure 0.1-10.0 bar higher than the pressurized air pressure in the inlet channel (5).

38. The method according to claim 36 or 37, wherein, The pressurized gas is exhaust gas.

39. The method according to any one of claims 36 to 38, wherein, The flow rate and / or pressure of the pressurized gas are adjusted according to the engine speed and / or load.

40. The method according to any one of claims 33 to 39, wherein, The fuel is injected into the inlet channel (5) at a pressure 1-50 bar higher than the pressure of the pressurized air in the inlet channel (5).

41. The method according to any one of claims 33 to 40, wherein, The sound field includes one or more peaks in the frequency range of 2-100kHz.

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