Dual-Catalyst Exhaust Layout for Faster Light-Off Emission Control
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Solution Overview
Problem
Existing exhaust gas aftertreatment systems in vehicles with internal combustion engines struggle to eliminate pollutant emissions during the catalytic light-off period, typically within 10-20 seconds after ignition.
Innovation Solution
The exhaust gas system includes a primary catalyst with a heat source to accelerate catalytic light-off, and a secondary catalyst that achieves light-off before the primary catalyst, with a valve to direct exhaust gas based on catalyst temperature, and a thermal interface to transfer heat between catalysts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single catalyst is used in the exhaust gas system, then the device complexity is low, but the pollutant removal efficiency during the catalytic light-off period is insufficient
Solution Approach 1:
The exhaust gas system is segmented into two distinct catalysts: a primary catalyst and a secondary catalyst. The secondary catalyst is positioned upstream to activate first during the CLO period and treat pollutants, while the primary catalyst activates later. This segmentation allows different catalysts to operate at different temperature ranges, effectively reducing emissions during the light-off period without requiring a single complex catalyst design.
2Loss of time
If a heat source is added to accelerate catalytic light-off, then the light-off time is reduced, but the device complexity and energy consumption increase
Solution Approach 1:
The system uses the hot exhaust gas from the engine itself to activate the secondary catalyst upstream, which then treats pollutants during the CLO period. The thermal energy already present in the exhaust stream is utilized to initiate catalytic activity, eliminating the need for external heating devices while still achieving rapid light-off and emission reduction.
3Object-generated harmful factors
If exhaust gas is always directed through the secondary catalyst, then pollutant treatment during CLO is improved, but the pressure drop and energy loss increase
Solution Approach 1:
The system incorporates a valve that dynamically directs exhaust gas flow based on operating conditions. During the CLO period when the primary catalyst is not yet active, the valve directs exhaust through the secondary catalyst for pollutant treatment. Once the primary catalyst reaches operating temperature, the valve redirects exhaust flow to bypass the secondary catalyst, minimizing pressure drop and energy loss while maintaining emission control effectiveness.
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 configuration reduces harmful emissions by efficiently treating exhaust gas during the catalytic light-off period, ensuring effective pollutant removal before release into the atmosphere.
Implementation Method 1
a heat source arranged about a portion of the main body and configured to supply heat to the primary catalyst during a catalytic light-off (CLO) period
Implementation Method 2
The thermal interface can be configured to transfer heat from the secondary catalyst to the primary catalyst when the valve is in the first position
Data Source
AI summary
A vehicle, comprising a vehicle body, an internal combustion engine coupled to the vehicle body and including an exhaust gas manifold, and an exhaust gas system coupled to the vehicle body. The exhaust gas system comprising a primary catalyst that includes a main body having a first end, a second end spaced from the first end, and at least one wall extending between the first end and the second end, an inlet coupled to the first end, and an outlet coupled to the second end. The main body being arranged downstream of the internal combustion engine and the inlet being communicatively coupled to the exhaust gas manifold. The exhaust gas system further including a heat source arranged about a portion of the main body and configured to supply heat to the primary catalyst during a catalytic light-off (CLO) period.