Engine gas injection control device and method based on actual scavenging state

Abstract

A gas injection control device and method for engines based on actual scavenging conditions is disclosed, relating to the field of gas fuel supply for internal combustion engines. This addresses the problem that existing internal combustion engine gas fuel supply devices use a fixed crankshaft angle pulse spectrum for gas supply, which cannot dynamically constrain the gas injection window in conjunction with real-time scavenging conditions, easily leading to gas escape. The device includes a scavenging acquisition module, a gas injection valve, a liquid ignition injector, a combustion detection module, an exhaust methane sensor, and a controller. The sensor acquires scavenging conditions and single-cycle combustion characteristics, while the methane sensor acquires exhaust gas feedback. The controller integrates a multi-functional module to assess gas escape and generate a dynamic injection window. It employs segmented, multi-valve differentiated gas supply, combined with three-layer feedback to correct injection parameters. In case of abnormal operating conditions, it reduces gas supply in stages or switches to pure liquid fuel to reduce gas escape and cycle fluctuations. It is also applicable to two-stroke engines where the cylinder head exhaust valve, exhaust port, or a combination of both form the exhaust passage.

Description

Technical Field

[0001] This invention relates to the field of gas fuel supply technology for internal combustion engines, specifically to a complete set of hardware for natural gas injection supply and a matching staged injection electronic control supply method for a marine two-stroke natural gas dual-fuel engine. Background Technology

[0002] Large marine two-stroke natural gas dual-fuel engines are equipped with independent gas injection supply hardware assemblies. They rely on gas injection valves to supply natural gas to the cylinders, combined with liquid ignition fuel to achieve dual-fuel operation. During the scavenging phase near bottom dead center, the two-stroke engine introduces fresh air into the cylinders through the scavenging port and expels burned gas through the exhaust valve or exhaust port. The effective area of ​​the scavenging port, the effective area of ​​the exhaust passage, the scavenging pressure, the exhaust back pressure, and the turbocharger's operating status jointly determine the actual scavenging process in each working cycle. In natural gas dual-fuel operation mode, natural gas injection needs to be coordinated with the end of scavenging, the closure of the exhaust passage, compression, mixing, and liquid fuel ignition processes. If natural gas enters the cylinder while the cylinder and exhaust passage are still strongly connected and the gas is still flowing significantly towards the exhaust side, some natural gas may enter the exhaust passage with the scavenging flow, creating risks of methane escape, fuel loss, and the accumulation of combustible gas in the exhaust system. If natural gas is injected too late, the target injection quantity may not be completed before the target ignition time, or the necessary mixing time may not be obtained, easily leading to localized over-richness, localized leanness, ignition delay fluctuations, combustion phase deviation, partial combustion, or misfire. Existing natural gas injection supply systems and associated control schemes have the following inherent defects at the fuel supply level: Traditional gas supply controllers use a fixed crankshaft angle pulse spectrum to limit the timing of natural gas supply, without dynamically constraining the gas supply window based on the real-time scavenging and gas exchange status of each cycle. The opening and closing times of the exhaust valves, the degree of scavenging port obstruction, and the pressure difference between the inside and outside of the cylinder of a two-stroke engine fluctuate in real time with the ship's load, turbocharger operating conditions, and exhaust back pressure. The duration of connection between the cylinder and the exhaust passage varies significantly in each cycle. If natural gas is supplied during the period when the cylinder has a large area of ​​connection with the exhaust passage, a large amount of gas will be discharged into the exhaust pipe with the scavenging flow, causing natural gas escape, reduced fuel efficiency, and the accumulation of combustible gas in the exhaust pipe, posing an explosion safety hazard.

[0003] The existing supply control only uses the nominal injection pulse width output by the controller as the basis for controlling the gas supply, without distinguishing between the total amount of gas injected into the cylinder and the effective amount of residual natural gas supply that remains in the cylinder after the exhaust passage is closed and can participate in combustion. Under the scavenging state cycle fluctuation, the quality of the effective residual gas supply corresponding to the same command injection gas supply varies significantly, and the actual fuel supply equivalence ratio of each cycle is unstable, directly causing large cyclic fluctuations in engine output torque and combustion phase.

[0004] Conventional gas supply relies solely on the single-cycle cylinder pressure signal to simply correct the injection volume for the next cycle, lacking statistical correction logic for multi-cycle gas supply stability. At the same time, the exhaust methane concentration feedback suffers from exhaust pipeline transport and sensor response delays. The existing system cannot correlate the methane signal with the corresponding historical cycle sequence, making it difficult to adaptively correct the supply deviation caused by scavenging escape in the long term, resulting in continuous deterioration of gas supply consistency over long-term operation.

[0005] In models with multiple gas injection valves connected in parallel, the existing supply system adopts a uniform injection timing and equal gas supply distribution strategy for all injection valves. It does not configure supply parameters differently according to the installation orientation of each injection valve relative to the exhaust channel and the main scavenging gas flow. The risk of gas escape from injection valves closer to the exhaust side is significantly higher, and the overall natural gas supply balance of the unit is poor.

[0006] When exhaust back pressure suddenly increases, exhaust valve movement deviates, or operating condition sensor signals fail, traditional gas supply systems lack safety downgrade supply logic such as graded reduction of gas supply, segmented cancellation of compensating injection, and emergency switching to pure diesel supply. Continuous supply of large amounts of natural gas under abnormal operating conditions poses a safety risk.

