CN118008647A - Coaxial fuel injection nozzle, fuel injection system and engine - Google Patents

Abstract

The present invention relates to a coaxial fuel injection nozzle, a fuel injection system and an engine, comprising a needle valve body with an inner cavity formed inside, a methanol needle valve slidably connected inside the needle valve body and having an inner cavity formed inside, and a diesel needle valve slidably connected inside the methanol needle valve; a first pressure chamber is formed between the top of the methanol needle valve and the needle valve body, a second pressure chamber is formed between the top of the diesel needle valve and the inner top surface of the methanol needle valve, and the first pressure chamber is connected to the outside of the fuel injection nozzle through a second diesel circuit that runs through the needle valve body. In the present invention, a double needle valve coaxial design is adopted to minimize the changes required to the existing engine. At the same time, high-pressure and normal-pressure fuel injection of two fuels can be achieved, and the injection amount, injection time, and injection angle can be accurately controlled, which can maximize the effect of ensuring the best atomization effect of the two fuels.

Description

Coaxial fuel injection nozzle, fuel injection system and engine

Technical Field

The invention relates to the field of engine combustion, and in particular to a coaxial fuel injection nozzle, a fuel injection system comprising the coaxial fuel injection nozzle, and an engine comprising the fuel injection system.

Background technique

With the advancement of engine combustion science and technology, the understanding and control of chemical reactions in combustion are becoming increasingly important, especially the control of fuel self-ignition. For traditional gasoline engines, due to the use of uniform mixture spark plug ignition technology, the combustion heat release curve is completely controlled by the ignition time, and the control requirements for fuel injection are not high. For traditional diesel engines, due to the use of diffusion flame compression ignition, the injection time can basically completely control the final heat release curve. However, traditional gasoline engines and diesel engines have their own shortcomings in thermal efficiency and pollutant emissions. In order to avoid the shortcomings of gasoline and diesel engines in these aspects, the advanced engine combustion technologies proposed in recent years have adopted a certain mode of homogeneous (or relatively homogeneous) mixture compression combustion mode. Homogeneous mixture compression ignition technology uses a large amount of advance injection to leave enough time for the fuel and air to mix, and then when the piston reaches the top dead center, the pressure and temperature in the cylinder reach the ignition point, and compression ignition ignites.

In addition, in order to reduce dependence on imported oil and natural gas, future transportation energy, especially heavy trucks, ships, and aircraft, will inevitably face the transition to renewable energy. Among them, they will inevitably face the challenge of fuel diversity. Among the existing alternative fuel options, such as methanol, ammonia, natural gas, and hydrogen, none of the alternative fuels has the same ignition characteristics as gasoline or diesel, and it is difficult to use them directly in existing engines.

The present invention takes methanol and diesel as examples. Methanol is difficult to be ignited directly in a diesel engine because the spontaneous combustion of methanol is worse than that of diesel. Therefore, these alternative fuels are generally used in combination with two fuels in existing engines. For example, when methanol is used in a diesel engine, a portion of diesel needs to be injected to play a role in combustion and ignition.

However, the existing dual-fuel injection system technology has restrictions on the injection sequence and injection time of the two fuels, making it difficult to achieve precise control.

Summary of the invention

In view of this, the present invention aims to provide a coaxial fuel injection nozzle, a fuel injection system and an engine.

To solve the problems raised in the above background technology.

To achieve the above object, the technical solution of the present invention is achieved as follows:

The present invention provides a coaxial fuel injection nozzle, comprising a needle valve body with an inner cavity formed therein, a methanol needle valve slidably connected inside the needle valve body and having an inner cavity formed therein, and a diesel needle valve slidably connected inside the methanol needle valve;

A first pressure chamber is formed between the top of the methanol needle valve and the inner side of the needle valve body, and a second pressure chamber is formed between the top of the diesel needle valve and the inner top surface of the methanol needle valve. The first pressure chamber is connected to the outside of the fuel injector through a second diesel circuit that runs through the needle valve body, and the second pressure chamber is connected to the outside of the fuel injector through a first diesel circuit that runs through the methanol needle valve and the needle valve body.

