Hydrogen ammonia emission generation prediction system and method based on in-cylinder combustion process and chemical reaction mechanism

Abstract

The invention discloses an in-cylinder combustion process and chemical reaction mechanism-based hydrogen ammonia emission generation prediction system and method, and relates to the technical field of hydrogen internal combustion engine tail gas emission control, and the system comprises an input variable acquisition module, a combustion simulation module, a chemical reaction simulation module, an emission generation prediction module and an output interface module; according to the method, a mechanism-driven multi-physics field coupling prediction system is constructed, the simplified assumption limitation of a traditional empirical model is broken through, high-precision dynamic analysis of the emission characteristics of the hydrogen-ammonia engine is achieved, in combustion process simulation, in-cylinder turbulence mixing and flame propagation details are accurately described by using a CFD model, and in-cylinder combustion simulation is achieved. The chemical reaction module can significantly improve the prediction credibility of unburned fuel residues and pollutant generation through sensitivity analysis and mechanism optimization, in addition, through real-time coupling sensor data and simulation calculation, the abnormal emission trend can be pre-judged in advance, and a feedforward control basis is provided for the ammonia injection amount, the EGR rate and the ignition angle.

Description

Technical Field

[0001] This invention relates to the field of exhaust emission control technology for hydrogen internal combustion engines, and in particular to a hydrogen ammonia emission generation prediction system and method based on in-cylinder combustion process and chemical reaction mechanism. Background Technology

[0002] A hydrogen internal combustion engine (H2ICE) is a type of internal combustion engine that uses hydrogen (H2) as its primary fuel. It generates heat energy by burning a mixture of hydrogen and air, converting that heat energy into mechanical energy. While its core working principle is similar to that of traditional gasoline or diesel internal combustion engines, significant differences exist in fuel characteristics, combustion processes, and emissions. The hydrogen internal combustion engine represents a crucial technological pathway for hydrogen energy utilization, particularly suitable for cost-sensitive applications requiring high power output. Its core technology lies in achieving efficient and clean energy conversion through optimized combustion control (such as hydrogen / ammonia co-combustion and EGR strategies) and emissions prediction.

[0003] The in-cylinder combustion process of a hydrogen internal combustion engine is the process of mixing and igniting hydrogen and air in the combustion chamber. It involves ultra-high-speed flame propagation and an extremely short ignition delay time, generating water vapor and releasing a large amount of heat energy, which drives the piston to move and achieve energy conversion. By conducting in-depth research on the in-cylinder combustion process and chemical reaction mechanism of hydrogen internal combustion engines and optimizing combustion control strategies, hydrogen internal combustion engines are expected to play an important role in the transportation and energy sectors, helping to achieve the goal of low-carbon and environmental protection.

[0004] Currently, hydrogen internal combustion engines have attracted much attention due to their clean combustion. However, during high-temperature combustion, they may still produce a certain amount of unburned ammonia and hydrogen residues. Existing emission control methods are mainly based on empirical models or simplified one-dimensional thermodynamic models, which cannot accurately reflect the actual chemical reaction mechanism in the cylinder and have insufficient prediction accuracy, thus limiting their application in control strategy design. Therefore, this invention proposes a hydrogen and ammonia emission generation prediction system and method based on the in-cylinder combustion process and chemical reaction mechanism to solve the problems existing in the prior art. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to propose a hydrogen and ammonia emission generation prediction system and method based on in-cylinder combustion process and chemical reaction mechanism. By integrating CFD and CHEMKIN simulation, a prediction system is constructed with in-cylinder pressure, temperature, and air-fuel ratio as the main input variables. The system accurately outputs the generation rate and emission trend of hydrogen and ammonia at different combustion stages, so as to accurately reflect the actual in-cylinder chemical reaction mechanism.

