Hydrogen internal combustion engine near-zero emission control method and system based on oxygen medium regulation

Abstract

The present application relates to a kind of hydrogen internal combustion engine near zero emission control method and system based on oxygen medium regulation, and multiple operating parameters including intake oxygen concentration are collected by engine control unit, and engine load is determined according to speed and torque and the pre-calibrated nitrogen oxide emission mapping is inquired.According to the preset emission limit, the maximum intake oxygen concentration that meets the limit value is obtained as the target value by the mapping backtracking, and the measured value is tracked by adjusting the low-pressure exhaust gas recirculation valve to directly inhibit the generation of nitrogen oxides.At the same time, based on the target torque and the target intake oxygen concentration, the target available oxygen proxy amount is calculated, the target intake volume is backtracked and converted into the target intake manifold pressure, and finally the measured pressure is tracked by adjusting the turbocharger to track the target.Compared with the prior art, the present application meets the strict emission requirements while ensuring the engine torque output, achieving the coordinated optimization of emission and power.

Description

Technical Field

[0001] This invention relates to the field of internal combustion engine control technology, and in particular to a near-zero emission control method and system for hydrogen internal combustion engines based on oxygen medium regulation. Background Technology

[0002] Hydrogen internal combustion engines have attracted widespread attention as a zero-carbon emission power system. Hydrogen fuel is characterized by its rapid combustion speed, low ignition energy, and high flame propagation speed, enabling hydrogen internal combustion engines to maintain good combustion stability even under lean-burn conditions. However, due to the high combustion temperature during hydrogen combustion, large amounts of thermal NOx (nitrogen oxides) are easily generated under medium-to-high loads and transient conditions, posing a major challenge to emission control of hydrogen internal combustion engines.

[0003] Traditional NOx control technologies for internal combustion engines mainly include EGR (Exhaust Gas Recirculation) and SCR (Selective Catalytic Reduction) aftertreatment technologies. EGR technology suppresses NOx formation by diverting a portion of exhaust gas back to the intake system, thereby lowering combustion temperature. In diesel and gasoline engines, EGR control typically uses the EGR rate (the ratio of recirculated exhaust gas mass to total intake air mass) or the EGR valve opening as the control target. Chinese patent CN108180071A discloses an intake system suitable for a direct-injection hydrogen internal combustion engine, including an intake module and an exhaust gas recirculation module. The ECU collects internal combustion engine operating status information through sensors and dynamically adjusts the hydrogen internal combustion engine's exhaust gas recirculation volume and air intake volume to control the in-cylinder temperature and suppress NOx formation. Although this technical solution employs EGR control, it still uses EGR flow rate or EGR rate as the control variable, rather than directly using intake oxygen concentration as the closed-loop control object.

[0004] Chinese patent CN101424230A discloses a device for controlling emissions from a hydrogen internal combustion engine using thermal exhaust gas recirculation. The engine control unit obtains an initial mixture concentration value from a table based on parameters such as engine speed and load, and then uses oxygen sensor feedback to correct and obtain the final mixture concentration. When the mixture concentration is greater than 0.5, the exhaust gas recirculation valve quickly opens to its maximum position, while simultaneously reducing the throttle opening angle to decrease the amount of air entering the engine. Although this technical solution introduces oxygen sensor feedback, its control target is the mixture concentration (the mass ratio of hydrogen to air), rather than the intake oxygen concentration, and the control strategy is based on on / off control of the mixture concentration threshold, lacking fine-grained closed-loop regulation.

[0005] Chinese patent CN1871415A discloses a method for achieving low-emission controlled-temperature combustion in an engine using direct post-fuel injection. This method uses a closed-loop EGR control valve to regulate the EGR flow rate, maintaining the inlet oxygen concentration and boost pressure within the critical range for controlled-temperature, low-emission combustion. While this technical solution involves the coordination of inlet oxygen concentration and boost pressure control, its application is to diesel engines, and the control strategy focuses on coordinating fuel supply and boost pressure under transient conditions. It does not establish a reverse-checking mechanism for NOx emission constraints and inlet oxygen concentration for the lean-burn characteristics of hydrogen internal combustion engines.