A methanol pressure chamber is provided at a lower position inside the needle valve body, and the methanol pressure chamber is communicated with the outside of the needle valve body through a methanol oil path penetrating the needle valve body; a diesel pressure chamber is provided at a lower position inside the methanol needle valve, and the diesel pressure chamber is communicated with the outside of the needle valve body through a diesel oil path penetrating the methanol needle valve and the needle valve body;

A methanol spray hole is provided at the bottom of the needle valve body, and the methanol pressure chamber is connected to the engine combustion chamber through the methanol spray hole. A diesel spray hole is provided at the part of the bottom of the methanol needle valve extending to the outside of the needle valve body, and the diesel pressure chamber is connected to the engine combustion chamber through the diesel spray hole.

Furthermore, the outer side wall of the needle valve body is provided with a protruding connection portion, a second diesel inlet and a methanol inlet connected to the diesel oil circuit and the methanol oil circuit, and a first diesel inlet connected to the first pressure chamber.

Furthermore, the bottom of the methanol pressure chamber is provided with an inclined surface, and the bottom of the methanol needle valve is provided with an inclined surface matching the bottom of the methanol pressure chamber, and when the inclined surface of the methanol pressure chamber abuts against the inclined surface of the methanol needle valve, a methanol sealing surface can be formed to prevent the methanol pressure chamber from communicating with the methanol spray hole;

The bottom of the diesel pressure chamber is provided with an inclined surface, and the side wall of the diesel needle valve is provided with an inclined surface matching the bottom of the diesel pressure chamber. When the inclined surface of the diesel pressure chamber abuts against the inclined surface of the diesel needle valve, a diesel sealing surface can be formed to prevent the diesel pressure chamber from communicating with the diesel spray hole.

Furthermore, the first diesel circuit and the second diesel circuit are provided with a first solenoid valve and a second solenoid valve, respectively.

Furthermore, when the methanol needle valve slides in the needle valve body, the outer side wall of the methanol needle valve is tightly fitted with the inner side wall of the needle valve body;

When the diesel needle valve slides in the methanol needle valve, the outer wall of the diesel needle valve is tightly fitted with the inner wall of the methanol needle valve.

Furthermore, a storage cavity is provided at the bottom of the methanol needle valve, the storage cavity is communicated with the diesel pressure chamber, and the storage cavity is communicated with the diesel injection hole.

Furthermore, at least two diesel injection holes and two methanol injection holes are provided respectively.

An oil injection system, the oil injection system is provided with the above-mentioned coaxial oil injection nozzle;

The fuel injection system includes a methanol common rail system and a diesel common rail system. The methanol common rail system includes a methanol oil pump, a methanol filter, a methanol fuel tank, a methanol pressure control valve and a methanol conduit that are connected in sequence. The diesel common rail system includes a diesel conduit, a diesel filter, a diesel fuel tank, a diesel pressure control valve and a diesel conduit that are connected in sequence.

The methanol conduit is in communication with the methanol inlet, and the diesel conduit is in communication with the first diesel inlet, the second diesel inlet, the first diesel circuit, and the second diesel circuit;

The methanol pressure control valve and the diesel pressure control valve are connected to a control unit.

An engine is provided with the above-mentioned fuel injection system.

Compared with the prior art, the present invention has the following advantages:

In the present invention, two different liquid fuels are independently controlled to be sprayed into the combustion chamber of the internal combustion engine. In addition, the fuel injector of the present invention adopts a double needle valve coaxial design, which minimizes the changes required to the existing engine. At the same time, high-pressure and normal-pressure fuel injection of the two fuels can be achieved, and the injection amount, injection time, and injection angle can be accurately controlled, which can maximize the effect of ensuring the best atomization effect of the two fuels.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

FIG1 is a schematic diagram of the structure of a fuel injection nozzle of the present invention;

FIG. 2 is a schematic diagram of the structure of the fuel injection system of the present invention.

