Rare combustion reliable ignition system structure of special hybrid engine based on multiple spark plugs and pre-combustion chambers and control method of lean combustion reliable ignition system structure

Abstract

The invention provides a lean-burn reliable ignition system structure of a special hybrid engine based on multiple spark plugs and a pre-combustion chamber and a control method of the lean-burn reliable ignition system structure. The structure comprises an engine body, a pre-combustion chamber, a side ignition unit and an external control module. The structure is lower in sensitivity to knocking boundaries and loads, and the combustion process of the internal combustion engine can be more controllable. According to the structure, the advantages of the three spark plugs and the precombustion chamber structure are combined, the fuel consumption rate of an engine can be effectively reduced, and meanwhile the circulation fluctuation rate of the engine in the combustion process is reduced. The ignition system can also flexibly adjust three spark plugs, an active / passive pre-combustion chamber, and a side spark plug and a pre-combustion chamber for cooperative ignition according to specific engine working conditions such as the air-fuel ratio, the rotating speed, the torque and the EGR rate, and the most reasonable ignition strategy under the complex working conditions can be achieved.

Description

Technical Field

[0001] This invention relates to the field of internal combustion engine technology, and in particular to a structure and control method of a lean-burn reliable ignition system for hybrid dedicated engines based on multiple spark plugs and a pre-combustion chamber. Background Technology

[0002] With the increasing demands for energy efficiency and emission performance in power systems, lean-burn technology has become a core research direction for internal combustion engines. To achieve reliable ignition under lean mixture conditions, existing technologies typically employ pre-combustion chamber ignition systems. Pre-combustion chamber technology ignites a richer mixture within a small pre-combustion chamber, generating a high-temperature, high-pressure jet flame that enters the main combustion chamber, thus achieving multi-point ignition. However, existing ignition systems still suffer from the following significant drawbacks in practical applications:

[0003] A. Due to the structural limitations of the pre-combustion chamber, a significant amount of knocking margin often occurs at the end of the main combustion chamber during combustion. Existing ignition systems struggle to precisely control the pressure rise rate and the final air-fuel mixture across the entire cylinder range, making the engine highly susceptible to knocking under high-load conditions and limiting further improvements in thermal efficiency.

[0004] B. Under extremely lean air-fuel mixture conditions, problems such as long ignition delay and excessively long flame propagation paths often occur.

[0005] C. Existing pre-combustion chamber structures have a low lean-burn limit at ignition. Once the excess air coefficient exceeds this limit, incomplete combustion leads to a rapid increase in the initial emissions of carbon monoxide (CO) and hydrocarbons (HC). Simultaneously, due to the tendency for localized high-temperature zones to form near the pre-combustion chamber, the reduction in nitrogen oxides (NOx) often falls short of optimal levels.

[0006] D. Existing ignition control modes lack the ability to flexibly adjust for complex operating conditions such as engine speed, torque, air-fuel ratio, and EGR rate. In specific environments such as hybrid power systems that require frequent changes in operating conditions, it is difficult to balance combustion stability under low loads with anti-knock performance under high loads, making it impossible to ensure that the engine always operates within its optimal efficiency range.

[0007] Therefore, there is an urgent need to develop a reliable ignition system structure and control method for lean combustion in hybrid dedicated engines based on multiple spark plugs and a pre-combustion chamber. Summary of the Invention

[0008] The purpose of this invention is to provide a structure and control method for a reliable lean-burn ignition system for hybrid dedicated engines based on multiple spark plugs and a pre-combustion chamber, in order to solve the problems existing in the prior art.

[0009] The technical solution adopted to achieve the purpose of this invention is as follows: a reliable ignition system for lean combustion of hybrid dedicated engine based on multiple spark plugs and pre-combustion chamber, including engine body, pre-combustion chamber, side-mounted ignition unit and external control module.

[0010] The engine body includes a cylinder block, a cylinder head, and a piston. The piston is disposed within the cylinder block. The cylinder head seals the cylinder block. The top of the piston, the inner wall of the cylinder block, and the bottom surface of the cylinder head together form the main combustion chamber. The cylinder head is provided with intake and exhaust ports.

