EP4735754A1 - Injection apparatus - Google Patents

Abstract

An injection apparatus (500) comprises: - an inlet (IN1) to receive a liquid (LIQ1), - a nozzle (NOZ1) having one or more orifices (OR1) to form droplets (P1) from the liquid (LIQ1), - one or more flow channels (DUC1) to convey the liquid (LIQ1), - a coupling element (M1) to couple ultrasound (UW1) to the liquid (LIQ1), and - a transducer (SPK1) to vibrate the coupling element (M1), wherein the liquid (LIQ1) is conveyed from the inlet (IN1) to the one or more orifices (OR1) via the one or more flow channels (DUC1), wherein the injection apparatus (500) is arranged to guide the ultrasound (UW1) from the coupling element (M1) to the nozzle (NOZ1) via the liquid (LIQ1) contained in the one or more flow channels (DUC1).

Description

INJECTION APPARATUS

FIELD

The present invention relates to injecting a liquid in a reciprocating internal combustion engine.

BACKGROUND

It is known that a fuel injector of an internal combustion engine may comprise an ultrasonic transducer on one end of an ultrasonic horn, such that the opposite end of the horn is immersed in the fuel close to the injector's exit orifices.

SUMMARY

An object is to provide an apparatus for injecting a liquid in an engine. An object is to provide a method for injecting a liquid in an engine. An object is to provide an engine, which comprises the injecting apparatus. An object is to provide a method for operating the engine.

According to an aspect, there is provided an apparatus according to claim 1 .

Further embodiments are defined in the other claims.

The scope of protection sought for various embodiments of the invention is set out by the independent claims. The embodiments, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the invention.

The apparatus may be used for injecting atomized liquid into the combustion space of a cylinder of a reciprocating internal combustion engine. The liquid may be injected either to an intake duct of the engine, or directly into the cylinder. The liquid may be e.g. a fuel or a liquid additive. The liquid may be e.g. diesel oil. The liquid may be e.g. methanol. The liquid may be e.g. liquified ammonia. The liquid additive may be e.g. water. The engine may be e.g. the main engine of a ship.

The atomizing nozzle of the apparatus comprises one or more orifices for atomizing the liquid, i.e. for converting an amount of the liquid into small droplets. The diameter of the formed droplets may be e.g. in the range of 1 m to 20 pm. The apparatus may utilize the ultrasound to facilitate the atomization. The apparatus may sonicate the liquid, i.e. may agitate the liquid by applying ultrasound energy. The apparatus may energize the liquid with the ultrasound. The ultrasound may e.g. reduce the size of the atomized droplets and/or may provide more uniform droplet size distribution. Large droplets, if entrained into the cylinder, may cause incomplete combustion and/or may compromise lubrication. The ultrasound may reduce the risk of forming large droplets.

The apparatus may comprise a flow control valve for starting and stopping a flow of the liquid. The apparatus may utilize the ultrasound to facilitate operation of the flow control valve. The ultrasound may e.g. allow more precise timing of the start of the liquid flow via the flow control valve. The precise start of the liquid flow may further reduce the risk of forming large droplets.

The apparatus comprises an ultrasonic transducer for generating the ultrasound. The apparatus may transmit the ultrasound from the transducer to the atomizing nozzle via the liquid. Transmitting the ultrasound to the atomizing nozzle via the liquid may allow increased freedom for selecting the position of the atomizing nozzle and for selecting the position of the transducer with respect to the cylinder head. For example, the atomizing nozzle may be mounted to a first position, and the transducer may be mounted to a second different position. The first position may be selected e.g. to optimize trajectories of the atomized droplets. The second position may be selected e.g. to ensure efficient cooling of the transducer.

The space around the cylinder head of the engine is typically limited. Transmitting the ultrasound via the liquid may allow increased freedom for selecting the positions of the various tubes, sensors, and cables which are connected to the cylinder head. The apparatus may use one or more flow channels for conveying the liquid to the atomizing nozzle, and the apparatus may use the liquid contained in said one or more flow channels for transmitting the ultrasound to the atomizing nozzle. In particular, the one or more flow channels and the liquid contained in them may be arranged to operate as a liquid waveguide, for guiding the ultrasound with relatively low losses.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following examples, several variations will be described in more detail with reference to the appended drawings, in which

Fig. 1a shows, by way of example, in a cross-sectional side view, an injection apparatus, in a situation where the flow control valve of the injection apparatus is closed,

Fig. 1 b shows, by way of example, in a cross-sectional side view, the injection apparatus, in a situation where the flow control valve is open,

Fig. 2 shows, by way of example, in a cross-sectional side view, an acoustic transmission line of the injection apparatus,

Fig. 3 shows, by way of example, in a cross-sectional side view, injecting atomized liquid to the intake duct of an engine,

Fig. 4a shows, by way of example, a control system of an engine,

Fig. 4b shows, by way of example, a control system of the injection apparatus,

Fig. 5 shows, by way of example, in a cross-sectional side view, an acoustic transmission line the injection apparatus, Fig. 6 shows, by way of example, in a three-dimensional view, the injection apparatus, and

Fig. 7 shows, by way of example, in a cross-sectional side view, an injection apparatus, in a situation where the flow control valve is open.

