Large Diesel Engine Transient Mode Control
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Solution Overview
Problem
Large diesel engines face challenges in maintaining reliable, efficient, and low-emission operation during sudden, frequent, or severe load changes, such as those encountered in heavy seas or maneuvering, particularly in gas mode, where the air-gas mixture can become too rich, leading to inefficient and polluting combustion.
Innovation Solution
A method for operating large diesel engines in a transient mode, where an upper limit is set for the amount of gas supplied, and an additional amount of liquid fuel is introduced to maintain target speed or torque, preventing excessively rapid combustion and allowing continued efficient operation in gas mode, even under load changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the amount of gas supplied is increased to meet high power demand, then the power output is improved, but the air-gas mixture becomes too rich leading to knocking combustion and engine damage
Solution Approach 1:
The control device dynamically adjusts the air-to-gas ratio parameter based on real-time operating conditions (load changes, scavenging air pressure). When sudden load increases occur, the system enriches the mixture within safe limits; when load decreases, it leans the mixture to prevent knocking, thus maintaining both power output and combustion stability across varying operating conditions
Solution Approach 2:
The system continuously monitors operating parameters (scavenging air pressure, load conditions) and uses this feedback to adjust the gas supply amount in real-time. The control device receives feedback about the current air-to-gas ratio and combustion state, then modifies the gas valve opening duration or position accordingly to maintain optimal combustion conditions and prevent knocking
2Object-generated harmful factors
If the air-to-gas ratio is optimized for efficient combustion, then the emission compliance is improved, but the response to sudden load changes becomes sluggish
Solution Approach 1:
The system transitions from static air-to-gas ratio settings to dynamic adjustment mechanisms. The control device continuously varies the gas supply parameters in response to changing load conditions, enabling the engine to maintain emission compliance during steady-state operation while rapidly adapting to sudden load changes without compromising combustion efficiency or increasing emissions
3Reliability
If the gas supply is limited to prevent knocking combustion, then the combustion stability is improved, but the power output becomes insufficient during high load demand
Solution Approach 1:
The control device detects impending load changes or anticipates high-power demand conditions and proactively adjusts the air-to-gas ratio before knocking occurs. By predicting load increases based on operational patterns or sensor inputs, the system pre-enriches the mixture to the appropriate level, ensuring both stability and sufficient power output are maintained without waiting for knocking to occur
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 method enables large diesel engines to maintain efficient and environmentally friendly operation during sudden load changes by preventing the air-gas mixture from becoming too rich, similar to operation in liquid mode, thereby reducing speed fluctuations and ensuring compliance with emission standards.
Implementation Method 1
the scavenging or charging air is usually made available by a turbocharger, which generates a scavenging or charging air pressure that depends on the load on the engine
Implementation Method 2
In liquid mode, the fuel is usually introduced directly into the combustion chamber of the cylinder and burns there according to the self-ignition principle
Implementation Method 3
In the gas mode, it is known to mix the gas in the gaseous state with the scavenging air according to the Otto principle in order to generate an ignitable mixture in the combustion chamber of the cylinder
Implementation Method 4
The mixture in the cylinder is usually ignited by injecting a small quantity of liquid fuel into the combustion chamber of the cylinder or into an antechamber at the right moment
Data Source
Figure 1~3
Figure 2
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. During operation in gas mode (10), a state of strong load changes is detected (13), and then the large diesel engine is operated in a transient mode comprising the following steps: - Setting a target value for the speed or torque of the engine; - Determining an upper limit for the quantity of gas (14) supplied as fuel per operating cycle of the large diesel engine; - Determining an additional quantity of liquid fuel (14) to be introduced into the combustion chamber in addition to the gas, the additional quantity being dimensioned such that the target value for the speed is achieved. Furthermore, a large diesel engine operated according to such a method is proposed.