Dual Fuel Engine Mode Transition via Post-TDC Injection
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Solution Overview
Problem
Dual fuel engines face challenges in smoothly transitioning between fuels, particularly from gas to liquid modes, which can lead to power surges and increased emissions due to incomplete combustion and residual gas exit.
Innovation Solution
Injecting liquid fuel during the combustion stroke after the piston has passed the top dead center, starting at a crankshaft angle of 5° to 20°, ensuring immediate combustion of gas and preventing excessive pressure rise, while maintaining full or 90% fuel feed from the outset to match energy content, and advancing injection to the compression stroke before TDC after a transition period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If liquid fuel is injected during combustion stroke after TDC, then smooth transition to liquid fuel mode is achieved with stable engine load and speed, but injection timing is delayed compared to conventional pre-TDC injection
Solution Approach 1:
The system performs preliminary detection of gas feed interruptions and prepares for fuel mode transition in advance. The control system monitors gas feed status and pre-configures the injection strategy before the actual transition occurs, ensuring smooth switching without power surges.
Solution Approach 2:
The invention changes the injection timing parameter from conventional pre-TDC (e.g., 10-20° before TDC) to post-TDC (5° to 25° after TDC) during fuel mode transition. This parameter change allows the liquid fuel to ignite reliably from compression heat while avoiding excessive pressure rise, achieving stable transition to liquid fuel mode.
2Productivity
If full or 90% fuel feed is provided from the outset during transition, then rapid adaptation and smooth transition are achieved, but excessive pressure rise may occur if injection timing is too early
Solution Approach 1:
The control system determines in advance whether a fuel mode transition is needed by monitoring gas feed status. By detecting the transition requirement before it occurs, the system can prepare the optimal injection strategy, allowing full fuel feed from the outset without causing excessive pressure rise.
Solution Approach 2:
The invention changes the injection timing parameter to post-TDC (5° to 25° after TDC) during fuel mode transition. This parameter change allows the liquid fuel to ignite reliably from compression heat while avoiding excessive pressure rise, enabling full or 90% fuel feed from the outset for rapid transition.
3Loss of time
If gas feed is stopped immediately during trip to liquid fuel, then transition response time is reduced, but residual gas in intake manifold may cause delayed combustion or emissions
Solution Approach 1:
The invention converts the potentially harmful residual gas in the intake manifold into a beneficial element by using it as additional fuel during the transition. The liquid fuel injection is timed to allow residual gas to be drawn into the cylinder and burned, converting what would be emissions into useful combustion energy.
Solution Approach 2:
The invention changes the liquid fuel injection timing to post-TDC (5° to 25° after TDC) during fuel mode transition. This parameter change ensures that residual gas in the intake manifold is properly utilized and burned, preventing unburned gas emissions while maintaining rapid transition response.
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
Enables a smooth transition from gas to liquid fuel mode with stable engine load and speed, low emissions, and rapid adaptation, preventing unburned gas exit and ensuring reliable ignition.
Implementation Method 1
The liquid fuel 20 is injected during a combustion stroke after the piston has passed the top dead center (TDC) when the piston is already moving towards the bottom dead center (BDC). This injected liquid fuel will ignite as a consequence of high temperature and pressure at the moment of injection
Data Source
Figure 1~2
Figure 3~4
AI summary
A method in controlling a dual fuel internal combustion four-stroke piston engine (1) comprising - a number of cylinders (5), a piston (50) is movable in a reciprocating manner between a top dead center (TDC) and a bottom dead center (BDC) inside the cylinder (5) defining a combustion chamber, - the engine (1) is configured to operate in two modes: - a gas mode for using gaseous main fuel (10), and - a liquid fuel mode for using liquid fuel (20) injected directly to the cylinder (5), - the engine (1) is configured to switch between the modes when needed, - in a situation where a trip or other shift from the gas mode to the liquid mode occurs on a running engine (1), the liquid fuel (20) is injected during a combustion stroke after the piston (50) has passed the top dead center (TDC) when the piston (50) is already moving towards the bottom dead center (BDC).