[0006] To achieve the objectives of this invention, the invention is implemented through the following technical solution: a hydrogen-ammonia emission generation prediction system based on in-cylinder combustion process and chemical reaction mechanism, comprising an input variable acquisition module, a combustion simulation module, a chemical reaction simulation module, an emission generation prediction module, and an output interface module, characterized in that:

[0007] The input variable acquisition module collects real-time data on cylinder pressure, temperature, air-fuel ratio, and ignition timing.

[0008] The combustion simulation module is based on CFD to construct a dynamic model of in-cylinder mixture formation and turbulent combustion.

[0009] The chemical reaction simulation module calls a multi-step chemical reaction kinetic mechanism model to simulate the reaction pathway and intermediate product formation process of hydrogen and ammonia under high temperature conditions.

[0010] The emissions generation prediction module outputs the real-time generation rate and cumulative emissions of hydrogen and ammonia based on combustion simulation and chemical reaction simulation results.

[0011] The output interface module transmits the prediction results to the engine control system to optimize the feedforward control strategy.

[0012] Further improvements are made in that the input variable acquisition module includes an in-cylinder pressure detection unit, an in-cylinder temperature detection unit, and an air-fuel ratio detection unit for real-time acquisition of combustion chamber data, as well as an ignition signal detection unit for synchronously recording ignition timing parameters.

[0013] Further improvements are made in that the combustion simulation module constructs a three-dimensional turbulent combustion field model based on CFD simulation, covering the mixed gas flow, turbulent diffusion and flame propagation process, and adopts adaptive mesh generation technology to dynamically adjust the mesh resolution of the combustion front region.

[0014] A further improvement is that the chemical reaction simulation module includes a chemical reaction mechanism database and an equivalent simplified chemical reaction model. The chemical reaction mechanism database covers elementary reaction pathways and intermediate species generation mechanisms, and the equivalent simplified chemical reaction model can replace the detailed model when computational resources are limited.

[0015] A further improvement is that the operation strategy of the emission generation prediction module is to calculate the generation rate of unburned hydrogen, unburned ammonia and nitrogen oxides during the combustion process step by step, and combine it with the opening sequence of the exhaust valve to output the cumulative emission of hydrogen and ammonia in a single cycle.

[0016] A further improvement is that the output interface module converts the predicted hydrogen / ammonia emission data into a feedforward control signal and transmits it to the engine electronic control unit or aftertreatment controller.

[0017] A further improvement lies in the coupling method between the combustion simulation module and the chemical reaction simulation module:

[0018] The local temperature, pressure, and concentration fields calculated by CFD are input into the chemical reaction solver in real time;

[0019] Based on the chemical timescale segmentation algorithm, decoupled iterative calculations of turbulent combustion and chemical reaction kinetics are realized.

[0020] The prediction method for hydrogen ammonia emission generation prediction system based on in-cylinder combustion process and chemical reaction mechanism includes the following steps:

[0021] Step 1: Input variable acquisition module collects the in-cylinder pressure, temperature, air-fuel ratio and ignition timing of the hydrogen internal combustion engine;

[0022] Step 2: The combustion simulation module simulates the in-cylinder turbulent combustion process based on a CFD model;

[0023] Step 3: The chemical reaction simulation module calls the multi-step chemical reaction kinetic model to calculate the hydrogen / ammonia generation pathway;

[0024] Step 4: The emission generation prediction module outputs prediction results, including hydrogen / ammonia generation rate and cumulative amount, and transmits the prediction results to the engine control system using the output interface module.

[0025] The beneficial effects of this invention are as follows: By constructing a mechanism-driven multiphysics coupling prediction system, this invention breaks through the simplification assumptions of traditional empirical models, achieving high-precision dynamic analysis of the emission characteristics of hydrogen-ammonia engines. In the combustion process simulation, the CFD model accurately depicts the details of in-cylinder turbulent mixing and flame propagation. The chemical reaction module, through sensitivity analysis and mechanism optimization, dynamically tracks the key pathways of NH3 cracking, H2 oxidation, and NOx generation, significantly improving the prediction reliability of unburned fuel residue and pollutant generation. In addition, by coupling sensor data and simulation calculations in real time, abnormal emission trends (such as NOx surges caused by local hydrogen enrichment) can be predicted in advance, providing feedforward control basis for ammonia injection quantity, EGR rate, and ignition angle, avoiding the lag of traditional feedback control, and providing reliable technical support for the clean and efficient operation of hydrogen-ammonia engines under all operating conditions. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the modular design structure of the hydrogen ammonia emission generation prediction system based on the in-cylinder combustion process and chemical reaction mechanism of the present invention.

