Elevated Idle Speed Unloads Hydrocarbon Deposits on Exhaust Catalysts
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Solution Overview
Problem
Hydrocarbon emissions deposited on exhaust after-treatment devices, such as oxidation catalysts in diesel engines and three-way catalysts in gasoline engines, can lead to elevated temperatures and damage when engines operate at idle for extended periods, especially at sub-freezing temperatures, reducing the efficiency of these devices.
Innovation Solution
A method and system that determine if the engine has been operating at a preset idle speed for a predetermined time, increasing the idle speed by a predetermined value to enhance the flow rate of exhaust gas through the after-treatment devices, thereby unloading deposited hydrocarbons, which can include enabling an elevated-idle switch and considering sub-freezing temperatures and vehicle modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the engine operates at idle speed for extended periods, then the engine can maintain operation, but hydrocarbon emissions accumulate on the after-treatment device causing elevated temperatures and potential damage
Solution Approach 1:
The system implements periodic monitoring of idle operation duration and triggers periodic regeneration cycles by increasing idle speed. The controller activates the elevated idle speed mode after detecting a predetermined amount of idle operation, creating a periodic action that prevents harmful accumulation while maintaining normal operation during non-critical periods.
Solution Approach 2:
The system changes the operational parameters of the engine by increasing idle speed from a preset value to an elevated value. This parameter change increases exhaust gas flow rate and temperature, transforming the exhaust conditions to enable thermal regeneration of the after-treatment device and prevent hydrocarbon accumulation.
2Productivity
If the idle speed is increased to unload hydrocarbons, then the flow rate of exhaust gas increases and emissions are removed, but fuel consumption increases
Solution Approach 1:
The elevated idle speed operation is implemented periodically rather than continuously. The controller monitors idle duration and only activates the high fuel-consumption mode when hydrocarbon accumulation reaches critical levels, thereby minimizing unnecessary fuel consumption while maintaining low emissions during normal operation.
Solution Approach 2:
The system uses the engine's own exhaust flow and thermal energy to perform the regeneration function. By increasing idle speed, the system generates sufficient exhaust flow and temperature to thermally regenerate the after-treatment device using the engine's own resources, eliminating the need for external regeneration systems or additional fuel injection.
3Duration of action of moving object
If the engine operates at sub-freezing temperatures, then the engine can maintain operation in cold conditions, but hydrocarbon emissions deposit more readily on the after-treatment device
Solution Approach 1:
The system includes a temperature sensor that detects sub-freezing conditions and pre-conditions the regeneration logic accordingly. When cold temperatures are detected, the controller is prepared to activate elevated idle speed more readily, performing preliminary preparation to prevent hydrocarbon accumulation before it becomes problematic.
Solution Approach 2:
The system changes operational parameters in response to temperature conditions. At sub-freezing temperatures, the controller modifies the idle speed increase strategy to ensure sufficient exhaust flow and temperature are achieved to counteract the reduced vaporization and oxidation efficiency that occurs in cold conditions.
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
Effectively unloads hydrocarbon emissions from after-treatment devices, preventing damage and maintaining their operational efficiency by increasing the exhaust gas flow rate and temperature, ensuring continued effective emission reduction.
Implementation Method 1
Such an oxidation catalyst is typically employed in order to oxidize and burn hydrocarbon emissions present in the exhaust flow
Data Source
AI summary
A method unloads hydrocarbon emissions deposited by an exhaust gas on an after-treatment device that is employed in an exhaust system for an internal combustion engine. The method includes determining whether the engine has been operating at a preset idle speed for a predetermined amount of time. The method also includes increasing the preset idle speed by a predetermined value if the engine has been operating at a preset idle speed for a predetermined amount of time. The increasing of the engine idle speed increases a flow rate of the exhaust gas to the after-treatment device and unloads the deposited hydrocarbon emissions. A system for unloading hydrocarbon emissions deposited on an after-treatment device and a vehicle employing such a system are also disclosed.