CN112780461B

CN112780461B - Direct injection type fuel supply system

Info

Publication number: CN112780461B
Application number: CN202110004891.8A
Authority: CN
Inventors: 王振宇; 卢广超; 姜楠; 董雪飞
Original assignee: Electronic Technology Research Institute Of China Aerospace; Aerospace Times Feihong Technology Co ltd
Current assignee: Electronic Technology Research Institute Of China Aerospace; Aerospace Times Feihong Technology Co ltd
Priority date: 2021-01-04
Filing date: 2021-01-04
Publication date: 2022-08-30
Anticipated expiration: 2041-01-04
Also published as: CN112780461A

Abstract

The invention relates to the field of unmanned aerial vehicle engines, and provides a direct injection type fuel supply system, which is used for a small two-stroke aviation piston engine and comprises an oil supply unit and an oil injection unit; the fuel supply unit is used for supplying fuel to the fuel injection unit; the fuel injection unit is used for injecting fuel into the cylinder body from the lower part of the cylinder side and combusting the fuel to obtain power; the oil injection direction of the oil injection unit and the vertical axis of the engine cylinder form a set included angle; the oil injection unit comprises an oil injector and an oil injector mounting base; the fuel injector is arranged on the lower portion of the side wall of the engine cylinder body through the fuel injector mounting base and is arranged opposite to the exhaust pipe of the engine cylinder. The invention overcomes the defect that the traditional direct injection type oil injection system is arranged at the position of a cylinder cover of the cylinder and needs to bear the high-temperature and high-pressure environment of a combustion chamber, and improves the working environment of the oil injector; layered scavenging is realized by controlling the oil injection time, and the short-circuit loss of fuel oil is reduced; simple structure, the overall arrangement is compact, and intensity is big, and the quality is light, and the later stage of being convenient for is dismantled and is maintained.

Description

Direct injection type fuel supply system

Technical Field

The invention relates to the field of unmanned aerial vehicle engines, in particular to a direct injection type fuel supply system which is particularly suitable for small and medium-sized low-speed long-endurance unmanned aerial vehicles.

Background

Direct injection in a cylinder is a common technical scheme capable of reducing oil consumption of an engine. At present, the fuel injection mode of the aviation piston engine mainly adopts the fuel injection of an air inlet channel. The fuel injection control of the air inlet channel is simple and easy to atomize, but the fuel injection process is strongly coupled with the scavenging process of the two-stroke piston engine and is influenced by the exhaust escape loss of the two-stroke engine, a large amount of fuel is discharged from an exhaust port without being combusted, and the fuel capture rate is low. Resulting in too high fuel consumption rate of the engine and poor economy of the engine.

The traditional direct injection type fuel supply system for the piston engine is complex in system and heavy in weight due to the fact that high-pressure injection is adopted, and cannot be applied to a small two-stroke aviation piston engine.

At present, a direct injection type fuel supply system applied to a two-stroke piston engine of a small unmanned aerial vehicle in China is still blank.

Disclosure of Invention

The invention aims to fill the blank of a direct injection type fuel supply system of a two-stroke piston engine applied to a small unmanned aerial vehicle in China, and provides the direct injection type fuel supply system, so that an oil beam is quickly atomized under the action of scavenging airflow after entering a cylinder, and the ignition condition is achieved.

The invention adopts the following technical scheme:

a direct injection fuel delivery system for a small two-stroke aviation piston engine, the system comprising a fuel supply unit and a fuel injection unit;

the fuel supply unit is used for supplying fuel to the fuel injection unit;

the fuel injection unit is used for injecting fuel into the cylinder body of the engine from the lower part (obliquely upward) of the cylinder side of the engine and combusting the fuel to obtain power; the oil injection direction of the oil injection unit and the axis of the engine cylinder (the axis of the motion direction of the piston is generally vertical) form a set included angle.

Further, the oil injection unit comprises an in-cylinder direct injection oil injector and an oil injector mounting base;

the oil sprayer is arranged on the lower part of the side wall of the cylinder body of the engine cylinder and is arranged opposite to the exhaust pipe of the engine cylinder; the fuel injector is fixedly installed through the fuel injector installation base.

Further, the installation method of the fuel injector comprises the following steps:

an oil sprayer mounting hole is reserved below the side portion of an engine cylinder, an oil sprayer mounting base is mounted on the oil sprayer mounting hole, the oil sprayer is mounted in the oil sprayer mounting hole, and the oil sprayer is fixed on the oil sprayer mounting base through a grounding wire clamp.