[0006] Therefore, there is a need for a hydrogen internal combustion engine control method that uses intake oxygen concentration as the unified control object, can coordinate the distribution of EGR dilution and boost charge compensation, and has reversible control logic when combustion stability is limited, so as to achieve low NOx and usable torque output under all operating conditions without relying on the conversion capability of aftertreatment devices. Summary of the Invention

[0007] The purpose of this invention is to provide a near-zero emission control method and system for hydrogen internal combustion engines based on oxygen medium regulation. It achieves integrated control of NOx suppression, torque maintenance and stability assurance with oxygen medium as the core, so that the engine can still achieve low NOx emissions and usable torque output even without configuring or relying on NOx after-treatment conversion capabilities.

[0008] The objective of this invention can be achieved through the following technical solutions: The first aspect of this invention provides a near-zero emission control method for a hydrogen internal combustion engine based on oxygen medium regulation, comprising the following steps: S1: Collects engine speed, current torque, measured intake oxygen concentration, measured exhaust nitrogen oxide concentration, intake manifold pressure, intake manifold temperature, and hydrogen injection mass per cycle through the engine control unit; S2: Determine the current engine load based on the current torque and the engine speed, and query the pre-calibrated nitrogen oxide emission mapping based on the engine speed and the current engine load to obtain the mapping relationship between nitrogen oxide concentration and intake oxygen concentration under the current operating conditions; S3: Based on the preset nitrogen oxide emission limit and combined with the measured exhaust nitrogen oxide concentration, the maximum intake oxygen concentration corresponding to meeting the emission limit is determined as the target intake oxygen concentration by looking up the mapping relationship. S4: Calculate the deviation between the target intake oxygen concentration and the measured intake oxygen concentration; S5: If the deviation exceeds the first preset threshold, the low-pressure exhaust gas recirculation valve is adjusted to make the measured intake oxygen concentration track the target intake oxygen concentration in a closed loop. At the same time, the target hydrogen injection quantity is determined based on the target torque, and the target available oxygen surcharge is calculated based on the target hydrogen injection quantity, the hydrogen injection mass per cycle, and the target excess air coefficient. Then, the target unit cycle intake volume is deduced from the target intake oxygen concentration and the target available oxygen surcharge. In combination with the intake manifold temperature, the target unit cycle intake volume is converted into the target intake manifold pressure. The turbocharger is adjusted to make the measured intake manifold pressure track the target intake manifold pressure in a closed loop.

[0009] Furthermore, S5 is followed by S6: The cyclic variation coefficient is calculated to monitor combustion stability. If the cyclic variation coefficient exceeds a second preset threshold, the ignition advance angle is adjusted to improve combustion stability. If the corrected cyclic variation coefficient still exceeds the second preset threshold, the target intake oxygen concentration is rolled back, and the target intake manifold pressure is updated synchronously based on the rolled-back target intake oxygen concentration.

[0010] The term "reverting to target intake oxygen concentration" refers to adjusting the control target from the currently set, lower (highly diluted) oxygen concentration value upwards (i.e., reverting) to a higher value. In the control logic of this invention, a lower target oxygen concentration means a higher EGR rate to achieve stricter emission suppression, but this may lead to combustion instability. When this occurs, the system will revert to the emission control target by reducing the EGR rate, i.e., increasing the oxygen concentration in the intake air to prioritize combustion stability, and simultaneously adjust the boost pressure to adapt to the new intake conditions.

[0011] Furthermore, in S1, the measured intake oxygen concentration is obtained by an intake oxygen concentration sensor located in the downstream intake manifold after the fresh air and low-pressure EGR have been fully mixed.

[0012] Furthermore, in S2, the pre-calibrated nitrogen oxide emission mapping is obtained through engine bench testing, and its specific establishment method includes: Under steady-state conditions with multiple different engine speed and load combinations, by adjusting the exhaust gas recirculation rate and intake oxygen concentration, the corresponding nitrogen oxide emission concentration is measured and recorded, forming a three-dimensional data mapping table with engine speed, load, and intake oxygen concentration as inputs and nitrogen oxide concentration as output.

