Dual Fuel Engine Knock Detection via Asymmetric Acoustic Weighting
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Solution Overview
Problem
Dual fuel engines face challenges in detecting and mitigating abnormal combustion events such as knock, pre-ignition, and misfire due to inherent mismatches in combustion modes and parameters optimized for diesel operation, with existing methods failing to accurately detect minor increases in knocking intensity and requiring significant differences between cycles.
Innovation Solution
The method involves sensing frequency components of acoustic signals during combustion cycles to determine in-cylinder pressure signals, calculating a knock index that weights rising edges more than falling edges, and performing mitigation strategies, including transitioning to single fuel mode, adjusting fuel proportions, and modifying ignition timing to address detected abnormal combustion characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If dual fuel engines operate with high compression ratios to maintain high thermal efficiency, then thermal efficiency is improved, but the engine becomes more susceptible to knock and abnormal combustion
Solution Approach 1:
The system performs preliminary detection of knock and abnormal combustion events by analyzing acoustic signals and in-cylinder pressure signals before severe damage occurs. The controller continuously monitors combustion characteristics and detects deviations from normal operation, enabling early intervention through mitigation strategies such as adjusting fuel injection timing or reducing fuel quantity to prevent catastrophic engine damage.
Solution Approach 2:
The system implements a closed-loop feedback mechanism where acoustic sensors and pressure sensors continuously monitor combustion events, and the controller adjusts operating parameters in real-time based on detected abnormal combustion characteristics. The knock detection algorithm compares current combustion events against reference patterns and dynamically modifies fuel injection strategies to maintain stable combustion while preserving high thermal efficiency.
2Reliability
If existing knock detection methods integrate knocking signals over multiple cycles, then false positives are reduced, but minor increases in knocking intensity cannot be detected
Solution Approach 1:
The knock detection algorithm applies asymmetric weighting to different phases of the combustion cycle, emphasizing the rising edge of in-cylinder pressure where knock events typically occur. By weighting abnormal combustion characteristics on the rising edge more than on the falling edge, the system enhances sensitivity to minor knock intensity increases while maintaining reliability through the multi-cycle integration approach.
Solution Approach 2:
The system applies localized analysis to specific portions of the combustion cycle by identifying and weighting abnormal combustion characteristics at critical phases. The knock index calculation focuses on specific time windows and pressure regions where knock events manifest most strongly, rather than uniformly processing the entire combustion cycle, thereby improving detection precision for minor knock events.
3Power
If dual fuel engines use premixed combustion mode, then power output is improved, but the engine becomes more susceptible to pre-ignition and knock
Solution Approach 1:
The system dynamically adjusts combustion parameters based on real-time detection of abnormal combustion events. When pre-ignition or knock is detected during premixed combustion mode, the controller dynamically modifies fuel injection timing, pilot fuel quantity, or main fuel quantity to suppress abnormal combustion while maintaining high power output. This dynamic adaptation allows the engine to operate in premixed mode with enhanced protection against pre-ignition and knock.
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 abnormal combustion events by accurately identifying engine knock and misfire, reducing the risk of engine damage and improving operational efficiency by adapting fuel and ignition settings in real-time.
Implementation Method 1
an acoustic signal sensor connected with the internal combustion engine for emitting signals representative of vibrational signals associated with combustion and responsive to frequency components representative of at least one of a normal combustion characteristic and an abnormal combustion characteristic
Implementation Method 2
the gaseous fuel forms a premixed air-fuel charge in the combustion chamber that when ignited burns with a premixed flame
Implementation Method 3
the combustion of the pilot fuel ignites the gaseous fuel
Implementation Method 4
the engine is fuelled with a gaseous fuel and diesel simultaneously. The gaseous fuel forms a premixed air-fuel charge in the combustion chamber
Data Source
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AI summary
Premixed engines including dual fuel engines can experience abnormal combustion characteristics including misfire, pre-ignition and knock. A method for detecting and mitigating abnormal combustion in an engine comprises sensing frequency components of an acoustic signal associated with a combustion chamber during a combustion cycle, the frequency components representative of at least one of a normal and an abnormal combustion characteristic; determining an in-cylinder pressure signal as a function of the acoustic signal; calculating as functions of the in- cylinder pressure signal at least one of a knock index, a gross indicated mean effective pressure and a start of combustion timing; detecting the abnormal combustion characteristic is at least one of (a) a misfire event when the gross indicated mean effective pressure is less than a predetermined mean effective pressure value; (b) a pre-ignition event when the start of combustion timing is advanced of a start of ignition timing; and (c) an engine knock event when the knock index is greater than a predetermined knock value; and performing a mitigation strategy for the detected abnormal combustion characteristic.