Prechamber jet pilot device integrated on a piston

Abstract

The application discloses a precombustion chamber jet piloting device integrated on a piston, which is characterized by a concave pool in the center of the top of the piston, an upper part of the concave pool being provided with a fence, a spherical flame injector being nested and welded in the fence above the concave pool, and the spherical flame injector covering the concave pool to form a cavity chamber. A plurality of jet pipes are arranged in the spherical flame injector. Two precombustion chambers are respectively communicated with the two sides of the fence, and the two precombustion chambers are located in the same plane but are asymmetrically arranged. The cavity chamber is provided with two conical passages respectively communicated with the two precombustion chambers, and two piloting injectors are respectively connected with the two precombustion chambers; two main fuel injectors are connected with a cylinder. The included angle between the central axis of the main fuel injector and the vertical direction is 120-140 degrees, and a scavenging port is arranged at the lower part of the cylinder. The main fuel enters the two precombustion chambers through the spherical flame injector, and the flame generated by the precombustion chamber ignites the main fuel in the cylinder through the spherical flame injector. The structure shortens the flame propagation distance and prevents the knocking phenomenon generated in the combustion chamber.

Description

[0001] This invention pertains to engine structure technology, specifically relating to a jet ignition system with a pre-combustion chamber on the piston.

[0002] Device. Background Technology

[0003] Faced with the energy shortages and the severe challenges of "dual-carbon" targets brought about by the annual increase in shipping trade, natural gas (CNG), with a lower carbon content than diesel, has been widely used in the field of marine engines as a major transitional alternative fuel. Low-speed two-stroke marine engines, with their large bore, low speed, long stroke, and high boost, have become the main power source in the ocean shipping sector. In recent years, marine dual-fuel engines have gradually occupied an important position in ocean-going vessels. Currently, 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 (approximately 300 bar), and after mixing with air, it exhibits diffusion combustion characteristics. Although a higher compression ratio is used to achieve higher thermal efficiency, it faces the problem of higher nitrogen oxide (NOx) emissions, failing to directly meet the International Maritime Organization's Tier III emission standards. Therefore, it is necessary to install exhaust aftertreatment devices or adopt in-engine purification technologies such as exhaust gas recirculation (EGR), which inevitably increases the engine's manufacturing cost significantly. For low-pressure injection dual-fuel engines, natural gas is injected into the cylinder at low pressure, where it is pre-mixed with air to form a homogeneous combustible mixture. Diesel fuel is injected directly into the pre-combustion chamber, and then ignites the premixed mixture in the main combustion chamber via a jet flame. This approach does not require additional aftertreatment devices or in-engine purification technologies to meet Tier III emission standards. Its thermodynamic cycle is similar to the Otto cycle. Considering the knocking limitations caused by auto-ignition of the end mixture at high compression ratios, a lower compression ratio is generally used, resulting in relatively lower thermal efficiency and a narrower operating range.

[0004] To address the problem of rough combustion and even knocking that easily occurs under high load in marine low-pressure injection dual-fuel engines, this invention proposes a pre-combustion chamber jet ignition system integrated on the piston. This system not only increases the compression ratio of the low-pressure injection dual-fuel engine but also suppresses rough combustion, thereby improving thermal efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide a pre-combustion chamber jet ignition system integrated on the piston, which suppresses knocking in marine dual-fuel engines under low-pressure injection conditions, improves the reliability of dual-fuel engines, and facilitates the scavenging and removal of exhaust gas from the pre-combustion chamber, thereby improving 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 will be described below.

[0007] An integrated pre-combustion chamber jet ignition device on a piston includes a piston and a cylinder. Its technical structure is as follows: a concave pool is located at the center of the piston top, with a baffle above the pool. A spherical flame injector is nested and welded within the baffle above the concave pool, covering the concave pool to form a cavity. The spherical surface of the flame injector has multiple injection holes. Two circular holes are located on each side of the baffle for access to a first and a second pre-combustion chamber, which are located on the same plane but asymmetrically arranged. The cavity has two conical channels communicating with the first and second pre-combustion chambers respectively. The first and second ignition injectors pass through the piston body and connect to the first and second pre-combustion chambers respectively; the first and second main fuel injectors are connected to the cylinder through drilled holes. The central axes of the first and second main fuel injectors form an angle of 125°–140° with the vertical direction, and the scavenging ports are located at the lower part of the cylinder. Before ignition, the main fuel injected by the two main fuel injectors enters the cylinder and simultaneously enters the combustion chamber through the spherical flame nozzle. It then passes through two conical channels into the two pre-combustion chambers and the two ignition injectors, respectively. When the piston moves upward to the ignition position, the two ignition injectors are first compressed and ignited, thus increasing the ignition energy. The high-energy flame generated in the two pre-combustion chambers ignites the main fuel through the spherical flame nozzles, causing the flame to propagate from the center of the combustion chamber to the surrounding cylinder walls.