[0007] In summary, existing two-stroke natural gas injection systems cannot dynamically constrain the natural gas supply window based on real-time scavenging and gas exchange status, and cannot accurately control the effective in-cylinder gas retention volume. They also have significant shortcomings in fuel supply stability, fuel utilization, and overall engine safety. There is an urgent need for a gas injection control method that combines the current cycle's actual scavenging status, natural gas escape risk, effective in-cylinder gas retention volume, single-cycle combustion feedback, multi-cycle stability feedback, and exhaust methane slow feedback to simultaneously reduce cycle variations and methane escape. Summary of the Invention

[0008] This invention addresses the shortcomings of existing internal combustion engine gas fuel supply devices that rely on fixed crankshaft pulse patterns. These devices fail to dynamically constrain the gas injection window in conjunction with real-time scavenging conditions, leading to easy gas escape. Furthermore, the controllers only regulate the nominal injection volume, failing to achieve precise supply based on the effective amount of natural gas retained in the cylinder. Additionally, they lack multi-layer closed-loop gas supply logic, including single-cycle rapid correction, multi-cycle statistical correction, and exhaust methane delay correlation. The multiple injection valves lack differentiated gas distribution strategies, and there is no graded gas supply degradation protection under abnormal conditions, resulting in poor overall fuel supply accuracy, gas supply balance, and operational safety. Therefore, this invention proposes an engine gas injection control device and method based on actual scavenging conditions. The invention achieves these technical problems through the following technical solutions: Option 1: This invention proposes an engine gas injection control device based on actual scavenging conditions. The device includes a scavenging condition parameter acquisition module, at least one gas injection valve, a liquid ignition fuel injector, a combustion state detection module, an exhaust methane detection module, and a controller. The scavenging state parameter acquisition module includes at least two of the following: crankshaft angle sensor, exhaust valve position sensor, cylinder pressure sensor, scavenging pressure sensor, exhaust pressure sensor, and turbocharger speed sensor. It is used to collect scavenging state parameters including exhaust valve lift, effective exhaust passage area, scavenging port obstruction ratio, piston position, cylinder pressure, scavenging pressure, exhaust back pressure, engine speed, turbocharger speed, scavenging or exhaust flow rate, and exhaust manifold pressure pulsation. The combustion state detection module is used to collect combustion state parameters such as single-cycle indicated average effective pressure (IMEP), CA10, CA50, CA90, peak cylinder pressure, maximum pressure rise rate, misfire or combustion signal, cycle variation coefficient (COVIMEP), and combustion phase standard deviation. The exhaust methane detection module is implemented using a methane concentration sensor installed in the exhaust branch pipe, exhaust main pipe, or downstream sampling pipeline, and is used to collect exhaust methane concentration feedback signals. The controller integrates a state parameter acquisition module, a scavenging state estimation module, a natural gas escape risk assessment module, an effective retained natural gas quantity estimation module, a target effective retained natural gas quantity determination module, a dynamic allowable injection window determination module, a gas injection control module, a single-cycle rapid feedback module, a multi-cycle stability correction module, an exhaust methane delay correlation module, and a fault degradation module. It is used to estimate the scavenging process and natural gas escape risk based on real-time acquired scavenging state parameters, generate a dynamic gas injection window, and plan segmented, multi-valve differentiated injection strategies. At the same time, it continuously corrects injection parameters by combining single-cycle combustion rapid feedback, multi-cycle combustion statistical feedback, and exhaust methane slow feedback with transmission delay. Under abnormal operating conditions, it performs graded degradation or pure liquid fuel switching protection, simultaneously achieving the dual control objectives of reducing methane escape and suppressing combustion cycle variations.

[0009] Furthermore, a preferred embodiment is provided, wherein the gas injection valve includes multiple sets of first injection valves, second injection valves, third injection valves and fourth injection valves arranged along the circumference of the cylinder. The controller independently configures the valve-level escape risk coefficient for each injection valve. The fourth injection valve, which is far from the exhaust passage and whose injection direction is opposite to the exhaust airflow, is set as a low-risk valve and is opened first. The second injection valve, which is close to the exhaust passage, is a high-risk valve and is opened later.

[0010] Furthermore, in a preferred embodiment, the scavenging air state parameter acquisition module further includes an optional scavenging air flow sensor and an exhaust air flow sensor for directly acquiring the scavenging air mass flow rate. s, exhaust mass flow rate e, Input scavenging state estimation module, used by the controller to automatically switch to pressure-geometric surrogate model to complete scavenging state estimation when the flow sensor fails.

[0011] Furthermore, a preferred embodiment is provided, wherein the gas injection control module supports three-stage segmented injection, including a first injection stage, a second injection stage, and a compensation injection stage. The first injection stage is executed when the scavenging completion reaches a first threshold. The second injection stage is executed after the exhaust passage is further closed. The compensation injection stage is only activated when the combustion feedback gas volume is insufficient, the injection window has a margin, and the escape risk meets the standard. When the exhaust back pressure increases, the window contracts, or the scavenging estimation confidence decreases, the controller 5 sequentially cancels the compensation injection stage and the second injection stage.

