EP4534818A1

EP4534818A1 - Two-stroke hydrogen engine

Info

Publication number: EP4534818A1
Application number: EP23811448.2A
Authority: EP
Inventors: Akiyoshi Wachi; Takuya Iwamoto; Yo ARAMAKI
Original assignee: Yamaha Motor Co Ltd
Current assignee: Yamaha Motor Co Ltd
Priority date: 2022-05-24
Filing date: 2023-03-30
Publication date: 2025-04-09
Also published as: WO2023228569A1; EP4534818A4; JPWO2023228569A1

Abstract

A hydrogen two-stroke engine 10 is a uniflow engine, and includes a cylinder 12, a piston 16 provided reciprocatably inside the cylinder 12, an intake port 26 provided in a side surface of the cylinder 12 in order to supply an intake to a combustion chamber 24, an exhaust port 28 provided in the cylinder 12, at a position higher than the intake port 26 for discharging from the combustion chamber 24, an exhaust valve 40 provided in the cylinder 12 in order to open and close the exhaust port 28, a hydrogen injector 44 provided in the cylinder 12 in order to directly inject a hydrogen fuel into the combustion chamber 24, and a supercharger 30 provided upstream of the intake port 26 in order to supercharge the intake from the intake port 26 to the combustion chamber 24. The hydrogen two-stroke engine 10 is suitably utilized in transportation equipment such as small mobility equipment 1.

Description

TECHNICAL FIELD

The present invention relates to hydrogen two-stroke engines, and more specifically to a uniflow hydrogen two-stroke engine.

BACKGROUND ART

As an example which is pertinent to conventional techniques of this kind, Patent Literature 1 discloses a two-stroke internal combustion engine. The two-stroke internal combustion engine includes a crank case having an upper crank case and a lower crank case. The upper crank case has an intake port for introducing a gaseous fuel which is based on hydrogen and oxygen and an exhaust port for discharging water vapor loaded with unconsumed gaseous fuel. A mixer disposed upstream of the intake port mixes hydrogen and oxygen with compressed air, and the resulting gaseous fuel is introduced from the intake port into the upper crank case.

CITATION LIST

PATENT LITERATURE

Patent Literature 1: JP-A 2020-515771

SUMMARY OF INVENTION

TECHNICAL PROBLEM

The two-stroke internal combustion engine disclosed in Patent Literature 1 has a configuration that the mixer mixes hydrogen, oxygen and compressed air in advance to prepare a mixed gas, which is then introduced as the gaseous fuel from the intake port into the crank case. As understood, according to Patent Literature 1, the two-stroke internal combustion engine requires a mixer provided externally, which leads to complicated configuration. Also, nothing is disclosed on a supercharger, so there is room for improved output and torque.
Therefore, a primary object of the present invention is to provide a hydrogen two-stroke engine capable of providing improved output and torque with a simple configuration.