[0011] The pre-combustion chamber is mounted on the cylinder head, with its lower end extending into the main combustion chamber. The pre-combustion chamber includes a pre-combustion chamber housing and a pre-combustion chamber spark plug. The pre-combustion chamber housing contains a pre-combustion chamber space. A pre-combustion chamber nozzle is provided at the bottom of the pre-combustion chamber housing. The pre-combustion chamber space is in fluid communication with the main combustion chamber through the pre-combustion chamber nozzle. The pre-combustion chamber spark plug is mounted on the pre-combustion chamber housing. The ignition end of the pre-combustion chamber spark plug extends into the pre-combustion chamber space.

[0012] The side-mounted ignition unit includes a first side-mounted spark plug and a second side-mounted spark plug. Both the first and second side-mounted spark plugs are mounted on the bottom surface of the cylinder head. The first and second side-mounted spark plugs are located on opposite sides of the pre-combustion chamber. The ignition ends of the first and second side-mounted spark plugs extend into the main combustion chamber.

[0013] The pre-combustion chamber spark plug, the first side-mounted spark plug, and the second side-mounted spark plug are all electrically connected to an external control module. The external control module independently controls the ignition timing and ignition energy of the pre-combustion chamber spark plug, the first side-mounted spark plug, and the second side-mounted spark plug.

[0014] Furthermore, the pre-combustion chamber is a passive pre-combustion chamber structure. Fuel replenishment relies on the pressure difference of the high-temperature, high-pressure gas during the compression stroke of the internal combustion engine.

[0015] Furthermore, the pre-combustion chamber is an active pre-combustion chamber structure. It also includes a fuel injector. The fuel injector is mounted on the pre-combustion chamber housing. The nozzle of the fuel injector extends into the pre-combustion chamber space. The fuel injector generates a fuel jet spray to independently replenish fuel into the pre-combustion chamber space. The external control module controls the fuel injection quantity and injection timing of the fuel injector.

[0016] Furthermore, the pre-combustion chamber nozzles are designed with a circular distribution around the perimeter. The combustion gases in the pre-combustion chamber are uniformly injected into the main combustion chamber in a dispersed pattern.

[0017] Furthermore, traditional gasoline fuel or hydrogen-ammonia zero-carbon fuel can be used.

[0018] The present invention also discloses a control method based on the above-described ignition system, comprising the following steps:

[0019] S1) Obtain the real-time operating parameters of the engine. The operating parameters include air-fuel ratio, engine speed, torque, and EGR rate.

[0020] S2) Determine the ignition strategy based on the operating parameters. The ignition strategy includes pre-combustion chamber-only ignition mode, three-spark plug ignition mode, and synergistic ignition mode.

[0021] S3) According to the determined ignition strategy, the external control module sends control signals to the pre-combustion chamber spark plug, the first side-mounted spark plug and the second side-mounted spark plug to independently adjust the ignition timing and ignition energy of each spark plug.

[0022] Furthermore, in the coordinated ignition mode, the external control module first controls the spark plug in the pre-combustion chamber to ignite, igniting the air-fuel mixture in the pre-combustion chamber to generate a high-temperature, high-pressure jet that enters the main combustion chamber to ignite the air-fuel mixture. Subsequently, based on the predicted knock margin, the external control module controls the first and second side-mounted spark plugs to ignite at specific times to eliminate the knock margin of the air-fuel mixture at the end of the main combustion chamber.

[0023] Furthermore, when the engine is detected to be operating under extremely lean mixture or high excess air coefficient conditions, the external control module adjusts the first and second side-mounted spark plugs to assist in ignition during the initial or middle stage of the jet flame propagation in the pre-combustion chamber, thereby shortening the average flame propagation distance and increasing the ignition energy of the mixture at the end of the main combustion chamber.

[0024] Furthermore, when the ignition system adopts an active pre-combustion chamber structure and uses hydrogen or ammonia as fuel, the external control module adjusts the air-fuel mixture ratio in the pre-combustion chamber by controlling the injection amount of the fuel injector, and coordinates with the ignition timing of the three spark plugs to improve the combustion propagation speed and stability of zero-carbon fuel.

[0025] The technical effects of this invention are beyond doubt:

[0026] A. During the combustion process of an internal combustion engine, the spark plug in the pre-combustion chamber is controlled first. Due to the presence of the pre-combustion chamber structure, the flame propagation speed can be effectively increased, achieving rapid and stable combustion. When the air-fuel mixture enters the cylinder, the ignition timing of the two spark plugs installed on the cylinder head is controlled separately, which can effectively eliminate the knock margin of the internal combustion engine, thereby completely eliminating the knock phenomenon during engine ignition and making the combustion process of the internal combustion engine more stable.