[0012] Option 2: An engine gas injection control method based on actual scavenging conditions, wherein the method is implemented based on the control device described in Option 1, and the method includes the following steps: Step 1: Obtain multiple scavenging state parameters corresponding to the current working cycle. At least one of the multiple scavenging state parameters is used to characterize the communication state between the cylinder and the exhaust passage, and at least another parameter is used to characterize the scavenging process, pressure boundary, or gas flow state of the cylinder. Step 2: Determine the scavenging completion status characterization parameters for the current working cycle based on the scavenging status parameter acquisition module, and estimate at least one of the following: residual exhaust gas status, air charge, natural gas escape risk, expected natural gas escape ratio, and expected effective retained natural gas volume. Step 3: Based on the scavenging completion status parameters, the connectivity between the cylinder and the exhaust passage, and the natural gas escape risk, determine the actual injection quantity for the current working cycle. Step 4: Based on at least one of the following: target effective natural gas retention volume, gas injection valve injection capacity, target ignition timing, minimum natural gas mixing time required, injection pressure difference between gas supply pressure and cylinder pressure, and permissible closing boundary of the gas injection valve, determine the target gas injection quantity and latest permissible injection timing for the current working cycle. Step 5: Form a dynamic allowable injection window for the current work cycle from the earliest allowable injection time and the latest allowable injection time, and determine at least one of the following within the dynamic allowable injection window: actual injection start point, actual injection end point, injection duration, number of injection segments, gas quantity in each injection segment, and injection distribution among multiple gas injection valves. Step 6: Obtain the single-cycle combustion state parameters of the current working cycle, and based on the deviation between the single-cycle combustion state parameters and the target combustion state, correct the target effective retained natural gas quantity, gas injection quantity, injection timing or segment ratio of the working cycle. Also, based on at least one of the combustion cycle variation characterization parameters of multiple consecutive working cycles and exhaust methane feedback associated with transport delay, correct the scavenging state estimation, natural gas escape risk threshold, dynamic allowable injection window or gas injection parameters of subsequent working cycles.

[0013] Furthermore, a preferred embodiment is provided, wherein the scavenging completion status characterization parameters in step 2 are at least one of the following: residual exhaust gas ratio, scavenging efficiency, charging efficiency, exhaust channel connectivity, estimated remaining scavenging time, and status estimation confidence level, and are solved by any one of the following methods: physical model, sensor signal fusion, calibration proxy model, and historical observer.

[0014] Furthermore, a preferred embodiment is provided, wherein the method for determining the actual injection quantity of the current working cycle in step 3 based on the scavenging completion status characterization parameters, the connectivity status between the cylinder and the exhaust passage, and the natural gas escape risk is as follows:

[0015] in, This is the commanded injection volume. To predict the proportion of natural gas escape.

[0016] Furthermore, a preferred embodiment is provided, wherein determining the earliest permissible injection time in step 3 includes: when the scavenging completion status characterization parameters reach the permissible conditions, the natural gas escape risk is lower than the risk threshold, and the connectivity between the cylinder and the exhaust passage meets the permissible conditions, the moment when the above conditions are met simultaneously for the first time, or the moment obtained by adding a safety margin thereafter, is determined as the earliest permissible injection time; when the exhaust back pressure increases, the exhaust valve closing is delayed, the exhaust pressure pulsation increases, or the confidence level of the state estimation decreases, the earliest permissible injection time is postponed.

[0017] Furthermore, a preferred embodiment is provided, wherein the single-cycle combustion state parameters mentioned in step 6 include at least one of the following: single-cycle indicated average effective pressure, output torque, instantaneous speed change, CA10, CA50, CA90, combustion duration, peak cylinder pressure, maximum pressure rise rate, heat release rate, misfire determination, and partial combustion determination. The single-cycle combustion state parameters are used to implement rapid feedback correction for one or more adjacent subsequent working cycles.

[0018] Furthermore, a preferred embodiment is provided in which the exhaust methane feedback is obtained by a methane concentration sensor or gaseous fuel concentration sensor installed in the exhaust branch pipe, exhaust main pipe or downstream sampling pipeline. The controller establishes an association between the exhaust methane feedback and the previous working cycle that generated the feedback based on the exhaust channel volume, exhaust mass flow rate, engine speed, sampling pipeline transport time, sensor sampling delay and sensor response characteristics, and corrects the escape risk model, safety margin or gas injection parameters of the working cycle.

[0019] The advantages of this invention are: The engine gas injection control device and method based on actual scavenging conditions described in this invention uses a controller to collect real-time scavenging parameters such as exhaust valve lift, cylinder-to-internal pressure difference, and effective scavenging / exhaust flow area. It assesses natural gas escape risk in real time and adaptively determines the earliest and latest permissible natural gas injection crankshaft angles for a single cycle, forming a dynamic injection window. This automatically avoids injection periods where there is significant communication between the cylinder and exhaust passages, and where gas is easily lost with the scavenging flow. Compared to traditional fixed crankshaft injection pulse patterns, this system constrains natural gas escape losses from the injection timing source, improving the effective utilization rate of natural gas fuel supply. Simultaneously, it prevents large accumulations of combustible gas in the exhaust pipe, reducing long-term safety hazards associated with the entire gas injection supply system.

[0020] The engine gas injection control device based on actual scavenging conditions described in this invention incorporates a real-time escape risk estimation algorithm. It calculates the expected gas escape ratio for a single cycle by combining the scavenging flow state, and then uses the target effective retained natural gas mass to inversely calculate the command injection gas volume. Simultaneously, it sets an escape compensation upper limit, preventing the injection pulse width from being increased indefinitely to offset gas loss. This effectively counteracts the interference of scavenging state fluctuations between cycles on the actual gas supply, stabilizes the natural gas supply in the cylinder for each cycle, and significantly improves the accuracy of gas injection supply metering and the stability of cycle gas supply.

