Water Injection for Catalyst Oxygen Saturation Reduction
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Solution Overview
Problem
During automatic engine stop-start operations, the catalyst in the exhaust becomes oxidized and depleted of water, leading to reduced NOx conversion efficiency upon engine restart, as oxygen saturation inhibits hydrogen formation, thereby degrading emissions control.
Innovation Solution
Injecting a water-containing fluid onto a closed intake valve during engine rest, allowing it to vaporize and displace oxygen in the catalyst, providing water for hydrogen formation and reducing oxygen saturation, which is then inducted into the cylinder and exhausted to the catalyst before engine restart.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the engine is automatically stopped to reduce fuel consumption, then fuel economy is improved, but the catalyst becomes oxidized and emissions control deteriorates upon restart
Solution Approach 1:
The system performs preliminary action by injecting water onto the intake valve before engine restart occurs. This water is vaporized during the subsequent intake stroke and delivered to the catalyst beforehand, reducing oxygen saturation and preparing the catalyst for effective NOx conversion upon restart, thus preventing emissions deterioration
Solution Approach 2:
The system converts the harmful oxidized state of the catalyst into a beneficial condition by using water injection to reduce oxygen saturation. The water vapor delivered to the catalyst during the restart cycle chemically reduces the oxidized catalyst surface, transforming the harmful oxidation state into a reduced state that is effective for NOx conversion
2Stability of the object's composition
If the catalyst is saturated with oxygen during engine stop, then the catalyst maintains oxidation state, but water availability for hydrogen formation is depleted
Solution Approach 1:
Water serves as an intermediary substance that addresses both the oxygen saturation and water depletion issues. The injected water vaporizes and delivers both water molecules (replenishing water stores) and hydrogen (for reducing the oxidized catalyst), acting as a dual-purpose mediator that simultaneously resolves the composition stability and quantity problems
3Reliability
If water-containing fluid is injected onto the intake valve, then oxygen saturation is reduced and water is provided for hydrogen formation, but additional system complexity is introduced
Solution Approach 1:
The water injection system serves multiple functions: it reduces oxygen saturation in the catalyst, provides water for hydrogen formation, and acts as a thermal management mechanism. By using a single water injection system to achieve multiple benefits, the patent minimizes additional complexity while maximizing emissions control reliability
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 method effectively reduces oxygen saturation in the catalyst and provides necessary water for hydrogen formation, improving emissions control during automatic engine restarts by ensuring efficient NOx conversion.
Implementation Method 1
Injecting a water-containing fluid onto a closed intake valve during engine rest, allowing it to vaporize
Implementation Method 2
the vaporized water-containing fluid may contribute water to the catalyst for hydrogen formation
Implementation Method 3
the vaporized water-containing fluid may be passed to the exhaust prior to the initiation of combustion
Data Source
AI summary
Embodiments for performing an automatic stop-start operation are provided. In one example, a method for an engine comprises during an automatic stop, injecting a water-containing fluid onto a closed intake valve of a cylinder while the engine is at rest, and on a subsequent restart, fueling the cylinder after at least one intake stroke and subsequent exhaust stroke are performed in the cylinder.