[0027] B. The three-spark plug structure is less sensitive to knock boundaries and loads, which makes the combustion process of the internal combustion engine more controllable. Combining the advantages of the three-spark plug with the pre-combustion chamber structure can effectively reduce the engine's fuel consumption rate and reduce the cycle fluctuation rate during the engine combustion process.

[0028] C. Based on specific engine operating conditions such as air-fuel ratio, speed, torque, and EGR rate, the three spark plugs, active / passive pre-combustion chamber, and side-mounted spark plugs and pre-combustion chamber can be flexibly adjusted to achieve the most reasonable ignition strategy under complex operating conditions. Attached Figure Description

[0029] Figure 1 This is a structural diagram of the pre-combustion chamber; Figure 1 a is the passive pre-combustion chamber; Figure 1 b is the active pre-combustion chamber;

[0030] Figure 2 This is a structural diagram of the ignition system; Figure 2 a is a three-spark plug structure equipped with a passive pre-combustion chamber; Figure 2 b is a three-spark plug structure equipped with a passive pre-combustion chamber;

[0031] Figure 3 This is a control strategy diagram for the control method.

[0032] In the diagram: 1. Pre-combustion chamber spark plug; 2. Pre-combustion chamber space; 3. Pre-combustion chamber nozzle; 4. Injector; 6. Fuel spray; 9. Intake manifold; 11. First side-mounted spark plug; 12. Piston; 15. Exhaust manifold; 17. Second side-mounted spark plug; 19. Cylinder block. Detailed Implementation

[0033] The present invention will be further described below with reference to embodiments, but it should not be construed that the scope of the present invention is limited to the following embodiments. Various substitutions and modifications made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention should be included within the scope of protection of the present invention.

[0034] Example 1:

[0035] See Figure 1 and Figure 2 This embodiment provides a reliable ignition system for lean combustion in a hybrid dedicated engine based on multiple spark plugs and a pre-combustion chamber, including an engine body, a pre-combustion chamber, a side-mounted ignition unit, and an external control module.

[0036] The engine body includes a cylinder block 19, a cylinder head, and a piston 12. The piston 12 is disposed within the cylinder block 19. The cylinder head seals the cylinder block 19. The top of the piston 12, the inner wall of the cylinder block 19, and the bottom surface of the cylinder head together form the main combustion chamber. An intake manifold 9 and an exhaust manifold 15 are disposed on the cylinder head.

[0037] The pre-combustion chamber is mounted on the cylinder head, with its lower end extending into the main combustion chamber. The pre-combustion chamber includes a pre-combustion chamber housing and a pre-combustion chamber spark plug 1. The pre-combustion chamber housing has a pre-combustion chamber space 2 inside. A pre-combustion chamber nozzle 3 is provided at the bottom of the pre-combustion chamber housing. The pre-combustion chamber space 2 is in fluid communication with the main combustion chamber through the pre-combustion chamber nozzle 3. The pre-combustion chamber spark plug 1 is mounted on the pre-combustion chamber housing. The ignition end of the pre-combustion chamber spark plug 1 extends into the pre-combustion chamber space 2.

[0038] The side-mounted ignition unit includes a first side-mounted spark plug 11 and a second side-mounted spark plug 17. Both the first side-mounted spark plug 11 and the second side-mounted spark plug 17 are mounted on the bottom surface of the cylinder head. The first side-mounted spark plug 11 and the second side-mounted spark plug 17 are located on opposite sides of the pre-combustion chamber. The ignition ends of the first side-mounted spark plug 11 and the second side-mounted spark plug 17 extend into the main combustion chamber.

[0039] The pre-combustion chamber spark plug 1, the first side-mounted spark plug 11, and the second side-mounted spark plug 17 are all electrically connected to an external control module. The external control module independently controls the ignition timing and ignition energy of the pre-combustion chamber spark plug 1, the first side-mounted spark plug 11, and the second side-mounted spark plug 17.

[0040] The ignition system can adapt to different air-fuel mixture concentrations. When the mixture is rich, the pre-combustion chamber technology can achieve earlier combustion under knock-limiting conditions. Although the pre-combustion chamber structure has unique advantages such as accelerating flame propagation speed and reducing fuel consumption, when the cylinder is filled with an extremely lean mixture with an excessive air coefficient, the combustion process of the internal combustion engine deteriorates significantly because the improvement effect of the passive pre-combustion chamber on the combustion phase gradually weakens. The three-spark plug structure can further shorten the average flame propagation distance and increase the ignition energy of the final mixture, effectively improving the combustion process of the pre-combustion chamber structure under extremely lean mixtures.

