High Compression Engine Combustion Chamber Gas Flow Optimization
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Solution Overview
Problem
In reciprocating internal combustion engines with a geometric compression ratio of 13.0 or greater, the high compression ratio restricts gas flow in the combustion chamber, leading to poor combusted-gas scavenging efficiency and intake-air charging efficiency, as the valve overlap period fails to enhance intake and exhaust capacities proportionally.
Innovation Solution
The engine design includes a valve overlap period with a condition of S1 ≥ S2, where S1 is the cross-sectional area of the combustion chamber along hypothetical cutting-planes parallel to the valve direction and S2 is the effective opening area between the valve head and seat, ensuring a sufficient gas-passage area to suppress gas-flow resistance, thereby improving scavenging and charging efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the geometric compression ratio is set at a high value (13.0 or greater) to improve thermal efficiency, then fuel economy is improved, but the volume of the combustion chamber becomes smaller which restricts gas flow in the intake-to-exhaust direction
Solution Approach 1:
The patent applies local quality by creating a specific region in the combustion chamber (the gas passage region) with different properties from the rest of the chamber. By ensuring that the cross-sectional area S1 in this specific region is greater than or equal to the effective opening area S2 of the valves, the patent locally optimizes the gas flow path to reduce resistance, while maintaining the overall high compression ratio geometry for thermal efficiency.
Solution Approach 2:
The patent addresses the gas flow restriction by considering the three-dimensional geometry of the combustion chamber more comprehensively. By defining hypothetical cutting planes parallel to the valve reciprocating direction and analyzing the cross-sectional area distribution throughout the chamber volume, the patent identifies and optimizes the gas passage region in a way that maintains high compression ratio while ensuring sufficient flow capacity in critical dimensions.
2Productivity
If the valve overlap period is set up to improve combusted-gas scavenging efficiency and intake-air charging efficiency, then gas exchange is improved, but in engines with high geometric compression ratio the intake and exhaust capacities are not enhanced in proportion to valve lift amount
Solution Approach 1:
The patent applies local quality by creating a specific region in the combustion chamber (the gas passage region) with different properties from the rest of the chamber. By ensuring that the cross-sectional area S1 in this specific region is greater than or equal to the effective opening area S2 of the valves, the patent locally optimizes the gas flow path to reduce resistance, while maintaining the overall high compression ratio geometry for thermal efficiency.
Solution Approach 2:
The patent addresses the gas flow restriction by considering the three-dimensional geometry of the combustion chamber more comprehensively. By defining hypothetical cutting planes parallel to the valve reciprocating direction and analyzing the cross-sectional area distribution throughout the chamber volume, the patent identifies and optimizes the gas passage region in a way that maintains high compression ratio while ensuring sufficient flow capacity in critical dimensions.
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
Disclosed is an internal combustion engine (A), which has a valve overlap period (T) during which an intake valve (1) and an exhaust valve (2) are opened, and a geometric compression ratio of 13.0 or greater. The engine (A) is designed to satisfy, at a center timing (Tc) of the valve overlap period (T), a conditional expression: S1 ≥ S2, where S1 is a cross-sectional area of a combustion chamber (4) taken along any selected one of a plurality of mutually parallel hypothetical cutting-planes (IP) each of which extends parallel to a linear reciprocating direction (d1 or d2) of at least one of the intake and exhaust valves (1, 2) and passes through a valve head (1a or 2a) of the at least one of the valves (1, 2), and S2 is an effective opening area defined between the valve head (1a or 2a) and a corresponding valve seat (11a or 12a) in a region on an outward side of the combustion chamber (4) relative to the selected hypothetical cutting-plane (IP). The present invention can reliably improve combusted-gas scavenging efficiency and intake-air charging efficiency.