[0027] Figure 2 This is a flowchart of the prediction method for the hydrogen ammonia emission generation prediction system based on the in-cylinder combustion process and chemical reaction mechanism of the present invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Hydrogen / ammonia emission generation prediction based on in-cylinder combustion process and chemical reaction mechanism refers to the development of ammonia combustion chemical reaction kinetic mechanism by studying the evolution of the composition and concentration of intermediate products in ammonia combustion process over time, in order to predict and control the emission generation of ammonia-hydrogen engines.

[0030] The combustion process of ammonia: When ammonia (NH3) burns in an engine, it reacts with oxygen to produce water (H3O) and nitrogen (N2), releasing energy in the process. However, due to the slow combustion rate and high ignition temperature of ammonia, direct combustion of ammonia is difficult.

[0031] The promoting effect of hydrogen: Adding hydrogen to ammonia can significantly improve the combustion rate and ignition performance of the mixture, promote the complete combustion of ammonia, and reduce the emission of unburned ammonia.

[0032] Predicting hydrogen / ammonia emission generation based on in-cylinder combustion processes and chemical reaction mechanisms can provide strong support for the efficient and clean operation of ammonia-hydrogen fuel engines, and promote the application of clean energy in the transportation sector.

[0033] Example 1

[0034] according to Figure 1 As shown, this embodiment provides a hydrogen ammonia emission generation prediction system based on in-cylinder combustion process and chemical reaction mechanism. The system consists of an input variable acquisition module for collecting in-cylinder data of a hydrogen internal combustion engine, a combustion simulation module for simulating the combustion process, a chemical reaction simulation module for simulating the chemical reaction process, an emission generation prediction module for generating hydrogen ammonia emission prediction results, and an output interface module for outputting the prediction results. Wherein:

[0035] The input variable acquisition module is used to collect data in the cylinder of the hydrogen internal combustion engine in real time, including pressure, temperature, air-fuel ratio and ignition timing. This module provides reliable input for subsequent simulation and prediction by accurately capturing the physicochemical state of combustion in the cylinder, and is the core guarantee for improving the emission control accuracy of hydrogen ammonia engine.

[0036] The combustion simulation module constructs a dynamic model of in-cylinder mixture formation and turbulent combustion based on CFD (Computational Fluid Dynamics). The turbulence model adopts the Realizable k-ε model under the RANS (Reynolds Average) framework, combined with the flame progress variable (FPV) method to describe turbulent combustion, thereby achieving an accurate description of the complex flow and combustion process in the engine combustion chamber. By adopting the Realizable k-ε turbulence model and the FPV method, the combustion simulation module can accurately describe the dynamic process of in-cylinder mixture formation and turbulent combustion in the engine, providing strong support for optimizing engine performance and emission control.

[0037] The chemical reaction simulation module calls upon a multi-step chemical reaction kinetic mechanism model to simulate the reaction pathway and intermediate product formation process of hydrogen and ammonia under high-temperature conditions. The module introduces a sensitivity analysis algorithm to screen key reaction steps that significantly affect emission generation and experimentally calibrates the kinetic parameters of key reaction steps, limiting the overall prediction error to within ±5% and reducing systematic errors. By introducing a sensitivity analysis algorithm and experimentally calibrating the kinetic parameters of key reaction steps, the chemical reaction simulation module can accurately simulate the reaction process of hydrogen and ammonia under high-temperature conditions, improve the accuracy of emission prediction, and provide strong support for optimizing engine performance and emission control.