[0013] Furthermore, in S5, the specific method for calculating the target available oxygen substitute based on the target hydrogen injection quantity, the hydrogen injection mass per cycle, and the target excess air coefficient includes: Based on the stoichiometric combustion characteristics of hydrogen, the target hydrogen injection quantity, the hydrogen injection mass per cycle, and the target excess air coefficient are multiplied together, and then multiplied by the theoretical air mass coefficient required for complete combustion of hydrogen, thereby calculating the target available oxygen substitute quantity. The target available oxygen substitute quantity is used to characterize the total amount of oxygen required to meet the target torque.

[0014] Furthermore, in S5, the specific method for deriving the target unit cycle intake volume based on the target intake oxygen concentration and the target available oxygen surcharge includes: The target available oxygen surcharge is divided by the target intake oxygen concentration to obtain the target unit cycle intake air volume. This calculation ensures that while the intake oxygen concentration is diluted and reduced to suppress the generation of nitrogen oxides, the engine output torque is maintained by compensating for the total intake air volume.

[0015] Furthermore, in S5, the specific method for converting the target unit cycle intake volume into the target intake manifold pressure includes: Multiply the target unit cycle intake air volume, the mixture constant, and the intake manifold temperature to obtain the first intermediate quantity; Simultaneously, the engine's charge efficiency and total displacement are obtained, and the two are multiplied together to obtain the second intermediate quantity; Divide the first intermediate value by the second intermediate value, and the result is the target intake manifold pressure.

[0016] Furthermore, in S5, the specific method for adjusting the low-pressure exhaust gas recirculation valve to enable the measured intake oxygen concentration to track the target intake oxygen concentration in a closed loop includes: Using the measured intake oxygen concentration as a feedback signal and the target intake oxygen concentration as a setpoint, the opening control command of the low-pressure exhaust gas recirculation valve is calculated using a proportional-integral-derivative control algorithm. By adjusting the opening, the recirculated exhaust gas flow rate is changed, so that the measured intake oxygen concentration dynamically converges to the target intake oxygen concentration.

[0017] Furthermore, in S5, the specific methods by which the measured intake manifold pressure is made to track the target intake manifold pressure in a closed loop by adjusting the turbocharger include: Using the measured intake manifold pressure as a feedback signal and the target intake manifold pressure as a setpoint, the control command of the turbocharger variable section actuator is calculated using a proportional-integral-derivative control algorithm. By adjusting the turbine flow cross section to change the intake pressure, the measured intake manifold pressure dynamically converges to the target intake manifold pressure.

[0018] Furthermore, in S6, the specific methods for modifying the ignition advance angle to improve combustion stability include: Calculate the difference between the current cycle variation coefficient and the second preset threshold. Based on the magnitude and direction of the difference, dynamically adjust the reference ignition advance angle according to the pre-calibrated proportional integral correction rule to suppress combustion cycle fluctuations until the cycle variation coefficient is lower than the second preset threshold.

[0019] The second aspect of the present invention provides a near-zero emission control system for a hydrogen internal combustion engine based on oxygen medium regulation, comprising an engine control unit, a plurality of sensors for collecting engine operating parameters, and a plurality of actuators for executing control commands. The sensors include a speed sensor, a torque sensor, an intake oxygen concentration sensor, an exhaust nitrogen oxide concentration sensor, an intake manifold pressure sensor, an intake manifold temperature sensor, and a hydrogen mass flow meter, which are respectively signal-connected to the engine control unit. The actuator includes a low-pressure EGR valve, a variable geometry turbocharger, and an ignition system, which are respectively connected to the engine control unit. The engine control unit applies the control method described above.

[0020] Compared with the prior art, the present invention has the following beneficial effects: Overall, this invention transforms traditional indirect EGR rate control into direct closed-loop control of intake oxygen concentration. It tracks the target value derived from emission limits using measured intake oxygen concentration, resulting in a shorter and more direct control path. This effectively reduces deviations caused by factors such as changes in exhaust residual oxygen, significantly suppressing nitrogen oxide emission spikes across all operating conditions, especially transient ones, and improving emission control consistency. While reducing intake oxygen concentration, this invention calculates the target available oxygen surcharge and back-calculates the required intake volume, using the turbocharger to dynamically compensate for the total intake charge. This allows the engine to maintain target torque output while meeting strict emission constraints, resolving the conflict between emission reduction and power performance. This method primarily relies on in-cylinder process optimization to achieve near-zero emissions, significantly reducing or eliminating the need for complex aftertreatment systems, effectively reducing the cost, size, and thermal management burden of aftertreatment devices.

