Multi-Fuel Engine Starting Control via Sequential Injection
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Solution Overview
Problem
The use of gaseous fuel for engine starting improves mixing and reduces emissions but limits spark retardation, which hampers catalyst temperature increase for emission control, creating a paradox where complete combustion benefits are compromised by reduced exhaust heat.
Innovation Solution
A method involving the sequential injection of gaseous and liquid fuels during engine starting, where gaseous fuel is injected during the intake stroke to form a lean mixture and liquid fuel is injected during compression or expansion to create a rich cloud near the spark plug, allowing for spark timing retardation and improved combustion stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If gaseous fuel is used during engine starting to improve mixing and reduce emissions, then combustion completeness is improved, but spark retardation capability deteriorates
Solution Approach 1:
The fuel injection system is segmented into two separate injectors: a port fuel injector for gaseous fuel and a direct injection injector for liquid fuel. This segmentation allows each fuel type to be delivered through optimized pathways, enabling the gaseous fuel to mix well with air while liquid fuel can be precisely delivered near the spark plug to support spark retardation
Solution Approach 2:
The system creates different fuel distribution qualities in different locations: gaseous fuel provides uniform distribution for complete combustion, while liquid fuel creates localized rich pockets near the spark plug. This local quality differentiation resolves the contradiction by allowing both well-mixed combustion and spark-retardation-supporting rich zones to coexist
2Temperature
If spark timing is retarded to increase exhaust temperature for faster catalyst light-off, then catalyst activation speed is improved, but combustion stability deteriorates when using gaseous fuel
Solution Approach 1:
Liquid fuel acts as an intermediary substance that bridges the gap between spark timing retardation and combustion stability. The liquid fuel's high energy density and localized delivery create reliable ignition kernels that stabilize combustion even when spark timing is significantly retarded, enabling both high exhaust temperature and stable combustion
3Object-generated harmful factors
If gaseous fuel is injected during intake stroke to form lean mixture, then emissions are reduced, but combustion reliability under spark retard conditions deteriorates
Solution Approach 1:
The system merges gaseous fuel injection during the intake stroke with liquid fuel injection during the compression stroke. This combination allows the lean gaseous fuel mixture to reduce emissions while the subsequently injected liquid fuel provides the additional energy density and localized richness needed to maintain combustion reliability under spark retard conditions
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 enables low engine-out emissions with well-mixed gaseous fuel combustion while allowing for reliable combustion and faster catalyst light-off by retarding spark timing, addressing the limitations of gaseous fuel use during engine starting.
Implementation Method 1
injecting gaseous fuel to the cylinder at least during or before an intake stroke of an engine cycle to form a well-mixed overall lean air-fuel mixture
Implementation Method 2
directly injecting liquid fuel to the cylinder at least during one of a compression and expansion stroke of the engine cycle to form a rich air-fuel cloud near the spark plug
Implementation Method 3
spark initiating combustion of the injected fuels
Data Source
AI summary
Various example approaches are described, one of which includes a method for controlling injection of gaseous and liquid fuel to a cylinder during engine starting. Specifically, gaseous fuel is injected during or before an intake stroke of the cycle to form a well-mixed overall lean air-fuel mixture, and then liquid fuel is directly injected to the cylinder at least during one of a compression and expansion stroke of the engine cycle to form a rich air-fuel cloud near the spark plug, where a spark initiates combustion of the injected fuels. In one example, the rich cloud enables additional spark retard, and thus faster catalyst light-off, while maintain acceptable combustion stability of the gaseous fuel.