[0041] Because the jet flame generated by the pre-combustion chamber structure can reach the narrow gap between the piston and cylinder in the early stages of combustion, thereby reducing emissions from incomplete combustion, ignition systems using a pre-combustion chamber structure can achieve lower initial CO and HC emissions compared to single-spark plug ignition. However, pre-combustion chamber structures, especially passive pre-combustion chamber structures, have a lower lean-burn limit at ignition. Once the excess air coefficient exceeds the lean-burn limit, CO and HC emissions will increase rapidly. Adding a three-piston ignition system to the pre-combustion chamber not only enhances the effect of the pre-combustion chamber in reducing emissions from incomplete combustion but also further improves the lean-burn limit of the internal combustion engine. This allows the internal combustion engine to achieve lower combustion emissions with a higher excess air coefficient, further improving the engine's emission performance.

[0042] The three-spark plug design effectively extends the lean-burn limit of internal combustion engines, enabling stable combustion of high air-fuel ratio mixtures while achieving lower fuel consumption compared to the single-spark plug design. Under the same air-fuel ratio conditions, the three-spark plug significantly accelerates the combustion rate of the lean mixture while maintaining the same knock tendency, reducing its sensitivity to airflow intensity, and shortening the ignition delay and combustion duration compared to the single-spark plug design.

[0043] Example 2:

[0044] The main content of this embodiment is the same as that of Embodiment 1, except that the pre-combustion chamber is a passive pre-combustion chamber structure. The passive pre-combustion chamber is fueled only by the pressure difference between the high-temperature and high-pressure gas in the pre-combustion chamber and the main combustion chamber during the cylinder compression stroke.

[0045] For the passive pre-combustion chamber, the pre-combustion chamber relies on the pressure difference of high-temperature and high-pressure gas during the compression stroke of the internal combustion engine to replenish fuel. When the mixture in the main combustion chamber enters the pre-combustion chamber, the spark plug 1 in the pre-combustion chamber ignites the mixture in the pre-combustion chamber, generating high-temperature and high-pressure gas. Subsequently, the gas enters the main combustion chamber through the pre-combustion chamber nozzle 3, which can enable the flame to enter the main combustion chamber more quickly and evenly, igniting most of the combustible mixture in the main combustion chamber, further promoting the combustion process, while reducing fuel consumption.

[0046] In richer air-fuel mixtures, passive pre-combustion chambers can achieve an earlier combustion phase under knock-limiting conditions. However, if the mixture is further diluted, the improvement in combustion phase achieved by passive pre-combustion chamber ignition gradually weakens, leading to a decrease in the consumption rate of the final mixture in the initial stages of combustion. In this case, using a three-spark plug system can further shorten the average flame propagation distance and increase the ignition energy of the final mixture under extremely lean conditions, thereby further improving combustion characteristics. Therefore, a three-spark plug system can compensate for the poor combustion characteristics of pre-combustion chamber ignition in high excess air-fuel mixtures, allowing the internal combustion engine to adapt to a wider range of combustion conditions.

[0047] Example 3:

[0048] This embodiment is similar in main content to Embodiment 1, except that the pre-combustion chamber is an active pre-combustion chamber structure. It also includes an injector 4. The injector 4 is mounted on the pre-combustion chamber housing. The nozzle of the injector 4 extends into the pre-combustion chamber space 2. The injector 4 generates a fuel jet spray 6 to independently replenish fuel into the pre-combustion chamber space 2. The external control module controls the fuel injection quantity and timing of the injector 4. The active pre-combustion chamber has a complete and independent fuel assistance system, which can replenish fuel to the pre-combustion chamber at any time.

[0049] Active pre-combustion chambers can precisely adjust the pre-combustion chamber concentration and ignition timing, adapting to different operating conditions. In contrast, passive pre-combustion chambers are highly dependent on the combustion state of the main combustion chamber, with limited room for dynamic adjustment, and are prone to combustion fluctuations under complex combustion conditions.