[0021] This invention uses the intake oxygen concentration xO2_in as a unified oxygen medium regulation quantity, transforming NOx control from "indirect control of EGR valve opening or EGR rate" to "direct control of oxygen medium intensity." Since thermal NOx is highly correlated with combustion temperature, and combustion temperature is directly affected by the intake oxygen concentration and dilution intensity, this invention uses NOx constraints to inversely determine xO2_in. tar Furthermore, by utilizing an intake oxygen concentration sensor to perform closed-loop tracking of xO2_in, the NOx control path is shortened, which can reduce deviations caused by changes in exhaust residual oxygen, EGR gas oxygen content, and EGR cooling efficiency, thereby suppressing NOx spikes under transient conditions and improving the consistency of NOx control across all operating conditions.

[0022] Regarding torque retention, traditional methods for reducing NOx often rely on delayed ignition or simply increasing the EGR rate, which can easily lead to a decrease in torque and a slower response. This invention, however, determines the xO2_in tar Then, the total charge is compensated by VGT boosting, and p is calculated in reverse according to the target torque. im tar This achieves a synergistic optimization effect where "oxygen is used to suppress NOx, and boosting is used to compensate for intake air volume." This synergistic strategy is particularly effective in scenarios such as acceleration and sudden load changes, because EGR changes and boosting responses can be coordinated and allocated under the same control framework, avoiding power loss or emission rebound caused by overuse of a single method.

[0023] Furthermore, the control objective of this invention is to reduce NOx through in-cylinder process control, eliminating the need for NOx aftertreatment devices such as SCRs, or making the control objective independent of their conversion capabilities. This reduces the volume, cost, thermal management, and maintenance burdens associated with aftertreatment, and avoids the limitations imposed by the aftertreatment efficiency window on the control strategy. Even in embodiments that still retain aftertreatment, this invention can serve as a front-end control to reduce the NOx load entering the aftertreatment system, helping to lower the aftertreatment temperature requirements and improve system lifespan and consistency. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a near-zero emission control method for hydrogen internal combustion engines based on oxygen medium regulation. Detailed Implementation

[0025] Overall, the purpose of this invention is to propose a control method for NOx suppression under all operating conditions of hydrogen internal combustion engines, which controls the intake oxygen concentration x O2_in As a unified oxygen medium control object, and with NOx emission constraints as the target, the target inlet oxygen concentration x required to meet the NOx limit is obtained through calibration mapping and reverse lookup. O2_in tar And through low-pressure EGR closed loop, x O2_in equals x O2_in tarThis reduces combustion temperature, thereby suppressing thermal NOx. Simultaneously, when a decrease in oxygen medium leads to a reduction in available oxygen per unit cycle and insufficient torque capacity, this invention compensates for the total intake charge through VGT (Vehicle Gas Tariff) boosting, enabling the engine to still achieve the target torque under NOx constraints. When high dilution causes increased cycle fluctuations, this invention determines combustion stability based on cycle fluctuations and corrects the ignition advance angle. If necessary, it performs oxygen medium target rollback and boosting target synchronous updates to avoid combustion instability or misfire. Thus, this invention achieves integrated control of NOx suppression, torque maintenance, and stability assurance, with oxygen medium as the core, enabling the engine to achieve low NOx emissions and available torque output even without or without relying on NOx aftertreatment conversion capabilities.

[0026] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Component models, material names, connection structures, control methods, algorithms, and other features not explicitly described in this technical solution are considered common technical features disclosed in the prior art.

[0027] Example 1 This embodiment provides a near-zero emission control method for hydrogen internal combustion engines based on oxygen medium regulation, including the following steps: S1: Collects engine speed, current torque, measured intake oxygen concentration, measured exhaust nitrogen oxide concentration, intake manifold pressure, intake manifold temperature, and hydrogen injection mass per cycle through the engine control unit; In S1, the measured intake oxygen concentration is obtained by an intake oxygen concentration sensor located in the downstream intake manifold after the fresh air and low-pressure EGR have been fully mixed.

