Dual Fuel Common Rail Transient Pressure Control
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Solution Overview
Problem
Dual fuel compression ignition engines face challenges in maintaining gaseous fuel pressure during fueling increase transients due to the highly compressible nature of natural gas, leading to potential deficits in gaseous rail pressure, which can affect engine performance.
Innovation Solution
A feed forward transient control algorithm is implemented to proactively increase the mass flow rate of gaseous fuel to the gaseous fuel common rail, responsive to changes in engine speed and load, by temporarily elevating the liquid fuel rail pressure to ensure sufficient gaseous fuel supply during transients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the mass flow rate of gaseous fuel is increased during a transient to meet high fuel demand, then the fueling speed improves, but the gaseous rail pressure drops due to the compressible nature of natural gas
Solution Approach 1:
The system proactively increases the mass flow rate of gaseous fuel to the common rail before the transient is complete, anticipating the pressure deficit that would otherwise occur. This preliminary action ensures adequate fuel supply during the transition from low to high fuel demand without allowing significant pressure drops
Solution Approach 2:
The electronic controller continuously monitors gaseous rail pressure and adjusts the mass flow rate accordingly. When a transient from low to high fuel demand is detected, the controller increases the gaseous fuel flow rate in response to pressure conditions, creating a closed-loop control system that maintains optimal pressure while meeting fuel demand
2Stability of the object's composition
If the gaseous fuel pressure is maintained low to prevent migration into liquid fuel rail, then fuel system stability improves, but the ability to rapidly increase fuel supply during transients deteriorates
Solution Approach 1:
The system dynamically adjusts the gaseous fuel pressure and mass flow rate based on operating conditions. During normal operation, pressure is maintained low to prevent migration, but during transients requiring high fuel demand, the system proactively increases mass flow rate to meet the elevated demand while managing pressure effects
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 strategy effectively reduces the severity of gaseous rail pressure deficits during fueling increase transients, enhancing the engine's responsiveness and stability by ensuring adequate gaseous fuel pressure, even during abrupt changes in fuel demand.
Implementation Method 1
a compression ignition engine is fueled predominately with natural gas originating from a gaseous fuel common rail, and liquid diesel fuel from a liquid fuel common rail that are directly injected into each engine cylinder. Both fuels are injected from the same fuel injector, and the relatively large charge of gaseous fuel is ignited by compression igniting a small pilot injection quantity of liquid diesel fuel.
Data Source
AI summary
A compression ignition engine is fueled from common rail fuel injectors that predominately inject natural gas fuel that is compression ignited with a small pilot injection of liquid diesel fuel. Before and after a rapid fueling increase transient, the liquid and gaseous rail pressures are controlled toward respective pressures based upon engine speed and load. During the transient, the liquid rail pressure is controlled toward an elevated liquid pressure in order to cause a surge in the supply of gaseous fuel to the gaseous fuel common rail to proactively satisfy the increased gaseous fuel injection rate while obviating a substantial pressure deficit in the gaseous fuel common rail.