Engine Pre-Ignition Control via Vibration Detection
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Solution Overview
Problem
Turbocharged engines with high compression ratios or boosted engines are prone to low-speed pre-ignition events due to elevated exhaust manifold pressures caused by late combustion, which can lead to unintended exhaust valve opening in neighboring cylinders, resulting in pre-ignition events, especially in small volume exhaust manifolds.
Innovation Solution
An engine controller senses block vibrations during an open exhaust valve of a cylinder undergoing late combustion and performs pre-ignition mitigating actions, such as fuel injection adjustments, to reduce the temperature of hot exhaust residuals and prevent forced entry into neighboring cylinders, using band-pass filters to differentiate between pre-ignition and knock events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If small volume exhaust manifolds are used to reduce turbo lag, then turbocharger response time is improved, but exhaust manifold pressure rises excessively during late combustion events causing unintended exhaust valve opening in neighboring cylinders
Solution Approach 1:
The system performs preliminary detection of late combustion events using knock sensors and vibration analysis before unintended exhaust valve opening occurs. By detecting the vibration signature of exhaust valve slamming during the exhaust stroke of the first cylinder, the system can preemptively enrich the mixture in the second cylinder to prevent pre-ignition from hot exhaust residuals.
Solution Approach 2:
The system introduces an intermediary control mechanism that monitors exhaust manifold pressure and vibration signatures to mediate between the high pressure generated by late combustion and the potential harm to neighboring cylinders. The controller uses this intermediary information to adjust fuel injection timing and quantity in affected cylinders.
2Measurement precision
If knock sensors are used to detect pre-ignition and knock events, then combustion abnormality detection is improved, but differentiation between pre-ignition, knock, and exhaust valve slamming is difficult
Solution Approach 1:
The system segments the detection of combustion abnormalities by analyzing vibration signals at different crank angle positions and using multiple knock sensors positioned at specific locations on the engine block. By dividing the detection task into temporal and spatial segments, the system can distinguish between pre-ignition (early combustion), knock (combustion pressure waves), and exhaust valve slamming (mechanical impact) based on their unique signatures.
Solution Approach 2:
The system uses mechanical vibration analysis as the primary detection mechanism, leveraging the distinct vibration signatures produced by different combustion abnormalities. Knock sensors detect and analyze these vibration patterns to identify and differentiate between pre-ignition events, knock events, and exhaust valve slamming, enabling precise targeting of mitigation strategies.
3Reliability
If fuel injection is enriched in affected cylinders to cool exhaust residuals, then pre-ignition prevention is improved, but engine efficiency decreases due to additional fuel consumption
Solution Approach 1:
The system applies local quality control by enriching fuel injection only in specific cylinders that are identified as receiving hot exhaust residuals, rather than enriching all cylinders uniformly. This localized approach targets the problem areas (cylinders experiencing pre-ignition risk) while maintaining normal fuel consumption in other cylinders, thereby minimizing overall energy loss.
Solution Approach 2:
The system dynamically changes fuel injection parameters (quantity and timing) based on real-time detection of late combustion events and exhaust valve slamming. By adjusting these parameters only when and where needed, the system prevents pre-ignition while minimizing unnecessary fuel consumption during normal operation.
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 detects and mitigates late-burn induced pre-ignition events by cooling the affected cylinder, reducing engine degradation and improving detection of unintended exhaust valve opening, while also reducing the risk of cascading pre-ignition events.
Implementation Method 1
sensed block vibration in a window during an open exhaust valve of a first cylinder undergoing a late combustion event
Implementation Method 2
the sensor output may be filtered through a first band-pass filter to filter out a first range of frequencies
Data Source
AI summary
Methods and systems are provided for reducing late burn induced cylinder pre-ignition events. Forced entry of residuals from a late burning cylinder into a neighboring cylinder may be detected based on engine block vibrations sensed in a window during an open exhaust valve of the late burning cylinder. In response to the entry of residuals, a pre-ignition mitigating action, such as fuel enrichment or deactivation, is performed in the neighboring cylinder.