Multimode Engine Fuel Transition Control
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Solution Overview
Problem
Multimode engines experience undesired speed fluctuations during transitions between fueling modes due to uncontrolled changes in fuel energy content and air charge parameters, particularly in single point injection systems where airflow adjustments are slow, leading to potential power surges and misfires.
Innovation Solution
A method that gradually adjusts the supply of liquid fuel in multiple steps, synchronized with the introduction or termination of gaseous fuel, based on prevailing speed and load conditions to maintain constant total energy content and avoid exceeding the lean limit of gas lambda, ensuring smooth transitions between diesel-only and pilot modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the transition between fueling modes is triggered and controlled based solely on speed and load without attempting to achieve a smooth transition, then the control system is simple, but the engine experiences undesired speed fluctuations and power surges
Solution Approach 1:
The patent segments the fuel transition process into multiple discrete steps. Instead of a single abrupt switch between diesel-only and pilot modes, the system divides the transition into incremental stages where diesel fuel quantity is reduced and gaseous fuel quantity is increased in separate controlled steps. This segmentation allows the control system to manage each step individually, maintaining speed stability without requiring overly complex control mechanisms.
Solution Approach 2:
The patent applies preliminary action by adjusting the diesel fuel quantity before completing the full transition to gaseous fuel mode. The control system progressively reduces diesel fuel in advance of the complete mode switch, and progressively increases gaseous fuel in advance of full gaseous operation. This preliminary adjustment of fuel quantities helps prevent sudden power changes and speed fluctuations during the transition process.
2Use of energy by moving object
If the quantity of diesel fuel is progressively increased during the transition period to maintain constant energy content, then the total fuel energy content remains stable, but the gas lambda may be outside of an optimal range causing combustion efficiency issues
Solution Approach 1:
The patent applies dynamics by making the fuel adjustment process adaptive rather than fixed. The control system monitors engine operating conditions including speed, load, and combustion parameters during the transition. Based on this real-time feedback, the system dynamically adjusts the rate and magnitude of diesel and gaseous fuel changes. This dynamic approach ensures that gas lambda remains within the optimal range for combustion efficiency while still achieving the desired constant energy content during transition.
Solution Approach 2:
The patent changes multiple parameters simultaneously during transition, not just fuel quantity. The system adjusts diesel fuel quantity, gaseous fuel quantity, and monitors combustion parameters like gas lambda and ignition timing. By coordinating changes in these related parameters, the system maintains both constant total energy content and optimal combustion efficiency throughout the transition period.
3Productivity
If gaseous fuel quantity is increased or decreased to transition modes, then the fuel mix changes, but existing airflow control devices cannot adjust airflow rapidly enough to obtain optimum lambda, leading to power surges and droops
Solution Approach 1:
The patent applies preliminary action by pre-calculating and pre-positioning the fuel quantities needed for each transition step. The control system determines the optimal diesel and gaseous fuel quantities in advance of each transition phase, based on the desired constant energy content and optimal combustion parameters. This preliminary fuel positioning allows the system to execute transitions at the desired speed without causing power instability, as the fuel mix is already prepared for the upcoming operating conditions.
Solution Approach 2:
The patent implements feedback control by continuously monitoring engine parameters during the transition process. The control system measures actual engine speed, load, and combustion characteristics, then uses this feedback to adjust the fuel delivery rates. This closed-loop feedback ensures that even though airflow control devices cannot adjust rapidly enough for ideal lambda optimization, the system compensates by adjusting fuel quantities to maintain stable power output and optimal combustion throughout the transition.
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 ensures a smooth transition between operating modes, maintaining engine torque and speed stability by incrementally adjusting diesel fuel supply in sync with gaseous fuel changes, reducing the likelihood of power surges and misfires, even in single point injection systems.
Implementation Method 1
a liquid fuel injector delivering liquid fuel to a combustion chamber of one of the cylinders
Implementation Method 2
a gaseous fuel injector introducing gaseous fuel into an air supply system upstream of the air intake manifold
Implementation Method 3
combustion efficiency of pilot ignited gaseous fuel depends on excess air ratio of gas and ignition timing
Data Source
AI summary
A method of transitioning between operating modes in a multimode engine including a diesel-only mode and a diesel pilot, gas mode includes first terminating or initiating the supply of a gaseous fuel, depending on whether the system is transitioning to or from the pilot mode, and thereafter decreasing or increasing the diesel fuel supply quantity. Liquid fuel supply quantity is preferably altered in steps rather than discretely in order to avoid exceeding the lean limit of gas lambda. The number of steps and the percentage decrease or increase in each step preferably varies based at least in part on prevailing speed and load conditions.