[0021] The engine gas injection control device based on actual scavenging conditions described in this invention integrates a three-level fuel supply feedback correction link, comprehensively and adaptively correcting injection parameters: The first level is a single-cycle combustion rapid feedback, which quickly corrects the gas injection quantity and injection segment timing for the next cycle based on real-time combustion signals such as IMEP, CA50, and misfire status, adapting to supply deviations caused by short-term load fluctuations. The second level is a multi-cycle statistical slow correction, which uses a sliding window to statistically analyze cycle variation coefficients and slowly and adaptively optimizes long-term supply reference parameters to suppress continuous supply deviations. The third level is an exhaust methane delay correlation correction, which, considering the lag characteristics of exhaust pipeline transport and sensor sampling, matches the methane concentration signal to the corresponding historical cycle, continuously iterating the escape risk model and optimizing the injection window safety margin. The synergistic effect of these three corrections gives the entire gas supply system strong operating condition adaptability, maintaining stable fuel supply characteristics across the entire load range.

[0022] The engine gas injection control device based on actual scavenging conditions described in this invention uses a controller that independently configures the escape risk coefficient of each injection valve according to its installation position relative to the exhaust passage and the main scavenging flow. Injection valves farther from the exhaust side with a lower risk of gas loss are prioritized for opening and allocated a larger gas supply. High-risk injection valves closer to the exhaust passage have their injection delayed and their single-stage supply reduced, achieving differentiated gas supply distribution across multiple valves in a time-sharing and quantity-based manner. This solves the problem of localized gas supply imbalance in cylinders caused by traditional uniform injection timing, significantly improving the uniformity of natural gas injection supply across the entire engine.

[0023] The engine gas injection control device based on actual scavenging conditions described in this invention divides a single natural gas supply into a two-stage supply structure: a basic main injection stage and a compensation injection stage. The basic main supply is executed after the scavenging completion rate is met. The compensation injection stage is activated only when the dynamic injection window margin is sufficient and the previous cycle's gas supply was insufficient. When exhaust back pressure increases and the risk of gas escape rises, the controller prioritizes canceling the compensation injection and gradually reduces the main injection volume. The gas supply segmentation strategy can be flexibly adjusted according to real-time scavenging conditions, balancing precise supply of small volumes at low loads with the demand for large volumes at high loads, thus broadening the applicable operating conditions of the entire gas injection supply system.

[0024] This invention is also applicable to two-stroke engines that use cylinder head exhaust valves, exhaust ports, or a combination of both to form an exhaust passage, and can be applied to longitudinal scavenging, recirculation scavenging, or crossflow scavenging structures. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the condition detection system for a two-stroke natural gas dual-fuel engine as described in Embodiment 1.

[0026] Figure 2 This is a schematic diagram of the gas injection control principle based on actual scavenging state and cyclic variation feedback as described in Implementation Method 1.

[0027] Figure 3 This is a schematic diagram of the scavenging state and dynamic gas injection timing within a working cycle as described in Implementation Method 1.

[0028] Figure 4 This is a schematic diagram of the cyclic variation feedback control based on single-cycle and multi-cycle combustion states as described in Implementation Method 1.

[0029] Figure 5 This is a schematic diagram of segmented gas injection based on scavenging completion level as described in Implementation Method 1.

[0030] Figure 6 This is a schematic diagram illustrating the differentiated regional risk control of multiple gas injection valves as described in Implementation Method 1.

[0031] Figure 7 This is a flowchart illustrating the engine gas injection control method based on actual scavenging conditions as described in Implementation Method 1.

[0032] The system includes a two-stroke natural gas dual-fuel engine 1, a cylinder block 10, a cylinder head 11, a cylinder 12, a piston 13, a main combustion chamber 14, a cylinder liner scavenging port 15, a scavenging air box 16, an exhaust passage 17, a cylinder head exhaust valve 18, an exhaust manifold 19, a first injection valve 20, a second injection valve 21, a third injection valve 22, and a fourth injection valve 23, a gas supply pipeline 24, a common rail gas system 25, a gas pressure regulation module 26, a liquid ignition fuel injector 30, a sensor module 4, a crankshaft angle sensor 40, an exhaust valve position sensor 41, a cylinder pressure sensor 42, a scavenging air pressure sensor 43, an exhaust pressure sensor 44, a scavenging air flow sensor 45, an exhaust air flow sensor 46, a methane concentration sensor 47, a torque detection module 48, a turbocharger speed sensor 49, a controller 5, and a status parameter acquisition module 50. The following modules are included: 51. Scavenging status estimation module; 52. Natural gas escape risk assessment module; 53. Effective retained natural gas volume estimation module; 54. Target effective retained natural gas volume determination module; 55. Earliest allowable injection time; 56. Latest allowable injection time; 57. Dynamic allowable injection window; 58. Gas injection control module; 59. Single cycle rapid feedback module; 60. Multi-cycle stability correction module; 61. Exhaust methane delay correlation module; 62. Fault degradation module; 70. Scavenging completion status characterization parameters; 71. Natural gas escape risk; 72. Effective flow area of ​​exhaust channel; 73. Effective flow area of ​​scavenging port; 74. Expected natural gas escape ratio; 75. Effective retained natural gas volume; 76. Single cycle indicated average effective pressure; 77. Target indicated average effective pressure; 78. Cycle variation coefficient; 80. First injection stage; 81. Second injection stage; 82. Compensation injection stage. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them.