DETAILED DESCRIPTION

Referring to Figs. 1 a and 1 b, the injection apparatus 500 may form one or more sprays JET1 , which comprise droplets P1. The droplets P1 may be formed by forcing the liquid LIQ1 to pass through one or more exit orifices OR1 . The flow of the liquid LIQ1 through the orifices OR1 may cause shear forces, which may convert the liquid into droplets P1 . The liquid LIQ1 may exit the apparatus 500 at the orifices OR1 .

The injection apparatus 500 may form microscopic droplets P1 by atomizing a liquid LIQ1. The injection apparatus 500 comprises an atomizing nozzle NOZ1 , which comprises one or more atomizing orifices OR1. The atomizing nozzle NOZ1 comprises one or more orifices OR1 for forming the droplets P1 from the liquid LIQ1 . The liquid LIQ1 may have a pressure PLIQI inside the apparatus 500. PG denotes the exterior pressure of the orifices OR1. The pressure difference across the orifices OR1 may be equal to PLIQI - PG. The pressure difference PLIQI - PG causes a flow of the liquid LIQ1 via the orifices OR1 . The pressurized liquid LIQ1 is forced to flow via the orifices OR1 . The velocity of the liquid LIQ1 at the orifices OR1 causes shear forces, which may exceed the surface tension of the liquid LIQ 1 , so as to enable the atomization.

The apparatus 500 may facilitate the atomization by applying ultrasound UW1 to the liquid LIQ1 . The apparatus 500 may sonicate the liquid LIQ1 . The apparatus 500 comprises a coupling element M1 , which is vibrated by an ultrasonic transducer SPK1. The vibrating coupling element M1 couples the ultrasound UW1 to the liquid LIQ1. The apparatus 500 comprises an inlet port IN1 for receiving the liquid LIQ1 , and one or more flow channels DLIC1 , DLIC2 for conveying the liquid LIQ1. The one or more flow channels DLIC1 , DLIC2 may convey the liquid LIQ1 to the nozzle NOZ1 .

The ultrasound UW1 may be transmitted to the nozzle NOZ1 via the liquid LIQ1 . The ultrasound UW1 may be transmitted to the nozzle NOZ1 via the liquid LIQ1 contained in the one or more flow channels DLIC1 , DLIC2.

The injection apparatus 500 may comprise:

- an inlet IN1 to receive a liquid LIQ1 ,

- a nozzle NOZ1 having one or more orifices OR1 to form droplets P1 from the liquid LIQ1 ,

- one or more flow channels DLIC1 to convey the liquid LIQ1 ,

- a coupling element M1 to couple ultrasound (UW1 ) to the liquid LIQ1 , and

- a transducer SPK1 to vibrate the coupling element M1 , wherein the liquid LIQ1 may be conveyed from the inlet IN1 to the one or more orifices OR1 via the one or more flow channels DLIC1 , wherein the injection apparatus 500 may be arranged to guide the ultrasound UW1 from the coupling element M1 to the nozzle NOZ1 via the liquid LIQ1 contained in the one or more flow channels DLIC1 .

The apparatus 500 may comprise a combiner unit CMB1 for combining the liquid LIQ1 with the ultrasound. The combiner unit CMB1 may comprise the inlet port IN1 , the coupling element M1 , and an opening to a flow channel DLIC1. The coupling element M1 may be arranged to direct ultrasound to the flow channel DLIC1. The apparatus 500 may have one or more flow channels DLIC1 for conveying the liquid LIQ1 from the combiner CMB1 to the nozzle NOZ1 .

The one or more flow channels DLIC1 , DLIC2 and the liquid LIQ1 contained in the flow channels may operate as a liquid waveguide WG1 to guide ultrasound UW1 to the nozzle NOZ1 via the liquid LIQ1 contained in the one or more flow channels DLIC1 , DLIC2. The apparatus 500 may be arranged to guide the ultrasound UW1 via the liquid LIQ1 of the liquid waveguide WG1 , in a situation where the one or more flow channels DIIC1 , DLIC2 are filled with the liquid LIQ1 .

The combiner unit CBM1 may convey the liquid LIQ1 from the inlet port IN1 to the liquid waveguide WG1. The flow channel DIIC1 may be in fluid communication with the inlet IN1 via the combiner unit CMB1 . The combiner unit CBM1 may couple the ultrasound UW1 to the liquid waveguide WG1. The ultrasound UW1 may propagate to the one or more orifices OR1 via the liquid waveguide WG1 .

The combiner CMB1 may comprise the coupling element M1 for coupling the ultrasound to the liquid LIQ1 , which is contained in the combiner CMB1. The coupling element M1 may be e.g. a vibrating membrane. The combiner CBM1 may comprise a hollow body 120. The coupling element M1 may be a portion of the body 120, or the coupling element M1 may be attached to the body 120. The coupling element M1 may be attached to the body 120 e.g. by a threaded joint, by welding or by press-fitting. The combiner CMB1 may optionally comprise a holding member 122 for attaching the coupling element M1 to the body 120. The holding member 122 may be attached to the body 120 e.g. by a threaded joint, by welding or by press-fitting. The combiner CMB1 may comprise solid material MAT1 , e.g. a metal.

