Engine Cold Start System Using Combustor and Three-Way Valve
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Solution Overview
Problem
Cold start emissions from internal combustion engines contribute significantly to tailpipe emissions, and existing methods to warm engine after-treatment devices often result in higher emissions due to the generation of emissions from combustors used to accelerate heating.
Innovation Solution
An exhaust system incorporating a combustor air pump, a passive NOx absorber, and an electric heater, which quickly heats engine after-treatment devices and reduces NOx emissions by processing combustor emissions through a selective catalyst reduction catalyst, thereby reducing tailpipe emissions and enabling faster engine starting with lower emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a combustor is used to quickly heat engine after-treatment devices, then the heating speed is improved, but tailpipe emissions increase due to combustor-generated emissions
Solution Approach 1:
The system performs preliminary heating of the after-treatment devices using a combustor before the main engine operation begins. The combustor is activated during engine cold start to rapidly bring the after-treatment devices up to operating temperature, and then shut off before the engine runs, so that combustor emissions do not reach the tailpipe during normal operation.
Solution Approach 2:
A three-way valve is introduced as an intermediary component to control the flow path of exhaust gases. This valve directs combustor emissions away from the tailpipe and toward the after-treatment devices for processing, while allowing clean engine exhaust to flow to the tailpipe during normal operation.
2Temperature
If engine operating adjustments are made to increase engine heat output, then after-treatment device activation is accelerated, but tailpipe emissions remain higher than desired
Solution Approach 1:
The three-way valve acts as a mediator to separate the heating function from the exhaust emission path. It allows the system to use engine heat output to warm after-treatment devices while preventing heated exhaust gases with high emissions from reaching the tailpipe during the warm-up phase.
Solution Approach 2:
The system extracts the heating function from the main exhaust flow path. By using a dedicated combustor and controlled valve system, the heating process is separated from the normal exhaust pathway, allowing emissions to be managed independently from the thermal energy utilization.
3Loss of time
If a combustor is used to warm after-treatment devices, then engine starting can occur sooner, but the combustor generates emissions that contribute to vehicle tailpipe emissions
Solution Approach 1:
The combustor performs preliminary heating of after-treatment devices before engine start, reducing the time needed for the engine to reach operational temperature. The combustor is activated during the cold start phase and then deactivated, allowing the engine to start sooner without the combustor emissions reaching the tailpipe during normal operation.
Solution Approach 2:
The three-way valve serves as an intermediary that manages the transition between combustor operation and engine operation. It directs combustor emissions to the after-treatment devices during heating, then switches to allow clean engine exhaust to the tailpipe once heating is complete and the engine is running.
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
The system effectively lowers tailpipe emissions by quickly heating engine after-treatment devices and reducing NOx emissions, allowing for sooner engine starting and purging the passive NOx absorber during engine shutdown to prepare for subsequent restarts, thus reducing overall emissions.
Implementation Method 1
a passive NOx absorber (PNA) positioned along the engine exhaust passage
Implementation Method 2
a selective catalyst reduction (SCR) catalyst positioned along the engine exhaust passage downstream of the PNA
Implementation Method 3
a combustor positioned along a first passage
Data Source
AI summary
Methods and systems for reducing emissions of an internal combustion engine are described. In one example, a combustor is applied post shutdown to purge stored NOx from a passive NOx absorber to prepare for a subsequent engine start. The trapped NOx is subsequently reduced via a selective catalytic reduction catalyst.