Further, the grounding wire clamp is connected with the oil sprayer mounting base through screws, and the oil sprayer mounting base is connected with the oil sprayer mounting hole through threads.

Further, sealing treatment is carried out between the fuel injector mounting base and the fuel injector mounting hole.

Furthermore, the included angle between the oil injection direction of the oil injector and the axis of the cylinder body of the cylinder is 45-60 degrees.

The included angle between the oil injection direction of the oil injector and the axis of the cylinder body of the cylinder is 52 degrees.

Further, the installation height of the oil injector is consistent with or slightly lower than the height of the exhaust port of the cylinder.

Further, the oil supply unit comprises an oil tank, an oil filter, an oil pump and an oil pressure regulator;

the oil tank is connected with the oil pump through an oil filter; one end of the oil pressure regulator is connected with the oil pump, and the other end of the oil pressure regulator is connected with the oil tank; and the oil pump is connected with an oil injector of the oil injection unit.

Furthermore, the oil filter comprises a rough filter and a fine filter, and the oil tank, the rough filter, the fine filter and the oil pump are sequentially connected.

Further, the present invention is suitable for use in small two-stroke aviation piston engines having a power range of 15-55 horsepower.

The invention also provides a small two-stroke aviation piston engine which adopts the direct injection type fuel supply system.

The invention has the beneficial effects that:

(1) the traditional direct injection type oil injection system is arranged at the position of a cylinder cover of a cylinder and needs to bear the high-temperature and high-pressure environment of a combustion chamber, and the oil injection system is arranged below a piston in a combustion stage in a way of arranging the side surface of the cylinder body, so that the high-temperature and high-pressure in the cylinder are effectively avoided, the working environment of an oil injector is improved, and the reliability of the system is improved;

(2) the scavenging mode is reflux scavenging, and the hedging air flow formed by the contraposition scavenging passage in the scavenging stage can effectively accelerate the fuel atomization, so that the fuel supply system can ensure the effective atomization of the fuel without providing higher injection pressure, and has the advantages of simple structure and high reliability compared with the traditional direct injection type fuel supply system;

(3) because the oil injection system is arranged on the side surface of the cylinder body, after the scavenging port is opened by the piston in a descending way, scavenging can be carried out by utilizing air firstly, and after the oil injection port is opened by the piston in the descending way, the layered scavenging is realized by controlling the oil injection time, so that the short-circuit loss of fuel oil is reduced;

(4) the fuel injector mounting hole is reserved in the side face of the cylinder body, and the fuel injector is fixedly mounted through the mounting mode of the mounting base and the grounding wire clamp.

Drawings

Fig. 1 is a schematic diagram showing the overall structure of a direct injection fuel supply system according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing the arrangement of the fuel injector on the side surface of the cylinder body in the embodiment.

FIG. 3 is a schematic view showing the distribution of exhaust ports and fuel injection ports on the joint surface (expanded surface) of the cylinder block in the embodiment.

FIG. 4 is a schematic diagram of an engine phase in an embodiment, where CA is crank angle; ATDC refers to after top dead center.

Wherein: 1-a grounding wire clamp; 2-a screw; 3, mounting a base of the oil injector; 4-mounting holes of the oil injector; 5-oil sprayer.

Detailed Description

Specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that technical features or combinations of technical features described in the following embodiments should not be considered as being isolated, and they may be combined with each other to achieve better technical effects.

The embodiment of the invention discloses a direct injection type fuel supply system, which comprises a fuel supply unit and a fuel injection unit; the fuel supply unit is used for supplying fuel to the fuel injection unit; the fuel injection unit is used for injecting fuel into the cylinder body of the engine from the lower part of the cylinder side of the engine and combusting the fuel to obtain power; and the oil injection direction of the oil injection unit and the vertical axis of the engine cylinder form a set included angle.

Preferably, as shown in fig. 1, the fuel supply unit includes a fuel tank, a fuel filter (coarse filter and fine filter), an oil pump, an oil pressure regulator, and the like, when the oil pump is operated, fuel in the fuel tank enters the fuel injector through the oil filter and the like, fuel in the oil passage is returned through the oil pressure regulator, and fuel injection pressure in the oil passage is maintained.

