Predictive Misfire Control in Spark Ignition Engines
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Solution Overview
Problem
Current spark-ignited (SI) engine technologies face challenges in predicting and controlling misfire and combustion cyclic variation, especially under high Exhaust Gas Recirculation (EGR) conditions, where Maximum Break Torque (MBT) timings are beyond misfire limits, leading to combustion instability and reduced operational efficiency.
Innovation Solution
A predictive modeling and mitigation methodology that estimates in-cylinder temperature and pressure, determines crank angle resolved flame velocity, and adjusts engine actuators, such as the external ignition source, to prevent misfire by correlating flame velocity with combustion phasing and turbulent combustion regimes, using models for flame kernel initiation, laminar flame speed, and turbulent combustion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If spark timing is advanced towards MBT timing to improve thermal efficiency, then thermal efficiency is improved, but misfire occurs due to combustion instability at high EGR dilution
Solution Approach 1:
The system performs preliminary detection of misfire conditions by monitoring combustion characteristics and predicting misfire risk before actual misfire occurs. The controller adjusts spark timing in advance based on predicted misfire probability, preventing misfire before it happens while maintaining advanced spark timing for thermal efficiency.
Solution Approach 2:
The system uses feedback from combustion sensors (such as ion current or pressure sensors) to continuously monitor combustion quality and detect early signs of misfire. This feedback is used to dynamically adjust spark timing and other combustion parameters to maintain stable combustion at advanced spark timings, resolving the contradiction between thermal efficiency and misfire prevention.
2Loss of energy
If high EGR dilution is used to reduce throttling losses, then thermal efficiency is improved, but the feasible spark timing range is reduced due to misfire limits
Solution Approach 1:
The system dynamically adjusts spark timing based on real-time combustion conditions and misfire probability predictions. Rather than using a fixed conservative spark timing limit, the system continuously adapts the feasible spark timing range according to actual combustion stability, allowing operation closer to misfire limits when conditions permit while maintaining stability when conditions deteriorate.
Solution Approach 2:
The system changes combustion parameters (such as ignition energy, spark duration, or secondary injection timing) in addition to spark timing to expand the feasible operating range at high EGR dilution. By modifying multiple parameters simultaneously, the system maintains stable combustion at more advanced spark timings, effectively increasing the feasible spark timing range despite high dilution.
3Ease of operation
If open-loop feed forward control with fixed misfire limits is used, then control simplicity is maintained, but the model cannot adapt to changing operating conditions
Solution Approach 1:
The system uses self-service by leveraging the engine's own combustion characteristics and sensor data to predict misfire conditions and adjust control parameters. The misfire prediction model is built using data from the engine itself (combustion pressure, ion current, or other combustion indicators), allowing the system to adapt to changing operating conditions using the engine's inherent information without requiring external complex modeling.
Solution Approach 2:
The system replaces complex mechanical experimentation and fixed lookup tables with a data-driven or physics-based misfire prediction model that computationally predicts misfire risk. This substitution allows continuous adaptation to changing operating conditions through software algorithms rather than requiring extensive re-calibration or physical experimentation for each new operating condition.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively predicts and mitigates misfire occurrence, reducing combustion cyclic variation and COV of IMEP, enabling continuous operation near misfire limits, thus enhancing the efficiency and stability of highly diluted SI engine combustion.
Implementation Method 1
The misfire model describes the early flame development period of 0 to 3 percent mass fraction burned and considers the effect of ignition characteristics, local fuel to air equivalence ratio, flame kernel initiation, and planar flame interaction with in-cylinder turbulence.
Implementation Method 2
The misfire model describes the early flame development period of 0 to 3 percent mass fraction burned and considers the effect of ignition characteristics, local fuel to air equivalence ratio, flame kernel initiation, and planar flame interaction with in-cylinder turbulence.
Data Source
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AI summary
A method and apparatus to predict and enable control of misfire that influences combustion cyclic variation and COV of IMEP in spark-ignited (SI) engine. The method includes obtaining engine data and determining temperature and pressure within a cylinder in response to engine data; determining crank angle resolved flame velocity evolution based on the engine data; comparing the crank angle resolved flame velocity to predetermined turbulent combustion regime data to determine a misfire occurrence; and updating a misfire occurrence indicator and outputting a control signal when the misfire occurrence indicator is greater than a predetermined limit, the control signal being capable of adjusting any engine actuators, such as external ignition source, of the spark-ignited engine on a cycle to cycle basis. The method and apparatus further includes correlating the crank angle resolved flame velocity to combustion phasing when the misfire occurrence indicator is less than the predetermined limit.