Description of reference numerals:

1. Needle valve body; 101. Methanol spray hole; 102. First pressure chamber; 2. Methanol needle valve; 201. Diesel spray hole; 202. Second pressure chamber; 3. Diesel needle valve; 4. First diesel inlet; 401. Second diesel inlet; 4011. Diesel oil circuit; 4012. Diesel pressure chamber; 5. Methanol inlet; 501. Methanol oil circuit; 502. Methanol pressure chamber; 6. First diesel circuit; 601. Second diesel circuit; 7. First solenoid valve; 701. Second solenoid valve; 8. Methanol sealing surface; 9. Diesel sealing surface; 10. Storage chamber; 11. Methanol oil pump; 1101. Methanol filter; 1102. Methanol tank; 1103. Methanol pressure control valve; 1104. Methanol conduit; 12. Diesel oil pump; 1201. Diesel filter; 1202. Diesel tank; 1203. Diesel pressure control valve; 1204. Diesel conduit; 13. Control unit.

Detailed ways

It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper", "lower", "inner", "back", etc. are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

In addition, in the description of the present invention, unless otherwise clearly defined, the terms "installed", "connected", "connection", and "connector" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood in combination with specific circumstances.

The present invention will be described in detail below with reference to FIGS. 1 to 2 in conjunction with embodiments.

Embodiment 1

In general, the present invention relates to a coaxial fuel injection nozzle, which is used for pre-injection of fuel when the engine is ignited. It comprises a needle valve body 1 with an inner cavity formed inside, a methanol needle valve 2 which is slidably connected inside the needle valve body 1 and has an inner cavity formed inside, and a diesel needle valve 3 which is slidably connected inside the methanol needle valve 2;

As shown in FIG1 , a first pressure chamber 102 is formed between the top of the methanol needle valve 2 and the inside of the needle valve body 1, and a second pressure chamber 202 is formed between the top of the diesel needle valve 3 and the inner top surface of the methanol needle valve 2. The first pressure chamber 102 is communicated with the outside of the fuel injector through the second diesel circuit 601 penetrating the needle valve body 1, and the second pressure chamber 202 is communicated with the outside of the fuel injector through the first diesel circuit 6 penetrating the methanol needle valve 2 and the needle valve body 1;

A methanol pressure chamber 502 is provided at the lower position inside the needle valve body 1, and the methanol pressure chamber 502 is communicated with the outside of the needle valve body 1 through a methanol oil path 501 penetrating the needle valve body 1. A diesel pressure chamber 4012 is provided at the lower position inside the methanol needle valve 2, and the diesel pressure chamber 4012 is communicated with the outside of the needle valve body 1 through a diesel oil path 4011 penetrating the methanol needle valve 2 and the needle valve body 1.

A methanol spray hole 101 is provided at the bottom of the needle valve body 1, and the methanol pressure chamber 502 is connected to the engine combustion chamber through the methanol spray hole 101. A diesel spray hole 201 is provided at the part of the bottom of the methanol needle valve 2 extending to the outside of the needle valve body 1, and the diesel pressure chamber 4012 is connected to the engine combustion chamber through the diesel spray hole 201.

As shown in FIG1 , in this embodiment, two different liquid fuels are independently controlled to be sprayed into the combustion chamber of the internal combustion engine. In addition, the fuel injector in the present invention adopts a double needle valve coaxial design, which minimizes the changes required to the existing engine. At the same time, high-pressure and normal-pressure fuel injection of the two fuels can be achieved, and the injection amount, injection time, and injection angle can be accurately controlled, which can maximize the best atomization effect of the two fuels.

Based on the above arrangement, as shown in FIG1 , methanol enters the methanol oil circuit 501 and the methanol pressure chamber 502 through the methanol inlet 5 for storage. When the injection strategy does not require the injection of methanol: since the bottom of the methanol pressure chamber 502 is provided with an inclined surface, the bottom of the methanol needle valve 2 is provided with an inclined surface that matches the bottom of the methanol pressure chamber 502, diesel enters the first pressure chamber 102 from the second diesel circuit 601, which will form pressure on the methanol needle valve 2, and the inclined surface of the methanol pressure chamber 502 will abut against the inclined surface of the methanol needle valve 2, thereby forming a methanol sealing surface 8 that prevents the methanol pressure chamber 502 from communicating with the methanol spray hole 101, thereby preventing the injection of methanol. When the injection strategy is to inject methanol: the diesel in the first pressure chamber 102 flows back out of the first pressure chamber, the methanol needle valve 2 will slide upward to open the methanol sealing surface 8, and due to the effect of pressure, methanol is ejected from the methanol pressure chamber 502 through the methanol spray hole 101 to the engine combustion chamber.