[0038] The emission generation prediction module calculates and outputs the generation rate and cumulative emission of hydrogen and ammonia in real time based on the results of combustion simulation and chemical reaction simulation, providing accurate data support for engine emission control. Through accurate simulation of combustion and chemical reaction processes, it calculates and outputs the generation rate and cumulative emission of hydrogen and ammonia in real time, providing important data support for engine emission control and performance optimization.

[0039] The output interface module transmits the prediction results to the engine control system to optimize the feedforward control strategy. By adopting a standardized communication protocol and interface design, the output interface module efficiently and safely transmits the prediction results of the emission generation prediction system to the engine control system, optimizes the feedforward control strategy, and achieves precise control of engine emissions.

[0040] In this embodiment, the input variable acquisition module includes an in-cylinder pressure detection unit, an in-cylinder temperature detection unit, and an air-fuel ratio detection unit for real-time acquisition of combustion chamber data, as well as an ignition signal detection unit for synchronously recording ignition timing parameters, wherein:

[0041] The cylinder pressure detection unit uses a high-frequency piezoelectric cylinder pressure sensor (such as Kistler 6125C) with a sampling frequency ≥100kHz. It is installed next to the spark plug at the top of the combustion chamber to capture the pressure fluctuation curve in real time.

[0042] The in-cylinder temperature detection unit uses a thermocouple temperature sensor with a fast response thin-film thermocouple (response time <1ms), which is arranged on the combustion chamber wall and near the combustion front area to monitor the local temperature gradient.

[0043] The air-fuel ratio detection unit integrates a wideband oxygen sensor (such as Bosch LSU 4.9) and, in conjunction with intake flow meter data, calculates the air-fuel ratio (λ) in real time.

[0044] The ignition signal acquisition unit includes a crankshaft position sensor and a magnetic ring transformer. The crankshaft position sensor is a magnetoelectric sensor with a resolution of ≤0.1° crankshaft angle, providing crankshaft speed and phase reference. The magnetic ring transformer uses a non-invasive method to capture the primary current signal of the ignition coil, and combines it with the crankshaft signal to analyze the ignition advance angle (accuracy ±0.5°). The two data are synchronously triggered by FPGA hardware to ensure that the pressure, temperature, air-fuel ratio and ignition signal are time-aligned, eliminating sensor signal delay differences.

[0045] In this embodiment, the combustion simulation module constructs a three-dimensional turbulent combustion field model based on CFD simulation, covering the process of gas mixture flow, turbulent diffusion and flame propagation. It also adopts adaptive mesh generation technology to dynamically adjust the mesh resolution of the combustion front region, which can accurately simulate the process of gas mixture flow, turbulent diffusion and flame propagation, thereby improving simulation accuracy and computational efficiency.

[0046] In this embodiment, the chemical reaction simulation module includes a chemical reaction mechanism database and an equivalent simplified chemical reaction model. The chemical reaction mechanism database covers elementary reaction pathways and intermediate species generation mechanisms. By integrating detailed ammonia-hydrogen-air reaction mechanisms (such as the Glarborg mechanism, which contains 53 species and 325 elementary reactions), the database calculates high-temperature reaction kinetic pathways in real time through a CHEMKIN format interface. The equivalent simplified chemical reaction model replaces the detailed model when computational resources are limited, maintaining the accuracy of key reaction pathways. By integrating detailed chemical reaction mechanisms and constructing equivalent simplified models, the chemical reaction simulation module can calculate high-temperature reaction kinetic pathways in real time, providing accurate data support for emission generation prediction. When computational resources are limited, the simplified model can improve computational efficiency while maintaining the accuracy of key reaction pathways, meeting the needs of practical applications.

