Purging Uncombusted Fuel from Engine Cylinders to Exhaust Catalyst
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Solution Overview
Problem
In plug-in hybrid electric vehicles, uncombusted fuel can migrate to the engine intake or exhaust manifold upon engine shutdown, leading to increased emissions and potential failure in emissions certification testing, as existing solutions like secondary air injection add complexity and hardware.
Innovation Solution
The method involves positioning engine cylinders with open intake and exhaust valves after shutdown, using a reversible vacuum pump to pressurize the engine intake and evacuate residual hydrocarbons and uncombusted fuel to the exhaust catalyst, which remains above light-off temperature, thereby reducing emissions without additional hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If secondary air injection methods are used to reduce uncombusted fuel escape, then emissions are reduced, but device complexity and hardware requirements increase
Solution Approach 1:
The exhaust catalyst performs dual functions: its primary function of treating exhaust gases during engine operation, and a secondary function of oxidizing uncombusted hydrocarbons during engine-off events. The system uses existing components (exhaust catalyst, intake/exhaust valves, vacuum pump) to achieve emissions reduction without adding dedicated hardware for post-shutdown emissions control.
Solution Approach 2:
The exhaust catalyst is utilized for multiple purposes: standard exhaust treatment during engine operation and hydrocarbon oxidation during engine-off events. This multi-functional use eliminates the need for separate emissions control hardware while maintaining effectiveness in reducing both active and residual emissions.
2Object-generated harmful factors
If engine cylinders are purged to exhaust catalyst, then uncombusted fuel is processed, but engine operation complexity increases
Solution Approach 1:
The system performs preliminary positioning of engine cylinders with open intake and exhaust valves before the purging operation begins. This preparatory action ensures proper gas flow paths are established before activating the vacuum pump, facilitating efficient hydrocarbon migration to the exhaust catalyst while maintaining straightforward control logic.
Solution Approach 2:
The system employs pneumatic principles by using a vacuum pump to create pressure differential that drives hydrocarbon migration from engine cylinders through the exhaust system to the catalyst. This pneumatic approach provides simple, reliable control without complex mechanical or electronic actuation mechanisms.
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 effectively reduces emissions by processing uncombusted hydrocarbons into less hazardous gases, decreasing the likelihood of their escape to the atmosphere and avoiding the need for additional hardware, thus enhancing emissions control without increasing manufacturing costs.
Implementation Method 1
purging contents of the first engine cylinder to an exhaust catalyst... processing uncombusted hydrocarbons into less hazardous gases
Implementation Method 2
using a reversible vacuum pump to pressurize the engine intake and evacuate residual hydrocarbons
Data Source
AI summary
A method for an engine is provided. Following an engine-off event, engine cylinders are sequentially positioned with an intake valve open and an exhaust valve open. The contents of the engine cylinder are then purged to an exhaust catalyst. In this way, existing vehicle hardware may be used to evacuate residual hydrocarbons and uncombusted fuel to the exhaust catalyst, provided the catalyst remains above the light-off temperature.