[0034] Implementation Method 1, see Figures 1 to 7 This embodiment describes an engine gas injection control device and method based on actual scavenging conditions. The aim is to determine the safe injection boundary through the current cycle rapid state, control the gas injection quantity by effectively retaining natural gas, suppress cycle variations through single-cycle and multi-cycle combustion feedback, and correct the escape risk model of subsequent cycles through delayed correlation exhaust methane feedback.

[0035] Example 1: Engine System and Basic Control Structure like Figure 1 and Figure 2As shown, this embodiment is applicable to a longitudinal scavenging two-stroke natural gas dual-fuel engine 1 with a cylinder head exhaust valve 18 and a cylinder liner scavenging port 15. The crankshaft angle sensor 40 outputs the crankshaft angle and engine speed, and the controller 5 obtains the piston 13 position and the effective flow area of ​​the cylinder liner scavenging port 15 according to the geometry of the crankshaft and connecting rod mechanism.

[0036] The exhaust valve position sensor 41 measures the actual lift of the cylinder head exhaust valve 18, and the controller 5 obtains the effective flow area of ​​the exhaust passage based on the exhaust valve profile, valve seat size, and flow coefficient calibration relationship. The in-cylinder pressure sensor 42, scavenging pressure sensor 43, and exhaust pressure sensor 44 respectively provide the current cycle pressure boundary.

[0037] The controller 5 sequentially performs scavenging state estimation, natural gas escape risk assessment, effective retained natural gas quantity estimation, target effective retained natural gas quantity determination, dynamic allowable injection window calculation, and gas injection control, and corrects subsequent cycles based on combustion feedback and exhaust methane feedback.

[0038] Example 2: Current Cyclic Scavenging Status and Escape Risk Estimation The scavenging state estimation module 51 updates the total cylinder mass, fresh air mass, and residual exhaust gas mass based on the effective flow area of ​​the scavenging port 73, the effective flow area of ​​the exhaust passage 72, the position of the piston 13, the engine speed, the cylinder pressure, the scavenging pressure, the exhaust pressure, and the optional scavenging and exhaust mass flow rates.

[0039] The scavenging completion status characterization parameter 70 is composed of the residual exhaust gas ratio, scavenging efficiency, cumulative exhaust mass, estimated remaining scavenging time, and the degree of cylinder-exhaust passage connectivity. For engines lacking flow sensors, it can be estimated using calibration mapping of mechanism geometry and pressure boundaries or a state observer.

[0040] The natural gas escape risk assessment module 52 predicts the gas flow direction and exhaust passage connectivity during natural gas injection at each candidate injection start point. When the exhaust passage still has a large effective area and the in-cylinder gas still flows towards the exhaust side, the escape risk is increased; when the exhaust passage closure degree increases and the cylinder enters the compression phase, the escape risk is reduced.

[0041] Example 3: Determination of Effective Retained Natural Gas Volume and Injection Volume Controller 5 decomposes the commanded injection quantity into the expected amount of natural gas escaping into the exhaust passage and the expected amount of effective retained natural gas in the cylinder. The target effective retained natural gas quantity is determined based on the current circulating fresh air charge, the target equivalence ratio, and the target output power.

[0042] When the expected escape ratio is small and the dynamic allowable window is sufficient, the commanded gas quantity can be compensated to a limited extent based on the target effective retained natural gas quantity and the expected escape ratio. When the compensation would cause the expected escape quantity to exceed the safety limit, the controller will no longer increase the gas quantity, but will reduce the gas substitution rate and increase the liquid ignition fuel quantity.

[0043] Therefore, the control objective has shifted from maintaining the nominal injection volume of each cycle to maintaining the effective retention of natural gas and the mixing state of each cycle close to the target under escape constraints.

[0044] Example 4: Determining the Dynamic Injection Window like Figure 3 As shown, the earliest permissible injection time 55 is the first time that the conditions for completion of scavenging are met simultaneously, the risk of natural gas escape is lower than the risk threshold, and the connectivity of the exhaust channel meets the permissible conditions. The safety margin can be increased based on the confidence level of the state estimation.

[0045] The latest permissible injection time 56 is determined by the earliest of the following: the mixing constraint boundary, the injection completion constraint boundary, the gas injection valve allowable closing boundary, and the injection pressure difference boundary. The actual injection start and end points are both located within the dynamic permissible injection window 57.

[0046] When the earliest permitted injection time is not earlier than the latest permitted injection time, or when the window width is insufficient to complete the safe gas volume, the controller cancels the current cycle gas injection or switches to liquid fuel mode.

[0047] Example 5: Single-loop fast feedback and multi-loop stability correction like Figure 4 As shown, after the current cycle combustion is completed, the single-cycle indicated average effective pressure (AAP) 76, CA10, CA50, combustion duration, peak pressure, and maximum pressure rise rate are calculated based on the in-cylinder pressure. If the single-cycle indicated average effective pressure is lower than the target and no high escape risk is detected, the target effective retained natural gas quantity for the next cycle can be increased or the second injection phase can be advanced within permissible limits. If the combustion phase is too early or the maximum pressure rise rate is too high, the injection can be delayed, the early injection ratio reduced, or the ignition fuel adjusted.

[0048] The controller calculates the COVIMEP and CA50 standard deviations within a predetermined number of cyclic sliding windows. When the statistical cyclic variation increases but the exhaust methane does not increase, the mixing time, segment ratio, and ignition parameters are adjusted first. When the cyclic variation and exhaust methane both increase, the earliest injection time is delayed first, the early fuel gas quantity is reduced, and the escape risk threshold is tightened.

