Gas Engine Water Injection Knock Control
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Solution Overview
Problem
Conventional gas engine control systems for suppressing knocking do not effectively adjust water injection based on the actual combustion state, leading to inefficient knocking suppression and engine performance.
Innovation Solution
A control system that measures the knocking occurrence ratio and adjusts water injection amounts based on deviations from a target value, combined with ignition timing compensation to optimize engine efficiency and prevent excessive knocking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the ignition timing is advanced to MBT to optimize efficiency, then the fuel efficiency and power generation efficiency are improved, but the temperature and pressure in the combustion chamber increase leading to more frequent knocking
Solution Approach 1:
Water is introduced as an intermediary substance into the combustion chamber to mediate between the need for advanced ignition timing (for efficiency) and the need to suppress knocking. The water evaporates and absorbs heat, acting as a thermal buffer that allows advanced ignition timing without excessive temperature rise that causes knocking.
Solution Approach 2:
The invention changes the thermal parameters of the combustion chamber by injecting water, which alters the temperature and pressure characteristics. This parameter change allows the ignition timing to be advanced while maintaining knocking-free operation through dynamic adjustment of water injection amount based on detected knocking levels.
2Object-affected harmful factors
If water is injected to suppress knocking, then the knocking occurrence is reduced, but the engine efficiency decreases due to retarding ignition timing
Solution Approach 1:
The system implements a feedback control mechanism where knocking detection results are used to adjust water injection amounts in real-time. This feedback loop allows the system to maintain minimal water injection (preserving efficiency) while suppressing knocking, rather than using fixed conservative ignition timing that would reduce efficiency.
Solution Approach 2:
The invention transitions from static ignition timing to dynamic control where both ignition timing and water injection amount are continuously adjusted based on real-time knocking detection. This dynamic approach allows the system to optimize efficiency by retarding timing only when necessary while using water injection as a responsive countermeasure.
3Ease of operation
If water injection amount is adjusted based on throttle opening degree and engine speed, then the control is simplified, but the knocking suppression is ineffective because it does not consider the actual combustion state
Solution Approach 1:
The invention introduces feedback from knocking detection sensors that directly measure the combustion state. This feedback signal is used to adjust water injection amounts, ensuring that suppression actions are based on actual knocking occurrence rather than inferred conditions, thereby significantly improving reliability while maintaining control simplicity.
Solution Approach 2:
The system uses self-diagnosis through knocking detection to automatically adjust water injection levels. The combustion system essentially monitors itself and triggers appropriate suppression measures only when needed, eliminating the need for complex external control while improving reliability through direct measurement of combustion conditions.
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
The system effectively suppresses knocking and improves gas engine efficiency by aligning water injection and ignition timing with actual combustion states, preventing excessive knocking occurrence and reducing NOx emissions.
Implementation Method 1
the cylinder is cooled by latent heat of evaporation of the water
Implementation Method 2
the cylinder is cooled by latent heat of evaporation of the water
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A control system (100) in a gas engine (1) comprises a water injection means (14) which injects water toward an interior of a cylinder (4) in the gas engine (1); a water injection control means (56) which controls the water injection section (14); and a knocking occurrence ratio measuring means (45) which measures a measurement value (RM) of a knocking occurrence ratio in the cylinder (4). The water injection control means (56) controls the water injection means (14) to set the amount of the water injected toward the interior of the cylinder (4), based on a deviation between the measurement value (RM) and a target value (RT).