Pre-combustion chamber jet ignition device integrated on piston

Abstract

The invention discloses a precombustion chamber jet ignition device integrated on a piston, and the precombustion chamber jet ignition device is structurally characterized in that a fence is arranged at the upper part of a concave pool in the center of the top of the piston, a spherical flamethrower is nested and welded in the fence above the concave pool, and the spherical flamethrower covers the concave pool to form a cavity. And a plurality of injection pipes are arranged in the spherical injector. The two sides of the fence are communicated with the two pre-combustion chambers correspondingly, and the pre-combustion chambers are located on the same plane but are asymmetrically arranged. The cavity chamber is provided with two conical channels which are respectively communicated with the two pre-combustion chambers, and the two ignition ejectors are respectively connected with the two pre-combustion chambers; the two main fuel injectors are connected with the cylinder. The included angle between the central axis of the main fuel injector and the vertical direction is 120-140 degrees, and the scavenging port is formed in the lower portion of the air cylinder. Main fuel enters the two pre-combustion chambers through the spherical flamethrowers, flames generated by the pre-combustion chambers ignite the main fuel in the cylinders through the spherical flamethrowers, the flame propagation distance is shortened through the structure, and the knocking phenomenon generated in the combustion chambers is prevented.

Description

[0001] The present invention belongs to the field of engine structure technology, and specifically relates to a jet ignition system with a pre-combustion chamber on a piston.

[0002] device. Background Art

[0003] Faced with the severe challenges of energy shortage and "dual carbon" goals brought about by the increasing shipping trade year by year, natural gas (CNG) with lower carbon content has been widely used as the main transitional alternative fuel in the field of ship engines compared to diesel. Low-speed two-stroke marine engines have become the main power source in the field of ocean-going transportation with their large cylinder diameter, low speed, long stroke and high boost. In recent years, marine dual-fuel engines have gradually occupied an important position in ocean-going shipping ships. At present, marine diesel / natural gas dual-fuel engines can be divided into high-pressure injection dual-fuel engines and low-pressure injection dual-fuel engines according to their technical characteristics. In the former, natural gas is directly injected into the combustion chamber at high pressure (about 300 bar), and after mixing with air, it exhibits diffusion combustion characteristics as a whole. Although a higher compression ratio is used to achieve higher thermal efficiency, it faces the problem of higher nitrogen oxide (NOx) emissions and cannot directly meet the Tier III emission standards of the International Maritime Organization. For this reason, it is necessary to install an exhaust gas after-treatment device or adopt an in-engine purification technology such as exhaust gas recirculation (EGR) technology, which will inevitably greatly increase the manufacturing cost of the engine. For low-pressure injection dual-fuel engines, natural gas is injected into the cylinder at low pressure and mixed with air in advance in the cylinder to form a uniform combustible mixture. Diesel is directly injected into the pre-combustion chamber, and then the premixed mixture in the main combustion chamber is ignited by the jet flame. This does not require the installation of additional after-treatment devices or the use of in-engine purification technology to meet Tier III emission standards. Its thermodynamic cycle work mode is similar to the Otto cycle. Considering the knock limitation caused by the self-ignition of the terminal mixture under high compression ratio, a lower compression ratio is generally used, the thermal efficiency is relatively low, and the operating conditions are relatively narrow.

[0004] In view of the problem of rough combustion and even detonation that is prone to occur under high load in marine low-pressure injection dual-fuel engines, the present invention proposes a pre-combustion chamber jet ignition system integrated on the piston, which suppresses rough combustion while improving the compression ratio of the low-pressure injection dual-fuel engine, thereby achieving the purpose of improving thermal efficiency. Summary of the invention

[0005] The purpose of the present invention is to provide a pre-combustion chamber jet ignition system integrated on the piston, which can suppress the detonation phenomenon of the dual-fuel engine under the condition of low-pressure injection for marine use, improve the reliability of the dual-fuel engine, and facilitate the scavenging and exhausting of the exhaust gas in the pre-combustion chamber, thereby improving the scavenging efficiency. It is particularly suitable for low-speed two-stroke dual-fuel marine engines with low-pressure injection.

[0006] The principle and technical solution of the device of the present invention are described below.