[0050] Example 4:

[0051] The main content of this embodiment is the same as any one of embodiments 1 to 3, wherein the pre-combustion chamber nozzle 3 adopts a four-sided annular distribution design. The combustion gas in the pre-combustion chamber is uniformly injected into the main combustion chamber in a four-sided divergent pattern, achieving a wider flame coverage. The pre-combustion chamber nozzle 3 has a small orifice diameter, and the pressure of the mixture increases sharply after being ignited by the spark plug, thus enabling the flame to enter the main combustion chamber more quickly and achieving rapid flame propagation.

[0052] Example 5:

[0053] This embodiment is essentially the same as any one of embodiments 1-4, except that it uses either conventional gasoline fuel or hydrogen-ammonia zero-carbon fuel. Adding ammonia to hydrogen effectively improves its combustion performance. Simultaneously, the pre-combustion chamber offers advantages such as multi-point ignition and accelerated flame propagation speed, providing unique advantages in accelerating hydrogen combustion flame propagation speed and improving hydrogen combustion stability. Furthermore, the active pre-combustion chamber can achieve more complete combustion by precisely controlling the fuel-air mixing ratio, improving combustion efficiency, reducing fuel consumption, and further reducing pollutant emissions. Therefore, this ignition system has broad application prospects in zero-carbon fuels.

[0054] Example 6:

[0055] See Figure 3 This embodiment provides a control method for any one of the ignition systems in Embodiments 1 to 5, including the following steps:

[0056] S1) Obtain the real-time operating parameters of the engine. The operating parameters include air-fuel ratio, engine speed, torque, and EGR rate.

[0057] S2) Determine the ignition strategy based on the operating parameters. The ignition strategy includes pre-combustion chamber-only ignition mode, three-spark plug ignition mode, and synergistic ignition mode.

[0058] S3) According to the determined ignition strategy, the external control module sends control signals to the pre-combustion chamber spark plug 1, the first side-mounted spark plug 11 and the second side-mounted spark plug 17 to independently adjust the ignition timing and ignition energy of each spark plug.

[0059] Example 7:

[0060] This embodiment is similar in main content to Embodiment 6. In the coordinated ignition mode, the external control module first controls the spark plug in the pre-combustion chamber to ignite the air-fuel mixture, generating a high-temperature, high-pressure jet that enters the main combustion chamber to ignite the air-fuel mixture. Subsequently, based on the predicted knock margin, the external control module controls the first side-mounted spark plug 11 and the second side-mounted spark plug 17 to ignite at specific times to eliminate the knock margin in the final mixture of the main combustion chamber. When the engine is detected to be operating under extremely lean mixture or high excess air coefficient conditions, the external control module adjusts the first side-mounted spark plug 11 and the second side-mounted spark plug 17 to assist in ignition during the initial or middle stages of the pre-combustion chamber jet flame propagation, shortening the average flame propagation distance and increasing the ignition energy of the final mixture of the main combustion chamber.

[0061] Example 8:

[0062] The main content of this embodiment is the same as that of embodiment 7. However, when the ignition system adopts an active pre-combustion chamber structure and uses hydrogen or ammonia as fuel, the external control module adjusts the air-fuel mixture ratio in the pre-combustion chamber by controlling the injection amount of the injector 4, and coordinates with the ignition timing of the three spark plugs to improve the combustion propagation speed and stability of zero-carbon fuel.

[0063] Examples 9-14:

[0064] To fully verify the technical feasibility, performance advantages, and wide applicability of Examples 1-8, Examples 9-14 underwent a series of rigorous bench tests, demonstrating their effectiveness from multiple dimensions, including combustion efficiency, stability, emission characteristics, fuel adaptability, and control strategies. Examples 9-14 collectively reveal the significant advancements of this ignition system compared to the traditional single-spark plug ignition method.

[0065] Example 9 used a 1.5L three-cylinder long-stroke hybrid engine. This engine employs a deep Miller cycle. Experiments were conducted using single and three spark plugs to investigate the changes in engine fuel consumption and combustion stability with increasing lambda. For the same compression ratio, before lambda reached 1.4, the fuel consumption of single and three spark plugs was essentially equivalent. As lambda further increased, the three spark plug exhibited higher combustion efficiency, and the lambda corresponding to the 3% combustion cycle fluctuation boundary was larger, resulting in a more significant overall reduction in fuel consumption. Specifically, at compression ratios of 15 and 16, the three spark plug could ultimately achieve stable combustion with a lambda exceeding 1.9, reducing minimum fuel consumption by approximately 5 g / (kW·h) compared to the single spark plug, corresponding to an increase in the absolute value of effective thermal efficiency of approximately 1%.