[0047] In this embodiment, the operation strategy of the emission generation prediction module is as follows: the generation rates of unburned hydrogen (H2), unburned ammonia (NH3), and nitrogen oxides (NOx) during combustion are calculated step by step over time, and combined with the opening sequence of the exhaust valve, the cumulative emission of hydrogen and ammonia in a single cycle is output, providing important data support for engine emission control and performance optimization, and realizing accurate prediction of engine emissions.

[0048] In this embodiment, the output interface module converts the predicted hydrogen / ammonia emission data into a feedforward control signal and transmits it to the engine electronic control unit (ECU) or aftertreatment controller to control the ammonia injection controller, exhaust gas recirculation (EGR) controller, and ignition control system to dynamically adjust. The control strategy is as follows:

[0049] Ammonia injection control: If unburned NH3 is predicted to exceed the threshold (e.g., 50 ppm), dynamically reduce the injection pulse width of the next cycle (step size 0.1 ms);

[0050] EGR rate adjustment: Based on the NOx prediction value, the EGR valve opening is controlled by PID control, with a target NOx ≤ 100ppm;

[0051] Ignition angle correction: When a risk of pre-ignition is detected (pressure rise rate > 10 MPa / ms), delay the ignition angle by 2° to 5°.

[0052] In this embodiment, the coupling method between the combustion simulation module and the chemical reaction simulation module is as follows:

[0053] The local temperature, pressure, and concentration fields calculated by CFD are input into the chemical reaction solver in real time;

[0054] Based on the chemical timescale segmentation algorithm, decoupled iterative calculations of turbulent combustion and chemical reaction kinetics are realized.

[0055] Example 2

[0056] See Figure 2 This embodiment provides a prediction method for a hydrogen ammonia emission generation prediction system based on in-cylinder combustion process and chemical reaction mechanism, including the following steps:

[0057] Step 1

[0058] The in-cylinder pressure, temperature, air-fuel ratio, and ignition timing of the hydrogen internal combustion engine are collected through the input variable acquisition module. The collected data undergoes the following preprocessing:

[0059] Cylinder pressure signal: Low-pass filtering (cutoff frequency 20kHz) to remove high-frequency noise;

[0060] Temperature signal: processed using a moving average filter (window width 10ms);

[0061] Air-fuel ratio calculation: Based on the oxygen sensor voltage-λ characteristic curve (pre-calibrated), combined with the real-time output λ value of intake air flow (accuracy ±0.05);

[0062] Step Two

[0063] The combustion simulation module simulates the in-cylinder turbulent combustion process based on a CFD model. The simulation process is as follows:

[0064] Initialization conditions: Import the initial pressure, temperature, air-fuel ratio and ignition angle of the current cycle, and set the transient solution time step (1μs);

[0065] Parallel computing: The combustion chamber mesh is divided into multiple subdomains and distributed to multiple GPU nodes to solve the flow-combustion coupling field simultaneously;

[0066] Step 3

[0067] The chemical reaction simulation module calls a multi-step chemical reaction kinetics model to calculate the hydrogen / ammonia formation pathway. The chemical reaction kinetics calculation is as follows:

[0068] Field variable transfer: Extract parameters such as T, P, [H2], and [NH3] from each grid cell from the CFD results and input them into the chemical reaction solver;

[0069] Chemical timescale segmentation: If the characteristic time of a chemical reaction (τ_chem) is much smaller than the flow time (τ_flow), the Operator Splitting method is used for decoupling and solution.

[0070] Step 4

[0071] The emission generation prediction module outputs prediction results including hydrogen / ammonia generation rate and cumulative amount, and uses the output interface module to transmit the prediction results to the engine control system. At the same time, it visualizes the results, generates cloud maps of cylinder temperature and unburned NH3 concentration distribution, and marks high emission risk areas.

[0072] The prediction results are converted into feedforward control signals to optimize ammonia injection quantity, EGR rate or ignition timing in real time, and key reaction parameters are calibrated through bench tests to keep the prediction error under all operating conditions within ±5%.