The coupling member M1 has a coupling surface SRF0, which is in contact with the liquid LIQ1 , which is contained in the combiner CMB1 . The pressure PLIQI of the liquid LIQ1 inside the combiner CMB1 may be higher than the ambient atmospheric pressure PA of outside the combiner CMB1 . The pressure difference PLIQI-PA may be e.g. greater than 100 kPa, greater than 1 MPa, or even greater than 10 MPa. The vibrating coupling element M1 may be arranged to bear the pressure difference PLIQI-PA.

The coupling element M1 may be a membrane, which is arranged to bear the pressure difference (PLIQI-PA) between the pressure PLIQI of the liquid LIQ1 and an ambient pressure PA, in a situation where the pressure difference (PLIQI-PA) is e.g. greater than 100 kPa, greater than 1 MPa, or even greater than 10 MPa.

The injection apparatus 500 may comprise a flow control valve VAL1 . The valve VAL1 may comprise a valve seat SEAT1 and a valve member PIN1 , which moves with respect to the valve seat SEAT1. The valve member PIN1 may be e.g. a needle. The valve member PIN1 may be pressed against the valve seat SEAT1 so as to prevent the flow of the liquid L IQ 1 via the valve VAL1 . The valve member PIN1 may be lifted away from the valve seat SEAT1 so as to allow the flow of the liquid LIQ1 to the one or more orifices OR1 via the valve VAL1. The injection apparatus 500 may comprise an actuator ACLI1 for opening and/or closing the valve VAL1. The injection apparatus 500 may comprise an actuator ACLI1 for moving the valve member PINT The actuator ACLI1 may be e.g. an electromagnetic actuator, which comprises an electromagnetic coil COIL1. The actuator ACU1 may receive an electric control signal via terminals N101 , N102. An electric current may be coupled to the coil COIL1 via terminals N101 , N102. The electric current may cause a magnetic field, which in turn may be arranged to move the valve member PIN1 with respect to the seat SEAT1 . The coil COIL1 may be optionally covered with a protective cover COV1 .

The injection apparatus 500 may comprise a resilient member SPR1 for pressing the valve member PIN1 against the seat SEAT1 when the actuator ACLI1 is not energized. The resilient member SPR1 may be e.g. a spring.

Fig. 1 a shows the valve VAL1 in the closed position, where the flow of the liquid is prevented. Fig. 1 b shows the valve in the open position, where the liquid is allowed to flow from the channel DLIC1 to the one or more orifices OR1 .

The injection apparatus 500 may comprise the flow control valve VAL1 for controlling the flow of the liquid LIQ1. The injection apparatus 500 may be arranged to guide the ultrasound UW1 from the coupling element M1 to the valve seat SEAT and/or to the one or more orifices OR1 via the valve VAL1 , in a situation where the valve VAL1 is open.

The valve element VAL1 may optionally comprise an internal flow channel (e.g. DLIC1 ) for conveying the liquid LIQ1 and for transmitting ultrasound UW1 via the liquid LIQ1 , which is contained in the channel DLIC1. The ultrasound may propagate via the liquid waveguide WG1 to the valve seat SEAT1 and/or to the one or more orifices OR1 .

The valve element VAL1 may optionally comprise one or more openings OPE1 for conveying the liquid LIQ1 from the internal channel (DLIC1 ) to a second external annular channel DLIC2. The second channel DLIC2 may be defined e.g. by the valve member PIN1 and the nozzle body 111. The liquid LIQ1 may flow in the annular channel DLIC2 between the valve member PIN1 and the nozzle body 111. The ultrasound may be transmitted via the annular channel DLIC2.

The transducer SPK1 converts electrical power into mechanical vibration. The transducer SPK1 may be e.g. a piezoelectric transducer, a capacitive transducer, a magnetostrictive transducer, or an electromagnetic transducer. The transducer SPK1 may be driven by a driving unit OSC1 , which provides alternating current and/or alternating voltage at the operating frequency fi. The apparatus 500 may comprise the driving unit OSC1 , which may be arranged to drive the transducer SPK1 at the operating frequency fi. The driving current and/or voltage may be coupled to the transducer SPK1 via input terminals N1 , N2. The transducer SPK1 may vibrate the coupling element M1 at the frequency fi. The transducer SPK1 may be arranged to vibrate at a vibration frequency (fi), which is in the range of 20 kHz to 3 MHz.