In the embodiment shown in fig. 1, a port injection injector (injector 2) and a direct injection injector (

injectors

1 and 3, respectively used for cylinders 1 and 2) are arranged at the same time, the injector for port injection is a common arrangement form of a gasoline engine, and the reason why the port injector is arranged in the embodiment is that: the oil injection pressure of the direct injection oil injector in the cylinder is 3bar, and the pressure is lower; therefore, in the starting process of the engine, or in the process of cooling or warming the engine, the in-cylinder direct injection gasoline atomization effect is not good enough, and an air inlet channel injection mode needs to be adopted in the starting process, and the in-cylinder direct injection mode is changed after the engine is warmed. FIG. 1 is a preferred embodiment. The invention is characterized in that the arrangement and the oil injection mode of the direct injection oil injector in the cylinder can be combined with the traditional oil injection mode of an air inlet channel to obtain better effect.

As shown in fig. 2, the fuel injection unit includes an in-cylinder direct injection injector 5 and an injector mount base 3; the oil injector 5 is arranged at the lower part of the side wall of the cylinder body of the engine cylinder and is arranged opposite to the exhaust pipe of the engine cylinder; the fuel injector 5 is fixedly installed through the fuel injector installation base 3.

The fuel injector 5 can be mounted in a variety of ways, and one preferred way is as follows: an oil sprayer mounting hole 4 is reserved below the side part of an engine cylinder, the oil sprayer mounting base 3 is mounted in the oil sprayer mounting hole 4, and the oil sprayer 5 is fixed in the oil sprayer mounting base 3 through a grounding wire clamp 1; the grounding wire clamp 1 is connected with the oil sprayer mounting base 3 through a screw 2, and the oil sprayer mounting base 3 is connected with the oil sprayer mounting hole 4 through threads and is sealed. The arrangement mode effectively improves the working environment of the oil sprayer 5 and effectively prolongs the service life of the oil sprayer 5. It should be noted that the skilled person may choose to mount the device in other ways, but all fall within the scope of the present invention.

As a preferred embodiment, the angle between the injection direction of the injector 5 (obliquely upwards) and the vertical axis of the cylinder block is 45 ° to 60 °, more preferably 52 °.

As a preferred embodiment, the installation height of the fuel injector 5 is consistent with or slightly lower than the height of the exhaust port of the cylinder, as shown in FIG. 3.

In the above embodiment, the injection port phase and the scavenging port phase are the same, and the injection angle is a set angle, for example, 52 ° with respect to the cylinder axis angle. When the engine works, the oil supply unit and the oil injection unit work simultaneously, the oil supply unit maintains fuel oil at a certain pressure through the oil pump, the oil injection unit does not inject oil after the air scavenging port and the oil injection port are opened downwards by the piston, waste gas is scavenged by air firstly, the loss of scavenged fuel oil is effectively reduced, the capture rate of the fuel oil is improved, then the fuel oil is injected into the cylinder at a proper oil injection time under the control of the ECU, and oil bundles interact with opposite air flows in the cylinder to form mixed gas and compress the mixed gas. In the example, the scavenging mode is backflow scavenging, and by arranging the oil injection unit at a proper position of the cylinder body, the scavenging air flow in the cylinder enables the oil beam to be quickly atomized, so that low-pressure direct injection is realized.

FIG. 4 illustrates an embodiment of the engine phasing principle: when the piston moves downwards, the exhaust port is opened at 96CA (CA is a crank angle) after the top dead center, the free exhaust stage is started, when the exhaust port is 128CA after the top dead center, the scavenging port and the oil injection port are opened, the mixed scavenging stage is started, when the exhaust port is 150CA after the top dead center, the oil injection of the oil injector is started, when the oil injection is completed, the piston moves upwards, the compression stage is started, and ignition is carried out about 30CA before the top dead center, the combustion is started, and the next cycle is started.

In the above embodiment, the injection timing is 150CA after top dead center, and may be adjusted according to actual conditions. The range of injection timing may be approximately 140CA-160CA after TDC. Because the oil injection time is influenced by factors such as air port-oil port arrangement, engine phase, air passage form and the like, necessary adjustment is needed according to actual conditions, and the general principle is that fuel oil can be fully mixed with air flow after entering an air cylinder, and relatively homogeneous mixed gas is formed.