SOLUTION TO PROBLEM

According to an aspect of the present invention, there is provided a uniflow hydrogen two-stroke engine including a cylinder; a piston provided reciprocatably inside the cylinder; an intake port provided in a side surface of the cylinder in order to supply an intake to a combustion chamber defined by the cylinder and the piston; an exhaust port provided in the cylinder, at a position higher than the intake port for discharging from the combustion chamber; an exhaust valve provided in the cylinder in order to open and close the exhaust port; a hydrogen injector provided in the cylinder in order to directly inject a hydrogen fuel into the combustion chamber; and a supercharger provided upstream of the intake port in order to supercharge the intake from the intake port to the combustion chamber.
In the present invention, exhaust is discharged from the combustion chamber in a uniflow. In other words, exhaust is discharged from the combustion chamber by the air which is introduced from the supercharger into the cylinder through the intake port, and the combustion chamber is loaded with the intake which contains oxygen. The hydrogen injector directly injects the hydrogen fuel into the combustion chamber, which is under the above-described state, whereby the mixed gas of compressed hydrogen and oxygen is formed inside the combustion chamber. As understood, it is possible to make the mixed gas inside the combustion chamber with a simple configuration without employing a mixer. Also, by supercharging the intake into the combustion chamber with the supercharger, it is possible to obtain a mixed gas which contains highly concentrated hydrogen and oxygen inside the combustion chamber, and thereby increase engine efficiency, leading to improved output and torque. Also, since it is possible to open and close the exhaust port with the exhaust valve, the two-stroke engine has an increased freedom in terms of location of the exhaust port in the cylinder, which makes it possible to obtain the cylinder of a simple configuration.
Preferably, the intake port is at a position higher than a bottom dead center of the piston and lower than a top dead center thereof while the exhaust port is at a higher position than the top dead center of the piston. In this case, at least when the piston is at the bottom dead center, it is possible to provide the intake smoothly from the intake port into the cylinder and eventually into the combustion chamber, and it is also possible to discharge the exhaust from the combustion chamber via the exhaust port at a desired timing regardless of the position of the piston. Also, the invention makes it possible to form a uniflow flow path which passes from the intake port located below, through the combustion chamber, and then through the exhaust port located above favorably.
Further, preferably, the hydrogen injector is at a position higher than the top dead center. In this case, it is possible to inject the hydrogen fuel directly into the combustion chamber at a desired timing, regardless of the position of the piston.
Further, preferably, the hydrogen two-stroke engine further includes a spark plug provided in the cylinder, at a position higher than the top dead center in order to provide ignition in the combustion chamber. In this case, it is possible to ignite the mixed gas inside the combustion chamber at a desired timing, regardless of the position of the piston.
Preferably, the spark plug is at a top portion in the combustion chamber. In this case, it is possible to reliably ignite the mixed gas inside the combustion chamber at a desired timing.
Further, preferably, the piston includes a piston ring slidable with respect to an inner circumferential surface of the cylinder, and the intake port is provided in a range where the piston ring is movable. In this case, it is possible to adjust the intake timing into the cylinder and eventually into the combustion chamber by way of positional relationship between the intake port and the piston ring, whereby it is possible to introduce the intake favorably into the combustion chamber when the intake port is at a higher position than the piston ring.
The hydrogen two-stroke engine according to the present invention does not emit carbon dioxide in its exhaust, so it can contribute carbon neutrality of transportation equipment and be utilized suitably in transportation equipment.
The hydrogen two-stroke engine according to the present invention does not emit carbon dioxide in its exhaust, can have improved power and torque even if the engine has a small displacement, and therefore can contribute carbon neutrality and improved output and torque in small mobility equipment, being suitable for use in small mobility equipment.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, there is provided a hydrogen two-stroke engine capable of providing improved output and torque with a simple configuration.