[0028] S2: Determine the current engine load based on the current torque and the engine speed, and query the pre-calibrated nitrogen oxide emission mapping based on the engine speed and the current engine load to obtain the mapping relationship between nitrogen oxide concentration and intake oxygen concentration under the current operating conditions; In specific implementation, in S2, the pre-calibrated nitrogen oxide emission mapping is obtained through engine bench testing, and its specific establishment method includes: Under steady-state conditions with multiple different engine speed and load combinations, by adjusting the exhaust gas recirculation rate and intake oxygen concentration, the corresponding nitrogen oxide emission concentration is measured and recorded, forming a three-dimensional data mapping table with engine speed, load, and intake oxygen concentration as inputs and nitrogen oxide concentration as output.

[0029] S3: Based on the preset nitrogen oxide emission limit and combined with the measured exhaust nitrogen oxide concentration, the maximum intake oxygen concentration corresponding to meeting the emission limit is determined as the target intake oxygen concentration by looking up the mapping relationship. S4: Calculate the deviation between the target intake oxygen concentration and the measured intake oxygen concentration; S5: If the deviation exceeds the first preset threshold, the low-pressure exhaust gas recirculation valve is adjusted to make the measured intake oxygen concentration track the target intake oxygen concentration in a closed loop. At the same time, the target hydrogen injection quantity is determined based on the target torque, and the target available oxygen surcharge is calculated based on the target hydrogen injection quantity, the hydrogen injection mass per cycle, and the target excess air coefficient. Then, the target unit cycle intake volume is deduced from the target intake oxygen concentration and the target available oxygen surcharge. In combination with the intake manifold temperature, the target unit cycle intake volume is converted into the target intake manifold pressure. The turbocharger is adjusted to make the measured intake manifold pressure track the target intake manifold pressure in a closed loop.

[0030] In specific implementation, S5 includes the following methods for calculating the target available oxygen substitute quantity based on the target hydrogen injection quantity, the hydrogen injection mass per cycle, and the target excess air coefficient: Based on the stoichiometric combustion characteristics of hydrogen, the target hydrogen injection quantity, the hydrogen injection mass per cycle, and the target excess air coefficient are multiplied together, and then multiplied by the theoretical air mass coefficient required for complete combustion of hydrogen, thereby calculating the target available oxygen substitute quantity. The target available oxygen substitute quantity is used to characterize the total amount of oxygen required to meet the target torque.

[0031] In specific implementation, S5 includes the following methods for deriving the target unit cycle intake volume based on the target intake oxygen concentration and the target available oxygen surcharge: The target available oxygen surcharge is divided by the target intake oxygen concentration to obtain the target unit cycle intake air volume. This calculation ensures that while the intake oxygen concentration is diluted and reduced to suppress the generation of nitrogen oxides, the engine output torque is maintained by compensating for the total intake air volume.

[0032] In specific implementation, S5 includes the following methods for converting the target unit cycle intake volume into the target intake manifold pressure: Multiply the target unit cycle intake air volume, the mixture constant, and the intake manifold temperature to obtain the first intermediate quantity; Simultaneously, the engine's charge efficiency and total displacement are obtained, and the two are multiplied together to obtain the second intermediate quantity; Divide the first intermediate value by the second intermediate value, and the result is the target intake manifold pressure.

[0033] In specific implementation, in S5, the specific methods for adjusting the low-pressure exhaust gas recirculation valve to make the measured intake oxygen concentration track the target intake oxygen concentration in a closed loop include: Using the measured intake oxygen concentration as a feedback signal and the target intake oxygen concentration as a setpoint, the opening control command of the low-pressure exhaust gas recirculation valve is calculated using a proportional-integral-derivative control algorithm. By adjusting the opening, the recirculated exhaust gas flow rate is changed, so that the measured intake oxygen concentration dynamically converges to the target intake oxygen concentration.