It should be noted that, as shown in FIG1 , based on the above configuration, diesel enters the diesel circuit and the diesel pressure chamber 4012 through the second diesel inlet 401 for storage. When the injection strategy does not require the injection of diesel: since the bottom of the diesel pressure chamber 4012 is provided with an inclined surface, and the side wall of the diesel needle valve 3 is provided with an inclined surface that matches the bottom of the diesel pressure chamber 4012, diesel will enter the second pressure chamber 202 from the first diesel circuit 6, thereby pressing the diesel needle valve 3, driving the inclined surface of the diesel pressure chamber 4012 to abut against the inclined surface of the diesel needle valve 3, forming a diesel sealing surface 9 that prevents the diesel pressure chamber 4012 from communicating with the diesel spray hole 201, thereby preventing the injection of diesel. When the injection strategy requires the injection of diesel, the diesel in the second pressure chamber 202 flows back, causing the diesel needle valve 3 to slide upward, opening the diesel sealing surface 9, and the diesel is sprayed into the engine combustion chamber through the diesel spray hole 201.

In actual operation, when the methanol needle valve 2 slides in the needle valve body 1, the outer wall of the methanol needle valve 2 is closely fitted with the inner wall of the needle valve body 1; when the diesel needle valve 3 slides in the methanol needle valve 2, the outer wall of the diesel needle valve 3 is closely fitted with the inner wall of the methanol needle valve 2. This can prevent methanol and diesel from leaking in the injection nozzle and mixing with each other, thereby affecting the start-up and ignition of the engine.

In addition, as a preference, at least two diesel injection holes 201 and methanol injection holes 101 are provided respectively, to ensure that the injection brightness of methanol and diesel can meet the requirements of the engine combustion chamber. The specific settings are made according to actual conditions and are not further limited here.

It should be further explained that the outer wall of the needle valve body 1 is provided with a protruding connection portion, a second diesel inlet 401 and a methanol inlet 5 connected to the diesel oil circuit 4011 and the methanol oil circuit 501 , and a first diesel inlet 4 connected to the first pressure chamber 102 .

In this embodiment, as shown in Figure 1, the connection portion can facilitate the second diesel inlet 401 and the methanol inlet 5 to be connected to external equipment for replenishing diesel and methanol. In addition, since the internal space of the first pressure chamber 102 is larger than the second pressure chamber 202, the first pressure chamber 102 needs more diesel to bite through the methanol needle valve 2, and the first diesel inlet 4 can relieve the diesel delivery pressure of the second diesel circuit 601 to the first pressure chamber 102.

As a preferred embodiment of the present invention, the first diesel circuit 6 and the second diesel circuit 601 are provided with a first solenoid valve 7 and a second solenoid valve 701 respectively, so that the delivery or backflow of diesel in the first diesel circuit 6 and the second diesel circuit 601 can be more conveniently controlled.

Since the diesel pressure chamber 4012 is inside the methanol needle valve 2, the diesel stored therein is less than the methanol in the methanol pressure chamber 502. In order to prevent the situation where the diesel injection cannot meet the combustion requirements, in this embodiment, a storage chamber 10 is provided at the bottom of the methanol needle valve 2. The storage chamber 10 is connected to the diesel pressure chamber 4012 and also to the diesel spray hole 201. The storage chamber 10 increases the storage capacity of the diesel.

In summary, the present invention can realize the independent injection of two fuels. The existing related dual-fuel injection system technology has restrictions on the injection sequence and injection time of the two fuels, while the dual-fuel coaxial injector of the present invention has no restrictions on the injection sequence and time of the two fuels. Any dual-fuel injection strategy such as single injection of one fuel, simultaneous injection of two fuels, and successive injection of two fuels can be realized. Flexible injection strategies make advanced combustion modes that use fuel chemical reaction activity as an important control method possible.

In addition, the dual fuels share a coaxial fuel injector, which reduces the space required to install extra fuel injectors in the engine cylinder head and reduces the complexity of the engine cylinder head design.

