Gas Engine Control for Multi-Cylinder Misfire Detection
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Solution Overview
Problem
Existing gas engines face challenges in accurately determining simultaneous misfires across multiple cylinders, leading to non-combusted fuel gas flowing into the exhaust system, which can cause combustion and damage to the engine and surroundings.
Innovation Solution
A controller system that detects simultaneous misfires in multiple cylinders by counting misfires within a single combustion cycle and sets a threshold value for cylinder number, triggering an emergency stop to prevent fuel gas density from reaching combustible levels in the exhaust path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing misfire detection techniques are used, then individual cylinder misfires can be detected, but simultaneous misfires across multiple cylinders cannot be accurately determined
Solution Approach 1:
The patent segments the misfire detection process into distinct stages: individual cylinder misfire determination, counting of misfired cylinders within a crank angle period, and simultaneous misfire determination when the count exceeds a threshold. This segmentation allows the system to handle multiple cylinders systematically without requiring complex multi-cylinder analysis algorithms.
Solution Approach 2:
The patent performs preliminary misfire determination for each cylinder individually before aggregating the results to detect simultaneous misfires. By pre-determining the misfire state of each cylinder based on in-cylinder pressure ratios, the system simplifies the subsequent simultaneous misfire detection process and enables rapid response.
2Productivity
If fuel gas supply continues during simultaneous misfire, then engine operation is maintained, but non-combusted fuel gas accumulates in exhaust path reaching combustible levels
Solution Approach 1:
The patent applies preliminary anti-action by shutting off the fuel gas supply immediately when simultaneous misfire is detected (when misfire count exceeds threshold within a crank angle period). This preventive action stops the accumulation of non-combusted fuel gas in the exhaust path before it can reach combustible levels, thereby preventing exhaust path combustion while maintaining engine safety.
Solution Approach 2:
The system continuously monitors in-cylinder pressure ratios and provides real-time feedback on misfire conditions. When the feedback indicates simultaneous misfire (threshold exceeded), the control device automatically adjusts the fuel gas supply, creating a closed-loop safety mechanism that prevents harmful accumulation.
3Loss of time
If misfire detection threshold is set low, then simultaneous misfires are detected quickly, but false positives increase reducing system reliability
Solution Approach 1:
The patent employs dynamic threshold adjustment based on operating conditions. The threshold for simultaneous misfire detection is not fixed but adapts to account for normal combustion variations, preventing false positives while maintaining rapid detection capability. This dynamic approach balances sensitivity with reliability.
Solution Approach 2:
The system changes the detection parameters (pressure ratio thresholds, crank angle period definitions, misfire count thresholds) based on engine operating conditions to optimize both detection speed and accuracy. By adjusting these parameters dynamically, the system achieves rapid simultaneous misfire detection without excessive false positives.
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
Accurately determines simultaneous misfires and quickly stops fuel gas supply to prevent combustion in the exhaust path, minimizing damage and ensuring safety.
Implementation Method 1
an in-cylinder pressure detector that detects an in-cylinder pressure based on a compression stroke
Implementation Method 2
determining a ratio of the detected in-cylinder pressure to a predetermined reference pressure
Implementation Method 3
a fuel gas supplied from a fuel supply path are mixed and supplied into a combustion chamber to be ignited and combusted
Data Source
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AI summary
A controller for a gas engine includes a cycle detection unit 67 configured to detect a crank angle period of a single combustion cycle of an engine including a plurality of cylinders based on a crank angle detection value inputted from a crank angle detector 75, a misfire detection unit 69 configured to detect a misfire in a combustion chamber 37 based on an in-cylinder pressure detection value inputted from the in-cylinder pressure detector 59, and a simultaneous misfire determination unit 73 configured to determine a simultaneous misfire of more than one cylinder when a total number of cylinders where the misfire is detected in the single combustion cycle by the misfire detection unit 69 is not less than a preset threshold value of a cylinder number. The fuel gas to all of the cylinders is shut off when the simultaneous misfire of more than one cylinder in the single combustion cycle is determined by the simultaneous misfire determination unit 73.