Exhaust Heater Control for Cold Start NOx Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
During light load or cold start operations, exhaust gas recirculation (EGR) is not effective due to condensation and corrosion issues, and selective catalytic reduction (SCR) systems are inactive, leading to diminished NOx emission control.
Innovation Solution
An exhaust system with a grid heater and bypass pathways is used to quickly heat the exhaust air flow, maintaining temperature and enabling EGR before the SCR system reaches active temperature, thereby reducing engine-out NOx emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If EGR is used during light load or cold start operation, then NOx production is reduced, but condensation and corrosion issues occur in power cylinders
Solution Approach 1:
The patent changes the temperature parameter of the exhaust gas by using a heater to raise it above the dew point, preventing condensation while allowing EGR to continue operating and reducing NOx emissions during cold start and light load conditions
2Object-generated harmful factors
If SCR system is used to remove NOx, then NOx emissions are reduced, but the system is not active at cold start operation
Solution Approach 1:
The patent applies preliminary action by using a heater to rapidly raise the exhaust gas temperature before the SCR system reaches its active temperature threshold, enabling NOx reduction to begin earlier and extending the duration of effective NOx control during cold start operation
3Temperature
If heater is used to heat exhaust air flow, then exhaust temperature increases quickly, but additional heating components are required
Solution Approach 1:
The patent applies multi-functionality by designing the heater to serve multiple purposes: it heats the exhaust gas to prevent condensation during EGR operation, rapidly raises temperature during cold start before SCR activation, and maintains temperature during light load operation, eliminating the need for separate systems for each function
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 allows for earlier EGR flow and faster exhaust temperature increase during cold starts and light load operations, reducing NOx emissions even before the SCR system is active, improving SCR efficiency and avoiding condensation issues.
Implementation Method 1
a grid heater or one or more bypasses are controlled to more quickly heat the exhaust air
Implementation Method 2
Exhaust gas recirculation (EGR) is a vehicle emission control used to reduce nitrogen oxide (NOx) production by recirculating a portion of an engine's exhaust gas back into the engine cylinders
Data Source
AI summary
One or more techniques and/or systems are disclosed for controlling exhaust heating to reduce engine out NOx emission. A heater is used for exhaust temperature control of an exhaust system and is activated at a non-active selective catalytic reduction (SCR) system temperature. One or more exhaust air flow bypasses are controlled during operation of the heater and heating of an exhaust air flow is maintained by the heater prior to activation of the SCR system.