BRIEF DESCRIPTION OF DRAWINGS

Fig. 1 is a schematic diagram which shows a hydrogen two-stroke engine according to an embodiment of the present invention.
Fig. 2 is an illustrative drawing for describing an operation of the hydrogen two-stroke engine in Fig. 1.
Fig. 3 is a schematic diagram which shows small mobility equipment provided with the hydrogen two-stroke engine in Fig. 1.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Referring to Fig. 1, a hydrogen two-stroke engine 10 according to an embodiment of the present invention is a uniflow two-stroke engine, and includes a cylinder 12. The cylinder 12 has a crank case 14 connected therewith. Inside the cylinder 12, a piston 16 is provided reciprocatably. The crank case 14 accommodates a crank shaft 18. The piston 16 and the crank shaft 18 are connected with each other by a connecting rod 20. The piston 16 includes a piston ring 22 which is slidable with respect to an inner circumferential surface of the cylinder 12. The piston ring 22 is provided near an upper end portion of the piston 16. The upper end portion of the piston 16 refers to an end portion of the piston 16 closer to a combustion chamber 24.
In order to supply an intake to the combustion chamber 24 which is defined by the cylinder 12 and the piston 16, an intake port 26 is provided on a side surface of the cylinder 12. An exhaust port 28 is provided in the cylinder 12, at a position higher than the intake port 26 for discharging from the combustion chamber 24.
The intake port 26 is located at a position higher than a bottom dead center of the piston 16 but lower than a top dead center thereof (see Fig. 2(b) and Fig. 2(d)). In other words, the intake port 26 is provided between the top dead center and the bottom dead center of the piston 16, i.e., in a range where an upper end portion of the piston 16 is movable. Also, the intake port 26 is provided in a range where the piston ring 22 is movable. Therefore, when the piston 16 is at the bottom dead center, the intake port 26 is at a higher position than the upper end portion of the piston 16, while it is at a lower position than the upper end portion of the piston 16 when the piston 16 is at the top dead center. Also, the exhaust port 28 is at a higher position than the top dead center of the piston 16.
In order to supercharge the intake from the intake port 26 to the combustion chamber 24, a supercharger 30 is provided upstream of the intake port 26. The intake port 26 and the supercharger 30 communicate with each other via an air intake pipe 32. The supercharger 30 may be provided by a turbocharger or a supercharger. Inside the air intake pipe 32, a throttle valve 34 is provided for adjusting an amount of supply of the intake.
In order to discharge exhaust from the combustion chamber 24, an exhaust pipe 36 is attached to the exhaust port 28. In order to purify the exhaust, a front catalyst 38 is provided inside the exhaust pipe 36. In order to open and close the exhaust port 28, an exhaust valve 40 is provided in the cylinder 12. In the present embodiment, the exhaust valve 40 is provided by a poppet valve.
In order to ignite the combustion chamber 24, a spark plug 42 is provided in the cylinder 12, at a position higher than the top dead center of the piston 16. The spark plug 42 is at a top portion in the combustion chamber 24.
In order to directly inject a hydrogen fuel into the combustion chamber 24, the cylinder 12 is provided with a hydrogen injector 44. The hydrogen injector 44 is at a higher position than the top dead center of the piston 16. The hydrogen injector 44 is connected with a hydrogen tank 48 via a regulator 46. The hydrogen injector 44 directly injects the hydrogen fuel supplied from the hydrogen tank 48, at an injection pressure adjusted by the regulator 46, into the combustion chamber 24.
In order to discharge a gas from a crank chamber 50 inside the crank case 14, the crank case 14 is provided with a discharge port 52, and the discharge port 52 has a discharge pipe 54 attached thereto. From the discharge pipe 54, a blow-by gas, for example, which is present inside the crank chamber 50 is discharged to the outside.
The hydrogen two-stroke engine 10 described thus far operates as follows for example.
First, as shown in Fig. 2(a), the piston 16 descends, and as the piston 16 comes to the bottom dead center, as shown in Fig. 2(b), the exhaust valve 40 opens the exhaust port 28. Then, as indicated by arrows in Fig. 2(b), the supercharger 30 supercharges the intake from the intake port 26 into the combustion chamber 24 and the combustion chamber 24 is scavenged. In other words, exhaust which contains water vapor is discharged in a uniflow from the combustion chamber 24. This replaces the gas inside the combustion chamber 24, i.e., an intake (air) which contains oxygen is introduced into the combustion chamber 24.
Thereafter, as the piston 16 ascends, the exhaust valve 40 begins to close the exhaust port 28. As shown in Fig. 2(c), when the piston ring 22 comes to a position higher than the intake port 26 where the combustion chamber 24 is no longer supplied with the intake, the exhaust port 28 is completely closed by the exhaust valve 40, whereby the combustion chamber 24 becomes a closed space.
Under the circumstances described above, the piston 16 continues to ascend toward the top dead center, bringing the combustion chamber 24 under an increasing compression. Then, as the hydrogen injector 44 makes direct injection of the hydrogen fuel into the combustion chamber 24 at a predetermined timing, a mixed, compressed gas of hydrogen and oxygen is formed inside the combustion chamber 24. Further, as shown in Fig. 2(d), at an approximate time point when the piston 16 reaches the top dead center, the spark plug 42 causes ignition in the combustion chamber 24, leading to a combustion (explosion) inside the combustion chamber 24.
Then, the piston 16 is pushed downward (toward the bottom dead center), bringing the hydrogen two-stroke engine 10 to the state shown in Fig. 2(a). Thereafter, the above-described cycle of actions is repeated. As described, in the hydrogen two-stroke engine 10, a cycle of intake, compression, combustion and exhaust is completed while the piston 16 makes one complete reciprocating movement. The hydrogen two-stroke engine 10 is suitably utilized in small mobility equipment 1 as shown in Fig. 3.
According to the hydrogen two-stroke engine 10 described above, exhaust is discharged from the combustion chamber 24 in a uniflow. In other words, exhaust is discharged from the combustion chamber 24 by the air which is introduced from the supercharger 30 into the cylinder 12 through the intake port 26, and the combustion chamber 24 is loaded with the intake which contains oxygen. The hydrogen injector 44 directly injects the hydrogen fuel into the combustion chamber 24, which is under the above-described state, whereby the mixed gas of compressed hydrogen and oxygen is formed inside the combustion chamber 24. As understood, it is possible to make the mixed gas inside the combustion chamber 24 with a simple configuration without employing a mixer. Also, by supercharging the intake into the combustion chamber 24 with the supercharger 30, it is possible to obtain a mixed gas which contains highly concentrated hydrogen and oxygen inside the combustion chamber 24, and thereby increase engine efficiency, leading to improved output and torque. Also, since it is possible to open and close the exhaust port 28 with the exhaust valve 40, the two-stroke engine has an increased freedom in terms of location of the exhaust port 28 in the cylinder 12, which makes it possible to obtain the cylinder 12 in a simple configuration.
The intake port 26 is at a position higher than the bottom dead center of the piston 16 but lower than the top dead center thereof while the exhaust port 28 is at a higher position than the top dead center of the piston 16. Therefore, at least when the piston 16 is at the bottom dead center, it is possible to provide the intake smoothly from the intake port 26 into the cylinder 12 and eventually into the combustion chamber 24, and it is also possible to discharge the exhaust from the combustion chamber 24 via the exhaust port 28 at a desired timing, regardless of the position of piston 16. Also, the invention makes it possible to form a uniflow flow path which passes from the intake port 26 located below, through the combustion chamber 24, and then through the exhaust port 28 located above favorably.
The hydrogen injector 44 is at a position higher than the top dead center of the piston 16. Therefore, it is possible to inject the hydrogen fuel directly into the combustion chamber 24 at a desired timing, regardless of the position of piston 16.
The spark plug 42 is provided at a position higher than the top dead center of the piston 16. Therefore, it is possible to ignite the mixed gas inside the combustion chamber 24 at a desired timing, regardless of the position of piston 16.
The spark plug is at a top portion in the combustion chamber 24. Therefore, it is possible to reliably ignite the mixed gas inside the combustion chamber 24 at a desired timing.
The intake port 26 is provided in a range of motion of the piston ring 22. Therefore, it is possible to adjust the intake timing into the cylinder 12 and eventually into the combustion chamber 24 by way of positional relationship between the intake port 26 and the piston ring 22, whereby it is possible to introduce the intake favorably into the combustion chamber 24 when the intake port 26 is at a higher position than the piston ring 22.
The hydrogen two-stroke engine 10 does not emit carbon dioxide in its exhaust, can have improved power and torque even if the engine has a small displacement, and therefore can contribute carbon neutrality and improved output and torque in the small mobility equipment 1, being suitable for use in the small mobility equipment 1.
It should be noted here that the hydrogen two-stroke engine 10 may be utilized not only in the small mobility equipment 1 but also in any transportation equipment. Since the hydrogen two-stroke engine 10 does not emit carbon dioxide in its exhaust, it can contribute carbon neutrality of transportation equipment and be utilized suitably in transportation equipment.
The present invention being thus far described in terms of preferred embodiments, it is obvious that these may be varied in many ways within the scope and the spirit of the present invention. The scope of the present invention is only limited by the accompanied claims.

