Gas Engine Ignition Timing Control via Virtual Knocking Ratio
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Solution Overview
Problem
Gas engines using fuel gases with high methane numbers experience knocking issues due to advanced ignition timing, leading to inefficient operation.
Innovation Solution
Converting the maximum cylinder pressure into a virtual knocking occurrence ratio, allowing for adjustments to ignition timing to prevent excessive pressure and maintain suitable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ignition timing is controlled based on the moving average value of the actual knocking occurrence ratio, then knocking can be prevented in conventional fuel gases, but the ignition timing becomes too advanced when using fuel gases with high methane numbers
Solution Approach 1:
The patent introduces a virtual knocking occurrence ratio as an intermediary parameter to bridge the gap between actual knocking detection and ignition timing control. When the moving average value of maximum pressure exceeds a reference value, the system calculates a virtual knocking occurrence ratio based on the pressure data, even when actual knocking is not detected. This virtual ratio serves as a mediator to provide appropriate ignition timing adjustment signals for high methane number fuels, resolving the contradiction between preventing knocking and maintaining suitable ignition timing.
Solution Approach 2:
The patent changes the parameter used for ignition timing control from solely relying on actual knocking occurrence ratio to incorporating a virtual knocking occurrence ratio derived from maximum pressure values. By transforming pressure data into a virtual knocking ratio parameter, the system adapts the control parameter to suit high methane number fuels that do not produce detectable knocking, thus resolving the timing advancement issue while maintaining reliability.
2Ease of operation
If the moving average value of maximum pressure in the cylinder is used to control ignition timing, then suitable timing can be achieved for high methane number fuels, but the system complexity increases
Solution Approach 1:
The patent makes the control system universal by enabling it to handle both conventional fuels (with actual knocking detection) and high methane number fuels (with virtual knocking ratio based on pressure). The system automatically selects between using actual knocking occurrence ratio or virtual knocking occurrence ratio based on the fuel type, achieving multi-functionality without requiring separate control systems, thus managing complexity while maintaining ease of operation across different fuel types.
3Power
If ignition timing is advanced to improve efficiency, then power output increases, but knocking occurs more frequently
Solution Approach 1:
The patent implements feedback control by continuously monitoring either actual knocking occurrence or virtual knocking occurrence ratio (derived from maximum pressure) and adjusting ignition timing accordingly. The controller compares the detected knocking ratio or virtual ratio against target values and dynamically adjusts ignition timing to maintain optimal power output while preventing excessive knocking, thus resolving the contradiction between power enhancement and knocking prevention through closed-loop feedback.
Data Source
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AI summary
A method of controlling a gas engine that is operated under lean-burn conditions, the method adjusting ignition timing such that a delay calculation value of an actual knocking occurrence ratio becomes a target occurrence ratio, the method comprising: when a delay calculation value of a maximum pressure in a cylinder of the gas engine is greater than or equal to a reference value, converting the delay calculation value into a virtual knocking occurrence ratio greater than or equal to a value that is greater than the target occurrence ratio; and either adding the virtual knocking occurrence ratio to the delay calculation value of the actual knocking occurrence ratio and then comparing the resulting delay calculation value of the actual knocking occurrence ratio with the target occurrence ratio, or comparing the virtual knocking occurrence ratio instead of the delay calculation value of the actual knocking occurrence ratio with the target occurrence ratio.