[0034] In specific implementation, S5 includes the following methods for adjusting the turbocharger to make the measured intake manifold pressure track the target intake manifold pressure in a closed loop: Using the measured intake manifold pressure as a feedback signal and the target intake manifold pressure as a setpoint, the control command of the turbocharger variable section actuator is calculated using a proportional-integral-derivative control algorithm. By adjusting the turbine flow cross section to change the intake pressure, the measured intake manifold pressure dynamically converges to the target intake manifold pressure.

[0035] The target torque is calculated by the vehicle controller based on the driver's pedal signal and the vehicle's operating status, and then sent to the engine control unit.

[0036] In specific implementation, in S5, the target hydrogen injection mass per cycle is determined based on the target torque by querying a pre-calibrated mapping table indexed by the target torque and engine speed. The specific method for calculating the target available oxygen surcharge is as follows: based on the stoichiometric combustion characteristics of hydrogen, the target hydrogen injection mass per cycle, the target excess air coefficient, and the theoretical air mass coefficient required for complete hydrogen combustion (e.g., a value of 8 in this embodiment) are multiplied together, i.e., calculated using the following formula: , where Ω O2 tar For the target available oxygen substitute quantity, m H2 To achieve the target hydrogen injection mass per cycle, λ tar The target excess air coefficient. This target can be characterized by the oxygen surcharge, which represents the total amount of oxygen required to meet the target torque.

[0037] In specific implementation, in S5, the step of adjusting the turbocharger to make the measured intake manifold pressure track the target intake manifold pressure in a closed loop also includes boundary processing: real-time monitoring of the position of the turbocharger actuator; if the actuator has reached its maximum operating position (e.g., VGT blades fully open or fully closed) and maintained for more than a preset time, but the deviation between the measured intake manifold pressure and the target intake manifold pressure still exceeds the allowable range, then it is determined that the boost capacity is insufficient. At this time, the control strategy triggers the rollback logic: gradually increasing the value of the target intake oxygen concentration (i.e., reducing the dilution intensity), and using the rolled-back target intake oxygen concentration as input, recalculating the target intake manifold pressure, thereby finding an achievable operating point that balances emissions and torque within the boost capacity limit.

[0038] S6: Calculate the cyclic variation coefficient to monitor combustion stability. If the cyclic variation coefficient exceeds the second preset threshold, adjust the ignition advance angle to improve combustion stability. If the corrected cyclic variation coefficient still exceeds the second preset threshold, the target intake oxygen concentration is rolled back, and the target intake manifold pressure is updated synchronously based on the rolled-back target intake oxygen concentration.

[0039] In specific implementation, S6 includes the following methods for modifying the ignition advance angle to improve combustion stability: Calculate the difference between the current cycle variation coefficient and the second preset threshold. Based on the magnitude and direction of the difference, dynamically adjust the reference ignition advance angle according to the pre-calibrated proportional integral correction rule to suppress combustion cycle fluctuations until the cycle variation coefficient is lower than the second preset threshold.

[0040] In specific implementation, in S6, the rollback of the target intake oxygen concentration follows these rules: a fixed absolute concentration value (e.g., 0.2% volume fraction) or a fixed relative proportion (e.g., 2% of the current value) is used as a rollback step. When the rollback condition is met, the current target intake oxygen concentration value is subtracted by a rollback step to obtain a new, higher target value. The phrase "synchronously updating the target intake manifold pressure based on the rolled-back target intake oxygen concentration" means substituting the new target intake oxygen concentration obtained after the rollback into the "counter-calculation of target unit cycle intake volume based on target intake oxygen concentration and target available oxygen surcharge" and subsequent conversion formulas described in claim S5, recalculating an updated, typically higher, target intake manifold pressure, and continuing closed-loop boost control with this new target.

[0041] This embodiment further explains the core control logic of the present invention based on formulas: (1) Definition of variables and symbols The following variables and symbols are used in this invention.