The transducer SPK1 may comprise an ultrasonic horn HORN1 to increase the amplitude of oscillation. The ultrasonic horn may have e.g. tapered, exponential, or catenoidal shape. The amplitude at the output end of a tapered horn HORN1 may be e.g. approximately 3 times the amplitude at the output end of a cylindrical bar, in a situation where the amplitude at the input end of the horn is equal to the amplitude at the input end of the cylindrical bar. The amplitude at the output end of an exponential horn HORN1 may be e.g. approximately 4 times the amplitude at the output end of a cylindrical bar when the amplitudes at the inputs are equal. The amplitude at the output end of a catenoidal horn HORN1 may be e.g. approximately 5 times the amplitude at the output end of a cylindrical bar when the amplitudes at the inputs are equal.

A control unit ECU1 of the apparatus 500 may control operation of the transducer SPK1 via the driver OSC1. The control unit ECU1 may provide a control signal Sosci to the driver OSC1 for starting and/or stopping oscillation of the transducer SPK1.

The nozzle NOZ1 may comprise a nozzle body 111. The nozzle body 111 may also operate as a sheath, which surrounds the valve member PIN1 and the valve seat SEAT1 . The apparatus 500 may comprise a valve guide member 112 for defining the transverse position of the valve member PIN1. The valve member PIN1 may be arranged to slide in the axial direction (SZ and/or -SZ) with respect to the valve guide member 112. In an embodiment, a portion of the nozzle body 111 may be arranged to operate as the valve guide member 112.

The injection apparatus 500 may comprise an injector unit 100. The injector unit 100 may comprise the injector nozzle NOZ1 , the one or more orifices OR1 , the valve VAL1 , and the actuator ACLI1 (e.g. COIL1 ).

The actuator ACU1 may also be e.g. a piezoelectric actuator.

The injection apparatus may have a central axis AX1. SX, SY, SZ denote orthogonal directions. The axis AX1 may be parallel with the direction SZ.

Fig. 2 shows, by way of example, the liquid LIQ1 , which is contained in the combiner CMB1 and in the flow channels DLIC1 , DLIC2, in the situation where the flow control valve VAL1 is open. The inlet port IN1 is in fluid communication with the one or more orifices OR1 via the flow channels DLIC1 , DLIC2.

The liquid LIQ1 has a free surface FSRF1 at an orifice OR1. The free surface FSRF1 is the interface between the liquid LIQ1 and a gas (AIR1 ). The gas may be e.g. air AIR1. The ultrasound UW1 , UW2 may facilitate the atomization by causing oscillation of the free surface FSRF1. The ultrasound UW1 , UW2 may facilitate the atomization also by inducing microscopic surface waves on the free surface FSRF1

The injection apparatus 500 has an acoustic transmission line APATH1 for transmitting ultrasound UW0, UW1 , UW2 from the coupling element M1 to the free surface FSRF1. The acoustic transmission line APATH1 has a length LAPATHI . The symbol LAPATHI may also refer to the distance LAPATHI between the coupling element M1 and the orifices OR1. The distance LAPATHI between the coupling element M1 and the one or more orifices OR1 may be e.g. in the range of 50 mm to 500 mm. The acoustic transmission line APATH1 comprises the liquid waveguide WG1. The liquid waveguide WG1 has a length LWGI . The symbol UWO may refer to ultrasound in the combiner CMB1. The symbol UW1 may refer to ultrasound in the first flow channel DIIC1 . The symbol UW2 may refer to ultrasound in the second flow channel DLIC2. The combiner CMB1 , the one or more flow channels DIIC1 , DLIC2, and the flow control valve VAL1 (when in the open position) may allow a flow FLOW1 of the liquid LIQ1 from the inlet IN1 to the orifices OR1. Internal surfaces of the combiner CMB1 may also define a flow channel DllCO for the liquid LIQ1 .

The symbol UWO may refer to primary ultrasound which propagates in the liquid LIQ1 in the vicinity of the wetted surface SRFO of the coupling member M1. The symbol UW1 may refer to the ultrasound which propagates in the liquid LIQ1 , which is contained in the first flow channel DUC1 . The symbol UW2 may refer to the ultrasound which propagates in the liquid LIQ1 , which is contained in the second flow channel DUC2. The coupling member M1 may form primary ultrasound UWO in the liquid L IQ 1 , which is contained in the combiner CMB1 . The combiner CMB1 may form first ultrasound UW1 by coupling a part of the primary ultrasound UWO into the liquid LIQ1 , which is contained in the first flow channel DUC1 . The liquid waveguide WG1 may form second ultrasound UW2 by coupling a part of the first ultrasound UW1 into the liquid LIQ1 , which is contained the second flow channel DUC2.

A part of the ultrasound may be reflected back at a location where the crosssection of the liquid waveguide WG1 changes. The acoustic impedance of the liquid waveguide WG1 may be changed at a location where the cross-section of the liquid waveguide WG1 changes. The sound pressure level (puw2) of the second ultrasound UW2 may be lower than the sound pressure level (puwo) of the primary ultrasound UWO.

