Variable Valve Timing in Gas Engines
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Solution Overview
Problem
Existing combustion engine technologies face inefficiencies in managing valve timings across varying load conditions, particularly in gaseous fuel modes, which affect knock margin and engine efficiency at different load levels.
Innovation Solution
A control device adjusts inlet valve closing timing based on engine load, switching from a first timing at medium loads to an earlier timing at high loads, utilizing a camshaft with eccentric disks and a control unit to rotate the camshaft and adjust valve and injection timings, optimizing the Miller cycle for efficiency and knock margin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed inlet valve closing timing is used, then the engine structure is simple, but engine efficiency and knock margin deteriorate at different load levels
Solution Approach 1:
The patent applies dynamics by making the inlet valve closing timing variable rather than fixed. The control device adjusts the inlet valve closing timing based on engine load conditions - using a first closing timing at medium loads and a second (earlier) closing timing at high loads. This dynamic adjustment optimizes engine efficiency and knock margin across different operating conditions while maintaining reasonable structural complexity through the use of a camshaft with eccentric disks.
2Reliability
If inlet valve closing timing is advanced at high loads, then knock margin improves, but engine power output may deteriorate
Solution Approach 1:
The patent applies parameter changes by adjusting the inlet valve closing timing parameter based on engine load. At high loads, the control device advances the inlet valve closing timing (second closing timing earlier than first closing timing) to increase knock margin. The camshaft with eccentric disks enables this timing parameter change while the control device optimizes the balance between knock margin improvement and power output maintenance by selecting appropriate timing based on actual operating conditions.
3Productivity
If variable valve timing is implemented, then engine efficiency improves across load ranges, but device complexity increases
Solution Approach 1:
The patent implements variable valve timing using a camshaft with eccentric disks that can rotate to different positions. The control device rotates the camshaft to select between different inlet valve closing timings based on engine load - medium load timing for efficiency at lower loads and advanced timing for high load conditions. This dynamic mechanism provides efficient operation across the full load range while maintaining manageable device complexity through a mechanical rotation system rather than more complex electronic actuation.
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 enhances engine efficiency and knock margin at high loads while maintaining stability at lower loads by adjusting valve and injection timings, allowing for efficient operation across a range of load conditions.
Implementation Method 1
utilizing a camshaft with eccentric disks and a control unit to rotate the camshaft and adjust valve and injection timings
Data Source
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AI summary
In a gas or dual fuel engine, an inlet valve closing timing is adjusted using a control device. In a medium load gaseous fuel mode, an inlet valve opens and closes late, and in a high load gaseous fuel mode the inlet valve opens and closes early. This results in a strong Miller cycle at high loads in the gaseous fuel mode. At very low loads, this strong Miller cycle is used to throttle the engine to achieve a stable operation of the same.