[0007] The pre-combustion chamber jet ignition device integrated on the piston comprises a piston and a cylinder. The technical structure is as follows: a concave pool is provided at the center of the top of the piston, a fence is provided on the upper part of the concave pool, a spherical flamethrower is nested and welded in the fence above the concave pool, and the spherical flamethrower covers the concave pool to form a hollow chamber. The spherical surface of the spherical flamethrower is provided with a plurality of injection holes. Two circular holes are provided on both sides of the fence respectively, which are used to pass into the first pre-combustion chamber and the second pre-combustion chamber. The two pre-combustion chambers are located in the same plane but are arranged asymmetrically. The hollow chamber is provided with two conical channels which are respectively connected to the first and second pre-combustion chambers. The first pilot injector and the second pilot injector pass through the piston body and are respectively connected to the first and second pre-combustion chambers; the first main fuel injector and the second main fuel injector are connected to the cylinder through a drilling hole. The angle between the central axis of the first and second main fuel injectors and the vertical direction is 125-140°, and the scavenging port is arranged at the lower part of the cylinder. Before ignition, the main fuel injected by the two main fuel injectors enters the cylinder and enters the empty chamber through the spherical flame spray hole, and then enters the two pre-combustion chambers and two pilot injectors through two conical channels. When the piston moves upward to the ignition position, the two pilot injectors are first compressed and ignited to spray flames, which can increase the ignition energy. The high-energy flames generated by the two pre-combustion chambers ignite the main fuel through the spherical flame device, so that the flame spreads from the center of the combustion chamber to the surrounding cylinder walls.

[0008] The working process of the present invention is:

[0009] During the scavenging process, the exhaust valve of the engine is opened, and when the piston runs to the bottom dead center in the cylinder, the scavenging port is connected to the cylinder. On the one hand, fresh air discharges the exhaust gas in the cylinder through the scavenging port; on the other hand, fresh air enters the first and second pre-combustion chambers through the scavenging port. Then, they enter the cavity through their respective tapered channels, and discharge the exhaust gas retained in the first and second pre-combustion chambers and the cavity.

[0010] Then the piston moves upward, the scavenging port and the exhaust valve are closed. In order to avoid leakage of the main fuel, the main fuel is injected after the exhaust valve is closed. The first and second main fuel injectors inject the main fuel into the cylinder at a certain angle and pressure. The two main fuels diffuse in the cylinder and mix with the ambient gas in the cylinder to form a combustible mixed gas. At the end of compression, the concentration of combustible gas in the cavity and on the top of the piston (with air) is higher than that in other areas of the cylinder. The mixed gas enters the first and second pre-combustion chambers respectively through the injection holes of the spherical flame injector.

[0011] The piston continues to move upward, and before approaching the top dead center of the cylinder, the first and second pilot injectors are connected to the first and second pre-combustion chambers respectively, and the cylinder is in a state of high temperature and high pressure. The pilot fuel begins to be injected into the two pre-combustion chambers, and the pilot fuel in the two pre-combustion chambers is quickly ignited at a higher pressure and temperature. The flame spreads to the cavity through the first and second pre-combustion chambers and the two channels. The flame generates a jet flame through the injection hole of the spherical flame injector to ignite the main fuel, so that the flame spreads evenly from the center of the cylinder to the surrounding walls, thereby igniting all the main fuel in the cylinder.

[0012] The piston moves downward to do work, and when it is completed, the exhaust valve opens and the engine begins a new cycle.

[0013] The current technical solution for traditional dual-fuel engines is a dual pre-combustion chamber structure set on the bottom edge of the cylinder head. In dual-fuel mode, due to the long propagation distance of the jet flame in the cylinder, the relatively dense terminal mixture triggers pre-ignition under high temperature and high pressure, resulting in unstable combustion and frequent knocking, which affects the reliability of the engine. In addition, the exhaust gas in the dual pre-combustion chamber structure on the cylinder head is difficult to be completely swept out, and the temperature and composition of the pre-combustion chamber are difficult to control, resulting in differences in the combustion intensity of the jet flame each time (cycle), which ultimately causes cyclic changes in the combustion of the main fuel in the cylinder.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] (1) The main fuel mixture with a high concentration enters the two pre-combustion chambers through the spherical flame jet nozzle, which can increase the energy of the flame when the jet enters the cylinder, avoid flameout and promote flame diffusion. The flame generated in the pre-combustion chamber is sprayed into the combustion chamber through the spherical flame jet, igniting the main fuel in the cylinder, shortening the flame propagation distance, avoiding uneven combustion of the terminal mixture and the engine fuel on the combustion chamber wall, and preventing the detonation phenomenon in the combustion chamber.

