Pre-chamber Engine Combustion Index for Efficiency and Knocking
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Solution Overview
Problem
Passive type pre-chamber ignition systems face challenges in simultaneously improving thermal efficiency in medium load engine operations and suppressing knocking in high load and high rotation operations, as the jet potential is uniquely determined by pre-chamber volume and injection hole specifications, making it difficult to meet both requirements effectively.
Innovation Solution
The engine design includes a main combustion chamber, a pre-chamber with multiple injection holes, and a spark plug, with a compression ratio between 14 and 24 and a specific index St·ε (product of total cross-sectional area of injection holes and compression ratio) ranging from 0.1496 to 0.8449 cm², which allows for adjustable jet potential to optimize thermal efficiency and prevent knocking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the pre-chamber specifications are determined to increase jet potential for medium load EGR operation, then thermal efficiency is improved, but knocking occurs easily in high load operation
Solution Approach 1:
The patent applies parameter changes by defining a specific range for the index St·ε (product of total cross-sectional area of injection holes and compression ratio) between 0.1496 cm² and 0.8449 cm². This parameter control allows the system to achieve optimal jet potential for medium load EGR operation while preventing excessive jet potential that would cause knocking in high load operation. The compression ratio is specifically set between 14 and 24 to work in conjunction with the St·ε index to balance thermal efficiency and knocking suppression.
2Object-affected harmful factors
If the pre-chamber specifications are determined to decrease jet potential to suppress knocking, then knocking is suppressed, but thermal efficiency in medium load operation cannot be improved
Solution Approach 1:
The patent resolves this contradiction by establishing a minimum threshold for the St·ε index (0.1496 cm²) that ensures sufficient jet potential to improve thermal efficiency in medium load EGR operation. By setting this lower bound, the system maintains adequate flame ejection capability to prevent misfire and improve combustion efficiency, while the upper bound (0.8449 cm²) prevents excessive jet potential that would cause knocking.
3Loss of energy
If the compression ratio is increased to improve thermal efficiency, then thermal efficiency is improved, but knocking occurs more easily in high load operation
Solution Approach 1:
The patent addresses this contradiction by setting the compression ratio within a specific range of 14 to 24, which balances thermal efficiency improvement with knocking suppression. This compression ratio range works in conjunction with the controlled St·ε index to achieve optimal performance across different load conditions.
Solution Approach 2:
The system dynamically adapts to different operating conditions through the interaction between the fixed compression ratio and the variable jet potential controlled by the St·ε index. The pre-chamber design allows the system to maintain appropriate flame ejection characteristics across medium and high load operations, effectively managing the trade-off between thermal efficiency and knocking suppression.
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 configuration enables improved thermal efficiency in medium load operations while suppressing knocking in high load and high rotation operations by maintaining the jet potential within a controlled range, ensuring efficient energy transfer and reduced knocking occurrences.
Implementation Method 1
a spark plug that ignites an air-fuel mixture in the pre-chamber
Implementation Method 2
guides the air-fuel mixture formed in the main combustion chamber in the compression stroke to the vicinity of the spark plug through the injection holes
Data Source
AI summary
To meet both a request to improve the thermal efficiency in the medium load operation of an engine and a request to suppress knocking in the high load and high rotation operation of the engine, the engine includes a main combustion chamber comprising a cylinder block, a cylinder head, and a piston; a pre-chamber having a plurality of injection holes that open into the main combustion chamber; and a spark plug that ignites an air-fuel mixture in the pre-chamber. A compression ratio of the main combustion chamber is not less than 14 and not more than 24. A first index, which is the product between a total cross-sectional area of the plurality of injection holes and the compression ratio, is not less than 0.1496 cm2 and not more than 0.8449 cm2.