Marine Engine Variable Compression Ratio for Torsional Resonance
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Solution Overview
Problem
Existing marine engines face a decrease in thermal efficiency when attempting to suppress resonance stress caused by torsional vibration of the rotary shaft system through adjustments like changing fuel injection timing or period.
Innovation Solution
A marine engine with a variable compression ratio mechanism that adjusts the top dead center position of the piston to maintain high compression ratios and suppress torsional stress using a feedback control system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If fuel injection timing or fuel injection period is changed to reduce excitation torque component, then resonance stress is suppressed, but thermal efficiency decreases
Solution Approach 1:
The invention changes the compression ratio parameter instead of fuel injection timing to suppress resonance stress. By dynamically adjusting the compression ratio based on detected resonance conditions, the system reduces excitation torque while preserving optimal combustion conditions that maintain thermal efficiency.
Solution Approach 2:
The invention introduces a dynamic compression ratio adjustment mechanism that adapts the compression ratio in real-time based on resonance detection. This dynamic approach allows the system to suppress resonance stress only when necessary while maintaining high compression ratios for efficient combustion during normal operation.
2Object-affected harmful factors
If engine rotation speed is controlled to fall out of barred range, then resonance stress is avoided, but operability decreases
Solution Approach 1:
The invention implements a feedback control system that detects resonance conditions and automatically adjusts the compression ratio in response. This closed-loop control allows the engine to operate through previously barred speed ranges by actively suppressing resonance stress, thereby improving operability without sacrificing structural safety.
Solution Approach 2:
Instead of restricting the engine to operate only outside barred speed ranges, the invention changes the compression ratio parameter to actively suppress resonance stress within barred ranges, allowing continuous operation across the full speed spectrum and improving navigational flexibility.
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
Suppresses resonance stress while maintaining thermal efficiency by dynamically adjusting the compression ratio, allowing navigation in resonance ranges without automatic engine speed control, thus enhancing operability.
Implementation Method 1
torsional vibration occurs. When an engine rotation speed falls within a resonance occurrence range, there is a fear in that the rotary shaft system may resonate
Data Source
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AI summary
Provided is a marine engine (100), including: a piston; and a compression ratio controller (182) configured to execute lowering processing of moving a top dead center position of the piston toward a bottom dead center side when an engine rotation speed falls within a resonance occurrence range set in advance. A geometrical compression ratio is reduced, and a resonance stress caused by a torsional vibration in a rotary system can thus be suppressed while suppressing a decrease in thermal efficiency compared with a case in which retarding control is applied to a fuel injection timing or a closing timing of an exhaust valve.