[0066] Example 10 employed both single-spark plug and three-spark plug structures. At compression ratios of 15 and 16, the peak heat release rate of the three-spark plug was significantly higher than that of the single-spark plug at compression ratio 15, mainly due to its higher in-cylinder airflow intensity. At compression ratio 16, the three-spark plug showed a particularly significant improvement in the early combustion rate, effectively reducing the sensitivity of the combustion process to airflow intensity. Furthermore, because the lambda required to reach the lean-burn limit is higher with three-spark plug ignition, the corresponding intake volume is larger, and the combustion phase is earlier, thus significantly increasing the maximum knock pressure.

[0067] Different The excess air coefficient has different effects on the combustion characteristics of this ignition system. As verified by bench tests in Example 11, in... Using passive pre-combustion chamber ignition allows for a more advanced combustion phase under detonation-limited conditions. This is mainly because, under richer mixture conditions, the passive pre-combustion chamber jet flame possesses higher ignition energy and a correspondingly stronger ignition capability. The resulting multi-point ignition significantly accelerates the combustion rate of the mixture. Especially in the early stages of combustion, the jet flame first reaches the detonation-prone area around the combustion chamber, rapidly consuming the end-of-combustion mixture and effectively reducing detonation tendency. Further increases in ignition frequency lead to a gradual decrease in the improvement of combustion phase from passive pre-combustion chamber ignition, while the corresponding increase in ignition delay and combustion duration becomes more pronounced. In contrast, with single spark plug ignition, the gradually increasing intake air volume combined with a high tumble design further enhances the turbulence intensity near top dead center, effectively increasing the flame front area and vortex breaking effect during premixed flame propagation. Under extremely lean air-fuel mixture conditions greater than 1.70, the engine exhibits superior combustion stability and a faster combustion rate. Building upon this, employing a three-spark plug ignition system can further shorten the average flame propagation distance and increase the ignition energy of the final air-fuel mixture, thereby further improving combustion characteristics. When the combustion intensity is increased to the lean-burn limit or maximum value, the combustion duration achievable with passive pre-combustion chamber ignition will increase by 9°CA compared to stoichiometric combustion. However, the combustion duration with three spark plugs will be shortened by nearly 4°CA compared to single spark plugs and passive pre-combustion chambers, and only increased by about 2°CA compared to stoichiometric combustion. Furthermore, the ignition delay period with three spark plugs is also shorter than with a single spark plug. This is mainly because in the initial stage of combustion, each spark plug consumes its surrounding mixture first, resulting in less interaction between them. Therefore, the more ignition points there are, the shorter the ignition delay period.

[0068] Example 12: Under operating conditions of 2000 r / min and BMEP (mean effective pressure) = 0.8 MPa, the initial gas emissions corresponding to different ignition methods will vary. Changes occur as the number of spark plugs increases. When using a three-spark plug ignition system, due to its maximum... The NOx emission can reach 1.95, thus reducing the initial NOx emission to 65 × 10⁻⁶, a reduction of approximately 98.4% compared to pure stoichiometric combustion under the same configuration. This is roughly equivalent to the average conversion efficiency of a three-way catalytic converter. In contrast, the initial NOx emission using passive pre-combustion chamber ignition at the lean-burn limit will reach over 200 × 10⁻⁶, a reduction of only about 92.3% compared to pure stoichiometric combustion. Furthermore, during the process of generating a high-temperature jet flame after the mixture is ignited in the passive pre-combustion chamber housing, a localized high-temperature zone is easily formed near the housing and the jet flame. Therefore, even under relatively lean mixture conditions, its NOx emission is still slightly higher. Meanwhile, passive pre-combustion chamber ignition achieves lower initial CO and HC emissions compared to single spark plug ignition. This is mainly because the jet flame generated by the passive pre-combustion chamber can reach the narrow gap between the piston and cylinder in the early stages of combustion, thereby reducing gas emissions due to incomplete combustion. Using a three-spark plug configuration with spark plugs on both sides can achieve a similar effect. However, the lean-burn limit is lower when using passive pre-combustion chamber ignition. At a value greater than 1.70, unstable combustion leads to a rapid increase in raw CO and HC emissions. In contrast, using three-spark plug ignition maintains consistently lower emission levels. Three-spark plug ignition exhibits significantly better fuel consumption and emission performance under lean-burn conditions. To further investigate the maximum thermal efficiency of three-spark plug ignition, two schemes were used based on the experimental equipment: RON 100 fuel and an electric supercharger. The optimized maximum thermal efficiency points for each test scheme were all around 2000 rpm, which is about 1000 rpm lower than the high-efficiency speed range of currently mass-produced conventional turbocharged engines. This is mainly because the high air dilution rate achieved by the three-spark plug ignition effectively suppresses knocking tendencies in the low-speed, high-load region. The reduction in the high-efficiency speed range is highly beneficial for improving vibration and noise (NVH) during vehicle matching. Furthermore, the maximum thermal efficiency points obtained under the three test schemes correspond to lean mixtures. All are 1.80±0.01. When using RON92 fuel, the engine can achieve a maximum effective thermal efficiency of 45.02%. Switching to RON100 fuel increases the maximum effective thermal efficiency to 45.63%, and further increasing it to 47.04% with the addition of an electric supercharger. However, the improvement in engine combustion process with an electric supercharger is not significant; the main factor contributing to the increase in thermal efficiency is the increase in positive pumping power.