[0008] The working process of this invention is as follows:

[0009] During scavenging, the engine exhaust valve opens, and when the piston reaches near the bottom dead center of the cylinder, the scavenging port connects with the cylinder. On one hand, fresh air expels the exhaust gas from the cylinder through the scavenging port; on the other hand, fresh air enters the first and second pre-combustion chambers through the scavenging port. Subsequently, it enters the cavity chamber through its respective conical passage, expelling the exhaust gas remaining in the first and second pre-combustion chambers and the cavity chamber.

[0010] Subsequently, the piston moves upward, and the scavenging port and exhaust valve close. To prevent main fuel leakage, main fuel is injected after the exhaust valve closes. The first and second main fuel injectors inject main fuel into the cylinder at a certain angle and pressure. The two main fuel streams diffuse within the cylinder and mix with the ambient gas to form a combustible mixture. This results in a higher concentration of combustible gas in the cylinder cavity and at the piston top (with air) at the end of compression compared to other areas of the cylinder. This mixture enters the first and second pre-combustion chambers through the injection holes of the spherical flame injector.

[0011] As the piston continues to move upward, before reaching top dead center, the first and second ignition injectors connect to the first and second pre-combustion chambers, respectively. At this point, the cylinder is under high temperature and pressure. Ignition fuel begins to be injected into the two pre-combustion chambers, where it is quickly ignited under high pressure and temperature. The flame propagates through the first and second pre-combustion chambers and the two channels to the cavity chamber. The flame then passes through the nozzle of the spherical flame injector, generating a jet flame that ignites the main fuel, causing the flame to spread 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 power, and after that, the exhaust valve opens, and the engine begins a new cycle.

[0013] The current traditional dual-fuel engine technology uses a dual pre-combustion chamber structure located on the bottom edge of the cylinder head. In dual-fuel mode, due to the excessively long propagation distance of the jet flame within the cylinder, the richer end mixture triggers pre-ignition under high temperature and pressure, leading to unstable combustion, frequent knocking, and affecting engine reliability. Furthermore, exhaust gases within the dual pre-combustion chamber structure on the cylinder head are difficult to completely scavenge, and the temperature and composition of the pre-combustion chambers are difficult to control. This results in variations in the combustion intensity of the jet flame in each cycle, ultimately causing cyclical fluctuations in the combustion of the main fuel within the cylinder.

[0014] Compared with the prior art, the beneficial effects of the present invention are:

[0015] (1) A high-concentration main fuel mixture enters the two pre-combustion chambers through the nozzle of the spherical flame injector, which increases the flame energy when the jet enters the cylinder, prevents flameout, and promotes flame diffusion. The flame generated in the pre-combustion chamber is sprayed into the combustion chamber through the spherical flame injector, igniting the main fuel in the cylinder, shortening the flame propagation distance, avoiding uneven combustion of the end mixture and engine fuel on the combustion chamber wall, and preventing knocking phenomena generated in the combustion chamber.

[0016] (2) During the scavenging stage, the scavenging port is connected to the pre-combustion chamber and the spherical flame injector on the top of the piston. During the scavenging process, the problem of exhaust gas being difficult to discharge from the pre-combustion chamber of the current dual-fuel engine is solved, which can effectively reduce the instability of the in-cylinder combustion cycle. Attached Figure Description

[0017] Figure 1 This is a simplified schematic diagram illustrating the principle and assembly structure of the present invention.

[0018] Figure 2 This is a schematic diagram of the assembly structure of the piston body and the flame injector in this invention.

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

[0020] Figure 4This is a cross-sectional view of the flame injector in this invention.

