Piston Top Surface Design for Prechamber Gas Engine Knocking
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Solution Overview
Problem
In prechamber-type gas engines, the formation of a region with delayed flame propagation leads to knocking, which reduces thermal efficiency and output, and existing solutions face challenges in manufacturing complexity and limited compression ratio improvement.
Innovation Solution
A piston top surface with a concentric cavity and land portions is designed, where the land portions are positioned between injection holes to reduce delayed flame diffusion, with a concave curved surface to facilitate smooth flame propagation and offset the flame momentum, thereby reducing the region of delayed flame propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional piston top surface is used, then the structure is simple, but a region with delayed flame propagation is formed between injection directions causing knocking
Solution Approach 1:
The piston top surface is designed with locally differentiated regions: a first region with land portions that have higher flame propagation speed, and a second region without land portions. This local quality differentiation ensures that the first region acts as a flame propagation path while the second region serves as a fuel injection target, eliminating delayed flame propagation regions and suppressing knocking without requiring complete structural redesign
Solution Approach 2:
The piston top surface is segmented into multiple functional regions: land portions in the first region that facilitate flame propagation, and open spaces in the second region that serve as fuel injection targets. This segmentation allows different areas to perform specialized functions, ensuring uniform flame propagation across the combustion chamber while maintaining structural simplicity
2Use of energy by moving object
If the flame propagation region is extended to improve combustion, then thermal efficiency improves, but the region of delayed flame propagation increases causing more knocking
Solution Approach 1:
The piston top surface implements local quality differentiation where the first region contains land portions that accelerate flame propagation, while the second region provides open spaces for fuel injection. This ensures that flame propagation occurs uniformly across all regions without creating delayed propagation zones, allowing thermal efficiency improvement without inducing knocking
Solution Approach 2:
The land portions are pre-formed on the piston top surface to create optimal flame propagation paths before combustion occurs. This preliminary structural preparation ensures that when fuel is injected into the second region, the flame propagates uniformly and immediately without creating delayed propagation regions that would cause knocking
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 design effectively suppresses knocking by minimizing the region of delayed flame propagation, enhancing combustion efficiency and improving thermal efficiency and output.
Implementation Method 1
a region where a flame propagation by a torch jet is delayed is reduced
Implementation Method 2
the bottom portion of the cavity has the concave curved surface such that a part of the bottom portion of the cavity on an axis line through the center of the piston and a tip portion of the land portion has a larger curvature than another part
Data Source
Figure 1
Figure 2a~3
Figure 4~5
AI summary
To provide a piston for a prechamber-type gas engine and a prechamber-type gas engine taking into consideration the shape of the piston top surface portion so that the region where flame propagation due to torch jet is delayed, a piston for a prechamber-type gas engine where torch jet formed by combustion a prechamber fuel in a precombustion chamber is injected to a main combustion chamber through a plurality of injection holes, includes a piston top surface portion having a land portion formed in a first region extending between axis line directions of adjacent injection holes, and the first region is positioned at a higher position than a second region extending across the axis line direction. The land portion is formed on a cavity formed in the piston top surface portion. A plurality of land portions are provided corresponding to the plurality of injection holes, and the plurality of land portions are provided so as to be offset toward a same direction from a middle position between axis line directions of adjacent injection holes.