[0069] Example 13 uses an active pre-combustion chamber with 7 nozzles and a nozzle diameter of 1 mm on a test bench engine. The total volume of the pre-combustion chamber is 1.5 cm³, accounting for 4.5% of the engine clearance volume. M8 threaded spark plugs are used to minimize the size of the pre-combustion chamber. The premixed gas pressure is set at 0.09 MPa, the pre-combustion chamber injection timing is 280° CABTDC, and the fuel percentage in the pre-combustion chamber is adjusted to a range of 0.54%–2.69%. The main combustion chamber injection quantity is calculated while maintaining a constant total injection quantity, and the main combustion chamber nozzle injection pulse width is adjusted. As the fuel percentage in the pre-combustion chamber increases, the IMEP (Indicated Mean Effective Pressure) first increases and then decreases, reaching its maximum value at 1.61%, resulting in minimal combustion cycle fluctuation and an indicated thermal efficiency of 39.4%, a 19.8% improvement compared to conventional spark plug ignition. Both the ignition delay period and combustion duration are the shortest. When the proportion of fuel injected into the pre-combustion chamber is too small, that is, when less premixed gas is injected, the scavenging effect on the pre-combustion chamber is weak, and the residual exhaust gas in the pre-combustion chamber cannot be completely removed. This will result in a leaner mixture concentration in the pre-combustion chamber at the time of ignition, thereby weakening the energy of the flame jet in the pre-combustion chamber. If the proportion of fuel injected into the pre-combustion chamber is too large, the amount of premixed gas entering the pre-combustion chamber will also increase. The gasoline premixed gas is prone to re-liquefaction in the pre-combustion chamber, resulting in incomplete combustion, which will affect the overall thermal efficiency.

[0070] Example 14 describes an ignition system combining three spark plugs with an active / passive pre-combustion chamber. Combined with a spark plug control system, this allows for flexible use of pre-combustion chamber spark plugs and side-mounted spark plugs depending on operating conditions. Based on the above examples, the proposed hybrid-specific engine lean-burn reliable ignition system structure based on multiple spark plugs and a pre-combustion chamber is expected to improve indicated thermal efficiency by approximately 20.8% and reduce minimum fuel consumption by approximately 7 g / (kW·h) compared to traditional single-spark plug ignition. Furthermore, it exhibits superior combustion performance and characteristics under lean-burn combustion and even extremely lean mixture conditions, increasing the lean-burn limit and shortening the estimated combustion duration by approximately 5°CA.