[0073] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A hydrogen and ammonia emission generation prediction system based on in-cylinder combustion process and chemical reaction mechanism, comprising an input variable acquisition module, a combustion simulation module, a chemical reaction simulation module, an emission generation prediction module, and an output interface module, characterized in that: The input variable acquisition module collects real-time data on cylinder pressure, temperature, air-fuel ratio, and ignition timing. The combustion simulation module is based on CFD to construct a dynamic model of in-cylinder mixture formation and turbulent combustion. The chemical reaction simulation module calls a multi-step chemical reaction kinetic mechanism model to simulate the reaction pathway and intermediate product formation process of hydrogen and ammonia under high temperature conditions. The emissions generation prediction module outputs the real-time generation rate and cumulative emissions of hydrogen and ammonia based on combustion simulation and chemical reaction simulation results. The output interface module transmits the prediction results to the engine control system to optimize the feedforward control strategy.

2. The hydrogen and ammonia emission generation prediction system based on in-cylinder combustion process and chemical reaction mechanism according to claim 1, characterized in that: The input variable acquisition module includes an in-cylinder pressure detection unit, an in-cylinder temperature detection unit, and an air-fuel ratio detection unit that acquire combustion chamber data in real time, as well as an ignition signal detection unit that synchronously records ignition timing parameters.

3. The hydrogen and ammonia emission generation prediction system based on in-cylinder combustion process and chemical reaction mechanism according to claim 1, characterized in that: The combustion simulation module constructs a three-dimensional turbulent combustion field model based on CFD simulation, covering the mixed gas flow, turbulent diffusion and flame propagation process, and adopts adaptive mesh generation technology to dynamically adjust the mesh resolution of the combustion front region.

4. The hydrogen and ammonia emission generation prediction system based on in-cylinder combustion process and chemical reaction mechanism according to claim 1, characterized in that: The chemical reaction simulation module includes a chemical reaction mechanism database and an equivalent simplified chemical reaction model. The chemical reaction mechanism database covers elementary reaction pathways and intermediate species generation mechanisms. The equivalent simplified chemical reaction model can replace the detailed model when computational resources are limited.

5. The hydrogen and ammonia emission generation prediction system based on in-cylinder combustion process and chemical reaction mechanism according to claim 1, characterized in that: The operation strategy of the emission generation prediction module is as follows: calculate the generation rate of unburned hydrogen, unburned ammonia and nitrogen oxides during the combustion process step by step, and output the cumulative emission of hydrogen and ammonia in a single cycle in combination with the opening sequence of the exhaust valve.

6. The hydrogen and ammonia emission generation prediction system based on in-cylinder combustion process and chemical reaction mechanism according to claim 1, characterized in that: The output interface module converts the predicted hydrogen / ammonia emission data into feedforward control signals and transmits them to the engine electronic control unit or aftertreatment controller.

7. The hydrogen and ammonia emission generation prediction system based on in-cylinder combustion process and chemical reaction mechanism according to claim 1, characterized in that: The coupling method between the combustion simulation module and the chemical reaction simulation module is as follows: The local temperature, pressure, and concentration fields calculated by CFD are input into the chemical reaction solver in real time; Based on the chemical timescale segmentation algorithm, decoupled iterative calculations of turbulent combustion and chemical reaction kinetics are realized.

8. A prediction method applied to the hydrogen and ammonia emission generation prediction system based on in-cylinder combustion process and chemical reaction mechanism as described in any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Input variable acquisition module collects the in-cylinder pressure, temperature, air-fuel ratio and ignition timing of the hydrogen internal combustion engine; Step 2: The combustion simulation module simulates the in-cylinder turbulent combustion process based on a CFD model; Step 3: The chemical reaction simulation module calls the multi-step chemical reaction kinetic model to calculate the hydrogen / ammonia generation pathway; Step 4: The emission generation prediction module outputs prediction results, including hydrogen / ammonia generation rate and cumulative amount, and transmits the prediction results to the engine control system using the output interface module.

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