[0016] (2) During the scavenging stage, the scavenging port is interconnected with the pre-combustion chamber and the spherical flame injector on the top of the piston. During the scavenging process, the problem of the difficulty in discharging exhaust gas in the pre-combustion chamber of the current dual-fuel engine is solved, and the instability of the combustion cycle in the cylinder can be effectively reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram showing the principle and assembly structure of the present invention.

[0018] Figure 2 It is a schematic diagram of the assembly structure of the piston body and the flamethrower in the present invention.

[0019] Figure 3 This is a structural diagram of the upper portion of the piston body with a flamethrower according to the present invention.

[0020] Figure 4It is a cross-sectional view of the flamethrower in the present invention.

[0021] Figure 5 This is a top view of the piston top structure in the present invention.

[0022] Figure 6 This is a schematic diagram showing the installation angle between the main fuel injector and the cylinder wall in the present invention.

[0023] Figure 7 This is a structural diagram of the angle between the two pre-combustion chambers on the piston of the present invention.

[0024] Figure 8 It is a schematic diagram of the piston body assembly structure in the present invention.

[0025] Fig. 9 This is a schematic diagram of the state in which the main fuel injection converges above the piston cavity according to an embodiment of the present invention. DETAILED DESCRIPTION

[0026] The structure of the present invention is further explained below in conjunction with the accompanying drawings and through specific embodiments. It should be noted that the given embodiments are only used to clearly explain the principles and structures of the present invention, and are not intended to limit the technical features of the present invention.

[0027] The specific structure of the pre-combustion chamber jet ignition device integrated on the piston is as follows: a concave pool is provided at the top center of the piston 1, a fence 1-1 is provided on the upper part of the concave pool, a spherical flamethrower 2 is nested and welded in the fence above the concave pool, and the spherical flamethrower covers the concave pool to form a cavity 1-2. The spherical surface of the spherical flamethrower is provided with a plurality of injection holes, and two circular holes 1-3 are provided on both sides of the fence respectively, for passing into the first pre-combustion chamber 1-4a and the second pre-combustion chamber 1-4b (such as Figure 1-4 ), the two pre-combustion chambers are located in the same plane but arranged asymmetrically (e.g. Figure 5 The hollow chamber is provided with two conical passages 1-5 which are connected to the first and second pre-combustion chambers respectively. The first pilot injector 3-1 and the second pilot injector 3-2 pass through the piston body and are connected to the first and second pre-combustion chambers respectively; the first main fuel injector 4-1 and the second main fuel injector 4-2 are connected to the cylinder through a drilling hole. The piston body structure is as follows Figure 8 shown.

[0028] The included angle β between the central axis of the first and second main fuel injectors and the vertical direction is 135° (as shown in FIG. Figure 6), which is suitable for forming a relatively concentrated main fuel ratio in the cavity at the end of piston compression. The scavenging port 5 is arranged at the lower part of the cylinder. Before ignition, the main fuel injected by the two main fuel injectors enters the cylinder, and at the same time enters the cavity through the spherical flame injection hole, and then passes through two conical channels to enter the two pre-combustion chambers and two pilot injectors respectively. When the piston moves upward to the ignition position, the two pilot injectors are first compressed and ignited to spray flames, increasing the ignition energy. The high-energy flames generated by the two pre-combustion chambers ignite the main fuel through the spherical flame device, so that the flame spreads from the center of the combustion chamber to the surrounding cylinder walls.

[0029] The hollow chamber is provided with two conical passages connected to the first and second pre-combustion chambers, and the angle between the first pre-combustion chamber and the second pre-combustion chamber on the plane is α=76° (such as Figure 7 ) to avoid interference between the flames of the two pre-combustion chambers forming jets.

