Dual Fuel Injector With Segmented Charge for Stable Compression Ignition
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Solution Overview
Problem
Existing dual fuel injection systems for internal combustion engines face challenges in effectively combining a liquid pilot fuel with a liquid primary fuel, leading to inefficient ignition and mixing, particularly in compression-ignition engines.
Innovation Solution
A dual fuel system with a dual fuel injector that includes a plunger, spill valve, and admission valve, forming a segmented fuel charge by displacing liquid primary fuel with liquid pilot fuel, allowing for controlled injection of leading pilot fuel followed by trailing primary fuel, utilizing different pressure levels to minimize mixing and ensure compression-ignition ignition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single injector is used to inject both diesel fuel and alternative fuel, then the device complexity is reduced, but the manufacturing precision and control of fuel injection timing and mixing is worsened
Solution Approach 1:
The single injector is segmented into multiple independent injection systems within one housing: a first injection system for diesel fuel with its own nozzle and control mechanism, and a second injection system for alternative fuel with separate nozzle and control. This segmentation allows precise control of each fuel type while maintaining a unified injector structure.
Solution Approach 2:
The second alternative fuel injection system is nested within the first diesel fuel injection system. The alternative fuel nozzle is positioned within the diesel fuel injection chamber, allowing the alternative fuel to be injected into the diesel fuel plume. This nested arrangement enables precise spatial control of fuel injection while keeping the injector structure compact.
2Reliability
If diesel fuel is injected to form a plume for compression ignition, then the ignition reliability is improved, but the mixing efficiency with alternative fuel is worsened
Solution Approach 1:
The alternative fuel is injected into the combustion chamber before the diesel fuel injection. This preliminary injection allows the alternative fuel to be positioned in the combustion chamber and partially mixed with air before the diesel fuel plume is formed, improving overall mixing efficiency while maintaining the diesel fuel's compression ignition reliability.
Solution Approach 2:
Air acts as an intermediary medium between the alternative fuel and diesel fuel. The alternative fuel is first mixed with air to form a pre-mixed charge, which then interacts with the diesel fuel plume. This intermediary mixing approach improves fuel-air mixing efficiency while preserving the diesel fuel's reliable compression ignition properties.
3Reliability
If pilot fuel is used to ignite primary fuel in dual fuel systems, then the ignition efficiency is improved, but the fuel mixing control is worsened
Solution Approach 1:
The fuel injection system is segmented into distinct pilot fuel injection and primary fuel injection subsystems. The pilot fuel (alternative fuel) injection is controlled separately from the primary fuel (diesel) injection, with independent timing control. This segmentation enables precise control of the pilot- primary fuel mixing process while maintaining efficient ignition.
Solution Approach 2:
The injection timing and duration of both pilot fuel and primary fuel are dynamically controlled based on operating conditions. The control system can adjust the timing of pilot fuel injection relative to primary fuel injection, and modify injection durations, to optimize mixing control under different engine loads and speeds while maintaining ignition efficiency.
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
The system achieves efficient and controlled injection of a segmented fuel charge, enhancing ignition efficiency and reducing fuel mixing, suitable for both legacy diesel engines and new systems with minimal modifications.
Implementation Method 1
A plunger of the dual fuel injector is movable in the plunger cavity from a retracted position to an advanced position, to increase a pressure of a primary fuel in the plunger cavity to an injection pressure
Implementation Method 2
a primary fuel ignitable in an engine combustion cylinder based on compression-ignition of the liquid pilot fuel
Implementation Method 3
igniting, within the combustion cylinder, the liquid primary fuel of the segmented fuel charge based on compression-ignition of the liquid pilot fuel of the segmented fuel charge
Data Source
AI summary
A dual fuel system for an internal combustion engine includes a first fuel supply of a liquid pilot fuel, a primary fuel supply of a liquid primary fuel, and a dual fuel injector. The dual fuel injector includes a spill valve fluidly connected with a plunger cavity and movable to control a start of injection and an end of injection, and an admission valve. The admission valve is movable to admit a pilot fuel into the fuel injector, such that the pilot fuel is conveyed through an outlet check to form, within a primary fuel passage fluidly connected to the plunger cavity, a segmented fuel charge of leading pilot fuel and trailing primary fuel by displacing some of the primary fuel. The liquid pilot fuel may be a higher cetane/lower octane liquid fuel, and the primary fuel may be a lower cetane/higher octane liquid fuel.