It should be understood that if the ignition characteristics of the renewable fuel are relatively poor, such as methanol, the renewable fuel can be used as one fuel in the dual-fuel system of the present invention, and a combustion aid, such as diesel or another ignition improver, can be used. On the contrary, if the ignition characteristics of the renewable fuel are too strong, another highly reactive fuel can be used as an ignition inhibitor. If the volatility of the renewable fuel is very poor, the size of the nozzle can be reduced, the pressure of the pressure chamber can be increased, and the atomization effect can be enhanced. If the volatility of the renewable fuel is very good, the size of the nozzle can be increased, the pressure of the pressure chamber can be reduced, and the cost can be reduced.

The dual fuel of the present invention is applicable to any dual liquid fuel. The present invention uses methanol and diesel as a specific embodiment for illustration, but is not limited to methanol and diesel. It can also be methanol and biodiesel, methanol and fuel ignition additives, ethanol and diesel, etc.

Embodiment 2

On the basis of the above embodiment, this embodiment provides an oil injection system, which is provided with the above coaxial oil injection nozzle.

As shown in Figure 2, the injection system includes a methanol common rail system and a diesel common rail system. The methanol common rail system includes a methanol oil pump 11, a methanol filter 1101, a methanol fuel tank 1102, a methanol pressure control valve 1103 and a methanol conduit 1104 that are connected in sequence. The diesel common rail system includes a diesel conduit 1204, a diesel filter 1201, a diesel fuel tank 1202, a diesel pressure control valve 1203 and a diesel conduit 1204 that are connected in sequence; the methanol conduit 1104 is connected to the methanol inlet 5, and the diesel conduit 1204 is connected to the first diesel inlet 4, the second diesel inlet 401, the first diesel circuit 6 and the second diesel circuit 601.

In this embodiment, methanol is pumped from the methanol tank 1102 into the methanol conduit 1104 through the operation of the methanol pump 11, and then input into the methanol pressure chamber 502 through the methanol inlet 5, and can be pressurized while being transported. The methanol filter 1101 can filter impurities in the methanol to prevent affecting the start of the engine, and the methanol pressure control valve 1103 can control the pressure in the methanol common rail system to prevent accidents.

As shown in FIG. 2 , in the diesel common rail system, the diesel is pumped from the diesel pump 12 into the diesel conduit 1204 through the operation of the diesel pump 12, and then enters the first pressure chamber 102 through the second diesel inlet 401 and the second diesel circuit 601, enters the diesel pressure chamber 4012 through the second diesel inlet 401, and enters the second pressure chamber 202 through the first diesel circuit 6. During operation, the diesel filter 1201 can filter impurities in the diesel to prevent affecting the start of the engine. The diesel pressure control valve 1203 can control the pressure in the diesel common rail system and the on/off of each pipeline to prevent accidents.

Based on the above arrangement, an on-off valve is provided at the connection point between the methanol conduit 1104 and the diesel conduit 1204 and the fuel injector to control the on-off of the connecting pipeline, which can reduce safety hazards and meet different work requirements.

It should be noted that the methanol pressure control valve 1103 and the diesel pressure control valve 1203 are connected to the control unit 13. The control unit 13 is an ECU, i.e., an onboard computer, which is composed of a microcontroller and peripheral circuits, and controls the fuel injection strategy through the ECU algorithm.

Embodiment 3

This embodiment relates to an engine, in which the fuel injection system involved in the second embodiment is provided.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (9)

1. A coaxial oil jet, characterized in that:

The diesel oil injection valve comprises a needle valve body (1) with an inner cavity formed inside, a methanol needle valve (2) with the inner cavity formed inside and connected with the needle valve body (1) in a sliding way, and a diesel oil needle valve (3) connected with the methanol needle valve (2) in a sliding way;

A first pressure cavity (102) is formed between the top of the methanol needle valve (2) and the inside of the needle valve body (1), a second pressure cavity (202) is formed between the top of the diesel needle valve (3) and the inside top surface of the methanol needle valve (2), the first pressure cavity (102) is communicated with the outside of the fuel injection nozzle through a second diesel loop (601) penetrating through the needle valve body (1), and the second pressure cavity (202) is communicated with the outside of the fuel injection nozzle through a first diesel loop (6) penetrating through the methanol needle valve (2) and the needle valve body (1);