[0042] n is the engine speed; T act The actual torque is the current torque; Load is the current load; x O2_in The intake oxygen concentration is measured by an intake oxygen concentration sensor, which is located downstream of the intake manifold after the fresh air has been thoroughly mixed with the low-pressure EGR; x O2_in tar The target intake oxygen concentration; NOx_act is the current measured NOx emission concentration, obtained from the exhaust NOx sensor; NOx_lim is the NOx limit or control upper limit; p im T is the intake manifold pressure. im Intake manifold temperature; p im tar Target intake manifold pressure; Vd η represents the total engine displacement. v For charge efficiency; R mix m is the gas constant of the mixed gas; H2 The mass of hydrogen injected per cycle; λ tar The target excess air coefficient; θ base The reference ignition advance angle; m in_cycle Total intake volume per unit cycle; Ω O2 The available oxygen substitute quantity; m in_cycle tar Target total intake volume per unit cycle; Ω O2 tar The target available oxygen substitute quantity.

[0043] (2) Control methods The control method of this invention is as follows: Figure 1 As shown: S1: Signal Acquisition. The ECU acquires n and T signals. act p im T im x O2_in m H2 NOx concentration; S2: Based on the current torque T act The load is obtained by looking up the table, and η is read. v , λ tar And the mapping f(n, Load, x) between NOx and oxygen concentration x; S3: Obtain x based on the emission limit NOx_lim O2_in tar ,in ; S4: If x O2_in tar equals x O2_in If yes, then execute S1; otherwise, execute S5. S5: Adjust the EGR valve to make x O2_in tar equals x O2_in To ensure torque requirements are met even after reducing intake oxygen concentration, this invention introduces calculations for "available oxygen displacement" and "target intake volume," using a turbocharger to compensate for power performance. The total intake mass per unit cycle is calculated using the following formula: Define the available oxygen proxy quantity , ,therefore , And read COV (cyclic variation coefficient); S6: If COV is less than the threshold, it means that the current combustion is stable. Repeat S1-S6 until the engine finishes running; if COV is greater than the threshold, adjust the ignition advance angle.

[0044] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A near-zero emission control method for a hydrogen internal combustion engine based on oxygen-medium regulation, characterized in that, Includes the following steps: S1: Collects engine speed, current torque, measured intake oxygen concentration, measured exhaust nitrogen oxide concentration, intake manifold pressure, intake manifold temperature, and hydrogen injection mass per cycle through the engine control unit; S2: Determine the current engine load based on the current torque and the engine speed, and query the pre-calibrated nitrogen oxide emission mapping based on the engine speed and the current engine load to obtain the mapping relationship between nitrogen oxide concentration and intake oxygen concentration under the current operating conditions; S3: Based on the preset nitrogen oxide emission limit and combined with the measured exhaust nitrogen oxide concentration, the maximum intake oxygen concentration corresponding to meeting the emission limit is determined as the target intake oxygen concentration by looking up the mapping relationship. S4: Calculate the deviation between the target intake oxygen concentration and the measured intake oxygen concentration; S5: If the deviation exceeds the first preset threshold, adjust the low-pressure exhaust gas recirculation valve to make the measured intake oxygen concentration track the target intake oxygen concentration. At the same time, determine the target hydrogen injection amount based on the target torque, and calculate the target available oxygen surcharge based on the target hydrogen injection amount, the hydrogen injection mass per cycle, and the target excess air coefficient. Then, back-calculate the target unit cycle intake volume based on the target intake oxygen concentration and the target available oxygen surcharge. Combined with the intake manifold temperature, convert the target unit cycle intake volume into the target intake manifold pressure. Adjust the turbocharger to make the measured intake manifold pressure track the target intake manifold pressure.

2. The near-zero emission control method for a hydrogen internal combustion engine based on oxygen medium regulation according to claim 1, characterized in that, S5 is followed by S6: The cyclic variation coefficient is calculated to monitor combustion stability. If the cyclic variation coefficient exceeds a second preset threshold, the ignition advance angle is adjusted to improve combustion stability. If the corrected cyclic variation coefficient still exceeds the second preset threshold, the target intake oxygen concentration is rolled back, and the target intake manifold pressure is updated synchronously based on the rolled-back target intake oxygen concentration.

3. The near-zero emission control method for a hydrogen internal combustion engine based on oxygen medium regulation according to claim 1, characterized in that, In S1, the measured intake oxygen concentration is obtained by an intake oxygen concentration sensor located in the downstream intake manifold after the fresh air and low-pressure EGR have been fully mixed.