[0049] Both single-cycle fast correction and multi-cycle statistical correction employ amplitude and rate-of-change limits to prevent excessive jumps in control parameters between adjacent cycles.

[0050] Example 6: Loop Correlation of Slow Feedback in Exhaust Methane The methane concentration sensor 47 is installed in the exhaust manifold, exhaust main 19, or downstream sampling line. The controller estimates the generation time of the methane signal based on the effective volume of the exhaust line, the estimated exhaust mass flow rate, the engine speed, the sampling line length, and the sensor response model.

[0051] Controller 5 establishes a probabilistic correlation between the detected peak or integral amount of methane concentration and one or more previous cycles. If the correlated methane escape continues to exceed the target, the scavenging completion threshold is gradually increased, the earliest injection safety margin is increased, the early injection ratio is reduced, or the target fuel gas substitution rate is reduced.

[0052] When the reliability of the exhaust methane signal is insufficient due to sensor failure, abnormal sampling flow, or exhaust dilution, only the rapid scavenging state and combustion feedback control are retained, and the slow timescale adaptive update is frozen.

[0053] Example 7: Segmented Injection Control like Figure 5 As shown, the controller 5 allocates the target gas quantity into a first injection section 80, a second injection section 81, and a compensation injection section 82. The first injection section 80 is executed after the scavenging state reaches a first threshold, and the second injection section 81 is executed after the exhaust passage is further closed and the expected effective retention ratio increases.

[0054] The compensating injection stage 82 is activated only when single-cycle combustion feedback indicates insufficient output in the previous cycle, the current cycle dynamic window still has margin, and the escape risk meets the requirements. If the window contracts, exhaust back pressure increases, or the confidence level of the state estimate decreases, the compensating injection stage is canceled first, followed by the second injection stage.

[0055] Staged injection allows for the injection of a small amount of natural gas before scavenging is fully completed but before the risk is within acceptable limits, and the main injection volume is completed after the exhaust passage is further closed, thus taking into account both mixing time and escape control.

[0056] Example 8: Differentiated control of multiple gas injection valves. The engine is equipped with multiple gas injection valves along the cylinder circumference or cylinder head, including a first injection valve 20, a second injection valve 21, a third injection valve 22, and a fourth injection valve 23. Each gas injection valve has a different positional relationship relative to the exhaust passage 17, the scavenging flow direction, and the cylinder space region.

[0057] The controller establishes a valve-level escape risk factor for each gas injection valve. Gas injection valves that are far from the exhaust passage, whose injection direction is towards the cylinder center, or that are contrary to the exhaust flow direction can be opened first. Gas injection valves that are close to the exhaust passage or whose jet may directly enter the exhaust side can be opened later, have their injection volume reduced, or be disabled in abnormal cycles.

[0058] When a gas injection valve experiences flow deviation, delayed closing, or malfunction, the controller reallocates the gas quantity if the capacity of other gas injection valves and the dynamic window allow; otherwise, it reduces the gas substitution rate.

[0059] Example 9: Sudden changes in exhaust back pressure and window degradation. When the exhaust pressure suddenly increases in the current cycle or several adjacent cycles, or when the pressure pulsation in the exhaust manifold increases, the earliest permissible injection time is postponed, while the latest permissible injection time, which is determined by the target ignition and mixing time, may remain basically unchanged. Therefore, the injection window is dynamically allowed to shrink.

[0060] The controller 5 recalculates the maximum amount of gas that can be safely completed based on the contracted window, and sequentially cancels the compensation injection section, reduces the gas quantity of the second injection section 81, increases the liquid ignition fuel, and limits the load. When the window is invalid, the natural gas injection for this cycle is canceled.

[0061] After the exhaust back pressure is restored, the controller needs to confirm the reliability of the status through several consecutive cycles before gradually restoring the gas substitution rate at a preset rate to avoid immediate restoration that could cause escape or combustion fluctuations.

[0062] Example 10: Sensor Fault and Safety Degradation. The fault degradation module 62 performs range, rate of change, redundancy consistency and model residual diagnosis on exhaust valve position, cylinder pressure, scavenging pressure, exhaust pressure, flow rate and methane concentration signals.

[0063] When the exhaust valve position sensor fails, controller 5 uses exhaust valve drive commands, actuator feedback, and changes in cylinder pressure and exhaust pressure to estimate the exhaust passage state. When the flow sensor fails, it uses pressure boundaries and mechanism geometry models to estimate the scavenging state.

[0064] In degraded estimation mode, controller 5 increases the earliest injection safety margin and reduces the allowable gas quantity. When the effective state parameters are insufficient to form a safe dynamic window, natural gas injection is canceled and the system switches to a liquid fuel safe operation mode. After fault recovery, gas operation is gradually restored after verification of signal rationality and continuous cycle stability.

[0065] Example 11: As Figure 7 As shown in this embodiment, the engine gas injection control method based on actual scavenging conditions includes the following steps: S101. Obtain the scavenging, exhaust, mechanism, and gas supply status parameters of the current cycle, and add the cycle number and crankshaft angle label.

[0066] S102. Estimate the scavenging completion rate, residual exhaust gas ratio, and fresh air charge using mechanism geometry, pressure boundary, flow rate, and model state.

[0067] S103. Assess the natural gas escape risk and expected escape rate for candidate injection periods.

[0068] S104. Determine the target effective amount of natural gas to be retained based on the target output, air charge, target equivalence ratio, and combustion feedback.

