Dual-Fuel Engine Mode Switching Control via Dynamic Threshold
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Solution Overview
Problem
Traditional dual-fuel engines face issues with sudden stops or excessive engine rotation due to fluctuating fuel supply during mode switching, particularly when switching from gas to diesel mode, leading to abnormal combustion or misfire, especially in large engines required for emergency navigation.
Innovation Solution
The engine device implements a control system that adjusts fuel supply by increasing the supply of one fuel to a switching threshold value through monotonic increase control and then switches to speed-governing control based on engine rotation number or load, with the option to stop the supply of the second fuel when it reaches a lower limit, ensuring stable operation by setting threshold values based on engine conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a constant threshold value is used for switching between speed-governing control and increase/decrease control, then the control system is simple, but the engine rotation number fluctuates rapidly and may cause sudden stop or overspeed
Solution Approach 1:
The patent applies dynamics by making the threshold value dynamic rather than constant. The threshold value is adjusted based on engine rotation number and load conditions, allowing the control system to adapt to varying operating states. This resolves the contradiction by preventing rapid rotation fluctuations and sudden stops while maintaining reasonable control system complexity through structured adjustment rules.
Solution Approach 2:
The patent changes the parameter of threshold value from a fixed constant to a variable parameter that depends on engine rotation number and load. By establishing adjustment rules that modify the threshold value according to operating conditions, the system achieves stable engine operation across different states without excessive complexity.
2Reliability
If the supply amount of fuel is increased to ensure adequate combustion, then combustion reliability improves, but the engine rotation number may become excessive (overspeed)
Solution Approach 1:
The patent adjusts the fuel supply threshold value parameter based on engine rotation number and load conditions. When rotation number is high or load is low, the threshold is reduced to prevent overspeed; when rotation number is low or load is high, the threshold is increased to ensure adequate combustion. This dynamic parameter adjustment resolves the contradiction between combustion reliability and rotation speed control.
Solution Approach 2:
The system dynamically adjusts fuel supply thresholds according to real-time engine operating conditions. By making the threshold value adaptive rather than fixed, the system simultaneously ensures adequate fuel supply for reliable combustion while preventing excessive rotation numbers through condition-based limitation.
3Speed
If the supply amount of fuel is decreased to prevent overspeed, then engine rotation number is controlled, but combustion may become insufficient causing misfire
Solution Approach 1:
The patent implements parameter changes by adjusting the fuel supply threshold value based on engine load and rotation number. When load is high or rotation number is low, the threshold is increased to ensure sufficient fuel for complete combustion; when load is low or rotation number is high, the threshold is decreased to control rotation. This resolves the contradiction between rotation control and combustion completeness.
Solution Approach 2:
The system dynamically modifies fuel supply thresholds according to operating conditions, ensuring that fuel supply is adequate for complete combustion when needed while controlling rotation number through condition-based threshold adjustment. This prevents misfire caused by insufficient fuel while maintaining rotation control.
4Device complexity
If a fixed switching threshold is used for fuel supply control, then the control logic is simple, but abnormal combustion or excessive in-cylinder pressure occurs during mode switching
Solution Approach 1:
The patent changes the switching threshold from a fixed value to a dynamically adjusted parameter based on engine rotation number and load. By establishing adjustment rules that modify the threshold according to operating conditions, the system prevents abnormal combustion and excessive in-cylinder pressure during mode switching while maintaining structured control logic.
Solution Approach 2:
The control logic becomes dynamic by adjusting the switching threshold based on real-time engine conditions. This prevents harmful effects during mode switching by adapting the threshold to current operating state, resolving the contradiction between control simplicity and prevention of abnormal combustion through systematic adjustment rules.
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 prevents engine rotation from exceeding safe limits, maintains responsiveness to load fluctuations, and prevents emergency stops by adjusting fuel supply according to engine load and rotation number, ensuring stable operation during mode switching.
Implementation Method 1
a gas injector which mixes a gaseous fuel with the air supplied from the intake manifold
Implementation Method 2
a main fuel injection valve configured to inject a liquid fuel into the cylinder for combustion
Implementation Method 3
a supply amount of a first fuel to be supplied in a post-switching operation mode is increased to a switching threshold value through an increase control which monotonously increases the supply amount, and then controlled by a speed-governing control based on an engine rotation number
Data Source
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AI summary
It is an object to provide an engine device that can achieve a stable operation, at a time of switching an operation mode. An engine device 21 of the present invention includes: an intake manifold 67 configured to supply air into a cylinder 77, an exhaust manifold 44 configured to output exhaust gas from the cylinder 77; a gas injector 98 which mixes a gaseous fuel with the air supplied from the intake manifold 67; and a main fuel injection valve 79 configured to inject a liquid fuel into the cylinder 77 for combustion. At a time of switching an operation mode from one another between the gas mode and the diesel mode, a supply amount of a first fuel to be supplied in a post-switching operation mode is increased to a switching threshold value through an increase control which monotonously increases the supply amount, and then controlled by a speed-governing control based on an engine rotation number. The switching threshold value is set based on the engine rotation number or an engine load.