4. The near-zero emission control method for a hydrogen internal combustion engine based on oxygen medium regulation according to claim 1, characterized in that, In S2, the pre-calibrated nitrogen oxide emission map is obtained through engine bench testing, and its specific establishment method includes: Under steady-state conditions with multiple different engine speed and load combinations, by adjusting the exhaust gas recirculation rate and intake oxygen concentration, the corresponding nitrogen oxide emission concentration is measured and recorded, forming a three-dimensional data mapping table with engine speed, load, and intake oxygen concentration as inputs and nitrogen oxide concentration as output.

5. The near-zero emission control method for a hydrogen internal combustion engine based on oxygen medium regulation according to claim 1, characterized in that, In S5, the specific methods for calculating the target available oxygen substitute quantity based on the target hydrogen injection quantity, the hydrogen injection mass per cycle, and the target excess air coefficient include: Based on the stoichiometric combustion characteristics of hydrogen, the target hydrogen injection quantity, the hydrogen injection mass per cycle, and the target excess air coefficient are multiplied together, and then multiplied by the theoretical air mass coefficient required for complete combustion of hydrogen, thereby calculating the target available oxygen substitute quantity. The target available oxygen substitute quantity is used to characterize the total amount of oxygen required to meet the target torque.

6. The near-zero emission control method for a hydrogen internal combustion engine based on oxygen medium regulation according to claim 1, characterized in that, In S5, the specific method for deriving the target unit cycle intake volume based on the target intake oxygen concentration and the target available oxygen surcharge includes: The target available oxygen supply is divided by the target intake oxygen concentration, and the resulting quotient is the target unit cycle intake volume.

7. The near-zero emission control method for a hydrogen internal combustion engine based on oxygen medium regulation according to claim 1, characterized in that, In S5, the specific methods for converting the target unit cycle intake volume into the target intake manifold pressure include: Multiply the target unit cycle intake air volume, the mixture constant, and the intake manifold temperature to obtain the first intermediate quantity; Simultaneously, the engine's charge efficiency and total displacement are obtained, and the two are multiplied together to obtain the second intermediate quantity; Divide the first intermediate value by the second intermediate value, and the result is the target intake manifold pressure.

8. The near-zero emission control method for a hydrogen internal combustion engine based on oxygen medium regulation according to claim 1, characterized in that, In S5, the specific methods for adjusting the low-pressure exhaust gas recirculation valve to make the measured intake air oxygen concentration track the target intake air oxygen concentration include: Using the measured intake oxygen concentration as a feedback signal and the target intake oxygen concentration as a setpoint, the opening control command of the low-pressure exhaust gas recirculation valve is calculated using a proportional-integral-derivative control algorithm. By adjusting the opening, the recirculated exhaust gas flow rate is changed, so that the measured intake oxygen concentration dynamically converges to the target intake oxygen concentration.

9. The near-zero emission control method for a hydrogen internal combustion engine based on oxygen medium regulation according to claim 1, characterized in that, In S5, the specific methods for adjusting the turbocharger to make the measured intake manifold pressure track the target intake manifold pressure include: Using the measured intake manifold pressure as a feedback signal and the target intake manifold pressure as a setpoint, the control command of the turbocharger variable section actuator is calculated using a proportional-integral-derivative control algorithm. By adjusting the turbine flow cross section to change the intake pressure, the measured intake manifold pressure dynamically converges to the target intake manifold pressure.

10. A near-zero emission control system for a hydrogen internal combustion engine based on oxygen medium regulation, comprising an engine control unit, several sensors for acquiring engine operating parameters, and several actuators for executing control commands, characterized in that, The sensors include a speed sensor, a torque sensor, an intake oxygen concentration sensor, an exhaust nitrogen oxide concentration sensor, an intake manifold pressure sensor, an intake manifold temperature sensor, and a hydrogen mass flow meter, which are respectively connected to the engine control unit. The actuator includes a low-pressure EGR valve, a variable geometry turbocharger, and an ignition system, which are respectively connected to the engine control unit. The engine control unit is used to execute the control method as described in claim 1.

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