The acoustic transmission line APATH1 may be dimensioned to have low losses. The liquid waveguide WG1 may be dimensioned to have low losses. The dimensions of the acoustic transmission line APATH1 may be selected e.g. such that the sound pressure level (puw2) in the liquid (LIQ1 ) at the one or more orifices (OR1 ) may be greater than 10% of the sound pressure level (puwo) in the liquid (LIQ1 ) at the coupling element (M1 ). The sound pressure is the local oscillating pressure deviation from the static pressure (PLIQI) of the liquid LIQ1. Said pressure deviation oscillates at the frequency fi of the ultrasound.

The flow channels DllCO, DLIC1 , DLIC2 may be dimensioned so as to reduce or avoid the reflections. In an embodiment, the apparatus 500 may comprise e.g. an impedance matching cone between a flow channel (e.g. DllCO) and the next flow channel (e.g. DLIC1 ), so as to reduce reflections.

In an embodiment, a reflected part of the ultrasound may also be arranged to contribute to forming a standing wave in the first acoustic path APATH1 . At least one portion of the waveguide WG1 may be dimensioned to resonate at the vibration frequency fi of the transducer SPK1 .

The acoustic transmission line APATH1 may be straight or curved. A straight acoustic transmission line APATH1 may e.g. reduce or minimize losses. A curved acoustic transmission line APATH1 may e.g. disposing the transducer to a suitable position with respect to components of an engine ENG1 , e.g. to facilitate maintenance of the engine, and/or to facilitate maintenance of the apparatus 500.

The flow channel DllCO, DIIC1 , DLIC2 may be e.g. straight, curved or angled. Straight channel may provide lower loss than curved or angled channels.

The injection apparatus 500 may comprise e.g. the actuator coil COIL1 to open and/or close the valve VAL1 . The distance LAPATHI between the coupling element M1 and the one or more orifices OR1 may be e.g. greater than the distance (Lei) between the actuator coil COIL1 and the one or more orifices OR1 . The distance LAPATHI between the coupling element M1 and the one or more orifices OR1 may be e.g. greater than the distance (Lc2) between the furthermost edge of the actuator coil COIL1 and the one or more orifices OR1 . The actuator coil COIL1 may be located between the coupling element M1 and the one or more orifices OR1. This may allow e.g. efficient cooling of the transducer SPK1 and/or the actuator ACII1 .

Referring to Fig. 3, a reciprocating internal combustion engine ENG1 may comprise a cylinder CYL1 , a cylinder head HEAD1 , an air intake duct MAN1 , and one or more valves VAL2. In an embodiment, an air intake manifold may distribute air to several cylinders CYL1 . The air intake duct MAN1 may also be a part of an air intake manifold. Fuel (e.g. FUEL2) may be combusted in the combustion space COMBU1 of the cylinder CYL1 . Combustion air AIR1 may be admitted to the combustion space COMBU1 via the air intake duct MAN1 and via the air intake valve VAL2.

An injection system 1000 of the engine ENG1 may comprise the injection apparatus 500 and the air intake MAN1. The injection system 1000 may form a mixture MIX1 of air AIR1 and the atomized liquid LIQ1 . The mixture MIX1 may be admitted to the combustion space COMBU1 via the valve VAL2.

The liquid LIQ1 may be a combustible substance. The liquid LIQ1 may be a fuel. The liquid LIQ1 may be e.g. methanol CH3OH, another combustible liquid, liquified ammonia NH3, or another liquified combustible gas. The liquid LIQ1 may be a non-combustible liquid additive, e.g. water H2O.

The cylinder head HEAD1 may optionally comprise one or more injector units 200, e.g. for injecting a fuel FUEL2 into the combustion space COMBU1 of the cylinder CYL1. In an embodiment, the injection apparatus 500 may inject atomized first fuel LIQ1 to the combustion space COMBU1 via the air intake MAN1 , and a second injector unit 200 may inject a second fuel FUEL1 directly to the combustion space COMBU1. The first fuel LIQ1 may be e.g. methanol or ammonia. The second fuel FUEL2 may be e.g. diesel oil. The atomized second fuel FUEL2 may be used e.g. as a pilot fuel to ignite the atomized liquid LIQ1 in the combustion space COMBU1 .

In an embodiment, the injection apparatus 500 may also be arranged to inject the atomized liquid LIQ1 directly to the combustion space COMBU1. The injection apparatus 500 may be mounted to the cylinder head HEAD1 instead or the second injector unit 200 or in addition to the second injector unit 200.

The pressurized liquid LIQ1 may be provided to the inlet IN1 of the apparatus 500 e.g. by a pump system (not shown).

The coupling element M1 bears the pressure difference PLIQI-PA between the internal pressure PLIQI of the apparatus 500 and the ambient pressure PA. Thanks to the coupling element M1 , the transducer SPK1 may be removed or replaced even when the engine ENG1 is running.

The flow control valve VAL1 of the injection apparatus 500 may be arranged to prevent unintentional flow via the orifices OR1 . The flow control valve VAL1 may isolate the flow ducts of the injection apparatus 500 from the intake MAN1 and/or from the combustion space COMBU1. Thanks to the flow control valve VAL1 , also the coupling element M1 may be removed or replaced even when the engine ENG1 is running.

