Engine Cold Start Emission Control via Segmented Exhaust Heating
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Solution Overview
Problem
Internal combustion engines face challenges in reducing emissions such as CO, HC, and NOx, as combustors installed in engine exhaust systems can generate these emissions, which are not effectively converted by after-treatment devices, leading to untreated emissions being released into the atmosphere.
Innovation Solution
An exhaust system design that includes a combustor air pump, an electric heater, a three-way valve, an oxidation catalyst, a urea injector, and a selective reduction catalyst, where the electric heater and selective reduction catalyst are positioned downstream of the combustor to heat and process combustor emissions before engine start, reducing NOx, CO, and HC emissions by activating engine after-treatment devices more efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a combustor is installed in the engine exhaust system to heat after-treatment devices, then the heating efficiency is improved, but untreated combustor emissions (CO, HC, NOx) are released into the atmosphere
Solution Approach 1:
The exhaust system is segmented into separate processing paths: one for engine exhaust gases through engine after-treatment devices, and another for combustor emissions through combustor after-treatment devices (oxidation catalyst and SCR catalyst). This segmentation allows each path to be optimized independently, with the combustor path equipped with dedicated emission processing capabilities.
Solution Approach 2:
Combustor after-treatment devices (oxidation catalyst and SCR catalyst) serve as intermediaries to process combustor emissions before they are released. The oxidation catalyst converts CO and HC, while the SCR catalyst reduces NOx, preventing these harmful emissions from reaching the atmosphere directly.
2Loss of time
If the combustor generates higher gas temperatures to reduce after-treatment device heating time, then the heating speed is improved, but the system robustness deteriorates due to temperature sensitivity of after-treatment devices
Solution Approach 1:
The system separates the heating function from the emission processing function. The combustor generates high-temperature gases for heating, while combustor after-treatment devices process the emissions. This segmentation allows the heating path to operate at high temperatures without compromising the reliability of emission processing devices.
Solution Approach 2:
Combustor after-treatment devices act as intermediaries between the high-temperature combustor gases and the atmosphere. These devices are specifically designed to handle combustor emission characteristics and can tolerate the higher temperatures associated with combustor operation, protecting the overall system from temperature-related damage.
3Device complexity
If engine after-treatment devices are used to process both engine and combustor emissions, then the device complexity is reduced, but the manufacturing precision deteriorates due to incompatible temperature requirements
Solution Approach 1:
The exhaust system is divided into separate after-treatment chains: engine after-treatment devices for engine exhaust and combustor after-treatment devices for combustor emissions. Each chain is optimized for its specific temperature and emission characteristics, ensuring high manufacturing precision and processing efficiency for each function.
Solution Approach 2:
Different after-treatment devices are applied to different emission sources based on their specific requirements. Combustor after-treatment devices are designed with local quality characteristics suitable for high-temperature combustor emissions, while engine after-treatment devices are optimized for engine exhaust conditions. This ensures each device operates at optimal performance.
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 lowers tailpipe emissions by processing combustor emissions through separate devices, reduces after-treatment device heating time, and increases system robustness by tolerating higher temperatures, thereby enhancing emission processing efficiency.
Implementation Method 1
an electric heater positioned along a second passage downstream of the three-way valve
Implementation Method 2
an oxidation catalyst or a three-way catalyst positioned along the second passage downstream of the electric heater
Implementation Method 3
a selective reduction catalyst (SCR) positioned along the second passage downstream of the oxidation catalyst or the three-way catalyst
Implementation Method 4
a urea injector positioned along the second passage downstream of the oxidation catalyst or the three-way catalyst
Data Source
AI summary
Methods and systems for reducing emissions of an internal combustion engine are described. In one example, an electric heater and a selective reduction catalyst are positioned in a passage downstream of a combustor where urea may be injected to the selective reduction catalyst to reduce NOx emissions that may be generated by the combustor.