Multi-Stroke Fuel Injection for Cold Start Emissions
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Solution Overview
Problem
Cold starting emissions for internal combustion engines are high due to fuel wetting of cylinder walls, inefficient thermal energy conversion, and suboptimal catalyst operation below threshold temperatures, leading to elevated tailpipe emissions.
Innovation Solution
Injecting fuel at least three times during a cylinder cycle, with two injections during the expansion stroke and initiating a spark between the last two fuel injections, to combust fuel and reduce cylinder pressure, thereby minimizing engine energy expenditure and maximizing catalyst heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional fuel injection and spark timing is used during cold starting, then the engine can start and rotate, but fuel wets the cylinder walls and piston, increasing hydrocarbon emissions
Solution Approach 1:
The fuel injection is divided into multiple separate injections (at least three times per cylinder cycle) rather than a single injection. This segmentation allows the fuel to be delivered in controlled portions, with the final injection occurring during the expansion stroke when the piston is moving downward, reducing contact time with cylinder walls and minimizing wetting-related emissions.
Solution Approach 2:
The spark timing is dynamically adjusted to occur between the second and third fuel injections during the expansion stroke, rather than following conventional timing. This dynamic timing adjustment ensures combustion occurs when the piston is moving downward, reducing compression work requirements and minimizing fuel wetting of cylinder surfaces.
2Loss of time
If more thermal energy is directed to catalyst heating, then catalyst light-off time is reduced, but less energy is available for rotating and heating the engine
Solution Approach 1:
The engine operates in a periodic cycle where fuel is injected and combusted multiple times per cylinder cycle, with the final combustion event specifically timed to occur during the expansion stroke. This periodic combustion pattern directs thermal energy toward the exhaust catalyst while the electric machine provides rotational energy during the intake and compression strokes when the cylinder is not combusting.
Solution Approach 2:
An electric machine acts as an intermediary to provide the rotational energy needed for engine operation during cold starting. This allows the combustion system to focus thermal energy on catalyst heating without compromising engine rotation, as the electric machine compensates for the reduced mechanical energy output from the engine.
3Power
If fuel is injected and combusted during compression stroke, then engine torque is generated for rotation, but indicated mean effective pressure increases, reducing energy available for catalyst heating
Solution Approach 1:
Instead of combusting fuel during the compression stroke to generate torque (conventional approach), the invention inverts the timing by combusting fuel during the expansion stroke. This inversion reduces the indicated mean effective pressure and directs more thermal energy to the exhaust catalyst, while the electric machine provides the necessary rotational torque.
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 reduces hydrocarbon emissions, lowers the time for the catalyst to reach light-off temperature, and enhances combustion stability during cold starts, ultimately decreasing engine-out and tailpipe emissions.
Implementation Method 1
injecting fuel to a cylinder of the internal combustion engine during a cycle of the cylinder
Implementation Method 2
combusting the fuel in the internal combustion engine
Implementation Method 3
initiating a spark in the cylinder between the last two fuel injections
Implementation Method 4
imparts more energy to catalyst heating
Data Source
AI summary
Systems and methods for cold starting an internal combustion engine are described. In one example, fuel is delivered in four equal amounts into a cylinder during a cycle of the cylinder. The fuel is injected so as to reduce cylinder wall wetting, raise combustion stability, and increase exhaust system heating.