Fig. 4a shows, by way of example, a control system SYS1 of an engine ENG1 . The engine ENG1 may be e.g. the engine discussed with reference to Fig. 3. The control system SYS1 may comprise a control unit ECII1 (or CNT1 ) for controlling operation of the injection apparatus 500 based on sensor data obtained from one or more sensors SEN1 , SEN2, SEN3. The control unit ECII1 may control operation of the transducer SPK1 via the driver OSC1. The control unit ECII1 may provide a control signal Sosci to the driver OSC1 for starting and/or stopping oscillation of the transducer SPK1 .

The control unit ECLI1 may control operation of the actuator ACII1 of the flow control valve VAL1 via a driver DRV1. The control unit ECII1 may provide a control signal SVALI to the driver DRV1 for opening and/or closing the flow control valve VAL1 .

The transducer SPK1 may be operated intermittently e.g. in order to reduce heating of the transducer and/or in order to increase operating life of the injection apparatus 500. The vibration of the transducer SPK1 may be started before opening the flow control valve VAL1 , so as to allow the ultrasound UW2 to propagate to the flow control valve VAL1 already before the flow control valve VAL1 is opened. The vibration of the transducer SPK1 may be stopped e.g. when the flow control valve VAL1 is closed.

The control unit ECII1 may optionally control operation of the second injector unit 200 via a driver DRV2. The control unit ECII1 may optionally control timing of operation of the valves VAL2 of the engine ENG1 via a driver DRV4. The sensor SEN1 may be e.g. a crankshaft position sensor, which provides sensor data indicative of the angular position of the crankshaft of the engine ENG1. The control system SYS1 may comprise a user interface LIIF1 for receiving user input from a user and/or for providing information to the user. The user interface LIIF1 may comprise e.g. a touchscreen and/or a manual handle for inputting a desired rotation speed of the engine ENG1. For example, the engine control unit ECII1 may be configured to control operation of the injection apparatus 500 so as to keep the actual rotation speed substantially equal to the desired rotation speed. The control system SYS1 may comprise a memory MEM1 for storing computer program code PRG1. The control unit ECII1 (or CNT1 ) may be configured to control operation of the injection apparatus 500 by executing the code PRG1 . The control system SYS1 may comprise a memory MEM2 for storing a control model MODEL1 . The control system SYS1 may be arranged to form control signals for the injection apparatus and for the engine by using the model MODEL1. The control system SYS1 may be arranged to determine optimum control signals from the sensor signal values by using the model MODEL1 . The control system SYS1 may be arranged to determine optimum timing of control signals for the transducer SPK1 and the flow control valve VAL1 , from the sensor signal values, by using the model MODEL1 .

The sensors SEN1 , SEN2, SEN3, may include e.g. sensors for measuring one or more of the following: air intake pressure (PG), air intake flow rate, air intake temperature, flow rate of a fuel, flow rate of the liquid (LIQ1 ), exhaust pressure, exhaust temperature, oxygen concentration in exhaust gas, rotation speed, fuel temperature, coolant temperature, camshaft position, valve position, etc.

Referring to Fig. 4b, a control system SYS2 of the injection apparatus 500 may comprise a control unit CNT 1 , the actuator ACLI1 of the flow control valve VAL1 , the driver DRV1 of the actuator ACII1 , and the driver OSC1 of the transducer SPK1. The control unit CNT1 may receive a control signal S500 from an engine control unit ECII1 . The control unit CNT1 may be configured to control operation of the flow control valve VAL1 and the transducer SPK1 based on the control signal S500. The control unit CNT1 may be configured to open and/or close the flow control valve VAL1 by providing a control signal SVALI . The control unit CNT1 may be configured to start and/or stop operation of the transducer SPK1 by providing a control signal Sosci.The control unit CNT1 may start and/or stop injection of the liquid LIQ1 based on the control signal S500. Referring to Fig. 5, the injection apparatus 500 may optionally have a second acoustic transmission line APATH2 for transmitting ultrasound LIW21 , LIW22 from the coupling element M1 to the one or more orifices OR1 entirely via solid materials MAT1 , MAT2.

In particular, the injection apparatus 500 may be arranged to operate such that ultrasound guided via solid parts (CMB1 , 111 ) of the injection apparatus 500 is in phase with ultrasound guided via the liquid LIQ1 , at the position of the one or more orifices OR1 , at the operating frequency fi of the transducer SPK1 .

The injection apparatus 500 may comprise a first acoustic transmission line APATH1 for transmitting ultrasound (UW1 ) from the coupling element M1 to the one or more orifices OR1 via the liquid LIQ1 , wherein the injection apparatus 500 may further comprise a second acoustic transmission line APATH2 for transmitting ultrasound LIW21 ,UW22 from the coupling element M1 to the one or more orifices OR1 entirely via solid materials MAT1 , MAT2.

The materials MAT1 , MAT2 and the dimensions of the injection apparatus may be selected such that ultrasound LIW22 guided via the second acoustic transmission line APATH2 is substantially in phase with ultrasound UW2 guided via the first acoustic transmission line APATH1 , at the position of the one or more orifices OR1 , at the operating frequency fi of the transducer SPK1 .