Claims

1. A lean burn reliable ignition system for a hybrid dedicated engine based on multiple spark plugs and pre-chamber, characterized by: The engine body, pre-chamber, side ignition unit and external control module are included. The engine body includes a cylinder block (19), a cylinder head and a piston (12); the piston (12) is arranged in the cylinder block (19); the cylinder head blocks the cylinder block (19); the top of the piston (12), the inner wall of the cylinder block (19) and the bottom surface of the cylinder head jointly form a main combustion chamber; the cylinder head is provided with an intake port (9) and an exhaust port (15); The pre-chamber is installed on the cylinder head and has a lower end extending into the main combustion chamber; the pre-chamber includes a pre-chamber shell and a pre-chamber spark plug (1); the pre-chamber shell has a pre-chamber space (2) inside; the pre-chamber shell is provided with a pre-chamber injection hole (3) at the bottom; the pre-chamber space (2) is in fluid communication with the main combustion chamber through the pre-chamber injection hole (3); the pre-chamber spark plug (1) is installed on the pre-chamber shell; the ignition end of the pre-chamber spark plug (1) extends into the pre-chamber space (2); The side ignition unit includes a first side spark plug (11) and a second side spark plug (17); the first side spark plug (11) and the second side spark plug (17) are both installed on the bottom surface of the cylinder head; the first side spark plug (11) and the second side spark plug (17) are respectively located on the two sides of the periphery of the pre-chamber; the ignition end of the first side spark plug (11) and the second side spark plug (17) extends into the main combustion chamber; The pre-chamber spark plug (1), the first side spark plug (11) and the second side spark plug (17) are all electrically connected with the external control module; the external control module independently controls the ignition time and ignition energy of the pre-chamber spark plug (1), the first side spark plug (11) and the second side spark plug (17).

2. The lean burn reliable ignition system for hybrid special engine based on multiple spark plug and pre-chamber according to claim 1, characterized in that: The pre-chamber is a passive pre-chamber structure; fuel is supplemented by the pressure difference of high-temperature and high-pressure gas in the compression stroke of the internal combustion engine.

3. The lean burn reliable ignition system for hybrid special engine based on multiple spark plug and pre-chamber according to claim 1, characterized in that: The pre-chamber is an active pre-chamber structure; further including an oil injector (4); the oil injector (4) is installed on the pre-chamber shell; the nozzle of the oil injector (4) extends into the pre-chamber space (2); the oil injector (4) generates an oil jet spray (6) to independently supplement fuel into the pre-chamber space (2); the external control module controls the oil injection amount and oil injection time of the oil injector (4).

4. The lean burn reliable ignition system for hybrid special engine based on multiple spark plug and pre-chamber according to claim 1, characterized in that: The pre-chamber injection hole (3) adopts a design of annular distribution around; the combustion gas in the pre-chamber is evenly injected into the main combustion chamber in a four-around divergent form.

5. The lean burn reliable ignition system for hybrid special engine based on multiple spark plug and pre-chamber according to claim 1, characterized in that: Traditional gasoline fuel or hydrogen-ammonia zero-carbon fuel is used.

6. A control method for the ignition system according to any one of claims 1 to 5, characterized in that, The method includes the following steps: S1) obtaining real-time working condition parameters of the engine; the working condition parameters include air-fuel ratio, speed, torque and EGR rate; S2) determining an ignition strategy according to the working condition parameters; the ignition strategy includes a pre-chamber-only ignition mode, a three-spark plug ignition mode and a coordinated ignition mode; S3) according to the determined ignition strategy, the external control module sends a control signal to the pre-chamber spark plug (1), the first side spark plug (11) and the second side spark plug (17) to independently adjust the ignition time and ignition energy of each spark plug.

7. The control method according to claim 6, characterized in that: In the cooperative ignition mode, the external control module first controls the pre-chamber spark plug to ignite, ignites the mixture in the pre-chamber to generate a high-temperature and high-pressure jet into the main combustion chamber to ignite the mixture in the main combustion chamber; then, the external control module controls the first side-mounted spark plug (11) and the second side-mounted spark plug (17) to ignite at a specific time according to the pre-judged knock residue, so as to eliminate the knock residue of the mixture at the end of the main combustion chamber.

8. The control method according to claim 7, characterized in that: When it is detected that the engine is in an extremely lean mixture working condition or a high excess air coefficient working condition, the external control module adjusts the first side-mounted spark plug (11) and the second side-mounted spark plug (17) to assist in ignition in the early or middle stage of the jet flame propagation in the pre-chamber, shortens the average flame propagation distance, and improves the ignition energy of the mixture at the end of the main combustion chamber.

9. The control method according to claim 7, characterized by: When the ignition system adopts an active pre-chamber structure and uses hydrogen or ammonia as fuel, the external control module adjusts the air-fuel mixing ratio in the pre-chamber by controlling the injection amount of the fuel injector (4), and cooperates with the ignition timing of the three spark plugs, so as to improve the combustion propagation speed and stability of the zero-carbon fuel.

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