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

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

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

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

[0025] Figure 9 This is a schematic diagram of the main fuel injection converging above the piston cavity in an embodiment of the present invention. Detailed Implementation

[0026] The structure of the present invention will be further explained below with reference to the accompanying drawings and specific embodiments. It should be noted that the given embodiments are only used to clearly explain the principles and structure 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: A concave pool is provided at the center of the top of the piston 1, and a baffle 1-1 is provided above the concave pool. A spherical flame injector 2 is nested and welded inside the baffle above the concave pool, and the spherical flame injector covers the concave pool to form a cavity 1-2. The spherical surface of the spherical flame injector has multiple injection holes, and two circular holes 1-3 are provided on each side of the baffle for introducing the first pre-combustion chamber 1-4a and the second pre-combustion chamber 1-4b (e.g., Figure 1-4 The two pre-combustion chambers are located on the same plane but are arranged asymmetrically (e.g., Figure 5 The cavity has two conical channels 1-5 that communicate with the first and second pre-combustion chambers, respectively. The first ignition injector 3-1 and the second ignition injector 3-2 pass through the piston body and connect 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 drilled holes. The piston body structure is as follows: Figure 8 As shown.

[0028] The angle β between the central axis of the first and second main fuel injectors and the vertical direction is 135° (e.g., Figure 6This design is suitable for creating a richer proportion of main fuel in the combustion chamber at the end of piston compression. The scavenging port 5 is located at the bottom of the cylinder. Before ignition, the main fuel injected by the two main fuel injectors enters the cylinder and simultaneously enters the combustion chamber through the spherical flame injection orifice. It then passes through two conical channels into the two pre-combustion chambers and the two ignition injectors, respectively. When the piston moves upward to the ignition position, the two ignition injectors are first compressed and ignited, increasing the ignition energy. The high-energy flame generated in the two pre-combustion chambers ignites the main fuel through the spherical flame injector, causing the flame to propagate from the center of the combustion chamber to the surrounding cylinder walls.

[0029] The cavity has two conical channels that connect to the first and second pre-combustion chambers. The angle α between the first and second pre-combustion chambers in the plane is 76° (e.g., Figure 7 This avoids interference between the flames forming jets in the two pre-combustion chambers.

[0030] The spherical flamethrower has a hollow structure and contains 14 nozzles, each 18 mm long and 3 mm in diameter. The nozzles have spray holes on their surface, which are evenly distributed around the center of the spherical flamethrower.

[0031] The first and second ignition injectors are both 3-hole injectors (e.g., Figure 5 The fuel injected by the two ignition injectors completely covers the first and second pre-combustion chambers, respectively. The installation positions of the two ignition injectors vary depending on the engine speed and stroke.

[0032] The inner walls of the injection pipes of the spherical flame injector on the piston body and the two channels are all smoothly machined. The cross-sections of the two pre-combustion chambers are circular or semi-elliptical, and the cross-sections of the conical channels connected to them are the same shape 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] As the piston moves to the vicinity of the scavenging port, the exhaust gas in the cylinder is discharged through the scavenging port and engine exhaust valve 6. The pressure difference between the scavenging port and the cylinder is relatively large. Under the action of the pressure difference, fresh air enters the two pre-combustion chambers through the scavenging port, and then enters the combustion chamber through two conical channels, where it participates in the combustion chamber together with the fuel in the pre-combustion chamber and the combustion chamber.

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

[0035] The first and second ignition injectors inject diesel fuel, with a total injection quantity of 0.227g. The injection start time is 351.5°C, and the injection duration is 0.6785°C. The engine scavenging process takes approximately 110-273.6 CAD. The first and second main fuel injectors inject natural gas, with the natural gas injection start time at 290.1°C, the injection duration at 8.6°C, and a total injection quantity of 22.1g. More detailed operating parameters are shown in Tables 1-3.

[0036] The working process of this invention is as follows:

[0037] During scavenging, the engine exhaust valve opens, and when the piston reaches near the bottom dead center of the cylinder, the scavenging port connects with the cylinder. On one hand, fresh air expels the exhaust gas from the cylinder through the scavenging port; on the other hand, fresh air enters the first and second pre-combustion chambers through the scavenging port. Subsequently, it enters the cavity chamber through its respective conical passage, expelling the exhaust gas remaining in the first and second pre-combustion chambers and the cavity chamber.

[0038] The piston then moves upward, closing the scavenging port and exhaust valve. To prevent main fuel leakage, the main fuel is contained within the closed exhaust valve. The first and second main fuel injectors inject natural gas into the cylinder at a β = 135° angle, with a pressure of 1.5 MPa and an injection duration of 8.6°CA. The two fuel jets converge at the center of the cylinder and move downwards (as shown in the image). Figure 9 (As shown by the dashed line), this causes a relatively rich proportion of natural gas to form in the piston top cavity at the end of compression. The two main fuel jets mix with the ambient gas in the cylinder to form a combustible mixture. The high-concentration main fuel mixture accumulates in the cavity and enters the first and second pre-combustion chambers respectively through the nozzles of the spherical flame injector.

