Pre-ignition Detection in Large Gas Engines
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Solution Overview
Problem
Existing methods for detecting pre-ignition in large engines, particularly in gas mode, are inadequate as pre-ignition often occurs before the piston reaches the top dead center, making simple cylinder pressure measurements at this point unreliable.
Innovation Solution
Measure cylinder pressure at two positions before the top dead center during the compression stroke, calculate a peak pressure, and compare it to a threshold value to detect pre-ignition by analyzing the pressure change relative to piston position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If simple cylinder pressure measurement at top dead center is used, then measurement simplicity is improved, but detection reliability deteriorates because pre-ignition often occurs before the piston reaches top dead center
Solution Approach 1:
The single pressure measurement at top dead center is segmented into multiple measurements at different piston positions (before top dead center and at top dead center). This segmentation allows detection of pressure changes during the compression stroke that indicate pre-ignition, resolving the contradiction by sacrificing some simplicity for significantly improved detection reliability.
2Reliability
If pressure measurement is taken before top dead center to detect pre-ignition, then detection reliability is improved, but measurement complexity increases
Solution Approach 1:
A crank angle sensor serves as an intermediary device to detect piston position and trigger pressure measurements at the correct timing. This intermediary enables reliable pre-ignition detection by ensuring measurements are taken at the appropriate crank angles, while keeping the overall system relatively simple through the use of a standard sensor.
3Measurement precision
If multiple pressure measurements are taken during compression stroke, then pre-ignition detection accuracy is improved, but measurement time increases
Solution Approach 1:
Pressure measurements are taken periodically at specific crank angle intervals during the compression stroke rather than continuously. This periodic measurement approach maintains high detection accuracy by capturing pressure at critical points while minimizing the total measurement time and data processing requirements.
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 method provides reliable detection of pre-ignition by accurately identifying pressure increases indicative of abnormal combustion, allowing for timely engine mode switching to prevent damage.
Implementation Method 1
a first pressure in the cylinder is measured at a first position of the piston, and a second pressure in the cylinder is measured at a second position of the piston
Implementation Method 2
combustion takes place by induced ignition of an ignitable pre-mixed air-fuel mixture
Implementation Method 3
the air-gas mixture is ignited at an induced ignition
Data Source
Figure 1
AI summary
A method for detecting pre-ignition in a large engine having at least one cylinder in which a piston is arranged movable back and forth in an axial direction between a bottom dead center and a top dead center, wherein the large engine can be operated at least in a gas mode, in which an amount of gas is introduced as fuel into the cylinder, the gas is mixed with scavenging air and combusted at an air-gas-ratio, wherein during operation in the gas mode a first pressure (P1, P1') in the cylinder is measured at a first position (KW1) of the piston, and a second pressure (P2, P2') in the cylinder is measured at a second position (KW2) of the piston, wherein the first position (KW1) and the second position (KW2) are after the bottom dead center and before the top dead center. A peak pressure (PC, PC') is calculated from the first pressure (P1, P1') and the second pressure (P2, P2'), and pre-ignition is detected by comparing the peak pressure (PC, PC') with a threshold value. Furthermore, a large engine is proposed.