According to the invention, the low-pressure direct injection is realized by arranging the oil injector 5 on the side surface of the cylinder body of the cylinder (for a gasoline engine, the injection pressure of the air inlet channel for injection is 2.5-3bar, and the fuel injection pressure of the in-cylinder direct injection is generally 120-200 bar; for the in-cylinder direct injection in the technical scheme of the invention, the injection pressure is 3bar, the injection pressure of the in-cylinder direct injection can be only adopted by adopting a common air inlet channel and is greatly smaller than the conventional fuel injection pressure of the in-cylinder direct injection, namely 120-200bar), so that the high-temperature and high-pressure working environment is improved; according to the installation strategy of the oil injection unit, the low-pressure fuel oil is atomized by mainly utilizing scavenging airflow in the cylinder, the layered scavenging process is realized, and compared with the traditional premixed scavenging mode, the fuel oil short-circuit loss can be reduced, so that the oil consumption level of the engine is reduced.

The opposite side of the exhaust port is provided with an oil nozzle, air is firstly utilized to ventilate in the initial scavenging section, the short-circuit loss of fuel oil is effectively reduced, then a proper oil injection angle is selected, the opposite air flow of the opposite scavenging passages is utilized to break the oil bundles, the oil bundles are further mixed, then the air flow of the backflow scavenging is utilized, and the mixed air is pushed to a combustion chamber along with the upward movement of a piston, so that the installation position and the angle of the oil injector ensure that the oil bundles can be rapidly atomized under the action of the air flow in the cylinder after entering the cylinder.

The phase of the oil injector is consistent with that of the scavenging port, the oil injector is arranged at the position of an oil injection port with the axial angle of 52 degrees (best embodiment) with the cylinder body, the oil injector mounting hole 4 and the oil injector mounting base 3 are arranged on the side face of the cylinder body, and the oil injector mounting hole and the oil injector mounting base are fastened by threads, so that the oil injector is compact in layout and simple in structure, and is beneficial to later-stage disassembly and maintenance.

While several embodiments of the present invention have been presented herein, it will be appreciated by those skilled in the art that changes may be made to the embodiments herein without departing from the spirit of the invention. The above examples are merely illustrative and should not be taken as limiting the scope of the invention.

Claims

1. A direct injection type fuel oil supply system is used for a small two-stroke aviation piston engine of a small and medium-sized low-speed long-endurance unmanned aerial vehicle and is characterized by comprising an oil supply unit and an oil injection unit;

the fuel supply unit is used for supplying fuel to the fuel injection unit;

the fuel injection unit is used for injecting fuel into the cylinder body of the engine from the lower part of the cylinder side of the engine and combusting the fuel to obtain power; the oil injection direction of the oil injection unit and the axis of the engine cylinder form a set included angle;

the oil injection unit comprises an in-cylinder direct injection oil injector and an oil injector mounting base;

the oil sprayer is arranged on the lower part of the side wall of the cylinder body of the engine cylinder and is arranged opposite to the exhaust pipe of the engine cylinder; the oil sprayer is fixedly installed through the oil sprayer installation base; the installation height of the oil injector is consistent with or slightly lower than the height of an air outlet of the cylinder;

the included angle between the oil injection direction of the oil injector and the axis of the cylinder body of the cylinder is 45-60 degrees;

when the piston moves downwards, the exhaust port is opened at 96CA after the top dead center, the free exhaust stage is started, when the piston moves 128CA after the top dead center, the scavenging port and the oil injection port are opened, the mixed scavenging stage is started, when the piston moves 150CA after the top dead center, the oil injection is started by the oil injector, when the oil injection is completed, the piston moves upwards, the compression stage is started, ignition is carried out at about 30CA before the top dead center, the combustion is started, and the next cycle is started; CA is the engine crank angle.

2. The direct injection fuel delivery system of claim 1, wherein the injector is mounted by:

3. The direct injection fuel delivery system of claim 2, wherein the ground line clip is bolted to the injector mounting base, and the injector mounting base is threadably engaged with the injector mounting hole.

4. The direct injection fuel delivery system of claim 1, wherein the injector injects fuel at an angle of 52 ° to the cylinder block axis.

5. The direct injection fuel delivery system of claim 1, wherein the fuel supply unit includes a fuel tank, a fuel filter, a fuel pump, and a fuel pressure regulator;

6. The direct injection fuel delivery system of claim 5, wherein the fuel filter includes a coarse filter and a fine filter, and the fuel tank, the coarse filter, the fine filter, and the fuel pump are connected in series.

7. A small two-stroke aviation piston engine, characterized in that it comprises a direct injection fuel supply system according to any one of claims 1 to 6.