Splitflow Catalyst System Cold Start Light-off
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Solution Overview
Problem
Existing exhaust catalyst systems are inefficient at low temperatures during cold start conditions, requiring elevated temperatures to operate effectively, which results in a fuel penalty when using methods like variable valve timing and active heating.
Innovation Solution
An exhaust gas catalyst system with concentric passages and a split flap valve, actuator, and control unit that selectively closes one passage to locally heat catalytic components, reducing the thermal mass needed for faster catalyst light-off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the catalyst is heated to elevated temperature to operate efficiently, then catalytic efficiency is improved, but fuel consumption increases
Solution Approach 1:
The exhaust canister is divided into multiple zones with different thermal characteristics. The outer passage contains catalytic components that are heated faster due to lower thermal mass, while the inner passage contains components that remain cooler. This segmentation allows different portions of the catalyst to operate at different temperatures, enabling efficient cold start performance without requiring the entire catalyst bed to reach high temperatures.
Solution Approach 2:
Different regions of the catalytic components are given different thermal properties through their positioning in concentric passages. The outer passage components experience faster heating and higher temperatures during cold start, while inner passage components maintain lower temperatures. This local differentiation of thermal quality allows the system to achieve effective catalysis at cold start without the fuel penalty associated with heating the entire catalyst volume.
2Speed
If the entire catalyst bed is heated rapidly, then catalytic light-off speed is improved, but thermal mass requirements increase fuel penalty
Solution Approach 1:
The catalyst bed is segmented into outer and inner passage zones with different thermal masses. The outer passage contains less thermal mass and is designed to heat up faster, providing rapid light-off for cold start emissions. The inner passage contains more thermal mass and heats more slowly, avoiding the need to heat large quantities of material to achieve fast light-off.
Solution Approach 2:
Instead of heating the entire catalyst bed uniformly, the system applies heating selectively to the outer passage components that require it for rapid light-off. The inner passage components are allowed to remain cooler, reducing the total thermal mass that must be heated while still achieving sufficient catalytic activity where needed.
3Ease of manufacture
If uniform catalytic components are used throughout the canister, then manufacturing simplicity is maintained, but thermal response uniformity worsens
Solution Approach 1:
While using uniform catalytic components for ease of manufacture, the system creates local quality differences through the concentric passage configuration. The outer passage components experience different thermal conditions (faster heating, higher temperatures) compared to inner passage components, achieving thermal response differentiation without requiring different catalyst materials or complex manufacturing processes.
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 solution enables faster catalyst light-off and reduced NOx emissions during cold starts without a fuel penalty, improving engine efficiency and meeting stringent emissions standards.
Implementation Method 1
The at least one exhaust canister includes a pair of concentric passages formed therein including a central passage and an outer passage. A split flap valve is positioned in the inlet. An actuator is coupled to the split flap valve. A control unit is operably connected to the actuator and selectively moves the split flap valve closing one of the concentric passages and locally heating a portion of the catalytic components.
Implementation Method 2
locally heating a portion of the catalytic components
Data Source
AI summary
An exhaust gas catalyst system that includes at least one exhaust canister including an inlet separated from an outlet with catalytic components positioned between the inlet and outlet. The at least one exhaust canister receives a flow of exhaust gas. The at least one exhaust canister includes a pair of concentric passages formed therein including a central passage and an outer passage. A split flap valve is positioned in the inlet. An actuator is coupled to the split flap valve. A control unit is operably connected to the actuator and selectively moves the split flap valve closing one of the concentric passages and locally heating a portion of the catalytic components.