[0069] S105. Determine the earliest permissible injection time based on escape constraints, and determine the latest permissible injection time based on injection capability, target ignition time, and mixing time, thus forming a dynamic permissible injection window.

[0070] S106. Calculate the total injection volume, injection start and end points, segment ratio, and multi-valve injection distribution within the dynamic allowable window, and verify the escape compensation upper limit.

[0071] S107, Perform gas injection and obtain current cycle cylinder pressure, output and combustion phase feedback.

[0072] S108. Determine whether the natural gas escape risk, dynamic window, effective amount of retained natural gas, and combustion deviation meet the requirements.

[0073] S109. Correct the immediately following loop based on the single loop feedback.

[0074] S110. Correct the multi-cycle control parameters based on the exhaust methane signal obtained from cyclic variation statistics and delay correlation.

[0075] S111. When there is insufficient window, excessive escape risk, continuous misfire, excessive cycle variation or status parameter failure, perform actions such as reducing gas volume, canceling injection section, increasing liquid fuel, limiting load, canceling gas injection or switching safety mode.

[0076] In summary, this implementation method comprehensively optimizes the gas injection supply electronic control system of a two-stroke natural gas dual-fuel engine. By dynamically defining the dynamic injection window of natural gas through real-time acquisition of scavenging-related operating parameters, the effective amount of natural gas retained in the cylinder is used as the core indicator for fuel supply regulation, and an upper limit constraint for escape compensation is set. It is combined with a three-layer closed-loop gas supply regulation logic of single-cycle rapid correction, multi-cycle statistical correction, and exhaust methane delay-related correction. At the same time, it integrates multiple supply regulation mechanisms such as segmented injection, differentiated allocation of multiple injection valves, and graded gas supply degradation based on operating conditions and sensor faults. From multiple dimensions such as gas supply timing constraints, accurate gas supply measurement, adaptive gas supply under all operating conditions, balanced circumferential gas supply in the cylinder, and gas supply safety protection under abnormal operating conditions, it comprehensively improves the metering accuracy, cycle gas supply consistency, and long-term operational safety performance of the entire gas injection supply equipment. It effectively reduces ineffective fuel escape loss during the gas injection process, reduces methane escape, and suppresses combustion cycle fluctuations.

[0077] Those skilled in the art will understand that the above description is merely a preferred embodiment of the present invention, and the features described in the various embodiments and / or technical solutions of this disclosure can be combined or combined in various ways, even if such combinations or combinations are not explicitly described in this disclosure. This is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0078] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if these modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include these modifications and modifications.

Claims

1. An engine gas injection control device based on actual scavenging conditions, characterized in that, The device includes a scavenging state parameter acquisition module, at least one gas injection valve, a liquid ignition fuel injector, a combustion state detection module, an exhaust methane detection module, and a controller (5). The scavenging state parameter acquisition module includes at least two of the following: crankshaft angle sensor, exhaust valve position sensor, cylinder pressure sensor, scavenging pressure sensor, exhaust pressure sensor, and turbocharger speed sensor. It is used to collect scavenging state parameters including exhaust valve lift, effective flow area of ​​exhaust passage, scavenging port obstruction ratio, piston position, cylinder pressure, scavenging pressure, exhaust back pressure, engine speed, turbocharger speed, scavenging or exhaust flow rate, and exhaust manifold pressure pulsation. The combustion state detection module is used to collect combustion state parameters such as single-cycle indicated average effective pressure (IMEP), CA10, CA50, CA90, peak cylinder pressure, maximum pressure rise rate, misfire or combustion signal, cycle variation coefficient (COVIMEP), and combustion phase standard deviation. The exhaust methane detection module is implemented by a methane concentration sensor installed in the exhaust branch pipe, exhaust main pipe or downstream sampling pipeline, and is used to collect exhaust methane concentration feedback signals. The controller (5) integrates a state parameter acquisition module, a scavenging state estimation module, a natural gas escape risk assessment module, an effective retained natural gas quantity estimation module, a target effective retained natural gas quantity determination module, a dynamic allowable injection window determination module, a gas injection control module, a single-cycle rapid feedback module, a multi-cycle stability correction module, an exhaust methane delay correlation module, and a fault degradation module. It is used to estimate the scavenging process and natural gas escape risk based on the real-time collected scavenging state parameters, generate a dynamic gas injection window and plan segmented, multi-valve differentiated injection strategies. At the same time, it continuously corrects the injection parameters by combining single-cycle combustion rapid feedback, multi-cycle combustion statistical feedback and exhaust methane slow feedback with transmission delay. Under abnormal operating conditions, it performs graded degradation or pure liquid fuel switching protection, and simultaneously achieves the dual control objectives of reducing methane escape and suppressing combustion cycle changes.

2. The engine gas injection control device based on actual scavenging conditions according to claim 1, characterized in that, The gas injection valve includes multiple sets of first injection valve (20), second injection valve (21), third injection valve (22), and fourth injection valve (23) arranged along the cylinder circumference; the controller (5) independently configures the valve level escape risk coefficient for each injection valve. The fourth injection valve (23), which is far from the exhaust passage (17) and whose injection direction is opposite to the exhaust airflow, is set as a low-risk valve and is opened first; the second injection valve (21), which is close to the exhaust passage (17), is a high-risk valve and is opened later.