REFERENCE SIGNS LIST

1: Small mobility equipment
10: Hydrogen two-stroke engine
12: Cylinder
14: Crank case
16: Piston
18: Crank shaft
20: Connecting rod
22: Piston ring
24: Combustion chamber
26: Intake port
28: Exhaust port
30: Supercharger
32: Air intake pipe
36: Exhaust pipe
40: Exhaust valve
42: Spark plug
44: Hydrogen injector

Claims

A uniflow hydrogen two-stroke engine comprising:
a cylinder;

a piston provided reciprocatably inside the cylinder;

an intake port provided in a side surface of the cylinder in order to supply an intake to a combustion chamber defined by the cylinder and the piston;

an exhaust port provided in the cylinder, at a position higher than the intake port for discharging from the combustion chamber;

an exhaust valve provided in the cylinder in order to open and close the exhaust port;

a hydrogen injector provided in the cylinder in order to directly inject a hydrogen fuel into the combustion chamber; and

a supercharger provided upstream of the intake port in order to supercharge the intake from the intake port to the combustion chamber.
The hydrogen two-stroke engine according to Claim 1, wherein
the intake port is at a position higher than a bottom dead center of the piston but lower than a top dead center thereof, and

the exhaust port is at a position higher than the top dead center of the piston.
The hydrogen two-stroke engine according to Claim 1 or 2, wherein the hydrogen injector is at a position higher than the top dead center.
The hydrogen two-stroke engine according to one of Claims 1 to 3, further comprising a spark plug provided in the cylinder, at a position higher than the top dead center in order to provide ignition in the combustion chamber.
The hydrogen two-stroke engine according to Claim 4, wherein the spark plug is at a top portion in the combustion chamber.
The hydrogen two-stroke engine according to one of Claims 1 to 5, wherein
the piston includes a piston ring slidable with respect to an inner circumferential surface of the cylinder, and

the intake port is provided in a range of motion of the piston ring.
The hydrogen two-stroke engine according to one of Claims 1 to 6, for use in transportation equipment.
The hydrogen two-stroke engine according to Claim 7, wherein the transportation equipment includes small mobility equipment.