The second acoustic transmission line APATH2 may e.g. comprise the combiner CMB1 and a body 111 of the nozzle NOZ1 . The combiner CMB1 may comprise material MAT1 . The nozzle body 111 may comprise material MAT2. The material MAT1 , MAT2 may be e.g. metal. The material MAT1 , MAT2 may be e.g. steel.

The injection apparatus 500 may be attached to an air intake duct MAN1 such that the air intake duct MAN1 allows vibration of the one or more orifices OR1 at the operating frequency fi of the transducer SPK1 , in the axial direction SZ. The ultrasound LIW22 may excite a standing wave in the second acoustic transmission line APATH2. In particular, the ultrasound LIW22 may excite a standing wave in the solid nozzle body 111. The standing wave may oscillate at the operating frequency fi of the transducer SPK1 . The one or more orifices OR1 may be located at an antinode of the standing wave, which is excited in the solid nozzle body 111. The node of the standing wave may remain substantially stationary, even if the antinode of said standing wave moves at the operating frequency fi of the transducer SPK1. The injection apparatus 500 may be supported at the location of the vibration node of the standing wave, and to allow vibration of the one or more orifices OR1 at the frequency fi of the ultrasound. The sealing SEAL1 may be arranged to allow vibration of the one or more orifices OR1 at the frequency fi of the ultrasound. The sealing SEAL1 may be e.g. a sliding sealing or a resilient sealing. The sealing SEAL1 may comprise e.g. an O- ring, which is made of an elastomer (rubber). The sealing SEAL1 may be located e.g. at the node, at the antinode, or at any location between a node and an antinode.

Alternatively, the injection apparatus 500 may be arranged to operate such that the ultrasound is guided to the free surface FSRF1 only via the first acoustic transmission line APATH1 , i.e. via the liquid LIQ1 . In that case the nozzle NOZ1 may also be attached to an air intake duct MAN1 such that the air intake duct MAN1 substantially prevents movement of the one or more orifices OR1 at the operating frequency fi of the transducer SPK1 .

Fig. 6 shows, by way of example, in a three-dimensional view, the injection apparatus 500.

Referring to Fig. 7, the injection apparatus 500 may optionally comprise one or more angled flow channels DLIC1 . The injection apparatus 500 may comprise one or more transverse flow channels DLIC1 . The injection apparatus 500 may comprise one or more curved flow channels DLIC1. The angled, curved and/or transverse flow channels may e.g. allow reducing the height of the injection apparatus 500 (in the axial direction SZ).

The apparatus 500 may comprise a transducer SPK1 , a combiner CMB1 , and an injector unit 100. The transducer SPK1 may vibrate the coupling element M1 . The vibrating coupling element M1 may couple the ultrasound UW1 to the liquid LIQ1 , which is contained in the combiner CMB1 and in the flow channels DLIC1 , DLIC2. The flow channels DLIC1 , DLIC2 and the liquid LIQ1 contained in the flow channels DUC, DLIC2 may operate as the liquid waveguide WG1 , to guide the ultrasound UW1 via the liquid LIQ1 from the coupling element M1 to the valve seat SEAT1. The flow channels DLIC1 , DLIC2 and the liquid LIQ1 contained in the flow channels DUC, DLIC2 may operate as the liquid waveguide WG1 , to guide the ultrasound UW1 via the liquid LIQ1 from the coupling element M1 to the one or more orifices OR1 , in a situation where the valve VAL1 is open.

In an embodiment, also a portion of a wall of a metal tube may be used as the coupling member M1 , to couple ultrasound to the liquid LIQ1. For example, the wall of a fuel inlet tube may be used as the coupling member M1 .

The valve VAL1 may be opened and/or closed by an actuator ACLI1. In an embodiment, the valve VAL1 may also be opened by using the hydraulic pressure PLIQI of the liquid LIQ1. For example, a part of the valve member PIN1 may operate as a piston of a hydraulic actuator. The valve VAL1 may be opened by using the pressure PLIQI , which acts on said piston. The valve VAL1 may be closed by using the restoring force of the spring SPR1 . The apparatus 500 may comprise the spring SPR1 and a link member 72 to transmit the restoring force from the spring SPR1 to the valve member PINT A first part of the liquid LIQ1 may be guided to the orifices OR1. The apparatus 500 may comprise a recirculation outlet OLIT1. A second part of the liquid LIQ1 may be recirculated via the outlet OLIT1 .

The combiner CMB1 may be attached to the injector unit 100. The injector unit 100 may comprise an injector body 76. The combiner CMB1 may be attached to the injector body 76. The nozzle NOZ1 may be attached to the injector body 76, or the nozzle NOZ1 may be a part of the injector body 76. The nozzle NOZ1 may be attached to the injector body 76 e.g. by a holding element 74. The apparatus 500 may comprise a holding element 78 for holding the spring SPR1 .

