Skip Fire Engine Control for Exhaust Temperature Management
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Solution Overview
Problem
Lean burn internal combustion engines face challenges in maintaining adequate exhaust gas temperature for efficient operation of aftertreatment systems, particularly at varying engine operating conditions, which affects emission control efficiency.
Innovation Solution
A skip fire engine control system dynamically adjusts the firing sequence of engine cylinders based on real-time data from oxygen sensors, NOx sensors, exhaust gas temperature, and other parameters to optimize exhaust gas temperature, ensuring it remains within the operational range of aftertreatment elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lean burn operation is used to improve fuel efficiency, then fuel economy is improved, but exhaust gas temperature decreases below the range required for efficient aftertreatment system operation
Solution Approach 1:
The system dynamically adjusts the firing sequence of cylinders based on real-time monitoring of exhaust gas temperature and aftertreatment system conditions. The engine control module modifies which cylinders fire on each cycle to maintain exhaust temperature within the optimal range for aftertreatment efficiency while preserving lean burn fuel economy benefits.
Solution Approach 2:
The system changes operational parameters by selectively activating or deactivating specific cylinders based on monitored conditions. When exhaust gas temperature drops below the threshold required for efficient aftertreatment operation, the system modifies the firing pattern to increase temperature, thereby resolving the contradiction between fuel efficiency and aftertreatment effectiveness.
2Reliability
If additional heating methods like hydrocarbon injection are used to maintain exhaust gas temperature, then aftertreatment system efficiency is improved, but fuel economy deteriorates
Solution Approach 1:
The system uses the engine's own combustion process to generate the required exhaust gas temperature through strategic cylinder firing patterns. By selectively firing cylinders, the system self-regulates exhaust temperature without requiring external heating sources or additional fuel injection, thereby maintaining aftertreatment efficiency while avoiding the fuel economy penalty of hydrocarbon injection.
Data Source
AI summary
A variety of methods and arrangements for controlling the exhaust gas temperature of a lean burn, skip fire controlled internal combustion engine are described. In one aspect, an engine controller includes an aftertreatment system monitor and a firing timing determination unit. The aftertreatment monitor obtains data relating to a temperature of one or more aftertreatment elements, such as a catalytic converter. Based at least partly on this data, the firing timing determination unit generates a firing sequence for operating the engine in a skip fire manner such that the temperature of the aftertreatment element is controlled within its effective operating range.