A methanol pressure chamber (502) is arranged at the lower position inside the needle valve body (1), the methanol pressure chamber (502) is communicated with the outside of the needle valve body (1) through a methanol oil path (501) penetrating through the needle valve body (1), a diesel pressure chamber (4012) is arranged at the lower position inside the methanol needle valve (2), and the diesel pressure chamber (4012) is communicated with the outside of the needle valve body (1) through a diesel oil path (4011) penetrating through the methanol needle valve (2) and the needle valve body (1);

The fuel injection valve is characterized in that a methanol spray hole (101) is formed in the bottom of the needle valve body (1), the methanol pressure chamber (502) is communicated with an engine combustion chamber through the methanol spray hole (101), a diesel spray hole (201) is formed in the portion, extending out of the outer side of the needle valve body (1), of the bottom of the methanol needle valve (2), and the diesel pressure chamber (4012) is communicated with the engine combustion chamber through the diesel spray hole (201).

2. A coaxial oil jet according to claim 1, wherein:

The outer side wall of the needle valve body (1) is provided with a convex connecting part, a second diesel inlet (401) and a methanol inlet (5) which are communicated with the diesel oil way (4011) and the methanol oil way (501) are arranged, and a first diesel inlet (4) which is communicated with the first pressure cavity (102) is also arranged.

3. A coaxial oil jet as claimed in claim 2, wherein:

The bottom of the methanol pressure chamber (502) is provided with an inclined plane, the bottom of the methanol needle valve (2) is provided with an inclined plane matched with the bottom of the methanol pressure chamber (502), and when the inclined plane of the methanol pressure chamber (502) is abutted against the inclined plane of the methanol needle valve (2), a methanol sealing surface (8) for preventing the methanol pressure chamber (502) from being communicated with the methanol spray hole (101) can be formed;

The bottom of the diesel oil pressure chamber (4012) is provided with an inclined plane, the side wall of the diesel oil needle valve (3) is provided with an inclined plane matched with the bottom of the diesel oil pressure chamber (4012), and when the inclined plane of the diesel oil pressure chamber (4012) is abutted to the inclined plane of the diesel oil needle valve (3), a diesel oil sealing surface (9) for preventing the diesel oil pressure chamber (4012) from being communicated with the diesel oil spray hole (201) can be formed.

4. A coaxial oil jet as claimed in claim 2, wherein:

The first diesel oil loop (6) and the second diesel oil loop (601) are respectively provided with a first electromagnetic valve (7) and a second electromagnetic valve (701).

5. A coaxial oil jet as claimed in claim 2, wherein:

when the methanol needle valve (2) slides in the needle valve body (1), the outer side wall of the methanol needle valve (2) is tightly attached to the inner side wall of the needle valve body (1);

when the diesel needle valve (3) slides in the methanol needle valve (2), the outer side wall of the diesel needle valve (3) is tightly attached to the inner side wall of the methanol needle valve (2).

6. A coaxial oil jet as claimed in claim 2, wherein:

The inner bottom of the methanol needle valve (2) is provided with a storage cavity (10), the storage cavity (10) is communicated with the diesel oil pressure chamber (4012), and the storage cavity (10) is communicated with the diesel oil spray hole (201).

7. A coaxial oil jet as claimed in claim 2, wherein:

At least two diesel spray holes (201) and at least two methanol spray holes (101) are respectively arranged.

8. A fuel injection system is characterized in that,

The fuel injection system is provided with the coaxial fuel injection nozzle as claimed in any one of claims 2 to 7;

The fuel injection system comprises a methanol common rail system and a diesel common rail system, wherein the methanol common rail system comprises a methanol oil pump (11), a methanol filter (1101), a methanol oil tank (1102), a methanol pressure control valve (1103) and a methanol conduit (1104) which are sequentially communicated, and the diesel common rail system comprises a diesel conduit (1204), a diesel filter (1201), a diesel oil tank (1202), a diesel pressure control valve (1203) and a diesel conduit (1204) which are sequentially communicated;

The methanol conduit (1104) is communicated with the methanol inlet (5), and the diesel conduit (1204) is communicated with the first diesel inlet (4), the second diesel inlet (401), the first diesel loop (6) and the second diesel loop (601);

the methanol pressure control valve (1103) and the diesel pressure control valve (1203) are connected with a control unit (13).

9. An engine, which is characterized in that,

An injection system according to claim 8 disposed within said engine.