[0030] The spherical flamethrower is a cavity structure. There are 14 nozzles in the spherical flamethrower. The nozzles are 18 mm long and 3 mm in diameter. Spray holes of the nozzles are formed on the surface of the spherical flamethrower. The spray holes are evenly spaced around the center of the surface of the spherical flamethrower.

[0031] The first pilot injector and the second pilot injector are three-hole injectors (such as Figure 5 ), the fuel injected by the two pilot injectors fully covers the first and second pre-combustion chambers respectively. The installation positions of the two pilot injectors vary with the engine speed and stroke.

[0032] The two pre-combustion chambers, the jet pipe of the spherical flame jet on the piston body and the inner walls of the two channels are all smoothed. The cross-sections of the two pre-combustion chambers are circular or semi-elliptical structures, and the cross-sections of the conical channels connected thereto are the same as the cross-sections of the pre-combustion chambers. The inner walls of the first pre-combustion chamber, the second pre-combustion chamber and the two conical channels are smoothly connected.

[0033] The piston moves to the vicinity of the scavenging port, and the exhaust gas in the cylinder is discharged through the scavenging port and the engine exhaust valve 6. The pressure difference between the scavenging port and the cylinder is large. Under the action of the pressure difference, the fresh air enters the two pre-combustion chambers through the scavenging port, and then enters the cavity through two tapered channels, and participates in the combustion chamber together with the fuel in the pre-combustion chamber and the cavity.

[0034] As an example, the cylinder stroke is 2050 mm, the rotation speed is 102 r / min, the load is 75%, and the maximum diameter of the piston is 500 mm.

[0035] The fuel injected by the first pilot injector and the second pilot injector is diesel, and the total injection amount of diesel fuel is 0.227g; the injection start time is 351.5°CA, and the injection duration is 0.6785°CA. The scavenging process of the engine is about 110-273.6CAD. The fuel injected by the first main fuel injector and the second main fuel injector is natural gas, the injection time of natural gas is 290.1°CA, the injection duration is 8.6°CA, and the total amount of injected natural gas is 22.1g. More detailed operating parameters are shown in Tables 1-3.

[0036] The working process of the present invention is:

[0037] During the scavenging process, the exhaust valve of the engine is opened, and when the piston runs to the bottom dead center in the cylinder, the scavenging port is connected to the cylinder. On the one hand, fresh air discharges the exhaust gas in the cylinder through the scavenging port; on the other hand, fresh air enters the first and second pre-combustion chambers through the scavenging port. Then, they enter the cavity through their respective tapered channels, and discharge the exhaust gas retained in the first and second pre-combustion chambers and the cavity.

[0038] Then the piston moves upward, the scavenging port and the exhaust valve are closed. To avoid leakage of the main fuel, the main fuel is closed at the exhaust valve. The natural gas injected by the first main fuel injector and the second main fuel injector is injected into the cylinder at β = 135°. The pressure of the natural gas is 1.5Mpa and the injection duration is 8.6°CA. The two fuel beams converge at the center of the cylinder and move downward (such as Fig. 9 The two main fuels mix with the ambient gas in the cylinder to form a combustible mixed gas. The main fuel mixed gas with a higher concentration gathers in the cavity and enters the first and second pre-combustion chambers through the spray holes of the spherical flame injector.

[0039] The piston continues to move upward, and before approaching the top dead center of the cylinder, the first and second pilot injectors are connected to the first and second pre-combustion chambers respectively, and the cylinder is in a state of high temperature and high pressure. Diesel begins to be injected into the first and second pre-combustion chambers by the first and second pilot injectors, and the injection duration is 0.6785°CA. The diesel in the first and second pre-combustion chambers is quickly ignited at a higher pressure and temperature, and the flame propagates to the cavity through the conical channel, and then reaches the spherical flame injector. The jet flame generated by the spherical flame injector injection tube (hole) ignites the natural gas, so that the flame spreads evenly from the center of the cylinder to the surrounding (cylinder) walls, and all the natural gas in the cylinder is ignited.

[0040] The piston moves downward to do work. After the work is completed, the exhaust valve opens and the engine starts a new cycle.

[0041] Experimental results show that when the traditional scheme increases the compression ratio from 12 to 16, the knock amplitude exceeds 0.5Mpa and the engine suffers from severe knock.

