Engine Shutdown Air Trapping for Fast Expansion Stroke Start
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Solution Overview
Problem
Existing engine starting methods using compression stroke combustion are delayed due to the need for rotational crankshaft angle and generate less torque due to exhaust gases in the cylinder during expansion stroke combustion, making it difficult to achieve quick engine start and desired torque output.
Innovation Solution
Ceasing fuel injection and holding the waste gate and throttle open to increase air flow, trapping fresh air in the cylinder, which enhances torque generation during expansion stroke combustion, allowing for quicker engine start and improved idle speed attainment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If fuel is combusted during compression stroke to start the engine, then the engine can generate torque, but the engine starting time is delayed because the engine has to rotate through crankshaft angle after combustion initiation
Solution Approach 1:
The patent applies preliminary action by opening the waste gate and throttle before fuel injection ceases, preparing the engine to trap fresh air in the cylinder during the expansion stroke. This advance preparation allows the engine to generate torque more quickly when restarted, reducing the delay associated with compression stroke combustion while maintaining adequate torque output.
2Loss of time
If fuel is combusted during expansion stroke to reduce starting time, then the engine starts faster, but torque generation is reduced because the cylinder contains exhaust gases
Solution Approach 1:
The waste gate and throttle are opened in advance before fuel injection stops, creating conditions that allow fresh air to be trapped in the cylinder during the expansion stroke. This preliminary preparation ensures that when fuel is injected and combusted during the expansion stroke, the cylinder contains fresh air rather than exhaust gases, maintaining high torque output while achieving fast engine start.
3Quantity of substance
If the waste gate and throttle are held open after fuel injection ceases, then air flow through the engine increases and fresh air is trapped in the cylinder, but the system complexity increases
Solution Approach 1:
The patent applies multi-functionality by using the waste gate and throttle components for dual purposes: their primary functions during normal engine operation and their additional function of trapping fresh air in the cylinder during engine shutdown and restart. This approach increases fresh air charge without adding new components, thereby avoiding increased system complexity.
Data Source
AI summary
Systems and methods for operating an engine that is started via expansion stroke combustion are described. In one example, the method increases air flow through the engine during an engine stopping process so that a larger amount of air may be trapped in a cylinder that is on its expansion stroke so that greater amounts of engine torque may be provided during engine starting.