3. The engine gas injection control device based on actual scavenging conditions according to claim 1, characterized in that, The scavenging air status parameter acquisition module also includes an optional scavenging air flow sensor (45) and an exhaust flow sensor (46) for directly acquiring the scavenging air mass flow rate. s, exhaust mass flow rate e, Input scavenging state estimation module (51), which is used to automatically switch the controller (5) to the pressure-geometric proxy model to complete the scavenging state estimation when the flow sensor fails.

4. The engine gas injection control device based on actual scavenging conditions according to claim 1, characterized in that, The gas injection control module supports three-stage segmented injection, including a first injection stage (80), a second injection stage (81), and a compensation injection stage (82). The first injection stage (80) is executed when the scavenging completion reaches the first threshold, the second injection stage (81) is executed after the exhaust passage is further closed, and the compensation injection stage (82) is only activated when the combustion feedback gas volume is insufficient, the injection window has a margin, and the escape risk meets the standard. When the exhaust back pressure increases, the window contracts, or the scavenging estimation confidence decreases, the controller (5) sequentially cancels the compensation injection stage (82) and the second injection stage (81).

5. An engine gas injection control method based on actual scavenging conditions, characterized in that, The method is implemented based on the control device according to any one of claims 1-4, and the method includes the following steps: Step 1: Obtain multiple scavenging state parameters corresponding to the current working cycle. At least one of the multiple scavenging state parameters is used to characterize the connection state between the cylinder and the exhaust passage, and at least another parameter is used to characterize the scavenging process, pressure boundary, or gas flow state of the cylinder. Step 2: Determine the scavenging completion status characterization parameters of the current working cycle according to the scavenging status parameter acquisition module, and estimate at least one of the following: residual exhaust gas status, air charge, natural gas escape risk, expected natural gas escape ratio, and expected effective retained natural gas volume. Step 3: Determine the actual injection quantity for the current working cycle based on the scavenging completion status characterization parameters, the connection status between the cylinder and the exhaust passage, and the natural gas escape risk; Step 4: Determine the target gas injection quantity and the latest allowable injection time for the current working cycle based on at least one of the following: target effective residual natural gas quantity, injection capacity of the gas injection valve, target ignition time, minimum mixing time required for natural gas, injection pressure difference between gas supply pressure and cylinder pressure, and allowable closing boundary of the gas injection valve. Step 5: Form a dynamic allowable injection window for the current working cycle from the earliest allowable injection time and the latest allowable injection time, and determine at least one of the following within the dynamic allowable injection window: actual injection start point, actual injection end point, injection duration, number of injection segments, gas quantity in each injection segment, and injection distribution among multiple gas injection valves; Step 6: Obtain the single-cycle combustion state parameters of the current working cycle, and correct the target effective retained natural gas quantity, gas injection quantity, injection time or segment ratio of the working cycle based on the deviation between the single-cycle combustion state parameters and the target combustion state; and correct the scavenging state estimation, natural gas escape risk threshold, dynamic allowable injection window or gas injection parameters of subsequent working cycles based on at least one of the combustion cycle variation characterization parameters of multiple consecutive working cycles and exhaust methane feedback associated with transport delay.

6. The engine gas injection control method based on actual scavenging conditions according to claim 5, characterized in that, In step 2, the parameters representing the completion status of scavenging are at least one of the following: residual exhaust gas ratio, scavenging efficiency, charging efficiency, exhaust channel connectivity, estimated remaining scavenging time, and state estimation confidence level. These parameters are solved using any one of the following methods: physical model, sensor signal fusion, calibration proxy model, or historical observer.

7. The engine gas injection control method based on actual scavenging conditions according to claim 5, characterized in that, The method for determining the actual injection quantity of the current working cycle in step 3 based on the scavenging completion status characterization parameters, the connectivity status between the cylinder and the exhaust passage, and the natural gas escape risk is as follows: in, This is the commanded injection volume. To predict the proportion of natural gas escape.

8. The engine gas injection control method based on actual scavenging conditions according to claim 5, characterized in that, Step 3, determining the earliest permissible injection time, includes: when the scavenging completion status characterization parameters reach the permissible conditions, the natural gas escape risk is lower than the risk threshold, and the connectivity between the cylinder and the exhaust passage meets the permissible conditions, the moment when the above conditions are met simultaneously for the first time, or the moment obtained by adding a safety margin thereafter, is determined as the earliest permissible injection time; when the exhaust back pressure increases, the exhaust valve closing is delayed, the exhaust pressure pulsation increases, or the confidence level of the state estimation decreases, the earliest permissible injection time is postponed.

9. The engine gas injection control method based on actual scavenging conditions according to claim 5, characterized in that, The single-cycle combustion state parameters mentioned in step 6 include at least one of the following: single-cycle indicated average effective pressure, output torque, instantaneous speed change, CA10, CA50, CA90, combustion duration, peak cylinder pressure, maximum pressure rise rate, heat release rate, misfire determination, and partial combustion determination; the single-cycle combustion state parameters are used to implement rapid feedback correction for one or more adjacent working cycles.

10. The engine gas injection control method based on actual scavenging conditions according to claim 5, characterized in that, The exhaust methane feedback is obtained by a methane concentration sensor or gaseous fuel concentration sensor installed in the exhaust branch pipe, exhaust main pipe or downstream sampling pipeline; the controller (5) establishes an association between the exhaust methane feedback and the preceding working cycle based on the exhaust channel volume, exhaust mass flow rate, engine speed, sampling pipeline transport time, sensor sampling delay and sensor response characteristics, and corrects the escape risk model, safety margin or gas injection parameters of the working cycle.

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