[0042] When the present invention is applied to a low-speed two-stroke diesel-natural gas dual-fuel engine with low-pressure injection, the knock amplitude can be suppressed to below 0.1 MPa under the condition of a compression ratio of 16, thereby achieving knock suppression. During the engine scavenging process, when the piston moves to the vicinity of the scavenging port, the combustion exhaust gas in the two pre-combustion chambers, the two conical channels, the cavity chamber, and the spherical flame injector is completely discharged.

[0043] The two pilot injectors are made by machined drillings, and their mounting positions vary with engine speed and stroke, and are suitable for injecting and igniting the main fuel contained in the two pre-combustion chambers.

[0044] Two main fuel injectors (such as Figure 6 , Fig. 9 ) is connected to the engine cylinder through a drilling hole, and the main fuel can enter the two pre-combustion chambers in turn through the hollow chamber of the spherical flame injector, which is suitable for increasing the jet flame energy when the jet flame enters the cylinder during the ignition and combustion process. The spherical flame injector is integrated with the piston body through nesting and welding. The following are the operating parameters involved in this embodiment.

[0045] 1. Engine parameter table of the embodiment

[0046]

[0047]

Claims

1. A pre-combustion chamber jet ignition device integrated on a piston, comprising a piston and a cylinder, characterized in that: A concave pool is provided at the center of the top of the piston (1), a enclosure (1-1) is provided on the upper part of the concave pool, a spherical flamethrower (2) is nested and welded in the enclosure above the concave pool, the spherical flamethrower covers the concave pool to form a hollow chamber (1-2), a spherical surface of the spherical flamethrower is provided with a plurality of injection holes, two circular holes (1-3) are provided on both sides of the enclosure respectively, for leading to a first pre-combustion chamber (1-4a) and a second pre-combustion chamber (1-4b), the two pre-combustion chambers are located in the same plane but are arranged asymmetrically, the hollow chamber is provided with two conical channels (1-5) respectively communicating with the first and second pre-combustion chambers, the first pilot injector (3-1) and the second pilot injector (3-2) pass through the piston body and are connected to the first and second pre-combustion chambers respectively; The first main fuel injector (4-1) and the second main fuel injector (4-2) are connected to the cylinder through a drilling hole. The central axis of the first and second main fuel injectors are at an angle of 120 to 140 degrees to the vertical direction. The scavenging port (5) is arranged at the lower part of the cylinder. Before ignition, the main fuel injected by the two main fuel injectors enters the cylinder and enters the cavity through the spherical flame spray hole at the same time, and then enters the two pre-combustion chambers and the two pilot injectors through two conical channels respectively. When the piston moves upward to the ignition position, the two pilot injectors are firstly compressed and ignited to spray flames, thereby increasing the ignition energy. The high-energy flames generated by the two pre-combustion chambers ignite the main fuel through the spherical flame device, so that the flame spreads from the center of the combustion chamber to the surrounding cylinder walls.

2. The pre-combustion chamber jet ignition device integrated on the piston according to claim 1, characterized in that: The angle between the first pre-combustion chamber and the second pre-combustion chamber on the plane is 70-80 degrees, so as to avoid interference between the flames of the jets formed by the two pre-combustion chambers.

3. The pre-combustion chamber jet ignition device integrated on the piston according to claim 1, characterized in that: The spherical flamethrower is a cavity structure, and a plurality of nozzles are arranged inside the spherical flamethrower. The nozzles are 18 mm long and 3 mm in diameter. Spray holes of the nozzles are formed on the surface of the spherical flamethrower, and the spray holes are evenly spaced around the center of the surface of the spherical flamethrower.

4. The pre-combustion chamber jet ignition device integrated on the piston according to claim 1, characterized in that: The number of spray holes of the first pilot injector and the second pilot injector are 1-4 respectively, and the fuel sprayed by the two pilot injectors fully covers the first and second pre-combustion chambers respectively.

5. The pre-combustion chamber jet ignition device integrated on the piston according to claim 1, characterized in that: The installation positions of the first and second pilot injectors vary with engine speed and stroke.

6. The pre-combustion chamber jet ignition device integrated on the piston according to claim 1, characterized in that: The two pre-combustion chambers, the nozzle in the spherical flame injector, and the inner walls of the two conical passages are all smoothly connected to the components.

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