[0039] As the piston continues its upward movement, nearing top dead center, the first and second ignition injectors connect to the first and second pre-combustion chambers, respectively, creating a high-temperature, high-pressure environment within the cylinder. Diesel fuel begins to be injected into the first and second pre-combustion chambers by the first and second ignition injectors, with an injection duration of 0.6785°C. The diesel fuel in the first and second pre-combustion chambers is quickly ignited under high pressure and temperature. The flame propagates through the conical channel to the cavity chamber and then to the spherical flame injector. The jet flame generated by the spherical flame injector's injection pipe (orifice) ignites the natural gas, causing the flame to propagate evenly from the cylinder center to the surrounding cylinder walls, thus igniting all the natural gas within the cylinder.

[0040] The piston moves downward to do power, and after the power is completed, the exhaust valve opens, and the engine begins a new cycle.

[0041] Experimental results show that when the compression ratio is increased from 12 to 16 using the traditional method, the knock amplitude exceeds 0.5 MPa, and the engine experiences severe knocking.

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

[0043] The two ignition injectors are manufactured by machining and drilling, and their installation position changes with the engine speed and stroke, making them suitable for injecting and igniting the main fuel contained in the two pre-combustion chambers.

[0044] Two main fuel injectors (such as Figure 6 , Figure 9 The spherical flame injector is connected to the engine cylinder via a drilled hole. The main fuel can sequentially pass through the cavity of the spherical flame injector into the two pre-combustion chambers, which is suitable for increasing the jet flame energy when it enters the cylinder during ignition and combustion. 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 for the embodiment

[0046]

[0047]

Claims

1. A pre-chamber jet pilot integrated on a piston, comprising a piston, a cylinder, characterized in that: The piston (1) is provided with a concave pool in the center of the top, and a fence (1-1) is arranged on the upper part of the concave pool. A spherical flame injector (2) is nested and welded in the fence above the concave pool. The spherical flame injector covers the concave pool to form a cavity chamber (1-2). The spherical surface of the spherical flame injector is provided with a plurality of injection holes. Two round holes (1-3) are arranged on the two sides of the fence respectively for the first pre-chamber (1-4a) and the second pre-chamber (1-4b). The two pre-chambers are located in the same plane but are asymmetrically arranged. The cavity chamber is provided with two tapered channels (1-5) respectively communicating with the first and second pre-chambers. A first pilot injector (3-1) and a second pilot injector (3-2) pass through the piston body and are connected with the first and second pre-chambers respectively. A first main fuel injector (4-1) and a second main fuel injector (4-2) are connected with the cylinder through drilling. The central axis of the first and second main fuel injectors forms an angle of 120-140° with the vertical direction. A 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 then enters the cavity chamber through the spherical flame injection hole. Then the main fuel enters the two pre-chambers and the two pilot injectors through the two tapered channels respectively. When the piston runs upward to the ignition position, the two pilot injectors are first compressed and fire to increase the ignition energy. The high-energy flame generated by the two pre-chambers ignites the main fuel through the spherical flame injector, so that the flame spreads from the center of the combustion chamber to the cylinder wall surface.

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

3. The integrated pilot on piston prechamber jet pilot apparatus of claim 1 wherein: The spherical flame injector is a cavity structure, and a plurality of injection pipes are arranged in the spherical flame injector. The length of the injection pipe is 18 mm, and the diameter is 3 mm. The injection holes of the injection pipes are formed on the surface of the spherical flame injector. The injection holes are uniformly and interval distributed along the center of the surface of the spherical flame injector.

4. The integrated pilot on piston prechamber jet pilot apparatus of claim 1 wherein: The number of injection holes of the first pilot injector and the second pilot injector is 1-4 respectively. The fuel injected by the two pilot injectors respectively fully covers the first and second pre-chambers.

5. The integrated pilot on piston prechamber jet pilot apparatus of claim 1 wherein: The installation positions of the first and second pilot injectors change with the engine speed and stroke.

6. The integrated pilot on piston prechamber jet pilot apparatus of claim 1 wherein: The inner walls of the two pre-chambers, the injection pipes in the spherical flame injector, and the two tapered channels are smoothly connected with the components.

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