Cold-Start Engine Torque Control for Exhaust Aftertreatment Heating
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Solution Overview
Problem
Existing methods for operating internal combustion engines fail to ensure immediate effectiveness of exhaust aftertreatment devices post-cold start, leading to potential non-compliance with pollutant emission limits due to insufficient heating and high exhaust gas mass flow during cold starts.
Innovation Solution
Limiting the operating torque of the combustion engine based on the temperature of the exhaust aftertreatment device until it reaches activation temperature, preventing driving operation if necessary, and employing measures to quickly heat the aftertreatment device, such as electric heating or retarding ignition timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the internal combustion engine operates at high power output immediately after cold start, then the vehicle can transition into driving mode, but the exhaust aftertreatment devices cannot effectively treat pollutants due to temperatures below activation temperature
Solution Approach 1:
The system performs preliminary heating of the exhaust aftertreatment devices using electric heating elements or burners before the engine reaches high power output. This preliminary action ensures the aftertreatment devices are at activation temperature before significant pollutant treatment is required, resolving the contradiction between immediate driving capability and emission effectiveness.
Solution Approach 2:
The engine control unit dynamically adjusts the torque limit based on the temperature of the exhaust aftertreatment devices. As the aftertreatment devices heat up and reach activation temperature, the torque limit is progressively increased, allowing the engine to transition from idle to full power output. This dynamic adjustment resolves the contradiction by making power availability dependent on aftertreatment readiness.
2Loss of time
If dedicated heating devices are used to heat exhaust aftertreatment devices, then the activation temperature is reached faster, but the device complexity and energy consumption increase
Solution Approach 1:
The heating system is designed to serve multiple functions: electric heating elements can provide both engine starting assistance and aftertreatment device heating, while burners can serve both as auxiliary heating sources and as part of the exhaust gas recirculation system. This multi-functionality reduces overall system complexity while maintaining effective heating capability.
Solution Approach 2:
The exhaust aftertreatment devices are heated using waste heat from the engine exhaust gas through recirculation systems. The engine's own exhaust heat, which would otherwise be wasted, is redirected to heat the aftertreatment devices, enabling self-service heating without requiring separate complex heating systems.
3Temperature
If in-engine measures are implemented to generate hot exhaust gas, then the exhaust aftertreatment devices heat up faster, but the engine operates at reduced efficiency
Solution Approach 1:
The engine operates in periodic cycles, alternating between efficiency-optimized mode and heating-optimized mode. During cold start, the engine periodically switches to a mode that generates hotter exhaust gas to heat the aftertreatment devices, then returns to efficiency-optimized mode once the aftertreatment devices reach activation temperature. This periodic switching limits the duration of reduced efficiency while achieving the necessary heating.
Solution Approach 2:
The engine control unit dynamically changes operating parameters such as injection timing, air-fuel ratio, and valve timing to optimize exhaust gas temperature during the heating phase. By precisely controlling these parameters, the engine can generate sufficiently hot exhaust gas for aftertreatment heating while minimizing the duration and magnitude of efficiency loss.
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
Ensures compliance with pollutant emission limits by maintaining the exhaust aftertreatment device above its activation temperature, minimizing vehicle operation restrictions, and optimizing engine operation for rapid heating.
Implementation Method 1
generate relatively hot exhaust gas by operating the combustion engine at a relatively low efficiency, thus enabling relatively rapid heating of the exhaust aftertreatment devices via the exhaust gas
Implementation Method 2
actively heat exhaust aftertreatment devices, which can be achieved using dedicated heating devices, such as electric heating elements or burners
Implementation Method 3
the exhaust aftertreatment devices integrated into the exhaust system, which may include one or more catalytic converters
Implementation Method 4
a particulate filter
Data Source
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Figure 3~4
Figure 5
AI summary
A method for operating a motor vehicle with an internal combustion engine comprising an internal combustion engine and an exhaust system with at least one exhaust aftertreatment device, wherein, after a cold start of the internal combustion engine in which the exhaust aftertreatment device has a temperature below a start-up temperature, operation of the internal combustion engine is limited by means of an engine control unit depending on the temperature of the exhaust aftertreatment device with respect to the torque (M) that can be delivered by the internal combustion engine, and wherein driving operation of the motor vehicle is prevented until a minimum limit value (MG) of the deliverable torque (M) is reached, is characterized in that the minimum limit value (MG) is varied depending on a driving resistance of the motor vehicle to be overcome.