Exhaust Valve Transient Control for Diesel Engine Load Changes
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Solution Overview
Problem
Large diesel engines face challenges in maintaining efficient, economical, and low-emission operation during sudden and frequent load changes, such as those encountered in heavy seas or maneuvering operations, due to difficulties in controlling the air-fuel ratio and meeting stringent exhaust gas limits.
Innovation Solution
A method that adjusts the transient closing angle of the exhaust valve and limits the amount of gas introduced into the cylinder, supplemented by additional liquid fuel, to maintain an optimal air-fuel mixture and compensate for variations in boost pressure, allowing continued operation in gas mode without knocking or misfiring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the engine operates in gas mode during sudden and frequent load changes, then emissions compliance is improved, but control stability deteriorates due to difficulty in maintaining optimal air-fuel ratio
Solution Approach 1:
The exhaust valve closing angle is made dynamically adjustable based on instantaneous load conditions. The control system continuously monitors load changes and adjusts the closing angle in real-time to maintain optimal air-fuel ratio during transient operations, enabling stable gas mode operation even during sudden load changes.
Solution Approach 2:
The invention changes the operating parameters of the exhaust valve (closing angle) in response to varying load conditions. By adjusting the closing angle parameter, the system optimizes the air-fuel mixture composition dynamically, ensuring both emissions compliance and control stability during transient operations.
2Stability of the object's composition
If the exhaust valve closing angle is adjusted to maintain optimal air-fuel ratio, then combustion stability is improved, but device complexity increases due to additional control mechanisms
Solution Approach 1:
The control system incorporates feedback mechanisms that monitor instantaneous load conditions and automatically adjust the exhaust valve closing angle accordingly. This closed-loop control maintains optimal combustion stability without requiring complex manual intervention or overly complicated control architecture.
3Reliability
If the amount of gas introduced into the cylinder is limited, then knocking combustion is prevented, but power output decreases
Solution Approach 1:
The invention optimizes the gas quantity parameter introduced into the cylinder based on instantaneous load conditions. By dynamically adjusting this parameter along with the exhaust valve closing angle, the system prevents knocking combustion while minimizing power loss during transient operations.
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 enables reliable, efficient, and environmentally friendly operation of dual-fuel large diesel engines during load changes, ensuring the air-fuel mixture remains within optimal limits, reducing engine speed fluctuations, and maintaining compliance with emissions regulations.
Implementation Method 1
determining a transient closing angle for the exhaust valve, at which the exhaust valve closes during a working cycle of the large diesel engine, by means of which the amount of air compressed in the cylinder can be influenced
Implementation Method 2
the scavenging or charge air is usually provided by a turbocharger, which generates a scavenging or charge air pressure that depends on the engine load
Data Source
Figure 1
Figure 2~5
Figure 3
AI summary
A method for operating a large diesel engine is proposed, which is operable at least in a gas mode in which a gas is introduced as fuel into a cylinder (21) and discharged through an exhaust valve (24) after combustion. During operation in gas mode (10), a state of strong load changes is detected (13), and the large diesel engine is then operated in a transient mode comprising the following steps: - determining a dwell angle for closing the exhaust valve in gas mode, - determining a correction value for the dwell angle (14), - determining a transient dwell angle (14) by relating the dwell angle to the correction value, - closing the exhaust valve at the transient dwell angle (15). Furthermore, a large diesel engine operated according to such a method is proposed.