For the person skilled in the art, it will be clear that modifications and variations of the devices and methods according to the present invention are perceivable. The figures are schematic. The particular embodiments described above with reference to the accompanying drawings are illustrative only and not meant to limit the scope of the invention, which is defined by the appended claims.

Claims

1 . An injection apparatus (500), comprising:

- an inlet ( I N 1 ) to receive a liquid (L IQ 1 ),

- a nozzle (NOZ1 ) having one or more orifices (OR1 ) to form droplets (P1 ) from the liquid (LIQ1 ),

- one or more flow channels (DLIC1 ) to convey the liquid (LIQ1 ),

- a coupling element (M1 ) to couple ultrasound (UW1 ) to the liquid (LIQ1 ), and

- a transducer (SPK1 ) to vibrate the coupling element (M1 ), wherein the liquid (LIQ1 ) is conveyed from the inlet (IN1 ) to the one or more orifices (OR1 ) via the one or more flow channels (DLIC1 ), wherein the injection apparatus (500) is arranged to guide the ultrasound (UW1 ) from the coupling element (M1 ) to the nozzle (NOZ1 ) via the liquid (LIQ1 ) contained in the one or more flow channels (DLIC1 ).

2. The injection apparatus (500) of claim 1 , wherein the one or more flow channels (DLIC1 ) and the liquid (LIQ1 ) contained in the flow channels (DLIC1 ) operate as a liquid waveguide (WG1 ) to guide the ultrasound (UW1 ) via the liquid (LIQ1 ) contained in the flow channels (DLIC1 ).

3. The injection apparatus (500) of claim 1 or 2, wherein the injection apparatus (500) comprises a first acoustic transmission line (APATH1 ) for transmitting ultrasound (UW1 ) from the coupling element (M1 ) to the one or more orifices (OR1 ) via the liquid (LIQ1 ), wherein the injection apparatus (500) comprises a second acoustic transmission line (APATH2) for transmitting ultrasound (LIW21 ,UW22) from the coupling element (M1 ) to the one or more orifices (OR1 ) entirely via solid materials (MAT1 , MAT2).

4. The apparatus (500) according to any of the claims 1 to 3, wherein the coupling element (M1 ) is a membrane, which is arranged to bear a pressure difference (PLIQI-PA) between the pressure (PLIQI) of the liquid (LIQ1 ) and an ambient pressure (PA), in a situation where the pressure difference (PLIQI-PA) is greater than 100 kPa.

5. The apparatus (500) according to any of the claims 1 to 4, wherein the distance (LAPATHI ) between the coupling element (M1 ) and the one or more orifices (OR1 ) is in the range of 50 mm to 500 mm.

6. The apparatus (500) according to any of the claims 1 to 5, wherein the injection apparatus (500) comprises a flow control valve (VAL1 ) for controlling the flow of the liquid (LIQ1 ), wherein the ultrasound (UW1 ) is guided from the coupling element (M1 ) to the one or more orifices (OR1 ) via the valve (VAL1 ), in a situation where the valve (VAL1 ) is open.

7. The apparatus (500) according to any of the claims 1 to 6, wherein the fuel injection apparatus (500) comprises a flow control valve (VAL1 ) for controlling the flow of the liquid (LIQ1 ), wherein the injection apparatus (500) comprises an actuator coil (COIL1 ) to open the valve (VAL1 ), and the distance (LAPATHI ) between the coupling element (M1 ) and the one or more orifices (OR1 ) is greater than the distance (Lei) between the actuator coil (COIL1 ) and the orifices (OR1 ).

8. The apparatus (500) according to any of the claims 1 to 7, wherein the transducer (SPK1 ) is arranged to vibrate at a vibration frequency (fi), which is in the range of 20 kHz to 3 MHz.

9. The apparatus (500) according to any of the claims 1 to 8, wherein at least one portion of the waveguide (WG1 ) is dimensioned to resonate at the vibration frequency (fi) of the transducer (SPK1 ).

10. The apparatus (500) according to any of the claims 1 to 9, wherein sound pressure level (puw2) in the liquid (LIQ1 ) at the one or more orifices (OR1 ) is greater than 10% of the sound pressure level (puwo) in the liquid (LIQ1 ) at the coupling element (M1 ).

11. A reciprocating internal combustion engine (ENG1 ), comprising the injection apparatus (500) according to any of the claims 1 to 10, wherein the injection apparatus (500) is arranged to inject the droplets (P1 ) to an intake duct (MAN1 ) of the engine (ENG1 ).

12. A reciprocating internal combustion engine (ENG1 ), comprising the injection apparatus (500) according to any of the claims 1 to 10, wherein the injection apparatus (500) is arranged to inject the droplets (P1 ) directly to a combustion space (COMBU1 ) of a cylinder (CYL1 ) of the engine (ENG1 ).

13. A method of operating the engine (ENG1 ) of claim 11 or 12, wherein the liquid (LIQ1 ) is methanol (CH3OH), ammonia (NH3), or water (H2O).

14. A method of operating the engine (ENG1 ) of claim 11 or 12, comprising replacing the transducer (SPK1 ) with a second transducer while the engine

(ENG1 ) is running.