SPCCI Engine Combustion Noise Reduction via Spatial Air-Fuel Segmentation
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Solution Overview
Problem
Premixed compression ignition engines face challenges in reducing combustion noise while maintaining thermal efficiency, as the air-fuel mixture tends to ignite simultaneously, leading to abrupt pressure rises and difficulty in controlling ignition timing.
Innovation Solution
A premixed compression ignition engine with a fuel injection device and an ignition device that controls the air-fuel mixture in a first area to be ignited by the ignition device, followed by self-ignition of the mixture in a second area due to pressure rise, with the air-fuel ratio in the entire combustion chamber made richer than stoichiometric in high load operations to suppress noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If premixed compression ignition combustion is performed to increase thermal efficiency, then thermal efficiency is improved, but combustion noise deteriorates due to simultaneous ignition and abrupt pressure rise
Solution Approach 1:
The combustion chamber is divided into multiple regions with different air-fuel ratios. The first region (near the spark plug) has a leaner air-fuel ratio and ignites first via spark ignition, while the second region (peripheral area) has a richer air-fuel ratio and ignites later via compression self-ignition. This spatial segmentation of the air-fuel mixture prevents simultaneous ignition throughout the chamber, reducing the abrupt pressure rise and combustion noise while maintaining high thermal efficiency.
Solution Approach 2:
Different regions of the combustion chamber are created with locally optimized air-fuel ratios. The first region near the spark plug electrode has a leaner mixture (higher air-fuel ratio) that is easier to ignite and burns faster, while the second peripheral region has a richer mixture (lower air-fuel ratio) that is harder to ignite and burns slower. This local quality differentiation enables controlled sequential combustion, resolving the contradiction between thermal efficiency and combustion noise.
2Loss of energy
If premixed compression ignition combustion is performed to increase compression ratio, then thermal efficiency is improved, but combustion start timing becomes difficult to control
Solution Approach 1:
The combustion process is segmented into two distinct stages: first, spark-ignited combustion in the lean mixture region near the spark plug; second, compression self-ignition in the rich mixture region at the periphery. This segmentation provides clear control points for combustion timing. The spark ignition timing can be precisely controlled by the ignition system, and the self-ignition timing is naturally delayed due to the richer mixture and lower temperature in the peripheral region, enabling reliable control of overall combustion start timing.
Solution Approach 2:
The air-fuel ratio parameter is varied spatially within the combustion chamber. By controlling the fuel injection amount and distribution, the system creates regions with different air-fuel ratios. The leaner first region ignites at an earlier timing controlled by the spark plug, while the richer second region ignites later through compression. This parameter change (air-fuel ratio distribution) enables independent control of ignition timing for different regions, resolving the timing control difficulty.
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 reduces combustion noise by controlling the air-fuel ratios in different areas of the combustion chamber, enhancing thermal efficiency and allowing for precise ignition timing control.
Implementation Method 1
an ignition device having an electrode portion that faces an inside of the combustion chamber and ignites an air-fuel mixture in the combustion chamber to apply ignition energy to the air-fuel mixture
Implementation Method 2
an air-fuel mixture formed in a second area of the combustion chamber located on an outer periphery of the first area is self-ignited and burned by a pressure rise in the combustion chamber due to the combustion of the air-fuel mixture in the first area
Data Source
AI summary
Control is performed so as to occur SPCCI combustion in which, after an air-fuel mixture in a first area of a combustion chamber that includes an electrode portion of an ignition device is burned by receiving ignition energy, an air-fuel mixture formed in a second area located on an outer periphery of the first area is self-ignited. Control is also performed such that, in a high load operation region of an SPCCI combustion execution region, an air-fuel ratio in the entire combustion chamber becomes richer than a stoichiometric air-fuel ratio and that an air-fuel ratio of the air-fuel mixture in the first area becomes leaner than an air-fuel ratio of the air-fuel mixture in the second area.